Дисертації з теми "Stems. leaves"
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Nellvecia, Madike Lerato. "Cytotoxic and genotoxic studies of crude extracts from the leaves, stems and roots of Tulbaghia Violacea." Thesis, Vaal University of Technology, 2017. http://hdl.handle.net/10352/364.
Анотація:
M. Tech. (Biotechnology, Faculty of Applied and Computer Science), Vaal University of TechnologyTulbaghia violacea Harv. (wild garlic) has been used in traditional medicine in Southern Africa for the treatment of various ailments. Despite the widespread use and popularity of this medicinal plant as a herbal medicine, there is contradictory evidence regarding the safety and toxicity of the plant. The phytochemical profiling of the plant has also been neglected in research. The determination of chemical constituents present in plant material as well as the potential toxicity found in plants are preliminary steps necessary for the discovery and development of novel therapeutic agents with improved efficacy. The aim of this study was to evaluate the cytotoxic and genotoxic potential of crude extracts from the leaves, stems and roots of T. violacea. This was performed in vitro using aqueous and ethanol extracts of the leaves, stems and roots. The aim of the study was achieved by three major objectives; (1) to identify the active phytocompounds present in the leaves, stems and roots, (2) to assess the cytotoxicity using the MTT (3-(4, 5-dimethylthiazolyl-2)-2, 5-diphenyltetrazolium bromide) cell proliferation assay, and (3) to evaluate the genotoxic potential of the leaf, stem and root water extracts using the Allium cepa assay. A total of 14 phytochemicals were each extracted separately with distilled water and 70% ethanol by maceration from the leaves, stem and roots of T. violacea. The results of the qualitative phytochemical analysis showed that pharmacologically active compounds such as tannins, terpenoids, flavonoids, saponins, proteins, steroids, cardiac glycosides, phenols and coumarins were present in some organs of T. violacea. However, phlobatannins, leucoanthocyanins, alkaloids, carbohydrates and anthocyanins were absent in all plant parts. Overall, the leaves of the plant contained more active compounds than those present in the stems and roots when both water and 70% ethanol were used as the extractants. The quantitative phytochemical analysis for the Total Flavonoids Content (TFC) and Total Phenolic Contents (TPC) was also assessed. The water (0.027 mg/g) and 70% ethanol (0.053 mg/g) were most effective in extracting flavonoids from the leaves while the least amounts were obtained from the stems and roots. This observation was similar to the TFC were the water extracts of the leaves were the most effective in extracting phenols followed by the stems and roots. The MTT assay was conducted using two cell lines RAW 264.7 and C2C12. The experiment was conducted in triplicates for the leaf, stem and root extracts (water and ethanol) of T. violacea. The experimental design employed a 23 factorial design where three independent variables (concentration, incubation time and type of extracts) were selected using two levels for each variable (high (+) and low (-)). The results illustrated that both the water and ethanol vi extracts only showed a significant reduction in the number of viable cells at the concentration higher than 250 μg/ml treatment for both RAW 264.7 and C2C12 cells. The ethanol extracts from the leaves, stems and roots were found to be toxic towards the RAW 264.7 cells even at lower concentrations at both 24 and 48 h incubation periods (% cell viability < 50%). The water extracts were non-toxic to RAW 264.7 cells except for the water stem extract which showed toxicity after 48 h incubation (IC50 = 9.475 (4.061 to 23.39)). For the C2C12 cells, the lowest potent toxic concentration was 250 μg/ml for the ethanol extract of the stem after 48 h incubation. Overall, the T. violacea plant extracts were non-toxic as percentage cell viability greater than 50% was noted for both extraction solvents in all the plant parts of T. violacea. No cytotoxic activity was observed in all T. violacea plant parts with the C2C12 cell line (IC50 > 30 μg/ml). For the Allium cepa assay, only the water crude extracts of the leaves, stems and roots of T. violacea were used. A similar trend of potent genotoxic activity in the water stem extracts compared to the leaf and root extracts at the concentration ranges studied. Similar to the MTT assay, it is clear from the study that at higher concentrations, the water crude extracts from the leaves, stems and roots of T. violacea is toxic. From this study, it can be concluded that the extraction of compounds using water is more efficient than using ethanol. Overall, the T. violacea leaf extracts extracted the most phytocompounds and showed the highest percentage of viable cells as well as desirable IC50 values. However, preparation of herbal remedies using T. violacea plant extracts should be done with caution due to their possible genotoxic and cytotoxic potential at higher concentrations. This study raises a need to further conduct in vivo cytogenetic studies to ascertain the possible toxic effects of T. violacea crude extracts.
2
Ellery, Julie. "The biology, ecology and pathology of potential fungal canker and leaf blight pathogen Auambalaria species on leaves and stems of Corymbia calophylla." Thesis, Ellery, Julie (2005) The biology, ecology and pathology of potential fungal canker and leaf blight pathogen Auambalaria species on leaves and stems of Corymbia calophylla. Honours thesis, Murdoch University, 2005. https://researchrepository.murdoch.edu.au/id/eprint/32599/.
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Bujor, Oana-Crina. "Extraction, identification and antioxidant activity of the phenolic secondary metabolites isolated from the leaves, stems and fruits of two shrubs of the Ericaceae family." Thesis, Avignon, 2016. http://www.theses.fr/2016AVIG0261/document.
Анотація:
La myrtille et l’airelle rouge, deux arbrisseaux de la famille des Ericacées, sont consommées comme des aliments, boissons et suppléments alimentaires pour leur valeur nutritionnelle et leur richesse en polyphénols antioxydants. Dans les plantes, la qualité et la quantité de composés phénoliques sont influencées par les parties morphologiques de la plante à utiliser. En particulier, les composés phénoliques des végétaux exercent leur activité antioxydante dans la protection des lipides alimentaires et le compartiment gastrique a été proposé comme le site majeur pour le stress oxydatif lié au régime alimentaire. L’objectif général de cette thèse était d’étudier les variations saisonnières des composés phénoliques d’extraits de feuilles, branches et fruits de la myrtille et de l’airelle rouge ainsi que l’activité antioxydante de ces extraits. Pour cette étude, des extraits aqueux et hydroéthanoliques (fruits uniquement) des échantillons collectés en mai, juillet et septembre pendant les années 2013-2014 ont été obtenus par extraction assistée par microondes.Les analyses qualitatives et quantitatives par UPLC / MS des extraits de la myrtille ont montré la présence de dérivés de l’acide caféique et de l’acide p-coumarique et des glycosides de flavonols dans les feuilles tandis que des oligomères de flavanols étaient aussi présents dans les branches, et ce dans des quantités élevées. La thioacidolyse a révélé de faibles degrés de polymérisation (2-4) et l’(-)-épicatéchine comme unité principale des flavan-3-ols. Il existe une très bonne corrélation entre la Somme des Composés phénoliques par UPLC et la Teneur en Polyphenols Totaux ou l’activité antioxydante dans le test DPPH, excepté pour les feuilles du mois de mai. Ces dernières sont relativement riches en dérives de l’acide p-coumarique. Les effets de la saison apparaissent plus marqués pour les feuilles qui présentent une plus grande activité antioxydante et teneur en polyphénols en juillet et septembre. Ces paramètres sont optimaux en juillet pour les branches de myrtille. La période de de cueillette peut être définie en fonction des structures phénoliques désirées.Dans l’airelle rouge, la présence prédominante de monomères et oligomères de flavanols et de glycosides de quercétine a été identifiée dans toutes les parties morphologiques. Les proanthocyanidines contiennent la (+)-catéchine et la (-)-épicatéchine comme unités d'extension et terminale. De plus, la teneur en polyphénols totaux (méthode de Folin, UPLC) a montré une augmentation légère mais significative de mai à septembre pour les feuilles et les branches. Cette augmentation a été confirmée pour l'activité antioxydante dans le test DPPH pour les feuilles et les branches en 2014.L’activité antioxydante des extraits de myrtille et d’airelle rouge lors de l’inhibition de l’oxydation lipidique (accumulation de diènes conjugués) a été évaluée dans des conditions in vitro simulant la digestion. Tout d'abord, l'inhibition de l’oxydation lipidique a été conduite sur des émulsions huile de tournesol-dans-eau stabilisées par la sérum albumine bovine (BSA) ou des phospholipides d’œuf (PL), qui simulent l’état physique des lipides alimentaires lors de la digestion gastrique. L’oxydation a été initiée par la metmyoglobine, une forme de fer apportée par la viande rouge. Dans les deux modèles d’émulsions, les extraits aqueux des branches et des feuilles et l’extrait hydroethanolique de fruit de myrtille sont des inhibiteurs plus efficaces de l'oxydation lipidique durant la première phase de digestion (pH 5) que durant la seconde phase (pH 3). D’autre part, un extrait de feuilles de myrtille a été testé dans un modèle complet de digestion in vitro statique (étapes orale, gastrique et intestinale). L'oxydation lipidique, rapide lors de la l’étape gastrique (systèmes BSA et PL) et puis plus lente lors de l'étape intestinale (système PL), a été totalement inhibée par l'extrait de feuilles de myrtilleBilberry and lingonberry, two shrubs of the Ericaceae family, are consumed as food, beverage and dietary supplements due to their nutritional value and richness in antioxidant polyphenols. In plants, the quality and quantity of phenolic compounds are influenced by the parts of the plant to be used. In particular, plant phenolic compounds provide antioxidant activity in the protection of dietary lipids from oxidation and the gastric compartment has been proposed as a major site for diet-related oxidative stress. The aim of this thesis is to simultaneously assess the seasonal variations of phenolic compounds in leaves, stems, and fruits of bilberry and lingonberry extracts, as well as their antioxidant activity. For this study, aqueous and hydroethanolic (only fruits) extracts of bilberry and lingonberry samples collected in May, July and September during the years 2013-2014 were obtained under microwave-assisted extraction.In bilberry extracts, qualitative and quantitative analyses by UPLC/MS showed the presence of caffeoyl derivatives, p-coumaroyl derivatives, and flavonol glycosides in leaves whereas in stems, flavanol oligomers were additionally identified in significant amounts. Thioacidolysis revealed low degrees of polymerization (2-4) and (-)-epicatechin as the main flavan-3-ol unit. The sum of the phenolic compounds by UPLC was highly correlated with the Total Polyphenol Content and the antioxidant activity in the DPPH test for all the extracts except those of May leaves. The latter were relatively richer in p-coumaric acid derivatives. Seasonal effects were more marked for leaves which exhibited higher antioxidant activities and phenolic contents in July and September when these parameters were maximum in July for bilberry stems. The harvest period can be refined based on the desired phenolic structures. For lingonberry, the predominant presence of monomers and oligomers of flavanols and quercetin glycosides was found in all the morphological parts. Proanthocyanidins contain (+)-catechin and (-)-epicatechin as both extension and terminal units. The sum of the phenolic compounds by UPLC was less correlated with the Total Polyphenol Content and the antioxidant activity in the DPPH test than in bilberry. Furthermore, the total phenolic content (Folin method, UPLC) showed a slight but significant increase from May to September for both leaves and stems. This increase was confirmed for the antioxidant activity by the DPPH test for both leaves and stems in 2014.The antioxidant activity of bilberry and lingonberry extracts against lipid oxidation (formation of lipid-derived conjugated dienes) was evaluated under in vitro simulated digestion conditions. Firstly, the inhibition of lipid oxidation was performed using sunflower oil-in-water emulsions stabilized by bovine serum albumin (BSA) or egg yolk phospholipids (PL), both emulsifiers mimicking dietary components. Oxidation was initiated by metmyoglobin, a form of dietary iron from red meat. In both emulsion models, aqueous extracts from stems and leaves and the hydroethanolic fruit extract of bilberry proved to be more efficient inhibitors of lipid oxidation in the early phase of digestion (pH 5) than during the second phase (pH 3). Secondly, a bilberry leaf extract was tested in the inhibition of lipid oxidation in a complete static in vitro digestion model (oral, gastric and intestinal phases). The fast lipid oxidation in the gastric step (BSA and PL systems) and the slower lipid oxidation in the intestinal step (PL system) were totally inhibited by the bilberry leaf extract
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Bensaid, Aicha. "Propriétés anti-oxydants, anti-inflammatoires et antispasmodiques d’Ocimum basilicum." Electronic Thesis or Diss., Université de Montpellier (2022-....), 2022. http://www.theses.fr/2022UMONG091.
Анотація:
Le basilic Ocimum basilicum L est une plante herbacée, aromatique et alimentaire, il est utilisé sous forme fraiche ou bien transformé dans certaines préparations culinaires, ainsi que dans la médecine traditionnelle. Les différentes parties de cette plante présentent des propriétés biologiques très importantes pour la santé humaine grâce à leur richesse en composés bioactifs. L’objectif de ce travail est basé sur la caractérisation différentielles entre les tiges et les feuilles d’Ocimum basilicum sur le profil phytochimique et l’évaluation de leurs propriétés antioxydantes, anti-inflammatoires et antispasmodiques. Les extraits de basilic ont présenté des profils phytochimique différents, et l’évaluation de leurs effets antioxydants par le test DPPH et ORAC ont montré que les extraits éthanoliques ont une activité plus importante en comparaison avec les extraits aqueux. L’étude des effets anti-inflammatoires des extraits éthanoliques de tiges et de feuilles de basilic in vitro dans un modèle cellulaire de macrophages J774 stimulés par le LPS/IFNγ a montré que les deux extraits ont un effet inhibiteur sur la production des médiateurs inflammatoires (oxide nitrique, interlukine-6, prostaglandine E2, monocyte chemoattractante protein-1). Par contre ces extraits ont augmenté la production de la cytokine pro-inflammatoire TNFα (Facteur de nécrose tumorale alpha). Par la suite les extraits aqueux ont montré un effet relaxant sur le muscle lisse intestinal de rat. Les résultats de cette étude ont indiqué que les deux parties de basilic feuilles et tiges ont des effets biologiques intéressants qui peuvent être valorisés sur le plan nutrition- santéBasil Ocimum basilicum L is an herbaceous, aromatic, and food crop, which is used fresh or processed in some culinary preparations, thus in traditional medicine. The different parts of this plant present very important biological properties for human health due to their richness in bioactive compounds. The objective of this work is based on the differential characterization of the phytochemical profile of the stems and leaves of Ocimum basilicum and the evaluation of its antioxidant, anti-inflammatory, and antispasmodic properties. The basil extracts showed different phytochemical profiles, and the evaluation of these antioxidant effects by DPPH and ORAC assay showed that the ethanolic extracts had a higher activity compared to the aqueous extracts. The study of the anti-inflammatory effects of ethanolic extracts of basil stems and leaves in vitro in a macrophage J774 cell model stimulated by LPS/IFNγ showed that both extracts had an inhibitory effect on the production of inflammatory mediators (nitric oxide, interlukin-6, prostaglandin E2, Monocyte chemoattractant protein-1), but increased the production of the pro-inflammatory cytokine TNFα (Tumour necrosis factor-alpha). Subsequently, the aqueous extracts showed a relaxing effect on rat intestinal smooth muscle. The results of this study indicated that both parts of basil leaves and stems have interesting biological effects that can be valorized in terms of nutrition and health
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Saad, Houda. "Développement de bio-composites à base de fibres végétales et de colles écologiques." Thesis, Pau, 2013. http://www.theses.fr/2013PAUU3039/document.
Анотація:
L’intégration des fibres naturelles cellulosiques de plantes annuelles ou de résidus agricoles ou agro-industriels dans l’élaboration de matériaux de structures composites et le développement de nouveaux liants biosourcés sont aujourd’hui un domaine de recherche d’intérêt croissant. La thèse s'est déroulée dans le cadre du programme « Eco-panneaux », dont les deux objectifs principaux furent tout d'abord de valoriser les fibres végétales d’origine tunisienne comme l’alfa, le jonc et les folioles de palme et ensuite d'évaluer le potentiel d'espèces végétales tunisiennes dont les écorces sont riches en tannins (fruit de grenade, racines du sumac et tronc de pin d’Alep). Les études de caractérisation des fibres ont montré que leurs masses volumiques sont inférieures à 1. Le calcul du point de saturation des fibres (FSP) montre des valeurs majoritairement comprises entre 60 et 100 %. Nous avons également pu caractériser la cinétique d'imprégnation d'eau pour chacune des fibres. L’imprégnation se stabilise après 24 h d’immersion. Riches en minéraux (concentrations supérieures à 1 %), les fibres ont montré des teneurs en cellulose, en lignines et en hémicellulose comparables à celles généralement rencontrées avec les fibres de bois. L’analyse thermogravimétrique (ATG) a permis de constater que les matrices végétales étudiées sont thermiquement stables pour des températures inférieures à 200°C. Le dosage colorimétrique pour étudier la composition en polyphénols des matrices tannifères, l’analyse infrarouge et l’étude structurale de l’extrait des tanins, ainsi que le calcul du « Stiasny number » , montrent la forte teneur de l’écorce de grenade en tanins hydrolysables et la richesse des écorces du tronc de pin d’Alep et des racines du sumac en tanins condensés. L’étude des propriétés thermiques des extraits de tanins par ATG montre que les tanins de pin d’Alep et du sumac sont thermiquement plus stables que ceux de la grenade. La colle formulée à partir d’hexamine et de tanins de pin d’Alep présente un module d’élasticité élevé. Alors que la colle à base de tanins de grenade forme le réseau le moins dense. Ces résultats ont été confirmés par l’étude de la résistance au cisaillement. L'étude réalisée sur les composites fibres-plâtre (mise en œuvre et caractérisation physico mécanique des composites) a montré que les fibres locales pourraient constituer une alternative aux fibres d'importation utilisées actuellement. Une première caractérisation de la conductivité thermique des panneaux isolants élaborés à partir des fibres locales et de colles de tanins montre une conductivité thermique moyenne de 0,106w/K.mThe integration of natural cellulosic fibers from annual plants and agricultural residues and agro-industrial materials in the development of composite structures and the development of new bio-based adhesives, are now a research field with growing interest. The thesis was conducted within the framework of "Eco-panels" program, which its two main objectives were firstly, to enhance plant fibers of Tunisian origin as alfa, rush and palm leaflets and then to evaluate the potential of Tunisian plant species whose bark is rich in tannins (pomegranate fruit, sumac roots and Aleppo pine trunk). The characterization studies of fibers showed that their densities are less than 1. The calculation of the fiber saturation point (FSP) shows values mostly between 60 and 100 %. We were also able to characterize the impregnation kinetics of water for each of these fibers. The impregnation stabilizes after 24 h of immersion. Rich in minerals (concentrations greater than 1 %), the fibers showed levels of cellulose, lignin and hemicellulose comparable to those generally encountered with wood fibers. The thermogravimetric analysis (TGA) shows that the plant matrices are thermally stable for temperatures below 200 ° C. The colorimetric assay of the polyphenolic composition of tanniferous matrices, the infrared analysis and the structural study of the tannins extract, as well as the calculation of "Stiasny number" show the high content in hydrolysable tannins for pomegranate barks and richness of Aleppo pine trunk barks and sumac roots barks in condensed tannins. The study by TGA of the thermal properties of tannins extracts shows that Aleppo pine and sumac tannins are thermally more stable than those of pomegranate. The formulation made from hexamine and Aleppo pine tannins has the greatest elasticity modulus. While the formulation prepared from pomegranate tannins forms the least dense network. These results were confirmed by the study of the shear strength. The study conducted on fiber-plaster composites (implementation and physico-mechanical characterization of composites) showed that local fiber could be an alternative to imported fibers used currently. A first characterization of the thermal conductivity of insulation panels made from local plant fibers and tannins adhesives shows an average conductivity of 0,106 W / Km
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Neumann, John A. P. "Variability in the relationship between leaf area and selected stem measures in Douglas fir." Thesis, University of British Columbia, 1990. http://hdl.handle.net/2429/28819.
Анотація:
Variability in the relationship between tree leaf area (TLA) and selected stem measurements was examined in three Douglas-fir stands (Pseudotsuga menziesii (Mirb.) Franco, var. menziesii) that were less than 50 years-old, spaced to approximately 550 to 650 stems/ha, and differed in soil moisture and nutrients. Attention was given to the effect of mean annual ring width (MARW), cross-sectional area of the live bark (ALB - a surrogate measure of relative nutrient storage in the stem), and cross-sectional area of the most recent annual rings equal in number to the number of whorls in the live crown (ALC), on variability in the relationship between TLA and cross-sectional area of sapwood (ASW).
At breast height, basal area, ASW, and cross-sectional area of sapwood plus live bark (ASWLB) were not linearly related to TLA, and linear regression equations using log transformed variables varied significantly between sites. Nonlinear regression equation for ASW at breast height was: TLA = 0.064ASẆ¹•³³ (I² = 0.856). Including D (the distance between breast height and the center of the live crown) in the nonlinear equation, did not significantly improve the regression.
Tree leaf area prediction models using stem measures from the base of live crown (blc) had higher adjusted R² values than models using stem measures from breast height.
At the blc, basal area, ASW, and ASWLB were linearly related to TLA (adjusted R² = 0.926, 0.908, and 0.934, respectively).
Multiplying ASW by MARW did not improve the fit of the regression models. Multiplying ASW by ALB improved the linearity of the relationship of ASW at breast height to TLA. The best fitting TLA model overall used the product of ASW at blc and ALB at blc as the independent variable (adjusted R² = 0.967).
The results indicate that research into the allometric relationship of TLA to stem measures should give consideration to more than hydraulic measures and include measures of bark function. At breast height and the blc, the independent variable ALC was linearly related to tree leaf area and had higher adjusted R² values than did ASW. In most trees the ALC stem measure was found to include a portion of heartwood area. The strong relationship between TLA and ALC suggests that a given transpiring leaf mass or area is related to a proportional amount of conducting stemwood and physical support stemwood.
A quick alternative approach for estimating individual tree leaf area using photographs taken at fixed distance and angle from the target tree did not result in a reliable tree leaf area prediction technique. The difficulty of obtaining views of the tree crown which were not obstructed by adjacent tree crowns was the major obstacle. Using a fixed distance and camera angle was a problem because of variable
tree heights. However, altering these fixed positions introduced additional variation into the tree leaf area estimation.
Mean specific leaf area (SLA) varied significantly by site, needle age class, and crown position. Mean SLA per needle age class per branch can be predicted with 95% confidence and a 10% allowable error using six 10-needle samples.Forestry, Faculty of
Graduate
7
Lechthaler, Silvia. "The hydraulic architecture of the plants: study of the allometric relations in stem and leaves." Doctoral thesis, Università degli studi di Padova, 2019. http://hdl.handle.net/11577/3426838.
Анотація:
The xylem in plants is formed by interconnected dead cells that allow the flow of water from the roots to the leaves. The ascent of sap is mainly passive and it is driven by water evaporation from the mesophyll cell walls in the leaf. The water evaporation generates capillary suction on the menisci at the micro-porous of cell walls, causing negative hydrostatic pressure that propagates down the water column in the xylem. Due to plants grow in height the length of the hydraulic path increases progressively posing the question whether the hydraulic resistance increases accordingly. There is evidence that plants have evolved xylem structures that compensate the possible increase of the hydraulic resistance imposed by path length, namely the tip-to-base conduits widening. Conduits widening has been reported in several species, both angiosperms and conifers, showing that the degree of widening from tip to the base of the stem is very similar among species, or in other words, that plants converge towards a universal xylem structure. Nevertheless, several points on the hydraulic architecture of plants remain to be elucidated.
A largely debated point is whether xylem anatomical traits (e.g. the absolute cell size) change with climatic conditions. Moreover, whether and how the conduits widening in the stem may affect the xylem anatomy of the leaf is still not fully understood. This PhD project aims to widen our understanding of the allometric relations of leaves and stem xylem, considering how the environmental conditions and the height of the plant affect the hydraulic architecture of the water transport system.
A methodological study (Study 1) has been performed on the xylem tissue of stems of Acacia trees grown in different water availability conditions. The main result was that, once the anatomical data were standardized for the tree height, the hydraulic architecture of the xylem did not change in relation to the environmental conditions.
Two studies have been performed on the hydraulic architecture of leaves. The main focus was on the anatomical traits of the xylem conduits in relation to the leaf dimensions and/or the position in the tree crown (height from the base of the stem). The main results were that the xylem traits scaled with the leaf area independently by the position in the crown (Study 2). A fine analysis of the leaf midrib (i.e. major leaf vein) has shown a rigid hydraulic architecture and tissues coordination (Study 3) that was well predicted by the distance from the leaf tip. Both studies showed that the dimensions of the terminal veins were conserved among leaves and within leaf suggesting that the hydraulic architecture of the xylem in the leaf evolved in a way to guarantee an equal distribution of the hydraulic resistances (and thus of the water) among leaves and within the leaf lamina.
Finally, we implemented the anatomical data of both stem and leaf into a hydraulic model to assess the distribution of resistances along the hydraulic path to evaluate how the anatomy of the transport system affects the physiology of the entire tree (Study 4).
This thesis has highlighted that the path length (i.e. the height of the plant and the dimensions of the leaf) is the main factor affecting the hydraulic architecture of the tree. The conduit dimension in both stem and leaf are determined by the distance from the terminal parts, stem apex or leaf tip respectively. Climatic conditions resulted to have marginal (non-significant) effect on the stem anatomical traits. In the leaf, the dimensions of the xylem conduits are statistically invariant with changes in plant size. This rigid hydraulic architecture of the tree, from the stem to the leaf, allows minimizing the effect of the path length on the hydraulic resistance, confining nearly the whole gradient of water potential within the leaves.Lo xilema nelle piante è formato da cellule morte interconnesse che consentono il flusso di acqua dalle radici alle foglie. L'ascesa della linfa è principalmente passiva ed è guidata dall'evaporazione dell'acqua dalle pareti cellulari del mesofillo nella foglia. L'evaporazione dell'acqua genera un'aspirazione capillare sui menischi a livello dei micro-pori delle pareti cellulari, causando una pressione idrostatica negativa che si propaga lungo la colonna d'acqua nello xilema. A causa dell’aumento in altezza delle piante, la lunghezza del percorso idrico aumenta progressivamente ponendo la domanda se la resistenza idraulica aumenta di conseguenza. Vi è evidenza che le piante hanno evoluto strutture xilematiche che compensano il possibile aumento della resistenza idraulica imposta dall'aumento della lunghezza del percorso, come ad esempio l'allargamento dei condotti dalla punta alla base. L’allargamento dei condotti è stato osservato in diverse specie, sia angiosperme sia conifere, dimostrando che il grado di allargamento dalla punta alla base dello stelo è molto simile tra le specie, o in altre parole, che le piante convergono verso una struttura xilema universale. Tuttavia, restano da chiarire diversi punti sull'architettura idraulica delle piante. Un punto largamente dibattuto è se tratti anatomici dello xilema (ad esempio la dimensione assoluta delle cellule) cambiano con le condizioni climatiche. Inoltre, se e come i condotti che si allargano nello stelo possano influenzare l'anatomia dello xilema della foglia non è ancora completamente compreso. Il progetto di questo dottorato mira ad ampliare la nostra comprensione delle relazioni allometriche nello xilema delle foglie e del fusto, considerando come le condizioni ambientali e l'altezza della pianta possano influenzare l'architettura idraulica del sistema di trasporto dell'acqua. Uno studio metodologico (Studio 1) è stato eseguito sul tessuto xilematico di fusti di alberi di acacia cresciuti in diverse condizioni di disponibilità idrica. Il risultato principale è stato che, una volta che i dati anatomici sono stati standardizzati per l'altezza dell'albero, l'architettura idraulica dello xilema non è cambiata in relazione alle condizioni ambientali. Sono stati eseguiti due studi sull'architettura idraulica delle foglie. L'obiettivo principale degli studi riguardava i tratti anatomici dei condotti dello xilema in relazione alle dimensioni della foglia e / o alla posizione nella chioma dell'albero (altezza dalla base del fusto). Dai risultati si evince che i tratti dello xilema si ridimensionano in base all'area fogliare indipendentemente dalla posizione nella chioma (Studio 2). Un'analisi fine della nervatura principale della foglia ha mostrato una rigida architettura idraulica e la coordinazione dei tessuti (Studio 3), ben predetta dalla distanza dalla punta della foglia. Entrambi gli studi hanno dimostrato che le dimensioni delle vene terminali sono conservate tra le foglie e all'interno della stessa foglia, suggerendo che l'architettura idraulica dello xilema si è evoluta in modo da garantire distribuzione omogenea delle resistenze idrauliche (e quindi dell'acqua) tra le foglie e lungo la lamina fogliare. Infine, abbiamo implementato i dati anatomici di fusto e foglia in un modello idraulico per stimare la distribuzione delle resistenze lungo il percorso idraulico per valutare in che modo l'anatomia del sistema di trasporto influisca sulla fisiologia dell'intero albero (Studio 4). Questa tesi ha evidenziato che la lunghezza del percorso (vale a dire l'altezza della pianta e le dimensioni della foglia) è il fattore principale che influenza l'architettura idraulica dell'albero. La dimensione del condotto sia nel fusto che nella foglia è determinata dalla distanza dalle parti terminali, rispettivamente l'apice del fusto o la punta della foglia. Le condizioni climatiche risultano avere un effetto marginale (non significativo) sui tratti anatomici del fusto e nella foglia, le dimensioni dei condotti dello xilema sono statisticamente indipendenti rispetto alle variazioni nelle dimensioni della pianta. Questa rigida architettura idraulica dell'albero, dal fusto alla foglia, consente di minimizzare l'effetto della lunghezza del percorso sulla resistenza idraulica, confinando quasi l'intero gradiente del potenziale idrico all'interno delle foglie.
8
Onyekwelu, Cindy. "WHY DO UNDERREPRESENTED MINORITIES LEAVE SCIENCE AND ENGINEERING?" Scholarship @ Claremont, 2018. http://scholarship.claremont.edu/pitzer_theses/89.
Анотація:
This paper extends upon Jennifer Hunt’s research on “Why do women leave science and engineering?”, that contributes to existing literature that overlooks underrepresented minorities level of commitment to STEM fields based on their STEM educational backgrounds and additional contributing factors that relates to women engineer’s leaving their felid to another felid that does not have any relation to their STEM degree. The following independent factors are the respondents’ gender, reasons for leaving the felid of major, how much does their highest degree relate to their current principle/ primary job, parents’ level of education, current citizenship status, level of highest degrees obtained and salary survey data impact on exit rates of STEM identifying URMs. This is done by running multiple linear regression statistical analysis models by creating dummy variables for underrepresented ethnic/ racial minority grouped all together and isolated each URMs’ group dependent variable along with the contributing factors as my independent variables. In order, to figure out which factors are heavily correlated to the exit rates of URMs departing from STEM fields. In addition to learning more about the reasons behind the increasing exit rates of STEM identifying URMs, I will be discussing the shortcomings of using the 2015 National College Graduate Survey as my data and how the survey respondents’ level of exposure to STEM education from their primary school years suggests that the respondent is more likely to stay within a STEM felid that collates with their highest STEM degree than someone who has rarely been exposure to STEM education from youth.
9
Sublette, Heidi. "An effective model of developing teacher leaders in STEM education." Thesis, Pepperdine University, 2013. http://pqdtopen.proquest.com/#viewpdf?dispub=3600294.
Анотація:
In the last 5 years, industries have begun to recognize a growing gap in the production of college graduates in areas of STEM. Researchers in various industries believe this gap will create a significant loss of competitive edge in the STEM fields, which will leave the United States pursuing STEM graduates from foreign countries and may ultimately leave the US behind in the industry of science, technology and innovation. This qualitative study analyzes the value and impact of STEM teacher leaders in secondary education. A phenomenological study was conducted with 10 secondary school science and math teacher leaders in order to gain a better understanding of teacher leaders' perceptions, classroom practices and the role of a STEM teacher leader. This study addresses the following research questions: 1) What attributes define effective STEM teacher leaders, according to teacher leaders who have completed the Center for Math and Science Teaching system? 2) What success strategies, among teacher leaders of the Center for Math and Science Teaching program, have enabled further development of teacher leadership? 3) What is the best model in developing teacher leaders, according to literature from 2005 to present? 4) What is an optimal model of developing STEM (science, technology, engineering, and math) teacher leaders within secondary education? This research aims to explore teacher leaders' perceptions of their role as a teacher leader based on strategies learned from CMAST and past experiences. Findings from this study provide critical data for making informed decisions on including important elements when implementing an effective STEM teacher leader system or program, and the impact it can create on science and math teaching and learning in secondary education. The investigator concludes this study with the development of a STEM teacher leader model that merges these findings with existing research.
10
Filho, Sérgio Gil de Toledo. "Avaliação da dinâmica da população de microrganismos em plantas de cana-de-açúcar IAC (93-3046)." Universidade de São Paulo, 2010. http://www.teses.usp.br/teses/disponiveis/11/11139/tde-22102010-083440/.
Анотація:
O número das espécies microbianas presentes na forragem no ato da colheita é responsável pelo padrão de fermentação da silagem, sendo que o número de unidades formadoras de colônia (ufc) é alterado ao longo do ciclo da cultura e das condições ambientais, e esse fato, influencia fortemente a eficácia de aditivos utilizados no processo. Neste contexto, três experimentos foram conduzidos a fim de caracterizar a população microbiana em plantas de cana-de-açúcar. No primeiro experimento foi caracterizada a população microbiana em plantas de cana-de-açúcar por meio da técnica de plaqueamento. Os tratamentos impostos foram compostos por duas fontes de adubação (NPK e NPK associado a esteco bovino curtido 120kg de N/ha) da cana-de-açúcar colhidas manualmente com vista à quantificação do número de bactérias ácido láticas, leveduras e mofos, bem como relacionar suas freqüências de ocorrência com efeitos ambientais, fonte de fertilizante e estádio de maturação, com colheitas realizadas aos 10, 12, 14 e 18 meses, correspondendo aos meses de Março, Maio, Julho e Novembro de 2009, respectivamente. No segundo experimento foram avaliadas as variáveis biométricas, morfológicas, dinâmica de acúmulo de MS e dos nutrientes em cana-de-açúcar submetida às fontes de fertilização, descritas anteriormente. No terceiro experimento foi realizada avaliação química e bromatológica de cana-de-açúcar submetida à fontes de adubação. O experimento composto por blocos inteiramente casualizados sendo 6 blocos subdivididos em 2 parcelas. Os dados gerados foram analisados pelo procedimento Proc Mixed e Proc NLIN, do programa SAS. Não se observou efeito do tratamento sobre nunhuma variável avaliada. A produtividade média de massa verde variou entre 162 e 188 tMV/ha, podendo ser considerada elevada. O número de folhas verdes partiu de 9,5 aos 10 meses e atingiu cerca de 10 aos 18, o que é esperado, uma vez que ao passar do tempo há aumento da biomassa das plantas. O mesmo se observo para folhas secas, partindo de cerca de zero folhas por planta até cerca de 3 folhas. O peso das folhas também foi crescente. O peso e comprimento do colmo aumentaram de Março para Maio, mas apartir de Maio e Julho esse crescimento foi estagnado, não aumentando significativamente devido à seca. Porém, apartir de Julho esse crescimento voltou a ocorrer com o aumento das chuvas. A cana-de-açúcar apresentou 10 oBrix aos 10 meses, 17oBrix aos 12 meses e 20obrix aos 20 meses. O índice de maturidade aumentou, saindo de 33,46 aos 10 meses e atingindo 88,5 aos 18 meses. Aos 12 meses a cana-de-açúcar apresentou teor de matéria seca de 24%, e aos 18 meses 28%. Os teores de FDN e FDA da planta inteira dimunuiu ao longo do tempo, dos 10 meses (61% e 38,4% de FDN e FDA, respectivamente) para os 12 meses e permanecendo constante até os 18 meses (55% e 35,6% de FDN e FDA, respctivamente). Foi observado que existe correlação positiva entre DIVMS e do oBrix,e a equação, DIVMS = 41,35 + oBrix ; com R2=0,73 e P<0,01 se estabelecendo como ferramenta importante para se estimar a DIVMS. Ao longo do tempo, a contagem de bactérias ácido láticas e de leveduras foi crescente. De forma geral, todas as frações da planta apresentaram contagem numericamente semelhante, partindo de cerca de 4log ufc/gMV aos 10 meses e atingindo cerca de 5,5 log ufc/gMV aos 18 meses. Aos 10 meses a planta inteira de cana-de-açúcar apresentou contagem de leveduras de 4 log ufc/g MV permanecendo constante até os 18 meses, quando atingiu 5,7 log ufc/g MV. A fonte de adubação, quer seja química ou orgânica, não interfere na população de microrganismos, que entretanto, varia em função do período experimental e das condições climáticas.The numbe of microbial species in forages during the ensiling is responsible for the silage fermentation, and the numbeof colony forming units (cfu) changes during the crop cycle and environmental conditions. It suggests that the initial microbial profile strongly influences the effectiveness of additives used in the process. In this context, we propose three trials to characterize the microbial population in plants of sugarcane. The first trial evaluated the microbial population in plants of sugarcane by the technique of pour plating. The treatment consisted of two levels of fertilization (NPK and NPK associated with solid manure - 120kg N / ha) applied immediately after sugarcane was harvested by hand. The objective was quantify the number of lactic acid bacteria, yeasts and molds, as well as relating their frequencies with environmental effects, fertilization and stage of maturation, with samples taken at 10, 12, 14 and 18 months, corresponding to the months of March, May, July and November 2009. The second trial measured the biometric variables, morphological, the accumulation of dry matter and nutrients in sugarcane subjected the sources of fertilization, as mensioned. The third trial performed chemical assessments of sugarcane subjected to the sources of fertilization. The trials consisted of a completely randomized design with six blocks sub-divided into two plots. Data were analyzed by the procedure Proc Mixed and Proc NLIN of SAS program. There was no effect of treatment in any trial. The fresh yield ranged from 162 to 188tGM/ha which can be considered high. The number of green leaves was increased from 9.5 to 10 to 10 to 18, which is expected, since there is an increase of plant biomass across the time. The same was observed for dead leaves, from about 0 leaves per plant up to 3 leaves. The weight of the leaves was also increased. The weight and length of the stem increased from March to May, and became more intensive from July with increasing rainfall. However, during the dry season (May - July) there was a decreased growing rate.The sugarcane oBrix was 10 at 10 months, 17 oBrix at 12 months and 20oBrix to 20 months. The maturity index increased, from 33.46 to 10 months reaching 88.5 at 18 months. At 12 months the sugarcane showed dry matter content of 24% and 28% at 18 month. The NDF and ADF of the whole plant decreased over time from 10 months (61% and 38.4% NDF and ADF, respectively) for 12 months and remained constant until 18 months (55% and 35 6% NDF and ADF, respectively). A is positive correlation between IVDMD and oBrix was observed, and the equation, IVDMD = 41.35 + oBrix, with R2 = 0.73 and P <0.01 is an important tool to estimate IVDMD. Over time, the counts of lactic acid bacteria were increased. In general, all plant fractions showed similar counts, starting from 4 log cfu/gGM to 10 months and reaching about 5.5 log cfu/gGM to 18 months. At 10 months the whole plant sugarcane had yeast count of 4 log cfu/gGM remaining constant until 18 months, when it reached 5.7 log cfu / g MV. The source of fertilizer, whether chemical or organic, does not interfere in the population of microorganisms, however, varies depending on the experimental period and climatic conditions.
11
Бодня, Оксана Юріївна. "Мутаційна мінливість індукована хімічними мутагенами в М2 у редьки сорту Факел". Магістерська робота, ЗНУ, 2020. https://dspace.znu.edu.ua/jspui/handle/12345/1399.
Анотація:
Бодня О. Ю. Мутаційна мінливість індукована хімічними мутагенами в М2 у редьки сорту Факел : кваліфікаційна робота магістра спеціальності 091 "Біологія" освітньої програми "Біологія" / наук. керівник А. І. Сорока. Запоріжжя : ЗНУ, 2020. 75 с.UA : Дипломна робота виконана на 75 сторінки друкованого тексту, містить 2 таблиці та 9 рисунків. Під час написання роботи було використано 50 літературних джерел, одне з них іноземною мовою. Об'єктом дослідження був сорт редьки олійної Факел, оброблений хімічним мутагеном та його вихідна форма. Актуальність проблеми – шляхом індукованого мутагенезу був отриманий цінний генетичний матеріал у багатьох сільськогосподарських культур. Окрім інших були отримані мутації, що проявляються на ранніх стадіях росту та розвитку, у тому числі з різним проявом на сім'ядольних листках. Ці мутації можуть бути використані як маркерні ознаки в селекції культури. Так як тема стосовно редьки олійної мало досліджена, то дослідження у вказаному напрямку являються необхідними і актуальними. Мета даної роботи полягала у спостереженні та виділенні нових груп мутацій під впливом етилметансульфонату під час проходження основних фаз вегетації культури та встановлення частоти виділених мутацій. В результаті дослідів у другому мутантному поколінні були отримані такі мутації: мутації з порушенням синтезу хлорофілу, мутації сім’ядольних та справжніх листків, мутації структури стебла та гілок, мутації квітки, мутації фізіологічних ознак. У 10 сімей контролю мутаційні зміни не виявлені. Загальна частота виділених мутацій склала 28,2 %. Слід зазначити, що ця частота мутацій є попередньою, оскільки остаточну частоту мутацій у другому мутантному поколінні можна встановити лише після перевірки успадкування виділених мутацій у наступному поколінні. Отже, використання хімічного мутагену етилметансульфонату у концентрації 0,01% було ефективним для одержання мутацій різного типу, у тому числі тих, що виявляються на ранніх стадіях росту та розвитку редьки олійної. У сучасному рослинництві редька олійна є відносно новою культурою, але вже активно починає використовуватись в сільському господарстві. Найбільше поширення культура отримала як сидерат. Але також знайшла своє місце застосування в харчовій промисловості, косметології, фармакології, кулінарії, виробництві біопалива. Тому будь-які досліди, пов’язані з отриманням цінного генетичного матеріалу, являються дуже необхідними. Саме в цьому і є значущість і новизна даної роботи.
EN : The Degree work is completed on 75 pages of printed text, contains 2 tables and 9 figures. During the writing were used 50 literary sources, one of them in a foreign language. The object of the research was a sort of oilseed radish Torch treated with a chemical mutagen and its original form. The topicality of the problem - by induced mutagenesis has been obtained valuable genetic material in many agricultural crops. Among others were obtained mutations that appear themselves in the early stages of growth and development, including various manifestations on cotyledons leaves. These mutations can be used as marker features in culture selection. As the topic of oilseed radish is poorly explored, research in this direction is necessary and relevant. The purpose of this work was to observe and selection new groups of mutations under the influence of ethyl methanesulfonate during the main phases of vegetation. In the second mutant generation as a result of experiments were received the following mutations: mutations with impaired chlorophyll synthesis, mutations of cotyledons leaves and true leaves, mutations of the structure of the stem and branches, mutations of the flower, mutations of physiological features. In 10 control families mutational changes were not detected. The overall frequency of isolated mutations was 28.2%. It should be noted that this mutation frequency is preliminary, because the final mutation frequency in the second generation can be established only after checking the inheritance of isolated mutations in the next generation. Therefore, the use of a chemical mutagen of ethyl methanesulfonate at a concentration of 0.01% was effective for obtaining mutations of various types, including those found in the early stages of growth and development of oil radish. In modern plant growing, oilseed radish is a relatively new crop, but it is already actively used in agriculture. Culture was most widely used as a siderate. But it has also found its application in food, cosmetology, pharmacology, cooking and production of biofuel. Therefore, any experiments related to obtaining valuable genetic material are very necessary. That is the significance and novelty of this work.
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Hutchinson, Anna E. "Perceptions of Teacher Leadership: The Influence of Organizational Structure on the Professional Identity of Urban STEM Teacher Leaders." University of Cincinnati / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1581333163812174.
13
Brown, Arogeanae Ronterria Dinita. "Reframing AgriCULTURAL Experiences, Narratives, and Careers for African American Youth: A Study of Community-based Programs Leaders' Motivations and Educational Space." Thesis, Virginia Tech, 2018. http://hdl.handle.net/10919/84495.
Анотація:
To uncover experiences specific to African Americans youth in agricultural and STEM (science, technology, engineering, mathematics) career explorations and to understand why African Americans are missing from agriculture and STEM, a systematic literature review and empirical study were conducted. Literature covering the current and past African American perceptions of agriculture and STEM discipline, and narratives and experiences of African Americans in agriculture, were reviewed to explain their influences on African American youth perceptions and interest to pursue careers in agriculture and STEM. However, literature also explained the role of agricultural programs in STEM and agricultural literacy. In one paper, Social Cognitive Career Theory was used to frame the career interest development process of the individual learner to reference African American Youth. This review captured African American's negative connotations of agricultural and STEM despite the knowledge and work African Americans have contributed to Agriculture and STEM since the formation of America. In addition, to address how to deter the negative connotations youth have, an empirical study was performed interviewing eight program leaders of community-based organizations that are engaging African American youth in agricultural and STEM education. Program leaders described their motivations and purpose as an act of service to the youth and the community as a way to provide youth with opportunities or capital as described by Bourdieu.Master of Science in Life Sciences
14
Bowers, Sharon W. "Supporting Elementary Education In-Service Teachers' Proficiency in Planning STEM-Centric Lessons." Diss., Virginia Tech, 2015. http://hdl.handle.net/10919/64380.
Анотація:
The purpose of this study was to explore the McDaniel College Elementary STEM Instructional Leader (ESIL) pilot cohort's ability to proficiently plan lessons that incorporated the Maryland State STEM Standards of Practice (SOP), targeting integration of STEM content, inquiry learning, students' abilities to collaborate as a STEM team and students' strategic application of technology. Data collection, in the form of reviewing and analyzing study participants' lesson plans and self-reflections, was completed by three independent assessors. The researcher examined the interrater reliability among the three assessors using the Fleiss' kappa statistic. A 0.91 proportion of agreement consensus was documented among the three assessors. A test of hypothetical value was conducted using the nonparametric Wilcoxon-signed-rank Test. Interpretation of the Wilcoxon-signed-rank Test results suggest that the sample population demonstrated proficient planning abilities for the four targeted Maryland State STEM SOP.
Findings from this research add to the field's knowledge of elements in the promotion of graduate coursework that leads to elementary in-service teachers' proficiency in planning STEM-centric lessons, however the findings also have broader implications for teacher education at large. The McDaniel College ESIL model could frame K-12 teacher education for both pre-service and in-service teachers. The pragmatic, hybrid experience maximizes flexibility, promotes analytical thinking and self-reflection and builds communication skills. The introduction and development of inquiry and design-based learning through the 7E Learning Cycle develops the teachers' understanding of practices promoted not only within the Maryland State STEM SOP, but also within the Next Generation Science Standards. The McDaniel College ESIL model also builds upon the collective efforts of academia, a non-profit STEM research facility, and local school divisions to align efforts that may lead to transformational changes for education. Essential ingredients for systemic change are embedded within the McDaniel ESIL model.Ed. D.
15
Sapian, A. S. "How to create a brand for 3 steps? Building successful sales funnels in business." Thesis, Київський національний університет технологій та дизайну, 2019. https://er.knutd.edu.ua/handle/123456789/14356.
16
Ziller, Michael [Verfasser]. "Overexpression of HoxA9 in CD150- hematopoietic stem cells leads to rapid progression of acute myeloid leukemia / Michael Ziller." Berlin : Medizinische Fakultät Charité - Universitätsmedizin Berlin, 2021. http://d-nb.info/1228859671/34.
17
Garrett, Dawn. "A quantitative study of STEM goal and role alignment across stakeholder leaders in California| Advocacy for application of a systems solution approach." Thesis, Pepperdine University, 2013. http://pqdtopen.proquest.com/#viewpdf?dispub=3587844.
Анотація:
Both the nation and California are faced with a critical threat to our long term strength and welfare due to an acknowledged deficit in STEM ready students and workers as we head into the 21st century. The STEM workforce gap requires integrated conversations and solutions as it impacts multiple stakeholder groups who do not necessarily fully comprehend each other's needs and challenges. There is a broad consensus that increasing the STEM workforce is critical to the U.S., impacting standard of living, as well as national security in areas such as international competitiveness, combating terrorism and addressing global warming, to name just a few. Historically, the world has looked to the U.S. as the globe's preeminent source of innovation. However, critical indicators have caused industry, educators, policy makers, and communities to take a deeper look at some alarming trends. For example, a U.S. Department of Commerce study noted that the U.S. has made no progress in its competiveness since 1999, and is beginning to lose ground to other countries that are actively building their scientific and technological infrastructures.
This study utilized the literature review to explore the power of applying system's thinking to this complex social problem. In addition, the study quantitatively demonstrated the current state of alignment in California across two key stakeholder group's leaders, industry and education by exploring the following areas: 1. Are the perceptions of two respondent stakeholder leader groups aligned relative to nine identified California STEM goals? 2. Are the perceptions of the assignment of roles across the California STEM stakeholders related to the two respondent group leaders' affiliation? 3. What is the current state of collaboration in California based on the perceptions of the two respondent groups' leaders?
The quantitative research demonstrated alignment of the key stakeholder leaders around what is important relative to the goals of California's STEM workforce gap as well as alignment around which stakeholder leaders should be executing specific tasks. The research also underscored an aligned understanding of the current lack of collaboration that exists across stakeholder leaders in California.
18
FURIA, SIMONE. "VALUE NOT DUMP." Doctoral thesis, Università degli Studi di Milano, 2013. http://hdl.handle.net/2434/217616.
Анотація:
ABSTRACT
Introduzione. Riparare il tessuto danneggiato per evitare complicanze postoperatorie e risparmiare il tessuto sano per garantire una buona funzionalità respiratoria sono due degli obiettivi del chirurgo toracico. Negli anni sono stati introdotti nella pratica clinica numerosi prodotti sintetici che riescono a simulare le caratteristiche meccaniche e fisiologiche del tessuto danneggiato, ma a fronte degli elevati costi, non sempre garantiscono risultati stabili. Il trapianto autologo di cellule staminali adipose (ASC) viene proposto come nuova strategia per promuovere la riparazione dei tessuti dopo l'intervento chirurgico.
Progetto di Ricerca. Il lipocentrifugato con le ASC è stato sottoposto ad una valutazione preclinica mediante saggi in vitro e in vivo per testare il potenziale riparativo sul tessuto polmonare e per chiarire il supposto effetto tumorigenico su eventuali residui neoplastici. Lo studio clinico è stato eseguito su 20 interventi di metastasectomia polmonare eseguita mediante laser di ultima generazione (2010nm wavelength). I principali end-point dello studio erano: 1) la fattibilità dell’applicazione di cellule staminali nella metastasectomia polmonare mediante laser Thulium (2010nm), 2) incidenza delle perdite aeree postoperatorie prolungate (>7 giorni) 3) fattibilità del prelievo di cellule staminali a livello della toracotomia sulla base del conteggio delle cellule staminali 4) impatto di questo tipo di procedura sulla funzionalità polmonare.
Risultati Clinici. Non abbiamo avuto alcun decesso perioperatorio. Dopo rimozione di lesioni centroparenchimali, 4 pazienti hanno sviluppato perdite aeree prolungate. In un paziente il drenaggio pleurico è stato rimosso in POD 13 e 3 pazienti sono stati dimessi con il tubo toracico collegato alla valvola di Heimlich. Non sono stati necessari re interventi per revisione dell’aerostasi. Un paziente ha sviluppato un ematoma nel sito di prelievo del tessuto adiposo. 4 casi di febbre sono stati risolti con terapia antibiotica. Le cellule staminali mesenchimali sono state rilevate in concentrazione> 1% in 13 casi. Età, sesso chemioterapia preoperatoria e indice di massa corporea non hanno influenzato il numero di cellule staminali. Nessuna significativa riduzione in termini di funzione polmonare è stata rilevata dopo l'intervento chirurgico. In nessun caso sono stati utilizzati materiali sintetici.
Conclusioni. Il nostro studio mostra che il tessuto grasso raccolto a livello dello strato sottocutaneo della toracotomia è una fonte di cellule staminali. I vantaggi portati da questa tecnica combinata possono essere misurati in termini di funzione respiratoria. Con un follow-up di 16 mesi non è stata osservata alcuna recidiva a livello del sito di applicazione del centrifugato adiposo.ABSTRACT Introduction. Repair damaged tissue to prevent postoperative complications and save healthy tissue to ensure good respiratory function are two of the objectives of the thoracic surgeon. Over the years have been introduced in clinical practice numerous synthetic products that are able to simulate the mechanical and physiological characteristics of the damaged tissue, but in the face of high costs, do not always guarantee stable results. The autologous adipose stem cells (ASC) is proposed as a new strategy to promote the repair of tissues after surgery. Research Project. The lipocentrifugated with the ASC has been subjected to a pre-clinical evaluation using in vitro and in vivo assays to test the reparative potential on lung tissue and to clarify the supposed tumorigenic effect of any residual neoplastic. The clinical study was performed on 20 pulmonary metastasectomies performed using last generation laser (wavelength 2010nm). The main endpoints of the study were: 1) the feasibility of pulmonary metastasectomy with Thulium laser (2010nm), 2) incidence of postoperative prolonged air leak (> 7 days) 3) feasibility of the harvesting of stem cells at the level of thoracotomy on the basis the cell count stem 4) impact of this type of procedure on respiratory function. Clinical Results. We had no perioperative death. After removal of lesions located deep in the parenchyma, 4 patients developed prolonged air leaks. In one patient the pleural drain was removed in POD 13 and 3 patients were discharged with a chest tube connected to the valve Heimlich. Redo surgery to improve the aerostasis was not required. One patient developed a hematoma at the site of collection of adipose tissue and 4 cases of fever have been resolved with antibiotic therapy. The mesenchymal stem cells were detected in concentrations> 1% in 13 cases. Age, sex, preoperative chemotherapy and body mass index did not affect the number of stem cells. No significant reduction in terms of lung function was measured after surgery. No synthetic materials were used. Conclusions. Our study shows that the fat tissue collected at the level of the subcutaneous layer of the thoracotomy is a useful source of stem cells. The advantages brought by this technique can be measured in terms of respiratory function. With a median follow-up of 16 months no recurrence was observed at the site of application of centrifuged fat graft.
19
Bray, Ross. "Evaluating the impacts of a STEM research placement program between a secondary school and a science research institute." Thesis, Queensland University of Technology, 2021. https://eprints.qut.edu.au/212449/1/Ross_Bray_Thesis.pdf.
Анотація:
Although there are currently various programs aimed at increasing the interest of high school students in science, technology, engineering and mathematics (STEM), very few programs have explored the students’ perceptions of the effectiveness of extracurricular STEM programs to their school learning and post-school aspirations. This research aimed to investigate high school students’ perceptions of a STEM research placement program integrated into their school curriculum, and how it contributed to their self-efficacy, attitude towards science and motivation to pursue a career in that field. A standard operating procedure (SOP) was then developed to inform future STEM-centred high school programs.
20
Lima, Débora Cristina da Silva. "Avaliação das atividades genotóxica e antigenotóxica do extrato etanólico de Lafoensia pacari A. St-Hil em bactérias e camundongos." Universidade Federal de Goiás, 2012. http://repositorio.bc.ufg.br/tede/handle/tede/7410.
Анотація:
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Conselho Nacional de Pesquisa e Desenvolvimento Científico e Tecnológico - CNPq
Lafoensia pacari A. St. Hil. (Lythraceae), popularly known in Brazil as “pacari”, is a species native of Cerrado. In folk medicine, the leaves and stem bark are used to treat cancer and as an anti-inflammatory and cicatrizant agent. Due to the wide use of this plant as a therapeutic resource, the present study evaluated the genotoxic, cytotoxic, antigenotoxic, and anticytotoxic activities of the ethanolic extract from L. pacari stem bark and leaves using the Ames test and the mouse bone marrow micronucleus test. Our results demonstrated that the ethanolic extract from L. pacari leaves, presented no mutagenic activity in bacteria, but presented a mild genotoxicity in the highest concentration at 24 h in mice bone marrow cells. Exhibited moderate cytotoxic effect on bacteria and a mild cytotoxic action in the highest concentration by micronucleus test. The extract showed antimutagenic activity by Ames test and in the micronucleus test demonstrated antigenotoxic action in all concentrations at 24 h, and in the lowest concentration at 48 h. Showed anticytotoxic effect in all concentrations and times tested. In the evaluation of the genotoxic, cytotoxic, antigenotoxic and anticytotoxic activities of the ethanolic extract from L. pacari stem bark, the results demonstrated that the extract exhibited no mutagenic activity in bacteria, however showed a mild genotoxicity in the highest concentration in mice. Exhibited moderate cytotoxic effect in bacteria and a mild cytotoxicity at 24 h by micronucleus test. Showed strong antimutagenic activity by Ames test, as well as antigenotoxic and anticytotoxic activities in the mouse bone marrow micronucleus test, demonstrating to be a strong protective agent against DNA damage.
Lafoensia pacari A. St-Hil, (Lythraceae) popularmente conhecida no Brasil como pacarí, é uma espécie nativa do Cerrado. Na medicina popular, suas folhas e casca do caule são utilizadas para tratar câncer, como um agente cicatrizante e antiinflamatório. Devido à grande utilização dessa planta como recurso terapêutico, o presente trabalho avaliou as atividades genotóxica, citotóxica, antigenotóxica e anticitotóxica do extrato etanólico das folhas e da casca do caule de L. pacari, utilizando o teste de mutagenicidade de Ames e o teste do micronúcleo em medula óssea de camundongos. Nossos resultados demonstraram que o extrato etanólico das folhas de L. pacarí, não apresentou atividade mutagênica em bactérias, mas apresentou uma leve genotoxicidade na concentração mais elevada em células de medula óssea de camundongos no tempo de 24 h. Exibiu efeito citotóxico moderado em bactérias e uma leve ação citotóxica, na concentração mais elevada no teste de micronúcleo. O extrato apresentou atividade antimutagênica pelo teste de Ames e no teste do micronúcleo demonstrou ação antigenotóxica em todas as concentrações no tempo de 24 h e na concentração mais baixa no tempo de 48 h. Apresentou efeito anticitotóxico em todas as concentrações e tempos testados. Na avaliação das atividades genotóxica, citotóxica, antigenotóxica e anticitotóxica do extrato etanólico da casca do caule de L. pacarí os resultados provaram que este extrato não exibiu atividade mutagênica em bactérias, no entanto apresentou uma genotoxicidade fraca na maior concentração em camundongos. Exibiu um efeito citotóxico moderado em bactérias e uma leve citotoxicidade, somente no tempo de 24 h pelo teste de micronúcleo. Apresentou forte atividade antimutagênica pelo teste Ames, bem como atividade antigenotóxica e anticitotoxica no teste de micronúcleo em medula óssea de camundongos, demonstrando ser um forte agente protetor contra danos no DNA.
21
Makwinya, Noel Mark. "Managing science teachers’ adoption of the 2005 Tanzanian Inquiry and Student-Centred Curriculum: Revealing schoolbased leaders’ practices and achievements." Thesis, Edith Cowan University, Research Online, Perth, Western Australia, 2020. https://ro.ecu.edu.au/theses/2289.
Анотація:
Many countries have made considerable changes to their education systems in response to the forces of globalisation. Tanzania is no exception. The most recent educational change attempt in Tanzania relates to the introduction of the 2005 Tanzanian Inquiry and Student- Centred Curriculum.
Sound change-leadership is a necessary condition for the realisation of change, particularly in influencing its adoption. Within the descriptive qualitative research paradigm, this study employed a Type IV (embedded and multiple) case-study design to examine and describe science teachers’ lived experiences in dealing with this latest Tanzanian curriculum and the role played by school-based leaders in influencing such experiences. The study was carried out in three case-study schools. Data regarding change leadership were collected from both teachers and school leaders by means of personal interviews, observations, and document reviews. Data regarding science teachers’ levels of adoption of this curriculum and related concerns, all of which helped to gauge the effectiveness of change-adoption leadership provided by School-Based Leaders, were collected using semi-structured interviews and a Stage of Concern Questionnaire and were triangulated through document reviews and inclass observations.
The findings show that school-based leaders in all case-study schools guided adoption of change primarily using authoritarian strategies. Nevertheless, there was some evidence to suggest that school-based leaders in the high performing and the medium performing casestudy schools tended to employ additional strategies that inclined towards collective and empowering leadership approaches. This difference appeared to covary with the science teachers’ levels of use of this curriculum and their concerns about it in the three case-study schools. Adoption challenges and those affecting leadership of change are also detailed.
These findings extend the ongoing academic discussion about the leadership of adoption of educational changes in schools. The understanding of pedagogical change gained through this study has implications for both policy and practice, and these are discussed in the last chapter. Leaders of these and other schools in equivalent contexts may use findings of this study to reflect upon their change-leadership practices in schools and improve the way they enhance pedagogical transformations and the professional development of their teachers.
22
Rakotonandrasana, Jean. "Modélisation de la décharge négative dans les longs intervalles d'air - Application à la foudre." Phd thesis, Ecole Centrale de Lyon, 2008. http://tel.archives-ouvertes.fr/tel-00372671.
Анотація:
Ce travail porte sur la modélisation de la décharge négative dans les grands intervalles d'air soumis à des ondes de tension de type bi-exponentielles (foudre ou manœuvre) ou constantes. Ainsi, un modèle dynamique et autonome permettant de prédire l'ensemble des paramètres macroscopiques de la décharge négative et tenant compte des différentes phases de propagation (initiation de la première couronne, système pilote, formation des leaders d'électrode et spatiaux, jonctions et ré-illuminations, saut final) jusqu'à l'arc en retour, est présenté. Ce modèle est basé sur des schémas électriques équivalents dont les paramètres varient avec le temps en fonction des caractéristiques du canal et de la géométrie de la décharge, les lois de l'électromagnétisme et la théorie des gaz. Les propagations des leaders et des streamers sont basées sur des critères de champs électriques tenant compte de l'aspect aléatoire du trajet de la décharge.Le modèle permet de déterminer les caractéristiques spatio-temporelles de la décharge telles que le courant du leader (canal principal), la charge correspondante, des trajectoires plausibles, sa vitesse instantanée, le gradient de potentiel et le rayon thermique du leader négatif d'électrode, la puissance et l'énergie injectées dans l'intervalle, l'instant et la tension d'amorçage ainsi que l'évolution de l'arc en retour. Il permet également, pour une configuration d'électrodes donnée, de déterminer la tension de claquage U50, constituant ainsi un outil appréciable pour le dimensionnement des structures isolantes. Les résultats issus de ce modèle sont en bon accord avec ceux obtenus expérimentalement.
Un modèle de foudre négatif a été également établi en se basant sur la grande similarité observée entre les grandes étincelles de laboratoire et les décharges atmosphériques. Les caractéristiques obtenues à partir de ce modèle ont été trouvées conformes aux mesures effectuées lors des décharges naturelles. L'environnement électromagnétique associé au précurseur de foudre a été ensuite caractérisé et les champs électriques et magnétiques obtenues sont aussi en bon accord avec celles relevées expérimentalement.
23
Génevé, Thomas. "Méthodes de diagnostic des piles à combustible." Phd thesis, Toulouse, INPT, 2016. http://oatao.univ-toulouse.fr/15589/1/TGENEVE.pdf.
Анотація:
La problématique développée dans cette thèse est le diagnostic des piles à combustible (PAC) de type « Proton Exchange Membrane » (PEM). Nous avons choisi d’axer ces travaux sur différentes méthodes de diagnostic, séparées en deux grandes thématiques, relativement différentes et donc indépendantes, qui forment les deux parties de cette thèse. Dans la première partie, intitulée « Méthodes de diagnostic des fuites internes », nous nous focaliserons sur un type de dégradation des PAC, celle de la membrane, et de sa conséquence principale, l’augmentation des fuites internes. Après avoir fait l’inventaire des différentes techniques de diagnostic possibles, nous avons eu l’opportunité d’en tester certaines sur un stack (empilement de cellules élémentaires) dégradé dont nous disposions. La voltammétrie cyclique semble la plus intéressante en terme de précision. Cependant, pour le diagnostic complet d’un stack, le niveau de fuite de chaque cellule doit être évalué. Il apparaît que cette opération est extrêmement chronophage ; nous avons donc dû mettre au point des méthodes alternatives à celles rencontrées fréquemment dans la littérature. Nous avons d’une part appliqué la voltammétrie cyclique directement aux bornes du stack et parallèlement nous avons mis au point une technique nouvelle de diagnostic des fuites internes d’une PAC. Ces méthodes seront testées sur trois stacks comportant chacun un nombre différent de cellules. La deuxième partie de ce manuscrit est intitulée « Méthodes de diagnostic en gaz actifs ». Nous aborderons dans un premier temps une méthode bien connue, la Spectroscopie d’Impédance Electrochimique (SIE). L’utilisation de cette technique soulève deux problématiques : le choix d’un modèle approprié pour décrire des phénomènes physico-chimiques variés puis la difficulté de converger vers un jeu unique de paramètres une fois le modèle établi. Partant de ce constat, nous avons développé une technique originale d’exploitation des SIE, basée sur un modèle électrique sans a priori, dont la construction va se faire automatiquement étape par étape. Cet algorithme sera validé de manière théorique sur des simulations, puis nous confirmerons son potentiel sur des données expérimentales issues d’essais de vieillissement de monocellules. Parallèlement, nous avons développé une technique alternative à la spectroscopie d’impédance, basée sur l’exploitation d’échelons de courant. Cette méthode permet d’extraire un spectre de constantes de temps sans passer par de l’identification paramétrique. Après une première validation théorique grâce à des simulations, nous avons éprouvé cette technique avec d’une part les données de vieillissement mentionnées précédemment ainsi qu’avec des données issues d’un essai d’engorgement d’une monocellule. Nous confirmerons que cette technique est bien adaptée pour effectuer du diagnostic en cours de fonctionnement.
24
Cavallin, Mara. "Physiopathologie moléculaire et cellulaire des anomalies du développement du cortex cérébral : le syndrome d'Aicardi WDR81 mutations cause extreme microcephaly and impair mitotic progression in human fibroblasts and Drosophila neural stem cells TLE1, a key player in neurogenesis, a new candidate gene for autosomal recessive postnatal microcephaly Mutations in TBR1 gene leads to cortical malformations and intellectual disability Aicardi syndrome: Exome, genome and RNA-sequencing of a large cohort of 19 patients failed to detect the genetic cause Recurrent RTTN mutation leading to severe microcephaly, polymicrogyria and growth restriction Recurrent KIF2A mutations are responsible for classic lissencephaly Recurrent KIF5C mutation leading to frontal pachygyria without microcephaly Rare ACTG1 variants in fetal microlissencephaly De novo TUBB2B mutation causes fetal akinesia deformation sequence with microlissencephaly: An unusual presentation of tubulinopathy A novel recurrent LIS1 splice site mutation in classic lissencephaly Further refinement of COL4A1 and COL4A2 related cortical malformations Prenatal and postnatal presentations of corpus callosum agenesis with polymicrogyria caused By EGP5 mutation Delineating FOXG1 syndrome from congenital microcephaly to hyperkinetic encephalopathy Delineating FOXG1 syndrome: From congenital microcephaly to hyperkinetic encephalopathy." Thesis, Sorbonne Paris Cité, 2019. https://wo.app.u-paris.fr/cgi-bin/WebObjects/TheseWeb.woa/wa/show?t=2213&f=18201.
Анотація:
Les malformations du cortex cérébral (MDC) représentent une cause importante de handicap et d'épilepsie pharmaco-résistante. Le séquençage à haut débit a permis une amélioration considérable de l'identification des bases moléculaires des MDC non syndromiques. Toutefois, certaines formes, notamment les MDC complexes, demeurent inexpliquées. Mon projet de thèse a pour objectif de progresser dans la compréhension des MDC complexes en utilisant deux modèles : les microlissencéphalies (MLIS) et le syndrome d'Aicardi (AIC), une forme syndromique particulière associant des malformations de l'oeil et du cerveau uniquement rapporté chez les filles. L'étude par séquençage d'exome en trios de 16 familles MLIS m'a permis d'identifier et de caractériser un nouveau gène, WDR81, impliqué dans le cycle cellulaire. Par la même stratégie, j'ai pu identifier un variant homozygote pathogène dans TLE1, un partenaire majeur de FOXG1 dans la balance prolifération/différenciation de progéniteurs neuronaux, dans une famille consanguine de microcéphalie postnatale dont le phénotype est proche du syndrome FOXG1. En parallèle, mes travaux ont permis de préciser les spectres phénotypiques associés à RTTN, EPG5, COL4A1, COL4A2, TBR1, KIF5C, KIF2A et FOXG1. La deuxième partie de mon projet avait pour objet l'identification des bases moléculaires du syndrome d'Aicardi à partir d'une cohorte internationale de 19 patientes. Après avoir exclu un biais d'inactivation du chromosome X et la présence de microremaniements chromosomiques, j'ai réalisé un séquençage d'exome en trio. Aucun variant récurrent n'a été retrouvé dans les séquences codantes. Dans un second temps, j'ai testé une approche combinant les données du séquençage de génome et l'analyse du transcriptome (RNA-Seq) sur fibroblastes, me permettant d'identifier des transcrits dérégulés qui étaient impliqués dans le développement du cerveau et de l'oeil. J'ai comparé les résultats de cette analyse avec ceux de l'analyse du génome dans le but d'identifier des variants dans ces gènes candidats. En conclusion, mon travail de thèse a permis d'améliorer la connaissance des bases moléculaires des MDC complexes et d'ouvrir des perspectives de nouveaux mécanismes tels que ceux engageant les gènes WDR81 et EPG5, et le rôle des endosomes et de l'autophagie dans les MDC, et aussi TLE1 comme nouvelle cause de microcéphalies postnatales. Mes travaux ont également permis de générer une collection de données de séquençage haut débit (WES, WGS et RNA-Seq) qui seront mises en commun dans le cadre d'un consortium international afin de développer des nouvelles stratégies d'analyse en particulier pour les séquences non codantes. Cette approche permettra également d'ouvrir la voie vers la compréhension des mécanismes cellulaires impliqués dans la formation du cerveau et de l' œilMalformations of cortical development (MCD) are a major cause of intellectual disability and drug-resistant epilepsy. Next Generation Sequencing (NGS) has considerably improved the identification of the molecular basis of non-syndromic MCD. However, certain forms, including complex MCD, remain unexplained. My PhD project aimed to improve the understanding of complex MCD using two disorders: Microlissencephaly (MLIS) and Aicardi Syndrome (AIC), the latter associating brain and eye malformations and only reported in girls. Trio Whole Exome Sequencing (WES) performed in 16 MLIS families allowed me to identify and functionally characterize a new MLIS gene, WDR81, in which mutations lead to cell cycle alteration. Moreover, using the same strategy, I was able to identify a pathogenic homozygous variant in TLE1 in a patient from consanguineous family with a postnatal microcephaly, suggestive of a FOXG1-like presentation. Interestingly, TLE1 is a major partner of FOXG1, a gene involved in maintaining the balance between progenitor proliferation and differentiation. In parallel, my work allowed me to redefine the phenotypic spectrum associated with RTTN, EPG5, COL4A1 and COL4A2, TBR1, KIF5C, KIF2A and FOXG1. The second part of my PhD program was aimed at identifying the genetic basis of AIC in an international cohort of 19 patients. After excluding a skewed X chromosome inactivation and the presence of chromosomal rearrangements, I performed WES in trios. The analysis of the data from WES did not allow me to identify any recurrent variants. I therefore tested a new approach combining Whole Genome Sequencing (WGS) and RNA-Sequencing (RNA-Seq) on fibroblast cells. I identified a number of deregulated transcripts implicated in brain and eye development. I compared the results of this analysis with the WGS analysis in order to find variants in these candidate genes. In conclusion, these studies have improved the knowledge of the molecular basis of complex MCD, such as TLE1 in postnatal microcephaly, and revealed the pathogenic mechanisms such as WDR81 in cell cycle progression and EPG5 in endosomes and autophagy. My work has also generated a collection of NGS data (WES, WGS and RNA-Seq) that will be shared in an international consortium to develop new analytical strategies, in particular for the non-coding DNA regions. This novel strategy provides opportunities to improve understanding of the cellular mechanisms involved in brain and eye development
25
Chen, Chien-Ting, and 陳建廷. "Chemical Constituents of the Leaves and Stems of Gelonium aequoreum." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/00115344314177833181.
Анотація:
碩士高雄醫學大學
天然藥物研究所
100
Gelonium, a genus of shrubs and small trees belonging to the Euphorbiaceae family, is distributed in the tropical and subtropical parts of Asia and Africa. This genus contains about 25 species, but only G. aequoreum is native to Taiwan. We had previously reported the isolation of gelomulide K from G. aequoreum, which acted as a caspase-independent cell death inducing agent that possesses synergic effect with paclitaxel in breast cancer cells and has low toxicity towards normal cells. Treatment with gelomulide K induced PARP-1 hyperactivation, AIF nuclear translocation, and cytoprotective autophagy, together with increased ROS production and decreased cellular GSH levels in MDA-MB-231 cancer cell line. In the present study, the dichloromethane-soluble extract of G. aequoreum leaves was chromatographed using silica gel to obtain gelomulide K (GK) and triterpenoids rich fractions. Bioguided fractionation of the triterpenoids-rich and GK-rich fractions yielded ten compounds, including one lupane-type triterpene: lupeol (1), one taraxerane-type triterpene: taraxerol (2), two oleanane-type triterpenes: germanicol (3), and ??-amyrin (4), one urasane-type triterpene: ??-amyrin (5), two D:C-friedourasane-type triterpenes: bauerenol (6), and multiflorenol (7), one novel triterpene: cyclogelonian-3??-ol (8) one fernane-type triterpene: fernenol (9), and one ent-abietane diterpenoid: gelomulide K (10). Among them, cyclogelonian-3??-ol (8) has a new skeleton of triterpenoid with a 13??,18??-cyclopropane function. The EtOAc and the n-BuOH layers of G. aequoreum stems were also investigated. Chromatographic separation of those layers yielded twenty compounds, including one lupane-type triterpene: lupenone (11), two oleanane-type triterpenes: olean-18-en-3-one (12), and olean-12-en-3-one (13), one urasane-type triterpene: ??-amyrenone (14), two D:C-friedourasane-type triterpenes: D:C-friedours-7-en-3-one (15), and multiflorenone (16), one new triterpene: cyclogelonian-3-one (17), one fernane-type triterpene: fernenone (18), three benzenoid: chrysophanol (19), halorosellin C (20), and baisubenzene (22). Among these isolates, 17 possesses a new chemical skeleton as that of compound 8, and compounds 20 and 22 are new. The biological activities of the isolates are currently under investigation.
26
Chen, Ting-ting, and 陳亭亭. "Studies on the Chemical Constituents in the Leaves and Stems of Mucuna macrocarpa WALLICH." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/38427495344257098828.
Анотація:
碩士中國醫藥大學
中國藥學研究所
93
Mucuna macrocarpa WALLICH is a native plant of Taiwan belonging to the Leguminosae family. It is a folk medicine being used for blood circulation, activating meridians and collaterals, moisten dryness, release stagnated lung-energy. This plant was also used in Taiwan folk medicine for diabetes mellitus. In the assay for DPPH scavenging effect, the fractions of crude extract, water layer, n-butanol layer, ethyl acetate layer and precipitates showed good free radical scavenging effects. In the phytochemical study, five compounds were isolated from M. macrocarpa and were identified as the mixture of -sitosterol and stigmasterol (H-1), betulin (C-1), medicarpin (E-1), sucrose (B-1), D-pinitol (B-2), -sitosterol-3-O--D-glucoside (N-1) and tetracosanoic acid 2,3-dihydroxypropyl ester (N-2)。 We also carried out the HPLC quantitative analysis of genistein in M. macrocarpa , in order to find out the composition of M. macrocarpa and its dependence of the efficiency. Content percentage of genistein was 0.001% in M. macrocarpa. This may suggest that the activities of M. macrocarpa was resulted together from many kinds of flavonoids and other constituents. Since this plant is rather common in Taiwan, further study and investigation of its active constituents may prove its potential biological activities and medicinal values.
27
Chung, Yu-ling, and 鍾玉玲. "Comparison of Antioxidative Activity of Crude Extracts from Leaves, Stems and Fruits of Morinda citrifolia (Noni)." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/56447932507810300280.
Анотація:
碩士嘉南藥理科技大學
生物科技研究所
92
Morinda citrifolia（Rubiaceae）, commonly known as Noni, is a plant typically found in the Hawaiian, Tahitian and tropical Asia. The bark, stem, roots, leaves, and fruits have been used traditionally as a folk remedy for many diseases including diabetes, hypertension, and cancer. The first purpose of this study was focused on the antioxidative properties of various crude extracts from leaves, stems and fruits of Noni. With the results of antioxidative analysis, the optimal material of Noni plant and extract condition would be defined. Hot water (80℃), 50% aqueous or absolute ethanol, ethyl acetate and supercritical fluid carbon dioxide (SF-CO2) were used as solvents to extract. The antioxidative activity of crude extracts were measured by Trolox equivalent antioxidant capacity (TEAC) assay, the reducing power assay, the bleaching of 2,2-diphenyl-1-picrylhydrazyl hydrate (DPPH) free radical, the scavenging ability of reactive oxygen species (superoxide ion, hydroxyl radical and hydrogen peroxides) and the chelating activity on ferrous ions. The results suggested that antioxidative activity of Noni’s extracts might be due to both polar and non-polar compounds. Hot water and 50 % aqueous ethanol extracts from leaves and stems exhibited higher chelating activity on ferrous ions. Ethyl acetate extracts from leaves showed the highest scavenging ability of superoxide ion, and SF-CO2（1500 psi）extracts from leaves displayed significantly the scavenging ability of hydrogen peroxides. On the other hand, the absolute ethanol extracts of Noni’s leaves and green stems, and the SF-CO2 （3500 psi） extracts of brown stems had higher scavenging ability to hydroxyl free radical. However, fruits extracts were showed very poor as antioxidants. To sum up, leaves of Noni exhibited higher and variety of antioxidative activity, which is comparable to that of both stems and fruits. Noni leaf is worth further research in purification and identification of active compounds. As for extraction condition, ethanol extracts had higher total antioxidative activity, especially in scavenging of hydroxyl radical. The second purpose was to study the relationship between the antioxidative activities and chemical constituents in the crude extracts of Noni. The data showed that ethanolic extracts of Noni’s leaves had higher total polyphenolic and flavonoid contents and revealed that these compounds played a part in antioxidative activities. However, SF-CO2 extraction of Noni generally had lower total polyphenolic contents. The third study was to prove the Noni’s extracts in the protection ability of biological cell membrane and DNA which were attacted by oxidative damage. The results indicated that the absolute ethanol extracts of Noni’s leaves display significantly the inhibition ability of lipid peroxidation of microsomes from LYD pig liver. The scavenging mechanism of the absolute ethanol extracts of Noni’s leaves might have relation with hydroxyl radical. The antioxidant components might be attributed to higher content of polyphenolic compounds. On the other hand, the hot water and 50% ethanolic extracts of Noni’s leaves display the better protection ability from hydroxyl radical-induced, DNA damage in human lymphocyte without cell membrane. The antioxidant mechanism may be attributed to a strong metal-chelating ability and their effectiveness as good scavengers of hydroxyl radicals. By contrast, the absolute ethanol and ethyl acetate extracts of Noni’s leaves showed the pro-oxidative activity in the higher dosage extracts (10-100 μg/mL). The higher reducing power, which reduced the ferric ion to ferrous ion, appeared to be responsible for the pro-oxidative activity of the absolute ethanol and ethyl acetate extracts of Noni’s leaves.
28
Wang, Yao-Ting, and 王耀霆. "Studies on the Bioactive Cucurbitane-Type Triterpenoids and Saponins from the Stems and Leaves of Momordica chanrantia." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/uh98bu.
Анотація:
碩士國立高雄大學
生命科學系碩士班
106
Momordica charantia, belonging to the genus Momordica (Cucurbitaceae), is an annual herbaceous plant originated in tropical areas in Asia. It is widely grown and used in Southeast Asia, China and Taiwan. It tastes extremely bitter, and possesses the traits of cool natured and functions of relieving summer-heat, clearing liver, improving vision and detoxifying. It has been proved that bitter melon exhibits many bioactivities, including anti-diabetic, anti- bacterial, antiviral and anti-cancer activities.The purpose of this study is looking for the new bioactive compounds from the stems and leaves of Momordica charantia. Chromatographic separation of the EtOAc extract of M. charantia using Si-60, ODS, HW40F columns and semi-preparative reverse-phase C18 HPLC resulted in the purification of 25 compounds, comprising twelve new triterpenoids 1–12, designated as 3β-hydroxy-9α-hydroperoxy-19- norcucurbita-5,24-dienyl-7β,23R-diacetate (1), 3β,7β-dihydroxycucurbita-5,24-dien-19-al (2), (23E) 3β,7β-dihydroxycucurbita-5,23-dien-19-al (3), (19R,23E) 5β,19-epoxy-25-hydro- peroxy-19-methoxycucurbita-6,23-dien-3β-ol (4), (19S,23E) 5β,19-epoxy-25-hydroperoxy- 19-methoxycucurbita-6,23-dien-3β-ol (5), (19R) 5β,19-epoxy-19-methoxycucurbita-6,24- dien-3β-ol (6), (19S) 5β,19-epoxy-19-methoxycucurbita-6,24-dien-3β-ol (7), (19R, 23E) 5β,19-epoxy-19-methoxycucurbita-6,23-dien-3β-ol (8), (19S,23E) 5β,19-epoxy-19-methoxy- cucurbita-6,23-dien-3β-ol (9), (19R) 5β,19-epoxy-19-methoxycucurbita-6-en-3β-ol (10), (23E) 3β-hydroxycucurbita-6,23-dien-5β,19-olide (11) and (19S,23R) 5β,19-epoxy- 19-methoxycucurbita-6-en-3β,23-diol (12), together with thirteen known compounds 13–25. The structures of these isolated metabolites were determined on the basis of their spectroscopic data including, NMR, ESIMS and IR data as well as comparison of the physical and spectroscopic data with those of the related known compounds. The in vitro cytotoxicity against triple negative breast cancer cell lines (MDA-MB-231) of all isolates were evaluated. Compounds 2, 3, 9, 12, 15 and 16 showed good cytotoxicity against MDA-MB-231 with IC50 values of 4.6, 8.2, 4.7, 9.5, 8.8 and 9.5 μM, respectively.
29
Nisoli, Cristiano. "Leaves and stems, rotons and solitons, magnets and arrays, one ground state lost, many found, and two fields." 2007. http://www.etda.libraries.psu.edu/theses/approved/WorldWideIndex/ETD-1851/index.html.
30
Mbugua, David M. "Effect of maturity on rumen degradation of tropical and temperate forage cell wall polysaccharides from leaves and stems." Thesis, 1993. http://hdl.handle.net/2429/2416.
Анотація:
Two main experiments were conducted in this study with the aim of better understanding the factors that influence the degradability of forages by ruminants. In the first part of the study, the degradability of leaf and stem fractions of two mature tropical forages, bana grass (Pennisetum purpureum) and silverleaf desmodium (Desmodium uncinatum) were determined by means of the In situ nylon bag technique.
The effective degradabilities of both bana grass stems and leaves DM (50h) were low (48.2% and 45.3% respectively) and did not differ (P > 0.05) for the two fractions. Desmodium stems were less degradable (P < 0.05) than the leaves (40.8%and 59.7% respectively). Neither grass leaves nor stems differed (P > 0.05) in effective degradability of NDF (49.0%vs 51.6% respectively) or its constituent polysaccharides. Bana leaves were higher (P < 0.05) in the potentially degradable DM, than the stems but did not differ (P > 0.05) in the rate at which this fraction was degraded. On the other hand, desmodium leaves were higher in the potentially degradable fraction and the rate at which it was degraded than the respective stems. NDF, cellulose and hemicellulose showed a similar trend.
The second part of this study was aimed at determining whether the degree of plant maturity has any effect on the distribution of cellulose and linear and branched fractions of hemicelluloses. Two temperate forages, orchard grass
(Dactylis qlomerata) and tall fescue (Festuca arundinacea) harvested at different stages of growth and separated into leaves and stems were used. The cell wall content (NDF) and hemicellulose A (linear xylan) showed an increasing trend with maturity in orchard grass but not in tall fescue. Hemicellulose B (branched xylan) in the sample used in this study did not seem to change with increasing maturity.
Stems (DM) of medium and late cut orchard grass were less effectively degradable (P < 0.05) than leaves (58.1% vs 62.0%and 52.6% vs 59.2% respectively). The potentially degradable fraction did not differ (P > 0.05) with maturation for the two fractions. The rate of degradation of this fraction was higher for leaves (P < 0.1). Tall fescue fractions did not differ (P> 0.05) in effective degradability and rate of degradation of the potentially degradable fraction.
Cellulose and hemicellulose A and B showed a declining trend in their effective degradabilities (50h). Among these polysaccharides hemicellulose B showed a relatively higher degradability than the other polymers. Hemicellulose A seemed the least degradable. It appeared that the polysaccharides of leaves were relatively more degradable than those of stems. Tall fescue polysaccharides seemed to differ in effective degradability in both leaves and stems at the two cutting dates other than for hemicellulose A. Hemicellulose B in orchard grass was associated with relatively high rates of degradation compared to the other polymers.
31
Huang, Tsung-Hsien, and 黃宗賢. "Studies on the Constituents and Their Antiplatelet and Anti- inflammatory Activities from the Stems and Leaves of Pogostemon cablin." Thesis, 1996. http://ndltd.ncl.edu.tw/handle/67911912168537548229.
Анотація:
碩士中國醫藥學院
藥物化學研究所
84
Six known compound: carvacrol (Ⅰ), mixture of α-amyrin and β-amyrin (Ⅱ), 4',5-dihydroxy-6,7-dimethoxyflavone (Ⅲ), 4',5,7-trihydroxy-3'-methoxy-flavone (Ⅳ), methyl caffeate (Ⅴ) and 5-hydroxy-6,7-dimethoxy-4'-O-β-D-glucoside (Ⅵ) have been isolated from the n-hexane, chloroform and ethyl acetate fractions of the methanolic crude extract. And, these compounds are isolated for the first time from the herb. The biological activities of carvacrol, mixture of α-amyrin and β-amyrin, 4',5-dihydroxy-6,7-dimethoxyflavone, methyl caffeate and 5-hydroxy-6,7-dimethoxy-flavone-4'-O-β-D-glucoside have been evaluated.The result shows that AA and collagen-induced platelet aggregation couldbe inhibited strongly by carvacrol and methyl caffeate, and 4',5-dihydroxy-6,7-dimethoxy-flavone-4'-O-β-D- glucoside exhibited the anti-inflammatoryactivity.
32
Wu, Chin-Yi, and 吳致怡. "Antimicrobial activities and distribution of the carvacrol and thymol in roots ,stems and leaves of Plectranthus amboinicus (Lour.) Spreng." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/85533669892228638685.
Анотація:
碩士國立東華大學
生命科學系
99
Plecteanthus amboinicus is a Lamiaceae perennial herbal plant.It contains some bioactive substances based on several researches,mainly focusing on carvacrol and thymol, for its anti-inflannatory and analgesic activities. This thesis study intented to determine the distribution of carvacrol and thymol in P. amboinicus.Assay of carvacrol and thymol in different parts of P. amboinicus,such as roots, stems and leaves, by HPLC (high-performance liquid chromatography) with the comparison between dried and fresh samples showing a significant difference in their distribution. The results indicated both compounds in leaves were more than those in roots and stems with or without dessication. Analysis of extracts from the P. amboinicus for its antimicrobial activities indicated P. amboinicus extracts did not inhibit the growth of E.coli KRX,but inhibited the growth of Arthrobacter ilicis D50. The results showed that the root extract had the highest inhibition activity.
33
Lo, Wen-Li, and 羅文利. "Studies on the Chemical Constituents and Biological Activities of the Mixture of Roots and Stems and Leaves of Euchresta formosana." Thesis, 2003. http://ndltd.ncl.edu.tw/handle/wsa264.
Анотація:
博士高雄醫學大學
藥學研究所
91
Euchresta formosana (Hayata) Ohwi (Leguminosae) is an evergreen and perennial shrub occurring in shady and humid places, especially distributed in Taiwan, Java, and Philippines. The roots of this plant have been used in folk medicine as a pain killer, particularly for the throat and snake wounds in Taiwan. As a part of our research on the biologically active components from Chinese medicinal plants, the roots and leaves of E. formosana were chosen to be investigated. Forty four compounds including eighteen coumaronochromones 、euchretins A-N (1-14), formosanatins A-D (15-18)]; two isoflavones [formononetin (27), retusin 8-methyl ether (33)]; one flavonol [quercetin (35)]; nine flavanones [euchrestaflavanones A-C (36-38), glabrol (39), euchrenones a1-a2 (40-41), euchrenone a11 (42), euchrenones a16-a17 (43-44)]; two pterocarpan [maackiain (45), trifolirhizin (46)]; two lupin alkaloids [(-)-cytisine (48), (+)-matrine (49)]; one cyclohex-2-en-1-one [blumenol A (51)]; and three benzenoids [vanillin (52), p-hydroxybenzoic acid (53), 3-(4-hydroxy-3-methoxyphenyl)-acrylic acid octadecyl ester (54)]; one coumestan [medicagol (55)]; one lignan [(+)-syringaresinol (56)], and four steroids [-sitosteryl D-glucoside (57), stigmasteryl D-glucoside (58), -sitosterol (59), and stigmasterol (60)] were isolated from the mixture of roots and stems of E. formosana. Seven coumaronochromones [euchretin A (1), euchretin C (3), euchretins F-I (6-9), euchretin N (14)]; sixteen isoflavones [tectorigenin (19), genistein (20), 7-hydroxy-3-(3- hydroxy-4-methoxyphenyl)chromen-4-one (21), biochanin A (22), 5,7,8-trihydroxy-3-(4-methoxyphenyl)chromen-4-one (23), euchrenones b1-b2 (24-25), flemiphyllin (26), formononetin (27), 6,7,4'- trihydroxyisoflavone (28), daidzein (29), 7-methoxy-2',4'- dihydroxyisoflavone (30), 3-(3,4-dimethoxyphenyl)-7,8-dihydroxy- chromon-4-one (31), 2'-hydroxylgenistein (32), retusin 8-methyl ether (33), euchrenone b16 (34)]; one flavonol [quercetin (35)]; two pterocarpans [maackiain (45), 2-methoxymaackiain (47)]; one chlorophyll [pheophytin-a (50)]; one cyclohex-2-en-1-one [blumenol A (51)]; two benzenoids [vanillin (52), p-hydroxybenzoic acid (53), 3-(4-hydroxy-3-methoxyphenyl)-acrylic acid octadecyl ester (54)]; one coumestan [medicagol (55)], and four steroids [-sitosteryl D-glucoside (57), stigmasteryl D-glucoside (58), -sitosterol (59), and stigmasterol (60)] from the leaves of E. formosana, had been isolated and characterized by spectral data and chemical related derivatives. Among these 60 compounds, 10-18 and 43-44 are new compounds. Among them, 6-9, 19-32, 34-35, 40-41, 46, 48-54, and 56-58, 60 are isolated for the first time from this plant. On antitumor bioassay, compounds 1, 10, and 13 were demonstrated to have moderate cytotoxicity against 59T cell line (human hepatoma cell, 52.0% , 87.5%, and 71.5% inhibition at the concentration of 10 μg/ml), and compound 10 was also found to be slightly active against SCM-1 cell line (stomach adencarcinoma cell, 53.0% inhibition at the concentration of 10 μg/ml). The rest of compounds exhibited no cytotoxic effect to Hone-1 (nasopharyngeal carcinoma), DLD1(human colon cancer cell), AGS (human gastric cancer cell), SKHep1 (human hepatocellular carcinoma cell), HepG2 (human hepatocellular carcinoma cell) and NUGC (human gastric carcinoma cell ) cell lines. On anti-HIV bioassay, compounds 13, 17, and 26 inhibited HIV replication in H9 lymphocyte cells with EC50 values of < 0.1, < 0.1, and 0.627μg/mL and therapeutic indexes (TI) of > 2.22, > 2.18, and 3.90, respectively. The biological evaluation of the flavonoids from this plant doesn’t demonstrate powerful effect with respect to their anti-HIV activities. On antiplatelet aggregation bioassay, compounds 19 (100μM) showed complete inhibition and 21 displayed strong effects toward the platelet aggregation induced by AA and collagen. Only compounds 20 and 28 (100μM) completely inhibited the collagen-induced platelet aggregation. Compound 6 (100μM) also displayed significant inhibition of the platelet aggregation induced by AA, collagen, especially the action induced by PAF. Compounds 25, 27, 45, and 50 (100μM) were remarkable inhibitors of platelet aggregation induced by collagen. Compounds 6, 19, and 21 was the most effective antiplatelet aggregation compounds. From the results obtained, the following structure-activity relationships can be drawn in terms of antiplatelet effects: 1. In general, isoflavones from this plant are significantly active against AA- and collagen-induced aggregation, while compounds of other types are not. 2. Aspirin is a cyclooxygenase inhibitor, and can prevent AA- or collagen- induced platelet aggregation except that caused by other inducers. Meanwhile, compound 19 exhibited the same inhibitory pattern as aspirin on platelet aggregation induced by AA- and collagen. Thus, the mechanism(s) of action for 19 may be the same as aspirin. However, the precise mechanism requires further investigation.
34
Marques, Mário Pedro da Silva. "Monitoring of ripening-derived composition and morphology modifications in Arbutus unedo L. fruits, and characterization of vitrified tissues." Master's thesis, 2019. http://hdl.handle.net/10316/88099.
Анотація:
Dissertação de Mestrado em Biodiversidade e Biotecnologia Vegetal apresentada à Faculdade de Ciências e TecnologiaA familía Ericaceae é constítuida por várias espécies economicamente importantes, tais como as pertencentes ao género Rhododendron and Vaccinium. Entre elas, o arbusto mediterrânico Arbutus unedo L. destaca-se do ponto de vista pomológico e ornamental. Para aprofundar o conhecimento sobre esta espécie, analisaram-se as alterações morfológicas e composicionais que ocorrem na ontogenia dos frutos, com o objetivo de identificar fatores e eventos relacionados com a sua maturação. Deste modo, os resultados da execução de FTIR revelaram alterações ao nível dos polissacarídeos estruturais da parede celular, entre frutos imaturos e maduros. Investigações espetroscópicas adicionais com biomassa intacta dos frutos, revelaram que existem variações composicionais, principalmente decorrentes de polissacarídeos da matriz, tais como as pectinas e hemicelulloses, e também celulose. No decorrer da maturação verificou-se também um aumento no teor de sólidos solúveis totais (˚Brix), e um decréscimo na acidez dos frutos. Por outro lado, a degradação de açúcares estruturais que advém da hidrólise e/ou do processo oxidativo, resulta num decréscimo acentuado da firmeza dos frutos, que leva ao seu amolecimento, e também a variações do seu diâmetro polar e equatorial. Além disso, traçou-se um perfil fenólico preliminar dos frutos recorrendo a RP-HPLC-PDA, concluindo-se que ocorrem poucas variações desses compostos durante a maturação. Por sua vez, no que diz respeito à vitrificação de tecidos, decorrente da sua cultura em meio líquido, investigou-se a parede celular de folhas e caules vitrificados, comparando depois com tecidos não vitrificados. As diferenças nos teores de celulose, polissacarídeos da matriz e lenhina, entre material in vitro não vitrificado e vitrificado, foram reveladas através de técnicas como FTIR., lenhina solúvel em brometo de acetil e quantificação de carbohidratos totais. Contrariamente ao que poderia ser expectável e ao que é normalmente indicado na literatura, os resultados obtidos mostraram, de forma consistente, um teor de lenhina mais elevado nas folhas do que nos caules. Por outro lado, através de microscopia ótica de campo claro, fluorescência e varrimento, revelaram-se informações meticulosas sobre a anatomia de A. unedo, através de comparações entre folhas e caules de um arbusto e de material in vitro, vitrificado e não vitrificado. Em comparação com folhas normais, as vitrificadas evidenciaram uma epiderme desorganizada e fina, com imensos complexos estomáticos anormais presentes na página inferior da folha. O mesófilo apresentava grandes espaços lacunares e não existia um parênquima em paliçada bem definido. No que diz respeito aos caules, as principais diferenças estão relacionadas com as células corticais muito espaçadas devido à presença de pronunciados espaços intercelulares. A presente dissertação contribui para um melhor conhecimento desta espécie economicamente importante, mas pouco conhecida, não só pelo melhor conhecimento do processo de maturação dos frutos, mas também por ajudar a perceber as alterações morfológicas e químicas num fenótipo vitrificado.
The Ericaceae family comprises a wide number of economic relevant species, such as the plants belonging to the Rhododendron and Vaccinium genera. Among them, the Mediterranean evergreen shrub Arbutus unedo L. outstands from the pomological and ornamental point of view. For an in-depth knowledge of this plant, the ripening-derived composition and morphology was monitored, aiming at identifying factors and events related with fruit maturation. Accordingly, to explore the ripening-derived compositional differences, FTIR spectroscopy was performed, founding chemical variations related to the structural polysaccharides of the cell wall, between immature and fully ripen fruits. Further spectroscopic investigations using the fruits intact biomass, revealed more variations, mainly due to matrix polysaccharides like pectins and hemicelluloses, and cellulose. The process of maturation was also found to be related to an increase of total soluble solids content (˚Brix), and a decrease in fruits acidity. Notwithstanding, the hydrolysis and/or oxidative derived-degradation of structural sugars, results in an extreme decline of fruit firmness, leading to fruit softening, and variations in the polar and equatorial diameters. Furthermore, a preliminary phenolic profile of the fruits was also investigated by RP-HPLC-PDA, and only slight variations of the phenolic compounds were observed during fruit maturation. On the other hand, concerning the vitrification (hyperhydricity) phenomenon that outcomes through the culture of axillary shoots in liquid medium, the cell wall of non-vitrified and vitrified in vitro shoots of A. unedo was evaluated, comparing leaves and stems. Regarding on the differences in the amounts of cellulose, matrix polysaccharides and lignin, compositional differences were uncovered in leaves and stems from in vitro shoots, using FTIR spectroscopy, acetyl-bromide soluble lignin method and total carbohydrates estimation. Unexpectedly, our results showed higher amounts of lignin in leaves, comparing to stems. Additionally, meticulous information about the A unedo anatomy was assessed by light, fluorescence and scanning electron microscopy, making comparisons between leaves and stems of non-vitrified and vitrified in vitro shoots, and tissues from a strawberry tree. Comparing with normal leaves, the vitrified ones showed to have a delicate and disorganized epidermis, with many abnormal stomata present in the abaxial surface. The mesophyll has wide lacunar spaces, and lack of palisade parenchyma. Concerning vitrified stems, the major differences relied on the the broad-spaced cortical cells. In the end, the present dissertation contributed to better characterization of this economic relevant species but largely unknown, not only for a better understanding on the fruits ripening events, but also by helping to unveil the chemical and anatomy-related factors of the vitrified phenotype.
Outro - This master thesis was supported by the Project “RENATURE – Valorization of the Natural Endogenous Resources of the Centro Region” (CENTRO-01-0145-FEDER-000007), funded by the Comissão de Coordenação da Região Centro (CCDR-C) and subsidized by the European Regional Developmental Fund (FEDER)
35
Cleemput, Stijn. "Breeding for a reduced glucosinolate content in the green mass of rapeseed to improve its suitability for biogas production." Doctoral thesis, 2011. http://hdl.handle.net/11858/00-1735-0000-0006-AB34-8.
36
Botha, Lynette Elizabeth. "Investigating the production of secondary metabolites effective in lowering blood glucose levels in Euclea Undulata Thunb. Var Myrtina (Ebenaceae)." Diss., 2016. http://hdl.handle.net/10500/21927.
Анотація:
Euclea undulata Thunb. var myrtina is a widely distributed shrub in South Africa. The roots are used by traditional healers for the treatment of diabetes. Research indicates that roots contain epicatechin, lupeol as well α-amyrin-3O-β-(5-hydroxy) ferulic acid. It was found that α-amyrin-3O-β-(5-hydroxy) ferulic acid inhibits α-glucosidase while epicatechin lowers glucose levels in the blood. Existing literature also indicates the presence of the naphthoquinone 7-methyl-juglone in the roots, although it was not detected in all cases. Due to its cytotoxic nature, 7-methyl-juglone poses a potential threat when E. undulata is used as medicinal treatment.
In order to assist the effective and safe use of this plant as a treatment for diabetes, this project aims to determine whether the presence of these metabolites is seasonal. It further aims to contribute to more sustainable harvesting methods by investigating stems and leaves in addition to the roots for the presence of these metabolites.Environmental Sciences
M. Sc. (Environmental Science)
37
Huang, Shiow-chyn, and 黃秀琴. "Chemical and Biological Investigation of Stem Bark of Citrus grandis f. buntan and Stem Bark and Leaves of Clausena excavata." Thesis, 1993. http://ndltd.ncl.edu.tw/handle/73093601490298139354.
38
Chou, En-tzu, and 周恩慈. "Studies on the chemical constituents and biological activities from the stem and leaves of Beilschmiedia tsangii." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/33044322881364055640.
Анотація:
碩士大仁科技大學
製藥科技研究所
94
Abstract Beilschmiedia tsangii Merr. (Lauraceae)1) is an evergreen tree, distributed in forests at low altitudes throughout southern Taiwan. Andiandric acids7), aporphine alkaloids4), bisbenzylisoquinoline alkaloids6), and arylpropanoids are widely distributed in plants of the genus Beilschmiedia. Some isolates exhibit biological activities, including antibacterial7) and antimalarial6) properties. However, the chemical constituents and biological activities of this plant have never been studied. Approximately 1000 species of Formosan plants have been screened for cytotoxicity, and B. tsangii was shown to be one of the active species. Investigation of CHCl3-soluble fraction of the stem of B. tsangii has led to the isolation of two new tetrahydrofuran-type lignans, beilschmin A (1) and beilschmin B (2), two new dihydrofuran-type lignan, beilschmin C (3) and beilschmin D (4), two new 1-phenylbutyl benzoates, tsangin A (5) and tsangin B (6), together with thirteen known compounds, including a tetrahydrofuran-type lignan, rel-(7S,8S,7’R,8’R)- 3,3’,4,4’,5,5’-hexamethoxylignan (7), seven steroids, β-sitosterol (8), β-sitostenone (9), 6α-hydroxystigmast-4-en-3-one (10), 6β-hydroxystigmast-4-en-3-one (11), 3β-hydroxystigmast-5-en-7-one (12), stigmast-4-en-3,6-dione (13) and ergosta-4,6,8(14),22-tetraen-3-one (14), a sesquiterpenoid, 2,6,11-tri- methyldodeca-2,6,10-triene (15), two benzaldehydes, vanillin (16) and 4-hydroxybenzaldehyde (17), a benzoquinone, α-tocopheryl quinone (18), and α-tocospiro B (19). In addition, investigation on the CHCl3-soluble fraction of the leaves of B. tsangii has led to the isolation of two new tetrahydrofuran-type lignans, beilschmin A (1) and beilschmin B (2), together with seven known compounds, including a tetrahydroxyfuran-type lignan, rel-(7S,8S,7’R,- 8’R)-3,3’,4,4’,5,5’-hexamethoxylignan (7), two steroids, β-sitosterol (8) and β-sitostenone (9), a benzoquinone, α-tocopheryl quinone (18), a triterpenoid, squalene (20), a tocopherone, α-tocopherol trimer B (21) and a aliphatic ester derivative, methyl linoleate (22). The structures of these new compounds were determined through spectral analyses. Among the isolates, compounds 1-3, 5, 6, 15, 18 and 19 exhibited cytotoxicities (IC50 values < 4 μg/mL) against P-388 and/or HT-29 cell lines in vitro. Compounds 1 and 2 also showed significant antitubercular activities in vitro (MIC = 2.5 and 7.5 μg/mL, respectively).
39
Blakewood, Amanda Marie. "Testing the Fit of a Model of Faculty Departure Intentions for Women Faculty in STEM and Non-STEM Disciplines." 2011. http://trace.tennessee.edu/utk_graddiss/1060.
Анотація:
Abstract
Much warranted attention over the past few decades has been devoted to the problem of retaining women faculty in academe, particularly in areas where they poorly represented such as in science, technology, engineering, and mathematics (STEM) fields. This study uses descriptive statistics and structural equation modeling techniques to test an existing model of general faculty departure intentions (Zhou & Volkwein, 2004) on three samples of faculty (a) women faculty, (b) women faculty in STEM, and (c) women faculty in non-STEM fields. Findings revealed that although several significant pathways to intention to leave for women faculty in STEM and in non-STEM fields were identified, the tested model is not an overall good fit of the data for any of the three samples, implying the need for new models of faculty departure intentions specifically for women in STEM and non-STEM disciplines. Implications for practice, theory, and future research are discussed.
40
Huang, Shi-Yu, and 黃士俞. "Studies on the Chemical Constituents and Cytotoxic Activities from the Stem Wood and Leaves of Hibiscus tiliaceus and the Stem Wood of Zanthoxylum integrifoliolum." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/33476255725275823555.
Анотація:
碩士大仁科技大學
製藥科技研究所
94
As a series of studies on the cytotoxic constituents of Formosan plants, many species have been screened for in vitro cytotoxic test. Among them, the MeOH extract of the stem wood and leaves of Hibiscus tiliaceus and the stem wood of Zanthoxylum integrifoliolum exhibited cytotoxic activities. Investigation of an EtOAc-soluble fraction of the stem wood of H. tiliaceus has led to the isolation of thirteen compounds, including hibiscusin (1), hibiscusamide (2), vanillic acid (3), p-hydroxybenzoic acid (4), syringic acid (5), p-hydroxybenzaldehyde (6), scopoletin (7), N- trans-feruloyltyramine (8), N-cis-feruloyltyramine (9), β-sitosterol (10), stigmasterol (11), β-sitostenone (12), and stigmasta-4,22-dien-3-one (13). In addition, seven compounds have been isolated from an EtOAc-soluble fraction of the leaves of Hibiscus tiliaceus, and the isolates included friedelan-3-one (14), epi-friedelinol (15), trans-phytol (16),α-tocopherol (17),α-tocopheryl quinone (18), β-sitosterol (10), and stigmasterol (11). Among them, 1 and 2 are new compounds. Investigation of an EtOAc-soluble fraction of the stem wood of Z. integrifoliolum has led to the isolation of seventeen compounds, including γ-fagarine (19), skimmianine (20), haplopine (21), robustine (22), tetracosyl ferulate (23), vanillin (24), canthin-6-one (25), 4-methoxy-1- methyl-2-quinolone (26), 6,7-dimethoxycoumarin (27), trans-coniferyl aldehyde (28), parthenin (29), evofolin-C (30), p-hydroxybenzaldehyde (6),β-sitosterol (10), stigmasterol (11), β-sitostenone (12), and stigmasta -4,22-dien-3-one (13). The structures of these isolates were determined through spectral analyses. Among them, 2, 8, 9, 18, 19, 20 and 25 showed significant cytotoxicities (IC50 values < 4 μg/mL) against P-388 cell line. In addition, 2, 19 and 21 also show significant cytotoxicities (IC50 values < 4 μg/mL) against HT-29 cell line.
41
Chen, Po-Hou, and 陳柏豪. "Studies on the Chemical Constituents and Biological Activities from the Stem Wood and Leaves of Zanthoxylum integrifoliolum." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/06816690293777478352.
Анотація:
碩士大仁科技大學
製藥科技研究所
95
Zanthoxylum integrifoliolum (Merr.) Merr (Rutaceae) is an evergreen tree distributed in northern Philippine and on Lanyu Island in Taiwan. In our studies on the anti-inflammatory constituents of Formosan plants, many species have been screened for in vitro anti-inflammatory activity to date and Z. integrifoliolum has been found to be one of the active species. Continuing investigation of an EtOAc-soluble fraction of the stem wood of Zanthoxylum integrifoliolum has led to the isolation of twenty-two compounds, including (R,E)-1-[4-(3-hydroxyprop-1 -enyl)phenoxy]-3-methylbutane-2,3-diol (1), 4-hydroxy-3-(3-methyl-2- butenyl)cinnamyl alcohol (2), 2,6-bis(1-phenylethyl)phenol (3), 2,4-bis(1-phenylethyl)phenol (4), 18-demethylparaensidimerin C (5), 4-[4-(3-hydroxypropenyl)phenoxy]-2-meyhylbut-2-en-1-ol (6), 1-[(3-methylbut-2-enyl)oxyl]-2-methoxy-4-(prop-1-en-3-ol)benzene (7), 1-(2-hydroxyphenyl)-1-(1-phenyl)ethane (8), paraensidimerin C (9), syringaldehyde (10), trans-p-coumaryl aldehyde (11), isoscopoletin (12), 6,7,8-trimethoxycoumarin (13), (-)-sesamin (14), (-)-syringaresinol (15), (-)-simulanol (16), (-)-5-methoxybalanophonin (17), (-)-balanophonin (18), (-)-dehydrodiconiferyl alcohol (19), N-methylflindersine (20), (R)-(+)-platydesmine (21) and decarine (22) . In addition, fifteen compounds have been isolated from an EtOAc-soluble fraction of the leaves of Zanthoxylum integrifoliolum, and the isolates included decarine (22), 1-hydroxyrutaecarpine (23), rutaecar- pine (24), (-)-sesamin (14), (+)-piperitol (25), ergosta-4,6,8(14),22- tetraen-3-one (26), β-sitosterol (27), β-sitostenone (28), stigmasta-4,22- dien-3-one (29), 3��-hydroxystigmast-5-en-7-one (30), methyl 4-hydroxy- benzoate (31), ��-tocopheryl quinone (32), (2E,4E)-N-isobutyl- 2,4-tetradecadienamide (33), squalene (34) and luvangetin (35). The structures of all isolates were determined through spectral analyses and comparison of their physical and spectral data with literature. Among them, 1-5 are new compounds. Compounds 16 and 20 exhibited potent inhibition against fMLP-induced superoxide production with IC50 = 11.83 ± 5.23 and 4.28 ± 0.89 �嵱, respectively. Compound 22 showed marked antitubercular activities (MIC = 12.5 �慊/mL) against Mycobac- terium tuberculosis H37Rv.
42
Lee, Hsinn-Hsing, and 李信興. "Studies on the Chemical and Cytotoxic Constituents from the Leaves of Muntingia calabura and the Stem Woods of Zanthoxylum pistaciiflorum." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/26272677681905925041.
Анотація:
碩士大仁科技大學
製藥科技研究所
93
As a series of studies on the chemical constitutents and cytotoxic activities of Formosan plants, the leaves of Muntingia calabura (Tiliaceae) and the stem wood of Zanthoxylum pistaciiflorum (Rutaceae) were investigated. Investigation on the leaves of Muntingia calabura has led to the isolation of forty compounds including: tectochrysin (1), 3,7-dimethoxy-5-hydroxyflavone (2), 5-hydroxy-3,6,7-trimethoxyflavone (3), 6,7-dimethoxy-5-hydroxyflavone (4), guaphaliin (5), 8-methoxy-3,5,7-trihydroxyflavone (6), izalpinin (7), 5,7-dihydroxy-3,8-dimethoxyflavone (8), galangin (9), chrysin (10), 5,4''-dihydroxy-3,7-dimethoxyflavone (11), 7-methoxyflavone (12), 5,7-dihydroxy-3-methoxyflavone (13), 5,7-dihydroxy-6-methoxyflavone (14), muntingone (15), (2S)-7-hydroxy-8-methoxyflavanone (16), (2S)-7-hydroxyflavanone (17), (2S)-5''-hydroxy-7,3'',4''-trimethoxyflavanone (18), (2R,3R)-(-)-3,5-dihydroxy-6,7-dimethoxyflavanone (19), (2S)-4''- hydroxy-7-methoxyflavanone (20), (2S)-5''-hydroxy-7,8,3'',4''-tetramethoxyflavan (21), (2S)-7,8,3'',4'',5''-pentamethoxyflavan (22), 2'',4''-dihydroxychalcone (23), larrein (24), 2'',4''-dihydroxy-3''-methoxydihyrochalcone (25), 2'',4''-dihydroxydihydrochalcone (26), (-)-3''-methoxy-2'',4'',β-trihydroxydihydrochalcone (27), 2,3-dihydroxy-4,3'',4'',5''-tetramethoxydihydrochalcone (28), methyl 4-hydroxybenzoate (29), Isovanillic acid (30), p-nitrophenol (31), methyl gallate (32), trans-methyl Ρ-coumarate (33), β-sitostenone (34), β-sitosterol (35), stigmasterol (36), β-amyrenone (37),α-tocopheryl quinone (38), δ-tocopherol (39) and α-tocospiro B (40). Fifteen compounds have been isolated from the stem woods of Zanthoxylum pistaciiflorum. The isolates included trans-methyl p-coumarate (33), β-sitostenone (34), β-sitosterol (35), robustine (41), dictamnine (42), γ-fagarine (43), skimmianine (44), syringaresinol (45), (-)-hinokinin (46), xanthoxylol 3,3-dimethylallyl ether (47), 5,5''-dimethoxy-7-oxolariciresinol (48), wutaiensal (49), glycocitridine (50), 3-(4-hydroxyphenyl)propionic acid methyl ester (51), and 3β-hydroxystigmast-5-en-7-one (52). The structures were elucidated by spectral analyses and comparison of their physical and spectral data with literature. Among them, 15, 18, 19, 25, 27 and 28 are new compounds. Compounds 18, 20, 23, 25 and 38 showed significant cytotoxicities (ED50 values < 4 g/mL) against P-388 cell line. In addition, compounds 23 and 25 also show significant cytotoxicities (ED50 values < 4 g/mL) against HT-29 cell line.
43
Köcher, Paul. "Hydraulic traits and their relevance for water use strategies in five broad-leaved tree species of a temperate mixed forest." Doctoral thesis, 2012. http://hdl.handle.net/11858/00-1735-0000-0001-BC4A-8.
44
Morton, Dawn Renee. "The correlation between church leaders' understanding of the issue of child sexual abuse and preventive steps taken within their churches." Thesis, 2005. http://hdl.handle.net/10392/388.
Анотація:
The research examined the relationship between knowledge of faith-based church leaders regarding the facts of child sexual abuse and the practice of child sexual abuse prevention steps utilized within the church. It examined the historical, theological, biblical, and ethical concerns about child sexual abuse and the church. The biblical accounts of David and Bathsheba along with the story of Tamar and Amnon were reflected upon within the historical and biblical context of sexual abuse. The theological understanding of sin and its results was analyzed in the context of child sexual abuse.
A chronological exploration of the history of child abuse in the United States along with statistics for the represented years was included in the study. Exploration of the abuse of power, the multileveled aspects of denial, the victim, the perpetrator, prevention steps available to the church and parental partnership were included. The common prevention steps discussed were: a written policy and procedure manual, screening form, interview, reference checks by phone or written, criminal background checks (fingerprinting), keeping doors open, windows in the classrooms, hall monitor system, a 2-adult rule, computer on-line check for sexual offenders, waiting six months from membership, prevention training at the local church, prevention training at denominational level, adequate church insurance, and a team of members ready to deal with any accusations that may occur.
There was a description of the research process. The study was descriptive quantitative research by use of a research instrument (developed from the precedent literature and validated by an expert panel) that examined the relationship between knowledge and practice of faith-based church leaders regarding child sexual abuse and prevention. The research instrument consisted of five sections: Demographics, Likert Response Scale, Prevention Steps Checklist, Hindrances, and Comments. The Likert Response Scale included questions on knowledge of child sexual abuse facts, knowledge of prevention steps, higher education, and the issue of denial among church leaders. There were 213 seminary students who were church leaders that participated in the research study.
Displays of the data, analysis of the data, and interpretation of the data were included along with a description of the research implications and applications, along with possible further research. Pearson r correlation was conducted to determine if there was a relationship found between knowledge and practice of church leaders. Recommendations were made to the church on the subject of child sexual abuse prevention.This item is only available to students and faculty of the Southern Baptist Theological Seminary. If you are not associated with SBTS, this dissertation may be purchased from http://disexpress.umi.com/dxweb or downloaded through ProQuest's Dissertation and Theses database if your institution subscribes to that service.
45
Vinas, Keila L. "Narratives of women's leadership identity development: an assessment of senior-level information technology (IT) leaders following participation in a women-only training program." Thesis, 2017. https://hdl.handle.net/2144/20896.
Анотація:
Despite having made significant strides in the overall labor market, women continue to lag behind men at the senior and executive C-suite levels. The gap is even more striking in organizations within the fields of Science, Technology, Engineering, and Math (STEM). Although women-only leadership trainings have gained recent popularity as a strategy to address this, scholarship on the efficacy of such programs is still fairly scant. This study aimed to fill this gap in the research by looking into how graduates of such a program used the tools and knowledge gained during the training, to determine if and how it has impacted, in their view, their identity as leaders.
Eighteen senior-level Information Technology (IT) leaders, graduates of the same in-house women-only leadership program were interviewed using a narrative inquiry approach. Data gathered during the interviews revealed which strategies participants put into practice, how they applied them, as well as the perceived outcomes that they derived. The narratives revealed women’s perspective of their leadership trajectory and their understanding of the training’s impact.
Interviews were analyzed using content and thematic coding. Analysis of the participants’ accounts pointed to the training’s ability to facilitate leadership identity development through the following means: (1) the promotion of practical skills, (2) increased self-awareness and realization of others’ perceptions, (3) feeling a sense of belonging and connectedness, and (4) feeling recognized and empowered. It was also clear that context plays a significant role on the impact that the training can have. Three themes related to this emerged; (1) the availability of advocates, (2) executive visibility, and (3) fit with the organization’s leadership culture and ability to lead authentically. Participants’ stories also revealed the ways in which the training affected their ability to deal with a male-dominated organization, which ultimately depended on how much of an effect they believed that being a woman has on their workplace experience.
Findings suggest that women-only leadership trainings can have a positive impact on senior-level leaders’ leadership identity, yet careful consideration must be paid to the contextual factors identified. Findings also provided concrete evidence pointing to the perceived effectiveness of specific program components.
46
Bates, Philip David. "Re-examining the initial steps of membrane and storage lipid assembly in pea leaves and soybean embryos the dominant flux of newly synthesized fatty acid incorporation into extra-plastidic glycerolipids is through phosphatidylcholine acyl editing /." Diss., 2008. http://proquest.umi.com/pqdweb?did=1681946151&sid=1&Fmt=2&clientId=3552&RQT=309&VName=PQD.
Анотація:
Thesis (Ph. D.)--Michigan State University. Biochemistry and Molecular Biology, 2008.Title from PDF t.p. (Proquest, viewed on Aug. 17, 2009) Includes bibliographical references (p. 187-203). Also issued in print.
47
Bean, Lynne. "The morphological revisions of freshwater fish from Late Jurassic - Early Cretaceous sites in Australia and other Gondwanan continents leads to new phylogenetic hypotheses of relationships among stem teleosts." Phd thesis, 2021. http://hdl.handle.net/1885/235247.
Анотація:
Australia has two important sites for freshwater Mesozoic fishes. The Talbragar Fossil Fish Bed in New South Wales is a Tithonian (Upper Jurassic) freshwater lake deposit containing the iconic form Cavenderichthys talbragarensis, first described by Woodward at the end of the 1800s. The Koonwarra Fossil Bed in Victoria is an Albian (Lower Cretaceous) freshwater lake deposit containing Waldmanichthys koonwarri, first described by Waldman about 50 years ago. Following the tradition of the time, both species were first ascribed to the genus Leptolepis. In 2015, these two species were placed into a newly erected family, Luisiellidae, with the Oxfordian-Tithonian fish Luisiella feruglioi from Argentinian Patagonia. This new family was interpreted as a stem teleost group, closer to Leptolepis coryphaenoides than to the crown-group Teleostei. That hypothesis was contrary to previous interpretations, which placed Cavenderichthys as a teleost incertae sedis in the crown Teleostei. This thesis re-examines the morphological characters of the Australian taxa, including 43 specimens of W. koonwarri, from Museum Victoria. Some new characters include the special configuration of the jaws and the position of the quadrate-mandibular articulation, the pattern of vertebrae at the level of the abdominal/caudal regions, and a stegural-like uroneural in the caudal skeleton. Finding new characters in Waldmanichthys called for reappraisals of the morphology of Cavenderichthys and Luisiella. In the case of Cavenderichthys, 126 specimens were re-examined, but for specimens of Luisiella, a conservative approach was followed, based on its last morphological description as well as photographs taken recently. The systematic position of the three Gondwanan taxa was re-evaluated using a pre-existing data matrix including 240 characters and 56 taxa. The new results give a very different scenario, with the three taxa included in the crown-group Teleostei. The family Luisiellidae is restricted to its type species Luisiella feruglioi. The two Australian fish taxa cluster together with Late Jurassic European taxa Leptolepides and Orthogonikleithrus, and are now ascribed to the family Orthogonikleithridae. The new results suggest that the three Gondwanan genera are stem taxa within the Osteoglossocephala (osteoglosomorphs plus more advanced teleosts), and their combination of morphological characters has a major effect on the interpretation of basal euteleosts, questioning some previous interpretations, as for instance, the homology of the stegural as an euteleostean character.
The family Archaeomaenidae has been accepted as holding the Australian species Archaeomaene tenuis, Madariscus robustus, and Wadeichthys oxyops, the Antarctic Oreochima ellioti, the Chinese Zaxilepis ginglongensis and the Mongolian Gurvanichthys mongoliensis. The anatomical redescription of Archaeomaene has provided evidence that Madariscus robustus is a synonym of Archaeomaene tenuis, as specimens formerly ascribed to Madariscus robustus are the larger specimens of an ontogenetic series of Archaeomaene tenuis. Similar anatomical redescriptions of Wadeichthys oxyops and Oreochima ellioti have provided further evidence confirming their positions in Archaeomaenidae. Two lesser known fish, Zaxilepis ginglongensis from China and Gurvanichthys mongoliensis from Mongolia have also been included in the phylogenetic analysis and confirmed as members of Archaeomaenidae, which are stem teleosts or teleosteomorphs phylogenetically close to the older Eurasian family Pholidophoridae. The new knowledge presented in this thesis illuminates the importance of Australian taxa in the Tree of Life of Fishes.
48
Shouqiang, Li. "The moderating role of leader-member exchange as a moderating variable on the relationship between perceived stress and burnout in clincians." Doctoral thesis, 2019. http://hdl.handle.net/10071/21298.
Анотація:
Under the influence of internal and external environment, Chinese clinician is under great pressure. Guided by Job Demands-Resources (JD-R) model and social exchange theory, this study explores the moderating role of Leader-Member Exchange (LMX) in managing the job burnout caused by perceived stress among clinicians in China.
Based on the extensive literature review on perceived stress, burnout and LMX, this study first discussed the impact of perceived stress on burnout and its three dimensions (namely emotional exhaustion, depersonalization and reduced accomplishment) among clinician, then examined the effects of LMX on burnout and its three dimensions, and lastly studied the mediating role of LMX between perceived stress and burnout. A questionnaire survey was conducted among three hospitals in Guangzhou and 434 valid responses were collected. Then data analysis and hypothesis test were carried out using IBM SPSS 19.0 and AMOS 21.0. The regression analyses showed that the perceived stress had a significant positive impact on burnout and its three dimensions. In addition, LMX moderates the relationship between perceived stress and burnout and its three dimensions such that the relationships are weaker for clinicians with higher LMX.
The findings of this study provided useful complementary insights for the research on perceived stress of clinician, and for better managing the burnout of clinicians in China.Sob a influência do meio envolvente e interno, os profissionais das saúdes chineses encontram-se sob grande pressão. Tomando por base o modelo das exigências de recursos (JD-R) e a teoria da troca social, este estudo explora o efeito moderador da LMX (Troca Líder-Membro) na gestão do burnout causado pelo stress percebido pelos profissionais das saúdes na China. Com base numa revisão extensa de literatura sobre stress percebido, burnout e LMX, este estudo discute primeiro o impacto do stress percebido e das suas três dimensões entre profissionais das saúdes, e examina os efeitos da LMX no burnout e nas suas três dimensões, e finalmente, estuda o papel mediador da LMX entre o stress percebido e o burnout. Realizou-se um inquérito por questionário junto de três hospitais em Cantão e recolheram-se 434 respostas válidas. Testaram-se as hipóteses por via de análise de dados utilizando o IBM SPSS 19-0 e o AMOS 21.0. As análises de regressão mostraram que o stress percebido exerce um impacto positivo no burnout e nas suas três dimensões; nomeadamente na exaustão emocional, na despersonalização e desempenho reduzido. Em acréscimo, a LMX modera a relação entre o stress percebido e o burnout e as suas três dimensões de tal forma que a relações se tornam mais fracas para os profissionais das saúdes que têm maior LMX. Os resultados deste estudo facultam um entendimento complementar útil para a investigação sobre o stress percebido nas profissionais da saúde e para melhor gerir o burnout profissionais da saúde na China.