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1
Ade-Ademilua, Omobolanle Elizabeth. "Plastochron index - an indicator of plant structure and function a case study using Pisum sativum L". Thesis, Rhodes University, 2006. http://hdl.handle.net/10962/d1003751.
Testo completoAbstract (sommario):
The use of chronological age for example, using days after sowing (DAS), or days after germination (DAG) as a time variable may result in the inherent variability between plants resulting in differences which can be large enough to obscure subtle developmental trends that become evident among plants sown at the same time. An alternative to DAS or DAG is the plastochron index (PI), first used by Erickson and Michelini (1957) as a morphological time scale and numerical index; which to according to the authors suggested and represented a more accurate reflection of the developmental status of a plant. The research presented in this thesis was therefore aimed specifically at utilizing the index in qualitative and quantitative analyses, to confirm its usefulness in analyzing and predicting plant growth and development. Specifically this research focused on investigating various morphological and physiological events that together, hopefully, would serve as a template for the prediction of the growth, development and reactions of Pisum sativum L. to different growth conditions. In Chapter 3, the use of the average length of the first pair of leaflets on each node as a suitable parameter for calculating PI in P. sativum is suggested. The results presented in Chapter 3 suggest that plant age is best expressed using the plastochron index, as this reflects the time interval between the initiations of successive pairs of leaflets. This section of the research has been published as “Ade-Ademilua OE, Botha CEJ (2005) A re-evaluation of plastochron index in peas - a case for using leaflet length. South African Journal of Botany 71: 76-80”. The PI formula developed was subsequently used in this research to conduct qualitative and quantitative investigations of plant growth and development in which all data and observations were related directly to the plastochron index. In Chapter 4, the sink to source transition in Pisum sativum L. leaves at different plastochron ages in nodulating plants was investigated using the phloem-mobile fluorescent marker, 5,6-carboxyfluorescein (5,6-CF). The results demonstrated that young leaves remained strong sinks up until LPI 0, after which sink-source transition occurred up to LPI 1.8 and leaflets transitioned to strong source systems by LPI 2.0. A well-developed cross-connected phloem system between paired leaflets in peas, and the petiole and the stem vascular supply was observed. The data presented in the second part of Chapter 4 suggest that the phloem transport between leaflet pairs is independent of the sink/source state of the leaflets, or of movement along the source to sink gradient. The data support the presence of a modular transport system which may ensure re-allocation and balancing between leaflets of the same physiological age and photosynthetic and transport status, thereby load-balancing the local transport system, before exporting to other younger (sink) regions. The investigation of leaf development using the plastochron index (Chapter 5) revealed that the formation of air spaces in the palisade and spongy mesophyll, one of the preparatory events for transition from sink to source state in developing leaves, occurs between LPI 0 and LPI 1 in pea leaflets. Results of the anatomical and ultrastructural study related to PI are presented in Chapter 5. The density of wall ingrowths in transfer cells of minor veins increased with LPI and appeared to be associated with the probable transition to source state and the related potential increase in the production of assimilates for export. The onset of wall ingrowth development in leaflets at LPI 0 provided evidence that sink-to-source transition commences at LPI 0 in P. sativum. Presumably-functional plasmodesmata as well as a few mature sieve elements were evident in class IV veins in the apical region of young and older leaflets at LPI 0. The number of mature sieve elements per vein however, increased with increasing LPI. Most class V veins were still undergoing division at LPI 0 and their sieve elements did not show signs of maturity until LPI 1. The increase in the number of mature metaphloem sieve elements in young, supposedly importing tissue at LPI 0 to older, supposedly exporting tissues at LPI 2 is evidence of the association between phloem maturation and transition from importing to exporting status. In Chapter 6, I report on the effects of elevated CO[subscript 2] on the growth and leaf development of nodulating and non-nodulating Pisum sativum L var. Greenfeast grown under controlled environment of the same nitrogen (6mM) and nitrogen- free nutrient solution conditions. Shortterm exposure to elevated CO[subscript 2] induced rapid plant growth, irrespective of treatment. However, long-term elevated CO[subscript 2] treatment did not affect rate of leaf appearance (RLA) in nodulated plants, irrespective of mineral N supply but enhanced RLA in non- nodulating plants supplied with mineral N. Supplied N resulted in a significant increase in leaflet elongation rate (LfER) under both ambient and elevated CO[subscript 2], but LfER was not significantly affected by nodulation but was increased by high CO[subscript 2]. This suggested that the growth of nodulating P. sativum L may not be significantly affected under CO[subscript 2] levels as high as 1000 μmol mol[superscript -1]. The data suggest that elevated CO[subscript 2] will enhance canopy size, provided adequate soil N is available and more so in non-nodulating plants. This section of the research has been published as “Ade-Ademilua OE, Botha CEJ (2004) The effects of elevated CO[subscript 2] and nitrogen availability supersedes the need for nodulation in peas grown under controlled environmental conditions. South African Journal of Botany 70: 816 – 823”. This thesis demonstrates that the similarity in the qualitative analyses results obtained from plants from different CO[subscript 2], nitrogen and nodulation treatment conditions, highlights the fact that plants of same PI value are at the same developmental state, irrespective of the growth condition. Furthermore, changes in plant structure and function observed under different growth conditions can be related simply to changes in plastochron index. The work presented in this thesis demonstrate that changes in plant structure and function analyzed are related to changes in PI. An important finding of this thesis is that with the use of PI, results can be compiled as a template for predicting the structure- function state of pea plants at any plastochron age, under any growth conditions, before using small representative sample populations.
2
Herdina. "Studies of nodulation, nodule function, and nitrogen fixation of Vicia faba L. and Pisum sativum L". Title page, contents and summary only, 1987. http://web4.library.adelaide.edu.au/theses/09PH/09phh541.pdf.
Testo completo
3
Doulis, Andreas G. "Antioxidant responses of pea (Pisum sativum L.) protoplasts". Diss., This resource online, 1994. http://scholar.lib.vt.edu/theses/available/etd-09192008-063125/.
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4
McCune, Letitia M. "Characterization of galactolipid synthesis in pea root plastids". Thesis, McGill University, 1995. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=22858.
Testo completoAbstract (sommario):
The capacity of pea root plastids for galactolipid synthesis was investigated utilizing radiolabelled acetate and UDP-galactose. Galactolipid biosynthesis was completely dependent on an exogenous supply of UDP-galactose. UDP-galactose stimulated both total lipid biosynthesis from acetate and the proportion of radioactivity accumulated in monogalactosyldiacylglycerol (MGDG). The proportion of MGDG synthesized was saturated at 30$ mu$M UDP-galactose and represented approximately 30% of the total lipid radioactivity after a one hour incubation. However, total lipid biosynthesis continued to increase with concentrations of UDP-galactose up to 75$ mu$M while the proportion of radioactivity in MGDG remained at 30%. MGDG biosynthesis was always accompanied by a corresponding decrease in the amount of diacylglycerol (DAG) accumulated. Digalactosyldiacylglycerol (DGDG) synthesis was not routinely observed in these experiments. These results suggest that the in vitro pathway for MGDG synthesis in the root plastids of pea (an 18:3 plant) is similar to 16:3 plants (FFA's$ to$PA$ to$DAG$ to$MGDG). The endogenous lipids, consistent with the thought of pea as an 18:3 plant, contained 80% C$ sb{18}$ in the fatty acids of MGDG, DGDG, TG and PC. However, in labelled acetate experiments palmitate was the predominately labelled fatty acid in all lipids except PC (where 80% was 18:1). The precursors PA and DAG had ratios of 16:0, 18:0, and 18:1 similar to that of MGDG. 70-80% of the label was associated with the sn-2 position of glycerolipids. The cofactors required for fatty acid synthesis were generally not as required for galactolipid synthesis. The results suggest that galactolipid synthesis relies primarily on endogenous DAG and only partly involves de novo fatty acid synthesis. (Abstract shortened by UMI.)
5
Xue, Lingru. "Glycerolipid biosynthesis in pea root plastids". Thesis, McGill University, 1993. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=26186.
Testo completoAbstract (sommario):
Pea root plastids were isolated by differential centrifugation and resulting crude plastid fraction was purified by centrifugation through 10%(v/v) Percoll. Marker enzymes indicated that greater than 50% of the plastids were recovered essentially free from mitochondrial and endoplasmic reticulum contamination. The optimum in vitro conditions for glycerolipid biosynthesis from (U-$ sp{14}$C) glycerol-3-phosphate have been determined. Total glycerolipid biosynthesis was approximately 15 nmole/hr/mg protein in the presence of 200 $ mu$M glycerol-3-phosphate, 0.5 mM each of NADH and NADPH, 15 mM KH$ sb2$CO$ sb3$, 0.05 mM CoA, and 2 mM each of ATP and MgCl$ sb2$, 100 mM Bis Tris Propane (pH 7.5) and incubated at the standard temperature of 25$ sp circ$C. ATP, Coenzyme A and a divalent cation are absolutely required for glycerolipid biosynthesis, whereas reduced nucleotides and bicarbonate improve the synthesis to varying degrees. Dihydroxyacetone phosphate had little effect, while dithiothreitol, detergent and Mn$ sp{2+}$ inhibited activity. Under the optimum conditions, isolated pea root plastids mainly synthesized approximately 15% phosphatidic acid, 16% phosphatidylcholine, 13% phosphatidylglycerol, 32% triacylglycerol. Galactolipid synthesis occurred only when UDP-galactose was supplied. Different concentrations of some cofactors resulted in alterations of glycerolipid distribution. Phospholipase A$ sb2$ and Rhizopus lipase digestions of phospholipids and neutral lipids revealed that radioactive fatty acids were preferentially esterified to position sn 2 of each glycerolipid with generally 2-4 times as much radioactivity as position sn 1. Pea root plastids are composed of approximately 62% phospholipid, 24% neutral lipid and 14% glycolipid. Within these classes PG, TAG, and the galactolipids are the major components representing 24, 12, and 12% of the total plastid lipids.
6
Qi, Qungang. "The role of glycolytic metabolism in fatty acid and glycerolipid biosynthesis in pea root plastids". Thesis, McGill University, 1995. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=39980.
Testo completoAbstract (sommario):
The interaction between the glycolytic metabolism and fatty acid and glycerolipid biosynthesis in pea root (Pisum sativum L.) plastids was assessed in this study. When various glycolytic intermediates were used to substitute for the APT requirement for fatty acid synthesis from acetate, phosphoenolpyruvate, 2-phosphoglycerate, fructose-6-phosphate and glucose-6-phosphate each gave 48, 17, 23 and 17%, respectively, of the ATP-control activity. Similarly, in the absence of exogenously supplied ATP, the optimized triose-phosphate shuttle, which consists of 2 mM dihydroxyacetone phosphate, 2 mM oxaloacetic acid and 4 mM inorganic phosphate, gave up to 44% the ATP-control activity in promoting fatty acid synthesis from acetate. These results suggest that 3-phosphoglycerate kinase and pyruvate kinase in these plastids can function in intraplastidic ATP production through substrate level phosphorylation. However, in all cases, exogenously supplied ATP gave the greatest rates of fatty acid and glycerolipid synthesis. Radiolabeled pyruvate, glucose, glucose-6-phosphate, and malate in comparison to acetate were all variously utilized for fatty acid and glycerolipid biosynthesis by the root plastid. At the highest concentrations tested (3-5 mM), the rates of incorporation of pyruvate, glucose-6-phosphate and acetate into fatty acids were 183, 154, 125 nd 99 nmol $ rm cdot h sp{-1} cdot mg sp{-1}$, respectively. Malate was the least effective precursor, giving less than 55 nmol $ rm cdot h sp{-1} cdot mg sp{-1}$. Acetate incorporation was approximately 55% dependent on exogenously supplied reduced nuclotides (NADPH and NADH), whereas the utilization of the remaining precursors was only approximately 10-20% dependent on NAD(P)H. These results indicate that the entire pathway of carbon flow from glycolysis, including pyruvate dehydrogenase (PDHase), to fatty acids is operating in pea root plastids. Further, the intraplastidic glycolytic pathway plays an important role in provi
7
Li, Hongping 1967. "Developmental relationships in the function of pea root plastids". Thesis, McGill University, 2000. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=30823.
Testo completoAbstract (sommario):
Germinating pea (Pisum sativum L.) roots were divided into five sequential 0.5 cm segments from the root tip. Pooled segments were analyzed for their protein, starch and lipid content as an indirect indication of plastid function. Fresh weights of root segments were lowest in the tips (4.45mug per segment) and progressively higher up to the fifth segment (11.09mug per segment). Total protein, starch and lipid content, on a per segment basis, were all highest in zone 1 (tip segment) and progressively lower up to zone 5. Plastids were isolated from each of the five root segments and analyzed for their capacity for lipid biosynthesis under several different in vitro conditions. Collectively, the observations presented here suggest that the relative contributions of plastids to the overall physiology of germinating pea roots gradually diminishes as root development proceeds, and that plastids isolated from progressively older root zones have increased capacity for glycolytic and/or pentose phosphate metabolism. (Abstract shortened by UMI.)
8
Stahl, Richard J. (Richard John). "Fatty acid and glycerolipid biosynthesis in pea root plastids". Thesis, McGill University, 1990. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=22389.
Testo completoAbstract (sommario):
Fatty acid biosynthesis from (1-$ sp{14}$C) acetate was optimized in plastids isolated from primary root tips of 7-day-old germinating pea seeds. Fatty acid synthesis was maximum at 82.3 nmol/hr/mg protein in the presence of 200$ mu$M acetate, 0.5mM each of NADH, NADPH and CoA, 6mM each of ATP and MgCl$ sb2$, 1mM each of MnCl$ sb2$ and glycerol-3-phosphate (G3P), 15mM KHCO$ sb3$, and 0.1M Bis tris propane, pH 8.0 incubated at 35C. At the standard incubation temperature of 25C, fatty acid synthesis was linear for up to 6 hours with 80 to 120 $ mu$g/ml plastid protein. ATP and CoA were absolute requirements, whereas divalent cations, potassium bicarbonate and reduced nucelotides all improved activity by 2 to 10 fold. Mg$ sp{2+}$ and NADH were the preferred cation and nucleotide, respectively. G3P and dihydroxyacetone phosphate had little effect, and dithiothreitol and detergents generally inhibited incorporation of $ sp{14}$C-acetate into fatty acid.Glycerolipid synthesis was obtained from $ sp{14}$C-acetate, (U-$ sp{14}$C) G3P and (U-$ sp{14}$C) glycerol at relative rates of 3.7:1.0:0.1, respectively. (Abstract shortened by UMI.)
9
Saquet, Adriano Arriel. "Physiology and biochemistry of Rocha pear during ripening and long-term controlled atmosphere storage". Doctoral thesis, ISA, 2017. http://hdl.handle.net/10400.5/14943.
Testo completoAbstract (sommario):
Doutoramento em Engenharia Agronómica - Instituto Superior de AgronomiaLong-term storage of pears is a challenge in the absence of treatment with diphenylamine, due to the development of physiological disorders. Aspects of the ripening physiology and biochemistry of pears, particularly those treated with the ethylene action inhibitor 1-methylcyclopropene, also remain unknown. The aims of this thesis were to map the gradients of adenylate nucleotides and energy charge in the fruit and their changes during fruit ripening and storage period, to compare instrumental and sensory assessments of ripening, to relate the fruit mineral composition to the development of internal storage disorders and determine the optimal storage conditions for long-term storage of ‘Rocha’ pear under controlled atmosphere. Significant radial gradient in energy charge from the skin tissues to the fruit center may be related to internal storage disorders. Significant radial gradients in Ca and B decreasing from the skin tissues toward the fruit center were also consistent with the location of internal storage disorders. However, ‘Rocha’ pear were able to adjust the energy charge during ripening and long-term storage even under low respiration rates induced by 1- methylcyclopropene treatment or low oxygen partial pressure. ‘Rocha’ pear was able to ripen immediately after harvest without chilling or exogenous ethylene application. ‘Rocha’ pear tolerated extremely low 0.5 kPa O2 during 257 d storage without developing storage disorders and kept acceptable firmness and skin color after 7 d shelf life. The 46 d delay in the pull down of O2 partial pressure was detrimental to quality maintenance of ‘Rocha’ pear during long-term controlled atmosphere storage
N/A
10
Lomas, Caroline Anne. "The effect of supplementary light on the behaviour, physiology and productivity of cattle". Thesis, Bangor University, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.239841.
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Bentley, David J. "Measurement of peak power output and the lactate threshold : significance for endurance cycling performance". Thesis, University of Bath, 2002. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.250852.
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Sevean, Sophie. "Propriétés biomécaniques de la peau". Paris 5, 1988. http://www.theses.fr/1988PA05P093.
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Synesius, Marie-Claude. "Peau noire et cosmétologie". Lille 2, 1995. http://www.theses.fr/1995LIL2P117.
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14
Rolland, Marie-Claire. "La peau humaine dans la litterature romaine : physiologie, pathologie, thérapeutique, esthétique, sémiologie". Thesis, Rennes 2, 2018. http://www.theses.fr/2018REN20022.
Testo completoAbstract (sommario):
Cette étude s’attache à l’observation et l’analyse des représentations de la peau humaine dans les textes latins des débuts de la littérature romaine (IIème s. av. J.-C.) à l’apogée de l’Empire romain (IIème s. apr. J.-C.). A la suite d’une recherche lexicale et sémantique approfondie sur le vocabulaire explicite de la peau, le thème de la peau est étudié à travers plusieurs champs disciplinaires permettant d’aborder les évocations implicites de la peau, son vocabulaire, ses images et ses significations. L’étude de la physiologie de la peau, appuyée sur l’héritage grec, permet d’en poser une définition chez les Romains, par sa nature, ses fonctions, ses transformations. Peu représentée à l’état normal et sain, la peau est soumise à de multiples violences et maux. L’analyse de la traumatologie de la peau, à travers les poèmes épiques, et de ses pathologies, évoquées dans le Traité de la médecine de Celse, donnent à voir une peau maltraitée, aux blessures fatales, mais d’une importance capitale dans le diagnostic clinique, permettant de jauger la santé – et surtout la maladie – du corps dans son ensemble. Les soins de la peau, thérapeutiques – pour la guérir, chez Celse –, cosmétiques ou commotiques – pour l’entretenir ou la masquer, chez Pline l’Ancien –, s’imposent à la peau, la malmènent eux aussi bien souvent. À côté de cette peau dégradée, coexiste la peau idéale de la poésie amoureuse, à voir et à toucher, entre esthétique et érotique. Enfin, la peau apparaît comme une interface qui transmet à la société romaine des signes selon des critères géographique, sociaux, biographiques, moraux et psychologiques. Elle signale l’appartenance de l’individu à un groupe et définit son identité dans ce groupeThe aim of this thesis is to observe and analyse representations of human skin in Latin literature from the 2nd century B.C. to the 2nd century A.D. Starting with a detailed lexical and semantic study of the vocabulary pertaining to the skin, the notion of skin is examined in various fields, allowing us to address implicit allusions to skin along with the associated vocabulary, images and meanings. A physiological approach, based on anatomical knowledge inherited from Greek philosophers, brings us to a definition of normal skin in terms of its nature, functions and changes. Rarely represented in its normal, healthy state, skin is subject to assaults and ill health in various ways. Analysing skin trauma in epic poems and skin pathology, which is referred to in Celsus’ De Medicina, reveals a prevailing representation of damaged and even fatally wounded skin, this being of utmost importance in clinical diagnosis, a means of measuring the health - and particularly illness - of the body as a whole. Therapeutics and cosmetics, in Celsus’ texts, aim to heal whereas in Pliny’s Naturalis Historia, the aim is to care for and mask imperfections. These often cause as much harm to the skin as good. This damaged skin coexists with ideal skin, mainly in elegiac poetry, a skin meant to be seen and touched, from an aesthetical and erotic perspective. Finally, human skin in Roman society acts as an interface, indicating to which social group anindividual may belong as much as one’s identity within that group, according to ethnical, social, biographical, moral and psychological criteria
15
Callahan, Zachary. "The Effect of Varying Cadence in Cycle Ergometry on Submaximal Predictions of Peak Oxygen Uptake". TopSCHOLAR®, 2006. http://digitalcommons.wku.edu/theses/445.
Testo completoAbstract (sommario):
The purpose of this study was to investigate the effect that varying cadence had on the ability of a submaximal cycle ergometry test to accurately predict peak oxygen uptake (VO2) using the standard YMCA protocol workloads. There has been limited scholarship investigating the effect that varying cadence has on trained cyclists and almost none on untrained participants. For this study twelve moderately healthy participants (age: 20.75 ± 1.87, body fat: 15.8 ± 4.91 %) who did not use cycling as part of their workout regime performed a peak VO2 cycle test and three randomized submaximal tests. The three submaximal tests followed the standard YMCA protocol except the cadence was increased to 70 rpm for one and 90 rpm for the other. Heart rate and RPE data were gathered every minute and upon completion of the submaximal tests, and a linear analysis was performed using age predicted maximal heart rate to estimate peak VO2 which was subsequently compared to measured VO2 peak obtained during maximal test to determine variability and error. Bland-Altman plot analysis revealed the standard YMCA protocol of 50-rpm underestimated 67.5% of the participant's predicted peak VO2 scores with large variability in all predictions with a standard deviation of 0.844 liters/minute. The 70-rpm protocol underestimated all predicted peak scores by an average of 19% with a standard deviation of 0.40 liters/minute. Just as the 50-rpm protocol, the 90-rpm protocol showed large variability with 75% of the predicted scores being underestimated and the standard deviation was 0.76 liters/minutes. This data demonstrates that varying cadence has a large effect on the ability of submaximal tests to accurately predict peak VO2 and further scholarship should be performed to determine other possible improvements in protocols to increase the validity and accuracy of submaximal tests.
16
Molès, Jean-Pierre. "Le gène TP53 et la physiologie cutanée". Montpellier 1, 1993. http://www.theses.fr/1993MON1T018.
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Zhou, Wen Xu. "Two-peak resonance of swimbladders in fish (acoustic measurement and analytical model)". Thesis, Georgia Institute of Technology, 1992. http://hdl.handle.net/1853/17504.
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Buchner, Sonya. "Coating of pears (var. 'Packhams Triumph') with Kafirin protein and its effect on postharvest physiology and shelf-life". Pretoria : [s.n.], 2006. http://upetd.up.ac.za/thesis/available/etd-07142008-140850.
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Nielsen, Corey Michael. "The Effect of Normobaric Hypoxia on Power Output During Multiple Wingate Anaerobic Tests". Kent State University / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=kent1490258656616795.
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Carpentier, Emmanuel. "Les huiles essentielles et la peau". Lille 2, 1996. http://www.theses.fr/1996LIL2P028.
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Sandberg, John B. "Acute Effects of Antagonist Stretching on Jump Height and Knee Extension Peak Torque". DigitalCommons@USU, 2012. https://digitalcommons.usu.edu/etd/1156.
Testo completoAbstract (sommario):
A great deal of research has shown decrements in force and power following static stretching. There has been little research investigating the acute effects of static stretching of the antagonist on the expression of strength and power. The purpose of this study was to investigate the effects of static stretching of the antagonist muscles on a variety of strength and power measures. Sixteen active males were tested for vertical jump height and isokinetic torque production in a slow knee extension (KES) at 60°/s and a fast knee extension (KEF) at 300°/s. Electromyography was taken during knee extension tests for the vastus lateralis and the biceps femoris muscles. Participants performed these tests in a randomized counterbalanced order with and without prior antagonist stretching. All variables for stretching and non-stretching treatments were compared using paired t tests at an alpha of .05. Paired samples t tests revealed a significant (p = .034) difference between stretch KEF and non-stretch KEF conditions. There was no significant (p > .05) difference between KES stretch and non-stretch conditions. Vertical jump height was significantly (p = .011) higher for the stretching treatment than the non-stretching treatment. Vertical jump power was also significantly higher (p = .005) in the stretch versus the non-stretch condition. Paired samples t test indicated no significant (p > .05) difference between testing conditions for electromyography, represented as a percentage of maximal voluntary contraction (MVC). These results suggest that stretching the antagonist hamstrings prior to high speed isokinetic knee extension increases torque production. It also demonstrated that stretching the hip flexors and dorsi flexors may enhance jump height and power. Practitioners may use this information to acutely enhance strength and power performances.
22
Burger, G. E. (Gerrit Erasmus). "Factors affecting shrivelling and friction discolouration of pears (Pyrus communis L. )". Thesis, Stellenbosch : University of Stellenbosch, 2005. http://hdl.handle.net/10019.1/16264.
Testo completoAbstract (sommario):
Thesis (MScAgric)--University of Stellenbosch, 2005.ENGLISH ABSTRACT: Shrivelling and friction discolouration (FD), as postharvest disorders, negatively influence the marketability and potential shelf life of pears. By investigating the contributing factors in each of the disorders, the potential involvement of handling and storage variables were determined. This allowed for a better understanding of the responsible factors that create susceptible environments for these disorders to occur. From the moment that pears are harvested they lose weight by means of transpiration and, to a lesser extent, respiration. When excessive losses are experienced, the fruit will appear shrivelled and the marketability and shelf life are negatively influenced. By minimizing the rates of weight loss, the occurrence of shrivelling among pears during the postharvest handling can be lessened. The periods that proved to be most conducive to shrivelling (during a simulated postharvest handling duration) were where temperatures above 0 °C were experienced. These short periods proved more perilous for shrivelling than lengthy storage durations at low temperatures. This influenced the transpiration rate in such a way that the driving force accelerated the rate of weight loss in all the cultivars that were studied. Removing field heat from fresh produce and maintaining the cold chain reduces the driving force behind the transpiration of the pears. In all the cultivars studied, ‘Packham’s Triumph’, ‘Beurrè Bosc’ and ‘Forelle’, smaller and less mature fruit were more inclined to appear shrivelled. The surface area to volume ratio is fundamental in determining the rate of weight loss. This was most evident in ‘Beurrè Bosc’. Although no reproducible results could be obtained from the morphological studies, literature has attributed this phenomenon to the composition and quantity of the cuticle layer. Reduction of weight loss was obtained by sealing of the fruit stem. This obstructed water movement from the fruit through the xylem conducting tissue to the surrounding atmosphere. Not only did the stem appear greener and fresher, but less weight loss and subsequent shrivel was noticeable in the treated fruit. This effect was most evident in ‘Packham’s Triumph’ and ‘Beurrè Bosc’, but not in ‘Forelle’. ‘Forelle’ typically has a very short, thin stem in comparison to the other two cultivars.All the cultivars showed visual shrivel symptoms after 11 days at 18 °C. Rate of weight loss was the lowest in ‘Packham’s Triumph’, but due to its prominent dimensions, it appeared shrivelled before any of the other cultivars. ‘Beurrè Bosc’ lost weight at the highest rate (0.42%.day-1). As fruit injury, in the presence of oxygen, is inevitable, the oxidative enzymatic browning of pears will always be troublesome. This defensive mechanism partially prevents the infection of the fruit where epidermal cells are injured. To minimize FD, impact and frictional forces need to be lower during both harvesting and handling practices. A laboratory scale method was developed through which reproduceable treatments could be performed, thereby subjecting the fruit to industry related friction, rather than impact, injury. By assessing the discolouration in terms of both extent and intensity, the influence of variables could be determined on both ‘Packham’s Triumph’ and ‘Doyenne du Comice’ pears. As also found in practice, ‘Doyenne du Comice’ proved to be far more susceptible to FD than ‘Packham’s Triumph’, although the activity of the enzyme, polyphenol oxidase (PPO) was found to be higher in the latter. Although no significant difference was found between the FD encountered at fruit temperature of 3 °C and 15 °C, discolouration was greater at the higher temperature. This might be attributed to a greater degree of water loss, lower cell turgidity or higher enzyme activity. Thus, fruit taken from storage and sorted directly thereafter will exhibit less FD. The contribution of condensation forming on the fruit, acting as lubrication, cannot be ignored. Such fruit, with high turgor pressure, might again be more susceptible to bruising which will only be revealed well after the injury. Since enzymes, which include PPO, catalyse biochemical reactions, the availability of sufficient substrate most probably regulates the extent of this biochemical discolouration. Harvesting at optimum maturity and preventing any unnecessary friction will most definitely reduce the occurrence of FD. The ultimate challenge remains to optimize sorting and packing conditions without compromising on fruit quality.
AFRIKAANSE OPSOMMING: Verrimpeling en friksie verbruining (FV), as na-oes defekte, het ’n negatiewe invloed op die bemarkbaarheid en potensiële raklewe van pere. Hierdie studie het die bydraende faktore vir elkeen van die defekte ondersoek. Daar is gepoog om die effek van verskillende hanteringsen opbergingsmetodes op bogenoemde defekte te bepaal. ‘n Beter begrip is verkry van die oorsaaklike faktore wat bydra tot die ontstaan van die betrokke defekte. Direk na die oes van pere, begin die vrug gewig verloor as gevolg van veral transpirasie. Oormatige verliese sal lei tot ’n vrug wat verrimpeld voorkom, met ‘n negatiewe invloed op die bemarkbaarheid en raklewe daarvan. Die voorkoms van die verrimpeling van pere tydens die na-oes hantering van die vrugte, kan verminder word deur vermindering van die tempo van gewigsverlies. Die periodes waartydens die verrimpeling veral voorgekom het, (soos gevind in ’n gesimuleerde na-oes hanteringsmodel) was wanneer temperature bo 0 °C ondervind is. Sulke kort periodes was meer geneig om aanleiding te gee tot verrimpeling as die verlengde periodes van opberging by lae temperature. Sulke periodes van hoër temperature het gelei tot versnelde transpirasie en ’n versnelde tempo van gewigsverlies in al die kultivars wat ondersoek is. Die transpirasietempo van pere kan verlaag word deur die verwydering van veld-hitte en deur die streng behoud van die koue-ketting. In al die kultivars wat ondersoek is, ‘Packham’s Triumph’, ‘Beurrè Bosc’ en ‘Forelle’, is gevind dat die kleiner en minder volwasse vrugte meer geneig was tot verrimpeling. Die oppervlak area tot volume verhouding is krities in die bepaling van die tempo van gewigsverlies. Hierdie bevinding was die prominentste in ‘Beurrè Bosc’. Alhoewel geen beduidende resultate verkry kon word van die morfologiese studies nie, is daar verskeie verwysings in die literatuur wat hierdie verskynsel toeskryf aan die samestelling en hoeveelheid van die kutikula laag. Vermindering van gewigsverlies is verkry deur verseëling van die vrugtestingel. Hierdie tegniek het gelei tot ’n blokkering van die watervloei van die vrug na die omgewing deur die xileem weefsel. Verseëling van die stingel het dit groener en varser laat voorkom, en het ook ’n merkbare vermindering in gewigsverlies en die daaropvolgende verrimpeling tot gevolg gehad. Die effek van stingel-verseëling was die prominentste in ‘Packham’s Triumph’ en‘Beurrè Bosc’. Dit was minder duidelik in ‘Forelle’ wat tipies gekenmerk word deur ‘n baie korter, dun stingel in vergelyking met die ander twee kultivars. Al die kultivars het makroskopiese verrimpeling getoon na ‘n opbergingperiode van 11 dae by 18 °C. Die tempo van gewigsverlies was die laagste in ‘Packham’s Triumph’ alhoewel dit eerste verrimpeld voorgekom het. Dit kan toegeskryf word aan die spesifieke afmetings van hierdie betrokke kultivar. ‘Beurrè Bosc’ het vinnigste gewig verloor (0.42%.dag-1). Aangesien die besering van vrugte, in die aanwesigheid van suurstof, onvermydelik is, sal oksidatiewe, ensiematiese verbruining van pere altyd problematies wees. Hierdie verdedigingsmeganisme voorkom tot ’n mate die infeksie van die vrug wanneer epidermale selle beskadig word. FV kan beperk word deur die vrugte tydens oes en hanteringsprosedures so min as moontlik bloot te stel aan impak en friksie kragte. ’n Laboratorium-model is ontwikkel ter nabootsing van die omstandighede in die industrie. Die vrugte is aan friksie, eerder as impak, onderwerp, soos ondervind in die industrie. Die omvang asook die intensiteit van die verbruining is gemeet in beide ‘Packham’s Triumph’ en ‘Doyenne du Comice’ pere. Op hierdie wyse kon die invloed van die onderskeie veranderlikes in elke kultivar bepaal word. Alhoewel die ensiematiese aktiwiteit van die polifenol oksidase ensiem (PFO) die hoogste in ‘Packham’s Triumph’ was, is gevind dat ‘Doyenne du Comice’ veel meer geneig was tot FV as ‘Packham’s Triumph’. Hierdie bevinding bevestig die verskynsel soos in die praktyk gevind. Alhoewel geen betekenisvolle verskil gevind is tussen FV by vrug temperatuur van 3 °C en 15 °C nie, was daar meer verbruining by die hoër temperatuur. Hierdie verskynsel kan toegeskryf word aan ’n groter mate van waterverlies, laer sel turgiditeit en hoër ensiem aktiwiteit. Dus sal vrugte wat direk na opberging gesorteer word, minder FV toon. Die bydrae van die kondensasie wat op die vrug vorm, en as ’n smeermiddel dien, kan nie geïgnoreer word nie. Sulke vrugte met hoër turgiditeit, mag egter meer vatbaar wees vir kneusing, wat egter eers ’n geruime tyd na die kneusing tevoorverskyn mag kom. Aangesien ensieme, wat PFO insluit, as katalis dien in biochemiese reaksies, sal die beskikbaarheid van voldoende substraat, na alle waarskynlikheid die omvang van die biochemiese verkleuring reguleer.Die oes van pere tydens optimum volwassenheid, en die voorkoming van onnodige friksie sal definitief die voorkoms van FV verminder. Die uitdaging is steeds om sortering- en verpakkingstegnieke verder te verfyn sonder om ’n negatiewe invloed op vrugtekwaliteit te hê.
23
Marty, Janelise. "Les moyens d'exploration de la microcirculation cutanée". Montpellier 1, 1992. http://www.theses.fr/1992MON11132.
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24
Temeghe, Laurice. "Les lipides épidermiques". Paris 5, 1998. http://www.theses.fr/1998PA05P051.
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25
Coulomb, Bernard. "Reconstruction in vitro d'une peau humaine vivante : modèle d'étude de la physiologie, de la physiopathologie et de la pharmacologie cutanée : applications thérapeutiques". Paris 11, 1988. http://www.theses.fr/1988PA112022.
Testo completoAbstract (sommario):
Le développement d'une peau humaine vivante in vitro aboutit à un modèle d'étude original de la biologie cellulaire au niveau d'un tissu ou d'un organe dont les associations cellules-cellules, ou cellules-matrice sont définies. De plus, la reconstruction d'une peau humaine est d'un intérêt primordial pour la couverture des grands brûlés. La peau équivalente, réalisée avec des cellules humaines normales ou pathologiques, est reconstruite en deux temps: le premier conduit à un derme équivalent, le second consiste à recouvrir ce derme équivalent par un épiderme. Cette peau permet non seulement l'étude de chacun de ces deux tissus, mais aussi l'étude des interactions dermo-épidermiques. Le derme équivalent est déjà par lui-même un modèle d'étude original. En effet, les fibroblastes cultivés en trois dimensions dans une matrice de collagène ont une différenciation proche de celle qu'ils ont in vivo. De plus, il est possible d'évaluer quantitativement des fonctions cellulaires qui ne peuvent pas être abordées dans d'autres systèmes de culture (telle que la contraction des fibroblastes), et de moduler ces fonctions par des agents pharmacologiques. L'utilisation de petites biopsies cutanées comme source d'épidermisation des dermes équivalents permet d'obtenir un épiderme proche de celui existant in vivo, et d'évaluer quantitativement la croissance et la différenciation épidermique. Mais l'intérêt majeur de cette peau vivante reconstruite est d'être modulable, tant au niveau des constituants du derme et de l'épiderme, qu'au niveau des associations dermo-épidermiques qu'elle autorise. Ainsi nous avons pu identifier différentes fonctions des fibroblastes normaux qui conduisent à favoriser l'épidermisation, et démontrer que des fibroblastes psoriasiques sont capables de stimuler de façon excessive la croissance de kératinocytes normaux. Ce modèle permettant l'étude des interactions dermo-épidermiques est un outil important pour la pharmacologie, car il permet d'identifier l'influence d'un agent pharmacologique sur chacun des deux tissus. Cette peau équivalente vivante est greffable chez l'homme. Son principal avantage est d'apporter, en même temps qu'une couverture épidermique, un tissu conjonctif dont la présence semble indispensable pour les qualités de la greffe à long terme.
26
Sherriff, C. "Physiologic specialization of the downy mildew fungus, Peronospora parasitica (Pers. Ex. Fr.)Fr., on Brassica crop species". Thesis, University of Nottingham, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.373340.
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27
Castel, Philippe. "La biométrologie cutanée : étude de la taille des kératinocytes". Toulouse 3, 1993. http://www.theses.fr/1993TOU32083.
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28
Swisher, Ann Marie, Jenna M. Kraska, Michael W. Ramsey, Keith B. Painter, C. Gooden, Andrew S. Layne, William A. Sands et al. "The Relationship of Peak Isometric Strength to Peak Aerobic Power and 3000 M Performance in Cross-country Runners". Digital Commons @ East Tennessee State University, 2008. https://dc.etsu.edu/etsu-works/4095.
Testo completoAbstract (sommario):
Certain variables: peak aerobic power (PAP), running economy, and lactate threshold, act as limiting factors for endurance running. However, all of the mechanisms underlying high-level endurance running are not completely clear. Alterations in maximum and explosive strength P27 have been shown to effect positive changes in endurance performance, likely by altering P28 running economy. If strength related factors affect running economy, then this should be evident in the running performance of long-distance runners and perhaps PAP. The purpose of this study was to examine the relationships between peak isometric strength (IPF), explosive strength (rate of force development, RFD), PAP and 3 k performance (3KT) among 5 female and 7 male (n = 12) X-country runners. Force-time curve analysis was conducted for each (2 trials) isometric pull and averaged for analyses. IPF and RFD from 0 - 200 ms were determined from appropriate curves. IPFs were normalized using an allometric (IPFa) scaling equation: absolute force/ (body mass (kg)0.67). ICCs were previously shown to be > 0.9. Relationships were established with Pearson's r; statistical differences with at-Test (p < 0.05). !PF, IPFa and RFD were not different between sexes. PAP was statistically greater in males. Correlations were: PAP vs 3KT (r = -0.92); !PF vs PAP (r = 0.58), 3KT (r = -0.66); IPFa vs PAP (r = 0.45), 3KT (r = 0.45). RFD vs PAP (r = 0.58), 3KT (r = -0.65). Results indicate that strength characteristics correlate moderately to strongly with PAP and 3KT. Data suggests that strong.
29
Ladreit, de Lacharrière Olivier. "Contribution à l'étude des peaux sensibles et réactives : aspects épidémiologiques, cliniques et physiopathologiques". Besançon, 2002. http://www.theses.fr/2002BESA0018.
Testo completoAbstract (sommario):
Exploration des peaux sensibles par des méthodes non-invasives et des tests pharmacologiques, chez 152 femmes âgées de 18 à 60 ans, représentatif des 887 femmes investiguées lors de la phase clinique de l'étude UK1. Variables explorées / méthodes utilisées / zone anatomique : hydratation / Corneometer / joue. - Fonction barrière / perte insensible en eau / joue. - Sébum / Sebutape / front. - Réaction cutanée aux irritants / patch tests / dos. - Test de réactivité au pH / test à l'acide lactique / sillon naso-génien. - Test de réactivité neurogène / test à la capsai͏̈cine / angle de la machoire. (Cf. P. 74)Environ la moitié des femmes et un tiers des hommes déclarent avoir la peau sensible. Celle-ci se définit comme une hyper-réactivité cutanée mettant en jeu des mécanismes non immunologiques. Les individus à peau sensible se plaignent en premier lieu de signes d'inconfort cutané au niveau du visage à type de sensations d'échauffements, de picotements ou de démangeaisons. Selon l'intensité des signes et les facteurs de réactivité cutanés, on peut décrire des peaux très sensibles avec un état d'intolérance parfois extrême de la peau; des peaux sensibles d'intensité modéré provoquées par des facteurs environnementaux ; peaux sensibles d'intensité modéré provoquées par l'application de produits topiques. L'atopie n'apparaît pas être un état de prédisposition conduisant inéluctablement à un état de peau sensible. La peau sensible n'est pas liée à une terrain allergique ni à des mécanismes allergiques. La peau sensible est un désordre cutané d'origine neuro-physiologique impliquant les nerfs sensitifs épidermiques
30
Kinser, Ann Marie. "Vibration and Stretching Effects on Flexibility and Explosive Strength in Gymnasts". Digital Commons @ East Tennessee State University, 2007. https://dc.etsu.edu/etd/2071.
Testo completoAbstract (sommario):
The purpose of this study was to determine the acute effects of stretching and local vibration on flexibility and explosive strength in competitive female gymnasts. Flexibility was measured in the forward-split position and jump characteristics were recorded using a force plate. Analysis included flight time (FT), jump height (JH), peak force (PF), instantaneous forces, and rates of force development (RFDs). Randomly assigned and counterbalanced groups were: simultaneous vibration-stretching (VS) (n=22), stretching-only (n=7), and vibration-only (n=8). VS showed statistically greater measures of flexibility in both the right and left leg, favored and non-favored legs pre- versus post-treatment. Vibration-only group resulted in statistically greater right forward-split flexibility and non-favored leg flexibility. There were no statistical differences in JH, FT, PF, instantaneous forces, or RFDs in the VS, stretching-only, and vibration-only groups' pre- versus post-treatment tests. The conclusion was simultaneous vibration-stretching greatly increased flexibility while not altering explosive strength.
31
Athias, Nicolas. "Méthodes d'analyse physico-chimiques du stratum corneum". Besançon, 1996. http://www.theses.fr/1996BESA3304.
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32
Bessoles, Florence. "Approche analytique des lipides cutanés". Toulouse 3, 1995. http://www.theses.fr/1995TOU32009.
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33
Brunel, Anne-Sylvie. "Etude du renouvellement de l'épiderme". Paris 5, 1994. http://www.theses.fr/1994PA05P218.
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34
Dumont, Valérie. "Développement de méthodes de dosage et de caractérisation de sphingolipides végétaux et microbiens". Toulouse, INPT, 1995. http://www.theses.fr/1995INPT020G.
Testo completoAbstract (sommario):
Des 1991, la moelle epiniere bovine, jusqu'alors source de choix pour l'extraction de sphingolipides destines aux formulations cosmetiques, a ete ecarte. Les recherches se sont alors orientees vers les sources vegetales et microbiennes. La premiere partie de ce travail a consiste en l'etablissement d'une methode de dosage des sphingolipides par l'intermediaire des sphingosines qui sont les structures communes a tous les sphingolipides. Apres hydrolyse des lipides et extractions specifiques, elles sont dosees par chromatographie sur couche mince (ccm) couplee a la densitometrie. Cette methode a ete applique a differentes sources potentielles. Une souche de levure (pichia membranefaciens) a ete retenue. La seconde partie concerne l'optimisation de la production de biomasse en fermenteurs. Dans une troisieme partie l'identification des sphingolipides a ete realisee par ccm. L'etude structurale faisant intervenir des techniques chromatographiques sur colonne ouverte, en phase gazeuse (cpg), cpg couplee a la spectrometrie de masse (ms), et en phase liquide ionique a haute performance (cihp) a permis la proposition d'une formule
35
Raynal, Pierre. "Les lipides du stratum corneum : analyse qualitative". Paris 5, 1997. http://www.theses.fr/1997PA05P173.
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36
Parison, Valérie. "Validation d'une nouvelle méthode de mesure de l'élasticité cutanée : le cutomètre (ND). Application à l'étude de l'effet de l'hydratation sur les propriétés biomécaniques de la peau". Paris 5, 1991. http://www.theses.fr/1991PA05P171.
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37
Salameh, Ahlam. "Graded Exercise Stress Testing: Treadmill Protocols Comparison Of Peak Exercise Times In Cardiac Patients". Akron, OH : University of Akron, 2009. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=akron1249833172.
Testo completoAbstract (sommario):
Thesis (M.S.)--University of Akron, Dept. of Sport Science and Wellness Education-Physical Education, 2009."August, 2009." Title from electronic thesis title page (viewed 10/7/2009) Advisor, Ronald Otterstetter; Committee members, James Rosneck, Laura Richardson; Department Chair, Victor Pinheiro; Dean of the College, Mark D. Shermis; Dean of the Graduate School, George R. Newkome. Includes bibliographical references.
38
Ruffner, Kayla L. "THE EFFECTS OF ESTROGEN PEAKS ON THE STRETCH REFLEX RESPONSE DURING THE MENSTRUAL CYCLE". Cleveland State University / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=csu1579519542553163.
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39
Cunanan, Aaron J., W. Guy Hornsby, Mark A. South, Alex Perkins, Kyle C. Pierce, Kimitake Sato e Michael H. Stone. "Training Implications of Peak Barbell Velocity Differences among Elite Men and Women Weightlifters". Digital Commons @ East Tennessee State University, 2016. https://dc.etsu.edu/etsu-works/5095.
Testo completoAbstract (sommario):
Peak barbell velocity is an important determinant of weightlifting performance 2 . However, direct comparisons of this measure between elite men and women weightlifters is limited 7,8 . Therefore, the present study sought to establish a reference of the current status and trajectory of sexbased peak barbell velocity differences among elite weightlifters. This study examined performances of men and women in the 69 kg weight class in order to obviate the influence of body mass on performance. The purpose of this investigation was to help practitioners identify training needs of elite men and women weightlifters to improve weightlifting performance based upon between-group differences in peak barbell velocity.
40
Saguet, Thibaut. "Le vieillissement cutané : caractérisation des capacités antioxydantes des fibroblastes et des kératinocytes humains en réponse à un stress photo-induit". Besançon, 2007. http://www.theses.fr/2007BESAA003.
Testo completoAbstract (sommario):
Les UV A et B participent au photovieillissement cutané en produisant un stress oxydant. Pour lutter contre ce stress, les kératinocytes et les fibroblastes cutanés possèdent un système de défenses antioxydantes. - La comparaison des capacités antioxydantes basales des fibroblastes de sujets jeunes et de sujets adultes fait apparaître des différences significatives : l'activité superoxyde dismutase est supérieure chez les fibroblastes de sujets jeunes et l'activité catalase y est inférieure. Les fibroblastes issus de sujets adultes sont les plus sensibles aux UVB. Les UV A provoquent une augmentation de la peroxydation lipidique au sein des fibroblastes concomitante à une activité superoxyde dismutase accrue. Chez les kératinocytes, les UV A engendrent une diminution de l'activité catalase. Des différences entre les systèmes de défenses antioxydantes des fibroblastes et des kératinocytes apparaissent après une irradiation UV A. Les kératinocytes se montrent alors plus résistants aux UV AUV A and B take part in photoaging by producing an oxidative stress, and the cutaneous keratinocytes and fibroblasts present antioxidant defence system. The basal antioxidant capacities of fibroblasts from young and adult donors show significant differences : superoxide dismutase activity is higher in fibroblasts from young donors and catalase activity is lower there. The fibroblasts resulting from adult donors are most sensitive to the UVB. The UV A cause an increase in lipid peroxidation in fibroblasts concomitant to an increase in superoxide dismutase activity. On keratinocytes, the UV A generate a reduced catalase activity. Differences between antioxidant defence systems in fibroblasts and keratinocytes appear after an UV A irradiation. Then, keratinocytes appear more resistant to the UV A
41
Blais, Mathieu. "Influence des facteurs neurotrophiques et des fibres nerveuses dans la peau reconstruite par génie tissulaire". Thesis, Université Laval, 2013. http://www.theses.ulaval.ca/2013/29969/29969.pdf.
Testo completoAbstract (sommario):
La peau est un organe densément innervé et vascularisé. L’établissement du réseau nerveux dépend de la sécrétion de signaux diffusibles dans la peau qui instruisent à distance certains neurones de s’y arboriser. Ces signaux sont les facteurs neurotrophiques. L’établissement du réseau vasculaire dépend aussi de la présence de signaux instructifs. Notre objectif général était de mieux comprendre l’influence des signaux neurotrophiques et aussi nerveux dans le contexte cutané. Les travaux présentés dans cette thèse décrivent de nouvelles interactions paracrines. Alors que certaines de ces interactions depuis la peau vers les neurones sensoriels et certaines depuis les neurones sensoriels vers le réseau vasculaire pour la vasodilatation sont déjà établies, nous décrivons l’influence des facteurs neurotrophiques sur le réseau vasculaire et l’influence des neurones sensoriels sur la réépithélialisation. Nous avons premièrement émis l’hypothèse qu’en plus d’influencer les neurones, les facteurs neurotrophiques influencent le réseau vasculaire. Nous montrons que le NGF, le BDNF, le NT-3 et le GDNF sont tous exprimés dans l'épiderme, que le NGF et le NT-3 sont exprimés par les fibroblastes et que le BDNF est produit par les cellules endothéliales. Les cellules de Schwann, également retrouvées dans la peau, produisent du NGF, BDNF et GDNF. Nous montrons que ces peptides sont de très puissants facteurs angiogéniques en utilisant un modèle de derme endothélialisé humain reconstruit par génie tissulaire. Une augmentation de 40 à 80 % du nombre de pseudocapillaires fut observée après l'addition de 10 ng/ml de NGF, 0,1 ng/ml de BDNF, 15 ng/ml de NT-3, et 50 ng/ml de GDNF. Cet effet angiogénique dépend de la liaison aux récepteurs de facteurs neurotrophiques TrkA, TrkB, GFRa-1 et c-ret, qui sont tous exprimés par les cellules endothéliales humaines. Cet effet a été bloqué pour les récepteurs Trk par l’addition de l'inhibiteur compétitif K252a. Ensuite, nous avons dans un deuxième temps émis l’hypothèse que les neurones sensoriels influencent directement la réépithélialisation. Pour vérifier cela, nous avons développé un nouveau modèle de réépithélialisation par génie tissulaire. Il est constitué d’un équivalent épidermique troué exprimant une protéine fluorescente verte qui a été empilé sur un équivalent dermique servant de substrat pour l’épiderme qui referme alors naturellement la plaie. L’équivalent est endothélialisé et innervé ou non par les neurones sensoriels de souris. Nous avons observé que la réépithélialisation est plus rapide en présence de neurones sensoriels. Nous avons démontré que les neurones sensoriels sécrètent une petite protéine dans notre modèle, soit de la substance P, et que les kératinocytes expriment le récepteur cellulaire NK1 de la substance P. Enfin, nous montrons que la substance P contribue à augmenter la vitesse de fermeture des plaies induites par les neurones à l'aide d’un agoniste et d’un antagoniste du récepteur NK1. L'ensemble des résultats procure une meilleure compréhension de l’importance des contextes neurotrophiques et nerveux dans la peau. Nos résultats pourraient laisser présager que d’améliorer la régénération nerveuse cutanée lorsqu’elle est déficiente améliorerait aussi l’homéostasie du tissu cutané.The skin is an organ densely innervated and vascularized. The establishment of the cutaneous nervous system depends on the secretion of neurotrophic factors by the skin. Meanwhile, the establishment of the vascular network also depends on soluble instructive cues. The work presented in this thesis describes new paracrine interactions. While interactions from skin to sensory neurons for the development of innervation and interactions from sensory neurons to blood vessel for vasodilation of the vasculature are described elsewhere, we demonstrate here the influence of neurotrophic factors on the vascular network and the influence of sensory neurons on the reepithelialization of wounds. Our overall goal was to clarify the influence of the neurotrophic and nervous contexts on the homeostasis of the skin. First, we hypothesized that in addition to their neuronal contribution, neurotrophic factors also influence the vascular network. We show that NGF, BDNF, NT-3 and GDNF are expressed in the epidermis, while NGF and NT-3 are expressed by fibroblasts and BDNF by endothelial cells. Finally, Schwann cells produce NGF, BDNF and GDNF. We show that these peptides are very potent angiogenic factors using a model of human endothelialized reconstructed dermis by tissue engineering. An increase of 40 to 80% of the number of capillary-like tubes was observed after the addition of 10 ng/ml NGF, 0.1 ng/ml of BDNF, 15 ng/ml of NT-3, and 50 ng/ml of GDNF. This angiogenic effect depends on the neurotrophic factor receptor TrkA, TrkB, GFRa-1 and c-ret that are all expressed by human endothelial cells. This effect was blocked by adding the Trk inhibitor K252a for NGF, BDNF and NT-3. Second, we hypothesized that sensory neurons directly influence reepithelialization by secreting the neuropeptide substance P. To verify this, we developed a new model of reepithelialization. It consists of a perforated epidermal equivalent expressing a green fluorescent protein stacked on a dermal equivalent that is used as a bed for reepithelialization. The reconstructed skin is endothelialized and innervated or not with sensory neurons of mouse. Sensory neurons produce substance P in the model and keratinocytes express the NK1 cell receptor for substance P. Keratinocyte migration was quantified by fluorescence. Reepithelialization was faster in presence of sensory neurons and we show that substance P contributes to this effect with agonist and antagonist of the NK1 cell receptor. The overall results provide a better understanding of the importance of the neurotrophic and sensory contexts in the skin. Thus, cutaneous innervation does not only contribute to the sensory detection. Our findings may suggest that improving nerve regeneration would improve skin long term tissue homeostasis.
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Derhy, Frédéric. "Prévention et réduction des cicatrices hypertrophiques ou chéloidiennes". Paris 5, 1993. http://www.theses.fr/1993PA05P103.
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Robert, Valérie. "Les céramides : des molécules clés de l'épiderme". Nancy 1, 1996. http://www.theses.fr/1996NAN10073.
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Coulomb, Bernard. "Reconstruction in vitro d'une peau humaine vivante modèle d'étude de la physiologie, de la physiopathologie et de la pharmacologie cutanée, applications thérapeutiques /". Grenoble 2 : ANRT, 1988. http://catalogue.bnf.fr/ark:/12148/cb37604095v.
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Comfort, Paul, Thomas Dos'Santos, Paul A. Jones, John J. McMahon, Timothy J. Suchomel, Caleb D. Bazyler e Michael H. Stone. "Normalisation of Early Isometric Force Production as a Percentage of Peak Force, During Multi-Joint Isometric Assessment". Digital Commons @ East Tennessee State University, 2019. https://dc.etsu.edu/etsu-works/5787.
Testo completoAbstract (sommario):
Purpose: To determine the reliability of early force production (50, 100, 150, 200, and 250 ms) relative to peak force (PF) during an isometric mid-thigh pull and to assess the relationships between these variables. Methods:: Male collegiate athletes (N = 29; age 21.1 [2.9] y, height 1.71 [0.07] m, body mass 71.3 [13.6] kg) performed isometric mid-thigh pulls during 2 separate testing sessions. Net PF and net force produced at each epoch were calculated. Within- and between-session reliabilities were determined using intraclass correlation coefficients and coefficient of variation percentages. In addition, Pearson correlation coefficients and coefficient of determination were calculated to examine the relationships between PF and time-specific force production. Results:: Net PF and time-specific force demonstrated very high to almost perfect reliability both within and between sessions (intraclass correlation coefficients .82–.97; coefficient of variation percentages 0.35%–1.23%). Similarly, time-specific force expressed as a percentage of PF demonstrated very high to almost perfect reliability both within and between sessions (intraclass correlation coefficients .76–.86; coefficient of variation percentages 0.32%–2.51%). Strong to nearly perfect relationships (r = .615–.881) exist between net PF and time-specific net force, with relationships improving over longer epochs. Conclusion:: Based on the smallest detectable difference, a change in force at 50 milliseconds expressed relative to PF > 10% and early force production (100, 150, 200, and 250 ms) expressed relative to PF of >2% should be considered meaningful. Expressing early force production as a percentage of PF is reliable and may provide greater insight into the adaptations to the previous training phase than PF alone.
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Boerem, David L. "Peak isokinetic torque of knee flexors and extensor muscles of college football players". Scholarly Commons, 1987. https://scholarlycommons.pacific.edu/uop_etds/499.
Testo completoAbstract (sommario):
The problem of the study addressed knee injuries in college football. Imbalance of the musculature surrounding the knee would predispose the athlete to knee injury. Recognition of those who have muscular deficiencies would be a primary way of preventing knee injuries. The focus of the study was to determine if there was a significant difference in peak isokinetic torque of knee flexor and extensor muscles across speeds (60 degrees/second, 180 degrees/ second and 300 degrees/second) of a college football team subsequent to participation in a spring football season.
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Kavanaugh, Ashley A., Michael W. Ramsey, William A. Sands, G. Gregory Haff e Michael H. Stone. "Acute Whole-Body Vibration Does Not Affect Static Jump Performance". Digital Commons @ East Tennessee State University, 2011. https://dc.etsu.edu/etsu-works/4118.
Testo completoAbstract (sommario):
Currently, whole-body vibration is being used to promote enhanced performance. Many coaches and athletes believe that it can acutely enhance explosive performance and power output. However, the scientific literature is unclear as to whether this enhancement occurs. The purpose of this study was to examine the acute effects of whole-body vibration on static jump performance, including jump height, peak force, rate of force development, and peak power. Fourteen recreationally active individuals (5 females, 9 males) participated in three separate randomized treatment sessions. Treatment 1 consisted of no vibration while treatment 2 and treatment 3 incorporated whole-body vibration. The whole-body vibration protocol consisted of three 30-s bouts of vibration performed at 30 Hz and low amplitude ( 3 mm) with a 30-s rest between bouts. Treatment 1 was identical in duration to both treatments 2 and 3, but did not contain any vibration. Five minutes after each treatment, the participants performed the static jump protocols. Two (data averaged) non-weighted static jumps and two 20 kg weighted jumps were performed. Treatments 1 vs. 2, 1 vs. 3, and 2 vs. 3 were calculated for each variable at both 0 kg and 20 kg. Jump height, peak force, rate of force development, and peak power were analysed using a one-way analysis of variance with repeated measures. The intra-class correlations comparing the two trials of each jump for each of the three treatments were ≥0.92. Compared with the no-vibration condition, jump height showed a non-significant increase as a result of whole-body vibration for both unweighted and weighted jumps; peak force, rate of force development, and peak power were not statistically different. The results indicate that whole-body vibration has no effect on jump height, peak force, rate of force development or peak power during static jumping.
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Prisby, Rhonda D., Michael W. Ramsey, Bradley J. Behnke, James M. Dominguez, Anthony J. Donato, Matthew R. Allen e Michael D. Delp. "Aging Reduces Skeletal Blood Flow, Endothelium-Dependent Vasodilation and Nitric Oxide Bioavailability in Rats". Digital Commons @ East Tennessee State University, 2007. https://dc.etsu.edu/etsu-works/4130.
Testo completoAbstract (sommario):
We determined whether aging diminishes bone blood flow and impairs endothelium‐dependent vasodilation. Femoral perfusion was lower in old animals, as well as endothelium‐dependent vasodilation and NO bioavailability. These effects could contribute to old age—related bone loss and the increased risk of fracture.
Introduction: Aging has been shown to diminish bone blood flow in rats and humans. The purpose of this study was to determine whether blood flow to regions of the femur perfused primarily through the principal nutrient artery (PNA) are diminished with aging and whether this putative reduction in flow is associated with impaired endothelium‐dependent vasodilation.
Materials and Methods: Blood flow was measured in conscious young adult (4–6 mo old) and aged (24–26 mo old) male Fischer‐344 rats using radiolabeled microspheres. Endothelium‐dependent vasodilation of the PNA was assessed in vitro using acetylcholine (ACh), whereas the contribution of the NO synthase (NOS) and cyclooxygenase (COX) signaling pathways to endothelium‐dependent vasodilation was determined using the NOS and COX inhibitors L‐NAME and indomethacin, respectively.
Results: Femoral blood flow in the aged rats was 21% and 28% lower in the proximal and distal metaphyses, respectively, and 45% lower in the diaphyseal marrow. Endothelium‐dependent vasodilation was reduced with old age (young: 83 ± 6% maximal relaxation; aged: 62 ± 5% maximal relaxation), whereas endothelium‐independent vasodilation (sodium nitroprusside) was unaffected by age. The reduction in endothelium‐dependent vasodilation was mediated through impairment of the NOS signaling pathway, which resulted in lower NO bioavailability (young: 168 ± 56 nM; aged: 50 ± 7 nM).
Conclusions: These data show that reductions in metaphyseal bone and diaphyseal marrow perfusion with old age are associated with diminished endothelium‐dependent vasodilation through an impairment of the NOS mechanism. Such age‐related changes in bone perfusion and vascular NO signaling could impact clinical bone loss, increase risk of fracture, and impair fracture healing in the elderly.
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Djavaheri-Mergny, Mojgan. "Effet des rayonnements ultraviolets A sur les processus d'endocytose et sur le métabolisme des lipides dans les fibroblastes et les kératinocytes humains en culture". Université de Paris-Sud. Faculté de pharmacie (Châtenay-Malabry, Hauts-de-Seine), 1993. http://www.theses.fr/1993PA114807.
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Auclair-Brialy, Florence. "Importance du débit sanguin cutané sur la rétention et la distribution localisée des médicaments appliqués sur la peau". Paris 11, 1991. http://www.theses.fr/1991PA114822.
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