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1
Jolayemi, Okanlawon Lekan, Jelili Titilola Opabode et Gueye Badara. « In vitro response of three contrasting cassava (Manihot esculenta Crantz) varieties to mannitol-induced drought stress ». Agricultura Tropica et Subtropica 51, no 3 (1 septembre 2018) : 125–31. http://dx.doi.org/10.2478/ats-2018-0014.
Texte intégralRésumé :
Abstract In vitro selection of drought-tolerant cassava varieties is essential for rapid breeding for drought tolerance. The objectives of this study were to determine the response of three contrasting cassava varieties to mannitol-induced drought stress to establish its suitability for in vitro screening and examine relationships among growth parameters. Plantlets were raised from nodal segments on Murashige and Skoog (MS) medium containing 0 (control), 5, 10, 15, 20, 25 and 30 g/l mannitol. Variety CH 140 had the highest survival of explants and frequency of root formation, while MV 99/0395 recorded the highest number of chlorotic leaves and the lowest survival of explants. The lowest numbers of leaves were produced at 25 and 30 g/l mannitol by the three varieties. In CH 140, the highest number of leaves was produced in medium free of mannitol, while the highest number of leaves was produced at 5 and 10 g/l mannitol in MV 99/0395 and TMS 01/1206, respectively. In TMS 01/1206, number of roots produced decreased as the concentration of mannitol in culture media increased, whereas in CH140, number of roots increased as the concentration of mannitol increased before decreasing; while in MV 99/0395, number of roots was not affected by an increase in mannitol concentration. As the concentration of mannitol in the culture media increased shoot height of plantlets decreased with a sharp decline at 20 mg/l mannitol. Concentration of mannitol and survival of explants had significant negative correlation with all parameters. However, frequency of root formation only had significant positive correlation with shoot length. The study concluded that differential responses were expressed by the three varieties to mannitol-induced drought stress and mannitol at 20 g/l concentration was a suitable in vitro drought inducing-agent for screening cassava varieties for drought tolerance.
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Jolayemi, Okanlawon Lekan, Jelili Titilola Opabode et Gueye Badara. « In vitro response of three contrasting cassava (Manihot esculenta Crantz) varieties to mannitol-induced drought stress ». Agricultura Tropica et Subtropica 51, no 3 (1 septembre 2018) : 125–31. http://dx.doi.org/10.1515/ats-2018-0014.
Texte intégralRésumé :
Abstract In vitro selection of drought-tolerant cassava varieties is essential for rapid breeding for drought tolerance. The objectives of this study were to determine the response of three contrasting cassava varieties to mannitol-induced drought stress to establish its suitability for in vitro screening and examine relationships among growth parameters. Plantlets were raised from nodal segments on Murashige and Skoog (MS) medium containing 0 (control), 5, 10, 15, 20, 25 and 30 g/l mannitol. Variety CH 140 had the highest survival of explants and frequency of root formation, while MV 99/0395 recorded the highest number of chlorotic leaves and the lowest survival of explants. The lowest numbers of leaves were produced at 25 and 30 g/l mannitol by the three varieties. In CH 140, the highest number of leaves was produced in medium free of mannitol, while the highest number of leaves was produced at 5 and 10 g/l mannitol in MV 99/0395 and TMS 01/1206, respectively. In TMS 01/1206, number of roots produced decreased as the concentration of mannitol in culture media increased, whereas in CH140, number of roots increased as the concentration of mannitol increased before decreasing; while in MV 99/0395, number of roots was not affected by an increase in mannitol concentration. As the concentration of mannitol in the culture media increased shoot height of plantlets decreased with a sharp decline at 20 mg/l mannitol. Concentration of mannitol and survival of explants had significant negative correlation with all parameters. However, frequency of root formation only had significant positive correlation with shoot length. The study concluded that differential responses were expressed by the three varieties to mannitol-induced drought stress and mannitol at 20 g/l concentration was a suitable in vitro drought inducing-agent for screening cassava varieties for drought tolerance.
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Stromberg, Zachary R., Rick E. Masonbrink et Melha Mellata. « Transcriptomic Analysis of Shiga Toxin-Producing Escherichia coli during Initial Contact with Cattle Colonic Explants ». Microorganisms 8, no 11 (27 octobre 2020) : 1662. http://dx.doi.org/10.3390/microorganisms8111662.
Texte intégralRésumé :
Foodborne pathogens are a public health threat globally. Shiga toxin-producing Escherichia coli (STEC), particularly O26, O111, and O157 STEC, are often associated with foodborne illness in humans. To create effective preharvest interventions, it is critical to understand which factors STEC strains use to colonize the gastrointestinal tract of cattle, which serves as the reservoir for these pathogens. Several colonization factors are known, but little is understood about initial STEC colonization factors. Our objective was to identify these factors via contrasting gene expression between nonpathogenic E. coli and STEC. Colonic explants were inoculated with nonpathogenic E. coli strain MG1655 or STEC strains (O26, O111, or O157), bacterial colonization levels were determined, and RNA was isolated and sequenced. STEC strains adhered to colonic explants at numerically but not significantly higher levels compared to MG1655. After incubation with colonic explants, flagellin (fliC) was upregulated (log2 fold-change = 4.0, p < 0.0001) in O157 STEC, and collectively, Lon protease (lon) was upregulated (log2 fold-change = 3.6, p = 0.0009) in STEC strains compared to MG1655. These results demonstrate that H7 flagellum and Lon protease may play roles in early colonization and could be potential targets to reduce colonization in cattle.
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Abbasi, Bilal, Aisha Siddiquah, Duangjai Tungmunnithum, Shankhamala Bose, Muhammad Younas, Laurine Garros, Samantha Drouet, Nathalie Giglioli-Guivarc’h et Christophe Hano. « Isodon rugosus (Wall. ex Benth.) Codd In Vitro Cultures : Establishment, Phytochemical Characterization and In Vitro Antioxidant and Anti-Aging Activities ». International Journal of Molecular Sciences 20, no 2 (21 janvier 2019) : 452. http://dx.doi.org/10.3390/ijms20020452.
Texte intégralRésumé :
Isodon rugosus (Wall. ex Benth.) Codd accumulates large amounts of phenolics and pentacyclic triterpenes. The present study deals with the in vitro callus induction from stem and leaf explants of I. rugosus under various plant growth regulators (PGRs) for the production of antioxidant and anti-ageing compounds. Among all the tested PGRs, thidiazuron (TDZ) used alone or in conjunction with α-napthalene acetic acid (NAA) induced highest callogenesis in stem-derived explants, as compared to leaf-derived explants. Stem-derived callus culture displayed maximum total phenolic content and antioxidant activity under optimum hormonal combination (3.0 mg/L TDZ + 1.0 mg/L NAA). HPLC analysis revealed the presence of plectranthoic acid (373.92 µg/g DW), oleanolic acid (287.58 µg/g DW), betulinic acid (90.51 µg/g DW), caffeic acid (91.71 µg/g DW), and rosmarinic acid (1732.61 µg/g DW). Complete antioxidant and anti-aging potential of extracts with very contrasting phytochemical profiles were investigated. Correlation analyses revealed rosmarinic acid as the main contributor for antioxidant activity and anti-aging hyaluronidase, advance glycation end-products inhibitions and SIRT1 activation, whereas, pentacyclic triterpenoids were correlated with elastase, collagenase, and tyrosinase inhibitions. Altogether, these results clearly evidenced the great valorization potential of I. rugosus calli for the production of antioxidant and anti-aging bioactive extracts for cosmetic applications.
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Niiniluoto, Ilkka. « Explanation by Idealized Theories ». Kairos. Journal of Philosophy & ; Science 20, no 1 (1 juin 2018) : 43–63. http://dx.doi.org/10.2478/kjps-2018-0003.
Texte intégralRésumé :
AbstractThe use of idealized scientific theories in explanations of empirical facts and regularities is problematic in two ways: they don’t satisfy the condition that the explanans is true, and they may fail to entail the explanandum. An attempt to deal with the latter problem was proposed by Hempel and Popper with their notion of approximate explanation. A more systematic perspective on idealized explanations was developed with the method of idealization and concretization by the Poznan school (Nowak, Krajewski) in the 1970s. If idealizational laws are treated as counterfactual conditionals, they can be true or truthlike, and the concretizations of such laws may increase their degree of truthlikeness. By replacing Hempel’s truth requirement with the condition that an explanatory theory is truthlike one can distinguish several important types of approximate, corrective, and contrastive explanations by idealized theories. The conclusions have important consequences for the debates about scientific realism and anti-realism.
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Starck, Zofia, et Barbara Witek-Czupryńska. « Diverse response of tomato fruit explants to high temperature ». Acta Societatis Botanicorum Poloniae 62, no 3-4 (2014) : 165–69. http://dx.doi.org/10.5586/asbp.1993.025.
Texte intégralRésumé :
Tomato explants (fruit with a pedicel and a piece of peduncle), with fruit growth stimulated by treating the flowers with NOA + GA<sub>3</sub> (NG-series) were used as a model system for studying the effect of high temperature on C-sucrose uptake, its distribution and Ca retranslocation. Two cultivars with contrasting responses to high temperature were compared. In sensitive cv. Roma heat stress during 22h (40<sup>o</sup>C for 10h and 30<sup>o</sup>C for 12h), drastically depressed the uptake of <sup>14</sup>C-sucrose coinciding with diminished fruit <sup>14</sup>C-supply. It also decreased the specific activity of soluble acid invertase and the calcium content. All these strong negative responses to high temperature were markedly reduced in the NG-treated series involving remobilization of Ca to the fruits and a higher stability of the invertase activity. This indicates the indirect role of flower treatment with NG in addaptation to heat stress. In tolerant cv. Robin even higher temperatures (42<sup>o</sup>C for 10h and 34<sup>o</sup>C for 12h) were not stressful. They did not affect the <sup>14</sup>C-sucrose uptake and stimulated <sup>14</sup>C-supply to the fruit. Increased specific activity of acid invertase and a higher calcium content were also recorded but only in the control explants. In contrast to cv. Roma elevated temperature was slightly stressful for cv. Robin explants of NG-series. The differences in response of both cultivar explants to elevated temperature, based on unequal fruit supply with <sup>14</sup>C-sucrose, seem to be causaly connected with two factors: the invertase activity being more or less sensitive to the heat stress, the ability to translocate Ca to the heated fruits.
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Donovan, N. J., C. A. Offord et J. L. Tyler. « Vegetative cutting and in vitro propagation of the tree waratah, Alloxylon flammeum P. Weston and Crisp (family Proteaceae) ». Australian Journal of Experimental Agriculture 39, no 2 (1999) : 225. http://dx.doi.org/10.1071/ea97106.
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Alloxylon flammeum is a rare and threatened Australian rainforest species that features spectacular red flowers and contrasting dark green foliage giving it potential as a cut flower crop. It also has potential as a rootstock for difficult to grow tree waratah species. There is, however, little published information on the propagation of Alloxylon spp. Here we show that A. flammeum can be propagated by vegetative cuttings and in vitro. The most commercially viable option is to propagate by cuttings using 8000 mg indole-3-butyric acid/L under intermittent mist with a root zone temperature of 24 ± 2˚C. Pre-treatment of A. flammeum stock plants with gibberellin (A4 and A7) spray before initiation into culture increased the success of initiation. The use of tip material resulted in minimal explant contamination and 1% sodium hypochlorite for 15 min was adequate for surface disinfection of material. Well elongated shoots were multiplied using 6-benzyladenine and 6-dimethylallyaminopurine (isopentyladenine), whilst thidiazuron-cultured shoots were numerous but short and unusable.
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Rehen, S. K., M. H. Varella, F. G. Freitas, M. O. Moraes et R. Linden. « Contrasting effects of protein synthesis inhibition and of cyclic AMP on apoptosis in the developing retina ». Development 122, no 5 (1 mai 1996) : 1439–48. http://dx.doi.org/10.1242/dev.122.5.1439.
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The role of protein synthesis in apoptosis was investigated in the retina of developing rats. In the neonatal retina, a ganglion cell layer, containing neurons with long, centrally projecting axons, is separated from an immature neuroblastic layer by a plexiform layer. This trilaminar pattern subsequently evolves to five alternating cell and plexiform layers that constitute the mature retina and a wave of programmed neuron death sweeps through the layers. Apoptosis due to axon damage was found in ganglion cells of retinal explants within 2 days in vitro and was prevented by inhibition of protein synthesis. Simultaneously, protein synthesis blockade induced apoptosis among the undamaged cells of the neuroblastic layer, which could be selectively prevented by an increase in intracellular cyclic AMP. Both the prevention and the induction of apoptosis among ganglion cells or neuroblastic cells, respectively, occurred after inhibition of protein synthesis in vivo. The results show the coexistence of two mechanisms of apoptosis within the organized retinal tissue. One mechanism is triggered in ganglion cells by direct damage and depends on the synthesis of proteins acting as positive modulators of apoptosis. A distinct, latent mechanism is found among immature neuroblasts and may be repressed by continuously synthesized negative modulators, or by an increase in intracellular cyclic AMP.
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Weenink, Don, David van der Duin, Laura Keesman, Rozalie Lekkerkerk, Floris Mosselman et Phie van Rompu. « Taking social ontology seriously : An interview with Jack Katz ». Ethnography 21, no 2 (25 février 2020) : 198–219. http://dx.doi.org/10.1177/1466138120907333.
Texte intégralRésumé :
This interview with Jack Katz offers an inspiring statement about how to study social life. It starts with a discussion of Katz’s three-dimensional social ontology; social life is constituted in embodied interactions in which people adjust to others and create transcendent meanings. Contrasting the ontology with anthropology’s ontological turn, we note that social ontology is about generating empirically accurate descriptions capturing the flow of social life. This leads to a critical discussion of sociology’s pre-occupation with explanans-driven theorizing. Touching upon macro–micro relationships, we consider what a phenomenology of collective emotions would look like. This brings us to emotional transformations, notably the notion of ‘falling’, an important theme in Katz’s work. The interview continues with advice of how to think beyond given categories, to consider the validity of ethnographic description and to look for the absurd. Finally, we conclude that ethnography has the potential to appeal to mass audiences.
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Belabbas, Hassiba, Santiago Zalvidea, Daniel Casellas, Jean-Pierre Molès, Olivier Galbes, Jacques Mercier et Bernard Jover. « Contrasting effect of exercise and angiotensin II hypertension on in vivo and in vitro cardiac angiogenesis in rats ». American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 295, no 5 (novembre 2008) : R1512—R1518. http://dx.doi.org/10.1152/ajpregu.00014.2008.
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Cardiac vessel density (β-actin immunolabeling) and angiogenic capacity of coronary artery explants (culture in collagen gel) was determined in hypertrophied heart obtained by exercise training (10 wk) or ANG II infusion for 10 days. A group of rats received ANG II the last 10 days of training. The heart weight index was similarly elevated after exercise, and ANG II-hypertension compared with controls (3.16 ± 0.09 and 3.11 ± 0.11 vs. 2.68 ± 0.08 mg/g, respectively), whereas tail cuff pressure (TCP) increased only in sedentary rats infused with ANG II. Vessel density was increased by 36% in trained rats and reduced by 30% in ANG II-infused rats. The number of sprouts generated by coronary rings was reduced by 50% in ANG II-infused rats and increased by 50% in exercise trained rats compared with controls (35 ± 4 and 113 ± 5 vs. 71 ± 1 sprouts per ring, respectively). Exercise-training partly prevented the hypertensive effect of ANG II (TCP of 141 ± 5 mmHg), whereas heart weight index (3.66 ± 0.06 mg/g body wt) was not lowered. Myocardial vessel density was normalized, and sprouting from coronary rings increased by 50% in trained rats infused with ANG II compared with sedentary normotensive rats. Cardiac VEGF (Western blot analysis) was higher in hypertensive rats and not affected by exercise. Facing a similar increase in cardiac mass, intense training, but not ANG II hypertension, is accompanied by an increase in vascular density of the heart. The effect of training is unlikely related to changes in resting VEGF and may represent enhanced angiogenic capacity of the coronary vascular bed.
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Palioto, Daniela Bazan, Ricardo Della Coletta, Hercílio Martelli Júnior, Julio Cesar Joly, Edgard Graner et Antonio Fernando Martorelli de Lima. « Comparação entre fibroblastos gengivais e do ligamento periodontal de um mesmo indivíduo ». Pesquisa Odontológica Brasileira 16, no 4 (décembre 2002) : 319–25. http://dx.doi.org/10.1590/s1517-74912002000400007.
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O objetivo deste estudo foi comparar as características morfológicas, o potencial proliferativo e a produção protéica de fibroblastos do ligamento periodontal (FLP) e de fibroblastos gengivais (FG). Os fibroblastos foram cultivados pela técnica do explante a partir de fragmentos da gengiva e do ligamento periodontal de um mesmo indivíduo. As células foram isoladas e plaqueadas para análise por microscopia de contraste de fase e microscopia óptica. O índice de proliferação celular foi determinado por contagem automática de células e pelo ensaio de incorporação de bromodioxiuridina (BrdU). A produção de proteína total foi verificada por eletroforese em gel de poliacrilamida e o perfil enzimático por análise zimográfica. Os FLP são maiores e mais alongados que os FG em condições de subconfluência e confluência celular. Os FLP demonstraram um potencial proliferativo significantemente maior que os FG. Os perfis protéico e enzimático foram similares entre os FLP e FG. Os resultados demonstram que os FLP e FG são diferentes na morfologia e na capacidade proliferativa, porém são semelhantes na produção protéica.
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Zhang, Mingqi, Zhuoshi Wang, Yan Zhao, Lirong Zhang, Ling Xu, Liu Cao et Wei He. « The Effect of Age on the Regenerative Potential of Human Eyelid Adipose-Derived Stem Cells ». Stem Cells International 2018 (2018) : 1–11. http://dx.doi.org/10.1155/2018/5654917.
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Human eyelid adipose-derived stem cells (HEASCs) are a new source of autologous mesenchymal stem cells, which are derived from neuroectoderm and potentially applied in the tissue regeneration and cell therapies. Based on the prevalence of blepharoplasty in Asia and the availability of HEASCs, we investigated the effect of donor age on their characteristics and regenerative potential of HEASCs in vitro. The HEASCs were isolated from patients of three groups: (1) <20 years (n=4), (2) >20 years, <45 years (n=5), and (3) >55 years (n=4). For each group, the proliferative capacity, colony-forming ability, surface markers, differentiation ability, wound healing function, and secreted protein were contrastively evaluated and quantified for statistical analysis. It was found that HEASCs were successfully isolated and cultured by an explant culture method. The proliferative rates, osteogenic and chondrogenic differentiation potentials, wound healing ability, and the expression of TGF-β1 and fibronectin protein of HEASCs significantly decreased as age increased. However, the expression of CD90 antigen and the adipogenic differentiation showed an age-related increase in HEASCs. As many degenerative diseases increase in prevalence with age, the age-related changes of the HEASCs proliferation potential, differentiation capacity, and wound healing ability should be taken into account whenever they are intended for use in research or cytotherapy.
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Edom-Vovard, F., V. Mouly, J. P. Barbet et G. S. Butler-Browne. « The four populations of myoblasts involved in human limb muscle formation are present from the onset of primary myotube formation ». Journal of Cell Science 112, no 2 (15 janvier 1999) : 191–99. http://dx.doi.org/10.1242/jcs.112.2.191.
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To understand how and when myogenic precursor cells become committed to their particular developmental programs, we have analysed the different populations of myoblasts which grow out from explants of muscle tissue isolated from human limb buds from the beginning of primary fibre formation throughout subsequent development and post-natal growth. Four phenotypically distinct types of myoblasts were identified on the basis of their expression of desmin, myogenin and myosin heavy chain isoforms (MyHC), and after 5 and 20 divisions, cells were cloned. All four types of myoblasts were present at the beginning of primary myogenesis. Each respective phenotype was stably heritable through cloning and subsequent proliferation. The type 1 clones correspond to a novel class of myoblasts never described during human development, that biochemically differentiates, but does not fuse. Type 2 clones are composed of small myotubes expressing only embryonic MyHC. Type 3 clones are composed of thin and long myotubes expressing both embryonic and fetal MyHCs. The type 4 clones are composed of myotubes that have a phenotype very similar to human satellite cells. Contrasting with others species, no other population of myoblasts appear during fetal development and only the relative number of these four types changes.
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Burton, Graham J., Tereza Cindrova-Davies, Hong wa Yung et Eric Jauniaux. « HYPOXIA AND REPRODUCTIVE HEALTH : Oxygen and development of the human placenta ». Reproduction 161, no 1 (janvier 2021) : F53—F65. http://dx.doi.org/10.1530/rep-20-0153.
Texte intégralRésumé :
Development of the human placenta takes place in contrasting oxygen concentrations at different stages of gestation, from ~20 mmHg during the first trimester rising to ~60 mmHg at the start of the second trimester before gradually declining to ~40 mmHg at term. In view of these changes, the early placenta has been described as ‘hypoxic’. However, placental metabolism is heavily glycolytic, supported by the rich supply of glucose from the endometrial glands, and there is no evidence of energy compromise. On the contrary, the trophoblast is highly proliferative, with the physiological low-oxygen environment promoting maintenance of stemness in progenitor populations. These conditions favour the formation of the cytotrophoblastic shell that encapsulates the conceptus and interfaces with the endometrium. Extravillous trophoblast cells on the outer surface of the shell undergo an epithelial-mesenchymal transition and acquire invasive potential. Experimental evidence suggests that these changes may be mediated by the higher oxygen concentration present within the placental bed. Interpreting in vitro data is often difficult, however, due to the use of non-physiological oxygen concentrations and trophoblast-like cell lines or explant models. Trophoblast is more vulnerable to hyperoxia or fluctuating levels of oxygen than to hypoxia, and some degree of placental oxidative stress likely occurs in all pregnancies towards term. In complications of pregnancy, such as early-onset pre-eclampsia, malperfusion generates high levels of oxidative stress, causing release of factors that precipitate the maternal syndrome. Further experiments are required using genuine trophoblast progenitor cells and physiological concentrations to fully elucidate the pathways by which oxygen regulates placental development.
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Korshikova, E. S., K. M. Ershova, Yu A. Moksheninova et Yu V. Ukhatova. « Efficiency of <i>in vitro</i> ; culture techniques applied to soybean (<i>Glycine max (L.) Merr.</i>) accessions from the VIR collection ». Proceedings on applied botany, genetics and breeding 182, no 4 (17 décembre 2021) : 137–42. http://dx.doi.org/10.30901/2227-8834-2021-4-137-142.
Texte intégralRésumé :
Using a wide range of modern biotechnologies and genetic techniques to study plant germplasm accessions held by VIR makes it possible to procure valuable results, required for the development of new high-yielding cultivars adapted to adverse environmental conditions and possessing specified technological properties, particularly to identify and mark new genes and alleles useful for plant breeding. This research trend is in line with Presidential Decree No. 680 “Concerning the development of genetic technologies in the Russian Federation”. Soybean is among the key crops in agricultural production, but the use of next-generation breeding tools to obtain new soybean cultivars with desired properties is still limited. Successful application of novel methods also requires new approaches to studying soybean accessions, specifically their ability to regenerate and produce calluses for subsequent inclusion in biotechnological programs.Ten soybean accessions of various origin, contrasting in ripening schedules, were selected to study the possibility of effective introduction into in vitro culture and further assessment of their ability to produce calluses and regenerate in in vitro culture. The work included evaluating the effects of different seed sterilization techniques (one-step sterilization, using a commercial bleach, and two-step one, combining the impacts of a chlorine-containing preparation and hydrogen peroxide), types of explants (epicotyls, hypocotyls, cotyledon nodes, and cotyledon leaf segments), and phytohormone composition of nutrient medium: (1) MS + 1.13 mg/L BAP + 0.5 mg/L HA, and (2) MS +1 mg/L BAP + 0.1 mg/L IAA).The assessment results showed that the option of two-step seed sterilization was the most effective for soybean at the stage of in vitro culture initiation, while hypocotyls, epicotyls, and cotyledon nodes had the highest callus formation ability in both types of nutrient media.
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Rodriguez-Ortiz, Suzel Rios-Ramirez,, Judith Ruiz Luna et Vicente Arturo Velasco Velasco. « In vitro formation of adventitious shoots on caulinary tissue of physiologically contrasting Agave angustifolia plants ». Emirates Journal of Food and Agriculture, 31 janvier 2018, 49. http://dx.doi.org/10.9755/ejfa.2018.v30.i1.1584.
Texte intégralRésumé :
To micropropagate agave plants, somatic tissue is obtained from selected plants that are conditioned for 2 to 6 months to improve their physiological condition and health before in vitro cultivation. The objective of this study was to evaluate the physiological condition of Agave angustifolia plants in terms of its effect on organogenic response in somatic tissue taken from these plants when they are established in similar culture media. In a nursery, growth of four groups of plants was evaluated when they were subjected to different types of irrigation for seven months: 1) water; 2) NS-50% (fertigation with nutrient solution at 50% strength); 3) NS-75%; and 4) NS-100%. At the end of the period, it was found that supplying nutrients is important for plants to achieve better physiological condition. The unfertilized plants and those that received NS-75% had increases of 3.8 and 7.8 leaves, 6.5 and 12.5 cm in length of the largest leaf, and 1610.3 and 4401.4 cm2 in leaf area. Stem tissue was obtained from these stock plants and cultured for 90 days in in vitro culture, and formation of adventitious shoots was assessed. The results showed that the magnitude of organogenesis in stem tissue for formation of adventitious shoots was positively related to the physiological condition of the stock plant. Explants taken from unfertilized stock plants formed 14.6 total shoots and 3.8 shoots on each explant, while those fertigated at 100% concentration of nutrients formed 32.7 total shoots and 8 shoots on each explant.
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Juárez-González, Vasti T., Brenda A. López-Ruiz, Patricia Baldrich, Eduardo Luján-Soto, Blake C. Meyers et Tzvetanka D. Dinkova. « The explant developmental stage profoundly impacts small RNA-mediated regulation at the dedifferentiation step of maize somatic embryogenesis ». Scientific Reports 9, no 1 (10 octobre 2019). http://dx.doi.org/10.1038/s41598-019-50962-y.
Texte intégralRésumé :
Abstract Maize somatic embryogenesis (SE) requires the induction of embryogenic callus and establishment of proliferation before plant regeneration. The molecular mechanisms underlying callus embryogenic potential are not well understood. Here we explored the role of small RNAs (sRNAs) and the accumulation of their target transcripts in maize SE at the dedifferentiation step using VS-535 zygotic embryos collected at distinct developmental stages and displaying contrasting in vitro embryogenic potential and morphology. MicroRNAs (miRNAs), trans-acting siRNAs (tasiRNAs), heterochromatic siRNAs (hc-siRNAs) populations and their RNA targets were analyzed by high-throughput sequencing. Abundances of specific miRNAs, tasiRNAs and targets were validated by qRT-PCR. Unique accumulation patterns were found for immature embryo at 15 Days After Pollination (DAP) and for the callus induction from this explant, as compared to 23 DAP and mature embryos. miR156, miR164, miR166, tasiARFs and the 24 nt hc-siRNAs displayed the most strikingly different patterns between explants and during dedifferentiation. According to their role in auxin responses and developmental cues, we conclude that sRNA-target regulation operating within the 15 DAP immature embryo explant provides key molecular hints as to why this stage is relevant for callus induction with successful proliferation and plant regeneration.
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Sánchez-Jiménez, David. « 50 anos de evolução nos estudos linguísticos transculturais : da Retórica Contrastiva à Retórica Intercultural ». Revista Eletrônica de Estudos Integrados em Discurso e Argumentação, 18 septembre 2020. http://dx.doi.org/10.47369/eidea-20-2-2798.
Texte intégralRésumé :
Este trabalho apresenta um panorama histórico dos estudos linguísticos transculturais, discorrendo sobre o surgimento da retórica contrastiva por meio do trabalho seminal de Robert Kaplan em 1966 e as contribuições de Ulla Connor ao rebatizar tais estudos como retórica intercultural. Explana-se também sobre as críticas endereçadas à retórica contrastiva feitas durante os anos 1980, 1990 e 2000 e de que maneira tais críticas redefiniram o quadro teórico-metodológico e o objeto de estudo da disciplina. Conclui-se com exposição de uma crítica à homogeneização das distintas culturas retóricas causada pela globalização e internacionalização do inglês no âmbito acadêmico e nas atividades profissionais.
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Victor, David G., Marcel Lumkowsky et Astrid Dannenberg. « Determining the credibility of commitments in international climate policy ». Nature Climate Change, 1 septembre 2022. http://dx.doi.org/10.1038/s41558-022-01454-x.
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AbstractThe Paris Agreement on climate change aims to improve cooperation by allowing governments to set their own commitments. Its success hinges on whether governments and investors believe those national commitments. To assess credibility, we interrogate a large novel sample of climate policy elites with decades of experience and well-placed to evaluate whether nations’ policy pledges are aligned with what they are politically and administratively able to implement. This expert assessment reveals that countries making the boldest pledges are also making the most credible pledges, contrasting theoretical warnings of a trade-off between ambition and credibility. We find that the quality of national political institutions is the largest explanator of the variation in credibility, and Europe’s credibility is exceptionally high. We also find that economic factors, such as the costs and benefits of controlling emissions, are statistically unimportant in explaining the credibility of national pledges to cooperate.
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Busch, Mathias, Haribaskar Ramachandran, Tina Wahle, Andrea Rossi et Roel P. F. Schins. « Investigating the Role of the NLRP3 Inflammasome Pathway in Acute Intestinal Inflammation : Use of THP-1 Knockout Cell Lines in an Advanced Triple Culture Model ». Frontiers in Immunology 13 (13 juillet 2022). http://dx.doi.org/10.3389/fimmu.2022.898039.
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The NLRP3 inflammasome plays an important role in intestinal homeostasis as well as inflammation. However, in vivo studies investigating the role of the NLRP3 inflammasome in inflammatory bowel disease (IBD) report contrasting results, leaving it unclear if the NLRP3 inflammasome augments or attenuates intestinal inflammation. To investigate the role of the NLRP3/caspase-1 pathway in a model of acute intestinal inflammation, we modified a previously established in vitro triple culture model of the healthy and inflamed intestine (Caco-2/HT29-MTX-E12/THP-1). Using THP-1 knockout cell lines, we analyzed how the NLRP3 inflammasome and its downstream enzyme caspase-1 (CASP1) affect inflammatory parameters including barrier integrity and cytotoxicity, as well as gene expression and secretion of pro-inflammatory cytokines and mucus. Furthermore, we investigated differences in inflammation-mediated cytotoxicity towards enterocyte-like (Caco-2) or goblet-like (HT29-MTX-E12) epithelial cells. As a complementary approach, inflammation-related cytotoxicity and gene expression of cytokines was analyzed in intestinal tissue explants from wildtype (WT) and Nlrp3-/- mice. Induction of intestinal inflammation impaired the barrier, caused cytotoxicity, and altered gene expression of pro-inflammatory cytokines and mucins in vitro, while the knockout of NLRP3 and CASP1 in THP 1 cells led to attenuation of these inflammatory parameters. The knockout of CASP1 tended to show a slightly stronger attenuating effect compared to the NLRP3 knockout model. We also found that the inflammation-mediated death of goblet-like cells is NLRP3/caspase-1 dependent. Furthermore, inflammation-related cytotoxicity and upregulation of pro-inflammatory cytokines was present in ileal tissue explants from WT, but not Nlrp3-/- mice. The here presented observations indicate a pro-inflammatory and adverse role of the NLRP3 inflammasome in macrophages during acute intestinal inflammation.
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Shveid Gerson, Daniela, Raquel Gerson‐Cwilich, Cesar Octavio Lara Torres, Alberto Chousleb de Kalach, José Luis Ventura Gallegos, Luis Ernesto Badillo‐Garcia, Juan Enrique Bargalló Rocha et al. « Establishment of triple-negative breast cancer cells based on BMI : A novel model in the correlation between obesity and breast cancer ». Frontiers in Oncology 12 (14 décembre 2022). http://dx.doi.org/10.3389/fonc.2022.988968.
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IntroductionObesity has been associated with an increased risk of biologically aggressive variants in breast cancer. Women with obesity often have tumors diagnosed at later stages of the disease, associated with a poorer prognosis and a different response to treatment. Human cell lines have been derived from specific subtypes of breast cancer and have served to define the cell physiology of corresponding breast cancer subtypes. However, there are no current cell lines for breast cancer specifically derived from patients with different BMIs. The availability of those breast cancer cell lines should allow to describe and unravel functional alterations linked to these comorbidities. MethodsCell cultures were established from tumor explants. Once generated, the triple negative subtype in a patient with obesity and a patient with a normal BMI were chosen for comparison. For cellular characterization, the following assays were conducted: proliferation assays, chemo – sensitivity assays for doxorubicin and paclitaxel, wound healing motility assays, matrix invasion assays, breast cancer cell growth to estradiol by chronic exposure to leptin, induction of endothelial permeability and tumorigenic potential in athymic mice with normo - versus hypercaloric diets with an evaluation of the epithelium – mesenchymal transformation proteins.ResultsTwo different cell lines, were established from patients with breast cancer: DSG-BC1, with a BMI of 21.9 kg/m2 and DSG-BC2, with a BMI of 31.5 kg/m2. In vitro, these two cell lines show differential growth rates, motility, chemosensitivity, vascular permeability, response to leptin with an activation of the JAK2/STAT3/AKT signaling pathway. In vivo, they displayed distinct tumorigenic potential. In particular, DSG-BC2, presented higher tumorigenicity when implanted in mice fed with a hypercaloric diet.DiscussionTo our knowledge, these primary cultures are the first in vitro representation of both breast cancer and obesity. DSG – BC2 presented a more aggressive in vivo and in vitro phenotype. These results support the hypothesis that breast cancer generated in an obese metabolic state may represent a contrasting variant within the same disease. This new model will allow both further comprehension, functional studies and the analysis of altered molecular mechanisms under the comorbidity of obesity and breast cancer.