19 research outputs found
LâĂ©tayage de la tĂąche complexe en SVT au lycĂ©e
Open inquiry learning is an educational approach widely promoted in secondary education since it promotes the development of students' skills. A key to the implementation of the open inquiry learning is the choice of scaffolds provided to the students. This work presents an experimental approach as well as considerations about the role and evaluation of the effectiveness of various types of scaffolds proposed for solving an open inquiry task performed by 10th grade high school students in life and Earth sciences. The analysis highlighted the important role of the scaffolds as they are the key to a more efficient differentiation (anticipation of the studentsâ needs, discharge the teacher, improvement of studentsâ autonomy...). However, a period of appropriation of the tools by the students is necessary and reinvestment of these scaffolds in various situations seems to be necessary in order to increase their efficiency.Le travail en tĂąche complexe est une approche pĂ©dagogique largement encouragĂ©e dans lâenseignement secondaire puisquâelle favorise le dĂ©veloppement des compĂ©tences des Ă©lĂšves. Une des clĂ©s de la mise en Ćuvre de la tĂąche complexe est le choix des Ă©tayages apportĂ©s aux Ă©lĂšves. Ce mĂ©moire prĂ©sente une expĂ©rience et un retour rĂ©flexif sur le rĂŽle et lâĂ©valuation de lâefficacitĂ© de divers types dâĂ©tayages proposĂ©s pour la rĂ©solution dâune tĂąche complexe en sciences de la vie et de la Terre en classe de seconde gĂ©nĂ©rale. Lâanalyse effectuĂ©e a permis de souligner le rĂŽle important des aides mises Ă disposition des Ă©lĂšves puisquâelles sont la clĂ© dâune diffĂ©renciation plus efficace (anticipation des besoins des Ă©lĂšves, dĂ©charge du professeur, gain en autonomie des Ă©lĂšvesâŠ). Il semble cependant quâune phase dâappropriation des aides soit nĂ©cessaire pour que ces Ă©tayages puissent ĂȘtre exploitĂ©s de maniĂšre plus efficiente par les Ă©lĂšves. RĂ©investir rĂ©guliĂšrement ces outils dâĂ©tayage pour diverses situations complexes (Ă tous niveaux du secondaire) apparait donc important pour en augmenter lâefficacitĂ©
ETUDE DES MECANISMES DU PRECONDITIONNEMENT MYOCARDIQUE CHEZ LE RAT (DOCTORAT (GENIE BIOLOGIQUE ET MEDICAL))
GRENOBLE1-BU MĂ©decine pharm. (385162101) / SudocPARIS-BIUM (751062103) / SudocPARIS-BIUP (751062107) / SudocSudocFranceF
Dietary selenium intake affects cardiac susceptibility to ischaemia/reperfusion in male senescent rats.
International audienceBACKGROUND: cardiovascular ageing is associated with an increase in cardiac susceptibility to ischaemia and reperfusion. This has been suggested to be partly related to an increased sensitivity of the myocardium to the reactive oxygen species that are produced during post-ischaemic reperfusion. The aim of the present study was therefore to determine whether increasing cardiac glutathione peroxidase activity by a selenium-enriched diet could afford some protection against ischaemia and reperfusion to senescent rat hearts. METHODS: 22 months old male Wistar rats received either a high-selenium (1.5 mg Se/kg diet) or a low-selenium (0.05 mg Se/kg diet) diet for 10 weeks. At the end of the diet, hearts were submitted to ischaemia and reperfusion ex vivo and either fixed for semi-quantitative analysis of ultrastructural damage by electron microscopy or used for glutathione peroxidase activity assessment. RESULTS: high-selenium supply increased cardiac total, mitochondrial and cytosolic glutathione peroxidase activities. Moreover, this diet induced a significant improvement of cardiac post-ischaemic functional recovery. Finally, this preservation of cardiac function was associated with a significant limitation of ultrastructural alterations of sarcomeres and mitochondria. CONCLUSION: our high-selenium diet considerably limits the sensitivity of senescent rat hearts to ischaemia and reperfusion. This finding suggests that peroxides might play a key role in the increase in cardiac sensitivity to ischaemia and reperfusion during ageing. Together with the observation that selenium status decreases with age in humans, our results indicate that reinforcing selenium supply could improve the prognosis of cardiovascular diseases in old patients
Delayed expression of cytokines after reperfused myocardial infarction: possible trigger for cardiac dysfunction and ventricular remodeling.
Previous studies have shown that 1 wk after permanent coronary artery ligation in rats, some cellular mechanisms involving TNF-alpha occur and contribute to the development of cardiac dysfunction and subsequent heart failure. The aim of the present study was to determine whether similar phenomena also occur after ischemia-reperfusion and whether cytokines other than TNF-alpha can also be involved. Anesthetized male Wistar rats were subjected to 1 h coronary occlusion followed by reperfusion. Cardiac geometry and function were assessed by echocardiography at days 5, 7, 8, and 10 postligation. Before death, heart function was assessed in vivo under basal conditions, as well as after volume overload. Finally, hearts were frozen for histoenzymologic assessment of infarct size and remodeling. The profile of cardiac cytokines was determined by ELISA and ChemiArray on heart tissue extracts. As expected, ischemia-reperfusion induced a progressive remodeling of the heart, characterized by left ventricular free-wall thinning and cavity dilation. Heart function was also decreased in ischemic rats during the first week after surgery. Interestingly, a transient and marked increase in TNF-alpha, IL-1beta, IL-6, cytokine-induced neutrophil chemoattractant (CINC) 2, CINC3, and macrophage inflammatory protein-3alpha was also observed in the myocardium of myocardial ischemia (MI) animals at day 8, whereas the expression of anti-inflammatory interleukins IL-4 and IL-10 remained unchanged. These results suggest that overexpression of proinflammatory cytokines occurring during the first week after ischemia-reperfusion may play a role in the adaptative process in the myocardium and contribute to early dysfunction and remodeling
Cardiac dysfunction in rats with dietary-induced insulin resistance associated with pharmacologically-induced dyslipidemia.
International audienceMetabolic disorders such as insulin resistance (IR) and dyslipidemia (DL) might contribute to the induction of diabetic cardiomyopathy (DCM). However, few relevant animal models are currently available for studying the time-course of DCM and evaluating experimental therapeutics. The present study proposes a rodent model of dietary-induced IR combined or not with DL in order to investigate the impact of chronic IR and DL on in vivo myocardial function. Male rats were fed a western-type diet (65% fat; 15% fructose; WD). DL was induced by combining the western diet with i.p. injections of a nonionic surface-active agent (P-407; 0.2 mg/kg, 3 times/wk; P-407). A chow diet was used as control. At 11 and 14 weeks, cardiac function was assessed by echocardiography. Fasting blood glucose increased in WD group while plasma lipids markedly accumulated in P-407 treated rats. Echocardiographic data showed no significant difference in cardiac geometry under basal conditions. Diastolic dysfunction was evidenced at 14 weeks by a significant decrease in E/A ratio in the P-407 group. Moreover, fractional shortening was significantly depressed under dobutamine stress in WD group at 14 weeks whereas systolic dysfunction appeared as early as 11 weeks and worsened at 14 weeks in P-407 animals. Finally, myocardial TNF-alpha tissue content increased in P-407 group. In conclusion, DL exacerbated cardiac lipotoxicity and functional complications associated with IR. This experimental model of combined IR and DL closely mimics the main clinical manifestations of DCM and might therefore constitute a useful tool for the evaluation of pharmacological treatments
Cardiac dysfunction in rats with dietary-induced insulin resistance associated with pharmacologically-induced dyslipidemia.
International audienceMetabolic disorders such as insulin resistance (IR) and dyslipidemia (DL) might contribute to the induction of diabetic cardiomyopathy (DCM). However, few relevant animal models are currently available for studying the time-course of DCM and evaluating experimental therapeutics. The present study proposes a rodent model of dietary-induced IR combined or not with DL in order to investigate the impact of chronic IR and DL on in vivo myocardial function. Male rats were fed a western-type diet (65% fat; 15% fructose; WD). DL was induced by combining the western diet with i.p. injections of a nonionic surface-active agent (P-407; 0.2 mg/kg, 3 times/wk; P-407). A chow diet was used as control. At 11 and 14 weeks, cardiac function was assessed by echocardiography. Fasting blood glucose increased in WD group while plasma lipids markedly accumulated in P-407 treated rats. Echocardiographic data showed no significant difference in cardiac geometry under basal conditions. Diastolic dysfunction was evidenced at 14 weeks by a significant decrease in E/A ratio in the P-407 group. Moreover, fractional shortening was significantly depressed under dobutamine stress in WD group at 14 weeks whereas systolic dysfunction appeared as early as 11 weeks and worsened at 14 weeks in P-407 animals. Finally, myocardial TNF-alpha tissue content increased in P-407 group. In conclusion, DL exacerbated cardiac lipotoxicity and functional complications associated with IR. This experimental model of combined IR and DL closely mimics the main clinical manifestations of DCM and might therefore constitute a useful tool for the evaluation of pharmacological treatments