Browsing by Author "Tchokonte-Nana, Venant"
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- ItemCellular mechanisms involved in the recapitulation of endocrine development in the duct ligated pancreas(Stellenbosch : University of Stellenbosch, 2011-03) Tchokonte-Nana, Venant; Page, Benedict; Du Toit, Don F.; University of Stellenbosch. Faculty of Health Sciences. Dept. of Biomedical Sciences. Anatomy and Histology.ENGLISH ABSTRACT: Diabetes mellitus is amongst the leading causes of morbidity and mortality in the world, affecting young, adult and old people. Beta cell replacement therapy for insulin delivery remains the ultimate remedy for diabetes. However, insufficient donor pancreas and the use of immunosuppressive drugs prevent the wide-spread of this therapy. Other avenues of self generated beta cells within the organ itself need to be explored. Therefore, understanding the chronobiology of cellular mechanisms in the lineage of beta cell induced neogenesis is a valuable tool in improving beta cell replacement in patients with diabetes. The aim of this study was to induce recapitulation of the morpho-genetic sequence of endocrine cells development in the pancreas of rats after the pancreatic duct ligation (PDL) procedure. Serial sections of PDL tissues of the pancreas were obtained from 78 Sprague- Dawley rats and were assessed morphologically. The immunofluorescent tissues were statistically analysed using a computerized morphometry technique. The protein expression indices of Caspase3, Insulin, Pdx1, Ngn3, NeuroD and Pax6 were quantified. The efficiency levels of coexpression of these homeodomain proteins separately with insulin were defined by the ratio of the mean value of insulin expression to the mean value of their respective protein expression. The morphological changes were characterized by the appearance of granulated acinar cells at 6 hours post-PDL and the proliferation of endocrine tissues from 84 hours through to 120 hours. The morpho-immunofluorescent evaluation showed the highest immunoreactivity of Caspase3 and Pdx1 at 6 hours, Ngn3 at 36 hours, Pax6 and insulin at 84 hours while NeuroD expression was at 120 hours. The immunohistofluorescent analysis showed that caspase3 and Pdx1 were the first to be expressed at 6 hours while the insulin and NeuroD expression appeared later at 84 hours and 120 hours, respectively. However, Pax6 expression was continuous across time periods post-PDL, while Ngn3 expression showed a peak at 36 hours. The efficiency (highest and earliest expression) of co-expression of all these homeodomain proteins with insulin was restricted between 12 hours and 24 hours. The optimal efficiency was at 12 hours by Ngn3 with insulin. A good efficiency was shown for Pdx1 with insulin, NeuroD with insulin and Pax6 with insulin at 12 hours and 24 hours, respectively. A low efficiency was observed for insulin and caspase3 co-expression at 24 hours. This study suggests that for transplantation, PDL tissues harvested at an early time post-PDL (between 12 and 24 hours) could yield a higher success rate; the study also provides evidence for a connection between morphological changes in the PDL pancreas and the protein synthesis necessary for the lineage of endocrine cell development.
- ItemHistomorphometric and radioimmunoassay studies of the rat endometrium following peanut oil treatment(Research and Clinical Center for Infertility, Shahid sadoughi University of Medical Sciences of Yazd, 2011-02) Tchokonte-Nana, Venant; Longo-Mbenza, BenjaminBackground: The pregnancy rate during in-vitro fertilization (IVF) following progesterone supplement still remains very low at around 20%. Objective: To investigate the effects of peanut oil itself on the endometrial receptivity, the pregnancy success rate and fertility during the peri-implantation time in hyper stimulated and normal rats. Materials and Methods: Thirty-six adult Sprague Dawley rats with at least four regular oestrus cycles were randomly divided into 4 groups: two groups were hyper stimulated by human chorionic gonadotropin (hCG) and treated with progesterone or with peanut oil; the two other groups were not hyper stimulated and treated with saline solution or peanut oil. On day 5.5 of pregnancy, the uterine horns were removed and blood was collected for histomorphometric and serum progesterone evaluation. 12 rats were allowed to continue the presumed pregnancy to term. Analysis of variance (ANOVA) and student t-test were used to compare the means of morphometric and radioimmunoassay data between groups. p-values less than 0.05 were considered statistically significant. Results: The mean values of morphometric parameters and serum progesterone varied significantly between the groups (ANOVA, p<0.0001). The lowest values of progesterone parameters were observed in the hyperstimulated groups that did not deliver pups; both hyperstimulated groups had deleterious luminal epithelium with varying degrees of mucosal projections. There were isolated decidualised zones observed in hyper stimulated peanut oil group, whereas peanut oil group had the highest number of implantation sites and deliveries. Conclusion: The results show that hype stimulation reduces the endometrial receptivity, while peanut oil increases endometrial receptivity, pregnancy rates and fertility by triggering decidualisation.
- ItemImmunohistomorphology of pancreatic islet microvasculature and the immunophenotypic analysis of CEPC in adult diabetic rats(Sociedad Chilena de Anatomia, 2017) Tchokonte-Nana, Venant; Le Roux, Danie Jacobus; Kotze, Patricia Clara; Ngounou, EleonoreENGLISH ABSTRACT: Hyperglycaemia is one of the main causes for the endothelial cell (EC) damage in diabetic patients. Even though circulating endothelial progenitor cells (CEPC) could be used as a prognosis for microvascular complications, there is very little information on the islet microvasculature. We analysed by immunohistochemistry and by flow cytometric immunophenotyping, the expression of CD34 on EC and the expressions of CD31, CD34, CD45 and CD133 on CEPC in Streptozotocin (STZ)-induced diabetic rats. Peripheral blood and tissue specimens were obtained from rats of different treatment regimens: STZ treatment, control saline (NS) and sodium citrate (CB) treatments. Blood cells were exposed to flow cytometric immunophenotyping for CD133, CD31, CD34, CD45 and CD133. While tissues from the pancreas, liver and kidney were routinely processed and stained immunohistochemically for CD34. There was a tendency of an increased in CD45-/CD133+/CD31+/CD34+ cells (0.04 ± 0.11 %) in diabetic rats compared to the controls (CB: 0.03 ± 0.04 %; Saline: 0.01 ± 0.03 %). But there was no significant statistical difference between them. The expression pattern of CD34 on the EC in the organs’ vascular beds including arterioles, venules, capillaries and sinusoids was extremely heterogeneous across and within treatment regimens. The ECs in the sinusoids of the liver presented similar CD34 expression patterns across different treatment regimens, while the expression of CD34 on the ECs of sinusoidal capillaries in the pancreas vary with the treatment regimen. We conclude that the degree of endothelial cell damage is not uniform across organs’ vascular beds in the rat, contrary to mice and humans. Furthermore, the sinusoids in the pancreas and the kidney may have the same degree of endothelial damage when exposed to the same deleterious causes.
- ItemMorphogenetic and clinical perspectives on the neogenesis of pancreatic duct ligation-induced islet cells : a review(Official Organ of Wroclaw University of Medicine, 2011) Tchokonte-Nana, Venant; Longo-Mbenza, Benjamin; Page, Benedict J.; Du Toit, Donald F.This review focuses on recent progress in understanding morphogenetic findings on the neogenesis of islet beta cells following Pancreatic Duct Ligation (PDL) in animal models. These results may give hope for modifications in the treatment of diabetes in general and transplantation in particular. On the basis of this review, translational studies should be developed to allow information on beta-cell neogenesis to be integrated into a potential therapy for Diabetes Mellitus (DM) in humans. Further studies on the development of animal models that will produce PDL islets for transplantation are urgently needed.