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Biomedical subjects

A Varas

Publications and source records attributed to A Varas.

42 records · Page 3Linked to original sources
PubMedDate not supplied

Changes in the thymus and spleen of the turtle Mauremys caspica after testosterone injection: a morphometric study.

To confirm a possible role of sex hormones in governing the seasonal variations affecting the reptilian lymphoid organs, a morphometric analysis was carried out on the thymus and spleen of turtles, Mauremys caspica, intraperitoneally injected with a single dose of testosterone propionate (TP) at the third week of June when physiological levels of testosterone are low. At 4 and 6 weeks, control turtles show an apparent lymphocyte mobilization both from thymus and spleen with a decrease in the percentage of thymic cortex, numbers of cortical lymphocytes, and mitotic index, but increased numbers of medullary lymphocytes. In the thymic cortex of treated turtles, there is a decrease in the same parameters but they occur in the first 2 weeks, whereas the medullary lymphocytes also undergo reduction at 4 and 6 weeks. In addition, the number of reticuloepithelial cells per area unit decreases at 2 weeks in the thymic cortex of treated turtles. These results are discussed from the point of view of a biphasic effect of testosterone on turtle lymphoid organs: In the first weeks, the changes observed could be attributed to the high levels of testosterone; after 4 and 6 weeks, variations are dependent both on long-term effects of testosterone and on those induced by the high values of corticosterone occurring in summer.

Animals↗
PubMedDate not supplied

Accelerated maturation of the thymic stroma in the progeny of adrenalectomized pregnant rats.

The possible role played by glucocorticoids (GCs) in the development of thymic stromal cell components has been studied in the progeny of adrenalectomized pregnant rats (FAdx), an experimental model which ensures the absence of GCs until the establishment of the fetal hypothalamus-pituitary gland-adrenal gland axis. As previously demonstrated for thymocytes, the lack of GCs early in ontogeny results in an accelerated maturation of the thymic stromal elements. Early expression of specific cell markers for thymic epithelial cell subsets and appearance of a well-established cytokeratin-positive epithelial cytoreticulum confirmed the ultrastructural evidence of a faster maturation of the thymic epithelium in FAdx than in FSham. A similar faster and stronger pattern of both class I and class II molecule expression on the epithelial cells occurred in the former fetuses than in control ones. Changes in the pattern of expression of laminin, but not that of fibronectin, throughout thymic maturation also reflected accelerated maturation. Immunohistochemically identified thymic macrophages appeared late in both FSham and FAdx but in higher numbers in these latter indirectly demonstrating their faster development. Finally, the maturation and turnover of thymic dendritic cells showed a remarkable acceleration in the FAdx. In 15- to 16-day-old FAdx thymuses there was a high number of dendritic cells which sharply decreased in the following days suggesting a massive migration to the periphery and/or in situ cell death. In parallel a new wave of dendritic cell progenitors began to differentiate in the FAdx thymuses but not in the FSham ones. The results are discussed from the view of close relationships known to occur between thymocytes and the stromal components, although a direct effect of GCs cannot be discarded.

Adrenalectomy↗