Malysheva S. Morphological and functional changes in thymus during aging and after pinealectomy

Dissertation is devoted to the study of morphological and functional changes of thymus during aging and after pinealectomy. It was determined that reduction of lymph tissue area and appropriate increase of fat tissue area are the basic structural manifestations of thymic age involution. Their proportion decreased during aging al-most by 24 times. It was discovered by electron micros-copy, that till 13 months of age the structure of thymus remains practically unchanged. Then, the following changes occur: redistribution of thymic cellular ele-ments, disconnection of cells, vacuolization of epithelio-cytes, and decrease in the amount of their organelles. Two types of thymic capillaries have been discovered, each of them having not only different structure and function, but also different changes during aging. As a result of pinealectomy, age involution of thymus of old animals was delayed. That was confirmed by in-crease of lymph tissue area as compared to controls, in-crease of vascularization level, less expressed destruction of cellular elements, increase of functional activity of thymocytes, epitheliocytes and capillary endothelium, higher activity of alkaline phosphatase in microcircula-tory bed. In young animals, on the contrary, the volume of lymph tissue decreased due to increased level oh thy-mocytes death by the mechanism of apoptosis that can be a consequence of failure of their differentiation. It was accompanied by increase of functional activity of thymo-cytes and epitheliocytes that was combined with devel-opment of destructive changes in mitochondria, their vacuolization and edema. Different reaction on pinealec-tomy of thymus of rats of different age groups can be of primary importance for understanding of mechanisms of its involution.