Ultrastructural changes in ageing lacrimal gland in Wistar rats.

We studied age-related ultrastructural reorganization in acinar cells and intercalary ducts of the lacrimal gland acini in 3-, 15-, and 24-month-old Wistar rats. Ultrastructural changes in the lacrimal gland progressed with age and led to dramatic ultrastructural reconstruction of the lacrimal gland at the age of 24 months. These changes mainly included complete destruction of acinar cells and increase in the number of enlarged branched ducts that filled the greater part of gland volume; these dusts were lined with epithelial cells with altered ultrastructure. Acinar cells in the acini communicate via special connecting intermembrane complexes formed by desmosomes and mitochondria adjacent to them in each contacting cell. It is assumed that association of mitochondria with desmosomes found in the acini is a special functional complex indicating that every single acinus is a functional formation. This assumption is indirectly confirmed by the fact that the destruction never occurred in a single cell, but always involved all cells constituting the acini. The revealed ultrastructural changes reflect age-related deterioration of the secretory function of the lacrimal gland.

[Structural and functional basis for accelerated thymic involution in OXYS rats].

Thymus involution is one of the most pronounced manifestations of aging immune system, associated with increase susceptibility to infections, autoimmune diseases and cancer. Its nature in normal aging is actively under investigation. Much less attention is paid to the study of mechanisms of accelerated thymic involution. Previously, we showed the connection of accelerated senescence in OXYS rats with accelerated thymic involution, the mechanisms of which remain unclear. The aim of the present work was to study multifunctional condition of thymic epithelial cells in aging OXYS rats. Immunohistochemical analysis showed the reduction of thymic epithelial cell net in OXYS rats, significant decrease in volume and surface area of epithelial cells in cortical substance as compared to control Wistar rats. Electron microscopic study revealed the marked changes of epithelial cell ultrastructure, namely the reduction of cytoplasm volume, sharp decrease in size and quantity of secretory vacuoles, the presence of multiple autophagosomes and phagolysomes. The results indicate that one of the possible mechanisms of epithelial cell net reduction in thymus of senescence-accelerated OXYS rats can be the aggravation of autophagy, probably associated with mitochondrial dysfunction typical for OXYS rats. Despite the known fact of slowing autophagy with aging in some tissues, the example of OXYS rats allows to suggest that chronic deviation of intensity of this process from physiological level, either to decrease or activation, can lead to degenerative changes in organs and finally form the progeric phenotype of the whole organism.