Thiamine pyrophosphatase cytochemistry in rat endometrium during the oestrous cycle

Distinct types of lipofuscin pigment in the hippocampus and cerebellum of aged cheirogaleid primates

The formation of autofluorescent lipopigment or lipofuscin is a highly consistent and reliable cytological change that correlates with cellular aging in postmitotic cells. One causal factor of lipofuscinogenesis involves free radical-induced lipid peroxidation. In mammals, dentate gyrus neurons and Purkinje cells are usually affected widely. In this study, we investigated the ultrastructure of lipofuscin deposits in large neurons of the dentate gyrus and in Purkinje cells of aged fat-tailed dwarf lemurs (Cheirogaleus medius Geoffroy, 1812) with electron and confocal microscopy and compared it with previous observations in other species. Cheirogaleid primates such as mouse and dwarf lemurs are archaic primates that provide interesting nonhuman models of aging. Our study revealed region-specific as well as species-specific characteristics of lipofuscin ultrastructure. This suggests differences in cellular metabolism and/or in organelles involved in lipofuscin production in cerebellar Purkinje cells and in hippocampal dentate gyrus neurons.

Correlation between nuclear bodies and estrogen receptors in endometrial epithelial cells of old rats

Nuclear bodies (NB) are prominent round structures in interchromatin regions of interphase nuclei, regarded as markers of stimulated rRNA synthesis. Their frequency was found to be estrogen-dependent and correlated with estrogen receptor (ER) content in endometrial epithelial cells of prepubertal and cyclic rats. The present study was designed to simultaneously examine the frequency of simple and complex NB and the status of ER in endometrial epithelia of old rats in relation to age and vaginal cytology. The vaginal cycles of old Wistar rats (n degree = 24) at 24, 28, 32, and 36 months of age, which were longitudinally monitored for at least 180 days by daily vaginal smears, were extremely irregular with a predominance of either persistent estrus or persistent diestrus over many days, weeks and even months. In all age groups ER-immunoexpression was very high (+3 = > 75%) in persistent-estrus rats and coincided with particularly frequent NB (2-3 simple NB out of 4-5 total NB per nuclear profile) in the tall epithelial cells with ultrastructural signs of intense protein synthesis. In persistent-diestrus rats isolated simple and complex NB (1 per nuclear profile) and an almost absent ER expression were distinctive of the nuclei in low, ultrastructurally "inactive" endometrial luminal and glandular epithelial cells. Thus, ER immunoexpression and NB frequency are also estrogen-dependent in old rats. Our findings show, for the first time, that ER immunoexpression in endometrial epithelial cells is down-regulated only in old rats in persistent diestrus, whereas in persistent-estrus rats intense ER expression harmonizes with high NB frequency, irrespective of animal age.

Ultrastructural localization of activity of phosphatases by low temperature incubation of unfixed cryostat sections

In the present study, we demonstrate the activity of several phosphatases ultrastructurally in long-term (up to 24 months) cold-stored (-80 degrees C) rat tissues. Phosphatase activity was histochemically studied with the use of unfixed cryostat sections in combination with low temperature (4 degrees C) incubation conditions in order to prevent inactivation of enzyme activity and to limit the loss of ultrastructure. 5'-Nucleotidase activity was observed at plasma membranes, mainly at bile canalicular membranes of hepatocytes in liver. Thiamine pyrophosphatase activity was detected not only in trans side cisternae but also in medial and cis side cisternae of Golgi complexes in the parotid gland. Glucose-6-phosphatase activity was localized in endoplasmic reticulum as well as at the outer membrane of the nuclear envelope. Acid phosphatase reaction product was found in lysosomes. Furthermore, the localization patterns of 5'-nucleotidase and thiamine pyrophosphatase activity were compared with those obtained after different fixation procedures such as immediate chemical fixation of tissues or fixation of tissues after freezing and thawing. The results showed similar localization patterns of these enzymes after the different pretreatments. However, with respect to the ultrastructural morphology, some damage was observed in unfixed material after incubation. It can be concluded that the procedure described here enables ultrastructural localization of activity of phosphatases in long-term cold-stored tissues. This procedure will be useful for a retrospective study on archival material when histochemical parameters are needed.