Relação entre a quantidade de AgNORS, atividade proliferativa e o estágio de desenvolvimento placentário em equinos

The Nucleolar Organizer Regions (NORs - nucleolar organizer regions) are used to describe regions of chromatin stained with silver nitrateand are related to the activity of rRNA synthesis and to the agility and speed of cell proliferation in the tissues studied. The objective of this study was to relate the amount of AgNORs, proliferative activity and stage of pregnancy in horses, using the coloring of Silver Nitrate. The embryonic attachments were collected, fixed in 10% buffered formaldehyde, embedded in paraplast and stained by silver nitrate. The groups were determined according to the gestational age. The amount of the coriumNOR found in early pregnancy indicates the onset of cell activity, and in that the pregnancy progresses, the amount of NOR increases, suggesting higher activity and increased synthesis of their importance in maintaining the fetus. Contrary to what occurs in the corium, the quantification of NORs was higher in late pregnancy than in the beginning, suggesting the stabilization of these membranes in late pregnancy. The chorionic girdleand the yolk sacwere found in early pregnancy and had lots of NORs, suggesting synthesis function and proliferation in early pregnancy, since their functions is maintenance of the embryo until the complete formation of the true placenta (chorio-allantoic membranes). We conclude that the membranes that develop in a progressive manner in accordance with the growing embryo/fetal (chorion, amnionand allantoic membranes) have an increased number of NORs and the membranes that involute after the formation of the embryo/fetus ( yolk sacand chorionic girdle) have a decrease in number, suggesting a reduction in proliferative activity in these membranes.