Ageing and testicular function in Octodon degus.
The present study analyses cell loss and proliferation which account for the decrease in the number of germ cell populations in the senile male Octodon degus. This is a good model to study ageing in wild animals, since it has recently been incorporated as a laboratory animal but still has a high degree of genetic heterogeneity, thus representing a situation found in natural systems. The cell loss from pachytene spermatocytes to round spermatids is estimated by cell counts in the cross section of seminiferous tubules. DNA testicular synthesis is measured by scintillation counting and the index of labelling of spermatogonia by radioautography of testes comparing sexually mature young animals and senile animals. Other determinations in both groups are testis weight, thickness of the albuginea and tubular wall, daily sperm production, percentage of depleted seminiferous tubules and nuclear cell diameters of germ cells. The results suggest a decrease in the number of cell population in the senile animals resulting from an increase in physiological cell loss coupled with a decreased proliferative spermatogonial activity. There is also a decreased yield of meiosis in terms of round spermatid production. Lowered testosterone levels both in plasma and testicular parenchymal fluid are found in senile animals. All these senescent changes reflect an altered remodelling activity of the seminiferous epithelium and presumably also of Leydig cells.