Effect of altering endogenous gonadotrophin concentrations on the kinetics of testicular germ cell turnover in the bonnet monkey (Macaca radiata)

Abstract

The role of FSH and diurnal testosterone rhythms in specific germ cell transformations during spermatogenesis were investigated using DNA flow cytometry and morphometry of the seminiferous epithelium of the adult male bonnet monkey (Macaca radiata), the endogenous hormone levels of which were altered by two different protocols. (1) Active immunization of five monkeys for 290 days using ovine FSH adsorbed on Alhydrogel resulted in the neutralization of endogenous FSH, leaving the LH and diurnal testosterone rhythms normal. (2) Desensitization of the pituitary gonadotrophs of ten monkeys by chronically infusing gonadotrophin-releasing hormone analogue, buserelin (50 micrograms/day release rate), via an Alzet pump implant (s.c.) led to a 60-80% reduction in LH and FSH as well as total abolition of testosterone rhythms. The basal testosterone level (3.3 +/- 2.0 micrograms/l), however, was maintained in this group by way of an s.c. testosterone silicone elastomer implant. Both of the treatments caused significant (P < 0.01) nearly identical reduction in testicular biopsy scores, mitotic indices and daily sperm production rates compared with respective controls. The germ cell DNA flow cytometric profiles of the two treatment groups, however, were fundamentally different from each other. The pituitary-desensitized group exhibited a significant (P < 0.001) increase in 2C (spermatogonial) and decrease in 1C (round spermatid) populations while S-phase (preleptotene spermatocytes) and 4C (primary spermatocytes) populations were normal, indicating an arrest in meiosis caused presumably by the lack of increment in nocturnal serum testosterone. In contrast, in the FSH-immunized group, at day 80 when the FSH deprivation was total, the primary block appeared to be at the conversion of spermatogonia (2C) to cells in S-phase and primary spermatocytes (4C reduced by > 90%). In addition, at this time, although the round spermatid (1C) population was reduced by 65% (P < 0.01) the elongate spermatid (HC) population showed an increase of 52% (P < 0.05). This, taken together with the fact that sperm output in the ejaculate is reduced by 80%, suggests a blockade in spermiogenesis and spermiation. Administration of booster injections of oFSH at time-points at which the antibody titre was markedly low (at days 84 and 180) resulted in a transient resurgence in spermatogenesis (at day 180 and 228), and this again was blocked by day 290 when the FSH antibody titre increased.(ABSTRACT TRUNCATED AT 400 WORDS)

Gonadotrophin-releasing hormone antagonist arrests premeiotic germ cell proliferation but does not inhibit meiosis in the male monkey: a quantitative analysis using 5-bromodeoxyuridine and dual parameter flow cytometry

“…These kinetic data suggest that ANT-induced germ cell depletion results from an arrest of spermatogonial divisions in the nonhuman primate. Our observations extend previous histological reports on the significant reduction of numbers of renewing spermatogonia after 28 days of ANT treatment (Weinbauer et al 1991) but do not confirm the assumption of a meiotic arrest as the cause of spermatogenic inhibition (Aravindan et al 1993). The data on proportions of 4C and 1C cells suggest that the number of cells available for meiosis is reduced by ANT, whereas the development into round spermatids is not prohibited.…”

“…The data on proportions of 4C and 1C cells suggest that the number of cells available for meiosis is reduced by ANT, whereas the development into round spermatids is not prohibited. Gonadotrophin deficiency in the nonhuman primate induces a marked increase in the number of 2C cells if expressed as percentage of the total number of cells analyzed (Weinbauer et al 1991, 1994, Aravindan et al 1993; this increase, however, is relative resulting from the loss of 1C and 4C cells. In fact, expression of 2C cell numbers per testis yields reduced numbers.…”

“…Detailed histological studies in the rat identified a specific loss of spermatocytes and spermatids as the earliest lesion following gonadotrophic hormone deprivation (Russell & Clermont 1977, Sinha-Hikim & Swerdloff 1993, O'Donnell et al 1996. In the nonhuman primate, loss of spermatogonia (Weinbauer et al 1991) and meiotic arrest (Aravindan et al 1993) have been suggested. Prolonged withdrawal of gonadotrophic hormones eliminates spermatids, spermatocytes and even differentiated spermatogonia in the monkey (Marshall et al 1986, Weinbauer et al 1991.…”

Susceptibility of Sperm Chromatin to Acid Denaturation in Situ: A Study in Endogenous Fsh-Deprived Adult Male Bonnet Monkeys (Macaca radiata)

“…The procedures used for semen collection and processing to determine sperm counts, viability, and gross motility have been described earlier [ 1,151.…”

Milestones in contraceptive vaccines development and hurdles in their application

“…Bio-neutralization activity of the immune sera was determined by using sheep testicular receptor binding inhibition assay, which basically involved incubation of particulate sheep testicular FSH receptor with 125 I-FSH in presence of immune serum samples. 49 To determine human spermatozoa fertilizing ability, an in-vitro sperm binding and penetration assay employing zona-free hamster eggs has also been developed. 50 The assay has an advantage as it avoids the ethical and logistic problems associated with the use of human eggs.…”