Bovine embryonic viability after in vitro fertilisation (IVF) was affected by addition of platelet-derived growth factor (PDGF) or growth factor combinations to gonadotrophin-supplemented serum-free medium for in vitro maturation (IVM). Thus, 0.1, 1.0 or 10.0 ng PDGF/ml combined with 500 ng follicle-stimulating hormone (FSH)/ml enhanced oocyte maturation as reflected by greater proportions (p < 0.05) of matured and inseminated oocytes developing to blastocysts in vitro than were afforded by PDGF alone, i.e. 32.4%, 28.2% and 31.0% respectively vs. 11.4%, 13.5% and 8.6% respectively. By contrast, luteinising hormone (LH, 500 ng/ml) combined with the same concentrations of PDGF did not increase the proportions of oocytes developing to blastocysts (16.2%, 12.5% and 16.9%). Epidermal growth factor (EGF) + insulin-like growth factor-I (IGF-I) with or without PDGF when added to low concentrations of FSH or LH did not significantly improve cleavage or morula development. Significant improvement (p & 0.05) in blastocyst formation was seen when FSH was supplemented with either EGF (38.0%) or EGF + IGF-I + PDGF (40.7%) compared with FSH alone (27.4%) or FSH + LH (24.3%), but no improvement followed FSH + EGF + IGF-I (33.6%) or FSH + LH + EGF + IGF-I + PDGF (29.2%) treatments for IVM. Results revealed a positive influence on blastocyst development of FSH and PDGF or EGF ± PDGF during IVM and suggest the possibility of a concerted action of gonadotrophins with growth factors in physiological (functional) oocyte maturation.

The effects of medium supplementation with oestrous goat serum and glycoprotein hormones on caprine oocyte maturation in vitro (IVM) were evidenced by proportions of resulting ova completing in vitro fertilisation (IVF) and development to the morula stage. Oocyte-cumulus complexes (OCCs) were harvested in follicular fluid from 2–5 mm diameter follicles. Oocyte maturation took place during 27 h in TCM-199 supplemented with 20% oestrous goat serum, oestradiol-17β (1.0 μg/ml), and either (a) 0.5 μg FSH/ml, (b) 100 μg LH/ml, (c) 100 μg LH + 0.5 μg FSH/ml, (d) 100 μg hCG + 0.5 μg FSH/ml, (e) 0.5 μg TSH/ml or (f) no added glycoprotein hormone (control). Of 353 immature oocytes cultured in seven experiments, 311 (88.1%) exhibited cumulus expansion at the end of the IVM interval; all normalappearing OCCs were inseminated. In vitro insemination was with ejaculated sperm treated with heparin (10 μg/ml) and caffeine (0.4 μg/ml). Proportions (%) of inseminated ova that were fertilised (cleaved) and that reached the morula stage after IVM with (a) FSH, (b) LH, (c) LH + FSH, (d) hCG + FSH, (e) TSH and (f) no added glycoprotein hormone were (a) 22/52 (42.3%) and 9/52 (17.3%), (b) 25/54 (46.3%) and 14/54 (25.9%), (c) 52/65 (80.0%) and 26/65 (40.0%), (d) 48/78 (61.5%) and 22/78 (28.2%), (e) 14/54 (25.9%) and 4/54 (7.4%), and (f) 11/50 (22.0%) and 1/50 (2.0%), respectively. All treatments yielded better results than IVM with no added glycoprotein hormone. After IVM with added LH + FSH higher proportions of oocytes were fertilised (p<0.05), and higher proportions reached the morula stage (p<0.05) when compared with other treatments.

Owing to the close phylogenetic relationship of Platyrrhini (New World monkeys) and Catarrhini (Old World monkeys) to man, nonhuman primates are often used as models for the study of male reproductive physiology and endocrinology. This review aims at providing new data and insights into comparative primate spermatogenesis, dealing specifically with quantitative aspects of germinal epithelial organisation and germ cell production, and with the roles of gonadotrophic hormones in this process.

Typically, the seminiferous epithelium is composed of specific germ cell associations (spermatogenic stages). In rodents, prosimians and most Catarrhini, tubular cross sections contain a single spermatogenic stage whereas in Platyrrhini, great apes and man multi-stage tubules are present. Since Platyrrhini represent a more basal type of primate, this spermatogenic feature must have developed convergently. The primate multi-stage tubular arrangement was previously believed to be associated with low spermatogenic efficiency. However, recent studies using new methodological approaches and comparing primate species from all taxa have revealed that multi-stage organisation is compatible with highly efficient spermatogenesis. In fact, meta-analysis demonstrated that the efficiency of spermatogenesis in several nonhuman primate species is comparable to that of rodents which are considered as species with highly efficient germ cell production. The duration of the spermatogenic process was not related to organisation or efficiency of spermatogenesis. Sertoli cell work load was species-specific but had no impact on germ cell numbers and on the efficiency of spermatogenesis.

The gonadotrophic hormones, luteinizing hormone (LH) and follicle stimulating hormone (FSH) are the primary regulators of primate testicular function. Recent studies revealed that in New World monkeys chorionic gonadotrophin (CG) – the primate pregnancy hormone – regulates testosterone production instead of LH. Receptor studies demonstrated a dual action of the closely related hormones LH and CG in primates. It is hypothesised that following the divergence of the Platyrrhini lineage from Catarrhini, the LH/CG system evolved independently with ancestral functions of the LH/CG system retained in the neotropical taxa.

In summary, key spermatogenic features are preserved across all primate taxa whereas male reproductive endocrinology features appear substantially different in the neotropical primates compared to other primate lineages.

A comparison was made of the stature of women, twinning rates, and breast cancer mortality for 32 countries. As height increased, so did twinning and breast cancer mortality (P < 0.005). Dizygotic twinning and breast cancer increased sharply with the mean height of the female population. With due caution in drawing causal inferences when uncontrolled confounding variables are present, it is suggested that these findings are an evolutionary consequence of the high mortality found in twin pregnancy.

It is estimated here that, at the time of conception, the mean coital rate of young women who subsequently bear DZ twins is about 6% higher than that of the general population of young married women. This differential seems too small to account wholly for the greater promptness in conceiving DZ twins. Accordingly, it is suggested that coital rate is associated with DZ twinning in two ways. The major link seems to be indirect and mediated by erotic response which causes an increase in gonadotrophin levels and thus in double ovulation. In a minority of cases, frequent coitus may give rise to DZ twins via superfecundation, but it seems that, in human beings, the corpus luteum of one ovum will usually inhibit fertilization of any further ova after a short interval. The evidence presented here, though indirect, seems to suggest that, under particularly erotic conditions, double ovulation is sometimes induced. It seems reasonable to infer that coitus also occasionally provokes or accelerates single ovulations, thus impugning some rhythm methods of contraception. But there seems no very good evidence that rape induces ovulation. Some notes are added on the implications of induced ovulation for estimates of fecundability and of the length of the fertile period.