To evaluate the role of vitamin B,, on spermatogenesis, the effects of dietary vitamin B,, deficiency on sperm maturation in developing rat fetuses and young growing rats were examined. The vitamin B,,-deficient diet was given to all the animals for three different periods: whole period (gestation to mature), gestation period (gestation to weaning), or immature period (3-12 weeks postnatal). Sperm examination revealed that the sperm count was markedly lower in male progeny (Fl) that were vitamin B,,-deficient during the whole period. In addition, a significantly higher number of abnormal sperm, such as tailless and amorphous sperm, was observed. In male rats that were vitamin B,,-deficient during the immature period, the incidence of abnormal sperms was 14.4% and 4.8% for tailless and short tail, respectively. The motion rates, such as path velocity and straight line velocity, were decreased to 20-40% of the control value in rats that were vitamin B,,-deficient both during the whole and gestation periods. However, no effects of vitamin B,, deficiency on sperm motility were observed during the immature and mature periods. From these findings, we suggest that dietary vitamin B,, deficiency during pregnancy may induce irreversible damage in the germ cells of embryos and affect the maturation of spermatozoa.Abbreviations used in this paper: B,,, vitamin BI2 (cobalamin); CH3-BI2 (Me-B,,), mecobalamin; CN-B,,, cyanocobalamin; MMA, methylmalonic acid; HPLC, high performance liquid chromatography

Seasonal change in spermatogenesis was examined in the restricted spermatogonium-type testes of a teleost, Oryzias latipes. Histological observation revealed that the number of each stage of germ cells during most of the non-reproductive season, from October to January (O-J period) was nearly half of that during the reproductive season, from May to July (M-J period), except for type B spermatogonia (B-gonia), which was actually equal. As a result, the ratio of primary spermatocytes (P-cytes) to B-gonia was remarkably small in the O-J period. Despite the differences between both time periods, the proliferative activity of type A spermatogonia (A-gonia), B-gonia, or P-cytes was at a similar level in both periods. Moreover, in cultured testes treated with bromodeoxyuridine as a cell-lineage tracer, P-cytes differentiated to spermatids in 11-15 days in both M-J and O-J periods. These indicate that spermatogenesis is active in each period at a different state. In the spermatogenic testis, A-gonial proliferation was maintained by human follicle stimulating hormone ⁄ luteinizing hormone in culture. Whereas cell death of B-gonia and ⁄ or P-cytes gradually increased in the M-J period in spite of those cells being constant in population sizes. In transition to the O-J period, A-gonia and P-cytes first decreased, which was accompanied by a decrease in proliferative activity of A-gonia and relative increase of dead cells from B-gonia and ⁄ or P-cytes against live P-cytes. These suggest that A-gonial proliferation and cell death of B-gonia and ⁄ or P-cytes that is induced coordinately with B-gonial differentiation are critical for the spermatogenic control.

To evaluate the role of vitamin B12 on spermatogenesis, the effects of dietary vitamin B12 deficiency on sperm maturation in developing rat fetuses and young growing rats were examined. The vitamin B12-deficient diet was given to all the animals for three different periods: whole period (gestation to mature), gestation period (gestation to weaning), or immature period (3-12 weeks postnatal). Sperm examination revealed that the sperm count was markedly lower in male progeny (F1) that were vitamin B12-deficient during the whole period. In addition, a significantly higher number of abnormal sperm, such as tailless and amorphous sperm, was observed. In male rats that were vitamin B12-deficient during the immature period, the incidence of abnormal sperms was 14.4% and 4.8% for tailless and short tail, respectively. The motion rates, such as path velocity and straight line velocity, were decreased to 20-40% of the control value in rats that were vitamin B12-deficient both during the whole and gestation periods. However, no effects of vitamin B12 deficiency on sperm motility were observed during the immature and mature periods. From these findings, we suggest that dietary vitamin B12 deficiency during pregnancy may induce irreversible damage in the germ cells of embryos and affect the maturation of spermatozoa.