Takayasu Nishida

Spermatogenic ability is different among males in different Y chromosome lineage

AbstractIt is a controversial question whether sperm concentrations in humans are changing. Several researchers have reported on environmental factors affecting sperm quality, but the influence of genetic factors is still not fully understood. In this study, we examined the relationship between Y chromosome haplotypes and sperm concentration in fertile males. In addition, we determined the haplotypes of azoospermic patients. The results show that the mean sperm concentration correlates with Y chromosome type. Moreover, the occurrence of azoospermia is related to one particular Y chromosome lineage. Thus, males with a certain haplotype are at a disadvantage for fathering children. The difference of spermatogenic ability among men is important not only in pursuing male competition as in the past but also as relates to the future of modern human males.

Semen quality of Japanese fertile men: A study of partners of pregnant women

During the recent years conflicting information on possible changes in semen quality has been published. These publications also indicate that geographical differences in semen quality may exist. However, no definitive evidence has been provided and additionally very little information regarding semen quality of Japanese men are available. Therefore, we undertook a cross‐sectional study of partners of pregnant women following the same protocol, which has already been used in four European cities. 351 male partners of pregnant women living in the Kawasaki/Yokohama area of Tokyo participated in the study. Of these 232 were recruited from 3 University Hospitals (UH) and 119 were recruited from 2 Private Hospitals (PH). The raw data of the median sperm concentrations were 92.4 (mill/ml) and 99.8 (mill/ml) for the participants from UH and PH respectively. In the analysis of the data the following parameters were taken into account as confounders: mens age, season of year, and abstinence period. We detected a clear seasonal variation in sperm counts with lowest sperm concentration and total sperm count in spring season and highest counts in autumn season with counts in summer and winter seasons being in between. We estimated the semen quality of a “standardised man” (30‐year‐old, fertile, ejaculation abstinence of 96 hours) for both autumn and spring season. The sperm concentration (mill/ml) for autumn/spring were: UH 89/54 and PH 105/63; for total sperm counts (mill): UH 282/151 and PH 315/169. As in the European study we detected a seasonal variation in sperm counts. However, in our study highest counts were detected in autumn season whereas the highest counts in the European study were detected in winter season. Likewise, the lowest counts were in spring and summer in Japan and Europe respectively. The estimated sperm counts of a “standardised Japanese fertile man” seem to be higher than counts in Denmark (Copenhagen) and France (Paris) but lower than counts in Scotland (Edinburgh) and Finland (Turku). It remains to be seen whether regional differences in semen quality exist in Japan.