Culture of mouse germ cells isolated from fetal gonads

Mouse germ cells isolated from male or female genital ridges at 121/2 days post coitum were cultured at room temperature for up to 6 days, with [3H]thymidine present in the culture medium for either the first 24 h or the last 24 h of each culture period. Germ cells were also isolated 131/2-161/2 days post coitum and cultured for 24 h in the presence of [3H]thymidine. The proportion of cells in metaphase, and the proportion of labelled interphase and metaphase nuclei, was recorded. The labelling index declined from 131/2 days onwards, after development either in vivo or in vitro. No labelled metaphase plates were seen after 24 h in the presence of [3H]thymidine, suggesting that under these culture conditions the duration of the G2 phase exceeded 24 h. The results showed that the culture system, in spite of the low temperature, allowed the germ cells to replicate their DNA and undergo mitosis for up to 6 days. Addition of db-cAMP to the culture medium proved highly toxic to male germ cells, and did not markedly increase the proliferation rate of female germ cells.