A sequential analysis of meiosis in the male mouse using a restricted spermatocyte population obtained by a hydroxyurea/triaziquone treatment.

A method is described to restrict the spermatocyte population in mice and other rodents using hydroxyurea (HU) and triaziquone (T). HU affects cells in S-phase, whereas T is an agent especially active on spermatogonia and not on spermatocytes. An application of three i.p. HU injections with 12 h intervals, followed about nine days later by one i.p. T injection creates two large gaps in the spermatogenic line. The two gaps enclose a small, well-defined group of primary spermatocytes in meiotic interphase. - The development of the restricted spermatocyte population is followed day by day. The analysis of meiosis in male mice has revealed the correct sequence of meiotic, and especially prophase I stages. On account of clearly visible differences in chromosome morphology the diplotene stage could be divided into three periods. It is suggested to use the following nomenclature: pre-diffuse diplotene, diffuse diplotene and post-difuse diplotene. The experiment was also informative about the timing of the stages in spermatocyte development by correlating the days at which the successive stages were observed with the corresponding stage of the epithelial cycle. The calculation of the position and duration of the diffuse diplotene, enables us to put forward a proposal about the significance of the diffuse diplotene. - A combination of the HU/T method with cell separation techniques provides good perspectives for detailed biochemical studies on processes taking place during meiosis.