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Organ cultures of mammalian testes. II. Meiotic chromosomes of adult mice in vitro.

Meiotic chromosomes of adult mice testes cultured in vitro have been studied. All meiotic stages are present and normal until the 8th day; suitable figures for chromosome studies may be obtained with routine cytogenetic methods. During the 9th and 10th day in vitro, the number of cells in meiotic progress falls abruptly. By the 14th day, only a few pachytene stages are still observed. This breakdown of meiosis, linked with the disappearance of the germ cell line, is not due to chromosome anomalies that could have arisen in the new environment. Labeling with tritiated thymidine suggests that spermatogonia do not enter meiotic division in vitro. Chromosomes observed with this technique belong to cells already involved in meiotic processes at time of the initiation of the culture.