Mechanism of sperm differentiation in amphibians.

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In order to know what determines the flagellar length in mature sperm. The Kinetics of flagellar growth was compared between xenopus and newt spermatids. The results showed that the growth rate and growing period were higher and longer by 2-3 times in the newt than in xenopus. The amount of tubulin pool did not change with time in either species. In Xenopus, tubulin synthesis stopped on the 6th day when the flagellar growth ceased. Whereas in the newt, synthesis continued even on the 12th day.Phase contrast microscopic observation about acrosomal formation in Xenopus spermatids and application of protein synthesis inhibitors indicate that the enlargement of the vesicles is due to the coalescence of the small vesicles and the formation of small proacrosomal vesicles from Golgi appratus do not require protein synthesis but the enlargement of the vesicles do so. It was also found that hypotonic treatment of the spermatids derived from a secondary spermatocyte induces the cell fusion of the spermatids, which results in the formation of synacrosomes.To elucidate the mechanism of mitochondrial assembly around the nuclei of spermatids. Several inhibitors were tested but had no effect. These results indicate that protein. RNA and carbohydrate synthesis. cytoskeletons. cAMP. ATP production. Ca^<2+> in spermatids and protein synthesis in mitochondria play no role in mitochondrial assembly around the spermatid nuclei. In a cell-free system. mitochondria from Xenopus liver attached to the spermatid nuclei. Whereas they did not to the nuclei of liver or primary spermatocytes. These results indicate that the nuclear change is responsible for the acquisition of the ability of mitochondrial assembly around the nuclei in Xenopus spermatids.