Spermatogenesis in the mouse. I. Autoradiographic studies of nuclear incorporation and loss of 3H-amino acids.

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Abstract
Autoradiographic and EM methods were used to correlate changes in nuceloproteins with nuclear fine structure during spermatogenesis in the mouse. Tests were fixed at daily intervals after intratesticular injection with labeled amino acid. [3H]Arginine, lysine, valine and proline were rapidly incorporated into primary spermatocyte nuclei, retained through subsequent spermatocyte divisions and through spermatid differentiation of step 12 of spermiogenesis, but were lost with spermatid differentiation beyong step 12. Arginine and lysine (not valine or proline) were rapidly incorporated into certain elongated spermatid nuclei but differed in their distributuon. Nuclei of late step 12-15 spermatids were initially labeled with arginine which was retained through subsequent spermatid differentiation and sperm maturation in the epididymis. Lysine was initially incorporated only into late step 12 and step 13 spermatid nuclei and was retained only to early step 14 of spermiogenesis. Spermatid incorporation of lysine coincided with the initiation of chromatin condensation in late step 12 nuclei. Lysine loss coincided with the completion of condensation in step 14 nuclei.