SPERMATOGONIAL STEM CELL RENEWAL IN THE MOUSE: I. NORMAL SITUATION

Abstract

ABSTRACT Spermatogenesis in the mouse has been investigated by counting the different kinds of spermatogonia throughout the cycle of the seminiferous epithelium. A description is given of the A isolated (A is ), A paired (A pr ) and A aligned (A al ) spermatogonia and the other A spermatogonia as they appear in tubules mounted in toto. This technique enabled A is , A pr and A al spermatogonia to be counted. Our results complete the evidence for the concept of a population of morphologically undifferentiated A spermatogonia preceding the A 1 spermatogonia in the line of spermatogenesis and that among these A spermatogonia, the A is cells are to be regarded as the stem cells of spermatogenesis. In population of A is , A pr and A al spermatogonia divisions take place during the life spans of A 2 , A 4 and In spermatogonia and also rarely during the life span of B spermatogonia. During the life spans of In and B spermatogonia the A al gradually differentiate into A 1 spermatogonia. About 10% of the total number of A spermatogonia in stages 7–8, mainly A isolated and some A paired , do not differentiate but start a new multiplication cycle.