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

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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 Aisolated (Ais), Apaired (Apr) and Aaligned (Aal) spermatogonia and the other A spermatogonia as they appear in tubules mounted in toto. This technique enabled Ais, Apr and Aal spermatogonia to be counted.Our results complete the evidence for the concept of a population of morphologically undifferentiated A spermatogonia preceding the A1 spermatogonia in the line of spermatogenesis and that among these A spermatogonia, the Ais cells are to be regarded as the stem cells of spermatogenesis.In population of Ais, Apr and Aal spermatogonia divisions take place during the life spans of A2, A4 and In spermatogonia and also rarely during the life span of B spermatogonia. During the life spans of In and B spermatogonia the Aal gradually differentiate into A1 spermatogonia. About 10% of the total number of A spermatogonia in stages 7–8, mainly Aisolated and some Apaired, do not differentiate but start a new multiplication cycle.
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