CHARACTERISTICS OF MITOTIC CELLS IN DEVELOPING AND ADULT TESTES WITH OBSERVATIONS ON CELL LINEAGES

This report describes characteristics of dividing cells, primarily in developing (10-40 day) rat testis and relates the structure of the div iding cells to the structure of interphase cells, Mitotic cells were c haracterized in seven zones, Dividing Sertoli cells were seen prior to day 15 and possessed distinct characteristics as compared with dividi ng germ cells, Myoid cells showed morphological characteristics of pre cursor myoid cells; 'clear cells' self-replicated in the myoid cell la yer; adult-type Leydig cells, some containing lipid, differentiated ea rly (10th-15th postnatal days) from fibroblast-like cells of the multi layered tubule wall and later (15th-25th postnatal days) from dividing differentiated and semi-differentiated Leydig cells within the lympha tic space; fibroblastic cells arose from cells with similar morphologi cal characteristics; semi-differentiated Leydig cells divided, and dif ferentiated Leydig cells in the lymphatic space self-renewed; undiffer entiated perivascular cells most likely gave rise to Leydig cells, per icytes; arteriolar smooth muscle cells and vascular endothelial cells arose from division of the pre-existing respective cell types, Fetal L eydig cells appeared to remain but, with time, they appeared to lose t heir lipid, The data suggest that (1) early recruitment of Leydig cell s from undifferentiated peritubular fibroblast-like cells, (2) later m itosis of differentiated and semi-differentiated Leydig cells primaril y in the interstitium but also in the perivascular region, and (3) the continued presence of pre-existing Leydig cells from the fetus consti tute the adult population, Leydig cell division in the adult mouse was documented, This study provides the necessary information for the rec ognition of cell divisions to study of cell lineages among testis cell s.