Primordial germ cell development in cultures of dispersed central disks of stage X chick blastoderms.

Central disk fragments cut from stage X chick blastoderms were dispersed and cultured on glass coverslips. After 48 hr of incubation the cultures showed various degrees of organization into three-layered aggregates in which no axis development was observed. Primordial germ cells (PGCs) were detected in all cultures. The number of PGCs was found to be correlated to the initial cell concentration in the suspension. By regression analysis it was found that in cultures initiated from 10 central disks or more, the mean number of PGCs per fragment was constant and matched the number of PGCs found for intact control central disks incubated for the same length of time. It appears that in cultures of stage X, the morphologic expression of PGCs is related to the level of differentiation and organization of the somatic cells in the culture, which, in turn, is dependent on the initial concentration of cells in the culture.