Germ plasm and germ cell migration in embryos developed from aged eggs of Rana Pipiens
Grundy, David Lynn
Master of Arts
A substantial amount of research supports the purported role of germ plasm as a cytdsplasmic determinant for germ cells, but the precise function of germ plasm is still unknown. In order to gain further information on the action of germ plasm, additional procedures must be established that will allow for experimental manipulation and observation of the germ plasm. As shown in this study, intrauterine ageing of Rana pipiens eggs affects both the sterility of larvae gonads, and the germ plasm of primordial germ cells, after the eggs have been fertilized and allowed to develop. Hie production of sterile gonads increases and the average number of gonadal germ cells significantly decreases in morphologically normal swimming larvae developed from aged eggs as compared to control larvae. Histological examinations of blastulae and gastrulae developed from aged and control eggs show significant differences in primordial germ cell location, and in the structure, location, and size of germ plasm. A larger proportion of primordial germ cells are located close to the vegetal pole in experimental versus control blastulae. Germ plasm is more often located in a peripheral or intermediate intracellular position and rarely seen in the nuclear position in blastulae developed from aged eggs as compared to control blastulae. Also, the volume of germ plasm decreases in experimental versus control blastulae. These studies indicate that intrauterine egg ageing could be used to alter germ plasm morghology, thus producing an observable marker that could be used to help elucidate the function of germ plasm.