Correlation between germinal vesicle and oocyte development in the adult Japanese quail (Coturnix coturnix japonica). A cytochemical and autoradiographic study

Continuity in the various developmental stages of the oocytes in the adult laying Japanese quail may be demonstrated with a method of whole stock labelling of their nuclei by successive applications of [3H]thymidine during their premeiotic period. Before they mature, the intraovarian oocytes of the adult Japanese quail go through three important successive stages. In each of these stages the chromosomes have a distinct morphology and cytochemical behaviour. During the first stage or prelampbrush chromosome stage, the chromosomes are Feulgen-positive or green after Unna, and on the autoradiographs show intense incorporation of [3H]uridine after injection of this RNA precursor into the animal. During the beginning of this period, which is of very variable duration, the oocyte seems to be in a state of structural stability. The most prominent feature found in the ooplasm of oocytes at this stage is the very large paranuclear Balbiani yolk-body complex, which can be found labelled after injection of [3H]thymidine into the animal. During the second stage or lampbrush chromosome stage, the Feulgen nuclear reaction in the chromosomes weakens or becomes negative and the paranuclear Balbiani yolk-body complex disappears. After Unna, the lampbrush chromosomes and their lateral loops are seen to be pyroninophilic. On the autoradiographs after intraperitoneal injection of [3H]uridine rapid and intense RNase-sensitive incorporation of this precursor over the chromosomes and nucleoplasm may be noted. During this stage there is thus both cytochemical and autoradiographic evidence for RNA synthesis in the rapidly enlarging germinal vesicle. During the third or postlampbrush stage activity in the germinal vesicle sharply decreases; the volume of the germinal vesicle no longer increases, the very contracted chromosomes are present in the form of Feulgenpositive vacuolized central spherules, and, after intraperitoneal injection of [3H]uridine into the adult laying quail, incorporation cannot be demonstrated in the chromosomes. By contrast, the fundamental part of the ooplasm derived from the cortex, at that moment shows both cytochemical and autoradiographic evidence of the presence and/or synthesis of nucleic acids. The postlampbrush stage is a characteristic feature of non-mature oocytes with a germinal disc and can only be found in regularly laying Japanese quails exposed to full daytime or continuous illumination.