L'utilisation de nucléosides dans l'ovaire du Grillon et ses variations au cours de l'ovogenèse

Incorporation of tritiated uridine during pachytene and diplotene stages in the oocytes of the Japanese quail (Coturnix coturnix japonica)

Incorporation of 3H-uridine was studied during pachytene and diplotene stages of quail oocytes. No labelling could be detected during early pachytene. During advanced and late pachytene, labelling simultaneously appeared on the macrochromosomes and on certain michromosomes in the zone where they emerge from the chromocentric surface periphery. The latter localization corresponds to the region of ribosomal RNA synthesis. At diplotene the same localizations were labelled with a considerably increased intensity.

[Synthesis of RNA and protein during oogenesis and early embryogenesis of Acheta domestica]

During maturation of the cricket oocyte principally r-RNA and little t-RNA are formed. Furthermore it is possible to label an RNA-fraction that can be referred to as m-RNA according to its velocity of sedimentation in a sucrose density gradient.Data are discussed showing that the r-RNA formed during oogenesis is probably stable at least up to the stage of yolk cleavage.The incorporation of labelled aminoacids into dechorionated eggs starts during very early cleavage stages, whereas an incorporation of labelled uridine is scarcely detectable. This indicates that although protein synthesis proceeds, practically no measurable RNA synthesis exists. From these data it is concluded that in the cricket egg - just as in amphibian and sea urchin eggs - the first protein synthesis proceeds mainly on preexisting m-RNA.

[The establishment of polarity and bilateral symmetry in the oocytes of Gryllus domesticus L.]

1. The origin of polarity and bilateral symmetry of oocytes inGryllus domesticus L. has been studied. 2. The histology of the ovary and the process of oogenesis are described. 3. The germinal vesicle shifts into the posterior half of the oocyte, when these cells are 60 to 100 μm in length, thus indicating for the first time oocytic anteroposterior polarity. 4. Bilateral symmetry first appears, when the follicle reaches a length of 450 to 550 μm. This change from radial to bilateral symmetry is the result of the germinal vesicle leaving its position in the long axis of the cell and moving perpendicularly to this axis towards the follicular epithelium. 5. In follicles 60 to 100 μm in length the nucleolus comes to lie, under the influence of gravity, in the geopetal quarter of the germinal vesicle, and remains there. 6. No correlation can be found between geopetal position of the nucleolus and bilateral symmetry of the oocyte. 7. Oogenesis and the establishment of axes in the oocytes are not affected by centrifuging adults and last instars. 8. When the oocyte nucleus touches the follicular epithelium, changes occur in the structure and function of some epithelial cells. Those close to the germinal vesicle, with flattened nuclei, show reduced yolk secretion. Those at the opposite side show enhanced secretory activity. Presumably as a result of this differential secretory activity the shape of the oocyte becomes curved. 9. Only intact vitellogenetic oocytes show a banana-like form. 10. The ultrastructural examination of the previtellogenetic follicle indicates no predisposition for the direction of displacement of the oocyte nucleus, and therefore no predisposition of the plane of bilateral symmetry. 11. The hypothesis is discussed that the germinal vesicle itself initiates and directs the appearance of bilateral symmetry in the oocyte.