Electron microscopic studies on the chromatin of blastoderm nuclei and yolk granules beneath blastoderm of fertilized and unincubated chicken eggs.

Chromatin prepared both from the yolk granules beneath the blastoderm and from the nuclei of the blastoderm cells of fertilized and unincubated chicken eggs was examined under electron microscope and its structure was compared. The results indicate that the above two kinds of chromatin fibers seem to have no apparent difference in structural relation and diameter. The electron microscopic appearances of the basic structures of both kinds of chromatin are all "beads-on-a-string"-shaped filaments. After the digestion of chromatin from both raw materials with DNase I, the connecting strings of chromatin fibers were cut off, only the scattered beads could be observed under electron microscope. The diameter of the scattered beads is equal to that of the beads on the chromatin fibers, and most of them are 150 A in diameter.

Time-lapse microcinematographic and phase contrast studies on the cell reformation of Chirocephalus yolk granules in vitro.

In this article we report on a time-lapse microcinematographic and phase contrast study of the cell reformation of yolk granules which were isolated from mature oocytes in the genital sac of the middle female intersex of Chirocephalus nankinensis. The observations on yolk granules were made in fixed positions and the morphological changes of cell reformation were continuously recorded in vitro. The transformation of yolk granules into cellular structures may be tentatively described as follows: At the early stages in culture, it can be seen that the granular or bubbly structures gradually appear within the hyaloid and homogeneous yolk granules; the appearance of yolk granules gradually changes from elliptical into round shape. With further transformation, their appearances in general take the shape of oblate spheroids, their size is smaller than before and inside the yolk granules their granular and bubbly structures become more and more obvious. Finally, the nuclear and cellular structures can be seen in these transforming yolks. By means of time-lapse microcinematographic and phase contrast examinations in fixed positions, single yolk granules obtained from the mature oocyte with little amounts of adhering cytoplasm are continuously recorded and have been shown to occur, steadily and gradually build up cellular structures by self-organization and self-assembly. Up to the present, we have cultured these kinds of cellular organizations repeatedly. Therefore, it can be concluded that the existence of cell reformation on the basis of yolk granules according to the dynamic morphological changes is an objective reality.