[Kinetics of cell populations at various stages of the histogenesis of tissues of the chorioallantois of the chick embryo. Parameters of cell cycles]. / Kinetika kletochnykh populiatsii na raznykh étapakh gistogeneza tkanei khorio-allantoisa kurinogo zarodysha. Parametry kletochnykh tsiklov.

By means of thymidine autoradiography, changes of the proliferative pool and those of the cellular cycle parameters have been studied in tissues of the chorioallantois and in the duodenal epithelium of the chick embryo at various stages of development. The decisive role in regulation of proliferation in the cell populations studied belongs to modifications of the proliferative pool.

[Kinetics of cellular populations at different stages of the histogenesis of tissues of the chorio-allantois of the chick embryo]. / Kinetika kletochnykh populiatsii na raznykh etapakh gistogeneza tkanei khorio-allantoisa kurinogo zarodysha.

Changes occurring in indices of cell fractions being at the phase of mitosis (Nm) and at the phase of DNA synthesis (NS) have been studied in the chorio-allantoic tissues and in epithelii of the duodenum and cloaca. Their dynamics differ essentially. In the chorio-allantois, decrease in the Nm up to the 14th day is evidently connected with the transfer of the cells into R2-state, and then decrease of the proliferative pool takes place. This is caused by outcome of the cells from the reproductive cycle into differentiation.

[Cell cycle parameters and proliferative activity in chorioallantois tissues at various stages in chick embryo development]. / Parametry kletochnogo tsikla i proliferativnaia aktivnost' v tkaniakh khorio-allantoisa na raznykh srokakh razvitiia kurinogo émbriona.

Two peculiarities of cell population kinetics are characteristic of the provisional tissues of the chick embryo chorioallantois. The one is that the proliferative pool is relatively small at relatively early stages of embryogenesis (8 day incubation). The other is that at the final stages of embryogenesis, when proliferative activity in the embryo cell populations is still high, the cell reproduction is practically stopped. The process of tissue differentiation in chorioallantois, on the one hand, is accompanied with a withdrawal of a considerable part of cells from the cycle of reproduction, but on the other hand this differentiation affects the cells that have remained in the proliferative compartment which is reflected in modifications of either the cell cycle structure or the cell population composition.

[Circulation time and dynamics of 3H-thymidine incorporation into DNA at various stages of chick embryo development]. / Vremia tsirkuliatsii i dinamik vkliucheniia 3H-timidina v DNK na raznykh stadiiakh razvitiia kurinogo émbriona.

The most adequate method for carrying out radioautographic investigation on proliferation in the chorioallantoic tissues and in the chick embryo proper is dropping 3H-thymidine on the membrane under the shell in the area where the chorioallantois grows under. Using the application method, the radioautographic analysis of proliferation could be performed by the saturation method.