Micronucleus formation in preimplanted mouse embryos cultured in vitro after irradiation with x-rays and neutrons

Preimplanted mouse embryos cultured in vitro were irradiated with X-rays and neutrons in the late G2-phase of the 2-cell stage. Both radiation qualities induced micronuclei at very low doses. The kinetics of micronucleus formation during the first and second cell cycles after X-irradiation depended on the radiation dose and on the extent of the division delay. New micronuclei appeared to be formed even after the third and later post-irradiation mitoses. The shape of the various dose-effect curves and the mechanism of micronucleus formation by the two radiation qualities are discussed.

Kinetics of cell proliferation in the pre-implanted mouse embryo in vivo and in vitro

The cell proliferation of pre-implanted mouse embryos was investigated after development in vivo and in vitro. The studies were started at the pronuclear stage, 2 h post conception (p.c.) and continued until the hatching of blastocysts, 120-144 h p.c. The number of cell nuclei, the DNA content of each nucleus, the mitotic index and the labelling index were determined. From these data it was possible to calculate the length of the cell generation cycle and its various phases. With the exception of the first cell cycle the S-phase was constant. The G1- as well as the G2-phase varied in length during the different cell cycles. From 31-72 h p.c. the increase in cell number was exponential. After cultivation in vitro this increase was smaller than in vivo. At later periods the proliferation rate decreased with proceeding development. In late blastocysts most of the cells were in the G1-phase. The development of the embryos was somewhat faster in vivo than in vitro. But in principle conditions were comparable.

Effect of catecholamines and sympatholytics on survival and circulatory parameters in protracted anaphylactic shock of guinea pigs

Protracted anaphylactic shock of guinea pigs led to death in over 90% of the animals, and good protection was obtained with an infusion of adrenaline after dibenamine pretreatment. Adrenaline alone, in doses which prevented the anaphylactic fall of arterial blood pressure, had no beneficial effect. Practolol abolished the therapeutic action of the combination of dibenamine/adrenaline. Stimulation of beta-receptors by isoproterenol did not increase the survival rate. With dopamine, however, a significant prolongation of the survival times was obtained.