Biomedical subjects

J Netíková

Publications and source records attributed to J Netíková.

46 records · Page 3Linked to original sources

PubMed1976

A radioprotective effect of calcium chloride in combination with cystamine, mexamine, and hypoxemic hypoxia in mice.

A mild protective effect of a solution of CaCl2 (3.21 g%) injected in a volume of 0.2 ml i.p. 30 minutes prior to irradiation was demonstrated in experiments with male mice in the strain C 57 B1/10. The pre-irradiation administration of CaCl2 increased the LD50/30 by approximately 60R as compared with control animals, to which an isoosmotic NaCl solution was injected. A more pronounced decrease of the post-irradiation mortality of the animals was reached by combined administration of CaCl2 with chemical protectors- cystamine or mexamine administered in relatively low s.c. doses, as well as by a combination of CaCl2 with the protective action of hypoxemic hypoxia. Under the conditions of combined protection, the administration of CaCl2 increased LD50/30 by approximately 100 to 130R. A higher rate of formation of endogenous spleen hematopoietic colonies was observed in the animals protected by calcium. Possible mechanisms of the radioprotective effect of calcium on the level of the hematopoietic stem cells are discussed.

Animals↗

PubMed1976

The relationship between the population size and the postirradiation mortality of mice with respect to individual differences in stress reactivity.

Differences in radiosensitivity, expressed by the death rate up to the 30th day after irradiation by single whole-body exposures in the region of LD50, were followed in mice caged in groups by five, 15 and 25 individuals. No marked differences in the whole=group mortality of differently sized collectives were detected. Preirradiation as well as postirradiation leucocyte counts (after a sublethal irradiation) exhibit, however, differences, which correspond to an assumed different degree of the adrenocortical activity in differently sized collectives. Also the follow-up of the stress reactivity of the animals by measuring the Na/K ratio in 24-hour-samples of urine prior to irradiation demonstrated marked differences between the groups with low number and high number of animals in a cage. By correlating values of this indirect indicator of the adrenocortical activity with manifestations of the individual radiosensitivity it was found that the extremely hyporeactive animals (belonging to groups with five animals per cage) and the extremely hyperreactive ones (belonging to groups with 25 animals per cage) exhibit a markedly higher mortality. The absence of differences in the whole-group mortality of differently sized collectives can be explained by the existence of nonlinear "U"-shaped relations between the adrenocortical activity and the individuals' radiosensitivity. The results support the conception on the unfavorable prognostic significance of unbalanced reactions of homeostatic functions of system regulation under conditions of radiation syndrome.

Animals↗

PubMed1975

The effect of dried thyroid gland pretreatment upon survival, formation of endogenous spleen colonies and differentiation of haemopoietic cell populations in x-irradiated mice.

Experiments on non-inbred H-strain male mice confirmed that their radioresistance could be increased by a stimulatory action of the thyroid hormones applied for three weeks preceding the radiation exposure. It was found that the 30-day survival after 750R rose between the 1st and the 5th day after the end of the pretreatment. The highest degree of radioresistance was observed, when the radiation exposure fell into the phase of gradual receding of increased metabolic rate. The relevant experimental groups showed a higher frequency of endogenous spleen colonies and an increased granulocytic differentiation of haemopoietic stem cells. Higher colony-forming activity was also found in animals irradiated immediately after the termination of pretreatment with thyroid, but without an increase in survival. The lack of radioprotective effect under those circumstances could be explained by the persisting hypermetabolic effect of the thyroid, and by the fact that an increased proportion of haemopoietic stem cells underwent differentiation into the erythroid line.

Animals↗

PubMed1974