Childhood leukaemia in Belarus, Russia, and Ukraine following the Chernobyl power station accident: results from an international collaborative population-based case-control study.

BACKGROUND: There is little evidence regarding the risk of leukaemia in children following exposure to radionuclides from the Chernobyl Nuclear Power Plant explosion on April 26, 1986. METHODS: This population-based case-control study investigated whether acute leukaemia is increased among children who were in utero or <6 years of age at the time of the Chernobyl accident. Confirmed cases of leukaemia diagnosed from April 26, 1986 through December 31, 2000 in contaminated regions of Belarus, Russia, and Ukraine were included. Two controls were matched to each case on sex, birth year, and residence. Accumulated absorbed radiation dose to the bone marrow was estimated for each subject. RESULTS: Median estimated radiation doses of participants were <10 mGy. A significant increase in leukaemia risk with increasing radiation dose to the bone marrow was found. This association was most evident in Ukraine, apparent (but not statistically significant) in Belarus, and not found in Russia. CONCLUSION: Taken at face value, these findings suggest that prolonged exposure to very low radiation doses may increase leukaemia risk as much as or even more than acute exposure. However the large and statistically significant dose-response might be accounted for, at least in part, by an overestimate of risk in Ukraine. Therefore, we conclude this study provides no convincing evidence of an increased risk of childhood leukaemia as a result of exposure to Chernobyl radiation, since it is unclear whether the results are due to a true radiation-related excess, a sampling-derived bias in Ukraine, or some combination thereof. However, the lack of significant dose-responses in Belarus and Russia also cannot convincingly rule out the possibility of an increase in leukaemia risk at low dose levels.

Stable and unstable aberrations in lymphocytes of Chernobyl accident clearance workers carrying rogue cells.

Cells with multiple chromosomal aberrations, the so-called rogue cells, were found in blood samples from more than 100 Chernobyl accident clearance workers. A comparative analysis of frequencies of stable and unstable chromosomal aberrations in two worker groups--those with or without rogue cells was made. A higher level of unstable aberrations in persons carrying rogue cells was observed. No difference in the level of stable aberrations between the groups was seen. The possibility of low dose alpha irradiation causing the chromosomal damage is raised.

[Kinetic parameters of the rat liver monooxygenase system in the early stages of chemical carcinogenesis]. / Kineticheskie parametry monooksigenaznoi sistemy pecheni krys na rannikh étapakh khimicheskogo kantserogeneza.

Functions of the liver monooxygenase system, participating in metabolism of 3,4-benzpyrene, were shown to vary significantly at different steps of carcinogenesis induced by 3,4-benzpyrene. These variations appear to be due to changes in the effect of monooxygenase-epoxide hydrase complex in rat liver microsomes.

Investigation of the type of induction of microsomal monooxygenases by polycyclic hydrocarbons.

The severity of the induced effect of the polycyclic hydrocarbon 3-methylcholanthrene on monooxygenase of the microsomal fraction of the liver as a function of the number of binding sites for this inducer in the active site of cytochrome P-450 was investigated. In vivo models, in which the primary bounding and metabolism of a polycyclic hydrocarbon in the microsomes is increased or sharply inhibited, are presented. It is concluded that in the mechanism of induction by 3-methylcholanthrene, the activation of synthesis of specific protein (cytochrome P-448) is accomplished not by the initial molecule of the inducer, but by products of its primary metabolism in the microsomes.

[A substrate-type induction of liver microsomal monooxygenases by phenobarbital]. / Substratnyi tip induktsii fenobarbitalom mikrosomal'nykh monooksigenaz v pecheni.

A possibility of step-wise induction of microsomal monooxygenases after injection of phenobarbital in the presence of 3-methylcholanthrene-caused induction was studied. It was found that the ratio of the high- and low-spin types of cytochrome, rather than the position of the CO-peak of its reduced form is a criterion for functional specificity of hemoprotein. Induction by phenobarbital appears possible under conditions when the inductor binding to microsomal hemoprotein is lacking, since cytochrome P-488 has no binding sites for phenobarbital. It is assumed that under microsomal monooxygenases induction by phenobarbital activation of genome and subsequent protein synthesis are operated by the substrate rather than by products of its primary metabolism in microsomes.