[Calculation of maximum allowable concentration of N-nitrosodimethylamine and N-nitrosodiethylamine based on chronic experiments in mice]. / Raschet PDK N-nitrozodimetilamina i N-nitrozodiétilamina po rezul'tatam khronicheskikh éksperimentov na myshakh.

Maximum allowable 24-hour human intakes of NDMA and NDEA, calculated with the use of a log-normal model, a model of logit-transformations and methods of confidence intervals and probability estimations, are 0.15 micrograms/kg and 0.03 micrograms/kg respectively. Maximum allowable concentrations for NDMA and NDEA in water are 5 micrograms/l and 1 microgram/l respectively.

[The dependence of the carcinogenic effect on the concentration of N-nitrosodimethylamine in (CBA x C57Bl/6)F1 mice and noninbred mice]. / Zavisimost' kantserogennogo éffekta ot kontsentratsii N-nitrozodimetilamina u myshei (CBA x C57Bl/6)F1 i nelineinykh myshei.

The relationship between the tumour frequency and nitrosodimethylamine (NDMA) concentration in drinking water was studied in the experiments involving 495 (CBA x C57Bl/6)F1 hybrid and 600 noninbred mice of both sex. At the NDMA concentrations of 0.04, 0.2, 1.0, 5.0 mg/l the tumour frequency was as follows: 21.6/26.2, 35.5/27.3, 57.4/56.4, 90.5/72.9% (20.0/20.0% in control) in hybrid mice; and 15.4/39.6, 18.2/43.5, 62.2/61.0, 76.5/87.5% (15.0/30.0% in control) in noninbred mice, respectively. In the given experiments the minimal effective NDMA concentration was 1.0 mg/l, and the maximal effective one--0.2 mg/l both for the hybrids and noninbred animals. The results of the research may be used for calculation of the MPC for NDMA.

[The dependence of the carcinogenic effect on the concentration of N-nitrosodiethylamine]. / Izuchenie zavisimosti kantserogennogo éffekta ot kontsentratsii N-nitrozodiétilamina.

In a 86-week-long experiment using 1087 mice (487 hybrids and 600 non-inbred animals), the concentration-effect relationship was studied for N-nitrosodiethylamine (NDEA) given in drinking water. NDEA concentrations of 0.08; 0.4; 2.0 and 10.0 mg/l produced tumors in male and female hybrids with the frequencies of 35.9/30.9, 49.9/43.6, 61.9/72.3 and 81.8/82.9%, respectively (20.0.20.0% in controls) whereas in non-inbred animals the frequencies were 15.6/34.2, 24.2/33.3, 35.9/57.1 and 78.4/80.9%, respectively (15.0/30.0% in controls). The "minimal effective" carcinogenic level of NDEA proved 0.4 mg/l for hybrids and 2.0 mg/l for non-inbred mice (P less than 0.05). No sex differences were found for frequency or histologic pattern of tumor. The data obtained can be used in calculating sanitary-hygienic standards for NDEA.

[Carcinogenicity of chloroform]. / Izuchenie kantserogennosti khloroforma.

Carcinogenicity of chloroform for various dosage and route of administration was assessed in CBA X C57B1/6 mice in a chronic experiment (250 or 15 mg/kg body weight in vegetable oil, intra-esophageally via a probe; or 300; 30; 3; 0.3 or 0.03 mg/l in drinking water). Chloroform did not reveal its carcinogenic properties unless a dose of 250 mg/kg was given.

[Features of the formation of conditioned secretory reflexes in response to the stimulation of different areas of the caudate nucleus of the dog]. / Osobennosti formirovaniia uslovnykh sekretornykh refleksov na stimuliatsiiu raznykh otdelov khvostatogo iadra u sobak.

Properties were studied of elaboration of conditioned alimentary secretory reflexes to threshold electric stimulation of the caudate nucleus in dogs. The rate of formation of such a reflex and its magnitude were considerably lower than in reflexes elaborated to distant stimuli. Latencies were longer; dynamics of conditioned and unconditioned secretory reactions was similar to that of reflexes to a weak stimulus--light. The motor component of the conditioned alimentary reaction, as a rule, was absent. Characteristics were revealed of formation of alimentary reflexes to stimulation of the dorsal and ventral parts of the head and body of the caudate nucleus.

[Carcinogenesis-modifying properties of aniline, carbon tetrachloride, benzene and ethanol]. / Izuchenie modifitsiruiuschikh kantserogenez svoistv anilina, chetyrekhkhloristogo ugleroda, benzola i étanola.

Aniline and ethanol properties modifying carcinogenesis were revealed in chronic 12-month experiment with 500 females of hybrid CBAXC57Bl/6 mice. The drugs were administered with water in combination with nitrosodiethylamine. The absence of a modifying effect in groups with carbon tetrachloride and benzene is attributed to the fact that concentrations of these chemicals used in the experiment were similar to those in the environment.

[Carcinogenic properties of nitrosodimethylamine when combined with benzene, cadmium, boron or ethanol]. / Kantserogennye svoistva nitrozodimetilamina pri kombinatsii ego s benzolom, kadmiem, borom ili étanolom.

A combination of benzene (5.0 mg/l) or cadmium (0.01 mg/l) with nitrosodimethylamine (drinking water, 9 months) produced a significantly higher tumor incidence in female CBA X C57B1/6 mouse hybrids. The said agents are capable of modifying the carcinogenicity of other substances when present in water in concentrations exceeding the permissible one.

[Characteristics of aniline, lead nitrate, carbon tetrachloride and formaldehyde as modifiers of chemical carcinogenesis]. / K kharakteristike anilina, nitrata svintsa, chetyrekhkhloristogo ugleroda i formal'degida kak modifikatorov khimicheskogo blastomogeneza.

The modifying effect of aniline, lead nitrate, carbon tetrachloride and formaldehyde on nitrosodimethylamine-induced blastogenesis was studied in chronic experiments on 750 CBA X C57 / Bl6 female mice. A mixture of carcinogen with aniline or formaldehyde given in drinking water for 39 weeks produced a significantly higher tumor incidence. A similar, though statistically insignificant, effect was registered for a mixture of carcinogen and lead citrate or carbon tetrachloride. It is emphasized that aniline and formaldehyde are capable of modifying effect at levels 10 times maximum allowable concentrations.

Hygienic evaluation and regulation of some environmental factors to counteract their potential carcinogenic hazards.

The evident growth of tumour morbidity makes analysis of the fundamental problems of neoplasm prophylaxis in man particularly urgent. The establishment of maximum permissible concentrations for carcinogenic agents calls for further exploration into the problem of threshold action of carcinogens and elaboration of a methodology for quantitative assessment of the biological effects of certain environmental factors. In particular, the available data on the ability of low-intensity environmental factors to modify the organism's general resistance and thereby produce in it conditions for materialization of the untoward effects of carcinogens invite further work in this direction. The study of environmental factors as possible modifiers of blastomatosis and investigation of the modification mechanisms involved are an immediate and topical task. Quantitative analysis of these modifying effects would allow establishment of well-grounded hygienic norms as the next step. Thus, study of the regularities involved, development of a fundamental methodology and accumulation of facts on the influence of low-intensity environmental factors on carcinogenesis and the cancer effect should be helpful in devising scientifically based measures of lowering the growth of tumour morbidity.