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barbiturates are combined there is an effective synergistic response. Analeptics such as picrotoxin and metrazol, which reverse the effects of barbiturates, similarly interrupt steroid anaesthesia. These unpublished observations may be of interest in the development of steroids that can produce safe and effective anaesthesia. American Institute of Stress, 124 Park Avenue, Yonkers, New York 10703, USA

PAUL J. ROSCH

Woodbury DM, Davenport VD Brain and plasma cartions and experimental seizures with normal and esoxycorticosterone treated rats Am J Physiol 1949, 157: 234-37. 2. Kerman EF. Experimental catelepsy in the rat produced by steroid hormone: desoxycorticosterone acetate and antagonistic effect of pentamethylenetetrazol (metrazol). Dis Nerv Sys 1947; 8: 313-15. 1.

Indoor radon exposure and cytogenetic

damage SIR,-Radon contributes to pulmonary carcinogenesis in uranium miners and is an important lung cancer risk in the general population. Correlation studies indicate an additional role for indoor radon exposure in the development of extrapulmonary cancers, suggesting that carcinogenic effects may not be restricted to lung epithelium.1.2 Studies in populations living and/or working in areas with increased background radiation have shown higher frequencies of peripheral lymphocyte chromosome aberrations, or hypoxanthine guanine phosphoribosyl transferase-locus (hprt) mutations.3Genetic effects in peripheral lymphocytes of radonexposed individuals may also indicate extrapulmonary distribution

of genotoxic particles. Our pilot study was designed to test the feasibility of multiple genetic marker analysis (sister chromatid exchanges, hprt mutadons, micronuclei, and chromosome aberrations in peripheral lymphocytes from subjects in the Netherlands and Belgium exposed to indoor radon concentrations in their dwellings (16-713

Bq/m3).

The table surnmarises indoor radon exposure and

cytogenetic indices in the 11 participants. With or without correction for confounding factors, such as passive smoking and age, there

was no

relation between the level of exposure and

of

micronuclei, chromosome aberrations, and sister chromatid exchanges in peripheral lymphocytes of exposed individuals, as assessed by standard procedures.7,8 For hprt mutations, we detected 6-thioguanine-resistant lymphocytes with 5-bromodeoxyuridine labelling and immunochemical staining. These mutations were inversely related to the level of exposure by linear regression (R = — 0-632, p < 0-05). After adjustment for age and peripheral lymphocyte proliferation rate by multiple regression, the relation between individual hprt mutation and occurrence

SISTER CHROMATID EXCHANGES (SCE) hprt MUTATIONS (MF), MICRONUCLEI (MN), AND CHROMOSOME ABERATIONS (CA) IN PERIPHERAL LYMPHOCYTES OF 11 SUBJECTS EXPOSED TO INDOOR RADON

Indoor radon concentrations were initially measured for at least 3 months by x tract detector in 1987-905,6 Radon concentration is shown as reassessed in 1991 by charcoal canister for 24 h, correlation between these measurements was significant SCE frequencies significantly correlated with exposure to (R=088, p

Indoor radon exposure and cytogenetic damage.

739 barbiturates are combined there is an effective synergistic response. Analeptics such as picrotoxin and metrazol, which reverse the effects of ba...
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