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972 The issue is still in doubt
METHODS FOR ASSESSING TOXICITY
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gradually to reach values of 54% (with I) and 64% (without I) of the initial oxygen consumption. These differences were not significant on account of the large scatter of results, but in any case they show no stimulating effect of I but rather indicate that the inhibitory action of the base (containing glycerine and petrolatum which are known to inhibit skin respiration) predominated. Whether I alone actually stimulates skirt respiration is now being examined. It does apparently stimulate the respiration of rat-liver homogertates and baker's yeast (Desperrois, Archs Biochim. Cosm. 1960/61, 4 (37), 25). Those interested in the composition of I will find it in the Merck Index. It contains no hormones affecting mammals.
METHODS FOR ASSESSING TOXICITY 972. The issue is still in doubt Ben, M. & Valentini, J. E. (1965). Determination of potential carcinogenic materials by the Iversen and Evensen technique. Proc. scient. Sect. Toilet Goods Ass. No. 43 (May), p. 44. A rapid screening test for potential carcinogens, involving estimation of succinic dehydrogenase (SD) activity in the skin of hairless mice at the site of application of a test substance, has been described by Iversen (Cited in F.C.T. 1963, 1, 158). The effects on enzyme activity of known carcinogens and of harmless substances showed a considerable overlap which made statistical evaluation difficult. The present authors have followed up this work by an investigation involving the application of a range of concentrations of known carcinogens and of analogues thought not to possess carcinogenic activity. At the higher concentrations, the carcinogens 3methylcholanthrene, benzopyrene, propiolactone, nitroquinoline-N-oxide, dimethylnitrosamine and isonicotinic acid hydrazide yielded significantly high figures, while the noncarcinogens cournarin, pyrene, diphenylnitrosamine and nitroquinoline gave rise to low figures. Urethane, a compound of questionable carcinogenic activity gave equivocal results. It is concluded that the increased SD activity of skin treated with a test compound appears to be correlated with carcinogenic activity. [The compounds tested represent but a small fraction of the known carcinogens. Many more such compounds will have to be assessed before the test can be accepted as a valid screening procedure. Not many cancer workers will be prepared to accept the authors' statement that urethane is a compound of questionable carcinogenic activity. The work of Tannenbaum (J. hath. Cancer Inst. 1963, 14, 341) for instance, shows clearly that urethane behaves as a classical carcinogen when given in appropriate doses. It would be interesting to observe the results given by "promoters" such as croton oil and non-carcinogenic skin irritants when tested by this technique.] 973. A new approach to pesticide testing
Klotzsche, C. (1964). Zur toxikologischen Priifung neuer insecticider Phosphors~iureester. Arch. Gewerbepath. Gewerbehyg. 21, 92. This study is concerned with the development of tests for determining the toxicity of organophosphorus pesticides which will afford some realistic estimate of their toxicity to man. Experiments are described in which rats poisoned with twice the LDs0 of various organophosphorus insecticides were treated with an antidote or a mixture of antidotes. The antidotes used were PAM (2-pyridine-aldoxime-methiodide) a reactivator of alkylphosphate-inhibited cholinesterase, and Bellafolin (a preparation of belladonna alkaloids).
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gradually to reach values of 54% (with I) and 64% (without I) of the initial oxygen consumption. These differences were not significant on account of the large scatter of results, but in any case they show no stimulating effect of I but rather indicate that the inhibitory action of the base (containing glycerine and petrolatum which are known to inhibit skin respiration) predominated. Whether I alone actually stimulates skirt respiration is now being examined. It does apparently stimulate the respiration of rat-liver homogertates and baker's yeast (Desperrois, Archs Biochim. Cosm. 1960/61, 4 (37), 25). Those interested in the composition of I will find it in the Merck Index. It contains no hormones affecting mammals.
METHODS FOR ASSESSING TOXICITY 972. The issue is still in doubt Ben, M. & Valentini, J. E. (1965). Determination of potential carcinogenic materials by the Iversen and Evensen technique. Proc. scient. Sect. Toilet Goods Ass. No. 43 (May), p. 44. A rapid screening test for potential carcinogens, involving estimation of succinic dehydrogenase (SD) activity in the skin of hairless mice at the site of application of a test substance, has been described by Iversen (Cited in F.C.T. 1963, 1, 158). The effects on enzyme activity of known carcinogens and of harmless substances showed a considerable overlap which made statistical evaluation difficult. The present authors have followed up this work by an investigation involving the application of a range of concentrations of known carcinogens and of analogues thought not to possess carcinogenic activity. At the higher concentrations, the carcinogens 3methylcholanthrene, benzopyrene, propiolactone, nitroquinoline-N-oxide, dimethylnitrosamine and isonicotinic acid hydrazide yielded significantly high figures, while the noncarcinogens cournarin, pyrene, diphenylnitrosamine and nitroquinoline gave rise to low figures. Urethane, a compound of questionable carcinogenic activity gave equivocal results. It is concluded that the increased SD activity of skin treated with a test compound appears to be correlated with carcinogenic activity. [The compounds tested represent but a small fraction of the known carcinogens. Many more such compounds will have to be assessed before the test can be accepted as a valid screening procedure. Not many cancer workers will be prepared to accept the authors' statement that urethane is a compound of questionable carcinogenic activity. The work of Tannenbaum (J. hath. Cancer Inst. 1963, 14, 341) for instance, shows clearly that urethane behaves as a classical carcinogen when given in appropriate doses. It would be interesting to observe the results given by "promoters" such as croton oil and non-carcinogenic skin irritants when tested by this technique.] 973. A new approach to pesticide testing
Klotzsche, C. (1964). Zur toxikologischen Priifung neuer insecticider Phosphors~iureester. Arch. Gewerbepath. Gewerbehyg. 21, 92. This study is concerned with the development of tests for determining the toxicity of organophosphorus pesticides which will afford some realistic estimate of their toxicity to man. Experiments are described in which rats poisoned with twice the LDs0 of various organophosphorus insecticides were treated with an antidote or a mixture of antidotes. The antidotes used were PAM (2-pyridine-aldoxime-methiodide) a reactivator of alkylphosphate-inhibited cholinesterase, and Bellafolin (a preparation of belladonna alkaloids).