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In keeping with earlier observations, it has been found that silica powder is capable of hydroxylating proline in simple in vitro systems.

Tryptophan was rapidly destroyed aerobically in the presence of Mn 2+ and sulfite. The rate of destruction was greatly increased when horseradish peroxidase was added. The optimal pH for the reaction was 8.0. The destruction of tryptophan was dependent on the aerobic oxidation of sulfite. Superoxide dismutase inhibited sulfite oxidation and thus inhibited the tryptophan destruction. Tracer studies indicate that tryptophan is converted into at least 4 products.

There has been concern in recent years about the cancerogenic potential of pesticidal residues in food. Since pesticide workers receive much higher exposure to such chemicals at the work level, an assessment of the range of materials with cancerogenic potential has been made by a review of the literature. One hundred and seventy-five papers bearing on the subject were found. Their review has disclosed that many pesticidal chemicals possess at least low levels of cancerogenic activity for laboratory species. The review has demonstrated the major effect of spontaneous tumor incidence when chemicals of low cancer producing potential are being evaluated. It has also been established that some carriers and vehicles of pesticidal chemicals are cancerogenic or co-cancerogenic in man. There is some evidence of synergistic action between ingredients of particular preparations but no indication of additive cancerogenic potential among the various pesticides studied.

The spatial distribution of episodes of extreme temperature occurring over 2, 5, 8, and 11 consecutive days are presented, based on data from 31 stations. Comparative data on normal temperatures are also presented. This paper offers some information on the climatology of heat waves in the United States.

The etiology of the so-called Itai-Itai disease has been thought to relate to malnutrition and dietary cadmium exposure. Itai-Itai disease, named after its severe pain, was endemic in Zinzu River area in Japan; its characteristic signs and symptoms were osteomalacia and renal tubular dysfunction. Urinary low-molecular-weight proteins have been reported to be characteristic of renal tubular dysfunction. The components of urinary low-molecular-weight proteins in Itai-Itai disease are suggested in this paper to be retinol-binding protein and β2-microglobulin as determined by gel filtration, disc electrophoresis and immunoassay. Furthermore, vitamin D administration at a large dose is discussed and thought to contribute to the aggravation of renal tubular dysfunction in Itai-Itai disease.

Protozoa are of particular importance in nature playing an active role in water purification. Since they are increasingly used as toxicological models in medicine and pharmacology, it is suggested that protozoa could be employed advantageously in the field of water pollution. Methods are described in this paper for short-term (acute) and long-term (chronic) toxicity evaluation in order to determine the degree of toxicity of various water-borne contaminants and to establish the tolerance to these agents. The technique consists in exposure of cultures of Paramecium caudatum Ehr. in serial dilution tests for short and extended time intervals. Results may be rapidly obtained within a few hours in the acute and within 2 weeks in the chronic tests.

Brain electrical changes were observed in rats chronically treated with NaNO2 in drinking water ranging in concentration from 100 to 2000 mg/l. The brain electrical patterns did not return to normal after the withdrawal of NaNO2, even at the lowest exposure dose of 100 mg/liter which was equivalent to a daily dose of 14 mg/kg. Each concentration of NaNO2 drinking solution presented a characteristic picture of its own, i.e., in the unfolding electroencephalogram several types of changes became discernible tallying with the specific dosages of NaNO2 drinking solutions consumed by the rats, having a strong common denominator. These brain electrical activity changes are discussed in this paper.

The results of some experimental investigations by the author and his collaborators during recent years are presented in this paper. The number of mouse lung adenomas induced by urethane is dose-dependent. This is true both for newborn mice and adult mice and also under conditions of transplacental transmission. The existence of a dose-response effect has also been shown for adenomas induced in embryonic lung tissue organ cultures by the injection of urethane into pregnant mice. The establishment in this laboratory of an experimental model of human lung cancer by intratracheal instillation of carcinogenic compounds into rats made possible a systematic study of dose-response effects in the induction of experimental bronchogenic carcinomas and precancerous lesions using benzo[a]pyrene, 1,2,5,6-dibenzanthracene, and 7,12-dimethyl-benz[a]anthracene. A decrease in the amount of carcinogen always resulted in a decrease in the induction rate of malignant tumours and precancerous lesions. Repeated injections stimulated the blastomogenic effect. “Borderline” doses did not induce cancer but precancerous lesions were found. “Noncarcinogenic” doses can be determined for each experiment and each carcinogen. The problem of maximum permissible dose or concentration of carcinogenic substances has been discussed but there is some difference of opinion on this question. Nevertheless, the regular experimental finding of a dose-response effect can serve as a basis for cancer prevention.