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Biomedical subjects

R Preussmann

Publications and source records attributed to R Preussmann.

At least 163 records · Page 9Linked to original sources
PubMed1976

Carcinogenicity in rats of high oral doses of N-nitroso-carbaryl, a nitrosated pesticide.

N-Nitrosocarbaryl was administered orally to 31 male Sprague-Dawley rats at doses of 130 mg/kg body weight (b.w.) twice weekly. Of the treated animals 29% died with squamous cell carcinomas of the forestomach after an average inductiom time of 167 days. The first carcinoma was observed as early as 63 days after the beginning of the experiment. In addition, 19% of the treated animals died with hyperkeratoses and 6% with papillomas in the forestomach. In contrast to the untreated controls, which had a normal life expectancy, treated animals had a very short life span due to high cumulative toxicity and the early appearance of tumors.

Administration, Oral↗
PubMed1976

Chemical carcinogens in the human environment; problems and quantitative aspects.

A short review on environmental carcinogenesis by chemicals is given. Problems related with the determination of carcinogenicity of chemicals are mentioned. Some critical factors in the monitoring of environmental carcinogens are discussed in relation to a quantification of human exposure to such compounds. An attempt at risk evaluation is made for polycyclic aromatic hydrocarbons, vinyl chloride, N-nitroso compounds and aflatoxins. It is concluded that there is a "threshold dose" for individual carcinogens that does not lead to tumor induction within the normal life span. The probability of multifactorial cause of human cancer by environmental carcinogens, however, does not allow the definition of "safe" levels of such compounds in view of syncarcinogenic and other enhancing and/or modifying effects.

Aflatoxins↗
PubMed1975

The effect of heavy metal ions on the rate of decomposition of N-ethyl-N-nitrosourea and other carcinogenic N-nitrosamides.

The decomposition of ethylnitrosourea (ENU) in aqueous solution is enhanced by Cu2+ ions. Ni2+ shows a similar, but less pronounced effect. The decomposition rate of N-methyl-N'-nitro-N-nitrosoguanidine (MNNG), a compound known to be relatively stable in aqueous solution, is strongly enhanced by the addition of Cu2+ and to a smaller extent also by Ni2+ ions. On the other hand the stability of N-methyl-N-nitrosourethane is not influenced by heavy meatal ions. The influence of Cu2+ ions on the decomposition rate of ENU is similar to that of OH-anions, influencing the reaction kinetics on a molar basis. The increase in decomposition rate of ENU by copper ions is not seen in the presence of blood serum or other complexing agents. The results are discussed in relation to the known enhancement in toxicity and carcinogenicity of ENU by heavy metal salts in animal experiments.

Blood↗
PubMed1975

[Rat urinary metabolites of (2-hydroxybutyl)-n-butylnitrosamine].

The chemical structure of 3 urinary metabolites of 2-hydroxy-di-n-butylnitrosamine has been identified by mass spectrometry. The results indicate that oxidation and formation of metabolites with shorter chain length may be explained by alpha-oxidation and subsequent degradation. This is an alternative to the beta-oxidation hypothesis of Krüger (1971).

Animals↗
PubMed1975

Nitrosation of phenacetin. Formation of N-nitroso-2-nitro-4-ethoxyacetanilide as an unstable product of the nitrosation in dilute aqueous-acidic solution.

Reaction of phenacetin with N2O4 in glacial acetic acid at 10(0) C gives N-nitroso-2-nitro-4-ethoxyacetanilide. This N-nitrosoacylarylamine is stable at low temperatures (--30 degress C) but unstable at ambient temperature. No intact N-nitroso-2-nitro-4-ethoxyacetanilide can be detected when phenacetin is nitrosated under conditions simulating those in the stomach (37 degrees C, pH 1). Instead, 2-nitro-4-ethoxybenzenediazonium chloride is the main reaction product found. Under the conditions applied, the N-nitrosoacylarylamine rapidly rearranges by 1,3-migration of the acetyl group. The resulting diazoester dissociates into the corresponding diazonium salt. Trapping of the diazonium ion with 1-naphthol as an azo dye provides a useful means to identify the parent N-nitroso compound and to measure colorimetrically its rate of formation. The yields obtained in dilute aqueous nitrosation mixtures are lower than expected; the reasons for this finding are discussed. Preliminary results of animal experiments show that the N-nitroso compound is a directly acting carcinogen.

Acetanilides↗