Sister chromatid exchange and chromosome aberration analysis with the use of several carcinogens and noncarcinogens

Several chemical carcinogens and noncarcinogens were tested for their ability to induce sister chromatid exchanges (SCE) and structural chromosome aberrations in cultured V79-4 Chinese hamster cells. All of the direct-acting carcinogens induced a large increase in SCE frequency. Two chemicals, which are mutagenic in microorganisms but whose carcinogenicity is poorly documented, also increased the frequency of SCE. Carcinogenic polycyclic hydrocarbons caused an increased incidence of SCE only when a metabolizing feeder layer was used, whereas no increase was observed with noncarcinogenic polycyclic hydrocarbons. The other noncarcinogens also did not influence the SCE frequency. Although some chemicals increased the frequency of structural chromosome aberrations, no correlation was found between the frequencies of SCE and aberrations.

[The phototoxic activity of carcinogenic polycyclic hydrocarbons and their degradation products in the biological test (author's transl)]

The phototoxic activity of carcinogenic polycyclic hydrocarbons was evaluated using ciliates of the species Tetrahymena pyriformis maintained in sterile, semisynthetic media. This ciliate-light-test was developed into and standardized for a rapid microbiological assay of carcinogenic activity of polycyclic aromatic hydrocarbons. --In this fashion, six polycyclic aromatic compounds with differing carcinogenic activities were tested:benzo(a)-pyrene, benzo(b)fluoranthene, indeno(1,2,3-c,d)pyrene, benzo(a)anthracene, fluoranthene, and cyclopenteno (c,d)pyrene. An essential parallelism between phototoxic and carcinogenic activities, resp., was clearly obvious. --The combined effects of benzo(a)pyrene and fluoride ions was also investigated using the ciliate-light-test. Fluoride ions in the concentration of 1 ppm did not affect the phototoxicity of benzo(a)pyrene, suggesting that fluorides possess no cocarcinogenic activities. --Degradation products of benzo(a)pyrene obtained by UV-irradiation (mixtures of quinones) were also tested for phototoxic activity. It could be shown that such degradation products entirely free from benzo(a)pyrene still possessed 50% of the activity of the original, non-irradiated solution. This is taken to indicate that the degradation products products resulting of UV-irradiation may still retain a measure of carcinogenic activity, --a finding of considerable importance from the viewpoint of environmental hygiene.

Characterization of the oxygen probe pyrenebutyric acid in rabbit heart mitochondria

The fluorescence of pyrenebutyric acid is quenched by oxygen and the quenching is a linear function of the oxygen concentration. In addition, pyrenebutyric acid has been shown to be readily taken up by the cell with a partition coefficient of approx. 200. Results are presented on the effect of pyrenebutyric acid on oxidative metabolism in rabbit heart mitochondria. 1. Pyrenebutyric acid is readily taken up by heart mitochondria: 0.843 +/- 0.087 nmol pyrenebutyric acid taken up by Mr/mg dried weight. 2. Pyrenebutyric acid does not alter the steady-state redox levels (State 1, 2, 4 or 5) of any member of the respiratory chain. 3. Pyrenebutyric acid does not alter the response of cytochrome b, cytochrome c or NADH in the State 4-3-4 transition induced by the addition of ADP. Thus pyrenebutyric acid would appear to be non-toxic to oxidative metabolism.

Effect of dissolved aromatic hydrocarbons on the growth of marine bacteria in batch culture

Dissolved aromatic hydrocarbons were found to decrease growth rate and maximum cell density of marine bacteria in batch cultures. The magnitude of the decrement was observed to be a function of concentration of the hydrocarbon and inherent toxicity. The inherent toxicity was observed to increase inversely with solubility such that naphthalene at 100 muM concentration demonstrated a toxic effect similar to benzopyrene at 0.02 muM. A partial oxidation product of naphthalene was found to be more effective in decreasing growth parameters than naphthalene at equivalent concentrations and to cause complete cessation of growth at the higher concentrations permitted by its polar structure.

[On the interaction of polycyclic aromatic hydrocarbons and light with regard to its syncarcinogenic effects (author's transl)]

The rapidly growing pollution of the human biosphaere with potentially carcinogenic agents gives increased relevance to questions concerning the interaction of both chemical and physical agents in carcinogenesis. One such combination of environmental agents - that between polycyclic aromatic hydrocarbons and light - which heretofore has received little attention from workers in the field of environmental research, was investigated in the present paper. The phototoxic (cytotoxic) effects of carcinogenic aromatic hydrocarbons was demonstrated using ciliates of the species Tetrahymena pyriformis as the sensitive substrate. The experiments were conducted both with the chemically pure compounds and with native soot containing the adsorbed hydrocarbons. The following results were obtained: 1. Phototoxicity for ciliates of the highly carcinogenic benzo(a)pyrene may still be demonstrated in dilutions containing but 2 ppb (mug/l) of the substance, while the non-carcinogenic benzo(e)pyrene and fluorenthene are only weakly toxic in much higher concentrations. 2. The combination of benzo(a)pyrene and fluoranthene produced neither an additive nor a quenching effect, i.e., the resulting phototoxicity merely reflected the action of benzo(a)pyrene. 3. No phototoxic effect was observed in case of the fluorescent carcinogen, aflatoxin B1, in concentrations up to 200 ppb. This is taken to indicate that the property of fluorescence of carcinogenic substances by itself does not account for the phototoxic phenomenon. 4. The intense phototoxic activity of native soot ingested by the ciliates was shown to be dependent on the amount of polycyclic hydrocarbons contained. 5. Removal of polycyclic aromatic hydrocarbons from the soot particles by extraction with benzene resulted in the loss of phototoxic activity.

Effect ofcholinergic ligands on the lipids of acetylcholine receptor-rich membrane preparations from Torpedo californica

Ion permeation, triggered by ligand-receptor interaction, is associated with the primary events of membrane depolarization at the neuromuscular junction and synaptic connections. To explore the possible sites of ion permeation, the long-lived fluorescent probe pyrene (fluorescence lifetime approximately 400 nsec) has been inserted into the lipid phase of acetylcholine receptor-rich membrane (AcChR-M) preparations from Torpedo californica. The pyrene probe is susceptible to both fluidity and permeability changes in the lipid bilayer. These changes are detected by variations in the rate of decay of the excited singlet state of pyrene after pulsation with a 10-nsec ruby laser flash. Variations of these lifetimes in the membrane preparations alone or in the presence of quenchers show that binding of cholinergic agonists and antagonists, neurotoxins, and local anesthetics to AcChR-M produces varying effects on the properties of the pyrene probe in the lipid phase. It is concluded that binding of cholinergic ligands to the receptor does not significantly alter the fluidity of permeability of the lipids in the bilayer contact with pyrene. On the other hand, local anesthetics do affect these properties.

The effects of unsubstituted polycyclic aromatic hydrocarbons on the growth of Escherichia coli

The effect on growth of E. coli of a series of 3-, 4-, and 5-ring unsubstituted polycyclic aromatic hydrocarbons (PAH) is determined at concentrations of 10-5M, 10-6M, and 10-7M. The angular hydrocarbon configurations of 1,2-benzanthracene, 1,2,5,6-dibenzanthracene (DIBA), and 3,4-benzpyrene (BP) promote growth; tetracene and pyrene have little or no effect on growth while at most concentrations anthracene, phenanthrene chrysene, 1,2,3,4-dibenzanthracene, and pentacene inhibit bacterial growth. No universal pattern of concentration effect is manifest, but based on the results an angular acene configuration is a necessary condition for growth stimulation.

Chromosome bands induced in human and Syrian hamster cells by chemical carcinogens

After 24 hours of treatment of human peripheral leucocyte cultures or Syrian hamster embryonic secondary cultures with some known chemical carcinogens at concentrations that produce transformation in vitro of hamster cells, the chromosomes of both types of cells exhibited typical G banding. Chromosome bands did not result with urethane, a compound which does not produce cytotoxicity or cause transformation by direct exposure of cells. Non-carcinogenic chemicals which do not inhibit cell multiplication also failed to produce bands. Cytogenetic analysis following removal of the carcinogens from the cultures indicated non-banded uniformly stained chromosomes. It is concluded that metaphases with chromosome bands are more likely to be the result of nonspecific toxicity rather than being related to the carcinogenic properties of the chemicals.