Cytochrome P-450 was induced both in the diploid wild-type D7 strain and in two isogenic DNA-repair-deficient strains (rad3 and rad56) of Saccharomyces cerevisiae following UV- and X-irradiation. The induction occurred only in logarithmic growth phase cells and it was transient showing a peak 3 h after irradiation. The maximal amount of cytochrome P-450 was directly proportional to the radiation dose applied. Under the same experimental conditions an increase of the catalase activity was also observed, suggesting that activated oxygen species produced by irradiation might be implicated in the induction of both enzymes. The sensitivity to H2O2 of cells containing high cytochrome P-450 levels was enhanced when this enzyme was specifically inhibited by tetrahydrofuran and metyrapone. This supports the hypothesis that cytochrome P-450, as well as catalase, might be involved in cell protection against oxidative damage.

Catalase↗

PubMedDate not supplied

Protective effect of lipoic acid against hydrogen peroxide in yeast cells.

Lipoic acid (LA) is found in all kinds of cells, it is widely used in medicine and as a dietary supplement, and it is involved in different physiological functions. Even if there are many papers regarding therapeutic effects of LA, medical research does not always support its effectiveness and little is known about LA metabolism in eukaryotic cells. In this work the probable protective effect of LA was investigated employing five strains of yeast Saccharomyces cerevisiae through short term assays. In particular LA behaviour in oxidative stress conditions was studied. For this purpose hydrogen peroxide was used as oxidant. In D7 strain, LA showed antimutagenic effects against hydrogen peroxide and decreased significantly cytochrome P450. To better elucidate the effect of LA the following yeast strains carrying deletions in superoxide dismutase genes (SOD) were employed: EG-103 (wild type), EG-110 strain (without mytochondrial SOD), EG-118 (without cytoplasmatic SOD) and EG-133 (without both enzymes). LA increased the number of mitotic divisions in EG-103, EG-110 and EG-133 and in growing cells (EG-103, EG-110, EG-118) it increased survival percentage with respect to hydrogen peroxide. The positive action was evident in D7 and in EG strains and it showed that LA can be protective and antimutagenic against oxidants in yeast cells, via its antioxidant activity.

Antimutagenic Agents↗

PubMedDate not supplied

Third International Conference on Mechanisms of Antimutagenesis and Anticarcinogenesis.

This conference, attended by scientists from 27 countries, focused on the most recent advances in the field of antimutagenesis and anticarcinogenesis. Particular emphasis was given to the mechanistic approach, which is believed to be an essential prerequisite for a safer and more effective implementation of chemoprevention of cancer and of mutation-related diseases. The arrangement of the six regular sessions basically followed and updated the detailed classification of mechanisms of inhibitors of mutagenesis and carcinogenesis proposed by S. De Flora and C. Ramel (Mutat. Res., 202: 285-306, 1988), covering both extracellular and cellular mechanisms involved in the prevention of mutations and cancer initiation, as well as in the modulation of later stages of the carcinogenesis process. In addition, a workshop was devoted to methodological aspects concerning the modulation of the genotoxic and carcinogenic response. The present report covers the main themes of overview lectures or research communications presented by more than 60 speakers. Most presentations were multi-authored, as the result of collaborative studies, in several cases at the international level, but only the names of speakers will be given.

Anticarcinogenic Agents↗

PubMedDate not supplied

Genetic activity of trichloroethylene in yeast.

Trichloroethylene (TCE) was tested for its ability to induce both point mutation and mitotic gene conversion in diploid strain of yeast. Saccharomyces cerevisiae (strain D7) was tested for both activities in culture with and without a mammalian microsomal activation system and in the intrasanguineous host-mediated assay in mice. Strain D4 (gene conversion) was tested only in the host-mediated assay. In suspension tests with D7, TCE was toxic but not genetically active without microsomal activation. When a mouse liver 10,000 xg supernatant was included in the suspension tests, dose related increases in both mutation and gene conversion were seen at survival levels of greater than 50 percent. In the host-mediated assay, TCE induced both point mutation and gene conversion in D7 and gene conversion in D4 when recovered from the liver and kidneys after both acute and subacute dosing. Yeasts recovered from the lungs showed little, if any, increase in either point mutation or gene conversion.

Mutagens↗

PubMedDate not supplied

Selenium: its important roles in life and contrasting aspects.

Explore the source record for details and available documents.

Animals↗

PubMedDate not supplied

Mutagenicity and toxicity of electromagnetic fields.

Humans are exposed daily to electromagnetic fields (EMFs) originating from a variety of devices and systems. During the 1980s many reports of potential mutagenic, teratogenic, and carcinogenic effects of EMFs were published, sometimes with contrasting results. To date, no study has established unequivocally a causal relationship between EMFs and cancer. Cell cultures can provide a simple and inexpensive tool for the study of the effects of EMFs. We have used the Chinese hamster V79 cell line to evaluate the influence of a sinusoidal EMF at 50-Hz with a constant flow of 2 G on the induction of HGPRT- mutants and on survival. Our results showed that the EMF employed did not induce any modification of mutation frequency, but the results on survival were contrasting. When only 10(2) cells were plated, a reduction in the number of colonies, reaching about 50% after 10 days of treatment, was observed; however, when 2 x 10(5) cells or more were seeded, no reduction in viability was recorded. An intercellular metabolic interaction may explain these results.

Animals↗

PubMedDate not supplied

Study of spermine and spermidine effects on Saccharomyces cerevisiae. Polyamine production in different growth conditions and in the presence of interleukin-2.

The role of polyamines during cell growth is still uncertain. Yeast cells possess an amine pathway similar to that described for animal cells. We studied the relationship between growth and polyamine production in yeast cells of Saccharomyces cerevisiae grown under various conditions. Polyamines were determined in homogenates of yeast cells by a rapid enzymatic assay, confirmed by thin-layer chromatography. Polyamine production is dependent on the growth conditions. The effects of spermine, spermidine, and interleukin-2 on yeast cells were investigated. Exogenous polyamines affected the endogenous pathway, and interleukin-2 treatment increase yeast growth and polyamine production.

Culture Media↗