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E Cundari

Publications and source records attributed to E Cundari.

44 records · Page 3Linked to original sources
PubMed1985

Conditions that influence the genetic activity of potassium dichromate and chromium chloride in Saccharomyces cerevisiae.

Potassium dichromate and chromium chloride were analyzed for their ability to induce mitotic gene conversion and point reverse mutation in D7 diploid strain of S. cerevisiae. We used cells from the stationary phase of growth with and without metabolic activation (S9 hepatic fraction) and cells from the logarithmic phase, that contain a high level of cytochrome P-450 and have a greater permeability. In the present work we confirmed the genetic activity of K2Cr2O7 in cells from the stationary phase, with and without S9 fraction and in cells from the logarithmic growth phase. A slight increase in genetic activity was observed in experiments with CrCl3 using phosphate buffer, but no genetic effects were noted in Tris-HCl buffer. Our studies suggest that phosphate ion may be the carrier responsible of the entrance of trivalent chromium in the cells. The higher cellular permeability may account for the different results obtained with both compounds in cells from the stationary and logarithmic phases of growth.

Biotransformation↗
PubMed1984

Comparative genetic activity of cis- and trans-1,2-dichloroethylene in yeast.

The cis and trans isomers of 1,2-dichloroethylene were tested for mutagenic effects in a diploid strain (D7) of the yeast Saccharomyces cerevisiae in suspension tests with and without a mammalian microsomal activation system, an S9 mouse liver fraction, and by an in vivo intrasanguineous host mediated assay. The effects of the same agents on aminopyrine N-demethylase activity and cytochrome P-450 level in liver were studied in nonpretreated and in phenobarbital + beta-naphtoflavone-pretreated mice. In the suspension test, both isomers exhibited dose dependent toxicity, and survival was lower with metabolic activation than without. In this test also, both isomers exhibited genetic activity as measured by increases in recombinants at the ade 2 locus in experiments with metabolic activation. In the host-mediated assay, only the cis isomer showed evidence of mutagenic activity with significant increases in convertants at the trp locus and revertants at the ilv locus. Such mutagenic activity was found both after acute and chronic doses and in liver, kidney, and lung tissue. The two isomers exhibited different effects with respect to aminopyrine N-demethylase activity and cytochrome P-450 level. In general, the trans isomer appeared to emphasize induction of enzyme activity or level while the cis isomer more frequently tended to inhibit activity or destroy the enzyme.

Aminopyrine N-Demethylase↗
PubMed1984

Genetic and biochemical investigation on chloral hydrate in vitro and in vivo.

Chloral hydrate (CH), a metabolite of trichloroethylene (TCE), was studied in vitro using the D7 diploid strain of Saccharomyces cerevisiae, with and without a mammalian microsomal activation system (S9 fraction), and in vivo by intrasanguineous host-mediated assay (HMA). The in vivo effects on the hepatic microsomal monooxygenase induced by CH in mice pretreated with beta-naphthoflavone (beta-NF) and Naphenobarbital (PB) were also investigated. Chloral hydrate induced a significant increase of mitotic gene conversion in D7 strain both in vivo and in vitro. The enzymatic determinations in mice showed a decrease in aminopyrine N-demethylase (APD) and p-nitroanisole O-demethylase (p-NAD) activities (about 37% and 29% respectively) after one acute dose of CH. Moreover, stability experiments, carried out in the conditions of the liver microsomal assay (LMA), showed an increase of residual activity, after 1 h of preincubation with respect to the control (about 22% and 9% for APD and p-NAD respectively).

Aminopyrine N-Demethylase↗
PubMed1984

Studies of genetic effects in the D7 strain of Saccharomyces cerevisiae under different conditions of pH.

The genetic effects of variation in pH in culture media and in suspension tests were examined in a diploid strain (D7) of the yeast, Saccharomyces cerevisiae. Deviation from the normal pH of 6.24 in the liquid culture medium, has a significant effect on cellular growth and on mitotic gene conversion at the trp5 locus. Frequencies of reversion at the ilv I-92 locus and of mitotic crossing-over at the ade2 locus are not significantly influenced. Suspension tests, performed using phosphate buffer (pH 5.8), strongly confirm the original results. Our data suggest that the increase in mitotic gene conversion under various conditions of pH is due to a specific effect of pH itself on the cells of S. cerevisiae. In fact, increases were obtained using the same pH in both cellular growth and non-growth conditions. The maximum effect detected with both procedures was obtained at pH 5.8; in the growth test, at this pH, gene conversion frequency appeared to be most pronounced, being about 10 times higher than that of the control. These results suggest that pH exerts its specific action both on growing and non-growing yeast cells, and the difference in induction of genetic effect between these two conditions is probably due to a time factor.

Cell Division↗
PubMed1983

Potassium nitrate and nitrosamine formation.

The influence of potassium nitrate on the formation of nitrosamines in salami was studied. Samples of salami were prepared, with and without the addition of potassium nitrate. Under the conditions of the experiment, potassium nitrate did not represent a source of either nitrite or nitrosamines. Independently of the presence of potassium nitrate in the sample formulation, the growth of bacterial flora reached a maximum in the first 20 days of the ripening process.

Bacteria↗
PubMedDate not supplied

Induction of cytochrome P-450 and catalase activity in Saccharomyces cerevisiae by UV and X-ray irradiation. Possible role for cytochrome P-450 in cell protection against oxidative damage.

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

Influence of spermidine on sister chromatid exchanges induced by alkylating agents in mammalian cells in vitro.

Sister chromatid exchanges (SCEs) are a very sensitive genetic end-point for in vitro identification of presumed carcinogenic and mutagenic agents, although the mechanism of their formation is still to be elucidated. The present work shows the influence of spermidine on SCE induction by two different DNA damaging agents: Mitomycin-C (MMC) and N-Methyl-N'-Nitro-N-Nitrosoguanidine (MNNG). The SCE level induced by MMC was significantly decreased by spermidine. On the contrary, MNNG-induced SCEs were not affected. It has recently been suggested that MMC, via its reduced metabolite mitosene, produces bulky mono-and bi-adducts in DNA, mainly located in the minor groove of the double helix. MNNG, instead, directly methylates several electrophilic sites of DNA bases, such as the N7 and the O6 of guanines and the N3 of adenines. Both MMC and MNNG, despite their different mechanism of action, are potent SCE inducers. Spermidine, similarly to its structural analogue Spermine, is known to interact with DNA phosphate groups and to bind reversibly to the minor groove, thus stabilizing the double helix structure. Spermidine, being therefore ineffective on the MNNG-mediated DNA methylation, might affect DNA, making it structurally unavailable for MMC binding.

Animals↗