Biomedical subjects

C Vaca

Publications and source records attributed to C Vaca.

6 recordsLinked to original sources

PubMed1993

Testing of quantitative parameters in the 32P-postlabelling method.

The 32P-postlabelling technique involves many steps that need to be carefully controlled in order to obtain a reliable quantitative determination of DNA adducts. We have studied several of the parameters involved in the DNA digestion procedures as well as those concerned in the phosphorylation reaction. Since adducts behave in very different ways in the labelling reaction, an individual protocol has to be worked out for each particular type of adduct. Quantitation is usually possible only if a synthesized standard of the adduct under investigation is run in parallel to the DNA samples throughout the whole procedure.

Adenosine Triphosphate↗

PubMed1992

On the bioactivation and genotoxic action of fluoranthene.

Fluoranthene (FA) was studied with respect to possible mechanisms of its high mutagenicity but low carcinogenicity, in comparison with the corresponding properties of benzo[a]pyrene (BaP), and with regard to the synergism of these two compounds shown by van Duuren and Goldschmidt (J Natl Cancer Inst 56, 1976, 1237). FA and BaP activated by S9 from Aroclor 1254 (PCB)-treated rats induce HPRT mutations in CHO cells with about equal effectiveness at the same exposure doses, which also lead to the same frequencies of repairable DNA adducts, enzyme-induced strand breaks being used as an indirect measure of adducts to DNA. FA was also shown to be an efficient inducer of SCE in human peripheral lymphocytes cocultivated with PCB-treated HepG2 cells or with liver cells from PCB-pretreated rats. For the induction of SCE, FA and BaP were shown to act additively. From metabolic studies with liver microsomes from C57Bl/6 mice it is concluded that, whereas BaP induces the metabolism of BaP to the mutagenic epoxide, neither BaP nor FA is able to induce the metabolism of FA. In mutation experiments with V79 cells (XEM2) constitutive for P450 IA1 activity, BaP 7,8-diol but not FA 2,3-diol provokes a high frequency of HPRT mutations. In cells constitutive for P450 IA2 enzymatic activity FA and BaP are but weakly mutagenic and practically nonmutagenic, respectively. Due to the additivity of the genotoxic effects of FA and BaP, induction of an error-prone condition by the latter compound seems to be excluded.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1992

Lipid peroxide levels in a murine adenocarcinoma exposed to hyperthermia: the role of glutathione depletion.

Increased lipid peroxide levels were obtained 1 h after a 60-min 43 degrees C hyperthermia treatment of a solid murine C3H mammary adenocarcinoma, grown subcutaneously in the hind paws of mice. Previous work from our group revealed that this heat treatment depletes the intracellular glutathione (GSH) content in this tumor. To investigate GSH depletion as one tentative mechanism behind the increased lipid peroxide levels obtained, we also measured the formation of lipid peroxidation products after extensive DL-buthionine-S,R-sulfoximine (BSO)-induced GSH depletion. The lipid peroxide effect provoked by BSO was less than that of the 60-min hyperthermia treatment. We therefore propose that the increased lipid peroxide levels induced by heat treatment do not correlate primarily with the observed decrease in GSH levels. Furthermore, in thermotolerance-induced tumors, lipid peroxide levels after a second heat treatment were observed to increase concomitantly with the cessation of thermotolerance. Lipid peroxide levels were also studied in liver, lung, and heart. Following BSO treatments, and up to 2-fold increase was observed in these organs in non-tumor-bearing mice. It was also observed that the intrinsic lipid peroxide levels in these organs from tumor-bearing mice were approximately 1.5- to 4-fold higher in comparison with non-tumor-bearing mice, thus indicating a systemic effect of the tumor implant.

Adenocarcinoma↗

PubMed1989

Incorporation of [3H]acetate into the membrane lipids of a murine tumour during the development of thermotolerance.

The incorporation of [3H]acetate into the membrane lipids of a C3H mammary adenocarcinoma, grown s.c. in the hind paw of CBA mice, was followed to estimate the effects on the de novo synthesis of membrane lipids after hyperthermic treatments. Thermotolerance developed in response to a heat treatment at 43 degrees C for 20 min, as verified through growth rate studies of tumours exposed to fractionated heat treatments. Our results show that, during the development of thermotolerance, the relative rates of incorporation of [3H]acetate into the major lipid classes of the tumour cell membranes change significantly. The de novo synthesis of phospholipids decreased while that of cholesteryl esters plus triglycerides increased. The incorporation of [3H]acetate into cholesterol remained constant. Consequently, the ratio [3H]cholesterol/[3H]lecithin increased significantly during the development of thermotolerance. When the incorporation of [3H]acetate was followed 72-96 h after the heat treatment, i.e. at the interval at which heat resistance was observed to approach that of control tumours, the incorporation into cholesterol was significantly reduced while incorporation into phospholipids increased to control levels. Thus, the ratio [3H]cholesterol/[3H]lecithin was significantly lower, when compared to that of control tumours. The functional relationship between the heat-induced changes in the de novo synthesis of membrane lipids and the development of thermotolerance is discussed with regard to a mechanism based on homeoviscous adaptation of the membranes.

Acetates↗

PubMed1987

Heat-induced changes in the incorporation of [H3]acetate in membrane lipids.

The effects of heat treatments at temperatures from 42 to 47 degrees C on the rate of incorporation of [3H]acetate into different classes of lipids have been studied in V-79 Chinese hamster cells. Thermotolerance induction and subtoxic heat treatments decreased the incorporation of [3H]acetate into phospholipids and caused the ratio [3H]cholesterol/[3H]phospholipids to increase several fold, and a positive correlation between heat dose and the ratio [3H]cholesterol/[3H]phospholipids was obtained for subtoxic hyperthermic treatments. The duration of this hyperthermic effect on the incorporation of [3H]acetate into the different lipid fractions was followed in pulse-label experiments. The highest increase of the ratio [3H]cholesterol/[3H]phospholipids was obtained during the first 24 h, but a significant elevation was also present for the 24-72 h pulse-labelled group. Thermotolerance induction was maximal 24 h after the heat treatment and then declined during the next 24 h. The increased [3H]cholesterol/[3H]phospholipid ratio observed in response to hyperthermia resembles the processes that serve to provide homeoviscous adaptation to sustain thermosensitive membrane-located functional groups, in analogy with the mechanisms responsible for thermal adaptation. However, the lack of a positive correlation between thermotolerance induction and the changes in lipid synthesis, for the whole time interval studied, remains to be further explored before any mechanistic interpretation of the data can be found.

Acetates↗

PubMedDate not supplied

32P-postlabelling analysis of DNA adducts in humans: adduct distribution and method improvement.

32P-Postlabelling was applied to study the distribution of adducts in white blood cells of foundry workers exposed to polycylic aromatic hydrocarbons. The distribution of the adducts among 63 workers followed an apparently trimodal pattern, which could relate to polymorphism in PAH metabolism. A modified postlabelling method is described and some parameters were tested for optimal labelling. The total volume of the polynucleotide kinase reaction is 2 microliters, which decreases exposure to radioactivity and costs of isotopes.

Animals↗