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Biomedical subjects

G Batist

Publications and source records attributed to G Batist.

At least 91 records · Page 5Linked to original sources
PubMed1989

Response to ischemia-reperfusion injury in hypertrophic heart. Role of free-radical metabolic pathways.

Clinical and experimental evidence demonstrates that hypertrophied cardiac tissue is more sensitive to ischemic injury than is normal myocardium. Recent studies indicate that cardiac ischemia-reperfusion injury involves the generation of toxic oxygen free radicals. We used the spontaneously hypertensive rat (SHR) model, with its otherwise genetically identical control (the Wistar-Kyoto [WKY] rat), to investigate the potential role of enzymes that generate and detoxify oxygen radicals in the sensitivity of hypertrophied heart to ischemia and reperfusion. Because hypertension develops progressively with age in SHRs, we assayed xanthine oxidase, superoxide dismutase, catalase, and glutathione peroxidase at three different time points and found significant fluctuations at different ages. At age 26 weeks, physiological measurements demonstrated hypertension and increased sensitivity to ischemia and reperfusion, measured as significantly decreased left ventricular recovery after injury. At this age, xanthine oxidase, which may generate oxygen radicals, was significantly increased in SHR compared with WKY rats (p = 0.003). Superoxide dismutase, which is a principal step in oxygen-radical detoxification, was significantly lower (p = 0.044). These data suggest that differences in the constitutive levels of oxygen-radical metabolic pathways are different in hypertrophied myocardium, and it is suggested that this finding may play a role in the response of these hearts to ischemia-reperfusion injury.

Animals↗
PubMed1989

The influence of dietary whey protein on tissue glutathione and the diseases of aging.

This study compared the effects of a whey-rich diet (20 g/100 g diet), with that of Purina mouse chow or casein-rich diet (20 g/100 g diet), on the liver and heart glutathione content and on the survival of old male C57BL/6NIA mice. The study was performed during a limited observation period of 6.3 months. In mice fed the whey protein-rich diet between 17 months and 20 months of age, the heart tissue and liver tissue glutathione content were enhanced significantly above the corresponding values of the casein diet-fed and Purina-fed mice. Mice fed the whey protein diet at the onset of senescence at 84 weeks, exhibited increased longevity as compared to mice fed Purina mouse chow over the 6.3 month observation period extending from the age of 21 months (corresponding to a human age of 55 years) to 26-27 months of age (corresponding to a human age of 80 years), during which time 55% mortality was observed. The corresponding mean survival time of mice fed the defined casein diet is almost identical to that of Purina-fed controls. Body weight curves were similar in all three dietary groups. Hence a whey protein diet appears to enhance the liver and heart glutathione concentration in aging mice and to increase longevity over a 6.3 month observation period.

Aging↗
PubMed1989

Radiation response of drug-resistant variants of a human breast cancer cell line.

The radiation response of drug-resistant variants of the human tumor breast cancer cell line MCF-7 has been investigated. Two sublines, one resistant to adriamycin (ADRR) and the other to melphalan (MLNR), have been selected by exposure to stepwise increasing concentrations of the respective drugs. ADRR cells are 200-fold resistant to adriamycin and cross-resistant to a number of other drugs and are characterized by the presence of elevated levels of selenium-dependent glutathione peroxidase and glutathione-S-transferase. MLNR cells are fourfold resistant to melphalan and cross-resistant to some other drugs. The only mechanism of drug resistance established for MLNR cells to date is an enhancement of DNA excision repair processes. While the spectrum of drug resistance and the underlying mechanisms differ for the two sublines, their response to radiation is qualitatively similar. Radiation survival curves for ADRR and MLNR cells differ from that for wild-type cells in a complex manner with, for the linear-quadratic model, a decrease in the size of alpha and an increase in the size of beta. There is a concomitant decrease in the size of the alpha/beta ratio which is greater for ADRR cells than for MLNR cells. Analysis of results using the multitarget model gave values of D0 of 1.48, 1.43, and 1.67 Gy for MCF-7 cells are not a consequence of cell kinetic differences between these sublines. Results of split-dose experiments indicated that for both drug-resistant sublines the extent of sublethal damage repair reflected the width of the shoulder on the single-dose survival curve. For MCF-7 cells in the stationary phase of growth, the drug-resistant sublines did not show cross-resistance to radiation; however, delayed subculture following irradiation of stationary-phase cultures increased survival to a greater extent for ADRR and MLNR cells than for wild-type cells.

Antineoplastic Agents↗
PubMed1989

Immunoenhancing property of dietary whey protein in mice: role of glutathione.

The spleen cells immune response to sheep red blood cells of C3H/HeJ mice fed a 20 g whey protein/100 g diet is substantially higher than that of mice fed an equivalent casein diet of similar nutritional efficiency. The present study indicates that the observed immunoenhancing effect of the whey protein mixture is dependent on the overall amino acid pattern resulting from the contribution of all its protein components. Whey protein contains substantially more cysteine than casein. Dietary cysteine is considered to be a rate limiting substrate for the synthesis of glutathione which is necessary for lymphocyte proliferation. Our studies show that enhancement of host humoral immune response is associated with greater and more sustained production of splenic glutathione during the antigen driven clonal expansion of the lymphocyte in whey protein fed mice in comparison to mice fed the equivalent casein or the cysteine-enriched casein diet. Hence the efficiency of dietary cysteine in inducing supernormal glutathione levels is greater when it is delivered in the whey protein than as free cysteine. Administration of S-(n-butyl) homocysteine sulfoximine, which reduces splenic glutathione level by half, produces a 4-5 fold drop in the humoral immune response of whey protein diet-fed mice. This is further evidence of the important role of glutathione in the immunoenhancing effect of dietary whey protein.

Animals↗
PubMed1989

Enhanced DNA cross-link removal: the apparent mechanism of resistance in a clinically relevant melphalan-resistant human breast cancer cell line.

Resistance to the cytotoxic effects of alkylating agents is a major limitation to their clinical efficacy. Although a number of animal and human tumor cell models have been developed to study this problem, it has proven difficult to achieve very high levels of resistance to alkylating agents in vitro. This is consistent with the recent clinical evidence that alkylator resistance can be overcome by dose escalations of less than 10-fold. A number of mechanisms of alkylator resistance have been described, more than one of which may occur in the same model. This paper describes a human breast cancer cell subline selected for 3-fold resistance to melphalan and cross-resistant to other alkylators in which only one of the previously described mechanisms of resistance, enhanced removal of DNA interstrand cross-linking, is demonstrable. Northern blot analysis using the human incisional repair gene ERCC-1 cDNA demonstrated that this particular gene product is not the altered function in these cells, so the molecular characterization of the observed enhanced repair is pending. Because these cells are also cross-resistant to radiation and to adriamycin and epipodophyllotoxin, they may represent a clinically relevant model in which to examine the role of DNA repair of lesions resulting from alkylators and other cytotoxic agents.

Blotting, Northern↗
PubMed1988

Induction of gamma-glutamyl transpeptidase activity by all-trans retinoic acid in cultured rat liver epithelial cells.

The induction of activity of gamma-glutamyl transpeptidase (GGT) by all-trans retinoic acid in a chemically transformed rat liver epithelial cell line has been investigated. Retinoic acid increased the level of the GGT mRNA and this enhancement was progressive, depending on the duration of exposure and on the concentration of retinoic acid in the culture medium. When retinoic acid was removed from cultures which had been exposed to it for 4 days, the induced GGT activity remained unchanged. In contrast to transformed cell lines, retinoic acid did not induce the activity of GGT in normal/non-transformed rat liver epithelial cells.

Animals↗
PubMed1987

Differential formation of hydroxyl radicals by adriamycin in sensitive and resistant MCF-7 human breast tumor cells: implications for the mechanism of action.

Adriamycin-stimulated formation of .OH in sensitive and resistant subline of human breast tumor cells (MCF-7) has been examined by electron spin resonance spectroscopy. It was shown that adriamycin significantly stimulated the formation of .OH spin adducts [5,5-dimethyl-1-pyrroline N-oxide (DMPO)-OH] in the sensitive cells but not in the resistant cells. By use of spin-broadening techniques and inhibition of .OH with high molecular weight poly(ethylene glycol), which does not enter intact cells, it was shown that 60-65% of adriamycin-induced .OH were located extracellularly and were metal ion dependent since they were decreased in the presence of desferal. Furthermore, superoxide dismutase and catalase, enzymes that detoxify superoxide and hydrogen peroxide, also significantly inhibited adriamycin-induced .OH formation and protected against the cytotoxicity of adriamycin. The differential .OH formation in these two cell lines is not due to diminished activities of flavin-dependent activating enzymes nor decreased accumulation of the drug in the cells but appears to be related to enhanced activities of detoxifying enzymes, particularly, glutathione peroxidases in the resistant cells.

Breast Neoplasms↗
PubMed1986

Overexpression of a novel anionic glutathione transferase in multidrug-resistant human breast cancer cells.

Adriamycin-resistant (AdrR) human breast cancer cells have been selected which exhibit cross-resistance to a wide range of anti-cancer drugs. This multidrug-resistant phenotype is associated with increases in the activities of glutathione peroxidase and glutathione transferase. The 45-fold increase in glutathione transferase activity is associated with the appearance of a new anionic isozyme in AdrR cells which is immunologically related to the anionic glutathione transferase present in human placenta. The increase in transferase and the level of drug resistance is relatively stable during passage of AdrR cells in the absence of adriamycin for over 10 months. A similar anionic glutathione transferase isozyme is also found in rat hyperplastic liver nodules, a preneoplastic state resulting from exposure to carcinogens. A rat cDNA which codes for the anionic glutathione transferase in rat hyperplastic nodules hybridizes to a 1.1-kilobase pair mRNA which is overexpressed in the AdrR MCF-7 cells. The anionic transferase has been purified from the AdrR cells and found to have characteristics which distinguish it from other anionic human glutathione transferases, including high levels of intrinsic peroxidase activity. The overexpression of a similar anionic glutathione transferase in human breast cancer cells selected for multidrug resistance and in rat hyperplastic liver nodules, which develop resistance to various hepatotoxins, suggests a possible role for this drug-conjugating enzyme in the mechanism of resistance in both of these states.

Animals↗
PubMed1986

Enzymatic defense against radiation damage in mice. Effect of selenium and vitamin E depletion.

Radiation effects are mediated in part by the generation of oxygen-derived free radicals and hydrogen peroxide. Membrane polyunsaturated fatty acids are important biological targets of these toxic molecules which cause lipid peroxidation. Radiation damage to DNA is also known to result in base hydroperoxides, especially thymidine hydroperoxide. Glutathione (GSH) is known to inhibit lipid peroxidation both chemically and through its interaction with the selenium-dependent glutathione peroxidase (GSH-Px). Although cytosolic GSH-Px can metabolize organic lipid peroxides in solution, it cannot metabolize phospholipid peroxides in micelles. This may be due to the interference of phase differences between the aqueous cytosol and the membrane, or the result of steric hindrance. Recent studies have suggested the presence of a membrane-bound GSH-dependent peroxidase system. We examined the cytosolic versus membrane-associated GSH-Px, in various tissues of mice on a selenium and vitamin E deficient diet, and found significant differences among organs in the distribution of enzyme activity in these two subcellular fractions. The effect of single high-dose whole body irradiation did not appear to be related to the activity of these enzymes.

Animals↗
PubMed1986

Similar biochemical changes associated with multidrug resistance in human breast cancer cells and carcinogen-induced resistance to xenobiotics in rats.

MCF7 human breast cancer cells selected for resistance to doxorubicin (adriamycin; DoxR) have developed the phenotype of multidrug resistance. Multidrug resistance in DoxR MCF7 cells (called AdrR MCF7 cell line in previous publications) is associated with biochemical changes similar to those induced by carcinogens in rat hyperplastic liver nodules (HNs) and associated with resistance to xenobiotics in that system. In HNs and DoxR cells, exposure to a single agent results in the selection of cells that are cross-resistant to a wide variety of structurally dissimilar toxic agents. Resistance in both systems is associated with decreases in intracellular accumulation of toxins and changes in phase I (decreased cytochrome P1-450) and phase II (increased glutathione transferase and glucuronyltransferase) drug-metabolizing activities. In HNs and DoxR cells, resistance is associated with the induction of relatively stable levels of an immunologically related anionic glutathione transferase isozyme (EC 2.5.1.18). The finding of similar biochemical changes associated with the development of resistance to various xenobiotics in HNs and to many naturally occurring antineoplastic agents and at least one carcinogen (benzo[a]pyrene) in DoxR MCF7 cells suggests that the mechanisms of resistance in these two models may be similar.

Animals↗
PubMed1986

Etoposide (VP-16) and cisplatin in previously treated small-cell lung cancer: clinical trial and in vitro correlates.

Treatment of patients with relapsed small-cell lung cancer (SCLC) has been uniformly unsuccessful. Recently, the combination of etoposide (VP-16) and cisplatin in this setting has been reported to result in up to 50% response rates. We treated 29 patients with relapsed SCLC with this combination and found only a 12% response rate. The discrepancy between our results and those of others is most likely due to differences in prior treatment of the patients, although the effect of dose and schedule modifications are considered. Our patients had received a six-drug regimen over a median of 7 months and had a median drug-free interval before this treatment of only 3 weeks. Evidence is presented that suggests that this aggressive initial therapy affected both host tolerance to further treatment and the development of tumor resistance at the cellular level.

Adult↗
PubMed1986

Differences in phosphate metabolite levels in drug-sensitive and -resistant human breast cancer cell lines determined by 31P magnetic resonance spectroscopy.

31P magnetic resonance spectra of perfused human breast cancer cells with the phenotype of pleiotropic drug resistance exhibit striking differences in the levels of phosphate metabolites from the wild-type, drug-sensitive parent cell line. Resistant cells demonstrated elevated levels of phosphocreatine and depressed levels of phosphomonoesters, phosphodiesters, and diphosphodiesters. These differences may reflect significant alterations in the control of bioenergetic metabolism between drug-resistant and -sensitive cells.

Breast Neoplasms↗
PubMed1986

Selenium-induced cytotoxicity of human leukemia cells: interaction with reduced glutathione.

Selenium exists in a number of forms with differing valence states, some of which have shown antitumor activity. We studied the tumoricidal activity of four currently available selenium forms against a human leukemia cell line and exploited the differences among them to investigate the mechanism of antitumor action. Only selenocystine and sodium selenite showed antitumor activity, and these were also the only compounds which demonstrated significant redox chemistry, including depletion of cellular glutathione, stimulation of glutathione reductase, and stimulation of oxygen consumption. The interaction of these two compounds with glutathione suggests an intriguing potential role for them in cancer therapy.

Cell Line↗
PubMed1985

Phase I and pharmacokinetic study of tiazofurin (TCAR, NSC 286193) administered by continuous infusion.

Tiazofurin (2-beta-D-ribofuranosylthiazole-4-carboxamide, TCAR) is a synthetic C-nucleoside that demonstrated significant in vivo activity against a variety of animal tumors as well as in vitro activity against human tumor-derived cell lines. Thirteen patients were treated with TCAR administered as a 5-day continuous infusion in this Phase I trial. Seventeen complete cycles were administered in three dose levels ranging from 550 to 1450 mg/M2. Dose-limiting toxicities were myelosuppression and neurotoxicity including severe lethargy. Other toxicities including superficial skin peeling, myalgias, and tearing were seen at all doses. One patient had chest pain on day 4 resulting in stopping the drug, however, there was no evidence of cardiac or pericardial disease. Uric acid levels rose within one day in the absence of allopurinol treatment. There were no treatment related deaths. HPLC measurement of drug levels demonstrated steady-state plasma levels during the infusion, and a half-life following the infusion of 7.7 +/- 0.6 hours. Minor abnormalities in renal function were associated with dramatic changes in pharmacokinetics and toxicity. No clinical responses were observed in this trial.

Adult↗