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Biomedical subjects

K Polasa

Publications and source records attributed to K Polasa.

16 recordsLinked to original sources
PubMed2006

Stem cell test: a practical tool in toxicogenomics.

During early embryonic development, at blastocyst stage, the embryo has an outer coat of cells and an inner cell mass (ICM). ICM is the reservoir of embryonic stem (ES) cells, which are pluripotent, i.e., have the potential to differentiate into all cell types of the body. Cell lines have been developed from ES cells. In addition, there are embryonic germ (EG) cell lines developed from progenitor germ cells, and embryonic carcinoma (EC) cell lines developed from teratomas. These cell lines are being used for the study of basic and applied aspects in medical therapeutics, and disease management. Another potential of these cell lines is in the field of environmental mutagenesis. In addition to ES cells, there are adult stem cells in and around different organs and tissues of the body. It is now possible to grow pure populations of specific cell types from these adult stem cells. Treating specific cell types with chemical or physical agents and measuring their response offers a shortcut to test the toxicity in various organ systems in the adult organism. For example, to evaluate the genotoxicity of a chemical (e.g., drug or pesticide) or a physical agent (e.g., ionizing radiation or non-ionizing electromagnetic radiation) during embryonic development, a large number of animals are being used. As an alternative, use of stem cell lines would be a feasible proposition. Using stem cell lines, efforts are being made to standardize the protocols, which will not only be useful in testing the toxicity of a chemical or a physical agent, but also in the field of drug development, environmental mutagenesis, biomonitoring and other studies.

Cell Differentiation↗
PubMed2004

Inhibition of B(a)P induced strand breaks in presence of curcumin.

Incidence of cancer at different sites may be related to oxidative damage to host genome by genotoxicants. These oxidative actions may be modified by phytochemicals present in foods. The non-nutritive dietary constituents which possess antimutagenic property appear to be promising chemopreventive agents. This study reports the protective effect of curcumin on B(a)P induced DNA damage in human peripheral blood lymphocyte cells. The study group consisted of 10 male smokers, 10 non-smokers and 10 non-smoking females aged between 25 and 45. The DNA damage was assessed using comet assay. In all the groups curcumin showed a dose-dependent inhibitory effect. The effect appeared to be sex dependent. There was no correlation between DNA damage and GST-Mu levels and levels of micronutrients namely Vitamins A, E and beta carotene. The results of this study are in line with our earlier observations on turmeric/curcumin as a potential chemopreventer.

Adult↗
PubMed1997

Reduction of urinary mutagen excretion in rats fed garlic.

Naturally occurring substances of plant origin are known to possess antimutagenic potential. Garlic (Allium sativum) was fed to rats in dried powdered form at 0.1%, 0.5% and 1% concentrations in their diet for 4 weeks. At the end of the experiment benzo[a]pyrene (1 mg/rat) was injected intraperitoneally and 24-h urine was collected from the rats. Urinary mutagens were quantitated by the Salmonella typhimurium assay. There was a significant reduction in the excretion of urinary mutagens by carcinogen-exposed rats fed garlic. Further, there was a stimulation in the activities of liver cytosolic glutathione-S-transferase and liver and lung quinone reductases. The study suggested that the antimutagenic potential of garlic may be mediated through induction of detoxification enzymes in target tissues.

Animals↗
PubMed1995

Diet, nutrition & cancer--the Indian scenario.

Cancer continues to be a major health problem despite advances in medical technology for its diagnosis and treatment. Hence prevention strategies are needed to decrease the burden of the disease. Of all the environmental factors, dietary components appear to play an important role in the initiation/progression of the disease. Nutrients and non-nutrients in the diet can influence the carcinogenic process at various stages, from initiation to overt manifestation. The National Institute of Nutrition has conducted studies on several aspects of diet-cancer inter-relationships. These include studies on metabolic susceptibility, case-control approach to determine the risk factors and intervention studies to determine the role of nutrients and non-nutrient components on preneoplastic events. Extensive work has been carried out demonstrating the antimutagenic/anticarcinogenic potential of some commonly consumed spices and vegetables such as turmeric, mustard, green leafy and allium species of vegetables. Dietary intervention for cancer prevention is needed to control the disease besides avoiding risk factors such as smoking and alcoholism and exposure to genotoxicants. Public education and awareness about the beneficial effects of consuming a healthy diet including plenty of fresh vegetables and fruits with spices such as turmeric in adequate amounts to prevent cancer are required.

Carcinogens↗
PubMed1994

Effect of Brassica nigra on benzo[a]pyrene mutagenicity.

Male rats were given diets containing Brassica nigra (mustard seed) powder at 0, 1, 5 or 10% for 1 month and then exposed to benzo[a]pyrene (B[a]P. 1 mg by ip injection). The antimutagenic effect due to mustard was assessed by testing the urine of rats fed diets with and without mustard. There was a significant (P < 0.001) reduction in reversion frequency of the TA98 and TA100 strains of Salmonella typhimurium in mustard-fed groups. This protective effect was seen with all three doses of mustard. The study demonstrated that mustard (Brassica nigra) can be a potent antagonist of the adverse biological effects of the ultimate metabolites of B[a]P, a ubiquitous environmental genotoxicant.

Animals↗
PubMed1993

Effect of turmeric on xenobiotic metabolising enzymes.

Diet contains several substances capable of inhibiting chemical carcinogenesis. It is known that such inhibitors may either act directly by scavenging the reactive substances or indirectly by promoting mechanisms which enhance detoxification. Turmeric which contains curcumin both in vitro and in vivo is an active antimutagen. Studies were therefore conducted to evaluate the effects of turmeric on xenobiotic metabolising enzymes in hepatic tissue of rats fed turmeric ranging from 0.5-10% in the diet. Enzymes such as aryl hydrocarbon hydroxylase, UDP glucuronyl transferase and glutathione-S-transferase were assayed after four weeks of turmeric fed diets. No significant differences were seen in the activating enzyme AHH. However, UDPGT was significantly elevated in rats fed 10% turmeric while GSHT registered a significant increase in 5 and 10% turmeric fed diet as compared to controls and 0.5-1.0% turmeric fed animals. The results suggest that turmeric may increase detoxification systems in addition to its anti-oxidant properties. Curcumin perhaps is the active principle in turmeric. Turmeric used widely as a spice would probably mitigate the effects of several dietary carcinogens.

Animals↗
PubMed1993

Photobiological activities of 1,6-dioxapyrene in pro- and eukaryotic cells.

The photobiological effect of a new pyrene derivative, 1,6-dioxapyrene (1,6-DP), was studied in Salmonella typhimurium (strain TA100) and in the diploid strain D7 of the yeast Saccharomyces cerevisiae. In Salmonella, 1,6-DP shows little mutagenicity in the dark in comparison to benzo[a]pyrene (B[a]P). This mutagenic activity decreases in the presence of liver S9 homogenates from Aroclor induced XVIInc/Z mice. However, in combination with 365 nm (UVA) radiation and in the absence of S9 mix, 1,6-DP behaves as an effective photodynamic compound inducing lethal and mutagenic effects in both organisms. In yeast, its activity, like that of B[a]P, is highly dependent on the presence of oxygen. For the same incident dose of UVA, 1,6-DP is, however, at least 6 times more effective than B[a]P in inducing cytotoxic and mutagenic effects. At equitoxic doses, 1,6-DP is as photomutagenic as B[a]P, suggesting that in both cases mutagenicity is due to similar mechanisms. Spectrophotometric measurements indicate physical interaction of 1,6-DP with DNA in the dark. Laser flash photolysis experiments show that 1,6-DP generates singlet oxygen with a quantum yield of 0.17. In vitro 1,6-DP produces oxidative damage to guanine bases specific for singlet oxygen mediated reactions. Alkaline step elution analysis of 1,6-DP plus UVA treated yeast cells indicates a decrease in average molecular weights in DNA and an induction of single strand breaks (ssb) originating from alkali labile sites. This effect is enhanced by D2O and is thus likely to be due to the production of singlet oxygen. The strand breaks appear to differ from those induced by gamma-rays because little, if any, repair of these ssb occurs during 30 min of post-treatment incubation in complete growth medium. These results suggest that the photobiological effects of 1,6-DP are due to oxidative damage in DNA mostly induced by singlet oxygen.

Benzo(a)pyrene↗
PubMed1993

Dose-dependent genotoxic effect of pan masala and areca nut in the Salmonella typhimurium assay.

Aqueous extracts of different brands of pan masala and scented supari were tested for mutagenicity by the Salmonella typhimurium assay using tester strains TA98 and TA100. These extracts were found to be mutagenic to both tester strains. The mutagenic effects of pan masala and scented supari extracts were similar to that produced by areca nut extract. The addition of 500 ppm saccharin to the supari extracts did not alter the mutagenic response.

Areca↗
PubMed1992

Effect of turmeric on urinary mutagens in smokers.

Curcumin, the active principle of turmeric, is known to act as an anti-oxidant, anti-mutagen and anti-carcinogen in experimental animals. In the present study, anti-mutagenic effects of turmeric were assessed in 16 chronic smokers. It was observed that turmeric, given in doses of 1.5 g/day for 30 days, significantly reduced the urinary excretion of mutagens in smokers. In contrast, in six non-smokers, who served as control, there was no change in the urinary excretion of mutagens after 30 days. Turmeric had no significant effect on serum aspartate aminotransferase and alanine aminotransferase, blood glucose, creatinine and lipid profile. These results indicate that dietary turmeric is an effective anti-mutagen and it may be useful in chemoprevention.

Adult↗
PubMed1991

Non-specific incision of DNA due to the presence of 8-methoxypsoralen photoinduced interstrand cross-links in Saccharomyces cerevisiae.

The repair of DNA interstrand cross-links (CL) induced by 8-methoxypsoralen (8-MOP) plus UVA irradiation was analyzed by the alkaline step elution technique. A double-exposure protocol was used with 8-MOP, starting with exposure to monochromatic 405-nm radiation inducing only DNA monoadducts (MA), followed, after washing out of unbound 8-MOP molecules, by a second exposure to 365-nm radiation inducing varying relative amounts of CL at a constant level of total photoadducts. In the range of doses used for the second exposure, repair of CL took place; however, in the presence of increased relative amounts of CL induced non-specific incision of DNA occurred. This endonucleolytic cleavage appears to be related to the increased mutagenic and recombinogenic effects observed at increased levels of CL.

Cross-Linking Reagents↗
PubMed1991

Turmeric (Curcuma longa)-induced reduction in urinary mutagens.

Rats were fed turmeric at various levels in the diet for up to 3 months and then exposed to benzo[a]pyrene (B[a]P) or 3-methylcholanthrene (3-MC) by ip injection. Urinary mutagens were detected using the Salmonella typhimurium assay. Turmeric fed at 0.5% and above inhibited B[a]P- and 3-MC-mediated mutagenicity. Turmeric did not adversely affect the food intake, or weight gain of the rats and no histological changes were detected. These findings are significant in view of the widespread exposure of humans to polycyclic aromatic hydrocarbons. The study has also revealed a useful in vivo model for testing the antimutagenicity.

Administration, Oral↗
PubMed1987

Mutagenicity tests of cashewnut shell liquid, rice-bran oil and other vegetable oils using the Salmonella typhimurium/microsome system.

In view of the shortage of edible oils in India, nutritional and toxicological evaluations have been carried out on some unconventional oils to determine whether they might be safe for human consumption. As part of these evaluations, eight unconventional oils were tested by the Ames mutagenicity assay, using Salmonella typhimurium strains TA98 and TA100 with and without metabolic activation with S-9 mix prepared from the livers of rats pretreated with sodium phenobarbitone or Aroclor 1254. Of the oils tested, metsa oil (Hibiscus sabdariffa) and cashewnut shell liquid were mutagenic with and without metabolic activation with S-9 of either source. No mutagenic activity (with or without S-9 of either source) was observed with any of the other oils tested (rice-bran oil, Cleome viscosa oil, mango-kernel oil, mahua oil, kapok oil and neem oil).

Animals↗
PubMed1984

Rifampicin kinetics in undernutrition.

Rifampicin 10 mg/kg was administered as a single dose to eight undernourished subjects, 10 well nourished subjects and 10 undernourished patients on continuous antituberculosis therapy as a single dose. The area under plasma time concentration (AUC0----infinity) and the peak concentration were significantly reduced in both the undernourished groups. The apparent oral and renal clearances were increased in both the undernourished groups. The (AUC0----infinity) was reduced in undernourished due to reduced absorption and/or changes in total body clearance or disposition. The plasma protein binding of the drug was significantly reduced in the undernourished resulting in increased free drug concentration. This might be sufficient to ensure adequate therapeutic efficacy. Therefore alteration in dosage regimes are not necessary in the undernourished.

Biological Assay↗
PubMed1983

Effect of food on bioavailability of rifampicin.

The area under the plasma concentration-time curve of rifampicin was determined with and without food administration in six healthy male volunteers. Rifampicin (10 mg/kg) was administered orally in the fasting state on one occasion and following a wheat-based breakfast on another. Administration of rifampicin with food reduced mean peak plasma concentration and prolonged the time to reach peak concentration (2 versus 4 hours). Total area under the concentration-time curve from 0 to 8 hours and the rate of absorption were also significantly reduced when rifampicin was administered with food.

Adult↗