Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P00492 (hypoxanthine-guanine phosphoribosyltransferase)
 2,385 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Human erythrocyte lysate proteins were resolved into over 250 discrete spots by two-dimensional electrophoresis using isoelectric focusing in the first dimension and electrophoresis in the presence of sodium dodecyl sulfate, (SDS) in the second. The overwhelming excess of hemoglobin has made such analyses difficult in the past. However, with the ISO-DALT two-dimensional electrophoresis system, large numbers of red cell proteins can be mapped in the presence of hemoglobin. When hemoglobin and several other major proteins are removed by adsorption to DEAE-cellulose, additional minor components are seen, giving a total of over 275. With the use of purified preparations, the map positions of five cell enzymes or their subunits were determined: pyruvate kinase, catalase, glucose-6-phosphate dehydrogenase, hypoxanthine phosphoribosyltransferase, and carbonic anhydrase. The mapping techniques described complement and extend those traditionally used to find human red cell protein variants.
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PMID:Red cell proteins. I. Two-dimensional mapping of human erythrocyte lysate proteins. 10 31

Simple and rapid radiochemical assay procedures for the forward (IMP synthesis) and reverse (IMP pyrophosphorolysis) reactions catalyzed by hypoxanthine phosphoribosyltransferase have been developed. Enzyme activity in the forward direction was assessed by measuring the amount of [8-14C]IMP formed from [8-14C]hypoxanthine following their separation by polyethyleneimine-cellulose TLC in methanol:water (1:1, v/v). [8-14C]IMP has been synthesized from [8-14C]hypoxanthine, using hypoxanthine phosphoribosyltransferase derived from human brain, with subsequent purification by elution from phenyl boronate-agarose. Enzyme activity in the reverse direction was assessed by measuring the amount of [8-14C]uric acid formed from the labeled IMP following their separation by polyethyleneimine-cellulose TLC in 0.2 M LiCl saturated with boric acid (pH 4.5):95% ethanol (1:1, v/v), the transferase reaction being coupled with excess xanthine oxidase and catalase to overcome the unfavorable equilibrium.
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PMID:Hypoxanthine phosphoribosyltransferase: radiochemical assay procedures for the forward and reverse reactions. 400 57

Chromium(VI) resistant Chinese hamster ovary (CHO) cell lines were established in this study by exposing parental CHO-K1 cells to sequential increases in CrO3 concentration. The final concentration of CrO3 used for selection was 7 microM for Cr7 and 16 microM for Cr16 cells. Cr16-1 was a subclone derived from Cr16 cells. Next, these resistant cells were cultured in media without CrO3 for more than 6 months. The resistance of these cells to CrO3 was determined by colony-forming ability following a 24-h treatment. The LD50 of CrO3 for chromium(VI) resistant cells was at least 25-fold higher than that of the parental cells. The cellular growth rate, chromosome number, and the hprt mutation frequency of these chromium(VI) resistant cells were quite similar to their parental cells. The glutathione level, glutathione S-transferase, catalase activity, and metallothionine mRNA level in Cr7 and Cr16-1 cells were not significantly different from their parental cells. Furthermore, Cr16-1 cells were as sensitive as CHO-K1 cells to free-radical generating agents, including hydrogen peroxide, nickel chloride, and methanesulfonate methyl ester, and emetine, i.e., a protein synthesis inhibitor. The uptake of chromium(VI) and the remaining amount of this metal in these resistant and the parental cell lines were assayed by atomic absorption spectrophotometry. Experimental results indicated that a vastly smaller amount of CrO3 entered the resistant cell lines than their parental cells did. A comparison was made of the sulfate uptake abilities of CHO-K1 and chromium(VI) resistant cell lines. These results revealed that the uptake of sulfate anion was substantially reduced in Cr7 and Cr16-1 cells. Extracellular chloride reduced sulfate uptake in CHO-K1 but not in Cr16-1 cells. Therefore, the major causative for chromium(VI) resistance in these resistant cells could possibly be due to the defects in SO4(2-)/C1- transport system for uptake chromium(VI).
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PMID:Long-term exposure to chromium(VI) oxide leads to defects in sulfate transport system in Chinese hamster ovary cells. 761 50

The molecular nature of mutations induced by Cd was investigated in this study to elucidate the role of Cd in the initiation of carcinogenesis. Exposing Chinese hamster ovary (CHO)-K1 cells to cadmium acetate markedly decreased the colony-forming ability of cells and induced mutation frequency in the hypoxanthine (guanine) phosphoribosyltransferase (hprt) gene. The mutation frequency induced by Cd at LD30-LD20 doses was approximately 20 times that of untreated cells. D-Mannitol, a scavenger of reactive oxygen species (ROS), significantly protects cells against Cd cytotoxicity and mutagenicity. Furthermore, non-cytotoxic doses of 3-amino-1,2,4-triazole, a catalase inhibitor, potentiates Cd cytotoxicity and mutagenicity. The cellular Cd uptake ability was not altered by the combined treatment with either D-mannitol or 3-amino-1,2,4-triazole. The GSH level and the activities of GSH peroxidase, GSSG reductase, and catalase in cells treated with Cd (4 microM, 4 h) decreased to 78%, 47%, 40%, and 22% of the untreated cells, respectively. Those enzymatic activities recovered to normal levels 8 h after removing Cd. Polymerase chain reaction and DNA sequencing analysis of 54 independent Cd mutants revealed Cd-induced base substitutions, splice mutations, and large genomic deletions. All six types of base substitutions were observed; however, base transversions (22/27; 81%) occurred more frequently than transitions (5/27; 19%). The frequencies of mutations occurring at T.A or G.C base pairs were roughly equal. Results in this study strongly suggest that Cd mutagenicity in CHO-K1 cells is ROS-dependent. Moreover, the unique mutational spectrum induced by Cd implies that specific DNA adducts generated through the interaction of Cd-DNA and ROS may play a role in the mutational specificity.
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PMID:Reactive oxygen species may participate in the mutagenicity and mutational spectrum of cadmium in Chinese hamster ovary-K1 cells. 895 Dec 41

To investigate mechanisms underlying development of lung adenomas and carcinomas in rats exposed to poorly soluble particles the relationships between particle exposure, inflammation and mutagenesis in rat alveolar type II cells were characterized. Rats were exposed to saline or saline suspensions of 10 and 100 mg/kg of alpha-quartz, carbon black or titanium dioxide by intratracheal instillation. Fifteen months after exposure, bronchoalveolar lavage (BAL) cells were characterized as to number and type and lung histopathology performed. The alveolar type II cells were isolated and cultured in 6 thioguanine (6TG) containing media to select for mutation in the hprt gene. The potential contribution of lung inflammatory cells to in vivo mutagenic responses, were evaluated by co-culturing BAL cells with the rat alveolar epithelial cell line, RLE-6TN for 24 h and the RLE-6TN cells selected for 6TG resistance. Neutrophilic inflammation was detected in all rats exposed to 10 and 100 mg/kg of alpha-quartz and carbon black and 100 mg/kg titanium dioxide; epithelial hyperplasia was observed in rats exposed to 10 and 100 mg/kg of alpha-quartz and 100 mg/kg carbon black. Hprt mutation frequency was increased in alveolar type II cells from rats exposed to 10 and 100 mg/kg of alpha-quartz, 100 mg/kg carbon black and 100 mg/kg titanium dioxide. In vitro exposure of RLE-6TN cells to BAL cells from rats treated with 10 and 100 mg/kg of alpha-quartz or 100 mg/kg carbon black increased hprt mutant frequency. Both macrophage and neutrophil enriched BAL cell populations were mutagenic to RLE-6TN cells, however, the mutagenic activity appeared greatest for neutrophils. Addition of catalase to BAL cell:RLE-6TN co-cultures inhibited the increase in hprt mutation frequency. These studies demonstrate exposure of rats to doses of particles producing significant neutrophilic inflammation is associated with increased mutation in rat alveolar type II cells. The ability of particle-elicited macrophages and neutrophils to exert a mutagenic effect on epithelial cells in vitro supports a role for these inflammatory cells in the in vivo mutagenic effects of particle exposure. The inhibition of BAL cell-induced mutations by catalase implies a role for cell-derived oxidants in this response.
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PMID:Effects of particle exposure and particle-elicited inflammatory cells on mutation in rat alveolar epithelial cells. 905 38

The accumulation of damage to cellular biomolecules, including DNA, over time may play a significant role in the aetiology of the ageing process. We have previously quantified DNA damage and mutation within cultured lymphocytes from healthy human male subjects in three different age groups (35-39, 50-54 and 65-69 years). The results of that study showed an age-related increase in DNA damage and mutations in lymphocytes. In addition, an age-related decrease in the capacity of the lymphocytes to repair H2O2-induced DNA damage was found. In this article, we report the findings of an extension to the earlier study. Thirty-one generally healthy male and female subjects between the ages of 75 and 80 years were recruited. Using a number of bioassays, we were able to determine; basal levels of DNA damage (for 18 subjects) and mutant frequency at the hypoxanthine phosphoribosyltransferase (hprt) gene locus (for 16 subjects) within cultured lymphocytes. In addition, in vivo antioxidant status (for all study subjects) and the capacity of lymphocytes to repair H2O2-induced DNA damage (for 18 subjects) were also assessed. The results obtained showed: that the mean basal level of DNA damage in lymphocytes from subjects in the 75- to 80-year age group (12.6 +/- 4.7%) was similar to that of the 35- to 39-year age group (13.3 +/- 3.3%), p = 0.42 (Mann-Whitney); there was no significant difference between log mean mutant frequency at the hprt gene locus in lymphocytes from the 75- to 80-year age group (0.31 +/- 0.33) compared to that observed in the 35- to 39-year age group (0.24 +/- 0.21; Student's t-test, t = 0.68, p > 0.05). Levels of the antioxidants glutathione peroxidase (GPx EC 1.11.1.9), catalase (CAT; EC 1.11.1.6) and caeruloplasmin (CPL; EC 1.16.3.1) were significantly elevated in the 75- to 80-year age group, compared to the 35- to 39-, 50- to 54- and 65- to 69-year age groups. Levels of bilirubin (BR) were reduced in the 75- to 80-year age group, the decrease being contributed by the female subjects. No differences in levels of superoxide dismutase (SOD; EC 1.15.1.1) or uric acid (UA) were found between the 4 age groups. Following treatment of lymphocytes with H2O2, we did not find any difference in the susceptibility of lymphocytes to DNA damage in the 75- to 80-year age group, compared to the other age groups. The DNA repair capacity in lymphocytes from individuals in the 75- to 80-year age group was similar to that of the 35- to 39-year age group, for all time points assessed. These results highlight the importance of DNA repair processes and antioxidant defence systems for maintaining genomic stability in vivo.
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PMID:In vivo antioxidant status, DNA damage, mutation and DNA repair capacity in cultured lymphocytes from healthy 75- to 80-year-old humans. 921 88

Cadmium and lead have been shown to induce cellular transformations and gene mutations in cultured rodent cells, as well as tumours in live animals. However, the mechanisms by which these metals cause cellular transformations and mutations in human cells have not been explored. In this study, we investigated the abilities of cadmium and lead to induce anchorage-independent transformations and hprt gene mutations in diploid human fibroblasts. Human fibroblasts were exposed to either cadmium acetate (0-60 microM) or lead acetate (0-2 mM) for 24 h. After removal of the metals, the cells were kept in exponential growth for 7 and 9 days before mutation and anchorage-independence assays were taken, respectively. Both cadmium and lead significantly induced anchorage-independent colonies in dose-dependent manners; the frequencies of anchorage-independent colonies induced by these metals were similar to those induced by N-methyl-N'-nitro-N-nitrosoguanidine at approximately equal cytotoxic dose ranges (30-10% survival). 3-Aminotriazole at non-cytotoxic dosages decreased catalase activity by >80%, and markedly enhanced cadmium-induced cytotoxicity and anchorage-independent colonies. Cadmium uptake by human fibroblasts was not affected by 3-aminotriazole co-administered with 10 microM of cadmium; whereas cadmium uptake and accumulation were enhanced 1.5-fold by 3-aminotriazole co-administered with 1-2.5 microM of cadmium. Lead-induced anchorage-independence or cytotoxicity was not affected by 3-aminotriazole co-treatment; however, 3-aminotriazole did significantly enhance lead uptake and accumulation in human fibroblasts. Neither cadmium- nor lead-induced 6-thioguanine-resistant mutation frequency in human fibroblasts. Co-administering these metals with 3-aminotriazole did not enhance mutations in human fibroblasts. These results suggest that cadmium and lead may both act as tumour promoters in diploid human fibroblasts, and that reactive oxygen species is more important in cadmium- than lead-induced cytotoxicity and anchorage-independence.
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PMID:Effect of 3-aminotriazole on anchorage independence and mutagenicity in cadmium- and lead-treated diploid human fibroblasts. 963 78

Cocaine is a widely abused drug. Recently, it has been shown to induce teratogenesis in both humans and animals. Cocaine-induced teratogenicity has been associated with reactive oxygen species (ROS), which are generated by cytochrome P450 during cocaine biotransformation. Since ROS have been reported to induce genotoxicity, it is of interest to know whether cocaine and/or its metabolites are also genotoxic. In this study, Chinese hamster ovary K1 cells were employed as a model system to investigate the genetic toxicity of cocaine in the presence or absence of rat liver S9 fraction. Cocaine-induced cytotoxicity was potentiated when S9 was present, indicating the cytochrome P450 metabolism plays a role in cocaine-mediated cytotoxicity. Cocaine treatments per se induced a few chromosome aberrations while treatments of cocaine plus S9 caused a significant increase in chromosome aberrations. In contrast, cocaine induced micronuclei (MN) formation and hypoxanthine-guanine phosphoribosyltransferase mutation only in the presence of S9. Therefore, cocaine itself is at best a weak clastogen, whereas metabolite(s) of cocaine is/are truly inducer(s) of clastogenesis and mutagenesis. Cocaine treatments alone also induced a significant increase in sister chromatid exchange frequency but the addition of S9 did not affect the results. Free radical scavengers, including superoxide dismutase and catalase, efficiently decreased the frequency of cocaine plus S9-induced MN, implying that ROS are indeed important components in cocaine-induced genotoxicity. The observation that non-toxic doses of cocaine can inhibit intercellular metabolic cooperation suggests that cocaine may also be a tumor promoter. Our data supports that cocaine could possess genotoxicity in addition to its well-known neurotoxicity and teratogenicity.
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PMID:Genetic toxicity of cocaine. 1038 89

We have investigated the ability of the naturally occurring plant essence vanillin (3-methoxy-4-hydroxybenzaldehyde) to inhibit mutation at the CD59 locus on human chromosome 11 by hydrogen peroxide, N-methyl-N-nitrosoguanidine, mitomycin C and (137)Cs gamma-radiation in human-hamster hybrid A(L) cells. Previous studies using vanillin have suggested that it can inhibit chromosome aberrations induced by hydrogen peroxide and mitomycin C, as well as inhibiting X-ray- and UV-induced mutations at the hprt locus. Other studies with vanillin have shown that it can increase both the toxicity and mutagenicity of ethyl methane sulfonate and increase the induction of sister chromatid exchange by mitomycin C and a variety of other mutagens. The increased sensitivity of the A(L) assay, which is due in part to its ability to detect both small (single locus) and large (multilocus) genetic damage, allows us to measure the effect of vanillin at low doses of mutagen. Vanillin is shown, in these studies, to inhibit mutation induced by hydrogen peroxide, N-methyl-N-nitrosoguanidine and mitomycin C, as well as to enhance the toxicity of these agents. Vanillin had no effect on either toxicity or mutation induced by (137)Cs gamma-radiation. The vanillin-induced potentiation of H(2)O(2) toxicity is shown not to involve inhibition of catalase or glutathione peroxidase. These results show that vanillin is able to inhibit mutation at the CD59 locus and modify toxicity in a mutagen-specific manner. Possible mechanisms to explain the action of vanillin include inhibition of a DNA repair process that leads to the death of potential mutants or enhancement of DNA repair pathways that protect from mutation but create lethal DNA lesions during the repair process.
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PMID:Vanillin (3-methoxy-4-hydroxybenzaldehyde) inhibits mutation induced by hydrogen peroxide, N-methyl-N-nitrosoguanidine and mitomycin C but not (137)Cs gamma-radiation at the CD59 locus in human-hamster hybrid A(L) cells. 1079 12

Previously, we have demonstrated that cadmium acetate significantly induces hprt mutation frequency in Chinese hamster ovary (CHO)-K1 and that 3-amino-1,2,4-triazole (3AT), a catalase inhibitor, potentiates the mutagenicity of cadmium [Chem. Res. Toxicol. 9 (1996) 1360-1367]. In this study, we investigate the role of intracellular peroxide in the molecular nature of mutations induced by cadmium. Using 2',7'-dichlorofluorescin diacetate and fluorescence spectrophotometry, we have shown that cadmium dose-dependently increased the amounts of intracellular peroxide and the levels were significantly enhanced by 3AT. Furthermore, we have characterized and compared the hprt mutation spectra in 6-thioguanine-resistant mutants derived from CHO-K1 cells exposed to 4 microM of cadmium acetate for 4h in the absence and presence of 3AT. The mutation frequency induced by cadmium and cadmium plus 3AT was 11- and 16-fold higher than that observed in untreated populations (2.2 x 10(-6)), respectively. A total of 40 and 51 independent hprt mutants were isolated from cadmium and cadmium plus 3AT treatments for mRNA-polymerase chain reaction (PCR), genomic DNA-PCR and DNA sequencing analyses. 3AT co-administration significantly enhanced the frequency of deletions induced by cadmium. Cadmium induced more transversions than transitions. In contrast, 3AT co-administration increased the frequency of GC-->AT transitions and decreased the frequencies of TA-->AT and TA-->GC transversions. Together, the results suggest that intracellular catalase is important to prevent the formation of oxidative DNA damage as well as deletions and GC-->AT transitions upon cadmium exposure.
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PMID:Alteration of cadmium-induced mutational spectrum by catalase depletion in Chinese hamster ovary-K1 cells. 1167 67


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