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R Langenbach

Publications and source records attributed to R Langenbach.

At least 73 records · Page 4Linked to original sources
PubMed1986

Rat and hamster hepatocyte-mediated induction of SCEs and mutation in V79 cells and mutation of salmonella by aminofluorene and dimethylnitrosamine.

Aminofluorene (AF) and dimethylnitrosamine (DMN) were examined for their ability to induce multiple genetic endpoints after rat and hamster hepatocyte metabolic activation. The endpoints measured included mutations at the Na+/K+-ATPase (ouabain resistance) and hypoxanthine-guanine-phosphoribosyltransferase (6-thioguanine resistance) loci, and sister-chromatid exchanges (SCEs) in Chinese hamster V79 cells, and mutation of Salmonella typhimurium strains TA98 and TA100. AF, with rat and hamster hepatocyte activation, induced only low levels of mutations at either loci in V79 cells but did induce SCEs. Mutation of Salmonella by AF after hepatocyte activation also occurred and was a sensitive endpoint for detecting this aromatic amine. DMN induced high levels of mutations at both loci in V79 cells in addition to SCEs in the presence of hepatocytes from both species. DMN was also mutagenic to Salmonella, but only with hamster hepatocytes. Salmonella did not respond as strongly to DMN as the V70 cells. Hamster hepatocytes were more active than rat hepatocytes in activating both carcinogens. The results indicate the variable sensitivity of the genetic endpoints and species differences in activation for two potent chemical carcinogens.

Animals↗
PubMed1985

Pattern recognition analysis of a set of mutagenic aliphatic N-nitrosamines.

A set of 21 mutagenic aliphatic N-nitrosamines were subjected to a pattern recognition analysis using ADAPT software. Four descriptors based on molecular connectivity, geometry and sigma charge on nitrogen were capable of achieving a 100% classification using the linear learning machine or iterative least squares algorithms. Three descriptors were capable of a 90.5% and two descriptors of a 85.7% overall correct classification. Three of the four descriptors were each capable of classifying 15 of the 16 active chemicals while it required three of the four descriptors to classify correctly two of the five inactive chemicals. These results are in concert with previous observations that molecular connectivity, geometry, and sigma charge on nitrogen are powerful descriptors for separating active from inactive mutagenic and carcinogenic N-nitrosamines.

Mutagens↗
PubMed1984

Rodent species and strain specificities for sister-chromatid exchange induction and gene mutagenesis effects from ethyl carbamate, ethyl N-hydroxycarbamate, and vinyl carbamate.

Ethyl carbamate (EC) and two related carcinogens, ethyl N-hydroxycarbamate (ENHC) and vinyl carbamate (VC), caused species-specific increases in sister-chromatid exchange (SCE) formation in the bone marrow cells of rodents. Mice exposed to 400 mg/kg of EC had SCE increases of 6-times-baseline, while rats, Chinese hamsters, and golden hamsters showed 3- to 4-times-baseline increases in response to this dose. Lesser, but still significant, differences were found for ENHC and VC; the severest effects consistently occurred in mice. Control bone marrow cell-cycle kinetics among the rodent species were similar. Mouse strains A and C57BL/6, which have high and low susceptibilities to EC induction of lung adenomas, respectively, showed nearly identical levels of SCE induction after in vivo exposure to these carbamates. However, testing of VC, a possible metabolite of EC, in vitro revealed strain-dependent liver enzyme (Aroclor-induced S-9 fraction) capabilities to convert VC to genotoxic products. SCE induction, gene mutation for 6-thioguanine and ouabain resistance, and cytotoxicity in Chinese hamster V79 cells were significantly greater when A strain S-9 enzymes were used as compared with C57BL/6 strain S-9 enzyme preparations. No effect on SCE of reseeding, compared with no reseeding, of VC-treated V79 cells was observed. At a concentration of 25 micrograms/ml, VC caused 6-times-baseline induction of SCE in the presence of A strain S-9 mix and 4-times-baseline induction in the presence of C57BL/6 strain S-9 mix. These in vitro strain-dependent patterns of response are relevant to the current theory that VC may be a proximate carcinogenic metabolite of EC.

Animals↗
PubMed1984

Morphogenesis of adult pancreas in vitro.

A procedure is described for maintaining primary culture of adult Syrian golden hamster pancreas cells for prolonged periods (14-16 days) on a layer of irradiated mouse fibroblast cell line: C3H10T1/2 cells. Morphologically the cultures of both exocrine and endocrine cells retained many characteristics of the pancreas in vivo. Three types of colonies were identified by light and electron microscopy. The Type-1 acinar cells exhibited rapid changes and cell selection during the first 5 days in culture. The ductular cells, Type-2 colonies, developed a stable slow-growing rate of stationary culture. Their colonies represented the most differentiated Type of in vitro cells and epithelial character, by developing characteristic "dome-formation". The islet cells, Type-3 colony maintained also their structural characteristics up to 14-16 days in culture. This study demonstrated the ability of fibroblastic feeder cells to promote the epithelial feature of adult hamster pancreas for prolonged periods in vitro.

Animals↗
PubMed1983

Bovine bladder and liver cell and homogenate-mediated mutagenesis of Salmonella typhimurium with aromatic amines.

Comparisons of aromatic amine activation were made by using intact cells or cell homogenates (S-9) from bovine bladder urothelium and liver. Since both liver and bladder are thought to contribute carcinogenic metabolites for bladder cancer initiation, comparisons of these two organs' relative ability to activate aromatic amines to mutagens were made. Salmonella typhimurium mutagenesis was used as an indication of mutagen production. Activation occurred in a dose dependent manner and no mutagenic response occurred unless activating cells or S-9 were present. Bladder urothelial cells metabolically activated the carcinogens, 2-amino-fluorene (AF), 2-acetylaminofluorene (AAF), 4-aminobiphenyl (4ABP), benzidine (BZ), and 2-naphthylamine (2NA) but not 1-naphythylamine (1NA), a non-carcinogen. Liver cells were less active than bladder cells in activating AF and AAF; but there was little or no hepatocyte activation of 4ABP, BZ, 2NA and 1NA. Intact bladder cells were more effective than bladder S-9 in activating AAF, but not in activating AF, 4ABP, BZ and 2NA. The liver S-9 showed more mutagenic activity with AF than did intact liver cells; the reverse was true for AAF, and bovine liver S-9 showed little or no activation of 4ABP, BZ, and 2NA. 1NA was not activated by either S-9 preparation. As was the case for intact cells, bladder S-9 was more effective than liver S-9 in activating the aromatic amines studied. The results demonstrate the capacity of bovine bladder urothelium to metabolically activate aromatic amines and suggest a role for the target organ itself in carcinogen activation. Information on the relative usefulness of intact cells versus S-9 preparations as activation systems was also obtained from these studies.

Amines↗
PubMed1983

Cell-mediated mutagenesis of Chinese hamster V79 cells and Salmonella typhimurium.

In the cell-mediated approach, intact cells metabolically activate the chemical and the genetic end points are measured in cocultivated or coincubated target cells. Cell-mediated systems have been used to study fundamental problems in carcinogenesis, such as organ and species specificity of carcinogen activation, and in screening for carcinogenic chemicals. In the studies discussed here, cells from various rat, hamster, or bovine tissues are used to metabolically activate the chemical, and mutation and/or SCE induction in V79 cells and mutation of S. typhimurium are measured as genetic end points. The detection of genetic activity of a chemical depends both on the cell (organ, species, type, etc.) used for metabolic activation and on the genetic end point measured. Hydrocarbons and nitrosamines are two classes of environmentally significant chemicals that are sensitively detected with cell-mediated systems. The cell-mediated approach provides a valuable metabolic activation component for short-term in vitro systems, and further studies are needed to utilize and evaluate its full potential.

Animals↗
PubMed1983

Activation of aromatic amines to mutagens by bovine bladder and liver cells.

A bovine bladder cell-mediated mutagenesis system using Chinese hamster V79 cells and Salmonella typhimurium as target organisms was developed to investigate the capacity of the bladder urothelium to activate chemical carcinogens. Bovine bladder epithelial cells can activate the aromatic amines AF and 4-ABP to intermediates which mutate V79 cells and S. typhimurium TA 98 and TA 100. DMBA was mutagenic to V79 cells but not detectably mutagenic to either Salmonella strain with bladder cell activation. The chemicals tested were not mutagenic to either target organism in the absence of bladder cells. In contrast to the response with DMBA, S. typhimurium was a more sensitive target for the arylamines than V79 cells. These data suggest the value of using multiple end points for assessing metabolic capability. The activation capability of intact bladder cells was compared to disrupted cells, and S-9 prepared from bladder cells used with and without cofactors. When intact cells or S-9 plus cofactors were used as the activation system a dose-dependent increase in revertants was observed for 4-ABP. A bovine liver cell-mediated bacterial mutagenesis system was also developed and the liver and bladder systems compared. For AF, bladder cells appear to be at least ten times more active per viable cell than hepatocytes in producing mutagenic intermediates, while 4-ABP is essentially not mutagenic in the hepatocyte-mediated system. A quantitative comparison of the relative importance of the liver and bladder to activate the chemicals is difficult to make but the data indicate the ability of the bladder epithelium to activate bladder carcinogens.

Amines↗
PubMed1983

Bovine bladder urothelial cell activation of carcinogens to metabolites mutagenic to Chinese hamster V79 cells and Salmonella typhimurium.

The ability of bovine bladder urothelial cells to activate genotoxic chemicals to mutagens was examined by cocultivating bladder cells with Chinese hamster V79 cells or Salmonella typhimurium as mutable targets. Activation of test chemicals to mutagenic intermediates by urothelial cells was detected by induction of 6-thioguanine resistance in V79 cells or by induction of histidine revertants in Salmonella. In the bladder cell-mediated V79 cell mutagenesis system, a significant increase in mutation frequency was induced by exposure to 7,12-dimethylbenz(a)anthracene and dimethylnitrosamine. The aromatic amines 2-aminofluorene, 2-acetylaminofluorene, and 4-aminobiphenyl were weakly mutagenic to V79 cells with bladder cell activation, while no mutagenic activity was detected with 1-naphthylamine, 2-naphthylamine, or benzidine. Because the mutagenic activity of the aromatic amines was low with V79 cells as the target, a bladder cell-mediated S. typhimurium system was developed for these chemicals. The aromatic amines 2-aminofluorene, 2-acetylaminofluorene, 4-aminobiphenyl and 2-naphthylamine were mutagenic to S. typhimurium TA98 and TA100 in the presence of bladder cells but not in their absence. Benzidine was mutagenic to TA98 but not to TA100. The putative noncarcinogen 1-naphthylamine was not mutagenic in the system. In contrast to the V79 data, 7,12-dimethylbenz(a)anthracene and dimethylnitrosamine were not mutagenic with either bacterial strain. Mutagenic responses were related to both the number of bladder cells used for activation and the concentration of test chemical in the Salmonella assay. The data demonstrate that bovine bladder urothelial cells can activate carcinogens from three chemical classes to mutagens and indicate the different sensitivities of V79 cells and S. typhimurium to genotoxic agents.

Animals↗
PubMed1982

Comparative genotoxicity studies of ethyl carbamate and related chemicals: further support for vinyl carbamate as a proximate carcinogenic metabolite.

In vivo and/or in vitro mammalian cell systems were used to evaluate sister chromatid exchange (SCE) induction and gene mutagenesis effects following exposure to ethyl carbamate (urethane), vinyl carbamate, ethyl N-hydroxycarbamate, and 2-hydroxyethyl carbamate. Although ethyl carbamate caused dose-dependent increases in SCE when injected into mice, it was ineffective for inducing SCE and gene mutation (6-thio-guanine resistance) in Chinese hamster V-79 cells cultured with or without the addition of S9 enzyme mix during treatment. Chemical-specific patterns of genotoxicity were evident for the known or suspect metabolites under test: only vinyl carbamate consistently (in vivo and in vitro) revealed strong activity for the genetic endpoints. SCE induction levels of 5-8 times baseline were observed after animal or cell culture exposures to vinyl carbamate. Doses required to produce this effect in V-79 cells in the presence of S9 mix were approximately 100 times lower than those needed when S9 was absent. The extensive gene mutagenesis (approaching 600 mutants/10(6) survivors) noted was completely dependent upon the presence of S9 mix. These observations are consistent with current theory holding that vinyl carbamate is a metabolic intermediate of ethyl carbamate, and is converted to the ultimately reactive species (presumably, vinyl carbamate epoxide) which is responsible for ethyl carbamate carcinogenesis.

Animals↗
PubMed1981

Maintenance of adult hamster pancreas cells on fibroblastic cells.

The maintenance of primary cultures of adult hamster pancreatic cells on layers of irradiated C3H/10T1/2 cells was studied. Various types of pancreatic cells, acinar, islet and ductular cells could be identified in the cultures by light and electron microscopy. Morphologically the various pancreatic cells retained many differentiated characteristics of their respective in vivo cells types. Insulin production was maintained at near Day 1 levels for the 16 d in culture for which it was measured. Colonies of epithelial cells continued to grow during a 20 d culture period. It is believed that this procedure for maintaining functional and growing pancreas cells in culture may be a useful in vitro model for studying the initiation of pancreatic carcinogenesis.

Animals↗
PubMed1981

Mutagenesis by chemical agents in V79 chinese hamster cells: a review and analysis of the literature. A report of the Gene-Tox Program.

The report reviews and evaluates the current literature (about 125 primary publications) on chemically induced specific locus mutations in the V79 Chinese hamster lung cell line. The V79 cell is convenient to use for mutagenesis studies since it has a rapid growth rate, high plating efficiency, and a stable karyotype. Mutation can be easily measured at either the hypoxanthine-guanine phosphoribosyl transferase or the Na+/K+ ATPase locus, both of which have been well characterized. Other less-studied markers are also described. We discuss the protocols for quantitative mutation studies including measurements of cytotoxicity, mutant expression times, mutant selection agents, cell densities during selection, and the stability and verification of mutant phenotypes. Mutations in the V79 cells by chemicals that require activation can be tested after their metabolism by cell homogenates or by intact cells, and the results with each type of activation are compared. For purposes of analysis, we classified a compound as mutagenic if it induced a mutation frequency that is at least 3 times higher than the spontaneous mutant frequency reported for that specific experiment. By this criterion two-thirds of the chemicals analyzed were mutagenic--; 11% with and 55% without metabolic activation. Of the 191 chemicals examined; 119 were polycyclic aromatic hydrocarbons; 25 were nitro or nitroso compounds, 9 were alkyl halides; 7 were purine or pyrimidine derivatives and the remaining 31 were from other chemical classes. We also defined mutagenic potency as the concentration of a compound that increases the mutant frequency by 10 times the spontaneous frequency. Mutagenic potencies of the compounds examined varied over a range of 5 X 10(6). We have also found large interlaboratory variations in the mutagenic potencies. Such variation in potency could be reduced by normalizing the results to a standard mutagen such as N-methyl-N'-nitro-N-nitrosoguanidine. The role of the V79 assay in mutagenicity and carcinogenicity testing is discussed and recommendations are suggested for future investigation.

Animals↗
PubMed1981

Lung and liver cell-mediated mutagenesis systems: specificities in the activation of chemical carcinogens.

A liver and lung cell-mediated-V79 cell mutagenesis system using intact cells as metabolic activation systems was employed to study the relative ability of cells from these organs to activate chemical carcinogens. Primary cultures of liver and lung cells from male Sprague Dawley rats were used to metabolically activate the chemicals and the mutation of Chinese hamster V79 cells to ouabain resistance used to detect mutagenic intermediates. 7,12-Dimethylbenz[a]anthracene and 3-methylcholanthrene, were more active in the lung system than in the liver cell system. Benzo[a]pyrene (B[a]P) was inactive in the liver cell-mediated system but mutagenic to V79 cells in the lung cell-mediated system. Dimethylnitrosamine (DMN) was inactive in the presence of liver cells. Aflatoxin B1 was mutagenic in the liver cell-mediated system, but only weakly mutagenic in the lung cell-mediated system. Because the mutagenicities of DMN and B[a]P were organ-specific, the metabolism of these carcinogens in the two primary cell systems was investigated. DMN was metabolized by liver but not by lung cells, possibly accounting for its lack of mutagenicity in the lung cell system. B[a]P was extensively metabolized by both cell types, but quantitative differences were observed when the metabolic products were analyzed by high pressure liquid chromatography. Comparing total organic and water soluble metabolites, lung cells produced similar amounts of 7,8- and 9,10-diols but little 4,5-diol, while liver cells produced equivalent total amounts of the three diols. Lung cells produced twice the amount of B[a]P glucuronide conjugates as liver cells, while liver cells produced twice the amount of B[a]P sulfate conjugates as lung. The data suggest that intact cells from various organs can be used as metabolic activating systems in vitro assays and that studies into organ specificity can be investigated by this approach.

Animals↗
PubMed1981

Inhibition of benzo(a)pyrene-induced transformation of C3H/10T1/2 cells by allylisopropylacetamide and isopropylvaleramide.

Allylisopropylacetamide (AIA) and isopropylvaleramide (IVA) have been demonstrated previously to protect in vivo against the acute toxicity and adrenal necrotic effect of 7,12-dimethylbenz(a)anthracene. In the present study, the influence of these two amides on the in vitro transforming ability of two potent carcinogens, benzo(a)pyrene [B(a)P] and 7,12-dimethylbenz(a)anthracene, on C3H10T1/2 cells was investigated. Both AIA and IVA showed a dose-dependent inhibition of B(a)P-induced transformation of C3H10T1/2 cells when added simultaneously for 24 hr with the carcinogen. While pretreatment, simultaneous treatment, and posttreatment of the cells with AIA or IVA inhibited transformation, the 24-hr posttreatment was somewhat more effective. The protective effect did not appear to results from alterations in B(a)P metabolism inasmuch as aryl hydrocarbon hydroxylase activity and the metabolic products of B(a)P detected by high-pressure liquid chromatography were not changed by AIA or IVA treatment. Furthermore, AIA and IVA did not selectively kill chemically transformed C3H10T1/2 cells, as indicated by the absence of their effect on an established, chemically transformed cell line. AIA and IVA also inhibited 7,12-dimethylbenz(a)anthracene-induced transformation of C3H10T1/2 cells. These data suggest that AIA and IVA may be useful protective agents and that they presumably exert their protective effect at some stage between the activation of the carcinogen and the expression of the transformed phenotype.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1981

Rat bladder cell-mediated mutagenesis od Chinese hamster V79 cells and metabolism of benzo[a]pyrene.

Primary rat bladder epithelial cells were cocultivated with Chinese hamster V79 cells in the presence of carcinogens, and the induction of 6-thioguanine resistance in the V79 cells was used as a marker of cell-mediated mutagenesis. The carcinogens dimethylnitrosamine, 7,12-dimethylbenz[a]anthracene, and benzo[a]pyrene (BP) were mutagenic to V79 cells in the presence of bladder cells but not in their absence. Analysis of BP metabolites formed by bladder cells indicated that 7,8-dihydro-7,8-dihydroxybenzo[a]pyrene, 9,10-dihydro-9,10-dihydroxybenzo[a]pyrene, benzo[a]pyrene-3,6-quinone, and 9-hydroxybenzo[a]pyrene were the major organic-soluble metabolites formed. Glucuronide and sulfate conjugates of BP metabolites were also produced by bladder cells. Mutagenesis data from the rat bladder system and previous data from rat liver and lung cell-mediated mutagenesis systems indicate that the cell-mediated mutagenesis approach may provide a useful approach for studying the organotropic effect of chemical carcinogens. Furthermore, the finding that rat bladder epithelium can metabolize some carcinogens offers new possibilities for the mechanism of initiation of bladder cancer.

9,10-Dimethyl-1,2-benzanthracene↗