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C E Piper

Publications and source records attributed to C E Piper.

At least 19 recordsLinked to original sources
PubMed1992

Promotional activities of the non-genotoxic carcinogen bemitradine (SC-33643).

Bemitradine (SC-33643), a diuretic antihypertensive agent, was studied for its carcinogenicity in a 2-year bioassay in Charles River CD rats via dietary admix at dosages of 50, 150 and 450 mg kg-1 for up to 97 weeks (after which they were followed for eight additional weeks without treatment). Body weights were decreased compared to controls: 5-15% in the female and 10-12% in the male dosage groups by week 105 of the study. Prolactin values were significantly increased in 150 and 450 mg kg-1 females. The compound caused significant increased incidences of liver, thyroid (both sexes) and mammary (females only) neoplasms. The metabolism of bemitradine was studied in both rats and man. Bemitradine and its primary metabolite (SC-36741; desethylbemitradine) were tested and found to be non-genotoxic in Ames, rat primary hepatocyte UDS, CHO/HGPRT, CHO cytogenetics, in vivo mouse micronucleus and mouse lymphoma TK+/- (bemitradine only) assays. Finally, in an altered hepatic foci (Y-glutamyl transpeptidase positive) promotion assay in female Charles River CD rats, bemitradine was found to be a promotor, though not as potent as phenobarbital. We concluded that bemitradine (which has been dropped from development) is a non-genotoxic carcinogen which appears to act by a hormonally modulated promotional activity in inducing tumors in the liver and mammary glands. Tumors seen in the thyroid were probably secondary to the effects of bemitradine on metabolism.

Animals↗
PubMed1992

Genotoxic properties of (E)-5-(2-bromovinyl)-2'-deoxyuridine (BVDU).

(E)-5-(2-bromovinyl)-2'-deoxyuridine (BVDU)is a 5-substituted 2'-deoxyuridine antiviral compound that inhibits thymidylate synthetase. The selectivity of BVDU for virus-infected cells has been attributed to phosphorylation of BVDU by a virus-induced thymidine kinase. Since the closely related compounds 5-bromo-2'-deoxyuridine and 5-iodo-2'-deoxyuridine are in vitro and in vivo mutagens, BVDU was tested for genotoxic activity in bacterial and mammalian cell mutation assays as well as in assays measuring DNA damage/repair and clastogenic activity. Mutation assays with BVDU at concentrations ranging from 10 to 5000 micrograms/plate using Salmonella typhimurium strains TA1535, TA1537, TA1538, TA98, and TA100 were negative, both with and without S9 activation. BVDU was also negative in the in vitro rat hepatocyte unscheduled DNA synthesis assay at concentrations of 750 and 1000 micrograms/ml. In contrast, BVDU was positive in the L5178Y TK +/- mouse lymphoma mutation assay without S9 activation at five concentrations ranging from 500 to 2000 micrograms/ml. A Chinese hamster ovary cell (CHO)/hypoxanthine guanine phosphoribosyl transferase gene mutation assay conducted without S9 over similar concentrations was negative. However, micronucleus induction by BVDU was detected without S9 activation at concentrations between 500 and 1750 micrograms/ml using both CHO and L5178Y cells. These results indicate that BVDU is a potential human clastogen.

Animals↗
PubMed1991

Chinese hamster ovary cell assays for mutation and chromosome damage: data from non-carcinogens.

In vitro genotoxicity tests are employed to screen chemicals for their capability to cause various DNA and chromosomal alterations, and the results are often used to predict their potential for carcinogenicity. However, there is controversy regarding the apparent low specificity of some in vitro genotoxicity assays, which result in a high false positive rate. Since we use and rely upon in vitro assays for risk assessment and prediction of carcinogenicity, this specificity issue is of serious concern to us. Hence, we selected ten compounds deemed non-carcinogens in the literature to test for the induction of gene mutation and chromosomal damage using the Chinese hamster ovary cell/hypoxanthine-guanine phosphoribosyl transferase (CHO/HGPRT) mutation assay performed concurrently with a CHO micronucleus assay. The chemical exposures for the two end-points were done simultaneously. The protocol for the two end-points was developed using the carcinogens N-methyl-N'-nitro-N-nitrosoguanidine, 3-methylcholanthrene, cyclophosphamide and 7,12-dimethylbenzanthracene. The non-carcinogens chosen were 4-nitro-o-phenylenediamine, p-phenylenediamine dihydrochloride, 3-nitropropionic acid, dichlorvos, 2-(chloromethyl)pyridine, N-(1-naphthyl)ethylenediamine 2HCl, O-anthranilic acid, 4-nitroanthranilic acid, anilazine and triphenyltin hydroxide. Each of these chemicals had been reported positive in the Ames test and/or the mouse lymphoma TK+/- mutation assay. In addition, eight of them were also reported positive in in vitro assays for chromosome aberrations and/or sister chromatid exchange (SCE). We found four of the ten chemicals negative for gene mutation and micronucleus induction without and with activation in the CHO/HGPRT mutation and CHO micronucleus assays. However, one of these four chemicals may be a potential carcinogen according to other carcinogenicity reviewers. Four other chemicals that induced only micronuclei were negative for gene mutation. Dichlorvos was positive for gene mutation and micronucleus induction without and with activation. This chemical has been shown recently to cause various tumors in rodents. One of the non-carcinogens was positive in the micronucleus test and equivocally positive in the mutation test. These results indicate that the CHO/HGPRT mutation assay may provide more relevant results than the CHO micronucleus assay, the mouse lymphoma mutation assay, or in vitro SCE and chromosome aberration assays when screening chemicals for potential carcinogenicity.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1990

Genetic toxicity of the benzene metabolite trans, trans-muconaldehyde in mammalian and bacterial cells.

Previous studies in our laboratory identified trans,trans-muconaldehyde (MUC), a six-carbon diene dialdehyde, as a microsomal metabolite of benzene. This ring-opened metabolite of benzene was also shown to be hematotoxic in mice in a manner similar to benzene. To further explore the role of MUC in relation to benzene toxicity, a number of test systems were utilized to determine its genotoxic potential. In B6C3F1 mice, MUC induced a highly significant increase in sister-chromatid exchange (SCE), the lowest effective dose being 3 mg/kg, but failed to induce any micronuclei (MN). In Chinese hamster ovary (CHO) cells, MUC at concentrations up to 0.8 micrograms/ml was negative in the hypoxanthine-guanine phosphoribosyl transferase (HGPRT) assay. Dose-related increases in the percentage of cells with MN were observed in CHO cells treated with 0.4-0.8 micrograms/ml MUC. MUC did not-cause unscheduled DNA synthesis in rat primary hepatocytes. Treatment of Salmonella typhimurium TA97 with MUC induced a low level of mutations at concentrations ranging from 10 to 70 micrograms/ml with or without S9 activation. MUC was inactive in strains TA1535, TA100, TA1538 and TA98. In CHO cells and rat primary hepatocytes, MUC was cytotoxic at 0.4 and 4.0 micrograms/ml, respectively. Concentrations of 100 micrograms/plate MUC were toxic for bacterial cells. The present findings indicate that MUC is nonmutagenic or minimally mutagenic in bacterial and mammalian in vitro systems. In mammalian cells, MUC is highly cytotoxic and genotoxic.

Aldehydes↗
PubMed1988

Evaluation of the division arrest method of the CHO/HGPRT mutation assay.

We have evaluated the division arrest method of the CHO/HGPRT mutation assay following the procedure described by O'Neill et al. Environ. Mutagen. 4, 421-434 (1982). This method simplifies the culture manipulations required during the expression period and can be readily adopted for screening mutagenic compounds. The mutation frequencies derived from the subculture method and the division arrest (no subculture) method after treatment of CHO-K1-BH4 cells with ethyl methanesulfonate were similar at all concentrations. The background mutation frequencies observed in the medium and solvent (0.5% DMSO) controls ranged from 0 to 9 colonies per 1 X 10(6) cells. Twenty to 24 h treatments, using the direct-acting compounds ethyl methanesulfonate, N-methyl-N'-nitro-N-nitrosoguanidine, ICR-191 acridine, 5-Bromo-2'-deoxyuridine, mitomycin C and high concentrations of thymidine produced positive mutagenic responses, while 2'-deoxyuridine and trifluorothymidine gave negative responses. Four-h treatments with Benzo[a]pyrene, diethylnitrosamine, 2-acetylaminofluorene, 3-methylcholanthrene and 2-aminoanthracene in the presence of S9 also produced positive results. Anthracene, fluorene and pyrene with S9 were negative. However we found that a toxic, non-mutagenic compound (anthracene) can yield sporadic increases in mutation frequencies (1 out of 10 replicates). Overall, our results indicate that the division arrest method of the CHO/HGPRT mutation assay can be reliably used for routine screening.

Animals↗
PubMed1988

A simplified protocol for the mouse bone marrow micronucleus assay.

Complex and expensive protocols involving multiple sampling times have been proposed and recommended for the in vivo mouse bone marrow micronucleus assay. The purpose of this study was to determine whether a simplified procedure employing two identical exposures and a single sampling time would be equally effective at detecting chemical clastogens. Furthermore, the utility of the protocol was investigated for both intraperitoneal and oral routes of administration. The results obtained from a group of chemicals spanning the known time range for maximum frequency of micronucleus induction prove the effectiveness of this simplified protocol.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1988

Experimental design for the C3H/10T1/2 CL8 cell transformation assay.

The C3H/10T1/2 CL8(10T1/2) cell transformation assay has been used as an important in vitro tool for screening potential carcinogens. In this paper we describe an experimental design that increases the sensitivity and specificity of the assay. One half of the total dishes was allocated to the solvent control and the other half was equally subdivided into four treatment dose groups of low to high cytotoxic effects. The transformation frequency was calculated on the basis of the number of dishes with Type III foci. Each treatment group, as well as the pooled treatment groups, was compared to the solvent control using Fisher's exact test. The sensitivity of our design, as evaluated by power analyses, greatly exceeded that of a standard test design in which about 20 dishes are allocated to each of the control and treatment groups. Furthermore, our use of an expanded number of control and treatment dishes reduces the chance for both false positive and false negative responses. Our experimental design is illustrated with data from experiments in which the transforming potential of two drugs, dimenhydrinate and SC-32006, was examined.

Animals↗
PubMed1988

Difference in metabolic profile of potassium canrenoate and spironolactone in the rat: mutagenic metabolites unique to potassium canrenoate.

The metabolic fates of potassium canrenoate (PC) and spironolactone (SP) were compared for the rat in vivo and in vitro. Approximately 18% of an in vivo dose of SP was metabolized to canrenone (CAN) and related compounds in the rat. In vitro, 20-30% of SP was dethioacetylated to CAN and its metabolites by rat liver 9000 g supernatant (S9). Thus, the major route of SP metabolism is via pathways that retain the sulfur moiety in the molecule. PC was metabolized by rat hepatic S9 to 6 alpha, 7 alpha- and 6 beta, 7 beta-epoxy-CAN. The beta-epoxide was further metabolized to its 3 alpha- and 3 beta-hydroxy derivatives as well as its glutathione (GSH) conjugate. Both 3 alpha- and 3 beta-hydroxy-6 beta, 7 beta-epoxy-CAN were shown to be direct acting mutagens in the mouse lymphoma assay, whereas 6 alpha, 7 alpha- and 6 beta, 7 beta-epoxy-CAN were not. These mutagenic metabolites, their precursor epoxides and their GSH conjugates were not formed from SP under identical conditions. The above findings appear to be due to inhibition of metabolism of CAN formed from SP by SP and/or its S-containing metabolites, since the in vitro metabolism of PC by rat hepatic microsomes was appreciably reduced in the presence of SP. The hypothesized mechanism(s) for this inhibition is that SP and its S-containing metabolites specifically inhibit an isozyme of hepatic cytochrome P-450 or SP is a preferred substrate over PC/CAN for the metabolizing enzymes. Absence of the CAN epoxide pathway in the metabolism of SP provides a possible explanation for the observed differences in the toxicological profiles of the two compounds.

Animals↗
PubMed1987

Decision criteria for the in vitro rat hepatocyte UDS assay.

The induction of unscheduled DNA synthesis (UDS) in rat primary hepatocytes is used as an in vitro screen for genotoxicity. The purpose of this study was to develop criteria for statistical evaluation of autoradiographic grain counts from the UDS assay. Based on our historical solvent control population (N = 17), we first established a predictive two-sided symmetric tolerance interval providing 95% confidence for coverage of 99% of the distribution of the mean net nuclear grain count for a new solvent control observation. The tolerance interval was determined to run from -2.82 to 4.03 net nuclear grains. When the concurrent solvent control (C) proves admissible (-2.82 less than C less than 4.03), the mean net nuclear grain counts from treatment groups are compared to the concurrent solvent control value. If the difference exceeds 3.09 at two successive concentrations, the test compound is considered positive. We have tested eight carcinogens (MNNG, AFB1, 4DAB, 4NQO, DMBA, 2AAF, DEN and 2AA) utilizing these criteria. All eight were positive. Four non-carcinogens (2AB, pyrene, anthracene and alpha NA) were negative. Each of these chemicals was tested twice using our standard protocol, which employs a preliminary range-finding cytotoxicity assay. We conclude that these criteria provide adequate sensitivity and specificity to be applicable for the evaluation of the results of routine UDS assays with compounds of unknown genotoxic potential.

Animals↗
PubMed1982

Selection of fetal bovine serum for use in the C3H/10T 1/2 CL8 cell transformation assay system.

The purpose of this communication is to report our experience concerning the variation in cloning efficiency and transformation frequency utilizing C3H/10T 1/2 CL8 cells with 23 different lots of fetal bovine sera. These sera were purchased from five different commercial sources. The standard cell transformation assay using 1,000 cells per dish and 3-methylcholanthrene (7.5 micrograms/ml) as the transforming agent was performed. The chemical exposure period was 3 days. The cloning efficiency was determined in parallel toxicity tests using 200 cells per dish. Only three out of 23 serum lots supported a strong response in cell transformation. The results indicated that variation in the ability of sera to support cell transformation was not supplier dependent. In addition, our results showed that serum lots exhibiting the best cloning efficiencies did not necessarily support cell transformation. It is apparent that reliance on cloning efficiency alone would be inadequate as a means of selecting a serum lot. We therefore recommend that a complete cell transformation assay be performed when selecting fetal bovine serum for use in this assay.

Animals↗
PubMed1982

Mutagenicity of metal salts in the L5178Y mouse lymphoma assay.

Eleven metals were examined for their potential to induce forward mutations at the thymidine kinase locus in L5178Y mouse lymphoma cells. The materials tested included AlCl3, CdSO4, HgCl2, K2CrO4, K2Cr2O7, MgCl2, MnCl2, NaAsO2, Na2HAsO4, NaCl, and Pb(NO3)2. Strong positive responses at survivals greater than 10% were observed with CdSO4, K2CrO4, K2Cr2O7, and MnCl2. Weak positive responses, yielding 2- to 3-fold increases in mutation frequency above the solvent control at greater than 10% survival, were seen with HgCl2, NaAsO2, Na2HAsO4, and Pb(NO3)2. Negative responses were obtained with MgCl2, NaCl, and AlCl3.

Animals↗
PubMed1981

An E coli microsuspension assay for the detection of DNA damage induced by direct-acting agents and promutagens.

We have devised a microsuspension assay utilizing E coli indicator strains WP2, WP2 uvrA, WP67, CM611, WP100, W3110polA+, and p3478 pola- for the detection of chemically-induced preferential kill of repair-deficient strains. Data are presented from tests of 77 compounds representing a wide range of chemical classes which demonstrate the efficiency of the E coli microsuspension assay as both a qualitative and quantitative screen of DNA-modifying activity. Furthermore, the use of a battery of indicator strains lacking different repair systems offers the advantage of providing preliminary information concerning the mechanism of DNA damage induction by a test agent.

Alkylating Agents↗
PubMed1981

Mutagenicity of alkyl glycidyl ethers in three short-term assays.

The mutagenic potential of glycidol and 7 alkyl glycidyl ethers having straight alkyl chains of 2, 4, 6, 8, 10, 12, and 14 carbon atoms were examined in a battery of in vitro assays. The battery consisted of the Salmonella/mammalian microsome assay, the L5178Y mouse lymphoma assay, and unscheduled DNA synthesis using W138 cells. The mutagenic potential of the compounds ranged from strongly mutagenic to non-mutagenic; glycidol exhibited the greatest activity. All the ethers through C-4 showed a definite response whole the C-8 or higher ethers showed very weak or no responses. Dose-response curves were obtained by all 3 assays for those compounds that exhibited mutagenic activity. The sensitivity of each assay is discussed, as are the effects of the liver microsome systems used for metabolic activation.

1-Propanol↗
PubMed1981

Role of colostrum and milk in the natural transmission of the bovine leukemia virus.

The role of colostrum and milk in the transmission of the bovine leukemia virus (BLV) was examined by monitoring the development of BLV infection in calves that were fed since birth on colostrum and milk from their BLV-positive dams and then reared in complete or partial isolation from infected cattle. Twenty-one of the 25 calves raised in complete isolation remained negative for BLV until the last evaluation. At this time, 14 calves were older than 28 months of age, and seven were 16 to 20 months old. Three calves in this group became BLV positive before the age of five months, and one became so at the age of 12 months. Of the 16 calves raised in partial isolation, two were positive at the ages of 11 and 18 months, respectively. The other 14 calves remained negative during the 26 to 29 months of observation. It is not known if the six animals that became BLV positive in these two groups were infected by milk, or prenatally, or during contact with their infected dams. While only six of the 41 calves raised in isolation became infected, all 18 calves raised in contact with BLV-positive cows became infected before the age of 26 to 29 months of age, and 12 were positive at 16 to 20 months of age. Thus, it is apparent that, under natural conditions, milk-borne transmission of BLV, if it occurs at all, is much less frequent than contact transmission, despite the fact that, as shown in previous studies, infectious BLV is present in the colostrum and milk of most BLV-positive cows. Passively acquired maternal antibodies to BLV were probably responsible for the resistance of the calves to milk-borne infection.

Animals↗
PubMed1978

An improved syncytia infectivity assay for the bovine leukemia virus.

Several factors that influence the sensitivity of the syncytia infectivity assay for the bovine leukemia virus (BLV) and BLV-infected lymphocytes have been examined. The use of early-passage indicator bovine embryonic spleen (BESP) cells and their pretreatment with diethylamino-ethyl-dextran (DEAE-D) was essential for optimal sensitivity. Polybrene was less effective than DEAE-D. The combination of DEAE-D and polybrene was more effective than DEAE-D alone when BLV-infected leukocytes were used as the inoculum, but not when the inoculum was a cell-free BLV preparation. Using BESP cell passages 4 to 11 as indicators, reproducible titers were obtained when aliquots of the same virus stock were assayed at different times after freezer storage. When assaying peripheral blood lymphocytes from infected cattle, optimal syncytia responses were observed consistently by inoculating 5 X 10(6) viable lymphocytes per 60-mm Falcon dish. Centrifugation of peripheral blood leukocytes from BLV-infected cattle in discontinuous bovine serum albumin gradients can be used to separate a subpopulation of infected lymphocytes. Use of this subpopulation as the inoculum, rather than unseparated buffy-coat leukocytes, greatly increases the sensitivity of the syncytia infectivity assay.

Animals↗