bluuebunny/crossref_metadata_2025_split huggingface dataset:
Nick translation—a new assay for monitoring dna damage and repair in cultured human fibroblasts
Authors: Snyder Ronald D. , Matheson Dale W. 
Published: February 2007

AbstractAn in vitro assay has been developed to detect DNA damage and repair following chemical treatment of human diploid fibroblasts. DNA damage is measured by following the Escherichia coli DNA polymerase I‐catalyzed incorporation of radiolabeled deoxycytidine triphosphate (dCTP) into the DNA of lysolecithin‐permeabilized cells. DNA strand breaks with free 3′ OH termini serve as template sites for incorporation, and decrease of this incorporation with time, following removal of the test chemical, indicates loss (repair) of initial damage. Inhibition of the DNA excision repair process by the addition of the repair inhibitors arabinofuranosyl cytosine (ara‐C) and hydroxyurea (HU) during the incubation period gives rise to an increased number of template sites, manifesting itself in increased incorporation and indicating the induction of long‐patch excision repair. This nick translation assay, originally proposed by Nose and Okamoto [1983], is very sensitive, allows detection and quantitation of both DNA damage and repair, distinguishes between various types of induced damage, does not require radioactive prelabeling of cells, and circumvents some of the problems inherent in unscheduled DNA synthesis (UDS) assays. The assay is also useful in detecting those agents that inhibit replicative DNA synthesis and/or the excision repair process.Results presented demonstrate that all 14 direct‐acting carcinogens tested and 8 of 14 carcinogens requiring metabolic activation give positive indication of DNA damage, repair, or both. Eleven of 14 noncarcinogens tested were scored as negative, the other 3 having previously been shown to interact with cellular DNA. This assay is shown to have predictive capability at least equal to that of UDS assays but to allow a broader spectrum of genotoxic effects to be analyzed.
Induction of sister chromatid exchanges by coal dust and tobacco snuff extracts in human peripheral lymphocytes
Authors: Tucker James D. , Ong Tong‐Man 
Published: February 2007

AbstractThe organic solvent extracts of sub‐bituminous coal dust and tobacco snuff, both together and separately, were tested for the induction of sister chromatid exchanges (SCEs) in human peripheral lymphocytes. The results indicate that these extracts induced SCEs, and that when tested together synergistically induced SCEs in two of three donors. Studies with the organic solvent extracts of all five ranks of coal indicate that the extracts of bituminous, lignite, and peat, but not anthracite, induced SCEs. Similar experiments conducted with water extracts show that bituminous, lignite, and peat, but not sub‐bituminous extracts, induced SCEs, and that anthracite was equivocal. To determine whether individuals differed in their SCE responses to coal dust extracts, lymphocytes from five donors were tested with organic solvent extracts of bituminous and sub‐bituminous coal. An analysis of variance indicates that the SCE response was significantly influenced by the donor (p < 0.0001) and each of the two coal extracts (p < 0.0001). From studies of workers occupationally exposed to coal dust, it is known that inhaled coal dust is cleared from the lungs by mucociliary action and introduced into the stomach by swallowing. Coal dust, or coal dust plus snuff, may be responsible for the increased frequency of gastric cancer observed in coal miners. The findings presented here suggest that coal dust, with or without tobacco snuff, may play a role in the elevated incidence of gastric cancer in coal miners. Because water extracts of some ranks of coal induced SCEs, there exists the possibility of adverse environmental effects due to coal leachates.
Chemical mutagenesis testing in Drosophila. III. Results of 48 coded compounds tested for the national toxicology program
Authors: Valencia R. , Mason J. M. , Woodruff R. C. , Zimmering S. 
Published: February 2007

AbstractForty‐eight chemicals were tested for mutagenicity in Drosophila melanogaster. Each compound was tested first for the induction of sex‐linked recessive lethals (SLRLs) by feeding the chemical in a solution of 5% aqueous sucrose. If it was not mutagenic by this route, the chemical was tested by injection in a solution of 0.7% aqueous NaCl. If found inactive, the compound was not tested further. If it was mutagenic, the compound was tested for the induction of reciprocal translocations (RTs) using the exposure protocol and germ cell stage that yielded positive results in the SLRL assay. Eight chemicals (diglycidylresorcinol ether, AF‐2, alloxan monohydrate, 1‐aziridine ethanol, p,p'‐DDE, dichloroacetonitrile, 1,3‐dichloropropene, and 3,3′‐dimethylbenzidine dihydrochloride) were found to induce SLRLs. Only diglycidylresorcinol ether also induced RTs.
Autoradiographic detection of diphtheria toxin resistant mutants in human diploid fibroblasts
Authors: Gupta Radhey S. , Singh Bhag 
Published: February 2007

AbstractAn autoradiographic procedure for the detection of diphtheria toxin (DT) resistant (DipR) mutants in human diploid fibroblast (HDF) cells has been developed. The assay is based on the observation that when HDFs from confluent cultures are seeded in medium containing 0.01 flocculating units/ml or higher concentration of DT, protein synthesis in sensitive cells is severely inhibited by 4–6 hr. If at this or later time, a radiolabeled protein precursor (eg, 3H‐leucine) is added to the culture, it is almost exclusively incorporated into the resistant cells, which are then readily identified by autoradiography. The DipR cells can also be identified by labeling in the presence of 3H‐thymidine, although a higher background is observed in these experiments. Reconstruction experiments using DipS and DipR HDFs show that the frequency of heavily labeled cells that are detected by autoradiography show an excellent correlation with the number of DipR cells added and to the number of DipR cells as detected by conventional colony forming assay. These studies provide strong evidence that the labeled cells identified by autoradiography are bona fide DipR mutants. The detection of DipR cells by autoradiography is apparently not affected by the presence of the sensitive cells in the mixtures. The spontaneous frequency of DipR cells in HDFs has been found to be in the range of 1–5 × 10−6, and this increases in a dose dependent manner upon treatment with the mutagen ethyl methanesulfonate. These results indicate that the autoradiographic assay could be used for quantitative mutagenesis. Since the autoradiographic assay does not depend on cell division, it may prove useful in estimating the incidence of pre‐existing mutations in cell populations that either do not divide or have very limited growth potential (eg, lymphocytes, muscle cells, neurons, senescent fibroblasts, etc).
The role of DNA sequence and structure of the electrophile on the mutagenicity of nitroarenes and arylamine derivatives
Authors: Rosenkranz Herbert S. , McCoy Elena C. , Frierson Manton , Klopman Gilles 
Published: February 2007

AbstractThe mutagenicities of a series of nitroarenes and related electrophilic metabolites of aromatic amines were studied in Salmonella typhimurium strains TA98 and TA97, which have, respectively, (GCGC/CGCG)2 and (CCC/GGG)2 as their mutational sites. For electrophiles, primarily bicyclic species, that form adducts with nucleophilic sites other than the C8 of guanine (G), the ratios of activities in the two strains is near unity. On the other hand, for electrophiles consisting of cyclic structures with more than two rings and that are reported to react solely with the C8 of G, the ratio of activities (TA98/TA97) is in excess of 1.6.Quantum mechanical calculations indicate that (1) in the plane of G, the N7. N3, and 06 of G are more likely nucleophilic targets than C8 and (2) adduct formation at the C8 of G requires electrophilic attack from above or below the plane of G. It is hypothesized that because of steric hindrances, nitroarenes and derivatives containing in excess of two rings cannot react with the preferred nucleophilic sites and, therefore, form adducts with the more accessible C8. However, such an out‐of‐the‐plane attack is influenced by the nature of the nearest neighbor, as evidenced by the difference in mutagenic responses of TA98 and TA97, alternating GCs being preferred over other combinations. Further quantum mechanical calculations indicate that the nature of the nearest neighbor does indeed affect the nucleophilicity of the C8 of G but that the expression of this effect is apparently masked by the overriding steric effects.
Embryonic exposure to aflatoxin‐B1: Mutagenicity and influence on development and immunity
Authors: Dietert R. R. , Qureshi M. A. , Nanna U. C. , Bloom S. E. 
Published: February 2007

AbstractChick embryos were mutagenized in ovo in order to study developmentally related alterations in immune functions in survivors of this prenatal toxicant insult. In this experimental system, a single exposure of 6‐day chick embryos to 0.1 μg aflatoxin‐B1 (AF‐B1) in 10 μ1 of acetone was employed, and the control embryos received 10 μ1 of solvent alone. This dosage of AF‐B1 administered to 6‐day embryos was found to increase the incidence of sister chromatid exchanges in blood cells approximately fivefold above the baseline observed in solvent controls. A second sham control, where no solvent was administered, was included in some experiments. The cell cycle times in blood increased slightly during the initial exposure to AF‐B1. However, a majority of the AF‐B1 and acetone exposed embryos survived and hatched without incident. Losses occurred mainly in the latter part of embryogenesis. After hatching, no significant differences were observed in body weight between different treatment groups up to 26 weeks of age and no change in primary humoral immunity was detected. In contrast, two parameters of cell‐mediated immunity, graft vs host (GvH), and cutaneous basophil hypersensitivity (CBH) reactions were both depressed as a result of exposure to AF‐B1. The AF‐B1 treatment group was significantly reduced in the GvH reaction compared with sham‐treated controls. In the CBH assay, AF‐B1‐exposed chicks showed reduced immunity compared with acetone controls. These results suggest that long‐term selective immune depression can occur following embryonic exposure to AF‐B1.
Investigations into the reported ability of cimetidine to initiate UDS in rat hepatocyte primary cultures
Authors: Lefevre P. A. , Ashby John 
Published: February 2007

AbstractCimetidine is widely prescribed as a palliative or cure for gastric disorders in man. It is known to be noncarcinogenic to rodents and has been shown to be inactive in a wide range of in vitro and in vivo genotoxicity assays. It was therefore of concern when an injectable formulation of this drug (Cimetex) was reported to initiate UDS in cultured primary rat hepatocytes [Martelli et al, 1983]. We have confirmed the ability of Cimetex to elicit UDS in primary hepatocytes and established that cimetidine itself is inactive. These data indicate that it is not cimetidine per se, but rather its protonated formulation which is responsible for the activity. These observations pose fundamental questions regarding the validity of the UDS end‐point when testing salts in vitro, rather than presenting a challenge to the nongenotoxic status of cimetidine.
Aroclor 1254 pretreatment effects on DNA repair in rat hepatocytes elicited by in vivo or in vitro exposure to various chemicals
Authors: Kornbrust Douglas , Dietz Dennis 
Published: February 2007

AbstractInducers of liver mixed function oxidase (MFO) activities have profound effects on the genotoxicity of substances that undergo metabolic activation by the MFO system. The polychlorinated biphenyl mixture Aroclor 1254 is a broad‐spectrum inducer of liver MFO activities that has been employed as a pretreatment to augment the metabolic activation capabilities of rat liver fractions used in a number of short‐term tests for genotoxicity, including the Ames Salmonella/bacterial mutagenicity assay. The present study was designed to characterize the effects of Aroclor pretreatment of rats on the DNA repair responses elicited by various chemicals in the in vitro hepatocyte primary culture/DNA repair (HPC/DR) assay as well as the in vivo/in vitro HPC/DR assay. The amount of DNA repair produced in vitro by diethylnitrosamine (DEN), benzo(a)pyrene (B(a)P), 3‐meth‐ylcholanthrene (3‐MC), 2‐acetylaminofluorene (2‐AAF), o‐aminoazotoluene (o‐AT), and aflatoxin B1 (AFB1) was significantly greater in hepatocytes derived from Aroclor‐pretreated rats than in control rat hepatocytes; in vitro responses to dimethylnitrosamine (DMN), 7,12‐dimethylbenzanthracene (DMBA), benzidine (BZ), and 2‐naphthylamine (2‐NA) were not significantly affected by Aroclor pretreatment. DNA repair elicited by the direct‐acting alkylating agents methyl methanesulfonate and N‐methyl‐N′‐nitro‐N‐nitrosoguanidine was also not increased by Aroclor pretreatment, which indicated that Aroclor does not exert a general stimulatory effect on the hepatocellular DNA repair capacity. Therefore, the pretreatment‐related potentiation of DNA repair observed for 6 out of 12 compounds tested in vitro was considered to be due to enhanced metabolic activation. These results suggested that pretreatment with Aroclor may increase the sensitivity of the in vitro HPC/DR assay to certain compounds. In contrast, Aroclor pretreatment had little effect on the amount of hepatocellular DNA repair elicited by in vivo administration of DMN, DEN, o‐AT, 2‐AAF, 3‐MC, or AFB1, which indicated that this pretreatment regimen may have little utility for improving the sensitivity of the in vivo/in vitro HPC/DR assay.
Rapid analysis of DNA strand breaks in soft tissues
Authors: Morris Stanton R. , Shertzer Howard G. 
Published: February 2007

AbstractA technique was developed to measure rapidly DNA strand breaks in soft tissues. This method measured the rate of alkaline unwinding of DNA, which was proportional to strand breakage. Alkaline unwinding of DNA was done by treating tissue homogenates with NaOH. Single‐stranded DNA was removed by extraction with aqueous phenol. DNA unwinding was quantitated by measuring the remaining double‐stranded DNA. Using the described technique, a dose‐effect relationship was observed between N‐nitrosodimethylamine (NDMA) and alkaline unwinding of mouse liver DNA.
Mutagenicity of chili extract and capsaicin in short‐term tests
Authors: Nagabhushan M. , Bhide S. V. 
Published: February 2007

AbstractVanillin, capsaicin and chili extracts were tested for mutagenicity in Salmonella typhimurium histidine‐deficient tester strains TA 98, TA 100, TA 1535. TA 1537, and TA 1538. Vanillin was nonmutagenic, whereas chili extract and capsaicin were mutagenic with metabolic activation. Capsaicin, an active component of chili extract, was the more potent mutagen. The positive samples were also tested in two mammalian test systems: the micronucleus test and the 8‐azaguanine‐resistant mutagenesis assay that used V79 Chinese hamster cells. It was observed that both were negative for the latter test at the dose level tested, whereas in the micronucleus test, only capsaicin was positive near the LD50 dose. Capsaicin also inhibited DNA synthesis in the testes of Swiss mice injected at two dose levels.
Classifying mutagens as to their specificity in causing the six possible transitions and transversions: A simple analysis using the salmonella mutagenicity assay
Authors: Levin David E. , Ames Bruce N. 
Published: February 2007

AbstractThe standard Salmonella tester strains used to detect base substitution mutations carry the hisG428 ochre mutation (TA102 and TA104) and the hisG46 missense mutation (TA100). These mutations can be reverted by base changes at their mutant his loci or at extragenic suppressor loci. The base changes resulting in each class of revertants of these mutations have been identified, and simple phenotypic screens have been developed to distinguish among them. Revertants at extragenic suppressor loci are distinguished from those at the his loci by their sensitivity to inhibitory histidine analogs. The four ochre suppressor loci of hisG428 are distinguished by their ability to support growth of nonsense mutants of phage P22. These screens are the basis for a rapid and simple system for determining the base substitution specificity of mutagens using hisG428‐ and hisG46‐containing tester strains. Diagnostic mutagens specific for each of the six possible base changes (transitions and transversions) have been identified. Using these diagnostic mutagens, two additional strains, each specifically reverted by a single base substitution mutation, have been developed to provide a minimum of two loci at which to detect each type of base change. The ability of this system to provide detailed information about mutational specificity in a variety of DNA repair backgrounds will allow further elucidation of the mechanisms of mutagenesis and DNA repair.
Sodium arsenite potentiates the clastogenicity and mutagenicity of dna crosslinking agents
Authors: Lee T. ‐C. , Lee K. C. , Tzeng Y. J. , Huang R. Y. , Jan K. Y. 
Published: February 2007

AbstractTo see if sodium arsenite enhances the clastogenicity and the mutagenicity of DNA crosslinking agents, Chinese hamster ovary (CHO) cells and human skin fibroblasts were exposed to cis‐diamminedichloroplatinum (II) (cis‐Pt(II)) or 8‐methoxypsoralen (8‐MOP) plus long‐wave ultraviolet light (UVA) and then to sodium arsenite. The results indicate that the clastogenicity of cis‐Pt(II) and 8‐MOP plus UVA are enhanced by the post‐treatment with sodium arsenite. Chromatid breaks and exchanges are predominantly increased in doubly treated cells. Furthermore, the mutagenicity of cis‐Pt(II) at the hypoxanthine‐guanine phosphoribosyl transferase locus is also potentiated by sodium arsenite in CHO cells.
Chemically induced aneuploidy in mammalian cells: Mechanisms and biological significance in cancer
Authors: Oshimura Mitsuo , Barrett J. Carl 
Published: February 2007

AbstractA growing body of evidence from human and animal cancer cytogenetics indicates that aneuploidy is an important chromosome change in carcinogenesis. Aneuploidy may be associated with a primary event of carcinogenesis in some cancers and a later change in other tumors. Evidence from in vitro cell transformation studies supports the idea that aneuploidy has a direct effect on the conversion of a normal cell to a preneoplastic or malignant cell. Induction of an aneuploid state in a preneoplastic or neoplastic cell could have any of the following four biological effects: a change in gene dosage, a change in gene balance, expression of a recessive mutation, or a change in genetic instability (which could secondarily lead to neoplasia). To understand the role of aneuploidy in carcinogenesis, cellular and molecular studies coupled with the cytogenetic studies will be required.There are a number of possible mechanisms by which chemicals might induce aneuploidy, including effects on microtubules, damage to essential elements for chromosome function (ie, centromeres, origins of replication, and telomeres), reduction in chromosome condensation or pairing, induction of chromosome interchanges, unresolved recombination structures, increased chromosome stickiness, damage to centrioles, impairment of chromosome alignment, ionic alterations during mitosis, damage to the nuclear membrane, and a physical disruption of chromosome segregation. Therefore, a number of different targets exist for chemically induced aneuploidy. Because the ability of certain chemicals to induce aneuploidy differs between mammalian cells and lower eukaryotic cells, it is important to study the mechanisms of aneuploidy induction in mammalian cells and to use mammalian cells in assays for potential aneuploidogens (chemicals that induce aneuploidy). Despite the wide use of mammalian cells for studying chemically induced mutagenesis and chromosome breakage, aneuploidy studies with mammalian cells are limited. The lack of a genetic assay with mammalian cells for aneuploidy is a serious limitation in these studies.
Chromosome analysis of trifluorothymidine‐resistant L5178y mouse lymphoma cell colonies
Authors: Blazak W. F. , Stewart B. E. , Galperin I. , Allen K. L. , Rudd C. J. , Mitchell A. D. , Caspary W. J. 
Published: February 2007

AbstractCells from small (σ) and large (σ) trifluorothymidine‐resistant (TFTr) colonies induced by chemical mutagen treatment of TK+/‐ L5178Y mouse lymphoma cells were examined for chromosomal abnormalities. Analysis of G‐banded metaphase chromosomes from 34 σ‐TFTr colonies revealed that cells from 20 (59%) possessed one or more chromosomal abnormalities. The most frequent (16/20 colonies) abnormality observed in cells from σ‐TFTr colonies involved the addition of extra chromatin to the distal region of one chromosome number 11. In 13 of these 16 colonies, the origin of the chromatin translocated to chromosome number 11 could not be identified; the chromatin was not missing elsewhere in the genome. The remaining three σ‐TFTr colonies with an abnormal chromosome number 11 had apparently whole chromosomes translocated, in tandem, to the distal region of chromosome number 11. Chromosomal abnormalities observed in cells from σ‐TFTr colonies with normal number 11 chromosomes included 2N/4N and 2N/4N/ 8N mosaicism (two colonies), a Robertsonian translocation involving chromosome 10 and a marker chromosome (one colony), and trisomy 7 (one colony). In most (14/16) σ‐TFTr colonies with structural damage to chromosome number 11, the cells within a colony were heterogeneous in that some possessed chromosomal damage whereas others were apparently normal. Analysis of chromosomes in cells from eight λ‐TFTr colonies revealed one colony in which all cells had a Robertsonian translocation involving chromosomes 1 and 16 plus other structural abnormalities. The chromosomes of cells from the remaining λ‐TFTr colonies were apparently normal.
A comparison of mutagenic and snbryotoxic effects of cyclophosphamide on the chick embryo
Authors: Novotná Boẑena , Jelinek Ríchard 
Published: February 2007

AbstractThe cytogenetic and embryotoxic effects of cyclophosphamide (CP) after injection on day 3 of single doses ranging from 0.1 to 30 μg were investigated in the chick embryo. The occurrence of embryotoxicity was checked on incubation day 8; clastogenic effects as well as mitotic indices were evaluated in primitive blood cells 6, 12, 18, 24 and 30 hr after the administration of CP. Teratogenic doses of CP induced high percentages of aberrant cells with many unstable aberrations. mitotic activity appeared to be inhibited at the early collection intervals. Non‐embryotoxic doses of CP also increased the incidence of aberrant cells without any substantial effect upon mitotic activity. Although the clastogenic effects of CP occur at lower doses than the teratogenic effects, the thresholds for both effects lie in the lower part of the embryotoxicity dose range, as estimated by the Chick embryotoxicity Screening Test (CHEST).