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K S Loveday

Publications and source records attributed to K S Loveday.

15 recordsLinked to original sources
PubMed1990

Chromosome aberration and sister chromatid exchange tests in Chinese hamster ovary cells in vitro. V: Results with 46 chemicals.

Forty-six coded chemicals were tested for their ability to induce sister chromatid exchanges (SCEs) and chromosomal aberrations (ABs) in cultured Chinese hamster ovary (CHO) cells using a standard protocol with and without exogenous metabolic activation. Sixteen chemicals were negative and 15 were positive in both assays; 15 were positive for SCEs only (one chemical that was positive for SCEs was equivocal for ABs), and no chemicals induced ABs only. The effect of cell harvest time on the ability to detect the induction of ABs was examined for 18 chemicals. Seven chemicals produced a positive response using both standard and extended harvest times, five were positive only using an extended harvest time, and six were negative using both harvest times. The relationship between cell cycle delay and SCE induction was also examined, and the two appear to be unrelated.

Animals↗
PubMed1990

Chromosome aberration and sister chromatid exchange test results with 42 chemicals.

Forty-two chemicals were tested for their ability to induce cytogenetic change in Chinese hamster ovary cells using assays for chromosome aberrations (ABS) and sister chromatid exchanges (SCE). These chemicals were included in the National Toxicology Program's evaluation of the ability of four in vitro short-term genetic toxicity assays to distinguish between rodent carcinogens and noncarcinogens. The conclusions of this comparison are presented in Zeiger et al. [Zeiger E, Haseman JK, Shelby MD, Margolin BH, Tennant RW (1990): [Environ Molec Mutagen 16(Suppl 18): 1-14]. The in vitro cytogenetic testing was conducted at four laboratories, each using a standard protocol to evaluate coded chemicals with and without exogenous metabolic activation. Most chemicals were tested in a single laboratory; however, two chemicals, tribromomethane and p-chloroaniline, were tested at two laboratories as part of an interlaboratory comparison. Four chemicals (C.I. basic red 9 HCl, 2-mercaptobenzothiazole, oxytetracycline HCl, and rotenone) were tested for SCE in one laboratory and in a different laboratory for ABS. Tetrakis(hydroxymethyl)phosphonium sulfate was tested at one laboratory and the chloride form was tested at a different laboratory. Twenty-five of the 42 chemicals tested induced SCE. Sixteen of these also induced ABS; all chemicals that induced ABS also induced SCE. There was approximately 79% reproducibility of results in repeat tests, thus, we conclude that this protocol is effective and reproducible in detecting ABS and SCE.

Animals↗
PubMed1989

Chromosome aberration and sister chromatid exchange tests in Chinese hamster ovary cells in vitro: II. Results with 20 chemicals.

Twenty chemicals were tested for their ability to induce sister chromatid exchanges (SCEs) and chromosomal aberrations (ABs) in cultured Chinese hamster ovary cells (CHO). These chemicals were tested with and without an added metabolic activation system (rat liver S9 fraction). Four chemicals were negative in both assays, 1 induced ABs only, and 15 were positive for SCEs; 6 of these 15 also induced ABs. The effect of cell harvest time on the ability to detect the induction of chromosomal aberrations was examined for six chemicals. Five of these had caused at least one of the following: cell cycle delay, aberrations observed in first division metaphase cells in the SCE assay, or a weak response in the standard AB assay (10-12-hr growth period). Three chemicals, chlorinated trisodium phosphate, 1,2-dibromo-3-chloropropane, and tetrakis(hydroxymethyl)phosphonium chloride, were positive using both the standard and extended harvest times. N-Nitrosodimethylamine and diphenhydramine HCl were only positive using an extended harvest time, and malonaldehyde was negative using both standard and extended harvest times.

Animals↗
PubMed1984

Induction of sister chromatid exchanges and gene mutations in Chinese hamster ovary cells by psoralens.

Three linear psoralen compounds, 8-methoxypsoralen (8-MOP), 5-methoxypsoralen (5-MOP), 3-carbethoxypsoralen (3-CP), and one angular psoralen, 5-methylangelicin (5-ANG), were tested for their ability to induce both sister chromatid exchanges (SCE) and gene mutations (hypoxanthine-guanine phosphoribosyltransferase locus) in vitro in Chinese hamster ovary cells (CHO line). All the compounds induced both SCE and mutations in the presence of UV irradiation (UVA; peak at 330-380 nm), but no increases were observed in its absence. The frequency of both responses increased with either 1) increasing concentration of compound with a fixed amount of UVA or 2) increasing amount of UVA with a fixed concentration of psoralen. Significant increases in SCE were seen for 8-MOP, 5-MOP, and 5-ANG at concentrations near 1 X 10(-6) M, whereas concentrations near 20 X 10(-6) M of 3-CP were needed before increases in SCE were observed. The induction of gene mutations followed a similar pattern; concentrations of 50-100 X 10(-6) M of 3-CP were needed to induce large increases in mutations, but much lower concentrations of 8-MOP, 5-MOP, and 5-ANG (5-10 X 10(-6) M) were sufficient to induce large increases in mutations. The ratio of induced mutations to induced SCE was similar for 8-MOP, 5-MOP, and 3-CP; that of 5-ANG was much higher, which indicated that the linear furocoumarins produce a different spectrum of DNA damage from that produced by the angular psoralen.

Animals↗
PubMed1979

The effect of a tumor promotor, 12-O-tetradecanoyl-phorbol-13-acetate (TPA), on sister-chromatid exchange formation in cultured Chinese hamster cells.

The tumor promoter 12-O-tetradecanoyl-phorbol-13-acetate (TPA) does not increase the sister-chromatid exchange (SCE) frequency in either Chinese hamster ovary (CHO) or lung (V 79) cells which are cultured in the presence of 5-bromodeoxyuridine. Moreover, TPA does not alter the induction of SCEs in CHO cells by mitomycin C during the first 3 cycles following addition of the alkylating agent. These SCE induction data do not by themselves support the hypothesis that tumor promotion by TPA depends on the enhancement of mitotic recombination.

Animals↗
PubMed1978

Search for DNA interchange corresponding to sister chromatid exchanges in Chinese hamster ovary cells.

Chinese hamster ovary cells (CHO) grown for one cycle in bromodeoxyuridine (BrdU) contain a small amount (0.5%) of unusually dense double stranded DNA. This dense DNA has been previously interpreted as being bifilarly substituted with BrdU and hence evidence that sister chromatid exchange (SCE) formation proceeds via the Holliday model of recombination. However, the amount of this dense DNA is 100 times greater than that expected based on the SCE frequency in similarly cultured CHO cells, and it is not increased by treating the cells with mitomycin C. Moreover, contrary to expectations for bifilary substituted DNA, the amount of this dense DNA is not reduced by growing BrdU-labeled cells for a second cycle in TdR. Finally, DNA isolated from CHO cells contains a minor band (0.5%) with a density 0.025 gm/cc greater than that of the main band, whether or not BrdU has been incorporated. These results call into question the identification of this unusually dense DNA as bifilarly substituted and hence its previously postulated relationship to SCE formation.

Bromodeoxyuridine↗
PubMed1978

DNA synthesis in competent Bacillus subtilis cells.

Competent cells of Bacillus subtilis incorporate degradation products from transfecting DNA into their chromosomal DNA. The sensitivity of this incorporation to inhibitors of bacterial DNA synthesis [phage infection or 6-(p-hydroxyphenylazo)-uracil] suggests that semiconservative DNA synthesis can occur in competent cells.

Bacillus subtilis↗
PubMed1978

Characterization of sister chromatid exchange induction by 8-methoxypsoralen plus near UV light.

The combination of 8-methoxypsoralen and near UV light is highly effective in inducing sister chromatid exchanges (SCEs) in Chinese hamster ovary cells. Appreciable increases in SCEs can be effected by treatments compatible with cell survival, and effects of a single dose of alkylation persist over multiple generations. Both the frequency and location of SCEs induced at different times within the DNA synthesis period varies in a manner indicating that exchange induction is restricted to regions which replicated during or after DNA damage.

Animals↗