Search PubMed⌕ Search

Biomedical subjects

C P Dougherty

Publications and source records attributed to C P Dougherty.

4 recordsLinked to original sources
PubMed2000

Dietary exposures to food contaminants across the United States.

Food consumption is an important route of human exposure to pesticides and industrial pollutants. Average dietary exposures to 37 pollutants were calculated for the whole United States population and for children under age 12 years by combining contaminant data with food consumption data and summing across food types. Pollutant exposures were compared to benchmark concentrations, which are based on standard toxicological references, for cancer and noncancer health effects. Average food ingestion exposures for the whole population exceeded benchmark concentrations for arsenic, chlordane, DDT, dieldrin, dioxins, and polychlorinated biphenyls, when nondetects were assumed to be equal to zero. For each of these pollutants, exposure through fish consumption accounts for a large percentage of food exposures. Exposure data for childhood age groups indicated that benchmark concentrations for the six identified pollutants are exceeded by the time age 12 years is reached. The methods used in this analysis could underestimate risks from childhood exposure, as children have a longer time to develop tumors and they may be more susceptible to carcinogens; therefore, there may be several additional contaminants of concern. In addition, several additional pollutants exceeded benchmark levels when nondetects were assumed to be equal to one half the detection limit. Uncertainties in exposure levels may be large, primarily because of numerous samples with contaminant levels below detection limits.

Adolescent↗
PubMed1981

Patterns of late replication in X chromosomes of human lymphoid cells.

Two predominant patterns of late X replication were observed in both short-term and established human lymphoid cultures. One pattern was found in a minority of short-term cultured T-cell metaphases, in most lectin-stimulated B cells, and, with minor variations, in established B-cell lines. In these cells, DNA replication terminated in the distal part of the long arm of the late X. A different pattern was found in the majority of lectin-simulated T cells and in the T-cell line CCRF-CEM. These cells exhibited terminal replication in a region of the long arm of the late X that was nearer to the centromere. It is speculated that the variations in replication patterns correlate with phenotypic and functional characteristics of human lymphoid subsets.

B-Lymphocytes↗
PubMed1980

Induction of sister chromatid exchanges by BUdR is largely independent of the BUdR content of DNA.

The halogenated thymidine (dT) analogue, 5-bromodeoxy-uridine (BUdR), has a variety of effects on mammalian cells, including toxicity, suppression of differentiation, and mutagenesis. Although it is generally assumed that the effects of BUdR are due primarily to its presence in DNA, results from our laboratory have raised doubts about such assumptions. We have shown, for example, that BUdR mutagenesis in mammalian cells is determined by the concentration of BUdR in the medium rather than in DNA, and that mutagenesis can be suppressed by deoxycytidine (dC) without changing the amount of BUdR in DNA. BUdR has also been shown to induce sister chromatid exchanges (SCEs) in mammalian cells. Initial results suggested that the relationship between BUdR and SCEs might not be explained by a single factor, and various correlations between BUdR and SCEs have been proposed. However, the results to date have been inconclusive, because the experiments did not resolve as independent variables the concentration of BUdR in the medium and the amount of BUdR incorporated into nuclear DNA. We have now carried out experiments to resolve these two factors; the results indicate that the major factor in determining the frequency of SCEs is the concentration of BUdR in the medium.

Animals↗