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R J Reynolds

Publications and source records attributed to R J Reynolds.

At least 37 records · Page 2Linked to original sources
PubMed1986

Bifilar enzyme-sensitive sites in ultraviolet-irradiated DNA are indicative of closely opposed cyclobutyl pyrimidine dimers.

Incubation of UV-irradiated DNA with pyrimidine dimer-DNA glycosylase in cell-free lysates prepared from Micrococcus luteus results in the appearance of double-strand breaks. It has previously been assumed that such double-strand breaks result from cleavage at closely opposed dimers. We have used hybrid molecules of bacteriophage T7 DNA comprised of two unirradiated strands, two UV-irradiated strands, or one unirradiated and one UV-irradiated strand to test this hypothesis. Bifilar cleavage was observed only with molecules consisting of two irradiated strands and no bifilar cleavage was observed after the monomerization of pyrimidine dimers by enzymatic photoreactivation. Our results indicate that at least 80% of the double-strand breaks result from cleavage at closely opposed dimers and that the induction of dimers in one strand does not influence the induction of dimers at closely opposed positions in the complementary strand of a DNA double helix.

Carbon Radioisotopes↗
PubMed1985

Induction of in vitro transformation by near-u.v. light and its interaction with beta-propiolactone.

The ability of u.v.-A light (320-400 nm) to induce cellular transformation in vitro and to modify chemical carcinogen-induced cellular transformation was investigated in BALB/c 3T3 cell cultures. When administered as a series of nontoxic exposures, u.v.-A alone was found to induce cellular transformation as a linear function of the numbers of u.v-A exposures. Possible interactions of u.v.-A with environmentally encountered chemical carcinogens were studied by examining the effects of u.v.-A light exposures on cellular transformation in cells exposed to the direct acting carcinogen, beta-propiolactone (BPL), an alkylating agent, with a standard initiation/promotion protocol. Twenty-four hours after a single treatment with 2.5 micrograms/ml of beta-propiolactone, cells were exposed to 3.0 kJ/m2 of u.v.-A light. U.v.-A exposures were repeated weekly for up to 5 weeks, after which cells were fixed, stained and dishes were scored for type III transformed foci. Weekly exposures to u.v.-A alone for 5 weeks induced approximately 3 foci/dish. Treatment with BPL alone induced approximately 1 focus/dish (background was 0.17 foci/dish). A combination of the two treatments resulted in a marked increase in the yield of transformed foci/dish, with the u.v.-A enhancement increasing with increasing numbers of exposures (approximately 10 foci/dish after a single exposure to BPL and five u.v.-A exposures). These results suggest a synergistic interaction between BPL and subsequent u.v.-A exposures in the induction of in vitro neoplastic transformation.

Animals↗
PubMed1985

Sequence specificity of DNA cleavage by Micrococcus luteus gamma endonuclease.

DNA fragments of defined sequence have been used to determine the sites of cleavage by gamma-endonuclease activity in extracts prepared from Micrococcus luteus. End-labeled DNA restriction fragments of pBR322 DNA that had been irradiated under nitrogen in the presence of potassium iodide or t-butanol were treated with M. luteus gamma endonuclease and analyzed on high resolution, denaturing, polyacrylamide gels. Gamma endonuclease was found to cleave irradiated DNA preferentially at the positions of cytosines and thymines. DNA cleavage occurred immediately to the 3' side of pyrimidines in irradiated DNA and resulted in fragments that terminate in a 5'-phosphoryl group. These studies indicate that both altered cytosines and thymines may be important DNA lesions requiring repair after exposure to gamma radiation.

Base Sequence↗
PubMed1984

Tissue morphology of Histoplasma capsulatum in acute histoplasmosis.

Reports of histopathology in acute histoplasmosis are rare. A case of fulminating acute histoplasmosis with hematogenous dissemination is described in which Histoplasma capsulatum was identified in transbronchial biopsy. This report represents the first morphologic description of H. capsulatum within human pulmonary tissue in the early phase of acute histoplasmosis. The yeast forms observed were of typical size, but they were present within the alveoli and were budding. No tissue granulomata were noted. This unusual morphology is in sharp contrast to the classic description of the organism in tissues and presented diagnostic difficulties, which are discussed in this report. Hematogenous dissemination is considered to be an important part of the pathogenesis of the disease, but it is rarely documented during the symptomatic phase of acute histoplasmosis. Cultural documentation of hematogenous dissemination was obtained in this patient. These observations stress the importance of obtaining culture material from extrapulmonary sites early in the course of acute histoplasmosis when a specific diagnosis is necessary.

Acute Disease↗
PubMed1981

Molecular mechanisms of pyrimidine dimer excision in Saccharomyces cerevisiae: incision of ultraviolet-irradiated deoxyribonucleic acid in vivo.

A group of genetically related ultraviolet (UV)-sensitive mutants of Saccharomyces cerevisiae has been examined in terms of their survival after exposure to UV radiation, their ability to carry out excision repair of pyrimidine dimers as measured by the loss of sites (pyrimidine dimers) sensitive to a dimer-specific enzyme probe, and in terms of their ability to effect incision of their deoxyribonucleic acid (DNA) during post-UV incubation in vivo (as measured by the detection of single-strand breaks in nuclear DNA). In addition to a haploid RAD(+) strain (S288C), 11 different mutants representing six RAD loci (RAD1, RAD2, RAD3, RAD4, RAD14, and RAD18) were examined. Quantitative analysis of excision repair capacity, as determined by the loss of sites in DNA sensitive to an enzyme preparation from M. luteus which is specific for pyrimidine dimers, revealed a profound defect in this parameter in all but three of the strains examined. The rad14-1 mutant showed reduced but significant residual capacity to remove enzyme-sensitive sites as did the rad2-4 mutant. The latter was the only one of three different rad2 alleles examined which was leaky in this respect. The UV-sensitive strain carrying the mutant allele rad18-1 exhibited normal loss of enzyme-sensitive sites consistent with its assignment to the RAD6 rather than the RAD3 epistatic group. All strains having mutant alleles of the RAD1, RAD2, RAD3, RAD4, and RAD14 loci showed no detectable incubation-dependent strand breaks in nuclear DNA after exposure to UV radiation. These experiments suggest that the RAD1, RAD2, RAD3, RAD4 (and probably RAD14) genes are all required for the incision of UV-irradiated DNA during pyrimidine dimer excision in vivo.

DNA Repair↗
PubMed1979

Gentamicin failure in staphylococcal bacteremia.

Gentamicin has been relied upon in some antibiotic combinations against Staphylococcus aureus, should it be present. Reported is a case of Staphylococcus aureus bacteremia treated inadvertently by gentamicin, and the gentamicin failed.

Drug Resistance, Microbial↗
PubMed1978

Removal of pyrimidine dimers from Saccharomyces cerevisiae nuclear DNA under nongrowth conditions as detected by a sensitive, enzymatic assay.

A sensitive and quantitative procedure for the detection of pyrimidine dimers in yesast nuclear DNA is described. The assay employs dimer-specific, endonuclease activities from Micrococcus luteus together with DNA sedimentation through calibrated, alkaline sucrose gradients to detect endonuclease-induced, single-strand breaks. Breaks were induced in a dose-dependent manner from 0 to 80 J m-2 at 254 nm and in numbers equivalent to the numbers of dimers induced by similar doses (Unrau et al., Biochim. Biophys. Acta, 312 (1973) 626--632). This procedure also allows the use of [6-3H] uridine to label cellular nucleic acids, but dose not require extensive DNA purification to eliminate concomitantly labeled RNA. Endonuclease-sensitive sites in the wild-type, haploid strain S288C, after irradiation with 5 J m-2 (254 nm), were removed in less than 5 min when cells were incubated in buffer (pH 7.0) at 28 degrees C. After irradiation with doses from 30 to 100 Jm-2 site removal in S288C required longer postirradiation incubations and was about 90% complete. In a radiation-sensitive strain carrying the mutant allele rad4-3 the number of endonuclease-sensitive sites remained constant for 6 h after irradiation with 5 Jm-2. The retention of sites in this strain indicates that it is defective in the excision of pyrimidine dimers.

Centrifugation, Density Gradient↗