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Biomedical subjects

W D Rupp

Publications and source records attributed to W D Rupp.

11 recordsLinked to original sources
PubMed1979

Potential radiosensitizing agents. Dinitroimidazoles.

New compounds of the nitroimidazole series have been synthesized as radiosensitizers which selectively sensitize hypoxic cells to the lethal effect of radiation. The reaction of 2,4(5)-dinitroimidazole (2) with chloroethanol or hydrochloric acid yielded 4(5)-nitro-5(4)-chloroimidazole (3), which upon reaction with ethylene oxide yielded the 4-nitro-5-chloroimidazole-1-ethanol (6). Reaction of 2 with ethylene oxide resulted in a mixture of two compounds, the 2,4-dinitroimidazole-1-ethanol (4) and 2,3-dihydro-5-nitroimidazo[2,1-b]oxazole (5). The structure of the new heterocyclic compound 5 was confirmed by 1H NMR, mass spectrum, and X-ray crystallography. These agents were tested for their ability to sensitize hypoxic Escherichia coli cells to killing by ionizing radiation. Compound 4 was found to be the most active agent of this series of compounds.

Chemical Phenomena↗
PubMed1979

Physical map of the recA gene.

We have cloned the recA gene of Echerichia coli K12 and some of its restriction fragments on the plasmid cloning vehicle pBR322. The recA gene was mapped with regard to the restriction sites of EcoRI, BamHI, Pst I, Hha I, Hae III, HinfI, and Taq I restriction endonucleases. The recA promoter was localized by the binding of RNA polymerase to restriction fragments. The initiation point of transcription of recA mRNA and the direction of transcription were determined from in vitro transcription of recA gene fragments and from analysis of the polypeptides made in maxicells that contain plasmids carrying only part of the recA gene.

Bacterial Proteins↗
PubMed1979

Simple method for identification of plasmid-coded proteins.

Proteins encoded by plasmid DNA are specifically labeled in UV-irradiated cells of Escherichia coli carrying recA and uvrA mutations because extensive degradation of the chromosome DNA occurs concurrently with amplification of plasmid DNA.

Bacterial Proteins↗
PubMed1978

Hypoxic radiosensitizers: prospects for effective compounds with fewer toxic side-effects.

Several radiosensitizing chemicals, including a family of simple nitroimidazoles, were examined in E. coli and compared with misonidazole for toxic side-effects on endpoints such as mutagenesis, cell killing and inhibition of the synthesis of the inducible enzyme beta-galactosidase. While all the compounds were similar to misonidazole or better in radiosensitization, marked differences in the various side effects were found. There results show that for E. coli it is possible to find compounds that sensitize as well as misonidazole but which have decreased mutagenicity and fewer other side-effects. Of the compounds examined, KA121 (2,5-dinitroimidazole) is the most promising for future study because it combines good radiosensitization with low mutagenicity and toxicity.

Escherichia coli↗
PubMed1975

Recombination and postreplication repair.

The available data concerning postreplication repair are summarized. In Escherichia coli, recombination is implicated in this repair because the recA+ gene is necessary and because strand exchanges occur that extend over long regions. Other experiments involving phage-induced resistance also point to an interrelation between recombination and repair. In this phenomenon, gene products of lambda bacteriophage are introduced into bacteria, resulting in an increased resistance of the cells when they are subsequently exposed to X rays.

Cell Survival↗
PubMed1975

DNA strand breaks measured within 100 milliseconds of irradiation of Escherichia coli by 4 MeV electrons.

A method was developed in which E. coli cells were irradiated with four MeV electrons and transferred to alkaline detergent within a fraction of a second. This technique minimizes the amount of repair of radiation damage before analysis without the necessity of using physical or chemical treatments to inhibit repair and alter the physiological condition of the cells. The yield of DNA strans breaks formed in covalent circular superhelical lambda DNA molecules superinfecting E. coli lysogens was about 4-fold greater when the cells were irradiated in oxygen than when they were irradiated under nitrogen anoxia. The same yields were obtained in phosphate buffer at 3 degrees and 22 degrees as well as in growth medium at 37 degrees, and the yields were not altered by the polA1 mutation. When E. coli lysogenic cells superinfected with lambda were irradiated with doses sufficient to introduce at least seven breaks in the phage DNA, the chromosomal DNA and the superinfecting phage DNA sedimented similarly in alkaline sucrose gradients, indicating that both DNAs were broken to a similar extent during irradiation. However, the yield of breaks calculated for chromosomal DNA in similar experiments was greater than the yield calculated from the first break introduced into covalent circular lambda DNA molecules. These apparently contradictory results are explicable either if the initial break in a superhelical molecule occurs with an efficiency different from that for subsequent breaks, or if the pulsed electron radiation produces a high proportion of double-strand breaks.

Centrifugation, Density Gradient↗
PubMed1975

Lambda bacteriophage gene produces and X-ray sensitivity of Escherichia coli: comparison of red-dependent and gam-dependent radioresistance.

When gene products of lambda bacteriophage are introduced into a cell by transient induction of a lysogen, increased resistance of the cells to X rays results. This phenomenon has been called phage-induced radioresistance. Genetic studies show at least two classes of induced radioresistance. The first type depends on the products of the lambda red genes and is observed in bacteria that are mutated in the recB gene. It is thought that the lambda red products compensate for the missing RecBC nuclease in the repair of X-ray damage. An optimal effect is obtained even when the lambda red products are supplied 1 h after irradiation. The lesions that are affected by the red-dependent process are probably not deoxyribonucleic acid strand breaks because the extent of deoxyribonucleic acid strand rejoining is not altered by the red products. The second type of phage-induced radioresistance requires the gam product of lambda and is observed in wild-type and polA strains. The lambda gam+ gene produce must be present immediately after irradiation to exert its full effect. In its presence, DNA breakdown is decreased, and a greater fraction of DNA is converted back to high molecular weight. Strains carrying lex, recA, or certain other combinations of mutations do not show any detectable phage-induced radioresistance.

Coliphages↗
PubMed1975

Biochemically aberrant Salmonella enteritidis ser. newington from human sources in Connecticut.

Three isolates of a lactose-fermenting, xylose-negative variety of Salmonella enteritidis ser. newington, identical in biochemical and serological reactions and in the antibiogram, were recovered from three patients in different areas of Connecticut in January 1974. Hydrogen sulfide production was not visible in Salmonella-Shigella agar, in triple sugar iron agar, and in Kligler iron agar but was noticed in lysine iron agar and on XLD agar, among others. The amount of fermentable carbohydrates present was found to correlate with failure to show hydrogen sulfide production (pH effect). In contrast to lactose-fermenting Salmonella strains reported by other authors, we could not elicit a direct transfer of the lac(+) character at frequencies above 10(-6). An epidemiological follow-up remained unsuccessful. Recommendations for the recognition of similar strains are presented.

Adult↗