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Biomedical subjects

D L Conley

Publications and source records attributed to D L Conley.

7 recordsLinked to original sources
PubMed1995

Effects of the pSC101 partition (par) locus on in vivo DNA supercoiling near the plasmid replication origin.

Previous work has shown that deletion of the partition (par) locus of plasmid pSC101 results in decreased overall superhelical density of plasmid DNA and concommitant inability of the plasmid to be stably inherited in populations of dividing cells. We report here that the biological effects of par correlate specifically with its ability to generate supercoils in vivo near the origin of pSC101 DNA replication. Using OsO4 reactivity of nucleotides adjoining 20 bp (G-C) tracts introduced into pSC101 DNA to measure local DNA supercoiling, we found that the wild type par locus generates supercoiling near the plasmid's replication origin adequate to convert a (G-C) tract in the region to Z form DNA. A 4 bp deletion that decreases par function, but produces no change in the overall superhelicity of pSC101 DNA as determined by chloroquine/agarose gel analysis, nevertheless reduced (G-C) tract supercoiling sufficiently to eliminate OsO4 reactivity. Mutation of the bacterial topA gene, which results in stabilized inheritance of par-deleted plasmids, restored supercoiling of (G-C) tracts in these plasmids and increased OsO4 reactivity in par+ replicons. Removal of par to a site more distant from the origin decreased supercoiling in a (G-C) tract adjacent to the origin and diminished par function. Collectively, these findings indicate that par activity is dependent on its ability to produce supercoiling at the replication origin rather than on the overall superhelical density of the plasmid DNA.

Bacterial Proteins↗
PubMed1995

Isolation and characterization of plasmid mutations that enable partitioning of pSC101 replicons lacking the partition (par) locus.

Second-site mutations that allow stable inheritance of partition-defective pSC101 plasmids mapped to seven distinct sites in the 5' half of the plasmid repA gene. While the mutations also elevated pSC101 copy number, there was no correlation between copy number increase and plasmid stability. Combinations of mutations enabled pSC101 DNA replication in the absence of integration host factor and also stabilized par-deleted plasmids in cells deficient in DNA gyrase or defective in DnaA binding. Our findings suggest that repA mutations compensate for par deletion by enabling the origin region RepA-DNA-DnaA complex to form under suboptimal conditions. They also provide evidence that this complex has a role in partitioning that is separate from its known ability to promote plasmid DNA replication.

Bacterial Proteins↗
PubMed1983

Automated high-performance liquid chromatographic column switching technique for the on-line clean-up and analysis of drugs in topical cream formulations.

The automation of a high-performance liquid chromatographic column switching technique for the on-line clean-up and analysis of drug substances in topical cream formulations is described. A short reversed-phase precolumn used for primary sample clean-up was coupled to a reversed-phase analytical column. This allowed cream samples dissolved in methanol-tetrahydrofuran to be injected directly into the analysis system without prior laborious and time-consuming clean-up procedures. This application was successfully extended to the analysis of sulconazole nitrate, and a triple corticoid cream. The effects of precolumns on some chromatographic parameters were studied.

Autoanalysis↗
PubMed1980

Running economy and distance running performance of highly trained athletes.

The purpose of the study was to determine the relationship between running economy and distance running performance in highly trained and experienced distance runners of comparable ability. Oxygen uptake (Vo2) during steady-state and maximal aerobic power (Vo2max) were measured during treadmill running using the open-circuit method. Distance running performance was determined in a nationally prominent 10 km race; all subjects (12 males) placed among the top 19 finishers. The subjects averaged 32.1 min on the 10 km run, 71.7 ml.kg-1.min-1 for Vo2max, and 44.7, 50.3, and 55.9 ml.kg-1.min-1 for steady-state Vo2 at three running paces (241, 268, and 295 m.min-1). The relationship between Vo2max and distance running performance was r = -0.12 (p = 0.35). The relationship between steady-state Vo2 at 241, 268 and 295 m.min-1 and 10 km time were r = 0.83, 0.82, and 0.79 (p < 0.01), respectively. Within this elite cluster of finishers, 65.4% of the variation observed in race performance time on the 10 km run could be explained by variation in running economy. It was concluded that among highly trained and experienced runners of comparable ability and similar Vo2max, running economy accounts for a large and significant amount of the variation observed in performance on a 10 km race.

Adolescent↗