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Biomedical subjects

W J Collins

Publications and source records attributed to W J Collins.

At least 19 recordsLinked to original sources
PubMed1996

Directed mutagenesis of the Rhodobacter capsulatus puhA gene and orf 214: pleiotropic effects on photosynthetic reaction center and light-harvesting 1 complexes.

Rhodobacter capsulatus puhA mutant strains containing either a nonpolar, translationally in-frame deletion or a polar insertion of an antibiotic resistance cartridge were constructed and evaluated for their photosynthetic growth properties, absorption spectroscopy profiles, and chromatophore protein compositions. Both types of mutants were found to be incapable of photosynthetic growth and deficient in the reaction center (RC) and light-harvesting 1 (LH1) complexes. The translationally in-frame puhA deletion strains were restored to the parental strain phenotypes by complementation with a plasmid containing the puhA gene, whereas the polar puhA mutants were not. Analogous nonpolar and polar disruptions of orf 214 (located immediately 3' of the puhA gene) were made, and the resultant mutant strains were evaluated as described above. The strain containing the nonpolar deletion of orf 214 exhibited severely impaired photosynthetic growth properties and had greatly reduced levels of the RC and LH1 complexes. Complementation of this strain with a plasmid that expressed orf 214 from the nifHDK promoter restored photosynthetic growth capability, as well as the RC and LH1 complexes. The polar disruption of orf 214 yielded cells that were incapable of photosynthetic growth and had even lower levels of the RC and LH1 complexes, and complementation in trans with orf 214 only marginally improved these deficiencies. These results indicate that orf 214 and at least one additional gene located 3' of orf 214 are required to obtain the RC and LH1 complexes, and transcription read-through from the puhA superoperon is necessary for optimal expression of these new photosynthesis genes.

Amino Acid Sequence↗
PubMed1993

Pilot clinical study of a fluoride resin and conditioning paste for desensitising dentine.

The clinical trial was carried out on 34 'hypersensitive' teeth in 10 subjects. Dentine sensitivity was measured as the pain perception thresholds to controlled air and probe stimuli. In each subject, pairs of teeth of comparable initial sensitivity were randomly assigned to a test (T) or control (C) treatment. All teeth were cleaned and a conditioning paste applied. Group T was treated with a topically-applied light-cured resin; Group C received a placebo, sham light-cured. Air sensitivity was remeasured after treatment, and the procedures were repeated after 1, 2, and 3 weeks. When comparing air thresholds before and after treatment at each visit, the test agent caused significantly greater reduction in sensitivity than the control. The median increase in air threshold in the test group was 2.5 s at visit no. 1, 1.3 s at visit no. 2 and 0.8 s at visit no. 3. Comparisons of the initial thresholds at each visit showed no significant long-term changes in sensitivity in either group.

Administration, Topical↗
PubMed1987

Thresholds of hypersensitive teeth to 2 forms of controlled stimulation.

2 new methods are described for measuring the sensitivity of dentine to mechanical (probe) and cold-air stimulation. The methods are suitable for clinical use and could be used in the evaluation of desensitising treatments. In addition to qualitative differences in the pattern of sensitivity of teeth to these stimuli, considerable variation was observed in the distribution of pain thresholds to probe and air stimulation. Thresholds were not significantly affected by the age or sex of the subjects, but mean thresholds of teeth sensitive to only one stimulus were significantly greater than thresholds of teeth sensitive to both stimuli; these differences were most marked in female subjects. Factors such as the qualitative differences in sensitivity to various stimuli and quantitative differences in the degree of sensitivity to the stimuli require to be considered in clinical evaluation of desensitizing treatments.

Adolescent↗
PubMed1984

Instrumentation for measurement of dental plaque thickness in situ.

A commercial digital micrometer has been modified mechanically and electronically to allow the measurement, in situ, of the thickness of dental plaque. The device detects initial contact between a moving probe and the plaque, and measures subsequent probe displacement through to the tooth surface. Instrument accuracy is +/- 5 micron over a displacement range of 0-5 mm, with 1 micron resolution. In practice, after a short 'learning' phase, reliable clinical results can be obtained.

Biomedical Engineering↗
PubMed1979

Diels-Alder adducts of fulvenes and halogenated dienes. Synthesis and insecticidal activity.

A series of eight adducts (1--8) of substituted fulvenes and polychlorinated cyclodienes was synthesized by Diels-Alder cyclization. The products isolated were the endo bicyclo adducts as determined by detailed 1H and 13C NMR spectral analysis. Steric hindrance of end-product bridge substituents coupled with bulky substituents at C6 of the fulvenes led to one isomeric product in most cases. Compounds 1--8 demonstrated weak insecticidal action in Musca domestica as determined by topical LD50 and oral LC50 assays.

Animals↗
PubMed1979

Pulmonary vasculitis complicating childhood ulcerative colitis.

A case of pulmonary vasculitis complicating ulcerative colitis is presented, and the literature is reviewed. Unexplained pulmonary problems complicating severe ulcerative colitis should prompt a review of rare etiologies to include pulmonary vasculitis, apical pulmonary fibrosis, and salicylazosulfapyridine-induced lung disease. Lung biopsy will establish a diagnosis of pulmonary vasculitis.

Age Factors↗