Biomedical subjects
R Davidson
Publications and source records attributed to R Davidson.
Casualty room presentations and schoolboy rugby union.
For eight years a casualty station has been operating during competition Rugby Union matches at a large Sydney School. During this time, both diagnosis and treatment have been recorded for every presentation. The casualty station was attended by 556 boys over this period, and approximately 50% of these presentations were for trivial injuries. Forty-three severe injuries occurred, of which most were fractures. The rate of presentation, and the pattern of injury, changed as a greater number of both minor and major injuries than did visitors. There was one injury in boys less than 12 years old, and the greatest incidence of injury was in boys aged from 16 to 18 years. It is concluded that there is a place for casualty services at schoolboy competition games, and that the supervised Rugby Union played in this and comparative school competitions is a reasonably safe game for boys less than 16 years old, to whom issues of schoolboy participation are most applicable.
Defect in biosynthesis of the linkage unit between peptidoglycan and teichoic acid in a bacteriophage-resistant mutant of Staphylococcus aureus.
The biosynthesis of the linkage region between peptidoglycan and the ribitol teichoic acid was investigated in the bacteriophage-resistant, teichoic acid-less mutant Staphylococcus aureus 52A5 (Chatterjee et al., J. Bacteriol. 100:846--853, 1969). Membrane preparations of this strain were found to be incapable of forming the first intermediate of the biosynthetic pathway, namely, the transfer of N-acetyl-D-glucosamine (GlcNAc) from UDP-GlcNAc to the acceptor molecule, which presumbably is undecaprenol phosphate (R. Bracha and L. Glaser, Biochem. Biophys. Res. Commun. 72:1091--1098, 1976). The addition of heat-inactivated membrane preparations of S. aureus 52A2 (which normally has ribitol teichoic acid) that had been preincubated with UDP-GlcNAc to membranes of strain 52A5 enabled the synthesis of teichoic acid. These data suggest that the mutational defect in the teichoic acid-less organism is in the synthesis of the first compound of the linkage unit, and this is apparently the reason for its absence in the cell walls.
Aspergillus oryzae acid proteinase. Purification and properties, and formation of pi-chymotrypsin.
An acid proteinase from Aspergillus oryzae was isolated from a commercial powder by successive (NH4)2SO4 fractionation, acetone precipitation, and ion-exchange chromatography on phosphate- and DEAE-cellulose columns. The purified enzyme was found to be homogeneous by ultracentrifuge-sedimentation analysis (S20, W equal 3.63S), but electrofocusing in polyacrylamide gels and electrophoresis at pH 3.2 revealed that it consists of two very closely migrating bands. No difference in the amino acid composition and enzymic activities of the two partially separated bands could be detected, and it was concluded that the acid proteinase exists in two molecular forms. The enzyme activates bovine trypsinogen and chymotrypsinogen at pH 3.5 (the kappacat. and Km values at 35degrees C are 11.3S- minus 1, 0.10mM and 1.14S- minus 1, 0.18mM respectively). It hydrolyses the Phe-Phe bond of the synthetic pepsin substrates Z-His-Phe-Phe-OEt (kappacat. equal 1.65S- minus 1, Km equal 0.640mM at pH 3.5, 30degrees C) and Z-Ala-Ala-Phe-Phe-OPy4Pr (kappacat. equal 0.37S- minus 1, Km equal 0.037 mM at pH2.9, 39degrees C), where Z represents benzyloxycarbonyl and OPy4Pr represents 3-(4-pyridyl)-propyl 1-ester. Activation of bovine chymotrypsinogen results from the cleavage of the Arg(15)-Ile(16) bond in the zymogen. No other cleavages were observed. The use of A. oryzae proteinase provides a simple tool for the production of pi-chymotrypsin in good yield and purity.
Serratia bacteremia from mean arterial pressure monitors.
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Disturbed behaviour in the older patient.
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Neurologic manifestations of embryonal rhabdomyosarcoma of the middle ear cleft.
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Factors influencing the "effective mating rate" of mammalian cells.
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Regulation of melanin synthesis in mammalian cells, as studied by somatic hybridization. 3. A method of increasing the frequency of cell fusion.
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Interactions between genomes in somatic cell hybrids: studies on the regulation of differentiation.
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Regulation of melanin synthesis in mammalian cells, as studied by somatic hybridization. I. Evidence for negative control.
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Regulation of melanin synthesis in mammalian cells, as studied by somatic hybridization. II. The level of regulation of 3,4-dihydroxyphenylalanine oxidase.
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Managing by objectives.
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Ophthalmological use of osmotic therapy.
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Titanium elastic nails for pediatric femur fractures: a multicenter study of early results with analysis of complications.
Titanium elastic nailing is used instead of traction and casting in many European centers, but limited availability has prevented widespread use in North America. Before a planned general release in America, titanium elastic nails (TENs) were trialed at several major pediatric trauma centers. This multicenter study is a critical analysis of early results and complications of the initial experience. Overall, TENs allowed rapid mobilization with few complications. The results were excellent or satisfactory in 57 of the 58 cases. No child lost rotational alignment in the postoperative period. Irritation of the soft tissue near the knee by the nail tip occurred in four patients, leading to a deeper infection in two cases. As indications, implantation technique, and aftercare are refined, TENs may prove to be the ideal implant to stabilize many pediatric femur fractures, avoiding the prolonged immobilization and complications of traction and spica casting.