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Biomedical subjects

C W Radcliffe

Publications and source records attributed to C W Radcliffe.

17 recordsLinked to original sources
PubMed1989

Characterization and localization of phosphatidylglycerophosphate and phosphatidylserine synthases in Rhodobacter sphaeroides.

Catalytic properties and membrane associations of the phosphatidylglycerophosphate (PGP) and phosphatidylserine (PS) synthases of Rhodobacter sphaeroides were examined to further characterize sites of phospholipid biosynthesis. In preparations of cytoplasmic membrane (CM) enriched in these activities, apparent Km values of PGP synthase were 90 microM for sn-glycerol-3-phosphate and 60 microM for CDP-diacylglycerol; the apparent Km of PS synthase for L-serine was near 165 microM. Both enzymes required Triton X-100 with optimal PS synthase activity at a detergent/CDP-diacylglycerol (mol/mol) ratio of 7.5:1.0, while for optimal PGP synthase, a range of 10-50:1.0 was observed. Unlike the enzyme in Escherichia coli and several other Gram-negative bacteria, the PS synthase activity had a specific requirement for magnesium and was tightly associated with membranes rather than ribosomes in crude cell extracts. Sedimentation studies suggested that the PGP synthase was distributed uniformly over the CM in both chemoheterotrophically and photoheterotrophically grown cells, while the PS synthase was confined mainly to a vesicular CM fraction. Solubilized PGP synthase activity migrated as a single band with a pI value near 5.5 in a chromato-focusing column and 5.8 on isoelectric focusing; in the latter procedure, the pI was shifted to 5.3 in the presence of CDP-diacylglycerol. The PGP synthase activity gave rise to a single polypeptide band in lithium dodecyl sulfate-polyacrylamide gel electrophoresis at 4 degrees C.

CDPdiacylglycerol-Serine O-Phosphatidyltransferase↗
PubMed1986

The University of California Biomechanics Laboratory four-bar polycentric knee linkage. A clinical trial in 20 active above-knee amputees.

A four-bar polycentric prosthetic knee linkage developed by the University of California Biomechanics Laboratory (UCBL) was tested clinically in 20 active veteran above-knee amputees. The mean follow-up period was 12.3 months. At final follow-up evaluation, positive subjective responses were reported by 80% of the amputees. More than one-third reported that the device was superior to any that they had used previously. Almost all subjects found that prior levels of daily activity and the ability to perform specific activities were maintained or enhanced. The increase in knee flexion afforded by the mechanism was found to be an advantage. There was no significant change in various fundamental gait parameters. Problems caused by excessive wear of anodized aluminum linkage pins and by air leaks in the pneumatic swing-phase control unit were corrected easily. These preliminary results encourage further clinical application and study of the UCBL four-bar polycentric knee.

Adult↗
PubMed1985

Sites of phospholipid biosynthesis during induction of intracytoplasmic membrane formation in Rhodopseudomonas sphaeroides.

A rapid, gratuitous and cell-division uncoupled induction of intracytoplasmic photosynthetic membrane formation was demonstrated in low-aeration suspensions of chemotrophically grown Rhodopseudomonas sphaeroides. Despite a nearly 2-fold increase in phospholipid levels, no significant increases were detected in the specific activities of CDP-1,2-diacyl-sn-glycerol:sn-glycerol-3-phosphate phosphatidyltransferase (phosphatidylglycerophosphate synthase, EC 2.7.8.5) and CDP-1,2-diacyl-sn-glycerol:L-serine O-phosphatidyltransferase (phosphatidylserine synthase, EC 2.7.8.8), the first committed enzymes of anionic and zwitterionic phospholipid biosyntheses, respectively. The distribution of phosphatidylglycerophosphate and phosphatidylserine synthase activities after rate-zone sedimentation of cell-free extracts indicated that intracytoplasmic membrane phospholipids were synthesized mainly within distinct domains of the conserved cytoplasmic membrane. Labeling studies with 32Pi and L-[3H]phenylalanine suggested that preexisting phospholipid was utilized initially as the matrix for insertion of intracytoplasmic membrane protein that was synthesized and assembled de novo during induction.

CDPdiacylglycerol-Serine O-Phosphatidyltransferase↗
PubMed1979

Asparaginase production by human clinical isolates of Vibrio succinogenes.

Three human isolates of Vibrio succinogenes produced asparaginase. Apparent Km's were 87,220, and 320 microM. The rate of glutamine hydrolysis was between 2.8 and 3.5% of the rate of asparagine hydrolysis. Asparaginase production was not induced by ammonium ions, and enzyme yields were lower than those obtained with the rumen strain.

Asparaginase↗
PubMed1978

Predicting metabolic cost of level walking.

Energy expenditure in walking is usually expressed as a function of walking speed. However, this relationship applies only to freely adopted step length-step rate patterns. Both the step length and the step rate must be used to preduct the energy expenditure for any combination of step length and step rate. Evidence on seven subjects indicates that the energy demand for such a combination can be determined by conducting two experiments. In the first, the subject is allowed to freely choose his own walking pattern to achieve a set of prescribed speeds. In the second, the speed is kept constant but the subject is forced to adopt a range of prescribed step rates. The results of the two experiments combined yield enough data to make possible the determination of the energy equation of the pattern, encompassing both "free" and "forced" gaits. Results show that the freely chosen step rate requires the least oxygen consumption at any given speed. Any other forced step rate at the same speed increases the oxygen cost over that required for the "free" step rate.

Adult↗