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Biomedical subjects

J H Powell

Publications and source records attributed to J H Powell.

30 records · Page 2Linked to original sources
PubMed1992

Photographic cockpit model for prescribing multifocals.

Recent interest in the relevancy of near vision tests for presbyopic aircrew members has led to the development of a photographic cockpit model. This model is used to prescribe more accurately for flying personnel. Prescriptions can be evaluated by use of trial lenses. This allows the aircrew members to experience the effect of viewing instruments in the cockpit of a C-130 aircraft.

Aircraft↗
PubMed1991

Effects of venous hypertension on rabbit free flap survival.

A two-stage project was developed to study the effect of increased venous pressure on blood flow and survival in microvascular free tissue transfers. A rabbit epigastric fasciocutaneous free flap model was used. The blood flow in the rabbit epigastric free flap is 1.07 +/- 0.06 ml/min. The average venous pressure is 8.6 +/- 1.7 cm water. A logarithmic relationship between blood flow and venous pressure was demonstrated, with a statistically significant decrease in blood flow to 20-35% of the control values when the venous pressure rose above 28-30 cm water. This study stands in support of the tolerance by free tissue transfers of pressures below this range. The results further show a positive correlation between increasing venous pressure and free flap failure.

Animals↗
PubMed1991

Antipyretic activity of tebufelone (NE-11740) in man.

Tebufelone (formerly NE-11740) is a member of the new class of di-tert-butyl-phenol anti-inflammatory agents. It has previously been reported that this new agent has potent analgesic, antipyretic, and anti-inflammatory effects using in vitro, in vivo, and ex vivo experimental models. A randomized, active- and placebo- controlled double-blinded study in 120 healthy males, 20 to 55 years old, was conducted to clinically assess tebufelone's antipyretic activity. Subjects received a single peroral dose of placebo, 650 mg aspirin (ASA), or tebufelone at doses of 25, 50, 100, or 200 mg. Thirty minutes later, E. coli endotoxin (2 ng/kg) was administered intravenously. Oral temperatures were recorded at 15 minute intervals from 30 minutes post dosing to 8 hours post endotoxin administration. Areas under the temperature curves (AUCs), adjusted for baseline, were significantly lower than placebo for ASA and all but the 25 mg tebufelone groups. An AUC dose-response equation estimates 60 mg tebufelone as equivalent to 650 mg ASA, with 50 mg tebufelone not significantly greater than 650 mg ASA. Side effects, attributable to the endotoxin, included mild flu-like symptoms and were worse in the placebo group and the non-efficacious 25 mg tebufelone group. Doses of 100 and 200 mg tebufelone had onset characteristics indistinguishable from 650 mg ASA, whereas 50 mg tebufelone showed significantly slower onset while suppressing temperature for a longer period than ASA. These results provide an important early demonstration of tebufelone's biological activity in man.

Adult↗
PubMed1990

Application of liquid chromatography with on-line radiochemical detection to metabolism studies on a novel class of analgesics.

Vanilloids are a class of compounds structurally related to capsaicin, the pungent principle of hot peppers, which are under development as a novel class of analgesics. Vanilloids undergo extensive first-pass metabolism when dosed orally to rats and mice. These compounds, as well as capsaicin, would be anticipated to be susceptible to three major routes of metabolism: (omega, beta)-oxidation of the alkyl side chain, hydrolysis of the amide bond and conjugation of the phenolic group. Olvanil [N-(3-methoxy-4-hydroxybenzyl)oleamide], radiolabelled with either 14C at the benzylic carbon or 3H in the oleyl side chain, was studied in various in vitro, in situ and in vivo metabolism models to determine the major route(s) of intestinal and hepatic metabolism in rats for this new class of compounds. Models used in metabolism studies included isolated hydrolytic enzymes, cell-free intestinal and liver supernatants, hepatocytes, enterocytes, perfused intestine and whole animal studies. Reversed-phase liquid chromatography (LC) with on-line radiochemical detection was used to examine the metabolic profiles from the different models. The major metabolic route for olvanil in both the intestine and the liver was found to be hydrolysis of the amide bond. The benefits of selective 14C and 3H labels in conjunction with LC with on-line radiochemical detection are discussed.

Analgesics↗
PubMed1989

The reflective practitioner in nursing.

This work is a study of eight practising registered nurses and their use of reflection-in-action in their everyday work. Schon's work on reflection-in-action forms the theoretical basis, and the research tool uses the work of Mezirow and Lazzara's use of Colaizzi's reduction. The findings are that, of the sample used, reflection-in-action is present extensively in the form of description and of planning of actions, but to a much lesser extent in the area of recognition of value judgements and the areas of reflection-in-action leading to learning taking place. Where these were present, albeit in small quantities, they were almost exclusively confined to the community nurses and the nurse practitioner. The tool also helped determine whether or not practice was founded on the use of nursing research and/or that of other disciplines. In the nurses studied here, this was somewhat erratic. With changes in technology, social and environmental changes, and the advancement of nursing and social science research, it is important for registered nurses to be able to both learn from their everyday work and use knowledge from nursing and other disciplines in this, rather than, as is demonstrated here, separate theory from practice and be relatively unable to learn from their work. In view of the changes presently proposed in nurse education, this work has implications for nurse educators as well as for practising nurses.

Awareness↗
PubMed1986

Techniques of wrist arthroscopy.

Wrist arthroscopy is a promising new technique for the evaluation of wrist pain or dysfunction. Cadaveric wrist specimens were used to devise safe and advantageous entry portals for arthroscopy and to establish respective advantages for each portal. Thirty-five clinical cases were used to correlate the laboratory experience and to refine a reproducible surgical technique. Seven portals are useful: five in the radiocarpal interval, one in the midcarpal area, and one in the distal radioulnar joint space. Detailed wrist anatomy is reviewed in this paper and must be thoroughly understood to interpret arthroscopic views. Blunt subcutaneous dissection protects cutaneous nerve branches at the various portals. Intraoperative photographs illustrate the excellent perspectives achieved using these techniques.

Arthroscopy↗
PubMed1986

Osteochondritis dissecans of the talus.

Osteochondritis dissecans of the body of the talus is a common entity; however, osteochondritis dissecans of the head of the talus has not been found in the orthopaedic literature. The authors report a case of a defect in the talar head following trauma to the ankle, which has radiographic characteristics of osteochondritis dissecans.

Adolescent↗
PubMed1984

In vitro response of hepatic lysosomes to endogenous and exogenous cationic compounds.

An investigation of the effect of four cationic compounds on rat liver lysosomes was carried out. Lysosomes from homogenized rat liver were isolated by differential centrifugation at 0-5 degrees C in 0.3 M sucrose. These lysosomes were then incubated for 1 hr at 37 degrees C in 0.25 M glycine solution containing widely varied concentrations of the test agent. The lysosomes were resedimented and the N-acetyl-beta-glucosaminidase (NAG) activity was measured in the supernatant and in the remaining pellet after disruption. Spermine, ferric ion, mepacrine, and gentamicin all produced dose-dependent effects on these lysosomes. Low concentrations of these compounds inhibited the release of NAG into the supernatant while high concentrations enhanced the release of NAG. This effect of these cationic compounds on the lysosomal membrane may be a mechanism by which they produce cellular toxicity with the organ or tissue selectivity being related to the distribution of the cation.

Acetylglucosaminidase↗
PubMed1983

Further studies of the response of kidney lysosomes to aminoglycosides and other cations.

Rat renal cortical lysosomes were isolated in 0.3 M sucrose containing 1 mM EDTA by differential centrifugation. Lysosomes were incubated in isotonic sucrose or isotonic glycine with various concentrations of endogenous and exogenous compounds at 37 degrees for 1 hr. Lysosomes were resedimented, and the N-acetyl-beta-glucosaminidase (NAG) activity was measured in the supernatant fraction and the disrupted pellet and the percentage of total NAG released was calculated. Gentamicin and its C1 and C2 components had similar potencies for inhibiting NAG release from lysosomes at low concentrations. The release of alpha-galactosidase and beta-galactosidase from lysosomes was also inhibited by streptomycin and gentamicin. Mepacrine at low concentrations stabilized lysosomes and at high concentrations disrupted lysosomes. This drug also enhanced the effect of low concentrations of gentamicin on lysosomes. Inositol hexaphosphoric acid was a potent antagonist of the effect of low concentrations of gentamicin and mepacrine on lysosomes. Rats were treated with gentamicin at doses of 40, 80 and 160 mg/kg for 1 and 3 days. NAG excretion in gentamicin-treated groups as compared to saline controls was unchanged at day 1. Only the 160 mg/kg treatment group showed a tendency toward elevated renal cortical NAG at day 1 (P less than 0.06). All treatment groups had elevated renal cortical NAG at day 3, while the 160 mg/kg group also had elevated NAG excretion. Lysine, arginine, L-canavanine and polymyxin B all affected NAG release from lysosomes in vitro. Lysine enhanced the disruptive effect of high gentamicin concentrations on lysosomes. Ferric and ferrous ions, tested over widely varied concentrations, inhibited NAG release at low concentrations while enhancing NAG release at high concentrations. We therefore conclude that the nephrotoxicity of aminoglycoside and other endogenous and exogenous renally excreted cationic compounds may be produced by their effects on lysosomes in the proximal renal tubule.

Acetylglucosaminidase↗