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Biomedical subjects

W D Fraser

Publications and source records attributed to W D Fraser.

176 records · Page 10Linked to original sources
PubMed1986

Activation of complement at plasma-air or serum-air interface of rabbits.

The possibility of the air-plasma interface giving rise to complement activation is investigated. After incubation of the plasma of a group of rabbits with zymosan and measurement of the degree of autologous polymorphonuclear leukocyte aggregation that follows the injection of a sample of the incubated plasma into a leukocyte suspension, it is found that the rabbits can be divided into two groups, sensitive and insensitive, depending on the degree of leukocytes aggregation. For the sensitive group it is found that both the plasma-air interface and the serum-air interface give rise to significant leukocyte aggregation. If the animal is decomplemented before the plasma is incubated in the presence of the air interface, there is no longer any significant leukocyte aggregation. It would appear that the complement system is activated by the presence of the air interface in plasma, but that fibrinogen does not play a pivotal role in the process.

Air↗
PubMed1986

Arginine infusion blocks the action of parathyroid hormone but not arginine vasopressin on the renal tubule in man.

Six male volunteers were infused with arginine (0.5 g/kg body weight) over 30 min, after an overnight fast and water deprivation. There was a significant decrease in renal phosphate clearance (P less than 0.025) and urinary cyclic adenosine monophosphate (cAMP) output (P less than 0.025) during the 60- to 90-min period after the beginning of the infusion; both returned to the preinfusion basal levels within 150 min. The plasma levels of parathyroid hormone (PTH) were not affected by the infusion and remained unchanged during the subsequent 150 min. Plasma levels of arginine vasopressin (AVP) were also not significantly affected although plasma osmolality increased by 6-9 mmol/kg in all subjects. The infusion resulted in a diuresis, and a fall in urine osmolality but a decrease in free-water clearance; creatinine clearance was not affected. Six other subjects were given a bolus of 230 i.u. PTH intravenously, and 20 days later this was repeated during an infusion of arginine (0.5 g/kg body weight). There was a significant decrease in urinary phosphate (P less than 0.025) and cAMP excretion (P less than 0.05) when PTH was given with arginine. It is suggested that arginine blocks the action of PTH on the proximal renal tubule but not that of vasopressin on the distal nephron and collecting ducts.

Arginine↗
PubMed1983

Fracture studies on a mammalian semicircular canal.

In the present work the pressures necessary to fracture the semicircular canal of the mammalian inner ear, specifically the squirrel monkey, have been investigated experimentally. The results indicate that individual canals can fracture when subjected to internal pressures of approximately 1.6 +/- 0.4 MPa. Simulation testing using Plexiglas and polycarbonate specimens, to represent the location of a possible osteoclast site within the bone forming a semicircular canal, demonstrates further that fracture of the canal can be initiated at this or even lower pressures when the pressure is generated within a simulated osteoclast site. These results provide useful information for a better understanding of the mechanisms by which bubble nucleation and growth could cause pressures of this magnitude within an osteoclast cavity during the decompression phase of a diving schedule.

Animals↗
PubMed1982

Postural stability during slow-onset and rapid-onset hypoxia.

The standing steadiness and postural tremor of seven male volunteers were examined during slow and rapid induction of hypoxia. Spectrum analysis of position coordinates and tremor data generated from a quartz multicomponent force measuring platform and a tremor transducer showed that postural tremor (pt) and anteroposterior sway (ay) increased significantly during hypoxia. Rate of onset of hypoxia, however, did not affect the development of the increased tremor, whereas rapid-onset hypoxia consistently induced a greater anteroposterior sway than slow-onset hypoxia. Lateral sway (ax) was not affected by either slow- or rapid-onset hypoxia; however, it was significantly greater when eyes were closed compared to when they were opened. Anteroposterior sway (ay) was also significantly greater when visual cues were eliminated during both slow- and rapid-onset hypoxia. Heart rate (HR) and cardiac index (CI) of subjects increased significantly during both conditions of hypoxia.

Adult↗
PubMedDate not supplied

Multicentre collaboration in perinatal trials in Canada.

From a request of the Ministry of Health, the Canadian Association of Professors of Obstetrics and Gynecology and the Medical Research Council played a leadership role in convening perinatal investigators of all 16 university departments. The consensus was reached that the best means to improve the health of Canadians was to treat and/or prevent prematurity. In the last 10 years, several multicentre clinical trials were designed and carried out on perinatal interventions. This multicentre Canadian collaboration has recently evolved in the formation of a permanent perinatal clinical trial network of more than 100 members.

Canada↗
PubMedDate not supplied

Maintenance of vitamin and trace element status in intravenous nutrition using a complete nutritive mixture.

Complete nutritive mixtures (CNM) of all intravenous nutrients including fat emulsions are being used increasingly because of their convenience. However, this may lead to chemical interactions and reduce the amount of active vitamins and trace elements made available to the patient. We have studied the effects on micronutrient status of provision of all nutrients in one 3-liter bag (CNM: amino acids, dextrose, Intralipid 20%, a nine-element trace metal mixture, and complete fat- and water-soluble vitamin mixtures) in 10 postoperative surgical patients [median intravenous nutrition (IVN) 14.5 days, range 7-38]. A similar group received the fat emulsion plus water- and fat-soluble vitamins as a separate infusion (SI) from a 3-liter bag (median IVN 14.0 days, range 8-28). Serum and urine magnesium, zinc, copper, manganese, chromium, and selenium, serum vitamins A, E, C, folate, and B12, RBC B1, B2 B6, and folate and leukocyte vitamin C were measured at weekly intervals. All patients in both groups maintained or improved their status for all the micronutrients analyzed. No significant differences between the CNM and SI groups were found in blood concentrations of any of the elements or vitamins. Only for urine copper did the CNM lead to increased excretion (1.51 +/- 0.59 mumol/24 hr; copper input 20 mumol/day), compared to SI (1.00 +/- 0.70 mumol/day, p less than 0.001 Mann-Whitney test) suggesting possible interaction. It is concluded that micronutrient status was maintained during short-term IVN with the CNM and that it did not lead to a significantly greater loss of vitamins or essential trace elements than the SI system.

Adult↗
PubMedDate not supplied

Semicircular canal fractures in squirrel monkeys resulting from rapid decompression. Interpretation and significance.

A recent histological study of monkeys rapidly decompressed from deep dives has revealed that, in some cases, there are fractures of the bone surrounding the semicircular canals. In some monkeys sacrificed within a few days of their dives, there are full thickness breaks across the bony canal walls. In others, sacrificed several months after a dive, these fractures have become infiltrated by the ectopic growth of new bone which also invades the otic fluid spaces. It now appears that the new bone growth is caused not only by a ripping or irritation of the endosteum, which lines the inside of the bony canals, but also, at least in some cases, by a rupturing of the very hard petrous bone itself. It is difficult to avoid the conclusion that, somehow, large forces are developed within the inner ear or within the petrous bone during decompression.

Animals↗
PubMedDate not supplied

Cost-effectiveness of midwifery services vs. medical services in Quebec. LEquipe dEvaluation des Projets-Pilotes Sages-Femmes.

This study compared the cost-effectiveness of midwife services provided in birth centres operating as pilot projects with current hospital-based medical services in the province of Quebec. One thousand midwives' clients were matched with 1,000 physicians' clients on the basis of socio-demographic characteristics and obstetrical risk. Direct costs for the prenatal, intrapartum and postpartum periods were estimated. Effectiveness was assessed on the basis of three clinical indicators and four indices related to the individualization of care as assessed by women. Results show that the costs of midwife services were barely lower than or equal to those of physician services, but cost-effectiveness ratios were to the advantage of the midwife group, except for one clinical indicator (neonatal ventilation). Overall, this study provides rational support for the process of legalizing midwifery in the province.

Birthing Centers↗