Search PubMed⌕ Search

Biomedical subjects

S White

Publications and source records attributed to S White.

At least 289 records · Page 16Linked to original sources
PubMed1979

Extracellular space of frog skeletal muscle in vivo and in vitro: relation to proton magnetic resonance relaxation times.

1. The Na and Cl distribution spaces of freshly isolated frog muscles are 16.7 and 12.6%, respectively. These values increase to 25.6 and 23.3%, respectively, on incubation. 2. The extracellular components of both Na and Cl efflux curves are significantly smaller in freshly isolated muscles (approximately 12%) than in incubated muscles (approximately 18%). The fast exchanging A component of the extracellular space is increased more by incubation than the more slowly exchanging B component. 3. The proton magnetic resonance (p.m.r.) transverse relaxation curve for the water of freshly isolated frog muscles did not show the long, slowly relaxing tail present in curves from muscles incubated in Ringer solution. 4. When muscles were incubated in hypertonic solutions the p.m.r. transverse relaxation curves could be resolved into three components whose sizes were consistent with the components present in the sodium and chloride efflux curves. The non-exponentiality of the p.m.r. transverse relaxation curve therfore appears to arise from water in both the A and B extracellular compartments of muscle. 5. Efflux analysis indicated that the cellular Na content of both freshly isolated and incubated frog muscle is similar to that predicted by others (Lev, 1964; Armstrong & Lee, 1971; Lee & Armstrong, 1974) from measurements of intracellular Na ion activity using Na-sensitive micro-electrodes. The remainder of the tissue Na was found in the more rapidly exchanging extracellular compartments. The results of these experiments are inconsistent with the presence of a substantial fraction of bound Na in frog muscle. 6. These experiments show that muscle extracellular space is smaller in vivo than in vitro. Efflux analysis is suggested as the most accurate method of assessing extra-cellular components.

Animals↗
PubMed1978

Low angle X-ray diffraction studies on stained rat tail tendons.

Low angle X-ray diffraction patterns of rat tail tendons with heavy metal stains added were examined to help clarify the effects of fixation and staining on collagen fibrils. Fixing and staining of rat tail tendon fibers gives an X-ray pattern with an intensified 3.8 nm row and the preservation of most equatorial features found in the native pattern. The presence of the native pattern features suggests the value of fixation in preserving native structure before staining. Staining of rat tail tendon fibers without prior fixation led to the disappearance of the native equatorial features and the appearance of a new broad row line corresponding to a spacing of around 10.0--17.5 nm. This observation suggests that some alteration has taken place in the native structure and may be related to electron microscopic observations of units of 10.0--20.0 nm in collagen fibrils under some disruptive or developmental conditions.

Animals↗
PubMed1978

In vivo studies with ambruticin in murine histoplasmosis.

Ambruticin (W7783) was evaluated in vivo in mice subacutely or nonlethally infected with Histoplasma capsulatum. Results were compared with those obtained with amphotericin B, the drug of choice in human histoplasmosis. In one experiment, ambruticin was shown to be capable of curing infected animals as evidenced by totally negative liver and spleen cultures obtained when mice were sacrificed after 4 weeks of oral treatment with 150 mg of drug per kg per day. The 50% cure dose for ambruticin was between 75 and 150 mg/kg per day; the 50% cure dose for oral amphotericin B in this experiment was between 1.56 and 6.25 mg/kg per day. In a second experiment, both oral ambruticin (150 mg/kg per day) and oral amphotericin B (25 mg/kg per day) were again curative, but to a lesser degree than in the first experiment. Biological cures were obtained with both drugs after 3 and 4 weeks of treatment but not after 2 weeks.

Amphotericin B↗
PubMed1976

Zinc nutrition of preschool children in the Denver Head Start program.

Low income diets provide relatively little zinc. This study was designed to evaluate the zinc nutritional states of 74 low income preschool children enrolled in the Denver Head Start Program. Zinc is necessary for normal growth, hence children were selected on the bases of low height percentiles. The mean (+/- SE) hair zinc concentration was 87.0 +/- 5.9 mug/g, and the mean plasma zinc concentration was 74.5 +/- 1.5 mug/100 ml. These levels were both lower (P is less than 0.005) than those of middle income children of similar age. Sixty-eight percent of the study group had a hair zinc concentration less than 70 mug/g and/or a plasma zinc concentration less than 68 mug/100 ml. These results indicate that inadequate zinc nutrition may be common among preschool children with low growth percentiles from low income families.

Body Height↗
PubMed1975

Central nervous system control of cardiorespiratory nasopharyngeal reflexes in the rabbit.

The role of different central nervous regions in the reflex apnea, bradycardia, and mesenteric vasoconstriction evoked by nasopharyngeal stimulation with cigarette smoke was examined in unanesthetized shamoperated, thalamic, and pontine rabbits with intact and sectioned carotid sinus and aortic nerves (CS and AN). Apnea occurred in all preparations. In pontine animals with intact CS and AN, the heart rate response was reduced but not the mesenteric vasoconstriction. The role of suprabulbar and bulbospinal regions became more apparent when individual components of the input profile were examined in animals with controlled ventilation. The bradycardia and mesenteric vasoconstriction evoked by apnea without smoke, but not by smoke without apnea, were reduced in pontine animals. Prior section of the CS and AN attenuated the response in all neural preparations but to the least extent when cerebral hemispheres were intact. The data indicate that the respiratory reflex is predominantly integrated at bulbospinal sites, but the cardiovascular reflex is integrated at both bulbospinal and suprabulbar sites, or is integrated at bulbospinal and modulated from suprabulbar sites.

Animals↗
PubMed1975

Studies on pressure-volume relationships in excised equine lungs.

Forty-eight lungs from fetal and neonatal horses were examined for pressure-volume relationships between pressures of 0 and 40 cmH2O. The inflation-deflation curves obtained were analysed by four different methods and the stability of the lung assessed in terms of hysteresis, stability indices and volume of air retained at maximal pressure (Vmax). Differences in the shape of the deflation curve between ventilated and non-ventilated lungs were similar to findings in other species. It is postulated that breathing alters lung-tissue elasticity during the neonatal period, as demonstrated by a significant increase in Vmax in specimens from foals breathing for more than 24 hr compared with those from stillborn foals or those aged less than 24 hr. Also, stability indices, such as those expressed by the % of air retained in the lungs on deflation from Vmax to 10 or 5 cmH2O pressure, are related to interfacial factors.

Animals↗
PubMed1975

Enzyme potentiated hyposensitization: IV. effect of protamine on the immunological behavior of beta glucuronidase in mice and patients with hay fever.

The ability of beta glucuronidase and a small dose of antigen to modify the anaphylactic reaction of previously sensitized mice has been further investigated. Protamine has an important effect on the immunological behavior of the enzyme. A trial on hay fever patients shows that the results in mice are relevant and that the method can produce significant clinical hyposensitization.

Animals↗
PubMed1971

The peripheral vascular response to severe exercise in untethered dogs before and after complete heart block.

The peripheral vascular response to severe exercise was studied in 11 healthy conscious dogs instrumented with Doppler ultrasonic flow probes on the mesenteric, renal, and iliac arteries, and miniature pressure gauges in the aorta. The response to severe exercise was restudied in six of these dogs after recovery from a second operation producing complete heart block by the injection of formalin into the atrioventricular (AV) node. Three of these dogs also exercised while their ventricles were paced at rates of 100/min and 200/min. The untethered normal dogs ran at speeds of 15-25 miles/hr behind a mobile recording unit for a distance averaging 1.5 miles, while continuous measurements of arterial blood pressure and blood flow were telemetered and recorded on magnetic tape. Severe exercise in normal dogs increased heart rate from 84 to 259/min, arterial pressure from 89 to 140 mm Hg, flow resistance in the mesenteric and renal beds by 59 and 52% respectively, and iliac blood flow 479% above control, while mesenteric and renal blood flows remained constant and iliac resistance decreased by 73%. In dogs with complete AV block, severe exercise at speeds of 10-18 miles/hr increased heart rate from 47 to 78/min, mean arterial pressure from 81 to 89 mm Hg, iliac flow 224%, resistance in the renal bed by 273%, and mesenteric bed by 222% while it decreased blood flow in mesenteric and renal beds by 61 and 65% respectively, and iliac resistance by 62%. A similar response occurred during exercise with pacing at 100/min, but when paced at 200/min a more normal exercise response reappeared. Thus, in normal dogs the peripheral vascular response to severe exercise involved increases in heart rate, arterial pressure and visceral resistance but visceral blood flow did not decrease. In dogs with heart block, where the ability to increase heart rate is severely compromised, compensatory reduction of mesenteric and renal blood flows occurred.

Abdomen↗