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Biomedical subjects

W F Wallace

Publications and source records attributed to W F Wallace.

At least 19 recordsLinked to original sources
PubMed1988

Short- and long-term academic predictors of medical student performance.

The relationship between entry qualifications and performance throughout the medical course was studied in individual cohorts of students admitted in the years 1977 to 1981. A modest but significant relationship with overall initial qualifications was found throughout the course. Students without biology showed a marked disadvantage in the first year but the effect did not persist. There were quite marked variations in all these effects between cohorts; studying only a single cohort could lead to inappropriate conclusions.

Achievement↗
PubMed1987

Comparison of the effects of inhaled ipratropium bromide and salbutamol on the bronchoconstrictor response to hypocapnic hyperventilation in normal subjects.

A double blind, placebo controlled comparison was made of the effects of nebulised ipratropium bromide (0.05 and 0.5 mg) and salbutamol (0.25 and 2.5 mg) on lung function and the airway response to hyperventilation in eight normal subjects. Both agents at both doses caused similar baseline bronchodilatation, confirming the presence of resting bronchomotor tone. The overall mean increases as percentages of control were 33% in specific airway conductance (sGaw), 10% in maximal flow after expiration of 50% of vital capacity, and 3.7% in FEV1. Hypocapnia (mean end tidal carbon dioxide tension 2.2 kPa) was produced by three minutes of voluntary hyperventilation and resulted in a mean fall in sGaw of 0.49 s-1 kPa-1 (20%). After inhalation of 0.25 mg salbutamol hypocapnic hyperventilation still produced a mean fall in sGaw of 0.55 s-1 kPa-1, whereas salbutamol 2.5 mg reduced this response to 0.15 s-1 kPa-1 (6%). After both doses of ipratropium the decrease in sGaw caused by hyperventilation was similar to the control. This suggests that bronchoconstriction in response to hypocapnic hyperventilation in normal subjects is not mediated via a cholinergic reflex.

Administration, Inhalation↗
PubMed1986

Ultrastructural evidence in rabbit ear arteries that barium enters smooth muscle cells through calcium channels.

The calcium channel blocker methoxyverapamil, at 10(-5) mol/l, abolished contractile responses of isolated perfused rabbit ear arteries to barium. Entry of barium into smooth muscle cells was detected by the presence of mitochondrial granules specific for barium. Methoxyverapamil (10(-5) mol/l) prevented the appearance of barium granules. In a further series of experiments, eight out of twelve arteries incubated with barium, 2.5 mmol/l, showed granules; when the incubate contained 2.5 mmol/l of both barium and calcium, granules were found in only one of twelve specimens; thus calcium appears to compete with barium for entry. These results are consistent with the hypothesis that contractile responses to barium depend on entry of barium into the cells through calcium channels.

Animals↗
PubMed1985

Mitochondrial granules: are they reliable markers for heavy metal cations?

Mitochondrial granules have been used as markers for heavy metal cations, but since such granules can also be found in tissues in the absence of such cations, an attempt was made to define conditions under which these different granules might be visualised. The tissue used was the smooth muscle of the central ear artery of the rabbit. In all studies, the presence or absence of mitochondrial granules was determined by several observers, using coded specimens so that the previous treatment of the specimens was not at the time known to the observers. Paired tissues were exposed for 30 or 90 minutes at 20, 30 or 39 degrees C to an incubate containing either 10 mmol/l barium or a control barium-free solution. After fixation in osmium tetroxide, there was no difference between the two groups; in both cases granules appeared more frequently the longer the time and the higher the temperature of incubation. In a further series where glutaraldehyde was the fixative, granules were identified in 23 out of 41 tissues incubated with barium, but in only 1 out of 41 control tissues (P less than 0.001). Electron probe microanalysis showed that granules in osmium-fixed tissues contained osmium as the main element, whereas granules in glutaraldehyde-fixed tissues which had been incubated with barium showed barium as the predominant cation. Thus mitochondrial granules can be reliable markers for heavy metal cations, but only under carefully controlled conditions.

Animals↗
PubMed1978

Effect of a surgically created side-to-side arteriovenous fistula on heat elimination from the human hand and forearm: evidence for a critical role of venous resistance in determining fistular flow.

1. In eight patients with a unilateral fistula between the radial artery and a nearby superficial vein, heat elimination from both hand and forearm, as measured by calorimetry, was always substantially greater on the side of the fistula (a mean excess from hand-plus-forearm 889 J/min). 2. Fistular blood flow measured by hand-plus-forearm plethysmography in these patients averaged 431ml/min. Correlation between fistular blood flow and heat elimination was poor (r = 0.70, P less than 0.06), probably because heat elimination due to the fistula takes place mainly from veins, whose pattern varies from patient to patient. 3. Approximately half of the total increased heat elimination due to the fistula is from the hand. Occlusion of the circulation to the hand caused fistular flow rate to be reduced by about half. This suggests that the main resistance to fistular is venous, proximal veins offering a similar resistance to distal veins. 4. The obligatory heat loss due to fistula is unlikely to embarrass temperature regulation, except in severe cold stress.

Adult↗
PubMed1976

The pattern of venous drainage of surgically created side-to-side arteriovenous fistulae in the human forearm.

1. The forearm and hand circulation in nine patients with a surgically created side-to-side fistula between the radial artery and a nearby superficial vein in the lower forearm has been investigated. 2. Dilated veins on the dorsum of the hand communicated with the fistula without intervening valvular obstruction. Skin temperature of both forearm and hand was greater on the side with the fistula in all cases. 3. Inflation of an occlusion cuff distal to the fistula markedly reduced apparent fistular flow. 4. It is concluded that the fistulae result in increased blood flow to the hand by retrograde flow from the fistula into the hand veins. Hand as well as forearm must be included in the plethysmographic measurement of blood flow in such cases.

Adult↗
PubMed1976

Measurement by venous occlusion plethysmography of blood flow through surgically created arteriovenous fistulae in the human forearm.

1. Plethysmographs containing the hand plus forearm were used to measure blood flow in patients with a srugically created arteriovenous fistula in one forearm. 2. Apparent flow rate was stable over a limited range of collecting pressures; the absolute value of these pressures varied from patient to patient. 3. After arterial occlusion, blood flow increased by a similar amount on the normal side and on the side with the fistula. 4. Occlusion of fistular flow produced no significant change in heart rate. 5. Fistular flow, estimated as the difference between flow on the two sides, averaged 525 ml/min in seventeen patients.

Arteriovenous Shunt, Surgical↗