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Biomedical subjects

D O'Leary

Publications and source records attributed to D O'Leary.

At least 73 records · Page 4Linked to original sources
PubMed1986

Human coffee drinking: manipulation of concentration and caffeine dose.

In a residential research ward coffee drinking was studied in 9 volunteer human subjects with histories of heavy coffee drinking. A series of five experiments was undertaken to characterize adlibitum coffee consumption and to investigate the effects of manipulating coffee concentration, caffeine dose per cup, and caffeine preloads prior to coffee drinking. Manipulations were double-blind and scheduled in randomized sequences across days. When cups of coffee were freely available, coffee drinking tended to be rather regularly spaced during the day with intercup intervals becoming progressively longer throughout the day; experimental manipulations showed that this lengthening of intercup intervals was not due to accumulating caffeine levels. Number of cups of coffee consumed was an inverted U-shaped function of both coffee concentration and caffeine dose per cup; however, coffee-concentration and dose-per-cup manipulations did not produce similar effects on other measures of coffee drinking (intercup interval, time to drink a cup, within-day distribution of cups). Caffeine preload produced dose-related decreases in number of cups consumed. As a whole, these experiments provide some limited evidence for both the suppressive and the reinforcing effects of caffeine on coffee consumption. Examination of total daily coffee and caffeine intake across experiments, however, provides no evidence for precise regulation (i.e., titration) of coffee or caffeine intake.

Caffeine↗
PubMed1985

Signals from the oropharynx may contribute to the diuresis which occurs in man to drinking isotonic fluids.

The drinking of a variety of isotonic salt solutions provoked a short load-dependent diuretic response in man, similar in latency to that of a water diuresis and reaching its maximum 40-60 min from the start of drinking. Subjects differed in the threshold load at which the response became evident, and also in the magnitude of their responses. Changes in free water clearance matched the increases in urinary minute volume, with no significant change in either urinary sodium or potassium excretion. Changes in urinary pH and in ammonium excretion were similar to those described for a water diuresis. Drinking an isotonic solution of mannitol provoked a diuresis similar to that of the salt solutions. All subjects had diarrhoea after drinking the mannitol. Signals arising from the oropharynx might be partly responsible for eliciting the diuresis. The significantly smaller urinary responses to infusions of isotonic salt solutions directly into the stomach support this view. The absence of a significant response to 'sham drinking' appears inconsistent with this, but oropharyngeal signals may only have a priming role in man and interact with other signals to give the full response.

Adult↗
PubMed1985

Corneal sensitivity in myasthenia gravis.

Corneal touch thresholds were measured in 11 people suffering from myasthenia gravis (MG) and in a control group of 20 subjects. The mean threshold in MG was 75.6 mg (SD 52) and in the control group 18.9 mg (SD 7.3); thresholds were thus significantly (p less than 0.01) raised in MG. Although it is not possible to say whether the sensory deficit is due to MG or to the treatment, the results implicate acetylcholine in sensory transduction in the cornea.

Adult↗
PubMed1984

Effect of high local temperature on reflex cutaneous vasodilation.

We examined the effect of high local forearm skin temperature (Tloc) on reflex cutaneous vasodilator responses to elevated whole-body skin (Tsk) and internal temperatures. One forearm was locally warmed to 42 degrees C while the other was left at ambient conditions to determine if a high Tloc could attenuate or abolish reflex vasodilation. Forearm blood flow (FBF) was monitored in both arms, increases being indicative of increases in skin blood flow (SkBF). In one protocol, Tsk was raised to 39-40 degrees C 30 min after Tloc in one arm had been raised to 42 degrees C. In a second protocol, Tsk and Tloc were elevated simultaneously. In protocol 1, the locally warmed arm showed little or no change in blood flow in response to increasing Tsk and esophageal temperature (average rise = 0.76 +/- 1.18 ml X 100 ml-1 X min-1), whereas FBF in the normothermic arm rose by an average of 8.84 +/- 3.85 ml X 100 ml-1 X min-1. In protocol 2, FBF in the normothermic arm converged with that in the warmed arm in three of four cases but did not surpass it. We conclude that local warming to 42 degrees C for 35-55 min prevents reflex forearm cutaneous vasodilator responses to whole-body heat stress. The data strongly suggest that this attenuation is via reduction or abolition of basal tone in the cutaneous arteriolar smooth muscle and that at a Tloc of 42 degrees C a maximum forearm SkBF has been achieved. Implicit in this conclusion is that local warming has been applied for a duration sufficient to achieve a plateau in FBF.

Adult↗
PubMed1984

Conformational stress and anastomotic hyperplasia.

Late failure of synthetic vascular grafts to small-diameter arteries (less than or equal to 4 mm) is commonly due to anastomotic hyperplasia. Theoretic analysis suggests that conformational changes at the anastomosis lead to high localized arterial wall stress caused by increases in radius of curvature of the artery (law of Laplace: tension = pressure X radius). Nine 3 kg rabbits had a plastic insert implanted into the infrarenal aorta. The insert was designed to recreate the conformational changes caused by the anastomosis of a synthetic graft to a small-diameter artery, without significantly altering blood flow. The increase in arterial wall tension created by the insert was calculated to be 80% to 100% over baseline values. Aortography, real-time ultrasound, and computed tomography (CT) scanning were done to confirm the absence of luminal thrombus formation or migration of the insert. Ultrasound and CT scans also confirmed the desired conformational changes in the aorta at the site of the insert. Aortas, with the inserts in place, were removed from 3 days to 6 months after implantation. Implantation times of 1 to 6 months resulted in a hyperplastic subintimal lesion characterized by fibrous tissue deposition, spindle cells (which may have been fibroblasts), and/or smooth muscle cells covered by endothelium. In contrast, two rabbits that had the insert placed and then removed at 1 minute and were allowed to survive for 37 and 72 days, respectively, demonstrated complete healing of the aorta without anastomotic hyperplasia. The arterial wall conformational changes induced in this experiment led to the formation of a lesion consistent with anastomotic hyperplasia. An increase in wall tension may have been the stimulus for this response. Prevention of anastomotic hyperplasia may require a means of uniting a graft to an artery without increasing wall tension.

Animals↗
PubMed1983

Improvement in neuropsychological performance in patients with refractory seizures after intensive diagnostic and therapeutic intervention.

Tests of cognitive, perceptual, motor, and memory function were administered to patients with refractory seizures before and after intensive treatment on a specialized epilepsy unit. Improved test performance related to withdrawal of barbiturates and an overall reduction in the number of antiepileptic drugs but not with reduction of seizure frequency.

Adolescent↗
PubMed1983

Cerebrally lateralized epileptogenic foci and performance on a verbal and visual-graphic learning task.

A set of verbal and visual-graphic learning tasks sensitive to differential cerebral hemisphere impairment was administered to 50 patients with epileptogenic focus localized in either the left or right cerebral hemisphere. Patients with left-hemisphere seizure-foci and those with generalized seizures performed the verbal task significantly more poorly than did patients with right-hemisphere epileptogenic foci. In contrast, there were no significant differences between groups on the non-verbal tasks. Results are discussed in light of findings in the literature relating cognitive dysfunction to epilepsy and with regard to the possible contribution of such dysfunction to patients' complaints.

Adolescent↗
PubMed1981

Comparison of five methods for the assay of serum gentamicin.

The microbiological bioassay, the adenylation method, and the radiometric, enzyme, and fluorescent immunoassay methods for assaying serum gentamicin were compared. The precision, reproducibility, and specificity of each method was assessed and proved satisfactory, with the exception of the radioimmunoassay, which gave artificially high results. Good correlations between the other four methods was obtained in a comparison involving 103 patient sera. The other aspects of performance were also compared, namely, simplicity, speed, cost, ease of automation, and application to large and small workloads. The enzyme immunoassay performed best in this comparison, being accurate, specific, rapid, and very simple to perform. However, other laboratories might find that workload, staffing, and available equipment make other methods more attractive.

Adenosine↗
PubMed1978

The discrepancy between retinoscopic and subjective measurements: Effect of age.

Comparison of the retinoscopic and subjective measurements of 1078 eyes of all ages showed that the discrepancy (retinoscopy--subjective) was positive and equal to 0.3--0.4 D in young eyes. The discrepancy diminished with age, eventually becoming negative in the 6th decade of life. The results are explained by postulating that retinoscopic light is reflected from the internal limiting membrane in young eyes and from a layer posterior to the photoreceptors in older eyes.

Accommodation, Ocular↗