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Biomedical subjects

J C Easton

Publications and source records attributed to J C Easton.

6 recordsLinked to original sources
PubMed1996

Effects of facial cooling on elderly and young subjects: interactions with breath-holding and lower body negative pressure.

1. The effects of convective facial cooling by cold air on arterial blood pressure, heart rate and finger blood flow and on the reflex interactions between facial cooling and respiratory and orthostatic cardiac reflexes have been examined in 28 young adults (20-39 years) and 17 elderly (66-78 years) volunteer subjects. 2. During 2 min facial cooling alone, bradycardia was smaller (P < 0.001) and reduction in finger blood flow smaller (P < 0.001) in elderly subjects than in young subjects. Increases in systolic blood pressure and mean arterial pressure were similar and diastolic pressure increased only in the young subjects. Systolic blood pressure and mean arterial pressure remained elevated in the elderly 1 min after facial cooling, but subsided in the young. 3. Arterial blood pressure increased more during a 30-s breath-hold in expiration than in inspiration (P < 0.001) in both groups, and this was exaggerated by breath-hold in expiration combined with facial cooling. The bradycardia produced by facial cooling and breath-holding in expiration was more pronounced in the young subjects than in the elderly (P < 0.002). 4. Interactions between facial cooling and orthostatic reflexes induced by lower-body negative pressure showed significantly different age-related linear trends. Facial cooling diminished the hypotension induced by lower-body negative pressure in both groups. Facial cooling had a greater effect in diminishing the lower-body negative pressure-induced tachycardia in the young than in the elderly. 5. The mechanism of alteration of the facial cooling response in elderly subjects could be largely impairment of arterial baroreflexes, particularly as a result of reduced cardiac vagal activity as well as impairment of cardiopulmonary reflexes with ageing.

Adult↗
PubMed1989

Gastric emptying after head injury.

Gastric emptying was measured in patients after head injury and compared with that of healthy volunteers using the rate of paracetamol absorption as an indicator of gastric emptying rate. There was a trend towards slower gastric emptying in the head injured patients, but the differences were not statistically significant.

Acetaminophen↗
PubMed1986

Increased platelet and red cell counts, blood viscosity, and plasma cholesterol levels during heat stress, and mortality from coronary and cerebral thrombosis.

Recorded deaths from coronary and cerebral thrombosis rise markedly in heat waves. In a British heat wave with little or no distortion due to air-conditioning, outside temperatures of 34.6 degrees C (maximum) and 20.8 degrees C (minimum) were followed by peak mortalities from coronary and cerebral thrombosis one to two days later. Experimental exposure of volunteers to moving air at 41 degrees C for six hours caused core temperature to rise 0.84 degree C, weight to fall 1.83 kg with sweating despite access to water, heart rate to increase 32 beats per minute, and arterial pressure to fall, particularly on standing. The red blood cell count increased 9 percent, and blood viscosity increased 24 percent, mostly after the first hour. The platelet count rose 18 percent, and the platelet volume fell, mostly in the first hour. The plasma cholesterol level increased 14 percent without a change in distribution among lipoprotein fractions. The changes seem able to explain the increased mortality from arterial thrombosis in hot weather.

Adult↗
PubMed1986

A placebo-controlled assessment of mequitazine and astemizole in tests of psychomotor ability.

This study was a single and repeated dose comparison of mequitazine 5 mg, astemizole 10 mg and placebo and their effects on CNS activity, psychomotor performance and subjective appraisals of alertness. Nine Caucasian female volunteers aged between 29 and 40 years, declared healthy following a medical examination and who showed sensitivity to antihistamine sedation, were admitted to the study. Subjects were allocated to treatment in a randomized block design by which each subject received single and repeat doses of mequitazine 5 mg, astemizole 10 mg and placebo under double-blind conditions. Objective assessments (choice reaction time, critical flicker fusion threshold, simulated car tracking task, Stroop test) and subjective assessments (sedation and sleep rating scales, adverse effects and event recording) were made. Assessments were performed on day 1 and day 8 at pre-dosing (0 h) and at 1.5, 3.5 and 5.5 h following drug administration. Choice reaction times were dissimilar 5.5 h post-drug administration, the mequitazine group having a reaction time comparable to baseline and faster than the astemizole and placebo treatment groups. However, none of the treatments produced any significant or consistent effects when assessed on objective and subjective measures of performance, critical flicker fusion threshold, sedation and sleep and there were no treatment differences in the nature and number of adverse effects reported.

Adult↗
PubMed1985

Effects of age on body temperature and blood pressure in cold environments.

Mean deep body temperature fell by 0.4 +/- 0.1 (SD) degrees C in five sedentary, clothed 63-70 year old men and by 0.1 +/- 0.1 degrees C in four young adults after 2 h exposure in still air at 6 degrees C (P less than 0.001). The mean increase in systolic and diastolic pressure was significantly greater (P less than 0.002) in the older subjects (24 +/- 4 mmHg systolic, 13 +/- 4 mmHg diastolic) than in the young (14 +/- 6 mmHg systolic, 7 +/- 3 mmHg diastolic) after 2 h at 6 degrees C. A small rise in blood pressure occurred in the older men at 12 degrees C, but there was no increase in either group at 15 degrees C. The association of variables is particularly marked between systolic blood pressure and core temperature changes at 6 degrees C. There were no appreciable cold-adaptive changes in blood pressure or thermoregulatory responses after 7-10 days repeated exposure to 6 degrees C for 4 h each day. Blood pressure elevation in the cold was slower but more marked in the older men. These changes in blood pressure may provide a possible basis for delineating low domestic limiting temperature conditions.

Adolescent↗