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Biomedical subjects

E N Hey

Publications and source records attributed to E N Hey.

67 records · Page 4Linked to original sources
PubMed1969

The effect of prolonged cold exposure on heat production in new-born rabbits.

1. The rates of oxygen consumption and the colonic temperatures were monitored from birth in rabbits delivered by Caesarean section at term. The rates of oxygen consumption at 25 and 36 degrees C rose over the first 12 hr of life.2. Thirty rabbits were kept unfed in an environment of 25 degrees C from birth. Extra oxygen consumption, in response to cold exposure, failed 24-34 hr later. Twenty-four of these rabbits were allowed to recover in an environment of 36 degrees C. The metabolic response to cold exposure did not return in those kept unfed or given glucose but those fed with rabbit's milk showed significant recovery when re-exposed to cold 4 or 18 hr later.3. The tissue glyceride content of brown and white adipose tissue and the liver were greatly reduced once the animals failed to respond to cold exposure and no significant rise was detected during the recovery period after a milk feed.4. Another twelve rabbits were kept unfed in an environment of 36 degrees C. These animals showed a poor metabolic response to cold exposure after 48 hr, although their brown adipose tissue was still replete with fat and the blood glucose rose to normal values during cold exposure.5. These results suggest that an increase in oxygen consumption in response to cold exposure can occur even though brown adipose tissue is largely depleted of glyceride provided that an alternative supply of fuel is available. Glucose alone is not an adequate source of energy.

Adipose Tissue↗
PubMed1969

Fat metabolism and heat production in young rabbits.

1. The rates of oxygen consumption were measured in 6-8-day-old rabbits at 34 and 15 degrees C after varying periods of starvation and cold exposure. At the start of the experiment the rabbits had been fasted for 24 hr. Eight rabbits were studied immediately, six after 24 and six after 48 hr in a cold environment (20 degrees C), and twelve after a further 48 hr in a warm environment (34 degrees C). All the animals had a similar increase in oxygen consumption during the final hour of cold exposure (15 degrees C).2. The rabbits kept at 20 degrees C lost 83% of the fat stored in their brown adipose tissue within 24 hr and a further 11% in the next 24 hr. The fat content of white adipose tissue had fallen by 75% at 48 hr. In contrast rabbits kept unfed at 34 degrees C had lost 47% of the fat in brown adipose tissue and 44% of the fat in white adipose tissue after 48 hr.3. In six rabbits subcutaneous thermocouples demonstrated that local heat production continued in brown adipose tissue after 48 hr cold exposure.4. In the rabbits kept at 34 degrees C the final cold exposure caused a large increase in the serum free fatty acid and glycerol concentrations. Much lower concentrations were found in rabbits kept at 20 degrees C.5. The results show that the fat stored in the brown adipose tissue of young rabbits exposed to cold is preferentially used for heat production. When this store of fat is exhausted, brown adipose tissue still produces heat presumably by oxidizing fat and glucose taken from the circulation.

Adipose Tissue↗
PubMedDate not supplied

Estimation of pulmonary arterial pressure in the newborn: study of the repeatability of four Doppler echocardiographic techniques.

Despite the increasing use of Doppler echocardiographic (DE) techniques to determine pulmonary arterial pressure in the neonate undergoing intensive care, there have been no studies comparing their repeatability in this population. Our objective was to compare the repeatability of four such techniques in neonates. The study was conducted in two regional neonatal units serving the North East of England. Group A (repeatability between observers): Two experienced observers performed detailed DE examinations, one directly after the other. Group B (within observer repeatability/temporal variability): One observer performed two examinations 1 hour apart. Group A comprised 15 preterm babies (26-36 weeks' gestation, 975-2915 g), most with mild respiratory failure; 4 healthy term babies; and 7 with congenital heart disease, in whom tricuspid regurgitation (TR) only was measured. Their ages were 18 hours to 12 days. Group B comprised 11 babies aged 12-64 hours with moderate to severe respiratory failure; 10 were preterm (26-36 weeks, 785-2800 g). We recorded four measurements: (1) Peak velocity of TR in m/s; (2) peak left-to-right ductal flow velocity (PDAmax in m/s); (3) TPV/RVET ratio; and (4) PEP/RVET ratio, where TPV = time to peak velocity at the pulmonary valve, PEP = right ventricular preejection period, and RVET = right ventricular ejection time. The Bland-Altman analysis was used to produce the coefficient of repeatability (CR: 95% confidence limits of repeatability), also expressed as a repeatability index (CR/mean value) and as a number of "confidence steps"-a measure of sensitivity of the technique to hemodynamic change (range of values within the population/CR). Between-observer and within-observer repeatabilities were similar. Within-observer CR and index (%) results were for TR +/- 0.26 m/s (9%); for PDAmax, +/- 0.48 m/s (39%); TPV/RVET 0.1:1.0 (34%), PEP/RVET 0.12:1.00 (36%). TR and PDAmax had the largest number of confidence steps in the expected range of values (TR 8.5; PDA max 6.5; TPV/RVET 3.2; PEP/RVET 3.2). The most repeatable technique was TR, but PDAmax would also be useful for a serial study owing to the potential for large change. Systolic time interval ratios were less repeatable and likely to be less sensitive indicators of hemodynamic change.

Blood Pressure↗
PubMedDate not supplied

Respiratory illness in children: do deprived children have worse coughs?

Parents of a stratified random sample of 234 children from 21 general practices in North East England were interviewed at home. All these children had been reported in a postal questionnaire as having had a cough between six and ten weeks before the interview. Interviews covered social characteristics of the family, the severity of the child's cough and the reactions of the parents to hypothetical sets of symptoms. The parents of children in materially deprived circumstances appeared to report worse coughs than other parents. We confirmed this finding by constructing a scale of perceived cough severity. However, we found no evidence that the inequality was due to exaggeration of the severity of the cough by materially deprived parents. Our conclusion that materially deprived children suffer worse respiratory illness is the more important because previous evidence suggests that the after-effects persist into adulthood.

Child↗