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Biomedical subjects

M J Hardman

Publications and source records attributed to M J Hardman.

62 records · Page 4Linked to original sources
PubMed1969

The effects of age and environmental temperature on the blood concentrations of glucose, free fatty acids and glycerol in new-born rabbits.

1. The concentration of blood glucose, free fatty acids and serum glycerol of the doe, new-born and young rabbits have been measured in order to evaluate the effects of age, starvation and environmental temperature on the circulating concentrations of these metabolites.2. The blood glucose, free fatty acid and glycerol concentrations were lower in the new-born than in the mother rabbit.3. Starvation for 24 hr of new-born and young rabbits in a thermal neutral environment did not alter the serum free fatty acid or glycerol concentrations. The blood glucose of unfed rabbits fell during the first 24 hr of life.4. Cold exposure (15 or 25 degrees C) for 1 hr caused a rise in the concentration of blood glucose, serum free fatty acids and glycerol.5. When the metabolic response of new-born and young rabbits to cold exposure was measured, it was found that there was a direct correlation between the serum glycerol concentration and the metabolic response. The greatest rise in the serum free fatty acids occurred in the blood of rabbits with the poorest metabolic response to cold.6. It is suggested that in the steady state during cold exposure the serum glycerol concentration may indicate the rate of triglyceride hydrolysis in brown adipose tissue.

Adipose Tissue, Brown↗
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

Effects of ethanol treatment and castration on liver alcohol dehydrogenase activity.

Induction of alcohol dehydrogenase (ADH) activity by chronic ethanol treatment and castration has previously been reported to occur in Sprague-Dawley rats. In the present study, no induction was found following chronic ethanol treatment and only a low level of induction was found with castration. However the activity of ADH was high in control animals compared with those used in other studies. The activity of ADH in control animals was not decreased by testosterone administration, which has been shown to reverse induction of the enzyme produced by chronic ethanol treatment or castration in other studies. It is concluded that the male Sprague-Dawley rat is not necessarily a suitable animal for the study of ADH induction by chronic ethanol treatment and that further unknown factors must be identified before the regulation of ADH activity in vivo is fully understood.

Alcohol Dehydrogenase↗