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Biomedical subjects

M J Hardman

Publications and source records attributed to M J Hardman.

At least 55 records · Page 3Linked to original sources
PubMed1973

Blood flow and fatty acid release by cervical adipose tissue of rabbits.

1. A direct technique was used to measure blood flow and exchange of metabolites by cervical adipose tissue in 3-month-old and adult rabbits.2. The initial blood flow from adipose tissue of fed 3-month-old rabbits was 0.45 ml./g tissue.min and the tissue released fatty acids and glycerol. In similar rabbits unfed for 24 hr, fatty acid release increased fourfold. Both the rate of blood flow and the arterio-venous difference of fatty acid increased. In fed adult rabbits blood flow was 0.16 ml./g tissue.min.3. Noradrenaline infusion in both young and adult rabbits stimulated a rapid and large increase in cervical adipose tissue blood flow together with an increase in fatty acid and glycerol release. Glucose uptake remained small. No increase in local heat production in cervical adipose tissue was detected during noradrenaline infusion.4. It is concluded that cervical adipose tissue in adult rabbits is actively concerned in energy storage and supply.

Adipose Tissue↗
PubMed1972

The action of insulin on brown adipose tissue in vivo.

1. The action of insulin on the net exchange of glucose, free fatty acids and glycerol by brown adipose tissue of young rabbits was investigated.2. Infusion of insulin (10,000 muu./kg.min I.V. for 10 min) caused a large increase in the uptake of glucose by brown adipose tissue of fed week-old rabbits. The release of fatty acids fell but glycerol release was unchanged.3. The brown adipose tissue of 9-day-old rabbits fasted in a warm environment had a high initial rate of fatty acid and glycerol release and low rates of glucose uptake. Insulin infusions (10,000 and 100 muu./kg.min) greatly reduced fatty acid release but had little or no effect on glucose uptake.4. The brown adipose tissue of 9-day-old rabbits fasted in a cold environment was depleted of fat and took up free fatty acid as well as glucose from the circulation. Infusion of insulin (10,000 muu./kg.min) caused a large increase in glucose uptake accompanied by a reduction in fatty acid uptake.5. The experiments support the view that insulin has a direct effect on fatty acid transport across the cell membrane.

Adipose Tissue, Brown↗
PubMed1971

Brown adipose tissue metabolism in vivo and serum insulin concentrations in rabbits soon after birth.

1. In rabbits kept unfed for 4 or 24 or 48 hr after delivery by Caesarean section at term, noradrenaline infusion (I.V. for 30 min) caused a similar increase in oxygen consumption but the increase in serum free fatty acid concentration was greatest in rabbits kept unfed for 48 hr.2. The brown adipose tissue of anaesthetized rabbits under 3 hr old took glucose from the circulation but did not release fatty acids. In similar rabbits noradrenaline infusion stimulated the tissue to generate heat, but there was no release of fatty acids even though the rate of triglyceride hydrolysis was high (as judged by the rate of glycerol release).3. In rabbits kept unfed for 48 hr from birth in a warm environment, brown adipose tissue released small amounts of fatty acids but continued to take glucose from the circulation. Heat production in response to noradrenaline infusion was accompanied by an increased release of fatty acids. The fat content of the brown adipose tissue did not fall with starvation.4. The mean serum insulin concentration of rabbits at birth was 54 muu./ml. compared to 23 muu./ml. in the mother. In new-born rabbits kept unfed for 48 hr the insulin concentration had fallen to 14 muu./ml.5. It is concluded (i) that at birth brown adipose tissue has the capacity to generate heat but the tissue is slow to release its stores of fat in response to starvation, (ii) that brown adipose tissue has a high rate of glucose uptake even during starvation and (iii) that the high circulating concentration of insulin may be responsible for the tissue's slow adaptation to the demands of starvation.

Adipose Tissue↗
PubMed1971

The effect of environmental conditions on the growth and function of brown adipose tissue.

1. Rabbits were reared from birth under one of two contrasting conditions. They were either well-fed and kept in a cool environment, or kept warm but fed on alternate days only. When they were a week old their metabolic responses to cold or the net exchanges of glucose, free fatty acid and glycerol by their brown adipose tissue in vivo before and during noradrenaline infusions were measured.2. The cold-reared rabbits grew normally, the under-fed rabbits were undersized; in both groups the brown adipose tissue wet weights were less than those normally found at birth. In cold-reared rabbits this was due largely to the low fat content, in the under-fed rabbits it was not.3. The rabbits' rates of oxygen consumption at a thermoneutral temperature and in response to cold was greater in the cold-reared rabbits.4. The increase in temperature over brown adipose tissue and the increase in blood flow in response to noradrenaline infusion was also greater in the cold-reared rabbits.5. Although the brown adipose tissue of cold-reared rabbits contained 30% fat it did not release fatty acids 24 hr after a feed. In contrast the brown adipose tissue of the under-fed rabbits released fatty acids at a high rate.6. It was concluded that both prolonged cold exposure and undernutrition influenced the function and development of brown adipose tissue during the first week of life. Cold exposure increases the thermogenic capacity of the tissue, undernutrition reduces it. The net release of fatty acids from brown adipose tissue, is, in part, dependent on the tissues' own intracellular requirements.

Adipose Tissue↗
PubMed1970

Fat metabolism in brown adipose tissue in vivo.

1. Noradrenaline infusions (I.V. for 30 min) in new-born and 1-week-old unanaesthetized rabbits caused a rapid and sustained rise in oxygen consumption and an increase in blood glucose, free fatty acid and glycerol concentrations. Similar changes occurred in anaesthetized 1-week-old rabbits.2. A simple direct method was used to measure the net exchange of metabolites across brown adipose tissue in anaesthetized young rabbits. It was found that the brown adipose tissue of rabbits reared from birth in a thermoneutral environment and studied when their next feed was due took glucose from and released fatty acids and glycerol into the circulation.3. Similar rabbits kept unfed for a further 48 hr in a warm environment released fatty acids and glycerol from their brown adipose tissue at a far greater rate, but the rate of glucose uptake was reduced.4. On the other hand the brown adipose tissue of rabbits kept unfed in a cold environment (20 degrees C) took up circulating free fatty acids as well as glucose and did not release glycerol. The brown adipose tissue of these rabbits was depleted of fat.5. The rate of blood flow through brown adipose tissue and the exchange of all three metabolites increased fourfold during noradrenaline infusion in the three groups of rabbits.6. It is concluded (i) that brown adipose tissue releases significant amounts of fatty acids and glycerol into the circulation and that this contribution is greatly increased with noradrenaline infusion and presumably cold exposure, and (ii) that brown adipose tissue depleted of fat produces heat by drawing free fatty acids as well as glucose from the circulation.

Adipose Tissue↗