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Biomedical subjects

G E Thompson

Publications and source records attributed to G E Thompson.

At least 55 records · Page 3Linked to original sources
PubMed1986

Fatty acids in the milk of goats after cessation of lactation.

Regular hand milking of six goats was discontinued after 32-35 weeks of lactation. A few days after milking out ceased, the concentration of triglyceride in peripheral blood plasma increased. Over a period of weeks, the concentration of triglyceride in small samples of fluid taken from the teat canal fell gradually. Lipase activity of the milk fluid was temporarily reduced shortly after milking out ended, but, despite this, its concentration of free fatty acids increased. It is suggested that free fatty acids are released during clearance of milk triglyceride from residual fluid in the mammary gland after cessation of lactation.

Animals↗
PubMed1986

Cold exposure and mammary exchanges of circulating thyroxine and oestrone sulphate in the goat.

The effects of cold exposure on arterial and mammary venous concentrations of thyroxine and oestrone sulphate, and on mammary blood flow, were measured in goats during different stages of pregnancy and lactation. There were no significant differences in net mammary uptake of thyroxine in four non-pregnant lactating goats exposed for 30 h to cold (-3 +/- 2 degrees C) or control (20 +/- 2 degrees C) temperatures. Cold exposure for 30 h of six lactating goats (approximately 85 d pregnant) stimulated a net mammary release into the circulation of oestrone sulphate (mean 294 ng/min); plasma cortisol concentrations also increased. Cold exposure at approximately 30 d of pregnancy increased cortisol concentrations but had no effect on release of oestrone sulphate.

Animals↗
PubMed1986

Vascular and lipolytic responses of the inguinal fat pad of the sheep to adrenergic stimulation, and the effects of denervation and autotransplantation.

Electrical stimulation of sympathetic nerves supplying an inguinal fat pad, in the anaesthetized sheep, produced effects on blood flow through the fat pad which differed when the nerves were intact or sectioned. Lipolysis was stimulated and the output of individual fatty acids into venous plasma was compared with their composition in the adipose tissue triglycerides. Close-arterial infusion of noradrenaline also produced lipolysis but, again, effects on the circulation differed when the fat pad was in situ or chronically autotransplanted to the neck. Close-arterial infusion of dopamine produced a similar response to noradrenaline. It is concluded that sympathetic nerves and noradrenaline may have a predominantly vasodilatory effect on adipose tissue in the sheep, but the response after acute or chronic denervation is predominantly vasoconstriction. Noradrenaline and dopamine stimulate fat mobilization independently, but the fatty acids mobilized may not be entirely representative of those stored in the adipose tissue triglyceride.

Adipose Tissue↗
PubMed1985

Prepartum milking and the onset of secretion of milk fat in the goat.

Late-pregnant goats were separated into two groups. A control group of four goats had small (approximately 3 ml) volumes of secretion expelled from one mammary gland at infrequent intervals between day 130 of gestation and parturition. An experimental group of five goats had as much secretion as possible removed from both glands twice daily beginning on day 137 of gestation and continuing until parturition. After parturition, both groups were milked twice daily. Regular 'milking out' before parturition stimulated secretion of triglyceride by the mammary gland, and most of the fatty acids secreted in the triglyceride before parturition had a chain length of 18 carbons. Secretion of 6-14-carbon chain-length fatty acids in the milk triglycerides increased after parturition. There was no evidence that the onset of secretion of medium-chain and long-chain fatty acids occurred at different times in the control animals. It is concluded that the onset of secretion of medium-chain and long-chain fatty acids in milk triglycerides can be dissociated, although both are normally synchronized with parturition. Removal of secretion by the offspring at parturition may be a stimulus for the onset of secretion of long-chain fatty acids, but the onset of secretion of medium-chain fatty acids is brought about by some other mechanism.

Animals↗
PubMed1985

Chemotherapeutic agents and modulation of natural killer cell activity in vitro.

This study investigated the effect of various clinically used chemotherapeutic agents on non-modulated and human alpha Interferon (IFN) modulated natural killer cell (NK) activity. The inhibitors of DNA synthesis, Adriamycin, Cis-Platinum, 5-Fluorouracil and Methotrexate, did not alter NK cell activity at comparable clinically used doses. Similarly, Vincristine and Vinblastine, which are antimitotic agents, did not affect the NK activity. Only inhibitors of RNA synthesis L-Asparaginase and Actinomycin D reduced non-modulated and IFN modulated NK cell activity.

Antineoplastic Agents↗
PubMed1984

Dopamine and lipolysis in adipose tissue of the sheep.

An inguinal fat pad preparation suitable for blood flow and lipolysis studies in the sheep is described. Infusion of dopamine at the rate of 0.8 microgram/min for 40 min increased blood plasma flow through the preparation, and increased the output of glycerol in its venous effluent suggesting fat mobilization. Infusion at the rate of 0.05 microgram/min had no detectable effect, and the responses to infusions at 15 micrograms/min were irregular. Dopamine, which is known to be present in sheep adipose tissue, may have a role in the regulation of blood flow and lipolysis.

Adipose Tissue↗
PubMed1984

Adrenocorticotrophic hormone stimulation of mammary secretion in lactating goats independent of increased mammary uptake of glucose.

The treatment of lactating goats with ACTH (single intramuscular injection) or cortisol (systemic infusion) resulted in an increase in milk yield and in the secretion of lactose, citrate and glucose into milk. The concentration of glucose in arterial plasma was also increased, resulting in a greater supply of glucose to the mammary gland. After ACTH treatment mammary uptake of glucose from the circulation did not increase and the balance between mammary uptake of glucose from blood and mammary output of glucose 'equivalents' into milk was significantly reduced. The results show that ACTH and cortisol can increase milk yield and lactose secretion by altering mammary metabolism of glucose.

Adrenocorticotropic Hormone↗
PubMed1983

The intake of milk by suckled, newborn lambs and the effects of twinning and cold exposure.

Clun Forest ewes with single and twin lambs were exposed to neutral (20 degrees) or cold (-1 degree) environmental temperatures, beginning soon after parturition, for 4 d. The intakes of milk, lactose and glycerides by the lambs were calculated from measurements of the rate of displacement of tritiated water (injected into the lambs) by non-radioactive water in milk from the ewes, and measurements of the concentration of lactose and glyceride glycerol in small samples of milk. The yield of milk from ewes bearing twin lambs was greater than the yield from single-bearing ewes in the neutral environment but, in both environments, twin lambs had lower intakes of milk and milk lactose and glycerides, and gained body-weight more slowly, than single lambs. Milk from twin-bearing ewes had a lower lactose concentration than milk from single-bearing ewes. Cold exposure reduced the intake of milk and milk lactose, and reduced the rate of weight gain, of single and twin lambs. Glyceride intake was not different in the two environments. There appears to be a conflict between reduced supply of milk by the ewe and increased demand for milk by the lamb in cold temperatures. Such a conflict is sharpened when twin lambs are born.

Animal Nutritional Physiological Phenomena↗
PubMed1983

Functional anatomy of the brachial plexus sheaths.

The brachial plexus sheath was examined in cadavers by using a combination of anatomic dissection, histologic preparations, and x-rays made after injection of x-ray contrast media, and in surgical patients by using computed tomography (CT) dye studies. The connective tissue forming the sheath was organized more densely proximally near its origin and became loosely organized distally as it ended by joining the medial intermuscular septum of the arm. The connective tissue forming the sheath extends inward, forming septa between components of the plexus. Thus, the sheath is a multicompartmented structure, formed by the thin connective tissue sheath surrounding the plexus and by the septa which extend inward from the sheath. A fascial compartment is created for each nerve, and this compartment serves to define the anatomic limits of that nerve. These compartments have potential clinical importance and implication in the techniques for brachial plexus block. They serve functionally to limit the circumferential spread of injected solutions of local anesthetics. These studies also indicate that injected anesthetic solutions spread easily in a longitudinal manner up and down the nerve and remain compartmentalized. The data presented here provide a rational explanation for the not uncommon occurrence of a profound block of rapid onset in one nerve, yet partial or absent block in other nerves, following any of the techniques of brachial plexus anesthesia.

Aged↗
PubMed1982

The effects of cold exposure of pregnant sheep on foetal plasma nutrients, hormones and birth weight.

1. Five pregnant sheep, with indwelling catheters positioned for withdrawal of maternal right-atrial and foetal arterial blood, were exposed for 2 h to neutral and to cold (-10 and wool-clipped) environmental temperatures. Acute maternal cold exposure increased the concentrations of glucose, glycerol and non-esterified fatty acids in maternal plasma and increased the concentration of glucose in foetal plasma, but not glycerol or non-esterified fatty acids. The concentration of corticosteroids in maternal plasma increased. The concentration of corticosteroids in foetal plasma did not change but the concentration of insulin increased. 2. Thirteen pregnant sheep were housed at thermoneutrality and thirteen similar sheep, fed the same amount of food, were clipped and exposed to cold during the last 5-6 weeks of pregnancy. Chronic maternal cold exposure increased the birth weight of both single and twin lambs. 3. It is concluded that exposure of pregnant sheep to cold can alter the partition of some nutrients between mother and foetus in favour of the foetus, and it is suggested how this may be brought about.

Adrenal Cortex Hormones↗
PubMed1982

Seasonal alteration in response to stress or physiological change.

Two pilot experiments are reported in which various combinations of stress, modifiers of glucose metabolism, and sulfur deficiency were investigated using urinary sulfur levels and tissue glucose and glycogen levels as indicators. Urinary sulfur levels increased under certain conditions of stress but decreased with the injection of Escherichia coli endotoxin, suggesting an anabolic reversal. Heart and blood glycogen levels fell in rats fed a sulfur-deficient diet. These results are discussed in relation to seasonal variations in protein and glucose metabolism.

Animals↗
PubMed1980

The effect of cold exposure on fluid balance, circulating arginine vasopressin concentration and milk secretion in the goat.

Total body water, water intake, urine output, milk yield, plasma, milk and urine osmolality and plasma arginine vasopressin concentration were measured in goats exposed to thermoneutral (20 degrees C) and cold (0-1.0 degrees C) environments for 24 h. Cold exposure caused the animals to reduce their water intake substantially. This was accompanied by a decrease in total body water and an increase in osmolality of plasma and milk. The output of urine decreased as cold exposure progressed but free water clearance by the kidney was not significantly different in thermoneutral and cold environments and cold exposure had no effect on circulating arginine vasopressin concentration. Milk yield was reduced by cold exposure and it is suggested that the reduced net movement of water from blood to milk is partly a consequence of the dehydration induced by cold exposure and that this, in turn, is due primarily to a decrease in water intake with no effective renal compensation.

Animals↗
PubMed1980

The distribution of blood flow in the udder of the sheep and changes brought about by cold exposure and lactation.

1. Microspheres have been injected into an external iliac artery of conscious female sheep in order to measure the distribution of blood flow in half the udder. Values were obtained from five non-lactating ewes in a neutral environment and in a cold environment. Values were also obtained from five lactating ewes in a neutral environment 27-36 days after parturition. 2. In non-lactating sheep in a neutral environment, blood flow to half the udder averaged 11.7 ml . min-1 of which 43% was distributed to lobulo-alveolar tissue, 10% to skin covering the udder, 2% to the teat, 20% to inguinal adipose tissue and 25% to lymph tissue. 3. Cold exposure significantly reduced udder skin and teat blood flow, by approximately the same amount as it reduced leg skin blood flow, but significantly increased blood flow to adipose tissue in the udder, so total blood flow to the udder was not affected. 4. In lactating sheep, blood flow to half the udder was significantly higher, averaging 357 ml . min-1. Flow to the teat was slightly greater than in non-lactating sheep in a neutral environment, but flow to lobulo-alveolar tissue was much greater and accounted for 98% of total blood flow in lactating sheep.

Adipose Tissue↗
PubMed1979

Free fatty acid oxidation in bovine muscle in vivo: effects of cold exposure and feeding.

A mixture of (1-14C)-labeled free fatty acids (FFA), complexed in bovine plasma, was infused into the abdominal aorta of conscious young steers exposed to thermoneutral or moderately cold conditions for several hours and fed 6 or 22 h before the experiment. The uptake, release, and oxidation of FFA in one hindlimb was calculated from simultaneous measurements of leg blood flow and arteriovenous difference in the specific activities of plasma 14C-FFA and blood 14CO2. Despite an invariable net release of FFA from the resting leg, uptake of 14C-FFA was considerable; of this only 14 and 3% was immediately converted to 14CO2 in fasted and fed steers, respectively. During cold exposure, increases in whole-body oxygen consumption (VO2), arterial concentration and turnover rate of plasma FFA, and a decrease in respiratory quotient were accompanied by much greater increases in VO2, uptake, and oxidation of FFA by the shivering leg. Even so, most FFA taken up were apparently not immediately oxidized to CO2, and possible alternatives for FFA metabolism in shivering muscle are discussed.

Animals↗