Search PubMed⌕ Search

Biomedical subjects

D H Snow

Publications and source records attributed to D H Snow.

At least 73 records · Page 4Linked to original sources
PubMed1982

Time course of ultrastructural changes in skeletal muscle after two types of exercise.

To ascertain the effects of sprint and endurance exercise on the time course of skeletal muscle mitochondrial changes, an ultrastructural study was conducted on four Thoroughbred horses. Skeletal muscle biopsies were taken at various intervals during and after the exercise. Transient mitochondrial alterations of varying degrees were observed following both types of exercise and were considered to be related to the development of fatigue. The degree of distortion of mitochondrial structure is considered not to represent the in vivo condition but the state of responsiveness to the fixation medium.

Animals↗
PubMed1981

Muscle fibre composition and glycogen depletion in horses competing in an endurance ride.

An investigation into fibre composition and glycogen depletion pattern within the middle gluteal of 16 horses participating in an 80 km endurance ride was carried out. Although the proportion of slow twitch high oxidative (ST) fibres in the horses varied between 7 and 38 per cent, it was found that the horses with the highest proportion of these fibres usually had the best performance records. The cross-sectional area of the fast twitch low oxidative (FT) fibres was greatest, with the ST and fast twitch high oxidative (FTH) being similar in size. Most marked histological evidence of glycogen depletion after the ride was in the ST fibres, which were apparently totally depleted. A variable degree of depletion was found in both the FTH and FT fibres. Biochemical measurement of muscle glycogen showed a 56 +/- 7.2 per cent (mean +/- SEM) decrease in content.

Animals↗
PubMed1981

The pharmacokinetics of meclofenamic acid in the horse.

The pharmacokinetics of meclofenamic acid were studied in Thoroughbred horses and in ponies. After intravenous (i.v.) administration of either 2 mg/kg or 4 mg/kg sodium meclofenamate the elimination half-life was of the order of 0.9 h while the volume of distribution was found to be 0.128 litre/kg. Elimination was in accordance with a one-compartment model. Following oral administration of either meclofenamic acid (4 mg/kg) or sodium meclofenamate (4 mg/kg) a much longer terminal half-life than that calculated for Kel from i.v. data was found. This anomaly indicated that the 'flip-flop' phenomenon was present, i.e. Ka exceeded Kel. More rapid and higher peak levels occurred following sodium meclofenamate than meclofenamic acid, although total bioavailability was similar. Studies in ponies with meclofenamic acid showed a lower absorption than that found in Thoroughbreds. Overnight fasting before meclofenamic acid administration did not alter the rate or extent of absorption. Intramuscular administration of sodium meclofenamate resulted in low plasma concentrations and after 25 h only 46% of the drug had been absorbed.

Administration, Oral↗
PubMed1981

Hormonal changes associated with long distance exercise.

The alteration in plasma concentration of a number of hormones was investigated following an 80 km endurance ride. A marked rise in plasma cortisol levels occurred in all 17 animals investigated. Although decreased glucose levels did not occur in all animals, insulin levels fell in all horses examined. A high correlation (r = 0.89) was found between post ride glucose and plasma insulin concentrations. The plasma levels of both noradrenaline and adrenaline were significantly elevated post ride.

Animals↗
PubMed1981

Skeletal muscle fibre composition in the dog and its relationship to athletic ability.

Skeletal limb muscles of the dog could generally be differentiated into three fibre types according to myosin adenosine triphosphatase (ATPase) (pH 9.4) and succinic dehydrogenase activities. However, because this was not always possible, for comparative purposes only, division into low myosin ATPase (slow twitch) type I and high myosin ATPase (fast twitch) type II fibres was used. The percentage of these fibre types in m deltoideus, m triceps brachii caput longum, m vastus lateralis, m gluteus medius, m biceps femoris and m semitendinosus was examined in the greyhound, crossbred and foxhound. In all muscles the greyhound had a significantly higher percentage of fibres with high myosin ATPase activity at pH 9.4 than the other breeds, with almost 100 per cent in most muscles examined. The activities of nine enzymes and glycogen concentration were determined in m gluteus medius and m semitendinosus of the greyhound and crossbred. Significantly higher levels of creatine kinase, aldolase, alanine aminotransferase and citrate synthase and significantly lower activities of 3-hydroxyacyl coenzyme A dehydrogenase and hexokinase were found in both muscles of the greyhound. The implications of these findings are discussed.

Adenosine Triphosphatases↗
PubMed1981

Phenylbutazone toxicosis in equidae: a biochemical and pathophysiological study.

Toxic effects of phenylbutazone (PBZ) in ponies and horses were studied, using a variety of biochemical, pathophysiologic, and pathologic methods. At dosage levels of 10 to 12 mg/kg of body weight/day for 8 to 10 days, ponies frequently developed clinical signs of toxicosis characterized by hypoproteinemia. Studies using 51CrCl3 demonstrated that PBZ caused a protein-losing gastroenteropathy. The plasma loss was usually associated with gastrointestinal ulceration, but sometimes occurred without obvious lesions in mildly affected animals. Similar studies (8.2 mg/kg/day for 13 days) in Thoroughbreds indicated that they were less susceptible to PBZ toxicity; however, a degree of hypoproteinemia occurred in 4 of 6 treated Thoroughbreds.

Animals↗
PubMed1980

Muscle fibre type composition of a number of limb muscles in different types of horse.

Skeletal muscle of the equine was differentiated into three fibre types according to myosin ATPase (pH 9.4) and succinic dehydrogenase activity. The percentage of these types was determined in the musculus deltoideus, m triceps brachii caput longum, m gluteus medius, m semitendinosis, m biceps femoris and m vastus lateralis of the thoroughbred, Shetland pony, pony, heavy hunter and donkey. In addition the m gluteus medius was examined in the arab and American racing quarterhorse. High myosin ATPase activity fibres varied from a mean of 93.2 per cent in the m gluteus medius of the quarterhorse to 58.2 per cent in the m vastus lateralis of the donkey. In the m gluteus medius it was found that the percentage of high mycosin ATPase (pH 9.4) fibres varied significantly among breeds and these differences were related to the sprinting speed of the breed.

Adenosine Triphosphatases↗
PubMed1979

Phenylbutazone toxicity in ponies.

The oral administration of phenylbutazone at a dose rate of approximately 10 mg per kg per day for seven to 14 days resulted in the development of signs of toxicity in seven of eight ponies treated. Clinical signs included anorexia, depression and abdominal oedema. Blood biochemical determinations showed a decrease in total plasma protein and calcium concentrations with an increase in urea concentration. These changes were considered indicative of water retention. Three of the ponies died during treatment following the development of shock. Shock was considered to arise from the submucosal oedema of the large intestine observed on necropsy. Oral ulceration was also found in these animals. In two ponies intravenous administration of phenylbutazone (4.0 mg per kg) for seven days was studied. In one of these ponies a marked decrease in total plasma protein concentration occurred.

Administration, Oral↗
PubMed1979

The effect of training and detraining on several enzymes in horse skeletal muscle.

Training and detraining had little effect on the activity of glycogen synthase, hexokinase, glycerol 3-phosphate dehydrogenase or total protein. The activity of 3-hydroxyacyl-CoA dehydrogenase increased markedly during training. After 5 weeks of detraining, the activity of 3-hydroxyacyl-CoA dehydrogenase was returning to pre-training values, whilst by 10-week detraining, the levels were increasing again.

3-Hydroxyacyl CoA Dehydrogenases↗
PubMed1979

Metabolic and physiological effects of adrenoceptor agonists and antagonists in the horse.

In the horse the effect of the adrenergenic agonists adrenaline, phenylephrine and salbutamol on haematocrit, plasma free fatty acid, glycerol and lactate levels were investigated. Effects on heart rate, sweating and muscle tremor were also studied. The effects of administration of the adrenoceptor antagonists propranolol, metoprolol, H35/25 and acepromazine on adrenaline-induced changes were examined. The results obtained with these agonists and antagonists suggest that the lipolysis and hyperglycaemia are mediated via beta-adrenoceptors. It appears that both beta1 and beta2 subtypes are involved. Muscle glycogenolysis, muscle tremor and sweating were mediated via beta2-adrenoceptors. Although salbutamol caused an elevation in haematocrit the other results support the alpha-mediation of adrenaline induced increases in haematocrit.

Acepromazine↗
PubMed1979

The actions of the beta-adrenoceptor blocking agents propranolol and metoprolol in the maximally exercised horse.

The effects of two beta-adrenoceptor antagonists, propranolol (0.2 mg/kg) and metoprolol (0.2 mg/kg) on some physiological and metabolic changes produced by maximal exercise in the horse were investigated. Both drugs reduced the elevation in heart rate seen immediately following exercise and reduced performance as was seen by the increased time taken to perform each gallop. The rise in plasma glucose, glycerol and lactate, and the fall in blood pH seen following exercise were attenuated by both drugs. However, a greater increase in plasma free fatty acids occurred. Exercise produced a nine- to 12-fold increase in plasma noradrenaline levels. Neither drug had any effect on resting levels of noradrenaline but after metoprolol the levels during exercise were increased.

Animals↗
PubMed1978

The effects of exercise and adrenaline infusion upon the blood levels of propranolol and antipyrine in the horse.

There are now several examples showing that experimentally induced changes in hepatic blood flow can have a marked effect upon the elimination of certain high clearance drugs. Changes in hepatic blood flow produced by exercise might therefore be expected to influence the clearance of these drugs. There was an increase of up to 100%, compound to control values, in the plasma levels of propranolol in horses given either d- or dl-propranolol, 0.2 mg/kg b.wt., and then subjected to sustained exercise for 30 minutes. There was, however, no similar increase with exercise in the plasma levels of antipyrine in horses given antipyrine, 50 mg/kg b.wt. Intravenous infusions of adrenaline, 1 microgram/kg b.wt./min for 10 minutes also produced an increase of about 70% in the plasma levels of d-propranolol.

Animals↗
PubMed1977

An evaluation of chemical restraining agents in the horse.

An evaluation of acepromazine (0.5 mg/kg intramuscularly), azaperone (0.7 and 0.9 mg/kg intramuscularly) and xylazine (2.0 mg/kg intramuscularly) as chemical restraining agents was carried out in seven horses. (Xylazine and azaperone were used at the recommended dose rates; acepromazine at five times the recommended dose rates). Of the three drugs administered only azaperone produced sufficient sedation in all the horses to allow a percutaneous needle muscle biopsy to be taken from six muscles. With acepromazine and xylazine this procedure could be successfully carried out in five and four horses respectively. Both acepromazine and azaperone produced a mild transient tachycardia and a fall in packed cell volume but all three drugs reduced the "stress" of muscle biopsy as measured by increases in heart rate. Azaperone produced an increase in plasma 11-OHCS levels when administered to control animals. The measurement of changes in plasma 11-OHCS levels was not found to be a satisfactory means of assessing any reduction of "stress" with some sedative agents.

11-Hydroxycorticosteroids↗
PubMed1977

Some metabolic effects of maximal exercise in the horse and adaptations with training.

The effects of intermittent maximal exercise (galloping) before and after a 10 week training programme were studied in 6 horses. Determinations were carried out on venous blood for packed cell volume, total plasma protein, glucose, glycerol, free fatty acids, lactate, 11-hydroxycorticosteroids, blood gases and pH. There were marked changes associated with galloping and some of these could be modified with training. The major findings included (i) an elevated blood glucose, (ii) a large increase in glycerol, which was greatest at 30 min post-exercise and was higher following training, (iii) smaller increases in free fatty acids following training, (iv) higher levels of lactate after training, (v) a marked fall in pH which was less after training, (vi) an increase in 11-hydroxycorticosteroids with possibly a more rapid return to resting levels following training. It was concluded that with maximal exercise in the horse both glycogen and free fatty acids served as important substrates for working muscle, and following training greater utilisation of both these substrates occurred.

Animals↗