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Biomedical subjects

D H Snow

Publications and source records attributed to D H Snow.

At least 37 records · Page 2Linked to original sources
PubMed1989

Effect of freeze-drying on measurements of pH in biopsy samples of the middle gluteal muscle of the horse: comparison of muscle pH to the pyruvate and lactate content.

Muscle biopsies taken after exercise, in comparison to those at rest, contain increased amounts of blood and this is a particular problem in studies of the horse. The inclusion of blood in muscle will introduce an upward bias in values of pH measured in muscle homogenates. In an attempt to control this, muscle biopsy samples of the middle gluteal from Thoroughbred horses were freeze-dried and dissected free of blood before determination of pH. Following exercise, muscle pH measured after freeze-drying was similar to that measured in homogenates prepared from frozen samples. In contrast, freeze-drying appeared to increase muscle pH in samples taken at rest. This was probably the result of loss of CO2 during freeze-drying. Muscle pH determined in freeze-dried samples taken at rest and after exercise was linearly related to pyruvate and lactate content (P less than 0.001). It is concluded that muscle samples taken after exercise can be freeze-dried and dissected free from blood before determination of pH, whereas this procedure will cause an alkaline shift in samples taken at rest.

Animals↗
PubMed1988

Changes in haematology and plasma biochemistry during maximal exercise in greyhounds.

The haematological and biochemical changes associated with racing over 235 and 420 metres were studied in 23 greyhounds. Blood samples were collected while the dogs were resting and immediately after and 30 minutes after racing. Significant increases in red blood cell count, haemoglobin concentration and haematocrit occurred. The increase in haematocrit was accompanied by increases in total plasma protein and creatinine concentrations. Blood lactate increased to 11.4 and 13.2 mmol/litre over 235 and 420 metres, respectively, and plasma glucose increased to 7.9 and 8.2 mmol/litre. After the 420 metres, the mean plasma ammonia concentration was 256 mumol/litre. Plasma free fatty acid concentrations also increased after dogs had run both distances. The highest concentrations of glycerol and uric acid were found 30 minutes after exercise.

Animals↗
PubMed1988

Effects of maximal exercise on the blood composition of the racing camel.

Haematological and blood biochemical changes were studied in nine camels after maximal exercise over 4 or 5 km. There was a lack of splenic reserve for red blood cells, indicated by a minimal increase in haemoglobin concentration and haematocrit. There were marked increases in plasma lactate (to over 20 mmol/litre), plasma ammonia and plasma glucose and a pronounced decrease in circulating free fatty acids. There were small but significant increases in plasma calcium, magnesium, sodium, potassium, chloride and phosphate concentrations.

Animals↗
PubMed1988

Circulatory, respiratory and metabolic responses in Thoroughbred horses during the first 400 meters of exercise.

These studies investigated circulatory, respiratory and metabolic responses in four Thoroughbred geldings during the first 400 metres of galloping (mean speed 14.4 +/- 0.38 m.s-1), cantering (mean speed 10.0 +/- 0.61 m.s-1) and walking (mean speed 1.58 +/- 0.05 m.s-1) from a standing start. A radio-controlled device which collected blood samples anaerobically during each 100 m section of the exercise track allowed analyses of changes in and functional relationships of the variables measured. During the 400 m gallop, the mean heart rate (HR) increased from 125 to 201 beats.min-1 and the haematocrit (Hct) from 0.513 to 0.589 l/l-1. The haemoglobin [Hb], lactate [LA] and potassium [K+] concentrations increased significantly, while the pH and the partial pressure of oxygen (PaO2) decreased significantly. The arterial partial pressure of carbon dioxide (PaCO2) and the plasma bicarbonate concentration did not change significantly. There were significant correlations between HR and Hct, HR and [Hb], HR and PaO2, HR and pH, HR and PvCO2, HR and [LA], HR and [K+], pH and [K+], Hct and PaO2, [Hb] and PaO2, PaCO2 and PaO2, [LA] and PaO2, pH and PaO2, [K+] and PaO2, stride frequency and PaO2. With the exception of the PvCO2 which increased significantly, changes in venous blood during the gallop were in the same direction as those of arterial blood. Thirty seconds before the start of the gallop, both HR and [Hb] were significantly higher than at rest, providing an approximate three-fold increase in oxygen delivery compared to that of the resting state.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

The effect of oral L-carnitine supplementation on the muscle and plasma concentrations in the Thoroughbred horse.

1. L-carnitine was administered orally to thoroughbred horses for 58 days. 2. Acceptability and effects on plasma, muscle and urine concentration were studied. 3. Ten-60 g/day (as 2-3 doses) was acceptable with no deleterious effects. 4. One x 10 g L-carnitine significantly raised the plasma-free carnitine concentration (7 hr post) from 21.2 to 31.8 mumol/l; 2 x 30 g increased the mean to 36.5 mumol/l. 5. Plasma acetylcarnitine increased from approximately 1 to 5.5 mumol/l (7 hr post) on 2 x 30 g/day. 6. Muscle total carnitine was unchanged over 58 days. 7. Urinary output accounted for 3.5-7.5% of added carnitine, indicating low intestinal absorption.

Administration, Oral↗
PubMed1988

The effects of high intensity exercise on the plasma concentration of lactate, potassium and other electrolytes.

To study the effect of short term high intensity exercise on plasma lactate, potassium, sodium and chloride concentrations, five Thoroughbred horses were galloped on a treadmill at a 5 degree incline. Following a standardised warm-up period, they were galloped at 8, 10, or 12 metres/sec for 2 mins. One horse also galloped at 14 metres/sec for 1.5 mins. Sequential arterial and/or venous blood samples were collected during exercise and recovery. At 12 metres/sec, the effect of different recovery modes, ie, standing, walking or trotting, on the electrolytes was also examined. There was a progressive rise in plasma potassium concentration during galloping, with peak values occurring at the end of the exercise bout. In some cases, values above 10 mmol/litre were recorded at the highest workloads. Plasma lactate concentrations peaked during early recovery, with values up to 32 mmol/litre. A high correlation existed between peak potassium and lactate concentrations (venous r = 0.923, and arterial r = 0.989). Following exercise there was a rapid return to baseline plasma potassium concentrations, but by 12 mins recovery there was still an elevated lactate concentration, the extent depending on the intensity of the exercise bout and the recovery mode. There was a small rise in plasma sodium but no significant change in plasma chloride concentrations during exercise. However, when adjusted for the decrease in plasma volume, as determined from total plasma protein concentration, there was a decrease in circulating amounts of both electrolytes.

Animals↗
PubMed1988

Metabolic changes in skeletal muscle and blood of greyhounds during 800-m track sprint.

The aim of this study was to examine some metabolic properties and changes that occur in skeletal muscle and blood of greyhounds after an 800-m sprint. Three prime moving fast-twitch muscles were selected: biceps femoris (BF), gastrocnemius (G), and vastus lateralis (VL). The amount of glycogen utilized during the event was 42.57, 43.86, and 42.73 mumol glucosyl units/g wet wt, respectively. Expressed as a function of race time (48.3 +/- 0.7 s, n = 3), the mean rate of glycogen breakdown was 53.48 +/- 0.5 mumol.g wet wt-1.min-1 during the sprint. This is equivalent to an ATP turnover of 160 mumol.g wet wt-1.min-1, assuming 100% anaerobic conversion to lactate. This represents a conservative estimate, since greyhound muscle is heterogeneous and comprised of a large percentage of fast-twitch oxidative fibers (Armstrong et al., Am. J. Anat. 163: 87-98, 1982). The large decrease in muscle glycogen was accompanied by a 6- to 7-fold increase in muscle lactate from 3.48 +/- 0.13 to 25.42 +/- 3.54 (BF), 2.54 +/- 1.05 to 18.96 +/- 2.60 (G), and 4.57 +/- 0.44 to 30.09 +/- 1.94 mumol.g wet wt (VL), and a fall in muscle pH from 6.88 +/- 0.03 to 6.40 +/- 0.02 (BF), 6.92 +/- 0.02 to 6.56 +/- 0.02 (G), and 6.93 +/- 0.02 to 6.47 +/- 0.01 (VL). Cytosolic phosphorylation potential in BF decreased 10-fold from 11,360 +/- 680 to 1,184 +/- 347, and redox potential decreased 5-fold, indicating a marked reduction in the cytosol at this time.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine Triphosphate↗
PubMed1987

Oral administration of ascorbic acid to horses.

The effects of oral administration of high doses of ascorbic acid on plasma concentrations were investigated in both experimental Thoroughbred horses and those within racing stables. A single oral dose (20 g) did not result in any increase in plasma concentrations. However, daily administration of either 4.5 g or 20 g doses resulted in significant increases in plasma concentrations. Monthly variations in plasma ascorbate concentrations were found in both supplemented (20 g daily) and unsupplemented stables. It is concluded that oral supplementation with ascorbic acid is a satisfactory route to increase plasma and tissue concentrations.

Administration, Oral↗
PubMed1987

Cardiac output and oxygen consumption in exercising Thoroughbred horses.

This study characterizes the effects of exercise on the cardiac output (Q) and the metabolic rate (VO2) of trained Thoroughbred racehorses. Heart rate, Q, and arteriovenous (a-v)O2 difference were measured at rest and at three levels of submaximal treadmill exercise (1.6 m/s walk and 3-4 m/s trot at 6% incline, and 6.5 m/s horizontal canter). Heart rate and (a-v)O2 difference were also measured during maximal exercise (12.5 m/s gallop, 5% incline) to obtain an estimate of maximum O2 uptake (VO2max). The walk, trot, and canter represented 25, 45, and 55% VO2max. Mean heart rate went from 48.9 (rest) to 197 beats/min (gallop). Q ranged from 106 (rest) to 571 ml.min-1.kg-1 (canter), and stroke volume went from 1.34 (rest) to a maximum of 1.58 liters (walk). Thoroughbreds were able to bring hematocrit from 38 (rest) to 63% (gallop), and this adjustment allowed them to reach an impressive (a-v)O2 difference of 23 vol%, which represents a fivefold increase over resting values. These outstanding athletes probably support an aerobic scope of 40-fold.

Animals↗
PubMed1987

Lactate kinetics in exercising Thoroughbred horses: regulation of turnover rate in plasma.

Plasma lactate turnover rate of Thoroughbred racehorses was measured by bolus injection of [U-14C]lactate at rest and two levels of submaximal treadmill exercise (3-4 m/s trot, 6% incline, and 6.5 m/s horizontal canter). Our goals were 1) to determine the relative effects of changes in cardiac output and in plasma lactate concentration on turnover rate [using cardiac output data from Weber et al. (28)] and 2) to assess the importance of lactate as a metabolic fuel in a trained animal athlete. Lactate turnover rates were 9.3 mumol.min-1.kg-1 (rest), 75.9 mumol.min-1.kg-1 at the beginning of the trot protocol [45% maximum O2 uptake (VO2max)], 50.3 mumol.min-1.kg-1 later in the same protocol (50% VO2max), and 66.1 mumol.min-1.kg-1 during the canter protocol (55% VO2max). Both changes in cardiac output and in plasma lactate concentration had a significant effect on turnover rate. Variation in plasma lactate fluxes of Thoroughbreds during exercise follows the standard mammalian pattern, but this substrate only plays a minor role as an oxidizable fuel in horses. The oxidation of plasma lactate accounts for less than 5% of metabolic rate (VO2) during submaximal work. Adjustments in cardiac output and in metabolite concentration represent, respectively, the coarse and fine controls for the regulation of plasma metabolite turnover rate.

Animals↗
PubMed1987

Metabolic response to maximal exercise of 800 and 2,000 m in the thoroughbred horse.

To define the metabolic response to maximal exercise in the thoroughbred horse under field conditions, muscle biopsies and venous blood samples were taken from five horses after a single 800-m gallop and from four horses after a single 2,000-m gallop. Muscle and blood samples were also collected during 60 min of recovery. After exercise muscle ATP contents were decreased by 30 +/- 7 (SD) and 47 +/- 3% after the 800- and 2,000-m gallops, respectively. As indicators of purine catabolism, ammonia and uric acid increased in plasma, the accumulation being greater after the 2,000-m gallop. Blood ammonia peaked immediately after exercise and uric acid after 40-60 min of recovery. Muscle glycogen utilization over the 800- and 2,000-m gallops averaged 2.68 +/- 0.90 and 1.06 +/- 0.12 mmol glucosyl units.kg dry muscle-1.s-1, respectively, and the total used amounted to 27.3 +/- 6.6 and 32.5 +/- 8.8% of the initial store. Muscle lactate accumulation averaged 123.5 +/- 49.7 and 167.3 +/- 20.7 mmol/kg dry muscle, respectively, and declined during recovery with half times of 22.9 +/- 4.2 and 18.9 +/- 6.6 min. Blood lactate peaked 5-10 min after exercise. Exercise resulted in only a small increase in muscle glycerol content, but this continued to rise during recovery reaching 9-12 mmol/kg dry muscle after 20 min. During this time the increase in muscle glycerol content exactly matched the decline in glycerol 3-phosphate.

Adenine Nucleotides↗
PubMed1986

Isolation and characterization of latherin, a surface-active protein from horse sweat.

A protein, latherin, with unusual surface activity was isolated from horse sweat by gel filtration and ion-exchange chromatography. The protein has a Stokes radius, determined by gel filtration, of 2.47 nm, and in the ultracentrifuge sediments as a single species with S20,W 2.05 S, indicating an Mr of 24,400. On SDS/polyacrylamide-gel electrophoresis the molecule behaves as a single peptide chain of apparent Mr 20,000. Latherin contains a high proportion of hydrophobic amino acids (37.2%), and the leucine content (24.5%) is exceptionally high. The unusual composition of the protein may account for apparent anomalies in the Mr of latherin determined by empirical methods. Evidence indicating that latherin is responsible for much of the surface activity of horse sweat was obtained by a simple assay for surface tension and by contact-angle measurements. Latherin adsorbs very readily at hydrophobic surfaces, rendering them wettable. A possible role for latherin in thermoregulation is proposed.

Amino Acids↗
PubMed1985

The inheritance of skeletal muscle fibre composition in mice.

Two inbred strains of mice C3H/HE and SWR, and generations produced by intercrossing, were studied to investigate the effect of heredity on muscle composition. The data were found to be consistent with a polygenic mode of inheritance. No simple effect of sex-linkage or maternal influence was evident. The heritability of fibre type percentage total fibre number and the relative size of Type I and Type II fibres were highly significant. Principal component analysis yielded a "genetic" vector which accounted for 57% of the variation in muscle fibre composition. Patterns of covariance of fibre type percentage, total fibre number and relative sizes of Type I and Type II fibres showed a single correlated response.

Animals↗