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Papers by David Marlin

Research paper thumbnail of Muscle buffering capacity and dipeptide content in the Thoroughbred horse, Greyhound dog and man

Comparative Biochemistry and Physiology a Comparative Physiology, Feb 1, 1990

1. Muscle buffering capacity (beta m) and dipeptide content were measured in locomotory muscles o... more 1. Muscle buffering capacity (beta m) and dipeptide content were measured in locomotory muscles of the Thoroughbred horse, Greyhound dog and Man. 2. Beta m and carnosine contents were highest in the horse. Anserine was only found in dog muscle. 3. The higher beta m in horse and dog muscle, compared with man, appears to be predominantly due to higher muscle contents of histidine containing dipeptides in these species.

Research paper thumbnail of Plasma aspartate aminotransferase and creatine kinaseactivities in thoroughbred racehorses in relation to age, sex, exercise and training

Vet J, 1998

In order to investigate the effect of age, sex and month on the response of plasma aspartate amin... more In order to investigate the effect of age, sex and month on the response of plasma aspartate aminotransferase(AST) and creatine kinase (CK) to exercise, blood samples were collected once a month between March and September from a group of 40 2- and 3-year-old (2yo and 3yo) thoroughbred racehorses (kept under the same managemental regimen) at rest before exercise (PRE) and at 2 (2H) and 24h (24H) post-exercise. The absolute change in activities between the 2H and PRE samples (2HΔ) and the 24H and PRE samples (24HΔ) was also calculated. Age had a significant effect on all measured and calculated parameters for colts (C), apart from 24HΔ CK but showed no effect in the fillies (F). Sex only had a significant effect in the 3yo in the 2HΔ CK. In the 2yo, significant effects of sex were found for both CK and AST in the PRE, 2H and 24H samples. The effect of month varied according to the classification group with only the 2yoC not showing any significant effect on any parameter. Fillies were, in general, more likely than colts to show greater than a twofold increase in CK activity at 2H post-exercise and the number of animals showing such an increase decreased as the season progressed. Very little change in AST activities occurred with exercise.

Research paper thumbnail of Metabolic response to maximal exercise of 800 and 2,000 m in the Thoroughbred horse

Journal of Applied Physiology

To define the metabolic response to maximal exercise in the thoroughbred horse under field condit... more 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.

Research paper thumbnail of Titrimetric determination of muscle buffering capacity (beta mtitr) in biopsy samples

Equine Veterinary Journal

In vitro titration of muscle homogenates has been used to assess muscle buffering capacity (beta ... more In vitro titration of muscle homogenates has been used to assess muscle buffering capacity (beta mtitr) in a variety of species. In the present study, factors likely to affect the estimation of beta mtitr were investigated. Also, values of beta mtitr from normal Thoroughbred horses are presented. A non-linear titration curve was obtained with addition of HCl to muscle homogenates. As a result, beta mtitr is expressed as the mumol H+ required to change the pH of 1g of dry muscle or wet muscle from 7.1 to 6.5. An effect of dilution on the initial pH was found below 40 mg wet muscle per ml homogenising reagent (10 mg dry muscle per ml) and on beta mtitr below 10 mg wet muscle. As a result, 40 mg wet muscle or 10 mg dry muscle per ml was chosen as the minimum concentration for determination of beta mtitr. Incubation of homogenates up to 60 mins did not affect beta mtitr significantly. As a mean, beta mtitr in wet muscle was approximately 25 per cent higher compared to dry muscle. The beta mtitr of dry muscle was increased by approximately 18 per cent when HCO3- was added in an amount equivalent to the calculated HCO3- content of wet muscle at rest. The homogenisation process resulted in complete loss of adenosine triphosphate and phosphocreatine with only small changes in adenosine diphosphate and adenosine monophosphate. It was concluded that the estimates of beta mtitr did not include any contribution from 'dynamic' buffering via rephosphorylation of adenosine diphosphate by phosphocreatine, and in dry muscle it was accounted for mainly through physico-chemical buffering by phosphates, proteins and dipeptides. beta mtitr determined in biopsy samples of muscle from 20 Thoroughbred horses ranged from 100.8 to 131.8 mumol H+/g dry muscle pH 7.1 to 6.5 (mean 121.2, sd +/- 7.4).

Research paper thumbnail of Post exercise changes in compartmental body temperature accompanying intermittent cold water cooling in the hyperthermic horse

Equine veterinary journal, 1998

Whereas the efficacy of cold water cooling of horses has been demonstrated by several studies, th... more Whereas the efficacy of cold water cooling of horses has been demonstrated by several studies, the dynamics of temperature changes within and between compartments (primarily muscle, blood [core], skin and deep core [rectal]) have not been investigated. Changes in body temperature associated with cold water cooling were investigated in the hyperthermic horse. Muscle (TMU), pulmonary artery (TPA), rectal (TREC), tail-skin (TTSK) and coat surface (TCOAT) temperatures, were monitored continuously in 5 Thoroughbred horses during and after exercise in hot humid (30 degrees C and 80% RH) conditions on a treadmill. Horses were cooled in the hot humid environment with cold water (approximately 6 degrees C) for 6 30 s periods. Between each 30 s cooling period the horses stood for 30 s. A total of 180 l of cold water was applied. Horses were monitored for a further 4 min following the final cooling period. From the end of exercise to the end of the final cooling (6.5 min), mean (+/- s.e.) rate...

Research paper thumbnail of Muscle buffering capacity and dipeptide content in the thoroughbred horse, greyhound dog and man

Comparative biochemistry and physiology. A, Comparative physiology, 1990

1. Muscle buffering capacity (beta m) and dipeptide content were measured in locomotory muscles o... more 1. Muscle buffering capacity (beta m) and dipeptide content were measured in locomotory muscles of the Thoroughbred horse, Greyhound dog and Man. 2. Beta m and carnosine contents were highest in the horse. Anserine was only found in dog muscle. 3. The higher beta m in horse and dog muscle, compared with man, appears to be predominantly due to higher muscle contents of histidine containing dipeptides in these species.

Research paper thumbnail of Estimation of the carnosine content of different fibre types in the middle gluteal muscle of the thoroughbred horse

The Journal of physiology, 1992

1. Skeletal muscle samples were obtained by needle biopsy from one of two depths of the m. gluteu... more 1. Skeletal muscle samples were obtained by needle biopsy from one of two depths of the m. gluteus medius in a group of twenty race-trained thoroughbred horses. 2. The content of carnosine was determined in each muscle sample, part of which was used for histochemical analysis. Fibres were classified as type I, type IIA or type IIB on the basis of the pH dependent lability of the myosin ATPase reaction. 3. Muscle samples with a higher type II fibre section area (FSA) have a higher carnosine content than those with a higher type I FSA. 4. Multiple linear regression analysis was used to estimate the mean carnosine content of individual fibre types. The results estimated a mean carnosine content in type I fibres of 54 mmol (kg dry muscle (DM))-1, in type IIA fibres 85 mmol (kg DM)-1 and in type IIB fibres 180 mmol (kg DM)-1. 5. Based on the estimated values of single fibre carnosine content, there was close concordance between the estimated and the measured carnosine content of mixed fi...

Research paper thumbnail of Changes in circulatory antioxidant status in horses during prolonged exercise

The Journal of nutrition, 2002

Prolonged low-medium intensity exercise is associated with increased oxidative stress in humans. ... more Prolonged low-medium intensity exercise is associated with increased oxidative stress in humans. We hypothesized that competitive equine endurance racing would induce changes in circulatory antioxidants and produce systemic oxidative stress. Forty horses competing in a 140-km endurance race in warm conditions [shade temperature 15-19 degrees C; 62-88% relative humidity (%RH)] were sampled before (Pre), immediately after exercise (End) and at approximately 16 h into recovery (+16 h). Plasma ascorbic acid concentration was not different between Pre [11.1 (median); 4.6-20.3 micromol/L (range)] and End [9.7; 3.0-38.9 (range) micromol/L] but was significantly decreased at +16 h (5.5; 2.8-15.5 micromol/L; P < 0.05). Total red cell hemolysate glutathione (TGSH) concentration was significantly reduced by exercise (Pre 1261; 883-1532 micromol/L; End 1065; 757-1334 micromol/L; P < 0.05) and at +16 h recovery (1032; 752-1362 micromol/L; P < 0.05). Glutathione redox ratio was unchanged...

Research paper thumbnail of Antioxidant supplementation in horses affected by recurrent airway obstruction

The Journal of nutrition, 2004

Journal of Nutrition Journal of Nutrition. Skip to main page content. ...

Research paper thumbnail of Skeletal muscle characteristics in 2 year-old race-trained thoroughbred horses

Comparative Biochemistry and Physiology Part A: Physiology, 1994

Skeletal muscle samples were obtained by needle biopsy from two depths of the m. gluteus medius o... more Skeletal muscle samples were obtained by needle biopsy from two depths of the m. gluteus medius of 50, young race-trained thoroughbred racehorses. Histochemical and biochemical characteristics of the muscle samples were analysed. Fibres were classilied as type I, type IIa or type IIb on the basis of the pH dependent lability of the myosin ATPase reaction.

Research paper thumbnail of Effect of intravenous lidocaine on heart rate, systolic arterial blood pressure and cough responses to endotracheal intubation in propofol-anaesthetized dogs

Veterinary Anaesthesia and Analgesia, 2007

Objective To evaluate the effect of intravenous lidocaine on coughing and variations in heart rat... more Objective To evaluate the effect of intravenous lidocaine on coughing and variations in heart rate (HR) and systolic arterial pressure (SAP) at endotracheal intubation in propofol-anaesthetized dogs.

Research paper thumbnail of Effects of syringe material and temperature and duration of storage on the stability of equine arterial blood gas variables

Veterinary Anaesthesia and Analgesia, 2004

Objectives To evaluate the consistency of partial pressures (P) of arterial oxygen (aO 2 ), arter... more Objectives To evaluate the consistency of partial pressures (P) of arterial oxygen (aO 2 ), arterial carbon dioxide (aCO 2 ) and pH measurements in equine carotid arterial blood samples taken into syringes made from three different materials and stored at room temperature or placed in iced water for measurement at three different times.

Research paper thumbnail of Increased cerebrospinal fluid uric acid concentrations in dogs with intracranial meningioma

Research paper thumbnail of Plasma aspartate aminotransferase and creatine kinaseactivities in thoroughbred racehorses in relation to age, sex, exercise and training

The Veterinary Journal, 1998

In order to investigate the effect of age, sex and month on the response of plasma aspartate amin... more In order to investigate the effect of age, sex and month on the response of plasma aspartate aminotransferase (AST) and creatine kinase (CK) to exercise, blood samples were collected once a month between March and September from a group of 40 2- and 3-year-old (2yo and 3yo) thoroughbred racehorses (kept under the same managemental regimen) at rest before exercise (PRE) and at 2 (2H) and 24 h (24H) post-exercise. The absolute change in activities between the 2H and PRE samples (2H delta) and the 24H and PRE samples (24H delta) was also calculated. Age had a significant effect on all measured and calculated parameters for colts (C), apart from 24H delta CK but showed no effect in the fillies (F). Sex only had a significant effect in the 3yo in the 2H delta CK. In the 2yo, significant effects of sex were found for both CK and AST in the PRE, 2H and 24H samples. The effect of month varied according to the classification group with only the 2yoC not showing any significant effect on any parameter. Fillies were, in general, more likely than colts to show greater than a twofold increase in CK activity at 2H post-exercise and the number of animals showing such an increase decreased as the season progressed. Very little change in AST activities occurred with exercise.

Research paper thumbnail of Effects of Cool and Hot Humid Environmental Conditions on Neuroendocrine Responses of Horses to Treadmill Exercise

The Veterinary Journal, 2002

To determine the effects of exercise, high heat and humidity and acclimation on plasma adrenaline... more To determine the effects of exercise, high heat and humidity and acclimation on plasma adrenaline, noradrenaline, b-endorphin and cortisol concentrations, five horses performed a competition exercise test (CET; designed to simulatethespeedandendurancetestofathree-dayevent)incooldry(CD)(20 C/40%RH)andhothumid(30 C/ 80% RH) conditions before (pre-acclimation) and after (post-acclimation) a 15 day period of humid heat acclimation. Plasma adrenaline and noradrenaline concentrations pre-acclimation were significantly increased compared with exercisein the CD trial at the end of PhasesC (P`0.05) and D (P`0.05and P`0.01, respectively) and at 2 min recovery (P`0.01), with adrenaline concentrations still elevated after 5 min of recovery (P`0.001). Plasma b-endorphin concentrations were increased at the end of Phases C (P`0.05) and X (P`0.01) and at 5 and 30 min recovery (P`0.05) in the pre-acclimation session. Plasma cortisol concentrations were elevated after the initial warmupperiodpre-acclimation(P`0.01)andattheendofPhaseC(P`0.05),comparedwiththeCDtrial.A15day period of acclimation significantly increased plasma adrenaline concentrations at 2 min recovery (P`0.001) and plasma cortisol concentration at the end of Phase B (P`0.01) compared with pre-acclimation. Acclimation did not significantly influence noradrenaline or b-endorphin responses to exercise, although there was a trend for plasma b-endorphin to be lower at the end of Phases C and X and after 30 min recovery compared with pre-acclimation. Plasma adrenaline, noradrenaline, b-endorphin and cortisol concentrations were increased by exercise in cool dry conditions and were further increased by the same exercise in hot humid conditions. Exercise responsespost-acclimation suggest that adrenaline andnoradrenaline may play a role intheadaptation of horses to thermal stress and that changes in plasma b-endorphin concentrations could be used as a sensitive indicator of thermal tolerance before and after acclimation. The use of plasma cortisol as a specific indicator of heat stress and thermal tolerance before or after acclimation in exercising horses appears limited.

Research paper thumbnail of Metabolic adaptation to a fat-supplemented diet by the thoroughbred horse

British Journal of Nutrition, 1997

Research paper thumbnail of Breath Condensate Hydrogen Peroxide Correlates with Both Airway Cytology and Epithelial Lining Fluid Ascorbic Acid Concentration in the Horse

Free Radical Research, 2004

The relationship between hydrogen peroxide (H2O2) concentration in expired breath condensate (EBC... more The relationship between hydrogen peroxide (H2O2) concentration in expired breath condensate (EBC) and cytology of the respiratory tract obtained from tracheal wash (TW) or bronchoalveolar lavage (BAL), and epithelial lining fluid (ELF) antioxidant status is unknown. To examine this we analysed the concentration of H2O2 in breath condensate from healthy horses and horses affected by recurrent airway obstruction (RAO), a condition considered to be an animal model of human asthma. The degree of airway inflammation was determined by assessing TW inflammation as mucus, cell density and neutrophil scores, and by BAL cytology. ELF antioxidant status was determined by measurement of ascorbic acid, dehydroascorbate, reduced and oxidised glutathione, uric acid and alpha-tocopherol concentrations. RAO-affected horses with marked airway inflammation had significantly higher concentrations of breath condensate H2O2 than control horses and RAO-affected horses in the absence of inflammation (2.0 +/- 0.5 micromol/l. 0.4 +/- 0.2 micromol/l and 0.9 +/- 0.2 micromol/l H2O2, respectively; p &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.0001). The concentration of breath condensate H2O2 was related inversely to the concentration of ascorbic acid in ELF (r = -0.80; p &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.0001) and correlated positively with TW inflammation score (r = 0.76, p &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.0001) and BAL neutrophil count (r = 0.80, p &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.0001). We conclude that the concentration of H2O2 in breath condensate influences the ELF ascorbic acid concentration and provides a non-invasive diagnostic indicator of the severity of neutrophilic airway inflammation.

Research paper thumbnail of Pulmonary Bioavailability of Ascorbic Acid in an Ascorbate-synthesising Species, the Horse

Free Radical Research, 2003

Vitamin C (ascorbic acid) is a non-enzymatic antioxidant important in protecting the lung against... more Vitamin C (ascorbic acid) is a non-enzymatic antioxidant important in protecting the lung against oxidative damage and is decreased in lung lining fluid of horses with airway inflammation. To examine possible therapeutic regimens in a species with ascorbate-synthesising capacity, we studied the effects of oral supplementation of two forms of ascorbic acid, (each equivalent to 20 mg ascorbic acid per kg body weight) on the pulmonary and systemic antioxidant status of six healthy ponies in a 3 x 3 Latin square design. Two weeks supplementation with ascorbyl palmitate significantly increased mean plasma ascorbic acid concentrations compared to control (29 +/- 5 and 18 +/- 7 micromol/l, respectively; p &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.05). Calcium ascorbyl-2-monophosphate, a more stable form of ascorbic acid, also increased mean plasma ascorbic acid concentrations, but not significantly (23 +/- 1 micromol/l; p = 0.07). The concentration of ascorbic acid in bronchoalveolar lavage fluid increased in five out of six ponies following supplementation with either ascorbyl palmitate or calcium ascorbyl-2-monophosphate compared with control (30 +/- 10, 25 +/- 4 and 18 +/- 8 micromol/l, respectively; p &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.01). Neither supplement altered the concentration of glutathione, uric acid or alpha-tocopherol in plasma or bronchoalveolar lavage fluid. In conclusion, the concentration of lung lining fluid ascorbic acid is increased following ascorbic acid supplementation (20 mg/kg body weight) in an ascorbate-synthesising species.

Research paper thumbnail of EFFECT OF ACUTE AIRWAY INFLAMMATION ON THE PULMONARY ANTIOXIDANT STATUS

Experimental Lung Research, 2005

Research paper thumbnail of Post exercise changes in compartimentai body temperature accompanying intermittent cold water cooling in the hyperthermic horse

Equine Veterinary Journal, 2000

... Post exercise changes in compartmental body temperature accompanying intermittent cold water ... more ... Post exercise changes in compartmental body temperature accompanying intermittent cold water cooling in the hyperthermic horse D. J. MARLIN*, CAROLINE M. SCOTT, C. A. ROBERTS, I. CASAS, G. HOLAHt and RC SCHROTER* ... Page 2. D. J. Marlin et al. -160 -140 - ...

Research paper thumbnail of Muscle buffering capacity and dipeptide content in the Thoroughbred horse, Greyhound dog and man

Comparative Biochemistry and Physiology a Comparative Physiology, Feb 1, 1990

1. Muscle buffering capacity (beta m) and dipeptide content were measured in locomotory muscles o... more 1. Muscle buffering capacity (beta m) and dipeptide content were measured in locomotory muscles of the Thoroughbred horse, Greyhound dog and Man. 2. Beta m and carnosine contents were highest in the horse. Anserine was only found in dog muscle. 3. The higher beta m in horse and dog muscle, compared with man, appears to be predominantly due to higher muscle contents of histidine containing dipeptides in these species.

Research paper thumbnail of Plasma aspartate aminotransferase and creatine kinaseactivities in thoroughbred racehorses in relation to age, sex, exercise and training

Vet J, 1998

In order to investigate the effect of age, sex and month on the response of plasma aspartate amin... more In order to investigate the effect of age, sex and month on the response of plasma aspartate aminotransferase(AST) and creatine kinase (CK) to exercise, blood samples were collected once a month between March and September from a group of 40 2- and 3-year-old (2yo and 3yo) thoroughbred racehorses (kept under the same managemental regimen) at rest before exercise (PRE) and at 2 (2H) and 24h (24H) post-exercise. The absolute change in activities between the 2H and PRE samples (2HΔ) and the 24H and PRE samples (24HΔ) was also calculated. Age had a significant effect on all measured and calculated parameters for colts (C), apart from 24HΔ CK but showed no effect in the fillies (F). Sex only had a significant effect in the 3yo in the 2HΔ CK. In the 2yo, significant effects of sex were found for both CK and AST in the PRE, 2H and 24H samples. The effect of month varied according to the classification group with only the 2yoC not showing any significant effect on any parameter. Fillies were, in general, more likely than colts to show greater than a twofold increase in CK activity at 2H post-exercise and the number of animals showing such an increase decreased as the season progressed. Very little change in AST activities occurred with exercise.

Research paper thumbnail of Metabolic response to maximal exercise of 800 and 2,000 m in the Thoroughbred horse

Journal of Applied Physiology

To define the metabolic response to maximal exercise in the thoroughbred horse under field condit... more 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.

Research paper thumbnail of Titrimetric determination of muscle buffering capacity (beta mtitr) in biopsy samples

Equine Veterinary Journal

In vitro titration of muscle homogenates has been used to assess muscle buffering capacity (beta ... more In vitro titration of muscle homogenates has been used to assess muscle buffering capacity (beta mtitr) in a variety of species. In the present study, factors likely to affect the estimation of beta mtitr were investigated. Also, values of beta mtitr from normal Thoroughbred horses are presented. A non-linear titration curve was obtained with addition of HCl to muscle homogenates. As a result, beta mtitr is expressed as the mumol H+ required to change the pH of 1g of dry muscle or wet muscle from 7.1 to 6.5. An effect of dilution on the initial pH was found below 40 mg wet muscle per ml homogenising reagent (10 mg dry muscle per ml) and on beta mtitr below 10 mg wet muscle. As a result, 40 mg wet muscle or 10 mg dry muscle per ml was chosen as the minimum concentration for determination of beta mtitr. Incubation of homogenates up to 60 mins did not affect beta mtitr significantly. As a mean, beta mtitr in wet muscle was approximately 25 per cent higher compared to dry muscle. The beta mtitr of dry muscle was increased by approximately 18 per cent when HCO3- was added in an amount equivalent to the calculated HCO3- content of wet muscle at rest. The homogenisation process resulted in complete loss of adenosine triphosphate and phosphocreatine with only small changes in adenosine diphosphate and adenosine monophosphate. It was concluded that the estimates of beta mtitr did not include any contribution from &#39;dynamic&#39; buffering via rephosphorylation of adenosine diphosphate by phosphocreatine, and in dry muscle it was accounted for mainly through physico-chemical buffering by phosphates, proteins and dipeptides. beta mtitr determined in biopsy samples of muscle from 20 Thoroughbred horses ranged from 100.8 to 131.8 mumol H+/g dry muscle pH 7.1 to 6.5 (mean 121.2, sd +/- 7.4).

Research paper thumbnail of Post exercise changes in compartmental body temperature accompanying intermittent cold water cooling in the hyperthermic horse

Equine veterinary journal, 1998

Whereas the efficacy of cold water cooling of horses has been demonstrated by several studies, th... more Whereas the efficacy of cold water cooling of horses has been demonstrated by several studies, the dynamics of temperature changes within and between compartments (primarily muscle, blood [core], skin and deep core [rectal]) have not been investigated. Changes in body temperature associated with cold water cooling were investigated in the hyperthermic horse. Muscle (TMU), pulmonary artery (TPA), rectal (TREC), tail-skin (TTSK) and coat surface (TCOAT) temperatures, were monitored continuously in 5 Thoroughbred horses during and after exercise in hot humid (30 degrees C and 80% RH) conditions on a treadmill. Horses were cooled in the hot humid environment with cold water (approximately 6 degrees C) for 6 30 s periods. Between each 30 s cooling period the horses stood for 30 s. A total of 180 l of cold water was applied. Horses were monitored for a further 4 min following the final cooling period. From the end of exercise to the end of the final cooling (6.5 min), mean (+/- s.e.) rate...

Research paper thumbnail of Muscle buffering capacity and dipeptide content in the thoroughbred horse, greyhound dog and man

Comparative biochemistry and physiology. A, Comparative physiology, 1990

1. Muscle buffering capacity (beta m) and dipeptide content were measured in locomotory muscles o... more 1. Muscle buffering capacity (beta m) and dipeptide content were measured in locomotory muscles of the Thoroughbred horse, Greyhound dog and Man. 2. Beta m and carnosine contents were highest in the horse. Anserine was only found in dog muscle. 3. The higher beta m in horse and dog muscle, compared with man, appears to be predominantly due to higher muscle contents of histidine containing dipeptides in these species.

Research paper thumbnail of Estimation of the carnosine content of different fibre types in the middle gluteal muscle of the thoroughbred horse

The Journal of physiology, 1992

1. Skeletal muscle samples were obtained by needle biopsy from one of two depths of the m. gluteu... more 1. Skeletal muscle samples were obtained by needle biopsy from one of two depths of the m. gluteus medius in a group of twenty race-trained thoroughbred horses. 2. The content of carnosine was determined in each muscle sample, part of which was used for histochemical analysis. Fibres were classified as type I, type IIA or type IIB on the basis of the pH dependent lability of the myosin ATPase reaction. 3. Muscle samples with a higher type II fibre section area (FSA) have a higher carnosine content than those with a higher type I FSA. 4. Multiple linear regression analysis was used to estimate the mean carnosine content of individual fibre types. The results estimated a mean carnosine content in type I fibres of 54 mmol (kg dry muscle (DM))-1, in type IIA fibres 85 mmol (kg DM)-1 and in type IIB fibres 180 mmol (kg DM)-1. 5. Based on the estimated values of single fibre carnosine content, there was close concordance between the estimated and the measured carnosine content of mixed fi...

Research paper thumbnail of Changes in circulatory antioxidant status in horses during prolonged exercise

The Journal of nutrition, 2002

Prolonged low-medium intensity exercise is associated with increased oxidative stress in humans. ... more Prolonged low-medium intensity exercise is associated with increased oxidative stress in humans. We hypothesized that competitive equine endurance racing would induce changes in circulatory antioxidants and produce systemic oxidative stress. Forty horses competing in a 140-km endurance race in warm conditions [shade temperature 15-19 degrees C; 62-88% relative humidity (%RH)] were sampled before (Pre), immediately after exercise (End) and at approximately 16 h into recovery (+16 h). Plasma ascorbic acid concentration was not different between Pre [11.1 (median); 4.6-20.3 micromol/L (range)] and End [9.7; 3.0-38.9 (range) micromol/L] but was significantly decreased at +16 h (5.5; 2.8-15.5 micromol/L; P < 0.05). Total red cell hemolysate glutathione (TGSH) concentration was significantly reduced by exercise (Pre 1261; 883-1532 micromol/L; End 1065; 757-1334 micromol/L; P < 0.05) and at +16 h recovery (1032; 752-1362 micromol/L; P < 0.05). Glutathione redox ratio was unchanged...

Research paper thumbnail of Antioxidant supplementation in horses affected by recurrent airway obstruction

The Journal of nutrition, 2004

Journal of Nutrition Journal of Nutrition. Skip to main page content. ...

Research paper thumbnail of Skeletal muscle characteristics in 2 year-old race-trained thoroughbred horses

Comparative Biochemistry and Physiology Part A: Physiology, 1994

Skeletal muscle samples were obtained by needle biopsy from two depths of the m. gluteus medius o... more Skeletal muscle samples were obtained by needle biopsy from two depths of the m. gluteus medius of 50, young race-trained thoroughbred racehorses. Histochemical and biochemical characteristics of the muscle samples were analysed. Fibres were classilied as type I, type IIa or type IIb on the basis of the pH dependent lability of the myosin ATPase reaction.

Research paper thumbnail of Effect of intravenous lidocaine on heart rate, systolic arterial blood pressure and cough responses to endotracheal intubation in propofol-anaesthetized dogs

Veterinary Anaesthesia and Analgesia, 2007

Objective To evaluate the effect of intravenous lidocaine on coughing and variations in heart rat... more Objective To evaluate the effect of intravenous lidocaine on coughing and variations in heart rate (HR) and systolic arterial pressure (SAP) at endotracheal intubation in propofol-anaesthetized dogs.

Research paper thumbnail of Effects of syringe material and temperature and duration of storage on the stability of equine arterial blood gas variables

Veterinary Anaesthesia and Analgesia, 2004

Objectives To evaluate the consistency of partial pressures (P) of arterial oxygen (aO 2 ), arter... more Objectives To evaluate the consistency of partial pressures (P) of arterial oxygen (aO 2 ), arterial carbon dioxide (aCO 2 ) and pH measurements in equine carotid arterial blood samples taken into syringes made from three different materials and stored at room temperature or placed in iced water for measurement at three different times.

Research paper thumbnail of Increased cerebrospinal fluid uric acid concentrations in dogs with intracranial meningioma

Research paper thumbnail of Plasma aspartate aminotransferase and creatine kinaseactivities in thoroughbred racehorses in relation to age, sex, exercise and training

The Veterinary Journal, 1998

In order to investigate the effect of age, sex and month on the response of plasma aspartate amin... more In order to investigate the effect of age, sex and month on the response of plasma aspartate aminotransferase (AST) and creatine kinase (CK) to exercise, blood samples were collected once a month between March and September from a group of 40 2- and 3-year-old (2yo and 3yo) thoroughbred racehorses (kept under the same managemental regimen) at rest before exercise (PRE) and at 2 (2H) and 24 h (24H) post-exercise. The absolute change in activities between the 2H and PRE samples (2H delta) and the 24H and PRE samples (24H delta) was also calculated. Age had a significant effect on all measured and calculated parameters for colts (C), apart from 24H delta CK but showed no effect in the fillies (F). Sex only had a significant effect in the 3yo in the 2H delta CK. In the 2yo, significant effects of sex were found for both CK and AST in the PRE, 2H and 24H samples. The effect of month varied according to the classification group with only the 2yoC not showing any significant effect on any parameter. Fillies were, in general, more likely than colts to show greater than a twofold increase in CK activity at 2H post-exercise and the number of animals showing such an increase decreased as the season progressed. Very little change in AST activities occurred with exercise.

Research paper thumbnail of Effects of Cool and Hot Humid Environmental Conditions on Neuroendocrine Responses of Horses to Treadmill Exercise

The Veterinary Journal, 2002

To determine the effects of exercise, high heat and humidity and acclimation on plasma adrenaline... more To determine the effects of exercise, high heat and humidity and acclimation on plasma adrenaline, noradrenaline, b-endorphin and cortisol concentrations, five horses performed a competition exercise test (CET; designed to simulatethespeedandendurancetestofathree-dayevent)incooldry(CD)(20 C/40%RH)andhothumid(30 C/ 80% RH) conditions before (pre-acclimation) and after (post-acclimation) a 15 day period of humid heat acclimation. Plasma adrenaline and noradrenaline concentrations pre-acclimation were significantly increased compared with exercisein the CD trial at the end of PhasesC (P`0.05) and D (P`0.05and P`0.01, respectively) and at 2 min recovery (P`0.01), with adrenaline concentrations still elevated after 5 min of recovery (P`0.001). Plasma b-endorphin concentrations were increased at the end of Phases C (P`0.05) and X (P`0.01) and at 5 and 30 min recovery (P`0.05) in the pre-acclimation session. Plasma cortisol concentrations were elevated after the initial warmupperiodpre-acclimation(P`0.01)andattheendofPhaseC(P`0.05),comparedwiththeCDtrial.A15day period of acclimation significantly increased plasma adrenaline concentrations at 2 min recovery (P`0.001) and plasma cortisol concentration at the end of Phase B (P`0.01) compared with pre-acclimation. Acclimation did not significantly influence noradrenaline or b-endorphin responses to exercise, although there was a trend for plasma b-endorphin to be lower at the end of Phases C and X and after 30 min recovery compared with pre-acclimation. Plasma adrenaline, noradrenaline, b-endorphin and cortisol concentrations were increased by exercise in cool dry conditions and were further increased by the same exercise in hot humid conditions. Exercise responsespost-acclimation suggest that adrenaline andnoradrenaline may play a role intheadaptation of horses to thermal stress and that changes in plasma b-endorphin concentrations could be used as a sensitive indicator of thermal tolerance before and after acclimation. The use of plasma cortisol as a specific indicator of heat stress and thermal tolerance before or after acclimation in exercising horses appears limited.

Research paper thumbnail of Metabolic adaptation to a fat-supplemented diet by the thoroughbred horse

British Journal of Nutrition, 1997

Research paper thumbnail of Breath Condensate Hydrogen Peroxide Correlates with Both Airway Cytology and Epithelial Lining Fluid Ascorbic Acid Concentration in the Horse

Free Radical Research, 2004

The relationship between hydrogen peroxide (H2O2) concentration in expired breath condensate (EBC... more The relationship between hydrogen peroxide (H2O2) concentration in expired breath condensate (EBC) and cytology of the respiratory tract obtained from tracheal wash (TW) or bronchoalveolar lavage (BAL), and epithelial lining fluid (ELF) antioxidant status is unknown. To examine this we analysed the concentration of H2O2 in breath condensate from healthy horses and horses affected by recurrent airway obstruction (RAO), a condition considered to be an animal model of human asthma. The degree of airway inflammation was determined by assessing TW inflammation as mucus, cell density and neutrophil scores, and by BAL cytology. ELF antioxidant status was determined by measurement of ascorbic acid, dehydroascorbate, reduced and oxidised glutathione, uric acid and alpha-tocopherol concentrations. RAO-affected horses with marked airway inflammation had significantly higher concentrations of breath condensate H2O2 than control horses and RAO-affected horses in the absence of inflammation (2.0 +/- 0.5 micromol/l. 0.4 +/- 0.2 micromol/l and 0.9 +/- 0.2 micromol/l H2O2, respectively; p &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.0001). The concentration of breath condensate H2O2 was related inversely to the concentration of ascorbic acid in ELF (r = -0.80; p &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.0001) and correlated positively with TW inflammation score (r = 0.76, p &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.0001) and BAL neutrophil count (r = 0.80, p &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.0001). We conclude that the concentration of H2O2 in breath condensate influences the ELF ascorbic acid concentration and provides a non-invasive diagnostic indicator of the severity of neutrophilic airway inflammation.

Research paper thumbnail of Pulmonary Bioavailability of Ascorbic Acid in an Ascorbate-synthesising Species, the Horse

Free Radical Research, 2003

Vitamin C (ascorbic acid) is a non-enzymatic antioxidant important in protecting the lung against... more Vitamin C (ascorbic acid) is a non-enzymatic antioxidant important in protecting the lung against oxidative damage and is decreased in lung lining fluid of horses with airway inflammation. To examine possible therapeutic regimens in a species with ascorbate-synthesising capacity, we studied the effects of oral supplementation of two forms of ascorbic acid, (each equivalent to 20 mg ascorbic acid per kg body weight) on the pulmonary and systemic antioxidant status of six healthy ponies in a 3 x 3 Latin square design. Two weeks supplementation with ascorbyl palmitate significantly increased mean plasma ascorbic acid concentrations compared to control (29 +/- 5 and 18 +/- 7 micromol/l, respectively; p &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.05). Calcium ascorbyl-2-monophosphate, a more stable form of ascorbic acid, also increased mean plasma ascorbic acid concentrations, but not significantly (23 +/- 1 micromol/l; p = 0.07). The concentration of ascorbic acid in bronchoalveolar lavage fluid increased in five out of six ponies following supplementation with either ascorbyl palmitate or calcium ascorbyl-2-monophosphate compared with control (30 +/- 10, 25 +/- 4 and 18 +/- 8 micromol/l, respectively; p &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.01). Neither supplement altered the concentration of glutathione, uric acid or alpha-tocopherol in plasma or bronchoalveolar lavage fluid. In conclusion, the concentration of lung lining fluid ascorbic acid is increased following ascorbic acid supplementation (20 mg/kg body weight) in an ascorbate-synthesising species.

Research paper thumbnail of EFFECT OF ACUTE AIRWAY INFLAMMATION ON THE PULMONARY ANTIOXIDANT STATUS

Experimental Lung Research, 2005

Research paper thumbnail of Post exercise changes in compartimentai body temperature accompanying intermittent cold water cooling in the hyperthermic horse

Equine Veterinary Journal, 2000

... Post exercise changes in compartmental body temperature accompanying intermittent cold water ... more ... Post exercise changes in compartmental body temperature accompanying intermittent cold water cooling in the hyperthermic horse D. J. MARLIN*, CAROLINE M. SCOTT, C. A. ROBERTS, I. CASAS, G. HOLAHt and RC SCHROTER* ... Page 2. D. J. Marlin et al. -160 -140 - ...