bluuebunny/crossref_metadata_2025 huggingface dataset:
Pulmonary vascular resistance of horses decreases with moderate exercise and remains unchanged as workload is increased to maximal exercise
Authors: MANOHAR M. , GOETZ T. E.
Published: June 2010

This study was carried out to examine changes in pulmonary vascular resistance (PVR) induced by moderate and strenuous exercise; the objective being to understand why pulmonary artery blood pressure of exercising horses increases progressively as work intensity increases. Pulmonary arterial and wedge pressures (referenced at the point of the left shoulder) were determined simultaneously with cardiac output in 2 groups of healthy, sound, exercise‐trained horses. Horses inGroup 1(n = 8) were studied at rest and during exercise performed at 8 and 13 m/s; the latter workload eliciting maximal heart rate (mean ± s.e. 212 ± 3 beats/min). Horses inGroup 2(n = 7 Thoroughbreds) were studied at rest and during galloping at 14.5 m/s on 5% uphill grade, a workload which elicited maximal heart rate (217 ± 3 beats/min) and could not be sustained for >90 s. Pulmonary vascular resistance was calculated by dividing pulmonary perfusion pressure gradient (i.e. mean pulmonary arterial pressure minus mean pulmonary wedge pressure) with cardiac output Pulmonary arterial and wedge pressures, pulmonary perfusion pressure gradient and cardiac output increased significantly (P<.05) with exercise in both groups. There were no differences in PVR between the 2 groups of horses at rest InGroup 1horses PVR decreased significantly (P<.05) with exercise at 8 m/s, but further pulmonary vasodilat0ion did not occur as workload increased to 13 m/s. During exercise at 14.5 m/s on 5% grade, PVR ofGroup 2horses also decreased significantly and was not different from values for 8 or 13 m/s inGroup 1horses. It is concluded that PVR reaches its nadir during moderate exercise, presumably due to upper limit of recruitment and distension having been reached. Therefore, in accordance with Ohm's law (P α Q × PVR), in going to higher workloads pulmonary blood flow (Q̇) remained the sole determinant of the rise in pulmonary arterial blood pressure (P). Our data also indicate that pulmonary artery wedge pressure is another variable that is important in determining the absolute value of pulmonary arterial blood pressure.
Feasibility of scintigraphy in exercise‐induced pulmonary haemorrhage detection and quantification: preliminary studies
Authors: VOTION DOMINIQUE M. , ROBERTS C. A. , MARLIN D. J. , LEKEUX P. M.
Published: June 2010

We hypothesised that scintigraphic imaging of the lungs following injection of 99mTc labelled red blood cells (99mTc‐RBC) in the exercising horse might enable exercise‐induced pulmonary haemorrhage (EIPH) quantification. Ideally, to favour detection of bleeding, circulating 99mTc‐RBC not involved in the haemorrhage should be removed from the circulation quickly. Altering RBC during labelling to stimulate splenic uptake of 99mTc‐RBC may encourage this.

In order to investigate this hypothesis, 99mTc‐RBC distribution was followed for 1 h in 2 groups of horses. Group 1 was injected i.v., at rest, with radioactive nondenatured RBC (99mTc‐NDRBC); Group 2 received labelled RBC partly denatured by heating (99mTc‐HDRBC). In Group 2, splenic uptake was higher at all times and radioactivity in the lung was proportionally higher and decreased less quickly than in Group 1. Hence, the time‐consuming 99mTc‐HDRBC labelling technique did not demonstrate any advantage over the easier 99mTc‐NDRBC labelling procedure.

Additionally, the feasibility of scintigraphic visualisation of a small amount of pulmonary bleeding was confirmed with the following trial: using an endoscope, a radioactive solution mimicking 50 ml of bleeding was deposited at the usual site of EIPH in a live horse. The radioactivity recorded in that area was compared to the one obtained in the same region in Group 1 and 2. The activity measured 20 min post endoscopy corresponded to 33% of the activity obtained in Group 1 vs. 8% in Group 2 at that timing. Once again, there was no advantage of using 99mTc‐HDRBC vs. 99mTc‐NDRBC.

These results demonstrated that small amounts of bleeding might potentially be detected with scintigraphy; they also suggest that the limiting factor for detecting small amounts of bleeding may be the level of lung background radioactivity.
Application of V200 values for evaluation of training effects in the young Thoroughbred under field conditions
Authors: KOBAYASHI M. , KURIBARA K. , AMADA A.
Published: June 2010

The purpose of this investigation was to study, under field conditions, the usefulness of an incremental exercise test to measure V200 (running velocity [V] at heart rate [HR] of 200 beats/min) for evaluation of training effects in the young Thoroughbred. Five to 112 two‐year‐old Thoroughbreds were used over 4 years to investigate the correlation between HR and V, the influence of the track and rider's weight to V200, reproducibility of V200 and the changes of V200 as training progresses. The high correlation coefficient between HR and V, and V200 were obtained in horses that exercised smoothly during gait changes and had acceleration during the canter in relaxed and nonexcitable states. The reproducibility of V200 as statistically significant providing the conditions were constant. Furthermore, the regression lines between HR and V gradually declined in parallel as training progressed. The average V200 in 2‐year‐old Thoroughbreds significantly increased from 623 ± 55 m/min to 691 ± 64 m/min after 5 months of training (P<.05). We concluded that V200 could easily be measured, that it was useful in evaluating treatment effect and that practical application under field conditions was possible.
EMG activity of the muscles of the neck and forelimbs during different forms of locomotion
Authors: TOKURIKI M. , OHTSUKI R. , KAl M. , HIRAGA A. , OKI H. , MIYAHARA Y. , AOKI O.
Published: June 2010

We recorded the electromyographic (EMG) activity of 7 skeletal muscles in the forequarters and 1 in the hindquarters of 6 Thoroughbred horses during overground walking, swimming in a circular pool, and walking and trotting in a water treadmill. Bipolar fine wire electrodes were inserted into the muscles and the EMG signals were recorded using a telemetric system. Thespleniusexhibited tonic EMG activity during swimming. Thebrachiocephalicsshowed its highest intensity during swimming followed by the walk and trot in the water treadmill and then walking overground. Thetriceps brachii caput longumhad a similar activity pattern to thebrachiocephalicus.Thebrachialisshowed only weak EMG activity in all 3 types of locomotion. Theextensor digitorum communishad higher intensity of EMG activity in the walk in the water treadmill than in other kinds of locomotion. Theflexor digitorum profundusexhibited the most intense EMG activity during swimming. These results indicated that swimming evoked strong EMG activity in the antigravity muscles in spite of reduced gravitational force. Walking in the water treadmill may require more intensified EMG activity of the forelimb than the trot in the same treadmill.
Chronological changes in superoxide‐scavenging ability and lipid peroxide concentration of equine serum due to stress from exercise and transport
Authors: ISHIDA N. , HOBO S. , TAKAHASHI T. , NANBO Y. , SATO F. , HASEGAWA T. , MUKOYAMA H.
Published: June 2010

It has been suggested that a variety of stresses on animals may accelerate their production of superoxide. Racehorses are considered to be exposed to substantial oxide stress due to transport and exercise for training and racing. To determine the effect of exercise and transport on racehorses in terms of superoxide and antioxidative ability, changes in the superoxide‐scavenging ability of equine serum were observed using electron spin resonance (ESR). Changes in the concentration of lipid peroxide, which is produced in equine serum by superoxide, were also examined.

The analysis revealed that lipid peroxide concentrations increased as a result of stress from exercise and transport. On the other hand, the superoxide‐scavenging ability of equine serum showed a decline during transport, which is in sharp contrast to the increase seen immediately after a race due to the severe load exerted in exercise.
Factors affecting accumulation of lactate in red blood cells
Authors: VäIHKÖNEN LEENA K. , HYYPPä S. , PÖSÖ A. REETA
Published: June 2010

In horses, both the post exercise distribution of lactate between plasma and red blood cells (RBC) and the activity of lactate transporters on the RBC membrane vary widely between individuals. In this study, we investigated the effects of pH, time and temperature on lactate distributionin vitro, and compared thein vitroactivity of lactate transporters with the accumulation of lactate into RBCin vivo.To accomplish this, we took venous blood samples at rest and after trotting races. The post exercise accumulation of lactate into RBC was shown to depend on the activity of lactate transporters. The results,in vitro, also indicate that pH, incubation time and temperature influence the activity of lactate transporters and the accumulation of lactate into RBC, underscoring the fact that in practice it is important to standardise the measurement conditions of lactate. These results support the view that whole blood lactate concentrations should be measured in estimating the accumulation of lactate from exercising muscles into the blood, because the effect of blood pH, temperature, time to centrifugation of the sample and also interindividual variation in lactate transport into RBC are therefore minimised.
Comparison of exercise tests in French trotters under training track, racetrack and treadmill conditions
Authors: COUROUCÉ ANNE , GEFFROY O. , BARREY E. , AUVINET B. , ROSE R. J.
Published: June 2010

Standardised exercise tests were performed at 2 different tracks and on an uninclined treadmill during the same week to determine the influence of exercise surface on different measured variables such as heart rate (HR), blood lactate concentration, packed cell volume, stride frequency, stride length, gait symmetry and regularity and on different derived physiological variables such as the speed at a HR of 200 beats/min (V200), the speed at a blood lactate concentration of 4 mmol/l (V4), the speed at a maximal HR (VHRmax). Five French Trotters, age 3 years, in training for 3 months prior to the test, performed 3 exercise tests on a training track (Test 1), a racetrack (Test 2) and an uninclined treadmill (Test 3). Test 1 utilised 3 steps each of 3 min at speeds of 490, 560 and 630 m/niin. Tests 2 and 3 utilised the same speeds and a fourth step in which the horse was accelerated for 30 s to speed approaching maximal. No significant differences (P<.05) were found for the physiological and locomotor variables between the 2 tracks. In contrast, there was a significant difference (P<.05) for these variables between the tracks and the treadmill, horses showing lower heart rate and blood lactate response, reduced stride frequency and increased stride length and regularity on the uninclined treadmill. We concluded that this standardised exercise test was repeatable on various tracks even when the surface and geometry vary. In contrast, both physiological and locomotor variables were different when comparing the tracks with the uninclined treadmill.
Effect of forage intake on bodyweight and performance
Authors: ELLIS J. M. , HOLLANDS T. , ALLEN D. E.
Published: June 2010

The horse evolved to survive on rations high in forage. Many performance horses are fed rations containing reduced levels of forage, with a corresponding increase in concentrate supply. Such reductions in forage intake are widely established to be associated with a corresponding number of physiological and psychological adaptations. Therefore, the influence of forage intake on bodyweight (bwt) and performance was investigated. Four Thoroughbred‐type geldings in light to moderate work received 4 diets (100% forage [100H]; 80% forage:20% concentrate [80H]; 60% forage:40% concentrate [60H] and 50% forage:50% concentrate [50H]) in a 4 times 4 Latin‐square design. A submaximal standardised exercise test (SET) was performed for each diet. Rate of passage, bwt and water intakes were measured throughout the trial and maximum, recovery heart rates and postexercise rectal temperatures recorded for each SET. Mean ± s.e. bwt was significantly (P<0.001) higher for the 100H compared to the 50H ration (556.89 and 546.28 kg, respectively). Rate of passage of digesta was significantly (P<0.01) slower for the 100H compared to the 50H ration. Water intakes and SET maximum and 1 min recovery heart rates were significantly (P<0.05) higher (mean ± s.e. 44.72 and 39.07 ***l/day, 186 and 165 beats/min, and 105 and 96 beats/min, respectively) for 100H compared to the 50H diet. Post‐SET rectal temperatures tended to increase with increasing forage intakes, although these effects were not significant (mean 39.85 and 38.65°C for the 100H and 50H diets, respectively). In conclusion, forage intake has significant effects on equine bwt and submaximal performance and a compromise needs to be made between the potential detrimental effects of high forage intake on performance and the potential detrimental effects of low forage intake on equine welfare.
Does training affect mRNA transciption for cytokine production in circulating leucocytes?
Authors: COLAHAN P. T. , KOLLIAS‐BAKER C. , LEUTENEGGER C. M. , JONES J. H.
Published: June 2010

Physical exertion is a stimulus for the upregulation of cytokine production including IL‐1β, IL‐1ra, IL‐2, IL‐4, IL‐6, IL‐10 and TNF‐α in horses. To investigate that hypothesis, we initiated training of 5 stall‐rested Thoroughbreds. Blood samples were drawn before and weekly during training. The relative transcription of mRNA within the leucocytes was measured using real time TaqMan quantitative PCR.

The training protocol was walking (3 min), trotting (3 min) and cantering/galloping (6 min) increasing in intensity weekly (6 to 12 m/s) and culminating in an intense exercise period. Comparisons of mRNA concentrations were made using a repeated measures ANOVA on ranks and a Student‐Newman‐Keuls pair‐wise multiple comparison (P<0.05).

The training programme or intense exercise bout did not affect IL‐2, IL‐4, IL‐6 and IL‐10. IL1‐β and TNF‐α transcription increased on Day 23. TNF‐α peaked on Day 23 and IL1‐β on Day 30. Neither demonstrated a response to intense exercise. IL‐1ra decreased significantly on Day 9; rose significantly from Day 9 to Days 16 and 23; remained significantly elevated through Days 30 and 37 over Day 9, and rose very slightly after intense exercise on Day 56.

Alterations in leukocyte cytokine responses may influence susceptibility to infectious disease, metabolic responses to exercise or exercised induced syndromes.
Effect of an endurance race on muscle amino acids, pro‐ and macroglycogen and triglycerides
Authors: ESSÉN‐GUSTAVSSON B. , JENSEN‐WAERN M.
Published: June 2010

Glycogenolysis and lipolysis are essential for energy production in muscle during prolonged exercise but less is known about the role of amino acid metabolism. The aim was to study the effect of an endurance race on pro‐ and macroglycogen, triglycerides and amino acid concentrations in muscle and on selected blood parameters, especially the amino acid response in the blood during the recovery phase.

Seven endurance‐trained horses completed a race covering 100–120 km. Blood samples were collected one day before the race, after the finish and 1 and 8 days after the race. Needle biopsy specimens from the gluteus medius muscle were taken on completion of the race and 8 days postrace.

The pro‐ and macroglycogen concentrations were lower and most amino acid concentrations were higher in the muscle after the finish of the race, than 8 days postrace, whereas the triglyceride concentrations did not differ. The concentrations of several amino acids in serum were higher during the recovery phase than before the race. The observed changes suggest that an endurance race influences amino acid metabolism and a net protein degradation may occur that persists during the recovery phase. Furthermore, the results suggest that macroglycogen is utilised to a greater extent than proglycogen during an endurance race. Further research is needed concerning amino acid metabolism during an endurance race as it seems to play an important role both for performance and recovery after exercise.
Dorsal metacarpal cortex ultrasound speed and bone size and shape
Authors: DAVIES H. M. S.
Published: June 2010

In Thoroughbred racehorses, the dorsal cortex (DC) of the third metacarpal bone (MC3) enlarges when horses are first exposed to fast exercise speeds. It is now possible to measure ultrasound speed through 3 to 5 mm depths of bone around the bone shaft using Sunlight Medical's ‘Omnisense’ machine. The aim of this experiment was to determine whether the ultrasound speed measured in the surface 3–5 mm of the midshaft dorsal cortex of MC3 could be related directly to the midshaft shape and size of the MC3s of young Thoroughbred racehorses at the same stage of training. Sixteen 2‐year‐old and sixteen 3 to 6‐year‐old racehorses, exercising at racing speed at the same training stable, had their ultrasound speed measured and were radiographed to measure their MC3 midshaft size (width of DC) and shape ([DC/palmar cortex] x [{DC+palmar cortex}/medulla widths]).

There were significant linear relationships between ultrasound speed and radiographic bone size and shape measurements. The faster ultrasound speeds were associated with bones that were both absolutely and proportionately thinner in the dorsal cortex in both groups of racehorses. The measurement of ultrasound speed with the Sunlight Omnisense machine should allow more detailed and accurate predictions to be made for responses of the bone to exercise in the midshaft of MC3 than is possible using radiographic size and shape measurements alone. This should make it possible to predict, for example, how soon after a change in bone shape a specific horse can race with minimal risk of damage to the newly‐forming bone surface.
Influence of draw reins on ground reaction forces at the trot
Authors: ROEPSTORFF L. , JOHNSTON C. , DREVEMO S. , GUSTÅS P.
Published: June 2010

According to riding texts, draw reins are supposed to support increased collection. This has not been measured objectively. Therefore, the objective of this study was to determine whether a horse ridden with draw reins would relatively increase weightbearing of the hindquarters while worked with the draw reins compared to a normal rein. Ground reaction forces were measured in 8 horses at the slow trot over a force plate in 3 different experimental setups: 1) riding with only a draw rein (DR); 2) riding with the combination of a normal and a draw rein (NR‐DR) and 3) riding with a normal rein (NR).

Horses ridden with NR‐DR showed significant higher vertical impulse in the hindlimb compared to riding both with only DR and only NR. Several significant differences were also seen in the horizontal force. It is concluded that draw reins, when used correctly, together with a normal rein, achieve the desired result of shifting the weight of the horse caudally. This was not the case when the draw rein was used alone. It is important that trainers, as well as veterinarians, recommending draw reins in a rehabilitation programme, know about these possible effects.
Hindlimb net joint energies during swing phase as a function of trotting velocity
Authors: CLAYTON H. M. , HOYT D. F. , WICKLER S. J. , COGGER E. A. , LANOVAZ J. L.
Published: June 2010

Net joint powers and energies have been described in walking horses during the swing phase of the stride in the fore‐ and hindlimb (Claytonet al.2001). During trotting, swing phase net joint powers have been described in the forelimb but not in the hindlimb. The effects of velocity on power profiles and energy patterns are important in relation to locomotor energetics. The objective of this study was to evaluate velocity‐dependent changes in hindlimb net energy profiles of the swing phase during trotting. Inverse dynamic analysis was used to calculate net joint energies at the hindlimb joints of 6 horses trotting overground at velocities ranging from 2.27‐5.17 m/s. At all velocities, there was net energy generation at the hip and tarsus and net energy absorption at the stifle, fetlock and coffin joints. Velocity‐dependent bursts of energy generation at the hip actively protracted the limb in early swing and initiated retraction in late swing. Synchronous with the bursts of energy generation at the hip were velocity‐dependent bursts of energy absorption across the stifle that acted to control flexion in early swing and extension in late swing. The distal limb was raised and lowered by velocity‐dependent bursts of energy generation that flexed the tarsus in early swing and extended it in late swing. The energy bursts in early swing increased linearly with velocity, whereas the energy bursts in late swing increased as a function of the square or cube of velocity.

The results contribute to understanding the mechanisms used to accelerate and decelerate the limbs more rapidly as velocity increases, which is an important consideration in racing and sporting performance.
Heterogeneity of intrapleural pressures during exercise
Authors: JONES J. H. , COX K. S. , TAKAHASHI T. , HIRAGA A. , YARBROUGH T. B. , PASCOE J. R.
Published: June 2010

We determined whether the caudodorsal region of the intrapleural space in exercising horses experiences larger pressure fluctuations than other regions and whether systematic phase‐shifting of peak intrapleural pressures along the length of the thorax suggests the existence of locomotor‐induced intrapleural pressure waves. We utilised percutaneous introducers and solid‐state pressure‐tip transducers implanted along the dorsal aspect of the thorax, mid‐thorax or oesophagus to measure regional intrapleural pressures while 3 horses galloped on a flat treadmill at 13–14 m/s, then recorded pressures from the same catheters when horses exercised intensely (heart rate 170–190 beats/min) while swimming with no ground concussion. Pressure excursions in the caudodorsal region did not vary systematically from other regions during galloping or swimming, nor more than a few torr between different locations. During swimming, peak expiratory pressures were higher than during galloping (68–79 vs. 26–32 torr), and horses breathed explosively at frequencies 5 times slower than while galloping (28 vs. 120/min). During galloping, individual catheter locations registered locomotor concussion; however, this was variable and did not indicate a systematic pressure wave passing through the lung or intrapleural space.
Lactate transport in red blood cells by monocarboxylate transporters
Authors: KOHO N. M. , VÄIHKÖNEN L. K. , PÖSÖ A. R.
Published: June 2010

The lactate transport activity of red blood cells (RBC) varies widely among different species; in equine RBC, the activity of the main lactate carrier, H+‐monocarboxylate co‐transporter (MCT), is distributed bimodally. The influence of lactate transport activity is measurable in vivo; after maximal exercise, the RBC lactate concentration in horses with high (HT) lactate transport activity is higher than in those with low (LT) activity. To study the expression of MCT in HT and LT horses, blood samples were taken from 10 horses at rest and after submaximal exercise. Blood and plasma lactate concentrations, lactate and pyruvate transport activities and the amounts of MCT1, MCT2 and MCT4 were measured. After exercise, RBC lactate concentration was higher in HT (n = 5) than in LT (n = 5) horses. At lactate concentrations of 0.25–30 mmol/l and at a pyruvate concentration of 1 mmol/l, transport activity was higher in HT horses. At a lactate concentration of 0.1 mmol/l, transport was similar. In Western blots, the signals for MCT1 and MCT2 were similar in both groups. The amount of CD147, a chaperone necessary for the activity of MCT1, was lower in LT horses. We suggest that MCT2 transports lactate at low concentrations, while MCT1 is needed at higher concentrations. MCT1 may be less active in LT horses and, therefore, during exercise their capacity to take up lactate is low.

Further studies are needed to show whether the differences in lactate influx in RBC affect the function of erythrocytes or the performance capacity of horses.
Does usefulness of potassium supplementation depend on speed?
Authors: HESS T. M. , KRONFELD D. S. , CARTER R. A. , TREIBER K. H. , BYRD B. M. , STANIAR W. B. , SMITH L. T. , GAY L. A. , HARRIS P. A.
Published: June 2010

Reasons for performing study:Electrolyte mixtures given to counter sweat loss usually contain abundant potassium. However, increases in plasma [K+] occur with exercise and supplementation may further increase plasma levels, potentially increasing the risk of neuromuscular hyperexcitability and development of adverse clinical sequellae. This proposition requires study.

Objectives:To compare effects of a K‐rich electrolyte supplement (EM+K) to a K‐free one (EM‐K) on plasma [K+], [Ca++] and acid‐base status during an endurance incremental exercise test on the treadmill.

Methods:The test consisted of 3 bouts (simulating loops in an endurance race) of 12 km performed at 6, then 7, then 8 m/sec with 25 min rest stops (S1, S2) between loops on 13 endurance trained Arabian horses (7 EM‐K, 6 EM+K). Electrolytes were supplied orally 60 mins before exercise (Pre) and at each stop. Blood samples were taken before exercise and during exercise, each S and 120 mins of recovery (R). Blood was analysed for pH, PCO2, packed cell volume (PCV), plasma [Na+], [K+], [Cl−], [Ca++], glucose, and lactate [La−]; plasma [H+] and osmolality (osm) were calculated. The dietary cation anion difference (DCAD) was calculated to be ‐27 meq/dose EM‐K and 109 meq in EM+K, respectively.

Results:Plasma [H+] decreased during the 6 and 7 m/sec loops, increased during the 8 m/sec loop, and returned to Pre at S1, S2 and R. Plasma [K+] was higher at 8 m/sec and plasma [Ca++] was overall lower in the EM+K group compared to EM‐K. Other findings included higher overall PCV, overall glucose, and [La−] during the 8 m/sec loop (P<0.040) in EM+K compared to EM‐K horses.

Conclusions:EM+K supplementation leads to higher plasma [K+] increasing the risk of neuromuscular hyperexcitability during exercise. Acute effects of a lower DCAD in EM‐K may have led to higher plasma [Ca++]. Potassium‐rich electrolytes may have triggered the release of epinephrine, contributing to higher PCV, glucose release and increased lactate production.

Potential relevance:Lower plasma [K+] and higher plasma [Ca++] with EM‐K supplementation may help reduce the risk of conditions associated with neuromuscular hyperexcitability occurring especially during higher speeds in endurance races.
Exercise and pharmacological stress echocardiography in healthy horses
Authors: SANDERSEN C. , DETILLEUX J. , ART T. , AMORY H.
Published: June 2010

Reasons for performing study:Stress echocardiography could be a useful diagnostic test in horses suspected to suffer from exercise‐induced myocardial dysfunction as a cause of exercise intolerance.

Objective:To evaluate the effect of treadmill exercise and pharmacological stress test on left ventricular echocardiographic parameters.

Methods:Echocardiography was performed in 2 groups of 5 healthy horses, either immediately after a near‐maximal treadmill exercise (Group EXE) or during a pharmacological challenge (Group DOB) consisting of 35 ug/kg atropine, followed by incremental dobutamine infusion rates of 2–6 ug/kg bwt/min for 5 min duration each, which led to a cumulative dobutamine dose of 100 ug/kg. Left ventricular M‐mode parameters were compared at rest and at heart rates of 80, 100, 110, 120 130, and 140 beats/min, within each group.

Results:In 2 horses ofGroup EXE, echocardiographic measurements were impossible at 140 and 130 beats/min, as their heart rates dropped too fast in the immediate post exercise period. In the remaining 3 horses image quality was not always satisfactory at heart rates of 130 and 140 beats/min. Systolic left ventricular parameters and fractional shortening measured at 130 and 140 beats/min were significantly different from values obtained at lower heart rates. Horses in Group DOB reached expected heart rates of 80 and 100 beats/min, after the administration of atropine and during a dobutamine infusion rate of 2 ug/kg bwt/min, respectively. Heart rates targets of 110, 120, 130, and 140 beats/min were reached at mean (± s.d.) dobutamine infusion rates of 2.8 ± 0.4, 3.2 ± 0.4, 4.0 ± 0.7, 5 ± 0.7 ug/kg bwt/min, respectively. Systolic left ventricular parameters and fractional shortening at heart rates of 110, 120, 130, and 140 beats/min, were significantly different from values obtained at lower heart rates.

Conclusion:The pharmacological stress test induced changes in ventricular dimensions at heart rates of 80 to 140 beats/min. Using this test, high quality images can easily be obtained at heart rates of 140 beats/min. Conversely, in post exercise echocardiography, obtaining good quality images at heart rates of 130 and 140 beats/min is difficult, which limits use of the technique in routine clinical settings.

Potential relevance:Further studies should demonstrate the potential of pharmacological stress test as a diagnostic tool in horses suffering from exercise‐induced myocardial dysfunction.
Investigation of blood oxidant/antioxidant markers in healthy competition horses of different breeds
Authors: KIRSCHVINK N. , de MOFFARTS B. , FARNIR F. , PINCEMAIL J. , LEKEUX P.
Published: June 2010

Reasons for performing study:There is increasing evidence that the equine athlete is exposed to exercise‐induced changes of its oxidant/antioxidant balance and antioxidant supplementation is frequently recommended. However, it is unknown whether there is a specific need for antioxidants according to performance, breed, gender or age.

Objectives:To assess whether breed‐, gender‐ and age‐related differences of blood oxidant/antioxidant markers occur in competition horses.

Methods:Healthy horses (n = 493) underwent oxidant/antioxidant blood marker determination. Vitamin E, lipophilic antioxidant capacity (ACL), ascorbic acid (AA), glutathione (GSH, GSSG), gluthione peroxidase (GPx), superoxide dismutase (SOD), selenium (Se), copper (Cu), zinc (Zn), lipid peroxides (Pool), oxidised proteins (Protox) were determined, as well as magnesium (Mg), creatine phosphokinase (CPK), lactate dehydrogenase (LDH), packed cell volume (PCV) and haemoglobin (Hb). A mixed linear model assessed the effect of breed, gender and age category. P<0.05 was considered significant.

Results:Thoroughbreds showed the highest values of vitamin E, ACL, GPx, PCV and Hb, whilst standardbreds had the highest values of AA and LDH. Jumping horses had the highest Protox values. Females had significantly higher SOD values, whereas most of the other markers were higher in stallions and geldings. Horses age 2–6 years had higher AA, SOD and LDH values than horses age >6 years. Correlation analyses were positive and significant between vitamin E and GPx, VitE and ACL, Se and GPx, Cu and Pool and negative between Pool and vitamin E, Pool and ACL, Protox and GPx, Protox and vitamin E.

Conclusions:Blood oxidant/ antioxidant status of horses is influenced by breed, gender and age. The correlation analyses suggest synergistic relations between GPx, vitamin E and Se and an antagonistic relation between Protox‐GPx, Protox‐vitamin E, and Pool‐vitamin E.

Potential relevance:The results of this investigation provide definition of the specific need for antioxidants and vitamins in competition horses.
Hormone response to training and competition in athletic horses
Authors: CAYADO P. , MUÑOZ‐ESCASSI B. , DOMÍNGUEZ C. , MANLEY W. , OLABARRI B. , DE LA MUELA M. SÁNCHEZ , CASTEJON F. , MARAÑON G. , VARA E.
Published: June 2010

Reasons for performing study: It is recognised that the amount of psychological stress that an animal encounters determines the degree of response of the hypothalamic‐pituitary‐adrenal (HPA) axis. In human athletes, the added emotive stress of competition is an important element in the adrenal response. The aim of this study was to examine the effect of show‐jumping as well as dressage on stress levels by comparing horses' stress response at a horse show compared to their familiar home.

Methods: Fifty‐one horses involved in competition were used. EDTA blood samples were collected before exercise, upon arrived to the schooling area (control), and k over a jump or dressage course. After sampling, plasma was separated and stored at ‐80°C until determinations of cortisol and ACTH were performed. Fourteen healthy horses not involved in competition were used as control group.

Results: Competition induced a significant increase in cortisol and ACTH responses in both, jumping and dressage horses and this effect was more apparent in dressage horses. When horses were most experienced, cortisol and ACTH responses were much lower.

Conclusion: This study shows that competition elicits a classic physiological stress response in horses and that different training programmes induce different responses. It suggests that horses involved in competition can provide a good model to study the exercise‐induced stress response.
Muscle characteristics of Dutch Warmblood foals with different genetic background at ages 6 and 12 months
Authors: RIETBROEK N. J. , DINGBOOM E. G. , EVERTS M. E.
Published: June 2010

Reasons of performing study:To obtain broader insight into the muscle of foals with different genetic background, muscle fibre composition, its post natal development and citrate synthase (CS) activity of thegluteus mediuswere investigated.

Hypothesis:Because muscle properties are influenced genetically and related directly to performace ability, muscle characteristics should be affected by selection and correspond with the requirement of ths sports selected for.

Methods:The foals were divided intoGroup A, (n = 16), considered an average of the population, andGroup B(n = 36), selected for showjumping. Biopsies were taken deeply from thegluteus mediusmuscle. Fibre type identification was performed immunohistochemically at ages 6 and 12 months. Citrate synthase activity was measured at age 6 months.

Results:age 6 months statistically significant differences were found betweenGroups AandBin the proportion oftype I, IIadandIIdfibres. Oxidative fibres (IandIIad) were more abundant inGroup B, while fast‐glycolytic fibres (IId) were more abundant inGroup A.Except forIIa, the fibre type composition at age 12 months had become equal in the 2 groups. The difference in the sum of oxidative fibres (I+IIad+IIad) between GroupsAandBat age 6 months was similar to the difference in CS activity at that age, although the latter was not significant.

Conclusions:At age 6 months the 2 groups had different proportions of fibretypes IandIId, but these differences had disappeared at age 12 months.

Potential relevance:The muscular response to training at an early age can be interpreted with knowledge of muscle characteristics and its post natal development in foals selected for showjumping.
X trisomy in a sterile mare
Authors: De LORENZI L. , MOLTENI L. , ZANNOTTI M. , GALLI C. , PARMA P.
Published: June 2010

This report concerns the cytogenetic analysis, using both C‐banding and fluorescence in situ hybridisation techniques, of a sterile mare. Results obtained revealed a 2n = 65, XXX condition with no sign of mosaicism. The work supports the suggestion that X trisomy, rare in horse, causes infertility in mares and is not associated to other clearly visible phenotypic features.
Colonic elongation inhibits pellet propulsion and migrating motor complexes in the murine large bowel
Authors: Heredia Dante J. , Dickson Eamonn J. , Bayguinov Peter O. , Hennig Grant W. , Smith Terence K.
Published: June 2010

The colonic migrating motor complex (CMMC) is a rhythmically occurring neurally mediated motor pattern. Although the CMMC spontaneously propagates along an empty colon it is responsible for faecal pellet propulsion in the murine large bowel. Unlike the peristaltic reflex, the CMMC is an ‘all or none’ event that appears to be dependent upon Dogiel Type II/AH neurons for its regenerative slow propagation down the colon. A reduction in the amplitude of CMMCs or an elongated colon have both been thought to underlie slow transit constipation, although whether these phenomena are related has not been considered. In this study we examined the mechanisms by which colonic elongation might affect the CMMC using video imaging of the colon, tension and electrophysiological recordings from the muscle and Ca2+ imaging of myenteric neurons. As faecal pellets were expelled from the murine colon, it shortened by up to ∼29%. Elongation of the colon resulted in a linear reduction in the velocity of a faecal pellet and the amplitude of spontaneous CMMCs. Elongation of the oral end of a colonic segment reduced the amplitude of CMMCs, whereas elongation of the anal end of the colon evoked a premature CMMC, and caused the majority of CMMCs to propagate in an anal to oral direction. Dogiel Type II/AH sensory neurons and most other myenteric neurons responded to oral elongation with reduced amplitude and frequency of spontaneous Ca2+ transients, whereas anal elongation increased their amplitude and frequency in most neurons. The inhibitory effects of colonic elongation were reduced by blocking nitric oxide (NO) production with l‐NA (100 μm) and soluble guanylate cyclase with 1H‐[1,2,4]oxadiazolo[4,3‐a]quinoxalin‐1‐one (ODQ; 10 μm); whereas, l‐arginine (1–2 mm) enhanced the inhibitory effects of colonic elongation. In conclusion, polarized neural reflexes can be triggered by longitudinal stretch. The dominant effect of elongation is to reduce CMMCs primarily by inhibiting Dogiel Type II/AH neurons, thus facilitating colonic accommodation and slow transit.
In vivo expression of G‐protein β1γ2 dimer in adult mouse skeletal muscle alters L‐type calcium current and excitation–contraction coupling
Authors: Weiss Norbert , Legrand Claude , Pouvreau Sandrine , Bichraoui Hicham , Allard Bruno , Zamponi Gerald W. , De Waard Michel , Jacquemond Vincent
Published: June 2010

A number of G‐protein‐coupled receptors are expressed in skeletal muscle but their roles in muscle physiology and downstream effector systems remain poorly investigated. Here we explored the functional importance of the G‐protein βγ (Gβγ) signalling pathway on voltage‐controlled Ca2+ homeostasis in single isolated adult skeletal muscle fibres. A GFP‐tagged Gβ1γ2 dimer was expressed in vivo in mice muscle fibres. The GFP fluorescence pattern was consistent with a Gβ1γ2 dimer localization in the transverse‐tubule membrane. Membrane current and indo‐1 fluorescence measurements performed under voltage‐clamp conditions reveal a drastic reduction of both L‐type Ca2+ current density and of peak amplitude of the voltage‐activated Ca2+ transient in Gβ1γ2‐expressing fibres. These effects were not observed upon expression of Gβ2γ2, Gβ3γ2 or Gβ4γ2. Our data suggest that the G‐protein β1γ2 dimer may play an important regulatory role in skeletal muscle excitation–contraction coupling.
A Convex Complementarity Approach for Simulating Large Granular Flows
Authors: Tasora Alessandro , Anitescu Mihai
Published: June 2010

Aiming at the simulation of dense granular flows, we propose and test a numerical method based on successive convex complementarity problems. This approach originates from a multibody description of the granular flow: all the particles are simulated as rigid bodies with arbitrary shapes and frictional contacts. Unlike the discrete element method (DEM), the proposed approach does not require small integration time steps typical of stiff particle interaction; this fact, together with the development of optimized algorithms that can run also on parallel computing architectures, allows an efficient application of the proposed methodology to granular flows with a large number of particles. We present an application to the analysis of the refueling flow in pebble-bed nuclear reactors. Extensive validation of our method against both DEM and physical experiments results indicates that essential collective characteristics of dense granular flow are accurately predicted.
A Quantitative Assessment of the Potential of Implicit Integration Methods for Molecular Dynamics Simulation
Authors: Schafer Nick , Negrut Dan
Published: June 2010

Implicit integration, unencumbered by numerical stability constraints, is attractive in molecular dynamics (MD) simulation due to its presumed ability to advance the simulation at large step sizes. It is not clear what step size values can be expected and if the larger step sizes will compensate for the computational overhead associated with an implicit integration method. The goal of this paper is to answer these questions and thereby assess quantitatively the potential of implicit integration in MD. Two implicit methods (midpoint and Hilber–Hughes–Taylor) are compared with the current standard for MD time integration (explicit velocity Verlet). The implicit algorithms were implemented in a research grade MD code, which used a first-principles interaction potential for biological molecules. The nonlinear systems of equations arising from the use of implicit methods were solved in a quasi-Newton framework. Aspects related to a Newton–Krylov type method are also briefly discussed. Although the energy conservation provided by the implicit methods was good, the integration step size lengths were limited by loss of convergence in the Newton iteration. Moreover, a spectral analysis of the dynamic response indicated that high frequencies present in the velocity and acceleration signals prevent a substantial increase in integration step size lengths. The overhead associated with implicit integration prevents this class of methods from having a decisive impact in MD simulation, a conclusion supported by a series of quantitative analyses summarized in the paper.
A Method for Measuring Wave Speed Dispersion in Arteries by Resonance
Authors: Zhang Xiaoming , Greenleaf James F.
Published: June 2010

Cardiovascular disease (CVD) has been the number one killer in the United States. It has long been recognized that a high percentage of all cardiovascular disease is associated with the hardening of arteries or arteriosclerosis. Several imaging techniques, including x-ray angiography, ultrasound, magnetic resonance imaging (MRI), etc., are available for imaging atherosclerotic arteries. Most imaging techniques measure luminal diameter, wall thickness and plaque volume. However, no current imaging methods can measure elasticity of the arterial wall. Pulse wave velocity (PWV) is a simple and robust method to measure arterial stiffness. However, PWV can not evaluate the local arterial stiffness. We have developed a novel ultrasound method for estimating local elasticity of arteries by the wave speed dispersion. In this paper, we present a method to measure the wave speed dispersion by resonance. Theory was developed to calculate the wave speed in cylindrical tubes. Experiments were done on a rubber tube. The resonance of the tube was generated by an air-coupled ultrasound transducer. The resonance frequency was measured by a laser vibrometer. Theoretical and experimental wave dispersions were compared. This method may be useful in characterizing the elastic properties of arterial samples where the wave speed dispersion can not be easily measured.
Analysis of Short Pulse Laser Interaction With Tissues for Tumor Detection
Authors: Sajjadi Amir Yousef , Pal Gopalendu , Mitra Kunal , Grace Michael
Published: June 2010

The objective of the work is to perform both experimental and numerical analysis of short pulse laser interaction with tissue medium with the goal of tumor / cancer diagnostics. Short pulse laser probing techniques for diagnostics have distinct advantages over very large pulse width or continuous wave lasers primarily due to the additional information conveyed by the temporal distribution of the optical signals. For short pulse laser source, the shape of output signal is a function of the optical properties of the medium and hence the scattered optical signal provides information about the medium characteristics. Two laser systems are used: a mode-locked short pulse laser (wavelength = 514 nm and pulsewidth = 200 ps) and a frequency doubled diode short pulse laser (wavelength = 776 nm and pulsewidth = 1.3 ps). The scattered optical signals are measured with a Hamamatsu streak camera. First in vitro experiments are performed on mouse skin tissue samples injected with India ink in order to simulate presence of inhomogeneities. Finally, in vivo imaging is performed on anaesthetized rats with tumorogenic agents injected inside skin tissues and on anaesthetized mouse with mammary tumors. Both the temporal and the spatial profiles of the scattered reflected optical signals are compared with the numerical modeling results obtained by solving the transient radiative transport equation using the discrete ordinates technique. The goal is to demonstrate the feasibility of the time-resolved technique in detecting tumors in animal model.
Biomechanical Evaluation of Autologous Mesenchymal Stem Cell Transplantation to Improve Fascial Repair
Authors: Marie Hazel , Fagan Diana L. , Heffner Jeremy
Published: June 2010

Hernia repair continues to be one of the major problems faced by surgeons. Up to 10% of laparotomies are complicated by post-operative incisional hernia, carrying with it a myriad of complications ranging from cosmetic disfigurement to life-threatening strangulation of the bowel [1]. A large percentage of these incisional hernias will recur following surgical repair leading to a more vicious cycle of hernia, followed by repair, followed by hernia. It is therefore imperative to create a more optimum wound-healing environment. The intent of this study was to investigate a novel approach for significantly reducing the initial occurrence of incisional hernia and their associated morbidities, thereby halting the vicious cycle of hernia formation.