bluuebunny/crossref_metadata_2025 huggingface dataset:
Observations on respiratory flow strategies during and after intense treadmill exercise to fatigue in Thoroughbred racehorses
Authors: CURTIS R. A. , KUSANO K. , EVANS D. L.
Published: June 2010

Reasons for performing study:Locomotor‐respiratory coupled (LRC) breath types are a feature of galloping exercise in horses. Differences in breath type have been demonstrated during exercise in particular the ‘big respiratory cycle’ (BRC) and ‘flow hesitation’. To investigate breath types during recovery and quantitatively investigate BRCs during exercise to understanding the mechanism driving BRCs.

Objectives:To investigate the occurrence of different breath types during and after intense treadmill exercise, and test the hypothesis that large breaths (BRCs) were a function of respiratory frequency.

Methods:Six trained and clinically normal Thoroughbred horses were exercise tested on a treadmill (slope 10%). Breath‐by‐breath pulmonary ventilation was measured continuously during exercise and recovery using a Quadflow mask.

Results:Five different breath types were identified, and classified as normal monophasic, normal biphasic, deglutition, effort pause, or large breaths. Exercising at 10 m/sec, the number of large breaths was significantly related to Rf (r=‐0.86, P = 0.03). During 120 sec after exercise there were 2 distinct populations of breaths, large and normal monophasic.

Conclusions:BRC type breaths are a normal feature of ventilation during and after intense exercise. In recovery there are two distinct breath populations. During exercise BRC frequency is inversely associated with respiratory frequency and highly dependant on the individual horse. From intense exercise to recovery, high flow rates and LRC limited tidal volumes are replaced by high tidal volumes and progressively decreasing flow rates. There is a temporal association between BRC occurrence and PECO2.

Potential relevance:Breath types and the physiological mechanism for driving each type is important in the clinical interpretation of respiratory disease or dysfunction. The demonstration of BRC association with PECO2may help understand the driving mechanism for the BRC. In pulmonary function testing, breath type is important in quantitative results. The demonstration that high tidal flows with limited tidal volumes during intense exercise being replaced by high tidal volumes and progressively decreasing flows in recovery has potential clinical relevance.
Effects of dietary glycaemic response after exercise on blood concentrations of substrates used indirectly for muscle glycogenesis
Authors: LACOMBE V. A. , HINCHCLIFF K. W. , KOHN C. W. , REED S. M. , TAYLOR L. E.
Published: June 2010

Reasons for performing study:Exercise depletes muscle glycogen stores, which could subsequently impair performance. Muscle glycogen replenishment is determined by substrate availability.

Objectives:To study the effects of feeding meals of varying glycaemic responses on blood concentrations of substrates used for glycogenesis in horses with exercise‐induced glycogen depletion.

Methods:In a 3‐way crossover study, 7 horses received each of 3 isocaloric diets for 72 h after undergoing glycogen‐depleting exercise: 1) a high soluble‐carbohydrate diet, which induced a high‐glycaemic (HGI) response; 2 and 3) a low soluble‐carbohydrate or a mixed soluble‐carbohydrate diet (control group), which both induced a similar low‐to‐moderate glycaemic (LGI) response. Muscle biopsies and venous samples were collected before and up to 72 h after exercise.

Results:Feeding HGI diet resulted in a higher (P<0.001) rate of muscle glycogenesis over 72 h compared to LGI diets. Plasma glycerol, triglyceride, lactate, serum NEFA and total protein concentrations, and haematocrit were significantly (P<0.001) higher after compared to before exercise. Whereas no significant overall dietary effect was observed on these metabolites over 72 h, there was a tendency for glycerol, NEFA and triglyceride concentrations to be lower for LGI compared to HGI diets over 6 h after exercise (P<0.05; 1, 6 and 4–6 h after exercise, respectively).

Conclusions:These data suggest that horses fed LGI meals after exercise had limited lipid utilisation without any significant shift of substrate utilisation toward gluconeogenesis, which could have contributed to the slower rate of muscle glycogenesis compared to horses fed HGI diets.
Route of carbohydrate administration affects early post exercise muscle glycogen storage in horses
Authors: GEOR R. J. , LARSEN L. , WATERFALL H. L. , STEWART‐HUNT L. , McCUTCHEON L. J.
Published: June 2010

Reasons for performing study:No studies in horses have examined the effect of route of carbohydrate (glucose) administration on the rate of muscle glycogen storage following glycogen‐depleting exercise.

Hypothesis:Glucose delivery from the gastrointestinal tract limits the rate of muscle glycogen storage following glycogen‐depleting exercise.

Methods:In a crossover design, 7 fit horses completed treadmill exercise (EX) on 3 occasions to deplete muscle glycogen by approximately 50%. After EX horses received: 1) i.v. glucose infusion (IV; 0.5 g/kg bwt/h for 6 h), 2) oral glucose boluses (OR; 1 g/kg bwt at 0, 2 and 4 h post EX) or 3) no glucose supplementation (CON). Blood samples for measurement of glucose and insulin concentrations were collected before EX and during the 6 h treatment period. Muscle biopsies for measurement of muscle glycogen content (GLY) and glycogen synthase (GS) activity were taken before and after exercise and at 3 and 6 h.

Results:Mean plasma glucose concentrations were significantly higher in IV and OR than in CON throughout treatment. The average serum insulin responses in IV and OR treatments were also significantly greater than in CON. After EX, GLY was not different among the 3 treatments. However, glycogen storage rates were significantly higher in IV than in CON and OR during the first 3 h and second 3 h of recovery, and GLY was significantly higher in IV than in OR and CON at 6 h of recovery. GS activity was significantly higher in IV than in OR and CON at 3 h of recovery.

Conclusions:Muscle glycogen storage in horses during a 6 h period after exercise was enhanced by i.v. glucose administration (3 g/kg) but not by an equivalent glucose dose administeredper os. While oral administration of glucose achieved a level of hyperglycaemia and hyperinsulinaemia that markedly accelerates glycogen storage in other species, the rate of glycogen storage following oral supplementation was not different to control conditions.

Potential relevance:Glucose supplementation via the i.v. route should be considered when rapid replenishment of muscle glycogen stores is desired.
Effect of amino acid and glucose administration following exercise on the turnover of muscle protein in the hindlimb femoral region of Thoroughbreds
Authors: MATSUI A. , OHMURA H. , ASAI Y. , TAKAHASHI T. , HIRAGA A. , OKAMURA K. , TOKIMURA H. , SUGINO T. , OBITSU T. , TANIGUCHI K.
Published: June 2010

Reasons for performing study: In man, muscle protein synthesis is accelerated by administering amino acids (AA) and glucose (Glu), because increased availability of amino acids and increased insulin secretion, is known to have a protein anabolic effect. However, in the horse, the effect on muscle hypertrophy of such nutrition management following exercise is unknown.

Objectives: To determine the effect of AA and Glu administration following exercise on muscle protein turnover in horses. We hypothesise that administration of AA and Glu after exercise effects muscle hypertrophy in horses, as already shown in man and other animals.

Methods: Measurements of the rate of synthesis (Rs) and rate of degradation (Rd) of muscle protein in the hindlimb femoral region of thoroughbred horses were conducted using the isotope dilution method to assess the differences between the artery and iliac vein. Six adult Thoroughbreds received a continuous infusion of L‐[ring‐2H5]‐phenylalanine during the study, the stable period for plasma isotope concentrations (60 min), resting periods (60 min), treadmill exercise (15 min) and recovery period (240 min). All horses were given 4 solutions (saline [Cont], 10% AA [10‐AA], 10% Glu [10‐Glu] and a mixture with 10% AA and 10% Glu [10‐Mix]) over 120 min after exercise, and the Rs and Rd of muscle protein in the hindlimb measured.

Results: The average Rs during the 75–120 min following administration of 10‐Mix was significantly greater than for the other solutions (P<0.05). The second most effective solution was 10‐AA, and there was no change in Rs after 10‐Glu.

Conclusions: Administration of AA following exercise accelerated Rs in the hindlimb femoral region, and this effect was enhanced when combined with glucose, because of increasing insulin secretion or a decreased requirement for AA for energy.

Potential relevance: Further studies are required regarding the effect on muscle hypertrophy of supplementing amino acids and glucose in the feed of exercising horses.
Double blind investigation of the effects of oral supplementation of combined glucosamine hydrochloride (GHCL) and chondroitin sulphate (CS) on stride characteristics of veteran horses
Authors: FORSYTH R. K. , BRIGDEN C. V. , NORTHROP A. J.
Published: June 2010

Reasons for performing study:Oral chondroprotective supplements are commercially popular for veteran (and other athletic or arthritic) horses prone to joint degeneration, yet lack conclusive scientific support.

Objectives:To quantify the effects of an oral joint supplement (combination glucosamine hydrochloride (GHCL), chondroitin sulphate (CS) and N‐acetyl‐D‐glucosamine)in vivoon stride parameters of veteran horses.

Methods:Twenty veteran horses were randomly assigned to a treatment (n=15) or placebo group (n = 5). Pre‐treatment gait characteristics were recorded at trot using digital video footage (50 Hz). The range of joint motion, stride length, and swing and stance duration were assessed using 2‐dimensional motion analysis. Treatment (or placebo) was administered daily for 12 weeks at the manufacturer's recommended dosage. Gait was reassessed every 4 weeks using the pre‐treatment protocol. Double blind procedure was implemented throughout. Relationships between variables were analysed using General Linear Model.

Results:Differences occurred in the treated horses by week 8. Range of joint motion increased significantly in the elbow (P<0.05), stifle and hind fetlock (P<0.01). Stride length increased significantly (P<0.05) with treatment. Swing duration was significantly increased at week 12 (P<0.05), whilst stance duration remained constant.

Conclusion:The oral chondroprotective offered symptomatic relief to veteran horses, evidenced by improved stride characteristics.

Potential relevance:Oral GHCL and CS supplementation may improve welfare by alleviating symptoms of degenerative joint disease.
Glucose dynamics during exercise: dietary energy sources affect minimal model parameters in trained Arabian geldings during endurance exercise
Authors: TREIBER K. H. , HESS T. M. , KRONFELD D. S. , BOSTON R. C. , GEOR R. J. , FRIERE M. , SILVA A. M. G. B. , HARRIS P. A.
Published: June 2010

Reasons for performing study:Glucose regulation is critical for health and exercise performance.

Objectives: To quantify the effects of exercise and diet on insulin sensitivity (SI), glucose effectiveness (Sg), acute insulin response to glucose (AIRg) and disposition index (DI) in horses.

Methods: This study applied the minimal model of glucose and insulin dynamics to exercise‐trained Arabian geldings during rest or constant moderate‐intensity exercise after 8 weeks adaptation to feeds high in sugar and starch (SS, n=6) or fat and fibre (FF, n = 6). Horses underwent 2 frequently sampled i.v. glucose tolerance tests (FSIGT). For both tests, a resting basal sample was collected, followed by an i.v. dose of 600 mg/kg bwt glucose defining 0 min of the test. Insulin (0.01 iu/kg bwt) was administered 20 min post glucose for each test. Resting horses were sampled for 240 min. The exercise FSIGT began after each horse had warmed‐up for 25 min on the treadmill at which point they had reached the speed representing 60% of their predetermined lactate breakpoint maintained for the rest of the FSIGT. Exercising horses were sampled identically to rest, but for only 150 min post glucose.

Results: Exercise increased (P≤0.008) SI, Sg and DI and decreased AIRg in all horses. Overall, horses adapted to FF tended to have higher SI (P=0.070) and DI (P = 0.058). During exercise, FF horses tended to have higher (P≤0.085) SI and DI, than SS horses and these variables tended to be increased more (P≤0.075) by exercise in FF horses than SS horses.

Conclusions: Insulin and glucose dynamics adjust during exercise, increasing plasma glucose uptake, presumably to meet demand by contracting skeletal muscle. Trained horses adapted to a high fat diet showed greater metabolic adjustment during exercise than trained horses adapted to a high starch and sugar diet, potentially allowing them to better meet energy demands.

Potential relevance: Nutrition and exercise impact glucose and insulin dynamics, potentially influencing health and performance.
Plasma glutamine concentrations in the horse following feeding and oral glutamine supplementation
Authors: HARRIS R. C. , HARRIS P. A. , ROUTLEDGE N. B. H. , NAYLOR J. R. J. , WILSON A. M.
Published: June 2010

Reasons for performing study:Pharmacological benefits of glutamine supplementation have been shown in athletically and clinically stressed human subjects. In the horse, infection and intense exercise have also been shown to significantly decrease plasma glutamine concentrations, but little is known on how best to supplement.

Objective:To evaluate whether ingestion of different foodstuffs, with or without L‐glutamine (G) or a peptide (Pep) containing 31.5% w/w G in a water‐stable form, could affect plasma glutamine concentrations (P‐GC).

Materials and methods:Nine feeds (molassed sugar beet‐pulp (mSB); naked oats (nO); commercial mix (CM); mSB with 30 or 60 mg/kg bwt G or the G‐molar equivalent of Pep; and CM with 60 mg/kg bwt G or equivalent Pep) were offered to 6 healthy mature horses on different days following overnight food restriction. The changes in P‐GC were monitored for 8 h post feeding.

Results:After 1.5 h mean ± s.d. ΔP‐GC were ‐0.9 ± 10.2% (mSB), +12.5 ± 7.1% (nO) and +44.7 ± 15.9% (CM; P<0.05). ΔP‐GC with mSB supplemented with G was +60.9 ± 30.0% (30 mg; P<0.05) and +156.8 ± 34.6% (60 mg; P<0.05) at 1 h; ΔP‐GC with Pep was 51.0 ± 31.0% (30 mg equivalent, P<0.05) and +91.1 ± 9.5% (60 mg equivalent, P<0.05) at 1 h. After 10 days of supplementation with 60 mg/kg bwt G, ΔP‐GC following a further 60 mg/kg bwt G challenge showed a similar increase at 1 h of +154.3 ± 37.9%; prevalues were unchanged. G and Pep added to CM, increased P‐GC by 246.3 ± 55.3 (+99.2%) and 252.3 ± 94.2 μmol/1 (96.7%) at 1.5 h with concentrations still above prevalues at 8 h (P<0.05). Apart from the CM (with or without supplement), pre P‐GC was always regained by 4 h. Plasma NH3and plasma protein concentrations were unaffected by supplementation with G or Pep.

Conclusion:P‐GC may be modified by appropriate supplementation with no apparent adverse effects.

Potential relevance:Increasing P‐GC through appropriate supplementation may be of benefit in the athletically or clinically stressed horse with lowered plasma glutamine concentrations.
Effects of different levels of calcium and phosphorus intake on calcium homeostasis in exercising horses
Authors: VERVUERT I. , STANIK K. , COENEN M.
Published: June 2010

Hypothesis:Increasing levels of dietary calcium (Ca) and phosphorous (P) might have a negative impact on parathyroid hormone (PTH) response and result in a more pronounced hypocalcaemia during high‐speed exercise in horses.

Material and methods:In successive order, five trained horses were fed 33 g Ca and 19 g P (˜100% NRC,adequateintake), 64 g Ca and 38 g P (moderately highintake) or 96 g Ca and 56 g P (highintake). Each horse was adapted to each diet over a 21 day period before undergoing a standardised exercise test (SET) on a treadmill. The SET comprised 5 steps (each step 4 min duration, 3% incline, first step 5 m/sec, followed by increments of 1 m/sec). Blood samples were taken at defined times.

Results:Blood lactate, plasma intact PTH (PTHi) and plasma inorganic P (Pi) increased during exercise (P<0.05), blood pH and blood ionised Ca2+(Ca2+, adjusted to a pH of 7.4) declined during SETs (P<0.05) whereas total plasma Ca (CaT) and Mg (MgT) remained constant. The most exaggerated drop in Ca2+and lactate peaks were found for the adequate Ca and P intake at 7, 8, and 9 m/sec during SET (treatment P<0.05). At 120 min after exercise, Ca2+levels exceeded resting concentrations with higher Ca2+values for the higher Ca intake (Ca2+: adequate 1.58 ± 0.07 mmol/1, moderately high 1.63 ± 0.04 mmol/1, high 1.65 ± 0.02 mmol/1, P<0.05). Concomitantly, 120 min after exercise, PTHireturned to basal concentrations with higher PTH concentrations for the adequate Ca intake than the other two treatments (PTHi: adequate 45.6 ± 72.8 pg/ml, moderately high 11.6 ± 13.6 pg/ml, high 2.6 ± 2.3 pg/ml, P<0.05). During recovery (30 min, 120 min and 24 h after exercise) MgTconcentrations were depressed (P<0.05) for the high Ca intake (P<0.05).

Conclusion:These results suggest that high dietary Ca and P intake did not impair PTH responses during exercise and recovery, but might depress Mg metabolism.

Potential relevance:High Ca and P intake might have some potential to increase the availability of blood Ca2+and Piin the recovery phase after intensive exercise, but detrimental effects on Mg homeostasis might offset this potential benefit.
Urinary excretion of dietary contaminants in horses
Authors: RESPONDEK F. , LALLEMAND A. , JULLIAND V. , BONNAIRE Y.
Published: June 2010

Reasons for performing study:Presence of drugs is completely prohibited in post racing urine samples by most of racing and competition authorities, even if environmental contamination might occur.

Objectives:To assess the daily dose of several contaminants absorbed through the diet that would result in detectable concentrations in urine.

Methods:Caffeine, theobromine, theophylline, atropine, scopolamine, bufotenine, DMT or morphine were administered orally to 6 horses, in different dosages, for 3 days before their urine was sampled for regular anti‐doping tests.

Results:Theobromine, theophylline, bufotenine and morphine daily intake >10 mg, 2 mg, 10 mg and 200 μg, respectively, by a performance horse, were found to result in detectable urinary concentrations. At the 2 tested doses, atropine (5 and 15 mg) and dimethyltryptamine (3 and 10 mg) were not detected in urine. For caffeine and scopolamine, even the lowest dosage tested (5 mg/horse/day and 2 mg/horse/day respectively) induced detectable concentrations of the molecule in urine.

Conclusions:Horses fed dietary contaminants, even at level much below the effective dosage, may be positive to anti‐doping urine analysis. Further research is needed to gain more confident results on a daily safe intake for caffeine and scopolamine.

Potential relevance:Selection of feed materials appears to be of great importance to prevent non voluntary positive result to anti‐doping tests.
Histological and histochemical characterisation of the equine soft palate muscles
Authors: HAWKES C. S. , HAHN C. N. , DIXON P. M.
Published: June 2010

Reasons for performing study:Dysfunction of the muscles is implicated in the pathogenesis of intermittent dorsal displacement of the soft palate (DDSP) in exercising horses. The histological features of normal equine soft palate muscles have not been previously described.

Objective:To describe the histological and morphometric features of normal equine soft palate muscles.

Methods:Thepalatinus, palatopharyngeus, levator veli palatiniandtensor veli palatinimuscles of 6 Thoroughbred type horses were examined histologically and histochemically to assess their general morphology, fibre‐type distribution and mean fibre diameter.

Results:The muscles of all 6 specimens showed very similar characteristics, including a low proportion oftype 1muscle fibres in the 4 different muscles examined, with the 3 muscles innervated by the pharyngeal branch of the vagus (i.e.palatopharyngeus, palatinusandlevator veli palatini) having significantly fewer (P<0.005)type 1muscle fibres compared to thetensor veli palatini.The mean fibre diameters were significantly (P<0.05) smallerin type 1thantype 2fibres in all muscles except thepalatinus. Considerable variability in mean fibre size diameter was evident in all muscles examined, withtype 1fibres in thelevator veli palatiniandrostral fasciculus of the palatopharyngeusand both fibre types in thecaudal fasciculus of the palatopharyngeushaving the most marked variation, with coefficients of variation >250 and the latter also having high levels of endomysial connective tissue. Thepalatinushad least variation in fibre size.

Conclusion and clinical relevance:Morphological characterisation of the normal soft palate muscles may provide reference values for future comparative studies with samples obtained from horses with palatal dysfunction. Thepalatinusappears to be the best muscle to histologically examine for evidence of muscle abnormality.
A comparison of four systems for scoring recovery quality after general anaesthesia in horses
Authors: VETTORATO E. , CHASE‐TOPPING M. E. , CLUTTON R. E.
Published: June 2010

Reason for performing study:The recovery quality scoring systems (RQSSs) in current use have not been critically reviewed for reliability.

Objective:To examine reliability (reproducibility) of 4 RQSSs when applied to a ranked series.

Methods:A DVD incorporating the recordings of 9 horses recovering from general anaesthesia was evaluated by final year students over 5 days. On Day 1, each evaluator ranked recoveries from 1–9 (1 = best). Over the following 4 days, each evaluator scored the same recoveries using 4 different RQSSs (3 of them in common usage and previously published) applied in random order. The scores from each RQSS were ranked and plotted against the Day 1 ranking of each evaluator to establish the extent of agreement using generalisability theory. The same 9 recoveries were also ranked by 12 experienced equine anaesthetists and the Spearman Rank Correlation coefficient calculated to determine the agreement between experienced and inexperienced evaluators.

Results:The recoveries were evaluated by 117 students. All 4 RQSSs were equally reliable with low (<4%) interobserver variability. The main (80%) source of total variation arose from differences between horses. The overall ranking within each RQSS was strongly correlated with Day 1 ranking. There was strong correlation (r = 0.983) between the students' ranking and that established by experienced anaesthetists. Interobserver reliability was similar with all 4 RQSSs.

Conclusion:All 4 RQSSs studied were similarly reliable.

Potential relevance:The selection of a universally acceptable RQSS from amongst the 4 examined can be based on criteria other than reliability, e.g. ease of use. This will facilitate wider scale multi‐centre studies in recovery quality after anaesthesia in horses.
The propagation of induced tendon lesions in the equine superficial digital flexor tendon: An ex vivo study
Authors: BOSCH G. , LAMERIS M. C. , Van Den BELT A. J. M. , BARNEVELD A. , Van WEEREN P. R.
Published: June 2010

Reasons for performing study: Clinical tendon lesions usually enlarge during the first days to weeks after sustaining the injury due to enzymatic and biomechanical influences. Limiting this enlargement would positively influence prognosis related to lesion size.

Objectives: To investigate the effect of cyclic loading on the propagation of enzymatically and physically induced tendon lesions and to assess the effect of immobilisation thereon in an ex vivo model.

Methods: Equine cadaver limbs with either physically or collagenase‐induced SDFT lesions were placed in a pneumatic loading device. Groups consisted of unloaded limbs, cyclically loaded limbs and cyclically loaded limbs with fibreglass cast immobilisation. Lesion size was evaluated ultrasonographically and macroscopically and load at failure was determined for groups where lesions enlarged.

Results: Physically induced lesions did not propagate after cyclical loading and were not further investigated. Collagenase‐induced lesions propagated significantly more after cyclical loading compared to unloaded limbs. This propagation could effectively be reduced by immobilisation through a lower limb cast. Immobilisation did not influence load at failure.

Conclusions: The combination of enzymatic and mechanical stimulation caused the lesions to propagate most. Casting appeared effectively to reduce the enlargement of the original tendon lesions in this ex vivo model, while it did not affect ultimate tendon strength.

Potential relevance: As prognosis of tendon injuries is related to lesion size, the outcome of this study warrants further investigations in vivo.
Two distinct and activity‐dependent mechanisms contribute to autoreceptor‐mediated inhibition of GABAergic afferents to hilar mossy cells
Authors: Lindsly Casie , Frazier Charles J.
Published: June 2010

We report that bath application of 3 μmcarbachol (CCh), a muscarinic acetylcholine receptor agonist, reduces evoked IPSC amplitude recorded from hilar mossy cells in the rat dentate gyrus through a presynaptic mechanism. While CCh has been shown to inhibit evoked IPSCs in other systems, this effect is intriguing in that it does not require inhibitory action of either presynaptic muscarinic receptors or presynaptic cannabinoid receptors. Previous work from our lab has shown that identical application of CCh produces an action potential‐dependent increase in ambient GABA in this system; however, inhibition of evoked IPSCs produced by both 3 and 10 μmCCh is insensitive to the GABABantagonist CGP52432. Therefore we hypothesized that CCh‐mediated inhibition of evoked IPSCs might be produced by activity‐dependent increases in ambient GABA and subsequent activation of presynaptic GABAAreceptors. Consistent with that hypothesis, we report that CCh‐mediated inhibition of evoked IPSCs appears to be well correlated with CCh‐mediated facilitation of spontaneous IPSCs and that CCh does not affect GABAB‐mediated IPSCs recorded in the presence of the GABAAreceptor antagonist picrotoxin. Intriguingly, however, we found that bath application of the GAT‐1 transport blocker NO‐711 (1 μm) produces inhibition of evoked IPSCs that is reversed by CGP52432, and that lower doses of CCh produce inhibition with greater CGP52432 sensitivity. These observations, combined with subsequent work on multiple pulse depression, reveal that feedback inhibition of GABAergic afferents to hilar mossy cells is governed by a complex relationship between two distinct and activity‐dependent mechanisms.
Development of calcium‐permeable AMPA receptors and their correlation with NMDA receptors in fast‐spiking interneurons of rat prefrontal cortex
Authors: Wang Huai‐Xing , Gao Wen‐Jun
Published: June 2010

Abnormal influx of Ca2+is thought to contribute to the neuronal injury associated with a number of brain disorders, and Ca2+‐permeable AMPA receptors (CP‐AMPARs) play a critical role in the pathological process. Despite the apparent vulnerability of fast‐spiking (FS) interneurons in neurological disorders, little is known about the CP‐AMPARs expressed by functionally identified FS interneurons in the developing prefrontal cortex (PFC). We investigated the development of inwardly rectifying AMPA receptor‐mediated currents and their correlation with NMDA receptor‐mediated currents in FS interneurons in the rat PFC. We found that 78% of the FS interneurons expressed a low rectification index, presumably Ca2+‐permeable AMPARs, with only 22% exhibiting AMPARs with a high rectification index, probably Ca2+impermeable (CI). FS interneurons with CP‐AMPARs exhibited properties distinct from those expressing CI‐AMPARs, although both displayed similar morphologies, passive membrane properties and AMPA currents at resting membrane potentials. The AMPA receptors also exhibited dramatic changes during cortical development with significantly more FS interneurons with CP‐AMPARs and a clearly decreased rectification index during adolescence. In addition, FS interneurons with CP‐AMPARs exhibited few or no NMDA currents, distinct frequency‐dependent synaptic facilitation, and protracted maturation in short‐term plasticity. These data suggest that CP‐AMPARs in FS interneurons may play a critical role in neuronal integration and that their characteristic properties may make these cells particularly vulnerable to disruptive influences in the PFC, thus contributing to the onset of many psychiatric disorders.
Intraspinally mediated state‐dependent enhancement of motoneurone excitability during fictive scratch in the adult decerebrate cat
Authors: Power Kevin E. , McCrea David A. , Fedirchuk Brent
Published: June 2010

This is the first study to report on the increase in motoneurone excitability during fictive scratch in adult decerebrate cats. Intracellular recordings from antidromically identified motoneurones revealed a decrease in the voltage threshold for spike initiation (Vth), a suppression of motoneurone afterhyperpolarization and activation of voltage‐dependent excitation at the onset of scratch. These state‐dependent changes recovered within 10–20 s after scratch and could be evoked after acute transection of the spinal cord at C1. Thus, there is a powerful intraspinal system that can quickly and reversibly re‐configure neuronal excitability during spinal network activation. Fictive scratch was evoked in spinal intact and transected decerebrate preparations by stroking the pinnae following topical curare application to the dorsal cervical spinal cord and neuromuscular block. Hyperpolarization of Vth occurred (mean −5.8 mV) in about 80% of ipsilateral flexor, extensor or bifunctional motoneurones during fictive scratch. The decrease in Vth began before any scratch‐evoked motoneurone activity as well as during the initial phase in which extensors are tonically hyperpolarized. The Vth of contralateral extensors depolarized by a mean of +3.7 mV during the tonic contralateral extensor activity accompanying ipsilateral scratch. There was a consistent and substantial reduction of afterhyperpolarization amplitude without large increases in motoneurone conductance in both spinal intact and transected preparations. Depolarizing current injection increased, and hyperpolarization decreased the amplitude of rhythmic scratch drive potentials in acute spinal preparations indicating that the spinal scratch‐generating network can activate voltage‐dependent conductances in motoneurones. The enhanced excitability in spinal preparations associated with fictive scratch indicates the existence of previously unrecognized, intraspinal mechanisms increasing motoneurone excitability.
Short‐term sprint interval training increases insulin sensitivity in healthy adults but does not affect the thermogenic response to β‐adrenergic stimulation
Authors: Richards Jennifer C. , Johnson Tyler K. , Kuzma Jessica N. , Lonac Mark C. , Schweder Melani M. , Voyles Wyatt F. , Bell Christopher
Published: June 2010

Sprint interval training (SIT) and traditional endurance training elicit similar physiological adaptations. From the perspective of metabolic function, superior glucose regulation is a common characteristic of endurance‐trained adults. Accordingly, we have investigated the hypothesis that short‐term SIT will increase insulin sensitivity in sedentary/recreationally active humans. Thirty one healthy adults were randomly assigned to one of three conditions: (1) SIT (n= 12): six sessions of repeated (4–7) 30 s bouts of very high‐intensity cycle ergometer exercise over 14 days; (2) sedentary control (n= 10); (3) single‐bout SIT (n= 9): one session of 4 × 30 s cycle ergometer sprints. Insulin sensitivity was determined (hyperinsulinaemic euglycaemic clamp) prior to and 72 h following each intervention. Compared with baseline, and sedentary and single‐bout controls, SIT increased insulin sensitivity (glucose infusion rate: 6.3 ± 0.6 vs. 8.0 ± 0.8 mg kg−1 min−1; mean ±s.e.m.; P= 0.04). In a separate study, we investigated the effect of SIT on the thermogenic response to beta‐adrenergic receptor (β‐AR) stimulation, an important determinant of energy balance. Compared with baseline, and sedentary and single‐bout control groups, SIT did not affect resting energy expenditure (EE: ventilated hood technique; 6274 ± 226 vs. 6079 ± 297 kJ day−1; P= 0.51) or the thermogenic response to isoproterenol (6, 12 and 24 ng (kg fat‐free mass)−1 min−1: %ΔEE 11 ± 2, 14 ± 3, 23 ± 2 vs. 11 ± 1, 16 ± 2, 25 ± 3; P= 0.79). Combined data from both studies revealed no effect of SIT on fasted circulating concentrations of glucose, insulin, adiponectin, pigment epithelial‐derived factor, non‐esterified fatty acids or noradrenaline (all P > 0.05). Sixteen minutes of high‐intensity exercise over 14 days augments insulin sensitivity but does not affect the thermogenic response to β‐AR stimulation.
ANCF Finite Element/Multibody System Formulation of the Ligament/Bone Insertion Site Constraints
Authors: Gantoi Florentina M. , Brown Michael A. , Shabana Ahmed A.
Published: June 2010

The focus of this investigation is to study the mechanics of the knee joint using new ligament/bone insertion site constraint models that require the integration of multibody system and large displacement finite element algorithms. Two different sets of clamped end conditions at the ligament/bone insertion site are examined using nonlinear large displacement absolute nodal coordinate formulation (ANCF) finite elements. The first set of end conditions, called the partially clamped joint, eliminates only the translations and rotations at a point, allowing for the cross section stretch and shear at the ligament/bone connection. The second joint, called the fully clamped joint, eliminates all the translation, rotation, and deformation degrees of freedom of the cross section at the ligament/bone insertion site. In the case of the fully clamped joint, the gradient vectors do not change their length and orientation, allowing for the use of the constant strain assumptions. The partially clamped joint, on the other hand, allows for the change in length and relative orientation of the gradient vectors at the bone/ligament insertion site, leading to the cross section deformation induced by knee movements. Nanson’s formula is applied as a measure of the deformation of the cross section in the case of the partially clamped joint. In this study, the major bones in the knee joint consisting of the femur, tibia, and fibula are modeled as rigid bodies while the ligaments structures are modeled using the large displacement ANCF finite elements. Two different ANCF finite element models are developed in this investigation: the first model employs the fully parameterized three-dimensional beam element while the second model employs the three-dimensional cable element. The three-dimensional fully parameterized beam element allows for a straight forward implementation of a neo-Hookean constitutive model that can be used to accurately predict the large displacement as experienced in knee flexation and rotation. At the ligament bone insertion site, the ANCF fully parameterized beam element is used to define a fully or partially constrained joint while the ANCF cable element can only be used to define one joint type. The fully and partially clamped joint constraints are satisfied at the position, velocity, and acceleration levels using a dynamic formulation that is based on an optimum sparse matrix structure. The approach described in this investigation can be used to develop more realistic models of the knee and is applicable to future research studies on ligaments, muscles, and soft tissues. In particular, the partially clamped joint representation of the ligament/bone insertion site constraints can be used to develop improved structural mechanics models of the knee.
Partitioned Dynamic Simulation of Multibody Systems
Authors: Sandhu Sukhpreet Singh , McPhee John
Published: June 2010

Partitioned dynamic simulation of multibody systems offers the benefit of increased modularity over direct simulation, thereby allowing for the use of softwares tailored to the needs of each physical subsystem. In this paper, the partitioned simulation of multibody systems is accomplished by deriving an explicit expression for the constraint forces acting between subsystems. These constraint forces form the basis of a coupling module that communicates results between subsystems, each of which can be simulated independently using tailored numerical solvers. We provide details of how this partitioned solution approach can be implemented in the framework of implicit and explicit time integrators. The computational efficiency of the proposed partitioned simulation approach is established, in comparison with direct simulation, by solving three suitable problems containing both rigid and deformable components.
Parameter Estimation of Multibody Models of Unstable Systems From Experimental Data, With Application to Rotorcraft Vehicles
Authors: Bottasso Carlo L. , Luraghi Fabio , Maffezzoli Andrea , Maisano Giorgio
Published: June 2010

In this paper, we consider the problem of estimating the parameters in mathematical models of complex systems from experimental observations; the methods and procedures that we develop are general, but in this work we make specific reference to the problem of parameter estimation for multibody-based rotorcraft vehicle models from flight test data. We consider methods that are applicable to unstable systems, since rotorcraft vehicles are typically unstable at least in certain flight regimes. Unstable vehicles must be operated in closed-loop, and this must be explicitly accounted for when formulating parameter estimation methods. We describe two alternative classes of methods in the time domain, namely, the recursive filtering and the batch optimization methods. In the recursive approach, we formulate a novel version of the extended Kalman filter that accounts for the presence of unobservable states in the model. In the case of the batch optimization methods, we present a formulation based on a new single-multiple shooting approach, specifically designed for models with slow and fast solution components. We perform some initial steps toward the validation of the proposed procedures with the help of applications regarding manned and unmanned rotorcraft vehicles.
Development of a “Smart” Dynamic Strain Measurement System for Turbine Engine Ground Testing
Authors: Reich Alton , Shaw James , Nelius Andrew
Published: June 2010

The Arnold Engineering Development Center (AEDC) testing complex includes more than 50 wind tunnels, test cells, arc heaters, and other specialized test facilities. Of these, 27 units have capabilities that are unmatched in the United States, and 14 are unmatched in the world. These unique facilities pose equally unique testing challenges, including several related to test preparation. A dynamic strain measurement system is being developed for turbine engine ground testing applications. The system is being developed to be compatible with the IEEE-1451 Smart Transducer Interface Standard in order to enable “plug and play” test set up. This will help to minimize the time between the test article installation and completion of test preparations. It will also help to minimize “manual” record keeping associated with testing. The system will also utilize the IEEE-1588 precision time protocol to maintain sampling synchronization. This paper discusses the development of the system consisting of the Smart Transducer Interface Modules (STIMs), the network interfaces (NCAPs), and the system server for control and data storage. It also discusses initial testing and evaluation of the system.
Three-Dimensional Numerical Simulation of the Fluid Dynamics in a Coronary Stent
Authors: Gori F. , Boghi A. , Amitrano M.
Published: June 2010

Stents are commonly used to restore blood flow in patients with severe coronary artery disease. Local hemodynamic variables, as wall shear stress, have an important role in the restenosis and their distribution depends on the stent geometry. The objective of the present study is to carry out CFD simulations in a realistic 3D geometry of a coronary stent in physiological conditions. A comparison is performed between two reconstructed stents, made of 12 rings and similar to the real coronary ones, which differ by the position of the struts, where the first type is with closed cells and the second one with open cells. The artery is modeled as a cylinder with rigid walls and the blood is assumed as incompressible Newtonian fluid in laminar flow with constant physical properties. The commercial computational fluid dynamic code FLUENT is used with a mesh composed of non uniform tetrahedrons. The simulations are performed in steady and unsteady state. Wall shear stresses, WSS, as well as its time variations, are investigated in unsteady state with the conclusion that the stent with closed cells have a better fluid dynamic behavior.
High Fidelity Computational Approach to Validate Spine Biomechanics Measurements: A Case Study to Correct Scoliosis
Authors: Addison B. , Sarigul-Klijn N. , Roberto R. , Jamali A. , Thompson M.
Published: June 2010

This paper presents a high fidelity computational approach to be used in validation of biomechanics experimental measurements. As a demonstration, a case study involving a spinous process implant to correct scoliosis is presented. The biomechanical behavior of the spinous process and implant under tensile loading is investigated using experiments and computations. The experimental study examined the ultimate strength of calf thoracic and lumbar spinous processes in three pullout directions. A statistical analysis was performed on the experimental results to reveal relationships and variations between pullout direction and vertebral type. The finite element high fidelity computational analysis was performed to validate the experimental results. In the process, the material properties of cortical and trabecular bone were elucidated for calf spinous processes. Good comparisons are obtained. The high fidelity computational approach detailed here should serve useful in validation of experimental values from spine biomechanics experimental.
Novel Magnetic Propulsion System for Capsule Endoscopy
Authors: Hu Chengzhi , Gao Mingyuan , Chen Zhenzhi , Zhang Honghai , Liu Sheng
Published: June 2010

For the purpose of realizing the noninvasive exploration of gastrointestinal tract, a novel magnetic propulsion system is proposed, which includes a patient support, a magnet assembly with two groups of permanent magnets positioned oppositely, and a magnet support. The proposed approach exploits permanent magnet and coupling movement of multi-axis components to generate quasi-static magnetic field for controlling the position, orientation, and movement of a self-propelled robotic endoscope in the gastrointestinal tract. By driving the five coupling axes, the proposed magnetic propulsion system is capable of steering the capsule endoscope through the intestinal tract in multi-directions of 2D space. Experiments in simulated intestinal tract are conducted to demonstrate controlled translation, rotation, and rototranslation of capsule endoscope. Finite Element Method is used to analyze navigation system’s mechanical properties and the distributions of magnetic field. The proposed technique has great potential of enabling the application of controlled magnetic navigation in the field of capsule endoscopy.
Liquid Gated Carbon Nanotubes Field Effect Transistors (LG-CNTFET) Platform for Herbicide Sensing
Authors: Tey J. N. , Gandhi S. , Wijaya I. P. M. , Wei J. , Suri C. R. , Rodriguez I. , Mhaisalkar S. G.
Published: June 2010

Single-walled carbon nanotube (SWCNT) is a one-dimensional system with all its carbon atoms present on the surface, hence its conductance is highly sensitive to the surrounding charge environment. Due to the extreme charge sensitivity, biocompatibility and chemical stability, SWCNT is particularly interested in biosensing application. In this paper, we demonstrated a practical approach of fabricating laminated SWCNT liquid gate field effect transistor (LGFET) through a solution processed route involving only two materials, PDMS and SWCNT. The laminated SWCNT LGFETs show great potential towards atrazine detection. The change in the detection signal in terms of conductance was deduced to be due to electrostatic gating mechanism caused by the localized interaction between CNT and the biomolecules. Although relatively high concentration was used in the experiment, the detection limit could be lowered down further by improving the signal-to-noise ratio of the measurement, which can be done through either signal amplification, and/or noise reduction.
Heat Transfer and Tissue Damage in Radiofrequency Ablation Therapy
Authors: Ulucakli M. Erol
Published: June 2010

Heat transfer in radiofrequency ablation therapy of liver tumors is discussed. Temporal and spatial temperature changes around a single needle and multi-prong ablation probes in monopolar and bipolar configurations based on a two-dimensional finite elements method are presented. The temperature changes and related heat transfer in the tissue model help to visualize the shape and size of the ablated region. The visualization of the tissue temperatures and their progression could be useful in clinical applications of ablation therapy. Finite-element based numerical simulation, while providing useful visualizations of the temperature changes in and around the tumor, underestimates the lesion size. The perfusion in the tissue and the possible presence of large blood vessels in or near the ablated domain, and the temperature dependency of the thermal and electrical properties of the tissue are significant complicating factors in modeling and clinical applications.
The Application of Vacuum Casting System for Simplifying the Design of Transtibial Sockets
Authors: Yang Huai-Sheng , Shiu Lai-Shing , Huang Kuo-Feng , Chi Chieh-Teng , Chang Hao-Chin
Published: June 2010

Prosthetic sockets are one of the most important pieces of equipment for a transtibial amputee to maintain a regular life. Rapid Prototyping is becoming mature and low-cost to fit the CAD system that can conserve the shapes of the stump and socket for reproducing the sockets. If the stump shape can be accurately obtained and the prosthetists’ expertise can be included in a CAD system, then a prosthetic socket will be easily designed by a prosthetist. The stump was scanned to get the shape for the construction and modification of the stump model in a CAD system. However, the stump trembled during the scanning process, the scanner was sensitive about the skin move, so that the scanned data will not exactly represent the real stump shape. This study used a vacuum casting system to gain the stump model instead of creating a positive plaster model in the traditional process of fabricating prosthetic sockets. The stump shape under various vacuum pressures was obtained using a scanning machine and built in a CAD system. The CAD model of the stump will be modified to meet the load-bearing capability of the specific amputee. The use of the vacuum casting method is expected to simplify the design of a socket that will be fabricated by a rapid prototyping machine. Simplifying the designs of transtibial socket can decrease the dependence of human experience and promote the quality and stability of prosthetic sockets.