The Effect of High Dose Vitamin D3 on Physical Performance in Frail Older Adults. A Feasibility Study.

BACKGROUND: Vitamin D deficiency is ubiquitous in frailty but the effectiveness of vitamin D supplementation to improve outcomes in frail individuals is unclear. It has been postulated that higher than the current recommended doses (800 IU/day) may be needed to achieve a neuromuscular effect in frail individuals. OBJECTIVES: 1) determine if 4000 IU per day of vitamin D3 is safe for frail older adults; and 2) establish the efficacy of this dose to improve physical performance outcomes in this population. DESIGN: Open-label, feasibility study. SETTING: Community retirement centre. PARTICIPANTS: 40 older adults with frail or pre-frail characteristics. INTERVENTION: 4000 IU of vitamin D3 and 1200 mcg of calcium carbonate daily for four months. MEASUREMENTS: Physical performance (grip strength, gait speed and short physical performance battery score), cognitive health and vitamin D and iPTH serum levels before and after the intervention. RESULTS: Frail individuals improved short physical performance battery score (1.19, p = 0.005), fast gait speed (4.65, p = 0.066) and vitamin D levels (7.81, p = 0.011). Only frail females made a significant improvement in grip strength (1.92, p = 0.003). Stratifying the sample by baseline vitamin D levels revealed that participants with vitamin D insufficiency (≤ 75 nmol/L) significantly improved short physical performance battery score (1.06, p = 0.04), fast gait speed (6.28, p = 0.004) and vitamin D levels (25.73, p = <0.0001). Pre-frail individuals, as well as those with sufficient vitamin D levels (> 75 nmol/L) made no significant improvement in any outcome. CONCLUSIONS: Vitamin D supplementation using 4000 IU/daily is safe and has a modest beneficial effect on physical performance for frail individuals and those with insufficient vitamin D levels. Participants with vitamin D insufficiency (≤ 75 nmol/L) showed greater benefits. Our feasibility study provides results to help calculate effect size for a future RCT.

Sex differences in quadriceps strength in OA.

The purposes of this study were to determine 1) whether sex differences in quadriceps torque and isotonic power persist when controlling for muscle volume (i. e., torque/muscle volume and power/muscle volume) in participants with knee osteoarthritis (OA) and 2) the factors responsible for potential sex differences. Isometric torque, isotonic power (the product of torque and velocity, measured at 10, 20, 30, 40 and 50% maximal voluntary contraction; MVC) and maximal unloaded velocity were assessed in men (n=16, mean age=62.1 ± 7.2) and women (n=17, mean age=60.4 ± 4.3) with knee OA. Torque and power were normalized to muscle volume. The interpolated twitch technique was used to measure voluntary activation (VA) and evoked twitch and torque-frequency characteristics were measured to obtain information about muscle fibre distribution. Torque and power at all loads were significantly lower in women (p<0.05). Sex differences in power were reduced by 50% when controlling for muscle volume but were still significant at 10-40% MVC (p<0.05). No differences in VA, torque-frequency properties or time-to-peak tension of the evoked twitch were observed (p>0.05). These results suggest that only minor sex differences in torque and power persist when controlling for muscle volume. As VA and contractile property differences were not observed, other factors seem to be responsible.

Quadriceps neuromuscular function and self-reported functional ability in knee osteoarthritis.

The purposes of this study were to determine 1) the relationships of self-reported function scores in patients with knee osteoarthritis (OA) to both maximal isometric torque and to isotonic power at a variety of loads, and 2) the degree to which muscle volume (MV) or voluntary activation (VA) are associated with torque and power measures in this population. Isometric maximal voluntary contraction (MVC) torque and isotonic power [performed at loads corresponding to 10, 20, 30, 40, and 50% MVC, and a minimal load ("Zero Load")] were measured in 40 participants with knee OA. Functional ability was measured with the Western Ontario and McMaster Osteoarthritis Index (WOMAC) function subscale. MV was determined with magnetic resonance imaging, and VA was measured with the interpolated twitch technique. In general, power measured at lower loads (Zero Load and 10-30% MVC, r(2) = 0.21-0.28, P < 0.05) predicted a greater proportion of the variance in function than MVC torque (r(2) = 0.18, P < 0.05), with power measured at Zero Load showing the strongest association (r(2) = 0. 28, P < 0.05). MV was the strongest predictor of MVC torque and power measures in multiple regression models (r(2) = 0.42-0.72). VA explained only 6% of the variance in MVC torque and was not significantly associated with power at any load (P > 0.05). Quadriceps MVC torque and power are associated with self-reported function in knee OA, but muscle power at lower loads is more predictive of function than MVC torque. The variance in MVC torque and power between participants is due predominantly to differences in MV and has little to do with deficits in VA.

The origins of neuromuscular fatigue post-stroke.

Fatigue post-stroke is a disabling and persistent symptom affecting many stroke survivors. Despite its high prevalence, the pathophysiology underlying this phenomenon remains obscure. The aim of the present study was to investigate the origins of neuromuscular fatigue post-stroke. Ten chronic stroke survivors and 10 controls sustained an isometric contraction at 30% of maximal voluntary contraction (MVC) with the ankle dorsiflexors. Motor evoked potential (MEP), cortical silent period (SP), voluntary activation, M wave and contractile properties were evaluated before, during and after fatigue among the paretic, non-paretic and control limbs. The pattern of response to fatigue in the non-paretic and control limbs was comparable; therefore, results are presented between the paretic and non-paretic limbs. Before fatigue, reduced MVC peak torque and MEP amplitude were observed on the paretic side in comparison with the non-paretic side. During fatigue, the cortical SP duration increased significantly in both limbs, whereas the MEP amplitude significantly increased only in the non-paretic limb. After fatigue, MVC peak torque decreased significantly in both limbs. Significant reductions in M wave and twitch peak torque were observed in both limbs, pointing to the development of peripheral fatigue. However, central fatigue, evident by a significant reduction in voluntary activation, was greater in the paretic than in the non-paretic limb. After stroke, an inability to increase central excitability in response to an increased cortical inhibition associated with the fatiguing contraction may contribute to central fatigue observed in the paretic limb, which may also be linked to increased self-reported fatigue during activities of daily living. These findings advance our understanding of the neuromuscular basis of fatigue post-stroke.

Probabilistic muscle characterization using QEMG: application to neuropathic muscle.

Clinicians who use electromyographic (EMG) signals to help determine the presence or absence of abnormality in a muscle often, with varying degrees of success, evaluate sets of motor unit potentials (MUPs) qualitatively and/or quantitatively to characterize the muscle in a clinically meaningful way. The resulting muscle characterization can be improved using automated analysis. As such, the intent of this study was to evaluate the performance of automated, conventional Means/Outlier and Probabilistic methods in converting MUP statistics into a concise, and clinically relevant, muscle characterization. Probabilistic methods combine the set of MUP characterizations, derived using Pattern Discovery (PD), of all MUPs detected from a muscle into a characterization measure that indicates normality or abnormality. Using MUP data from healthy control subjects and patients with known neuropathic disorders, a Probabilistic method that used Bayes' rule to combine MUP characterizations into a Bayesian muscle characterization (BMC) achieved a categorization accuracy of 79.7% compared to 76.4% using the Mean method (P > 0.1) for biceps muscles and 94.6% accuracy for the BMC method compared to 85.8% using the Mean method (P < 0.01) for first dorsal interosseous muscles. The BMC method can facilitate the determination of "possible," "probable," or "definite" levels for a given muscle categorization (e.g., neuropathic) whereas the conventional Means and Outlier methods support only a dichotomous "normal" or "abnormal" decision. This work demonstrates that the BMC method can provide information that may be more useful in supporting clinical decisions than that provided by the conventional Means or Outlier methods.

Inter-rater reliability of motor unit number estimates and quantitative motor unit analysis in the tibialis anterior muscle.

OBJECTIVE: To establish the inter-rater reliability of decomposition-based quantitative electromyography (DQEMG) derived motor unit number estimates (MUNEs) and quantitative motor unit (MU) analysis. METHODS: Using DQEMG, two examiners independently obtained a sample of needle and surface-detected motor unit potentials (MUPs) from the tibialis anterior muscle from 10 subjects. Coupled with a maximal M wave, surface-detected MUPs were used to derive a MUNE for each subject and each examiner. Additionally, size-related parameters of the individual MUs were obtained following quantitative MUP analysis. RESULTS: Test-retest MUNE values were similar with high reliability observed between examiners (ICC=0.87). Additionally, MUNE variability from test-retest as quantified by a 95% confidence interval was relatively low (+/-28 MUs). Lastly, quantitative data pertaining to MU size, complexity and firing rate were similar between examiners. CONCLUSION: MUNEs and quantitative MU data can be obtained with high reliability by two independent examiners using DQEMG. SIGNIFICANCE: Establishing the inter-rater reliability of MUNEs and quantitative MU analysis using DQEMG is central to the clinical applicability of the technique. In addition to assessing response to treatments over time, multiple clinicians may be involved in the longitudinal assessment of the MU pool of individuals with disorders of the central or peripheral nervous system.

Decision support for QEMG.

For clinicians to use quantitative electromyography (QEMG) to help determine the presence or absence of neuromuscular disease, they must manually interpret an exhaustive set of motor unit potential (MUP) or interference pattern statistics to formulate a clinically useful muscle characterization. A new method is presented for automatically categorizing a set of quantitative electromyographic (EMG) data as characteristic of data acquired from a muscle affected by a myopathic, normal or neuropathic disease process, based on discovering patterns of MUP feature values. From their numbers of occurrence in a set of training data, representative of each muscle category, discovered patterns of MUP feature values are expressed as conditional probabilities of detecting such MUPs in each category of muscle. The conditional probabilities of each MUP in a set of MUPs acquired from an examined muscle are combined using Bayes' rule to estimate conditional probabilities of the examined muscle being of each category type. Using simulated and clinical data, the ability of a "pattern discovery" based Bayesian (PD-based Bayesian) method to correctly categorize sets of test MUP data was compared to conventional methods which use data means and outliers. The simulated data were created by modeling the effects of myopathic and neuropathic diseases using a physiologically based EMG signal simulator. The clinical data was from controls and patients with known neuropathic disorders. PD-based Bayesian muscle characterization had an accuracy of 84.4% compared to 51.9% for the means and outlier based method when using all MUP features considered. PD-based Bayesian methods can accurately characterize a muscle. PD-based Bayesian muscle characterization automatically maximizes both sensitivity and specificity and provides transparent rationalizations for its characterizations. This leads to the expectation that clinicians using PD-based Bayesian muscle characterization will be provided with improved decision support compared to that provided by the status quo means and outlier based methods.

Evaluation of dimethyl sulphoxide effects on initial response to endotoxin in the horse.

REASONS FOR PERFORMING STUDY: Endotoxaemia is one of the most severe and ubiquitous disease processes in horses. Although dimethyl sulphoxide (DMSO) is used clinically in horses, there is no study indicating its efficacy in endotoxaemic horses. HYPOTHESIS: DMSO ameliorates the clinical response to i.v. lipopolysaccharide (LPS) administration. METHODS: Eighteen horses were assigned randomly to one of 4 groups: Normosol-LPS (0.2 mug/kg bwt, i.v.); DMSO (1 g/kg bwt, i.v.)-saline; high-dose DMSO (1 g/kg bwt, i.v.)LPS; low-dose DMSO (20 mg/kg bwt, i.v.)-LPS. Horses participating in the DMSO-saline group were later assigned randomly to one of the LPS groups. Data for physical parameters, white blood cell counts, plasma TNF-alpha, and blood lactate and glucose concentrations were examined for the effect of treatment using a repeated-measures mixed-model ANOVA. A value of P<0.05 was considered significant. RESULTS: Endotoxaemia occurred in all horses receiving LPS, as indicated by the clinical score, physical parameters, haemoconcentration and leucopenia. High-dose DMSO ameliorated the effect of LPS on fever. DMSO, at either dose, but did not have a significant effect on LPS-induced changes in all other evaluated parameters. CONCLUSIONS: In this study, DMSO had minimal effects on clinical signs of induced endotoxaemia in horses. The effects were manifested by amelioration of LPS-induced fever.

Motor unit potential characterization using "pattern discovery".

Typically in clinical practice, electromyographers use qualitative auditory and visual analysis of electromyographic (EMG) signals to help infer if a neuromuscular disorder is present and if it is neuropathic or myopathic. Quantitative EMG methods exist that can more accurately measure feature values but require qualitative interpretation of a large number of statistics. Electrophysiological characterization of a neuromuscular system can be improved through the quantitative interpretation of EMG statistics. The aim of the present study was to compare the accuracy of pattern discovery (PD) characterization of motor unit potentials (MUPs) to other classifiers commonly used in the medical field. In addition, a demonstration of PD's transparency is provided. The transparency of PD characterization is a result of observing statistically significant events known as patterns. Using clinical MUP data from normal subjects and patients with known neuropathic disorders, PD achieved an error rate of 30.3% versus 29.8% for a Naïve Bayes classifier, 30.1% for a Decision Tree and 29% for discriminant analysis. Similar results were found for simulated EMG data. PD characterization succeeded in interpreting the information extracted from MUPs and transforming it into knowledge that is consistent with the literature and that can be valuable for the capture and transparent expression of clinically useful knowledge.

O2 uptake kinetics, pyruvate dehydrogenase activity, and muscle deoxygenation in young and older adults during the transition to moderate-intensity exercise.

The adaptation of pulmonary O(2) uptake (Vo(2)(p)) kinetics is slowed in older compared with young adults during the transition to moderate-intensity exercise. In this study, we examined the relationship between Vo(2)(p) kinetics and mitochondrial pyruvate dehydrogenase (PDH) activity in young (n = 7) and older (n = 6) adults. Subjects performed cycle exercise to a work rate corresponding to approximately 90% of estimated lactate threshold. Phase 2 Vo(2)(p) kinetics were slower (P < 0.05) in older (tau = 40 +/- 17 s) compared with young (tau = 21 +/- 6 s) adults. Relative phosphocreatine (PCr) breakdown was greater (P < 0.05) at 30 s in older compared with young adults. Absolute PCr breakdown at 6 min was greater (P < 0.05) in older compared with young adults. In young adults, PDH activity increased (P < 0.05) from baseline to 30 s, with no further change observed at 6 min. In older adults, PDH activity during baseline exercise was similar to that seen in young adults. During the exercise transition, PDH activity did not increase (P > 0.05) at 30 s of exercise but was elevated (P < 0.05) after 6 min. The change in deoxyhemoglobin (HHb) was greater for a given Vo(2)(p) in older adults, and there was a similar time course of HHb accompanying the slower Vo(2)(p) kinetics in the older adults, suggesting a slower adaptation of bulk O(2) delivery in older adults. In conclusion, the slower adaptation of Vo(2)(p) in older adults is likely a result of both an increased metabolic inertia and lower O(2) availability.

Effects of a concentrated lidocaine solution on the acute phase stress response to dehorning in dairy calves.

The objective of this study was to more fully define the surgical stress response to dehorning by heat cauterization in dairy calves by measuring behavioral, hormonal, inflammatory, and immunological markers of stress and to determine whether a nerve block of the surgical site with a concentrated solution of lidocaine (5%) reduces the degree of stress. Thirty-two 10- to 12-wk-old female Holstein calves were randomly allotted to 1 of 4 treatments: 5% lidocaine followed by dehorning, 2% lidocaine followed by dehorning, saline followed by dehorning, or 5% lidocaine followed by sham dehorning. Plasma cortisol concentration was measured in blood samples collected via a jugular catheter at -0.5, 0, 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 6, 9, 12, 24, 48, and 72 h. Various other blood constituents were measured in samples collected at -0.5, 12, 24, 48, and 72 h. Feeding, drinking, scratching, grooming, rubbing, licking, and inactivity behaviors were observed in the standing and recumbent positions using a 10-min scan sampling method analyzed on a time period and daily basis for 72 h following the dehorning procedure. The frequency of vocalization, kicking, and lying in the chute during the dehorning procedure were also assessed. The overall plasma cortisol concentrations were higher in calves subjected to dehorning than in control calves. Compared with the control group, the saline-treated calves had a higher cortisol concentration at 30 and 60 min postdehorning. Plasma cortisol concentrations were higher in all groups at 30 min postdehorning than at other sampling times. The percentage of circulating neutrophils and the neutrophil:lymphocyte ratio were increased in the saline and 2% lidocaine group. Total plasma protein, fibrinogen, and alpha1-acid glycoprotein concentrations were similar among treatments. The behavioral response to dehorning, as manifested by kicking while in the chute, was greater in the saline and 2% lidocaine group than in the control or 5% lidocaine treatment groups. In the postdehorning period, the percentage of time calves spent performing various maintenance behaviors did not differ among treatments. Thus, injection of 5% lidocaine may not provide any added comfort after the dehorning but may decrease the overall stress response during the procedure.

Prior heavy exercise elevates pyruvate dehydrogenase activity and speeds O2 uptake kinetics during subsequent moderate-intensity exercise in healthy young adults.

The adaptation of pulmonary oxygen uptake (.VO2) during the transition to moderate-intensity exercise (Mod) is faster following a prior bout of heavy-intensity exercise. In the present study we examined the activation of pyruvate dehydrogenase (PDHa) during Mod both with and without prior heavy-intensity exercise. Subjects (n = 9) performed a Mod(1)-heavy-intensity-Mod(2) exercise protocol preceded by 20 W baseline. Breath-by-breath .VO2 kinetics and near-infrared spectroscopy-derived muscle oxygenation were measured continuously, and muscle biopsy samples were taken at specific times during the transition to Mod. In Mod(1), PDHa increased from baseline (1.08 +/- 0.2 mmol min(-1) (kg wet wt)(-1)) to 30 s (2.05 +/- 0.2 mmol min(-1) (kg wet wt)(-1)), with no additional change at 6 min exercise (2.07 +/- 0.3 mmol min(-1) (kg wet wt)(-1)). In Mod(2), PDHa was already elevated at baseline (1.88 +/- 0.3 mmol min(-1) (kg wet wt)(-1)) and was greater than in Mod(1), and did not change at 30 s (1.96 +/- 0.2 mmol min(-1) (kg wet wt)(-1)) but increased at 6 min exercise (2.70 +/- 0.3 mmol min(-1) (kg wet wt)(-1)). The time constant of .VO2 was lower in Mod(2) (19 +/- 2 s) than Mod(1) (24 +/- 3 s). Phosphocreatine (PCr) breakdown from baseline to 30 s was greater (P < 0.05) in Mod(1) (13.6 +/- 6.7 mmol (kg dry wt)(-1)) than Mod(2) (6.5 +/- 6.2 mmol (kg dry wt)(-1)) but total PCr breakdown was similar between conditions (Mod(1), 14.8 +/- 7.4 mmol (kg dry wt)(-1); Mod(2), 20.1 +/- 8.0 mmol (kg dry wt)(-1)). Both oxyhaemoglobin and total haemoglobin were elevated prior to and throughout Mod(2) compared with Mod(1). In conclusion, the greater PDHa at baseline prior to Mod(2) compared with Mod(1) may have contributed in part to the faster .VO2 kinetics in Mod(2). That oxyhaemoglobin and total haemoglobin were elevated prior to Mod(2) suggests that greater muscle perfusion may also have contributed to the observed faster .VO2 kinetics. These findings are consistent with metabolic inertia, via delayed activation of PDH, in part limiting the adaptation of pulmonary .VO2 and muscle O2 consumption during the normal transition to exercise.

Effect of a constant rate infusion of lidocaine on the quality of recovery from sevoflurane or isoflurane general anaesthesia in horses.

REASONS FOR PERFORMING STUDY: Lidocaine constant rate infusions (CRIs) are common as an intraoperative adjunct to general anaesthesia, but their influence on quality of recovery has not been thoroughly determined. OBJECTIVES: To determine the effects of an intraoperative i.v. CRI of lidocaine on the quality of recovery from isoflurane or sevoflurane anaesthesia in horses undergoing various surgical procedures, using a modified recovery score system. HYPOTHESIS: The administration of intraoperative lidocaine CRI decreases the quality of recovery in horses. METHODS: Lidocaine (2 mg/kg bwt bolus followed by 50 microg/kg bwt/min) or saline was administered for the duration of surgery or until 30 mins before the end of surgery under isoflurane (n = 27) and sevoflurane (n = 27). RESULTS: Horses receiving lidocaine until the end of surgery had a significantly higher degree of ataxia and a tendency towards significance for a lower quality of recovery. There was no correlation between lidocaine plasma concentrations at recovery and the quality of recovery. CONCLUSIONS: Intraoperative CRI of lidocaine affects the degree of ataxia and may decrease the quality of recovery. POTENTIAL RELEVANCE: Discontinuing lidocaine CRI 30 mins before the end of surgery is recommended to reduce ataxia during the recovery period.

Effect of systemic lidocaine on visceral and somatic nociception in conscious horses.

REASONS FOR PERFORMING STUDY: Commonly used analgesics (nonsteroidal anti-inflammatory agents, opioids and alpha2-agonists) have unwanted side effects. An effective alternative with minimal adverse effects would benefit clinical equine pain management. OBJECTIVES: To compare the effect of lidocaine or saline on duodenal and rectal distension threshold pressure and somatic thermal threshold in conscious mature horses. HYPOTHESIS: Systemically administered lidocaine would increase somatic and visceral nociceptive thresholds. METHODS: Lidocaine (2 mg/kg bwt bolus followed by 50 microg/kg bwt/min for 2 h) or saline was administered to 6 horses each carrying a permanently implanted gastric cannula, in a randomised, blinded cross-over design. Thermal threshold was measured using a probe containing a heater element placed over the withers which supplied heat until the horse responded. A barostatically controlled intraduodenal balloon was distended until a discomfort response was obtained. A rectal balloon was inflated until extruded or signs of discomfort noted. RESULTS: Thermal threshold was increased significantly 30 and 90 mins after the start of lidocaine infusion. There was no change in duodenal distension pressure and a small but clinically insignificant change in colorectal distension pressure in the lidocaine group. CONCLUSIONS: At the dose used, systemically administered lidocaine produced thermal antinociception but minimal changes in visceral nociception. POTENTIAL RELEVANCE: At these doses, lidocaine may play a role in somatic analgesia in horses.

Creatine monohydrate enhances strength and body composition in Duchenne muscular dystrophy.

OBJECTIVE: To determine whether creatine monohydrate (CrM) supplementation increases strength and fat-free mass (FFM) in boys with Duchenne muscular dystrophy (DD). METHODS: Thirty boys with DD (50% were taking corticosteroids) completed a double-blind, randomized, cross-over trial with 4 months of CrM (about 0.10 g/kg/day), 6-week wash-out, and 4 months of placebo. Measurements were completed of pulmonary function, compound manual muscle and handgrip strength, functional tasks, activity of daily living, body composition, serum creatine kinase and gamma-glutamyl transferase activity and creatinine, urinary markers of myofibrillar protein breakdown (3-methylhistidine), DNA oxidative stress (8-hydroxy-2-deoxyguanosine [8-OH-2-dG]), and bone degradation (N-telopeptides). RESULTS: During the CrM treatment phase, there was an increase in handgrip strength in the dominant hand and FFM (p < 0.05), with a trend toward a loss of global muscle strength (p = 0.056) only for the placebo phase, with no improvements in functional tasks or activities of daily living. Corticosteroid use, but not CrM treatment, was associated with a lower 8-OH-2-dG/creatinine (p < 0.05), and CrM treatment was associated with a reduction in N-telopeptides (p < 0.05). CONCLUSIONS: Four months of CrM supplementation led to increases in FFM and handgrip strength in the dominant hand and a reduction in a marker of bone breakdown and was well tolerated in children with DD.

Effects of lipopolysaccharide and phenylbutazone on gastric contents in the horse.

REASONS FOR PERFORMING STUDY: Endotoxaemia causes a disruption of gastrointestinal motility in the horse but there is no information on its effects on gastric secretion. Lipopolysaccharide (LPS) administration is known to affect gastric secretion in other species. HYPOTHESIS: That LPS, a toxic component of Gram-negative bacteria, would reduce gastric acid secretion and that pretreatment with phenylbutazone (PBZ) would block the effects of LPS. METHODS: The effects of LPS and PBZ on gastric contents were investigated in fasted, mature horses, with permanent gastric cannulae. Horses were pretreated with either saline or PBZ 15 mins before a 60 min infusion of either LPS or saline. Gastric contents were collected at 15 min intervals for 3 h, beginning 15 mins after the start of the LPS or saline infusion. RESULTS: Lipopolysaccharide significantly decreased gastric acid output, [K+] and potassium output and increased [Na+] and sodium output. Phenylbutazone did not affect basal gastric acid secretion but decreased LPS-induced changes in the secreted volume, [Na+] and sodium output. CONCLUSIONS: This study provides evidence that LPS affects gastric acid secretion in the horse and that these LPS-induced changes are mediated, in part, by prostaglandins. POTENTIAL RELEVANCE: Lipopolysaccharide administration can induce changes in the composition of gastric contents in the horse but further work is needed to determine the source of these changes.