The effect of feeding a commercial feedstuff on gastric squamous gastric disease (ESGD) healing and prevention of recurrence

Feedstuffs are often recommended to mitigate potential damage from acid associated with equine squamous gastric disease (ESGD). In acidic conditions, pectin alters its structure to one like mucus and binds the stomach mucosa, whilst alfalfa has a strong intrinsic acid buffering capacity. The study aimed to determine whether feeding a commercial beet pulp/alfalfa/oat fibre mix aids ESGD healing and/or prevention of recurrence. Ten adult horses with naturally occurring ESGD were included. All animals were treated with omeprazole as per the attending veterinarian's recommendation and randomly allocated to also be fed a commercial beet pulp/alfalfa/oat fibre mix (1Kg/horse divided into 2 meals/day; n=5) or no additional feed (n=5) for one month. Gastroscopy was then repeated to assess response to therapy. If the ESGD had healed, omeprazole therapy was discontinued, and the commercial feed given to all horses for a further month. Gastroscopy was repeated to determine ESGD recurrence. The mean (±SD) age of the horses was 11.6 (±3.8) years; 4 mares and 6 geldings; various breeds were represented; and the median (range) initial ESGD grade was 2 (2-4). ESGD had healed (grade 0/4) in all animals after one month. After a further month, ESGD had recurred in significantly (p=0.04) more animals that did not receive the commercial feed initially (3/5; 60%; mean [range] ESGD grade 3 [0,4]) compared to those that did (0/5; 0%; mean [range] ESGD grade 0 [0,0]). Thus, the commercial beet pulp/alfalfa/oat fibre mix aided prevention of ESGD recurrence when fed during the healing and prevention phases.

Short Communication: Identification of equine corticotropin-like intermediate lobe peptide (CLIP) binding to an adrenocortipcotrophic hormone (ACTH) assay capture antibody

A chemiluminescent immunoassay is commonly employed to measure adrenocorticotrophic hormone (ACTH) concentrations to assist pituitary pars intermedia dysfunction diagnosis. In a previous study, seasonally-dependent assay cross-reactivity to endogenous equine corticotropin-like intermediate lobe peptide (CLIP, ACTH 18-39) was suspected. The present study aimed to demonstrate binding of endogenous equine CLIP to the capture antibody of the ACTH chemiluminescent immunoassay. Liquid chromatography - mass spectrometry (LCMS) methods were optimised to identify selected ions from synthetic human ACTH, α-melanocyte stimulating hormone (α-MSH, ACTH 1-17) and CLIP. Synthetic ACTH and CLIP bound to the capture antibody of the chemiluminescent ACTH assay, but α-MSH did not. Equine endogenous CLIP was detected by LCMS in pony plasma taken in the autumn and could be eluted from the capture antibody of the ACTH chemiluminescent immunoassay. Further research is required to enable quantification of CLIP. Equine CLIP may alter measured ACTH concentrations in vivo.

Cell specific microvesicles vary with season and disease predisposition in healthy and previously laminitic ponies

Microvesicles are small (up to 1 μm) vesicles found in plasma and other bodily fluids. They are recognised as part of the normal system of inter-cellular communication but altered numbers are also used as biomarkers of disease. Microvesicles have not been studied in detail in the horse but may be relevant to diseases such as laminitis. Identification of equine cell specific microvesicles was performed by developing a panel of cross reactive antibodies to use in flow cytometry to detect microvesicles of platelet, leucocyte and endothelial origin in plasma from healthy ponies and those predisposed to laminitis. The total number and proportion of microvesicles from the different cell types varied with season and there were more annexin V positive endothelial MV in non laminitic ponies compared to previously laminitic ponies. Development of this antibody panel and the technique for measuring microvesicles in the horse opens a new field for further investigation of these important structures in equine health and disease.

Plasma adrenocorticotropic hormone (ACTH) concentrations in ponies measured by two different assays suggests seasonal cross-reactivity or interference

BACKGROUND

Analysis of plasma adrenocorticotropic hormone concentration [ACTH] aids diagnosis of pituitary pars intermedia dysfunction (PPID). Comparisons of the validated chemiluminescent-immunoassay (CI) and immunofluorescent (IF) assays are limited.

OBJECTIVES

To compare the results of [ACTH] analysis by CI and IF methods of samples collected in autumn and spring and assess cross-reactivity.

STUDY DESIGN

Method comparison.

METHODS

Plasma from nonlaminitic ponies was analysed concurrently using the IF and CI methods in autumn and the following spring. Diagnostic thresholds for the IF method were derived using ROC curves and Youden indices to correspond with CI thresholds. Assay specificity was assessed using commercially available ACTH fragments and degradation products of endogenous ACTH.

RESULTS

CI and IF methods yielded different results (P<0.001); mean differences (CI-IF), (95% confidence intervals): Autumn (n=99) 38.6 (30.6-46.5) pg/ml, Spring (n=88) 5.1 (3.9-6.3) pg/ml. The association between CI and IF results differed in autumn and spring, consistent with seasonally dependent cross-reactivity or interference. Good (κ=0.66-0.74) agreement was obtained for binary interpretation in spring between IF and CI using thresholds of >24 and >29 pg/ml respectively and in autumn between IF and CI using thresholds of >27 and >47 pg/ml respectively or >33 and >77 pg/ml respectively. Of 88 ponies with both spring and autumn samples, 56 (64%) exceeded a published autumn CI threshold (>47 pg/ml), of which 39 (70%) were below the equivalent threshold (<29 pg/ml) the following spring without treatment. The CI assay showed apparent increases in [ACTH] following addition of CLIP (ACTH 18-39). Degradation of ACTH during storage affected the assays differently.

MAIN LIMITATIONS

Limited numbers of PPID cases were included. Immunoreactivity of commercially available peptides may differ from their endogenous equivalents.

CONCLUSIONS

The methods yielded different absolute values but the agreement for binary classification was good. An altered pituitary secretome in autumn that affects apparent [ACTH] values is likely. The Summary is available in Spanish - see Supporting information.

Use of the oral sugar test in ponies when performed with or without prior fasting

BACKGROUND

It is recommended that the oral sugar test (OST) for insulin dysregulation (ID) be performed after an overnight fast, but fasting is impractical in ponies kept solely at pasture. There are few data on OST repeatability and reliability in ponies.

OBJECTIVES

To report 1) whether OST results obtained in the morning after an overnight fast or without fasting in the afternoon (FASTING/FED) can be used interchangeably, 2) time of highest insulin concentration T_max [insulin], repeatability and reliability of insulin response to the OST when FASTING or FED and 3) dichotomous agreement (ID/normal) within a small sample when FASTING or FED.

STUDY DESIGN

Method comparison study.

METHODS

Oral sugar tests were performed on four occasions in 10 adult native British ponies, twice FASTING and twice FED. Insulin concentrations were measured by radioimmunoassay at 0-120 min (T_{0,30,60,75,90,120} ). Differences between FASTING and FED results were assessed using mixed effects models. Indices of repeatability and reliability were calculated; dichotomous agreement was reported using kappa statistics.

RESULTS

Serum [insulin] was significantly (P≤0.05) higher at T₆₀ -T₉₀ with prior fasting (estimated differences [95% confidence intervals]): T₆₀ : 23.5 μiu/ml (8.7-38.4 μiu/ml), T₇₅ : 27.1 μiu/ml (12.3-41.8 μiu/ml), T₉₀ : 15.1 (0.36-29.9 μiu/ml). Most frequently, T_max [ins] occurred at T₃₀ . At any single time point, within-subject coefficients of variation were: FASTING: 40% and FED: 31%. The 95% limits for repeatability were FASTING: 29-340%, FED: 41-240%. Test reliabilities were FASTING: 0.70 and FED: 0.67. For dichotomous interpretation similar results (kappa = 0.7) were obtained using cut-offs of [Insulin] >60 μiu/ml at T₆₀ or T₉₀ for FASTING and [Insulin] >51 μiu/ml at T₃₀ or T₆₀ for FED samples.

MAIN LIMITATIONS

Oral sugar tests were performed on a small number of animals on one pasture during one season (spring).

CONCLUSIONS

Clinicians should beware of interpreting changes in absolute OST results owing to poor repeatability. When stabling is unavailable, OSTs of ponies at pasture may yield similar dichotomous results without prior fasting.

Prospective cohort study evaluating risk factors for the development of pasture-associated laminitis in the United Kingdom

BACKGROUND

Certain individuals appear to be predisposed to recurrent pasture-associated laminitis. Previous studies have predominantly investigated risk factors only after disease occurrence.

OBJECTIVES

To investigate risk factors for pasture-associated laminitis prior to disease occurrence.

STUDY DESIGN

Prospective cohort study.

METHODS

Non-laminitic ponies aged ≥7 years were recruited. Body condition score (BCS), height, weight, crest height and thickness were measured and an overnight dexamethasone suppression test performed. Plasma or serum adiponectin, leptin, triglyceride, basal insulin, insulin post-dexamethasone, insulin-like growth factor 1 (IGF-1), IGF binding protein 1 (IGFBP-1), IGFBP-3, C-reactive protein, von Willebrand's factor, soluble E-selectin and P-selectin concentrations were assayed. Follow-up data were obtained from owners annually for 3 years to ascertain occurrences of veterinarian-diagnosed pasture-associated laminitis. Data were analysed by multivariate logistic regression. Receiver operating characteristic (ROC) curves analysis was performed for significant risk factors and cut-off values determined.

RESULTS

A total of 446 animals with a median (interquartile range) age of 15 (10-20) years were recruited. Of these, 50.4% were mares and 49.6% were geldings. The most common breeds were Welsh (36.4%), Shetland (17.0%) and cob (9.4%). Overall, 72.2% of animals were overweight/obese (BCS 7-9/9), 27.3% were of ideal weight (BCS 4-6/9) and 0.5% were underweight (BCS 1-3/9). After 1, 2 and 3 years, respectively, 18 (4.0%), 30 (6.7%) and 44 (9.9%) animals were reported to have had laminitis. Plasma adiponectin, and serum basal (insulin) and (insulin) post-dexamethasone levels were significantly (P ≤ 0.05) associated with laminitis occurrence cumulatively after 1, 2 and 3 years. Use of the area under the ROC curves to distinguish animals that did and did not develop laminitis showed good (basal [insulin] after 1 year), fair (all others) or poor ([insulin] post-dexamethasone) levels of accuracy.

MAIN LIMITATIONS

Animals were evaluated at a single time point and biomarkers were assayed using single assays.

CONCLUSIONS

Risk factors for future laminitis prior to disease occurrence include low plasma adiponectin and high serum basal insulin or insulin post-dexamethasone concentrations.

Clinical Research Abstracts of the British Equine Veterinary Association Congress 2015

REASONS FOR PERFORMING STUDY

The birthweight of Thoroughbred foals has increased in recent years. It is unknown whether this is associated with increased broodmare obesity or endocrine dysfunction.

OBJECTIVES

To determine insulin, leptin and triglyceride concentrations in obese and non-obese Thoroughbred mares throughout gestation and to investigate their association with foal birthweight.

STUDY DESIGN

Prospective, cohort study.

METHODS

Fifty-seven pregnant Thoroughbred mares were included in the study. From 40 days post-breeding, body condition score (BCS), weight and venous blood samples were obtained every 60 days throughout gestation. Feed was withheld for 6 h before blood sampling. Serum/plasma insulin, leptin and triglyceride concentrations were measured using validated/standard methods. Foal birthweight was recorded. Association of hormone or triglyceride concentration with time, BCS and birthweight were analysed using a linear mixed effects model. A Pearson correlation co-efficient was calculated between hormone or triglyceride concentration, BCS and birthweight.

RESULTS

Serum insulin concentrations were significantly greater (P<0.05) at 0-59 days compared with 240-299 days and at 60-119 days compared with 180-359 days gestation. 55% of mares had BCS ≥ 7. There was 1.5% incidence of fasting hyperinsulinaemia throughout gestation and no association of fasting insulin concentration with BCS. Leptin concentration was significantly (P<0.0001) greater at 180-239 days compared with all other time points and was significantly (r = 0.29, P<0.0003) correlated with BCS. Triglyceride concentration was significantly (P<0.02) greater at 240-299 days compared with earlier time points but was not associated with BCS. Foal birthweight was significantly positively correlated with BCS (r = 0.13, P<0.001) and inversely correlated with leptin concentration at 60-119 days and 240-299 days gestation (r = -0.64, P<0.05).

CONCLUSIONS

Mare BCS correlated with foal birthweight such that obese mares had heavier foals. Significant fasting hyperinsulinaemia was not identified in this population. Increased leptin concentration in early and late gestation was associated with decreased foal birthweight and may be useful to predict foal birthweight. Ethical animal research: Informed client consent was obtained for all animals used in the study.

SOURCE OF FUNDING

Private donor. Competing interests: None declared.

The effect of exercise on plasma concentrations of inflammatory markers in normal and previously laminitic ponies

REASONS FOR PERFORMING STUDY

The mechanisms underlying predisposition to pasture-associated laminitis remain unclear; chronic inflammation is implicated, and this may be exacerbated by physical inactivity.

OBJECTIVES

To determine whether exercise affects the inflammatory profile of normal and previously laminitic ponies.

STUDY DESIGN

Prospective case-control study.

METHODS

The short (1 day) and longer term (14 days) effects of low intensity (10 min walking and 5 min trotting) exercise on plasma inflammatory marker concentrations in normal (NL) and previously laminitic (PL) nonobese ponies (n = 6/group) was determined. Plasma concentrations of TNF-α, serum amyloid A (SAA), haptoglobin, insulin, adiponectin and fibrinogen were assayed by validated/standard methods. Data were analysed using a linear mixed effects model.

RESULTS

Before exercise, plasma [adiponectin] was significantly (P = 0.0001) lower in PL (mean ± s.d. 2.4 ± 0.1 ng/l) than in NL (4.03 ± 0.2 ng/l), but exercise had no effect. Previous laminitis and exercise had no effect on plasma [TNF-α] or [fibrinogen]. Serum amyloid A concentrations in all ponies were significantly (P = 0.00001) reduced after longer term exercise compared to Day 1 values. Plasma [haptoglobin] was significantly (P = 0.00001) higher in PL compared to NL on Day 1. This difference was no longer apparent after longer term exercise, such that [haptoglobin] in PL had decreased to concentrations similar to NL. Following short-term exercise, all ponies had an initial decrease in serum [insulin] immediately after exercise, followed by an increase peaking 10 min after exercise cessation, before returning to pre-exercise values. On Day 14 these fluctuations were significantly (P = 0.001) reduced in all ponies.

CONCLUSIONS

Fourteen days of low intensity exercise significantly decreased [SAA] in all ponies and plasma [haptoglobin] in PL such that it was no longer increased compared to NL. Regular low intensity exercise appears to have an anti-inflammatory effect, which is possibly greater in PL and so may be beneficial in reducing this putative risk factor in pasture-associated laminitis.

Plasma fructosamine concentrations in horses with pituitary pars intermedia dysfunction with and without laminitis

REASONS FOR PERFORMING STUDY

Plasma fructosamine concentration ([fructosamine]) is believed to reflect medium term, average blood glucose concentration and in a previous study was higher in horses with active laminitis than in normal horses. Pituitary pars intermedia dysfunction (PPID) is associated with hyperglycaemia and laminitis.

OBJECTIVES

To test the hypotheses that: [fructosamine] is higher in PPID cases than normal animals; furthermore, that within cases of PPID [fructosamine] is higher in those with active laminitis than nonlaminitic cases and in cases that have been affected by active laminitis in the preceding year than those that have not.

STUDY DESIGN

Observational, case-control/cross-sectional study.

METHODS

[Fructosamine] was measured in cases of PPID (n = 46) and normal animals (n = 139). A normal range was calculated; values were compared between the 2 groups and within the PPID group, between cases with and without active laminitis and between cases that had and had not been affected by active laminitis in the preceding year.

RESULTS

In normal animals mean [fructosamine] was 248.7 μmol/l; the normal range (mean ± 2 s.d.) was 195.5-301.9 μmol/l. Plasma [fructosamine] was not higher in PPID cases than in normal animals. In PPID cases, [fructosamine] was significantly (P = 0.006) higher in cases with active laminitis (mean ± s.d. 261.2 ± 39.2 μmol/l) compared with those without active laminitis (234.5 ± 32.9 μmol/), but [fructosamine] was not higher in cases that had been affected by active laminitis in the preceding year than those that had not.

CONCLUSIONS

In horses affected by PPID, [fructosamine] is higher in cases with active laminitis than in cases without active laminitis.

POTENTIAL RELEVANCE

Clinical use of [fructosamine] is limited due to overlap with the normal range. Further studies into glucose and protein metabolism in cases of PPID are warranted.

Seasonal and annual influence on insulin and cortisol results from overnight dexamethasone suppression tests in normal ponies and ponies predisposed to laminitis

REASONS FOR PERFORMING STUDY

A simple, accurate test for identifying individual animals at increased risk of laminitis would aid prevention. Laminitis-prone ponies have a greater serum insulin response to dexamethasone administration than normal ponies in the summer, but the response during different seasons is unknown.

OBJECTIVE

To test the hypothesis that previously laminitic ponies have a greater insulin response to dexamethasone than normal ponies, which is present during all seasons.

STUDY DESIGN

Prospective longitudinal study.

METHODS

Overnight dexamethasone suppression tests were performed on 7 normal ponies and 5 previously laminitic ponies in spring 2009 and 2010, summer 2008 and 2010, autumn 2009 and winter 2008, while the ponies were at pasture. In spring 2010, a dexamethasone suppression test was performed after the ponies had been fed only hay for 3 weeks. Serum cortisol and insulin concentrations pre- and post dexamethasone were measured. Linear mixed models were used to analyse the data.

RESULTS

Insulin concentrations pre- and post dexamethasone were significantly higher in previously laminitic ponies than in normal ponies during spring 2009 and summer 2008, but there was no difference between groups in spring 2010, summer 2010, autumn 2009 or winter 2008. Insulin concentration varied significantly with season. Diet had no apparent effect on insulin concentration pre- or post dexamethasone in spring 2010. Cortisol concentrations post dexamethasone were significantly higher in previously laminitic ponies than in normal ponies in autumn 2009, with concentrations above the reference range (<25 nmol/l) in both groups in summer 2008 and autumn 2009. Individual ponies had insufficient cortisol suppression in all seasons.

CONCLUSIONS

There were significant differences between groups in insulin and cortisol concentrations post dexamethasone during some seasons, but this was not present in all years. Wide interindividual variation in response limits the usefulness of a dexamethasone suppression test for predicting the susceptibility of an individual animal to laminitis.

POTENTIAL RELEVANCE

Abnormal insulin and cortisol responses to dexamethasone must be interpreted in the light of the individual animal, seasonal and annual variation reported here.

Seasonal variation in maintenance of phenylephrine-induced tone in isolated equine digital arteries under hypoxic or hyperoxic conditions in vitro

Digital vasoconstriction, ischaemia and hypoxia may predispose to acute laminitis. Laminitis incidence varies seasonally, peaking in spring and summer. Direct seasonal influences on equine digital artery (EDA) contractility have not been investigated. This study assessed seasonal variation in maintenance of phenylephrine (PHE)-induced tone in isolated EDAs under hypoxic (95% nitrogen) and hyperoxic (95% oxygen) conditions. The objective was to measure change in arterial tone over time after constriction to a plateau with PHE. Tone was measured at plateau and over time and percentage change calculated. Hyperoxic EDAs maintained PHE-induced tone over 1 h with no seasonal variation. Hypoxic EDAs relaxed in fall (median [inter-quartile range] 59% [44-77%] decrease from plateau; P=0.008), contracted in spring (65% [20-192%] increase from plateau; P=0.03) and did not significantly change tone in winter (18% [0-28%] decrease; P=0.13). Continued contraction under hypoxic conditions in spring may contribute to digital vasoconstriction.

Epidemiological study of pasture-associated laminitis and concurrent risk factors in the South of England

A retrospective study of laminitis was carried out to identify risk factors associated with this disease on an East Anglian farm with approximately 1000 animals living in an area of 1000 acres. Medical records between January 1997 and May 2000 and between April 2005 and March 2008 were reviewed, and the age, sex, weight (kg), height (inches [in] and hands [H]) and weight-to-height ratio (kg/in) was recorded. The prevalence, incidence and seasonality of laminitis were determined and their relationship to the monthly temperature, rainfall and hours of sunshine was evaluated. Averaged over the six years, the highest prevalence (2.6 per cent) and incidence (16 cases/1000 animals) of laminitis occurred in May. The findings of a multivariate analysis revealed that females (P=0.007, odds ratio [OR] 1.46, 95 per cent confidence interval [CI] 1.1053 to 1.9646) and light animals (P ≤ 0.001, OR=0.995, 95 per cent CI =0.9932 to 0.9963) had the greatest risk of developing laminitis. A positive association was found between hours of sunshine and incidence (P=0.007, relative risk [RR] 1.009, 95 per cent CI 1.001 to 1.012) and prevalence (P=0.002, RR 1.008, 95 per cent CI 1.003 to 1.012) of laminitis. The data suggest that there is a relationship between season, sex of the animal and the development of laminitis.

Endotoxin-induced digital vasoconstriction in horses: associated changes in plasma concentrations of vasoconstrictor mediators

REASONS FOR PERFORMING STUDY

Lipopolysaccharide (LPS) infusion reduces digital perfusion, but the mediators responsible remain undetermined.

OBJECTIVES

To identify vasoconstrictor mediators released following LPS infusion and relate their appearance in plasma to digital blood flow alterations.

METHODS

Blood flow in the lateral digital vessels of 6 Thoroughbred horses, following a 30 min infusion of LPS (E. coli 055:B5; 30 ng/kg), was measured using Doppler ultrasonography. Concomitant measurements of hoof wall and coronary band surface temperatures (HWST and CBST) were made. Serial blood samples were collected and plasma LPS, tumour necrosis factor alpha (TNFalpha), 5-HT, thromboxane B2 (TxB2) and endothelin measured.

RESULTS

Plasma LPS concentrations reached a maximum of 13.2 pg/ml during the infusion, followed by an increase in plasma TNFalpha concentration. Digital arterial and venous blood flow decreased by 43 and 63%, respectively; HWST and CBST similarly decreased. Systemic blood pressure remained unaltered. Plasma concentrations of TxB2 and 5-HT increased, coinciding with the onset of digital hypoperfusion. Plasma endothelin concentrations remained unchanged.

CONCLUSIONS

The temporal relationship between the onset of digital hypoperfusion and increases in plasma 5-HT and TxB2 concentrations is consistent with these platelet-derived mediators being associated with LPS-induced laminitis.

POTENTIAL RELEVANCE

These experimental data support the use of anti-platelet therapy in the prevention of laminitis associated with endotoxaemic conditions.

The effects of vasoactive amines found in the equine hindgut on digital blood flow in the normal horse

REASONS FOR PERFORMING STUDY

Disturbances of digital blood flow are thought to be fundamental to the pathophysiology of acute laminitis. However, factors linking the initiating events in the equine hindgut with these disturbances in the foot remain to be determined.

HYPOTHESIS

Amine compounds, formed by bacteria in the equine hindgut, have digital vasoconstrictor effects in vivo.

METHODS

Tryptamine (1.6 microg/kg/min) and phenylethylamine (2.13 microg/kg/min) were infused i.v. into standing nonsedated horses. Digital blood flow was measured by Doppler ultrasound and foot surface temperature was monitored. Plasma 5-hydroxytryptamine (5-HT) concentrations were measured by HPLC.

RESULTS

Tryptamine and phenylethylamine infusions had no effect on systemic arterial blood pressure or heart rate, but caused significant decreases in digital arterial blood flow (mean +/- s.e. 29.2 +/- 8.5 and 18.4 +/- 6.8%, respectively). Both amines also caused decreases in dorsal hoof wall temperature (0.6 +/- 0.1 and 0.5 +/- 0.1 degrees C for tryptamine and phenylethylamine, respectively) and concomitant increases in plasma 5-HT concentration.

CONCLUSIONS

Tryptamine and phenylethylamine caused reduction of digital blood flow, effects which may have been mediated, in part, via displacement of 5-HT from platelets.

POTENTIAL RELEVANCE

Amine compounds occurring in the equine hindgut, if released into the circulation following carbohydrate overload, could contribute to selective digital vasoconstriction. Further work in ponies and horses, with naturally occurring laminitis, is necessary to determine whether amines represent a therapeutic target in this disease.

Regulation of platelet activating factor-induced equine platelet activation by intracellular kinases

Lipopolysaccharide (LPS) can activate equine platelets directly or indirectly, via leukocyte-derived platelet activating factor (PAF). Thromboxane (Tx) production by LPS-stimulated equine platelets requires p38 MAPK and this kinase has been suggested as a therapeutic target in endotoxaemia. The present study has utilised selective inhibitors to investigate the role of p38 MAPK and two other kinases, phosphatidylinositol-3 kinase (PI3K) and protein kinase C (PKC), in regulating PAF-induced Tx production, aggregation and 5-HT release in equine platelets, and the modification of these responses by LPS. LPS enhanced PAF-induced 5-HT release, an effect that was reduced by the p38 MAPK inhibitor, SB203580 (60 +/- 8% reduction; n = 6). SB203580 did not affect responses to PAF alone; whereas inhibition of PKC reduced PAF-induced 5-HT release, Tx production and aggregation (maximal inhibition by the PKCdelta inhibitor, rottlerin: 69 +/- 13%, 63 +/- 14% and 97 +/- 1%, respectively; n = 6). Wortmannin and LY249002, which inhibit PI3K, also caused significant inhibition of PAF-induced aggregation (maximal inhibition 78 +/- 3% and 88 +/- 2%, respectively; n = 6). These data suggest that inhibition of platelet p38 MAPK may be of benefit in equine endotoxaemia by counteracting some of the effects of LPS. However, detrimental effects of platelet activation mediated by PAF and not enhanced by LPS are unlikely to be markedly affected.

Effects of sedation with acepromazine on echocardiographic measurements in eight healthy thoroughbred horses

Eight normal thoroughbred horses were examined by echocardiography before and 10 minutes after they had been sedated by the intravenous administration of 0.03 mg/kg acepromazine. There were significant (P<0.025) increases in the diameters of the pulmonary artery and the aorta, measured at end-systole, and in the thickness of the interventricular septum, measured at end-systole and end-diastole. In addition, there was a significant (P<0.001) decrease in the diameter of the left atrium measured at end-diastole. The remaining cardiac dimensions, all the indices of cardiac function, and the occurrence and severity of valvular regurgitation were not affected by sedation.

Endotoxin-induced activation of equine platelets: evidence for direct activation of p38 MAPK pathways and vasoactive mediator production

OBJECTIVE AND DESIGN

The aim of this study was to determine the effects of endotoxin on p38 MAPK activation in equine platelets and leukocytes in vivo and in vitro and its role in thromboxane (Tx) production with reference to equine endotoxaemia.

METHODS

Six adult Thoroughbred horses were used for in vivo infusion studies and separate in vitro studies. For in vivo studies, following collection of a pre-infusion sample, horses were infused with E. Coli O55:B5 LPS (30 ng/kg; 30 min) during and after which platelets were harvested. For in vitro studies isolated platelets and leukocytes were exposed to LPS (10 pg/ml-1 microg/ml). p38 MAPK activity was assessed by SDS-PAGE followed by immunoblotting. TxA2 release was measured by radioimmunoassay.

RESULTS

LPS infusion caused increased phospho-p38 MAPK in equine platelets and leukocytes (1492 +/- 486 % and 83 +/- 45 above basal, respectively) from 10 min after the start of the infusion, which returned to basal by 60 min. In vitro, platelets were 1,000 times more sensitive to LPS than leukocytes in terms of both TxA2 production (EC50 66 pg/ml versus 110 ng/ml, respectively) and p38 MAPK phosphorylation (EC50 11.1 +/- 2 pg/ml versus 14.8 +/- 4 ng/ml, respectively). p38 MAPK inhibitors SB203580 and PD169316 attenuated LPS-induced TxA2 release in platelets, but not leukocytes.

CONCLUSIONS

In vivo, LPS stimulates TxA2 production and p38 MAPK phosphorylation in equine platelets and leukocytes at a concentration within a similar range to those reported in clinical endotoxaemia. These data suggest that LPS-induced eicosanoid production in the early phase of clinical endotoxaemia may involve direct effects of LPS upon platelets, mediated via activation of p38 MAPK.

Use of nuclear scintigraphy with 99m Tc- HMPAO-labelled leucocytes to assess small intestinal malabsorption in 17 horses

The diagnostic and prognostic value of nuclear scintigraphy with technetium-99m-labelled hexamethyl-propyleneamine oxime-labelled leucocytes was assessed in 17 horses with weight loss due to gastrointestinal malabsorption by comparing the results with the results obtained from 13 normal control horses. Intestinal uptake of activity was detected in 12 of the 17 cases but none of the control horses. The technique was therefore specific for intestinal pathology, but failed to detect some horses that might have had intestinal pathology. No indications of the horses' specific pathology were obtained, and their prognosis or response to treatment could not be predicted.

Four cases of equine polysaccharide storage myopathy in the United Kingdom

This paper describes four cases of equine polysaccharide storage myopathy which were confirmed by histological examination of muscle biopsy specimens. The horses were of mixed breeding, with warmblood and thoroughbred dominating. They all had recurrent episodes of rhabdomyolysis, indicated by clinical signs and increased plasma levels of muscle enzymes. They were managed conservatively and have continued athletic careers despite their disease.

Chronic nodular panniculitis in a three-year-old mare

The clinical signs of chronic nodular panniculitis in a three-year-old mare were consistent with a diagnosis of sterile nodular panniculitis, but the mare had histopathological signs of both generalised steatitis and sterile nodular panniculitis. The mare was deficient in vitamin E and selenium.

Coronary band dystrophy in two horses

Two mature large-breed horses with coronary band dystrophy and chorioptic mange are described. They both had clinical signs of coronary band scaling and crusting but were not lame. Coronary band dystrophy can be differentiated from similar clinical conditions on the basis of the histological appearance of skin biopsy specimens, and by the exclusion of other possible disease processes. Its aetiology is uncertain, but probably involves a localised defect of keratinisation affecting the specialised epithelium of the coronary band.