Melinda H. MacDonald

Effect of lipopolysaccharide infusion on gene expression of inflammatory cytokines in normal horses in vivo

Horses are exquisitely sensitive to bacterial endotoxin and endotoxaemia is common in colic cases. In this study, gene expression of inflammatory cytokines was characterised in the blood of healthy horses following i.v. administration of lipopolysaccharide (LPS). Six horses received an LPS infusion and 6 controls received an equivalent volume of saline. Gene expression of genes encoding interleukin (IL)-1alpha, IL-1beta, IL-6, IL-8, and tumour necrosis factor-alpha (TNF-alpha) was quantified by real-time PCR. Gene expression of all inflammatory cytokines was upregulated following administration of LPS. Interleukin-1alpha, IL-1beta, IL-8 and TNF-alpha gene expression peaked at 60 min, while IL-6 expression peaked at 90 min post LPS infusion. Interleukin-1beta and IL-6 messenger RNA expression levels were above the baseline values 3 h post LPS infusion, whereas IL-1alpha, IL-8 and TNF-alpha expression levels returned to baseline values by 3 h after LPS infusion. It was concluded that LPS infusion upregulated gene expression of inflammatory cytokines in the blood of healthy horses.

Effects of intravenous administration of pirfenidone on horses with experimentally induced endotoxemia.

OBJECTIVE To characterize effects of IV administration of pirfenidone on clinical, biochemical, and hematologic variables and circulating tumor necrosis factor (TNF)-alpha concentrations in horses after infusion of a low dose of endotoxin. ANIMALS 18 healthy adult horses. PROCEDURES Horses were randomly assigned to 3 groups (n = 6 horses/group) and administered an IV infusion of 30 ng of endotoxin/kg or saline (0.9% NaCl) solution during a 30-minute period. Lipopolysaccharide-pirfenidone horses received endotoxin followed by pirfenidone (loading dose of 11.6 mg/kg and then constant rate infusion [CRI] at 9.9 mg/kg/h for 3 hours). Lipopolysaccharide-saline horses received endotoxin followed by infusion (loading dose and CRI for 3 hours) of saline solution. Saline-pirfenidone horses received saline solution followed by pirfenidone (loading dose and then CRI for 3 hours). Physical examination variables were recorded and blood samples collected at predetermined intervals throughout the 24-hour study period. Blood samples were used for CBCs, biochemical analyses, and determinations of TNF-alpha concentrations. RESULTS IV infusion of pirfenidone after administration of a low dose of endotoxin failed to attenuate the clinical, clinicopathologic, or cytokine alterations that developed secondary to endotoxin exposure. Intravenous infusion of pirfenidone after administration of saline solution induced mild transient clinical signs, but associated clinicopathologic changes were not detected. CONCLUSIONS AND CLINICAL RELEVANCE IV administration of pirfenidone was tolerated with only mild transient clinical adverse effects during infusion. However, administration of pirfenidone did not protect horses from the systemic effects of experimentally induced endotoxemia. Further studies of related, but more potent, drugs may be warranted.

Characterization of age- and location-associated variations in the composition of articular cartilage from the equine metacarpophalangeal joint

Abstract Objective: To characterize the impact of age, gender, location and individual animal variation on the composition of articular cartilage from the metacarpophalangeal joint of horses. Design: Cartilage specimens were obtained from the metacarpophalangeal joints of 28 male, female and castrated male horses ranging in age from one day to 27 years of age. Cartilage samples from the distal metacarpus, proximal first phalanx and proximal sesamoids were analyzed separately. Chondrocyte number, DNA content, proteoglycan concentration and total collagen content were determined for each animal and joint location. Results: Age and joint location had a significant effect on chondrocyte number and DNA content with higher cell counts and DNA content detected in cartilage from the youngest age groups and in cartilage from the metacarpus and proximal sesamoids. The influence of age on chondrocyte numbers was not significant in horses over two years of age. Both age and joint location also influenced total proteoglycan and collagen content. Lower proteoglycan and collagen concentrations were detected in younger horses, and cartilage from the metacarpus had lower proteoglycan and collagen concentrations than that from other joint locations. Gender did not appear to influence chondrocyte number or matrix content of equine articular cartilage. However, there was significant residual variation in cellularity, proteoglycan levels and collagen content between individual animals that could not be explained by the signalment factors considered in this study. Conclusions: Future studies examining equine articular cartilage should avoid direct morphologic comparisons between animals of different ages, and any comparisons made between individuals should be interpreted cautiously. In addition, in vitro tissue culture models should avoid the use of cartilage pooled from different animals or from different locations within the same joint.

Clinical Examination of the Equine Head

Examination of the equine head should be a routine part of any complete physical examination. It can be performed rapidly and efficiently while providing important information about the health and function of several major body systems.

Pharmacokinetics and clinical effects of pirfenidone administered intravenously in horses

OBJECTIVE To characterize the plasma pharmacokinetics and clinical effects of pirfenidone administered IV in healthy horses. ANIMALS 6 adult horses. PROCEDURES A 15 mg/kg dose of pirfenidone was administered IV over 5 minutes. Physical variables were recorded and blood samples collected prior to infusion; 2.5 minutes after beginning infusion; at the end of infusion; and at 3, 6, 9, 12, 15, 20, 25, 30, 40, 50, 60, 75, and 90 minutes and 2, 2.5, 3, 4, 6, 8, 12, and 24 hours after completion of infusion. Plasma concentrations of pirfenidone and its metabolites were determined. RESULTS Mild clinical effects, including tachycardia and muscle fasciculations, were observed during drug administration but stopped at the end of the infusion. Pirfenidone and 2 metabolites, hydroxypirfenidone and carboxypirfenidone, were detected by the end of the 5-minute infusion. Mean peak plasma concentration of pirfenidone was 182.5 micromol/L, detected at the end of the infusion. Mean peak plasma concentrations of hydroxypirfenidone and carboxypirfenidone were 1.07 and 3.4 micromol/L, respectively, at 40 minutes after infusion. No parent drug or metabolites were detected at 24 hours. Distribution of pirfenidone best fit a 2-compartment model, and the drug had mean +/- SEM elimination half-life of 86.0 +/- 4.7 minutes, mean body clearance of 6.54 +/- 0.45 mL/kg/min, and apparent volume of distribution at steady state of 0.791 +/- 0.056 L/kg. CONCLUSIONS AND CLINICAL RELEVANCE Intravenous administration of pirfenidone was tolerated with transient adverse affects during infusion, and drug clearance was rapid.

Equine Articular Synovial Cysts: 16 Cases

OBJECTIVE To report the clinical findings, diagnosis, treatment and outcome of equine patients with articular synovial cysts. STUDY DESIGN Retrospective case series. ANIMALS Horses (n = 16) with articular synovial cysts. METHODS Horses diagnosed with articular synovial cysts (1988-2009) at 2 veterinary teaching hospitals were studied. Signalment, history, clinical signs, diagnostic methods and treatment were retrieved and telephone follow-up was obtained. RESULTS Sixteen horses with articular synovial cysts were identified. Lameness was the reason for referral in most (n = 9) horses. Diagnosis was based on a combination of palpation and imaging studies, including radiography, ultrasonography and/or arthrography. Excision of the cyst was performed in 8 horses. Outcome was available for 4 surgically and 2 conservatively treated horses. Lameness resolved in 3 horses treated surgically and the 4th died for unrelated reasons. The 2 conservatively treated horses performed satisfactorily for the rest of their career. CONCLUSIONS Equine articular synovial cysts are rare and can be associated with lameness. The cysts had a synovial lining in all horses where it was assessed. Surgical excision may be successful in resolving the lameness and allowing selected horses to return to work.Objective To report the clinical findings, diagnosis, treatment and outcome of equine patients with articular synovial cysts. Study Design Retrospective case series. Animals Horses (n = 16) with articular synovial cysts. Methods Horses diagnosed with articular synovial cysts (1988–2009) at 2 veterinary teaching hospitals were studied. Signalment, history, clinical signs, diagnostic methods and treatment were retrieved and telephone follow-up was obtained. Results Sixteen horses with articular synovial cysts were identified. Lameness was the reason for referral in most (n = 9) horses. Diagnosis was based on a combination of palpation and imaging studies, including radiography, ultrasonography and/or arthrography. Excision of the cyst was performed in 8 horses. Outcome was available for 4 surgically and 2 conservatively treated horses. Lameness resolved in 3 horses treated surgically and the 4th died for unrelated reasons. The 2 conservatively treated horses performed satisfactorily for the rest of their career. Conclusions Equine articular synovial cysts are rare and can be associated with lameness. The cysts had a synovial lining in all horses where it was assessed. Surgical excision may be successful in resolving the lameness and allowing selected horses to return to work.

Mass spectral measurements of the apoHDL in horse (Equus caballus) cerebrospinal fluid

As a continuation of our proteogenomic studies of equine apolipoproteins, we have obtained molecular masses for several of the apolipoproteins associated with the HDL in horse cerebrospinal fluid (CSF). Using electrospray-ionization mass spectrometry (ESI-MS), we report on values for apolipoproteins, A-I and A-II, as well as acylated apoA-I. In comparison with our previously published data on equine plasma apolipoproteins, there appears to be a higher percentage of acylated apoA-I in the CSF than in plasma. As was the case in plasma, apoA-II circulates as a homodimer. These studies also revealed a protein with a mass of 34,468Da that we are speculating is the value for horse apoE.