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Abstract

Objective

To evaluate the effect of topically applied dimethylsulfoxide (DMSO) on lipopolysaccharide (LPS)-induced synovitis in the mid-carpal joint.

Animals

6 sound, healthy, adult horses (12 carpi).

Procedure

In a double-blinded, crossover, paired study with a 1-week washout period, mid-carpal joints were allocated to group 1 (DMSO, n = 6) or group 2 (control, n = 6). Each joint was injected with 1.3 ml (0.0125 ng/dl) of LPS to induce synovitis. For group-1 joints, DMSO gel (15 g; 90%) was applied after injection of LPS and at 12-hour intervals for 60 hours. Joints of group 2 received LPS, but not DMSO gel. All horses were evaluated by serial lameness examinations and synovial fluid analyses (total and differential WBC count and total protein concentration) at 12- hour intervals for 60 hours after LPS injection. Plasma and synovial fluid were obtained at baseline and 36 hours to document presence of DMSO.

Results

Mean WBC concentration was significantly (P < 0.05) lower in group-1, compared with group-2 joints, at 24 hours and had a trend to be lower at 36 hours. Mean total neutrophil count was significantly lower in group-1, compared with group-2 joints at 24 hours. In group-1 joints, DMSO was detected by use of gas chromatography in the synovial fluid of 5 of 6 joints and in plasma from 1 of 6 horses.

Conclusion

Topically applied DMSO penetrated into synovial fluid in sufficient quantities to be detected and to decrease joint inflammation. (Am J Vet Res 1998;59:1149-1152)

Free access
in American Journal of Veterinary Research

Abstract

Objective

To quantitate nitric oxide synthase (NOS) activity in healthy and interleukin 1β (IL-1β)-exposed equine synovial membrane.

Animals

6 healthy horses, 2 to 8 years old.

Procedure

Recombinant human IL-1β (0.35 ng/kg of body weight) was injected intra-articularly into 1 metacarpophalangeal joint of each horse. The contralateral joint served as an unexposed control. All horses were euthanatized 6 hours after injection of IL-1β, and synovial membrane specimens were assayed for NOS activity by measuring conversion of arginine to citrulline. Severity of inflammation was semiquantitated by analysis of synovial fluids and histologic examination of synovial membrane.

Results

Equine synovial membrane had minimal NOS activity. A significant difference was not detected in NOS activity between control and IL-1β-exposed specimens. Histologic examination revealed a neutrophilic infiltrate in synovial membrane exposed to IL-1β. Synovial fluid from IL-1β-exposed joints had a moderate inflammatory response and significantly greater concentrations of IL-1β and interleukin-6 than fluid from healthy joints.

Conclusion

Healthy equine synovial membrane had low NOS activity that was not affected by exposure to IL-1β. (Am J Vet Res 1999;60:714-716)

Free access
in American Journal of Veterinary Research

Abstract

Objective

To provide quantitative assessment of forces affecting filtration of synovial fluid in response to incremental changes in arterial and venous hemodynamics.

Animals

7 clinically normal adult horses.

Procedure

Using a stationary, isolated metacarpophalangeal joint preparation, blood flow (Qacir), tissue perfusion, arterial pressure (Pacir), venous pressure (Pvcir), transsynovial fluid flow, total vascular resistance, vascular compliance, and tissue compliance were evaluated before and after arterial and venous pressure manipulations. At isogravimetric conditions, pre- and postcapillary resistance and ratios, osmotic reflection coefficient (σd), capillary pressure, net filtration pressure, and transitional microvascular pressure were determined.

Results

Synovial tissue blood flow was similar before, immediately after, and 3.5 hours after joint isolation. The σd for the joint was low, owing to the high oncotic pressure of synovial fluid at filtration-independent states. Transsynovial flow occurred in preference to lymph flow because of the high permeability of synovial tissue (low σd). Synovial fluid production and transfluid flow (synovium weight gain) increased at Pacir > 200 mm of Hg, indicating a threshold phenomenon for synovial filtration. Net filtration pressure > 6 mm of Hg is needed to effect an increase in synovial fluid flow, and pressure of approximately 11 mm of Hg is necessary to increase lymphatic flow. Vascular compliance in the joint was low, but increased markedly with Pvcir. Vascular and tissue compliance increased with increased Pacir. Vascular compliance changes caused by increased arterial pressure were minimal, compared with those caused by increased venous pressure owing to the greater elastance of arteries and the larger muscular arterial wall.

Conclusion

This isolated joint preparation permitted evaluation of codependent hemodynamic, microvascular, and transsynovial flow responses to hemodynamic manipulations. Synovial tissue permeability was markedly affected by increased vascular forces altering filtration pressures toward synovial fluid production. (Am J Vet Res 1998;59:495–503)

Free access
in American Journal of Veterinary Research

Abstract

Objective—To evaluate clinical safety of administration of injectable enrofloxacin.

Design—Randomized controlled clinical trial.

Animals—24 adult horses.

Procedures—Healthy horses were randomly allocated into 4 equal groups that received placebo injections (control) or IV administration of enrofloxacin (5 mg/kg [2.3 mg/lb], 15 mg/kg [6.8 mg/lb], or 25 mg/kg [11.4 mg/lb] of body weight, q 24 h) for 21 days. Joint angles, cross-sectional area of superficial and deep digital flexor and calcaneal tendons, carpal or tarsal osteophytes or lucency, and midcarpal and tarsocrural articular cartilage lesions were measured. Physical and lameness examinations were performed daily. Measurements were repeated after day 21, and articular cartilage and bone biopsy specimens were examined.

Results—Enrofloxacin did not induce changes in most variables during administration or for 7 days after administration. One horse (dosage, 15 mg/kg) developed lameness and cellulitis around the tarsal plantar ligament during the last week of administration. One horse (dosage, 15 mg/kg) developed mild superficial digital flexor tendinitis, and 1 horse (dosage, 25 mg/kg) developed tarsal sheath effusion without lameness 3 days after the last administration. High doses of enrofloxacin (15 and 25 mg/kg) administered by bolus injection intermittently induced transient neurologic signs that completely resolved within 10 minutes without long-term effects. Slower injection and dilution of the dose ameliorated the neurologic signs. Adverse reactions were not detected with a 5 mg/kg dose administered IV as a bolus.

Conclusions and Clinical Relevance—Enrofloxacin administered IV once daily at the rate of 5 mg/kg for 3 weeks is safe in adult horses. (J Am Vet Med Assoc 2000;217:1514–1521)

Full access
in Journal of the American Veterinary Medical Association