Recombinant equine interferon-beta 1 (reqIFN-beta 1) induces an antiviral state in blood mononuclear cells (BMC) of horses. Maximal protection against replication of vesicular stomatitis virus is achieved 6 hours after treatment with IFN in vitro and in vivo. Duration of the protective effect depends on the dose of IFN in vitro and in vivo. Availability of reqIFN-beta 1 in cultures of BMC for up to 48 hours does not prolong the antiviral state. The protective effect on BMC after treatment with IFN has similar duration in vivo and in vitro. Monitoring of the effect of IFN in vivo is, thus, simplified because the antiviral state may be recorded by testing cells twice (ie, before and 6 hours after application of interferon). All further tests may be performed in vitro. Multiple administrations of reqIFN-beta 1 do not prolong duration of the protective phases after each administration. Duration of the antiviral state depends only on the dose of reqIFN-beta 1.

We characterized the clinicopathologic manifestations of experimentally induced endotoxin-induced mastitis. Responses to hypertonic fluid therapy also were assessed. Eight cows received 1 mg of endotoxin by in infusion in the left forequarter. Four hours after endotoxin administration, cows received 0.9% NaCl, 5 ml/kg of body weight (n = 4) or 7.5% NaCl, 5 ml/kg (n = 4) IV. Endotoxin-infused cows had expanded plasma volume, hyponatremia, transient hyperchloremia and hypophosphatemia, increased serum glucose concentration, and decreased serum activities of liver- and muscle-specific enzymes. Calculated plasma volume increased at 6 hours in cows receiving hypertonic NaCl, and at 12, 24, and 48 hours after endotoxin infusion in both groups. Concurrent observations of decreased serum protein concentration, erythrocyte count, and hematocrit supported observations of increased plasma volume. Relative plasma volume was greater in cows receiving hypertonic NaCl (124.3%) than in cows receiving isotonic NaCl (106.6%) at 6 hours after endotoxin infusion. Cattle receiving hypertonic NaCl had increased voluntary water intake after IV fluid administration. Increased water consumption was not accompanied by increased body weight, indicating probable occurrence of offsetting body water loss. Serum sodium concentration in cows receiving hypertonic NaCl was increased 2 hours after fluid administration, but the magnitude of the change was minimal (< 4 mmol/L) and transient, indicating rapid equilibration with either interstitial or intracellular spaces. Serum sodium concentration was decreased in cows receiving isotonic NaCl at 12, 24, and 48 hours after endotoxin administration, compared with concentration prior to endotoxin administration, indicating selective loss of sodium.

Development of an arthroscopic approach to the caudal pouches of the equine stifle has been necessary because cranial approaches do not allow access to articular lesions in the caudal aspect of the joint. Therefore, the anatomy of the caudal region was examined in 52 cadaver limbs by use of gross dissection, x-ray-computed tomography, fluoroscopy, or arthroscopy. Additionally, using arthroscopic techniques developed in equine cadaver limbs, 3 stifles from 2 anesthetized horses were arthroscopically explored. Fluoroscopy was used to verify needle placement for joint injection and filling patterns of each femorotibial joint. The medial femorotibial joint sac (n = 4) held a mean +/- SD 41.67 +/- 5.77 ml of injection fluid, and the lateral femorotibial joint sac (n = 4) held a mean 61.67 +/- 2.89 ml of injection fluid. Vital structures that inadvertently could be damaged during arthroscopy of the caudal pouches of the stifle included the peroneal nerve (located approx 7 cm caudal to the lateral collateral ligament), the popliteal artery and vein (situated directly between the medial and lateral femoral condyles), and the lateral femoral condyle (most often traumatized during arthroscopy). The tendon of the popliteus muscle, which is contiguous with the joint capsule of the caudal pouch of the lateral femorotibial joint, made arthroscopic exploration of this pouch particularly difficult.