The breaking strength (stress at failure) of equine third metacarpal bones, with and without clustered drill holes, was determined in vitro. Paired ossa metacarpalia II-IV of 39 horses (n = 39) between 2 and 7 years old were tested in palmarodorsal 3-point bending. Four treatments were compared. Clustered 2.7- or 3.5-mm drill holes, in a 4- or 7-hole pattern, were made in the dorsal cortex of the distal diaphysis of the left third metacarpal bone. Undrilled right third metacarpi were used as controls. Bones with clustered drill holes failed by an oblique fracture through 1 or more drill holes, whereas undrilled bones failed with a middiaphyseal transverse fracture. Clustered drill holes acted as a stress concentrator and significantly (P < 0.05) decreased the stress required for failure. However, differences in breaking strength between treatment groups were not significant (P > 0.05).

An experimental model of keratoconjunctivitis sicca (KCS) was produced by removing the lacrimal gland and the gland of the third eyelid from the left eye of 6 cats. The right eye of each cat was left intact and used as a control. After 2 weeks, cats were euthanatized and the central portion of the upper eyelid from both eyes of each cat was excised. Histologic sections were stained with either hematoxylin and eosin or with a battery of biotinylated lectins including concanavalin A (conA), soybean agglutinin (SBA), wheat germ agglutinin (WGA), succinylated wheat germ agglutinin (S-WGA), Ulex europaeus agglutinin I (UEA), Dolichos biflorus agglutinin (DBA), Ricinus communis agglutinin (RCA), peanut agglutinin (PNA), and PNA pretreated with neuraminidase. Consistent differences in histologic features were not observed between conjunctivas with KCS and control conjunctivas. A variable degree of mononuclear cell infiltration of the substantia propria was observed in control conjunctivas and those with KCS. In both groups, conjunctival goblet cell density decreased and epithelial stratification increased as the degree of submucosal inflammatory cell infiltration increased. Lectin binding sites for DBA, WGA, S-WGA, UEA, PNA, and PNA pretreated with neuraminidase were detected on conjunctival goblet cells of conjunctivas with KCS and control conjunctivas. The mucus/glycocalyx layer of conjunctival epithelial cells in both groups of conjunctivas bound lectins RCA, WGA, UEA, and conA, but inconsistently bound S-WGA. In both groups, DBA principally bound to the mucus layer overlying normal epithelium, whereas PNA pretreated with neuraminidase consistently bound to the mucus layer of stratified epithelial surfaces free of goblet cells. Binding of SBA to goblet cells and the mucus/glycocalyx layer was variable.

An in vitro bioassay system was used to study the effects of cyclopiazonic acid (CPA) mycotoxin on cardiac muscle. Acute exposure to 6 microgram of CPA/ml of modified Krebs-Henseleit solution significantly (P < 0.05) decreased 5 in vitro turkey cardiac muscle performance criteria: maximal weight a muscle could lift; maximal contraction velocity; relaxation velocity; time to peak contraction; and total time for muscle contraction and relaxation. The effect on these 5 criteria appeared to result from intracellular changes partially associated with calcium availability and were irreversible, suggesting that physiologic changes had developed after acute exposure to CPA.

Bovine leukemia virus (BLV) was transmitted by horse flies, Tabanus fuscicostatus, from a cow with a lymphocyte count of 31,500/mm3 to goats and dairy calves. As few as 10 and 20 flies transmitted BLV to goats and calves respectively, but the minimal number of flies required to transmit the infection was not established. Groups of 150 and 100 T fuscicostatus transmitted BLV to beef calves from a cow with a lymphocyte count of 14,600/mm3. These results support a role for horse flies in the horizontal transmission of BLV.

Cardiovascular consequences of butorphanol tartrate (0.2 mg/kg of body weight, IV) administration during isoflurane (1.7% end-tidal concentration) anesthesia were determined in mechanically ventilated healthy dogs. Butorphanol administration caused significant (P less than or equal to 0.05) reductions in mean, systolic, and diastolic arterial blood pressures; cardiac output; and rate-pressure product.

Microvascular circulation of the ascending colon in healthy horses was studied using microangiography, light microscopy, and scanning electron microscopy. The pelvic flexure with 30 cm of ventral and dorsal colon attached was removed from 14 adult horses immediately after horses were euthanatized. The lumen was flushed with warm water, and this section of the ascending colon was placed in a 37-C bath of isotonic NaCl. In sections from 8 horses, colic vessels were perfused with a radio-opaque medium for microangiography. After angiographic evaluation, tissue sections were prepared for light microscopic observation, using standard histologic methods. In sections from 6 horses, injection replicas were made by perfusing the vessels with 2 types of plastics. The results of microangiography, light microscopy, and scanning electron microscopy of vascular replicas were correlated, providing acomprehensive documentation of the microvasculature of the ascending colon at the pelvic flexure. Arteries branched from mesenteric colic vessels approximately every 2 cm toward the colonic tissue. Immediately after branching, arterial vessels formed an anastomotic plexus, the colonic rete. However, each branch from the colic vessel eventually continued into the colonic tissue. A second set of vessels originated from the colonic rete and supplied the mesenteric lymph nodes. Arterial vessels penetrated the tunica muscularis into the sub-mucosa 3 to 4 cm toward the antimesenteric border forming a submucosal vascular network. From the submucosal arterioles, branching took place at right angles to supply the mucosal capillaries. Capillaries surrounded the colonic glands and anastomosed at the luminal surface, forming a superficial luminal honeycomb-appearing vascular plexus. Venules, sparsely distributed, drained the superficial plexus. Arterial venous anastomoses were not observed within the mucosa.

Twenty-one mixed-breed pony foals, reared and maintained under parasite-free conditions, were used to test the efficacy of ivermectin in oral drench and paste formulations (200 microgram/kg) against 11-day-old migrating larvae of Parascaris equorum. Three replicates of 4 foals and 3 replicates of 3 foals were formed on the basis of age. Foals in replicates of 4 were randomly allocated to be indicators, or to receive vehicle (control) or ivermectin paste or ivermectin liquid. Foals in replicates of 3 were randomly allocated to receive vehicle or ivermectin paste or ivermectin liquid. The recovery of larvae from the lungs, liver, and small intestines of the indicator foals showed that 99.9% of the larvae were in the lungs 11 days after inoculation (day 0 of treatment). The recoveries of larvae from lungs and small intestines of controls at 25 days after inoculation indicated that all larvae had migrated to the small intestine by this time. The mean length of larvae recovered from the lungs (11 days after inoculation) was 0.87 mm; the mean length of those recovered from the small intestine (25 days after inoculation) was 3.65 mm. Using larvae recovered from small intestinal contents for calculations, ivermectin in both formulations was 100% effective against 11-day P equorum (P less than 0.01, compared with control group geometric mean of 1498.4).

Fifty-five dogs, naturally infected with Taenia sp or Dipylidium caninum or both, were assigned to the following treatment groups for dose titration studies with epsiprantel: nonmedicated control dogs (n = 14), medicated dogs given a dosage of 2.75 mg/kg of body weight (n = 15), medicated dogs given a dosage of 5.5 mg/kg (n = 16), and medicated dogs given a dosage of 8.25 mg/kg (n = 10). Medication was given orally in a tablet formulation. Feces were examined for cestodes passed and the gastrointestinal tract was examined at necropsy for retained cestodes. Efficacy of epsiprantel was 92.9% against Taenia and 44.8% against Dipylidium for a dosage of 2.75 mg/kg, 100% against Taenia and 99.8% against Dipylidium for a dosage of 5.5 mg/kg, and 94.6% against Taenia and 100% against Dipylidium for a dosage of 8.25 mg/kg. For dose confirmation, 36 dogs naturally infected with Taenia sp or D caninum or both were allotted to 2 treatment groups: nomedicated control dogs (n = 16) and dogs medicated with epsiprantel at a dosage of 5.5 mg/kg (n = 20). Efficacy was 100% for both Taenia sp and D caninum.