In dogs, the retina develops during the postnatal period in a manner similar to that in other animals born with closed eyelids. Photoreceptor inner segments are initially observed as a cytoplasmic bulge protruding sclerad through the external limiting membrane. Outer segment formation begins when a centriole within the inner segment attaches to the distal inner segment cell membrane. A few round mitochondria are observed within the early inner segments. As maturation proceeds, the number of mitochondria within the inner segments increases and the mitochondria elongate, orienting parallel to the long axis of the inner segment.

The blood supply patterns to the spinal cord were examined and compared in 15 dogs and 10 cats by use of dissection and radiographic visualization. The lowest percentages of radicular contributions and the smallest diameter vessels were found in the thoracic part of the spinal cord. The central arteries were fewest in number in the thoracic region and unilaterally or bilaterally supplied the gray matter. The percentage of bilaterally distributed central arteries increased from the cervical to the lumbar regions. The anastomotic plexus on the surface of the spinal cord was found to be most dense in the cervical and lumbar regions.

Effectiveness of a pentavalent leptospiral vaccine to protect cattle from infection and reproductive problems caused by Leptospira interrogans serovar hardjo type hardjo-bovis was evaluated. Seven cows were vaccinated once and 8 cows were vaccinated twice with a USDA-licensed pentavalent leptospiral vaccine. Five cows were maintained as nonvaccinated controls. Cows were bred 1 to 2 months after the last vaccination. During the 4th to 6th month of gestation, all cows were challenge exposed on 4 occasions by conjunctival instillation of 10(8) serovar hardjo type hardjo-bovis organisms and on 3 occasions by conjunctival instillation of urine from a cow shedding hardjo-bovis. All control cows and 13 of 15 vaccinated cows became inf ected and shed leptospires in the urine. Leptospires were detected in fewer urine samples collected from vaccinated cows, compared with those collected from control cows. Four stillborn calves and 3 weak calves born to control and vaccinated cows. Leptospires were detected in the kidneys of 11 apparently healthy calves born to vaccinated and control cows. Agglutinating antibodies were not detected in the precolostral serum of these calves.

Bronchoalveolar lavage fluid was collected from 12 anesthetized cats by use of an endotracheal tube and syringe adapter. The safety of the technique was evaluated by monitoring mucous membrane color, capillary refill time, pulse rate, respiratory rate, ECG, and arterial blood gas tensions and by necropsy findings. Group A consisted of 3 cats that were administered (by lavage) 4 aliquots of 20 ml of saline solution during anesthesia for placement of femoral artery catheters. Group B consisted of 4 cats that were administered a smaller total volume of saline solution (3 aliquots of 5 ml/kg of body weight) during a separate anesthetic period, other than the one for placement of catheters. Group C consisted of 5 cats administered 3 aliquots (5 ml/kg) of saline solution during a separate anesthetic period and administered supplemental oxygen for 5 to 10 minutes before and for 20 minutes after the lavage procedure. Group-A cats had a prolonged recovery period that was attributed to the lengthy anesthetic period required for placement of femoral catheters. The effect was eliminated in the cats of the other groups in which the lavage procedure itself accounted for only 5 to 10 minutes of anesthetic time. Evaluation of mucous membrane color, capillary refill time, ECG, pulse, and respiratory rate revealed no persistent abnormalities. Transient increase in pulse and respiratory rate was seen in some cats. Blood gas analysis revealed noticeable decrease in arterial oxygen pressures (PaO2) after the lavage procedure. In group-C cats, oxygen supplementation allowed the maintenance of normal or above normal PaO2. When oxygen was discontinued at 20 minutes, PaO2 was maintained at greater than or equal to 60 mm of Hg. The variability in oxygen pressures did not appear to correlate with the volume of fluid remaining in the lungs. Histologic evaluation of the lungs revealed no changes attributable to the lavage procedure. Most cats had minimal to mild inflammatory changes, and 4 cats had moderate to moderately severe bronchopneumonia. These changes were reflected in the bronchoalveolar lavage fluid, indicating that they were present at the time of lavage.

Effects of ketamine, xylazine, and a combination of ketamine and xylazine were studied in 12 male Pekin ducks (7 to 12 weeks old; mean [+/- SD] body weight, 3.1 +/- 0.3 kg). After venous and arterial catheterization and fixation of a temperature probe in the cloaca, each awake duck was confined, but not restrained, in an open box in a dimly lit room. Blood pressure and lead-II ECG were recorded. Three arterial blood samples were collected every 15 minutes over a 45-minute period (control period) and were analyzed for pHa, Paco2 and Pao2. After the control period, each duck was assigned at random to 1 of 3 drug groups: (1) ketamine (KET; 20 mg/kg of body weight, IV), (2) xylazine (XYL; 1 mg/kg, IV), and (3) KET + XYL (KET 20 mg/kg and XYL, 1 mg/kg; IV). Measurements were made at 1, 5, 10, 15, 30, 45, 60, and 90 minutes after drug administration. All ducks survived the drug study. Cloacal temperature was significantly (P less than or equal to 0.05) increased above control cloacal temperature at 90 minutes after the administration of ketamine, and from 10 through 90 minutes after administration of ketamine plus xylazine. In ducks of the KET group, pHa, Paco2, and Pao2, remained unchanged after administration of the drug. In ducks of the XYL group, pHa and Pao2 decreased significantly (P less than or equal to 0.05) from control values for all time points up to and including 15 minutes after drug administration. In ducks of the KET + XYL group, pHa and Pa02 were significantly (P less than or equal to 0.05) decreased at all time points up to and including 45 and 15 minutes, respectively, after administration of the drugs. In ducks of the XYL group, Paco2 increased significantly (P less than 0.05) during the first 15 minutes after drug administration, and for 45 minutes after administration of KET + XYL. Results indicated that ketamine when given alone to ducks, was not associated with pulmonary depression. There was drug-associated respiratory depression after IV administration of XYL or KET + XYL.

Efficacy of oral administration of 20 mg of triclaben-dazole/kg of body weight was evaluated against 12-week Fascioloides magna infections in 12 sheep, each inoculated orally with 250 viable metacercariae. From 6 sheep treated with triclabendazole, 1 immature F magna was recovered, whereas 116 F magna with a mean length of 19 +/- 6.5 mm were recovered from 6 untreated control sheep. Efficacy of triclabendazole was 99.14%. Signs of toxicosis or illness were not observed in the sheep.

Cerebrospinal fluid obtained from clinically normal free-ranging raccoons was analyzed and compared with CSF obtained from raccoons vaccinated orally with vaccinia-rabies glycoprotein (V-RG) recombinant virus vaccine and subsequently challenged peripherally with street rabies virus, and CSF from naive, rabies virus challenge-exposed control raccoons. Significant differences were not found in CSF of free-ranging or V-RG recombinant virus vaccine recipient raccoons, and there was no evidence of CNS invasion by V-RG virus. The CSF of naive, rabies challenge-exposed control raccoons contained high numbers of lymphocytes and monocytes, compatible with rabies virus encephalitis. Although V-RG orally vaccinated challenge-exposed raccoons were protected from lethal rabies virus infection, mild lymphocytic pleocytosis was evident at 90 days after challenge exposure.

Oxytetracycline (OTC) pharmacokinetic values in plasma and bile were ascertained after IV administration of the drug. At 6 hours after administration of 1 mg of OTC/kg of body weight, 2.15% of the dose was found in the bile and 37.6% was found in the urine. At 2 hours after administration, the peak bile-to-plasma OTC concentration ratio was 60:1. Bioavailability of OTC was 47.6% when it was administered orally to fasted turkeys and was 9.4% when administered to fed turkeys.

The in vitro reactivity of vasoconstrictive mediators that are implicated in acute laminitis was determined in palmar and plantar digital arteries and veins obtained from healthy horses and in palmar digital vessels of horses with early laminitis (Obel grade I). To obtain baseline reactivity data, 3 experiments were conducted, using healthy horses: (1) the reactivity of palmar and plantar digital arteries and veins to angiotensin II, norephinephrine, and 5-hydroxytryptamine (serotonin) were compared; (2) the direct effects of bacterial endotoxin on vascular reactivity were assessed; and (3) the reactivity of palmar digital arteries and veins to angiotensin II, norepinephrine, prostaglandin F2 alpha (PGF2 alpha), sertonin, and a thromboxane-endoperoxide analog (U46619) were determined. The vascular reactivity of these same 5 vasoconstrictors then was determined in horses with early laminitis and was compared with data from healthy (control) horses. Obel grade-I laminitis was experimentally induced in horses using carbohydrate overload. Dose responses were conducted for each agent at concentrations between 10(-8)M and 10(-4)M. The potency of a drug was defined as the mean effective concentration necessary to induce 50% of maximal contraction (EC50). There were no differences in EC50 concentrations and in maximal contractions between forelimb and hind limb arteries and veins for angiotensin II, norepinephrine, and serotonin. Incubation with endotoxin had no effect on the reactivity of arteries and veins to angiotension II, norepinephrine, and serotonin. In healthy horses, serotonin and U46619 were more potent arterial constrictors than were norepinephrine PGF2 alpha, and angiotensin II. In veins, serotonin, U46619, and angiotension II were similar in potency, and all were significantly (P less than 0.05) more potent than were norepinephrine and PGF2 alpha. Serotonin induced greater arterial constriction than did all other agents tested. There were no differences in the maximal venoconstriction induced by norepinephrine, PGF2 alpha, serotonin, and U46619. Angiotensin II induced the least amount of arterial and venous constriction. Maximal contractions were significantly (P less than 0.05) greater for veins than for arteries for all agents evaluated, except for angiotensin II. In horses with early laminitis, angiotensin II and serotonin were the most potent (smallest EC50 values) constricting agents for the arterial and venous segments and norepinephrine and PGF2 alpha were the least potent. Serotonin and norepinephrine induced significantly (P less than 0.05) greater venoconstriction than did the other agents. Angiotensin II induced the least arterial and venous contraction. For all agonists except angiotensin II, the mean EC50 values for vessels from horses with early laminitis were either similar or greater than those for vessels from control horses. The EC50 values for norepinephrine and the thromboxane analog were significantly (P less than 0.05) greater for vessels from horses with early laminitis, compared with those from control horses. The mean maximal contractions for all vasoconstrictors, except angiotensin II, were significantly (P less than 0.05) less for vessels from horses with early laminitis. Significantly greater venous-to-arterial maximal contraction ratios were found for norepinephrine and serotonin in horses with laminitis, compared with those ratios in control horses. These data suggested that the digital vasculature of horses with early laminitis was not more sensitive to the vasoconstrictor substances tested and that the vessels were significantly less repsonsive than was vasculature from the control horses. However, the venous-to-arterial contraction ratios were either the same or significantly (P less than 0.05) greater in horses with laminitis.

Bovine blood mononuclear cells were separated into 2 fractions by use of centrifugl elutriation. Total recovery, as well as recovery of each fraction, was greater than that obtained by use of Ficoll-sodium diatrizoate separation. The lymphocyte fraction contained less than 1% granulocytes, and the granulocyte fraction contained only 7% lymphocyte contamination. The technique was reproducible and results proved to be comparable with those of Ficoll-sodium diatrizoate density-gradient centrifugation; furthermore, the method is considerably cheaper and less time-consuming for processing large volumes of blood. Viability of cells separated by elutriation always was greater than 98%, whereas viability of cells separated by Ficoll-sodium diatrizoate was greater than 95%. Also, mitogen activation of lymphocytes separated by elutriation was superior to that of lymphocytes separated by Ficoll-sodium diatrizoate centrifugation.