Total serum hemolytic complement (CH50) activity was determined for 3 semi-inbred strains of miniature swine (SLAa, SLAc, SLAd) and 1 recombinant strain SLAg (ABCcDd), each homozygous for a distinct major histocompability complex haplotype. Initial determination was made at 8 weeks of age, prior to standardized immunization, the second at age 12 weeks, after immunization. Analysis of variance was by least-squares method, using a linear model on data from 33 litters by 14 sires and 16 dams. Analysis of variance indicated that the combined effects of haplotype, sire, dam, litter, and gender accounted for 47.63% of the total variation in preimmunization CH50 values. Dam (P less than or equal to 0.06) and litter (P less than or equal to 0.03) significantly influenced preimmunization complement activity. Although swine leukocyte antigen (SLA) haplotype was not significant in the model, least-squares mean comparisons between haplotypes suggested that ac, dg, and gg pigs tended to have comparatively low preimmunization CH50 values. The model did not account for significant variability in postimmunization CH50 values, but least-squares means indicated that dd, dg, and gg haplotypes tended to have lower values than did other haplotypes tested. Mean CH50 units for 8-and 12-week-old pigs were 41.32 +/- 20.49 and 59.50 +/- 54.35, respectively. There was a significant difference (P less than or equal to 0.001) in CH50 activity between 8- and 12-week-old pigs associated with immunization, because CH50 of nonimmunized controls did not differ at 8 and 12 weeks.

Intraocular pressure (IOP) was determined in right eyes of 20 healthy dogs after sodium hyaluronate (1%, n = 5), sodium chondroitin sulfate (4%) and sodium hyaluronate (3%, n = 5), hydroxypropyl methylcellulose (2%, n = 5), or balanced salt solution (control, n = 5) was injected into the anterior chamber. Applanation tonometry was used to measure IOP in both eyes of each dog for up to 168 hours. The 3 viscoelastic solutions resulted in an increased mean IOP by postinjection hours (PIH) 2; from PIH 12 until PIH 72, the IOP was significantly (P less than 0.001) lower than baseline. The control group did not have an increase in IOP at PIH 2; mean IOP decreased below baseline measurements within 2 hours and remained lower until PIH 72. Mean differences in IOP were not found among treated eyes (P = 0.50), and a significant interaction of any treated eyes in a group was not detected (P = 0.21). By PIH 168, the IOP approached baseline values in all groups.

Strain gauge rosettes were bonded to the dorsal, lateral, medial, and plantar aspects of the third metatarsal bone in the hind limbs of 6 ponies. The maximal compressive principal strain was approximately -600 X 10(-6) m/m, and exceeded the amplitudes of the tensile strains at all aspects of the bone. After transformation, the shear strain and the principal strains parallel and perpendicular to the bone were obtained. The first peak in the bending strain was higher in the dorsal and lateral aspects, and the second peak was higher in the medial and plantar aspects. Young modulus of elasticity was determined in a 4-point bending test at the dorsal and plantar sides; it averaged 19.5 GPa in tension and compression. Applying linear bending theory, the eccentricity of an axial force parallel or a bending force perpendicular to the bone were calculated. The position where the total force penetrated the tarsometatarsal joint surface was largely within the joint surface, indicating that the joint is merely loaded in (eccentric) compression.

Three sheep, a foal, a pony, and a calf were anesthetized and ventilated for short periods, using a high-frequency oscillatory ventilator. The efficiency of CO2 elimination was characterized at various oscillatory frequencies (50 to 30 Hz) and various tidal volumes, although the tidal volume used was always less than the measured dead space of the animal. In general, increasing either the oscillatory frequency or tidal volume increased CO2 elimination, but increasing the tidal volume had more effect. The relationship between these 3 variables was best described by a power law equation. Ventilatory frequencies and tidal volumes required to maintain eucapnia in the species studied were extrapolated from the results and, when technically possible, the potential of the technique to maintain eucapnia was tested in extended runs. The animals were supported successfully over this period, with normal blood gas tensions and no detrimental effects to heart rate and rhythm or arterial blood pressure.

Smooth muscle strips from the midcervical portion of the trachea and bronchial smooth muscle strips from third-generation airways of horses were placed in tissue baths, and isometric contractile force was measured. Active force was measured in response to electrical stimulation and exogenous acetylcholine. Square-wave electrical stimuli were applied at various voltages (10, 12, 15, 18, 20, 25 V), frequencies (3, 5, 10, 15, 20, 25, 30 Hz), and pulse durations (0.2, 0.5, 1.0, 1.5, 2.0 ms). Isometric contractile force increased as voltage, frequency, and pulse duration increased. Maximal contractile response to electrical stimulation was obtained at 18 V, 25 Hz, and 0.5 ms. Atropine (10-6M) or tetrodotoxin (3 X 10-6M) blocked the contraction, indicating that the contractile response was attributable to the release of neurotransmitter from cholinergic nerves. Cumulative concentration-response curves to acetylcholine (10-9M through 10-4M) were determined. Isometric contractile force increased as acetylcholine concentration increased. There was a significant (P less than 0.05) difference in the 50% effective dose for acetylcholine in tracheal smooth muscle and bronchial smooth muscle. The mean (+/- SD) contractile response to maximal electrical stimulus was 89% (+/- 7.4%) of that in response to 10-4M acetylcholine in tracheal smooth muscle and was 68% (+/- 10.4%) of the response to 10-4M acetylcholine in bronchial smooth muscle.

Ten tumors from 7 dogs were analyzed for estrogen receptors. Of 9 determined to be mast cell tumors, 6 were determined not to have estrogen receptors (less than 3 fmol of estradiol/mg of cytosol protein) and 3 were questionable (3 to 10 fmol of estradiol/mg). One tumor was a mixed mammary tumor and was determined to have estrogen receptors (12 fmol of estradiol/mg). Histologic grading of the mast cell tumors did not suggest a correlation with estrogen receptor values.

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.

Exogenously administered vasopressors (sympathomimetics were evaluated in isoflurane-anesthetized dogs to determine the effects of these drugs on cardiovascular function before and after hemorrhage. Six dogs were anesthetized with thiamylal sodium (20 mg/kg of body weight) and isoflurane (1.25 minimal alveolar concentration) in 100% oxygen. After instrumentation, cardiac output, systemic arterial blood pressure, heart rate (HR), left ventricular pressure, pulmonary arterial pressure, and an index of cardiac contractility (dP/dT) were measured. Stroke volume, cardiac index (CI), stroke index (SI), rate-pressure product, and systemic vascular resistance (SVR) were calculated. Epinephrine (0.1, 0.3, and 0.5 micrograms/kg/min [low, medium, and high doses, respectively]) and dobutamine (1, 5, and 10 micrograms/kg/min [low, medium, and high doses, respectively]) were infused. Methoxamine was given in a bolus of 0.22 mg/kg, IV. All measurements were taken at 2.5 minutes after infusion, and were repeated after removal of 40% of the estimated blood volume. Before hemorrhage, administration of high doses of dobutamine and medium and high doses of epinephrine were equally effective at increasing CI and SI. The dP/dT was increase to the greatest degree by administration of high doses of dobutamine. Administration of the low dose of dobutamine increased dP/dT, whereas administration of the low dose of epinephrine increased CI, HR, and SI, and decreased SVR. The HR and SVR were not increased by administration of any dose of dobutamine or of the medium and high doses of epinephrine. However, methoxamine increased SVR and decreased HR. Methoxamine decreased CI, SI, and dP/dT, but increased systemic arterial pressure to the same degree as that attributed to administration of high doses of dobutamine and epinephrine. After hemorrhage, effectiveness of the drugs in eliciting a response was unchanged, except for a decreased ability of dobutamine to increase rate-pressure product. Further, when the results of this study were compared with those of an earlier halothane study, there were no significant differences in the response of a variable to drug infusion on the basis of the anethetic. The drugs were equally effective with halothane or isoflurane anesthesia. Results inidcated that dobutamine and ephinephrine are effective short-term treatments for hypovolemia during volume resuscitation, and that they work equally well with halothane or isoflurane anesthesia.

Lateral cecal arterial blood flow, carotid arterial pressure, heart rate, and mechanical activity in the duodenum, right ventral colon, cecal body, and cecal apex were measured in 6 conscious healthy horses for 60 minutes during and for 120 minutes after IV infusion of 0.9% NaCl solution (control) or fenoldopam. There were no significant changes in these measurements during or after infusion of 0.9% NaCl (saline) solution. Fenoldopam, a selective dopamine- 1 receptor agonist, was administered in saline solution at dosages of 0.01, 0.05, and 0.1 ug/kg/min. Intravenous infusion of fenoldopam at 0.01 ug/kg/min significantly increased heart rate, but did not change average carotid arterial pressure or lateral cecal arterial blood flow. Intravenous infusion of fenoldopam at both 0.05 and 0.1 ug/kg/min significantly increased heart rate, significantly decreased average carotid arterial pressure, and significantly increased lateral cecal arterial blood flow. Intravenous infusion of fenoldopam at 0.01, 0.05 and 0.1 ug/kg/min did not significantly change the mechanical activity measured by the area under the strain gauge defection curve for the duodenum, right ventral colon, cecal body, or cecal apex. These results suggest that dopaminergic-1 receptors are present on the colonic vascudopaminergic-1 receptors exist on the visceral smooth muscle of the duodenum, right ventral colon, cecal body, or cecal apex of horses.