Glutamine has been shown to be an important metabolic substrate of enterocytes in many animals, including cats, dogs, hamsters, human beings, monkeys, rabbits, rats, and sheep. To determine whether glutamine is important in the metabolism of cells of the equine gastrointestinal tract, we examined transintestinal differences in glutamine concentrations in the arterial and venous circulation, and measured activity of the major glutamine catabolizing enzyme, glutaminase. Arteriovenous differences provide an index of the amount of a given substrate removed by the tissue across which the measurements are made, and commonly are expressed as a percentage of substrate removed, or percent extraction. Arteriovenous differences for glutamine were determined in 7 anesthetized adult horses (weight, 450 to 500 kg) before and after an IV glutamine infusion. The mean baseline arterial glutamine concentration (+/- SEM) was 572 +/- 24 microM; this concentration quadrupled (to 2,167 +/- 135 microM, P < 0.01) 1 minute after IV bolus infusion of a 17.5-g glutamine load. Baseline extraction by the portal-drained viscera was 7.5 +/- 1.5%; this value increased to 18 +/- 2% at 1 minute (P < 0.01) and had returned to baseline values 60 minutes later. Arteriovenous differences were greatest across the jejunum (11.8 +/- 1.8% in the baseline period vs 33.1 +/- 3.1% at 1 minute, P < 0.001), with smaller differences across the colon, suggesting that the jejunum was the more avid utilizer of glutamine. Glutaminase activity was 4.38 +/- 0.16 and 4.00 +/- 0.60 micromol/mg of protein/h under standard conditions in jejunal and ileal mucosa, respectively. Kinetic studies of jejunal glutaminase revealed the enzyme to have a Km of 3.81 +/- 0.35 mM and a Vmax of 8.08 +/- 0.54 micromol/mg of protein/h, suggesting that the small intestine of horses has a high capacity to extract and metabolize circulating glutamine.

Ovine progressive pneumonia (OPP) is a lentivirus-induced disease of sheep in the United States that is similar, if not identical, to maedi/visna in many other countries. Prevalence estimates of seropositivity to this virus in sheep in the United States have been confined to limited groups or flocks of sheep and have varied from 1 to 90%. In this study of detection of antibodies against OPP virus, we found a lower general prevalence of antibodies to OPP virus in sheep than was previously reported. Of 16,827 sheep from 29 states in the United States, 26% were seropositive and 48% of 164 flocks that were tested had 1 or more seropositive sheep. Seropositivity to OPP virus for sheep within special categories was determined, although nonrandom samples that were available may have biased the results. Within regions of the United States, prevalence was highest in the Rocky Mountain region at 49% and lowest in the northern Atlantic region at 9%. Seropositive sheep were not evenly distributed among flocks, but were clustered in a few flocks of sheep. A high number of flocks had no or few seropositive sheep. Prevalence increased with age from 4% at < 1 year to a plateau of 34% at 4 years. Seropositivity was variable among breeds and was not associated with sex, wool class, or place of origin of ancestors.

The effects of 3 commonly used dosages (0.3, 0.5, and 1.1 mg/kg of body weight, IV) of xylazine on ventilatory function were evaluated in 6 Thoroughbred geldings. Altered respiratory patterns developed with all doses of xylazine, and horses had apneic periods lasting 7 to 70 seconds at the 1.1 mg/kg dosage. Respiratory rate, minute volume, and partial pressure of oxygen in arterial blood (PaO2) decreased significantly (P < 0.001) with time after administration of xylazine, but significant differences were not detected among dosages. After an initial insignificant decrease at 1 minute after injection, tidal volume progressively increased and at 5 minutes after injection, tidal volume was significantly (P < 0.01) greater than values obtained before injection. Partial pressure of carbon dioxide in arterial blood (PaCO2) was insignificantly increased. After administration of xylazine at a dosage of 1.1 mg/kg, the mean maximal decrease in PaO2 was 28.2 +/- 8.7 mm of Hg and 22.2 +/- 4.9 mm of Hg, measured with and without a respiratory mask, respectively. Similarly, the mean maximal increase in PaCO2 was 4.5 +/- 2.3 mm of Hg and 4.2 +/- 2.4 mm of Hg, measured with and without the respiratory mask, respectively. Significant interaction between use of mask and time was not detected, although the changes in PaO2 were slightly attenuated when horses were not masked. The temporal effects of xylazine on ventilatory function in horses should be considered in selecting a sedative when ventilation is inadequate or when pulmonary function testing is to be performed.

The immunomodulating polypeptide interleukin 1 beta (IL-1 beta) has been shown to be homologous to osteoclast-activating factor and is capable of stimulating increased osteoclastic bone resorption. This effect prompted an investigation into the potential use of IL-1 beta for prevention of parturient paresis, a disease of dairy cows characterized by hypocalcemia and poor osteoclastic resorption of bone. Six nonpregnant cows were treated with a high dosage of IL-1 beta (166 ng/kg of body weight) every 8 hours for 4 days. The IL-1 beta treatment significantly (P < 0.05) increased urinary hydroxyproline excretion, an index of osteoclast activity, indicating that bone calcium resorption might be stimulated by IL-1 beta treatment of cows. However, IL-1 beta treatment also caused transient fever, inappetence, increased pulse and respiratory rate, and diuresis. The acute, but transient, effect of IL-1 beta treatment was to cause a decrease in plasma calcium and phosphorus concentrations. The pleiotropic effects of IL-1 beta administration negated the positive effects on osteoclastic bone resorption, and indicates that this cytokine may be of minimal benefit for prevention of parturient paresis.

Twelve Beagles were inoculated with concanavalin A, and after a mean ninefold increase in antibody titer, 1 mg of concanavalin A was infused into each renal artery of each dog to induce in situ immune complex glomerulonephritis. Starting 4 weeks after renal arterial infusion, 6 dogs were treated orally 3 times daily with 30 mg of 3-methyl-2 (3 pyridyl)-1-indoleoctanoic acid (CGS 12970)/kg of body weight, a thromboxane synthetase inhibitor, and 6 dogs (control group) received a gelatin capsule 3 times daily. Endogenous creatinine clearance and 24-hour urinary excretion of protein and thromboxane B2 were determined for each dog prior to renal arterial infusion, at the initiation of treatment and at 2, 4, 6, and 8 weeks after initiation of treatment. In addition, methyoxy-(3)H inulin clearance was determined at initiation of treatment and 4 and 8 weeks later. Renal specimens were examined histologically at the initiation of treatment and 4 and 8 weeks later. Glomerular mononuclear profiles/micrometers(3) were determined from at least 10 equatorially sectioned glomeruli from each dog. Paired t tests were used to compare mean values at the various time points to the respective mean baseline value and 2-sample t tests were used to evaluate differences between treatment groups. At the start of treatment (4 weeks after renal arterial infusion of concanavalin A), histologic evaluation of renal specimens revealed glomerular epithelial crescent formation, mononuclear cell proliferation, and infiltration of neutrophils. Mononuclear cell profiles and urinary excretion of protein and thromboxane B2 were significantly increased, but endogenous creatinine clearance values were unchanged. Treatment with CGS 12970 did not affect endogenous creatinine clearance, methyoxy-(3)H inulin clearance, or glomeruli, however, CGS 12970 treatment significantly decreased urinary excretion of protein and thromboxane B2 when compared with values in the control group. These findings suggested that thromboxane has a role in the pathogenesis of established glomerulonephritis and that thromboxane synthetase inhibition treatment may be beneficial in dogs with established glomerulonephritis.

Mast cells isolated from feline splenic mastocytomas were cultured to study their structural and functional properties. isolated cells from various cats were grown as monolayer cultures for a mean of 56 days (range, 30 to 76 days). Cat mast cells released allergic mediators in response to compound 48/80, anti-cat serum antibodies, and concanavalin A. On the basis of the finding that secretion from cat mast cells was stimulated by anti-cat serum antibodies and concanavalin A, these cells contain surface-bound immunoglobulins. The presence of mast cell-sensitizing antibodies has been suspected in cats, but never before directly demonstrated. Cultured cat mast cells have cytochemical and functional characteristics common to connective tissue-type mast cells and provide one of the few non-rodent models of cultured cells for the study of this type of mast cell.

Concanavalin A (conA) blast proliferation as a quantitative measure of lymphoblast proliferative capacity by blood mononuclear cell supernatants was measured in cattle naturally infected with Mycobacterium paratuberculosis and in healthy control cattle. Blast cell proliferation was significantly reduced in infected animals, compared with control cattle when blood mononuclear cells were stimulated with conA. Proliferation was significantly greater than media control when M bovis purified protein derivative and johnin were used to stimulate cells from the infected group. After sensitizing control and affected cattle with M paratuberculosis bacterin (live M bovis and keyhole limpet hemocyanin in Freund's incomplete adjuvant), infected animals had no difference in blast cell proliferative capacity with the mycobacterial antigens and cona stimulation, whereas healthy animals had significantly increased blast proliferation in response to all the sensitizing antigens. The blast cell proliferative capacity in infected animals with keyhole limpet hemocyanin stimulation was increased significantly after sensitization; however, it remained significantly less than that in the sensitized control group. These data indicate that cattle naturally infected with M paratuberculosis probably produce suboptimal interleukin-2 (IL-2) activity in response to a potent IL-2 inducer (conA) and fail to optimize IL-2 activity when sensitized with a potent immunogen (keyhole limpet hemocyanin).

Bovine blood lymphocytes, depleted of macrophages by absorption on plasma-gelatin coated plastic flasks, followed by passage through Sephadex G-10 columns, failed to respond to pokeweed mitogen stimulation. Adherent monocytes or alveolar macrophages added to purified lymphocyte preparations at 10% or less were able to restore the transformation response. Exposure of alveolar macrophages or purified lymphocytes to 2 bovine respiratory syncytial virus strains for 24 hours substantially reduced the transformation response when mixed with uninfected lymphocytes or macrophages. Exposure of alveolar macrophages or purified lymphocytes to 2 bovine parainfluenza type 3 virus strains produced a similar reduction in activity after 48 hours, Heat inactivation of the viruses removed their inhibitory ability. Immunofluorescence studies revealed that both alveolar macrophages and lymphocytes were permissive for parainfluenza type 3 virus, whereas only a small number of alveolar macrophages and lymphocytes were infected with respiratory syncytial virus. The results suggest that both viruses are capable of adversely affecting the interaction between macrophages and lymphocytes, although the mechanisms by which this is achieved may be different.

The microvascular anatomic features of the small intestine was described by correlating results of microangiography, light microscopy, gross studies, and scanning electron microscopy of vascular replicas in 14 horses. After heparinization, the horses were euthanatized, a length of jejunum was transected, and blood was flushed free of the circulation, using isotonic NaCl solution. In six horses, the circulatory system was perfused with a modified radiopaque medium and evaluated radiographically. These sections were then evaluated by standard histologic methods. Sections from 8 horses were perfused with 1 of 2 types of plastics and studied grossly or by scanning electron microscopy. The marginal arterial arcade gives rise to vessels that enter the jejunum at the mesenteric angle. These vessels penetrated either directly, by branching and entering on both sides of the mesenteric angle, or supplying only 1 side of the mesenteric angle. All these vessels continued in the submucosa branching extensively, forming a submucosal plexus. This submucosal plexus supplied the tunica muscularis, tunica serosa, and the mucosa. Vessels within the 2 muscle layers ran parallel to the muscle fibers and, consequently, perpendicular to each other. The arterial supply to the mucosa penetrated the muscularis mucosae and branched to supply 2 mucosal capillary networks. An eccentrically placed arteriole penetrated the base of the villus and spiralled to the tip where it "fountained" into a mesh-like capillary network, which descended peripherally in the villus to drain via 1 to 3, but most commonly 2 venules. Venules from adjacent villi united and drained via the submucosal veins. The second capillary network supplied the glands of the intestinal crypts. The capillary network around adjacent glands anastomosed just below the luminal surface. There were connections between this network and the base of the villus capillary network. Drainage of the glandular capillary network was through these connections and through the villus venules. There was no evidence of arterovenous anastomoses.

Membrane associated proteins from 8 untypeable Pasteurella haemolytica strains were separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and compared with those of P haemolytica serotypes 1 and 2. Cattle antisera obtained from P haemolytica serotype 1 vaccine trials were used in immunoblotting assays to compare the membrane proteins from the 8 untypeable strains with those from P haemolytica serotypes 1 and 2. Densitometry was used to identify bands, and using linear regression analyses, the peak area optical densities (measuring antibody response) were correlated to lesion scores from the vaccinated calves. Significant antibody responses to proteins of 99, 69, 60, 55, 47, 45, 39, 33, 30, 16, and 14.5 kDa were detected for 4 or more of the 8 P haemolytica untypeable strains. Serotypes 1 and 2 of P haemolytica contained a comigrating 30-kDa protein. Antibody responses to proteins of 39, 33, and 32.5 kDa were significant for 3 of the untypeable strains and had significant correlation to lesion scores. Antibody responses to various other proteins were significant for 2 untypeable strains each.