The hypothalamic-pituitary-adrenocortical (HPA) axis was studied in 8 healthy cats after administration of supraphysiologic doses of methylprednisolone (MP). Ovine corticotropin-releasing hormone (oCRH) administration increased cortisol and adrenocorticotropic hormone (ACTH) concentrations. Significant (P < 0.05) suppression of cortisol and a trend toward suppression of ACTH was observed after 1 week of MP administration. The HPA axis quickly recovered from suppressive effects of MP 1 week after administration of the steroid was discontinued. Side effects of oCRH administration were minimal in 7 cats; however, 1 cat had a severe hypotensive reaction. Clinical abnormalities were not associated with MP administration. The HPA axis was suppressed by supraphysiologic doses of MP in all treated cats that lacked clinical signs consistent with iatrogenic HPA axis suppression. Despite the relatively active pars intermedia in cats, compared with human beings and dogs, feedback of MP on the HPA axis resulted in similar trends in oCRH-stimulated ACTH and cortisol concentrations as observed in human beings and dogs. Lack of consistent correlation between ACTH and cortisol concentrations was observed in 3 cats and possibly was related to the active pars intermedia in the cat.

In an effort to better understand the role of vasodilators in the management of pulmonary hypertension associated with chronic heartworm disease (HWD), pulmonary hemodynamic measurements were obtained from 7 experimentally infected, anesthetized dogs before and after hydralazine administration (mean dose, 1.96 mg/kg of body weight). Five dogs were maintained on room air, while 2 were maintained on 100% oxygen during the hydralazine study. The hemodynamic effect of hydralazine in dogs with HWD was evaluated, using heart rate, cardiac index, mean pulmonary artery pressure, mean arterial pressure, total pulmonary resistance, total systemic resistance, total systemic resistance/total pulmonary resistance, left ventricular dP/dt(max), left ventricular end diastolic pressure, and left and right ventricular double products ([mean arterial pressure X heart rate] and [mean pulmonary artery pressure X heart rate], respectively). Responders were defined as those in which total pulmonary resistance decreased greater than or equal to 20% without an increase in mean pulmonary arterial pressure and in which heart rate increase was less than or equal to 10%. Comparison was also made between maximal hemodynamic effect of hydralazine with that after 100% oxygen administration for 15 minutes to previously normoxemic dogs (n = 5). Significance was determined if P < 0.05, using the paired t-test. Hydralazine induced significant reductions in mean pulmonary and systemic arterial pressures and total pulmonary resistance, with no significant change in heart rate, cardiac index, total systemic resistance, left ventricular dP/dt(max), left ventricular end diastolic pressure, or right and left ventricular double products. Four (57%) of the 7 dogs studied were considered responders. Pretreatment cardiac index, mean pulmonary artery pressure, and total pulmonary resistance did not allow differentiation of responders from nonresponders.

Plasma insulin concentration of many species has a characteristic early or acute-phase response in the minutes after IV administration of glucose, However, the plasma insulin response of horses soon after the Iv administration of glucose has not been examined, whereas the more prolonged response has been evaluated. We examined the plasma insulin and glucose concentration responses of adult mares during the 30 minutes after rapid Iv administration of glucose (0.33 g/kg of body weight). Plasma glucose concentration peaked at 664 +/- 54 mg/dl within I minute of cessation of glucose administration, whereas insulin concentration peaked at 326 +/- 24 pmol/L at 2 minutes after the end of glucose administration. Thus, these mares had an acute insulin response, consistent with that observed in other species, including dogs, human beings, and cattle.

An ELISA was developed to detect antibodies to the 41-kd flagellin (P41) of Borrelia burgdorferi in serum obtained from cattle. Absorption studies, immunoblot analysis, immunoelectron microscopy, and correlation of results of the P41-ELISA and the P39-ELISA as well as measurement of the antibody to P41 in calves challenge-exposed with Borrelia theileri were used to assess the specificity of the P41-ELISA. Antigens derived from Escherichia coli, Leptospira interrogans serovar hardjo, and B burgdorferi were used for absorption studies and immunoblot analysis. Antibodies to P41 of B burgdorferi cross-reacted with antigens of E coli, but were not cross-reactive with L hardjo. A value 3 SD higher than the mean of the negative-control population of cattle was defined as the minimum value cutoff value) for a positive result by the P41-ELISA. Use of this value for classification of test results reduced the predicted rate of false-positive results attributable to E coli cross-reactivity to 1%. Immunoblot analysis revealed that test-positive serum from cattle reacted mainly with 41-, 39-, 34-, and 31-kd proteins of B burgdorferi, as well as several smaller proteins. Immunoelectron microscopy revealed that serum from cattle that was test-positive by the P41-ELISA bound to the flagellin and outer membrane of B burgdorferi. Results of absorption studies, immunoblot analysis, and immunoelectron microscopy were correlated and indicated that serum from cattle that was test-positive by P41-ELISA had stronger reactivity to B burgdorferi antigens than to antigens of E coli or L hardjo. The concentrations of antibodies measured by P41-ELISA and P39-ELISA testing were highly correlated [R(2)=0.78]. Calves challenge-exposed with B theileri also had test-positive results by the P-41-ELISA as early as 2 weeks after exposure, but serum antibody concentrations decreased to prechallenge-exposure concentrations by 9 weeks after exposure.

Vaccina virus (VV) infection induces specific antibodies and cytotoxic T cells in various animal species. Therefore, helper T cells also should be induced that stimulate the humoral and cellular immune responses. We determined such helper T-cell activity in 2 species after VV infection. Rabbits and rhesus macaques were infected with the Copenhagen strain of VV or with recombinant VV expressing retroviral proteins. Animals of both species developed antibodies and specific proliferative T-cell response. This reactivity could be enhanced by booster infection with VV. The proliferating macaque cells were CD4+ and major histocompatability complex class II-restricted. These data confirm the broad immunogenicity of VV. Expression of additional polypeptides expressed from a recombinant VV does not lead to altered immune response to VV antigens. However, strength of the helper T-cell response, as well as clinical reactions, differed between macaques and rabbits. Infection with recombinant VV as delivery vectors offers the opportunity for combined vaccination against recombinant proteins and does not diminish cellular and humoral immune responses to VV itself.

Right atrial, pulmonary artery, pulmonary capillary, pulmonary artery wedge, and systemic blood pressures of strenuously exercising horses increase markedly. As a consequence, myocardial metabolic O2 demand in exercising horses must be high. Experiments were, therefore, carried out on 9 healthy, exercise-conditioned horses (2.5 to 8 years old; 481 +/- 16 kg) to ascertain the regional distribution of myocardial blood supply in the atria and ventricles at rest and during exercise. Blood flow was measured, using 15-micrometer-diameter radionuclide-labeled microspheres that were injected into the left ventricle while reference blood samples were being withdrawn at a constant rate from the thoracic aorta. Myocardial blood flow was determined at rest and during 2 exercise bouts performed on a high-speed treadmill at 8 and 13 m/s (0% grade). The sequence of exercise bouts was randomized among horses, and a 60-minute rest period was permitted between exercise bouts. There was considerable heterogeneity in the distribution of myocardial perfusion in the atria and the ventricles at rest; the right atrial myocardium received significantly (P < 0.05) less perfusion than did the left atrium, and these values were significantly (P < 0.05) less than those for the respective ventricular myocardium. The right ventricular myocardial blood flow also was significantly less than that in the left ventricle. With exercise, myocardial blood flow in all regions increased progressively with increasing work intensity and marked coronary vasodilation was observed in all cardiac regions. During exercise at 8 or 13 m/s, right and left atrial myocardial blood flows (per unit weight basis) were not different from each other. Although at treadmill speed of 8 m/s, left ventricular myocardial blood flow exceeded that in the right ventricle, this was not the case at 13 m/s, when perfusion values (per unit weight basis) became similar.

A commercial rapid-absorbed ELISA developed to detect antibodies to Mycobacterium paratuberculosis in bovine serum was modified for use with goat serum. Diagnostic sensitivity was evaluated, using a group of 163 goats from a herd with endemic paratuberculosis. Blood and fecal samples were obtained simultaneously, and prevalence of shedding of M paratuberculosis in the feces was estimated by detection of DNA of the mycobacterial insertion sequence, IS900, using a commercial test kit. Diagnostic specificity was evaluated, using blood samples from a total of 123 goats in 10 herds that were considered clinically free of paratuberculosis. The IS900 DNA was detected in 35 of the 163 goats (21%) from the infected herd. Serum antibody to M paratuberculosis was detected in 19 of the 35 IS900 DNA-positive goats, for apparent sensitivity of 54%. Serum antibody was detected in 18 of the 128 IS900 DNA-negative goats from the infected herd. Negative results for serum antibody to M paratuberculosis were obtained for all 123 goats from the herds that were considered clinically free of paratuberculosis.

Biplanar radiography was used to study normal growth of the left and right radius in 5 Beagles and growth of the left radius alone in 15 additional Beagles. We explored the applicability of this radiographic method in veterinary medicine by measuring the contribution to total radius length from each growth plate. Spherical tantalum markers (0.5 mm) were embedded in the proximal epiphysis, diaphysis, and distal epiphysis of each dog's radius at 10 weeks of age. Simultaneous biplanar radiographic views were obtained every 4 weeks until skeletal maturity was documented. A three-dimensional coordinate system was constructed allowing for measurement of growth (in millimeters). Resolution of the measuring system was 0.074 mm. Mean +/- SEM length of the skeletally mature Beagle's radius, as measured from proximal epiphyseal bead to distal epiphyseal bead, was 95.33 +/- 1.07 mm. The percentage of contribution to the total radius length from the proximal and distal growth plates was 36.76 and 64.73%, respectively, with 95% confidence interval of 2.29%. The percentage of contribution to radius length from the distal radial growth plate increased for each consecutive time segment, with the distal radial physis contributing 61.75% from 10 to 14 weeks of age and increasing to 70.22% from 22 to 26 weeks of age. Significant growth was not observed after 26 weeks of age. The period of most rapid growth was between 10 and 14 weeks of age. Biplanar radiography was accurate and precise in quantifying the relative contribution of the proximal and distal growth plate to radius length in Beagles. The method is applicable in veterinary research or clinical medicine for monitoring of axial and angular growth: physiologic, iatrogenic, or pathologic.

Polymyxin B and an antiserum against an Re mutant Salmonella typhimurium were evaluated for protective effect in an equine model of endotoxemia. Six 3- to 5-month-old foals were given endotoxin (0.25 micrograms/kg of body weight) IV after no pretreatment, or pretreatment with polymyxin B (6,000 U/kg, IV) or S typhimurium antiserum (1.5 ml/kg, IV). When given without pretreatment, endotoxin caused transient recumbency and increases in rectal temperature, and heart and respiratory rates. In addition, leukopenia and increases in circulating tumor necrosis factor (TNF) and interleukin 6 (IL-6) activities were detected. Compared with results obtained when endotoxin was given alone, pretreatment with polymyxin B resulted in significantly (P < 0.05) lower maximal plasma TNF and IL-6 activities, and significantly lower rectal temperature and respiratory rate. In contrast, compared with effects of endotoxin given without pretreatment, use of antiserum was associated with significantly (P < 0.05) higher respiratory rate, maximal plasma IL-6 activity, and total TNF response (as determined by areas under curves of plasma TNF vs time). These results indicate that polymyxin B may have potential as a treatment for equine endotoxemia. Salmonella typhimurium antiserum had no positive effect in this model, and, under certain conditions, may exacerbate the actions of endotoxin.