We performed dual-energy x-ray absorptiometry (craniocaudal and lateromedial views) on 10 pairs of humeruses, radiuses, femurs, and tibias from dogs, using an alignment jig, to determine the homotypic bone mineral density variations of long bones. The bones were divided into 3 regions: proximal, middle, and distal parts of the diaphysis. The bone mineral density of cortical bone, medullary bone, and total bone was determined. Of 160 homotypic comparisons, 21 indicated significant (P less than or equal to 0.05) differences between right and left bones at either a region or location. These differences were observed most frequently in the craniocaudal view and were probably secondary to positioning errors. Evaluation of elliptical bones, such as the radius, also indicated that, when the thicker dimension, such as the lateromedial view of the radius was measured, the bone mineral density of regions-of-interest in that view was greater than that in the opposite view (ie, craniocaudal view of the radius). This study validates the concept of using the contralateral limb as the control condition in orthopedic studies of dogs, particularly when evaluating the densitometric properties of long bones. This study also emphasizes the importance of accurate positioning to prevent inadvertent alteration of bone mineral density results when using dual-energy x-ray absorptiometry. Dual-energy x-ray absorptiometry is particularly susceptible to positioning errors, because it converts a 3-dimensional structure into a 2-dimensional image.

Effects of the neuromuscular blocking agent succinylcholine (n = 9), the centrally acting skeletal muscle relaxant diazepam (n = 11), and the direct-acting skeletal muscle relaxant dantrolene sodium (n = 8) on the urethral pressure profile were evaluated in anesthetized, healthy, sexually intact, adult male cats. Intravenous administration of succinylcholine (0.075 mg/kg of body weight) significantly decreased mean absolute pressure in the prostatic and post-prostatic/penile intraurethral segments by -9.5 and -6.5 mm of Hg, respectively (P = 0.0002 and P = 0.0006, respectively). Dantrolene (1.0 mg/kg, IV) significantly decreased mean prostatic and postprostatic/ penile intraurethral segmental pressures by -3.5 and -2.8 mm of Hg, respectively (P = 0.005 and P = 0.0181, respectively). Diazepam (0.8 mg/kg, IV) did not significantly alter mean intraurethral segmental pressures. None of the drugs caused a change in segmental lengths of the urethra. These results indicate that skeletal muscle makes a substantial contribution to intraurethral tone in anesthetized, healthy, sexually intact male cats and that skeletal muscle relaxation may be successful in reducing prostatic and post-prostatic/penile urethral segmental tone in male cats. These results also suggest that dantrolene sodium may be valuable for the pharmacologic management of urethral disorders in male cats.

Pharmacologically induced splenic contraction might be useful during certain medical or surgical procedures in horses. The effects of phenylephrine, an alpha 1-adrenergic receptor agonist, on hemodynamic function and splenic dimensions were examined in 6 healthy adult horses. Phenylephrine infusion (1, 3, or 6 microgram/kg of body weight/min for 15 minutes) resulted in a dose-related increase in mean pulmonary artery pressure; right atrial pressure; systolic, mean, and diastolic arterial pressures; and packed cell volume (P = 0.0001). Concurrent decreases in heart rate and specific cardiac output (P = 0.0001) were detected, but stroke volume did not vary significantly. The rate-pressure product was increased only at the highest phenylephrine dosage (P = 0.012). Bradycardia was observed at all dosages during drug infusion, and second-degree atrioventricular block was detected in 88% of horses during infusion. Phenylephrine administration caused dose-dependent splenic contraction, as detected by ultrasonographic measurements of splenic area and thickness (P = 0.0001). At the 3- and 6-microgram/kg/min infusion rates, splenic area was reduced to 28 and 17% of baseline measurement, respectively. Splenic dimensions had returned to baseline values by 35 minutes after the end of infusion. Infusion of phenylephrine at a dosage of 3 microgram/kg/min for 15 minutes can be used to induce splenic contraction in horses.

Association between individual cumulative milk yield and various reproductive disorders in 56,772 Finnish Ayrshire cows belonging to 5,912 herds in 80 communities was studied. All cows delivered calves between September 1985 and September 1986. Five logistic regression models were fitted, 1 for each outcome disorder of interest: early metritis, late metritis, silent heat, ovarian cyst, and other infertility. Cumulative individual 37-day milk yield was used in the early metritis model, and cumulative individual 60-day milk yield was used in the other models, on the basis of median days in milk when these disorders developed. Cumulative 305-day herd milk yield, parity, calving season, presence or absence of other disorders, and community were also included in the models. Point estimates from the models represented odds ratios for the likelihood of having the outcome disorder.Lactational incidence risks for the 5 reproductive disorders studied were: early metritis (2.4%), late metritis (1.1%), silent heat (5.4%), ovarian cyst (6.6%), and other infertility (2.1%). The risk of early metritis decreased with increasing 37-day milk yield. The risk of silent heat, ovarian cyst, and other infertility increased with increasing 60-day milk yield; 60-day milk yield had no effect on late metritis. The 305-day herd milk yield increased the risk of early metritis, ovarian cyst, and other infertility; it had no effect on late metritis or silent heat. Parity had an effect on all disorders, except late metritis. Cows that delivered calves during the colder, darker seasons of the year had a higher risk of reproductive disorders than did those that delivered calves at other times of the year. A number of other disorders, reproductive and otherwise, were significant predictors of development of the outcome disorders.

Neospora caninum causes serious disease in dogs, and it, or a similar parasite, is a major cause of abortion in cattle. Little is known about the susceptibility of this protozoan to antimicrobial agents. We studied several antimicrobial agents to determine which classes might have activity against this parasite. We also determined whether activity of such agents was coccidiocidal or coccidiostatic. A 2-day of treatment, monoclonal antibody-based enzyme immunoassay and a 5-day of treatment, cell culture flask (CCF), lesion-based assay were developed to examine the ability of test agents to inhibit tachyzoite multiplication. Seven sulfonamides were examined, with the following activities observed: sulfathiazole greater than or equal to sulfamethoxazole > sulfadiazine > sulfaquinoxaline greater than or equal to sulfamethazine > sulfadimethoxine > sulfamerazine. Dapsone, a sulfone, had little activity. Six dihydrofolate reductase/thymidylate synthase inhibitors were examined, with the following activities observed: piritrexim > pyrimethamine > ormetoprim > trimethoprim = diaveridine > methotrexate. Six ionophorous antibiotics were examined; lasalocid, maduramicin, monensin, narasin, and salinomycin had equivalent activities, but alborixin was toxic for host cells at the lowest concentration examined. Three macrolide antibiotics--azithromycin, clarithromycin, and erythromycin--were examined and had equivalent activities. Two tetracycline antibiotics, doxycycline and minocycline, were examined and had equivalent activities. Three lincosamide antibiotics were examined, with the following activities observed: clindamycin hydrochloride > clindamycin phosphate > lincomycin hydrochloride. Pentamidine and 6 of its analogs were examined, and only hexamidine and 1,4-Di[4-(2-imidazolinyl)-2-methoxy-phenoxylbutane had activity. Eight miscellaneous antiprotozoal agents were examined for activity. Amprolium, metronidazole, paromomycin, and roxarsone had little activity. Arprinocid, diclazuril, nitrofurazone, and robenidine had good activity. Eleven agents were examined in both assays, whereas 32 agents were examined in the CCF assay only. The enzyme immunoassay and CCF assay provided similar results for agents that rapidly killed tachyzoites. However, agents that inhibited development, but were not rapidly fatal for tachyzoites, had better activity in the CCF assay. Of the classes of agents examined, the dihydrofolate reductase/thymidylate synthase inhibitors, 2 of the 6 pentamidine analogs, and the ionophores were coccidiocidal and the sulfonamides, macrolides, tetracyclines, and lincosamides were coccidiostatic. Of the miscellaneous agents examined, arprinocid, nitrofurazone, and robenidine were coccidiocidal and diclazuril was coccidiostatic.

An ELISA containing lipoarabinomannan (LAM) antigen was used to detect antibodies in milk and serum for diagnosis of Mycobacterium paratuberculosis infection in dairy cattle. In experiment 1, milk and serum samples were obtained from 25 cows, and subjected to LAM ELISA testing immediately, and after 1 year of storage at -70 C. Milk samples, with and without a commonly used chemical preservative, were tested. There was no significant difference in LAM ELISA results between fresh and frozen samples or between preserved and unpreserved milk samples. In experiment 2, milk samples were collected daily from 30 cows over a 14-day period. The day-to-day coefficient of variation was 0.19 for milk LAM ELISA and was 0.15 for serum LAM ELISA, with no statistically significant time effect detected. In experiment 3, single milk, serum, and fecal samples were obtained from 764 cows. The fecal samples were cultured for M paratuberculosis to identify infected cows, and the serum and milk samples were subjected to LAM ELISA testing. Results were compared, using the area under the receiver operating characteristic curves. The milk LAM ELISA had specificity (+/- 95% confidence limits) of 87 +/- 8.1% when the cutoff was set at 50% sensitivity, and specificity of 83 +/- 9.1% when sensitivity was set at 60%. The area under the receiver operating characteristic curve was 0.85 +/- 0.03 for the milk ELISA and 0.75 +/- 0.02 for the serum ELISA. In this population of cattle, the milk LAM ELISA had comparable accuracy to serum LAM ELISA, although the milk LAM ELISA was slightly less reproducible (higher coefficient of variation).

Force plate gait analysis was used to study the effects of subject stance time and velocity on ground reaction forces in 6 adult Greyhounds at the trot. Data for 210 valid trials were obtained. Stance time negatively correlated with velocity (r = -0.85 for the forelimbs, r = -0.61 for the hind limbs), decreasing as velocity increased. Stance time in the forelimbs and hind limbs correlated more closely with changes in vertical peak force and impulse than did velocity. The trials were divided into 3 distinct velocity ranges (V1 = 1.5 to 1.8 m/s, V2 = 2.1 to 2.4 m/s, and V3 = 2.7 to 3.0 m/s), 3 distinct forelimb stance time ranges (FST1 = 0.144 to 0.176 second, FST2 = 0.185 to 0.217 second, and FST3 = 0.225 to 0.258 second), and 3 distinct hind limb stance time ranges (HST1 = 0.105 to 0.132 second, HST2 = 0.139 to 0.165 second, and HST3 = 0.172 to 0.198 second). Peak forces increased as velocity increased and decreased as stance time increased. Vertical impulse decreased as velocity increased and increased as stance time increased. The relation between stance time, subject velocity, and ground reaction forces was documented for clinically normal Greyhounds at the trot. Changes in stance time accurately reflected changes in subject velocity and ground reaction forces in clinically normal dogs and could be used to normalize trial data within a sampling period.

We measured immunoreactive (IR) plasma concentrations of the proopiomelanocortin (POMC)-derived. peptides (adrenocorticotropic hormone [ACTH]; beta-endorphin/beta-lipotropin [beta END/beta LPH]; and alpha-melanocyte stimulating hormone [alpha MSH]) and of cortisol in 100 clinically normal cats. Median plasma concentration of IR-ACTH was 2.7 pmol/L (range, less than or equal to 1.1 to 22 pmol/L), of beta END/beta LPH was 28 pmol/L (range, 3.8 to 130 pmol/L), of alpha MSH was 36 pmol/L (range, less than or equal to 3.6 to 200 pmol/L), and of cortisol was 35 nmol/L (range, 5 to 140 nmol/L). Plasma concentrations of IR-ACTH, alpha MSH, and beta END/beta LPH were at or below the assay sensitivity in 34, 3, and 0% of the cats, respectively. We did not detect a correlation between plasma concentrations of IR-ACTH and beta END/beta LPH (r = 0.23) or between plasma concentrations of IR-ACTH and alpha MSH (r = 0.19). However, there was a significant (P < 0.001) correlation between plasma concentrations of IR-beta END/beta LPH and alpha MSH (r = 0.81). There was not a significant correlation between plasma concentration of cortisol and plasma concentration of any of the IR-POMC peptides. High plasma concentrations of IR-alpha MSH and beta END, POMC peptides secreted predominantly by melanotrophs in other species, indicate that clinically normal cats have an actively secreting pars intermedia. Although the beta END/beta LPH assay used in this study measures the pars distalis-derived peptide beta-LPH, as well as beta END itself, over 95% of the IR-beta END/beta LPH activity in feline plasma containing high concentrations of alpha MSH, but low concentrations of IR-ACTH, was found to coelute with human beta END on gel filtration chromatography. In contrast to the high plasma concentrations of IR-alpha MSH and beta END/ beta LPH, many cats had low to undetectable concentrations of IR-ACTH, a peptide secreted predominantly by pars distalis corticotrophs. The pattern of plasma POMC peptide concentrations found in cats is similar to that reported in rats, but is markedly different from that reported in dogs, in which the secretion of pars intermedia POMC peptides is normally low.

Effects of furosemide administration on exertion-induced changes in plasma renin activity and plasma concentrations of atrial natriuretic peptide and aldosterone in horses during sustained submaximal exertion were examined. Furosemide (1 mg/kg of body weight) or heparinized saline solution was administered IV to each of 6 mares not conditioned to exercise, either 4 hours or 2 minutes before 60 minutes of sustained submaximal running on a treadmill. Horses ran at a speed that induced heart rate approximately 65% of maximal after saline treatment. After 15 minutes of running, furosemide suppressed the exertion-induced increase in plasma concentrations of atrial natriuretic peptide (mean [95% confidence interval] values of 63.9 [9.9 to 421] pg/ml vs 100 [15.4 to 652] pg/ml after furosemide or saline treatment, respectively), and enhanced the response of plasma renin activity to exertion (18.6 [5.7 to 60.4] ng/ml/h vs 6.0 [1.8 to 19.4] ng/ml/h, respectively). An effect of furosemide on the exertion-induced increase in plasma aldosterone concentration was not detected.

Members of the genus Salmonella were identified in feces from horses, using the polymerase chain reaction (PCR) and genus-specific olignucleotide primers. Feces from healthy horses were determined to be culture-negative for Salmonella spp. Fecal samples were inoculated with known numbers of colony-forming units (CFU) of S anatum, S derby, S enteritidis, S heidelberg, S newport, and S typhimurium. The DNA was extracted from fecal samples and amplified by PCP, using genus-specific primers. Sensitivity of the assay extended to 10(3) CFU of Salmonella sp/g of feces, sensitivity of microbiologic culture with enrichment extended to 10(2) CFU of Salmonella sp/g of feces. Feces that were not inoculated with Salmonella spp were negative by the PCR. Detection of salmonellae in feces was possible, using the PCR, within 10 to 12 hours from the time of submission of samples.