Ouabain, a cardiac glycoside, binds to the Na+-K+i-adenosine triphosphatase (Na+ pump) and prevents active transport of Na+ and K+ across cell membranes. We used [3H]ouabain to quantify the number and affinity of Na+ pumps in skeletal muscle from Quarter Horses with the muscular disorder hyperkalemic periodic paralysis (HYPP). [3H]Ouabain-binding properties of gluteal muscle from clinically normal and affected horses were used to determine whether altered Na+ pump number or affinity could contribute to the pathologic features of muscle in affected horses. Foals and adult horses with HYPP were compared with age-matched clinically normal horses. The number of [3H]ouabain-binding sites in adult gluteal muscle was not different between the 2 types of horses (85.7 +/- 8.9 pmol of [3H]ouabain-binding sites/g [wet muscle weight] in horses with HYPP vs 100.2 +/- 8.8 pmol/g in clinically normal adult horses). Gluteal muscles in HYPP-affected and clinically normal foals also contained a similar number of [3H]ouabain-binding sites (222.3 +/- 21.0 pmol/g vs 225.3 +/- 24.2 pmol/g, respectively). The affinity of these binding sites for ouabain was not different, between adults or foals, in clinically normal or affected horses. Our results indicate that membrane events underlying the periodic episodes of paralysis in horses with HYPP are not attributable to quantitative changes in Na+ pump number or affinity. Our data cannot exclude the possibility that the specific activity of the Na+ pump is altered in muscle from HYPP-affected horses.

Protein profiles of whole homogenates of anconeus (slow twitch) and biceps femoris (fast twitch) muscles of clinically normal dogs and of Labrador Retrievers with hereditary myopathy (HM) were resolved on flat bed polyacrylamide isoelectric-focusing gels. Three methods of sample solubilization were performed. The solubilization buffer, with high concentrations of urea, precipitated the zwitterionic detergent, but use of the buffer containing 3% NP-40, 9.2M urea, and 0.1M arginine resulted in better resolution and stability of pH gradient. Gels of anconeus muscle from clinically normal dogs contained 2 protein bands specific to anconeus muscle, whereas gels of biceps femoris muscle from clinically normal dogs contained 3 protein bands amplified in biceps femoris muscle that were barely detectable in anconeus muscle. The staining intensity of protein bands in biceps femoris muscles from Labrador Retrievers with HM was decreased, relative to controls. The quantitative analysis of peak height ratios of biceps femoris muscle revealed significant (P less than 0.05) differences between profiles of clinically normal dogs and Labrador Retrievers with HM.

The fiber type, fiber size, and capillary geometric features were determined from the center of the proximal half of the left and right semitendinosus muscles in 5 mixed-breed dogs, 5 hound-type dogs, and 5 Beagles. There were no significant differences between the left and right muscles of each dog. Comparisons among the 3 groups of dogs revealed that the hound-type dogs had the largest fibers (type I and type II); however, the 3 groups were similar in their fiber-type percentages and their capillary geometric features.

Pharmacokinetic variables of skeletal muscle creatine kinase (CK) activity after IV administration of a muscle extract; CK bioavailability after IM administration of the muscle extract; and effect of IM administration of saline solution, to appreciate the possible release of CK consecutive to muscle puncture, were determined in 6 cows. A general equation for the quantitative estimation of skeletal muscle damage also was derived. Administration of saline solution IM had no effect on plasma CK activity (ANOVA, P > 0.05) in any of the cows. After IV administration of the muscle extract (150 U/kg of body weight), mean volume of the central compartment, plasma half-life, and plasma clearance of CK were 0.027 +/- 0.007 L/kg, 520 +/- 109 minutes, and 6.43 +/- 2.29 ml/kg/h, respectively. After IM administration (150 U/kg), mean bioavailability of CK was 51 +/- 17% and maximal plasma CK activity (500 +/- 97 U/L) was observed at 454 +/- 131 minutes. The rate of CK activity entry into plasma was determined by use of deconvolution analysis. Two peaks were observed; the first appeared before the 30th minute after IM administration, and the second appeared at 3.3 +/- 1.1 hours. Amplitudes were 6.31 +/- 4.45 and 6.57 +/- 3.08 U/kg/h, for the first and the second peaks, respectively. The quantity of CK liberated from control muscle was 0.69 +/- 0.12 U/kg/h, corresponding to a normal daily catabolism of 5.8 +/- 1.0 mg of muscle/kg. From these results, the following equation can be proposed to determine the corresponding mean equivalent of destroyed muscle (Qmuscle, test article) after IM administration of a test article: Qmuscle, test article (g/kg) = 4.41 X 10(-6) AUC (U/h/L), with AUC being the CK plasma activity area under the curve.

During the hunting season of 1992, 322 black bears from Pennsylvania were examined for Toxoplasma gondii- and Trichinella spp-induced infections. Toxoplasma gondii antibodies were found in 79.8% of 322 bears--titer < 1:25 in 65 (20.2%), 1:25 in 18 (5.6%), 1:50 in 11 (34.5%) and 1:500 in 128 (38.7%) bears--by use of the modified agglutination test. Muscle tissues from 89 of these bears were bioassayed for T gondii parasites. Muscles from 64 bears, including heart from 1 bear, and heart alone from another bear, were digested in pepsin, and the digested samples were bioassayed in mice. Toxoplasma gondii was isolated from 5 bears; from the heart of 1, heart and skeletal muscles of 1, and skeletal muscles of 3. The T gondii antibody titers for the 5 bears with detectable T gondii were: greater than or equal to 1:25 in all 5 bears by use of the modified agglutination test; < 1:10 (3 bears, considered Toxoplasma-negative), 1:20 and 1:320 by use of the Sabin-Feldman dye test; < 1:64 (3 bears, considered Toxoplasma-negative), 1:128, 1:512 by use of the indirect hemagglutination test, and < 1:16 (2 bears, considered Toxoplasma-negative), 1:32, 1:64, and 1:512 by use of the latex agglutination test. Toxoplasma gondii was not isolated from feces of 5 cats fed muscles from the remaining 25 bears with T gondii antibody titer < 1:25. Tissue cysts of the 4 T gondii isolates from bears were rendered noninfective by freezing at -13 C. Antibodies against Trichinella spp were found in 6 (1.8%) of 319 bear sera; Trichinella spp larvae were detected in muscle digests of 2 of 63 bears, and in histologic sections of muscles from 3 of 162 bears. Genetic typing indicated that the 2 Trichinella isolates from bears were a sylvatic genotype and were not the species found in domestic pigs.