Plasma indicators of muscle damage in a model of nutritional myopathy in weaner sheep

SUMMARY Subclinical nutritional myopathy was induced in 5-month-old sheep by feeding them a diet low in vitamin E and selenium. Subsequently clinical myopathy was induced by dosing with protected polyunsaturated fatty acids. Plasma activities of creatine kinase (CK), pyruvate kinase, aspartate aminotransferase (AST), alanine aminotransferase (ALT), lactate dehydrogenase and aldolase, enzymes of muscle origin, all remained above their reference ranges in clinically affected sheep, but fluctuated widely. Similar fluctuations occurred in subclinically affected animals, resulting in some activities being within the reference ranges and some above, at different times. Plasma malondialdehyde, an indicator of lipid peroxidation, proved of no diagnostic value. Terminal plasma CK activities were significantly correlated with microscopic damage in the vastus lateralis (VL), but not the vastus intermedius (VI) or the tensor fascia lata (TFL) muscles. AST was the most highly correlated with damage in VI and VL. In two clinically affected sheep successfully treated with an oral dose of α-tocopherol actetate all enzymes decreased steadily to within their reference ranges, at rates probably related to their plasma half-lives. These results suggest that measurement of plasma CK activity would be useful in monitoring recovery of treated sheep.     

Distribution of tissue enzymes in three species of pinnipeds.

In domestic animal medicine, changes in serum enzyme levels are routinely used as diagnostic tools to detect liver disease. Hepatic disease occurs in pinnipeds, but limited data are available on the tissue distribution of serum enzymes in marine mammals. The objectives of this study were to determine the tissue distribution of seven serum enzymes in three pinniped species. Enzymes evaluated were alanine aminotransferase (ALT), aspartate aminotransferase (AST), sorbitol dehydrogenase (SDH), lactate dehydrogenase (LDH), creatine kinase (CK), alkaline phosphatase (ALP), and gamma-glutamyl transferase (GGT) in tissues from California sea lions (Zalophus californianus) (n = 5), harbor seals (Phoca vitulina) (n = 5), and northern elephant seals (Mirounga angustirostris) (n = 5) that stranded and then died at a rehabilitation center. Samples were evaluated in duplicate from liver, skeletal muscle, cardiac muscle, kidney, adrenal, spleen, pancreas, lung, lymph node, and intestine. Patterns of tissue enzyme distribution were similar in all species, with SDH activity highest in liver and kidney, CK activity highest in skeletal and cardiac muscle, ALP activity highest in adrenal, and GGT activity highest in the kidney. Aspartate aminotransferase and LDH activities were less specific, with high activity in multiple tissues. Tissue ALT activity was high in the liver of all species, but was also high in cardiac muscle (California sea lions), skeletal muscle (harbor seals), and kidney (elephant seals). These results suggest that concurrent analysis of SDH, ALT, and CK would provide high specificity and sensitivity for the detection of hepatic lesions, and allow differentiation of liver from skeletal muscle lesions in pinniped species.     

Tissue and plasma enzyme activities in juvenile green iguanas

OBJECTIVE: To determine activities of intracellular enzymes in 8 major organs in juvenile green iguanas and to compare tissue and plasma activities. ANIMALS: 6 green iguanas < 1 year old. PROCEDURE: Lysates of liver, kidney, epaxial muscle, heart, lung, spleen, small intestine, and pancreas were analyzed for alkaline phosphatase (ALP), lactate dehydrogenase (LDH), aspartate transaminase (AST), alanine transaminase (ALT), gamma-glutamyltransferase (GGT), creatine kinase (CK), glutamate dehydrogenase (GMD), and amylase (AMS) activities. RESULTS: In general, low tissue enzyme activity coincided with low plasma activity. The CK activity was high in epaxial muscle and the heart and low in all other tissues tested. The AMS activity was found exclusively in the pancreas. Moderate LDH and AST activities were found in all tissues. Low ALT and ALP activities were found in a variety of tissues. Plasma and tissue activities of GGT and GMD were low or undetectable. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that plasma CK activity may be muscle specific in iguanas, but high values may not always indicate overt muscle disease. The AMS activity may be specific for the pancreas, but the wide range of plasma activity would likely limit its diagnostic usefulness. Activities of AST and LDH may reflect tissue damage or inflammation, but probably do not reflect damage to specific tissues or organs.     

Comparison of blood aminotransferase methods for assessment of myopathy and hepatopathy in Florida manatees (Trichechus manatus latirostris)

Muscle injury is common in Florida manatees (Trichechus manatus latirostris). Plasma aspartate aminotransferase (AST) is frequently used to assess muscular damage in capture myopathy and traumatic injury. Therefore, accurate measurement of AST and alanine aminotransferase (ALT) is important in managed, free-ranging animals, as well as in those rehabilitating from injury. Activities of these enzymes, however, are usually not increased in manatees with either acute or chronic muscle damage, despite marked increases in plasma creatine kinase activity. It is hypothesized that this absence of response is due to apoenzymes in the blood not detected by commonly used veterinary assays. Addition of coenzyme pyridoxal-5-phosphate (P5P or vitamin B6) should, therefore, result in higher measured enzyme activities. The objective of this study was to determine the most accurate, precise, and diagnostically useful method for aminotransferase measurement in manatees that can be used in veterinary practices and diagnostic laboratories. Additionally, appropriate collection and storage techniques were assessed. The use of an optimized commercial wet chemical assay with 100 micromol P5P resulted in a positive bias of measured enzyme activities in a healthy population of animals. However, AST and ALT were still much lower than that typically observed in domestic animals and should not be used alone in the assessment of capture myopathy and muscular trauma. Additionally, the dry chemistry analyzer, typically used in clinics, reported significantly higher and less precise AST and ALT activities with poor correlation to those measured with wet chemical methods found in diagnostic laboratories. Therefore, these results cannot be clinically compared. Overall, the optimized wet chemical method was the most precise and diagnostically useful measurement of aminotransferase in samples. Additionally, there was a statistically significant difference between paired serum and plasma measurement, indicating that separate reference intervals should be established for serum and plasma. Finally, storage of these enzymes at -70 degrees C for 1 mo resulted in up to a 25% decrease in enzymatic activity in manatee plasma.     

Seasonal changes in reproductive parameters and seminal plasma constituents of rams in Afyon province of Turkey

The objective of the present study was to describe seasonal changes in semen quality, serum testosterone and seminal plasma constituents for 9 months in 10 rams from a mature local (Daglic) and imported breed (Chios) under Afyon province conditions typical for the internal Anatolian region. Sperm motility and sperm concentration and testosterone level were higher, percentage of abnormal spermatozoa was the lowest during autumn. The biochemical analyses of ram seminal plasma indicated that the highest values of total protein, albumin (A), globulin (G), total lipid and cholesterol were recorded in autumn while A/G ratio exhibited the lowest values. Aspartate amino transferase (AST) activity and AST/ALT ratio recorded the lowest values, while moderate values were recorded for alanine amino transferase (ALT) activity in autumn. The results suggest that the rams under Afyon province conditions show seasonal changes for some reproductive parameters and seminal plasma constituents.     

Increased Serum Alanine Aminotransferase Activity Associated With Muscle Necrosis in the Dog

Serum activity of alanine aminotransferase (ALT) was consistently increased in dogs with canine X-linked muscular dystrophy (CXMD), a primary myopathy characterized by profound and on-going skeletal muscle necrosis. In order to determine whether the ALT was of liver origin, serum activity of creatine kinase (CK), aspartate aminotransferase (AST), ALT, and sorbitol dehydrogenase (SDH) obtained from dystrophic dogs was compared with enzyme activity present in clinically normal dogs. In dystrophic dogs at all ages tested, serum activity of CK, AST, and ALT was increased, and significant increases were present in dogs four weeks or older. In contrast, SDH activity in dystrophic dogs was not statistically different from values in clinically normal dogs. Ultrastructural examination of liver tissue revealed no evidence of hepatic degeneration in dystrophic dogs. It was concluded that increased serum activity of ALT in the dog may be associated with severe skeletal muscle degeneration, without concurrent hepatocellular necrosis.     

Incidence of polysaccharide storage myopathy in draft horse-related breeds: a necropsy study of 37 horses and a mule.

Skeletal muscle samples from 38 draft horse-related animals 1-23 years of age were evaluated for evidence of aggregates of glycogen and complex polysaccharide characteristic of equine polysaccharide storage myopathy (EPSSM). Cardiac muscle from 12 of these horses was also examined. Antemortem serum levels of creatine kinase (CK) and aspartate aminotransferase (AST) from 9 horses with EPSSM and 5 horses without EPSSM were compared. Skeletal muscle from 17 horses contained inclusions of periodic acid-Schiff (PAS)-positive, amylase-resistant complex polysaccharide. Similar inclusions were also present in the cardiac muscle of 1 horse. A vacuolar myopathy with aggregates of PAS-positive, amylase-sensitive glycogen was seen in 8 other horses, and these findings are also considered diagnostic for EPSSM. Antemortem serum activities of CK and AST were often higher in EPSSM horses than in horses without EPSSM. Using the presence of amylase-resistant complex polysaccharide as the criterion for diagnosis of EPSSM, the incidence in this population was 45%. Inclusion of horses with aggregates of glycogen but no amylase-resistant complex polysaccharide as representative of the range of pathologic findings in horses with EPSSM resulted in a 66% incidence in this population.     

A study of nutritional myopathy in weaner sheep

The effectiveness of various treatments upon, and pathological and biochemical changes in, ovine weaner nutritional myopathy were observed. Clinical myopathy was already apparent in the sheep at the start of the study, and they were fed decreasing amounts of a ration containing low levels of selenium and alpha-tocopherol, and periodically deprived of water. In spite of this management there was a spontaneous remission of the clinical myopathy in the sheep, but a subclinical myopathy was identified in some of the sheep at the end of the trail. The conclusions were that the myopathy was not caused by a low dietary intake of selenium and/or alpha-tocopherol alone, that alpha-tocopherol was involved in the aetiology, that alpha-tocopherol was completely effective and selenium possibly partially effective in treating it, and that the condition may be a Type II muscle fibre disease. Data on plasma creatine phosphokinase and erythrocyte glutathione peroxidase activities, and terminal liver selenium and alpha-tocopherol concentrations are presented, and their roles in the diagnosis of ovine weaner nutritional myopathy discussed.     

Plasma biochemistry of one-humped camel (Camelus dromedarius): Effects of anticoagulants and comparison with serum

The effects of various types of anticoagulants on plasma biochemistry were studied in man and various animals but limited informations are existing for camel plasma biochemistry. Eleven clinically healthy one-humped camels were blood sampled in different tubes containing different anticoagulants and plain tubes for harvesting plasma and serum. The concentrations of glucose, cholesterol, triglyceride, total bilirubin, urea, creatinine, total protein, albumin, calcium, inorganic phosphorus, magnesium, and chloride and the activity of aspartate aminotransferase (AST), alanine aminotransferase (ALT), alkaline phosphatase (ALP), creatine kinase (CK) and gamma glutamyl transferase (GGT) were measured. Except for the amounts of AST, ALT, CK, total bilirubin, and inorganic phosphorus, other measured parameters were significantly lower in citrated plasma than in serum. Most parameters did not show any difference, but significant increase for CK activity and significant decrease for GGT, cholesterol, creatinine and chloride were seen when heparin was used as anticoagulant. Using EDTA as an anticoagulant caused a significant difference in the amounts of some measured parameters in plasma except glucose, AST, ALT, GGT, cholesterol, albumin, total protein, bilirubin, and triglyceride in comparison with serum.     

Plasma biochemistry of one-humped camel (Camelus dromedarius): effects of anticoagulants and comparison with serum

The effects of various types of anticoagulants on plasma biochemistry were studied in man and various animals but limited informations are existing for camel plasma biochemistry. Eleven clinically healthy one-humped camels were blood sampled in different tubes containing different anticoagulants and plain tubes for harvesting plasma and serum. The concentrations of glucose, cholesterol, triglyceride, total bilirubin, urea, creatinine, total protein, albumin, calcium, inorganic phosphorus, magnesium, and chloride and the activity of aspartate aminotransferase (AST), alanine aminotransferase (ALT), alkaline phosphatase (ALP), creatine kinase (CK) and gamma glutamyl transferase (GGT) were measured. Except for the amounts of AST, ALT, CK, total bilirubin, and inorganic phosphorus, other measured parameters were significantly lower in citrated plasma than in serum. Most parameters did not show any difference, but significant increase for CK activity and significant decrease for GGT, cholesterol, creatinine and chloride were seen when heparin was used as anticoagulant. Using EDTA as an anticoagulant caused a significant difference in the amounts of some measured parameters in plasma except glucose, AST, ALT, GGT, cholesterol, albumin, total protein, bilirubin, and triglyceride in comparison with serum.     

Serum enzyme activity evaluated in budgerigars (Melopsittacus undulatus) inflicted with muscle injury

Aspartate aminotransferase (AST), alanine aminotransferase (ALT), creatine kinase (CK) and lactate dehydrogenase (LDH) concentrations were measured in 73 budgerigars. In spite of increases in the serum concentration of AST and ALT the loss of enzyme activity from the injection site occurred at about the same rate for all four enzymes tested. The rate constants, calculated in birds administered muscle extract via the intravenous or the intramuscular route of injection, disclosed that in subjects treated intramuscularly the serum enzyme elevation was dependent on the elimination half-life of the enzyme and partly on the rate at which the particular enzyme was absorbed into the bloods-tream. Moreover, serum enzyme elevations correlated inversely with total clearance. To determine the aetiology of blood enzyme elevation in budgerigars, for diagnostic purposes, the absorption rate, total clearance and elimination half-life of each of these four enzymes are deemed valuable components.     

Salinomycin poisoning in point-of-lay turkeys

Salinomycin poisoning occurred in a flock of 700 point-of-lay turkeys; 400 birds died over 7 days as a result of consuming feed contaminated with 50 ppm salinomycin. No gross lesions were detected. Histologic evidence of a myopathy was most readily detected in leg muscles of turkeys 5 to 7 d after ingesting salinomycin. Feeding trials were undertaken and individual susceptibility to the drug was found to vary greatly. In affected birds the plasma concentrations of creatine kinase (CK) and aspartate aminotransferase (AST) were found to be in the range of 500,000 to 2,500,000 IU/l and 9000 to 25,000 IU/l, respectively. The marked increase in the plasma activities of these enzymes preceded histological evidence of segmental muscle necrosis.     

The use of selected plasma enzyme activities for the diagnosis of fatty liver-hemorrhagic syndrome in laying hens

Profiles of plasma enzymes were compared in two strains of single comb white leghorn laying hens, a normal commercial strain and strain UCD-003, which is highly susceptible to fatty liver-hemorrhagic syndrome. Plasma activity of lactate dehydrogenase (LDH), glutamate dehydrogenase (GDH), aspartate aminotransferase (AST), alanine aminotransferase (ALT), and creatine kinase (CK) averaged 194 +/- 27, 4.0 +/- 2.8, 146 +/- 20, 1.0 +/- 1.0, and 1041 +/- 268 U/liter, respectively in normal birds. Activities of LDH, GDH, AST, and ALT, but not CK, were significantly higher in UCD-003 than in normal hens. A bimodal distribution of activities of all enzymes was found in the UCD-003 hens, with some birds showing activities comparable with those of the normal hens and others with values that were 2-10 times greater than those found in normal hens. These results are consistent with the extensive hepatic lesions observed in the UCD-003 strain of birds. Average gross hemorrhagic scores from visual inspection (scale of 0-3) were 0.28 +/- 0.45 in normal birds and 1.63 +/- 0.94 in the UCD-003 birds. Even though no clear relationship was found between plasma enzyme activities and the extent of liver hemorrhage in individual birds, the UCD-003 hens consistently had average values significantly higher for plasma enzymes that indicate liver damage. The results suggest that measurement of enzyme activities indicative of liver damage in birds, particularly AST, LDH, and GDH, is a valuable tool in the diagnosis of fatty liver-hemorrhagic syndrome in a flock of layers.     

Hematology, plasma biochemistry, and tissue enzyme activities of invasive red lionfish captured off North Carolina, USA

The red lionfish Pterois volitans is important not only in the aquarium trade but also as an invasive species in the western Atlantic. Introduced to waters off the southeastern coast of the United States, red lionfish have rapidly spread along much of the East Coast and throughout Bermuda, the Bahamas, and much of the Caribbean. Hematology and plasma biochemistry were evaluated in red lionfish captured from the offshore waters of North Carolina to establish baseline parameters for individual and population health assessment. Blood smears were evaluated for total and differential white blood cell counts, and routine clinical biochemical profiles were performed on plasma samples. To improve the interpretive value of routine plasma biochemistry profiles, tissue enzyme activities (alkaline phosphatase [ALP], alanine aminotransferase [ALT], aspartate aminotransferase [AST], gamma-glutamyl transferase [GGT], lactate dehydrogenase [LD], and creatine kinase [CK]) were analyzed from liver, kidney, skeletal muscle, gastrointestinal tract, and heart tissues from five fish. The hematological and plasma biochemical values were similar to those of other marine teleosts except that the estimated white blood cell counts were much lower than those routinely found in many species. The tissue enzyme activity findings suggest that plasma LD, CK, and AST offer clinical relevance in the assessment of red lionfish.     

Effectiveness of α-tocopherol and selenium supplements in preventing lupinosis-associated myopathy in sheep

Objective To compare the effectiveness of combined selenium and α-tocopherol acetate treatments in preventing lupinosis-associated myopathy in sheep.
Design Measurement of plasma muscle and liver enzymes, and histopathological examination of muscle and liver in the treatment groups.
Procedure The treatments were: subcutaneous injections of selenomethionine and vitamin E (sc(SeM+E)) , an intraruminal selenium pellet and oral doses of vitamin E and intramuscular injections of selenomethionine combined with either oral doses of vitamin E (imSeM+orE) or intramuscular injections of vitamin E in an oily carrier. Another group received no supplements, while a control group was given selenium pellets on day 0 and fortnightly oral doses of vitamin E from day 0 to 72. To produce lupinosis-associated myopathy, the sheep were fed a diet low in vitamin E and given repeated injections of a crude extract of Diaphorthe toxica. Groups sc(SeM+E) and imSeM+orE were stressed by dosing with protected polyunsaturated fatty acids from day 56 onwards.
Results Lupinosis-associated myopathy was induced in all unsupplemented sheep. In these sheep the storage of Se increased and that of vitamin E decreased. The subcutaneous treatment was highly effective in preventing lupinosis-associated myopathy and also produced the highest vitamin E concentrations in plasma and liver. Supplemental vitamin E was more efficacious than supplemental Se. Concentrations of vitamin E in the livers of sheep given intramuscular vitamin E were higher than expected based on plasma concentrations. Oral doses of vitamin E proved the least effective method of increasing concentrations in liver. Lupinosis did not affect Se concentrations in liver or muscle.
Conclusion The sc(SeM+E) treatment is highly effective in preventing lupinosis-associated myopathy but needs to be further assessed when selenium and vitamin E are both limiting in the diet.     

Blood biochemical profiles of thai indigenous and Simmental x Brahman crossbred cattle in the Central Thailand

Plasma biochemical profiles were studied in 112 mature (3 to 5-year-old) healthy cattle comprised of 61 Thai indigenous and 51 Simmental x Brahman crossbred male and cyclic female cattle at Nongkwang (Central Thailand) Livestock Research and Breeding Center, Thailand. Data were analysed for the effect of breed and sex. The results showed that the plasma glucose and gamma-glutamyl transferase (GGT) in the two breeds were significantly (P < 0.05) different. Furthermore, the urea, creatinine, albumin, total protein, aspartate amino transferase (AST), alanine amino transferase (ALT) and alkaline phosphatase (ALP) levels in Thai indigenous were significantly (P < 0.01) higher than in crossbred cattle. However, creatine kinase did not significantly differ in crossbred and indigenous animals. A sex difference was found in glucose level with male Thai indigenous having significantly higher levels (P < 0.05) than the other three groups. Plasma urea concentration in male crossbred cattle was lower than in the other groups (P < 0.05). Female crossbred cattle had significantly (P < 0.05) lower plasma creatinine levels than the other animals. Furthermore, levels of albumin in male and total protein in female crossbred were the lowest (P < 0.05) among the groups. The AST, ALT, ALP and GGT levels were significantly (P < 0.05) different between male and female. Female crossbred cattle had the lowest (P < 0.05) AST and GGT levels, whereas lowest (P < 0.05) ALT and ALP concentration was determined in male individuals of these breeds.     

Effects of Common Anticoagulants on Routine Plasma Biochemistry of Horse and Comparison with Serum

The effects of various types of anticoagulants on plasma biochemistry have been studied in humans and various animals; however, limited information exists for effects on horse plasma biochemistry. Ten clinically healthy Thoroughbred horses were blood sampled in tubes containing different anticoagulants as well as no anticoagulant. The concentrations of glucose, cholesterol, triglyceride, total bilirubin, blood urea nitrogen (BUN), creatinine, total protein, albumin, calcium, inorganic phosphorus, magnesium and iron, and the activity of aspartate aminotransferase (AST), alanine aminotransferase (ALT), alkaline phosphatase (ALP), creatine kinase (CK), and gamma glutamyl transferase (GGT) were measured. Except for the amounts of inorganic phosphorus, magnesium, and GGT, other measured parameters were significantly lower in citrated plasma than in serum. When corrected for dilution, significant differences were seen for the amounts of glucose, cholesterol, triglyceride, bilirubin, calcium, iron, and the activity of ALT, ALP, and CK in citrated plasma. Most parameters did not show any difference; however, significant decreases in BUN, total bilirubin, ALT, and CK activity were seen when heparin was used as an anticoagulant. When compared with serum, using ethylenediaminetetra-acetic acid (EDTA) as an anticoagulant produced a significant difference in the amounts of measured plasma parameters with the exception of GGT, albumin, creatinine, inorganic phosphorus, and triglyceride.     

Effect of nickel deficiency on biochemical variables in serum, liver, heart and kidneys of goats.

Nickel deficiency was induced in 2- to 4-year-old goats by feeding 0.1 mg Ni/kg dry matter with a semisynthetic diet. The control group consumed 5.0 mg Ni/kg d.m. Activity of several enzymes (SDH, LDH, HBDH, AST, ALT, ALD, CK, CHE) was determined in the serum, liver, heart and kidneys. Serum urea-N level was also measured and transmission electron microscopic (TEM) examinations were performed. Signs characteristic of nickel deficiency (retarded growth, increased mortality of dam and offspring, parakeratosis of the skin) appeared in the low-nickel group. The activity of SDH and ALD, as well as the level of urea-N was significantly lower in the serum of Ni-deficient animals than in the control. Ni-deficient animals also had significantly lower enzyme activities in the heart (SDH, HBDH, AST, ALT, ALD and CK), liver (SDH and CHE) and kidneys (HBDH and CK). Electron micrographs showed degeneration of cardiac and skeletal muscle in the Ni-deficient animals. Ni deficiency elicited changes primarily in the heart and these resulted in depressed activity of several enzymes.     

饲粮类型对育肥湖羊肌肉脂肪酸和氨基酸组成的影响

本试验旨在研究不同饲粮类型对育肥湖羊肌肉脂肪酸和氨基酸组成的影响。选用90只体重为(24.65±2.80)kg的90日龄健康公湖羊,随机分为3组,分别饲喂传统精粗饲粮+舔砖(CK组)、全混合饲粮(TMR组)、粗料+精料颗粒料(CP组),每组3个重复,每个重复10只羊。预试期10 d,正试期120 d。结果表明:饲粮类型对育肥湖羊血清和肝脏的总超氧化物歧化酶、谷胱甘肽过氧化物酶、过氧化氢酶活性和丙二醛含量以及总抗氧化能力均无显著影响;与CK组相比,TMR组育肥湖羊背最长肌中棕榈酸和总的饱和脂肪酸的比例分别降低了10.77%和9.18%(P<0.05),但CK与CP组差异不显著;TMR组油酸和总的单不饱和脂肪酸的比例较CK组分别升高了4.78%和4.71%(P<0.05),但CK与CP组差异不显著;与CK组相比,TMR组湖羊肌肉中异亮氨酸和必需氨基酸含量分别上升了10.34%和4.45%(P<0.05);TMR组非必需氨基酸和总氨基酸含量较CK组分别升高了2.33%和3.42%(P<0.05),但CK与CP组差异不显著。上述结果提示,与传统精粗饲粮相比,TMR可显著增加育肥湖羊肌肉中不饱和脂肪酸和必需氨基酸含量,降低饱和脂肪酸比例,改善肉品质,提升羊肉的营养食用价值。     

Canine inflammatory myopathies: a clinicopathologic review of 200 cases

A retrospective study was performed on 200 randomly selected cases of inflammatory myopathy in dogs from diagnostic muscle biopsies received at the Comparative Neuromuscular Laboratory, University of California, San Diego. The most common clinical signs in dogs diagnosed with an inflammatory myopathy were generalized weakness, stilted gait, dysphagia, masticatory or generalized muscle atrophy, inability to open the jaw, megaesophagus, and dysphonia. Myalgia was rarely described. Age of onset ranged from 0.25 to 14 years. Genders were equally represented. Breed distribution approximated the 2002 American Kennel Club registration statistics (r = .85) with the notable exception of Boxers and Newfoundlands. From the results of muscle biopsies, clinical signs, and presence or absence of antibodies against type 2M fibers, dogs were classified as a generalized inflammatory myopathy (gIM)--including immune-mediated polymyositis; infectious and preneoplastic myositis; and, rarely, dermatomyositislike or overlap syndromes or unclassified myositis-or a focal inflammatory myopathy (flM)--including masticatory muscle and extraocular myositis. Average creatine kinase (CK) and aspartate aminotransferase (AST) concentrations in gIMs were significantly higher than those with fIMs (P < .05). Neoplasia developed in 12 of 200 dogs within 12 months of diagnosis of polymyositis, with lymphoma diagnosed in 6 of 32 Boxers. Inflammatory myopathy was associated with antibody titers against infectious diseases in 38 dogs. Neospora caninum and Hepatozoon americanum cysts were found in tissues of 2 dogs not serologically tested. Antibodies against an unidentified sarcolemmal antigen were found in 9 of 19 Newfoundlands with polymyositis. The spectrum of canine inflammatory myopathies can be broad, with infectious etiologies relatively common, and can include preneoplastic and uncharacterized syndromes.