Superficial digital flexor tendon lesions in racehorses as a sequela to muscle fatigue: a preliminary study

REASON FOR PERFORMING STUDY: Racing and training related lesions of the forelimb superficial digital flexor tendon are a common career ending injury to racehorses but aetiology and/or predisposing causes of the injury are not completely understood. OBJECTIVES: Although the injury takes place within the tendon, the lesion must be considered within the context of the function of the complete suspensory system of the distal limb, including the associated muscles. METHODS: Both muscle and tendon function were investigated in vivo using implanted strain gauges in 3 Thoroughbred horses walking, trotting and cantering on a motorised treadmill. These data were combined with assessments of muscle architecture and fibre composition to arrive at an overview of the contribution of each muscle-tendon unit during locomotion. RESULTS: The superficial digital flexor muscle has fatigue-resistant and high force production properties that allow its tendon to store and return elastic energy, predominantly at the trot. As running speed increases, deep digital flexor tendon force increases and it stabilises hyperextension of the fetlock, thus reinforcing the superficial digital flexor in limb load support. The deep digital flexor muscle has fast contracting properties that render it susceptible to fatigue. CONCLUSION: Based on these measurements and supporting evidence from the literature, it is proposed that overloading of the superficial digital flexor tendon results from fatigue of the synergistic, faster contracting deep digital flexor muscle. POTENTIAL RELEVANCE: Future research investigating distal limb system function as a whole should help refine clinical diagnostic procedures and exercise training approaches that will lead to more effective prevention and treatment of digital flexor tendon injuries in equine athletes.     

The proportions of muscle, bone and fat in two different types of dog

This study compares the proportions of muscle, bone and fat (obtained by gross dissection) in greyhounds--a breed selected for high speed running--and other dogs, both at maturity and during growth. In adults the proportion of muscle is significantly greater in the 'athletic' greyhound. The proportion of muscle decreases but not significantly with detraining. Adult greyhounds have less fat (even when detrained) than other dogs, but the skeleton provides a similar proportion of liveweight in both types of dog when adult. The greater growth rate of muscle in athletes explains the difference in adult proportions.     

Evaluation of jitter by stimulated single-fiber electromyography in normal dogs

Single-fiber electromyography (SFEMG), a technique used to investigate neuromuscular transmission, has been described previously in the pelvic limb of dogs. Because preferential involvement of isolated muscle groups can occur in disorders of neuromuscular transmission, SFEMG was done in the peroneus longus (PL), extensor carpi radialis (ECR), and orbicularis oculi (OO) muscles of 10 adult, clinically normal dogs. Jitter was calculated as the mean absolute value of the consecutive differences in latency of 50 single muscle fiber action potentials after stimulation of intramuscular nerve bundles at the level of the motor point in at least 20 muscle fibers per muscle. Bilateral recordings were performed in 3 dogs. Mean jitter values were determined for each muscle, and differences among muscle groups and among dogs were compared. The upper limits of mean consecutive difference (mean plus 3 standard deviations) for the PL, ECR, and OO muscles were 21.94, 22.53, and 23.39 micros, respectively, and the upper limit of mean consecutive difference for individual muscle fibers in the respective fiber pools was 28.62, 36.39, and 35.68 micros. Jitter values for the ECR and OO were significantly higher than the jitter value for the PL muscle (P < .05). Significant differences among muscles or dogs or between sides were not observed for the ECR. Significant differences among dogs were observed for OO jitter values and were attributed to extremely low jitter values in 1 dog. Significant differences were demonstrated between sides for the PL and were attributed to small sample size. Results of this study provide normative data that can be used in the application of the stimulated SFEMG technique to dogs with suspected disorders of neuromuscular transmission.     

The Ecological Distribution of Small Mammals on Bugala Island,Lake Victoria

In human subjects, large variations between individuals (up to 3-fold) exist in the capacity for endurance exercise performance. In a heterogeneous population, endurance performance is strongly related to whole body maximal oxygen uptake (VO₂ max). This is in part genotype dependent (?25%) but is adaptable with training. However, this relationship does not hold within a homogeneous group of well-trained runners. Other phySiOlogical characteristics must contribute to endurance performance and these may include specific advantageous skeletal muscle phenotypes. Muscle fibre type distribution is also heterogeneous, although less adaptable. In contrast, muscle oxidative enzyme capacity is highly adaptable with training. The genetic influences on these muscle characteristics have been indirectly investigated by comparing African endurance athletes, who dominate world-class events, to Caucasian endurance athletes. We have established that African runners have greater resistance to fatigue than Caucasians (p < 0.01) and 50% greater oxidative enzyme activity in vastus lateralis samples (p < 0.05), despite somewhat lower Type I fibre proportion. These differences were not inherently present in a group of sedentary Africans, suggesting that the genotypic influence on athletic performance may be a superior adaptation to training, rather than a baseline genetic effect. Combined physiological and genetic studies are likely to elucidate a polygenetic basis for superior endurance performance.     

Glomerular disease

Glomerular diseases are a leading cause of chronic kidney disease in dogs but seem to be less common in cats. Glomerular diseases are diverse, and a renal biopsy is needed to determine the specific glomerular disease that is present in any animal. Familial glomerulopathies occur in many breeds of dogs. However, most dogs with glomerular disease have acquired glomerular injury that is either immune-complex mediated or due to systemic factors, both of which are believed to be the result of a disease process elsewhere in the body (i.e., neoplastic, infectious, and noninfectious inflammatory disorders). A thorough clinical evaluation is indicated in all dogs suspected of having glomerular disease and should include an extensive evaluation for potential predisposing disorders. Nonspecific management of dogs with glomerular disease can be divided into 3 major categories: (1) treatment of potential predisposing disorders, (2) management of proteinuria, and (3) management of uremia and other complications of glomerular disease and chronic kidney disease. Specific management of specific glomerular diseases has not been fully studied in dogs. However, it may be reasonable to consider immunosuppressive therapy in dogs that have developed a form of glomerulonephritis secondary to a steroid-responsive disease (e.g., systemic lupus erythematosus) or have immune-mediated lesions that have been documented in renal biopsy specimens. Appropriate patient monitoring during therapy is important for maximizing patient care. The prognosis for dogs and cats with glomerular disease is variable and probably dependent on a combination of factors. The purpose of this article is to discuss the general diagnosis and management of dogs with glomerular disease.     

Muscular dystrophy in female dogs

The most common form of muscular dystrophy in dogs and humans is caused by mutations in the dystrophin gene. The dystrophin gene is located on the X chromosome, and, therefore, disease-causing mutations in dystrophin occur most often in males. Therefore, females with dystrophin deficiency or other forms of muscular dystrophy may be undiagnosed or misdiagnosed. Immunohistochemistry was used to analyze dystrophin and a number of other muscle proteins associated with muscular dystrophy in humans, including sarcoglycans and laminin alpha2, in muscle biopsy specimens from 5 female dogs with pathologic changes consistent with muscular dystrophy. The female dogs were presented with a variety of clinical signs including generalized weakness, muscle wasting, tremors, exercise intolerance, gait abnormalities, and limb deformity. Serum creatine kinase activity was variably high. One dog had no detectable dystrophin in the muscle; another was mosaic, with some fibers normal and others partly dystrophin-deficient. A 3rd dog had normal dystrophin but no detectable laminin alpha2. Two dogs could not be classified. This study demonstrates the occurrence of dystrophin- and laminin alpha2-associated muscular dystrophy and the difficulty in clinical diagnosis of these disorders in female dogs.     

Ultrasonographic evaluation of normal canine iliopsoas muscle

The aim of this study was to describe the normal ultrasonographic appearance of the iliopsoas muscle and related landmarks. Hind limbs of five dog cadavers with no history of lameness were evaluated. The origin and mid-body of the psoas major and the common insertion of the iliacus and psoas major on the lesser trochanter of the femur were identified and evaluated. New methylene blue was injected under ultrasonographic guidance at the three sites. Dissection was performed to confirm placement of the dye. The L3 origin, mid-body, and insertion of the muscle were identified in all dogs and were consistent in appearance and compatible with the general appearance of muscle and tendons. The L2 origin was consistently difficult to image. The same ultrasound technique was subsequently applied to four healthy dogs, and consistent images of the iliopsoas muscle and associated landmarks were obtained. In this study, the major structures of the iliopsoas could be identified and in all dogs had a similar appearance. Ultrasound is an important tool for the diagnosis of musculotendinous injury and may be useful for identification of ilipsoas injury as a cause of lameness in the dog.     

Mineral metabolism in dogs during training and work stress

The contents of basic mineral elements (Na, K, Mg, Ca, P, Cl) were investigated in service dogs during their long-term basic training; the dogs belonged to two age categories, and the influence of different work stress (sentry, tracker, watch dogs) on the changes in the contents of these elements was also studied. Great changes in the dynamics of individual elements were demonstrated during the long-term training, signalling the beginning of muscular insufficiency and fatigue in the course of training, as well as the onset of adaptation processes to the psychic and physical stress (Na, K, Mg). The increased contents of Ca and P at the beginning and during the intensive training with a risk of bone demineralization, indicate the beginning of osteopathy, disorders of muscular and nervous irritability and unbalanced feed rations. The satisfactory adaptation process with the stabilized internal environment in the sphere of minerals metabolism is documented in service dogs by the long-term and qualitatively different work stress. The results of our studies can be included into the tests of training and work stress in service dogs.     

Myotonia and disorders of altered muscle cell membrane excitability.

Altered excitability of the skeletal muscle membrane (sarcolemma) can result in clinical signs of muscle dysfunction. Hyperexcitability of the sarcolemma results in myotonia, and hypoexcitability results in paresis or paralysis. Our understanding of the physiologic and molecular bases of disorders of sarcolemmal excitability is rapidly increasing as techniques for evaluation are improved. This article reviews muscle excitability disorders in dogs and cats and their pathogenesis.     

The Growth of the Transverse Sectional Area (TSA) of M. Semitendinosus in the Dog and Horse and its Relation to Athletic Ability in the Two Species

The transverse sectional area (TSA) of m. semitendinosus grows at a greater rate than the 2/3 power of liveweight in both Greyhounds and Thoroughbreds (athletic animals) while it increases at a rate proportional to liveweight in other breeds of dogs and horses (non-athletes). Although the TSA of the muscle in the adult athletes of both species is greater than that of the less fortunate fellow specific members there is no significant difference in the TSA of the muscle between the perinates of the two types of animals within each species. Thoroughbred cross horses have TSA values similar to those of Thoroughbreds.     

Electrophoretic fractionation of creatine kinase isoenzymes and macroenzymes in clinically healthy dogs and cats and preliminary evaluation in central neurologic disease

Background: Information about the electrophoretic distribution of CK‐MM, CK‐MB, and CK‐BB, serum creatine kinase (CK) isoenzymes that are indicators of skeletal muscle, cardiac muscle, and brain lesions, respectively, and CK macroenzymes (macro‐CK1 and macro‐CK2) in dogs and cats with and without central neurologic disease is scant and equivocal. Objectives: The objectives of this study were to describe the electrophoretic distribution of CK isoenzymes and macroenzymes in healthy dogs and cats and to provide a preliminary assessment of the utility of CK enzymatic electrophoresis in dogs and cats with central neurologic disease. Methods: Electrophoretic separation of serum CK isoenzymes and macroenzymes was performed on freeze‐thawed serum samples from 20 healthy dogs and 3 dogs with central neurologic disease and from 14 healthy cats and 6 cats with neurologic feline infectious peritonitis (FIP). Electrophoretic separation was also performed on supernatants of homogenized brain, skeletal muscle, and cardiac muscle from both species, to assess the tissue distribution of isoenyzmes in dogs and cats. Results: CK‐MM was the predominant isoenzyme in the serum of healthy dogs and cats, followed by macro‐CK2 and CK‐BB in dogs and by both macroenzymes in cats. In dogs, CK‐MB was essentially absent from both serum and homogenized hearts. CK‐BB increased in dogs with neurologic disease. In cats, CK‐BB was essentially absent from serum, but was present in brain homogenates. Two of 6 cats with FIP had increased macro‐CK1 and increased CK‐BB activity. Conclusions: This study identified the electophoretic distribution of CK isoenzymes and macroenzymes of dogs and cats and provided encouraging data about the possible use of CK‐BB as a biomarker for canine neurologic disorders, but not for FIP.     

Prevalence of gastric lesions in racing Alaskan sled dogs

Human and equine athletes are reported to have a high prevalence of gastric disease, and anecdotal evidence suggests a similar phenomenon applies to racing sled dogs. To investigate the prevalence of gastric disease in racing sled dogs, we conducted 2 gastroscopy studies on dogs competing in the annual Iditarod Sled Dog Race. A pilot study of dogs that were either dropped from the 2000 Iditarod Sled Dog Race because of illness or that finished the race indicated that, approximately 5 days after competing, 10 of 28 dogs (35%) had endoscopic evidence of gastric ulceration, erosion, or hemorrhage. The next year, an endoscopic study of 73 dogs participating in the 2001 Iditarod race was performed in order to evaluate a larger population of dogs. Data from 70 of these dogs could be used; 34 (48.5%) had ulceration, erosion, gastric hemorrhage, or some combination of these findings. When this group of 70 dogs was compared retrospectively to a control group of 87 dogs presented to the Texas A&M University (TAMU) Veterinary Medical Teaching Hospital, the Iditarod sled dogs had a significantly higher prevalence (P = .049) of gastric lesions. These findings suggest that, similar to athletes of other species, elite canine athletes have an increased prevalence of gastric disease compared to the canine population at large.     

Characterization and mode of inheritance of a paroxysmal dyskinesia in Chinook dogs

Background: Paroxysmal dyskinesias are episodes of abnormal, involuntary movement or muscle tone, distinguished from seizures by the character of the episode and lack of seizure activity on ictal EEG. Hypothesis: Paroxysmal dyskinesia is an inherited, autosomal recessive disorder in Chinook dogs. Animals: Families of Chinook dogs with paroxysmal dyskinesia. Methods: Pedigrees and medical histories were reviewed for 299 Chinook dogs. A family of 51 dogs was used for analysis. Episodes were classified as seizures, paroxysmal dyskinesia, or unknown, and segregation analysis was performed. Results: Paroxysmal dyskinesia was identified in 16 of 51 dogs and characterized by an inability to stand or ambulate, head tremors, and involuntary flexion of 1 or multiple limbs, without autonomic signs or loss of consciousness. Episode duration varied from minutes to an hour. Inter‐ictal EEGs recorded on 2 dogs with dyskinesia were normal. Three dogs with dyskinesia also had generalized tonic‐clonic seizures. One of 51 dogs had episodes of undetermined type. Phenotype was unknown for 6 of 51 dogs, and 28 dogs were unaffected. Segregation was consistent with an autosomal recessive trait. Conclusions and Clinical Importance: This movement disorder is prevalent in the Chinook breed, and consistent with a partially penetrant autosomal recessive or polygenic trait. Insufficient evidence exists for definitive localization; episodes may be of basal nuclear origin, but atypical seizures and muscle membrane disorders remain possible etiologies. The generalized seizures may be a variant phenotype of the same mutation that results in dyskinesia, or the 2 syndromes may be independent.     

Effect of protein intake during training on biochemical and performance variables in sled dogs.

OBJECTIVE: To determine effects of protein intake on blood variables, plasma volume, and maximal oxygen uptake (VO2max) in sled dogs undergoing rigorous training. ANIMALS: 32 Alaskan sled dogs, between 2 and 6 years old. PROCEDURE: Dogs were assigned to 1 of 4 groups on the basis of age, sex, and ability. Isocaloric diets containing 18% (diet A), 23% (diet B), 29% (diet C), or 35% (diet D) of energy as protein were assigned randomly to each group and fed 1 month before and during a 12-week training period. Maximal oxygen uptake was measured at 0 (before training) and 12 weeks. Body weight, protein and energy intake, plasma volume, PCV, hemoglobin concentration, and serum biochemical variables were measured at 0, 8, and 12 weeks. RESULTS: Serum biochemical variables, PCV, and hemoglobin concentration remained within reference ranges for all dogs. Dogs fed diet A had a decrease in VO2max and a greater rate of soft tissue injury throughout training, compared with dogs fed the other diets. At 12 weeks, dogs fed diets C and D had greater serum sodium concentration and hemoglobin concentration than did dogs fed diet A. Dogs fed diet D also had more plasma volume at 12 weeks than did dogs of any other group. CONCLUSIONS AND CLINICAL RELEVANCE: Consumption of a diet with 18% dietary protein on an energy basis (3.0 g of protein/kg of body weight) is insufficient to meet the metabolic requirements of sled dogs in training. For intense interval work, a diet with 35% dietary protein as energy (6.0 g of protein/kg) may provide a performance advantage by promoting an increase in plasma volume.     

Myocardial damage in dogs affected by heartworm disease (Dirofilaria immitis): Immunohistochemical study of cardiac myoglobin and troponin I in naturally infected dogs

It has recently been reported that dogs affected by canine heartworm disease (Dirofilaria immitis) can show an increase in plasma levels of myoglobin and cardiac troponin I, two markers of muscle/myocardial injury. In order to determine if this increase is due to myocardial damage, the right ventricle of 24 naturally infected dogs was examined by routine histology and immunohistochemistry with anti-myoglobin and anti-cardiac troponin I antibodies. Microscopic lesions included necrosis and myocyte vacuolization, and were associated with loss of staining for one or both proteins. Results confirm that increased levels of myoglobin and cardiac troponin I are indicative of myocardial damage in dogs affected by heartworm disease.     

Isolation and measurement of carbonic anhydrase isoenzyme III in plasma, sera, and tissues of dogs

OBJECTIVE: To purify canine carbonic anhydrase isoenzyme III (CA-III) and determine plasma, serum, and tissue concentrations of CA-III in healthy dogs and dogs with experimentally induced muscle damage. ANIMALS: 121 healthy Beagles. PROCEDURE: Muscle was obtained from 2 Beagles after euthanasia, and CA-III was purified and characterized by use of column chromatography and electrophoresis, respectively. A CA-III-specific ELISA was developed to determine concentrations of CA-III in plasma of 116 dogs and tissues of 1 dog. Serum creatine kinase (CK) activity and CA-III concentration were also determined before and after induction of muscle damage by IM injection of 2 ml of 10% lidocaine to 2 dogs. RESULTS: Canine CA-III had a molecular weight of 28 kd and an isoelectric point of 8.2. Mean (+/- SD) concentration of CA-III in plasma of healthy dogs was 16.91 +/- 9.55 ng/ml. The highest tissue concentration of CA-III was detected in skeletal muscle. Serum concentration of CA-III increased and peaked within the first 2 to 3 hours after induction of muscle damage. The increase in CA-III concentration was more rapid than that of CK activity, and concentration reached its maximum and returned to baseline sooner than did CK activity. CONCLUSIONS AND CLINICAL RELEVANCE: The CA-III ELISA we developed was a sensitive method for determining CA-III concentrations in plasma, serum samples, and tissue specimens of dogs. Use of this ELISA requires only a small volume of serum and may enable the study of changes in CA isoenzyme concentrations associated with muscle disorders in dogs.     

Effect of Supplementation With Omega-3 Fatty Acids,Magnesium, and Zinc on Canine Behavioral Disorders: Results of a Pilot Study

Recent discoveries have shown that the chances of a dog developing a behavioral disorder may depend upon a number of factors including nutrition. The current pilot study was designed to provide an assessment of the efficacy of a dietary supplement containing omega-3 fatty acids, magnesium, and zinc on some common behavioral disorders in a population of Iranian domestic dogs. In total, 48 dogs including 6 dogs without any behavior disorder (control group) and 42 dogs with at least 1 common behavioral disorder, namely excessive activity, inappropriate elimination, fearfulness, destructiveness, and aggression toward unfamiliar people and dogs (test group), were given daily oral dose of gelatin capsules of fish oil supplements containing 330 mg eicosapentaenoic acid and 480 mg docosahexaenoic acid. Moreover, all dogs received 12-15 mg/kg of magnesium citrate and 5 mg/kg of zinc sulfate. Data were obtained using a questionnaire that dog owners were invited to fill out 2 times before (Days 0 and 42) and 2 times after the supplement treatment period (Days 84 and 126). The questionnaire asked owners whether their dog had exhibited any of the 6 common behavioral disorders on a 5-point Likert-like scale ranging from 0 (never or very rarely) to 4 (very often). The results showed no significant changes for any of the evaluated behavior disorders scale in the control group. In dogs with behavior disorders, results showed a significant reduction in the median score for the severity of fearfulness (P?=?.0083), destructiveness (P?=?.002), and inappropriate elimination (P < .001). In addition, there were no significant differences in the median score for the severity of excessive activity (P = .162), aggression toward dogs (P = .281), and aggression toward unfamiliar people (P = .09) during the course of the study. Results of the study reported here support the hypothesis that a combination of omega-3 fatty acids, magnesium, and zinc may improve some of the behavioral disorders.     

Characterization of an antibody panel for immunohistochemical analysis of canine muscle cells

Immunohistochemistry is an indispensable tool in the assessment and characterization of lineage-specific differentiation of grafted cells in cell-based-therapy. This strategy is under investigation for the treatment of many muscle disorders and different animals such as dogs are used as models to study the tissue regeneration. The aim of the present study was to characterize an antibody panel for the analysis of canine muscle cells, useful in routinely processed formalin-fixed paraffin-embedded tissues. Overall, 12 antibodies (8 mouse monoclonal and 4 goat polyclonal), validated for use on human tissues tested for cross-reactivity on canine smooth muscle (bladder, intestine, and uterus), skeletal muscle and heart. Specific staining was achieved with eight antibodies, of which six were cytoplasmic markers (desmin, HDAC8, MHC, SMA, Troponin I and Troponin T) and two were cardiac nuclear markers (GATA-4 and Nkx-2.5). This antibody panel may be useful not only for the evaluation of cell-based therapies in muscle disorders, but also for the evaluation of canine soft tissue neoplasms in veterinary pathology.     

Stretching Exercises for Horses: Are They Effective?

This article aims to present research in both animals and humans that support the use of stretching exercises in horses as a means of increasing range of motion, improving body flexibility and posture, and preventing injury by strengthening the supportive tissues. Too often veterinarians may overlook the importance of stretch exercises. This could partially be due to a lack of familiarity of what type of exercises to recommend, how to perform them, or where to obtain the desired information. Studies demonstrate the beneficial effects of stretching, warm-up, and temperature on the mechanical properties of muscle, potentially reducing the risk of strain injury to muscles. Evidence demonstrates that various approaches to conditioning that include warm-up and stretching along with other techniques such as strength training and proprioceptive training enhance performance and prevent certain types of injury. In addition, stretching of specific muscles and articulations for specific activities might enhance the effectiveness of these other pre-exercise activities, which is consistent with a multifactorial model for injury prevention. Stretches are either dynamic (having motion) or static (having no motion). Dynamic stretching involves moving parts of the body and gradually increasing reach, speed of movement, or both. It is controlled movement or swings that gently take the limb to the limits of range of motion. Static stretching consists of stretching a muscle (or group of muscles) to its farthest point and then maintaining or holding that position. Passive or relaxed and isometric stretching are both types of static stretches. Passive or relaxed is where a position is maintained by holding it with some other part of your body, or with the assistance of a partner or some other apparatus. This type of stretching is the most common type used with stretching exercises in horses as we control the motion and positioning desired. Slow, relaxed stretching is useful in relieving spasms in muscles that are healing after an injury. Relaxed stretching is also good for “cooling down” after a workout and helps reduce postworkout muscle fatigue and soreness. A case study and an example of a stretch exercise program and what to look for in a “how to” guide is also presented.