[Bronchodilator therapy in the prevention of COPD exacerbations]. / El tratamiento broncodilatador en la prevención de las exacerbaciones de la EPOC.

The natural course of chronic obstructive pulmonary disease usually includes exacerbations. chronic obstructive pulmonary disease patients suffer from 1-4 exacerbations per year on average. These are associated with worsening quality of life and increased mortality. Reducing and controlling the number of exacerbations is one of the main goals of chronic obstructive pulmonary disease treatment. Among current treatments, tiotropium is the active substance with the strongest evidence in the reduction of moderate/severe exacerbations, together with a good safety and tolerability profile. The addition of olodaterol to tiotropium offers well-tolerated and effective double bronchodilation for improving lung function, quality of life, and decreased dyspnoea compared to its single components. This also reduces the annual rate of moderate/severe exacerbations vs. tiotropium by 7%, although not reaching the pre-specified statistical significance level of P<.01.

Prevalence, risk factors and genetic parameters of cresty neck in Pura Raza Español horses.

REASONS FOR PERFORMING STUDY: Cresty neck is a relatively common morphological defect in Pura Raza Español horses and other Baroque type horse breeds, which adversely affects the breeding industry. OBJECTIVES: To establish the within-breed prevalence, possible associated factors and heritability of cresty neck in Pura Raza Español horses. STUDY DESIGN: Cross-sectional analysis of a large worldwide database of Pura Raza Español horses. METHODS: The database included evaluations of 10,929 Pura Raza Español horses from 24 countries. Cresty neck score, on a 9 point scale, girth-to-height ratio, height at the withers, length of neck, head-neck junction and neck-body junction were recorded. A Bayesian genetic animal model included the following systematic effects: girth-to-height ratio, age, sex, coat colour and geographical area of the stud. Animal and residual effects were included as random effects. RESULTS: Within this Pura Raza Español population, 8.91% had a cresty neck score ≥5, which is the threshold for penalty or disqualification in the studbook of the breed. The age, sex, coat colour and stud geographical area were significantly associated with cresty neck score. The estimated heritability coefficient for cresty neck score was 0.37 (s.d. = 0.034) and genetic correlation between cresty neck score and other conformational traits ranged from -0.06 (height-at-withers) to -0.21 (neck-body junction). CONCLUSIONS: Cresty neck is a prevalent defect in Pura Raza Español horses, associated with age, sex, coat colour and other conformational traits, with a moderate level of heritability. Breeding to select against this condition may therefore be beneficial in this breed.

[Reliability of a chronic obstructive pulmonary disease diagnosis register in Primary Care]. / Fiabilidad del registro del diagnóstico de la enfermedad pulmonar obstructiva crónica en Atención Primaria.

INTRODUCTION/OBJECTIVE: One of main limitations in studies of COPD in health databases could be the low quality of the information. Our first aim was evaluate reliability of the registry of COPD diagnosis register in Primary Care. A description and comparison is also presented of the characteristics of the patients according to the diagnostic confirmation. MATERIAL AND METHODS: A cross-sectional study using healthcare databases of Cantabria. A pre-selected sample of 1,457 patients was obtained in which COPD diagnosis was specifically registered. COPD confirmation was classified into confirmed COPD, not confirmed-not rejected COPD, and diagnostic error (over-diagnosis). Descriptive and clinical characteristics, comorbidities, and treatments were collected in each group. RESULTS: COPD was confirmed in 766 patients: 52.6% (95%CI: 49.9-55.2). Prevalence of over-diagnosis was 7.2% (95%CI: 5.9-8.6). There were statistically significant gender differences. In the COPD confirmed group age, tobacco consumption and severity according to FEV1 was higher. An average of 1.95 bronchial exacerbations during the last 4years was observed among diagnostic errors. Inhaled corticosteroids were prescribed in 74.9% of COPD confirmed patients, and in 41.9% of over-diagnosed patients. CONCLUSIONS: The reliability of the COPD register was deficient, with only 52.6% with a confirmed diagnosis. Stable treatment for COPD was prescribed in all groups, highlighting the use of inhaled corticosteroids.

Eosinophilic Enteritis in Horses with Motor Neuron Disease.

BACKGROUND: Equine motor neuron disease (EMND) is a neuromuscular disorder that affects adult horses. Although EMND has been linked to vitamin E deficiency, its etiopathogenesis is poorly understood. OBJECTIVES: To describe clinical features, laboratory results, and postmortem findings in a series of young horses with motor neuron disease (MND). ANIMALS: A herd of 15 young Andalusian horses with weakness, weight loss, muscle atrophy, and muscle fasciculations related to restricted intake of green forage. METHODS: A case series is presented in which horses were subjected to a clinical examination and plasma vitamin E measurement. Five severely affected horses were euthanized for detailed postmortem examination. Muscle specimens were taken from the M. sacrocaudalis dorsalis medialis and the M. gluteus medius for histopathologic and morphometric evaluation. RESULTS: MND was diagnosed in 5 horses based on clinical signs, low serum levels of vitamin E (0.11 ± 0.05 mg/dL; normal range,: 0.3-1.5 mg/dL), changes in muscle histopathology (neurogenic atrophy), and spinal cord lesions (neuronal chromatolysis in ventral horns). An unexpected postmortem finding was the presence of intestinal inflammation (catarrhal enteritis, edema, and eosinophilic infiltrate) associated with the presence of giant ciliated protozoa in all of the horses. CONCLUSIONS: Although a mechanistic link could not be established, it is hypothesized that intestinal inflammation may have been involved in the decreased absorption of vitamin E, thus favoring the development of MND.

Intervención grupal del síndrome subacromial en atención primaria / A group intervention for shoulder impingement syndrome in primary care

Introducción. El aumento de consultas por dolor de hombro en los servicios de rehabilitación impone buscar alternativas eficientes para mejorar su manejo. Objetivos. Evaluar la efectividad de un programa de rehabilitación grupal para mejorar la funcionalidad y el dolor en pacientes afectos de síndrome subacromial y ver qué variables se asocian a un mejor resultado funcional final. Métodos. Estudio longitudinal prospectivo de intervención antes/después. Muestra: 211 pacientes. La intervención consistió en 10 sesiones de electroterapia analgésica individual, 5 sesiones de cinesiterapia grupal y una sesión informativa: «escuela de hombro». El seguimiento fue de un año. Medimos la funcionalidad con el test de Constant y el dolor con la escala visual analógica. Pruebas estadísticas: chi cuadrado, T-test, ANOVA y regresión lineal múltiple (p < 0,05). Resultados. La funcionalidad mejoró significativamente en los 4 períodos estudiados respecto al valor inicial y se estabilizó a los 6 meses. El perfil de paciente que obtuvo mayor funcionalidad fue: mujer, mayor de 60 años, sin dolor en reposo inicial y laboralmente no activa. La mejora del dolor observada a largo plazo no fue significativa. El consumo de analgésicos se redujo significativamente a los 3 meses. La adherencia al tratamiento domiciliario de ejercicios fue del 81% a los 3 y 6 meses y del 70,6% al año. Conclusiones. La aplicación de un programa de rehabilitación grupal en pacientes afectos de síndrome subacromial se ha mostrado efectivo para mejorar la funcionalidad a largo plazo. Sin embargo, el dolor no ha mostrado mejoría significativa a lo largo del estudio (AU)

Introduction. Due to the increase in consultations for shoulder pain in rehabilitation services, there is a need for efficient alternatives to improve the management of this disorder. Objectives. To evaluate the effectiveness of a supervised group exercise program to improve functionality and pain in patients with shoulder impingement syndrome and to identify the variables that are associated with a better functional outcome. Methods. A prospective longitudinal, pre and post intervention study was carried out in a sample of 211 patients. The treatment consisted of 10 individual sessions of analgesic electrotherapy, 5 sessions of group exercise therapy and an educational session: «shoulder school». One year follow-up was performed. Shoulder function and pain were assessed using Constant's test and the visual analogue scale. The statistical analysis was carried out with the chi-square test, T-test, ANOVA and multiple linear regression (P < .05). Results. Functionality improved significantly in all periods studied compared with baseline and stabilized at 6 months. The profile of patients who achieved greater functionality was female, older than 60 years, with no initial rest pain and occupationally inactive. Long-term pain improvement was not significant. Analgesic use was significantly reduced at 3 months. Adherence to home exercise treatment was 81% at 3 and 6 months and 70.6% at one year. Conclusions. The application of a group rehabilitation program in patients with shoulder impingement syndrome was effective in improving long-term functionality. However, there was no significant pain improvement during the study (AU)

Effect of different blood-guided conditioning programmes on skeletal muscle ultrastructure and histochemistry of sport horses.

The effects of three different blood-guided conditioning programmes on ultrastructural and histochemical features of the gluteus medius muscle of 2-year-old sport horses were examined. Six non-trained Haflinger horses performed three consecutive conditioning programmes of varying lactate-guided intensities [velocities eliciting blood lactate concentrations of 1.5 (v1.5 ), 2.5 (v2.5 ) and 4 (v4 ) mm respectively] and durations (25 and 45 min). Each conditioning programme lasted 6 weeks and was followed by a 5-week resting period. Pre-, post- and deconditioning muscle biopsies were analysed. Although training and detraining adaptations were similar in nature, they varied significantly in magnitude among the three different conditioning programmes. Overall, the adaptations consisted in significant increases in size of mitochondria and myofibrils, as well as a hypertrophy of myofibrillar ATPase type IIA muscle fibres and a reduction in number of type IIx low-oxidative fibres. Together, these changes are compatible with a significant improvement in both muscle aerobic capacity and muscle strength. The use of v1.5 and v2.5 as the exercise intensities for 45 min elicited more significant adaptations in muscle, whereas conditioning horses at v4 for 25 min evoked minimal changes. Most of these muscular adaptations returned towards the pre-conditioning status after 5 weeks of inactivity. It is concluded that exercises of low or moderate intensities (in the range between v1.5 and v2.5 ) and long duration (45 min) are more effective for improving muscle features associated with stamina and power in sport horses than exercises of higher intensity (equivalent to v4 ) and shorter duration (25 min).

Unexplained underperformance syndrome in sport horses: classification, potential causes and recognition.

When inadequate training stress is applied and recovery time is insufficient, performance reduction and chronic maladaptation occurs. Known as overtraining syndrome (OTS), this complex condition afflicts horses in top training. The name of the syndrome implies causation and it is necessary to differentiate it from over-reaching, a term used in horses that, after suffering a loss of performance without an obvious clinical reason, recover their performance within 1 or 2 weeks. The term OTS should be used for horses in heavy training losing performance without an obvious clinical reason and which is sustained for > 2 weeks. Despite considerable scientific investigations, the underlying mechanisms are still poorly understood and there are no objective biomarkers for OTS. An imbalance between training and recovery seems to be the primary cause of this dysfunction. However, other factors such as transport, feeding, subclinical disease and general management may play a role. There is now sufficient evidence that red cell hypervolaemia is not a mechanism for the OTS in horses. A dysfunction of the hypothalamo-pituitary-adrenocortical axis is momentarily the only mechanism that may be related to the development of this syndrome. In the absence of a scoring system to assess the psychological status of horses, the most effective method for diagnosis is the thorough assessment of the history and presenting complaint (length of unexplained performance deficit, weight loss despite adequate feed intake, concurrence of unspecific subclinical problems, unsuccessful treatments and changes of behaviour). Standardised exercise tests are suggested to provide a way to detect subtle changes in hormonal responses in the individual, which may make an important contribution to the detection of early overtraining. But further longitudinal studies are needed to clarify mechanism(s) underlying OTS and to establish the potential for the use of a physiological test as a predictive tool of this disorder.

A scientific background for skeletal muscle conditioning in equine practice.

The main goal of any conditioning programme in athletic horses is to improve performance by inducing physiological changes within the animal's body. Equine skeletal muscles have a considerable potential to adapt during training and these adaptations have important physiological implications that influence stamina, strength and speed. Although there is an extensive specialized literature in this regard, scientific based muscle conditioning methods have not been introduced sufficiently in the equine sport practice. After a brief synopsis of both equine muscle exercise physiology and muscular adaptations to training, including their physiological significance, this review focuses on specific training programmes that induce muscular adaptations in athletic horses. The article addresses the following principal question: what kind of stimuli for what kind of muscular adaptations? The experimental data are discussed separately for racehorses (thoroughbreds, trotters and endurance horses) and sport horses (dressage, show jumpers and carriage). Finally, published results about the influence of relevant training parameters (such as intensity, duration and type of exercise) on muscular responses are discussed, as well as those concerning overtraining and detraining. The article closes with some concluding remarks on importance of their application in practice.

Contribution of exercise intensity and duration to training-linked myosin transitions in thoroughbreds.

REASONS FOR PERFORMING STUDY: The influence of relevant exercise parameters such as intensity and duration of exercise on the muscular response to training has not been reported in Thoroughbreds. This knowledge may be of great value in practice. OBJECTIVE: To define the relative contribution of the intensity and duration of exercise on the myosin heavy chain (MHC) response to training in Thoroughbred racehorses. METHODS: Six 2-3-year-old Thoroughbreds, following a randomised 6 x 6 latin square design, performed 6 consecutive conditioning programmes of varying lactate-guided intensities and durations. Each programme lasted 22 days and consisted of 11 exercise sessions once a day, every second day on a 6% inclined treadmill followed by a 10 day resting period between consecutive programmes. Gluteus muscle biopsies (depth, 2 and 6 cm) were taken before, and after, each programme and electrophoretically analysed for MHCs. RESULTS: Overall, training increased the fraction of MHC IIA (mean +/- s.d., 41.1 +/- 3.5% to 43.4 +/- 4.42% P<0.001) and decreased that of MHC IIX isoform (from 50.2 +/- 4.4% to 47.4 +/- 5.6% P<0.001). Exercise intensity fixed effects on fast MHCs were highly significant (P<0.01), whereas exercise duration only had a marginal effect (P<0.1) on the IIA:IIX MHC ratio. On a per-individual basis, training impact on fast MHCs was only significant (P<0.05) in horses exercised for the longest duration at both intensities. CONCLUSION: The short-term training-induced up-regulation of MHC IIA and down-regulation of MHC IIX in Thoroughbreds are more dependent on intensity than duration of exercise. However, protocols with exercises of moderate intensity and long duration can induce MHC changes similar to those promoted by programmes with exercises of higher intensities. POTENTIAL RELEVANCE: Exercises for up to 25 min/day at velocities eliciting a blood lactate concentration between 2.5 and 4 mmol/l every second day for 3 weeks improve stamina in Thoroughbreds.

Oral L-carnitine combined with training promotes changes in skeletal muscle.

The purpose of this study was to determine whether oral L-carnitine supplementation enhances the responses of skeletal muscle to training in seven 2-year-old Standardbreds. Four horses were supplemented with 10 g/day L-carnitine for 10 weeks and 3 horses served as controls. All horses were exercised regularly every second day on a treadmill for 5 weeks (training period) and housed in individual boxes for 5 additional weeks (detraining period). The training period consisted of 8 high- and 8 low-speed exercises carried out in alternating sequence. Gluteus medius muscle biopsies were taken at Weeks 0 (pretraining), 5 (post-training) and 10 (detraining). Muscular adaptations to training were observed mainly in the L-carnitine-supplemented horses and included an increase in the percentage of type IIA fibres (delta35%, P<0.05), atrophy of type I fibres (delta24%, P<0.01), a rise in the capillary-to-fibre ratio (delta40%, P<0.01) and an increase in the quantitative reaction of periodic acid Schiff stain (delta11%, P<0.05), used as an indicator of intrafibre glycogen content. After detraining, most of these adaptations reverted towards the pretraining situation. Therefore, exogenous carnitine has an additive effect on muscular responses to training and this should be favourable to improve athletic performance. Nevertheless, further studies are necessary to show whether muscle carnitine content is a limiting factor for fatty acid oxidation.

Early evaluation of dressage ability in different breeds.

Dressage is one of the Olympic equestrian sports practiced in several countries using different horse breeds. Specific characteristics of the walk, trot and canter are required for dressage. It has been assumed that some of these traits could be selected for genetically and contribute to dressage performance. The purpose of this study was to compare the walk, trot and conformation characteristics in young horses of different breeds used for dressage. A total of 142 horses age 3 years were classified into 3 groups of breeds (German, French and Spanish saddle horses) and tested using the same procedure. The skeletal conformation measurements were made by image analysis. Gait variables of the walk and trot were measured by the accelerometric gait analysis system Equimetrix. Discriminant analysis could explain the variability between the groups by taking into account the walk (P<0.0003), trot (P<0.0001) and conformation variables (P<0.0001). Many gait and conformation variables were significantly different between the breeds. In summary, the German horses had gait characteristics more adapted for dressage competition, and the results of this group could be used as a reference for early evaluation in dressage. Purebred Spanish horses could be considered as a reference for collected gaits used for farm work and old academic dressage. The gait and conformation tests could be applied in a breeding or crossing plan to detect more accurately young horses with good dressage ability.

Effects of repeated biopsying on muscle tissue in horses.

The collection of muscle samples in horses to estimate their performance potential, adaptations to training and diagnosis of exertional myopathies is of increasing interest. This study was designed to examine whether repeated biopsying of the gluteus medius muscle at 7 week intervals alters morphology and muscle fibre variables in the sampling area. The gluteus had been biopsied 3 times previously, each biopsy separated by a 7 week interval. Seven weeks after the last biopsy, this study was initiated. Percutaneous needle biopsies were taken from left and right muscles at 2 depths (2 and 6 cm) and at 2 sites for each depth (22 and 25 cm from the tuber coxae) of 7 mature Thoroughbreds. The 22 cm site was located close (2 cm caudal) to an area of the muscle that had been biopsied previously. The 25 cm site was 5 cm apart from this area. A total of 52 samples were available for histology, electron microscopy and immunohistochemistry. The latter was used to study percentages, sizes and capillaries of muscle fibre types. Most muscle samples collected (75%) had normal morphology, but the remaining 25% showed signs of muscle repair. In some circumstances, they showed regenerative signs of complete muscle repair, while in others ineffective muscle repair (scar formation) was evident. Nevertheless, sufficient normal tissue was always available for measuring routine muscle variables. Samples collected 3 cm laterally apart showed large differences with regard to muscle fibre type variables examined. These results show that repeated muscle samples in intervals of 7 weeks do not have effects that would impair evaluation of muscle fibre variables for diagnosis of effectivity of conditioning programmes. Furthermore, they emphasise that the only way of keeping variations through sample collection technique small is to standardise all biopsying techniques accurately.

Polysaccharide storage myopathy in the M. longissimus lumborum of showjumpers and dressage horses with back pain.

This study was designed to investigate whether horses with clinical signs of back pain due to suspected soft tissue injuries were affected by polysaccharide storage myopathy (PSSM). Diagnosis of PSSM in muscle biopsies obtained from the M. longissimus lumborum of 5 showjumpers and 4 dressage horses with a history of back pain is reported. M. longissimus lumborum biopsies of these horses were characterised histopathologically and in 3/9 cases also by electron microscopy. Observations were compared with M. gluteus biopsies of the same horses, and with M. gluteus biopsies obtained from 6 Standardbreds with recurrent exertional rhabdomyolysis and from 6 healthy trotters. M. longissimus biopsies from horses with back pain showed pathognomonic signs of PSSM, i.e. high glycogen and/or abnormal complex amylase-resistant polysaccharide deposits. Similar features were found in M. gluteus biopsies of the same horses. Sections of horses with rhabdomyolysis had increased PAS stain when compared with healthy horses, but did not show amylase-resistant material. Qualitative observations were corroborated by quantitative histochemistry (optical densities) of sections stained with PAS and amylase PAS. This study demonstrated the presence of PSSM in the M. longissimus of showjumpers and dressage horses with back pain and indicates that epaxial muscle biopsy is an option in diagnosing back problems in horses when clinical examination and imaging techniques do not provide a precise diagnosis.

Effects of transcutaneous short-term electrical stimulation on M. vastus lateralis characteristics of healthy young men.

Fifteen healthy, untrained male subjects (mean age +/- SD, 22 +/- 5 years) were used to examine the plasticity of myosin heavy chain phenotype, size, oxidative capacity and capillarization of skeletal muscle fibre types with short-term electrical stimulation (ES). Ten subjects were electro-stimulated on both quadriceps muscles with a frequency of 45-60 Hz, with 12 s of stimulation followed by 8 s of recovery for a total of 30 min per day, 3 days per week for 6 weeks. The remaining five subjects served as controls. Two vastus lateralis muscle biopsy samples were removed from each subject before (week 0) and after (week 6) ES training. A standardized exercise test on a cycle ergometer was performed by each subject before and after the experimental period and several indicators of whole-body aerobic capacity were estimated. The so-called electromyographic threshold was also determined during the tests. Muscle biopsy samples were analysed by electrophoresis, immunohistochemistry and quantitative histochemistry. Myosin heavy chain (MHC) composition, muscle fibre type distribution, fibre areas, oxidative capacity and capillaries of each fibre type were estimated. Muscular changes with ES revealed an increase of fibres expressing MHC-IIA, and a decrease of fibres expressing MHC-IIX and MHC-I, as well as an increase of the oxidative capacity and mean number of capillaries of fast-twitch (type II) fibres with minimal muscle fibre hypertrophy. These adaptations seem related to a bi-directional transformation from both MHC isoforms I and IIX towards the MHC-IIA isoform. The aerobic performance and electromyographic variables at the whole-body level were not altered by ES. These results indicate that the particular short-term ES training protocol tested in the present study induces significant adaptations in histochemical and metabolic machineries of human skeletal muscle. The results also offer new perspectives for realistic applications of ES in various clinical situations and sport training.

Coordinated changes of kinematics and muscle fibre properties with prolonged endurance training.

The objective of this study was to investigate the relationship between kinematic variables and muscle characteristics by determining (1) if heavy endurance training alters these variables and (2) if such modifications occur in a coordinated manner. Fifteen Andalusian stallions age 41-45 months were used. Five horses were used as controls and 10 horses underwent a training programme based on aerobic exercise for 8 months. Intensity of exercise was adjusted individually for each horse according to a standardised exercise test. Stride kinematic characteristics at the trot were analysed by videography and gluteus medius muscle biopsies were removed before and after the experiment. Muscle samples were analysed immunohistochemically for fibre types and fibre sizes. After training, stride frequency increased (6%, P < 0.05), whereas stride duration and stance time of the stride decreased (6 and 10% respectively, P < 0.05 in both). The percentage of type IIA fibres increased (25%, P < 0.01), whereas the percentage of type IIX fibres decreased (80%, P < 0.001). Training had no significant effect on the percentage of types IIAX and I fibres. After training, mean lesser fibre diameters of types I and IIA fibres increased (13 and 10%, respectively; P < 0.05). These results suggest that prolonged endurance training alters kinematic and muscle fibre properties in a coordinated manner, reflecting a greater stability and more efficient propulsion associated with an increase in muscle fatigue resistance and strength. This adaptive response has an impact on athletic performance.

Co-ordinated expression of contractile and non-contractile features of control equine muscle fibre types characterised by immunostaining of myosin heavy chains.

Combined methodologies of immunohistochemistry, histochemistry and photometric image analysis were applied: (1) to characterise control equine skeletal muscle fibres according to their myosin heavy chain (MyHC) composition and (2) to determine on a fibre-to-fibre basis the correlation between contractile [i.e. MyHC(s), myofibrillar ATPase (mATPase) and sarco(endo)plasmic reticulum Ca(2+)-ATPase (SERCA) isoforms], metabolic [i.e. succinate dehydrogenase (SDH) and alpha-glycerophosphate dehydrogenase (GPD) activities, glycogen and phospholamban (PLB) contents], and morphological [i.e. cross-sectional area (CSA), capillary and nuclear densities] features of individual myofibres. An accurate delineation of MyHC-based fibre types was obtained with the immunohistochemical method developed. This protocol showed a high sensitivity and objectivity to delineate hybrid fibres with overwhelming dominance of one MyHC isoform and, furthermore, it allowed a semiquantitative delineation of fast hybrid fibres according to the predominant MyHC isoform expressed. The phenotypic differences in contractile, metabolic and morphological properties seen between fibre types were related to MyHC content. Slow fibres had the lowest mATPase activity (related to shortening velocity), the highest SDH activity (oxidative capacity), the lowest GPD activity (glycolytic metabolism) and glycogen content, the smallest CSA, the greatest capillary and nuclear densities, and expressed slow SERCA isoform and PLB, but not the fast SERCA isoform. The reverse pattern was true for pure IID/X fibres, and type IIA fibres had intermediate properties. Hybrid IIAD/X fibres had mean values intermediate to those of their respective pure phenotypes. Discrimination of fibres according to their MyHC content was possible on the basis of their contractile and non-contractile profiles. These intrafibre interdependencies suggest that, even when controlled by different mechanisms, myofibres of control horses exhibit a high degree of co-ordination in their physiological, biochemical and anatomical features.

Limb myosin heavy chain isoproteins and muscle fiber types in the adult goat (Capra hircus).

The primary focus of this study was the accurate classification of limb skeletal muscle fiber types in adult goats (Capra hircus) according to the myosin heavy chain (MHC) isoform they express. Combined methodologies of gel electrophoresis, immunoblotting, immunohistochemistry, myofibrillar ATPase (mATPase), and quantitative metabolic enzyme histochemistry of M. semitendinosus samples were developed. Three MHCs were identified and tentatively designated as types I, IIA, and IIX. Five fiber types were defined immunohistochemically according to their MHC content: I, I+IIA, IIA, IIAX, and IIX. The hybrid fast-twitch fibers (IIAX) totaled 21% of the fiber population analyzed. The three major pure fibers (I, IIA, and IIX) could be objectively separated upon the basis of their mATPase activities after acid and alkaline preincubations. The prominent number of hybrid fibers, however, could not be delineated with these mATPase methods. Metabolic and size properties of muscle fibers varied according to their MHC content, but overlapped the full range of muscle fiber phenotypes. These integrated data demonstrate that type II skeletal muscle fibers of small ruminants have been misclassified in previous studies. The immunohistochemical approach developed in the present study offers new prospects for muscle fiber typing in caprine experimental studies and meat production technologies.