Muscle fiber types in horses refer to the classification of muscle fibers based on their metabolic and contractile properties. These fibers are categorized into different types, primarily type I (slow-twitch) and type II (fast-twitch), with type II further subdivided into type IIa and type IIb. Type I fibers are known for their endurance capabilities and rely on aerobic metabolism, whereas type II fibers are associated with strength and speed, utilizing anaerobic pathways. The distribution and proportion of these muscle fiber types can vary significantly among horse breeds and individuals, influencing their performance in various equestrian disciplines. This page compiles peer-reviewed research studies and scholarly articles that investigate the characteristics, distribution, and functional implications of muscle fiber types in equine physiology and performance.
McGowan C.Traumatic muscle injuries are likely to be frequent in athletic horses yet are often overlooked. These injuries usually involve internal (intrinsic) trauma, and particularly occur in athletic horses exercising at higher intensities, at unaccustomed workloads, or performing work requiring sudden acceleration, deceleration, and/or direction changes. These injuries can present with signs ranging from acute pain and lameness in a localized region to unexplained elevations of muscle enzymes on routine blood tests with or without poor performance. They include exercise-induced muscle damage such as ...
Finno CJ.In the field of equine muscle disorders, many conditions have a genetic basis. Therefore, genetic testing is an important part of the diagnostic evaluation. Validated genetic tests are currently available for 5 equine muscle disorders: hyperkalemic periodic paralysis, malignant hyperthermia, glycogen branching enzyme disease, type 1 polysaccharide storage myopathy, and myosin heavy chain myopathy. These diseases should be tested for in the appropriate breeds with clinical signs of disease or as part of breeding management. Genetic testing in veterinary medicine is not regulated, and therefore,...
Durward-Akhurst SA, Valberg SJ.Several inflammatory myopathies have an infectious or immune-mediated basis in the horse. Myosin heavy chain myopathy is caused by a codominant missense variant in MYH1 and has 3 clinical presentations: immune-mediated myositis, calciphylaxis, and nonexertional rhabdomyolysis in Quarter Horse-related breeds. An infarctive form of purpura hemorrhagica affects numerous breeds, presenting with focal firm, painful muscle swelling, and subsequent infarction of multiple tissues. While Streptococcus equi equi is often the inciting cause, anaplasmosis, sarcocystis, piroplasmosis, viruses, and vaccines...
Valberg SJ, Williams ZJ.Myofibrillar myopathy (MFM) is characterized by segmental disarray of myofibrils and ectopic accumulation of a protein called desmin. Previously thought to be a glycogen storage disease, MFM is now recognized as a stand-alone myopathy. Endurance Arabians with MFM usually present with exertional rhabdomyolysis (MFM-ER) at the end of races, elevated serum muscle enzymes, and myoglobinuria. Warmblood horses with MFM (MFM-WB) usually present with pain-associated behaviors such as exercise intolerance, reluctance to engage hind quarter muscles, shifting lameness and normal serum muscle enzymes. Bot...
Aleman M.Muscle disease has various clinical manifestations that range from exertional and non-exertional rhabdomyolysis, fasciculations, weakness, rigidity, stiffness, gait abnormalities, poor performance, and alterations in muscle mass and tone. Neurogenic disorders and non-neurogenic disorders such as primary muscle disease can cause muscle atrophy and changes in muscle tone. Myotonic disorders can have a genetic (eg, inherited channelopathies) or acquired (eg, electrolyte derangements) origin. Normal muscle enzyme activities do not rule out a myopathic disorder as the underlying cause of muscle atr...
Carvalho Serena G, Marchezan Piva M, Viezzer Bianchi M, Fernandes da Fonseca HC, Chitolina Pupin R, Martins Basso R, Secorun Borges A....In horses, systemic calcinosis is a rare syndrome characterised by muscle lesion associated with the mineralisation of large muscle groups or other organs, in the absence of an alternative cause for the calcification, such as toxic, enzootic or metabolic. Molecular and histopathological aspects of the disease are still poorly elucidated. Objective: To describe the epidemiological, pathological and molecular aspects of systemic calcinosis in a convenience sample of six horses submitted to necropsy in the Southern and Midwestern regions of Brazil. Methods: Retrospective exploratory study. Method...
Myćka G, Ropka-Molik K, Cywińska A, Stefaniuk-Szmukier M.Among numerous genes that have been a focus of equine genetic research, the (Klotho) and (Alpha-actinin-3) genes stand out due to their significant roles in muscle function and overall health, as well as performance ability. Previous studies on Arabian horses and other mammalians have shown that both and occur in different isoforms that seem to have different roles in metabolism. The main purpose of this present study was to describe different isoforms (, , , , , ) expression levels affected by the endurance effort in Arabian horses. Methods: Blood samples were taken from a group of = 10 ...
Valberg SJ, Porter A.Muscle biopsy is often required to provide a definitive diagnosis for neuromuscular disorders and can be performed using open surgical or percutaneous needle biopsy techniques. Fresh samples that are subsequently frozen in the laboratory are preferred by laboratories engaged in research, whereas formalin-fixed muscle is processed by diagnostic laboratories with specialized tinctorial and immunohistochemical techniques. Interpretation by an experienced histopathologist, combined with the signalment, history, and clinical input, is essential for establishing a diagnosis. This article outlines be...
Davis MS, Bayly WM, Hansen CM, Barrett MR, Blake CA.The intracellular environment of skeletal muscle can develop pronounced hyperthermia and acidosis during strenuous exercise, and these alterations in the typical intracellular conditions have been shown to alter mitochondrial respiration. However, the impact of these conditions on ATP synthesis is poorly understood. We used Thoroughbred racehorses to test the hypothesis that both hyperthermia and acidosis decrease the rate of ATP synthesis, but that athletic conditioning mitigates this loss of phosphorylation capacity. Isolated mitochondria were harvested from skeletal muscle before and after ...
Hepworth-Warren KL, Goldsmith D, Tsoi M, Gerras A, Noll C, Pinn-Woodcock T, Moreira A, Penttila K, Ballou ME, Dembek KA, Valberg SJ.To describe the clinical findings, outcomes, and muscle histopathology in warmblood horses that developed severe rhabdomyolysis in the perianesthetic period despite remaining stable while under general anesthesia. Methods: 7 warmblood horses, 6 geldings and 1 mare, with a median age of 9 years (range, 4 to 18 years) and median weight of 615 kg (range, 550 to 703 kg). Records from the Valberg Neuromuscular Diagnostic Laboratory and Michigan State University were reviewed (2016 to 2023) to identify warmbloods with postanesthetic myopathy (PAM). Methods: Warmblood horses with no history of myopat...
Pereira AT, Pozzobon R, Dos Anjos BL, Chaves LT, Smilgys ÉC, Thoma AJS, Lunkes VL, de Oliveira JS, de Andrade CM, Soares JCM.Criollo breed is quite popular in Brazil, mainly in the Southern Region, and the long loop rodeo is one of the main sports modality adapted to this breed. The purpose of this study was to assess changes in the muscle and oxidative functions caused by exercises practiced in this sports modality. Data such as exercising frequency, covered distance, mean duration time and number of runs, and blood samples at the following times: before the tournament, on the final day of the event, and 18-24 h after the end of the tournament were collected. Were assessed lactate and the enzymes aspartate aminotra...
Graham-Thiers PM, Bowen LK.Twelve horses weighing 570 ± 35 kg were split into two groups (standard protein, STD, and balanced protein, BAL) to evaluate the effect of balanced vs. unbalanced protein on muscle mass. Groups were fed grass hay and a 12% CP feed (one formulated for balanced protein). Horses were out of work for 14 wk prior and participated in 1 to 2 h of light-to-moderate exercise 5 d/wk for 12 wk. A 4-d total urine and feces collection period was conducted at the start and end of the study. Urine and feces samples were analyzed for nitrogen (N) to calculate N balance. Muscle mass status was evalua...
Takahashi K, Mukai K, Ebisuda Y, Sugiyama F, Yoshida T, Hatta H, Kitaoka Y.Evidence suggests that positive pacing strategy improves exercise performance and fatigue tolerance in athletic events lasting 1-5 min. This study investigated muscle metabolic responses to positive and negative pacing strategies in Thoroughbred horses. Eight Thoroughbred horses performed 2 min treadmill running using positive (1 min at 110% maximal O uptake [V̇Omax], followed by 1 min at 90% V̇Omax) and negative (1 min at 90% V̇Omax, followed by 1 min at 110% V̇Omax) pacing strategies. The arterial-mixed venous O difference did not significantly differ between the two strategies. Pl...
Wolschrijn CF, Smit IH, Schouten J, Moller Te NCR.Facial expressions are important in pain recognition in horses, but current observation-based pain scales remain subjective. A promising technique to quantitatively measure subtle changes in expression patterns, including changes invisible to the human eye, is surface electromyography (sEMG). To achieve high-quality and reliable sEMG signals, unilateral placement of bipolar electrodes is required in relation to the motor endplates (MEP). We aimed to localize the nerve entry points (NEPs; where the nerve branch first pierced the muscle belly) and the direction of the terminal nerve endings to e...
Ding W, Gong W, Liu H, Hu H, Shi L, Ren X, Cao Y, Zhang A, Shi X, Li Z, Bou T, Dugarjaviin M, Bai D.The growth and development of myofibers, as the fundamental units comprising muscle tissue, and their composition type are indeed among the most crucial factors influencing skeletal muscle types. Muscle fiber adaptation is closely associated with alterations in physiological conditions. Muscle fiber types undergo dynamic changes in fetus and adult horses. Our aim is to investigate the mechanisms influencing the differences in muscle fiber types between fetal and adult stages of Mongolian horses. The study investigated the distribution of muscle fiber types within longissimus dorsi muscle of fe...
Wang J, Ren W, Sun Z, Han Z, Zeng Y, Meng J, Yao X.This study conducted a thorough analysis of the myofiber type composition in the extensor digitorum longus muscle (EDL) and soleus muscle (SOL) of Kazakh horses, across different genders (male and female). The results showed significant differences in myofiber type composition between EDL and SOL, with a higher proportion of Type I fibers in SOL muscles and a greater prevalence of Type II fibers in EDL muscles. Additionally, the myofiber diameter in Kazakh horses was relatively small, potentially related to the tenderness and edible quality of their muscles. Using high-throughput sequencing te...
Takahashi Y, Takahashi T, Mukai K, Ebisuda Y, Ohmura H.Understanding how muscle activity changes with different surface grades during canter is essential for developing training protocols in Thoroughbreds because canter is their primary gait in training and races. We measured the spatiotemporal parameters and the activation of 12 surface muscles in the leading limb side of 7 Thoroughbreds. Horses were equipped with hoof strain gauges and cantered at 10 m/s on a treadmill set to grades of -4%, 0%, 4%, and 8%, randomly, for 30 seconds each without a lead change. Integrated electromyography (iEMG) values during stance and swing phases were calculated...
Argüelles D, Saitua A, Miraz R, Calle-González N, Requena F, Nocera I, Vitale V, Sgorbini M, Muñoz A.It has been reported that capacitive resistive electric transfer (CRET) increases blood circulation, hemoglobin oxygenation and temperature in muscles. The attributed benefits of these changes have been linked to improved athletic performance, enhanced muscle flexibility and fastening recovery from exercise-induced fatigue. For all of this, the present research aims to investigate whether the application of CRET 24 h before exercise affects the accelerometric pattern in horses during exercise. Six sound Standardbred trotters were subjected to a CRET session of 40 min of duration, applied on ...
Oliveira BE, Canola PA.Ultrasonographic imaging of the diaphragm is a non-invasive alternative for respiratory function evaluation in horses. This study aimed to measure diaphragm thickness, thickening (change in thickness with contraction) and thickening fraction in healthy adult horses during tidal breathing and forced vital capacity. Correlation between body weight (≤400 kg and >400 kg) and diaphragm thickness was investigated. To that purpose, 20 adult horses, weight 409±50 kg, height 1.47±0.05 m, and age 16±6 years were included in the study. Diaphragm thickness was measured at end-inspiration and end-e...
Sponseller B, Evans T.Boxelder and sycamore maple contain hypoglycin A (HGA), the toxic metabolite of which, MCPA-CoA, inhibits fatty acid β-oxidation, causing seasonal pasture myopathy (SPM) or atypical myopathy (AM), respectively. White snakeroot and rayless goldenrod contain multiple benzofuran ketones (BFKs). The identity/toxicity of BFKs appear variable, possibly involving interactions between toxins/toxic metabolites, but ultimately inhibit cellular energy metabolism. Unthrifty horses grazing sparse pastures during the fall appear predisposed to these plant-associated, frequently fatal, toxic myopathies. Tox...
Xing J, Xie L, Qi X, Liu G, Akhtar MF, Li X, Bou G, Bai D, Zhao Y, Dugarjaviin M, Zhang X.The proliferation and differentiation of skeletal muscle satellite cells (SCs) are necessary for the development of mature skeletal muscle. Leucine (Leu) is both an essential amino acid (EAA) and a branched-chain amino acid (BCAA), which has attracted worldwide attention due to its ability to repair and become new fibers. We separated the equine SCs into the control group (CON) and the Leu-supplemented group (LEU), which the cells were cultured in Leu-deprived and Leu-supplemented media respectively. We combined the transcriptome (RNA-Seq) and quantitative proteome (TMT) profiling analyses on ...
Bou T, Ding W, Ren X, Liu H, Gong W, Jia Z, Zhang X, Dugarjaviin M, Bai D.Traditional Mongolian endurance training is an effective way to improve the athletic ability of the horse for endurance events and is widely used. This incorporates aerobic exercise and intermittent fasting and these altered physiologic conditions are associated with switches between muscle fibre types. Objective: To better understand the adaption of horse skeletal muscle to traditional Mongolian endurance training from muscle fibre characteristics and transcriptional levels and to explore possible molecular mechanisms associated with the endurance performance of horses. Methods: Before-after ...
Lean NE, Franklin SH, Steel C, Woolford L, White J, Ahern BJ.Little is known about potential differences in the left recurrent laryngeal nerve (Lrln) and left cricoarytenoideus dorsalis (LCAD) muscle between domestic and feral horse populations. If a difference exists, feral horses may provide a useful control population for research related to recurrent laryngeal neuropathy (RLN) and increase our understanding of potential population pressures influencing the incidence RLN. The objective of this study was to compare the Lrln and LCAD of domestic and feral horses using histological and immunohistochemical techniques (IHC). Sixteen horses, domestic (n = ...
Valberg SJ, Velez-Irizarry D, Williams ZJ, Pagan JD, Mesquita V, Waldridge B, Maresca-Fichter H.Horses have a slow rate of muscle glycogen repletion relative to other species for unknown reasons. Our aim was to determine the expression of glucose transporters () and genes impacting GLUT4 expression and translocation in the gluteal muscle. Five fit Thoroughbred horses performed glycogen-depleting exercises on high-starch (HS, 2869 g starch/day) and low-starch, high-fat diets (LS-HF, 358 g starch/d) with gluteal muscle biopsies obtained before and after depletion and during repletion. Muscle glycogen declined by ≈30% on both diets with little increase during repletion on LS-HF. Transcrip...
Kis J, Rózsa L, Husvéth F, Mezőszentgyörgyi D, Kovács S, Bakos Z, Zsolnai A, Anton I.The g.66493737C/T polymorphism of the myostatin gene (MSTN) majorly influences muscle fiber composition and best race distance of Thoroughbreds. Thus, a better understanding of this process may lead to superior genetic exploitation for maximizing Thoroughbred athletic potential. Our objective is to investigate whether myostatin genotypes are associated with muscular development and cardiac variables of Thoroughbreds. Echocardiography and muscular ultrasonography were performed on three groups having C/C, C/T, and T/T genotypes, respectively. Each group consisted of 22 animals. Homogeneity of v...
Bou T, Ding W, Liu H, Gong W, Jia Z, Dugarjaviin M, Bai D.The proportion of different muscle fibers is essential for the horse breed's aptitude for athletic activities. Adaptation of locomotor muscle is correlated with altered physiologic conditions. To investigate the adaptive changes of muscle fiber phenotype and transcriptome in horse skeletal muscle during dietary restriction (DR). The muscle fiber type distribution and deep RNA-seq analysis of detecting differentially expressed mRNAs (DEGs), miRNA (DEMIRs), lncRNAs (DELs), circRNAs (DECs), and their function analysis were investigated in gluteus medius muscle of Mongolian horses during DR. A tot...
Kent E, Coleman S, Bruemmer J, Casagrande RR, Levihn C, Romo G, Herkelman K, Hess T.Antioxidant supplementation decreases postexercise oxidative stress but could also decrease muscle protein synthesis. This study compared the effects of three diets: low antioxidant (control, CON), high antioxidant (AO), and branched-chain amino acid high antioxidant (BCAO) supplementation on postexercise protein synthesis and oxidative stress. We hypothesized that supplementing antioxidants with branched-chain amino acids(BCAA) would reduce oxidative stress without hindering muscle protein synthesis. Eighteen mixed-breed polo horses (11 mares and 7 geldings, with age range between 5 and 18 ye...
Rooney MF, Neto NGB, Monaghan MG, Hill EW, Porter RK.Thoroughbred racehorse performance is largely influenced by a major quantitative trait locus at the () gene which determines aptitude for certain race distances due to a promoter region insertion mutation influencing functional phenotypes in skeletal muscle. To develop an system for functional experiments we established three novel equine skeletal muscle cell lines reflecting the variation in phenotype associated with genotype (CC/II, CT/IN and TT/NN for SNP g.66493737C > T/SINE insertion 227 bp polymorphism). Primary equine skeletal muscle myoblasts, isolated from Thoroughbred horse , we...
Valberg SJ, Iglewski H, Henry ML, Schultz AE, McKenzie EC.Selective breeding and discipline specific training has led to equine breeds adept at various athletic disciplines. Breed-specific skeletal muscle adaptations have been studied in many breeds but not Warmbloods (WB). We evaluated gluteal muscle contractile muscle fiber types and citrate synthase activity (CS), a marker for mitochondrial volume density, in WB trained for dressage (second level-Grand Prix) contrasted with Quarter Horses (QH). Gluteus medius muscle biopsies from 14 unfit/18 fit dressage-trained WB and 20 unfit/16 fit reining/working cow QH were analyzed fluorometrically and fiber...
Campos Schweitzer A, Mespoulhès-Rivière C, Möller D, Ducharme N, Genton M, Farfan M, Rossignol F.Selective laryngeal reinnervation using the first and second cervical nerve (C1C2) is a treatment option for recurrent laryngeal neuropathy that aims to restore the function of the cricoarytenoideus dorsalis (CAD) muscle. Despite the technique's satisfying success rate, it has several limitations. These triggered the search for another potential donor nerve that could reduce CAD muscle fatigue and shorten rehabilitation. The ventral branch of the spinal accessory nerve, providing motor innervation to the sternomandibularis (SM) muscle, was identified as a potentially well-adapted nerve. Object...
Li C, White SH, Warren LK, Wohlgemuth SE.Skeletal muscle function, aerobic capacity, and mitochondrial (Mt) function have been found to decline with age in humans and rodents. However, not much is known about age-related changes in Mt function in equine skeletal muscle. Here, we compared fiber-type composition and Mt function in gluteus medius and triceps brachii muscle between young (age 1.8 ± 0.1 yr, n = 24) and aged (age 17-25 yr, n = 10) American Quarter Horses. The percentage of myosin heavy chain (MHC) IIX was lower in aged compared with young muscles (gluteus, P = 0.092; triceps, P = 0.012), while the percentages of MHC I (gl...
Serrano AL, Petrie JL, Rivero JL, Hermanson JW.To date, four different myosin heavy chain (MyHC) isoforms have been identified in adult skeletal muscle of a number of species: types I, IIa, IIx or IId, and IIb. The aim of this study was to investigate the distribution of various MyHC isoforms in the equine gluteus medius and gluteus profundus muscles in relation with several morphometric variables of muscle fibers. Methods: Samples from different depths of the gluteus medius muscle (2, 4, 6, and 8 cm) and gluteus profundus muscle of five sedentary horses were examined by MyHC gel electrophoresis, monoclonal antibodies staining against fast...
Rooney MF, Porter RK, Katz LM, Hill EW.Variation in the myostatin (MSTN) gene has been reported to be associated with race distance, body composition and skeletal muscle fibre composition in the horse. The aim of the present study was to test the hypothesis that MSTN variation influences mitochondrial phenotypes in equine skeletal muscle. Mitochondrial abundance and skeletal muscle fibre types were measured in whole muscle biopsies from the gluteus medius of n = 82 untrained (21 ± 3 months) Thoroughbred horses. Skeletal muscle fibre type proportions were significantly (p < 0.01) different among the three MSTN genotypes and mito...
Watson JC, Wilson AM.Three muscles from the proximal equine forelimb were dissected in order to investigate their potential to contribute to proximal limb mechanics. Muscle mass, fibre length, tendon mass and tendon length were measured from biceps brachii, triceps brachii, supraspinatus and lacertus fibrosus (biceps lateral head mass 171-343.4 g and fibre length 0.5-0.8 cm; biceps medial head mass 283-500 g and fibre length 2.2-4 cm; biceps tendon mass 121.8-260 g and tendon length 35-44 cm; triceps long head mass 3200-6663 g and fibre length 19-26.3 cm; triceps lateral head mass 513.8-1240 g and fibre length 17....
Kawai M, Aida H, Hiraga A, Miyata H.Although satellite cells are well known as muscle stem cells capable of adding myonuclei during muscle repair and hypertrophy, the response of satellite cells in horse muscles to a run to exhaustion is still unknown. Objective: To investigate the time course of satellite cell activation in Thoroughbred horse muscle after running to exhaustion. We hypothesised that this type of intense exercise would induce satellite cell activation in skeletal muscle similar to a resistance exercise. Methods: Nine de-trained Thoroughbred horses (6 geldings and 3 mares) aged 3-6 years were studied. Biopsy sampl...
Barrey E, Mucher E, Jeansoule N, Larcher T, Guigand L, Herszberg B, Chaffaux S, Guérin G, Mata X, Benech P, Canale M, Alibert O, Maltere P, Gidrol X.Several cases of myopathies have been observed in the horse Norman Cob breed. Muscle histology examinations revealed that some families suffer from a polysaccharide storage myopathy (PSSM). It is assumed that a gene expression signature related to PSSM should be observed at the transcriptional level because the glycogen storage disease could also be linked to other dysfunctions in gene regulation. Thus, the functional genomic approach could be conducted in order to provide new knowledge about the metabolic disorders related to PSSM. We propose exploring the PSSM muscle fiber metabolic disorder...
Williams TM, Dobson GP, Mathieu-Costello O, Morsbach D, Worley MB, Phillips JA.To establish a skeletal muscle profile for elite sprinters, we obtained muscle biopsy samples from the vastus lateralis, gastrocnemius and soleus of African cheetahs (Acinonyx jubatus). Muscle ultrastructure was characterized by the fiber type composition and mitochondrial volume density of each sample. Maximum enzyme activity, myoglobin content and mixed fiber metabolite content were used to assess the major biochemical pathways. The results demonstrate a preponderance of fast-twitch fibers in the locomotor muscles of cheetahs; 83% of the total number of fibers examined in the vastus laterali...
Gunn HM.Histochemical profiles of individual muscle fibres were established using myosin adenosine triphosphatase (myosin ATPase), succinate dehydrogenase (SDHase), and glycogen phosphorylase (GPase) reactions in three muscles (semitendinosus, diaphragm, and pectoralis transversus) of the horse and dog. The major histochemical difference between fibres lies in their myosin ATPase activity; fibres can be subdivided into those with a high and those with a low activity. In horse muscle, all fibres have a high activity of GPase. In the diaphragm and pectoralis transversus, all fibres have a high SDHase ac...
McCutcheon LJ, Geor RJ, Hinchcliff KW.The effect of warm-up exercise on energy metabolism and muscle glycogenolysis during sprint exercise (Spr) was examined in six fit Standardbred horses exercised at 115% of maximal O(2) consumption (VO(2 max)) until fatigued, 5 min after each of three protocols: 1) no warm-up (NWU); 2) 10 min at 50% of VO(2 max) [low-intensity warm-up (LWU)]; and 3) 7 min at 50% VO(2 max) followed by 45-s intervals at 80, 90, and 100% VO(2 max) [high-intensity warm-up (HWU)]. Warm-up increased (P < 0.0001) muscle temperature (T(m)) at the onset of Spr in LWU (38.3 +/- 0.2 degrees C) and HWU (40.0 +/- 0. 3 de...
Tulloch LK, Perkins JD, Piercy RJ.Skeletal muscle is composed of a heterogeneous mixture of several fibre types, each with specific physiological properties. In equine muscle, identification of these individual fibres (fibre typing) is important for both exercise physiology and pathological studies. Traditionally, fibre typing has been achieved by adenosine triphosphatase (ATPase) histochemistry or by immunoperoxidase labelling with antibodies directed at myosin heavy chain isoforms. ATPase histochemistry can be temperamental and lacks specificity, and both techniques require staining of serial cryosections to reveal the entir...
Srikanth K, Kim NY, Park W, Kim JM, Kim KD, Lee KT, Son JH, Chai HH, Choi JW, Jang GW, Kim H, Ryu YC, Nam JW, Park JE, Kim JM, Lim D.The Jeju horse, indigenous to the Jeju Island in Korea may have originated from Mongolian horses. Adaptations to the local harsh environment have conferred Jeju horse with unique traits such as small-sized body, stocky head, and shorter limbs. These characteristics have not been studied previously at the genomic level. Therefore, we sequenced and compared the genome of 41 horses belonging to 6 breeds. We identified numerous breed-specific non-synonymous SNPs and loss-of-function mutants. Demographic and admixture analyses showed that, though Jeju horse is genetically the closest to the Mongol...
Bao T, Han H, Li B, Zhao Y, Bou G, Zhang X, Du M, Zhao R, Mongke T, Laxima , Ding W, Jia Z, Dugarjaviin M, Bai D.Skeletal muscle is the largest organ system in the mammalian body and plays a key role in locomotion of horses. Fast and slow muscle fibers have different abilities and functions to adapt to exercises. To investigate the RNA and miRNA expression profiles in the muscles with different muscle fiber compositions on Mongolian horses. We examined the muscle fiber type population and produced deep RNA sequencing for different parts of skeletal muscles. And chose two of them with the highest difference in fast and slow muscle fiber population (splenius and gluteus medius) for comparing the gene expre...
Essén-Gustavsson B, Lindholm A.Muscle biopsies were taken from the middle gluteus muscle of 36 Standardbred horses. Twelve of the horses were inactive, while 24 were actively trained and raced. Twelve of the trained horses were moderate performers, with a mean racing time of 1 min 21 secs per km (741 m/min) and the other 12 were excellent performers, with a mean racing time of 1 min 16 secs per km (789 m/min). The percentage and mean area of Type I fibres were similar in all three groups of horses. Marked differences were found among the subgroups of Type II fibres. The well-trained horses had a higher proportion of Type II...
McCutcheon LJ, Byrd SK, Hodgson DR.Thoroughbred horses were exercised to fatigue at 40, 85, and 100% of their maximal oxygen consumption (VO2max) on a treadmill and completed a 1,600-m gallop on a track to identify the effect of exercise of various durations and intensities on the ultrastructure of mitochondria and sarcoplasmic reticulum (SR) from the middle gluteal muscle. The percentage of the total area occupied by mitochondria and SR increased in electron micrographs of muscle samples collected at the termination of exercise and at 30 and 60 min of recovery compared with those collected before exercise. Mitochondrial area i...
Sung SE, Hwang M, Kim AY, Lee EM, Lee EJ, Hwang SK, Kim SY, Kim HK, Jeong KS.Mesenchymal stem cells could potentially be used in the clinical treatment of muscle disorders and muscle regeneration. Adipose-derived stem cells (ADSCs) can be easily isolated from adipose tissue, as opposed to stem cells of other tissues. We believe that cell therapy using ADSCs could be applied to muscle disorders in horses and other species. We sought to improve the myogenic differentiation potential of equine ADSCs (eqADSCs) using a MyoD lentiviral vector. MyoD lentiviruses were transduced into eqADSCs and selected using puromycin. Cells were cultured in differentiation media containing ...
Guy PS, Snow DH.1. Percutaneous needle biopsies were obtained from six limb muscles in six horses before and during a training programme of 10 or 15 weeks designed to involve both aerobic and anaerobic work. In a subsequent detraining period, biopsies were also taken after 5 and 10 weeks. 2. Samples were analysed biochemically for enzyme activity of lactic dehydrogenase (LDH), creatine phosphokinase (CPK), aldolase (ALD), citrate synthase (CS), aspartate aminotransferase (AST), and alanine aminotransferase (ALT) and for glycogen content. Fibre typing was carried out histochemically before and 10 weeks after c...
Valberg SJ, Cardinet GH, Carlson GP, DiMauro S.A polysaccharide storage myopathy is described in nine Quarterhorses, Quarterhorse crossbreds, American Paints and Appaloosa horses which had a history of recurrent exertional rhabdomyolysis. Muscle biopsies were characterized by high muscle glycogen concentrations with up to 5% of type 2 muscle fibers containing inclusions which stained positively with the periodic acid Schiff (PAS) stain. The inclusions were classified as an acid mucopolysaccharide, based on their histochemical staining characteristics. Ultrastructural studies revealed that the inclusions were composed of beta glycogen parti...
Finno CJ, Gianino G, Perumbakkam S, Williams ZJ, Bordbari MH, Gardner KL, Burns E, Peng S, Durward-Akhurst SA, Valberg SJ.The cause of immune-mediated myositis (IMM), characterized by recurrent, rapid-onset muscle atrophy in Quarter Horses (QH), is unknown. The histopathologic hallmark of IMM is lymphocytic infiltration of myofibers. The purpose of this study was to identify putative functional variants associated with equine IMM. A genome-wide association (GWA) study was performed on 36 IMM QHs and 54 breed matched unaffected QHs from the same environment using the Equine SNP50 and SNP70 genotyping arrays. A mixed model analysis identified nine SNPs within a ~ 2.87 Mb region on chr11 that were significantly (...
Rivero JL, Talmadge RJ, Edgerton VR.The aim of this study was to characterize the myosin heavy chain (MyHC) isoforms present in equine skeletal muscle. Methods: Muscle biopsies were removed from the superficial region of the gluteus medius muscle of five mature horses and analyzed by immunohistochemistry (using a battery of monoclonal antibodies specific for rat MyHC isoforms) and sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Results: Immunohistochemistry allowed subdivision of three different muscle fiber populations containing a single MyHC, one slow and two fast, and two hybrid populations, one containing slow an...
Eto D, Yamano S, Mukai K, Sugiura T, Nasu T, Tokuriki M, Miyata H.We hypothesize that high intensity training for Thoroughbred horses that have been subjected to conventional training could further improve the metabolic properties of the middle gluteal muscle. Nine well-trained horses were subjected to high intensity (80-100% Vdot;O(2)max, 5 minx2) training for 12 weeks. Biopsy samples were obtained from the muscle before and after 4 and 12 weeks of training. Three of the 9 horses did not complete the training programme. In the remaining 6 horses, activities of succinic dehydrogenase (SDH), phosphofructokinase (PFK) and 3-hydroxy acyl CoA dehydrogenase (HAD)...
Kayar SR, Hoppeler H, Lindstedt SL, Claassen H, Jones JH, Essen-Gustavsson B, Taylor CR.The relationship between maximal oxygen consumption rate (VO2max) and mitochondrial content of skeletal muscles was examined in horses and steers (n = 3 each). Samples of the heart left ventricle, diaphragm, m. vastus medialis, m. semitendinosus, m. cutaneous thoracicus and m. masseter, as well as samples of muscles collected in a whole-body sampling procedure, were analyzed by electron microscopy. VO2max per kilogram body mass was 2.7 x greater in horses than steers. This higher VO2max was in proportion to the higher total volume of mitochondria in horse versus steer muscle when analyzed from...
de Meeûs d'Argenteuil C, Boshuizen B, Oosterlinck M, van de Winkel D, De Spiegelaere W, de Bruijn CM, Goethals K, Vanderperren K, Delesalle CJG.Equine bioenergetics have predominantly been studied focusing on glycogen and fatty acids. Combining omics with conventional techniques allows for an integrative approach to broadly explore and identify important biomolecules. Friesian horses were aquatrained (n = 5) or dry treadmill trained (n = 7) (8 weeks) and monitored for: evolution of muscle diameter in response to aquatraining and dry treadmill training, fiber type composition and fiber cross-sectional area of the M. pectoralis, M. vastus lateralis and M. semitendinosus and untargeted metabolomics of the M. pectoralis and M. vastus late...
Essén B, Lindholm A, Thornton J.Fibre characteristics and enzyme activities were determined for the gluteus, semitendinosus, vastus lateralis and triceps brachii muscles of 55 Standardbred trotters of different ages. Four fibre types (I, IIA, IIB, IIC) were demonstrated by histochemical staining of myofibrillar adenosine triphosphatase after preincubation at different pH values. Type II fibres predominated in all the muscles and the type IIA/IIB ratio was higher in horses over 5 years than in younger horses, except in the vastus in which the IIA/IIB ratio did not change with age. The vastus had the highest proportion of type...
Yamano S, Eto D, Sugiura T, Kai M, Hiraga A, Tokuriki M, Miyata H.To determine the effect of growth and training on metabolic properties in muscle fibers of the gluteus medius muscle in adolescent Thoroughbred horses. Methods: Twenty 2-year-old Thoroughbreds. Methods: Horses were randomly assigned to 2 groups. Horses in the training group were trained for 16 weeks, and control horses were kept on pasture without training. Samples were obtained by use of a needle-biopsy technique from the middle gluteus muscle of each horse before and after the training period. Composition and oxidative enzyme (succinic dehydrogenase [SDHI) activity of each fiber type were de...
Ochala J, Finno CJ, Valberg SJ.Myosinopathies are defined as a group of muscle disorders characterized by mutations in genes encoding myosin heavy chains. Their exact molecular and cellular mechanisms remain unclear. In the present study, we have focused our attention on a -related E321G amino acid substitution within the head region of the type IIx skeletal myosin heavy chain, associated with clinical signs of atrophy, inflammation and/or profound rhabdomyolysis, known as equine myosin heavy chain myopathy. We performed Mant-ATP chase experiments together with force measurements on isolated IIx myofibres from control horse...
Marx JO, Olsson MC, Larsson L.To fully understand the effect of scaling on skeletal muscle shortening velocity (V (0)), it is important to know which phenotypic characteristics drive the changes between species. The purpose of the current investigation was to compare the effects of body mass and femur length, as an estimate of total limb length, on V (0) in species that cover a 100,000-fold range of body masses. Using the slack test procedure, V (0) was determined for fibers expressing types I and IIa myosin heavy chain (MyHC) isoforms in the mouse, rat, dog, human, horse, and rhinoceros under identical experimental condit...
Rivero JL, Ruz MC, Serrano AL, Diz AM.Twenty adult (5 to 14 years old) sedentary stallions of several breeds (8 Andalusians, 7 Arabians and 5 Anglo-Arabians) were endurance-trained for 3 months. Duplicate biopsies from 2 different depths (20 mm, superficial sampling site; 60 mm, deep sampling site) of the gluteus medius muscle were collected before and after training and after 3 months of detraining. Few significant changes in muscle fibre type composition were recorded in response to training. The percentage of type I fibres in the deep sampling site of the muscle in Andalusian horses and of type IIB oxidative fibres in the super...
McCue ME, Armién AG, Lucio M, Mickelson JR, Valberg SJ.Polysaccharide storage myopathy (PSSM) has been found in more than 35 different horse breeds through identification of abnormal storage of polysaccharide in muscle biopsies. A dominant mutation in the glycogen synthase 1 gene (GYS1) accounts for a substantial proportion of PSSM cases in at least 17 breeds, including Quarter Horses, but some horses diagnosed with PSSM by muscle histopathologic analysis are negative for the mutation. We hypothesized that a second distinct form of glycogen storage disease exists in GYS1-negative horses with PSSM. The objectives of this study were to compare the h...
Kayar SR, Hoppeler H, Essen-Gustavsson B, Schwerzmann K.A morphometric analysis was performed on horse muscle tissue to quantify mitochondrial distribution relative to capillaries. Samples of M. vastus medialis, M. semitendinosus, M. masseter and M. cutaneus thoracicus were preserved in a glutaraldehyde fixative for electron microscopy, or frozen for biochemical and histochemical analysis. These four muscles varied from highly oxidative in type, consisting nearly completely of type I fibres, in masseter, to highly glycolytic, primarily type IIb fibres, in cutaneus. In all four muscles, mitochondria were found in highest volume density near capillar...
