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Topic:Muscle
The topic of muscle in horses encompasses the study of equine muscle structure, function, and physiology. Muscles in horses are responsible for movement, posture, and various metabolic processes. They are composed of muscle fibers that contract and relax to produce motion and generate force. Research in this area often focuses on muscle development, adaptation to exercise, and the impact of nutrition and training on muscle performance. Conditions such as muscle fatigue, injury, and disorders like equine exertional rhabdomyolysis are also explored. This page compiles peer-reviewed research studies and scholarly articles that investigate the anatomy, physiology, and clinical aspects of muscle in equine species.
Tiger snake (Notechis scutatus) envenomation in a horse. A 7-year-old Thoroughbred gelding presented with muscle fasciculation, reluctance to move, profuse sweating, tachycardia, tachypnoea and a localised, unilateral swelling on the muzzle. History and physical examination were suggestive of snake envenomation. Methods: A sandwich ELISA for the detection of snake venom was performed on serum and urine samples. Results: The test performed on urine confirmed a diagnosis of tiger snake envenomation. Conclusions: The response to treatment with antivenom and supportive medical therapy was excellent.
In vitro effects of lidocaine on contractility of circular and longitudinal equine intestinal smooth muscle. The purpose of the study was to compare the contractility-enhancing effects of lidocaine in equine jejunal circular (CSM) and longitudinal smooth muscle (LSM) in vitro. In previous studies, more pronounced effects of lidocaine were observed in ischaemia-reperfusion (IR) injured smooth muscle. Therefore in this study, effects were examined in both non-injured control tissues and tissues challenged by a defined, artificial IR injury. Isometric contractile performance of CSM and LSM, assessed by frequency (F), amplitude (A) and mean active force (MAF) of contractions, was defined as contractility...
Characterization of prostaglandin E2 receptors (EP2, EP4) in the horse oviduct. Biological effects of prostaglandin E2 are mediated via one of four receptors designated EP1, EP2, EP3 and EP4 which are encoded by separate genes. In general, EP1 and EP3 induce smooth muscle contraction whereas EP2 and EP4 induce smooth muscle relaxation. The objective of the current study was to characterize the expression of the genes for PGE2 receptors (EP2 and EP4) in the horse oviduct based upon immunohistochemistry (IHC) and quantitative PCR (qPCR). Oviductal tissue was collected from mares at estrus (n=5), at 5 days post-ovulation (n=4), and from prepubertal mares (n=5). Isthmic and a...
The effect of a hippotherapy session on spatiotemporal parameters of gait in children with cerebral palsy – pilot study. Hippotherapy has been shown to produce beneficial effects by improving the most difficult motor functions, such as sitting, running, jumping, coordination, as well as balance and muscle strength in children with motor developmental delays. The aim of this study was to analyze the effect of hippotherapy on spatiotemporal parameters of gait in cerebrally palsied children. Methods: 16 ambulatory cerebrally palsied children (GMFCS Level I-III; Female: 10, Male: 6; Age: 5.7-17.5 years old) qualified for hippotherapy were investigated. Basic spatiotemporal parameters of gait, including walking speed...
Non-invasive assessment of equine muscular function: A case study. Assessment of muscle function after an injury or during recovery is of great importance in the veterinary field. Accelerometry, bioimpedance analysis and mechanomyography/acoustic myography have been used to assess human muscular problems, but have not been applied to the veterinary clinic. We report the clinical use of these techniques in a 12-year-old Danish Warmblood horse presenting with recurring and shifting lameness. Acoustic myography, assessing both the amplitude and frequency of active muscles, was employed to locate the specific area of muscle injury, the right hip, which exhibited ...
Experimental rayless goldenrod (Isocoma pluriflora) toxicosis in horses. Rayless goldenrod (Isocoma pluriflora) sporadically poisons horses and other livestock in the southwestern United States. Similar to livestock poisoning by white snakeroot (Ageratina altissima) in the midwestern United States, previous research suggests that benzofuran ketones (BFK: tremetone, dehydrotremetone, 6-hydroxytremetone, and 3-oxyangeloyl-tremetone) are responsible for the toxicity of rayless goldenrod. However, experimental reproduction of rayless goldenrod-induced disease and detailed descriptions of poisoning in horses with known concentrations of tremetone and other BFK has not b...
Muscle reaction function of individuals with intellectual disabilities may be improved through therapeutic use of a horse. Reaction time and muscle activation deficits might limit the individual's autonomy in activities of daily living and in participating in recreational activities. The aim of the present study was to assess the effects of a 14-week hippotherapy exercise program on movement reaction time and muscle activation in adolescents with intellectual disability (ID). Nineteen adolescents with moderate ID were assigned either to an experimental group (n=10) or a control group (n=9). The experimental group attended a hippotherapy exercise program, consisting of two 30-min sessions per week for 14 weeks. Rea...
Effect of gluteus medius muscle sample collection depth on postprandial mammalian target of rapamycin signaling in mature Thoroughbred mares. To determine the effect of biopsy collection depth on the postprandial activation of mammalian target of rapamycin (mTOR) signaling factors, particularly protein kinase B, ribosomal protein S6 kinase, ribosomal protein S6, and eukaryotic initiation factor 4E binding protein 1 in middle-aged horses. Methods: 6 healthy Thoroughbred mares (mean ± SD age, 13.4 ± 3.4 years). Methods: Horses were fed a high-protein feed at 3 g/kg. Sixty minutes after horses were fed, the percutaneous needle biopsy technique was used to collect biopsy specimens from the gluteus medius muscle at 6, 8, and 10 cm belo...
Three cases of a presumptive atypical myopathy in New Zealand horses. Three weanling Thoroughbred fillies were presented during autumn with depression, muscle rigidity and, in one case, colic symptoms and cardiovascular shock. Results: All fillies had abnormal physical examinations that included elevated heart rates and respiratory rates coupled with muscle rigidity through the back and rump. Biochemistry revealed markedly elevated creatinine kinase and aspartate aminotransferase which indicated a myopathy. Methods: All three horses were diagnosed with presumptive equine atypical myopathy. The horses received supportive therapy as per the literature available at...
Characterization and osteogenic potential of equine muscle tissue- and periosteal tissue-derived mesenchymal stem cells in comparison with bone marrow- and adipose tissue-derived mesenchymal stem cells. To characterize equine muscle tissue- and periosteal tissue-derived cells as mesenchymal stem cells (MSCs) and assess their proliferation capacity and osteogenic potential in comparison with bone marrow- and adipose tissue-derived MSCs. Methods: Tissues from 10 equine cadavers. Methods: Cells were isolated from left semitendinosus muscle tissue, periosteal tissue from the distomedial aspect of the right tibia, bone marrow aspirates from the fourth and fifth sternebrae, and adipose tissue from the left subcutaneous region. Mesenchymal stem cells were characterized on the basis of morphology, ad...
Vacuolar myopathy in an adult Warmblood horse. Histopathological interpretation of semimembranosus muscle samples from an adult Warmblood mare with clinical signs suggestive of exertional rhabdomyolysis and intermittent mild elevations in muscle enzyme activities revealed abundant sarcoplasmic vacuoles in all fibre-types containing fine, apparently proteinaceous debris. Vacuolar contents stained lightly with PAS, but did not appear to contain amylopectate, lipid or acid phosphatase and their periphery was unstained with dystrophin immunohistochemistry. Electron microscopy revealed that vacuoles were not membrane bound. No vacuoles were det...
Amino acid utilization by the hindlimb of warmblood horses at rest and following low intensity exercise. In particular branched-chain amino acids might limit muscle protein loss in pathological conditions. Little is known on basic amino acid utilization of muscle in horses. Objective: To assess amino acid utilization by the hindlimb of horses at rest and following low intensity exercise. ANIMALS & METHODS: Amino acid uptake by the hindlimb was investigated using the arteriovenous difference technique. Blood from six warmblood mares (mean age 12 ± 3 (SD) years and weighing 538 ± 39 kg) was collected simultaneously from the (transverse) facial artery and from the caudal vena cava. Food was wi...
Histopathologic findings in the sacrocaudalis dorsalis medialis muscle of horses with vitamin E-responsive muscle atrophy and weakness. To characterize clinical findings, outcomes, muscle characteristics, and serum or muscle concentrations of α-tocopherol for horses with vitamin E-responsive signs of muscle atrophy and weakness consistent with signs of equine motor neuron disease (EMND). Methods: Retrospective case-control study. Methods: 8 affected (case) adult horses with acute (n = 3) or chronic (5) gross muscle atrophy that improved with vitamin E treatment and 14 clinically normal (control) adult horses with adequate (within reference range; 8) or low (6) muscle concentrations of α-tocopherol. Methods: Medical records w...
In vivo and in vitro effects of neostigmine on gastrointestinal tract motility of horses. To determine the response to neostigmine of the contractile activity of the jejunum and pelvic flexure and the effects of a continuous rate infusion (CRI) of neostigmine in horses. Methods: 7 adult horses and tissue from 12 adult horses. Methods: A CRI of neostigmine (0.008 mg/kg/h) or placebo was administered to 6 horses in a crossover study design. Gastric emptying was evaluated by the acetaminophen test. The frequency of defecation and urination and the consistency and weight of feces were recorded throughout the experiment. The effect of neostigmine on smooth muscle contractile activity wa...
Effect of acute exercise on monocarboxylate transporters 1 and 4 in untrained and trained Thoroughbreds. To evaluate the effects of a single incremental exercise test (IET) on mRNA expression and protein content of monocarboxylate transporter (MCT) 1 and MCT4 in the gluteus medius muscle of Thoroughbreds. Methods: 12 Thoroughbreds (6 males and 6 females; age, 3 to 4 years). Methods: Horses underwent an IET before and after 18 weeks of high-intensity exercise training (HIT). Horses were exercised at 90% of maximal oxygen consumption for 3 minutes during the initial 10 weeks of HIT and 110% of maximal oxygen consumption for 3 minutes during the last 8 weeks of HIT. Gluteus medius muscle biopsy spec...
Pharmacokinetics of midazolam after intravenous administration to horses. Midazolam is used to control seizures in horses and to enhance muscle relaxation, but its pharmacokinetics are unknown. Objective: To determine the pharmacokinetics and sedative effects of midazolam in horses. Methods: Blinded, randomised, crossover design. Methods: Midazolam was administered i.v. at either 0.05 or 0.1 mg/kg bwt to 6 horses on 2 occasions at least 7 days apart using a crossover design. Blood samples were collected before and at predetermined times through 24 h after administration. Serum midazolam concentrations were determined by a liquid chromatography tandem-mass spectromet...
Morphometric analyses of the body and the branches of the normal third interosseous muscle (suspensory ligament) in Standardbreds. The third interosseous muscle (suspensory ligament, TIOM) is composed of connective tissue (CT) with a variable proportion of muscle (MT) and adipose tissue (AT). The aim of our study is to quantify the CT, MT and AT within the body and the branches of right thoracic and pelvic limbs TIOM in sound horses to determine whether there are differences in CT, MT and AT between age, sex, limbs and levels. Right limbs from 11 sound horses were collected. Samples from 6 levels of the TIOM were embedded in paraffin or in Tissue-Tek(®) . Most of the paraffin sections were shredded. Using the cryosection...
Muscle and tendon heating rates with therapeutic ultrasound in horses. To (1) determine the temperature change in equine tendon and muscle during therapeutic ultrasound and (2) develop guidelines for treating horses for muscular or tendinous injury using therapeutic ultrasound. Methods: Experimental, in vivo study. Methods: Adult horses (n = 10). Methods: Thermistors were inserted in the superficial and deep digital flexor tendons (SDFT and DDFT) of the thoracic limbs of 10 adult horses. On the left, 3.3 MHz therapeutic continuous ultrasound was done for 10 minutes at an intensity of 1.0 W/cm(2) and for the right thoracic limb at 1.5 W/cm(2). Thermistors were pla...
Balanced anesthesia and constant-rate infusions in horses. Balanced anesthetic techniques are commonly used in equine patients, and include the combination of a volatile anesthetic with at least one injectable anesthetic throughout the maintenance period. Injectable anesthetics used in balanced anesthesia include the α2-agonists, lidocaine, ketamine, and opioids, and those with muscle-relaxant properties such as benzodiazepines and guaifenesin. Administration of these injectable anesthetics is best using constant-rate infusions based on the pharmacokinetics of the drug, which allows steady-state concentrations and predictable pharmacodynamic actions....
Lidocaine and structure-related mexiletine induce similar contractility-enhancing effects in ischaemia-reperfusion injured equine intestinal smooth muscle in vitro. Postoperative ileus (POI) is a severe complication following small intestinal surgery in horses. It was hypothesised that prokinetic effects of lidocaine, the most commonly chosen drug for treatment of POI, resulted from drug integration into smooth muscle (SM) cell membranes, thereby modulating cell membrane properties. This would probably depend on the structural and lipophilic characteristics of lidocaine. To assess the influence of molecular structure and lipophilicity on prokinetic effects in vitro, the current study compared the effects of lidocaine with four structure-related drugs, nam...
Growth, training response and health in Standardbred yearlings fed a forage-only diet. The aim of this study was to, from a holistic perspective, describe the effects of a forage-only feeding system and a conventional training program on young Standardbred horses and compare data with similar observations from the literature. Sixteen Standardbred colts fed a forage-only diet for 4 months from breaking (August to December) and with the goal to vigorously trot 5 to 7 km at a speed of 5.6 m/s (3 min/km) were studied. The horses were fed grass haylage (56 to 61% dry matter (DM), 2.80 to 3.02 Mcal DE/kg DM and 130 to 152 g CP/kg DM) ad libitum, 1 kg of a lucerne product and minerals....
Therapeutic horse back riding of a spinal cord injured veteran: a case study. To determine an incomplete spinal cord injured veteran's experience following participation in a therapeutic horseback riding program. Methods: Following the establishment of a nationwide therapeutic riding program for America's wounded service veterans in 2007, a Certified Rehabilitation Registered Nurse from the Michael E. DeBakey Veteran Affairs Medical Center worked with an incomplete spinal cord injured veteran who participated in the Horses for Heroes program. Results: This program resulted in many benefits for the veteran, including an increase in balance, muscle strength, and self-este...
Muscle satellite cells are activated after exercise to exhaustion in Thoroughbred horses. 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...
Effects of high-intensity training on lipid metabolism in Thoroughbreds. To investigate the effects of high-intensity training (HIT) on carbohydrate and fat metabolism in Thoroughbreds. Methods: 12 Thoroughbreds (3 to 4 years old; 6 males and 6 females). Methods: Horses performed HIT for 18 weeks. They ran at 90% or 110% of maximal oxygen consumption ((V)O(2max)) for 3 minutes (5 d/wk) and were subjected to incremental exercise testing (IET) before and after training. Blood samples were collected during IET, and muscle samples were obtained from the gluteus medius muscle immediately after IET. Phosphofructokinase, citrate synthase, and β-3-hydroxyacyl CoA dehydrog...
Whole transcriptome analyses of six thoroughbred horses before and after exercise using RNA-Seq. Thoroughbred horses are the most expensive domestic animals, and their running ability and knowledge about their muscle-related diseases are important in animal genetics. While the horse reference genome is available, there has been no large-scale functional annotation of the genome using expressed genes derived from transcriptomes. Results: We present a large-scale analysis of whole transcriptome data. We sequenced the whole mRNA from the blood and muscle tissues of six thoroughbred horses before and after exercise. By comparing current genome annotations, we identified 32,361 unigene cluster...
Structural and oxygen binding properties of dimeric horse myoglobin. Myoglobin (Mb) stores dioxygen in muscles, and is a fundamental model protein widely used in molecular design. The presence of dimeric Mb has been known for more than forty years, but its structural and oxygen binding properties remain unknown. From an X-ray crystallographic analysis at 1.05 Å resolution, we found that dimeric metMb exhibits a domain-swapped structure with two extended α-helices. Each new long α-helix is formed by the E and F helices and the EF-loop of the original monomer, and as a result the proximal and distal histidines of the heme originate from different protomers. Th...
Developmental regulation of the activation of translation initiation factors of skeletal muscle in response to feeding in horses. To determine whether feeding-induced activation of translation initiation factors, specifically protein kinase B, ribosomal protein S6 kinase (S6K1), ribosomal protein S6 (rpS6), and eukaryotic initiation factor 4E binding protein 1, in horses is affected by age. Methods: 6 yearlings, six 2-year-old horses, and 6 mature horses. Methods: After an 18-hour period of feed withholding, horses consumed a high-protein meal (2 g/kg) at time 0 and 30 minutes (postprandial state) or continued to have feed withheld (postabsorptive state). Blood samples were collected for the duration of the experimental ...
Contractile responses of isolated equine digital arteries under hypoxic or hyperoxic conditions in vitro: role of reactive oxygen species and Rho kinase. The underlying pathophysiological triggers for equine acute laminitis are unknown, although digital vasoconstriction, ischaemia, hypoxia and reperfusion injury may be involved. The contractile responses of isolated equine digital arteries (EDAs), harvested from the hindlimbs of normal horses postmortem at an abattoir, were studied acutely (up to 3 h) under hyperoxic (95% oxygen, 5% CO2 ) and hypoxic (95% nitrogen, 5% CO2 ) conditions in organ baths. Phenylephrine (PHE; 10(-6) m), 5-hydroxytryptamine (5-HT; 10(-7) m) and high potassium (K(+) ; 118 mm) caused contraction in EDAs which was signif...
