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Topic:Physiology
The physiology of horses encompasses the study of the biological functions and processes that occur within the equine body. This includes the examination of various systems such as the cardiovascular, respiratory, musculoskeletal, digestive, and nervous systems. Understanding equine physiology is essential for comprehending how horses adapt to different environmental conditions, perform physical activities, and respond to health challenges. Research in this field often focuses on the mechanisms of energy metabolism, thermoregulation, and muscle function during exercise, as well as the physiological responses to stress and disease. This page compiles peer-reviewed research studies and scholarly articles that explore the diverse aspects of equine physiology, providing insights into the biological processes that support the health and performance of horses.
beta-Subunit 102-104 residues are crucial to confer FSH activity to equine LH/CG but are not sufficient to confer FSH activity to human CG. Horse LH/CG (eLH/CG) and donkey LH/CG (dkLH/CG) are strictly LH-specific in their respective homologous species. However, both bind to the FSH receptors from non-equid species, whereas the zebra hormone (zbLH/CG) does not. The FSH/LH ratio of eLH/CG and of the alphadkbetae hybrid is about tenfold higher than that of dkLH/CG and of the alphaebetadk hybrid, showing that the betae subunit contains the structural features responsible for the high FSH activity of eLH/CG. Only six amino acid positions (51, 94, 95, 102, 103 and 106) are unique to the betae subunit when compared with the betadk and be...
Effect of load on preferred speed and cost of transport. Horses have a tendency to utilize a relatively narrow set of speeds near the middle of a much broader range they are capable of using within a particular gait, i.e., a preferred speed. Possible explanations for this behavior include minimizing musculoskeletal stresses and maximizing metabolic economy. If metabolic economy (cost of transport, CT) and preferred speeds are linked, then shifts in CT should produce shifts in preferred speed. To test this hypothesis, preferred speed was measured in trotting horses (n = 7) unloaded on the level and loaded with 19% of their body weight on the level. T...
In situ zymography: topographical considerations. In situ gelatin zymography is a simple technique providing valuable information about the cellular and tissue localization of gelatinases. Until recently, the use of this technique has been confined to soft, relatively homogeneous tissue. In this report in situ zymography has been utilized to assess the sub-lamellar location of gelatinases in the hard, semi-keratinized epidermal layer and the adjacent soft connective tissue matrix of the dermis of the equine hoof. We show that alterations in the orientation at which the tissue is dipped and withdrawn from the emulsion cause profound alteration...
Effect of cooling of equine spermatozoa before freezing on post-thaw motility: preliminary results. The ability to ship cooled stallion semen to a facility that specializes in cryopreservation of spermatozoa would permit stallions to remain at home while their semen is cryopreserved at facilities having the equipment and expertise to freeze the semen properly. To accomplish this goal, methods must be developed to freeze cooled shipped semen. Three experiments were conducted to determine the most appropriate spermatozoal extender, package, time of centrifugation, spermatozoal concentration and length of time after collection that spermatozoa can be cooled before cryopreservation. In the first...
Production of reactive oxygen species in neutrophils after repeated bouts of exercise in standardbred trotters. Six trained Standardbred trotters exercised on a racetrack on 2 days with a 3-day interval. On both exercise days the horses trotted three different exercise bouts with increasing intensity with 60-min intervals. Exercise-induced stress was manifested as leucocytosis, an increase in the neutrophil:lymphocyte (N:L) ratio, and increased capacity to produce reactive oxygen species in the peripheral blood as indicated by an increase in whole blood chemiluminescence. The leucocytosis was mainly due to neutrophilia, which lasted for 6 h. Production of reactive oxygen species per single neutrophil sh...
Glycerol hyperhydration in resting horses. To determine whether administration of glycerol-containing solutions induces a state of transient hyperhydration in resting euhydrated horses, changes in plasma and urine constituents were measured in four horses for 1 h before and 5 h after nasogastric administration of each of four treatments (Experiment 1). Treatments were applied in a randomized fashion and included: (1) 1.0 g.kg(-)(1)glycerol in 8 L of water (G); (2) 8 L of water (W); (3) 8 L of 0.9% NaCl solution (S); and (4) 1.0 g.kg(-)(1)glycerol in 8 L of 0.9% NaCl solution (GS). In a subsequent study, voluntary water intake was measu...
Ultrasound-spirometry and capnography in horses: analysis of measurement reliability. Ultrasound-spirometry and capnography and the evaluation of corresponding 'single-breath diagrams for CO2' (SBD-CO2) is a relatively new, non-invasive method for assessing pulmonary function in horses. The relative variation and the reliability of observations within measurement sessions were calculated for expiratory tidal volume, for expired CO2 volume (%) and for the phase II and phase III slopes of the SBD-CO2 in horses without pulmonary disease and in horses suffering from differing degrees of chronic obstructive pulmonary disease. The coefficient of variation of expiratory tidal volume r...
Scanning electron microscopic study of the posterior ciliary veins in domestic ungulates. Vascular corrosion casts of 12 equine, 15 bovine and 50 porcine eyes were studied scanning electron microscopically for the presence of posterior ciliary veins. These veins drain a postequatorial segment of the choroid and emerge near the posterior bulbar pole. They complement the four vorticose veins that emerge near or at the equatorial zone of the eyeball and the slender choroidoretinal veins that drain the peridiscal area of the choroid. Posterior ciliary veins were observed in all equine and bovine eyes examined. In these species they presented a large variation in size, number and positi...
Expression of 3beta-hydroxysteroid dehydrogenase, cytochrome p450 17alpha-hydroxylase/17,20-lyase and cytochrome p450 aromatase enzymes in corpora lutea of diestrous and early pregnant mares. In the pregnant mare, luteal estrogen production increases at the onset of equine chorionic gonadotropin (eCG) secretion by endometrial cups. In previous studies, we have demonstrated that eCG stimulates luteal androgen and estrogen production in pregnant mares. To further elucidate the regulation of steroidogenesis within the equine corpus luteum (CL) of pregnancy, we examined the expression of 3beta-hydroxysteroid dehydrogenase (3beta-HSD), cytochrome P450 17alpha-hydroxylase/17,20 lyase (P450(17alpha)) and cytochrome P450 aromatase (P450(arom)) in luteal tissue samples collected during dies...
In vitro evidence for a bacterial pathogenesis of equine laminitis. Utilizing an in vitro laminitis explant model, we have investigated how bacterial broth cultures and purified bacterial proteases activate matrix metalloproteinases (MMPs) and alter structural integrity of cultured equine lamellar hoof explants. Four Gram-positive Streptococcus spp. and three Gram-negative bacteria all induced a dose-dependent activation of MMP-2 and MMP-9 and caused lamellar explants to separate. MMP activation was deemed to have occurred if a specific MMP inhibitor, batimastat, blocked MMP activity and prevented lamellar separation. Thermolysin and streptococcal pyrogenic ex...
Cytokeratins of the stratum medium and stratum internum of the equine hoof wall in acute laminitis. The cytoskeleton of living keratinocytes consists mainly of cytokeratins that have polymerised into intermediate filaments. The aim of this study was to describe the expression of cytokeratins in the living epidermal cells of the weight-bearing parts of the equine hoof wall during acute spontaneous laminitis. A total of 9 hooves from 3 horses subjected to euthanasia within 48 h of the first clinical signs of laminitis were sectioned and examined. The cytokeratins in the stratum medium and stratum internum of the hoof wall were characterized by 1- and 2-dimensional gel electrophoresis, and the ...
Adherence of eosinophils from allergic and normal ponies to cultured equine endothelial cells. To compare adherence of stimulated and unstimulated eosinophils from allergic and normal ponies to cultured equine vascular endothelial cells (equine digital vein endothelial cells; EDVEC) and examine the effect of eosinophil-derived factor(s) on cell adherence. Methods: Eosinophil adherence to unstimulated EDVEC or EDVEC pretreated with IL-1beta or supernatants from stimulated eosinophils was measured. Supernatants were also assayed for TNFalpha and IL-1beta-like bioactivity. Results: Adherence of unstimulated and rhIL-5 (10 ng/ml)-stimulated eosinophils from allergic ponies to rhIL-1beta-tre...
[ACTH stimulation test for the determination of salivary cortisol and of cortisol responses as markers of the training status/fitness of warm-blooded sports horses]. Previous work (Marc et al., 2000) suggested that plasma cortisol responses to treadmill exercise or ACTH injection are a reliable marker for performance evaluation in warmblood horses. For practical purposes blood sample collections and treadmill exercise tests are somewhat troublesome and time consuming. The goal of this study was thus to evaluate the use of saliva for cortisol determination (by direct EIA) as a marker for performance and to investigate the reliability and repeatability of plasma cortisol responses to a single i.v. injection of ACTH (50 micrograms or 250 micrograms). Furtherm...
Effects of a histamine type 2 receptor antagonist, BMY-26539-01, on equine gastric acid secretion. A dose-response study was undertaken of the effects of a newly developed histamine type 2 receptor antagonist, BMY-26539-01, on gastric acid secretion in 4 fasted horses. Doses of 0.1 mg/kg, 0.3 mg/kg, 0.5 mg/kg, or placebo were administered in a randomly assigned treatment sequence. Hydrogen ion concentration and pH were variable during baseline measurements in all 4 animals; however, following BMY-26539-01 administration, mean pH increased and hydrogen ion concentration decreased in a dose-related pattern. At the 0.3 mg/kg and 0.5 mg/kg dose levels, pH remained elevated for > 4 h and >...
[Receptor sialylsugar chains as determinants of host range of influenza viruses]. All types of the hemagglutinin(HA) of human, pig, horse and aq. bird influenza A viruses, recognize sialyl lacto-series type I and II sugar chains(Sialic acid(SA) alpha 2-3(6)Gal beta 1-3(4) GlcNAc beta 1-) in glycoproteins and glycolipids in the target cells as common receptor molecules. Avian and equine influenza viruses preferentially binds the terminal sialic acid alpha 2-3Gal(SA2-3Gal) linkage, while human influenza viruses preferentially bind the SA2-6Gal linkage. SA distribution in animal species influence influenza virus host range. Swine trachea has both receptors for avian influenza ...
The hindlimb in walking horses: 1. Kinematics and ground reaction forces. The objective was to study associations between kinematics and ground reaction forces in the hindlimb of walking horses. Video (60 Hz) and force (2000 Hz) data were gathered for 8 strides from each of 5 sound horses during the walk. Sagittal plane kinematics were measured concurrently with the vertical and longitudinal ground reaction forces. The hindlimb showed rapid loading and braking in the initial 10% stride. The stifle, tarsal and coffin joints flexed and the fetlock joint extended during this period of rapid loading. The vertical ground reaction force showed 2 peaks separated by a dip; ...
Nucleotide and deduced amino acid sequence of equine retinal and pineal gland phosducin. To determine the full-length complementary DNA (cDNA) sequence of equine retinal and pineal gland phosducin (PHD) and to clone these sequences. Methods: Samples of equine retinal RNA. Methods: A primer set was designed for use in identifying a fragment of the equine PHD nucleotide sequence, derived from retinal RNA samples, and subsequently for use to deduce specific primers for additional examination. The full-length cDNA was determined by the method of rapid amplification of cDNA ends (RACE). For full-length cDNA, newly designed primers were used. Nucleotide sequences were analyzed by use of...
Aggregation behavior and electrophoretic mobility of red blood cells in various mammalian species. Differences of red blood cell (RBC) aggregation among various mammalian species has been previously reported for whole blood, for RBC in autologous plasma, and for washed RBC re-suspended in polymer solutions. The latter observation implies the role of cellular factors, yet comparative studies of such factors are relatively limited. The present study thus investigated RBC aggregation and RBC electrophoretic mobility (EPM) for guinea pigs, rabbits, rats, humans and horses; RBC were re-suspended in isotonic 500 kDa dextran solutions for the EPM and aggregation measurements, with aggregation stud...
Age-related changes in the testes of horses. Atrophy of seminiferous tubules and interstitial fibrosis are frequently observed in aged horses. Samples from 8 male Thoroughbreds, age 4-24 years, were subjected to histological, electron microscopical and immunohistochemical examination and statistical analysis. There were statistically significant increases in collagen fibres in the lamina propria of seminiferous tubules and testicular interstitium in 3 horses age 23 and 24 years compared with 5 horses age 4-20 years (P<0.001). Lamina propria surrounding atrophic tubules was thickened by an increase in collagen type IV and elastic fibre...
The distribution of intratubular dentine in equine incisors: a scanning electron microscopic study. The distribution of intratubular (peritubular) dentine was studied by scanning electron microscopy in 12 equine incisor teeth. High levels of intratubular dentine were found in the peripheral regions of the dentine. In these areas, a marked asymmetry occurred, as intratubular dentine was predominantly deposited onto the side of the dentinal tubular walls nearest to the dentino-enamel junction. The quantity and asymmetry of intratubular dentine were reduced towards the centre of the tooth. The significance of these variations in the amount and distribution of intratubular dentine between the di...
The hindlimb in walking horses: 2. Net joint moments and joint powers. The objective of the study was to describe net joint moments and joint powers in the equine hindlimb during walking. The subjects were 5 sound horses. Kinematic and force data were collected synchronously and combined with morphometric information to determine net joint moments at each hindlimb joint throughout stance and swing. The results showed that the net joint moment was on the caudal/plantar side of all hindlimb joints at the start of stance when the limb was being actively retracted. It moved to the cranial/dorsal side around 24% stride at the hip and stifle and in terminal stance at t...
Effects of enrofloxacin and magnesium deficiency on matrix metabolism in equine articular cartilage. To investigate the effects of enrofloxacin and magnesium deficiency on explants of equine articular cartilage. Methods: Articular cartilage explants and cultured chondrocytes obtained from adult and neonatal horses. Methods: Full-thickness explants and cultured chondrocytes were incubated in complete or magnesium-deficient media containing enrofloxacin at concentrations of 0, 1, 5, 25, 100, and 500 microg/ml. Incorporation and release of sulfate 35S over 24 hours were used to assess glycosaminoglycan (GAG) synthesis and degradation. An assay that measured binding of dimethylmethylene blue dye ...
Repeatability of diagnostic ultrasonography in the assessment of the equine superficial digital flexor tendon. A quantitative investigation of the variation that can occur during the course of ultrasonography of the equine superficial digital flexor tendons (SDFT) was undertaken. The aim of this investigation was to use an objective measure, namely the measurement of CSA, to quantify the variability occurring during the course of the ultrasonographic assessment of the equine SDFT. The effects of 3 variables on the CSA measurements were determined. 1) Image acquisition operator (IAc): two different operators undertaking the ultrasonographic examination; 2) image analysis operator (IAn): two different op...
Effect of a leukocyte-depleting filter in an extracorporeal circuit used for low-flow ischemia and reperfusion of equine jejunum. To determine effect of leukocyte depletion on hematologic, morphologic, and metabolic variables of equine jejunum after induction of arterial low-flow ischemia and reperfusion by use of an extracorporeal circuit. Methods: 14 healthy adult horses. Methods: A segment of jejunum was surgically removed and maintained in an isolated circuit for 3 hours (control group), arterial flow was reduced to 20% of baseline for 40 minutes followed by 1 hour of reperfusion (low-flow group), or leukocyte depletion was filter-induced, and low-flow ischemia and reperfusion were conducted as in the low-flow contro...
Comparative responses of bronchial rings to mediators of airway hyperreactivity in healthy horses and those affected with summer pasture-associated obstructive pulmonary disease. To compare responses of bronchial rings obtained from healthy horses and horses affected with summer pasture-associated obstructive pulmonary disease (SPAOPD) to selected mediators of airway hyperreactivity in vitro. Methods: Bronchial rings from 6 healthy horses and 6 horses affected with SPAOPD. Methods: Bronchial rings obtained from each group of horses were mounted in organ baths and attached to force transducers interfaced with a polygraph. After applying 2g of tension, each ring was allowed to equilibrate for 45 minutes in Tyrode's solution at 37 C. Cumulative concentration-response rela...
Ectopic transplantation of equine invasive trophoblast. A system for transplanting invasive equine trophoblast (i.e., chorionic girdle) to ectopic sites has been developed as a means to study the differentiation of this tissue and to assess maternal immune responses to the conceptus tissue in a site outside the uterus. Chorionic girdle was isolated from Day 33 to 34 conceptuses and surgically placed into the vulvar mucosa or subdermal skin of recipient mares. Biopsy specimens of the graft sites for immunohistochemical staining were taken at weekly or biweekly intervals after grafting. Serum samples were collected from each recipient and tested for ...
