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.
al-Timimi I, Gaillard JL, Amri H, Silberzahn P.Whereas mare corpus luteum does not produce androgens or estrogens in vivo, the incubation of mare corpus luteum microsomes with progesterone and NADPH resulted in 17 alpha-hydroxyprogesterone and estrogen production with a small yield of androstenedione. In the presence of an aromatase inhibitor (4-hydroxyandrostenedione), 17 alpha-hydroxyprogesterone and androstenedione were accumulated. Aromatization of testosterone and androstenedione occurred via stereospecific loss of the 1 beta, 2 beta hydrogen atoms and was inhibited by MgCl2, KCl, and EDTA. The Km of estrogen synthetase from equine co...
Ammons SF, Threlfall WR, Kline RC.Body temperature and serum progesterone concentrations were measured in mares to determine if a change in either could be useful in predicting estrus, ovulation or parturition. There was no significant correlation (P > 0.1) between rectal temperature and the environmental temperature or progesterone concentration. Progesterone concentration did correlate with stage of estrous cycle and the stage of pregnancy. Significant differences (P < 0.05) in temperature were noted at different times throughout the day. No change in temperature occurred that could be utilized to predict estrus, ovula...
Samuelson D, Smith P, Brooks D.The iridocorneal angle of the horse was anteriorly lined by a pectinate ligament, consisting of several layers of vertically oriented collagenous beams, that were interrupted by a network of extracellular spaces. The anterior chamber angle consisted mostly of a large uveal trabecular meshwork that was composed of widely-spaced, thick trabeculae. These trabeculae were attached in part posteriorly to extensions of the ciliary body musculature and anteriorly inserted into the prominent pectinate ligament. The corneoscleral trabecular meshwork was shaped hemiobovately and formed the external bound...
Tate LP, Sweeney CL, Cullen JM, Corbett WT, Newman HC, Brown TC, Ketner MT.A neodymium:yttrium aluminum garnet (Nd:YAG) laser was used to study effects of applying laser irradiation transendoscopically to the corniculate process of the arytenoid cartilage in horses. Dosimetry was established initially in vitro in 10 corniculate cartilages that were irradiated and examined histologically to determine penetration depths at selected power settings. Eleven horses were given xylazine IV and butorphoral tartrate IV, and their left ventricle and corniculate process were irradiated. Six horses had left laryngeal hemiplegia and were euthanatized and necropsied 14 weeks after ...
Johnson L, Tatum ME.The temporal appearance of seasonal changes in numbers of Leydig, Sertoli, and germ cells was evaluated to determine if seasonally increased daily spermatozoan production might be preceded by changes in numbers of either of two somatic testicular cells. A significant increase in numbers of spermatogonia and Sertoli cells preceded the significant increase in number of Leydig cells in the approaching breeding season. Seasonal changes in parenchymal weight and in numbers of Sertoli cells, Leydig cells, and germ cells were maximal in May and June. Numbers of A or B spermatogonia in June were 2.4 t...
Parks AH, Scott EA, Cox JE, Stick JA.Six horses with monorchidism, identified at surgery for cryptorchidectomy, are reported. All six presented with a single scrotal testis. Following surgical removal of one testis, they were either hormonally, anatomically or behaviourally determined to be geldings. Three other horses reported in the literature are reviewed. Of these nine cases of monorchidism, eight were thought to be caused by testicular degeneration and one by testicular agenesis. The vaginal process was present in all of the former and absent in the latter. The left side was involved in five of these eight horses. In seven, ...
Tovar P, Escabias MI, Santisteban R.A study of electrocardiograms recorded from foals during the first two weeks of life has been made in order to detect any changes of the cardiac activation and recuperation processes during this period. A stepwise discriminant analysis revealed significant differences between the first and second week of age, fundamentally on the basis of the T and P wave amplitudes which gave the lowest values at 14 days, and on the PQ segment duration that showed the highest values at the same age.
Zicker SC, Brumbaugh GW.The effect of phenylbutazone (4.4 mg/kg of body weight, IV, q 24 h, for 5 days) on glucose tolerance and on secretion of insulin in 6 healthy geldings was determined. Phenylbutazone significantly lowered fasting concentrations of glucose in plasma but did not significantly change the concentration of insulin in serum. There was no significant effect of phenylbutazone on glucose tolerance, on secretion of insulin, or on the area under the insulin/glucose ratio vs time curve in healthy geldings, as determined by paired t test analysis.
Schamhardt HC, Hartman W, Lammertink JL.Strain gauge rosettes were bonded to the dorsal, lateral, medial, and plantar aspects of the third metatarsal bone in the hind limbs of 6 ponies. The maximal compressive principal strain was approximately -600 X 10(-6) m/m, and exceeded the amplitudes of the tensile strains at all aspects of the bone. After transformation, the shear strain and the principal strains parallel and perpendicular to the bone were obtained. The first peak in the bending strain was higher in the dorsal and lateral aspects, and the second peak was higher in the medial and plantar aspects. Young modulus of elasticity w...
Ginther OJ.Recent findings on the origin and development of twins from ovulation (Day 0) to fixation (mean: Day 16) are reviewed. Available data show that almost all twins originate from multiple ovulations. Results of recent ultrasound studies indicate that the number of days between double ovulations does not affect the conception rate per ovum or embryo survival during the first 16 days after each ovulation. Embryo reduction is the natural elimination of excess embryos so that only one embryo enters the foetal stage. In two studies, embryo reduction before or on the day of fixation was not considered ...
West HJ.In 18 horses there was no effect of age or sex on plasma activities of gamma-glutamyl transferase (gamma-GT), 5'-nucleotidase (5'-NT) and leucine aminopeptidase (LAP). All the enzymes were equally stable after storage for one month at -20 degrees C and there was no significant difference between their activities in serum and plasma in clinically normal horses. The pattern of release of gamma-GT, 5'-NT and LAP into plasma was studied in 114 horses which had a variety of orthopaedic, gastrointestinal, cardiovascular and hepatic (necrosis, lipidosis, neoplasia and cirrhosis) conditions. A definit...
Gallivan GJ, McDonell WN, Forrest JB.Ventilation and gas exchange were studied in healthy, adult horses and cows, two large species with different lung structures and different breathing patterns. The oxygen uptake (VO2), carbon dioxide output (VCO2), respiratory rate (fR), minute ventilation (VE), alveolar ventilation (VA), alveolar oxygen pressure (PAO2), and VE/VO2 ratio were higher in the cows, while the tidal volume (VT) and physiological dead space (VD) were larger in the horses. The arterial blood gases, alveolar-arterial oxygen pressure difference (PAO2-PaO2) and VD/VT ratio did not differ between the two species. The hig...
Pearson EG, Riebold TW.A representative of each of 3 types of bronchodilators was given iv to horses with clinical signs of chronic obstructive pulmonary disease. We used atropine (0.01 mg/kg of body weight) as an anticholinergic, isoproterenol HCl as a beta-adrenergic, and aminophylline, the soluble salt of theophylline, as a methylxanthine. Response to these drugs was evaluated by measuring maximal change in intrathoracic pressures (delta Ppl) and observing clinical signs. Atropine caused a significant (P less than 0.01) reduction in delta Ppl, compared with that caused by aminophylline. Atropine caused the delta ...
Drummond WH, Sanchez IR, Kosch PC, Webb AI.Adult ponies develop pulmonary hypertension at altitude (Bisgard, Orr and Will 1975), but the neonatal response to acute hypoxaemia is unknown. Seven foals aged five days were instrumented with a systemic and a Swan-Ganz pulmonary artery catheter while anesthetised and intubated. Cardiac index, pulmonary (PAP) and systemic (SAP) vascular pressures were measured as the foals breathed gas mixtures with FI02 of 8 to 94 per cent. Because foramen ovale or ductus arteriosus shunts might have altered thermodilution cardiac index measurements in the stressed foals, the ratio, PAP/SAP was calculated to...
Nett TM, Shoemaker CF, Squires EL.High concentrations of estrogens in the peripheral circulation during late gestation inhibit synthesis of LH and markedly reduce pituitary content of LH at the end of pregnancy in most domestic species. Because blood concentrations of estrogen peak shortly before mid-gestation in the mare and then gradually decrease until parturition, we hypothesized that pituitary content of LH may increase during late gestation. To test this hypothesis 10 horse mares were challenged with a maximally stimulatory dose (2 micrograms/kg) of GnRH on d 240 and 320 of gestation and d 3 after parturition. A separate...
Dacquet C, Loirand G, Rakotoarisoa L, Mironneau C, Mironneau J.1. Specific binding of the calcium-antagonist dihydropyridine derivative, (+)-[3H]-PN 200-110 (isradipine), to cell membranes of equine portal vein smooth muscle was compared with binding to intact strips isolated from rat portal veins. 2. Specific binding to vascular smooth muscle membranes was of high affinity, saturable and reversible. The dissociation constant obtained from association and dissociation kinetics of (+)-[3H]-PN 200-110 was similar to that obtained from equilibrium binding and competition experiments. 3. Specific binding of (+)-[3H]-PN 200-110 was completely displaced by unla...
Jasko DJ, Smith K, Little TV, Lein D, Foote RH.A spectrophotometric procedure was developed and evaluated for the objective measurement of equine spermatozoan motility. A 100 mul sample of a sperm suspension, prepared by the removal of seminal plasma, was layered under a column of optically clear medium in a specially designed spectrophotometric cuvette maintained at 37 degrees C. Changes in light transmittance above the interface of the sperm suspension and medium were recorded on chart paper. As sperm cells swam into the medium, a decrease in light transmittance was recorded as a deflection on the chart paper. Chart recordings were analy...
Clayton HM, Townsend HG.A photographic method was used to measure axial rotation, dorsoventral flexion and extension and lateral bending at each intervertebral joint complex from the occiput to the first thoracic vertebra in spinal segments from 19 foals under 12 months of age and 14 horses over three years of age. Comparisons between the two groups showed that there was a general reduction in cervical spinal mobility with age. For the three types of movement at the eight joints tested, adults' mobility exceeded that of foals in only three cases (axial rotation and lateral bending at the A-O joint, and lateral bendin...
Gallivan GJ, McDonell WN, Forrest JB.Pulmonary mechanics and lung volumes were measured in horses and cows to determine if differences in breathing pattern between the two species were due to differences in the mechanical properties of the lungs. Tidal volume (VT) was larger in the horses, while the respiratory rate (fR) and minute ventilation (VE) were higher in the cows. The horses often had a double peak in airflow during inspiration and, or, expiration, while the cows had a single peak during expiration. Measured lung volumes were larger in the horses and they had a higher dynamic lung compliance (Cdyn,L), although the static...
Hüthwohl H, Weiss R, Schmeer N, Schliesser T.Classification based on biochemical characteristics of 389 strains of plasma-coagulase-negative (plc-) staphylococci isolated from the genital tract of mares and stallions resulted in the following distribution of species: St. sciuri 130 (33.4%), St. equorum 42 (10.8%), St. xylosus 16 (4.1%), St. epidermidis 35 (9.0%), St. simulans 24 (6.2%), St. haemolyticus 33 (8.5%), St. warneri 18 (4.6%), St. lentus 12 (3.1%), St. hyicus 11 (2.8%). Strains of St. cohnii, St. capitis, St. gallinarum, St. saprophyticus and St. hominis have only been found sporadically (a. 1%). 48 (12.3%) strains could not be...
Baxter GM, Tackett RL, Moore JN.Palmar digital arteries and veins removed surgically from healthy horses under general anesthesia were cut into 4 mm vascular rings, suspended in tissue baths, and attached to force displacement transducers for continuous measurement of vascular tension. In vitro vascular responses were determined for acetylcholine, acepromazine, isoxsuprine hydrochloride (isoxsuprine), prostaglandin E2 (PGE2), and prostaglandin I2 (prostacyclin). After preconstriction with norepinephrine hydrochloride (norepinephrine), or prostaglandin F2 alpha (PGF2 alpha), the concentrations needed to produce 50% maximum re...
Tekin N, Wöckener A, Klug E.The effect of a skim milk extender and a glycine-containing extender on sperm motility and acrosome morphology of stallion semen was examined. There was no difference concerning acrosome morphology. After 24 hours of preservation motility of the ejaculates diluted with glycine extender was significantly superior to those handled with skim milk extender. Storage at 5 degrees C in all cases gave better results than storage at room temperature. Skim milk extender is an appropriate diluent when the semen is used for al on the day of its collection, whereas the glycine-containing extender offers th...
Ricci G, Del Boccio G, Pennelli A, Aceto A, Whitehead EP, Federici G.Glutathione transferase (EC 2.5.1.18) from horse erythrocytes has been purified and some molecular and kinetic properties have been investigated. It appears to be a dimeric protein composed of subunits of about 23 kDa, indistinguishable either in sodium dodecyl sulfate or in urea electrophoresis. Amino acid composition, substrate specificities, sensitivity to inhibitors, CD spectra, and immunological studies provide evidence that the horse enzyme is related to the pi class transferases. This enzyme has only two reactive thiol groups/dimer whose integrity appears to be essential for the activit...
Heath TJ, Perkins NR.The pathways through which lymph flows from terminal afferent lymphatics to the lymph sinuses, and from the sinuses to initial efferent lymphatics, were studied in horse lymph nodes by using Microfil casts and electron microscopy. Terminal afferent lymphatics are continuous with the subcapsular sinus through oval holes, about 3 microns wide, along their length, and through larger openings near their end. Other terminal afferents penetrate into the node within trabeculae and are supported by processes across the lumen. They connect with trabecular and medullary sinuses through oval or round hol...
Pool RR, Meagher DM, Stover SM.Navicular syndrome is a degenerative disorder of the distal half of the flexor surface of the proximal sesamoid bone that is predisposed by faulty foot conformation. In horses that become symptomatic, the faulty conformation results in sustained application of nonphysiologic pressure by the deep digital flexor tendon against the flexor cortex of the bone. This force stimulates an intense bone remodeling response in order to attenuate the pressure. An unfortunate sequela of this response is active hyperemia and edema formation in the medullary cavity of the bone. The edema is organized by fibro...
Kowalczyk DF, Beech J, Littlejohn D.The pharmacokinetics of theophylline were determined in 6 healthy horses after a single IV administration of 12 mg of aminophylline/kg of body weight (equivalent to 9.44 mg of theophylline/kg). Serum theophylline was measured after the IV dose at 0.25, 0.5, 1, 2, 4, 6, 8, 12, and 15 hours. Serum concentration plotted against time on semilogarithmic coordinates, indicated that theophylline in 5 horses was best described by a 2-compartment open model and in 1 horse by a 1-compartment open model. The following mean pharmacokinetic values were determined; elimination half-life = 11.9 hours, distri...
Varner DD, Forrest DW, Fuentes F, Taylor TS, Hooper RN, Brinsko SP, Blanchard TL.Eighteen fertile mares were used to determine the effects of the oestrous cycle and location in the reproductive tract on the amount and concentration of glycosaminoglycans in luminal fluids. Ovariohysterectomies were performed in 3 groups of 6 mares on Day 3 of behavioural oestrus, within 6 h after ovulation or on Day 8 of dioestrus. The lumina of the uterine horns and oviducts ipsilateral and contralateral to the active ovary were flushed and fluid was aspirated from the dominant follicle in the oestrous preovulation group. Glycosaminoglycans and protein concentrations were measured in these...
To evaluate the effect of four recumbent body positions on intraocular pressure (IOP) in anesthetized normal horses. Methods: Ten nonglaucomatous adult horses. Methods: Intraocular pressure was measured with a rebound tonometer in both eyes of standing sedated horses (baseline), then under general anesthesia during four randomized recumbent body positions, including Trendelenburg (Tr; 15-degree head down), reverse Trendelenburg (RTr; 15-degree head up), dorsal, and lateral; only the superior eye was measured in lateral positions. The mean of 3 IOP readings was taken at each position, allowing ...
Draper ACE, Cahalan SD, Goodwin D, Perkins J, Piercy RJ.Equine recurrent laryngeal neuropathy (RLN) is a naturally occurring model of length-dependent axonopathy characterized by asymmetrical degeneration of recurrent laryngeal nerve axons (RLn). Distal RLn degeneration is marked, but it is unclear whether degeneration extends to include cell bodies (consistent with a neuronopathy). With examiners blinded to RLN severity, brainstem location, and side, we examined correlations between RLN severity (assessed using left distal RLn myelinated axon count) and histopathological features (including chromatolysis and glial responses) in the nucleus ambiguu...
Mahony C, Rantanen NW, DeMichael JA, Kincaid B.Spontaneous echocardiographic contrast is the term used by ultrasonographers to describe particulate material visible in intracardiac blood by ultrasound. The purpose of the present study was to determine the prevalence of spontaneous contrast in a farm population of Thoroughbreds and in the farm's racehorses. The results showed that spontaneous echocardiographic contrast is common in Thoroughbreds, and that the prevalence of contrast is affected by age, male gender, racing and pregnancy. The amount of right-sided cardiac contrast was quantitated by videodensitometry and was increased in horse...
Eiler H, Goble D, Oliver J.The plasma concentration of hydrocortisone was determined in mares given either cosyntropin (100 IU, given IV) or corticotropin (200 IU, given IM). Plasma hydrocortisone concentrations of the mares treated with cosyntropin increased by 46%, 57% and 80% at 30, 60, and 120 minutes, respectively, when compared with base-line values; these values returned to base line at 240 minutes. In mares treated with corticotropin, mean plasma hydrocortisone concentrations increased by 42%, 143%, 101% and 155% at 30, 60, 120, and 240 minutes, respectively, when compared with base-line values. Differences in t...
Oliveira SN, Segabinazzi LGTM, Canuto L, Lisboa FP, Medrado FE, Dell'Aqua JA, Aguiar AJA, Papa FO.The goal of this study was to compare the efficiency of histrelin acetate (GnRH analog) and human chorionic gonadotropin (hCG) to hasten ovulation in Brazilian Northeastern jennies (Equus africanus asinus). Thirty cycles of ten jennies were randomly assigned in one of the three groups: G0 (control group), saline; G1, 250 μg of histrelin acetate; G2, 2500 IU of hCG. Jennies were evaluated by transrectal palpation and ultrasonography, and had the administration of an ovulation-inducing agent when a follicle measuring between 29 and 32 mm of diameter was diagnosed. Jennies were monitored every...
Bailey SR, Andrews MJ, Elliott J, Cunningham FM.Altered platelet responsiveness has been demonstrated in human atopic dermatitis. This study has compared the in vitro function of platelets from normal ponies and those with the allergic skin disease, sweet itch. Methods: Ponies with a clinical history of sweet itch and normal ponies were used as blood donors. Methods: PAF and ADP-induced platelet aggregation was measured and TxB2 production quantitated at the time of maximal aggregation; 12-HETE was additionally measured in some samples. Agonist-induced release of 3[H]5-HT was also studied. Results: Although both PAF and ADP caused equine pl...
Soma LR, Uboh CE, Guan F, Birks EK, Teleis DC, Rudy JA, Tsang DS, Watson AO.To determine pharmacokinetics and excretion of phenytoin in horses. Methods: 6 adult horses. Methods: Using a crossover design, phenytoin was administered (8.8 mg/kg of body weight, IV and PO) to 6 horses to determine bioavailability (F). Phenytoin also was administered orally twice daily for 5 days to those same 6 horses to determine steady-state concentrations and excretion patterns. Blood and urine samples were collected for analysis. Results: Mean (+/- SD) elimination half-life following a single IV or PO administration was 12.6+/-2.8 and 13.9+/-6.3 hours, respectively, and was 11.2+/-4.0 ...
Bayly WM, Slocombe RF.Effects of respiratory tract obstructions on ventilatory mechanics in horses exercising at high speeds were tested with a fibreglass replica of the airways (nares to mainstem bronchi) of an adult horse. Segmental pressures were recorded at six sites along the model at four different unidirectional flows (1300-4100 litre min-1), and the respective resistances (R) to airflow were calculated. The external nares and the larynx made the greatest contributions to the total resistance (RTOT) when no obstruction was present. Modifying the model to simulate severe pharyngeal lymphoid hyperplasia (PLH) ...
de Paula VB, Canola PA, Rivera GG, Z Filho D, Amaral GPD, Ferraz GC, Ferraudo AS, Canola JC.To investigate effects of postural changes and bladder distention on intrabladder pressure whilst estimating intra-abdominal pressure in horses. Two-year cohort study. Patients admitted for elective surgical procedures unrelated to gastrointestinal or genitourinary tract. School of Agricultural and Veterinarian Sciences, Jaboticabal, SP, Brazil. 20 adult horses, 11 males (stallions and geldings) and 9 females; between 3.5 and 12 years, weighing 350 to 500 kg. Intra-abdominal pressure was directly-recorded through abdominocentesis at the ventral midline with a fluid-filled system. Intrabladder ...
Drevemo S, Johnston C, Roepstorff L, Gustås P.Nerve blocks and intra-articular anaesthesia are used extensively as routine methods in lameness evaluation. The method is based on the assumption that the technique itself does not change the movement pattern. The aim of this study was to carry out a quantitative kinematic study to confirm or reject the hypothesis that high palmar digital nerve block (HPDN) and intra-articular fetlock joint anaesthesia (IAF) influence significantly the movement pattern of the horse. Seven Standardbred horses trotting at 4.5 m/s were recorded at 240 Hz on a treadmill before and after anaesthesia by use of a Pr...
Glycogen in skeletal muscle is a major source of energy during exercise and an important determinant of endurance capacity, so that its measurement may provide a meaningful marker of athletes' preparation and a possible predictor of performance, both in humans and in equines. Gold standard of glycogen concentration measurement is the histochemical and biochemical analysis of biopsy-derived muscle tissue, an invasive and potentially injuring procedure. Recently, high-frequency ultrasound (US) technology is being exploited in human sports medicine to estimate muscle glycogen content. Therefore, ...
Santos VG, Bettencourt EM, Ginther OJ.Persistent CL (PCL; n = 10) in mares was studied daily from Day 20 (Day 0 = ovulation) to the ending ovulation. In addition, the 10 days before ovulation at the end of a PCL were compared with the end of an interovulatory interval (IOI; n = 28) during the same months. Concentration of P4, cross-sectional area of CL, and percentage of CL with Doppler signals of blood flow during PCLs remained constant from 64 to about 33 days before the end of luteolysis and then decreased linearly. Concentration of LH between Day 20 and beginning of the ovulatory LH surge increased linearly. A dominant follicl...
Van de Water E, Oosterlinck M, Pille F.The effects of handler position and perineural anaesthesia in sound horses need investigation to facilitate interpretation of pressure plate analysis in lame horses. Objective: To evaluate the effect of handler position and perineural anaesthesia on limb loading and particularly hoof balance in sound horses. Methods: Nonrandomised crossover study. Methods: Six sound horses were walked and trotted over a pressure plate, with the handler on the left and subsequently on the right side, and finally after a bilateral low palmar digital nerve block. One week later this procedure was repeated before ...
Creel JA, Stover SM, Martin RB, Fyhrie DP, Hazelwood SJ, Gibeling JC.The compliance technique has been used to monitor crack length during fracture and fatigue testing of materials. Difficulties arise when this technique is applied to anisotropic biological materials such as bone. In this tutorial, two different methods of analyzing compliance calibration data are described: the standard ASTM method and a new approach developed by the authors specifically for anisotropic materials. An example is given showing how data from equine cortical bone can be analyzed. In this example, calibration tests were conducted on thirty-six three point bend specimens machined fr...
Gil L, Saura S, Echegaray A, Martinez F, de Blas I, Akourki A, Gonzalez N, Espinosa E, Josa A.The present study evaluated the effect of supplementing the medium used to mature equine oocytes in vitro with oestrous mare serum (EMS) or horse follicular fluid (HFF). To this end, 144 ovaries were obtained from mares aged 16-21 months and transported to the laboratory in Dulbecco's phosphate buffered saline (D-PBS) at 30 degrees C. Oocytes were harvested from the ovaries by slicing, and then selected for in vitro maturation (IVM) according to the number of cumulus cell layers and the characteristics of the cytoplasm. The selected oocytes were washed three times in TCM199 medium plus HEPES (...
Derrick D, Gick B.During locomotion, humans switch gaits from walking to running, and horses from walking to trotting to cantering to galloping, as they increase their movement rate. It is unknown whether gait change leading to a wider movement rate range is limited to locomotive-type behaviours, or instead is a general property of any rate-varying motor system. The tongue during speech provides a motor system that can address this gap. In controlled speech experiments, using phrases containing complex tongue-movement sequences, we demonstrate distinct gaits in tongue movement at different speech rates. As spea...
Rovel T, Duchateau L, Saunders J, Vandenberghe F, Vanderperren K.Narrowing of the equine cervicothoracic intervertebral foramina (IF) has the potential to cause forelimb lameness and/or neck pain although limited information is available on CT of the IF. The aims of this retrospective, analytical study were to describe a protocol for quantifying CT cervicothoracic IF size; evaluate the repeatability of IF size measures; test associations between IF size and adjacent articular process (AP) size, ventral extent, and anatomic location; and determine the proportion of IF with narrowing. Computed tomographic images were acquired in 20 Warmblood horses that prese...
Zhang CH, Grünig G, Davis W, Antczak DF.The regulatory effects of phorbol myristate acetate (PMA) on the expression of the CD4 molecule on horse T cells were investigated. On both peripheral blood lymphocytes and thymocytes, PMA resulted in a rapid and transient down-regulation of equine CD4 expression, but had no such effect on the surface expression of equine CD5, CD8 or major histocompatibility complex (MHC) class I and class II molecules. Over 75% of the surface CD4 molecules per cell were lost after a 4 h exposure to PMA at 37 degrees C. The regulation of equine CD4 expression induced by PMA was temperature dependent and revers...
Ferrante PL, Kronfeld DS.Collection of a satisfactory blood sample requires special procedures to prevent changes in glucose and lactate content after the sample has been obtained. Changes in measured plasma glucose and blood lactate concentrations attributable to anticoagulants and storage procedures, respectively, were examined in blood samples obtained from horses at rest and after exercise. To evaluate the effect of anticoagulants on measured plasma glucose concentration, blood was preserved with either sodium fluoride/potassium oxalate or lithium heparin. Measured plasma glucose concentration in blood obtained at...
Jarosinski SK, Sampson SN, Russell L.Injection of the centrodistal (CD) joint in the horse is a commonly performed procedure for both diagnostic and therapeutic purposes. This procedure can be technically challenging, and while radiographic guidance has been previously used, ultrasound localised injection of the CD joint has not been described. Objective: The purpose of this study was to explore the feasibility of using ultrasound localisation to increase the accuracy of CD joint injection. Methods: Experimental method assessment. Methods: One operator performed the ultrasound and injection of 24 CD joints in 12 sedated horses. T...
Bousfield GR, Ward DN.Ovine (o) and equine (e) LH alpha-subunits were reduced and reoxidized using conditions known to be effective for bovine and human alpha-subunits. The major product of oLH alpha refolding was alpha-subunit monomer. In contrast, eLH alpha formed a 121,000 mol wt aggregate. Monomeric eLH alpha was recovered, but in greatly reduced yield. To test the effects of carbohydrate variation on the aggregation of equine alpha-subunits, all of the equine gonadotropin alpha-subunits (eFSH alpha, eCG alpha, eLH alpha, and free alpha-subunit) were reduced and reoxidized. In each case, the major product was t...
Rahnama S, Vathsangam N, Spence R, Anderson ST, de Laat MA, Bailey S, Sillence MN.Prolonged hyperinsulinemia is thought to be the cause of equine endocrinopathic laminitis, a common and crippling disease of the foot, for which there are no pharmacologic treatments other than pain relief. It has been suggested that insulin causes its effects on the lamellae by activating IGF-1 receptors (IGF-1R), as insulin receptors (InsR) are scarce in this tissue, whereas IGF-1R are abundant and become downregulated after prolonged insulin infusion. As a first step toward confirming this mechanism and beginning to develop a therapeutic anti-IGF-1R monoclonal antibody (mAb) for horses, it ...
Santos M, López-Sanromán J, García-Iturralde P, Fuente M, Tendillo FJ.To determine the cardiopulmonary effects of desflurane (DES) in horses. Methods: Six healthy adult horses, three males and three females, aged 9 +/- 4 (mean +/- SD) years and weighing 370 +/- 36 kg. Methods: Anaesthesia was induced with an O2 (10 L minute(-1)) and DES mixture (vaporizer setting 18%). After oro-tracheal intubation, horses were positioned in right lateral recumbency. Anaesthesia was maintained with DES in O2 (20 mL kg(-1) minute(-1)) delivered through a large animal circle breathing system. The minimum alveolar concentration of DES (MAC(DES)) that prevented purposeful movement i...
Swanson CR, Muir WW.The influence of pharmacologic enhancement of cardiac output on the alveolar-to-arterial oxygen tension (difference (P[A-a]O2), physiologic right-to-left shunt fraction (Qs/Qt), and physiologic dead space-to-tidal volume ratio (VD/VT) ws studied in halothane-anesthetized horses in left lateral, right lateral, and dorsal recumbencies. Adult horses were anesthetized, using xylazine (2.2 mg/kg, IM), guaifenesin (50 mg/kg, IV), thiamylal (4.4 mg/kg, IV), and halothane (1.5% to 2% inspired) in 100% O2. Mechanical ventilation was controlled to maintain arterial eucapnia (PaCO2) 35 to 45 mm of Hg) fo...
Carstanjen B, Hoyle NR, Gabriel A, Hars O, Sandersen C, Amory H, Remy B.To evaluate a human assay for quantification of carboxy-terminal cross-linking telopeptide of type I collagen (CTX-I), assess the influence of age on plasma CTX-I concentration, investigate the relationship between plasma CTX-I and serum osteocalcin concentrations, and determine whether concentrations of plasma CTX-I or serum osteocalcin fluctuate in circadian manner in horses. HORSES: 75 clinically normal horses. Methods: Cross-reactivity between equine serum CTX-I and CTX-I antibodies in an automated electrochemiluminescent sandwich antibody assay (ECLIA) was evaluated via a specificity test...
Muylle S, Simoens P, Lauwers H.The objective of this study was to examine the diameter, extent, orientation and contents of dentinal tubules in order to validate the hypothesis of pigment penetration into the dental star of equine incisival occlusal surfaces. The time of appearance and the configuration of the dental star on the incisival occlusal surface are macroscopically visible features that, along with other more reliable parameters, are used for the determination of horses' age. Although dental stars are an integral part of the equine incisor occlusive surface, the exact nature and microstructure of the dental star a...
Sirois J, Kimmich TL, Fortune JE.Estrous cycles in mares have several unique characteristics, including the presence of a long period of estrus and the absence of a typical LH surge. Like follicles of other species, equine preovulatory follicles are characterized by their ability to secrete large amounts of 17 beta-estradiol, but it is not clear which follicular cell type is responsible for estradiol synthesis in mares. To better understand the relative roles of theca interna and granulosa cells in follicular steroidogenesis, presumptive ovulatory follicles were obtained from mares during early estrus (first or second day of ...
Frey LP, Kline KH, Foreman JH, Lyman JT.The efficacy of using calcium carbonate as an osmolar control treatment for acid-base studies in horses receiving alkalizing compounds was evaluated. Six mares were nasogastrically intubated with isomolar quantities of sodium or calcium as sodium bicarbonate or calcium carbonate or with water during three treatment periods. Doses of the carbonic acid salts were 500 mg/kg sodium bicarbonate mixed with 4 L of distilled water (positive control) and 595 mg/kg calcium carbonate mixed with 2 L of distilled water to yield isoosmolar treatments. Four liters of distilled water served as the negative co...
