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.
INGRAM DG.A method is described for the quantitative measurement of the reactions between sensitized cells and horse complement and between alexinated cells and conglutinin. The method is laborious but its application has allowed the determination of the optimal times of the reactions at various temperatures. The results obtained in these experiments indicate that the alexinated configuration with which conglutinin and immuno-conglutinin react is not one of the recognized intermediates formed during the process of immune haemolysis.
HOLT JP, RHODE EA, PEOPLES SA, KINES H.Studies of left ventricular volume and pressure have been carried out in the control state in four classes of intact anesthetized mammals (horses, cattle, swine, and dogs), body weights of which varied 54-fold. On the basis of these studies of both large and small hearts, extending over a wide range, a pattern of function for the left ventricle of all mammals has been described. Mathematical equations are given describing the interrelationships between left ventricular end-diastolic volume and end-systolic volume, stroke volume, cardiac output, stroke-work, heart rate, and total peripheral res...
SHORT RV.A comparison has been made between the steroids present in equine follicular fluid and luteal tissue. Follicular fluid was found to contain progesterone, 17α-hydroxyprogesterone, androstenedione, epitestosterone, 19-norandrostenedione, oestrone, oestradiol-17β and 6α-hydroxyoestradiol-17β, in confirmation of previous studies. On the other hand, luteal tissue contained large amounts of progesterone and 20α-hydroxypregn-4-en-3-one, and a small quantity of 17α-hydroxyprogesterone. No C18 or C19 steroids could be detected.
These findings are therefore interpreted as evidence in favour of ...
Basova NE, Kormilitsin BN, Perchenok AIu, Rozengart EV, Saakov VS, Suvorov AA.There was studied action of aliphatic alcohols (ethanol, propanol, isopropanol, n-butanol, isobutanol, secbutanol, tretbetanol) and pH on various kinds of reactional capability the serum cholinesterase. At the alcohols-affected inhibition of the cholinesterase hydrolytic activity, the determining role was played not the total number carbon atoms in the alcohol molecule, but by the "effective length" of the carbohydrate chain. The fact that the presence of alcohols did not affect parameters of the reverse cholinesterase inhibition with onium ions tetramethylammonium and choline allows suggestin...
Sato F, Hasegawa T, Katayama Y, Ishida N.Complementary DNA (cDNA) encoding equine dopamine beta-hydroxylase (DBH) was amplified with a combination of reverse transcription-polymerase chain reaction (RT-PCR) and rapid amplification of cDNA ends (RACE) method, and their nucleotide sequences (Accession No. AB029430: the DDBJ nucleotide sequence database) was determined. A total of 3842 bp cDNA sequence was consisted with 5 bp of 5' flanking untranslated sequence, 1833 bp of open reading frame encoding 610 amino acids, and 2004 bp of 3' flanking untranslated sequence. The deduced amino acid sequence of equine DBH was very similar to the ...
Bakos Z, Vörös K.Since percussion started to be a method forgotten and not trusted by many practitioners, the aim of the study was to demonstrate whether this procedure could deliver exact data if done accurately and by a practised examiner. The trial presented here included 31 healthy warm-blooded horses. Percussion of the area of cardiac dullness and then echocardiographic imaging of the same region were performed. To obtain the relevant measurement points, the 4th and 5th intercostal spaces (ICS) were used on the left and the 4th ICS on the right side. On the left side, the dorsal border of cardiac dullness...
Enders AC, Liu IK.The free allantois and allantochorion of conceptuses from 17 mares between 20 and 90 days of gestation were examined to determine the manner in which the associated mesodermal derivatives differentiated. It was found that a robust basement membrane developed under the allantoic endoderm, and that this basement membrane was partially isolated from the vascular layer of the allantois by a mesothelial layer and an exocelom-like space. The exocelom-like space persisted until approximately the stage of villous formation, and remnants of the space persisted over larger allantoic vessels even later. ...
Zander R, Flachowsky G, Schubert R, Gruhn K.The nylon-bag method was applied for determination of the rumen degradation of dry matter and nitrogen of 15N-labelled wheat straw. For the experiment 4 wethers fitted with a rumen cannula were used. The bags containing 15N straw were introduced into the rumen and withdrawn 3, 6 or 12 h after incubation. In a second experiment the apparent 15N-digestibility of the same straw was determined in wether and pony. The dry matter disappearance varied between 6 and 23%. For 15N-labelled straw the disappearance of 15N was higher than that of total N. 12 h after incubation 71% of 15N and only 25% of to...
Tyler CR, Filby AL, Bickley LK, Cumming RI, Gibson R, Labadie P, Katsu Y, Liney KE, Shears JA, Silva-Castro V, Urushitani H, Lange A, Winter MJ....Many factors have been considered in evaluations of the risk-benefit balance of hormone replacement therapy (HRT), used for treating menopausal symptoms in women, but not its potential risks for the environment We investigated the possible environmental health implications of conjugated equine estrogens (CEEs), the most common components of HRT, including their discharge into the environment, their uptake, potency, and ability to induce biological effects in wildlife. Influents and effluents from four U.K. sewage treatment works (STWs), and bile of effluent-exposed fish, were screened for six ...
Brice AG, Forster HV, Pan LG, Lowry TF, Murphy CL, Mead J.We studied the changes in breathing and respiratory muscle electromyograms (EMG) during passively induced increases in end-expiratory lung volume (EELV) in awake normal (N), hilar nerve-denervated (HND), carotid body-denervated (CBD), and HND + CBD ponies. EELV was increased by applying continuous negative pressure (-10 and -20 cmH2O) around the torso of the standing pony. In all groups, negative pressure produced sustained increases in EELV that were linearly related to the degree of negative pressure. Elevated EELV decreased breathing frequency (f) in N and CBD ponies but increased f in HND ...
Ben-Menahem D, Grotjan HE.Chorionic gonadotropins (CG) are unique because they have a carboxyl terminal peptide (CTP) extension on their beta subunits that prolongs circulatory survival. CGbeta genes from the human being and horse have evolved from ancestral luteinizing hormone (LH) beta genes by different pathways that involve deletions that change the reading frames and yield a CTP. Here we further review our previous analysis, aimed at determining whether LHbeta genes in non-primate, non-equid species inherently possess DNA sequences that encode CTP-like domains. In multiple mammalian species, simple frame-shift mut...
Yamada S, Suruga K, Ogawa M, Hama T, Satoh T, Kawachi R, Nishio T, Oku T.The appearance of NO2- reducing activity of cytochrome c (Cyt c) upon heat denaturation was investigated with equine heart Cyt c. Denatured equine heart Cyt c (dCyt c), which was treated at 100 degrees C for 30 min, had NO2- reducing activity in the presence of dithionite and methylviologen in an aqueous solution under anaerobic conditions. In contrast, hemoglobin and myoglobin had no such activity under the same conditions. Using spectroscopic methods, we found that the appearance of this activity in the Cyt c was due to the following intramolecular changes: unfolding of the peptide chain, ex...
Schmid RL, Kato H, Herickhoff LA, Schenk JL, McCue PM, Chung YG, Squires EL.In Expt 1, compact cumulus oocyte complexes (COCs) were matured in: (i) control medium (Hepes-buffered TCM-199 with 10% oestrous cow serum (OCS) + oestradiol, LH and FSH); (ii) Hepes-buffered TCM-199 with 20% follicular fluid; or (iii) control medium containing 250 ng progesterone ml(-1). Mature oocytes were collected by transvaginal aspiration as a positive control for the in vitro maturation (IVM) treatments. Oocytes were fertilized by ICSI and cultured in Menezo's B2 + 5% fetal calf serum (FCS). There were no significant differences among IVM treatments. In Expt 2, oocytes with expanded COC...
Daniel GB, Tucker RL, Buckman T, Daniel SL.Isolated equine granulocytes (WBC), radiolabeled with 99mTc-hexamethylpropyleneamine oxime (99mTc-HMPAO) or 111In-oxine, were evaluated in vitro for their labeling characteristics, viability, and phagocytic function over a 6-hour postlabeling period. Mean +/- SD labeling efficiency for 111In-oxine-WBC was 62.2 +/- 15.3%, which was significantly (P less than 0.001) higher than that for 99mTc-HMPAO-WBC (32.0 +/- 17.0%). In vitro elution of radiolabel from cells was significantly (P less than 0.02) greater for 99mTc-HMPAO-WBC at 0.5, 2, and 4 hours, but was not significantly different from elutio...
Yee S, Peyton DH.The redistribution of the initially-formed myoglobin heme-insertion isomers from the initially formed 50/50 mixture to the equilibrium ratio of 90/10 has long been assumed to occur by one of two mechanisms, both of which require the rupture of the heme iron-protein bond (La Mar, G.N., Toi, H. and Krishnamoorthi, K. (1984) J. Am. Chem. Soc. 106, 6395-6401). In this study we compared the use of nuclear magnetic resonance and optical spectroscopic techniques as methods for studying the reorientation of heme within myoglobin. We found that kinetics determinations of the heme insertion isomer redis...
Taylor EL, Sellon DC, Wardrop KJ, Hines MT, Kingston JK.To assess safety and determine effects of IV administration of formaldehyde on hemostatic variables in healthy horses. Methods: 7 healthy adult horses. Methods: Clinical signs and results of CBC, serum biochemical analyses, and coagulation testing including template bleeding time (TBT) and activated clotting time (ACT) were compared in horses given a dose of 0.37% formaldehyde or lactated Ringer's solution (LRS), IV, in a 2-way crossover design. In a subsequent experiment, horses received an infusion of 0.74% formaldehyde or LRS. In another experiment, horses were treated with aspirin to impai...
Hellyer PW, Dodam JR, Light GS.Dynamic baroreflex sensitivity for increasing arterial pressure (DBSI) was used to quantitatively assess the effects of anesthesia on the heart rate/arterial pressure relationship during rapid (less than or equal to 2 minutes) pressure changes in the horse. Anesthesia was induced with IV administration of xylazine and ketamine and maintained with halothane at a constant end-tidal concentration of 1.1 to 1.2% (1.25 to 1.3 minimal alveolar concentration). Systolic arterial pressure (SAP) was increased a minimum of 30 mm of Hg in response to an IV bolus injection of phenylephrine HCl. Linear regr...
Skarda RT, Muir WW.To determine effects of i.v. administered yohimbine on perineal analgesia, cardiovascular and respiratory activity, and head and pelvic limb position in healthy mares following epidural administration of detomidine hydrochloride solution. Methods: 8 healthy mares. Methods: Each mare received detomidine hydrochloride (0.06 mg/kg of body weight), administered in the caudal epidural space, followed 61 minutes later by yohimbine (0.05 mg/kg; test) or sterile saline (0.9% NaCl) solution (control), administered i.v., in a randomized, crossover study design with > or = 2 weeks between treatments. ...
Bianchi M.In 13 horses from both sexes, between 5 months and 18 years of age, in good nutritional state, statistical evaluations of fat cell sizes were performed in 16 body regions. From direct and indirect measurements referred to the cell diameter and cell number in equivalent areas, carried out on sections from paraffin embedded material and on preparations of dissociated whole cells, it emerged that the adipose cells of the subserous fat of the abdominal floor are consistently the largest, whereas those of the orbital fat body and supraorbital fossa are the smallest. In the other regions the cells h...
Ramírez A CE, Hurtado-Macías A, Talamantes R, Flores E, Ladrón de Guevara HP, Delgado JI, Estrella RA, Riestra JM, Montes JM, Esmonde-White K....Guided bone regeneration surgeries are based on grafting a scaffold in the site to be repaired. The main focus of the scaffold is to provide mechanical support to newly formed blood vessels and cells that will colonize the grafted site, achiving bone regenertation. In this regards, the aim of this study was to characterize the anatomy, structular, surface morphologycal, chemical composition, and nanomechanical properties of ostrich and equine trabecular bone. Ostrich and equine specimens were obtained from a local abattoir and bone was obtained by blunt dissection, n = 5. Tissue bone anatomy...
Makhaeva GF, Shataeva GA, Iankovskaia VL, Fetisov VI, Loshadkin NA.The interaction of human erythrocyte acetylcholinesterase, horse serum butyrylcholinesterase and rat liver carboxylesterase with insecticides (RO)2P(O)SCH(COOEt)SP(O)(OR)2 (I) and (RO)2P(O)SCH(COOEt)OP(S)(OR)2 (II) was studied. The type I and II compounds were not hydrolyzed by carboxylesterase and inhibited the esterases irreversibly. A complex pattern of inhibition of acetylcholinesterase and butyrylcholinesterase by these compounds was caused by kinetically-manifested formation of an enzyme-inhibitor complex. The compounds I and II were more selective towards butyrylcholinesterase than towa...
Mieszkowska M, Holak P, Zhalniarovich Y, Mieszkowski M, Domagalska-Stomska K.A sound knowledge of horseshoe impact on blood flow parameters is required for making shoeing decisions and selecting the most appropriate types of shoes. The aim of this study was to determine the effect of horse shoeing with egg bar shoes and shoes with wedge pads on blood flow parameters in the lateral palmar digital artery measured by Doppler ultrasound. The study was conducted on 16 horses divided into two groups. Horses from group 1 were shod with egg bar shoes. Horses from group 2 were shod with shoes with wedge pads. Doppler ultrasound parameters of the lateral palmar digital artery at...
Rakotoarisoa L, Mironneau C, Sayet I, Mironneau J.Specific binding of the Ca++ antagonist desmethoxyverapamil, (-)-[3H]D888, to cell membranes of equine portal vein smooth muscle was inhibited in a concentration-dependent manner by guanosine 5'-O-(gamma-thio)triphosphate and ATP but was little affected by guanosine 5'-O-(beta-thio)diphosphate, noradrenaline or phorbol 12-myristate 13-acetate ester. Inhibition constants for GTP and ATP were in the range of 0.1 to 0.3 mM. From Scatchard plots and dissociation kinetic experiments, it is proposed that D888 high affinity binding sites are transferred into low affinity sites. In intact strips of ra...
Hubbard CD, Shoupe TS.A transient phase for the hydrolysis of indophenyl acetate by the commercial preparation of horse serum cholinesterase was observed on a stopped-flow spectrophotometer. It was found that the transient process is a reaction of the ester with a major component of the preparation and is not caused by the serum cholinesterase enzyme. This noncholinesterase component was isolated and the dependence of its concentration and that of the ester upon the transient liberation of the indophenolate ion were determined. Studies with the isolated component and subsequent analyses have led to the tentative id...
Saint-Dizier M, Chopineau M, Dupont J, Combarnous Y.The full-length equine luteinizing hormone/chorionic gonadotropin (LH/CG) receptor (eLH/CG-RA) cDNA and two alternatively spliced isoforms (eLH/CG-RB,C) were isolated from luteal tissue and characterized using a combination of reverse transcription-polymerase chain reaction (RT-PCR) and 5'-rapid amplification of cDNA ends. The 680-amino acid full sequence of eLH/CG-RA displayed 87-92% homology with other mammalian LH/CG-Rs. The eLH/CG-RB and eLH/CG-RC cDNA isoforms were truncated from the 3'-end of exon X: eLH/CG-RB spliced out of frame into the last exon whereas eLH/CG-RC contained an in-fram...
Niyom S, Mama KR, King M, Contino E, Ferris D, Valdes-Martinez A, Frisbie DD, McIlwraith W, Zumbrunnen J.This study investigated the influence of changing recumbency and mode of ventilation over repeated anesthesias on the alveolar to arterial oxygen tension gradient (PO) and laboratory analytes in eight horses during a year-long imaging study. Anesthesia was induced with xylazine, diazepam or guaifenesin, and ketamine and maintained with isoflurane. Horses were positioned in right or left lateral recumbency for computed tomography. Ventilation was controlled during 47% of the anesthetics. Blood was sampled from an arterial catheter prior to (30 ± 5 min from connection to anesthetic circuit), wi...
Melrose PA, Douglas RH.Scanning electron microscopy showed that cells in the infundibular recess of prepubertal female horses were devoid of cilia and sparsely covered with stubby microvilli and small blebs, whereas superior ventricular areas were covered with cilia. Ciliated ependymal cells in supraoptic-suprachiasmatic areas were associated with extensive blebbing, and folded tissue adjacent to the inferior borders of the mamillary body displayed distinct bands of cilia regularly interrupted by areas of sparsely ciliated cells which appeared to be undergoing ciliogenesis. Arcuate ependymal areas had well developed...
Eddy AL, Galuppo LD, Stover SM, Taylor KT, Jensen DG.To compare mechanical properties and failure characteristics of 2 methods of fixation for repair of a transverse, midbody fracture of the proximal sesamoid bone (PSB): 4.5-mm AO cortical bone screw (AO) placed in lag fashion and 4/5-mm Acutrak (AT) self-compressing screw. Methods: An in vitro biomechanical evaluation of intact forelimb preparations and forelimb preparations with a simulated midbody PSB fracture stabilized by a bone screw. Methods: Sixteen paired and 8 unilateral cadaveric equine forelimbs. Methods: A midbody transverse osteotomy was created in the medial PSB of bilateral forel...
Martin EM, Schirmer JM, Jones SL, Davis JL.Misoprostol is an E prostanoid (EP) 2, 3 and 4 receptor agonist that is anecdotally used to treat and prevent NSAID-induced GI injury in horses. Misoprostol elicits anti-inflammatory effects in vivo in men and rodents, and inhibits TNFα production in equine leucocytes in vitro. Objective: Define the pharmacokinetic parameters of oral misoprostol in horses, and determine the inhibitory effect of oral misoprostol administration on equine leucocyte TNFα production in an ex vivo inflammation model. Methods: Pharmacokinetic study, ex vivo experimental study. Methods: Six healthy adult horses ...
Tamayo-Arango LJ, Mejía-Durango MA.Gross anatomy is considered one of the most challenging subjects in teaching veterinary medicine. The use of body painting is reported in teaching surface human anatomy, but such reports are scarce in veterinary medicine. The aim of this study was to describe a practical session for teaching surface anatomy using body painting with second-semester students of veterinary medicine. Two practical sessions using live animals (equine and bovine) were offered with a focus on the locomotor and nervous systems and splanchnology. Students believed that the body painting sessions helped them to understa...
Thompson DL, Reville SI, Derrick DJ.Five mature Quarterhorse mares were bled every 30 min for 25 h on day 50 of pregnancy to determine the short-term mode of secretion of equine chorionic gonadotropin (eCG). Three other mares with persistent endometrial cups after abortion were administered gonadotropin releasing hormone (GnRH; 1.0 mug/kg of body weight) and were bled immediately prior to and at 15, 30, 45, 60, 90, 120, 180 and 240 min after GnRH. Concentrations of eCG in plasma of pregnant mares were constant over the 24-h period; the variation of each mare's individual values was no greater (P>.05) than the predicted random...
Camp CJ, Leid HW.Extracts of Onchocerca cervicalis, an equine parasite, were incubated with radiolabeled equine neutrophils and neutrophil migration was assessed for factors derived from the parasite itself or for host-derived factors after incubation of these same parasite extracts with equine serum. No stimulus for cell migration was observed in saline extracts of adult worms, uterine microfilariae, or skin microfilariae at any dosage tested. However, after incubation of saline extracts with fresh normal equine sera a marked stimulus for neutrophil migration was observed. Ablation of this biologic activity w...
Collins ND, LeRoy BE, Vap L.Extremely high bicarbonate (HCO3-) and anion gap values were measured in two horses and a calf using the Hitachi 911 automated serum biochemistry analyzer. All three animals had severe muscle disease as evidenced by markedly increased aspartate aminotransferase and creatine kinase activities. Laboratory error was suspected as the source of the increased HCO3- because values calculated from blood gas analysis were normal. It was hypothesized that increased serum lactate dehydrogenase (LDH) activity and pyruvate concentration overwhelmed the oxamate LDH inhibitor in the enzymatic HCO3- assay, re...
