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.
Brugmans F, Venner M, Menzel D, Mischke R.The purpose of this study was to investigate the usefulness of two heat-precipitation techniques (Schalm- and Millar-method) as screening tests to measure plasma fibrinogen concentration in horses. Based on the measurement of samples from 108 different horses, the coefficient of correlation (CC) for the relationship between the results with the Schalm- and with the reference-method (Jacobsson) were much lower (r = 0.78) than between the Millar- and Jacobsson-method (r = 0.94). Furthermore the Schalm-method was less precise as reflected by the greater coefficient of variation (CV, within-run pr...
Ludewig T.Corpora amylacea are present in all the mammary glands of the investigated animals (ewe, goat, and mares). Generally, they are comparable to the cow regarding to its distribution, frequency, size, morphological structure, and staining properties. Corpora amylacea occur most frequently in the ewe, and in non-lactating mammary glands. In lactating mammary glands they are mostly situated in the alveoles. During gestation they are located outside of the alveoles and in the interalveolar connective tissue. Only in very few cases corpora amylacea are found inside and outside of the alveoles in the s...
Moens Y, Lagerweij E, Gootjes P, Poortman J.To study effects of intermittent positive-pressure ventilation (IPPV) with large tidal volumes and addition of positive end-expiratory pressure (PEEP) on maldistribution of ventilation in anesthetized horses positioned in lateral recumbency. Methods: 6 healthy adult horses. Methods: Anesthesia was induced by i.v. infusion of thiopental sodium and guiafenesin and was maintained with supplemental doses of thiopental and i.v. infusion of chloral hydrate. Functional separation of the lungs was achieved, using a tube-in-tube intubation technique. Intermittent positive-pressure ventilation of both l...
Becker CK, Savelberg HH, Buchner HH, Barneveld A.To evaluate posttrauma biomechanical behavior of the scar attributable to desmotomy of the accessory ligament of the deep digital flexor tendon (AL-DDFT), compared with the histomorphologic and ultrasonographic appearance. Methods: 5 Standardbred trotters. Methods: Gross appearance, length, cross-sectional area (CSA), in vitro material properties, and ultrasonographic and histomorphologic features were studied 6 months after desmotomy. Tensile tests were conducted, with forces and elongation simultaneously recorded. Surgically treated limbs were compared with nontreated contralateral limbs. Re...
Lester GD, Merritt AM, Neuwirth L, Vetro-Widenhouse T, Steible C, Rice B.To determine effect of xylazine hydrochloride (XYL), yohimbine hydrochloride (YOH), bethanechol chloride (BET), neostigmine methyl sulfate (NEO), or flunixin meglumine (FLU) on ileocecocolic myoelectric activity and passage of radiolabeled markers from the cecum. Methods: 6 healthy adult ponies. Methods: A cecal cannula was surgically implanted, and 12 were sutured to the ileum, cecum, and right ventral colon. After a 12-hour nonfeeding period, 370 MBq of technetium 99m-labeled sulfur colloid in egg albumen and 37 MBq of indium 111-labeled diethyltriaminepentaacetic acid in 60 ml of water were...
Lester GD, Merritt AM, Neuwirth L, Vetro-Widenhouse T, Steible C, Rice B.To determine the effect of erythromycin lactobionate (ERY) on ileocecocolic myoelectric activity and passage of radiolabeled markers from the cecum. Methods: 6 healthy adult ponies. Methods: After a 12-hour nonfeeding period, 370 MBq of technetium 99m-labeled sulfur colloid in egg albumen and 37 MBq of indium 111-labeled diethyltriaminepentaacetic acid in 60 ml of water were administered directly into the cecal apex. The following drug concentrations were tested: ERY, 0.01, 0.10, 1.0, and 10.0 mg/kg of body weight; ERY, 0.10 mg/kg bolus; and saline (0.9% NaCl) solution, 10 ml. All treatments, ...
Kooreman K, Babbs C, Fessler J.To evaluate and compare oxidative processes during ischemia and reperfusion of the equine large colon and jejunum. Methods: 2 groups of 6 anesthetized horses undergoing a terminal procedure. Methods: Isolated loops of large colon and jejunum were subjected to 2 hours of ischemia, followed by 2 hours of reperfusion. Tissue specimens were taken after 105 minutes of ischemia and 10, 30, 60, and 120 minutes of reperfusion. Mesenteric arterial and venous blood samples were collected for blood gas analysis at the same times to evaluate ischemia and reoxygenation. Oxidative processes in tissues were ...
Dyke TM, Sams RA, Hinchcliff KW.To measure renal clearance of antipyrine and urinary excretion of antipyrine (AP) metabolites in horses by use of validated high-performance liquid chromatography (HPLC) methods. Methods: 8 Standardbred mares. Methods: HPLC methods for measurement of AP in equine plasma and AP and its metabolites in equine urine were validated. Antipyrine (20 mg/kg of body weight) was administered i.v., and blood samples and urine specimens were collected over 24 hours. Results: Median plasma clearance of AP in horses was 6.2 ml/min/kg, of which < 2% could be attributed to renal clearance. Urinary excretion...
Lester GD, Merritt AM, Neuwirth L, Vetro-Widenhouse T, Steible C, Rice B, Mauragis DF, Madison JB.To determine normal cecal emptying curves for liquid- and solid-phase radiolabeled markers and to further define myoelectric patterns of the ileum, cecum, and colon in healthy ponies. Methods: 6 adult ponies. Methods: A cecal cannula and 12 bipolar Ag-AgCl recording electrodes were sutured to the ileum, cecum, and right ventral colon of the ponies. Radioisotopes, indium 111-labeled diethyltriaminepentaacetic acid (111In-DTPA) and technetium 99m (99mTc)-labeled sulfur colloid bound to egg albumen, were introduced through the cannula directly into the cecal body. Movement of these markers from t...
Stanley SM, Kent S, Rodgers JP.In this study the equine metabolism of fluoxymesterone (9alpha-fluoro-11beta-17beta-dihydroxy-17alpha-meth ylandrost-4-ene-3-one) given orally has been investigated. The parent material was not detected, but two major 16-hydroxy metabolites which corresponded to a mono- and a di-hydroxylation product were evident. One of the hydroxylation positions was identified as C-16. Phase II metabolism in the form of glucuronide formation was also common. These steroids will provide target compounds for confirming abuse of this drug in the horse.
Rakhit S, Murdoch R, Wilson SM.Adrenaline, forskolin and ATP all evoked accumulation of cyclic AMP in equine sweat gland epithelial cells, although the response to adrenaline was more transient than that to forskolin and ATP. Cells preincubated in adrenaline (10 micromol l-1, 32 min) showed essentially complete, homologous desensitisation, and this phenomenon reversed slowly (half-time 6.3+/-0.9 h). After 10 min of recovery from preincubation in adrenaline, isobutylmethylxanthine (IBMX, 5 mmol l-1) had no effect upon the desensitisation and the cells showed no loss of sensitivity to ATP and forskolin. After 10 h, however, t...
von Zallinger C, Tempel K.A review of the latest literature concerning the present level of radiation therapy in veterinary medicine is given. In a general section physico-technical as well as biological fundamentals are discussed. In the special part of the paper indications for a radiation therapy of dogs, cats and horses are stated. In this respect the basis for a decision is the TNM-classification into different clinical stages according to the directions of the WHO. Tumors of the hemolymphatic system are very responsive to radiation therapy. While epithelial tumors are sensitive, tumors arising from the mesenchyma...
van den Hoogen BM, van Weeren PR, Lopes-Cardozo M, van Golde LM, Barneveld A, van de Lest CH.The amount of uronic acid residues in samples containing glycosaminoglycans or pectin is an important parameter in the quantitative and structural analysis of these complex carbohydrates. This paper describes a method to determine the content of uronic acids in biological samples, using conventional polystyrene microtiter plates and microtiter plate-reading equipment with standard interference filters (i.e., 540 or 492 nm). This assay is a modification of a commonly used procedure, viz. hydrolysis of uronic acid containing carbohydrate polymers in 80% sulfuric acid containing tetraborate ions ...
Goudet G, Leclercq L, Bézard J, Duchamp G, Guillaume D, Palmer E.This study reports the follicular growth and oocyte competence for in vitro maturation and fertilization under the influence of circulating eCG. Three to 7 successive ultrasound-guided follicular punctures were performed on 4 pregnant mares from Day 23 until Day 75 of pregnancy and on 5 control mares whose embryonic vesicle was crushed on Day 22. All follicles larger than 5 mm were punctured 24 h after the largest follicle reached 18 mm. Expanded cumulus oocyte complexes (COCs) were stained at recovery to analyze the nuclear stage. Compact COCs were cultured in vitro for 46 h and either staine...
Elliott J, Brady FE.Isolated equine digital veins (EDVs) which had been denuded of their endothelium were used to study adenosine receptors causing vasodilation. When the blood vessel wall tension was raised with the thromboxanemimetic, U44069 (30 nM), the order of vasodilator potency of adenosine receptor agonists was: 5'-N-ethylcarboxamidoadenosine (NECA) > 2-p-(2-carboxyethyl)phenyl amino-5'-N-ethylcarboxamido-adenosine (CGS 21680) > 5'-N-methylcarboxamido-adenosine (MECA) > N6-cyclohexyladenosine (CHA) > N6-cyclopentyladenosine (CPA) > N6-2-(4-Aminophenyl)ethyladenosine (APNEA) > adenosine. ...
Brazil TJ, Rossi AG, Haslett C, McGorum B, Dixon PM, Chilvers ER.The synthetic formylpeptide fMLP is widely used as a model chemoattractant and secretagogue for mammalian neutrophils. Despite possessing fMLP receptors, equine neutrophils do not produce superoxide anions in response to fMLP and there is no inflammatory reaction in the horse when fMLP is injected intradermally. The functional capability of these receptors was investigated after pretreatment with recognized priming agents. Purified neutrophils were pretreated with lipopolysaccharide (LPS), platelet-activating factor (PAF), or tumor necrosis factor alpha (TNF-alpha) and superoxide anion generat...
Méndez A, Martín de las Mulas J, Bautista MJ, Chacón F, Millán Y, Fondevila D, Pumarola M.The presence and distribution of S100 protein (alpha and beta subunits), cytokeratin polypeptides, glial fibrillary acidic protein, neurofilaments, vimentin, neuron specific enolase, synaptophysin, HLA class II DR antigen, and pituitary hormones (prolactin, adrenocorticotropic hormone and human chorionic gonadotrophin) in stellate cells were studied immunohistochemically in four normal canine pituitary glands, five canine pituitary adenomas, two canine pituitary carcinomas and two equine pituitary adenomas (with surrounding normal glandular tissue). Stellate cells of the pars distalis and pars...
Moslemi S, Seralini GE.In order to approach the detailed structure-function relationships of aromatase, we studied the inhibitory and inactivatory potencies of several steroidal androstenedione analogues (1: 4-hydroxyandrostenedione, 2: 4-acetoxyandrostenedione and 3: 7 alpha-(4'-amino)phenylthio-4-androstene-3, 17-dione) and non-steroidal imidazole derivatives (4: ketoconazole, 5: miconazole and 6: fadrozole) on equine aromatase in placental microsomes, a well established mammalian model. Human placental microsomes and the purified enzyme from equine testis were also used to compare inhibition by 1 and 2. In equine...
Reilly GC, Currey JD, Goodship AE.Exercise can have a profound effect on bone mass, but little is known of its effect on bone's material properties. In this experiment, our hypothesis was that a large difference in the training regimen of young thoroughbreds would produce a measurable difference in the mechanical properties of their bone material. When they were about 19 months old, eight thoroughbred racehorses were given one of two exercise regimens that lasted for 19 weeks: four horses (controls) were walked for 40 minutes a day but had no other exercise, and the remaining four (exercised) were additionally trotted for 20 m...
Nogueira GP, Barnabe RC.Thoroughbred fillies were divided into three groups according to age: group 1, 7 fillies aged 1 to 2 years (G1) starting the training program; group 2, 9 fillies aged 2 to 3 years (G2) in a full training program; group 3, 8 older fillies 3 to 4 years of age (G3) training and racing. Blood samples were collected weekly from July to December. Cortisol was quantified using a solid phase DPC kit. The intra- and interassay coefficients of variation were 12.5% and 15.65% and sensitivity was 1.9 +/- 0.2 nmol/l. The semester average of cortisol levels varied between groups: G1 = 148.8 +/- 6.7, G2 = 12...
Hoffman AM, Mazan MR, Ellenberg S.To correlate indices of airway reactivity to bronchoalveolar lavage (BAL) fluid cytologic features in horses with a recent decline in exercise tolerance. Methods: 20 actively working horses from 2 to 24 years old. Methods: Bronchoalveolar lavage fluid samples were obtained and analyzed. Forced oscillatory mechanics (1-7 Hz) technique was used for measurements of total respiratory system resistance (RRS), compliance (CRS), and resonant frequency (fres). Changes in RRS (1 Hz) during histamine challenge were used to generate histamine dose-response curves, from which the provocative concentration...
Ingle-Fehr JE, Baxter GM.To measure blood flow in the palmar digital artery and laminae corium, using ultrasonic and laser Doppler flowmetry, respectively. Methods: 6 healthy horses. Methods: Digital blood flow and laminar perfusion, respectively, were measured by placing a flow probe around the palmar digital artery and a laser Doppler flow probe in a hole in the dorsal aspect of the hoof wall. All horses were given saline (0.9% NaCl) solution (1 L, IV, during a 30-minute period). Seven days later, each horse was given endotoxin (0.1 microgram/kg of body weight, IV, in 1 L of saline solution, during a 30-minute perio...
Hopper SA, Schneider RK, Ratzlaff MH, White KK, Johnson CH.To determine the ability of a full-limb transfixation pin cast to protect the distal portion of the equine forelimb from weight-bearing forces by measuring bone strain in vitro on cadaver limbs loaded in a mechanical testing machine. Methods: 6 forelimbs from 6 horses. Methods: Each limb was instrumented with 3 unidirectional metal foil electrical resistant strain gauges. Gauges were placed on the dorsal aspect of the distal portion of the radius and the mid-dorsal portion of the cortex of the third metacarpal bone and the first phalanx. Each limb was tested 3 times, once supported with a tran...
Hopper SA, Schneider RK, Ratzlaff MH, White KK, Johnson CH.To determine the effect of pin hole size and number on the breaking strength of the adult equine radius when loaded in torsion to failure. Methods: 54 pairs of equine radii from adult horses. Methods: For test one, 12 pairs of radii were used to determine the effect of pin hole size on torsional breaking strength. A 6.35-mm hole was drilled in 1 radius, and a 9.5-mm hole was drilled in the contralateral radius. For test two, 36 pairs of radii were randomly assigned to 1 of 3 treatment groups (n = 12) to determine the effect of pin hole number on the torsional breaking strength of the equine ra...
Harris DB, Harris RC, Wilson AM, Goodship A.Muscle ATP loss with exercise has implications both to the causes of fatigue and muscle damage. To study this at the single muscle fibre level, five trained thoroughbred horses performed consecutive 90 second gallops on an inclined treadmill followed by a final gallop to fatigue. Biopsies of the m. gluteus medius were taken at rest, post-exercise and during 24 hour recovery. Blood lactate was 20.0 mmol litre-1 or more, and plasma NH3 300-800 mumol litre-1, following the final gallop. Minimal changes occurred in the plasma markers, CK and AST. ATP loss with exercise was 32.2 (SD 12.2) per cent....
Foster AP, Cunningham FM.Equine eosinophils and neutrophils are believed to play an important part in the protection of horses against parasitic and bacterial invasion. Eosinophils may also play a key role in the pathogenesis of equine inflammatory conditions such as the allergic skin disease, insect hypersensitivity. The factors which stimulate the respiratory burst of equine eosinophils and neutrophils are poorly understood. The first aim of the present study was to determine the effects of the phorbol ester, phorbol myristate acetate (PMA), which is believed to activate intracellular protein kinase C, and opsonised...
Ramirez S, Wolfsheimer KJ, Moore RM, Mora F, Bueno AC, Mirza T.The objectives of this study were to determine if phenylbutazone decreased serum thyroxine (TT4) and free thyroxine (FT4) concentrations using radioimmunoassay and equilibrium dialysis techniques in horses, and, if so, an additional objective was to determine the duration of this decreased concentration once phenylbutazone administration was discontinued. Serum TT4 and FT4 concentrations were determined before and after administration of 4.4 mg/kg of phenylbutazone i.v. bid for 5 days. Treatment with phenylbutazone caused a significant decrease in TT4 and FT4 concentrations (P < .05). Serum...
Carter RA, Ericsson SA, Corn CD, Weyerts PR, Dart MG, Escue SG, Mesta J.The objective of this study was to determine if spermatozoal reduction of the dyes methylene green to colorless and resazurin to pink or colorless was associated with the fertility potential of an equine semen sample. Fifty samples from 38 stallions were evaluated for the number of spermatozoa per milliliter and number of motile sperm per milliliter. Methylene green (20 micrograms/mL of semen) or resazurin (85 micrograms/mL of semen) was added to 3-mL aliquots of semen. Semen samples were identified as having low fertility potential (< 200 x 10(6) total cells/mL and or = 200 x 10(6) total ...
Wille KH, Zahner M.The vascular system of the large intestine of 12 horses was examined by means of vascular corrosion casts, histology and transmission electron microscopy providing the following results. The Aa. et Vv. breves et longae leave the mesenteric vessels, respectively the subserously on the teniae lying cecal vessels to reach the tela subserosa at the mesenteric margin. The short vessels enter the deeper layers of the wall instantly, whereas the Aa. et Vv. longae move towards the submucosa by penetrating the muscular layers after a variable subserous course. The tela submucosa contains an arterial an...
Freeman DE, Kleinzeller A, Donawick WJ, Topkis VA.When sheets of mucosa from the cecum of clinically normal horses were incubated in vitro with radiolabeled L-alanine, they could accumulate this amino acid against an apparent concentration gradient after 60 to 150 minutes of incubation. The active transport system for L-alanine was on the serosal surface of the mucosal sheet only. L-Alanine accumulation at 60 minutes was partly inhibited by 20 mM glycine (P less than 0.01), 0.5 mM ouabain (P less than 0.05), and Na deprivation (P less than 0.02). Anoxia for 60 minutes increased L-alanine accumulation, but had adverse effects on cell structure...
Ohtani N, Kitagawa K, Mikami K, Kitawaki K, Akiyama J, Fuchikami M, Uchiyama H, Ohta M.There are many obvious health benefits to riding, including developing a strong core and legs, but there are also many less obvious benefits, such as increased confidence and introspection. Few studies have addressed the effects of horseback riding on children and the mechanisms underlying how riding affects humans. We examined the effects of horseback riding on the ability to distinguish Go/No-go tasks and solve arithmetic problems in children. Methods: The subjects were 34 boys and 72 girls, aged 10-12 years old, which were divided into three groups (horse riding, walking, and resting). Th...
Sandersen CF, Detilleux J, de Moffarts B, Van Loon G, Amory H.The aim of this study was to investigate the effect of combined atropine low-dose dobutamine stress test on left ventricular parameters in adult warmblood horses, to establish a potential protocol for pharmacological stress echocardiography. Seven healthy untrained warmblood horses aged 9 to 22 years were used. Heart rate (HR) and left ventricular B- and M-mode dimensions were recorded at baseline and during stress testing with 35 microg/kg atropine IV followed by incremental dobutamine infusion of 2 to 6 microg/kg/min. HR increased significantly (P < .05) during the pharmacological challen...
Martinez CR, Santangelo KS, Olver CS.Whole transferrin receptor (TfR) is present in reticulocyte exosomes. Soluble transferrin receptor (sTfR) is cleaved from whole TfR in human plasma, with the remnant cytoplasmic domain (cTfR) remaining membrane associated. In humans, sTfR is a biomarker that can detect iron deficiency in the presence of inflammatory disease. This condition is still a diagnostic dilemma in veterinary species. We aimed to (1) confirm the presence of exosomes and exosome-associated TfR in the serum of dogs, cats, and horses; and (2) to assess and compare the proportion of cTfR to total (cTfR + whole) in exoso...
Newkirk KM, Ehrensing G, Odoi A, Boston RC, Frank N.OBJECTIVE To assess insulin, glucagon, and somatostatin expression within pancreatic islets of horses with and without insulin resistance. ANIMALS 10 insulin-resistant horses and 13 insulin-sensitive horses. PROCEDURES For each horse, food was withheld for at least 10 hours before a blood sample was collected for determination of serum insulin concentration. Horses with a serum insulin concentration 20 μU/mL underwent a frequently sampled IV glucose tolerance test to determine sensitivity to insulin by minimal model analysis. Horses with a sensitivity to insulin < 1.0 × 10 L•min•mU w...
Harris P, Marlin D, Gray J.A similar and significant (P less than 0.001) increase in plasma thyroxine (T4) concentration was seen in seven clinically normal thoroughbred horses 2 h after the intravenous administration of either 2.5 iu or 5 iu of thyroid stimulating hormone (TSH) with a peak response around 4 h after administration. The intravenous administration of 0.2, 0.5 or 1 mg thyrotrophin releasing hormone (TRH) resulted in a significant (P less than 0.01) increase in T4 concentration in three groups of animals; six thoroughbreds in full work, five thoroughbreds at rest and four ponies at rest. The peak response w...
Batson EL, Reilly GC, Currey JD, Balderson DS.The metacarpal of the horse is severely loaded during vigorous exercise. Metacarpal specimens have a greater impact strength in young horses that have been exercised than in those that have only been walked. We did not find a corresponding difference in the radius of the same horses. We show that cranial (anterior) cortical bone from the radius, which is loaded in tension during locomotion, has a greater Young's modulus, and tensile and bending strength, than bone from the caudal (posterior) cortex, which is loaded in compression. Caudal bone is, however, stronger in compression. The differenc...
Naylor RJ, Piercy RJ.To produce a clonal equine myoblast cell line that retains the ability to divide for multiple passages and differentiate into multinucleated myotubes during specific conditions. Methods: Cultured primary equine skeletal muscle-derived cells from a healthy Thoroughbred. Methods: Cell cultures were transfected by electroporation with a plasmid (pNIT) that expresses the temperature-sensitive simian vacuolating virus 40 large T antigen (TAg), which can be controlled by a doxycycline-responsive promoter. Cells that stably integrated the TAg were selected and expanded to passage 25. For each passage...
Hodgson DR, Rose RJ.Muscle biopsy samples were collected from the middle gluteal muscle of seven horses undergoing a nine-month endurance training programme. Samples were collected before the programme began and again after three, six and nine months of training. A fifth sample was collected three months after training ceased. Serial muscle sections were reacted histochemically for myosin adenosine triphosphatase after either acid (pH 4.3 and 4.6) or alkaline (pH 10.3) pre-incubation, and muscle fibres identified as type I, IIA, IIB or IIC. The oxidative capacity of individual fibres was assessed, using the reduc...
Gargiulo AM, Pedini V, Ceccarelli P.The glycoconjugate content of major horse salivary glands was investigated by means of horseradish peroxidase-conjugated lectins. Qualitative differences were observed in the terminal sugar residues of secretory glycoproteins and glycoconjugates linked to the apical surface of excretory duct epithelial cells. Mucous acinar cells in mandibular and sublingual glands contained oligosaccharides with D-galactose, alpha- and beta-N-acetylgalactosamine, N-acetylglucosamine and fucose residues, whereas mandibular, sublingual and parotid serous cells contained only oligosaccharides with terminal alpha-...
Magnuson NS, McGuire TC, Banks KL, Perryman LE.The in vitro and in vivo effects of corticosteroids on peripheral blood lymphocytes (PBL) from ponies were studied. Prednisolone inhibited lymphocyte stimulation by phytohemagglutin (PHA) in a dose-dependent manner, without inducing lysis even at large doses. The PBL from horses heterozygous for the combined immunodeficiency trait responded to corticosteroid treatment the same as did PBL from normal ponies. Removal of the corticosteroid after incubation with PBL from normal ponies partially restored responsiveness of these cells to PHA. Chronic in vivo treatment of ponies with corticosteroids ...
Smyth PA, Rifkin RE, Jackson RL, Reid Hanson R.The naturally occurring structure of articular cartilage has proven to be an effective means for the facilitation of motion and load support in equine and other animal joints. Cartilage has been found to be a complex and dynamic medium, which has led to an incomplete understanding of the nature and operating mechanisms acting within a joint. Although cartilage has biphasic and triphasic properties, it is believed that the performance of equine articular joints is influenced by the surface roughness of the joint cartilage (Ateshian et al., '98; Chan et al., 2011; Yao and Unsworth, '93). Various...
Daunt DA, Dunlop CI, Chapman PL, Shafer SL, Ruskoaho H, Vakkuri O, Hodgson DS, Tyler LM, Maze M.Cardiopulmonary and behavioral responses to detomidine, a potent alpha 2-adrenergic agonist, were determined at 4 plasma concentrations in standing horses. After instrumentation and baseline measurements in 7 horses (mean +/- SD for age and body weight, 6 +/- 2 years, and 531 +/- 48.5 kg, respectively), detomidine was infused to maintain 4 plasma concentrations: 2.1 +/- 0.5 (infusion 1), 7.2 +/- 3.5 (infusion 2), 19.1 +/- 5.1. (infusion 3), and 42.9 +/- 10 (infusion 4) ng/ml, by use of a computer-controlled infusion system. Detomidine caused concentration-dependent sedation and somnolence. The...
Cox S, Villarino N, Doherty T.The determination of the pharmacokinetic parameters of tramadol in plasma and a better characterization of its metabolites after oral administration to horses is necessary to design dosage regimens to achieve target plasma concentrations that are associated with analgesia. The purpose of this study was to determine the pharmacokinetics and elimination pattern in urine of tramadol and its metabolites after oral administration to horses. Tramadol was administered orally to six horses and its half-life, T(max) and C(max) in plasma were 10.1, 0.59 h, and 132.7 ng/mL, respectively. The half-life, T...
Martin-Flores M.This article briefly reviews the physiology of the neuromuscular junction and the pharmacologic mechanisms of neuromuscular blocking agents. The clinical use of modern agents is discussed. Monitoring techniques used to assess the level of neuromuscular block and to exclude residual paralysis at the end of an anesthetic procedure are reviewed.
Wagner FC, Reese S, Gerlach K, Böttcher P, Mülling CKW.Long-term cyclic tensile testing with equine palmar/plantar tendons have not yet been performed due to problems in fixing equine tendons securely and loading them cyclically. It is well established that the biomechanical response of tendons varies during cyclic loading over time. The aim of this study was to develop a clamping device that enables repetitive cyclic tensile testing of equine superficial digital flexor tendon for at least 60 loading cycles and for 5 min. Results: A novel cryo-clamp was developed and built. Healthy and collagenase-treated pony SDFTs were mounted in the custom-ma...
Rashmir-Raven A, Lavagnino M, Sedlak A, Gardner K, Arnoczky S.Hereditary equine regional dermal asthenia (HERDA) is a genetic disorder of collagen resulting in fragile, hyper-extensible skin and ulcerative lesions. The predominance of skin lesions have been shown to occur on the dorsum of HERDA-affected horses. While this has been postulated to be due to increased exposure to sunlight of these areas, the precise pathological mechanism which causes this to occur is unclear. Objective: We hypothesized that an increase in collagenase activity, that has been associated with the exposure of dermal fibroblasts to sunlight, will significantly degrade the materi...
Foreyt WJ, Lagerquist JE.Peripheral blood neutrophils from horses, cattle, and Rocky Mountain bighorn sheep (Ovis canadensis canadensis) were evaluated for susceptibility to cytotoxin-dependent lysis of different biotypes and serotypes of Pasteurella haemolytica of domestic sheep, cattle, bighorn sheep, or mountain goat (Oreamnos americana) origin utilizing a cytotoxicity assay which measures the degree of bacteria cytotoxin-killing of neutrophils. All isolates of P. haemolytica (biotypes A and T) were noncytotoxic to horse neutrophils. Thirteen of 18 R haemolytica biotype A isolates were cytotoxic (> 50% neutrophi...
Siwińska N, Żak-Bochenek A, Paszkowska M, Karczewski M, Długopolska D, Haider W.Colic, a condition affecting the gastrointestinal tract of horses, manifests as severe pain and may be a life-threatening condition. It is possible to distinguish between an acute, disposable process, as well as recurrent colic symptoms (abdominal pain) caused by an ongoing chronic inflammatory process. This paper presents a retrospective analysis of the histopathological findings of duodenal and rectal samples taken from horses with recurrent colic, with the aim to determine the frequency and extent of inflammation. The samples, i.e., duodenal biopsy (60 samples) and rectal biopsy (17 samples...
Fitzharris LE, Meehan LJ, Hezzell MJ, Allen KJ.The diaphragm is an important respiratory muscle, playing a key role during exercise. In humans, diaphragm thickness increases in response to training and is correlated with inspiratory strength. In order to assess respiratory strength in the horse, new evaluation techniques are required and measurement of diaphragm thickness, in a non-invasive and repeatable manner, is a possible approach. The purposes of this four-part, prospective, pilot study were to develop and describe a repeatable method to measure the diaphragm thickness, using ultrasonography, in Thoroughbred racehorses. A standardize...
Siwinska N, Michalek M, Zak A, Slowikowska M, Noszczyk-Nowak A, Niedzwiedz A, Paslawska U.Precise understanding of the dimensions of the vascular lumina is essential for accurate interpretation of cardiac vessels imaging. To the authors' best knowledge, this is the first study focusing on the ultrasound measurement of the right coronary artery (RCA) in the horse. The aim of this study was to determine both the ultrasonographic range of the normal diameter and lumen area of the RCA in horses and the influence of gender, age and level of training on the RCA dimensions. An additional aim of the study was to assess intra- and inter-observer repeatability of the collected measurements. ...
Tucker ML, Wilson DG, Reinink SK, Carmalt JL.To characterize the 3-D geometry of the equine larynx replicating laryngeal hemiplegia and 4 surgical interventions by use of CT under steady-state airflow conditions. Secondly, to use fluid mechanic principles of flow through a constriction to establish the relationship between measured airflow geometries with impedance for each surgical procedure. Methods: 10 cadaveric horse larynges. Methods: While CT scans were performed, inhalation during exercise conditions was replicated for each of the following 5 conditions: laryngeal hemiplegia, left laryngoplasty with ventriculocordectomy, left lary...
Clemmons AJ, Thompson DL, Johnson L.Gross observation of testicular parenchyma of 1.5- to 2-yr-old horses reveals both light and dark regions. If this gross, differential shading reflects quantitative differences in the development of spermatogenesis and interstitial cell populations, the horse may prove to be a useful model for study of the paracrine relationships associated with initiation of spermatogenesis. The objective of this study was to characterize seminiferous tubules and interstitium of testes with gross, differential shading. Testes with both light and dark regions of parenchyma were obtained from horses 1.5-2 yr ol...
Morris DD, Strzemienski PJ, Gaulin G, Spencer P.Neutrophil function was evaluated in six clinically normal adult horses, immediately before and 3-6 hours after they were given one dose of hydrocortisone sodium succinate (1 mg/kg body weight). Random migration, stimulated migration to zymosan-activated serum, bacterial phagocytosis and bactericidal capacity of neutrophils were determined in vitro. The mean indices of stimulated migration (net migration and migration ratio) were significantly greater after CS administration (net migration = 62 +/- 23 micron; migration ratio = 11.5 +/- 6.7) than before CS administration (net migration = 44 +/-...
Canisso IF, Ball BA, Troedsson MH, Silva ES, Davolli GM.The objectives of this study were to determine pH of the mammary gland secretions and the corresponding electrolyte concentrations in prefoaling mares. Pregnant mares (seven primiparous and seven multiparous) were monitored daily from 310-320 days of gestation until parturition. Prefoaling mammary gland secretions were collected, and pH was immediately determined with a pH meter and pH strip test. An aliquot of prefoaling mammary secretions was frozen and stored until further analyses. After parturition, samples from day -4 to 0 (day of foaling) were thawed and electrolyte concentrations (ie, ...
Anderson BG, Anderson WD.The use of methyl methacrylate corrosion-casts has made it possible to examine the intracranial microvasculature on a three-dimensional scale with the scanning electron microscope. By this means we have compared regions of four cerebral and cerebellar arteries among three domestic animal species. The results of this study suggest that there are from one to three different levels of interarteriolar anastomosis between branches of the same or adjacent vessels. In the horse and ox anastomoses were demonstrated (1) at the level of the precapillary arterioles, (2) along the arterioles, and (3) betw...
Dobrinski I, Jacob JR, Tennant BC, Ball BA.Equine oviductal epithelial cells (OEC) were transformed with simian virus 40 large T antigen (SV 40 T-ag) to create a cell line for the study of the interaction of equine spermatozoa with oviductal epithelium. One cell line was established based on the expression of the SV 40 T-ag and extended lifespan in culture. Immortalized equine OEC retained the characteristics of differentiated OEC such as the formation of monolayers with characteristic epithelial morphology and cell polarization as well as expression of cytokeratin and equine major histocompatibility complex I. Monolayers of immortaliz...
Greene SA, Thurmon JC, Tranquilli WJ, Benson GJ.Serum insulin and plasma glucose concentrations were determined in 8 mares. Four IV treatments were studied: xylazine (1.1 mg/kg of body weight); yohimbine (0.125 mg/kg); yohimbine (0.125 mg/kg) followed 5 minutes later by xylazine (1.1 mg/kg); and 5 ml of isotonic saline solution as a control. Blood samples were collected before (time 0) and at 5, 15, 30, 60, 120, and 180 minutes after drug administration. Serum insulin concentration decreased and plasma glucose concentration increased in mares given xylazine. Plasma glucose concentration was unchanged in control mares and in mares given yohi...
Lisowski ZM, Sauter KA, Waddell LA, Hume DA, Pirie RS, Hudson NPH.Intestinal macrophages are the largest group of mononuclear phagocytes in the body and play a role in intestinal innate immunity, neuroimmune interactions and maintaining intestinal homeostasis. Conversely, they also are implicated in numerous pathologies of the gastrointestinal tract, such as postoperative ileus and inflammatory bowel disease. As a result, macrophages could be potential therapeutic targets. To date, there are limited studies on the morphology and distribution of macrophages in the equine gastrointestinal tract (GIT). The aim of this study was to identify the location and abun...
Longworth KE, Jarvis KA, Tyler WS, Steffey EP, Staub NC.Seven horses (4 anesthetized and 3 awake) and 2 ponies (anesthetized) were studied to evaluate the high sensitivity of the pulmonary circulation of the horse to various blood-borne particles, and to establish the presence of intravascular macrophages in the lung. Pulmonary and systemic pressures and cardiac output before and during particle injection were measured in some animals. An anesthetized foal had a large increase in pulmonary arterial pressure (32 and 34 mm of Hg) within 1 minute of IV administration of small test doses of radioactively labeled liposomes (2.5 mumol/kg of body weight) ...
