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Topic:Physiology
The physiology of horses encompasses the study of the biological functions and processes that occur within the equine body. This includes the examination of various systems such as the cardiovascular, respiratory, musculoskeletal, digestive, and nervous systems. Understanding equine physiology is essential for comprehending how horses adapt to different environmental conditions, perform physical activities, and respond to health challenges. Research in this field often focuses on the mechanisms of energy metabolism, thermoregulation, and muscle function during exercise, as well as the physiological responses to stress and disease. This page compiles peer-reviewed research studies and scholarly articles that explore the diverse aspects of equine physiology, providing insights into the biological processes that support the health and performance of horses.
Water intake and fluid shifts in horses: effects of hydration status during two exercise tests. In the present study, the main objective was to study factors affecting postexercise voluntary water intake in horses. Four Standardbred horses (mean +/- s.e. bwt 500 +/- 8 kg) were used to study water intake and effects of altering hydration status before an incremental exercise test (INCR) and a 40 min constant velocity exercise test (CONST) on a treadmill. Exercise was performed during normohydration (N), after dehydration for 24 h (DEH) and after hyperhydration with 12 l water 30 min before exercise (HH). DEH resulted in a bodyweight loss of 3% and there were signs of some fluid uptake pri...
High expression in adult horse of PLRP2 displaying a low phospholipase activity. The physiological role of the two lipase-related proteins, PLRP1 and PLRP2, still remains obscure although some propositions have been made concerning PLRP2. In this paper, we report the presence of high amounts of PLRP2 in adult horse pancreas whereas no PLRP1 could be detected. As well, a non-parallel expression of PLRP2 and PLRP1 is observed in adult cat and dog, since no PLRP2 could be detected in these two species. In adult ox, neither PLRP2 nor PLRP1 could be found. These findings are in favor of a different regulation of the expression of the genes encoding pancreatic lipase and the rel...
Oxidative monensin metabolism and cytochrome P450 3A content and functions in liver microsomes from horses, pigs, broiler chicks, cattle and rats. The oxidative metabolism of monensin, an ionophore antibiotic extensively used in veterinary practice as a coccidiostat and a growth promoter, was studied in hepatic microsomal preparations from horses, pigs, broiler chicks, cattle and rats. As assayed by the measurement of the amount of the released formaldehyde, the rate of monensin O-demethylation was nearly of the same order of magnitude in all species, but total monensin metabolism, which was estimated by measuring the rate of substrate disappearance by a high-performance liquid chromatography (HPLC) method, was highest in cattle, interme...
Cultivation and characterisation of primary and subcultured equine keratinocytes. We describe the establishment and characterisation of equine keratinocyte cultures with maintenance of a high proliferative capacity up to the second passage. Improved attachment and growth were obtained by seeding primary cells on equine feeder layers. Subcultured keratinocytes showed optimal growth when seeded on collagen type I. The proliferation rate of cells on this substrate exceeded that seen for cells seeded on equine feeder layers. By immunohistochemistry, epithelial origin and state of differentiation of the equine keratinocytes were determined. They expressed keratin and desmoplakin...
Mechanistic basis for the gas exchange threshold in Thoroughbred horses. The exercising Thoroughbred horse (TB) is capable of exceptional cardiopulmonary performance. However, because the ventilatory equivalent for O2 (VE/VO2) does not increase above the gas exchange threshold (Tge), hypercapnia and hypoxemia accompany intense exercise in the TB compared with humans, in whom VE/VO2 increases during supra-Tge work, which both removes the CO2 produced by the HCO buffering of lactic acid and prevents arterial partial pressure of CO2 (PaCO2) from rising. We used breath-by-breath techniques to analyze the relationship between CO2 output (VCO2) and VO2 [V-slope lactate t...
Growth hormone response to a novel growth hormone-releasing tripeptide in horses: interaction with gonadotropin-releasing hormone, thyrotropin-releasing hormone, and sulpiride. A series of experiments was performed to determine the factor(s) responsible for an apparent inhibition of GH secretion in mares administered the GH secretagogue EP51389 in combination with GnRH, thyrotropin-releasing hormone (TRH), and sulpiride. Experiment 1 tested the repeatability of the original observation: 10 mares received EP51389 at 10 microg/kg BW; five received TRH (10 microg/kg BW), GnRH (1 microg/kg BW), and sulpiride (100 microg/kg BW) immediately before EP51389, and five received saline. The mixture of TRH, GnRH, and sulpiride reduced (P = 0.0034) the GH response to EP51389, con...
Faecal oestrogens and progesterone metabolites in mares of different breeds during the last trimester of pregnancy. Non-invasive pregnancy diagnosis in mares by measuring faecal oestrogens has been performed over years with great accuracy. However, results have indicated breed-related differences in the amount of excreted steroids during late pregnancy. Therefore faecal samples were collected during the last 4 months of pregnancy of Thoroughbred (n = 10), New Forest pony (n = 9), Shetland pony (n = 10) and Iceland pony mares (n = 11). Concentrations of oestrogens, 20alpha-hydroxy- and 20-oxopregnanes were measured using enzyme immunoassays. Breed differences concerning both levels (though significant only i...
A comparison of the mechanical strength of two stapled anastomosis techniques for equine small intestine. To compare bursting strength, time of construction, and cost of a closed one-stage, stapled functional end-to-end jejunojejunostomy (FEE) with a stapled side-to-side jejunojejunostomy (STS). Methods: Experimental, randomized block design. Methods: Seven adult horses without gastrointestinal disease. Methods: The jejunum was isolated, and three FEE, three STS, and three control segments were created in each horse using a randomized block design. Anastomosis time was recorded. The intraluminal pressure at failure and mode of failure were recorded. Length at failure was measured on digitized imag...
Kinematic characteristics of Andalusian, Arabian and Anglo-Arabian horses: a comparative study. The aim of this study was to compare the kinematic trot characteristics of three different breeds of horse: Andalusian (AN, n = 15), Arabian (AR, n = 7) and Anglo-Arabian (AA, n = 5) using standard computer-assisted videography (25 Hz). Linear, temporal and angular parameters in fore- and hind limbs were analysed in six randomly selected strides per horse. Normalised angle-time diagrams along the complete stride were obtained for all joints angles in each breed and specific kinematic characteristics were detected graphically. AA horses displayed longer swing durations in both limbs ans a short...
An evaluation of two autologous tendon grafting techniques in ponies. To compare the healing and mechanical strength of a multiple split autologous tendon graft (MG) to a whole autologous tendon graft (WG) in the deep digital flexor tendon of ponies. Methods: In vitro evaluation of two different tendon-grafting techniques. Methods: Six ponies of mixed gender and age. Methods: Tenotomies performed in forelimb deep digital flexor tendons (DDFT) distal to the insertion of the accessory ligament (AL-DDFT) were repaired with free autologous grafts from the hindlimb lateral digital extensor tendon (LDET). Grafts were either whole (WG) or split into three longitudinal ...
Daily treatment of growing foals with equine somatotropin: pathologic and endocrinologic assessments at necropsy and residual effects in live animals. This experiment assessed the effects of 12 mo of daily treatment of young horses with recombinant equine somatotropin (eST) on 1) carcass and internal organ traits at necropsy and 2) residual effects in live horses for 60 d after cessation of treatment. Seven horses received eST daily at 20 microg/kg BW; seven others received vehicle (controls). Four horses from each group were killed at the end of treatment. There were few effects of eST treatment on hematologic assessments or histopathologic evaluations of internal organs. Treatment with eST increased the weights of the right adrenal gland (...
Developmental competence in vivo and in vitro of in vitro-matured equine oocytes fertilized by intracytoplasmic sperm injection with fresh or frozen-thawed spermatozoa. This study was undertaken to evaluate the development of equine oocytes in vitro and in vivo after intracytoplasmic sperm injection (ICSI) with either fresh or frozen-thawed spermatozoa, without the use of additional activation treatments. Oocytes were collected from ovaries obtained from an abattoir and oocytes classified as having expanded cumulus cells were matured in M199 with 10% fetal bovine serum and 5 microU FSH ml(-1). After 24-26 h of in vitro maturation, oocytes with a first polar body were selected for manipulation. Fresh ejaculated stallion spermatozoa were used for the experiment...
A cytochrome c mutant with high electron transfer and antioxidant activities but devoid of apoptogenic effect. A cytochrome c mutant lacking apoptogenic function but competent in electron transfer and antioxidant activities has been constructed. To this end, mutant species of horse and yeast cytochromes c with substitutions in the N-terminal alpha-helix or position 72 were obtained. It was found that yeast cytochrome c was much less effective than the horse protein in activating respiration of rat liver mitoplasts deficient in endogenous cytochrome c as well as in inhibition of H(2)O(2) production by the initial segment of the respiratory chain of intact rat heart mitochondria. The major role in the di...
Characterization of the H- and L-subunit ratios of ferritins by sodium dodecyl sulfate-capillary gel electrophoresis. Sodium dodecyl sulfate-capillary gel electrophoresis (SDS-CGE) was used to characterize the H- and L-subunit ratios of several mammalian ferritins and one bacterioferritin. Traditionally, SDS-PAGE has been used to characterize the H- and L-subunit ratios in ferritin; however, this technique is relatively slow and requires staining, destaining, and scanning before the data can be processed. In addition, the H- and L-subunits of ferritin are fairly close in molecular weight (approximately 21,000 and approximately 20,000, respectively) and are often difficult to resolve in SDS-PAGE slab gels. In ...
5-Hydroxytryptamine mediated contractions in isolated preparations of equine ileum and pelvic flexure: pharmacological characterization of a new 5-HT(4) agonist. The effects of 5-hydroxytryptamine (5-HT), HTF 919, a new 5-HT(4) agonist, and the antagonists SB 203-186 (5-HT(4)) and tropisetron (5-HT(3)) on intestinal motility were tested in vitro on isolated preparations of horse ileum and pelvic flexure. Concentration-response curves were created by cumulative application of the agonists with or without preincubation of the antagonists. The 5-HT preparation induced a concentration-dependent contraction in equine ileum and pelvic flexure. The results indicate that 5-HT receptors are present in all parts of equine intestine investigated in this study. Tr...
Detection of lipid peroxidation in equine spermatozoa based upon the lipophilic fluorescent dye C1l-BODIPY581/591. The lipophilic fluorescent probe, 4,4-difluoro-5-(4-phenyl-1 ,3-butadienyl)-4-bora-3a,4a-diaza-s-indacene-3-undecanoic acid (C11-BODIPY581/591) was used to evaluate changes in lipid peroxidation in equine spermatozoa during both short-term exposure to ferrous sulfate and sodium ascorbate in the presence of cumene hydroperoxide as well as during storage of spermatozoa at 5 degrees C for 48 hours. Peroxidation of C11-BODIPY581/591 was accompanied by a shift in fluorescence from red to green, and the relative amount of nonoxidized probe was determined as the ratio of red:(red + green) fluorescenc...
The testis as a major source of circulating inhibins in the male equine fetus during the second half of gestation. Immunolocalization of the inhibin (a) and inhibin/activin (beta3A and betaB) subunit proteins in equine fetal testes was investigated to determine the ability of the fetal testis to produce inhibins at 120, 150, 200, and 250 days of gestation. In addition, concentrations of immunoreactive (ir)-inhibin, inhibin pro-aC, and inhibin A in both the maternal and fetal circulation were measured. It was found that plasma concentrations of ir-inhibin, inhibin pro-alphaC, and inhibin A were much higher (P < .05) in the fetal than in the maternal circulation at any stage of gestation examined. Similar...
Cell death during natural and induced luteal regression in mares. In mares, little information is available on the type of cell death that occurs during natural and induced luteal regression. Corpora lutea were collected from mares in the early luteal phase, days 3-4 (n = 4); mid-luteal phase, day 10 (n = 5); early regression, day 14 (n = 4); late regression, day 17 (n = 4); and 12 and 36 h (n = 3 per group) after PGF2alpha administration on day 10. Histological and ultrastructural sections were examined and TUNEL was used to detect DNA fragmentation. In early luteal regression, there were more pyknotic luteal cells and extracellular round dense bodies compa...
Prostaglandin E(2) and F(2 alpha) production by equine conceptuses and concentrations in conceptus fluids and uterine flushings recovered from early pregnant and dioestrous mares. A growing equine conceptus must suppress the cyclical release of PGF(2 alpha) from the endometrium to effect maternal recognition of its presence in the uterus. Paradoxically, the conceptus itself secretes PGF(2 alpha), together with other prostaglandins. In this study, the PGF(2 alpha) and PGE(2) content of, and production in vitro by, day 10-32 equine conceptuses were measured and the influence of pregnancy on the concentrations of these prostaglandins in the uterine lumen was examined. In vitro, the release of both prostaglandins per mg conceptus tissue was very high on day 10 after ovulati...
Recombinant equine interleukin-1beta induces putative mediators of articular cartilage degradation in equine chondrocytes. Interleukin-1 is considered a central mediator of cartilage loss in osteoarthritis in several species, however an equine recombinant form of this cytokine is not readily available for in vitro use in equine osteoarthritis research. Equine recombinant interleukin-1beta was cloned and expressed and its effects on the expression and activity of selected chondrocytic proteins implicated in cartilage matrix degradation were characterized. Reverse transcriptase polymerase chain reaction methods were used to amplify the entire coding region of the equine IL-1beta mRNA, which was cloned into an expres...
Effect of dietary medium chain triacylglycerols on plasma triacylglycerol levels in horses. The hypothesis tested was that the feeding of medium chain triacylglycerols (MCT) to horses would raise the level of plasma triacylglycerols by increasing the availability of glucose as lipogenic substrate, implying that the MCT effect would be greater with glucose in the diet instead of cellulose. A Latin square experiment was carried out with 4 horses and 4 dietary treatments. The experimental periods lasted 21 d. Blood samples were taken 16 h after feeding. The diets consisted of hay and experimental concentrates, differing in fat source (MCT or soybean oil) and carbohydrate source (corn st...
Microanatomic characteristics of the insertion of the distal sesamoidean impar ligament and deep digital flexor tendon on the distal phalanx in healthy feet obtained from horses. To describe microanatomic characteristics of the insertion of the aistal sesamoidean impar ligament (DSIL) and deep digital flexor tendon (DDFT) on the distal phalanx in horses. Methods: Healthy feet obtained from 62 horses of various breeds. Methods: Feet from 23 horses were used to histologically examine the insertion of the DSIL and DDFT (n = 7), its vasculature (10), and neural elements (6). In 39 other horses, the insertion zone was examined for proteoglycan. Results: The insertion of the DSIL and dorsal half of the DDFT contained bundles of collagen fibers with intervening loose connecti...
Quantitative analysis of motor unit action potentials in the subclavian muscle of healthy horses. To evaluate the application of analysis of motor unit action potentials (MUAP) in horses and to obtain values of MUAP for the subclavian muscle of horses. Methods: 10 healthy adult Dutch Warmblood horses. Methods: Electromyographic examination of the subclavian muscle in conscious nonsedated horses was performed to evaluate insertional activity, spontaneous activity, MUAP variables, and recruitment patterns. Muscle and body temperatures were measured at the beginning and end of the procedure. Amplitude, duration, number of phases, and number of changes in direction (ie, turns) for all represen...
Use of an extracorporeal circuit to evaluate effects of intraluminal distention and decompression on the equine jejunum. To use an extracorporeal circuit to evaluate effects of intraluminal distention on the jejunum of healthy horses. Methods: 2 jejunal segments from each of 5 horses. Methods: Jejunal segments were harvested and maintained in an extracorporeal circuit. One segment was subjected to distention (intraluminal pressure, 25 cm H2O) followed by decompression, and 1 segment was maintained without distention. The influence of distention-decompression on vascular resistance was calculated. Mucosal permeability was evaluated by measuring the clearance of albumin from blood to lumen. After distention and de...
Evaluation of acetaminophen absorption in horses with experimentally induced delayed gastric emptying. To evaluate the correlation between the half-time of liquid-phase gastric emptying (T50) determined by use of nuclear scintigraphy, using technetiumTc 99m pentetate, and absorption variables of orally administered acetaminophen in horses with experimentally delayed gastric emptying. Methods: 6 mature horses. Methods: Delayed gastric emptying was induced by IV injection of atropine sulfate. Twenty minutes later, acetaminophen and technetium Tc 99m pentetate were administered simultaneously via nasogastric tube. Serial lateral images of the stomach region were obtained, using a gamma camera. Pow...
[The origin and function of the enamel cup, infundibulum dentis, on the incisors of the horse]. The enamel cups of equids originated phylogenetically through several phases in Oligocene and Miocene horses, which readjusted from hard to soft leaf food and from double nutrition (leaves and grass) to a pure grass intake. This has been proved experimentally. The resulting construction of the incisor is continually changed on its occlusal surface by erosion according to the pattern of the enamel crests. Referring to the whole incisor tooth, this results in an equid life cycle in which the good grip of the occlusal surface and the efficiency of ingestion favours the young, sexually mature hors...
Lactobacillus equi sp. nov., a predominant intestinal Lactobacillus species of the horse isolated from faeces of healthy horses. Lactobacillus equi sp. nov. is described on the basis of 18 strains isolated as one of the predominant intestinal lactobacilli from horse faecal specimens. These 18 strains were isolated from 10 horses of 6 different farms out of 20 horses of 10 farms examined. They were gram-positive, facultatively anaerobic, catalase-negative, non-spore-forming, non-motile, lactic-acid-homofermentative rods. The DNA G+C content was 38.9+/-0.8 mol %. DNA-DNA hybridization failed to associate these strains closely with any of the validly described type strains used. Analysis of the 16S rRNA gene sequence of re...
Inducible nitric oxide expression in equine articular chondrocytes: effects of antiinflammatory compounds. To determine the effects of recombinant equine IL-1beta and a number of antiinflammatory compounds on the expression and activity of inducible nitric oxide synthase (iNOS) in cultured equine chondrocytes. Methods: RT-PCR methods were used to amplify a portion of the equine iNOS message to prepare an RNA probe. Northern blot analysis was used to quantify the expression of iNOS in first passage cultures of equine articular chondrocytes propagated in the presence or absence of recombinant equine interleukin-1beta (reIL-1beta), dexamethasone (DEX), polysulfated glycosaminoglycan (PSGAG), hyalurona...
The influence of maternal size on placental, fetal and postnatal growth in the horse. II. Endocrinology of pregnancy. Within-breed artificial insemination and between-breed embryo transfer were carried out in small pony (P) and large Thoroughbred (Tb) mares to create 4 types of horse pregnancy in which the fetus experienced spatial and nutritional deprivation (Tb-in-P; n=8), luxury (P-in-Tb; n=7) or normality (Tb-in-Tb; n=7 and P-in-P; n=7) in utero. Measurement of equine chorionic gonadotrophin (eCG), total conjugated oestrogens and progestagen concentrations in serial peripheral serum samples recovered from all the mares throughout gestation showed that the amount of eCG produced during the first half of ge...
