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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.
[Dynamics of the functional, biochemical and hormonal indices of racehorses]. Parallel physiologic, biochemical, and hormonal investigations of racehorses were carried out within the time period of a training cycle. The changes found in the physiologic and biochemical indices were said to be in a general relationship with the amount of physical training of the animals, at the same time reflecting some seasonal variations. The changes in the level of T-4 and cortisol were found to be in direct relationship with the continuation of training.
Identification of the second alpha-2-antiprotease of equine serum as antithrombin III. The alpha-2-protease inhibitor, of 65,000 daltons molecular weight, described by several authors in horse plasma and also present as a contaminant in alpha-1-isoinhibitor isolates previously described by us (Pellegrini & von Fellenberg (1980) Biochim. biophys. Acta 616, 351-361) has now been isolated to purity and identified as antithrombin III. The inhibitor is composed of a single polypeptide chain as judged by SDS polyacrylamide gel electrophoresis. The inhibitor was effective only against trypsin and thrombin. Serological cross-reaction existed between the inhibitor and the antiserum t...
Immunochemical demonstration of a new pregnancy protein in the mare. An antiserum against the serum of a pregnant mare was absorbed with stallion serum. This antiserum then gave two precipitates in crossed immunoelectrophoresis with serum from pregnant mares as the antigen. The two precipitates exhibited beta-1 and alpha-2 electrophoretic mobility. Identity was demonstrated between the alpha-2 mobile protein and PMSG. The absorbed antiserum inhibited the biological action of the PMSG preparation when tested in mouse ovarian weight assays. The beta-1 mobile protein was not detected in the serum from non-pregnant mares, stallions or geldings and was detected earl...
Comparison of the hydroxyacids from the epidermis and from the sebaceous glands of the horse. The acylglucosylceramides were isolated from the polar lipids of horse epidermis and examined to determine whether the component omega-hydroxyacids are straight chained as in the corresponding lipids from pig epidermis or branched as in horse sebum. The hydroxyacids from horse epidermis were found to be almost entirely straight chained compounds. The results indicate that sebaceous glands, although derived from epidermal cells, have evolved independent pathways of lipid metabolism.
Quantitative culture of Rhodococcus equi from the feces of horse. The selective isolation of R. equi in NANC medium was made by quantitative culture of the organism in the feces. R. equi was observed in the feces of all the mares and foals investigated. The mean viable count of R. equi organisms in 1 gram of feces was 8.42 X 10(2) in the mares and 7.57 X 10(2) in the foals, and its 95% confidence limits were in a range of 6.48 X 10(2) to 1.09 X 10(3) and 4.19 X 10(2) to 1.37 X 10(3), respectively. This result indicates that R. equi is a member of the normal intestinal flora in the horse.
Sound speed in pulmonary parenchyma. The time it takes audible sound waves to travel across a lobe of excised horse lung was measured. Sound speed, which is the slope in the relationship between transit time and distance across the lobe, was estimated by linear regression analysis. Sound-speed estimates for air-filled lungs varied between 25 and 70 m/s, depending on lung volume. These speeds are less than 5% of sound speed in tissue and less than 20% of sound speed in air. Filling the lung with helium or sulfur hexafluoride, whose free-field sound speeds are 970 and 140 m/s, respectively, changed sound speed +/- 10% relative to a...
S-adenosylhomocysteine hydrolase activity in horses, Equus cabalus, with severe combined immunodeficiency. 1. Activities of S-adenosylhomocysteine (AdoHcy) hydrolase were measured in tissues of horses with severe combined immunodeficiency. No decrease in activity of the enzyme was detected.
2. The activity in erythrocytes was 14.2 ± 9.2 nmol AdoHcy formed/min/g hemoglobin and in fibroblasts it was 28.0 ± 7.9 nmol AdoHcy formed/min/108 cells.
3. Km values were obtained for hemolysates (0.77 μM) and for fibroblast lysates (0.59 μM).
4. Effects of 2′-deoxyadenosine on enzyme inactivation were studied.
Characterisation of the alpha 1-protease inhibitor system in Thoroughbred horse plasma by horizontal two-dimensional (ISO-DALT) electrophoresis. 1. Protein staining. The isoelectric points and the molecular weights of the major components of the eight Thoroughbred protease inhibitor (Pi) types have been determined by polyacrylamide gel isoelectric focusing and polyacrylamide gel pore gradient (ISO-DALT) electrophoresis respectively. The major Pi proteins focus in the range pH 3.74-4.43 and have molecular weights ranging from 55 000-72 000 daltons. Using the ISO-DALT method of electrophoresis, protein maps for the eight Thoroughbred Pi types have been presented for the first time. None of the homozygous Pi types are identical except for the types S1 and S2 ...
Variation in skin surface lipid composition among the Equidae. Skin surface lipids from Equus caballus, E. przewalskii, E. asinus, E. grevyi, E. hemionus onager and a mule (E. asinus/E. caballus) were analyzed in detail. In all species the surface lipid mixtures consisted of giant-ring lactones, cholesterol, cholesteryl esters and minor amounts of wax diesters. In E. caballus, the lactone hydroxyacids were entirely branched chained, while in E. asinus and E. grevyi they were almost exclusively straight chained. In E. przewalskii, the onager and the mule there were both straight and branched chain hydroxyacid lactones. These results are in harmony with pub...
Effects of naloxone on endotoxin-induced changes in ponies. The value of naloxone (1 mg/kg of body weight/hr for 4 hrs), a beta-endorphin antagonist, was assessed in the management of endotoxin-induced shock in ponies. Three groups of 5 ponies each were used: controls, ponies given Escherichia coli endotoxin put untreated, and ponies given endotoxin and then treated with naloxone. Endotoxin-induced changes in hemodynamics, blood chemical values, regional blood flow, plasma enzymes, and energy supplies were measured at selected times during the first 6 hours after endotoxin was given. There was no evidence that beta-endorphins released during shock were...
Infectivity of sarcocystis from donkey for horse via sporocysts from dogs. The dog is the final host for sarcosporidia cysts from the oesophagus and diaphragm of donkeys from Sardinia. The prepatent period lasted 9 to 10 days. Sporocysts measured 12.2-13.8 X 9.2-9.9 microns. Infection of a horse with 10(5) donkey/dog sporocysts increased the rectal temperature to more than 40 degrees C on days 10 and 20 after infection. On day 138 p.i. predominantly immature cysts containing metrocytes were found, especially in the oesophagus. Infection on day 117 p.i. with 2 X 10(5) horse/dog sporocysts did not give rise to a temperature increase during the following 21 days. The fi...
Genetic linkage between the loci for phosphohexose isomerase (PHI) and a serum protein (Xk) in horses. Genetic linkage between the equine loci for phosphohexose isomerase (PHI) and serum Xk protein was demonstrated by means of segregation data from three sire families. The recombination frequency was estimated from pooled data to be 0.23 +/- 0.02; a significant heterogeneity between sires for estimates of the recombination frequency was observed. No indication of linkage was detected between Xk and 14 other blood marker loci. Linkage between the Xk locus and the locus for soluble malic enzyme (ME1) has recently been reported in horses. An equine linkage group designated LG IV comprising the thr...
Comparative studies of the effect of thermal stimulation on the permeability of the luminal cell junctions of the sweat gland to lanthanum. Lanthanum injected intradermally in vivo into the skin of cattle, sheep, goats and ponies penetrated the intercellular spaces of the sweat glands. It was not, however, detected in the glandular lumen either visually or by electron probe microanalysis even at elevated ambient temperatures when the animals were sweating. It is concluded that the luminal intercellular connections between epithelial cells in these glands are tight junctions, which remain so during sweating despite the occurrence of cell death and extrusion into the lumen.
Factors in the control of feed intake of horses and ponies. Ponies are large nonruminant herbivores which are capable of utilizing the products of both enzymatic digestion in the small intestine and bacterial fermentation (volatile fatty acids, VFAs) in the cecum and large colon as sources of metabolizable energy. Recent studies have demonstrated that ponies utilize nutrient stimuli from both carbohydrate and fat digestion in the small intestine and VFAs in the cecum and large colon in the control of meal frequency. These animals, however, rely primarily upon oropharyngeal and external stimuli to control the size and duration of meals. This is perhaps ...
A study of physical demands in riding. Thirteen experienced riders and three elite riders underwent bicycle ergometer tests at submaximal and maximal workloads. Oxygen uptake, pulmonary ventilation and heart rate were also studied during riding at a walk, a trot and a canter. The mean maximal oxygen uptake of the experienced riders in the ergometer test (2.71 . min-1) was superior to the average maximal oxygen uptake of other groups of the same age and sex. The average oxygen uptake of the experienced riders in trot sitting was 1.701 . min-1, trot rising 1.681 . min-1 and in canter 1.801 . min-1. The experienced riders used at leas...
Electron microscopic study of the veins of the dermal lamellae of the equine hoof wall. The venous organisation of the dermal lamellae of the equine hoof wall of 18 pairs of forelimb hooves from clinically healthy horses was studied using plastic vascular corrosion casts, and scanning electron microscopic and histological techniques. A consistent pattern of venous organisation was observed in the dermal lamella of the toe, quarter and heel regions. The lamellar corium had an extensive interconnecting capillary network which drained into axially located veins of the primary dermal lamella. Many of the capillaries had a proximodistal orientation and most of those located at the int...
Subcellular localization and properties of the NAD(P)H oxidase from equine polymorphonuclear leukocytes. The subcellular distribution of the superoxide-forming enzyme in horse polymorphonuclear leukocytes was investigated. After activation of the cells with sodium oleate, a relatively stable and NAD(P)H-dependent oxygen consumption and superoxide production was found in association with the plasma membranes. The pH dependence displayed an optimum near neutrality. The apparent Km values were 38 x 10(-6) mol/l for NADPH and 1,560 x 10(-6) mol/l for NADH, suggesting that NADPH is the physiological donor. The rates of oxygen uptake, O2- production, and NADP consumption were consistent with the stoich...
Isolation and characterization of horse alpha 2-macroglobulin protease inhibitor. Several publications have described in the past properties of partly purified horse alpha 2-macroglobulin (alpha 2M) which are strikingly different from the human alpha 2M. Horse alpha 2M was therefore isolated to purity by classical procedures, i.e. affinity chromatography, ion exchange chromatography and gel filtration, and its properties are compared with those of its human counterpart. The molecular weight of the native protein and its subunits, the isoelectrofocusing pattern and the change in electrophoretic mobility caused by interaction with protease were similar to those of human alpha...
Bone stress in the horse forelimb during locomotion at different gaits: a comparison of two experimental methods. Longitudinal stresses acting in the cranial and caudal cortices of the radius and the dorsal and palmar cortices of the metacarpus in the horse were determined using two independent methods simultaneously. One approach involved the use of rosette strain gauges to record in vivo bone strain; the other involved filming the position of the horse's forelimb as it passed over a force plate. Agreement between the two analyses was better for the radius than for the metacarpus. Both methods showed the radius to be loaded primarily in sagittal bending, acting to place the caudal cortex in compression a...
Geometric properties of equine metacarpi. Paired equine metacarpals were harvested, cleaned and sectioned transversely every 20 mm, and the bone geometry analyzed with a computer program. The cross-sectional area is largest in the middle third of the bone, and tapers off at either end. The principal axes are typically within 15 degrees of the anatomical axis, with the distal end rotated internally relative to the proximal end. At midshafts the bending stiffness in the antero-posterior plane is about 2/3 of the stiffness in the medio-lateral plane. The torsional stiffness is highest proximally. The equine third metacarpal appears to be...
Inheritance of an abnormal haemoglobin haplotype in horses and its possible influence on blood values. In a breeding experiment a stallion of the native Norwegian Trotter breed with an abnormal Hb haplotype (N) and with the Hb type BI/N, sired 6 offspring. The abnormal haplotype controls one α-chain only, having lysine at position 60 and phenylalanine at position 24. Three of the offspring received the N haplotype from the sire and the BII haplotype from the dam, whereas the other 3 offspring received BI from the sire. The BII/N horses have two Hb components after alkaline electrophoresis or isoelectric focusing with the ratio between the fast and the slow band (anodal, cathodal) being approxi...
Kinetic and structural relationships of transition monomeric and oligomeric carboxyl- and choline-esterases. The kinetic and structural relationships of eight electrophoretically pure mammalian serum and liver serine carboxylesterases (CE) and cholinesterases (ChE) have been studied. Eight CE's and ChE's, which were fully resolved but only partially purified, provided additional information. Five of the electrophoretically pure esterases were monomeric, and of these, four belonged to a new and widely distributed class. These four monomeric esterases hydrolyzed choline esters, but at widely differing rates. Thus two were termed monomeric butyrylcholinesterases, mBuChE I and II, and two were monomeric ...
