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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.
Biochemical characterization of equine herpesvirus type 3-induced deoxythymidine kinase purified from lytically infected horse embryo dermal fibroblasts. Infection of horse KyED cells with equine herpesvirus type 3 (EHV-3) resulted in a sevenfold increase in cytosol deoxythymidine kinase (dTK) activity. The EHV-3 dTK was purified from KyED cytosol dTK by affinity chromatography on deoxythymidine-Sepharose and characterized with respect to its electrophoretic mobility, molecular weight, substrate specificity, phosphate donor specificity, and immunological specificity. The purified EHV-3 dTK migrated in polyacrylamide gels with an Rf of 0.30 and sedimented in glycerol gradients with an S value of 5.13, corresponding to a molecular weight of 83,00...
Comparison of circulatory and respiratory effects of isoflurane and halothane anesthesia in horses. Circulatory and respiratory effects of alveolar concentrations of 1.31, 1.97, and 2.62 vol% of isoflurane in oxygen were studied in eight young, healthy horses during spontaneous and controlled ventilation. These isoflurane concentrations were equivalent, respectively, to 1.0, 1.5, and 2.0 times the minimal alveolar concentration of isoflurane, which prevents movement in horses in response to a standard pain stimulus. Results of the isoflurane studies were compared with similarly derived findings in these same horses during equipotent halothane in oxygen anesthesia. Isoflurane, similar to halo...
Biochemical effects of succinylcholine chloride in mechanically ventilated horses anesthetized with halothane in oxygen. Succinylcholine chloride administered to horses anesthetized with halothane in oxygen and mechanically ventilated, caused slight but statistically insignificant (P less than 0.01) increases in creatine phosphokinase, lactic dehydrogenase, and aspartate aminotransferase activity. The increases in these enzymes have been explained on the basis of muscle damage resulting from succinylcholine chloride induced muscle fasciculations and by hypoperfusion of tissues due to depression of the cardiovascular system caused by general anesthesia. These changes were not clinically apparent based upon the ab...
Cardiorespiratory adjustments to tethered-swimming in the horse. The cardiorespiratory and metabolic responses to various levels of tethered-swimming were evaluated in 5 sedentary horses. Cardiac output (Q) and heart rate (HR) correlated highly (r = 0.89 and 0.94 respectively) with work effort (WE) expressed as kg pulled . kg body wt-1 . 10-2. While swimming, stroke volume (SV) was reduced at the lowest workloads, but increased with increasing WE so that at the highest workloads it had returned to the on-land standing SV. Pressures in the pulmonic as well as on both sides of the systemic circulation were considerably elevated by this form of exercise, altho...
Surgical implantation of cardiovascular devices in the thorax of the horse. A surgical thoracotomy and implantation of an electromagnetic flow probe around the ascending aorta and catheters in the left ventricular (LV) apex of the horse were evaluated. Sixteen operations were done: 4 horses were used for acute experiments, 4 horses died from surgical manipulation, and 8 horses were studied chronically for 18 to 57 days. The electromagnetic flow probe allowed continuous measurement of stroke volume and heart rate. The LV apical catheters, in conjunction with thermal dilution techniques and pressure-sensitive devices, allowed measurement and calculation of mean arterial...
Electromagnetic measurement of cardiac output during exercise in the horse. Aortic root blood flow was measured with an electromagnetic (EM) flow meter in unanesthetized horses during rest and exercise. The cardiac output response to exercise, as determined by the EM technique, was compared with the response reported by others who used indicator dilution techniques with good agreement. The EM method will allow making measurement of cardiovascular responses to exercise in the horse, not obtainable with other techniques.
The effect of trypsin digestion on the structure and iron-donating properties of transferrins from several species. The effect of trypsin digestion on iron-saturated and iron-free (apo) human, rabbit, bovine, pig and horse tranferrins has been studied. Iron-binding fragments were produced only from iron-saturated pig and bovine transferrins although some cleavage of the polypeptide chain occurred in all cases. The apo-transferrins were generally degraded to a greater extent than the corresponding iron-saturated proteins. The ability of the different transferrins to donate iron to rabbit reticulocytes varied in the order rabbit approximately pig greater than human approximately horse greater than bovine. Try...
Equine locomotion: 2. The analysis of coordination between limbs of trotting standardbreds. A high-speed cinematographic analysis of interlimb time and linear gait characteristics was carried out at racing speed (12.0 m/sec; 1:23.6 min/km) in 30 clinically sound Standard-bred trotters. In respect of the whole group of horses the racing trot was found to be a very regular and symmetric gait. The variation coefficient between different horses ranged from 8 to 21 per cent depending on the particular characteristic being investigated. The variations recorded in individual animals were about 60 per cent less than those found for the whole group. The most stable characteristics were the du...
Vascular responses in equine thoracic limb during and after pneumatic tourniquet application. Vascular responses occurring with pneumatic tourniquet application were evaluated in the equine thoracic limb. Recordings of pressure (arterial and venous) and flow (arterial) distal to the tourniquet were made for 60 minutes. Reactive hyperemia was observed; however the increased flow was neither of a sufficient duration nor of a great enough volume for total repayment of flow loss.
Low doses of oxytocin can induce foaling at term. Levels of the major circulating metabolite of prostaglandin F-2 alpha, 13, 14 dihydro-15-oxo-prostaglandin F-2 alpha (PGFM) were measured during the induction of foaling using small (2.5-10 iu) intravenous doses of oxytocin. PGFM levels rose rapidly in all animals within 15 min of injection and were associated with typical signs of second stage labour. Because these small doses of oxytocin are effective in successfully triggering parturition it is suggested that higher doses (40-120 iu) used to induce birth in other studies are unnecessary and could be potentially dangerous to the foetal foal....
Equine locomotion: 3. The reproducibility of gait in standardbred trotters. The reproducibility of certain gait characteristics was investigated in Standardbred trotters at a speed of 12.0 m/sec. Twenty-two horses were recorded twice on the same day and 4 of them on a third occasion 3 years later. The short-term reproducibility was shown to be very good. In the long-term study it was found that the stride length and duration of swing and stride had increased. This was interpreted as an effect of training.
Renin, aldosterone and cortisol in the thoroughbred horse. To assess the renin-aldosterone system in a large mammal, simultaneous morning activities of plasma renin and concentrations of aldosterone and cortisol were measured in 25 thoroughbred horses. Renin was relatively low in all horses (0.16 +/- 0.02 (S.E.M.) ng angiotensin I/ml per h), levels of aldosterone in plasma were 527 +/- 130 pmol/1 and levels of cortisol in plasma were 141 +/- 11 nmol/l. Levels of aldosterone were significantly correlated with levels of renin in all horses (r = 0.62, P less than 0.001) but not with those of cortisol, and renin was negatively correlated with age in male ...
Equine locomotion; 1. The analysis of linear and temporal stride characteristics of trotting standardbreds. The movements of the individual limbs of 30 clinically sound Standardbred trotters were studied using high-speed cinematography. At a speed of 12 metres per second (m/sec; 1:23.6 min/km) the mean stride length was 545 cm and the mean duration of the stride was 455 milliseconds (msecs). The stance phase in the forelimbs was 100 msecs and 177 msecs in the hindlimbs. This difference was due to a longer restraint period in the hindlimbs and resulted in slightly shorter swing phases for the hindlimbs. The variations in any particular horse for stride length and for the duration of stride, stance, s...
Evaluation of the demand valve for resuscitation of horses. Arterial blood gas values, rate of pulmonary nitrogen washout, respiratory rate, arterial blood pressure, heart rate, and cardiac output were determined during ventilation of six anesthetized horses, with a demand valve. The horses were allowed to ventilate spontaneously, or intermittent positive pressure ventilation was utilized. When compared with spontaneous ventilation, intermittent positive pressure ventilation caused a significant increase in the rate of pulmonary nitrogen washout and a significant decrease of arterial carbon dioxide. It was concluded that intermittent positive pressure ...
Suppressor T cells in tolerance to deaggregated horse anti-human thymocyte globulin in man. To understand the mechanism by which deaggregated horse anti-human thymocyte globulin (dATG) fails to induce untoward immunological reactions in man, three patients who received ATG and two patients who received dATG were studied for evidence of sensitization or tolerance to the foreign globulin. The ATG but not the dATG recipients developed allergic or serum sickness reactions; antihorse serum antibody could be detected in their serum and their blood cells proliferated in vitro in the presence of horse serum and secreted antihorse serum antibodies (P less than 0.001). Tolerance of the dATG re...
The immunological approach to pregnancy diagnosis: a review. The developing embryo/fetus bears antigens which are foreign to the mother and it could be expected that immune rejection of the conceptus would occur. One of the reasons why the fetus is not rejected is because a depression of the maternal immune response takes place during pregnancy. Serum from pregnant animals of several species has been shown to contain a factor, early pregnancy factor (EPF), which is immunosuppressive. EPF has been detected as early as six hours after mating and its detection could aid diagnosis of early pregnancy in all species.
Involvement of lysines-72 and -79 in the alkaline isomerization of horse heart ferricytochrome c. Spectrophotometric titrations of five singly modified horse heart ferricytochromes c, specifically (trifluoromethyl)phenylcarbamylated (CF3PhNHCO-) or trifluoroacetylated (CF3CO-) at lysines-13, -72, and -79, were carried out. The CF3PhNHCO-Lys-13, Lys-79, and CF3CO-Lys-79 derivatives all underwent alkaline isomerization with loss of the 695-nm band to low-spin species with an apparent pK of about 8.9, as did the unmodified cytochrome. However, modification of lysine-72 appeared to alter the reaction pathway since the CF3PhNHCO-Lys-72 derivative isomerized to a high-spin form with an apparent ...
Purification by affinity chromatography and characterization of a neutral alpha-glucosidase from horse kidney. A horse kidney neutral alpha-D-glucosidase (alpha-D-glucoside glucohydrolase, EC 3.2.1.20) was purified about 580-fold with a yield of 33% by an affinity chromatography technique using the p-aminophenyl-beta-D-maltoside, a substrate derivative, as ligand. The purified enzyme, homogeneous in polyacrylamide gel electrophoresis, was a glycoprotein with a molecular weight of 280 000 as calculated by gel filtration and its isoelectric focusing points was found to be pH 4.1. The purified enzyme was able to hydrolyze various substrates having (alpha-1,2), (alpha-1,3), (alpha-1,4), and (alpha-1,6) glu...
Urinary excretion of arsenic from horses injected with an organic arsenical compound. Five doses of sodium cacodylate (194 mg) were administered intravenously to two horses at two-day intervals. The arsenic content of daily urine samples was determined for five days after the final dose, by which time urinary arsenic concentrations were close to those of control samples. It was considered that these results reflected a common property of organic arsenicals viz. more rapid excretion by mammals than is the case with inorganic arsenic compounds.
