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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.
Drug interactions in the horse: effects of chloramphenicol, quinidine, and oxyphenbutazone on phenylbutazone metabolism. The plasma half-life of phenylbutazone in horses was not increased after pretreatment with chloramphenicol or quinidine, but was increased after oxyphenbutazone. This increased plasma half-life after oxyphenbutazone is consistent with observations in other species and suggests that oxyphenbutazone inhibits the metabolism of phenylbutazone in horses. Lack of inhibition of phenylbutazone metabolism in the horse by chloramphenicol and quinidine is inconsistent with results obtained in other species.
Comparative study of the dorsal motor nucleus of the vagus nerve. Quantitative studies were made of cells in the dorsal motor nucleus of the vagus nerve in the horse, dog, cat, pig, sheep, goat, and calf. This nucleus was larger in ruminants than in nonruminants. Some cells in all parts of the nucleus supplied visceral structures in the head, cervical, thoracic, and abdominal regions; however, a definite topographic localization did exist within the nucleus. Eighty percent of the cells which supplied the abdominal viscera were in the rostral and rostral-middle regions. The cells which supplied the thoracic viscera were distributed almost equally within the r...
The activity of some nucleolytic enzymes in semen and in the secretion of the male reproductive tract. The activity of 5'-nucleotidase (EC 1.3.5), cyclic nucleotide phosphodiesterase (EC 2.1.4.17), non-specific phosphodiesterase (EC 3.1.4.1) and ribonuclease (EC 1.7.7.16)has been investigated in the seminal plasma of whole semen and in the secretions of the seminal vesicle, prostate and epididymis of the bull, boar, ram, stallion, jackass, rabbit and man. Bull seminal plasma showed the highest activity for 5'-nucleotidase, cyclic nucleotide phosphodiesterase and ribonuclease; in contrast, stallion and jackass semen were very poor in these enzymes. Ram, rabbit and boar seminal plasma showed inte...
Rapid heterolysis of indophenyl acetate by a constituent of a preparation of horse serum cholinesterase. 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...
A comparative study of experimental and spontaneous emphysema. Normal lung architecture of the rat, mouse, hamster, horse, and human was compared to that of emphysematous lungs from the same species by utilizing a light microscope and a scanning electron microscope (SEM). The results obtained by SEM examination of normal and emphysematous lungs corresponded to those obtained with the light microscope. However, the SEM provided a view of alveoli and airway morphology not obtainable with the light microscope. Because of the variability in pore size and number of pores per alveolus, a pore-to-alveolus ratio was determined with the SEM on the normal lungs of ...
Comparative studies on the gastric glycopeptide in eleven animal species. 1. Glycopeptides in the stomachs of eleven mammalian species, including human, rabbit, horse, cow, pig, goat, sheep, dog, cat, guinea pig and rat were assayed by determining the carbohydrate content of materials which remained after proteolysis. 2. The glycopeptide content was higher in the mucosa than in the muscular layer including serosa, especially in the porcine stomach and the fourth stomachs of the ruminants than in the stomachs of any other animals. 3. The glycopeptide, which was stained with both alcian blue and PAS, was absent or sparingly present in the mucosae of the human, rabbit,...
Identification of the PR prealbumin proteins in horse serum. The Pr protein, which is one of the major equine acidic prealbumins and which consists of a large number of phenotypes, has been studied with regard to its chemical identity. Serum samples of known Pr phenotype which had been treated with varying amounts of bovine trypsin were subjected to starch gel electrophoresis at pH 4.8. When a certain amount of trypsin was used, the Pr protein was markedly affected, whereas the other acidic prealbumins retained their normal electrophoreitic pattern. Extracts from three different regions of the acidic prealbumin field were tested by the casein precipitat...
Proton-dependent dissociation equilibrium of hemoglobin. 1. A 700-nanometer light-scattering study on horse methemoglobin in the pH range 4.8 to 7.2. The effect of proton concentration upon the subunit dissociation of horse methemoglobin has been investigated at two ionic strengths by light scattering photometry at 700 nm. Differential refractometry revealed a slight but systematic decrease of the specific refractive index increment with decreasing protein concentration for solutions in dialytic equilibrium with the solvent. In the pH range 4.8-7.2 the dissociation can be described by a simple equilibrium between tetramers and dimers. The dissociation constant Kd of the met derivative is found to be very similar to those of the O2- and CO-l...
Isolation, identification and quantitation of serum 5alpha-pregnane-3,20-dione and its relationship to progesterone in the pregnant mare. 5alpha-pregnane-3,20-dione was isolated from pooled pregnant mare serum using Sephadex LH-20 column chromatography and identified by the use of radioimmunoassay, gas-liquid chromatography and gas-liquid chromatography-mass spectrometry analyses. 5beta-pregnane-3,20-dione was not cross-reactive with the radioimmunoassay system and was not detected by gas-liquid chromatography. Peripheral blood levels of progesterone and 5alphs-pregnane-3,20-dione were determined by radioimmunoassay in four Quarter Horse mares for the first 150 days of gestation. Progesterone and 5alpha-pregnane-3,20-dione decli...
Effects of training on resting and postexercise ECG in standardbred horses, using a standardized exercise test. Five healthy, mature, previously trained Standardbred horses were given no exercise (left in a stall) for 4 months, then jogged (slow exercise) for 3 weeks, and placed in a 6-week training period. Cardiac variables were measured at the beginning of training and after 14, 20, 35, and 42 days of training before and at 10, 15, 20, 25, and 30 minutes after a 1.8-km (in 3:12 +/- 2 seconds) standard, submaximal exercise test on a deep 0.53-km track. There was no significant change during the 6-week conditioning period in the following variables at rest or at any of the times observed during recovery...
Pregnant mare serum gonadotrophin: ratio of follicle-stimulating hormone and luteinizing hormone activities measured by radioreceptor assay. Specific radioreceptor assays for FSH and LH, which employ tissue receptors from rat testis and highly purified human FSH (LER 1575-C) and LH (Hartree IRC-2, 24/6/69) as standards, have been developed to determine the FSH-like and LH-like activities in pregnant mare serum gonadotropin (PMSG). Measurements of FSH and LH concentrations in the serum of six pregnant Pony mares showed that the ratio of these two activities did not vary significantly between mares and remained constant between days 40 and 80 of gestation with a value of 1-45 +/- 0-04 (S.E.M.). The FSH:LH ratio of PMSG produced by cu...
Ventilatory control in peripheral chemoreceptor-denervated ponies during chronic hypoxemia. The present study was designed to provide further insight into the role of the carotid and aortic chemoreceptors in ventilatory (VE) acclimatization during sojourn at altitude. Measurements were made: 1) on 10 ponies near sea level (SL, 740 Torr) under normal conditions, 2) on 6 of these at SL following chemoreceptor denervation (CD), and 3) subsequently on all 10 during 4 days of hypobaric hypoxia (PaO2 = 40-47 Torr). CD resulteo in hypoventilation at SL (deltaPaCO2 = d8 Torr, P less than 0.05), and it prevented hyperventilation normally observed with injection of NaCN and acute exposure to h...
Copper and the oxidation of hemoglobin: a comparison of horse and human hemoglobins. Oxidation studies of hemoglobin by Cu(II) indicate that for horse hemoglobin, up to a Cu(II)/heme molar ratio of 0.5, all of the Cu(II) added is used to rapidly oxidize the heme. On the other hand, most of the Cu(II) added to human hemoglobin at low Cu(II)/heme molar ratios is unable to oxidize the heme. Only at Cu(II)/heme molar ratios greater than 0.5 does the amount of oxidation per added Cu(II) approach that of horse hemoglobin. At the same time, binding studies indicate that human hemoglobin has an additional binding site involving one copper for every two hemes, which has a higher copper...
Oldest horse brains: more advanced than previously realized. Previous interpretations of early horse brains were based on an incorrectly identified fossil endocast, now believed to be from a condylarth. Newly prepared endocasts of Hyracotherium, the oldest horse and one of the earliest perissodactyls, reveal a relatively larger brain, with a more expanded neocortex, than existed in the condylarth ancestors of perissodactyls. Fifty million years ago, horse brains had suprasylvian, ectolateral, and lateral sulci, but the frontal lobe was undeveloped.
Electron capture detection of an apomorphine heptafluorobutyrate derivative at low picogram levels. An electron capturing derivative of apomorphine was prepared by incubating the drug with heptafluorobutyric anhydride (HFBA), triethylamine and heat. Mass spectral analysis suggests that HFBA reacts with both phenolic hydroxyl groups on apomorphine to give a derivative detectable at low picogram levels. This method is sufficiently sensitive for pharmacokinetic studies in the horse and is likely applicable to other dopaminergic analogues of apomorphine.
Force plate studies of equine biomechanics. The force plate can measure a wide range of effects in the horse. The same instrument can record forces from more than a ton in the galloping animal to 25 g associated with the action of the heart. In all probability, the force plate will develop into a valuable clinical instrument.
Pregnant mare’s serum gonadotrophin. I. Progesterone or prolactin and the reversal of antifertility efficacy of pregnant mare’s serum gonadotrophin. A single consistent luteolytic dose of 10 IU PMSG given on day 5 of pregnancy caused complete resorption of foetuses and placentae associated with a polyfollicular ovarian state in rats. Concomitant treatment with progesterone or prolactin given concurrently with PMSG was found to overcome the antifertility efficacy of PMSG and maintained the endocrine balance favouring pregnancy maintenance. It was postulated that the PMSG-induced ovarian polyfolliculogenesis might be responsible for luteolysis of the corpus luteum gravidarum.
Regional coronary blood flow in ponies. Regional coronary blood flow was measured by injecting radioactive microspheres (15 mum +/- 5 in diameter) into the left atrium of anesthetized ponies with surgically prepared open thorax before and during occlusion of the coronary arteries. The normal blood flow to the myocardium of the interventricular septum and the left ventricular wall were highest, followed in decreasing order by the right ventricular wall, the interatrial septum, the atrial walls, and the valves. Measurement of transmural blood flow in the normal left ventricle yielded a mean endocardial/epicardial flow ratio of 1.36 in...
