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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.
Plasma progestins in pregnant, postpartum and cycling mares. Jugular vein plasma from 13 mares was extracted with diethyl ether and chromatographed on Sephadex LH-20 columns (.5 × 9 cm) after which progesterone and 17α-hydroxyprogesterone (170HP) were quantified by a competitive protein binding radioassay. During pregnancy, progesterone increased (P < .05) from 1.1 ± .4 ng/ml (mean ± SE) on day 0 to 7.5 ± 1.2 ng/ml on day 8 followed by a transient (nonsignificant) decrease to 4.8 ± .4 ng/ml on day 28. From days 28 to 44 progesterone again increased (P < .05) attaining a maximum concentration of 15.2 ± 1.4 ng/ml on day 64. Thereafter progesterone ...
Effect of centrifugation and seminal plasma on motility and fertility of stallion and bull spermatozoa. The effect of centrifugation of diluted and undiluted semen on equine and bovine spermatozoan motility and fertility was examined, as was the effect of seminal plasma and dilution on stallion spermatozoa during incubation before and after freezing. Centrifugation at 370 g or 829 g was not detrimental (P greater than 0.05) to prefreeze or postfreeze motility if a final concentration of 10% seminal plasma was present. A reduction of seminal plasma from 10% to 2% significantly (P smaller than 0.05) reduced motility. A centrifugal force of 956 g significantly reduced prefreeze but not postfreeze m...
Effect of prednisolone on the leukocyte counts of ponies and on the reactivity of lymphocytes in vitro and in vivo. Treatment of ponies with a single dose of prednisolone markedly reduced the number of blood lymphocytes. A decrease of the number of eosinophils was also observed. In contrast, the number of neutrophils significantly increased. These profound changes were temporary and returned to the pretreatment level within 48 h. The number of monocytes did not show any of the significant changes post-prednisolone treatment. The reactivity of the blood lymphocytes of these ponies, in vitro, to stimulation with phytohemagglutinin (PHA) or streptokinase-strepto-dornase (SK-SD) was measured by incorporation of...
Certain physiochemical properties of uterine tubal fluid, follicular fluid, and blood plasma in the mare. Uterine tubal fluids were collected twice a day from mares for 5 consecutive estrous cycles between March 15 and September 1. Follicular fluids were aspirated from the follicles of exteriorized ovaries of 3 mares between days 2 and 5 of estrus. Uterine tubal fluid and follicular fluid were analyzed for osmolarity, dry matter, total lipids, total free fatty acids, glucose, fructose, and lactic acid. Blood samples were collected (jugular venipuncture) throughout the estrous cycle, and the same physical and biochemical analyses were made on blood plasma. A difference (P less than 0.01) was found ...
Ventilatory alterations in normal horses in response to changes in inspired oxygen and carbon dioxide. The influence of various concentrations of CO2 and O2 in the inspired gases on minute volume (V), tidal volume (VT), and respiratory rate (breaths per min; BPM) was examined in nonanesthetized, nonsedated normal horses. The VT and BPM increased linearly in response to increases in inspired CO2 concentration and curvilinearly in response to decreases in inspired Os concentration. The V increased curvilinearly in response to both increases in inspired CO2 concentration and decreases in inspired O2 concentration.
Identification of the lysine residue modified during the activation of acetimidylation of horse liver alcohol dehydrogenase. A single amino group in horse liver alcohol dehydrogenase was modified with methyl(14C)acetimidate by a differential labeling procedure. Lysine residues outside the active site were modified with ethyl acetimidate while a lysine residue in the active site was protected by the formation of an enzyme-NAD+-pyrazole complex. After the protecting reagents were removed, the enzyme was treated with methyl(14C)acetimidate. Enzyme activity was enhanced 13-fold as 1.1 (14C)acetimidyl group was incorporated per active site. A labeled peptide was isolated from a tryptic-chymotryptic digest of the modified...
Binding of Au(CN)2- and Pt(CN)4-2- to horse liver alcohol dehydrogenase. A 35C1NMR relaxation study. The binding of Au(CN)2- and Pt(CN)4-2- ions to the coenzyme binding site of horse liver alcohol dehydrogenase (alcohol : NAD+ oxidoreductase EC 1.1.1.1) has been studied by 35C1 nuclear magnetic relaxation. Longitudinal relaxation rates were analyzed in terms of a simple model and binding constants for Au(CN)2-, Pt(CN)4-2- and C1- were estimated. From a comparison between transverse and longitudinal relaxation rates the correlation time and the quadrupole coupling constant of bound chloride ion were obtained. The quadrupole coupling constant estimated from a simple electrostatic model for chlo...
Hyperlipoproteinaemia in ponies: mechanisms and response to therapy. (I) The lipid and lipoprotein concentrations in sera of 4 healthy and 9 hyperlipaemic patients were determined. From the results of the analyses, it is suggested that three types of hyperlipoproteinaemia can be distinguished in ponies: (a) Type 1, characterised by a very pronounced increase in only the very low density lipoproteins (VLDL); (b) Type 2, in which there is a pronounced increase in the chylomicrons (Chylo) and the very low density lipoproteins (VLDL); (c) Type 3, which can be the result of fasting and is characterised by a moderate increase in the concentration of chylomicrons and ...
Conformational studies of equilibrium structures in fragments of horse heart cytochrome c. Ultraviolet absorption and circular dichroism studies have been carried out on horse heart apo-cytochrome c and heme-free peptide fragments obtained by cyanogen bromide cleavage of the native protein. It was noted that the various peptides assume predominantly an unordered conformation in water solution. Increasing ionic strength and addition of 2-chloroethanol increase the right-handed helical content. Guanidinium hydrochloride favors the coil state. It was also demonstrated that two non-interacting helical regions of different stability are present in the apo-protein in 2-chloroethanol.
[Comparative study of the optimum pH value of serum alkaline phosphatase in various species of farm animals]. Investigations were carried out on the alkaline phosphatase in the sera of cattle, horses, pigs, sheep, goats, and chickens, the pH value of the buffer used being 9.0-9.8-10.0-10.2-10.6 and 11.0, and the method applied--that of Richterich. The pH value at which the serum alkaline phosphatase in the various farm animals and birds was most active was found to vary to a large extent. Optimal values for the enzyme's activity usually range as follows: cattle, 10.2; pigs and goats, 10.0; sheep,--10.2; horses,--9.8; chickens,--10.6.
Renal clearance and excretion of endogenous substances in the small pony. Renal clearance and excretion of endogenous substances were studied in 13 small adult ponies (152 plus or minus 93 (standard deviation (SD)) kg). Normal data of serum and urinary concentrations, clearance, and excretion of creatinine, osmolality, free water, sodium, potassium, and chloride during a 12-hour period are presented. Significant linear regressions on body weight (BW) were obtained for creatinine clearance (Ccr (ml/hr) = 127.2 times BW (kg) - 1553), osmolar clearance (Cosm(ml/hr) = 1.81 times BW (kg) m0.3), and free water (CH2O(ml/hr) = - 1.43 BW (kg) - 25.0). Compared with renal exc...
Osteoporosis in a six year old pony. A case of what can be presumed to be secondary nutritional hyperparathyroidism, due to high phosphorus diet, in a six year old pony is discussed. The findings are compared to those found when the disease occurs in young growing horses.
The sensitizing properties of anti-mouse anti-thymocyte horse serum. The authors have compared the anaphylaxis due to active and passive sensitization of mice. In the case of active sensitizing, anti-mouse anti-thymocyte horse serum (ATS), and/or normal horse serum (NHS), whereas in the case of passive sensitizing, plasma, peripheral leukocytes, spleen cells and thymocytes of sensitized animals were used. Provocation of shock was carried out by intravenous administration of ATS or NHS. Irreversible anaphylaxis occurred in a significantly higher rate in the case of ATS than NHS sensitivity, produced either actively, or passively. Differences have been found also...
Enzyme activity in the serum of thoroughbred horses in the United Kingdom. This paper records the concentrations of aspartate amino transferase (A.A.T.), creatine kinase (C.P.K.), sorbitol dehydrogenase (S.D.H.), alpha-hydroxybuturate dehydrogenase (alpha-H.B.D.) and alkaline phosphatase (A.P.) activity observed in the sera of Thoroughbred horses in the United Kingdom, at rest and during training. The methods of analysis have been selected to achieve the optimum precision when used for horse serum. During training A.A.T., C.P.K. and alpha-H.B.D. are related and demonstrate intermittent periods of increasing activity. S.D.H. remains unchanged but demonstrates increase...
[Cecal motricity and ceco-iliac transit in the horse]. Electrical spiking activity of the caecum is increased eight-fold and the rate of passage of digesta is increased four-fold when the volume of caecal contents is doubled. The role of caecal motility in regulating the volume of caecal contents is discussed.
Presence of the arteria caroticobasilaris in the horse. The consistent presence of the caroticobasilar artery was observed and discussed in view of the anatomical normalities in the horse. The persistence of the above vessel was correlated with the developmental changes in the cranial and cerebral arteries.
