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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.
Segmental epidural and subarachnoid analgesia in conscious horses: a comparative study. Six adult horses were used to compare the effects of segmental epidural analgesia (SEA) and segmental subarachnoid analgesia (SSA). A 17-gauge Huber point directional needle was used to place a catheter with stylet into the epidural space or the subarachnoid space at the lumbosacral intervertebral junction and to catheterize the thoracolumbar epidural or subarachnoid space. The position of the catheter was confirmed radiographically. A 2% solution of mepivacaine hydrochloride was used at average doses of 80 mg (4 ml) to produce SEA and 30 mg (1.5 ml) to produce SSA. Onset of analgesia in respo...
Enzymatic trimethylation of lysine-72 in cytochrome c. The present observations are the continuation of our earlier study on the physicochemical mechanism of protein-lysine methylation. In this paper the electrophoretic behaviour (pI values) of two chemically modified horse heart cytochromes c at lysine-72 with trifluoromethylphenylcarbamoyl (neutral group) or carboxydinitrophenyl (acidic group) is compared with the enzymatically methylated cytochrome c. The results indicate that although both chemically modified cytochromes c have lower pI values than the unmodified cytochrome c, the enzymatic methylation appears to be much more efficient in lowe...
Induction of multiple ovulations during the ovulatory season in mares. The efficacy of an equine pituitary extract for induction of multiple ovulations during the ovulatory season was studied in 112 horse mares in four experiments. Combined for all experiments, 70% of the mares (78/112) had multiple ovulations for an average of 3.0 ovulations per mare. The interval between first and last ovulation was decreased (P<0.01) when human chorionic gonadotropin (hCG) was included in the treatment regimen (0.0+/-0.0 versus 1.6+/-0.4 days). Ovulation rate was lower (P<0.01) when extract treatment was initiated at day 19 (1.3+/-0.2) than when initiated at day 15 post-...
Effect of cardiac arrhythmia on left ventricular and aortic blood pressure parameters in the horse. Transaortic blood pressures were recorded in seven horses using catheter mounted transducers during various types of supraventricular arrhythmia. Changes in left ventricular (LV) and aortic (Ao) pulse contours were associated with variation in pulse interval (PI). When PI lengthened there was a rise in LV end diastolic pressure (LVEDP) associated with a prolonged filling time. In contrast, a long PI resulted in a reduced end diastolic Ao pressure (AoEDP) due to a prolonged arterial 'run off'. LVdP/dt max representing the peak rate of rise of pressure during the isovolumic contraction period wa...
Measurement of superoxide dismutase, diamine oxidase and caeruloplasmin oxidase in the blood of thoroughbreds. Methods were developed for the measurement of superoxide dismutase (SOD), diamine oxidase (DAO) and caeruloplasmin oxidase in the blood of thoroughbred horses. These enzymes were measured in 178 normal thoroughbreds stabled throughout the United Kingdom. The relationships between the activities of SOD, DAO and caeruloplasmin oxidase and the blood concentrations of their associated trace metals (copper, zinc and manganese) were studied in 52 of the thoroughbreds. Trace metals were measured by electrothermal atomic absorption spectrophotometry. No relationships were found between the activities ...
Sodium and potassium ion-dependent change in oligomerization of Na,K-ATPase in C12E8 detected by low-angle laser light scattering technique in combination with high performance porous silica-gel chromatography. Approximate molecular weights and the subunit structures of Na,K-ATPase from horse kidney were estimated by means of the combination of porous silica gel chromatography, laser light scattering (LS) and refractive index (RI) measurements in C12E8. When the enzymes were eluted with NaCl- or KCl-containing solution, 3 or 4 protein peaks, respectively were detected except that of low molecular weight range. These peaks were tentatively named Na-1, Na-2, Na-2', Na-3 (NaCl-containing eluents), K-1, K-2, K-3 (KCl-containing eluents), respectively. Na,K-ATPase and K-p-nitrophenylphosphatase activities...
Linkage of the equine serum esterase (Es) and mitochondrial glutamate oxaloacetate transaminase (GOTM) loci. A horse-mouse homology. Three previously described electrophoretic phenotypes of mitochondrial glutamate oxaloacetate transaminase (GOTM) in horse leukocytes are shown to be controlled by two codominant alleles at a single autosomal locus. The GOTM locus is linked to the serum esterase locus (Es), as no recombination between these loci was observed among 16 informative offspring in one sire family. The results assign GOTM to equine linkage group (LG) II. The hypothesis that a part of LG II (e-Es) shares homologies with mouse chromosome 8 is thus confirmed, as the murine homologue of GOTM is located within the cluster...
Equine anhidrosis: a review of pathophysiologic mechanisms. Anhidrosis is loss of the ability to sweat. The problem is seen in horses kept in a hot humid climate, and it may cause severe impairment of thermoregulation in the equine athlete. British Thoroughbreds imported to her tropical colonies are the earliest recorded cases, and since then the syndrome has come to be described as one of Thoroughbreds, usually performance athletes, undergoing acclimatization to heat and humidity. A recent epidemiologic study of cases in Florida has shown, however, that many different breeds, and long time inhabitants of a hot climate, may be affected. Equine sweat gl...
Inhibition of motility of bovine, canine and equine spermatozoa by artificial vagina lubricants. The effects of four vaginal lubricants on progressive spermatozoal motility were evaluated. Neat semen was exposed to 0, 5, or 10% (w/v) of H-R, sterile K-Y, nonsterile K-Y or Maxilube lubricating jellies for 10 min at 37 degrees C and then extended to 10x10(6) spermatozoa/ml. Spermatozoal motility was evaluated after 0, 1, 2, 4 and 6 or 8 h of incubation at 37 degrees C. For bovine spermatozoa, sterile K-Y jelly at 10% suppressed motility (P<0.05), but nonsterile K-Y, H-R and Maxilube jellies had no effect. Maxilube was toxic (P<0.01) to canine spermatozoa and is not recommended for use...
Luteal luteinizing hormone receptors during the postovulatory period in the mare. Changes in serum luteinizing hormone (LH) and progesterone concentrations, number of luteal unoccupied LH receptors, receptor affinity constants, luteal weights and luteal progesterone concentrations were determined during the postovulatory period in the mare. The number of unoccupied LH receptors and receptor affinity was less during the early (Days 1-4) and late [Day 15 through 3rd day after start of corpus luteum (CL) regression] luteal phases than during the mid-luteal (Days 9-14) phase of the postovulatory period (P less than 0.01). The number of LH receptors per CL increased 21-fold (P l...
Unfolding pathway of myoglobin. Evidence for a multistate process. The free energy of unfolding of horse myoglobin has been calculated from the denaturation pattern induced by guanidine hydrochloride as well as by acid. The delta GH2O, i.e., the value in the absence of denaturant obtained by using the two-state transition model, was found to be 25% lower than that determined from the acid denaturation pattern, i.e., 12.0 kcal/mol, although the extent of protein denaturation produced by acid was much lower. The amount of helical structure surviving the acid-induced conformational change was estimated to be 50% of that present in the native protein, and it coul...
Interspecies activation of lecithin-cholesterol acyltransferase by apolipoprotein A-I isolated from the plasma of humans, horses, sheep, goats and rabbits. The abilities of apolipoprotein A-I species isolated from humans, horses, sheep, goats and rabbits to activate purified human lecithin-cholesterol acyltransferase and the enzyme from homologous plasmas and plasma of other mammalian species were compared. Each purified apolipoprotein A-I species was individually incorporated into phosphatidylcholine/cholesterol vesicles by the cholate dialysis method to form proteoliposome common substrates (apolipoprotein A-I/phosphatidylcholine/cholesterol molar ratio of 1:250:12.5) for the enzyme activity assay. All apolipoprotein A-I species tested had the ...
Concentration of nucleotides and deoxynucleotides in peripheral and phytohemagglutinin-stimulated mammalian lymphocytes. Effects of adenosine and deoxyadenosine. Concentrations of purine and pyrimidine ribonucleotides were measured with HPLC in lymphocytes of man, horse, pig and sheep and in rat thymocytes. The ATP concentration was highest in lymphocytes of all species and about 850 pmol/10(6) cells in human and equine lymphocytes, higher in porcine and lower in ovine lymphocytes and rat thymocytes. The GTP concentration was comparable in human, equine and porcine lymphocytes, but lower in ovine lymphocytes. ATP concentration was also measured in lymphocytes of man, horse and pig with a luciferin-luciferase assay. During culturing with or without phyt...
Ultrastructure of the equine hoof wall secondary epidermal lamellae. The ultrastructure of cells of the secondary epidermal lamellae from the hoof wall of 8 adult horses was described. Stages of progressive keratinization were not observed in this cell population. The morphologic features of cells of the secondary epidermal lamellae indicated that these lamellae were composed of nonmobile populations of cells and that primary epidermal lamellae moved past the secondary lamellae by breaking of the desmosomes connecting these 2 cell populations. Seemingly, debris present in the intercellular space between primary and secondary lamellae was a by-product of this re...
Sensory nerve conduction velocities in forelimb of ponies. Normal nerve conduction velocity values in 10 ponies were determined for sensory nerve fibers in the median and ulnar nerves. A percutaneous signal-averaging technique was developed and used. Medial and lateral palmar digital nerves on the abaxial surface of the proximal sesamoid bones were used as the sites for percutaneous stimulation, whereas recording sites included the medial and lateral palmar nerves just distal to the carpus and the median and ulnar nerves in the middle of the radius. Sensory nerve conduction velocities can be evaluated simply and clinically in the limbs of horses, usin...
Composition of sweat of the horse during prolonged epinephrine (adrenaline) infusion, heat exposure, and exercise. Temporal changes in sweat composition were studied in 4 horses during epinephrine (adrenaline) infusion (0.13 to 0.31 micrograms/kg/min for 3 hours), heat exposure (41 C, [33 C wet bulb] for 5 to 6 hours), and exercise (16 to 18 km/hr for 58 to 80 km). Four ponies also were studied during heat exposure. Sweat produced by each of the stimuli was hypertonic for Na+, K+, and Cl-. These electrolyte concentrations remained constant during the central period of the experiments, with changes occurring near the beginning and toward the end. The Na+ was significantly higher and K+ significantly lower i...
Regional myocardial blood flow and coronary vascular reserve in unanesthetized ponies during pacing-induced ventricular tachycardia. To examine the effects of tachycardia on coronary circulation, transmural distribution of myocardial blood flow (MBF, 15-micron diameter radionuclide-labeled microspheres) was studied in six healthy adult ponies at rest (heart rate = 60 +/- 7 beats . min-1), during ventricular pacing at 150 and 200 beats . min-1, as well as with ventricular pacing at 250 beats . min-1 before and during maximal coronary vasodilatation (iv adenosine infusion; 4 mumole . kg-1 . min-1). Mean aortic pressure and cardiac output were unchanged from control values with ventricular pacing. Whereas ventricular pacing at...
Simplified technique for histochemical determination of three fiber types in equine skeletal muscle. For determination of 3 muscle fiber types in equine skeletal muscle, a comparison of 2 preincubation buffers, each followed by myosin adenosine triphosphatase staining, was made. Serial sections of the muscle samples (n = 75) were preincubated in an acid buffer (pH 4.6) or a formaldehyde-glycine buffer (pH 7.25) and then were stained for myosin adenosine triphosphatase. Differentiation of muscle fibers into type I, IIA, and IIB was identical with both techniques; however, in the samples prepared at pH 4.6, type I fibers were black; type IIA, light gray; and type IIB, dark gray. In the samples ...
Using red blood cell creatine concentration to evaluate the equine erythropoietic response. Red blood cell creatine concentration was examined to determine its association with the equine erythropoietic response. Studies were conducted on 9 healthy horses, 4 healthy ponies, 24 anemia horses, and 2 horses in which anemia was experimentally induced. A modified Jaffe reaction was used to measure RBC creatine concentration. The mean RBC creatine concentration of the 9 healthy horses was 5.72 +/- 0.42 mg/dl, and that of the 4 healthy ponies was 2.59 +/- 0.31 mg/dl. Density-separation of erythrocytes from the healthy horses revealed significantly higher (P less than 0.001) creatine content...
Effects of training on cardiorespiratory function in the horse. The effects of 5- and 10-wk treadmill exercise training on cardiorespiratory function were evaluated in the horse. Cardiac output (Q), heart rate (HR), and stroke volume (SV), as well as left ventricular (LVP), aortic (AoP), and mean right atrial (RAP) pressures and the peak first time derivative of LVP (LV dP/dtmax), were measured at rest and at five different levels of exercise up to 90% of initial predicted maximal HR (HRmax). Oxygen uptake (VO2) and respiratory exchange ratio (R) were also obtained under the same conditions. At rest, although HR was no different after training, LV dP/dtmax...
Properties and distribution of phosphatidylinositol-specific phospholipase C in human and horse platelets. Phospholipase C has been studied in homogenates, total particulate and soluble fractions of horse and human platelets. This enzyme, assayed with exogenous L-3-phosphatidyl[14C]inositol, is predominantly localized in the soluble fraction and its distribution parallels that of lactate dehydrogenase. A small percentage of activity present in the particulate fraction seems to be due to contamination with soluble enzyme. Enzyme from horse and human platelets appears identical, having a Km of 0.10-0.15 mM, acid pH optimum (pH 5.5) and showing Ca2+-dependency and weak inhibition by deoxycholate. Anal...
