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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.
Hemodynamics and myocardial function during acute hypoxia in the pony. Hemodynamics and myocardial contractility were evaluated in 6 unanesthetized ponies during hypocapnic and isocapnic hypoxia and during hypocapnic hypoxia after beta adrenergic blockade with propranolol. Hypocapnic hypoxia, with a mean arterial oxygen pressure (PaO2) of 41.9 mm of Hg, produced a decrease in stroke index and an increase in heart rate, with no change of cardiac index. A moderate increase in left ventricular contractility occurred during hypocapnic hypoxia. Beta adrenergic blockade abolished changes in nearly all indices of left ventricular contractility during hypocapnic hypoxia,...
Prostaglandin F2alpha specific binding in equine corpora lutea. Preliminary studies indicate the presence of PGF2alpha specific binding sites in membrane fractions prepared from equine corpora lutea. The equilibrium binding data indicate an apparent dissociation constant of 3.2 X 10(-9)M and the concentration of binding sites of -0.1 pmoles/mg membrane protein. Competition of several natural prostaglandins for equine luteal PGF2alpha specific binding sites indicates specificity for the 9alpha-hydroxyl moiety and the 5,6-cis doublebond. Significant increases in relative binding affinities were demonstrated for PGF2alpha analogs with a phenyl ring introduced...
Amino acid sequence of phospholipase A2 from horse pancreas. The complete amino acid sequence of phosphlipase A2 (EC 3.1.1.4) from horse pancreas was determined. The protein controls of a single polypeptide chain of 125 amino acids and has a molecular weight of 13,927. The chain is crosslinked by seven disulfide bridges. The sequence was determined by automated Edman degradation of the intact protein and several of the large peptide fragments. Smaller peptides were analyzed by manual Edman degradation. Fragmentation of the peptide chain was accomplished by enzymatic digestion with trypsin, chymotrypsin, and thermolysin. The final overlap was found by di...
Steady state kinetics and binding of eukaryotic cytochromes c with yeast cytochrome c peroxidase. 1. The steady state kinetics for the oxidation of ferrocytochrome c by yeast cytochrome c peroxidase are biphasic under most conditions. The same biphasic kinetics were observed for yeast iso-1, yeast iso-2, horse, tuna, and cicada cytochromes c. On changing ionic strength, buffer anions, and pH, the apparent Km values for the initial phase (Km1) varied relatively little while the corresponding apparent maximal velocities varied over a much larger range. 2. The highest apparent Vmax1 for horse cytochrome c is attained at relatively low pH (congruent to 6.0) and low ionic strength (congruent to...
Transmission of the cytochrome c structural gene in horse-donkey crosses. Donkey cytochrome c was shown to differ from horse cytochrome c by having a serine in position 47 rather than a threonine. The rest of the amino acid sequences are identical. Mules and hinnies, both males and females, carry equal amounts of horse and donkey cytochromes c. The same ratio is found in hinnies in preparations from heart tissue and from skeletal muscle. These results demonstrate that cytochrome c is transmitted in horse-donkey crosses as a simple Mendelian character which is neither sex-linked nor shows dominance. The cytochrome c gene is therefore located in the nuclear genome, as...
Guanidination of horse methemoglobin. Reaction of horse methemoglobin with O-methylisourea at pH 10.2 results in 95% conversion of lysine residues to homoarginine. Analysis of the chymotryptic peptides showed that no single ϵ-amino group was unreactive. Guanidination decreases the dependence of the sedimentation coefficient on hydrogen ion concentration in the range of pH 8 to 11 and did not affect the dependence on protein concentration at pH 7. These results support the conclusion that the lysine side chains involved in subunit contacts have sufficient freedom to accommodate the small changes in bulk and geometry associated wit...
Determination of total and ultrafilterable calcium and magnesium in normal equine serum. Total and ultrafilterable calcium (Ca) and magnesium (Mg) values were determined for Shetland pony stallions, stallions, and pregnant and diestrous mares, using a simple, inexpensive, quick procedure to obtain an ultrafiltrate of serum. There was no significant difference between horses and ponies, between stallions and mares, or between pregnant and nonpregnant mares. The percentage of total serum Ca that was ultrafilterable was 63.4+/-1.7 for horses and 64.8+/-2.2 for ponies. The percentage of total serum Mg that was ultrafilterable was 75.6+/-1.5 for horses and 77.0+/-1.7 for ponies. Total ...
Cardiac Arrhythmias in the horse. Electrocardiograms were obtained from normal horses and from horses with cardiac or other organic disease that affected the cardiac rhythm. Tracings were obtained from a base-apex bipolar monitor lead, with the negative electrode attached to the skin in the right jugular furrow and the positive electrode attached to the skin on the ventral medline, beneath the apex of the heart. Each arrhythmia was discussed relative to importance and probable cause.
Effects of preanesthetic medication, anesthesia, and position of recumbency on central venous pressure in horses. Central venous pressure (cvp) was recorded in horses before and after tranquilization and during halothane-maintained anesthesia in lateral or dorsal recumbency. The cvp was significantly decreased after administration of acetylpromazine, when compared with base line measurements and measurements taken after xylazine administration. After induction of anesthesia, cvp increased with time for 75 minutes, and values in lateral recumbency were significantly higher than those in dorsal recumbency.
A study of correlation of closure of the distal radial physis with performance and injury in the Standardbred. The distal radial physes of 113 two-year-old Standardbreds were radiographed an average of 2.6 times each during an average of 4.72 +/- 1.7 months, beginning May 1, 1975. The radiograph of each physis was graded C, B-, B, B+, or A (closed), and the date of closure was determined by a method that proved to be reliable. The average age of closure of the distal radial physes was 29.8 +/- 1.6 months, with age of closure ranging from 26 to 35 months. There were no statistical differences between age of physeal closure of colts, geldings, or fillies; pacers or trotters; "well-bred" or other horses, ...
Amino acid composition of casein isolated from the milks of different species. Casein was isolated from the milks of the following species: cow, horse, pig, reindeer, caribou, moose, harp seal, musk-ox, polar bear, dall sheep, and fin whale. The caseins were subjected to acid hydrolysis, the resultant amino acids were converted to their n-butyl-N-trifluoroacetyl esters, and the amino acid composition of the caseins was determined by gas chromatographic analysis of these esters. Notable among the results was the close similarity, with respect to amino acid composition, of reindeer and caribou caseins. The results of the amino acid analyses of the other caseins are present...
Reaction of bovine and equine growth hormones with tetranitromethane. Bovine and equine growth hormones were chemically modified with tetranitromethane, at pH 7.4 during 5 h and at pH 8.0 in the presence of 8 M urea during 1 h. a) Both hormones have very similar but not identical reactivities. b) The nitration of the reactive tyrosines and tryptophan residues at pH 7.4 produces no detectable changes in their immunological or somatotrophic activities. C) The nitration of all tyrosine residues in both hormones gives rise to a complete loss of somatographic activity with no alteration of the immunological activity.
Purification and characterization of equine herpesvirus-induced DNA. Infection of cells with equine herpesvirus type 1 (EHV-1) or type 3 (EHV-3) resulted in the induction of a DNA polymerase activity distinguishable from host cell DNA polymerases by its high salt requirement for maximal activity. By column chromatography on DEAE-cellulose, DNA-cellulose, phosphocellulose, and hydroxyapatite, the EHV-1-induced polymerase was purified 500-fold with 1–2% recovery of total activity from the nuclei of infected hamster livers. The final enzyme preparation was homogeneous as judged by electrophoresis in sodium dodecyl sulfate-polyacrylamide gels. Calculations based ...
Relationship of protein concentration and water content of equine serum and plasma samples. A highly significant correlation between the water content and protein concentration of equine serum and plasma samples was demonstrated over a wide range of concentrations. A close correlation was also observed between protein concentration as estimated by refractometry and as determined by the biuret procedure for equine serum and plasma samples.
Studies on cytochrome c. XIV. Synthesis of the protected heptadecapeptide (sequence 88-104) of horse heart cytochrome c. A solution synthesis is described of the partially protected N alpha-benzyloxycarbonylheptadecapeptide Z-Lys (Tfa)-Thr-Glu-Arg-Glu-Asp-Leu-Ile-Ala-Tyr-Leu-Lys (Tfa)-Lys (Tfa)-Ala-Thr-Asn-Glu (OBu t)-OBu t corresponding to sequence 88-104 of horse heart cytochrome c. The synthesis is achieved through the preparation of two subunits H1 (sequence 88-96) and H2 (sequence 97-104) and their linkage by an azide coupling step.
Effect of imidocarb dipropionate and hemicastration on spermatogenesis in pony stallions. The effect of imidocarb dipropionate [3, 3' bis-(2-imidazolin-2-yl) carbanilide dipropionate] on spermatogenesis in 3 pony stallions was studied. The drug alone had no deleterious effect on spermatogenesis when given intramuscularly 4 times at a dosage level of 4 mg/kg at 72-hour intervals. Hemicastration, with or without subsequent drug treatment, caused almost complete cessation of spermatogenesis 30 days after the operation.
Surgical repair of cleft soft palate in the horse. A technique for the surgical repair of a cleft soft palate in the horse is described. A symphysiotomy approach was employed to repair the anterior end of the cleft palate, and the posterior part was approached via a pharyingotomy incision.
