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Topic:Biochemistry
The study of biochemistry in horses encompasses the chemical processes and substances that occur within equine organisms. This field investigates the molecular interactions and pathways that are fundamental to horse physiology, including metabolism, enzyme activity, and genetic expression. Key areas of interest include the examination of metabolic disorders, nutrient absorption, and the biochemical basis of muscle function and energy production. Researchers utilize biochemical analysis to understand health and disease mechanisms in horses, contributing to the development of diagnostic tools and therapeutic strategies. This page gathers peer-reviewed studies and scholarly articles that explore various biochemical processes and their implications for equine health and performance.
Allergen-specific ELISA for horse IgE. An enzyme-linked immuno sorbent assay (ELISA) for measuring horse IgE specific to ovalbumin, bencylpenicilloic acid and odinitrocarboxyphenol is described. We used a sandwich type of ELISA by which horse serum was incubated in antigen-coated tubes containing one additional polystyrene ball, followed by rabbit anti horse IgE serum. The tubes were then incubated with biotinylated goat anti rabbit globulin followed by avidin coupled to phosphatase. Endpoint titrations were compared. The ELISA is highly reproducible due to the pretreatment of the polystyrene with glutaraldehyde. The increased anti...
Biochemical and haematological effects of a revised dosage schedule of phenylbutazone in horses. Five pairs of matched horses were used to study the biochemical and haematological effects of a revised dosage schedule of phenylbutazone. One group of five horses received a phenylbutazone paste formulation daily for 12 days and a second group of five animals received a placebo preparation for a similar time. Some statistically significant differences were recorded from pretreatment levels in both groups of horses. These changes represented instability in baseline levels and could not be ascribed to phenylbutazone administration.
[Study of conformational changes in alcohol dehydrogenase during its interaction with silochrome adsorbent by the EPR spectroscopy method]. The possible use of EPR spectroscopy (spin labelling) for the study of horse liver alcohol dehydrogenase with a silochrome adsorbent is discussed. The rotatory diffusion of nitroxyl labels chemically linked to the enzyme was studied with reference to the time of the enzyme incubation with the adsorbent and the degree of its accumulation on the adsorbent surface. The mobility of nitroxyl radicals attached to the protein globules was shown to increase with time. It was concluded that the conformation of the enzyme molecules changes during their interaction with the adsorbent.
Fatty acid composition of serum lipids in fasting ponies. Alterations in the fatty acid distribution of total lipid extracts and 4 of the major lipid subclasses of serum in ponies fasted overnight and for 4 and 7 days were determined. Although increases in 16:0, 16:1, and 18:3 omega 3 were observed, decreased amounts of 18:0 and 18:2 omega 6 combined to cause no significant change in the saturated to unsaturated fatty acid ratio in the total extracts. Phospholipid became somewhat preferentially enriched in saturated fatty acids due to a decrease in 18:1, although this response was variable. The free fatty acid and triglyceride fractions both showed i...
Chemiluminescence response of equine alveolar macrophages during stimulation with latex beads, or IgG-opsonized sheep red blood cells. Isolated equine alveolar macrophages were shown to generate a luminol-dependent light response when challenged with a phagocytic stimulus. The chemiluminescent response was not detected with luminol prepared at 1.0 x 10(-5) or 1.0 x 10(-4) molar concentrations, but was readily quantitated when used at a 1.0 x 10(-3) molar concentration. Challenge of the alveolar macrophages with latex particles or with equine IgG-coated sheep red blood cells elicited the luminol-dependent light response, whereas unchallenged equine alveolar macrophages or those challenged with unopsonized erythrocytes failed t...
Aggregation of equine platelets by PAF (platelet-activating factor). Platelet-activating factor (PAF), a lipid released as a result of immediate allergic reactions from basophils and mast cells as well as by a variety of other cell types and stimuli, is one of the most potent platelet agonists and hypotensive agents known. Equine platelets stimulated over a wide range of PAF concentrations aggregated in a time- and dose-dependent manner. Maximum aggregation was observed at concentrations of PAF as low as 3.58 x 10(-14) M with platelet-rich plasma (PRP) and 3.58 x 10(-16) M with washed platelets. Furthermore, the aggregation observed did not appear to be breed-d...
Localization of the second calcium ion binding site in porcine and equine phospholipase A2. At alkaline pH porcine pancreatic phospholipase A2 is known to bind two Ca2+ ions per protein molecule. One Ca2+ ion is strongly bound to the active site and is essential for enzyme activity. A second Ca2+ ion binds more weakly to the protein and improves the affinity of the enzyme for lipid-water interfaces severalfold at high pH values. A group having a pK around 6 controls enzyme binding to lipid-water interfaces in the absence of Ca2+. By use of proton titration techniques this group is now identified to be a carboxylate having an abnormally high pK. Its pK shifts to a value around 4.5 in ...
Isolation of horse mononuclear cells, especially of monocytes, on Isopaque-Ficoll neutral density gradient. Horse mononuclear cells were separated from whole blood using neutral density gradient centrifugation on Isopaque-Ficoll. The resulting cell suspension was comparable in composition with similarly prepared human and bovine mononuclear cell preparations. The relative concentration of monocytes was increased by the use of a gradient with density lower than that originally proposed by Böyum (Böyum, A. 1968. Scand. J. Clin. Lab. Investig. 21 supple. 97:77-89). Contamination by neutrophils was limited either by using a gradient medium of lower density or by replacing Isopaque-Ficoll by Percoll-0....
Pharmacokinetics and protein binding of morphine in horses. Morphine could be detected in horses dosed with 0.1 mg of drug/kg of body weight for up to 48 hours in blood and 144 hours in urine. This dose of morphine elicited no observable effects and is a suggested analgesic dose. Computer analysis revealed that a 3-compartment open system was the best fitting model with a serum half life (t1/2(beta)) of 87.9 minutes and a urine t1/2(beta) of 101.1 minutes. Binding to equine serum proteins was linear over a drug concentration range of 3.88 X 10(-5)M to 3.50 X 10(-8)M and averaged 31.6%. In RBC-partitioning experiments, 78.1% of the drug was found in the...
Adaptation of human diploid fibroblasts in vitro to serum from different sources. The growth of two human diploid skin fibroblast cell lines, originally grown in medium supplemented with foetal bovine serum and later adapted to medium supplemented with newborn bovine, bovine calf or horse serum, has been studied. Prolonged generation times increased cell volumes and decreased plating efficiencies were observed in cultures grown in newborn bovine, bovine calf or horse serum. In general, the deleterious effects were most severe as a result of growth in bovine calf or horse serum. In the light of the present findings, we believe investigators should exert great caution in swit...
Selective crystallization of horse isoferritins. Various precipitating agents were examined in order to crystallize horse heart and spleen ferritins. Cadmium sulfate induced the crystallization of the spleen ferritin, while 2-methyl-2,4-pentanediol and poly(ethylene glycol) only induced that of the heart ferritin. Isoelectric focusing analysis showed that the crystals grown from cadmium sulfate contained only the more acidic isoferritins, and those grown from methyl pentanediol only the less acidic isoferritins. Heart ferritin crystallizes in a cubic space group, as previously reported for spleen ferritin crystals grown from cadmium sulfate....
An energetic basis of equine performance. Although different physiological and behavioural attributes are needed for various types of equine competition, successful racing depends primarily on the animal's metabolic ability to convert chemical energy to mechanical energy--the function of muscle. Components of these energetic processes include the rate, efficiency and interaction of aerobic and anaerobic metabolism in muscle and the supply and utilisation of fuel. In anaerobic work like racing, fatigue processes may be largely regarded as a function of an intramuscular fuel (phosphogen) depletion, despite the fact that substrates are s...
Testosterone administration to mares during estrus: duration of estrus and diestrus and concentrations of LH and FSH in plasma. To study the possible role of ovarian androgens in regulation of follicle stimulating hormone (FSH) secretion in the cycling mare, five mature, intact mares were treated with testosterone (20 micrograms/kg of body weight) daily during estrus; five control mares received safflower oil on the same schedule. Mares were teased for estrus and samples of jugular blood were drawn daily through one full estrous cycle. Concentrations of FSH in plasma were measured by a newly developed radioimmunoassay based on anti-ovine FSH serum and radioiodinated equine FSH. Testosterone treatment during estrus had ...
Use of procainamide gels in the purification of human and horse serum cholinesterases. Two large-scale methods based primarily on the use of procainamide-Sepharose gels were developed for the purification of horse and human serum non-specific cholinesterases. With method I, the procainamide-Sepharose 4B gel was used in the first step to handle large volumes of serum. With method II, the procainamide-Sepharose 4B gel was used in the final step to obtain pure enzyme. Although both methods gave electrophoretically pure cholinesterase preparations in good yields, they were significantly more efficient at purifying the horse enzyme than the human enzyme. To study this problem, the re...
Biochemical and haematological effects of phenylbutazone in horses. Five matched pairs of horses were used to investigate the effects of phenylbutazone on a range of physiological, biochemical and haematological variables. The drug was given by mouth daily for 15 consecutive days at the manufacturer's recommended dose rates to one group of horses (Group A); the second group (Group B) received equivalent doses of a placebo. For some of the measured parameters, significant changes were recorded in both groups, indicating background instability. Significant decreases in serum total protein, albumin, plasma pH, viscosity and magnesium, and an increase in albumin: ...
The metabolism of fenclofenac in the horse. 14C-Fenclofenac (2-(2'-4'-dichlorophenoxy)-phenylacetic acid) was administered orally to horses, and urinary metabolites investigated by chromatography. Fenclofenac was rapidly absorbed and eliminated, with a plasma half-life (t1/2) of 2.3 h, with 83.2 and 85.8% of the dose being recovered in the urine in 0-24 h. The major urinary metabolite was the ester glucuronide (58.8, 70.0% dose), and evidence is presented that this metabolite undergoes a structural rearrangement to give beta-glucuronidase-resistant isomers. The other 14C-labelled components in horse urine were unchanged fenclofenac (13....
Morphologic and biochemical changes in cartilage of foals treated with dexamethasone. Epiphyseal and articular cartilages were examined in pony foals treated with intramuscular injections of either 0.5 mg dexamethasone per 100 kg bodyweight daily for 3, 8 or 11 months, or 5.0 mg per 100 kg for 11 months, and in horse foals treated with 5.0 mg per 100 kg for 20 weeks. The proximal femoral growth plates exhibited increased spatial separation between chondrocyte columns, narrowed zones of disorganized columnar and hypertrophic cartilage, abnormal penetration of hypertrophic cartilage by metaphyseal capillaries, retained cartilage in the spongiosa, distal terminal plate formation, ...
Changes in plasma biochemistry in horses competing in a 160 km endurance ride. Plasma biochemical values were measured in 14 horses, before a 160 km endurance ride, immediately after 85 km, immediately after 160 km, after 30 min recovery period and the day after the ride. For statistical analysis, a group of 7 horses that completed the ride at a mean speed of 234 metres per min (m/min) (Fast Group) was compared with 7 horses that completed the ride at a mean speed of 144 m/min (Slow Group). Estimations were made of sodium, potassium, chloride, bicarbonate, glucose, creatinine, urea, bilirubin, iron, total protein, albumin, calcium, phosphate, cholesterol, alkaline phosph...
Examination of the origin of increased equine serum alkaline phosphatase concentrations. Serum alkaline phosphatase activity was found to be increased in 32.6% of equine samples analyzed at the Ontario Veterinary College over an 18 month period. An attempt was made using sensitivity to L-phenylalanine and heat to identify the origin of increased serum alkaline phosphatase isoenzymes present in 44 clinical cases. No difference in sensitivity to either procedure was observed for serum alkaline phosphatase from groups of foals and horses representing different clinical problems. Alkaline phosphatase of osseous tissue origin appeared to be the major source of activity for each group o...
Identification and measurement of testosterone in plasma and follicular fluid of the mare, using gas chromatography-mass spectrometry associated with isotope dilution. Testosterone has been identified by mass spectrometry in blood and follicular fluid aspirated from mature Graafian follicles of mares. Quantitative measurements made by gas chromatography-mass spectrometry have validated the determination of plasma testosterone made by radioimmunoassay. However, because of high levels of epitestosterone (17 alpha-hydroxyandrost-4-en-3-one) in the follicular fluid, radioimmunoassay overestimates the true concentrations of testosterone. The occurrence of testosterone in mare follicular fluid at a concentration which is two orders of magnitude higher than that in...
A comparative study of the effect of triazine herbicides on alcohol dehydrogenases isolated from various sources. The studied herbicides (terbutylazine, simazine) inhibit the activity of plant, animal, and yeast alcohol dehydrogenases. The inhibition constant Ki for alcohol dehydrogenase (ADH) isolated from peas and bakers' yeast equals approximately 10(-4) M, and that for ADH isolated from horse liver is of the order of 10(-5) M. The character of inhibition for all the herbicides studied for the reaction catalyzed by pea, liver, and yeast ADH is always noncompetitive toward ethanol and competitive with respect to NAD. The inhibition constants for the enzyme isolated from peas are pH independent. The inte...
Synthesis and properties of equine beta-melanotropin analogs with substitution in residue position 1. Five analogs of equine β-melanotropin have been synthesized by the solid phase method. The NH2-terminal aspartic acid was substituted with amino acids (Gly, Trp, Ile, Lys and Nα-acetyl-Asp) differing widely in physicochemical properties. On the basis of their lipolytic potencies it was concluded that this position plays a negligible role in this activity.
Biosynthesis of 3 beta-hydroxy-5,7-pregnadien-20-one by the horse fetal gonad. The production of equilin and the other ring B-unsaturated estrogens by the pregnant mare is anomalous in that they are biosynthesised by a cholesterol-independent pathway. Fetal horse gonads were incubated with tritiated sodium acetate and radiochemically pure 3 beta-hydroxy-5,7-pregnadien-20-one and 3 beta-hydroxy-5,7-androstadien-17-one were isolated. A fetal gonad--placental system is proposed for equilin production, 3 beta-hydroxy-5,7-pregnadien-20-one being a precursor for 3 beta-hydroxy-5,7-androstadien-17-one in the fetal gonad and the latter being the precursor of equilin in the place...
The effect of nutritional stress on the plasma progestagen levels and embryonic mortality in twin pregnancies of mares. Two thoroughbred mares bearing twins as diagnosed by rectal palpation, were subjected to nutritional stress by drastically reducing the daily ration. This resulted in a marked reduction in plasma progestagen levels and the death of either one or both of the twin embryos.
Plasma cortisol variations induced in the stallion by mating. Plasma cortisol variations have been determined by radioimmunoassay in 5 stallions during mating and in 2 teasers during oestrous female exposure. In all the animals, cortisol plasma levels consistently increase (71.1 ng/ml vs 44.0 and 63.0 ng/ml vs 35.1, in the stallions and in the teasers, respectively) 7-30 min after female exposure; 120 min after exposure, cortisol concentrations are again low.
Thyroid-stimulating hormone: response test in healthy horses, and effect of phenylbutazone on equine thyroid hormones. Adult horses showed a mild diurnal variation in equine plasma thyroxine (T4) concentrations, but not triiodothyronine (T3). Plasma T4 concentrations tended to be higher between 5 PM and 8 PM than at 8 AM. Increases in plasma T4 and T3 were similar in adult healthy horses given 5, 10, or 20 IU of thyroid-stimulating hormone (TSH). The T4 peaked at approximately twice (2.0 +/- 0.4 times) as high as the base line at 6 to 12 hours after the TSH was given. The greatest change from base line T3 occurred at 1 to 3 hours after the TSH was given, but the magnitude of increase was widely variable (4.36 ...
The pharmacokinetics, plasma protein binding and time response relationships of 2-amino-5-phenyl-2-oxazolin-4-one (pemoline) in the horse. The disposition kinetics of pemoline after iv and oral administration of 2.4 mg/kg of the drug were studied. The elimination half-life was 39.4 hr. The mean volume of distribution was 1.5 liters/kg indicating extensive tissue distribution and sequestration for an amphoteric drug. Plasma protein binding determined by in vitro equilibrium dialysis was concentration dependent. The mean binding capacity was found to be 0.80 mu-mol/g, an apparent dissociation constant of 3.73 X 10(-5) molar, and a total plasma protein concentration of 64.7 g/liter. The mean systemic availability by oral administrat...
Dansylarginine N-(3-ethyl-1.5-pentanediyl)amide. A potent and selective fluorescent inhibitor of butyrylcholinesterase. Interactions between dansylarginine N-(3-ethyl-1,5-pentanediyl)amide (DAPA) and the cholinesterases were examined by the techniques of enzyme kinetics and fluorescence spectroscopy. When tested with partially purified enzyme preparations, DAPA was a potent inhibitor of butyrylcholinesterase (IC50 = 2 x 10(-7) M) but not of acetylcholinesterase (IC50 = 4 x 10(-4) M). For a detailed study of the effects of DAPA on butyrylcholinesterase (BuChE), the enzyme was purified to homogeneity from horse serum, with the aid of affinity chromatography on N-methyl acridinium. The kinetics of the inhibition o...
