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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.
High resolution R-bands produced in equine chromosomes after incorporation of bromodeoxyuridine. Cell synchronization was used to obtain an adequate percentage of very long chromosomes in equine mitotic spreads. Reported here is our variation, adapted to horse chromosomes, of a method using excess thymidine followed by bromodeoxyuridine incorporation. This technique routinely yields excellent quality cells, predominantly in prometaphase and prophase. Among other differences with the standard technique, this method does not use Colcemid, which, in addition to inhibiting spindle fiber formation, also increases chromosome contraction resulting in thicker and thus fewer bands. Consequently, h...
Disposition of sulfadimidine and its N4-acetyl and hydroxy metabolites in horse plasma. The plasma disposition of sulfadimidine (SDM) and its metabolites N4-acetylsulfadimidine (N4-SDM), 6-hydroxymethyl-4-methyl-pyrimidine (SCH2OH) and 5-hydroxy-4,6-dimethyl-pyrimidine (SOH), was studied in three horses following intravenous administration of SDM at dose levels of 20 and 200 mg/kg in cross-over trials. The percentages of N4-SDM (0.58-0.90%), SOH (0.83-6.75%) and SCH2OH (0.38-0.71%) in plasma, expressed as a percentage of the total sulfonamide concentration, were small and their plasma concentrations were parallel with SDM from 4 h following administration. At high doses (200 mg/k...
Incorporation of L-75Se-cystine in tissue fragments from the matrix of the hoof and the claw–a tool for studying the pathogenesis of laminitis? An in vitro method has been designed and used to study the incorporation of 75Se-cystine into matrix fragments from hooves and claws of healthy horses and cattle. Tissue fragments from the zone of keratinisation were incubated with L-75Se-cystine in a tissue culture medium for 4 to 6 h, during which time there was continuous incorporation of the labelled selenocystine. The incorporation was greatly decreased by adding L-cystine to the incubation mixture. It is concluded that the incorporation of 75Se-cystine depends on the presence of a specific receptor for cystine in the tissue fragments stu...
The influence of dietary selenium levels on blood levels of selenium and glutathione peroxidase activity in the horse. Twenty mature geldings, averaging 535 kg, were used to determine the influence of dietary selenium (Se) on the blood levels of Se and Se-dependent glutathione peroxidase (SeGSH-Px) activity in the horse. Horses were randomly assigned within breed to four treatments consisting of five horses each and fed a basal diet containing .06 ppm of naturally occurring Se. Diets were supplemented with .05, .10 and .20 ppm Se, as sodium selenite. Blood was drawn for 2 wk before, and for 12 wk following, the inclusion of supplement Se in the diets. Whole blood and plasma Se concentrations and plasma SeGSH-P...
Properties of monoclonal antibodies against glycoproteins of western equine encephalitis virus. To analyze the biological activities of the alphavirus glycoproteins, eight different monoclonal antibodies against the two glycoproteins of western equine encephalitis virus were isolated. Five of the eight monoclonal antibodies were shown to be specific for E1 and three for E2 protein by an enzyme-linked immunosorbent assay and by radioimmunoprecipitation. Three of the five anti-E1 and all of the anti-E2 monoclonal antibodies inhibited hemagglutination by purified virions. One anti-E1 and two anti-E2 monoclonal antibodies possessed high virus-neutralizing activity.
Demonstration of a COOH-terminal extension on equine lutropin by means of a common acid-labile bond in equine lutropin and equine chorionic gonadotropin. The beta subunits of equine lutropin and equine chorionic gonadotropin were incubated in 0.013 N HCl for 30 min at 110 degrees C and separated into two fragments by reverse-phase high performance liquid chromatography. The amino acid and carbohydrate compositions of both fragments from each subunit were analyzed. The results demonstrated that equine lutropin-beta has a glycosylated COOH-terminal extension that differs only in carbohydrate composition from the COOH-terminal portion of equine chorionic gonadotropin-beta. This is the first demonstration of a glycosylated COOH-terminal extension i...
Kinetic studies of the unfolding-refolding of horse muscle phosphoglycerate kinase induced by guanidine hydrochloride. The kinetics of the unfolding and refolding of horse muscle phosphoglycerate kinase were studied with three different signals: fluorescence emission intensity at 336 nm (excitation at 292 nm), ellipticity at 220 nm, and enzyme activity. The results corroborate the conclusion on the existence of intermediates in the folding pathway obtained from equilibrium studies. Kinetic studies showed at least two phases of refolding, as revealed by fluorescence as well as by circular dichroism measurements. During the fast phase, an intermediate was formed with a fluorescence intensity higher than that of ...
Pharmacokinetics of small doses of 3-methylindole given to horses. The pharmacokinetics of 3-methylindole (3MI) given orally in 2 doses (10 mg/kg and 20 mg/kg) to horses were determined. The pharmacokinetic plasma-concentration profiles for 3MI (10- and 20-mg/kg dosages) in horses were represented by a 2-compartment open model with first-order absorption, as determined by nonlinear least-squares regression analysis. Absorption of 3MI at both dosages was rapid. Comparisons of the peak plasma concentrations, the postdistribution half lives, total clearances, and areas under the curve of the plasma-concentration profiles between the 10- and the 20-mg/kg dosages ...
Mechanism of renal excretion of creatinine by the pony. Free-flow and stop-flow procedures conducted on 2 female and 2 testosterone-treated castrated male ponies indicated that [14C]inulin and exogenous creatinine clearance values were the same. These results indicated that creatinine was neither reabsorbed nor secreted by the renal tubules and that exogenous creatinine clearance was an accurate method for determining glomerular filtration rate. As in other species which have been studied, endogenous creatinine clearance probably underestimated glomerular filtration rate because of the presence of noncreatinine chromogens in plasma.
Proteinase inhibitors of horse seminal plasma. A high molecular mass, acid-soluble proteinase inhibitor. Horse seminal plasma does not possess a proteinase inhibitor corresponding to human HUSI-I (human seminal plasma inhibitor). Instead a protein complex of high relative molecular mass (Mr) containing proteinase inhibitory activity was detected, which was called horse seminal plasma protein complex or HSPC. The compound had a broad enzyme-inhibiting spectrum. Its Mr was estimated to be 800 000 and it was composed of 7 different polypeptides with Mr values ranging from 11 000 to 30 000. Its carbohydrate content was between 3.5% and 5%. Despite the high molecular mass, the complex was soluble in d...
Enzyme histochemical features of equine gluteus muscle fibers. Gluteal muscle specimens were taken from 4 horses. From 1 of the 4 gluteal muscles, serial sections were prepared. Individual muscle fibers were identified and studied, using photomicrographs of sections stained by different enzyme histochemical methods. In specimens in which cytoplasmic soluble enzymes were studied, use was made of the semi-permeable membrane technique to hamper enzyme diffusion into reaction fluids. Enzymes involved in glycogenolysis, glycolysis, the tricarboxylic acid cycle, synthesis of reduced nicotinamide adenine dinucleotide phosphate, the pentose phosphate cycle, the a...
Identification of metabolites of methylprednisolone in equine urine. Methylprednisolone and three metabolites, 17,21-dihydroxy-6 alpha-methyl-1,4-pregnadiene-3,11,20-trione, 6 alpha-methyl-17,20 beta,21-trihydroxy-1,4-pregnadiene-3,11-dione, and 6 alpha-methyl-11 beta,17,20 beta,21-tetrahydroxy-1,4-pregnadien-3-one were detected in equine urine after intraarticular administration of methylprednisolone acetate. All four compounds were excreted both in the unconjugated form and as glucuronic acid conjugates. They were identified by comparing data obtained from analyses by high performance liquid chromatography, thin-layer chromatography, ultraviolet spectroscopy ...
Pre-alpha 2-elastase inhibitor of the horse: a hybrid molecule between alpha 1-proteinase inhibitor and alpha 2-beta 1-glycoprotein. Pre-alpha 2-elastase inhibitor of horse plasma has recently been isolated in our laboratory. In this article we demonstrate that the inhibitor is a composite structure built of alpha 1-proteinase inhibitor and alpha 1-beta 1-glycoprotein. The compound inhibitor is biologically active, although it has previously been shown that its enzyme specificity is different from that of free alpha 1-proteinase inhibitor. Our observations are based on immunochemical cross-reactions between pre-alpha 1-elastase inhibitor and antibodies to alpha 2-beta 1-glycoprotein as well as antibodies to alpha 1-proteina...
Protein requirements of mature working horses. Eighteen mature horses were used to study proteins requirements of working horses. Treatments included intense exercise, medium exercise and maintenance in a 3 X 3 factorial arrangement with three levels of calculated dietary crude protein (CP; 8.5, 7.0 and 5.5%). The horses were on the various exercise-protein treatments for 60 d, then fasted 4 d to evaluate their N status after the treatment period. Exercise had no significant effect on body weight over the feeding and fasting periods. No one exercise or protein treatment expressed the classical low plasma albumin or total protein concentrat...
Effects of dihydrotestosterone benzoate administration on gonadotropin secretion in ovariectomized pony mares. Eight long-term ovariectomized pony mares were treated with either dihydrotestosterone (DHT) benzoate (400 micrograms/kg body weight) in safflower oil or an equivalent amount of oil every other day for 21 d to determine the effects of DHT on follicle stimulating hormone (FSH) and luteinizing hormone (LH) concentrations in blood samples drawn once daily and after administration of three successive injections of gonadotropin releasing hormone (GnRH). The GnRH injections were given at 4-h intervals on the day following the last DHT or oil injection. Treatment with DHT benzoate did not alter (P gr...
Effects of a submaximal treadmill training programme on histochemical properties, enzyme activities and glycogen utilisation of skeletal muscle in the horse. The effects of training on skeletal muscle composition were studied in four Standardbred geldings given a seven week submaximal treadmill training programme. Before the start of training, muscle biopsies were collected from the left middle gluteal muscle for the determination of muscle fibre types, oxidative capacity and capillary numbers using histochemical techniques. The concentrations of citrate synthase, 3-hydroxyacyl-CoA dehydrogenase (HAD), lactate dehydrogenase and total muscle glycogen were measured using fluorometric methods. Muscle biopsy samples were repeated after one, three, five...
Functional and biochemical characterization of immunologically derived equine platelet-activating factor. Antigen-specific challenge of equine leukocytes induced the non-lytic release of a platelet-activating factor in vitro. The equine platelet-activating factor stimulated the release of serotonin from equine platelets in a dose-responsive manner, independent of the presence of cyclo-oxygenase pathway inhibitors such as indomethacin. Rabbit platelets were also responsive to equine platelet-activating factor. The release of equine platelet-activating factor was a rapid reaction with near maximal secretion taking place in 30 seconds. Addition of equine platelet-activating factor to washed equine pl...
Enhanced prostacyclin biosynthesis and decreased thromboxane formation by 3-dimethylamino 5-(2′,6′-dichlorobenzylidene) 6-methyl (4H)-pyridazine (PC 89). The effects of 3-dimethylamino 5-(2',6'-dichlorobenzylidene) 6-methyl (4H)-pyridazine (PC 89) on the biosynthesis of PG I2 and TX A2 using horse aorta and horse platelet microsomes as sources of enzymes and arachidonic acid as substrate, were investigated. PC 89 (1.10(-6) M- 1.10(-3) M) dose-dependently - enhanced the biosynthesis of PG I2: the AD50 was 6.8 X 10(-6) M +/- 1.2 X 10(-9) M, the Vmax did not vary significantly with concentrations: PC 89 increased the affinity of enzyme for substrate - but inhibited TX A2 biosynthesis (ID50 = 3.31 X 10(-3) M +/- 4.8 X 10(-7) M): this inhibiting act...
Measurement of the time between biosynthesis and surface excretion of sebaceous lipids in the horse. The time between the biosynthesis and excretion of sebum to the skin surface of the horse was examined by in vivo intradermal injection of [1-14C]acetate followed by periodic surface lipid collections. The radiolabelling of the major neutral lipid classes, equolides (giant ring omega-lactones, C32-C36) and cholesteryl esters, was evaluated by thin-layer chromatography and autoradiography. The distribution of radioactivity within the monounsaturated equolides was examined by oxidative fragmentation and evaluation of the products. A peak of radioactivity in the equolides and cholesteryl esters o...
Quantitative determination of betamethasone and its major metabolite in equine urine by micro-liquid chromatography-mass spectrometry. Micro-liquid chromatography-mass spectrometry (micro-LC-MS) was utilized to quantitatively determine betamethasone and its major unconjugated metabolite, 6 beta-hydroxybetamethasone, in equine plasma and urine. The advantage of micro-LC-MS over conventional gas chromatography-mass spectrometry in corticosteroid determination is illustrated and the reliable, steadfast nature of micro-LC-MS is demonstrated through example.
Mammalian ribonucleases. The absence of a glycosylated Asn-Pro-Thr sequence in horse ribonuclease and the presence of tryptophan at position 39 in horse and dromedary ribonuclease. Parts of the amino acid sequences of horse and dromedary pancreatic ribonuclease were reinvestigated. The sequence of residues 21-25 in horse ribonuclease is Ser-Asn-Pro-Thr-Tyr or Ser-Asn-Ser-Thr-Tyr. The asparagine in the latter sequence is glycosylated. Horse ribonuclease possesses four additional amino acid residues at the C-terminus, like a number of other ribonucleases. Position 39 in horse and dromedary ribonuclease is not deleted but is occupied by tryptophan.
Thyroid hormone binding in serum of 15 vertebrate species: isolation of thyroxine-binding globulin and prealbumin analogs. The binding of [125I]T4 to serum proteins was studied in human, monkey, cattle, sheep, goat, water buffalo, horse, swine, dog, cat, rabbit, rat, chicken, frog, and salmon. Attempts were made to isolate thyroxine-binding globulin (TBG) and thyroxine-binding prealbumin (TBPA) from serum of all species, utilizing purification methods based on the specific properties of these proteins. TBPA was found to exist in all species examined. The protein was found anodal to albumin only in human, monkey, horse, and chicken. In cattle, swine, dog, cat, rabbit, frog, and salmon, TBPA was found cathodal to al...
The amino-acid sequence of beta-lactoglobulin II from horse colostrum (Equus caballus, Perissodactyla): beta-lactoglobulins are retinol-binding proteins. beta-Lactoglobulin isolated from horse colostrum is heterogeneous and contains two components: beta-lactoglobulin I and beta-lactoglobulin II. These two proteins are monomeric and show differences in their electrophoretic mobilities, chain lengths and primary structures. The complete amino-acid sequence of beta-lactoglobulin II was determined by automated Edman degradation of the intact protein and of the peptides derived from these by digestion with trypsin or chymotrypsin and by chemical cleavage with cyanogen bromide. Unlike other beta-lactoglobulins which contain 162 amino acids, horse bet...
An investigation, in vitro, of the actions of three Western Australian snakes on the blood coagulation of the dog, cat, horse and wallaby. Venoms of the tiger snake and brown snake were procoagulant, in vitro, when tested with cat, dog, horse and wallaby plasma. In the absence of calcium and phospholipid the coagulant activity of tiger snake venom was minimal. In contrast, brown snake venom alone had marked procoagulant activity. This activity, however, was enhanced by the presence of calcium and phospholipid. Death adder venom exerted an anticoagulant effect. Apparent species' differences in susceptibility to the coagulant venoms were noted. However, the probable explanation of these differences was attributed to variation in th...
Effects of phenylbutazone and oxyphenbutazone on basic drug detection in high performance thin layer chromatographic systems. Interference or 'masking' in thin layer chromatography occurs when the presence of one drug on a thin layer plate physically obscures or interferes with the detection of another drug. We investigated the ability of phenylbutazone and oxyphenbutazone to mask or interfere with the detection by high performance thin layer chromatography (HPTLC) of basic drugs used illegally in horse racing. Of fifty-five basic drugs called 'positive' since 1981 by laboratories affiliated with the Association of Official Racing Chemists (AORC), forty did not comigrate with phenylbutazone or oxyphenbutazone and cou...
The sequence of equine muscle carbonic anhydrase. The sequence of equine muscle carbonic anhydrase (CA-III) has been determined. The 2 reactive cysteines of the 5 such residues have been localized. A strong sequence homology to other mammalian carbonic anhydrases exists, and 91% of the residues in the equine and bovine muscle forms are identical.
Unusual compound of small molecular weight in the serum of horses with acute grass sickness. An unusual compound of small molecular weight has been detected in serum from horses with acute grass sickness by solvent extractions and thin-layer chromatography. The substance has not been detected in the serum of normal horses or cases of equine colic and apparently disappears from grass sickness serum after two to three days of clinical illness. Although this compound is found in sera which are known to possess in vivo neurotoxicity, this property could not be demonstrated in either the total chloroform extract which contains the compound or in the hydrophilic serum components remaining a...
