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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.
Modulation of equine tracheal smooth muscle contractility by epithelial-derived and cyclooxygenase metabolites. The role of epithelium in the modulation of contractile responses to electrical field stimulation (EFS), acetylcholine (ACh), and KCl were studied in vitro in strips of equine tracheal smooth muscle (TSM). EFS with 0.5 ms pulses of voltage (70 V) resulted in frequency dependent contractions of equine TSM that were sensitive to tetrodotoxin (TTX) and atropine. In TSM without epithelium, preincubation with indomethacin significantly potentiated contractile responses to EFS. The potentiating effect of indomethacin on EFS contractions was abolished by the addition of 3 nM prostaglandin E2 (PGE2). ...
Concentrations of arachidonate metabolites, steroids and histamine in preovulatory horse follicles after administration of human chorionic gonadotrophin and the effect of intrafollicular injection of indomethacin. This study investigated the sequence of hormonal changes within the preovulatory follicles of mares. Mares were injected i.v. with 2500 IU human chorionic gonadotrophin (hCG) when a preovulatory follicle of 35 mm in diameter was detected. Fluid was aspirated from preovulatory follicles before (0 h), and 12, 24 and 36 h after administration of hCG. Concentrations of progesterone, prostaglandin (PG) E2, PGF, 6-keto-PGF1 alpha and thromboxane B2 in follicular fluid increased significantly (P less than 0.01) between 0 and 36 h. At 36 h, PGE2 was present in highest concentrations, followed by PGF a...
1H NMR resonance assignments in a paramagnetic heme protein by two-dimensional spectroscopy: heme resonances in equine met-azido myoglobin. Specific heme protons for the majority of resonances in the downfield resolved region of equine met-azido myoglobin have been assigned using solely the two-dimensional 1H NMR experiments NOESY and COSY. Metazido myoglobin provides a useful test case for the applicability of these techniques to paramagnetic proteins for the following reasons. First met-azido myoglobin is a mixed spin-state protein, with significantly shorter relaxation times and broadened lines relative to pure low-spin systems (eg., met-cyano myoglobin). Second, met-azido hemoglobin and met-azido myoglobin are important as mod...
Contribution of delta bilirubin to the interpretation of hyperbilirubinemia in the horse – a pilot study. A study was conducted to examine the relationship of delta bilirubin to traditional bilirubin fractions to determine if delta bilirubin might assist in differentiating causes of hyperbilirubinemia in the horse. A recently introduced thin-film method was used for delta bilirubin determination. Thin-film and the traditional diazo methods were used for determining total, unconjugated, and conjugated bilirubin fractions. Sera from 38 healthy and 85 sick horses were examined.Thin-film serum delta bilirubin determination does not appear to assist in differentiating causes of unconjugated hyperbiliru...
Maternal and umbilical venous plasma lipid concentrations at delivery in the mare. The concentrations and fatty acid composition of the plasma free fatty acid, triacylglycerol and phospholipid fractions were determined in maternal and umbilical cord vein blood samples taken at delivery from 17 mares. Maternal and umbilical vein plasma free fatty acid concentrations were of a similar order and a positive correlation was found between the two levels suggesting that the equine placenta is permeable to fatty acid. Substantial amounts of the essential fatty acids and their longer chain derivatives were seen in both umbilical vein plasma free fatty acid and phospholipid fractions ...
Immunohistolocalization of the carbonic anhydrase isozymes I, II and III in equine salivary glands. The immunolocalization of carbonic anhydrase isozymes in equine salivary glands was investigated for assessment of their biologic functions. In parotid glands, duct segments showed reactivity with CA-I and CA-III. CA-III was selectively located in duct segments, particularly in the basal cells of the interlobular duct. Serous acinar cells were positive for CA-I and CA-II. In submandibular glands, CA-I and CA-II were present in serous demilune and duct segments. CA-II was selectively located in the duct segments, as also noted in the parotid gland. In sublingual glands, CA-I and CA-II were loca...
A combination histochemical stain for equine muscle. The purpose of this study was to find a combination histochemical staining technique for the evaluation of equine skeletal muscle that is reliable and effective, while offering a substantial reduction in the labor and cost involved with currently used individual histochemical methods. Several combinations under varying conditions of pH were studied. The most uniform results were obtained using an acid preincubation step at an optimal pH of 4.2 followed by reduced nicotinamide adenine dinucleotide-tetrazolium reductase (NADH-TR) and the remainder of the acid-ATPase procedure.
Proliferation of chick embryo neuroblasts grown in the presence of horse serum requires exogenous transferrin. We have previously shown that neuroblasts from cerebral hemispheres of 6-day-old chick embryos are able to proliferate when grown in the presence of fetal calf serum. We report here that in the presence of horse serum alone the proliferative rate of neuroblasts is strongly reduced. A high proliferative rate is restored upon the addition of bovine transferrin and to a lesser extent with added FeSO4 or hemin. These findings suggest that the transferrin of horse serum cannot be used by chick neuroblasts in vitro, while bovine transferrin exogenously added is active in promoting cell proliferation...
Assessment of histamine, bradykinin, prostaglandins E1 and E2 and carrageenin as vascular permeability agents in the horse. The vascular leakage induced by histamine, bradykinin, serotonin and prostaglandin E1 and E2 was assessed. The test agents were injected intradermally into the shaved thoracic skin of horses and the vascular leakage estimated either semi-quantitatively by recording the diameter of the lesions or by measuring the actual volume of extravasated plasma in microliters using iodine-125-labelled human serum albumin (125I-HSA) as a marker in the blood plasma. Using the latter method, the vascular leakage induced by carrageenin and the effect of coadministered prostaglandins E1 and E2 upon the vascular...
Pharmacodynamics and pharmacokinetics of miloxicam in the horse. The novel non-steroidal anti-inflammatory drug (NSAID) miloxicam was administered intravenously to six New Forest ponies at a dosage rate of 0.6 mg/kg in a two-part cross-over study. In each part, three horses received miloxicam and three were given a placebo preparation. The actions of miloxicam, compared to placebo, were assessed in a carrageenan-sponge model of acute inflammation. The rise in skin temperature over the site of the acute inflammatory reaction was less in treated ponies, but differences were not statistically significant. Concentrations of the enzymes acid phosphatase (AP) and...
The development of a gas chromatographic/mass spectrometric screening procedure to detect the administration of anabolic steroids to the horse. A screening procedure for anabolic steroid residues in horse urine has been developed based upon solid-phase extraction and gas chromatographic/mass spectrometric analysis in the selected ion mode. For moderate sample throughput the method provides a viable alternative to radioimmunoassay screening and has advantages over the latter technique due to its flexibility, specificity and ability to detect a number of steroids in a single analysis. Full automation of the gas chromatographic/mass spectrometric analysis is an additional feature of the methodology.
Comparative properties of three functionally different but structurally related serpin variants from horse plasma. Three structurally related but functionally different serpins from horse plasma were isolated and characterized. In spite of their identical N-terminal sequences, which show some similarity to that of human alpha 1-proteinase inhibitor, the reactive-centre loops of each of these proteins show extensive variation. Only inhibitor I, with a P1 methionine residue, resembles human alpha 1-PI with regard to (a) similarity of amino acid sequence in the vicinity of the reactive-site peptide bond, (b) broad inhibitory specificity, (c) sensitivity to oxidative inactivation and (d) high rate of reactivit...
Characterization and mapping of melatonin receptors in the brain of three mammalian species: rabbit, horse and sheep. A comparative in vitro binding study. Melatonin receptors were characterized in the brains of three mammals (rabbit, horse and sheep) by an in vitro binding technique, using 2-[125I]iodomelatonin as labelled ligand. Although binding sites for melatonin have been described recently in several vertebrate species (including the sheep), the rabbit and the horse have not been the subject of investigation so far. Apart from characterization, the present report describes receptor distribution in a number of brain regions, thus allowing for direct interspecies comparison under the same methodological conditions. 2-[125I]iodomelatonin labe...
1H and 119Sn magnetic resonance study of the SnIV protoporphyrin IX complex of equine myoglobin. Structure of the porphyrin-binding pocket. Tin protoporphyrin IX (SnPP) is being used in the treatment of hyperbilirubinemia. We have studied the SnPP complex with equine myoglobin (EqMb) by 1H and 119Sn nuclear magnetic resonance spectroscopy (NMR) as a general model for SnPP interaction with hemoproteins. The complex formed from SnPP and EqMb, SnPP.EqMb, was found to have essentially the same porphyrin-binding pocket as EqMbCO, including the same porphyrin orientation in the major form of EqMbCO. 119Sn NMR spectroscopy has been used to demonstrate that the proximal His93F8-metal coordination is likely to be intact in SnPP.EqMb. Minor...
Heart rate, blood biochemistry and performance of horses competing in a 100 km endurance ride. To determine whether a clinical examination was adequate to assess the fitness of horses in an endurance ride, and to characterise the relationship between a clinical assessment of the horse's fitness and its blood biochemistry, 23 horses were monitored before, during and after an 87 to 100 km endurance ride. Blood samples were taken before the ride, at three checkpoints on the ride, immediately after the ride and one day later for the determination of packed cell volume, total protein, lactate, glucose, non-esterified fatty acids, creatine phosphokinase, aspartate aminotransferase and plasma ...
Colonic adenocarcinoma with osseous metaplasia in a horse. Rectal palpation of a 30-year-old mixed-breed mare with chronic weight loss and intermittent, refractory abdominal pain revealed a mass in the right caudoventral portion of the abdomen. Hematologic and serum biochemical findings were normal except for slight mature neutrophilia and mildly high alkaline phosphatase activity and total bilirubin concentration. Cytologic examination of a specimen obtained by abdominocentesis revealed equal numbers of nondegenerative neutrophils and macrophages, but no evidence of neoplastic cells. The mare continued to have signs of abdominal discomfort and was eu...
Analysis of equine humoral immune responses to the transmembrane envelope glycoprotein (gp45) of equine infectious anemia virus. Defined segments of the transmembrane envelope glycoprotein (gp45) of equine infectious anemia virus were expressed as TrpLE fusion proteins and examined for their reactivity in Western immunoblots against a diverse panel of equine immune sera. The most immunogenic region of gp45 was localized to its amino terminus, positioned between the hydrophobic fusion and the transmembrane domains. A series of overlapping synthetic peptides were used in enzyme-linked immunosorbent assays to define an immunodominant epitope within this region. In contrast, the carboxy-terminal half of gp45 displayed both ...
Effects of hydroxyflutamide on rats treated with a superovulatory dose of pregnant mare serum gonadotropin. Immature female rats treated with superovulatory doses of pregnant mare serum gonadotropin (PMSG) were used to study the effects of the antiandrogen hydroxyflutamide on steroid production, particularly the biologically active androgens, in two experiments. In the first experiment, animals were given either 5 mg hydroxyflutamide or vehicle alone at 30 and 36 h following 40 IU PMSG. Compared with the vehicle group, hydroxyflutamide treatment significantly reduced the percentage of degenerate oocytes recovered from oviducts (p less than 0.05). Serum levels of testosterone and androstenedione, and...
Effects of conjugated equine estrogen with and without three different progestogens on lipoproteins, high-density lipoprotein subfractions, and apolipoprotein A-I. The effects of conjugated equine estrogen and subsequent cyclical progestogen supplementation on lipoprotein and apolipoprotein A-I levels were investigated in three groups of postmenopausal women. Unopposed conjugated equine estrogen (0.625 mg) lowered total cholesterol 4-8% and low-density lipoprotein (LDL) cholesterol 12-19% below pre-treatment levels in all three groups. Levels of high-density lipoprotein (HDL) cholesterol and apolipoprotein A-I were increased 9-13 and 9-18%, respectively, with unopposed estrogen. The increase in HDL cholesterol was mainly due to increases in the high-dens...
Steroidogenesis by equine preovulatory follicles: relative roles of theca interna and granulosa cells. Estrous cycles in mares have several unique characteristics, including the presence of a long period of estrus and the absence of a typical LH surge. Like follicles of other species, equine preovulatory follicles are characterized by their ability to secrete large amounts of 17 beta-estradiol, but it is not clear which follicular cell type is responsible for estradiol synthesis in mares. To better understand the relative roles of theca interna and granulosa cells in follicular steroidogenesis, presumptive ovulatory follicles were obtained from mares during early estrus (first or second day of ...
Distribution of filipin-sterol complexes in the plasma membrane of stallion spermatozoa during the epididymal maturation process. The presence and distribution of cholesterol in mature and immature epididymal spermatozoa was analyzed using filipin as a cytochemical tool in freeze-fracture replicas and thin section preparations. The polyenic-antibiotic filipin formed complexes with 3, beta -OH sterols, producing characteristic protrusions, or pits, that were heterogeneously distributed in the plasma membrane of stallion spermatozoa, revealing a specific organization in a functionally specialized area of the gamete. The acrosomal region of the sperm head presented a significantly higher density of filipin sterol complexes ...
Evaluation of progesterone deficiency as a cause of fetal death in mares with experimentally induced endotoxemia. The role of decreased luteal activity in embryonic loss after induced endotoxemia was studied in mares 21 to 35 days pregnant. Fourteen pregnant mares were treated daily with 44 mg of altrenogest to compensate for the loss of endogenous progesterone secretion caused by prostaglandin F2 alpha (PGF2 alpha) synthesis and release following intravenous administration of Salmonella typhimurium endotoxin. Altrenogest was administered daily from the day of endotoxin injection until day 40 of gestation (group 1; n = 7), until day 70 (group 2; n = 5), or until day 50 (group 3; n = 2). In all mares, secr...
Equine chorionic gonadotropin. Cells from the chorionic girdle of the equine trophoblast invade the maternal endometrium at day 36 of gestation and become established as secretory elements known as the endometrial cups. These structures, which persist for 40-60 days, produce a gonadotropin which can be found in circulation until about day 130 of gestation. This glycoprotein has been identified in the horse and the donkey, with the former having received much better characterization. It consists of 2 noncovalently linked peptide chains; an alpha-subunit of 96 amino acids, which is common to that found in other horse glycopro...
Steroid 21-hydroxylase activity in equine ovarian follicles evidenced by isotope dilution-mass spectrometry. Steroid 21-hydroxylase activity of the microsome-enriched fraction of follicular linings from equine ovaries has been demonstrated by gas chromatography-mass spectrometry. The 21-hydroxylated metabolites were quantified by isotope dilution with deuterated analogues. The two most abundant potential substrates for follicular steroid 21-hydroxylase, progesterone (P) and 17-hydroxyprogesterone (17OHP), were converted respectively to 11-deoxycorticosterone (DOC) and 11-deoxycortisol with corresponding apparent specific activities of 308 and 24 pmol/mg protein/h and apparent Km values of 1.1 and 6.4...
Effect of aspiration of the preovulatory follicle on luteinization, corpus luteum function, and peripheral plasma gonadotropin concentrations in the mare. Follicular fluid from small- to medium-sized follicles has been shown to have an inhibiting effect on luteinization of granulosa cells in vitro. This study was conducted to investigate the effect of in vivo removal of follicular fluid on luteinization, peripheral gonadotropin concentrations, and ovulation of secondary follicles in the mare. Follicular fluid was aspirated from the preovulatory follicles of mares when the diameter of the follicle was 30-34 mm (Group A), 35-39 mm (Group B), or 40-44 mm (Group C). Mares in Group D served as controls and the preovulatory follicle was not aspirated....
Different combinations of regulatory elements may explain why placenta-specific expression of the glycoprotein hormone alpha-subunit gene occurs only in primates and horses. Expression of the glycoprotein hormone alpha-subunit gene occurs in the pituitary of all mammals but in placenta of only primates and horses. In humans, two different elements, termed upstream regulatory element (URE) and cAMP response element (CRE), are required for placenta-specific expression of the alpha-subunit gene. The URE binds a protein unique to placenta whereas the CRE binds a ubiquitous protein. Comparative analysis of the promoter-regulatory region of the alpha-subunit gene from a number of mammals indicates that a functional URE has been retained and suggests the potential for pl...
Biochemical study of repair of induced osteochondral defects of the distal portion of the radial carpal bone in horses by use of periosteal autografts. Periosteal autografts were used for repair of large osteochondral defects in 10 horses aged 2 to 3 years old. In each horse, osteochondral defects measuring 1.0 x 1.0 cm2 were induced bilaterally on the distal articular surface of each radial carpal bone. Control and experimental defects were drilled. Periosteum was harvested from the proximal portion of the tibia and was glued into the principal defects, using a fibrin adhesive. Control defects were glued, but were not grafted. Sixteen weeks after the grafting procedure, the quality of the repair tissue of control and grafted defects was asse...
Serum bile acid composition of the dog, cow, horse and human. The fractionation of serum bile acids was performed in the dog, cow, horse, and human by high performance liquid chromatography equipped with an immobilized 3 alpha-hydroxysteroid dehydrogenase (3 alpha-HSD) column. There were significant differences in the bile acid compositions, conjugation patterns and quantities of each bile acid among these animals. Cholic acid was the major primary bile acid in the dog and cow, which constituted 62.9% and 83.5%, respectively, whereas chenodeoxycholic acid was the major acid in the horse and human, which constituted 68.4% and 46.3%, respectively. Taurine ...
[The effects of crude drugs using diuretic on horse kidney (Na+ + K+)-adenosine triphosphatase]. In the folk-medicine, several kinds of crude drugs are used as diuretics. Twenty three kinds of diuretic drugs were chosen, and examined for their effects on the horse kidney (Na+ + K+)-adenosine triphosphatase (ATPase), which is an intrinsic enzyme of the plasma membrane and responsible for the active transport of Na+ and K+ across the membrane. Twenty one out of twenty three kinds of ethanol extracts of diuretic drugs inhibited the kidney (Na+ + K+)-ATPase activity. The intensity of the inhibition of these drugs was compared by estimating the amounts of their ethanol extracts which inhibited...
