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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.
Effect of sodium bicarbonate administration on blood constituents of horses. To describe changes in blood constituents of horses after oral and i.v. administration of sodium bicarbonate (NaHCO3), and to determine whether the changes are dose dependent. Methods: 6 adult Standardbred mares. Methods: 3 oral doses (1,500, 1,000, and 250 mg/kg of body weight) or 1 intravenous dose (250 mg/kg, 5% solution) of NaHCO3 in 3 L of water, or water (3 L orally), were given to the mares; then changes in blood constituents were measured. Access to food and water was denied during the experiment. Blood samples were collected immediately before treatment and at hourly intervals for 12 ...
Effect of dietary vitamin E supplementation on the integrity of skeletal muscle in exercised horses. The effect of vitamin E intake on indicators of muscle integrity was studied in exercised horses. Nineteen horses were blocked by sex and then assigned to one of three diets: no supplemental vitamin E (BASAL), BASAL plus 80 IU of supplemental vitamin E/kg DM (80), or BASAL plus 300 IU of supplemental vitamin E/kg DM (300). The BASAL diet contained less than 44 IU of vitamin E/kg DM, but it was adequate in all other nutrients. During the 90-d treatment period, horses were exercised 5 d/wk; in addition, serum and middle gluteal muscle alpha-tocopherol concentrations were measured at 0, 30, and 9...
Effect of insulin-induced hypoglycaemia on secretion patterns and rates of corticotrophin-releasing hormone, arginine vasopressin and adrenocorticotrophin in horses. To study the effect of hypoglycaemia on secretion rates of corticotrophin-releasing hormone (CRH), arginine vasopressin (AVP) and ACTH in a non-ruminant species, a non-surgical method was used to collect pituitary venous (PitVen) blood every 0.5 or 1 min from seven horses before and after insulin administration (0.4 U/kg i.v.). To assess the effect of PitVen cannulation on results, peripheral hormones were also measured before and after insulin in five horses without PitVen cannulae. Insulin administration lowered plasma glucose in all horses (P < 0.0001; paired t-test). Cortisol concentrat...
Enzyme immunoassay for measuring 25-hydroxyvitamin D3 in serum. We developed a rapid, competitive enzyme immunoassay (EIA) for measuring 25-hydroxyvitamin D3 [25(OH)D3] in serum. The EIA was based upon 25(OH)D3-3-hemisuccinate covalently coupled to secondary amino groups grafted onto the polystyrene surface of microtiter wells. Optimal coupling conditions were established, and we found that inclusion of 40 mumol/L chloramine T, an agent not previously described for use in coupling to these plates, resulted in both more reproducible coupling as well as more than a twofold increase in the coupling efficiency. Before EIA, 25(OH)D3 was extracted from the serum...
Cloning, sequencing and in vitro functional expression of recombinant donkey follicle-stimulating hormone receptor: a new insight into the binding specificity of gonadotrophin receptors. Among all mammalian FSH receptors (FSH-R; including donkey (dk) FSH-R), only horse (hs) FSH-R does not bind hsLH/chorionic gonadotrophin (CG). In order to delineate the structural origin of hsFSH-R specificity precisely, we have cloned dkFSH-R cDNA from donkey testis mRNA by RT-PCR. Transiently expressed dkFSH-R endowed COS-7 cells with both hsLH/CG- and FSH-binding activity, as well as FSH-induced cAMP production. The deduced dkFSH-R amino acid sequence shares 96% identity with the hsFSH-R: notably, in the hormone-binding domain, the specificity of hsFSH-R may be ascribed to only four diverge...
Fetal calcium homeostasis. The mammalian fetus is maintained hypercalcaemic relative to its mother primarily by the action of a placental calcium pump located in the basal plasma membrane of the trophoblast. It is suggested that the activity of this pump is stimulated by a mid-molecular fragment of parathyroid hormone-related protein [PTHrP(38-94NH2)], produced in the placenta (and also in the parathyroid glands of fetal lambs and calves) as a result of post translational processing. In the sheep, calcitriol is an important determinant of fetal calcium homeostasis and it, too, stimulates the transport of calcium across ...
Structural characterisation and comparison of the native and A-states of equine lysozyme. Native state 1H NMR resonance assignments for 125 of the 129 residues of equine lysozyme have enabled measurement of the hydrogen exchange kinetics for over 60 backbone amide and three tryptophan indole hydrogen atoms in the native state. Native holo equine lysozyme hydrogen exchange protection factors are as large as 10(6), the most protected residues being located in elements of secondary structure. High exchange protection in the domain interface correlates with the binding of Ca2+ in this region. Equine lysozyme differs from most non-Ca2+ binding lysozymes in forming a highly populated par...
Characterization and mutational studies of equine infectious anemia virus dUTPase. The macrophage tropic lentivirus, equine infectious anemia virus (EIAV), encodes a dUTPase in the pol gene that is required for efficient replication in macrophages. Two naturally occurring variants of the enzyme were expressed as recombinant proteins in Escherichia coli; metal chelate affinity chromatography was used to purify histidine-tagged recombinant enzymes to greater than 80% homogeneity in a single chromatographic step. Biochemical and enzymatic analyses of these preparations suggest that this method yields dUTPase that is suitable for detailed mutational analysis. Specific activities...
Low-molecular-weight displacers for high-resolution protein separations. The resolving power of displacement chromatography using low-molecular-weight displacers was investigated using a model mixture containing bovine and horse heart cytochrome c. The linear and nonlinear adsorption behavior of these two proteins was examined in cation-exchange chromatography and shown to be quite similar. Furthermore, an analysis of the dynamic affinity of these proteins indicated extremely similar affinities under displacement conditions. Despite the extreme similarities in the adsorption behavior, displacement chromatography using a protected amino acid displacer resulted in ex...
Cortisol concentrations in post competition horse urine: a French and British survey. The purpose of the present report was to estimate the population parameters of cortisol concentrations in urine, an endogenous hormone used as a 'doping' agent and for which an international threshold (1.0 micrograms/ml) has been proposed. Two data bases (French and UK) corresponding to 112 and 142 samples, respectively were considered. Urine was collected under specific post competition conditions. Cortisol concentrations were obtained by validated methods (HPLC for the French samples, and GC-MS for UK samples). No difference was observed between the 2 data sets and statistical analyses were ...
A unique metabolite of nimesulide. Nimesulide is a nonsteroidal anti-inflammatory drug recently detected in equine blood and urine samples taken at the race track. The detection of the drug in a blood sample led to the identification of an unknown thin-layer chromatographic (TLC) spot in track urine samples as a metabolite of nimesulide. Characterization of the unknown TLC spot and comparison with the synthesized compound shows that the unknown TLC spot is a previously unreported equine metabolite of nimesulide. The metabolite was identified as resulting from the reduction of the nitro group on nimesulide to an amino group. Thi...
The relationship between the concentration of ionised calcium and parathyroid hormone-related protein (PTHrP[1-34]) in the milk of mares. Once lactation is established in mares, there is little change in the ionised calcium concentration in their milk. In contrast, the concentration of PTHrP(1-34) in the milk increases to a maximum level by the end of the second week of lactation, near which it remains for the rest of the lactation. As found in other species, the concentration of PTHrP(1-34) in mare's milk is considerably higher than that in plasma, sampled at the same time. No significant correlation could be demonstrated between the concentrations of PTHrP(1-34) and ionised calcium in the milk except during the last 10 weeks o...
Cloning of equine type II procollagen and the modulation of its expression in cultured equine articular chondrocytes. The complete nucleotide sequence of equine type II procollagen has not been previously reported, and equine-specific probes have not been available. We report the complete sequence and discuss the molecular characteristics of equine type II procollagen mRNA which was cloned from a cDNA library prepared from mRNA isolated from equine articular chondrocytes. The coding sequence (4257 bp) was 92.4% homologous to the cDNA of the human sequence, and the propeptide was 97% identical to the human sequence. We demonstrated that when equine chondrocytes are grown in phenotypically-maintained cultures, ...
Functional characterization of equine neutrophils in response to calcium ionophore A23187 and phorbol myristate acetate ex vivo. Equine neutrophils (PMN) play a critical role in inflammatory processes in horses. The objective of this study was to characterize equine PMN function ex vivo following stimulation with calcium ionophore A23187 (A23187) and phorbol myristate acetate (PMA). These stimulants trigger different branches of the PMN activation process that occurs in vivo. Equine PMN were isolated from the whole blood of six clinically normal geldings using a one-step discontinuous Percoll gradient technique. Neutrophil aggregation, degranulation, and superoxide anion production were evaluated in assay systems which ...
Purification and characterization of a hemolysin produced by Vibrio mimicus. Vibrio mimicus is a causative agent of human gastroenteritis. This pathogen secretes a pore-forming toxin, V. mimicus hemolysin (VMH), which causes hemolysis by three sequential steps: binding to an erythrocyte membrane, formation of a transmembrane pore, and disruption of the cell membrane. VMH with a molecular mass of 63 kDa was purified by ammonium sulfate precipitation and column chromatography with phenyl Sepharose HP and Superose 6 HR. The hemolytic reaction induced by VMH continued up to disruption of all erythrocytes in the assay system. Moreover, VMH that bound preliminarily to erythr...
The effects of ischemia and reperfusion on mucosal respiratory function, adenosine triphosphate, electrolyte, and water content in the ascending colon of ponies. The purpose of this study was to examine the effects of ischemia and reperfusion on the biochemical integrity of equine colonic mucosa to assess the relative roles of ischemic- and reperfusion-induced damage. Methods: Two hours of no-flow ischemia experimentally induced by 720 degrees counterclockwise ascending colon volvulus followed by 2 hours reperfusion after derotation. Methods: Ten ponies. Methods: Ascending colon biopsies were obtained every hour for measurement of mucosal adenosine triphosphate (ATP), water, sodium, and potassium content. Additional samples were homogenized for assay o...
The effect of strenuous versus moderate exercise on the metabolism of proteoglycans in articular cartilage from different weight-bearing regions of the equine third carpal bone. Articular cartilage degeneration in the middle carpal joint is a common problem in racing horses. This study evaluated the effect of exercise on the in-vitro synthesis of the large aggregating proteoglycans (aggrecan) and two small proteoglycans, biglycan and decorin, in articular cartilage taken from three weight bearing regions of the third carpal bone of horses which were subjected to moderate or strenuous exercise. Twelve Standardbred horses free from clinical and radiographic disease of the middle carpal joint were subjected to an 8 week moderate exercise program. The horses were then ran...
Role of endothelium and nitric oxide in the response of equine colonic arterial rings to vasoconstrictor agents. To determine the in vitro contractile responses of equine colonic arteries to angiotensin II, histamine, serotonin, norepinephrine, prostaglandin F2 alpha, vasopressin, and a thromboxane-B2-analogue. Methods: The tension generated in colonic arterial rings placed in organ baths with oxygenated Tyrode's solution at 37 degrees C after exposure to the previously mentioned chemical agents was measured using force-transducers interfaced with a polygraph. Methods: Large colon arterial rings collected from eight horses. Methods: The rings were allowed to equilibrate for 45 minutes after applying 2 g ...
Importance of sphingolipids and inhibitors of sphingolipid metabolism as components of animal diets. Sphingolipids are highly bioactive compounds that participate in the regulation of cell growth, differentiation, diverse cell functions, and apoptosis. They are present in both plant and animal foods in appreciable amounts, but little is known about their nutritional significance. Recent studies have shown that feeding sphingomyelin to female CF1 mice treated with a colon carcinogen (1,2-dimethylhydrazine) reduced the number of aberrant colonic crypt foci; longer-term feeding also affected the appearance of colonic adenocarcinomas. Therefore, dietary sphingolipids should be considered in studi...
Insulin-like growth factor 1 and corticosteroid modulation of chondrocyte metabolic and mitogenic activities in interleukin 1-conditioned equine cartilage. To evaluate potential stimulatory or matrix-sparing effects of insulin-like growth factor 1 (IGF-1), alone or in combination with a corticosteroid, in an interleukin 1 (IL-1)-induced model of cartilage degradation. Methods: Cartilage from the weightbearing surfaces of trochlea and condyles of clinically normal 2-year-old male horses. Methods: Triamcinolone acetonide and IGF-1 effects were evaluated by assessing: matrix responses by sulfated glycosaminoglycan (GAG) assay and [35S]sulfated GAG synthesis; collagen content by hydroxyproline assay; and mitogenic response by [3H]thymidine incorporat...
Distribution and functional effects of neuropeptide Y on equine ureteral smooth muscle and resistance arteries. The distribution of neuropeptide Y (NPY)-immunoreactive (IR) nerves, as well as the functional effects of NPY and the Y1- and Y2-receptor agonists, [Leu31,Pro34]NPY and NPY(13-36), respectively, have been investigated in vitro in both visceral and arterial smooth muscle of the horse intravesical ureter. NPY-IR nerve fibres were widely distributed along the entire length of the ureter, although the intravesical part was the most richly innervated region, and the only one where NPY-IR ganglion cells were found. NPY (10(-7) M) did not affect either basal tone or spontaneous rhythmic contractions ...
Isolation and characterization of heparin- and phosphorylcholine-binding proteins of boar and stallion seminal plasma. Primary structure of porcine pB1. In the bovine, seminal plasma heparin-binding proteins bind to sperm lipids containing the phosphorylcholine group and mediate the capacitating effects of heparin-like glycosaminoglycans during sperm residence in the female genital tract. We report the characterization of heparin- and phosphorylcholine-binding proteins of stallion and boar seminal plasma. Horse seminal plasma proteins HSP-1 and HSP-2, and boar protein pB1, belong to the same family as the bull heparin- and phosphorylcholine-binding proteins BSP-A1/2, BSP-A3, and BSP-30K. We have determined the amino acid sequence and posttrans...
Cloning, expression, purification, and characterization of the major core protein (p26) from equine infectious anemia virus. The gene coding for the major core protein (p26) of the lentivirus equine infectious anemia virus (EIAV) was cloned from EIAV infected serum, expressed in E. coli, and the resultant protein purified to electrophoretic homogeneity. The protein was expressed in a soluble form and was purified by conventional protein separation methods. When analyzed by SDS-PAGE, under both reducing and non-reducing conditions, the purified protein migrated as a 26 kDa monomer. Recombinant p26 (rp26), therefore, does not contain any intermolecular disulfide bond. Gel filtration chromatography also indicated that ...
In-vitro modulation of plasminogen activator activity, prostaglandin E and nitric oxide production by interleukin-1 in pregnant mare serum gonadotrophin-primed theca-interstitial cells. To examine the participation of the theca-interstitial (TI) compartment in cytokine modulation of ovarian function, the effects of interleukin-1beta (IL-1) on plasminogen activator (PA) activity and on prostaglandin E (PGE) and nitric oxide (NO) production were examined in cultures of pregnant mare serum gonadotrophin (PMSG)-primed rat TI cells. Exposure to IL-1 (10 ng/ml) resulted in a 25% reduction (P < 0.001) in PA activity, concurrent with a 4.6-fold increase in the ability of the corresponding conditioned media to inhibit exogenous urokinase activity. IL-1 also produced a 4.7-fold incr...
Biotransformation of chlorzoxazone by hepatic microsomes from humans and ten other mammalian species. The 6-hydroxylation of chlorzoxazone (CLZ) is currently being used in both in vivo and in vitro studies to quantify cytochrome P450 2E1 (CYP2E1) activity in humans. Comparatively little is known with regard to the biotransformation of this drug in other species. The NADPH-dependent biotransformation of CLZ was therefore studied using hepatic microsomes derived from humans and ten other mammalian species. In all species, 6-hydroxychlorzoxazone (6OH-CLZ) was the only metabolic product that could be identified by HPLC with ultraviolet detection. Enzyme kinetic analysis was used to characterize th...
Membrane contact with oviductal epithelium modulates the intracellular calcium concentration of equine spermatozoa in vitro. Interaction of equine spermatozoa with oviductal epithelial cells (OEC) prolongs sperm viability and maintains low intracellular calcium concentration ([Ca2+]i) in spermatozoa. Experiments were designed to investigate 1) whether release of spermatozoa from OEC in vitro is associated with elevated [Ca2+]i and 2) whether soluble products from OEC or direct membrane contact between spermatozoa and OEC mediates the effects of OEC on sperm [Ca2+]i. In the first experiment, changes in [Ca2+]i in spermatozoa loaded with indo-1 acetoxymethylester were determined in motile spermatozoa released from OEC...
Molten globule state of equine beta-lactoglobulin. The acid-unfolded state of equine beta-lactoglobulin was characterized by means of circular dichroism, nuclear magnetic resonance, analytical gel-filtration chromatography, and analytical centrifugation. The acid-unfolded state of equine beta-lactoglobulin has a substantial secondary structure as shown by the far-ultraviolet circular dichroism spectrum but lacks persistent tertiary packing of the side chains as indicated by the near-ultraviolet circular dichroism and nuclear magnetic resonance spectra. It is nearly as compact as the native conformation as shown by the gel filtration and sedime...
Prolactin, gonadotropin, and hair shedding responses to daily sulpiride administration in geldings in winter. This experiment was designed to determine 1) the efficacy of daily s.c. injections of a dopamine antagonist, sulpiride, for increasing prolactin secretion in geldings in winter and 2) whether increasing prolactin concentrations would hasten the onset of hair shedding or enhance gonadotropin secretion. Five geldings each received vehicle (vegetable oil) or sulpiride (100 mg in vehicle) daily from February 8 through March 29. On February 8 and every 7 d thereafter through March 29, blood samples were drawn around treatment injections and hair samples were collected. On March 30, all geldings rec...
