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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.
Distribution of lactate in plasma and erythrocytes during and after exercise in horses. The distribution of lactate between red blood cells (RBC) and plasma was examined at rest, during exercise and 30 min after exercise in six Standardbred horses. Lactate and water concentrations were measured in blood and plasma samples collected prior to exercise, during the last 15 s of each step of an incremental exercise test and at 5 min intervals during the first 30 min after exercise. The mean ratio of RBC lactate concentration (RBCLa) to plasma lactate concentration (PLa) prior to exercise was 1.02 +/- 0.34. Haemoconcentration during exercise was associated with more rapid accumulation ...
Testosterone administration to mares: criteria for detection of testosterone abuse by analysis of metabolites in plasma and urine. A pharmacological dose of a long-acting testosterone ester, testosterone hexahydrobenzoate, was administered intramuscularly to two mares. The time course for some characteristic metabolites in blood and urine was then studied using an analytical method based on gas chromatography-mass spectrometry associated with stable isotope dilution. Among the plasma analytes, testosterone glucuronide was found to be the most adequate indicator for the monitoring of exogenous testosterone up to 2 weeks postadministration if a threshold value of 200 ng/L was applied. In urine, the simultaneous measurement ...
Regulatory function of the equine herpesvirus 1 ICP27 gene product. The UL3 protein of equine herpesvirus 1 (EHV-1) KyA strain is a homolog of the ICP27 alpha regulatory protein of herpes simplex virus type 1 (HSV-1) and the ORF 4 protein of varicella-zoster virus. To characterize the regulatory function of the UL3 gene product, a UL3 gene expression vector (pSVUL3) and a vector expressing a truncated version of the UL3 gene (pSVUL3P) were generated. These effector plasmids, in combination with an EHV-1 immediate-early (IE) gene expression vector (pSVIE) and chimeric EHV-1 promoter-chloramphenicol acetyltransferase (CAT) reporter constructs, were used in trans...
Interaction of beta-lactoglobulin with retinol and fatty acids and its role as a possible biological function for this protein: a review. beta-Lactoglobulin is the major whey protein in the milk of ruminants and some nonruminants, such as pigs and horses. Although beta-lactoglobulin was first isolated 60 yr ago, no function has been definitely ascribed to beta-lactoglobulin. Recent x-ray crystallographic studies have advanced knowledge of the structure of beta-lactoglobulin, which is homologous with that of retinol-binding protein and lipocalycins; the function of these proteins seems to be participation in the transport of small hydrophobic substances. By analogy, this protein has been suggested as having a role as a transporte...
Development of an ELISA using a universal method of enzyme-labelling drug-specific antibodies. Part I: Detection of dexamethasone in equine urine. The development, validation, and application of an ELISA for dexamethasone in equine urine is described. The drug-protein conjugate was immobilised in microtitre plate wells and antiserum raised against the same drug-protein conjugate was allowed to compete with sample or standard drug and the immobilised drug-protein conjugate. The proportion of antiserum binding to the immobilised drug-protein conjugate was detected using a biotinylated protein G/extravidin-alkaline phosphatase complex in situ and measurement of the substrate product. The method was used to detect the presence of drug-derive...
A novel Ca(2+)-dependent step in exocytosis subsequent to vesicle fusion. Exocytosis begins with formation of a small fusion pore which then expands allowing rapid release of granular contents. We studied the influence of cytoplasmic free Ca2+ ([Ca2+]i) on the conductance of the initial pore and on the dynamics of subsequent expansion in horse eosinophils using the patch clamp technique. The mean initial conductance is approximately 200 pS independent of [Ca2+]i. This value is close to that previously found in beige mouse mast cells. The pore subsequently expands by 18 nS/s at [Ca2+]i < 10 nM, by 40 nS/s at [Ca2+]i = 1.5 microM and by 90 nS/s at [Ca2+]i = 10 micr...
Substitutions of isoleucine residues at the adenine binding site activate horse liver alcohol dehydrogenase. The contributions of isoleucine residues 224 and 269 of horse liver alcohol dehydrogenase to binding of the adenine moiety of NAD and to catalysis were studied by replacing Ile-224 with glycine (I224G) and Ile-269 with serine (I269S). The kinetic mechanisms of wild-type and both mutated liver enzymes were ordered. Affinities for several adenosine derivatives were decreased 5-50-fold by both substitutions. The I269S mutation differentially destabilized binding of the complete coenzyme, as affinities for NAD+ and NADH were decreased about 60-fold with the I224G enzyme and 350-fold for the I269S ...
Permeation of small molecules into the cavity of ferritin as revealed by proton nuclear magnetic resonance relaxation. The NMR relaxation technique was used to investigate the permeation of molecules into the cavity of ferritin. Spin-lattice relaxation times in the rotating frame of various probe molecules were measured for solutions of recombinant horse L-apoferritin without iron and horse spleen apoferritin with very small amounts of ferric ions. The results show that molecules larger than the size of the ferritin channels can pass through the channels into the ferritin interior, and that the maximum size of molecules for the permeation is smaller than maltotriose.
Lipid metabolism in horses with hyperadrenocorticism. Lipid metabolism was studied in 21 horses with hyperadrenocorticism. To be included in the study, horses had to have histologic evidence of a pars intermedia adenoma found at necropsy (n = 9), a baseline ACTH concentration greater than 400 pg/ml (n = 6), or a plasma cortisol concentration 2 hours after i.v. administration of 25 IU of ACTH greater than 413 nmol/L (n = 16). Mean +/- SD baseline plasma cortisol concentration was 338 +/- 261 nmol/L (n = 20), mean +/- SD plasma insulin concentration was 97 +/- 54 microU/ml (n = 15), mean +/- SD plasma beta-hydroxybutyrate concentration was 1.8 +/- ...
Responsiveness of equine basilar artery to transmural nerve stimulation differs from that of porcine and bovine basilar arteries in vitro. Transmural nerve stimulation (TNS) induced relaxations in porcine and bovine basilar arteries which were abolished by tetrodotoxin (TTX) and by L-nitro-arginine (LNAG). However, TNS induced contractions in equine basilar artery which were abolished by TTX and by guanethidine, but not by LNAG. These results suggest that the TNS-induced contractions of equine basilar arteries may be mediated by norepinephrine release.
Proteoglycan metabolism of equine articular cartilage and its modulation by insulin-like growth factors. The effect of human recombinant insulin-like growth factor 1 (rhIGF-1) on proteoglycan (PG) metabolism of full thickness equine articular cartilage explants was investigated. PG synthesis was stimulated at all ages, but higher concentrations of rhIGF-1 were required for maximal stimulation of adult cartilage. There were no changes in the hydrodynamic size, electrophoretic heterogeneity or composition of proteoglycans isolated from rhIGF-1-stimulated cartilage. rhIGF-1 reduced the rate of turnover of both newly synthesized and endogenous proteoglycans in all ages of cartilage investigated. The ...
Pharmacokinetics of ketoprofen after multiple intravenous doses to mares. The pharmacokinetics and urinary excretion of ketoprofen in six healthy mares after the first and last of five daily intravenous doses of 2.2 mg of ketoprofen per kg body weight were investigated using a high-performance liquid chromatographic (HPLC) method for determining plasma and urinary ketoprofen concentrations. Plasma ketoprofen concentrations declined triexponentially after each dose with no significant differences in plasma concentrations or pharmacokinetic parameter values between the first and last doses. The harmonic mean of the terminal elimination half-life of ketoprofen after th...
Comparative views of electrophysiological parameters of large intestinal segments in pig, sheep, pony, guinea pig and rat. Short circuit current (ISC) and transepithelial conductance (gt) across sheets of epithelia were measured in the caecum, the proximal and the distal colon of pig, sheep, pony, rat and guinea pig. The electrical parameters underline the basic segmental and species differences. The diversity of ISC demonstrates the different nature of electrogenic transport mechanisms, and data clearly show the heterogeneity with respect to transport mechanisms along the large intestine in the various species. The great differences in amiloride sensitive ISC indicate the variabilities in the electrogenic Na tran...
Synthesis and processing of equine herpesvirus 1 glycoprotein D. Previous studies (C. C. Flowers and D. J. O'Callaghan, 1992, Virology 190, 307-315) employed peptide-specific antibodies to identify the product of the glycoprotein D (gD) gene of equine herpesvirus 1 strain Kentucky A (KyA). gD polypeptides of 55 and 58 kDa were detected in EHV-1-infected L-M cells, and the 58-kDa protein was observed in the membrane fraction of EHV-1 virions. In this report, the kinetics of synthesis and processing of gD polypeptides are described. One-hour pulse-labeling of EHV-1-infected L-M cells revealed that gD proteins are first detected at 6 hr after infection and tha...
Eicosanoid concentrations in digital venous blood from horses with chronic laminitis. The eicosanoids are a family of lipid-derived autocoids that are released in response to a variety of physical and hormonal stimuli. In this study, prostaglandin E2 (PGE2) and leukotriene B4 (LTB4) were measured in the digital veins of clinically normal horses and horses with chronic laminitis to determine whether these arachidonic acid metabolites have a role in mediating signs of hoof pain and lesions associated with chronic laminitis. Horses were evaluated at rest and after a brief exercise period, to determine whether eicosanoids are released into the circulation after mild concussion. Dig...
Enantioselective glucuronidation and subsequent biliary excretion of carprofen in horses. Carprofen (CPF) enantiomers and their glucuronide conjugates (GLUC) were measured in plasma and bile of horses after IV administration of the racemic compound (0.7 mg/kg of body weight). The CPF was detectable in plasma for up to 72 hours after dosing, whereas GLUC appeared early (time for maximal plasma concentration, 1 hour) and was measurable transiently at low concentration (maximal plasma concentration, 0.5 microgram/ml). The enantiospecific plasma profiles indicated a clear predominance of R-CPF, whereas the stereoselectivity of the glucuronides favored S-GLUC. At 1, 2, and 12 hours afte...
Local and remote matrix responses to chondrocyte-laden collagen scaffold implantation in extensive articular cartilage defects. Chondrocyte-laden collagen scaffolds were evaluated in extensive cartilage defects in an equine model. Arthroscopic techniques were used to implant a chondrocyte-collagen culture product in 15-mm defects in the lateral trochlear ridge of the femoropatellar joint of 12 horses. Ungrafted control defects were formed in the opposite joint. Groups of six horses were terminated at 4 and 8 months after implantation and the repair sites, adjacent cartilage, and remote cartilage within each femoropatellar joint examined biochemically. Eight months following surgery the relative proportions of type II c...
Accumulation of chromotrope 2R positive cells in equine endometrium during early pregnancy and expression of transforming growth factor-beta 2 (TGF-beta 2). Endometrial tissue from the gravid uterine horn of pregnant mares was examined by northern analysis and in situ hybridization for mRNA that hybridized to cDNA and RNA probes generated from a mouse TGF-beta 2 1.2 kb cDNA clone. The mouse cDNA probe hybridized to characteristic TGF-beta 2 mRNA transcripts on a northern blot of total RNA isolated from horse endometrium collected at day 45 of gestation. Two major 4.0 and 3.5 kb transcripts and possibly a minor 1.6 kb transcript were observed, consistent with specific hybridization to equine TGF-beta 2 mRNA. By in situ hybridization, riboprobes tra...
Catecholamine affects acetylcholine release in trachea: alpha 2-mediated inhibition and beta 2-mediated augmentation. We investigated the effects of catecholamines on acetylcholine (ACh) release from equine airway parasympathetic nerves. Trachealis strips were suspended in 2-ml tissue baths with Krebs-Henseleit solution containing atropine (10(-7) M), neostigmine (10(-6) M), and guanethidine (10(-5) M). Electrical field stimulation (20 V, 0.5 ms, 0.5 Hz, for 15 min) was applied, and ACh was measured by high-performance liquid chromatography with electrochemical detection. Epinephrine (Epi) and norepinephrine (NE) inhibited ACh release in a concentration-dependent manner. Inhibition was attenuated by the alpha...
In vitro 19-norandrogen synthesis by equine placenta requires the participation of aromatase. Explants of equine full-term placenta have been shown to synthesize 19-norandrogens from labelled androgens. Steroid metabolites were purified by silica-gel column chromatography then analysed and quantified by c18-reverse-phase HPLC coupled to a radioactive flow detector. 19-Norandrostenedione was subsequently recrystallized to constant specific activity, providing unequivocal evidence of its synthesis by the equine placenta. 19-Norandrostenedione synthesis appeared to be localized in the microsomal fraction. Regardless of the substrate used, formation of 19-norandrogens was far weaker than t...
Immunohistochemical localisation of steroidogenic enzymes and phenylethanolamine-N-methyl-transferase (PNMT) in the adrenal gland of the fetal and newborn foal. An increase in fetal adrenal cortisol output signals the onset of parturition in many animal species but, in the fetal horse, plasma concentrations of cortisol remain low for much of late pregnancy, with a rise occurring only very close to the time of birth (term 320-360 days). Immunohistochemistry was used to determine the localisation and changes in distribution of key steroidogenic enzymes for cortisol production; P450scc, P450C17 and 3 beta-hydroxysteroid dehydrogenase (3 beta HSD) in adrenal tissue from fetal and newborn horses and these findings were correlated with the appearance of imm...
The equine endometrial cup reaction: a review. The function of eCG in equine pregnancy is far from clear but it has become evident that eCG has little or no FSH activity in the horse and is therefore probably not responsible for the secondary ovulations. eCG does have luteotrophic activity and it could play a role in the resurgence of the primary corpus luteum (1,7,44). Some evidence exists that the receptor population on the equine gonads is heterogenous in a way that makes it possible to distinguish eCG from eLH, resulting in different post-receptor effects (7). There is also evidence that eCG itself is heterogenous, both in glycosylatio...
D-glucose transport and glycolytic enzyme activities in erythrocytes of dogs, pigs, cats, horses, cattle and sheep. The activities of D-glucose transport (D-GT) and the glycolytic enzymes hexokinase (HK) and pyruvate kinase (PK), were measured in the erythrocytes of dogs, pigs, cats, horses, cattle and sheep. The erythrocytes of dogs had the highest activities of D-GT, HK and PK, significantly higher than the activities in the erythrocytes of the herbivores. The activities of D-GT and HK in cat erythrocytes were significantly lower than in those of dogs. The differences between the activities of D-GT in the erythrocytes of the different species followed the differences in activities of HK but not those in t...
Regulation of granule size in human and horse eosinophils by number of fusion events among unit granules. 1. We have investigated the granule size distributions in human and horse eosinophils by time-resolved patch-clamp capacitance measurements. 2. During exocytosis of single granules the electrical capacitance of the plasma membrane increases in discrete steps. The steps in horse cells are about six times larger than those in human cells in accordance with the difference in granule size. 3. In both species a multimodal capacitance step size distribution is observed with a first peak at 6-7 fF corresponding to granules with a diameter of about 450-500 nm and a surface area of about 0.7 microns2, ...
The proximal ligand variant His93Tyr of horse heart myoglobin. The spectroscopic and structural properties of the His93Tyr variant of horse heart myoglobin have been studied to assess the effects of replacing the proximal His residue of this protein with a tyrosyl residue as occurs in catalases from various sources. The variant in the ferric form exhibits electronic spectra that are independent of pH between pH 7 and 10, and it exhibits changes in absorption maxima and intensity that are consistent with a five-coordinate heme iron center at the active site. The EPR spectrum of the variant is that of a high-spin, rhombic system similar to that reported for...
Changes in equine endometrial retinol-binding protein RNA during the estrous cycle and early pregnancy and with exogenous steroids. A cDNA library was constructed from poly(A) RNA obtained from Day 14 nonbred equine endometrium. A cDNA probe for porcine retinol-binding protein (RBP) was used to screen the library, and a complete cDNA sequence (1133 bp, excluding the poly(A) tail) was obtained. Endometrial biopsies were obtained from cycling, nonbred mares at Days 0, 1, 4, 8, 10, 11, 13, and 15 and from pregnant mares at Days 11, 13, 15, and 17 after ovulation (n = 2 mares each day). Endometrial biopsies were also taken from 18 noncycling anestrous mares after the following treatments: C (vehicle control for 1 day, n = 3), ...
Determination of carbonic anhydrase III isoenzyme concentration in sera of racehorses with exertional rhabdomyolysis. The concentration of carbonic anhydrase III isoenzyme (CA-III) in serum samples from 216 clinically normal Thoroughbreds was determined by use of an enzyme immunoassay. The concentration range of CA-III was from 16.0 to 254.5 ng/ml (mean, 56.5 +/- 11.9 ng/ml). Significant differences were not detected according to age or sex. To confirm whether serum CA-III concentration was high in horses with muscle disease, serum samples of 11 horses with exertional rhabdomyolysis were analyzed by enzyme immunoassay. Their serum CA-III concentration was about 56 times (3,136 +/- 2,610 ng/ml) that of healthy...
Validation of the shrinkage temperature of animal tissue for bioprosthetic heart valve application by differential scanning calorimetry. Shrinkage temperature is most often used to report the degree of cross-linking in glutaraldehyde-fixed animal tissue for use in bioprosthetic heart valve fabrication. Present practice utilizes the measurement of hydrothermal shrinkage observed when a sample is subjected to a temperature programme. This measurement at best gives a general indication of the efficiency of the treatment, i.e. the extent of cross-linking in the tissue. When differential scanning calorimetry has been used, the ambiguity arising from the scant reporting of the protocols used does not permit easy comparison of experim...
Characterisation of a membrane receptor on ruminants and equine platelets and peripheral blood leukocytes similar to the human integrin receptor glycoprotein IIb/IIIa (CD41/61). This paper describes two anti-glycoprotein IIb/IIIa or CD41/61 murine monoclonal antibodies (Co.35E4 and Co.2oA1). The cellular distribution and apparent molecular weight of the antigen detected by these antibodies is consistent with their reaction with ruminant and equine glycoprotein IIb/IIIa. Biochemical analysis of the equine molecule using sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) revealed bands of 24, 100 and 110 kDa under reducing conditions and 115 and 80 kDa under nonreducing conditions. Biochemical analysis of ruminant antigen revealed that the 24 kDa band...
