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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.
Erythrocyte aggregation tendency and cellular properties in horse, human, and rat: a comparative study. Horse blood has a higher tendency to form red blood cell (RBC) aggregates compared with human blood, with this enhanced aggregation previously attributed to differences in plasma factors. Our results confirm this observation and further indicate that washed horse RBC also have a significantly higher aggregation tendency in dextran 70 solutions (i.e., horse RBC have a higher "aggregability"). In contrast, the aggregation tendency of rat RBC, both in autologous plasma and in dextran 70, is significantly less compared with human and horse RBC. Other rheological findings for horse and rat RBC incl...
Effect of changes in respiratory blood parameters on equine red blood cell K-Cl cotransporter. K influx into equine red blood cells (RBCs) was measured using 86Rb as a tracer for K under conditions designed to mimic the changes in respiratory blood parameters that occur in vivo during strenuous exercise. The effects on K influx of physiological changes in pH, cell volume, O2 tension (PO2), CO2 tension (PCO2), and bicarbonate and lactate concentrations were defined. Physiological PO2 exerted a dominant controlling influence on the H(+)-stimulated Cl-dependent K influx, consistent with effects on the K-Cl cotransporter, PO2 required for half-maximal activity was 37 +/- 3 mmHg (4.9 kPa). A...
Total protein and immunoglobulin concentrations in equine tears. Lacrimal fluid represents a major ocular surface defensive mechanism providing different concentrations of all immunoglobulin classes. In this report, four classes of immunoglobulins (IgA, IgM, IgG and IgGT) have been measured in horse tears. As in others species, IgA is the main immunoglobulin responsible for local protection and constitutes quantitatively, 50% of all lacrimal proteins. The rest of immunoglobulins studied are normally present in equine tear fluid (though in lower concentration) and contribute to ocular surface immune protection. Female and adult horses showed significant high...
Purification and characterization of equine testicular cytochrome P-450 aromatase: comparison with the human enzyme. Cytochrome P-450 aromatase was purified by five chromatographic steps from adult stallion testis. It was first separated from NADPH-cytochrome P-450 reductase (reductase) on omega-aminohexyl-Sepharose 4B then purified to homogeneity on concanavalin A-Sepharose 4B, hydroxyapatite-Sepharose 4B, DEAE-Sepharose CL-6B and on a second hydroxyapatite-Sepharose 4B. On the other hand, purifications of the equine testicular and rat liver reductases, which allowed the reconstitution of aromatase activity in vitro, were achieved for each species in one chromatographic step on an adenosine 2',5'-diphosphat...
A sensitive electrophoretic method for the quantification of myosin heavy chain isoforms in horse skeletal muscle: histochemical and immunocytochemical verifications. In adult horses, three myosin heavy chain (MyHC) isoforms can be identified by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and immunohistochemistry using specific anti-MyHC monoclonal antibodies. This report studies the suitability of a consistent SDS-PAGE technique for quantifying MyHC profiles in homogenized cryostate sections of equine gluteus medius muscle biopsies (n = 18). The method used (previously described by R. J. Talmadge and R. R. Roy; J. Appl. Physiol. 1993, 75, 2337-2340) resolved MyHCs in three bands: I, IIB or IIX, and IIA from the fastest to the slowe...
Evidence that the alpha-subunit influences the specificity of receptor binding of the equine gonadotrophins. Horse LH/chorionic gonadotrophin (eLH/CG) exhibits, in addition to its normal LH activity, a high FSH activity in all other species tested. Donkey LH/CG (dkLH/CG) also exhibits FSH activity in other species, but about ten times less than the horse hormone. In order to understand the molecular basis of these dual gonadotrophic activities of eLH/CG and dkLH/CG better, we expressed, in COS-7 cells, hybrids between horse and donkey subunits, between horse or donkey alpha-subunit and human CG beta (hCG beta), and also between the porcine alpha-subunit and horse or donkey LH/CG beta. The resultant r...
Postnatal decline in gonadal secretion of dehydroepiandrosterone and 3 beta-hydroxyandrosta-5,7-dien-17-one in the newborn foal. Dehydroepiandrosterone (DHEA) and 3 beta-hydroxyandrosta-5,7-dien-17-one (7-dehydro-DHEA) are secreted in large quantities by the remarkably hypertrophied fetal gonads of both sexes in the pregnant mare. Their secretion serves as the fetal component of a feto-placental unit for oestrogen production in equine pregnancies. They are secreted in large amounts but show a decline in late pregnancy when the fetal gonads regress and levels of oestrogens in the mare fall as a consequence. We have examined the levels of these precursor steroids in the newborn foal in the first days after birth. DHEA and...
Isolation of Streptococcus equi subsp. equi from thoroughbred horses in a racehorse-breeding area of Japan. For determination whether strangles has invaded the Hidaka district of Hokkaido, the main racehorse-breeding area of Japan, a epizootiological survey with bacterial isolation was carried out during the breeding season in 1995. Streptococcus equi subsp. equi, which is the causative agent of strangles, was isolated from two Thoroughbred horses with submandibular lymphadenitis. Isolates were identified by serological grouping, biochemical tests and analysis of cell surface proteins by Western immunoblotting. Through this survey, it revealed that S. equi subsp. equi has invaded the Hidaka district...
Mechanism of capsaicin-induced relaxation in equine tracheal smooth muscle. The effects of capsaicin and neuropeptides were examined in equine tracheal smooth muscle (TSM). Neither capsaicin nor substance P (SP) contracted TSM. Capsaicin (100 microM) elicited relaxation in TSM contracted with methacholine. This relaxation was not mimicked by SP or calcitonin gene-related peptide (CGRP). Relaxation was not attenuated by removal of the epithelium or by pretreatment of tissue with meclofenamate or the nitric oxide (NO) synthase inhibitor NG-nitro-L-arginine. Previous exposure of TSM to capsaicin did not eliminate the relaxation responses to subsequent capsaicin. Although...
Effects of insulin and insulin-like growth factors I and II on the growth of equine fetal and neonatal chondrocytes. The effects of insulin and insulin-like growth factors (IGFs) I and II on fetal and foal chondrocytes were investigated in vitro. Chondrocytes from the lateral trochlear ridge of the distal femur were obtained from 2 fetuses (280 and 320 days gestation) and one 4-day-old foal and cultured. Membrane proteins consistent with type 1 and type 2 IGF receptors were demonstrated by radioligand cross linking and equilibrium binding analysis. It was demonstrated that both IGF-I and IGF-II acted as mitogens for isolated equine chondrocytes when present as the sole mitogenic factor in monolayer culture. ...
Stress response to chronic inflammation in the horse. Five clinically healthy Thoroughbred geldings were injected with Freund's adjuvant 3 times to induce a chronic inflammatory response. Blood was collected at various times before and after adjuvant administration. Clinical responses (rectal temperature and general demeanor) were also monitored. Adjuvant injection induced increases in rectal temperature and plasma fibrinogen concentration (maximum levels measured were mean +/- s.d. 39.7 +/- 0.5 degrees C and 8.2 +/- 0.3 g/l, respectively), indicative of an inflammatory response. A mild clinical depression was also observed in the horses for 24 h...
Differences between longitudinal and circular smooth muscle in beta-adrenergic control of motility of isolated equine ileum. To identify beta-adrenoceptor subtypes involved in motility inhibition of circular and longitudinal smooth muscle layers of equine ileum. Methods: Isolated strips of equine ileum circular smooth muscle and membrane preparations from circular and longitudinal muscle layers. Methods: Functional assays of circular muscle preparations and radioligand binding assays and measurements of cAMP production in smooth muscle membranes from circular and longitudinal layers. Results: Selective beta-adrenergic agonists exerted inhibitory effects on circular muscle preparations. Binding studies of cell membra...
Skeletal muscle histology and biochemistry of an elite sprinter, the African cheetah. To establish a skeletal muscle profile for elite sprinters, we obtained muscle biopsy samples from the vastus lateralis, gastrocnemius and soleus of African cheetahs (Acinonyx jubatus). Muscle ultrastructure was characterized by the fiber type composition and mitochondrial volume density of each sample. Maximum enzyme activity, myoglobin content and mixed fiber metabolite content were used to assess the major biochemical pathways. The results demonstrate a preponderance of fast-twitch fibers in the locomotor muscles of cheetahs; 83% of the total number of fibers examined in the vastus laterali...
Quantitative comparison on the refinement of horse antivenom by salt fractionation and ion-exchange chromatography. A quantitative comparison was made on the fractionation of pepsin-digested horse antivenoms by ammonium sulfate (AS) fractional precipitation and ion-exchange chromatography on Q-Sepharose. In the precipitation process, pepsin digested horse anti-Naja kaouthia serum was precipitated by 30% saturated AS followed by 50% saturated AS. The recovery of antibody activity [as measured by an enzyme-linked immunosorbent assay (ELISA) against the cobra postsynaptic neurotoxin 3] from the 30-50% saturated AS precipitate was 53% with a 1.93-fold purification. For the chromatographic process, the behavior ...
Models in vivo of wound healing in the horse and the role of growth factors. Abstract Wound models attempt to simulate the natural healing processes in wounds. However, all models have significant limitations due to the complexity of the tissue repair process. Much can be learned from wound models in vitro by the use of cell culture techniques. The horse can provide a suitable naturally occurring model of chronic wound healing because it has many similarities to wound healing encountered in human medicine. The tissue architecture was investigated with regard to extracellular matrix and growth factor distribution during wound healing and growth factors were consisten...
Immunolocalization of 3 beta-hydroxysteroid dehydrogenase, cytochrome P450 17 alpha-hydroxylase/17,20-lyase and cytochrome P450 aromatase in the equine corpus luteum of dioestrus and early pregnancy. The onset of equine chorionic gonadotrophin (eCG) secretion in pregnant mares is associated with an increase in luteal androgen and oestrogen production. The luteal cell type(s) responsible for the increased production of androgens and oestrogens has not been identified in the equine corpus luteum. In this study, we examined the pattern of expression of 3 beta-hydroxysteroid dehydrogenase (3 beta-HSD), cytochrome P450 17 alpha-hydroxylase/17,20-lyase (P450(17 alpha)) and cytochrome P450 aromatase (P450arom) by immunohistochemistry in equine luteal tissue collected during dioestrus (days 7-10; ...
Matrix metalloproteinases 2 and 9 in equine synovial fluids. Matrix metalloproteinases (MMPs) may be important in the destruction of cartilage seen in equine osteoarthritis and may be detectable in synovial fluid. Synovial fluids were obtained from normal equine joints and from joints of horses with aseptic and septic joint diseases. The total MMP gelatinase enzyme activities were measured by gelatin zymography and image analysis of the gels. The bioactivity of gelatinase in synovial fluid was determined by a gelatin degradation ELISA. Potential MMP-2 & MMP-9 monomer enzyme activities were significantly elevated in both septic and aseptic joint dise...
Effects of intravenous administration of sodium hyaluronate on carpal joints in exercising horses after arthroscopic surgery and osteochondral fragmentation. To evaluate the effects of arthroscopic surgery, osteochondral fragmentation, and treatment with IV administered hyaluronate on histologic, histochemical, and biochemical measurements within the carpal joints of horses. Methods: 12 clinically normal horses, 2 to 7 years of age. Methods: Horses had an osteochondral fragment created at the distal aspect of the radiocarpal bone of 1 randomly chosen middle carpal joint to simulate osteochondral fragmentation. Horses were treated with 40 mg of hyaluronate or saline solution (placebo) intravenously once a week for 3 consecutive weeks (days 13, 20, a...
Measurement of total body water content in horses, using deuterium oxide dilution. To measure total body water (TBW) content in horses, using deuterium oxide (D2O) dilution. Methods: Six 8- to 10-year-old healthy untrained mixed-breed horses, weighing (mean +/-SD) 503.4 +/- 64.0 kg. Methods: After a 12-hour nonfeeding period, 6 horses were given D2O (0.14 g/kg of body weight) via nasogastric tube. Blood samples were collected from a preplaced indwelling jugular vein catheter prior to and 1 to 8, 10, 12, 14, and 24 hours after administration of D2O. Blood samples were centrifuged immediately, and plasma was collected and stored at -70 C until analysis. The D2O content in plas...
Characterisation of equine matrix metalloproteinase 2 and 9; and identification of the cellular sources of these enzymes in joints. The cellular production by resident articular cells and infiltrating inflammatory cells of the gelatinase matrix metalloproteinases (MMP) was investigated by tissue culture methods and analysis of cell supernatants by gelatin zymography. Peripheral blood neutrophils in short term culture produced MMP-9, as did peripheral blood monocytes in culture. Isolated articular chondrocytes in monolayer culture produced both MMP-2 and MMP-9, although articular cartilage maintained as explant culture produced MMP-2 alone. Synovial fibroblasts grown in monolayer culture produced MMP-2 alone, although synov...
Extraction and quantification of acrosin, beta-N-acetylglucosaminidase, and arylsulfatase-A from equine ejaculated spermatozoa. Acrosin, Arysulfatase A, and beta-N-acetylglucosaminidase are three key enzymes localized within the mammalian acrosome that play a pivotal role in the penetration of the oocyte. The objectives of this study were to compare two methods of enzyme extraction based on the activities of these enzymes from equine spermatozoa. Method A utilized a 0.5 M Tris-maleate buffer containing 0.1% Triton X-100 and Hyamine 2389. Method B used 0.05 M Tris-HCl, 0.05 M MgCl2 in 0.05 M Tris-maleate, followed by 0.05 M Tris-maleate containing 0.1% Triton X-100. Results indicated that acrosin was initially bound in ...
The effect of pulsatile gonadotropin-releasing hormone and estradiol administration on luteinizing hormone and follicle-stimulating hormone concentrations in pituitary stalk-sectioned ovariectomized pony mares. Hourly pulses of gonadotropin-releasing hormone (GnRH) or bi-daily injections of estradiol (E2) can increase luteinizing hormone (LH) secretion in ovariectomized, anestrous pony mares. However, the site (pituitary versus hypothalamus) of positive feedback of estradiol on gonadotropin secretion has not been described in mares. Thus, one of our objectives involved investigating the feedback of estradiol on the pituitary. The second objective consisted of determining if hourly pulses of GnRH could re-establish physiological LH and FSH concentrations after pituitary stalk-section (PSS), and the th...
Mechanisms of echinocytosis induced by Crotalus atrox venom. Transient echinocytosis has been reported in association with snake envenomation in humans and dogs. An in vitro model of echinocytosis induced by venom of crotalus atrox (western diamondback rattlesnake) was established to characterize erythrocyte morphologic changes and to investigate potential mechanisms of echinocytic transformation. Erythrocyte morphologic changes produced after the addition of venom to canine, feline, equine, and human blood were characterized by dose-dependent echinocytosis. Type III echinocytosis were consistently induced in vitro at a dose comparable to in vivo enveno...
Role of endothelium and nitric oxide in the in vitro response of equine colonic venous rings to vasoconstrictor agents. To determine in vitro contractile responses of equine colonic veins to various vasoconstrictor agents. Methods: Colonic veins collected from 8 adult horses. Methods: Veins were cut into 4-mm-wide rings, placed in organ baths at 37 C, and attached to a force-transducer interfaced with a polygraph; 2 g of tension was applied, and rings were allowed to equilibrate for 45 minutes. Bath solution was replaced, and tension was reapplied at 15-minute intervals. Cumulative concentration responses (10(-8) to 10(-4) M) were determined for each agent, using separate rings (n = 8). Three vein groups were e...
Metabolic adaptation to fat-supplemented diet by the thoroughbred horse. Following 10 weeks of fat supplementation a group of aerobically trained thoroughbred horses exhibited a significant decrease in postprandial plasma triacylglycerol concentration. This decrease was associated with a mean 50% increase in plasma total lipase activity following pentosan polysulfate administration and an increase in postprandial plasma cholesterol concentration. A significant increase in the activity of muscle citrate synthase (EC 4.1.3.7), expressed as a ratio to the total fractional area occupied by type I and type IIa muscle fibres, was also observed. No significant change in t...
Vitamin A repletion in thoroughbred mares with retinyl palmitate or beta-carotene. Forty-five Thoroughbred mares used in an 8-mo depletion study were kept for an additional 20 mo on the same three forage diets (15 mares each): 2-yr-old orchardgrass hay and vitamin A-free concentrate on a drylot (HC); pasture, orchardgrass/alfalfa hay, and vitamin A-free concentrate (PHC); or pasture and orchardgrass/alfalfa hay only (PH). Each diet group was divided into three subgroups, and mares (n = 5) in each group were given either retinyl palmitate (A) at twice the NRC (1989) recommended daily intake, the equivalent amount of vitamin A in the form of water-dispersible beta-carotene (B)...
In vitro comparison of cytochrome P450-mediated metabolic activities in human, dog, cat, and horse. As domestic animals such as cat, horse, and dog increasingly become the clinical targets for drug discovery programs, the need to understand how these animals metabolize xenobiotics becomes more important. In the present study, substrates and inhibitors that were reported to be selective for particular P450 isozymes were used as probes to study in vitro metabolism in horse, dog, cat, and human liver microsomes. Seven selective catalytic activity markers for cytochrome P450-mediated reactions were measured: phenacetin O-deethylase (P4501A1/2), coumarin 7-hydroxylase (P4502A6), tolbutamide hydro...
IL-1 beta induces the degradation of equine articular cartilage by a mechanism that is not mediated by nitric oxide. Proteoglycan degradation was induced in young equine articular cartilage explants cultured for eight days in the presence of 50 ng/ml recombinant human interleukin-1 beta. Degradation was initiated after 6 hours of exposure to the cytokine. This was accompanied by an induction of nitric oxide synthesis and a decrease in the incorporation of [36S]sulphate into the glycosaminoglycan chains of proteoglycans. The addition of 1mM N-iminoethyl-L-ornithine (an inhibitor of nitric oxide synthase) to the explant cultures in the presence of rhIL-1 beta suppressed the synthesis of NO and restored proteog...
Isolation and characterization of a protein with homology to angiotensin converting enzyme from the periacrosomal plasma membrane of equine spermatozoa. The periacrosomal plasma membrane of spermatozoa is involved in sperm binding to oviductal epithelial cells and to the zona pellucida. A protein of 68-70 kD molecular mass was purified biochemically from the isolated periacrosomal plasma membrane of equine spermatozoa as a possible receptor for adhesion of spermatozoa to oviductal epithelial cells. A polyclonal antibody raised in rabbits against the purified equine sperm membrane protein recognized the 70 kD and an antigenically related to 32 kD protein in preparations of isolated periacrosomal sperm plasma membrane and in detergent extracted ...
