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Topic:Hemoglobin
Hemoglobin is an iron-containing protein found in the red blood cells of horses, responsible for the transport of oxygen from the lungs to the tissues and the return of carbon dioxide from the tissues to the lungs. It plays a vital role in maintaining cellular respiration and energy metabolism. The structure and function of hemoglobin can be influenced by various factors, including genetics, age, and health status. Research into equine hemoglobin includes studies on its biochemical properties, the impact of different physiological and pathological conditions on its levels, and its importance in performance and endurance. This page compiles peer-reviewed research studies and scholarly articles that explore the characteristics, regulation, and clinical implications of hemoglobin in equine physiology and health.
Acid-base and electrolyte effects of shortening steeplechase in a three-day-event. This study was designed to characterise the acid-base and electrolyte effects of shortening the distance required during steeplechase (Phase B) in the face of hot and humid weather conditions during a treadmill-simulated Speed and Endurance test. Eight conditioned Thoroughbred horses underwent 3 randomised permutations of a standardised exercise test on a high speed treadmill. Each test consisted of trotting at 3.7 m/s for 10 min (Phase A); galloping at 11 m/s (Phase B) for 4 (cool laboratory conditions), 3 (hot and humid), or 2 (hot and humid) min; trotting at 3.7 m/s for 30 min (Phase C); an...
The effects of oxygenation upon the Cl-dependent K flux pathway in equine red cells. The effects of oxygen tension (PO2) upon the K influx pathways of equine red cells have been studied using 86Rb+ as congener for K. Equilibration of cells in 100% nitrogen led to a low and Cl-independent K flux. Change to an atmosphere of 100% air led to a rapid sixfold increase in K flux. The oxygen-activated flux was entirely Cl dependent and was maintained for up to 3 h. Oxygenation-evoked activation was dependent upon PO2 over the physiological range with little effect up to 70% saturation of haemoglobin with oxygen but significant effects between 70 and 100%. K flux at low PO2 was unaffec...
Oxygen affinity and Bohr effect responses to 2,3-diphosphoglycerate in equine and human blood. The dependence of blood oxygen affinity and the Bohr effect on the concentration of 2,3-diphosphoglycerate (DPG) in erythrocytes was investigated in 24 trotter horses and 24 healthy men. The oxygen tension at half saturation and standard conditions (P50st at pH 7.4, PCO2(40) mmHg and 37 degrees C) and the carbon dioxide or fixed-acid-induced Bohr effect (dlogP50/dpH) were determined. Samples of fresh blood and blood depleted of or enriched with DPG were studied. In the absence of measurable DPG, the equine and human blood had similar mean (SD) values of P50st (16.6 [0.6] and 16.2 [0.7] mmHg, r...
Effect of training on diverse hematologic parameters in Andalusian horses. A study has been made of the variations experienced by the hemogram and blood volume indices in 16 Andalusian horses after carrying out an exercise test of increasing intensity consisting of 3 sequences of 1000 m each, before and after being subjected to a daily exercise programme for two months. Samples were taken by external jugular vein puncture: while at rest, within the first minute of finalizing each exercise stage and at 10 and 15 minutes of recovery. Both the red blood cells and the hematocrit value showed a significant decrease in their mean values after two months training; conversel...
Involvement of nitric oxide in the non-adrenergic non-cholinergic neurotransmission of horse deep penile arteries: role of charybdotoxin-sensitive K(+)-channels. 1. The involvement of nitric oxide (NO) and the signal transduction mechanisms mediating neurogenic relaxations were investigated in deep intracavernous penile arteries with an internal lumen diameter of 600-900 microns, isolated from the corpus cavernosum of young horses. 2. The presence of nitric oxide synthase (NOS)-positive nerves was examined in cross and longitudinal sections of isolated penile arteries processed for NADPH-diaphorase (NADPH-d) histochemistry. NADPH-d-positive nerve fibres were observed in the adventitia-media junction of deep penile arteries and in relation to the trabec...
Near infrared spectroscopy of pedal haemodynamics and oxygenation in normal and laminitic horses. The present study applies near infrared spectroscopy (NIRS) to the haemodynamics of the pedal circulation in normal and laminitic horses. NIRS is a noninvasive technique which uses changes in light absorption at 4 wavelengths to provide information on the changes in cytochrome aa3 (cyt aa3) reduction-oxidation (redox) status, and changes in the tissue concentration of oxyhaemoglobin (O2Hb), deoxyhaemoglobin (HHb) and therefore total haemoglobin (tHb). Other studies have shown NIRS to be sensitive to changes in tissue oxygenation and perfusion in human cerebral and limb circulation. In this stu...
Comparison of the effects of low-molecular-weight and unfractioned heparin in horses. Thirty healthy male horses were allotted to 3 groups and treated blindly during 4 days. Group-1 horses received unfractioned calcium heparin (100 IU/kg of body weight, SC, q 12 h). Group-2 horses received a single dose of a low-molecular-weight heparin (50 anti-Xa IU/kg, SC) every morning, and a similar volume of saline solution every evening. Group-3 horses received the vehicle (saline solution), SC, every 12 hours. Citrated and EDTA-anticoagulated blood samples were collected before starting the medication (T-0) and once daily 3 hours after each morning injection (T-3, T-27, T-51, and T-75)....
Digital Starling forces and hemodynamics during early laminitis induced by an aqueous extract of black walnut (Juglans nigra) in horses. Starling forces and hemodynamics in the digits of 5 horses were studied during early laminitis induced by oral administration of an aqueous extract of black walnut (Juglans nigra). The black walnut extract was prepared from heartwood shavings and was administered by nasogastric tube. Heart and respiratory rates, rectal temperature, central venous and arterial pressures, digital pulses, and signs of lameness were monitored. Blood samples were collected for determination of WBC count, hemoglobin concentration, and PCV and for endotoxin and tumor necrosis factor assays. Total WBC count and centra...
Sympathoadrenal and other endocrine and metabolic responses to hypoglycaemia in the fetal foal during late gestation. In the present study, ten insulin challenge tests were carried out on nine chronically catheterized fetal foals between 253 and 314 days gestation (term > 320 days). Changes in fetal plasma concentrations of glucose, catecholamines, cortisol, ACTH, free fatty acid (FFA) and lactate were measured before and after a bolus dose of insulin (0.5-2.0 u/kg I.V.). Fetal blood gases, pH, haemoglobin levels and heart rate were measured throughout the 2-3h experimental period. The fetuses fell into two distinct groups on the basis of proximity to delivery and basal plasma cortisol and catecholamine level...
Acid-base variables during incremental exercise in sprint-trained horses fed a high-fat diet. Seven Arabian horses performed a standard incremental exercise test on a high-speed treadmill at 6% slope then were randomly assigned to two diets, a control diet of ground hay and concentrates and a similar diet with 10% added fat (by weight). Horses were sprint-trained 4 d/wk, and two additional exercise tests were performed at 5-wk intervals. Heart rates and rectal temperatures were monitored and venous blood samples were collected at rest and at each speed increment. Whole blood was analyzed for glucose, lactate, and hemoglobin concentrations, and plasma was analyzed for pH, pCO2, albumin,...
Hypoxic helium breathing does not reduce alveolar-arterial PO2 difference in the horse. In a previous study we evaluated the mechanism of alveolar-arterial PO2 (AaPO2) reduction when nitrogen is replaced with helium in normoxia (FIO2 = 0.21). The reduction in AaPO2 was not due to changes in VA/Q inequality, pulmonary O2 diffusing capacity, or cardiac output, but to more complete diffusion equilibration as a consequence of the higher ventilation and thus PAO2 (which reduced the average slope of the hemoglobin O2 dissociation curve (ODC), and thus enhanced diffusive equilibration). We hypothesized that hypoxic He/O2 breathing in contrast would not reduce the AaPO2 because PAO2 and ...
Comparative hematological study of two breeds of foals (Andalusian and Arab) subjected to exercise of progressive intensity. Exercise-induced hematological alterations were studied in 20 four-year old foals, 11 Andalusian and 9 Arabian. They were subjected to a test exercise program consisting of 4 levels of gradually increasing intensity (15, 20, 25 and 30 km/hr) with a duration of 5 min each. Blood samples were taken during resting, after each exercise level and at 10 and 30 min of recovery from exercise. The following hematic parameters were analyzed: red blood count, hematocrit value, hemoglobin, volumetric indexes (MCV, MCH and MHCH) and total plasma proteins. The alterations as a result of the physical effort ...
Clinical pathology and hemostatic abnormalities in experimental African horsesickness. Infection of naive North American horses with 10(4) cell culture infectious doses (CCID50) of virulence variants of African horsesickness virus (AHSV), designated AHSV/4SP, AHSV/9PI, and AHSV/4PI, reproduced three classical forms of African horsesickness: acute (pulmonary), subacute (cardiac), and febrile, respectively. Distinct clinicopathologic and hemostatic abnormalities were associated with each form of disease. Hemostatic abnormalities included increased concentration of fibrin degradation products and prolongation of prothrombin, activated partial thromboplastin, and thrombin clotting t...
Electrostatics of hemoglobins from measurements of the electric dichroism and computer simulations. Hemoglobins from normal human cells, from sickle cells, and from horse were investigated by electrooptical methods in their oxy and deoxy forms. The reduced linear dichroism measured as a function of the electric field strength demonstrates the existence of permanent dipole moments in the range of 250-400 Debye units. The reduced limiting dichroism is relatively small (< or = 0.1); it is negative for hemoglobin from sickle cells and positive for the hemoglobins from normal human cells and from horse. The dichroism decay time constants are in the range from about 55 to 90 ns. Calculations of th...
Haematuria, pigmenturia and proteinuria in exercising horses. The effects of exercise on urinary excretion of red blood cells, pigments (haemoglobin and myoglobin) and protein were studied in 8 mares performing treadmill exercise at speeds eliciting 40, 60 and 95% of the maximal oxygen consumption (VO2max). Gross haematuria and pigmenturia were observed in all horses during exercise at the 2 higher intensities, while these findings were detected in only one of 8 mares during exercise at 40% of the VO2max. For the remaining 7 mares exercised at 40% of the VO2max, increased urinary excretion of red blood cells (RBCs) and pigments was evident after centrifu...
Hemodynamic responses of horses to anesthesia and surgery, before and after administration of a low dose of endotoxin. Seven horses, which were part of an investigation of the effect of endotoxin administration on vascular reactivity, were anesthetized on two separate occasions for surgical excision of 4-cm sections of palmar digital artery and vein. On the first occasion, the horses were given an infusion of 1 L 0.9% NaCl solution intravenously (i.v.) just before induction of anesthesia (control); on the second occasion, the horses received an infusion of 1 L 0.9% NaCl containing Escherichia coli endotoxin, 0.1 microgram/kg (endotoxin). On both occasions, anesthesia was induced with xylazine, guaifenesin, and...
[Case report: polycythemia in a horse]. A 13 year old Thoroughbred gelding was presented with a history of a single episode of collapse during mild exercise. Clinical examination revealed a high packed cell volume (PCV) of 72%, a haemoglobin concentration of 24.9 g/l and 15.2 millions erythrocytes/microliters. Despite continuous intravenous infusion therapy with large volumes, the PCV never decreased to a physiological level. The animal showed a normal appetite and no signs of discomfort or syncope. Arterial blood gas values were in the normal range as well as the concentration of erythropoietin (measured by radioimmunoassay, RIA). ...
Plasma beta-endorphin response of thoroughbred horses to maximal exercise. Ten horses underwent a standardised strenuous treadmill exercise test, before, during and after which measurements were made of plasma beta-endorphin and cortisol concentrations, blood lactate, glucose, haemoglobin and pH, the activities of creatine kinase, lactate dehydrogenase and aspartate amino-transferase, and heart rate, oxygen uptake and expired minute volume. The correlations between the exercise-induced response of beta-endorphin and the changes observed in the other physiological measurements were examined. There was a large variation in the beta-endorphin response of the horses to e...
Capacity for red blood cell aggregation is higher in athletic mammalian species than in sedentary species. The purpose of this study was to show that two rheological parameters, red blood cell (RBC) sedimentation rate and apparent blood viscosity at low shear rate, characterizing the degree of RBC aggregation, correlate significantly with the maximal mass-specific rate of oxygen consumption or aerobic capacity (VO2max). Comparisons were made within two groups of similarly sized athletic and sedentary species: group 1, pronghorn antelope, dog, goat, and sheep; and group 2, horse and cow. The pronghorn antelope (Antilocapra americana) is one of the most athletic mammals, and we have obtained data on ...
Capillary blood transit time in muscles in relation to body size and aerobic capacity. The mean minimal transit time for blood in muscle capillaries (tc) was estimated in six species, spanning two orders of magnitude in body mass and aerobic capacity: horse, steer, dog, goat, fox and agouti. Arterial (CaO2) and mixed venous (CvO2) blood O2 concentrations, blood hemoglobin concentrations ([Hb]) and oxygen uptake rates were measured while the animals ran on a treadmill at a speed that elicited the maximal oxygen consumption rate (VO2max) from each animal. Blood flow to the muscles (Qm) was assumed to be 85% of cardiac output, which was calculated using the Fick relationship. Total...
Gait and respiration in standardbred horses when pacing and galloping. The relationship between gait and the respiratory response to exercise was examined in five standardbred racehorses which exercised on a treadmill at a pace and a gallop. After an initial warm-up, respiratory rate and stride frequency were measured after one and two minutes of treadmill exercise at 80 per cent of maximal oxygen consumption (VO2max), after one minute at 100 per cent VO2max and after two minutes at 100 per cent VO2max (galloping horses only). Exercise at 100 per cent VO2max continued until the horses showed signs of fatigue. Arterial blood was collected during exercise and when ...
Temperature and pH effects on the oxygen equilibrium curve of the thoroughbred horse. A new oxygen equilibrium curve is defined for the Thoroughbred horse under standard conditions of 37 degrees C, pH = 7.4 and PCO2 = 5.33 kPa. The "standard" P50 for the Thoroughbred is, at 2.83 +/- 0.04 (SE of mean) kPa, significantly lower than that found for the Hanoverian horse (3.17 +/- 0.03 kPa) by Clerbaux et al. (Can. J. Vet. Res. 50: 188-192, 1986), and lower than other values for horses in the literature. Using data from Butler et al. (J. Exp. Biol. 179: 159-180, 1993), curves were also constructed, in vitro, under simulated conditions of intense exercise to examine the individual eff...
[Prognostic parameters in equine colic]. A retrospective study was performed on 271 horses with colic referred to the I. Medizinische Tierklinik within a period of 2 years, to examine the prognostic value of different clinical and diagnostic laboratory parameters by Student's t-test and the Chi-quadratic test. The following quantitative parameters presented a highly significant prognostic value (P < 0.0001): capillary refill time, pulse rate, heart rate, respiratory rate, hematocrit, hemoglobin concentration, blood lactate, base excess and anion gap. The intensity of colic signs, the degree of disturbance of the patient's gen...
Comparison of ventilatory responses to sustained reduction in arterial oxygen tension vs. content in awake ponies. To gain insight into central and peripheral contributions to changes in breathing during hypoxia, we compared effects on breathing of reducing inspired PO2 (hypoxic hypoxia) with reducing arterial O2 content (CaO2) through elevation of carboxy-hemoglobin (COHb) (CO hypoxia). Twelve awake ponies were studied during 1 h of breathing room air followed by 6 h when COHb was increased to 25% and CaO2 was decreased by 17%. When COHb was increased, arterial PCO2 (PaCO2) increased gradually to 1.3 Torr above (P < 0.05) control level between 30 and 45 min of CO exposure. Pulmonary ventilation (VE) de...
Specific immune responses are required to control parasitemia in Babesia equi infection. Horses possessing a normal immune system and spleen often control infection caused by Babesia equi. However, splenectomized horses are unable to control B. equi infection and usually succumb to the infection. To investigate the role of the spleen in the control of B. equi infection in the absence of specific immune responses, two 1-month-old foals with severe combined immunodeficiency (SCID) and two age-matched normal foals were inoculated with B. equi. The SCID foals became febrile seven days postinoculation and developed terminal parasitemias of 41 and 29%. The SCID foals had greater than 50...
Evaluation of pulse oximetry in horses surgically treated for colic. All 43 horses anaesthetised for colic surgery were premedicated with xylazine or diazepam. Anaesthesia was induced with guaifenesin and ketamine, horses were placed in dorsal recumbency and anaesthesia was maintained with isoflurane in oxygen and mechanical ventilation. Haemoglobin saturation readings (SpO2) were taken with a pulse oximeter and compared with computed haemoglobin saturation (SaO2) from arterial blood samples. Readings were taken over a range of SaO2 of 78-100%, mean arterial blood pressure ranged from 24 to 108 mmHg and PaO2 ranged from 53 to 490 mmHg. Analysis of 107 readings ...
[Hematological reference values for foals in the first two months of life]. Hematologic reference values were established in 18 healthy foals in the first two months of life. Blood samples were collected prior to colostrum consumption and at 30 hours, 1 week, 3, 5, 7 and 9 weeks of age. PCV, Hb and RBC decreased during the first week and RBC, but not PCV and Hb, increased toward the end of the second month. With the exception of the sample at 1 week, the foals had mean RBC values significantly higher than those of controls. Mean MCV and MCH did not change during the first week, but decreased slightly thereafter; all means were smaller than in controls. The numbers of ...
[Possibilities and limits of pulse oximetry for monitoring anesthesia in horses]. In this paper the measurement technique pulse oximetry is examined in 25 halothane-anaesthetized horses. Furthermore measures are presented which lead to a successful sensor placement at the tongue of the horse. The hemoglobin saturation determined by the pulse oximeter (SaO2) correlated very well with the hemoglobin saturation calculated by blood gas analysis (sO2). Nevertheless in the range of low saturation the pulse oximeter increasingly overestimates sO2. Pulse oximetry is an important progress in equine patient monitoring. A decline of oxygen saturation in the blood is detected immediate...
Kinetics and haematological effects of erythropoietin in horses. A plasma kinetic study of erythropoietin (EPO) was carried out in 4 horses after subcutaneous administration (30 IU/kg bwt) of recombinant human erythropoietin (rhEPO). At standardized intervals for 48 h before injection and for 60 h post-administration, the EPO plasma levels were determined with an immunoradiometric assay based on a sandwich technique. The peak plasma concentration (30-113 mIU/ml) was observed after a delay ranging from 6 to 9 h post-administration and the drug levels reached a physiological value around 60 h following rhEPO injection. Moreover, reference values for plasma EP...
Comparative study of the oxyhaemoglobin dissociation curve of four mammals: man, dog, horse and cattle. 1. The entire oxygen dissociation curve (ODC) and the effects of temperature, pH and 2,3-diphosphoglycerate (DPG) on this curve, have been compared in four mammalians: man, dog, horse and cattle. 2. If the oxyphoric capacities are similar between these species (around 1.39 ml O2/gHb), their P50, measured in standard conditions, i.e. at pH 7.4; pCO2 40 mmHg and T 37 degrees C, varies between 23.8 (+/- 0.8) mmHg for the horse, 25.0 (+/- 1.4) mmHg for cattle, 26.6 (+/- 1.2) for man and 28.8 (+/- 2.6) mmHg for the dog. 3. The higher dispersion of the dog's P 50 is due to difference between breeds;...
