Topic:Calcium
Calcium is a mineral that is essential for various physiological processes in horses, including bone development, muscle function, and nerve transmission. It is a critical component of the equine diet and is involved in maintaining skeletal integrity and supporting metabolic functions. Calcium levels in horses are regulated through dietary intake, absorption in the gastrointestinal tract, and hormonal control mechanisms involving the parathyroid hormone and vitamin D. Imbalances in calcium levels can lead to health issues such as metabolic bone disease or hypocalcemia. This page compiles peer-reviewed research studies and scholarly articles that explore the metabolism, dietary requirements, and health implications of calcium in equine nutrition and physiology.
The unfolding thermodynamics of c-type lysozymes: a calorimetric study of the heat denaturation of equine lysozyme. The energetics of the temperature-induced unfolding of equine lysozyme was studied calorimetrically and compared with that of two structurally homologous proteins: hen egg white lysozyme and alpha-lactalbumin. The structure of each of these proteins is characterized by the presence of a deep cleft that divides the molecule into two regions called the alpha and beta domains. In equine lysozyme and alpha-lactalbumin the latter domain specifically binds Ca2+. It is shown that, in contrast to hen egg white lysozyme in which the alpha and beta domains unfold as a single cooperative unit, in equine ...
Indwelling cecal catheters for fluid administration in ponies. Two different fluid solutions were infused through percutaneous cecal catheters in 6 healthy ponies to determine the effects on body weight; CBC; packed cell volume (PCV); total plasma protein concentration; plasma fibrinogen concentration; abdominal fluid analysis; concentrations of blood urea nitrogen (BUN), serum creatinine, Ca, total CO2 (TCO2), Na, Cl, K, and P; and fractional clearance (FC) of Na, Cl, K, and P. During intracecal administration of solution 1, FCNa and FCCl were significantly increased, whereas FCK and BUN were significantly decreased. During administration of solution 2, ...
Sr2+ can become incorporated into an agonist-sensitive, cytoplasmic Ca2+ store in a cell line derived from the equine sweat gland epithelium. We have explored the properties of a Ca(2+)-dependent cell-signalling pathway that becomes active when cultured equine sweat gland cells are stimulated with ATP. The ATP-regulated, Ca(2+)-influx pathway allowed Sr2+ to enter the cytoplasm but permitted only a minimal influx of Ba2+. Experiments in which cells were repeatedly stimulated with ATP suggested that Sr2+, but not Ba2+, could become incorporated into the agonist-sensitive, cytoplasmic Ca2+ store. Further evidence for this was provided by experiments using ionomycin, a Ca2+ ionophore which has no affinity for Sr2+.
Elevated myoplasmic calcium in exercise-induced equine rhabdomyolysis. Exertional rhabdomyolysis is a myopathy of unknown pathophysiology. We measured intracellular resting calcium concentration ([Ca2+]i) by means of Ca(2+)-selective microelectrodes in intercostal muscle fibers from horses suffering from rhabdomyolysis, and from horses with no evidence of neuromuscular disorder. [Ca2+]i was several-fold higher in muscle fibers from horses suffering from rhabdomyolysis when compared to controls. Treatment of rhabdomyolytic horses with dantrolene, an agent that prevents Ca2+ release from the sarcoplasmic reticulum, reduced [Ca2+]i toward control values, and acceler...
Effect of phenytoin on skeletal muscle from quarter horses with hyperkalaemic periodic paralysis. The contractile activity, the threshold for calcium-induced calcium release in fractions of sarcoplasmic reticulum and the potassium concentration were determined in preparations of semimembranosus muscle from normal quarter horses and quarter horses with hyperkalaemic periodic paralysis before and after they were treated with phenytoin. Before the treatment there was no difference in caffeine contracture or electrically elicited twitch response between the two groups. For one week after the treatment, the time to peak tension of caffeine contractures was significantly (P < 0.005) reduced i...
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...
Crystalline composition of equine urinary sabulous deposits. The composition and crystal morphology of 141 equine sabulous deposits were determined by infrared spectroscopy (IR), scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX). The IR analysis revealed that all investigated deposits contained calcium carbonates (calcite, CaCO3, and/or vaterite, CaCO3) as major constituents; 42 samples were composed of calcite and vaterite, 33 of calcite, 18 of calcite/vaterite and calcium oxalate, and 17 of vaterite. The remaining specimens contained calcite/vaterite and other compounds (calcium phosphates, sulphate and/or oxalates and/or s...
Voltage-gated ion channelopathies: inherited disorders caused by abnormal sodium, chloride, and calcium regulation in skeletal muscle. The pathological genetic defects in the inherited myotonias and periodic paralyses were recently elucidated using molecular genetic studies. These disorders are usually transmitted as a dominant trait from an affected parent to a child. The many clinical symptoms include cold-induced uncontrollable contraction of muscle, potassium-induced contraction and paralysis, myotonia with dramatic muscular hypertrophy, muscle stiffness, and insulin-induced paralysis (in males). Horses afflicted with the disorder can suddenly collapse, despite an impressive physique. In the past three years, these clinic...
Effect of glucose in the culture medium on development of horse oocytes matured and microfertilized in vitro. The development of in-vitro matured and microfertilized horse oocytes was examined in vitro. Fertilized oocytes were produced by 20-h insemination of in-vitro matured and partially zona-removed oocytes with frozen spermatozoa that had been treated with caffeine/calcium ionophore A23187 (fertilization rate 34.2%, monospermy rate 76.9%). Embryonic development was assessed by the number of nuclei stained with Giemsa solution. In Experiment 1, a continuous 8-day culture of the microfertilized oocytes in TCM199 or modified synthetic oviduct fluid (m-SOF) supplemented with 10% fetal bovine serum or ...
Effect of serum on intracellular calcium homeostasis and survival of primary cortical and hippocampal CA1 neurons following brief glutamate treatment. Glutamate neurotoxicity was studied in primary neuronal cultures prepared from rat cerebral cortex and hippocampal CA1 sector. Neurons were cultivated with 5% native horse serum and then exposed to 0.1 or 1.0 mM glutamate for 5 min. Subsequently, neurons were allowed to recover for 24 hours either in the presence or in the absence of 5% native horse serum. In the absence of serum, neurons showed morphological signs of degeneration and exhibited marked loss of vitality as tested by vital staining and release of lactate dehydrogenase (LDH). In contrast, when neurons were cultivated in the presen...
Studies on the presence of magnesium in visceral amyloid. The Magneson and Titan yellow tests were used to detect Mg in amyloid deposits in primary and secondary amyloidosis, in a pituitary tumour and in a case of equine cutaneous amyloidosis. Especially vascular amyloid deposits turned out to contain high levels of Mg. The significance of these findings remains unclear at present. Competition between Mg and Ca, the relationship between Mg in elastic fibres and amyloid P-component, and the high water content of amyloid along with the interaction of Mg with water are discussed.
Artificially dehydrated lucerne for horses. Artificially dehydrated lucerne produced in the United Kingdom has been shown to be a better source of nutrients for horses than grass hay. Horses eat more lucerne when it is pelleted, and the processing has little effect on its nutritive value. Lucerne does not appear to contain any antinutritional factors of significance to horses. Lucerne contains readily available calcium and protein and can thus be used as a cereal-balancer or to upgrade poor quality roughages. Because lucerne is a good source of digestible nutrients it has therapeutic applications, including the correction of electrolyte...
In vitro fertilization rate of horse oocytes with partially removed zonae. Frozen-thawed ejaculated stallion spermatozoa were preincubated for 3 h in BO medium containing 5 mM caffeine and then treated with 0.1 micro M calcium ionophore A23187 for 60 sec. Aliquots of the sperm suspension (final concentration 1-2 x 10(7)/ml) were added to the oocytes which had been matured in vitro for 32 h. In Experiment 1, there were 3 groups of oocytes; cumulus intact, denuded zona-intact, and zona-free. Cumulus cells were removed with 0.5% hyaluronidase and the zona pellucida with 0.1% protease. The oocytes were fixed 20 h after insemination with acetic acid:ethanol (1:3) and stai...
Ultrastructure and mineral composition of urinary calculi from horses. Urinary calculi from 17 horses with urolithiasis were examined to study their mineral content and ultrastructure. Among the analytic methods used were X-ray diffractometry, scanning electron microscopy, and electron microprobe analysis. The calculi initially were observed by use of a stereoscopic dissecting microscope and generally were found to have nodular surfaces surrounding a banded or granular-to-chalky interior. Observation by scanning electron microscopy revealed an intricate pattern of irregularly concentric, fine bands and spherules. These had a round, finely banded, globular texture...
Models of the three-dimensional structures of echidna, horse, and pigeon lysozymes: calcium-binding lysozymes and their relationship with alpha-lactalbumins. Similarities in amino acid sequences, three-dimensional structures, and the exon-intron patterns of their genes have indicated that c-type lysozymes and alpha-lactalbumins are homologous proteins, i.e., descended by divergent evolution from a common ancestor. Like the alpha-lactalbumins, echidna milk, horse milk, and pigeon eggwhite lysozymes all bind Ca(II). Models of their three-dimensional structures, based on their amino acid sequences and the known crystal structures of domestic hen eggwhite and human lysozymes and baboon and human alpha-lactalbumins, have been built. The several structur...
Crystals in equine articular cartilage. Crystal deposits have been observed in equine articular cartilage and identified by scanning electron microscopy and X-ray diffraction as octacalcium phosphate and calcium pyrophosphate dihydrate. Of 89 equine fetlock joints examined 10 contained evidence of calcification visible by eye. It is suggested that the deposition of crystals may be a mediator of arthritis in horses and may also cause damage directly.
Extracellular ATP can activate autonomic signal transduction pathways in cultured equine sweat gland epithelial cells. Changes in intracellular free calcium concentration ([Ca2+]i) were monitored in a cell line that was derived from the equine sweat gland epithelium. ATP and closely related compounds could increase [Ca2+]i with a rank order of potency of UTP > or = ATP > ADP >> AMP = adenosine = alpha,beta-methylene-ATP. The responses to ATP and to UTP were initiated by the release of calcium from an internal store and subsequently sustained by calcium influx. The rise in [Ca2+]i thus seems to be mediated by P2U receptors that are coupled to phosphoinositidase C. Some desensitisation of this respon...
[Total Ca contents in blood cells and plasma of the irradiated animals]. It was found that the total Ca content in erythrocytes from irradiated sheep and horses increased by 10-40% from 1st till 5th days after irradiation, the intracellular Mg content being unchanged. More than 2-fold increase in total Ca content in lymphocytes during first 15 days was revealed, while in platelets only a trend for a growth in acute period of radiation disease was detected. On the contrary, no reliable changes in total Ca content in plasma after irradiation were observed. This fact indicates that Ca accumulation in blood cells after whole-body irradiation is due to disturbance in in...
Effects of storage time and temperature on ionized calcium concentration in equine blood, plasma, and serum. Stability of ionized calcium (Ca2+) concentrations and pH values in equine venous samples (n = 12 in each group) stored at 4 C for 3, 9, 24, and 48 hours (blood, plasma, and serum) or for 240 hours (plasma and serum), and at -20 C for 240 hours (plasma and serum), was studied. Storage of equine blood, plasma, and serum samples at 4 C for up to 48 hours and of serum samples at 4 C for up to 240 hours, despite appreciable pH changes, was associated with < 1.5% change in blood, plasma, and serum Ca2+ concentrations. Therefore, Ca2+ concentration in equine blood, plasma, and serum samples store...
Comparison of the effects of ketoprofen and flunixin meglumine on the in vitro response of equine peripheral blood monocytes to bacterial endotoxin. The purpose of this study was to investigate the in vitro effects of flunixin meglumine, a cyclo-oxygenase inhibitor, and ketoprofen, a reported cyclo-oxygenase and lipoxygenase inhibitor, on the synthesis of cyclo-oxygenase end-products thromboxane B2 and prostaglandin E2, lipoxygenase derived 12-hydroxyeicosatetraenoic acid, tumor necrosis factor and tissue factor. Six adult horses were each randomly administered flunixin meglumine (1.1 mg/kg) or ketoprofen (2.2 mg/kg) intravenously every 12 hours with the drug treatments separated by two weeks. Blood samples were obtained prior to initiatin...
Systemic bone growth factors in light breed mares and their foals. There is a high incidence of bony pathology in race horses. Thus, plasma GH, IGF-1, osteocalcin (OC), calcium (Ca) and inorganic phosphorus (P) concentrations were measured in 12 healthy Selle Français foals and their dams during the first five months after birth. Plasma IGF-1 and OC concentrations were higher in foals than in mares (336 +/- 25 vs 230 +/- 18 ng/ml, P < 0.05; 52.5 +/- 3.2 vs 4.9 +/- 0.1 ng/mg, P < 0.01, respectively). A significant positive linear relationship could be established between these two parameters in foals (IGF-1 = 19 + 0.619 OC; P < 0.05). Another strikin...
The role of sweat in maintaining the stimulation of effort homeostasis in horses. Sweat secretion was analyzed quantitatively and qualitatively in 20 horses after a 5 min. gallop at 450 m/min. The analysis revealed concentration of proteins 63.3 +/- 6.47 g/l, mainly albumins, a high level of sodium 254.43 +/- 62.84 mM/,l chloride 268.68 +/- 98.46 mM/l, potassium 98.95 +/- 49.62 mM/l and calcium 4.14 +/- 0.8 mM/l. A dependence was found between the protein concentration in serum and its quantity in sweat and between the level of potassium in sweat and its loss from the cells within a range 8.6 to 25.8 mM/l. The hypertonic horse sweat protects organism for excessive water los...
Energy metabolism, replicative ability, intracellular calcium concentration, and ionic channels of horse articular chondrocytes. Some aspects of the physiology of chondrocytes from horse articular cartilage were studied, since this animal model can be helpful in understanding arthritic processes. The replicative ability of articular chondrocytes, measured by the incorporation of [3H]thymidine, and their capacity of proteoglycan production, evaluated from the incorporation of [35S] sulfate, are very low. In addition, these cells do not differentiate in vitro as shown by the constant specific activity of alkaline phosphatase measured at different times in culture. Two types of potassium channels were identified by patch c...
Prevalence and risk factors in serous arthritis in the carpal joint of Norwegian coldblooded trotters. Of 508 four-year-old coldblooded trotters examined for carpitis, 135 (27%) had the condition. Thirty horses had unilateral carpitis on the left frontlimb, 52 on the right frontlimb and 53 had bilateral carpitis. Of these horses, 105 were stallions, 135 were geldings and 269 were mares. The prevalence of carpitis in these three groups was 25%, 25% and 28%, respectively. Information was obtained on the training regimes in four periods of the life of 378 horses. The odds ratios for the training variables were of the same order in all four periods. In logistic regression analyses on the training v...
[HYPP–hyperkalemic periodic paralysis in horses]. A literature review of the clinical syndrome HYPP (Hyperkalemic periodic paralysis) affecting Quarter Horses is given. HYPP is characterized by sporadic attacks of muscle tremors, weakness and/or collapse, lasting for variable periods of time. Diagnosis is based on physical findings in association with hyperkalemia. In horses with HYPP, the regulation of ion transport through the sodium channels in the muscle cells occasionally fails, causing uncontrollable muscle twitching. Further investigations into molecular genetics reveals a mutation in the gene responsible for sodium and potassium regul...
Partially folded states of equine lysozyme. Structural characterization and significance for protein folding. Despite their homologous structure, c-type lysozymes and alpha-lactalbumins have been found to differ profoundly in their unfolding behavior, in that the alpha-lactalbumins readily enter a partially unfolded collapsed state (the "molten globule"), whereas lysozymes unfold cooperatively to a highly unfolded state. The calcium-binding property of lysozyme from equine milk provides an evolutionary link between the two families of proteins. We demonstrate here that equine lysozyme undergoes a two-stage unfolding transition upon heating or in the presence of guanidine hydrochloride that is highly d...
Failure of calcium channel blockade to prevent intra-abdominal adhesions in ponies. Intra-abdominal adhesions were created by localized serosal trauma in 11 adult ponies at three locations on the small intestine. Six ponies received verapamil hydrochloride (0.2 mg/kg) subcutaneously every eight hours for three days, and five ponies received an equal volume of saline solution at the same intervals. The investigators were not informed which treatments the ponies received. Systolic, diastolic, and mean carotid arterial pressures and heart rates were measured six hours before surgery, and then 0.5, 1, 1.5, and 8 hours after the first treatment on each day for three days. One pony...
Effect of heparin on capacitation/acrosome reaction of equine sperm. The onset of sperm capacitation/acrosome reaction was evaluated using heparin. Equine semen was incubated at 38 degrees C for 4.5 h in culture medium with and without 10 micrograms/mL heparin and with and without 0.1 microM of Ca2+ ionophore. Sperm acrosome reaction was detected using chlortetracycline fluorescence (CTC) and transmission electron microscopy (TEM). The CTC assay provided staining patterns that corresponded with the capacitation/acrosome reaction in other mammalian species (man, mouse, guinea pig). The percentages of incapacitated sperm (PUC), capacitated acrosome-intact sperm (...
Investigation of stimulus-secretion coupling in equine sweat gland epithelia using cell culture techniques. When sweat glands isolated from samples of horse skin were explanted and cultured under favourable conditions, they could exhibit cellular outgrowth. This growth could be maintained for 2-4 weeks and these primary cultures were then disaggregated and the resultant cell suspensions used to initiate epithelial cell lines. Secretion from intact equine sweat glands is regulated by beta 2-adrenoceptors and appears to be mediated by cyclic AMP, but there is evidence that calcium may also play a role. Adrenaline could increase the cyclic AMP content of the cultured cells and this response was mediate...
Effects of gestation, lactation, and maternal calcium intake on mechanical strength of equine bone. Skeletal homeostasis during late gestation, lactation, and the post-lactational recovery period is poorly understood. In an experiment using an animal model (the horse), metacarpal breaking strengths (MBS) estimated via transmission ultrasonics were examined during the last 12 weeks of gestation and for 40 weeks after parturition. MBS increased during the last 6-10 weeks of gestation in mares fed amounts of calcium (Ca) recommended by the National Research Council; maximum MBS coincided with the week of parturition. In contrast, MBS in mares fed 20% less Ca remained relatively constant during ...