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Topic:Physiology
The physiology of horses encompasses the study of the biological functions and processes that occur within the equine body. This includes the examination of various systems such as the cardiovascular, respiratory, musculoskeletal, digestive, and nervous systems. Understanding equine physiology is essential for comprehending how horses adapt to different environmental conditions, perform physical activities, and respond to health challenges. Research in this field often focuses on the mechanisms of energy metabolism, thermoregulation, and muscle function during exercise, as well as the physiological responses to stress and disease. This page compiles peer-reviewed research studies and scholarly articles that explore the diverse aspects of equine physiology, providing insights into the biological processes that support the health and performance of horses.
Effects of semen storage and separation techniques on sperm DNA fragmentation. To determine the effect of semen storage and separation techniques on sperm DNA fragmentation. Methods: Controlled clinical study. Methods: An assisted reproductive technology laboratory. Methods: Thirty normoozospermic semen samples obtained from patients undergoing infertility evaluation. Methods: One aliquot from each sample was immediately prepared (control) for the sperm chromatin dispersion assay (SCD). Aliquots used to assess storage techniques were treated in the following ways: snap frozen by liquid nitrogen immersion, slow frozen with Tris-yolk buffer and glycerol, kept on ice for 24...
The interstitial cells of Cajal of the equine gastrointestinal tract: what we know so far. Gastrointestinal motility disorders are a serious problem in both veterinary and human medicine and may represent a dysfunction of the neural, muscular or pacemaker components (interstitial cells of Cajal) of bowel control. The interstitial cells of Cajal are considered to be the pacemakers and mediators of certain forms of neurotransmission in the gastrointestinal tract. These cells have been implicated, either primarily or secondarily, in the pathogenesis of gastrointestinal disease processes in which there is a prominent element of disturbance to intestinal motility. In the horse, their inv...
Proinflammatory cytokine responses of cultured equine keratinocytes to bacterial pathogen-associated molecular pattern motifs. Further knowledge of equine keratinocyte physiology and keratinocyte response to various stimuli is important in developing a better understanding of disease states involving the epidermis. Objective: To assess the inflammatory cytokine response of cultured equine keratinocytes to various pathogen-associated molecular pattern molecules (PAMPs) from both Gram-negative and positive bacteria likely to be present in equine sepsis. Methods: Keratinocytes were isolated from skin of 2 horses and primary cultures performed. Keratinocytes were harvested for RNA extraction after exposure to lipopolysacc...
Corticosteroid-associated laminitis. A direct causal association between corticosteroid use and laminitis has yet to be proven scientifically, and there have been few studies specifically addressing this aspect. New evidence, however, is improving the understanding of the causes of laminitis, particularly related to endocrine factors. The focus of this article is discussing the circumstances under which steroids might cause this condition.
Hyperinsulinemic laminitis. Laminitis occurring in association with hyperinsulinemia is frequently encountered in today's equine population. New evidence suggests that hyperinsulinemia is the direct cause of this form of laminitis, rather than insulin resistance per se. The mechanism by which elevated serum insulin concentrations result in lamellar dysfunction is currently under investigation by many researchers and the use of a new insulin infusion model for investigating the pathogenesis of insulin-associated laminitis will doubtless enhance progress in this field of research. By focusing on the metabolic and vascular ...
Tear volume, turnover rate, and flow rate in ophthalmologically normal horses. To determine tear volume, turnover rate, and flow rate in ophthalmologically normal horses by use of fluorophotometry. Methods: 12 mares free of ophthalmic disease. Methods: 2 microL of 10% sodium fluorescein was instilled onto 1 eye of each horse, and tear samples were collected via microcapillary tubes from the inferonasal conjunctival culde-sac at 0, 2, 4, 6, 10, 15, and 20 minutes after instillation. Collected tear samples were then measured for fluorescein concentrations with a computerized scanning ocular fluorophotometer. A decay curve plot of concentration changes over time was used to...
The relationship between digital perfusion pressure and hoof lamellar blood flow in isoflurane-anesthetized horses. Digital perfusion pressure (DPP) equals mean arterial pressure (MAP) at the hoof coronet minus digital interstitial pressure (DIP) within the hoof. To test whether lamellar blood flow (LBF) changes proportionately to DPP, anesthesia was induced and maintained with isoflurane in six horses to target a MAP of 60 mmHg. Arterial, venous, and hoof interstitial pressures were measured in each pelvic limb. LBF was measured using fluorescent microspheres during dobutamine infusions targeting either 60 (low), 80 (medium), or 100 (high) mmHg MAP. Following euthanasia, hoof lamina was collected for micro...
Evaluation of healthy equine eyes by use of retinoscopy, keratometry, and ultrasonographic biometry. To assess natural variations in degree of refraction, corneal curvature, corneal astigmatism, corneal radius, and intraocular distance of healthy equine eyes. Methods: 159 horses with healthy eyes that were admitted to a veterinary teaching hospital for nonophthalmic surgeries. Methods: Eyes of horses were examined with a retinoscope prior to anesthesia and with a keratograph and A- and B-scan ultrasonographic biometers during surgery. In addition, manual caliper measurements of horizontal and vertical corneal radii were obtained. Results: Mean +/- SD degree of refraction in the horizontal mer...
In vitro expression of receptor activator of nuclear factor-kappaB ligand and osteoprotegerin in cultured equine articular cells. To determine concentrations of receptor activator of nuclear factor-kappaB ligand (RANKL) and osteoprotegerin (OPG) in equine chondrocytes and synoviocytes and to quantify changes in the OPG:RANKL ratio in response to exogenous factors. Methods: Samples of articular cartilage and synovium with grossly normal appearance obtained from metacarpophalangeal and metatarsophalangeal joints of 5 adult (1- to 8-year-old) horses. Methods: Cell cultures of chondrocytes and synoviocytes were incubated with human recombinant interleukin-1beta (hrIL-1beta; 10 ng/mL), lipopolysaccharide (LPS; 10 microg/mL), ...
Redox cycling of catechol estrogens generating apurinic/apyrimidinic sites and 8-oxo-deoxyguanosine via reactive oxygen species differentiates equine and human estrogens. Metabolic activation of estrogens to catechols and further oxidation to highly reactive o-quinones generates DNA damage including apurinic/apyrimidinic (AP) sites. 4-Hydroxyequilenin (4-OHEN) is the major catechol metabolite of equine estrogens present in estrogen replacement formulations, known to cause DNA strand breaks, oxidized bases, and stable and depurinating adducts. However, the direct formation of AP sites by 4-OHEN has not been characterized. In the present study, the induction of AP sites in vitro by 4-OHEN and the endogenous catechol estrogen metabolite, 4-hydroxyestrone (4-OHE), ...
Light and electron microscopy studies of the midgut and salivary glands of second and third instars of the horse stomach bot, Gasterophilus intestinalis. A morphological study of the midgut and salivary glands of second and third instars of Gasterophilus intestinalis (De Geer) (Diptera: Oestridae) was conducted by light, scanning and transmission electron microscopy. The midgut is anteriorly delimited by a proventriculus, without caeca, and is composed of posterior foregut and anterior midgut tissue from which a double-layered peritrophic matrix is produced. The midgut can be divided into anterior, median and posterior regions on the basis of the structural and physiological variations of the columnar cells which occur along its length. Two oth...
Nutritional aspects of post exercise skeletal muscle glycogen synthesis in horses: a comparative review. Carbohydrate (CHO) stored in the form of skeletal muscle glycogen is the main energy source for glycolytic and oxidative ATP production during vigorous exercise in mammals. In man, horse and dog both short-term high intensity and prolonged submaximal exercise deplete muscle glycogen. In horses, however, muscle glycogen synthesis is 2-3-fold slower than in man and rat, even when a diet high in soluble CHO is fed. There appear to be significant differences in CHO and glycogen metabolism between horses and other mammals, and it is becoming increasingly clear that many conclusions drawn from human...
Hyperleptinemia in mares and geldings: assessment of insulin sensitivity from glucose responses to insulin injection. Four experiments were conducted 1) to assess the use of glucose responses to insulin injections as a means of estimating insulin sensitivity in horses and 2) to compare the insulin sensitivities of normal horses vs. those displaying hyperleptinemia (HL). In Exp. 1, HL mares and geldings (n = 4 each) and 4 mares and geldings with normal leptin concentrations (NL) were injected intravenously with 20 and 100 mU/kg of BW of bovine insulin on 2 separate occasions in December 2008. In Exp. 2, the experimental protocol was repeated in late April 2009. In Exp. 1, the 20 mU/kg of BW dose of insulin cau...
Identification of phosphorylation sites of equine beta-casein isoforms. Equine beta-casein is phosphorylated at variable degrees and isoforms carrying 3 to 7 phosphate groups (3P-7P) have been found in milk, but the phosphorylated amino acid residues of each isoform are not yet identified. In the present work, the different phosphorylation variants were first isolated by ion-exchange chromatography and then hydrolysed by trypsin to generate caseinophosphopeptides (CPPs), each containing all the potential phosphorylation sites. The equine CPPs were prepared by metal oxide affinity chromatography, a method based on the affinity of phosphate groups towards titanium d...
A secondary isotope effect study of equine serum butyrylcholinesterase-catalyzed hydrolysis of acetylthiocholine. beta-Secondary deuterium isotope effects have been measured for equine serum butyrylcholinesterase-catalyzed hydrolysis of acetyl-L(3)-thiocholine (L=H or (2)H). The dependencies of initial rates on isotopic substrate concentrations show close adherence to Michaelis-Menten kinetics, and yield the following isotope effects: (D3)k(cat)/K(m)=0.98+/-0.02 and (D3)k(cat)=1.10+/-0.02. The modestly inverse isotope effect on k(cat)/K(m) is consistent with partial rate limitation by a step that converts the sp(2)-hybridized ester carbonyl of the E+A reactant state into a quasi-tetrahedral transition sta...
Mr imaging features of surgically induced core lesions in the equine superficial digital flexor tendon. Tendon injuries are common in athletic humans and horses. Ultrasonography is the diagnostic method of choice in horses with tendon injuries but there is increasing application of magnetic resonance (MR) imaging to monitor and follow-up tendon healing. A core lesion was created in the superficial digital flexor tendon (SDFT) of each forelimb of four horses. One of the four horses was euthanized at 2, 4, 8, and 12 weeks after creation of the lesion. MR examinations of the SDFT were performed immediately post mortem in a 1.5 T Siemens Symphony magnet and compared with histologic findings. Measure...
Focal skeletal muscle uptake of 99mTechnetium-hydroxymethylene diphosphonate following peroneal nerve blocks in horses. We have observed focal skeletal muscle uptake of 99mTechnetium-hydroxymethylene diphosphonate (Tc-HDP), which could mimic a tibial lesion, in horses following peroneal nerve blocks. To characterize this observation further, 45 bone phase scintigrams were performed in 12 horses undergoing peroneal nerve blocks. Scans were performed before, and 1, 3, 7, and 14 days postblock. The superficial and deep branches of the peroneal nerve were blocked by injecting 10 ml of 2% mepivacaine in one limb and 20 ml in the other. Images were evaluated for uptake at the block site and uptake likely to mimic a t...
Distal interphalangeal articular cartilage assessment using low-field magnetic resonance imaging. The suitability of low-field magnetic resonance (MR) imaging for assessment of articular cartilage has been questioned, based on insufficient image quality. The purposes of this study were to describe the MR anatomy of the normal distal interphalangeal (DIP) cartilage, and to evaluate the sensitivity and accuracy of low-field MR imaging for identification of cartilage erosions that were created ex vivo. Imaging sequences included sagittal and dorsal multiple-oblique T1-weighted gradient-recalled echo (GRE) and sagittal dual echo sequences. In the thickest regions, normal cartilage appeared as ...
Comparison of endoscopy, histology, and cytokine mRNA of the equine gastric mucosa. In recent years, gastric ulceration has been recognized as a common, possibly performance-limiting disease, of adult horses. The aim of this study was to compare endoscopic features, histological diagnosis, and mRNA levels of various cytokines (TNF-alpha, IL-1beta, and IL-13) from horse gastric biopsies. Eleven horses suffering from equine gastric ulcer syndrome and seven horses with normal histological gastric features were assessed. No correlation between endoscopic features and histology (i.e., the gold standard) was observed. Based on histological diagnosis, a significant (p < 0.05) increa...
On the search for in vitro in vivo correlations in the field of intra-articular drug delivery: administration of sodium diatrizoate to the horse. Development of suitable in vitro release models for formulation development as well as quality control purposes has to be initiated in the early design phase of injectable depots. Optimally, construction of an in vitro release model may lead to the establishment of in vitro in vivo correlations. By using a model compound (sodium diatrizoate, DTZ), the purpose of this study was to investigate the possibility of establishing in vitro in vivo relations between the DTZ disappearance profile obtained from the donor compartment of the rotating dialysis cell model and the joint disappearance profile ...
Determination of (13)C/(12)C ratios of urinary excreted boldenone and its main metabolite 5beta-androst-1-en-17beta-ol-3-one. Boldenone (androsta-1,4-dien-17beta-ol-3-one, Bo) is an anabolic steroid known to have been used in cattle breeding or equine sport as a doping agent for many years. Although not clinically approved for human application, Bo or its main metabolite 5beta-androst-1-en-17beta-ol-3-one (BM1) were detected in several doping control samples. For more than 15 years the possibility of endogenous Bo production in human beings has been discussed. This is a challenging issue for doping control laboratories as Bo belongs to the list of prohibited substances of the World Anti-Doping Agency and therefore th...
Membrane lipids of the stallion spermatozoon in relation to sperm quality and susceptibility to lipid peroxidation. Lipids were extracted from ejaculated spermatozoa from seven individual stallions to distinguish neutral lipids (NL) and polar lipids (PL) and determine their variation among stallions and their relationship with sperm quality and sperm susceptibility to lipid peroxidation. The isolated fatty acids were correlated with sperm quality (membrane integrity, mitochondrial membrane potential (ΔΨm) and expression of active caspases) and the sensitivity of the sperm plasma membrane to LPO. The miristic (C14: 0), palmitic (C16: 0), stearic (C18: 0) and oleic (C18: 1n9) acids were predominant among th...
Selenium in blood, semen, seminal plasma and spermatozoa of stallions and its relationship to sperm quality. The essential trace element selenium is indispensable for male fertility in mammals. Until now, little data existed regarding the relationship between selenium and sperm quality in the stallion. Selenium, or selenium-dependent glutathione peroxidase activity, was determined in red blood cells, semen, seminal plasma and spermatozoa, and the percentages of spermatozoa with progressive motility (PMS), intact membranes (PMI), altered (positive) acrosomal status (PAS) and detectable DNA damage, determined by the sperm chromatin structure assay, were evaluated in 41 healthy stallions (three samples ...
Tachypnea and antipyresis in febrile horses after sedation with alpha-agonists. Signs of tachypnea after sedation of febrile horses with alpha2-agonists have been noted previously but have not been further investigated. Objective: To examine the effects of xylazine and detomidine on respiratory rate and rectal temperature in febrile horses and to investigate if either drug would be less likely than the other to cause changes in these variables. Methods: Nine febrile horses and 9 healthy horses were included in the study. Methods: Horses were randomly assigned to sedation with xylazine 0.5 mg/kg or detomidine 0.01 mg/kg. Heart rate and respiratory rate were recorded before...
Inhibition of the mitochondrial permeability transition pore reduces “apoptosis like” changes during cryopreservation of stallion spermatozoa. In order to evaluate to what extent the changes that occur during cryopreservation involve the mitochondrial permeability transition pore (PT-pore), a specific inhibitor was used during the cryopreservation process of stallion spermatozoa. Four ejaculates from each of 7 stallions were frozen using a standard protocol. Before freezing, each ejaculate was split into three subsamples. The first was supplemented with 2.5 microM bongkrekic acid (BA) and the second with 5 microM BA. The third subsample served as control. The BA significantly reduced the percentage of spermatozoa depicting active cas...
A comparison of the moment arms of pelvic limb muscles in horses bred for acceleration (Quarter Horse) and endurance (Arab). Selective breeding for performance has resulted in distinct breeds of horse, such as the Quarter Horse (bred for acceleration) and the Arab (bred for endurance). Rapid acceleration, seen during Quarter Horse racing, requires fast powerful muscular contraction and the generation of large joint torques, particularly by the hind limb muscles. This study compared hind limb moment arm lengths in the Quarter Horse and Arab. We hypothesized that Quarter Horse hind limb extensor muscles would have longer moment arms when compared to the Arab, conferring a greater potential for torque generation at the...
Concentrations of altrenogest in plasma of mares and foals and in allantoic and amniotic fluid at parturition. Treatment with the progestin altrenogest is widely used in pregnant mares. The fact that foals born from healthy mares treated with altrenogest until term suffered from neonatal problems raises the question of direct effects of altrenogest on vital functions in the neonate. We have therefore investigated altrenogest concentrations in maternal and neonatal blood plasma and in fetal fluids. Pregnant mares were treated with altrenogest orally once daily (0,088 mg/kg bodyweight, n = 7) or left untreated (n = 8) from 280 d of gestation until foaling. Altrenogest concentration was determined in plas...
