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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.
The interaction of equine lysozyme:oleic acid complexes with lipid membranes suggests a cargo off-loading mechanism. The normal function of equine lysozyme (EL) is the hydrolysis of peptidoglycan residues of bacterial cell walls. EL is closely related to alpha-lactalbumins with respect to sequence and structure and further possesses the calcium binding site of alpha-lactalbumins. Recently, EL multimeric complexes with oleic acids (ELOAs) were shown to possess tinctorial and morphological properties, similar to amyloidal aggregates, and to be cytotoxic. ELOA's interactions with phospholipid membranes appear to be central to its biological action, similar to human alpha-lactalbumin made lethal to tumor cells. ...
Endotoxin-induced HIF-1alpha stabilisation in equine endothelial cells: synergistic action with hypoxia. Hypoxia may enhance the deleterious effects of lipopolysaccharide (LPS) in the endotoxaemic horse. This study has examined some of the actions of LPS and hypoxia, alone and in combination, on cultured equine digital vein endothelial cells (EDVEC) and the signalling molecules involved. Methods: EDVEC were exposed to LPS, 5% O(2) and LPS then 5% O(2) for up to 24 h. HIF-1alpha stabilisation, neutrophil adhesion and EDVEC permeability were assessed by immunoblotting, measurement of myeloperoxidase and movement of FITC-dextran, respectively. Pharmacological inhibitors were used to assess the roles...
Characterization of extracellular matrix macromolecules in primary cultures of equine keratinocytes. Most research to date involving laminins and extracellular matrix protein function in both normal and pathological conditions involves in vitro culture of keratinocytes. Few methods are established to allow for prolonged propagation of keratinocytes from equine tissues, including the hoof lamellae. In this study we modified cell isolation and culture techniques to allow for proliferation and sub-culturing of equine lamellar keratinocytes. Additionally, the production and processing of extracellular matrix molecules by skin and lamellar keratinocytes were studied. Results: Physical and proteoly...
Depletion of urinary zilpaterol residues in horses as measured by ELISA and UPLC-MS/MS. Three horses were dosed with dietary zilpaterol and the urine concentrations measured from withdrawal day 0 to withdrawal day 21. The analyses were carried out using both enzyme-linked immunosorbent assay (ELISA) and an ultraperformance liquid chromatography with triple-quadrupole-tandem mass spectrometric detection (UPLC-MS/MS). The UPLC-MS/MS method was developed to provide rapid analysis with positive analyte identification by following three product ions and computing the two independent ion ratios. When urinary zilpaterol concentrations were between 0.2 and 2 ng/mL, the ELISA had interday...
Determination of oral tramadol pharmacokinetics in horses. The determination of the pharmacokinetic parameters of tramadol in plasma and a better characterization of its metabolites after oral administration to horses is necessary to design dosage regimens to achieve target plasma concentrations that are associated with analgesia. The purpose of this study was to determine the pharmacokinetics and elimination pattern in urine of tramadol and its metabolites after oral administration to horses. Tramadol was administered orally to six horses and its half-life, T(max) and C(max) in plasma were 10.1, 0.59 h, and 132.7 ng/mL, respectively. The half-life, T...
Cloning, comparative sequence analysis and mRNA expression of calcium-transporting genes in horses. Epithelial calcium transport occurs by paracellular and transcellular mechanisms. Transcellular transport in intestinal and renal epithelia involves several transport proteins, including transient receptor potential vanilloid member 5 (TRPV5), member 6 (TRPV6), calbindin D9k (CB9), calbindin D28k (CB28), sodium calcium exchanger 1 (NCX1), plasma membrane calcium ATPase 1 (PMCA1), and the vitamin D receptor (VDR). We are interested in the horse because of its unique calcium physiology (high blood calcium, high intestinal calcium absorption, high renal excretion of calcium, low vitamin D concent...
Short-term feed restriction decreases the systemic and intrafollicular concentrations of leptin and increases the vascularity of the preovulatory follicle in mares. The objective of this study was to evaluate the effect of short-term feed restriction on characteristics of the preovulatory follicle and on concentrations of systemic hormones (leptin, follicle-stimulating hormone [FSH], luteinizing hormone [LH]) and follicular fluid hormones and growth factors (leptin, estradiol, inhibin-A, activin-A, free insulin-like growth factor-1 [IGF1], insulin-like growth factor binding protein 2 [IGFBP2], vascular endothelial growth factor [VEGF]). Mares were submitted to a short-term (48 h) feed restriction when the expected ovulatory follicle was > or =27 mm (Hour ...
Characterization of the haem-uptake system of the equine pathogen Streptococcus equi subsp. equi. Streptococcus equi possesses a haem-uptake system homologous to that of Streptococcus pyogenes and Streptococcus zooepidemicus. The system consists of two ligand-binding proteins (Shr and Shp) and proteins (HtsA-C) with homology to an ABC transporter. The haem-uptake system of S. equi differs from that of S. pyogenes and S. zooepidemicus in that Shr is truncated by two-thirds. This study focused on the SeShr, SeShp and SeHtsA proteins of S. equi. Analysis of shr, shp and shphtsA knockout mutants showed that all three proteins were expressed in vitro and that expression was upregulated under co...
The effect of platelet-rich plasma on the neovascularization of surgically created equine superficial digital flexor tendon lesions. The repair process of tendon injuries, which are common in both human and equine athletes, is slow and the quality of the repair tissue is often inferior to the original tendon tissue, which frequently leads to re-injury. The relatively poor vascularization of tendons is considered to be one of the reasons for their limited healing potential. Recently, platelet-rich plasma (PRP), an autologous concentrate of platelets, rich in growth factors, has been shown to enhance the repair process of injured tendons. This effect has been ascribed to the high levels of growth factors in PRP, several of wh...
Comparison of the morphology of the limbs of juvenile and adult horses (Equus caballus) and their implications on the locomotor biomechanics. We analyzed the morphology and the walk-trot and trot-gallop transition velocities of nine juvenile horses and compared them with their mothers. We also compared the relative stride length and the duty factor of the juveniles with respect to adults at three equivalent trotting speeds (Froude numbers 0.5, 0.75, and 1.0), to determine dynamic similarity. Juveniles had a negative allometry in their leg bones, mainly because of little size changes of the distal portions. The negative allometry of extremities allows juveniles to increase stride length without increasing step frequency, which can be...
Comparative study of the properties of tendinocytes derived from three different sites in the equine superficial digital flexor tendon. This aim of this study was to determine the characteristic differences in tendinocytes derived from three sites of the equine superficial digital flexor tendon (SDFT)-proximally the myotendinous junction (MTJ), mid-metacarpal (mM) and osteotendinous junction (OTJ)-in morphology, proliferation, and ability for synthesis of collagen and matrix metalloproteinases (MMPs). Little difference was observed in cell proliferation. Addition of tumor necrosis factor (TNF) alpha to the culture medium resulted in increased collagen synthesis by tendinocytes from all three sites. The amount of collagen synth...
Comparative analysis of vocalizations of thoroughbred mares (Equus caballus) between estrus and diestrus. We investigated the differences between vocalizations of mares in estrus and diestrus and determined the spectrographic parameters to discriminate estrus from diestrus. Thoroughbred brood mares (n=89) were exposed to a teasing procedure for 3 min, and we recorded all vocalizations emitted from them. Among the mares, 56.5% of estrus and 78.6% of diestrus mares emitted calls toward an approaching stallion, indicating that there was higher tendency in the occurrence rate of vocal responses in diestrus than estrus mares. We analyzed the spectrographic data of the mares (25 estrus and 22 diestrus m...
Effects of domperidone on digital laminar microvascular blood flow in clinically normal adult horses. To determine effects of domperidone and acepromazine maleate on microvascular blood flow in digital laminae of clinically normal adult horses. Methods: 8 clinically normal adult horses (4 mares and 4 geldings). Methods: In a 4-period crossover study, domperidone was administered PO at 1.1 mg/ kg and 5.5 mg/kg and IV at 0.2 mg/kg; acepromazine was administered IV at 0.04 mg/kg. The washout period between treatments was 1 week. A 3-minute measurement of laminar microvascular blood flow (LMBF) was obtained with laser Doppler flowmetry. Baseline measurements were obtained at -2, -1, and 0 hours pr...
Role of prolactin in the gonadotroph responsiveness to gonadotrophin-releasing hormone during the equine annual reproductive cycle. A combined suppressive effect of prolactin (PRL) and dopamine on the secretion of luteinising hormone (LH) at the level of the pituitary gland has been identified in sheep, a short-day breeder. However, little is known about the role of PRL in the intra-pituitary regulation of the gonadotrophic axis in long-day breeders. In the present study, we investigated the effects of PRL on LH and follicle-stimulating hormone (FSH) secretion during the equine annual reproductive cycle. Horse pituitaries were obtained during the breeding season (BS) and nonbreeding season (NBS). Cells were dispersed, plat...
Probiotics in animal nutrition and health. The use of probiotics for farm animals has increased considerably over the last 15 years. Probiotics are defined as live microorganisms which can confer a health benefit for the host when administered in appropriate and regular quantities. Once ingested, the probiotic microorganisms can modulate the balance and activities of the gastrointestinal microbiota, whose role is fundamental to gut homeostasis. It has been demonstrated that numerous factors, such as dietary and management constraints, can strongly affect the structure and activities of the gut microbial communities, leading to impaired...
Alternative instrumentation for the analysis of total carbon dioxide (TCO(2)) in equine plasma. The analysis of total carbon dioxide (TCO(2)) in equine plasma is conventionally done in Australia and elsewhere using Beckman Synchron EL-ISE(R) analysers. This instrument is no longer being manufactured and has not been supported by the supplier since December 2008. For testing for TCO(2) to continue, it is necessary to evaluate and commission alternative instrumentation. In this paper, we compare the Beckman Synchron EL-ISE, the Beckman Synchron CX5, the Beckman UniCel DxC 600 and the Randox Daytona instruments. Results indicate that all four instruments perform in accordance with the manuf...
Maximal lactate steady state during exercise in blood of horses. The speed producing the maximal lactate steady state (maxLASS) is supposed to be the optimal speed to condition for endurance. The maxLASS was defined as the maximal speed at which the blood lactate concentration ([LA]) between the 5th and the 25th min of continuous exercise did not increase by more than 1 mmol/L. According to the aerobic-anaerobic lactate threshold concept determined in humans, maxLASS corresponds to v(4) [speed in a standardized exercise test (SET) shown to produce an [LA] of 4 mmol/L; generalized to v(i) for the speed producing an [LA] of i mmol/L]. Four Thoroughbreds were ...
Effects of dexamethasone and hydroxyzine treatment on intradermal testing and allergen-specific IgE serum testing results in horses. To determine whether dexamethasone or hydroxyzine affect intradermal testing (IDT) and allergen-specific IgE serum testing (ASIST) results in horses, these tests were performed serially in five horses without signs of atopic dermatitis before and after treatment with the drugs. IDT consisted of saline, histamine (1:100,000 w/v) and eight commercial extracts; results were evaluated as subjective scores by comparison to saline (0) and histamine (4) and as objective measurement of wheal diameter (mm). After baseline testing, dexamethasone (20 mg) was administered intramuscularly daily for 7 days....
Simplified method to measure glucocorticoid metabolites in faeces of horses. Glucocorticoids or their metabolites can be measured in several body fluids or excreta, including plasma, saliva, urine and faeces. In recent years the measurement of glucocorticoid metabolites (GCMs) in faeces has gained increasing attention, because of its suitability for wild populations. In horses, however, the group-specific enzyme immunoassay described so far has a limited practicability due to its complex extraction procedure. Therefore, we tested the applicability of other enzyme immunoassays for glucocorticoid metabolites. The present study clearly proved that an enzyme immunoassay (E...
The relationship between concentrations of vitamin D-binding protein (DBP) in serum and colostrum of mares and in serum of their foals in the neonatal period. Vitamin D-binding protein (DBP) participates in the actin scavenger system, it is a carrier of vitamin D and its derivatives, it manifests the capacity to bind mainly monounsaturated and saturated fatty acids, it binds to the surface of several cells and enhances chemotactic activity of C5a of the complement. The present study was aimed at answering the question whether serum DBP level in mares is related to levels of this protein in colostrum and in serum of its progeny. For this purpose, sera from 77 mares, colostra from 72 mares and sera from 69 Thoroughbred foals were collected. Mother's a...
Magnetic resonance signal changes during time in equine limbs refrigerated at 4 degrees C. When ex vivo magnetic resonance (MR) imaging studies are undertaken, specimen conservation should be taken into account when interpreting MR imaging results. The purpose of this study was to assess MR changes during time in the anatomic structures of the equine digit on eight cadaver limbs stored at 4 degrees C. The digits were imaged within 12 h after death and then after 1, 2, 7, and 14 days of refrigeration. After the last examination, four feet were warmed at room temperature for 24 h and reimaged. Sequences used were turbo spin echo (TSE) T1, TSE T2, short tau inversion recovery (STIR), a...
Lectin-binding sites on ejaculated stallion sperm during breeding and non-breeding periods. Stallion sperm from semen collected in Southern Italy during the breeding (June-July) and non-breeding (December-January) periods were analyzed by means of twelve lectins to evaluate the glycoconjugate pattern and to verify whether there are any seasonal differences in the glycosylation pattern of the sperm glycocalyx. The acrosomal cap showed reactivity for Maackia amurensis (MAL II), Sambucus nigra (SNA), Arachis hypogaea (PNA), Glycine max (SBA), Helix pomatia (HPA), Canavalia ensiformis (Con A) Triticum vulgaris (WGA), and Griffonia simplicifolia isolectin II (GSA II) in breeding and non-b...
Characterization of a stretch-activated potassium channel in chondrocytes. Chondrocytes possess the capacity to transduce load-induced mechanical stimuli into electrochemical signals. The aim of this study was to functionally characterize an ion channel activated in response to membrane stretch in isolated primary equine chondrocytes. We used patch-clamp electrophysiology to functionally characterize this channel and immunohistochemistry to examine its distribution in articular cartilage. In cell-attached patch experiments, the application of negative pressures to the patch pipette (in the range of 20-200 mmHg) activated ion channel currents in six of seven patches. ...
A study of the thickness of cheek teeth subocclusal secondary dentine in horses of different ages. There is limited knowledge on the thickness of subocclusal secondary dentine in equine cheek teeth (CT). Objective: Subocclusal secondary dentine is of consistent thickness above different pulp horns in individual horses and its thickness increases with age. Methods: 408 permanent CT were extracted post mortem from 17 horses aged 4-30 years, with no history of dental disease. The CT were sectioned longitudinally in the medio-lateral (bucco-palatal/lingual) plane through each pulp horn, and the thickness of the secondary dentine overlying each pulp horn was measured directly. Results: The suboc...
Equine laminitis: induced by 48 h hyperinsulinaemia in Standardbred horses. Hyperinsulinaemia is known to induce laminitis experimentally in healthy ponies with no history of the condition. Horses are more insulin sensitive than ponies and whether prolonged hyperinsulinaemia and euglycaemia would have a similar laminitogenic effect requires study. Objective: To determine if laminitis results when the prolonged euglycaemic hyperinsulinaemic clamp technique (p-EHC) is applied to clinically normal Standardbred horses, and to monitor hoof wall temperature seeking an association between vascular activity and laminitis development. Methods: Eight young, clinically normal St...
A review of tendon injury: why is the equine superficial digital flexor tendon most at risk? Tendon injury is one of the most common causes of wastage in the performance horse; the majority of tendon injuries occur to the superficial digital flexor tendon (SDFT) whereas few occur to the common digital extensor tendon. This review outlines the epidemiology and aetiology of equine tendon injury, reviews the different functions of the tendons in the equine forelimb and suggests possible reasons for the high rate of failure of the SDFT. An understanding of the mechanisms leading to matrix degeneration and subsequent tendon gross failure is the key to developing appropriate treatment and p...
Measurement of C-peptide concentrations and responses to somatostatin, glucose infusion, and insulin resistance in horses. Hyperinsulinaemia is detected in horses with insulin resistance (IR) and has previously been attributed to increased pancreatic insulin secretion. Connecting peptide (C-peptide) can be measured to assess pancreatic function because it is secreted in equimolar amounts with insulin and does not undergo hepatic clearance. Objective: A human double antibody radioimmunoassay (RIA) detects C-peptide in equine serum and concentrations would reflect responses to different stimuli and conditions. Methods: A validation procedure was performed to assess the RIA. Six mature mares were selected and somatos...
Effect of season on fresh and cryopreserved stallion semen. The objective of this study was to determine the effect of season on sperm quality variables, expression of the fertility-related protein SP22 and selected mRNA transcripts in fresh and cryopreserved stallion sperm. Four stallions were collected in each of the four seasons: summer, fall, winter and spring. Ejaculates were divided and then evaluated for motility, morphology, SP22 staining and expression of selected mRNAs as either fresh semen samples or cryopreserved samples. A significant interaction between season and cryopreservation status was found for total and progressive sperm motility....
Isolation and cultivation of equine corneal keratocytes, fibroblasts and myofibroblasts. To establish an in vitro model for the investigation of equine corneal wound healing. To accomplish this goal, a protocol to isolate and culture equine corneal keratocytes, fibroblasts and myofibroblasts was developed. ANIMAL MATERIAL: Equine corneal buttons were aseptically harvested from healthy research horses undergoing humane euthanasia for reasons unrelated to this study. Slit-lamp biomicroscopy was performed prior to euthanasia by a board-certified veterinary ophthalmologist to ensure that all samples were harvested from horses free of anterior segment disease. Methods: Equine corneal s...
Factors affecting the relationship between arterial and end-tidal carbon dioxide pressures in the anaesthetised horse. To assess the effects of the duration of anaesthesia, position of recumbency, mode of ventilation, anaesthetic drug protocol, patient age and type of surgical procedure on the usefulness of capnometry as a measure of the partial pressure of arterial carbon dioxide (P(a)co(2)) during general anaesthesia in horses. Methods: A prospective study compared the P(a)co(2) values with those of partial pressure of end-tidal carbon dioxide (ETco(2)) in horses anaesthetised for elective or emergency surgical procedures. The difference between P(a)co(2) and ETco(2) (P(a)co(2)- ETco(2)) and the physiologica...
