Topic:Capillaries
Capillaries in horses are small blood vessels that form a network between arterioles and venules, facilitating the exchange of oxygen, nutrients, and waste products between blood and tissues. These microvessels are integral to the circulatory system, ensuring that tissues receive adequate blood supply and metabolic exchange. The structure and function of capillaries can vary depending on the specific tissue or organ they serve, influencing factors such as permeability and flow rate. Research in equine capillary function often focuses on topics such as blood flow regulation, the impact of exercise on capillary density and function, and the role of capillaries in various equine health conditions. This page compiles peer-reviewed research studies and scholarly articles that explore the anatomy, physiology, and clinical implications of capillary function in horses.
Effect of High-Intensity Training in Normobaric Hypoxia on Thoroughbred Skeletal Muscle. Hypoxic training is believed to increase endurance capacity in association with hypoxia inducible factor-1 (HIF-1), a modulator of vascular endothelial growth factor-A (VEGF-A), and to influence activation of satellite cells (SCs). However, the effect of hypoxic training on SC activation and its relation to angiogenesis has not been thoroughly investigated. Eight Thoroughbred horses were subjected to normoxic (F = 21%) or hypoxic (F = 15%) training for 3 days/week (100% [Formula: see text]) for 4 weeks. Incremental exercise tests (IET) were conducted on a treadmill under normoxia and the ...
Endoscopic Evaluation of Angiogenesis in the Large Airways of Horses with Heaves Using Narrow Band Imaging. Heaves is a severe debilitating condition of horses, characterized by lower airway inflammation and permanent structural changes of the bronchial wall. Chronic inflammation promotes the formation of new vessels, a phenomenon known as angiogenesis. Narrow band imaging (NBI) endoscopy is a noninvasive technique that enhances the visualization of submucosal vessels, and commonly is employed for the study of angiogenesis in human patients. Objective: Using NBI, we aimed to determine whether or not the central airways of horses with heaves undergo angiogenesis. Methods: Horses with heaves during ex...
Microangiographic Comparison of the Effects of 3 Loop Pulley and 6 Strand Savage Tenorrhaphy Techniques on Equine Superficial Digital Flexor Tendon. The 6-strand Savage (SSS) tenorrhaphy pattern is biomechanically superior to the commonly employed 3-loop pulley (3LP); however, its effects on intrinsic tendon vasculature remain unknown. The objective of this study was to compare perfusion of intrinsic vasculature of the equine superficial digital flexor tendon (SDFT) after 3LP and SSS tenorrhaphies. We hypothesized that the SSS technique would significantly decrease vascular perfusion compared to the 3LP technique. Methods: Ex vivo, randomized, paired design. Methods: Horses (n = 9) METHODS: Under general anesthesia, 9 pairs of forelimb...
Effects of an anabolic steroid (Durateston) on testicular angiogenesis in peripubertal stallions. The aim of this study was to determine the effect of the anabolic steroid testosterone on the testicular vascularization, angiogenesis and expression of angiogenic factors, and their receptors in testes of peripubertal stallions. Seven peripubertal stallions were treated with Durateston and castrated either 4 (treatment group 1 [TG1]) or 12 weeks (TG2) after the last injection. The castration of seven untreated control stallions (control group [CG]) took place within the same time. In the testicular specimens, volume density (VD), numerical density (ND), and area of vessels were determined mor...
Effects of vascular elastosis on uterine blood flow and perfusion in anesthetized mares. In the uterus of the mare, data obtained using transrectal Doppler ultrasonography indicate that uterine blood flow (UBF) is dynamic and changes throughout the estrous cycle. Degenerative lesions in the uterus are associated with subfertility and infertility. Among these lesions, vascular elastosis has been reported in aged, multiparous, and infertile mares. Angiosis of the uterine vasculature could potentially compromise UBF. The objectives of this experiment are to determine levels of UBF and perfusion of reproductively healthy mares and compare them to levels of subfertile/infertile mares a...
Isolation of equine endothelial cells and life cell angiogenesis assay. Arterial or venous thromboses are frequent clinical complications with the risk of fatal progression. Recent studies suggest the disruption of angiogenesis in the course of thrombus resolution as the underlying pathomechanism. Very similar to the situation in human patients, equine vessels have been described to be particularly susceptible to thrombosis. In contrast to humans, equine donors are readily available to obtain organs and tissues for isolation of endothelial cells. Objective of this study was to isolate equine endothelial cells and develop an angiogenesis assay from primary cultures...
Comparative quantitative study of astrocytes and capillary distribution in optic nerve laminar regions. Retinal ganglion cell (RGC) axonal structure and function in the optic nerve head (ONH) is predominantly supported by astrocytes and capillaries. There is good experimental evidence to demonstrate that RGC axons are perturbed in a non-uniform manner following ONH injury and it is likely that the pattern of RGC axonal modification bears some correlation with the quantitative properties of astrocytes and capillaries within laminar compartments. Although there have been some excellent topographic studies concerning glial and microvascular networks in the ONH our knowledge regarding the quantitati...
The microvasculature in the equine distal phalanx: implications for fracture healing. To describe the intra-osseous microvasculature of the distal phalanx of the equine forelimb with regard to its potential clinical relevance. Methods: Eleven clinically normal equine forelimbs were used from six adult horses (range: 4 to 18 years old) euthanatized for reasons unrelated to lameness. In each limb the median artery was catheterized at the level of the carpus and India ink was injected under constant manual pressure. The limbs were frozen and 5 mm thick sections of the foot were cut in the sagittal, coronal, or transverse planes on a band saw. The sections were fixed in 10% formali...
Allometry of left ventricular myocardial innervation. Body mass (BM) of terrestrial mammalian species ranges from a few grams in the case of the Etruscan shrew to a few tonnes for an elephant. The mass-specific metabolic rate, as well as heart rate, decrease with increasing BM, whereas heart mass is proportional to BM. In the present study, we investigated the scaling behaviour of several compartments of the left ventricular myocardium, notably its innervation, capillaries and cardiomyocytes. Myocardial samples were taken from 10 mammalian species with BM between approximately 2 g and 900 kg. Samples were analysed by design-based stereology and e...
Microvasculature of the suspensory ligament of the forelimb of horses. To determine the microvascular anatomy of the suspensory ligament of the forelimb of horses. Methods: 17 cadaveric forelimbs from 9 adult horses with no known history of forelimb lameness. Methods: The median artery of the forelimb was cannulated proximal to the antebrachiocarpal joint and injected with contrast medium for CT evaluation of the gross vasculature (n = 2) or India ink to evaluate the microvasculature (12). Routine histologic evaluation was performed on an additional 3 forelimbs to confirm the microvascular anatomy. Results: The vascular supply of the suspensory ligament of the fo...
Verrucous hemangioma with pseudoepitheliomatous epidermal hyperplasia in an adult horse. Verrucous hemangiomas are a rare specific variant of equine skin tumors not well described in the literature. An 8-year-old gelding presented a unilateral lesion on the pastern. Macroscopically, the mass showed a warty and verrucous surface with focal ulcerations. The histology showed a dermal proliferation of endothelial-layered capillaries and venules separated by a delicate stroma of scant fibroblasts and collagen deposition, with pseudoepitheliomatous hyperplasia (exuberant reactive irregular epithelial hyperplasia with tongue-like projections extending into the dermis, mimicking downgrowt...
Identification of target cells of a European equine arteritis virus strain in experimentally infected ponies. Currently, little is known on the cellular pathogenesis of equine arteritis virus (EAV). The purpose of the present study was to identify the target cells in ponies experimentally inoculated with EAV 08P178 (EU, clade-1). EAV-target organs (respiratory tissues with associated lymphoid tissues and large intestines), collected at 3 and 7 days post inoculation (dpi) and with virus titers≥10(5.0) TCID50/g, were processed with double immunofluorescence staining for the simultaneous detection of EAV N-protein and one of the following cell markers: CD172a (myeloid cells), CD3 (T lymphocytes), IgM (...
Distribution of venous remodeling in exercise-induced pulmonary hemorrhage of horses follows reported blood flow distribution in the equine lung. Exercise-induced pulmonary hemorrhage (EIPH), which has been reported in humans and a variety of domestic animals following strenuous exercise, is most often documented in racehorses. Remodeling of pulmonary veins (VR) in equine EIPH was recently described, suggesting that it contributes to the pathogenesis of the disease. The cause of VR is unknown. We tested the hypothesis that the development of VR follows pulmonary blood flow distribution, preferentially occurring in the caudodorsal lung region. Furthermore, we hypothesized that VR underpins development of the other lesions of EIPH patholo...
The evolution of epitheliochorial placentation. Epitheliochorial placentation is a derived condition and has evolved separately in strepsirrhine primates and laurasiatherians (pangolins, whales, and hoofed mammals). Usually it is associated with a long gestation period, small litters, and precocial young. Oxygen transfer is facilitated by indenting of the uterine and trophoblast epithelia by maternal and fetal capillaries, respectively. Histotrophic nutrition is important, and adaptations include areolas and hemophagous regions. In pigs and horses, for example, iron is transported as uteroferrin secreted from the uterine glands and taken up...
Exercise-induced pulmonary hemorrhage in horses: the role of pulmonary veins. While airway endoscopy and bronchoalveolar lavage are the methodsof choice for diagnosing exercise-induced pulmonary hemorrhage (EIPH), these techniques do not allow accurate evaluation of the severity of bleeding. EIPH pathology is characterized by occlusive remodeling of pulmonary veins. Affected veins have large collagen deposits in their walls, which reduces their lumens. In the caudodorsal regions, pulmonary vein wall remodeling is associated with hemosiderin accumulation, bronchial circulation angiogenesis, and fibrosis of the alveolar interstitium, bronchovascular bundle, septa, and ple...
Immunohistochemical analysis of MCT1 and CD147 in equine skeletal muscle fibres. Monocarboxylate transporter 1 (MCT1) and its ancillary protein CD147 facilitate efflux of lactate from the muscle. Expression of MCT1 and CD147 were studied with immunohistochemistry in type I, IIA, IIAB and IIB fibres of equine gluteal muscle. Staining intensity of MCT1 in the cytoplasm as well as in the membranes of fibre types decreased in the order I=IIA>IIAB>IIB and correlated with the oxidative capacity. Capillaries were pronounced in the MCT1 staining. CD147 antibody stained plasma membranes of all fibre types evenly, whereas the staining in the cytoplasm followed that of MCT1. In...
Regional distribution of collagen and haemosiderin in the lungs of horses with exercise-induced pulmonary haemorrhage. Regional veno-occlusive remodelling of pulmonary veins in EIPH-affected horses, suggests that pulmonary veins may be central to pathogenesis. The current study quantified site-specific changes in vein walls, collagen and haemosiderin accumulation, and pleural vascular profiles in the lungs of horses suffering EIPH. Objective: In the caudodorsal lung regions of EIPH-affected horses, there is veno-occlusive remodelling with haemosiderosis, angiogenesis and fibrosis of the interstitium, interlobular septa and pleura. Methods: Morphometric methods were used to analyse the distribution and accumula...
Histomorphological and immunohistochemical study of angiogenesis and angiogenic factors in the ovary of the mare. Cyclical ovaries of 18 mares were examined histologically and immunohistochemically for vascular endothelial growth factor A and B (VEGF A; VEGF B), angiopoietin1 and 2 (Ang1; Ang2), vascular endothelial growth factor receptor 1 and 2 (VEGF-R1; VEGF-R2), angiopoietin receptor (Tie2) and von Willebrand factor. The most intensive coexpression of the examined factors and receptors was detected in the periovulatory period, when a distinctive ovarian angiogenesis takes place, being essential for tertiary follicle maturation and for the endocrine function of the Corpus luteum. Based on the immunohis...
Equine laminitis: a journey to the dark side of venous. Equine laminitis is a crippling condition that continues to defy repeated efforts to delineate the precise mechanisms involved and develop effective therapeutic strategies for use in the clinic. In this article, the possible role of dysfunction of the laminar vasculature is discussed, with particular emphasis on the venous side of the laminar microvasculature and the possible role(s) that metabolic syndrome and thrombosis may play in the dysfunction observed in the laminar microvasculature during the development of laminitis.
Histological and immunohistochemical characterization of equine anovulatory haemorrhagic follicles (AHFs). Anovulatory haemorrhagic follicles (AHFs) are often the reason for ovulation failure in the mare. As the underlying factors that lead to AHF development are not well understood, it was of interest to investigate the vascularization of AHFs compared with normal follicles and corpora lutea (controls). In the present study, the ovarian cell populations investigated immunohistochemically included granulosa and luteal cells as well as various vascular structures. None of these cell types showed differences in the expression of vascular endothelial growth factor A (VEGF-A) between control ovaries co...
Fat embolism secondary to yellow fat disease in an Appaloosa horse. A 4-year-old female Appaloosa horse was referred to the Department of Comparative Pathology, Veterinary Faculty, with a history of colic and acute respiratory distress. At necropsy, gross lesions consisted of extensive firm, multinodular, hemorrhagic foci in fat tissues with yellow-brown discoloration. The most affected areas were peritoneal fat and perirenal, epicardial, and subcutaneous adipose tissues. Other findings were hepatic lipidosis and multiple 1-1.5 cm hemorrhagic foci scattered in both lungs. Histopathological examination revealed severe degeneration and necrosis of adipose tissue...
Intake and excretion of disodium monomethylarsonate in horses: a speciation study. Capillary electrophoresis coupled to inductively coupled plasma mass spectrometry was used in a speciation study on disodium monomethylarsonate (DS-MMA(V)) and its metabolites in horses, to which the drug was administered by intramuscular injection on five consecutive days at a single arsenic dosage of 270 mg day(-1). Samples of urine, whole blood, plasma, and mane hair were analyzed before, during, and after drug administration. The data show that blood clearing and urinary excretion of MMA is a fast process following first-order kinetics with biological half-lives of about 38 h and 44 h for ...
Measurement of equine laminar blood flow and vascular permeability by use of dynamic contrast-enhanced computed tomography. To define the reference range for laminar blood flow (BF) and vascular permeability (VPM) in horses without laminitis by use of dynamic contrast-enhanced computed tomography (CT). Methods: 9 adult horses that were not lame and had no abnormalities of the laminae or phalanges detectable via radiographic examination. Methods: Each horse was anesthetized by use of a routine protocol. Horses were placed in right or left lateral recumbency with the dependent forelimb in the CT gantry; only 1 limb of each horse was scanned. Serial 10-mm collimated transverse CT images were acquired at the same locat...
Effect of exercise on development of capillary supply and oxidative capacity in skeletal muscle of horses. To determine whether postnatal development of oxidative capacity and capillary supply of skeletal muscle is affected by various movement regimens in horses. Methods: 35 foals. Methods: Dutch Warmblood foals were allocated into 3 groups (box stall rest, box stall rest with training, and free pasture exercise). Training comprised an increasing number of gallop sprints from 1 week after birth to 22 weeks of age. From 22 to 48 weeks, the 3 groups were combined and allowed to exercise freely. Capillary supply (diffusion index [ie, area supplied by 1 capillary]), citrate synthase (CS) activity, and ...
Immunohistochemical localization of vascular endothelial growth factor (VEGF) and its two receptors (Flt-I and KDR) in the endometrium and placenta of the mare during the oestrous cycle and pregnancy. Polyclonal antisera for vascular endothelial growth factor (VEGF) and its two main receptor molecules, VEGF-I (Flt) and VEGF-II (KDR), were used in a conventional immunocytochemical staining method to localize these angiogenic ligand molecules in the endometrium and placenta of the mare during the oestrous cycle and pregnancy. The anti-VEGF and anti-Flt sera both labelled the lumenal and glandular epithelia of the endometrium throughout the oestrous cycle and both the invasive trophoblast cells of the endometrial cups and the non-invasive trophoblast of the allantochorion in pregnancy. The ant...
Cooling augments vasoconstriction mediated by 5-HT1 and alpha2-adrenoceptors in the isolated equine digital vein: involvement of Rho kinase. The vasculature of the equine digit fulfils an important role in thermoregulation. In other species, it has been found that cooling may enhance the response of cutaneous vessels to 5-hydroxytryptamine (5-HT) and alpha(2)-adrenoceptor agonists. Translocation of alpha(2)-adrenoceptors to the smooth muscle cell membrane, mediated by Rho kinase, is thought to be involved in the cooling-enhanced response in mouse tail arteries. However, little is known about the effect of cooling on 5-HT receptor function. The present investigation compared the response of 5-bromo-6-(2-imidazolin-2-ylamino) quinoxa...
Effects of chronic acetazolamide administration on fluid flux from the pulmonary vasculature at rest and during exercise in horses. Horses develop high pulmonary pressures during exercise, which force fluid out of pulmonary capillaries. Specific airway diseases in horses, especially those associated with hypoxaemia, hypercapnoea and acidosis may influence pulmonary haemodynamics and pulmonary interstitial fluid equilibrium. Objective: This study was designed to determine fluid flux (J(V-A) l/min) across the lung in exercising horses treated chronically with acetazolamide. Methods: Six horses were exercised on a treadmill until fatigue without (Con) and with chronic carbonic anhydrase (CA) inhibition (AczTr) and associated ...