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Topic:Blood Vessels
Blood vessels in horses are integral components of the circulatory system, responsible for the transportation of blood throughout the body. They consist of arteries, veins, and capillaries, each serving distinct functions in maintaining circulatory efficiency. Arteries carry oxygen-rich blood away from the heart to various tissues, while veins return deoxygenated blood back to the heart. Capillaries facilitate the exchange of nutrients, gases, and waste products between blood and tissues. The structure and function of equine blood vessels are subjects of study due to their role in health and disease, including conditions such as laminitis and equine metabolic syndrome. This page compiles peer-reviewed research studies and scholarly articles that explore the anatomy, physiology, and pathophysiology of blood vessels in horses.
Transrectal Doppler sonography of uterine and umbilical blood flow during pregnancy in mares. Transrectal color Doppler sonography was used to investigate uterine and umbilical blood flow during pregnancy (duration, 46-48 weeks) in four mares. The resistance index (RI) and blood flow volume (VOL) of the uterine arteries ipsilateral and contralateral to the conceptus, and the presence of an early diastolic notch in the Doppler wave, were evaluated every 4 week throughout pregnancy. Fetal blood flow was calculated semiquantitatively every 2 week (from 20 to 40 weeks), using the RI of the umbilical arteries. During the entire period of investigation, there were no significant individual v...
The effect of acetylsalicylic acid and captopril on uterine and ovarian blood flow during the estrous cycle in mares. In previous studies, transrectal color Doppler sonography was used to demonstrate an increase in genital blood flow resistance in subfertile mares. The objectives of the present study were to determine the effects of an anticoagulant (acetylsalicylic acid) and a vasodilator (captopril) on uterine and ovarian perfusion and plasma progesterone concentrations in cycling mares. From Day 1 to 11 of an estrous cycle (Day 0=day of ovulation following prostaglandin-induced luteolysis), five Trotter mares were given 2500 mg lactose, 2500 mg ASA, or 50 mg captopril twice daily in their feed (one compoun...
Evaluation of a vessel-sealing device for small intestinal resection and anastomosis in normal horses. To compare arterial bursting pressure after vessel closure using a vessel-sealing device (LigaSure Atlas Laparoscopic Sealer/Divider Instrument; Valleylab, Boulder, CO), a ligate-and-divide stapling device (LDS), and 2-0 polydioxanone suture. To evaluate the LigaSure Atlas as a method for ligation of the mesenteric vasculature during small intestinal resection in normal horses. Methods: Experimental study. Methods: Part A: jejunal segments from 19 horses. Part B: 6 horses, aged 1 to 18 years, weighing 330 to 509 kg. Methods: Part A: Jejunal segments with mesenteric vessels were collected from ...
Characterisation of the response of equine digital arteries and veins to substance P. Substance P (SP), a potent vasodilator, has been detected in equine digital sensory-motor nerves. The aim of the study was to characterise the functional responses of equine digital blood vessels to exogenous SP. Pre-constricted equine digital arteries (EDA) and veins (EDV) vasodilated in a biphasic, endothelium- and concentration-dependent manner to SP. A nitric oxide (NO) synthase inhibitor Nomega-nitro-L-arginine methyl ester hydrochloride (L-NAME; 300 microm) inhibited both phases of the relaxation response curve of EDAs to SP by >70%. In EDVs, the first relaxant phase to SP was largely...
Do Thoroughbred and Standardbred horses have similar increases in pulmonary vascular pressures during exertion? To test the hypothesis that the pulmonary vascular pressures of Thoroughbred and Standardbred horses behave similarly during exertion. Measurements were made on 5 Thoroughbred and 5 Standardbred horses on a treadmill at rest and during 3-minute exercise intervals at speeds predicted to produce 75%, 90%, and 100% maximal heart rate. Left forelimb acceleration, heart rate, esophageal pressure, and pulmonary artery pressure were measured continuously. Pulmonary capillary and wedge pressures were measured during intermittent occlusion of the pulmonary artery. Breathing rate and gait frequency were...
Characterization and comparison of the responses of equine digital arteries and veins to endothelin-1. To compare the responses of equine digital arteries (EDAs) and equine digital veins (EDVs) to endothelin-1 (ET-1) and determine the role of the endothelium and type of receptors involved in the modulation and mediation of those responses, respectively. Methods: 5 to 9 palmar digital vessels/experiment from 28 healthy horses. Methods: Rings of dissected vessels were mounted under tension between force transducer wires in organ baths containing Krebs-Henseleit solution at 30 degrees C. Responses of EDAs and EDVs (with intact [+e] or denuded [-e] endothelium) to cumulative concentrations of ET-1 ...
Comparative histology of the laminar bone between young calves and foals. Laminar bone or primary plexiform tissue, not Haversian bone, shows an alternative concentric pattern of laminar-bone units or plates around the bone marrow periphery of long bones, although the laminar bone is gradually replaced by osteons during the growth period. One laminar-bone unit is constructed with a hypercalcified line in the center, woven bone on both sides of the line, and lamellar bone with laminated appositional lines. Such a laminar bone showing a homogeneous calcification has been reported in young calves and some young large animals, but it has not been reported in foals altho...
Immunohistochemical study of equine endometrial extracellular matrix during the oestrous cycle. This study was designed to identify the distribution of type IV collagen, laminin, and fibronectin with an avidin-biotin method in sections of equine endometrial samples, fixed in Bouin's solution and embedded in paraffin wax. Thirty endometrial biopsies were collected at three different stages of the oestrous cycle. The basement membrane of luminal epithelium reacted positively with antibody against type IV collagen. Both type IV collagen and laminin were found in the basement membranes of endometrial glands, and fibronectin occurred diffusely in the interstitial tissue. Blood vessels express...
Inclined running increases pulmonary haemorrhage in the Thoroughbred horse. Capillary stress failure-induced (exercise-induced) pulmonary haemorrhage (EIPH) during intense running in horses is thought to involve both intravascular (i.e. mean pulmonary arterial pressure [Ppa] > 100 mmHg) and extravascular (e.g. negative inspiratory pressure swings) mechanisms. Objective: That inclined running would reduce breathing frequency (coupled to stride frequency) and increase tidal volume thus increasing lung volume changes and intrapleural pressure swings resulting in more pronounced EIPH. Methods: Six Thoroughbred horses were run to volitional fatigue (incremental step tes...
The cardiopulmonary effects of severe blood loss in anesthetized horses. To characterize the acute cardiopulmonary effects of severe hemorrhage in anesthetized horses. Methods: Prospective experimental study. Methods: Three geldings and six mares, aged 14.4 +/- 2.7 years, weighing 486 +/- 41 kg (range: 425-550 kg). Methods: Horses were anesthetized using xylazine, guaifenesin, ketamine and halothane or isoflurane. Cardiovascular variables, hematocrit, total solids, capillary refill time (CRT) and color of mucous membranes were measured as blood was collected from the carotid artery into sterile plastic bags. Arterial blood gas analysis was also performed. Results: ...
Effects of monoamines formed in the cecum of horses on equine digital blood vessels and platelets. To determine in vitro vasoactive potency of monoamines formed in the cecum and found in the systemic circulation of horses. Methods: Segments of digital blood vessels obtained from 6 healthy mixed-breed horses and ponies euthanatized at an abattoir and platelets isolated from 4 healthy ponies. Methods: Paired rings of digital artery and vein from the same horse were examined, and isometric tension was recorded. Concentration-response curves for tryptamine (TRP), tyramine (TYR), phenylethylamine (PEA), isoamylamine (IAA), and isobutylamine (IBA) were obtained. Vasoconstrictor mechanisms were in...
Intravascular papillary endothelial hyperplasia of the conjunctiva in a horse. Vascular tumors of the conjunctiva in the horse are rare. We present a unique case of an intravascular papillary endothelial hyperplasia of the conjunctiva. Methods: Horse. Methods: Case report. A 6-year-old-mare presented with a red mass in the conjunctiva of the left eye. After complete ophthalmologic examination the lesion was excised. The tissue was processed for light microscopy and studied histopathologically. Results: Pathologic examination revealed a nonencapsulated vascular lesion composed of confluent vascular spaces filled by multiple papillary structures composed of a central colla...
Muscarinic receptor subtypes mediate vasorelaxation in isolated horse deep dorsal penile vein. To investigate the effect of acetylcholine (ACh) on horse deep dorsal penile vein and to characterize the muscarinic receptor subtypes involved in this response. Methods: Vein rings were mounted in an organ bath chamber, and the isometric tension was recorded. Results: In phenylephrine-contracted veins, ACh (1 nM to 1 microM) induced endothelium-dependent relaxation. The muscarinic receptor antagonist, atropine, produced parallel rightward shifts of the ACh response curves (pA2 = 10.04; pK(B) = 9.98). Carbachol (10 nM to 100 microM) also evoked relaxation in the vein segments, but showed a low...
Transrectal Doppler sonography of uterine blood flow during early pregnancy in mares. Transrectal color Doppler sonography was used for the noninvasive investigation of uterine blood flow in five mares. Both the left and right uterine arteries were scanned to obtain blood flow velocity waveforms during two consecutive estrous cycles and two early pregnancies in each mare. Blood flow was expressed as the time-averaged maximum velocity (TAMV) and the resistance index (RI). In all pregnancies the embryonic vesicle could be detected for the first time on Day 11 (day of ovulation: Day 0). No differences in mean TAMV and RI values of both uterine arteries were observed in comparison ...
Evaluation of beta3-adrenoceptor-mediated relaxation in intact and endotoxin-treated equine digital veins. To investigate the functional expression of beta3-adrenoceptors (beta3-ARs) in equine digital veins (EDVs) and to examine whether beta3-AR relaxation was altered in EDVs incubated with endotoxin. Methods: Forelimbs obtained from 30 horses. Methods: Forelimbs were obtained from horses in an abattoir. Equine digital veins were carefully removed from distal portions of the forelimbs. Rings of dissected EDVs were mounted in 5-mL organ baths to record isometric tension in the presence of various beta3-AR agonists (SR 58611A, ZD 2079, and ZM 215001). Results: In intact EDVs, isoprenaline, SR 58611A,...
[The occurrence of hemodynamic effective elements in the intestinal blood vessel system]. Arterioles, precapillary sphincters, capillary endothelium, and pericytes probably regulate the blood flow in the intestinal microvascular bed similar to other regions of the body because of their equipment with contractile filaments. Only throttle veins with their arrangement of pools and their characteristics probably exert influence on the hemodynamic qualities of the blood flow in the intestinal mucosa.
Nitric oxide, inducible nitric oxide synthase and inflammation in veterinary medicine. Inflammation is a process consisting of a complex of cytological and chemical reactions which occur in and around affected blood vessels and adjacent tissues in response to an injury caused by a physical, chemical or biological insult. Much work has been performed in the past several years investigating inducible nitric oxide synthase (NOS, EC 1.14.13.39) and nitric oxide in inflammation. This has resulted in a rapid increase in knowledge about iNOS and nitric oxide. Nitric oxide formation from inducible NOS is regulated by numerous inflammatory mediators, often with contradictory effects, dep...
Uptake of 5-hydroxytryptamine by equine digital vein endothelial cells: inhibition by amines found in the equine caecum. 5-hydroxytryptamine (5-HT; serotonin) is a potent vasoconstrictor of equine digital blood vessels and has been implicated in the pathogenesis of acute laminitis. Objective: The aims of this study were firstly to examine whether cells of the digital blood vessel wall exhibited an active uptake mechanism for 5-HT and to characterise its efficiency; and secondly, to study the potential inhibitory effect on this process of other amines, produced in the equine caecum. Methods: Confluent monolayers of equine digital vein endothelial cells (EDVEC) and equine digital vein smooth muscle cells (EDVSMC) ...
Identification and quantification of amines in the equine caecum. Acute laminitis has been associated with the release of compounds, as yet unidentified, produced by hindgut fermentation which affect blood flow to the digit. The objectives of this study were to identify amine compounds in equine caecal and colonic contents, some of which are known to have vasoactive properties. In addition, the concentrations of amines in caecal contents of horses fed either grass or hay diets were compared. Fifteen amines were identified in equine hindgut contents in concentrations greater than 1 microM. The caecal concentrations of phenylethylamine, isoamylamine, cadaverin...
Angiogenesis and vascular endothelial growth factor expression in the equine corpus luteum. Precise pharmacological control of the corpus luteum is important in the manipulation of the oestrous cycle in mares. Angiogenesis plays a key role in the growth and regression of the corpus luteum; therefore, influencing the vasculature of the corpus luteum may offer a novel method for controlling its lifespan. In the present study, changes in angiogenesis and vascular expression of endothelial growth factor (VEGF) were evaluated throughout the luteal phase and after PGF(2alpha)-induced luteolysis. Corpora lutea were collected from mares in the early luteal phase (days 3-4), mid-luteal phase ...
Seasonal serum concentrations of melatonin in cycling and noncycling mares. To determine whether secretory patterns of melatonin change throughout the seasons in mares, blood samples were drawn byvenipuncture from nine mares at noon and midnight for five successive days at monthly intervals from August through July at the University of Missouri in Columbia, MO. In addition, during September, December, March, and June, blood samples were drawn from indwelling catheters at 2-h intervals for 48 or 72 h. Mares were predominantly Quarter Horses weighing approximately 450 kg and ranged from 3 to 12 yr of age. Mares were housed in outdoor paddocks with three-sided run-in she...
Evaluation of a combined laser Doppler flowmetry and iontophoresis technique for the assessment of equine cutaneous microvascular function. A combined laser Doppler flowmetry and iontophoresis (LDFI) technique, used routinely to assess human microvascular function, was evaluated as a noninvasive technique for assessment of equine microvascular function, to facilitate the study of diseases such as laminitis. Baseline and vasoactive agonist-induced (acetylcholine and nitroprusside) microvascular flux was quantified at 2 sites (on the dorsal pastern adjacent to the coronary band and over the gluteals) in 6 clinically normal horses on 5 or 6 separate occasions under standardised conditions. Both agonists significantly increased microv...
Thermoregulatory-induced compromise of muscle blood flow in ponies during intense exercise in the heat: a contributor to the onset of fatigue? Cardiac output (Q) and tissue blood flows (BF) were measured in four ponies at rest, after 30 min of moderate exercise (ME) (approximately 30% VO2max) and following moderately intense exercise (M-IE) (approximately 65%) until fatigue, in a mildly hot (MH) environment (dry bulb temperature = 41 degrees C, wet bulb temperature = 27.5 degrees C). Exercise at both intensities resulted in increases in Q (15.6 +/- 1.7 [rest] vs. 35.8 +/- 2.6 [ME] vs. 48.6 +/- 3.9 [M-IE] l/min) and VO2 (4.7 +/- 0.9 vs. 24.5 +/- 1.2 vs. 55.8 +/- 5.8 ml/kg/min). When compared to ME, M-IE resulted in decreases in BF to ...
Equid herpesvirus 1 infection of endothelial cells requires activation of putative adhesion molecules: an in vitro model. Antisera to activated equine endothelial cells, which detected surface molecules of 116 kD, 97 kD, 42 kD and 38 kD, were made to investigate the role of endothelial adhesion molecules in equid herpes virus 1 infection. These putative adhesion molecules could be induced by 17-beta oestradiol, chorionic gonadotrophin, or IL-2, as well as by LPS and PWM. In an in vitro flow system, using equine veins or arteries, equid herpesvirus 1 in leucocytes was only transferred to infect endothelial cells if both leucocytes and endothelial cells expressed these surface molecules. Blocking of the membrane mo...
Metastatic melanoma in horses. The clinical and pathologic findings are reviewed for 14 horses with metastatic melanoma. All were older gray horses, with an average age of 16 years. The most common sites of primary tumors were the ventral tail, perineum, and parotid salivary gland. Metastases were found in multiple locations and caused a variety of clinical syndromes. The most common sites for metastases were the lymph nodes, liver, spleen, skeletal muscle, lungs, and surrounding or within blood vessels throughout the body. Many of the horses had dermal melanomas for years (range 1-6 years) before succumbing to metastatic d...
Characterization of morphology and angiogenesis in follicles of mares during spring transition and the breeding season. The mare is a seasonal breeder and undergoes a period of ovarian transition in spring between winter anoestrus and cyclicity. During spring transition LH concentrations are low and many mares have successive large anovulatory follicular waves which reach the size of preovulatory follicles. Follicular angiogenesis is essential for growth and health of preovulatory follicles. The aim of the present study was to investigate the morphology and vascularity of transitional anovulatory follicles. On gross inspection, the wall of transitional follicles was visibly less well vascularized than that of p...
A study on the pathogenesis of equine sesamoiditis: the effects of experimental occlusion of the sesamoidean artery. In this study the potential role of circulatory disturbances in the pathogenesis of sesamoiditis was investigated by studying the clinical and histological effects of experimental occlusion of the sesamoidean artery, which is the main nutrient artery of the proximal sesamoid bone (PSB). For this purpose, five adult Dutch Warmblood horses were used in which the sesamoidean artery was occluded with polyvinyl alcohol foam particles. Bone labelling was carried out with oxytetracycline and calcein. All animal were checked clinically three times a week and radiographically at days 14, 21, 28 and 35....
Does haemorheology explain the paradox of hypoxemia during exercise in elite athletes or thoroughbred horses? Exercise-induced arterial hypoxemia (EIAH), i.e., a significant drop of O2 arterial partial pressure during sea level exercise, has been shown in both aerobically trained athletes and athletic animal species. The mechanisms potentially involved include ventilation/perfusion inequality and/or pulmonary diffusing capacity limitation. In thoroughbred horses, EIAH is going with pulmonary haemorrhage (EIPH). Stress failure of pulmonary capillaries leading to diffusion limitation has been proposed. Indeed, during intense exercise, the increased cardiac output and blood viscosity combine to rise capi...
Equine endotoxemia: pathomorphological aspects of endotoxin-induced damage in equine mesenteric arteries. To evaluate the effects of endotoxin on the morphology of the equine mesenteric vasculature, each of two thoroughbred horses were given two intravenous injections (24 h apart) of a sublethal dose of endotoxin (10 microg/kg). Each injection produced results similar to those of clinical cases of equine colic with obstructive nature of the loop of bowel: diarrhoea within 2 h after administration, followed by cessation of both faecal excretion and sounds of intestinal peristalsis. The most prominent morphological change was the development of moniliform appearance of small mesenteric arteries, in ...
Uterine and ovarian blood flow during the estrous cycle in mares. Uterine and ovarian blood flow was investigated in four mares during two consecutive estrous cycles using transrectal color Doppler sonography. The uterine and ovarian arteries of both sides were scanned to obtain waves of blood flow velocity. The pulsatility index (PI) reflected blood flow. There were significant time trends in PI values of all uterine and ovarian blood vessels during the estrous cycle (P < 0.05). PI values did not differ between the uterine arteries ipsi- and contralateral to the corpus luteum or the ovulatory follicle. PI values of the uterine arteries showed a wave shap...
