Pathophysiology in horses involves the study of functional changes that occur in the body as a result of disease or injury. This field examines the mechanisms through which diseases develop and progress, as well as how they affect the body's normal physiological processes. In equine research, pathophysiology encompasses a wide range of conditions, including respiratory disorders, musculoskeletal injuries, gastrointestinal diseases, and metabolic syndromes. Understanding these processes helps in identifying potential therapeutic targets and developing effective treatment strategies. This page collects peer-reviewed research studies and scholarly articles that explore the underlying mechanisms, clinical manifestations, and implications of various pathophysiological conditions in equine health.
Spurlock GH, Landry SL, Sams R, McGuirk S, Muir WW.Plasma volume, extracellular fluid volume (ECFV), and total body water (TBW) were measured before and after endotoxin (Escherichia coli) administration in 6 conscious adult horses. Evan's blue dye, sodium thiocyanate, and antipyrine were the test substances used to estimate plasma volume, ECFV, and TBW, respectively. Pharmacokinetic analysis of plasma concentration vs time was used to determine changes in body fluid compartments. The pathophysiologic effects of endotoxin were monitored by clinical evaluation, blood chemical changes, and blood gas determinations. All horses became dyspneic with...
Davies JV, Gerring EL.Small intestinal ischaemia is a cause of pain in man and horses. Occlusion of the vascular supply to Thiry loops in experimental ponies caused severe discomfort and loss of motility within a few minutes but these effects could not be reproduced by a similar procedure in intact gut preparations. However, embolisation of the mural vascular network produced ischaemia of the small intestine of anaesthetised ponies which led to a cessation of motility in the affected segments, though unaffected segments became hypermotile with a characteristic motility pattern. These results suggest the need for re...
Reef VB.Cardiac disease in the equine neonate occurs infrequently. Murmurs are often heard in foals and are not considered significant unless they persist beyond 4 days of age. Congenital cardiac defects are the most common form of primary cardiac disease in the foal, with ventricular septal defects occurring most frequently. Other neonatal foal diseases such as ruptured bladders, white muscle disease, neonatal respiratory distress syndrome, and septicemia have secondary cardiac involvement.
Derksen FJ, Scott D, Robinson NE, Slocombe RF, Armstrong PJ.Pulmonary function and airway reactivity to IV histamine were measured in a group of ponies with a history of recurrent airway obstruction (heaves) and their age-, weight-, and gender-matched controls. Ponies were studied during a period of clinical remission (period A), after exposure to a barn environment (period B), and twice during a 2-week recovery phase (periods C and D). At periods A, C, and D, PaO2, dynamic compliance (Cdyn), pulmonary resistance, tidal volume, respiratory frequency, and the log dose of histamine required to reduce Cdyn to 65% of base-line value (log ED65Cdyn) of princ...
Barclay WP, Foerner JJ, Phillips TN.Axial sesamoid injuries were found in 4 of 18 horses with lateral condylar fractures of the metacarpus or metatarsus. The injuries appeared as axial sesamoid fractures or progressive demineralization of the axial border of one of the sesamoids. None of the horses with axial sesamoid injuries returned to performance soundness. Axial sesamoid injury appeared to be an indication of severe fetlock trauma due to condylar fracture. Such injuries appeared to indicate a poor prognosis for return to performance soundness.
Derksen FJ, Robinson NE, Armstrong PJ, Stick JA, Slocombe RF.We measured lung function and airway reactivity to histamine administered by aerosol in two groups of ponies. Principal ponies had a history of heaves, a disease characterized by recurrent airway obstruction when ponies are housed in a barn and fed hay; control ponies had no history of airway obstruction. Ponies were paired (principal and control) and measurements were made when principal ponies were at pasture and in clinical remission (period A), following barn housing when principal ponies had acute airway obstruction (period B), and after a further 1 and 2 wk at pasture (periods C and D). ...
Templeton CB, Bottoms GD, Fessler JF, Turek JJ, Boon GD.The objectives of this study were to determine the pathophysiological effects of increasing amounts of endotoxin administered intraperitoneally (IP) for 24 hr at which time an intravenous (IV) injection of endotoxin was given. The ability of flunixin meglumine (FM), a nonsteroidal antiinflammatory drug with antiprostaglandin activity, to provide protective effects was also determined. Eight ponies were divided into two groups of four ponies each; one group (untreated) received endotoxin only and the other group (treated) received endotoxin while being treated with flunixin. Hemodynamic and ser...
Miller PJ, Holmes JR.Beat-to-beat variation in the amplitude of the QRS waveform from 13 horses with second degree partial atrioventricular block was examined using an orthogonal lead (X,Y,Z) system. The peak positive deflections (XR, YR and ZR) and peak negative deflections (XQS, YS and ZQ) were regressed against PR and RR intervals. XQS was used to indicate that the peak negative deflection in X could have been a Q or S wave. XR and YR were directly related to PR (P less than 0.001) and XQS and YS were inversely related to PR (P less than 0.001). YR was also directly related to RR (P less than 0.001) but not so ...
Hines MT.The continued study of immunology and its relationship to diseases of the eye will hopefully give some insight into the pathogenic mechanisms of certain ocular diseases of many species, including the horse. It may lead to a better understanding of equine recurrent uveitis, a disease that has remained an enigma for years and that now appears to be an immunologic hypersensitivity response to a number of varied antigens. The precise mechanism of the inflammation is still unclear, and the immunologic response may be variable or mixed depending upon the inciting antigen. Other ophthalmic diseases i...
Cordy DR.Bacterial meningoventriculitis was studied in 26 neonatal ungulates. Preceded by a substantial bacteremia, usually due to Escherichia coli, the fibrinopurulent inflammation involved leptomeninges, choroid plexuses, and ventricle walls, but largely spared the neuraxial parenchyma. It is proposed that this surface-relatedness results from the transport of bacteria by monocytes of low bactericidal power, migrating by normal pathways to maintain significant surface populations of macrophages. The neuraxial parenchyma is spared because of its normal lack of a macrophage population. A similar pathog...
Vivrette SL, Reimers TJ, Krook L.Hypothyroidism was diagnosed in a 5-month-old Thorough-bred colt by clinical and clinico-pathology examinations, thyroid stimulating hormone response test and by microscopic evaluation of the thyroid gland. Skeletal lesions included delayed appearance of ossification centers and delayed development of bone in cartilage models, delayed closure of epiphyseal plates, transverse trabeculation in metaphyses, osteochondrosis dissecans and subchondral cysts.
Bayly WM, Grant BD, Breeze RG.Arterial blood gas and acid-base values during maximal exercise over a 1.2 km distance were recorded in four Thoroughbred horses before and after the chemical induction of pharyngeal lymphoid hyperplasia (PLH). Samples were collected after galloping 0.8 km and 1.2 km, immediately upon stopping and 5 mins after exercising. In only one horse was any difference noted in the pre and post PLH induction results. The horse was more hypercapnoeic at the 1.2 km mark and also took much longer to complete the gallop when it had PLH. However, it also had signs of lower respiratory disease. In the other ho...
Epstein V.Hyperkalaemia affected the equine myocardium. The minimum plasma potassium concentration required to induce electrocardiographic changes was 6.2 mmol/litre and severe cardiotoxic effects were observed at levels of 8.0 to 10.1 mmol/litre in this experimental situation. The most consistent sign of hyperkalaemia was broadening and flattening of the P wave, which was generally associated with a change in T waves in the chest lead from negative to positive. The more pronounced the hyperkalaemia, the less pronounced the P wave and the more peaked positive the T wave. Severe hyperkalaemia was associa...
Hatheway CH, Snyder JD, Seals JE, Edell TA, Lewis GE.Serum levels of equine-botulism antitoxin to toxin types A, B, and E were measured in four type-A botulism patients who had received equine-botulism antitoxin. High circulating levels capable of neutralizing in excess of 1 X 10(8), 9 X 10(7), and 6 X 10(6) 50% mouse lethal doses of toxin of types A, B, and E, respectively, were detected. There was little depletion of type-A antitoxin even though two of the patients had circulating type-A toxin before treatment. The half-life for antitoxin persistence for one patient was calculated as being 6.5, 7.6, and 5.3 days for antitoxin types A, B, and E...
Amis TC, Pascoe JR, Hornof W.The regional distribution of ventilation to perfusion ratios (VA/Q) in the lungs of 8 healthy standing Thoroughbred geldings (4.4 +/- 1.5 years, 465.7 +/- 46.6 kg) was studied, using steady-state inhalation and IV infusion of the radioactive gas krypton-81m. The VA/Q was uniformly distributed within a vertical lung strip centered over the 9th rib on the right side. Ventilation per unit of alveolar volume (V/VA) assessed from the clearance of inhaled radioactive gas in 5 horses increased from 0.49 +/- 0.13 (arbitrary units) in nondependent lung zones to 1.45 +/- 0.16 in dependent lung zones. Se...
Meschter CL, Maylin GA, Krook L.Three mature Thoroughbred geldings were given 13.63 mg phenylbutazone/Kg bodyweight intravenously for 3 days and repeated in one horse 4 days later. After 4, 7 and 10 days (double treatment), degeneration of the wall of small veins occurred in all horses. The veins were dilated and/or showed hyalin degeneration. The phlebopathy was interpreted to be paramount in phenylbutazone intoxication. All other manifestations, including erythro- and leukodiapedesis, submucosal edema and ulceration of the gastrointestinal mucosa, phlebothrombosis and significant changes in the hemogram and serum chemistry...
Miller PJ, Holmes JR.Systolic time intervals (STIs), isovolumic contraction time (ICT) and left ventricular ejection time (LVET) were recorded from seven horses with supraventricular arrhythmia. The STIs were measured over a number of beats (33 to 100) directly from the left ventricular (LV) and aortic (Ao) pressure contours which were recorded simultaneously using two catheter-mounted transducers. ICT was significantly (P less than 0.01) and directly related to beat-by-beat heart rate (HR = 60/pulse interval) and LVET was significantly (P less than 0.01) and inversely related to heart rate in each of five horses....
Burkhardt E, von Saldern F, Huskamp B.On clinical examination, a six-year-old Hassian gray gelding with a history of impaired performance, slight cough, colic, and edema of the ventral abdomen, prepuce and the legs had reduced skin turgor, pale mucous membranes, forced costoabdominal breathing, reduced venous return, enlarged lymph nodes, and splenomegaly. Hematologic findings revealed anemia, leukocytosis and a high percentage of monocytoid leukemic cells. Generalized lymphadenopathy, splenomegaly, ascites, hydrothorax, and a diffusely thickened gut wall were found at necropsy. Massive infiltration with monocytoid leukemic cells ...
Breeze RG, Legreid WW, Bayly WM, Wilson BJ.Perilla ketone was assessed for its usefulness as a model of equine restrictive pulmonary disease. Three ponies were given 18 mg/kg bodyweight synthetic perilla ketone in dimethyl-sulphoxide. Within 24 h of administration, respiratory rate, peak inspiratory and expiratory flow rates and minute volume were increased. By 48 h there was a significant decrease in tidal volume, and blood pH and base excess were also decreased but not outside normal limits. At necropsy there was congestion and oedema of the lungs. Histologically there was diffuse alveolar injury but no evidence of significant obstru...
Updike SJ.Equine tarsocrural collateral ligaments (CL) were dissected grossly. The areas of attachment and fiber arrangements were described for the long lateral CL, long medial CL, 3 short lateral CL, and 3 short medial CL. Sequential cutting of CL in any order indicated that the short medial CL were responsible for the snap-joint phenomenon observed at the equine tarsocrural joint.
Muir WW, McGuirk SM.Hemodynamic measurements were obtained from 17 horses with atrial fibrillation or flutter. Eight horses had atrial fibrillation of unknown duration. In 7 horses, atrial fibrillation developed during anesthesia. Atrial flutter developed during recovery from anesthesia in 2 horses. Hemodynamic measurements were considered normal in 7 of 8 conscious horses with atrial fibrillation. Cardiac output was decreased and pulmonary arterial blood pressure and right atrial pressure were increased in 1 conscious horse which had signs of congestive heart failure. Arterial blood pressure decreased in 5 of 7 ...
Garrett BJ, Holtan DW, Cheeke PR, Schmitz JA, Rogers QR.Dried tansy ragwort, which contains pyrrolizidine alkaloids, was fed as 10% of a complete diet to ponies, with and without a mixture of additives. The additives provided a dietary supplement equivalent to 1% cysteine, 0.75% butylated hydroxyanisole, 200 micrograms of vitamin B12/kg of feed, and 5 mg of folic acid/kg of feed. The additives did not alter tansy ragwort toxicity, as assessed by survival time, liver changes, sulfobromophthalein (BSP) clearance rate, serum gamma-glutamyl transpeptidase activity, and plasma amino acid patterns. In ponies fed tansy ragwort, BSP clearance rate was a se...
Breeze RG, Brown CM, Turk MA.3-methylindole was administered orally and intravenously to horses and ponies in order to determine the ability of this chemical to provide a model of equine pulmonary disease. Both routes produced a severe and sometimes fatal pulmonary disease, characterised by bronchiolitis. Clinical signs developed 48 to 72 h after dosing and were most severe between Days 4 and 10 post dosing. Intravenous administration of 3-methylindole produced lung injury more rapidly and at a lower dose rate than the oral route. It is suggested that the respiratory condition induced by this chemical could become a metho...
Stewart JH, Rose RJ, Young IH, Costas L.The distribution of ventilation-perfusion (VA/Q) ratios, before and after 100 per cent oxygen, was studied in an induced-premature foal at 4 h and again at eleven days of age, using the multiple inert gas elimination technique. The major finding was an absence of low VA/Q ratios when breathing air, indicating that low PaO2 in the neonatal period was totally attributable to the right-to-left shunt. At 4 h of age the PaO2 was 5.48 kPa and the right-to-left shunt represented 33.4 per cent of the cardiac output. At eleven days of age the PaO2 was 9.76 kPa and right-to-left shunt was 10.1 per cent ...
Paradis MR.Neoplasia of the central nervous system (CNS) can be divided into two main categories: nonpituitary CNS neoplasia and pituitary adenomas. Nonpituitary CNS neoplasias are generally compressive in nature, although some are also invasive. The majority of reported CNS tumors are secondary with only a few originating from nervous tissue. Pituitary adenomas predominantly occur in the pars intermedia of the older horse. Clinical signs, diagnostic testing, and possible treatments are discussed.
McClintock SA, Hutchins DR, Laing EA, Brownlow MA.Six adult horses with normal blood gas values, normal thoracic radiographs and free from overt signs of respiratory disease were confined in flotation tanks for periods from one to seven weeks. With one exception, they all coughed, had a variable amount of nasal discharge and, at autopsy, showed cranio-ventral alterations to their lungs which were characterised by patchy irregular areas of absorption atelectasis with or without an inflammatory reaction and an accompanying alveolar emphysema.
Kotzé SH, Soley JT.Spirally arranged bundles of sub-endothelial smooth muscle enfold the small to medium-sized submucosal veins in the equine ileocecal junction. The muscle bundles, accompanied by the endothelial lining, bulge into the lumen of the vessels, partly occluding the latter. Transmission electron microscopy of the muscle cells reveals features consistent with vascular smooth muscle ultrastructure. It is proposed that the throttling effect of the muscle bundles causes engorgement of the submucosal venous plexus, which then assists in the closing of the ileocecal orifice.
Bayly WM, Elfers RS, Liggitt HD, Brobst DF, Gavin PR, Reed SM.Acute renal failure was produced in 5 ponies which had received mercuric chloride (0.25 mg/kg) and potassium dichromate (3 mg/kg) intravenously each day for 5 days. Failure was due to acute nephrosis. This was indicated clinically by daily monitoring of the urine output, and B-mode ultrasonography of both kidneys after administering the fifth dose of the chemical agents. Euthanasia was performed after days 14, 9, 5, 8 and 5 respectively in each of the ponies, and the presence of renal disease confirmed by gross and microscopic post mortem examination. The nature of the kidney lesions observed ...
Mason DE, Ainsworth DM, Robertson JT.Responding to an equine respiratory emergency requires rapid localization of the problem and appropriate choices for therapy. Localizing the cause of respiratory distress is aided by history and thorough physical examination. When examining the patient, one must focus on the presenting signs as indicators of URT or LRT dysfunction. Table 3 summarizes the characteristic presenting signs based on respiratory tract location and suggests the initial treatment course indicated. Respiratory distress in the absence of signs related to the pulmonary system suggests inadequate oxygen delivery secondary...
Freeman DE, Kilgallon EG.To determine if venous strangulation obstruction (VSO) of the distal half of the equine small intestine would increase length of that segment. Methods: Halothane-anesthetized horses were assigned randomly to 3 groups of 5 horses: Group 1 (controls)--the entire small intestine was measured and rubber-shod clamps were applied to mark each end of the most distal 50% of the small intestine; Group 2--same procedure, except that VSO was induced in the distal 50% of the small intestine for 180 minutes; and Group 3--same initial procedure, except that VSO was induced for 90 minutes and followed by rep...
Menozzi A, Pozzoli C, Poli E, Delvescovo B, Serventi P, Bertini S.We investigated the effects of nonselective muscarinic antagonist (atropine) and of selective muscarinic subtype 1 (M1), 2 (M2), 3 (M3) antagonists (VU0255035, methoctramine, pFHHSiD, respectively) on the contractions evoked by electrical field stimulation (EFS) or by exogenous ACh in isolated horse bronchial muscle. Atropine completely inhibited neurogenic contractions in a concentration-dependent fashion, whereas selective muscarinic antagonists induced relevant modifications only at the highest concentration tested. Experiments with selective muscarinic antagonists in combination showed tha...
Belknap JK, Derksen FJ, Nickels FA, Stick JA, Robinson NE.Upper airway flow mechanics and arterial blood gas measurements were used to assess the efficacy of subtotal arytenoidectomy for treatment of induced left laryngeal hemiplegia in horses. Measurements were collected with the horses at rest, and trotting or pacing on a treadmill (6.38 degrees incline) at speeds of 4.2 and 7.0 m/s. Experimental protocols were performed after right common carotid artery exteriorization (baseline), after left recurrent laryngeal neurectomy (LRLN), and after left subtotal arytenoidectomy. At baseline, increasing treadmill speed progressively increased peak inspirato...
Attenburrow DP, Flack FC, Portergill MJ.Peak expiratory sound intensity (dB SPL), obtained by means of a radiostethoscope, and peak expiratory flow rate, obtained using a mask incorporating a thermistor flow sensor, were measured in six Thoroughbreds over a range of stride rates from 100 to 140 strides per min. The results show linear relationships between peak dB SPL and stride rate, peak expiratory flow rate and stride rate and also between peak expiratory flow rate and peak dB SPL. Peak expiratory dB SPL can therefore indicate peak expiratory flow rate.
van der Kolk JH, Wensing T, Kalsbeek HC, Breukink HJ.Lipid metabolism was studied in 21 horses with hyperadrenocorticism. To be included in the study, horses had to have histologic evidence of a pars intermedia adenoma found at necropsy (n = 9), a baseline ACTH concentration greater than 400 pg/ml (n = 6), or a plasma cortisol concentration 2 hours after i.v. administration of 25 IU of ACTH greater than 413 nmol/L (n = 16). Mean +/- SD baseline plasma cortisol concentration was 338 +/- 261 nmol/L (n = 20), mean +/- SD plasma insulin concentration was 97 +/- 54 microU/ml (n = 15), mean +/- SD plasma beta-hydroxybutyrate concentration was 1.8 +/- ...
Wyse CA, Love S, Christley RM, Yam PS, Cooper JM, Cumming DR, Preston T.Oxidative stress refers to an imbalance between the production of oxidising free radicals and the antioxidant defenses of the cell, and is associated with many pathogenic processes. Oxidative damage to cellular lipids results in the evolution of pentane and ethane gas, and detection of these hydrocarbons in the exhaled breath can be used to monitor in vivo oxidative stress. The aim of this study was to validate a gas chromatography (GC) method for measurement of breath pentane in the horse. The GC-system developed showed good specificity for discrimination of pentane from other breath hydrocar...
Stewart RH.Traumatic injury to the central nervous system causes immediate damage and sets in motion a complex series of pathophysiologic events that result in further neuronal injury. This secondary damage seems to be related to changes in blood flow and pressure on a systemic, regional, and microvascular level. Currently, there is evidence that these changes are, in part, mediated by endogenous opioids and arachidonic acid metabolites, namely thromboxane A2. Medical management is generally designed to intervene at one or more stages in this secondary cascade of events. Further research should lead us t...
Jackson DS.This paper reviews some of the biochemical modifications involved in fibrous tissue formation and discusses possible ways of controlling fibrosis in clinical conditions. The lathyritic agents, beta-aminoproprionitrile (BAPN) and penicillamine, appear in certain situations to be able to control fibrosis by blocking the biosynthesis of collagen. There are no compounds that are yet known which are capable of reversing pre-existing fibrosis and future research may perhaps be more profitably directed towards the stimulation of collagen catabolism rather than the inhibition of its synthesis.
Bailey SR, Andrews MJ, Elliott J, Cunningham F.Platelets are thought to play a role in equine diseases such as acute laminitis and verminous arteritis and may be involved in allergic disease. Mediators implicated in the pathophysiology of these conditions activate platelets and responses may be enhanced by interactions between mediators. The present study compared platelet aggregation, thromboxane production and release of radiolabelled [(3)H]5- HT in response to 5- HT, histamine, ADP and PAF alone and in combination in vitro.PAF caused concentration-related aggregation, [(3)H]5- HT release and thromboxane production. In contrast, ADP caus...
Harrison IW, Speirs VC, Braund KG, Steiss JE.Laryngeal hemiplegia was induced in 4 ponies via a left recurrent laryngeal neurectomy. Reinnervation of the denervated left cricoarytenoideus dorsalis muscle was then attempted using a muscle pedicle graft from the right cricoarytenoideus dorsalis muscle. In 3 ponies there was no return of abductor function and failure of graft survival. In the fourth pony there was return of abductor function along with survival of the muscle bridge, however, there was evidence of reinnervation across the neurectomy site. Muscle-to-muscle neurotization of the paralyzed equine larynx, utilizing the cricoaryte...
McKenzie EC, Firshman AM.Chronic exertional rhabdomyolysis represents a syndrome of recurrent exercise-associated muscle damage in horses that arises from a variety of etiologies. Major advances have been made in the understanding of the pathophysiology of this disease, and causative genetic defects have been recently identified for two conditions-polysaccharide storage myopathy of quarter horses, paints, warm bloods, and draft breeds. Dietary management in combination with a regular exercise regimen comprises the most effective means for control of clinical signs.
Olson NC.Effects of endotoxemia on lung water, hemodynamics, and gas exchange were determined in ponies breathing a mixture of halothane and 100% O2. Escherichia coli endotoxin was infused IV at 20 micrograms/kg of body weight for 1 hour followed by 10 micrograms/kg/hr the subsequent 4 hours. By 0.25 hour, endotoxin increased mean pulmonary artery pressure and pulmonary vascular resistance; this was followed by a return to base-line values by 0.5 and 1 hour, respectively. A 2nd increase in pulmonary vascular resistance occurred by 5 hours of endotoxemia. During the last 2 hours of endotoxin infusion, c...
Sembrat RF, Di Stazio J, Stremple JF.This study was conducted to determine the feasibility of using alert, conscious ponies as a model for septic shock in man. Ten ponies were given 0.7-5 X 10(9) organisms/kg of body weight of live E coli intravenously over one hour. All ponies died and exhibited signs of low cardiac output septic shock. significant decreases were found in cardiac index to 3.15 +/- 0.1 liters/min/m2 (P less than 0.05), white blood cell count to 1,930 +/- 100 cells/m3 (P less than 0.05), preterminal blood glucose to 75 +/- 5 mg/dl (P less than 0.05), PaO2 to 75.7 +/- 5.7 mm Hg (P less than 0.05), and pH to 7.15 +/...
Katz LM, Marr CM, Elliott J.To compare responses of equine digital arteries (EDAs) and veins (EDVs) to human-αcalcitonin gene-related peptide (hαCGRP), evaluate effect of the endothelium, and characterize receptors and sources of endogenous CGRP. Methods: Palmar digital vessels (5 to 9/experiment) from healthy adult horses killed at an abattoir. Methods: Vessel rings were mounted under tension in organ baths containing Krebs-Henseleit solution at 30 °C, with relaxation responses examined in vessels preconstricted with a thromboxane-mimetic (3 × 10(-8)M). Responses of endothelium-intact (+e) and -denuded (-e) EDAs and...
Clayton HM, Duncan JL, Dargie JD.The mechanisms involved in the pathophysiological disturbances associated with the presence of mature Parascaris equorum in the small intestine were investigated with radioisotopic techniques. The results suggested that, compared with worm-free controls, infected foals had a reduction in gut motility, an increase in the body solids ratio, a lowering of the body pool of albumin and a decreased ability to incorporate dietary methionine into plasma protein.
Weaver MP, Shaw DJ, Munaiwa G, Fitzpatrick DP, Bellenger CR.The objectives of this study were to topographically map pressure distribution across the palmar surface of the navicular bone in response to forces applied by the deep digital flexor tendon (DDFT), and evaluate the effect of raising the heels in vitro . A rig was constructed to hold an equine cadaver limb and apply controlled pressure to the navicular bone from the DDFT. Pressure-sensitive paper was used to quantify and map the resultant pressure. Changes in response to heel wedges (5 degrees and 10 degrees ) were recorded. The areas subject to maximum pressure from the DDFT were: the central...
Stitz L, Richt JA, Rott R.An overview of the pathogenesis of Borna disease (BD) in rats as a model for the naturally occurring infection in horses and sheep is presented. Our findings revealed a virus infection in which a virus-specific T cell-mediated immune response leads to disease. The immune cells capable of mediating this immunopathological reaction were defined as helper/inducer T cells. In all, the described observations indicate that CD4+ T cells and macrophages trigger a delayed-type hypersensitivity reaction and cause BD together with other cells of the immune system.
Littlejohn A, Bowles F, Maluleka W.The percentage venous admixture was calculated in 21 clinically normal horses and ponies and in 13 horses and ponies with chronic obstructure pulmonary disease (COPD). The oxygen contents of pulmonary end-capillary blood, arterial and mixed venous blood were calculated from blood and respiratory gas values and substituted in the shunt equation. The mean percentage venous admixture of the COPD subjects was significantly greater than that of the normal subjects. It was concluded that a larger proportion of alveoli in the lungs of COPD subjects were hypoventilated than that of alveoli of the norm...
Mallem MY, Thuleau A, Noireaud J, Desfontis JC, Gogny M.To investigate the role of superoxide anions in the lipopolysaccharide (LPS)-induced impairment of beta-adrenoceptor-mediated equine digital vein (EDV) vasodilation. Methods: EDVs isolated from forelimbs of 24 healthy adult horses. Methods: Endothelium-intact or endothelium-denuded EDV rings were incubated with or without LPS (10 microg/mL) of Escherichia coli (O55:B5) for 4 hours. Cumulative concentration-relaxation curves resulting from administration of isoprenaline, a nonselective beta-adrenoceptor agonist, or from administration of SR 58611A, a selective beta(3)-adrenoceptor agonist, were...
Jaeschke G, Rudolph R.Clinicopathological aspects of equine leukosis are discussed in a review. Among various other findings, only hypercalcaemia accompanied by paraneoplastic syndrome in the course of equine leukosis, increased values of alkaline phosphatase as usual in tumorous diseases, and hypalbuminaemia and hypergammaglobulinaemia in mesentric and intestinal forms of equine leukosis seem to have some diagnostic and pathogenetic significance. Changed values of further parameters are more or less non-specific concomitant signs, indicating that other organs or organ systems have been affected. However, in case o...
Deaton CM, Brown-Feltner H, Henley WE, Roberts CA, Lekeux P, Schroter RC, Marlin DJ.Pulmonary capillary stress failure, largely as a result of high pulmonary vascular pressures, has been implicated in the aetiology of EIPH. However, the role of the respiratory system in determining the magnitude of EIPH has received little attention. Objective: Horses breathing a gas of greater density than air will exhibit greater transmural pulmonary arterial pressures (TPAP) and more severe EIPH, and horses breathing a gas of lower density than air will exhibit lower TPAP and less severe EIPH, both compared with horses breathing air. Methods: Following a warm-up, 8 Thoroughbred horses were...
Svalastoga E.Microangiographical investigations of the navicular bone in horses with navicular disease show, compared to similar investigations of normal navicular bones, that, in general, the vascular pattern is preserved but the vessels are dilated with "pooling" of the contrast medium subchondrally under facies flexoria. Similar changes may be observed in cases of human arthrosis. The present investigation therefore supports the view that navicular disease is a disease which resembles arthrosis.
O'Callaghan MW.When performed on selected clinical cases, ventilation/perfusion scintigraphy provides valuable additional information on regional lung function that is not obtainable from conventional thoracic radiographs. This is particularly true of horses with EIPH, COPD, and those suspected of having some form of small-airway disease. For horses with EIPH, the presence of a perfusion deficit on the scan is considered a key prognostic sign, because it is likely in these cases that irreversible bronchial arterial takeover has occurred in the affected areas of lung. Findings from horses with COPD have impro...
Collins MH.The placenta provides many critical services to the developing foetus. Proper placental implantation, growth and function are necessary for normal foetal growth and development. Placental structure varies widely among species but all mammalian placentas have a convoluted materno-foetal interface that may be quite simple or highly complex; the more complicated interdigitations tend to characterise smaller placentas that have limited areas of contact between the placenta and the endometrium. The intimacy of the contact between maternal and foetal tissue varies from apposition only, as in the equ...
