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Topic:Platelets

Platelets are small, anucleated cell fragments derived from megakaryocytes in the bone marrow, playing a key role in hemostasis and thrombosis in horses. They contribute to the formation of blood clots by adhering to the site of vascular injury, aggregating with one another, and facilitating the coagulation process. In equine medicine, platelet count and function are important parameters in assessing bleeding disorders and thrombotic conditions. Variations in platelet count can indicate underlying health issues, such as inflammation, infection, or bone marrow disorders. This page compiles peer-reviewed research studies and scholarly articles that explore the physiology, pathology, and clinical implications of platelets in equine health.
Granules of blood eosinophils are stained directly by anti-immunoglobulin fluorescein isothiocyanate conjugates.
American journal of veterinary research    November 1, 1983   Volume 44, Issue 11 2060-2063 
Floyd K, Suter PF, Lutz H.Direct staining of the granules of blood eosinophils by anti-immunoglobulin fluorescein isothiocyanate (FITC) conjugates was observed when feline blood smears were tested for presence of feline leukemia virus (FeLV) antigen by immunofluorescent antibody. When blood smears of other species including swine, horses, cattle, dogs, sheep, birds, and human beings were examined, direct staining of eosinophils by FITC conjugates was also detected. This FITC staining was restricted to eosinophils and was not observed in neutrophils, lymphocytes, and platelets. Direct FITC staining of eosinophils does n...
Disseminated intravascular coagulation in experimental intestinal strangulation obstruction in ponies.
American journal of veterinary research    November 1, 1983   Volume 44, Issue 11 2115-2122 
Pablo LS, Purohit RC, Teer PA, Newton JC, Hammond LS.Total strangulation obstruction of the caudal part of the jejunum was induced in 3 groups (each of 3 ponies) for 2, 4, and 6 hours. Coagulation tests which included blood platelet counts, prothrombin time, activated partial thromboplastin time, activated coagulation time, plasma fibrinogen level, and fibrin/fibrinogen degradation products assay were performed at specified time intervals for 1 week or until death of the experimental ponies. Another 3 ponies (sham-operated) were similarly treated, except that intestinal strangulation obstruction (ISO) was not induced. Necropsy was done on ponies...
Modulation of equine platelet function by diethylcarbamazine (DEC).
The American journal of pathology    October 1, 1983   Volume 113, Issue 1 1-7 
Kowalski KA, McConnell LA, Sadoff DA, Leid RW.Equine platelets, when treated with the anthelmintic drug diethylcarbamazine (DEC), gave a dose-dependent release of radiolabeled serotonin without concomitant aggregation. At levels of the drug that gave only minimal release of radiolabel, marked dose-dependent inhibition of platelet aggregation to three of four platelet agonists tested--adenosine diphosphate (ADP), collagen, and arachidonic acid--was observed. With ADP, inhibition was observed to be reversed by removal of DEC prior to agonist challenge. However, with collagen, inhibition was only partially reduced by prior removal of DEC; wh...
Idiopathic thrombocytopenic purpura in two horses.
Journal of the American Veterinary Medical Association    August 1, 1983   Volume 183, Issue 3 328-330 
Larson VL, Perman V, Stevens JB.No abstract available
Properties and distribution of phosphatidylinositol-specific phospholipase C in human and horse platelets.
Biochimica et biophysica acta    July 12, 1983   Volume 752, Issue 2 329-338 doi: 10.1016/0005-2760(83)90131-5
Siess W, Lapetina EG.Phospholipase C has been studied in homogenates, total particulate and soluble fractions of horse and human platelets. This enzyme, assayed with exogenous L-3-phosphatidyl[14C]inositol, is predominantly localized in the soluble fraction and its distribution parallels that of lactate dehydrogenase. A small percentage of activity present in the particulate fraction seems to be due to contamination with soluble enzyme. Enzyme from horse and human platelets appears identical, having a Km of 0.10-0.15 mM, acid pH optimum (pH 5.5) and showing Ca2+-dependency and weak inhibition by deoxycholate. Anal...
Aggregation of equine platelets by PAF (platelet-activating factor).
Inflammation    June 1, 1983   Volume 7, Issue 2 197-203 doi: 10.1007/BF00917823
Suquet CM, Leid RW.Platelet-activating factor (PAF), a lipid released as a result of immediate allergic reactions from basophils and mast cells as well as by a variety of other cell types and stimuli, is one of the most potent platelet agonists and hypotensive agents known. Equine platelets stimulated over a wide range of PAF concentrations aggregated in a time- and dose-dependent manner. Maximum aggregation was observed at concentrations of PAF as low as 3.58 x 10(-14) M with platelet-rich plasma (PRP) and 3.58 x 10(-16) M with washed platelets. Furthermore, the aggregation observed did not appear to be breed-d...
Comparative effects of phenylbutazone, naproxen and flunixin meglumine on equine platelet aggregation and platelet factor 3 availability in vitro.
Canadian journal of comparative medicine : Revue canadienne de medecine comparee    April 1, 1983   Volume 47, Issue 2 172-179 
Johnstone IB.Nonsteroidal anti-inflammatory drugs are commonly used in the treatment of inflammatory conditions, and have potential value in the treatment of thrombotic disease in the horse. This study compares the potency of three nonsteroidal anti-inflammatory drugs phenylbutazone, naproxen (equiproxen) and flunixin meglumine (banamine) with respect to their effects on equine platelets. Two functional responses of horse platelets were evaluated in vitro: their ability to aggregate and their ability to make available platelet factor 3 procoagulant activity. Flunixin at a concentration of 10(-6) M signific...
The effects of dipyridamole on TXA2 formation by horse platelet microsomes.
Prostaglandins, leukotrienes, and medicine    February 1, 1983   Volume 10, Issue 2 179-185 doi: 10.1016/s0262-1746(83)80008-0
Katano Y, Imai S.The effects of dipyridamole on thromboxane A2 formation by horse platelet microsomes were studied in comparison with those of imidazole, a prototype inhibitor of TXA2 synthetase and nifedipine, a calcium antagonistic vasodilator. Thromboxane A2 was synthesized by incubating PGH2 with horse platelet microsomes and was assayed on the superfused rabbit aorta. Dipyridamole induced as strong an inhibition of TXA2 synthesis as imidazole, while nifedipine was without effects. The possible beneficial clinical outcomes of this effect of dipyridamole are discussed.
Platelet-activating factor stimulates metabolism of phosphoinositides in horse platelets: possible relationship to Ca2+ mobilization during stimulation.
Proceedings of the National Academy of Sciences of the United States of America    February 1, 1983   Volume 80, Issue 4 965-968 doi: 10.1073/pnas.80.4.965
Billah MM, Lapetina EG.Stimulation of horse platelets with platelet-activating factor (PAF) induces a rapid degradation of phosphatidylinositol 4,5-bisphosphate [PtdIns(4,5)P2]. Addition of 0.1 microM PAF for 5 sec to platelets prelabeled with 32P induces a 50% loss of [32P]PtdIns(4,5)P2. 32P-Labeled phosphatidylinositol 4-monophosphate (PtdIns4P) and [32P]phosphatidylinositol (PtdIns) also are decreased, albeit at a slower rate. Loss of 32P radioactivity correlates with a net loss of fatty acids from both polyphosphoinositides. Stimulation of platelets with PAF also produces formation of [32P]phosphatidic acid and ...
Relapsing idiopathic thrombocytopenia in a horse.
Equine veterinary journal    January 1, 1983   Volume 15, Issue 1 73-75 doi: 10.1111/j.2042-3306.1983.tb01715.x
Morris DD, Whitlock RH.TEIROMBOCYTOPENIA can be caused by failure of production or increased destruction of platelets, resulting in a bleeding diathesis, characterised by mucosal petechiac and haemorrhage into various organs. In humans, some drugs (cg, phenylbutazone and chloramphenicol) cause idiosyncratic marrow suppression and subsequent thrombocytopenia. Bone marrow suppression is also well documented in humans and small animals receiving cytotoxic drugs (Calabresi 1979; MacEwen 1980). Decreased megakaryocytic proliferation is rarely recognised in large animals. The most prevalent causes of thrombocytopenia are ...
Circulating endotoxin-like substance(s) and altered hemostasis in horses with gastrointestinal disorders: an interim report.
American journal of veterinary research    December 1, 1982   Volume 43, Issue 12 2233-2238 
Meyers K, Reed S, Keck M, Clem M, Bayly W.Twenty-three horses with clinical signs of gastrointestinal disease were evaluated once or serially during the course of the disease for the presence or absence of circulating endotoxin-like substances (ET+ or ET-) and whether the horses were negative, positive, or very positive for serum fibrin/fibrinogen degradation products (FDP-, FDP+, or FDP++). In addition, platelet count, activated partial thromboplastin time (APTT), and 1-stage prothrombin time (OSPT) were measured. When examined initially, 5 horses were ET-/FDP-, 8 were ET-/FDP+, 7 were ET+/FDP-, 3 were ET+/FDP+, and none was ET+/FDP+...
Platelet-activating factor stimulates the phosphatidylinositol cycle. Appearance of phosphatidic acid is associated with the release of serotonin in horse platelets.
The Journal of biological chemistry    July 10, 1982   Volume 257, Issue 13 7314-7317 
Lapetina EG.The addition of platelet-activating factor to horse platelets prelabeled with (32P)orthophosphate induces the rapid formation of [32P]phosphatidic acid. This is subsequently followed by a considerable increase in the labeling of phosphatidylinositol. Activation of the formation of phosphatidic acid by platelet-activating factor is evident at a concentration of 1 nM, is maximal at 0.1 microM, and independent of the presence or absence of plasma in the medium. In horse platelets prelabeled with [14C]arachidonic acid, platelet-activating factor stimulates the rapid formation of [14C]phosphatidic ...
Idiopathic thrombocytopenic purpura in the horse.
Journal of the American Veterinary Medical Association    June 15, 1982   Volume 180, Issue 12 1422-1424 
Byars TD, Greene CE.No abstract available
Haematological changes during development of acute laminitis hypertension.
Equine veterinary journal    October 1, 1981   Volume 13, Issue 4 240-242 doi: 10.1111/j.2042-3306.1981.tb03506.x
Moore JN, Garner HE, Coffman JR.Experimental carbohydrate overload of 15 horses resulted in consistent haematological changes during development of laminitis hypertension. Significant alterations in packed cell volume, leucocyte differential count, serum glucose levels and protein values occurred before onset of Obel grade 3 lameness and hyperkinetic circulatory state. Blood platelets were significantly decreased 8 h after the onset of severe lameness. Findings in this study were indicative of haemoconcentration due to compartmental fluid shifts and leucocytic stress response consistent with increased circulating adrenogluco...
The interaction of equine platelet tropomyosin with skeletal muscle actin.
The Journal of biological chemistry    July 25, 1981   Volume 256, Issue 14 7257-7261 
Côté GP, Smillie LB.Whereas skeletal muscle tropomyosin binds strongly to muscle F-actin in a buffer containing 30 mM KCl and 1-2 mM free Mg2+, equine platelet tropomyosin only binds stoichiometrically (1 tropomyosin molecule per 6 actin monomers) at higher Mg2+ concentrations (7-8 mM free Mg2+). At low free Mg2+ concentrations (1.5 mM) the binding of the platelet protein is only marginally increased by raising the KCl concentration to an optimal value (0.10-0.20 M). This weaker binding can be attributed to the relatively poor head-to-tail polymerization of platelet tropomyosin and its fewer actin-binding sites. ...
Idiopathic thrombocytopenia in a mare.
Modern veterinary practice    May 1, 1981   Volume 62, Issue 5 392 
Hammill D, Helton M.No abstract available
Effect of aspirin on haemostasis in the horse.
Research in veterinary science    March 1, 1981   Volume 30, Issue 2 241-242 
Judson DG, Barton M.No abstract available
Hemostasis and bleeding disorders.
Veterinary medicine, small animal clinician : VM, SAC    July 1, 1980   Volume 75, Issue 7 1157-1164 
Coffman J.No abstract available
Clinical pharmacology of salicylates.
Journal of the American Veterinary Medical Association    January 1, 1980   Volume 176, Issue 1 65-66 
Davis LE.No abstract available
Identification and genetics of horse lymphocyte alloantigens.
Immunogenetics    January 1, 1980   Volume 11, Issue 5 499-506 doi: 10.1007/BF01567818
Bailey E.Six hundred horses were tested with lymphocytotoxic antisera derived from 550 parous mares and 58 antisera produced by alloimmunization with horse blood cells. Seven equine lymphocyte specificities were identified using correlation analysis of the test data, absorption analysis and lysostripping. These specificities are expressed on lymphocytes and platelets, but not on red blood cells (RBC). Therefore, these specificities do not appear to be products of any of the eight known blood group systems of the horse. The distribution of these specificities in 113 Thoroughbred horses and 57 Arabian ho...
Phenylbutazone inhibition of equine platelet function.
American journal of veterinary research    February 1, 1979   Volume 40, Issue 2 265-270 
Meyers KM, Lindner C, Katz J, Grant B.Nonsteroidal anti-inflammatory drugs impair platelet aggregation and secretion in man, pigs, and rabbits and inhibit platelet thromboxane/prostaglandin synthesis. The present investigation studied the effects of phenylbutazone on platelet aggregation and bleeding times in the horse. Aggregation responses to adenosine diphosphate and collagen were markedly impaired 15 minutes and 2 hours after treatment, but 4 hours after treatment, platelet responses approximated those prior to treatment. The in vivo effect of phenylbutazone correlated with its plasma concentrations. Phenylbutazone, like aspir...
Dipyridamole and platelet function.
Lancet (London, England)    December 9, 1978   Volume 2, Issue 8102 1257-1259 
No abstract available
Platelet tropomyosin: lack of binding to skeletal muscle troponin and correlation with sequence.
FEBS letters    October 1, 1978   Volume 94, Issue 1 131-135 doi: 10.1016/0014-5793(78)80922-3
Côté GP, Lewis WG, Pato MD, Smillie LB.No abstract available
[Comparative study of six methods for lymphocyte isolation from several mammalian sources and determination of their carbohydrate composition (author’s transl)].
Revista espanola de fisiologia    September 1, 1978   Volume 34, Issue 3 339-344 
Hueso P, Rocha M.The present paper deals with a comparative study on six methods for isolation of peripheral blood lymphocytes from various mammalian sources: Bos taurus L. (adult cow), Equus caballus L. (adult horse), Equus asinus L. (adult and young donkeys) and Sus scropha L. (adult pig). The following systems were used: a) Filtration through sand columns (a modification of Blaszczyszyn's method); b) Sodium metrizoate and "Ficoll 400" c) "Lymphoprep"; d) "Urovison" and dextran T150 (a modification of GILI et al.'s method); e) "Urografin" and dextran T150; f) "Ficoll-Paque". The final preparation of lymphocy...
Comparison of the effects of prostacyclin (PGI2), prostaglandin E1 and D2 on platelet aggregation in different species.
Prostaglandins    September 1, 1978   Volume 16, Issue 3 373-388 doi: 10.1016/0090-6980(78)90216-2
Whittle BJ, Moncada S, Vane JR.The activity of prostacyclin (PGI2), PGE1 or PGD2 as inhibitors of platelet aggregation in plasma from human, dog, rabbit, rat, sheep and horse was investigated. Prostacyclin was the most potent inhibitor in all species. PGD2 was a weak inhibitor in dog, rabbit and rat plasma whereas PGE1 and prostacyclin were highly active. Theophylline or dipyridamole potentiated the inhibition of human platelet aggregation by prostacyclin, PGE1 or PGD2. Compound N-0164 abolished the inhibition by PGD2 of human platelet aggregation but did not inhibit the effects of PGE1 or prostacyclin. The results suggest ...
Effect of exercise on platelet size and number in ponies.
The Veterinary record    December 10, 1977   Volume 101, Issue 24 488 
Lepherd EE.No abstract available
The diagnosis, management and treatment of bleeding disorders. Part 2.
Modern veterinary practice    September 1, 1977   Volume 58, Issue 9 756-762 
Dodds WJ.No abstract available
The kinetics of hematopoiesis in the light horse II. The hematological response to hemorrhagic anemia. Lumsden JH, Valli VE, McSherry BJ, Robinson GA, Claxton MJ.Hemorrhagic anemia was experimentally produced in three Standardbred horses by removing approximately 63% of the red cell mass and the accompanying plasma during a three day interval. Red cell parameters were examined daily for 45 days and then weekly until termination of the experiment 250 days after production of the anemia. Leukocytes, platelets and bone marrow aspirates were examined at regular intervals for 25 days after the final phlebotomy. At 24 hours after the last bleeding, 75-selenomethionine was injected intravenously to measure the lifespan of the newly produced erythrocytes. The ...
A scanning electron microscopic study of platelets of certain animal species.
Thrombosis et diathesis haemorrhagica    June 30, 1975   Volume 33, Issue 3 501-507 
Jain NC.Comparative morphology of platelets of the dog, cat, cow, horse, sheep, and goat was studied with the scanning electron microscope and was found generally similar. Most of the platelets were slightly biconvex of flat with relatively smooth surface and even contour. Some of these platelets had few short marginal filaments, oriny protuberances on the surface. A small number of platelets exhibited surface irregularity and few long pseudopods which were thought to result from platelet activation during the processing of blood. The number os such irregular platelets increased in stored blood and in...
The kinetics of hematopoiesis in the light horse. I. The lifespan of peripheral blood cells in the normal horse. Carter EI, Valli VE, McSherry BJ, Milne FJ, Robinson GA, Lumsden JH.Three Standardbred horses were given 0.2 mg (1 mCi) of (75)selenomethionine intravenously and a second group of three were given 10 mCi of tritiated diisopropylfluorophosphate (0.5 mg) intravenously. Observations on labeled cells were continued for 250 days after radioselenium injection and 160 days after tritium injection. The lifespan of erythrocytes using (75)selenmethionine was 155 +/- 10 days and 148 +/- 7.8 days using tritiated diisopropylfluorophosphate. There was no significant difference at the 10% level between the lifespans, using these labels. The uptake of radioselenium into eryth...