Term
| what species do not have a developed canalicular system of membrane invaginations in their platelets? |
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Definition
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Term
| What are the functions of the dense endoplasmic reticulum in platelets? |
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Definition
stores calcium (involved in platelet activation)
important for thromboxane synthesis (vasoconstriction and platelet aggregation) |
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Term
| what do platelet alpha granules contain? |
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Definition
| proteins involved in hemostasis and vessel repair |
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Term
| What do platelet dense granules contain? |
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Definition
| Ca, Mg, ADP, ATP, serotonin |
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Term
| What are the tissue sites of thrombopoeitin production? |
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Definition
| hepatocytes, renal tubular epithelium, stromal cells of the bone marrow |
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Term
| How old are reticulated platelets in dogs? |
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Definition
<24h old
**reticulated platelets contain increased cytoplasmic RNA |
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Term
| What conditions have been associated with pulmonary sequestration of platelets? |
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Definition
| hypothermia and endotoxemia |
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Term
| What is the total megakaryocyte maturation time in rodents and people? |
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Definition
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Term
| Why is platelet lifespan decreased in any thrombocytopenic condition, even if the major driving force of the thrombocytopenia is decreased bone marrow production? |
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Definition
| due to the fixed platelet requirements necessary to maintain vascular integrity. In thrombocytopenic animals a substantially greater percentage of circulating platelets are consumed during routine maintenance. |
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Term
| What is the effect of splenectomy on circulating platelet lifespan in dogs? |
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Definition
| splenectomized dogs have almost a 50% longer platelet life span (8 days) compared to nonsplenectomized dogs (5-6 days) |
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Term
| What non-hemostatic processes are platelets involved in? |
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Definition
inflammation and wound healing
*PLT interact with WBC and release vasoactive amines, cytokines, mitogens, and growth factors |
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Term
| How is the PDW calculated on the ADVIA? |
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Definition
100 X (SD of MPV)/MPV
**the standard deviation of the platelet volumes as a percentage of the MPV |
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Term
| What is mean platelet component concentration (MPC) used to assess? |
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Definition
MPC is an approximation of average platelet density and is used to assess platelet activation (normally associated with granule secretion and decreased MPC)
**can be affected by anticoagulant, sample age, storage temp and iatrogenic activation |
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Term
| What type of blood tubes can minimize platelet clumping the most (esp. in cats)? |
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Definition
CTAD tubes
citrate, theophylline, dipyridamole, and adenosine |
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Term
| In what species are impedance platelet counts generally reliable? |
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Definition
dogs, horses and cattle
**cats have more variability in platelet volume and tend to have larger platelets (and always have smaller red blood cells) so impedance methods are less accurate in cats |
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Term
| What can result in falsely elevated PLT when using optical or laser flow cytometers? |
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Definition
| lipid droplets can scatter light similarly to platelets which can result in falsely elevated PLT with flow cytometer hematology analyzers |
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Term
| What is the effect of EDTA and Citrate on MPV over time (when using impedance measurements)? |
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Definition
| both increased MPV over time, however the effect is more pronounced with EDTA |
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Term
| What is the effect of sample storage time on MPV (when measured by the ADVIA)? |
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Definition
There is an initial decrease in MPV, after which MPV values increased over time*
**this is largely minimized by storing samples at 4C (refrigerated) |
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Term
| What conditions, other than accelerated thrombopoesis, can be associated with increased numbers of macroplatelets? |
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Definition
congenital platelet disorders (e.g. CKCS)
myelodysplastic syndromes
splenic contraction
FeLV infection (not a consistent finding, likely associated with secondary myelodysplasia) |
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Term
| Which species have the most prominent platelet granules? |
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Definition
cats and cows
**least prominent in horses |
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Term
| What dog breeds have low [PLT] in health? |
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Definition
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Term
| T/F platelet sequestration stimulates thrombopoesis |
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Definition
FALSE
decreased platelet mass results in less binding and removal of thrombopoetin and is therefore a stimulus for platelet production. With platelet sequestration there is no decreased in platelet mass, and therefore no stimulus for thrombopoesis |
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Term
| What is the typical time frame of thrombocytopenia following administration of chemotherapeutic agents? |
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Definition
| 1-2 weeks after drug administration |
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Term
| What toxins/drugs are associated with predictable and dose dependent myelosuppressive effects? |
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Definition
chemotherapeutic agents
estrogen (exogenous or endogenous e.g. stroll cell tumors, ovarian granulosa cell neoplasms, rarely testicular interstitial cell neoplasms)
bracken fern (ruminants)
trichothecene mycotoxins (ruminants)
albendazole (dog) |
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Term
| What drugs/toxins have been associated with idiosyncratic myelosuppresive effects? |
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Definition
phenylbutazone and meclofenamic acid (NSAIDs in dogs and horses)
TMS
Griseofulvin and albendazole (cats) |
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Term
| What viruses are associated with direct infection of megakaryocytes or megakaryocytic precursors and thrombocytopenia secondary to decreased throbopoeisis or megakaryopoisis? |
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Definition
bovine viral diarrhea virus (not persistently infected individuals)
canine distemper virus |
|
|
Term
| What is the pathogenesis of thrombocytopenia associated with equine infectious anemia virus? |
|
Definition
| production of myelosuppressive cytokines |
|
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Term
| What are two causes of alloimmune thrombocytopenia? |
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Definition
antibodies derived from colostrum or blood products
as opposed to autoimmune (immune attack against autoantigens) and secondary to adsorbed antigens (e.g. neoplasia, infection, drug/toxin) |
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Term
| What drugs have been associated with ITP in dogs? Cats? Horses? |
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Definition
Dogs- gold salts, sulfonamides (+/- trimethoprim)
Cats- methimazole, propylthiouracil (also for hyperthyroidism)
Horses- penicillin and TMS |
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Term
| What infectious agents have been associated with a component of immune mediated thrombocytopenia in domestic animals? |
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Definition
| Ehrlichia, anaplasma, rocky mountain spotted fever, histoplasma, leishmania, distemper (and modified live vaccines), equine infectious anemia, and babesia |
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Term
| In what species has neonatal alloimmune thrombocytopenia been reported? What is the pathogenesis? |
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Definition
Horses, mule foals and pigs
Passively acquired (normally via colostrum) maternal alloantibodies to paternal epitopes on neonate's platelets. Concurrent neutropenia and ulcerative dermatitis have been observed in foals. |
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Term
| What are hypothesized mechanisms for thrombocytopenia secondary to anaphylaxis (type 1 hypersensitivity)? |
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Definition
| thrombocytopenia may be secondary to inflammatory mediators, DIC, or immune-complex interactions with platelets (e.g. membrane receptors for IgE are present in some species) |
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Term
| How does living at high altitudes affect [PLT]? |
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Definition
| animals living at high altitudes may have increased [PLT] |
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Term
| What bone marrow findings differ in cases of essential thromboctosis in comparison with acute megakaryoblastic leukemia (AML M7)? |
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Definition
essential thrombocytosis: increased number of mature megs (may have some atypic)
vs. AML M7 (acute megakaryoblastic leukemia): >30% megakaryoblasts +/- fibrosis. Megakaryoblasts may also be in the blood and other organs. Peripherally there may be thrombocytosis OR thrombocytopenia |
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Term
| What is a potential site of platelet release in animals with reactive thrombocytosis, secondary to exercise? |
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Definition
lungs
*also spleen, however, exercise induced thrombocytosis may occur in splenectomized humans |
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Term
| What mechanisms contribute to transiet (but sometimes may persist for weeks) thrombocytosis following splenectomy? |
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Definition
| increased blood concentrations of thrombopoeitin, decreased platelet sequestration, decreased platelet destruction (mononuclear phagocyte system) |
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Term
| What thrombopathia has been described in Otterhounds? |
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Definition
Glanzmann Thrombasthenia
Mutation in gene encoding glyocprotein IIb (fibrinogen receptor) --> impaired clot formation. Affected dogs may also have increased MPV |
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Term
| Describe the methodology used to detect reticulated platelets? |
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Definition
| platelets are incubated with thiazole orange, a fluorescent dye that binds to platelet RNA and granules nucleotides. Flow cytometry is used to determine the percentage of platelets with increased fluorescence (i.e. percentage of reticulated platelets) |
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Term
| Although testing for antiplatelet antibodies is not necessarily a recommended diagnostic procedure for suspected IMT if pursued what type of assay is preferred? |
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Definition
| Direct platelet assays that test for antibodies on the surface of patient's platelets (as opposed to indirect assay that test for antibodies in the patient's plasma or serum) |
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Term
| What is the diagnostic sensitivity of direct megakaryocytic immunofluorescence assays for the diagnosis of IMT? |
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Definition
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