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Topic: Platelet


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  American Red Cross
Platelet donors have the satisfaction of knowing that their donation will be saving a life within just a few days.
Until recently, the only way to collect enough platelets for a single transfusion was to take blood donations from 5 to 10 donors, separate the platelets from the other blood cells, and combine the platelets to obtain a large enough quantity for transfusion.
By appropriately adjusting the instrument, a selected portion of the blood, such as the platelets, can be recovered, while the rest of the blood is returned to the donor either into the same vein or into a vein in the other arm.
www.redcross.org /services/biomed/0,1082,0_19_,00.html   (507 words)

  
  Platelet Immunology Laboratory | About This Lab
The Platelet Immunology Laboratory was established over 20 years ago in response to the need to identify and characterize antibodies in alloimmunized thrombocytopenic patients with the goal of identifying compatible donors.
The development of a platelet antibody laboratory was a logical extension of the research studies on platelet transfusion therapy that were initiated by Dr. Sherrill Slichter when she joined the Puget Sound Blood Center in 1970.
With the availability of platelets for transfusion and their rapidly increasing use, the development of alloimmune platelet refractoriness became a recognized consequence of repeated platelet transfusions in chronically-thrombocytopenic patients.
www.psbc.org /lab_platelet/index.htm   (483 words)

  
  Chasing after the causes of platelet disorders - College of American Pathologists   (Site not responding. Last check: )
Platelets have numerous intrinsic glycoproteins attached to the outer surface of their plasma membrane that are receptors for such ligands as fibrinogen, collagen, thrombin, and thrombospondin to von Willebrand factor and fibronectin.
Platelet membrane phospholipids are rearranged during activation, and phosphatidyl serine is transferred from the inner table to the outer table of the platelet membrane, providing a binding site for phospholipid-dependent coagulation complexes that activate factor X and prothrombin.
Platelet dysfunction is often observed with chronic renal failure or liver disease in patients suffering from a variety of myeloproliferative and lymphoproliferative disorders-for example, polycythemia vera, myelofibrosis, paroxysmal nocturnal hemoglobinuria, acute myelogenous leukemia, and hairy cell leukemia.
www.cap.org /apps/docs/cap_today/feature_stories/platelet_disorders_feature.html   (4233 words)

  
  Platelet information - Search.com   (Site not responding. Last check: )
Platelets or thrombocytes are the blood cell fragments that are involved in the cellular mechanisms that lead to the formation of blood clots.
Platelets are produced in the bone marrow; the progenitor cell for platelets is the megakaryocyte.
Platelets are activated when brought into contact with collagen (which is exposed when the endothelial blood vessel lining is damaged), thrombin (primarily through PAR-1), ADP, with receptors expressed on white blood cells or the endothelial cells of the blood vessels, among other activators.
c10-ss-1-lb.cnet.com /reference/Platelet?redir=1   (1053 words)

  
 Platelet definition - Medical Dictionary definitions of popular medical terms easily defined on MedTerms
Platelet: An irregular, disc-shaped element in the blood that assists in blood clotting.
During normal blood clotting, the platelets clump together (aggregate).
Although platelets are often classed as blood cells, they are actually fragments of large bone marrow cells called megakaryocytes.
www.medterms.com /script/main/art.asp?articlekey=4941   (194 words)

  
 AllRefer Health - Congenital Platelet Function Defects (Bernard-Soulier Syndrome, Glanzmann's Thrombasthenia, Platelet ...
Congenital platelet function defects are disorders of platelet function, the blood cells essential for the coagulation of the blood, that is present at birth.
Congenital platelet function defects are bleeding disorders characterized by abnormal platelet function in spite of normal platelet counts.
Bernard-Soulier syndrome is a congenital disorder where the platelets lack receptors to adhere to the walls of the blood vessels.
health.allrefer.com /health/congenital-platelet-function-defects-info.html   (397 words)

  
 Low Platelet Count, Blood Disorders, THE MERCK MANUAL OF HEALTH & AGING
A low platelet count (called thrombocytopenia) refers to an abnormally low number of platelets, the particles in blood that help with clotting.
Usually, the platelet count is about 150,000 to 350,000 platelets in a microliter of blood.
Blood tests are done to determine the platelet count and thus confirm the diagnosis.
www.merck.com /pubs/mmanual_ha/sec3/ch49/ch49c.html   (669 words)

  
 [No title]
Platelet count and PT should be reviewed in patients in whom you have reason to believe they could be abnormal.
For example, safe platelet counts are different in sedentary persons and those with active lifestyles, and certain agents (such as alkylating agents) should be avoided in patients who wish to have children.
Third, the elevation of the platelet count in RT patients lasts only for a limited period of time and the abnormalities of plasma vWF are reversible with a normalization of the platelet count.
www.lycos.com /info/platelet-count.html   (646 words)

  
 Platelet Summary
Platelets, which are also called thrombocytes, are small disk-shaped blood cells produced in the bone marrow and involved in the process of blood clotting.
Platelets are formed in the bone marrow a spongy tissue located inside the long bones of the body as fragments of a large precursor cell (a megakaryocyte).
Platelets or thrombocytes are the blood cells that are involved in the cellular mechanisms of primary haemostasis that lead to the formation of blood clots.
www.bookrags.com /Platelet   (2480 words)

  
 Guidance for Industry - For Platelet Testing and Evaluation of Platelet Substitute Products
In addition, platelets also recruit neutrophils and monocytes by exposing P-selectin on their surface, contribute to signal transduction in neutrophils and endothelial cells by trans-cellular metabolism of released lipid precursors, serve as a site for activated clotting factor assembly and exert a physical force to retract clots.
Thus, platelet substitutes may be able to replace one part of the platelet response and be used in specific clinical situations, such as acute trauma, as opposed to long term prophylaxis.
Platelet substitutes which aim to be alternatives to the current platelet product should demonstrate a clear benefit-to-risk ratio before they are considered for clinical trials.
www.fda.gov /cber/gdlns/platelet.htm   (2425 words)

  
 Platelet transfusions : Cancerbackup
Platelets are made in large numbers by the bone marrow (the spongy material inside the bones).
People who donate blood and platelets are carefully screened to assess their risk of having an infection or virus, such as hepatitis, HIV or malaria.
The platelets are not given to a patient until all tests from the blood are found to be negative.
www.cancerbackup.org.uk /Treatments/Supportivetherapies/Platelettransfusions   (1263 words)

  
 Platelet Aggregation
Various platelet aggregating agents (agonists) are added to aliquots of the platelet-rich plasma, and the resulting platelet aggregation is measured in an aggregometer.
Platelet storage pool disorders are characterized by deficiencies in alpha or dense platelet granules.
In gray platelet syndrome, platelets are large; thrombocytopenia may be present; and beta-thromboglobulin (a research test) is decreased in platelets but may be elevated in plasma.
www.massgeneral.org /pathology/coagbook/CO003900.htm   (1006 words)

  
 Ask The Experts: High Platelet Count Information by MedicineNet.com
Platelets are the smallest cell-like structures in the blood and are important for blood clotting and plugging damaged blood vessels.
Platelet counts are usually done by laboratory machines that also count other blood elements such as the white and red cells.
Normal platelet counts are in the range of 150,000 to 400,000 per microliter (or 150 - 400 x 109 per liter), but the normal range for the platelet count varies slightly among different laboratories.
www.medicinenet.com /script/main/art.asp?articlekey=79481   (264 words)

  
 eMedicine - Platelet Disorders : Article by Perumal Thiagarajan, MD
The platelets arise from the cytoplasmic fragmentation of megakaryocytes in the bone marrow and circulate in blood as disk-shaped anucleate particles.
ADP is present in the dense granules of platelets as a storage pool, which is not used in the normal metabolic activity of platelets (in contrast to the metabolic pool).
Platelet transfusions are administered to patients with severe clinical bleeding, and a sustained increase in platelet counts is sometimes observed in those with ITP.
www.emedicine.com /med/topic987.htm   (9099 words)

  
 Platelet Count: The Test
A platelet count is often ordered as a standard part of a complete blood count, which may be done as part of an annual physical examination.
While the platelets may be normal in number, their ability to stick together is impaired due to a decrease in von Willebrand’s factor, a protein needed to initiate the clotting process.
Some may have a tendency to bleed due to the lack of stickiness of the platelets, yet in others, the platelets retain their stickiness but, because they are increased in number, tend to stick to each other, forming a clump that can get stuck within a blood vessel and cause damage, including death (thromboembolism).
www.labtestsonline.org /understanding/analytes/platelet/test.html   (505 words)

  
 Platelet function disorders
Platelets are elements within the bloodstream that recognize and cling to damaged areas inside blood vessels.
Platelets are formed in the bone marrow--a spongy tissue located inside the long bones of the body--as fragments of a large precursor cell (a megakaryocyte).
Platelet function disorders can be inherited, but they may also occur as a symptom of acquired diseases or as a side effect of certain drugs, including aspirin.
www.healthatoz.com /healthatoz/Atoz/ency/platelet_function_disorders.jsp   (738 words)

  
 Platelet Count | AHealthyMe.com
Platelets, which are also called thrombocytes, are small disk-shaped blood cells produced in the bone marrow and involved in the process of blood clotting.
The primary functions of a platelet count are to assist in the diagnosis of bleeding disorders and to monitor patients who are being treated for any disease involving bone marrow failure.
If a platelet and another blood cell pass through the counter at the same time, the instrument will not count the larger cell because of the size exclusion limits, which will cause the instrument to accidentally miss the platelet.
www.ahealthyme.com /topic/topic100587309   (1025 words)

  
 Qualitative Platelet Disorders
Platelets attach to the lining of the injured blood vessel and begin the first phase of the clotting process.
After platelets initially begin to adhere to the wall of an injured blood vessel, additional platelets are called to the site of injury.
A qualitative platelet disorder may involve missing or defective proteins on the surface of the platelet membrane or a deficiency or abnormality in the platelet granules or their contents (storage pool disorder) which affect platelet function (see Table I).
www.med.umich.edu /1libr/aha/umqpd.htm   (778 words)

  
 Platelet Disorders
Mild to moderate thrombocytopenia is caused by platelet sequestration when there is an associated mild reduction in neutrophil count and hemoglobin and with minimal impairment of hematopoiesis on bone marrow examination.
Qualitative platelet disorders are suggested by a prolonged bleeding time (abnormal platelet function screen) or clinical evidence of bleeding in the setting of a normal platelet count and coagulation studies.
Whether acute or chronic, is associated with platelet dysfunction that is multifactorial in origin: increased FDPs from activation of the fibrinolytic pathway compromise platelet function, and release of platelet factor 3 from platelets is impaired in patients with cirrhosis or other cause of hepatic dysfunction.
www.clevelandclinicmeded.com /diseasemanagement/hematology/platelet/platelet.htm   (4074 words)

  
 Platelet count
Platelets are produced in the bone marrow and removed by the spleen when they are damaged or old.
Platelet counts under 50,000 put a patient at risk of severe bleeding and platelet counts under 20,000 may cause spontaneous and fatal intracranial bleeding.
When the platelet count is high, some of the platelets may be abnormal forms that do not function correctly to assist in the coagulation process.
www.rnceus.com /coag/coagplate.html   (367 words)

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