Blood platelet

Contamination of blood products with lymphocytes can lead to transfusion-induced reactions ranging from a mild fever to severe reactions such as alloimmunization and graft versus host disease (GvHD), in which the transfused lymphocytes (graft) survive the defensive immune reaction of the patient (host) and start a reaction which destroys the cells of the host. The patient also may develop an immune response to the human leukocyte antigen (HLA) type of the graft s cells and reject all platelet transfusions that do not match their own HLA system. The HLA system, found on blood platelets and lymphocytes, is more compHcated than, but similar to, the ABO blood group system of red cells. 

Platelets. Blood platelets play a key role in the prevention of blood loss from intact vessels, and the arrest of bleeding from injured vessels. 

The aperture impedance principle of blood cell counting and sizing, also called the Coulter principle (5), exploits the high electrical resistivity of blood cell membranes. Red blood cells, white blood cells, and blood platelets can all be counted. In the aperture impedance method, blood cells are first diluted and suspended ia an electrolytic medium, then drawn through a narrow orifice (aperture) separating two electrodes (Fig. 1). In the simplest form of the method, a d-c current flows between the electrodes, which are held at different electrical potentials. The resistive cells reduce the current as the cells pass through the aperture, and the current drop is sensed as a change in the aperture resistance. 

Benzene zero 0.005 Anemia decrease in blood platelets increased risk of cancer Discharge from factories leaching from gas storage tanks and landfills... 

Compound D is an effective inhibitor of TXA2 biosynthesis in human blood platelets at the micromolar level. 

Lipoxygenation is the major pathway of dioxygenation of arachidonic acid in blood platelets and leads to the 12-5-hydroperoxy acid 12-HPETE and the corresponding 12-hydroxy acid 12-HETE. Several pathways for the synthesis of 12-HETE have been developed. However, despite the availability of this substance, its biological role remains undetermined. 

Synthesis of 12-(5)-10-hydroxy-/ra/is-ll,12-epoxyeicosa-5,9,14-(Z)-trienoic acids, position isomers of hepoxylins isolated from blood platelets (Ref. 2) ... 

Animal cells can modify arachidonic acid and other polyunsaturated fatty acids, in processes often involving cyclization and oxygenation, to produce so-called local hormones that (1) exert their effects at very low concentrations and (2) usually act near their sites of synthesis. These substances include the prostaglandins (PG) (Figure 25.27) as well as thromboxanes (Tx), leukotrienes, and other hydroxyeicosanoic acids. Thromboxanes, discovered in blood platelets (thrombocytes), are cyclic ethers (TxBg is actually a hemiacetal see Figure 25.27) with a hydroxyl group at C-15. 

Blut mehl, n. blood meal, mittel, n. (Med.) blood tonic. plflttchen, n. blood plate, blood platelet. reinigung, /. blood purification, blutrot, a. blood red. 

Therapeutic Function Blood platelet aggregation inhibitor... 

Haemostasis is the mechanism activated after damage to the blood vessel wall that ensures that blood loss is restricted. Blood platelets are are activated and adhere to elements on the damaged lumenal surface of the vessel, eventually forming a platelet plug that stops the leakage of blood. Fibrinolytic mechanisms later produce lysis of the platelet mass when repair of the vessel has occurred. 

Thrombocytopenia is a decrease in the number of circulating blood platelets (below 150 x 109/L). Although severe thrombocytopenia can lead to... 

Unlike aspirin and other cyclooxygenase inhibitors that work on the COX-1 and COX-2 enzymes, acetaminophen works on the COX-3 enzyme, which is present in the spinal column and brain. This helps it to avoid shutting down prostaglandin function elsewhere in the body, which is why it has no anti-inflammatory effects and does not affect blood platelets or the stomach lining. 

Submembranous microtubules are often present in parallel bundles beneath the plasma membrane in the cells of higher plants, particularly during cell wall formation (Hardham and Gimning, 1978). Circular submembranous bundles of microtubules are a feature of bird erythrocytes and mammalian blood platelets, where they maintain the discoid shape of these structures (Dustin, 1980). 

Blood platelets are key players in the blood-clotting mechanism. These tiny fragments of cytoplasm are shed into the circulation from the surface of megakaryocytes located in the bone marrow. When the lining of a blood vessel is injured, activated platelets release clotting factors, adhere to each other and to damaged surfaces, and send out numerous filopodia. The shape changes that occur in activated platelets are the result of actin polymerization. Before activation, there are no microfilaments because profilin binds to G-actin and prevents its polymerization. After activation, profilin dissociates from G-actin, and bundles and networks of F-actin filaments rapidly appear within the platelet. 

Different t T)es of body cells show different sensitivities to nuclear radiation. Cells that divide most rapidly tend to be most easily damaged. These include bone marrow, white blood cells, blood platelets, the lining of the gastrointestinal tract, and cells in the gonads. Consequently, the S3Tnptoms of radiation sickness include loss of blood functions and gastrointestinal distress. 

Thrombocytopenia Persistent decrease in the number of blood platelets. 

Brandt E, Petersen F, Fudwig A, Ehlert JE, Bock L, Flad HD. The beta-thrombo-globulins and platelet factor 4 blood platelet-derived CXC chemokines with divergent roles in early neutrophil regulation. J Feukoc Biol 2000 67(4) 471 178. 

L. Gordon and A. J. Milner, Blood platelets as multifunctional cells, in Platelets in Biology and Pathology... 

Champier, J., Claustrat, B., Besancon, R. el al. (1997). Evidence for tryptophan hydroxylase and hydroxy-indol-O-methyl-transferase mRNAs in human blood platelets. Life Sci 60, 2191-7. 

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