ristocetin การใช้

• The ristocetin cofactor activity and loss of large vWF multimers are similar to vWD type 2B.
• Thus, the ristocetin cofactor activity depends only upon high-molecular multimers of the factor present in circulating plasma.
• Platelet aggregation is normal with ristocetin, but impaired with other agonists such as ADP, thrombin, collagen or epinephrine.
• The ristocetin cofactor activity is low when the patient's platelet-poor plasma is assayed against formalin-fixed, normal donor platelets.
• "' Ristocetin "'is an antibiotic, obtained from " Amycolatopsis lurida ", previously used to treat staphylococcal infections.
• However, when the assay is performed with the patient's own platelets ( platelet-rich plasma ), a lower-than-normal amount of ristocetin causes aggregation to occur.
• In some types of vWD ( types 2B and platelet-type ), even very small amounts of ristocetin cause platelet aggregation when the patient's platelet-rich plasma is used.
• Through an unknown mechanism, the antibiotic ristocetin causes von Willebrand factor to bind the platelet receptor glycoprotein Ib ( GpIb ), so when ristocetin is added to normal blood, it causes agglutination.
• Through an unknown mechanism, the antibiotic ristocetin causes von Willebrand factor to bind the platelet receptor glycoprotein Ib ( GpIb ), so when ristocetin is added to normal blood, it causes agglutination.
• In all forms of the ristocetin assay, the platelets are fixed in formalin prior to the assay to prevent von Willebrand's factor stored in platelet granules from being released and participating in platelet aggregation.
• Platelet agglutination caused by ristocetin can occur only in the presence of von Willebrand factor multimers, so if ristocetin is added to blood lacking the factor ( or its receptor see below ), the platelets will not clump.
• Platelet agglutination caused by ristocetin can occur only in the presence of von Willebrand factor multimers, so if ristocetin is added to blood lacking the factor ( or its receptor see below ), the platelets will not clump.
• Thus, if the patient's platelet-poor plasma is used, the ristocetin cofactor assay will not agglutinate standardized platelets ( i . e ., pooled platelets from normal donors that are fixed in formalin ), similar to the other types of vWD.
• In an unknown fashion, the antibiotic ristocetin causes von Willebrand factor to bind the platelet receptor glycoprotein Ib ( GpIb ), so when ristocetin is added to normal blood, it causes agglutination of fixed platelets or initiates the initial agglutination phase of aggregation of live platelets.
• In an unknown fashion, the antibiotic ristocetin causes von Willebrand factor to bind the platelet receptor glycoprotein Ib ( GpIb ), so when ristocetin is added to normal blood, it causes agglutination of fixed platelets or initiates the initial agglutination phase of aggregation of live platelets.
• Abnormalities of the GPIb-V-IX complex result in abnormal appearance and functioning of platelets resulting in Bernard-Soulier syndrome ( BSS ), a condition first described by Bernard J and Soulier J . P . It is a rare hereditary bleeding disorder most commonly with an autosomal recessive inheritance and diagnosed based on prolonged skin-bleeding time, a reduced number of very large platelets ( macrothrombocytopenia ) and defective ristocetin-induced platelet agglutination.