Platelet accumulation, measurement

In summary, the capillary perfusion system represents a simple in vitrc technique for the quantitation of protein adsorption and platelet accumulation on artificial surfaces under well defined hydrodynamic conditions (0-4.,000 s ). Radioisotopic methods enable simultaneous study of platelet deposition and adsorption of one or more plasma proteins. Experiments may be performed using washed platelet suspensions or anticoagulated whole blood, platelet deposition being measured in the latter case by surface phase radioimmunoassay with a... 

Bikunin (Bik), a peptide excreted in the urine, is one of the primary inhibitors of the trypsin family of serine proteases. This peptide plays a key role in inflammation and innate immunity because of its two Kunitz-type binding domains [1, 2], Bik suppresses proteolytic activity in a variety of tissues and can also exert localized anti-inflammatory effect [3-5], Inflammation is an important indicator of infection, cancer, and tissue injury in acute and chronic states. In acute inflammation, fluids and plasma components accumulate in the affected tissues due to vascular dilation. Subsequent activation of platelets and increased presence of immune cells occur during repair. Long-standing inflammation may be present before the disorder is identified. Due to its inhibitory role and potential use as an early marker of inflammation, we will review the synthesis, structure, pathophysiology of Bik as well as the various approaches for its measurement in this chapter. 

Measurement of Phosphoinositide Turnover. As a result of these labeling experiments, two analytical procedures can be used to assess the involvement of the phosphoinositides in stimulus-induced activation of platelets by the agonist, PAF. One uses the measurement of the change in phosphoinositide levels per se as determined by [32P]phosphate labeling, and the other uses an assay to determine the accumulation of [3H]inositol phosphates through myo-[3H]inositol labeling. 

At present the use of activity measurements to quantitate plasma, serum, or urinary levels of the GST are inadequate. With CDNB it is difficult to obtain sufficient sensitivity to allow the measurement of the levels in normal subjects (A4). In addition many drugs and endogenous substances may inhibit the activity to values that lie within the reference range. For example bile salts and bilirubin inhibit GST activity (H17) and since both of these nonsubstrate ligands are increased in liver disease their accumulation in plasma could theoretically suppress GST activity to within the reference range. An important problem with GST activity measurements concerns the ubiquitous nature of the GST since poor organ specificity will result unless specific isoenzymes are measured. For example, platelets, erythrocytes, and white cells contain high levels of the isoenzyme and these cells may release their GST into plasma prior to separation of the blood sample (G4, H52, L12, M8, Rll, S43). With the substrates that are available to date, the activity measurements are inadequate for clinical use. 

The ex vivo flow-through couette method provides a very convenient model for assessing the effect of drugs on the thrombogenic process. By directly monitoring the accumulation of radioisotope in the couette device, a direct measure of the kinetics of thrombus accumulation can be obtained. An example of the deposition of platelets on the rod surface after the administration of systemic heparin is shown in Figure 10 (4). In this experiment... 

Results are similar when one aggregates washed platelet suspensions with PGH2. Exogenous addition of the immediate substrate for the thromboxane synthetase bypasses the cyclooxygenase enzyme, but TxB2, measured by radioimmunoassay accumulates, and aggregation accompanies the accumulation [Figure 2]. 

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