Blood platelet retention

Figure 3. Passivation of polymers of the acrylate series (A) and the methacrylate series (B) by preliminary exposure to platelet-poor plasma (PPP) before whole blood platelet retention vs alkyl side chain length. (Replotted from data in Fig. 5 of Ref. 17.)...

Figure 9 Degree of platelet retention in unheparinized rabbits undergoing simulated extracorporeal membrane oxygenation (ECMO) whose extracorporeal blood conduits are lined with MAHMA/NO-containing PVC to inhibit platelet adhesion ( ) as compared with controls whose tubing is made of undiazeniumdiolated PVC ( ). [Adapted from Reference 13 with permission.]...

Circulating radiolabeled platelets adhered and aggregated on two polyethylene catheters inserted retrograde into the carotid arteries. Increasing platelet retention is shown in the sequence A through EThe beginning of thrombus dissolution is seen in F . The small platelet collection is best shown in the precatheter sample (A). Blood was drawn... 

Several polymers were evaluated in the form of a surface coating on glass beads packed in columns to determine their ability to retain platelets when whole human blood passes over the surface. This ability was measured as the platelet retention index p, the fraction of platelets retained on the column. Lowest values of p were found for poly(ethylene oxide), polypropylene oxide), poly(tetramethylene oxide) (in the form of polyurethanes), and polydimethylsiloxane. Highest values (around 0.8) were found for cross-linked poly(vinyl alcohol) and the copolymers of ethylenediamine with diisocyanates. Intermediate values were found for polystyrene and its copolymers with methyl acrylate, for polyacrylate, and for poly(methyl methacrylate). The results are interpreted in terms of possible hydrophobic and hydrogen bonding interactions with plasma proteins. 

This chapter deals with a specific test of blood-surface interaction in vitro platelet retention in a column of beads (due to platelet adhesion and aggregation). Protein adsorption precedes platelet adsorption, and thus the in vitro platelet retention test involves competitive and sequential adsorption of proteins, the outcome of which produces surfaces having widely varying degrees of platelet retention. Except in the case of thrombin (3), plasma protein absorption on these surfaces has not been studied. 

We tested the hypothesis that the platelet retention index should increase as polymer composition varied from 100 mol % methyl acrylate to 100 mol % styrene, the respective platelet retention indices p being about 0.25 and 0.55 for the homopolymers. The results are shown in Figure 3, wherein p increases to a maximum near 40% styrene. When the surfaces were incubated in platelet-poor plasma before contact with whole blood, the values of p were much reduced (from 0.25 to 0.05 for methyl acrylate) for copolymers containing up to 60 mol % styrene. Copolymers of higher styrene content were not rendered significantly less retentive by plasma pretreatment. 

Preincubation of surfaces with platelet-poor plasma substantially reduced the platelet retention index of polyacrylates and polymethacrylates, but hardly altered the retention index of polystyrene or copolymers with methyl acrylate that are rich in styrene. Even without plasma pretreatment, the surface, when exposed to whole blood, was probably first contacted by molecular elements (including the proteins) before the cellular elements arrived. What then is the mode of action of plasma pretreatment Several hypotheses, none conclusive, can be advanced, such as ... 

Molecular models (2) of the hard-segment phase of segmented polyether polyurethanes tested in the in vitro bead column (4) show a high platelet retention index (p = 0.8) regardless of molecular composition. The variable p is defined as the fraction of platelets in whole citrated human blood entering a test column that are retained on the bead surfaces, averaged for... 

Upon contact with blood, polyethers absorb varying amounts of water and undergo partial dissolution while remaining partially crystalline. They show platelet retention index values around 0.2-0.3. 

The platelet count is determined for the blood samples emerging, aliquot by aliquot and is averaged for 5 aliquots and the number of donors. This average divided by the platelet count in the blood in the holding syringe is called the recovery index r. The platelet retention index p is defined simply as... 

Coller, B. S., and Zucker, M. B. Reversible decrease in platelet retention by glass bead columns ( adhesiveness ) induced by disturbing the blood. Proc. Soc. Exp. Biol. 

Dion et al. (1993) evaluated the in vitro platelet retention of the new prosthetic heart valve that was designed by FII Company and Pr. Baudet, composed of Ti6A14V titanium alloy coated with DLC (obtained by CVD). The retention and adhesion of platelets was evaluated by analyzing radioactivity on the exposed wall of test or control tubes through which a blood cell suspension containing In-labelled platelets had circulated. Their results showed that on DLC/Ti6A14V, platelets adhered twice the amount that they did on the reference material (a silicone medical-grade elastomer the behaviour of which in contact with blood is the same as that observed with the National Institutes of Health-recommended polydimethyl siloxane) (Dion et al., 1993). 

Fig. 9. Retention behavior of blood cells on poly(HEMA co[jV-methyl-/V-(4-vinylphenethyl) ethylenediamine (HAV) (pH 7.2, 23 °C flow rate, 0.4 ml/min flow time, 3,5 min). Open circles, lymphocytes closed squares, platelets open triangles, erythrocytes AVEMA, N-methyl- V-(4-vinyl-phenethyl)ethylenediamine [Ref. 115]...

Peerscfake EIB. Glycoprotein lib and nia retention on fibrinogen-coated surfaces after lysis of adherent platelets. Blood 1995 82 3358-3363. 

This is unfortunate because the theoretical advantage of nanosystems is their small size, allowing freer movement than microspheres in the circulation, including the lymph and in tissues. Flow rates are important not least in the determination of the possibility of nanoparticle interaction with endothelial receptors prior to internalization, or indeed in the decoupling of carriers and receptors due to shear forces. Flow of nanoparticles is a vital element in extravasation and in the enhanced permeation and retention (EPR) effect. What is the influence of nanoparticle size on particle flow in the circulation And, with the advent of CNTs in particular, what is the influence of shape on flow and fate CNTs certainly behave differently in the blood from spherical C60 fidlerenes. CNTs activate human platelets and induce them to aggregate, whereas their spherical analogues do not... 

Initial work on radiolabeling of autologous polymorphonuclear leukocytes was performed by McAfee and Thakur [30]. One of the compounds they examined was the nonpolar, lipid-soluble complex 8-hydroxyquinoline (oxine) (Fig. 2). Indium forms a neutral, lipid-soluble complex with oxine which will penetrate cellular membranes. Subsequently, studies showed that this technique could be used to label leukocytes and platelets with retention of biological activity [31]. After diffusing intracellularly, the ln-oxine complex dissociates and the " In is bound to nuclear and cytoplasmic proteins (Fig. 3) [32-34]. Due to the high stability of indium with the blood protein transferrin, it is necessary to label platelets or WBCs in the absence of plasma. In addition, a final wash of the labeled cells using plasma will remove any loosely bound indium by complexation with transferrin [35,36]. 

Sachais BS, Kuo A, Nassar T, et al. Platelet factor 4 binds to low-density lipoprotein receptors and dismpts the endocytic machinery, resulting in retention of low-density lipoprotein on the cell surface. Blood 2002 99 3613-3622. 

An inverse relationship has been reported between tumor cell-derived NO and platelet aggregation in metastatic human colorectal carcinoma cell line (Gasic et al. 1968). Since platelets store angiogenic factors and stimulate vessel growth leading to the retention of metastasizing tumor cells in blood vessels, it may indicate that iNOS-derived NO has anti-tumorigenic role. 

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