Reginald G. Mason

Effect of Fibrinogen Concentration on Platelet Adhesion to Glass

Summary The extent to which platelets adhere to glass is dependent on fibrinogen concentration. Platelet adhesion increased progressively in a linear fashion when increasing concentrations of purified fibrinogen (0.5-14.0 mg/100 ml) were added to the blood of a patient with congenital afibrinogenemia.

Studies of an activity from endothelial cells that inhibits platelet aggregation, serotonin release, and clot retraction.

Abstract An activity present in endothelial cells of human umbilical vein origin has been found to inhibit aggregation, serotonin release, and clot retraction. This activity appears to reside in molecules of small size that can be released from in situ or isolated endothelial cells by freeze-thaw treatment or by exposure of cells to ADP, collagen, epinephrine, or thrombin. Relative amounts of inhibitory activity released from endothelial cells vary with the specific platelet aggregating agent used as release inducer and are influenced by use of in situ or isolated cells. Varying the concentration of aggregating agent varied proportionally the amount of inhibitory activity released from in situ but not from isolated endothelial cells.

SOME EFFECTS OF NICOTINE ON PLATELETS

Platelet function is known to be influenced by a wide variety of chemical, biochemical, and pharmacologic agents (1,2). One report indicates that nicotine does have an effect upon platelet function (3) while other reports deny this (4-6). Since nicotine is a commonly encountered substance in our society and can even reach toxic levels in the body under special circumstances (7), the present study was undertaken to clarify the effects of nicotine on platelets. In this study, nonsmokers, moderate smokers, and heavy smokers served as donors of blood used in the platelet function studies.

EFFECT OF SULFHYDRYL INHIBITORS ON PLATELET AGGLUTINABILITY.

Summary 1. In the presence of Ca++ or Mg++, ADP induces agglutination of platelets washed at 4°C. 2. The sulfhydryl inhibitors PCMB, NEM, and MMN inhibit the ability of washed canine platelets to agglutinate with thrombin or ADP in the presence of Ca++. 3. The effectiveness of PCMB in inhibiting platelet agglutinability is dependent upon thrombin concentration used to induce agglutination. The inhibitory action of PCMB is independent of changes in ADP concentration. 4. MMN causes deagglutination of platelets from clumps formed in the presence of 1.0 U/ml thrombin and Ca++, if the MMN is added to the platelet clumps within 30 seconds of agglutination. 5. MMN, at non-inhibitory concentrations (2.0 × 10-5 m or less), induces rapid and intense platelet agglutination in the presence of Ca++.

Studies of proteins elutable from cuprophane exposed to human plasma.

Abstract The proteins elutable under certain conditions from Cuprophane exposed to platelet-poor plasma (PPP) have been studied. Normal PPP was exposed to untreated Cuprophane, to Cuprophane pretreated with human albumin, or to Cuprophane pretreated with heparin. PPP from donors receiving aspirin therapy was exposed also to untreated Cuprophane. Experiments were conducted in a test column especially designed for optimal exposure of plasma to Cuprophane. Polyacrylamide gel disc electrophoresis was used to detect the plasma proteins recovered from Cuprophane. The results indicate that 1) Cuprophane-PPP exposure time had no effect on the number of different species of proteins recovered from untreated Cuprophane; 2) the number of proteins recoverable from albumin precoated Cuprophane increased with longer Cuprophane-PPP exposure time; 3) pretreatment of Cuprophane with heparin also increased the number of proteins recoverable initially; however, decreasing numbers of proteins were recovered after prolonged periods of plasma exposure; and 4) aspirin therapy increased the number of proteins recoverable. This latter increase was related directly to the length of PPP-Cuprophane exposure time. The proteins recovered were identified tentatively and the results discussed.

Studies of the proteins elutable from certain artificial surfaces exposed to human plasma

Abstract The proteins elutable under certain conditions from glass, silicone-coated glass, and Cuprophane exposed to normal, afibrinogenemic, or Factor XII-deficient plasmas have been studied. The methods of protein detection employed include polyacrylamide gel disc electrophoresis and a modified method of immunodiffusion. The results indicate that most of the adsorbed plasma proteins are loosely adherent to all three artificial surfaces. In addition, certain plasma proteins appear to adsorb strongly to glass, less strongly to silicone-coated glass, and least strongly to Cuprophane. Albumin and IgG were identified immunologically as two of the proteins which could be eluted from test surfaces even after extensive washing. Tentative identification of other eluted proteins was made. Factor XII activity was recovered in dissimilar quantities from glass beads exposed to normal or afibrinogenemic plasma. The possible interplay between Factor XII, fibrinogen, and other plasma proteins at interfaces is discussed as it may relate to adsorption of proteins to artificial surfaces.

Extracorporeal Thrombogenesis: Mechanisms and Prevention

The exposure of blood to artificial surfaces either extracorporeally or intracorporeally initiates a number of diverse reactions (1–4). Immediately following the exposure of most artificial surfaces to blood, various plasma proteins begin to adsorb to those surfaces. The interaction of plasma proteins with artificial surfaces can initiate the activation of the intrinsic and extrinsic blood coagulation, the kinin, the complement, and the fibrinolytic systems. Ultimately, thrombin may be formed, and this enzyme may adhere to artificial surfaces in an active state. While various proteins are adsorbing to an artificial surface and establishing an equilibrium state, blood cells begin to adhere to the adsorbed protein layer. Erythrocytes seem to adhere poorly to such a surface, but platelets and leukocytes, especially neutrophils, are attracted to the adsorbed protein layer, frequently in large numbers. Adhesion of leukocytes to the artificial surface may lead to activation of the extrinsic blood coagulation system through the exposure of tissue factor on the plasma membranes of the adherent cells.

The subcellular distribution and partial characterization of cholinesterase activities of canine platelets.

The multiple cholinesterase activities in canine platelets have been investigated. Platelets were homogenized by rapid decompression under nitrogen, glass tube/Teflon pestle, and glycerol lysis techniques. Rapid decompression under nitrogen technique was found to be the most efficient and gentle method for cell disruption. Homogenates were subfractionated using sodium diatrizoate density gradients. Marker enzyme assays and pulse labeling experiments with 5-hydroxyl[14C] tryptamine and [125I] thrombin on prepared subcellular fractions confirmed that the soluble, plasma membrane and the granule-1 fractions were all in reasonably pure form. Furthermore, labeling of the plasma membrane with [125I] thrombin is cited as the first successful attempt at attaining significantly bound marker for this structure. Cholinesterase activity distributions measured in these fractions indicated that about 30% of the activity was present in the plasma membrane, 50% in granule-1 and 5% in soluble fractions. Kinetic data of cholinesterase activities obtained from intact platelets, plasma membrane preparations and platelet release supernatants indicated that they are strikingly similar.

Acetylcholine, cholinesterase activity, and the aggregability of human platelets.

Summary Washed human platelets and isolated platelet-membrane fractions have been shown to have cholinesterase activity distinct from that of erythrocytes. In intact platelets the cholinesterase activity is affected by thrombin, ADP, epinephrine, or collagen. Other agents were shown to influence cholinesterase activity and seven of these also inhibited platelet aggregation induced by thrombin, ADP, or collagen. The relationship of acetylcholine and cholinesterase activity to platelet aggregation is discussed in light of these findings.

Inhibition of Human Platelet-Collagen Adhesion Reaction by Amitriptyline and Imipramine

Summary The capability of human blood platelets to adhere spontaneously to collagen, both in citrated and EDTA platelet-rich plasma, was shown to be inhibited markedly in the presence of imipramine or amitriptyline. Adhesion of platelets to collagen was quantitated by a method specific for adhesion. A possible similarity between the mechanism of platelet aggregation and that of platelet-collagen adhesion is suggested.