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At least 127 records · Page 7Linked to original sources
PubMed1991

Superoxide dismutase cooperates with prostacyclin to inhibit platelet aggregation: a comparative study in washed platelets and platelet rich plasma.

The role of superoxide anions (O2-) in human platelet aggregation in Krebs' buffer or plasma was investigated. In indomethacin (10 microM)-treated washed platelets superoxide dismutase (SOD; 60 U/ml) or ferricytochrome c (FCC; 70 microM) inhibited platelet aggregation by thrombin but not that by collagen or ADP. In addition, in indomethacin (10 microM)-treated washed platelets, SOD significantly potentiated the anti-aggregatory activity of prostacyclin (PGI2) or iloprost when thrombin but not collagen was used as the aggregating agent. In platelet rich plasma, SOD (60 U/ml) did not inhibit platelet aggregation nor did it potentiate the anti-aggregatory activity of iloprost when ADP, collagen or thrombin were used as aggregating agents. Thus, O2- participate in the aggregatory activity of thrombin but not collagen or ADP and PGI2 or iloprost, by reducing the sensitivity of platelets to thrombin, co-operate with SOD to inhibit thrombin-induced platelet aggregation. The interpretation of the use of SOD in experiments involving endothelium-derived relaxing factor (NO) is discussed.

Adenosine Diphosphate↗
PubMed1989

[Relation of the level of platelet membrane glycoproteins, platelet adhesion, platelet aggregation and traditional Chinese medicine syndrome patterns of coronary heart disease].

This experiment made quantitative analysis of platelet GPlb of 56 patients with coronary heart disease and with McAb SZ-2 resisting to human being platelet GP by using the method of indirect immunity fluorescence saturation, observed the changes of coronary heart patients' platelet GPlb based on TCM differentiation of the pattern, and determined the level of PAdT, PAgT. The results showed that the level of platelet GPlb of coronary heart disease was higher than normal. Among them, the acute myocardiac infarction group was the most obvious, followed by the unstable angina pectoris group and the stable angina pectoris group. The level of PAdT, PAgT of coronary heart patients was higher than those of the normal group (P less than 0.005, 0.05); the level of platelet GPlb in blood stasis syndrome group was higher remarkably than the group of having no blood stasis syndrome and the normal (P less than 0.001). These results suggested that it played an important part in the occurrence and development of coronary heart disease as manifested by abnormal increase of platelet GPlb, and enhancement of platelet's adherence and aggregation. The abnormal increase of platelet GPlb is due to pathological mechanism of blood stasis syndrome of coronary heart disease. This experiment also provided a fresh evidence to TCM differentiation of the pattern and treatment of coronary heart disease.

Adult↗
PubMed1988

Platelet parameters. Part I. Platelet counts and mean platelet volume in normal and pregnant subjects.

Platelet counts and mean platelet volume (MPV) were studied in 564 normal subjects and 297 pregnant women using a Coulter Model S-Plus electronic counter. The reproducibility of these measurements both intra- and inter-sample was documented. The mean platelet count in the normal group was 283 x 10(9)/l while the mean MPV was 9.32 fl. An inverse correlation between platelet volume and platelet number was documented (r = -0.38; P less than 0.0001). By interval analysis, this inverse relationship was shown to be non-linear. In the pregnant subjects there appeared to be a progressive decrease in platelet count with advancing gestation; this reached a significant level when the first and third trimesters were compared with each other (P less than 0.05). The MPV was unchanged. The fact that the platelet count decreased in proportion to the red cell count suggested that a common factor, such as haemodilution, was in part responsible. There was again an inverse relationship between MPV and platelet number (r = -0.39; P less than 0.0001) shown to be non-linear by interval analysis.

Blood Platelets↗
PubMed1995

[Shear-induced platelet aggregation (SIPA) monitoring of hemostatic effect during platelet transfusion in a patient with Glanzmann's thrombasthenia: a comparison between SIPA and conventional platelet aggregation].

Shear-induced platelet aggregation (SIPA) in a patient with Glanzmann's thrombasthenia was examined during platelet infusion therapy. Prior to platelet infusion, SIPA measured with the modified cone-and-plate type viscometer, as well as ADP-and collagen-induced platelet aggregation measured with the conventional platelet aggregometer, were absent. The patient's SIPA after multiple infusions of platelet, in parallel with the bleeding time and the clinical hemostatic effect, improved to the normal level, while ADP-and collagen-induced platelet aggregation remained abnormal. These observations imply that SIPA is physiologically more relevant than the conventional agonist-induced platelet aggregometry in this type of the disease.

Adenosine Diphosphate↗
PubMed1989

Sheep platelets as a model for human platelets: evidence for specific PAF (platelet activating factor) receptors.

In a number of animals, the platelet response to Platelet Activating Factor (PAF) has been shown to differ considerably from that in humans. However, aggregation, release and particularly shape change were quite similar for human and sheep platelets. In this study, aggregation and shape change analysis were used to measure the response of sheep platelets to various synthetic analogs of PAF. Response is greatly reduced with no alkyl group in position 2 of PAF and decreases progressively as the number of carbons of the alkyl gets larger than three. A reduction of activity is also seen as the ether linkage at position 1 of PAF is replaced by an ester linkage. These changes are indicative of a specific membrane receptor for PAF in sheep platelets and confirm the usefulness of sheep platelets as a model for PAF-platelet interaction in humans.

Animals↗
PubMed1988

Lipoxygenase activities of human platelets and their subcellular fractions: comparison between lipoxygenase-deficient platelets and normal platelets.

Lipoxygenase activities were estimated in washed platelets (intact platelets) and their subcellular fractions obtained from 7 patients with deficient platelet lipoxygenase activities and 9 normal subjects. From sonicated platelet preparations, 12,000 g supernatant (F-I), cytosol (F-II) and microsomal fractions (F-III) were prepared by differential centrifugation. When 12-hydroxyeicosatetraenoic acid (12-HETE) produced by the incubation of arachidonic acid with intact platelets or each of their subcellular fractions from normal subjects was measured by reversed-phase high-performance liquid chromatography analysis, the lipoxygenase activities of F-I, F-II and F-III were 87%, 31% and 17%, respectively, of the enzyme activity of intact platelets. One of the patients showed no detectable lipoxygenase activity in any preparation, while the other patients showed reduced enzyme activities in all preparations. The addition of CaCl2 significantly increased 12-HETE synthesis solely by F-I from these patients. In most of these patients, contrary to normal subjects, it appeared that the lipoxygenase activity was not fully expressed in intact platelets, since the F-I produced more 12-HETE than the intact platelets.

12-Hydroxy-5,8,10,14-eicosatetraenoic Acid↗
PubMed1988

Refractoriness to platelet transfusion after single-donor consecutive platelet transfusions and its relationship to platelet antibodies.

In thirty patients with acute leukemia and severe aplastic anemia receiving random single donor platelet transfusions, the development of refractoriness by consecutive platelet transfusions with cytapheresis and its relationship to the appearance of anti-platelet antibodies were investigated. The median number of platelet transfusions inducing refractoriness was 13 times, and 20% of the patients remained unrefractory despite of the repeated multiple platelet transfusions up to 20 to 25 times. The results of anti-platelet antibody tasts by the enzyme-linked immunosorbent assay(ELISA) and immunofluorescent techniques(IFT) showed no statistically significant relationship with the refractoriness (p greater than 0.1). Although there was significant correlation between the results of ELISA and IFT, both tests were insufficient to find out refractoriness even with the use of pooled platelets from multiple donors as target cells. This study shows that 13 single donor platelet transfusions result in refractoriness, that both ELISA and IFT are insufficient to detect refractoriness despite of their significant correlation, and that other methods than these are needed in order to detect alloimmunization.

Adolescent↗
PubMed1983

Storage of platelets for tests of platelet function: effects of pH on platelet aggregation and liberation of beta-thromboglobulin.

Platelet aggregation responses are influenced by conditions of storage of platelet-rich plasma (PRP). The aim of the present study was to further define the necessity for pH control during storage of PRP for tests of platelet function. Aliquots of citrated PRP were maintained at different pH levels by alteration of the CO2 content of the atmosphere in an incubation chamber. At intervals over 2-2 1/2 hours, plasma beta-thromboglobulin and 14C-serotonin were measured as well as platelet aggregation induced by ADP and collagen. At each time a dose response curve was studied for aliquots stored at each pH level. When two aliquots were maintained at different pH levels in the range 6.85-7.90, there was a significant increase in aggregation at the higher pH, even when the pH difference was as small as 0.2 units. In this range, pH did not influence the rate of deterioration of the aggregation response, but when pH was above 8.0, there was marked deterioration of the response. Increased pH was associated with an increase in plasma levels of beta-thromboglobulin and 14C-serotonin, which was more marked when pH was above 8.0. It appears that increases in pH are harmful to platelets and even small pH changes should be avoided during storage of platelet-rich plasma for tests of platelet function.

Adenosine Diphosphate↗
PubMed1994

Platelet release reaction during EDTA-induced platelet agglutinations and inhibition of EDTA-induced platelet agglutination by anti-glycoprotein II b/III a complex monoclonal antibody.

To characterize the nature of EDTA-induced platelet agglutination, the spontaneous release of beta-thromboglobulin (beta-TG) and platelet factor 4 (PF4) was examined during EDTA-induced platelet agglutinations. A slight release of beta-TG and PF4 was observed when EDTA-anticoagulated whole blood from cases with EDTA-induced platelet agglutination was kept for 60 minutes, whereas a high spontaneous release of these proteins was found from normal blood anticoagulated with EDTA. These findings imply that EDTA-dependent platelet agglutinin may stabilize the platelet membrane surfaces. Secondly, we found that pretreatment of fresh blood with anti-glycoprotein (GP) II b/III a complex monoclonal antibody dramatically reduced EDTA-induced platelet agglutinations. This study indicated that the binding sites of EDTA-dependent antibody might be GP II b/III a complex. The use of an anti-GP II b/III a complex monoclonal antibody may be useful in avoiding analytical errors in some cases with EDTA-induced pseudothrombocytopenia.

Adenosine Diphosphate↗
PubMed1998

Quantitative assessment of platelets, platelet microparticles, and platelet aggregates with flow cytometry.

With fluorescent beads it has become possible to determine absolute numbers of cells in a given sample instead of relative percentages on a standard flow cytometer. This study assesses the ability to count platelets, microparticles, and aggregates with a flow cytometer. Whole blood was stimulated with 0.1 U thrombin per milliliter. Platelet and microparticle counts decreased, while the number of aggregates increased. Unactivated whole blood was diluted with buffer and showed a corresponding decrease in the concentration of platelets, microparticles, and aggregates. The platelet count on the flow cytometer was always in good correlation with counts on an automated blood analyzer. Only the cytometer, and not the automated analyzer, was able to detect and count microparticles and aggregates. In highly diluted samples of unactivated whole blood there was a spurious relative increase in CD62p-positive platelets because of a surplus of anti-CD62p antibodies and a relative increase in microparticles. Flow cytometry is a valuable method for counting platelets, aggregates, and microparticles in unstimulated and activated blood samples. If the platelet count changes and drops to less than 50% of the count for which the amount of antibody and the cytometer settings have initially been adjusted, care has to be taken to avoid misinterpretation.

Antibodies, Monoclonal↗
PubMed1994

Laboratory diagnosis of heparin-associated thrombocytopenia and comparison of platelet aggregation test, heparin-induced platelet activation test, and platelet factor 4/heparin enzyme-linked immunosorbent assay.

BACKGROUND: As clinical diagnosis of heparin-associated thrombocytopenia (HAT) is often difficult, confirmation by sensitive laboratory assays is desirable. STUDY DESIGN AND METHODS: The sensitivity of the heparin-induced platelet activation (HIPA) test and the platelet aggregation test (PAT) was prospectively compared by using the sera of 209 patients with the putative diagnosis of HAT. Both assays were performed concomitantly with platelets of the same four donors using a different combination of donors from day to day. Further, all sera were assessed with a platelet factor 4 (PF4)/heparin enzyme-linked immunosorbent assay (ELISA). RESULTS: Positive results were obtained with 33 percent of sera in the PF4/heparin ELISA, with 33.5 percent of sera in the HIPA test, and with 11.5 percent of sera in the PAT. The PF4/heparin ELISA and the HIPA test showed no difference in sensitivity (p = 0.27 by McNemar's test) and were more sensitive than PAT (p < 10(-8) by McNemar's test). However, they recognized different patient cohorts. Nine HIPA-indeterminate and 12 HIPA-negative sera were positive in the PF4/heparin ELISA. Eight of the nine indeterminate sera caused platelet activation with high heparin concentrations in the HIPA test. Eleven of the 12 negative sera contained no IgG, but 9 contained IgM and 2 contained IgA HAT antibodies. Four sera that were indeterminate in the PF4/heparin ELISA and 18 sera that were negative were positive in the HIPA test. None of the sera that were positive in the PAT was missed in the HIPA test, but two of those were negative in the PF4/heparin ELISA. All sera were assessed with four low-molecular-weight heparins and a low-molecular-weight heparinoid in the HIPA test with platelets from the same four donors. Low-molecular-weight heparin caused platelet activation with positive sera in 98 percent of tests, and the heparinoid did so in 10 percent; in a further 12.8 percent, crossreactivity to the low-molecular-weight heparinoid could not be excluded. CONCLUSION: The majority of HAT antibodies react with a PF4/heparin complex, but there is strong evidence that other antigens are involved in some patients. The HIPA test and the PF4/heparin ELISA are sensitive for diagnosing HAT, and they complement one another.

Enzyme-Linked Immunosorbent Assay↗
PubMed2001

Platelet interactions with liposomes carrying recombinant platelet membrane glycoproteins or fibrinogen: approach to platelet substitutes.

Liposomes carrying both recombinant platelet membrane glycoproteins GPIa/IIa (rGPIa/IIa) and GPIb alpha (rGPIb alpha) (rGPIa/IIa-Ib alpha-liposomes), or fibrinogen (Fbg-liposomes) were prepared. Their interactions with platelets on a collagen surface under flow conditions were evaluated using a recirculating flow chamber, mounted on an epifluorescence microscope, which allows for real-time visualization of fluorescence-labeled liposomes or platelets interacting with the surface. Adhesion of platelets to the collagen surface increased with increasing the shear rate from 600 to 2400 s(-1). Also, the percentages of surface coverage of rGPIa/IIa-Ib alpha-liposomes or Fbg-liposomes increased with increasing platelet adhesion. These phenomena were attenuated by a peptide containing arginine-glycine-aspartic acid (RGD-peptide), or prostaglandin E1 (PGE), but not by a peptide containing arginine-glycine-glutamic acid (RGE-peptide). In a homogeneous solution, rGPIa/IIa-Ib alpha-liposomes and Fbg-liposomes enhanced platelet aggregation in a dose-dependent manner, as evaluated using an aggregometer. These findings suggest that rGPIa/IIa-Ib alpha-liposomes and Fbg-liposomes form aggregates at the site of injury in blood vessels, resulting in stationary adhesion together with activated platelets.

Antigens, CD↗
PubMed1994

Influence of Pall Pl-50 platelet filters on lactate dehydrogenase, platelet factor 4, and complement factor 3 in stored platelet concentrates.

BACKGROUND: The study examines Pall Pl-50 platelet filters with respect to their influence on some biochemical properties of platelet concentrates. MATERIAL AND METHODS: Ten pairs of pooled platelet preparations, each consisting of 3 platelet concentrates, were studied. On day 1, one of the preparations was filtered and the other served as an identical non-filtered control. Immediately after filtration platelet counts, the levels of desarginated activated complement factor 3 (C3a), extracellular levels of lactate dehydrogenase (LDH) and extracellular and total concentrations of platelet factor 4 (PF4) were determined in both concentrates. After 5 days sterility testing and determination of extracellular levels of PF4 and LDH were performed. RESULTS: Extracellular concentrations of PF4 and C3a decreased immediately after filtration (p < 0.01). Furthermore, Pall Pl-50 filters caused cellular instability reflected by an increased release of PF4 (p < 0.01) during subsequent storage. CONCLUSION: Platelet concentrates filtered with Pall Pl-50 would not appear suitable for storage.

Blood Preservation↗
PubMedDate not supplied

Correlation of platelet concentration in platelet-rich plasma to the extraction method, age, sex, and platelet count of the donor.

An important reason to improve methods of isolating platelet-rich plasma (PRP) is the potential use of autologous platelet growth factors. In addition to discontinuous plasma separation, a second method for extraction of PRP has now become available, which can be performed directly by the surgeon. In this study, the suitability of the 2 methods of producing PRP was compared. Whole blood was drawn from 158 healthy donors (112 men, 46 women) aged 20 to 62 years (mean 34, SD 10). The PRP was separated by the discontinuous plasma separation method (by the blood bank) or by the so-called "buffy coat" method (the "self-concentration" method, analogous to the PRP Kit, Curasan, Kleinostheim, Germany). Platelet counts differed significantly according to donor blood (median men 237,500/microL, women 272,000/microL), blood bank PRP preparation (median men 1,302,000/microL, women 1,548,500/microL), and self-concentrated PRP (median men 944,000/microL, women 1,026,000/microL). The platelet concentration of the blood bank PRP correlated with the platelet count in the donor whole blood (Spearman's correlation coefficient r(s) = 0.73). However, there was no significant correlation between the platelet count of self-concentrated PRP and donor whole blood (r(s) = 0.22). Significant but irrelevant influences of sex on platelet concentration were found, but no influence of age was detected.

Adult↗
PubMed1986

Cationized ferritin as a platelet-stimulating surface probe. Binding to platelets and effects on platelet function.

Polycationic derivatives of ferritin containing primary amino groups (CFah) or tertiary amino groups (CFdmp) were potent platelet agonists inducing shape change, aggregation and secretion, but also agglutination in the presence of EDTA. Pretreatment of platelets with neuraminidase, PGE1, indomethacin, or creatine kinase/creatine phosphate inhibited CF-induced activation. In contrast, neuraminidase and PGE1 increased the agglutination by CF, indicating an inverse relationship between activation and CF-induced agglutination. At pH 7.4, the cationic charges of CFdmp exceeded those of CFah by a factor of 1.5 and the platelets bound approximately 1.5 times more CFah than CFdmp, suggesting the same number of anionic surface sites for both CF preparations. The capacity of the platelets to bind CF was diminished by 55% at 0 degree C or by 62% after aldehyde fixation and by 13% with PGE1. This suggests that the binding capacity depends on the mobility of the binding sites in the plane of the membrane but is only slightly increased by platelet activation. Binding to fixed or cold platelets approached equilibrium within a few seconds whereas saturation required several minutes at 37 degrees C. Neuraminidase preferentially reduced the slow binding and much less the rapid binding. Since activation by CF developed during seconds, suppressible by a brief treatment with neuraminidase 25 mU/ml, a small portion of neuraminidase-sensitive sites appears to be necessary for CF-induced platelet activation. Full activation and agglutination occurred at CF concentrations far below saturating concentrations. The results show that neither CF-induced activation nor agglutination depend on a simple neutralization of the negative surface charge.

Agglutination↗
PubMed1985

Nomenclature of secreted platelet proteins--report of the Working Party on Secreted Platelet Proteins of the Subcommittee on Platelets.

Standard nomenclature for a number of secreted platelet proteins was agreed upon by The Working Party on Secreted Platelet Proteins of the Subcommittee on Platelets. Platelet factor 4 will continue to be used for the molecule with high heparin affinity, subunit molecular weight of 7780, and the described amino acid sequence. beta-Thromboglobulin will be used to designate beta-Thromboglobulin (81 amino acids/subunit, beta-mobility on cellulose-acetate electrophoresis, pI 7), low-affinity platelet factor 4 (85 amino acids/subunit, gamma-mobility on cellulose-acetate electrophoresis, pI 8), and platelet basic protein (94 amino acids/subunit, pI 10) when these are measured immunologically in plasma, but that thromboglobulin with a superscript designation of the pI should be used when assays are conducted on samples after isoelectric focusing, and a subscript amino-terminal amino acid can be added when a purified protein is described. Thrombospondin will continue to be the designation for the high molecular weight trimer that has previously been called thrombospondin or glycoprotein G. Platelet derived growth factor will be used for the group of closely related proteins of molecular weight about 30,000 and isoelectric point about 10.

Animals↗
PubMed1986

Cryopreservation of dog platelets with dimethyl sulfoxide: therapeutic effectiveness of cryopreserved platelets in the treatment of thrombocytopenic dogs, and the effect of platelet storage at -80 degrees C.

Dog platelets were frozen with 6% dimethyl sulfoxide at 2-3 degrees C per minute in a -80 degrees C mechanical freezer. The frozen platelets were stored at -80 degrees C for as long as 39 months. After storage at -80 degrees C for less than 1 year, platelet in vitro freeze-thaw-wash recovery values were 70%, and in vivo survival values 1 to 2 hr after transfusion were 40% those of fresh platelets. After 2 years or longer storage, in vitro freeze-thaw-wash recovery values were 60%, and in vivo survival values 1 to 2 hr after transfusion were 20% those of fresh platelets. These results indicate that significant deterioration of the dog platelets occurred between the first and second year of storage at -80 degrees C. Platelets that were stored frozen at -80 degrees C for less than 1 year and washed before transfusion into lethally irradiated thrombocytopenic dogs were hemostatically effective.

Animals↗