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Molecular and Cellular Biochemistry Dec 1978This article summarizes recent ultrastructure findings from our laboratory and documents some of the information accumulated primarily since 1975 from many laboratories.... (Review)
Review
This article summarizes recent ultrastructure findings from our laboratory and documents some of the information accumulated primarily since 1975 from many laboratories. Special attention is given to documentation by scanning electron microscopy which affords insight into platelet activation (adhesion, aggregation, release/secretion) and especially platelet-vessel wall interactions. Structural physiology of platelets is considered in some detail as a basis for understanding platelet disorders contributing to clinical problems of thrombosis and hemorrhage. The impaired ability of von Willebrand platelets to adhere to injured vessel wall is reported using the human umbilical vein perfusion model. Relationships between platelets and blood coagulation factors focus on the exquisite sensitivity of platelets to minute amounts of thrombin. Unmasking of platelet factor 3 sites is identified on activated platelets, after glutaraldehyde fixation, by their reaction ot latex bearing anti-platelet factor 3 markers. The basis for platelet-collagen interactions is reviewed. Conditions for and possible mechanisms behind platelet interaction with vessel wall are discussed. Ex vivo flowing blood-vessel wall models offer opportunities for improved understanding of the platelets role(s) in vascular diseases.
Topics: Blood Platelets; Disease; Humans; Microscopy, Electron, Scanning; Platelet Aggregation
PubMed: 370550
DOI: 10.1007/BF00496238 -
Klinicheskaia Laboratornaia Diagnostika 2019Platelets play fundamental role in ensuring the hemostatic function in blood. In addition to this canonical function, the blood plates play angiotrophic, immunological,... (Review)
Review
Platelets play fundamental role in ensuring the hemostatic function in blood. In addition to this canonical function, the blood plates play angiotrophic, immunological, transport role, participate in the activation of plasma hemostasis, retraction of a blood clot, and can record circulating immune complexes. The review article presents current data on the structure and conjugation of molecular rearrangements of platelet ultrastructures associated with the functioning of an open canalicular platelet system, a dense tubular system, and a platelet cytoplasmic membrane. The main types of resting platelet metabolism, and the processes underlying the activation of platelets associated with the enhancement of carbohydrate and fatty acid catabolism are characterized, as well as some signaling pathways that regulate processes of induction of platelet aggregation. The data show the value of lipid components of activated platelet membranes, including phospholipids of various classes, glycolipids and cholesterol. The role of regulatory processes associated with the non-covalent modification of certain platelet proteins with fatty acids is reflected. Fundamental questions of platelet metabolism are relevant nowadays and require a combined approach of studying them, which can potentially solve many problems of clinical laboratory diagnostics, pathobiochemistry, and pharmacology. In preparing the review, we used sources from international and russian databases: Scopus, Web of Science, RSCI.
Topics: Blood Platelets; Hemostasis; Humans; Platelet Aggregation; Thrombosis
PubMed: 31012555
DOI: 10.18821/0869-2084-2019-64-3-164-169 -
Platelets Nov 2004In this brief review of the literature it is pointed out that during platelet activation and degranulation platelet alpha granules leave the platelet interior through... (Review)
Review
In this brief review of the literature it is pointed out that during platelet activation and degranulation platelet alpha granules leave the platelet interior through blebs in platelet plasma membrane and through the tips of the pseudopods, and then accumulate in the external milieu. There they undergo disintegration and secondary adhesion to the platelet plasma membranes. During their disintegration they expose their tightly packed GPIIb-IIIa complexes, annexin V stainable aminophospholipids, factor V, and the membrane markers CD62 and CD63. There is also demasking of lysosomal acid phosphatase activity and microvesicle formation. Lysosomal nature of platelet alpha granules is mentioned. It is suggested that platelet alpha granules are the sole source of platelet procoagulant activity and platelet microparticles (MP) or microvesicles (MV). The implications of this concept for antiplatelet therapy are discussed. A relationship of this process to tissue factor exposure and apoptosis is suggested.
Topics: Animals; Blood Coagulation; Blood Platelets; Cytoplasmic Granules; Humans; Platelet Activation
PubMed: 15745311
DOI: 10.1080/09537100410001721315 -
Seminars in Hematology Jan 1971
Review
Topics: Adenine Nucleotides; Blood Coagulation; Blood Platelet Disorders; Blood Platelets; Cell Membrane; Phosphatidylethanolamines
PubMed: 5542296
DOI: No ID Found -
Clinical Chemistry and Laboratory... Apr 2012Studies on platelet function have accelerated and gained popularity since the advent of novel treatment modalities and techniques on atherosclerotic vascular disease,... (Review)
Review
Studies on platelet function have accelerated and gained popularity since the advent of novel treatment modalities and techniques on atherosclerotic vascular disease, such as antiplatelet drugs and stents. Today it is widely known that platelets exert a fundamental role in inflammation in addition to their long known role in homeostasis and thrombotic events. Interaction with endothelial cells and leukocytes mediates inflammation, contributes to atherogenesis and modulates immune activity. Platelet activation which is a central factor in many arterial disorders may be triggered by multiple pathways. Platelet activation is shown as forming a larger shape, aggregation and releasing various active contents. Mean platelet volume is a marker of platelet size, function and activation. Increased mean platelet volume is shown by active and large platelets that release more thromboxane A2 than smaller ones. The aim of this review is to determine whether early detection of platelet activation via increased mean platelet volume would help to recognize the pro-inflammatory state and administer appropriate and effective treatment properly. An easily detectable marker by using a prompt and functional technique would help our approach to inflammation caused by platelets.
Topics: Blood Platelets; Cell Size; Humans; Thrombosis
PubMed: 22112054
DOI: 10.1515/CCLM.2011.806 -
Blood Jul 1988Recent studies on platelet heterogeneity support the hypothesis that platelet production is regulated to maintain a constant functional platelet mass. In concept this... (Review)
Review
Recent studies on platelet heterogeneity support the hypothesis that platelet production is regulated to maintain a constant functional platelet mass. In concept this form of regulation is analogous to the manner by which RBC production is controlled to maintain the oxygen-carrying capacity of blood. The platelet mass appears to correlate more closely with platelet function than the platelet count alone, since several factors in addition to the platelet count have been shown to influence the platelets' hemostatic function. These factors include platelet size, density, age, and previous hemostatic interactions. Application of these concepts to clinical problems has provided important insights into platelet physiology and reactivity. Failure to account for differences in platelet heterogeneity among individuals may introduce significant errors in the interpretation of data from laboratory and clinical investigations. However, despite advances, a number of practical issues remain to be resolved before measurements of platelet heterogeneity become accepted as routine clinical tests and are used in the diagnosis of pathologic states.
Topics: Animals; Blood Platelets; Cell Survival; Humans; Platelet Count
PubMed: 3291975
DOI: No ID Found -
Mini Reviews in Medicinal Chemistry Feb 2011Blood platelets play a crucial role in the primary hemostasis and vessel wall repair. However; platelet hyperactivation is implicated in the pathogenesis of... (Review)
Review
Blood platelets play a crucial role in the primary hemostasis and vessel wall repair. However; platelet hyperactivation is implicated in the pathogenesis of cardiovascular diseases such as thrombosis, atherosclerosis and stroke. Epidemiological data have suggested that regular consumption of fruits and vegetables, which are rich in flavonoids, is associated to a reduction in cardiovascular events. The cardioprotective effect of flavonoids is partly due to the inhibition of platelet function. However; the mechanisms underlying the anti-platelet effect of these compounds remain unclear. The aim of this review is to discuss the role of platelets in cardiovascular disease and to provide an overview of the potential anti-platelet effect of flavonoids, focusing on the various platelet signaling pathways modulated by flavonoids, including oxidative stress, protein tyrosine phosphorylation, calcium mobilization and nitric oxide pathway. The understanding of these mechanisms will be helpful in the development of new anti-platelet agents based on flavonoids with fewer or no adverse effects.
Topics: Blood Platelets; Cardiovascular Diseases; Flavonoids; Humans; Signal Transduction
PubMed: 21222578
DOI: 10.2174/138955711794519537 -
Free Radical Biology & Medicine 1997This article reviews our current understanding of the role of oxygen free radicals in platelet activation. Several studies have indicated that platelets, in analogy to... (Review)
Review
This article reviews our current understanding of the role of oxygen free radicals in platelet activation. Several studies have indicated that platelets, in analogy to other circulating blood cells, are able to produce oxygen free radicals, which are likely to play an important role in the mechanism of platelet activation and aggregation. Platelet activation has been obtained with very low, physiologically relevant concentrations of radicals generated chemically, by leukocytes, and by hemoglobin derived from membrane leakage of erythrocytes. Knowledge of the role of reactive species in platelet physiology is relevant because platelets are brought into close contact with other cells capable of producing free radicals, such as neutrophils, macrophages, and endothelial cells, during the formation of thrombus. The physiopatological importance of these findings is high because it is now emerging that free radicals may have a role in the mechanism of atherosclerosis and its thrombotic complications, where the causative role of platelets is well documented. This background suggests therapeutic interventions with antioxidants as antiplatelet agents to improve the pharmacological effect of classical antiplatelet drug such as aspirin.
Topics: Antioxidants; Blood Platelets; Free Radicals; Humans; Oxygen; Platelet Activation
PubMed: 9034239
DOI: 10.1016/s0891-5849(96)00488-1 -
The Journal of Surgical Research Nov 1982Although platelets have been associated with angina pectoris, myocardial infarction, and sudden death, the platelet's capacity for induction and propagation of cardiac...
Although platelets have been associated with angina pectoris, myocardial infarction, and sudden death, the platelet's capacity for induction and propagation of cardiac ischemia remains incompletely defined. We therefore evaluated the effects of platelet activation occurring within the coronary circulation and tested the hypothesis that inhibition of platelet function would prevent platelet-induced cardiac ischemia. Human platelets were isolated from blood obtained from normal donors by Sepharose 2B column chromatography, resuspended in Hepes buffer, and added to the perfusate of a Langendorff rabbit heart (platelet counts greater than 10,000/microliters). Without, and with low dose (10 microM) prostaglandin E1 (PGE1), a reversible inhibitor of platelet function, immediate and irreversible global cardiac ischemia, as monitored by NADH fluorescent photography, ensued (N = 4) following platelet activation with thrombin (0.1 to 1 U/ml). Higher concentrations of PGE1 (0.1 to 1 mM, N = 2) or aspirin ingestion (1000 mg taken approximately 12, 4, and 1 hr prior to experiment, N = 2) completely prevented this platelet-induced myocardial ischemia. Aspirin, unlike PGE1, was effective despite its inability to block thrombin-induced platelet aggregation in our in vitro gel-filtered system. We conclude that activation of platelets within the coronary circulation is sufficient for induction of irreversible cardiac ischemia. The efficacy of aspirin, a cyclooxygenase inhibitor, further suggests that the products of arachidonate metabolism (e.g., thromboxanes) have a fundamental role in the genesis of platelet-mediated myocardial ischemia.
Topics: Animals; Blood Platelets; Blood Transfusion; Coronary Circulation; Coronary Disease; Humans; Prostaglandins E; Rabbits
PubMed: 7132326
DOI: 10.1016/0022-4804(82)90055-5 -
Journal of Thrombosis and Thrombolysis Jan 2014Platelets, anucleated cells with a central role in hemostasis and inflammation, contain messenger RNAs and microRNAs of unknown functionality and clinical relevance.... (Review)
Review
Platelets, anucleated cells with a central role in hemostasis and inflammation, contain messenger RNAs and microRNAs of unknown functionality and clinical relevance. Historically, platelet RNA was viewed as merely a remnant of platelet biogenesis; however, several studies now refute this assumption. Studies have shown that platelets can actively translate RNA to protein and that specific RNA profiles correlate with select human clinical phenotypes. These studies support a more fluid role for platelet RNA in platelet function and disease development. Our lab and others have recently studied the platelet's unique ability to transfer RNA to recipient cells and the effect this transfer has on the recipient cells' functions. This transfer may represent a previously unknown form of vascular cell communication and modulation. Unlike the well-characterized thrombotic properties of platelets, the nature and purpose of platelet RNA transfer has not been determined, partly due to limitations in techniques used to manipulate platelet RNA profiles. Defining the mechanism of RNA transfer and its role in the vascular system will allow for the better understanding of how platelets function in both their traditional thrombotic role and non-traditional functions, potentially having widespread implications in several fields.
Topics: Animals; Biomarkers; Blood Platelets; Humans; MicroRNAs; Platelet Activation; RNA, Messenger; Thrombosis
PubMed: 24163053
DOI: 10.1007/s11239-013-1001-1