Hyperlactacidemia as a factor of thrombocyte adhesiveness

Résumé Les auteurs, après avoir montré le rôle probable de l'hyperlactacidémie dans l'apparition du sludge, du blocage du SRE, de l'dème des cellules endothéliales des vaisseaux et de l'dème intraglial, montrent dans le présent travail sa responsabilité probable dans l'agrégation des plaquettes sanguines de l'homme et du rat, en dehors de toute influence de pH.     

Accumulation of 5-hydroxydopamine in 5-HT storage organelles of cat platelets and concomitant changes in platelet aggregation

Zusammenfassung 5-HO-DA, das in den Vesikeln der peripheren adrenergen Nervenendigungen gespeichert und als falscher Transmitter freigesetzt wird, wird auch in den Serotonin-Speicher-Granula der Thrombozyten hochgradig angereichert, ohne jedoch das endogene Serotonin freizusetzen. Gleichzeitig wird die durch Serotonin hervorgerufene Thrombozytenaggregation blockiert.     

Cytosolic calcium in platelet activation

Experiments with permeabilised platelets, and with intact platelets loaded with fluorescent Ca²⁺-indicators, over the past several years have greatly extended our knowledge and understanding of cytosolic Ca²⁺ as a platelet activator and its interactions with other cytosolic regulators. This article outlines insights, gained from the use of the fluorescent dyes, into maintenance and restoration of basal [Ca²⁺]_i, mechanisms of receptor-mediated Ca²⁺-mobilisation and quantitation of [Ca²⁺]_i/response relations in intact human platelets.     

Cytosolic calcium in platelet activation

Experiments with permeabilised platelets, and with intact platelets loaded with fluorescent Ca2+-indicators, over the past several years have greatly extended our knowledge and understanding of cytosolic Ca2+ as a platelet activator and its interactions with other cytosolic regulators. This article outlines insights, gained from the use of the fluorescent dyes, into maintenance and restoration of basal [Ca2+]i, mechanisms of receptor-mediated Ca2+-mobilisation and quantitation of [Ca2+]i/response relations in intact human platelets.     

The release of platelet factor 4 during platelet aggregation and the possible significance of this reaction in hemostasis

Résumé Nous avons constaté que le facteur plaquettaire 4 est libéré au début de l'aggrégation des plaquettes par l'ADP et l'adrénaline. Ce phénomène a pu être mis en évidence en étudiant l'activité antihéparinique et l'activité paracoagulante (coagulation non enzymatique de complexes solubles de monomères de fibrine) du facteur plaquettaire 4.     

Beta-blocking drugs and human platelet aggregation in vitro

Riassunto L'effeto inibente di farmaci -bloccanti sull'aggregazione di piastrine umane indotta in vitro mediante ADP è risultato proporzionale alle dosi dei farmaci impiegati. La seguente scala gerarchica di potenza è disposta in ordine decrescente di attività: pindolol, K 4423, propranolol, INPEA.     

Artero-venous differences in blood platelet clumping by ADP

Riassunto È stata studiata con aggregometro l'aggregazione delle piastrine di ratto in PRP ottenuto da sangue arterioso e da diversi vasi venosi. È risultato che l'effetto aggregante dell'ADP è molto più marcato sulle piastrine venose che su quelle arteriose.     

Effect of platelet membranes on the electrophoretic pattern of 6-phosphogluconic dehydrogenase from platelet lysates

Riassunto L'incubazione di lisati piastrinici con NADP provoca inattivazione della 6PGD e ne modifica la migrazione elettroforetica. Non si osserva invece attivazione della GSSG-R.

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Supported by a grant from the Consiglio Nazionale delle Ricerche Contratto No 70.00378/18/115.3565. Roma (Italy).     

Reelin is a platelet protein and functions as a positive regulator of platelet spreading on fibrinogen

Abnormalities of platelet functions have been linked to reelin-impaired neuronal disorders. However, little attention has been given to understanding the interplay between reelin and platelet. In this study, reelin was found to present in the human platelets and megakaryocyte-like leukemic cells. Reelin-binding assays revealed that extracellular reelin can interact with platelets through the receptor belonging to the low density lipoprotein receptor gene family. The reelin-to-platelet interactions enhance platelet spreading on fibrinogen concomitant with the augmentation of lamellipodia formation and F-actin bundling. In contrast, reelin has no effect on integrin αIIbβ3 activation and agonist-induced platelet aggregation. Molecular analysis revealed that the up-regulation of Rac1 activity and the inhibition of protein kinase C δ-Thr505 phosphorylation are important for reelin-mediated enhancement of platelet spreading on fibrinogen. These findings demonstrate for the first time that reelin is present in platelets and the reelin-to-platelet interactions play a novel role in platelet signaling and functions.     

Reserpine and human platelet 5-hydroxytryptamine

Zusammenfassung Nach einmaliger intramuskulärer Injektion von 1 mg Reserpin sinkt beim Menschen der 5-Oxytryptamingehalt der Blutplättchen zwei Tage lang ab, um bis zum neunten Tag auf unbestimmbarem Wert zu verharren. Während dieser Zeit ist die 5-OT-Aufnahmefähigkeit der Plättchen vermindert. Der Oxytryptamingehalt der Plättchen erreicht seinen Ausgangswert erst ungefähr 3 Wochen nach der Reserpingabe.Die Ansicht, dass die Plättchen freies 5-Oxytryptamin aus dem Kreislauf aufnehmen, wäre mit diesem Ergebnis zu vereinbaren. Die Dauer des Effektes könnte bedeuten, dass Reserpin entweder auf Plättchenvorstadien im Knochenmark wirkt oder aber dass die Lebensdauer der Plättchen in Wirklichkeit länger ist, als neuerdings angenommen wird.