Platelets in the Carcinoid Syndrome: A Chemical and Ultrastructural Investigation

Abstract

SUMMARY A combined chemical and electron microscopic study of normal platelets and platelets from patients with the carcinoid syndrome has revealed an association between their serotonin content and certain alterations in their cytoplasmic structure. In addition to a fibrillary structure of possible cytoskeletal significance, platelets also contain a system of microtubules and vesicles. When the platelet serotonin content is high this tubular structure is prominent and communicates with large vacuoles which may contain granular material. Normal platelets incubated with serotonin show similar alterations in structure. In addition, serial investigations of platelets from two carcinoid patients suggest that in addition to the normal active transport process for absorbing serotonin a diffusion process can operate when the cell is exposed to high environmental concentrations. The significance of these storage mechanisms in relation to normal and elevated platelet serotonin concentration is discussed.

Defective Binding of Thrombin to Platelets in Myeloid Leukaemia

“…The materials which are secreted from the platelets during the release reaction are located in the cytoplasmic granules. Abnormalities in the number, size and structure of platelet granules have been reported in refractory anaemia, Down's syndrome and the carcinoid syndrome (Maldonado, 1975;Boisseau & Le Menn, 1974;White & Davis, 1969;Crawford et al, 1967).…”

Platelet vacuoles in a dog with severe nonregenerative anemia: evidence of platelet autophagy

“…Vacuolated platelets have been described in pigs afflicted with porcine stress syndrome, in dogs with acute megakaryoblastic leukemia, and in a dog with probable essential thrombocythemia . Similar dysplastic changes in platelets have been reported more frequently in people, including patients suffering from carcinoid syndrome, thrombopathic thrombocytopenia, Parkinson's disease, Bernard–Soulier syndrome, chronic mercury exposure, gray platelet syndrome, and various leukemias . With the exception of gray platelet syndrome in people, the platelet vacuoles in all of these conditions were interpreted as dilated regions of the OCS, but confirmation by TEM was not performed in all cases.…”

“…The OCS allows platelets to increase their surface membrane capacity during activation. Distension of the OCS is generally regarded as a nonspecific finding, but supportive of an underlying pathologic phenomenon based on previous reports . Lanthanum nitrate particles have been used to demonstrate that some platelet vacuoles in patients with gray platelet syndrome are continuous with the OCS, whereas others are not .…”

“…Distension of the OCS is generally regarded as a nonspecific finding, but supportive of an underlying pathologic phenomenon based on previous reports. [2][3][4][5][6][7][8][9][10][11][12][13][14] Lanthanum nitrate particles have been used to demonstrate that some platelet vacuoles in patients with gray platelet syndrome are continuous with the OCS, whereas others are not. 13 The vacuoles that did not communicate with the OCS contained digesting cytoplasmic structures, and were thought to represent autophagic vacuoles.…”

Methodological Investigations on the in Vitro Uptake of 5‐hydroxytryptamin by Human Blood Platelets

“…Most investigators use EDTA as anticoagulant for incubations (e. g., Hughes & Bradie (1959), Weissbach & Redfield (1960), Crawford et al (1967), Sneddon (1969). When blood platelets are treated with EDTA, they undergo changes in shape from their normal disc-like form to a more spherical configuration with a 30 o/o increase in volume (Zucker & Borelli (1954), Aster ( 1966 ) .…”