Thermotropic state transition in isolated platelet membranes studied by Raman spectroscopy.

The thermotropic state transition of the lipids in isolated platelet membranes has been studied by Raman spectroscopy in the temperature range from -3 degrees C to +45 degrees C using the (C-H) stretching vibrations, carotenoid(s) vibrations at 1530 cm-1 and 1160 cm-1, as well as the skeletal optical vibrations. 1. The increase of temperature causes a decrease in intensity of the 2885 cm-1 band relative to the 2855 cm-1 one. The evaluation of the ratio I2885/I2855 as a function of temperature indicates a double thermotropic state transition of platelet membrane lipids: the first one near 5 degrees C and the second near 17.5 degrees C. 2. The ratio I1530/I1160 shows that the intensity variations in the carotenoid(s) peaks follow the second lipid transition. Thus, it seems that the platelet membrane carotenoid(s) might be linked to the lipids which undergo transition near 17.5 degrees C. 3. The spectral changes in the skeletal optical range suggest a considerable proportion of all trans chains in the membrane lipids at lower temperatures whereas gauche structures seem to be introduced at higher temperatures.

[Volume distribution studies on the platelet populations (author's transl)]. / Etude sur la distribution des volumes des populations plaquettaires.

The volume distribution into human platelet populations was investigated in order to determine if thereis a relationship between the cell density and the cell size and if the isolated platelets are homogeneous populations of cells. The platelet populations were isolated from platelet rich plasma or from washed platelets by isopycnic centrifugation on sucrose density gradients. Platelet volume was measured electronically with Coulter F or Coulter Z Bic coupled with Channelyser C 1000. The results show that there exists a direct relationship between platelet density and size, since the volumetric parameters gradually increase from the small platelets of lower density to the larger ones isolated at higher density. Evidence was also obtained that the isolated populations of platelets were heterogeneous and their volume distribution was log-normal. Both the heavy and the light platelet populations were found as a mixture of mainly large or mainly small platelets respectively.

[Altered platelet surface glycoproteins in chronic myeloid leukemia (author's transl)]. / Glycoprotéines de surface altérées des plaquettes de leucémie myéloïde chronique

The present status of knowledge about the platelet membrane components suggests that glycoproteins (GP) are involved in the intercellular platelet specific reactions, such as adhesion and aggregation. Normal human platelets and platelet membranes solubilized under dissociating conditions produce characteristic polypeptide and GP electrophoretic patterns (PAGE). Platelets and isolated platelet membranes from patients with chronic myeloid leukemia (CML) presented dissimilarities of their glycoconjugates as compared to the normal platelets. The modification of the electrophoretic banding visualized by the periodic acid-Schiff's reagent (PAS) consisted in the decrease of the 155,000 GP L, the presence of two PAS positive bands in the area of the 135,000 normal PAS positive GP LL and a variable decrease of the 100,000 GP LLL (Apparent mol. wt. are indicated). In addition, preliminary data showed an increased catalytic transfer of the labelled galactosyl and N acetygalactosaminyl residues from exogenous nucleotide 14C-sugar precursors onto the CML-platelet endogenous sugar acceptors. These firstly reported data on molecular abnormalities of the platelet membrane GP in CML, suggested their possible relationship with the impaired platelet adhesion and aggregation occurring in this disease or the ability of leukemic platelets to express modified surface membrane components.

[Membrane glycoproteins and platelet protein glycosylation in chronic myeloid leukemia]. / Etudes sur les glycoprotéines membranaires et la glycosylation des protéines des plaquettes dans la leucémie myéloïde chronique

SDS-polyacrylamide gel electrophoresis of solubilized whole platelets and isolated platelet membranes from patients with chronic myeloid leukemia (CML) as compared to the normal platelet-Schiff-stained glycoproteins (GP) (noted GP I, II, III of app. MW 155, 130 and 100.10(3) daltons, respectively), showed the following modifications: the decrease of GP I; the presence of the GP II and GP IIx doublet; the moderate and variable decrease of the GP III; the increase of the platelet glycolipid. No significant differences were detectable on the polypeptide patterns from CML platelets in respect to the normal 20-25 protein constituents. Using a radio-isotopic method it has been measured as an elevated catalytic transfer of the galactosyl and N-acetylgalactosaminyl residues from nucléotide 14C sugar derivatives onto the endogenous acceptors of platelets from CML. The results obtained suggested that CML platelets with recognized abnormal functions, have modifications at the level of the macromolecular surface glycoprotein constituents and/or changes of the glycoconjugates reactive structures involved in the devopment of the periodic acid-Schiff reaction as also in the transfer reaction of the sugar residues.

Studies on human platelets stored at 20-22 degrees C without agitation.

Human blood platelets in ACD plasma were stored in sterile plastic bags for 24-96 h at the ambient temperature without agitation. No spontaneous aggregation nor bacterial contamination were noted. A progressive loss of the following parameters was seen: platelet count; ADP-, thrombin-, collagen-, and epinephrine-induced platelet aggregation; platelet factor 3 activity; reversible response to the osmotic shock; volumetric constants; amount of UV-absorbant material; 14C-5-hydroxytryptamine and 3H-adenosine uptake and release; platelet population pattern and glycogen synthesis activity. The platelet aggregation and release, the osmotic shock test, and the platelet population pattern appear to better illustrate the early changes during platelet storage and to account for the 25-42% of recirculation of 24 h stored platelets administered into thrombocytopenic patients. As stated by Murphy and Gaardner, platelets stored at 20-22 degrees C with or without agitation, although having failed to retain total functional and biochemical capacities, paradoxically seem to recuperate in vivo as shown by survival data and hemostatic effects.

[Hereditary hypogranular thrombocytopathic thrombocytopenia. Ultrastructural study of a megakaryocytopathy (author's transl)]. / Thrombocytopéne thrombocytopathique hypogranulaire héréditaire. Etude ultrastructurale d'une mégacaryocytopathie

The ultrastructure of megakaryocytes and blood platelets has been studied in 3 members of a Swiss family, in which a haemorrhagic diathesis of varying degree occurred in at least three generations. Blood platelets show an extremely low number of dense granules, slightly increased mean diameter and irregular distribution of glycogen in unusually large clusters. The number of megakaryocytes in bone marrow is normal. Electron microscopy shows asynchronous development of their structural components: a severe defect in maturation of specific granules is followed by retardation and irregularity in the demarcation of the "platelet prospective fields", Golgi membranes have few vesicles, glycogen occurs partly in huge clusters and megakaryocytes with mature platelet fields are very rare. The ultrastructural picture of platelet formation in megakaryocytes indicates that this haemorrhagic syndrome may be understood as a megakaryocytopathy. The results of functional and biochemical analyses performed on blood platelets show a defect in both phases of aggregation and in PF 3 availability, normal survival, decreased total sialic acid content, and absence of the heaviest platelet population ("D") isolated by discontinuous sucrose gradient. The autosomal dominant transmission of this together with its concomitance with blood group O suggest its relationship with the familial thrombopathic thrombocytopenia described in 1968 by Kurstjens and al. in a Dutch family [13].