The thermotropic state transition of the lipids in isolated platelet membranes has been studied by Ranian spectroscopy in the temperature range from -3 "C to + 45 "C using the (C -H) stretching vibrations, carotenoid (s) vibrations at 1530cmp' and 1160cm-', as well as the skeletal optical vibrations.1. The increase of temperature causes a decrease in intensity of the 2885 cm-* band relative to the 2855 cm-' one.The evaluation of the ratio 12885/Z2855 as a function of temperature indicates a double thermotropic state transition of platelet membrane lipids: the first one near 5°C and the second near 17.5"C.2. The ratio 11530/11160 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 "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.There is evidence that the plasma membrane of blood platelets plays an important role in the platelet function [I].In an approach to the molecular organisation of platelet membranes we have undertaken Raman and infrared spectroscopic studies on intact platelet as well as on isolated platelet membranes [2-41. In the course of these studies, besides the presence of carotenoid(s) in platelet membranes [2], a thermotropic state transition of the platelet membrane lipid molecules has been signalized [4].Raman spectroscopy has provided information about thermotropic state transitions which occur in model membrane systems ([5] and references therein) and in lipids [6,7], as well as in plasma membranes isolated from various types of cells, such as erythrocytes [8], lymphocytes [9] or thymocytes [lo]. Therefore, in an attempt to know more about the characteristics and thermal response of platelet membrane components, we have investigated the variations of the Raman scattering as a function of temperature over the range -3 "C to + 45 "C.The present work analyses the main variations with temperature of Raman scattering which are due to (a) (C-H) stretching vibrations (2800-3000 cm-I ) ; (b) resonanceenhancedvibrations, v(-C=C-)andv(=C-C=)ofplatelet membrane-bound carotenoid(s) previously identified [2] and (c) skeletal optical v(C-C) vibrations (1000-1150cm-').Results are reported which show that the lipids in platelet membrane do undergo a double thermotropic state transition: the first one between 0 "C and 7 "C and the second one between 13°C and 20 "C. The spectral characteristics indicate that the carotenoid(s) present in platelet membranes, in addition to the carotenoid-protein complexes that are formed [2], might also be linked to the lipids which undergo transition between 13°C and 20 "C. MATERIALS AND METHODSPreparation of Platelet Membranes. Platelets were isolated by differential centrifugation from fresh human blood anticoagulated with citrate/d...
To better preserve human platelets in hyper‐citrated plasma in siliconized glassware, the authors recommend centrifugation between 7 and 10 C rather than at 4 C and the dispersion of the button of platelets either by the “propipette” method (drawing the supernatant plasma just above the deposited platelets up and down a pipette) or by a mechanical method using a Whirli mixer. With these methods of dispersion, the rise of acid nitro‐phenylphosphatase in platelets and plasma during one day of storage is less than with the use of a scraping method. The in vitro ADP‐induced aggregation is also well preserved at 4 and at 8 C. Electron microscopic studies do not reveal detectable differences in platelet morphology at these temperatures after one day of storage. The use of radiochromium for platelet tagging does not entirely support the above results but this method is probably not the best for measuring platelet viability during storage. One‐day storage at 37 C results in the non‐aggregability of platelets, conspicuous increase in platelet nitrophenylphosphatase and considerable morphological modifications of platelets, as has been observed by Firkin.7
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 °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.
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