El sistema antioxidativo y morfología de los trombocitos en un grupo poblacional en primavera / The antioxidant system and morphology of thrombocytes in a population group during the spring

En un grupo de 25 individuos masculinos con edades comprendidas entre 16 y 29 años se observó, al estudiar la reserva de antioxidantes durante la primavera, aumento de la concentración de vitamina C, así mismo se apreció disminución del tanto por ciento de eritrocitos hemolizados y de la activación de la peroxidación con respecto a la URSS y poca activación de la trombocitopoyesis

Beneficial effect of brief pre-transfusion incubation of platelets at 37 degrees C.

The effects of brief warming of stored platelet concentrates were assessed in 15 children undergoing transfusion for stable thrombocytopenia due to chemotherapy (n = 13) or aplastic anaemia. Half of a pool of platelet concentrates stored at 22 degrees C was incubated at 37 degrees C for 1 hour and the other half at room temperature. Each patient received one bag of warmed and one of unwarmed cells transfused in random order 2 h apart. Platelet warming improved transfusion efficacy, as assessed on the basis of corrected platelet count increments (CCIs) and platelet morphology. Compared with unwarmed bags, warmed bags had a higher morphology score (p = 0.0001) and a higher CCI (adjusted for the transfusion order) at 1 h (n = 11; p = 0.014) and at 2 h (n = 15, p = 0.006) post transfusion. Thus, with platelets stored at room temperature bags warmed before transfusion to 37 degrees C for 1 h provide a larger number of circulating platelets after transfusion than do unwarmed bags.

[Blood platelet changes in myeloproliferative disorders]. / Alterazioni piastriniche in corso di disordini mieloproliferativi.

Morphofunctional alterations to the platelets in myeloproliferative disorders (MPD), conditions featuring clonal rearrangement of the haemopoietic stem-cell, were examined. These platelet anomalies including morphological alterations, acquired storage pool disease, membrane alterations, altered arachidonic acid metabolism and structural alterations to the von Willebrand factor may cause thromboembolisms or haemorrhages that are responsible for a significant incidence of morbidity and mortality. In contrast the reduced mitogenic activity of the platelets may be of significant prognostic value since it proves the anomalous transformation of the megakaryocytic clone. The main in vivo and in vitro tests (bleeding time and the study of platelet aggregation) were investigate as indicators of platelet function. Unfortunately, these tests proved of little use for the early diagnosis of haemorrhage or thromboembolism in MPD.

Storage of platelets for tests of platelet function: effects of temperature on platelet aggregation, platelet morphology and liberation of beta-thromboglobulin.

We have studied the effect of temperature on platelets during storage for tests of platelet function. Aliquots of PRP were stored at constant pH at 37 degrees C, room temperature and 4 degrees C. At intervals up to five hours, samples were taken for estimation of platelet shape, plasma levels of beta-thromboglobulin and 14C-serotonin, and assessment of platelet aggregation in response to a range of concentrations of ADP and collagen. When PRP was stored at 37 degrees C there was a gradual decrease in the aggregation response during the period of storage. At room temperature the decrease was slower but the response to ADP often increased dramatically before decreasing; at this temperature there was pronounced liberation of beta TG while there was none at 37 degrees C. Platelets stored at 37 degrees C were smooth and elliptical when examined by electron microscopy, but those stored at room temperature showed partial loss of discoid shape and formation of some pseudopodia. Storage at 4 degrees C was associated with total loss of discoid shape and formation of many large pseudopodia. Light transmission studies also showed loss of discoid shape at room temperature and 4 degrees C. We conclude that storage at 4 degrees C or at room temperature causes platelet activation. To avoid this PRP should be stored at 37 degrees C prior to tests of platelet function.

Effect of methods of platelet resuspension on stored platelets.

Platelets are prepared from whole blood by differential centrifugation. Following their isolation as a platelet button, platelets are allowed to rest for a short period in the residual plasma before resuspension. In this study, the feasibility of resuspending platelets without this rest period is studied. A total of 35 platelet concentrates (PC) were prepared from blood collected in CPDA-1 and resuspended by one of the following four methods: (1) no resting period, PC placed on a rotator immediately after preparation, (2) a 1.5 hour rest period and gentle shaking prior to rotation, (3) no rest period and immediate gentle shaking prior to rotation, and (4) a 1.5 hour resting phase and no shaking prior to rotation. Following the previous processing, all platelet concentrates were stored for 72 hours on an elliptical platelet rotator at 20 to 24 degrees C to provide continuous agitation. A number of in vitro tests were used as indicators of platelet viability during storage. These included platelet morphology, pO2, pCO2, pH, osmotic recovery, number of platelets in the concentrate, and platelet volume distribution. Our findings demonstrate that platelets are of similar quality after storage in all of the four groups described. Our studies suggest that the resting phase is unnecessary for platelet preparation. The elimination of the resting phase would allow platelet concentrates to be available sooner and improve cost-effectiveness of platelet preparation.

Enhanced thrombin and plasmin activity with exercise in man.

We measured products of thrombin and plasmin action and of the platelet release reaction during exercise to determine if the well-known effect of exercise on in vitro coagulation and fibrinolytic tests reflects activity of these systems in vivo. Plasma fibrinopeptide A, produced by thrombin-mediated proteolysis of fibrinogen, increased with graded treadmill and cycle exercise to postexercise levels of 20--30 times resting values. Fibrin/fibrinogen-related D antigen increased in a similar fashion with peak levels at maximal O2 uptake. Plasma-activated partial thromboplastin times fell as fibrinopeptide A levels increased. Unheated fibrin plate lysis areas increased as D antigen concentrations rose, indicating increased release of plasminogen activator. In contrast to activation of the soluble coagulation and fibrinolytic systems, platelet counts and plasma levels of beta-thromboglobulin, a platelet release protein, did not change significantly with exercise. The effect of exercise on thrombin and plasmin was not influenced by prior physical training, but appeared to be less with cycle exercise than with treadmill exercise.