Arachidonic acid metabolism in platelets of patients with essential thrombocythaemia.

Platelet aggregation tests and studies comprising [14C] arachidonic acid [14C]AA incorporation, release and metabolism were performed in resting and thrombinstimulated platelets of 11 patients with essential thrombocythaemia (ET) and 11 normal subjects. Nine patients had abnormal aggregation tests. Incorporation and distribution of [14C]AA in main platelet phospholipids (PLs) was similar in both groups. Activated platelets of patients with ET released more radioactivity from PLs that controls (13.7 +/- 5.4% versus 8.2 +/- 1.9%, p < 0.01). The formation of 12-L-hydroxy-5,8,10-heptadecatrienoic acid (HHT) was also increased (3.3 +/- 1.4% of total radioactivity versus 1.6 +/- 0.4% in controls (p < 0.0001). The same results were obtained for the generation of thromboxane B2 (p < 0.01). We did not detect differences in the formation of 12-L-hydroxy- 5,8,10,14-eicosatetraenoic acid (3.3 +/- 1.7% in patents versus 2.0 +/- 0.5% in controls). These results indicate that platelets of patients with ET have an increased activity of phospholipases and suggest a facilitated metabolism of arachidonate by the prostaglandinsynthetase pathway. Our results also demonstrate that impairment of aggregation tests in these patients was not due to a defective activity of the enzymes involved in the release and metabolism of AA by platelets.

[Von Willebrand disease: characteristics and response to desmopressin. Study of 103 cases]. / Enfermedad de Von Willebrand: características y respuesta a desmopresina. Estudio de 103 casos.

BACKGROUND: To describe the main characteristics and response to desmopressin infusion in 103 patients suffering from von Willebrand disease (vWD). PATIENTS AND METHODS: The criteria for diagnosis were (except for type 2N) the coexistence of von Willebrand factor ristocetin cofactor (vWF:RCo) activity < 50 U/dl with bleeding disease or one of the following data: von Willebrand factor antigen (vWF:Ag) activity < 50 U/dl, factor VIII (FVIII) activity < 50 U/dl or the existence of a increased bleeding time (BT). Multimeric studies of vWF were performed in 51 cases and ristocetin induced platelet aggregation (RIPA) was also performed. RESULTS: Spontaneous bleeding was found in 36 patients, while in 18 cases the diagnosis was done after surgical bleeding. Thirteen patients (6 presenting with mild bleeding) were studied for abnormalities in the routine preanestesic tests. Other 22 patients were diagnosed with vWD by familial studies. There were 3 patients with type 2B, 1 case with type 2N and other patient with type 3. BT was found increased in 26 out of 58 patients. The activities of vWF:CoR and vWF:Ag were 38.4 (9.4) U/dl and 45.8 (23.2) U/dl, respectively, while the activity of FVIII was 49.9 (20.8) U/dl. Prophylactic DDAVP (desmopressin) was infused in 32 patients. After 1 h, basal activities of vWF:CoR and vWF:Ag were increased by 3.1 (3.2) and 3.4 (3.1) times, respectively, and maintained for 3 h. FVIII activity increased 3.6 (2.3) times the basal levels decreasing after 3 h (2.9 [2.1]; p < 0.01). The BT was corrected in 8 out of ten patients. CONCLUSIONS: vWD is a major cause of surgical bleeding. Preanestesic anamnesis and coagulation tests can be useful to identify vWD. Many patients with vWD have normal BT. A failure in the response to desmopressin infusion is unusual.

Red cell lipid abnormalities in acquired acanthocytosis are extended to platelets.

Acquired acanthocytosis (AA) is an uncommon disease characterized by the presence of abnormal red cells (acanthocytes) in the blood smears of affected subjects. Acanthocyte membrane is enriched in cholesterol by an abnormal plasma lipoprotein. We studied the existence of similar changes in platelets of one patient with AA. Red cell cholesterol/phospholipid (Ch/PL) ratio in the patient was 1.6 (normal 1.1 +/- 0.1). Phosphatidylcholine (PC) comprised 36% of total phospholipid (30.7 +/- 1.8% in controls). Platelets showed aberrant morphology in the blood smears, and the ratio Ch/PL was high in comparison with normal platelets (1.4 v 0.6 +/- 0.1). PC comprised 52% of total PL (39.6 +/- 1.9% in normal platelets). Normal platelets incubated with autologous plasma for 24 h maintained a Ch/PL ratio of 0.7, whereas this value changed to 1.4 when these cells were incubated with plasma from the patient. These results suggest that platelets of patients affected by AA acquire the same biochemical abnormality as red cells.

Platelets isolated by albumin gradient retain normal activation pathways.

Isolated platelets from samples with low counts produce technical problems. Albumin gradient (AG) has been shown to be useful for this purpose, preserving the aggregating response of these cells. The influence of this method in the enzymatic pathways that regulate the platelet activation is studied. Platelets were isolated by either AG or conventional centrifugation methods and labelled with C-14-arachidonic acid (C-14-AA). Isolated platelets were activated with thrombin (5 U/ml) and lipids were extracted according to Bligh and Dyer. Platelet phospholipids and prostanoids were resolved by TLC. The incorporation of C-14-AA by platelets was similar by both methods (31.7 +/- 18% versus 47.2 +/- 6.9%), as well as the distribution of C-14-AA in the five major platelet phospholipids. Formation of radioactive thromboxane B2, hydroxyheptadecatrienoic acid and hydroxyeicosatetraenoic acid by activated platelets was also similar by both methods. These findings suggest that platelet isolation by albumin gradient preserves the enzymatic pathways responsible for the activation of these cells.

Phospholipid determination in platelets, plasma and red cells of patients with chronic myeloproliferative disorders.

Red cell phospholipids (PLs) were assessed in 11 patients with essential thrombocythemia and 5 patients with polycythemia vera. Platelet and plasma PLs were also determined in 10 of these patients, and the results were compared with studies performed in 16 healthy volunteers. The amount of platelet PLs in patients was similar to controls (556 +/- 90 mmol/10(9) cells, versus 481 +/- 91 mmol/10(9) cells), as was the percentage of the main specimens of these compounds, including phosphatidylserine (11.1 +/- 0.8%), which is relevant for platelet procoagulant activity. We did not find differences between red cell PLs of patients (300 +/- 60 nmol/10(9) cells), versus controls (289 +/- 71 nmol/10(9) cells), and the sphingomyelin/phosphatidylcholine ratio in these cells was the same in both groups (0.75 +/- 0.1). Finally, we did not detect any alteration in the amount of plasma PLs specimens.

Plasma phospholipids and platelet function in uremic patients.

An increased activity of phospholipase A2 has been observed in the plasma of patients with uremia. This enzyme converts phosphatidylcholine to lysophosphatidylcholine (LPC), an inhibitor of platelet aggregation. We measured the levels of plasma phospholipids including LPC, and platelet aggregation in 7 patients with uremia. Platelet response to agonists was defective, mainly with collagen (p < 0.001). The patients' levels of LPC in plasma were similar to those of controls (109.7 +/- 41.6 vs. 80.4 +/- 16.8 nmol/ml) and did not correlate with the platelet response to adenosine diphosphate (r = -0.51). The amount of phosphatidylcholine was increased with respect to normal plasma (1,041.0 +/- 201.8 vs. 760.8 +/- 142.7 nmol/ml, p < 0.01), while the levels of other phospholipids were normal. These results do not suggest a participation of plasma LPC in the genesis of the platelet defect observed in patients with uremia.

Lipid composition of platelets in patients with uremia.

AIMS: The lipid composition of platelets and the function of these cells in patients with uremia were studied. METHODS: Fourteen patients and 14 normal volunteers were studied. Platelet lipids including phospholipids and cholesterol, as well as the platelet aggregation response to agonists, were studied. RESULTS: The amount of platelet phospholipids was decreased in patients compared to controls (338.0 +/- 79 vs. 511.6 +/- 125 nmol/10(9) cells; p < 0.001), while the percentage of the five main specimens of these compounds was normal. The content of platelet cholesterol in patients (97.8 +/- 17.0 microg/10(9) cells) was similar to that in controls (91.7 +/- 26.0 microg/10(9) cells). Consequently, the cholesterol:phospholipid ratio in uremic platelets was increased (0.75 +/- 0.1 vs. 0.46 +/- 0.1; p < 0.01). Although this feature is associated with hyperreactive platelets, the aggregation tests were defective for adenosin diphosphate (p < 0.01), arachidonic acid (p < 0.01), epinephrine (p < 0.01) and collagen (p < 0.001). This behavior is probably due to the multifactorial platelet defect described in uremia.

Increased levels of plasma von Willebrand factor in migraine crisis.

INTRODUCTION: To evaluate the participation of the vessel wall in the pathogenesis of migraine attack, we measured the plasma levels of von Willebrand factor (vWF), a protein secreted from the endothelial cells. MATERIAL & METHODS: 17 patients suffering from migraine without aura and 25 healthy volunteers were studied. von Willebrand factor and platelet aggregation tests were studied by conventional methods. RESULTS: The levels of vWF:antigen increased from 72.4 +/- 29 U/dl in the intercrisis to 130.2 +/- 75 U/dl during the attack (p < 0.01). We did not detect difference in the platelet aggregability in both phases. Plasma vWF activity measured as ristocetin cofactor (vWF:RCo) was similar in intercrisis and crisis (100.6 +/- 31 U/dl vs 94.5 +/- 44 U/dl). CONCLUSIONS: There is a plasma release of vWF molecules during the migraine crisis. This feature is not platelet dependent and is probably a consequence of endothelial stress.

Lipid composition of platelets in patients suffering from migraine without aura.

Patients with migraine have a platelet hyperaggregability. As this alteration could be the consequence of an abnormal lipid composition of platelet membranes, we studied the phospholipid specimens and the cholesterol/phospholipid ratio in platelet of neuron patients suffering from migraine. The cholesterol/phospholipid ratio was 0.7 +/- 0.1 (normal 0.6 +/- 0.1, molar ratio). The proportion of five main platelet phospholipids components including phosphatidylcholine, phosphatidylethanolamine, sphingomyelin, phosphatidylserine, and phosphatidylinositol, were also normal. These data suggest that platelet hyperactivity in patients with migraine is not due to an altered lipid content of those cells.

La duración de la formación de Oncología y la historia natural de los tumores / Oncology training period and natural history of tumors

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Toxicidad por sobredosis de mitomicina / Toxicity of mitomycin-C overdose

La toxicidad hematológica de la mitomicina C es tardía y puede aparecer meses después de la administración del fármaco. Es excepcional encontrar casos de toxicidad por sobredosis de mitomicina. Presentamos un caso de aplasia medular severa y prolongada tras sobredosificación de mitomicina-C. La dosis total acumulada (100 mg/m2) fue prácticamente el doble de la que se recomienda habitualmente y se administró con una pauta semanal a lo largo de cinco semanas. El paciente ingresó tres meses después de la primera dosis con deterioro del estado general, aplasia medular confirmada mediante biopsia y ascitis secundaria a recidiva abdominal de adenocarcinoma gástrico. La toxicidad hematológica se mantuvo durante los 69 días que duró el ingreso y no comenzó a recuperarse hasta casi cinco meses después de la primera dosis de mitomicina (AU)

Sepsis con origen en neoplasia de mama / Sepsis as a consequence of breast cancer

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