Blood Platelet Behaviour during and after Open-heart Surgery

In view of the high incidence of thromboembolic complications after the insertion of cardiac valve prostheses, platelet adhesiveness and aggregation was measured in whole blood before, during, and for several days after this operation in 10 patients. Cardiopulmonary bypass resulted in a profound decrease in the platelet count, in the number of adhesive platelets, and in platelet aggregation. These changes returned to near preoperative levels by the sixth postoperative day. Thereafter a consistent and sustained increase in platelet count, in the number of adhesive platelets, and in platelet aggregation was observed. The results suggest that the prevalence of thromboembolism after valve replacement may be due partly to changes in platelet behaviour.     

Abnormalities of platelet aggregation in chronic myeloproliferative disorders

A large variety of platelet dysfunctions has been described in chronic myeloproliferative disorders. These abnormalities may be due to deficiency of platelet granules, arahidonic acid metabolism defects or platelet membrane glycoproteins abnormalities. In this study we intend to detect the incidence of platelet function defects in 76 patients with various types of chronic myeloproliferative disorders. The platelet activity was studied in vitro by measuring platelet aggregation in response to ADP, epinephrine, collagen, arachidonic acid and ristocetin. These results were subsequently correlated with bleeding time and clinical aspects (bleeding or thrombosis). We found complex changes in platelet response with all agonists, in varied proportions. These abnormalities include absent, decreased or abnormal platelet aggregation response. In a few cases we found a markedly decreased, almost absent platelet response to all agonists while in some patients a normal platelet aggregation was noted. The correlation between these results and template bleeding time, thrombotic or hemorrhagic events and the type of diseases was difficult to establish and sometimes conflictual. Despite this fact, we consider that investigating platelet aggregation may be useful not only for the assesment of the hemostatic balance in chronic myeloproliferative disorders but also for a better insight into cell abnormalities occuring in these pathologic conditions.     

Effects of dietary polyunsaturated fatty acid on platelet aggregation in rats

In the present study, we changed the fatty acid profile in blood and platelet membranes by dietary manipulation, and examined the effect on platelet aggregation in rats. Fifty-five rats were divided into five groups and fed for 56 days with 1% cholesterol and different types of fatty acid-rich diets: basal, lard, lard + fish oil, soybean oil, and soybean oil + fish oil. a decrease in serum arachidonic acid (20:4, omega-6, AA) and an increase in serum eicosapentaenoic acid (20:5, omega-3, EPA) were found in all experimental dietary groups fed with refined fish oil. Similar changes in the polyunsaturated fatty acids were also found in the platelet membrane phospholipids. Platelet aggregation, quantitated by the slope and height of the aggregation curve induced by different concentrations of ADP in a platelet aggregometer, was inhibited in all groups fed with refined fish oil. This inhibition of platelet aggregation may be related to an increase in the ratio of EPA and AA in the platelet membrane phospholipids after dietary manipulation. The differences in the platelet aggregation and thromboxane B2 (TXB2) concentration between the lard and the lard + fish oil groups were more profound than that between the soybean oil and the soybean oil + fish oil group. However, the malondialdehyde (MDA) concentration revealed no significant differences between the five groups.     

Relationship of turbidity to the stages of platelet aggregation

The process of platelet aggregation as detected by turbidity changes in the platelet aggregometer was studied relative to light scattering by large particles. For latex beads a plot of light scattering intensity/unit mass versus particle size gave increased light scattering intensity for small particle sizes but decreased scattering at large particle size. This behavior is predicted by Rayleigh-Gans theory. These results were related to the platelet aggregometer, an optical instrument used to measure the association of small particles (monomeric platelets) to large particles (platelet aggregates). Formalin-fixed platelets do not show changes in light transmission due to energy-requiring processes, such as shape change, so that turbidity changes in the presence of aggregating agents could be attributed to a change in platelet aggregation state. Small platelet aggregates showed increased turbidity compared to a similar mass of monomeric platelets. In fact, very large platelet aggregates that were visible to the unaided eye were needed to produce a decrease in light scattering intensity. Thus, turbidity can either increase or decrease with platelet aggregation depending on the size of the aggregates. Studies of platelet aggregation that show no initial increase in turbidity must be characterized by dominance of large platelet aggregates and monomeric platelets.     

Changes in Functional Activity of Platelets after Repeated Physical Exercise

The changes in platelet aggregation and retraction parameters were studied in 23 young men with high working capacities (PWC₁₇₀ > 130 W) after dosed repeated exercise with two equal loads of a moderate (N ₁ = 1.36 W/kg, t ₁ = 6.94 min) and a high (N ₂ = 2.87 W/kg, t ₂ = 3.09 min) intensity with a 1-h rest between them. Three types of response of ADP-dependent platelet aggregation to the exercise were revealed: an increase after each load and a decrease to the initial value at rest; an increase after the first load, persistence at rest, and a decrease after the second load; and a decrease after both loads and restoration at rest. The changes in platelet activity in the different types of response depended on the initial values and the course of the rest. The changes in most parameters of aggregation and retraction after loads and at rest correlated with their initial values. Muscular activity raised platelet aggregability when it was initially low and lowered it when it was initially high. The preceding muscle load amplified these correlations, and the repeated muscle load amplified them even more pronouncedly.__________Translated from Fiziologiya Cheloveka, Vol. 31, No. 4, 2005, pp. 102–107.Original Russian Text Copyright © 2005 by Golyshenkov, Mel’nikova, Tairova.     

Age-related hematological changes in normal F344 rats: during the neonatal period.

In order to clarify age-related changes in hematological values of normal rats after birth, blood samples from neonatal F344 rats of both sexes were examined periodically during the period from 0 to 40 days postpartum. The erythrocyte count (RBC) increased with time after birth as a function of age. In contrast, the reticulocyte count (Retics) continuously decreased with time after birth. Hemoglobin (Hb), hematocrit (Ht), and the mean corpuscular hemoglobin concentration (MCHC) tended to decrease after birth until weaning (about 21 days postpartum), but they began to increase after weaning. Mean corpuscular volume (MCV) and mean corpuscular hemoglobin (MCH) also gradually decreased after birth until weaning, but they were unchanged thereafter. The platelet count (PLT) gradually increased after birth and reached a plateau at weaning. Microscopic examination of blood smears revealed that erythrocytes at birth had characteristic morphological features such as anisocytosis, polychromasia, basophilic stippling, Howell-Jolly body, and erythroblastosis. These characteristic features, however, disappeared by 30 days after birth. The total leukocyte count (WBC) gradually increased with time after birth, due to an increase in the number of lymphocytes. The lymphocyte count started to rapidly increase within several days after birth and the increase continued thereafter. Other differential leukocyte counts also showed various characteristic patterns of changes during the neonatal period. There were no apparent differences between males and females in these changes in hematological values.     

Characterization of platelet abnormalities of Tester Moriyama (TM) rats with storage pool deficiency

Platelet abnormalities of Tester Moriyama (TM) rats, which have prolonged bleeding time with normal platelet count, were characterized by comparison with those of fawn-hooded (FH) rats with platelet storage pool deficiency (SPD). Morphologically, the dense granules were virtually lacking in platelets from TM and FH rats. Platelets from TM and FH rats aggregated in response to adenosine diphosphate (ADP), but failed to have secondary aggregation. In contrast, platelet aggregation was completely absent in response to 1 to 20 micrograms of collagen/ml, although partial aggregation was observed at the higher dosage of 50 micrograms/ml. Normal amounts of platelet membrane glycoproteins IIb/IIIa were expressed in TM and FH rats, but platelet adenosine triphosphate (ATP) and ADP contents were lower than those in platelets from control Wistar rats. Platelet ATP-to-ADP ratio of TM and FH rats was significantly higher than that of Wistar rats. Serotonin content in platelets from TM and FH rats was 20 to 25% that of Wistar rat platelets. These results suggested that platelet abnormalities of TM rats are a typical characteristic of platelet SPD and are similar to those of FH rats, which are genetically different from TM rats. Therefore, TM rats may serve as a useful animal model for the study of platelet SPD.     

急、慢性缺氧对大鼠凝血机能的影响

本文讨论了实验性缺氧对大鼠凝血机能产生的影响。实验结果表明,大鼠在模拟8000米高度两小时后,血小板凝聚性、血小板因子3活性明显增加,纤溶活性下降,同时,纤维蛋白原含量和因子X也明显下降。大鼠在模拟7000米经36天间歇性慢性缺氧,血小板计数、血小板凝聚性,血小板因子3活性、纤维蛋白原含量、因子X活性均显著增加,部分凝血活酶时间缩短、纤溶活性下降,明显地出现凝血增强的趋势。本文还讨论了抗缺氧药物复方党参、异叶青兰对人鼠急性缺氧时凝血机能的影响。     

The effects of short-term training on platelet functions and total antioxidant capacity in rats

The purpose of the present study was to investigate the effect of short-term endurance training on plasma total antioxidant status (TAS) and on in vitro platelet aggregation and ATP release. Blood samples were collected from the abdominal aorta of rats following short-term treadmill exercise (25 m/min, 0 % grade, 30 min) for three consecutive days, as well as in non-exercised control group. Platelet aggregation and platelet ATP release were evaluated by impedance and bioluminescence techniques, respectively. Plasma TAS was measured spectrophotometrically. Plasma TAS was higher and ADP-induced platelet ATP release was lower in the short-term training group with respect to the control group (p<0.001). Significant negative correlation (r = -0.56, p<0.05) was found between plasma TAS and ADP-induced platelet ATP release. Neither ADP- and collagen-induced maximum aggregation rate nor collagen-induced platelet ATP release were significantly different between the groups. According to these results, short-term training caused an alteration in platelet functions limited to the secretion response, which may be related to the oxidant/antioxidant balance changes favoring the antioxidants. The improved plasma total antioxidant capacity was possibly sufficient to prevent exercise-induced oxidative damage, and the adaptive response of platelets might be associated with enhanced antioxidant status.     

Transient deficiency of peripheral blood accessory cells in supporting T cell mitogenesis in patients suffering from chronic idiopathic thrombocytopenic purpura after intravenous gammaglobulin treatment

Mitogenic response of blood lymphocytes to phytohemagglutinin (PHA) and to OKT3 monoclonal antibodies was investigated in 7 patients suffering from chronic idiopathic thrombocytopenic purpura (ITP) before, during and after high-dose intravenous (i.v.) immunogammaglobulin (IgG) infusion. The platelet count rose above the pre-treatment values during infusion therapy in all patients but one. Five out of seven patients presented elevated platelet-associated IgG (PA-IgG) levels at the time of the first infusion; four of these showed an increase in platelet count and a transient reduction or normalization of PA-IgG after IgG infusion. Five out of seven patients showed an impairment of T lymphocyte mitogenic response to PHA and OKT3 before therapy. All patients responded to IgG therapy with a transient deficiency of FcR mediated monocytes (Mo) in supporting T cell mitogenesis induced by both mitogens during and after IgG infusion. This reduced cooperative capability of Mo disappeared at various times after the end of therapy (range 3-12 days). The transient alteration of Mo function, possibly due to a modification in the surface number or in the affinity of Fc-receptors, can explain in part, the increase in platelet count during and after IgSRK infusion.     

Increased factor VIII/vWf levels in patients with reduced platelet number

Factor VIII/von Willebrand factor (VIII/vWf) related properties were studied in twenty six patients with thrombocytopenia. Fifteen patients were affected by idiopathic thrombocytopenic purpura (ITP) and 11 patients by thrombocytopenia of a different nature or non-ITP (n-ITP). All patients showed an enhancement of platelet associated IgG (PAIgG). A significant increase of factor VIII ristocetin cofactor (VIII R: RCoF) and factor VIII related antigen (VIII R:Ag) was found in ITP patients while normal values were observed for factor VIII coagulant (VIII:C). All factor VIII/vWf components, on the contrary, were increased in n-ITP group with a prevalence of VIII R:RCoF as observed in ITP group even though with lower mean values. Multimeric analysis of VIII/vWf demonstrated a higher concentration of all multimeric components, with major representation of higher molecular weight multimers (HMWM) in patients of both groups. Two patients were studied before and after improvement in platelet count. A decrease of vWf related properties (VIII R:RCoF and VIII R:Ag) concomitant with the increase in platelet count was found. In n-ITP patients a statistical correlation between VIII R:RCoF and PAIgG was also observed while no correlation was found between other factor VIII/vWf components and PAIgG both in ITP and n-ITP patients.     

Blood viscosity parameter correlation with types of leukemia.

We investigated the hemorheological, hematological and biochemical parameters in 30 cases of acute lymphocytic leukemia (ALL), 21 cases of acute myelogenous leukemia (AML) and 30 cases of chronic myelogenous leukemia (CML). The parameters studied include whole blood viscosity, plasma viscosity, erythrocyte sedimentation rate (ESR), red cell filterability, hematocrit, platelet count and aggregation, fibrinogen, hemoglobin, leucocyte count, bleeding time and lactate dehydrogenase activity (LDH). In the cases of ALL we observed significant decrease in whole blood viscosity, hemoglobin, hematocrit and platelet count but an increase in plasma viscosity, fibrinogen, bleeding time and LDH activity. In the cases of AML, we observed increase in whole blood viscosity, plasma viscosity, ESR, fibrinogen, leucocyte count, bleeding time and LDH activity but decrease in the hemoglobin, hematocrit and platelet count. In the cases of CML, we observed an increase of whole blood viscosity, plasma viscosity, ESR, fibrinogen elevation but decreases in bleeding time. In all cases, red cell filterability was unaffected.     

Effect of altitude exposure on platelets.

Since decompression from depth is known to produce a fall in platelet count, the effect of altitude decompression and high-altitude exposure on platelets was investigated. Sixteen subjects decompressed without hypoxia to 20,000 ft simulated altitude for two hours showed a significant (P less than 0.01) drop in circulating platelet count of approximately 10% for three days following decompression. Four of five subjects similarly exposed had a shortened autologous platelet survival compared to that prior to exposure. Subjects exposed to 9,800 ft and then 17,600 ft in a mountain environment showed a significant mean decrease in platelet count on day 2 of 7% and 25% respectively, which had returned to control by day 5. Nonhypoxic and hypoxic decompressed rabbits which received homologous chromium-51-labeled platelets had an increase in lung radioactivity compared with sea-level controls. It is postulated that altitude decompression produces platelet reductions similar to these seen after decompression from depth, and that platelets sequester in the pulmonary vascular bed.     

犬心肌缺血早期血小板聚集功能和冠脉侧支循环的改变

本实验在18只麻醉开胸犬观察了急性心肌缺血早期血小板聚集功能和冠脉侧支循环功能的变化。实验结果如下:阻断冠脉后心肌缺血区血液中血小板聚集率(PAgR)增大,血小板计数(PC)减少。缺血50min时,PAgR增大58.7±5.6％,PC减少39.5±23.6％,与对照值有明显差异(均为P<0.01)。与此同时,在控制血压条件下,心肌缺血早期单位压力差下冠脉侧支血流量的变化与对照值无明显差异,而根据Wyatt等公式计算的流经缺血区末梢血管的有效侧支血流量明显降低,缺血50min时较对照值降低23.5±9.7％(P<0.05)。PAgR变化与有效侧支血流量改变呈明显负相关(r=-0.887,P<0.01);冠脉侧支指数与梗塞范围呈明显负相关(r=-0.847,P<0.01)。阻断冠脉前静脉注射血小板聚集功能抑制剂阿斯匹林,可明显减轻上述各项参数的异常变化。这些结果提示,心肌缺血早期血小板聚集功能的异常变化虽然对冠脉侧支血管的血流阻力影响较小,但却使流经缺血区末梢血管的有效侧支血流量明显减小,进而扩大梗塞范围。     

Effects of bopindolol on platelet function in hypertension at rest and during exercise

The effects of bopindolol, a new nonselective beta-blocking agent, on platelet function have been studied in 10 male hypertensive patients given the drug (1 mg/day) in turn for eight weeks. Bopindolol significantly (p less than 0.01) decreased the bicycle exercise- (1.5 W/kg body weight for 6 minutes) induced increase in platelet aggregation. During bopindolol-treatment both the slope and the height of the platelet aggregation response curve were moderately decreased at rest before exercise and significantly (p less than 0.05) decreased at rest after exercise. During exercise the slope amounted to 75.4 +/- 44 degrees before and to 70.8 +/- 5.3 degrees after therapy (p less than 0.01), the height to 64.0 +/- 11.9% before and to 58.1 +/- 14.7% (p less than 0.05) after therapy. Furthermore, bopindolol significantly increased the exercise-induced decrease in platelet sensitivity to PGI2 (p less than 0.05; IC-50-value: 2.10 +/- 0.47 vs 1.88 +/- 0.31 ng/ml) and PGD2 (p less than 0.05; IC-50-value: (19.88 +/- 2.10 vs 18.57 +/- 1.63 ng/ml). Bopindolol also significantly (p less than 0.05) decreased the exercise-induced elevation in serum-TXB2 (244.9 +/- 35.2 vs 237.3 +/- 27.2 ng/ml) and plasma-TXB2 (15.7 +/- 6.3 vs 13.1 +/- 3.7 pg/ml). The platelet count, the plasma levels of 6-oxo-PGF1 alpha, beta-thromboglobulin (beta-TG) and platelet factor 4 (PF4) were not affected by bopindolol. It is concluded that bopindolol favourably affects platelet function, in that it lowers exercise-induced platelet aggregation and TXB2-formation in therapeutical doses and increases platelet sensitivity to antiaggregatory prostaglandins.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of bed rest on the adenine nucleotides concentration in human blood platelets.

The effect of immobilization in bed on metabolism and function of human blood platelet was studied. Blood platelets taken from patients with bone fractures after long term bed rest (14 days and 28 days) demonstrated significantly reduced concentration of total adenine nucleotides (after 28 days reduction about 30%). This decrease of total platelet adenine nucleotides after immobilization in bed is probably caused by stimulation of platelet secretory process. Thrombin which released from control platelets 58.2% +/- 1.5% of total adenine nucleotides liberated decreased amounts (only 23.1% +/- 3.3% of total) of nucleotides from patient platelets isolated after 28 days of immobilization in bed. Loss of nucleotides from platelets was accompanied by slightly increased extent of platelet aggregation. It is concluded that during bed rest the reactivity of blood platelets (aggregation and release reaction) is stimulated.     

Megaloblastic anemia in patients receiving total parenteral nutrition without folic acid or vitamin B12 supplementation.

Pancytopenia developed in four patients receiving postoperatively total parenteral nutrition (TPN). Symptoms and signs were related mainly to underlying bowel disease. Hematologic abnormalities, first noted from 4 to 7 weeks following institution of TPN, consisted of normocytic anemia (mean decrease in hemoglobin value, 2.2 g/dL), occasional macrocytes being noted, leukopenia (range of leukocyte counts, 1.2 to 3.6 X 10(9) L), some hypersegmented neutrophils being detected, and clinically significant thrombocytopenia (range of platelet counts, 25 to 52 X 10(9)/L). In all patients the bone marrow showed megaloblastic changes, with ring sideroblasts, although pyridoxine was included in the TPN regimens. Serum vitamin B12 values were normal in one patient and at the lower limit of normal in the other two patients in whom it was measured, while serum or erythrocyte folate values, or both, were reduced in three patients. Full hematologic response was observed in the four patients after folic acid replacement therapy; leukocytosis and thrombocytosis were noted in three. Thus, folic acid and possibly vitamin B12 should be added routinely to TPN regimens to prevent deficiency of either substance.     

In vitro and in vivo effects of selenium and selenium with vitamin E on platelet functions in diabetic rats relationship to platelet sorbitol and fatty acid distribution

In vitro 30 min of incubation with selenomethionine (Sm)+vitamin E multiplied by about five platelet selenium (Se) decreased significantly platelet thrombin and ADP-induced aggregation decrease. Four groups of streptozotocin-induced diabetic rats were fed with a supplemented purified diet with an Se-rich yeast (Selenion): DSel, Sm: DSm, Sm α-tocopherol: DSmE or unsupplemented diet: D. After 24 wk of supplementation, only a decrease in thrombin-induced aggregation in group DSel compared to DSm and DSmE and D was observed. However, after 24 wk of diet compared to 14 wk, in group D and DSm, a significant increase in thrombin-induced aggregation occurred (p<0.0001), whereas a significant decrease in groups DSel and DSmE (p<0.0001,p<0.03) was noted. After 21 wk of diet, in DSmE, platelet adhesion to fibronectin was significantly decreased compared to group D (p<0.05). These changes in DSmE were associated with a significant decrease in platelet sorbitol (p<0.02) and a very significant increase in platelet Se (p<0.0005). Sm associated with vitamin E would appear more efficient to prevent oxidative damage of diabetic platelet membrane and thus to modulate its hyperactivity.     

Essential Thrombocythaemia and Peripheral Gangrene

Six patients are described in whom gangrene of one or more toes occurred as the presenting feature of essential thrombocythaemia. Spontaneous platelet aggregation was observed in platelet-rich plasma from four patients and platelet aggregation after the addition of adenosine diphosphate and collagen was highly abnormal in samples from all six. All of the patients described dramatic relief of pain within six hours of ingestion of aspirin and this coincided with disappearance of the spontaneous platelet aggregation and collagen-induced platelet aggregation. Treatment with phosphorus-32 corrected the platelet count and there were no further recurrences of peripheral vascular disease. Platelet function tests performed at the time all gave normal results. It is concluded that essential thrombocythaemia is an important and treatable cause of peripheral vascular disease.     

Prostacyclin prolongs viability of washed human platelets

The functional viability of stored human platelets, washed in the presence and absence of prostacyclin, was examined over a 96 h period. Platelet counts, aggregation responses and cyclic AMP levels were monitored as well as the spontaneous generation of thromboxane B2 and the liberation of labelled oleate from cellular phosphatides. In suspensions prepared without prostacyclin in the medium, platelet counts declined rapidly as did the sensitivity to aggregating agents. In addition, substantial amounts of thromboxane B2 were generated during preparation and storage and oleate liberation occurred at a rapid rate. In contrast, in prostacyclin-washed platelets, aggregation was maintained throughout the study period and there was little generation of thromboxane B2. Moreover, only a gradual decrease in platelet count and a slow increase in the rate of oleate liberation was observed when compared with controls. However, cyclic AMP levels rapidly declined when platelets were resuspended in prostacyclin-free medium.