Healthy Platelets Research Articles

Participation of alpha IIb beta 3 in platelet microparticle generation by collagen plus thrombin.

We investigated the role of alpha IIb beta 3 in microparticle generation by normal and thrombasthenic platelets stimulated with collagen plus thrombin. Microparticle generation by normal platelets was scarcely inhibited by monoclonal antibodies for glycoprotein Ib and glycoprotein IX. Although one monoclonal anti-alpha IIb beta 3 antibody (NNKY1-32) partly inhibited microparticle generation, 3 other monoclonal anti-alpha IIb beta 3 antibodies had little effect. However, the combination of 4 monoclonal anti-alpha IIb beta 3 antibodies or treatment with a polyclonal anti-alpha IIb beta 3 antibody significantly inhibited microparticle generation (p < 0.05). Microparticle generation by thrombasthenic platelets also occurred after stimulation with collagen plus thrombin, although at a significantly lower level compared with normal platelets. Monoclonal antibodies for resting alpha IIb beta 3, P-selectin, activated alpha IIb beta 3 and beta 2-glycoprotein I bound to microparticles from healthy platelets. In contrast, only a monoclonal antibody for beta2-glycoprotein I bound to thrombasthenic microparticles. These results suggest that microparticle generation by collagen plus thrombin occurs via two different mechanisms which are dependent and independent of alpha IIb beta 3, respectively. The alpha IIb beta 3-dependent mechanism appears to require activation of alpha IIb beta 3.

Blood rheology after renal transplantation.

Cardiovascular complications seriously affect posttransplant survival in patients after successful renal transplantation. Abnormalities in blood rheology may contribute to these complications. Therefore, we studied the blood rheology before and during a 1-year observation period after grafting in 9 patients by serial measurements of fibrinogen, red cell aggregation, hematocrit, spontaneous platelet aggregation, and plasma viscosity. Prior to grafting, fibrinogen and red cell aggregation were found to be increased in patients on regular hemodialysis as compared with healthy controls, whereas hematocrit and platelet aggregation were markedly reduced. After successful transplantation, the platelet aggregation progressively rose together with the hematocrit, while fibrinogen and red cell aggregation remained abnormally high. Our findings suggest that abnormal blood rheology in patients with chronic renal failure does not improve in response to successful renal transplantation: fibrinogen and red cell aggregation remain abnormally high; further, the overall blood flow properties are supposed to deteriorate due to the postoperative increase in hematocrit and spontaneous platelet aggregation. Adverse rheological conditions thus resulting may contribute to the increased frequency of vascular events observed in transplanted patients.

Specific activation of platelets from patients allergic to Dermatophagoides pteronyssinus by synthetic peptides derived from the allergen Der p I.

Previous studies have shown that Fc epsilon RII-bearing platelets from patients with allergic disorders could be stimulated either by anti-human IgE antibodies or the relevant allergens to generate cytotoxic mediators. In this report, the reactivity of platelets from Dermatophagoides pteronyssinus (D. pt)-sensitive patients to three Der p I-derived synthetic peptides (52-71, 117-133 and 188-199) was investigated. The platelet stimulation observed in D. pt-sensitive patients was demonstrated to be allergen-specific and to be mediated by IgE. These Der p I-derived peptides failed to stimulate platelets from healthy donors or platelets from non-D. pt-allergic patients. D. pt-sensitive patients responded more frequently to the peptides 52-71 and 117-133 than to the peptide 188-199. Thus, in this model, synthetic peptides selected for their assumed accessibility on the native antigen could be associated to an IgE-dependent biological activity.

Platelet aggregation induced by uncommon serotypes of Streptococcus sanguis isolated from patients with Behçet's disease

Uncommon serotypes were tested for their ability to induce aggregation in platelet-rich plasma. Both uncommon and common serotypes induced platelet aggregation in rabbit platelet-rich plasma, but serotonin release was higher with the uncommon serotypes. Aggregation at ATP release varied between uncommon and common serotypes. With human platelet-rich plasma, only uncommon serotypes showed aggregation. Differences in serotype selectivity and the rate of aggregation were noted among platelet donors. About half of the patients with Behçet's disease and 30% of health controls showed platelet aggregation. Plasma from non-responder patients with Behçet's disease inhibited aggregation of healthy responder platelets within 20 min. Thus selective binding of uncommon serotypes of Strep. sanguis to plateletes might cause the vasculitis in Behçet's disease.

Recombinant hirudin in healthy men and platelet function

Recombinant hirudin in healthy men and platelet function

ＩｇＥと血小板機能との関連性について

We investigated the binding form of IgE to platelets and the relationship between IgE and platelet function. When the paraformaldehyde (PFA)-fixed platelets were incubated with the IgE-protein from human myeloma (M-IgE), the platelet-associated IgE (PAIgE) of Glanzmann's thrombasthenic platelets was significantly less than that of healthy control. The binding of M-IgE to the healthy PFA-fixed platelets was in-hibited by the pretreatment of the platelets with monoclonal anti-GPIIb/IIIa complex antibody or Arg-Gly-Asp-Ser (RGDS), but not monoclonal anti-GP I b antibody or heat aggregated IgG. When the unfixed platelets which had been activated with PAF or ADP were incubated with the M-IgE, the PAIgE increased significantly. The increased PAIgE hardly effected on not only the platelet aggregation or platelet secretion but also the increase of [Ca2+]i by activation. These results suggest that IgE binds to not the Fc-receptor but the GPIIb/IIIa-related receptor on the platelet surface. This binding increases with the platelet activation, whereas the increased IgE dose not appear to effect on the platelet function.

Native fluorescence of platelets from patients with occlusive arterial disease

Healthy platelets exhibit a fluorescence band with a peak at 475 nm if excited at 360 nm. This peak increases first with the progression of occlusive arterial disease (OAD) followed by a decrease at an advanced stage. Concomitantly, a new fluorescence band at 445 nm will appear, which increases steadily with the progression of OAD. These findings can be explained by the oxidation of NADH (fluorescence at 475 nm) to NAD (445 nm) and support, thus, the assumption that oxidative processes are involved in the formation of OAD.

125I-Angiotensin II binding to human blood cells.

The binding of 125I-angiotensin II to human blood cells was investigated. Blood was drawn from healthy volunteers and platelets prepared with minimal contamination of red cells and white blood cells (less than 0.1%). Using thin layer chromatography, degradation of 125I-angiotensin II by platelets could be demonstrated in the presence of various enzyme inhibitors. However, when incubated with 1 mM diisopropylfluorophosphate (DFP) or 1 mg/ml bacitracin, no breakdown of 125I-angiotensin II could be detected. The amount of specifically bound 125I-angiotensin II increased linearly with the number of cells per tube. Binding reached a plateau within 90-120 min at 37 degrees C, and was stable thereafter. Specific binding was reversible. No binding could be detected at 4 degrees C. Specific binding of 125I-angiotensin II was saturable. Scatchard analysis of binding by platelets of healthy volunteers revealed one class of binding sites with an apparent Kd of 127 +/- 16 pM and a maximal binding capacity of 7.9 +/- 1.5 binding sites per cell. Competitive displacement of 125I-angiotensin II binding by angiotensin II-analogues showed a rank order of effectiveness. Unrelated peptides, e.g. bradykinin, vasopressin and enkephalin, did not displace specifically bound angiotensin II. Human mononuclear leucocytes were prepared by a Ficoll-isopaque gradient. However, these cells could not be used for studies of specific binding, since enzymatic degradation of 125I-angiotensin II could not be prevented despite addition of various enzyme inhibitors. Time-dependent uptake of 125I-angiotensin II showed no stable plateau. Thus our study shows specific binding of 125I-angiotensin II to human platelets.(ABSTRACT TRUNCATED AT 250 WORDS)

A mathematical model and numerical method for studying platelet adhesion and aggregation during blood clotting

The repair of small blood vessels and the pathological growth of internal blood clots involve the formation of platelet aggregates adhering to portions of the vessel wall. Our microscopic model represents blood by a suspension of discrete massless platelets in a viscous incompressible fluid. Platelets are initially noncohesive; however, if stimulated by an above-threshold concentration of the chemical ADP or by contact with the adhesive injured region of the vessel wall, they become cohesive and secrete more ADP into the fluid. Cohesion between platelets and adhesion of a platelet to the injured wall are modeled by creating elastic links. Repulsive forces prevent a platelet from coming too close to another platelet or to the wall. The forces affect the fluid motion in the neighborhood of an aggregate. The platelets and secreted ADP both move by fluid advection and diffusion. The equations of the model are studied numerically in two dimensions. The platelet forces are calculated implicitly by minimizing a nonlinear energy function. Our minimization scheme merges Gill and Murray's ( Math. Programming 7 (1974) , 311) modified Newton's method with elements of the Yale sparse matrix package. The stream-function' formulation' of the Stokes' equations for the fluid motion under the influence of platelet forces is solved using Bjorstad's biharmonic solver (“Numerical Solution of the Biharmonic Equation,” Ph. D. Thesis, Stanford University, 1980). The ADP transport equation is solved with an alternating-direction implicit scheme. A linked-list data structure is introduced to keep track of changing platelet states and changing configurations of interplatelet links. Results of calculations with healthy platelets and with diseased platelets are presented.

Comparison of the microviscosity of the platelets and the lymphocytes obtained from diabetic patients and healthy subjects, and effects of pantethine on these microviscosities

This study elucidates the relationship among hypercoagulability, microviscosity of platelet and lymphocyte, and lipids in serum and platelet of hyperlipidemic patients, especially of diabetes mellitus. The effect of pantethine on these parameters is also studied.The microviscosity was measured with the microviscosimeter (The Elscint Co. Ltd. Israel) using DPH labeling at 25°C for 60min. Aggregation of the platelet induced by ADP was obtained with the Sienco dual sample aggregation meter (The Sienco, Inc. USA). Pantethine (The Daiichi-Seiyaku KK, Japan) was injected intravenously 10mg/kg or 100mg/kg and the venous blood added heparin or sodium citrate was taken before and 15min after injection. In vitro effect of pantethine on the microviscosity of platelets and lymphocytes was also studied successively at 15, 60, and 180min after incubation.The microviscosity of healthy lymphocytes was 2.88±0.140 (M±SD) at 25°C, and 2.86±0.275 in diabetic lymphocytes with greater variation than healthy lymphocytes. Serum phospholipid was well correlated negatively with lymphocyte microviscosity (r=-0.34, p<0.05), but not with cholesterol, triglyceride and free fatty acid. Higher microviscosity was observed in platelets than lymphocytes, and in healthy platelets than diabetic platelets. Pretreatment (extra vivo) of healthy and diabetic platelets with pantethine at 10mg/ml concentration increased their microviscosities. Intravenously injected pantethine (10mg/kg) decreased ADP aggregation in 33.3% of cases, and increased in 26.7% at 15min after injection. Phospholipid in cases of decreased ADP aggregation reduced after injection of pantethine in both serum and platelets, in spite of few changes in cholesterol of serum and platelets, and in triglyceride and free fatty acid of serum. Fifteen min after injection of 100mg/kg of pantethine, the microviscosity increased slightly in platelets and lymphocytes in 2 diabetic patients out of three.Incubation of platelets and lymphocytes in vitro with 1, 10, 100mg/ml of pantethine, the microviscosity increased at 60min in platelet and at 15min in lymphocyte.As conclusion, the microviscosity of platelets was higher than lymphocytes. Healthy platelets had higher poise than diabetic platelets. Pantethine increased microviscosity of platelets and lymphocytes in vivo as well as in vitro. These changes of microviscosities were correlated with phospholipid level in serum and platelet negatively and molar ratio of cholesterol/phospholipid, positively.

ELEMENTAL ANALYSIS OF HUMAN PLATELETS ON FRESH AIR-DRIED BLOOD SMEARS BY WAVE DISPERSIVE X-RAY MICROANALYSIS USING STEM EQUIPMENT

Wave dispersive X-ray microanalysis was performed on platelets and red blood cells of a healthy male and a von Willebrand patient, and mast cells and lymphocytes of the mouse peritoneal fluid. A STEM equipment of target method was modified by replacing grid holders with carbon rod tubes and the reflecting stage with a carbon disc for microanalysis, attempting to decrease the background noises. In secondary electron images at acceleration voltage of 15-45kV and absorption current of 0.03-0.1nA, the above cells were recognized and also identified in back scattered electron images at an absorption current of 0.1-0.5μA by their profiles and relationship with other cells. High peaks of characteristic X-ray counts of Na-, P-, S-, Cl and K-Kα were disclosed in the analysis of cells. Ca- and Mg-Kα were distinctly disclosed in that of the healthy male and Ca- or Mg-Kα was not in that of patient platelets. Analysis of healthy male platelets, mouse mast cells and lymphocytes by means of the pulse height analyzers detected Zn-Kα and Zn-Lα. Electron microscopy of healthy male platelets disclosed the dense bodies but platelets of the patient failed to reveal them.

Peripheral platelet count in response to salbutamol before and after adrenergic beta-receptor blockade.

The effect of salbutamol (a comparatively selective adrenergic beta2-receptor agonist) on the peripheral platelet concentration was studied before and after the ingestion of either 50 mg metoprolol or 40 mg propranolol. The study was carried out on healthy males volunteers and autologous 51Cr-labelled platelets were employed at the experiments. Salbutamol was infused intravenously over a period of 6 min in a dose of 0.27 microgram.kg(-1). min(-1). Prior to metoprolol and propranolol administration a statistically significant lowering in platelet-bound radioactivity (PBR) was obtained in response to the salbutamol infusions. This salbutamol-induced fall in PBR was completely blocked by propranolol but was left unaffected by metoprolol. It is concluded that adrenergic beta2-receptor stimulation induces a transient lowering of the peripheral platelet count.