Abnormal Platelet Serotonin Uptake and Binding Sites in Myeloproliferative Disorders

1984 ◽  
Vol 51 (03) ◽  
pp. 349-353 ◽  
Author(s):  
C Caranobe ◽  
P Sié ◽  
F Fernandez ◽  
J Pris ◽  
S Moatti ◽  
...  
Keyword(s):  
Binding Sites ◽  
High Capacity ◽  
Specific Inhibitor ◽  
Myeloproliferative Disorders ◽  
Normal Subjects ◽  
Binding Data ◽  
Full Explanation ◽  
Number Of Binding Sites ◽  
5 Ht Uptake ◽  
Kinetics Of

SummaryA simultaneous investigation of the kinetics of serotonin (5 HT) uptake and of binding sites was carried out in the platelets of normal subjects and of 10 patients affected with various types of myeloproliferative disorders (MD). The 5 HT uptake was analysed according to the Lineweaver-Burk and the Eadie-Hofstee methods. With the two methods, the patient’s platelets exhibited a dramatic reduction of the Vi max and of the Km; in some patients the Eadie-Hofstee analysis revealed that a passive diffusion phenomenon is superimposed on the active 5 HT uptake at least for the higher concentration used. The binding data were analysed with the Scatchard method. Two classes of binding sites (high affinity - low capacity, low affinity - high capacity) were found in normal subjects and patients. Pharmacological studies with imipramine, a specific inhibitor of 5 HT uptake, suggested that both the sites are involved in 5 HT uptake. The number of both binding sites was significantly decreased in patient’s platelets while the affinity constants of these binding sites were not significantly reduced in comparison with those of the control subjects. No correlations were found between Vi max, Km and the number of binding sites. These results suggest that a reduction in the number of platelet membrane acceptors for 5 HT commonly occurs in myeloproliferative disorders but does not provide a full explanation of the uptake defect.

Abnormal Platelet Serotonin Uptake And Binding Sites In Myeloproliferative Disorders

1981 ◽  
Author(s):  
C Caranobe ◽  
P Sié ◽  
C Nouvel ◽  
G Laurent ◽  
J Pris ◽  
...  
Keyword(s):  
Binding Sites ◽  
High Capacity ◽  
Myeloproliferative Disorders ◽  
Binding Assays ◽  
Dense Granules ◽  
Plot Analysis ◽  
Binding Data ◽  
Plasmatic Membrane ◽  
Number Of Binding Sites ◽  
5 Ht Uptake

We previously shown that the platelets of patients suffering from myeloproliferative disorders (MD) present not only a reduced capacity to store serotonin (5 HT) in their dense granules but also a dramatic reduction in the initial velocity (Vi) of 5 HT uptake ; this suggests that the abnormalities are not restricted to the dense granules but involve the transport mechanism accross the platelet membrane.The present study concerns the 5 HT binding sites of MD platelets which present such a reduction of the Vi Max (Li- neweaver-Burke plot) of the 5 HT uptake. Binding assays were performed according to the method of Schik et al. (Biochem. Pharmacol. 1979, 28, 2667). Schatchard plot analysis of the binding data revealed two binding sites both in normals and patients : site A with a high affinity and a low capacity and site B with a low affinity and a high capacity.Thus the abnormal 5 HT transport accross the plasmatic membrane is the consequence of a quantitative reduction of the 5 HT binding sites and not of a qualitative defect of these sites. Nevertheless, in spite of the reduction of the number of binding sites, 5 HT-induced platelet aggregation was found normal in these patients.

THE PLATELET “REBOUND-PHENOMENON” DURING PROLONGED, CONTINUOUS PGI2 INFUSION OCCURS AT THE RECEPTOR LEVEL

1987 ◽  
Author(s):  
G Steurer ◽  
H Sinzinger ◽  
P Fitscha
Keyword(s):  
Binding Sites ◽  
Venous Blood ◽  
Intermittent Infusion ◽  
Receptor Level ◽  
Binding Data ◽  
Post Infusion ◽  
Number Of Binding Sites ◽  
Rebound Phenomenon ◽  
Infusion Regimen

During earlier attempts in optimizing the therapeutic regimen with PGI2 we were able to discover an “ intra- and post-infusion platelet rebound” being characterized by an activated platelet function and a diminished responsiveness of platelets to the action of PGI2 in-vitro.In order to verify this phenomenon at the receptor level we infused continuously 6 patients suffering from peripheral vascular disease (PVD) with PGI2 at a rate of 5 ng/kg/min for 5 days. Anticoagulated venous blood has been drawn at different intervals. Saturation binding experiments on platelet membrane fraction have been performed using [3H]iloprost, a stable PGI2 analoque. Analysis of the binding data according to Scatchard demonstrated a decrease of receptor affinity with an increased number of binding sites.It is concluded, that intrainfusion rebound occurs at the receptor level, whereas the postinfusion rebound does not. This is a further piece of evidence that an intermittent infusion regimen is preferable.

The Binding Of 125I-Von Willebrand Factor To Human Platelets In The Presence Of Ristocetin

1981 ◽  
Author(s):  
P Silber ◽  
T H Finlay
Keyword(s):  
Von Willebrand Factor ◽  
Binding Sites ◽  
Binding Constant ◽  
Specific Binding ◽  
Human Platelets ◽  
Scatchard Analysis ◽  
Binding Data ◽  
Number Of Binding Sites ◽  
Von Willebrand ◽  
Willebrand Factor

The effect of ristocetin on the binding of 125I-porcine von Willebrand factor to human platelets was studied. Previously, we had shown that 125I-porcine von Willebrand factor binds to human platelets in the absence of ristocetin. The present work demonstrates that binding is stimulated by ristocetin and this stimulation is maximal at a ristocetin concentration of 2 mg/ml. At a ristocetin concentration of 0.5 mg/ml, Scatchard analysis indicates a binding constant of 5.18 × 10-9M and the presence of 105,000 binding sites. This compares with our previous finding, in the absence of ristocetin, of a binding constant of 2.92 × 10-7M and 4760 binding sites. These binding data assume the porcine von Willebrand factor to be a tetramer with a molecular weight of 9 × 105. This study indicates that ristocetin causes tighter binding and increases the number of binding sites on human platelets for porcine von Willebrand factor. Unlabelled porcine von Willebrand factor competitively inhibits the specific binding of the labelled protein and gives a binding constant of 0.17 × 10-9M. Similar results were obtained using human von Willebrand factor.

scholarly journals High-affinity prorenin binding to cardiac man-6-P/IGF-II receptors precedes proteolytic activation to renin

2001 ◽  
Vol 280 (4) ◽  
pp. H1706-H1715 ◽  
Author(s):  
Jasper J. Saris ◽  
Frans H. M. Derkx ◽  
René J. A. De Bruin ◽  
Dick H. W. Dekkers ◽  
Jos M. J. Lamers ◽  
...  
Keyword(s):  
Amniotic Fluid ◽  
Binding Sites ◽  
Neonatal Rat ◽  
Proteolytic Activation ◽  
Rat Cardiomyocytes ◽  
High Affinity ◽  
Neonatal Rat Cardiomyocytes ◽  
Factor Ii ◽  
Number Of Binding Sites ◽  
Kinetics Of

Mannose-6-phosphate (man-6-P)/insulin-like growth factor-II (man-6-P/IgF-II) receptors are involved in the activation of recombinant human prorenin by cardiomyocytes. To investigate the kinetics of this process, the nature of activation, the existence of other prorenin receptors, and binding of native prorenin, neonatal rat cardiomyocytes were incubated with recombinant, renal, or amniotic fluid prorenin with or without man-6-P. Intact and activated prorenin were measured in cell lysates with prosegment- and renin-specific antibodies, respectively. The dissociation constant ( Kd) and maximum number of binding sites (Bmax) for prorenin binding to man-6-P/IGF-II receptors were 0.6 ± 0.1 nM and 3,840 ± 510 receptors/myocyte, respectively. The capacity for prorenin internalization was greater than 10 times Bmax. Levels of internalized intact prorenin decreased rapidly (half-life = 5 ± 3 min) indicating proteolytic prosegment removal. Prorenin subdivision into man-6-P-free and man-6-P-containing fractions revealed that only the latter was bound. Cells also bound and activated renal but not amniotic fluid prorenin. We concluded that cardiomyocytes display high-affinity binding of renal but not extrarenal prorenin exclusively via man-6-P/IGF-II receptors. Binding precedes internalization and proteolytic activation to renin thereby supporting the concept of cardiac angiotensin formation by renal prorenin.

Spectrometric, Thermodynamic, pH Metric and Viscometric Studies on the Binding of TEALS as Surfactant with Albumin as Biopolymer

2020 ◽  
Vol 10 (1) ◽  
pp. 47-64
Author(s):  
Shveta Acharya ◽  
Arun Kumar Sharma
Keyword(s):  
Binding Sites ◽  
Equilibrium Dialysis ◽  
Protein Molecule ◽  
Structure Characterization ◽  
Binding Interaction ◽  
Practical Applications ◽  
Egg Protein ◽  
Binding Data ◽  
Number Of Binding Sites ◽  
Lower Temperature

Background:: Since the interactions of small anions with protein are very important in their transportation and distribution processes in biological systems, it is helpful to study these interactions to understand the nature of the transportation and distribution processes. Therefore, it is aimed to study the interaction of albumin with surfactant molecule by different physical methods. Objective:: Present work attempts to work on assessing the structure, characterization of the surfactants as TEALS (tri-ethanalamine lauryl sulphate) binding sites, with albumin involved in various process of living being are discussed. Method:: The binding of surfactant TEALS to egg protein has been studied at different pH values and temperatures by spectrophotometric and equilibrium dialysis methods. The binding data were found to be pH and temperature dependent. The binding data studied by the absorbance method, were found approximately identical with those obtained from the equilibrium dialysis method. Results:: The association constants and the number of binding sites were calculated from Scatchard plots and found to be at maximum at lower pH and at lower temperature. The free energy of the combining sites was lowest at higher pH and highest at low pH. Therefore, a lower temperature and a lower pH offered more sites in the protein molecule for interaction with surfactant. The ΔG (free energies of aggregation) associated with the binding interaction of the surfactants and protein were calculated. The negative values of the ΔG confirm the feasibility of interaction between the surfactant and protein. All the observations recorded in this paper indicate that the TEALS has a good affinity of binding with egg protein and the number of binding sites is dependent on various physical and chemical factors. Conclusion:: On the basis of the results of the experiments which were conducted to examine the interaction between anionic surfactant and protein by measuring the various parameters of the solutions, it is concluded that the interaction of surfactant and protein gives an idea of fundamental understanding of the structure of surfactant-protein complex and their practical applications in every field.

scholarly journals Characterization of pancreatic b-cell receptors binding sulfanilamides under conditions of experimental diabetes mellitus

1996 ◽  
Vol 42 (5) ◽  
pp. 37-39
Author(s):  
V. N. Babichev ◽  
I. P. Savelyeva ◽  
M. I. Balabolkin
Keyword(s):  
Diabetes Mellitus ◽  
B Cells ◽  
Binding Sites ◽  
Binding Capacity ◽  
High Capacity ◽  
Experimental Diabetes Mellitus ◽  
Number Of Binding Sites ◽  
Pancreatic B Cells ◽  
Two Parameters

The receptor properties of pancreatic b-cells functionally attenuated under the effect of streptozotocin during therapy with sulfanilamides widely used in diabetes mellitus (glibenclamide, glipizide, and gliclazide) were studied. These drugs were shown to be characterized by the high capacity to specifically bind to receptors, which virtually do not differ from those of intact b-cells. The receptors were characterized by two parameters: the number of binding sites and dissociation constant. Glibenclamide has demonstrated high binding capacity. The binding of these agents was reversible. The authors do not identify the studied receptors of sulfanilamides with the K+-ATP channels which are also known as the active conductors of the information carried by sulfanilamides in the mechanism of insulin secretion.

Exercise and insulin stimulate skeletal muscle glucose transport through different mechanisms

1989 ◽  
Vol 256 (2) ◽  
pp. E227-E230 ◽  
Author(s):  
E. Sternlicht ◽  
R. J. Barnard ◽  
G. K. Grimditch
Keyword(s):  
Skeletal Muscle ◽  
Glucose Transport ◽  
Binding Sites ◽  
Turnover Rate ◽  
Acute Exercise ◽  
Cytochalasin B ◽  
Number Of Binding Sites ◽  
Muscle Glucose Transport ◽  
Kinetics Of ◽  
Transport Molecules

This study was designed to examine the effects of acute exercise, insulin stimulation, and their combination on the kinetics of glucose transport in rat skeletal muscle. Sarcolemmal (SL) membranes were isolated from control (C), acute exercise (E), insulin-stimulated (I), and combined (E + I) rats. Michaelis-Menten kinetics indicated that the Vmax for glucose transport was increased after each perturbation compared with C but were not different from each other (E, 4,334 +/- 377; I, 4,424 +/- 668; E + I, 4,338 +/- 602; and C, 1,366 +/- 124 pmol.mg protein-1.s-1). The apparent Km was unchanged. Scatchard plots of cytochalasin B binding sites indicated that both I and E + I increased the number of binding sites compared both E and C (9.4 +/- 0.5 and 7.8 +/- 0.5 vs. 5.1 +/- 0.2 and 5.5 +/- 0.3 pmol/mg protein) without altering the dissociation constant. The increase in Vmax was greater than the increase in cytochalasin B binding sites indicating that both I and E + I caused an increase in the turnover rate of transport molecules as well as an increase in the total number of transport molecules. Because there was no change in the Km for glucose transport and no increase in cytochalasin B binding sites after exercise, the increase in Vmax was due solely to an increased turnover rate of existing transport molecules.

scholarly journals Molecular stripping, targets and decoys as modulators of oscillations in the NF-κB/IκBα/DNA genetic network

2016 ◽  
Vol 13 (122) ◽  
pp. 20160606 ◽  
Author(s):  
Zhipeng Wang ◽  
Davit A. Potoyan ◽  
Peter G. Wolynes
Keyword(s):  
Gene Expression ◽  
Systems Biology ◽  
Binding Sites ◽  
Regulatory Network ◽  
Genetic Network ◽  
Eukaryotic Transcription ◽  
Number Of Binding Sites ◽  
Kinetics Of ◽  
Downstream Gene Expression

Eukaryotic transcription factors in the NF-κB family are central components of an extensive genetic network that activates cellular responses to inflammation and to a host of other external stressors. This network consists of feedback loops that involve the inhibitor IκBα, numerous downstream functional targets, and still more numerous binding sites that do not appear to be directly functional. Under steady stimulation, the regulatory network of NF-κB becomes oscillatory, and temporal patterns of NF-κB pulses appear to govern the patterns of downstream gene expression needed for immune response. Understanding how the information from external stress passes to oscillatory signals and is then ultimately relayed to gene expression is a general issue in systems biology. Recently, in vitro kinetic experiments as well as molecular simulations suggest that active stripping of NF-κB by IκBα from its binding sites can modify the traditional systems biology view of NF-κB/IκBα gene circuits. In this work, we revise the commonly adopted minimal model of the NF-κB regulatory network to account for the presence of the large number of binding sites for NF-κB along with dissociation from these sites that may proceed either by passive unbinding or by active molecular stripping. We identify regimes where the kinetics of target and decoy unbinding and molecular stripping enter a dynamic tug of war that may either compensate each other or amplify nuclear NF-κB activity, leading to distinct oscillatory patterns. Our finding that decoys and stripping play a key role in shaping the NF-κB oscillations suggests strategies to control NF-κB responses by introducing artificial decoys therapeutically.

scholarly journals Kinetics of hexokinase D (‘glucokinase’) with inosine triphosphate as phosphate donor. Loss of kinetic co-operativity with respect to glucose

1987 ◽  
Vol 245 (3) ◽  
pp. 625-629 ◽  
Author(s):  
D Pollard-Knight ◽  
A Cornish-Bowden
Keyword(s):  
High Glucose ◽  
Kinetic Models ◽  
Binding Sites ◽  
Ternary Complex ◽  
Hill Coefficient ◽  
Phosphate Donor ◽  
Km Value ◽  
Number Of Binding Sites ◽  
The Hill ◽  
Kinetics Of

When ATP, the normal phosphate donor for hexokinase D (‘glucokinase’), is replaced by ITP, the positive co-operativity with respect to glucose disappears. This may be rationalized in relation to kinetic models for hexokinase D co-operativity, which assume that with the normal substrates the chemical reaction and subsequent release of products occur so rapidly that binding of substrates cannot approach equilibrium and is therefore not constrained by the thermodynamic requirement that the Hill coefficient for substrate binding cannot exceed the number of binding sites. ITP is a much poorer substrate than ATP, however: its Km value at high glucose concentrations is 24 times the value for ATP, whereas the value of the limiting rate V is decreased about 8-fold. Consequently it is no longer possible for the ternary complex to be converted into products rapidly enough to generate kinetic co-operativity. The negative co-operativity with respect to glucose observed in 2H2O with ATP as phosphate donor also disappears when ITP is used instead of ATP.

Description of a Simple Model for the Study of Bone Calcium Metabolism

1980 ◽  
Vol 19 (01) ◽  
pp. 11-15
Author(s):  
G. Roncari ◽  
L. Rapisardi ◽  
L. Conte ◽  
G. Pedroli
Keyword(s):  
Simple Model ◽  
Calcium Metabolism ◽  
Good Description ◽  
Radioactive Tracer ◽  
Normal Subjects ◽  
Bone Diseases ◽  
Compartment System ◽  
Bone Calcium ◽  
Finite Period ◽  
Kinetics Of

A simple model for the study of bone calcium metabolism is proposed. It describes the kinetics of a radioactive tracer in terms of an open single compartment system with an expanding volume for a finite period of time. In addition to the simplicity of the hypotheses introduced, the model is able to give a good description of the biological processes which regulate calcium kinetics. Moreover the functional parameters can be easily calculated, even just graphically. 15 normal subjects and 22 patients affected by various bone diseases were studied. The results were compared with those obtained by using the model proposed by Burkinshaw et al. and the method described by Reeve et al.

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