scholarly journals Conformational Expansion of Tau in Condensates Promotes Irreversible Aggregation

2021 ◽  
Author(s):  
Jitao Wen ◽  
Liu Hong ◽  
Georg Krainer ◽  
Qiong-Qiong Yao ◽  
Tuomas P. J. Knowles ◽  
...  
Keyword(s):  
Irreversible Aggregation

A Monoclonal Antibody to the Human Platelet Glycoprotein II b/III a Complex Induces Platelet Activation

1988 ◽  
Vol 60 (01) ◽  
pp. 068-074 ◽  
Author(s):  
Piet W Modderman ◽  
Han G Huisman ◽  
Jan A van Mourik ◽  
Albert E G Kr von dem Borne
Keyword(s):  
Human Platelet ◽  
Adenosine Diphosphate ◽  
Dense Granule ◽  
Platelet Glycoprotein ◽  
Activated Platelets ◽  
Complex Functions ◽  
Slow Aggregation ◽  
Irreversible Aggregation ◽  
Platelet Release ◽  
Aggregation Of Platelets

SummaryThe platelet glycoprotein (GP) IIb/IIIa complex functions as the receptor for fibrinogen on activated platelets. The effects of two anti-GPIIb/IIIa monoclonal antibodies on platelet function were studied. These antibodies, 6C9 and C17, recognized different epitopes, which were exclusively present on the undissociated GPIIb/IIIa complex. Whereas C17 inhibited the binding of fibrinogen to platelets and platelet aggregation induced by adenosine diphosphate (ADP) or collagen, 6C9 caused irreversible aggregation of platelets, both in the presence and absence of extracellular fibrinogen. When incubated with unstirred (nonaggregating) platelets, 6C9 induced release of alpha and dense granule-constituents as well as binding of 125I-fibrinogen to platelets. The latter was evidently mediated in part by platelet-derived ADP, since it was inhibited to a large extent by apyrase, the ADP-hydrolyzing enzyme. F(ab’)2 fragments of 6C9 did not induce platelet-release reactions but caused (slow) aggregation of platelets in the presence of extracellular fibrinogen.These results indicate that binding of an antibody to a specific site on the platelet GPIIb/IIIa complex may cause fibrinogen-mediated aggregation. The Fc part of the platelet-bound antibody appears to be involved in the induction of platelet release.

Transmembrane Calcium Influx Associated with von Willebrand Factor Binding to GP Ib in the Initiation of Shear-Induced Platelet Aggregation

1993 ◽  
Vol 69 (05) ◽  
pp. 496-502 ◽  
Author(s):  
Yasuo Ikeda ◽  
Makoto Handa ◽  
Tetsuji Kamata ◽  
Koichi Kawano ◽  
Yohko Kawai ◽  
...  
Keyword(s):  
Shear Force ◽  
Calcium Influx ◽  
Fold Increase ◽  
Intracellular Camp ◽  
Recombinant Fragment ◽  
Transmembrane Flux ◽  
Irreversible Aggregation ◽  
Von Willebrand ◽  
Willebrand Factor ◽  
Camp Levels

SummaryWe found that the binding of multimeric vWF to GP Ib under a shear force of 108 dynes/cm2 resulted in the transmembrane flux of Ca2+ ions with a two-to three-fold increase in their intracellular concentration ([Ca2+]i). The blockage of this event, obtained by inhibiting the vWF-GP Ib interaction, suppressed aggregation. In contrast, the blockage of vWF binding to GP IIb-IIIa, as well as the prevention of activation caused by increased intracellular cAMP levels, inhibited aggregation but had no significant effect on [Ca2+]i increase. A monomeric recombinant fragment of vWF containing the GP Ib-binding domain of the molecule (residues 445-733) prevented all effects mediated by multimeric vWF but, by itself, failed to support the increase in [Ca2+]i and aggregation. These results suggest that the binding of multimeric vWF to GP Ib initiates platelets aggregation induced by high shear stress by mediating a transmembrane flux of Ca2+ ions, perhaps through a receptor-dependent calcium channel. The increase in [Ca2+]i may act as an intracellular message and cause the activation of GP IIb-IIIa; the latter receptor then binds vWF and mediates irreversible aggregation.

Aggregation of Cat Platelets in Vitro

1970 ◽  
Vol 23 (03) ◽  
pp. 601-620 ◽  
Author(s):  
Th. B Tschopp
Keyword(s):  
Adenosine Monophosphate ◽  
Blood Collection ◽  
Base Line ◽  
Reversible Aggregation ◽  
Low Concentrations ◽  
Irreversible Aggregation ◽  
High Concentrations ◽  
Two Phases ◽  
Improved Technique

SummaryAggregation of cat platelets in the citrated plasma is examined by means of Born’s absorptiometer. A marked tendency of the platelets of this species to spontaneous aggregation necessitated first of all the development of an improved technique of blood collection.A hypothesis according to which 5-HT is released from the platelets, explains the absence of oscillations on the base line of the absorptiometer, the absence of platelet swelling, when ADP is added, and the effect of stirring on the aggregation curves in cat PRP. The average volume of cat platelets amounts to 10.46 μ3 when directly fixed in the blood, when fixed from PRP to 12.17 μ3, when fixed from stirred PRP to 13.51 μ3.In low concentrations (0.3-2 μM) ADP produce reversible aggregation; in narrowly restricted, individually dissimilar mean concentrations irreversible aggregation in two phases and in high concentrations, irreversible aggregation in one phase. Like ADP serotonin produces 2 phase irreversible aggregation in concentrations of 3-10 μM, but unlike ADP, the aggregation velocity decreases again with high 5-HT concentrations (>100 μM). Adrenaline does not produce aggregation and it is likely that adenosine and adenosine monophosphate inhibit the aggregation by serotonin but not by ADP. Species differences in the aggregation of human, rabbit and cat platelets are discussed.

Aggregation of whey proteins during storage of acidified milk

1976 ◽  
Vol 43 (1) ◽  
pp. 45-51 ◽  
Author(s):  
P. J. Argyle ◽  
N. Jones ◽  
R. C. Chandan ◽  
J. F. Gordon
Keyword(s):  
Physical Properties ◽  
Milk Fat ◽  
Dairy Products ◽  
Storage Temperature ◽  
Whey Proteins ◽  
Disc Electrophoresis ◽  
Protein Fractions ◽  
Irreversible Aggregation ◽  
Acid Whey

SummarySlow, irreversible aggregation of whey proteins in acidified milk or whey at pH 3·4–4·6 held for up to 10 d at 35–45°C was revealed by the reduction of discrete bands in disc electrophoresis. The aggregation was confirmed by precipitation of protein observed in stored, acid whey. The rate of aggregation of all protein fractions increased with the acidity and the storage temperature. It was enhanced by the presence of casein, but was unaffected by the presence of milk fat or by pasteurization of the fresh, unacidified milk at 70°C. The effect may contribute to the physical properties of certain fresh cheeses and other cultured dairy products.

Prevention of irreversible aggregation of whey soy proteins in their foam fractionation from soy whey wastewater

2016 ◽  
Vol 11 (5) ◽  
pp. 673-682 ◽  
Author(s):  
Rui Li ◽  
Zhaoliang Wu ◽  
Yanji Wang ◽  
Linlin Ding ◽  
Wei Liu
Keyword(s):  
Soy Proteins ◽  
Foam Fractionation ◽  
Irreversible Aggregation

Local structure at a ferrofluid surface: chain-like aggregates revealed by non-specular X-ray reflection

2003 ◽  
Vol 36 (2) ◽  
pp. 244-248 ◽  
Author(s):  
I. Takahashi ◽  
N. Tanaka ◽  
S. Doi
Keyword(s):  
Surface Tension ◽  
Fractal Dimension ◽  
Local Structure ◽  
Fine Particles ◽  
Capillary Waves ◽  
Aggregation Kinetics ◽  
X Ray ◽  
Surface Fluctuations ◽  
Irreversible Aggregation ◽  
A Chain

The surface structure of a ferrofluid was investigated by means of non-specular X-ray reflection. Strong intensity that is impossible to explain by surface fluctuations due to capillary waves was observed. It can be related to lateral correlation within aggregates of super-paramagnetic fine particles in the vicinity of the specimen surface. The fractal dimension of these surface-induced aggregates and the surface-tension coefficient of the ferrofluid were simultaneously determined. The fractal dimension was found to be around 1.1, indicating a chain-like character of the aggregates that have few branches. Strong and anisotropic interaction among the particles, as well as irreversible aggregation kinetics must be the origin of such a high-density and low-fractal-dimension system of dipolar 10 nm sized particles. The temperature variation of the fractal dimension indicated that the fractal aggregates stabilize themselves by losing their branches at increasing temperatures.

Arginine vasopressin release from human platelets after irreversible aggregation

1990 ◽  
Vol 78 (1) ◽  
pp. 113-116 ◽  
Author(s):  
Giovanni Anfossi ◽  
Elena Mularoni ◽  
Mariella Trovati ◽  
Paola Massucco ◽  
Luigi Mattiello ◽  
...  
Keyword(s):  
Platelet Aggregation ◽  
Arginine Vasopressin ◽  
Platelet Rich Plasma ◽  
Human Platelets ◽  
Vasopressin Release ◽  
Irreversible Aggregation ◽  
Local Release

1. The release of arginine vasopressin from human platelets was investigated in platelet-rich plasma after irreversible aggregation induced by adenosine 5′-pyrophosphate, collagen, sodium arachidonate, thrombin and adrenaline in vitro. 2. Arginine vasopressin levels were significantly higher in the supernatant from stimulated platelet-rich plasma than from unstimulated samples, reaching 3.5 × 10−12 (range 1.6–12.5 × 10−12) mol/l in the absence of an aggregating agent, 8.8 × 10−12 (range 4.2–17.5 × 10−12) mol/l after adenosine 5′-pyrophosphate, 13.7 × 10−12 (2.2–63.2 × 10−12) mol/l after collagen, 7.8 × 10−12 (2.2–14.6 × 10−12) mol/l after sodium arachidonate, 7.8 × 10−12 (2.2–16.3 × 10−12) mol/l after thrombin and 12.2 × 10−12 (4.8–32.1 × 10−12) mol/l after adrenaline. 3. An arginine vasopressin level of 18 × 10−12 mol/l, which can be achieved physiologically, increased the sensitivity of platelets to adenosine 5′-pyrophosphate and collagen in vitro; the same concentration of arginine vasopressin caused a potentiation of the effect of catecholamines on the response of platelets to sodium arachidonate. 4. These results indicate that intraplatelet arginine vasopressin is released during aggregation and suggest that a local release of arginine vasopressin could occur after complete platelet aggregation in vivo.

The chaperone proteins HSP70, HSP40/DnaJ and GRP78/BiP suppress misfolding and formation of β-sheet-containing aggregates by human amylin: a potential role for defective chaperone biology in Type 2 diabetes

2010 ◽  
Vol 432 (1) ◽  
pp. 113-121 ◽  
Author(s):  
Vita Chien ◽  
Jacqueline F. Aitken ◽  
Shaoping Zhang ◽  
Christina M. Buchanan ◽  
Anthony Hickey ◽  
...  
Keyword(s):  
Type 2 Diabetes ◽  
Potential Role ◽  
Β Cell ◽  
Molar Ratios ◽  
Irreversible Aggregation ◽  
Chaperone Binding ◽  
Human Amylin ◽  
Β Sheet ◽  
Glucose Regulated Protein

Misfolding of the islet β-cell peptide hA (human amylin) into β-sheet-containing oligomers is linked to β-cell apoptosis and the pathogenesis of T2DM (Type 2 diabetes mellitus). In the present study, we have investigated the possible effects on hA misfolding of the chaperones HSP (heat-shock protein) 70, GRP78/BiP (glucose-regulated protein of 78 kDa/immunoglobulin heavy-chain-binding protein) and HSP40/DnaJ. We demonstrate that hA underwent spontaneous time-dependent β-sheet formation and aggregation by thioflavin-T fluorescence in solution, whereas rA (rat amylin) did not. HSP70, GRP78/BiP and HSP40/DnaJ each independently suppressed hA misfolding. Maximal molar protein/hA ratios at which chaperone activity was detected were 1:200 (HSP70, HSP40/DnaJ and GRP78/BiP). By contrast, none of the chaperones modified the secondary structure of rA. hA, but not rA, was co-precipitated independently with HSP70 and GRP78/BiP by anti-amylin antibodies. As these effects occur at molar ratios consistent with chaperone binding to relatively rare misfolded hA species, we conclude that HSP70 and GRP78/BiP can detect and bind misfolded hA oligomers, thereby effectively protecting hA against bulk misfolding and irreversible aggregation. Defective β-cell chaperone biology could contribute to hA misfolding and initiation of apoptosis in T2DM.

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