Mechanochemical Phenomena. I. Chemical Flow in Raw and Vulcanized Rubber

1963 ◽  
Vol 36 (2) ◽  
pp. 473-479
Author(s):  
G. L. Slonimskii ◽  
E. V. Reztsova
Keyword(s):  
Free Radicals ◽  
Essential Role ◽  
Mechanical Processing ◽  
Technological Properties ◽  
Laboratory Assessment ◽  
Crosslinked Polymers ◽  
Vulcanized Rubber ◽  
Kinetics Of

Abstract 1. The authors demonstrate the essential role of mechanochemical phenomena in processing. Attention is paid to the necessity of taking into account the phenomenon of chemical flow. 2. From the example of various vulcanizates there is demonstrated the possibility of mechanical processing of crosslinked polymers. Attention is paid to the significance of mechanochemical phenomena in reclaiming. 3. A demonstration is given of the influence of small additions of substances which form free radicals or which interact with them, upon the kinetics of the alteration of the properties of a polymer on prolonged milling. Attention is paid to the possibility of controlling the properties of a polymer during processing. 4. The authors show the necessity of taking into account the phenomenon of chemical flow in developing objective methods of laboratory assessment of the technological properties of polymers.

scholarly journals CaATP prolongs strong actomyosin binding and promotes futile myosin stroke

2019 ◽  
Author(s):  
Jinghua Ge ◽  
Akhil Gargey ◽  
Irina V. Nesmelova ◽  
Yuri E. Nesmelov
Keyword(s):  
Muscle Activation ◽  
Essential Role ◽  
Thick Filament ◽  
Power Stroke ◽  
Muscle Rigidity ◽  
Thin Filaments ◽  
Calcium Buffer ◽  
Actomyosin Interaction ◽  
Kinetics Of

AbstractCalcium plays an essential role in muscle contraction, regulating actomyosin interaction by binding troponin of thin filaments. There are several buffers for calcium in muscle, and those buffers play a crucial role in the formation of the transient calcium wave in sarcomere upon muscle activation. One such calcium buffer in muscle is ATP. ATP is a fuel molecule, and the important role of MgATP in muscle is to bind myosin and supply energy for the power stroke. Myosin is not a specific ATPase, and CaATP also supports myosin ATPase activity. The concentration of CaATP in sarcomeres reaches 1% of all ATP available. Since 294 myosin molecules form a thick filament, naïve estimation gives three heads per filament with CaATP bound, instead of MgATP. We found that CaATP dissociates actomyosin slower than MgATP, thus increasing the time of the strong actomyosin binding. The rate of the basal CaATPase is faster than that of MgATPase, myosin readily produces futile stroke with CaATP. When calcium is upregulated, as in malignant hyperthermia, kinetics of myosin and actomyosin interaction with CaATP suggest that myosin CaATPase activity may contribute to observed muscle rigidity and enhanced muscle thermogenesis.

Essential role of Sharpin in TNFα dependent NFκB activation in primary hepatocytes

2012 ◽  
Vol 50 (01) ◽  
Author(s):  
N Lange ◽  
S Sieber ◽  
A Erhardt ◽  
G Sass ◽  
HJ Kreienkamp ◽  
...  
Keyword(s):  
Essential Role ◽  
Primary Hepatocytes

Different Abilities of Thrombin Receptor Activating Peptide and Thrombin to Induce Platelet Calcium Rise and Full Release Reaction

1995 ◽  
Vol 74 (05) ◽  
pp. 1323-1328 ◽  
Author(s):  
Dominique Lasne ◽  
José Donato ◽  
Hervé Falet ◽  
Francine Rendu
Keyword(s):  
Essential Role ◽  
Calcium Influx ◽  
Dense Granule ◽  
Receptor Interaction ◽  
Thrombin Receptor ◽  
Release Reaction ◽  
External Calcium ◽  
Maximum Rise ◽  
Granule Release

SummarySynthetic peptides (TRAP or Thrombin Receptor Activating Peptide) corresponding to at least the first five aminoacids of the new N-terminal tail generated after thrombin proteolysis of its receptor are effective to mimic thrombin. We have studied two different TRAPs (SFLLR, and SFLLRN) in their effectiveness to induce the different platelet responses in comparison with thrombin. Using Indo-1/AM- labelled platelets, the maximum rise in cytoplasmic ionized calcium was lower with TRAPs than with thrombin. At threshold concentrations allowing maximal aggregation (50 μM SFLLR, 5 μM SFLLRN and 1 nM thrombin) the TRAPs-induced release reaction was about the same level as with thrombin, except when external calcium was removed by addition of 1 mM EDTA. In these conditions, the dense granule release induced by TRAPs was reduced by over 60%, that of lysosome release by 75%, compared to only 15% of reduction in the presence of thrombin. Thus calcium influx was more important for TRAPs-induced release than for thrombin-induced release. At strong concentrations giving maximal aggregation and release in the absence of secondary mediators (by pretreatment with ADP scavengers plus aspirin), SFLLRN mobilized less calcium, with a fast return towards the basal level and induced smaller lysosome release than did thrombin. The results further demonstrate the essential role of external calcium in triggering sustained and full platelet responses, and emphasize the major difference between TRAP and thrombin in mobilizing [Ca2+]j. Thus, apart from the proteolysis of the seven transmembrane receptor, another thrombin binding site or thrombin receptor interaction is required to obtain full and complete responses.

Collagen-Induced Platelet Aggregation: -Evidence Against the Essential Role of Platelet Adenosine Diphosphate

1979 ◽  
Vol 42 (04) ◽  
pp. 1193-1206 ◽  
Author(s):  
Barbara Nunn
Keyword(s):  
Platelet Aggregation ◽  
Time Course ◽  
Essential Role ◽  
Atp Release ◽  
Adenosine Diphosphate ◽  
Human Platelets ◽  
High Doses ◽  
Induced Aggregation

SummaryThe hypothesis that platelet ADP is responsible for collagen-induced aggregation has been re-examined. It was found that the concentration of ADP obtaining in human PRP at the onset of aggregation was not sufficient to account for that aggregation. Furthermore, the time-course of collagen-induced release in human PRP was the same as that in sheep PRP where ADP does not cause release. These findings are not consistent with claims that ADP alone perpetuates a collagen-initiated release-aggregation-release sequence. The effects of high doses of collagen, which released 4-5 μM ADP, were not inhibited by 500 pM adenosine, a concentration that greatly reduced the effect of 300 μM ADP. Collagen caused aggregation in ADP-refractory PRP and in platelet suspensions unresponsive to 1 mM ADP. Thus human platelets can aggregate in response to collagen under circumstances in which they cannot respond to ADP. Apyrase inhibited aggregation and ATP release in platelet suspensions but not in human PRP. Evidence is presented that the means currently used to examine the role of ADP in aggregation require investigation.

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