Antagonism by phosphate buffer of the twitch loss in isolated muscle fibers produced by calcium-free solutions

1978 ◽  
Vol 56 (3) ◽  
pp. 523-526 ◽  
Author(s):  
G. B. Frank
Keyword(s):  
Calcium Ions ◽  
Phosphate Buffer ◽  
Mechanical Response ◽  
Surface Membrane ◽  
Skeletal Muscle Fiber ◽  
Phosphate Ions ◽  
Membrane Bound ◽  
T Tubules ◽  
Time Required ◽  
External Calcium

In 37 of 41 isolated frog skeletal muscle fiber preparations (one, two, or three fibers) the twitch was eliminated or reduced to < 10% of control by exposing the fibers to a 0-caicium, bicarbonate-buffered solution for 10 min or less. Replacing the bicarbonate by a phosphate buffer either prevented twitch inhibition or increased the 0-calcium exposure time required for its production. It is concluded that surface membrane-bound calcium ions (presumably in the t-tubules) are required to couple the action potential to the mechanical response and that phosphate ions inhibit the loss of the membrane-bound calcium ions into an external calcium-free solution.

Influence of Calcium Ions on the Plant Cell Surface: Membrane Fusions and Conformational Changes

1974 ◽  
Vol 32 ◽  
pp. 154-155
Author(s):  
D. James Morré ◽  
Charles E. Bracker ◽  
William J. VanDerWoude
Keyword(s):  
Cell Wall ◽  
Cell Surface ◽  
Conformational Changes ◽  
Calcium Ions ◽  
Surface Membrane ◽  
Carboxyl Groups ◽  
Cross Linking ◽  
Ultrastructural Evidence ◽  
Glycine Max L ◽  
Wall Extensibility

Calcium ions in the concentration range 5-100 mM inhibit auxin-induced cell elongation and wall extensibility of plant stems. Inhibition of wall extensibility requires that the tissue be living; growth inhibition cannot be explained on the basis of cross-linking of carboxyl groups of cell wall uronides by calcium ions. In this study, ultrastructural evidence was sought for an interaction of calcium ions with some component other than the wall at the cell surface of soybean (Glycine max (L.) Merr.) hypocotyls.

Study of Bio-Mineralization of BCP with Compensation of Calcium and Phosphate Ions

2009 ◽  
Vol 610-613 ◽  
pp. 1391-1394
Author(s):  
Hua De Zheng ◽  
Ying Jun Wang ◽  
Qiang Ma ◽  
Cheng Yun Ning ◽  
Xiao Feng Chen
Keyword(s):  
Free Energy ◽  
Calcium Phosphate ◽  
Calcium Ions ◽  
Biphasic Calcium Phosphate ◽  
Porous Ceramic ◽  
Apatite Layer ◽  
Apatite Formation ◽  
Phosphate Ions

In the present study, an Intelligent Multi-parameter Simulated Evaluation in vitro （IMSE system） was used to study the deposition properties of apatite formation on the surface of biphasic calcium phosphate porous ceramic (BCP) from static and dynamic r-SBF. Results showed that apatite formed on the surface of BCP from static and dynamic r-SBF differed between each other. In static r-SBF, ions were transferred by diffusion, which could not compensate the consuming of calcium ions, and mist apatite layer was formed on the surface of samples. But in the dynamic r-SBF, simulated fluid was adjusted precisely and flowed forcedly, the concentrations of ions were homogeneous; with the compensation of ions, calcium and phosphate were supersaturated, and the free energy of apatite formation was negative, bone-like apatite sheets were formed on the surface of samples.

Nitrendipine blocks high potassium contractures but not twitches in rat skeletal muscle

1988 ◽  
Vol 66 (9) ◽  
pp. 1210-1213 ◽  
Author(s):  
G. B. Frank ◽  
L. Konya ◽  
T. Subrahmanyam Sudha
Keyword(s):  
Skeletal Muscle ◽  
Calcium Ions ◽  
Calcium Uptake ◽  
Channel Blocker ◽  
Mechanical Response ◽  
Extracellular Calcium ◽  
The Other ◽  
Rat Skeletal Muscle ◽  
Potassium Depolarization ◽  
High Potassium

The effects of the organic calcium channel blocker nitrendipine was tested on electrically evoked twitches and on potassium depolarization-induced contractures of rat lumbricalis muscles. Nitrendipine (10−7 to 5 × 10−5 M) blocked only the potassium contractures. It was concluded that blocking calcium uptake through the slow voltage-senstitive calcium channels during potassium depolarization blocks the mechanical response of the muscle. Thus extracellular calcium ions are required for the excitation–contraction (E–C) coupling during depolarization contractures. On the other hand, electrically evoked twitches were not affected by nitrendipine; therefore, extracellular calcium ions entering via the slow voltage-sensitive channels are not required for E–C coupling during the twitch.

scholarly journals Matrix metalloproteinases cleave membrane-bound PD-L1 on CD90+ (myo-)fibroblasts in Crohn’s disease and regulate Th1/Th17 cell responses

2019 ◽  
Vol 32 (1) ◽  
pp. 57-68 ◽  
Author(s):  
Jose E Aguirre ◽  
Ellen J Beswick ◽  
Carl Grim ◽  
Gabriela Uribe ◽  
Marissa Tafoya ◽  
...  
Keyword(s):  
Crohn’S Disease ◽  
Crohn's Disease ◽  
Matrix Metalloproteinases ◽  
Immune Responses ◽  
Neutralizing Antibodies ◽  
Surface Membrane ◽  
Cell Activity ◽  
Th1 Cell ◽  
Mmp Inhibitors ◽  
Membrane Bound

Abstract Increased T helper (Th)1/Th17 immune responses are a hallmark of Crohn’s disease (CD) immunopathogenesis. CD90+ (myo-)fibroblasts (MFs) are abundant cells in the normal (N) intestinal mucosa contributing to mucosal tolerance via suppression of Th1 cell activity through cell surface membrane-bound PD-L1 (mPD-L1). CD-MFs have a decreased level of mPD-L1. Consequently, mPD-L1-mediated suppression of Th1 cells by CD-MFs is decreased, yet the mechanism responsible for the reduction in mPDL-1 is unknown. Increased expression of matrix metalloproteinases (MMPs) has been reported in CD. Herein we observed that when compared to N- and ulcerative colitis (UC)-MFs, CD-MFs increase in LPS-inducible levels of MMP-7 and -9 with a significant increase in both basal and inducible MMP-10. A similar pattern of MMP expression was observed in the CD-inflamed mucosa. Treatment of N-MFs with a combination of recombinant human MMP-7, -9 and -10 significantly decreased mPD-L1. In contrast, inhibition of MMP activity with MMP inhibitors or anti-MMP-10 neutralizing antibodies restores mPD-L1 on CD-MFs. CD-MFs demonstrated reduced capacity to suppress Th1 and Th17 responses from activated CD4+ T cells. By contrast, supplementation of the CD-MF:T-cell co-cultures with MMP inhibitors or anti-MMP neutralizing antibodies restored the CD-MF-mediated suppression. Our data suggest that (i) increased MMP-10 expression by CD-MFs and concomitant cleavage of PD-L1 from the surface of CD-MFs are likely to be one of the factors contributing to the decrease of mPD-L1-mediated suppression of Th1/Th17 cells in CD; and (ii) MMPs are likely to have a significant role in the intestinal mucosal immune responses.

scholarly journals EXTERNAL CALCIUM IONS AND MECHANICAL RESPONSES OF THE AORTA ISOLATED FROM THE CHOLESTEROL-FED RABBIT

1974 ◽  
Vol 24 (1) ◽  
pp. 167-169 ◽  
Author(s):  
Issei TAKAYANAGI ◽  
Masaatsu UCHIDA ◽  
Keijiro TAKAGI ◽  
Yasuo ABE
Keyword(s):  
Calcium Ions ◽  
Mechanical Responses ◽  
External Calcium

scholarly journals Activation of sea urchin eggs by inositol phosphates is independent of external calcium

1988 ◽  
Vol 252 (1) ◽  
pp. 257-262 ◽  
Author(s):  
I Crossley ◽  
K Swann ◽  
E Chambers ◽  
M Whitaker
Keyword(s):  
Sea Urchin ◽  
Calcium Ions ◽  
Sea Water ◽  
Inositol Phosphates ◽  
Inositol Phosphate ◽  
Egg Activation ◽  
Lytechinus Variegatus ◽  
Lytechinus Pictus ◽  
Sea Urchin Eggs ◽  
External Calcium

We investigated the contribution of external calcium ions to inositol phosphate-induced exocytosis in sea urchin eggs. We show that: (a) inositol phosphates activate eggs of the sea urchin species Lytechinus pictus and Lytechinus variegatus independently of external calcium ions; (b) the magnitude and duration of the inositol phosphate induced calcium changes are independent of external calcium; (c) in calcium-free seawater, increasing the volume of inositol trisphosphate solution injected decreased the extent of egg activation; (d) eggs in calcium-free sea water are more easily damaged by microinjection; microinjection of larger volumes increased leakage from eggs pre-loaded with fluorescent dye. We conclude that inositol phosphates do not require external calcium ions to activate sea urchin eggs. This is entirely consistent with their role as internal messengers at fertilization. The increased damage caused to eggs in calcium-free seawater injected with large volumes may allow the EGTA present in the seawater to enter the egg and chelate any calcium released by the inositol phosphates. This may explain the discrepancy between this and earlier reports.

Trans and surface membrane bound zervamicin IIB: 13C-MAOSS-NMR at high spinning speed

2006 ◽  
Vol 35 (4) ◽  
pp. 285-293 ◽  
Author(s):  
J. Raap ◽  
J. Hollander ◽  
T. V. Ovchinnikova ◽  
N. V. Swischeva ◽  
D. Skladnev ◽  
...  
Keyword(s):  
Surface Membrane ◽  
Membrane Bound ◽  
Spinning Speed
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