The contractile basis of ameboid movement. II. Structure and contractility of motile extracts and plasmalemma-ectoplasm ghosts.

The role of calcium and magnesium-ATP on the structure and contractility in motile extracts of Amoeba proteus and plasmalemma-ectoplasm "ghosts" of Chaos carolinensis has been investigated by correlating light and electron microscope observations with turbidity and birefringence measurements. The extract is nonmotile and contains very few F-actin filaments and myosin aggregates when prepared in the presence of both low calcium ion and ATP concentrations at an ionic strength of I = 0.05, pH 6.8. The addition of 1.0 mM magnesium chloride, 1.0 mM ATP, in the presence of a low calcium ion concentration (relaxation solution) induced the formation of some fibrous bundles of actin without contracting, whereas the addition of a micromolar concentration of calcium in addition to 1.0 mM magnesium-ATP (contraction solution) (Taylor, D. L., J. S. Condeelis, P. L. Moore, and R. D. Allen. 1973. J. Cell Biol. 59:378-394) initiated the formation of large arrays of F-actin filaments followed by contractions. Furthermore, plasmalemma-ectoplasm ghosts prepared in the relaxation solution exhibited very few straight F-actin filaments and myosin aggregates. In contrast, plasmalemmaectoplasm ghosts treated with the contraction solution contained many straight F-actin filaments and myosin aggregates. The increase in the structure of ameba cytoplasm at the endoplasm-ectoplasm interface can be explained by a combination of the transformation of actin from a less filamentous to a more structured filamentous state possibly involving the cross-linking of actin to form fibrillar arrays (see above-mentioned reference) followed by contractions of the actin and myosin along an undetermined distance of the endoplasm and/or ectoplasm.

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Oscillatory membrane potential changes in cells of mesenchymal origin: the role of an intracellular calcium regulating system

Journal of Experimental Biology ◽

10.1242/jeb.81.1.49 ◽

1979 ◽

Vol 81 (1) ◽

pp. 49-61

Author(s):

P. G. Nelson ◽

M. P. Henkart

Keyword(s):

Endoplasmic Reticulum ◽

Membrane Potential ◽

Intracellular Calcium ◽

Calcium Ion ◽

Surface Membrane ◽

Ion Concentration ◽

Free Calcium ◽

Potassium Ions ◽

Calcium Ion Concentration

A number of mesenchymal cells (fibroblasts, macrophages and megakaryocytes) respond to a variety of stimuli with large hyperpolarizations lasting several seconds (the H.A. response). The H.A. responses can occur as repetitive trains or oscillations. These hyperpolarizations are due to an increase of the surface membrane permeability to potassium ions which is probably mediated by an increase in the cytoplasmic free calcium ion concentration. Evidence is discussed which suggests that the source of this increased calcium, is least in part, an intracellular sequestering system, probably the endoplasmic reticulum. A model capable of producing oscillatory changes in membrane potential is proposed based on such an intracellular calcium sequestering and releasing system.

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Two competitive nucleation mechanisms of calcium carbonate biomineralization in response to surface functionality in low calcium ion concentration solution

Regenerative Biomaterials ◽

10.1093/rb/rbv010 ◽

2015 ◽

Vol 2 (3) ◽

pp. 187-195 ◽

Cited By ~ 14

Author(s):

Hua Deng ◽

Shuo Wang ◽

Xiumei Wang ◽

Chang Du ◽

Xingcan Shen ◽

...

Keyword(s):

Calcium Carbonate ◽

Calcium Ion ◽

Ion Concentration ◽

Surface Functionality ◽

Low Calcium ◽

Nucleation Mechanisms ◽

Calcium Ion Concentration

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Supplementary material to "Decoupling salinity and carbonate chemistry: Low calcium ion concentration rather than salinity limits calcification in Baltic Sea mussels"

10.5194/bg-2020-382-supplement ◽

2020 ◽

Author(s):

Trystan Sanders ◽

Jörn Thomsen ◽

Jens Daniel Müller ◽

Gregor Rehder ◽

Frank Melzner

Keyword(s):

Baltic Sea ◽

Calcium Ion ◽

Ion Concentration ◽

Carbonate Chemistry ◽

Low Calcium ◽

Supplementary Material ◽

Calcium Ion Concentration

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Tetany: quantitative interrelationships between calcium and alkalosis

American Journal of Physiology-Legacy Content ◽

10.1152/ajplegacy.1975.228.4.1082 ◽

1975 ◽

Vol 228 (4) ◽

pp. 1082-1086 ◽

Cited By ~ 17

Author(s):

JW Edmondson ◽

RE Brashear ◽

TK Li

Keyword(s):

Calcium Ion ◽

Ion Concentration ◽

Acid Base Balance ◽

Rate Of Development ◽

Arterial Ph ◽

Base Balance ◽

The Central Nervous System ◽

Calcium Ion Concentration ◽

Hypocapnic Alkalosis

Tetany occurs with hypocalcemia and alkalosis or both. The interrelationship of calcium and acid-base balance necessary for inducing tetany, the role of the central nervous system, and the rate of development of hypocalcemia have been investigated. Tetany occurred in less than 50 percent of one group of dogs made alkalotic by hyperventilation or made hypocalcemic by infusion of ethylene glycol-bis(beta-amino ethyl ether) N, N'-tetraacetate. In contrast, hypocalcemia combined with hypocapnic alkalosis always produced tetany. Slowly evolving hypocalcemia was achieved inanother group of dogs by thyroparathyroidectomy, and tetany was induced postoperatively by hypocapnic alkalosis. An identical relationship between serum calcium ion concentration and arterial pH or CO2 tension was found in both groups. Tetany could not be related to the cerebrospinal fluid (CSF) calcium ion content in either group. Hypocalcemia and alkalosis are therefore coparticipants in the development of tetany and are independent of the rate of development of hypocalcemia and of CSF calcium ion concentration. The importance of alkalosis in tetany with hypoparathyroidism is emphasized.

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