Binding of Ca Ions by Paramecium caudatum

Binding of 45Ca by live Paramecium caudatum was determined under various external ionic conditions. It was found that calcium uptake was separable into at least two components, a rapid and a slow one. The rapid component was influenced by the presence of certain other ions in a manner which agrees with the law of mass action. It appears that an ion exchange system may be involved in a binding equilibrium established between Paramecium, Ca++, and certain other ions. K+, Rb+, and Ba++ in the equilibrium medium are among those ions which inhibit calcium uptake. It is proposed that liberation of Ca++ from binding sites on Paramecium by an exchange reaction with competing ions is the first step in the mechanism of ciliary reversal in the response to external application of these ions.

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Ionic Control of the Reversal Response of Cilia in Paramecium caudatum

The Journal of General Physiology ◽

10.1085/jgp.51.1.85 ◽

1968 ◽

Vol 51 (1) ◽

pp. 85-103 ◽

Cited By ~ 85

Author(s):

Yutaka Naitoh

Keyword(s):

Cation Exchange ◽

Calcium Ions ◽

Time Course ◽

Calcium Release ◽

Published Data ◽

Paramecium Caudatum ◽

Exchange System ◽

Contractile System ◽

Ciliary Reversal ◽

Final Amount

The duration of ciliary reversal of Paramecium caudatum in response to changes in external ionic factors was determined with various ionic compositions of both equilibration and stimulation media. The reversal response was found to occur when calcium ions bound by an inferred cellular cation exchange system were liberated in exchange for externally applied cations other than calcium. Factors which affect the duration of the response were (a) initial amount of calcium bound by the cation exchange system, (b) final amount of calcium bound by the system after equilibration with the stimulation medium, and (c) concentration of calcium ions in the stimulation medium. An empirical equation is presented which relates the duration of the response to these three factors. On the basis of these and previously published data, the following hypothesis is proposed for the mechanism underlying ciliary reversal in response to cationic stimulation: Ca++ liberated from the cellular cation exchange system activates a contractile system which is energized by ATP. Contraction of this component results in the reversal of effective beat direction of cilia by a mechanism not yet understood. The duration of reversal in live paramecia is related to the time course of bound calcium release.

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Evaluation of Three Constants Involved in the Binding of Corticosterone to Plasma Proteins in the Rat

Canadian Journal of Biochemistry ◽

10.1139/o74-016 ◽

1974 ◽

Vol 52 (2) ◽

pp. 101-105 ◽

Cited By ~ 6

Author(s):

Michel Jobin ◽

François Perrin

Keyword(s):

Binding Sites ◽

Plasma Proteins ◽

Association Constant ◽

Equilibrium Dialysis ◽

Confidence Region ◽

Rat Plasma ◽

Mass Action ◽

Law Of Mass Action ◽

Likelihood Principle ◽

Method Of Calculation

Equilibrium dialysis was used to evaluate three constants involved in the binding of corticosterone to transcortin and albumin in rat plasma, namely ST (concentration of binding sites of transcortin), KT (association constant of transcortin), and SAKA (binding constant of albumin). Undiluted plasma from rats adrenalectomized 24 h earlier was enriched with increasing amounts of corticosterone (0–5.0 μg/ml) and dialyzed for 4.3 h at 37 °C.Assuming that the law of mass action applies to the interaction between corticosterone and its two binding proteins, the values of ST, KT, and SAKA were estimated by means of a new method of calculation. Derived from the maximum likelihood principle, this method allows computation of a confidence region for the parameters. The following values and statistical bounds were obtained:[Formula: see text]

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Genetic recombination as a generalised gradient flow

Monatshefte für Mathematik ◽

10.1007/s00605-021-01612-x ◽

2021 ◽

Author(s):

Frederic Alberti

Keyword(s):

Arbitrary Number ◽

Genetic Recombination ◽

Reaction Network ◽

Gradient Flow ◽

Mass Action ◽

Gradient System ◽

Gradient Structure ◽

Law Of Mass Action ◽

Reversible Chemical Reaction ◽

Time Partitioning

AbstractIt is well known that the classical recombination equation for two parent individuals is equivalent to the law of mass action of a strongly reversible chemical reaction network, and can thus be reformulated as a generalised gradient system. Here, this is generalised to the case of an arbitrary number of parents. Furthermore, the gradient structure of the backward-time partitioning process is investigated.

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Cell surface-binding sites for progesterone mediate calcium uptake in human sperm.

Journal of Biological Chemistry ◽

10.1016/s0021-9258(18)55113-9 ◽

1991 ◽

Vol 266 (28) ◽

pp. 18655-18659 ◽

Cited By ~ 1

Author(s):

P.F. Blackmore ◽

J. Neulen ◽

F. Lattanzio ◽

S.J. Beebe

Keyword(s):

Cell Surface ◽

Binding Sites ◽

Calcium Uptake ◽

Human Sperm ◽

Surface Binding ◽

Cell Surface Binding

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Movement of Calcium Ions and their Role in the Activation of Platelets

Thrombosis and Haemostasis ◽

10.1055/s-0038-1648654 ◽

1978 ◽

Vol 40 (02) ◽

pp. 212-218 ◽

Cited By ~ 60

Author(s):

P Massini ◽

R Käser-Glanzmann ◽

E F Lüscher

Keyword(s):

Plasma Membrane ◽

Platelet Activation ◽

Calcium Ions ◽

Binding Sites ◽

Shape Change ◽

Release Reaction ◽

Dense Bodies ◽

Activated Platelets ◽

Different Types ◽

Ca Ions

SummaryThe increase of the cytoplasmic Ca-concentration plays a central role in the initiation of platelet activation. Four kinds of movements of Ca-ions are presumed to occur during this process: a) Ca-ions liberated from membranes induce the rapid shape change, b) Vesicular organelles release Ca-ions into the cytoplasm which initiate the release reaction, c) The storage organelles called dense bodies, secrete their contents including Ca-ions to the outside during the release reaction, d) At the same time a rearrangement of the plasma membrane occurs, resulting in an increase in its permeability for Ca-ions as well as in an increase in the number of Ca-binding sites.Since most processes occurring during platelet activation are reversible, the platelet must be equipped with a mechanism which removes Ca-ions from the cytoplasm. A vesicular fraction obtained from homogenized platelets indeed accumulates Ca actively. This Ca- pump is stimulated by cyclic AMP and protein kinase; it may be involved in the recovery of platelets after activation.It becomes increasingly clear that the various manifestations of platelet activation are triggered by a rise in the cytoplasmic Ca2+-concentration. The evidence for this and possible mechanisms involved are discussed in some detail in the contributions by Detwiler et al. and by Gerrard and White to this symposium. In this article we shall discuss four different types of mobilization of Ca-ions which occur in the course of the activation of platelets. In addition, at least one transport step involved in the removal of Ca2+ must occur during relaxation of activated platelets.

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