The Calcium Content of Frog Nerve

Tipton, Samuel R.

doi:10.1152/ajplegacy.1934.109.3.457

Cited by 9 publications

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“…The pool size and the influx rate are practically the same as those reported for muscle and nerve (4,14,(19)(20)(21). Furthermore, this exchangeable pool is roughly 40% of the total cellular calcium measured in cells deprived of their coat by trypsin-EDTA (1) and is identical to the exchangeable calcium reported in muscle and nerve (4,(9)(10)(11)(12). We conclude, therefore, that the slow component measured in our system represents the exchangeable intraceUular calcium compartment.…”

Section: Calcium F L U X E S In Hela Cells M E a S U R E D By T R A Csupporting

confidence: 82%

“…On the basis of the measurements in HeLa cells presented in Table II it would appear that only 450-/0 of the intracellular calcium would be exchangeable. In support of these calculations, studies of calcium exchange in muscle and nerve also reveal that 400-/0 only of the intracellular calcium pool is exchangeable (9)(10)(11)(12). When the cellular calcium concentration is expressed on the basis of the water content of the ceils, it is found to be 0.224 mmole/kg cell water.…”

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confidence: 71%

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Kinetic Analyses of Calcium Movements in HeLa Cell Cultures

Borle

1969

The Journal of General Physiology

115

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Calcium influx was studied in monolayerg of HeLa cells to determine the number of exchangeable and nonexchangeable pools and the rate constant of the different fluxes. Of the two exchangeable pools, one has a very fast rate of exchange with a half-time of 1.54 illin, a compartment size of 1.06 m#moles/mg cell protein, and an exchange rate of 474 #/~moles/(mg protein. rain). This compartment is likely to be extracellular and could represent calcium exchange between the extracellular fluids and surface binding sites of the cell membrane. The second exchangeable pool has a half-time of exchange of 31 rain, a compartment size of 2.69 m/~moles/mg cell protein (0.224 millimole calcium/kg cell water), and a flux rate of 0.0546 v#mole cm -~ sec -t. This compartment can be considered to be the intracellular pool of exchangeable calcium. An unexchangeable intracellular pool of calcium of 3.05 m#moles/mg cell protein was detected implying that only 45 % of the intracellular calcium is exchangeable. In addition, a large extracellular pool of calcium has been found to be unexchangeable, probably a part of the cell glycocalix. Finally, dinitrophenol 10 -8 M does not affect the slow component of the calcium uptake curve which brings new evidence that calcium entry into the cell is not a metabolically dependent process.The study of cellular calcium metabolism presents several difficulties. A cell, for instance, cannot be considered an homogeneous pool of calcium. There are at least two calcium compartments of different magnitude showing markedly different properties (1, 2). One of these compartments is even not part of the cell itself but lies outside the plasma membrane and has been called "cell coat" or "glycocalix" (1-3). The second, the cellular calcium compartment, is undoubtedly divided into several pools, but for the time being we shall consider intracellular calcium as one compartment. Until now we have attempted to dissect these two main compartments by chemically stripping the ceils from their coat with trypsin-EDTA in order to identify the properties of 43

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Section: Calcium F L U X E S In Hela Cells M E a S U R E D By T R A Csupporting

confidence: 82%

Section: Symbolsmentioning

confidence: 71%

Kinetic Analyses of Calcium Movements in HeLa Cell Cultures

Borle

1969

The Journal of General Physiology

115

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“…Some samples of 5-and 6-day-old rabbit blastocytes were analysed and found to contain about 1 m-mole Ca/kg (P. R. Lewis & C. Lutwak-Mann, unpublished), while values of the same order have been obtained for muscle (Fenn, Cobb, Manery & Bloor, 1938;Slater & Cleland, 1953). Tipton (1934) reported rather higher values for frog nerve, but here much of the calcium is probably associated with the phospholipids of the myelin sheath.…”

Section: Analysis Of the Calcium In Squid Axoplasmmentioning

confidence: 94%

The intracellular calcium contents of some invertebrate nerves

Keynes¹,

Lewis²

1956

The Journal of Physiology

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Estimates of the calcium content of a variety of whole tissues have been reported, but there are indications that much of this calcium is extracellular, and there is little reliable information about the intracellular calcium concentration in living cells. In the course of an investigation on the role of calcium in invertebrate nerves (for preliminary accounts see Frankenhaeuser & Hodgkin, 1955; Fliickiger & Keynes, 1955) a knowledge of the amount of calcium in nerve axoplasm became important. A micromethod for the determination of quantities of calcium of the order of 1,ug or less was therefore developed by one of us (P.R. L.), and its application to estimate the internal calcium of squid giant axons and of whole crab nerves is described here. METHODS Principle of the analytical techniqueThe analytical procedure was developed from the visual titration method due to Schwarzenbach and his collaborators (Schwarzenbach, Biedermann & Bangerter, 1946;Schwarzenbach & Gysling, 1949; see also Martell & Calvin, 1952). It consists in titrating calcium, in alkaline solution, against a solution of versene (the disodium salt of ethylenediamine tetracetic acid) in the presence of murexide (ammonium purpurate). Versene is a powerful chelating agent for many ofthe polyvalent metals, and combines quantitatively with the calcium; the murexide acts as an indicator, combining with any free calcium ions to form a red-coloured complex, which decomposes to liberate the purple-coloured purpurate ion when the concentration of ionic calcium falls on completing the titration.The main problem in scaling down this technique lay in the detection of the end-point-when the last trace of red disappears from an otherwise purple solution. With the very small amount of indicator that could be tolerated in titrating, say 1 ,ug of calcium, the end-point cannot be distinguished visually. The micro-titration was therefore performed in a colorimeter cell, in position in the colorimeter, and the extinction of the solution was measured with a suitable blue filter after each addition of versene. The end-point was easily determined from a plot of extinction against volume of versene added. Fales (1953) has used a similar method on a somewhat larger scale for the determination of serum calcium, and Karsten, Kies, van Engelen & de Hoog (1955) * Present address: Anatomy School, University of Cambridge.

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2010

Calcium Binding Proteins

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The Calcium Content of Frog Nerve

Cited by 9 publications

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Kinetic Analyses of Calcium Movements in HeLa Cell Cultures

Kinetic Analyses of Calcium Movements in HeLa Cell Cultures

The intracellular calcium contents of some invertebrate nerves

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