Intracellular ions

6 Intracellular Ions. - A review of NMR and its application in biomedicine has been produced. 

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Figure 11. A summary cartoon illustrating the relationships between the first messengers and the release of Ca ions from the SR, the various pathways that influence the intracellular ion concentration, and the activation of MLCK, which leads to contraction.

However, repeated excitations do produce a Na and K shift over the muscle membrane, with extrusion of K and uptake of Na. This will change the intracellular ion composition, in spite of the counteracting effect of the Na -K pump. 

Fig. 6. Double-barrel micropipet ISE for measuring transient intracellular ion activities, (From 11, with permission)...

Microelectrodes can be made sufficiently small to measure intracellular ion activities, as shown schematically in Fig. 5 The micro ion-selective electrode is inserted into a single cell by means of a micromanipulator. The intracellular activity of the... 

The difficulties of intensity-based flow cytometry are illustrated by the present difficulties of cell-by-cell measurements of intracellular calcium. This can be accomplished using the calcium probe Indo-l,(34 38) but requires an ultraviolet (UV) laser source which is not routinely available in flow cytometry (Indo-1 is an emission wavelength ratiometric probe). Flow cytometers routinely have argon ion laser sources with outputs of 488 or 514 nm. Measurement of intracellular ions other than Ca2+ is nearly impossible. (The SNAFL and SNARF probes should allow pH measurement from the wavelength-ratiometric data.(15))... 

Daptomycin has a unique mechanism of action it disrupts the bacterial membrane of Gram-positive organisms by forming channels across it. These channels permit the leakage of intracellular ions, eventually leading to cell death. Resistance to daptomycin is rare, at least so far. 

The concentrations and distribution of electrolytes are not fixed, because cell membranes are permeant to ions and to water. Movement of ions and water in and out of cells is determined by the balance of thermodynamic forces, which are normally close to equilibrium. Selective changes of ion concentrations cause movement of water in or out of cells to compensate for these alterations. The kidneys are a major site where changes in salt or water are sensed. The loss of fluids due to illness or disease may alter intracellular and extracellular electrolyte concentrations, with attendant changes in fluid movement in or out of cells. Changes of extracellular or intracellular ion concentrations, particularly for potassium, sodium, and calcium, can have profound effects on neuronal excitability and contractility of the heart and other muscles. 

Dubovsky SL, Lee C, Christiano J, et al Elevated platelet intracellular calcium concentration in bipolar depression. Biol Psychiatry 29 441-450, 1991a Dubovsky SL, Lee C, Christiano J, et al Lithium lowers platelet intracellular ion concentration in bipolar patients. Lithium 2 167-174, 1991b Dubovsky SL, Murphy J, Thomas M, et al Abnormal intracellular calcium ion concentration in platelets and lymphocytes of bipolar patients. Am J Psychiatry 149 118-120, 1992a... 

EDTA penetrates cell membranes relatively poorly and therefore chelates extracellular metal ions much more effectively than intracellular ions. 

Flood A, Headrick JP (2001) Functional characterization of coronary vascular adenosine receptors in the mouse. Br J Pharmacol 133(7) 1063-1072 Fralix TA, Murphy E, London RE, Steenbergen C (1993) Protective effects of adenosine in the perfused rat heart changes in metabolism and intracellular ion homeostasis. Am J Physiol 264(4 Pt 1) C986-C994... 

One of the exciting developments associated with ion-selective electrodes has been the fabrication of microelectrodes capable of monitoring an intracellular ion concentration. The history of these developments from the mid-1950s has been reviewed.88 a symposium held in 1996 was devoted to the history of ion-selective electrodes. One paper discussed their development and commercialization,89 another described how the 1970s was the decade in which they really became established,90 a third outlined their industrial applications,91 and a fourth traced the evolution of blood chemistry analyses using them.92 The first attempts to construct biochemical sensors by immobilizing enzymes on electrodes date from the 1960s.93... 

Hensel, R., and H. Konig (1988). Thermoadaptation of methanogenic bacteria by intracellular ion concentration. FEMS Microbiol. Lett. 49 75-79. 

NMR can help to monitor energization, see, e.g. [121, 273], especially the levels of 31P-containing metabolites, e.g. [45, 366], enzyme kinetics, compartmentalized intracellular ion activities, the fate of 3H-, 2H-, 13C-, 15N-, or 19F-labeled tracers, e.g. [108,109], 02 tension, compartmentalized redox potential, membrane potential, cell number or cell volume, see [133], and even pH. Major drawbacks are the cost of the equipment, the low intrinsic sensitivity and the interpretation of spectra [430]. 

FIGURE 4.4 Assays commonly used in ion channel research. FRET = fluorescence resonance energy transfer Im = transmembrane current Vm = transmembrane potential AVm = change in transmembrane potential A mn = change in concentration of intracellular ion AAS = atomic absorption spectrometry. 

Fluorescent macrocycles have also been used to complex intracellular ions and image vital tissues. 8-Hydroxyquinoline derivatives of diaza-18-crown-6 have been used complex intracellular Mg2+ in mouse mammary cells. Fluorescent images of the vital cells were obtained by two-photon microscopy <2006JA344>. 

DOT CLASSIFICATION 4.3 Label Dangerous When Wet SAFETY PROFILE Moderately toxic by intraperitoneal route. A ver reactive alkaK metal (more reactive than potassium or cesium). In the body, rubidium substitutes for potassium as an intracellular ion. The ratio of Rb/K intake is important in the toxicology of rubidium. A ratio above 40% is dangerous. In rats, a failure to gain weight is the first symptom, followed by ataxia and hyperirritabihty. Symptoms include skin ulcers, poor hair coat, sensitivity, and extreme nervousness leading to convulsions and death. 

Oren, A., Heldal, M., and Norland, S. (1997). X-ray microanalysis of intracellular ions in the anaerobic halophilic eubacterium. Haloanaerohium praevalens. Can.J. Microbiol. 43, 588-592. 

In organisms without strikingly high intracellular ion concentrations (e.g. members of the Crenarchaeota), some of their proteins show a low intrinsic stability in vitro (e.g., aminopeptidase from S. solfataricus [36] or endonuclease Sual from S. acidocaldarius [37]), suggesting that more or less specific interactions with other cell constituents are likely important to stabilize the native state of the intracellular enzymes at high temperatures. 

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