Intracellular ion concentration

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.

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... 

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. 

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. 

The advantages of the isolated vessel technique in defining microvascular physiologic and pathophysiologic mechanisms are 1) The vessels are studied in the absence of a neurohumoral and parenchymal tissue environment, 2) it allows for direct assessment of vascular responses in defined segments, 3) transmural pressure is controlled, 4) hormones and drugs can be added to the bathing media or luminal perfusate, 5) intracellular ion concentrations can be measured by fluorescence microscopy and membrane potentials can be recorded with microelectrodes. 

MEMBRANE TRANSPORT Membrane transport mechanisms are vital to living organisms. Ions and molecules constantly move across cell plasma membranes and across the membranes of organelles. This flux must be carefully regulated to meet each cell s metabolic needs. For example, a cell s plasma membrane regulates the entrance of nutrient molecules and the exit of waste products. Additionally, it regulates intracellular ion concentrations. Because lipid bilayers are generally impenetrable to ions and polar substances, specific transport components must be inserted into cellular membranes. Several examples of these structures, referred to as transport proteins or permeases, are discussed. 

Membrane potential, Na -K -ATPase activity, intracellular ion concentrations... 

ATP hydrolysis is used to phosphorylate an internal domain and change the transporters conformation so that bound Na ions are released to the outside, and two external ions bind. binding triggers hydrolysis of the bound phosphate group and a return to the original conformation, accompanied by release of ions inside the cell. As a consequence, cells are able to maintain a much lower intracellular Na concentration and much higher intracellular ion concentration than present in the external fluid. 

Specimen Extracellular (intracellular) ion concentration (mM) Resting potential (mV) at normal physiological pH Reference"... 

The earliest type of ionophore-based potentiometric microelectrodes were prepared in the mid 1970s from micrometer-sized glass pipettes, filled at the end with the ionophore-doped hydrophobic phase (Figure 16). " For speciality applications, in particular, in biochemical and medical research, these microelectrodes continue to have a variety of applications. Particularly noteworthy are then-use to study intracellular ion concentrations, the release and uptake of ions into ceUs, and their recent use as... 

There is, thus, at present, no reason to suppose that early shutoff by HSV, involving displacement of ribosomes from mRNA, is caused by changes in intracellular ion concentrations. Delayed shutoff by those viruses that do not cause early virion-associated shutoff may possibly be related to a late increase in permeability of the... 

Thus, the available data presented above indicate that in vaccinia virus infections the alteration of the intracellular ion concentrations does not play a primary role in the selective inhibition of host protein synthesis. 

In normal cells, ion transport is regulated by the Na /K" -dependent ATPase (sodium pump Dahl and Hokin, 1974). Inhibition of the sodium pump should result in alteration of ionic environment inside infected cells. To test this hypothesis further, Garry et al. (1919b) studied the effect of ouabain, a specific inhibitor of the sodium pump. At a concentration of ouabain which inhibited protein synthesis in uninfected cells by 95% or more, viral protein synthesis was not affected. Ouabain treatment raises the intracellular Na ion concentration and simultaneously decreases the intracellular ion concentration of uninfected cells. The effect of SIN virus infection is similar to that of ouabain treatment, suggesting that the sodium pump is indeed inhibited by virus infection. 

Silver, LA., Deas, J. and Erecinska, M. (2001) Interactions of bioactive glasses with osteoblasts in vitro effects of 45 S 5 Bioglass , and 58S and 77S bioactive glasses on metabolism, intracellular ion concentrations and cell viability. Eiomaterials, 22(2), 175-85. 

Miyakawa, A. Kamiya, K. Hirano, M. Measurement of intracellular ion concentrations using fluorescent dye prohes. Ger. Offen. DE 4239016, 1993 Chem. Abstr. 1993, 119, 112934. 

Hamana K, Hamana H, Niitsu M, Samejima K, Sakane T, Yokota A (1994) Occurrence of tertiary and quaternary branched polyamines in thermophilic Archaebacteria. Microbios 79 109-119 Hensel R, Konig H (1988) Thermoadaptation of methanogenic bacteria by intracellular ion concentration. FFMS Microbiol Lett 49 75-79... 

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