K+ concentration

Hypokalemia is a reduction of plasma K+ concentration below 3.5 mM. Hypokalemia can result from a reduction in dietary K+ intake and from a shift of K into the intracellular space. The most common of hypokalemia, however, is renal K+ loss (i.e., caused by diuretics). 

Although vitamin K is a fat soluble vitamin, only little stores are found in the body which have to be refilled permanently via dietary input. The role of vitamin K derived from bacteria in the colon is controversely discussed, as the concentration of biliary acids for the resorption the fatsoluble vitamin K is very low in the colon. In addition, only diseases of the small intestine lead to a deficit in vitamin K concentration which cannot be restored by K2 production of colonic bacteria. However, watersoluble vitamin Ks can be resorbed by the colonic mucosa. Maybe because of the little stores for vitamin K, the process of vitamin K-dependent carboxylation of proteins is part of a cycle with several steps during which vitamin K normally is regenerated (see Fig. 1) and thus can be used several times. 

Fig. 4. K/Na ratios and (Na + K) concentrations in sap from leaves of disomic D genome substitution lines in Triticum turgidum cv. Langdon grown in NaCl (150 mol m plus CaCl2 at 7.5 mol m ). Data of Gorham etal. (1987)...

In general, cells maintain a low inttaceUulat Na concentration and a high intracellular K+ concentration (Table 41-1), along with a net negative electrical potential inside. The pump that maintains these gradients is an ATPase that is activated by Na and (Na -K ATPase see Figure 41-13). The ATPase is an integral... 

Cl -channels, which serve to take up Cl when the membrane voltage is depolarized, e.g., by an increase in ambient K -concentration, other GABA-sensitive Cl -channels have been found in recent studies [29]. The functional role of these channels has yet to be defined. 

Figure 1.86. Variation in chemical compositions (in molal unit) of hydrothermal solution with temperature. Thermochemical data used for the calculations are from Helgeson (1969). Calculation method is given in Shikazono (1978a). Chloride concentration in hydrothermal solution is assumed to be 1 mol/kg H2O. A-B Na concentration in solution in equilibrium with low albite and adularia, C-D K concentration in solution in equilibrium with low albite and adularia, E-F HaSiOa concentration in equilibrium with quartz, G-H Ca + concentration in equilibrium with albite and anorthite (Shikazono, 1978a, 1988b).

Fig. 2.13. (A) Temperature dependence of pH in Japanese thermal waters. Lines indicate the temperature dependence of pH when pH is buffered by the K-feldspar-K-mica-quartz (or chalcedony at less than 200°C) assemblage at a Na + K concentration of 0.1 and 0.01 mol/kg H2O. Symbols are as in Fig. 2.11. (B) Temperature dependence of pH of Icelandic thermal waters. Large circles indicate well discharges. Small dots represent hot spring waters (Chiba, 1991).

The normal UAG ranges from 0 to 5 mEq/L (mmol/L) and represents the presence of unmeasured urinary anions. In metabolic acidosis, the excretion of NH4+ and concurrent CP should increase markedly if renal acidification is intact. This results in UAG values from -20 to -50 mEq/L (mmol/L). This occurs because the urinary CP concentration now markedly exceeds the urinary Na+ and K+ concentrations. Diagnoses consistent with an excessively negative UAG include proximal (type 2) renal tubular acidosis, diarrhea, or administration of acetazo-lamide or hydrochloric acid (HC1). Excessively positive values of the UAG suggest a distal (type 1) renal tubular acidosis. 

Reversal potentials for LSD were also determined over a range of external K+ concentrations. According to the Nemst equation, reversal potentials should shift approximately 60 mV per 10-fold shift in K+ concentration if K+ were the ionic species involved in a conductance change. Reversal potentials of LSD were found to shift almost exactly to the extent predicted by the Nemst equation for a K+-dependent potential. Of course, there are several different types of K+ conductances that could be activated by LSD, including the Ca2+-dependent outward current. To evaluate the latter possibility, midbrain slices were exposed... 

Ealy, G.K., Concentration of Copper and Copper Oxides by Flotation at Nacimiento, Mining Congress Journal, Nr 33, pp. 63-66, 1973. 

Figure 5.4 Least-square fit of the K concentration data in Alibert and Carron (1980) experiment of diffusion at basalt-rhyolite interface by a polynomial of degree (n — 1) with n = 6 (top) and n = 10 (bottom). When n increases from 6 to 10, the solution begins oscillating between the data.

Calcium ion movements are sensitive to the concentration of other cations. In one study, it was found that Ca influx into cells might occur through K+ inward rectifier channels when extracellular K+ ion concentration fell below 1 mM. These channels became Ca -permeable only when the extracellular K+ concentration decreased to 1 mM or below. The same study found that the addition of different divalent cations revealed that Ba +, but not NT+, Cd +, Sr, or Mg +, reversibly blocked the Ca influx into cells during low external Intracellular proteins requiring calcium ion must be very selective for Ca because the concentration of free Mg + (2.5 mM) and K+ (-100 mM) are much higher. Intracellular Ca + concentrations must be kept at very low levels because calcium ions inhibit the activity of Mg +-dependent enzymes. In addition, the precipitation of sparingly soluble calcium salts may cause serious problems within a cell. 

Make a judgment about the optimum proteinase K concentration for different tissue sections, and select that particular concentration for a future final experiment. 

KCl solution for 24 hours. After being removed from the salt solutions, the membranes were rinsed thoroughly with distilled, deionized water. The salt solutions were analyzed with a Varlan 175 series atomic absorption spectrometer (AAS). Na and K concentrations were determined using the 590.8 nm and 768.5 nm absorption bands, respectively. Before and after the ion-exchange studies, the membranes were dried and analyzed with ESCA and NAA. 

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