Rubidium uptake

Smyth, D.A. and W.M. Dugger. 1980. Effects of boron deficiency on rubidium uptake and photosynthesis in the diatom Cylindrothecafusiformis. Plant Physiol. 66 692-695. 

Figure 7.31. Kinetics of rubidium uptake by plant roots in the presence of sodium (Na+) (adapted from Epstein and Hagen, 1952).

Rubidium uptake via the transport system was measured in depleted cells of Methanospirillum hungatei [272]. At low external Rb concentration the accumulation gradient was significantly larger (2300-fold) than could be explained by the existing membrane potential ( —120 mV). The driving force for Rb" uptake has not been elucidated. 

The rubidium content of the flora is species-specific, and is seen to vary with the age of the plants, the rubidium concentration of the soils, and their pH value. An acid pH value of the soil supports rubidium uptake (Tyler 1983, 1997, Tyler and Zohlen 1998). 

Lowenstein JM (1962) Increased rubidium uptake by red cells during pregnancy. Am J Physiol 203 1191-1192. 

Pettersson S and Jensen P (1979) Regulation of rubidium uptake in sunflower roots. Physiol Plant 45 83-87. 

Aschner M, Eberle NB, Miller K, Kimelberg HK. 1990. Interactions of methylmercury with rat primary astrocyte cultures inhibition of rubidium and glutamate uptake and induction of swelling. Brain Res 530 245-250. 

Hall JL, Yeo AR, Flowers TJ. Uptake and localisation of rubidium in the halophyte Suaeda maritima. Zeit Pflanzenphysiol 1974 71 200-206. 

Rubidium-82 myocardial perfusion images are used to study patients with myocardial ischemia or infarction. An example of this study is shown in Figure 8. Three patients with known myocardial infarction were imaged with Rb-82. Twenty millicuries of Rb-82 were administered in a 20 ml bolus in 20 sec. Data accumulated from 0-90 seconds post infusion show the blood pool as the radioactivity enters the right side of the heart, flows out to the lungs, and returns to the left side of the heart. Data accumulated from 90-300 seconds reflect uptake of Rb-82 in the myocardium as distributed by blood flow. These results by a non-invasive procedure correlated with the results of catheterized contrast x-ray studies (27,28). 

Brain Studies. Rubidium-82 has also been used to study blood brain barrier changes in patients with brain tumors or Alzheimer s type senile dementia (28-30). The method of study is similar to the heart studies without gating. Figure 11 shows the uptake of Rb-82 in the three levels of a brain tumor. This non-invasive procedure provides information on the size and vascularity of the tumor. In the slice OM + 10 there is a vascular rim and a necrotic center in the tumor. The metabolism of glucose was determined in the same tumor patient using F-fluorodeoxyglucose produced on a cyclotron and the results correlated well with Rb-82 distribution. 

High Temperature Measurements of the Rates of Uptake of Molybdenum Oxide, Tellurium Oxide, and Rubidium Oxide Vapors by Selected Oxide Substrates... 

The rates of uptake of molybdenum, tellurium, and rubidium oxide vapors by substrates of calcium ferrite and a clay loam have been measured in air over a temperature range of 900° to 1500°C. and a partial pressure range of about 10r7 to 10 atm. The measured rates of uptake of molybdenum and tellurium oxide vapors by molten calcium ferrite and of rubidium oxide vapor by both molten clay loam and calcium ferrite were controlled by the rates of diffusion of the oxide vapors through the air. The measured rates of uptake of molybdenum and tellurium oxide vapors by molten clay loam were controlled by a combination of a slow surface reaction and slow diffusion of the condensate into the substrate. 

This paper presents the more important data and conclusions from three reports which describe the uptake behavior of the vaporized oxides of molybdenum, tellurium, and rubidium by molten and solid substrates at high temperatures (I, 2, 3). These oxides were used as the vapor species because of their relatively high volatility and because of their importance as radioactive constituents, or the precursors of important constituents, of radioactive fallout particles. 

Figures 6 and 7 show the uptake of rubidium oxide vapor by various sized particles of clay loam and calcium ferrite at 1400°C. There is uncertainty as to the molecular species found in rubidium oxide vapor under the experimental conditions. Data furnished by Bedford and Jackson indicate that the vapor should consist of a mixture of RbO and Rb molecules with RbO predominating (4). Experimental work by Norman and Staley indicate that the vapor should consist predominately of Rb with minor amounts of Rt O molecules (13). To calculate vapor pressures it was assumed that the vapor consisted only of RbO. Since the molecular weight of Rb is only 16% less than that of RbO, no large error is introduced by this assumption even if the vapor consists of Rb molecules.

Figures 8, 10, and 12 show the initial rates (at t = 0) of uptake of the molybdenum, tellurium, and rubidium oxide vapors by samples of...

For the uptake of molybdenum oxide vapor by the clay loam particles, the uptake of rubidium oxide vapor by the calcium ferrite, and the uptake of the tellurium oxide by both the clay loam and the calcium ferrite, the uptake vs. time plots are curved, and it is not immediately obvious what the rate-determining steps are. Plots of amounts of uptake at constant time and initial rates of uptake vs. particle diameters and diameters squared were therefore made. 

These plots show that for the uptake of both tellurium and rubidium oxide vapors by the calcium ferrite particles the rate-determining step is also the diffusion of the oxide vapor molecules through the air. The curvature of the plots showing amounts of uptake vs. time is caused by... 

Figure 7.26. Normal and linearized Michaelis-Menten plots describing rubidium (Rb+) uptake by plant roots under three different concentrations of K+ (competitive process) (from Epstein and Hagen, 1952, with permission).

Flora, Essentiality, and Toxicity It appears that rubidium is easily taken up by plants, and may partly substitute for potassium sites, though not in a metabolic role. At high concentrations, therefore, rubidium is rather toxic to plants. The essentiality of rubidium in plant physiology has not yet been fully defined, and in spite of chemical similarities between rubidium and potassium, the uptake and transportation... 

Tyler G (1983) Rubidium — availability and plant uptake in natural soils. Soil Sd Plant Anal 14 1075-1080. 

Tyler G (1997) Influence of acidity and potassium saturation on plant uptake of indigenous soil rubidium. Environ Exp Botany 38 181 — 186. 

Dopant uptake is much higher in this case, y = 0.85, which implies a Cs -Cs spacing of Si 3.9 A. The authors point out, in a comparison with the structures found in doped polyacetylene, that the occurrence of either three-fold or four-fold column structures depends on the size ratio of the projected polymer chain (Totor dimension ) and the ion. In polyacetylene, Na ions leads to three-fold columns as in PPV, but for doping the columns in polyacetylene are formed by four chains, in contrast to the result for PPV. This is because the rotor size of a polyacetylene chain is smaller than that of PPV (Table 1.7). Rubidium doping of PPV represents an intermediate case, for which, apparently, neither three-fold nor four-fold... 

After oral administration of RbCl, peak rubidium plasma levels are generally attained 60-90 min later. The metal is then rapidly distributed to other tissues. Although rubidium follows the potassium pathway within the body, there are sufficient differences in membrane selectivity to result in different patterns of retention and secretion. The highest rates of uptake occur (in decreasing order) in liver > lymph nodes > striatal muscle > heart, kidney, and lung [26]. Erythrocytes show a maximum uptake within 30 min and maintain elevated levels despite rapidly diminishing plasma concentrations [26]. Under steady-state conditions, the erythrocyte-to-plasma ratio can approach 25 1 [27]. Besides erythrocytes, tissues such as spleen and liver show a tendency for higher intracellular-to-extracellular ratios than that of potassium [28]. An exception to this is... 

This little story is mainly about my associations with potassium and rubidium, two elements in the alkali metal series of the periodic table. My Ph.D. thesis at the University of California in Berkeley (1934-1937) was concerned with potassium metabolism in the rat during pregnancy and lactation. In those days nutrition research was the major activity in biochemistry in the United States. In the course of my work I found among other things that the essential element, potassium, could be replaced by rubidium for growth of the rat, although after a time nervous disturbances and other toxic manifestations resulted. Rubidium is, in fact, transported by the same system which tissues use to take up potassium, so that nowadays one often measures potassium uptake activity with the radioactive isotope, Rb. The rubidium isotope happens to have a longer half-life and is more convenient to use than... 

The effect of serum in stimulating the uptake of the rubidium isotope is detectable in only 2 minutes (Fig. 1). The effect is rapidly reversed when serum is removed. It can be... 

Fig. 7.2. Plots of the reciprocal of the concentration of rubidium ions [Rb+] against the reciprocal of the rate of uptake of these ions (1/F). Concentrations in m-equivalents per litre. Uptake rates in m-equivalents per gram of tissue per hoiu. (a) shows competitive inhibition of Rb uptake by potassium ions, K+. (b) shows non-competitive inhibition of Rb+ uptake by lithium, Li+. (After E. Epstein and C. E. Hagen, Plant Physiology, 27 457, 1952, from J. F. Sutcliffe, Mineral Salts Absorption in Plants, Pergamon Press, Oxford, 1962.)...

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