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The effects of adding LiCl, RbCl, KCl or NaCl to sea water at concentrations up to 30 mmoles/1 on the frequency of contraction of jellyfish (Aurelia aurita) suggest that studies on phylogenetically low animals with relatively simple nervous systems may be of use to determine mechanisms of action of lithium and rudidium on movements.
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The influence of various concentrations of the thiol isomer of Systox on Rb absorption by excised barley leaf tissue was compared with the effect of DNP and DCMU. Rb absorption, regardless of the external salt concentration, was progressively reduced as the Systox concentration in the external solution was increased from 0.25 to 1.0 mM. Under anaerobic conditions, light-enhanced Rb absorption by leaf tissue was not influenced by Systox treatments. DNP treatment reduced ion absorption by leaf tissue. In the dark, the relative inhibitory effect of DNP and Systox treatment on Rb absorption was greater than in the light. The combination of Systox plus DNP inhibited Rb absorption more than did separate treatment with either compound. DCMU treatments in the light resulted in a reduction of light-enhanced Rb uptake. Also in the light, the combination of DCMU with Sytox, DNP, or both, inhibited Rb uptake more than did separate treatments of Systox, DNP, or Systox plus DNP. It is suggested that the inhibitory effect of Systox on Rb absorption by leaf tissue is due to partial inhibition of oxidative phosphorylation. Moreover, since light-enhanced Rb absorption is not affected by Systox, it is concluded that Systox has no effect either on the photophosphorylation reactions or on the utilization of high-energy phosphorylated compounds.
The endogenous concentrations of Rb and Cs have been determined in needles of 56 trees (Norway spruce, Picea abies) from eight different sites. Analysis was done by instrumental neutron activation. Concentrations were found to have a very large range (3-28,000 ng Cs/g and 1-190 micrograms Rb/g). The values on a given site have a tendency toward a log-normal distribution. There is a significant correlation between Rb and Cs, but the correlation is not linear. The concentrations of both elements are a function of the needle age. They decrease smoothly, approaching a constant value, when going from needle age class 1 to 5. It is shown that one algebraic function describes this biodynamic behavior on all sites and at all concentration levels. The function and its parameters are discussed.
BACKGROUND: Recent reports on 13N-labeled ammonia (13N-ammonia) positron emission tomographic (PET) imaging have suggested a relative reduction of measured tracer activity in the posterolateral wall. Such inhomogeneity of tracer distribution could potentially affect accuracy for detection of disease. The aim of this study was to compare the regional distribution of 13N-ammonia with 82Rb and 62Cu-labeled PTSM (62Cu-PTSM) to identify tracer-specific patterns that may be important in the clinical interpretation of cardiac flow studies. METHODS AND RESULTS: Twenty-eight healthy volunteers underwent PET imaging at rest with either 13N-ammonia (n = 14), 82Rb (n = 8), or 62Cu-PTSM (n = 6). Eight subjects given 13N-ammonia also underwent imaging after adenosine. Activity measured in the posterolateral wall on transaxial images was significantly lower than in the septum for 13N-ammonia, both at rest (p < 0.005) and after adenosine (p < 0.05). No differences were detected for 82Rb or 62Cu-PTSM. The septum/posterolateral wall activity ratios for 13N-ammonia, 82Rb, and 62Cu-PTSM were 1.15 +/- 0.07, 1.00 +/- 0.06, and 0.97 +/- 0.08, respectively (p < 0.001). Regional analysis of image data showed the percent of maximal activity data for 13N-ammonia in the lateral wall to be less than that of other regions (p < 0.001) and in the inferior wall to be greater than in the anterior and lateral walls (p < 0.001). For 62Cu-PTSM, activity in the inferior wall was greater than that in other regions (p < 0.005). No regional differences were detected for 82Rb. CONCLUSIONS: The relatively increased wall activity with 13N-ammonia and 62Cu-PTSM is most likely due to cross-contamination of activity from the liver. The significant reduction in activity in the lateral wall with 13N-ammonia, which persists after adenosine, is most likely related to regional heterogeneity in 13N-ammonia retention and may reflect regional differences in metabolic-trapping mechanisms for 13N-ammonia. Further investigation is required to elucidate the underlying mechanism of this phenomenon. Reduced tracer retention in the lateral wall segment as a normal variant must be considered when evaluating clinical 13N-ammonia PET studies.
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The membrane potential across the cytoplasmic membrane of EDTA-treated cells of a K+ transport-negative mutant of Escherichia coli K-12 was estimated from the equilibrium distribution of different lipid-soluble cations. With glucose as a substrate and at low K+ out, the membrane potential calculated from the distribution ratio of 86Rb+ in the presence of valinomycin (delta psi rb+) was considerably higher than that indicated by the [3H]tetraphenylphosphonium cation (delta psi TPP+). The lipid-soluble anion phenyldicarbaundecaborane (PCB-) increased delta psi TPP+ close to delta psi Rb+. To investigate whether these results were due to different binding of the cations to cellular components, residual Rb+ and TPP+ uptake was measured in cells permeabilized with 5% n-butanol (by volume). In those cells the distribution ratios or Rb+, K+ and Na+ approached a value of 4, indicating that the uptake of all three ions was driven by a residual negative surface potential or transmembrane Donnan potential (internally negative). The distribution ratio of TPP+ was 3--4-times higher than that of other cations and up to 10 mM TPP+ out was almost independent of the added TPP+ concentration. This extra uptake presumably represents binding of TPP+ to the cellular membranes. Thus, at pH 7.5, delta psi Rb+ was about 180--200 mV, whereas after correction for binding delta psi TPP+ was 110--150 and 150--170 mV in the absence and presence of PCB-, respectively. It is proposed that TPP+ indicates too low a potential, because by its strong binding it decreases the negative surface potential of the cytoplasmic membrane, and thereby inhibits its own further uptake. This is taken to mean that TPP+ distribution can be used as a qualitative probe only for the bacterial membrane potential.
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(1) The effect of surface charge upon the kinetics of monovalent cation translocation via a two-site mechanism is investigated theroretically. (2) According to the model dealt with, typical relations are expected for the dependence of the kinetic parameters of the translocation process upon the concentration of a polyvalent cation, differing essentially from those derived for the case in which the membrane carries no excess charge. (3) Even when a polyvalent cation does not compete with the substrate cation for binding to the translocation sites, apparently competitive inhibition may occur when the membrane is negatively charged. (4) The model is tested experimentally by studying the effects of the polyvalent cations Mg2+, Sr2+, Ca2+, Ba2+ and Al3+ upon Rb+ uptake into yeast cells at pH 4.5 A good applicability is found. (5) Equimolar concentrations of polyvalent cations reduce the rate of the Rb+ uptake into yeast cells in the order Mg2+ less than Sr2+ less than Ca2+ less than Ba2+ less than Al3+. (6) The conclusion is reached that the reduction in the rate of Rb+ uptake caused by the polyvalent cations applied results mainly from screening of the negative fixed charges on the membrane surface and binding to these negative sites rather than competition with Rb+ for the transport sites. (7) The results of our investigation indicate the affinity of the alkaline-earth cations for the negative fixed charges on the surface to the yeast cell membrane increases in the orther Mg2+ less than Sr2 less than Ca2+ less than Ba2+. (8) Probably mainly phosphoryl groups determine the net charge on the membrane of the yeast cell at a medium pH of 4.5.
Escherichia coli cells pre-loaded with 86Rb+ begin to lose 86Rb+ immediately after phage T5 addition. The loss proceeds with negative-exponential (first-order) kinetics for up to approximately 15 min after phage addition. The constant which characterizes the rate of loss increases with increasing numbers of infecting phage per cell. It is known that anaerobic, fermenting cells of E. coli show a two-step increase in 8-anilino-1-naphthalene sulfonate (ANS) fluorescence upon infection with bacteriophage T5; the first rise begins immediately upon phage addition, the second 6 min later. The onset of 86Rb+ release, therefore, is correlated with the first fluorescence rise with respect to timing and response to the multiplicity of infection.
1. Ouabain-sensitive 86Rb+ uptake by tissue preparations has been used as an estimate of Na+ pump activity. This uptake, however, may be a measure of the Na+ influx rate, rather than capacity of the Na+ pump, since intracellular Na+ concentration is a determinant of the active Na+/Rb+ exchange reaction under certain conditions. This aspect was examined by studying the effect of altered Na+ influx rate on ouabain-sensitive 86Rb+ uptake in atrial preparations of guinea pig hearts. 2. Electrical stimulation markedly enhanced ouabain-sensitive 86Rb+ uptake without affecting nonspecific, ouabain-insensitive uptake. Paired-pulse stimulation studies indicate that the stimulation-induced enhancement of 86Rb+ uptake is due to membrane depolarizations, and hence related to the rate of Na+ influx. 3. Alterations in the extracellular Ca2+ concentration failed to affect the 86Rb+ uptake indicating that the force of contraction does not influence 86Rb+ uptake. 4. Reduced Na+ influx by low extracellular Na+ concentration decreased 86Rb+ uptake, and an increased Na+ influx by a Na+-specific ionophore, monensin, enhanced 86Rb+ uptake in quiescent atria. 5. Grayanotoxins, agents that increase transmembrane Na+ influx, and high concentrations of monensin appear to have inhibitory effects on ouabain-sensitive 86Rb+ uptake in electrically stimulated and in quiescent atria. 6. Electrical stimulation or monensin enhanced ouabain binding to (Na+ + K+)-ATPase and also increased the potency of ouabain to inhibit 86Rb+ uptake indicating that the intracellular Na+ available to the Na+ pump is increased under these conditions. 7. The ouabain-sensitive 86Rb+ uptake in electrically stimulated atria was less sensitive to alterations in the extracellular Na+ concentration, temperature and monensin than that in quiescent atria. 8. These results indicate that the rate of Na+ influx is the primary determinant of ouabain-sensitive 86Rb+ uptake in isolated atria. Electrical stimulation most effectively increases the Na+ available to the Na+ pump system. The ouabain-sensitive 86Rb+ uptake by atrial preparations under electrical stimulation at a relatively high frequency seems to represent the maximal capacity of the Na+ pump in this tissue.
(1) The significance of the specific (ouabain-sensitive) 86Rb+ or 42K+ uptake by cardiac muscle preparations which are not 'sodium-loaded' was studied. (2) In left atrial preparations of guinea-pig heart, resting 86Rb+ uptake was relatively low. It was markedly increased by electrical stimulation. This stimulated uptake was further enhanced by isoproterenol and inhibited by verapamil. (3) In rat atria, the resting 86Rb+ uptake was somewhat higher than in guinea-pig atria, and the increase in uptake caused by electrical stimulation was smaller. In guinea-pig right ventricular papillary muscle, the resting uptake was highest among those tissues studied, and the response to electrical stimulation was smallest. In the latter tissue, verapamil produced only a minimal inhibition of the specific 86Rb+ uptake. (4) The effect of the frequency of electrical stimulation of 86Rb+ uptake paralleled its influence on the force of contraction, suggesting the involvement of intracellular sodium in both events. (5) In both left atrial and right papillary muscle preparations of guinea-pig heart, specific 42K+ uptake observed with 5.8 mM K+ was relatively high, and was increased only slightly by electrical stimulation. This electrical stimulation, however, increased ouabain-induced inhibition of 42K+ uptake, suggesting that the stimulation increases the amount of Na+ available to the sodium pump. (6) When the K+ concentration was 1 mM, the resting 42K+ uptake was low, and could be enhanced by electrical stimulation. (7) Thus, in cardiac muscle preparations which are not sodium loaded, the specific 86Rb+ or 42K+ uptake can be used to estimate the rate of sodium influx, which is equivalent to the rate of sodium efflux under steady-state conditions, provided that neither Rb+ nor K+ is in excess compared to the Na+ available to the pump. If Rb+ or K+ is in excess, its specific uptake may not reflect changes in transmembrane Na+ movement.
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