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PubMed1992

The effects of monovalent cations Li+, Na+, K+, NH4+, Rb+ and Cs+ on the solid and solution structures of the nucleic acid components. Metal ion binding and sugar conformation.

The interactions of the monovalent ions Li+, Na+, K+, NH4+, Rb+ and Cs+ with adenosine-5'-monophosphoric acid (H2-AMP), guanosine-5'-monophosphoric acid (H2-GMP) and deoxyguanosine-5'-monophosphoric acid (H2-dGMP) were investigated in aqueous solution at physiological pH. The crystalline salts M2-nucleotide.nH2O, where M = Li+, Na+, K+ NH4+, Rb+ and Cs+, nucleotide = AMP, GMP and dGMP anions and n = 2-4 were isolated and characterized by Fourier Transform infrared (FTIR) and 1H-NMR spectroscopy. Spectroscopic evidence showed that these ions are in the form of M(H2O)n+ with no direct metal-nucleotide interaction, in aqueous solution. In the solid state, Li+ ions bind to the base N-7 site and the phosphate group (inner-sphere), while the NH4+ cations are in the vicinity of the N-7 position and the phosphate group, through hydrogen bonding systems. The Na-nucleotides and K-nucleotides are structurally similar. The Na+ ions bind to the phosphate group of the AMP through metal hydration shell (outer-sphere), whereas in the Na2-GMP, the hydrated metal ions bind to the base N-7 or the ribose hydroxyl groups (inner-sphere). The Na2-dGMP contains hydrated metal-carbonyl and metal-phosphate bindings (inner-sphere). The Rb+ and Cs+ ions are directly bonded to the phosphate groups and indirectly to the base moieties (via H2O). The ribose moiety shows C2'-endo/anti conformation for the free AMP acid and its alkali metal ion salts. In the free GMP acid, the ribose ring exhibits C3'-endo/anti conformer, while a C2'-endo/anti sugar pucker was found in the Na2-GMP and K2-GMP salts and a C3'-endo/anti conformation for the Li+, NH4+, Rb+ and Cs+ salts. The deoxyribose has C3'-endo/anti conformation in the free dGMP acid and O4'-endo/anti in the Na2-dGMP, K2-dGMP and a C3'-endo/anti for the Li+, NH4+, Rb+ and Cs+ salts. An equilibrium mixture of the C2'-endo/anti and C3'-endo/anti sugar puckers was found for these metal-nucleotide salts in aqueous solution.

Adenosine Monophosphate↗
PubMed1994

DNA in glasses at 77 K: high energy ionizing radiation versus UV electron ejection.

Most in the field of ionizing radiation damage to DNA in frozen aqueous solutions agree that two major types of radical ions are formed, i.e. G+/A+ and T-/C-. The main evidence stems from EPR and strand break studies. Fluid solutions exposed to laser light are known to give G+ and esolv- with low yields of single strand breaks. We have explored this contrast by photoionizing DNA solutions at 77 K, in the expectation that this would prevent the formation of esolv- and hence that the results might be similar to those for high energy radiation. They are not: the results show only the formation of G+ (or) (A+), the fate of the ejected electrons is unclear except for sodium perchlorate glasses when they react to give O-.

DNA↗
PubMed1968

The role of sodium and potassium ions in the generation of the electro-olfactogram.

In order to clarify whether or not the electronegative olfactory mucosal potentials (EOG) are generator potentials, the effects of changed ionic enviroment were studied. The EOG decreased in amplitude and in some cases nearly or completely disappeared, when Na(+) in the bathing Ringer solution was replaced by sucrose, Li(+), choline(+), tetraethylammonium(+) (TEA), or hydrazine. In the K(+)-free Ringer solution, the negative EOG's initially increased and then decreased in amplitude. In Ringer's solution with increased K(+), the negative EOG's increased in amplitude. When K(+) was increased in exchange for Na(+) in Ringer's solution, the negative EOG's decreased, disappeared, and then reversed their polarity (Fig. 6). Next, when the K(+) was replaced by equimolar sucrose, Li(+), choline(+), TEA(+), hydrazine, or Na(+), the reversed potentials recovered completely only in Na(+)-Ringer's solution, but never in the other solutions. Thus, the essential role of Na(+) and K(+) in the negative EOG's was demonstrated. Ba(++) was found to depress selectively the electropositive EOG, but it hardly decreased and never increased the negative EOG. Hence, it is concluded that Ba(++) interferes only with Cl(-) influx, and that the negative EOG's are elicited by an increase in permeability of the olfactory receptive membrane to Na(+) and K(+), but not to Cl(-). From the ionic mechanism it is inferred that the negative EOG's are in most cases composites of generator and positive potentials.

Animals↗
PubMed1987

Acetylcholine receptor-controlled ion translocation caused by phenyltrimethylammonium and nereistoxin: simple estimation of equilibrium constants of the minimal model.

The rate of slow Li+ influx and the fraction of active form of acetylcholine receptor (AChR) of Electrophorus electricus membrane vesicles at equilibrium between the active and desensitized forms of the receptor were measured in the presence of various concentrations of phenyltrimethylammonium (PTA) and nereistoxin (NTX), by a simple filtration assay and flame emission spectroscopy. The equilibrium constants of these ligands in the minimal model, which accounts for the AChR-mediated ion flux, were estimated simply from these two measurements, since the equilibrium constants for acetylcholine (ACh) and carbamylcholine (Carb) estimated from two kinetic measurements agreed well with those estimated from five sophisticated kinetic measurements of AChR-mediated ion fluxes. PTA showed high potency but not high efficacy, and showed inhibition when large doses were applied. NTX showed both low potency and low efficacy and acted as an inhibitor when it was added with Carb. The apparent dissociation constants of these three agonists evaluated from the minimal model and the equilibrium constants agreed with those obtained by assay of inhibition of radiolabeled ligand binding.

Animals↗
PubMed2003

Regulation of K+ transport in tomato roots by the TSS1 locus. Implications in salt tolerance.

The tss1 tomato (Lycopersicon esculentum) mutant exhibited reduced growth in low K+ and hypersensitivity to Na+ and Li+. Increased Ca2+ in the culture medium suppressed the Na+ hypersensitivity and the growth defect on low K+ medium of tss1 seedlings. Interestingly, removing NH4+ from the growth medium suppressed all growth defects of tss1, suggesting a defective NH4(+)-insensitive component of K+ transport. We performed electrophysiological studies to understand the contribution of the NH4(+)-sensitive and -insensitive components of K+ transport in wild-type and tss1 roots. Although at 1 mm Ca2+ we found no differences in affinity for K+ uptake between wild type and tss1 in the absence of NH4+, the maximum depolarization value was about one-half in tss1, suggesting that a set of K+ transporters is inactive in the mutant. However, these transporters became active by raising the external Ca2+ concentration. In the presence of NH4+, a reduced affinity for K+ was observed in both types of seedlings, but tss1 at 1 mm Ca2+ exhibited a 2-fold higher Km than wild type did. This defect was again corrected by raising the external concentration of Ca2+. Therefore, membrane potential measurements in root cells indicated that tss1 is affected in both NH4(+)-sensitive and -insensitive components of K+ transport at low Ca2+ concentrations and that this defective transport is rescued by increasing the concentration of Ca2+. Our results suggest that the TSS1 gene product is part of a crucial pathway mediating the beneficial effects of Ca2+ involved in K+ nutrition and salt tolerance.

Alleles↗
PubMed1992

Use of topical lithium succinate in the treatment of seborrhoeic dermatitis.

Twenty-one patients with seborrhoeic dermatitis were included in an open trial of lithium succinate ointment (LSO) for a total duration of 8 weeks. The same clinician made assessments of the severity of redness, scaling, greasiness and overall clinical impression of the condition every 2 weeks. Because the results appeared to be satisfactory, we decided to perform a double-blind, placebo-controlled trial of LSO. Thirty patients with seborrhoeic dermatitis were included. The results also demonstrated the beneficial effect of LSO. A significantly higher number of patients treated with LSO showed remission or marked improvement compared with placebo. The main adverse events demonstrated consisted of minor transient skin irritation and/or stinging sensation. Studying the in vivo inhibitory effect of LSO on the growth of Pityrosporum revealed that Pityrosporum did not significantly have its growth inhibited by lithium. Topical lithium succinate appears to be a safe and an effective treatment for seborrhoeic dermatitis. The product presumably acts as an anti-inflammatory agent.

Adolescent↗
PubMed2006

Modified coin cells for in situ Raman spectroelectrochemical measurements of Li(x)V2O5 for lithium rechargeable batteries.

In situ Raman spectroscopy is an extremely valuable technique for investigating fundamental reactions that occur inside lithium rechargeable batteries. However, specialized in situ Raman spectroelectrochemical cells must be constructed to perform these experiments. These cells are often quite different from the cells used in normal electrochemical investigations. More importantly, the number of cells is usually limited by construction costs; thus, routine usage of in situ Raman spectroscopy is hampered for most laboratories. This paper describes a modification to industrially available coin cells that facilitates routine in situ Raman spectroelectrochemical measurements of lithium batteries. To test this strategy, in situ Raman spectroelectrochemical measurements are performed on Li//V2O5 cells. Various phases of Li(x)V2O5 could be identified in the modified coin cells with Raman spectroscopy, and the electrochemical cycling performance between in situ and unmodified cells is nearly identical.

Electric Power Supplies↗
PubMed1989

Lithium salts adopted for psychopharmacological use as the modulators of protein synthesis in the brain: analytical review.

The investigations of the effects of Lithium salts on protein synthesis activity with special reference to neurochemical aspects may provide a fruitful development of a system of safe and effective, psychopharmacological methods for treatment and prevention of the Lithium-curable mental disorders complicated by general neurological (neuropathological) symptoms.

Animals↗
PubMed2000

Abnormal thiol group modulation of sodium-lithium countertransport and membrane fluidity is associated with a disturbed relationship between serum triacylglycerols and membrane function in type II diabetes.

In essential hypertension and diabetic nephropathy, sodium-lithium countertransport (Na-Li CT) is an inherited marker, subject to metabolic influences, of cardiovascular risk. Studies in Type II diabetes, taking clinical phenotypes as their starting point, are conflicting. We sought to identify Na-Li CT kinetic abnormalities in Type II diabetes, and only subsequently to seek relationships with clinical variables. Na-Li CT kinetics, membrane fluidity and their modulation by thiol proteins were measured in erythrocytes from 38 patients with Type II diabetes and in 16 normal control subjects. In untreated erythrocytes, Na-Li CT kinetics were similar. Thiol protein alkylation with N-ethylmaleimide generally caused both V(max) and K(m) to fall, but caused K(m) to rise in erythrocytes from 13 out of 38 diabetic subjects, whose native K(m) was low (P=0. 0013 compared with control). V(max) and serum triacylglycerol levels were related in normal controls (r(s)=0.54, P=0.038) and in diabetic subjects whose K(m) fell after N-ethylmaleimide (n=25, r(s)=0.62, P=0.001). Where the K(m) rose after N-ethylmaleimide, V(max) and triacylglycerol levels were not related (n=13, r(s)=-0.39, P=0.183) and membrane fluidity did not increase after N-ethylmaleimide. However, these subgroups were indistinguishable in terms of blood pressure, albuminuria, glycaemia or lipid profiles. Thus abnormalities in the regulation of Na-Li CT and membrane fluidity by key thiol proteins, resembling those seen in essential hypertension and diabetic nephropathy, were apparent in one-third of subjects with Type II diabetes. Membrane abnormalities may indicate a common pathological mechanism. The prognostic significance of Na-Li CT kinetic abnormalities in Type II diabetes must now be confirmed.

Adult↗
PubMed1976

Size-dependent allosteric effects of monovalent cations on rabbit liver fructose-1,6-bisphosphatase.

Effects of monovalent cations on the neutral rabbit liver fructose-1,6-bisphosphatase are multifunctional and dependent on their nonhydrated ionic size. (a) The maximal velocity is increased by addition of monovalent cations with the optimum stimulation occurring with a nonhydrated ionic radius of 1.2 A in the presence of a chelating agent such as EDTA. (B) Activation curves are sigmoidal with n values varying from 1.5 to 2.3 as ionic radius of monovalent cation increases. The apparent Ka values from 16.0 to 180 mM, obtained for various monovalent cations, have a linear relationship to ionic radii of cations. (c) At lower concentrations of fructose 1,6-bisphosphate monovalent cations show the inhibitory effect and the apparent Km for fructose 1,6-bisphosphate is increased as the concentration of monovalent cation is increased. A linear relationship is obtained between the slopes of increase in the Km and the reciprocals of ionic volume of monovalent cations. (d) The apparent Ka for Mg2+ is also increased as the concentration of monovalent cation is increased, and a linear relationship is obtained again between the increases in Ka and the reciprocals of ionic volume of monovalent cations. The cooperative nature for Mg2+ saturation is decreased as the Ka increases. (e) The apparent Ki for AMP is also linearly altered as the concentration of monovalent cation is varied. However, the alteration of the Ki is unusual, that is, the smaller cations than K+ increase the Ki (Li+ greater than Na+ greater than NH4+), whereas the larger cations decrease the value ((CH2CH2OH)3N+ greater than Cs+ greater than Rb+). The effect of K+ is insignificant. Alterations in the Ki are also linearly related to the reciprocals of ionic volume of monovalent cations. The cooperative nature for AMP inhibition is decreased or increased as the Ki increased or decreased. (f) In the absence of the chelating agent, the curves for Mg2+ saturation and AMP inhibition were hyperbolic without monovalent cations. By addition of monovalent cation the Ka for Mg+2+ or Ki for AMP is increased and cooperative natures for binding of both ligands are induced. For nonspherical monovalent cations, the application of "functional ionic radius" is proposed. Functional ionic radii of NH4+, (CH2OH)3CNH3+, and (CH2CH2OH)3N+ are estimated to be 1.17, 2.55, and 2.87 A, respectively. The presence of two distinct sites for the actions of monovalent cations is suggested.

Allosteric Regulation↗