The Nature of the In Vivo Sodium and Chloride Uptake Mechanisms through the Epithelium of the Chilean Frog Calyptocephalella gayi (Dum. et Bibr., 1841) : Exchanges of hydrogen against sodium and of bicarbonate against chloride

The Chilean frog, Calyptocephallela gayi, placed in dilute NaCl solutions may pump Na⁺ and Cl^- at very different rates depending on the kind of bath solutions in which it was preadapted. Furthermore, Na⁺ and Cl^- may be absorbed from solutions in which the accompanying coion, such as sulfate and choline, respectively, is impermeant. In all these cases it is obligatory to postulate the existence of two ionic exchange mechanisms, Cl^- and Na⁺, being exchanged against endogenous anions and cations, respectively. It has been determined that Na⁺ is exchanged against endogenous H⁺ and that Cl^- is exchanged against HCO₃^-. In animals pumping Na⁺ and Cl^- from dilute NaCl solutions Na⁺ or Cl^- uptake may be selectively inhibited, while the flux of the accompanying ion remains unchanged. This is considered to be an additional proof that both Na⁺ and Cl^- fluxes are always independent. The role of the ionic exchange mechanisms in the direct regulation of the Na⁺ and Cl^- levels in the internal medium is discussed as well as their relationship in the regulation of the acid-base equilibrium; other physioecological considerations have been treated.     

黄河口湿地柽柳灌丛土壤盐渍化特征

为探究黄河三角洲湿地柽柳灌丛下土壤的盐渍化特征，在黄河三角洲国家级自然保护区(37°35''-12''N，118°33''-119°20''E)黄河入海口附近，根据长势基本一致的原则分别在碱蓬群落、柽柳群落和芦苇群落各选3株柽柳，采集柽柳灌丛下土壤样品，分析土壤盐分和盐碱化参数的空间分布以及距基茎不同距离处研究对象(土壤总盐(TS)、电导率(EC)、pH、交换性钠百分率(ESP))和环境因子(Na⁺、K⁺、Ca²⁺、Mg²⁺、Cl^-、HCO₃^-、SO^2-₄)之间的关系。结果表明：(1)研究区土壤为弱碱化盐土，离子含量由高到低依次为Cl^->Na⁺>SO^2-₄ >Ca²⁺>Mg²⁺>HCO^-₃>K⁺。除pH在土壤表层数值最低外，表层土壤TS、EC、ESP和盐分离子大于深层土壤，显示表聚性。(2)土壤盐分和盐碱化参数空间分布总体为：在柽柳基茎周围形成"盐谷"、"碱谷"效应， Na⁺、Mg²⁺、Cl^-表现为"盐谷"，K⁺ 、SO^2-₄ 、Ca²⁺ 表现为"盐岛"。(3)在整个土壤剖面中，与TS、EC相关性最强的阴阳离子为Mg²⁺、Cl^-，从灌丛中心到灌丛间裸地Ca²⁺、SO^2-₄与TS、EC的相关性逐渐减弱，Mg²⁺、Cl^-与TS、EC的相关性逐渐增强。Ca²⁺和SO^2-₄与pH表现为较强的负相关性；与ESP相关性最强的阴离子为HCO^-₃，与之相关性最强的阳离子为Na⁺和K⁺，并且Na⁺和K⁺与ESP的相关性表现出从灌丛中心向外逐渐增强。(4)土壤盐渍化主要受控于Na⁺，从灌丛下到灌丛间裸地Cl^-对盐渍化程度的影响逐渐增加，SO^2-₄的影响逐渐降低。     

CO-REQUIREMENT FOR CALCIUM AND POTASSIUM IN THE GERMINATION OF SPORES OF THE FERN ONOCLEA SENSIBILIS

Spores of Onoclea sensibilis L. do not germinate on distilled H₂O if they are pretreated for sufficient time with dilute NaClO solution. However, spores will germinate, after NaClO pretreatment, on a simple mineral medium containing the major and trace elements. Complete germination after pretreatment also is obtained on a solution containing only Ca²⁺ and K⁺ as the cations, but neither ion by itself is sufficient. Rb⁺, but not Li⁺ or Na⁺, can replace K⁺. Hypochlorite-treated spores do not require the continuous presence of Ca²⁺ and K⁺ to germinate; exposure during the first 4 hr of culture, with the remainder of the time on distilled H₂O, is sufficient. Extraction of spores with ethylene glycol bis(aminoethyl ether) tetraacetic acid [EGTA] makes their germination dependent on Ca²⁺, as reported by other workers, but it does not produce a co-requirement for K⁺. Colorimetric analysis with arsenazo III confirms that Ca²⁺ is extracted from Onoclea spores by NaClO. Extractable Ca²⁺ amounts to about 78 nmol/mg spore dry wt. Of this amount, 31% is contained in the perispore. The perispore comprises 13% of the total spore dry wt.     

渗透胁迫和离子毒害对转Bt基因棉幼苗生长及离子分布的影响

研究了渗透和盐胁迫处理对转Bt基因抗虫棉(Gossypium hirsutum) 99B种子的萌发和幼苗生长的影响,以及幼苗不同器官离子吸收和分配的差异。结果表明:渗透和盐胁迫均对转Bt基因抗虫棉幼苗的生长有抑制作用,其中PEG的抑制作用最强,而3种盐的抑制程度以CaCl₂>NaCl>Na₂SO₄,且在Na⁺含量相同时,Cl^-的毒害大于SO₄^2-。渗透胁迫下使根、茎和叶中的Na⁺和Cl^-含量提高,K⁺、Ca²⁺、SO₄^2-含量和K⁺/Na⁺、Ca²⁺/Na⁺和SO₄^2-/Cl^-比值降低,且地上部的变化幅度大于地下部的,其中以PEG的影响最为显著,其次是CaCl₂,Na₂SO₄处理最弱。这些说明,转Bt基因抗虫棉99B的耐盐性较弱。     

Effects of salinity on uptake and distribution of Na+, Cl- and K+ in two wheat cultivars

Plants of two wheat (Triticum aestivum L.) cultivars differing in salt tolerance were grown in sand with nutrient solutions. 35-d-old plants were subjected to 5 levels of salinity created by adding NaCl, CaCl₂ and Na₂SO₄. Growth reduction caused by salinity was accompanied by increased Na⁺ and Cl^- concentrations, Na⁺/K⁺ ratio, and decreased concentration of K⁺. The salt tolerant cv. Kharchia 65 showed better ionic regulation. Salinity up to 15.7 dS m^-1 induced increased uptake of Na⁺ and Cl^- but higher levels of salinity were not accompanied by further increase in uptake of these ions. Observed increases in Na⁺ and Cl^- concentrations at higher salinities seemed to be the consequence of reduction in growth. Uptake of K⁺ was decreased; more in salt sensitive cultivar. This was also accompanied by differences in its distribution.     

Influence of anions on the potassium status and productivity of kiwifruit (Actinidia deliciosa) vines

The effects of K fertiliser (160 kg ha^-1) applied with Cl^- or SO₄ ^2- as the accompanying anion on the K nutrition of kiwifruit (Actinidia deliciosa var. deliciosa) were assessed in a field experiment, using vines with varying degrees of K deficiency. Leaf K concentrations in spring were significantly higher for vines receiving KCl, compared to those receiving K₂SO₄. This effect did not interact significantly with the degree of K deficiency, and persisted for about 6 weeks. Subsequently there was no significant difference between the leaf K concentrations for the vines receiving KCl or K₂SO₄. Applying K as KCl increased the leaf Cl concentration, especially in spring, while applying K as K₂SO₄ had no significant effect on the leaf S concentration at that time. These results implied a greater requirement for organic acid anions for K⁺ uptake from K₂SO₄ than from KCl, and the importance of organic acid anions for K⁺ uptake from different sources of K fertiliser is discussed. This transient effect of the accompanying anion on leaf K status was associated with large effects on flowering, and fruit yields were about 28% higher for plants receiving KCl rather than K₂SO₄.The effects on growth and tissue nutrient composition of varying the concentrations of Cl^-, NO₃ ^-, SO₄ ^2- and H₂PO₄ ^- around the roots of kiwifruit vines were examined in a solution culture experiment. For H₂PO₄ ^-, plant growth was very similar over a wide range of rates of addition. For the other anions, the range between deficiency and toxicity was clearly delineated. For Cl^- and NO₃ ^-, toxicity was associated with high tissue concentrations of Cl and N, respectively, and was consistent with competition for uptake between Cl^- and NO₃ ^-. However, for SO₄ ^2-, toxicity was associated with only a small increase in the tissue S concentration relative to that associated with maximum growth, and appeared to result more from effects on uptake of other anions and cations rather than from direct effects of high tissue S concentrations.It is concluded that the sensitivity of kiwifruit to the anion accompanying K⁺ in fertiliser may be related to the unusually high requirement for Cl previously reported for this species.     

Effect of pH and Sodium Ion on Germination of Alkalophilic Bacillus Species

The factors affecting the germination of spores of alkalophilic Bacillus species have been studied. The optimum pH for germination of spores of alkalophilic Bacillus No. 2b-2 was about 10 and NaCl (Na⁺) stimulated germination considerably. The optimum concentration of NaCl for germination was about 0.2 M. Other cations such as K⁺, NH₄⁺, Rb ⁺ , Cs⁺ and Ca²⁺ did not stimulate germination. Li⁺ showed a weak activity for stimulating germination. Na⁺ ions stimulated the early step of germination. It was necessary for Na⁺ ions to co-exsist with the germinants in the germination of spores and the effect of Na⁺ was reversible. The same results were obtained for the germination of alkalophilic Bacillus No. 16-2 and No. 20.     

THE PERMEABILITY OF PINCHED-OFF NERVE ENDINGS TO SODIUM, POTASSIUM AND CHLORIDE AND THE EFFECTS OF GRAMICIDIN

Abstract—

• 1 The passive permeability of synaptosomes to ions was measured by a light-scattering technique. Synaptosomes were freely permeable to acetate, HCO₃^_, SCN^?and NH₄⁺ and were impermeable to choline and SO₄^2-.
• 2 Gramicidin D selectively increased the permeability of synaptosomes to Na⁺ and K⁺ ions.
• 3 The relative permeabilities of Na⁺, K⁺ and Cl^?, measured in the presence of a number of more permeant counter-ions, was in the ratio 1:19:12. These values are discussed in terms of the source of the resting potential.

     

The Effects of Various Ions on Resting and Spike Potentials of Barnacle Muscle Fibers

Effects of monovalent cations and some anions on the electrical properties of the barnacle muscle fiber membrane were studied when the intra- or extracellular concentrations of those ions were altered by longitudinal intra-cellular injection. The resting potential of the normal fiber decreases linearly with increase of logarithm of [K⁺]_out and the decrement for a tenfold increase in [K⁺]_out is 58 mv when the product, [K⁺]_out ·[Cl^-]_out, is kept constant. It also decreases with decreasing [K⁺]_in but is always less than expected theoretically. The deviation becomes larger as [K⁺]_in increases and the resting potential finally starts to decrease with increasing [K⁺]_in for [K⁺]_in > 250 mM. When the internal K⁺ concentration is decreased the overshoot of the spike potential increases and the time course of the spike potential becomes more prolonged. In substituting for the internal K⁺, Na⁺ and sucrose affect the resting and spike potentials similarly. Some organic cations (guanidine, choline, tris, and TMA) behave like sucrose while some other organic cations (TEA, TPA, and TBA) have a specific effect and prolong the spike potential if they are applied intracellularly or extracellularly. In all cases the active membrane potential increases linearly with the logarithm of [Ca⁺⁺]_out/[K⁺]_in and the increment is about 29 mv for tenfold increase in this ratio. The fiber membrane is permeable to Cl^- and other smaller anions (Br^- and I^-) but not to acetate^- and larger anions (citrate^-, sulfate^-, and methanesulfonate^-).     

淋洗与植物作用耦合对盐渍化土壤的改良效应

以甘肃秦王川引大灌区盐渍化土壤为背景,以当地5种耐盐植物为材料,采用根袋法盆栽试验动态研究了淋洗结合植物种植对盐渍化土壤改良的效应。结果表明:与种前相比,单纯的淋洗作用对土壤pH值影响不大,而淋洗结合植物种植明显降低了土壤pH值,且根际土壤pH值小于非根际土壤的,5种耐盐植物中霸王根际土壤pH值降低幅度最大,达0.6个单位。K+、Ca2+、Na+、Mg2+、Cl-和SO2-4在5种植物根际土壤中均有不同程度的富集,富集程度因物种的不同而不同,随培养时间的延长而呈波动状态。5种供试植物和对照组土壤中的6种主要的可溶性盐分离子随淋洗次数和培养时间的延长呈下降趋势。在培养120d后,单纯淋洗的土壤中K+、Ca2+、Na+、Mg2+、Cl-和SO2-4的含量相比种前平均分别降低了33.3%、26.1%、35.6%、32.5%、35.5%和36.3%,植物吸收带走的上述各离子的含量平均分别占种前的46.2%、8.1%、30.2%、7.2%和21.6%,其中霸王吸收带走的盐分离子最多,而淋洗结合种植植物的土壤中上述各离子的含量与种前相比平均分别降低了67.25%、63.73%、83.8%、67.5%、81.55%和78.46%,由此可见,淋洗结合植物种植的脱盐效果优于单纯淋洗,且土壤中主要的盐分离子Na+、Cl-和SO2-4的含量降低幅度最大,通过计算得出,在Cl-、SO2-4和Na+减少的总量中还有37.73%的Na+、38.22%的Cl-和35.14%的SO2-4的减少量是由植物根系的物理化学作用机制引起的。     

Ecophysiologic investigations in the family of the Mesembryanthemaceae

Summary Overnight accumulation of malate, citrate, and isocitrate in a large number of species of Mesembryanthemaceae grown under identical environmental conditions was studied. Of the 27 species investigated, 24 showed malate accumulation, which in 3 cases was accompanied by considerable overnight accumulation of citrate. In the leaves of the same plants, the Na⁺, K⁺, Cl^-, SO₄ ^2-, and PO₄ ^3- contents were determined. Although the plants were not exposed to substrates of high NaCl content, they exhibited extraordinarily high levels of Na⁺ and Cl^-. All plants accumulated, much more Na⁺ than K⁺. No readily discernible correlation between the amount of any particular ion and the extend of CAM was found. It is concluded that halophilism and CAM are widespread phenomena in the family of Mesembryanthemaceae that possess ecologic significance.Abbreviations CAM Crassulacean Acid Metabolism - PEP Phosphoenolpyruvate On leave from Canberra     

Influence of salts and pH on the growth as well as NADH oxidase of the halotolerant bacterium A505

Growth yield of the halotolerant bacterium A505 was increased by the supplement of Na⁺, K⁺, or Rb⁺ into the culture media with pH 7.5, and inhibited by Li⁺ or Cs⁺. In the presence of less than 0.1 M NaCl or KCl alkaline growth media, pH 9.2 to 9.7, afforded optimal growth of this strain. Intracellular ion content of this microbe changed reflecting on the Na⁺ or K⁺ concentration in the media, although it tended to accumulate K⁺ and extrude Na⁺ in the media without NaCl supplemented. A 1.2 to 1.4-fold stimulation of in vitro NADH oxidase activity was obtained by supplement of salts, except for LiCl. The rate of NADH oxidation in the absence of salts correlated with the pH and showed clear maxima at pH about 8, irrespective of growth conditions. In the presence of 0.5 M NaCl or KCl, on the other hand, pH dependence was less significant and showed only a flat maximum at pH around 7. Effects of anions on NADH oxidase were realized following the lyotropic series: SO ₄ ^2- >F^->CH₃COO^->Cl^->I^->SCN^-, aside from NO ₃ ^- , which exhibited the largest stimulation on enzyme activity in all the anions examined.Abbreviations HEPES 4-(2-hydroxyethyl)-1-piperazine-ethanesulfonic acid - HQNO 2-heptyl-4-hydroxyquinoline-N-oxide - MES 4-morpholineethanesulfonic acid - Tris tris(hydroxy-methyl)methylamine     

基于典范对应分析的滨海湿地土壤季节性盐渍化特征

为了更好地开发利用黄河三角洲湿地土壤资源和生态环境建设,运用单因素方差分析(One-way ANOVA)和典范对应分析方法(CCA),对黄河口湿地0—10 cm土壤全盐量(TS)、盐分离子组成、pH、钠吸附比(SAR)、电导率(EC)的季节性变化特征及数量关系进行了分析。结果表明:该区土壤属于盐土类型,春季(5月)、夏季(8月)、秋季(10月)全盐含量均高于17.9 g/kg,且春季、秋季的含盐量高于夏季,造成春、秋季积盐,夏季脱盐。盐分阳离子以Na~+为主,阴离子以Cl~-为主,除Mg~(2+)在夏季、秋季和Cl~-在秋季表现出强烈的变异性外,其余离子在不同季节均表现出中等强度的变异性。春季,Cl~-与Na~+、Mg~(2+),SO■与K~+;夏季,Cl~-与HCO~-_3,SO■与Mg~(2+)、Ca~(2+),Ca~(2+)与Mg~(2+);秋季,Cl~-与SO■,SO■与Mg~(2+),Ca~(2+)与Mg~(2+),均有很好的关联性。pH值均介于7.7—8.1之间,各个季节受盐分离子的影响较小,分布较为均匀。SAR介于3.08—5.29之间,春季受控于HCO~-_3;夏季受控于K~+;秋季受各离子的影响均较小,分布较为均匀。EC介于7.16—13.04 mS/cm,春季受各离子的影响均较小,其空间分布较为均匀;夏季受控于SO■、Ca~(2+)、Mg~(2+);秋季受控于Na~+。TS与Cl~-、Na~+、Mg~(2+)在季节变化上的差异性一致,且各个季节均受控于Cl~-。故通过合理的措施控制或减少Cl~-来源是一条减轻黄河口湿地土壤盐渍化的合适途径。     

Ionic effects on bumetanide binding to the activated Na/K/2Cl cotransporter: Selectivity and kinetic properties of ion binding sites

Summary The loop diuretic bumetanide binds specifically to the Na/K/2Cl cotransporter of many cell types including duck erythrocytes. Membranes isolated from these erythrocytes retain the ability to bind bumetanide when cells are exposed to cotransport activity stimuli prior to membrane isolation. An extensive study of the effects of ions on specific [³H]bumetanide binding to such membranes is presented here and compared to the activity of these ions in supporting transport function in intact cells. Both Na⁺ and K⁺ enhanced bumetanide binding in a saturable manner consistent with a single-site interaction. The K _m for each ion was dependent on the concentration of the other cation suggesting heterotropic cooperative interactions between the Na⁺ and K⁺ binding sites. Na⁺ and K⁺ were partially replaceable, with the selectivity of the Na⁺ site being Na⁺ > Li⁺ > NH ₄ ⁺ ; N-methyl-d-glucamine⁺, choline⁺ and tetramethylammonium⁺ also supported a small amount of specific binding when substituted for Na⁺. The selectivity of the K⁺ site was K⁺ Rb⁺ > NH ₄ ⁺ > Cs⁺; N-methyl-d-glucamine⁺, choline⁺ and tetramethylammonium⁺ were inactive at this site. The results of transport experiments revealed a slightly different pattern. Li⁺ could partially substitute for Na⁺ in supporting coteansport, but other monovalent cations were completely inactive. The order of potency at the K⁺ site was NH ₄ ⁺ > K⁺ Rb⁺ > Cs⁺ other monovalent cations. The effect of Cl^- on bumetanide binding was biphasic, being stimulatory at low [Cl^-] but inhibitory at high [Cl^-]. As this implies the existence of two Cl^- binding sites (termed Cl _H and Cl _L for the high- and low- affinity sites, respectively) each phase was examined individually. Cl^- binding to Cl _H could be described by a rectangular hyperbola with a K _m of 2.5 mm, while kinetic analysis of the inhibition of bumetanide binding at high [Cl^-] revealed that it was of a noncompetitive type (K _i = 112.9 mm). The selectivity of anion binding to the two sites was distinct. Cl _H was highly selective with Cl^- > SCN^- > Br^-; F^-, NO ₃ ^- , ClO ₄ ^- , MeSO ₄ ^- , gluconate^- and SO ₄ ^2- were inactive. The efficacy of anion inhibition of binding to Cl _L was ClO ₄ ^- > I^- > SCN^- > NO₃ > Cl^-; F^-, MeSO ₄ ^- , gluconate^-, and SO ₄ ^2- were inactive. Thus, Cl _H is much more selective than Cl _L and largely accounts for the specificity of the system with respect to anion transport. SO ₄ ^- , NO ₃ ^- , I^-, SCN^- and ClO ₄ ^- did not support cotransport when bound to Cl _L and the latter three anions were inhibitory. Mg²⁺ was found to stimulate binding at a narrowly defined peak around 1.5 mm, but was inhibitory at higher concentrations. Other divalent cations caused a similar inhibition of bumetanide binding but did not exert a stimulatory effect at 1.5 mm. Divalent cations have little effect on cotransport in intact cells at concentrations up to 20 mm, suggesting that their effects on diuretic binding reflect interactions at internally disposed sites. Bumetanide binding was optimal at a pH of 7.8–8.1 and declined sharply as the pH was lowered towards 6. The titration curve correlated well with the effect of pH on cotransport in intact cells; the inhibitory effect of low pH suggests that protonation of the cotransporter may inhibit its function.We thank Drs. Brad Pewitt, John Westley and Mrinalini Rao for discussion, Sara Leung and Artelia Watson for their excellent technical assistance, and Dr. R.J. Turner for his gift of [³H] bumetanide. This work was supported in part by Cystic Fibrosis Center grant #CF RO11 7-04.     

Relation between Ion Accumulation of Salt-Sensitive and Isolated Stable Salt-Tolerant Cell Lines of Citrus aurantium

Four selected NaCl-tolerant cell lines of Sour orange (Citrus aurantium) were compared with the nonselected cell line in their growth and internal ion content of Na⁺, K⁺, and Cl⁻ when exposed to increasing NaCl concentrations. No difference was found among the various NaCl-tolerant cell lines in Na⁺ and Cl⁻ uptake, and all these cell lines took up similar or even larger amounts of Na⁺ and Cl⁻ than the NaCl-sensitive cell line. Exposure of cells of NaCl-sensitive and NaCl-tolerant lines to equal external concentrations of NaCl, resulted in a greater loss of K⁺ from the NaCl-sensitive cell line. This observation leads to the conclusion that growth and ability to retain high levels of internal K⁺ are correlated. Exposure of the NaCl-tolerant cell lines to salts other than NaCl resulted in even greater tolerance to Na₂SO₄, but rather poor tolerance to K⁺ introduced as either K₂SO₄ or KCl; the latter has a stronger inhibitory effect. The NaCl-sensitive cell line proved to be more sensitive to replacement of Na⁺ by K⁺. Analyses of internal Na⁺, K⁺, and Cl⁻ concentrations failed to identify any particular internal ion concentration which could serve as a reliable marker for salt tolerance.     

Anion sensitivity of motility and step-down photophobic responses of Euglena gracilis

The motility and step-down photophobic responses of Euglena are influenced by inorganic and organic anions. Persistent motility (with Ca²⁺, Mg²⁺ and K⁺ present) is supported with chloride or sulfate but not with acetate, nitrate or propionate as the only added anions. Cells in media containing acetate displayed a cell aggregation (clumping) behavior that was both red light sensitive and, under some conditions, was accompanied by suppression of the step-down photophobic response. Addition of sodium salts (Cl^-, SO ₄ ^2- , acetate or propionate) to cells in Cl^- or SO ₄ ^2- based media had differential effects on the duration of the step-down photophobic responses induced by blue light removal: anions alter the response. In addition, cells in all Cl^- containing media showed constant photophobic response duration following repeated stimulation. Cells in some SO₄ ^2- containing media, however, showed response summation to repeated stimulation. This latter effect was reversible and was overcome by the addition of chloride anions.     

A study of Li+-selective permeation through lipid bilayer membranes mediated by a new ionophore (AS701)

The neutral, noncyclic, imide and ether containing ionophore AS701, has been developed as Li⁺-selective molecule, to be used potentially as an aid in the Li⁺-therapy of manic-depressive illness. The present report is a characterization of this molecule in neutral lipid bilayer membranes. This ionophore was found to the bilayers Li⁺-selective, acting as a selective carrier of monovalent cations. In addition, this molecule was found to be capable of acting as a selective carrier of monovalent anions. For both types of ions, the rate-limitting step in the process of permeation was found to be the diffusion of the carrier-ion complex through the membrane. The membrane-permeating species were found to be 2 : 1 carrier-ion complexes, carrying either a monovalent cation or a monovalent anion. The selectivity sequences among the ions studied being: Li⁺(1) > ClO₄^?(0.7) > Na⁺(0.07) > K⁺(0.016) > Rb⁺(0.0095) > Cs⁺(0.0083) > Cl^?(0.001). Mg²⁺ and SO₄^2? were found to be impermeant (under present experimental conditions). This sequence shows that the AS701 molecule has low selectivity for ions present in biological media, among those studied (i.e. Na⁺, K⁺, Mg²⁺, Cl^2? and SO₄^2?). This indicates that these ions will not interfere in the Li⁺ permeability induced by this carrier in vivo, and that the carrier will not interfere in the normal transport processes of these ions.     

Formation and role of glycine betaine in the moderate halophile Vibrio costicola

The moderate halophile Vibrio costicola, growing on a chemically-defined medium, transformed choline into glycine betaine (betaine) by the membrane-bound enzyme choline dehydrogenase and the cytoplasmic enzyme betainal (betaine aldehyde) dehydrogenase. Choline dehydrogenase was strongly induced and betainal dehydrogenase less strongly induced by choline. The formation of these enzymes was also regulated by the NaCl concentration of the growth medium, increasing with increasing NaCl concentrations. Intracellular betaine concentrations also increased with increasing choline and NaCl concentrations in the medium. This increase was almost completely blocked by chloramphenicol, which does not block the increase in salt-tolerant active transport on transfer from a low to a high salt concentration.Choline dehydrogenase was inhibited by chloride salts of Na⁺, K⁺, and NH _inf4 ^su+ , the inhibition being due to the Cl^- ions. Betainal dehydrogenase was stimulated by 0.5 M salts and could function in up to 2.0 M salts.Cells grew as well in the presence as in the absence of choline in 0.5 M and 1.0 M NaCl, but formed no intracellular betaine. Choline stimulated growth in 2.0 M NaCl and was essential for growth in 3.0 M NaCl. Thus, while betaine is important for some of the adaptations to high salt concentration by V. costicola, it by no means accounts for all of them.Abbreviations CDMM chemically-defined minimal medium - PPT proteose-peptone tryptone medium - SDS sodium dodecyl sulfate Deceased, 1987     

Sodium plays a more important role than potassium and chloride in growth of <Emphasis Type="Italic">Salicornia europaea</Emphasis>

Salicornia europaea is a succulent euhalophyte that belongs to the Chenopodiaceae family. It is found that moderate concentration of NaCl can dramatically stimulate the growth of S. europaea plants. To elucidate the mechanism underlying the phenomenon, morphological and physiological changes of S. europaea in response to different ions, including cations (Na⁺, K⁺, Li⁺, Cs⁺) and anions (Cl⁻, NO₃ ⁻, CH₃COO⁻) were investigated, and the effects of Na⁺, Cl⁻ and K⁺ on the growth of S. europaea were also studied. Na⁺ was more effective than K⁺ and Cl⁻ in stimulating shoot succulence, cell expansion, and stomatal opening. Plants treated with Na⁺ (including NaCl, Na⁺, NaNO₃) showed better plant growth, increased photosynthesis and less cell membrane damage than those untreated and treated with 200 mM of Cl⁻ and K⁺ (including KCl and KNO₃). Both SEM-X-Ray microanalysis and flame emission results revealed that well developed S. europaea plants had a higher content of sodium but lower potassium and chlorine. It is concluded that sodium plays a more important role in the growth and development of S. europaea than potassium and chloride.     

Ionic Requirements for the Specific Binding of [3H]GBR 12783 to a Site Associated with the Dopamine Uptake Carrier

At 0°C, when Na⁺ was the only cation present in the incubation medium, increasing the Na⁺ concentration from 3 to 10 mM enhanced the affinity of [³H]l-[2-(di-phenylmethoxy)ethyl]-4-(3-phenyl-2-propenyl)piperazine ([³H]GBR 12783) for the specific binding site present in rat striatal membranes without affecting the 5_max. For higher Na⁺ concentrations, specific binding values plateaued and then slightly decreased at 130 mM Na⁺. In a 10 mM Na⁺ medium, the K_D and the B_max were, respectively, 0.23 nM and 12.9 pmol/mg of protein. In the presence of 0.4 nM [³H]GBR 12783, the half-maximal specific binding occurred at 5 mM Na⁺. A similar Na⁺ dependence was observed at 20°C. Scatchard plots indicated that K⁺, Ca²⁺, Mg²⁺, and Tris⁺ acted like competitive inhibitors of the specific binding of [³H]GBR 12783. The inhibitory potency of various cations (K⁺, Ca²⁺, Mg²⁺, Tris⁺, Li⁺ and choline) was enhanced when the Na⁺ concentration was decreased from 130 to 10 mM. In a 10 mM Na⁺ medium, the rank order of inhibitory potency was Ca²⁺ (0.13 mM) > Mg²⁺ > Tris⁺ > K⁺ (15 mM). The requirement for Na⁺ was rather specific, because none of the other cations acted as a substitute for Na⁺. No anionic requirement was found: Cl^-, Br^-, and F^- were equipotent. These results suggest that low Na⁺ concentrations are required for maximal binding; higher Na⁺ concentrations protect the specific binding site against the inhibitory effect of other cations.