Isoform-specific modulation of Na+, K+-ATPase alpha-subunit gene expression in hypertension

Sodium, potassium-adenosine triphosphatase (Na+, K+-ATPase) is hypothesized to be involved in systemic vascular hypertension through its effects on smooth muscle reactivity and myocardial contractility. By means of RNA blot analyses of cardiac, aortic, and skeletal muscle RNAs in two rat hypertensive models, Na+,K+-ATPase alpha-subunit messenger RNA isoforms (alpha 2 and alpha 3) were shown to be deinduced in response to increased intravascular pressure. The changes were observed after 48 hours or more of experimental hypertension. Under these conditions, there is coordinate induction of another alpha isoform (alpha 1) and of beta-subunit messenger RNAs, probably in response to alterations in sodium flux rather than to elevated blood pressure.     

T-cell recognition of Ia molecules selectively altered by a single amino acid substitution

T lymphocytes recognize foreign antigen together with allele-specific determinants on membrane-bound class I and class II (Ia) gene products of the major histocompatibility complex. To identify amino acids of class II molecules critical to this recognition process, the genes encoding the beta chains of the I-Ak molecule were cloned from a wild-type B-cell hybridoma and from an immunoselected variant subline showing distinct serological and T-cell stimulatory properties. Nucleotide sequencing and DNA-mediated gene transfer established that a single base transition (G----A) encoding a change from glutamic acid to lysine at position 67 in the I-Ak beta molecule accounted for all the observed phenotypic changes of the variant cells. These results confirm the importance of residues 62 to 78 in the amino terminal domain of I-A beta for class II-restricted T-cell recognition of antigen and demonstrate the ability of a single substitution in this region to alter this recognition event.     

Widespread occurrence in frogs and toads of skin compounds interacting with the ouabain site of Na+, K+-ATPase

Amphibians of the family Bufonidae contain high levels of skin compounds that both inhibit Na+- and K+-dependent adenosinetriphosphatase and antagonize the binding of ouabain to the enzyme. In species of Bufo and Atelopus, these compounds are relatively nonpolar bufodienolides, whereas Dendrophryniscus and Melanophryniscus contain more polar compounds of unknown structure. Skin extracts from 30 of 48 species of frogs representing an additional eight families contained relatively low levels of compounds that inhibit binding of ouabain to Na+,K+-adenosinetriphosphatase. The widespread occurrence of low levels of inhibitory compounds is consonant with the role for these compounds as physiological regulators of Na+,K+-adenosinetriphosphatase in amphibian skin; high levels in the Bufonidae probably also serve as a defense against some predators.     

盐胁迫对香蕉幼苗体内Na^＋和K^＋含量及其分布的影响

采用营养液栽培,以香蕉幼苗为试材,研究了盐胁迫对香蕉幼苗根部、假茎和叶片各部位Na^＋和K^＋含量以及K＋／Na^＋的影响。结果表明,与对照相比植株体内Na^＋的含量增加,而植物体内K^＋含量减少,K^＋／Na^＋下降显著。     

盐胁迫对蓖麻Na+、K+吸收分布和叶绿素荧光的影响

[目的]探讨蓖麻的耐盐机制。[方法]比较了栽培蓖麻淄蓖6号和天然生长于滨海盐碱地的野生蓖麻体内K+、Na+的分布特点、叶绿素荧光参数、植株生长状况和叶片渗透调节能力对NaC l处理的响应。[结果]野生蓖麻较栽培蓖麻具更明显的喜盐特性;蓖麻的耐盐机制在于促进K+的吸收和向地上部的运输,进而维持叶片的K+/Na+平衡;通过维持光系统Ⅱ的稳定性进而维持盐胁迫下叶片的光合速率。[结论]该研究为蓖麻在盐碱滩涂地的推广应用提供了理论依据。     

不同盐碱条件下白榆器官中K~+、Na~+、Ca~(2+)和Mg~(2+)分布特征

为了探明白榆(Ulmus pumila)适应盐碱环境的机理,以高盐、中低盐、非盐碱3个土壤盐分立地条件下生长的白榆为试验材料,研究不同盐分浓度下新叶、老叶、新枝、老枝和根5个营养器官中4种金属盐离子分布特征.结果表明,白榆体内K 、Na 、Ca2 和Mg2 不同部位的含量不同,并存在显著差异;白榆各部位K 、Na 含量随着生长地区土壤盐分的增加而增加;K /Na 幼嫩器官显著高于成熟器官,茎叶显著高于根部;含盐中低等土壤中生长的白榆K /Na 高于高盐和非盐碱土壤中生长白榆.白榆器官中K 、Na 、Ca2 对盐碱的敏感性高于Mg2 ,K 和Na 是4种金属盐离子中白榆在盐渍生境下进行渗透调节作用的主要因素.     

盐胁迫对蓖麻Na~+、K~+吸收分布特点和叶绿素荧光的影响(英文)

[Objective] The aim of this study is to reveal the salt resistance of castor. [Method] Under salt stress, the growth, osmotic potential, chlorophyll fluorescence parameters, Na~+ and K~+ uptakes and transports in the seedlings of two Ricinus communis varieties (cultivar castor ‘Zibi 6’ and wild castor which grew naturally in coastal saline-alkali land), were comparatively studied. [Result] Wild castor preformed better in halophilism than that of cultivar castor Zibi 6 under the NaCl treatment. One of the salt tolerant mechanisms of castor is to improve K~+ uptake and transport to overground portion, thus to maintain K~+/Na~+ homeostasis in leaves; on the other hand, the high stability of Photoreaction System Ⅱ (PS Ⅱ) plays a key role in maintaining the leaf photosynthetic rate under salt stress. [Conclusion] The results of this study provided theoretical basis for the extension and application of castor in saline beach.     

钠、钾和钙离子对小麦幼苗叶片质膜透性和组织活力的效应

在等渗和等阴离子有效浓度条件下,Ｎａ＾＋和Ｋ＾＋的单效效应都使小麦幼苗叶片的质膜透性增大,且Ｎａ＾＋〉Ｋ＾＋,而Ｃａ＾２＋的单独效应却使其减小;Ｋ＾＋和Ｃａ＾２＋的单独效应都使小麦叶片组织ＴＴＣ还原率增大,且Ｃａ＾２＋〉Ｋ＾＋,而Ｎａ＾＋的单独效应却使其减小。     

Alteration of four identified K+ currents in Drosophila muscle by mutations in eag

Voltage-clamp analysis of Drosophila larval muscle revealed that ether à go-go (eag) mutations affected all identified potassium currents, including those specifically eliminated by mutations in the Shaker or slowpoke gene. Together with DNA sequence analysis, the results suggest that the eag locus encodes a subunit common to different potassium channels. Thus, combinatorial assembly of polypeptides from different genes may contribute to potassium channel diversity.     

NaCl对咸海卡拉白鱼血清离子、皮质醇和组织Na+,K+-ATP酶活性的影响

将卡拉白鱼(Chalcalburnus chalcoides aralensis)在分别含NaCl 0,2,4,6,8 g/L的水体中饲养30 d后发现,NaCl质量浓度2 g/L和4 g/L组鱼相对增重率与对照组相比无显著性差异,生长良好;6 g/L和8 g/L组鱼相对增重率低于对照组(P<0.05),生长受抑制。血清渗透压随盐度升高而增高(P>0.05);NaCl 4,6,8 g/L组血的Na ,Cl-浓度高于对照组(P<0.05);6 g/L和8 g/L组血K 浓度低于对照组(P<0.05);鳃Na ,K -ATP酶活性除8 g/L组下降外,其余各组鱼均高于对照(P<0.05);血清皮质醇水平随NaCl的升高而呈线性增加的趋势(P>0.05)。     

盐胁迫对芦笋幼苗生长和体内 Na＋，K＋，Ca2＋分布的影响

以芦笋品种 NJ978为试材,研究了 NaCl 胁迫对芦笋幼苗生长及体内 Na ＋,K ＋,Ca2＋吸收和分布的影响,结果表明：盐分对芦笋幼苗生长的抑制作用随 NaCl 浓度的增加而加剧,低盐胁迫下（NaCl ≤50 mmol/L ）,芦笋生长与对照没有显著差异,高盐胁迫（200～300 mmol/L NaCl）显著抑制了幼苗生长。随 NaCl 浓度的增加,芦笋体内Na ＋含量增加,K ＋,Ca2＋含量降低。芦笋根系对 Na ＋有一定的截留能力,低盐环境下（NaCl ≤100 mmol/L ）,根部Na ＋迅速增加,而地上部 Na ＋增加缓慢,从而抑制了 Na ＋向地上部运输,并维持了地上部相对稳定的 K ＋,Ca2＋平衡;外界 NaCl 浓度高于根系 Na ＋截留阈值后（100 mmol/L）,大量的 Na ＋运输至地上部并限制了 K ＋,Ca2＋的吸收,表现为 K ＋/Na ＋和 Ca2＋/Na ＋迅速下降。芦笋根系对 K ＋,Ca2＋,Na ＋选择吸收性（ASK ,Na ,ASCa ,Na ）随盐胁迫增加而变高;根部向地上部运输 K ＋,Ca2＋能力（TSK ,Na ,TSCa ,Na ）在0～100 mmol/L NaCl 水平下逐渐升高,之后迅速下降。以上结果表明：根部对 Na ＋的截留和 Na ＋,K ＋,Ca2＋在器官水平上的再分布是芦笋适应盐胁迫的重要机制之一。     

H_2O_2预处理对盐胁迫下黄瓜幼苗生长和K~+,Na~+,Cl~-分布的影响

以黄瓜品种津春2号为试材,采用营养液水培,研究了H2O2预处理对NaCl胁迫下幼苗植株不同器官中K+,Na+和Cl-含量的影响。结果表明,NaCl胁迫下黄瓜植株体内K+含量下降、Na+和Cl-含量升高、K/Na和Cl/Na比值降低;H2O2预处理抑制了盐胁迫下黄瓜幼苗植株体内K+含量的降低,减少了Na+和Cl-在叶片的积累,提高了K+,Na+吸收和运输的选择性及K/Na比值,缓解了盐胁迫的伤害,改善了盐胁迫下黄瓜幼苗的生长,显著提高了根、茎、叶的干重和幼苗株高。说明,叶面喷施外源H2O2可通过调控盐胁迫下植株体内离子在器官水平的区域化分布,进而提高黄瓜幼苗的耐盐性。     

混合药剂吸湿回干技术对盐碱胁迫大豆苗期植株K~+、Ca~(2+)和Na~+的影响

为明确不同处理对大豆苗期耐盐碱能力的影响,对大豆种子采取引发剂处理、水处理和未处理三种处理方式,研究了盐碱胁迫下苗期植株K~+、Ca~(2+)和Na~+的变化。结果表明:种子引发剂处理的苗期植株,在盐碱胁迫下其地上部和地下部Na~+、K~+和Ca~(2+)含量均高于未处理和水处理;引发剂处理的TSK,Na最高,而其TSCa,Na高于水处理,低于未处理。通过混合药剂吸湿回干技术处理,可以增强大豆种子的抗盐碱性,为解决大豆耐盐碱能力提供新的理论依据。     

Membrane anchoring of a human IgG Fc receptor (CD16) determined by a single amino acid

CD16 is a low-affinity immunoglobulin G (IgG) Fc receptor that is expressed on natural killer (NK) cells, granulocytes, activated macrophages, and some T lymphocytes. Two similar genes, CD16-I and CD16-II, encode membrane glycoproteins that are anchored by phosphatidylinositol (PI)-glycan and transmembrane polypeptides, respectively. The primary structural requirements for PI-linkage were examined by constructing a series of hybrid cDNA molecules. Although both cDNA's have an identical COOH-terminal hydrophobic segment, CD16-I has Ser203 whereas CD16-II has Phe203. Conversion of Phe to Ser in CD16-II permits expression of a PI-glycan-anchored glycoprotein, whereas conversion of Ser to Phe in CD16-I prevents PI-glycan linkage.     

Cu、Zn对烤烟幼苗吸收K、Ca、Fe的影响

研究了溶液培养条件下Cu．Zn对烟草幼苗吸收K．Ca、Fe的影响。结果表明，烟草幼苗对Cu．Zn的吸收随溶液中Cu^2 、Zn^2 浓度的升高而增加，Zn对Cu的吸收起抑制作用。Ca吸收随溶液Cu^2 浓度的升高而呈下降趋势，而随溶液Zn^2 浓度的升高而有增加趋势；K吸收随溶液中Cu^2 、Zn^2 浓度的增大在茎叶中有升高趋势，而在根部有下降趋势；幼苗对于Fe吸收随溶液中Cu^2 、Zn^2 浓度的增大而略有增加，但差异不显著。     

Effects of polyamines on K+, Na+ and Cl− content and distribution in different organs of cucumber (Cucumis sativus L.) seedlings under NaCl stress

Seedlings from the salt-sensitive cucumber cultivar Jinchun No. 2 and the salt-tolerant cucumber cultivar Changchun Mici were exposed for 8 days to 50 mmol/L NaCl in the absence or in the presence of exogenous foliar spraying PAs [putrescine (Put), spermidine (Spd), and spermine (Spm) 1 mmol/L] to compare the effects of different kinds of polyamines (PAs) on plant tolerance to salinity. This paper studied the effects of exogenous PAs on K⁺, Na⁺ and Cl⁻ in different organs of cucumber seedlings. The results showed that K⁺ content as well as the ratios of K/Na and Cl/Na decreased, while Na⁺ and Cl⁻ concentrations increased in salt-treated cucumber seedlings. The differences in K⁺, Na⁺ and Cl⁻ content and the K/Na and Cl/Na ratios were greater for the salt sensitive cultivar Jinchun No. 2 than for the salt-tolerant cultivar Changchun Mici. Cucumber seedlings treated with exogenous polyamines and combined with salinity exhibited a higher level of K⁺ accumulation and lower levels of Na⁺ and Cl⁻ accumulation compared with the seedlings treated only with salt stress. Among the three kinds of polyamines, Spd and Spm were more effective in inhibiting the accumulation of Na⁺ and reduction of K⁺. However, Put was more effective in reducing Cl⁻ accumulation. Furthermore, all of the three kinds of exogenous polyamines could increase the ratio of K/Na, improving the absorption and transport selectivities of K⁺ and Na⁺ from stems to leaves for both cultivars. In conclusion, exogenous polyamines could alleviate salt damage to some extent and enhance the accumulation of biomass. Among the three kinds of polyamines, spermidine was most effective. Exogenous polyamines could improve tolerance of cucumber seedlings under salt stress by regulating the absorption and distribution of ions in different organs. __________ Translated from Acta Ecologica Sinica, 2007, 27(3): 1122–1129 [译自: 生态学报]     

Restoration by calmodulin of a Ca2+-dependent K+ current missing in a mutant of Paramecium

A combination of genetics, biochemistry, and biophysics was used to show that calmodulin is involved in the regulation of an ion channel. Calmodulin restored the Ca2+-dependent K+ current in pantophobiac, a mutant in Paramecium that lacks this current. The restoration of the current occurred within 2 hours after the injection of 1 picogram of wild-type calmodulin into the mutant. The current remained for approximately 30 hours before the mutant phenotype returned. The injection of calmodulin isolated from pantophobiac had no effect. These results imply that calmodulin is required for the function or regulation of the Ca2+-dependent K+ current in Paramecium.     

Sustained dendritic gradients of Ca2+ induced by excitatory amino acids in CA1 hippocampal neurons

Spatially resolved measurements of intracellular free calcium and of the changes produced by excitatory amino acids were made in neurons isolated from adult mammalian brain. Extremely long-lasting (minutes) Ca2+ gradients were induced in the apical dendrites of hippocampal CA1 neurons after brief (1 to 3 seconds), local application of either glutamate or N-methyl-D-aspartate (NMDA). These gradients reflect the continuous flux of Ca2+ into the dendrite. The sustained gradients, but not the immediate transient response to the agonists, were prevented by prior treatment with the protein kinase C inhibitor sphingosine. Expression of the long-lasting Ca2+ gradients generally required a priming or conditioning stimulus with the excitatory agonist. The findings demonstrate a coupling between NMDA receptor activation and long-lasting intracellular Ca2+ elevation that could contribute to certain use-dependent modifications of synaptic responses in hippocampal CA1 neurons.     

Repair of the secretion defect in the Z form of alpha 1-antitrypsin by addition of a second mutation

Homozygous inheritance of the Z-type mutant form of the alpha 1-antitrypsin (alpha 1AT) gene results in the most common form of alpha 1AT deficiency, a human hereditary disease associated with a high risk for the development of emphysema and an increased incidence of neonatal hepatitis. The alpha 1AT-synthesizing cells of individuals with the Z gene have normal alpha 1AT messenger RNA levels, but alpha 1AT secretion is markedly reduced secondary to accumulation of newly synthesized alpha 1AT in the rough endoplasmic reticulum. Crystallographic analysis of alpha 1AT predicts that in normal alpha 1AT, a negatively charged Glu342 is adjacent to positively charged Lys290. Thus the Glu342----Lys342 Z mutation caused the loss of a normal salt bridge, resulting in the intracellular aggregation of the Z molecule. The prediction was made that a second mutation in the alpha 1AT genet that changed the positively charged Lys290 to a negatively charged Glu290 would correct the secretion defect. When the second mutation was added to the Z-type complementary DNA, the resulting gene directed the synthesis and secretion of amounts of alpha 1AT similar to that directed by the normal alpha 1AT complementary DNA in an in vitro eukaryotic expression system. This suggests the possibility that a human hereditary disease can be corrected by inserting an additional mutation in the same gene.     

Binding of HTLV-III/LAV to T4+ T cells by a complex of the 110K viral protein and the T4 molecule

Human T-lymphotropic virus type III (HTLV-III) or lymphadenopathy-associated virus (LAV) is tropic for human T cells with the helper-inducer phenotype, as defined by reactivity with monoclonal antibodies specific for the T4 molecule. Treatment of T4+ T cells with monoclonal antibodies to T4 antigen blocks HTLV-III/LAV binding, syncytia formation, and infectivity. Thus, it has been inferred that the T4 molecule itself is a virus receptor. In the present studies, the surfaces of T4+ T cells were labeled radioactively, and then the cells were exposed to virus. After the cells were lysed, HTLV-III/LAV antibodies were found to precipitate a surface protein with a molecular weight of 58,000 (58K). By blocking and absorption experiments, this 58K protein was identified as the T4 molecule. No cell-surface structures other than the T4 molecule were involved in the antibody-antigen complex formation. Two monoclonal antibodies, each reactive with a separate epitope of the T4 molecule, were tested for their binding capacities in the presence of HTLV-III/LAV. When HTLV-III/LAV was bound to T4+ T cells, the virus blocked the binding of one of the monoclonal antibodies, T4A (OKT4A), but not of the other, T4 (OKT4). When HTLV-III/LAV was internally radiolabeled and bound to T4+ T cells which were then lysed, a viral glycoprotein of 110K (gp110) coprecipitated with the T4 molecule. The binding of gp110 to the T4 molecule may thus be a major factor in HTLV-III/LAV tropism and may prove useful in developing therapeutic or preventive measures for the acquired immune deficiency syndrome.