The plasma membrane transport systems and adaptation to salinity

Salt stress represents one of the environmental challenges that drastically affect plant growth and yield. Evidence suggests that glycophytes and halophytes have a salt tolerance mechanisms working at the cellular level, and the plasma membrane (PM) is believed to be one facet of the cellular mechanisms. The responses of the PM transport proteins to salinity in contrasting species/cultivars were discussed. The review provides a comprehensive overview of the recent advances describing the crucial roles that the PM transport systems have in plant adaptation to salt. Several lines of evidence were presented to demonstrate the correlation between the PM transport proteins and adaptation of plants to high salinity. How alterations in these transport systems of the PM allow plants to cope with the salt stress was also addressed. Although inconsistencies exist in some of the information related to the responses of the PM transport proteins to salinity in different species/cultivars, their key roles in adaptation of plants to high salinity is obvious and evident, and cannot be precluded. Despite the promising results, detailed investigations at the cellular/molecular level are needed in some issues of the PM transport systems in response to salinity to further evaluate their implication in salt tolerance.     

Large diameter of palytoxin-induced Na/K pump channels and modulation of palytoxin interaction by Na/K pump ligands

Palytoxin binds to Na/K pumps to generate nonselective cation channels whose pore likely comprises at least part of the pump's ion translocation pathway. We systematically analyzed palytoxin's interactions with native human Na/K pumps in outside-out patches from HEK293 cells over a broad range of ionic and nucleotide conditions, and with or without cardiotonic steroids. With 5 mM internal (pipette) [MgATP], palytoxin activated the conductance with an apparent affinity that was highest for Na(+)-containing (K(+)-free) external and internal solutions, lowest for K(+)-containing (Na(+)-free) external and internal solutions, and intermediate for the mixed external Na(+)/internal K(+), and external K(+)/internal Na(+) conditions; with Na(+) solutions and MgATP, the mean dwell time of palytoxin on the Na/K pump was about one day. With Na(+) solutions, the apparent affinity for palytoxin action was low after equilibration of patches with nucleotide-free pipette solution. That apparent affinity was increased in two phases as the equilibrating [MgATP] was raised over the submicromolar, and submillimolar, ranges, but was increased by pipette MgAMPPNP in a single phase, over the submillimolar range; the apparent affinity at saturating [MgAMPPNP] remained approximately 30-fold lower than at saturating [MgATP]. After palytoxin washout, the conductance decay that reflects palytoxin unbinding was accelerated by cardiotonic steroid. When Na/K pumps were preincubated with cardiotonic steroid, subsequent activation of palytoxin-induced conductance was greatly slowed, even after washout of the cardiotonic steroid, but activation could still be accelerated by increasing palytoxin concentration. These results indicate that palytoxin and a cardiotonic steroid can simultaneously occupy the same Na/K pump, each destabilizing the other. The palytoxin-induced channels were permeable to several large organic cations, including N-methyl-d-glucamine(+), suggesting that the narrowest section of the pore must be approximately 7.5 A wide. Enhanced understanding of palytoxin action now allows its use for examining the structures and mechanisms of the gates that occlude/deocclude transported ions during the normal Na/K pump cycle.     

Strength, diversity and plasticity of postmating reproductive barriers between two hybridizing oak species (Quercus robur L. and Quercus petraea (Matt) Liebl.)

Very little is known about the nature and strength of reproductive isolation (RI) in Quercus species, despite extensive research on the estimation and evolutionary significance of hybridization rates. We characterized postmating pre- and postzygotic RI between two hybridizing oak species, Quercus robur and Quercus petraea, using a large set of controlled crosses between different genotypes. Various traits potentially associated with reproductive barriers were quantified at several life history stages, from pollen-pistil interactions to seed set and progeny fitness-related traits. Results indicate strong intrinsic postmating prezygotic barriers, with significant barriers also at the postzygotic level, but relatively weaker extrinsic barriers on early hybrid fitness measures assessed in controlled conditions. Using general linear modelling of common garden data with clonal replicates, we showed that most traits exhibited important genotypic differences, as well as different levels of sensitivity to micro-environmental heterogeneity. These new findings suggest a large potential genetic diversity and plasticity of reproductive barriers and are confronted with hybridization evidence in these oak species.     

艾氏乳腺癌腹水细胞质膜NADH-铁氰化钾氧化还原酶质子泵活性诱导细胞与脂质体融合

在本文中,我们用荧光能量共振转移分析和荧光显微技术证明,小鼠艾氏乳腺癌腹水细胞质膜NADH-铁氰化钾氧化还原反应的电子传递所偶联的质子泵活性能诱导细胞与人工脂质体融合。糖酵解代谢的抑制剂碘乙酸能抑制融合,同时融合过程是吸取质子的。近几年来,我们实验室已报道了多种生物膜质子泵均具有诱导膜融合的功能。因此,质子泵诱导膜融合可能具有比较广泛的生理意义。并为细胞中存在有受能量代谢控制的驱动膜融合的生理机制提供了实验证据。     

Dependence of the membrane potential of Chara cells on external pH in the presence or absence of internal adenosinetriphosphate

The dependence of the membrane potential (E_m) and the membrane resistance (R_m) of Chara australis R. Brown on the pH of the external medium (pH₀) was studied by controlling the activity of the plasmamembrane H⁺ pump under both light and dark conditions. The activity of the pump was controlled by regulating the internal ATP or Mg²⁺ concentration in tonoplast-free cells prepared by vacuolar perfusion. In these cells, which contained Mg · ATP (mgATP cells), E_m and R_m were very sensitive to pH₀, as in normal cells. E_m was more negative in light than in the dark at all pH₀ values tested. Tonoplast-free cells with very low [ATP]_i (-ATP cells) or [Mg²⁺]_i (-Mg cells) showed very weak dependence of E_m and R_m on pH₀. Thus, the active and not the passive component of E_m was sensitive to pH₀. At the same time, the high permeability of the plasma membrane to H⁺ was questioned. In both-ATP cells and-Mg cells, E_m was scarcely affected and R_m markedly decreased on illumination.Abbreviations CyDTA 1,2-cyclohexanediamine-N,N-tetraacetic acid - EGTA ethyleneglycol-bis-(-aminoethylether)N,N-tetraacetic acid - HK hexokinase     

The sodium cycle. II. Na-coupled oxidative phosphorylation in Vibrio alginolyticus cells

The role of Na⁺ in Vibrio alginolyticus oxidative phosphorylation has been studied. It has been found that the addition of a respiratory substrate, lactate, to bacterial cells exhausted in endogenous pools of substrates and ATP has a strong stimulating effect on oxygen consumption and ATP synthesis. Phosphorylation is found to be sensitive to anaerobiosis as well as to HQNO, an agent inhibiting the Na⁺-motive respiratory chain of V. alginolyticus. Na⁺ loaded cells incubated in a K⁺ or Li⁺ medium fail to synthesize ATP in response to lactate addition. The addition of Na⁺ at a concentration comparable to that inside the cell is shown to abolish the inhibiting effect of the high intracellular Na⁺ level. Neither lactate oxidation nor Δω generation coupled with this oxidation is increased by external Na⁺ in the Na⁺-loaded cells. It is concluded that oxidative ATP synthesis in V. alginolyticus cells is inhibited by the artificially imposed reverse ΔPNa, i.e., [Na⁺]_in > [Na⁺]_out. Oxidative phosphorylation is resistant to a protonophorous uncoupler (0.1 mM CCCP) in the K⁺-loaded cells incubated in a high Na⁺ medium, i.e., when ΔpNa of the proper direction ([Na⁺]_in < [Na⁺]_out) is present. The addition of monensin in the presence of CCCP completely arrests the ATP synthesis. Monensin without CCCP is ineffective. Oxidative phosphorylation in the same cells incubated in a high K⁺ medium (ΔpNa is low) is decreased by CCCP even without monensin. Artificial formation of ΔpNa by adding 0.25 M NaCl to the K⁺-loaded cells (Na⁺ pulse) results in a temporary increase in the ATP level which spontaneously decreases again within a few minutes. Na⁺ pulse-induced ATP synthesis is completely abolished by monensin and is resistant to CCCP, valinomycin and HQNO. 0.05 M NaCl increases the ATP level only slightly. Thus, V. alginolyticus cells at alkaline pH represent the first example of an oxidative phosphorylation system which uses Na⁺ instead of H⁺ as the coupling ion.     

不同分娩镇痛时机对初产妇产程进展、母婴结局及早期盆底功能的影响

摘要 目的：探讨不同分娩镇痛时机对初产妇产程进展、母婴结局及早期盆底功能的影响。方法：选择2019年4月至2022年8月我院收治的148例拟接受硬膜外分娩镇痛的产妇,按照随机数字表法分为两组。A组（74例）于宫口扩张≤2 cm开始分娩镇痛,B组（74例）于宫口扩张＞2 cm进行分娩镇痛。比较两组产程、宫口扩张全时间、催产素使用、疼痛、母婴结局、盆底肌电指标以及盆底障碍发生情况。结果：A组宫口扩张全时间、第一产程、第二产程、压力性尿失禁发生率低于B组（P＜0.05）,催产素使用率、中转剖宫产率高于B组（P＜0.05）。A组给药30 min（T1）、60 min（T2）、宫口扩张7-8 cm（T3）、宫口扩张全（T4）视觉模拟评分法（VAS）评分均低于B组（P＜0.05）。A组Ⅰ类肌纤维肌电压、Ⅱ类肌纤维肌电压高于B组（P＜0.05）,Ⅰ类肌纤维疲劳度绝对值、Ⅱ类肌纤维疲劳度绝对值低于B组（P＜0.05）。结论：宫口扩张≤2 cm实施硬膜外分娩镇痛,可降低分娩对女性盆底肌群的损伤;宫口扩张＞2 cm实施硬膜外分娩镇痛,中转剖宫产率、产程中催产素使用率相对较低,应结合产妇的个体情况,综合考虑利弊选择最佳的镇痛时机。     

Assembly and Regulation of the Yeast Vacuolar H+-ATPase

The yeast vacuolar proton-translocating ATPase (V-ATPase) is an excellent model for V-ATPases in all eukaryotic cells. Activity of the yeast V-ATPase is reversibly down-regulated by disassembly of the peripheral (V₁) sector, which contains the ATP-binding sites, from the membrane (V₀) sector, which contains the proton pore. A similar regulatory mechanism has been found in Manduca sexta and is believed to operate in other eukaryotes. We are interested in the mechanism of reversible disassembly and its implications for V-ATPase structure. In this review, we focus on (1) characterization of the yeast V-ATPase stalk subunits, which form the interface between V₁ and V₀, (2) potential mechanisms of silencing ATP hydrolytic activity in disassembled V₁ sectors, and (3) the structure and function of RAVE, a recently discovered complex that regulates V-ATPase assembly.     

门冬胰岛素与人普通胰岛素及胰岛素泵在2型糖尿病患者围手术期的疗效比较

目的：探讨速效胰岛素类似物（门冬胰岛素,诺和锐）与人普通胰岛素（诺和灵R）及胰岛素泵在2型糖尿病（T2DM）围手术期治疗中的有效性和安全性。方法：158例围手术期T2DM患者随机分为胰岛素泵输注门冬胰岛素治疗CSII组52例,门冬胰岛素多次皮下注射治疗MSII（A）组56例,人普通胰岛素多次皮下注射治疗MSII（B）组50例。观察各组患者治疗前后空腹和餐后2h血糖变化、血糖迭标时间、胰岛素用量、低血糖发生率及术后并发症发生率。结果：3组治疗后血糖均明显低于抬疗前,CSII组治疗后血糖低于MSII（A）组（P〈o．05）,MSII（A）组治疗后血糖低于MSII（B）组（P〈0．05）;术后并发症CSII组低于MSII（A）组（P〈0．05）,MSII㈧组低于MSII（B）组（P〈0．05）。结论：门冬胰岛素对T2DM围手术期血糖控制有较好的有效性、安全性和顺应性,胰岛素泵是2型糖尿病患者围手术期胰岛素输注的最佳模式。