红树林植物木榄水通道基因的克隆和表达

根据植物水通道基因保守区设计简并引物,采用RT-PCR方法,从木榄树叶中分离出水通道基因的cDNA片段;3′RACE获得3′端cDNA序列;再经5′RACE获得5′端部分cDNA序列,命名为PIP2,GenBank登录号为EF126757。该基因全长843个碱基,编码281个氨基酸,具有典型的植物水通道基因结构。该基因编码的蛋白质与含羞草(PIP2;5)、欧洲葡萄(PIP)、拟南芥(PIP3)等水通道蛋白的同源性分别为90%、91%、88%。Northern杂交分析表明,该基因在木榄树不同器官中的表达差异明显:根部有较高的表达水平,茎部较弱,而在叶中只能检测到微弱的信号。     

Aquaporin-11 containing a divergent NPA motif has normal water channel activity

Recently, two novel mammalian aquaporins (AQPs), AQPs 11 and 12, have been identified and classified as members of a new AQP subfamily, the “subcellular AQPs”. In members of this subfamily one of the two asparagine-proline-alanine (NPA) motifs, which play a crucial role in selective water conduction, are not completely conserved. Mouse AQP11 (mAQP11) was expressed in Sf9 cells and purified using the detergent Fos-choline 10. The protein was reconstituted into liposomes, which were used for water conduction studies with a stopped-flow device. Single water permeability (pf) of AQP11 was measured to be 1.72 ± 0.03 × 10^− 13 cm³/s, suggesting that other members of the subfamily with incompletely conserved NPA motifs may also function as water channels.     

PDGF-B Is Required for Development of the Glymphatic System

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Expression of astrocytic genes coding for proteins implicated in neural excitation and brain edema is altered after acute liver failure

In vitro and in vivo studies have suggested that reduced astrocytic uptake of neuronally released glutamate, alterations in expression of glial fibrillary acidic protein (GFAP) and aquaporin‐4 (AQP‐4) contribute to brain edema in acute liver failure (ALF). However, there is no evidence to date to suggest that these alterations occur in patients with ALF. We analyzed the mRNA expression of excitatory amino acid transporters (EAAT‐1, EAAT‐2), GFAP, and AQP‐4 in the cerebral cortex obtained at autopsy from eight patients with ALF and from seven patients with no evidence of hepatic or neurological disorders by real‐time PCR, and protein expression was assessed using immunoblotting and immunohistochemistry. We demonstrated a significant decrease in GFAP mRNA and protein levels in ALF patients compared to controls. While the loss of EAAT‐2 protein in ALF samples was post‐translational in nature, EAAT‐1 protein remained within normal limits. Immunohistochemistry confirmed that, in all cases, the losses of EAAT‐2 and GFAP were uniquely astrocytic in their localization. AQP‐4 mRNA expression was significantly increased and its immunohistochemistry demonstrated increased AQP‐4 immunoreactivity in the glial end‐feet process surrounding the microvessels. These findings provide evidence of selective alterations in the expression of genes coding for key astrocytic proteins implicated in central nervous system (CNS) excitability and brain edema in human ALF.

     

Do root hydraulic properties change during the early vegetative stage of plant development in barley (Hordeum vulgare)?

Background and Aims

As annual crops develop, transpirational water loss increases substantially. This increase has to be matched by an increase in water uptake through the root system. The aim of this study was to assess the contributions of changes in intrinsic root hydraulic conductivity (Lp, water uptake per unit root surface area, driving force and time), driving force and root surface area to developmental increases in root water uptake.

Methods

Hydroponically grown barley plants were analysed during four windows of their vegetative stage of development, when they were 9–13, 14–18, 19–23 and 24–28 d old. Hydraulic conductivity was determined for individual roots (Lp) and for entire root systems (Lp_r). Osmotic Lp of individual seminal and adventitious roots and osmotic Lp_r of the root system were determined in exudation experiments. Hydrostatic Lp of individual roots was determined by root pressure probe analyses, and hydrostatic Lp_r of the root system was derived from analyses of transpiring plants.

Key Results

Although osmotic and hydrostatic Lp and Lp_r values increased initially during development and were correlated positively with plant transpiration rate, their overall developmental increases (about 2-fold) were small compared with increases in transpirational water loss and root surface area (about 10- to 40-fold). The water potential gradient driving water uptake in transpiring plants more than doubled during development, and potentially contributed to the increases in plant water flow. Osmotic Lp_r of entire root systems and hydrostatic Lp_r of transpiring plants were similar, suggesting that the main radial transport path in roots was the cell-to-cell path at all developmental stages.

Conclusions

Increase in the surface area of root system, and not changes in intrinsic root hydraulic properties, is the main means through which barley plants grown hydroponically sustain an increase in transpirational water loss during their vegetative development.     

Salt stress triggers enhanced cycling of Arabidopsis root plasma-membrane aquaporins

Aquaporins of the plasma membrane intrinsic protein (PIP) subfamily are channels which facilitate the diffusion of water across the plant plasma membrane (PM). Although PIPs have been considered as canonical protein markers of this compartment, their endomembrane trafficking is still not well documented. We recently obtained insights into the constitutive cycling of PIPs in Arabidopsis root cells by means of fluorescence recovery after photobleaching (FRAP). This work also uncovered the behavior of the model isoform AtPIP2;1 in response to NaCl. The present addendum connects these findings to another recent work which describes the dynamic properties of AtPIP2;1 in the PM in normal and salt stress conditions by means of single particle tracking (SPT) and fluorescence correlation spectroscopy (FCS). The results suggest that membrane rafts play an important role in the partitioning of AtPIP2;1 in normal conditions and that clathrin-mediated endocytosis is predominant. In salt stress conditions, the rate of AtPIP2;1 cycling was enhanced and endocytosis was cooperated by a membrane raft-associated salt-induced pathway and a clathrin-dependent pathway.     

A re-examination of the minor role of unstirred layers during the measurement of transport coefficients of Chara corallina internodes with the cell pressure probe

The impact of unstirred layers (USLs) during cell pressure probe experiments with Chara corallina internodes has been quantified. The results show that the hydraulic conductivity (Lp) measured in hydrostatic relaxations was not significantly affected by USLs even in the presence of high water flow intensities ('sweep-away effect'). During pressure clamp, there was a reversible reduction in Lp by 20%, which was explained by the constriction of water to aquaporins (AQPs) in the C. corallina membrane and a rapid diffusional equilibration of solutes in arrays where water protruded across AQPs. In osmotic experiments, Lp, and permeability (Ps) and reflection (sigma s) coefficients increased as external flow rate of medium increased, indicating some effects of external USLs. However, the effect was levelling off at 'usual' flow rates of 0.20-0.30 m s(-1) and in the presence of vigorous stirring by air bubbles, suggesting a maximum thickness of external USLs of around 30 microm including the cell wall. Because the diameters of internodes were around 1 mm, internal USLs could have played a significant or even a dominating role, at least in the presence of the rapidly permeating solutes used [acetone, 2-propanol and dimethylformamide (DMF)]. A comparison of calculated (diffusion kinetics) and of measured permeabilities indicated an upper limit of the contribution of USLs for the rapidly moving solute acetone of 29%, and of 15% for the less rapidly permeating DME The results throw some doubt on recent claims that in C. corallina, USLs rather than the cell membrane dominate solute uptake, at least for the most rapidly moving solute acetone.     

3种模拟中医体征的体虚便秘大鼠模型建立及效果观察

目的：分别建立大鼠血虚、阴虚和阳虚便秘模型并比较其结肠动力、结肠水代谢、结肠黏液分泌和结肠水通道蛋白2（AQP2）的表达水平。方法：40只SD大鼠,雌雄各半,随机分为4组（n=10）：正常对照组（N）、血虚便秘组（XC）、阴虚便秘组（YC）、阳虚便秘组（YAC）。分别采用放血+洛哌丁胺、甲状腺素+洛哌丁胺、冰水刺激+洛哌丁胺建立血虚便秘、阴虚便秘、阳虚便秘大鼠模型,放血每周1次,药物每天灌胃1次,连续42 d。检测大鼠活动状态、体质量、大便性状、口肛传输时间、小肠推进率、粪便和结肠含水量等体征指标,对结肠组织进行AB-PAS染色和免疫组化染色,观察黏液分泌情况和AQP2表达水平。结果：与正常对照组比较,3种模型大鼠体重增长减慢;造模第40天自主活动量变化率由大到小依次为YC、XC和YAC;造模第30天出现固体硬质粪便,粪便评分升高顺序为XC、YC和YAC;口肛传输时间均显著延长、小肠推进率均显著降低（P < 0.05,P < 0.01）,肠动力减低顺序为YC、YAC和XC;粪便含水量均显著减少（P < 0.05,P < 0.01）,XC和YAC组大鼠结肠含水量显著减少（P < 0.05,P <0.01）,YC大鼠结肠含水量有减少趋势,结肠水代谢顺序为YC、YAC和XC;3种模型大鼠结肠黏膜层腺管和杯状细胞出现不同程度缩小,黏液分泌减少,分泌功能障碍顺序为YAC、YC和XC,且近端和远端结肠AQP2的表达均显著增加（P < 0.05,P < 0.01）,增加顺序近端结肠为YAC、YC、XC,远端结肠为YAC、XC和YC。结论：复合因素长期刺激均可建立符合中医体征的便秘大鼠模型,且各模型大鼠结肠运动、结肠水代谢、结肠黏液分泌和AQP2表达水平存在一定的差异。