Aluminium Stress Affects Nitrogen Fixation and Assimilation in Soybean (Glycine max L.)

Nitrogen fixation and assimilation in nodules and roots were studied in soybean (Glycine max L.) exposed to different levels of aluminium (Al) stress (0, 50, 200 and 500 μM). Al at 500 μM induced oxidative stress, which became evident from an increase in lipid peroxidation accompanied by a concomitant decline in antioxidant enzyme activities and leghaemoglobin breakdown. Consequently, there was also a reduction in nitrogenase activity. However, the leghaemoglobin levels and nitrogenase activity were unexpectedly found to be higher in nodules when the plants were treated with 200 μM Al. Of the enzymes involved in nitrogen assimilation, the activity of glutamate dehydrogenase-NADH was reduced in nodules under Al stress, but it was significantly higher in roots at 500 μM Al as compared to that in the control. In nodules, the glutamine synthetase/glutamate synthase-NADH pathway, assayed in terms of activity and expression of both the enzymes, was inhibited at >50 μM Al; but in roots this inhibitory effect was apparent only at 500 μM Al. No significant changes in ammonium and protein contents were recorded in the nodules or roots when the plants were treated with 50 μM Al. However, Al at ≥200 μM significantly increased the ammonium levels and decreased the protein content in the nodules. But these contrasting effects on ammonium and protein contents due to Al stress were observed in the roots only at 500 μM Al. The results suggest that the effect of Al stress on nitrogen assimilation is more conspicuous in nodules than that in the roots of soybean plants.     

Combined effect of gamma radiation,hot water and sodium bicarbonate on quality and chemical constituents of stored mandarin fruits

The combined effect of gamma radiation and both hot water and sodium carbonate on physiological decay and chemical constituents of stored mandarin fruits was investigated in this work. In this consideration, the studied fruits were gamma irradiated at doses of 0, 0.3, 0.6, 1.2 and 2.4 KGy. Then, the irradiated and non-irradiated fruits were treated either by hot water or sodium bicarbonate to examine their capacity to give a further maintenance and increasing shelf life or storage periods of mandarin. Treated and non-treated fruit samples were taken at intervals of 10 days and up to 60 days. Physiological decay, total acidity, vitamin C, total sugars and TSS were investigated during the different intervals. Gamma radiation treatments showed a promising effect for maintaining the studied fruits and retarding the development of decay. On the other hand, applying both hot water and sodium bicarbonate as a further combined treatments induced a powerful effect on delaying decay development, keeping the chemical constituents near to the normal level and in turn maximizing shelf life and storage periods of the fruits under investigation.     

The cardiac electrogenic sodium/bicarbonate cotransporter (NBCe1) is activated by aldosterone through the G protein-coupled receptor 30 (GPR 30)

The sodium/bicarbonate cotransporter (NBC) transports extracellular Na⁺ and HCO₃^? into the cytoplasm upon intracellular acidosis, restoring the acidic pH_i to near neutral values. Two different NBC isoforms have been described in the heart, the electroneutral NBCn1 (1Na⁺:1HCO₃^?) and the electrogenic NBCe1 (1Na⁺:2HCO₃^?). Certain non-genomic effects of aldosterone (Ald) were due to an orphan G protein-couple receptor 30 (GPR30). We have recently demonstrated that Ald activates GPR30 in adult rat ventricular myocytes, which transactivates the epidermal growth factor receptor (EGFR) and in turn triggers a reactive oxygen species (ROS)- and PI3K/AKT-dependent pathway, leading to the stimulation of NBC. The aim of this study was to investigate the NBC isoform involved in the Ald/GPR30-induced NBC activation. Using specific NBCe1 inhibitory antibodies (a-L3) we demonstrated that Ald does not affect NBCn1 activity. Ald was able to increase NBCe1 activity recorded in isolation. Using immunofluorescence and confocal microscopy analysis we showed in this work that both NBCe1 and GPR30 are localized in t-tubules. In conclusion, we have demonstrated that NBCe1 is the NBC isoform activated by Ald in the heart.     

Decreased pCO(2) accumulation by eliminating bicarbonate addition to high cell-density cultures

High-density perfusion cultivation of mammalian cells can result in elevated bioreactor CO(2) partial pressure (pCO(2)), a condition that can negatively influence growth, metabolism, productivity, and protein glycosylation. For BHK cells in a perfusion culture at 20 x 10(6) cells/mL, the bioreactor pCO(2) exceeded 225 mm Hg with approximate contributions of 25% from cellular respiration, 35% from medium NaHCO(3), and 40% from NaHCO(3) added for pH control. Recognizing the limitations to the practicality of gas sparging for CO(2) removal in perfusion systems, a strategy based on CO(2) reduction at the source was investigated. The NaHCO(3) in the medium was replaced with a MOPS-Histidine buffer, while Na(2)CO(3) replaced NaHCO(3) for pH control. These changes resulted in 63-70% pCO(2) reductions in multiple 15 L perfusion bioreactors, and were reproducible at the manufacturing-scale. Bioreactor pCO(2) values after these modifications were in the 68-85 mm Hg range, pCO(2) reductions consistent with those theoretically expected. Low bioreactor pCO(2) was accompanied by both 68-123% increased growth rates and 58-92% increased specific productivity. Bioreactor pCO(2) reduction and the resulting positive implications for cell growth and productivity were brought about by process changes that were readily implemented and robust. This philosophy of pCO(2) reduction at the source through medium and base modification should be readily applicable to large-scale fed-batch cultivation of mammalian cells.     

The mechanism of bicarbonate assimilation by the polar leaves of Potamogeton and Elodea. CO2 concentrations at the leaf surface

Abstract. Photosynthetic utilization of HCO, in leaves of Poiamogeton and Elodea occurs at the lower leaf side, with subsequent OH∼ release at the upper side. It is accompanied by transport of cations, in the present experiment K +, across the leaf. The resulting pH and K+ concentration changes near the leaf surface were recorded with miniature electrodes. From the pH and K+ concentration the concentrations of the different inorganic carbon species were calculated and compared with photosynthetic O, production. HCO⁻₃ utilization is accompanied by a drastic increase in the free CO₂ concentration near the lower epidermis. Experiments with CO₂− and HCO₃⁻free solutions showed an oscillating acidification near the lower epidermis and alkalinization near the upper epidermis. It is concluded that the acidification results from the activity of light-dependent H+ pumps. The finding that an increase in pH at the upper side always coincided with a decrease at the lower in these experiments shows that the H+ pumps and the OH− extruding mechanism are coupled although occurring in different cell layers. Previously we have suggested that the first step in the process of photosynthetic HCO₃⁻ utilization is external conversion of HCO₃⁻" by acidification caused by light-dependent H+ pumps. The present results strongly support this hypothesis. Two possible pathways for the accompanying K + transport are discussed. The model presented here explains the known inhibiting effects of buffers and high pH on photosynlhetic HCO₃⁻ utilization.     

雌性生殖道碳酸氢根分泌机制及其对精子受精能力的影响

雌性生殖道内微环境对精子获得受精能力所依赖的一系列分子事件起关键性作用。研究表明,雌性生殖道含有高浓度的碳酸氢根,而且已经证明此阴离子对精子功能(包括精子运动,精子获能,超激活运动以及顶体反应)起重要的作用。本综述详细总结了雌性生殖道内微环境碳酸氢根对精子功能的影响及其分子机制,并探讨子宫内碳酸氢根的分泌机制。同时对碳酸氢根分泌受损可能是女性不育的一个病因提供了最新证据。     

Mechanism of ammonium adsorption from wastewater by modified bentonite and optimization by response surface

Three modified bentonites, dry alkali modification, thermal modification, and acid modification, were prepared and characterized by XRD and FTIR. Batch experiments were performed to evaluate their efficiency as adsorbent for ammonium removal. Multi-variables interaction effects were evaluated by Response Surface Methodology. The results showed that the adsorption efficiency of ammonium by dry alkali modification bentonite was the best in three modified methods; the next was that of thermal modification. The crystalline structure of bentonite was significantly changed with dry alkali modification. Na₂SiO₃ and Na₂AlSi₃O₈(OH) were achieved by bentonite with powder NaOH modification. The increase in the mole ratio of exchangeable cations indicated that the adsorption efficiency of ammonium increased; while the layer spacing of bentonite expanded with the amount of the adsorbed water and hydrated water increased by thermal modification. In multi-variables interaction effects (holding time, calcination temperature, pH, dosage), the most significant factors were calcination temperature and dosage.     

杨树基因组AMT转运蛋白的生物信息学特性

本研究中,通过隐马尔科夫模型(HMM)和杨树蛋白质库搜索,共找到17个杨树铵转运体蛋白(PtAMTs).利用生物信息学方法,我们对杨树家族17条AMT蛋白序列的系统发生和AMT基因组定位进行分析,然后对其氨基酸组成成分、理化性质以及二级结构进行预测和分析,同时还分析了杨树与拟南芥、水稻、番茄、百脉根和欧洲油菜的AMT基因家族之间的联系.二级结构预测结果发现不同成员间氨基酸数目、氨基酸序列间的疏水性存在一定的差异;α-螺旋和无规则卷曲为主要二级结构组成部分.同源性比对分析表明,PtAMT基因家族主要分为2个亚家族,AMT1 (11个成员)和AMT2 (6个成员),基因结果分析表明AMT2亚家族成员不含内含子.杨树AMT蛋白的亚细胞定位分析表明PtAMT主要定位于膜结构上.电子表达图谱分析结果表明:只有XP_002309151和 XP_002334025基因有对应的EST序列,并有相应的电子表达谱,并主要在花蕾表达.