脑缺血/再灌对蒙古沙土鼠海马突触体酪氨酸磷酸化的影响

用蒙古沙土鼠双侧颈总动脉结扎（ＢＣＡＯ）前脑缺血模型,研究缺血／再灌对海马突触体蛋白酪氨酸磷酸休的影响及ＮＭＤＡ受体（ＮＲ）非竞争性拮抗剂氯胺酮（Ｋｅｔａｍｉｎｅ,ＫＴ）、Ｌ－型电压门控钙离子通道（Ｌ－ｔｙｐｅ ｖｏｌｔａｇｅ ｇａｔｅｄｃａｌｃｉｕｍ ｃｈａｎｎｅｌ,Ｌ－型ＶＧＣＣ）拮抗剂硝苯吡啶（ｎｉｆｅｄｉｐｉｎｅ,ＮＤ）及非ＮＲ拮抗６,７－二硝基喹恶啉上卫四（６,７－ｄｉ－ｎｉｔｒｏｐｕ     

MEK�CERK-dependent multiple caspase activation by mitochondrial proapoptotic Bcl-2 family proteins is essential for heavy ion irradiation-induced glioma cell death

Recently developed heavy ion irradiation therapy using a carbon beam (CB) against systemic malignancy has numerous advantages. However, the clinical results of CB therapy against glioblastoma still have room for improvement. Therefore, we tried to clarify the molecular mechanism of CB-induced glioma cell death. T98G and U251 human glioblastoma cell lines were irradiated by CB, and caspase-dependent apoptosis was induced in both cell lines in a dose-dependent manner. Knockdown of Bax (BCL-2-associated X protein) and Bak (BCL-2-associated killer) and overexpression of Bcl-2 or Bcl-xl (B-cell lymphoma-extra large) showed the involvement of Bcl-2 family proteins upstream of caspase activation, including caspase-8, in CB-induced glioma cell death. We also detected the activation of extracellular signal-regulated kinase (ERK) and the knockdown of ERK regulator mitogen-activated protein kinase kinase (MEK)1/2 or overexpression of a dominant-negative (DN) ERK inhibited CB-induced glioma cell death upstream of the mitochondria. In addition, application of MEK-specific inhibitors for defined periods showed that the recovery of activation of ERK between 2 and 36 h after irradiation is essential for CB-induced glioma cell death. Furthermore, MEK inhibitors or overexpression of a DN ERK failed to significantly inhibit X-ray-induced T98G and U251 cell death. These results suggested that the MEK–ERK cascade has a crucial role in CB-induced glioma cell death, which is known to have a limited contribution to X-ray-induced glioma cell death.     

Viroporins

Viroporins are a group of proteins that participate in several viral functions, including the promotion of release of viral particles from cells. These proteins also affect cellular functions, including the cell vesicle system, glycoprotein trafficking and membrane permeability. Viroporins are not essential for the replication of viruses, but their presence enhances virus growth. Comprising some 60-120 amino acids, viroporins have a hydrophobic transmembrane domain that interacts with and expands the lipid bilayer. Some viroporins also contain other motifs, such as basic amino acid residues or a domain rich in aromatic amino acids that confers on the protein the ability to interact with the interfacial lipid bilayer. Viroporin oligomerization gives rise to hydrophilic pores at the membranes of virus-infected cells. As the list of known viroporins steadily grows, recent research efforts focus on deciphering the actions of the viroporins poliovirus 2B, alphavirus 6K, HIV-1 Vpu and influenza virus M2. All these proteins can enhance the passage of ions and small molecules through membranes depending on their concentration gradient. Future work will lengthen the list of viroporins and will provide a deeper understanding of their mechanisms of action.     

Altered growth kinetics precede calcium-induced differentiation in mouse epidermal cells

Summary Primary cultures of newborn mouse epidermal cells proliferate rapidly and with a high growth fraction for several months when grown in medium with low calcium (0.02 to 0.1 mM). Addition of calcium to levels generally used in culture medium (1.2 mM) was followed by rapid changes in the pattern of proliferation. By using a combination of technics (a stathmokinetic method, autoradiography, [³H]thymidine incorporation into DNA, DNA flow cytometry) it was found that cell flux was blocked for 5 to 6 h, followed by a short rise in the mitotic rate at 10 h, and a gradual fall in all growth parameters until about 32 h after the calcium switch. There was no accumulation of cells in any particular cell cycle phase. The results indicate that the calcium switch is followed by a strong reduction in cell flux from G₁ whereas the majority of the cells that had left G₁ at the time of the switch completed one cell division before cessation of all proliferative activity. Both before and after the switch the primary epidermal cultures consisted of one diploid and one tetraploid G₁ DNA stemline that seemed to react in the same way to calcium. This work reported in this paper was undertaken during the tenure of an American Cancer Society-Eleanor Roosevelt-International Cancer Fellowship awarded by the International Union Against Cancer (K. E.). The project was supported by funds partly provided by the International Cancer Research Data Bank Program of the National Cancer Institute, National Institutes of Health, Bethesda, MD, under contract N01-C0-65341 (International Cancer Research Technology Transfer) and partly by the International Union Against Cancer (O.P.F.C.).     

Role of calcium in differentiation of murine erythroleu-kemia cells

Calcium plays a crucial role in the normal and abnomal cell metabolism.The role of calcium in the differentiation process of murine erythroleukemia cells(MELC)remains controversial.Here,based upon quantitative measurement of fluorescence in single cells,a method was developed to investigate the intracellular free calcium[Ca^2 ]i concentration and DNA contents simultaneously,by employing the fluorescent probe,fluo-3 acetoxymethyl ester and DNA dye Hoechst 33342.During MELC differentiation.[Ca^2 ]i concentration incresed.We also demonstrated that calcium ionophore,A23187,enhanced the HMB-induced MELC differentiation,while verapamil,an inhibitor of calcuim uptake,slightly reduced differentiation.These results suggested that an increase in the [Ca^2 ]i level was an essential step in HMBA-induced MELC differentiation.     

碱蓬属植物耐盐机理研究进展

碱蓬属(Suaeda)植物是一类典型的真盐生植物,属于重要的盐生植物资源,全球广泛分布.人们已经对20种碱蓬属植物进行了观察和盐胁迫实验,研究了不同器官或组织的生理生化特征及其对盐胁迫的反应,并基于这些研究分析了盐胁迫的应答机制.叶片肉质化、细胞内离子区域化、渗透调节物质增加和抗氧化系统能力增强是碱蓬属植物响应和适应盐胁迫的重要方式和途径.但迄今为止的研究工作尚有一定的局限性,主要包括:研究工作主要集中在植物地上部分,而对植物地下部分的研究较少;多是少数生物学指标或生理学现象的单独观察,而缺乏对生理代谢过程的整体和综合分析;针对某种碱蓬的独立分析较多,而与近缘种的比较研究较少;植物对中性盐胁迫的反应研究较多,而对碱性盐的研究较少.为进一步系统阐明碱蓬属植物的耐盐机制,今后的工作应注重碱蓬属植物响应和适应盐胁迫的信号网络和调控机制研究,基于系统生物学研究思路,采用现代组学技术探索该属植物响应盐胁迫的由复杂信号网络调控的特殊生理特征和特异代谢途径.     

短杆菌肽通道内离子K~＋，Na~＋，Li~＋与水的相关性

基于右手螺旋短杆菌肽Ａ离子通道模型,利用分子动力学计算机模拟方法研究了通道内离子Ｋ＋,Ｎａ＋,Ｌｉ＋与水分子的相关性．     

Calcium spikes in a leech nonspiking neuron

The NS neurons are nonspiking cells, present as pairs in each midbody ganglion of the leech nervous system, which display a very extensive arborization. They were shown to regulate the coactivation of motoneurons. Here we have investigated the electrophysiological properties of these neurons under the hypothesis that transmission along the extensive neurites requires the aid of voltage-dependent conductances. The results indicate that NS neurons respond to electrical stimulation with a spike-like event, which was not an all-or-none but rather a graded phenomenon that depended on the intensity and duration of the electrical stimulus. The spike-like response was activated at a membrane potential of approximately −50 mV; its amplitude was a logarithmic function of the extracellular Ca²⁺ concentration and was unaffected by a broad range of changes in the extracellular Na⁺ concentration; intracellular application of tetraethylammonium (TEA) caused a large increase in its amplitude and duration. These data indicate that NS neurons bear voltage-dependent low-threshold Ca²⁺ and TEA-sensitive K⁺ conductances that could contribute to shaping synaptic signals, or transmission along the extensive neuritic tree.     

Significance of metal ion supplementation in the fermentation medium on the structure and anti-tumor activity of Tuber polysaccharides produced by submerged culture of Tuber melanosporum

The significance of metal ion supplementation in the fermentation medium on the structure and anti-tumor activity of Tuber polysaccharides was systematically studied in the submerged fermentation of Tuber melanosporum. The lowest weight-average molecular weight (M_w) (i.e., 115.3 × 10⁴ g/mol) of intracellular polysaccharides (IPS) was obtained when Mg²⁺ and K⁺ was added in the fermentation medium. The IPS with the lower M_w exhibited a higher inhibition ratio against S-180 tumor cells. The compact conformation of extracellular polysaccharides (EPS) was formed when only K⁺ was supplied in the fermentation medium. Interestingly, EPS with compact conformation exhibited a higher inhibition ratio (i.e., 59.2%) than EPS with branched polymer chain (i.e., 9.2%) against A549 tumor cells. The highest inhibition ratio for EPS with α-glycosidic linkages against the tumor cell line HepG2 reached 32.2% when Mg²⁺ or K⁺ was supplied in the fermentation medium. The addition of metal ion Mg²⁺, K⁺, and their combination to the fermentation medium is a vital factor affecting the structures of Tuber polysaccharides, which further determine their anti-tumor activities. The information obtained in this work will be useful for the efficient and directed production of polysaccharides with anti-tumor activities by the submerged fermentation of edible fungi mycelium.     

ITMSQ: A software tool for N‐ and C‐terminal fragment ion pairs based isobaric tandem mass spectrometry quantification

Tandem MS (MS2) quantification using the series of N‐ and C‐terminal fragment ion pairs generated from isobaric‐labelled peptides was recently considered an accurate strategy in quantitative proteomics. However, the presence of multiplexed terminal fragment ion in MS2 spectra may reduce the efficiency of peptide identification, resulting in lower identification scores or even incorrect assignments. To address this issue, we developed a quantitative software tool, denoted isobaric tandem MS quantification (ITMSQ), to improve N‐ and C‐terminal fragment ion pairs based isobaric MS2 quantification. A spectrum splitting module was designed to separate the MS2 spectra from different samples, increasing the accuracy of both identification and quantification. ITMSQ offers a convenient interface through which parameters can be changed along with the labelling method, and the result files and all of the intermediate files can be exported. We performed an analysis of in vivo terminal amino acid labelling labelled HeLa samples and found that the numbers of quantified proteins and peptides increased by 13.64 and 27.52% after spectrum splitting, respectively. In conclusion, ITMSQ provides an accurate and reliable quantitative solutionfor N‐ and C‐terminal fragment ion pairs based isobaric MS2 quantitative methods.