中国水仙(Narcissus tazetta var.chinensis)的组织培养

以栽培的中国水仙Narcissus tazetta var.Chinensis鳞茎为实验材料,采取“无液处理”的简捷方法获取外植体,并筛选出中国水仙离体鳞茎培养的最佳培养基。     

Mechanisms of the acute ischemia-induced arrhythmogenesis--a simulation study

The underlying ionic mechanisms of ischemic-induced arrhythmia were studied by the computer simulation method. To approximate the real situation, ischemic cells were simulated by considering the three major component conditions of acute ischemia (elevated extracellular K(+) concentration, acidosis and anoxia) at the level of ionic currents and ionic concentrations, and a round ischemic zone was introduced into a homogeneous healthy sheet to avoid sharp angle of the ischemic tissue. The constructed models were solved using the operator splitting and adaptive time step methods, and the perturbation finite difference (PFD) scheme was first used to integrate the partial differential equations (PDEs) in the model. The numerical experiments showed that the action potential durations (APDs) of ischemic cells did not exhibited rate adaptation characteristic, resulting in flattening of the APD restitution curve. With reduction of sodium channel availability and long recovery of excitability, refractory period of the ischemic tissue was significantly prolonged, and could no longer be considered as same as APD. Slope of the conduction velocity (CV) restitution curve increased both in normal and ischemic region when pacing cycle length (PCL) was short, and refractory period dispersion increased with shortening of PCL as well. Therefore, dynamic changes of CV and dispersion of refractory period rather than APD were suggested to be the fundamental mechanisms of arrhythmia in regional ischemic myocardium.     

Identification and characterization of the retinoic acid response elements in the human RIG1 gene promoter

The expression of retinoic acid-induced gene 1 (RIG1), a class II tumor suppressor gene, is induced in cells treated with retinoids. RIG1 has been shown to express ubiquitously and the increased expression of this gene appears to suppress cell proliferation. Recent studies also demonstrated that this gene may play an important role in cell differentiation and the progression of cancer. In spite of the remarkable regulatory role of this protein, the molecular mechanism of RIG1 expression induced by retinoids remains to be clarified. The present study was designed to study the molecular mechanism underlying the all-trans retinoic acid (atRA)-mediated induction of RIG1 gene expression. Polymerase chain reaction was used to generate a total of 10 luciferase constructs that contain various fragments of the RIG1 5'-genomic region. These constructs were then transfected into human gastric cancer SC-M1 and breast cancer T47D cells for transactivation analysis. atRA exhibited a significant induction in luciferase activity only through the -4910/-5509 fragment of the 5'-genomic region of RIG1 gene relative to the translation initiation site. Further analysis of this promoter fragment indicated that the primary atRA response region is located in between -5048 and -5403 of the RIG1 gene. Within this region, a direct repeat sequence with five nucleotide spacing, 5'-TGACCTctattTGCCCT-3' (DR5, -5243/-5259), and an inverted repeat sequence with six nucleotide spacing, 5'-AGGCCAtggtaaTGGCCT-3' (IR6, -5323/-5340), were identified. Deletion and mutation of the DR5, but not the IR6 element, abolished the atRA-mediated activity. Electrophoretic mobility shift assays with nuclear extract from atRA-treated cells indicated the binding of retinoic acid receptor (RAR) and retinoid X receptor (RXR) heterodimers specifically to this response element. In addition to the functional DR5, the region contains many other potential sequence elements that are required to maximize the atRA-mediated induction. Taken together, we have identified and characterized the functional atRA response element that is responsible for the atRA-mediated induction of RIG1 gene.     

高通量细菌鉴定方法研究进展

高通量细菌鉴定是微生物领域的重要研究课题,对于疾病诊断和环境监测具有重要意义。相比传统的表型鉴定方法,分子遗传学鉴定方法具有稳定性高、检测周期短以及成本较低等特点,成为了主流的鉴定方法。特别是下一代DNA测序技术、核酸分子检测基础上的细菌检测芯片、质谱技术基础上的蛋白质图谱分析为高通量、快速、准确乃至定量的细菌鉴定提供了可行性方案。     

临泽绿洲边缘区棉花群体光合速率、蒸腾速率及水分利用效率

在甘肃河西走廊中部黑河中游绿洲边缘区,于6月下旬和8月上旬,利用Li-8100土壤碳通量测定系统与改进的同化箱联合对田间条件下早熟陆地棉(Gossypium hirsutum)品种新陆早8号的群体光合特性进行了研究.结果表明：试验地6月下旬的土壤呼吸速率和土壤蒸发速率显著高于8月上旬（P＜0.01）;棉花群体光合速率日变化均呈“单峰型”,6月下旬的群体光合速率显著高于8月上旬,其日平均值分别为（43.11±1.26）和（24.53±0.60）μmol CO₂·m^-2·s^-1, 差异极显著（P＜0.01）;群体蒸腾速率日变化也呈“单峰型”,6月下旬和8月上旬的日平均值分别为（3.10±0.34）和（1.60±0.26）mmol H₂O·m^-2·s^-1,两者存在极显著差异（P＜0.01）;6月下旬和8月上旬的群体水分利用效率日平均值分别为（15.67±1.77）和（23.08±5.54） mmol CO₂·mol^-1 H₂O,但差异不显著（P＞0.05）.两生育时期棉花群体光合速率与温度、光合有效辐射及土壤含水量均呈正相关关系.表明棉花群体光合速率在6月下旬和8月上旬均没有出现中午光合下调,8月由于土壤水分降低和植物叶片衰老,棉花群体光合速率和蒸腾速率显著降低,但水分利用效率并无显著下降.     

Denaturation and unfolding of human anaphylatoxin C3a: an unusually low covalent stability of its native disulfide bonds

The complement C3a anaphylatoxin is a major molecular mediator of innate immunity. It is a potent activator of mast cells, basophils and eosinophils and causes smooth muscle contraction. Structurally, C3a is a relatively small protein (77 amino acids) comprising a N-terminal domain connected by 3 native disulfide bonds and a helical C-terminal segment. The structural stability of C3a has been investigated here using three different methods: Disulfide scrambling; Differential CD spectroscopy; and Reductive unfolding. Two uncommon features regarding the stability of C3a and the structure of denatured C3a have been observed in this study. (a) There is an unusual disconnection between the conformational stability of C3a and the covalent stability of its three native disulfide bonds that is not seen with other disulfide proteins. As measured by both methods of disulfide scrambling and differential CD spectroscopy, the native C3a exhibits a global conformational stability that is comparable to numerous proteins with similar size and disulfide content, all with mid-point denaturation of [GdmCl]_1/2 at 3.4-5 M. These proteins include hirudin, tick anticoagulant protein and leech carboxypeptidase inhibitor. However, the native disulfide bonds of C3a is 150-1000 fold less stable than those proteins as evaluated by the method of reductive unfolding. The 3 native disulfide bonds of C3a can be collectively and quantitatively reduced with as low as 1 mM of dithiothreitol within 5 min. The fragility of the native disulfide bonds of C3a has not yet been observed with other native disulfide proteins. (b) Using the method of disulfide scrambling, denatured C3a was shown to consist of diverse isomers adopting varied extent of unfolding. Among them, the most extensively unfolded isomer of denatured C3a is found to assume beads-form disulfide pattern, comprising Cys³⁶-Cys⁴⁹ and two disulfide bonds formed by two pair of consecutive cysteines, Cys²²-Cys²³ and Cys⁵⁶-Cys⁵⁷, a unique disulfide structure of polypeptide that has not been documented previously.     

人类新基因WDR24的研究初报

WD40家族是一类结构保守、功能复杂的蛋白.目前很多研究显示该家族成员通过参与MAPK信号途径调控细胞内信号转导而影响细胞的基本生命活动.为了鉴定参与细胞生命活动的新基因,运用同源基因克隆法,通过PCR技术扩增获得一个新的人类基因WDR24, 其cDNA全长3 302 bp,2 373 bp长的开放阅读框编码由790个氨基酸残基组成的蛋白质.生物信息学分析表明,WDR24蛋白在进化上高度保守,与其他脊椎动物中的同源蛋白组成了一个功能未知的亚家族.蛋白序列分析显示其中有6个WD40重复序列和1个ERK的停泊位点D-domain.RT-PCR分析表明,该基因在所有被检测的人类胚胎组织中表达.