噬菌体展示库筛选细胞特异分子的进展

介绍噬菌体展示技术的原理和发展,尤其是噬菌体展示技术在筛选细胞特异分子的策略方面的进展。该技术通过20年的发展已成为一种研究抗原一抗体作用、蛋白质相互作用、蛋白一药物相互作用甚至蛋白质一核酸作用的分析手段,但涉及到以完整细胞、器官或组织等复杂的生物活性分子表面为靶标则筛选效果尚不理想。关键是要减少噬菌体展示分子与靶标的非特异性结合,利用更为严格的经过改进的筛选策略。该技术的优势预示着它将广泛被应用于基础理论和研究实践中。     

几种微生物杀虫蛋白基因研究进展

在过去几年中,已经鉴定并克隆出一些新的苏云金芽孢杆菌杀虫晶体蛋白基因和其他类型的微生物杀虫蛋白基因。其中来自嗜虫沙雷氏菌,双酶梭状芽孢杆菌,球形芽孢杆菌,嗜线虫致病杆菌,发光杆菌和金龟子绿僵菌的新型杀虫蛋白基因在抗虫遗传工程中具有良好的应用前景     

Biotransformation of podophyllotoxin by Hordeum vulgare cell suspension cultures

Hordeum vulgare cell suspension cultures were used to modify podophyllotoxin (1) One major product (1a) and one minor product (1b) were detected in both the culture medium and cells. To optimize the yield of compound 1a, we showed that: (1) the optimal concentration of added podophyllotoxin (1) was 33 mg L^-1; higher concentrations caused cell toxicity; (2) the stage of the cell cycle (lag/log/stationary) at which podophyllotoxin was added only marginally affected the yield of compound 1a; the optimal addition time was after lag phase, in which the yield of compound 1a reached ca. 76%, and (3) biotransformation of podophyllotoxin (1) was relatively slow; podophyllotoxin fed at 4 days after subculture resulted in yields of compound 1a of ca. 56, 64 and 76% after an additional 3, 6 and 10 days of incubation, respectively. Product 1a was purified and identified as isopicropodophyllone (1a) based on MS and NMR data.     

Microbial dysbiosis and mortality during mechanical ventilation: a prospective observational study

Background

Host-associated microbial communities have important roles in tissue homeostasis and overall health. Severe perturbations can occur within these microbial communities during critical illness due to underlying diseases and clinical interventions, potentially influencing patient outcomes. We sought to profile the microbial composition of critically ill mechanically ventilated patients, and to determine whether microbial diversity is associated with illness severity and mortality.

Methods

We conducted a prospective, observational study of mechanically ventilated critically ill patients with a high incidence of pneumonia in 2 intensive care units (ICUs) in Hamilton, Canada, nested within a randomized trial for the prevention of healthcare-associated infections. The microbial profiles of specimens from 3 anatomical sites (respiratory, and upper and lower gastrointestinal tracts) were characterized using 16S ribosomal RNA gene sequencing.

Results

We collected 65 specimens from 34 ICU patients enrolled in the trial (29 endotracheal aspirates, 26 gastric aspirates and 10 stool specimens). Specimens were collected at a median time of 3?days (lower respiratory tract and gastric aspirates; interquartile range [IQR] 2–4) and 6?days (stool; IQR 4.25–6.75) following ICU admission. We observed a loss of biogeographical distinction between the lower respiratory tract and gastrointestinal tract microbiota during critical illness. Moreover, microbial diversity in the respiratory tract was inversely correlated with APACHE II score (r?=???0.46, p?=?0.013) and was associated with hospital mortality (Median Shannon index: Discharged alive; 1.964 vs. Deceased; 1.348, p?=?0.045).

Conclusions

The composition of the host-associated microbial communities is severely perturbed during critical illness. Reduced microbial diversity reflects high illness severity and is associated with mortality. Microbial diversity may be a biomarker of prognostic value in mechanically ventilated patients.

Trial registration

ClinicalTrials.gov ID NCT01782755. Registered February 4 2013.

     

Effects of MEK inhibitor U0126 on meiotic progression in mouse oocytes： microtuble organization, asymmetric division and metaphase Ⅱ arrest

In this study we used U0126, a potent and specific inhibitor of MEK, to study the roles of MEK/ERK/p90~(rsk) signaling pathway in the meiotic cell cycle of mouse oocytes. The phosphorylation of MAP kinase and p90~(rsk) in the oocytes treated with 1.5 μM U0126 was the same as that in oocytes cultured in drug-free medium. With 1.5 μM U0126 treatment, the spindles appeared normal as they formed in oocytes, but failed to maintain its structure. Instead, the spindle lost one pole or elongated extraordinarily. After further culture, some oocytes extruded gigantic polar bodies (>30 μm) that later divided into two small ones. Some oocytes underwent symmetric division and produced two equal-size daughter cells in which normal spindles formed. In oocytes with different division patterns, MAP kinase was normally phosphorylated. When the concentration of U0126 was increased to 15 mM, the phosphorylation of both MAPK and p90~(rsk) were inhibited, while symmetric division was decreased. When incubating in medium c     

Gene expression profile favoring phenotypic reversion: a clue for mechanism of tumor suppression by NF-IL6 3'UTR

Transfection of cDNA in 3'untranslated region of human nuclear factor for interleukin-6 (NF-IL6 3'UTR) induced tumor suppression in a human hepatoma cell line. cDNA array analysis was used to reveal changes in gene expression profile leading to tumor suppression The results indicate that this suppression was not due to activation of dsRNA-dependent protein kinase, nor to inactivation of oncogenes; rather, all the changes in expression of known genes, induced by NF-IL6 3'UTR cDNA may be ascribed to the suppression of cellular malignancy. Therefore, our results imply that this 3'untranslated region may have played role of a regulator of gene expression profile.     

LKB1及其生物学功能

LKB1基因是一种保守的抑癌基因,其编码产物LKB1即丝氨酸-苏氨酸激酶11(serine/threonine kinase,STK11)。LKB1与细胞极性调节、男性精子形成、肿瘤及细胞代谢等方面有关。本文阐述了近年来LKB1的最新研究进展。     

昆虫激肽的生理功能及机制

昆虫激肽是一类高度保守的小分子神经活性物质,自其从马德拉蟑螂脑中分离得到至今,人们在多种无脊椎动物体内均发现了这一激肽家族成员。它们具有促进昆虫后肠收缩、马氏管扭动、原尿分泌,调节血淋巴量和水盐平衡,使马氏管跨膜电位去极化,抑制昆虫体内消化酶释放、幼虫体重增长等功能。然而,天然的昆虫激肽很容易被蛋白酶所降解,因此须对其进行结构改造及构效关系研究,以开发出更有潜力的假肽和非肽模拟抗酶解昆虫激肽类似物,对今后实现环境友好型害虫防治策略具有重要意义。     

辽宁碱蓬胆碱单加氧酶基因克隆及转基因烟草的耐盐性

甜菜碱是生物体内普遍存在的一种很有效的渗透调节剂。在高等植物中,甜菜碱由胆碱经两步酶催氧化得到,即：胆碱→甜菜碱醛→甜菜碱,催化第一步反应的酶是胆碱单加氧酶（choline monooxygenase,CMO)。用RT-PCR和RACE技术从盐生植物辽宁碱蓬（Suaeda liaotungensis Kitag)中分离了CMOcDNA全序列,其中包括5′端非编码区123bp,3′端非编码区368bp。开放阅读框1329bp,编码一个由442个氨基酸构成的多肽,与菠菜,甜菜和山菠菜CMO的氨基酸序列同源性分别为77%,72%和74%。克隆了其编码区。构建了植物表达载体pBI121-CMO。根癌土壤杆菌（Agrobacterium tumefaciens)介导转化烟草（Nictiana tabacumL.cv.89),获得卡那霉素抗性植株,PCR和Southern杂交均证明外源CMO基因已整合到烟草基因组中,转基因烟草的甜菜碱含量明显高于对照。转基因烟草膜的相对电导率明显低于对照,说明盐胁迫下转基因烟草的膜结构所受损伤小于对照。转基因烟草具有一定的耐盐性。能在含250mmol/LNaCl的培养基中正常生长。