For use with the Ussing system for no-destructive TEER measurement of epithelial tissue
- Variety of sizes for all your applications
Options
| Order code | Reservoir Opening | Half-Chamber Volume | Pin Circle Diameter | Surface area |
| CHM1 (Medium) | 12 mm | 1.0 mL | 17 mm | 113 mm2 (1.13 cm2) |
| CHM2 (Small) | 9 mm | 0.75 mL | 12 mm | 63.5 mm2 |
| CHM3 (Large) | 13.5 mm | 1.2 mL | 18.5 mm | 143 mm2 |
| CHM5 (Snap) | 12 mm | 1.7 mL | N/A | 113 mm2 (1.13 cm2) |
| CHM6 (Rect, Small) | Rectangle of 9.5*5 + 5 mm diameter | 0.8 mL | 7x16.5 mm | 67.125 mm2 |
| CHM7 (Rect, Large) | Rectangle of 23*7 + 7 mm diameter | 5.5 mL | 9x32 mm | 199.465 mm2 |
| CHM8 (X-small) | 4 mm | 0.5 mL | 5.5 mm | 12.56 mm2 |
Assembled chambers are 101.6mm (4") long.
WPI’s classical Ussing Chambers are well established perfusion chambers that are easy to operate, easy to control temperature, and easy to clean after use. The Ussing Chambers are machined from solid acrylic with eight entry ports for fluid lines, electrodes, or agar bridges. For easy, leak-free attachment of tubing and electrodes, all eight ports are luer type. The four ports for voltage and current electrodes are recessed to prevent formation of air bubbles in the chamber. The fluid compartments in each side of the chamber are separated by the epithelial membrane being studied. Sharp stainless steel pins on oneside of the chamber hold the membrane in position and mate with holes in the opposite chamber interface.
Specific Details for CMH4
In the CHM4, tissue is held by an O-ring instead of pins.
Specific Details for CMH5
The CHM5 chamber adapts the Costar Snapwell, a cell culture insert for monolayer cell culture, into WPI’s “classical” epithelial voltage clamp system. Until now, classical Ussing Chambers have not been widely used for monolayer cell culture inserts because most inserts have a very deep profile, limiting good fluid perfusion at the surface of the membrane - and limiting voltage electrodes from measuring the potential close to the surface of the membrane.
CHM5 solves these problems:
- Perfusion fluid is introduced into the chamber at an angle so that it will flow directly to the surface of the membrane.
- The voltage electrode is also inserted into the chamber at an angle so as to reduce the distance between the surface of the membrane and the electrode.
Specific Details for CMH6
This small chamber with rectangular openings was designed for tubular tissue from small animals such as the mouse intestinal tract membrane. The rectangular opening more closely matches the shape of the tissue than would a circular opening, significantly increasing the membrane area available for testing. The larger membrane area increases the transport rate of low permeability chemicals; it also reduces the electrical resistance of the system for easier current clamping.
Specific Details for CMH7
This small chamber with rectangular openings was designed for rat intestinal tract membrane. The rectangular opening more closely matches the shape of the tissue than would a circular opening, significantly increasing the membrane area available for testing. The larger membrane area increases the transport rate of low permeability chemicals; it also reduces the electrical resistance of the system for easier current clamping.
R.B. Canani, P. Cirillo, G. Mallardo, V. Buccigrossi, A. Secondo, L. Annunziato E. Bruzzese, F. Albano, F. Selvaggi, A. Guarino "Effects of HIV-1 Tat protein on ion secretion and on cell proliferation in human intestinal epithelial cells" Gastroenterology 124. 2003: 368-376
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是不是CRISPRall-in-one只能设置一个sgRNA？
尽量简洁
科学家发现，细菌在遭遇噬菌体等病毒侵染之后，可以获得其部分DNA（脱氧核糖核酸）片段并整合进基因组形成记忆，当再次遭到入侵时，转录出相应的RNA（核糖核酸），利用其中的“定位信息”引导Cas蛋白复合物定位和切割、彻底地摧毁入侵病毒的DNA。CRISPR／Cas9技术就是利用这一原理，用一种定制的RNA引导Cas，对预设DNA位点进行切割，造成DNA断裂，启动细胞内基因组修复机制，实现基因敲除、特异突变的修复或引入和定点转基因等。
作为一种 RNA 导向的 dsDNA 结合蛋白，Cas9 效应物核酸酶是已知的第一个统一因子（unifying factor），能够共定位 RNA、DNA 和蛋白，从而拥有巨大的改造潜力。将蛋白与无核酸酶的 Cas9（ Cas9 nuclease-null）融合，并表达适当的 sgRNA ，可靶定任何 dsDNA 序列，而 sgRNA 的末端可连接到目标DNA，不影响 Cas9 的结合。因此，Cas9 能在任何 dsDNA 序列处带来任何融合蛋白及 RNA，这为生物体的研究和改造带来巨大潜力。向左转|向右转
http://www.nature.com/nature/journal/v520/n7546/full/nature14299.html
CRISPR derived RNA
就是用来抵御病毒侵袭/躲避哺乳动物免疫反应的基因系统衍生的RNA。
是的，确切来说是大量表达。 大肠杆菌是基因重组技术中常用的细菌，将外源目的基因(如人胰岛素基因)导入大肠杆菌后可在大肠杆菌内表达目的蛋白(如胰岛素)，由于细菌繁殖速度快，通过发酵便可在短时间内获得大量胰岛素，再经多步分离、纯化便得到了药用胰岛素。
流程大概是这样的：首先获得小鼠ES细胞系，测试ES细胞嵌合入受体囊胚的能力之后根据不同基因、不同目的设计并构建打靶载体，将打靶载体转入一定数目ES细胞中，然后鉴定出带有发生正确同源重组的突变中靶ES细胞。通过显微注射或者胚胎融合的方法将经过遗传修饰的ES细胞引入受体胚胎内。经过遗传修饰的ES细胞可以发育为嵌合体动物的生殖细胞，是的经过修饰的遗传信息经生殖系遗传，从而得到带有修饰基因的突变小鼠，而后可以对其进行表型分析。
缺点：质粒仍然较大，转染难度相对较大。具有碱基识别偏好性，局限了基因编辑的运用范围，而且会导致不同基因位点编辑效率不同。筛选仍然需要较大工作量。
昨日，NatureMethods上发表的一篇论文指出：CRISPR-Cas9基因编辑技术导致数百种意料之外的脱靶突变，该论文在业界引发了不小的轰动，也使该技术遭到了质疑。
众所周知，CRISPR-Cas9基因编辑技术凭借其简易、高效和多样化的特点，目前被越来越多的人认为是癌症的“控制中心”，可以用来修复导致失明的基因突变、治疗生物的遗传疾病、甚至通过编辑人类胚胎基因来找出导致不孕和流产的原因。
蛋白质数据库中编号为5AXW的金黄色葡萄球菌的Cas9蛋白晶状结构
然而，昨日发表的论文联合作者、哥伦比亚大学医学中心的StephenTsang博士说，“我们一致认为，CRISPR引起的偏靶突变这一发现具有非常严重的潜在危害，其中包括单核苷酸突变和基因组非编码区域的突变。”
在这项研究中，研究人员对课题组此前获得的进行过CRISPR基因编辑的小鼠进行了全基因组测序，并进行了健康程度比对。
他们发现：CRISPR基因编辑技术确实成功修复了小鼠体内导致失明的基因，但通过全基因组测序后发现小鼠体内有超过1500个单核苷酸发生突变，并且有100个以上的位点发生发生了大片段的缺失和插入。
同时，Tsang研究团队的报告指出：上述这些突变无一通过计算机设置的算法预测到。
NatureMethod论文中的部分关键实验结果统计
StephenTsang博士进一步说道，“研究人员一般并不会使用全基因组测序手段去检测脱靶效应导致的基因突变位点，并且可能忽视了潜在的重要突变位点，因为即便是单碱基突变也有可能造成较大的影响。我们希望，这一研究结果能够鼓励其他人使用全基因组测序作为确定CRISPR技术所有脱靶效应的方法，从而达到更安全、更精准的基因编辑”。
当谈及对于CRISPR技术用于疾病治疗的前景，该研究的共同通讯作者VinitMahajan博士说：“虽然我们依然对CRISPR持乐观态度。但作为医生，我们知道，每一种新疗法都有一些潜在的副作用，我们需要知道这些副作用是什么。”
参考资料：https://www.sciencealert.com/turns-out-crispr-gene-editing-can-cause-hundreds-of-unexpected-mutations
https://eurekalert.org/pub_releases/2017-05/cumc-cge052617.php
https://phys.org/news/2017-05-crispr-gene-hundreds-unintended-mutations.html
https://phys.org/news/2017-04-accurate-dna-method.html
