关于comet-fish。其实fish 技术就用于检测染色体上具体的基因。这个基因对损伤的敏感性一般要比其他的强。现在最热门的就是检测tp53基因。而且通过这种检测。可以确定更多对人体有害的环境因素。有兴趣的话可以看看下面的摘要:In addition to exogenous risk factors, the development of head and neck cancer is based on genetic alterations and individual
sensitivity to mutagens. The DNA-damaging effect of xenobiotics and the location of chromosomal changes warrant further
investigation. The aim of this study was to evaluate variance in structural genetic changes in human epithelia as target cells for
head and neck carcinogenesis. The combination of the single-cell gel electrophoresis (Comet) assay with the fluorescence in situ
hybridization (FISH) technique is presented to examine differences in sensitivity to DNA-damage induction and in alterations
of chromosomes 1, 3, 5 and 8 in patients with and without squamous cell carcinoma of the oropharynx.
Macroscopically healthy biopsies from the mucosa, taken at a distance from the tumor of 10 patients with oropharyngeal
carcinoma and from 10 patients without tumor were harvested during surgery. Cells were isolated by enzymatic digestion and
incubated with benzo[a]pyrene-diolepoxide (BPDE), causing DNA-adduct formation by covalent binding of BPDE with DNA
bases. The cells were subsequently analyzed by means of the Comet assay to separate DNA fragments and to visualize the DNAdamage.
A hybridization mixture with whole-chromosome paints for Chr1, Chr3, Chr5 and Chr8 was added. After fluorescent
staining, the entire DNA and the DNA of chromosomes 1, 3, 5 and 8 were evaluated by digital analysis.
BPDE caused significant DNA damage in oropharyngeal mucosa cells of patients with and patients without carcinoma.
No differences in the amount of DNA damage could be observed between patients suffering from sqamous cell carcinoma
and patients without malignancy. Evaluation of chromosomal alterations, however, revealed significantly higher damage levels
in chromosomes 3, 5 and 8 compared with chromosome 1 in tumor patients. In contrast, for patients without oropharyngeal
carcinoma no differences in chromosomal alterations could be observed.作者: 一叶 时间: 2011-12-2 11:16
中性单细胞凝胶电泳步骤:(以淋巴细胞为例)
1) 淋巴细胞的提取
① 取各组荷瘤鼠外周血0.2ml,肝素抗凝,加入到等体积淋巴细胞分离液上,3500r/min离心4min。
② 取中间层淋巴细胞并加入PBS至5 ml, 1500r/min离心8min。
③ 重复洗涤细胞两次。
2) 琼脂糖玻片的制备
① 制好微型电泳槽。
② 使用两层凝胶法,第一层为100μl 0.75%正常熔点琼脂糖凝胶, 第二层为75μl 0.75%低熔点琼脂糖凝胶和25μl淋巴细胞的混合液。
3) 细胞裂解、电泳
① 好的玻片浸入新配的预冷的(4ºC)中性裂解液中裂解1.5h。
② 取出玻片,用双蒸水浸没漂洗。
③ 将玻片置于0.5%电泳液中先解旋20分钟,然后电泳20min,电压20V,电流200毫安。
4) 染色
用溴化乙啶(2μg/ml) 染色。
用双蒸水冲去多余染液,滤纸洗去多余水分。
5)读片和分析
① 用荧光显微镜(激发波长515-560nm)观察玻片,每张胶随机抓
取100个慧星图像并用数码相机拍照后输入计算机储存。
② 用CASP软件分析系统分析慧星图像。作者: zhezhe 时间: 2011-12-2 14:41
As a result of the loss of DNA supercoiling at low concentrations of genotoxins or DNA fragmentation at high concentrations, more fluorescence was observed in the tail relative to the head in damaged cells. DNA fragments migrate more freely in the gel than the loops and cause the formation of more elongated tails
同意楼上的观点,吖啶橙毒性确实小,安全第一。
如果用毛玻片出现上述现象的话,可以尝试我以前说过的方法,自制电泳槽,(我又卖瓜了)。
低熔点的凝胶还是很好买的,一般的试剂公司都可以买到,SCGE 实验相对比较简单,我认为没必要买试剂盒。作者: one 时间: 2011-12-2 16:29
老师,我做了两次彗星电泳,结果都差不多。
我用的是人肺癌A549细胞。空白和喜树碱(300um/L)的结果几乎一样。也就是说喜树碱没有令细胞凋亡。但是与报道以及我的流式结果,和实验前普通显微镜下的观察结果不一致。我不知道我为什么做不出凋亡。以下是我的实验过程。
步骤:
一、 细胞悬液的制备:
1. 吸弃旧培养基,PBS冲洗2遍.
2. 0.25%胰酶消化,待细胞变圆,间隙增大,立即终止消化,用弯头吸管轻轻吹打细胞,使成细胞悬液,加入离心管,1000rpm,离心10min,弃上清,以PBS悬浮细胞。暗室下进行。
二、铺胶
1. 我用的是单面单头载玻片以及普通盖玻片。
2. 第一层胶:0.5%NMPA 100μl于磨砂玻片面,盖上盖玻片,-20度5min使其固化;
第二层胶:37℃ 0.5%LMPA 100μl+30-50μl(1-2x106)细胞悬液混匀,铺于第一层胶上,盖新盖玻片,-20度5min,使其固化。
三、细胞溶解:
1. 玻片浸入新鲜配制的冰凉细胞溶解液中,4℃ 放置2小时。
细胞溶解液配制
NaCl 146.1 g
Na2EDTA 37.2 g
Tris base 1.2 g
用NaOH调节pH至10。
肌氨酸钠1%。
Triton X-100 至 1%
DMSO 至 10%。
用去离子水定容至890ml。过滤除菌,为贮备液。室温保存。
4、碱化处理及电泳:取出玻片,放入水平电泳槽中(正极端),并列放置,不留空隙。倒入新鲜配制的冰冷电泳缓冲应用液,高于胶2mm,无气泡。放置10分钟,25V, 100mA电泳20分钟(我室的电泳仪电流升不上去)。
电泳缓冲应用液:
10N NaOH 30.0 ml(12克)
200mM EDTA 5.0 ml (二钠为0.372g)
5、中和:
切断电源,取出玻片,置染缸,中和缓冲液浸洗,3次×5min。
中和缓冲液:
Tris base 48.5 g
去离子水 定容至1000ml
用>10 N HCl调节pH至7.5。
6、PI染色
7、镜检作者: one 时间: 2011-12-2 16:30
今天我看到Biochemical Pharmacology 69 (2005) 113–121 上发表的一篇文献,其中也提到彗星电泳的方法。我摘录了其中的一段。
2.5. Single cell gel electrophoresis (Comet assay)
Nuclei were isolated from A2780wt cells by incubating whole cells in a buffer containing 5 mM MgCl2, 1mM EGTA, 1 mM KH2PO4, 150 mM NaCl for 20 min on ice with gentle rocking. Plasma membrane disruption and nuclei integrity were checked under the microscope. Isolated nuclei were exposed to the drugs at 10 mMfor 30 min at 37 8C or to H2O2 for 5 min. DNA breaks were detected as previously described [8]. Briefly, nuclei were embedded in agarose gel and then spread on a polylysinated microscope slide. Nuclei were lysed in 2.5 MNaCl, 10 mMTris–HCl, 100 mM Na2EDTA, 1% Triton, 10% DMSO, pH 10,for 1 h at 4 8C. After lysis, nuclei were preincubated for 20 min at 4 8C in the electrophoresis buffer (0.3 M NaOH, 1 mM Na2EDTA, pH 13.5) and then subjected to alkaline gel electrophoresis (300 mA, 4 8C, 20 min). Nuclear DNA was stained using SYBR-gold (Molecular Probes). Slides were analysed by automatic image analysis (Casys system, Synoptics Ltd.) to quantitate DNA damage. The tail moment, calculated by multiplying the total intensity of the comet tail by the migration distance from the centr ofthe comet head, was used to measure DNA damage. Fifty nuclei for each experimental point were scored blind from two slides.
作者先把细胞破膜提出细胞核,然后加药处理一段时间,再裂解,跑电泳,染色镜检。
我不明白作者为何要提出细胞核再加药呢?作者用的阳性药是顺铂,喜树碱和H2O2.理论上顺铂和喜树碱都可以使细胞凋亡。
大家是否可以说说自己的看法?作者: 一叶 时间: 2011-12-2 16:31 标题: 回复 #237 one 的帖子
哦,这是人肝癌细胞BEL-7402.不过我的实验不是为了看凋亡。我收集细胞后,用膜裂解液(5 mM MgCl2, 1mM EGTA, 1 mM KH2PO4, 150 mM NaCl.)破膜取细胞核,加入药物(如喜树碱)37度孵育30min。之后的步骤和各位一样了。以下是我的参考文献:
2.5. Single cell gel electrophoresis (Comet assay)
Nuclei were isolated from A2780wt cells by incubating
whole cells in a buffer containing 5 mM MgCl2, 1mM
EGTA, 1 mM KH2PO4, 150 mM NaCl for 20 min on ice
with gentle rocking. Plasma membrane disruption and
nuclei integrity were checked under the microscope. Isolated
nuclei were exposed to the drugs at 10 uM for 30 min
at 37 oC or to H2O2 for 5 min. DNA breaks were detected
as previously described [8]. Briefly, nuclei were embedded
in agarose gel and then spread on a polylysinated microscope
slide. Nuclei were lysed in 2.5 MNaCl, 10 mMTris–
HCl, 100 mM Na2EDTA, 1% Triton, 10% DMSO, pH 10,
for 1 h at 4 8C. After lysis, nuclei were preincubated for
20 min at 4 8C in the electrophoresis buffer (0.3 M NaOH,
1 mM Na2EDTA, pH 13.5) and then subjected to alkaline
gel electrophoresis (300 mA, 4 8C, 20 min). Nuclear DNA
was stained using SYBR-gold (Molecular Probes). Slides
were analysed by automatic image analysis (Casys system,
Synoptics Ltd.) to quantitate DNA damage. The tail
moment, calculated by multiplying the total intensity of
the comet tail by the migration distance from the center of
the comet head, was used to measure DNA damage. Fifty
nuclei for each experimental point were scored blind from
two slides.
摘自:Thiocolchicine dimers: a novel class of topoisomerase-I inhibitors,Biochemical Pharmacology 69 (2005) 113–121
彗星总长、尾长、尾DNA含量都是可测的。
尾矩:尾长×尾部DNA含量
Olive尾矩:(彗星头部重心与尾部重心间距离)×尾部DNA含量
上述指标均可通过彗星分析软件获得。
哪个好:应该是复合指标(如尾矩和O尾矩)比较好,更准确。因为单一指标在损伤因素强度达到一定阈值后可能会出现平台,超出其描述范围。
尾长、尾矩、Olive尾矩、尾部DNA百分含量在对彗星的描述中应该是很必要的,另外,彗星细胞率也不容忽视。
介绍几篇综述:
Journal of Chromatography B, 1999, 722: 225–254
Single cell gel electrophoresis assay: methodology and applications
E. Rojas, M.C. Lopez, M. Valverde
Mutagenesis. 2003 , 18(1):45-51.
Recommendations for conducting the in vivo alkaline Comet assay. 4th International Comet Assay Workshop.
Hartmann A, Agurell E, Beevers C, Brendler-Schwaab S, Burlinson B, Clay P, Collins A, Smith A, Speit G, Thybaud V, Tice RR; 4th International Comet Assay Workshop.
Environ Mol Mutagen. 2000;35(3):206-21.
Single cell gel/comet assay: guidelines for in vitro and in vivo genetic toxicology testing.
R. R. Tice, E. Agurell, D. Anderson, B. Burlinson, A. Hartmann, H. Kobayashi, Y. Miyamae, E. Rojas, JC. Ryu, and Y. F. Sasaki
第四届彗星分析研讨会讨论了SCGE的方法问题,【the 4th International Comet Assay Workshop (Ulm, Germany,22–25 July 2001) 】
专家组认为加肌氨酸钠是多余的。
(The addition of 1% N-lauroylsarcosine is now considered redundant. )作者: 一叶 时间: 2011-12-3 17:18
谢谢乌贼老弟群友,电压问题主要是电泳仪中间坏了一次,换个电泳仪就行的。还想问一下大家,为什么CASP不能分析银染的彗星图象?
前几天看到一篇文献,介绍了彗星电泳的升级版--FHA(The fast halo assay),省略了很多步骤,只经过裂解和染色两步,直接可以看到DNA的损伤,具有很多的优点,似乎有代替彗星电泳的趋势,(后附有FHA的照片)不知大家有没有接触过,对此有什么看法。
电压问题主要是电泳仪中间坏了一次,换个电泳仪就行的。还想问一下大家,为什么CASP不能分析银染的彗星图象?
前几天看到一篇文献,介绍了彗星电泳的升级版--FHA(The fast halo assay),省略了很多步骤,只经过裂解和染色两步,直接可以看到DNA的损伤,具有很多的优点,似乎有代替彗星电泳的趋势,(后附有FHA的照片)不知大家有没有接触过,对此有什么看法。
我也看过这文献,The fast halo assay: An improved method to quantify genomic DNA strand breakage at the single-cell level,确实非常简便,应该说是晕圈分析的升级版,但我觉得不能称为彗星电泳的升级版,二者各有千秋。怎样进一步准确量化晕圈的各项指标,以更加准确评价细胞的DNA损伤水平是这个方法需要进一步解决的问题。我想试一下,毕竟是一个新东西,选一个好的软件是很关键的吧。作者: zhezhe 时间: 2011-12-5 10:49
请教用gene finder 染料的战友,在彗星电泳中的使用方法,谢谢。 使用这个染料时还用不用加大电压?我们实验室的电泳仪电压老上不去,一接通电源电泳仪就显示稳流,电压根本调不了,愁死了快。作者: 乌贼老弟 时间: 2011-12-5 10:51
还有就是我配的细胞裂解液总是不能完全溶解, 尤其是当加入了Triton X-100和DMSO后,液面上出现会很多泡沫还有白色的小固体不溶,磁力棒搅拌了20分钟也没溶,一直呈悬浊液状态.
下面是我依照的细胞裂解液(每1000m1)的配制方法:
2.5 m m o l/L N a Cl 146 .1g
100 mmol/L EDTA 37.2g
10 mmol/L Tris 1.2g
用NaOH调PH=10
1%肌氨酸钠 10g
用去离子水定容至890ml.120摄氏度高温灭菌,为贮备液,室温保存。
现在才真正的接触到具体的实验--单细胞凝胶电泳!我的实验进程比较顺利,而且图象也不用CASP或其他软件进行分析,直接用软件里的标尺(这个abc816和一叶老师也提过有这个取代像素的问题,真是有先见啊,佩服)就可以得到数据了!条件经过几次的摸索今天也定了下来,但是在这几次的摸索中,很多经验也是从帖子中得来的,电压的高低,裂解液要透明,裂解时间的把握等等,都是帖子里看来的。这里谢过所有的战友们,你们的问题使我有了今天的成功!
一叶老师说过:ALL FOR ONE , ONE FOR ALL!为了感谢一叶老师以及各位战友,我总结了一下我们实验室在这个试验当中关于防止EB污染的试验操作,在这些操作中我们尽量将污染降低到最小化,但是每个环节不可能都是最佳的,希望各位战友也说说你们实验室是怎样防止EB污染的,相互学习,做出一个最佳的防止EB污染的试验操作方法,将EB的污染最低化。为单细胞凝胶电泳技术的标准化做出些许努力! 作者: 一叶 时间: 2011-12-6 15:36
我做的图片都是散的,不是真正的前面一个圆的亮的,后面有托尾,无论损伤浓度达到多少图片都是散的,看到有人提到裂解过头的问题,我想请问大家:裂解过头是该怎么理解呢?因为我感觉DNA基因组被包在核膜里,裂解就是把核膜给去掉,应该不会把DNA给裂解散了呀?到底是为什么呢?作者: DNA 时间: 2011-12-6 15:51
电泳仪和电泳槽的牌子型号不重要,只要是质量可靠的厂家生产的就行了。在电泳过程中一般很难做到同时稳压稳流,你可以试试通过调节液面高度来调节,实在不行的话起码要做到稳压。一定要根据你的电泳槽大小来计算合适的V/cm,一般要求是0.7-1.0V/cm就可以了。
具体内容可参考以下文献:
1. Single Cell Gel/Comet Assay: Guidelines For In Vitro and In Vivo Genetic Toxicology Testing 2000
2. The comet assay: topical issues 2008作者: loli 时间: 2011-12-6 17:44 标题: 回复 #933 dotaaa 的帖子
我看一篇2009发的外文,说的是碱性彗星会使蛋白变性,难以维持其空间结构,检测的多是单链断裂。而中性可以保住双链之间的空间结构而检测双链断裂。不知对不?各位能否解答一下,真的有点混了。还有就是中性指的是什么?是裂解液还是什么啊?大部分文献都是说PH值10几,最少的也是8.0多,根据中学的化学知识那我理解的PH值是7.0左右的才是中性吗?请各位指教一下。呵呵。作者: TAT 时间: 2011-12-7 15:03
用于彗星实验的PBS都是0.1M的吧,我好像都没见过用0.01M的浓度。0.1和0.01M浓度PBS的区别我还真不太清楚,问了下其他做细胞实验的同事也都说不好,据我所知0.1M的浓度才是用于细胞的啊,0.01M浓度的PBS一般都用于蛋白、病毒或免疫实验。如果有用这种浓度PBS的文献可发上来我们学习一下。一叶老师也是用的0.1M浓度(参看他在38页的回答)。而且在彗星实验中PBS的用途并不是培养细胞啊,它只是用作混悬细胞的载体而已。作者: one 时间: 2011-12-7 16:27
一叶老师推荐的综述:
Journal of Chromatography B, 1999, 722: 225–254
Single cell gel electrophoresis assay: methodology and applications
E. Rojas, M.C. Lopez, M. Valverde
Mutagenesis. 2003 , 18(1):45-51.
Recommendations for conducting the in vivo alkaline Comet assay. 4th International Comet Assay Workshop.
Hartmann A, Agurell E, Beevers C, Brendler-Schwaab S, Burlinson B, Clay P, Collins A, Smith A, Speit G, Thybaud V, Tice RR; 4th International Comet Assay Workshop.
Environ Mol Mutagen. 2000;35(3):206-21.
Single cell gel/comet assay: guidelines for in vitro and in vivo genetic toxicology testing.
R. R. Tice, E. Agurell, D. Anderson, B. Burlinson, A. Hartmann, H. Kobayashi, Y. Miyamae, E. Rojas, JC. Ryu, and Y. F. Sasaki作者: 911 时间: 2011-12-7 16:31
Electrophoresis buffer (900 ml, 300 mmol dm -3NaOH, 0. 1% 8-hydroxyquinoline, 2% dimethyl sul-phoxide, 10 mmol dm -3 disodium EDTA) was gently poured into the assembly . This volume usually covers the slides to a height of 6 mm above the surface of slides . This solution must not be reused . After 20 min to allow for DNA unwinding, electrophoresis (25V, 60 min) and recirculation (100 ml/min) were started simultaneously. The temperature of the buffer was 22 . 5° C at the beginning of electrophoresis but increased to 27 . 5 ° C by the end of run.
这是一篇文献里面的内容,recirculation (100 ml/min) were started 怎么理解,恳请高手给与帮助作者: loli 时间: 2011-12-7 16:35 标题: 回复 #1177 911 的帖子
配裂解液时先把原液配好,PH调到10,溶液变澄清时就可以放到冰箱里了,使用时直接按比例加入DMSO和Triton X 100就可以了,不用再调PH了。Triton X-100是一种非离子型表面活性剂(或称清洁剂),它能溶解脂质,以增加抗体对细胞膜的通透性。就像洗衣粉里加的表面活性剂一样,加了之后会有点浑浊,需要放到冰箱里静置一会。为什么要放冰箱?个人感觉裂解液温度越高越浑浊(曾经试过把裂解液放到37度,结果浑到不行)。至于荧光显微镜的镜头倍数,一般20或40,常用40,油镜放大倍数太大了,没有必要。
我做裸藻,方法跟R. R. Tice的Single Cell Gel/Comet Assay: Guidelines for In Vitro and In Vivo Genetic Toxicology Testing中基本一致。从去年开始跟着师姐做了六七次彗星预实验,全没做出来。背景很红,而且在染色前在荧光显微镜下看做好的片子就是红色的。每次重做都会把某一项条件改变下对比,但是就是没想到EB,有点菜。。
2.5 m m o l/L N a Cl 146 .1g
100 mmol/L EDTA2NA .2H2O 37.2g
10 mmol/L Tris 1.2g
用NaOH调PH=10
1%肌氨酸钠 10g
用去离子水定容至890ml.120摄氏度高温灭菌,为贮备液,4度保存 实验前至少一小时进行细胞液裂解应用液的配制:加1%)Triton X-100和10%DMSO,冷藏。
4 解旋和电泳
将玻片放在电泳液:Na2EDTA 0.372g、NaOH12g溶于1000ml水 中4度解旋半小时,然后电泳,条件为25V,300MA,30min
5 中和 tris pH7.4中和15min
6 20ug/ml EB染色,观察。