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26.  A do-it-yourself protocol for simple transcription activator-like effector assembly 
TALEs (transcription activator-like effectors) are powerful molecules that have broad applications in genetic and epigenetic manipulations. The simple design of TALEs, coupled with high binding predictability and specificity, is bringing genome engineering power to the standard molecular laboratory. Currently, however, custom TALE assembly is either costly or limited to few research centers, due to complicated assembly protocols, long set-up time and specific training requirements.
We streamlined a Golden Gate-based method for custom TALE assembly. First, by providing ready-made, quality-controlled monomers, we eliminated the procedures for error-prone and time-consuming set-up. Second, we optimized the protocol toward a fast, two-day assembly of custom TALEs, based on four thermocycling reactions. Third, we increased the versatility for diverse downstream applications by providing series of vector sets to generate both TALENs (TALE nucleases) and TALE-TFs (TALE-transcription factors) under the control of different promoters. Finally, we validated our system by assembling a number of TALENs and TALE-TFs with DNA sequencing confirmation. We further demonstrated that an assembled TALE-TF was able to transactivate a luciferase reporter gene and a TALEN pair was able to cut its target.
We established and validated a do-it-yourself system that enables individual researchers to assemble TALENs and TALE-TFs within 2 days. The simplified TALE assembly combined with multiple choices of vectors will facilitate the broad use of TALE technology.
PMCID: PMC3554550  PMID: 23316790
TALEN; TALE-TF; Golden Gate; Transcription-activator-like effector
27.  Determine the quality of human embryonic stem colonies with laser light scattering patterns 
With the prompt developments of regenerative medicine, the potential clinical applications of human embryonic stem cells have attracted intense attention. However, the labor-intensive and complex manual cell selection processes required during embryonic stem cell culturing have seriously limited large-scale production and broad applications. Thus, availability of a label-free, non-invasive platform to replace the current cumbersome manual selection has become a critical need.
A non-invasive, label-free, and time-efficient optical platform for determining the quality of human embryonic stem cell colonies was developed by analyzing the scattering signals from those stem cell colonies. Additionally, confocal microscopy revealed that the cell colony morphology and surface structures were correlated with the resulting characteristic light scattering patterns. Standard immunostaining assay (Oct-4) was also utilized to validate the quality-determination from this light scattering protocol. The platform developed here can therefore provide identification accuracy of up to 87% for colony determination.
Our study here demonstrated that light scattering patterns can serve as a feasible alternative approach to replace conventional manual selection for human embryonic stem cell cultures.
PMCID: PMC3560278  PMID: 23316759
Light-scattering; Human embryonic stem cell; Pluripotency; Label-free detection
28.  A new method of kidney biopsy using low dose CT-guidance with coaxial trocar and bard biopsy gun 
To explore a new method of kidney biopsy with coaxial trocar and bard biopsy gun under low dose computed tomography (CT)-guidance and evaluate its accuracy, safety, and efficacy.
Sixty patients underwent renal biopsy under CT-guidance. They were randomly divided into two groups: group I, low dose CT-guided (120 kV and 25 or 50 mAs) and group II, standard dose CT-guided (120 kV and 250 mAs). For group I, the coaxial trocar was accurately placed adjacent to the renal capsule of the lower pole, the needle core was removed, and samples were obtained with a bard biopsy gun. For group II, the coaxial trocar was not used. Total number of passes, mean biopsy diameter, mean glomeruli per specimen, mean operation time, mean scanning time, and mean radiation dose were noted. Dose-length product (DLP) was used to calculate the radiation doses. After 24 hours of the biopsy, ultrasound was repeated to identify any subcapsular hematoma.
Success rate of biopsy in group I was 100% while using low dose CT-guidance along with coaxial trocar renal. There was no statistic differences bewteen group I and II in the total number of passes, mean biopsy diameter, mean glomeruli per specimen and mean time of operation and CT scanning. The average DLP of group I was lower as compared to the value of group II (p <0.05).
Kidney biopsy using coaxial trocar and bard biopsy gun under low dose CT was an accurate, simple and safe method for diagnosis and treatment of kidney diseases. It can be used for repeat and multiple biopsies, particularly suitable for obese and renal atrophy patients in whom the kidneys are difficult to image.
PMCID: PMC3561167  PMID: 23294600
Kidney biopsy; Low dose CT scanning; Bard biopsy gun; Coaxial trocar
29.  Spontaneous arthritis and ankylosis in male DBA/1 mice: further evidence for a role of behavioral factors in “stress-induced arthritis” 
Ageing male DBA/1 mice spontaneously develop arthritis in the hind paws. We and others have demonstrated that this model shares striking features with human spondyloarthritis, in particular entheseal involvement, progressive ankylosis but also dactylitis. Here, we report on our recent experience with this model highlighting how changes in the animal facility affect the development of the disease.
Ageing male DBA/1 mice from different litters were caged together (6 mice per cage) at the age of 10 weeks. The mice were checked twice a week for clinical signs of arthritis. Disease severity was assessed in further detail post-mortem by scoring for histomorphological characteristics. DBA/1 mice spontaneously develop macroscopically detectable arthritis, presenting as joint swelling or toe stiffness. Standard settings with open cages lead to an almost 100% incidence by the age of 26 weeks. The introduction of larger cages and filter tops reducing exposure to other cages dramatically affected incidence. Other negative factors include excess bedding material reducing the impact of walking and running. Switching back to the original conditions resulted again in a high incidence, further optimized by sensory exposure to female mice. We also showed that the related DBA/2 strain is sensitive to the disease.
Changing environmental factors in the housing conditions of DBA/1 mice severely affects the spontaneous development of arthritis. This points out that the model is very sensitive to external stress and sensory factors that are likely affecting the behavior of the male mice and that the model needs to be optimized in different situations.
PMCID: PMC3537550  PMID: 23253472
Spondyloarthritis; Spontaneous arthritis; Behavioral factors; Ankylosis
30.  Modified protocol for in vivo imaging of wild-type mouse retina with customized miniature spectral domain optical coherence tomography (SD-OCT) device 
This protocol outlines and evaluates a modified scanning procedure for a customized spectral domain optical coherence tomography (SD-OCT) imaging apparatus within the wild-type C57Bl/6 mouse posterior segment. This modified protocol allows for the capture of a 50 degree field of view spanning 3 mm by 3 mm perimeter with the optic disc as the central point. By utilizing this scanning protocol a more reliable measurement of retinal thickness can be achieved outside the fluctuating region of the optic disc. This protocol, when applied to this high resolution device, enables non-invasive in vivo histological imaging and biometric assessment of the various layers of the rodent posterior segment within a 20 – 30 min procedural time-frame. This protocol could establish a standardized method for evaluating morphological changes, with this commercial SDOCT device, when assessing longitudinal disease pathophysiology and treatment response in mouse models for future vision science research.
PMCID: PMC3520836  PMID: 23057840
Spectral domain optical coherence tomography; Customized; Retinal imaging; Mouse
31.  A robust dual reporter system to visualize and quantify gene expression mediated by transcription activator-like effectors 
Transcription activator-like effectors (TALEs) are a class of naturally occurring transcription effectors that recognize specific DNA sequences and modulate gene expression. The modularity of TALEs DNA binding domain enables sequence-specific perturbation and offers broad applications in genetic and epigenetic studies. Although the efficient construction of TALEs has been established, robust functional tools to assess their functions remain lacking.
We established a dual reporter system that was specifically designed for real-time monitoring and quantifying gene expression mediated by TALEs. We validated both sensitivity and specificity of this dual-reporter system in mammalian cells, and demonstrated that this dual reporter system is robust and potentially amenable to high throughput (HTP) applications.
We have designed, constructed and validated a novel dual reporter system for assessing TALE mediated gene regulations. This system offers a robust and easy-to- use tool for real-time monitoring and quantifying gene expression in mammalian cells.
PMCID: PMC3509018  PMID: 22871120
Dual reporter; Gene editing; Transcription activator-like effector; Green fluorescent protein; Firefly luciferase
32.  Competitive DNA transfection formulation via electroporation for human adipose stem cells and mesenchymal stem cells 
Adipose stem cells have a strong potential for use in cell-based therapy, but the current nucleofection technique, which relies on unknown buffers, prevents their use.
We developed an optimal nucleofection formulation for human adipose stem cells by using a three-step method that we had developed previously. This method was designed to determine the optimal formulation for nucleofection that was capable of meeting or surpassing the established commercial buffer (Amaxa), in particular for murine adipose stem cells. By using this same buffer, we determined that the same formulation yields optimal transfection efficiency in human mesenchymal stem cells.
Our findings suggest that transfection efficiency in human stem cells can be boosted with proper formulation.
PMCID: PMC3388581  PMID: 22512891
Electroporation; Formulation; Stem cells; Transfection; Cell therapy
33.  Novel mouse mammary cell lines for in vivo bioluminescence imaging (BLI) of bone metastasis 
Tumor cell lines that can be tracked in vivo during tumorigenesis and metastasis provide vital tools for studying the specific cellular mechanisms that mediate these processes as well as investigating therapeutic targets to inhibit them. The goal of this study was to engineer imageable mouse mammary tumor cell lines with discrete propensities to metastasize to bone in vivo. Two novel luciferase expressing cell lines were developed and characterized for use in the study of breast cancer metastasis to bone in a syngeneic mouse model.
The 4 T1.2 luc3 and 66c14 luc2 cell lines were shown to have high levels of bioluminescence intensity in vitro and in vivo after orthotopic injection into mouse mammary fat pads. The 4 T1.2 luc3 cell line was found to closely model the sites of metastases seen in human patients including lung, liver, and bone. Specifically, 4 T1.2 luc3 cells demonstrated a high incidence of metastasis to spine, with an ex-vivo BLI intensity three orders of magnitude above the commercially available 4 T1 luc2 cells. 66c14 luc2 cells also demonstrated metastasis to spine, which was lower than that of 4 T1.2 luc3 cells but higher than 4 T1 luc2 cells, in addition to previously unreported metastases in the liver. High osteolytic activity of the 4 T1.2 luc3 cells in vivo in the bone microenvironment was also detected.
The engineered 4 T1.2 luc3 and 66c14 luc2 cell lines described in this study are valuable tools for studying the cellular events moderating the metastasis of breast tumor cells to bone.
PMCID: PMC3473320  PMID: 22510147
Breast cancer; Mammary cancer; Bone metastasis; in vivo imaging; 4 T1 cells; 4 T1.2 cells; Osteolysis; Syngeneic Balb/c model
34.  A reinvestigation of somatic hypermethylation at the PTEN CpG island in cancer cell lines 
PTEN is an important tumour suppressor gene that is mutated in Cowden syndrome as well as various sporadic cancers. CpG island hypermethylation is another route to tumour suppressor gene inactivation, however, the literature regarding PTEN hypermethylation in cancer is controversial. Furthermore, investigation of the methylation status of the PTEN CpG island is challenging due to sequence homology with the PTEN pseudogene, PTENP1. PTEN shares a CpG island promoter with another gene known as KLLN. Here we present a thorough reinvestigation of the methylation status of the PTEN CpG island in DNA from colorectal, breast, ovarian, glioma, lung and haematological cancer cell lines.
Using a range of bisulphite-based PCR assays we investigated 6 regions across the PTEN CpG island. We found that regions 1-4 were not methylated in cancer cell lines (0/36). By allelic bisulphite sequencing and pyrosequencing methylation was detected in regions 5 and 6 in colorectal, breast and haematological cancer cell lines. However, methylation detected in this region was associated with the PTENP1 promoter and not the PTEN CpG island.
We show that methylation of the PTEN CpG island is a rare event in cancer cell lines and that apparent methylation most likely originates from homologous regions of the PTENP1 pseudogene promoter. Future studies should utilize assays that reliably discriminate between PTEN and PTENP1 to avoid data misinterpretation.
PMCID: PMC3342897  PMID: 22490388
DNA methylation; Epigenetic; PTEN; KILLIN; PTENP1; Pseudogene; Cowden syndrome
35.  A microplate technique to simultaneously assay calcium accumulation in endoplasmic reticulum and SERCA release of inorganic phosphate 
Traditional analyses of calcium homeostasis have separately quantified either calcium accumulation or release mechanisms. To define the system as a whole, however, requires multiple experimental techniques to examine both accumulation and release. Here we describe a technique that couples the simultaneous quantification of radio-labeled calcium accumulation in endoplasmic reticulum (ER) microsomes with the release of inorganic phosphate (Pi) by the hydrolytic activity of sarco-endoplasmic reticulum calcium ATPase (SERCA) all in the convenience of a 96-well format.
PMCID: PMC3388579  PMID: 22472432
Calcium; SERCA activity; Microsomes; Inorganic phosphate; Malachite green
36.  An improved competitive inhibition enzymatic immunoassay method for tetrodotoxin quantification 
Quantifying tetrodotoxin (TTX) has been a challenge in both ecological and medical research due to the cost, time and training required of most quantification techniques. Here we present a modified Competitive Inhibition Enzymatic Immunoassay for the quantification of TTX, and to aid researchers in the optimization of this technique for widespread use with a high degree of accuracy and repeatability.
PMCID: PMC3337821  PMID: 22410273
Tetrodotoxin; CIEIA; HPLC
37.  Frequency shifting approach towards textual transcription of heartbeat sounds 
Auscultation is an approach for diagnosing many cardiovascular problems. Automatic analysis of heartbeat sounds and extraction of its audio features can assist physicians towards diagnosing diseases. Textual transcription allows recording a continuous heart sound stream using a text format which can be stored in very small memory in comparison with other audio formats. In addition, a text-based data allows applying indexing and searching techniques to access to the critical events. Hence, the transcribed heartbeat sounds provides useful information to monitor the behavior of a patient for the long duration of time. This paper proposes a frequency shifting method in order to improve the performance of the transcription. The main objective of this study is to transfer the heartbeat sounds to the music domain. The proposed technique is tested with 100 samples which were recorded from different heart diseases categories. The observed results show that, the proposed shifting method significantly improves the performance of the transcription.
PMCID: PMC3396354  PMID: 21970368
38.  A Method to Study the Epigenetic Chromatin States of Rare Hematopoietic Stem and Progenitor Cells; MiniChIP–Chip 
Dynamic chromatin structure is a fundamental property of gene transcriptional regulation, and has emerged as a critical modulator of physiological processes during cellular differentiation and development. Analysis of chromatin structure using molecular biology and biochemical assays in rare somatic stem and progenitor cells is key for understanding these processes but poses a great challenge because of their reliance on millions of cells. Through the development of a miniaturized genome-scale chromatin immunoprecipitation method (miniChIP–chip), we have documented the genome-wide chromatin states of low abundant populations that comprise hematopoietic stem cells and immediate progeny residing in murine bone marrow. In this report, we describe the miniChIP methodology that can be used for increasing an understanding of the epigenetic mechanisms underlying hematopoietic stem and progenitor cell function. Application of this method will reveal the contribution of dynamic chromatin structure in regulating the function of other somatic stem cell populations, and how this process becomes perturbed in pathological conditions.
PMCID: PMC3396287  PMID: 21406121
Miniaturized chromatin immunoprecipitation assays; Microarray technology; Histone modifications; Stem and progenitor cells; Epigenetic regulation; Lineage commitment
39.  Rapid site-directed domain scanning mutagenesis of enteropathogenic Escherichia coli espD 
We developed a rapid mutagenesis method based on a modification of the QuikChange® system (Stratagene) to systemically replace endogenous gene sequences with a unique similar size sequence tag. The modifications are as follows: 1: the length of the anchoring homologous sequences of both mutagenesis primers were increased to 16 - 22 bp to achieve melting temperatures greater than 80°C. 2: the final concentrations of both primers were increased to 5-10 ng/μl and the final concentration of template to 1-2 ng/μl. 3: the annealing temperature was adjusted when necessary from 52°C to 58°C. We generated 25 sequential mutants in the cloned espD gene (1.2 kb), which encodes an essential component of the type III secretion translocon required for the pathogenesis of enteropathogenic E. coli (EPEC) infection. Each mutation consisted of the replacement of 15 codons (45 bp) with 8 codons representing a 24 bp sequence containing three unique restriction endonuclease sites (KpnI/MfeI/SpeI) starting from the second codon. The insertion of the restriction endonuclease sites provides a convenient method for further insertions of purification and/or epitope tags into permissive domains. This method is rapid, site-directed and allows for the systematic creation of mutants evenly distributed throughout the entire gene of interest.
PMCID: PMC2211572  PMID: 18213361
Mutagenesis, Site-Directed; Polymerase Chain Reaction; Plasmids; Sequence Deletion
40.  Rapid cryopreservation of five mammalian and one mosquito cell line at -80°C while attached to flasks in a serum free cryopreservative 
Cell culturing, and the requisite storage of cell lines at ultra-low temperatures, is used in most laboratories studying or using eukaryotic proteomics, genomics, microarray, and RNA technologies. In this study we have observed that A72(dog), CRFK(cat), NB324K(human), MCF7(human), WI38(human), and C636(mosquito) cells were effectively cryopreserved at -80°C while attached to the substratum of 25cm2 tissue culture flasks. This was accomplished using a serum free crypreservative recently developed by Corsini and co-workers. The technique allows for significant savings of time and money in laboratories that rapidly process numerous cell lines.
PMCID: PMC1190376  PMID: 16136221
Cryopreservation; Culture Media, Serum-Free; Cells, Cultured
41.  Synthesis, Purification and Crystallization of Guanine-rich RNA Oligonucleotides 
Guanine-rich RNA oligonucleotides display many novel structural motifs in recent crystal structures. Here we describe the procedures of the chemical synthesis and the purification of such RNA molecules that are suitable for X-ray crystallographic studies. Modifications of the previous purification methods allow us to obtain better yields in shorter time. We also provide 24 screening conditions that are very effective in crystallization of the guanine-rich RNA oligonucleotides. Optimal crystallization conditions are usually achieved by adjustment of the concentration of the metal ions and pH of the buffer. Crystals obtained by this method usually diffract to high resolution.
PMCID: PMC531606  PMID: 15562298
Isolation and Purification; Crystallization; Oligonucleotides
42.  The Use of Antisense Oligonucleotides in Evaluating Survivin as a Therapeutic Target for Radiation Sensitization in Lung Cancer 
Elucidating the mechanism of over and under expression of proteins is critical in developing a better understanding of cancer. Multiple techniques are used to examine differential expression of proteins in cells and assess changes in protein expression in response to therapies such as radiation. Reduced expression can be caused by protein inactivation, mRNA instability, or reduced transcription. The following protocol was used to determine the mechanism for the reduced expression of an antiapoptotic factor, survivin, in normal tissues in response to radiation and the defect in cancer cells that prevents this reduction. We also examined ways to overcome survivin over expression in cancer cells in order to sensitize them to radiation. We will focus on the use of antisense oligonucleotides, cell cycle analysis, and luciferase reporter genes.
PMCID: PMC524213  PMID: 15514699
Survivin; Antisense oligonucleotides; Luciferase
43.  Serum-Free Cryopreservation of Five Mammalian Cell Lines in Either a Pelleted or Suspended State 
Herein we have explored two practical aspects of cryopreserving cultured mammalian cells during routine laboratory maintenance. First, we have examined the possibility of using a serum-free, hence more affordable, cryopreservative. Using five mammalian lines (Crandell Feline Kidney, MCF7, A72, WI 38 and NB324K), we found that the serum-free alternative preserves nearly as efficiently as the serum-containing preservatives. Second, we compared cryostorage of those cells in suspended versus a pellet form using both aforementioned cryopreservatives. Under our conditions, cells were in general recovered equally well in a suspended versus a pellet form.
PMCID: PMC389905  PMID: 15103400
Cryopreservation; Cells, Cultured; Culture Media, Serum-Free
44.  Experimental modulation of capsule size in Cryptococcus neoformans  
Experimental modulation of capsule size is an important technique for the study of the virulence of the encapsulated pathogen Cryptococcus neoformans. In this paper, we summarize the techniques available for experimental modulation of capsule size in this yeast and describe improved methods to induce capsule size changes. The response of the yeast to the various stimuli is highly dependent on the cryptococcal strain. A high CO2 atmosphere and a low iron concentration have been used classically to increase capsule size. Unfortunately, these stimuli are not reliable for inducing capsular enlargement in all strains. Recently we have identified new and simpler conditions for inducing capsule enlargement that consistently elicited this effect. Specifically, we noted that mammalian serum or diluted Sabouraud broth in MOPS buffer pH 7.3 efficiently induced capsule growth. Media that slowed the growth rate of the yeast correlated with an increase in capsule size. Finally, we summarize the most commonly used media that induce capsule growth in C. neoformans.
PMCID: PMC389900  PMID: 15103395
Cryptococcus neoformans; Infection; Virulence
45.  A screen to identify drug resistant variants to target-directed anti-cancer agents 
The discovery of oncogenes and signal transduction pathways important for mitogenesis has triggered the development of target-specific small molecule anti-cancer compounds. As exemplified by imatinib (Gleevec), a specific inhibitor of the Chronic Myeloid Leukemia (CML)-associated Bcr-Abl kinase, these agents promise impressive activity in clinical trials, with low levels of clinical toxicity. However, such therapy is susceptible to the emergence of drug resistance due to amino acid substitutions in the target protein. Defining the spectrum of such mutations is important for patient monitoring and the design of next-generation inhibitors. Using imatinib and BCR/ABL as a paradigm for a drug-target pair, we recently reported a retroviral vector-based screening strategy to identify the spectrum of resistance-conferring mutations. Here we provide a detailed methodology for the screen, which can be generally applied to any drug-target pair.
PMCID: PMC248481  PMID: 14615817
Genes, ABL; Chronic myeloid leukemia; Drug resistance
46.  Enhancement of anti-murine colon cancer immunity by fusion of a SARS fragment to a low-immunogenic carcinoembryonic antigen 
It is widely understood that tumor cells express tumor-associated antigens (TAAs), of which many are usually in low immunogenicity; for example, carcinoembryonic antigen (CEA) is specifically expressed on human colon cancer cells and is viewed as a low-immunogenic TAA. How to activate host immunity against specific TAAs and to suppress tumor growth therefore becomes important in cancer therapy development.
To enhance the immune efficiency of CEA in mice that received, we fused a partial CEA gene with exogenous SARS-CoV fragments. Oral vaccination of an attenuated Salmonella typhimurium strain transformed with plasmids encoding CEA-SARS-CoV fusion gene into BALB/c mice elicited significant increases in TNF-α and IL-10 in the serum. In addition, a smaller tumor volume was observed in CT26/CEA-bearing mice who received CEA-SARS-CoV gene therapy in comparison with those administered CEA alone.
The administration of fusing CEA-SARS-CoV fragments may provide a promising strategy for strengthening the anti-tumor efficacy against low-immunogenic endogenous tumor antigens.
PMCID: PMC3298716  PMID: 22304896
immunotherapy; tumor-derived peptide; tumor vaccine; low-immunogenicity
47.  A method for non-invasive genotyping of APCmin/+ mice using fecal samples 
The APCmin/+ mouse is commonly used in cancer research and is just one of many genetically altered models that is currently being developed. With high numbers of breeding programs, it is important to have a simple method that can be used to genotype the mice non-invasively. Here we report a reproducible method for genotyping mice with DNA extracted from fecal samples. Comparison of fecal results with those obtained from intestinal tissue DNA and clinical outcome (presence/absence of tumors) showed this technique to have 100% accuracy. This non-invasive method of genotyping may be applied to other transgenic mouse models.
PMCID: PMC3293049  PMID: 22284906
APCmin/+; feces; genotyping; cancer; non-invasive
48.  Gene-targeted embryonic stem cells: real-time PCR assay for estimation of the number of neomycin selection cassettes 
In the preparation of transgenic murine ES cells it is important to verify the construct has a single insertion, because an ectopic neomycin phosphortransferase positive selection cassette (NEO) may cause a position effect. During a recent work, where a knockin SCA28 mouse was prepared, we developed two assays based on Real-Time PCR using both SYBR Green and specific minor groove binder (MGB) probes to evaluate the copies of NEO using the comparative delta-delta Ct method versus the Rpp30 reference gene.
We compared the results from Southern blot, routinely used to quantify NEO copies, with the two Real-Time PCR assays. Twenty-two clones containing the single NEO copy showed values of 0.98 ± 0.24 (mean ± 2 S.D.), and were clearly distinguishable from clones with two or more NEO copies.
This method was found to be useful, easy, sensitive and fast and could substitute for the widely used, but laborious Southern blot method.
PMCID: PMC3226651  PMID: 22035318
49.  An automated cell-counting algorithm for fluorescently-stained cells in migration assays 
A cell-counting algorithm, developed in Matlab®, was created to efficiently count migrated fluorescently-stained cells on membranes from migration assays. At each concentration of cells used (10,000, and 100,000 cells), images were acquired at 2.5 ×, 5 ×, and 10 × objective magnifications. Automated cell counts strongly correlated to manual counts (r2 = 0.99, P < 0.0001 for a total of 47 images), with no difference in the measurements between methods under all conditions. We conclude that our automated method is accurate, more efficient, and void of variability and potential observer bias normally associated with manual counting.
PMCID: PMC3214125  PMID: 22011343
automated cell counting; threshold; migration assays; manual cell counting
50.  Rapid generation of long tandem DNA repeat arrays by homologous recombination in yeast to study their function in mammalian genomes 
We describe here a method to rapidly convert any desirable DNA fragment, as small as 100 bp, into long tandem DNA arrays up to 140 kb in size that are inserted into a microbe vector. This method includes rolling-circle phi29 amplification (RCA) of the sequence in vitro and assembly of the RCA products in vivo by homologous recombination in the yeast Saccharomyces cerevisiae. The method was successfully used for a functional analysis of centromeric and pericentromeric repeats and construction of new vehicles for gene delivery to mammalian cells. The method may have general application in elucidating the role of tandem repeats in chromosome organization and dynamics. Each cycle of the protocol takes ~ two weeks to complete.
PMCID: PMC3200152  PMID: 21982381

Results 26-50 (227)