Biomedical subjects

Steve Kah Weng Oh

Publications and source records attributed to Steve Kah Weng Oh.

3 recordsLinked to original sources

PubMed2006

Establishing efficient siRNA knockdown in mouse embryonic stem cells.

FAM-labeled oligo dT (FAMdT) was utilized as a means to gauge efficient transfection of small nucleic acids into mouse embryonic stem cell (mESC) colonies. Using colonies grown overnight, transfection was restricted largely to the periphery of the colonies with only a 40% decrease in Oct-3/4 RNA transcript levels following cognate Oct-3/4, small interfering RNA (siRNA) delivery. However, transfection of mESC 4 h after seeding gave greater than 90% cells being successfully transfected based on quantitative real-time PCR detection of approximately 90% Oct-3/4 RNA transcript knockdown. This method provides an economical and efficient means by which to determine effective transfection conditions, and establish efficient siRNA knockdown of reportedly difficult to transfect cell lines such as mESC.

Animals↗

PubMed2005

Perfusion cultures of human embryonic stem cells.

Human embryonic stem cells (hESC) are self-renewing pluripotent cells capable of differentiating into cells representative of all three embryonic germ layers. Hence, they hold great potential for regenerative medicine. However, significant cell numbers are required to fulfill their potential therapeutic applications. In this study, perfusion with supplemented conditioned media (SCM), produced by mouse embryonic fibroblasts (MEF), was adopted to improve cell densities of hESC cultures. Perfusion enhanced hESC numbers by 70% compared to static conditions, on both organ culture dish (OCD) and petri dish cultures. All cultures maintained healthy expression of the pluripotent marker, Oct-4 transcription factor. In vivo, perfused hESC formed teratomas in severe combined immunodeficiency (SCID) mice models that represent the three embryonic germ layers. When SCM was produced with lower concentrations of MEF, hESC densities and Oct-4 levels were reduced. Hence, perfusion with SCM is a potential feeding method for scale-up production of hESC.

Animals↗

PubMed2005

Quantitative real-time polymerase chain reaction for determination of plasmid copy number in bacteria.

A method for determination of plasmid copy number (PCN) in bacteria by real-time quantitative polymerase chain reaction (QPCR) was developed as an alternative to current PCN assays. Conventional methods for PCN estimation are generally not of high throughput, laborious, have low reproducibility, require large amounts of biological samples and are applicable only for a narrow dynamic range. Real-time QPCR, using the ABI Prism 7000, was able to sensitively detect the quantity of the pUC ori based plasmid, NS3, transformed into Escherichia coli host, DH5alpha, to be 411+/-6.1. The PCN of pBR322 plasmid DNA in DH5alpha was estimated to be 40+/-0.6 which is within its previously reported PCN range of approximately 30 to 70. QPCR was found to show good reproducibility and high sensitivity in detecting a two fold difference in template concentration, and a wide linear dynamic range covering 0.5 pg to 50 ng of DNA. PCNs of DH5alpha bearing plasmids pBR322 and NS3 computed from real-time QPCR assay were validated by that of agarose gel assay, and a marginal difference of only 13.0% and 10.7% was found for the two plasmids respectively. The QPCR assay was able to detect changes in PCN of plasmid producing DH5alpha during the course of a 2 l batch fermentation.

Culture Media↗