The Microscale Life Sciences Center desires an automated count of fluorescing live/dead biological cells from images obtained via microscopy. Various cell counting procedures were explored in the literature. Four methods were tried: threshold segmentation, watershed segmentation, crosscorrelation, and a threshold “real-time” cross-correlation hybrid. The threshold technique produced the best re...

The capacity to distinguish between living and dead cells is an important, but often unrealized, attribute of rapid detection methods for foodborne pathogens. In this study, the numbers of enterohemorrhagic Escherichia coli O157:H7 after inoculation onto Romaine lettuce plants and on plastic (abiotic) surfaces were measured over time by culturing, and quantitative PCR (qPCR), propidium monoazid...

Vitrifying oocytes is a potentially valuable means of preserving the female germ line, but significantly compromises oocyte developmental competence. This study examined the hypothesis that the cumulus complex protects the oocyte during vitrification. Vitrified-warmed immature cumulus oocyte complexes (COCs) were labelled with a plasma membrane impermeant DNA marker (ethidium homodimer-1) to ex...

In this study we evaluated the effect of chitosan nanoparticles on the acid tolerance response (ATR) of adhered Streptococcus mutans. An ATR was induced by exposing S. mutans to pH 5.5 for 2 h and confirmed by exposing the acid-adapted cells to pH 3.5 for 30 min, with the majority of cells appearing viable according to the LIVE/DEAD® technique. However, when chitosan nanoparticles were present ...

Standard measurements of free thiol on cell surfaces use the uptake of thiol-reactive substances which are incapable of traversing the membrane (reviewed in [l]). One problem is that dead cells are incapable of excluding such reagents, so that there is a risk of systematically high bias in the results, especially in delicate cells from patients. For example, one group showed a 3OOO% increase in...

BACKGROUND Conventional acid-fast bacilli (AFB) staining cannot differentiate viable from dead cells. Propidium monoazide (PMA) is a photoreactive DNA-binding dye that inhibits PCR amplification by DNA modification. We evaluated whether PMA real-time PCR is suitable for the early detection of viable Mycobacterium tuberculosis (MTB) in clinical respiratory specimens. METHODS A total of 15 dilu...