Re:Death by light (Score 2, Informative)

Until June, I had been working in a live-cell imaging laboratory for nearly four years. There's a whole list of criteria that will cell proliferation while being grown on a microscope. My lab had (before I arrived) already proven they could grow cells on a microscope stage that would match cells grown in an incubator (ie, number of mitotic events). These like this are important.

A few people have mentioned bits about imaging and I thought I'd kind of list the important ones:

• 'Normal' brightfield
• Phase-Contrast
• Confocal
• DIC, AFM, and others

'Normal' brightfield microscopes are the kind that you'll find in a high school classroom. They work because the sample absorbs light. When they talk about fixing and staining cells, you can use these. Usually cells are transparent and won't attenuate light as it passes through the cell.

Confocal works by exciting a fluorophor with a laser and measuring the emitted photons. Its neat. But you're pointing a laser at a cell.

DIC, AFM and others work on varied principles. AFM is atomic force. They basically poke a cell and measure how it pushes back. But you're poking a cell. DIC are light based but as far as I have seen not extremely popular in the field of live cell imaging for one reason or another.

Phase-Contrast I left till last as its really the only microscope that can be used for live-cell imaging. It works by measuring not how much the light is attenutated, but how much its slowed as it passes through the cell. Basically, a small fraction of light is slowed and difracted as it passes through the sample. The light that passes through unaffected is attenuated after the sample so it and the two groups have approximately the same intensity. Then normal interference will give an image on the detector.

As usual for science articles, it got most of the details wrong. We've had phase-contrast microscopes for over 50 years now. Zernike got the Nobel Prize for inventing them in 1953 http://nobelprize.org/educational_games/physics/mi croscopes/phase/index.html We can use these to measure living cells. We could do drug screening. Nothing the article said was really new and frankly it was rather irritating.

What is exciting though is the fact that this might allow the machine vision guys to be able to reliably segment live-cell image data. Currently this is a problem with no *acceptable* solution. [By acceptable I mean to say, something that has an accuracy over 90-95% for any cell line I give it as well as not using anything like a nuclear stain] Once we get this level of segmentation there is an unlimited number of things we can do:

• Personalized drug screening: Part of your tumor is checked against as many as 96 drug coctail combinations. You get the one that works best. Not the one that works best for 60% of people in a study
• Determining a patients response to radiation. For some cancers, about 50% of people need radiation AND chemotherapy. Chemotherapy can be cancerous (ironic, no?) The 50% of people that DON'T need chemo, still get chemo cause we can't predict if they need it or not, and seeing as the only to find out is to let them get cancer again...
• Primary research in the area of whole-cell systems would grow enormously. Current studies include numbers like 20-30 cells. Your average live-cell experiment will capture as many as 200 to 400 cells. And thats a small one.