fuzzy balls in my culture! - Help (Jul/26/2008 )

I am growing adherent cells. I plated them in a 96 well plate to do proliferation assays using MTT. They all appear fine, happy and completly free of contamination.....media is clear and under the microscope the only thing I see is my happy little cells growing. However...I just had a horrifying moment when I added the MTT and came back a few hours to add the stop solution I noticed the color change was much darker than it should be. I looked under the microscope and saw my cells but also dark fuzzy balls!!!! What is it and where did it come from? Is it in my MTT? Is it in my culture and I just cant see it without the MTT???

Is it dark( purple) spindly stuff that you are seeing? That's just MTT binding to your cells.

Did you try doing a blank? ie. medium + MTT only (no cells). Is your MTT freshly prepared? Is it possible that your MTT is contaminated?