cell death in plates

[Thomas Kreuzer]

Hello fellow netters,

I have been faced with a problem recently , for which I can find no solution 
altough it may be trivial.
I seed HeLa - cells on standard 6-well cell culture plates (Costar) in 1 ml
DMEM plus 5 % FCS , let them attach to the bottom overnight and then change 
the medium according to the tests I want to perform afterwards. I have noticed 
for some time that the cells in certain wells show a different behaviour than 
the others. For example: If I number the wells from left to right 1 to 3 in 
the upper row and 4 to 6 in the lower , the cells in number 4 are always more 
difficult to get off the bottom of the well with trypsin. First I thought it 
might be a handling problem during the tests , but last time I decided to let 
the cells grow for one additional day on the plate before the test , so I did 
not change the medium after the first night , but left it for further 24 hours.
When I looked through the microscope afterwards , I noticed that the cells in 
wells 1,2,3 and 5 had grown well , while in number 4 and 6 most of the cells 
were dead , altough an equal amount of cells had been attached to the bottom 
after the first night in all wells. The conditions were the same for all 6 
wells.  
So my question is: has anybody noticed a similar effect or has some 
suggestions why this might happen ?

Thanks in advance,
Tom
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Tom Kreuzer
Institute for Biochemistry,K-F-University Graz,Halbaerthgasse 5,A-8010 Graz,Austria
thomas.kreuzer at kfunigraz.ac.at