wierd cell culture contam

Manuel Maria SIMON Simon at mail.boku.ac.at
Mon Apr 3 10:37:22 EST 1995

> C.J. Hussussian, MD (cjh at nchgr.nih.gov) wrote:
> : I am having a persistant and frustrating contamination problem with my
> : tissue culture. I am doing double transfections in MELANOMA cell lines
> : grown in DMEM. It seems that after a couple of weeks (the timing is
> : random), I begin to see black dots in the medium. 
> Hmmmm...My guess is that your melanoma cells are producing melanin.  
> Melanocytes, as you probably know, generate the pigment that contributes 
> to those nice tans so rarely seen this time of year in Boston.  Melanoma 
> cells often turn media black.  Good Luck! --

We also had sort of a problem with a black sort of black spots. They 
always apeared after a two to three weeks period of culture. 
The spots apparently came slower than the cells, one could wash 
them away with PBS but after some weeks they appeared again.
Of course fungizides were applied but did not help. One possible explanation
is the glutamin precipitates giving rise to black grains. Also 
components of the serum could have been precipitated.
I would also check if the medium alone (or conditioned medium) 
contains the spots after some three weeks of incubation.

In our case neither the fresh medium nor conditioned medium (one week)
alone produced such strange effects, therefore we sipmly ignored it
and after a while the spots disappeard!

Manuel M. SIMON PhD
Center of Applied Genetics
Univ. BOKU Vienna

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