Is it possible that your flurochrome is self-shading?  Also, with DIC or
any other method you are likely to see less useful detail deeper into a
cell, than at the surface, because of the buildup of background
out-of-focus detail compared to the surface.  Unless a clearing agent is
used, this will just be a matter of thickness of the sample.  Birefringent
starch grains are of course a nuisance to any polarization based imaging,
like DIC.

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*       Anthony Moss                    voice  (334)844-9257            *
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On Mon, 11 May 1998, Jette Wendt-Larsen wrote:

> Dear confocalists,
> When I scan spherical (diam. 10 um) cell along the z-axis
> the intensity and sharpness decreases in the lower z-planes
> and often the bottom part is not visible at all. This has
> happened with several fluorocromes and independent of the
> distance of the cell to the coverslip. The same is seen when
> more flattened cells (5 um thick) are imaged.
>   The decrease appears as soon as the equator of the cell is
> passed and becomes more prominent with z.
>   The blurring is also seen when I use Nomarski in brightfield.
>   The cells contain big starch grains, which are birefringent
> structures and not labelled.
>   To me it does not look like an effect of refractive index
> mismatch between immersion oil-water medium, but perhaps between
> immersion oil-starch.
>   Any help will be very appreciated since 3-D imaging of whole
> cells is twice as informative than of half cells!
>
>                           Best regards Jette
>