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Just to add a few penn'orth to the many helpful responses already
posted ....

There are two types of lens you might consider.  A dipping lens
is low cost and designed to work in saline solutions (typically
they have ceramic bodies) so it shouldn't be worrried by your
hyper-saline conditions, though it won't be optically corrected
for it.  Working distance is typically long, so with no
coverslip the possibility of moving your cells is always there,
though you are unlikely to squish them.

The expensive confocal water-immersion lenses are designed
for pure water not saline but since they use a coverslip
the lens doesn't come into contact with your culture medium.
So with ordinary care there is no risk to the lens. These
lenses have a correction collar so you can compensate for
your salt solution by using a very thin (0 or 00) coverslip
and setting the collar (by trial and error)to a thicker
value.   Usually these have a longer working distance than
oil lenses of similar power so, along with the lower
viscosity of water, your problems of cell squish should
be reduced.  A gasket of thin paper or plastic film, standing
the coverslip off the slide by a few microns, could also
help with this.

                                        Guy


>         We have a user who wishes to image some archebacteria which grow
> in clusters up to 100 microns in diameter.  One question is:  do
> the cells and the spaces between them change in character and
> chemical composition from the outside to the inner parts of the
> cluster.  Thus we need to use an ion probe and take Z-series, but
> the problem is that the clusters are very "squishy" and any
> movement of the standard oil-immersion 60x lens on the coverslip
> causes the shape of even 15um diameter clusters (smaller than the
> coverslip-to-slide distance) to distort.  It appears that the
> rapid Z-step of the lens cause a pressure pulse in the fluid, and
> thus accurate 3D reconstruction is difficult.
>         My question is, would a water immersion lens produce the same
> effects?  I've never used one and it is an expensive item to buy -
> the medium is a fairly concentrated salt solution so Olympus might
> not be too happy about a trial!  Also we may want to vary the
> medium, so can the effects of altered refractive index be
> compensated for?
>         Thanks, Ian.
>
> ---Dr. I.E.G.Morrison       [log in to unmask]
>    Dept.Biological Sciences, University of Essex
>    Wivenhoe Park, Colchester, Essex CO4 3SQ
> ---Tel: 01206-872246           Fax: 01206-872592---
>


--
Associate Professor Guy Cox
Electron Microscope Unit,
University of Sydney,
NSW 2006, Australia

Phone:+61 2 9351 3176    Fax:+61 2 9351 7682
http://www.guycox.net