Hi Vanessa,

There are probably two causes of this: 1) the freeze spray is probably doing more harm than good.  The blocks will end up too cold and will be very hard, causing difficulties.  Ideal sectioning temperature varies with the tissue, but is generally somewhere around -20 C.  If you freeze in Liq NO2, then you must alolow the tissue to stabilise to ambient cryostat temp. before sectioning.  2) Inadequate adhesion of the tissue / embedding medium to the block.  This will cause 'chatters', chunks out of block, poor quality sections, the list goes on...  This is a difficult one to get around when it becomes a problem.  We generally put some OCT on a warm chuck, freeze this to get a flat surface, the freeze the tissue with some more OCT onto this.

My two cents worth, anyway.

Best of luck,
Aidan
New Zealand

_____________________________________
a i d a n   c   s c h u r r
 section head, histology
  department of pathology
hutt valley health
high street, lower hutt
wellington
new zealand
telephone ++64 4 5709173
facsimile ++64 4 5709214

>>> Vanessa Heim <heimvk@bu.edu> 1:19:42 a.m. Friday, 8 December 2000 >>>
Thank you to everyone that has repsonded to my problem of sections
falling off the slides during staining.  I actually have another problem
that I have been encountering quite frequently...I seem to have trouble
consistently getting great sections.  Some days the sections are
beautiful and otherdays I destroy the tissue block just trying to get a
few good sections.  We are using a cryostat machine now and was
wondering if anyone had some advice for me on this issue.  I have tried
changing the angle of the knife, I have changed the blade on several
occasions..I even freeze the tissue before sectioning and use a freeze
spray during the procedure to keep the sample cool.  Is there a special
way to freeze the samples before cutting or protocols available
specifically for processing/freezing tissues specifically for the
cryostat???  I have looked online and haven't come up with anything too
substaintial.  Like I said earlier this is all  new to me so any help
would be greatly appreciated.


Vanessa Heim
Boston University Medical Center
Research-Dept Urology/Surgery
Boston VA Hospital
Boston, MA  02130