Stephanie,

What do you mean by venetian blinds?  Do you mean your tissue is 
shattering horizontally as it comes across the knife?  If so, your 
cutting temperature is probably too cold.  This often occurs in my 
lab when graduate students come into section. I tell them to increase 
the temperature by increments of 2-3 degrees until the horizontal 
shattering stops.  This almost always cures the problem.  By the way, 
the type of fixative affects optimal cryosectioning temperature.  One 
student found a citation where the researchers added picric acid to 
their NBF.  This fixation did cure the problem she was having with 
her embryonic rat brain slices, but she had to raise the temperature 
at which she was cryosectioning to alleviate the horizontal 
shattering.

In general, brain tissue requires warmer cutting temperatures than 
other tissue.  In our lab, we cut most tissue at -20 C, but we cut 
brain tissue at around -16 C or warmer.

I hope this helps.

Karen
University of Oregon





>Stephanie,
>Was everything firmly locked into place? it sounds a bit like chattering
>rather than insufficient fixing, though of course, this is just my
>experience....
>
>Emma Carter
>Oxford BioMedica (UK)Ltd
>
>>  -----Original Message-----
>>  From:	Stephanie Moore
>>  Sent:	Friday, January 12, 2001 3:23 PM
>>  To:	HistoNet Server
>>  Subject:	"Venetian Blind" Artefact
>>
>>  I have recently experienced what I believe to be this artefact while
>>  slicing
>>  sections of squirrel brain.  I know that this was not properly sunk
>>  and also that
>>  it was likely in too little volume of paraformaldehyde (4%) fixative.
>>  The person
>>  who gave me the specimen is not very experienced, but wanted to slice
>>  it anyway.
>>  My question is, does insufficient cryoprotection from sucrose cause
>>  ventetian
>>  blinds?  I use a cryostat set at -20C chamber temperature and -18C
>>  object
>>  temperature, and Tussue Tek OCT medium for embedding the specimen.
>>