Re: [Histonet] Exploding skin samples

From:"Vinnie Della Speranza"

I'm inclined to agree with Ford. exploding sections have not been adequately infiltrated with paraffin. This could be due to water or fat that was not effectively removed during dehydration and clearing. 

One further note. On a processor that only has two paraffin stations, I encourage you to reduce the time in the first paraffin as it is almost always contaminated with xylene. the second paraffin is the important one in this scenario so you might consider using 15 or 20 minutes in the first paraffin and maybe 45 minutes in the second.

Lastly, Gayle is correct that alcohol should not follow xylene in your processing scheme. Your tissues must be infiltrated with xylene if you are to succeed in paraffin infiltration.

Vinnie Della Speranza
Manager for Anatomic Pathology Services
Medical University of South Carolina
165 Ashley Avenue  Suite 309
Charleston, SC 29425
Ph: 843-792-6353
fax: 843-792-8974

>>> "Ford Royer"  06/21/04 02:11PM >>>
It has been a loooong time since I did this, but what sticks in my mind 
is that tissue sections would "explode" in the water bath if they had 
not be dehydrated enough. i.e. Water was still present in the 
intracellular structures either from the original cytoplasm (tissue not 
completely fixed) or from the NBF.  Again if memory serves, we increased 
the times for the alcohol to make sure all of the water was out of the 
cells before bridging through xylene to paraffin.

....or do I have this all backwards?

~ Ford
Ford M. Royer, MT(ASC)
Former Lab Rat
Analytical Instruments, llc
Minneapolis, MN 55427
(800) 565-1895, Ext. 17

Gayle Callis wrote:

>I think your skin samples are overdehydrated and a different fixation would
>not improve anything.  How long did you fix with NBF?  If it is totally
>fixed, then you will have few problems since the skin is so thin.  If the
>skin is NOT totally fixed the alcohol will complete the job and you will
>have trouble cutting. 
>If the tissue is fixed completely before processing, mouse skin is thin!
>should be 100% with NBF for sure.  
>Start in 70%, 80%, 95% X 2, 100 X 2, xylene X 2, paraffin X 2. You can keep
>the same times or increase to 45 min each change.  
>Why are you doing alcohol xylene,, then alcohol again?  Normally, one goes
>to xylene changes and not back into alcohol, with the thin skin, water
>carryover is probably a nil factor. Personally, I would eliminate the
>xylene/alcohol, really not necessary and contributes to overdrying and
>hardening of tissue, you have far more absolutes in the end than you need.  
>Do you NOT use vacuum and pressure?  A dip and dunk situation?  
>Make sure your paraffin is NOT over 60C, and you could increase this to 45
>min, or put another paraffin in a hot oven and have a third change to make
>sure you have no xylene carryover into last paraffin. 
>also, keep temp of waterbath a bit cooler - not sure what paraffin you are
>using nor waterbath temp.  
> At 05:26 PM 6/21/2004 +0100, you wrote:
>>I have been given some mouse skin fixed in formalin (neutral buffered from
>>Sigma, equivalent to what we used to call 10% neutral buffered formalin). I
>>have tried several processes and even tried post fixing in Bouin's fluid as
>>suggested by a former colleague who did a lot of rat skin sections in a
>>previous job. They are spreading on the waterbath, especially around the fat
>>layer at the base of the dermis. It is important to us to get good sections
>>of these samples, can anyone suggest any other procedures I can try? My
>>process times were 30 minutes in 50, 60, 70, 80, 90., 100% ethanol, one
>>ethanol for 1 hour, 50:50 ethanol/xylene 30 mins, ethanol 30 mins, 2
>>xylenes 30 mins, 2 x paraffin for 30 mins, embed. I only have 2 wax baths on
>>my processor and have tried returning samples to wax for longer impregnation
>>times without success. 
>>I propose to try out a number of different fixatives such as formol alcohol,
>>methacarn, Bouin's as primary fixation and compare with NBF. Any suggestions
>>would be most gratefully received.
>>Thanks a lot
>>Margaret Blount
>>Chief Technician
>>Clinical Biochemistry
>>University of Cambridge
>>Addenbrooke's Hospital
>>Hills Road
>>CB2 2QR 
>>Histonet mailing list
>Gayle Callis
>Research Histopathology Supervisor
>Veterinary Molecular Biology 
>Montana State University - Bozeman
>PO Box 173610
>Bozeman MT 59717-3610
>406 994-6367 (lab with voice mail)
>406 994-4303 (FAX)
>Histonet mailing list
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