[Histonet] Frozen IF Specimen Storage: Is -80 C really necessary; will -20 C work?

[Tony Henwood (SCHN)]

The following (from "The Book" - that may never be published!):

It is also important to remember that -20oC is not suitable for storing frozen tissue. Have you ever noticed that meat stored too long in the freezer suffers "freezer-burn"; it appears dried-out? The condition is primarily caused by sublimation. Water evaporates at all temperatures, even from the surface of solid ice. If air adjacent to ice is cold enough (so the ice won't melt) and the air is dry enough, water molecules go directly from solid phase (ice) to gaseous phase (vapour) without going through a liquid phase. When the constantly vibrating water molecules in foods stored in a freezer migrate to the surface, crystals of ice outside of the solid food are formed, and some water molecules escape into the air (by sublimation). The meat parts now deprived of moisture become dry and shrivelled and look burnt. In meats, air can cause fats to oxidize.

Frost-free freezers are the result of having a fan and air circulation inside the freezer. The sub-zero temperature combined with the air circulation that keeps the air arid significantly accelerates the sublimation process. This keeps freezer walls and shelves free of ice, although ice-cubes will continually sublimate.

Regards 
Tony Henwood JP, MSc, BAppSc, GradDipSysAnalys, CT(ASC), FFSc(RCPA) 
Laboratory Manager & Senior Scientist, the Children's Hospital at Westmead
Adjunct Fellow, School of Medicine, University of Western Sydney 

Tel: 612 9845 3306 
Fax: 612 9845 3318 
Pathology Department
the children's hospital at westmead
Cnr Hawkesbury Road and Hainsworth Street, Westmead
Locked Bag 4001, Westmead NSW 2145, AUSTRALIA 

-----Original Message-----
From: histonet-bounces <@t> lists.utsouthwestern.edu [mailto:histonet-bounces <@t> lists.utsouthwestern.edu] On Behalf Of Rene J Buesa
Sent: Tuesday, 12 November 2013 3:09 AM
To: DAVID HENDERSON; histonet <@t> lists.utsouthwestern.edu
Subject: Re: [Histonet] Frozen IF Specimen Storage: Is -80 C really necessary; will -20 C work?

I really do not know of any study comparing -20ºC vs -80ºC or if this -80ºC is the result of a commercially driven  "ideal" storage method. I advise you to check about any bibliographic references BUT meanwhile I also advise you to keep your precious and irreplaceable material at -80ºC. I do not think that you should risk losing all your samples just to work "on the cheap". 
I always kept my tumor bank and IF samples at -80ºC and when our freezer also died year ago, I was lucky enough to get the approval to buy a new one.
 Do not rush to save money
René J.


________________________________
From: DAVID HENDERSON <dhenders01 <@t> msn.com>
To: "histonet <@t> lists.utsouthwestern.edu" <histonet <@t> lists.utsouthwestern.edu> 
Sent: Sunday, November 10, 2013 6:56 PM
Subject: [Histonet] Frozen IF Specimen Storage: Is -80 C really necessary; will -20 C work?


We routinely store our frozen IF specimens (renal and skin biopsies) embedded in OCT and sealed in plastic bags for at least 4 yrs in a -80C freezer. Cases that are positively diagnosed by the pathologist, are used as positive controls for subsequent IF staining. In practice, most positive controls are used within 1-2 years of their original storage.

Our -80C freezer has died, and we are temporarily storing in a different -80C freezer in another building on campus. My supervisor asked me to research whether or not a -20C freezer will suffice for our storage needs, or must we anti up for the much more costly -80C replacement or repair. 

I would appreciate receiving suggestions backed by experience, or educated thoughts about the advisability of -20C storage of specimens for future IF staining.

Thanks,
David Henderson, HTL
RML, Tulsa, OK

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