X-Message-Number: 9518
Date: Sat, 18 Apr 1998 21:46:39 -0700 (PDT)
From: Doug Skrecky <>
Subject: fractures in cryopreserved arteries

uthors
  Pegg DE.  Wusteman MC.  Boylan S.
Institution
  Biology Department, University of York, United Kingdom.
Title
  Fractures in cryopreserved elastic arteries.
Source
  Cryobiology.  34(2):183-92, 1997 Mar.
Abstract
  The aim of this study was to define the conditions under which macroscopic
  fractures occur in vascular tissue during cryopreservation and to develop a
  practical cryopreservation method that prevents fracturing. The common
  carotid artery of the rabbit was subjected to a cryopreservation process that
  has been optimised for retention of in vitro function and cytological
  structure. This involves the stepwise addition and subsequent removal of
  dimethyl sulfoxide using a calculated protocol that avoids osmotic injury and
  minimises toxic action, controlled cooling, storage at -180 degrees C, and
  rapid warming. Seventy-five percent of such arteries were grossly fractured.
  The cooling and warming conditions were systematically varied to determine
  when in the cooling/storage/warming process the fractures occurred.
  Differential scanning calorimetry was then used to identify any corresponding
  thermal events. It was found that the fractures occurred as the temperature
  range -150 to -100 degrees C was traversed during the warming phase of the
  process. The glass transition temperature of a maximally freeze-concentrated
  solution of the cryoprotectant used was found to be -123 degrees C. Reducing
  the warming rate between the storage temperature (-180 degrees C) and -100
  degrees C to < 50 degrees C/min prevented the fractures. Subsequent thawing
  could then be carried out rapidly in a 37 degrees C water bath without risk
  of fracture. We suggest that the fractures probably result from the thermal
  stresses created by rapid warming of the vitreous material that is produced
  by freeze-concentration of the aqueous phase. Relatively slow warming to -100
  degrees C, at which temperature the vitreous material has softened, reduces
  these stresses and avoids the fractures.

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