X-Message-Number: 12085
Date: Wed, 7 Jul 1999 23:53:27 -0700 (PDT)
From: Doug Skrecky <>
Subject: does cryonics need membrane stabilizers?

  De Leeuw FE.  De Leeuw AM.  Den Daas JH.  Colenbrander B.  Verkleij AJ.
  Department of Molecular Cell Biology, University of Utrecht, The Netherlands.
  Effects of various cryoprotective agents and
  membrane-stabilizing compounds on bull sperm
  membrane integrity after cooling and freezing.
  Cryobiology.  30(1):32-44, 1993 Feb.
  In this study attempts were made to improve the survival rates of bull
  spermatozoa after freezing/thawing and to clarify the importance of certain
  agents to the cryopreservation of spermatozoa. For that purpose the standard
  freezing extender was modified by the addition of different concentrations of
  various cryoprotectants and membrane-stabilizing agents:
  glycerol, 1,2-propanediol, polyvinylpyrrolidone, sucrose, egg yolk, lipid
  vesicles, and bovine serum albumin (BSA). Sperm membrane
  impermeability toward H33258 was employed as the parameter for sperm
  integrity during cooling and after freezing/thawing. Exclusion of glycerol
  from the extender did not significantly affect sperm integrity. Replacing 6%
  glycerol by 6% 1,2-propanediol resulted in reduced sperm survival, whereas
  replacement of glycerol by 62.5 mM sucrose slightly improved survival rates.
  Addition of 5 or 10% polyvinylpyrrolidone (either or not in combination with
  0.5 M sucrose) significantly reduced sperm integrity. Excluding egg yolk from
  the extender caused a serious decrease of sperm survival after both cooling
  and freezing. The cryoprotection offered by egg yolk could not be mimicked by
  dioleoylphosphatidylcholine (DOPC) vesicles or DOPC/phosphatidic
  acid/cholesterol vesicles in concentrations up to 29 or 9 mM, respectively.
  However, the freezing extender containing 6.5 mM DOPC vesicles in combination
  with 6% BSA yielded results which did not significantly differ from those
  obtained with the standard extender; higher vesicle concentrations combined
  with BSA might produce even better results. Further research on the
  cryopreservation of bovine spermatozoa should focus on
  membrane stabilization since the
  membrane-stabilizing compounds yield more promising results
  than the ice-preventing agents.

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