X-Message-Number: 12847
Date: Fri, 26 Nov 1999 08:40:43 -0800 (PST)
From: Doug Skrecky <>
Subject: egg yolk helps prevent membrane damage

Authors
  Alvarez JG.  Storey BT.
Institution
  Department of Obstetrics and Gynecology, University of Pennsylvania Medical
  Center, Philadelphia 19104-6080.
Title
  Evidence that membrane
  stress contributes more than lipid
  peroxidation to sublethal cryodamage in cryopreserved human sperm: glycerol
  and other polyols as sole cryoprotectant.
Source
  Journal of Andrology.  14(3):199-209, 1993 May-Jun.
Abstract
  One effect of cryopreservation on human sperm is sublethal cryodamage, in
  which cell viability post-thaw is lost more rapidly at later times than in
  fresh cells. We hypothesized two modes of sublethal cryodamage: one is
  peroxidation-related involving plasma membrane damage due to
  lipid peroxidation; the other is membrane
  stress-related involving membrane
  embrittlement during phase transitions occurring during freeze-thaw. If the
  peroxidation-related mode contributed substantially to sublethal cryodamage,
  the hypothesis predicts that lipid peroxidation inhibitors
  should reduce this damage. To test this prediction, we examined the effect of
  the lipid peroxidation inhibitors, hypotaurine, bovine serum albumin (BSA),
  and alpha-tocopherol (Vit. E) on the time to loss of motility (TLM), taken as
  a measure of cell viability over time, for sperm samples cryopreserved in
  glycerol plus egg yolk medium. These agents had no effect on TLM of these
  samples, indicating that this mode
  contributes little to sublethal cryodamage. If the
  membrane stress-related mode contributed,
  the hypothesis predicts rapid recovery of motility in the presence of egg
  yolk plus glycerol, but slow recovery in the presence of glycerol alone. It
  also predicts that an appropriate polyol may be both
  necessary and sufficient for cryopreservation. In the presence of egg yolk
  plus glycerol, motility recovery was complete within 5 minutes, but the
  percent motile cells then decreased linearly with time. With glycerol alone
  in the range 3-12%, at 5 minutes post-thaw the percent motile cells was
  5-10%, but by 40 minutes post-thaw had risen to 60-80%, approaching
  that in the fresh sample, and was maintained up to 4 hours.
  In the absence of glycerol, the percentage of motile cells post-thaw was nil
  and remained nil up to 4 hours. The polyols, erythritol, ribitol, and
  sorbitol had similar effects to that of glycerol, but the
  recovery of motility was not as complete. These results indicate
  that the membrane
  stress-related mode contributes
  substantially to sublethal cryodamage. They also indicate
  that glycerol and other polyols can function alone as
  cryoprotectants, but that recovery of motility is slow in
  these systems.

  (Note: Higher molecular weight polyols are much more likely
         to induce osmotic membrane disruption than glycerol,
         if the polyol is added rapidly.)

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