X-Message-Number: 15362
Date: Wed, 17 Jan 2001 05:14:18 -0800 (PST)
From: Doug Skrecky <>
Subject: PEG greatly increases oocyte survival

Title
  Vitrification of mature mouse oocytes: improved results following addition of
  polyethylene glycol to a dimethyl sulfoxide solution.
Source
  Cryobiology.  34(3):295-301, 1997 May.
Abstract
  Oocytes have been successfully cryopreserved using rapid and slow freezing
  procedures; however, variability in the success of replicates has limited its
  practical application. We have evaluated the potentially beneficial effects
  of adding 1 mg/ml of the polymer polyethylene glycol (PEG)
  (M(r) 8000) to a 6 M dimethyl sulfoxide (Me2SO) vitrification solution.
  Stepwise addition of cryoprotectant, either with or without
  PEG, was performed at room temperature (19-21 degrees C).
  Oocytes were then loaded in plastic insemination straws and held in liquid
  nitrogen vapour at -140 degrees C for 3 min prior to storage in liquid
  nitrogen. Oocytes were warmed rapidly to room temperature and removal of
  cryoprotective agent was effected in the presence of 1 M sucrose solution.
  Viability was assessed by vitro fertilization. Oocytes cryopreserved after
  exposure to 6 M Me2SO in the absence of PEG showed 60%
  normality, 80% fertilization, and 55% development to blastocyst, median of 11
  replicate experiments (191 oocytes). Individual replicates yield highly
  variable survival which ranged from 0 to 100%. The addition of
  PEG significantly improved oocyte normality to 95% (range
  76-100%; median of 9 replicate experiments, 301 oocytes). Rates of
  fertilization (91%; 60-100%) and development of blastocyst (73%; 67-92) were
  also improved. The addition of 1 mg/ml PEG to a 6 M Me2SO
  solution resulted in greatly improved viability of oocytes following
  cryopreservation and vastly reduced the variability seen
  with Me2SO solution alone.

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