X-Message-Number: 12283
Date: Thu, 19 Aug 1999 08:48:05 -0700 (PDT)
From: Doug Skrecky <>
Subject: vitrification with ethylene glycol

  Sommerfeld V.  Niemann H.
  Department of Biotechnology, Institut fur Tierzucht und Tierverhalten, (FAL)
  Mariensee, Neustadt, 31535, Germany.
  Cryopreservation of bovine in vitro produced embryos using ethylene glycol in
  controlled freezing or vitrification.
  Cryobiology.  38(2):95-105, 1999 Mar.
  In this study, the cryoprotectant ethylene glycol (EG) was tested for its
  ability to improve and facilitate the cryopreservation of in vitro produced
  (IVP) bovine embryos. Embryos were cryopreserved in EG solutions supplemented
  with either newborn calf serum (NBCS) or polyvinyl alcohol (PVA). To assess
  EG toxicity, the embryos were equilibrated in EG concentrations from 1.8 to
  8.9 M at room temperature for 10 min and then cultured for 72 h on a cumulus
  cell monolayer. The hatching rate was highest for day 7 blastocysts frozen in
  3.6 M EG (98%) and was not different from the control group (85%). The
  controlled freezing (0.3 degrees C/min to -35 degrees C) of expanded day 7
  blastocysts resulted in a hatching rate of 81%, which was similar to that of
  the nonfrozen controls (76%). Differential staining revealed only very few
  degenerate blastomeres attributed to freezing and thawing. Upon direct
  nonsurgical transfer of day 7 expanded blastocysts frozen in 3.6 M EG, a
  pregnancy rate of 43% was achieved, while the pregnancy rate after transfer
  of other developmental stages was significantly lower (22% with expanded day
  8 blastocysts). When bovine IVP embryos were incubated at room temperature in
  7.2 M EG preceded by preequilibration in 3.6 M EG, the hatching rate of day 7
  expanded blastocysts reached 93%. Upon vitrification of IVP
  day 7 and day 8 blastocysts and expanded blastocysts in 7.2 M EG, the latter
  showed a higher hatching rate (42%) than blastocysts (12%). Overall, PVA as
  supplement to the basic freezing solution instead of NBCS had deleterious
  effects on survival after controlled freezing or
  vitrification. The simple cryopreservation protocol employed
  in this study and the low toxicity of ethylene glycol highlight the
  usefulness of this approach for controlled freezing of IVP embryos. However,
  further experiments are needed to improve the pregnancy rate following embryo
  transfer and to enhance survival after vitrification.
  Copyright 1999 Academic Press.

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