Pak Vet J, 2012,
Structural Changes in Cattle Immature Oocytes Subjected to Slow
Freezing and Vitrification
H. Wahid*, M. Thein1, E.A. El-Hafez2, M.O.
Abas3, K. Mohd Azam4, O. Fauziah5,
Y. Rosnina and H. Hajarian6
Faculty of Veterinary Medicine, Universiti Putra Malaysia, 43400
Serdang, Selangor, Malaysia; 1Department of Surgery and
Reproduction, Faculty of Veterinary Science, Yezin, Nay Pyi Taw,
of Veterinary Medicine, Assiut University, Egypt; 3Agro-Biotechnology
Institute, Ministry of Science, Technology and Innovation,
Aras 3-7, Blok C4, Parcel C, 62662 Putrajaya,
of Veterinary Medicine, Universiti Malaysia Kelantan,
Karung Berkunci 36, Pengkalan Chepa, 16100 Kota Bharu, Kelantan,
of Medicine and Health Sciences, Universiti Putra Malaysia, 43400
Serdang, Selangor, Malaysia; 6Department of Animal
Science, Faculty of Agriculture, Razi University, Iran.
This study was conducted to evaluate
the effect of different cryopreservation methods (slow-freezing and
vitrification) on structural changes of bovine immature oocytes.
Bovine ovaries were collected from
local abattoirs. Cumulus-oocyte-complexes (COCs) were retrieved using
aspiration method from 2-6 mm follicles. In Experiment 1, selected oocytes were
randomly divided into 4 treatment groups namely freezing solution-exposed,
frozen-thawed, vitrification solution-exposed and vitrified-thawed and then
oocytes abnormalities were examined under a stereomicroscope.
In Experiment 2, oocytes were randomly allocated to the same grouping as
experiment 1 plus control group. Following freezing or vitrification, all
fixed in glutaraldehyde
and processed for transmission electron microscopy. In experiment 1, there was a
higher incidence of abnormalities in the frozen-thawed and vitrified-warmed
oocytes compared to those in freezing solution and vitrification
solution-exposed groups (P<0.05). In experiment 2, there were marked alterations
in the perivitelline space, microvilli and vesicles of frozen-thawed and
vitrified-warmed oocytes characterized by loss of elasticity and integrity of
cytoplasmic processes and microvilli following cooling and warming. In
ethylene glycol-based freezing and vitrification solutions are suitable choices
for cryopreservation of immature oocytes and most organelles are able to retain
their normal morphology following cryopreservation and thawing processes.