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RESEARCH ARTICLE

Ultrastructure and mitochondrial numbers in pre- and postpubertal pig oocytes

Hanne Skovsgaard Pedersen A E , Henrik Callesen A , Peter Løvendahl B , Fenghua Chen C , Jens Randel Nyengaard C , Nanett Kvist Nikolaisen D , Peter Holm D and Poul Hyttel D
+ Author Affiliations
- Author Affiliations

A Department of Animal Science, Aarhus University, Blichers Allé 20, DK-8830 Tjele, Denmark.

B Department of Molecular Biology and Genetics, Aarhus University, Blichers Allé 20, DK-8830 Tjele, Denmark.

C Stereology and Electron Microscopy Laboratory, Centre for Stochastic Geometry and Advanced Bioimaging, Aarhus University, Nørrebrogade 44, DK-8000 Aarhus C, Denmark.

D Department of Veterinary Clinical and Animal Science, University of Copenhagen, Dyrlægevej 16, DK-1870 Frederiksberg C, Denmark.

E Corresponding author. Email: hanne.skovsgaard@agrsci.dk

Reproduction, Fertility and Development 28(5) 586-598 https://doi.org/10.1071/RD14220
Submitted: 19 June 2014  Accepted: 19 August 2014   Published: 25 September 2014

Abstract

Prepubertal pig oocytes are associated with lower developmental competence. The aim of this experiment was to conduct an exhaustive survey of oocyte ultrastructure and to use a design-unbiased stereological approach to quantify the numerical density and total number of mitochondria in oocytes with different diameters from pre- and postpubertal pigs. The ultrastructure of smaller prepubertal immature oocytes indicated active cells in close contact with cumulus cells. The postpubertal oocytes were more quiescent cell types. The small prepubertal oocytes had a lower total mitochondrial number, but no differences were observed in mitochondrial densities between groups. Mature postpubertal oocytes adhered to the following characteristics: presence of metaphase II, lack of contact between cumulus cells and oocyte, absence of rough endoplasmic reticulum and Golgi complexes, peripheral location of cortical granules and central localisation of mitochondria, vesicles and lipid droplets. Prepubertal oocytes displayed more variation. The ultrastructure of large pre- and postpubertal oocytes was compatible with higher developmental competence, whereas that of smaller prepubertal oocytes could explain their reduced capacity. The higher number of mitochondria in large pre- and postpubertal oocytes could have an influence on oocyte competence, by increasing the pool of mitochondria available for early embryonic development.

Additional keywords: mitochondria, oocyte quality, stereology, transmission electron microscopy.


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