Pronuclear synchronization and nuclear morphology of mature and in vitro matured oocytes in the rat: An ultrastructural study

  • M. Cincik
  • B. Baykal
  • S. Zeteroglu
  • G. Onalan
  • S. T. Ceyhan
  • R. Ergur
Articles Cell Growth/Differentiation/Apoptosis


The objective of this study was to evaluate synchronous and asynchronous pronucleus (PN) formation and the related patterns of juxtapositional nucleolus (n) formation in immature (prophase I [PI] and metaphase I [MI]) and mature (metaphase II [MII]) oocytes after fertilization, both ultrastructurally and at the level of light microscope. A single dose of 15 IU gonadotrophin was injected subcutaneously to twenty four 26-wk-old, female Wistar rats to induce ovulation. Human chorionic gonadotrophin (4 IU) was administered 40 h later, and after 4–6 h the ovaries were dissected, and the oocytes were aspirated. A total of 214 rat oocytes were classified according to a maturation index as follows: group I, 80 PI oocytes; group II, 50 MI oocytes; and group III, 84 MII oocytes. Immature oocytes were in vitro matured for 18–36 h. Spermatozoa were acquired by microepididymal sperm aspiration and processed using swim-up technique. Intracytoplasmic sperm injection was performed on mature oocytes after 2 h of incubation and on in vitro matured (IVM) oocytes 4 h after maturation. Pronuclear synchronization [both pronucleases (PNs) centrally located, equal sized, with equal numbers and sizes of juxtapositional nucleoli (Nn)] was observed in fertilized oocytes. Asynchronous PN formation (diversity between male and female PNs, related to dimensions, localization, and the number of Nn) in groups I, II, and III was found in 75, 86, and 47% of preembryos, respectively. There was a significant difference of synchronous pronuclear formation between mature and IVM oocytes (P<0.05). In IVM oocytes, asynchronous PN formation is high, and juxtapositional pronucleolar patterns are observed to be low by transmission electron microscope (TEM).

Key words

pronucleus asynchronous pronuclear morphology nucleolus TEM 


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Copyright information

© Society for In Vitro Biology 2005

Authors and Affiliations

  • M. Cincik
    • 1
    • 2
  • B. Baykal
    • 1
  • S. Zeteroglu
    • 3
  • G. Onalan
    • 4
  • S. T. Ceyhan
    • 5
  • R. Ergur
    • 6
  1. 1.Department of Histology and EmbryologyGulhane Military Medical AcademyAnkaraTurkey
  2. 2.ART Laboratory, Division of Reproductive Endocrinology, Department of Obstetrics and GynecologyGulhane Military Medical AcademyAnkaraTurkey
  3. 3.Department of Obstetrics and Gynecology, Faculty of MedicineMustafa Kemal UniversityAntakyaTurkey
  4. 4.Centrum IVF ClinicAnkaraTurkey
  5. 5.Division of Reproductive Endocrinology, Department of Obstetrics and GynecologyGulhane Military Medical AcademyAnkaroTurkey
  6. 6.Division of Reproductive Endocrinology, Department of Obstetrics and Gynecology, Haydarpasa HospitalGulhane Military Medical AcademyIstanbulTurkey

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