title: Evaluation of zona pellucida birefringence intensity during in vitro maturation of oocytes from stimulated cycles.
abstract: BACKGROUND
  This study evaluated whether there is a relationship between the zona pellucida birefringence (ZP-BF) intensity and the nuclear (NM) and cytoplasmic (CM) in vitro maturation of human oocytes from stimulated cycles.
  
  
  RESULTS
  The ZP-BF was evaluated under an inverted microscope with a polarizing optical system and was scored as high/positive (when the ZP image presented a uniform and intense birefringence) or low/negative (when the image presented moderate and heterogeneous birefringence). CM was analyzed by evaluating the distribution of cortical granules (CGs) throughout the ooplasm by immunofluorescence staining. CM was classified as: complete, when CG was localized in the periphery; incomplete, when oocytes presented a cluster of CGs in the center; or in transition, when oocytes had both in clusters throughout cytoplasm and distributed in a layer in the cytoplasm periphery Nuclear maturation: From a total of 83 germinal vesicle (GV) stage oocytes, 58 of oocytes (69.9%) reached NM at the metaphase II stage. From these 58 oocytes matured in vitro, the high/positively scoring ZP-BF was presented in 82.7% of oocytes at the GV stage, in 75.8% of oocytes when at the metaphase I, and in 82.7% when oocytes reached MII. No relationship was observed between NM and ZP-BF positive/negative scores (P = 0.55). These variables had a low Pearson's correlation coefficient (r = 0.081). Cytoplasmic maturation: A total of 85 in vitro-matured MII oocytes were fixed for CM evaluation. Forty-nine oocytes of them (57.6%) showed the complete CM, 30 (61.2%) presented a high/positively scoring ZP-BF and 19 (38.8%) had a low/negatively scoring ZP-BF. From 36 oocytes (42.3%) with incomplete CM, 18 (50%) presented a high/positively scoring ZPBF and 18 (50%) had a low/negatively scoring ZP-BF. No relationship was observed between CM and ZP-BF positive/negative scores (P = 0.42). These variables had a low Pearson's correlation coefficient (r = 0.11).
  
  
  CONCLUSIONS
  The current study demonstrated an absence of relationship between ZP-BF high/positive or low/negative score and nuclear and cytoplasmic in vitro maturation of oocytes from stimulation cycles.
authors.affiliation: Department of Gynecology and Obstetrics, Botucatu Medical School, São Paulo State University-UNESP, Botucatu, Brazil.
authors.forename: Claudia G
authors.initials: CG
authors.lastname: Petersen
authors.forename: Laura D
authors.initials: LD
authors.lastname: Vagnini
authors.forename: Ana L
authors.initials: AL
authors.lastname: Mauri
authors.forename: Fabiana C
authors.initials: FC
authors.lastname: Massaro
authors.forename: Liliane F I
authors.initials: LF
authors.lastname: Silva
authors.forename: Mario
authors.initials: M
authors.lastname: Cavagna
authors.forename: Ricardo L R
authors.initials: RL
authors.lastname: Baruffi
authors.forename: Joao B A
authors.initials: JB
authors.lastname: Oliveira
authors.forename: José G
authors.initials: JG
authors.lastname: Franco
mesh_terms: D001718:Birefringence; D002467:Cell Nucleus / Q000502:physiology; D002478:Cells, Cultured; D003593:Cytoplasm / Q000502:physiology; D005260:Female; D006801:Humans; D009865:Oocytes / Q000166:cytology / Q000502:physiology*; D009866:Oogenesis / Q000502:physiology*; D010062:Ovulation Induction; D011786:Quality Control; D012107:Research Design; D015044:Zona Pellucida / Q000502:physiology*