title: Prematuration of bovine oocytes with butyrolactone I reversibly arrests meiosis without increasing meiotic abnormalities after in vitro maturation.
abstract: OBJECTIVE
  Asynchrony between nuclear and cytoplasmic maturation, and possibly damage to the oocyte meiotic spindle, limits the application of in vitro maturation (IVM) in assisted reproduction. Several studies have suggested that Prematuration with meiosis blockers may improve oocyte quality after IVM, favoring early embryogenesis. Thus, we investigated the effect of Prematuration with the nuclear maturation inhibitor butyrolactone I (BLI) on the meiotic spindle and chromosomal configuration of bovine oocytes.
  
  
  METHODS
  Immature oocytes obtained from cows slaughtered in a slaughterhouse (n=840) were divided into the following groups: (1) control (n=325), submitted only to IVM in TCM199 for 24h; (2) BLI 18h (n=208) submitted to meiotic blockage with 100 microM BLI for 24h (Prematuration) and then induction of IVM in TCM199 for 18h; and (3) BLI 24h (n=307), pre-matured with 100 microM BLI for 24h followed by 24h of IVM in TCM199. The oocytes were then fixed, stained by immunofluorescence for morphological visualization of both microtubules and chromatin, and evaluated.
  
  
  RESULTS
  Meiotic arrest occurred in 90.2% of the oocytes cultured with BLI. Maturation rates were similar for all groups (80.3%, 73.6% and 82.7% for the control, BLI 18h and BLI 24h groups, respectively). We observed 81.3% normal oocytes in metaphase II in the control group, and 80.0% and 81.2% in the BLI 18h and BLI 24h groups, respectively. The incidence of meiotic anomalies did not differ between groups (18.7%, 20.0% and 18.8% for the control, BLI 18h and BLI 24h, respectively).
  
  
  CONCLUSIONS
  Prematuration with butyrolactone I reversibly arrests meiosis without damaging the meiotic spindle or the chromosome distribution of bovine oocytes after in vitro maturation.
authors.affiliation: Departamento de Ginecologia e Obstetrícia, Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, São Paulo, Brazil.
authors.forename: Elisa Melo
authors.initials: EM
authors.lastname: Ferreira
authors.forename: Alessandra Aparecida
authors.initials: AA
authors.lastname: Vireque
authors.forename: Paulo Roberto
authors.initials: PR
authors.lastname: Adona
authors.forename: Rui Alberto
authors.initials: RA
authors.lastname: Ferriani
authors.forename: Paula Andrea
authors.initials: PA
authors.lastname: Navarro
mesh_terms: D015107:4-Butyrolactone / Q000031:analogs & derivatives* / Q000494:pharmacology; D000818:Animals; D002417:Cattle; D002875:Chromosomes / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D005260:Female; D008540:Meiosis / Q000187:drug effects*; D008870:Microtubules / Q000187:drug effects; D023421:Models, Animal; D009865:Oocytes / Q000166:cytology / Q000187:drug effects* / Q000502:physiology*; D047428:Protein Kinase Inhibitors / Q000494:pharmacology*; D027724:Reproductive Techniques, Assisted; D008941:Spindle Apparatus / Q000187:drug effects
chemical_list: D047428:Protein Kinase Inhibitors; C082868:butyrolactone I; D015107:4-Butyrolactone