title: Organelle reorganization in bovine oocytes during dominant follicle growth and regression.
abstract: BACKGROUND
  We tested the hypothesis that organelles in bovine oocytes undergo changes in number and spatial distribution in a manner specific for phase of follicle development.
  
  
  METHODS
  Cumulus-oocyte-complexes were collected from Hereford heifers by ultrasound-guided follicle aspiration from dominant follicles in the growing phase (n = 5; Day 0 = ovulation), static phase (n = 5), regressing phase (n = 7) of Wave 1 and from preovulatory follicles (n = 5). Oocytes were processed and transmission electron micrographs of ooplasm representing peripheral, perinuclear and central regions were evaluated using standard stereological methods.
  
  
  RESULTS
  The number of mitochondria and volume occupied by lipid droplets was higher (P < 0.03) in oocytes from regressing follicles (193.0 ± 10.4/1000 μm(3) and 3.5 ± 0.7 %) than growing and preovulatory stages (118.7 ± 14.4/1000 μm(3) and 1.1 ± 0.3 %; 150.5 ± 28.7/1000 μm(3) and 1.6 ± 0.2 %, respectively). Oocytes from growing, static and preovulatory follicles had >70 % mitochondria in the peripheral regions whereas oocytes from regressing follicles had an even distribution. Oocytes from growing follicles had more lipid droplets in peripheral region than in central region (86.9 vs. 13.1 %). Percent surface area of mitochondria in contact with lipid droplets increased from growing (2.3 %) to static, regressing or preovulatory follicle stage (8.9, 6.1 and 6.2 %). The amount, size and distribution of other organelles did not differ among phases (P > 0.11).
  
  
  CONCLUSIONS
  Our hypothesis was supported in that mitochondrial number increased and translocation occurred from a peripheral to an even distribution as follicles entered the regressing phase. In addition, lipid droplets underwent spatial reorganization from a peripheral to an even distribution during the growing phase and mitochondria-lipid contact area increased with follicle maturation.
authors.affiliation: Department of Veterinary Biomedical Sciences, Western College of Veterinary Medicine, University of Saskatchewan, 52 Campus Drive, Saskatoon, SK, S7N 5B4, Canada. dinesh.dadarwal@usask.ca.
authors.forename: D
authors.initials: D
authors.lastname: Dadarwal
authors.affiliation: Department of Veterinary Biomedical Sciences, Western College of Veterinary Medicine, University of Saskatchewan, 52 Campus Drive, Saskatoon, SK, S7N 5B4, Canada. gpa623@mail.usask.ca.
authors.forename: G P
authors.initials: GP
authors.lastname: Adams
authors.affiliation: Department of Veterinary Clinical and Animal Sciences, University of Copenhagen, Groennegaardsvej 7, DK-1870, Frederiksberg C, Denmark. poh@life.ku.dk.
authors.forename: P
authors.initials: P
authors.lastname: Hyttel
authors.affiliation: Universidad Católica de Córdoba, Reproduccion animal, Cordoba, X5000IYG, Argentina. gbrogliatti@hotmail.com.
authors.forename: G M
authors.initials: GM
authors.lastname: Brogliatti
authors.affiliation: Department of Veterinary Biomedical Sciences, Western College of Veterinary Medicine, University of Saskatchewan, 52 Campus Drive, Saskatoon, SK, S7N 5B4, Canada. sarah.caldwell@usask.ca.
authors.forename: S
authors.initials: S
authors.lastname: Caldwell
authors.affiliation: Department of Veterinary Biomedical Sciences, Western College of Veterinary Medicine, University of Saskatchewan, 52 Campus Drive, Saskatoon, SK, S7N 5B4, Canada. jaswant.singh@usask.ca.
authors.forename: Jaswant
authors.initials: J
authors.lastname: Singh
mesh_terms: D000818:Animals; D002417:Cattle / Q000254:growth & development* / Q000378:metabolism; D005260:Female; D015571:Follicular Fluid / Q000378:metabolism; D009865:Oocytes / Q000254:growth & development / Q000378:metabolism / Q000648:ultrastructure*; D015388:Organelles / Q000378:metabolism / Q000648:ultrastructure; D006080:Ovarian Follicle / Q000254:growth & development*