Oocyte satellites in vitro. A) Early stage after oocyte (o) division producing the satellite (s) cell. Asterisks indicate additional small satellites. B) Oocyte growth and regressing satellite (rs) with vacuolization in the perinuclear space (arrowhead). C) Progressive oocyte growth and its separation (arrowhead) from the satellite remnants (sr). D) Large isolated oocyte exhibits germinal vesicle (gv) and a thick zona pellucida (zp) cytoplasmic membrane. Panels A-D adapted with permission from , © Wiley-Liss, Inc.