Figure 6

In vitro developing oocytes are supplied with meiotically nonfunctional organelles from fibroblasts or satellite cells. Time lapse photography shows that early developing oocytes (o, panel A) are low in optically dense cytoplasmic organelles (white open arrow). They can be joined (arrowhead) by fibroblast-like cells (fb), providing additional organelles. Such fibroblast-type cells initially show optically dense organelles close to the nucleus (black solid arrow), but not in the arm extended toward the oocyte (white solid arrow). Within 10 min (panel B), however, the optically dense organelles are apparent in the extended arm (solid black arrow) and within adjacent oocyte cytoplasm (black arrowhead) and distant oocyte regions (black open arrow). At 4h 25 min (panel C), however, the fibro-oocyte (fbo) hybrid is formed and regressing oocyte (ro) exhibits depletion of organelles (arrow) accumulated by the fibroblast (arrowhead). Alternatively, the developing oocytes (o, panel D) deficient in cytoplasmic organelles (white arrow) exploit the satellite cells (s), which are produced by the oocytes themselves. The oocyte is supplied by suicidal satellite cell by a tube like ring canal - (black arrowhead; see inset). In panel E the oocyte exhibits enhanced content of the optically dense organelles (black arrow) and the ring canal draining the satellite disappears (white arrowhead - see inset). The satellite cell size is reduced (dashed line) and the perinuclear space is altered (compare with panel D). Oocytes enriched by satellites’ organelles (panel F) exhibit good morphology [200 micron size, germinal vesicle (gv), and thick zona pellucida (zp)], but are unable to resume meiosis II due to the lack of meiotically functional organelles provided by secondary Balbiani body derived from granulosa cells in vivo. Bar in A for A-E. Panel C reprinted from Ref. [26]: © Antonin Bukovsky. Other panels adapted from Ref. [34], with a permission: © Wiley-Liss, Inc.