Figure 1
Selected TLVM panels of Rhesus sperm incorporation and pronuclear apposition during IVF. (A1–A6): male sperm head events during IVF (arrowheads) showing incorporation (A1,A2) followed by cortical rotation, first toward the site of the oocyte’s spindle region (A3–A4) and subsequently to a distal cortical site (A5–A6). The sperm head shows firm attachment to the oocyte’s cortex during penetration, even as cortical rotation powers sperm translocation. The sperm head is delayed in conversion to a fully decondensed MPn. (A7–A12): corresponding image panels from the TLVM video showing the position of the second meiotic spindle (A7–A8, arrows), FPn formation (A9–A11, arrows) and migration to the cortically residing sperm head (A12, arrow), mediated by the assembled sperm aster. Extrusion of the 2nd PB is not visible in these panels. (B1–B12). Classical rhesus IVF and pronuclear apposition beginning 3 hrs post-insemination show sperm head plasma membrane penetration (B1, arrowhead), MPn formation (B2–B3, arrowheads), male and female pronuclear apposition (B4: MPn, arrowhead; FPn, arrow), and typical radial cortical parental genome orientation by the middle of interphase, with the MPn closest to the oocyte’s cortex (B5–B6, arrowheads) and the female distal within the cytoplasm (B5-B6, arrows). Note the orientation of the apposed pronuclei is oblique to the A → V axis. (B7–B12): corresponding images of FPn events. After 2nd PB extrusion by 3 hrs post-insemination, the FPn forms near the cortex (B7–B9, arrows), swiftly migrates to the MPn utilizing microtubules of the assembled sperm aster (B10–B11, arrows), and ultimately positions distal to the cortically residing MPn (B12; FPn: arrow; MPn: arrowhead). The small arrows trace the sperm axoneme in (A1–A5,B1–B4). Time is given in hours:minutes (h:m) post-IVF. All panels represent selected HMC images from a TLVM recording. Bar = 20 µm.
