Fig. 6.

Reactive SCs growing from transplanted nerves induce the retraction of portions of nerve terminals in host muscles. A, SCs (arrowhead), labeled with anti-s100, have grown from a transplanted foreign nerve and contacted terminal SCs (arrow) at a junction in the host muscle. The host terminal SCs are more intensely labeled with anti-s100 and are themselves extending processes. One of the host SC somata appears displaced somewhat from the endplate. B, The nerve terminal at this junction is poorly organized and has sprouted along the transplanted SCs and the processes growing from the host SCs.C–R, High-magnification images of three junctions affected by the transplanted, foreign SCs. Junctions were triple-labeled as in Figure 2; color montages as in Figure 5. Anti-synaptophysin alone was used to label the nerve terminal in D, F and P, R. C–F, An endplate that has been contacted by transplanted SCs for only a short time. Transplanted SCs (arrow in C, F) have contacted the lower half of this junction; synaptophysin (D) staining density is decreased in the area of contact, leaving portions of the underlying AChR cluster (E) uncovered. Nerve terminal branches in the areas of this junction that have not been contacted by the transplanted SCs remain well organized. G–J,K–N, O–R, Three endplates that have been overgrown by transplanted SCs. SC bodies (arrowheads inG, K, O) are poorly organized at these endplates. Areas of these endplates no longer apposed by nerve terminal branches (identified with arrows in H, J, L, N) are devoid of SC somata. Scale bars: A, B, 50 μm;C–R, 20 μm.