Figure 1.

Rabbits manifest myasthenia gravis (MG)-like paresis after immunization with MuSK protein. (A) Two rabbits representative of four animals with outcomes manifested myasthenic weakness after immunization with the recombinant MuSK protein. After three injections of MuSK protein, M1 and M2 rabbits manifested flaccid weakness within three and nine weeks respectively. M2 rabbit developed severe exhaustion with muscle weakness. (B) Cross-sections from the soleus muscles of two paretic (M1 and M2) and a normal rabbits (Normal) were stained with H&E. Muscle fibers in M1 paretic rabbit showed only subtle changes in shape and smallness, whereas an atrophy of muscles fibers in M2 paretic rabbit was observed as small angular fibers (indicated by arrows). Scale bar, 50 mm. (C) Electromyograms recorded from M1 paretic rabbit. The retro-auricular branch of the facial nerve was continuously by a constant current stimulator delivered square-wave pulses of 0.1 msec during at 20 Hz, and the compound muscle action potential (CMAP, second peak observed on the oscilloscope screen recorded at the indicated time-points during stimulation) shows a decremental pattern, consistent with MG. Reproduced from Shigemoto et al., 2006 (16), with permission.