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Julius-Robert Lukas, Roland Blumer, Michaela Denk, Isabella Baumgartner, Winfried Neuhuber, Robert Mayr; Innervated Myotendinous Cylinders in Human Extraocular Muscles. Invest. Ophthalmol. Vis. Sci. 2000;41(9):2422-2431.
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purpose. To analyze palisade endings and their end organs, the so-called
innervated myotendinous cylinders (IMCs), of human extraocular muscle
(EOM) in more detail and to clarify with the help of
double-fluorescent labeling and electron microscopy whether terminals
in IMCs are sensory, serving proprioception.
methods. EOMs obtained from a donated cadaver (66 years) and distal parts of
EOMs from multiorgan donors (35, 53 years) were processed for
double-fluorescent labeling. Antibodies against the protein gene
product 9.5 and α-bungarotoxin labeling were used on cryostat
sections of distal myotendons. EOMs from multiorgan donors (2, 17
years) were prepared for electron microscopy.
results. Palisade endings investing muscle fiber tips established contacts with
tendon fibrils and the muscle fiber attached. α-Bungarotoxin bound to
myoneural contacts but not to axonal varicosities in the tendon
compartment. Ultrastructural analysis revealed that palisade endings
form IMCs, which were associated exclusively with multiply innervated
global layer muscle fibers. IMCs consisted of a muscle fiber tendon
junction, tightly enclosed by fibrocytes, and a supplying axon with
preterminals and terminals. Terminals contained mitochondria, few
neurotubuli, few neurofilaments, and accumulations of clear vesicles of
uniform size. A basal lamina always intervened between axolemma and
tendon fibrils as well as between axolemma and muscle fiber cell
conclusions. Palisade endings of human EOM form IMCs as in cat, monkey, and sheep.
In contrast to animals, myoneural contacts in human IMCs are almost
certainly motor, whereas terminals contacting tendon fibrils are
arguably sensory. Thus, IMCs might be best described as“
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