Cation binding at the node of Ranvier in biopsied peripheral nerves of patients with Charcot-Marie-Tooth disease type 1A and hereditary neuropathy with liability to pressure palsies |
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Authors: | H Yoshikawa Tomoya Nishimura Misako Kaido Keiko Toyooka Harutoshi Fujimura Saburo Sakoda Takehiko Yanagihara |
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Institution: | (1) Department of Neurology, Osaka University Medical School, 2-2 Yamadaoka Suita, Osaka 565, Japan, JP |
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Abstract: | The node of Ranvier in myelinated fibers is known to have an affinity to bind cations. Demyelination and remyelination due
to abnormal expression of a myelin protein may affect cation binding or vice versa under pathological conditions. To study
the cation binding at the node of Ranvier in inherited demyelinating neuropathies associated with over- and under-expression
of the peripheral myelin protein 22 (PMP-22), the reaction with ferric ion and ferrocyanide was used to visualize the cation
binding sites in biopsied nerves of four patiens with Charcot-Marie-Tooth disease type 1A (CMT1A) and two patients with hereditary
neuropathy with liability to pressure palsies (HNPP), and the results were compared with those of four patients having acquired
neuropathies with normal PMP-22 expression. In CMT1A, nodal widening or paranodal demyelination was associated with dense
precipitates focally on both sides of the widened node. Although fainter precipitates were present at the node between remyelinated
internodes, the percentage of nodes exhibiting the reaction product between normal and remyelinated internodes was not statistically
different from that between normal internodes in CMT1A. In acquired neuropathies, on the other hand, the difference was significant
between the two (P < 0.05), with reduction between normal and remyelinated internodes. At the nodes neighboring demylinated internodes, the
percentage of nodes exhibiting the reaction product was reduced significantly in both CMT1A and acquired neuropathies, but
to a lesser degree in CMT1A. Precipitates were clearly seen at the nodes neighboring a tomaculum in HNPP. The results suggest
that preserved cation binding at the node may allow nerves to keep the electrical excitability in CMT1A and HNPP where myelin
remodeling takes place at high frequency.
Received: 6 June 1995 / Revised: 28 September 1995 / Revised, accepted: 29 November 1995 |
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Keywords: | Charcot-Marie-Tooth disease type 1A Ferric ion-ferrocyanide Hereditary neuropathy with liability to pressure palsies Node of Ranvier Peripheral myelin protein 22 |
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