Restricted growth of Schwann cells lacking Cajal bands slows conduction in myelinated nerves.

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Bibliographic Details
Title:	Restricted growth of Schwann cells lacking Cajal bands slows conduction in myelinated nerves.
Authors:	Court, Felipe A., Sherman, Diane L., Pratt, Thomas, Garry, Emer M., Ribchester, Richard R., Cottreall, David F., Fleetwood-Walker, Susan M., Brophy, Peter J.
Source:	Nature. 9/9/2004, Vol. 431 Issue 7005, p191-195. 5p.
Subjects:	Nerves, Impulse (Psychology), Nodes of Ranvier, Vertebrates, Cells, Cytoplasm
Abstract:	Nerve impulses are propagated at nodes of Ranvier in the myclinated nerves of vertebrates. Internodal distances have been proposed to affect the velocity of nerve impulse conduction1; however, direct evidence is lacking, and the cellular mechanisms that might regulate the length of the myclinated segments are unknown. Ramón y Cajal described longitudinal and transverse bands of cytoplasm or trabeculae in intemodal Schwann cells and suggested that they had a nutritive function2. Here we show that internodal growth in wild-type nerves is precisely matched to nerve extension, but disruption of the cytoplasmic bands in Periaxin-null mice impairs Schwann cell elongation during nerve growth. By contrast, myelination proceeds normally. The capacity of wild-type and mutant Schwann cells to elongate is cell-autonomous, indicating that passive stretching can account for the lengthening of the internode during limb growth. As predicted on theoretical grounds, decreased internodal distances strikingly decrease conduction velocities and so affect motor function. We propose that microtubule-based transport in the longitudinal bands of Cajal permits internodal Schwann cells to lengthen in response to axonal growth, thus ensuring rapid nerve impulse transmission. [ABSTRACT FROM AUTHOR]
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Database:	Psychology and Behavioral Sciences Collection

Description
Abstract:	Nerve impulses are propagated at nodes of Ranvier in the myclinated nerves of vertebrates. Internodal distances have been proposed to affect the velocity of nerve impulse conduction1; however, direct evidence is lacking, and the cellular mechanisms that might regulate the length of the myclinated segments are unknown. Ramón y Cajal described longitudinal and transverse bands of cytoplasm or trabeculae in intemodal Schwann cells and suggested that they had a nutritive function2. Here we show that internodal growth in wild-type nerves is precisely matched to nerve extension, but disruption of the cytoplasmic bands in Periaxin-null mice impairs Schwann cell elongation during nerve growth. By contrast, myelination proceeds normally. The capacity of wild-type and mutant Schwann cells to elongate is cell-autonomous, indicating that passive stretching can account for the lengthening of the internode during limb growth. As predicted on theoretical grounds, decreased internodal distances strikingly decrease conduction velocities and so affect motor function. We propose that microtubule-based transport in the longitudinal bands of Cajal permits internodal Schwann cells to lengthen in response to axonal growth, thus ensuring rapid nerve impulse transmission. [ABSTRACT FROM AUTHOR]
ISSN:	00280836
DOI:	10.1038/nature02841