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L E Westrum

Publications and source records attributed to L E Westrum.

5 recordsLinked to original sources
PubMed1979

Marginal bundles of axoplasmic microtubules at nodes of Ranvier within muscle.

Using a special albumin technique, nodes of Ranvier have been examined within frog skeletal muscle, sciatic nerve and rat and frog cerebrum. Initial segments have been examined in cerebrum of frog and rat. Mictotubules usually run longitudinally through these regions, but within the bare area of the intramuscular node of Ranvier, annular or helical bundles of microtubules run in a marginal band at right angles to the more centrally placed longitudinal microtubules. These nodal bare areas show a pronounced convexity and it is suggested that the annular microtubules serve to maintain this convexity during muscle contraction.

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PubMed1978

Synapse development within the spinal trigeminal nucleus.

Pars interpolaris of the spinal trigeminal nucleus of kittens has been studied with the electron microscope at birth and at several subsequent ages during the first month of life. Attention has been given to ultrastructural maturational changes that occur in this neuropil, especially events in synaptogenesis. The results of this investigation include the following observations: (1) the neuropil, even at the earliest ages studied (three-hour-old kittens), is strikingly mature, necessitating a quantitative assessment in order to determine subtle developmental changes in synaptic patterns; (2) the number of axoaxonic contacts at birth are few, and their emergence is essentially a postnatal phenomenon; (3) it appears that the immature Gray type II or symmetrical synapse possesses distinct cleft material and dense, parallel membrane specializations. Synaptic vesicle accumulation at this contact appears to occur after the membrane specializations have formed. A previous study by Kerr26 has shown a reduced potential for primary afferent reorganization with the spinal trigeminal nucleus when kittens are subjected to trigeminal rhizotomy after three days of age. Our observations on the development of axoaxonic synaptic arrangements in the neonatal period may provide an explanation for these earlier results.

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PubMed1977

Microtubules associated with postsynaptic 'thickenings'.

Using a new albumin technique, microtubules can be seen closely related to or associated with the postsynaptic 'thickening' of mature and immature central nervous synapses. Thus in conventionally fixed synapses (without albumin pretreatment) where microtubules cannot usually be observed running into the postsynaptic dense material, this material could perhaps, in part, consist of the debris of in vivo microtubules. Smooth endoplasmic reticulum (ER) is often seen associated with the microtubules near the postsynaptic 'thickening'. Microtubules, and possibly smooth ER, may have an important role in the initiation of synapse formation and in the maintenance of mature synapses.

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