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Binggeli, Richard L.; Paule, W. J.
doi: 10.1002/cne.901370102pmid: 5808801
Studies of electron micrographs of pigeon optic nerve showed numerous unmyelinated fibers (29% of total) and more than twice as many total fibers as previously reported. The 2.4 million axons had a mean diameter below 1 μ, close to the limit of resolution of light microscopy. This probably accounts for the large discrepancy between light and electron microscopic counts. Studies of retinal whole mounts showed an irregular distribution of cells in the ganglion cell layer including a minor posterior fovea and an area of increased density in the posterior‐superior quadrant. Sample counts produced an estimate of over 4.8 million cell bodies in this layer. Cytological investigation indicated that over 85% of these cells were neuronal. The considerable excess of neuron cell bodies over axons in thought to be explained by the presence of large numbers of amacrine cells, cells which do not project axons into the optic nerve.
Nadol, Joseph B.; Darin de Lorenzo, A. J.
doi: 10.1002/cne.901370103pmid: 5808800
The dendritic processes and terminals of the abdominal muscle receptor organ of the lobster have been studied with the electron microscope. In both the “fast” and “slow” adapting components of the muscle receptor organ, dendritic processes ramify within the body of the stretch muscle in a zone of “relative muscle exclusion,” where the continuity of the muscle bundle is interrupted by a zone of connective tissue. The cell bodies and larger dendritic processes are ensheathed in alternate layers of connective tissue and Schwann cells, but the smallest dendritic twigs are entirely divested of their Schwann cell envelope. The membrane of the dendritic terminations is intimately applied to either connective tissue of the zone of relative muscle exclusion or to the sarcolemma of the stretch muscle. This apposition is interpreted as morphological specialization for transduction or mechanoelectric conversion. It is suggested that these two types of dendritic terminals may represent two distinct sites for transduction and may also mediate different modalities of input.
Tigges, Johannes; Tigges, Margarete
doi: 10.1002/cne.901370104pmid: 4980138
After unilateral eye removal in Erinaceus and Galago, Nauta‐gygax and Fink‐Heimer silver impregnation methods were used to study the accessory optic system. In Erinaceus the accessory optic fibers terminate contralaterally in the dorsal lateral and medial terminal nuclei of the accessory optic system; in Galago only the dorsal and lateral terminal nuclei are seen.
Ellenberger, Carl; Hanaway, Joseph; Netsky, Martin G.
doi: 10.1002/cne.901370105pmid: 5808802
Interkinetic nuclear migrations studied by redioautography in the medullar neuroepithelium of the 14‐day rat embryo are similar to those in other areas of the neuraxis in other species. The cell cycle lasts approximately 12 hours. Olivary neurons are produced along the length of the alar plate on embryonic days 14 and 15, mostly on day 14. Between 36 and 48 hours after injection of thymidine‐ H3, labeled cells migrate into the mantle layer and are more concentrated in the alar lamina than in the basal lamina. The olivary primordium appears in the ventromedial medulla on day 17 and is almost mature by day 21. Labeled neurons in the alar lamina migrate to the primordium in two bands, the marginal and the submarginal migration strands. From these strands, labeled cells move into the ventrolateral and ventromedial portions of the olivary complex, Newly arrived neurons push the existing cells dorsally. By embryonic day 21, as proliferation of cells in the neuroepithelium ceases, the migration strands disappear, and the olive in fully formed.
doi: 10.1002/cne.901370106pmid: 4185526
The developmental differentiation of the hypothalamo‐hypophyseal system and its disposition in the adult normal minnow is described. Neurosecretory stainable material is present either as granules or droplets in the nucleus preopticus and it is suggested that they are related with one another and follow a sequence in their developmental appearance. This differentiation of the neuorsecretory material and its distribution along the preoptico‐hypophyseal tract suggests a strong basis in support of the “transport‐hypothesis” of Bargmann and Scharrer ('51). The presences of the Herring bodies and peripheral movement of the neurosecretory material along the axon is suggestive of the functional role performed by the tract in the process of storage and release of hormone into the circulation.
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