摘要:

AbstractAn ipsilateral pathway to the commissural zone of the dentate fascia has been demonstrated in the rat using the Fink‐Heimer silver impregnation method. The pathway arises in one or both of the CA3c and CA4 hippocampal subfields. As lesions of these structures normally will cause degeneration of commissural fibers terminating in the dentate fascia, animals without commissural fibers were provided for this study. This was done by transecting the hippocampal commissures in eight day old rats which were allowed to survive until the adult stage at which time all stainable, degenerating commissural fibers had disappeared. Lesions involving the CA3c/4‐subfields were then made. The resulting degeneration in the commissural zone of the dentate fascia was shown to be of purely ipsilateral origin.Fibers of this pathway display a spread along the longitudinal septotemporal axis of the hippocampal formation. The spread in the “septal” direction (ascent) is in general greater than the descent in the temporal direction, and the more “septal” the lesion is placed, the further does the degeneration extend in the septal direction. The most ascending fibers occupy a juxtagranular position along the medial crus of the dentate granule cells. The most descending (temporal) fibers are seen superficially in the commissural zone along the lateral crus.The pyramids of CA3c and the modified pyramids of CA4 are considered the most probable cells of origin of this system.The ipsilateral system may possibly be absent in normal rats. In view of the early age at which decommissuration was carried out in the experimental animals, axonal sprouting, resulting in the appearance of fibers which may normally be absent, cannot

ISSN:0092-7317    

DOI:10.1002/cne.901420402

出版商:The Wistar Institute of Anatomy and Biology    

年代:1971

数据来源: WILEY

摘要:

AbstractA hitherto undescribed pathway from the hippocampus to the entorhinal area has been found in the albino rat in experimental studies by the silver‐impregnation technique of Fink and Heimer ('67) and a modification there of by the present author ('70). Animals in which the hippocampal formation had been deprived of commissural and other afferents by a preliminary operation at the age of eight days were used to faciliate the search for the site of origin of the pathway. Lesions in various parts of the hippocampus showed the origin to be restricted to subfield CA3 in approximately the temporal third of the hippocampus. The axons run caudally in the stratum radiatum and stratum lacunosummoleculare, and terminate in the medial part of the entorhinal area in a distinct zone corresponding to layer IV of Lorente de Nó ('33, '34). By the aid of alternating series of sections impregnated with silver and incubated for acetyl‐cholinesterase, the zone of termination was shown to be identical with the acetyl‐cholinesterase positive band at the level of layer IV. In the dorso‐ventral sense the fibers exhibit a topical organization, terminal degeneration at different levels of the entorhinal area depending on the levels of CA3 damaged. The mean course of the fibers from each level of CA3 seems to be roughly horizontal. A hippocampoentorhinal neuron circuit is

ISSN:0092-7317    

DOI:10.1002/cne.901420403

出版商:The Wistar Institute of Anatomy and Biology    

年代:1971

数据来源: WILEY

摘要:

AbstractNumerous basal processes of ependymal cells extend peripherally into every cell group and area of the hypothalamus of the four species of mammals examined: mouse, rat, rabbit and cat. With Golgi‐Cox impregnation and Nissl counterstaining, ependymal cell processes appear to have a variety of forms and of intricate structural relationships with neurons and capillaries within the hypothalamus. It is proposed that hypothalamic ependymal cells and their processes function as a communication system between the cerebrospinal fluid of the third ventricle and neurons and capillaries within the hypothalamus. The role that such a system may play in the regulation of adenohypophysial function is discussed.It was also noted that in all hypothalamic cell groups, dendrites of some neurons extend to the ependymal layer.An unusual cell, resembling microglia forms, within the infundibular nucleus appears to be selectively impregnated by the Golgi‐Cox technique employed. The cell is characteristic of the infundibular nucleus and, with rare exceptions, is confined to that cell group. Some of these spider‐cells lie on the ependymal layer and also have endfeet extending to the ventricular surface of the epe

ISSN:0092-7317    

DOI:10.1002/cne.901420404

出版商:The Wistar Institute of Anatomy and Biology    

年代:1971

数据来源: WILEY

摘要:

AbstractRegenerative activity within perikarya of peripheral neurons was studied using light microscopic and standard autoradiographic techniques. Relative incorporation of H3‐leucine into injured neurons was used as an index of their regenerative activity. Reversible and irreversible sciatic nerve injuries were used as the experimental model. Results were correlated with microscopic and functional assessment of progress in nerve regeneration in each animal.Both reversible and irreversible axonal injuries resulted in chromatolysis and initially decreased 30 minute incorporation of the labeled axonal protein precursor into injured cells. A late increase in 30 minute incorporation of the labeled amino acid occurred only in animals subjected to reversible axon injury. In sometimes greater than normal cytoplasmic basophilia and always accompanied demonstrable return of nerve function.These findings are correlated with present concepts of perikaryal synthetic requirements during the various phases of peripheral axon regeneration. It is suggested that the increased synthetic activity within the perikaryon necessary for axon maturation results from the return of a trophic perikaryal stimulus from reinnervated peripheral structure

ISSN:0092-7317    

DOI:10.1002/cne.901420405

出版商:The Wistar Institute of Anatomy and Biology    

年代:1971

数据来源: WILEY

摘要:

AbstractThe external potential field along the functionally isolated medullated giant fiber of the shrimp (Penaeus setiferus) was recorded during impulse conduction using 1MNaCl‐filled glass capillary electrodes. The giant fiber displays no nodes of Ranvier, yet shows a conduction velocity greater than 90m/second at 20°C. Recordings from most parts of the myelin‐covered giant fiber surface showed only small monophasic positive potentials. However, at the areas of giant fiber‐motor giant fiber synapses and where giant fiber axons branch into abdominal ganglia, a small positivity was followed by a negativity (sink of the action current). The local application of action potential depressants to these areas abolished the negativity and converted it into positivity, and consequently impulse conduction was blocked. Application of the action potential depressants to other areas of the giant fiber did not block impulse conduction. The sink of the action current was not found from the axolemma in the myelin cylinder; this part of the axolemma together with the low resistance gap fluid simply serves as a passive current conductor. Light and electron microscopic studies of the two functionally excitable areas revealed the absence of a myelin sheath in some small areas of both regions. Thus, impulse conduction appears to be saltatory, and these excitable areas function as nodes of R

ISSN:0092-7317    

DOI:10.1002/cne.901420406

出版商:The Wistar Institute of Anatomy and Biology    

年代:1971

数据来源: WILEY

摘要:

AbstractVisually evoked unit responses of the tectum were studied in the squirrel monkey. The results showed that the superior colliculus had a definite functional laminar organization. Units responding to diffuse light were found in the upper part of the stratum griseum superficiale, units having antagonistically segregated receptive fields in the middle portion, and units sensitive to moving objects in the lower portion as well as in the stratum opticum. Retinotopic projection was also observed. The pretectal region contained mainly “tonic‐on” and “inhibitory” units. No specific localization was observed in the distribution of th

ISSN:0092-7317    

DOI:10.1002/cne.901420407

出版商:The Wistar Institute of Anatomy and Biology    

年代:1971

数据来源: WILEY

ISSN:0092-7317    

DOI:10.1002/cne.901420401

出版商:The Wistar Institute of Anatomy and Biology    

年代:1971

数据来源: WILEY