摘要:

AbstractElectron microscopic examination of several thalamic nuclei undergoing neural degeneration following ablation of their cortical projection fields revealed reactive changes in vessels unrelated to direct mechanical trauma. A series of 30 rabbits were studied at post‐operative survivals of one to 238 days. Many neurons display signs of retrograde atrophy within the first week accompanied by a distinct increase in the number of perivascular cells within the basal lamina surrounding venules and large capillaries. This reaction was optimally observed between 5 and 98 days post‐operatively and was limited to the circumscribed zones of degeneration. In early stages, some vessels displayed margination of hematogenous elements, predominantly agranular leukocytes, of which some examples were seen in phases suggestive of diapedesis. Cells within the perivascular space exhibited diverse morphology. In addition to the indigenous “pericyte” population, there were numerous agranular leukocytes, and a few plasma cells and eosinophils. Within the second to third week postoperatively, some perivascular elements become enlarged and display electron‐lucent lipid vacuoles and PTA‐positive dense bodies of complex morphology, many of which are clearly lysosomal in nature. This cellular reaction persists for three to four months, after which time the cytoplasm displays evidence of cholesterol crystals and lysosomal transformations suggestive of terminal or residual bodies. Morphological criteria for identifying the possible origin of vacuolated, lysosomeladen perivascular cells are presented for a consideration of their possible derivation from pericytes and/or hematogenous elements. Of the several hypotheses considered to account for these findings, it appears likely that lipid and protein end‐products of neural degeneration provide the stimulus for perivascular aggregation and subsequent t

ISSN:0092-7317    

DOI:10.1002/cne.901480302

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1973

数据来源: WILEY

摘要:

AbstractSurgical destruction of the cortical projections of thalamic neurons results in rapid and profound atrophy of these neurons accompanied by a variety of non‐neuronal reactive changes. During the first post‐operative week, non‐neuronal elements, distinct from astrocytes and normal oligodendrocytes and tentatively designated as “M” cells, become evident in the degenerating thalamic nuclei. Some “M” cells are characterized by heterochromatin nuclei and numerous free ribosomes, and resemble the agranular leukocytes accumulating simultaneously within the perivascular space of small vessels coursing through these regions (Matthews and Kruger, '73). Examples of such cells were sometimes seen bridging the external basal lamina. Other “M” cells display many profiles of granular endoplasmic reticulum and fewer free ribosomes but cannot be precisely classified as to nature and possible source. From the second through fourteenth week, “M” cells increase in prominence and accumulate electronlucent lipid vacuoles and phosphotungstic acid (PTA) positive dense bodies, presumably lysosomes, until these enlarged lipid‐laden cells constitute the predominant non‐neuronal entities in the zone of degeneration, in addition to hypertrophied astrocytes. Thirty‐four weeks post‐operatively “M” cells have decreased in size and apparent numbers, and dense bodies display a lessened affinity for PTA in addition to morphologic patterns suggestive of terminal lysosomes. Normal light and dark oligodendrocytes are encountered within the zone of degeneration throughout the entire survival period.It is suggested that a significant proportion of “M” cells are of mesodermal (hematogenous; perivascular) origin although “M” cells display sufficient diversity of morphology to warrant consideration of additional sources for the reactive vacuolated forms. The experimental observations are discussed in relation to past and present concepts concerning the nature, origin and pathologic transform

ISSN:0092-7317    

DOI:10.1002/cne.901480303

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1973

数据来源: WILEY

摘要:

AbstractThe distribution of cervicothoracic (C1–T2) dorsal roots to the cuneate and accessory cuneate nuclei was studied in the rat with the Fink‐ Heimer I technique following single extradural rhizotomies. Cytoarchitectural analysis of the cuneate nucleus revealed an anatomically distinct caudal and rostral region. The caudal region was characterized by discrete aggregates of cells arranged as “slabs” or “bricks” which continue vertically almost to the ventral limit of the cuneate nucleus. In contrast, the cells of the rostral region were organized in a non‐focal manner.The projection of the cervicothoracic dorsal roots to the cuneate nucleus reflected the cytoarchitectural pattern observed; non‐focal terminal fields of degeneration in the rostral region and discrete “terminal field bands” of degeneration isolated from one another by degeneration‐free zones in the caudal region. However, the projections of dorsal roots C5 and T2 to the caudal region is non‐focal.In both regions of the cuneate nucleus, the distribution of dorsal root degeneration was topographically organized with cranial roots terminating ventrolaterally and more caudal roots, dorsomedially. The amount of intersegmental overlap of dorsal root terminal fields was greater in the rostral than in the caudal region.Individual dorsal roots projected differentially to the two regions of the cuneate nucleus. Roots C3 and C4 distributed primarily to the rostral region whereas C5 to T1 distributed to both regions. T2 root projected primarily to the caudal region. Dorsal roots C1 and C2 did not terminate in either region of the cuneate nucleus.All roots studied projected heavily and topographically to the accessory cuneate nucleus. Extensive overlap of the very dense terminal fields characterized the dorsal root projections to the accessory cuneate nucleus.On the basis of cytoarchitectonics and dorsal root projections, a dual organization of the cuneate nucleus was revealed. This organization reflected previous anatomical and electrophysiological studies in the rat and paralleled the organization described in the dorsal column nuclei of the cat. The significance of the dual organization with respect to dorsal column function was discussed, as was the finding of the lack of C1 and C2 dorsal root projections

ISSN:0092-7317    

DOI:10.1002/cne.901480304

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1973

数据来源: WILEY

摘要:

AbstractThe large, well developed superior colliculus of the tree shrew with its highly differentiated layers is ideal for analyzing the connections of individual layers. Our most significant finding concerns the differences between the projections of the superficial and deep layers. Lesions limited to those strata which receive projections from the retina and striate cortex (superficial 3 layers) result in terminal degeneration almost exclusively within the pulvinar, the pretectal area, and the dorsal and ventral lateral geniculate nuclei. In each case, the greatest amount of degeneration was present in the pulvinar, supporting previous suggestions that the tecto‐pulvinar pathway conveys visual information. In sharp contrast, lesions limited to the deep layers which receive multimodal input from nonstriate areas of the neocortex and from a variety of subcortical centers, produce terminal degeneration in entirely different thalamic nuclei — certain intralaminar nuclei, the subthalamic region, and a region homologous to the posterior nuclear group of Rose and Woolsey ('49). The deep lesions also result in terminal degeneration within the inferior colliculus, the parabigeminal nucleus, the reticulo‐tegmental nucleus, and the inferior olivary nucleus, as well as in the brainstem reticular formation. Finally, deep lesions produced scattered degenerating fibers in the motor facial nucleus. Our results favor a division of the tree shrew superior colliculus into superficial and deep portions based on strikingly different projection patterns and may be useful in resolving certain problems of thalamic hom

ISSN:0092-7317    

DOI:10.1002/cne.901480305

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1973

数据来源: WILEY

摘要:

AbstractThe medial superior olive (MSO) was studied in normal animals to determine the types of synaptic endings and their distribution over the surface of MSO neurons. Unilateral lesions were made in the anteroventral cochlear nucleus (AVCN) of experimental animals to determine the source of at least one synaptic type in the MSO.The surfaces of MSO neurons in normal animals were studded with three distinct types of synaptic endings distinguished mainly by the size of their synaptic vesicles. There were endings with large vesicles, 510 Å in mean diameter; endings with small vesicles, 380 Å; and endings with vesicles intermediate in size. 435 Å. The large vesicle ending typically was greater than 2 μm in maximum diameter. It appeared as the termination of a myelinated axon or as a swollen portion of a node and made multiple asymmetrical synapses. Large vesicle endings occurred exclusively on dendrites where they formed 85% of the synaptic endings. Small vesicle endings typically were less than 2 μm in diameter. They appeared as the termination of a fine unmyelinated axon and made only one symmetrical synapse. Small vesicle boutons occurred infrequently over the entire neuronal surface. Intermediate vesicle synaptic endings were similar to large vesicle endings except that they were present only on the cell body, axon hillock, and proximal portions of the dendrites where they formed most of the synapses.In AVCN lesioned animals degenerating myelinated axons and large vesicle synaptic endings were distributed to the lateral dendrites of the ipsilateral MSO and medial dendrites of the contralateral one. In addition, a few degenerating axons and large vesicle endings were found among the ipsilateral medial dendrites. The changes in the degenerating endings were characterized by an early proliferation of neurofilaments and swelling of the endings followed by collapse of the endings and increase in electron density, disappearance of filaments and synaptic vesicles, and phagocytosis of the degenerated endings by reactive glial cells. No degenerative changes were observed in the small and intermediate vesicle endings.The results of this study indicate that the more numerous large vesicle endings presynaptic to the MSO dendrites are the axon terminals of neurons in the AVCN. The persistence after lesions of the small and intermediate vesicle endings suggests that they arise from as yet unidentified sou

ISSN:0092-7317    

DOI:10.1002/cne.901480306

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1973

数据来源: WILEY

ISSN:0092-7317    

DOI:10.1002/cne.901480301

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1973

数据来源: WILEY