摘要:

AbstractCerebellar mossy, parallel, basket and Golgi axons were used to study the variables contributing to vesicle shape.It has been found that, when aldehydes are used as a primary fixative, synaptic vesicles can be either small round vesicles (less than 400 Å in diameter), large round vesicles (400–500 Å in diameter) or flat, with a ratio of large to small diameters of 2 or greater (500–600 Å × 250 Å). The proportion of round vesicles as well as the presence and the number of flat vesicles in each axon depend basically upon the osmotic pressure of the buffer. Concentration of aldehydes, duration of the fixation and dehydration, temperature of the fixative, etc. do not affect the synaptic vesicle shape. With buffers (phosphate and sodium cacodylate) of low osmolarity, mossy and parallel axons exhibit a round synaptic vesicle population and no flat vesicles are seen at all. With the same low osmolarity buffers, basket and Golgi axons have a synaptic vesicle population that is mainly round with a low proportion of flat vesicles. As the osmolarity of the buffers is increased, the number of flat vesicles in basket and Golgi axons increases. In mossy and parallel axons the flat vesicles are present with highest osmolarities but always in a lower proportion than in basket and Golgi axons.Quantitative observations indicate that each axon type, under given conditions of fixation, exhibits a mixed vesicle population with a characteristic vesicle ratio. Although this vesicle ratio is modified significantly with changes in the osmotic pressure of the buffer, each axon type exhibits a different and characteristic modification of its vesicle ratio. These observations show that the vesicle ratio and its changes in different conditions of fixation are useful parameters for classify

ISSN:0092-7317    

DOI:10.1002/cne.901420302

出版商:The Wistar Institute of Anatomy and Biology    

年代:1971

数据来源: WILEY

摘要:

AbstractA total of 27 adult phalangers was employed to investigate the pattern of neocortical projections to the pontine and medullary portions of the brain stem. Lesions restricted to neocortical areas rostral to the orbital sulcus resulted in fiber degeneration which distributed mainly to midline and medial areas of the pontine and medullary reticular formation. The greatest amount of fiber degeneration was located within the superior central nucleus, the nucleus of the pontine raphe, the nucleus pontis centralis oralis and the nucleus pontis centralis caudalis. However, a few degenerating fibers were present within the nucleus gigantocellularis and the magnocellular portion of the medullary raphe. In contrast, lesions which were located just caudal to the orbital sulcus resulted in fiber degeneration chiefly within the more lateral parvocellular reticular formation and within the subnucleus dorsalis of the nucleus medullae oblongatae centralis. In such cases, additional degenerating fibers were present within the dorsal column nuclei and within more medial areas of the reticular formation. In those brains with ventral parietal ablations, degenerating fibers were present within the chief sensory and spinal nuclei of the trigeminal complex and the closely adjacent reticular formation. All of the above neocortical lesions resulted in fiber degeneration within the basilar pontine gray. In those specimens subjected to caudal (striate and peristriate) or ventrocaudal (temporal) lesions, degenerating fibers were present within the basilar pontine gray, but not within other areas of the pons or the medulla oblongata.

ISSN:0092-7317    

DOI:10.1002/cne.901420303

出版商:The Wistar Institute of Anatomy and Biology    

年代:1971

数据来源: WILEY

摘要:

AbstractThe enlargement of synaptic vesicles in degenerating terminals which has recently been demonstrated in the pigeon retino‐tectal fibers as an early sign of secondary degeneration, is confirmed in the rat cortico‐caudate system. Enlarged synaptic vesicles appear already five hours postoperatively in endings which subsequently undergo the classical changes of Wallerian degeneration. Three categories of terminals, SS−, SL−and F‐terminals, are defined on the basis of shape and size of synaptic vesicles in the normal rat caudate nucleus. Only the first category is involved after cortical ablation, while the others remain

ISSN:0092-7317    

DOI:10.1002/cne.901420304

出版商:The Wistar Institute of Anatomy and Biology    

年代:1971

数据来源: WILEY

摘要:

AbstractThe aim of this study was to compare the projections of the dorsal column nuclei and spinal pathways to the brainstem and thalamus inTupaia glis. Animals with unilateral lesions in the dorsal column nuclei or with lateral hemisections were perfused after 5 to 14 days survival time and sections were treated with Nauta or Fink/Heimer silver impregnation methods. The findings indicate that efferent fibers of dorsal column nuclei terminate not only in the thalamus but also in the dorsal accessory nucleus of the inferior olive and bilaterally in the external nucleus of the inferior colliculus. Some fibers terminate in periaqueductal gray and a few in pontine nuclei. In the diencephalon, efferents of the dorsal column nuclei were found to terminate in the posterior group (PO), ventroposterior nucleus (VP) and zona incerta. Spinal efferents were traced to the medial and dorsal accessory nuclei of the inferior olive, medullary and mesencephalic reticular formation, facial and vestibular nuclei, cuneiform nucleus, locus caeruleus, parabrachial nuclei and periaqueductal gray, and also to the external nucleus of the inferior colliculus. Evidence was found of more limited additional spinal projections to PO intralaminar nuclei and VP. The results of this study indicate that the dorsal column system, generally considered to be a phylogenetically new direct pathway to the thalamus, contains other components comparable to some of the spinal efferent connections with the brainstem. Moreover, even in this intermediate form, whose exact taxonomic position is unsettled, the dorsal column‐medial lemniscus system to the thalamus appears to be of greater volume than the anterolateral spinothalamic connectio

ISSN:0092-7317    

DOI:10.1002/cne.901420305

出版商:The Wistar Institute of Anatomy and Biology    

年代:1971

数据来源: WILEY

摘要:

AbstractSections prepared by the Nauta and Nissl methods have been used to study the subcortical distribution of axon and cell degeneration in rabbits after lesions in visual areas I and II (V I and V II) of the cerebral cortex. Degeneration was limited to the side of the lesions. Following lesions of either V I or V II, two distinct groups of degenerating axons were traced caudally. (i) One of these groups projected through the optic tract and its subjacent nuclei. The terminal portions of its axons were found to form zones of pericellular fiber (or boutonal) degeneration in the thalamic reticular nucleus (TRN), the ventral and dorsal lateral geniculate nuclei (LGv, LGd), the pulvinar (Pul), the nuclei praetectalis anterior and posterior (dorsal and lateral parts respectively), the nucleus tractus opticus, and the superior colliculus (SC). In the TRN, LGd, Pul, and nuclei praetectalis anterior and posterior the zones of degeneration were disposed into distinct columns. After lesions involving V II the terminal portions of these axons were also seen to form zones of pericellular fiber degeneration in the nuclei praetectalis and posterior (ventral and medial parts respectively), the ventrolateral thalamic nucleus, and the zona incerta. (ii) The second group of degenerating axons traversed the cerebral peduncle and the terminal portions of its axons were shown to form zones of pericellular fiber degeneration in the basal pons.Retinotopically organized projections from V I were recognized in the LGv, LGd, Pul, nuclei praetectalis anterior and posterior (dorsal and lateral parts respectively), and SC; and the evidence reveals the presence of similarly organized projections from V II. Other retinotopically organized projections from the visual areas could not be demonstrated.The data support the view that the collateral branches of visual cortical axons serve as a principal source of input to some of the cellular components receiving innervation from the visual areas.Cellular degeneration was confined to the LGd and then present only with lesions involving V I. With each such lesion, the cellular degeneration formed a distinct column within the LGd, and this column and the one consisting of pericellular fiber (or boutonal) degeneration were consistently found to overlap.

ISSN:0092-7317    

DOI:10.1002/cne.901420306

出版商:The Wistar Institute of Anatomy and Biology    

年代:1971

数据来源: WILEY

摘要:

AbstractEarly climbing fiber metamorphosis has been studied in 250 Golgi preparations of 5–12 day postnatal rat cerebellum, and in less numerous 12–18 day ones. EM controls were provided for the early phase covering maturation of Purkinje cytoplasm, status of axonal neuropil, and synapses between the evanescent nid structure and Purkinje soma membrane.Ramon y Cajal (1890, '11), Athias (1897) and others have contributed extensively to climbing fiber histogenesis. Our results are confirmatory but support more varied developmental detail including that of axonal collateralization within the granular layer, all of which may not persist to maturity. Distinguishing characteristics of climbing fibers are recognized early in histogenesis, including varicosities, redundancies in course, and a manner of branching called cross‐over. The curvaceous path a climbing fiber pursues across the granular layer can be corrected at the ganglionic level by a horizontal segment having length equivalent to the offset. These and other redundancies may straighten out with areal expansion of cortical surface as compared to the restricted white matter base.While supporting multiple innervation of nids by local collateralizations proceeding from stem axons in white matter, the study does not preclude a one to one relationship between adult climbing fiber and Purkinje cell as basic design. Unknown factors are the relative amounts of local collateralization proceeding from several versus a single axon stem, and the extent to which branches are issued from a single fiber to different

ISSN:0092-7317    

DOI:10.1002/cne.901420307

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.901420301

出版商:The Wistar Institute of Anatomy and Biology    

年代:1971

数据来源: WILEY