摘要:

Endocranial casts of 12 genera of extinctcanids, covering a time span of 30 million years, and of all living canid genera provide information on brain evolution in that carnivoran family. The oldest canid brains had only suprasylvian and coronolateral sulci, a widely exposed cerebellum with a straight posterior vermis, a high rhinal fissure and a strikingly undeveloped frontal lobe. By 25 million years ago, ectosylvian, ectolateral and presylvian sulci had appeared, and by about 12 million years ago, a Sylvian sulcus had developed, expansion of the temporal lobe and of orbital and sigmoid gyri was noticeable, and lobule VII of the cerebellar vermis had enlarged and twisted in the line leading to modern canids. Ansate, postcruciate and cruciate sulci developed along with the expansion of the sigmoid gyri. Canid brains 15–30 million years old average slightly smaller relative to body size than do modern canid brains, while later fossil canid brains are about the same relative size as modern ones. Modern canid brains are relatively uniform in external morphology, differing mainly in the relative size of the prorean gyru

ISSN:0006-8977    

DOI:10.1159/000124409

出版商:S. Karger AG    

年代:1973

数据来源: Karger

摘要:

Endocranial casts of 12 genera of extinctcanids, covering a time span of 30 million years, and of all living canid genera provide information on brain evolution in that carnivoran family. The oldest canid brains had only suprasylvian and coronolateral sulci, a widely exposed cerebellum with a straight posterior vermis, a high rhinal fissure and a strikingly undeveloped frontal lobe. By 25 million years ago, ectosylvian, ectolateral and presylvian sulci had appeared, and by about 12 million years ago, a Sylvian sulcus had developed, expansion of the temporal lobe and of orbital and sigmoid gyri was noticeable, and lobule VII of the cerebellar vermis had enlarged and twisted in the line leading to modern canids. Ansate, postcruciate and cruciate sulci developed along with the expansion of the sigmoid gyri. Canid brains 15–30 million years old average slightly smaller relative to body size than do modern canid brains, while later fossil canid brains are about the same relative size as modern ones. Modern canid brains are relatively uniform in external morphology, differing mainly in the relative size of the prorean gyru

ISSN:0006-8977    

DOI:10.1159/000124410

出版商:S. Karger AG    

年代:1973

数据来源: Karger

摘要:

The normal fine structure of the inferior pulvinar of the thalamus has been studied in Macaca mulatta. At least three types of axonal terminals can be distinguished: large, dense (type I) terminals containing rounded vesicles; medium-sized, pale (type II) terminals containing pleomorphic and flattened vesicles, and small, dense (type III) terminals containing rounded vesicles.Type I terminals form asymmetrical axo-dendritic synapses with large secondary dendrites and asymmetrical axo-axonal synapses with type II terminals, at which the latter invariably constitute the postsynaptic element. Type I terminals also form multiple, usually asymmetrical, filamentous contacts with secondary dendrites. Type II terminals form usually symmetrical axo-dendritic synaptic junctions with secondary dendrites, except in the synaptic complexes where these junctions are usually asymmetrical. Type III terminals form (asymmetrical) synaptic junctions only with dendrites; the junctions are most commonly and characteristically effected with fine, distal dendrites, and much less commonly with secondary dendrites. Synaptic contacts with somata and primary dendrites have not been found, nor ''presynaptic dendrites''. Occasional dendro-dendritic filamentous junctions have been observed. The dominant synaptological feature of the neuropil is the occurrence of localised aggregations of secondary dendrites and synaptic knobs of types I and II which have been termed synaptic complexes; the latter resemble closely the synaptic glomeruli of certain other thalamic nuclei. The synaptic complexes of the inferior pulvinar, however, are but poorly encapsulated by glial lamellae. The most meaningful subdivision of the synaptic zone of the neuropil is into proximal (i.e. secondary dendritic) and distal dendritic types, each of distinctive and fairly homogeneous synaptic organization.Two to nine days after occipital lobotomy, almost all type I terminals were found to exhibit degenerative change of the neurofilamentous hyperplastic type; no subsequent electron-dense transformation of the affected visual corticofugal profiles has been observed. Terminals of types II and III remained completely normal. A number of electron-dense profiles interpreted as somata and dendrites showing acute retrograde necrosis or indirect Wallerian degeneration, were also observed.

ISSN:0006-8977    

DOI:10.1159/000124411

出版商:S. Karger AG    

年代:1973

数据来源: Karger

摘要:

The normal fine structure of the inferior pulvinar of the thalamus has been studied in Macaca mulatta. At least three types of axonal terminals can be distinguished: large, dense (type I) terminals containing rounded vesicles; medium-sized, pale (type II) terminals containing pleomorphic and flattened vesicles, and small, dense (type III) terminals containing rounded vesicles.Type I terminals form asymmetrical axo-dendritic synapses with large secondary dendrites and asymmetrical axo-axonal synapses with type II terminals, at which the latter invariably constitute the postsynaptic element. Type I terminals also form multiple, usually asymmetrical, filamentous contacts with secondary dendrites. Type II terminals form usually symmetrical axo-dendritic synaptic junctions with secondary dendrites, except in the synaptic complexes where these junctions are usually asymmetrical. Type III terminals form (asymmetrical) synaptic junctions only with dendrites; the junctions are most commonly and characteristically effected with fine, distal dendrites, and much less commonly with secondary dendrites. Synaptic contacts with somata and primary dendrites have not been found, nor ''presynaptic dendrites''. Occasional dendro-dendritic filamentous junctions have been observed. The dominant synaptological feature of the neuropil is the occurrence of localised aggregations of secondary dendrites and synaptic knobs of types I and II which have been termed synaptic complexes; the latter resemble closely the synaptic glomeruli of certain other thalamic nuclei. The synaptic complexes of the inferior pulvinar, however, are but poorly encapsulated by glial lamellae. The most meaningful subdivision of the synaptic zone of the neuropil is into proximal (i.e. secondary dendritic) and distal dendritic types, each of distinctive and fairly homogeneous synaptic organization.Two to nine days after occipital lobotomy, almost all type I terminals were found to exhibit degenerative change of the neurofilamentous hyperplastic type; no subsequent electron-dense transformation of the affected visual corticofugal profiles has been observed. Terminals of types II and III remained completely normal. A number of electron-dense profiles interpreted as somata and dendrites showing acute retrograde necrosis or indirect Wallerian degeneration, were also observed.

ISSN:0006-8977    

DOI:10.1159/000124412

出版商:S. Karger AG    

年代:1973

数据来源: Karger

摘要:

The normal fine structure of the inferior pulvinar of the thalamus has been studied in Macaca mulatta. At least three types of axonal terminals can be distinguished: large, dense (type I) terminals containing rounded vesicles; medium-sized, pale (type II) terminals containing pleomorphic and flattened vesicles, and small, dense (type III) terminals containing rounded vesicles.Type I terminals form asymmetrical axo-dendritic synapses with large secondary dendrites and asymmetrical axo-axonal synapses with type II terminals, at which the latter invariably constitute the postsynaptic element. Type I terminals also form multiple, usually asymmetrical, filamentous contacts with secondary dendrites. Type II terminals form usually symmetrical axo-dendritic synaptic junctions with secondary dendrites, except in the synaptic complexes where these junctions are usually asymmetrical. Type III terminals form (asymmetrical) synaptic junctions only with dendrites; the junctions are most commonly and characteristically effected with fine, distal dendrites, and much less commonly with secondary dendrites. Synaptic contacts with somata and primary dendrites have not been found, nor ''presynaptic dendrites''. Occasional dendro-dendritic filamentous junctions have been observed. The dominant synaptological feature of the neuropil is the occurrence of localised aggregations of secondary dendrites and synaptic knobs of types I and II which have been termed synaptic complexes; the latter resemble closely the synaptic glomeruli of certain other thalamic nuclei. The synaptic complexes of the inferior pulvinar, however, are but poorly encapsulated by glial lamellae. The most meaningful subdivision of the synaptic zone of the neuropil is into proximal (i.e. secondary dendritic) and distal dendritic types, each of distinctive and fairly homogeneous synaptic organization.Two to nine days after occipital lobotomy, almost all type I terminals were found to exhibit degenerative change of the neurofilamentous hyperplastic type; no subsequent electron-dense transformation of the affected visual corticofugal profiles has been observed. Terminals of types II and III remained completely normal. A number of electron-dense profiles interpreted as somata and dendrites showing acute retrograde necrosis or indirect Wallerian degeneration, were also observed.

ISSN:0006-8977    

DOI:10.1159/000124413

出版商:S. Karger AG    

年代:1973

数据来源: Karger

ISSN:0006-8977    

DOI:10.1159/000124414

出版商:S. Karger AG    

年代:1973

数据来源: Karger

ISSN:0006-8977    

DOI:10.1159/000124415

出版商:S. Karger AG    

年代:1973

数据来源: Karger