摘要:

AbstractThe distribution and morphological characteristics of monoamine (MA)‐containing neuronal somata in the brain stem of kittens and of adult cats were studied by means of the Falck‐Hillarp histofluorescence method. This investigation has shown, among other things, that in the mibrain of the cat the catecholamine (CA) perikarya are chiefly confined to the pars compacta of the substantia nigra, the ventromedial tegmental area, the nucleus linearis rostralis and the nucleus parabrachialis pigmentosus. Numerous CA neurons are also present in the dorsolateral part of the pontine tegmentum but also within the nucleus subcoeruleus, in nuclei lemnisci lateralis dorsalis and in nuclei parabrachialis lateralis and medialis. In the medulla, a few CA neuronal somata are lying near the hypoglossal nucleus whereas a larger number of CA cell bodies occur at the level of nucleus reticularis lateralis and in nucleus paragigantocellularis lateralis. On the other hand, most of the serotonin (5‐HT) perikarya are confined to the raphe nuclei of the brain stem: nuclei raphe dorsalis, centralis superior, raphe pontis, raphe magnus, raphe pallidus and raphe obscurus. Some 5‐HT neuronal somata are also found lateral to the pyramidal tract and to the inferior olivary complex. The various similarities and differences in respect to the pattern of the topographical distribution of MA neurons in the brain stem of the cat as compared to that of other mammals are di

ISSN:0092-7317    

DOI:10.1002/cne.901790402

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

年代:1978

数据来源: WILEY

摘要:

AbstractThe normal fine structure of glia and neuropil in the various regional subdivisions of the hypothalamic ventromedial nucleus in the adult male albino rat is described in this report. Although most HVM astrocytes throughout the nucleus appear ordinary in cytology, certain astrocytes found in the posterior ventrolateral subdivision of the nucleus appear somewhat reactive, in that they contain numerous thick fascicles of gliofibrils and pleomorphic dense bodies. The processes of these reactive astrocytes elaborate multiple, concentric lamellae which encapsulate small, round, pyknotic masses (probably degenerate axonal elements). These degenerate profiles, which are greatly outnumbered by normal HVM boutons, may represent synaptic contacts that deteriorate spontaneously in the normal adult HVM. Other signs of spontaneous degeneration occurring within this neuropil include the occasional presence of large masses of necrotic debris which appear engulfed by microglia. These findings suggest the presence in the normal adult HVM neuropil of a low‐grade degenerative process with attendant gliosis, which is topographically centered about the posterior ventrolateral region of the nucleus.Regions of neuropil containing degenerate boutons also contain altered neuronal processes, some of which may be growth cones. The topographic proximity of the degenerating boutons to possible signs of axonal or dendritic regeneration indicates that certain synaptic circuits in the normal adult HVM may be plastic, and subject to spontaneous remodellin

ISSN:0092-7317    

DOI:10.1002/cne.901790403

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

年代:1978

数据来源: WILEY

摘要:

AbstractThe principal findings of this report on the morphology and electrophysiology of the possum optic nerve are:(i)There are about 230,000 fibres in the optic nerve. This fibre count, based on electron microscopy, is slightly less than a previously reported estimate of the total number of ganglion cells in the possum retina.(ii)The majority (>98%) of the fibres of the optic nerve are myelinated axons of retinal ganglion cells. The diameters of these fibres range from 0.4–4.6 μm (axon diameter range: 0.3–3.8 μm) and the frequency distribution of the fibre diameters (and axon diameters) is positively skewed and unimodal.(iii)The antidromic compound action potential of the possum optic nerve shows four negative peaks following stimulation of the optic chiasm. These peaks are associated with four conduction latency groups of fibres which have been designated t1, t2, t3and t4in order of increasing conduction latency.(iv)The mean peak conduction velocities of the fibres in the conduction latency groups are 13.1 ms−1(t1), 8.1 ms−1(t2), 5.7 ms−1(t3) and 3.1 ms−1(t4).(V)There is no direct correlation between the frequency distribution of fibre (or axon) diameters as measured by electron microscopy of transverse sections of fixed optic nerve and the conduction latency groups.(vi)The reconstruction of the possum optic nerve compound action potential on the basis of either axon or fibre diameter frequency distribution does not provide an acceptable, indirect correlation between the morphology and the electrophysiology of thi

ISSN:0092-7317    

DOI:10.1002/cne.901790404

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

年代:1978

数据来源: WILEY

摘要:

AbstractThe antidromic compound action potential recorded near the centre of the possum optic disc, following stimulation of the optic chiasm, has four negative peaks corresponding to the optic nerve conduction latency groups t1, t2, t3and t4. The t2peak is reduced in the compound action potential recorded from the nasal margin of the optic disc but is prominent on the opposite side at the superior temporal margin. The t4peak may be absent in this vicinity.The frequency distributions of the diameters of intraretinal ganglion cell axons at the nasal margin and at the superior temporal margin of the optic disc are bimodal. Neither of these size distributions can be directly correlated with the multipeaked antidromic compound action potentials recorded at these same sites. However, by considering the frequency distribution difference between these sites, it is possible to infer (i) that the optic nerve t2group may be represented intraretinally on the temporal side by a population of medium sized axons with a modal diameter of 0.8 μm and (ii) that the t4group may be represented intraretinally on the nasal side by a population of small axons with modal diameter 0.3 μm.In addition, a correlation of axon sizes with previously reported regional variations in the sizes of ganglion cell somas suggests that the optic nerve t4conduction latency group may arise from small ganglion cells in the nasal streak and nasal peripheral retina and that the t2group may arise from medium sized cells in the temporal area centrali

ISSN:0092-7317    

DOI:10.1002/cne.901790405

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

年代:1978

数据来源: WILEY

摘要:

AbstractRapid Golgi preparations from area 17 of young adult rats have been studied to determine the morphology and distribution of non‐pyramidal neurons. Such cells were observed in all of the cellular laminae of the cortex, but were particularly prevalent in layers IV and V. Non‐pyramidal neurons were categorized according to two features: (1) dendritic projection pattern, and (2) abundance of dendritic spines. Dendritic patterns were classified asmultipolar,bitufted, andbipolar, and spine patterns asspinous, sparsely spinous, andspine‐free. Spinous dendrites were associated only with multipolar neurons, while sparsely spinous and spine‐free dendrites were each associated with cells of all three non‐pyramidal dendritic patterns. The most frequently observed non‐pyramidal cell types were multipolar cells of the spine‐free and sparsely spinous varieties. All of the general cell types encountered have been described in the literature on non‐pyramidal neurons, indicating the lack of any unique forms in rat area 17. An analysis of the dendritic projections of individual non‐pyramidal neurons through particular cortical laminae made possible an evaluation of common sources of dendrites present in the neuropil of each layer. Non‐pyramidal cell axons were impregnated only in small numbers. Spinous multipolar axons invariably exhibited a descending main branch, while the axons of bipolar neurons were distributed in a narrow vertical field. Axonal patterns of remaining cell types, including Golgi type II arborizations, did not appear to correlate consistently with dendritic morphology. Axons of the basket cell type and “horsetail” axons associated with double bouquet cells of Cajal's original ty

ISSN:0092-7317    

DOI:10.1002/cne.901790406

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

年代:1978

数据来源: WILEY

摘要:

AbstractThe techniques of reconstructions of cells from serial thin sections and autoradiography after tritiated thymidine injections have been employed to study the early histogenesis of the cerebral cortex in the embryonic day‐15 (E15) mouse. The autoradiographic studies show that cells below the E15 cortical plate in the intermediate layer are destined to migrate through the preexisting cortical plate cells to take up a more superficial position. Having this information, it has been possible, through reconstructions of large numbers of cells (more than 150) throughout the thickness of the cerebral vesicle, to identify some of the important morphogenetic events of cortical histogenesis. The following scheme is proposed. The first step in neuronal differentiation involves the detachment of the ventricularly directed process of the ventricular cell from the junctional region next to the ventricle. In thin sections, these junctions have the appearance of zonulae adherentes, but freeze cleavage experiments performed in this study show that, in addition, some of them resemble small gap junctions while others appear to be remnants of tight junctions or possibly linear gap junctions. Detachment of the ventricular process accompanies the migration of the nucleus and perikaryon through the ventricular layer. Within the intermediate layer the migrating cells become rounded and sprout numerous processes. Some cells may undergo a mitotic division at this stage. Eventually the differentiating cells sprout a longer lateral process which is oriented tangentially to the pial surface. This process originates from the anterior surface of the soma and at its tip has the characteristics of an axonal growth cone. The cells migrate externally and radially with simultaneous elongation of the primitive axon. In the subcortical plate region of the intermediate layer all cells contain an anteriorly directed axon. Subsequently the cells sprout an apical process which extends into the cortical plate, and the nucleus and perikaryon apparently migrate radially within this process. The result is that the primitive axon first descends into the intermediate layer proper before turning to run tangentially. Dendritic growth and further differentiation begins once the cells reach their definitive position in the cortical plate.One interesting finding is the presence of eight cells in the cortical plate without long anteriorly directed axons. Yet, autoradiographic data show that subcortical plate cells are the immediate precursors of cortical plate cells, and all 28/s28 reconstructed subcortical plate cells have long anteriorly directed axons. Thus, it is possible that the long axon of some cells may be lost as the cells continue to differentiate in the cortical plate. In fact, one cell has been found which appears to be in the process of losing its anteriorly directed axon.A number of molecular layer cells have also been reconstructed. These cells have several processes oriented tangentially to the pial surface. The identity of these processes could not always be determined. Occasional asymmetric synapses have been found between unidentified axons and the horizontal cell soma or its processes. Autoradiographic studies show that horizontal cells have the earliest time of origin of any cortical cell typ

ISSN:0092-7317    

DOI:10.1002/cne.901790407

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

年代:1978

数据来源: WILEY

摘要:

AbstractPostnatal development of the cerebellar cortex has been compared in staggerer mutant and unaffected littermate mice. From postnatal day 3 to about day 21 the external granular layer in staggerer mice is decreased in thickness and area, and the number of postmitotic granule cell neurons is reduced. Those granule cells that are generated seem to differentiate normally, with the remarkable exception that they from only primitive junctions with Purkinje cell dendritic shafts. These specialized junctions are not superseded by the normal parallel fiber: Purkinje spine synapses and disappear by the third week. Purkinje cell somata and dendrites are smaller than normal at all stages examined. The dendrites are not confined to the sagittal plane as in the normal and, unique among mutant or other animals described to date, they exhibit virtually no branchlet spines. All other cortical synaptic relations of granule and Purkinje cells, including climbing fiber: Purkinje spine synapses, appear qualitatively normal. However, by 28 days virtually all staggerer granule cells have degenerated. While the primary genetic defect remains unknown, we postulate that the morphological abnormalities may be attributable to a block in the normal developmental relationship between granule cells and Purkinje cells. The small cell size and failure to form branchlet spines suggest that the Purkinje cell abnormality may be closer to the primary effect of the mutant gene than the more flagrant hypoplasia and degeneration of granule cell neurons.

ISSN:0092-7317    

DOI:10.1002/cne.901790408

出版商:The Wistar Institute of Anatomy and Biology    

年代:1978

数据来源: WILEY

ISSN:0092-7317    

DOI:10.1002/cne.901790401

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

年代:1978

数据来源: WILEY