摘要:

AbstractThe multilamellate glial sheath of mixed nerve roots of the sixth abdominal ganglion of crayfish contains numerous hemi‐desmosomes which appear to attach glial lamellae to material in adjacent extracellular clefts. These junctions, which have been described in detail in an earlier report (Shivers and Brightman, '76), are irregular in shape, punctuate and may be as large as 1 μm in diameter. Surgical interruption of sixth ganglion nerve roots results in regeneration of motor axons and their multilamellate glial sheaths. As the glial processes grow and re‐establish a highly organized axon sheath, hemi‐desmosomes appear. These junctions are present at the advancing edge of glial processes as well as on their lateral margins. Developing hemi‐desmosomes are characterized as a diffuse aggregation of 120–130 Å intramembrane particles which are present three weeks following nerve section. As growth and reorganization of the sheath proceeds, the intramembrane particles appear to aggregate and form irregular clusters of varying dimensions. Regenerating nerves freeze‐cleaved 8 to 16 weeks following surgery exhibit junctional particle aggregates similar to those in normal unoperated nerve roots. Origin of the intramembrane particles which comprise the junctional aggre gates in unknown. Perhaps they are synthesizedde novoby the regenerating glial cells or, they may be remnants of complexes which became dispersed following surgery. This is the first report of a freeze‐fracture study of hemi‐desmosome plasticity in an invertebra

ISSN:0092-7317    

DOI:10.1002/cne.901730102

出版商:The Wistar Institute of Anatomy and Biology    

年代:1977

数据来源: WILEY

摘要:

AbstractThe origin, course, and termination of the commissural projection of the superior colliculus were studied using the orthograde autoradiographic tracing method and the retrograde method utilizing horseradish peroxidase.The complementary and mutually confirming sets of data showed that the commissural fibers interconnect a restricted region of the colliculi. This region includes thestrata grisea intermediumandprofundumand to a lesser degree thestratumopticum. It extends throughout only the rostral part of the colliculus where it ends abruptly at a level slightly less than half the distance from the anterior border of the deep gray layers. By using the needle used for isotope injection to record multiunit reponses to somatic and visual stimuli, direct evidence was obtained that this region falls within that functional area of the colliculus devoted to face representation and central vision. The results also suggested that more commissural fibers arise from lateral than medial parts of this region and that many fibers interconnect corresponding points in the colliculi. In addition to intertectal connections, the commissural projection contains decussating axons which terminate in tegmental structures and within a restricted zone of the central gray matter directly overlying the oculomotor complex.The results are discussed in relation to the possible role the commissural projection plays in the regulation of eye and head movements.

ISSN:0092-7317    

DOI:10.1002/cne.901730103

出版商:The Wistar Institute of Anatomy and Biology    

年代:1977

数据来源: WILEY

摘要:

AbstractThe neuronal generation patterns of hippocampal pyramids were analyzed in two inbred strains of house mice (SM/J and BALB/cJ) using tritiated thymidine radioautography. These two strains of mice possess markedly different patterns of mossy fiber synapses upon pyramidal neurons within a specific segment of regio inferior. The results of this study show that this same segment of regio inferior also displays markedly different patterns of pyramidal neuron generation in the two strains. Specifically, the pyramids of this segment of regio inferior are generated according to the typical [inside‐out] sequence in SM/J mice, but this pattern is reversed into an [outside‐in]sequence in BALB/cJ mice. The remaining segment of regio inferior, and all of regio superior, is formed in an inside‐out sequence in both strains. These results strongly suggest that altered temporal patterns of pyramidal neuron generation may play a major role in determining mossy fiber connectivity pat

ISSN:0092-7317    

DOI:10.1002/cne.901730104

出版商:The Wistar Institute of Anatomy and Biology    

年代:1977

数据来源: WILEY

摘要:

AbstractThe cells of origin of the corticostriatal projection have been identified in squirrel monkeys by the use of the retrograde horseradish peroxidase method. In the subfields of the somatic sensory, motor, parietal and frontal areas of the cortex, cells projecting to the ipsilateral striatum are relatively sparsely distributed and form a group of small‐ to medium‐sized pyramidal cells with an average somal diameter from area to area of 14‐16 μm. Such cells are found only in layer V of the cortex (mainly in the more superficial parts of the layer). Since they are consistently smaller than the pyramidal cells of layer V that project to the brainstem and spinal cord and since they lie outside layer VI which gives rise to corticothalamic axons, the corticostriatal axons are unlikely to be collaterals of axons projecting to other sites.The cells of origin of the'crossed corticostriatal projection are also found in layer V and are pyramidal cells with somal diameters in the same range as above. They are found only in areas 4, 8 and 6.Studies with the anterograde, autoradiographic method in rhesus, cynomologous and squirrel monkeys, indicate that the somatic sensory areas project to most of the antero‐posterior extent of the ipsilateral putamen. Subareas 3a, 3b, 1 and 2 of the somatic sensory cortex project to the same region and the projection overlaps similarly extensive projections from the motor and certain other areas of the cortex. However, in each case the pattern of terminal labeling is in the form of interrupted clusters, strips and bands. A single small injection of the cortex is associated with only one or two such clusters of terminal labeling. This seems to imply that individual corticostriatal fibers end in a very restricted manner and that the terminal ramifications of fibers from one cortical area may alternate in the putamen with those arising in oth

ISSN:0092-7317    

DOI:10.1002/cne.901730105

出版商:The Wistar Institute of Anatomy and Biology    

年代:1977

数据来源: WILEY

摘要:

AbstractThe distribution of cortical projections from areas 17, 18, and 19 to the lateral thalamus, pretectum, and superior colliculus was investigated with the autoradiographic tracing method. Cortical areas 17, 18 and 19 were demonstrated to project retinotopically and in register upon the dorsal lateral geniculate nucleus, medial interlaminar nucleus, lateral zone of the lateral posterior complex, nucleus of the optic tract and superior colliculus. Area 19 was shown to project retinotopically upon the pulvinar nucleus. Clear retinotopic organization was not demonstrable in the projections of areas 17, 18 and 19 to the reticular complex of the thalamus and ventral lateral geniculate nucleus, or in the projection of area 19 to the anterior pretectal nucleus.The cortical projections were employed to define the retinotopic organization of the nucleus of the optic tract, pulvinar nucleus, and lateral zone of the lateral posterior complex. The cortical projections show the vertical meridian to be represented caudally, with the lower visual field represented laterally, and the upper visual field medially, within the nucleus of the optic tract. The projections of area 19 to the pulvinar nucleus demonstrate the lower visual field to be represented rostrally and the upper visual field caudally in this nucleus; the vertical meridian to be represented at the lateral border and the visual field periphery to be represented at the medial border of the pulvinar nucleus. Cortical projections to the lateral zone of the lateral posterior complex demonstrate the lower visual field to be represented rostrally and the upper visual field caudally; the vertical meridian to be represented at the medial limit and the visual field periphery at the lateral border of the termination zones.On the basis of the experimental findings, a new terminology is introduced for the feline lateral posterior complex. Divisions are proposed which correspond to zones with demonstrably distinct afferent input. The pulvinar nucleus is defined by the distribution of projections from area 19. Three flanking divisions are defined within the lateral posterior complex; a lateral division recipient of projections from area 17, 18 and 19, an interjacent division recipient of projections of the superficial layers of the superior colliculus, and a medial division flanking the tectorecipient zone medially.

ISSN:0092-7317    

DOI:10.1002/cne.901730106

出版商:The Wistar Institute of Anatomy and Biology    

年代:1977

数据来源: WILEY

摘要:

AbstractThe afferent connections of the habenular complex in the rat were examined by injecting horseradish peroxidase (HRP) into discrete portions of the habenular nuclei by microelectrophoresis.1. HRP deposits confined to the lateral half of the lateral habenular nucleus labeled a multitude of cells in the entopeduncular nucleus. Numerous labeled cells also appeared in such cases in the lateral hypothalamus, indicating that the lateral habenular nucleus is a major convergence point of projections from these otherwise.2. HRP injected into the medial part of the lateral habenular nucleus labeled cells in the same regions, but more in the diagonal band and fewer in the entopeduncular nucleus than were labeled by more lateral injections. The contrast suggests that the projections from the basal forebrain and entopeduncular nucleus to the lateral habenular nucleus are somewhat topographically organized.3. Injections of the medial habenular nucleus labeled an abundance of cells in the posterior parts of the supracommissural septum, but also a small number of cells in the diagonal band and mesencephalic raphe.4. HRP injected into the stria medullaris labeled cells in all of the afore‐mentioned areas and, in addition, cells in several olfactory structures, confirming that HRP may be taken up by fibers of passage and label their cells of origin, and suggesting that olfactory structures contribute fibers to the stria medullaris that do not terminate in the habenul

ISSN:0092-7317    

DOI:10.1002/cne.901730107

出版商:The Wistar Institute of Anatomy and Biology    

年代:1977

数据来源: WILEY

摘要:

AbstractThe efferent projections from the cortical area 8 (frontal eye field) have been re‐examined in four adult monkeys (Macaca fascicularis) by injecting small amounts of H3‐proline into the rostral bank of sulcus arcuatus and using the autoradiographic tracing technique. Ipsilateral cortical projections could be traced into specific areas of the depths of sulcus principalis, sulcus temporalis superior and sulcus intraparietalis. Label was found contralaterally in area 8. Subcortical connections were observed ipsilaterally to n. caudatus, putamen, claustrum, n. ventralis anterior pars magnocellularis, n. medialis dorsalis pars multiformis and pars densocellularis, n. centralis lateralis and paracentralis, n. parafascicularis, n. pulvinar oralis, zona incerta, n. subthalamicus, pretectal area, colliculus superior and griseum pontis as well as to the ipsi‐ and contralateral n. reticularis tegmenti pontis. Negative results were obtained with respect to the oculomotor nuclei, n. interstitialis and Darkschewitsch as well as to the paramedian pontine reticular form

ISSN:0092-7317    

DOI:10.1002/cne.901730108

出版商:The Wistar Institute of Anatomy and Biology    

年代:1977

数据来源: WILEY

摘要:

AbstractThe pattern of normal nerve fibers associated with barrel‐shaped structures in the somatosensory cortex of both young and adult mice, has been studied using a reduced silver method. In adult animals, the [barrel] sides and septa can be seen to contain densely packed bundles of nerve fibers running vertically between layers III and V. In parasagittal sections, these fibers appear as very dark bands between adjacent barrels, while in tangential sections the fibers, cut in crosssection, appear as rings of dark spots concentrated around the barrel edges. In contrast to this, barrels in immature animals have dark, evenly stained centers and pale, cell dense sides. This immature pattern can first be distinguished in 2‐day‐old animals and persists until 18 to 19 days. Between 18 and 24 days a change from the immature to the adult pattern occurs with the appearance of darkly stained, fine fibers within layer IV, particularly within the barrel sides. It is suggested that the immature pattern is due, primarily, to the staining of thalamic afferents while the adult pattern appears with the development of intracortical and association fibers. Electron microscopy, on tissue previously treated by the silver method, shows that the silver deposits are mainly attached to longitudinal elements of the axoplasm and not associated with myelin. This may explain the success of this method in showing fibers in young, unmyelinated b

ISSN:0092-7317    

DOI:10.1002/cne.901730109

出版商:The Wistar Institute of Anatomy and Biology    

年代:1977

数据来源: WILEY

摘要:

AbstractThe present study is an analysis of the ventral roots in the rat. The smallest myelinated fibers are found in segments T1‐L2 and L6‐S1. These fibers are regarded as preganglionic efferents and the L6‐S1 outflow is more cranial than the sacral parasympathetic outflow in other animals. Large numbers of unmyelinated axons are seen in segments T1‐L2 and L6‐S1, the same segments that contain the smallest myelinated fibers. This data will be used as a baseline for determining the functional categories of the unmyelina

ISSN:0092-7317    

DOI:10.1002/cne.901730110

出版商:The Wistar Institute of Anatomy and Biology    

年代:1977

数据来源: WILEY

摘要:

AbstractLesions were made in the visual system in a series of cat fetuses of known gestational age, and fiber and terminal degeneration were stained by the Eager method.The times of development of the retinal projection, of the thalamocortical and corticothalamic projections of area 17 of the visual cortex, and of the intrinsic fibers in the visual cortex were examined.Enucleation of one eye resulted in degeneration being detected bilaterally in the lateral geniculate nuclei (LGN), superior colliculi (SC) and optic tracts. The optic nerves reached the optic chiasm by the thirtieth embryonic day (E30) and the optic tract connections with the LGN and SC were made by E37. The projection always appeared stronger in the contralateral LGN and SC, and the amount of degeneration increased in both sides with increasing age.A parasagittal knife cut was made in the dorsomedial crest of the visual cortex. Where the lesion passed through the cellular layers of the cortex, intrinsic fibers were cut when these were present. The deeper part of the incision through the white matter undercut the medial wall of the visual cortex, interrupting thalamocortical and corticothalamic fibers when these were present.The longer horizontal fibers that were intrinsic to the visual cortex began to develop during the last two weeks of gestation but were not fully developed at birth. In the undercut visual cortex distant from the place of entry of the lesion, and before the intrinsic fibers of the cortex had developed, degeneration was found in layers 1 and 4, demonstrating the presence of a thalamocortical pathway. The youngest fetus to show this degeneration was operated at E48. This degeneration was not present three days earlier at E45. Fiber plexuses that have been described earlier in development (Marin‐Padilla, '71; Cragg, 75) do not appear to degenerate after undercutting the cortex.The corticothalamic pathway to the lateral posterior nucleus medial to the LGN was developed at E45. The descending pathways to the ipsilateral LGN and SC were developed by E48, but it is not known whether they are present before this.Thus degeneration has been used to detect the development of axonal pathways in the fetus for the first time; the major afferent and efferent pathways are developed at an earlier stage than has previously been describe

ISSN:0092-7317    

DOI:10.1002/cne.901730111

出版商:The Wistar Institute of Anatomy and Biology    

年代:1977

数据来源: WILEY