摘要:

AbstractDetails of neuronal reorganization were investigated in golden hamster pups 10 days after neonatal olfactory lesions. Pups sustained unilateral olfactory tract section (ULOT) or unilateral olfactory bulbectomy (UOB) on postnatal day 5 (P5) and were then behaviorally tested through P15. UOBs were sacrificed after P15 to assess the extent of lesions. ULOTs were processed with degeneration techniques to demonstrate the terminal distribution of bulb fibers whose path had been either deflected or severed by the early tract section.Ten days after complete tract section, extensive sprouting of bulb fibers had occurred rostral to the cut in olfactory as well as adjacent nonolfactory (e.g., neocortical) regions. The pattern of rostral sprouting was similar to, and in some cases exceeded, that described in adults subjected to neonatal tract sections (Devor, 76b). Fibers grew caudally past the cut following aberrant paths to reinnervate limited regions of the olfactory tubercle and less frequently, the piriform cortex. Unlike the continuous band of terminals soon in the caudal field of adults given neonatal tract sections, at this early stage of regrowth, fibers were organized in small discontinuous fascicles that tended to cluster at the islands of Calleja of the tubercle. Although these fibers innervated a relatively restricted region in comparison with normal innervation, their connections were apparently functional, as measured by a thermotaxis behavioral assay for the effects of UOB. The ther‐motaxis behavior of most pups showing tubercle reinnervation returned to normal, while the behavior of pups without tubercle reinnervation remained similar to UOBs (Small and Leonard, ′82). Excessive rostral sprouting and invasion of neocortex were seen in all tract‐sectioned pups and were, therefore, apparently not sufficient to sustain normal behavior on this assay.Regrowth of sensory olfactory fibers and extensive formation of glo‐meruli in the anterior olfactory nucleus and, occasionally, in prefrontal neocortex were found following olfactory bulbectomy. There was no correlation between the extent of glomerulization and the behavioral performance, however.The olfactory system provides an appropriate system for investigating the parameters governing age‐dependent axonal sprouting and functional recovery following early bra

ISSN:0092-7317    

DOI:10.1002/cne.902140402

出版商:Alan R. Liss, Inc.    

年代:1983

数据来源: WILEY

摘要:

AbstractThe present study defined the time course of terminal proliferation (the growth of presynaptic processes) and reactive Synaptogenesis in the dentate gyrus of the adult rat. Quantitative electron microscopic analyses were carried out in the dentate gyrus 2, 4, 6, 8, 10, 12, 14 days and 7 months after destruction of the ipsilateral entorhinal cortex and in the contralateral (control) dentate gyrus. At each survival interval, counts were made from photographic montages of (1)terminals(presynaptic processes with or without contacts with postsynaptic elements), (2)intact synapses, (3)degenerating synapses, (4)degeneration(degenerating presynaptic processes), and (5)multiple synapses(terminals making more than one synaptic contact). Terminal density was initially reduced to about 13% of control in the middle molecular layer at 2 and 4 days postlesion, and to about 26% of control in the outer. The density of terminals began to increase between 4 and 6 days postlesion, reaching a plateau by day 12. Synapse density was reduced to about 8% and 12% of control in the middle and outer molecular layer respectively. Synapse density increased about 5‐fold between 8 and 12 days postlesion, but continued to increase in the period between 14 days and 7 months postlesion. At 2 days postlesion, the number of intact terminals that are lost corresponds to the number of degenerating presynaptic processes. This correspondence is not present at 4 days postlesion, however, suggesting a rapid removal of degenerating terminals. In contrast, even at 2 days post‐lesion, the number of intact synapses that are lost does not correspond to the number of degenerating synapses. Between 2 and 10 days postlesion, the number of postsynaptic specializations is about 60% of control, but recovers slightly by 12‐14 days postlesion. Qualitative and quantitative evidence suggested a collapse of spines into configurations that resembled shaft synapses. There appeared to be a deformation of degenerating presynaptic processes resulting in the appearance of multiple synapse configurations prior to reinnervation. The combined results suggest that terminal proliferation precedes reactive Synaptogenesis in the dentate gyrus by 2‐4 days, that terminal proliferation is essentially complete by 12 days while reactive Synaptogenesis continues, and that multiple synapses arise at least in part as a result of a deformation of degenerating presynaptic processes rather than as a consequence of the induction of additional contacts on existing presynaptic te

ISSN:0092-7317    

DOI:10.1002/cne.902140403

出版商:Alan R. Liss, Inc.    

年代:1983

数据来源: WILEY

摘要:

AbstractThe organization of the dendritic tree and the morphology of individual dendrites of the dentate granule cell were analyzed qualitatively and quantitatively by means of the rapid Golgi technique 2, 4, 8, 10, 14, 30, 60, and 250 days after unilateral lesions of the entorhinal cortex (EC). Three dendritic field parameters were analyzed from camera lucida drawings of de‐nervated granule cells at each survival time: (1) dendritic field spread, (2) dendritic length, and (3) dendritic branching. Cells in the contralateral dentate gyrus served as controls. Spines were counted at each postlesion interval from material stained with a modification of the Golgi‐Kopsch method. The amount of tissue occupied by dendritic shafts at different postlesion intervals was also evaluated in samples of the ventral leaf of the dentate gyrus prepared for electron microscopy. After unilateral lesions of the EC, dendrites of the granule cells undergo modifications which appear to represent deterioration and recovery. When the dendrites reach the denervated zone, they abruptly change their orientation and tend to follow a course parallel to the granule cell layer. In contrast to normal dendrites, those in the denervated neuropil only occasionally reach the outer boundaries of the molecular layer. At the time of maximal denervation there is often a sudden reduction in dendritic diameter as the dendrite enters the denervated zone. Varicosities are also prominent. The alterations in individual dendrites are not evident 2 days after the lesion, are fully developed 10 days after deafferentation; and disappear for the most part by 30 days postlesion. The quantitative analysis of Golgi‐stained granule cells reveals that there is a 40% reduction in the total length of the granule cell dendritic tree. Electron microscopic analysis confirms the Golgi observations, indicating that the amount of neuropil occupied by dendritic shafts in the denervated zone is initially reduced and later recovers to values close to those observed in control animals. While the apparent dendritic loss is mainly restricted to the denervated zone, significant modifications occur in the inner npnde‐nervated molecular layer; there is an increase in the length of primary dendrites as evidenced by an increase in the distance to the first branch point. There is also a polarized redistribution of 1st, 2nd, 3rd, and 4th branch points toward the middle and outer molecular layer that persists even 30 days after the lesion. The results are discussed in terms of the capabilities of the granule cells of the dentate gyrus to reorganize and remodel their dendritic surface after partial deaffere

ISSN:0092-7317    

DOI:10.1002/cne.902140404

出版商:Alan R. Liss, Inc.    

年代:1983

数据来源: WILEY

摘要:

AbstractCobaltous‐lysine was applied to one optic nerve of normal goldfish in order to determine the source of the centrifugal innervation of the retina. Cobalt‐filled cells were not observed in the optic tectum, pretectum, thal‐amus, or hypothalamus. However, filled cells were observed outside the central nervous system either interspersed between the olfactory nerve fibers orrostrally along the ventromedial aspect of the olfactory bulbs. These cells appear to correspond to the ganglion cells of the nervus terminalis. The cells were located bilaterally and had dendrites that branched in close proximity to the cell body and axons that coursed caudally through the medial olfactory tract. The axons traveled in the ventral forebrain and entered the optic tracts. The axons also gave off fine branches that appeared to terminate in the vicinity of the anterior commissure and in the preoptic region. Application of cobaltous‐lysine to a cut olfactory tract resulted in cobalt‐filled fibers in the optic tracts, retinal optic fiber layer, and retinal ganglion cell layer. However, the precise terminations of these fibers within the retina could not be readily established. The results are discussed with respect to the plethora of sources of retinopetal cells observed by others in fish and with respect to the innervation of the retina by luteinizing hormone‐releasing ho

ISSN:0092-7317    

DOI:10.1002/cne.902140405

出版商:Alan R. Liss, Inc.    

年代:1983

数据来源: WILEY

摘要:

AbstractTritiatedproline or horseradish peroxidase (HRP) was injected into the middle ectosylvian auditory cortex (AI) of one hemisphere in kittens during the first few weeks postpartum. Survival time was 24–96 hours. The tetra‐methylbenzidine (TMB) (Mesulam '78) method was used to process the HRP material. By the first postnatal day (PND 1) most neurons retrogradely filled in the contralateral auditory cortex form a densely packed, continuous band that presumably represents mainly layer III. This continuous pattern is in contrast to that seen in the adult cat where callosal neurons tend to aggregate in clusters. Other retrogradely labelled cells are more sparsely distributed in deeper layers with the greatest accumulation being in layer VI. At this time callosal neurons are elongated, with their long axes parallel to radial cell columns. In autoradiographs on PND 2, silver grains are seen throughout the thickness of the cortex, indicating that callosal axons have reached the upper layers of the gray matter. Neither the alternating vertical columns nor the laminar bands of callosal afferents that characterize this projection in the adult are clearly seen in kittens of this age. By PND 8–12 the segregation of callosal afferents into vertical bands is evident in the gray matter; by PND 18 this pattern is well developed. On the other hand, the somata of callosal neurons of layer III retain their juvenile distribution well into the seventh postnatal week and show adultlike aggregations sometime around the 14th week after birth. Projections to the medial geniculate body, inferior colliculus, putamen, caudate nucleus, and pons are clearly evident early in the first postnatal

ISSN:0092-7317    

DOI:10.1002/cne.902140406

出版商:Alan R. Liss, Inc.    

年代:1983

数据来源: WILEY

摘要:

AbstractTyrosine hydroxylaselike immunoreactivity is associated with several different classes of neurons in the main olfactory bulb of the hamster. Most of the tyrosine hydroxylaselike immunoreactive (THLI) neurons are located in the glomerular layer and in the outer two‐thirds of the external plexiform layer. The majority of THLI neurons in the glomerular layer have somal sizes and dendritic features which correspond to those of external tufted cells. A small population of THLI periglomerular cells also is present. The majority of THLI neurons in the external plexiform layer have the morphological characteristics of middle tufted cells. A small population of THLI neurons which appear to be Van Gehuchten cells is distributed throughout the external plexiform layer and in the mitral body layer. Small populations of THLI deep short‐axon cells are distributed throughout the mitral body, internal plexiform, and granule cell layers. Tyrosine hydroxylase‐positive fibers of central origin also are observed in the main olfactory bulb. They may originate from THLI neurons in the anterior olfactory nucleus, ventral hippocampal rudiment, dorsal peduncular cortex, septal and basal portions of the vertical limb and nucleus of the horizontal limb of the diagonal band, lateral and dorsal hypothalamus, ventral tegmental area and substantia nigra, dorsal and median raphe nuclei, and locus ceruleus. The frontal neocortex, infralimbic and anterior cingulate cortex, and medial amygdaloid nucleus also contain THLI neurons.In contrast to the widespread distribution of tyrosine hydroxylaselike immunoreactivity in the main olfactory bulb, substance P‐like immunoreactivity is restricted to external tufted cells and to centrifugal afferents which may originate in the dorsal and median raphe nuclei. Both types of immunoreactivity appear to be present in centrifugal afferents to the accessory olfactory bulb, but THLI neurons are extremely rare and no neurons with substance P‐like immunoreactivity have been observed in the accessory olfactory bulb. Intraventricular injections of colchicine which were expected to enhance the labeling of neuronal somata did not alter the relative incidences of labeling among the various classes of neurons in the olfactory bulbs.These findings provide immunocytochemical evidence that populations of superficially situated tufted cells in the main olfactory bulb are functionally distinct from the deeper‐lying output neurons and from output neurons in the accessory olfactory bulb, that populations of catecholami‐nergic neurons are present within several olfactory and related cortical structures in addition to the olfactory bulbs, that the medical septum‐diagonal band complex also contains catecholaminergic neurons, and that a substantial population of neurons in the dorsal raphe nucleus is capable of vat

ISSN:0092-7317    

DOI:10.1002/cne.902140407

出版商:Alan R. Liss, Inc.    

年代:1983

数据来源: WILEY

摘要:

AbstractAnatomical parameters derived from an analysis of 35 male brains, ranging in age from 137 days after conception (DAC) to 99 years, were studied in reference to the development of the human visual cortex (area 17). Distinct structuring of laminae V and VI of area 17 is present at 137 DAC, contrasting with the relative undifferentiation of area 18 at this time. Both the differentiation of the visual cortex into the fundamental six laminae of Brodmann and the emergence of the stripe of Gennari occur between 180 and 190 DAC. At this time, sublamina IVa emerges as a separate entity, external to a transient, trilaminated cortical complex of which the two internal components form sublamina IVc while the external component becomes a part of sublamina IVb (stripe of Gennari). Lamination in area 18 follows a different time course than area 17, appearing at about 160 DAC and achieving a definite six‐layered structure at the 185th DAC. The widths of the laminae in both areas continue to fluctuate after the 190th DAC while the cellular density appears to decrease. The fresh volume of the visual cortex was determined from stained serial sections of the brain, following adjustment for artifactual shrinkage. Approximations of values utilizing the 3‐, 4‐, and 5‐parametric logistic functions reveal that maximum growth of this area occurs at birth, with area 17 attaining 50% of its maximum volume. The maximum volume is reached at the 300th DAC and it apparently begins to decrease in the first decade. The visual cortex develops at a considerably faster rate and reaches its maximal volume much earlier than does the whole brain, cerebellum, or hippocampal fo

ISSN:0092-7317    

DOI:10.1002/cne.902140408

出版商:Alan R. Liss, Inc.    

年代:1983

数据来源: WILEY

摘要:

AbstractTwo intracellularly stained gastrocnemius a‐motoneurons of the FF‐type (Burke et al., ′73) were studied ultrastructurally. The architecture and synaptology of the cell bodies and proximal dendrites were analyzed from long series of consecutive sections according to, a methgd previously described (Conradi et al., ′79a). Several of the dendrites had a base diameter exceeding 10 μm. The proportion of the cell surface area covered by boutons was 40‐50% for the soma and about 70% for the proximal dendrites. In both regions, about 20‐25% of the boutons were of the S‐type and 60‐70% of the F‐type. In general, the type FF α‐motoneurons exhibited the same gross synaptological characteristics as those found earlier in type FR α‐motoneurons (Kellerth et al., ′79), although the large boutons of the C‐type were more frequent on the proximal dendrites and axon hillocks of the present cells. M‐boutons of dorsal root origin were found on several of the proximal dendrites. The observed regional differences in the spectrum of boutons on the motoneuron surface seem to follow gradients operating in the somato‐fugal direction, and they are apparently independent of the size or dir

ISSN:0092-7317    

DOI:10.1002/cne.902140409

出版商:Alan R. Liss, Inc.    

年代:1983

数据来源: WILEY

摘要:

AbstractIntracerebral injections of the neuron‐destroying agent, kainic acid, and electron microscopic examination of the injected and the target areas, have been used in order to confirm some controversial anatomical connections in the Septohabenulointerpeduncular system. Kainic acid injections in the lateral habenula (LHb) caused the selective degeneration of several LHb neurons, sparing the neurons of the medial habenula (MHb). Degenerating terminals were found in well‐known target areas of the LHb (dorsal and median raphe nuclei) and, in addition, in the interpeduncular nucleus (IPN), thus confirming the existence of a small LHb‐IPN projection. Kainic acid injections in the nucleus of the diagonal band of Broca (NDBB) resulted in severe ncuronal degeneration in the nucleus itself and in terminal degeneration in the LHb and MHb as well as, to a lesser extent, in the IPN. No evidence of distant neuronal damage was apparent by light (conventional and cupric‐silver stain) and electron microscopic examination, in nuclei receiving afferent inputs from the injected areas and projecting in turn to the target areas. Furthermore, terminal degeneration was not observed in the Hb and IPN after injections of kainic acid in areas not projecting toward these nuclei (hippocampus and striatum). In the present study, therefore, problems of interpretation due to the possible occurrence of distant neuronal damage could be overcome by control tests.On the basis of the selectivity and sensitivity of its action, kainic acid seems particularly useful in the study of small projections and in attempts to discriminate between differential connections of adjacent neuronal popu

ISSN:0092-7317    

DOI:10.1002/cne.902140410

出版商:Alan R. Liss, Inc.    

年代:1983

数据来源: WILEY

ISSN:0092-7317    

DOI:10.1002/cne.902140401

出版商:Alan R. Liss, Inc.    

年代:1983

数据来源: WILEY