摘要:

AbstractRegional variations in cell‐packing density, culminating in the formation of cell clusters, is now a recognized morphological characteristic of the striatum that has been correlated, in some instances, with either regional histochemical variations or the distribution pattern of afferent fiber systems, or both. Within these cluster regions a further level of organization exists, in the form of discrete neuronal aggregates. The light microscopic morphology of these neurons and the nature of their intercellular contacts at the electron microscope level form the focus of this report. The neurons composing such aggregates are characterized by contiguous soma‐somatic or soma‐dendritic contact with extended regions of junctionlike symmetrical and consistent contacts where the distance between the cytoplasmic membranes of apposing neurons narrows to as close as 7 nm. Coated vesicles close to the contact areas are common. Three‐dimensional computer reconstructions of serial 1 μm sections through aggregates in either the caudatoputamen or nucleus accumbens reveal “chains” of contiguous cells that frequently involve as many as 60 neurons. These contiguous cell aggregates are discrete entities within the larger clusters or islands. It is postulated that the cellular aggregates may represent the fundamental level of striatal organization and may be local modules for intrinsic information processing, modifying extrinsic data processed through the biochemical compartmentalization of the striatum imparted by striosomes, neuropeptides, and dopaminergic, thalamic and cortic

ISSN:0092-7317    

DOI:10.1002/cne.903050302

出版商:Wiley‐Liss, Inc.    

年代:1991

数据来源: WILEY

摘要:

AbstractPyramidal neurons within the cerebral cortex are known to make long‐range horizontal connections via an extensive axonal collateral system. The synaptic characteristics and specificities of these connections were studied at the ultrastructural level. Two superficial layer pyramidal cells in the primate striate cortex were labeled by intracellular injections with horseradish peroxidase (HRP) and their axon terminals were subsequently examined with the technique of electron microscopic (EM) serial reconstruction. At the light microscopic level both cells showed the characteristic pattern of widespread, clustered axon collaterals. We examined collateral clusters located near the dendritic field (proximal) and approximately 0.5 mm away (distal). The synapses were of the asymmetric/round vesicle variety (type I), and were therefore presumably excitatory. Three‐quarters of the postsynaptic targets were the dendritic spines of other pyramidal cells. A few of the axodendritic synapses were with the shafts of pyramidal cells, bringing the proportion of pyramidal cell targets to 80%. The remaining labeled endings were made with the dendritic shafts of smooth stellate cells, which are presumed to be (GABA)ergic inhibitory cells. On the basis of serial reconstruction of a few of these cells and their dendrites, a likely candidate for one target inhibitory cell is the small‐medium basket cell. Taken together, this pattern of outputs suggests a mixture of postsynaptic effects mediated by monosynaptic excitation followed by combined disynaptic inhibition and excitation. As a consequence the horizontal connections may well be the substrate for the variety of influences observed between the receptive field center and its sur

ISSN:0092-7317    

DOI:10.1002/cne.903050303

出版商:Wiley‐Liss, Inc.    

年代:1991

数据来源: WILEY

摘要:

AbstractThe distribution of vasoactive intestinal peptide (VIP) binding sites in the pigeon brain was examined by in vitro autoradiography on slide‐mounted sections. A fully characterized monoiodinated form of VIP, which maintains the biological activity of the native peptide, was used throughout this study. The highest densities of binding sites were observed in the hyperstriatum dorsale, archistriatum, auditory field L of neostriatum, area corticoidea dorsolateralis and temporo‐parieto‐occipitalis, area parahippocampalis, tectum opticum, nucleus dorsomedialis anterior thalami, and in the periventricular area of the hypothalamus. Lower densities of specific binding occurred in the neostriatum, hyperstriatum ventrale and nucleus septi lateralis, dorsolateral area of the thalamus, and lateral and posteromedial hypothalamus. Very low to background levels of VIP binding were detected in the ectostriatum, paleostriatum primitivum, paleostriatum augmentatum, lobus parolfactorius, nucleus accumbens, most of the brainstem, and the cerebellum.The distribution of VTP‐containing fibers and terminals was examined by indirect immunofluorescence using a polyclonal antibody against porcine VIP. Fibers and terminals were observed in the area corticoidea dorsolateralis, area parahippocampalis, hippocampus, hyperstriatum accessorium, hyperstriatum dorsale, archistriatum, tuberculum olfactorium, nuclei dorsolateralis and dorsomedialis of the thalamus, and throughout the hypothalamus and the median eminence. Long projecting fibers were visualized in the tractus septohippocampalis. In the brainstem VIP immunoreactive fibers and terminals were observed mainly in the substantia grisea centralis, fasciculus longitudinalis medialis, lemniscus lateralis, and in the area surrounding the nuclei of the 7th, 9th, and 10th cranial nerves. The correlation between the distribution of VIP binding sites and immunoreactive fibers and terminals was assessed in a restricted number of regions. A qualitatively good matching was found in the area corticoidea dorsolateralis, hyperstriatum dorsale, hyperstriatum accessorium, nucleus septi lateralis, nuclei dorsomedialis and dorsolateralis thalami, and in some hypothalamic areas. A striking mismatch occurred in the hyperstriatum ventrale, neostriatum, tectum opticum (high to moderate density of binding sites but only few immunoreactive profiles), and in the tuberculum olfactorium, median eminence, and spinal cord (lower density of binding sites but abundant immunoreactive profiles). The paleostriatum, lobus parolfactorius, and ectostriatum were virtually devoid of both binding sites and immunoreactive profiles. The results are discussed in relationto the know action of VIP in the rodent and avian brain and are compared with previous observations on the distribution of VIP binding in the central nervous system of other vert

ISSN:0092-7317    

DOI:10.1002/cne.903050304

出版商:Wiley‐Liss, Inc.    

年代:1991

数据来源: WILEY

摘要:

AbstractAn immunohistochemical study of opioid peptides in the hypophysis of the axolotl,Ambystoma mexicanum, was carried out with antisera against leu‐enkephalin, beta‐endorphin, met‐enkephalin, and dynorphin A (1–8). We found leu‐enkephalin immunoreactivity in some fibers of the neural lobe and the median eminence. In contrast to previous reports on mammals and other vertebrates, we found leu‐enkephalin immunoreactivity in many cells scattered throughout the anterior lobe. As in other vertebrates, the beta‐endorphin immunoreactivity was present in all the cells of the intermediate lobe and in a few cells of the anterior lobe. Met‐enkephalin and dynorphin A (1–8) immunoreactivities were only present in the neural lobe and the median eminence. The presence of leu‐enkephalin and beta‐endorphin in the anterior lobe suggests that these peptides could be acting as hormones released from the hypophysis of the unme

ISSN:0092-7317    

DOI:10.1002/cne.903050305

出版商:Wiley‐Liss, Inc.    

年代:1991

数据来源: WILEY

摘要:

AbstractLurcheris an autosomal dominant mutation in the mouse. Heterozygote (+/Lc) animals lose 100% of their cerebellar Purkinje cells during the first postnatal month. Aggregation chimeras made between +/Lcand wild‐type embryos have been used to demonstrate that this neuronal cell death is a cell autonomous property of the +/LcPurkinje cells. Inlurcherchimeras, all +/LcPCs die while wild‐type Purkinje cells survive in the numbers expected. Although they are normal in number, previous work from our laboratories has shown that when the genetically wild‐type Purkinje cells are present in the mosaic environment of thelurcherchimeric mouse they develop a very unusual morphology. Their dendritic trees are small, and the caliber of their dendrites is increased. This paper examines the fine structure of these unusual cells as well as their afferent fibers. Purkinje cell somas in thelurcherchimera have an increased number of lysosomes and the rough endoplasmic reticulum is improperly configured. In the majority of the Purkinje cell dendrites the organelles are disorganized; it is not certain whether this is a cause or a consequence of the increase in dendritic caliber previously reported. Presynaptic fibers have been examined and, while all classes of expected synapses can be observed, the numbers of synaptic profiles visible in any one thin section are reduced. Climbing fiber terminations on the Purkinje cells were smaller than normal with a greatly diminished number of constituent vesicles. Unexpectedly, we found unusual morphologies among the Bergmann glial fibers and the presence of unusual (or ectopic) astrocytic like glial cells near the pial surface. These changes in turn were accompanied by an increase in the number of glial‐like fibers near the pia in some parts of the chimeric cerebellar cortex. The results are discussed in light of our knowledge of other mutant mice, and a hypothesis is put forward to explain some of our

ISSN:0092-7317    

DOI:10.1002/cne.903050306

出版商:Wiley‐Liss, Inc.    

年代:1991

数据来源: WILEY

摘要:

AbstractAfter horseradish peroxidase (HRP) injections were made in limited sectors of the main olfactory bulb in the adult frogRana pipiens, the cellular morphology of mitral cells and granule cells impregnated with HRP were examined in uninjected regions of the bulb. Mitral cells were observed to possess glomerular dendrites and prominent secondary dendrites, both of which have smooth shafts. The glomerular dendrites may be multiple, are often branched, and may arise from secondary dendrites, as well as from the cell body. The axon may also arise from a secondary dendrite. Granule cells have simple or branched peripheral dendrites, and these are spiny, where they intermingle with the mitral cell secondary dendrites. The prominence of the secondary dendrites of frog mitral cells contrasts sharply with their reported insignificance in urodeles, as studied in earlier literature.The layers of the main olfactory bulb are not as fully concentric in the frog, as they are in mammals. The implantation cone and glomerular layer occupy a small part of the surface area of the olfactory bulb on its anteroventral aspect, while the perimeters of the subjacent layers extend farther posteriorly and dorsally in successive steps. The granule cell core extends well beyond the perimeter of the mitral cell layer in a posterior direction. Long secondary dendrites of mitral cells also extend posteriorly beyond the perimeter of the mitral cell‐external plexiform layer and interlace with granule cell peripheral dendrites in a plexiform layer external to the posterior region of the granule cell core. This layer, thesuperficial plexiform layer, forms an apron around the posterior segment of the olfactory bulb and contributes to the interbulbar adhesion. It appears likely that it is an extension to the microcircuitry typically confined within the external plexiform layer in mammalian specie

ISSN:0092-7317    

DOI:10.1002/cne.903050307

出版商:Wiley‐Liss, Inc.    

年代:1991

数据来源: WILEY

摘要:

AbstractThe central projections of the main olfactory bulb and the accessory olfactory bulb of the adult leopard frog (Rana pipiens) were reexamined, by using a horseradish peroxidase anterograde tracing method that fills axons with a continuous deposit of reaction product. The fine morphology preserved by this method allowed the terminal fields of the projection tracts to be delineated reliably, and for the first time. Herrick's amygdala has been newly subdivided into cortical and medial nuclei on the basis of cytoarchitecture, dendritic morphology, and the differential projections of the main and accessory olfactory tracts.The main olfactory bulb projects through the medial and lateral olfactory tracts to the postolfactory eminence, the rostral end of the medial cortex, the rostral end of the medial septal nucleus, the cortical amygdaloid nucleus, the nucleus of the hemispheric sulcus, and both the dorsal and ventral divisions of the lateral cortex, including its retrobulbar fringe. The lateral olfactory tract overlaps the dorsal edge of the striatal plate along the ventral border of the lateral cortex, but it is not certain whether any striatal cells are postsynaptic to the tract fibers. The lateral cortex is the largest of these territories, and receives the terminals of the main olfactory projection throughout its extent. It extends from the olfactory bulb to the posterior pole, and from the striatum to the summit of the hemisphere, where it borders the dorsal cortex. The medial and lateral olfactory tracts combine in the region of the amygdala to form a part of the stria medullaris thalami. These fibers cross in the habenular commissure and terminate in the contralateral cortical amygdaloid nucleus and periamygdaloid part of the lateral cortex. Cells projecting to the main olfactory bulb are found in the diagonal band and adjacent cell groups, but there is no evidence of an interbulbar projection arising from either the olfactory bulb proper or a putative anterior olfactory nucleus.The accessory olfactory bulb projects through the accessory olfactory tract to the medial and cortical amygdaloid nuclei. A fascicle of the tract crosses in the anterior commissure to terminate in the contralateral amygdala. While the main and accessory olfactory projections may converge in the cortical amygdaloid nucleus, the medial amygdaloid nucleus is connected exclusively with the accessory olfactory bulb.

ISSN:0092-7317    

DOI:10.1002/cne.903050308

出版商:Wiley‐Liss, Inc.    

年代:1991

数据来源: WILEY

摘要:

AbstractThe organization of GABAergic elements in the histaminergic tuberomammillary nucleus has been examined by using antibodies against γ‐aminobutyric acid (GABA) and light and electron microscopy.Most neuronal perikarya of the ventral subgroup of the tuberomammillary nucleus were GABA immunoreactive (GABA‐i). The morphology of the GABA‐i perikarya was similar to the morphology of histaminergic perikarya described by Hayashi et al. ('84:J. Comp. Neurol. 229:233–241) and Wouterlood et al. ('86:J. Comp. Neurol. 252:227–243).The GABA‐i perikarya were contacted by relatively few terminals. The mean bouton covering ratio of GABA‐i perikarya was 6.1%, whereas the mean bouton covering ratio for GABA‐i dendrites in the tuberomammillary nucleus was 31%. Some of the presynaptic terminals were GABA‐i. In addition, GABA‐i perikarya and dendrites formed close contacts that never presented synaptic specializations. These results suggest that neurons of the histaminergic tuberomammillary nucleus contain the neurotransmitter GABA. Furthermore, GABA may act as a modulator of cellular processes within the tube

ISSN:0092-7317    

DOI:10.1002/cne.903050309

出版商:Wiley‐Liss, Inc.    

年代:1991

数据来源: WILEY

摘要:

AbstractRetrograde transport ofPhaseolus vulgarisleucoagglutinin (PHA‐L), fluorogold, fast blue, rhodamine labelled microspheres, and horseradish peroxidase (HRP) was employed to study the distribution, laminar location within the optic tectum, and morphology of tectal cells projecting upon the isthmo‐optic nucleus (ION) and the nucleus isthmi, pars parvocellularis (Ipc), in the pigeon and chick.Following injections into the ION, all retrograde markers labelled tecto‐ION neurons and their dendrites in the ipsilateral tectum. The cells were located within a relatively narrow band at the border between layers 9 and 10 of the stratum griseum et fibrosum superficial (SGFS). Retrogradely labelled neuronal somata were different in both dendritic branching and shape; however, tecto‐ION neurons generally possessed non‐spiny radially oriented and multi‐branched dendrites. The apical processes extended into the retino‐recipient layers (2–7) of the SGFS and basal dendrites extended into layers 12–14 of the SGFS. Positive neuronal somata were observed throughout the rostro‐caudal extent of the optic tectum. The average distance between adjacent tecto‐ION neurons varied from one region to another. Specifically, retro‐gradely labelled cells were more numerous in the caudal, lateral, and ventral tectum, and less numerous at rostro‐dorsal levels. Approximately 12,000 tecto‐ION neurons were labelled within the ipsilateral optic tectum following either PHA‐L or fluorescent dye injections.While the regional distribution of tecto‐Ipc neurons was not examined, the morphology indicated that the cells had a single radially oriented dendritic process. Therefore, the apical dendrites are more restricted than those of tecto‐ION cells. Moreover, the dendrites were spiny and arborized within layers 3, 5, and 9 of the ipsilateral optic tectum. The axon of tecto‐Ipc cells arise from the apical process as a shepherd's crook and descend into the deep layers of the optic tectum.These results indicate that (1) tecto‐ION and tecto‐Ipc neurons are possibly monosynaptically activated by retinal input, (2) tecto‐ION neurons are heterogeneous in morphology, and (3) there is a differential distribution of the tecto‐ION neurons throughout the rostro‐caudal extent of the optic tectum, suggesting a greater representation of the caudo‐ventral portion of the optic tectum within the ION.The discussion primarily concerns the organization of the retino‐tecto‐ION‐retinal circuit in light of the distribution and mo

ISSN:0092-7317    

DOI:10.1002/cne.903050310

出版商:Wiley‐Liss, Inc.    

年代:1991

数据来源: WILEY

摘要:

AbstractThe topographic distribution of Alz‐50 containing profiles was determined within the hippocampal formation and anterior parahippocampal gyrus by using a monoclonal antibody directed against the A68 protein in normal and Alzheimer's diseased (AD) brains. Although there was a paucity of immunoreactive neuropil in the normal hippocampal complex, there were a few Alz‐50 positive neurons that occupied the hippocampal subfield, CA2. In most AD cases, Alz‐50 immunoreactive neuropil was prominent in the outer two‐thirds of the molecular layer of the dentate gyrus, although a few cases exhibited staining in the inner third of the molecular layer. CA2 was characterized by an increased density of neuropil staining within stratum pyramidale. The neuropil in subfield CA1 was stained densely with Alz‐50 in strata oriens, pyramidale, and at the border between strata lacunosum‐moleculare and radiatum. Alz‐50 immunostained neurites occupied primarily the lateral two‐thirds of the subiculum proper, whereas only sparse staining was seen in the adjacent presubiculum. Alz‐50 neuropil and neuronal staining displayed three distinct laminar patterns along the mediolateral extent of the entorhinal cortex, whereas the perirhinal cortex exhibited a bilaminar pattern of immunoreactivity involving heavy staining in layers 1–3 as compared to layer 5. In general, the density of Alz‐50 neurite staining in the neuropil appeared inversely proportional to the distribution of Alz‐50 immunoreactivity within dendritic and somal compartments. Interestingly, the patterns of Alz‐50 staining observed in the hippocampal complex in AD coincides with patterns of well‐characterized afferent fiber pathways to these regions, thus further supporting the suggestion that hippocampal subfield specific pathology effectively disconnects medial temporal structures fr

ISSN:0092-7317    

DOI:10.1002/cne.903050311

出版商:Wiley‐Liss, Inc.    

年代:1991

数据来源: WILEY