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Query: UNIPROT:P50583 (asymmetrical)
 12,197 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In order to determine whether the cholinergic fibres that innervate the substantia nigra make synaptic contact with dopaminergic neurons of the substantia nigra pars compacta, a double immunocytochemical study was carried out in the rat and ferret. Sections of perfusion-fixed mesencephalon were incubated first to reveal choline acetyltransferase immunoreactivity to label the cholinergic terminals and then tyrosine hydroxylase immunoreactivity to label the dopaminergic neurons. Each antigen was localized using peroxidase reactions but with different chromogens. At the light microscopic level, in confirmation of previous observations, choline acetyltransferase-immunoreactive axons and axonal boutons were found throughout the substantia nigra. The highest density of these axons was found in the pars compacta where they were often seen in close apposition to tyrosine hydroxylase-immunoreactive cell bodies and dendrites. In the ferret where the choline acetyltransferase immunostaining was particularly strong, bundles of immunoreactive fibres were seen to run through the reticulata perpendicular to the pars compacta. These bundles were associated with tyrosine hydroxylase-immunoreactive dendrites that descended into the reticulata. The choline acetyltransferase-immunoreactive fibres made "climbing fibre"-type multiple contacts with the tyrosine hydroxylase positive dendrites. At the electron microscopic level the choline acetyltransferase-immunoreactive axons were seen to give rise to vesicle-filled boutons that formed asymmetrical synaptic specializations with nigral dendrites and perikarya. The synapses were often associated with sub-junctional dense bodies. On many occasions the postsynaptic structures contained the tyrosine hydroxylase immunoreaction product, thus identifying them as dopaminergic. It is concluded that at least one of the synaptic targets of cholinergic terminals in the substantia nigra are the dendrites and perikarya of dopaminergic neurons and that in the ferret at least, the dendrites of dopaminergic neurons that descend into the pars reticulata receive multiple synaptic inputs from individual cholinergic axons.
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PMID:Cholinergic input to dopaminergic neurons in the substantia nigra: a double immunocytochemical study. 167 2

The morphological characteristics of the synaptic contacts in the ruff of the cichlid fish Hemichromis bimaculatus were studies using the combined Golgi-electron microscope technique. Ruffed cells were located in the glomerular and plexiform layers and exhibited a pyriform or round cell body and numerous thin dendritic branches that were highly ramified. Four different segments could be distinguished on the initial portion of the axon (IP) according to the number and density of protrusions. These protrusions or lateral appendages are highly interdigitated, forming a characteristic synaptic field: the ruff. The ruff displayed a very high number of synapses with terminals showing a varied morphology. Protrusions of the ruff were both presynaptic and postsynaptic, taking also part in reciprocal pairs of synapses. Synapses from the ruff to the adjacent prolongation are asymmetrical, the prolongation to protrusion synapses being symmetrical. The axonal shaft participates in fewer synaptic contacts. Boutons contacting with one protrusion can synapt with other one, and can also receive an asymmetric synapse from another terminal, forming a serial synapse. This constitutes the most complex synaptic system observed in the glomerular layer of the olfactory bulb in any vertebrate. The synaptology of the ruffed cell IP is compared with previous reports on other species, with the teleostean mitral cells and with the IP of higher vertebrates neurons, the ruffed cells showing a completely different synaptic pattern.
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PMID:Ruffed cells in the olfactory bulb of freshwater teleosts. II. A Golgi/EM study of the ruff. 172 80

In Golgi impregnated ectostriatum centrale of telencephalon of one-day-old chicken two types of neuron: projection neuron and interneuron with large axonal field and varicose axonal preterminals and terminals, were identified and examined in EM preparates. In the serial EM sections the morphological features of the two neurons types were observed. The projection neuron is characterized by the few axo-somatic synapses on the cell membrane, which are of symmetrical type. The INs, however, have numerous axo-somatic synapses on cell membrane both of symmetrical and asymmetrical types. Also the axonterminals were analysed.
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PMID:EM Golgi study on neurons of ectostriatum centrale in telencephalon of one-day-old chicken's brains. 172 74

We studied the morphology and center-surround organization of Lucifer Yellow injected OFF- and ON-center bipolar cells in the light-adapted Xenopus retina and the effects of glycine and GABA on their cone-mediated light responses. In both classes of cell, prominent antagonistic surround responses up to 20 mV in amplitude could be evoked without first suppressing the center responses with steady illumination. An additional feature of the light-evoked bipolar cell response was a pronounced (up to -24 mV) delayed hyperpolarizing after potential (DHAP) which followed the depolarizing responses of both classes of bipolar cell. The morphological features of dye-injected bipolar cells conformed to the general idea of segregation of ON and OFF pathways in the inner and outer interplexiform layer, however, the morphology of axonal arborizations was different for both classes. OFF-center cells ramified symmetrically around the primary branchpoint, whereas ON-center cells had a strongly asymmetrical arrangement of their axonal tree. The center and surround responses were differentially sensitive to glycine and GABA. Glycine eliminated the antagonistic surround responses in both OFF and ON cells; the center responses were reduced to some extent but were not eliminated. In contrast, GABA affected the hyperpolarizing responses much more strongly than the depolarizing response components. That is, the amplitude of the center response in the OFF cell and the surround response in the ON cell was reduced 80-90% during exposure to GABA, whereas the surround and center depolarizations of OFF and ON cells, respectively, were reduced only 0-10%. Our findings implicate a role for GABAergic and glycinergic pathways in the center-surround organization of bipolar cells in Xenopus retina. In addition, the results suggest that the pathways mediating center-surround antagonism may be different in OFF-bipolar cells vs. ON-bipolar cells.
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PMID:Physiological and morphological properties of off- and on-center bipolar cells in the Xenopus retina: effects of glycine and GABA. 175 22

Paraneoplastic vasculitic neuropathy has been recently described. We report the first case of this disorder which responded both clinically and electrophysiologically to cyclophosphamide treatment. A 54-year-old woman with a history of metastatic endometrial carcinoma in remission had asymmetrical polyneuropathy, electrophysiological findings consistent with a diffuse axonal neuropathy, high sedimentation rate and spinal fluid protein, and microvasculitis with axonal degeneration on nerve biopsy. The patient was treated with 150 mg of cyclophosphamide daily with gradual clinical and electrophysiological improvement.
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PMID:Paraneoplastic vasculitic neuropathy: a treatable neuropathy. 184 91

Serotonin (5-HT) immunocytochemistry was used at the electron microscopic level to examine 5-HT neurons reinnervating and hyperinnervating the hippocampus of adult rat, three to four months after a total 5-HT denervation and subsequent graft of embryonic raphe cells. The study focused on immunostained nerve cell bodies, dendrites and axon terminals (varicosities) in the core of grafts, and on a large single section sampling of axon terminals from a CA3 and a dentate gyrus sector of the outgrowth, which were systematically compared to the endogenous 5-HT innervation of the same regions described in a companion paper. The shape, size and synaptic investment of the grafted 5-HT somata and their dendrites resembled those of in situ 5-HT neurons. Clusters of small, clear vesicles were sometimes seen along these 5-HT dendrites. 5-HT axonal varicosities were fairly numerous in the core. A few were directly apposed to, or made asymmetrical synaptic contact with the immunostained dendrites and perikarya, but the vast majority showed no indication of junctional specialization (synaptic incidence of 19%, as stereologically extrapolated for whole varicosities). Occasional myelinated 5-HT axons were also present in the core of grafts. In the two outgrowth sectors, the graft-borne 5-HT varicosities were similar in size, content, frequency of synaptic contact and identity of junctional and appositional elements, irrespective of their laminar location. Moreover, none of these parameters were significantly different from those of the endogenous innervation. Notably, in spite of their excessive number, the synaptic incidence of the outgrowth 5-HT varicosities remained inferior to 20%. The similarity between the respective microenvironments of the supernumerary, graft-borne 5-HT terminals and of their normal counterparts could only be explained by a random intratissular distribution of these varicosities in both the normal and the grafted hippocampus. Thus, in spite of their transplantation and growth into an abnormal milieu, and the fact that they hyperinnervated the host tissue, the grafted embryonic 5-HT neurons appeared committed to express a particular set of intrinsic and relational morphological features corresponding to their normal adult characteristics.
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PMID:Ultrastructural features of serotonin neurons grafted to adult rat hippocampus: an immunocytochemical analysis of their cell bodies and axon terminals. 195 16

This is one of a series of papers aimed at identifying the synaptic output patterns of the local and distant projections of subgroups of pyramidal neurons. The subgroups are defined by the target site to which their main axon projects. Pyramidal neurons in areas 1 and 40 of mouse cerebral cortex were labeled by the retrograde transport of horseradish peroxidase (HRP) transported from severed callosal axons in the contralateral hemisphere. Terminals of the local axon collaterals of these neurons ("intrinsic" terminals) were identified in somatosensory areas 1 and 40, and their distribution and synaptic connectivity were examined. Also examined were the synaptic connections of "extrinsic" callosal axon terminals labeled by lesion induced degeneration consequent to the severing of callosal fibers. A post-lesion survival time of 3 days was chosen because by this time the extrinsic terminals were all degenerating, whereas the intrinsic terminals were labeled by HRP. Both intrinsic and extrinsic callosal axon terminals occurred in all layers of the cortex where they formed only asymmetrical synapses. Layers II and III contained the highest concentrations of both types of callosal axon terminal. Analyses of serial thin sections through layers II and III in both areas 1 and 40 yielded similar results: 97% of the extrinsic (277 total sample) and of the intrinsic (1215 total sample) callosal axon terminals synapsed onto dendritic spines, likely those of pyramidal neurons; the remainder synapsed onto dendritic shafts of both spiny and nonspiny neurons. Thus the synaptic output patterns of intrinsic vs. extrinsic callosal axon terminals are strikingly similar. Moreover, the high proportion of axospinous synapses formed by both types of terminal contrasts with the proportion of asymmetrical, axospinous synapses that occur in the surrounding neuropil where only about 80% of the asymmetrical synapses are onto spines. This result is in accord with previous quantitative studies of the synaptic connectivities of both extrinsic and intrinsic axonal pathways in the cortex (White and Keller, 1989: Cortical Circuits; Boston: Birkhauser): in all instances, axonal pathways are highly selective for the types of elements with which they synapse.
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PMID:Synapses made by axons of callosal projection neurons in mouse somatosensory cortex: emphasis on intrinsic connections. 201 38

Light and electron microscope studies on normal and experimental material in the lateral superior olive (LSO) of cat revealed the presence of three types of neurons: (i) fusiform cells characterized by the large number of terminals articulating with them and projecting to the nuclei of the lateral lemniscus (NLL) and central nucleus of the inferior colliculus (CNIC) (ii) marginal cells embedded in the neuropil of the fibrous capsule and sharing input and output characteristics with the fusiform neurons (iii) multipolar cells with spinous dendrites, local axonal spread and synaptic relation restricted to few afferents only. Four distinct types of axon terminals were distinguished on the basis of their size, vesicle content, membrane attachments, postsynaptic relations and origin. (i) Large terminals with asymmetrical membrane contacts and round vesicles (AR) were of ipsilateral cochlear nucleus origin and articulated predominantly with fusiform and marginal projection cells. (ii) The majority of small AR type terminals arose from the spherical cells of the ipsilateral nucleus of the trapezoid body (NTB). Their number was larger on the fusiform and marginal cells. (iii) Medium sized terminals of symmetrical membrane apposition and pleomorphic vesicles originated from the ipsilateral NLL and CNIC. Their quantitative distribution indicated preference for the multipolar cells. (iv) Profiles with symmetrical membrane contacts and flattened vesicles (SF) type were considered to be terminals of the spinous multipolar interneurons, thus local in origin.
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PMID:Types of neurons and synaptic relations in the lateral superior olive of the cat: normal structure and experimental observations. 210 2

A combination of electron microscopic immunocytochemistry and autoradiography was employed to examine the synaptic organization of thyrotropin-releasing hormone (TRH) neurons in the periventricular subdivision of the paraventricular nucleus of the rat hypothalamus. TRH neurons were identified by immunocytochemistry. Selective uptake of tritiated serotonin (5-HT) was used to identify serotoninergic elements. TRH-immunoreactive axon terminals were found to be in synaptic contact with TRH-immunoreactive dendrites and with unlabeled dendritic branchlets. There were direct appositions between radiolabeled 5-HT terminals and TRH-immunoreactive dendrites, but differential synaptic contacts between 5-HT axonal elements and TRH neurons were not seen. TRH-immunopositive cell bodies and dendrites received a very intense innervation by unlabeled axon terminals or axonal varicosities showing morphologically defined synaptic junctions. These were mostly of the asymmetrical variety and different types could be distinguished. The findings substantiate the view that TRH neurons of the periventricular subvision of the paraventricular nucleus may be influenced by TRH axons, serotoninergic fibers and a large number of unidentified nerve terminals.
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PMID:Ultrastructural analysis of the innervation of TRH-immunoreactive neuronal elements located in the periventricular subdivision of the paraventricular nucleus of the rat hypothalamus. 212 84

An electron microscope study of retrogradely labelled neurons in layer VI of the primary auditory cortex (AI) after injection of the horseradish peroxidase to the medial geniculate body was carried out in cats. Three-eight synapses (4.6 +/- 0.6 at an average) were revealed on the somata profiles of these retrogradely labelled cortico-geniculate neurons. Synapses occupied 10.8 +/- 1.0% of the somatic profile of cortico-geniculate neurons. Almost all (98.7%) of these axosomatic synapses had symmetrical contacts and were formed by axonal terminals with small elongated synaptic vesicles. HRP retrogradely labelled axonal terminals of geniculo-cortical fibres were revealed in neuropil of layer VI. They contained large round synaptic vesicles and formed asymmetrical synapses, mainly on spines. The role of axo-somatic synapses in regulation of the activity of cortico-geniculate neurons was discussed.
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PMID:[An electron microscopic study of the origins of the projections of the first auditory area of the cortex (AI) to the medial geniculate body in cats]. 219 74


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