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

The fine structure and types of contact made by GABAergic elements in the septal nuclei were studied at the electronmicroscopic level by means of peroxidase immunocytochemistry, using anti-GABA antibodies. Observations were made on normal and colchicine-injected rats. GABA-immunoreactivity was distributed within somata, dendrites, axonal varicosities and terminals, and myelinated axons. The peroxidase reaction product was diffuse in the cytoplasm; cytoplasmic organelles were generally devoid of immunoreactivity, while showing a strong reaction on the outer surface of their membrane. GABA-immunoreactive (GABA-I) neurons were small (10 microns on average) to medium (20 microns) in size, with round or multipolar cell bodies. Additionally, labeled large (30 microns) cells were observed within the myelinated fibers of the medial septal nucleus after intraseptal administration of colchicine. No difference in the ultrastructural features and distribution of the immunoreactivity of the 2 kinds of cell was noticed, except for a higher number of synaptic contacts on large neurons of the medial septum. GABA-I cells of the medial and lateral nuclei received synapses on their soma and dendrites, made by both immunonegative and GABA-I terminals. Nonimmunoreactive boutons contacting GABA-I cell bodies were of 2 types: those containing small, clear synaptic vesicles and those that additionally contained large dense vesicles. Synaptic vesicles of GABA-I boutons were rarely labeled internally, but showed varying electron densities. Synapses made by GABA-I boutons on GABA-I or unlabeled somata and dendrites were always of symmetrical type. Synapses made by non-GABA-I boutons on GABA-I cells were either symmetrical or asymmetrical.
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PMID:An ultrastructural study of GABA-immunoreactive neurons and terminals in the septum of the rat. 354 51

Retinorecipient regions of the ventral lateral geniculate nucleus of the thalamus and the superior colliculus of the midbrain are linked by reciprocal axonal projections. In this study we have investigated the ultrastructural characteristics, the distribution, and the postsynaptic targets of the terminals of axons projecting to the ventral lateral geniculate nucleus from the superior colliculus. Horseradish peroxidase was injected into the superior colliculi of adult albino rats, and the Hanker-Yates method was used to visualize anterogradely and retrogradely transported peroxidase in the ventral lateral geniculate nuclei 24 hours following the injection. Labelled terminals were found in the lateral and ventrolateral parts of the external division of the ipsilateral ventral lateral geniculate nucleus. The labelled terminals were confined to areas of simple, nonglomerular neuropil. They were 0.45-1.5 micron in diameter; contained small, dark mitochondria and spherical synaptic vesicles; and established Gray type I (asymmetrical) synaptic contacts with the dendritic shafts, dendritic spines, and occasionally cell bodies of cells with the ultrastructural characteristics of projection cells. A few labelled terminals established synaptic contact with retrogradely labelled cells. Thus, in the rat, the projection from the superior colliculus gives rise to a uniform population of axon terminals in the nonglomerular neuropil of the lateral portion of the ventral lateral geniculate nucleus, which synapse with, and are probably excitatory to, geniculocollicular and other projection cells.
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PMID:Ultrastructural organisation of the projection from the superior colliculus to the ventral lateral geniculate nucleus of the rat. 357 17

The structural features of two physiologically-characterised pyramidal neurons (PC1 and PC2) closely situated in layer 5b in the visual cortex (area 17) of a single cat were studied using a combination of electrophysiological and anatomical techniques. Both PC1 and PC2 had exceptionally large somata (30-40 microns in diameter). On the basis of this and other morphological features cell PC1 was classified as a Meynert cell. PC1 possessed a very large (2.75 degrees X 4.50 degrees) binocularly driven standard complex receptive field. PC2 was also binocularly driven with a small, B-type receptive field. Both cells had the same preference for the direction and orientation of visual stimuli. PC1 and PC2 could be antidromically activated from stimulating electrodes positioned above the dorsal lateral geniculate nucleus with a response latency indicating that these cells probably innervated the visual tectum or pretectum. In addition to corticoefferent axons, the two neurons possessed extensive intracortical axon arbors that ramified extensively in layers 5 and 6 of the medial and lateral banks of the lateral gyrus in area 17. Axon collaterals from both PC1 and PC2 also innervated a small common target region in area 18. A total of 313 boutons from the axonal arbors of PC1 and PC2 were examined in the electron microscope. All of the identified synaptic junctions were found to establish Gray type 1 asymmetrical contacts. The combined ultrastructural data for both neurons indicated that 80% of boutons were onto dendritic spine heads, with 14%, 6%, and 1% onto small-, medium-, and large-calibre dendritic shafts, respectively. The spectrum of postsynaptic targets showed little variation with respect to lamina, distance from somata, or cortical area. Other large pyramidal neurons in layer 5 and spiny neurons in layer 6 were identified as receiving synaptic input from either PC1 or PC2. Using a computer graphics system, rotations of the bouton distributions revealed the existence of a clustered innervation of layers 5 and 6 in areas 17 and 18 derived from the two identified neurons. The bouton distributions strongly resembled the tangential pattern described previously for the functional slab-like organisation of the cortex. The results provide a morphological basis for the clustered intrinsic connectivity of pyramidal cells in layers 5 and 6 of the cat visual cortex. Furthermore, the results indicate the widespread excitatory influence of large pyramidal neurons on other cells projecting subcortically to sites dealing with visually guided behavior.
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PMID:Connections between pyramidal neurons in layer 5 of cat visual cortex (area 17). 358 61

The synaptic organization of the subthalamic nucleus (Sth) of the cat has been investigated by means of electron microscopy. On the basis of the following criteria: the size and the shape of the synaptic boutons, their origin, the size and the shape of the synaptic vesicles, the distribution and density of the vesicular population, and the characteristics of the active synaptic zones, several types of synaptic boutons have been discriminated: F1, F2, SR, LR1, LR2, d.c.v., and "d" profiles. The F1 and F2 types have pleomorphic vesicles and form symmetrical synapses with the neuronal perikarya, the proximal dendrites and their spines, as well as with the initial axonal segments. The SR, LR1 and LR2 types contain round or oval vesicles and form asymmetrical synapses mainly with middle sized and small dendrites, and their spines. The d.c.v. boutons contain a mixed population of clear synaptic vesicles and dense core vesicles. The d.c.v. type forms asymmetrical synapses. The "d" profiles share identical features with the vesicle containing dendrites. The F2, SR, LR1, LR2, and "d" profiles take part in synaptic diads and/or triads, and occasionally participate in the synaptic glomeruli. The LR1 and LR2 take part in glomeruluslike formations. The Sth has a distinct synaptic pattern that permits its discrimination as a separate ultrastructural entity. The Sth seems to share some common ultrastructural features with the thalamic nuclei. On the other hand, the ultrastructural aspects of the Sth are much more different from its closest embryological allies: the both pallidal segments, and the zona reticulata of the substantia nigra.
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PMID:The fine structure of the subthalamic nucleus in the cat. II. Synaptic organization. Comparisons with the synaptology and afferent connections of the pallidal complex and the substantia nigra. 365 32

The serotonin and noradrenaline innervations of the rat oculomotor nucleus were examined by high resolution radioautography after in vivo labeling with tritiated 5-hydroxytryptamine and dopamine, respectively. Noradrenaline as well as serotonin endings (axonal varicosities) pervaded the entire nucleus, but the latter were at least six times more numerous (1.3 X 10(6) per mm3 of tissue) and were often found in the immediate vicinity of neuronal somata and proximal dendrites. The axon terminals of both types were of similar size and exhibited some large dense-cored vesicles in association with aggregated small and clear vesicles. The dense-cored vesicles were, however, more frequent and the content in clear vesicles more pleomorphic in serotonin than noradrenaline endings. In single thin sections, the proportion of noradrenaline and serotonin profiles exhibiting a synaptic junction was relatively small (15%). These were either symmetrical or asymmetrical when made on dendritic branches but invariably symmetrical on spines. In addition, a significant number of serotonin terminals were seen in close apposition or synaptic contact with neuronal perikarya and large dendrites, allowing for a direct, "proximal" action of serotonin. Moreover, many such terminals appeared to be coupled with unlabeled endings of another category, characterized by dispersed, uniformly round and clear synaptic vesicles, providing an alternate route for a proximal effect of serotonin in the oculomotor nucleus. In line with previous investigations on other motor nuclei, these data support the likelihood of a close involvement of both noradrenaline and serotonin in the control of motoneuronal activity.
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PMID:Monoamine innervation of the oculomotor nucleus in the rat. A radioautographic study. 371 41

The nuclei of the torus semicircularis, in particular the laminar nucleus, have been functionally implicated in sound localization, vocalization, and mating behavior. In the red-eared turtle the ventromedial region of the laminar nucleus (containing two discrete dense cellular areas and the surrounding neuropil) was examined electron microscopically in the present study. Neuronal cell bodies in the two cellular areas were different in size, shape, cytoplasmic constituents, and their relationship to each other. Cell bodies in the layer beneath the ependymal surface were almost always surrounded by lamellae while cell bodies in the layer above the central nucleus were in close apposition. We are speculating that cell bodies in the superficial layer may be neuroendocrine in nature. This speculation is based on the presence of lipidlike droplets within cell bodies, and previous findings indicating steroid binding and synthesis in this region in reptilian brains. Cell bodies located above the central nucleus were characteristic in that they contained lamellar bodies and extensive well-developed Golgi regions. Closely apposed groups of these cell bodies were frequently surrounded by or in close apposition to large axonal profiles. These profiles were filled with clear core vesicles, numerous mitochondria, and clusters of small dense core particles. Synaptic contacts between large axonal profiles and cell bodies were not observed. The neuropil surrounding cell bodies of the inner layer of this region of the laminar nucleus contained glomeruli composed of a central axon surrounded, and in synaptic contact, with dendrites. Throughout the area of the laminar nucleus studied, synapses appeared to be primarily of the asymmetrical type.
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PMID:Ultrastructural features of the ventromedial region of the laminar nucleus in the red-eared turtle (Chrysemys scripta elegans). 372 69

This anterograde horseradish peroxidase study examines the morphology and synaptic connections of a population of primary axons which terminate in the dorsal one-half of the border zone (BZ) of rat trigeminal nucleus oralis. Unmyelinated parent fibers in the spinal V tract enter BZ directly and each terminate by continuing as a sparsely branched, long caudally directed strand containing several axonal endings. Primary endings lie in glomeruli where each forms an asymmetrical synapse on a central dendrite. Other glomerular components include two types of non-primary endings. One contains flattened synaptic vesicles, and forms a symmetrical synapse on either the primary ending or the central dendrite, while the other contains pleomorphic synaptic vesicles and establishes a symmetrical synapse on the central dendrite.
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PMID:Morphology and synaptic connections of unmyelinated primary axons in the border zone of rat trigeminal nucleus oralis. 377 35

The anterograde transport of horseradish peroxidase (HRP) was used to examine the morphology and synaptic connections of a morphologically distinct group of small-diameter primary trigeminal axons that arborize throughout the border zone (BZ) of rat trigeminal nucleus oralis. Thinly myelinated parent branches (0.75-1.5 micron in diameter) descending in the spinal V tract (SVT) were seen to issue medially directed collaterals that entered BZ, where they branched and eventually terminated by giving rise to thin terminal strands characterized by several relatively widely spaced axonal endings. Based on the size and morphology of the parent branches in SVT, in the root entry zone, and in the sensory root of the trigeminal nerve, these primary axonal (P) endings are considered to be derived from small-diameter myelinated primary trigeminal axons (SDMA). The P endings measured 1-2 micron in diameter and contained numerous agranular spherical (40-60 nm) synaptic vesicles. In the BZ neuropil, most P endings lay in glomeruli, where each formed at least one asymmetrical axodendritic synapse on a dendritic shaft. It is at these synapses that this group of primary axons is thought to transfer its input directly to the dendritic arbors of BZ neurons. A small (0.5-1.5 micron) axonal (F) ending filled with flattened synaptic vesicles (29 X 60 nm) was observed to form at least one symmetrical to intermediate axoaxonic synapse on the P ending, as well as at least one axodendritic synapse on the same dendritic shaft receiving the primary input. Some F endings only contacted dendritic shafts. In view of their symmetrical to intermediate synaptic contacts, F endings are thought to belong to axons derived from at least one source that can inhibit or diminish the firing rate of BZ neurons in response to SDMA input. This would be accomplished either postsynaptically through the axodendritic synapses on the dendritic shafts, and/or presynaptically through the axoaxonic synapses on the P endings.
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PMID:Morphology and synaptic connections of small myelinated primary trigeminal axons arborizing among neurons in the border zone of rat trigeminal nucleus oralis. 380 36

The macromolecular structure of axonal membrane from dorsal funiculi of control and irradiated spinal cord of 45-day-old rats was examined with freeze-fracture electron microscopy. In control spinal cords, virtually all myelination is mediated by oligodendrocytes, and the internodal axonal membrane of these fibres displays highly asymmetrical partitioning of intramembranous particles (IMPs). The internodal P-face particle density is approximately 2350IMPs per micron 2, whereas the E-face IMP density is approximately 150 per micron 2. In control dorsal spinal roots, myelination is mediated by Schwann cells, and the ultrastructure of the internodal axolemma of the myelinated fibres is similar to that displayed by myelinated fibres of dorsal funiculi. On the internodal P-face of Schwann cell-myelinated fibres the IMP density is approximately 2350 per micron 2, whereas on the E-face the density is approximately 175 per micron 2. Irradiation of the lumbosacral spinal cord at 3 days of age results in a glial cell-deficient region within the spinal cord such that myelination in irradiated dorsal funiculi is delayed and subsequent myelination is mediated by both oligodendrocytes and Schwann cells. By 45 days of age, dorsal funiculi of irradiated spinal cords are well populated with fibres myelinated by oligodendrocytes and Schwann cells. However, fibres myelinated by oligodendrocytes display very thin myelin sheaths whereas Schwann cell-myelinated fibres exhibit myelin sheaths with normal thicknesses. Internodal membrane of fibres myelinated by Schwann cells and oligodendrocytes exhibit similar macromolecular structure, with approximately 2400 IMPs per micron 2 on P-faces and approximately 150 IMPs per micron 2 on E-faces. Occasional large (greater than 1.5 micron diameter) axons without glial-Schwann cell ensheathment are observed. These axons display a high density of P-face particles (approximately 2000 per micron 2) and a moderate density (approximately 350 per micron 2) of E-face IMPs on their fracture faces. These results demonstrate that CNS fibers exhibit similar axonal membrane ultrastructure irrespective of whether they are myelinated by Schwann cells or oligodendrocytes, or whether myelination is delayed. Moreover, when myelination does not occur, the axolemmal E-face IMP density, which may be related to the density of voltage-sensitive sodium channels, is not reduced.
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PMID:Effects of delayed myelination by oligodendrocytes and Schwann cells on the macromolecular structure of axonal membrane in rat spinal cord. 381 78

The solitary nucleus is the first level of the central nervous system where processing of taste information can occur. A structural basis for that processing was investigated. Facial taste afferent axons were labelled by application of horseradish peroxidase to either the chorda tympani or the geniculate ganglion. The labelled afferent fibers in the rostral solitary nucleus were studied with light and electron microscopy. Preterminal facial taste afferent axons enter the nucleus from the solitary tract with a pronounced lateral to medial trajectory. The axons bear numerous preterminal and terminal swellings that, with the electron microscope, were identified as synaptic endings located in glomeruli. The endings are ovoid or scalloped, indented by structures that surround them. The primary afferent endings contain large, round vesicles and synapse, by means of slightly asymmetrical junctional complexes, on small dendrites and spines. Two types of unlabelled endings, surrounding the labelled ones, contact the dendrites receiving taste afferent input or contact the endings of taste afferent axons themselves. One type is variable in size and contains scattered large round vesicles. It resembles a presynaptic dendrite. The other is a small axonal ending packed with small, pleomorphic vesicles, that engages in symmetrical junctions. The synaptic milieu of the taste endings allows for the possibility of modulation of taste-elicited activity in afferent endings or second-order neurons by other, possibly interneuronal, inputs.
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PMID:Anatomy of the gustatory system in the hamster: synaptology of facial afferent terminals in the solitary nucleus. 395 91


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