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

Using a modification of the peroxidase-antiperoxidase technique, serotonin immunoreactivity was localized at the ultrastructural level in the nucleus of the solitary tract of the cat. Structures containing serotonin immunoreactivity included unmyelinated axons, varicosities (0.5 to 2 micrometers in diameter), and synaptic terminals. The serotonin-containing synaptic terminals were found less frequently than axons or varicosities. Within unmyelinated axons and varicosities, the immunoreactivity was associated mainly with large granular vesicles (80 to 150 nm). While large granular vesicles were found in all immunoreactive structures, greater numbers were observed in axons and nonsynaptic varicosities. Serial sections of several nonsynaptic serotonin-immunoreactive varicosities indicated the lack of synaptic specializations associated with these structures. In a typical section, only one or two granular vesicles were in synaptic terminals which contained numerous small clear vesicles. Serotonin-immunoreactive terminals formed asymmetrical contacts with dendrites and spines. No synaptic contacts involving immunoreactive terminals were found on cell bodies or other axonal structures. Serotonin-containing neuronal perikarya within the nucleus of the solitary tract were never observed. The abundance of nonsynaptic varicosities containing large granular vesicles suggests a possible neurohumoral role for serotonin within the feline nucleus of the solitary tract. This is discussed in relation to previous reports concerning the paucity of genuine synaptic contacts involving serotonin in other regions of the central nervous system. The presence of serotonin-immunoreactive terminals in the nucleus of the solitary tract also suggests its function as a putative neurotransmitter.
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PMID:The ultrastructural localization of serotonin immunoreactivity within the nucleus of the solitary tract of the cat. 675 49

A total of nine monkeys (Macaca fascicularis) of both sexes was used for the present study. Eight monkeys were used for either motor or sensory cortical lesions, and were allowed to survive for 1--7 days post-operatively. No degenerating nerve terminals were observed 1 day following either motor or sensory cortical lesions. After a motor cortical lesion, most degenerating terminals were seen on the third and only a few on the fifth day. Following a sensory cortical lesion, most degenerating terminals were seen on the fifth and fewer on the third and seventh days. Two types of degenerative changes were observed: granular and electron-dense. Granular change was more evident after the shorter survival periods, while the electron-dense type of degeneration was more commonly seen in animals which were allowed to survive longer after operation. The cortical axon terminals were small and contained either round or flattened synaptic vesicles. Most of those axons containing flattened vesicles originated from the sensory cortex, but a few came from the motor cortex. Vice versa, most of those axons containing round vesicles appeared to arise from the motor cortex and only a few from the sensory cortex. Cortical axon terminals containing round synaptic vesicles formed asymmetrical synapses with small to medium-sized dendrites poor in organelles. In a few instances such cortical terminals were observed to be postsynaptic to other axon terminals containing flattened vesicles. No cortical axon terminal was observed to terminate presynaptically on another axon terminal. Cortical terminals containing flattened vesicles formed symmetrical synapses with dendritic profiles of varying diameters, some of which were the proximal dendrites of Group II neurons. No cortical axon terminals containing flattened vesicles have been observed to form axo-axonal synapses in the cuneate neuropil.
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PMID:Experimental degeneration of motor and sensory cortical terminals in the cuneate nucleus of the monkey (Macaca fascicularis). 676 75

The ultrastructure of the vasopressin neurons of the paraventricular nucleus of the hypothalamus was studied by immunocytochemical techniques. Tissue antigen was detected in unembedded tissue sections using a monoclonal antibody that recognizes vasopressin but not oxytocin or vasotocin. At the light-microscopic level, reaction product was seen to fill the cytoplasm of the neuron cell body as well as large portions of the dendrite and axon. Immunoreactive spines were seen on both somatic and dendritic surfaces and their presence was confirmed at the ultrastructural level. In the light-microscope, axonal processes do not have spines and are thinner and more varicose than dendritic processes. At the electron-microscopic level, both axons and dendrites of the vasopressin cells are filled with reactive neurosecretory granules. The presence of large numbers of these organelles made it difficult to distinguish proximal dendrites from Herring bodies (axonal swellings). At the ultrastructural level, reaction product was also observed in the cytoplasm of all segments of the vasopressin cells. The presence of reaction product outside of membranous compartments is undoubtably due to disruption of membranes by detergent treatment or exposure to basic pH. However, the staining procedure used did allow us to examine the synaptic input to the vasopressin cells. All portions of the vasopressin neuron receive a diverse innervation. The somata have synapses on their surfaces and on spines. These axo-somatic terminals are primarily, but not exclusively, symmetrical and the presynaptic elements contain spherical or elongate vesicles. On the dendrites, terminals again were observed on the surface or on spines. these axo-dendritic synapses were usually asymmetrical. The presynaptic elements contained clear spherical, elongate or pleomorphic vesicles. Occasional varicosities with dense-core granules were seen to make en passant contacts with dendrites; these contacts did not have obvious membrane specializations. Input to vasopressin axons was studied both along the paraventricular-neurohypophysial tract and in the median eminence. Vasopressin axons receive a synaptic input (axo-axonic), predominately of the asymmetric variety with clear, spherical vesicles in the presynaptic element. These findings demonstrate that the vasopressin neurons of the paraventricular nucleus receive a diverse innervation.
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PMID:Ultrastructural studies of vasopressin neurons of the paraventricular nucleus of the hypothalamus using a monoclonal antibody to vasopressin: analysis of synaptic input. 687 93

Young adult cats were subjected to unilateral ablation of the frontal and prefrontal cerebral cortex and were allowed to survive for 4 to 5 days. Routine electron microscopic technique was employed to examine orthograde degenerative changes in the ipsilateral and contralateral substantia nigra (Ni). A moderate number of degenerating synaptic boutons (d. s. b.) were observed in the ipsilateral Ni-pars comacta, and only very few d.s.b. were observed in the ipsilateral Ni-pars reticulata. The d. s. b. exhibited features attributed to the dark degeneration type, and might be referred to two main categories; "small-round-vesicle bouton" and "large-round-vesicle bouton" (Hajdu et al., 1973; Hassler et al. 1975). The d. s. b. performed asymmetrical synapses with dendrites of varying size, much more rarely -- with the neuronal perikarya, and extremely rarely -- with initial axonal segments. No degeneration was observed in the contralateral Ni.
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PMID:Electron microscopic evidence for the existence of a corticonigral tract in the cat. 709 90

Serotoninergic axonal endings in layers I and II of the medullary and spinal dorsal horn of the cat were ultrastructurally characterized following uptake of [3H]serotonin. The two most common types were dome-shaped endings which could be distinguished by the size and shape of their agranular synaptic vesicles. The two types of endings were found throughout layers I and II, but were most numerous in layer I. The labeled endings formed both symmetrical and asymmetrical synapses on dendritic shafts and spines, and occasionally a symmetrical synapse on a neuronal soma. Using the technique of anterograde transport of [3H]amino acid, two morphologically identical types of endings were demonstrated as originating from neurons in the caudal raphe nuclei and adjacent reticular formation.
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PMID:Ultrastructure of descending serotoninergic axonal endings in layers I and II of the dorsal horn. 728 39

The axolemma of nonmyelinated fibres from the corpus callosum and cerebellar cortex (C.N.S.) and the vagus nerve (P.N.S.) was investigated with freeze-fracture electron microscopy. The major observations of this study are as follows: (1) there is a highly asymmetrical distribution of intramembranous particles between the E- and P-fracture faces in both C.N.S. and P.N.S. fibres; (2) the total number of particles on the P-faces of all axonal types studied is considerably greater than that on the E-face; (3) the number of particles on the E-faces of C.N.S. axons is greater than that on the E-faces of P.N.S. axons; and (4) the percentage of large (greater than 9.6 nm) particles is greater on the E-face than on the P-face regardless of the axon studied. The results are compared with previous freeze-fracture investigations on the nodal and intermodal membranes of myelinated fibres.
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PMID:Freeze-fracture ultrastructure of rat C.N.S. and P.N.S. nonmyelinated axolemma. 731 Apr 84

The axonal endings formed on the somata of neurons in the brainstem auditory nucleus magnocellularis (NM) were measured and classified in thin-sectioned material from adult chickens. Degeneration of primary endings after destruction of the basilar papilla and labeling of cochlear nerve fibers by injection of horseradish peroxidase (HRP) into the inner ear were used to determine which ending types arise from the cochlear ganglion. About 60% of the perikaryal surface is apposed by primary type terminals. These primary endbulbs are characterized by round clear synaptic vesicles distributed at an average density of 63 vesicles/micrometers 2 and a number of small, punctate, highly asymmetrical synaptic contacts. The primary type is the only class of endings which disappears after destruction of the basilar papilla and which is consistently labeled after HRP injections into the ear. These endings probably account for the "fast" EPSP seen in NM during stimulation of the cochlear nerve. NM neurons receive two types of nonprimary ending. About 13% of the perikaryal surface is apposed by a morphologically homogeneous class of small "symmetrical" endings; these are characterized by a flattened rhomboidal shape, numerous mitochondria, frequent coated vesicles, and small round or ovoid synaptic vesicles at an average density of 165 vesicles/micrometers 2. Most of the length of the apposition between ending and cell body is occupied by a synaptic complex with thin symmetrical presynaptic and postsynaptic densities. These endings were frequently found on short somatic processes. The second nonprimary axosomatic ending type in NM is most easily identified in experimental material; these endings occupy about 5% of the cell surface area and have a distinctly rounded profile in cross section. These endings typically exhibit clear round synaptic vesicles at a density of 111 vesicles/micrometers 2 arrayed before synaptic contacts which occupy a substantially larger fraction of the total apposition length than in the endbulbs. Many of these synaptic contacts show well-defined presynaptic grids and have postsynaptic densities intermediate in width between the endbulbs and the symmetrical endings. This second type of nonprimary ending may be responsible for the long-latency excitatory post-synaptic potentials seen in intracellular recordings from NM during electrical stimulation of the cochlear nerve. The morphology and distribution of the three ending types does not differ significantly along the posterior-to-anterior axis of NM.
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PMID:Morphology of axosomatic endings in an avian cochlear nucleus: nucleus magnocellularis of the chicken. 732 Feb 34

Axonal projections of medial brain stem areas rich in serotonin-containing neurons were identified in layers I and II of cat medullary dorsal horn using EM autoradiography. Following [3H]amino acid injections into the brain stem, labeled axonal endings were found throughout layers I and II but were most numerous in layer I. Three different morphological types of endings could be distinguished. Each type resembled serotonergic axonal endings identified in previous experiments. The labeled endings formed both symmetrical and asymmetrical synapses on dendritic shafts and spines and occasionally on a neuronal soma suggesting that the major site of action of the descending serotonergic afferents is on the neurons in layers I and II.
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PMID:Ultrastructural analysis of medial brain stem afferents to the superficial dorsal horn. 747 Aug 60

The superior olivary complex is the first site in the central auditory system where binaural interactions occur. The output of these nuclei is direct to the central nucleus of the inferior colliculus, where binaural inputs synapse with monaural afferents such as those from the cochlear nuclei. Despite the importance of the olivary pathways for binaural information processing, little is known about their synaptic organization in the colliculus. The present study investigates the structure of the projections from the lateral and medial superior olivary nuclei to the inferior colliculus at the electron microscopic level. Stereotaxic placement and electrophysiological responses to binaural sounds were used to locate the superior olive. Anterograde axonal transport of 3H-leucine was combined with light and electron microscopic autoradiography to reveal the location and morphology of the olivary axonal endings. The results show that the superior olivary complex contributes different patterns of synaptic input to the central nucleus of the inferior colliculus. Each projection from the superior olivary complex to the colliculus differs in the number and combinations of endings. Axonal endings from the ipsilateral medial superior olive were exclusively the round (R) type that contain round synaptic vesicles and make asymmetrical synaptic junctions. This morphology is usually associated with excitatory synapses and neurotransmitters such as glutamate. Endings from medial superior olive terminate densely in the central nucleus. The projection from the contralateral lateral superior olive also terminates primarily as R endings. This projection also includes small numbers of pleomorphic (PL) endings that contain pleomorphic synaptic vesicles and usually make symmetrical synaptic junctions. The PL morphology is associated with inhibitory synapses and transmitters such as gamma-aminobutyric acid and glycine. All endings from the contralateral lateral superior olive terminate much less densely than endings from the medial olive. In contrast, the projection from the ipsilateral lateral superior olive contributes both R and PL endings in roughly equal proportions. These ipsilateral afferents are heterogeneous in density and can terminate in lower or higher concentrations than endings from the contralateral side. These data show that the superior olive is a major contributor to the synaptic organization of the central nucleus of the inferior colliculus. The ipsilateral projections of the medial and lateral superior olive may produce higher concentrations of R endings than other inputs to the central nucleus. Such endings may participate in excitatory synapses. The highest concentrations of PL endings come from the ipsilateral lateral superior olive.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Axonal projections from the lateral and medial superior olive to the inferior colliculus of the cat: a study using electron microscopic autoradiography. 749 62

A combined anterograde axonal degeneration and Golgi electron microscopic (Golgi-EM) study was undertaken to identify thalamocortical synaptic connections between axon terminals from the mediodorsal thalamic nucleus (MD) and pyramidal cells in layers III and V of the agranular prelimbic cortex in the rat. The morphological characteristics of thalamocortical synapses from MD were also examined by labeling axon terminals with anterograde transport of wheat germ agglutinin-horseradish peroxidase (WGA-HRP). WGA-HRP labeled axon terminals from MD to the prelimbic cortex were small in size (0.5-1 microns in diameter), contained round synaptic vesicles, and formed axospinous synapses with asymmetrical membrane thickenings. With Golgi-EM methods, gold-toned apical dendrites in layer III were analyzed by reconstruction of serial ultrathin sections. Following lesions in the thalamus, degenerating thalamocortical axon terminals formed asymmetrical contacts exclusively on dendritic spines of the identified apical dendrites. More thalamocortical synapses were found on apical dendrites of layer V pyramidal cells than on apical dendrites of layer III pyramidal cells. In addition to thalamocortical synapses, a very few unlabeled symmetrical synapses were found on apical dendrites and somata of pyramidal cells, but they were not quantified and their sources are unknown.
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PMID:Thalamocortical synapses between axons from the mediodorsal thalamic nucleus and pyramidal cells in the prelimbic cortex of the rat. 754 20


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