Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P50583 (asymmetrical)
 12,197 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A high affinity calcium-binding protein has recently been purified from the adrenal medulla (Kuo, I.C.Y., and Coffee, C.J. (1976) J. Biol. Chem. 251, 1603-1609). This protein is closely related in its chemical and physical properties to troponin-C (TN-C) of muscle tissue. Further examination of the adrenal medulla protein indicates that the removal of calcium is accompanied by a marked change in the conformation. This change in structure is similar, if not identical, to the calcium-dependent conformational change which has been described for skeletal muscle TN-C (Murray, A.C., and Kay, C.M. (1972) Biochemistry 11, 2622). The far ultraviolet circular dichroism spectrum of native adrenal medulla calcium-binding protein (AM-CBP) shows characteristic helical ellipticity bands at 222 and 207 nm. The helical content, as estimated from these data, is between 40 and 45%. Removal of calcium is accompanied by a change in ellipticity which corresponds to a decrease from 40 to 20% in the helical content. The near-ultraviolet circular dichroism spectrum shows negative dichroic bands at 262 and 268 nm which are characteristic of phenylalanine. These bands are relatively insensitive to changes in the calcium ion concentration. Sedimentation velocity studies likewise are indicative of a calcium-dependent structural alteration. The sedimentation coefficient of the native protein was observed to be 1.89 S. Similar measurements performed in the presence of 3 mM ethylene glycol bis(beta-aminoethyl ether) N,N, N', N'-tetraacetic acid (EGTA) gave a sedimentation coefficient of 1.50 S. The molecular weight, as determined by sedimentation equilibrium studies, was 16,000 regardless of whether the measurements were made in the presence of CaCl2 or EGTA. From the elution properties of AM-CBP on Sephadex G-100, the Stokes radius was observed to be 19.8 A in the presence of calcium and 21.9 A in the presence of EGTA. All of these changes which were induced by the addition of EGTA were completely reversible by the readdition of excess CaCl2. These data suggest that the removal of calcium from AM-CBP is accompanied by a pronounced conformational change which occurs without a molecular weight change. The decreased sedimentation coefficient, the increased Stokes radius, and the reduced helical content, which are observed for the apoprotein, indicate that removal of calcium results in a transformation from a compact symmetrical structure to one that is less ordered and more asymmetrical.
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PMID:Bovine adrenal medulla troponin-C. Demonstration of a calcium-dependent conformational change. 97 71

We addressed the question whether the projection neurons of the olfactory bulb, i.e. the mitral and tufted cells, are immunoreactive for the calcium-binding protein, calretinin. The following approaches were adopted: (1) light and electron microscopic calretinin-immunocytochemistry; (2) neuroanatomical tracing combined with calretinin-immunocytochemistry according to double-peroxidase and double-fluorescence protocols; (3) unilateral lesion of the olfactory bulb combined with calretinin-immunocytochemistry. The experiments were carried out in rats. Immunostaining of brain sections revealed weakly calretinin-immunopositive mitral cell bodies. Tufted cells were immunonegative. In contrast, fibers in the lateral olfactory tract were strongly immunopositive. Dense immunostaining was also present in a superficial band in layer I of the olfactory tubercle, piriform cortex, periamygdaloid cortex, and in the lateral entorhinal cortex. In electron microscopic preparations of these target areas we observed immunoreaction product in axons and axon terminals. The latter invariably formed asymmetrical synapses, mostly with dendritic spines. Injections of the neuroanatomical tracer biotinylated dextran amine (BDA) into the olfactory bulb produced labeled fibers which remained completely restricted to the superficial, calretinin-immunopositive band in layer I in the above-mentioned cortical forebrain areas. We noted colocalization of transported BDA and calretinin-immunoreactivity in mitral cells, in fibers in the lateral olfactory tract and in fibers in the piriform cortex. Olfactory bulb lesions produced depletion of calretinin-immunoreactivity in the lateral olfactory tract and the superficial band in the olfactory cortex-related areas. Together these data firmly indicate that mitral cells and their axons are calretinin-immunoreactive.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Calretinin-immunoreactivity in mitral cells of the rat olfactory bulb. 755 32

Previous studies have demonstrated that the calcium-binding protein parvalbumin, is located within a population of GABAergic interneurons in the neostriatum of the rat. Anatomical studies have revealed that these cells receive asymmetrical synaptic input from terminals that are similar to identified cortical terminals and that they innervate neurons with the ultrastructural features of medium spiny cells. Furthermore, electrophysiological studies suggest that some GABAergic interneurons in the neostriatum receive direct excitatory input from the cortex and inhibit medium spiny cells following cortical stimulation. The main objectives of the present study were (i) to determine whether parvalbumin-immunoreactive neurons in the rat receive direct synaptic input from the cortex, (ii) to determine whether parvalbumin-immunopositive axon terminals innervate identified striatal projection neurons and (iii) to chemically characterize this anatomical circuit at the fine structural level. Rats received stereotaxic injections of biocytin in the frontal cortex or injections of neurobiotin in the substantia nigra. Following an appropriate survival time, the animals were perfused and the brains were sectioned and treated to reveal the transported tracers. Sections containing the neostriatum were treated for simultaneous localization of the transported tracer and parvalbumin immunoreactivity. Tracer deposits in the cortex gave rise to massive terminal and fibre labelling in the neostriatum. Parvalbumin-immunoreactive elements located within fields of anterogradely labelled terminals were examined in the electron microscope and corticostriatal terminals were found to form asymmetrical synaptic specializations with all parts of parvalbumin-immunoreactive neurons that were examined. Tracer deposits in the substantia nigra produced retrograde labelling of a subpopulation of striatonigral neurons. Areas of the neostriatum and nucleus accumbens containing retrogradely labelled neurons and parvalbumin-immunoreactive structures were selected for electron microscopy. Parvalbumin-immunopositive axon terminals formed symmetrical synaptic specializations with the perikarya of retrogradely labelled medium spiny projection neurons. Postembedding immunocytochemistry for GABA revealed that parvalbumin-immunoreactive boutons in synaptic contact with medium spiny neurons were GABA-positive. These data demonstrate directly a neural circuit whereby cortical information may be passed to medium spiny cells, via GABAergic interneurons, in the form of inhibition and provide an anatomical substrate for the feed-forward inhibition that has been detected in spiny neurons in electrophysiological experiments.
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PMID:Synaptic input and output of parvalbumin-immunoreactive neurons in the neostriatum of the rat. 787 Mar 1

The complete axon arborization of a single CA3 pyramidal cell has been reconstructed from 32 (60 microns thick) sections from the rat hippocampus following in vivo intracellular injection of neurobiotin. The same sections were double-immunostained for parvalbumin--a calcium-binding protein selectively present in two types of GABAergic interneurons, the basket and chandelier cells--in order to map boutons of the pyramidal cell in contact with dendrites and somata of these specific subsets of interneurons visualized in a Golgi-like manner. The axon of the pyramidal cell formed 15,295 boutons, 63.8% of which were in stratum oriens, 15.4% in stratum pyramidale and 20.8% in stratum radiatum. Only 2.1% of the axon terminals contacted parvalbumin-positive neurons. Most of these were single contacts (84.7%), but double or triple contacts (15.3%) were also found. The majority of the boutons terminated on dendrites (84.1%) of parvalbumin-positive cells, less frequently on cell bodies (15.9%). In order to estimate the proportion of contacts representing synapses, 16 light microscopically identified contacts between boutons of the filled pyramidal cell axon and the parvalbumin-positive targets were examined by correlated electron microscopy. Thirteen of them were found to be asymmetrical synapses, and in the remaining three cases synapses between the labelled profiles could not be confirmed. We conclude that the physiologically effective excitatory connections between single pyramidal cells and postsynaptic inhibitory neurons are mediated by a small number of contacts, mostly by a single synapse. This results in a high degree of convergence and divergence in hippocampal networks.
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PMID:Complete axon arborization of a single CA3 pyramidal cell in the rat hippocampus, and its relationship with postsynaptic parvalbumin-containing interneurons. 812 22

Neurons containing a calcium-binding protein parvalbumin in the external plexiform layer of the rat olfactory bulb were identified light microscopically with the pre-embedding immunocytochemistry and were subsequently analysed with the electron microscopic serial-sectioning and three-dimensional reconstructions. In the present study we chose several different types of parvalbumin-immunoreactive neurons identified light microscopically as Van Gehuchten cell type, superficial short-axon cell type and multipolar cell type. Parvalbumin-immunoreactive somata were similar to one another in their ultrastructural characteristics, showing nuclear indentations, moderately developed Golgi apparatus and abundant mitochondria; these structural features appeared to resemble those of the short axon cells around the glomeruli and in the granule cell layer reported in previous electron microscopic studies. All neurons analysed in the present study made symmetrical synapses on to dendrites and somata of presumed mitral/tufted cells and received asymmetrical synapses from them, and occasionally formed reciprocal synapses with them. On the parvalbumin-immunoreactive processes, the asymmetrical synapses nearly equalled the symmetrical ones in number and about 30-50% of them were identified as reciprocal pairs. In contrast, no presynaptic sites were observed on parvalbumin-immunoreactive somata, and thick portions (more than approximately 2 microns in diameter) of the proximal dendrites, where they were occasionally postsynaptic in some asymmetrical and symmetrical synapses from parvalbumin-immunonegative profiles. Characteristically, parvalbumin-immunoreactive process frequently make direct contacts with one another; processes regarded light microscopically as arising from a soma or a dendrite or parvalbumin-immunoreactive neurons were sometimes revealed to be separate but directly contacting processes with electron microscopic examinations. Although puncta adherentia were occasionally observed between these contact sites, so far neither gap junctions nor chemical synapses were observed. Until now, it has been believed that in the external plexiform layer only granule cells form reciprocal synapses with mitral/tufted cells. However, the present study clearly demonstrates that interneurons different from granule cells, namely GABAergic neurons containing a calcium-binding protein parvalbumin, also make reciprocal synapses with mitral/tufted cells in the external plexiform layer. Therefore, neuronal processes making reciprocal synapses with mitral/tufted cells in the external plexiform layer cannot be determined a priori as granule cell processes.
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PMID:Electron microscopic serial-sectioning/reconstruction study of parvalbumin-containing neurons in the external plexiform layer of the rat olfactory bulb. 873 15

Previous immunocytochemical studies in the cerebral cortex of various species have shown that the calcium-binding protein calretinin (CR) labels specific subpopulations of nonspiny nonpyramidal cells (interneurons). The present study attempts to characterize morphologically and chemically the microcircuitry of CR-immunoreactive (CR-ir) neurons in the human temporal neocortex. Postembedding immunocytochemistry for CR and GABA and combination immunocytochemistry for CR and nonphosphorylated neurofilament protein (NPNFP) or for CR and the calcium-binding proteins parvalbumin (PV) and calbindin (CB) showed CR multiterminal endings frequently innervating the distal apical dendrite or the cell body and proximal dendrites of NPNFP-ir or CB-ir pyramidal cells, respectively. Cell bodies of interneurons immunoreactive for CB or PV were innervated only occasionally by CR multiterminal endings, whereas certain GABA neurons were surrounded by them. Furthermore, CR-ir axon terminals formed either symmetrical (the majority) or asymmetrical synapses with a variety of postsynaptic elements. These results indicate that different subpopulations of CR interneurons exist that are specialized for selective innervation of somatic or dendritic regions of certain pyramidal and nonpyramidal neurons.
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PMID:Synaptic connections of calretinin-immunoreactive neurons in the human neocortex. 918 52