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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 46 (1986), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: Muscarinic acetylcholine receptors from bovine cerebral cortex were solubilized in digitonin for the subsequent determination of several biochemical properties. The digitonin-solubilized receptors were representative of the entire membrane-bound population of muscarinic receptors with respect to carbohydrate content, isoelectric point, and molecular weight. The glycoprotein nature of the solubilized receptors was demonstrated by their quantitative binding to wheat germ agglutinin-aga-rose. The presence of a bound antagonist did not decrease the extent of receptor binding to this lectin. Treatment of receptors with neuraminidase to remove N-acetylneuraminic acid residues reduced binding to wheat germ agglutinin-agarose by 40%; further treatment with endo-glycosidases D and H, to remove all N-linked carbohydrate, decreased binding by a total of 67%. Removal of N-acetylneuraminic acid residues had no effect on agonist binding properties of the membrane-bound receptors. The carbohydrate-specific enzymes were further used to assess the contribution of carbohydrate to the isoelectric point and molecular weight of the receptor. Muscarinic receptors solubilized in either digitonin or Triton X-100 focused as one major species with a pI of 4.3. Neuraminidase treatment resulted in an increase of 0.17 units in the pi of the receptor. Muscarinic receptors labeled with the covalent muscarinic antagonist propylbenzilylcholine mustard migrated as a single major polypeptide with a molecular weight of 73,000 on sodium dodecyl sulfate-urea-polyacrylamide gels. The exclusion of urea from these gels severely retarded receptor mobility, indicating a strong tendency for aggregation of receptors in SDS. Removal of N-linked carbohydrate by endoglycosidase treatment reduced the molecular weight of the antagonist binding polypeptide by no more than 5%. These results demonstrate the glycoprotein nature of muscarinic receptors from mammalian cerebral cortex and provide evidence for their heterogeneity with respect to carbohydrate content.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: In this study the subunits of the dihydropyridine-sensitive L-type Ca2+ channels (L-channels) expressed in rat pinealocytes were characterized using reverse transcription (RT)-PCR analysis, and the modulation of these channels by adrenergic agonists and by pituitary adenylate cyclase-activating polypeptide (PACAP) was studied using the patch-clamp technique. RT-PCR analysis showed that rat pinealocytes expressed α1D, α2b, β2, and β4 Ca2+-channel subunit mRNAs. Other α1 subunit transcripts were either not expressed or present at very low levels, indicating that the pinealocytes express predominantly α1D L-channels. Electrophysiological studies confirmed that the pineal expressed a single population of L-channels. The L-channel currents were inhibited by two agonists that elevate cyclic AMP: the β-adrenergic agonist isoproterenol and PACAP. Similar inhibition was observed with a cyclic AMP analogue, 8-bromo-cyclic AMP. The presence of a cyclic AMP antagonist, Rp-adenosine 3′,5′-cyclic monophosphorothioate, blocked the inhibition by isoproterenol and PACAP. Norepinephrine, a mixed α- and β-adrenergic agonist, also inhibited the L-channel currents, but the inhibition was smaller. The smaller inhibition by norepinephrine was secondary to the simultaneous activation of α- and β-adrenergic receptors. These results indicate that (a) pinealocytes express predominantly α1D L-channels, and (b) the β-adrenergic agonist isoproterenol and PACAP inhibit the L-channel currents through elevation of cyclic AMP. However, an α-adrenergic-mediated mechanism also appears to be involved in the effect of norepinephrine on the L-channel currents.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Using as probe a cDNA encoding the membrane form of guanylate eyclase from the sea urchin Arbacia punctulata6, we isolated partial-length putative guanylate cyclase clones from FIG. 1 Nucleotide sequence and predicted amino acid sequence of rat brain guanylate cyclase cDNA. Nucleotides and amino ...
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1573-6830
    Keywords: calcium channels ; NG108-15 cells ; molecular cloning ; transcription ; gene expression regulation ; enhancer element ; trinucleotide repeat ; metal response element
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary 1. The transcriptional regulation of the rat brain L-type calcium channel α1D subunit (RBα1D) gene was investigated using NG108-15 neuroblastoma-glioma cells. 2. Differentiation of NG108-15 cells in the presence of prostaglandin E1 or retinoic acid resulted in the appearance of mRNA encoding the RBα1D subunit detected using Northern blot analysis. 3. A rat genomic DNA library was screened, and a 15.2-kb clone was isolated and partially sequenced which included part of the 5′ upstream sequence through the initial part of intron 2 of the RBα1D gene. 4. Deletion analysis, using a CAT reporter gene and transfected NG108-15 cells, revealed that the 1.2-kb 5′-upstream sequence from the RBα1D gene contains cis-acting positive and negative regulatory elements. A deletion of the 3′ end of exon 1 also suggested the presence of regulatory elements in the first exon. 5. DNase footprinting of exon 1 of the RBα1D gene revealed two regions protected from digestion by specific protein binding, and the second region included an (ATG)7 trinucleotide repeat sequence. Electrophoretic mobility shift assays confirmed nuclear protein(s) binding to the (ATG)7 sequence. 6. The (ATG)7 sequence functions as a enhancer when linked to a thymidine kinase promoter and a CAT reporter gene. 7. These results provide the initial description of the transcriptional regulation of the RBα1D gene and identify a novel enhancer that consists of an (ATG)7 trinucleotide repeat sequence.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Cellular and molecular neurobiology 18 (1998), S. 211-230 
    ISSN: 1573-6830
    Keywords: oxytocin ; vasopressin ; prohormone convertase ; axonal transport ; kinesin ; calcium channels ; SNARE hypothesis ; exocytosis ; synaptotagmin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract 1. The diversity of molecules involved in various aspects of neurosecretion, such asproprotein processing, axonal transport of large dense core vesicles (LDCVs), and regulated secretion, is discussed in the context of the hypothalamo-neurohypophysial system (HNS). 2. Recent studies have uncovered a family of at least seven processing enzymes known as proprotein convertases (PCs) which are involved in proteolytically cleaving protein precursors at paired basic amino acid motifs to yield biologically active peptides. Three of these, PC1(3), 2, and 5, are found in neurons and are involved in producing regulatedsecretory peptide products. 3. The axonal transport of LDCVs occurs on microtubule tracks by still unknown mechanisms. There are over 11 distinct kinesin-related molecules that have now beenidentified as possible microtubule motor candidates. 4. Calcium channels in the nervous system are known to be derived from at leastfive α-subunit and four β-subunit genes with multiple alternatively spliced isoforms in each case. These could account, in part, for the varied calcium currents found in the HNS. 5. The large number of proteins and isoforms now demonstrated to be involved inregulated secretion are discussed, with a focus on LDCV compositions and the synaptotag-min gene family.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Mammalian genome 8 (1997), S. B456 
    ISSN: 1432-1777
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Type of Medium: Electronic Resource
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