Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:2.7.7.49 (reverse transcriptase)
31,746 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

5-Lipoxygenase-activating protein (FLAP) is an 18-kDa integral membrane protein required, in peripheral cells, for the activation of 5-lipoxygenase (5-LO) and for the resulting synthesis of leukotrienes from arachidonic acid. In the brain, the leukotrienes have been implicated in several pathophysiological events and in the electrophysiological effect of somatostatin, yet the cellular origin and role of these messenger molecules are still poorly understood. In the present study, we used reverse transcriptase-polymerase chain reaction, in situ hybridization, and immunohistochemistry to demonstrate that 5-LO and FLAP are expressed in various regions of the rat brain, including hippocampus, cerebellum, primary olfactory cortex, superficial neocortex, thalamus, hypothalamus, and brainstem. Highest levels of expression were observed in cerebellum and hippocampus. In the latter we demonstrate the colocalization of 5-LO and FLAP in CA1 pyramidal neurons. Moreover, electrophysiological experiments show that selective inhibition of FLAP with the compound MK-886 (0.25-1 microM) prevents the somatostatin-induced augmentation of the hippocampal K+ M-current. Our results provide necessary evidence for the presence and signaling role of 5-LO and FLAP in central neurons and strongly support their proposed participation in somatostatin-receptor transmembrane signaling.
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PMID:Arachidonate 5-lipoxygenase and its activating protein: prominent hippocampal expression and role in somatostatin signaling. 852 47

Olfactory receptor neurons are continuously replaced postnatally through the initiation of the division and terminal differentiation of progenitor cells located in the basal layer of the olfactory epithelium. Although the factors that regulate this process in vivo are not known, recent in vitro studies demonstrated that members of the epidermal growth factor (EGF) family including transforming growth factor-alpha (TGF alpha) and EGF are highly potent in promoting the proliferation of progenitor cells, suggesting a role for the EGF receptor (EGFR), which is the molecular receptor for both mitogens. We have examined the expression of EGFR mRNA and protein in the olfactory epithelium by using reverse transcriptase-polymerase chain reaction (RT-PCR) and Western blot analysis and have examined their cellular localization with in situ RT-PCR and immunocytochemistry. RT-PCR and Southern blot analysis demonstrated that EGFR mRNA is expressed in the olfactory mucosa and also in the positive control tissues, kidney and tongue. The 170-kDa EGFR protein was identified with Western blot analysis in the olfactory epithelium and control tissues. Our results using in situ RT-PCR localized EGFR mRNA-expressing cells more extensively in the basal cell layer of the epithelium than did the immunocytochemical methods. These results suggest that EGFR mediates the mitogenic effect of TGF alpha and/or EGF on the quiescent basal cells to initiate the cell cycle.
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PMID:Epidermal growth factor receptor mRNA and protein are expressed in progenitor cells of the olfactory epithelium. 888 29

We have identified three genes encoding previously uncharacterized chemoreceptors expressed in rat sensory and reproductive tissues using a reverse transcriptase polymerase chain reaction strategy. Degenerate oligonucleotides designed from conserved sequences in the rat olfactory receptor gene family were used to amplify candidate receptor gene products expressed in taste tissue. Sequence analysis of three distinct clonal isolates revealed that the gene products from taste bud were 30-75% identical to previously identified olfactory receptor genes. The genomic coding sequences predicted protein structures with seven membrane spanning regions that have strong conservation relative to other members of the G-protein-coupled olfactory receptor gene family. Transcripts for each of the three gene products were detected exclusively in taste, olfactory and male reproductive tissue. Sequence analysis of the polymerase chain reaction products confirmed that identical transcripts were expressed in all three tissues. These findings are the first demonstration that identical olfactory receptor-like gene are expressed in three distinct tissues.
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PMID:Chemoreceptors expressed in taste, olfactory and male reproductive tissues. 892 83

The growth and differentiation of olfactory sensory neurons are regulated tightly. We had shown previously, by immunohistochemistry, that transforming growth factor-alpha (TGF-alpha) and epidermal growth factor (EGF) receptor are present in the olfactory epithelium of untreated adult rats and that TGF-alpha is a potent mitogen of olfactory epithelium in vitro. Expression of EGF receptor and TGF-alpha was detected primarily in horizontal basal cells and supporting cells but rarely in globose basal cells, which suggested that EGF receptor is not a likely candidate for the mitotic regulator of sensory neurons. In order to expand the search for candidate regulators, we have now examined other members of the EGF family of receptors and ligands. By utilizing reverse transcriptase-polymerase chain reaction (RT-PCR) methodology, we have detected the messenger RNA encoding the protein of the neu gene (p185neu) and Neu differentiation factor (NDF) isoforms in the olfactory mucosa. Immunohistochemical localization of p185neu and NDF indicates expression of these proteins in the olfactory epithelium of adult rats in regions where globose basal cells and immature sensory neurons are found, as well as in the ensheathing cells of the olfactory nerve. The presence of neu and NDF transcripts in the olfactory tissue and the localization of their encoded polypeptides to proliferative regions of the epithelium suggest involvement of these gene products in the regulated proliferation/differntiation of the sensory neurons.
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PMID:Expression of neu and Neu differentiation factor in the olfactory mucosa of rat. 901 Jul 26

In this study, we analysed the molecular heterogeneity and synaptic localization of the N-methyl-D-aspartate receptor subunit 1 and the alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA) receptor subunit 1 in the olfactory bulb glomerular synaptic circuitry. Semiquantitative reverse transcriptase polymerase chain reaction showed that approximately 40% of the N-methyl-D-aspartate receptor subunit 1 messenger RNA splice variants contain the N1 exon, which conveys specific functional properties on the channel. In other forebrain and hindbrain regions that we examined, the ratio of the N1-containing (receptor subunit 1(1XX)) to N1-lacking (receptor subunit 1(0XX)) N-methyl-D-aspartate receptor subunit 1 messenger RNAs varied considerably. The cellular and subcellular distribution of N-methyl-D-aspartate receptor subunit 1 and AMPA receptor subunit 1 was investigated with antibodies generated against the C-terminal domain of the individual subunits [Petralia R. S. et al. (1994) J. Neurosci. 14, 667 696; Wenthold R. J. et al. (1992) J. biol Chem. 267, 501 507]. Both N-methyl-D-aspartate receptor subunit 1 and AMPA receptor subunit 1 were localized to the postsynaptic density of asymmetric synapses established by olfactory receptor neuron terminals with the dendrites of mitral and tufted cells. Not all of these synapses, however, were labelled. These results are consistent with the notion that glutamate is the neurotransmitter at the olfactory nerve to mitral and tufted cell synapses, and suggest a high heterogeneity in the expression of the postsynaptic glutamate receptors.
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PMID:Glutamate receptors in the olfactory bulb synaptic circuitry: heterogeneity and synaptic localization of N-methyl-D-aspartate receptor subunit 1 and AMPA receptor subunit 1. 913 51

Gonadotropin-releasing hormone (GnRH) is encoded by the proGnRH gene which contains four exons and three introns. In this study, two immortalized GnRH-expressing cell lines (Gn11 and NLT) were characterized. The NLT and Gn11 cells, derived from a same brain tumor in a transgenic mouse, display neuronal morphology and neuron-specific markers. However, NLT cells secrete much higher levels of GnRH than Gn11 cells. To delineate the mechanism underlying this difference, reverse transcriptase-polymerase chain reaction and RNase protection assays were performed to examine proGnRH gene expression. While the mature proGnRH mRNA was predominately expressed in NLT cells, Gn11 cells express an abundant short transcript. Sequence analysis revealed that this short transcript contains exons 1, 3, and 4, but not exon 2, which encodes the GnRH decapeptide. RNase protection assays demonstrated that NLT cells express much higher levels of mature proGnRH mRNA than Gn11 cells. The lower level of GnRH secreting capacity in Gn11 cells is due, in part, to decreased expression of mature proGnRH mRNA. When proGnRH gene expression in the mouse brain was examined, the same short splicing variant was observed in the olfactory area and preoptic area-anterior hypothalamus. But the prevalent transcript in these regions was the mature proGnRH mRNA. In contrast, only the mature proGnRH mRNA was found in the caudal hypothalamus. These results suggest that alternative splicing may be one of the mechanisms regulating proGnRH gene expression in the animal brain.
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PMID:An alternative gonadotropin-releasing hormone (GnRH) RNA splicing product found in cultured GnRH neurons and mouse hypothalamus. 913 17

The channel properties of the multimeric ionotropic glutamate receptors can be regulated by their subunit composition. The relationship between the structure and physiological functions of glutamate receptors, however, is difficult to study in the CNS because of the large number of these subunits, their widespread distribution, and neuronal heterogeneity. To avoid these difficulties, and to uncover possible novel functions of ionotropic glutamate receptors in sensory neurons, we examined the expression of non-N-methyl-D-aspartate glutamate receptor subunits in a simple neuronal system: the olfactory epithelium. It contains only one neuronal type, the olfactory receptor neuron, that receives no synaptic innervation within the epithelium and therefore should not require conventional postsynaptic glutamate receptors. The axons of these neurons, however, terminate and release glutamate in the glomerular region of the olfactory bulb, and may contain presynaptic glutamate receptors. By reverse transcriptase-polymerase chain reaction amplification and RNase protection assays, we showed that a subset of non-N-methyl-D-aspartate receptor subunits is expressed in the olfactory epithelium. The most abundant is KA2, which can form kainate-selective ion channels with GluR5 or GluR6. Messenger RNAs for GluR6, and for the alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionate/kainate-type (AMPA/KA) GluR2 and GluR3 subunits, are also present, but at levels lower than that of KA2 by an order of magnitude. In situ hybridization and immunocytochemistry localized KA2 to only the olfactory receptor neurons, and not to any other cell type in the olfactory epithelium. Surprisingly, antibodies against KA2 or GluR5/6/7 primarily stained the olfactory neuron dendritic knobs that are specialized for odorant signalling at the sensory epithelial lumenal surface, and the olfactory neuron axon bundles that project to the olfactory bulb. The presence of a limited subset of non-N-methyl-D-aspartate receptor subunits in the olfactory epithelium, and the localization of a kainate-selective receptor to both the axons and specialized dendritic knobs of olfactory receptor neurons, which receive no known synaptic input, suggest that these non-N-methyl-D-aspartate receptor subtypes may mediate either novel non-synaptic functions in the olfactory neuron dendrites or presynaptic functions in the olfactory nerve terminals or axons. These data also suggest that the olfactory sensory system, possessing a relatively simple anatomical organization and a limited number of glutamate receptor subunits, may be useful for elucidating facets of the complex relationships between subunit composition and physiological function of ionotropic glutamate receptors.
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PMID:Expression of non-N-methyl-D-aspartate glutamate receptor subunits in the olfactory epithelium. 920 Jul 25

The expression of the mitochondrial benzodiazepine receptor gene was assayed by a semi-quantitative non-radioactive reverse transcriptase polymerase chain reaction (RT-PCR) assay. The level of amplified mitochondrial benzodiazepine receptor mRNA was expressed as a ratio of either glyceraldehyde-3-phosphate dehydrogenase (GAPDH) or beta-actin mRNA co-amplified in the same RT-PCR assay. The relative amounts of mitochondrial benzodiazepine receptor RNA in several rat tissues were found to be similar to the previously reported relative amount of mitochondrial benzodiazepine receptor binding sites. The level of these binding sites has also been reported to be altered by stress stimuli. In this study we specifically measured the effect of stress on the mRNA levels of the mitochondrial benzodiazepine receptor as an alternative method to the binding assay in an attempt to understand the mechanism by which stress alters binding. Sprague-Dawley male rats were either forced to swim for 15 min in 18 degrees C water or restrained in a plastic cylinder for 45 min either once, or twice daily for 7 days. Neither the swim stress, nor acute or chronic restraint stress, caused a measurable statistically significant relative change in mitochondrial benzodiazepine receptor mRNA in the adrenal gland, kidney, testis and olfactory bulb. However, daily treatment of rats for 7 days with 4 mg/kg of dexamethasone caused a significant decrease in mitochondrial benzodiazepine receptor gene expression in adrenal glands. This finding and the measurement of the relative levels of mitochondrial benzodiazepine receptor mRNA in the various tissues indicate that mitochondrial benzodiazepine receptor density is regulated to some extent at the gene expression level. However, the lack of detectable stress-induced changes in mRNA levels for this receptor seem to indicate that either mRNA changes were below detectable levels or that other mechanisms may be involved in the previously reported stress-induced changes of mitochondrial benzodiazepine receptor density. Because the focus of this work was on the regulation of mitochondrial benzodiazepine receptor gene expression, ligand binding studies to determine changes in receptor densities were not performed.
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PMID:Dexamethasone, but not stress, induce measurable changes of mitochondrial benzodiazepine receptor mRNA levels in rats. 927 84

Borna disease virus (BDV), a neurotropic virus naturally infecting horses and sheep, has been suggested to be associated with human psychiatric disorders. Thus far no extensive studies have been done, providing the evidence of BDV genome in normal human brain tissue. We therefore examined four brain regions of 30 normal autopsy brains for BDV p24 genome. By highly sensitive nested reverse transcriptase (RT)-mediated PCR analysis, we found positive PCR products in two brains: one in frontal and temporal cortices and hippocampus and another in frontal cortex and olfactory bulb. Our results suggest that BDV can infect human brain tissue latently, without causing an apparent neuropsychiatric disorder.
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PMID:Detection of Borna disease virus genome in normal human brain tissue. 937 35

The Pa and Pb promoters of the Atlantic salmon (Salmo salar) GnRH gene were fused together or individually to the Escherichia coli lacZ gene, and their transcriptional activities were measured in transient expression assays in zebrafish (Danio rerio). In 48-hour embryos, both promoters were preferentially expressed in the brain, whereas a cytomegalovirus (CMV) promoter-lacZ fusion gene displayed high levels of activity in nonbrain tissues. Pa and Pb exhibited different cell specificity in the forebrain. Pb was active in large neuron-like cells exclusive in the olfactory placode region, whereas Pa appeared active in nonneuron-like cells in the forebrain. In Atlantic salmon forebrain tissue, both Pa and Pb exhibited endogenous activity, as assessed by reverse transcriptase-polymerase chain reaction (RT-PCR) analysis. However, only the Pb transcript contained the prepro-GnRH exon II-IV sequences, suggesting that Pa activity may not be related to GnRH production in this species.
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PMID:A functional study of the salmon GnRH promoter. 941 92


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