Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.1.27.5 (RNase)
 17,967 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Of the 15 nicotinic ACh receptor genes identified in vertebrates, only four (alpha 1, beta 1, gamma, and delta) have been shown to be expressed in embryonic skeletal muscle at early times. In mammalian muscle a fifth gene (epsilon) replaces the gamma gene in expression at later times. The remaining 10 nicotinic receptor genes identified to date (alpha 2-alpha 8, beta 2-beta 4) are expressed in the nervous system and are considered neuronal genes. Using RNase protection assays, we show here that four of the neuronal-type genes (alpha 4, alpha 5, alpha 7, and beta 4) are expressed in developing chick skeletal muscle. Two of them (alpha 4 and alpha 7) decline substantially in transcript abundance between embryonic days 11 and 17, as does alpha 1, while the other two (alpha 5 and beta 4) show only moderate decreases over the same time period. At embryonic day 8, alpha 7 transcripts are nearly 20% as abundant as alpha 1 transcripts. In situ hybridizations confirm the presence of alpha 7 transcripts in muscle cells both in cell culture and in embryonic tissue. No evidence was found for expression of the alpha 2, alpha 3, alpha 8, or beta 3 genes in muscle. Immunoprecipitations and immunoblot analysis using subunit-specific monoclonal antibodies reveal alpha 7 protein in muscle, and the amount of protein rises and declines with the amount of alpha 7 mRNA during development. Sucrose gradient analysis demonstrates that the alpha 7 protein is present in muscle as a species of 10S, the size expected for a nicotinic receptor. The alpha 7 species in muscle binds alpha-bungarotoxin but does not contain alpha 1 subunits, indicating that the two kinds of alpha-type gene products segregate during assembly. The results suggest that neuronal AChRs may play a role in early muscle development.
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PMID:Expression of neuronal acetylcholine receptor genes in vertebrate skeletal muscle during development. 786 4

A cDNA encoding the beta subunit of the Xenopus muscle nicotinic acetylcholine receptor (AChR) was cloned from an embryonic Xenopus cDNA library. The predicted mature polypeptide has 469 amino acids and four membrane spanning regions corresponding to the M1-M4 regions identified in other AChR subunit clones. The polypeptide bears greater homology to beta subunits of Torpedo and mouse than to alpha, gamma or delta subunits of Xenopus. The earliest beta subunit transcripts were detected by RNase protection assays at the neural plate stage of development (stage 14) and the level of transcripts, as a fraction of total RNA, continued to increase through the age of hatching (stages 34-36). Co-injection of Xenopus alpha, beta, gamma and delta cRNAs into Xenopus oocytes led to expression of functional AChRs. Micromolar concentrations of ACh activated depolarizing AChR currents which reversed at -5 mV and were blocked by alpha bungarotoxin. Injection of alpha, gamma and delta subunits alone did not yield detectable ACh responses. With the cloning of the Xenopus beta subunit, structure/function relations of AChRs can now be studied using receptors composed entirely of Xenopus subunits.
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PMID:Structure and expression of the nicotinic acetylcholine receptor beta subunit of Xenopus laevis. 808 30

A large family of genes encoding subunits of nicotinic ACh receptors (AChRs) has been identified in vertebrates and shown to be expressed in the nervous system. The multiplicity of genes raises questions about which gene products coassemble to produce native receptor subtypes and how the expression of receptor genes is regulated in neurons. We report here that five neuronal AChR genes are expressed in the chick ciliary ganglion at both early and late times in development. Quantitative RNase protection experiments demonstrated that at embryonic day 18 (E18) the ganglion contains about 1800 copies of alpha 7 transcript per neuron, 900 copies of alpha 3 transcript per neuron, and 200-300 copies each of alpha 5, beta 2, and beta 4 transcripts per neuron. The same five genes are expressed at significantly lower levels at E8 but show the same rank order of abundance in transcripts per neuron. Few, if any, transcripts were found for the alpha 2, alpha 4, alpha 8, and beta 3 AChR genes in ciliary ganglion RNA at either E8 or E18. The 6- and 13-fold increases previously reported for two classes of AChRs on the neurons between E8 and E18 approximate the 4-14-fold increases observed here in AChR gene mRNA levels per neuron over the same time period. The alpha 3, alpha 5, alpha 7, and beta 4 genes have previously been correlated with subunits of ciliary ganglion AChRs, but the beta 2 gene has not. The abundance of beta 2 transcripts raises the possibility either that the known AChRs in the ganglion have a more complex subunit composition than previously described or that additional receptor subtypes remain to be discovered. Northern blot analysis revealed no changes in transcript pattern for the alpha 3, alpha 5, and beta 4 genes between E8 and E18; a small change may occur in the transcript pattern for the alpha 7 gene. In situ hybridizations demonstrated that alpha 5 and beta 4 transcripts are expressed in essentially all ciliary ganglion neurons as has been shown previously for the more abundant alpha 3 transcript and inferred for the alpha 7 transcript. The results indicate that neurons can stably coexpress multiple AChR genes, including three of the alpha type, and that transcript levels may be rate limiting for accumulation of AChRs during development.
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PMID:Coexpression of multiple acetylcholine receptor genes in neurons: quantification of transcripts during development. 850 30

Relaxation of the trabecular smooth muscle, which is necessary for penile erection, is controlled locally by neurotransmitters and vasoactive agents. The goal of this study was to identify and characterize muscarinic acetylcholine receptor (mAChR) subtypes expressed in cultured human corpus cavernosum smooth muscle cells (HCC SMC). Binding analysis with L-[benzilic-4,4'-3H(N)]quinuclidinyl benzilate ([3H]QNB) demonstrated the expression of specific muscarinic receptor binding sites in HCC SMC. Analysis of total RNA isolated from whole corpus cavernosum tissue and smooth muscle cells, by RNase protection assays, demonstrated the expression of mRNA transcripts for m1, m2, m3, and m4 mAChR subtypes in whole tissue and m2 and m4 subtypes in cultured cells. In situ hybridization with specific m2 and m4 probes further confirmed the expression of m2 and m4 mRNA transcripts in cultured cells. Carbachol (CCh), a nonselective cholinergic agonist, inhibited cAMP synthesis at low concentrations (0.1-1 microM) and stimulated cAMP synthesis at high concentrations (100 microM), in cultured HCC SMC. CCh (100 microM) further augmented forskolin (FSK), isoproterenol (ISO), and prostaglandin E1 (PGE1)-induced cAMP synthesis. These observations suggest that, in vivo, in HCC, ACh may activate m3 mAChR subtypes on endothelial cells or m2 and m4 subtypes on the SMC. Although m2 and m4 are thought to inhibit adenylate cyclase (AC), the augmentation of cAMP synthesis by high concentrations of CCh in SMC suggests an alternative mechanism of coupling to G-proteins that stimulates AC activity. These studies show that HCC tissue expresses different subtypes of mAChR (m1, m2, m3, and m4), whereas cultured HCC SMC express m2 and m4 subtypes. It is suggested that m2 and m4 receptor subtypes may play an important role in maintaining trabecular smooth muscle tone in vivo. The augmentation of FSK-, ISO, and PGE1-induced cAMP synthesis by CCh suggests possible development of a multidrug therapeutic approach to treatment of erectile dysfunction.
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PMID:Expression of functional muscarinic acetylcholine receptor subtypes in human corpus cavernosum and in cultured smooth muscle cells. 872 95

1. We performed an RNase protection assay on cultured C2C12 mouse myotubes, demonstrating that the gamma subunit of the fetal muscle acetylcholine receptor (AChR) exists as two splice variants, which differ in the presence of the amino terminal exon 5. 2. We studied unitary ACh-evoked events in fibres acutely dissociated from the hindlimb flexor digitorum brevis muscle of BALB/C mice aged between embryonic day 16 (E16) and postnatal day 6 (P6). 3. At all ages, the channel conductance was about 30 pS, typical of the fetal form of the AChR. The mean open time increased significantly from 6 ms at E16 to 9 ms at E19, then decreased to about 5 ms during the first postnatal week. The lengthening of the open time was considerably delayed in hypothyroid mice. Data were recorded at 24-26 degrees C. 4. On the basis of previously reported experiments in heterologous expression systems, we suggest that the modulation of channel open time is related to the expression of the AChR incorporating the gammas subunit. These events might be coupled to the crucial modifications in muscle innervation that take place during the same developmental period.
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PMID:The open duration of fetal ACh receptor-channel changes during mouse muscle development. 950 4

The goal of this study was to determine whether hypoxia alters expression of endothelial nitric oxide synthase (eNOS) in the systemic circulation. Rats breathed either air or 10% oxygen for 12 hours, 48 hours, or 7 days. Thoracic aortas were excised and either mounted in organ bath myographs or frozen in liquid nitrogen for later extraction of protein and RNA. eNOS protein (Western blotting) was decreased (20% of normoxic control) after 12 hours, 48 hours, and 7 days of hypoxia. eNOS mRNA (ribonuclease protection assay) was similarly reduced. Acetylcholine (10(-4) mol/L) reversed phenylephrine (10(-5) mol/L) preconstriction by 53.3+/-5.6% in aortic rings from normoxic rats and 26.1+/-4.8% in rings from rats exposed to hypoxia for 48 hours (P<0.05), with comparable impairment of relaxation by the calcium ionophore A23187 (10(-5) mol/L). Responses to diethylamine nitric oxide and 8-bromo-cGMP were unaffected. Aortic cGMP levels after incubation with acetylcholine (10(-6) mol/L) averaged 14.0+/-1.8 fmol/mg in rings from normoxic rats compared with 8.7+/-1.0 fmol/mg in rings from hypoxic rats (P<0. 05). Similarly, nitrate concentration (by capillary electrophoresis) in the media in which the rings were incubated was reduced in the hypoxic group (5.6+/-0.23 micromol/L for hypoxic rats and 7.8+/-0.7 micromol/L for normoxic rats). Impaired endothelial NO release may handicap the vascular responses that defend vital organ function during hypoxia.
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PMID:Downregulation of endothelial nitric oxide synthase in rat aorta after prolonged hypoxia in vivo. 1074 3

Hyperthyroidism is associated with low exercise tolerance despite high cardiac output and sometimes with the development of heart failure. L-type calcium channels may play a role in the mechanism, but this has not been fully understood. We examined the effects of thyroid hormone on gene expression and function of L-type calcium channels in rat ventricles by the ribonuclease protection assay and whole-cell patch-clamp technique, respectively. The effects of bisoprolol, beta-blocking agent, on the regulation of calcium channel by thyroid hormone was also studied. In hyperthyroid animals, the mRNA of the calcium channel alpha1c subunit was reduced on day 4, compared with that in euthyroid animals, and remained low on day 8. Bisoprolol did not affect the thyroid hormone mediated decrease in alpha1c subunit mRNA. While L-type calcium current was greater in hyperthyroid than euthyroid myocytes on day 4, it was smaller on day 8. In addition, the isoproterenol-induced increase in calcium current in euthyroid rats was attenuated in hyperthyroid rats. Acetylcholine decreased calcium current in hyperthyroid myocytes, but not in euthyroid myocytes. In conclusion, L-type calcium current was increased by thyroid hormone in rat ventricular myocytes by the activation of the adenylate cyclase cascade, despite a decreased calcium channel gene expression. These genomic and non-genomic modifications may play an important role in the association of high cardiac output with low exercise tolerance, and in the development of heart failure in hyperthyroidism.
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PMID:Genomic and non-genomic regulation of L-type calcium channels in rat ventricle by thyroid hormone. 1623 92