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M Mishina

Publications and source records attributed to M Mishina.

At least 181 records · Page 10Linked to original sources
PubMed1988

Tissue distribution of mRNAs encoding muscarinic acetylcholine receptor subtypes.

The tissue distribution of the mRNAs encoding muscarinic acetylcholine receptors (mAChRs) I, II, III and IV has been investigated by blot hybridization analysis with specific probes. This study indicates that exocrine glands contain both mAChR I and III mRNAs, whereas smooth muscles contain both mAChR II and III mRNAs. All four mAChR mRNAs are present in cerebrum, whereas only mAChR II mRNA is found in heart.

Animals↗
PubMed1988

Rings of negatively charged amino acids determine the acetylcholine receptor channel conductance.

The structure-function relationship of the nicotinic acetylcholine receptor (AChR) has been effectively studied by the combination of complementary DNA manipulation and single-channel current analysis. Previous work with chimaeras between the Torpedo californica and bovine AChR delta-subunits has shown that the region comprising the hydrophobic segment M2 and its vicinity contains an important determinant of the rate of ion transport through the AChR channel. It has also been suggested that this region is responsible for the reduction in channel conductance caused by divalent cations and that segment M2 contributes to the binding site of noncompetitive antagonists. To identify those amino acid residues that interact with permeating ions, we have introduced various point mutations into the Torpedo AChR subunit cDNAs to alter the net charge of the charged or glutamine residues around the proposed transmembrane segments. The single-channel conductance properties of these AChR mutants expressed in Xenopus laevis oocytes indicate that three clusters of negatively charged and glutamine residues neighbouring segment M2 of the alpha-, beta-, gamma- and delta-subunits, probably forming three anionic rings, are major determinants of the rate of ion transport.

Amino Acid Sequence↗
PubMed1988

Selective coupling with K+ currents of muscarinic acetylcholine receptor subtypes in NG108-15 cells.

The primary structures of two muscarinic acetylcholine receptor (mAChR) species, designated as mAChR I and mAChR II, have been elucidated by cloning and sequence analysis of DNAs complementary to the porcine cerebral and cardiac messenger RNAs, respectively. mAChR I and mAChR II expressed in Xenopus oocytes differ from each other both in acetylcholine-induced response and in antagonist binding properties. These results, together with the differential tissue location of the two mAChR mRNAs, have indicated that pharmacologically distinguishable subtypes of the mAChR represent distinct gene products. The primary structures of two additional mammalian mAChR species, designated as mAChR III and mAChR IV, have subsequently been deduced from the nucleotide sequences of the cloned cDNAs or genomic DNAs. We report here that mAChR I and mAChR III expressed in NG108-15 neuroblastoma-glioma hybrid cells, but not mAChR II and mAChR IV, efficiently mediate phosphoinositide hydrolysis, activation of a Ca2+-dependent K+ current and inhibition of the M-current, a voltage-dependent K+ current sensitive to muscarinic agonists.

Acetylcholine↗
PubMed1988

Polypoid endobronchial extension from invasive thymoma.

A case of invasive thymoma which was manifest clinically as bronchial obstruction and metastatic liver tumour is presented. Autopsy revealed a unique polypoid endobronchial extension of the neoplasm. This represents a previously unrecognized pattern of secondary bronchial involvement by invasive thymoma.

Bronchial Neoplasms↗
PubMed1987

Effects of substitution of putative transmembrane segments on nicotinic acetylcholine receptor function.

Mutants of the Torpedo nicotinic acetylcholine receptor in which each of the putative transmembrane segments of the alpha-subunit is replaced by the hydrophobic transmembrane segment of the vesicular stomatitis virus glycoprotein or of the human interleukin-2 receptor have been produced in Xenopus oocytes by cDNA manipulations. Functional analysis of these mutants shows that the hydrophobic segment M4 can be replaced by foreign transmembrane sequences without loss of channel activity. It is also suggested that the hydrophobic segments M1, M2 and M3 and the amphipathic segment MA are important for efficient expression of the acetylcholine receptor on the cell surface and that the specific amino acid sequence of segment M2 may be involved in channel activity.

Animals↗
PubMed1987

Functional properties of nicotinic acetylcholine receptor subunits expressed in various combinations.

The four kinds of subunits of the Torpedo californica nicotinic acetylcholine receptor have been produced in various combinations by injecting Xenopus oocytes with the corresponding subunit-specific mRNAs synthesized by transcription in vitro of the cloned cDNAs. Functional analysis suggests that association of the alpha-subunit with either the gamma- or the delta-subunit is a prerequisite for generating the conformation necessary for agonist binding. The acetylcholine receptor devoid of either the beta-, gamma- or delta-subunit exhibits weak channel activity.

Animals↗
PubMed1987

Functional expression of cloned cDNA encoding the alpha-subunit of adenylate cyclase-stimulating G-protein.

Cloned cDNA encoding the alpha-subunit of the adenylate cyclase-stimulating G-protein (Gs), carried by a simian virus 40 vector, has been introduced into the cyc- variant of S49 lymphoma cells by electroporation. In contrast to untransfected cys- cells, clones transformed with the cDNA exhibit an increase in intracellular cyclic AMP concentration in response to a beta-adrenergic agonist.

Adenylyl Cyclases↗
PubMed1986

Patch clamp measurements on Xenopus laevis oocytes: currents through endogenous channels and implanted acetylcholine receptor and sodium channels.

Functional acetylcholine receptor (AChR) and sodium channels were expressed in the membrane of Xenopus laevis oocytes following injection with poly(A)+-mRNA extracted from denervated rat leg muscle. Whole-cell currents, activated by acetylcholine or by depolarizing voltage steps had properties comparable to those observed in rat muscle. Oocytes injected with specific mRNA, transcribed from cDNA templates and coding for the AChR of Torpedo electric organ, expressed functional AChR channels at a much higher density. Single-channel currents were recorded from the oocyte plasma membrane following removal of the follicle cell layer and the vitelline membrane from the oocyte. The follicle cell layer was removed enzymatically with collagenase. The vitelline membrane was removed either mechanically after briefly exposing the oocyte to a hypertonic solution, or by enzyme treatment with pronase. Stretch activated (s.a.) currents were observed in most recordings from cell-attached patches obtained with standard patch pipettes. S.a.-currents were evoked by negative or positive pressure (greater than or equal to 5 mbar) applied to the inside of the pipette, and were observed in both normal and mRNA injected oocytes indicating that they are endogenous to the oocyte membrane. The s.a.-channels are cation selective and their conductance is 28 pS in normal frog Ringer's solution (20 +/- 1 degree C). Their gating is voltage dependent, and their open probability increases toward more positive membrane potentials. The density of s.a.-channels is estimated to be 0.5-2 channels per micron 2 of oocyte plasma membrane. In cell-attached patches s.a.-currents are observed much less frequently when current measurement is restricted to smaller patches of 3-5 micron 2 area using thick-walled pipettes with narrow tips. In outside-out patches s.a.-currents occur much less frequently than in cell-attached or inside-out patches. AChR-channel and sodium channel currents were observed only in a minority of patches from oocytes injected with poly(A)+-mRNA from rat muscle. AChR-channel currents were seen in all patches of oocytes injected with specific mRNA coding for Torpedo AChR. In normal frog Ringer's solution (20 +/- 2 degrees C) the conductance of implanted rat muscle AChR-channels was 38 pS and that of sodium channels 20 pS. The conductance of implanted Torpedo AChR channels was 40 pS. The conductance of implanted channels was similar in cell-attached and in cell-free patches.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1985

A physiological study on acetylcholine receptor expressed in Xenopus oocytes from cloned cDNAs.

Nicotinic ACh receptor was expressed in Xenopus oocytes by injecting mRNAs produced from cloned cDNAs encoding the four subunits of ACh receptor of Torpedo californica. ACh responses recorded from oocytes 3 days after injection of the mRNAs were reversibly blocked by d-tubocurarine (1-2 microM), indicating that the newly synthesized receptor is of nicotinic type. The reversal potential of ACh response was found at around -1 - -5 mV. The reversal potential was not changed by removal of extracellular C1-, suggesting that the ionic channel of the newly expressed ACh receptor is permeable only to cations. Repetitive applications of ACh caused desensitization of the receptor. The rate of the desensitization was greater when the membrane potential was more negative. Subunit deletion studies showed that all four subunits are required for the formation of ACh receptors with normal ACh sensitivity. However, ACh receptors without delta subunit responded to ACh with low sensitivity. Studies on ACh receptor mutants with -subunits altered by site directed mutagenesis of the cDNA suggest that the anphipathic segment is involved in the channel function of the receptor as well as the four hydrophobic segments since partial deletion of amino acids in these segments essentially abolished ACh sensitivity with relatively little change in 125I-alpha-bungarotoxin binding activity.

Animals↗
PubMed1985

[Clinical evaluation of the TMS-19-Q.GC tablet in odontogenic infections. A comparative double-blind study with josamycin].

Clinical efficacy and safety of TMS-19-Q.GC tablet (TMS), a new macrolide antibiotic preparation, were compared with those of josamycin (JM) in the treatment of acute odontogenic infection under multicentered double-blind controlled study at the daily dosage of 600 mg of TMS or 1,200 mg of JM. The results obtained were as follows: The patients entered into the study were 265 cases and 112 in TMS group and 111 in JM group were adopted to evaluate for the efficacy. The evaluation was made by 2 ways i.e. changes in total clinical scores of the symptom and the doctors assessment. Efficacy rating of TMS and JM were 81.3 and 82.0% judged by the score and 73.2 and 77.5% judged by doctors in charge respectively. In the cases with 15 to 20 of total scores at the initial visit, considered to be suitable for the evaluation of antibiotics, the efficacy rating of both drugs were 86.7% in TMS and 84.6% in JM. Organisms were isolated from 34 cases in TMS and 40 in JM and the clinical effectiveness in those cases were almost the same. Slight adverse reactions were observed in 6 cases (4.6%) of TMS group and 1 (0.8%) of JM. In 3 cases (4 incidences) of TMS group and 1 of JM slightly abnormal laboratory findings were found. On the statistical analysis of the data regarding efficacy, safety and usefulness, both drugs had no significant difference. From these results, TMS was considered as effective as JM in the treatment of acute odontogenic infection at a daily half doses of JM.

Acute Disease↗
PubMed1984

Benign mesenchymoma of the sole.

Benign mesenchymoma is a mixed tumor that has at least two mesenchymal components in addition to fibrous tissue. A case of benign mesenchymoma of the sole in a 7-year-old boy is presented. The literature is reviewed and discussed.

Child↗
PubMed1983

Sequence requirement for transcription in vitro of the human corticotropin/beta-lipotropin precursor gene.

Using HeLa whole cell extracts, we have demonstrated that transcription in vitro of the cloned human and bovine corticotropin/beta-lipotropin precursor genes is initiated accurately and efficiently. DNA sequences required for promoter function have been assessed by using a series of 5'-deletion mutants of a fusion gene that contains the 5'-flanking sequence and capping site of the human corticotropin/beta-lipotropin precursor gene and the structural sequence of the herpes simplex virus thymidine kinase gene. The results obtained have shown that the region between 22 base pairs and 35 base pairs upstream from the capping site is essential for the correct and efficient transcriptional initiation in vitro. Thus, the 'TATA box' present in this region seems to be the main promoter element for transcription of the human corticotropin/beta-lipotropin precursor gene in the HeLa cell-free system. We have also developed a transcription system in vitro from the corticotropin-producing mouse pituitary tumor cell line AtT-20 in culture. Deletion mapping of the fusion gene promoter has indicated that the 'TATA box' region is required for the accurate and efficient transcriptional initiation in this system as well. Characteristic of this system is that the deletion of the sequence lying between 53 base pairs and 59 base pairs upstream from the capping site increases the transcriptional efficiency. Because this effect is observed in the AtT-20 cell-free system, but hardly in the HeLa cell-free system, it seems reasonable to assume that the interaction of this upstream sequence with some factor(s) in the AtT-20 cell extract is responsible for the modulation of transcription of the human corticotropin/beta-lipotropin precursor gene.

Adrenocorticotropic Hormone↗
PubMed1983

Isolation and characterization of the mouse corticotropin-beta-lipotropin precursor gene and a related pseudogene.

Two mouse genomic DNA sequences homologous with human corticotropin-beta-lipotropin precursor gene sequences have been cloned. One of them represents the functional corticotropin-beta-lipotropin precursor gene, which exhibits a structural organization similar to those of its bovine and human counterparts. The other represents a pseudogene that corresponds to the functional mouse gene sequence encoding the carboxy-terminal 143 amino acid residues (including corticotropin and beta-lipotropin) and the 3'-untranslated region.

Animals↗
PubMed1983

Sequence requirement for transcription in vivo of the human preproenkephalin A gene.

The nucleotide sequence of the 5'-flanking region of the cloned human preproenkephalin A gene, extending to 949 bp upstream of the capping site, has been determined. The preproenkephalin A gene, when joined with an SV40 vector and introduced into COS monkey cells, is efficiently transcribed from its own promoter. To assess the DNA sequence required for promoter function, we have constructed a series of 5'-deletion mutants of a fusion gene that consists of the 949-bp 5'-flanking sequence and capping site of the preproenkephalin A gene and the structural sequence of the herpes simplex virus thymidine kinase gene. The deletions up to 757-172 bp upstream of the capping site exert essentially no effect on the expression of the fusion gene, whereas the deletions up to 145, 111, 81 and 67 bp upstream of the capping site result in a gradual decrease in the transcriptional efficiency. No detectable amount of the fusion gene transcript is produced with the mutants having deletions up to 67, 43 and 28 bp upstream of the capping site. These results indicate that a functional promoter of the preproenkephalin A gene lies between 67 and 171 bp upstream of the capping site. This promoter region corresponds to a highly GC-rich segment with short repeated sequences and palindromes.

Base Composition↗