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Biomedical subjects

E Kawashima

Publications and source records attributed to E Kawashima.

At least 37 records · Page 2Linked to original sources
PubMed1996

Cloning OF P2X5 and P2X6 receptors and the distribution and properties of an extended family of ATP-gated ion channels.

Two new P2X receptor cDNAs (P2X5 and P2X6) were isolated and expressed. All six proteins are 36-48 percent identical and seem to have two transmembrane segments with a large extracellular loop. Functionally, P2X5 and P2X6 receptors most resemble P2X2 and P2X4; they desensitize only slowly and do not respond to alpha beta methylene-ATP. P2X6 receptors, like P2X4, receptors, are not blocked by the antagonists suramin and pyridoxal-5-phosphate-6-azophenyl-2',4'-disulfonic acid. P2X6 and P2X5 receptors express at lower levels than P2X1-P2X4 receptors do, perhaps indicating that they do not normally form homomultimeric channels. P2X6 and P2X4 are the receptors expressed most heavily in brain, where their RNAs have a widespread and extensively overlapping distribution. The spinal cord expresses all receptors except P2X3. P2X2, P2X4, and P2X6, are the most abundant in the dorsal horn. Sensory neurons of the trigeminal, dorsal root, and nodose ganglia express all six RNAs; P2X3 is found only there. The functional properties and tissue distribution of these six P2X receptors indicate new roles for ATP-gated ion channels.

Adenosine Triphosphate↗
PubMed1996

Stimulation of atrial natriuretic peptide release by neurokinins in neonatal rat ventricular cardiomyocytes.

The effect of substance P (SP) on atrial natriuretic peptide (ANP) release was studied in neonatal rat ventricular cardiomyocytes. Incubation of cells with SP led to a marked increase in ANP secretion, a response accompanied by increases in alpha-type protein kinase C (PKC) in the membranous cell fraction and 6-keto-prostaglandin F1 alpha (6-keto-PGF1 alpha) formation and a small increase in adenosine 3',5'-cyclic monophosphate (cAMP) production. A role for PKC in SP-induced 6-keto-PGF1 alpha formation and ANP release was apparent insofar as the responses were suppressed by PKC inhibitors and in PKC-downregulated cells. Furthermore, SP-induced 6-keto-PGF1 alpha production was strongly correlated with SP-induced ANP secretion (r = 0.91, P < 0.0001, n = 27), suggesting a role for prostaglandins in SP-mediated ANP release. Supporting this, indomethacin abolished SP-induced ANP release, whereas PGE2, PGF2 alpha, and prostacyclin (PGI2) promoted ANP secretion in this system. Both the profile of SP-induced cAMP production and results obtained with prostaglandin antagonists suggest that a prostanoid FP receptor is at the basis of this response. Finally, both neurokinins A and B induced similar ANP responses, whereas cultured cells were found to contain mRNA transcripts coding for both neurokinin NK1 and NK3 receptor subtypes. Overall, these results suggest that SP induces ANP secretion in neonatal ventricular cardiomyocytes through a PKC- and prostaglandin-dependent signaling pathway.

6-Ketoprostaglandin F1 alpha↗
PubMed1996

[Partial rupture progressing to complete rupture of the left ventricular anterior papillary muscle after acute myocardial infarction: a case report].

A 71-year old man presented with partial rupture progressing to complete rupture of the left ventricular anterior papillary muscle after acute anterolateral myocardial infarction. The progressive rupture was demonstrated by transthoracic and transesophageal echocardiography. Transthoracic echocardiography showed exaggerated systolic prolapse of the anterior mitral leaflet with grade III mitral regurgitation and partial disruption of the anterolateral papillary muscle, but transesophageal echocardiography during surgery disclosed the progression of the partial rupture to complete rupture. The flail anterior mitral leaflet with severe mitral regurgitation and the head of the ruptured papillary muscle into the left atrium in systole were confirmed. The patient was treated by coronary artery bypass grafting and mitral valve prosthesis using a St. Jude Medical valve with good outcome.

Aged↗
PubMed1995

Synthesis of [5'-11C]ribonucleoside and -2'-deoyribonucleoside derivatives from D-ribose.

An approach to the synthesis of 2'-deoxy[5'-13C]ribonucleosides was achieved by the coupling reaction of a nucleic acid base derivative with D-[5-13C]ribose derivative (8). Compound 8 was derived from D-ribose (1) by way of methyl 2,3-di-O-benzyl(Bn)-D-ribofuranoside (2), 2,3-di-O-Bn-D-ribose diethyl dithioacetal (3), 2,3-di-O-Bn-D-ribose dibenzyl acetal (4), and 4-aldehydo-2,3-di-O-Bn-D-erythrose dibenzyl acetal (5), which was then successively subjected to Wittig reaction using Ph3P13CH3I-BuLi, highly stereoselective hydroxylation with OsO4 to give 2,3-di-O-Bn-D-ribose dibenzyl acetal (7), debenzylation with H2-Pd/C. The resulting 8 was subjected to coupling reaction with a nucleic acid base to give [5'-13C]ribonucleosides. The products were derived into the corresponding 2'-deoxy[5'-13C]ribonucleoside derivatives by the established manner.

Carbon Isotopes↗
PubMed1994

Benzimidazole ribonucleosides: design, synthesis, and antiviral activity of certain 2-(alkylthio)- and 2-(benzylthio)-5,6-dichloro-1-(beta-D-ribofuranosyl)benzimidazoles.

Several 2-alkylthio- and 2-benzylthio derivatives of 5,6-dichloro-1-(beta-D-ribofuranosyl)benzimidazole (DRB) have been designed and synthesized from 5,6-dichloro-1-(beta-D-ribofuranosyl)-benzimidazole-2-thione. All compounds were evaluated for activity against human cytomegalovirus (HCMV) and/or herpes simplex virus type-1 (HSV-1). Three different cytotoxicity assays were used to determine if the compounds were toxic to uninfected cells. Most of the 2-alkylthio compounds were either inactive against HCMV and HSV-1 or were active only at concentrations at or near those which produced toxicity in uninfected cells. The best separation between activity against HCMV and cytotoxicity was observed with the 2-benzylthio analog 7. This prompted us to synthesize the substituted 2-benzylthio analogs 11-23 using a Topliss Tree approach. None of these compounds were more active than compound 7; most of the analogs were weakly active against both HCMV and HSV-1, but the activity was not separated from cytotoxicity. On the basis of both antiviral and cytotoxicity data, compound 7 was the best compound in the series. It was more active against HCMV than DRB (the 2-unsubstituted analog), acyclovir, and foscarnet, but it was less active than ganciclovir.

Antiviral Agents↗
PubMed1994

NK1 receptor expression by cholinergic interneurones in human striatum.

Neurokinin-1 (NK1) receptor expression in human striatum was analysed using the polymerase chain reaction. To determine whether cholinergic interneurones express this receptor, in situ hybridization histochemistry was then applied to caudate nucleus and putamen. Radioactive oligonucleotide probes specific for choline acetyltransferase (ChAT) and NK1 receptor mRNA were used on adjacent cryostat sections. All of the 160 identified neurones positive for ChAT were also labelled for NK1 receptor. Moreover, in the caudate nucleus, NK1 receptor mRNA was detected in a population of large neurones that were not cholinergic. These results are consistent with the hypothesis that NK1 receptor-mediated mechanisms are involved in the function of cholinergic interneurones. This might be relevant to pharmacological or pathophysiological situations where substance P inputs are modified.

Aged↗
PubMed1994

Calcium influx and protein kinase C alpha activation mediate arachidonic acid mobilization by the human NK-2 receptor expressed in Chinese hamster ovary cells.

We have cloned a cDNA encoding the human ileal neurokinin-2 (NK-2) receptor which mediates powerful neurokinin A-stimulated arachidonic acid (AA) and prostaglandin release when expressed in CHO cells. Two major signal transduction events appear to underlie this response. Firstly, AA liberation is critically dependent upon agonist-stimulated influx of extracellular Ca2+ although not release from intracellular stores. Secondly, NK-2 receptor-linked AA mobilization requires concomitant PKC activation and based upon limited subtype immunodetectability as well as toxin, identical pretreatment inhibits AA release partially and blocks PKC alpha translocation completely. These observations indicate that in this cell system AA liberation reflects NK-2 receptor-dependent activation of two distinct but converging signal transduction pathways regulated by different G-protein species and involving Ca2+ influx and PKC alpha activation.

Animals↗
PubMed1994

Organization of the mouse 5-HT3 receptor gene and functional expression of two splice variants.

The structure of the mouse 5-HT3 receptor gene, 5-HT3R-A, is most similar to nicotinic acetylcholine receptor (nAChR) genes, in particular to the gene encoding the neuronal nAChR subunit alpha 7. These genes share among other things the location of three adjacent introns, suggesting that 5-HT3R-A and nAChR genes arose from a common precursor gene. The alternative use of two adjacent splice acceptor sites in intron 8 creates, in addition to the original 5-HT3R-A cDNA (5-HT3R-AL), a shorter isoform (5-HT3R-AS) which lacks six codons in the segment that translates into the major intracellular domain. This splice consensus sequence is not found in human genomic DNA. In mouse, we demonstrate by RNAse protection assay that 5-HT3R-AS mRNA is approximately 5 times more abundant than 5-HT3R-AL mRNA in both neuroblastoma cell lines and neuronal tissues. We used the Semliki Forest virus expression system for electrophysiological characterization of 5-HT3R-AS and 5-HT3R-AL in mammalian cells. No differences in electrophysiological characteristics, such as voltage dependence, desensitization kinetics, or unitary conductance were found between homomeric 5-HT3R-AS and 5-HT3R-AL receptors. Their properties are very similar to those of 5-HT3 receptors in mouse neuroblastoma cell lines.

Alternative Splicing↗
PubMed1993

Characterization of a novel exon within the D3 receptor gene giving rise to an mRNA isoform expressed in rat brain.

A novel D3 receptor cDNA containing an insertion of 84 bp has been isolated from a series of alternatively spliced D3 receptor cDNAs by polymerase chain reaction on RNA isolated from rat basal forebrain. Sequence analysis of both subcloned cDNAs and genomic DNA clones, has identified a 84 bp insertion resulting in a 28 amino acid insertion in the first extracellular loop. A comparison of the cDNA sequence of the novel D3 cDNA and the isolated genomic sequence indicates that the novel insertion corresponds to a new exon and arises via an alternative splicing event. The mRNA for the novel insertion could be detected by PCR in several areas of the brain co-localized with the wild type form of the D3 receptor. Moreover, genomic Southern blot analyses suggest that the D3-receptor exon giving rise to this novel D3 mRNA variant might exist in other species.

Alternative Splicing↗
PubMed1993

Expression and characterization of human D4 dopamine receptors in baculovirus-infected insect cells.

The human D4 dopamine receptor has been genetically engineered for expression in insect cells using the baculovirus system. A D4 cDNA gene fusion construct [(1991) Nature 350, 610-614] was synthetically modified to remove two introns from the coding region, and expressed in S. frugiperda (Sf9) cells as a fusion with a short sequence from the polyhedrin protein. Binding assays with [3H]spiperone indicated high levels of D4 receptor binding 90 h after infection and a pharmacological profile identical to that reported for D4 receptors expressed in COS-7 cells using the cDNA gene hybrid. We also show that the agonist binding affinity of D4 receptors expressed in Sf9 cells can be shifted by GTP-gamma-S, indicating coupling to G-proteins.

Animals↗
PubMed1993

A case report of isolated levocardia without intracardiac anomalies associated with sick sinus syndrome.

A 42-year-old female with cardiomegaly showed bradycardia without syncope. Clinical data showed that she had an isolated levocardia with interruption of the inferior vena cava. Isolated levocardia was defined as a normally placed heart associated with situs ambiguus of other viscera. She did not have intracardiac anomalies. Isolated levocardia without intracardiac anomalies, as in this case, has only been reported in 13 other cases. Isolated levocardia is often accompanied by severe complex intracardiac anomalies and, therefore, most of the patients have a short life span. Situs ambiguus, especially left isomerism, is frequently associated with deteriorated sinus node function, and an interruption of the inferior vena cava may also be an indication of this phenomenon. Therefore, the patient's sinus node function was examined using an electrophysiological study and a 24-hour ambulatory electrocardiogram. Sick sinus syndrome was finally confirmed.

Adult↗
PubMed1993

Precise analyses of DNA structure by NMR.

Novel 1H NMR techniques were developed and applied to the analyses of the DNA structure. They distinguished the base proton signals of cytosine (uracil) from those of the other bases. Two dimensional experiments were also performed by using these techniques, and were found to be useful for signal assignments. Moreover, the (2'R)-[2'-2H]-labeled DNA 10-mer and 17-mer were synthesized to be used for the determination of precise structures. These stereoselective [2'-2H]-labeling made possible explicit stereospecific assignments and exact determination of the vicinal coupling constants, 3JHH, and thus the conformation of each deoxyribose ring was accurately determined.

Cytosine↗
PubMed1992

Molecular characterisation, expression and localisation of human neurokinin-3 receptor.

The complete amino acid sequence of the human neurokinin-3 receptor was deduced by DNA sequence analysis of human genomic fragments. Comparison of the predicted primary structure with those for the human neurokinin receptors 1 and 2 shows a highly conserved pattern of seven hydrophobic regions with maximum divergence occurring at the amino- and carboxy-termini. The position of intron-exon junctions are identical to those in other reported neurokinin genes. Using a chimeric genomic-cDNA gene, the human NK-3 receptor was expressed in Xenopus laevis oocytes where it mediates membrane conductance changes in response to its agonist, neurokinin B. More significantly, expression of the gene in mammalian cells resulted in detection of receptor binding as well as neurokinin-stimulated calcium mobilization and arachidonic acid release, all displaying the pharmacological characteristics expected of a neurokinin-3 receptor. By using the polymerase chain reaction we have shown that mRNA for the human neurokinin-3 receptor is expressed predominantly in the central nervous system.

Adult↗
PubMed1992

A novel transthyretin mutation associated with familial amyloidotic polyneuropathy.

We characterized the mutation associated with familial amyloidotic polyneuropathy in a Japanese patient. Sequence analysis of polymerase chain reaction-amplified exons of the transthyretin gene revealed a novel point mutation resulting in a substitution of arginine for glycine at position 47. The mutation was confirmed using allele-specific olgonucleotide hybridization procedures. This most likely represents a de novo mutation since neither parent carries the mutant allele.

Adult↗