Biomedical subjects

T Imai

Publications and source records attributed to T Imai.

At least 613 records · Page 34Linked to original sources

PubMed1993

Identification and characterization of a cDNA, which is highly homologous to the ribonucleoprotein gene, from a locus (D10S102) closely linked to MEN2 (multiple endocrine neoplasia type 2).

We previously reported a nearly 1-Mb contig of cosmid and YAC clones at D10S102, a locus that is tightly linked to the gene responsible for multiple endocrine neoplasia type 2 (MEN2A). Subclones of 159 genomic EcoRI fragments in the contig were tested on "zoo blot" to detect DNA sequences conserved in various species. Nine fragments found to contain conserved sequences were used as probes for screening cDNA libraries. One of these probes, y300-pL50, recognized a cDNA from a human fetal brain library. The cDNA encoded a protein consisting of 270 amino acids, whose predicted sequence has a high degree of homology to heterogeneous nuclear ribonuclear protein. This expressed sequence may be a candidate for the gene responsible for MEN2A.

Amino Acid Sequence↗

PubMed1993

In vitro translation of mRNA from rat peritoneal and intestinal mucosal mast cells.

We isolated RNA from in vivo-derived rat peritoneal (PMC) and intestinal mucosal mast cells (IMMC) and assessed the in vitro translation products of these two mast cell types using rabbit reticulocyte lysate and wheat germ systems. The translated polypeptides were analyzed by one- and two-dimensional gel electrophoresis. Fluorographic analyses established that polypeptides with a spectrum of molecular size and pI were produced by both PMC and IMMC. Immunoprecipitation studies with anti-rat mast cell protease (RMCP) I antibodies detected a band at 31 kD from products of PMC RNA assessed by one-dimensional electrophoresis, whereas anti-RMCP II antibodies precipitated a band of 27 kD from products of IMMC RNA. This is the first report of translation products of IMMC and of the translated precursors of RMCP I and RMCP II.

Animals↗

PubMed1993

Heparin has an inhibitory effect on endothelin-1 synthesis and release by endothelial cells.

We studied the inhibitory effects of heparin on basal and agonist-induced endothelin-1 biosynthesis and release from cultured bovine endothelial cells. Heparin dose-dependently and similarly inhibited endothelin-1 release, inositol trisphosphate production, and intracellular free Ca2+ levels stimulated by thrombin. Hirudin fragment had an inhibitory effect on thrombin-induced endothelin-1 release, whereas anti-thrombomodulin antibody had no effect. Heparin completely blocked phorbol ester-induced endothelin-1 release, whereas it had a partial inhibitory effect on endothelin-1 release stimulated by angiotensin and vasopressin. Northern blot analysis using complementary DNA for bovine preproendothelin-1 as a probe revealed that heparin reduced not only the basal but also the stimulated expression of preproendothelin-1 messenger RNA by thrombin and phorbol ester. These data suggest that heparin, in addition to its antithrombin effect, has an inhibitory effect on the biosynthesis and release of endothelin-1, possibly by inhibiting protein kinase C-dependent pathway.

Animals↗

PubMed1993

Induction of nitric oxide synthase gene by interleukin in vascular smooth muscle cells.

To elucidate whether cytokines induce nitric oxide synthase in vascular smooth muscle cells, we studied the effects of human recombinant interleukin-1 beta on the synthesis and release of nitric oxide in cultured rat vascular smooth muscle cells by measurement of NO2-/NO3- levels. Furthermore, we performed Northern blot analysis using subcloned polymerase chain reaction products as probes for constitutive and inducible nitric oxide synthase. Interleukin-1 beta dose dependently (1 to 20 ng/mL) stimulated NO2-/NO3- production as a function of time. Northern blotting demonstrated the interleukin-1 beta-induced expression of messenger RNA for an inducible but not for the constitutive nitric oxide synthase after 3 hours. NG-Monomethyl L-arginine completely blocked the interleukin-1 beta-induced NO2-/NO3- production, the effect of which was reversed by L-arginine but not by D-arginine. Dexamethasone inhibited the interleukin-1 beta-induced NO2-/NO3- production in a dose-dependent manner (10(-9) to 10(-7) M) and the interleukin-1 beta-inducible nitric oxide synthase messenger RNA levels. Neither a calmodulin inhibitor (W-7) nor a protein kinase C inhibitor (staurosporine) showed any effects on the induction of nitric oxide synthase transcripts or production of NO2-/NO3- stimulated by interleukin-1 beta, whereas cycloheximide and actinomycin D completely inhibited the basal and stimulated NO2-/NO3- production. These data demonstrate for the first time that interleukin-1 beta induces gene expression of inducible nitric oxide synthase and its de novo protein synthesis in rat vascular smooth muscle cells, thereby leading to generation of nitric oxide via Ca2+/calmodulin-independent and protein kinase C-independent mechanisms.

Alkaloids↗

PubMed1993

Endothelin receptor subtype B mediates synthesis of nitric oxide by cultured bovine endothelial cells.

Endothelins (ET) produce endothelium-dependent vasodilation through nitric oxide (NO) synthesis. The present study was designed to elucidate the cellular mechanism by which ET induces synthesis and release of endothelium-derived NO by cultured bovine endothelial cells (EC). Binding studies revealed that bovine EC membrane had the binding sites of a novel agonist (BQ3020) for non-isopeptide-selective receptor subtype (ETB). Affinity labeling studies showed a major labeled band with the apparent molecular mass of 50 kD. Northern blot analysis demonstrated the expression of mRNA for ETB receptor. BQ3020 rapidly and dose dependently induced formation of inositol-1,4,5-triphosphate and increased intracellular Ca2+ concentrations in fura-2-loaded cells. Concomitantly, BQ3020 dose dependently stimulated production of both nitrate/nitrite (NOx) and cyclic GMP; a highly significant correlation existed between NOx and cGMP production. The stimulatory effect on NOx and cGMP production by ETB agonist was inhibited by NO synthase inhibitor monomethyl-L-arginine; this effect was reversed by coaddition of L-arginine, but not D-arginine. NOx and cGMP production stimulated by BQ3020 was inhibited by pretreatment with pertussis toxin. ETB agonist-induced NOx production was blocked by a calmodulin inhibitor and an intracellular Ca2+ chelator, but not by an extracellular Ca2+ chelator or a Ca2+ channel blocker. These data suggest that endothelins stimulate ETB receptor-mediated phosphoinositide breakdown via pertussis toxin-sensitive G-protein(s), which triggers release of intracellular Ca2+, thereby activating Ca2+/calmodulin-dependent NO synthase in EC.

Amino Acid Oxidoreductases↗

PubMed1993

Pituitary carcinoma of pars distalis as a common neoplasm in Fischer-344 rats.

The incidence of invasive spontaneous pituitary carcinomas in Fischer-344 rats were studied. The pituitaries were examined histopathologically together with surrounding tissues including sphenoid bone. The incidence of carcinoma was higher than that previously reported in Fischer-344 rats. All the carcinomas observed in this study showed evidence of local invasion either ventrally into bone and bone marrow or laterally into peripheral nerves and blood vessels. No dorsal infiltration into the brain was recognized. Pituitary carcinoma with local invasion is a relatively common neoplasm when examined histopathologically together with the surrounding tissues.

Adenocarcinoma↗

PubMed1993

Endothelin receptor subtypes are coupled to adenylate cyclase via different guanyl nucleotide-binding proteins in vasculature.

We have studied whether endothelin (ET) isopeptides have any effects on adenylate cyclase activity via different guanyl nucleotide-binding proteins (G-proteins) in cultured rat vascular smooth muscle cells (VSMC) and bovine endothelial cells (EC). Northern blot analysis clearly demonstrated gene expression of ETA receptors in VSMC and ETB receptors in EC. ET-1 dose-dependently (10(-9)-10(-6) M) stimulated cAMP formation in VSMC, whose effect was inhibited completely by ETA receptor antagonist (BQ-123) but not by indomethacin or quinacrine. The ET-1-induced cAMP formation was additive with isoproterenol but not with cholera toxin. In contrast, ET-3 and ETB receptor agonist (BQ-3020) dose-dependently (10(-9)-10(-6) M) inhibited forskolin-stimulated cAMP formation in EC, whose effect was completely abolished by pertussis toxin. Cholera toxin ADP ribosylated 45- and 52-kilodalton proteins in VSMC, whereas pertussis toxin ADP ribosylated the 41-kilodalton protein in EC. These data suggest that, in addition to phospholipase C via Gq, ETA and ETB receptor subtypes are functionally coupled to adenylate cyclase, possibly via Gs in VSMC and Gi in EC, respectively.

Adenylate Cyclase Toxin↗

PubMed1993

Cellular mechanism of natriuretic peptides-induced inhibition of endothelin-1 biosynthesis in rat endothelial cells.

We studied the cellular mechanism by which natriuretic peptides inhibit the synthesis and release of endothelin-1 (ET-1) in cultured rat aortic endothelial cells (EC). Atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) showed dose-dependent and equipotent effects on displacement of [125I]ANP binding and generation of cGMP production in rat EC, whereas C-type natriuretic peptide and biologically inactive ANP analog had lesser effects. ANP and BNP as well as 8-bromo-cGMP had potent inhibitory effects on immunoreactive ET-1 release, the transient increase in the intracellular Ca2+ concentration, and the formation of inositol 1,4,5-trisphosphate stimulated by thrombin in rat EC. A cGMP-dependent protein kinase inhibitor (KT5823), but not a cAMP-dependent protein kinase inhibitor (KT5720), completely abolished the inhibitory effect of ANP on thrombin-induced immunoreactive Et-1 release. Northern blot analysis using cDNA for rat prepro-ET-1 as a probe showed that ANP and 8-bromo-cGMP, but not C-type natriuretic peptide, inhibited thrombin-induced prepro-ET-1 mRNA expression, whose effect was abolished by KT5823. These data suggest that ANP and BNP inhibit the thrombin-induced synthesis and release of ET-1 in cultured rat aortic EC by blocking phosphoinositide breakdown, possibly via natriuretic peptides type A receptor-mediated cGMP-dependent mechanism.

Animals↗

PubMed1993

Controlled-release preparation of indomethacin using calcium alginate gel.

Alginate gel beads containing indomethacin (IMC) were prepared using a gelation of alginate with calcium cation. Though IMC was not released from the beads at pH 1.2 because of its extremely low solubility in aqueous media, it was released according to the swelling of alginate gel at pH 6.8. The release of IMC from the beads decreased with the decreasing ratio of mannuronic acid (M) to guluronic acid (G) in alginate, and with the larger molecular weight of alginate. The maximum concentration and the area under the time curve of plasma concentration of IMC after oral administration of alginate gel beads to beagle dogs were lower than those of IMC powder. The absorption rate of IMC was lower and more prolonged after administration of beads containing IMC than IMC powder alone. The high plasma concentration of IMC was maintained because absorption continued for a longer period when the bead consisting of the alginate with 0.65 M-block/G-block ratio and 66000 molecular weight was administered. The availability of alginate gel beads of IMC was further demonstrated by oral administration to human volunteers. A serum concentration which was comparable to maximum serum concentration was maintained from 2 to 6 h after administration, while an effective serum concentration was maintained even 12 h after administration of the beads. These data suggest that alginate is useful for a controlled-release formulation of IMC.

Administration, Oral↗

PubMed1993

Stereoselective disposition of pranoprofen, a nonsteroidal antiinflammatory drug, in rabbits.

The stereoselective disposition of pranoprofen, a nonsteroidal antiinflammatory drug, was studied in rabbits. Plasma levels of S(+)-pranoprofen after oral and i.v. administration of the racemate pranoprofen were always higher than those of the R(-)-isomer. The elimination rate constant of the R(-)-isomer (2.74 h-1), calculated using a 2-compartment model, was significantly larger than that of the S(+)-isomer (2.14 h-1), while no significant difference was observed in the absorption rate constants between enantiomers. Pranoprofen was excreted in the urine exclusively in the form of pranoprofen glucuronide. The glucuronide of R(-)-isomer was excreted more rapidly than the S(+)-isomer. However, no metabolite of pranoprofen was detected in plasma, owing to its instability in liver and plasma. Moreover, the elimination of the S(+)- and R(-)-isomers of pranoprofen was more rapid when the enantiomers were separately administered than when administered as the racemate. The R(-)-isomer showed a significantly higher elimination rate than the S(+)-isomer, compared to what was observed upon the administration of the racemate. No inversion to an R(-)-form or S(+)-form to their corresponding antipode after administration of the isomers separately was detected. Pranoprofen, especially the R(-)-isomer, was significantly distributed in the kidney. An in vitro metabolism experiment of pranoprofen showed the predominant glucuronidation to be in the kidney rather than in the liver because of rapid hydrolysis of glucuronide in the liver.(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Oral↗

PubMed1993

Preparation and evaluation of a controlled-release formulation of nifedipine using alginate gel beads.

Alginate gel beads containing nifedipine (NP) were prepared using a gelation of alginate with calcium cations. The dissolution and absorption of NP from alginate gel beads were evaluated as a controlled-release formulation of NP. The release of NP from alginate gel beads was affected by the composition of uronic acid in alginate, and by the NP content in alginate gel beads. NP absorption after oral administration to beagle dogs of alginate gel beads prepared by air-drying was significantly lower than that after the administration of NP powder alone, due to the limited release of NP from the alginate gel beads in the gastrointestinal tract. On the other hand, the alginate gel beads prepared by freeze-drying improved the absorption of NP because of the increasing disintegration of alginate gel beads with decreasing structural strength. However, this method had poor reproducibility, compared with air-dried alginate gel beads. The gel beads with added alginate propylene glycol ester (PGA) swelled and released calcium ions rapidly, even in water. This is because PGA gels weakly to the calcium cation. Consequently, it was observed that NP release from the PGA gel beads was highly accelerated compared to the release from alginate gel beads. The higher serum level of NP with large variance was obtained after the oral administration of the PGA gel beads. Gel beads consisting of a 1:1 ratio of PGA to alginate had intermediate characteristics between the alginate and PGA gel beads in respect to NP release and absorption.(ABSTRACT TRUNCATED AT 250 WORDS)

Alginates↗

PubMed1993

Effects of quinotolast, a new orally active antiallergic drug, on experimental allergic models.

The effects of a new antiallergic drug, quinotolast [sodium 5-(4-oxo-1-phenoxy-4H-quinolizine-3-carboxamido)tetrazolate monohydrate], were studied and compared with those of tranilast, amlexanox, pemirolast, repirinast and disodium cromoglycate (DSCG) in experimental allergic models. Quinotolast potently inhibited such type I allergic reactions as passive cutaneous anaphylaxis (PCA) and anaphylactic bronchoconstriction in rats by both intravenous and oral dosing. All of these effects were stronger than those of the reference drugs tested. Quinotolast inhibited histamine release from rat peritoneal cells, but it had no antagonistic effect on histamine-, serotonin-, platelet activating factor- or bradykinin-induced cutaneous reactions in rats. Moreover, it was clearly demonstrated that quinotolast and DSCG had a cross tachyphylaxis to inhibit PCA in rats, suggesting that these drugs, at least in part, share the same mechanism of action. Furthermore, quinotolast potently inhibited PCA in guinea pigs in which DSCG and other reference drugs showed poor inhibitory activity. Quinotolast also showed stronger inhibitory effects on histamine and peptide leukotrienes release from guinea pig lung fragments or mouse cultured mast cells than the other drugs tested. Thus, the effect of quinotolast on type I allergic reaction would seem to be based on an inhibition of mediator release from inflammatory cells including mast cells. The results suggest that quinotolast will be beneficial in the treatment of type I allergy-related diseases.

Administration, Oral↗

PubMed1993

cDNAs encoding for storage proteins in the tubers of taro (Colocasia esculenta Schott).

Two major protein groups of taro (Colocasia esculenta) tuber were purified, and their antisera were used for the screening of the cDNA library constructed from poly(A)+ RNA of taro tuber. A cDNA clone obtained by screening with an anti-12 kD protein antiserum had an insert 1058 bp-long, and an open reading frame for a peptide of 268 amino acids. The analyses of the N-terminal amino acid sequence and in vitro translation product suggested that the protein was synthesized as a peptide with a molecular weight of 27 kD, and then processed into two mature peptides with a molecular weight of 12.5 and 13.9 kD and an extra peptide with a molecular weight of 0.6 kD. The cDNA clones obtained using the anti-25 kD protein antiserum were highly homologous with each other. One of them had an insert 958 bp-long and an open reading frame for a peptide with 209 amino acids. The amino acid sequence deduced from the nucleotide sequence of this clone indicated that the 25 kD proteins were homologous to the trypsin inhibitors of soybean and winged bean as well as sporamins, the storage proteins of sweet potato.

Amino Acid Sequence↗

PubMed1993

Interleukin-1 beta induces nitric oxide production by a mouse pituitary tumour cell line (AtT20/D16).

To elucidate whether anterior pituitary cells express the nitric oxide (NO) synthase gene, we studied the synthesis of NO and the expression of NO synthase (NOS) mRNA by a mouse pituitary tumour cell line (AtT20/D16). Interleukin-1 beta (IL-1 beta) stimulated production of NO2-/NO3-(NOx) in a time-dependent manner and both NOx and cyclic GMP formation were stimulated in a dose-dependent manner by IL-1 beta. IL-1 beta-induced NOx production and intracellular cyclic GMP formation were similarly blocked by an NO synthase inhibitor, NG-monomethyl-L-arginine (LNMMA), whose effect was reversed by L-arginine, but not by D-arginine. Dexamethasone inhibited IL-1 beta-induced NOx production in a dose-dependent manner. A calmodulin inhibitor (W-7) showed no effect on IL-1 beta-induced NOx production, whereas cycloheximide and the actinomycin D completely inhibited NOx production. Northern blot analysis using cDNA for mouse macrophage-inducible NOS as a probe revealed the expression of inducible NOS mRNA in the cells only after exposure to IL-1 beta. Although IL-1 beta stimulated ACTH release from tumour cells, LNMMA failed to affect ACTH release stimulated by IL-1 beta. These results demonstrate for the first time that a pituitary tumour cell line (AtT20/D16) possesses cytokine-inducible and Ca2+/calmodulin-independent NOS, although NO may not be involved in ACTH release.

Amino Acid Oxidoreductases↗

PubMed1993

[An elderly case of supernormal conduction in the posterior division of the left bundle branch].

An electrophysiologic study was performed in a 95-year-old man with bifascicular block (right bundle branch block and left anterior hemiblock). During sinus rhythm (AA interval = 980 ms), every sinus beat was conducted to the ventricle. The AH interval was 130 ms and HV interval was 50 ms. A programmed premature atrial stimulation was performed after 8 paced beats at a slightly shorter cycle length than the sinus cycle length (900 ms). As the atrial coupling interval was shortened, the H1H2 interval also shortened. At an H1H2 interval of 680 ms the premature atrial beat was blocked distal to the recording site of the His potential. The block persisted up to an H1H2 interval of 560 ms. AV conduction resumed paradoxically when the H1H2 interval was further shortened to intervals lasting 540-490 ms. During this period the H2V2 interval was 50 ms. At still shorter H1H2 intervals, H2 was again blocked. The H2V2 intervals during this phase of improved conduction were unchanged compared with those of other conducted beats. Therefore normalization due to the gap phenomenon could be ruled out, and the improved conduction could be explained by a phenomenon of supernormal conduction in the posterior division of left bundle branch.

Aged↗

PubMed1993

[Long-term follow-up study after permanent pacemaker implantation in patients aged 60 years or over with sick sinus syndrome].

Ninety-five patients aged 60 years or over with a permanent pacemaker implanted for sick sinus syndrome were divided into two groups: 32 patients with physiological pacing (group P) and 63 patients with ventricular pacing (group V). The mean follow-up period was 45.0 +/- 36.6 months in group P and 50.3 +/- 37.8 months in group V. Paroxysmal atrial fibrillation (Af) occurred in 28% of group P and 71% of group V (p < 0.05). The incidence of stable Af was also lower in group P than in group V (9% vs. 30%, p < 0.05). None of group P with only bradyarrhythmia had stable Af. However, 6 of 21 patients (29%) in group V with bradyarrhythmia showed stable Af. There was no significant difference in stable Af between group P with bradycardia-tachycardia syndrome (BTS) and group V with BTS (19% vs. 31%). A lower incidence of embolic events was also observed in group P (3% vs. 25%, p < 0.05). Nine of 16 patients with embolic events in group V died of complications following embolism (8 patients; cerebral embolism, one patients: renal and superior mesenteric arterial embolism). The survival rates at 5 and 10 years were 80% and 69%, respectively, for group P and 56% and 33% for group V (p < 0.01). Thus, with regard to permanent pacing for patients with sick sinus syndrome, physiological pacing should be selected for control of morbidity and total mortality.

Aged↗

PubMed1993

[Characteristics of bladder tumors showing positive urinary cytology--respective analysis in differentiated and undifferentiated type].

To study the characters of bladder tumors which showed positive urinary cytologies, the results of urinary cytology of untreated bladder tumor patients in our hospital during 10 years between July 1980 and June 1990 were evaluated according to the degree of tumor differentiation, namely differentiated type which did not contain grade 3, and undifferentiated type which contained grade 3. Concerning the differentiated tumors, positive rate of cytology was 37.3% on the whole. Positive rates of multiple tumors or tumors around internal urethral orifice were significantly high, and those of tumors larger than 3 cm, tumors located on posterior wall, left wall or throughout the entire surface, were higher than the overall positive rates. Repeated examinations of yielded increased rates of positive cytology results. Concerning the undifferentiated tumors, the positive rate of cytology was 90.0% on the whole, was not influenced by tumor sizes or locations, and was consistently observed irrespective of the number of times of cytologic examination.

Aged↗

PubMed1993

[Effect of indomethacin on the release of chemical mediators from human peripheral leukocytes].

We studied the effect of indomethacin (IND) on the release of chemical mediators from human peripheral leukocytes and the relation of prostaglandin (PG) E2 and PGI2 to that effect. We stimulated the leukocyte suspensions with calcium ionophore A23187 (CaI, 10(-6) M) accompanied with IND (10(-5) M), PGE2 (10(-5) M) or PGI2 (10(-5) M) and measured the levels in histamine (HA), leukotriene C4/D4/E4 (peptide-LTs) and LTB4 in the supernatant fluid. The increase of HA levels induced by CaI was significantly enhanced by IND (p < 0.01), and the enhancement was significantly inhibited by PGE2 (p < 0.05) and PGI2 (p < 0.01). The release of peptide-LTs was not enhanced by IND and was inhibited significantly by PGE2 (p < 0.05) and PGI2 (p < 0.01). IND did not affect the release of LTB4 induced by CaI. However, LTB4 release was also significantly inhibited by PGE2 and PGI2 (p < 0.01). These results suggest that the inhibitory effect of IND on the production of PGE2 and PGI2 results in the enhancement of HA release. PGE2 and PGI2 have a potent inhibitory effect on the release of HA, peptide-LTs and LTB4 from human leukocytes.

Adult↗