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T Kitazawa

Publications and source records attributed to T Kitazawa.

At least 73 records · Page 4Linked to original sources
PubMed1994

Stimulating action of KW-5139 (Leu13-motilin) on gastrointestinal motility in the rabbit.

1. The gastrointestinal motor stimulating action of the motilin analogue, KW-5139 (Leu13-motilin), was investigated both in the anaesthetized rabbit and in rabbit isolated smooth muscle tissues. 2. KW-5139 (0.3-10 micrograms kg-1, i.v.) produced motor stimulating actions in the gastric antrum, ileum and descending colon, the excitatory responses of which were initiated at the same time but declined with different time courses. The rank order of the excitatory response was: descending colon > or = gastric antrum >> ileum. 3. Atropine (1-3 mg kg-1, i.v.) or naloxone (1 mg kg-1, i.v.) completely suppressed the excitatory response to KW-5139 in the gastric antrum, but only partially attenuated that in the descending colon. This suggests that the mechanism of the excitatory response is different in the gastric antrum and the descending colon, and that cholinergic neural pathway is involved in the response of the gastric antrum. 4. KW-5139 (0.1 nM-1 microM) caused concentration-dependent contractions of the gastric antrum, duodenum, jejunum, ileum and the descending colon in vitro. In the rabbit intestine, the contractile response to KW-5139 was strongest in the duodenum and weakest in the ileum. 5. The contractile response to KW-5139 in the intestinal segments were not affected by tetrodotoxin, but were decreased by verapamil, or pretreatment with a high concentration of porcine motilin, confirming the involvement of motilin receptors in the response to KW-5139. 6. The present results suggest that the rabbit is a suitable species for the investigation of motilin on gut motility, because of the high responsiveness of the descending colon as well as the upper gastrointestinal tract.

Animals↗
PubMed1994

Enhancement by KW-5092, a novel gastroprokinetic agent, of the gastrointestinal motor activity in dogs.

KW-5092 ([1-[2-[[[5-(piperidinomethyl)-2- furanyl]methyl]amino]ethyl]-2-imidazolidinylidene) propanedinitrile fumarate) is a novel gastroprokinetic agent with acetylcholinesterase (AChE) inhibitory activity and acetylcholine (ACh) release facilitatory activity. The present study examined the effects of KW-5092 on gastrointestinal (GI) motor activity in dogs. In anesthetized dogs, KW-5092 at 0.03 to 1 mg/kg, i.v. dose-dependently enhanced the gastric antral and the colonic motor activity. Neostigmine, an AChE inhibitor, enhanced the motor activity at 0.03 and 0.1 mg/kg, i.v. Ranitidine, a histamine H2-receptor antagonist with AChE inhibitory activity and ACh release facilitatory activity, enhanced the motor activity but decreased blood pressure at 1 to 10 mg/kg, i.v. In conscious dogs, KW-5092 at 0.03 to 1 mg/kg, i.v. or 1 to 10 mg/kg, p.o. dose-dependently enhanced the gastric antral, duodenal, ileal and the colonic motor activities. Neostigmine at 0.1 mg/kg, i.v. or 3 mg/kg, p.o. enhanced the duodenal, ileal and colonic motor activities, but induced excitement, slavering, vomiting and diarrhea. Ranitidine at 3 mg/kg, i.v. enhanced the gastric antral and colonic motor activities, but induced collapse or akinesia. The present results suggest that KW-5092 enhances the GI motor activity in a wide range from the gastric antrum to the colon and does not induce behavioral and cardiovascular side effects. KW-5092 may be a useful drug for the treatment of GI motility dysfunctions.

Acetylcholine↗
PubMed1994

Protective effect of cisapride against indomethacin-induced obstruction of the gastric mucosal hemodynamics in rats.

We investigated the effect of cisapride, a gastroprokinetic agent, on the obstructed gastric mucosal hemodynamics induced by indomethacin using an organ reflectance spectrophotometry system in rats. Indomethacin (10 mg/kg, i.v.) reduced both the gastric mucosal blood volume and the gastric mucosal blood oxygenation. Pretreatment with cisapride (0.1 mg/kg, i.v.) prevented these deteriorations. The presently-clarified gastric mucosal protective effect of cisapride may contribute to its therapeutic efficacy.

Animals↗
PubMed1993

Synthesis of 2-imidazolidinylidenepropanedinitrile derivatives as stimulators of gastrointestinal motility.

Ranitidine (1), the histamine H2-receptor antagonist, has been previously reported to increase gastric emptying and gastric motility by inhibition of acetylcholinesterase (AChE) and enhancement of acetylcholine (ACh) release. In order to obtain potent gastroprokinetic agents, a new series of ranitidine derivatives (5-32) possessing a nitrogen atom instead of a sulfur atom (B) was synthesized and their AChE inhibitory activity and potentiating action on electrically evoked contractions of guinea pig ileum were evaluated. Modification of substituents R1 and R2 markedly influenced the activities. In particular, compound 19, (1-[2-[[[5-(piperidinomethyl)-2-furanyl]methyl]amino]-ethyl]-2- imidazolidinylidene)propanedinitrile fumarate, showed 20 and 100 times more potent AChE inhibitory activity and potentiating action on the ileal contraction, respectively, than ranitidine. Furthermore, compound 19 (KW-5092) enhanced gastrointestinal motility in anesthetized rabbits along with a negligible histamine H2-receptor blocking activity.

Animals↗
PubMed1993

The Leu13-motilin (KW-5139)-evoked release of acetylcholine from enteric neurones in the rabbit duodenum.

1. Involvement of cholinergic mechanisms in the contractile response to Leu13-motilin (LMT, KW-5139) was investigated in rabbit duodenal segments, and longitudinal muscle-myenteric plexus (LM-MP) preparations preincubated wtih [3H]-choline. 2. Contractile response to LMT (0.1 nM-1 microM) consisted of an initial rapid (phasic) contraction and a tonic contraction slowly fading to a sustained plateau. LMT caused a concentration-dependent phasic contraction of rabbit isolated duodenal segments. The EC50 value was 2.5 nM and the maximum amplitude of the contraction was 103% of the response induced by acetylcholine (ACh, 100 microM). Neither tetrodotoxin nor atropine changed the EC50 value or the maximum amplitude of the response to LMT. 3. Both atropine and tetrodotoxin decreased the amplitude and accelerated fading of the tonic contraction produced by LMT. 4. LMT (30 nM-3 microM) induced an increase of 3H-outflow, in a concentration-dependent manner. The LMT-induced increase of 3H-outflow was prevented by removal of external Ca2+ or by the presence of tetrodotoxin. 5. Porcine motilin (10 nM-1 microM) also stimulated the release of 3H at a similar concentration-range to that seen with LMT. 6. Pretreatment with LMT (3 microM for 20 min) decreased LMT- and the porcine motilin-evoked release of 3H but did not alter the high K(+)-evoked release. 7. Our results suggest that LMT and porcine motilin stimulate the release of ACh from enteric neurones through the same receptor, and that the release of ACh plays a role in tonic components of contraction in the rabbit duodenum.

Acetylcholine↗
PubMed1993

Nucleotide sequence of the glycoprotein C (gC) homologous gene of Marek's disease virus (MDV) serotype 2 and comparison of gC homologous genes among three serotypes of MDV.

The sequence analysis of the genomic region of Marek's disease virus (MDV) serotype 2 (MDV2) which had homology with the gene encoding MDV serotype 1 (MDV1) homologue of glycoprotein C (gC) of herpes simplex virus revealed that there was a single open reading frame (ORF) capable of encoding 479 amino acids. The predicted protein from this ORF had strong hydrophobic regions in both the amino and carboxyl termini and several potential N-linked glycosylation sites, as seen in those from the ORFs of MDV1 and MDV serotype 3 (MDV3 = herpesvirus of turkeys (HVT)) gC homologues. By northern-blot analysis using a DNA fragment located in the MDV2 gC homologue ORF as a probe, 3.6 and 1.9 kb RNA transcripts were identified in MDV2-infected cells. When the alignment of amino acid sequences of the gC homologous genes of three MDV serotypes were compared, the homology between MDV1 and MDV2 and that between MDV1 and HVT showed about 76% identity, whereas that between MDV2 and HVT was about 70% identity. These results suggested a possibility that the evolutionary distance between MDV1 and MDV2 and between MDV1 and HVT is shorter than that between MDV2 and HVT.

Amino Acid Sequence↗
PubMed1992

Kinetics of Ca2+ release and contraction induced by photolysis of caged D-myo-inositol 1,4,5-trisphosphate in smooth muscle. The effects of heparin, procaine, and adenine nucleotides.

The kinetics of Ca2+ release and contraction induced by photolytic release of inositol 1,4,5-trisphosphate (InsP3) were determined in permeabilized smooth muscle. The rate of Ca2+ release was half-maximal at 1 microM InsP3. The concentration-dependent delay of Ca2+ release at saturating InsP3 concentration was approximately 10 ms and within the uncertainty of the measurements. The relationship between the delay and InsP3 concentration showed no evidence of a high level (n = 4 or higher) of cooperativity but could not distinguish between no cooperativity (n = 1) or a low level (n = 2) of cooperativity. Submaximal [InsP3] caused only partial Ca2+ release from the InsP3-sensitive stores. InsP3-induced Ca2+ release was markedly potentiated by ATP or by adenosine 5'-(beta,gamma-methylene-triphosphate), but neither the rate nor the amplitude of release was significantly affected by procaine (2-5 mM). Heparin increased the delay between photolysis and Ca2+ release, indicating that the off rate of inert ligand(s) bound to InsP3 receptors may contribute to the physiological delay in Ca2+ release. There was a much longer (370 ms +/- 45 S.E.) delay between the rise of Ca2+ and force development, presumably reflecting events preceding and associated with myosin light chain phosphorylation.

Adenine Nucleotides↗
PubMed1992

Myosin light chain phosphatase activities and the effects of phosphatase inhibitors in tonic and phasic smooth muscle.

Phosphatase inhibitors microcystin-LR, tautomycin, and okadaic acid caused contraction and increased 20-kDa myosin light chain (MLC20) phosphorylation in Ca(2+)-free solutions in both phasic and tonic smooth muscle permeabilized with beta-escin, and inhibited the heavy meromyosin (HMM) phosphatase activity of smooth muscle homogenates with the same potency sequence: microcystin-LR greater than tautomycin greater than okadaic acid. The sensitivity to all three inhibitors was significantly higher, the half-times of relaxation and dephosphorylation were 4-6 times longer, and the HMM phosphatase and MLC20 kinase activity/smooth muscle cell wet weight was 2.0- and 1.9-fold lower in the tonic, femoral artery, than in the phasic, ileum or portal vein, smooth muscle. Preincubation with 0.2 microM inhibitor-2 decreased the HMM phosphatase activity by 35% in the ileum and by 60% in the femoral artery. The results suggest that the HMM phosphatases of smooth muscle have properties common to type 1 protein phosphatases, but are inhibited only partially by high concentrations of inhibitor-2, and that the lower HMM phosphatase activity of tonic smooth muscle may contribute to its greater sensitivity to phosphatase inhibitors and its slower rate of relaxation.

Animals↗
PubMed1992

The restriction endonuclease map of Marek's disease virus (MDV) serotype 2 and collinear relationship among three serotypes of MDV.

A BamHI, EcoRI, and XhoI restriction endonuclease map of Marek's disease virus (MDV) serotype 2 (MDV2) DNA was constructed by double-digest analyses of 28 cloned BamHI and 11 cloned EcoRI fragments of MDV2 DNA, followed by hybridization tests of these cloned BamHI DNA fragments with electrophoretically separated digests of MDV2-infected cell DNA. On this map, MDV2 genome consisted of two segments which have unique regions inserted between two inverted repeat regions as observed in MDV serotype 1 and 3 genomes. Further, the DNA homology among three serotypes of MDV was examined by hybridization under less stringent conditions using cloned BamHI fragments of MDV2 DNA. Most of the MDV2 fragments located within the unique regions hybridized with MDV serotype 1 and 3 DNAs, indicating the presence of the collinear relationship among three serotypes. In addition, MDV2 DNA fragments which hybridized with the DNA fragments encoding MDV1 gp57-65 (or A antigen) or MDV1 gp100, gp60, gp49 (or B antigen) were identified and these fragments of serotypes 1 and 2 found to be collinear.

Animals↗
PubMed1992

Mechanism of inhibitory effects of azelastine on smooth muscle contraction.

The mechanism of inhibitory effects of azelastine, an antiallergic and antiasthmatic agent, on depolarization- and alpha-1 adrenergic agonist-induced contractions of intact smooth muscle was studied. The effects of azelastine on membrane currents were determined in isolated guinea pig ileum smooth muscle cells with the whole-cell clamp technique; the effects on contraction were evaluated in receptor- and G-protein-coupled, alpha-toxin-permeabilized rabbit femoral artery and portal vein smooth muscle strips. Azelastine (1-20 microM), like dihydropyridines, inhibited spontaneous rhythmic and high K(+)-induced contractions, mainly through inhibition of the voltage-dependent (L-type) Ca++ current. The tonic component of high K+ contractions was inhibited more than the phasic component, correlating to voltage-dependent inhibition of Ca++ current by the drug. Azelastine (IC50 of 0.25 microM), a known histamine blocker, also reversibly inhibited alpha-1 agonist-induced contractions in the presence and absence of extracellular Ca++. Both major pathways of pharmacomechanical coupling, agonist-induced Ca++ release from the sarcoplasmic reticulum and Ca++ sensitization of the regulatory/contractile apparatus were blocked by the same concentration of drug in permeabilized as in intact muscle. Inositol 1,4,5-trisphosphate-induced Ca++ release and guanosine 5'-O-(tau-thiotriphosphate)-induced Ca++ sensitization, however, were not inhibited. Azelastine at high (greater than 10 microM) concentrations reversibly inhibited Ca(++)-activated contraction, more potently at lower Ca++ concentration and in phasic smooth muscle, but inhibited neither adenosine 5'-O-(tau-thiotriphosphate)-induced, Ca(++)-independent nor phorbol ester-induced contractions. These results indicate that azelastine is a genuine Ca++ antagonist that inhibits voltage-gated Ca++ inward current and agonist-induced Ca++ release and Ca++ sensitization.

Animals↗
PubMed1992

Tissue-specific expression of two isoforms of chicken fibroblast growth factor receptor, bek and Cek3.

Chicken bek and Cek3 are isoforms of the fibroblast growth factor receptor which consist of primary structures that are identical except for a variation within the last of three immunoglobulin-like repeats in the ligand-binding domain. Northern blot analysis using isoform-specific probes revealed that the bek mRNA is expressed exclusively in lung, whereas the Cek3 mRNA is expressed prominently in brain and weakly in lung. We further localized these transcripts in brain and lung by in situ hybridization histochemistry. In lung, the expression of the bek and Cek3 transcripts was distinguished in the smooth muscle of the parabronchus and in the arterial adventitia. On the other hand, in brain, the Cek3 transcript was detected in three areas: the corpus medullare of the metencephalon (cerebellum), the archiastriatum of the telencephalon, and the ependymal cells of the ventriculare of the mesencephalon. Two putative exons corresponding to isoform-specific sequences, respectively, were found to be closely located on the chicken genome. These results indicate that bek/Cek3 isoforms are derived from the same premessenger and that their expression is regulated in a tissue- or even area-specific manner. Moreover, another potential isoform produced by a new splice site within the Cek3-specific exon has been isolated.

Animals↗
PubMed1991

G protein-mediated inhibition of myosin light-chain phosphatase in vascular smooth muscle.

The mechanism of G protein-mediated sensitization of the contractile apparatus of smooth muscle to Ca2+ was studied in receptor-coupled alpha-toxin-permeabilized rabbit portal vein smooth muscle. To test the hypothesis that Ca2+ sensitization is due to inhibition of myosin light-chain (MLC) phosphatase activity, we measured the effect of guanosine 5'-[gamma-thio]triphosphate and phenylephrine on the rate of MLC dephosphorylation in muscles preactivated with Ca2+ and incubated in Ca(2+)- and ATP-free solution containing 1-(5-chloronaphthalene-1-sulfonyl)-1H-hexahydro-1,4-diazepine (ML-9) to block MLC kinase activity. Guanosine 5'-[gamma-thio]triphosphate alone (300 microM) or in combination (3 microM) with phenylephrine decreased the rates of relaxation and dephosphorylation of MLC to about half of control values; this inhibition is sufficient to account for maximal G protein-mediated Ca2+ sensitization of MLC phosphorylation. The rate of thiophosphorylation of MLC with adenosine 5'-[gamma-thio]-triphosphate was not affected by guanosine 5'-[gamma-thio]triphosphate. We suggest that inhibition of protein phosphatase(s) by G protein(s) may have important regulatory functions.

Adenosine Triphosphate↗
PubMed1991

G-protein-mediated Ca2+ sensitization of smooth muscle contraction through myosin light chain phosphorylation.

The Ca2+ sensitivities of tonic (pulmonary and femoral artery) and phasic (portal vein and ileum) smooth muscles and the effects of guanosine 5'-O-(gamma-thiotriphosphate) (GTP gamma S) and norepinephrine on Ca2+ sensitivity of force development and myosin light chain (MLC20) phosphorylation were determined in permeabilized preparations that retained coupled receptors and endogenous calmodulin. The Ca2+ sensitivity of force was higher (approximately 3-fold) in the tonic than in the phasic smooth muscles. The nucleotide specificity of Ca2+ sensitization was: GTP gamma S much greater than GTP greater than ITP much greater than CTP = UTP. Baseline phosphorylation (7% at pCa greater than 8) and maximal phosphorylation (58% at pCa 5.0) were both lower in portal vein than in femoral artery (20 and 97%). Norepinephrine and GTP gamma S increased phosphorylation at constant [Ca2+] (pCa 7.0-6.5). MLC20 phosphorylation induced by norepinephrine was completely inhibited by guanosine 5'-O-(beta-thiodiphosphate) (GDP beta S). In portal vein at pCa 5, GTP gamma S increased phosphorylation from 58%, the maximal Ca2(+)-activated value, to 75%, and at pCa greater than 8, from 7 to 13%. In femoral artery at pCa 5, neither phosphorylation (97%) nor force was affected by GTP gamma S, while at pCa greater than 8, GTP gamma S caused an increase in force (16% of maximum) with a borderline increase in MLC20 phosphorylation (from 20 to 27%). MLC20 phosphorylation (up to 100%) was positively correlated with force. The major results support the hypothesis that the G-protein coupled Ca2(+)-sensitizing effect of agonists on force development is secondary to increased MLC20 phosphorylation.

Adrenergic alpha-Agonists↗
PubMed1991

Excitatory responses to scyliorhinins I and II in smooth muscle strips isolated from the carp intestinal bulb (Cyprinus carpio).

1. The effects of scyliorhinins I (SCY I) and II (SCY II) on longitudinal (LM) and circular muscle (CM) strips isolated from the carp intestinal bulb were investigated in vitro and compared with that of substance P (SP). 2. SP (0.3 nM-1 microM), SCY I (0.3-300 nM) and SCY II (0.3 nM-1 microM) caused transient concentration-dependent contractions of LM strips. The EC50 values for SP, SCY I and SCY II were 16 nM, 15 nM and 39 nM, respectively. Tetrodotoxin and atropine partly decreased the contractile responses to SP, neurokinin A and neurokinin B, but did not change those to SCY I and SCY II. Spantide, methysergide, pyrilamine and naloxone did not decrease the contractile responses to SP, SCY I and SCY II. SP-induced desensitization selectively decreased the responsiveness of LM strips to SCY I and SCY II, and in addition, SCY I- or SCY II-induced desensitization decreased that to SP, SCY I and SCY II. 3. SP, SCY I and SCY II (1 nM-1 microM) caused concentration-dependent contraction of CM strips. The time course of the contractile response of CM strips was different from that of LM strips. Neither tetrodotoxin, atropine, methysergide nor spantide decreased the contractile responses to these tachykinins. 4. These results indicate that SCY I and SCY II act directly on tachykinin receptors located on smooth muscle cells and thus cause the excitatory response in the carp intestinal bulb.

Amino Acid Sequence↗
PubMed1991

Isolation of chicken-bek and a related gene; identification of structural variation in the ligand-binding domains of the FGF-receptor family.

cDNA clones carrying the chicken-bek gene and a related gene were isolated. Deducing the amino acid sequence of chicken-bek allowed us to predict that it encodes for a receptor tyrosine kinase related to the fibroblast growth factor (FGF) receptor, and that the chicken-bek gene and Cek3 are closely related. However, a significant structural difference was identified between chicken-bek and Cek3 within the putative extracellular region, in such a manner that the structure of the immunoglobulin-like domain was conserved. A probe specific to the altered structure detected mRNA in the tissues as did a probe common to bek and Cek3, indicating heterogeneity in the FGF-receptor family in a novel manner. Furthermore, another bek-like gene was isolated and the expressions of its mRNA and protein product were analysed in tissues and cultured cells.

Amino Acid Sequence↗