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Biomedical subjects

T Ohnuki

Publications and source records attributed to T Ohnuki.

At least 37 records · Page 2Linked to original sources
PubMed1999

Identification of binding sites of bopindolol and its two metabolites with beta1-adrenoceptors by molecular modeling: comparison with beta2 adrenoceptors.

This study was designed to examine the importance of interaction in the bindings of nonselective beta-blockers to beta1-adrenoceptors (beta1-ARs) as compared with beta2-ARs, using molecular modeling. The beta-blockers used in this study were bopindolol [4-(benzoyloxy-3-t- butylaminopropyl)-2-methylindol hydrogen malomate], its two metabolites [18-502 - hydrolyzed bopindolol or 4-(3-t-butylamino-2-hydroxypropoxy)-2-methyl indole - and 20-785 - 4-(3-t-butylaminopropoxy)-2-carboxyl indole], and propranolol. Molecular modeling was performed on an Indigo2 workstation (Silicon Graphic) using Discover/Insight II (Molecular Simulations) software. Through molecular modeling, possible binding sites for these drugs were suggested to lie between helices 3, 4, 5, and 6 of the beta1-AR. The amine, benzoic acid, indole methyl, t-butyl, phenyl, and indole functional groups of bopindolol possibly interact with Asp138 (transmembrane - TM - 3), Ser190 (TM 4), Ala343 (TM 6), Val137 (TM 3), Pro339 (TM6), Cys336 (TM 4), Leu237 (TM 5), and Pro236 (TM 5) of beta1-AR, respectively, by either hydrogen bonding or hydrophobic interactions. In addition, 18-502, 20-785, and propranolol also interacted with sites at the same positions as those of beta2-ARs. Thus, the results of the present study suggested that although Ala343 and Val137 of beta1-AR among these amino acids were different from those of beta2-AR, the interactions at the same sites between ligands and amino acids of beta1-AR as those of beta2-ARs may occur because these drugs are nonselective.

Adrenergic beta-Antagonists↗
PubMed1999

Sustaining effects of bopindolol on inhibitory chronotropic actions in guinea pig atria.

The dissociating and/or residual inhibitory effects of bopindolol from beta-adrenoceptors (ARs) of atria strips pretreated with this drug and washed out with buffers on isoprenaline-induced chronotropic actions were determined. The effects of this drug were compared with those of its active metabolite 18-502, propranolol, and pindolol. Our results are as follows: (1) Lower concentrations of bopindolol (10(-9) and 10(-8) mol/l) and the active metabolite 18-502 (10(-9) mol/l), propranolol (10(-8) and 10(-6) mol/l) and pindolol (10(-8) mol/l) produced rightward shifts of concentration-response curves of isoprenaline. (2) Higher concentrations of bopindolol (10(-7) mol/l) and 18-502 (10(-8) and 10(-7) mol/l) produced a reduced maximum response by isoprenaline. (3) Bopindolol (10(-9)-10(-7) mol/l), 18-502 (10(-9)-10(-7) mol/l) and propranolol (10(-7) and 10(-6) mol/l) did not recover to control levels at 180 min even after washout with buffers. In conclusion, bopindolol and 18-502 may slowly dissociate and act as noncompetitive beta-antagonists rather than readily reversible beta-AR antagonists. These effects may differ from those of propranolol and pindolol, although propranolol did not recover to control levels after washout with buffer.

Adrenergic beta-Agonists↗
PubMed1999

Tamsulosin: assessment of affinityof (3)H-P razosin binding to two alpha-1- adrenoceptor subtypes in the canine aorta.

This study was performed to assess the affinity of tamsulosin to the alpha(1L)- in addition to alpha(1B)-adrenoceptor (alpha(1)-AR) subtypes coexisting in the canine aorta using the radioligand binding assay. The antagonistic effects of this drug on contraction of the rat aorta were also assessed, and the results were compared with those obtained with prazosin, amosulalol, labetalol, ketanserin, clonidine and propranolol. The pKi value of tamsulosin to the alpha(1L)-subtype was lower than those of prazosin and HV-723, but higher than those of amosulalol, ketanserin and labetalol. The pKi value of tamsulosin for the alpha(1B)-subtype in the canine aorta was similar to that of prazosin. However, this drug showed a higher pKi value than amosulalol, HV-723, labetalol and ketanserin. On the other hand, the order of inhibition potencies for contraction of the rat aorta by phenylephrine was as follows: prazosin > tamsulosin > amosulalol > HV-723 > labetalol > ketanserin > clonidine > propranolol. Thus, although the affinity of tamsulosin to the alpha(1B)-AR subtype in the canine aorta was as high as that in the bovine prostate reported in our previous study, the affinity (pKi 7. 87) of this drug to alpha(1L)-AR in the canine aorta was lower than that (pKi 8.99) in the bovine prostate. These observations suggested that the pharmacological potencies of tamsulosin in the aorta and prostate may be different.

Adrenergic alpha-Antagonists↗
PubMed1999

[Modeling study of three-dimensional structure of human beta adrenoceptors and receptor-antagonists interactions].

We deduced the three dimensional structures of transmembrane regions in human beta adrenoceptors by computer simulating using the 2D electron density maps of bacteriorhodopsin and frog rhodopsin as templates. The deduced membrane-spanning helical regions, their arrangements and axes to the membrane plain were different between two models. Typical beta adrenergic antagonist, propranolol, and long-lasting beta antagonist, bopindolol, were docked in these models. The receptor-antagonist interactions were different between both models, in which the 3, 4, 5 and 6th transmembrane domains might participate in the antagonists-binding in both models, however, the amino acid residues in the domains contributing to the binding might be different between models. Propranolol and bopindolol have high affinity to beta 1 and beta 2 subtypes, but low affinity to beta 3 subtype. The simulated receptor-antagonist relationships could account, in part, for the selectivity of the antagonists to the beta subtypes.

Adrenergic beta-Antagonists↗
PubMed1999

TMC-86A, B and TMC-96, new proteasome inhibitors from Streptomyces sp. TC 1084 and Saccharothrix sp. TC 1094. I. Taxonomy, fermentation, isolation, and biological activities.

TMC-86A, B and TMC-96, new 20S proteasome inhibitors with an epoxy-beta-aminoketone moiety, were isolated from the fermentation broth of Streptomyces sp. TC 1084 and Saccharothrix sp. TC 1094, respectively. TMC-86A, B and TMC-96 inhibited the chymotrypsin-like and peptidylglutamyl-peptide hydrolyzing activities of 20S proteasome with the following IC50 values: TMC-86A, 5.1 microM and 3.7microM; TMC-86B, 1.1 microM and 31 microM; TMC-96, 2.9 microM and 3.5 microM, respectively. TMC-86A, B and TMC-96 exhibited the weak inhibitory activity against the trypsin-like activity of 20S proteasome with IC50 values of 51 microM, 250 microM, and 36 microM, respectively. They did not inhibit m-calpain, cathepsin L, and trypsin at 100 microM, suggesting their high specificity for proteasome. Taxonomy of the producing strains is also described.

Actinomycetales↗
PubMed1999

TMC-66, a new endothelin converting enzyme inhibitor produced by Streptomyces sp. A5008.

A new endothelin converting enzyme (ECE) inhibitor, TMC-66 was isolated from the fermentation broth of Streptomyces sp. A5008. The structure of TMC-66 was elucidated by spectroscopic analyses to be a new member of benzo[a]naphthacenequinone class of antibiotics. TMC-66 had a highly selective inhibitory activity for ECE with an IC50 value of 2.9 microM. Taxonomy of the producing strain is also described.

Animals↗
PubMed1999

[The use of the Wallstent prosthesis in the treatment of superior vena cava syndrome].

Five patients (4 men and one woman) aged 48-82 years who were suffering from superior vena cava (SVC) syndrome had Wallstent implanted percutaneously to relieve the obstruction. After stent placement, all cases received anticoagulant therapy with heparin. However one transient stent thrombosis occurred, stent placement resulted in complete relief of all patients. Wallstent placement could be an extremely useful treatment for SVC syndrome and should be the treatment of choice in all cases where SVC obstruction occurs or recurs, following chemotherapy or radiotherapy.

Aged↗
PubMed1999

[Relationship between p 53 gene mutation and MDR 1 gene expression in surgically resected non-small cell lung cancer].

The resistance of tumor cells to chemotherapeutic drugs is a major obstacle to successful cancer chemotherapy. Expression of the MDR 1 gene, which encodes for a transmembrane efflux pump (P-glycoprotein), leads to decreased intracellular accumulation and resistance to a variety of anticancer drugs. Recently, one mutant p 53 form was shown to stimulate the MDR 1 gene promoter in vitro, whereas wild-type p 53 repressed this activity. We examined the relationship between p 53 gene mutation and MDR 1 gene expression in specimens from non-small cell lung cancer patients. Tumor samples were obtained from 21 patients during surgery. Mutations of exon 5 through exon 8 of the p 53 gene were detected by the polymerase chain reaction single strand conformation polymorphism method. MDR 1 expression was semi-quantified by the reverse transcriptase polymerase chain reaction method. We identified p 53 gene mutation in samples from 7 patients. MDR 1 gene expression was observed in samples from 20 patients. The expressivity of the MDR 1 gene tended to be higher in patients with adenocarcinoma. No significant relationship between p 53 mutation and MDR 1 expressivity was observed in our study.

Adenocarcinoma↗
PubMed1998

A potent dipeptide inhibitor of dipeptidyl peptidase IV.

A series of novel potent inhibitors of dipeptidyl peptidase IV (DPP-IV) has been developed. A brief structure-activity relationship of the inhibitors was investigated. The dipeptide TSL-225, tryptophyl-1,2,3,4-tetrahydroisoquinoline-3-carboxylic acid, was identified with the critical structure for the inhibitory activity.

Dipeptidyl Peptidase 4↗
PubMed1998

Identification of DNA gyrase inhibitor (GyrI) in Escherichia coli.

DNA gyrase is an essential enzyme in DNA replication in Escherichia coli. It mediates the introduction of negative supercoils near oriC, removal of positive supercoils ahead of the growing DNA fork, and separation of the two daughter duplexes. In the course of purifying DNA gyrase from E. coli KL16, we found an 18-kDa protein that inhibited the supercoiling activity of DNA gyrase, and we coined it DNA gyrase inhibitory protein (GyrI). Its NH2-terminal amino acid sequence of 16 residues was determined to be identical to that of a putative gene product (a polypeptide of 157 amino acids) encoded by yeeB (EMBL accession no. U00009) and sbmC (Baquero, M. R., Bouzon, M., Varea, J., and Moreno, F. (1995) Mol. Microbiol. 18, 301-311) of E. coli. Assuming the identity of the gene (gyrI) encoding GyrI with the previously reported genes yeeB and sbmC, we cloned the gene after amplification by polymerase chain reaction and purified the 18-kDa protein from an E. coli strain overexpressing it. The purified 18-kDa protein was confirmed to inhibit the supercoiling activity of DNA gyrase in vitro. In vivo, both overexpression and antisense expression of the gyrI gene induced filamentous growth of cells and suppressed cell proliferation. GyrI protein is the first identified chromosomally nucleoid-encoded regulatory factor of DNA gyrase in E. coli.

Amino Acid Sequence↗
PubMed1998

Does potassium ion concentration affect lung preservation?

To evaluate the influence of potassium ion concentration in an organ preservation solution on lung preservation, four types of solutions were produced. These preservation solutions consisted of sodium and potassium ions on the cation and phosphate ions on the anion with glucose. Contents of solutions were: (1) 155 mmol/l Na+, 0 mmol/l K+; (2) 150 mmol/l Na+, 5 mmol/l K+; (3) 20 mmol/l Na+, 135 mmol/l K+; and (4) 0 mmol/l Na+, 155 mmol/l K+. All four solutions possessed the same osmolarity, the same pH in the same temperature, and the same buffer action. Lungs were preserved at 7 degrees C in these solutions for 24 h and evaluated in a rat lung perfusion system with perfluorochemical emulsion. Pressure-limited perfusions with pressure-limited ventilation were carried out for 20 min before and after preservation. Thereafter, the recovery ratios of pulmonary arterial flow (Q), tidal volume (VT), oxygen tension of the pulmonary venous effluent (PPVO2), and wet-to-dry ratios were compared. The recovery ratios of Q were better in low, but not zero, potassium solutions, whereas wet-to-dry ratios were kept lower in high potassium solutions. No difference in pulmonary compliance or gas exchange was observed against a great change in potassium ion concentration. Therefore, the potassium ion concentration did not play a major role in lung preservation.

Animals↗
PubMed1998

Studies on relationships between chemical structure and beta-blocking potency of bopindolol and its two metabolites.

The structure-activity relationships of bopindolol and its two metabolites (18-502 and 20-785) and their beta-blocking potencies in the human beta2-adrenoceptor (AR) were assessed using molecular modeling on an INDIGO2 workstation (SGI Co., Ltd.) and DISCOVER/INSIGHT II (Biosym Co., Ltd.). Through modeling, possible binding sites for these agents were hypothesized to involve the 3rd, 4th, 5th and 6th helices of the beta2-AR, and these shared a common interaction site at Asp113 in helix 3. The different chemical structure of these three agents, however, showed binding to different binding sites (amino acids). This study therefore suggests that different beta-blocking potencies of these agents may be due to different chemical structure.

Adrenergic beta-Antagonists↗
PubMed1998

Anti-arthritic effects of the novel dipeptidyl peptidase IV inhibitors TMC-2A and TSL-225.

We evaluated the immunopharmacological effects of two novel dipeptidyl peptidase IV (DP IV) inhibitors, TMC-2A [(2S,2S',2S'')-2-[2'-[2''-amino-3''-(-indol-3'''-yl)-1''-oxopropyl]-1',2 ',3',4'-tetrahydro-6',8'-dihydroxy-7'-methoxyisoquinol-3-yl-car bonylamino]-4-hydroxymethyl-5-hydroxypentanoic acid] and TSL-225 (tryptophyl-1,2,3,4-tetrahydroisoquinoline-3-carboxylic acid). TMC-2A, produced by Aspergillus sp. A374, inhibited rat kidney DP IV uncompetitively, with a Ki value of 5.3 microM. In vivo, TMC-2A suppressed alkyldiamine (N,N-dioctadecyl-N',N-bis(2-hydroxyethyl)propanediamine)-induced arthritis. We developed a chemically modified inhibitor, TSL-225, with potency similar to that of TMC-2A. TSL-225 inhibited DP IV uncompetitively, with a Ki value of 3.6 microM. TSL-225 was also effective against adjuvant-induced arthritis. These results suggest that TMC-2A and its derivatives may have therapeutic potential for the treatment of inflammatory diseases such as rheumatoid arthritis.

Adjuvants, Immunologic↗
PubMed1998

Tamsulosin: assessment of affinity of 3H-prazosin bindings to two alpha1-adrenoceptor subtypes (alpha1H and alpha1L) in bovine prostate and rat heart and brain.

1. The present study was designed to assess the displacement potencies of tamsulosin to 3H-prazosin bindings in two alpha1-adrenoceptor (AR) subtypes (alpha1H and alpha1L) in bovine prostate, rat heart and brain compared with those of amosulalol, labetalol, ketanserin, clonidine and propranolol. 2. The pKi values of tamsulosin to alpha1H and alpha1L subtypes in bovine prostate were 9.13 and 8.99 and these values were almost the same as those of prazosin. On the other hand, low pKi binding values of amosulalol, labetalol, ketanserin, clonidine and propranolol to these subtypes were observed. 3. Low pKi values of tamsulosin to alpha2- and beta-ARs and muscarinic and 5HT2 receptors in the rat brain were observed. 4. These results suggest that tamsulosin has high affinities to alpha1L-AR subtypes in bovine prostate and rat hearts as well as alpha1H-AR subtypes, implying an inhibitory effect of this drug on the contraction of the prostate.

Adrenergic alpha-Antagonists↗
PubMed1998

Discrimination of alpha1-adrenoceptor subtypes in rat aorta and prostate.

This study was designed to further discriminate alpha1-adrenoceptor subtypes in rat aorta and prostate using functional experiments. Responses induced by phenylephrine were equilibrated in both tissues. The pA2 values and slope factors of several alpha1-antagonists were assessed using concentration-response curves. The antagonists used were prazosin, WB-4101, 5-methylurapidil (5-MU), HV-723, and tamsulosin. In addition, the effects of chloroethylclonidine (CEC) and nifedipine on phenylephrine-induced contractions were investigated. A high pA2 value for prazosin was observed in both tissues (aorta 9.84, prostate 9.19) and the ranking of each drug's pA2 value is as follows: tamsulosin > prazosin > WB-4101 > HV-723 > 5-MU in the aorta, and tamsulosin > prazosin > 5-MU > WB-4101 = HV-723 in the prostate. A significant difference between the pA2 value of each drug except for tamsulosin in the aorta and in prostate was observed (p < 0.01). Inhibition of contraction by pretreatment with CEC was 83.9 +/- 2.42% in the aorta, and 6.17 +/- 0.94% in the prostate. On the other hand, inhibition of maximal response by pretreatment with nifedipine (1 micromol/l) was 35.1 +/- 2.2% in the aorta and 24.5 +/- 3.1% in the prostate. A good correlation between these pA2 values and pKi values for recombinant human alpha1b-adrenoceptor expressed in CHO cells (aorta) and alpha1a-subtypes of CEC pretreated rat hippocampus (prostate) were observed. In conclusion, these results suggest that: (1) the contraction of these two tissues is mediated by alpha1H-adrenoceptor with a high affinity for prazosin; (2) alpha1H-adrenoceptors correspond to alpha1b-(aorta) and alpha1a-subtypes (prostate), and (3) each alpha1-adrenoceptor subtype in the aorta and prostate may be alpha1b-(aorta) and alpha1a-subtypes (prostate), respectively.

Acetonitriles↗
PubMed1998

Bopindolol: a slowly dissociating antagonist from the beta-adrenoceptors in guinea pig atria.

The dissociating and/or residual inhibitory effects of bopindolol from beta-adrenoceptors of atria strips pretreated with this drug which was then washed out with buffers on the responses to isoprenaline were determined and compared with those of propranolol, pindolol, atenolol, and the two active metabolites of bopindolol: 18-502 and 20-785. Low concentrations of bopindolol (10(-9) to 10(-8) mol/l) and the active metabolite 18-502 (10(-9) mol/l) produced rightward shifts of the concentration-response curves. On the other hand, high concentrations of bopindolol (10(-7) mol/l) and metabolite 18-502 (10(-8) and 10(-7) mol/l) produced a reduced maximum response by isoprenaline, suggesting that these nonparallel rightward shifts have pD2 values of 7.57 (bopindolol) and 7.67 (18-502), respectively, at 0 min after washout with buffers. Pindolol (10(-7) mol/l) and propranolol (10(-7) and 10(-8) mol/l) also produced a rightward shift of isoprenaline response curves, and these concentration-response curves in guinea pig atria strips pretreated with pindolol (10(-7) mol/l) and propranolol (10(-6) mol/l) recovered to control levels. Neither of these drugs, however, reduced the maximum response by isoprenaline. A high concentration (10(-5) mol/l) of atenolol was required for a rightward shift of the isoprenaline concentration-response curve, and this drug also did not reduce the maximum response. Thus, we conclude that bopindolol and metabolite 18-502 slowly dissociate and act as noncompetitive beta-antagonists rather than easily reversible beta-adrenoceptor antagonists.

Adrenergic beta-Agonists↗
PubMed1998

TMC-49A, a novel transcriptional up-regulator of low density lipoprotein receptor, produced by Streptomyces sp. AS1345.

Microbial metabolites were screened for a transcriptional up-regulator of low density lipoprotein (LDL) receptor by a reporter assay. TMC-49A was discovered as an up-regulator obtained from the fermentation broth of Streptomyces sp. AS1345. The structure of TMC-49A was elucidated to be butyl N-phenethylcarbamate by spectroscopic analyses. This compound enhanced the synthesis of LDL receptor in human hepatoma HepG2 cells as assessed by a receptor binding assay. Taxonomy of the producing strain is also described.

Carbamates↗