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Biomedical subjects

M Ihara

Publications and source records attributed to M Ihara.

At least 109 records · Page 6Linked to original sources
PubMed1992

Human big-endothelin-1 and endothelin-1 release prostacyclin via the activation of ET1 receptors in the rat perfused lung.

Although ET1 and ET2 binding sites were found in rat lung membranes, a selective ET1 receptor antagonist, BQ-123 (10 microM), did not displace [125I]-endothelin-1 ([125I]ET-1) from ET2 sites, illustrating the selectivity of the angatonist for ET1 receptors. In rat perfused lungs, BQ-123 (1 microM) markedly reduced the prostacyclin (PGI2) releasing properties of endothelin-1 (ET-1: 5 nM) and human big-ET-1 (100 nM) suggesting that both peptides induce the release of PGI2 via the selective activation of ET1 receptors.

Animals↗
PubMed1992

Structure-activity relationship for ETB agonism in truncated endothelin-1 analogs.

The essential part of the ETB-selective agonist N-acetyl-GluAlaValTyrPheAlaHisLeuAspIleIleTrp (N-Ac-4AlaET-1(10-21)) for ETB agonism was studied by single amino acid replacement. Single L-alanine substitutions at positions 14, 17, 20 and 21 and the corresponding D-amino acid substitutions at positions 14 and 16-21 resulted in remarkable decreases in ETB binding activity. Furthermore, these analogs elicited endothelium-dependent vasorelaxation in parallel with ETB binding activity. These data indicate that the amino acid residues of Phe14, Leu17, Ile20 and Trp21 and the backbone structure at Phe14 and His16-Trp21 in ET-1 are important for ETB agonism.

Alanine↗
PubMed1992

Amino acid sequences of ferredoxins from Alocasia macrorrhiza Schott in Papua New Guinea.

The amino acid sequences of ferredoxin isoproteins (Fd A and Fd B) from Alocasia macrorrhiza Schott in Papua New Guinea were determined. They consisted of single polypeptide chains of 97 and 98 residues, respectively, and both Fds had a molecular mass of 10,800 Da. There was an 88% identity between the sequences of the isoproteins (Fd A and Fd B). These sequences were compared with those of the closely related plant Fds and their phylogenetic relationships are discussed.

Amino Acid Sequence↗
PubMed1991

[Ala1,3,11,15]endothelin-1 analogs with ETB agonistic activity.

A linear peptide analog of endothelin (ET)-1, [Ala1,3,11,15]ET-1 (4AlaET-1), and its truncated peptide analogs were synthesized to study the structural requirements of ET-1 for the recognition of ETs-nonselective ETB receptors. ET-1 exhibited sub-nanomolar binding to two distinct ET receptor subtypes (ETA and ETB), but 4AlaET-1 bound to ETB with an affinity 1,700 times higher than that seen during binding to ETA. The truncated linear peptides 4AlaET-1(6-21), 4AlaET-1(8-21) and N-acetyl-4AlaET-1(10-21) still had high affinity for ETB, whereas 4AlaET-1(6-20) and 4AlaET-1(11-21) displayed remarkably reduced affinity for ETB. Therefore, ET-1 requires the Glu10-Trp21 sequence for ETB binding, but not the disulfide bridges. These ETB-binding peptides elicit endothelium-dependent vasorelaxation of porcine pulmonary arteries in parallel with the binding affinity for ETB, suggesting that they are ETB agonists.

Amino Acid Sequence↗
PubMed1991

An endothelin receptor (ETA) antagonist isolated from Streptomyces misakiensis.

A competitive endothelin (ET) antagonist, BE-18257B, was isolated from the fermentation products of Streptomyces misakiensis. It is a novel cyclic pentapeptide, cyclo(-D-Glu-L-Ala-allo-D-Ile-L-Leu-D-Trp-), and binds to ETA receptors (ET-1 selective) in cardiovascular tissues, but not to ETB receptors (equally sensitive to isopeptides of ET family) in kidney, adrenal gland and cerebellum tissues. BE-18257B also antagonizes ET-1-induced vasoconstriction in rabbit iliac artery and pressor action in rats. Thus it is a selective ETA antagonist and should provide a valuable tool for elucidation of the pharmacological and pathophysiological roles of ET-1.

Animals↗
PubMed1991

Advanced gastric cancer associated with acute myelocytic leukemia--report of a case.

A case of advanced gastric cancer associated with acute myelocytic leukemia (AML) is reported. Synchronous double malignancies of gastric cancer and AML are very rare. Combination chemotherapy (BHAC-DMP) was used as the method for induction and consolidation therapy for AML and a complete remission was obtained. However, it failed to show any therapeutic effect on the gastric cancer. A radical subtotal gastrectomy was performed with lymphadenectomy. During the postoperative course, both respiratory failure and severe thrombocytopenia progressed. Fortunately, the patient responded well to mechanical ventilation and the administration of heparin. She was discharged on day 52 after surgery, and no sign of recurrence of either gastric cancer or AML has been observed over the one-year period following the gastrectomy. In principle, in order to achieve a good prognosis, a radical resection should be carried out for gastric cancer associated with AML. However, chemotherapy for AML might make the patient vulnerable to surgical stress, although we could not demonstrate any concrete evidence which could prove the impairment of host immunity in this case. It is, therefore, possible that not only the relapse of AML but also the impairment of host immunity may cause some other difficulties during the post-gastrectomy course.

Aged↗
PubMed1991

Establishment of a monoclonal antibody recognizing cyclobutane-type thymine dimers in DNA: a comparative study with 64M-1 antibody specific for (6-4)photoproducts.

We obtained a monoclonal antibody (TDM-1) binding to 313-nm UV-irradiated DNA in the presence of acetophenone. The binding of TDM-1 to 254-nm UV-irradiated DNA was not reduced with the subsequent irradiation of 313-nm UV. Furthermore, the treatment of UV-irradiated DNA with photolyase from E. coli and visible light exposure reduced both the antibody binding and the amount of thymine dimers in the DNA. A competitive inhibition assay revealed that the binding of TDM-1 to UV-irradiated DNA was inhibited with photolyase, but not with 64M-1 antibody specific for (6-4)photoproducts. These results suggest that TDM-1 antibody recognizes cyclobutane-type thymine dimers in DNA. Using TDM-1 and 64M-1 antibodies, we differentially measured each type of damage in DNA extracted from UV-irradiated mammalian cells. Repair experiments confirm that thymine dimers are excised from UV-irradiated cellular DNA more slowly than (6-4)photoproducts, and that the excision rates of thymine dimers and (6-4)photoproducts are lower in mouse NIH3T3 cells than in human cells.

Acetophenones↗
PubMed1991

Two endothelin receptor subtypes in porcine arteries.

Endothelin-1 (ET-1) and ET-3 caused constrictions of endothelium-denuded porcine coronary artery strips with different concentration-response curves: a typical sigmoidal curve to ET-1 and a two-phase sigmoidal curve to ET-3. Binding assays using a membrane preparation demonstrated different Bmax values for [125I]ET-1 and [125I]ET-3 binding. In addition, [125I]ET-1 binding was inhibited by ET-1 and ET-3 with different potencies (ET-1 greater than ET-3), while [125I]ET-3 binding was inhibited by both ETs equally. From these results, two distinct ET receptor subtypes were proposed in the artery; site 1 (selective to ET-1) and site 2 (equally sensitive to both ETs). However, only site 1 was identified on cultured arterial smooth muscle cells (VSMCs) by the binding assay, and this was confirmed since only ET-1 (not ET-3) caused a significant increase in the intracellular free Ca2+ concentration. Therefore, it seems likely that vasoconstriction is mediated via the binding of ET-1 to site 1 (VSMCs) and site 2 (non-VSMCs), or the binding of ET-3 to site 2 (non-VSMCs). Furthermore, site 2 was predominant in nonvascular tissues such as lung, kidney, and cerebellum, thereby suggesting that site 1 may exist in limited tissues such as VSMCs.

Animals↗
PubMed1991

Heterogeneity of cloned cell lines established from a transplantable rat malignant fibrous histiocytoma.

Four cloned cell lines, MT-7, MT-8, MT-9 and MT-10, were established from a transplantable malignant fibrous histiocytoma (MFH) of F344 rats to investigate the histogenesis of the tumor. Cells of MT-7, MT-9 and MT-10 had fine structures characteristic of histiocytes, such as numerous cell processes, many lysosomes and well-developed cytoplasmic organelles. They stained positively for histiocytic lysosomal and antigenic markers. In addition, MT-9 cells contained microfilaments and well-developed RER in their cytoplasm, suggesting that they may be facultative fibroblasts. MT-8 cells stained weakly for histiocytic markers and had scant cytoplasmic organelles. They were identified as undifferentiated mesenchymal cells. The tumors induced in syngeneic rats by inoculating MT-7 or MT-10 consisted of a mixture of the pleomorphic, myxoid and storiform types of MFH, and those by MT-9 were of the storiform type. Cells forming these tumors stained positively for histiocytic markers. Tumors induced by MT-8 consisted of undifferentiated cells negative to these stainings. The histogenesis of MFH is surmised to be related to various differentiation stages shifting from undifferentiated cells to histiocytic cells capable of acting as facultative fibroblasts.

Animals↗
PubMed1991

Simultaneous establishment of monoclonal antibodies specific for either cyclobutane pyrimidine dimer or (6-4)photoproduct from the same mouse immunized with ultraviolet-irradiated DNA.

Six new monoclonal antibodies (TDM-2, TDM-3, 64M-2, 64M-3, 64M-4 and 64M-5) specific for ultraviolet (UV) induced DNA damage have been established. In the antibody characterization experiments, two TDM antibodies were found to show a dose-dependent binding to UV-irradiated DNA (UV-DNA), decrease of binding to UV-DNA after cyclobutane pyrimidine dimer photoreactivation, binding to DNA containing cyclobutane thymine dimers, and unchanged binding to UV-DNA after photoisomerization of (6-4)photoproducts to Dewar photoproducts. These results indicated that the epitope of TDM monoclonal antibodies was the cyclobutane pyrimidine dimer in DNA. On the other hand, four 64M antibodies were found to show a dose-dependent binding to UV-DNA, unchanged binding to UV-DNA after cyclobutane pyrimidine dimer photoreactivation, undetectable binding to DNA containing thymine dimers, and decrease of binding to UV-DNA after photoisomerization of (6-4)photoproducts. These results indicated that the epitope of 64M antibodies was the (6-4)photoproduct in DNA. This is the first report of the simultaneous establishment of monoclonal antibodies against the two different types of photolesions from the same mouse. By using these monoclonal antibodies, we have succeeded in measuring both cyclobutane pyrimidine dimers and (6-4)photoproducts in the DNA from human primary cells irradiated with physiological UV doses.

Animals↗
PubMed1991

Transplantable mononuclear cell leukemia in F344 rat with particular reference to nodular tumor developing at the transplant site.

A transplantable mononuclear cell leukemia (MCL) was established from spontaneous MCL in an F344 rat. In this work, we paid special attention to a nodular tumor, named MCL-YSK, developed at the subcutaneous transplant site. MCL-YSK was serially passaged in subcutaneous tissue of syngeneic rats up to the 19th generation. Transplants from MCL-YSK grew into nodules 3 cm in diameter and 11.3 g in weight 9 weeks after subcutaneous implantation. Neoplastic cells forming the nodules had azurophilic cytoplasmic granules, which ultrastructurally appeared to be lysosomes. The cells reacted positively for acid phosphatase and nonspecific esterase, but not for alkaline phosphatase, alpha-1 antitrypsin and lysozyme, nor reacted with anti-rat monocyte/macrophage monoclonal antibody and anti-rat CD-8 monoclonal antibody. They possessed Fc-receptor. Leukemic cells first appeared in the peripheral blood 6 weeks after transplantation when subcutaneous nodules reached an average diameter of one cm. Subsequently, leukemic changes progressed in recipients as MCL-YSK grew larger. The recipients died during the period from 8 to 12 weeks after transplantation, showing anemia, depression, splenohepatomegaly and lymph node enlargement. Diffuse or focal proliferation of sprinkled tumor cells was present in many organs. Hematologic changes suggestive of hemolytic anemia, elevated plasma enzymes and decreased drug-metabolizing enzymes, indicative of hepatic malfunction, were seen in transplant recipients. MCL-YSK was easily transplanted into athymic nude mice. The transplanted mice showed leukemic changes similar to those observed in rats with transplanted MCL-YSK.

Animals↗
PubMed1991

Endothelin-binding inhibitors, BE-18257A and BE-18257B II. Structure determination.

The structures of novel endothelin-binding inhibitors, BE-18257A and BE-18257B, were elucidated by spectral analyses and chemical studies. Both inhibitors were found to have a cyclic pentapeptide structure containing three D-form amino acid residues, namely, the structures of BE-18257A and BE-18257B were elucidated to be cyclo(-D-Glu-L-Ala-D-Val-L-Leu-D-Trp-) and cyclo(-D-Glu-L-Ala-allo-D-Ile-L-Leu-D-Trp-), respectively.

Endothelins↗
PubMed1990

Hydrolysis and acyl migration of a catechol monoester of L-dopa: L-3-(3-hydroxy-4-pivaloyloxyphenyl)alanine.

Hydrolysis and acyl migration studies on L-3-(3-hydroxy-4-pivaloyloxyphenyl)alanine (1, NB-355), which produced long-lasting plasma L-dopa levels after oral dosing, have been conducted. Compound 1 exists as pure 4-O-pivaloyl-L-dopa in the solid state, but it converts rapidly to a mixture of the 3- and 4-O-isomers in solution. The rate of acyl migration increased with increases in pH and temperature, and the content of the 4-O-isomer in the equilibrium state was 53-59%. The hydrolysis rate of 1 to L-dopa (6) also increased with increases in pH and temperature, and accelerated steeply at neutral and alkaline pH. The rapid hydrolysis at neutral pH was not observed with O-pivaloyl-L-tyrosine (3), di-O-pivaloyl-L-dopa (4), or L-dopa methyl ester (5). Because of this chemical lability, 1 was hydrolyzed in rat plasma far faster than the other tested catechol esters. However, in rat intestinal homogenate at pH 6.0, 1 was hydrolyzed at the slowest rate among the tested esters, predominantly by a diisofluorophosphate (DFP)-sensitive esterase. Thus, 1 showed a unique in vitro profile on hydrolysis and acyl migration due to the existence of a neighboring hydroxyl group. The stability of 1 in the intestine might be essential for the long-lasting plasma L-dopa profile after oral dosing of 1.

Acylation↗
PubMed1989

A new potential prodrug to improve the duration of L-dopa: L-3-(3-hydroxy-4-pivaloyloxyphenyl)alanine.

L-3-(3-Hydroxy-4-pivaloyloxyphenyl)alanine (1, NB-355) is a novel L-dopa prodrug. After oral administration with carbidopa in rats, 1 demonstrated 2.3 times longer duration (MRT) and 1.4 times larger bioavailability (AUC) on plasma L-dopa concentrations than those of L-dopa itself. Similar results were obtained in dogs. The prolonged profile of L-dopa was parallel to that of carbidopa, and the intact ester was undetectable in rat plasma. After intravenous administration in rats, 1 was converted quickly and completely to L-dopa in the systemic circulation. It was also noted that the oral LD50 value of 1 was greater than 6 g/kg in mice. These data suggest that 1 will offer long-lasting L-dopa therapy for the treatment of Parkinson's disease with little concern about toxicity.

Animals↗
PubMed1989

Influence of cholesterol administration and aging on the development of pulmonary foam cells in F344 rats.

The influence of experimentally induced hyperlipidemia and aging on the development of pulmonary foam cells (PFCs) was examined in Fischer 344 rats. The male and female rats were administered orally with cholesterol at a dosage level of 1000 mg/kg/day for 30 days from 6 to 10 weeks or from 33 to 37 weeks of age. The control rats received the vehicle only in the same manner. Plasma levels of total cholesterol, phospholipid, triglyceride (TG), beta-lipoprotein (beta-LP) and calcium in both control and cholesterol-administered groups were higher at 37 weeks than at 10 weeks of age. Plasma beta-LP and TG levels in the treated groups were significantly higher or tended to be higher than those of the controls at 10 and 37 weeks of age. Males of the treated group showed the highest level of beta-LP at 37 weeks of age, positively correlated with the highest incidence of PFCs. PFCs developed singly or in a small cluster in peribronchial and subpleural regions. PFCs had an abundant cytoplasm filled with many fine vacuoles containing neutral lipid and cholesterol. PFCs stained with PAS and reacted immunohistochemically with both anti-rat monocytes/macrophages monoclonal antibody and anti-lysozyme antibody. Moderately swollen macrophages with a foamy appearance were detected in perivascular connective tissues of the lungs and they were considered to represent an initial stage of the development of PFCs. These observations suggest that hyperlipidemic conditions, particularly hyper beta-lipoproteinemia, resulting from cholesterol administration or aging may be involved in the development of PFCs in rats.

Aging↗