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H Hori

Publications and source records attributed to H Hori.

At least 163 records · Page 9Linked to original sources
PubMed1999

Lung metastasis suppression of the bifunctional new radiosensitizer KIN-806.

KIN-806 is one of the newly developed 2-nitroimidazole derivative hypoxic cell radiosensitizers. The tumor growth control and the suppression of lung metastasis induced by KIN-806 were evaluated. Female C3H/He mice and SCCVII tumor cells were used. 30 Gy or 40 Gy was delivered as local irradiation. 0.2 g/kg or 0.4 g/kg KIN-806 was administered 30 min before this treatment to the KIN-806 administered groups. The enhancement ratio of KIN-806 evaluated using the growth delay method was 1.8. KIN-806 showed an excellent effect as a radiosensitizer. Furthermore, KIN-806 suppressed lung metastasis regardless of radiation, and the control of the metastatic lung nodules did not depend on the irradiation dose but rather on the KIN-806 dose (0.2 g/kg < 0.4 g/kg). KIN-806 is a promising bifunctional radiosensitizer which promotes anti-tumor activity in addition to having a radiosensitizing effect.

Animals↗
PubMed1999

[An experimental study of the protective effect of lazaroid (U-74389G) on cisplatin-induced toxicity].

Lazaroids, a novel series of 21-aminosteroids without glucocorticoid action, have the properties of free radical scavenging and potent inhibition of lipid peroxidation. U-74389G is one of the Lazaroid compounds. These compounds have shown excellent effect on central nervous system trauma and ischemia in experimental animals. The present study was designed to investigate whether Lazaroid (U-74389G) has a protective effect on Cisplatin (CDDP)-induced toxicity. Fisher 344 rats were used in this study. The animals were divided into three groups: I) CDDP 0.9 mg/kg i.v. alone; II) CDDP 0.9 mg/kg i.v. 1 hr after the p.o. administration of U-74389G 10 mg/kg; III) physiological saline 2.5 ml/kg i.v. instead of CDDP, for 7-10 days. First, the protective effect of Lazaroid (U-74389G) on CDDP-induced ototoxicity was studied. Cochlear damage was evaluated by means of the compound action potential (CAP) and histological examination using scanning electron microscopy. The degree of elevation of CAP thresholds and the rate of missing outer hair cells were significantly reduced in Group II as compared to Group I. These results clearly demonstrate that Lazaroid (U-74389G) has a protective effect on CDDP-induced ototoxicity. Second, the protective effect of Lazaroid (U-74389G) on CDDP-induced nephrotoxicity was studied. Nephrotoxicity was evaluated by means of serum BUN level and histopathological examination. There was no significant difference in serum BUN level and little difference of renal histopathological findings between Group I and Group II. Lazaroid (U-74389G) was not found to ameliorate CDDP-induced nephrotoxicity. Third, the influence of Lazaroid (U-74389G) on the antitumor effect of CDDP was investigated in rats inoculated subcutaneously with SCC-158 squamous-cell carcinoma cells. There was no significant difference of Tumor Growth Rate (TGR) between Group I and Group II. The result suggests that the combined administration does not alter the antitumor activity of CDDP. In conclusion, the combined administration of CDDP with Lazaroid (U-74389G) ameliorates CDDP-induced ototoxicity without decreasing the antitumor activity of CDDP.

Animals↗
PubMed1999

Simple synthesis of alpha-cyano-alpha-fluoro-p-tolylacetic acid (CFTA), a new efficient chiral derivatizing agent.

The new chiral derivatizing agent, alpha-cyano-alpha-fluoro-p-tolylacetic acid (CFTA) (2) was prepared in optically pure form by Candida rugosa lipase (CRL)-mediated kinetic resolution of racemic CFTA ethyl ester (CFTA Et ester) (1). The ester was obtained by fluorination of ethyl alpha-cyano-p-tolylacetate with FClO3. The CFTA method has proven to be significantly superior for enantiomeric excess (e.e.) determinations when compared to the MTPA method, particularly in those compounds that have a remotely disposed chiral center.

Acetates↗
PubMed1999

Delayed cytotoxicity of 6-mercaptopurine is compatible with mitotic death caused by DNA damage due to incorporation of 6-thioguanine into DNA as 6-thioguanine nucleotide.

Many protocol studies have shown that low dose 6-mercaptopurine (6MP) in maintenance chemotherapy for childhood acute lymphoblastic leukemia (ALL) can be utilized to cure the disease. Mitotic or reproductive cell death has been recognized after G2 arrest when cells are treated with antitumor agents. The precise mechanism of mode of action of 6MP still remains unclear. We found delayed cytotoxic effect of 6MP in P388 murine leukemic cells. Morphological study showed that 6MP induced delayed death was characterized by an enlargement of cell size and multinucleated nuclei. Agarose gel electrophoresis of fragmented DNA from cells treated with 6MP showed the typical ladder pattern. These findings were compatible with mitotic death. Our results make us hypothesize that the delayed cytotoxicity of 6MP is one of the drug induced mitotic deaths caused by DNA damage due to incorporation of 6-thioguanine (6TG) into DNA as thioguanine nucleotide (TGN). Mitotic death may be a mechanism for killing the cycling cells from residual leukemic cells in G0 or long G1 phases in the treatment of childhood ALL.

Animals↗
PubMed1998

Excision of the tol2 transposable element of the medaka fish, Oryzias latipes, in zebrafish, Danio rerio.

The Tol2 element is a transposable element in Oryzias latipes (the medaka fish) found in the tyrosinase gene locus of the tyrosinase-deficient mutant medaka fish and has been shown to be excised from the genome during medaka embryogenesis (Koga, A., Suzuki, M., Inagaki, H., Bessho, Y., Hori, H., 1996. Transposon element in fish. Nature 383, 30). It is, however, not known whether the Tol2 element is an autonomous element. To determine whether the cloned Tol2 element is an autonomous element and whether excision can occur also in the other fish species, the plasmid DNA harboring the Tol2 element was injected to fertilized eggs of zebrafish, Danio rerio, and the total DNA extracted from the embryos 9-10h after the injection was analyzed by PCR. When a plasmid with the full-length Tol2 element was used for the microinjection, in 39 out of 43 injected embryos, we found generation of short PCR products indicative of the loss of the Tol2 element from the injected plasmid. Ten of these cases were analyzed at the DNA sequence level, and nine of them showed either precise excision of the Tol2 element (three cases) or nearly precise excision of the element with the addition of a few nucleotides of the target duplication (six cases). When a deletion version of the Tol2 element that retained the terminal inverted repeats but lacked about one-fourth of the open reading frame-coding region was used for the microinjection, such short PCR products could not be amplified from any of the injected embryos (0 out of 30). Thus, the Tol2 element is capable of excision in zebrafish embryos, presumably dependent on a putative transposase encoded by the Tol2 element itself. This transient embryonic excision assay using zebrafish should be useful to analyze the structure and the function of the transposase and cis-elements necessary for excision. Also, this study implies the potential use of the Tol2 element in transgenesis and insertional mutagenesis in both zebrafish and the medaka fish.

Animals↗
PubMed1998

TX-1877: design, synthesis, and biological activities as a BRM-functional hypoxic cell radiosensitizer.

PURPOSE: 2-Nitroimidazole acetamide TX-1877 and its derivatives (TX-1877 analogs) were designed, synthesized, and evaluated by their in vitro and in vivo radiosensitization, tumor growth control, suppression of lung metastasis, and immunopotentiation, as biological response modifier (BRM)-functional hypoxic cell radiosensitizers. MATERIALS AND METHODS: TX-1877 analogs were designed and synthesized in our laboratory. In vitro radiosensitizing ability was estimated using EMT6/KU cells under hypoxic conditions. In vivo radiosensitization, antimetastasis, and immunopotentiation were evaluated using female C3H/He mice bearing the SCCVII tumor. Days (15 or 10) after the inoculation of 10(5) SCCVII tumor cells into the hinder thigh, a drug (0.4 mg/g) was administered i.p. and local irradiation of 30 Gy was given at 30 min after its administration. Tumor growth was observed for 20 days and mice were euthanized to count the number of metastatic nodules on the surface of the lungs. Tumor tissues were extirpated and stained by the ABC method at 1, 2, and 3 weeks after treatment for immunological evaluation. RESULTS: Novel types of bifunctional radiosensitizers, TX-1877 and its analogs possessing BRM-functions (i.e., antimetastatic and immunopotentiation effects) were developed. In vitro radiosensitizing abilities of TX-1877 and its analogs, with their partition coefficient values of more than 0.050, were comparable to misonidazole (MISO) at their doses of 1 mM. Tumor regrowth was suppressed evidently 20 days after the treatment in the irradiated group with TX-1877 (TX-1877 plus R) and with KIN-806 (KIN-806 plus R). The former group reduced markedly the mean number of metastatic lung nodules regardless of radiation therapy. TX-1877 and KIN-806 plus R induced helper T lymphocytes. The TX-1877, TX-1877 plus R, KIN-806, and KIN-806 plus R enhanced macrophage infiltration for 3 weeks after treatment. CONCLUSION: TX-1877 is an excellent BRM-functional hypoxic cell radiosensitizer, expected to be useful for clinical use.

Animals↗
PubMed1998

Substrate recognition of tRNA (Guanosine-2'-)-methyltransferase from Thermus thermophilus HB27.

Transfer RNA (guanosine-2'-)-methyltransferase (Gm-methylase, EC 2.1. 1.32) from Thermus thermophilus HB27 is one of the tRNA ribose modification enzymes. The broad substrate specificity of Gm-methylase has so far been elucidated using various species of tRNAs from native sources, suggesting that the common structures in tRNAs are recognized by the enzyme. In this study, by using 28 yeast tRNAPhe variants obtained by transcription with T7 RNA polymerase, it was revealed that the nucleotide residues G18 and G19 and the D-stem structure are essentially required for Gm-methylase recognition, and that the key sequence for the substrate is pyrimidine (Py)17G18G19. The other conserved sequences were found not to be essential, but U8, G15, G26, G46, U54, U55, and C56 considerably affected the methylation efficiency. These residues are located within a limited space embedded in the L-shaped three-dimensional structure of tRNA. Therefore, disruption of the three-dimensional structure of the substrate tRNA is necessary for the catalytic center of Gm-methylase to be able to access the target site in the tRNA, suggesting that the interaction of Gm-methylase with tRNA consists of multiple steps. This postulation was confirmed by inhibition experiments using nonsubstrate tRNA variants which functioned as competitive inhibitors against usual substrate tRNAs.

Bacterial Proteins↗
PubMed1998

Detection of a tryptophan radical as an intermediate species in the reaction of horseradish peroxidase mutant (Phe-221 --> Trp) and hydrogen peroxide.

The crucial reaction intermediate in the reaction of peroxidase with hydrogen peroxide (H2O2), compound I, contains a porphyrin pi-cation radical in horseradish peroxidase (HRP), which catalyzes oxidation of small organic and inorganic compounds, whereas cytochrome c peroxidase (CcP) has a radical center on the tryptophan residue (Trp-191) and oxidizes the redox partner, cytochrome c. To investigate the roles of the amino acid residue near the heme active center in discriminating the function of the peroxidases in these two enzymes, we prepared a CcP-like HRP mutant, F221W (Phe-221 --> Trp). Although the rapid spectral scanning and stopped-flow experiments confirmed that the F221W mutant reacts with H2O2 to form the porphyrin pi-cation radical at the same rate as for the wild-type enzyme, the characteristic spectral features of the porphyrin pi-cation radical disappeared rapidly, and were converted to the compound II-type spectrum. The EPR spectrum of the resultant species produced by reduction of the porphyrin pi-cation radical, however, was quite different from that of compound II in HRP, showing typical signals from a Trp radical as found for CcP. The sequential radical formation from the porphyrin ring to the Trp residue implies that the proximal Trp is a key residue in the process of the radical transfer from the porphyrin ring, which differentiates the function of peroxidases.

Calcium↗
PubMed1998

20beta-hydroxy-C21-steroid 20beta-oxidase activity of cytochrome P450c21 purified from bovine adrenocortical microsomes.

We showed previously that cytochrome P450c21 (CYP21A1) from bovine adrenocortical microsomes has a putative 20beta-oxidase activity for 20beta-hydroxyprogesterone leading to a conversion to progesterone [M. Tsubaki, K. Morimoto, S. Tomita, S. Miura, Y. Ichikawa, A. Miyatake, F. Masuya, H. Hori, Biochim. Biophys. Acta 1259 (1995) 89-98]. We have extended the investigation on the 20beta-oxidase activity of cytochrome P450c21. Combination of 17alpha, 20beta-dihydroxyprogesterone with purified cytochrome P450c21 in oxidized form caused an induction of a typical type I difference spectrum (a peak at 390 nm and a trough at 420 nm) with a spectral dissociation constant of 2.3 microM. EPR spectrum at low temperature (15 K) exhibited an appearance of a new low-spin signal at gz=2.42, gy=2.21, and gx=1.966 and an increase in intensity of the high-spin signal (g=8.06, 3.54) upon formation of the enzyme-steroid complex, as previously found for 17alpha-hydroxyprogesterone and 20beta-hydroxyprogesterone. The enzymatic activity for 17alpha, 20beta-dihydroxyprogesterone was confirmed in a reconstituted system consisting of cytochrome P450c21 and NADPH-cytochrome P450 reductase. 17alpha,20beta-Dihydroxyprogesterone was converted to 17alpha-hydroxyprogesterone via the 20beta-oxidase reaction. The high turnover numbers of the 20beta-oxidase activity for 20beta-hydroxy-c21-steroids suggests that this activity is likely to have some physiological roles. Cytochrome P450c21 and 20beta-hydroxysteroid dehydrogenase may regulate the androgen biosynthesis catalyzed by cytochrome P450c17alpha with controlling the concentration of 20beta-hydroxy-C21-steroids.

Adrenal Glands↗
PubMed1998

Substitutions of conserved aromatic amino acid residues in subunit I perturb the metal centers of the Escherichia coli bo-type ubiquinol oxidase.

Cytochrome bo is a four-subunit quinol oxidase in the aerobic respiratory chain of Escherichia coli and functions as a redox-coupled proton pump. Subunit I binds all the redox metal centers, low-spin heme b, high-spin heme o, and CuB, whose axial ligands have been identified to be six invariant histidines. This work explored the possible roles of the aromatic amino acid residues conserved in the putative transmembrane helices (or at the boundary of the membrane) of subunit I. Sixteen aromatic amino acid residues were individually substituted by Leu, except for Tyr61 and Trp282 by Phe and Phe415 by Trp. Leu substitutions of Trp280 and Tyr288 in helix VI, Trp331 in loop VII-VIII, and Phe348 in helix VIII reduced the catalytic activity, whereas all other mutations did not affect the in vivo activity. Spectroscopic analyses of the purified mutant enzymes revealed that the defects were attributable to perturbations of the binuclear center. On the basis of these findings and recent crystallographic studies on cytochrome c oxidases, we discuss the possible roles of the conserved aromatic amino acid residues in subunit I of the heme-copper terminal oxidases.

Amino Acid Sequence↗
PubMed1998

The methylthioadenosine phosphorylase gene is frequently co-deleted with the p16INK4a gene in acute type adult T-cell leukemia.

Adult T-cell leukemia (ATL) is a retrovirus-associated leukemia with poor prognosis and often has deletions of the p16INK4a and p15INK4b genes on chromosome 9p21. The gene for methylthioadenosine phosphorylase (MTAP), a purine and methionine metabolic enzyme, resides approximately 100 Kb telomeric to the p16INK4a gene and is frequently co-deleted with the tumor suppressor gene in a variety of cancers. This enzyme deficiency can be exploited for selective chemotherapy with de novo purine synthesis inhibitors and/or methionine depletion. To determine whether ATL can be a candidate for selective chemotherapy based on genetic alterations on chromosome 9p21, we analyzed the MTAP gene in 41 samples from ATL patients (27 acute type and 14 chronic type ATL) and 3 cell lines established from ATL patients. Five samples from the acute type had deletions of the MTAP gene (4 total deletions and 1 partial deletion of exons 6-8). The MTAP gene was always co-deleted with p16INK4a. No deletion of the MTAP gene was detected in samples from the chronic type. Of 3 cell lines, 2 showed partial deletions of exons 5-8 of the MTAP gene, and 1 lost all exons. The p16INK4a gene was deleted in all cell lines. In conclusion, deletions of the MTAP gene were found in 5 of 27 acute type ATL samples. Acute type ATL with MTAP deficiency can be a good candidate for selective chemotherapy by depleting purines and/or methionine.

Adult↗
PubMed1998

Effects of (+)-8',8',8'-trifluoroabscisic acid on alpha-amylase expression and sugar accumulation in rice cells.

The effects of (+)-8',8',8'-trifluoroabscisic acid (trifluoro-ABA) on alpha-amylase expression were studied in rice embryoless half-seeds, scutella, and suspension-cultured cells derived from the embryo, and the effects of the analog on sugar accumulation were also studied in scutella and suspension-cultured cells. Treatment with (+)-trifluoro-ABA strongly inhibited the gibberellic acid-inducible expression of alpha-amylase I-1 encoded by RAmy1A in the aleurone layers of embryoless half-seeds at the levels of transcription, protein synthesis, and enzyme activity. It was also found that (+)-trifluoro-ABA stimulated (i) the uptake of glucose from the incubation medium and (ii) the synthesis of sucrose in scutellar tissues and suspension-cultured cells of rice. The biological activity of (+)-trifluoro-ABA was found to be more potent and persistent than that of natural ABA. We further examined the effects of trifluoro-ABA on the expression of alpha-amylase I-1 in scutellar tissues and suspension-cultured cells. It was found that (+)-trifluoro-ABA did not inhibit the formation of alpha-amylase I-1 in the absence of external glucose. However, glucose and (+)-trifluoro-ABA cooperatively suppressed the formation of alpha-amylase I-1. Judging from these results, we conclude that the regulatory mechanism for the expression of alpha-amylase I-1 in the scutellar epithelium is distinguishable from that operating in the aleurone layer.

Abscisic Acid↗
PubMed1998

Retinyl palmitate reduces hepatic fibrosis in rats induced by dimethylnitrosamine or pig serum.

BACKGROUND/AIMS: Lipid peroxidation has been found to be associated with Ito cell activation. Ito cells are the principal collagen-producing cells and the main storage sites of retinoids. However, the relationship between retinoids and hepatic fibrosis is complex. The aim of this study was to elucidate the role of retinoids as a fibrosuppressant: the effects of retinoids on hepatic fibrosis induced in rats by dimethylnitrosamine or pig serum, as well as on rat Ito cells in primary culture, were examined in order to assess the antioxidant activity of retinoids. METHODS: Male Wistar rats were given a single injection of 40 mg/kg dimethylnitrosamine or 0.5 ml PS twice weekly for 10 weeks. In each model, rats were treated with retinyl palmitate for 2 weeks before hepatotoxin treatments or for the last 2 weeks of the treatments. The cumulative amount of retinyl palmitate administered in each experiment was 2, 10, or 20x10(4) IU/rat. RESULTS: Retinyl palmitate treatment before or after administration of dimethylnitrosamine or pig serum suppressed the induction of hepatic fibrosis, restored hepatic retinyl palmitate levels, prevented increases in hepatic levels of collagen and malondialdehyde, a product of lipid peroxidation, and prevented increases in deposition of type III collagen and the number of alpha-smooth muscle actin (alpha-SMA) positive-Ito cells in the liver. Retinyl palmitate supplementation resulted in a dose-dependent reduction of alpha-SMA expression and an oxidative burst in cultured Ito cells. In addition, retinyl palmitate inhibited Fe2+/adenosine 5'-diphosphate-induced lipid peroxidation in rat liver mitochondria and showed radical scavenging activity. CONCLUSIONS: These findings suggest that retinyl palmitate may suppress the induction of hepatic fibrosis, at least in part, by the inhibition of Ito cell activation through its antioxidant activity.

Animals↗