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T Okino

Publications and source records attributed to T Okino.

At least 19 recordsLinked to original sources
PubMed2004

Characterization of the preferred stereochemistry for the neuropharmacologic actions of antillatoxin.

Antillatoxin is a potent ichthyotoxin and cytotoxin previously discovered from the marine cyanobacterium Lyngbya majuscula. Ensuing studies of its mechanism of action showed it to activate the mammalian voltage-gated sodium channel at a pharmacological site that is distinct from any previously described. The structure of antillatoxin, initially formulated from spectroscopic information, was subsequently corrected at one stereocenter (C-4) as a result of synthesis of four different antillatoxin stereoisomers (all possible C-4 and C-5 diastereomers). In the current study these four stereoisomers, (4R,5R)-, (4S,5R)-, (4S,5S)-, and (4R,5S)-antillatoxin, were characterized in five different biological assay systems: ichthyotoxicity to goldfish, microphysiometry using cerebellar granule cells (CGCs), lactose dehydrogenase efflux from CGCs, monitoring of intracellular Ca(2+) concentrations in CGCs, and cytotoxicity to Neuro 2a cells. Across these various biological measures there was great consistency in that the natural antillatoxin (the 4R,5R-isomer) was greater than 25-fold more potent than any of the other stereoisomers. Detailed NMR studies provided a number of torsion and distance constraints that were modeled using the MM2 force field to yield predicted solution structures of the four antillatoxin stereoisomers. The macrocycle and side chain of natural (4R,5R)-antillatoxin present an overall "L-shaped" topology with an accumulation of polar substituents on the external surface of the macrocycle and a hydrogen bond between N(H)-7' and the C(O)-1 carbonyl. The decreased potency of the three non-naturally occurring antillatoxin stereoisomers is certainly a result of their dramatically altered overall molecular topologies.

Animals↗
PubMed2002

Use of nitrogen stable isotope ratio of periphyton for monitoring nitrogen sources in a river system.

In order to confirm the usefulness of the N stable isotope ratio of periphyton (mainly composed of attached algae) as an indicator for monitoring the N sources in river watersheds, we measured the isotope ratio of periphyton along the Chikuma River. In the river, both the concentrations of dissolved total nitrogen (DTN) and the delta15N values of periphyton increased downstream. Specific nitrogen loading rates (SNLR) calculated from administrative data also showed an increase downstream from 7 to 11 kg N ha(-1) yr(-1), with the increasing contribution by sewage and livestock waste from 6 to 40% to total N loading. There are significant positive relationships between the DTN concentration and the SNLR (r2=0.54, P<0.05), and the delta15N values of periphyton and the SNLR (r2=0.78, P<0.05). The increase in DTN concentration reflected the increase in input of N loading. The increase in delta15N of periphyton might reflect the increase in relative contribution by sewage and livestock waste down the river, especially the increase in sewage. The present study indicates the usefulness of the N stable isotope ratio of periphyton as an indicator for monitoring N sources in a river system.

Animals↗
PubMed2001

Chiral phosphine-free Pd-mediated asymmetric allylation of prochiral enolate with a chiral phase-transfer catalyst.

[reaction: see text]. A chiral phase-transfer catalyst has been applied to the asymmetric allylation of the tert-butyl glycinate-benzophenone Schiff base with various allylic acetates for the first time to give the allylated products in good yields and with comparable to higher enantioselectivity than for asymmetric alkylation at the same temperature (91-96% ee) without any chiral ligands for coordinating to the palladium.

Alkylation↗
PubMed2001

Antillatoxin is a marine cyanobacterial toxin that potently activates voltage-gated sodium channels.

Antillatoxin (ATX) is a lipopeptide derived from the pantropical marine cyanobacterium Lyngbya majuscula. ATX is neurotoxic in primary cultures of rat cerebellar granule cells, and this neuronal death is prevented by either N-methyl-d-aspartate (NMDA) receptor antagonists or tetrodotoxin. To further explore the potential interaction of ATX with voltage-gated sodium channels, we assessed the influence of tetrodotoxin on ATX-induced Ca2+ influx in cerebellar granule cells. The rapid increase in intracellular Ca2+ produced by ATX (100 nM) was antagonized in a concentration-dependent manner by tetrodotoxin. Additional, more direct, evidence for an interaction with voltage-gated sodium channels was derived from the ATX-induced allosteric enhancement of [3H]batrachotoxin binding to neurotoxin site 2 of the alpha subunit of the sodium channel. ATX, moreover, produced a strong synergistic stimulation of [3H]batrachotoxin binding in combination with brevetoxin, which is a ligand for neurotoxin site 5 on the voltage-gated sodium channel. Positive allosteric interactions were not observed between ATX and either alpha-scorpion toxin or the pyrethroid deltamethrin. That ATX interaction with voltage-gated sodium channels produces a gain of function was demonstrated by the concentration-dependent and tetrodotoxin-sensitive stimulation of 22Na+ influx in cerebellar granule cells exposed to ATX. Together these results demonstrate that the lipopeptide ATX is an activator of voltage-gated sodium channels. The neurotoxic actions of ATX therefore resemble those of brevetoxins that produce neural insult through depolarization-evoked Na+ load, glutamate release, relief of Mg2+ block of NMDA receptors, and Ca2+ influx.

Animals↗
PubMed2001

Asymmetric alkylation of tert-butyl glycinate Schiff base with chiral quaternary ammonium salt under micellar conditions.

[reaction: see text] The asymmetric alkylation of the tert-butyl glycinate-benzophenone Schiff base 1 with various arylmethyl bromides catalyzed by O-allyl-N-(9-anthracenylmethyl)cinchonidinium bromide (2) proceeded smoothly under micellar conditions (5 equiv of 1 M KOH and 0.4 equiv of Triton X-100) to give the alkylated products in good yields and with good enantioselectivity (72-85% ee), depending on the electrophiles.

Journal Article↗
PubMed2001

Massaliatrema misgurni n. sp. (Trematoda: Heterophyidae) whose metacercariae encyst in loaches (Misgurnus anguillicaudatus).

Hitherto unknown metacercariae were found encysted in loaches (Misgurnus anguillicaudatus) from China. They were experimentally fed to golden hamsters, and gravid adults were recovered 1 week post-infection from their small intestines. A new species, Massaliatrema misgurni n. sp. (Heterophyidae), is described from the adults. This new species is different from M. gyrinicola Dollfus and Timon-David, 1960, in having a smaller acetabulum/oral sucker ratio, less branched vitellaria widely entering the intercecal anteroacetabular area and an almost median seminal receptacle; and from M. yamashitai Kamiya and Ohbayashi, 1975, in having a larger acetabulum/oral sucker ratio, with the seminal vesicle situated in the uterine loop and the vitellaria entering the intercecal anteroacetabular area. This report is the first record of M. anguillicaudatus as a second intermediate host of the genus Massaliatrema Dollfus and Timon-David, 1960.

Animals↗
PubMed2001

Antillatoxin B, a neurotoxic lipopeptide from the marine cyanobacterium Lyngbya majuscula.

Bioassay-guided fractionation of organic extracts from two Lyngbya majuscula collections led to the isolation of a new secondary metabolite, antillatoxin B, an unusual N-methyl homophenylalanine analogue of the potent neurotoxin antillatoxin. Its structure was deduced from 2D NMR and data comparisons with antillatoxin. Antillatoxin B exhibited significant sodium channel-activating (EC(50) = 1.77 microM) and ichthyotoxic (LC(50) = 1 microM) properties.

Animals↗
PubMed2001

Immunohistochemical analysis of distribution of RON receptor tyrosine kinase in human digestive organs.

The immunohistochemical distribution of RON receptor tyrosine kinase in digestive organs of both human fetus and adult, including the esophagus, stomach, duodenum, small intestine, colon, rectum, liver, gallbladder, pancreas, and spleen, was investigated semiquantitively using an affinity-purified rabbit polyclonal antibody. RON was observed to be widely distributed throughout various digestive organs and cell types in humans. The immunoreactivity for RON was observed in the epithelium of the esophagus, small intestine, colon, hepatocytes, Kupffer cells, and splenic macrophages both in the adult and the fetus, suggesting that the MSP/RON signaling pathway possesses the proper biological properties to possibly be involved in morphogenesis or differentiation of cells in these organs and cell types. Several organs differed in immunoreactivity between adult and fetus. No immunoreactive cells were found in the pancreas of adults; however, immunoreactivity was observed in acinar cells and in some of the duct or ductular cells and endocrine cells of the islet of the fetus. Similarly, immunoreactivity was not observed in gastric mucosa except in the intestinal metaplastic cells in adults; however, immunoreactivity was found in the foveolar epithelium of the stomach of the fetus. Although the biological significance of RON in malignancy is unclear, the presence of RON immunoreactivity in the fetus and it lack in the adult may indicate that RON is a oncofetal substance in human pancreas and stomach.

Adult↗
PubMed2001

Sequential histopathological changes in vivo after suicide gene therapy of gastric cancer induced by N-methyl-N'-nitro-N-nitrosoguanidine in rats.

Gastrointestinal cancer is the most important clinical target of gene therapy. Suicide gene therapy, such as with the herpes simplex virus type 1 thymidine kinase (HSV-TK) gene, has been shown to exert antitumor efficacy in various cancer models in vitro. We previously reported in situ gene transfer and gene therapy for gastric cancer induced by N-ethyl-N'-nitro-N-nitrosoguanidine (ENNG) in dogs. Here, we describe the sequential histopathological changes after suicide gene therapy of N-methyl-N'-nitro-N-nitrosoguanidine (MNNG)-induced gastric cancer in rats. Gastric tumors were induced by MNNG in 38 / 73 (52%) of Wistar strain rats. The suicide gene therapy group (14 rats) was subjected to in situ gene transfer with a recombinant adenovirus vector carrying the HSV-TK gene driven by CAG promoter (Ad.CAGHSV-TK) in gastric tumor, followed by the antiviral drug ganciclovir (GCV). To observe the histopathological changes at various times after HSV-TK / GCV gene therapy, groups of animals were sacrificed at 3, 8, and 30 days after gene transfer. Apoptosis in the gastric tumors was detected by the TUNEL method to assess the efficacy of HSV-TK / GCV gene therapy, and it was marked in the 8- and 30-day treatment groups compared to the sham operation controls (P < 0.001). Various histopathological changes, degeneration of cancer tissue and fibrosis after necrosis and apoptosis were significantly greater in the 30-day treatment group. The HSV-TK gene was detectable in peripheral blood by PCR until 30 days after gene transfer. These results may be useful in devising a method of suicide gene therapy for humans.

Adenoviridae↗
PubMed2001

[Gastric cancer--novel strategy of gene therapy for gastric cancer].

Recently stage-oriented treatment for gastric cancer has been done in Japan. Endoscopic mucosal resection for intramucosal cancer and wedge resection under laparoscopy for minimal invasive cancer in the stomach have been performed. For advanced gastric cancer, extended lymph node dissection(D2) has been applied as standard treatment in Japan. However, new strategy has been required for advanced gastric cancer with distant lymph node metastasis and/or peritoneal dissemination. It is well known that gene therapy for cancer has limitation of efficacy, but we believe the new strategy will be available in post-genome era for gastric cancer treatment using 1. developing novel adenovirus, 2. usage of drug delivery system and 3. effective treatment for adverse effect.

Adenoviridae↗
PubMed2000

Hermitamides A and B, toxic malyngamide-type natural products from the marine cyanobacterium Lyngbya majuscula.

A Papua New Guinea collection of the marine cyanobacterium Lyngbya majuscula yielded two new and toxic natural products, hermitamides A (1) and B (2). The hermitamides were isolated using a brine shrimp (Artemia salina) toxicity assay. Planar chemical structures of 1 and 2 were established through 1D and 2D NMR, as well as FABMS data. Semisyntheses of hermitamides A (1) and B (2) were achieved by coupling the acid chloride derivative of 7(S)-methoxytetradec-4(E)-enoic acid (4), obtained from the same cyanobacterium collection, and the respective free amines, phenethylamine and tryptamine. Hermitamides A (1) and B (2) exhibited LD(50) values of 5 microM and 18 microM in the brine shrimp bioassay, and an IC(50) values of 2.2 microM and 5.5 microM to Neuro-2a neuroblastoma cells in tissue culture, respectively. Hermitamide A was mildly ichthyotoxic to goldfish, with an LD(50) value of 19 microM, while hermitamide B was inactive at 25 microM.

Amides↗
PubMed1999

Induction of human leukocyte antigen (HLA)-A2-restricted and MAGE-3-gene-derived peptide-specific cytolytic T lymphocytes using cultured dendritic cells from an HLA-A2 esophageal cancer patient.

BACKGROUND AND OBJECTIVES: Using peripheral blood mononuclear cells (PBMCs) from a 10-year survivor with established human leukocyte antigen (HLA)-A2(+) and MAGE-3(+) esophageal cancer cell line (KYSE-170), we examined the induction of HLA-A2-restricted and MAGE-3-gene-derived peptide (FLWGPRALV, amino acids 271-279)-specific cytolytic T lymphocytes (CTLs). METHODS: Autologous dendritic cells (DCs) cultured with granulocyte-macrophage colony stimulating factor and interleukin-4 were used as antigen presenting cells. PBMCs were stimulated by peptide-pulsed DCs in vitro. RESULTS: PBMC cocultured with FLWGPRALV-pulsed DCs could induce the relevant peptide-specific CTLs, which had tumor necrosis factor production and specific cytotoxicity against relevant peptide-pulsed autologous DCs (34%, effector:target ratio = 40:1). Moreover, they showed specific cytotoxicity against the autologous esophageal cancer cell line KYSE-170 (17%, effector:target ratio = 40:1). CONCLUSIONS: These results suggest that FLWGPRALV-pulsed cultured DCs would be a potent candidate for peptide vaccine against HLA-A2(+) and MAGE-3(+) esophageal cancer.

Antigen-Presenting Cells↗
PubMed1999

Reduction of tumorigenicity by an interferon-gamma-gene-transduced tumor on another syngeneic tumor in a murine model.

To evaluate the effect of interferon-gamma-gene-transduced cells, DS mice were inoculated into their footpads with syngeneic mammary adenocarcinoma SC42 admixed with interferon-gamma producing mammary adenocarcinoma SC115Kgamma, which had been established by an interferon-gamma-gene transduction in another syngeneic mammary adenocarcinoma SC115 using retroviral vectors. These mice rejected both tumor cells and developed resistance to subsequent challenges with either SC115 or SC42 cells inoculated into their opposite posterior footpads. These results thus indicate that systemic immunological memory to each of the independent tumor cell lines developed in these mice. Although the SC42 cells admixed with irradiated SC115Kgamma cells were rejected by these mice, the SC42 cells admixed with irradiated SC115neoR, in which the neo-gene had been transduced, were observed to proliferate. Tumor rejection was reversed by an in vivo administration of anti-interferon-gamma antibody, thus suggesting that locally produced interferon-gamma plays an important role in tumor elimination and immunological memory induction. In conclusion, interferon-gamma-gene-transduced tumor cells are therefore considered to have a therapeutic potential for other types of malignant tumor cell lines.

Adenocarcinoma↗
PubMed1999

Epithelioid trophoblastic tumor: morphological and immunohistochemical study of three lung lesions.

Epithelioid trophoblastic tumor (ETT) is a term proposed for an unusual variant of trophoblastic tumor that is closely related to choriocarcinoma but shows monomorphic growth of highly atypical trophoblastic cells instead of the typical dimorphic pattern of choriocarcinoma. We report here 3 cases of ETT, all of which were lung lesions probably originating from uterine trophoblastic disease. The antecedent pregnancies of the 3 cases were hydatidiform mole, invasive mole, and term pregnancy, respectively. The tumors were composed of highly atypical mononucleate cells, which mainly involved alveolar spaces, forming nests with central eosinophilic necrosis. Multinucleate giant cells were found within the nests, but they were fewer in number than in typical choriocarcinoma. The tumors were not associated with extensive hemorrhage or necrosis, except for 1 case, in which the ETT was combined with typical dimorphic choriocarcinoma. Immunohistochemically, multinucleate giant cells and occasional mononucleate tumor cells showed positivity for human chorionic gonadotropin. Staining for human placental lactogen was positive in rare multinucleate giant cells, and in 1 case, tumor cells showed diffuse positivity for placental alkaline phosphatase. Because ETT has a remarkably epithelioid appearance in cytological and architectural features, differentiation from the epithelial malignancies is problematic. Trophoblastic markers are frequently expressed in nontrophoblastic tumors, and reactivity for those markers alone is not sufficient for exclusion of other tumors. Rather, evidence of ETT comes from a combination of morphological features, immunohistochemical study, and clinical history.

Adult↗
PubMed1999

In situ gene transfer and suicide gene therapy of gastric cancer induced by N-ethyl-N'-nitro-N-nitrosoguanidine in dogs.

Gene therapy could potentially revolutionize the treatment of gastrointestinal (GI) tract cancer. The aim of this study was to establish a practical method of gene transfer which would be applicable to human gastric cancer. Retrovirus or/and adenovirus vectors carrying the lacZ marker gene were transferred in situ by needle through an endoscopic biopsy channel into primary gastric cancer in six male beagle dogs that had been treated with N-ethyl-N'-nitro-N-nitrosoguanidine (ENNG). In addition, an adenovirus vector carrying the herpes simplex virus thymidine kinase (Ad.CAGHSV-TK) gene was introduced in situ into cancer tissues in the stomach of three dogs, and the animals were treated with intravenous ganciclovir (GCV). Retrovirus-producing cells which expressed the lacZ gene were specifically localized to the injection site in the stomach. The lacZ gene was more widely transferred into the tumor by the adenovirus vector than by retrovirus-producing cells. Improvement of the needle used for gene transfer and the use of multiple injections per tumor led to more diffuse transfer of the vector into the tumor. The Ad.CAGlacZ gene was also transferred into regional lymph nodes of the stomach. Moderate to diffuse degeneration of the primary cancer tissues of the stomach was found after Ad.CAGHSV-TK/GCV gene therapy. Moreover, almost complete tissue degeneration was observed in the regional lymph nodes of the stomach. An adverse effect of HSV-TK/GCV gene therapy was acute hepatotoxicity, which was not found after Ad.CAGlacZ gene transfer, but was found after high-titer Ad.CAGHSV-TK gene transfer followed by GCV. These findings suggest that in situ gene transfer of a suicide gene followed by prodrug treatment may be applicable not only to primary tumors, but also to lymph node metastases of gastric cancer, though further study of both beneficial and adverse effects is required before clinical usage.

Adenoviridae↗
PubMed1999

Prognostic values of MUC-1 molecule expressing cytokine receptor-like epitope and DF3 in patients with gastric carcinoma.

As recently reported, DF3/MUC-1 molecules having cytokine receptor-like sequences (CRL) at the extracellular region, are likely to function in signal transduction pathways. To elucidate the functional significance of CRL expressed on the DF3/MUC1 molecule, immunohistochemical localization of CRL and/or DF3 was investigated in cases of 115 patients with gastric carcinomas, treated by surgical resection. CRL was detected in 65 of 115 patients (56.5%), DF3 in 85 (73.9%), and both DF3 and CRL in 52 (45.2%). The combined immunohistochemical analysis of CRL and/or DF3, revealed that simultaneous expression of DF3 and CRL (DF3+/CRL+) significantly correlated to lymph node metastasis and to blood vessel invasion, and that patients with DF3+/CRL+-tumors survived for a significantly shorter period after surgery than did the other three groups (DF3+/CRL-, DF3-/CRL+, and DF3-/CRL-). Multivariate analysis showed independent prognostic significance for DF3+/CRL+ expression (hazard ratio [HR]=2.733, P=0.0085), and surgical cure (HR=4.334, P=0.003). To investigate the biological role of the simultaneous expression of DF3 and CRL, we constructed DF3-/CRL+ (NR-MC-38) and DF3+/CRL+ (R-MC-38) cells by transducing a mouse colon adenocarcinoma cell line MC-38 expressing neither DF3 nor CRL with MUC-1 cDNA containing ten tandem repeats (R-MC-38) or MUC-1 cDNA devoid of tandem repeats (NR-MC-38). R-MC-38 (DF3+/CRL+) cells were more invasive than NR-MC-38 (DF3-/CRL+) and MC-38 (DF3-/CRL-) cells. When these transfectants were incubated with pAb CRL, the invasiveness of R-MC-38 (DF3+/CRL+) was strikingly elevated over the case with native MC-38 (DF3-/CRL-) and NR-MC-38 (DF3-/CRL+) cells. The pAb CRL-induced invasiveness of R-MC-38 cells was inhibited by adding mAb DF3 or CRL peptides together with pAb CRL. These results suggest that an expression of DF3/MUC1 is highly associated with cell-invasiveness, and the DF3/MUC1-associated invasiveness is amplified by CRL. Thus DF3+/CRL+-MUC-1 molecule seems to be closely involved in a poor prognosis for gastric cancer patients.

Adult↗
PubMed1999

Presence of RON receptor tyrosine kinase and its splicing variant in malignant and non-malignant human colonic mucosa.

The presence of RON and its variant isoform in malignant and non-malignant human colonic tissues was examined by immunohistochemistry using paraffin-embedded sections and RT-PCR analysis followed by direct sequencing of PCR product using RNAs isolated from frozen tissues. In normal colonic mucosa, RON was uniformly expressed in crypt cells, especially in the bottom of crypta. On the other hand, the expression was distributed heterogeneously in adenomas and in colon cancer. The expression of RON was significantly related to the degree of differentiation of colon cancer and the deletion of the expression was observed in colon cancer specimens with high incidence. The RT-PCR analysis of RNA isolated from non-malignant and malignant colonic tissue revealed the presence of two RON mRNA isoforms with 432-bp and 286-bp. Direct sequencing of major product of 432-bp was revealed to be identical to that of human wild-type RON. On the other hand, major product of 286-bp was revealed to be almost identical to that of a splicing variant of RON transcript which has been found in human gastric cancer cell line, KATO-III. The results obtained in this study may indicate that both wild-type RON and its variant isoform play an important role in regulating the normal function of colonic mucosa such as differentiation and motile activity and the expression of both wild-type RON and its variant isoform could be considered to be reduced during malignancy of human colonic mucosa.

Adenocarcinoma↗