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Biomedical subjects

S Okabe

Publications and source records attributed to S Okabe.

At least 181 records · Page 10Linked to original sources
PubMed1996

A new process of cancer prevention mediated through inhibition of tumor necrosis factor alpha expression.

Mechanisms of cancer prevention were studied using structurally different cancer-preventive agents, sarcophytol A, canventol, (-)-epigallo-catechin gallate, and tamoxifen, based on our evidence that tumor necrosis factor alpha (TNF-alpha) acts as an endogenous tumor promoter relevant to human carcinogenesis. Pretreatment with the four preventive agents commonly inhibited TNF-alpha mRNA expression and TNF-alpha release in BALB/3T3 cells induced by a tumor promoter, okadaic acid, whereas the expression of early response genes (c-jun, junB, c-fos, and fosB) was enhanced. These results strongly suggest that inhibition of TNF-alpha mRNA expression and its release is a new process of cancer prevention.

3T3 Cells↗
PubMed1996

Adenovirus-mediated prodrug gene therapy for carcinoembryonic antigen-producing human gastric carcinoma cells in vitro.

We analyzed the ability of a recombinant replication-defective adenovirus vector with the carcinoembryonic antigen (CEA) promotor to transfer the thymidine kinase gene of herpes simplex virus (HSVtk) into gastric cancer cells to confer sensitivity to ganciclovir (GCV). CEA-producing gastric cancer cell lines (MKN28 and MKN45), a CEA-nonproducing gastric cancer cell line (MKN1), and a human uterine cervical cancer cell line (HeLa) were infected with a recombinant adenovirus carrying lacZ reporter gene coupled to the CEA promoter (AdCEAlacZ). The efficiency of AdCEAlacZ-mediated gene transfer was correlated with the amount of CEA produced by each cell line. Furthermore, the 50% growth inhibitory concentrations (IC50) of GCV were 21 and 5.8 microm for MKN28 and MKN45, respectively, when infected with a recombinant adenovirus carrying the HSVtk gene coupled to the CEA promoter (AdCEAtk). However, MKN1 and HeLa cells infected with AdCEAtk remained resistant to GCV (IC50 > 300 microm of GCV). In addition, a bystander killing effect was demonstrated against MKN45 cells when only 20% of AdCEAtk-infected cells were mixed with uninfected cells. These data indicate the potential for targeted gene therapy using the cell type-specific promotor of the CEA gene against gastric cancers that produce CEA.

Adenoviridae↗
PubMed1996

In vivo antitumor effect of cytotoxic T lymphocytes engineered to produce interferon-gamma by adenovirus-mediated genetic transduction.

Immunotherapy with adoptive transfer of genetically-modified cytotoxic T lymphocytes (CTL) is a promising approach for cancer gene therapy. We developed an adoptive therapy model with murine tumor-specific CTL, to which very efficient (up to 100%) gene introduction was achieved by using recombinant adenoviral vectors. Through a comparative study on the antitumor effects of CTL genetically modified with cytokine genes, transduction with interferon-gamma gene resulted in a prominent increase in therapeutic efficacy of CTL in both metastatic and subcutaneous tumor models. Further additive effect was obtained by the adoptive cellular therapy in combination with vaccination of cytokine gene-modified tumor cells. Our findings provide a hopeful strategy of adoptive immunotherapy for human cancers.

Adenoviridae↗
PubMed1996

Comparison of the primary structure of waxy proteins (granule-bound starch synthase) between polyploid wheats and related diploid species.

The waxy proteins encoded by the genomes A, B, and D in polyploid wheats and related diploid species were isolated by SDS-PAGE. The N-terminal amino acid sequences of mature proteins and V8 protease-induced fragments were determined. A total of five amino acid substitutions was detected in these sequences, which represent about 10% of the whole sequences of the waxy proteins. A comparison of these sequences in polyploid wheats with those in related diploid species revealed the following: (i) waxy proteins encoded by the A genome of polyploid wheats were identical to that of Triticum monococcum, (ii) the waxy protein encoded by the B genome of T. turgidum was identical to that of T. searsii, but differed from those of T. speltoides and T. longissimum by one amino acid substitution, (iii) the waxy protein encoded by the B genome of T. aestivum differed from that encoded by the B genome of T. turgidum by one amino acid substitution, and (iv) the waxy protein encoded by the D genome of T. aestivum was identical to that of T. tauschii.

Amino Acid Sequence↗
PubMed1996

Designing of chimeric DNA/RNA hammerhead ribozymes to be targeted against AML1/MTG8 mRNA.

For therapeutic purposes, two chimeric DNA/RNA hammerhead ribozymes were synthesized to cleave AML1/MTG8, the t(8;21)-associated fusion mRNA of acute myeloid leukemia. One ribozyme, A/MRZ-1, recognizes the area adjacent to the fusion point between AML1 and MTG8, and cleaves six bases downstream from this point. The other, MRZ-1, recognizes the MTG8 sequence. Both ribozymes cleaved synthetic chimeric DNA/RNA substrates at theoretical sites. Neither cleaved AML1 RNA. A/MRZ-1 cleaved only AML1/MTG8 RNA, and MRZ-1 cleaved both AML1/MTG8 and MTG8 RNAs. The two ribozymes showed growth inhibition of an acute myeloid leukemia cell line carrying t(8;21), SKNO-1 cells. The same extent of growth inhibition was attained by antisense oligonucleotides against AML1/MTG8 RNA. The results suggest that the ribozyme has the potential to be developed as a useful agent for gene therapy, in particular for leukemia with t(8;21).

Antineoplastic Agents↗
PubMed1996

Pathways mediating pentagastrin-induced mucosal blood flow response in rat stomachs.

The mechanisms of pentagastrin-induced gastric mucosal blood flow (GMBF) response were investigated in anesthetized rats. A rat stomach was mounted on an ex vivo chamber, perfused with saline, and GMBF was measured by a laser Doppler flowmetry simultaneously with acid secretion. Pentagastrin infused intravenously produced a dose-dependent increase of GMBF as well as acid secretion, and its effect reached a maximum at 120 microgram/kg/hr (maximal dose). Pretreatment with omeprazole (60 mg/kg, intraperitoneally) completely inhibited the acid secretory response and the enhancement of GMBF induced by both submaximal (60 micrograms/kg/hr) and maximal doses of pentagastrin. In contrast, the luminal perfusion with glycine (200 mM) to remove luminal H+ almost totally attenuated the increase of GMBF caused by the submaximal dose of pentagastrin, without any effect on acid secretion, but partially suppressed such GMBF responses caused by the maximal dose. Subcutaneous pretreatment with indomethacin, a cyclooxygenase inhibitor, significantly mitigated GMBF response caused by both submaximal and maximal doses of pentagastrin, whereas 8-phenyltheophylline (8-PT), an adenosine antagonist, showed a significant inhibition of GMBF response caused by only the maximal dose. However, the combined administration of 8-PT with glycine perfusion further attenuated GMBF response caused by the maximal dose of pentagastrin, and the additional treatment with indomethacin completely blocked this this GMBF response. We conclude that pentagastrin-induced GMBF responses are mediated by at least two different pathways; one is related to luminal H+ and the other to the parietal cell activity, depending on the dose of pentagastrin. In addition, the latter pathway may be mediated by adenosine, while endogenous prostaglandins may be involved in both pathways.

Animals↗
PubMed1996

Stimulatory effects of sucralfate on secretion and synthesis of mucus by rabbit gastric mucosal cells. Involvement of phospholipase C.

We examined the effects of sucralfate on the secretion and synthesis of mucus by cultured rabbit gastric mucosal cells, and the underlying intracellular mechanism. Treatment of mucosal cells with sucralfate (>0.5 mg/ml) for 4 and 8 hr caused a significant increase in the inositol triphosphate (IP3) content in the cells. Neomycin (a phospholipase C inhibitor) at 1 mM markedly inhibited the sucralfate-induced increases in both the IP3 content and mucus secretion and synthesis. Neither 10 nM staurosporine, 1 mM H-7 (protein kinase C inhibitors), nor 5 microM indomethacin (a cyclooxygenase inhibitor) affected the stimulatory effects of sucralfate on mucus secretion and synthesis, but 10 microM TMB-8 (an antagonist of intracellular Ca2+ mobilization)abolished its effects. Taken together, these results demonstrate that sucralfate acts directly an gastric mucosal cells, inducing increases in mucus secretion and synthesis, and that sucralfate causes an increase in the IP3 content, probably through activation of phospholipase C, and the subsequent IP3-elicited Ca2+ mobilization may be involved in the stimulatory effects of sucralfate.

Animals↗
PubMed1996

Giant degenerative perineurial cell tumor.

We report a case of giant perineurial cell tumor, probably benign, with extensive degenerative changes. The secondary changes were reminiscent of those in giant ancient neurilemomas. To our knowledge, there has been no documentation of the imaging features in perineurioma. The MR findings of the present tumor, especially on T2-weighted images, correlated well with the histologic appearance.

Aged↗
PubMed1996

Vasoinhibitory effect of leminoprazole, a H+,K(+)-ATPase inhibitor, on rat aortic rings.

1. In isolated rat aortic rings, leminoprazole (2-[2-N-methyl-N-(2-methylpropyl)amino]benzylsulfinyl benzimidazole) (10(-6) - 10(-4) M) inhibited contractile responses to phenylephrine (PE), KCl and Ca2+ in KCl-depolarized tissues in a Ca2+ free medium. Leminoprazole also relaxed the aorta contracted by PE and KCl. 2. The relaxing effect of leminoprazole was markedly inhibited by nifedipine and verapamil (inhibitors of voltage operated Ca2+ channels). Relaxation induced by verapamil, but not by nifedipine, was inhibited by pre-treatment by leminoprazole. 3. The relaxing effect of leminoprazole was also inhibited by NG-monomethyl-L-arginine (a nitric oxide synthase inhibitor), methylene blue (a guanylate cyclase inhibitor) or endothelium removal but not by indomethacin (a cyclooxygenase inhibitor), glyburide (a KATP channel inhibitor) or iberiotoxin (a KCa channel inhibitor). 4. Zaprinast (a cGMP-phosphodiesterase inhibitor) also inhibited the relaxing action of leminoprazole. In addition, relaxation induced by nitroglycerin was potentiated by leminoprazole. 5. Further, in the presence of methylene blue, residual relaxation induced by leminoprazole was still potentiated by verapamil. 6. These results suggest that the vasoinhibitory effect of leminoprazole in rat aortic rings is due to the increased level of cGMP through inhibition of cGMP-phosphodiesterase and also due to inhibition of voltage operated Ca2+ channels.

Animals↗
PubMed1996

Development of neuronal precursor cells and functional postmitotic neurons from embryonic stem cells in vitro.

To understand the mechanism of the sequential restriction of multipotency of stem cells during development, we have established culture conditions that allow the differentiation of neuroepithelial precursor cells from embryonic stem (ES) cells. A highly enriched population of neuroepithelial precursor cells derived from ES cells proliferates in the presence of basic fibroblast growth factor (bFGF). These cells differentiate into both neurons and glia following withdrawal of bFGF. By further differentiating the cells in serum-containing medium, the neurons express a wide variety of neuron-specific genes and generate both excitatory and inhibitory synaptic connections. The expression pattern of position-specific neural markers suggests the presence of a variety of central nervous system (CNS) neuronal cell types. These findings indicate that neuronal precursor cells can be isolated from ES cells and that these cells can efficiently differentiate into functional post-mitotic neurons of diverse CNS structures.

Animals↗
PubMed1996

In vitro catalytic activities of DNA/RNA chimeric hammerhead ribozymes against AML1-MTG8 mRNA, a fused gene transcript in acute myeloid leukemia with t(8;21).

In order to design the best construct for therapeutic hammerhead ribozymes against AML1-MTG8, the t(8;21)-associated fusion mRNA of acute myeloid leukemia, we synthesized DNA/RNA chimeric ribozymes directed to the area adjacent to the fusion point between AML1 and MTG8. Catalytic efficiency and fusion gene specificity of ribozymes were examined by kinetic studies of the cleavage reactions of AML1-MTG8, AML1, and MTG8 RNAs transcribed in vitro. Ribozyme 2 (Rz2) specifically cleaved AML1-MTG8 RNA at three nucleotides downstream of the fusion junction with high efficiency. The highest cleavage efficiency was achieved by Rz4.3, which targeted non-contiguous sequences and cleaved at 19 nucleotides downstream of the fusion junction. Rz4.3 also cleaved MTG8 RNA but the cleavage efficiency was three orders of magnitude lower than that for AML1-MTG8 RNA. Therefore, Rz4.3 and Rz2 are the proper ribozymes for in vivo application to modulate gene expression of the AML1-MTG8.

Acute Disease↗
PubMed1996

Tumor-specific gene expression in carcinoembryonic antigen--producing gastric cancer cells using adenovirus vectors.

BACKGROUND & AIMS: An increase of carcinoembryonic antigen (CEA) expression is noted in about 40% of patients with gastric cancer. Adenovirus-mediated gene therapy using the CEA promoter was investigated as a way to specifically target human CEA-producing gastric tumors. METHODS: Recombinant adenovirus vectors carrying a CEA promoter linked to the lacZ gene (AdCEA lacZ) or the cytosine deaminase gene (AdCEA-CD) were constructed. After infection with these vectors, CEA-producing (MKN45 and MKN28) and non-CEA-producing (MKN1) gastric cancer cells were analyzed for transgene expression and sensitivity to 5-fluorocytosine. RESULTS: The lacZ gene was expressed selectively in CEA-producing AdCEA-lacZ-infected cells in vitro and in vivo. Transduction of the vector containing the CEA-regulated cytosine deaminase gene (AdCEA-CD) resulted in extraordinary sensitivity of MKN45 and MKN28 cells to 5-fluorocytosine. This effect was not observed in MKN1 cells. Moreover, AdCEA-CD-infected MKN45 cells showed a profound in vitro neighbor cell killing effect in the presence of 5-fluorocytosine. This effect was attributed to the diffusion of 5-fluorouracil, resulting from conversion of 5-fluorocytosine to 5-fluorouracil by the cytosine deaminase-expressing cells. CONCLUSIONS: The results of this study suggest that use of a CEA promoter in an adenovirus vector could confer selective expression of the cytosine deaminase gene in CEA-producing gastric cancer cells, rendering the transduced cells susceptible to 5 fluorocytosine. This system may be useful in gene therapy that targets CEA-producing gastric carcinomas.

Adenoviridae↗
PubMed1996

Anti-cancer effects of morphine through inhibition of tumour necrosis factor-alpha release and mRNA expression.

Morphine is mainly used to relieve pain in the terminal stage of cancer patients. We found that morphine has inhibitory effects on growth of various human cancer cell lines, with IC50 from 2.7 to 8.8 mM, and BALB/3T3 cells, with IC50 of 1.5 mM. Although the IC50 values were relatively high, we decided to study the mechanisms of anti-carcinogenic effects of morphine. Morphine inhibited activation of protein kinase C induced by teleocidin, one of the 12-O-tetradecanoylphorbol-13-acetate (TPA)-type tumour promoters (IC50, 1 mM). Based on our previous evidence that tumour necrosis factor-alpha (TNF-alpha) acts as an endogenous tumour promoter on BALB/3T3 cells initiated with 3-methylcholanthrene, we found that morphine dose-dependently inhibited TnF-alpha release from KATO III cells (IC50, 5.6 mM) and also from BALB/3T3 cells (IC50, 1.3 mM) induced by okadaic acid, one of the non-TPA type tumour promoters. Moreover, morphine inhibited expression of TNF-alpha mRNA in BALB/3T3 cells (IC50, 1.6 mM), but not expression of early response genes. Morphine may improve condition of cancer patients by suppression of tumour growth and reduction of amounts of an endogenous tumor promoter, TNF-alpha, in tissues. The high dosage of morphine required to induce anticarcinogenic effects is also discussed.

3T3 Cells↗
PubMed1996

Role of 5HT1 receptors in the control of hypoglossal motoneurons in vivo.

Recordings from serotonin (5HT)-containing neurons of the brainstem suggest that their effects on upper airway, including hypoglossal (XII), motoneurons are maximal during wakefulness and minimal during rapid eye movement (REM) sleep. Several distinct 5HT receptors are present in the XII nucleus. In this study, we assessed the effects mediated by type 1 receptors. We microinjected 5HT1 receptor agonists or antagonists into the XII nucleus of anesthetized, paralyzed, vagotomized, and artificially ventilated rats and observed the resulting changes in XII nerve activity. Both CGS-12066 and 8-OH-DPAT (5HT1B and 5HT1A receptor agonists, respectively) suppressed XII nerve activity in a dose-dependent manner by about 20%. MAN-190, a putative 5HT1A receptor antagonist, had no effect, Based on the relative potencies of the two agonists, we conclude that they may both act through 5HT1B receptors and that 5HT1A receptors are absent from the XII nucleus of adult rats. If the effects mediated by 5HT1B receptors are endogenously active, their withdrawal during REM sleep may to some degree counterbalance the disfacilitation of XII motoneurons resulting from the withdrawal of their 5HT-mediated postsynaptic excitation.

Animals↗
PubMed1996

A case of cutaneous malignant fibrous histiocytoma.

A 54-year-old Japanese man with cutaneous malignant fibrous histiocytoma on the back is reported. He not only had a past history of thyroid cancer 1 year prior to the onset of the skin tumor, but also had simultaneous bladder cancer. Despite the early, wide resection, the prognosis was rapid and progressive. Histologically, the primary lesion of the skin tumor was difficult to differentiate from dermatofibrosarcoma protuberans; however, the recurrent and the metastatic lesions changed in appearance.

Fatal Outcome↗
PubMed1996

Anti-tumor promoting activity of canventol and its synthetic analogs through inhibition of protein isoprenylation.

Canventol, a synthetic compound, is a new inhibitor of tumor promotion on mouse skin by okadaic acid. We previously reported that canventol acts by inhibiting both protein isoprenylation and tumor necrosis factor-alpha (TNF-alpha) release. In this study we examined the potencies of 10 newly synthesized canventol analogs through their effect on mevalonate metabolism, and then examined 3 representative analogs for inhibition of protein isoprenylation. Since canventol in vitro did not directly inhibit farnesyl protein transferase or geranylgeranyl protein transferase-I, the effects of canventol and its synthetic analogs on the fate of [3H]mevalonate in cells were studied. Canventol at 500 microM changed the ratio of newly synthesized sterols (cholesterol and lathosterol) to ubiquinones from 0.7 to 8.2 in NIH/3T3 cells which had previously been labeled with [3H]mevalonate, suggesting that the altered pattern of mevalonate metabolism is associated with inhibition of protein isoprenylation in the cells. We named this ratio the inhibition of protein isoprenylation index (IPI index). The 10 analogs showed a wide range of IPI indices. Two analogs, S3 and S9 had effects similar to, or stronger than, canventol. Three analogs, C44, C46 and C47, with lower IPI indices, inhibited tumor promotion on mouse skin slightly less than canventol itself did. This study shows that inhibition of protein isoprenylation in the cells, indicated by an increase in the IPI index, is a new biomarker for estimating inhibition of tumor promotion.

3T3 Cells↗