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286 results on '"Kontani, K"'

2. Development of the hybrid electric field meter for simultaneous measuring of vertical and horizontal electric fields of the thundercloud

Author

Tantisattayakul, T., Masugata, K., Kitamura, I., and Kontani, K.

Subjects
Electric fields -- Research, Electric discharges -- Research, Electric discharges through gases -- Research, Electric measurements, Business, Computers, Electronics, Electronics and electrical industries
Abstract

This correspondence presents a development of hybrid electric field meter methodology. This particular field meter can simultaneously measure the vertical and horizontal electric fields of the thundercloud. The additional horizontal electric field provides the useful information of the direction of thunderclouds. The capability of the apparatus was experimentally evaluated and has been confirmed that it has the satisfactory sensitivity to both components of electric field. Additionally, an instance of observation results of the cloud-to-ground and ground-to-cloud lightning discharge has been presented. Index Terms--Electric field measurement, hybrid electric field meter (HEM), lightning discharge, thundercloud.

Published
2006

8. Active Transport and Diffusion Barriers Restrict Joubert Syndrome-Associated ARl 13B/ARL-13 to an Inv-like Ciliary Membrane Subdomain

Author

Cevik, S., Sanders, A.A., Wijk, E. van, Boldt, K., Clarke, L., Reeuwijk, J. van, Hori, Y., Horn, N., Hetterschijt, L., Wdowicz, A., Mullins, A., Kida, K., Kaplan, O.I., Beersum, S.E.C. van, Wu, K., Letteboer, S.J.F., Mans, D.A., Katada, T., Kontani, K., Ueffing, M., Roepman, R., Kremer, H., Blacque, O.E., Cevik, S., Sanders, A.A., Wijk, E. van, Boldt, K., Clarke, L., Reeuwijk, J. van, Hori, Y., Horn, N., Hetterschijt, L., Wdowicz, A., Mullins, A., Kida, K., Kaplan, O.I., Beersum, S.E.C. van, Wu, K., Letteboer, S.J.F., Mans, D.A., Katada, T., Kontani, K., Ueffing, M., Roepman, R., Kremer, H., and Blacque, O.E.

Abstract

Contains fulltext : 125199.pdf (publisher's version ) (Open Access)

Published
2013

9. Retrospective analysis of the survival benefit of chemotherapy for recurrent or advanced epithelial ovarian carcinoma in patients previously treated with paclitaxel plus platinum-based chemotherapy.

Author

Nishikawa, A., Hashimoto, H., Takeda, M., Kontani, K., Miyatake, T., Mimura, M., Nagamatsu, M., and Yokoi, T.

Abstract

Aim: The outcomes of treatment for women with recurrent or advanced epithelial ovarian carcinoma previously treated with paclitaxel plus platinum-based chemotherapy were analyzed. Materials and Methods: Retrospective analysis was performed in a total of 65 series of treatments provided for 35 patients with a history of paclitaxel plus platinum-based chemotherapy. The chemotherapy regimens used were classified into the following four types for analysis: conventional paclitaxel plus carboplatin therapy (TC arm), pegylated liposomal doxorubicin-containing regimens (PLD arm), CPT-11-containing regimens (CPT-11 arm), and others. Disease-control rates (DCRs) were compared and subjected to univariate analysis. Progression-free survival (PFS) was determined from the date of the first cycle of each chemotherapy with the Kaplan-Meier method, and comparisons were performed using the log-rank test. Results: DCR was 80%, 71%, and 26% for the TC, PLD, and CPT-11 arms, respectively. The median PFS was 286, 372, and 76 days for the TC, PLD, and CPT-11 arms, respectively. There was no discernible difference in PFS between the TC and the PLD arm. In contrast, PFS of the CPT- 11 arm was significantly shorter than that of the TC and PLD arms. In addition, three of seven (42.9%) treatments in the PLD arm maintained a progression-free period for longer than one year, while only one of 25 (4%) treatments in the TC arm maintained a progression- free period for more than one year. Conclusions: The PFS of PLD is similar to that of TC. PLD-containing regimens might have a potential benefit with a higher PFS over one year than the TC regimen. [ABSTRACT FROM AUTHOR]

Published
2016
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10. Mapping of the catalytic and epitopic sites of human CD38/NAD+ glycohydrolase to a functional domain in the carboxyl terminus

Author

Shinichi Hoshino, Kukimoto, I., Kontani, K., Inoue, S., Kanda, Y., Malavasi, F., and Katada, T.

Subjects
Membrane Glycoproteins, Immunology, ADP-ribosyl Cyclase 1, Antigens, Differentiation, Catalysis, Peptide Fragments, Cell Line, Protein Structure, Tertiary, Antigens, CD, Mutagenesis, Tumor Cells, Cultured, Immunology and Allergy, Animals, Humans, ADP-ribosyl Cyclase, N-Glycosyl Hydrolases, Epitope Mapping
Abstract

We reported that 1) ecto-NAD+ glycohydrolase (NADase) activity induced upon differentiation of HL-60 cells is localized on the extracellular carboxyl-terminal side of CD38 and that 2) CD38 ligation by specific mAbs is followed by protein tyrosine phosphorylation in the cells. The strategy selected for identifying the relevant catalytic domains of the molecule relies upon the production in COS-7 cells of carboxyl-terminal deletion mutants of CD38. The mutants with fewer than 15 amino acids deleted at the carboxyl terminus of the 300-amino acid wild-type molecule maintained NADase activity, whereas those with more than 27 amino acids deleted did not. The general inference is that the carboxyl-terminal 273-285 sequence bears the site of enzyme activity. Introduction of site-directed mutation of a conserved cysteine residue (Cys275), located in the 273-285 sequence, completely abolished NADase activity. The second issue resolved in this work is the definition of an epitope of the agonistic anti-CD38 mAbs. To this aim, a panel of selected anti-CD38 mAbs was tested using these mutants and various CD38 fragments as the target in immunoblot analyses. All of the epitopes recognized by mAbs inducing protein tyrosine phosphorylation were mapped on an identical site containing the carboxyl-terminal sequence of 273-285. The conclusion is that the discrete carboxyl-terminal sequence identified in the present study not only plays a key role in its ecto-NADase activity, but actually constitutes the epitopes exploited by the agonistic anti-CD38 mAbs for transmembrane signaling.

Published
1997

13. Tissue-specific suppressor T cells involved in self-tolerance are activated extrathymically by self-antigens

Author

Taguchi, O, Kontani, K, Ikeda, H, Kezuka, T, Takeuchi, M, and Takahashi, T

Subjects
Male, Mice, Inbred A, Prostate, Thymus Gland, Lymphocyte Activation, Autoantigens, T-Lymphocytes, Regulatory, Autoimmune Diseases, Prostatitis, Mice, Inbred C57BL, Mice, Immune Tolerance, Animals, Female, Spleen, Research Article, Autoantibodies
Abstract

Autoimmune prostatitis developed spontaneously in (C57BL/6N x A/J)F1 (B6A) mice, when thymectomy (Tx) was conducted on day 3 after birth (Tx-3). The lesion could be prevented by a single injection of CD4+ spleen cells (4 x 10(6)) from normal males, but not from normal females or newborn orchidectomized (Orx-0) mice. However, when spleen cells were obtained from Orx-0 mice that had received a dihydrotestosterone (DHT) pellet when adult to develop a mature prostate, prostatitis could be prevented, suggesting that immune tolerance to prostate antigen(s) is maintained by a CD4+ tissue-specific suppressor T cell (Ts) population(s), which is activated by a specific autoantigen(s) in the mature prostate. The result that even CD4+ cells from Orx-0 mice that were thymectomized as adults and treated thereafter with DHT were effective for prevention of prostatitis suggests that activation of this Ts population takes place in the peripheral lymphoid organs, and that it maintains peripheral tolerance to autoantigen in the prostate of these mice and probably also in normal mice.

Published
1994

39. NCC-ST-439

Author

Narita, T., primary, Funahashi, H., additional, Kontani, K., additional, and Kannagi, R., additional

Published
1994
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44. RASSF7 negatively regulates pro-apoptotic JNK signaling by inhibiting the activity of phosphorylated-MKK7.

Author

Takahashi, S., Ebihara, A., Kajiho, H., Kontani, K., Nishina, H., and Katada, T.

Subjects
RAS proteins, APOPTOSIS, PHYSIOLOGICAL control systems, CELL death, PROTEIN kinases, CARCINOGENESIS, CELLULAR signal transduction
Abstract

Members of the Ras-association domain family (RASSF) of proteins influence apoptosis and cell cycling but little is known about the mechanisms. Here, we show that RASSF7 interacts with N-Ras and mitogen-activated protein kinase kinase 7 (MKK7) to negatively regulate c-Jun N-terminal kinase (JNK) signaling. Stress-induced JNK activation and apoptosis were markedly enhanced in cells depleted of RASSF7 or N-Ras by RNAi knockdown. An interaction with RASSF7 promoted the phosphorylated state of MKK7 but inhibited this kinase's ability to activate JNK. RASSF7 required its RA domain for both interaction with GTP-bound N-Ras and the anti-apoptotic response to stress stimuli. Following prolonged stress, however, RASSF7's anti-apoptotic effect was eliminated because of degradation of RASSF7 protein via the ubiquitin-proteasome pathway. Our results indicate that RASSF7 acts in concert with N-Ras to constitute a stress-sensitive temporary mechanism of apoptotic regulation. With initial stress, RASSF7/N-Ras promotes cell survival by inhibiting the MKK7/JNK pathway. However, with prolonged stress, RASSF7 protein undergoes degradation that allows cell death signaling to proceed. Our findings may account for the association of elevated RASSF7 with tumorigenesis. [ABSTRACT FROM AUTHOR]

Published
2011
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46. Tissue-specific suppressor T cells involved in self-tolerance are activated extrathymically by self-antigens.

Author

Taguchi, O., Kontani, K., Ikeda, H., Kezuka, T., Takeuchi, M., and Takahashi, T.

Subjects
*PROSTATITIS, *AUTOIMMUNE diseases, *THYMECTOMY, *SPLEEN, *IMMUNOLOGICAL tolerance, *SUPPRESSOR cells
Abstract

Autoimmunc prostatitis developed spontaneously in (C57BL/6N × A/J)F1 (B6A) mice, when thymectomy (Tx) was conducted on day 3 after birth (Tx-3). The lesion could be prevented by a single injection of CD4+ spleen cells (4 × 106) from normal males, but not from normal females or newborn orehidectomized (Orx-0) mice. However, when spleen cells were obtained from Orx-0 mice that had received a dihydrotestosterone (DHT) pellet when adult to develop a mature prostate, prostatitis could be prevented, suggesting that immune tolerance to prostate antigen(s) is maintained by a CD4+ tissue-specific suppressor T cell (Ts) population(s), which is activated by a specific autoantigen(s) in the mature prostate. The result that even CD4+ cells from Orx-0 mice that were thymectomized as adults and treated thereafter with DHT were effective for prevention of prostatitis suggests that activation of this Ts population takes place in the peripheral lymphoid organs, and that it maintains peripheral tolerance to autoantigen in the prostate of these mice and probably also in normal mice. [ABSTRACT FROM AUTHOR]

Published
1994

47. Increase of cGMP, cADP-ribose and inositol 1,4,5-trisphosphate preceding Ca(2+) transients in fertilization of sea urchin eggs.

Author

Kuroda, R, Kontani, K, Kanda, Y, Katada, T, Nakano, T, Satoh, Y, Suzuki, N, and Kuroda, H

Abstract

Transient increases, or oscillations, of cytoplasmic free Ca(2+) concentration, [Ca(2+)](i), occur during fertilization of animal egg cells. In sea urchin eggs, the increased Ca(2+) is derived from intracellular stores, but the principal signaling and release system involved has not yet been agreed upon. Possible candidates are the inositol 1,4,5-trisphosphate receptor/channel (IP(3)R) and the ryanodine receptor/channel (RyR) which is activated by cGMP or cyclic ADP-ribose (cADPR). Thus, it seemed that direct measurements of the likely second messenger candidates during sea urchin fertilization would be essential to an understanding of the Ca(2+) signaling pathway. We therefore measured the cGMP, cADPR and inositol 1,4,5-trisphosphate (IP(3)) contents of sea urchin eggs during the early stages of fertilization and compared these with the [Ca(2+)](i) rise in the presence or absence of an inhibitor against soluble guanylate cyclase. We obtained three major experimental results: (1) cytosolic cGMP levels began to rise first, followed by cADPR and IP(3) levels, all almost doubling before the explosive increase of [Ca(2+)](i); (2) most of the rise in IP(3) occurred after the Ca(2+) peak; IP(3) production could also be induced by the artificial elevation of [Ca(2+)](i), suggesting the large increase in IP(3) is a consequence, rather than a cause, of the Ca(2+) transient; (3) the measured increase in cGMP was produced by the soluble guanylate cyclase of eggs, and inhibition of soluble guanylate cyclase of eggs diminished the production of both cADPR and IP(3) and the [Ca(2+)](i) increase without the delay of Ca(2+) transients. Taken together, these results suggest that the RyR pathway involving cGMP and cADPR is not solely responsible for the initiating event, but contributes to the Ca(2+) transients by stimulating IP(3) production during fertilization of sea urchin eggs.

Published
2001

49. Molecular mechanism of human CD38 gene expression by retinoic acid. Identification of retinoic acid response element in the first intron.

Author

Kishimoto, H, Hoshino, S, Ohori, M, Kontani, K, Nishina, H, Suzawa, M, Kato, S, and Katada, T

Abstract

CD38 is a nonlineage-restricted type II transmembrane glycoprotein possessing ecto-NAD+ glycohydrolase activity. Because of its unique expression pattern in lymphocyte differentiation, it appears to function as an immunoregulatory molecule. We previously reported that CD38 was specifically induced by all-trans-retinoic acid (RA) in human promyelocytic leukemia HL-60 cells. Here we studied the molecular mechanism of the RA-dependent induction of human CD38. The expression of CD38 mRNA by RA appeared to be caused by the transcriptional stimulation of the gene, since it was blocked by an RNA synthesis inhibitor, but not by a protein synthesis inhibitor. In search of the RA response element (RARE) possibly present in human CD38 gene promoter, we isolated and sequenced the genomic DNA covering the 5'-flanking region, exon 1, and partial intron 1. Transient transfection experiments revealed that the responsiveness to RA was conferred through an RARE consisting of two direct repeat TGACCT-like hexamer motifs with a 5-nucleotide spacer, which was located in the first intron rather than the 5'-flanking region of the CD38 gene. This RARE interacted with heterodimer composed of RA receptor and retinoid X receptor in vitro. Thus, the RA-induced expression of the human CD38 gene was demonstrated to be mediated through the RARE located in the first intron.

Published
1998

50. Inhibition of NAD+ glycohydrolase and ADP-ribosyl cyclase activities of leukocyte cell surface antigen CD38 by gangliosides.

Author

Hara-Yokoyama, M, Kukimoto, I, Nishina, H, Kontani, K, Hirabayashi, Y, Irie, F, Sugiya, H, Furuyama, S, and Katada, T

Abstract

We have recently reported that gangliosides act as inhibitors of ADP-ribosyltransferases and NAD+ glycohydrolases (NADase) of pertussis toxin and the C3 exoenzyme from Clostridium botulinum (Hara-Yokoyama, M., Hirabayashi, Y., Irie, F., Syuto, B., Moriishi, K., Sugiya, H., and Furuyama, S. (1995) J. Biol. Chem. 270, 8115-8121). Here, we investigated the effect of gangliosides on the enzymatic activity of leukocyte cell surface antigen CD38, which is identified as an ecto-NADase (Kontani, K., Nishina, H., Ohoka, Y., Takahashi, K., and Katada, T. (1993) J. Biol. Chem. 268, 16895-16898). Gangliosides GM1a and GQ1balpha inhibited the NADase activity in the immunoprecipitate of anti-CD38 antibody from the membrane extract of retinoic acid-treated human leukemic HL-60 cells. Gangliosides also inhibited the NADase activity of the extracellular domain of CD38 antigen that was deprived of the transmembrane domain and was expressed in Escherichia coli as a fusion protein with maltose-binding protein (MBP-CD38). The order of the inhibitory effect of purified ganglioside species on the NADase activity on MBP-CD38 was as follows: GQ1balpha > GT1b, GQ1b > GD1a, GD1b, GM1a, GM1b, GD3, GM3. GQ1balpha inhibited the NADase of MBP-CD38 in a noncompetitive manner versus NAD+ with a Ki value of about 0.3 microM. Neither ceramide nor the oligosaccharide moiety of GQ1balpha had an effect on the NADase activity. GQ1balpha, GT1b, and GQ1b also efficiently inhibited the ADP-ribosyl cyclase activity of MBP-CD38. At present, gangliosides are the only endogenous species that can block the enzymatic activity of CD38 antigen. The present results suggest a potential role of gangliosides as inhibitors of the ecto-NADases.

Published
1996

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