Naoko Iida-Tanaka

Publications of Naoko Iida-Tanaka

• Blocking effect of NIP-142 on the KCNQ1/KCNE1 channel current expressed in HEK293 cells.

  Authors: Iyuki Namekata, Noriko Tsuruoka, Yayoi Tsuneoka, Tomoyuki Matsuda, Akira Takahara, Yoshio Tanaka, Takeshi Suzuki, Tetsuo Takahashi, Naoko Iida-Tanaka, Hikaru Tanaka

  Biological & pharmaceutical bulletin. 01/2011; 34(1):153-5.

  We examined the effect of NIP-142, a benzopyran compound with terminating effect on experimental atrial arrhythmia, on the KCNQ1/KCNE1 channel, which underlies the slow component of the cardiacWe examined the effect of NIP-142, a benzopyran compound with terminating effect on experimental atrial arrhythmia, on the KCNQ1/KCNE1 channel, which underlies the slow component of the cardiac delayed rectifier potassium channel (I(Ks)). NIP-142, as well as chromanol 293B, showed concentration-dependent blockade of the current expressed in HEK293 cells; the EC(50) value of NIP-142 and chromanol 293B for the inhibition of tail current was 13.2 µM and 4.9 µM, respectively. These results indicate that NIP-142 has blocking effect on the KCNQ1/KCNE1 channel current.

• Effects of S(+)-efonidipine on the rabbit sinus node action potential and calcium channel subunits Ca(V)1.2, Ca(V)1.3 and Ca(V)3.1.

  Authors: Hikaru Tanaka, Iyuki Namekata, Toru Ogawa, Yayoi Tsuneoka, Chisa Komikado, Akira Takahara, Naoko Iida-Tanaka, Hiroko Izumi-Nakaseko, Hiromichi Tsuru, Satomi Adachi-Akahane

  European journal of pharmacology. 12/2010; 649(1-3):263-7.

  The effect of S(+)-efonidipine on sinus node action potential and calcium channel α-subunits was examined. The slope of the phase 4 depolarization of isolated rabbit sinus node tissue wasThe effect of S(+)-efonidipine on sinus node action potential and calcium channel α-subunits was examined. The slope of the phase 4 depolarization of isolated rabbit sinus node tissue was significantly reduced by S(+)-efonidipine (1 μM), slightly reduced by nifedipine (1 μM), but was not affected by R(-)-efonidipine. S(+)-efonidipine (1 μM), inhibited the expressed Ca(V)1.2, Ca(V)1.3 and Ca(V)3.1 channel currents by 75.7%, 75.3% and 94.0%, nifedipine 84.0%, 43.2% and 14.9%, and R(-)-efonidipine 30.0%, 19.6% and 92.8%, respectively. Thus, the prolongation of the phase 4 depolarization of the rabbit sinus node by S(+)-efonidipine may be explained by blockade of the Ca(V)1.3 channel current.

• Effect of NIP-142 on potassium channel alpha-subunits Kv1.5, Kv4.2 and Kv4.3, and mouse atrial repolarization.

  Authors: Hikaru Tanaka, Iyuki Namekata, Shogo Hamaguchi, Taro Kawamura, Hiroyuki Masuda, Yoshio Tanaka, Naoko Iida-Tanaka, Akira Takahara

  Biological & pharmaceutical bulletin. 01/2010; 33(1):138-41.

  Effects of NIP-142, a benzopyran compound which terminates experimental atrial arrhythmia, on potassium channel alpha-subunits and mouse atrial repolarization were examined. NIP-142Effects of NIP-142, a benzopyran compound which terminates experimental atrial arrhythmia, on potassium channel alpha-subunits and mouse atrial repolarization were examined. NIP-142 concentration-dependently blocked the outward current through potassium channel alpha subunits Kv1.5, Kv4.2 and Kv4.3 expressed in Xenopus oocytes. In isolated mouse atrial myocardia, NIP-142 prolonged the action potential duration and effective refractory period, and increased the contractile force. These results suggest that NIP-142 blocks the potassium channels underlying the transient and sustained outward currents, which may contribute to its antiarrhythmic activity.

• Efficient in vivo gene transfection by stable DNA/PEI complexes coated by hyaluronic acid.

  Authors: Tomoko Ito, Naoko Iida-Tanaka, Yoshiyuki Koyama

  Journal of drug targeting. 06/2008; 16(4):276-81.

  Plasmid DNA was mixed with polyethyleneimine (PEI) and hyaluronic acid (HA) to afford ternary complexes with negative surface charge regardless of the mixing order. They showed reduced non-specificPlasmid DNA was mixed with polyethyleneimine (PEI) and hyaluronic acid (HA) to afford ternary complexes with negative surface charge regardless of the mixing order. They showed reduced non-specific interactions with blood components. When DNA and PEI were mixed at a high concentration such as that used in in vivo experiments, they soon aggregated, and large particles were formed. On the other hand, pre-addition of HA to DNA prior to PEI effectively diminished the aggregation, and 10% (in volume) of the complexes remained as small particles with a diameter below 80 nm. Those negatively charged small ternary complexes induced a much stronger extra-gene expression in tumor than binary DNA/PEI complex after intratumoral or intravenous injection into the mice bearing B16 cells.

• Membrane-labeled MDCK cells and confocal microscopy for the analyses of cellular volume and morphology.

  Authors: Naoko Iida-Tanaka, Iyuki Namekata, Miku Tamura, Yuko Kawamata, Toru Kawanishi, Hikaru Tanaka

  Biological & pharmaceutical bulletin. 05/2008; 31(4):731-4.

  A clone of Madin-Darby canine kidney (MDCK) cells whose cell membrane was stably labeled with expressed cyan fluorescent protein (CFP) was established, and changes in their volume and shape inducedA clone of Madin-Darby canine kidney (MDCK) cells whose cell membrane was stably labeled with expressed cyan fluorescent protein (CFP) was established, and changes in their volume and shape induced by hyposmotic stress were analyzed with confocal microscopy. The membrane-targeted CFP was present not only on the cell membrane but also in the endoplasmic reticulum and Golgi apparatus, but was excluded from the mitochondria and cell nucleus. During hyposmosis, the initial swelling and the following regulatory volume decrease could be accurately measured by summation of the cellular volume in every confocal slice crossing the cell at different heights. Changes in the cellular height roughly paralleled the changes in cellular volume when the mean value was compared, but dissociation as much as 30% was observed for individual cells due to changes in cell shape. The present experimental system, which enables direct measurement of cell volume and simultaneous observation of various intracellular phenomena, would be useful for further investigation of cellular volume regulation.

• Highly efficient in vivo gene transfection by plasmid/PEI complexes coated by anionic PEG derivatives bearing carboxyl groups and RGD peptide.

  Authors: Mitsuko Sakae, Tomoko Ito, Chieko Yoshihara, Naoko Iida-Tanaka, Hironobu Yanagie, Masazumi Eriguchi, Yoshiyuki Koyama

  Biomedicine & pharmacotherapy = Biomedecine & pharmacotherapie. 02/2008;

  A new class of an anionic poly (ethylene glycol) derivative, PEG-Suc, bearing 17.7 pairs of carboxylic acid-side chains was synthesized. PEG-Suc deposited onto the DNA/polyethyleneimine complexesA new class of an anionic poly (ethylene glycol) derivative, PEG-Suc, bearing 17.7 pairs of carboxylic acid-side chains was synthesized. PEG-Suc deposited onto the DNA/polyethyleneimine complexes without destroying them even at high dose ratio. Coating of the DNA complexes by PEG-Suc recharged their surface to negative, and effectively protected them from the albumin-induced aggregation. Paired carboxyl groups in the side chains showed higher proton sponge effect. Negatively charged surface would diminish the electrostatic binding of the complexes to the cells, and the transfection efficiency on the cultured cells was not high. RGD peptide side chain as a ligand to malignant cell surfaces was then introduced to compensate the reduced electrical adhesion. RGD-PEG-Suc-coated plasmid/PEI complex brought about more than 3 times higher reporter protein activity on the cultured B16 cells. Those bio-compatible DNA complexes with ligand attained very high gene expression in tumor, lung, and liver after injection into mouse tail vein.

• Involvement of intracellular Ca(2+) in the regulatory volume decrease after hyposmotic swelling in MDCK cells.

  Authors: Naoko Iida-Tanaka, Iyuki Namekata, Megumi Kaneko, Miku Tamura, Toru Kawanishi, Ryu Nakamura, Koki Shigenobu, Hikaru Tanaka

  Journal of pharmacological sciences. 09/2007; 104(4):397-401.

  We examined the source of Ca(2+) involved in the volume regulation of Madin-Darby canine kidney (MDCK) cells with confocal microscopy and fluoroprobes. Hyposmosis induced a transient increase in cellWe examined the source of Ca(2+) involved in the volume regulation of Madin-Darby canine kidney (MDCK) cells with confocal microscopy and fluoroprobes. Hyposmosis induced a transient increase in cell volume, as well as cytoplasmic Ca(2+), which peaked at 3 to 5 min and gradually decreased to reach the initial value within about 30 min. This late decrease in cell volume, as well as the transient rise in cytoplasmic Ca(2+), was reduced in Ca(2+)-free solution and was abolished by pretreatment with thapsigargin. In conclusion, Ca(2+) released from the intracellular store contributes to the regulatory volume decrease following hyposmotic swelling in MDCK cells.

• Involvement of the Na+/Ca2+ exchanger in ouabain-induced inotropy and arrhythmogenesis in guinea-pig myocardium as revealed by SEA0400.

  Authors: Hikaru Tanaka, Hideaki Shimada, Iyuki Namekata, Toru Kawanishi, Naoko Iida-Tanaka, Koki Shigenobu

  Journal of pharmacological sciences. 03/2007; 103(2):241-6.

  Involvement of the Na+/Ca2+ exchanger in ouabain-induced inotropy and arrhythmogenesis was examined with a specific inhibitor, SEA0400. In right ventricular papillary muscle isolated from guinea-pigInvolvement of the Na+/Ca2+ exchanger in ouabain-induced inotropy and arrhythmogenesis was examined with a specific inhibitor, SEA0400. In right ventricular papillary muscle isolated from guinea-pig ventricle, 1 microM SEA0400, which specifically inhibits the Na+/Ca2+ exchanger by 80%, reduced the ouabain (1 microM)-induced positive inotropy by 40%, but had no effect on the inotropy induced by 100 microM isobutyl methylxantine. SEA0400 significantly inhibited the contracture induced by low Na+ solution. In HEK293 cells expressing the Na+/Ca2+ exchanger, 1 microM ouabain induced an increase in intracellular Ca2+, which was inhibited by SEA0400. The arrhythmic contractions induced by 3 microM ouabain were significantly reduced by SEA0400. These results provide pharmacological evidence that the Na+/Ca2+ exchanger is involved in ouabain-induced inotropy and arrhythmogenesis.

• Novel carbohydrate-binding activity of bovine liver beta-glucuronidase toward lactose/N-acetyllactosamine sequences.

  Authors: Hiroko Matsushita-Oikawa, Mayumi Komatsu, Naoko Iida-Tanaka, Hiromi Sakagami, Tetsuko Kanamori, Isamu Matsumoto, Nobuko Seno, Haruko Ogawa

  Glycobiology. 11/2006; 16(10):891-901.

  Beta-glucuronidase is a lysosomal enzyme that plays an essential role in normal turnover of glycosaminoglycans and remodeling of the extracellular matrix components in both physiological andBeta-glucuronidase is a lysosomal enzyme that plays an essential role in normal turnover of glycosaminoglycans and remodeling of the extracellular matrix components in both physiological and inflammatory states. The regulation mechanisms of enzyme activity and protein targeting of beta-glucuronidase have implications for the development of a variety of therapeutics. In this study, the effectiveness of various carbohydrate-immobilized adsorbents for the isolation of bovine liver beta-glucuronidase (BLG) from other glycosidases was tested. Beta-glucuronidase and contaminating glycosidases in commercial BLG preparations bound to and were coeluted from adsorbents immobilized with the substrate or an inhibitor of beta-glucuronidase, whereas beta-glucuronidase was found to bind exclusively with lactamyl-Sepharose among the adsorbents tested and to be effectively separated from other enzymes. Binding and elution studies demonstrated that the interaction of beta-glucuronidase with lactamyl-Sepharose is pH dependent and carbohydrate specific. BLG was purified to homogeneity by lactamyl affinity chromatography and subsequent anion-exchange high-performance liquid chromatography (HPLC). Lactose was found to activate beta-glucuronidase noncompetitively, indicating that the lactose-binding site is different from the substrate-binding site. Binding studies with biotinyl glycoproteins, lipids, and synthetic sugar probes revealed that beta-glucuronidase binds to N-acetyllactosamine/lactose-containing glycoconjugates at neutral pH. The results indicated the presence of N-acetyllactosamine/lactose-binding activity in BLG and provided an effective purification method utilizing the novel carbohydrate binding activity. The biological significance of the carbohydrate-specific interaction of beta-glucuronidase, which is different from the substrate recognition, is discussed.

• Quantitative fluorescence measurement of cardiac Na+/Ca2+ exchanger inhibition by kinetic analysis in stably transfected HEK293 cells.

  Authors: Iyuki Namekata, Toru Kawanishi, Naoko Iida-Tanaka, Hikaru Tanaka, Koki Shigenobu

  Journal of pharmacological sciences. 09/2006; 101(4):356-60.

  We developed a method to quantitatively evaluate the potency of Na+/Ca2+ exchanger (NCX) inhibitors with fluorescence microscopy in NCX1-transfected HEK 293 cells. The reverse mode and forward modeWe developed a method to quantitatively evaluate the potency of Na+/Ca2+ exchanger (NCX) inhibitors with fluorescence microscopy in NCX1-transfected HEK 293 cells. The reverse mode and forward mode NCX activities were measured as the ascending slope of the early phase increase in cytoplasmic Ca2+ concentration after change to low Na+ extracellular solution and the descending rate (inverse of the exponential time constant) on return to normal solution, respectively. Both modes of NCX were inhibited by SEA0400 (2-[4-[(2,5-difluorophenyl)methoxy]phenoxy]-5-ethoxyaniline) and KB-R7943 (2-[2-[4-(4-nitrobenzyloxy)phenyl]ethyl]isothiourea methanesulfonate), and the concentration-inhibition relationships for both inhibitors were in good agreement with those previously reported in voltage clamped cardiomyocytes.

• Blockade by NIP-142, an antiarrhythmic agent, of carbachol-induced atrial action potential shortening and GIRK1/4 channel.

  Authors: Tomoyuki Matsuda, Mie Ito, Sayoko Ishimaru, Noriko Tsuruoka, Tomoaki Saito, Naoko Iida-Tanaka, Norio Hashimoto, Toru Yamashita, Nobutomo Tsuruzoe, Hikaru Tanaka, Koki Shigenobu

  Journal of pharmacological sciences. 09/2006; 101(4):303-10.

  Mechanisms for the atria-specific action potential-prolonging action of NIP-142 ((3R*,4S*)-4-cyclopropylamino-3,4-dihydro-2,2-dimethyl-6-(4-methoxyphenylacetylamino)-7-nitro-2H-1-benzopyran-3-ol), aMechanisms for the atria-specific action potential-prolonging action of NIP-142 ((3R*,4S*)-4-cyclopropylamino-3,4-dihydro-2,2-dimethyl-6-(4-methoxyphenylacetylamino)-7-nitro-2H-1-benzopyran-3-ol), a benzopyran compound that terminates experimental atrial arrhythmia, was examined. In isolated guinea-pig atrial tissue, NIP-142 reversed the shortening of action potential duration induced by either carbachol or adenosine. These effects were mimicked by tertiapin, but not by E-4031. NIP-142 concentration-dependently blocked the human G protein-coupled inwardly rectifying potassium channel current (GIRK1/4 channel current) expressed in HEK-293 cells with an EC50 value of 0.64 microM. At higher concentrations, NIP-142 blocked the human ether a go-go related gene (HERG) channel current with an EC50 value of 44 microM. In isolated guinea-pig papillary muscles, NIP-142 had no effect on the negative inotropic effect of carbachol under beta-adrenergic stimulation, indicating lack of effect on the muscarinic receptor and Gi protein. These results suggest that NIP-142 directly inhibits the acetylcholine-activated potassium current.

• Hyaluronic acid and its derivative as a multi-functional gene expression enhancer: protection from non-specific interactions, adhesion to targeted cells, and transcriptional activation.

  Authors: Tomoko Ito, Naoko Iida-Tanaka, Takuro Niidome, Takahito Kawano, Koji Kubo, Kenichi Yoshikawa, Toshinori Sato, Zhihong Yang, Yoshiyuki Koyama

  Journal of controlled release : official journal of the Controlled Release Society. 06/2006; 112(3):382-8.

  Hyaluronic acid (HA), a natural anionic mucopolysaccharide, can be deposited onto the cationic surface of DNA/polyethyleneimine (PEI) complexes to recharge the surface potential and reduceHyaluronic acid (HA), a natural anionic mucopolysaccharide, can be deposited onto the cationic surface of DNA/polyethyleneimine (PEI) complexes to recharge the surface potential and reduce nonspecific interactions with proteins. HA can also be used as a ligand to target specific cell receptors. Furthermore, HA-coating enhanced the transcriptional activity of the plasmid/PEI complexes, probably by loosening the tight binding between DNA and PEI, which facilitated the approach of transcription factors. Amphoteric HA derivative having spermine side chains (Spn-HA) with a structure similar to HMG protein showed higher transcription-enhancing activity than HA. Plasmid/PEI/Spn-HA ternary complex exhibited 29-fold higher transgene expression efficiency than naked plasmid/PEI complexes in CHO cells.

• Enhancement of transcriptional activity of DNA complexes by amphoteric PEG derivative.

  Authors: Yoshiyuki Koyama, Misa Yamashita, Naoko Iida-Tanaka, Tomoko Ito

  Biomacromolecules. 05/2006; 7(4):1274-9.

  A water-soluble PEG derivative having both amino and carboxylic acid side chains (PEG-AC) was synthesized and explored for its transcription- and transfection-enhancing activity. PEG-AC could beA water-soluble PEG derivative having both amino and carboxylic acid side chains (PEG-AC) was synthesized and explored for its transcription- and transfection-enhancing activity. PEG-AC could be deposited onto the surface of DNA/polycation complexes to form a ternary complex with slightly negative surface potential. PEG-AC-coating on the plasmid/PEI complexes obviously enhanced their transcriptional activity, and 31-fold higher consumption of UTP was observed. Amphoteric PEG-AC would loosen the tightly compacted DNA/PEI complex and facilitate the approach of transcriptional factors. PEG-AC also evidently improved the transgene expression level on the cultured CHO cells.

• De-N-acetyllactotriaosylceramide as a novel cationic glycosphingolipid of bovine brain white matter: isolation and characterization.

  Authors: Toshiyuki Hikita, Keiko Tadano-Aritomi, Naoko Iida-Tanaka, Ineo Ishizuka, Senitiroh Hakomori

  Biochemistry. 08/2005; 44(27):9555-62.

  A novel cationic lipid was separated from bovine brain white matter by a series of chromatographies on carboxymethyl-Sephadex and silica gel in chloroform and methanol. Its structure was identifiedA novel cationic lipid was separated from bovine brain white matter by a series of chromatographies on carboxymethyl-Sephadex and silica gel in chloroform and methanol. Its structure was identified unambiguously as de-N-acetyllactotriaosylceramide (deNAcLc(3)Cer) by mass spectrometry and (1)H NMR. The natural occurrence of this glycolipid in white matter extract was detected by immunostaining of thin-layer chromatography with monoclonal antibody 5F5, which is directed to deNAcLc(3)Cer and recognizes the terminal beta-glucosaminyl (GlcNH(2)) residue, having a free NH(2) group. A de-N-acetylase capable of hydrolyzing the N-acetyl group of Lc(3)Cer was detected in bovine brain extract using N-[(14)C]acetyl-labeled Lc(3)Cer as a substrate. The biogenesis and possible functional significance of deNAcLc(3)Cer are discussed.

• Atria selective prolongation by NIP-142, an antiarrhythmic agent, of refractory period and action potential duration in guinea pig myocardium.

  Authors: Tomoyuki Matsuda, Kentaro Takeda, Mie Ito, Reiko Yamagishi, Miku Tamura, Hideki Nakamura, Noriko Tsuruoka, Tomoaki Saito, Haruko Masumiya, Takeshi Suzuki, Naoko Iida-Tanaka, Maho Itokawa-Matsuda, Toru Yamashita, Nobutomo Tsuruzoe, Hikaru Tanaka, Koki Shigenobu

  Journal of pharmacological sciences. 06/2005; 98(1):33-40.

  NIP-142 is a novel benzopyran compound that was shown to prolong the atrial effective refractory period and terminate experimental atrial fibrillation in the dog. In the present study, we examinedNIP-142 is a novel benzopyran compound that was shown to prolong the atrial effective refractory period and terminate experimental atrial fibrillation in the dog. In the present study, we examined the effects of NIP-142 on isolated guinea pig myocardium and on the G-protein-coupled inwardly rectifying potassium channel current (acetylcholine-activated potassium current; I(KACh)) expressed in Xenopus oocytes. NIP-142 (10 and 100 microM) concentration-dependently prolonged the refractory period and action potential duration in the atrium but not in the ventricle. E-4031 and 4-aminopyridine prolonged action potential duration in both left atrium and right ventricle. Prolongation by NIP-142 of the atrial action potential duration was observed at stimulation frequencies between 0.5 and 5 Hz. In contrast, the prolongation by E-4031 was not observed at higher frequencies. Tertiapin, a blocker of I(KACh), prolonged action potential duration in the atrium but not in the ventricle. NIP-142 completely reversed the carbachol-induced shortening of atrial action potential duration. NIP-142 (1 to 100 microM), as well as tertiapin (0.1 to 100 nM), concentration-dependently blocked I(KACh) expressed in Xenopus oocytes; the blockade by NIP-142 was not affected by membrane voltage. In conclusion, NIP-142 was shown to prolong atrial refractory period and action potential duration through blockade of I(KACh) which may possibly explain its previously described antiarrhythmic activity. NIP-142 has pharmacological properties that are different from classical class III antiarrhythmic agents such as atria specificity and lack of reverse frequency dependence, and thus appears promising for the treatment of supraventricular arrhythmia.

• Metabolism of sulfolipids in isolated renal tubules from rat.

  Authors: Ken-Ichi Nagai, Keiko Tadano-Aritomi, Naoko Iida-Tanaka, Hideki Yoshizawa, Ineo Ishizuka

  Comparative biochemistry and physiology. Part B, Biochemistry & molecular biology. 04/2005; 140(3):487-95.

  Proximal-rich tubules were prepared from rat kidneys by using collagenase treatment. The isolated rat renal tubules were compared with the intact kidney on the following characteristics. (1)Proximal-rich tubules were prepared from rat kidneys by using collagenase treatment. The isolated rat renal tubules were compared with the intact kidney on the following characteristics. (1) Composition of the sulfoglycolipid. (2) Sulfoglycolipid metabolism based on incorporation of [35S]sulfate or some properties of sulfoglycolipid metabolism, including the activities of anabolic and catabolic enzymes. The results indicated following characteristics of the isolated renal tubules in comparison to the kidney in vivo. (1) The sulfoglycolipid compositions are qualitatively similar, except that the content of glucosyl sulfatide, Gg3Cer II3-sulfate, and GM4 was slightly higher in the isolated tubules. (2) The apparent half-lives (15-55 min) of sulfoglycolipids in the isolated tubules could indicate the existence of a rapid turnover pool of these lipids. (3) The sulfotransferase and sulfatase activities related to sulfoamphiphiles in the renal tubule were similar to those reported for the whole kidney. Based on the above criteria, we conclude that the isolated rat renal tubule should be a useful metabolic system for clarification of the short-term physiological events, up to 90 min, of proximal tubular sulfoglycolipids. By using the present system, we showed that biosynthesis of the renal total sulfoglycolipid was significantly elevated in rats deprived of water for 24 h.

• Lack of action potential-prolonging effect of terfenadine on rabbit myocardial tissue preparations.

  Authors: Haruko Masumiya, Mariko Saito, Mie Ito, Tomoyuki Matsuda, Kazuo Noguchi, Naoko Iida-Tanaka, Hikaru Tanaka, Koki Shigenobu

  Biological & pharmaceutical bulletin. 02/2004; 27(1):131-5.

  The effects of terfenadine, an antiallergic drug also known for its QT-prolonging and arrhythmogenic activities, on the action potential of isolated myocardial tissue preparations from rabbits wereThe effects of terfenadine, an antiallergic drug also known for its QT-prolonging and arrhythmogenic activities, on the action potential of isolated myocardial tissue preparations from rabbits were examined with microelectrode techniques. In the Purkinje fibers and atrium, terfenadine concentration dependently decreased the maximum rate of rise (+.V(max)) without affecting other action potential parameters. In the ventricle, terfenadine had little effect on action potential configuration. In the sinoatrial node, terfenadine 20 microM prolonged cycle length mainly through inhibition of +.V(max). Terfenadine 1 microM completely inhibited the human ether a go-go-related gene (HERG) channel current expressed in HEK293 cells in the same experimental solution as in microelectrode experiments. The lack of terfenadine effect on the action potential duration suggests that there are drugs for which the HERG channel inhibitory action underlying in vivo QT prolongation cannot be evaluated based on their action potential-prolonging activity in isolated myocardial tissue preparations.

• Conformational studies of a novel cationic glycolipid, glyceroplasmalopsychosine, from bovine brain by NMR spectroscopy.

  Authors: Naoko Iida-Tanaka, Toshiyuki Hikita, Sen-itiroh Hakomori, Ineo Ishizuka

  Carbohydrate research. 11/2002; 337(19):1775-9.

  A novel glycosphingolipid containing a long chain aldehyde conjugated to galactose and glycerol, Gro1(3)-O-CH((CH(2))(n)CH(3))-O-6Galbeta-sphingosine (glyceroplasmalopsychosine) has been studied byA novel glycosphingolipid containing a long chain aldehyde conjugated to galactose and glycerol, Gro1(3)-O-CH((CH(2))(n)CH(3))-O-6Galbeta-sphingosine (glyceroplasmalopsychosine) has been studied by NMR spectroscopy (Hikita et al. J. Biol. Chem. 2001, 276, 23084-23091). We further report here on the conformation showing the galactose and the glycerol at the end of two parallel hydrophobic chains, i.e. the sphingosine and the fatty aldehyde. This is proposed based on the interproton distances derived from ROESY experiments and 3 J (H,H) coupling constants. The absence of any intraresidual NOEs between protons in the glycerol residue suggested that the C-C-2 and C-C-3 bonds in the glycerol may be rotating freely, supporting the proposed conformation in which the unique terminal glycerol is in an environment with a minimal steric hindrance. The present study proposes a conformation of glyceroplasmalopsychosine greatly different from the two conventional plasmalopsychosines possessing a fatty aldehyde chain oriented in an opposite direction to the sphingosine.

• Cationic glycosphingolipids in neuronal tissues and their possible biological significance.

  Authors: Toshiyuki Hikita, Keiko Tadano-Aritomi, Naoko Iida-Tanaka, Steven B Levery, Ineo Ishizuka, Senitiroh Hakomori

  Neurochemical research. 09/2002; 27(7-8):575-81.

  During the course of studies on natural occurrence of sphingosine base in brain, cationic glycosphingolipids bound to carboxymethyl-Sephadex and eluted with triethylamine in organic solvents wereDuring the course of studies on natural occurrence of sphingosine base in brain, cationic glycosphingolipids bound to carboxymethyl-Sephadex and eluted with triethylamine in organic solvents were isolated and characterized. Four classes of compounds were identified: (i) plasmalopsychosine-A and -B; (ii) glyceroplasmalopsychosine; (iii) glycosphingolipids having de-N-acetyl-hexosamine, e.g., de-N-acetyl-Lc3Cer; (iv) glycosylsphingosine, i.e., lysoglycosphingolipid. Only two kinds, galactosylsphingosine (psychosine) and lactosylsphingosine, were found to occur naturally in brain. All these compounds were isolated from extract of brain white matter. Their occurrence, quantity, and distribution pattern differ from one species to another. Their quantity is much lower than that of regular acidic and neutral glycosphingolipids. They may interact with regular glycosphingolipids in glycosphingolipid-enriched microdomains to elicit signal transduction, to modify cellular phenotype, although studies along this line are highly limited at this time.

• Chemical structures and immunolocalization of glycosphingolipids isolated from Diphyllobothrium hottai adult worms and plerocercoids.

  Authors: Hideyuki Iriko, Kazuo Nakamura, Hisako Kojima, Naoko Iida-Tanaka, Takeshi Kasama, Yasushi Kawakami, Ineo Ishizuka, Akihiko Uchida, Yoshihiko Murata, Yoichi Tamai

  European journal of biochemistry / FEBS. 08/2002; 269(14):3549-59.

  Glycosphingolipids (GSLs) were purified from adults and plerocercoids of the tapeworm Diphyllobothrium hottai, and their chemical structures were determined. Total lipid fractions prepared fromGlycosphingolipids (GSLs) were purified from adults and plerocercoids of the tapeworm Diphyllobothrium hottai, and their chemical structures were determined. Total lipid fractions prepared from chloroform/methanol extracts of whole tissues were fractionated successively on ion-exchange chromatography, silicic acid column chromatography, and preparative TLC. The purified GSLs were characterized by methylation analysis, TLC-immunostaining, liquid secondary ion MS, MALDI-TOF MS, and 1H-NMR. Ten GSLs were isolated from adult worms and four from plerocercoids, comprising mono-, di-, tri-, tetra-, and pentasaccharides. The GSL Gal beta 1-4(Fuc alpha 1-3)Glc beta 1-3Gal beta 1-Cer was found in adult worms but not in plerocercoids, whereas Ga lbeta 1-4 (Fuc alpha 1-3)Glc beta 1-3(Gal beta 1-6)Gal beta 1-Cer was found in both adult worms and plerocercoids. We previously found a similar series of GSLs in plerocercoids of the cestode Spirometra erinaceieuropaei, and termed them 'spirometosides'[Kawakami, Y. et al. (1996) Eur J. Biochem. 239, 905-911]. The core structure of spirometosides, Gal beta 1-4Glc beta 1-3 Gal beta 1-Cer, may have taxonomic significance, being characteristic of pseudophyllidean tapeworms. In the present study, GSL compositions were significantly different between adults and plerocercoids, and growth-dependent changes in composition were documented. We found a novel dihexosylceramide, Glc beta 1-3Gal beta 1-Cer, which is a possible precursor for spirometosides. Immunohistochemical examination showed that spirometoside GSLs are highly enriched in the inner surface of bothria, the major point of contact between the adult worm and the host's intestine. Our findings indicate that spirometosides are involved in host-parasite interaction.