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Noboru Kitamura

Publications and source records attributed to Noboru Kitamura.

At least 37 records · Page 2Linked to original sources
PubMed2004

A spectroscopic and photophysical study on molecular recognition via hydrogen-bonding and pi-pi stacking interactions.

Spectroscopic and photophysical properties of a Kemp's tricarboxylic acid derivative having an anthracene chromophore (I) upon recognition of 9-butyladenine (BA) in chloroform were studied in detail. Molecular recognition of BA by I via hydrogen-bonding and pi-pi stacking interactions were sensed successfully on the basis of absorption and fluorescence spectroscopies, by which the binding constant of the I:BA complex was determined to be 240 M(-1). The fluorescence quantum yield and lifetime of I in the absence of BA were 0.24 and 5.6 ns, respectively, while those in the presence of an enough amount of BA increased to 0.35 and 13 ns, respectively. These values demonstrated that the nonradiative decay rate constant of I decreased from 13.6 x 10(7) to 5.0 x 10(7) s(-1) upon binding with BA. Such changes in the photophysical properties of I before and after complexation with BA were discussed in terms of hydrogen-bonding and pi-pi stacking interactions between I and BA. In particular, intramolecular hydrogen-bonding between the amide and imide groups in was shown to play important roles in determining the photophysical characteristics of I before complexation, while intermolecular hydrogen-bonding between I and BA governed the excited-state properties of the I:BA complex. The change in the hydrodynamic diameter of I before and after complexation with BA was also discussed on the basis of the results by fluorescence dynamic anisotropy measurements.

Absorption↗
PubMed2004

Time-resolved total internal reflection fluorescence study on hybridization of complementary single-stranded DNAs at a water/oil interface.

Hybridization of complementary single-stranded DNAs (ssDNA) at a water/CCl4 interface was studied on the basis of picosecond total internal reflection fluorescence spectroscopy. Complementary ssDNAs dissolved in water were shown to produce the relevant double-stranded DNA (dsDNA) at a water/CCl4 interface in the presence of octadecylamine (ODA) in the oil phase, while hybridization between ssDNAs did not proceed in the water phase, as demonstrated by the fluorescence dynamics of ethidium bromide as a probe for the DNA structure. The structures of dsDNA and the roles of ODA in hybridization of ssDNA at the interface were discussed.

Amines↗
PubMed2004

Thrombophilic dysfibrinogen Tokyo V with the amino acid substitution of gammaAla327Thr: formation of fragile but fibrinolysis-resistant fibrin clots and its relevance to arterial thromboembolism.

Thrombophilic dysfibrinogen Tokyo V was identified in a 43-year-old man with recurrent thromboembolism. Based on analyses of the patient fibrinogen genes, the amino acid sequence of the aberrant fibrinogen peptide, and deglycosylation experiments, fibrinogen Tokyo V was shown to have an amino acid substitution of gamma Ala327Thr and possibly extra glycosylation at gamma Asn325 because the mutation confers the N-linked glycosylation consensus sequence Asn-X-Thr. The mutation resulted in impaired function and hypofibrinogenemia (hypodysfibrinogen). Polymerization of fibrin monomers derived from patient fibrinogen was severely impaired with a partial correction in the presence of calcium, resulting in very low clottability. Additionally, a large amount of soluble cross-linked fibrin was formed upon thrombin treatment in the presence of factor XIII and calcium. However, Tokyo V-derived fibrin was resistant to degradation by tissue plasminogen activator (tPA)-catalyzed plasmin digestion. The structure of Tokyo V fibrin appeared severely perturbed, since there are large pores inside the tangled fibrin networks and fiber ends at the boundaries. Taken together, these data suggest that Tokyo V fibrin clots are fragile, so that fibrinolysis-resistant insoluble fibrin and soluble fibrin polymers may be released to the circulation, partly accounting for the recurrent embolic episodes in the patient.

Adult↗
PubMed2004

Early bone marrow hematopoietic defect in simian/human immunodeficiency virus C2/1-infected macaques and relevance to advance of disease.

To clarify hematological abnormalities following infection with human immunodeficiency virus (HIV), we examined the hematopoietic capability of bone marrow by using cynomolgus monkeys infected with pathogenic simian/human immunodeficiency virus (SHIV) strain C2/1, an animal model of HIV infection. The relationship between the progress of the infection and the CD4/CD8 ratio of T lymphocytes or the amount of SHIV C2/1 viral load in the peripheral blood was also investigated. A colony assay was performed to assess the hematopoietic capability of bone marrow stem cells during the early and advanced phases of the infection. Colonies of granulocytes-macrophages (GM) were examined by PCR for the presence of the SIVmac239 gag region to reveal direct viral infection. There was a remarkable decrease in the CFU-GM growth on days 1 and 3 postinoculation, followed by recovery on day 56. During the more advanced stage, the CFU-GM growth decreased again. There was minimal evidence of direct viral infection of pooled cultured CFU-GM despite the continuously low CD4/CD8 ratios. These results indicate that the decrease in colony formation by bone marrow stem cells is reversible and fluctuates with the advance of the disease. This decrease was not due to direct viral infection of CFU-GM. Our data may support the concept that, in the early phase, production of inhibitory factors or deficiency of a stimulatory cytokine is responsible for some of the bone marrow defects described in the SHIV C2/1 model.

Animals↗
PubMed2004

Photoinduced redox cycle of riboflavin at a water/oil interface.

A photoinduced redox reaction cycle of Riboflavin (RF) at a water/CCl4 interface was studied directly by means of both steady-state and time-resolved total internal reflection (TIR) fluorescence spectroscopies. The TIR fluorescence spectrum of RF observed at the water/CCl4 interface with the maximum wavelength of 517 nm was assigned to the pi-pi* transition from the excited singlet-state of the isoalloxazine chromophore in RF. Upon prolonged laser irradiation (400 nm) in the presence of N,N-dioctadecyl-[1,3,5]triazine-2,4,6-triamine (DTT) as a guest for RF in the CCl4 phase, on the other hand, a new TIR fluorescence band appeared at around 480 nm. Furthermore, the fluorescence intensity at around 480 nm increased in the presence of acetic acid in the water phase. Detailed studies demonstrated that the new fluorescence band should be ascribed to 1,5-dihydoroflavin (RFH2). The present results indicated that RFH2 was produced through the photoreaction of the RF-DTT hydrogen-bonded complex formed at the water/CCl4 interface, whose reaction mechanisms were discussed on the basis of the results observed by fluorescence spectra/dynamics measurements under the TIR conditions as well as by transient absorption spectroscopy.

Journal Article↗
PubMed2004

An application of plastic microchannel-microheater chips to a thermal synthetic reaction.

Polystyrol microchannel-microheater chips were fabricated on the basis of imprinting and photolithography techniques. The solution (i.e., methanol) temperature in the vicinity of the microheater (width = 100 or 200 microm and length = 100 microm) integrated in the channel (width = 100 microm and depth = 20 microm) was evaluated on the basis of the temperature-dependent fluorescence lifetime of Rhodamine B as a function of a flow rate and the voltage applied to the heater. The study demonstrated that the fabricated chip acted certainly as a microheater. The chip was then applied to the thermal reaction between benzaldehyde and malononitrile in methanol. Under optimum conditions, benzilidenemalononitrile as the product of the reaction was obtained in a 96% yield with the reaction time of 84 s.

Journal Article↗
PubMed2004

[A case of anorexia nervosa associated with delirium because of refeeding syndrome].

We experienced a case of anorexia nervosa (AN) associated with refeeding syndrome (RS). The patient was a 24-year-old woman who was taken to the hospital emergency room in a hypoglycemic coma as a result of aggravated emaciation due to AN. On the admission day, she had severe emaciation (BW, 27kg; BMI, 11.4), malnutritional hepatitis, bradycardia, hypotension, hypothermia and hypophosphatemia. After she was intravenously administered glucose, her level of consciousness rapidly improved. On the 7th day, we started intravenous hyperalimentation (IVH). On the 13th day, she developed delirium. Because the delirium appeared after administration of IVH, we diagnosed her with RS. An EEG study disclosed frequent high-amplitude generalized slow waves. SPECT (99mTc ethyl cysteinate dimer) showed a bilateral decrease in the average blood flow. Regional blood flow was decreased bilaterally in the frontal and temporal lobes, and in the thalamus. After she recovered from the delirium and her state of nutrition improved, follow-up EEG and SPECT studies showed a decreased frequency of generalized slow waves and improved blood flow, respectively. Her serum values of P, K, and Mg had been within the normal ranges in the course of the delirium. Thus, before giving more calories to a severely malnourished patient, a physician should consider the possibility that RS will occur, even when serum electrolytes are within the normal ranges.

Adult↗
PubMed2003

A spectroelectrochemical study on perylene cation radical in polymer microchannel-microelectrode chips.

Polymer microchannel chips (depth 20 microm and width 100 microm) integrated with band electrodes were fabricated by photolithography and imprinting methods, and applied to a spectroelectrochemical study on the cation radical of perylene (Pe). A propylene carbonate solution of Pe was brought into the channel chip by pressure driven flow and Pe was oxidized at the working band electrode (WE) in the channel. Simultaneously, absorption measurements of the solution phase in the downstream side of the electrode (30 microm from WE) were conducted on the basis of space resolved spectroscopy. The decrease in the absorbance of Pe at 438 nm upon electrolysis accompanied an appearance of the absorption band around 538 nm, which was assigned to that of the Pe cation radical. When the perylene solution was introduced to the microchip at a slow flow velocity, the dimer cation radical of Pe was shown to be produced in the channel chip. The formation and disappearance processes of the monomer and dimer cation radicals of Pe in the channel were followed by flow velocity and position dependencies of the absorption spectra.

Journal Article↗
PubMed2003

Direct observation of molecular recognition mediated by triple hydrogen bonds at a water/oil interface: time-resolved total internal reflection fluorometry study.

Molecular recognition mediated by hydrogen-bonding interactions at a water/CCl(4) interface was investigated directly by means of time-resolved total internal reflection (TIR) fluorescence spectroscopy. The TIR fluorescence decay profile of riboflavin (RF) in the absence of a guest in the CCl(4) phase was fitted satisfactorily by a single-exponential function. In the presence of N,N-dioctadecyl-[1,3,5]triazine-2,4,6-triamine (DTT) as a guest in the CCl(4) phase, on the other hand, the fluorescence decay profiles were best fitted by double-exponential functions with the relevant amplitude (A(i)) being varied with the concentration of DTT. Furthermore, the rotational reorientation time of RF at the interface determined by fluorescence dynamic anisotropy was 210 ps in the absence of DTT, while fast (160-220 ps) and slow (670-750 ps) rotational reorientation times were observed in the presence of DTT. This slow rotational reorientation time was shown to ascribe to that of the RF-DDT complex formed at the water/CCl(4) interface. These results indicate that molecular recognition mediated by complementary hydrogen bonding takes place effectively at the water/CCl(4) interface, which was observed directly by both fluorescence dynamics and fluorescence dynamic anisotropy measurements under the TIR conditions.

Journal Article↗
PubMed2003

Preparation, structures, and redox and emission characteristics of the isothiocyanate complexes of hexarhenium(III) clusters [Re6(mu3-E)8(NCS)6]4- (E = S, Se).

Hexarhenium(III) complexes with terminal isothiocyanate ligands, [(n-C(4)H(9))(4)N](4)[Re(6)(mu(3)-S)(8)(NCS)(6)] (1) and (L)(4)[Re(6)(mu(3)-Se)(8)(NCS)(6)] (L(+) = PPN(+) (2a), (n-C(4)H(9))(4)N(+) (2b)), have been prepared by three different methods. Complex 1 was prepared by the reaction of [(n-C(4)H(9))(4)N](4)[Re(6)(mu(3)-S)(8)Cl(6)] with molten KSCN at 200 degrees C, while 2b was obtained by refluxing the chlorobenzene-DMF (2:1 v/v) solution of [Re(6)(mu(3)-Se)(8)(CH(3)CN)(6)](SbF(6))(2) and [(n-C(4)H(9))(4)N]SCN. The [Re(6)(mu(3)-Se)(8)(NCS)(6)](4)(-) anion was also obtained from a mixture of Cs(2)[Re(6)(mu(3)-Se)(8)Br(4)] and KSCN in C(2)H(5)OH by a mechanochemical activation at room temperature for 20 h and isolated as 2a. The X-ray structures of 1 and 2a.4DMF have been determined (1, C(70)H(144)N(10)S(14)Re(6), monoclinic, space group P2(1)/n (No. 14), a = 14.464(7) A, b = 22.059(6) A, c = 16.642(8) A, beta = 113.62(3) degrees, V = 4864(3) A(3), Z = 2; 2a.4DMF, C(162)H(144)N(14)O(4)P(8)S(6)Se(8)Re(6), triclinic, space group P1 (No. 2), a = 15.263(2) A, b = 16.429(2) A, c = 17.111(3) A, alpha = 84.07(1) degrees, beta = 84.95(1) degrees, gamma = 74.21(1) degrees, V = 4098.3(8) A(3), Z = 1). All the NCS(-) ligands in both complexes are coordinated to the metal center via nitrogen site with the Re-N distances in the range of 2.07-2.13 A. The redox potentials of the reversible Re(III)(6)/Re(III)(5)Re(IV) process in acetonitrile are +0.84 and +0.70 V vs. Ag/AgCl for [Re(6)(mu(3)-S)(8)(NCS)(6)](4)(-) and [Re(6)(mu(3)-Se)(8)(NCS)(6)](4)(-), respectively, which are the most positive among the known hexarhenium complexes with six terminal anionic ligands. The complexes show strong red luminescence with the emission maxima (lambda(max)/nm), lifetimes (tau(em)/micros), and quantum yields (phi(em)) being 745 and 715, 10.4 and 11.8, and 0.091 and 0.15 for 1 and 2b, respectively, in acetonitrile. The data reasonably well fit in the energy-gap plots of other hexarhenium(III) complexes. The temperature dependence of the emission spectra and tau(em) of 1 and [(n-C(4)H(9))(4)N](4)[Re(6)(mu(3)-S)(8)Cl(6)] are also reported.

Journal Article↗
PubMed2003

Characteristic electrochemical responses of polymer microchannel-microelectrode chips.

Polymer microchannel chips (dimension of the channel, 20 microm (depth) x 100 microm (width)) integrated with dual microband electrodes were fabricated by an imprinting method, and their characteristic electrochemical responses were elucidated in detail. A silicon micromachined template fabricated by photolithography and dry etching techniques was used for imprinting. An aqueous solution of a ferrocene derivative was brought into the microchannel by pressure-driven flow, and the electrode responses were studied on the basis of voltammetry and chronoamperometry. A linear sweep voltammetry of 1-hydroxyethylferrocene (FeCp-OH) in water demonstrated that the electrode responses in the microchannel chip were best characterized by one-dimensional diffusion along the channel length, reflecting the structural dimension of the channel. In generation-collection mode experiments, furthermore, a collection efficiency as high as approximately 90% was attained in the microchannel owing to both restricted space and characteristics of solution flow in the channel. It was confirmed that diffusion and solution flow made molecular transport very efficient in the microchannel. The experimental results were also compared with those predicted by computer simulations.

Journal Article↗
PubMed2003

Synapse-associated protein 90/postsynaptic density-95-associated protein (SAPAP) is expressed differentially in phencyclidine-treated rats and is increased in the nucleus accumbens of patients with schizophrenia.

Phencyclidine (PCP) induces a psychotomimetic state that closely resembles schizophrenia. Therefore, PCP-treated animals can provide a model for schizophrenia. Using differential display, we identified a gene regulated by the delayed action of PCP in rat nucleus accumbens (NAcs). Sequence analysis showed that the cDNA clone obtained was identical to rat synapse-associated protein 90/postsynaptic density-95-associated protein 1 (SAPAP1). Quantitative reverse transcriptase (RT)-PCR analysis showed that SAPAP1 mRNA had increased significantly in rat NAc (P<0.0001) and hippocampus (P<0.01) 24 h after a PCP (10 mg/kg) injection as compared to the controls. Immunoquantification using an anti-SAPAP1 antibody indicated that immunoreactivity for SAPAP1 increased significantly (P&<0.05) in the NAcs of unmedicated patients with schizophrenia, as compared to the control subjects and medicated patients with schizophrenia. Our findings support the hypothesis that there is abnormal glutamatergic neurotransmission in schizophrenia and show evidence of abnormalities in the intracellular signal transduction via N-methyl-D-aspartate (NMDA) receptors.

Adult↗
PubMed2003

Channel shape effects on the solution-flow characteristics and the liquid/liquid extraction efficiency in polymer microchannel chips.

A polymer microchannel chip with a symmetrical or unsymmetrical zigzag-side-walled structure was fabricated by an imprinting method, and applied to study shape effects on solution flow characteristics as well as on the liquid/liquid extraction efficiency of an aluminium(III) chelate complex (Al-DHAB: DHAB = o,o'-dihydroxyazobenzene) in a microchannel chip. In an unsymmetrical zigzag-side-walled channel chip (us-channel), an oil/water interface was sinusoidal, while that in a symmetrical zigzag-side-walled channel chip (s-channel) was flat as long as the observation was made under an optical microscope. It was demonstrated that the efficiency of the water-to-oil (1-butanol) extraction of Al-DHAB in the microchannel was governed by the contact time between the two phases. As the most important results, furthermore, the extraction efficiency was higher in the us-channel, as compared with that in the s-channel, owing to the sinusoidal liquid/liquid interfacial structure and, therefore, to the high interfacial area between the two phases.

Journal Article↗
PubMed2003

Multibacterial sepsis in an alcohol abuser with hepatic cirrhosis.

An alcohol abuser with hepatitis C developed multibacterial sepsis. His mean 100% alcohol intake reached 400 ml/day. In January 2001, he suddenly experienced fever (39 degrees C) with no other symptoms. One week later, he was admitted to our hospital and was subsequently diagnosed with sepsis associated with four species of bacteria (Streptococcus constellatus, Fusobacterium mortiferum, Bacteroides thetaiotaomicron, and non-spore-forming anaerobic gram-positive bacillus). A drip infusion of imipenem/cilastatin was administrated, resulting in a successful therapeutic outcome. No underlying disorder was found except for gastric ulcers and hepatic cirrhosis. Damaged gastric mucosa was assumed to be the possible cause and route for the bacterial invasion.

Aged↗
PubMed2002

Photocyanation of pyrene across an oil/water interface in a polymer microchannel chip.

Photocyanation of pyrene (PyH) across an oil/water interface was explored by using two types of polymer microchannel chip. The chips (channel depth of 20 microm and width of 100 microm) were fabricated on the basis of photolithography and an imprinting method, with micromachined silicon templates being used for imprinting. As a typical example of the photoreaction, an aqueous NaCN solution and a propylene carbonate solution of PyH and 1,4-dicyanobenzene were brought separately into a Y-structured microchannel chip with the same flow velocity by pressure driven flow. Light irradiation onto the whole of the channel chip by a high-pressure Hg lamp resulted in formation of 1-cyanopyrene (PyCN), as confirmed by GC-MS analysis of the oil phase. The results demonstrated that the interfacial photochemical reaction of PyH proceeded successfully along the water/oil solution flow in the microchannel. Under optimum conditions by using a three-layer channel chip, absolute PyCN yields as high as 73% were attained with a reaction time of 210 s.

Journal Article↗
PubMed2002

Decreased calcineurin and increased phosphothreonine-DARPP-32 in the striatum of rats behaviorally sensitized to methamphetamine.

We investigated changes in signal transduction via calcineurin (CaN) in the striatum of rats behaviorally sensitized to methamphetamine (Meth). The rats were injected with Meth (4 mg/kg, s.c.) five times a week for 3 weeks and then were given a challenge dose of Meth (2 mg/kg, s.c.). Seven days after the challenge test, we determined the levels of CaN Aalpha and Abeta by Western blotting. We further immunoquantified DARPP-32 (dopamine- and cAMP-regulated phosphoprotein, mw 32,000) and phosphothreonine-DARPP-32, which can be dephosphorylated at threonine sites by CaN. We found that both CaN Aalpha and Abeta were significantly decreased in the particulate fractions but were not changed in the soluble fractions from the striatum of Meth-sensitized rats as compared with control rats. The same findings were observed in the striatum of rats 6 h after the injection of PCP (10 mg/kg, s.c.). In the striatum of Meth-sensitized rats, phosphothreonine-DARPP-32 immunoreactivities significantly increased, but DARPP-32 immunoreactivities were not significantly different from those of the control rats. These results indicate that the activity of signal transduction via CaN is functionally decreased in the striatum of Meth-sensitized rats.

Animals↗