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Biomedical subjects

N Kobayashi

Publications and source records attributed to N Kobayashi.

At least 73 records · Page 4Linked to original sources
PubMed2002

Modeling of mercury sorption by activated carbon in a confined, a semi-fluidized, and a fluidized bed.

A process model was developed to simulate elemental mercury sorption by activated carbon in three distinct beds, namely a confined, a semi-fluidized, and a fluidized bed. The model involved the coupling of a kinetic model based on the mechanisms of surface equilibrium and external mass transfer, and a material balance model based on the tank-in-series approach. For surface equilibrium, three different equilibrium laws were used in the model, namely the Henry's Law, the Langmuir isotherm and the Freundlich isotherm. Literature mercury sorption data were used to determine the best-fit values of parameters for these equilibrium expressions. The parameter-fitted model was then used to simulate mercury sorption processes in the three distinct beds. The simulation parameters were mercury concentration, gas flow rate, adsorption temperature and the degree of semi-fluidization. The simulation results have indicated that the model is capable of describing the literature available mercury sorption data. All the three surface equilibrium laws appear to simulate the adsorption profiles equally well mainly because the sorption process occurs in an extremely low concentration range. The simulation results for the three distinct beds have suggested that the confined bed has the best mercury control performance; however, it generates the highest pressure-drop across the bed. A fluidized bed creates the least pressure drop; however, its sorption performance is poor. A semi-fluidized bed offers acceptable performance with affordable pressure-drops and can be a practical candidate for the process.

Adsorption↗
PubMed2002

IL-10 enhances B-cell IgE synthesis by promoting differentiation into plasma cells, a process that is inhibited by CD27/CD70 interaction.

Interleukin-10 (IL-10) is a major regulatory cytokine of inflammatory responses that is considered to play an important role in specific immunotherapy. However, whether IL-10 enhances or inhibits B-cell IgE production has remained a matter of contention. To clarify the effect of IL-10 on IgE synthesis in the presence of IL-4 and CD40 signalling, we examined B-cell proliferation, germline epsilon transcripts and plasma cell differentiation. In addition, the effect of CD27 signalling on IgE synthesis in the presence of IL-10, IL-4 and CD40 signalling was investigated. IL-10 facilitated the production of IgE in mononuclear cells and highly purified B-cells, enhanced B-cell proliferation and, most importantly, promoted the generation of plasma cells. However, IL-10 did not enhance expression of germline epsilon transcripts. The addition of CD27 signalling through the use of CD32-CD27 ligand (CD70) double transfectants significantly diminished the B-cell proliferation, IgE synthesis and plasma cell differentiation enhanced by IL-10. IL-10 enhances B-cell IgE production by promoting differentiation into plasma cells. CD27/CD70 interactions under IL-10 and sufficient CD40 cosignalling exert the opposite effect on IgE synthesis. The results of this study indicate that precautions are critical when planning immunotherapy using IL-10 in IgE-related allergic diseases.

Adult↗
PubMed2002

Genomic diversity of group A rotavirus strains infecting humans in eastern India.

Between 1998 and 2000, a total of 266 samples were found positive for group A rotaviruses by RNA electrophoresis. Samples were collected from patients admitted to two leading hospitals in Calcutta. Serotyping could be done only with 22% of the positive samples, leaving 78% untypeable. The G (VP7 genotypes) and P (VP4 genotypes) types were determined for 159 samples by reverse transcription and multiplex PCR. The predominant genotype was G1P[8] (20%), followed by G2P[4] (15%) and G4P[8] (6%). A number of uncommon genotypes, G1P[4] (4%), G2P[8] (2.5%), G2P[6] (0.6%), G4P[4] (2.5%), and G4P[6] (1.25%), were also detected during this study period. Twenty two percent of specimens showed mixed infections, 38 (24%) of the total samples remained untypeable for either VP7 or VP4, while only 4 (2.5%) of the samples were untypeable for both genes. Eleven specimens collected from Manipur were also genotyped and revealed a very high degree of genomic reassortment.

Child, Preschool↗
PubMed2002

Detection of a human rotavirus with G12 and P[9] specificity in Thailand.

G12 rotavirus has not been detected anywhere in the world since the first detection of a human strain, L26 (G12, P1B[4]), in the Philippines in 1990. In this study, we isolated a human rotavirus (strain T152) with a VP7 of G12 specificity from the stool of an 11-month-old diarrheic patient in Thailand. The strain T152 exhibited a long RNA pattern and subgroup I specificity. In the comparison of the nucleotide and amino acid sequences of the VP7 gene of strain T152 with those of rotaviruses with different G type specificities, strain T152 showed the highest identity, 90.9 and 93.9%, respectively, to G12 prototype strain L26. In contrast, the VP4 gene of strain T152 showed the highest identity with P[9] specificity of human strains K8 and AU-1 and feline strains Cat2 and FRV-1, with homologies of 89.3 to 90.6% at the nucleotide level and 93.9 to 95.6% at the amino acid level. Thus, strain T152 was found to be a natural reassortant strain with G12 and P[9] specificities.

Amino Acid Sequence↗
PubMed2002

Maternal immune responses and risk of infant infection with HIV-1 after a short course Zidovudine in a cohort of HIV-1 infected pregnant women in rural Kenya.

OBJECTIVE: To investigate the effects of short-course nucleoside reverse transcriptase inhibitor (Zidovudine, ZDW/AZT) on maternal immune responses and risk of infant infection with HIV-1 among rural-based mothers in western Kenya. DESIGN: A prospective cohort study involving HIV-1 seropositive pregnant mothers and their infants. SUBJECTS: One hundred and seven HIV-1 seropositive asymptomatic pregnant women and their infants. METHODS: After informed consent, the women were enrolled at gestation age between 16-24 weeks. For cultural and economic reasons, all mothers were allowed to breast feed their infants. Short-course antepartum regime of AZT was administered to all mothers starting at 36 weeks gestation until start of labour. Maternal absolute CD4+ T cell subset assays were performed before 3rd trimester (about 36 weeks gestation) and after a 4-week therapy of AZT (at least one month post-nuptially). Infant HIV-1 status was determined by HIV-1 DNA polymerase chain reaction (PCR) on samples sequentially taken at 1, 2, 3, 4, 6 and 9 months and confirmed by serology at 18 months of age. INTERVENTIONS: Antepartum short-course orally administered AZT: 300mg twice-daily starting at 36 weeks gestation until start of labour, 300mg at labour onset and 300mg every three hours during labour until delivery. MAIN OUTCOME MEASURES: Maternal CD4+ T cell counts before and after AZT treatment. Determination of infant HIV-1 infection status. RESULTS: Among 107 women sampled, only 59 received full dose of AZT and thus qualified for present analysis. Of these, 12 infected their children with HIV, while 47 did not. Comparison of CD4+ T cells before and after AZT treatment scored a significant rise in all mothers (P = 0.01). This increase in CD4+ T cells was not significant among mothers who infected their infants with HIV-1 (P = 0.474). However, a significant rise in CD4+ T cells following AZT therapy was observed only in mothers who did not transmit HIV-1 to their infants (P=0.014). CONCLUSION: These data suggest that a rise in the CD4+ T cell counts following short AZT regimen, now widely in use in resource-weak countries, may be evidence of the active suppression of the replication of HIV. However, further studies to examine the multi-factorial effect of CD4+ lymphocytes and pregnancy on MTCT of HIV need to be carried out to help fully explain the effect of AZT on immune response and whether the CD4+T cell count can be used as a true test of immunological normalisation during antiretroviral therapy.

Adult↗
PubMed2001

Synthesis, structure, spectroscopic properties, and electrochemistry of rare earth sandwich compounds with mixed 2,3-naphthalocyaninato and octaethylporphyrinato ligands.

A series of 14 heteroleptic rare earth sandwich complexes [M(III)-(nc)(oep)] (M=Y, La-Lu except Ce and Pm; nc=2,3-naphthalocyaninate; oep = octaethylporphyrinate) have been prepared by a one-pot procedure from corresponding [M(acac)3] . nH2O (acac = acetylacetonate), metal-free porphyrin H2(oep), and naphthalonitrile the presence of 1,8-diazabicyclo[5,4,0]undec-7-ene (DBU) in n-octanol. The molecular structures of four of these complexes (M = Sm, Gd, Y, Lu) are isostructural, exhibiting a slightly distorted square antiprismatic geometry with two domed ligands. The interplanar distance decreases from 2.823 to 2.646 A along the series as a result of lanthanide contraction. The whole series of complexes have also been characterized spectroscopically. All the electronic absorptions, except the two B-bands due to nc and the oep rings, are metal-dependent, indicating that there are substantial pi-pi interactions. The hole or the unpaired electron in these double-deckers is delocalized over both macrocyclic ligands, as evidenced by the co-appearance of the IR marker bands for the nc*- (1315-1325 cm(-1)) and oep*- (1510-1531 cm(-1)) T radical ions. Three one-electron oxidation couples and up to three one-electron reduction couples have been revealed by electrochemical methods. All the potentials are linearly dependent on the size of the metal center. The changes in absorption spectra during the first electro-oxidation and reduction of the La(III), Eu(III), and Y(III) double-deckers have also been studied spectroelectrochemically. The spectral data recorded for [M(III)(nc)(oep)]-(M = Y, La-Lu except Ce and Pm) reduced chemically with hydrazine hydrate are in accord with those obtained by spectroelectrochemical methods. The first heteroleptic naphthalocyaninate-containing triple-deckers [M(III)2(nc)-(oep)2] (M = Nd, Eu) have also been prepared by a raise-by-one-story method by using [M(III)(nc)(oep)] (M = Nd, Eu), [M(acac)3] . nH2O (M = Nd, Eu), and H2(oep) as starting materials. The compounds adopt a symmetrical triple-decker structure with two outer oep rings and one inner nc ring, which has been confirmed by 'H NMR spectroscopy and X-ray structural determination of the Nd complex. Both compounds give a near-IR absorption at 1021 nm (for M=Nd) or 1101 nm (for M = Eu), which has rarely been observed for neutral (or hole-free) triple-decker complexes and can be ascribed to the lowest-energy Q'(0, 0) transition. Similarly to the double-decker analogues. these triple-decker complexes undergo a series of one-electron transfer processes with a relatively small potential gap (1.1 -1.2 V) between the first oxidation and the first reduction.

Journal Article↗
PubMed2001

Immunoproteasome assembly and antigen presentation in mice lacking both PA28alpha and PA28beta.

Two members of the proteasome activator, PA28alpha and PA28beta, form a heteropolymer that binds to both ends of the 20S proteasome. Evidence in vitro indicates that this interferon-gamma (IFN-gamma)-inducible heteropolymer is involved in the processing of intracellular antigens, but its functions in vivo remain elusive. To investigate the role of PA28alpha/beta in vivo, we generated mice deficient in both PA28alpha and PA28beta genes. The ATP-dependent proteolytic activities were decreased in PA28alpha(-/-)/beta(-/-) cells, suggesting that 'hybrid proteasomes' are involved in protein degradation. Treatment of PA28alpha(-/-)/beta(-/-) cells with IFN-gamma resulted in sufficient induction of the 'immunoproteasome'. Moreover, splenocytes from PA28alpha(-/-)/beta(-/-) mice displayed no apparent defects in processing of ovalbumin. These results are in marked contrast to the previous finding that immunoproteasome assembly and immune responses were impaired in PA28beta(-/-) mice. PA28alpha(-/-)/beta(-/-) mice also showed apparently normal immune responses against infection with influenza A virus. However, they almost completely lost the ability to process a melanoma antigen TRP2-derived peptide. Hence, PA28alpha/beta is not a prerequisite for antigen presentation in general, but plays an essential role for the processing of certain antigens.

Adenosine Triphosphate↗
PubMed2001

Synthesis of multicomponent systems composed of one phthalocyanine and four terpyridine ligands.

Two phthalocyanine-based multiple ligands were synthesized and characterized. Photochemical and electrochemical properties were measured for zinc(II) phthalocyanines covalently linked with four ruthenium(II) bisterpyridyl complexes. The absorption and electrochemical results are indicative of electronic interaction between two photoactive and redox-active components. Fluorescence spectroscopy of the five nuclear complexes provides evidence of an efficient photoinduced intramolecular energy transfer between the ruthenium-based metal-to-ligand charge-transfer (MLCT) chromophores and the zinc(II) phthalocyanine core. The absorption and fluorescence spectra of the phthalocyanine-based multiple ligands change dramatically as a result of the coordination of metal ions with peripheral terpyridine ligands. This change of fluorescence intensity upon addition of metal ions can apply to an output signal for metal ion sensing. The direct attachment of metal ion receptors with a zinc phthalocyanine core enhanced efficiency of the energy- and electron-transfer reaction from the core to the metal complexes.

Journal Article↗
PubMed2001

Effects of cilnidipine on nitric oxide and endothelin-1 expression and extracellular signal-regulated kinase in hypertensive rats.

We evaluated the effects of cilnidipine, a long-acting Ca(2+) channel antagonist, on endothelial nitric oxide synthase (eNOS), preproendothelin-1 and endothelin ETA receptor expression in the left ventricle, and evaluated the relations between these effects and coronary microvascular remodeling and extracellular signal-regulated kinases belonging to one subfamily of mitogen-activated protein kinases in deoxycorticosterone acetate (DOCA)-salt hypertensive rats. Cilnidipine (DOCA-cilnidipine, 1 mg/kg/day, subdepressor dose) or vehicle (DOCA-vehicle) was given after induction of DOCA-salt hypertension for 5 weeks. The eNOS mRNA and protein expression in the left ventricle was significantly lower in DOCA-vehicle than in control rats and significantly higher in DOCA-cilnidipine than in DOCA-vehicle rats. Preproendothelin-1 and endothelin ETA receptor expression levels and phospho-p42/p44 extracellular signal-regulated kinase activities were significantly increased in DOCA-vehicle compared with control rats and significantly suppressed in DOCA-cilnidipine compared with DOCA-vehicle rats. DOCA-vehicle rats showed a significant increase in the wall-to-lumen ratio, perivascular fibrosis and myocardial fibrosis, with all these parameters being significantly improved by cilnidipine. These results led us to conclude that phospho-p42/p44 extracellular signal-regulated kinase activities may contribute to the coronary microvascular remodeling of DOCA rats and that protective effects of cilnidipine on cardiovascular remodeling may be at least in part mediated by an increased eNOS expression and a decreased endothelin-1 and endothelin ETA receptor expression in the left ventricle.

Animals↗
PubMed2001

Construction of regulated nanospace around a porphyrin core.

A series of 1,3,5-phenylene-based rigid dendritic porphyrins were synthesized by Suzuki coupling between a porphyrin core and dendron units. The intramolecular energy transfer was studied by absorption and fluorescence spectroscopies. The encapsulation of the porphyrin core within the 1,3,5-phenylene dendron units was found to provide highly efficient energy transfer from the dendron units to the porphyrin core. The dendritic wedge structure affected the energy transfer efficiency. The 1,3,5-phenylene-based rigid dendron units act as highly efficient light-harvesting antennae. These dendritic porphyrins have also been examined as C(60) hosts and substrate-selective oxidation catalysts. The attachment of the second generation of 1,3,5-phenylene-based dendron units with the porphyrin core enabled a stable inclusion of C(60) in toluene. Furthermore, the size and shape of the nanospace in the rigid dendritic porphyrins were found to affect the selectivity of substrates in the catalytic olefin oxidations.

Energy Transfer↗
PubMed2001

Electro-optic response of a ferroelectric liquid crystal in thick free-standing films.

We study the electro-optic response of a ferroelectric liquid crystal in free-standing films as thick as the helical pitch. In the films thicker than about one pitch, two relaxation modes are observed in the frequency spectra. The relaxation frequency of the slower mode decreases when increasing the film thickness, while that of the faster mode, which appears at approximately 1 kHz, is almost independent of the film thickness. In thinner films, a single relaxation mode is observed at several hundred Hz. The obtained relaxation spectra are discussed in comparison to the theoretical spectra of the phase mode in a system of finite length along the helical axis calculated by Urbanc and Zeks [Phys. Rev. E 52, 3892 (1995)].

Journal Article↗
PubMed2001

Protective effect of heat preconditioning of rat liver graft resulting in improved transplant survival.

BACKGROUND: The protective effect of heat preconditioning of the liver against ischemia-reperfusion injury has been reported mostly in models of transient ischemia in relation to heat shock protein 70 (HSP70). We estimated the effect of heat preconditioning of liver grafts on the transplant survival rate and on apoptosis of sinusoidal endothelial cells (SEC) as well as hepatocytes in a rat model of liver transplantation. METHODS: Donor rats of the heat shock (HS) group were subjected to heat preconditioning 48 hr before graft harvest, and HSP70 levels were estimated by. Western blot analysis and immunohistochemistry. The liver isografts from the HS group and control (C) group were preserved in Euro-Collins solution for 6 or 8 hr and transplanted orthotopically. Serum hyaluronic acid and alanine aminotransferase were measured, and apoptosis of the SEC and hepatocytes was analyzed by terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end-labeling staining and electron microscopy. RESULTS: HSP70 expression was detected not only in hepatocytes but also in SEC. In the 8-hr preservation model, the 1-week survival rate was 60% in the HS group and 0% in the C group. Serum hyaluronic acid and alanine aminotransferase levels in the HS group were significantly lower than those in the C group at 3 hr after reperfusion, and the number of terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end-labeling-positive SEC in the C group (35.2%) was markedly increased compared with the HS group (10.1%). Electron microscopic examination confirmed the features of apoptosis of SEC. CONCLUSIONS: Heat preconditioning of the graft improved the survival rate of the liver transplants. Induction of HSP70 in SEC as well as in hepatocytes might attenuate preservation-reperfusion injury by inhibiting apoptosis of SEC.

Alanine Transaminase↗
PubMed2001

Segregation of TRAF6-mediated signaling pathways clarifies its role in osteoclastogenesis.

Signals emanating from the receptor for interleukin-1 (IL-1), lipopolysaccharide (LPS) or osteoclast differentiation factor/receptor activator of NF kappa B ligand (ODF/RANKL) stimulate transcription factors AP-1 through mitogen-activated protein kinase (MAPK) activation and NF kappa B through I kappa B kinase (IKK) activation. These kinases are thought to be activated by tumor necrosis factor receptor-associated factor 6 (TRAF6). However, molecular mechanisms by which TRAF6 activates various downstream kinases remain to be elucidated. We identified functional domains of TRAF6 under physiological conditions established by appropriate expression of TRAF6 mutants in TRAF6-deficient cells. In IL-1 and LPS signaling pathways, the RING finger and first zinc finger domains are not required for NF kappa B activation but are required for full activation of MAPK. However, IL-1 and LPS signals utilize distinct regions within the zinc finger domains of TRAF6 to activate NF kappa B. Furthermore, the RING finger domain is not required for differentiation of splenocytes to multinuclear osteoclasts, but is essential for osteoclast maturation. Thus, TRAF6 plays essential roles in both the differentiation and maturation of osteoclasts by activating various kinases via its multiple domains.

Animals↗