RESUMO
The superconducting (SC) phase diagram in uranium ditelluride is explored under magnetic fields (H) along the hard magnetic b axis using a high-quality single crystal with T_{c}=2.1 K. Simultaneous electrical resistivity and ac magnetic susceptibility measurements discern low- and high-field SC (LFSC and HFSC, respectively) phases with contrasting field-angular dependence. Crystal quality increases the upper critical field of the LFSC phase, but the H^{*} of â¼15 T, at which the HFSC phase appears, is always the same through the various crystals. A phase boundary signature is also observed inside the LFSC phase near H^{*}, indicating an intermediate SC phase characterized by small flux pinning forces.
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We have developed a high-pressure electron spin resonance probe and successfully installed into the world's highest-field cryogen-free superconducting magnet having a maximum central field of 24.6â¯T. The high pressure of 2.5â¯GPa is achieved by the specially designed piston-cylinder pressure cell using THz-wave-transparent components. In the first application of this high-pressure high-field ESR system, we observed that the orthogonal dimer spin system SrCu2(BO3)2 undergoes a quantum phase transition from the dimer singlet ground to the plaquette singlet ground states.
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A distinct thermal Hall signal is observed in a quantum spin liquid candidate Ba_{3}CuSb_{2}O_{9}. The transverse thermal conductivity shows a power-law temperature dependence below 50 K, where a spin gap opens. We suggest that because of the very low longitudinal thermal conductivity and the thermal Hall signals, a phonon Hall effect is induced by strong phonon scattering of orphan Cu^{2+} spins formed in the random domains of the Cu^{2+}-Sb^{5+} dumbbells in Ba_{3}CuSb_{2}O_{9}.
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We report an experimental investigation of the magnetic field effect (MFE) in polymer bulk heterojunction devices at temperatures below 10 K using photocarrier extraction by linearly increasing voltages. The examined devices were composed of an active layer of poly(3-hexylthiophene) and [6,6]-phenyl-C61-butyric acid methyl ester. In the experiments, the delay time (td) dependence of the MFE was investigated in detail. For td < 80 µs, a positive MFE was observed in the field region B < 0.1 T and a negative MFE was observed for B > 0.2 T. For td > 8 ms, only a positive MFE proportional to B2 was observed. For the photocurrent pulse detected immediately after light irradiation, the MFE was negligibly small. In a high magnetic field of 15 T, a significant MFE exceeding 80% was observed at 1.8 K for td = 800 ms. We discuss the results based on a model of triplet-singlet (or singlet-triplet) conversion in the magnetic field and estimate the exchange integral for the charge-transfer exciton in this photovoltaic cell.
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We have measured spin Hall effects in spin glass metals, CuMnBi alloys, with the spin absorption method in the lateral spin valve structure. Far above the spin glass temperature T(g) where the magnetic moments of Mn impurities are randomly frozen, the spin Hall angle of a CuMnBi ternary alloy is as large as that of a CuBi binary alloy. Surprisingly, however, it starts to decrease at about 4T(g) and becomes as little as 7 times smaller at 0.5T(g). A similar tendency was also observed in anomalous Hall effects in the ternary alloys. We propose an explanation in terms of a simple model considering the relative dynamics between the localized moment and the conduction electron spin.
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The current-voltage characteristics in the charge order state of the two-dimensional organic conductor α-(BEDT-TTF)(2)I(3) exhibit power law behavior at low temperatures. The power law is understood in terms of the electric-field-dependent potential between electrons and holes, which are thermally excited from the charge order state. The power law exponent steeply changes from 1 to 3 in the range from 30 to 45 K with decreasing temperature, thereby suggesting the occurrence of a Kosterlitz-Thouless-type transition; many (few) unbound electron-hole pairs are thermally excited above (below) the transition. The effects of the finite size and interlayer coupling on the power law behavior are discussed.
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Oculodentodigital Dysplasia (ODDD) is a rare syndrome involving anomalies in eye, tooth, and digit formation, caused by mutations in CX43/GJA1. In addition to classic dental features, ODDD includes oral and craniofacial accessory symptoms such as characteristic facial appearance and cleft palate. However, there have been no reports of ODDD accompanied by cleft lip. Herein we report, for the first time, a male, sporadic, Asian proband presenting bilateral cleft lip. By direct sequence analysis, our proband was diagnosed as having ODDD with a heterozygous mutation, codon 142 G>A in GJA1 and CX43E48K. We excluded the possibility of pathogenic mutations in B3GALTL, BMP4, TFAP2A, PVRL1, IRF6, and MSX1. To address how CX43/GJA1 is related to cleft lip, we performed immunohistochemistry using mouse and human mid-facial tissue. CX43 expression was detected in the nasal compartment and nasal and maxillary processes at murine developmental stage E12.5. Furthermore, CX43 expression was found in the epithelial tissue inside the human subepithelial cleft lip that completes epithelial fusion. Therefore, we suggest that CX43/GJA1 is involved in lip formation. Our case report of ODDD with a bilateral cleft lip suggests that CX43/GJA1 might be a novel candidate gene for syndromic cleft lip.
Assuntos
Fenda Labial/genética , Conexina 43/genética , Anormalidades do Olho/genética , Dedos/anormalidades , Anormalidades Dentárias/genética , Anormalidades Múltiplas/genética , Adenina , Animais , Proteína Morfogenética Óssea 4/genética , Pré-Escolar , Epitélio/patologia , Éxons/genética , Galactosiltransferases/genética , Glucosiltransferases/genética , Ácido Glutâmico/genética , Guanina , Heterozigoto , Humanos , Lactente , Íntrons/genética , Lábio/patologia , Lisina/genética , Masculino , Camundongos , Modelos Animais , Polimorfismo de Nucleotídeo Único/genética , Fator de Transcrição AP-2/genéticaRESUMO
We report the results of the angular-dependent magnetoresistance oscillations (AMROs), which can determine the shape of bulk Fermi surfaces (FSs) in quasi-two-dimensional (Q2D) systems, in a highly hole-doped Fe-based superconductor KFe2As2 with Tc ≈ 3.7 K. From the AMROs, we determined the two Q2D FSs with rounded-square cross sections, correspond to 12% and 17% of the first Brillouin zone. The rounded-squared shape of the FS cross section is also confirmed by the analyses of the interlayer transport under in-plane fields. From the obtained FS shape, we infer the character of the 3d orbitals that contribute to the FSs.
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Systematic measurements of the magnetocaloric effect, heat capacity, and magnetic torque under a high magnetic field up to 35 T are performed in the spin density wave (SDW) phase of a quasi-one-dimensional organic conductor (TMTSF)2ClO4. In the SDW phase above 26 T, where the quantum Hall effect is broken, rapid oscillations (ROs) in these thermodynamic quantities are observed, which provides clear evidence of the density-of-state (DOS) oscillation near the Fermi level. The resistance is semiconducting and the heat capacity divided by temperature is extrapolated to zero at 0 K in the SDW phase, showing that all the energy bands are gapped, and there is no DOS at the Fermi level. The results show that the ROs are ascribed to the DOS oscillation of the quasiparticle excitation.
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A novel technique of high-frequency electron spin resonance (ESR) in a pulsed magnetic field is presented. Our technique is based on the magnetic detection of a magnetization change associated with the ESR absorption using a microcantilever. We successfully observed ESR signals of a microcrystal (mass approximately 1 microg) in the millimeter-wave region up to 130 GHz in pulsed magnetic fields of up to 2.4 T. This result corresponds to the spin sensitivity of approximately 10(11) spins/G, which is four orders of magnitude better than that of conventional transmission-type ESR techniques.
RESUMO
Highly sensitive magnetic detection of electron spin resonance (ESR) using a microcantilever is presented. By combining a modulation technique with the use of a piezoresistive cantilever, we successfully observed ESR signals of a tiny single crystal (mass<1 microg) of Co Tutton salt, Co(NH(4))(2)(SO(4))(2) x 6 H(2)O, in the frequency region of 80-240 GHz. The achieved spin sensitivity was approximately 10(9) spins/G at 4.5 K, providing promising applications to high-resolution and high-sensitivity terahertz ESR.
Assuntos
Espectroscopia de Ressonância de Spin Eletrônica , Magnetismo , Micro-Ondas , Anisotropia , Cobalto/química , Cristalização , Sensibilidade e EspecificidadeRESUMO
DC-SIGN, a type II membrane protein with a C-type lectin binding domain that is highly expressed on mucosal dendritic cells (DCs) and certain macrophages in vivo, binds to ICAM-3, ICAM-2, and human and simian immunodeficiency viruses (HIV and SIV). Virus captured by DC-SIGN can be presented to T cells, resulting in efficient virus infection, perhaps representing a mechanism by which virus can be ferried via normal DC trafficking from mucosal tissues to lymphoid organs in vivo. To develop reagents needed to characterize the expression and in vivo functions of DC-SIGN, we cloned, expressed, and analyzed rhesus macaque, pigtailed macaque, and murine DC-SIGN and made a panel of monoclonal antibodies (MAbs) to human DC-SIGN. Rhesus and pigtailed macaque DC-SIGN proteins were highly similar to human DC-SIGN and bound and transmitted HIV type 1 (HIV-1), HIV-2, and SIV to receptor-positive cells. In contrast, while competent to bind virus, murine DC-SIGN did not transmit virus to receptor-positive cells under the conditions tested. Thus, mere binding of virus to a C-type lectin does not necessarily mean that transmission will occur. The murine and macaque DC-SIGN molecules all bound ICAM-3. We mapped the determinants recognized by a panel of 16 MAbs to the repeat region, the lectin binding domain, and the extreme C terminus of DC-SIGN. One MAb was specific for DC-SIGN, failing to cross-react with DC-SIGNR. Most MAbs cross-reacted with rhesus and pigtailed macaque DC-SIGN, although none recognized murine DC-SIGN. Fifteen of the MAbs recognized DC-SIGN on DCs, with MAbs to the repeat region generally reacting most strongly. We conclude that rhesus and pigtailed macaque DC-SIGN proteins are structurally and functionally similar to human DC-SIGN and that the reagents that we have developed will make it possible to study the expression and function of this molecule in vivo.
Assuntos
Moléculas de Adesão Celular , Lectinas Tipo C , Lectinas/fisiologia , Receptores de Superfície Celular/fisiologia , Sequência de Aminoácidos , Animais , Anticorpos Monoclonais/imunologia , Mapeamento de Epitopos , Humanos , Lectinas/química , Lectinas/imunologia , Lectinas/metabolismo , Macaca mulatta , Macaca nemestrina , Camundongos , Camundongos Endogâmicos BALB C , Dados de Sequência Molecular , Coelhos , Receptores de Superfície Celular/química , Receptores de Superfície Celular/imunologiaRESUMO
Immunoglobulin E (IgE)-dependent histamine release from purified rat peritoneal mast cells (PMC) is very low in comparison to that from a non-purified preparation (PEC). The reduced histamine release from PMC is recovered or potentiated by reconstitution with separated non-mast cells (NMC). In the present study, further characterization was undertaken to elucidate the mechanisms involved. Sensitized mast cells were recovered from peritoneal cavities of rats, and purified by density gradient centrifugation with Percoll. Effects of NMC reconstitution, membrane fraction of NMC, NMC incubation supernatant, adhesion molecules and extracellular matrix proteins on IgE-dependent histamine release from PMC were examined. IgE-dependent histamine release was significantly potentiated by NMC reconstitution to PMC. The potentiation was dependent on the concentration of NMC reconstituted and reached a plateau after 30 min incubation. Increasing concentration of PMC did not affect the histamine release. Membrane fraction prepared from NMC also potentiated PMC histamine release in a dose-dependent manner. The potentiation reached a plateau in 5 min. Furthermore, incubation supernatant of NMC potentiated PMC histamine release. Antibodies against intercellular adhesion molecule (ICAM)-1, lymphocyte function-associated antigen (LFA)-1, very late activation antigen (VLA)-1, VLA-4 and VLA-6, and fibronectin did not affect the potentiation of PMC histamine release by NMC reconstitution. Fibronectin, laminin and collagen failed to potentiate PMC histamine release. These results indicate that the membrane component(s) of NMC in the rat peritoneal cavity seems to modulate IgE-dependent histamine release from peritoneal mast cells of rats, and that the active molecule(s) may be released from NMC. Adhesion molecules such as ICAM-1, LFA-1 and VLA are not involved.
Assuntos
Liberação de Histamina/efeitos dos fármacos , Mastócitos/metabolismo , Animais , Soluções Tampão , Membrana Celular/química , Membrana Celular/metabolismo , Separação Celular , Proteínas da Matriz Extracelular/biossíntese , Imunoglobulina E/biossíntese , Técnicas In Vitro , Indicadores e Reagentes , Integrina alfa4beta1 , Integrinas , Masculino , Mastócitos/efeitos dos fármacos , Ratos , Ratos Wistar , Receptores de Retorno de Linfócitos , Receptores de Antígeno muito Tardio/metabolismoRESUMO
Epicutaneous antigen challenge in passively sensitized mice with IgE produces a biphasic cutaneous response which peaks 1 h (immediate-phase reaction) and 24 h (late-phase reaction; LPR) after the antigen challenge. In this model, anaphylactic degranulation and interleukin 6 (IL-6) expression between 4 and 8 h are observed in resident mast cells as the preceding stage of LPR. Prednisolone at a dose of 3 mg kg(-1) clearly inhibited the LPR when administered 2 h before and 4 h after antigen challenge. Slight or no inhibition of LPR was observed by prednisolone administered 6-12 h after challenge. Histologically, prednisolone treatment 2 h before antigen challenge completely inhibited edema and inflammatory cell infiltration, while treatment at 6 h did not at all. In order to investigate the relationship between inhibition of LPR by prednisolone and mast cell activation, the effects of prednisolone on degranulation of mast cells and IL-6 expression in mast cells were investigated. 8 h after antigen challenge, prednisolone clearly inhibited the increase in the number of anaphylactic degranulated and IL-6-positive mast cells by administration 2 h before challenge, but did not affect it by administration 6 h after challenge. These data indicate that the inhibitory mechanism of prednisolone on LPR, at least, involves the inhibition of mast cell activation before LPR.
Assuntos
Glucocorticoides/farmacologia , Hipersensibilidade Tardia/prevenção & controle , Mastócitos/efeitos dos fármacos , Prednisolona/farmacologia , Animais , Degranulação Celular , Dinitrofluorbenzeno/imunologia , Feminino , Hipersensibilidade Tardia/imunologia , Imunoglobulina E/imunologia , Imuno-Histoquímica , Interleucina-6/biossíntese , Mastócitos/fisiologia , Mastócitos/ultraestrutura , Camundongos , Camundongos Endogâmicos BALB C , Microscopia Eletrônica , Pele/efeitos dos fármacos , Pele/imunologia , Organismos Livres de Patógenos Específicos , Fatores de TempoRESUMO
A spore cortex-lytic enzyme of Clostridium perfringens S40 is synthesized during sporulation as a precursor consisting of four domains. After cleavage of an N-terminal preregion and a C-terminal proregion, inactive proenzyme (termed C35) is converted to active enzyme by processing of an N-terminal prosequence with germination-specific protease (GSP) during germination. The present results demonstrated that the cleaved N-terminal prepeptide remained associated with C35. After the isolated complex was denatured and dissociated in 6 M urea solution, removal of urea regenerated a prepeptide-C35 complex which produces active enzyme when incubated with GSP. However, isolated C35 alone could not be activated by GSP. The prepeptide-C35 complex was more heat stable than active enzyme. Thus, non-covalent attachment of the prepeptide to C35 is required to assist correct folding of C35 and to stabilize its conformation, suggesting that the prepeptide functions as an intramolecular chaperone. Recombinant proteins, which have prepeptide covalently bonded to C35, were processed by GSP as well as the in vivo prepeptide-C35 complex, and the full length of the N-terminal presequence was needed to fulfil its role. Although the C-terminal prosequence is present as an independent domain which is not involved in the activation process of the enzyme, it appears that the N-terminal prosequence contributes to the regulation of enzyme activity as an inhibitor of the enzyme.
Assuntos
Proteínas de Bactérias , Clostridium perfringens/enzimologia , Hidrolases/biossíntese , Esporos Bacterianos/enzimologia , Sequência de Aminoácidos , Sequência de Bases , Clostridium perfringens/crescimento & desenvolvimento , Primers do DNA , Ativação Enzimática , Hidrolases/química , Hidrolases/metabolismo , Dados de Sequência Molecular , Conformação Proteica , Esporos Bacterianos/crescimento & desenvolvimentoRESUMO
BACKGROUND: In mice that are passively sensitized to IgE, cutaneous antigen challenge produces a biphasic response with peaks at 1 and 24 hours after challenge. OBJECTIVE: We investigated the role of mast cells in the IgE-mediated late-phase reaction in mice. METHODS: We histologically and ultrastructurally investigated the morphologic changes of mast cells during the biphasic responses. RESULTS: Degranulation of mast cells, which was observed between 4 and 24 hours after challenge, reached a peak at 8 hours. Piecemeal degranulation was seen during the immediate phase reaction. The number of IL-6-positive mast cells was increased after 4 hours in both IgE-sensitized and unsensitized mice, but positive cells showed a greater increase in sensitized mice and reached a peak after 8 hours. With in situ hybridization experiments, mast cells were positive for IL-6 messenger RNA at 6 hours after challenge. CONCLUSION: These findings indicate that anaphylactic degranulation of mast cells and the expression of IL-6 mRNA within 4 hours after antigen challenge are important for the onset of the late-phase allergic cutaneous reaction in mice.
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Dermatite Atópica/etiologia , Hipersensibilidade Tardia/etiologia , Imunoglobulina E/farmacologia , Mastócitos/fisiologia , Animais , Feminino , Imuno-Histoquímica , Interleucina-6/biossíntese , Interleucina-6/genética , Mastócitos/ultraestrutura , Camundongos , Camundongos Endogâmicos BALB C , Microscopia Eletrônica , RNA Mensageiro/metabolismoRESUMO
Minimally invasive surgery has revolutionized the treatment of gastrointestinal tumors. Submucosal tumors (SMTs) of the stomach can be resected using laparoscopic techniques. Between 1993 and 1997, laparoscopic wedge resection was performed in 34 patients with an SMT of the stomach. The tumors ranged from 8 to 60 mm in diameter. All surgical margins were clear. The average operative time was 131 minutes. Most of the patients began eating on the first postoperative day and were discharged within 5 to 7 days. Histopathologic examination of the tumors showed gastrointestinal stromal tumor (n = 14), ectopic pancreas (n = 7), leiomyosarcoma (n = 4), schwannoma (n = 3), carcinoid (n = 2), leiomyoma (n = 2), an inflammatory lesion caused by parasites (n = 1), and cyst (n = 1). No recurrences were observed over the 5-year follow-up period. A solid SMT of the stomach larger than 20 mm in diameter can be treated using laparoscopic wedge resection.
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Laparoscopia , Neoplasias Gástricas/cirurgia , Adulto , Idoso , Idoso de 80 Anos ou mais , Estudos de Viabilidade , Feminino , Humanos , Masculino , Pessoa de Meia-IdadeRESUMO
Human cultured mast cells (HCMC) secrete histamine, sulfidoleukotrienes (LTs), and prostaglandin D(2) (PGD(2)), and produce a variety of cytokines after aggregation of high-affinity receptors for IgE (FcepsilonRI). With respect to the mitogen-activated protein kinase (MAPK) family, extracellular signal-regulated kinases (ERKs), c-Jun NH(2)-terminal kinases (JNKs), and p38 mitogen-activated protein kinase (p38 MAPK) are known. To investigate the roles of these kinase pathways for mediator release from human mast cells, we examined the participation of the activation of these kinases in mediator release, using 1,4-diamino-2, 3-dicyano-1,4-bis(2-aminophenylthio)butadiene (U0126), an ERK pathway inhibitor, and 4-(4-fluorophenyl)-2-(4-methylsulfinylphenyl)-5-(4-pyridyl)1H-imid azo le (SB203580), a p38 MAPK pathway inhibitor. U0126 inhibited ERK activation, LT and PGD(2) release, and granulocyte macrophage-colony stimulating factor (GM-CSF) production after stimulation of HCMC. SB203580, on the other hand, potentiated JNK activation and GM-CSF production. The findings of the present study demonstrated that: (i) the release of arachidonic acid metabolites is mediated by the ERK pathway; (ii) GM-CSF production may be driven by both the ERK and JNK pathways; and (iii) the p38 MAPK pathway negatively regulates the JNK pathway. This suggests that MAPK pathways play important roles in mediator release from human mast cells.
Assuntos
Sistema de Sinalização das MAP Quinases/fisiologia , Mastócitos/metabolismo , Proteínas Quinases Ativadas por Mitógeno/metabolismo , Butadienos/farmacologia , Células Cultivadas , Inibidores Enzimáticos/farmacologia , Humanos , Imidazóis/farmacologia , Imunoglobulina E/imunologia , Proteínas Quinases JNK Ativadas por Mitógeno , Mastócitos/efeitos dos fármacos , Mastócitos/enzimologia , Proteínas Quinases Ativadas por Mitógeno/antagonistas & inibidores , Nitrilas/farmacologia , Piridinas/farmacologia , Proteínas Quinases p38 Ativadas por MitógenoRESUMO
BACKGROUND: Matrix metalloproteinases (MMPs), enzymes capable of degrading collagens and other extracellular matrix components, have been implicated in gastric ulcer formation. However, the effect on MMP expression of Helicobacter pylori, also implicated in these lesions, has not been studied to our knowledge. AIM: To seek links between H. pylori and MMP expression likely to affect gastric ulcer formation. After fibroblasts from human gastric wall were cocultured with H. pylori. concentrations of MMP-1 and -2 in the medium were determined by enzyme-linked immunosorbent assays. RESULTS: Whereas MMP-1 was not detected in media from fibroblasts or H. pylori culture alone, MMP-1 was detected in cocultures (P<0.01). Similar amounts of MMP-2 were detected in medium from fibroblasts cultured alone and with H. pylori. No MMP-2 production by H. pylori cultured alone was detected. CONCLUSIONS: MMP-1 appears to be important in gastric ulcer pathogenesis, and MMP-1 induction by H. pylori may impede gastric ulcer healing.
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Fibroblastos/enzimologia , Mucosa Gástrica/citologia , Helicobacter pylori , Metaloproteinase 1 da Matriz/biossíntese , Úlcera Gástrica/microbiologia , Células Cultivadas , Mucosa Gástrica/enzimologia , Infecções por Helicobacter/complicações , Humanos , Masculino , Metaloproteinase 2 da Matriz/biossíntese , Pessoa de Meia-Idade , Úlcera Gástrica/enzimologia , Úlcera Gástrica/etiologiaRESUMO
BACKGROUND: Flavonoids have a variety of activities including anti-allergic activities, and are known to inhibit histamine release from human basophils and murine mast cells. OBJECTIVE: The effects of luteolin, a flavone, on the immunoglobulin (Ig) E-mediated allergic mediator release from human cultured mast cells (HCMCs) were investigated and compared with those of baicalein and quercetin. METHODS: HCMCs were sensitized with IgE, and then treated with flavonoids before challenge with antihuman IgE. The amount of released mediators was determined as was mobilization of intracellular Ca2+ concentration, protein kinase C (PKC) translocation and phosphorylation of intracellular proteins were detected after anti-IgE stimulation. RESULTS: Luteolin, baicalein and quercetin inhibited the release of histamine, leukotrienes (LTs), prostaglandin D2 (PGD2), and granulocyte macrophage-colony stimulating factor (GM-CSF) from HCMC in a concentration-dependent manner. Additionally, the three flavonoids inhibited A23187-induced histamine release. As concerns Ca2+ signalling, luteolin and quercetin inhibited Ca2+ influx strongly, although baicalein did slightly. With regard to PKC signalling, luteolin and quercetin inhibited PKC translocation and PKC activity strongly, although baicalein did slightly. The suppression of Ca2+ and PKC signallings might contribute to the inhibition of mediator release. The activation of extracellular signal-regulated kinases (ERKs) and c-Jun NH2-terminal kinase (JNK), that were activated just before the release of LTs and PGD2 and GM-CSF mRNA expression in IgE-mediated signal transduction events, were clearly suppressed by luteolin and quercetin. In contrast, the flavonoids did not affect the activation of p38 mitogen-activated protein kinase (p38 MAPK) pathway. CONCLUSION: These results indicate that luteolin is a potent inhibitor of human mast cell activation through the inhibition of Ca2+ influx and PKC activation.