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BACKGROUND: The J-Land 3S trial demonstrated that landiolol is effective and tolerated for treating sepsis-related tachyarrhythmias. Patient characteristics (e.g. baseline heart rate [HR], type of tachyarrhythmia, and concomitant disorders) may impact the outcomes of landiolol therapy. We performed subanalyses of J-Land 3S to evaluate the impact of patient characteristics on the efficacy and safety of landiolol for treating sepsis-related tachyarrhythmia. METHODS: Patients (≥20 years old; N = 151) hospitalised with sepsis at 54 participating hospitals in Japan with HR ≥100 beats/min for ≥10 min accompanied by diagnosis of tachyarrhythmia were randomised 1:1 to conventional sepsis therapy alone (control group) or conventional sepsis therapy plus landiolol (landiolol group). The efficacy and safety of landiolol were assessed in prespecified analyses of patients divided into subgroups by baseline characteristics and in post hoc, multivariate analyses with adjustment for age and HR at baseline. FINDINGS: The percentage of patients with HR of 60-94 beats/min at 24 h after randomisation (primary endpoint) was greater in the landiolol group in most subgroups in univariate unadjusted analyses and in multivariate logistic regression. The incidence of new-onset arrhythmia by 168 h and mortality by 28 days were also lower in the landiolol group in most subgroups in univariate and multivariate Cox proportional hazards models. No subgroups showed a markedly higher incidence of adverse events in univariate or multivariate logistic regression analyses. INTERPRETATION: These results of the J-Land 3S study suggest that the efficacy and safety of landiolol are generally unaffected by key patient characteristics. FUNDING: Ono Pharmaceutical Co., Ltd.
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In vitro antigen stimulation of peripheral blood mononuclear cells (PBMCs) does not induce immunoglobulin (Ig) production. However, pretreatment of PBMCs with l-leucyl-l-leucine methyl ester (LLME) prior to in vitro stimulation removes the suppression of Ig production. In the present study, we attempted to identify the target cells of LLME and determine the mechanisms by which Ig production in PBMCs is suppressed. We found that CD14(+) monocytes are involved in the suppression of Ig production in PBMCs. Furthermore, we confirmed that heavy-chain ferritin derived from CD14(+) monocytes suppresses Ig production in PBMCs, possibly through iron sequestration.
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Apoferritinas/metabolismo , Linfocitos B/inmunología , Leucocitos Mononucleares/inmunología , Monocitos/metabolismo , Formación de Anticuerpos/efectos de los fármacos , Apoferritinas/inmunología , Comunicación Celular , Células Cultivadas , Dipéptidos/química , Dipéptidos/farmacología , Humanos , Terapia de Inmunosupresión , Hierro/metabolismo , Receptores de Lipopolisacáridos/metabolismo , Activación de Linfocitos/efectos de los fármacos , Éteres Metílicos/química , Éteres Metílicos/farmacología , Monocitos/efectos de los fármacos , Monocitos/inmunologíaRESUMEN
In this study, we developed a compact wireless Laplacian electrode module for electromyograms (EMGs). One of the advantages of the Laplacian electrode configuration is that EMGs obtained with it are expected to be sensitive to the firing of the muscle directly beneath the measurement site. The performance of the developed electrode module was investigated in two human interface applications: character-input interface and detection of finger movement during finger Braille typing. In the former application, the electrode module was combined with an EMG-mouse click converter circuit. In the latter, four electrode modules were used for detection of finger movements during finger Braille typing. Investigation on the character-input interface indicated that characters could be input stably by contraction of (a) the masseter, (b) trapezius, (c) anterior tibialis and (d) flexor carpi ulnaris muscles. This wide applicability is desirable when the interface is applied to persons with physical disabilities because the disability differs one to another. The investigation also demonstrated that the electrode module can work properly without any skin preparation. Finger movement detection experiments showed that each finger movement was more clearly detectable when comparing to EMGs recorded with conventional electrodes, suggesting that the Laplacian electrode module is more suitable for detecting the timing of finger movement during typing. This could be because the Laplacian configuration enables us to record EMGs just beneath the electrode. These results demonstrate the advantages of the Laplacian electrode module.
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Electromiografía/instrumentación , Interfaz Usuario-Computador , Tecnología Inalámbrica/instrumentación , Electrodos , Dedos/fisiología , Humanos , Movimiento , Contracción Muscular/fisiología , Músculo Esquelético/fisiología , Programas InformáticosRESUMEN
The Drosophila transglutaminase gene (CG7356) encodes two transglutaminases, dTG-A and dTG-B. To understand the roles of dTG-B during the development of the fly, we examined phenotypes induced through ectopic expression of dTG-B. Overexpression of dTG-B induced rough eye and extra wing crossvein phenotypes. These phenotypes were similar to those observed in the case of targeted overexpression of dTG-A.
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Proteínas de Drosophila/metabolismo , Drosophila/metabolismo , Ojo/enzimología , Transglutaminasas/metabolismo , Alas de Animales/enzimología , Animales , Drosophila/genética , Proteínas de Drosophila/genética , Ojo/anatomía & histología , Ojo/metabolismo , Expresión Génica , Mutación , Fenotipo , Transglutaminasas/genética , Alas de Animales/anatomía & histología , Alas de Animales/metabolismoRESUMEN
To determine the roles of Drosophila transglutaminase-A (dTG-A), we examined a phenotype induced through ectopic expression of dTG-A. Overexpression of dTG-A in the wing imaginal disc induced an extra wing crossvein phenotype. This phenotype was suppressed by crossing with epidermal growth factor receptor (Egfr) signaling pathway mutant flies. These results indicate that this phenotype, induced by dTG-A, is related to enhancement of the Egfr signaling pathway.
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Drosophila melanogaster/anatomía & histología , Drosophila melanogaster/enzimología , Fenotipo , Transglutaminasas/genética , Alas de Animales/anatomía & histología , Alas de Animales/enzimología , Animales , Drosophila melanogaster/genética , Expresión GénicaRESUMEN
Transglutaminases (TGs) catalyze the cross-linking of proteins and are involved in various biological processes in mammals. In invertebrates, except for the involvement in the hemolymph clotting, the functions of TG have not been revealed. Drosophila has a single TG gene (CG7356), from which two kinds of mRNAs (dTG-RA and dTG-RB) are formed. RT-PCR analyses indicated that both dTGs-RA and -RB are synthesized in all the developmental stages tested. To reveal the roles of dTG during the development, we examined a phenotype induced through the ectopic expression of dTG by using a GAL4-UAS targeted expression system. Over-expression of dTG-A in the eye imaginal disc of larva induced a rough eye phenotype in adult compound eyes. Co-expression of P35, an inhibitor of apoptosis, suppressed the rough eye phenotype, suggesting that the rough eye phenotype induced by the over-expression of dTG-A in the eye imaginal disc is due to the occurrence of apoptosis. The rough eye phenotype induced by the over-expression of dTG-A was suppressed by the crossing with mutant fly lines lacking Drosophila JNK gene basket (bsk) or Drosophila JNKK gene hemipterous. FLP-out experiments using an enhancer trap line showed that the over-expression of dTG-A in the eye imaginal disc increased the puckered enhancer activity, a reporter of Bsk activity. These results suggested that the rough eye phenotype induced by the over-expression of dTG-A is related to an enhancement of JNK signaling pathway.
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Apoptosis , Drosophila melanogaster/metabolismo , Ojo/metabolismo , Ojo/patología , Regulación del Desarrollo de la Expresión Génica , MAP Quinasa Quinasa 4/metabolismo , Transglutaminasas/fisiología , Secuencia de Aminoácidos , Animales , Animales Modificados Genéticamente , Western Blotting , Drosophila melanogaster/crecimiento & desarrollo , Ojo/crecimiento & desarrollo , Femenino , Técnicas para Inmunoenzimas , MAP Quinasa Quinasa 4/genética , Masculino , Datos de Secuencia Molecular , Mutación/genética , Fenotipo , ARN Mensajero/genética , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Homología de Secuencia de AminoácidoRESUMEN
BACKGROUND: During melanogenesis, the activity of tyrosinase (the key enzyme for melanin synthesis) is important in the diagnosis of melanomas. METHODS: Nine samples were included in this study, based on the availability of four malignant melanomas and five benign tumours. Our new approach is based on a combination of the DOPA oxidase and the glyoxylic acid (GA) methods for catecholamine (named the 'DOPA-GA method'). Here, we compared the conventional DOPA oxidase method with that of the DOPA-GA method. RESULTS: In all malignant melanomas, the fluorescence intensity of the DOPA-GA method was strongly expressed within the cytoplasm. The melanoma cells showed an obvious sensitivity compared with the Laidlaw and Blackberg method, as did the melanocytes in the normal skin. Detection was easier with the DOPA-GA method than the Laidlaw and Blackberg method. Hence, we developed a sensitive and rapid method with a total assay time of less than 30 min. CONCLUSION: DOPA-GA reflects tyrosinase activity in melanocytic tumours, and our new approach is an improvement on the conventional DOPA oxidase method, with regard to both specificity and sensitivity. The DOPA-GA method will be useful for routine pathological testing and melanogenetic studies of melanocytes and melanocytic tumours.
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Dihidroxifenilalanina , Glioxilatos , Melanocitos/patología , Melanoma/diagnóstico , Neoplasias Cutáneas/diagnóstico , Diagnóstico Diferencial , Humanos , Melanocitos/enzimología , Melanoma/enzimología , Microscopía Fluorescente/métodos , Monofenol Monooxigenasa/metabolismo , Neoplasias Cutáneas/enzimologíaRESUMEN
Transglutaminases (TGs) are a family of enzymes that catalyze Ca(2+)-dependent post-translational modification of proteins by introducing protein-protein crosslinks (between specific glutamine and lysine residues), amine incorporation, and site-specific deamidation. In this study, new amine acceptor protein substrates of TG were isolated from rat liver extract and identified using 5-(biotinamido) pentylamine, a biotinylated primary amine substrate, as a probe. TG protein substrate candidates labeled with biotin by endogenous TG activity were isolated and recovered by avidin column chromatography. Proteins with molecular masses of 40, 42, and 45 kDa were the main components of the labeled proteins. Determination of their partial amino acid sequences and immunoblotting analyses were done to identify them. The 45-kDa protein was identical with betaine-homocysteine S-methyltransferase (EC 2.2.2.5), which was identified in our previous study. The 40- and 42-kDa proteins were identified as arginase-I (EC 3.5.3.1) and fructose-1,6-bisphosphatase (EC 3.1.3.11) respectively. TG catalyzed incorporation of 5-(biotinamido) pentylamine into both arginase-I and fructose-1,6-bisphosphatase purified from rat liver was confirmed in vitro. These results suggest that these two enzymes are the new protein substrate candidates of TG and that they can be modified post-translationally by cellular TG.
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Aminas/metabolismo , Técnicas Biosensibles/métodos , Biotina/análogos & derivados , Extractos Hepáticos/metabolismo , Proteínas/análisis , Proteínas/metabolismo , Transglutaminasas/metabolismo , Secuencia de Aminoácidos , Animales , Anticuerpos/inmunología , Arginasa/inmunología , Arginasa/metabolismo , Biotina/metabolismo , Biotinilación , Electroforesis en Gel de Poliacrilamida , Fructosa-Bifosfatasa/inmunología , Fructosa-Bifosfatasa/metabolismo , Cobayas , Immunoblotting , Datos de Secuencia Molecular , Unión Proteica , Proteínas/química , Proteínas/inmunología , Ratas , Ratas WistarRESUMEN
Treatment of exponentially growing MCF-7 human breast carcinoma cells with tamoxifen (TAM) inhibits cell growth in a dose-dependent manner. However, the molecular basis for the drug's activity and its relationship to the cell cycle have not yet been clearly established. In this study, we analyzed cell cycle-related proteins used for immunoblotting and flow cytometry in TAM-treated MCF-7 cells. In addition, the ratio of apoptosis in the cell was analyzed using labeling of DNA strand breaks (TdT assay). In flow-cytometric DNA distribution analysis, the S-phase fraction showed a marked decrease and a concomitant increase in G1- and G2-phase cells accompanying the inhibitory effect of TAM; these changes were time- and dose-dependent. Immunoblotting revealed that the levels of p53 and p21(WAF1/CIP1) in TAM-treated cells increased in a time- and dose-dependent manner, whereas those of p27(KIP1) and p16 slightly increased or remained unchanged. Furthermore, cyclin D3 and B showed sharp decreases, in contrast with p53 and p21(WAF1/CIP1) DNA-apoptosis dual analysis using flow cytometry revealed that the TAM-treated samples contained apoptotic cells, the majority of which were arrested in G1 or G2 and showed suppression of Bcl-2 protein. These results suggest that the tumorigenic effect of TAM on MCF-7 cells arises through antitumor effects that are due to the expression of cyclin-dependent kinase inhibitors, especially p21(WAF1/CIP1) and these are regulated by the decrease of wild-type p53. The proposed mechanism is similar to that underlying the cytotoxic effects of other agents and ionizing irradiation that cause DNA damage.
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Antineoplásicos Hormonales/farmacología , Neoplasias de la Mama/metabolismo , Neoplasias de la Mama/patología , Carcinoma/metabolismo , Carcinoma/patología , Proteínas Inhibidoras de las Quinasas Dependientes de la Ciclina/metabolismo , Fase G1/efectos de los fármacos , Tamoxifeno/farmacología , Apoptosis , Inhibidor p21 de las Quinasas Dependientes de la Ciclina/metabolismo , Relación Dosis-Respuesta a Droga , Femenino , Regulación Neoplásica de la Expresión Génica , Humanos , Factores de Tiempo , Células Tumorales Cultivadas , Proteína p53 Supresora de Tumor/metabolismoRESUMEN
Previously, we have established an in vitro immunization method to induce antigen-specific antibody-producing B cells. In the present study, we have attempted to clarify the mechanisms that regulate antibody production by in vitro immunized peripheral blood mononuclear cells (PBMC). Freshly isolated PBMC did not induce antibody production following in vitro immunization, but expressed the interleukin (IL)-10 gene. On the other hand, PBMC pretreated with L: -leucyl-L: -leucine methyl ester (LLME) induced antibody production, but did not express the IL-10 gene. IL-10 induced functional impairment of CD4(+) Th cells and CD11c(+) DC, resulting in the suppression of antibody production by in vitro immunized PBMC.
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For comparative biochemical interest, we analyzed the structures of N-glycans in a squid belonging to the Lophotrochozoa, one of the protostome clades. N-Glycans were prepared from squid skin by hydrazinolysis and re-N-acetylation followed by fluorescent tagging with 2-aminopyridine. The labeled N-glycans were purified, and their structures were determined by the two-dimensional HPLC mapping method combined with glycosidase digestions and mass spectrometry. We found that high mannose-type glycans, paucimannose-type glycans and complex-type glycans with a type-1 structure (Galbeta1-3GlcNAc) were dominant in squid skin. The complex-type glycans detected in the squid were similar to those in vertebrates, but have not yet been found in the Ecdysozoa, which is another protostome clade. However, paucimannose-type glycans are commonly found in the Ecdysozoa. Thus, the N-glycan structures of the squid belonging to the Lophotrochozoa have features common to those in vertebrates and the Ecdysozoa including insects and nematodes.
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Decapodiformes/química , Polisacáridos/química , Animales , Secuencia de Carbohidratos , Cromatografía Líquida de Alta Presión , Datos de Secuencia Molecular , Polisacáridos/aislamiento & purificación , Polisacáridos/metabolismo , Piel/química , beta-Galactosidasa/metabolismo , beta-N-Acetilhexosaminidasas/metabolismoRESUMEN
We previously developed an in vitro immunization (IVI) protocol of human peripheral blood mononuclear cells (PBMC) for generating antigen-specific human antibodies. In order to clarify whether IVI protocolinduces antigen-specific B cell responses in PBMC, we analyzed family gene usage and sequence of the variable region gene of immunoglobulin heavy chain (VH gene) of the antibody produced from the in vitro immunized PBMC. Sequence homology analyses of VH gene demonstrated that a larger repertoire of B cells can be sensitized with mite-extract than with cholera toxin B subunit and rice allergen. Further, antigen-specific B cells were efficiently expanded by using CpG oligodeoxynucleotide as adjuvant. These results suggest that appropriate combination of sensitizing antigen and adjuvant is primarily important for expansion of antigen-specific B cells in IVI protocol.
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Finger braille is one of the communication methods for the deaf blind. The interpreter types braille codes on the fingers of deaf blind. Finger braille seems to be the most suitable medium for real-time communication by its speed and accuracy of transmitting characters. We hypothesize that the prosody information exists in the time structure and strength of finger braille typing. Prosody is the paralinguistic information that has functions to transmit the sentence structure, prominence, emotions and other form of information in real time communication. In this study, we measured the surface electromyography (sEMG) of finger movement to analyze the typing strength of finger braille. We found that the typing strength increases at the beginning of a phrase and a prominent phrase. The result shows the possibility that the prosody in the typing strength of finger braille can be applied to create an interpreter system for the deafblind.
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Electromiografía/instrumentación , Electromiografía/métodos , Auxiliares Sensoriales , Ceguera , Sordera , Dedos , Humanos , Japón , Lenguaje , Lingüística , Masculino , Movimiento , Lectura , Reproducibilidad de los Resultados , TactoRESUMEN
Some mutants of Caenorhabditis elegans show altered patterns of ectopic binding with wheat germ agglutinin (WGA). Some of these mutants also have defects of morphogenesis and movement during development. To clarify the structures of WGA-ligands in C. elegans that may be involved in developmental events, we have analyzed glycan structures capable of binding WGA. We isolated glycoproteins from wild-type C. elegans by WGA-affinity chromatography, and analyzed their glycan structures by a combination of hydrazine degradation and fluorescent labeling. The glycoproteins had oligomannose-type and complex-type N-glycans that included agalacto-biantenna and agalacto-tetraantenna glycans. Although the complex-type glycans carried beta-GlcNAc residues at their non-reducing ends, they did not bind to the WGA-agarose-resin. Thus, it was suggested that these N-glycans were not responsible for WGA-binding of the isolated glycoproteins. Hydrazinolysis of the glycoproteins also released a considerable amount of GalNAc monosaccharide. It was surmised that N-acetylgalactosamine was derived from mucin-type O-glycans with the Tn-antigen structure (GalNAcalpha1-O-Ser/Thr). WGA-blotting assay of neoglycoproteins revealed that a cluster of Tn-antigens was a good ligand for WGA. These results suggested that the WGA-ligand in C. elegans is a cluster of alpha-GalNAc monosaccharides linked to mucin-like glycoprotein(s). The observations reported in this paper emphasize the possible significance of mucin-type O-glycans in the development of a multicellular organism.
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Proteínas de Caenorhabditis elegans/química , Caenorhabditis elegans/química , Glicoproteínas/química , Polisacáridos/análisis , Aglutininas del Germen de Trigo/metabolismo , Animales , Secuencia de Carbohidratos , Electroforesis en Gel de Poliacrilamida , Ligandos , Datos de Secuencia Molecular , Mucinas , Solubilidad , Relación Estructura-ActividadRESUMEN
The cell line D29, which was easily and rapidly established by the promoter-activated production and glutamine synthetase hybrid system, secreted recombinant human interleukin-6 (hIL-6) at a productivity rate of 39.5 mug 10(-6) cells day(-1), one of the highest reported levels worldwide. The productivity rate was about 130-fold higher than that of the cell line A7, which was established without both promoter activation and gene amplification. Although D29 cells had a high copy number and high mRNA level of the hIL-6 gene as well as a high secretion rate of hIL-6, large amounts of intracellular hIL-6 protein accumulated in D29 cells compared to A7 cells. Northern blotting analysis showed no change in the GRP78/BiP expression level in D29 cells. In contrast, an electrophoresis mobility shift assay revealed strong activation of NF-kappaB in D29 cells. These results suggest that large amounts of hIL-6 translated from large amounts of hIL-6 mRNA cause excess accumulation of intact hIL-6 in the endoplasmic reticulum (ER), and that subsequent negative feedback signals via the ER overload response inhibit hIL-6 protein secretion. To enhance the hIL-6 productivity rate of D29 cells by releasing the negative feedback signals, the effect of pyrrolidinedithiocarbamate, an inhibitor of NF-kappaB activation, was examined. Suppression of NF-kappaB activation in D29 cells produced a 25% augmentation of the hIL-6 productivity rate. Therefore, in highly productive cells like D29 cells, the release of negative feedback signals could increase the total amount of recombinant protein secretion.
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In the two-stage cell transformation theory, cancer cells first receive initiation, which is mainly caused by DNA damage, and then promotion, which enhances transformation. Murine Balb/c 3T3 cells are widely used for transformation experiments because they lose contact inhibition ability when transformed. Electrolyzed reduced water (ERW), which is produced near a cathode during electrolysis of water, is an alkaline drinking water that is beneficial to health. ERW contains a high concentration of dissolved hydrogen and scavenge reactive oxygen species (ROS), along with a small amount of platinum (Pt) nanoparticles (Pt nps) derived from Pt-coated titanium electrodes. Pt nps stably disperse in aqueous solution for a long time, and convert hydrogen molecules to active hydrogen (atomic hydrogen) that can scavenge ROS. Therefore, ERW supplemented with synthesized Pt nps is a model strong reduced water. This is the first report that ERW supplemented with synthesized Pt nps strongly prevents transformation of Balb/c 3T3 cells. ERW was prepared by electrolysis of 0.002 M NaOH solution using a batch-type electrolysis device. Balb/c 3T3 cells were treated with 3-methyl cholanthrene (MCA) as an initiation substance, followed by treatment with phorbol-12-myristate-13-acetate (PMA) as a promotion substance. MCA/PMA-induced formation of a transformation focus was strongly suppressed by ERW supplemented with Pt nps but not by ERW or Pt nps individually. ERW supplemented with Pt nps suppressed transformation at the promoter stage, not at initiation, suggesting that ERW supplemented with Pt nps suppressed the PMA-induced augmentation of intracellular ROS. ERW supplemented with Pt nps is a potential new antioxidant against carcinogenesis.
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Fucoidan is a uniquely-structured sulfated polysaccharide found in the cell walls of several types of brown seaweed that has recently, especially as enzyme-digested fucoidan extract, attracted a lot attention due to its anti-tumor potential. In this study, we evaluated the effects of enzyme-digested fucoidan extracts prepared from seaweed Mozuku of Cladosiphon novae-caledoniae kylin on in vitro invasion and angiogenesis abilities of human tumor cells. First, we evaluated the effect of the fucoidan extracts on oxidative stress of tumor cells, and demonstrated that intracellular H(2)O(2) level and released H(2)O(2) from tumor cells were both greatly repressed upon the treatment with the fucoidan extracts, suggesting that fucoidan extracts ameliorate oxidative stress of tumor cells. Next, we tested for the effects of fucoidan extracts on invasion ability of human fibrosarcoma HT1080 cells, showing that fucoidan extracts significantly inhibit their invasion, possibly via suppressing matrix metalloproteinases (MMPs) MMP-2/9 activities. Further, we investigated the effects of the fucoidan extracts on angiogenesis of human uterine carcinoma HeLa cells, and found that fucoidan extracts suppressed expression and secretion of an angiogenesis factor vascular endothelial growth factor (VEGF), resulting in suppressed vascular tubules formation of tumor cells. The results taken together clarified that enzyme-digested fucoidan extracts from Cladosiphon novae-caledoniae kylin possess inhibitory effects on invasion and angiogenesis of tumor cells. These effects might, at least partially, be elicited by the antioxidative potential of enzyme digested fucoidan extracts.
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Since the successful completion of the Human Genome Project, increasing concern is being directed toward the polymorphic aspect of the genome and its clinical relevance. A form of single-strand DNA-conformation polymorphism analysis (SSCP) employing nondenaturing slab-gel electrophoresis (SGE) is applicable to the genetic diagnosis of bladder cancer from urine samples. To bring this technique into routine clinical practice, the use of capillary electrophoresis (CE) is naturally favorable in terms of speed and automation. However, the resolving power of SSCP, a prerequisite basis for reliability required in diagnostics, remains as a challenge for CE systems. We thus focused on this topic and conducted studies on CE instruments equipped with a single capillary or an array of multiple capillaries, using the resolution (Rs) as a quantitative scale for the resolving power. Polymer concentration and buffer are shown to be the decisive parameters. High Rs values of >2.5 are achieved for representative SNPs markers under the optimized conditions, without sacrificing such intrinsic advantages of CE over SGE as the 10-fold quicker migration time and operation that is reproducible, continuous, and automatic. The strategies presented broaden the limits of CE in both the current and related applications.
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Electroforesis Capilar/métodos , Polimorfismo Conformacional Retorcido-Simple , Tampones (Química) , Marcadores Genéticos , Repeticiones de Microsatélite/genética , Reproducibilidad de los ResultadosRESUMEN
Transglutaminases catalyze the cross-linking and amine incorporation of proteins, and are implicated in various biological phenomena. To elucidate the physiological roles of transglutaminase at the molecular level, we need to identify its physiological protein substrates and clarify the relationship between transglutaminase modification of protein substrates and biological responses. Here we examined whether betaine-homocysteine S-methyltransferase (BHMT: EC 2.1.1.5) can be a substrate of tissue-type transglutaminase by in vitro experiments using porcine liver BHMT and guinea pig liver transglutarninase. Guinea pig liver transglutaminase incorporated 5-(biotinamido) pentylamine and [3H] histamine into BHMT in a time-dependent manner. Putrescine and spermidine also seemed to be incorporated into BHMT by transglutaminase. In the absence of the primary amines, BHMT subunits were cross-linked intra- and intermolecularly. BHMT activity was decreased significantly through the cross-linking by transglutaminase. Histamine incorporation slightly reduced the BHMT activity. Peptide fragments of BHMT containing the glutamine residues reactive for transglutaminase reaction were isolated through biotin labelling, proteinase digestion, biotin-avidin a affinity separation, and reverse phase HPLC. The results of amino acid sequence analyses of these peptides and sequence homology alignment with other mammalian liver BHMT subunits showed that these reactive glutamine residues were located in the region near the carboxyl terminal of porcine BHMT subunit. These results suggested that the liver BHMT can be modified by tissue-type transglutaminase and its activity is regulated repressively by the modification, especially by the cross-linking. This regulatory reaction might be involved in the regulation of homocysteine metabolism in the liver.