Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 13 de 13
Filtrar
Más filtros










Base de datos
Intervalo de año de publicación
1.
Gynecol Oncol ; 146(2): 334-339, 2017 08.
Artículo en Inglés | MEDLINE | ID: mdl-28587748

RESUMEN

INTRODUCTION: Cervical cancer is the fourth most common female cancer worldwide. The prognosis for women with advanced-stage or recurrent cervical cancer remains poor and response to treatment is variable. Standardized management protocols leave little room for individualization. We report on a novel blood-based liquid biopsy for specific PIK3CA mutations as a clinically useful biomarker in patients with invasive cervical cancer. METHODS: One hundred seventeen Hong Kong Chinese women with primary invasive cervical cancer and their pre-treatment plasma samples were investigated. Two PIK3CA mutations, p.E542K and p.E545K were measured in cell free DNA (cfDNA) extracted from plasma using droplet digital PCR. This liquid biopsy of PIK3CA in cervical cancer was correlated to clinico-pathological features to verify the potential of PIK3CA as a clinically useful molecular biomarker for predicting disease prognosis and monitoring for progression. RESULTS: PIK3CA mutations, either p.E542K or p.E545K, were detected in plasma cfDNA from 22.2% of the patients. PIK3CA mutation status was significantly correlated to median tumor size (p<0.01). PIK3CA mutations detected in the plasma were significantly associated with decreased disease-free survival and overall survival (p<0.05). CONCLUSIONS: As a liquid molecular biopsy, analysis of circulating PIK3CA mutations shows promise as a way to refine risk stratification of individual patients with cervical cancer, and provides a platform for further research to offer individualized therapy with the purpose of improving outcomes.


Asunto(s)
Adenocarcinoma/sangre , Biomarcadores de Tumor/sangre , Carcinoma de Células Escamosas/sangre , ADN de Neoplasias/sangre , Fosfatidilinositol 3-Quinasas/genética , Neoplasias del Cuello Uterino/sangre , Adenocarcinoma/genética , Adenocarcinoma/mortalidad , Adenocarcinoma/patología , Pueblo Asiatico , Biomarcadores de Tumor/genética , Carcinoma de Células Escamosas/genética , Carcinoma de Células Escamosas/mortalidad , Carcinoma de Células Escamosas/patología , Fosfatidilinositol 3-Quinasa Clase I , Análisis Mutacional de ADN , Supervivencia sin Enfermedad , Estudios de Factibilidad , Femenino , Hong Kong , Humanos , Persona de Mediana Edad , Reacción en Cadena de la Polimerasa , Carga Tumoral , Neoplasias del Cuello Uterino/genética , Neoplasias del Cuello Uterino/mortalidad , Neoplasias del Cuello Uterino/patología
2.
Nat Commun ; 8: 14147, 2017 01 27.
Artículo en Inglés | MEDLINE | ID: mdl-28128199

RESUMEN

The adipokine adipocyte fatty acid-binding protein (A-FABP) has been implicated in obesity-related cardio-metabolic complications. Here we show that A-FABP increases thermogenesis by promoting the conversion of T4 to T3 in brown adipocytes. We find that A-FABP levels are increased in both white (WAT) and brown (BAT) adipose tissues and the bloodstream in response to thermogenic stimuli. A-FABP knockout mice have reduced thermogenesis and whole-body energy expenditure after cold stress or after feeding a high-fat diet, which can be reversed by infusion of recombinant A-FABP. Mechanistically, A-FABP induces the expression of type-II iodothyronine deiodinase in BAT via inhibition of the nuclear receptor liver X receptor α, thereby leading to the conversion of thyroid hormone from its inactive form T4 to active T3. The thermogenic responses to T4 are abrogated in A-FABP KO mice, but enhanced by A-FABP. Thus, A-FABP acts as a physiological stimulator of BAT-mediated adaptive thermogenesis.


Asunto(s)
Adipocitos Marrones/metabolismo , Proteínas de Unión a Ácidos Grasos/fisiología , Termogénesis/fisiología , Tiroxina/metabolismo , Triyodotironina/metabolismo , Tejido Adiposo Pardo/citología , Tejido Adiposo Pardo/metabolismo , Tejido Adiposo Blanco/metabolismo , Animales , Células Cultivadas , Citoplasma/metabolismo , Dieta Alta en Grasa/efectos adversos , Modelos Animales de Enfermedad , Metabolismo Energético/fisiología , Proteínas de Unión a Ácidos Grasos/genética , Humanos , Yoduro Peroxidasa/metabolismo , Receptores X del Hígado/metabolismo , Masculino , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Obesidad/etiología , Obesidad/metabolismo , Cultivo Primario de Células , Transducción de Señal/fisiología , Yodotironina Deyodinasa Tipo II
3.
Environ Sci Technol ; 48(1): 182-9, 2014.
Artículo en Inglés | MEDLINE | ID: mdl-24308778

RESUMEN

Radioactivity can influence surface interactions, but its effects on particle aggregation kinetics have not been included in transport modeling of radioactive particles. In this research, experimental and theoretical studies have been performed to investigate the influence of radioactivity on surface charging and aggregation kinetics of radioactive particles in the atmosphere. Radioactivity-induced charging mechanisms have been investigated at the microscopic level, and heterogeneous surface potential caused by radioactivity is reported. The radioactivity-induced surface charging is highly influenced by several parameters, such as rate and type of radioactive decay. A population balance model, including interparticle forces, has been employed to study the effects of radioactivity on particle aggregation kinetics in air. It has been found that radioactivity can hinder aggregation of particles because of similar surface charging caused by the decay process. Experimental and theoretical studies provide useful insights into the understanding of transport characteristics of radioactive particles emitted from severe nuclear events, such as the recent accident of Fukushima or deliberate explosions of radiological devices.


Asunto(s)
Contaminantes Radiactivos del Aire/química , Atmósfera/química , Modelos Teóricos , Radioisótopos de Cesio/química , Cinética , Microscopía Electrónica de Rastreo/métodos , Tamaño de la Partícula , Polonio/química , Radiactividad , Reproducibilidad de los Resultados , Propiedades de Superficie
4.
Langmuir ; 29(38): 11876-83, 2013 Sep 24.
Artículo en Inglés | MEDLINE | ID: mdl-23971793

RESUMEN

Radioactive particles may acquire surface potential through self-charging, and thus can behave differently from natural aerosols in atmospheric systems with respect to aggregation, deposition, resuspension, and transport to areas surrounding a radioactive source. This work focuses on the adhesive force between radioactive particles and metallic surfaces, which relates to the deposition and resuspension of particles on surrounding surfaces. Scanning surface potential microscopy was employed to measure the surface potential of radioactive gold foil. Atomic force microscopy was used to investigate the adhesive force for gold that acquired surface charge either by irradiation or by application of an equivalent electrical bias. Overall, the adhesive force increases with increasing surface potential or relative humidity. However, a behavior that does not follow the general trend was observed for the irradiated gold at a high decay rate. A comparison between experimental measurements and calculated values revealed that the surface potential promotes adhesion. The contribution of the electrostatic force at high levels of relative humidity was lower than the one found using theoretical calculations due to the effects caused by enhanced adsorption rate of water molecules under a high surface charge density. The results of this study can be used to provide a better understanding of the behavior of radioactive particles in atmospheric systems.


Asunto(s)
Coloides/química , Oro/química , Adhesivos , Microscopía de Fuerza Atómica , Radioisótopos/química , Propiedades de Superficie
5.
J Hepatol ; 58(2): 358-64, 2013 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-23108115

RESUMEN

BACKGROUND & AIMS: Adipocyte fatty acid binding protein (A-FABP) is a key mediator of inflammatory response in macrophages. Increased hepatic expression and circulating levels of A-FABP have been observed in patients with non-alcoholic fatty liver disease (NAFLD). Here, we investigated the role of A-FABP in both lipopolysaccaride (LPS)-induced acute liver injury and high fat high cholesterol (HFHC) diet-induced NAFLD in mice. METHODS: Mice with LPS-induced acute liver injury and HFHC diet-induced obesity were treated with the A-FABP inhibitor BMS309403. Liver tissues of the mice were analyzed by immunohistochemistry, Western blot or real-time PCR. RESULTS: A-FABP expression in Kupffer cells was significantly elevated in mice with LPS-induced acute liver injury and HFHC diet-induced obesity, as compared to their healthy controls. Pretreatment of mice with BMS309403 led to a diminished LPS-induced elevation in serum levels of alanine transaminase and hepatic production of pro-inflammatory cytokines. Likewise, chronic treatment of HFHC diet-induced obese mice with BMS309403 ameliorated hepatic steatosis, macrophage infiltration, and cellular ballooning of hepatocytes. Such improvements in liver function and morphology were accompanied by significantly decreased activation of both c-Jun and NF-κB. Pretreatment with BMS309403 suppressed both LPS- and palmitate-induced pro-inflammatory responses in isolated rat Kupffer cells. Adenovirus-mediated ectopic expression of A-FABP alone was sufficient to induce liver injury and inflammation in mice. CONCLUSIONS: These findings suggest that A-FABP is an important contributor to both LPS-induced acute liver injury and diet-induced NAFLD by potentiating inflammation in Kupffer cells. Pharmacological inhibition of A-FABP may represent a promising modality for obesity-related non-alcoholic steatohepatitis.


Asunto(s)
Lesión Pulmonar Aguda/inducido químicamente , Lesión Pulmonar Aguda/prevención & control , Compuestos de Bifenilo/farmacología , Grasas de la Dieta/efectos adversos , Proteínas de Unión a Ácidos Grasos/antagonistas & inhibidores , Hígado Graso/inducido químicamente , Hígado Graso/prevención & control , Lipopolisacáridos/efectos adversos , Pirazoles/farmacología , Lesión Pulmonar Aguda/metabolismo , Adenoviridae/genética , Animales , Colesterol en la Dieta/efectos adversos , Citocinas/metabolismo , Modelos Animales de Enfermedad , Proteínas de Unión a Ácidos Grasos/efectos de los fármacos , Proteínas de Unión a Ácidos Grasos/genética , Proteínas de Unión a Ácidos Grasos/metabolismo , Proteínas de Unión a Ácidos Grasos/fisiología , Hígado Graso/metabolismo , Macrófagos del Hígado/efectos de los fármacos , Macrófagos del Hígado/metabolismo , Macrófagos del Hígado/patología , Hígado/efectos de los fármacos , Hígado/metabolismo , Hígado/patología , Macrófagos/efectos de los fármacos , Macrófagos/metabolismo , Macrófagos/patología , Masculino , Ratones , Ratones Endogámicos C57BL , Ratones Mutantes , FN-kappa B/metabolismo , Enfermedad del Hígado Graso no Alcohólico , Proteínas Proto-Oncogénicas c-jun/metabolismo
6.
IEEE Trans Nanobioscience ; 10(3): 201-8, 2011 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-21926029

RESUMEN

In oxygenic plants, photons are captured with high quantum efficiency by two specialized reaction centers (RC) called Photosystem I (PS I) and Photosystem II (PS II). The captured photon triggers rapid charge separation and the photon energy is converted into an electrostatic potential across the nanometer-scale (~6 nm) reaction centers. The exogenous photovoltages from a single PS I RC have been previously measured using the technique of Kelvin force probe microscopy (KFM). However, biomolecular photovoltaic applications require two-terminal devices. This paper presents for the first time, a micro-device for detection and characterization of isolated PS I RCs. The device is based on an AlGaN/GaN high electron mobility transistor (HEMT) structure. AlGaN/GaN HEMTs show high current throughputs and greater sensitivity to surface charges compared to other field-effect devices. PS I complexes immobilized on the floating gate of AlGaN/GaN HEMTs resulted in significant changes in the device characteristics under illumination. An analytical model has been developed to estimate the RCs of a major orientation on the functionalized gate surface of the HEMTs.


Asunto(s)
Técnicas Biosensibles , Complejo de Proteína del Fotosistema I/química , Transistores Electrónicos , Aluminio/química , Electrones , Galio/química , Oro/química , Mercaptoetanol/química , Microscopía de Fuerza Atómica , Nitrógeno/química , Fotones , Espectrofotometría Ultravioleta
7.
Environ Sci Technol ; 44(16): 6209-14, 2010 Aug 15.
Artículo en Inglés | MEDLINE | ID: mdl-20666490

RESUMEN

Electrostatic force is investigated as one of the components of the adhesion force between Bacillus thuringiensis (Bt) spores and planar surfaces. The surface potentials of a Bt spore and a mica surface are experimentally obtained using a combined atomic force microscopy (AFM)-scanning surface potential microscopy technique. On the basis of experimental information, the surface charge density of the spores is estimated at 0.03 microC/cm(2) at 20% relative humidity and decreases with increasing humidity. The Coulombic force is introduced for the spore-mica system (both charged, nonconductive surfaces), and an electrostatic image force is introduced to the spore-gold system because gold is electrically conductive. The Coulombic force for spore-mica is repulsive because the components are similarly charged, while the image force for the spore-gold system is attractive. The magnitude of both forces decreases with increasing humidity. The electrostatic forces are added to other force components, e.g., van der Waals and capillary forces, to obtain the adhesion force for each system. The adhesion forces measured by AFM are compared to the estimated values. It is shown that the electrostatic (Coulombic and image) forces play a significant role in the adhesion force between spores and planar surfaces.


Asunto(s)
Bacillus thuringiensis/fisiología , Adhesión Bacteriana/fisiología , Electricidad Estática , Silicatos de Aluminio/farmacología , Bacillus thuringiensis/efectos de los fármacos , Adhesión Bacteriana/efectos de los fármacos , Oro/farmacología , Microscopía de Fuerza Atómica , Esporas Bacterianas/efectos de los fármacos , Esporas Bacterianas/fisiología , Propiedades de Superficie/efectos de los fármacos
8.
Environ Sci Technol ; 44(1): 290-6, 2010 Jan 01.
Artículo en Inglés | MEDLINE | ID: mdl-19928904

RESUMEN

Adhesion of spores of Bacillus thuringiensis (Bt) and spherical silica particles on surfaces was experimentally and theoretically investigated in this study. Topography analysis via atomic force microscopy (AFM) and electron microscopy indicates that Bt spores are rod shaped, approximately 1.3 mum in length and approximately 0.8 mum in diameter. The adhesion force of Bt spores and silica particles on gold-coated glass was measured at various relative humidity (RH) levels by AFM. It was expected that the adhesion force would vary with RH because the individual force components contributing to the adhesion force depend on RH. The adhesion force between a particle and a planar surface in atmospheric environments was modeled as the contribution of three major force components: capillary, van der Waals, and electrostatic interaction forces. Adhesion force measurements for Bt spore (silica particle) and the gold surface system were comparable with calculations. Modeling results show that there is a critical RH value, which depends on the hydrophobicity of the materials involved, below which the water meniscus does not form and the contribution of the capillary force is zero. As RH increases, the van der Waals force decreases while the capillary force increases to a maximum value.


Asunto(s)
Bacillus thuringiensis/fisiología , Esporas Bacterianas , Microscopía de Fuerza Atómica , Microscopía Electrónica de Transmisión de Rastreo , Modelos Teóricos
9.
J Phys Chem B ; 110(22): 10982-90, 2006 Jun 08.
Artículo en Inglés | MEDLINE | ID: mdl-16771351

RESUMEN

We report the direct measurement of photoinduced surface potential differences of wild-type (WT) and mutant D96N bacteriorhodopsin (BR) membranes at pH 7 and 10.5. Atomic force microscopy (AFM) and scanning surface potential microscopy (SSPM) were used to measure the BR membrane with the extracellular side facing up. We present AFM and SSPM images of WT and mutant D96N in which the light-dark transition occurred in the mid-scan of a single BR membrane. Photosteady-state populations of the M state were generated to facilitate measurement in each sample. The photoinduced surface potential of D96N is 63 mV (peak to valley) at pH 10.5 and is 48 mV at pH 7. The photoinduced surface potential of WT is 37 mV at pH 10.5 and approximately 0 at pH 7. Signal magnitudes are proportional to the amount of M produced at each pH. The results indicated that the surface potentials were generated by photoformation of surface charges on the extracellular side of the membrane. Higher surface potential correlated with a longer lifetime of the charges. A mechanistic basis for these signals is proposed, and it is concluded that they represent a steady-state measurement of the B2 photovoltage.


Asunto(s)
Bacteriorodopsinas/química , Mutación , Bacteriorodopsinas/genética , Microscopía de Fuerza Atómica , Modelos Moleculares , Fotoquímica
10.
Ultramicroscopy ; 106(8-9): 795-9, 2006.
Artículo en Inglés | MEDLINE | ID: mdl-16678968

RESUMEN

Microcantilevers undergo quasi-static bending due to adsorption-induced stress when adsorption is confined to a single surface. Understanding the origin of surface stress is crucial for optimizing sensor performance. We have investigated the effect of surface morphology of gold-coated cantilevers on the adsorption characteristics of self-assembled monolayers of alkanethiols. Self-assembly of alkanethiols from liquid phase closely follows Langmuir-type kinetics up to a single monolayer assembly. Our results indicate that alkanethiol adsorption-induced surface stress is largely unaffected by surface roughness of the cantilever. Unlike prior reports that suggest surface roughness enhances adsorption-induced stress, we observe that nanometer-size roughness slightly decreases surface stress and adsorption kinetics.


Asunto(s)
Alcanos/química , Microscopía de Sonda de Barrido/métodos , Compuestos de Sulfhidrilo/química , Alcanos/análisis , Oro , Cinética , Microscopía de Fuerza Atómica , Silicio , Compuestos de Sulfhidrilo/análisis , Propiedades de Superficie
11.
IEEE Trans Nanobioscience ; 4(2): 196-200, 2005 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-16117027

RESUMEN

Photosynthetic reaction centers are integral plant membrane protein complexes and molecular photovoltaic structures. We report here that addition of Photosystem I (PSI)-proteoliposomes to retinoblastoma cells imparts photosensitivity to these mammalian cells, as demonstrated by light-induced movement of calcium ions. Control experiments with liposomes lacking PSI demonstrated no photosensitivity. The data demonstrate that PSI, a nanoscale molecular photovoltaic structure extracted from plants, can impart a photoresponse to mammalian cells in vitro.


Asunto(s)
Señalización del Calcio/fisiología , Complejo de Proteína del Fotosistema I/metabolismo , Complejo de Proteína del Fotosistema I/efectos de la radiación , Hojas de la Planta/metabolismo , Retina/metabolismo , Retina/efectos de la radiación , Spinacia oleracea/metabolismo , Señalización del Calcio/efectos de la radiación , Línea Celular , Relación Dosis-Respuesta en la Radiación , Humanos , Luz , Fotobiología/métodos , Dosis de Radiación
12.
J Phys Chem B ; 109(12): 5409-13, 2005 Mar 31.
Artículo en Inglés | MEDLINE | ID: mdl-16851572

RESUMEN

A method of imaging nanometer metallocatalysts formed by photosynthetic precipitation of the water-soluble transition-metal compounds [PtCl(6)](2-) and [RuCl(6)](2-) is reported. Hexachloroplatinate and hexachlororuthenate can accept up to four electrons from Photosystem I (PSI) reaction centers in photosynthetic thylakoid membranes, thereby converting [PtCl(6)](2-) and [RuCl(6)](2-) anions to either metallic platinum (Pt) and ruthenium (Ru) and/or partially oxidized nanometer catalysts at the reducing sides of PSI molecules. Use of this method can potentially create nanometer-sized Pt and/or bimetallic catalysts (such as Pt-Ru) on biomembranes and molecules at pH 7 and room temperature with preservation of the biological function of the molecules.


Asunto(s)
Fotosíntesis/fisiología , Elementos de Transición/química , Agua/química , Catálisis , Microscopía de Fuerza Atómica , Microscopía Electrónica de Rastreo , Complejo de Proteína del Fotosistema I/química , Complejo de Proteína del Fotosistema I/metabolismo , Platino (Metal)/química , Rutenio/química , Tilacoides/química , Tilacoides/metabolismo , Tilacoides/ultraestructura
13.
Biosens Bioelectron ; 18(7): 917-23, 2003 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-12713915

RESUMEN

Bacterial cellulose is a versatile renewable biomaterial that can be used as a hydrophilic matrix for the incorporation of metals into thin, flexible, thermally stable membranes. In contrast to plant cellulose, we found it catalyzed the deposition of metals within its structure to generate a finely divided homogeneous catalyst layer. Experimental data suggested that bacterial cellulose possessed reducing groups capable of initiating the precipitation of palladium, gold, and silver from aqueous solution. Since the bacterial cellulose contained water equivalent to at least 200 times the dry weight of the cellulose, it was dried to a thin membranous structure suitable for the construction of membrane electrode assemblies (MEAs). Results of our study with palladium-cellulose showed that it was capable of catalyzing the generation of hydrogen when incubated with sodium dithionite and generated an electrical current from hydrogen in an MEA containing native cellulose as the polyelectrolyte membrane (PEM). Advantages of using native and metallized bacterial cellulose membranes in an MEA over other PEMs such as Nafion 117 include its higher thermal stability to 130 degrees C and lower gas crossover.


Asunto(s)
Materiales Biocompatibles , Fuentes de Energía Bioeléctrica , Celulosa , Paladio , Técnicas Biosensibles , Gluconobacter/química , Microscopía de Fuerza Atómica
SELECCIÓN DE REFERENCIAS
DETALLE DE LA BÚSQUEDA
...