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1.
Clin Exp Immunol ; 190(2): 258-267, 2017 11.
Artigo em Inglês | MEDLINE | ID: mdl-28714582

RESUMO

The pathogenesis of sepsis involves a dual inflammatory response, with a hyperinflammatory phase followed by, or in combination with, a hypoinflammatory phase. The adhesion molecules lymphocyte function-associated antigen (LFA-1) (CD11a/CD18) and macrophage-1 (Mac-1) (CD11b/CD18) support leucocyte adhesion to intercellular adhesion molecules and phagocytosis through complement opsonization, both processes relevant to the immune response during sepsis. Here, we investigate the role of soluble (s)CD18 in sepsis with emphasis on sCD18 as a mechanistic biomarker of immune reactions and outcome of sepsis. sCD18 levels were measured in 15 septic and 15 critically ill non-septic patients. Fifteen healthy volunteers served as controls. CD18 shedding from human mononuclear cells was increased in vitro by several proinflammatory mediators relevant in sepsis. sCD18 inhibited cell adhesion to the complement fragment iC3b, which is a ligand for CD11b/CD18, also known as Mac-1 or complement receptor 3. Serum sCD18 levels in sepsis non-survivors displayed two distinct peaks permitting a partitioning into two groups, namely sCD18 'high' and sCD18 'low', with median levels of sCD18 at 2158 mU/ml [interquartile range (IQR) 2093-2811 mU/ml] and 488 mU/ml (IQR 360-617 mU/ml), respectively, at the day of intensive care unit admission. Serum sCD18 levels partitioned sepsis non-survivors into one group of 'high' sCD18 and low CRP and another group with 'low' sCD18 and high C-reactive protein. Together with the mechanistic data generated in vitro, we suggest the partitioning in sCD18 to reflect a compensatory anti-inflammatory response syndrome and hyperinflammation, respectively, manifested as part of sepsis.


Assuntos
Antígenos CD18/sangue , Sepse/imunologia , Choque Séptico/imunologia , Adulto , Idoso , Idoso de 80 Anos ou mais , Biomarcadores/sangue , Adesão Celular , Feminino , Humanos , Unidades de Terapia Intensiva , Leucócitos Mononucleares/efeitos dos fármacos , Leucócitos Mononucleares/imunologia , Lipopolissacarídeos/imunologia , Antígeno-1 Associado à Função Linfocitária/metabolismo , Antígeno de Macrófago 1/metabolismo , Masculino , Pessoa de Meia-Idade , Sepse/fisiopatologia , Choque Séptico/fisiopatologia , Resultado do Tratamento
2.
Nanotechnology ; 28(5): 055201, 2017 Feb 03.
Artigo em Inglês | MEDLINE | ID: mdl-28008871

RESUMO

Nanotextured surfaces provide an ideal platform for efficiently capturing and emitting light. However, the increased surface area in combination with surface defects induced by nanostructuring e.g. using reactive ion etching (RIE) negatively affects the device's active region and, thus, drastically decreases device performance. In this work, the influence of structural defects and surface states on the optical and electrical performance of InGaN/GaN nanorod (NR) light emitting diodes (LEDs) fabricated by top-down RIE of c-plane GaN with InGaN quantum wells was investigated. After proper surface treatment a significantly improved device performance could be shown. Therefore, wet chemical removal of damaged material in KOH solution followed by atomic layer deposition of only 10 [Formula: see text] alumina as wide bandgap oxide for passivation were successfully applied. Raman spectroscopy revealed that the initially compressively strained InGaN/GaN LED layer stack turned into a virtually completely relaxed GaN and partially relaxed InGaN combination after RIE etching of NRs. Time-correlated single photon counting provides evidence that both treatments-chemical etching and alumina deposition-reduce the number of pathways for non-radiative recombination. Steady-state photoluminescence revealed that the luminescent performance of the NR LEDs is increased by about 50% after KOH and 80% after additional alumina passivation. Finally, complete NR LED devices with a suspended graphene contact were fabricated, for which the effectiveness of the alumina passivation was successfully demonstrated by electroluminescence measurements.

3.
Neuroscience ; 290: 126-37, 2015 Apr 02.
Artigo em Inglês | MEDLINE | ID: mdl-25637492

RESUMO

G-protein-coupled receptor 41 (GPR41) also called free fatty acid receptor 3 (FFAR3) is a Gαi-coupled receptor activated by short-chain fatty acids (SCFAs) mainly produced from dietary complex carbohydrate fibers in the large intestine as products of fermentation by microbiota. FFAR3 is expressed in enteroendocrine cells, but has recently also been shown to be present in sympathetic neurons of the superior cervical ganglion. The aim of this study was to investigate whether the FFAR3 is present in other autonomic and sensory ganglia possibly influencing gut physiology. Cryostat sections were cut of autonomic and sensory ganglia of a transgenic reporter mouse expressing the monomeric red fluorescent protein (mRFP) gene under the control of the FFAR3 promoter. Control for specific expression was also done by immunohistochemistry with an antibody against the reporter protein. mRFP expression was as expected found not only in neurons of the superior cervical ganglion, but also in sympathetic ganglia of the thoracic and lumbar sympathetic trunk. Further, neurons in prevertebral ganglia expressed the mRFP reporter. FFAR3-mRFP-expressing neurons were also present in both autonomic and sensory ganglia such as the vagal ganglion, the spinal dorsal root ganglion and the trigeminal ganglion. No expression was observed in the brain or spinal cord. By use of radioactive-labeled antisense DNA probes, mRNA encoding the FFAR3 was found to be present in cells of the same ganglia. Further, the expression of the FFAR3 in the ganglia of the transgenic mice was confirmed by immunohistochemistry using an antibody directed against the receptor protein, and double labeling colocalized mRFP and the FFAR3-protein in the same neurons. Finally, quantitative real-time polymerase chain reaction (qRT-PCR) on extracts from the ganglia supported the presence mRNA encoding the FFAR3 in most of the investigated tissues. These data indicate that FFAR3 is expressed on postganglionic sympathetic and sensory neurons in both the autonomic and somatic peripheral nervous system and that SCFAs act not only through the enteroendocrine system but also directly by modifying physiological reflexes integrating the peripheral nervous system and the gastro-intestinal tract.


Assuntos
Gânglios Espinais/metabolismo , Gânglios Simpáticos/metabolismo , Neurônios/metabolismo , Receptores Acoplados a Proteínas G/metabolismo , Gânglio Trigeminal/metabolismo , Animais , Autorradiografia , Encéfalo/metabolismo , Imuno-Histoquímica , Hibridização In Situ , Proteínas Luminescentes/genética , Proteínas Luminescentes/metabolismo , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Microscopia de Fluorescência , Fotomicrografia , Regiões Promotoras Genéticas , RNA Mensageiro/metabolismo , Reação em Cadeia da Polimerase em Tempo Real , Receptores Acoplados a Proteínas G/genética , Medula Espinal/metabolismo , Proteína Vermelha Fluorescente
4.
Neuropeptides ; 48(6): 335-44, 2014 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-25267070

RESUMO

Neuropeptide Y (NPY) causes anxiolytic- and antidepressant-like effects after central administration in rodents. These effects could theoretically be utilized in future gene therapy for anxiety and depression using viral vectors for induction of overexpression of NPY in specific brain regions. Using a recombinant adeno-associated viral (rAAV) vector, we addressed this idea by testing effects on anxiolytic- and depression-like behaviours in adult mice after overexpression of NPY transgene in the amygdala and/or hippocampus, two brain regions implicated in emotional behaviours. In the amygdala, injections of rAAV-NPY caused significant anxiolytic-like effect in the open field, elevated plus maze, and light-dark transition tests. In the hippocampus, rAAV-NPY treatment was associated with anxiolytic-like effect only in the elevated plus maze. No additive effect was observed after combined rAAV-NPY injection into both the amygdala and hippocampus where anxiolytic-like effect was found in the elevated plus maze and light-dark transition tests. Antidepressant-like effects were not detected in any of the rAAV-NPY injected groups. Immobility was even increased in the tail suspension and forced swim tests after intra-amygdaloid rAAV-NPY. Taken together, the present data show that rAAV-NPY treatment may confer non-additive anxiolytic-like effect after injection into the amygdala or hippocampus, being most pronounced in the amygdala.


Assuntos
Tonsila do Cerebelo/metabolismo , Ansiolíticos/administração & dosagem , Ansiedade/metabolismo , Dependovirus/genética , Vetores Genéticos/administração & dosagem , Hipocampo/metabolismo , Neuropeptídeo Y/biossíntese , Animais , Ansiedade/genética , Ansiedade/virologia , Depressão/genética , Depressão/metabolismo , Depressão/virologia , Masculino , Camundongos , Atividade Motora , Neuropeptídeo Y/genética
5.
Nanoscale ; 6(14): 7897-902, 2014 Jul 21.
Artigo em Inglês | MEDLINE | ID: mdl-24830733

RESUMO

Vertically aligned silicon nanowire (SiNW) diodes are promising candidates for the integration into various opto-electronic device concepts for e.g. sensing or solar energy conversion. Individual SiNW p-n diodes have intensively been studied, but to date an assessment of their device performance once integrated on a silicon substrate has not been made. We show that using a scanning electron microscope (SEM) equipped with a nano-manipulator and an optical fiber feed-through for tunable (wavelength, power using a tunable laser source) sample illumination, the dark and illuminated current-voltage (I-V) curve of individual SiNW diodes on the substrate wafer can be measured. Surprisingly, the I-V-curve of the serially coupled system composed of SiNW/wafers is accurately described by an equivalent circuit model of a single diode and diode parameters like series and shunting resistivity, diode ideality factor and photocurrent can be retrieved from a fit. We show that the photo-carrier collection efficiency (PCE) of the integrated diode illuminated with variable wavelength and intensity light directly gives insight into the quality of the device design at the nanoscale. We find that the PCE decreases for high light intensities and photocurrent densities, due to the fact that considerable amounts of photo-excited carriers generated within the substrate lead to a decrease in shunting resistivity of the SiNW diode and deteriorate its rectification. The PCE decreases systematically for smaller wavelengths of visible light, showing the possibility of monitoring the effectiveness of the SiNW device surface passivation using the shown measurement technique. The integrated device was pre-characterized using secondary ion mass spectrometry (SIMS), TCAD simulations and electron beam induced current (EBIC) measurements to validate the properties of the characterized material at the single SiNW diode level.

6.
Phys Rev Lett ; 112(15): 155502, 2014 Apr 18.
Artigo em Inglês | MEDLINE | ID: mdl-24785050

RESUMO

We demonstrate a novel doping mechanism of silicon, namely n-type transfer doping by adsorbed organic cobaltocene (CoCp2*) molecules. The amount of transferred charge as a function of coverage is monitored by following the ensuing band bending via surface sensitive core-level photoelectron spectroscopy. The concomitant loss of electrons in the CoCp2* adlayer is quantified by the relative intensities of chemically shifted Co2p components in core-level photoelectron spectroscopy which correspond to charged and neutral molecules. Using a previously developed model for transfer doping, the evolution in relative intensities of the two components as a function of coverage has been reproduced successfully. A single, molecule-specific parameter, the negative donor energy of -(0.50±0.15) eV suffices to describe the self-limiting doping process with a maximum areal density of transferred electrons of 2×1013 cm-2 in agreement with the measured downward band bending. The advantage of this doping mechanism over conventional doping for nanostructures is addressed.

7.
Nanotechnology ; 25(17): 175601, 2014 May 02.
Artigo em Inglês | MEDLINE | ID: mdl-24717841

RESUMO

Vertically aligned silicon nanowire (SiNW) arrays have been fabricated over a large area using a silver-assisted single-step electroless wet chemical etching (EWCE) method, which involves the etching of silicon wafers in aqueous hydrofluoric acid (HF) and silver nitrate (AgNO3) solution. A comprehensive systematic investigation on the influence of different parameters, such as the etching time (up to 15 h), solution temperature (10-80 °C), AgNO3 (5-200 mM) and HF (2-22 M) concentrations, and properties of the multi-crystalline silicon (mc-Si) wafers, is presented to establish a relationship of these parameters with the SiNW morphology. A linear dependence of the NW length on the etch time is obtained even at higher temperature (10-50 °C). The activation energy for the formation of SiNWs on Si(100) has been found to be equal to ∼0.51 eV . It has been shown for the first time that the surface area of the Si wafer exposed to the etching solution is an important parameter in determining the etching kinetics in the single-step process. Our results establish that single-step EWCE offers a wide range of parameters by means of which high quality vertical SiNWs can be produced in a very simple and controlled manner. A mechanism for explaining the influence of various parameters on the evolution of the NW structure is discussed. Furthermore, the SiNW arrays have extremely low reflectance (as low as <3% for Si(100) NWs and <12% for mc-Si NWs) compared to ∼35% for the polished surface in the 350-1000 nm wavelength range. The remarkably low reflection surface of SiNW arrays has great potential for use as an effective light absorber material in novel photovoltaic architectures, and other optoelectronic and photonic devices.

8.
Opt Express ; 21(19): 22754-61, 2013 Sep 23.
Artigo em Inglês | MEDLINE | ID: mdl-24104162

RESUMO

Nanoparticles of transparent conducting oxides, such as indium tin oxide, can be used in printing techniques to generate functional layers for various optoelectronic devices. Since these deposition methods do not create fully consolidated films, the optical properties of such layers are expected to be notably different from those of the bulk material and should be characterized on their own. In this work we present a way to measure the effective refractive index of a particulate ITO layer by refraction of light. The obtained data points are used to identify an accurate layer model for spectroscopic ellipsometry. In this way the complex refractive index of the particle layer is determined in a wide spectral range from ultra violet to near infrared.

9.
Neuropeptides ; 46(2): 71-9, 2012 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-22342800

RESUMO

Neuropeptide Y (NPY) has been implicated in anxiolytic- and antidepressant-like behaviour as well as seizure-suppressant effects in rodents. Although these effects appear to be predominantly mediated via other NPY receptors (Y1 and/or Y2), several studies have also indicated a role for Y5 receptors. Gene therapy using recombinant viral vectors to induce overexpression of NPY, Y1 or Y2 receptors in the hippocampus or amygdala has previously been shown to modulate emotional behaviour and seizures in rodents. The present study explored the potential effects of gene therapy with the Y5 receptor, by testing effects of recombinant adeno-associated viral vector (rAAV) encoding Y5 (rAAV-Y5) in anxiety- and depression-like behaviour as well as in kainate-induced seizures in adult mice. The rAAV-Y5 vector injected into the hippocampus and amygdala induced a pronounced and sustained increase in Y5 receptor mRNA expression and functional Y5 receptor binding, but no significant effects were found with regard to anxiety- and depression-like behaviours or seizure susceptibility. Instead, rAAV-mediated Y5 receptor transgene overexpression resulted in moderate hyperactivity in the open field test. These results do not support a potential role for single transgene overexpression of Y5 receptors for modulating anxiety-/depression-like behaviours or seizures in adult mice. Whether the induction of hyperactivity by rAAV-Y5 could be relevant for other conditions remains to be studied.


Assuntos
Ansiedade/fisiopatologia , Depressão/fisiopatologia , Hipercinese/metabolismo , Receptores de Neuropeptídeo Y/metabolismo , Convulsões/metabolismo , Tonsila do Cerebelo/efeitos dos fármacos , Tonsila do Cerebelo/metabolismo , Animais , Ansiolíticos/farmacologia , Antidepressivos/farmacologia , Comportamento Animal/fisiologia , Terapia Genética , Vetores Genéticos/uso terapêutico , Hipocampo/efeitos dos fármacos , Hipocampo/metabolismo , Masculino , Camundongos , Camundongos Endogâmicos BALB C , Neuropeptídeo Y/metabolismo , Neuropeptídeo Y/farmacologia , Receptores de Neuropeptídeo Y/agonistas , Convulsões/induzido quimicamente , Convulsões/terapia
10.
J Neurosci Res ; 90(2): 498-507, 2012 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-21971867

RESUMO

Neuropeptide Y (NPY) exerts anxiolytic- and antidepressant-like effects in rodents that appear to be mediated via Y1 receptors. Gene therapy using recombinant viral vectors to induce overexpression of NPY in the hippocampus or amygdala has previously been shown to confer anxiolytic-like effect in rodents. The present study explored an alternative and more specific approach: overexpression of Y1 receptors. Using a recombinant adeno-associated viral vector (rAAV) encoding the Y1 gene (rAAV-Y1), we, for the first time, induced overexpression of functional transgene Y1 receptors in the hippocampus of adult mice and tested the animals in anxiety- and depression-like behavior. Hippocampal Y1 receptors have been suggested to mediate seizure-promoting effect, so the effects of rAAV-induced Y1 receptor overexpression were also tested in kainate-induced seizures. Y1 receptor transgene overexpression was found to be associated with modest anxiolytic-like effect in the open field and elevated plus maze tests, but no effect was seen on depression-like behavior using the tail suspension and forced swim tests. However, the rAAV-Y1 vector modestly aggravated kainate-induced seizures. These data indicate that rAAV-induced overexpression of Y1 receptors in the hippocampus could confer anxiolytic-like effect accompanied by a moderate proconvulsant adverse effect. Further studies are clearly needed to determine whether Y1 gene therapy might have a future role in the treatment of anxiety disorders.


Assuntos
Ansiolíticos/administração & dosagem , Convulsivantes/administração & dosagem , Dependovirus/genética , Regulação Viral da Expressão Gênica , Vetores Genéticos/administração & dosagem , Hipocampo/metabolismo , Receptores de Neuropeptídeo Y/biossíntese , Convulsões/metabolismo , Animais , Convulsivantes/toxicidade , Vetores Genéticos/toxicidade , Masculino , Camundongos , Receptores de Neuropeptídeo Y/genética , Proteínas Recombinantes de Fusão/genética , Convulsões/genética , Convulsões/virologia
11.
Neurochem Int ; 59(6): 837-46, 2011 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-21871511

RESUMO

Inflammation is an important hallmark of all neurodegenerative diseases and activation of different glial populations may be involved in the progression of some of these disorders. Especially, the activation of astroglia can lead to long-term detrimental morphological changes, such as scar formation. Therefore, improved strategies to modulate inflammation in these cells are currently being investigated. We investigated the interaction of phosphodiesterase (PDE) 4 inhibitors, such as rolipram, with other agents raising cellular cAMP levels. When used alone, none of the PDE4 inhibitors increased cAMP levels. The adenylate cyclase activator forskolin, the ß(2)-adrenergic agonist clenbuterol and the mixed ß(1)/ß(2)-adrenergic agonist isoproterenol increased intracellular cAMP levels of cortical murine astrocytes. This increase was synergistically elevated by rolipram or the PDE4 inhibitor RO-201724, but not by inhibition of PDE3. Inflammatory stimulation of the cells with the cytokines TNF-α, IL-1ß and IFN-γ strongly induced PDE4B and augmented overall PDE4 activity, while PDE3 activity was low. Clenbuterol and forskolin caused downregulation of cytokines and chemokines such as IL-6 and MCP-1. This effect was further enhanced by rolipram, but not by the PDE3 inhibitor milrinone. The cAMP-raising drug combinations attenuated the upregulation of TNF-α and IL-6 mRNA and the secretion of IL-6, but did not affect initial NF-κB signalling triggered by the stimulating cytokines. These results indicate that PDE4 may be a valuable anti-inflammatory target in brain diseases, especially under conditions associated with stimulation of cAMP-augmenting astrocyte receptors as is observed by clenbuterol treatment.


Assuntos
Agonistas Adrenérgicos beta/farmacologia , Anti-Inflamatórios não Esteroides/farmacologia , Astrócitos/efeitos dos fármacos , AMP Cíclico/biossíntese , Líquido Intracelular/efeitos dos fármacos , Inibidores da Fosfodiesterase 4/farmacologia , Receptores Adrenérgicos beta 2/fisiologia , Regulação para Cima/efeitos dos fármacos , Animais , Astrócitos/metabolismo , Astrócitos/patologia , Córtex Cerebral/citologia , Córtex Cerebral/efeitos dos fármacos , Córtex Cerebral/patologia , Quimioterapia Combinada/métodos , Feminino , Líquido Intracelular/metabolismo , Camundongos , Camundongos Endogâmicos C57BL , Cultura Primária de Células , Regulação para Cima/fisiologia
12.
Neuropeptides ; 45(5): 337-41, 2011 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-21820174

RESUMO

Induction of seizures by electroconvulsive stimulation (ECS) is amongst the most efficacious treatments for major depression. However, the working mechanism by which ECS exerts its antidepressant effects remains elusive. The galanin system is regulated by ECS in seizure-prone brain regions and has been shown to modulate depression-like behaviour. To further explore its potential role in the antidepressant effects of ECS the galanin system was investigated by in situ hybridisation and [(125)I]-galanin receptor binding during repeated ECS in the locus coeruleus, dorsal raphe and discrete nuclei of the hypothalamus. Adult mice were treated with ECS once daily for 14 consecutive days, a paradigm previously shown to exert antidepressant-like effects. Significant increases in galanin transcription were found in the locus coeruleus and dorsomedial nuclei of the hypothalamus. In addition, GalR2 mRNA levels in the ventro- and dorsomedial nuclei of the hypothalamus were upregulated whereas no GalR1 mRNA upregulation was observed. [(125)I]-galanin receptor binding was downregulated in the ventromedial nuclei of the hypothalamus and dorsal raphe. These data show that the galanin system is regulated by repeated ECS in brain regions involved in monoaminergic neurotransmission and stress modulation thus indicating a possible role of the galanin system in the therapeutic effects of ECS.


Assuntos
Tronco Encefálico/metabolismo , Eletrochoque , Galanina/metabolismo , Hipotálamo/metabolismo , Receptor Tipo 2 de Galanina/metabolismo , Animais , Regulação para Baixo , Galanina/genética , Masculino , Camundongos , Núcleos da Rafe/metabolismo , Receptor Tipo 1 de Galanina/metabolismo
13.
Behav Brain Res ; 216(2): 585-91, 2011 Jan 20.
Artigo em Inglês | MEDLINE | ID: mdl-20816900

RESUMO

Stressful life events and chronic stress are implicated in the development of depressive disorder in humans. Neuropeptide Y (NPY) and galanin have been shown to modulate the stress response, and exert antidepressant-like effects in rodents. To further investigate these neuropeptides in depression-like behaviour, NPY and galanin gene expression was studied in brains of mice subjected to chronic restraint stress (CRS) and concomitant treatment with the antidepressant fluoxetine (FLX). CRS caused a significant increase in depression-like behaviour that was associated with increased NPY mRNA levels in the medial amygdala. Concomitant FLX treatment reverted depression-like effects of CRS and led to significant increases in levels of NPY and galanin mRNA in the dentate gyrus, amygdala, and piriform cortex. These findings suggest that effects on NPY and galanin gene expression could play a role in the antidepressant effects of FLX.


Assuntos
Encéfalo/metabolismo , Depressão/metabolismo , Fluoxetina/farmacologia , Galanina/metabolismo , Neuropeptídeo Y/metabolismo , Inibidores Seletivos de Recaptação de Serotonina/farmacologia , Tonsila do Cerebelo/efeitos dos fármacos , Tonsila do Cerebelo/metabolismo , Animais , Encéfalo/efeitos dos fármacos , Giro Denteado/efeitos dos fármacos , Giro Denteado/metabolismo , Depressão/tratamento farmacológico , Depressão/etiologia , Galanina/efeitos dos fármacos , Galanina/genética , Masculino , Camundongos , Neuropeptídeo Y/efeitos dos fármacos , Neuropeptídeo Y/genética , Giro Para-Hipocampal/efeitos dos fármacos , Giro Para-Hipocampal/metabolismo , RNA Mensageiro/análise , Restrição Física/fisiologia , Restrição Física/psicologia , Lobo Temporal/efeitos dos fármacos , Lobo Temporal/metabolismo
14.
J Neurosci Res ; 88(16): 3635-43, 2010 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-20936701

RESUMO

Even though induction of seizures by electroconvulsive stimulation (ECS) is a treatment widely used for major depression in humans, the working mechanism of ECS remains uncertain. The antiepileptic effect of ECS has been suggested to be involved in mediating the therapeutic effect of ECS. The neuropeptide galanin exerts antiepileptic and antidepressant-like effects and has also been implicated in the pathophysiology of depression. To explore a potential role of galanin in working mechanisms of ECS, the present study examined effects of repeated ECS on the galanin system using QRT-PCR, in situ hybridization, and [(125) I]galanin receptor binding. ECS was administered to adult mice daily for 14 days, and this paradigm was confirmed to exert antidepressant-like effect in the tail suspension test. Prominent increases in galanin gene expression were found in several brain regions involved in regulation of epileptic activity and depression, including the piriform cortex, hippocampal dentate gyrus, and amygdala. Likewise, GalR2 gene expression was up-regulated in both the central and the medial amygdala, whereas GalR1 gene expression showed a modest down-regulation in the medial amygdala. [(125) I]galanin receptor binding in the piriform cortex, hippocampus, and amygdala was found to be significantly down-regulated. These data show that the galanin system is regulated by repeated ECS in a number of brain regions implicated in seizure regulation and depression. These changes may play a role in the therapeutic effect of ECS.


Assuntos
Encéfalo/metabolismo , Depressão/metabolismo , Eletrochoque , Galanina/metabolismo , Convulsões/metabolismo , Animais , Encéfalo/fisiopatologia , Depressão/terapia , Eletroconvulsoterapia , Regulação da Expressão Gênica/fisiologia , Masculino , Camundongos , Distribuição Tecidual
15.
Nanotechnology ; 20(40): 405607, 2009 Oct 07.
Artigo em Inglês | MEDLINE | ID: mdl-19738306

RESUMO

The oxidation behavior of Si nanowires (SiNWs) grown by the gold (Au) catalyzed vapor-liquid-solid (VLS) growth process in an electron beam evaporation (EBE) reactor is studied. The VLS SiNWs exhibit hexagonal shape with essentially {112} facets where each facet shows a saw-tooth faceting itself, consisting of alternating {111} and {113} facets. Depending on growth temperatures (450-750 degrees C) and evaporation currents (40-80 mA) that determine the silicon vapor supply, this facet formation is more or less pronounced. The diffusion of Au atoms on the faceted SiNW surfaces and the formation of Au nanoparticles on the SiNW facets during growth and during ex situ annealing are studied. Upon diffusion, the Au atoms agglomerate and form Au nanoparticles that preferably arrange themselves on {113} facets. Upon annealing in air at temperatures between 800 and 950 degrees C the gold nanoparticles agglomerate further and form bigger particles of a few tens of nm in diameter that reside at the interface between the growing silica (SiO(2)) layer and the SiNW itself, which in turn shrinks during SiNW oxidation. The oxide layer thickness and the oxide appearance depend on the annealing conditions (time and temperature) and systematically varied oxidation processing is described in this paper as investigated by cross-sectional transmission electron microscopy (TEM) including high resolution studies as well as scanning electron microscopy (SEM) studies. Our results strongly suggest that the SiNWs can be fully oxidized, thus forming silica NWs that can either keep their initial shape or, under certain annealing conditions, do not keep their initial wire shape but assume a bamboo-like shape that forms most likely as a result of locally high stresses that are related to nanocrack formation. The nanocracks form in the growing oxide layer mediated by the presence of Au nanoparticles that yield gold-enhanced SiNW oxidation and thus a faster oxidation rate.


Assuntos
Ouro/química , Nanopartículas Metálicas/química , Nanofios/química , Silício/química , Microscopia Eletrônica de Varredura , Nanotecnologia/métodos
16.
Nanotechnology ; 20(16): 165301, 2009 Apr 22.
Artigo em Inglês | MEDLINE | ID: mdl-19420566

RESUMO

We use nanoscale (20-300 nm in diameter) single crystalline gold (Au)-caps on silicon nanowires (NWs) grown by the vapor-liquid-solid (VLS) growth mechanism to enhance the fluorescence photoluminescence (PL) signals of highly dilute core/shell CdSeTe/ZnS quantum dots (QDs) in aqueous solution (10(-5) M). For NWs without Au-caps, as they appear, for example, after Au etching in aqua regia or buffered KI/I(2)-solution, essentially no fluorescence signal of the same diluted QDs could be observed. Fluorescence PL signals were measured using excitation with a laser wavelength of 633 nm. The signal enhancement by single crystalline, nanoscale Au-caps is discussed and interpreted based on finite element modeling (FEM).

17.
Nano Lett ; 9(4): 1341-4, 2009 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-19256535

RESUMO

The electrical properties of vertically aligned silicon nanowires doped by ion implantation are studied in this paper by a combination of electron beam-induced current imaging and two terminal current-voltage measurements. By varying the implantation parameters in several process steps, uniform p- and n-doping profiles as well as p-n junctions along the nanowire axis are realized. The effective doping is demonstrated by electron beam-induced current imaging on single nanowires, and current-voltage measurements show their well-defined rectifying behavior.

18.
Nano Lett ; 9(4): 1549-54, 2009 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-19281253

RESUMO

Silicon nanowire (SiNW)-based solar cells on glass substrates have been fabricated by wet electroless chemical etching (using silver nitrate and hydrofluoric acid) of 2.7 microm multicrystalline p(+)nn(+) doped silicon layers thereby creating the nanowire structure. Low reflectance (<10%, at 300-800 nm) and a strong broadband optical absorption (>90% at 500 nm) have been measured. The highest open-circuit voltage (V(oc)) and short-circuit current density (J(sc)) for AM1.5 illumination were 450 mV and 40 mA/cm(2), respectively at a maximum power conversion efficiency of 4.4%.

19.
Nano Lett ; 7(1): 75-80, 2007 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-17212443

RESUMO

We show that hemispherical gold droplets on top of silicon nanowires when grown by the vapor-liquid-solid (VLS) mechanism, can produce a significant enhancement of Raman scattered signals. Signal enhancement for a few or even just single gold droplets is demonstrated by analyzing the enhanced Raman signature of malachite green molecules. For this experiment, trenches (approximately 800 nm wide) were etched in a silicon-on-insulator (SOI) wafer along <110> crystallographic directions that constitute sidewalls ({110} surfaces) suitable for the growth of silicon nanowires in <111> directions with the intention that the gold droplets on the silicon nanowires can meet somewhere in the trench when growth time is carefully selected. Another way to realize gold nanostructures in close vicinity is to attach a silicon nanowire with a gold droplet onto an atomic force microscopy (AFM) tip and to bring this tip toward another gold-coated AFM tip where malachite green molecules were deposited prior to the measurements. In both experiments, signal enhancement of characteristic Raman bands of malachite green molecules was observed. This indicates that silicon nanowires with gold droplets atop can act as efficient probes for tip-enhanced Raman spectroscopy (TERS). In our article, we show that a nanowire TERS probe can be fabricated by welding nanowires with gold droplets to AFM tips in a scanning electron microscope (SEM). TERS tips made from nanowires could improve the spatial resolution of Raman spectroscopy so that measurements on the nanometer scale are possible.


Assuntos
Ouro/química , Nanofios , Silício/química , Microscopia de Força Atômica , Microscopia Eletrônica de Varredura
20.
Nanotechnology ; 18(3): 035503, 2007 Jan 24.
Artigo em Inglês | MEDLINE | ID: mdl-19636122

RESUMO

Silicon nanowires grown by the vapour-liquid-solid growth mechanism with gold as the catalyst show gold caps approximately 50-400 nm in diameter with an almost ideal hemispherical shape atop a silicon column. These gold caps are extremely well suited for exploiting the tip or surface enhanced Raman scattering effects since they assume the right size on the nanometre scale and a reproducible, almost ideal hemispherical shape. On attaching a nanowire with a gold cap to an atomic force microscopy (AFM) tip, the signal enhancement by the gold nanoparticle can be used to spatially resolve a Raman signal. Applications of this novel nanowire based technical tip enhanced Raman scattering solution are widespread and lie in the fields of biomedical and life sciences as well as security (e.g. detection of bacteria and explosives) and in the field of solid state research, e.g. in silicon technology where the material composition, doping, crystal orientation and lattice strain can be probed by Raman spectroscopy. A prerequisite for obtaining this spatial resolution in nano-Raman spectroscopy is the attachment of a nanowire with a gold cap to an AFM tip. This attachment by welding a nanowire in a scanning electron microscope to an AFM tip is demonstrated in this paper.

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