Label-free DNA detection of hepatitis C virus based on modified conducting polypyrrole films at microelectrodes and atomic force microscopy tip-integrated electrodes

We present a new strategy for the label-free electrochemical detection of DNA hybridization for detecting hepatitis C virus based on electrostatic modulation of the ion-exchange kinetics of a polypyrrole film deposited at microelectrodes. Synthetic single-stranded 18-mer HCV genotype-1-specific probe DNA has been immobilized at a 2,5-bis(2-thienyl)-N-(3-phosphoryl-n-alkyl)pyrrole film established by electropolymerization at the previously formed polypyrrole layer. HCV DNA sequences (244-mer) resulting from the reverse transcriptase-linked polymerase chain reaction amplification of the original viral RNA were monitored by affecting the ion-exchange properties of the polypyrrole film. The performance of this miniaturized DNA sensor system was studied in respect to selectivity, sensitivity, and reproducibility. The limit of detection was determined at 1.82 x 10(-21) mol L-1. Control experiments were performed with cDNA from HCV genotypes 2a/c, 2b, and 3 and did not show any unspecific binding. Additionally, the influence of the spacer length of 2,5-bis(2-thienyl)-N-(3-phosphoryl-n-alkyl)pyrrole on the behavior of the DNA sensor was investigated. This biosensing scheme was finally extended to the electrochemical detection of DNA at submicrometer-sized DNA biosensors integrated into bifunctional atomic force scanning electrochemical microscopy probes. The 18-mer DNA target was again monitored by following the ion-exchange properties of the polypyrrole film. Control experiments were performed with 12-base pair mismatched sequences.

A study of the scutellum in eight Chagas disease vector species from genus Triatoma (Hemiptera, Reduviidae) using optical and scanning electron microscopy

The aim of this study was to analyze the external morphology of the scutellum through optical microscopy and scanning electron microscopy (SEM) in male specimens of Triatoma costalimai, T. delpontei, T. eratyrusiformis, T. matogrossensis, T. infestans melanosoma, T. sherlocki, T. tibiamaculata, and T. vandae. A total of 30 photographs of the scutellum were made. Magnification varied from 50X to 750X. Regarding depth and forms of the central depression, the heart-shaped form was predominant, with some exceptions, so that this shape appears to be a common characteristic for species of genus Triatoma Laporte, 1832. In T. eratyrusiformis, a kind of sensillum with important taxonomic value was observed. The different sizes and shapes of the designs found on the posterior process of the scutellum were also of important taxonomic interest. The study of the scutellum based on SEM showed valuable characteristics, allowing the use of this structure to aid the diagnosis of triatomine species. Thus, more specimens in subsequent studies and analyses of morphometric parameters should contribute to agreement on phylogenetic aspects in this genus. A Key to eight species of Triatoma based on male scutellar morphology is presented.

Morphological analysis of the corneal endothelium in eyes of dogs using specular microscopy

Foram estudados 20 olhos de 10 cães sem raça definida, machos e fêmeas com 6 anos de idade. A morfologia das células do endotélio da córnea foi analisada utilizando-se microscópio especular de contato. Foram estudadas as regiões central e periférica da córnea. de cada região da córnea foram realizadas três micrografias. de cada micrografia foram analisadas no mínimo 100 células endoteliais. Foram obtidos os valores do polimegatismo e pleomorfismo. O endotélio corneano de cães caracterizou-se por uma monocamada de células poligonais uniformes em tamanho e forma. A forma predominante das células endoteliais foi hexagonal. O índice de polimegatismo foi 0.22. Este estudo demonstrou que a morfologia das células do endotélio da córnea de cães é semelhante à observada em humanos.

The use of scaning electron microscopy in postvaccinal evaluation of tracheal epithelium of Coturnix coturnix japonica

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Scanning electron microscopy of the corneal endothelium of ostrich

Objetivou-se examinar a superfície posterior do endotélio corneano e realizar análise morfométrica das células endoteliais da córnea de avestruz (Struthio camelus) valendo-se da microscopia eletrônica de varredura. Avaliaram-se o número de lados, a área celular média, a densidade celular e o coeficiente de variação da área celular. O endotélio corneano de avestruz constitui-se de células poligonais uniformes em tamanho e forma, e com poucas interdigitações das bordas celulares. Visibilizaram-se microvilosidades na superfície celular. A área celular média foi de 269±18µm² e a densidade celular foi de 3717±240 células mm-2. O coeficiente de variação foi de 0,06 e o percentual de células hexagonais de 75%. Não foram observadas diferenças significativas entre os parâmetros avaliados entre os olhos esquerdo e direito. Este estudo demonstrou que o endotélio corneano de avestruz é semelhante ao descrito em outros vertebrados.

Study of the biodegradation of a polymer derived from castor oil by scanning electron microscopy, thermogravimetry and infrared spectroscopy

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Filmes finos de SrBi2Ta2O9 processados em forno microondas

Filmes finos de SrBi2Ta2O9 foram depositados em substratos de Pt/Ti/SiO2/Si e, pela primeira vez, sinterizados em forno microondas doméstico. Os padrões de difração de raios X mostraram que os filmes são policristalinos. O processamento por microondas permite utilizar baixa temperatura na síntese e obter filmes com boas propriedades elétricas. Ensaios de microscopia eletrônica de varredura (MEV) e de Força Atômica (MFA) revelam boa aderência entre filme e substrato, com microestrutura de superfície apresentando grãos finos e esféricos e rugosidade de 4,7 nm. A constante dielétrica e o fator de dissipação, para freqüência de 100 KHz, à temperatura ambiente, foram de 77 e 0,04, respectivamente. A polarização remanescente (2Pr) e o campo coercitivo (Ec) foram 1,04 miC/cm² e 33 kV/cm. O comportamento da densidade de corrente de fuga revela três mecanismos de condução: linear, ôhmico e outro mecanismo que pode ser atribuído à corrente de Schottky. Dos padrões de DRX, análises das imagens por MEV e topografia de superfície por MFA observa-se que 10 min de tratamento térmico a 550 ºC, em forno microondas, é tempo suficiente para se obter a cristalização do filme.

Experimental paracoccidioidomycosis in hamster: transmission electron microscopy of inoculation site lesion

Estudou-se sequencialmente, à microscopia eletrônica de transmissão, a interação entre Paracoccidioides brasiliensis (Pb) e células inflamatórias em hamsters inoculados por via intratesticular. Seis horas após inoculações havia predominância de neutrófilos, estando presentes algumas células mononucleares e eosinófilos. Os neutrófilos foram progressivamente substituídos por células mononucleares. Fungos viáveis apresentavam-se fagocitados ou circunscritos por células inflamatórias, geralmente com ampla interface hospedeiro-parasita. Fungos mortos ou degenerados eram acompanhados de interfase estreita. A camada externa da parede do Pb era às vezes quebrada quando em contacto com neutrófilos, em vários pontos, sendo os fragmentos dessa parede descamados e fagocitados. Células fúngicas pequenas com um único núcleo se relacionavam com ampla interfase enquanto as células maiores e multinucleadas apresentavam paredes irregulares, por vezes, contendo lomasoma e/ou estrutura semelhante à mielina. Diferentes padrões de interação do Pb com células do hospedeiro podem ser decorrentes do a fluxo de células inflamatórias funcionalmente diferentes ao local de inoculação ou à idade dos fungos ou ambos os fatores.

Ferroelectric and microstructural characteristics of SrBi2Ta2O9 thin films crystallized by the rapid thermal annealing process

Ferroelectric SrBi2Ta2O9 thin films on Pt/Ti/SiO2/Si were successfully synthesized by the modified polymeric precursor method. The films were deposited by spin coating and crystallized by rapid thermal annealing in a halogen lamp furnace, followed by postannealing at temperatures ranging from 700 degreesC to 800 degreesC in an oxygen atmosphere. Microstructural and phase evaluations were followed by x-ray diffraction and atomic force microscopy. The films displayed spherical grain structures with a superficial roughness of approximately 3-6 nm. The dielectric constant values were 121 and 248 for films treated at 700 degreesC and 800 degreesC, respectively. The P-E curve showed a voltage shift toward the positive side, which was attributed to crystallization under the halogen illumination. The remanent polarization (2P(r)) and coercive field (E-c) were 7.1 muC/cm(2) and 113 kV/cm, and 18.8 muC/cm(2) and 93 kV/cm for the films treated at 700 degreesC and 800 degreesC, respectively. (C) 2001 American Institute of Physics.

Phase formation and characterization of BaBi2Ta2O9 obtained by mixed oxide procedure

Ferroelectric layefed-perovskite BaBi2Ta2O9 (BBT) has been prepared successfully by solid-state reaction. The influence of pressure and temperature/time annealing regime on the BBT phase formation was analyzed. The powders were characterized by thermal analysis and Xray diffraction and the sintered pellets by scanning electron microscopy. The crystalline BBT phase, free of secondary phases was obtained at 950 degreesC for 2 h. For an applied field strength of 380 kV/cm, a remnant polarization of 7.6 muC/cm(2) and an electric coercive field of 45.7 kV/cm were obtained. (C) 2004 Elsevier B.V. All rights reserved.

Morphometric analysis of the corneal endothelium of Yacare caiman (Caiman yacare) using scanning electron microscopy

The objective of this study was to examine the endothelial surface morphology and to perform morphometric analysis of the corneal endothelial cells of Yacare caiman (Caiman yacare) using scanning electron microscopy. Morphometric analysis with regard to polygonality, mean cell area, cell density and coefficient of variation of mean cell area was performed. Cell areas were measured using image analysis software. The normal corneal endothelium of Yacare caiman consisted of polygonal cells of uniform size and shape with interdigitations of the cell borders. Microvilli appeared as protrusions on the cellular surface. The average cell area was 270 +/- 24 mum(2) and the endothelial cell density was 3704 +/- 324 cells/mm(2). The coefficient of variation of cell area was 0.22. This study demonstrates that the Yacare caiman corneal endothelium is similar to those described in other vertebrates.

Effect of processing route on the phase formation and properties of Bi4Ti3O12 ceramics

Our efforts were directed to the preparation of bismuth titanate-Bi4Ti3O12 (BIT) by two procedures: mechanically assisted synthesis and polymeric precursor method to display a variety of their advantages. To follow the nucleation and phase formation of BIT, XRD and Rietveld refinement analysis were used and it was shown that Bi4Ti3O12 ceramic can been successfully prepared from nano-sized powders obtained by both methods. The ferroelectric properties were determined and the loops from BIT obtained by polymeric precursor method were not fully saturated with a remnant polarization of 20 mu C/cm(2) and coercitive field of 1500 kV/cm. BIT obtained from powders prepared by mechanically assisted synthesis shows a remnant polarization of 0.65 mu C/cm(2) and coercitive field of 1050 kV/cm. The grain morphology may be the factor causing the observed differences. (C) 2005 Published by Elsevier Ltd and Techna Group S.r.l.