Papers by Ana Flávia Belchior de Andrade
The development of a selective and sensitive electrochemical DNA biosensor for detection of the p... more The development of a selective and sensitive electrochemical DNA biosensor for detection of the pathogen Bacillus anthracis is proposed here. The technique is based on the characteristic cyclic voltammetry (CV) redox peaks and the very selective nature of DNA hybridization. The designed system consists of a self-assembled layer of mercaptohexanol (MCH) and thiol linked probe (ssDNAthiol) immobilized on gold-modified screen-printed electrodes. This direct detection technique studies the change in potential and intensity of the surface-modified screen-printed electrodes when a 5mM Fe(CN)6 3- solution in 0.1M KClis presented to the electrodic system in the range between -0.5 to 0.7V. The increase or decrease in the electron transfer along with the varied redox potential during immobilization of the probe and hybridization of the target was observed as CV peak current and potential change. The proposed system showed reliable results with sensitivity up to 10pM and selective enough to di...
The development of a selective and sensitive electrochemical DNA biosensor for detection of the p... more The development of a selective and sensitive electrochemical DNA biosensor for detection of the pathogen Bacillus anthracis is proposed here. The technique is based on the characteristic cyclic voltammetry (CV) redox peaks and the very selective nature of DNA hybridization. The designed system consists of a self-assembled layer of mercaptohexanol (MCH) and thiol linked probe (ssDNA-thiol) immobilized on gold-modified screen-printed electrodes. This direct detection technique studies the change in potential and intensity of the surface-modified screen-printed electrodes when a 5mM Fe(CN) 6 3-solution in 0.1M KClis presented to the electrodic system in the range between-0.5 to 0.7V. The increase or decrease in the electron transfer along with the varied redox potential during immobilization of the probe and hybridization of the target was observed as CV peak current and potential change. The proposed system showed reliable results with sensitivity up to 10pM and selective enough to distinguish signals from DNA fragments presenting 1bp mismatches. The fabricated system with the thiol probe once produced could be shelved for 2-3 months.Thus the strong selective binding nature of the DNA along with the sensitive CV characters, prove to be an efficient system for reliable detection of pathogens.
Fatal car–pedestrian collisions are a very common accident type in the Brazilian Federal District... more Fatal car–pedestrian collisions are a very common accident type in the Brazilian Federal District, with 121 occurrences registered in 2012. More than 40% of all pedestrian fatalities occurred at highways. It is known that the most common reason for pedestrians to be on the highways is to cross the roads; however, this is not the safest way to do this. In this regard, this paper aims to map all these kinds of events, in order to investigate the causes and propose solutions to ensure the best and safest conditions for pedestrians. For this purpose, all police data and forensic reports were investigated. Statistical results showed, for example, that car–pedestrian accidents occur more frequently at night, with the vehicle being driven by men aged between 24 and 30 years old. In addition, normally the victims are male, wearing dark color clothes, are 30 to 50 years of age and have consumed alcoholic beverages. Besides this, the geographical locations of all 52 accidents revealed that: (i) more than 90% of the events occurred less than 100m away from a bus stop; and (ii) there was no pedestrian bridge or zebra crossing nearby. Furthermore, no fatal accidents were registered within a radius of 500m from all pedestrian bridges, reinforcing the importance and the efficiency of this apparatus. Thus, from the results of this research, a few suggestions have been proposed to reduce these events. Moreover, it is believed that they can support new public policies related to traffic on highways.
Resumo O sangue é o fluido corpóreo mais comumente encontrado em cenas de crime. Testes presuntiv... more Resumo O sangue é o fluido corpóreo mais comumente encontrado em cenas de crime. Testes presuntivos de passo único foram concebidos como testes imunológicos rápidos para a detecção qualitativa de hemoglobina humana em amostras de fezes (sangue oculto em fezes). A utilidade desses testes para fins forenses já foi demonstrada anteriormente. Neste artigo, apresentamos um estudo de comparação entre o kit Hexagon OBTI e kit FOB Passo Único Bioeasy nas análises de amostras de sangue diluído. Com o Hexagon OBTI kit, são alcançados resultados positivos em diluições de sangue total de até 1:1.000. A sensibilidade do teste diminui com amostras envelhecidas, se estas não foram armazenadas em baixas temperaturas, independentemente de qual teste presuntivo é usado. Testes de sangue total devem ser analisados com cautela tendo em vista que o efeito prozona pode interferir nos resultados. Comparando ambos os testes, OBTI Hexagon Kit é mais sensível na detecção de sangue diluído, mostrando uma janela de detecção mais ampla em todas as condições estudadas. Esse achado é interessante quando se analisa amostras forenses já que geralmente não estão disponíveis informações prévias relativas às amostras analisadas. Abstract Blood is one of the most common body fluid found at crime scenes. One-step presumptive tests have been designed as a rapid immunological test for the qualitative detection of human hemoglobin in stool samples (faecal occult blood) their usefulness for forensic purposes has been demonstrated before. In this study, we compare Hexagon OBTI kit and FOB One-step Bioeasy kit sensitivity in the analysis of diluted blood samples. With Hexagon OBTI, positive test results are achieved in whole blood dilutions up to 1:1,000. Sensitivity decreased with aged samples, if samples were not stored under low temperatures regardless of which presumptive test is used. Whole blood tests must take into consideration that " hook " effect may interfere. Comparing both tests, OBTI Hexagon Kit is more sensible to detect diluted blood, showing a wider detection window in all conditions. This is interesting when analyzing forensic samples as forensic analysts usually do not know about the history of the analyzed sample before its collection.
RB1 mutations accountable for biallelic inactivation are crucial events in the development of ret... more RB1 mutations accountable for biallelic inactivation are crucial events in the development of reti-noblastoma because a first mutation (M1) predisposes to retinoblastoma while a second mutation (M2) is required for tumor development. Mutational analyses of this gene showed a wide spectrum of genetic alterations (single base substitutions, insertions, or deletions, as well as small and large deletions). The most frequent second hit in retinoblastoma patients is loss of heterozygosity (LOH) followed by promoter methylation. Molecular analyses of RB1 mutations were conducted in 36 patients (20 unilateral and 16 bilateral) using polymerase chain reaction–mediated single-strand conformation polymorphism (SSCP) analysis, sequencing, and LOH analysis. Sixty-four amplified fragments showing abnormal SSCP patterns were sequenced, and mutations were confirmed in five patients (13.89%). Four mutations were located at coding regions, and a fifth one was found at an exon–intron junction. Two mutations were C/T transitions, two were small-length deletions, and one was a G/A transition. A total of 47.05% patients showed LOH. In one patient, the parental origen of the mutated allele was detected: the allele retained in the tumor was the paternal one. This work helps to characterize the spectrum of mutations in the Brazilian population, and to confirm that formaldehyde-fixed paraffin tissue can provide valuable information on the RB1 status in retinoblastoma patients.
2004. Karyologic diversification and phylogenetic relationships of the genus Thalpomys (Rodentia,... more 2004. Karyologic diversification and phylogenetic relationships of the genus Thalpomys (Rodentia, Sigmodontinae). Acta Theriologica 49: 181–190. We describe the karyotype of Thalpomys species, from different Brazilian localities of the Cerrado. Thalpomys cerradensis Herskovitz, 1990 showed 2n = 36, FN = 34 and T. lasiotis Thomas, 1916 2n = 38, FN = 38. Comparisons of G-band karyotypes showed evident inter-specific homologies indicating that their chromosome complements could be derived from one another by two presumed rearrangements. Both species showed pericentromeric C-band regions in almost all chromosomes but a comparison with CMA3/DA/DAPI staining indicated that the molecular content of heterochromatic regions was different. T. lasiotis specimens from two different localities differed in the morphology of the X chromosome due to the presence of a short heterochromatic arm. These chromosome types are apparently fixed in each population rather than maintained as a polymorphic variation. Phylogenetic analyses supported the monophyly of the genus Thalpomys but was not capable of elucidating its phylogenetic relationship to other Akodontini rodents. These analyses also showed inter-individual variation in T. lasiotis, even within a given population. Phylogenetic analyses placed T. lasiotis specimens with different karyotypes in different monophyletic branches. Molecular and karyologic data confirmed the identity of the genus Thalpomys.
A new karyological variant of the Sigmodontinae genus Oecomys was detected in specimens from Braz... more A new karyological variant of the Sigmodontinae genus Oecomys was detected in specimens from Brazilian Pantanal. Karyologic analyses showed 2n = 72 and FN = 90, which differs from all known chromosomal complements of the genus. This new karyomorph showed distinctive morphological attributes and could not be attributed to any described Oecomys species. Molecular analysis using cytochrome-b sequence data suggested the monophyly of Oecomys. Maximum-likelihood analyses placed the Oecomys sp. haplotype clade as the sister branch to Oecomys bicolor, whereas maximum-parsimony analyses did not resolve its relationship with the other Oecomys species. Kimura's two parameters distance estimates between this and other Oecomys species are high, and active gene flow has been found not to coex-ist with these divergence estimates. Résumé : Un nouveau variant caryotypique au sein du genre Oecomys, lequel appartient aux sigmodontinés, a été dé-tecté chez des spécimens du Pantanal brésilien. Des analyses caryotypiques ont montré que chez ce groupe 2n = 72 et que FN = 90, des caractéristiques distinguant le caryotype au sein de ce groupe de tous les autres compléments chro-mosomiques connus au sein de ce genre. Ce nouveau caryotype possédait des attributs morphologiques distinctifs et il ne pouvait être attribué à aucune des espèces connues d'Oecomys. Une analyse moléculaire réalisée sur la séquence du gène codant pour la cytochrome-b a suggéré une origene monophylétique chez les Oecomys. Des analyses de vraisem-blance maximale ont placé le clade des Oecomys sp. comme une branche soeur de l'Oecomys bicolor tandis que des analyses de parcimonie n'ont pas permis de révéler les relations avec les autres espèces du genre Oecomys. Les estimés de distance à deux paramètres de Kimura entre l'Oecomys sp. et les autres espèces d'Oecomys étaient élevées et il a été trouvé que les flux géniques ne pouvaient co-exister avec ces estimations de la divergence.
Memorias Do Instituto Oswaldo Cruz, 2006
among geographical regions. In order to determine the prevalence of HBV and HCV infection in volu... more among geographical regions. In order to determine the prevalence of HBV and HCV infection in voluntary blood donors we evaluated the prevalence of HBsAg, anti-HBc, and anti-HCV markers of 128,497 blood donor samples collected from 1998 to 2005 in the state of Rio de Janeiro. These markers were analyzed by immunoenzymatic tests, as determined by the Ministry of Health. Data were obtained from the Sorology Laboratory of the Hemoterapy Service of the Instituto Nacional de Câncer, Rio de Janeiro. Overall prevalence estimates were: 0.27% for HBsAg, 3.68% for anti-HBc, and 0.90% for anti-HCV. There was a significant decrease in the overall prevalence of HBsAg (from 0.36 to 0.14%) and anti-HBc (from 6.12 to 2.05%) in the period encompassed between 1998-2005. Similarly, there was a decline in anti-HCV prevalence rates in Brazilian blood donors, from 1.04% in 1998 to 0.79% in 2004, with an increase of HCV prevalence to 1.09% in 2005. These prevalence estimates were higher than those found in other countries, indicating high rates of infection by HBV and HCV and a persistent risk of HBV and HCV transmission by transfusion.
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Papers by Ana Flávia Belchior de Andrade