Peptide Characterization of Mature Fluorotic and Control Human Enamel

Abstract Exposure to high fluoride levels during amelogenesis causes enamel fluorosis. This study aimed to determine and compare the amino acid sequences in the enamel of fluorotic and control teeth. This investigation included enamel samples obtained from erupted and non-erupted third molars with either TF grade 4-6 (n=7) fluorosis or no sign of fluorosis (controls, n=7). The samples were kept frozen at -20 °C until protein extraction. Samples were etched and processed with a cocktail of proteinase inhibitors and immediately analyzed. Matrix Assisted Laser Desorption/Ionization-Time-Of-Flight/Time-of-Flight Mass Spectrometry (MALDI-TOF/TOF) followed by MASCOT search aided the peptides analysis. The more abundant peptides bore the N-terminal amelogenin sequences WYQSIRPPYP (which is specific for the X-encoded amelogenin) and MPLPPHPGHPGYINF (which does not show sexual dimorphism) were not different in control or fluorotic enamel. There was no missing proteolytic cleavage in the fluorotic samples, which suggested that the increased amount of protein described in fluorotic enamel did not stem from the decreased ability of proteinases to cleave the proteins in humans. This study showed how to successfully obtain peptide from superficial enamel. A relatively low number of teeth was sufficient to provide good data on the actual peptides found in mature enamel.

Resumo Exposição a altos níveis de flúor durante a amelogênese causa fluorose no esmalte. Este estudo tem como objetivo determinar e comparar as sequências de aminoácidos presentes no esmalte de dentes controles e fluoróticos. A investigação incluiu amostras de esmalte obtidas de terceiros molares erupcionados e não erupcionados, ambas ou com grau de fluorose TF 4-6 (n=7) ou sem sinais de fluorose (controles, n=7), congelados a -20 oC até a extração das proteínas. As amostras sofreram ataque ácido e foram processadas utilizando um coquetel de inibidores de proteinases, sendo imediatamente analisadas. MALDI-TOF/TOF seguido pela pesquisa com MASCOT foram utilizados para a análise dos peptídeos. Os peptídeos mais abundantes foram das amelogeninas com sequências N-terminal WYQSIRPPYP (que é codificada especificamente pela amelogenina X) e MPLPPHPGHPGYINF (que não apresenta dimorfismo sexual algum), não havendo diferenças entre dentes fluoróticos e controles. Nenhuma alteração na proteólise ocorreu nas amostras fluoróticas, o que sugere que o aumento na quantidade de proteínas existentes nas amostras fluoróticas não está correlacionada a habilidade das proteinases em clivar as proteínas em humanos. Este estudo mostrou como extrair com sucesso peptídeos do esmalte superficial. Um número relativamente baixo de dentes foram suficientes para se obter ótimos dados a respeito de peptídeos encontrados no esmalte maduro.

New insights into trypanosomatid U5 small nuclear ribonucleoproteins

Several protozoan parasites exist in the Trypanosomatidae family, including various agents of human diseases. Multiple lines of evidence suggest that important differences are present between the translational and mRNA processing (trans splicing) systems of trypanosomatids and other eukaryotes. In this context, certain small complexes of RNA and protein, which are named small nuclear ribonucleoproteins (U snRNPs), have an essential role in pre-mRNA processing, mainly during splicing. Even though they are well defined in mammals, snRNPs are still not well characterized in trypanosomatids. This study shows that a U5-15K protein is highly conserved among various trypanosomatid species. Tandem affinity pull-down assays revealed that this protein interacts with a novel U5-102K protein, which suggests the presence of a sub-complex that is potentially involved in the assembly of U4/U6-U5 tri-snRNPs. Functional analyses showed that U5-15K is essential for cell viability and is somehow involved with the trans and cis splicing machinery. Similar tandem affinity experiments with a trypanonosomatid U5-Cwc21 protein led to the purification of four U5 snRNP specific proteins and a Sm core, suggesting U5-Cwc-21 participation in the 35S U5 snRNP particle. Of these proteins, U5-200K was molecularly characterized. U5-200K has conserved domains, such as the DEAD/DEAH box helicase and Sec63 domains and displays a strong interaction with U5 snRNA.

Câncer de tireóide: o comprometimento bilateral constitui fator de risco? Revisäo de 473 casos operados e seguidos até 35 anos / Thyroid cancer: the bilateral compromissing constitute a risk factor? Review of 473 cases operated and following to 35 years

Os autores apresentam uma revisão de cinco mil tireoidectomias realizadas de 1962 a 1999. A amostra mostrou 473 casos de carcinoma diferenciado tireóideo operados na Seção de Cirurgia Endócrina do Serviço de Cirurgia Geral do Hospital do Servidor Público Estadual, São Paulo. O tratamento básico do tumor primário consiste na completa extirpação da glândula (tireoidectomia total). No exame histológico do material cirúrgico, ambos lobos da glândula foram examinados. Houve uma lesão bilateral em 36 por cento dos casos, e unilateral no restante (64 por cento). O acompanhamento destes pacientes (teste de Kaplan-Meier, Regressão de Danos Proporcionais e teste de logrank) mostrou probabilidade de sobrevida de 91 por cento para os casos unilaterais e 70 por cento para os bilaterais (p<0,0001).