RESUMO
Aging of dental zirconia roughens its surface through low temperature degradation. We hypothesized that age-related roughening of zirconia crowns may cause detrimental wear to the enamel of an opposing tooth. To test our hypothesis, we subjected artificially aged zirconia and reference specimens to simulated mastication in a wear device and measured the wear of an opposing enamel cusp. Additionally, the roughness of the pretest surfaces was measured. The zirconia specimens, artificially aged by autoclave, showed no significant increase in roughness compared to the nonaged specimens. Furthermore, no significant difference in material or opposing enamel wear between the aged and nonaged zirconia was seen. All zirconia specimens showed less material and opposing enamel wear than the enamel to enamel control or veneering porcelain specimens. Scanning electron micrographs showed relatively smooth surfaces of aged and nonaged zirconia following wear testing. The micrographs of the veneering ceramic showed sharp fractured edges and fragments of wear debris. Zirconia may be considered a wear-friendly material for restorations opposing enamel, even after simulated aging.
Assuntos
Coroas/efeitos adversos , Esmalte Dentário/lesões , Desgaste dos Dentes/etiologia , Zircônio , Porcelana Dentária/efeitos adversos , Humanos , Incisivo/lesões , Microscopia Eletrônica de VarreduraRESUMO
BACKGROUND: DNA methylation is of pivotal importance during development. Previous genome-wide studies identified numerous differentially methylated regions upon differentiation of stem cells, many of them associated with transcriptional start sites. RESULTS: We present the first genome-wide, single-base-resolution view into DNA methylation dynamics during differentiation of a mammalian epithelial stem cell: the mouse small intestinal Lgr5+ stem cell. Very little change was observed at transcriptional start sites and our data suggest that differentiation-related genes are already primed for expression in the stem cell. Genome-wide, only 50 differentially methylated regions were identified. Almost all of these loci represent enhancers driving gene expression in the differentiated part of the small intestine. Finally, we show that binding of the transcription factor Tcf4 correlates with hypo-methylation and demonstrate that Tcf4 is one of the factors contributing to formation of differentially methylated regions. CONCLUSIONS: Our results reveal limited DNA methylation dynamics during small intestine stem cell differentiation and an impact of transcription factor binding on shaping the DNA methylation landscape during differentiation of stem cells in vivo.
Assuntos
Células-Tronco Adultas/metabolismo , Fatores de Transcrição de Zíper de Leucina e Hélice-Alça-Hélix Básicos/metabolismo , Diferenciação Celular , Intestino Delgado/citologia , Animais , Cromatina/metabolismo , Metilação de DNA , Regulação da Expressão Gênica , Camundongos , Dados de Sequência Molecular , Receptores Acoplados a Proteínas G/metabolismo , Fator de Transcrição 4RESUMO
A case of disseminated Fusarium sp. infection in a bone-marrow transplant patient is described. The most likely source of the organism was food, and the importance of a specially prepared diet in immunosuppressed individuals is emphasized.
Assuntos
Fusarium , Terapia de Imunossupressão/efeitos adversos , Micoses/etiologia , Adulto , Transplante de Medula Óssea , Alimentos , Humanos , Leucemia Mieloide Aguda/terapia , Masculino , Micoses/diagnóstico , Complicações Pós-OperatóriasRESUMO
Twelve methods for the demonstration of bacterial penicillinase production by strains of Haemophilus influenzae and Staphylococcus aureus are compared, and their suitability for routine clinical laboratory use is evaluated. The acidometric agar plate method is recommended.