Stretch-induced damage in endothelial monolayers

Endothelial cells are constantly exposed to mechanical stimuli, of which mechanical stretch has shown various beneficial or deleterious effects depending on whether loads are within physiological or pathological levels, respectively. Vascular properties change with age, and on a cell-scale, senescence elicits changes in endothelial cell mechanical properties that together can impair its response to stretch. Here, high-rate uniaxial stretch experiments were performed to quantify and compare the stretch-induced damage of monolayers consisting of young, senescent, and aged endothelial populations. The aged and senescent phenotypes were more fragile to stretch-induced damage. Prominent damage was detected by immunofluorescence and scanning electron microscopy as intercellular and intracellular void formation. Damage increased proportionally to the applied level of deformation and, for the aged and senescent phenotype, induced significant detachment of cells at lower levels of stretch compared to the young counterpart. Based on the phenotypic difference in cell-substrate adhesion of senescent cells indicating more mature focal adhesions, a discrete network model of endothelial cells being stretched was developed. The model showed that the more affine deformation of senescent cells increased their intracellular energy, thus enhancing the tendency for cellular damage and impending detachment. Next to quantifying for the first-time critical levels of endothelial stretch, the present results indicate that young cells are more resilient to deformation and that the fragility of senescent cells may be associated with their stronger adhesion to the substrate

A persistência da teoria da degeneração indígena e do colonialismo nos fundamentos da arqueologia brasileira The persistence of the theory of indigenous degeneration and colonialism within the theoretical foundations of Brazilian archeology

Examina a persistência de certos fundamentos teóricos da arqueologia brasileira e do pensamento americanista. Por meio da comparação entre alguns temas da obra de personagens seminais como Karl Friedrich Philipp von Martius, Francisco Adolfo de Varnhagen e Betty Jane Meggers, analisam-se traços temáticos e políticos comuns que marcam uma secular continuidade da teoria da degeneração indígena e do argumento colonialista.<br>The article examines the persistence of certain theoretical foundations of Brazilian archeology and Americanist thought. The theory of indigenous degeneration and the colonialist argument display a secular continuity characterized by common political and thematic lines. This is analyzed through a comparison of some of the topics addressed in the works of seminal figures like Karl Friedrich Philipp von Martius, Francisco Adolfo de Varnhagen, and Betty Jane Meggers