RESUMEN
Organisms have to be sufficiently robust to environmental and genetic perturbations, yet plastic enough to cope with stressful scenarios to which they are not fully adapted. How this apparent conflict between robustness and plasticity is resolved at the cellular and whole organism levels is not clear. Here we review and discuss evidence in flies suggesting that the environment can modulate the balance between robustness and plasticity. The outcomes of this modulation can vary from mild sensitizations that are hardly noticeable, to overt qualitative changes in phenotype. The effects could be at both the cellular and whole organism levels and can include cellular de-/trans-differentiation ('Cellular reprogramming') and gross disfigurements such as homeotic transformations ('Tissue/whole organism reprogramming'). When the stress is mild enough, plastic changes in some processes may prevent drastic changes in more robust traits such as cell identity and tissue integrity. However, when the stress is sufficiently severe, this buffering may no longer be able to prevent such overt changes, and the resulting phenotypic variability could be subjected to selection and might assist survival at the population level. This article is part of a Special Issue entitled: Stress as a fundamental theme in cell plasticity.
Asunto(s)
Dípteros/crecimiento & desarrollo , Dípteros/fisiología , Estrés Fisiológico/fisiología , Animales , Tipificación del Cuerpo/genética , Desdiferenciación Celular/genética , Dípteros/genética , Drosophila/crecimiento & desarrollo , Drosophila/fisiología , Ambiente , MicroARNs/fisiología , Selección GenéticaRESUMEN
Extensive atomic force and electron microscopy reveal a new, generic DNA-colloid complex with a fixed number of DNA bases per colloid. The fiber shaped complex is stable in the presence of excess colloids in the solution. As more DNA is added to the solution and the ratio between colloids and DNA approaches the fiber's stoichiometry, the system undergoes a sharp coagulation transition. The system is restabilized at even higher DNA concentrations through localization of small colloid clusters on extensive DNA networks.
Asunto(s)
ADN/química , Oro Coloide/química , Bacteriófago lambda/química , ADN Viral/química , Microscopía de Fuerza Atómica , Microscopía Electrónica de Rastreo , Electricidad EstáticaRESUMEN
In the last few years it has been realized that the intervals of spontaneous spiking events in the intact heart exhibit coexisting scale-invariant count fluctuations and anticorrelated interspike intervals fluctuations. Here, we show experimentally that this feature is an intrinsic property of single isolated heart cells, which is preserved when the cells couple into networks. We present a model explaining this behavior at both the single cell and network levels.