An epithelial cell destined for apoptosis signals its neighbors to extrude it by an actin- and myosin-dependent mechanism

AbstractBackground: Simple epithelia encase developing embryos and organs. Although these epithelia consist of only one or two layers of cells, they must provide tight barriers for the tissues that they envelop. Apoptosis occurring within these simple epithelia could compromise this barrier. How, then, does an epithelium remove apoptotic cells without disrupting its function as a barrier?Results: We show that apoptotic cells are extruded from a simple epithelium by the concerted contraction of their neighbors. A ring of actin and myosin forms both within the apoptotic cell and in the cells surrounding it, and contraction of the ring formed in the live neighbors is required for apoptotic cell extrusion, as injection of a Rho GTPase inhibitor into these cells completely blocks extrusion. Addition of apoptotic MDCK cells to an intact monolayer induces the formation of actin cables in the cells contacted, suggesting that the signal to form the cable comes from the dying cell. The signal is produced very early in the apoptotic process, before procaspase activation, cell shrinkage, or phosphatidylserine exposure. Remarkably, electrical resistance studies show that epithelial barrier function is maintained, even when large numbers of dying cells are being extruded.Conclusions: We propose that apoptotic cell extrusion is important for the preservation of epithelial barrier function during cell death. Our results suggest that an early signal from the dying cell activates Rho in live neighbors to extrude the apoptotic cell out of the epithelium

Cuantificadores de información basados en wavelets leaders aplicados a la segmentación de imágenes satelitales

Las imágenes satelitales brindan un gran volumen y variedad de información sobre la superficie terrestre y sus recursos. Un paso de suma importancia en el análisis de estas imágenes es susegmentación; la misma puede llevarse adelante a través de dos enfoques: por medio de la clasificación de regiones con diferentes texturas, o a través de la obtención de los bordes de dichas regiones. La idea central de este trabajo es aprovechar el formalismo de Wavelets, y particularmente las Wavelets leaders, en conjunto con herramientas de la teoría de información para la detección de bordes en imágenes satelitales. Este grupo ha definido la Entropía leaders y ha obtenido algunos resultados promisorios mediante su aplicación a imágenes ópticas. Este trabajo presenta variaciones de esta entropía usando otras medidas de información, como la entropía de Renyi, la medida de información de Fisher y complejidad estadística como una forma de perfeccionar las clasificaciones obtenidas. A partir de ello se muestran las aplicaciones de estos nuevos cuantificadores a imágenes.Publicado en: Mecánica Computacional vol. XXXV no.44Facultad de Ingenierí

Computer simulations of 10-km-diameter asteroid impacts into oceanic and continental sites: Preliminary results on atmospheric passage, cratering and ejecta dynamics

A series of analytical calculations of large scale cratering events for both oceanic and continental sites were made in order to examine their effects on the target media and atmosphere. The first analytical studies that were completed consists of computer simulations of the dynamics of: (1) the passage of a 10 km diameter asteroid moving at 20 km/sec through the Earth's atmosphere, and (2) the impact cratering events in both oceanic and continental environments. Calculation of the dynamics associated with the passage of the asteroid through the atmosphere showed strong effects on the surrounding air mass. The calculations of the impact cratering events showed equally dramatic effects on the oceanic and continental environments. These effects are briefly discussed

Laser-annealing Josephson junctions for yielding scaled-up superconducting quantum processors

As superconducting quantum circuits scale to larger sizes, the problem of frequency crowding proves a formidable task. Here we present a solution for this problem in fixed-frequency qubit architectures. By systematically adjusting qubit frequencies post-fabrication, we show a nearly ten-fold improvement in the precision of setting qubit frequencies. To assess scalability, we identify the types of 'frequency collisions' that will impair a transmon qubit and cross-resonance gate architecture. Using statistical modeling, we compute the probability of evading all such conditions, as a function of qubit frequency precision. We find that without post-fabrication tuning, the probability of finding a workable lattice quickly approaches 0. However with the demonstrated precisions it is possible to find collision-free lattices with favorable yield. These techniques and models are currently employed in available quantum systems and will be indispensable as systems continue to scale to larger sizes.Comment: 9 pages, 6 figures, Supplementary Information. Update to correct typo in author name and in text. Updated acknowledgements and corrected typo in acknowledgement

Actin behavior in bulk cytoplasm is cell cycle regulated in early vertebrate embryos

The mechanical properties of cells change as they proceed through the cell cycle, primarily owing to regulation of actin and myosin II. Most models for cell mechanics focus on actomyosin in the cortex and ignore possible roles in bulk cytoplasm. We explored cell cycle regulation of bulk cytoplasmic actomyosin in Xenopus egg extracts, which is almost undiluted cytoplasm from unfertilized eggs. We observed dramatic gelation-contraction of actomyosin in mitotic (M phase) extract where Cdk1 activity is high, but not in interphase (I-phase) extract. In spread droplets, M-phase extract exhibited regular, periodic pulses of gelation-contraction a few minutes apart that continued for many minutes. Comparing actin nucleation, disassembly and myosin II activity between M-phase and I-phase extracts, we conclude that regulation of nucleation is likely to be the most important for cell cycle regulation. We then imaged F-actin in early zebrafish blastomeres using a GFP–Utrophin probe. Polymerization in bulk cytoplasm around vesicles increased dramatically during mitosis, consistent with enhanced nucleation. We conclude that F-actin polymerization in bulk cytoplasm is cell cycle regulated in early vertebrate embryos and discuss possible biological functions of this regulation

Babesiosis in Immunocompetent Patients, Europe

We report 2 cases of babesiosis in immunocompetent patients in France. A severe influenza-like disease developed in both patients 2 weeks after they had been bitten by ticks. Diagnosis was obtained from blood smears, and Babesia divergens was identified by PCR in 1 case. Babesiosis in Europe occurs in healthy patients, not only in splenectomized patients

Intrinsic electrochemical activity of single walled carbon nanotube–Nafion assemblies

The intrinsic electrochemical properties and activity of single walled carbon nanotube (SWNT) network electrodes modified by a drop-cast Nafion film have been determined using the one electron oxidation of ferrocene trimethyl ammonium (FcTMA+) as a model redox probe in the Nafion film. Facilitated by the very low transport coefficient of FcTMA+ in Nafion (apparent diffusion coefficient of 1.8 × 10−10 cm2 s−1), SWNTs in the 2-D network behave as individual elements, at short (practical) times, each with their own characteristic diffusion, independent of neighbouring sites, and the response is diagnostic of the proportion of SWNTs active in the composite. Data are analysed using candidate models for cases where: (i) electron transfer events only occur at discrete sites along the sidewall (with a defect density typical of chemical vapour deposition SWNTs); (ii) all of the SWNTs in a network are active. The first case predicts currents that are much smaller than seen experimentally, indicating that significant portions of SWNTs are active in the SWNT–Nafion composite. However, the predictions for a fully active SWNT result in higher currents than seen experimentally, indicating that a fraction of SWNTs are not connected and/or that not all SWNTs are wetted completely by the Nafion film to provide full access of the redox mediator to the SWNT surface

Choice and caring : the experiences of parents supporting young people with Autistic Spectrum Conditions as they move into adulthood

This paper reports findings about parents' experiences of caring for young people with Autistic Spectrum Conditions (ASCs) moving into adulthood. In-depth interviews were conducted with 38 parents of young people (15-21 years) with ASCs. Data were analysed thematically. In the perceived absence of service support, parents acted as 'care-coordinators' and 'life-supporters' for their child as they moved into adulthood. These roles came with little choice, emotional demands and personal restrictions. Being supported was important for parents, but preferences differed regarding what this should look like. Implications for policy are discussed