On the Nature of Walking and Learning Pedestrian Environments

This phase of a one-year urban design research project focuses on the question of how to measure variables that impact walking for health, spiritual renewal and commuting and how to design to encourage pedestrians to walk. The results of this phase of the research project contribute to (1) identification of significant environmental variables to which pedestrians respond, (2) the creation of a video and still imagery archive of ranked pedestrian spatial sequences, and (3) a data base for pedestrian design . The research project is attached to a landscape architecture design studio at Texas A&M University. A multi-disciplinary team of graduate students oversees the literature research, the technical video and graphic support and the development of software technology. A videographic data base of a variety of pedestrian spatial sequences, with both qualitative and quantitative attributes has emerged as a result of the research to date. The case studies used in the research are specific pedestrian routes that the students selected based upon their everyday experience of commuting, health and spiritual renewal walks

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

Transportation + Street Trees:: Effect of the Urban Design Industry's Roadside Landscape Improvement Standards on Driver and Pedestrian Performance

The purpose of the research is to examine the effect of industry standard urban design treatments for streetscaping of Main Streets on traffic accident rates and the pedestrian's perception of accessibility and safety. Existing research (Rosenblatt, Bahar) has indicated that the use of roadside landscaping is reducing vehicular traffic accident rates both in terms of frequency and severity. This paper identifies the next research steps being developed at Texas A&M University which will create better understanding of the impact of specific streetscape design treatment on pedestrian safety and accessibility. These standards will be evaluated for the effect on bicycle, pedestrian and wheelchair performance within the treated corridors

Epithelial cell extrusion requires the sphingosine-1-phosphate receptor 2 pathway

Apoptotic epithelial cells signal to neighboring cells to induce dying cell extrusion by releasing sphingosine-1-phosphate

Programmed cell death:A new way worms get rid of unwanted cells

The genetics and predictable cell death lineages in Caenorhabditis elegans have been critical for identifying a conserved apoptosis pathway. Yet, cells still die in mutants that disrupt this pathway. A recent study shows that this death occurs by cell shedding

New emerging roles for epithelial cell extrusion

Epithelia use a unique process called ‘cell extrusion’ to remove cells from a layer, while preserving their barrier function. Specifically, a cell destined to die triggers formation of an actin- and myosin-ring in the live neighboring epithelial cells surrounding it, which squeeze the dying cell out. During extrusion, the surrounding cells expand toward one another and meet to fill the gap left by the extruded cell. Recent studies have revealed new roles of extrusion in controlling developmental morphogenesis, maintaining homeostatic cell numbers, and how this process is usurped during bacterial pathogenesis. Here, we review recent advances in new processes that require cell extrusion and the signaling pathways controlling it