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"Richmond, David"
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Skelly's Halloween
When a fall causes Skelly B. Skeleton to come apart on Halloween, his animal friends try to put him back together based on their own bodies.
Book
A Doppler effect in embryonic pattern formation
During embryonic development, temporal and spatial cues are coordinated to generate a segmented body axis. In sequentially segmenting animals, the rhythm of segmentation is reported to be controlled by the time scale of genetic oscillations that periodically trigger new segment formation. However, we present real-time measurements of genetic oscillations in zebrafish embryos showing that their time scale is not sufficient to explain the temporal period of segmentation. A second time scale, the rate of tissue shortening, contributes to the period of segmentation through a Doppler effect. This contribution is modulated by a gradual change in the oscillation profile across the tissue. We conclude that the rhythm of segmentation is an emergent property controlled by the time scale of genetic oscillations, the change of oscillation profile, and tissue shortening.
Journal Article
Daredevil. Born again
\"Karen Page, Matt Murdock's former lover, has traded away the Man Without Fear's secret identity for a drug fix. Now, Daredevil must find strength as the Kingpin of Crime wastes no time taking him down as low as a human can get\"--P. [4] of cover.
Book
Bacterial variability in the mammalian gut captured by a single-cell synthetic oscillator
Synthetic gene oscillators have the potential to control timed functions and periodic gene expression in engineered cells. Such oscillators have been refined in bacteria in vitro, however, these systems have lacked the robustness and precision necessary for applications in complex in vivo environments, such as the mammalian gut. Here, we demonstrate the implementation of a synthetic oscillator capable of keeping robust time in the mouse gut over periods of days. The oscillations provide a marker of bacterial growth at a single-cell level enabling quantification of bacterial dynamics in response to inflammation and underlying variations in the gut microbiota. Our work directly detects increased bacterial growth heterogeneity during disease and differences between spatial niches in the gut, demonstrating the deployment of a precise engineered genetic oscillator in real-life settings.
Synthetic gene oscillators can be used to control timed function and periodic expression of genes. Here the authors demonstrate in vivo implementation in the mammalian gut that can keep time over several days.
Journal Article
You're it : crisis, change, and how to lead when it matters most /
\"Today, in an instant, leaders can find themselves face-to-face with crisis. An active shooter. A media controversy. A data breach. In You're It, the faculty of the National Preparedness Leadership Initiative at Harvard University takes you to the front lines of some of the toughest decisions facing our nation's leaders-from how to mobilize during a hurricane or in the aftermath of a bombing to halting a raging pandemic. They also take readers through the tough decision-making inside the world's largest companies, hottest startups, and leading nonprofits.\"--Provided by publisher.
Book
Forming giant vesicles with controlled membrane composition, asymmetry, and contents
Growing knowledge of the key molecular components involved in biological processes such as endocytosis, exocytosis, and motility has enabled direct testing of proposed mechanistic models by reconstitution. However, current techniques for building increasingly complex cellular structures and functions from purified components are limited in their ability to create conditions that emulate the physical and biochemical constraints of real cells. Here we present an integrated method for forming giant unilamellar vesicles with simultaneous control over (i) lipid composition and asymmetry, (ii) oriented membrane protein incorporation, and (iii) internal contents. As an application of this method, we constructed a synthetic system in which membrane proteins were delivered to the outside of giant vesicles, mimicking aspects of exocytosis. Using confocal fluorescence microscopy, we visualized small encapsulated vesicles docking and mixing membrane components with the giant vesicle membrane, resulting in exposure of previously encapsulated membrane proteins to the external environment. This method for creating giant vesicles can be used to test models of biological processes that depend on confined volume and complex membrane composition, and it may be useful in constructing functional systems for therapeutic and biomaterials applications.
Journal Article
Membrane-induced bundling of actin filaments
Cells can change shape by reorganizing the actin filaments that make up the cytoskeleton, and this is usually achieved through protein interactions. But it seems that the cell membrane, by virtue of its elasticity, can also influence the bundling of actin filaments.
Dynamic interplay between the plasma membrane and underlying cytoskeleton is essential for cellular shape change. Spatial organization of actin filaments, the growth of which generates membrane deformations during motility
1
, phagocytosis
2
, endocytosis
3
and cytokinesis
4
, is mediated by specific protein–protein interactions that branch, crosslink and bundle filaments into networks that interact with the membrane. Although membrane curvature has been found to influence binding of proteins with curvature-sensitive domains
5
, the direct effect of membrane elasticity on cytoskeletal network organization is not clear. Here, we show through
in vitro
reconstitution and elastic modelling that a lipid bilayer can drive the emergence of bundled actin filament protrusions from branched actin filament networks, thus playing a role normally attributed to actin-binding proteins. Formation of these filopodium-like protrusions with only a minimal set of purified proteins points to an active participation of the membrane in organizing actin filaments at the plasma membrane. In this way, elastic interactions between the membrane and cytoskeleton can cooperate with accessory proteins to drive cellular shape change.
Journal Article
Unilamellar vesicle formation and encapsulation by microfluidic jetting
Compartmentalization of biomolecules within lipid membranes is a fundamental requirement of living systems and an essential feature of many pharmaceutical therapies. However, applications of membrane-enclosed solutions of proteins, DNA, and other biologically active compounds have been limited by the difficulty of forming unilamellar vesicles with controlled contents in a repeatable manner. Here, we demonstrate a method for simultaneously creating and loading giant unilamellar vesicles (GUVs) using a pulsed microfluidic jet. Akin to blowing a bubble, the microfluidic jet deforms a planar lipid bilayer into a vesicle that is filled with solution from the jet and separates from the planar bilayer. In contrast with existing techniques, our method rapidly generates multiple monodisperse, unilamellar vesicles containing solutions of unrestricted composition and molecular weight. Using the microfluidic jetting technique, we demonstrate repeatable encapsulation of 500-nm particles into GUVs and show that functional pore proteins can be incorporated into the vesicle membrane to mediate transport. The ability of microfluidic jetting to controllably encapsulate solutions inside of GUVs creates new opportunities for the study and use of compartmentalized biomolecular systems in science, industry, and medicine.
Journal Article