2,516 research outputs found
Reply to ``Comment on `Insulating Behavior of -DNA on the Micron Scale' "
In our experiment, we found that the resistance of vacuum-dried -DNA
exceeds at 295 K. Bechhoefer and Sen have raised a number of
objections to our conclusion. We provide counter arguments to support our
original conclusion.Comment: 1 page reply to comment, 1 figur
αV-Integrins Are Required for Mechanotransduction in MDCK Epithelial Cells
The properties of epithelial cells within tissues are regulated by their immediate microenvironment, which consists of neighboring cells and the extracellular matrix (ECM). Integrin heterodimers orchestrate dynamic assembly and disassembly of cell-ECM connections and thereby convey biochemical and mechanical information from the ECM into cells. However, the specific contributions and functional hierarchy between different integrin heterodimers in the regulation of focal adhesion dynamics in epithelial cells are incompletely understood. Here, we have studied the functions of RGD-binding αV-integrins in a Madin Darby Canine Kidney (MDCK) cell model and found that αV-integrins regulate the maturation of focal adhesions (FAs) and cell spreading. αV-integrin-deficient MDCK cells bound collagen I (Col I) substrate via α2β1-integrins but failed to efficiently recruit FA components such as talin, focal adhesion kinase (FAK), vinculin and integrin-linked kinase (ILK). The apparent inability to mature α2β1-integrin-mediated FAs and link them to cellular actin cytoskeleton led to disrupted mechanotransduction in αV-integrin deficient cells seeded onto Col I substrate
The intersection of pharmacology, imaging, and genetics in the development of personalized medicine
We currently rely on large randomized controlled trials
and meta-analyses to make clinical decisions; this places
us at a risk of discarding subgroup or individually specific treatment options owing to their failure to prove efficacious across entire populations. There is a new era
emerging in personalized medicine that will focus on
individual differences that are not evident phenomenologically. Much research is directed towards identifying genes, endophenotypes, and biomarkers of disease that
will facilitate diagnosis and predict treatment outcome.
We are at the threshold of being able to predict treatment response, primarily through genetics and neuroimaging. In this review we discuss the most promising
markers of treatment response and adverse effects emerging from the areas of pharmacogenetics and neuroimaging in depression and schizophrenia.peer-reviewe
Preservation of information in a prebiotic package model
The coexistence between different informational molecules has been the
preferred mode to circumvent the limitation posed by imperfect replication on
the amount of information stored by each of these molecules. Here we reexamine
a classic package model in which distinct information carriers or templates are
forced to coexist within vesicles, which in turn can proliferate freely through
binary division. The combined dynamics of vesicles and templates is described
by a multitype branching process which allows us to write equations for the
average number of the different types of vesicles as well as for their
extinction probabilities. The threshold phenomenon associated to the extinction
of the vesicle population is studied quantitatively using finite-size scaling
techniques. We conclude that the resultant coexistence is too frail in the
presence of parasites and so confinement of templates in vesicles without an
explicit mechanism of cooperation does not resolve the information crisis of
prebiotic evolution.Comment: 9 pages, 8 figures, accepted version, to be published in PR
Analysis of Diffusion of Ras2 in Saccharomyces cerevisiae Using Fluorescence Recovery after Photobleaching
Binding, lateral diffusion and exchange are fundamental dynamic processes
involved in protein association with cellular membranes. In this study, we
developed numerical simulations of lateral diffusion and exchange of
fluorophores in membranes with arbitrary bleach geometry and exchange of the
membrane localized fluorophore with the cytosol during Fluorescence Recovery
after Photobleaching (FRAP) experiments. The model simulations were used to
design FRAP experiments with varying bleach region sizes on plasma-membrane
localized wild type GFP-Ras2 with a dual lipid anchor and mutant GFP-Ras2C318S
with a single lipid anchor in live yeast cells to investigate diffusional
mobility and the presence of any exchange processes operating in the time scale
of our experiments. Model parameters estimated using data from FRAP experiments
with a 1 micron x 1 micron bleach region-of-interest (ROI) and a 0.5 micron x
0.5 micron bleach ROI showed that GFP-Ras2, single or dual lipid modified,
diffuses as single species with no evidence of exchange with a cytoplasmic
pool. This is the first report of Ras2 mobility in yeast plasma membrane. The
methods developed in this study are generally applicable for studying diffusion
and exchange of membrane associated fluorophores using FRAP on commercial
confocal laser scanning microscopes.Comment: Accepted for publication in Physical Biology (2010). 28 pages, 7
figures, 3 table
Straight GDP-Tubulin Protofilaments Form in the Presence of Taxol
International audienceMicrotubules exist in dynamic equilibrium, growing and shrinking by the addition or loss of tubulin dimers from the ends of protofilaments. The hydrolysis of GTP in b-tubulin destabilizes the microtubule lattice by increasing the curvature of protofilaments in the microtubule and putting strain on the lattice. The ob- servation that protofilament curvature depends on GTP hydrolysis suggests that microtubule destabil- izers and stabilizers work by modulating the curvature of the microtubule lattice itself. Indeed, the microtu- bule destabilizer MCAK has been shown to increase the curvature of protofilaments during depolymeriza- tion. Here, we show that the atomic force microscopy (AFM) of individual tubulin protofilaments provides sufficient resolution to allow the imaging of single pro- tofilaments in their native environment. By using this assay, we confirm previous results for the effects of GTP hydrolysis and MCAK on the conformation of pro- tofilaments. We go on to show that taxol stabilizes microtubules by straightening the GDP protofilament and slowing down the transition of protofilaments from straight to a curved configuration
The 35Cl/37Cl isotopic ratio in dense molecular clouds: HIFI observations of hydrogen chloride towards W3A
We report on the detection with the HIFI instrument on board the Herschel
satellite of the two hydrogen chloride isotopologues, H35Cl and H37Cl, towards
the massive star-forming region W3A. The J=1-0 line of both species was
observed with receiver 1b of the HIFI instrument at 625.9 and 624.9 GHz. The
different hyperfine components were resolved. The observations were modeled
with a non-local, non-LTE radiative transfer model that includes hyperfine line
overlap and radiative pumping by dust. Both effects are found to play an
important role in the emerging intensity from the different hyperfine
components. The inferred H35Cl column density (a few times 1e14 cm^-2), and
fractional abundance relative to H nuclei (~7.5e^-10), supports an upper limit
to the gas phase chlorine depletion of ~200. Our best-fit model estimate of the
H35Cl/H37Cl abundance ratio is ~2.1+/-0.5, slightly lower, but still compatible
with the solar isotopic abundance ratio (~3.1). Since both species were
observed simultaneously, this is the first accurate estimation of the
[35Cl]/[37Cl] isotopic ratio in molecular clouds. Our models indicate that even
for large line opacities and possible hyperfine intensity anomalies, the H35Cl
and H37Cl J=1-0 integrated line-intensity ratio provides a good estimate of the
35Cl/37Cl isotopic abundance ratio.Comment: Accepted for publication in Astronomy and Astrophysics (Herschel
special issue
Control of Directed Cell Migration In Vivo by Membrane-to-Cortex Attachment
Analysis of cell migration in vivo combined with biophysical measurements reveals how membrane-to-cortex attachment fine-tunes the type of protrusions formed by cells and, as a consequence, controls directed migration during zebrafish gastrulation
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