18,068 research outputs found
Activation of the P2Y2 receptor regulates bone cell function by enhancing ATP release
Bone cells constitutively release ATP into the extracellular environment where it acts locally via P2 receptors to regulate bone cell function. Whilst P2Y2 receptor stimulation regulates bone mineralisation, the functional effects of this receptor in osteoclasts remain unknown. This investigation used the P2Y2 receptor knockout (P2Y2R−/−) mouse model to investigate the role of this receptor in bone. MicroCT analysis of P2Y2R−/− mice demonstrated age-related increases in trabecular bone volume (≤48%), number (≤30%) and thickness (≤17%). In vitro P2Y2R−/− osteoblasts displayed a 3-fold increase in bone formation and alkaline phosphatase activity, whilst P2Y2R−/− osteoclasts exhibited a 65% reduction in resorptive activity. Serum cross-linked C-telopeptide levels (CTX, resorption marker) were also decreased (≤35%). The resorption defect in P2Y2R−/− osteoclasts was rescued by the addition of exogenous ATP, suggesting that an ATP deficit could be a key factor in the reduced function of these cells. In agreement, we found that basal ATP release was reduced up to 53% in P2Y2R−/− osteoclasts. The P2Y2 receptor agonists, UTP and 2-thioUTP, increased osteoclast activity and ATP release in wild-type but not in P2Y2R−/− cells. This indicates that the P2Y2 receptor may regulate osteoclast function indirectly by promoting ATP release. UTP and 2-thioUTP also stimulate ATP release from osteoblasts suggesting that the P2Y2 receptor exerts a similar function in these cells. Taken together, our findings are consistent with the notion that the primary action of P2Y2 receptor signalling in bone is to regulate extracellular ATP levels
(Super)twistors and (super)strings
The Lagrangian formulation of the D=4 bosonic string and superstring in terms
of the (super)twistors is considered. The (super)twistor form of the equations
of motion is derived and the kappa-symmetry transformation for the
supertwistors is given. It is shown that the covariant kappa-symmetry gauge
fixation results in the action quadratic in the (super)twistor variables.Comment: LaTeX, 17 page
Microgastrinae (Hymenoptera: Braconidae) parasitizing Epirrita autumnata (Lepidoptera: Geometridae) larvae in Fennoscandia with description of Cotesia autumnatae Shaw, sp. n.
The microgastrine subset of hymenopteran parasitoids of the geometrid Epirrita
autumnata is investigated in Fennoscandia. Ecology, including population dynamics,
of the moth has been intensively studied in northern and mountainous
Finland, Norway and Sweden. Recently supported hypotheses about the causes
of its cyclic population dynamics stress the role of parasitoids, while the
parasitoid complex with some 15 species is insufficiently known. The complex
includes four solitarymicrogastrine species, Protapanteles anchisiades (Nixon),
P. immunis (Wesmael), Cotesia salebrosa (Marshall) and C. autumnatae Shaw,
sp. n. Here, we provide detailed figures for the latter, which is morphologically
close to C. jucunda (Marshall), and describe the species as new to science. We
also providemore general habitus figures of the other three species, as well as an
identification key for the four species, aiming to aid recognition of these species
by ecologists dealingwithmicrogastrine parasitoids of E. autumnata and their alternative
geometrid hosts
A Note on the Gauge Equivalence between the Manin-Radul and Laberge-Mathieu Super KdV Hierarchies
The gauge equivalence between the Manin-Radul and Laberge-Mathieu super KdV
hierarchies is revisited. Apart from the Inami-Kanno transformation, we show
that there is another gauge transformation which also possess the canonical
property. We explore the relationship of these two gauge transformations from
the Kupershmidt-Wilson theorem viewpoint and, as a by-product, obtain the
Darboux-Backlund transformation for the Manin-Radul super KdV hierarchy. The
geometrical intepretation of these transformations is also briefly discussed.Comment: 8 pages, revtex, 1 figur
All-Optical Switching Demonstration using Two-Photon Absorption and the Classical Zeno Effect
Low-contrast all-optical Zeno switching has been demonstrated in a silicon
nitride microdisk resonator coupled to a hot atomic vapor. The device is based
on the suppression of the field build-up within a microcavity due to
non-degenerate two-photon absorption. This experiment used one beam in a
resonator and one in free-space due to limitations related to device physics.
These results suggest that a similar scheme with both beams resonant in the
cavity would correspond to input power levels near 20 nW.Comment: 4 pages, 5 figure
National evaluation of the neighbourhood nurseries: integrated report
Report description: The NNI was launched in 2001 to provide high quality childcare in the most disadvantaged neighbourhoods of England, to help parents into employment, reduce child poverty and boost children’s development. By 2005 45,000 new childcare places had been created in approximately 1,400 neighbourhood nurseries.
This report brings together the findings of the four individual strands of the National Evaluation of Neighbourhood Nurseries Initiative as shown above and makes a number of recommendations.
The report shows the rationale for the government’s strategy in targeting disadvantaged neighbourhoods and in focusing on high quality childcare to provide the link between raising parental employment and income and improving children’s life chances
Turbulent thermal diffusion in a multi-fan turbulence generator with the imposed mean temperature gradient
We studied experimentally the effect of turbulent thermal diffusion in a
multi-fan turbulence generator which produces a nearly homogeneous and
isotropic flow with a small mean velocity. Using Particle Image Velocimetry and
Image Processing techniques we showed that in a turbulent flow with an imposed
mean vertical temperature gradient (stably stratified flow) particles
accumulate in the regions with the mean temperature minimum. These experiments
detected the effect of turbulent thermal diffusion in a multi-fan turbulence
generator for relatively high Reynolds numbers. The experimental results are in
compliance with the results of the previous experimental studies of turbulent
thermal diffusion in oscillating grids turbulence (Buchholz et al. 2004;
Eidelman et al. 2004). We demonstrated that turbulent thermal diffusion is an
universal phenomenon. It occurs independently of the method of turbulence
generation, and the qualitative behavior of particle spatial distribution in
these very different turbulent flows is similar. Competition between turbulent
fluxes caused by turbulent thermal diffusion and turbulent diffusion determines
the formation of particle inhomogeneities.Comment: 9 pages, 9 figure, REVTEX4, Experiments in Fluids, in pres
Distribution of dwell times of a ribosome: effects of infidelity, kinetic proofreading and ribosome crowding
Ribosome is a molecular machine that polymerizes a protein where the sequence
of the amino acid residues, the monomers of the protein, is dictated by the
sequence of codons (triplets of nucleotides) on a messenger RNA (mRNA) that
serves as the template. The ribosome is a molecular motor that utilizes the
template mRNA strand also as the track. Thus, in each step the ribosome moves
forward by one codon and, simultaneously, elongates the protein by one amino
acid. We present a theoretical model that captures most of the main steps in
the mechano-chemical cycle of a ribosome. The stochastic movement of the
ribosome consists of an alternating sequence of pause and translocation; the
sum of the durations of a pause and the following translocation is the time of
dwell of the ribosome at the corresponding codon. We derive the analytical
expression for the distribution of the dwell times of a ribosome in our model.
Whereever experimental data are available, our theoretical predictions are
consistent with those results. We suggest appropriate experiments to test the
new predictions of our model, particularly, the effects of the quality control
mechanism of the ribosome and that of their crowding on the mRNA track.Comment: This is an author-created, un-copyedited version of an article
accepted for publication in Physical Biology. IOP Publishing Ltd is not
responsible for any errors or omissions in this version of the manuscript or
any version derived from it. The definitive publisher authenticated version
is available online at DOI:10.1088/1478-3975/8/2/02600
On the B\"acklund Transformation for the Moyal Korteweg-de Vries Hierarchy
We study the B\"acklund symmetry for the Moyal Korteweg-de Vries (KdV)
hierarchy based on the Kuperschmidt-Wilson Theorem associated with second
Gelfand-Dickey structure with respect to the Moyal bracket, which generalizes
the result of Adler for the ordinary KdV.Comment: 9 pages, Revte
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