324 research outputs found
Involvement of fatty acid pathways and cortical interaction of the pronuclear complex in Caenorhabditis elegans embryonic polarity.
BACKGROUND: Cell polarity is essential for many decisions made during development. While investigation of polarity-specific factors has yielded great insights into the polarization process, little is known on how these polarity-specific factors link to the basic cellular mechanisms that function in non-polarity aspects of the cell. To better understand the mechanisms that establish embryonic polarity, we investigated genes required for polarity in the one-cell C. elegans embryo that are also required for other non-polarity functions. This has led to the identification of the Pod-class of mutants that are characterized by osmosensitive embryos and defects in anterior-posterior polarity. RESULTS: Mutation in either of two loci of this class, emb-8 and pod-2, disrupts embryonic polarization and results in osmotically-sensitive embryos. Loss of emb-8, a previously uncharacterized polarity gene, causes mislocalization of PAR-3 and PAR-2 that molecularly mark the anterior and posterior cortices. emb-8 encodes NADPH-cytochrome P450 reductase, a protein supplying electrons to cytochrome P450-family enzymes, some of which catalyze fatty acid modifications. Cloning of the previously characterized polarity gene pod-2 reveals it encodes acetyl-CoA carboxylase, an enzyme that catalyzes the first step in de novo fatty acid synthesis. Depletion of fatty acid synthase, the next enzyme in the biosynthetic pathway, by RNA-interference (RNAi) also causes similar loss of one-cell polarity. Furthermore, pod-2 polarity defects can be rescued by addition of exogenous fatty acids. By following the behavior of the pronucleus in emb-8 and pod-2 mutant embryos, we demonstrate that loss of polarity correlates with impaired interaction between the pronucleus-centrosome complex and the posterior cortex. CONCLUSIONS: The characterization of emb-8 and pod-2 mutant embryos suggests that the pronucleus-centrosome complex interaction with the cortex plays a direct role in establishing polarity and that fatty acid pathways are important for this polarizing event.RIGHTS : This article is licensed under the BioMed Central licence at http://www.biomedcentral.com/about/license which is similar to the 'Creative Commons Attribution Licence'. In brief you may : copy, distribute, and display the work; make derivative works; or make commercial use of the work - under the following conditions: the original author must be given credit; for any reuse or distribution, it must be made clear to others what the license terms of this work are
Chemically engineered extracts of St John’s wort as sources of polyprenylated acylphloroglucinols to prevent endothelial dysfunction
International audienc
Dissipation of vibration in rough contact
The relationship which links the normal vibration occurring during the sliding of rough surfaces and the nominal contact area is investigated. Two regimes are found. In the first one, the vibrational level does not depend on the contact area, while in the second one, it is propor- tional to the contact area. A theoretical model is proposed. It is based on the assumption that the vibrational level results from a competition between two processes of vibration damping, the internal damping of the material and the contact damping occurring at the interface
13C-NMR dereplication of complex mixtures: predicted vs experimental chemical shifts databases
Influence of Multiharmonics Excitation on Rattle Noise in Automotive Gearboxes
We consider the automotive gearbox rattle noise resulting from vibro-impacts that can occur between the idle gears under excessive velocity fluctuations of the shaft-driving gears imposed by engine torque fluctuation. Even if the rattling phenomenon has no consequence on reliability, it may be particularly annoying for vehicle interior sound quality and acoustic comfort. The main parameters governing such kind of vibrations are the excitation source associated with engine torque fluctuation which can be modeled by an imposed displacement of the driveline, the inertia of the idle gear, the drag torque acting during the free flight motion, and the impact laws. In the case of rattle, it is reasonable to assume that duration of impacts between teeth is very short compared to the excitation period. Then, these impacts are modeled by a coefficient of restitution law. The excitation source is not composed only with fundamental component but also with other harmonic components. This study presents some effects of these additional components on the dynamic response of the idle gear
The Spitzer Survey of the Small Magellanic Cloud: S3MC Imaging and Photometry in the Mid- and Far-Infrared Wavebands
We present the initial results from the Spitzer Survey of the Small
Magellanic Cloud (S3MC), which imaged the star-forming body of the Small
Magellanic Cloud (SMC) in all seven MIPS and IRAC wavebands. We find that the
F_8/F_24 ratio (an estimate of PAH abundance) has large spatial variations and
takes a wide range of values that are unrelated to metallicity but
anticorrelated with 24 um brightness and F_24/F_70 ratio. This suggests that
photodestruction is primarily responsible for the low abundance of PAHs
observed in star-forming low-metallicity galaxies. We use the S3MC images to
compile a photometric catalog of ~400,000 mid- and far-infrared point sources
in the SMC. The sources detected at the longest wavelengths fall into four main
categories: 1) bright 5.8 um sources with very faint optical counterparts and
very red mid-infrared colors ([5.8]-[8.0]>1.2), which we identify as YSOs. 2)
Bright mid-infrared sources with mildly red colors (0.16<[5.8]-[8.0]<0.6),
identified as carbon stars. 3) Bright mid-infrared sources with neutral colors
and bright optical counterparts, corresponding to oxygen-rich evolved stars.
And, 4) unreddened early B stars (B3 to O9) with a large 24 um excess. This
excess is reminiscent of debris disks, and is detected in only a small fraction
of these stars (<5%). The majority of the brightest infrared point sources in
the SMC fall into groups one to three. We use this photometric information to
produce a catalog of 282 bright YSOs in the SMC with a very low level of
contamination (~7%).Comment: Accepted for publication in The Astrophysical Journal. Given the
draconian figure file-size limits implemented in astro-ph, readers are
encouraged to download the manuscript with full quality images from
http://celestial.berkeley.edu/spitzer/publications/s3mcsurvey.pd
Three-micron spectra of AGB stars and supergiants in nearby galaxies
The dependence of stellar molecular bands on the metallicity is studied using
infrared L-band spectra of AGB stars (both carbon-rich and oxygen-rich) and
M-type supergiants in the Large and Small Magellanic Clouds (LMC and SMC) and
in the Sagittarius Dwarf Spheroidal Galaxy. The spectra cover SiO bands for
oxygen-rich stars, and acetylene (C2H2), CH and HCN bands for carbon-rich AGB
stars. The equivalent width of acetylene is found to be high even at low
metallicity. The high C2H2 abundance can be explained with a high
carbon-to-oxygen (C/O) ratio for lower metallicity carbon stars. In contrast,
the HCN equivalent width is low: fewer than half of the extra-galactic carbon
stars show the 3.5micron HCN band, and only a few LMC stars show high HCN
equivalent width. HCN abundances are limited by both nitrogen and carbon
elemental abundances. The amount of synthesized nitrogen depends on the initial
mass, and stars with high luminosity (i.e. high initial mass) could have a high
HCN abundance. CH bands are found in both the extra-galactic and Galactic
carbon stars. None of the oxygen-rich LMC stars show SiO bands, except one
possible detection in a low quality spectrum. The limits on the equivalent
widths of the SiO bands are below the expectation of up to 30angstrom for LMC
metallicity. Several possible explanations are discussed. The observations
imply that LMC and SMC carbon stars could reach mass-loss rates as high as
their Galactic counterparts, because there are more carbon atoms available and
more carbonaceous dust can be formed. On the other hand, the lack of SiO
suggests less dust and lower mass-loss rates in low-metallicity oxygen-rich
stars. The effect on the ISM dust enrichment is discussed.Comment: accepted for A&
Determination of the uptake and translocation of nitrogen applied at different growth stages of a melon crop (Cucumis melo L.) using 15N isotope.
In order to establish a rational nitrogen (N) fertilisation and reduce groundwater contamination, a clearer understanding of the N distribution through the growing season and its dynamics inside the plant is crucial. In two successive years, a melon crop (Cucumis melo L. cv. Sancho) was grown under field conditions to determine the uptake of N fertiliser, applied by means of fertigation at different stages of plant growth, and to follow the translocation of N in the plant using 15N-labelled N. In 2006, two experiments were carried out. In the first experiment, labelled 15N fertiliser was supplied at the female-bloom stage and in the second, at the end of fruit ripening. Labelled 15N fertiliser was made from 15NH415NO3 (10 at.% 15N) and 9.6 kg N ha−1 were applied in each experiment over 6 days (1.6 kg N ha−1 d−1). In 2007, the 15N treatment consisted of applying 20.4 kg N ha−1 as 15NH415NO3 (10 at.% 15N) in the middle of fruit growth, over 6 days (3.4 kg N ha−1 d−1). In addition, 93 and 95 kg N ha−1 were supplied daily by fertigation as ammonium nitrate in 2006 and 2007, respectively. The results obtained in 2006 suggest that the uptake of N derived from labelled fertiliser by the above-ground parts of the plants was not affected by the time of fertiliser application. At the female-flowering and fruit-ripening stages, the N content derived from 15N-labelled fertiliser was close to 0.435 g m−2 (about 45% of the N applied), while in the middle of fruit growth it was 1.45 g m−2 (71% of the N applied). The N application time affected the amount of N derived from labelled fertiliser that was translocated to the fruits. When the N was supplied later, the N translocation was lower, ranging between 54% at female flowering and 32% at the end of fruit ripening. Approximately 85% of the N translocated came from the leaf when the N was applied at female flowering or in the middle of fruit growth. This value decreased to 72% when the 15N application was at the end of fruit ripening. The ammonium nitrate became available to the plant between 2 and 2.5 weeks after its application. Although the leaf N uptake varied during the crop cycle, the N absorption rate in the whole plant was linear, suggesting that the melon crop could be fertilised with constant daily N amounts until 2–3 weeks before the last harvest
Whole inactivated virus influenza vaccine is superior to subunit vaccine in inducing immune responses and secretion of proinflammatory cytokines by DCs
Background For protection against (re-) infection by influenza virus not only the magnitude of the immune response but also its quality in terms of antibody subclass and T helper profile is important. Information about the type of immune response elicited by vaccination is therefore urgently needed. Objectives The aim of the study was to evaluate in detail the immune response elicited by three current influenza vaccine formulations and to shed light on vaccine characteristics which determine this response. Methods Mice were immunized with whole inactivated virus (WIV), virosomes (VS) or subunit vaccine (SU). Following subsequent infection with live virus, serum antibody titers and Th cell responses were measured. The effects of the vaccines on cytokine production by conventional and plasmacytoid dendritic cells were investigated in vitro. Results and conclusions In Balb/c mice (Th2 prone) as well as in C57Bl/6 mice (Th1 prone), WIV induced consistently higher hemagglutination-inhibition titers and virus-neutralizing antibody titers than VS or SU. In contrast to VS and SU, WIV stimulated the production of the antibody subclasses IgG2a (Balb/c) and IgG2c (C57BL/6), considered to be particularly important for viral clearance, and activation of IFN-gamma-producing T cells. Similar to live virus, WIV stimulated the production of proinflammatory cytokines by conventional dendritic cells and IFN-alpha by plasmacytoid cells, while VS and SU had little effect on cytokine synthesis by either cell type. We conclude that vaccination with WIV in contrast to VS or SU results in the desired Th1 response presumably by induction of type I interferon and other proinflammatory cytokines
The course of depressive symptoms in primary care patients with type 2 diabetes: results from the Diabetes, Depression, Type D Personality Zuidoost-Brabant (DiaDDZoB) Study
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