5,693 research outputs found
FZL, a dynamin-like protein localized to curved grana edges, is required for efficient photosynthetic electron transfer in Arabidopsis
Photosynthetic electron transfer and its regulation processes take place on thylakoid membranes, and the thylakoid of vascular plants exhibits particularly intricate structure consisting of stacked grana and flat stroma lamellae. It is known that several membrane remodeling proteins contribute to maintain the thylakoid structure, and one putative example is FUZZY ONION LIKE (FZL). In this study, we re-evaluated the controversial function of FZL in thylakoid membrane remodeling and in photosynthesis. We investigated the sub-membrane localization of FZL and found that it is enriched on curved grana edges of thylakoid membranes, consistent with the previously proposed model that FZL mediates fusion of grana and stroma lamellae at the interfaces. The mature fzl thylakoid morphology characterized with the staggered and less connected grana seems to agree with this model as well. In the photosynthetic analysis, the fzl knockout mutants in Arabidopsis displayed reduced electron flow, likely resulting in higher oxidative levels of Photosystem I (PSI) and smaller proton motive force (pmf). However, nonphotochemical quenching (NPQ) of chlorophyll fluorescence was excessively enhanced considering the pmf levels in fzl, and we found that introducing kea3-1 mutation, lowering pH in thylakoid lumen, synergistically reinforced the photosynthetic disorder in the fzl mutant background. We also showed that state transitions normally occurred in fzl, and that they were not involved in the photosynthetic disorders in fzl. We discuss the possible mechanisms by which the altered thylakoid morphology in fzl leads to the photosynthetic modifications
Internal shock model for the X-ray flares of Swift J1644+57
Swift J1644+57 is an unusual transient event, likely powered by the tidal
disruption of a star by a massive black hole. There are multiple short
timescales X-ray flares were seen over a span of several days. We propose that
these flares could be produced by internal shocks. In the internal shock model,
the forward and reverse shocks are produced by collisions between relativistic
shells ejected from central engine. The synchrotron emission from the forward
and reverse shocks could dominate at two quite different energy bands under
some conditions, the relativistic reverse shock dominates the X-ray emission
and the Newtonian forward shock dominates the infrared and optical emission. We
show that the spectral energy distribution of Swift J1644+57 could be explained
by internal shock model.Comment: 6 pages, 3 figures, accepted for publication in MNRA
Neurokinin-1 Receptor Immunoreactive Neuronal Elements in the Superficial Dorsal Horn of the Chicken Spinal Cord: With Special Reference to Their Relationship with the Tachykinin-containing Central Axon Terminals in Synaptic Glomeruli
Synaptic glomeruli that involve tachykinin-containing primary afferent central terminals are numerous in lamina II of the chicken spinal cord. Therefore, a certain amount of noxious information is likely to be modulated in these structures in chickens. In this study, we used immunohistochemistry with confocal and electron microscopy to investigate whether neurokinin-1 receptor (NK-1R)-expressing neuronal elements are in contact with the central primary afferent terminals in synaptic glomeruli of the chicken spinal cord. We also investigated which neuronal elements (axon terminals, dendrites, cell bodies) and which neurons in the spinal cord possess NK-1R, and are possibly influenced by tachykinin in the glomeruli. By confocal microscopy, NK-1R immunoreactivities were seen in a variety of neuronal cell bodies, their dendrites and smaller fibers of unknown origin. Some of the NK-1R immunoreactive profiles also expressed GABA immunoreactivities. A close association was observed between the NK-1R-immunoreactive neurons and tachykinin-immunoreactive axonal varicosities. By electron microscopy, NK-1R immunoreactivity was seen in cell bodies, conventional dendrites and vesicle-containing dendrites in laminae I and II. Among these elements, dendrites and vesicle-containing dendrites made contact with tachykinin-containing central terminals in the synaptic glomeruli. These results indicate that tachykinin-containing central terminals in the chicken spinal cord can modulate second-order neuronal elements in the synaptic glomeruli
12CO, 13CO and C18O observations along the major axes of nearby bright infrared galaxies
We present simultaneous observations of CO,13CO and C18O J=1-0 emission in 11
nearby (cz<1000 km/s) bright infrared galaxies. Both 12CO and 13CO are detected
in the centers of all galaxies, except for 13CO in NGC 3031. We have also
detected C18O, CS J=2-1, and HCO+ J=1-0 emission in the nuclear regions of M82
and M51. These are the first systematical extragalactic detections of 12CO and
its isotopes from the PMO 14m telescope. We have conducted half-beam spacing
mapping of M82 over an area of 4'*2.5' and major axis mapping of NGC 3627, NGC
3628, NGC 4631, and M51. The radial distributions of 12CO and 13CO in NGC 3627,
NGC 3628, and M51 can be well fitted by an exponential profile. The 12CO/13CO
intensity ratio,R,decreases monotonically with galactocentric radius in all
mapped sources. The average R in the center and disk of the galaxies are
9.9+/-3.0 and 5.6+/-1.9 respectively, much lower than the peculiar R(~24) found
in the center of M82. The intensity ratios of 13CO/C18O, 13CO/HCO+ and 13CO/CS
(either ours or literature data) show little variations with galactocentric
radius, in sharp contrast with the greatly varied R. This supports the notion
that the observed gradient in R could be the results of the variations of the
physical conditions across the disks. The H_2 column density derived from C18O
shows that the Galactic standard conversion factor (X-factor) overestimates the
amount of the molecular gas in M82 by a factor of ~2.5. These observations
suggest that the X-factor in active star-forming regions (i.e., nuclear
regions) should be lower than that in normal star-forming disks, and the
gradient in R can be used to trace the variations of the X-factor.Comment: 27 pages, 7 figures, accepted by RA
Vascular composition data supporting the role of N-3 polyunsaturated fatty acids in the prevention of cardiovascular disease events
AbstractN-3 polyunsaturated fatty acids (PUFAs) are thought to have protective effects against cardiovascular disease. Here, we report the relationship between serum PUFA concentrations and plaque composition, as evaluated by virtual histology-intravascular ultrasound (VH-IVUS). Consecutive patients (n=61) who underwent percutaneous coronary intervention (PCI) were pre-operatively examined using VH-IVUS to assess the composition of culprit plaques. Gray-scale IVUS and VH-IVUS data of fibrous, fibro-fatty, necrotic core, and dense calcium regions of plaques were estimated at the minimal luminal area sites of culprit lesions. Serum levels of high-sensitivity C-reactive protein (hsCRP) and PUFAs, including eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), and arachidonic acid (AA), were compared between patients with (ACS, n=27) and without acute coronary syndrome (non-ACS, n=34) before PCI. Multiple logistic regression analysis of the data showed that EPA/AA under the median was more highly associated with ACS than hsCRP over the median. In addition, EPA/AA was negatively correlated with the percentage of fibrous plaque regions and EPA/AA and DHA/AA were positively correlated with the percentage of dense calcium regions in plaques. Furthermore, the correlation index of EPA/AA was the most highly (R=0.513) correlated with the percentage of dense calcium regions in plaques
A Comprehensive Analysis of Fermi Gamma-Ray Burst Data. I. Spectral Components and Their Possible Physical Origins of LAT/GBM GRBs
We present a systematic analysis of the spectral and temporal properties of
17 GRBs co-detected by GBM and LAT on board the Fermi satellite by May 2010. We
performed a time-resolved spectral analysis of all the bursts with the finest
temporal resolution allowed by statistics, in order to avoid temporal smearing
of different spectral components. We found that the time-resolved spectra of 14
out of 17 GRBs are best modeled with the Band function over the entire Fermi
spectral range, which may suggest a common origin for emissions detected by LAT
and GBM. GRB 090902B and GRB 090510 require the superposition between an MeV
component and an extra power law component, with the former having a sharp
cutoff above E_p. For GRB 090902B, this MeV component becomes progressively
narrower as the time bin gets smaller, and can be fit with a Planck function as
the time bin becomes small enough. In general, we speculate that
phenomenologically there may be three elemental spectral components : (I) a
Band-function component (e.g. in GRB 080916C) that extends in a wide energy
range and does not narrow with reducing time bins, which may be of the
non-thermal origin; (II) a quasi-thermal component (e.g. in GRB 090902B) with
the spectra progressively narrowing with reducing time bins; and (III) another
non-thermal power law component extending to high energies. The spectra of
different bursts may be decomposed into one or more of these elemental
components. We compare this sample with the BATSE sample and investigate some
correlations among spectral parameters. We discuss the physical implications of
the data analysis results for GRB prompt emission, including jet compositions
(matter-dominated vs. Poynting-flux-dominated outflow), emission sites
(internal shock, external shock or photosphere), as well as radiation
mechanisms (synchrotron, synchrotron self-Compton, or thermal Compton
upscattering).Comment: 61 pages, 25 figures, 3 tables. 2011 ApJ in pres
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