627 research outputs found
Domino Rh-catalyzed hydroformylation–doublecyclization of o-amino cinnamyl derivatives:applications to the formal total syntheses ofphysostigmine and physovenine
A parallel, versatile and efficient route to synthesis of pyrrolidinoindoline and tetrahydrofuranoindoline alkaloids from cinnamyl derivatives has been developed, featuring a domino Rh-catalyzed hydroformylation–double cyclization sequence. This method can be applied to the syntheses of anti-Alzheimer drugs such as physostigmine and physovenine
Evolution of long centromeres in fire ants
Background: Centromeres are essential for accurate chromosome segregation, yet sequence conservation is low even among closely related species. Centromere drive predicts rapid turnover because some centromeric sequences may compete better than others during female meiosis. In addition to sequence composition, longer centromeres may have a transmission advantage.
Results: We report the first observations of extremely long centromeres, covering on average 34 % of the chromosomes, in the red imported fire ant Solenopsis invicta. By comparison, cytological examination of Solenopsis geminata revealed typical small centromeric constrictions. Bioinformatics and molecular analyses identified CenSol, the major centromeric satellite DNA repeat. We found that CenSol sequences are very similar between the two species but the CenSol copy number in S. invicta is much greater than that in S. geminata. In addition, centromere expansion in S. invicta is not correlated with the duplication of CenH3. Comparative analyses revealed that several closely related fire ant species also possess long centromeres.
Conclusions: Our results are consistent with a model of simple runaway centromere expansion due to centromere drive. We suggest expanded centromeres may be more prevalent in hymenopteran insects, which use haplodiploid sex determination, than previously considered
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α-Lactosylceramide Protects Against iNKT-Mediated Murine Airway Hyperreactivity and Liver Injury Through Competitive Inhibition of Cd1d Binding.
Invariant natural killer T (iNKT) cells, which are activated by T cell receptor (TCR)-dependent recognition of lipid-based antigens presented by the CD1d molecule, have been shown to participate in the pathogenesis of many diseases, including asthma and liver injury. Previous studies have shown the inhibition of iNKT cell activation using lipid antagonists can attenuate iNKT cell-induced disease pathogenesis. Hence, the development of iNKT cell-targeted glycolipids can facilitate the discovery of new therapeutics. In this study, we synthesized and evaluated α-lactosylceramide (α-LacCer), an α-galactosylceramide (α-GalCer) analog with lactose substitution for the galactose head and a shortened acyl chain in the ceramide tail, toward iNKT cell activation. We demonstrated that α-LacCer was a weak inducer for both mouse and human iNKT cell activation and cytokine production, and the iNKT induction by α-LacCer was CD1d-dependent. However, when co-administered with α-GalCer, α-LacCer inhibited α-GalCer-induced IL-4 and IFN-γ production from iNKT cells. Consequently, α-LacCer also ameliorated both α-GalCer and GSL-1-induced airway hyperreactivity and α-GalCer-induced neutrophilia when co-administered in vivo. Furthermore, we were able to inhibit the increases of ConA-induced AST, ALT and IFN-γ serum levels through α-LacCer pre-treatment, suggesting α-LacCer could protect against ConA-induced liver injury. Mechanistically, we discerned that α-LacCer suppressed α-GalCer-stimulated cytokine production through competing for CD1d binding. Since iNKT cells play a critical role in the development of AHR and liver injury, the inhibition of iNKT cell activation by α-LacCer present a possible new approach in treating iNKT cell-mediated diseases
Asteroid Spin-Rate Study using the Intermediate Palomar Transient Factory
Two dedicated asteroid rotation-period surveys have been carried out using
data taken on January 6-9 and February 20-23 of 2014 by the Intermediate
Palomar Transient Factory (iPTF) in the ~band with -min cadence.
The total survey area covered 174~deg in the ecliptic plane. Reliable
rotation periods for 1,438 asteroids are obtained from a larger data set of
6,551 mostly main-belt asteroids, each with ~detections. Analysis of
1751, PTF based, reliable rotation periods clearly shows the "spin barrier" at
~hours for "rubble-pile" asteroids. We also found a new large-sized
super-fast rotator, 2005 UW163 (Chang et al., 2014), and other five candidates
as well. Our spin-rate distributions of asteroids with ~km shows
number decrease when frequency greater than 5 rev/day, which is consistent to
that of the Asteroid Light Curve Database (LCDB, Warner et al., 2009) and the
result of (Masiero et al., 2009). We found the discrepancy in the spin-rate
distribution between our result and (Pravec et al., 2008, update 2014-04-20) is
mainly from asteroids with mag that might be primarily due to
different survey strategies. For asteroids with ~km, we found a
significant number drop at rev/day. The YORP effect timescale for
small-sized asteroid is shorter that makes more elongate objets spun up to
reach their spin-rate limit and results in break-up. The K-S test suggests a
possible difference in the spin-rate distributions of C- and S-type asteroids.
We also find that C-type asteroids have a smaller spin-rate limit than the
S-type, which agrees with the general sense that the C-type has lower bulk
density than the S-type.Comment: Submitted to ApJ (Jan, 2015). Accepted by ApJ (June, 2015). The whole
set of the folded lightcurves will be available on the published articl
Pair-density wave signature observed by x-ray scattering in La-based high- cuprates
Suggestive, but indirect evidence of the existence of pair-density wave (PDW)
order in several high- cuprates has been reported. As this
constitutes a new quantum phase of matter, it is important to {\it establish}
its existence at least somewhere in the phase diagram. However, a direct
correspondence between experiment and theory has remained elusive. Here, we
report the observation of a theoretically predicted PDW {\it bulk} signature in
two La-based cuprates, Sr-doped LaBaCuO and Fe-doped
LaSrCuO, through a comprehensive study that incorporates
zero-magnetic field x-ray scattering, neutron scattering, and transport
measurements. Specifically, we observe the emergence of so-called "1Q" order,
which is to say subharmonic order associated with the charge-density wave (CDW)
stripes, in a range of temperatures in which independent evidence suggests the
co-existence of PDW long-range order and fluctuating uniform superconducting
order. The subharmonic order is most pronounced around a half-integer
-vector, where the CDW diffraction peak is also strongest. This is
consistent with the theoretical proposal that the cancellation of the Josephson
coupling ("layer-decoupling"), is a signature of PDW order and that it is
commensurately locked to the density wave stripes that are known to alternate
orientation between adjacent layers. Even if the PDW is not the "mother of all
state", it is at least a close relative -- possibly a second cousin
313 new asteroid rotation periods from Palomar Transient Factory observations
A new asteroid rotation period survey have been carried out by using the
Palomar Transient Factory (PTF). Twelve consecutive PTF fields, which covered
an area of 87 deg in the ecliptic plane, were observed in band with a
cadence of 20 min during February 15--18, 2013. We detected 2500 known
asteroids with a diameter range of 0.5 km 200 km. Of these, 313
objects had highly reliable rotation periods and exhibited the "spin barrier"
at hours. In contrast to the flat spin rate distribution of the
asteroids with 3 km 15 km shown by Pravec et al. (2008), our
results deviated somewhat from a Maxwellian distribution and showed a decrease
at the spin rate greater than 5 rev/day. One super-fast-rotator candidate and
two possible binary asteroids were also found in this work.Comment: 18 pages, 20 figures and 2 very long table
Analgesic and Anti-Inflammatory Activities of Methanol Extract of Ficus pumila L. in Mice
This study investigated possible analgesic and anti-inflammatory mechanisms of the methanol extract of Ficus pumila (FPMeOH). Analgesic effects were evaluated in two models including acetic acid-induced writhing response and formalin-induced paw licking. The results showed FPMeOH decreased writhing response in the acetic acid assay and licking time in the formalin test. The anti-inflammatory effect was evaluated by λ-carrageenan-induced mouse paw edema and histopathological analyses. FPMeOH significantly decreased the volume of paw edema induced by λ-carrageenan. Histopathologically, FPMeOH abated the level of tissue destruction and swelling of the edema paws. This study indicated anti-inflammatory mechanism of FPMeOH may be due to declined levels of NO and MDA in the edema paw through increasing the activities of SOD, GPx, and GRd in the liver. Additionally, FPMeOH also decreased the level of inflammatory mediators such as IL-1β, TNF-α, and COX-2. HPLC fingerprint was established and the contents of three active ingredients, rutin, luteolin, and apigenin, were quantitatively determined. This study provided evidence for the classical treatment of Ficus pumila in inflammatory diseases
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