YongFu Wang

Short interfering RNA against the PDCD5 attenuates cell apoptosis and caspase-3 activity induced by Bax overexpression

The programmed cell death 5 (PDCD5) protein plays an important apoptosis-accelerating role in cells undergoing apoptosis. Decreased expression of PDCD5 has been detected in various human carcinomas. Here we describe that one potent short interfering RNA (siRNA) against the PDCD5 (siPDCD5) specifically inhibits the expression of PDCD5 at both the mRNA and protein level. Cells with decreased PDCD5 expression displayed reduced sensitivity to an apoptotic stimulus induced by Bax overexpression in HeLa, HEK293 and 293T cell lines. Furthermore, we also show that siPDCD5 inhibited both caspase-3 activity and procaspase-3 cleavage. Suppressed expression of PDCD5 attenuates the release of cytochrome c from mitochondria to cytosol induced by Bax overexpression. This phenomenon is accompanied by the reduced translocation of Bax from the cytosol to mitochondria. MTT assay shows that targeted suppression of PDCD5 expression markedly promoted cell proliferation in Hela and HEK293 cell lines. Our data suggests that PDCD5 may exert its effects through pathway of mitochondria by modulating Bax translocation, cytochrome c release and caspase 3 activation directly or indirectly, and that decreased PDCD5 expression may be one of the mechanisms by which tumor cells achieve resistance to apoptotic stimulus induced by anticancer drugs.

Cluster observations of simultaneous resonant interactions of ULF waves with energetic electrons and thermal ion species in the inner magnetosphere

[1] In this study, we report in situ observations on the simultaneous periodic modulations in the drifting energetic electrons (∼100 keV) and in the bouncing thermal ion species (O + at ∼4.5 keV and H + at ∼280 eV) with the same frequency of 3.3 mHz during the storm recovery phase on 21 October 2001. The Cluster fleet was traveling outbound in the inner magnetosphere from the Southern to Northern Hemisphere on the morning sector (0900 MLT). The ultra‐low‐frequency (ULF) waves from the magnetic field and electric field measurements show a mixture of several dominant wave components in the transverse modes. The poloidal mode at the modulation frequency of 3.3 mHz appears to be a standing wave with an odd harmonic, although other wave components reveal propagating features. The radial extent of this standing wave is around 0.58 RE. The oscillation periods of the energetic electron fluxes (∼100 keV) and the thermal O + (∼4.5 keV) and H + (∼280 eV) fluxes are observed the same as the period of the poloidal standing wave, indicating that the energetic electrons and the thermal ion species are modulating by the same wave. Further, we suggest the simultaneous drift resonances of the energetic electrons around 94 keV and the bounce resonances of the thermal O + around 4.5 keV and H + around 280 eV with the same poloidal standing wave. In addition, the electron energy spectra variations reveal the accelerations of the electrons in the energy range of 50∼110 keV, which are most likely due to the drift resonances. This is the first study to show both energetic particles (radiation belt population, ∼ a few hundred keV) and thermal ions (background plasma population, ∼ a few keV) can be affected by the same ULF wave simultaneously. Furthermore, this study implies that the superdense ionospheric origin O + ions in the inner magnetosphere during storm times can modify the local field line eigenfrequency and result in the energetic electron accelerations by the ULF waves in the deep region of the radiation belt.

Cluster observations of the entry layer equatorward of the cusp under northward interplanetary magnetic field

[1] Various boundary crossings in the vicinity of the high-altitude cusp region were experienced by the Cluster spacecraft when the interplanetary magnetic field (IMF) was northward. In contrast to the southward IMF cases, in which a turbulent and diffusive entry layer is present equatorward of the cusp, a transition layer (without significant turbulence and diffusive properties) that shows clear differences in plasma parameters (sometimes step-like profile) compared to the adjacent regions was observed. We suggest that this transition layer, which contains both magnetosheath and magnetospheric populations, is the entry layer during northward IMF conditions. This transition layer is possibly formed by dual-lobe reconnection when the IMF is northward. The plasma property and the closed field line geometry of this layer indicate that it is possibly linked to the low-latitude boundary layer. The width of this layer varies from 480 to 2200 km. The results support the notion that high-latitude dual-lobe reconnection is a potential mechanism of the transport of solar wind into the magnetosphere during northward IMF through the formation of a high-altitude entry layer. The observations of different sublayers with evident density and temperature differences are consistent with the view that the reconnection process at the magnetopause is not steady.

Interactions of energetic electrons with ULF waves triggered by interplanetary shock: Van Allen Probes observations in the magnetotail

We present in situ observations of a shock-induced substorm-like event on 13 April 2013 observed by the newly launched Van Allen twin probes. Substorm-like electron injections with energy of 30–500 keV were observed in the region from L∼5.2 to 5.5 immediately after the shock arrival (followed by energetic electron drift echoes). Meanwhile, the electron flux was clearly and strongly varying on the ULF wave time scale. It is found that both toroidal and poloidal mode ULF waves with a period of 150 s emerged following the magnetotail magnetic field reconfiguration after the interplanetary (IP) shock passage. The poloidal mode is more intense than the toroidal mode. The 90° phase shift between the poloidal mode Br and Ea suggests the standing poloidal waves in the Northern Hemisphere. Furthermore, the energetic electron flux modulations indicate that the azimuthal wave number is ∼14. Direct evidence of drift resonance between the injected electrons and the excited poloidal ULF wave has been obtained. The resonant energy is estimated to be between 150 keV and 230 keV. Two possible scenaria on ULF wave triggering are discussed: vortex-like flow structure-driven field line resonance and ULF wave growth through drift resonance. It is found that the IP shock may trigger intense ULF wave and energetic electron behavior at L∼3 to 6 on the nightside, while the time profile of the wave is different from dayside cases.

Functional Vanilloid Receptor-1 in Human Submandibular Glands

Vanilloid receptor-1 (VR1) was originally found in the nervous system. Recent evidence indicates that VR1 is also expressed in various cell types. We hypothesized that VR1 exists in the human submandibular gland (SMG) and is involved in regulating salivary secretion. VR1 mRNA and protein were expressed in human SMGs and a human salivary intercalated duct cell line. VR1 was mainly located in serous acinar and ductal cells, but not in mucous acinar cells. Capsaicin, an agonist of VR1, increased intracellular free calcium, enhanced phosphorylation of extracellular signal-regulated kinase, and induced the trafficking of aquaporin 5 (AQP5) from the cytoplasm to the plasma membrane. These effects were abolished by pre-treatment with the VR1 antagonist capsazepine. Furthermore, capsaicin cream applied to the skin covering the submandibular area increased salivary secretion. These findings indicated that a functional VR1 is expressed in the human SMG and is involved in regulating salivary secretion by mediating AQP5 trafficking.

Pitch angle evolutions of oxygen ions driven by storm time ULF poloidal standing waves

We present the first systematic observational study on the pitch angle evolutions of O(+) ions associated with ULF Pc5 poloidal standing waves excited during geomagnetic storms. The O(+) ion measurements are made on board the CLUSTER satellites with the Composition Distribution Function (CODIF) instrument, which covers energies from 1 to 40 keV, a low-energy portion of the ring current. We find that the nature of the ion flux oscillation strongly depends on the magnetic latitude of observation. Near the magnetic equator, the flux oscillation appears only around 0 degrees and 180 degrees pitch angles with no phase delay, which can result from wave-particle interactions in a fundamental mode standing wave with a strong poloidal component. Away from the equator, however, the flux oscillation appears in a wide range of pitch angles with strong pitch angle dispersion that reverses sign from the Southern Hemisphere to the Northern Hemisphere. The latitude dependence of the dispersion signature is explained by combining the ion energy modulation near the equator and the time of flight effect of ion bounce motion. The analysis technique shown in this study can be used to diagnose the field line mode structure of ULF waves.

Novel Identification of a Four-base-pair Deletion Mutation in PITX2 in a Rieger Syndrome Family

Rieger syndrome is one of the most serious causes of tooth agenesis. Mutations in the PITX2, FOXC1, and PAX6 genes have been associated with Rieger syndrome. We have studied a three-generation Chinese family affected with Rieger syndrome and showing prominent dental abnormalities. Mutational screening and sequence analysis of the PITX2 gene revealed a previously unidentified four-base-pair deletion of nucleotides 717-720 in exon 5 in all affected members. The mutation causes a frame shift after Thr44, the 7th amino acid of the homeo-domain, and introduces a premature stop codon in the gene sequence. This deletion is the first unquestionable loss-of-function mutation, deleting all the functionally important parts of the protein. Our novel discovery indicates that the oligodontia and other phenotypes of Rieger syndrome observed in this family are due to this PITX2 mutation, and these data further support the critical role of PIXT2 in tooth morphogenesis.

Generation of proton aurora by magnetosonic waves.

Earths proton aurora occurs over a broad MLT region and is produced by the precipitation of low-energy (2–10 keV) plasmasheet protons. Proton precipitation can alter chemical compositions of the atmosphere, linking solar activity with global climate variability. Previous studies proposed that electromagnetic ion cyclotron waves can resonate with protons, producing proton scattering precipitation. A long-outstanding question still remains whether there is another mechanism responsible for the proton aurora. Here, by performing satellite data analysis and diffusion equation calculations, we show that fast magnetosonic waves can produce trapped proton scattering that yields proton aurora. This provides a new insight into the mechanism of proton aurora. Furthermore, a ray-tracing study demonstrates that magnetosonic wave propagates over a broad MLT region, consistent with the global distribution of proton aurora.

Determining the mechanism of cusp proton aurora

Earths cusp proton aurora occurs near the prenoon and is primarily produced by the precipitation of solar energetic (2–10 keV) protons. Cusp auroral precipitation provides a direct source of energy for the high-latitude dayside upper atmosphere, contributing to chemical composition change and global climate variability. Previous studies have indicated that magnetic reconnection allows solar energetic protons to cross the magnetopause and enter the cusp region, producing cusp auroral precipitation. However, energetic protons are easily trapped in the cusp region due to a minimum magnetic field existing there. Hence, the mechanism of cusp proton aurora has remained a significant challenge for tens of years. Based on the satellite data and calculations of diffusion equation, we demonstrate that EMIC waves can yield the trapped proton scattering that causes cusp proton aurora. This moves forward a step toward identifying the generation mechanism of cusp proton aurora.

Outward expansion of the lunar wake: ARTEMIS observations

Magnetohydrodynamics (MHD) predicts that lunar wake expands outward at magnetosonic velocities in all directions perpendicular to background solar wind; however, fluid theories emphasize that lunar wake expands outward at sound speeds mainly along the interplanetary magnetic field (IMF). Early observations supported the MHD predictions in the near-moon region despite lack of solar wind and IMF observations. Thanks to the special orbit design of the ARTEMIS mission, the solar wind conditions are well determined at the time of concurrent observations in the lunar wake. 164 wake crossings made by ARTEMIS are statistically studied in this paper. Observations indicated that, in either distant or near-Moon regions, the lunar wake expands outward at the fast MHD wave velocities. This simple model provides a powerful way to determine wake boundaries, particularly at large distances where the boundary signatures are indistinct, thus allowing further studies on the Moon-solar wind/crustal field-solar wind interactions. Citation: Zhang, H., et al. (2012), Outward expansion of the lunar wake: ARTEMIS observations, Geophys. Res. Lett., 39, L18104, doi: 10.1029/2012GL052839.