Frost damage of bricks composing a railway tunnel monument in Central Japan: field monitoring and laboratory simulation

International audienceBricks of tunnels and bridges of Usui Pass railway (Japan) exposed to north are subject to frost damage. Average depth of erosion due to detachment of angular blocks is around 1-1.5 cm. In order to assess this weathering and to understand its mechanism, an experimental study was carried out in the field and laboratory. Field monitoring showed the combination of seasonal and diurnal freezing with a maximum of heave when the freezing front reached 5 cm depth. Bricks taken from the site were submitted to unidirectional freezing at capillary and vacuum saturation in the laboratory. Results showed that frost damage of bricks was favoured by high saturation level and repetition of freeze-thaw cycles

Activation of ADF/cofilin by phosphorylation-regulated Slingshot phosphatase is required for the meiotic spindle assembly in Xenopus laevis oocytes

We identify Xenopus ADF/cofilin (XAC) and its activator, Slingshot phosphatase (XSSH), as key regulators of actin dynamics essential for spindle microtubule assembly during Xenopus oocyte maturation. Phosphorylation of XSSH at multiple sites within the tail domain occurs just after germinal vesicle breakdown (GVBD) and is accompanied by dephosphorylation of XAC, which was mostly phosphorylated in immature oocytes. This XAC dephosphorylation after GVBD is completely suppressed by latrunculin B, an actin monomer-sequestering drug. On the other hand, jasplakinolide, an F-actin-stabilizing drug, induces dephosphorylation of XAC. Effects of latrunculin B and jasplakinolide are reconstituted in cytostatic factor-arrested extracts (CSF extracts), and XAC dephosphorylation is abolished by depletion of XSSH from CSF extracts, suggesting that XSSH functions as an actin filament sensor to facilitate actin filament dynamics via XAC activation. Injection of anti-XSSH antibody, which blocks full phosphorylation of XSSH after GVBD, inhibits both meiotic spindle formation and XAC dephosphorylation. Coinjection of constitutively active XAC with the antibody suppresses this phenotype. Treatment of oocytes with jasplakinolide also impairs spindle formation. These results strongly suggest that elevation of actin dynamics by XAC activation through XSSH phosphorylation is required for meiotic spindle assembly in Xenopus laevis

Genetic screen in Drosophila muscle identifies autophagy-mediated T-tubule remodeling and a Rab2 role in autophagy.

Transverse (T)-tubules make-up a specialized network of tubulated muscle cell membranes involved in excitation-contraction coupling for power of contraction. Little is known about how T-tubules maintain highly organized structures and contacts throughout the contractile system despite the ongoing muscle remodeling that occurs with muscle atrophy, damage and aging. We uncovered an essential role for autophagy in T-tubule remodeling with genetic screens of a developmentally regulated remodeling program in Drosophila abdominal muscles. Here, we show that autophagy is both upregulated with and required for progression through T-tubule disassembly stages. Along with known mediators of autophagosome-lysosome fusion, our screens uncovered an unexpected shared role for Rab2 with a broadly conserved function in autophagic clearance. Rab2 localizes to autophagosomes and binds to HOPS complex members, suggesting a direct role in autophagosome tethering/fusion. Together, the high membrane flux with muscle remodeling permits unprecedented analysis both of T-tubule dynamics and fundamental trafficking mechanisms

Comparison of Molecular Structures Determined by Electron Diffraction and Spectroscopy. Ethane and Diborane

Gas‐phase average structures for the ground‐vibrational state (rz)(rz) for ethane and diborane have been determined by a critical comparison of the experimental results obtained from electron diffraction (average internuclear distances rgrg) and those obtained from high‐resolution infrared and Raman spectroscopy (rotational constants Bz(α)Bz(α)). Experimental values have been taken from the recent literature and converted into the average structure (rzorrα0)(rzorrα0). The rgrg and rα0rα0 distances determined from electron diffraction carry uncertainties less than those in the rzrz distances determined from rotational constants, because the latter structures are very sensitive to assumptions about the unknown isotope differences in the structures. On the other hand, the average moments of inertia from spectroscopy are much more precise than those calculated from diffraction internuclear distances. Examinations of the data have led to the following rzrz structures with standard errors: For C2H6, rz(C�H)=1.0957±0.002Å,rz(C�C)=1.5319±0.002Å,and∠C�C�H=111.5°±0.3°; for C2D6, rz(C�D)=1.0941±0.002Å,rz(C�C)=1.5300±0.002Å,and∠C�C�D=111.4°±0.3°; and for B2H6, rz(B�Ht)=1.192±0.01Å,rz(B�Hb)=1.329±0.005Å,rz(B�B)=1.770±0.005Å, ∠Ht�B�Ht=121.8°±3°,and∠Hb�B�Hb=96.5°±0.5°. It was possible to increase the resolving power of the diffraction analysis of diborane by inclusion of calculated B☒H mean amplitudes.The effective complementary use of electron‐diffraction and spectroscopic data for determining reliable gas‐phase structures and the relative merits of the two alternative representations of the average structure (rgandrz)(rgandrz) have been discussed.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/70372/2/JCPSA6-49-10-4456-1.pd

Representations of molecular force fields. V. On the equilibrium structure of methane

The correction from mean (rg) to equilibrium (re) bond lengths in methane is reinvestigated in response to suggestions that the original Kuchitsu–Bartell (KB) corrections were excessive by as much as 0.006 Å. It is found that the KB model anharmonic force field with its original parameterization does overcorrect, relative to the new Pulay ab initio force field, but only by 10% of the original (rg−re) corrections, or 0.0022 Å for CH4 and 0.0015 Å for CD4. The KB model with the more recent MUB‐2 nonbonded parameterization gives results in close accord with the ab initio results, supporting the utility of the augmented anharmonic Urey–Bradley representation of force fields. Reported discrepancies between experimental and theoretical methane bond lengths cannot be due solely to the form of or original parameterization of the KB model field.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/69576/2/JCPSA6-68-3-1213-1.pd

Electron‐Diffraction Study of Ammonia and Deuteroammonia

The gas‐phase structures of NH3 and ND3 molecules were determined by the sector‐microphotometer method of electron diffraction. The following internuclear distances rgrg and mean amplitudes lele with estimated standard errors were obtained: For NH3, rg(N − H)  =  1.0302 ± 0.002Å,rg(H − H)  =  1.662 ± 0.010Å,le(N − H)  =  0.0731 ± 0.002Å,le(H − H)  =  0.125 ± 0.006Årg(N−H)=1.0302±0.002Å,rg(H−H)=1.662±0.010Å,le(N−H)=0.0731±0.002Å,le(H−H)=0.125±0.006Å, and for ND3, rg(N − D)  =  1.0266 ± 0.003Å,rg(D − D)  =  1.654 ± 0.008Å,le(N − D)  =  0.0611 ± 0.002Å,le(D − D)  =  0.101 ± 0.006Årg(N−D)=1.0266±0.003Å,rg(D−D)=1.654±0.008Å,le(N−D)=0.0611±0.002Å,le(D−D)=0.101±0.006Å, with the parameter κκ representing bond‐stretching anharmonicity fixed at 1.0 × 10−5 and 0.5 × 10−5 Å3 for N☒H and N☒D, respectively. Effects of anharmonicity and isotope differences in the structural parameters analogous to those in CH4 and CD4 were observed. The rα0rα0 and rere bond distances calculated from the above rgrg distances are found to be consistent with the corresponding rzrz and rere distances derived from the spectroscopic rotational constants of Benedict and Plyler. The isotope effects reported by Bell and by Halevi for the dipole moment and polarizability of ammonia are discussed briefly in the light of the present results.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/69943/2/JCPSA6-49-6-2488-1.pd

STING自然免疫シグナルの収束を制御する分子機構の解明

要約のみTohoku University田口友彦課

COI1-dependent jasmonate signalling affects growth, metabolites production and cell wall protein composition in Arabidopsis

Background and Aims: Cultured cell suspensions have been the preferred model to study the apoplast as well as to monitor metabolic and cell cycle-related changes. Previous work showed that methyl jasmonate (MeJA) inhibits leaf growth in a CORONATINE INSENSITIVE 1 (COI1)-dependent manner, with COI1 being the jasmonate (JA) receptor. Here, the effect of COI1 overexpression on the growth of stably transformed arabidopsis cell cultures is described. Methods: Time-course experiments were carried out to analyse gene expression, and protein and metabolite levels. Key Results: Both MeJA treatment and the overexpression of COI1 modify growth, by altering cell proliferation and expansion. DNA content as well as transcript patterns of cell cycle and cell wall remodelling markers were altered. COI1 overexpression also increases the protein levels of OLIGOGALACTURONIDE OXIDASE 1, BETA-GLUCOSIDASE/ENDOGLUCANASES and POLYGALACTURONASE INHIBITING PROTEIN2, reinforcing the role of COI1 in mediating defence responses and highlighting a link between cell wall loosening and growth regulation. Moreover, changes in the levels of the primary metabolites alanine, serine and succinic acid of MeJA-treated Arabidopsis cell cultures were observed. In addition, COI1 overexpression positively affects the availability of metabolites such as β-alanine, threonic acid, putrescine, glucose and myo-inositol, thereby providing a connection between JA-inhibited growth and stress responses. Conclusions: This study contributes to the understanding of the regulation of growth and the production of metabolic resources by JAs and COI1. This will have important implications in dissecting the complex relationships between hormonal and cell wall signalling in plants. The work also provides tools to uncover novel mechanisms co-ordinating cell division and post-mitotic cell expansion in the absence of organ developmental control