NG2 cells response to axonal alteration in the spinal cord white matter in mice with genetic disruption of neurofilament light subunit expression

<p>Abstract</p> <p>Background</p> <p>Chondroitin sulphate proteoglycan (NG2) expressing cells, morphologically characterized by multi-branched processes and small cell bodies, are the 4^thcommonest cell population of non-neuronal cell type in the central nervous system (CNS). They can interact with nodes of Ranvier, receive synaptic input, generate action potential and respond to some pathological stimuli, but the function of the cells is still unclear. We assumed the NG2 cells may play an active role in neuropathogenesis and aimed to determine if NG2 cells could sense and response to the alterations in the axonal contents caused by disruption of neurofilament light subunit (NFL) expression.</p> <p>Results</p> <p>In the early neuropathological development stage, our study showed that the diameter of axons of upper motor neurons of NFL-/- mice decreased significantly while the thickness of their myelin sheath increased remarkably. Although there was an obvious morphological distortion in axons with occasionally partial demyelination, no obvious changes in expression of myelin proteins was detected. Parallel to these changes in the axons and their myelination, the processes of NG2 cells were disconnected from the nodes of Ranvier and extended further, suggesting that these cells in the spinal cord white matter could sense the alteration in axonal contents caused by disruption of NFL expression before astrocytic and microglial activation.</p> <p>Conclusion</p> <p>The structural configuration determined by the NFL gene may be important for maintenance of normal morphology of myelinated axons. The NG2 cells might serve as an early sensor for the delivery of information from impaired neurons to the local environment.</p

Spatial heterogeneity of tectonic stress and friction in the crust: new evidence from earthquake focal mechanisms in Taiwan

We performed inversions of earthquake focal mechanisms in central Taiwan to investigate the heterogeneity of the stress field and fault strength, and temporal variations of stress parameters, friction and pore pressure associated with the 1999 Chi-Chi earthquake. We divided the focal mechanism data into two groups: before and after the Chi-Chi earthquake, and analysed them separately. With the assumption of a uniform stress field, the friction coefficient is mostly within a range of 0.2–0.4 in central Taiwan, which is lower than the commonly quoted laboratory result, 0.6–0.85. The low friction coefficient is also inferred by the rotation of principal stress axes after the Chi-Chi earthquake. By contrast, if we assume that the friction is constant and failures occur on optimally oriented planes, we find that the resulting stress orientations must be spatially variable. However, a large dispersion of stress orientations is not seen in borehole breakouts and fault slip data, implying a constant friction model might be ruled out. Our analysis suggests that either the distribution of the coefficient of friction or pore pressure changed during the 1999 Chi-Chi earthquake. We infer that the pore pressure probably rose in the Chi-Chi rupture area and northern Longitudinal Valley and dropped in the areas south of the coseismic rupture area after the main shock

2-Chloro­ethyl 4-nitro­benzoate

The title compound, C9H8ClNO4, crystallizes with two mol­ecules in the asymmetric unit. In each mol­ecule, the carboxyl­ate group is nearly coplanar with the benzene ring, forming dihedral angles of 2.4 (1) and 4.9 (1)°. In the crystal, mol­ecules are linked through weak C—H⋯O and C—H⋯Cl hydrogen bonds. A short O⋯N contact of 2.7660 (19) Å occurs between the nitro groups of adjacent mol­ecules

5,6,7,8-Tetra­hydro­naphthalene-1-carboxylic acid

In the mol­ecule of the title compound, C11H12O2, the cyclo­hexane ring adopts a half-chair conformation. In the crystal structure, mol­ecules are linked into centrosymmetric dimers by pairs of O—H⋯O hydrogen bonds, and the dimers are linked together by π–π inter­actions [centroid–centroid distance = 3.8310 (13) Å] and C—H⋯O bonds

Isopropyl 4-nitro­benzoate

In the mol­ecule of the title compound, C10H11NO4, the nitro group is approximately coplanar with the benzene ring [dihedral angle = 4.57 (10)°], while the carboxyl­ate group is slightly twisted, making an angle of 12.16 (8)°. In the crystal, weak inter­molecular C—H⋯O hydrogen bonding and π–π stacking inter­actions [centroid–centroid distances = 3.670 (2) and 3.665 (2) Å] are observed

2,3,5-Trimethyl-1,4-hydro­quinone

The mol­ecule of the title compound, C9H12O2, is approximately planar (mean atomic deviation = 0.0346 Å) and disposed about a crystallographic centre of symmetry. The H atom of the benzene ring is disordered over four orientations, with occupancies of 0.100 (3) and 0.401 (3) at the C atoms in the 2- and 3-positions and the same at their symmetric location. The H atoms of methyl group at the 2-position are disordered over two positions of equal occupancy. In the crystal structure, adjacent mol­ecules are linked through O—H⋯O hydrogen bonds, forming a two-dimensional network

Ethyl 4-chloro-3,5-dinitro­benzoate

In the title compound, C9H7ClN2O6, the nitro groups and the ester group make dihedral angles of 44.0 (1), 89.6 (1) and 164.1 (1)°, respectively, with the benzene ring. In the crystal, mol­ecules are linked through weak C—H⋯O hydrogen-bonding inter­actions. Mol­ecules are stacked via π–π inter­actions about inversion centers, with a centroid–centroid distance of 3.671 (2) Å