Academia Sinica

About: Academia Sinica is a facility organization based out in Taipei, Taiwan. It is known for research contribution in the topics: Population & Galaxy. The organization has 52086 authors who have published 65998 publications receiving 1728114 citations. The organization is also known as: Central Research Academy.

Design and construction of a linear shear stress flow chamber

Abstract: A new paralle plate flow chamber that has a linear variation of shear stress, starting from a predetermined maximum value at the entrance and falling to zero at the exit, has been designed and tested. This is in contrast to the usual rect-angular channel plan which produces a constant shear stress over the entire length. The new design is based on the theory of Hele-Shaw flow between parallel plates. To verify the efficacy of the flow channel, the effect of fluid shear stress on platelet adhesion to a fibrinogen-coated glass surface was tested. The percentage of attached platelets after 5 min of shear stress is shown to be a function of shear stress. With this new flow chamber, cell-cell interactions can be studied efficiently over a wide range of shear stress using a single run at constant discharge.

Japanese encephalitis virus infection initiates endoplasmic reticulum stress and an unfolded protein response.

Abstract: The malfunctioning of the endoplasmic reticulum (ER) of cells in hosts ranging from yeast to mammals can trigger an unfolded protein response (UPR). Such malfunctioning can result from a variety of ER stresses, including the inhibition of protein glycosylation and calcium imbalance. To cope with ER stresses, cells may rely on the UPR to send a signal(s) from the ER to the nucleus to stimulate appropriate cellular responses, including induction of chaperone expression. During Japanese encephalitis virus (JEV) infection, the lumen of the ER rapidly accumulates substantial amounts of viral proteins for virus progeny production. In the present study, we demonstrate that as evidenced by certain chaperone inductions, JEV infection triggers the UPR in fibroblast BHK-21 cells and in neuronal N18 and NT-2 cells, in which JEV results in apoptotic cell death. By contrast, no UPR was observed in apoptosis-resistant K562 cells infected by JEV. JEV infection also activates expression of CHOP/GADD153, a distinctive transcription factor often induced by the UPR, and appears to trigger activation of p38 mitogen-activated protein kinase, a posttranslational activator of CHOP. Ectopic enforcement of CHOP expression enhanced JEV-induced apoptosis, whereas treatment with a p38-specific inhibitor, SB203580, partially blocked JEV-induced apoptosis. Interestingly, bcl-2 overexpression and treatment with a pancaspase inhibitor, z-VAD-fmk, inhibited CHOP induction and diminished JEV-induced apoptosis, suggesting that Bcl-2 and caspases could be the upstream regulators of CHOP. Our results thus suggest that virus-induced ER stress may participate, via p38-dependent and CHOP-mediated pathways, in the apoptotic process triggered by JEV infection.

Ca 3 P 2 and other topological semimetals with line nodes and drumhead surface states

Abstract: Topological nodal line semimetals exhibit protected one-dimensional Fermi lines, which arise due to an intricate interplay between the symmetry and topology of the electronic wave functions. In this paper, the authors derive the $\mathbb{Z}$ invariants that guarantee the stability of the line nodes in the bulk under reflection symmetry and show that a quantized Berry phase (i.e, a ${\mathbb{Z}}_{2}$ invariant) leads to the appearance of protected surfaces states, which take the shape of a drumhead. Most importantly, a relation between the $\mathbb{Z}$ invariant, which characterizes the bulk, and the quantized Berry phase is derived. This relation is generally applicable to any topological nodal line semimetal with or without spin-orbit coupling. Moreover, it is shown that the Berry phase invariant can be simply obtained by computing the reflection parity eigenvalues. As a representative example of a topological nodal line semimetal, the authors examine Ca${}_{3}$P${}_{2}$, which has been identified as an ideal system with the line nodes at the Fermi energy. Using numerical calculations, they show that the drumhead surface state of Ca${}_{3}$P${}_{2}$ has a rather weak dispersion, which implies that correlation effects are enhanced at the surface.