J.W. Seo

Phospholipase A2β mediates light-induced stomatal opening in Arabidopsis

Phospholipase A2 (PLA2) catalyses the hydrolysis of phospholipids into lysophospholipids and free fatty acids. Physiological studies have indicated that PLA2 is involved in stomatal movement. However, genetic evidence of a role of PLA2 in guard cell signalling has not yet been reported. To identify PLA2 gene(s) that is (are) involved in light-induced stomatal opening, stomatal movement was examined in Arabidopsis thaliana plants in which the expression of PLA2 isoforms was reduced or knocked-out. Light-induced stomatal opening in PLA2α knockout plants did not differ from wild-type plants. Plants in which PLA2β was silenced by RNA interference exhibited delayed light-induced stomatal opening, and this phenotype was reversed by exogenous lysophospholipids, which are products of PLA2. Stomatal opening in transgenic plants that over-expressed PLA2β was faster than wild-type plants. The expression of PLA2β was localized to the endoplasmic reticulum of guard cells, and increased in response to light in the mature leaf. Aristolochic acid, which inhibits light-induced stomatal opening, inhibited the activity of purified PLA2β. Collectively, these results provide evidence that PLA2β is involved in light-induced stomatal opening in Arabidopsis.

Circuit model for two-electrode AC discharge

This paper presents a circuit model for a two-electrode AC discharge, which has two electrodes separated from the discharge gap by an insulator. The model consists of a series connection of an equivalent circuit for plasma and two capacitors for insulator. The equivalent circuit for plasma was constructed using the measured electrical properties of a two-electrode DC discharge. The validity of model was checked with experiments on a three-electrode test device; two electrodes exposed to the discharge gap and the other electrode separated from the discharge gap by an insulator. The measured voltages of the test device are compared with those obtained by circuit simulation. For various waveforms, which are being used widely to drive an AC plasma display panel, the results of circuit simulation agree well with experiment.

Quantitative Probing of Cu2+ Ions Naturally Present in Single Living Cells

Quantitative probing of Cu(2+) ions naturally present in single living cells is realized by developing a quantum-dot-embedded nanowire-waveguide probe. The intracellular Cu(2+) ion concentration is quantified by direct monitoring of photoluminescence quenching during the insertion of the nanowire in a living neuron. The measured intracellular Cu(2+) ion concentration is 3.34 ± 1.04 × 10(-6) m (mean ± s.e.m.) in single hippocampal neurons.

Cell parameter extraction method for AC plasma display panels

Abstract This paper presents a cell parameter extraction method for three-electrode AC plasma display panels (PDPs). This method uses three different two-electrode AC discharges to extract the cell capacitances. The drive point capacitances of the cell with and without a two-electrode dark discharge were measured, and the cell capacitances were extracted from them. The extracted cell capacitances agree well with those obtained from a three-dimensional electromagnetic simulation. Electrical equivalent circuits of the plasma were constructed using Jungs model [Y.K. Jung, J.W. Seo, Y.H. Kim, B.K. Kang, Circuit model for two-electrode AC discharge, IEEE Trans. Plasma Sci., 31(3), pp. 362–368, 2003.] and the measured firing voltages. A circuit model for the cell was constructed using the cell capacitances and the equivalent circuits for the plasma. The results of electrical simulation using this circuit model agree well with the measurements, indicating that the presented circuit model would be useful for simulating the electrical behaviors of a three-electrode AC PDP.

Versatile energy recovery circuit for driving AC plasma display panel with single sustain circuit board

This paper presents an energy recovery (ER) circuit which can operate either in a series or a parallel resonance mode and can drive an AC plasma display panel (PDP) with a single sustain circuit board. The proposed ER circuit consists of one energy storage capacitor, two energy recovery inductors, and three insulated-gate bipolar transistors. The circuit operations in the series and parallel resonance modes are similar to conventional ones, except for the leading edge of the first sustain pulse and the trailing edge of the last sustain pulse. To reduce power consumption in the parallel resonance mode of operation, these two pulse edges are generated using a series resonance between the panel capacitance and the energy recovery inductor. The proposed circuit had energy recovery efficiencies in both the series and parallel resonance modes that were nearly the same as the efficiency of the conventional series resonance ER circuit. Experimental results on a 42-inch XGA single-scan PDP show that the proposed ER circuit is suitable for use in a PDP drive circuit.

Heterogeneous nuclear ribonucleoprotein (hnRNP) L promotes DNA damage-induced cell apoptosis by enhancing the translation of p53

The tumor suppressor p53 is an essential gene in the induction of cell cycle arrest, DNA repair, and apoptosis. p53 protein is induced under cellular stress, blocking cell cycle progression and inducing DNA repair. Under DNA damage conditions, it has been reported that post-transcriptional regulation of p53 mRNA contributes to the increase in p53 protein level. Here we demonstrate that heterogeneous nuclear ribonucleoprotein (hnRNP) L enhances p53 mRNA translation. We found that hnRNP L is increased and binds to the 5’UTR of p53 mRNA in response to DNA damage. Increased hnRNP L caused enhancement of p53 mRNA translation. Conversely, p53 protein levels were decreased following hnRNP L knock-down, rendering them resistant to apoptosis and arrest in the G2/M phase after DNA damage. Thus, our findings suggest that hnRNP L functions as a positive regulator of p53 translation and promotes cell cycle arrest and apoptosis.

Nanowires: Quantitative Probing of Cu(2+) Ions Naturally Present in Single Living Cells (Adv. Mater. 21/2016).

Quantitative probing of the Cu(2+) ions naturally present in single living cells is accomplished by a probe made from a quantum-dot-embedded-nanowire waveguide. After inserting the active nanowire-based waveguide probe into single living cells, J. H. Je and co-workers directly observe photoluminescence (PL) quenching of the embedded quantum dots by the Cu(2+) ions diffused into the probe as described on page 4071. This results in quantitative measurement of intracellular Cu(2+) ions.