Changes in Photochemical Efficiency and Differential Induction of Superoxide Dismutase in Response to Combined Stresses of Chilling Temperature and Relatively High Irradiation in Two <em>Chlorella</em> Strains

The green algae Chlorella sp. DT (DT) and Chlorella pyrenoidosa 211-8b (8b) had similar cell growth rates and photochemical efficiency (Fv/Fm) when they were cultivated under a moderate irradiance of 120 μmol photons m−2 s−1 in combination with a series of temperatures that decreased from 32 to 7°C. Upon shifting the cultures to the relatively high irradiance of 240 μmol photons m−2 s−1, DT exhibited higher cell growth rates than 8b under the chilling temperatures of 20°C and 15°C and differences in the Fv/Fm and Chl a/b ratios from 8b. In particular, DT possessed more new differentially induced SOD isoforms than 8b

A practical web-based approach to generating topic hierarchy for text segments

It is crucial in many information systems to organize short text segments, such as keywords in documents and queries from users, into a well-formed topic hierarchy. In this paper, we address the problem of generating topic hierarchies for diverse text segments with a general and practical approach that uses the Web as an additional knowledge source. Unlike long documents, short text segments typically do not contain enough information to extract reliable features. This work investigates the possibilities of using highly ranked search-result snippets to enrich the representation of text segments. A hierarchical clustering algorithm is then applied to create the hierarchical topic structure of text segments. Different from traditional clustering algorithms, which tend to pro-duce cluster hierarchies with a very unnatural shape, the approach tries to produce a more natural and comprehen-sive hierarchy. Extensive experiments were conducted on different domains of text segments. The obtained results have shown the potential of the proposed approach, which is believed able to benefit many information systems

Functional roles of arginine residues in mung bean vacuolar H+-pyrophosphatase

AbstractPlant vacuolar H+-translocating inorganic pyrophosphatase (V-PPase EC 3.6.1.1) utilizes inorganic pyrophosphate (PPi) as an energy source to generate a H+ gradient potential for the secondary transport of ions and metabolites across the vacuole membrane. In this study, functional roles of arginine residues in mung bean V-PPase were determined by site-directed mutagenesis. Alignment of amino-acid sequence of K+-dependent V-PPases from several organisms showed that 11 of all 15 arginine residues were highly conserved. Arginine residues were individually substituted by alanine residues to produce R→A-substituted V-PPases, which were then heterologously expressed in yeast. The characteristics of mutant variants were subsequently scrutinized. As a result, most R→A-substituted V-PPases exhibited similar enzymatic activities to the wild-type with exception that R242A, R523A, and R609A mutants markedly lost their abilities of PPi hydrolysis and associated H+-translocation. Moreover, mutation on these three arginines altered the optimal pH and significantly reduced K+-stimulation for enzymatic activities, implying a conformational change or a modification in enzymatic reaction upon substitution. In particular, R242A performed striking resistance to specific arginine-modifiers, 2,3-butanedione and phenylglyoxal, revealing that Arg242 is most likely the primary target residue for these two reagents. The mutation at Arg242 also removed F− inhibition that is presumably derived from the interfering in the formation of substrate complex Mg2+–PPi. Our results suggest accordingly that active pocket of V-PPase probably contains the essential Arg242 which is embedded in a more hydrophobic environment

Simultaneous Penile Gangrene and Testicular Infarction Secondary to Calciphylaxis in a Uremic Patient

We report here a 46-year-old man with end stage renal disease (ESRD) secondary to type 2 diabetes, who had been on hemodialysis for 5 years. He had a painful glans lesion for 1 week. Five days later, he also complained of right testicular pain. Computed tomography of the pelvis demonstrated calcification of both penile arteries. Scrotal sonography revealed right testicular infarction. He received partial penectomy and right orchiectomy because of progressive lesions and intractable pain. Pathologic examination revealed testicular and penile tissue with necrotizing inflammation accompanied by multifocal calcification in the tunica media, compatible with calciphylaxis. This is the first report to document simultaneous penile gangrene and testicular infarction secondary to calciphylaxis

Resonance in modulation instability from non-instantaneous nonlinearities

To explore resonance phenomena in the nonlinear region, we show by experimental measurements and theoretical analyses that resonance happens in modulation instability (MI) from non-instantaneous nonlinearities in photorefractive crystals. With a temporally periodic modulation in the external bias voltage, corresponding to a modulation in the nonlinear strength, an enhancement in the visibility of MI at resonant frequency is reported through spontaneous optical pattern formations. Modeled by such temporally periodic nonlinear driving force to the system, theoretical curves obtained from a nonlinear non-instantaneous Schr\"{o}dinger equation give good agreement to experimental data. As MI is a universal signature of symmetry-breaking phenomena, our observation on the resonance in MI may provide a control on chaotic, solitary, and turbulence waves.Comment: 5 pages, 4 figure

Knockdown of PsbO leads to induction of HydA and production of photobiological H2 in the green alga Chlorella sp. DT

Green algae are able to convert solar energy to H2 via the photosynthetic electron transport pathway under certain conditions. Algal hydrogenase (HydA, encoded by HYDA) is in charge of catalyzing the reaction: 2H+ + 2e− ↔ H2 but usually inhibited by O2, a byproduct of photosynthesis. The aim of this study was to knockdown PsbO (encoded by psbO), a subunit concerned with O2 evolution, so that it would lead to HydA induction. The alga, Chlorella sp. DT, was then transformed with short interference RNA antisense-psbO (siRNA-psbO) fragments. The algal mutants were selected by checking for the existence of siRNA-psbO fragments in their genomes and the low amount of PsbO proteins. The HYDA transcription and the HydA expression were observed in the PsbO-knockdown mutants. Under semi-aerobic condition, PsbO-knockdown mutants could photobiologically produce H2 which increased by as much as 10-fold in comparison to the wild type