Four-helix bundle: a ubiquitous sensory module in prokaryotic signal transduction

MOTIVATION: Transmembrane chemoreceptors in Escherichia coli utilize ligand-binding domains for detecting various external signals. The structure of this domain in the E.coli aspartate receptor, Tar, is known and its signal transduction mechanism is under investigation. Current domain models for this important sensory module are inaccurate and, therefore, cannot reveal the distribution of this domain within the current genomic landscape. RESULTS: We carried out sensitive and exhaustive PSI-BLAST searches initiated with the sequence corresponding to a known structure of the four-helix, ligand-binding domain of the aspartate chemoreceptor. From the resulting sequences, we built a multiple sequence alignment for this domain family, which confirmed that the current TarH model is erroneous and fails to detect most of the domain homologs. In the process, we developed a technique that visualizes the secondary structure prediction of each protein sequence in order to improve the multiple sequence alignment. We found that the four-helix up-and-down bundle represents a large domain family and includes representatives of all major classes of prokaryotic signal transduction, namely histidine kinases, di-guanylate cyclases and chemotaxis receptors.     

Retrocrural Space Involvement on Computed Tomography as a Predictor of Mortality and Disease Severity in Acute Pancreatitis

Background

Because computed tomography (CT) has advantages for visualizing the manifestation of necrosis and local complications, a series of scoring systems based on CT manifestations have been developed for assessing the clinical outcomes of acute pancreatitis (AP), including the CT severity index (CTSI), modified CTSI, etc. Despite the internationally accepted CTSI having been successfully used to predict the overall mortality and disease severity of AP, recent literature has revealed the limitations of the CTSI. Using the Delphi method, we establish a new scoring system based on retrocrural space involvement (RCSI), and compared its effectiveness at evaluating the mortality and severity of AP with that of the CTSI.

Methods

We reviewed CT images of 257 patients with AP taken within 3–5 days of admission in 2012. The RCSI scoring system, which includes assessment of infectious conditions involving the retrocrural space and the adjacent pleural cavity, was established using the Delphi method. Two radiologists independently assessed the RCSI and CTSI scores. The predictive points of the RCSI and CTSI scoring systems in evaluating the mortality and severity of AP were estimated using receiver operating characteristic (ROC) curves.

Principal Findings

The RCSI score can accurately predict the mortality and disease severity. The area under the ROC curve for the RCSI versus CTSI score was 0.962±0.011 versus 0.900±0.021 for predicting the mortality, and 0.888±0.025 versus 0.904±0.020 for predicting the severity of AP. Applying ROC analysis to our data showed that a RCSI score of 4 was the best cutoff value, above which mortality could be identified.

Conclusion

The Delphi method was innovatively adopted to establish a scoring system to predict the clinical outcome of AP. The RCSI scoring system can predict the mortality of AP better than the CTSI system, and the severity of AP equally as well.     

Oxygen taxis and proton motive force in Azospirillum brasilense.

The microaerophilic nitrogen-fixing bacterium Azospirillum brasilense formed a sharply defined band in a spatial gradient of oxygen. As a result of aerotaxis, the bacteria were attracted to a specific low concentration of oxygen (3 to 5 microM). Bacteria swimming away from the aerotactic band were repelled by the higher or lower concentration of oxygen that they encountered and returned to the band. This behavior was confirmed by using temporal gradients of oxygen. The cellular energy level in A. brasilense, monitored by measuring the proton motive force, was maximal at 3 to 5 microM oxygen. The proton motive force was lower at oxygen concentrations that were higher or lower than the preferred oxygen concentration. Bacteria swimming toward the aerotactic band would experience an increase in the proton motive force, and bacteria swimming away from the band would experience a decrease in the proton motive force. It is proposed that the change in the proton motive force is the signal that regulates positive and negative aerotaxis. The preferred oxygen concentration for aerotaxis was similar to the preferred oxygen concentration for nitrogen fixation. Aerotaxis is an important adaptive behavioral response that can guide these free-living diazotrophs to the optimal niche for nitrogen fixation in the rhizosphere.     

山茶属五种植物叶片解剖特征及与光合生理相关性研究

利用扫描电子显微镜观察山茶属（ＣａｍｅｌｌｉａＬｉｎｎ．）五种植物叶片解剖特征,并与光合生理相关性进行分析。实验选择的五种植物均为Ｃ３植物,其中小黄花茶（ＣａｍｅｌｌｉａｌｕｔｅｏｆｌｏｒａＹ．Ｋ．Ｌｉ）和四球茶（Ｃ．ｔａｃｈａｎｇｅｎｓｉｓＦ．Ｃ．Ｚｈａｎｇ）为阴性植物．叶绿素含量较高;咸宁短柱茶（Ｃ．ｓａｌｕｅｎｅｎｓｉｓＳｔａｐｆ．ｅｘＢｅａｎ．）为偏阴性植物,叶绿素含量较低;美丽红山茶（Ｃ．ｄｅｌｉｃａｔａＹ．Ｋ．Ｌｉ）和狭叶瘤果茶（Ｃ．ｎｅｒｉｉｆｏｌｉａＣｈａｎｇ）则属于半阴性植物。它们的光合生理指标值差异取决于叶片解剖特征的差异;与光补偿点,光饱和点,净光合速率（Ｐｎ）,光呼吸速率（Ｐｒ）,暗呼吸速率（Ｄｒ）相关性最密切的解剖指标是栅栏组织厚度、栅栏组织中的细胞层数、栅栏细胞内的叶绿体数,栅栏组织厚与叶厚的比值、与栅栏细胞粗度的比值、与海绵组织厚度的比值．叶片上表皮厚、上表皮角质层厚及下表皮气孔密度亦与上述光合生理指标呈弱正相关,叶片大小、气孔器大小及气孔口长则与上述光合生理指标呈弱负相关;下表皮厚、海绵组织厚度及栅栏细胞内叶绿体大小与各项光合生理指标几乎无关。该五种植物的叶片解剖和光合生理特     

Cross-Culture Validation of the HIV/AIDS Stress Scale: The Development of a Revised Chinese Version

BackgroundBeing HIV-infected is a stressful experience for many individuals. To assess HIV-related stress in the Chinese context, a measure with satisfied psychometric properties is yet underdeveloped. This study aimed to examine the psychometric characteristics of a simplified Chinese version of the HIV/AIDS Stress Scale (SS-HIV) among people living with HIV/AIDS in central China.MethodA total of 667 people living with HIV (92% were male) were recruited from March 1^st 2014 to August 31^th 2015 by consecutive sampling. A standard questionnaire package containing the Chinese HIV/AIDS Stress Scale (CSS-HIV), the Chinese Patient Health Questionnaire-9 (PHQ-9), and the Chinese Generalized Anxiety Disorder Scale (GAD-7) were administered to all participants, and 38 of the participants were selected randomly to be re-tested in four weeks after the initial testing.ResultsOur data supported that a revised 17-item CSS-HIV had adequate psychometric properties. It consisted of 3 factors: emotional stress (6 items), social stress (6 items) and instrumental stress (5 items). The overall Cronbach’s α was 0.906, and the test-retest reliability coefficient was 0.832. The revised CSS-HIV was significantly correlated with the number of HIV-related symptoms, as well as scores on the PHQ-9 and GAD-7, indicating acceptable concurrent validity.ConclusionThe 17-item Chinese version of the SS-HIV has potential research and clinical utility in identifying important stressors among the Chinese HIV-infected population and in understanding the effects of stress on adjustment to HIV.     

Ready player one? Autophagy shapes resistance to photodynamic therapy in cancers

Photodynamic therapy (PDT) is a procedure used in cancer therapy that has been shown to be useful for certain indications. Considerable evidence suggests that PDT might be superior to conventional modalities for some indications. In this report, we examine the relationship between PDT responsiveness and autophagy, which can exert a cytoprotective effect. Autophagy is an essential physiological process that maintains cellular homeostasis by degrading dysfunctional or impaired cellular components and organelles via a lysosome-based pathway. Autophagy, which includes macroautophagy and microautophagy, can be a factor that decreases or abolishes responses to various therapeutic protocols. We systematically discuss the mechanisms underlying cell-fate decisions elicited by PDT; analyse the principles of PDT-induced autophagy, macroautophagy and microautophagy; and present evidence to support the notion that autophagy is a critical mechanism in resistance to PDT. A combined strategy involving autophagy inhibitors may be able to further enhance PDT efficacy. Finally, we provide suggestions for future studies, note where our understanding of the relevant molecular regulators is deficient, and discuss the correlations among PDT-induced resistance and autophagy, especially microautophagy.     

Quantification of the magnification and distortion effects of a pediatric flexible video-bronchoscope

Background

Flexible video bronchoscopes, in particular the Olympus BF Type 3C160, are commonly used in pediatric respiratory medicine. There is no data on the magnification and distortion effects of these bronchoscopes yet important clinical decisions are made from the images. The aim of this study was to systematically describe the magnification and distortion of flexible bronchoscope images taken at various distances from the object.

Methods

Using images of known objects and processing these by digital video and computer programs both magnification and distortion scales were derived.

Results

Magnification changes as a linear function between 100 mm (×1) and 10 mm (×9.55) and then as an exponential function between 10 mm and 3 mm (×40) from the object. Magnification depends on the axis of orientation of the object to the optic axis or geometrical axis of the bronchoscope. Magnification also varies across the field of view with the central magnification being 39% greater than at the periphery of the field of view at 15 mm from the object. However, in the paediatric situation the diameter of the orifices is usually less than 10 mm and thus this limits the exposure to these peripheral limits of magnification reduction. Intraclass correlations for measurements and repeatability studies between instruments are very high, r = 0.96. Distortion occurs as both barrel and geometric types but both types are heterogeneous across the field of view. Distortion of geometric type ranges up to 30% at 3 mm from the object but may be as low as 5% depending on the position of the object in relation to the optic axis.

Conclusion

We conclude that the optimal working distance range is between 40 and 10 mm from the object. However the clinician should be cognisant of both variations in magnification and distortion in clinical judgements.