植物根系吸水机理的研究进展

近年来,植物根系吸水机理在细胞、组织和整体水平上的研究进展非常迅速,对阐明植物抗旱机制及其高效利用有限水资源途径的探讨具有重要意义.本文主要对植物根的复合结构和根系在土壤中的分布、根系中水流性质等方面的最新研究状况进行了概述,特别详细地论述了水通道蛋白的表达及功能与根系中水分运动的关系、以及根系输水的调节和根系吸水过程中的信号传导方面的研究动态,并且评价了根的复合运输模型和根系吸水的数学模型等,最后就其可能生理意义及其应用前景作了评述.     

Combining Evidence of Preferential Gene-Tissue Relationships from Multiple Sources

An important challenge in drug discovery and disease prognosis is to predict genes that are preferentially expressed in one or a few tissues, i.e. showing a considerably higher expression in one tissue(s) compared to the others. Although several data sources and methods have been published explicitly for this purpose, they often disagree and it is not evident how to retrieve these genes and how to distinguish true biological findings from those that are due to choice-of-method and/or experimental settings. In this work we have developed a computational approach that combines results from multiple methods and datasets with the aim to eliminate method/study-specific biases and to improve the predictability of preferentially expressed human genes. A rule-based score is used to merge and assign support to the results. Five sets of genes with known tissue specificity were used for parameter pruning and cross-validation. In total we identify 3434 tissue-specific genes. We compare the genes of highest scores with the public databases: PaGenBase (microarray), TiGER (EST) and HPA (protein expression data). The results have 85% overlap to PaGenBase, 71% to TiGER and only 28% to HPA. 99% of our predictions have support from at least one of these databases. Our approach also performs better than any of the databases on identifying drug targets and biomarkers with known tissue-specificity.     

Evaluation of Lactobacilli from Human Sources for Uptake and Accumulation of Selenium

The trace mineral selenium (Se) is currently in demand for health supplements for human and animal nutrition. In the present study, 25 isolates of Lactobacillus species of human origin from Indian population were screened for their ability to uptake and accumulate Se in a more bioavailable form. Total Se accumulated by cells was measured by inductively coupled plasma emission spectrometry (ICPES) after wet digestion of Se-enriched cultures. Ten out of 25 isolates grew luxuriantly, as red pigmented colonies, on medium amended with different concentrations of sodium selenite. All the strains when grown in a culture medium supplemented with 10 μg/mL sodium selenite (corresponding to 4.5 μg/mL Se) resulted in Se accumulation in the range of 129.5 to 820.0 μg/g of dry weight (d.w.) as measured using the ICPES method. Elemental Se produced due to reduction of sodium selenite by bacteria was seen as irregular globules under the scanning electron microscope (SEM). Out of all the tested cultures, Lactobacillus reuteri NCDC77 was found to have the greatest ability to uptake Se (28.8 % of inorganic Se in medium) and total Se accumulated was up to 820 μg/g d.w., significantly higher than that of control (742.5 μg/g d.w.). The findings of present study indicate that lactobacilli from human sources have the ability for uptake and accumulation of Se, and the prolific strain has the potential to be explored as an alternative source of organic dietary Se.     

诱导型一氧化氮合酶抑制剂研发现状

一氧化氮(NO)对炎症性疾病的治疗作用近来引起了广泛的重视。诱导型一氧化合成酶(iNOS)被发现广泛地参与趋炎因子表达和反应性氧化产物(ROS)/反应性氮化产物(RNS)的产生,从而进一步证明了一氧化氮在炎症病理发生发展中的关键作用。由于传统的抗炎药物环氧合酶-2(COX-2)抑制剂被报导有较多副作用,新型抑制炎症药物的研究开发势在必行。本文分别介绍了化学来源、生物来源、植物来原性iNOS抑制剂阻的开发、研究现状,阐述了其在断炎症信息传递通道中的作用。表明了iNOS抑制剂防止炎症损害的相关机理,提出iNOs不仅能在初始阶段影响炎症的发生,也对抑制和终结炎症有作用。最后进一步介绍了用中草药研发iNOs抑制剂的可能性,展望了于中药在该领域内的巨大前景。     

Protein Complex Identification by Integrating Protein-Protein Interaction Evidence from Multiple Sources

Background

Understanding protein complexes is important for understanding the science of cellular organization and function. Many computational methods have been developed to identify protein complexes from experimentally obtained protein-protein interaction (PPI) networks. However, interaction information obtained experimentally can be unreliable and incomplete. Reconstructing these PPI networks with PPI evidences from other sources can improve protein complex identification.

Results

We combined PPI information from 6 different sources and obtained a reconstructed PPI network for yeast through machine learning. Some popular protein complex identification methods were then applied to detect yeast protein complexes using the new PPI networks. Our evaluation indicates that protein complex identification algorithms using the reconstructed PPI network significantly outperform ones on experimentally verified PPI networks.

Conclusions

We conclude that incorporating PPI information from other sources can improve the effectiveness of protein complex identification.     

Boosting Probabilistic Graphical Model Inference by Incorporating Prior Knowledge from Multiple Sources

Inferring regulatory networks from experimental data via probabilistic graphical models is a popular framework to gain insights into biological systems. However, the inherent noise in experimental data coupled with a limited sample size reduces the performance of network reverse engineering. Prior knowledge from existing sources of biological information can address this low signal to noise problem by biasing the network inference towards biologically plausible network structures. Although integrating various sources of information is desirable, their heterogeneous nature makes this task challenging. We propose two computational methods to incorporate various information sources into a probabilistic consensus structure prior to be used in graphical model inference. Our first model, called Latent Factor Model (LFM), assumes a high degree of correlation among external information sources and reconstructs a hidden variable as a common source in a Bayesian manner. The second model, a Noisy-OR, picks up the strongest support for an interaction among information sources in a probabilistic fashion. Our extensive computational studies on KEGG signaling pathways as well as on gene expression data from breast cancer and yeast heat shock response reveal that both approaches can significantly enhance the reconstruction accuracy of Bayesian Networks compared to other competing methods as well as to the situation without any prior. Our framework allows for using diverse information sources, like pathway databases, GO terms and protein domain data, etc. and is flexible enough to integrate new sources, if available.     

Uptake of Vibrio cholerae Biotype eltor from Contaminated Water by Water Hyacinth (Eichornia crassipes)

Vibrio cholerae biotype eltor appears to concentrate on the surface of the water hyacinth (Eichornia crassipes), thereby enhancing its survival and its potential for transmission through waterways of cholera-endemic regions such as Bangladesh.     

Comparative Studies on Water Uptake and Water Permeability of Potato Tissue under the Effect of Indoleacetic Acid, Chloramphenicol and Actinomycin D

The water uptake of potato tuber tissue under the influence of chloramphenicol and actinomycin D was compared with that of indoleacetic acid. Both antibiotics decreased the water absorption as compared to the effect of indoleacetic acid. This decrease, in the early hours (3 to 6 h), is due to diminished water permeability. In the later period (6 to 48 h), it is instead a result of a reduction in wall extensibility.     

Studies on Uptake and Loss of Water by Barley Roots in Relation to Changes in Root Resistance

The uptake and loss of water by roots of young barley plantshave been measured using tracer techniques in sand culture undercontrasting conditions of transpiration and water potentialdifference. The results are compared with direct potometricmeasurements of water uptake. The apparent resistance to flowof water changed in response to differences in water potentialbetween the leaves and the root medium and in transpirationrate. We examine the significance of this in relation to netloss of water and possible mobilization of nutrients from drysoil. With the aid of a mathematical model, some considerationis given to the role of the endodermis as a barrier to diffusivemovement of water in the older parts of the root system.     

见证调水源区冬季冰情

2007年1月底我们来到大渡河上的壤塘县杜柯河,气温在零下二十多度,寒意浓浓.海拔2800多米的河段出现了流冰和河面冰盖,成群的牛羊在河冰面上悠闲地走动,一位放牧的藏族妇女用惊奇的目光打量我们这一群对冰河感兴趣的人.夜晚到达壤塘县城,全城无电,笼罩在黑暗之中.经了解,电站因无水和冰冻发不出电,已经有两个多月了.     

Oscillatory Transpiration and Water Uptake of Avena Plants

The action of D₂O on oscillatory transpiration of Avena plants was investigated. D₂O affects the amplitude and the period of the oscillations when given as a root medium to intact plants. The period is then dependent on the amplitude. From such experiments it is not possible to conclude whether the period change is simply due to the changed amplitude or to a change in the stomatal parameters. When given to xylem compressed, excised plants without roots, the D₂O hardly affects the amplitude of the oscillations but the period is increased. Thus, the period of the self-sustained transpiratory oscillations is lengthened by D₂O action on the stomatal parameters. Phase and amplitude changes of the oscillatory transpiration caused by short D₂O pulses given both to intact and excised plants, are discussed. The following conclusion is emphasized: a substance which affects the root system can also cause profound changes in the stomatal water regulation.     

Endogenous Rhythmicity in Water Uptake by Seeds

Water uptake (after 4 h imbibition) as a function of the momentof its onset shows rhythms with a period length of approx. 6h. The period length is not affected by a increase in temperatureof 10 °C, suggesting that the oscillation is endogenousin character. Furthermore, heat-killed seeds show no oscillationsin water uptake, indicating that the rhythm described originatesfrom the temperature-sensitive component of imbibition. Phaseolus vulgaris, french bean, imbibition, oscillation in imbibition     

Uptake and Function Studies of Maternal Milk-derived MicroRNAs

MicroRNAs (miRNAs) are important regulators of cell-autonomous gene expression that influence many biological processes. They are also released from cells and are present in virtually all body fluids, including blood, urine, saliva, sweat, and milk. The functional role of nutritionally obtained extracellular miRNAs is controversial, and irrefutable demonstration of exogenous miRNA uptake by cells and canonical miRNA function is still lacking. Here we show that miRNAs are present at high levels in the milk of lactating mice. To investigate intestinal uptake of miRNAs in newborn mice, we employed genetic models in which newborn miR-375 and miR-200c/141 knockout mice received milk from wild-type foster mothers. Analysis of the intestinal epithelium, blood, liver, and spleen revealed no evidence for miRNA uptake. miR-375 levels in hepatocytes were at the limit of detection and remained orders of magnitude below the threshold for target gene regulation (between 1000 and 10,000 copies/cell). Furthermore, our study revealed rapid degradation of milk miRNAs in intestinal fluid. Together, our results indicate a nutritional rather than gene-regulatory role of miRNAs in the milk of newborn mice.     

Oscillatory Transpiration and Water Uptake of Avena Plants

The transpiration rate of oat plants, 6 days old, has been investigated. Dependent on the irradiance level of the white light used in the experiments, the transpiration rate oscillated with different period times. In darkness or at low irradiances the period was about 100–110 min. At higher irradiances the period was about 40 min. At intermediate irradiances autocorrelation analysis was used to find the period content of the transpiration rate. It was concluded that two oscillatory systems were present in the plants, characterized by their different periods. When plants cultivated in a light/dark cycle were used, the transpiration oscillations were influenced by a circadian rhythm. Oscillations in darkness were then most pronounced in the mornings. Plants cultivated in continuous light did not show such a circadian rhythm, but the oscillations died out after about 20 h. Kinetin induced transpiration oscillations in darkness and made them sustain for a longer time.     

Oscillatory Transpiration and Water Uptake of Avena Plants

Xylem vessels in the lower part of the leaf of young Avena plants have been exposed to deformation by application of an external pressure. In this way a resistance to the water flow at the deformation site has been achieved, inducing undamped oscillations in transpiration and water uptake, even after removal of the root system.     

Oscillatory Transpiration and Water Uptake of Avena Plants

The oscillatory transpiration of 6 days old Avena plants was investigated with respect to the water potential of the root medium. The desired water potential was obtained by means of mannitol solutions. When the water potential was lowered (“mannitol step”), the amplitude of the oscillations decreased. Below –3.0 bars no oscillations persisted. A detailed study was made of the phase changes of the oscillations caused by a short time decrease of the water potential of the root medium (“mannitol pulse”). The duration of these short term treatments was either 9.0, 3.0 or J.5 min. The experimental results are discussed on the basis of an electric analogue previously presented in the literature. Published simulations based on the model were in clear contrast to the present experimental results as well as to earlier results in the literature. However, simulations in the present paper showed that the model could explain the experimental results if suitable parameter values were chosen.     

Sequencing-Based Analysis of the Bacterial and Fungal Composition of Kefir Grains and Milks from Multiple Sources

Kefir is a fermented milk-based beverage to which a number of health-promoting properties have been attributed. The microbes responsible for the fermentation of milk to produce kefir consist of a complex association of bacteria and yeasts, bound within a polysaccharide matrix, known as the kefir grain. The consistency of this microbial population, and that present in the resultant beverage, has been the subject of a number of previous, almost exclusively culture-based, studies which have indicated differences depending on geographical location and culture conditions. However, culture-based identification studies are limited by virtue of only detecting species with the ability to grow on the specific medium used and thus culture-independent, molecular-based techniques offer the potential for a more comprehensive analysis of such communities. Here we describe a detailed investigation of the microbial population, both bacterial and fungal, of kefir, using high-throughput sequencing to analyse 25 kefir milks and associated grains sourced from 8 geographically distinct regions. This is the first occasion that this technology has been employed to investigate the fungal component of these populations or to reveal the microbial composition of such an extensive number of kefir grains or milks. As a result several genera and species not previously identified in kefir were revealed. Our analysis shows that the bacterial populations in kefir are dominated by 2 phyla, the Firmicutes and the Proteobacteria. It was also established that the fungal populations of kefir were dominated by the genera Kazachstania, Kluyveromyces and Naumovozyma, but that a variable sub-dominant population also exists.     

Spiraling Down Hillslopes: Nutrient Uptake from Water Tracks in a Warming Arctic

Ecosystems - Hydrologic flowpaths might propagate biogeochemical signals among connected ecosystems or alter and dampen signals because of reactions or retention occurring during transport. In the...