A direct comparison of exogenous and endogenous inhibition of return and selective attention mechanisms in the somatosensory system

The interaction of excitation and inhibition in responses due to attentional mechanisms in the visual system has been investigated. The studies reported herein use the tactile system of humans to test a specific hypothesis about the processes of attention that have never been directly addressed. Both exogenous and endogenous Inhibition of Return (IOR) reaction-time paradigms with a 100?Hz, 35?µm of peak displacement amplitude were used. In these experiments multiple Stimulus Onset Asynchronies were tested which made it difficult for subjects to learn timing patterns. We tested whether a detection time to a target which is to be attended to is a composite of at least two underlying mechanisms. These mechanisms were explored using exogenous and endogenous IOR experiments. It is hypothesized that these mechanisms work in a push–pull fashion: one deploying attention when new events occur, and the other withdrawing attention (“Disengagement”) after it has been deployed. Based on the results, a new hypothesis is proposed stating that one form of attention (selective attention) competes with IOR in determining the time taken to detect a target in the tactile system.     

增强UV-B辐射对高山植物歪头菜生长及内源激素变化的影响

以青藏高原野生豆科牧草歪头菜(Vicia unijuga A.Br.)为材料,模拟甘南夏季晴朗无云天空平流层臭氧衰减9%的UV-B辐射强度(6.4 kJ/m²),分析增强UV-B辐射条件下植株内源激素水平和全氮含量随时间变化及其与生长特性的关系。结果显示:(1)来自高寒地区野生歪头菜在增强UV-B辐射的最初阶段(10 d左右)会产生对紫外胁迫的应激性响应,其内源生长激素吲哚乙酸(IAA)、玉米素(ZT)、赤霉素类(GAs)和6-苄氨基嘌呤(6-BA)含量水平以及全氮含量均明显高于对照,生长指标也相应升高。(2)随着处理时间延长,歪头菜内源生长激素含量开始迅速降低,并于处理后30 d时降至最低,处理后40 d时全氮含量也显著低于对照;同时,随着生长激素和全氮含量降低,植株生长也受到强烈抑制。(3)在处理后40 d时歪头菜内源ABA才被检测到,说明细胞膜伤害发生的时间相对较晚。研究表明,来自高寒环境的植物种歪头菜经历长期自然选择和适应,形成了对强UV-B辐射的应激响应机制,使辐射伤害延迟,内源激素含量变化与该应激响应有密切关系。     

Using enzymes to remove biofilms of bacterial isolates sampled in the food-industry

The aim of this study was to analyze the cleaning efficiency of polysaccharidases and proteolytic enzymes against biofilms of bacterial species found in food industry processing lines and to study enzyme effects on the composition of extracellular polymeric substances (EPS) and biofilm removal in a Clean-in-Place (CIP) procedure. The screening of 7 proteases and polysaccharidases for removal of biofilms of 16 bacterial species was first evaluated using a microtiter plate assay. The alkaline pH buffer removed more biofilm biomass as well as affecting a larger range of bacterial species. The two serine proteases and α-amylase were the most efficient enzymes. Proteolytic enzymes promoted biofilm removal of a larger range of bacterial species than polysaccharidases. Using three isolates derived from two bacterial species widely found in food processing lines (Pseudomonas fluorescens and the Bacillus cereus group), biofilms were developed on stainless steel slides and enzymatic solutions were used to remove the biofilms using CIP procedure. Serine proteases were more efficient in removing cells of Bacillus biofilms than polysaccharidases. However, polysaccharidases were more efficient in removing P. fluorescens biofilms than serine proteases. Solubilization of enzymes with a buffer containing surfactants, and dispersing and chelating agents enhanced the efficiency of polysaccharidases and proteases respectively in removing biofilms of Bacillus and P. fluorescens. A combination of enzymes targeting several components of EPS, surfactants, dispersing and chelating agents would be an efficient alternative to chemical cleaning agents.     

The Influence of Antimicrobial Peptides and Mucolytics on the Integrity of Biofilms Consisting of Bacteria and Yeasts as Affecting Voice Prosthetic Air Flow Resistances

The integrity of biofilms on voice prostheses used to rehabilitate speech in laryngectomized patients causes unwanted increases in airflow resistance, impeding speech. Biofilm integrity is ensured by extracellular polymeric substances (EPS). This study aimed to determine whether synthetic salivary peptides or mucolytics, including N-acetylcysteine and ascorbic acid, influence the integrity of voice prosthetic biofilms. Biofilms were grown on voice prostheses in an artificial throat model and exposed to synthetic salivary peptides, mucolytics and two different antiseptics (chlorhexidine and Triclosan). Synthetic salivary peptides did not reduce the air flow resistance of voice prostheses after biofilm formation. Although both chlorhexidine and Triclosan reduced microbial numbers on the prostheses, only the Triclosan-containing positive control reduced the air flow resistance. Unlike ascorbic acid, the mucolytic N-acetylcysteine removed most EPS from the biofilms and induced a decrease in air flow resistance.     

Antifouling substances of natural origin: Activity of benzoquinone compounds from Maesa Lanceolata against marine crustaceans

A screening of antifouling activity from plants extracts led to selection and further study of Maesa lanceolata Forssk. Two p‐benzoquinone compounds were isolated from the fruits and found to be active against Artemia salina. The anti‐crustacean activity of both p‐benzoquinones is reported for the first time.     

Impact of cranberry juice on initial adhesion of the EPS producing bacterium Burkholderia cepacia

The impact of cranberry juice was investigated with respect to the initial adhesion of three isogenic strains of the bacterium Burkholderia cepacia with different extracellular polymeric substance (EPS) producing capacities, viz. a wild-type cepacian EPS producer PC184 and its mutant strains PC184rml with reduced EPS production and PC184bceK with a deficiency in EPS production. Adhesion experiments conducted in a parallel-plate flow chamber demonstrated that, in the absence of cranberry juice, strain PC184 had a significantly higher adhesive capacity compared to the mutant strains. In the presence of cranberry juice, the adhesive capacity of the EPS-producing strain PC184 was largely reduced, while cranberry juice had little impact on the adhesion behavior of either mutant strain. Thermodynamic modeling supported the results from adhesion experiments. Surface force apparatus (SFA) and scanning electron microscope (SEM) studies demonstrated a strong association between cranberry juice components and bacterial EPS. It was concluded that cranberry juice components could impact bacterial initial adhesion by adhering to the EPS and impairing the adhesive capacity of the cells, which provides an insight into the development of novel treatment strategies to block the biofilm formation associated with bacterial infection.     

Beyond Eyeballing: Fitting Models to Experimental Data

Abstract

As we learn more about the biology of the Toll-like receptors (TLRs), a wide range of molecules that can activate this fascinating family of pattern recognition receptors emerges. In addition to conserved pathogenic components, endogenous danger signals created upon tissue damage are also sensed by TLRs. Detection of these types of stimuli results in TLR mediated inflammation that is vital to fight pathogenic invasion and drive tissue repair. Aberrant activation of TLRs by pathogenic and endogenous ligands has also been linked with the pathogenesis of an increasing number of infectious and autoimmune diseases, respectively. Most recently, allergen activation of TLRs has also been described, creating a third broad class of TLR stimulus that has helped to shed light on the pathogenesis of allergic disease. To date, microbial activation of TLRs remains best characterized. Each member of the TLR family senses a specific subset of pathogenic ligands, pathogen associated molecular patterns (PAMPS), and a wealth of structural and biochemical data continues to reveal the molecular mechanisms of TLR activation by PAMPs, and to demonstrate how receptor specificity is achieved. In contrast, the mechanisms by which endogenous molecules and allergens activate TLRs remain much more mysterious. Here, we provide an overview of our current knowledge of how very diverse stimuli activate the same TLRs and the structural basis of these modes of immunity.     

Chronophysiology of the cardiovascular system

The development of ambulatory blood pressure monitoring devices and the beat-by-beat measurement of heart rate have enabled it to be established that there are circadian rhythms in heart rate and blood pressure in subjects living normally. Investigations of these variables have led to quantification of their fall at night, and rapid rise on awakening and becoming active in the morning. These changes are of particular interest insofar as abnormalities in them are associated with cardiovascular problems and morbidity in patients and also act as risk factors in otherwise healthy individuals. It has also been shown that there are many other variables of the cardiovascular system. The causes of the circadian rhythms in heart rate and blood pressure are outlined, with particular stress upon the role of the autonomic nervous system, as assessed from low- and high-frequency components of the variation in heart rate measured beat-by-beat. Activity increases blood pressure, but there is evidence that this “reactivity” varies with time of day, and this also might be related to cardiovascular morbidity. Based upon data from several sources, including night work, resting subjects and bed-ridden patients, it is concluded that the contribution of the “body clock” to producing the circadian rhythm in heart rate and blood pressure is relatively small. A bias towards an exogenous cause applies also to most other circadian rhythms in the cardiovascular system. Knowledge of circadian rhythmicity in cardiovascular system, together with an understanding of its causes, provides a rationale for advice to reduce cardiovascular risk and to assess the efficacy of therapies.     

Does secondary chemistry enable lichens to grow on iron-rich substrates?

Lichen substances are shown to increase or to inhibit the adsorption of Fe at cation exchange sites. The influence on the adsorption strongly differs between individual lichen substances and is different for Fe²⁺ and Fe³⁺. These results add a new biological role to the known functions of lichen secondary metabolites. In an experiment with cellulose filters, which were soaked with acetone solutions of lichen substances and were then incubated with micromolar solutions of FeCl₂ or FeCl₃, many lichen substances were found to increase Fe³⁺ adsorption, whereas others had no effect. Most lichen substances had no effect on Fe²⁺ adsorption, but two were found to reduce and one to increase the level of adsorption. Lichens of Fe-poor and -rich sites contain lichen substances with different adsorption behavior towards Fe²⁺ and Fe³⁺. All the studied lichen substances, which only occur in lichens of Fe-poor sites, turned out to be effective Fe³⁺ adsorbents. Lichens of Fe-bearing rock and slag, however, were found to lack lichen substances, or to contain substances that did not adsorb Fe³⁺ and had no effect on Fe²⁺ adsorption, or thirdly, to contain substances that increased Fe³⁺ adsorption, but decreased Fe²⁺ adsorption. These results suggest that lichen substances do play a significant role in Fe adsorption in lichens and determine their tolerance to excess concentrations of Fe. Notwithstanding the strong correlation between the secondary chemistry of lichen species and their preference for Fe-rich or Fe-poor substrates, the postulated mechanism of temporary Fe adsorption by lichen substances has to be subject of future biochemical research.     

银杏芽中内源激素与大小年结实的关系

为探讨银杏大、小年结实现象的生理原因,于2004～2005年,用ELISA(间接酶联免疫法)对银杏大年树和小年树果芽和叶芽内的IAA,GA,ZR和ABA含量进行了对比测定。结果表明:大年树IAA、ZR和ABA含量在果芽和叶芽之间的比值均高于小年树,GA含量在果芽和叶芽之间的比值则低于小年树,有利果芽分化生长,形成大年;果芽中较高水平的ZR、IAA和ABA与较低水平的GA,以及萌芽前期较高的IAA/GA,ZR/GA和ABA/GA等比值,有利果芽分化,形成大年;叶芽中较高的ZR、IAA和较低的ABA有利于形成大年生长,尤其是ZR含量在萌芽前期或中期升高与形成大年生长关系密切。