Role of recombination in the evolution of the model plant pathogen Pseudomonas syringae pv. tomato DC3000, a very atypical tomato strain

Pseudomonas syringae pv. tomato strain DC3000 (PtoDC3000) is one of the most intensively studied bacterial plant pathogens today. Here we report a thorough investigation into PtoDC3000 and close relatives isolated from Antirrhinum majus (snapdragon), Apium graveolens (celery), and Solanaceae and Brassicaceae species. Multilocus sequence typing (MLST) was used to resolve the precise phylogenetic relationship between isolates and to determine the importance of recombination in their evolution. MLST data were correlated with an analysis of the locus coding for the type III secreted (T3S) effector AvrPto1 to investigate the role of recombination in the evolution of effector repertoires. Host range tests were performed to determine if closely related isolates from different plants have different host ranges. It was found that PtoDC3000 is located in the same phylogenetic cluster as isolates from several Brassicaceae and Solanaceae species and that these isolates have a relatively wide host range that includes tomato, Arabidopsis thaliana, and cauliflower. All other analyzed tomato isolates from three different continents form a distinct cluster and are pathogenic only on tomato. Therefore, PtoDC3000 is a very unusual tomato isolate. Several recombination breakpoints were detected within sequenced gene fragments, and population genetic tests indicate that recombination contributed more than mutation to the variation between isolates. Moreover, recombination may play an important role in the reassortment of T3S effectors between strains. The data are finally discussed from a taxonomic standpoint, and P. syringae pv. tomato is proposed to be divided into two pathovars.     

Acquisition of full-field strain distributions on ovine fracture callus cross-sections with electronic speckle pattern interferometry

This study evaluated the feasibility of assessing continuous strain distributions on fracture callus cross-sections with an electronic speckle pattern interferometry (ESPI) system. Mid-sagittal callus cross-sections were harvested from ovine tibiae. One low stiffness (LS) specimen and one high stiffness (HS) specimen were selected to evaluate the feasibility for strain acquisition over a range of callus properties. The HS specimen was 147 times stiffer in compression than the LS specimen. ESPI captured continuous strain distributions on both specimens. Peak strain was located adjacent to cortical boundaries in the osteotomy gap. In response to 5N compression, peak compressive strain of 5.8% in the LS specimen was over two orders of magnitude higher than peak compressive strain of 0.013% in the HS specimen. In conclusion, ESPI-based strain acquisition enables reproducible quantification of strain distributions on callus cross-sections. Such measurements may support validation of computational models and evaluation of experimental results in fracture healing research.     

Association between stressful life events and exacerbation in multiple sclerosis: a meta-analysis

Objective To quantify the association between stressful life events and exacerbations of multiple sclerosis.Data sources PubMed, PsychInfo, and Psychological Abstracts searched for empirical papers from 1965 to February 2003 with terms “stress”, “trauma”, and “multiple sclerosis”.Review methods Three investigators independently reviewed papers for inclusion/exclusion criteria and extracted the relevant data, including methods, sample statistics, and outcomes.Results Of 20 studies identified, 14 were included. The meta-analysis showed a significant increase in risk of exacerbation in multiple sclerosis after stressful life events, with a weighted average effect size of d = 0.53 (95% confidence interval 0.40 to 0.65), P < 0.0001. The studies were homogenous, Q = 16.62, P = 0.22, I² = 21.8%. Neither sampling nor study methods had any effect on study outcomes.Conclusions There is a consistent association between stressful life events and subsequent exacerbation in multiple sclerosis. However these data do not allow the linking of specific stressors to exacerbations nor should they be used to infer that patients are responsible for their exacerbations. Investigation of the psychological, neuroendocrine, and immune mediators of stressful life events on exacerbation may lead to new behavioural and pharmacological strategies targeting potential links between stress and exacerbation.     

一种新的肝细胞生成素（HPO）转录本及其生物学活性

利用 5′RACE技术从人胎肝组织中分离一种新形式的肝细胞生成素 (HPO 2 0 5 )cDNA ,其编码蛋白质氨基酸序列的N端较已报道的人肝细胞生成素HPO(hepatopoietin)多 80个氨基酸 ,推测其蛋白质分子量为 2 3kD。RT PCR检测HPOmRNA在多种肝癌细胞中表达 ,Western印迹可检测到 2 3kDHPO 2 0 5表达 ,表明此种形式HPO在自然状态下存在。将构建的HPO 2 0 5真核表达载体转染入COS 7细胞 ,其表达蛋白质能够刺激HepG2肝癌细胞DNA合成 ;将HPO 2 0 5、HPO和荷空表达载体分别转染入低水平表达HPO的Bel 740 2肝癌细胞株 ,发现HPO 2 0 5比HPO具有较强的激活MAPK磷酸化的活性。细胞周期分析稳定转染HPO 2 0 5 ,HPO细胞的增殖周期也支持这一结论。这些结果表明HPO 2 0 5具有刺激肝源性细胞增殖的活性 ,并提示HPO 2 0 5可能较HPO有更强的生物学活性     

Dynamics of concentrations and nutrient fluxes in the xylem of Ricinus communis– diurnal course, impact of nutrient availability and nutrient uptake

Diurnal courses of nutrient transport in the xylem and their response to external availability of nutrients were studied. In soil culture, maximal concentrations in all analysed substances were observed during night‐time. Over experimental periods of up to 20 d, concentrations of some ions increased, most by accumulation in the soil. Stringent nutrient conditions were established in a novel pressure chamber. An aeroponic nutrient delivery system inside allows the sampling of xylem sap from intact plants under full control of the nutrient conditions at the root. Analysis of xylem transport under these highly defined conditions established that (1) diurnal variations in concentrations and fluxes in the xylem are dominated by plant‐internal processes; (2) concentrations of nutrients in the xylem sap are highly but specifically correlated with each other; (3) nitrate uptake and nitrate flux to the shoot are largely uncoupled; and (4) in continuous light, diurnal variations of xylem sap concentrations vanish. Step changes in nitrate concentrations of the nutrient solution established that (5) the concomitant increase in nitrate concentration and flux in the xylem is delayed by 2–3 h and is only transient. Diurnal variations of xylem sap composition and use of the new technique to elucidate xylem‐transport mechanisms are discussed.     

Are We Modular Lying Cues Detectors? The Answer Is “Yes,Sometimes”.

We quickly form first impressions about newly encountered people guiding our subsequent behaviour (approach, avoidance). Such instant judgments might be innate and automatic, being performed unconsciously and independently to other cognitive processes. Lying detection might be subject to such a modular process. Unfortunately, numerous studies highlighted problems with lying detection paradigms such as high error rates and learning effects. Additionally, humans should be motivated doing both detecting others’ lies and disguising own lies. Disguising own lies might even be more challenging than detecting other people’s lies. Thus, when trying to disguise cheating behaviour, liars might display a mixture of disguising (fake) trust cues and uncontrolled lying cues making the interpretation of the expression difficult (perceivers are guessing). In two consecutive online studies, we tested whether seeing an increasing amount (range 0–4) of lying cues (LC) and non-lying cues (NLC) on a standard face results in enhanced guessing behaviour (studies 1 and 2) and that enhanced guessing is accompanied by slower responding (study 2). Results showed that pronounced guessing and slowest responding occurred for faces with an intermediate number and not with the highest number of LC and NLC. In particular, LC were more important than NLC to uncertain lying decisions. Thus, only a few LC may interfere with automatic processing of lying detection (irrespective of NLC), probably because too little lying cue information is yet available.     

Development of intracytoplasmic lumina in diethylnitrosamine-induced tracheal papillomas of Syrian golden hamster

Tracheal papillomas in the Syrian golden hamster were induced with diethylnitrosamine (DEN). Intracytoplasmic lumina filled with mucus were studied by light and electron microscopy. The sequence of lumen genesis is described ultrastructurally. Mucus substances in the center of intracytoplasmic lumen are presumed to be condensations of cell coat macromolecules. The intracytoplasmic lumen is discussed as a common feature of the adenoid component in epithelial neoplasms.     

Die Bedeutung des Phytochroms für die Entwicklung der Kapazität für Photophosphorylierung

Die Entwicklung der Kapazität für Photophosphorylierung in den epi-gäischen Kotyledonen des Senfkeimlings wird durch Phytochrom (P_fr) reguliert. Wird der P_fr-Gehalt sehr niedrig gehalten, bildet sich keine Kapazität für Photophosphorylierung aus, auch wenn sich die Bildung von Chlorophyll normal vollzieht. Phytochrom (P_fr) kann die Kapazität für Photophosphorylierung nur dann ?induzieren”, wenn die Kotyledonen mit dem oberen Teil des Hypokotyls (Haken) verbunden sind. Hingegen ist die Chlorophyllbildung der Kotyledonen mit und ohne Haken gleich. Während sich der Effekt des P_fr auf die Kapazität für Photophosphorylierung relativ schnell (innerhalb von 15 min) ausprägt, ist der Effekt des P_fr auf die Chlorophyllbildung langsam. Er manifestiert sich erst etwa 2 h nach Lichtbeginn. Es wird der Schluß gezogen, daß die multiple Kontrolle von Piastidenfunktionen durch Phytochrom (P_fr) auf verschiedene, voneinander unabhängige Primärwirkungen des Phytochroms zurückzuführen ist. Mit Unterstützung der Deutschen Forschungsgemeinschaft (SFB 46). Wir danken Dr. E. Schäfer für die Bestimmung der Photogleichgewichte des Phytochromsystems bei Dichromatbestrahlung und Frau I. Schneider für gewissenhafte technische Mitarbeit.     

Lipid storage in cultured articular chondrocytes due to prostanoid precursors and a prostanoid synthesis inhibitor

Lapine articular chondrocytes were subcultured in the presence or absence of the prostanoid precursors, arachidonic acid or dihomo-gamma-linolenic acid, and the cyclooxygenase inhibitor indomethacin. Lipid storage was studied microscopically using the Sudan black staining method. Control chondrocyte cultures showed a weakly positive staining reaction until confluence was reached, at which point the intra-cytoplasmic lipid content decreased. Both arachidonic acid and dihomo-gamma-linolenic acid at 100 mumol/l caused a marked increase in lipid storage which continued even after confluence was achieved. 1 mumol/l concentrations were indistinguishable from controls, whereas 10 mumol/l concentrations elicited a slight increase in lipid storage compared with controls. The prostaglandin cyclooxygenase inhibitor indomethacin did not affect chondrocyte lipid storage. However, administration of a prostanoid precursor in the presence of indomethacin caused a massive increase in intra-cytoplasmic storage of lipid, eventually leading to cell death. A possible explanation is that indomethacin may alter chondrocyte lipid metabolism in the presence of substrate molecules by rechanneling lipid synthesis away from the prostaglandin pathway to other lipid synthetic pathways.