耐氨固氮菌接种水稻所需最低活菌数的测定

耐氨固氮菌在谷芽上能生长,每粒谷芽上的菌数可达１０４－１０５个。当７０％以上的秧苗带有耐氨固氮菌时,经根系交叉感染能使所有的秧苗根系带上耐氨固氮菌。菌液浸泡谷芽接种水稻,耐氨固氮菌数／谷芽数达２０时,可使７０％的谷芽接种上菌,有２１０以上时,可使１００％的谷芽接种上菌。菌液淋施秧苗接种水稻,耐氨固氮菌数／秧苗数为１６００以上时,１００％的秧苗带有耐氨菌。菌液浸泡秧根接种水稻,耐氨固氮菌数／秧苗数为７０个以上时,可使１００％的秧苗根部带有耐氨菌。     

生物制药的现状和未来（二）：发展趋势与希望

随着基因组和蛋白质组研究的深入,越来越多的与人类疾病发展相关的靶标被确定,使得我们能够研发更精确的药物来防治这些疾病。这意味着生物制药将有更多机会获得突破性进展,最终将使更多更好的生物技术药物被批准上市。综述了生物制药发展的几个趋势,主要有:(1)哺乳动物细胞表达的产品将在相当长的时间内占统治地位;(2)治疗性抗体将会是生物制药领域第二次创新高潮;(3)越来越多分子量大、结构复杂的功能蛋白将被开发成生物技术药物,尤其是用于治疗遗传性疾病的药物;(4)对已批准上市的生物技术药物的化学修饰尤其是PEG化以改善药物性能;(5)通过某些药物的定点突变获得第二代新生物技术药物,如胰岛素、EPO和t-PA的突变体;(6)组织工程、细胞治疗和基因治疗充满了机遇和挑战。     

Improving protein solubility: the use of the Escherichia coli dihydrofolate reductase gene as a fusion reporter

We have devised a strategy for screening mutant libraries for enzyme variants with enhanced solubility. The method is based on the observation that Escherichia coli can become insensitive to the antibiotic trimethoprim (TMP) if dihydrofolate reductase (DHFR) is expressed at an appropriate level. DHFR is a very soluble protein and can be expressed at levels that exceed normally lethal concentrations of TMP. In our approach, the gene encoding an insoluble target protein is placed in a vector so that the translated protein will be fused to DHFR. The resulting fusion protein will form inclusion bodies and inactivate DHFR-the cells will be susceptible to TMP. Mutations to the target protein that make it more soluble will also make the fusion protein more soluble so that DHFR will be at least partially active-the cells will be resistant to TMP. As the solubility of the target protein increases, the cells will become more resistant to TMP. The system was tested with a putative acetyltransferase (ACE) from a strain of the marine bacterium Vibrio fischerii. The gene encoding this protein was of interest since it is part of a mobile gene cassette within an integron array of the strain in question. After multiple rounds of shuffling and selection, ACE mutants were produced that had significantly improved solubility.     

Expert status and performance

Expert judgements are essential when time and resources are stretched or we face novel dilemmas requiring fast solutions. Good advice can save lives and large sums of money. Typically, experts are defined by their qualifications, track record and experience. The social expectation hypothesis argues that more highly regarded and more experienced experts will give better advice. We asked experts to predict how they will perform, and how their peers will perform, on sets of questions. The results indicate that the way experts regard each other is consistent, but unfortunately, ranks are a poor guide to actual performance. Expert advice will be more accurate if technical decisions routinely use broadly-defined expert groups, structured question protocols and feedback.     

Diffusion of synthetic biology: a challenge to biosafety

One of the main aims of synthetic biology is to make biology easier to engineer. Major efforts in synthetic biology are made to develop a toolbox to design biological systems without having to go through a massive research and technology process. With this “de-skilling” agenda, synthetic biology might finally unleash the full potential of biotechnology and spark a wave of innovation, as more and more people have the necessary skills to engineer biology. But this ultimate domestication of biology could easily lead to unprecedented safety challenges that need to be addressed: more and more people outside the traditional biotechnology community will create self-replicating machines (life) for civil and defence applications, “biohackers” will engineer new life forms at their kitchen table; and illicit substances will be produced synthetically and much cheaper. Such a scenario is a messy and dangerous one, and we need to think about appropriate safety standards now.     

On the changes in the structure of two algal populations: species diversity and stability

Two assumptions were made: 1. when comparing two sample places in the same pond, the one taken nearer to the water edge will show a more diversified populations structure. 2. The population taken nearer to the water edge having a more diversified population structure will be more self-regulatory than the one taken from the open water.For each of those two assumptions a quantitative measure was proposed. The calculated coefficients did seem to confirm the assumptions.     

病毒抗原糖基化与免疫关系的研究进展

糖基化是蛋白质的一种重要的翻译后修饰,在影响蛋白质的结构和功能方面扮演着重要角色。许多病毒抗原都有糖基化的现象,糖基化会改变病毒对宿主的免疫逃避、病毒抗原的免疫原性等。了解病毒抗原糖基化与免疫之间的关系,将有助于抗病毒疫苗的研究。     

Cost-effective designs for linkage disequilibrium mapping of complex traits

The current development of densely spaced collections of single nucleotide polymorphisms (SNPs) will lead to genomewide association studies for a wide range of diseases in many different populations. Determinations of the appropriate number of SNPs to genotype involve a balancing of power and cost. Several variables are important in these determinations. We show that there are different combinations of sample size and marker density that can be expected to achieve the same power. Within certain bounds, investigators can choose between designs with more subjects and fewer markers or those with more markers and fewer subjects. Which designs are more cost-effective depends on the cost of phenotyping versus the cost of genotyping. We show that, under the assumption of a set cost for genotyping, one can calculate a "threshold cost" for phenotyping; when phenotyping costs per subject are less than this threshold, designs with more subjects will be more cost-effective than designs with more markers. This framework for determining a cost-effective study will aid in the planning of studies, especially if there are choices to be made with respect to phenotyping methods or study populations.     

Boreal Riparian Vegetation Under Climate Change

Riparian zones in boreal areas such as humid landscapes on minerogenic soils are characterized by diverse, productive, and dynamic vegetation which will rapidly react to climate change. Climate-change models predict that in most parts of the boreal region these zones will be affected by various combinations of increased temperature, less seasonal variation in runoff, increased average discharge, changes in groundwater supply, and a more dynamic ice regime. Increasing temperatures will favor invasion of exotic species whereas species losses are likely to be minor. The hydrologic changes will cause a narrowing of the riparian zone and, therefore, locally reduce species richness whereas effects on primary production are more difficult to predict. More shifts between freezing and thawing during winter will lead to increased dynamics of ice formation and ice disturbance, potentially fostering a more dynamic and species-rich riparian vegetation. Restoration measures that increase water retention and shade, and that reduce habitats for exotic plant species adjacent to rivers can be applied especially in streams and rivers that have been channelized or deprived of their riparian forest to reduce the effects of climate change on riparian ecosystems.     

Recent progress in the study of G protein-coupled receptors with molecular dynamics computer simulations

G protein-coupled receptors (GPCRs) are a large, biomedically important family of proteins, and the recent explosion of new high-resolution structural information about them has provided an enormous opportunity for computational modeling to make major contributions. In particular, molecular dynamics simulations have become a driving factor in many areas of GPCR biophysics, improving our understanding of lipid-protein interaction, activation mechanisms, and internal hydration. Given that computers will continue to get faster and more structures will be solved, the importance of computational methods will only continue to grow, particularly as simulation research is more closely coupled to experiment.     

Is the productivity of vegetation plots higher or lower when there are more species? Variable predictions from interaction of the ‘sampling effect’ and ‘competitive dominance effect’ on the habitat templet

Using a habitat templet model, we predict that the productivity (total biomass) of plots within a plant community may be positively, negatively or not at all related to variation in the number of species per plot, depending on successional stage (time since major disturbance) and habitat carrying capacity (reflecting the total resource supplying power of the habitat). For plots of a given size, a positive relationship between productivity and species richness is predicted in recently disturbed habitats because local neighbourhoods here will have been assembled largely stochastically, usually from a pool of available species with a right‐skewed size frequency distribution. Hence, in the earliest stages of succession, plots will have relatively high total biomass only if they contain at least some of the relatively uncommon larger species which will, in turn, be more likely in those neighbourhoods that contain more species (the sampling effect). Among these will also be some of the more common smaller species; hence, these high biomass, species‐rich plots should have relatively low species evenness, in contrast to what is predicted under effects involving species complementarity. In late succession, the plots with high total biomass will still be those that contain relatively large species but these plots will now contain relatively few species owing to increased competitive exclusion over time (the competitive dominance effect). In intermediate stages of succession, no relationship between plot productivity and species richness is predicted because the opposing sampling and competitive dominance effects cancel each other out. We predict that the intensity of both the sampling and competitive dominance effects on the productivity/species richness relationship will decrease with decreasing habitat carrying capacity (e.g. decreasing substrate fertility) owing to the inherently lower variance in between‐plot productivity that is predicted for more resource‐impoverished habitats.     

Amoeboid Chemotaxis

Chemotaxis is the directed movement of a cell towards a gradient of chemicals such as chemokines or growth factors. This phenomenon can be studied in organisms ranging from bacteria to mammalian cells and here we will focus on eukaryotic amoeboid chemotaxis. Chemotactic responses are mediated by two major classes of receptors: GPCR’s and RTK’s, with multiple pathways signaling downstream of them, certain ones functioning in parallel. In this review we address two important features of amoeboid chemotaxis that will be important for further advances in the field. First, the application of in vivo imaging will be critical for providing insight into the functional requirements for chemotactic responses. We will briefly cover a number of systems in which in vivo imaging is providing new insights. Second, due to the network-type design of signaling pathways of eukaryotic chemotaxis, more refined phenotypic analysis will be necessary, and we will discuss recent analyses of the role of the phosphoinositide 3-kinase pathway in this light. We will close with some speculations regarding future applications of more detailed in vivo analysis and mechanistic understanding of eukaryotic amoeboid chemotaxis.     

Minimally invasive surgery. Implications for hospitals,health workers,and patients.

Minimally invasive surgery is one of the great innovations of health care in the 20th century. It promises to revolutionise surgery by allowing many more operations to be performed with minimal hospitalisation. Pressure from patients has caused many techniques to spread rapidly before they have been adequately assessed. This must be resisted, and policy makers must pay more attention to minimally invasive surgery to ensure that good assessments are made. The widespread use of minimally invasive techniques has important implications for hospitals and health workers. As more patients are treated on an outpatient basis, fewer hospital beds will be needed, and traditional operating rooms will have to adapt to a greater turnover of patients. Surgeons will have to acquire new operating skills, possibly requiring formal training and accreditation, and, as different specialties fight for control of new technologies, surgery may eventually be merged with internal medicine so that specialists will deal with organ systems. Postoperative care will have to be carried out in the community rather than in hospitals, and policy makers will need to reorganise their health systems to cope with these developments.     

对执行护航任务舰艇官兵的情绪研究

目的:近年来,随着执行护航任务的日趋常态化,舰艇官兵要面临一系列的身心考验,可能会出现一定的情绪问题。本文的目的是为了更清楚的了解护航任务期间官兵的情绪变化和情绪问题,以便更好为官兵服务。方法:本文通过使用SAS、SDS及POMS量表对执行护航的舰艇官兵情绪进行跟踪研究。结果:结果表明,执行任务官兵的焦虑、抑郁体验及心境纷乱程度得分均显著高于军人常模,从时间变量来看,护航焦虑体验最高的是护航初期,抑郁体验最高的是护航中期,护航后期的心境纷乱程度最低。结论:护航任务官兵焦虑、抑郁情绪明显,心境状态受任务影响显著,并且随任务执行的时间,在任务的不同阶段存在不同的表现。     

基于表面肌电信号的肘关节运动角度的提取

随着人口老龄化问题的越来越严重,医疗护理机器人的开发,今后将会有大量的需求,基于表面肌电信号的医疗护理机器人的开发将是其中的一个热点.本文提出了基于Bayesian正则化的多层感知器人工神经网络方法来提取人体肘关节运动角度,解决了普通神经网络对于表面肌电信号这一复杂亚高斯随机信号泛化能力不强的缺点,有助于将表面肌电信号的研究推向医疗护理机器人研发的实际应用阶段.     

Microbial lipases as virulence factors

Up to now, lipases of microbial origin are known to be very useful in a palette of industrial applications. But it becomes more and more obvious that extracellular lipases also play a role during microbial infections. This review will focus on the virulent traits of these secreted enzymes from bacteria and fungi. Special emphasis will be laid on Candida albicans research. This human pathogenic fungus possesses a lipase gene family, which is expressed and differentially regulated under a variety of in vitro conditions. First results show that this isoenzyme family is also expressed during an experimental infection.

In addition, putative functions of extracellular lipases of pathogenic micro-organisms will be discussed.     

Augmented visual feedback of movement performance to enhance walking recovery after stroke: study protocol for a pilot randomised controlled trial

ABSTRACT: BACKGROUND: Increasing evidence suggests that use of augmented visual feedback could be a useful approach to stroke rehabilitation. In current clinical practice, visual feedback of movement performance is often limited to the use of mirrors or video. However, neither approach is optimal since cognitive and self-image issues can distract or distress patients and their movement can be obscured by clothing or limited viewpoints. Three-dimensional motion capture has the potential to provide accurate kinematic data required for objective assessment and feedback in the clinical environment. However, such data are currently presented in numerical or graphical format, which is often impractical in a clinical setting. Our hypothesis is that presenting this kinematic data using bespoke visualisation software, which is tailored for gait rehabilitation after stroke, will provide a means whereby feedback of movement performance can be communicated in a more meaningful way to patients. This will result in increased patient understanding of their rehabilitation and will enable progress to be tracked in a more accessible way. METHODS: The hypothesis will be assessed using an exploratory (phase II) randomised controlled trial. Stroke survivors eligible for this trial will be in the subacute stage of stroke and have impaired walking ability (Functional Ambulation Classification of 1 or more). Participants (n = 45) will be randomised into three groups to compare the use of the visualisation software during overground physical therapy gait training against an intensity-matched and attention-matched placebo group and a usual care control group. The primary outcome measure will be walking speed. Secondary measures will be Functional Ambulation Category, Timed Up and Go, Rivermead Visual Gait Assessment, Stroke Impact Scale-16 and spatiotemporal parameters associated with walking. Additional qualitative measures will be used to assess the participant's experience of the visual feedback provided in the study. DISCUSSION: Results from the trial will explore whether the early provision of visual feedback of biomechanical movement performance during gait rehabilitation demonstrates improved mobility outcomes after stroke and increased patient understanding of their rehabilitation.Trial registrationCurrent Controlled Trials ISRCTN79005974.     

Assembly rules operate only in equilibrium communities: Is it true?

Very little is known of how disturbance affects community assembly rules. We examine this in three disturbance states in each of two ski areas on southern New Zealand mountains. Theory suggests that a community will become progressively more spatially organized during recovery from disturbance. Firstly, different patches of the community should become more similar through time, but this was seen in only one of the two areas and even then only examining species presence/absence. Secondly, it has been suggested that spatial autocorrelation will be stronger in less‐disturbed conditions, that is, there will be a stronger pattern of more distant patches being more dissimilar in species composition. This was generally borne out. However, the method indicated more point randomness in less‐disturbed sites. Assembly rules might be seen in species abundances. Previous work has found maximum evenness of abundances in later successional communities, but the pattern here was the opposite: high evenness in the most disturbed communities. The literature suggests that in undisturbed communities the distribution of species abundances (relative abundance distribution) will be general lognormal, and we further argue that the identity of the species across occupying rank positions in that distribution should be more consistent (rank consistency). Both predictions were borne out in one area, but neither in the other. Many workers suggest that niche‐based assembly rules will be stronger in undisturbed communities. However, there was only weak evidence of constancy in species richness. Local species assemblages tended to contain a relatively constant representation from different morphological/taxonomic guilds (guild proportionality) and this was significant in some tests, but contrary to theory this effect occurred mainly in the most disturbed sites. It is concluded that there is only limited truth in the frequent assumption that community structure is stronger in undisturbed, equilibrium communities.     

工业菌种改良述评

微生物菌种是发酵工业的基础。菌种筛选和持续不断的改良贯彻于发酵过程始终。传统的(经典的)诱变—筛选仍是目前最实用的常规技术;以基因工程为核心的现代生物技术正越来越显示出其在菌种改良上的魅力,并将最终成为微生物育种的主导技术。     

Pondering the future.

Despite growing tensions as the Canadian health care system evolves, the system will survive over the next decade and strengthen its societal objectives, sometimes dragging physicians along. With the shift of the intellectual centre away from the universities, research and researchers will find funding security but career insecurity in the private sector. The independent investigator will become rare as "big science" becomes the norm, and basic science departments will have a decade of confusion as they struggle for a new place in the renewed medical schools. The move toward problem-based, community-oriented medical education will be completed, clinical faculty will become salaried and the smaller numbers of graduates will be more controlled in their practices. Medicine as a profession will adopt a renewed philosophical framework and will broaden in its scope to the benefit of Canadians.