金龟子绿僵菌在森林土壤中的分布及对松墨天牛致病性测定

松墨天牛是重大森林植物检疫性病害——松材线虫病的主要媒介昆虫。本研究于2005年8月～2006年8月从福建、江西两省共110个林分样区(其中松林88个样区)采集土壤样品330份,采用选择性培养基分离土壤中的金龟子绿僵菌。从21个样区的26份土样中分离出的金龟子绿僵菌占采集样区的19．1％和样品的7．9％,成菌落数(CFU)500～72500CFU/g,表明金龟子绿僵菌在森林土壤中有较为广泛的分布。对分离到的9个产孢量高的菌株,采用浸渍法(1×10~7孢子/mL)接种3～4龄健康松墨天牛幼虫,采用跗节接种法接种2～15日龄健康成虫,测定其致病力。结果表明,MaYTTR-03、MaYTTR-04菌株对松墨天牛幼虫和成虫均有较高致病力,表现出良好的生防潜力。     

An ant colony optimization approach to flexible protein–ligand docking

The prediction of the complex structure of a small ligand with a protein, the so-called protein–ligand docking problem, is a central part of the rational drug design process. For this purpose, we introduce the docking algorithm PLANTS (Protein–Ligand ANT System), which is based on ant colony optimization, one of the most successful swarm intelligence techniques. We study the effectiveness of PLANTS for several parameter settings and present a direct comparison of PLANTS’s performance to a state-of-the-art program called GOLD, which is based on a genetic algorithm and frequently used in the pharmaceutical industry for this task. Last but not least, we also show that PLANTS can make effective use of protein flexibility giving example results on cross-docking and virtual screening experiments for protein kinase A. This article is based on a paper that won the best paper award at ANTS 2006, the 5th International Workshop on Ant Colony Optimization and Swarm Intelligence held in Brussels, Belgium, 2006. This article includes new types of experiments and also the possibility of considering flexibility of protein side-chains.     

Entailment of ambiguity

Everything in Rosen's work flows from the principle of 'closure to efficient cause', the necessary and sufficient distinguishing feature of complexity, and a necessary distinguishing feature of an organism. Some students of Rosen find considerable confusion over the meaning of 'closure to efficient cause'. Such confusion is unnecessary. The matter is entirely cleared up by the (M,R)-system, a set of three algebraic maps. Each map must include one of the others in its co-domain, and is itself in the co-domain of the remaining map. Structurally, the three maps form a circular hierarchy of containment. This peculiar structure is Rosen's closure. Since each map represents an efficient cause, they reveal the character of efficient cause. The efficient cause of a process is represented as its 'dynamical law', and is a constraint that arises from the intersection of the morphology of the process and the inherent constraints in reality represented by the 'laws of Nature'. A critical, observable property (evidently unnoticed by Rosen), entailed by the closure, is its inherent ambiguity. From a foundation of ambiguity, the bizarre properties of complexity (e.g., non-computability, non-fractionability, undecidability, and incompleteness) follow in a straightforward manner, often with proofs simpler than those that Rosen discovered.     

Early queen infection shapes developmental dynamics and induces long-term disease protection in incipient ant colonies

Infections early in life can have enduring effects on an organism's development and immunity. In this study, we show that this equally applies to developing ‘superorganisms’––incipient social insect colonies. When we exposed newly mated Lasius niger ant queens to a low pathogen dose, their colonies grew more slowly than controls before winter, but reached similar sizes afterwards. Independent of exposure, queen hibernation survival improved when the ratio of pupae to workers was small. Queens that reared fewer pupae before worker emergence exhibited lower pathogen levels, indicating that high brood rearing efforts interfere with the ability of the queen's immune system to suppress pathogen proliferation. Early-life queen pathogen exposure also improved the immunocompetence of her worker offspring, as demonstrated by challenging the workers to the same pathogen a year later. Transgenerational transfer of the queen's pathogen experience to her workforce can hence durably reduce the disease susceptibility of the whole superorganism.     

The comparative study of the effects of Fe2O3 and TiO2 micro- and nanoparticles on oxidative states of lung and bone marrow tissues and colony stimulating factor secretion

Nowadays, increased use of nanomaterials in industry and biomedicine poses potential risks to human health and the environment. Studying their possible toxicological effects is therefore of great significance. The present investigation was designed to examine the status of oxidative stress induced by nanoparticles (NPs) of ferric oxide (Fe₂O ₃) and titanium oxide (TiO ₂) with their micro-sized counterpart on mouse lung and bone marrow–derived normal tissue cells. We assessed the induction of oxidative stress by measuring its indicators such as antioxidant scavenging activity of superoxide dismutase and catalase as well as malondialdehyde concentration. Moreover, colony formation of bone marrow cells was assayed following induction with colony stimulating factor (CSF) from lung cells. NPs had a more potent stimulatory effect on the oxidative stress status than their micron-sized counterparts. In addition, the highest level of oxidative stress derived from TiO ₂ NPs was observed in both tissue types. Cotreatment with NPs and the antioxidant α-tocopherol reduced antioxidant activities and membrane lipid peroxidation (LPO) in the lung cells, but increased CSF-induced colony formation activity of bone marrow cells, suggesting that oxidative stress may be the cause of the cytotoxic effects of NPs. It is concluded that free radicals generated following exposure to NPs resulted in significant oxidative stress in mouse cells, indicated by increased LPO and antioxidant enzyme activity and decreased colony formation.     

Effects of fleas on nest success of Arctic barnacle geese: experimentally testing the mechanism

Parasites have detrimental effects on their hosts’ fitness. Therefore, behavioural adaptations have evolved to avoid parasites or, when an individual is already in contact with a parasite, prevent or minimize infections. Such anti‐parasite behaviours can be very effective, but can also be costly for the host. Specifically, ectoparasites can elicit strong host anti‐parasite behaviours and interactions between fleas (Siphonaptera) and their hosts are one of the best studied. In altricial bird species, nest fleas can negatively affect both parent and offspring fitness components. However, knowledge on the effects of fleas on precocial bird species is scarce. Research on geese in the Canadian Arctic indicated that fleas have a negative impact on reproductive success. One possible hypothesis is that fleas may affect female incubation behaviour. Breeding females with many fleas in their nest may increase the frequency and/or duration of incubation breaks and could even totally desert their nest. The aim of our study was to 1) determine if a similar negative relationship existed between flea abundance and reproductive success in our study colony of Arctic breeding barnacle geese Branta leucopsis and 2) experimentally quantify if such effects could be explained by a negative effect of nest fleas on female behaviour. We compared host anti‐parasite and incubation behaviour between experimentally flea‐reduced and control nests using wildlife cameras and temperature loggers. We found that flea abundance was negatively associated with hatching success. We found little experimental support, however, for changes in behaviour of the breeding female as a possible mechanism to explain this effect.     

Monitoring clinical trials with multiple arms

In order to benefit from the substantial overhead expenses of a large group sequential clinical trial, the simultaneous investigation of several competing treatments becomes more popular. If at some interim analysis any treatment arm reveals itself to be inferior to any other treatment under investigation, this inferior arm may be or may even need to be dropped for ethical and/or economic reasons. Recently proposed methods for monitoring and analysis of group sequential clinical trials with multiple treatment arms are compared and discussed. The main focus of the article is on the application and extension of (adaptive) closed testing procedures in the group sequential setting that strongly control the familywise error rate. A numerical example is given for illustration.     

Trophallaxis Mediates Uniformity of Colony Odor in Cataglyphis iberica Ants (Hymenoptera, Formicidae)

We studied the effect of nestmate separation on trophallaxis in the polydomous ant Cataglyphis iberica. After dividing three colonies into two equivalent subgroups, one queenright and one queenless, we quantified the frequency of trophallaxis within each subgroup, between the workers from the two subgroups (mixed trophallaxis), and trophallaxis involving the queen. Observations of trophallaxis were conducted over four periods of time: for 2 weeks before the separation of the two subgroups, 8 weeks during separation, immediately after reunification, and 3 weeks following reunification. Subgroups were identically fed on the eve of each day of observation. Group separation induced an increase in mixed frequencies of trophallaxis just after reunification, after which trophallaxis returned to the initial level observed before separation. Previous results showed that group separation in C. iberica induces hydrocarbon profile divergence and that reunification restores this chemical modification. The current results seem to indicate that increased trophallaxis permits a uniform odor to be reestablished among previously separated ants. Trophallaxis involving the queen is infrequent and does not seem to be crucial in the process of odor exchange. Our data confirm that trophallaxis plays a key role in establishing the Gestalt colony odor, particularly among naturally separated satellite nests in a polydomous species like C. iberica.     

The relationship between multiple mating by queens, within-colony genetic variability and fitness in the ant Lasius niger

Multiple mating has been suggested to benefit social insect queens because high genetic variation within colonies might decrease the load imposed by sterile diploid males, enhance resistance to parasites and pathogens, and lead to a more effective division of labour and/or a wider range of tolerable environmental conditions. We tested these hypotheses in the ant Lasius niger with three population samples from Switzerland and Sweden. We found no diploid males in young or mature colonies suggesting a lack of diploid male load. Colonies with multiply-mated queens were not larger nor did they produce more sexuals than colonies with singly-mated queens. We did find a significantly lower frequency of multiple mating among newly mated queens than among the queens heading mature colonies in one population sample (Switzerland 1997). However, this result was not repeated in the other study population, or in the following year in the Swiss population.