Cooperative vigilance: the guanaco's (Lama guanicoe) key antipredator mechanism

The concept of sociality has been associated with the effectiveness of antipredator mechanisms, like cooperative vigilance and the dilution effect. Lama guanicoe (guanaco) is a social native herbivore in South America and a social species. The objectives of this study were to evaluate the antipredator responses of different-sized groups of guanacos in areas with varying predation risks and to determine antipredator mechanisms in guanacos. For this, we measured different antipredator responses to a potential predator (human subjects). Detection of predator and flight distances from predator both increased with a greater number of guanacos per group and with greater distances among guanacos within the social group. Both buffer distance and flight time decreased with a greater number of guanacos per group, but increased with greater distances among guanacos inside the social group. Solitary adult males moved shorter distance and mixed groups moved greater distances. Flight distances were greater in areas with tall and dense vegetation than in areas with low vegetation. Buffer distance and flight time were shorter in undulating land than on flat lands, and groups were usually observed on hill slopes. Our results suggest that the benefit of social grouping in guanacos is the increased probability of avoiding predator with cooperative vigilance and not with the dilution effect. This means that a predator could be detected earlier when approaching a guanaco group than when approaching a solitary individuals and could thus be avoided.     

Informative Dorfman screening

Since the early 1940s, group testing (pooled testing) has been used to reduce costs in a variety of applications, including infectious disease screening, drug discovery, and genetics. In such applications, the goal is often to classify individuals as positive or negative using initial group testing results and the subsequent process of decoding of positive pools. Many decoding algorithms have been proposed, but most fail to acknowledge, and to further exploit, the heterogeneous nature of the individuals being screened. In this article, we use individuals' risk probabilities to formulate new informative decoding algorithms that implement Dorfman retesting in a heterogeneous population. We introduce the concept of "thresholding" to classify individuals as "high" or "low risk," so that separate, risk-specific algorithms may be used, while simultaneously identifying pool sizes that minimize the expected number of tests. When compared to competing algorithms which treat the population as homogeneous, we show that significant gains in testing efficiency can be realized with virtually no loss in screening accuracy. An important additional benefit is that our new procedures are easy to implement. We apply our methods to chlamydia and gonorrhea data collected recently in Nebraska as part of the Infertility Prevention Project.     

Tau Oligomers Impair Artificial Membrane Integrity and Cellular Viability

The microtubule-associated protein Tau is mainly expressed in neurons, where it binds and stabilizes microtubules. In Alzheimer disease and other tauopathies, Tau protein has a reduced affinity toward microtubules. As a consequence, Tau protein detaches from microtubules and eventually aggregates into β-sheet-containing filaments. The fibrillization of monomeric Tau to filaments is a multistep process that involves the formation of various aggregates, including spherical and protofibrillar oligomers. Previous concepts, primarily developed for Aβ and α-synuclein, propose these oligomeric intermediates as the primary cytotoxic species mediating their deleterious effects through membrane permeabilization. In the present study, we thus analyzed whether this concept can also be applied to Tau protein. To this end, viability and membrane integrity were assessed on SH-SY5Y neuroblastoma cells and artificial phospholipid vesicles, treated with Tau monomers, Tau aggregation intermediates, or Tau fibrils. Our findings suggest that oligomeric Tau aggregation intermediates are the most toxic compounds of Tau fibrillogenesis, which effectively decrease cell viability and increase phospholipid vesicle leakage. Our data integrate Tau protein into the class of amyloidogenic proteins and enforce the hypothesis of a common toxicity-mediating mechanism for amyloidogenic proteins.     

Clinical dextran purified by fractional ultrafiltration coupled with water washing

Dextran with extremely narrow molecular weight distribution (MWD) is demanded for clinical use. To elucidate the effect of fractional ultrafiltration on the purification of clinical dextran, a range of ultrafiltration membranes with 100, 30, 5 and 1 kDa molecular weight cut-off (MWCO) were applied. High Performance Gel Permeation Chromatography (HPGPC) analysis indicated that the MWD of ultrafiltrated dextran fractions are wide, with polydispersity index (D) between 2.2 and 5.4, suggesting that the MWD of dextran is hard to be strictly controlled by fractional ultrafitration. However, when coupled with water washing during ultrafiltration process, the homogeneity of dextran was greatly improved. An ultrafiltration fraction of 5-30 kDa (Mw ≈ 35 kDa) with narrow MWD (D = 1.2) was obtained after 5 times of water washing. The results show that fractional ultrafiltration coupled with water washing can be used as a simple and effective method to improve the quality of clinical dextran.     

形成性评价在医学微生物教学中的应用体会

形成性评价注重的是学习过程和师生互动,由反馈-鼓励-指导三个环节组成.形成性评价有利于对学生自主学习和创新思维能力的培养.本文就医学微生物教学中形成性评价的应用从提高教师的认识、具体实施过程以及应用过程中的收获谈了自己的体会.     

Blueprints for viral capsids in the family of polyomaviridae

In a seminal paper, Caspar and Klug [1962. Physical principles in the construction of regular viruses. Cold Spring Harbor Symp. Quant. Biol. 27, 1-24] derived a family of surface lattices as blueprints for the structural organisation of the protein shells, called viral capsids, which encapsulate and hence protect the viral genome. These lattices schematically encode, and hence predict, the locations of the proteins in the viral capsids. Despite the huge success and numerous applications of this theory in virology, experimental results have provided evidence for the fact that it is too restrictive to describe all known viruses [Casjens, S., 1985. Virus Structure and Assembly. Jones and Bartlett, Boston, MA]. Especially, the family of Polyomaviridae, which contains cancer-causing viruses, falls out of the scope of this theory.In [Twarock, R., 2004. A tiling approach to virus capsid assembly explaining a structural puzzle in virology. J. Theor. Biol. 226, 477], we have shown that a member of the family of Polyomaviridae can be described via an icosahedrally symmetric tiling. We show here that all viruses in this family can be described by tilings with vertices corresponding to subsets of a quasi-lattice that is constructed based on an affine extended Coxeter group, and we use this methodology to derive their coordinates explicitly. Since the particles appear as different subsets of the same quasi-lattice, their relative sizes are predicted by this approach, and there hence exists only one scaling factor that relates the sizes of all particles collectively to their biological counterparts. It is the first mathematical result that provides a common organisational principle for different types of viral particles in the family of Polyomaviridae, and paves the way for modelling Polyomaviridae polymorphism.     

86株A群链球菌耐药性检测与分析

目的探讨A群链球菌对多种抗生素的耐药性,更好地指导临床用药。方法收集本院2005年度检出的39株和2006年度检出的47株A群链球菌的药物敏感试验结果,使用X^2检验比较A群链球菌耐药率。结果2006年度和上一年度相比A群链球菌对红霉素、克林霉素、阿齐霉素的耐药率增高显著（P〈0．05）,而对氯霉素、四环素的耐药性无明显改变（P〉0．05）,未发现耐万古霉素、青霉素、头孢吡肟、头孢噻肟的菌株。结论加强对A群链球菌耐药性检测及调查分析,对指导临床用药有重要意义。     

创新型单手操作新生儿复苏器的研制

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Assignment of MS-based metabolomic datasets via compound interaction pair mapping

Assignment of physical meaning to mass spectrometry (MS) data peaks is an important scientific challenge for metabolomics investigators. Improvements in instrumental mass accuracy reduce the number of spurious database matches, however, this alone is insufficient for accurate, unique high-throughput assignment. We present a method for clustering MS instrumental artifacts and a stochastic local search algorithm for the automated assignment of large, complex MS-based metabolomic datasets. Artifact peaks and their associated source peaks are grouped into “instrumental clusters.” Instrumental clusters, peaks grouped together by shared peak shape in the temporal domain, serve as a guide for the number of assignments necessary to completely explain a given dataset. We refine mass only assignments through the intersection of peak correlation pairs with a database of biochemically relevant interaction pairs. Further refinement is achieved through a stochastic local search optimization algorithm that selects individual assignments for each instrumental cluster. The algorithm works by choosing the peak assignment that maximally explains the connectivity of a given cluster. We demonstrate that this methodology provides a significant advantage over standard methods for the assignment of metabolites in a UPLC-MS diabetes dataset. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.