Trypanosoma cruzi: Synergistic cytotoxicity of multiple amphipathic anti-microbial peptides to T. cruzi and potential bacterial hosts

The parasite Trypanasoma cruzi is responsible for Chagas disease and its triatomine vector, Rhodnius prolixus, has a symbiotic relationship with the soil bacterium, Rhodococcus rhodnii.R. rhodnii that was previously genetically engineered to produce the anti-microbial peptide, cecropin A was co-infected with T. cruzi into R. prolixus resulting in clearance of the infectious T. cruzi in 65% of the vectors. Similar anti-microbial peptides have been isolated elsewhere and were studied for differential toxicity against T. cruzi and R. rhodnii. Of the six anti-microbial peptides tested, apidaecin, magainin II, melittin, and cecropin A were deemed potential candidates for the Chagas paratransgenic system as they were capable of killing T.cruzi at concentrations that exhibit little or no toxic effects on R. rhodnii. Subsequent treatments of T. cruzi with these peptides in pair-wise combinations resulted in synergistic killing, indicating that improvement of the 65% parasite clearance seen in previous experiments may be possible utilizing combinations of different anti-microbial peptides.     

Expressions for the Fractional Modification in Different Monocyclic Enzyme Cascade Systems: Analysis of their Validity Tested by Numerical Integration

This paper presents the derivation, under a minimal set of assumptions, of a general expression for the steady-state fractional modification of an interconvertible protein involved in four different schemes of monocyclic enzyme cascade systems. From this general expression we derive, as particular cases, other, simpler expressions by applying additional assumptions and which have, therefore, a smaller range of validity. Some of these particular expressions coincide with those already obtained in previous contributions on individualised analyses. We discuss the relationships between the kinetic parameters and the concentrations needed for the fulfilment of the additional assumptions. The goodness of the analysis was tested by reference to the shape in the steady-state of the simulated time progress curves obtained by numerical integration.     

The role of topography in promoting fractal patchiness in a carbonate shelf landscape

Satellite remote sensing has shown numerous aspects of coral reef seascapes to be fractal. That is, they display characteristics of scale-invariance and complexity. To date, an understanding of why reefscapes adopt this curious scaling has been lacking. This property was investigated using high-resolution terrain models built using bathymetric LiDAR soundings of the shallow Puerto Rico insular shelf. A computer-simulation model constructed using simple random processes was adequate to describe many of the intricacies of actual coral reef terrain. This model, based on fractional Brownian motion (fBm), produced surfaces that were visually and statistically indistinguishable from natural seabeds, at spatial scales of 0.001–25 km². The conformity between model and nature allowed us to ascertain the importance of topography as a driver for the fractal patchiness that has been shown to occur in plan-view maps of reefscapes (e.g. Purkis et al. J Sediment Res 75:861–876, 2005, J Geol 115:493–508, 2007). For the considered Puerto Rican shelf, the necessary Brownian-like seabed topography likely arose through karst erosion overprinted by several episodes of reef development. Communicated by Geology Editor Dr. Bernhard Riegl     

Mathematical model for adaptive evolution of populations based on a complex domain

A mutation is ultimately essential for adaptive evolution in all populations. It arises all the time, but is mostly fixed by enzymes. Further, most do consider that the evolution mechanism is by a natural assortment of variations in organisms in line for random variations in their DNA, and the suggestions for this are overwhelming. The altering of the construction of a gene, causing a different form that may be communicated to succeeding generations, produced by the modification of single base units in DNA, or the deletion, insertion, or rearrangement of larger units of chromosomes or genes. This altering is called a mutation. In this paper, a mathematical model is introduced to this reality. The model describes the time and space for the evolution. The tool is based on a complex domain for the space. We show that the evolution is distributed with the hypergeometric function. The Boundedness of the evolution is imposed by utilizing the Koebe function.     

河南荥阳官庄遗址两周时期人牙结石的植物淀粉粒

本文对河南官庄遗址两周时期人牙结石开展了淀粉粒分析,发现了数量丰富的淀粉粒以及少量植硅体。可鉴定形态的淀粉粒主要来自粟、黍、小麦、小豆等农作物以及坚果、块茎植物;植硅体中则有来自水稻颖片的双峰型植硅体。此次研究表明官庄先民食物来源广泛,包括多种农作物和采集植物,其中粟黍类农作物在食物构成中占据主要地位,而小麦所占比例很可能已仅次于粟黍。结合包括官庄遗址和周边若干遗址的浮选结果,两周时期中原腹心地区仍是北方传统的粟作农业,但农作物种植已明显多样化;与此同时,小麦在农作物体系中的重要性增加,中原地区农作物种植体系由以粟黍为主转向以小麦为主的趋势已经出现。     

两种虫草相关真菌分级醇沉胞外多糖对果蝇寿命及SOD和MDA的影响

目的研究多糖对果蝇寿命及超氧化物歧化酶(SOD)和丙二醛(MDA)的影响。方法通过将不同浓度乙醇分级沉淀得到的两种虫草相关真菌蝙蝠蛾拟青霉和地生枝顶孢霉胞外多糖分别添加到果蝇饲料中,研究不同多糖组分对果蝇寿命及其体内SOD和MDA含量的影响。结果蝙蝠蛾拟青霉胞外多糖组分P60能显著延长雌雄果蝇的平均寿命,分别达17.04%和18.36%,显著提高雌雄果蝇体内SOD活力(28.02%和26.85%),MDA含量分别降低了50.67%和54.30%;地生枝顶孢霉胞外多糖组分G50显著延长雌雄果蝇的平均寿命,分别达到15.62%和15.96%,显著提高雌雄果蝇体内SOD活力,分别为42.55%和26.74%,明显降低MDA含量,分别为47.30%和49.00%。结论多糖组分P60和G50能显著延长果蝇寿命,提高其SOD活力和降低MDA含量。     

Fractional cable equation models for anomalous electrodiffusion in nerve cells: infinite domain solutions

We introduce fractional Nernst-Planck equations and derive fractional cable equations as macroscopic models for electrodiffusion of ions in nerve cells when molecular diffusion is anomalous subdiffusion due to binding, crowding or trapping. The anomalous subdiffusion is modelled by replacing diffusion constants with time dependent operators parameterized by fractional order exponents. Solutions are obtained as functions of the scaling parameters for infinite cables and semi-infinite cables with instantaneous current injections. Voltage attenuation along dendrites in response to alpha function synaptic inputs is computed. Action potential firing rates are also derived based on simple integrate and fire versions of the models. Our results show that electrotonic properties and firing rates of nerve cells are altered by anomalous subdiffusion in these models. We have suggested electrophysiological experiments to calibrate and validate the models.