The Interaction of Equine Lysozyme:Oleic Acid Complexes with Lipid Membranes Suggests a Cargo Off-Loading Mechanism

The normal function of equine lysozyme (EL) is the hydrolysis of peptidoglycan residues of bacterial cell walls. EL is closely related to α-lactalbumins with respect to sequence and structure and further possesses the calcium binding site of α-lactalbumins. Recently, EL multimeric complexes with oleic acids (ELOAs) were shown to possess tinctorial and morphological properties, similar to amyloidal aggregates, and to be cytotoxic. ELOA's interactions with phospholipid membranes appear to be central to its biological action, similar to human α-lactalbumin made lethal to tumor cells. Here, we describe the interaction of ELOA with phospholipid membranes. Confocal scanning laser microscopy shows that ELOA, but not native EL, accumulates on the surface of giant unilamellar vesicles, without inducing significant membrane permeability. Quartz crystal microbalance with dissipation data indicated an essentially non-disruptive binding of ELOA to supported lipid bilayers, leading to formation of highly dissipative and “soft” lipid membrane; at higher concentrations of ELOA, the lipid membrane desorbs from the surface probably as bilayer sheets of vesicles. This membrane rearrangement occurred to a similar extent when free oleic acid (OA) was added, but not when free OA was removed from ELOA by prior incubation with bovine serum albumin, emphasizing the role of OA in this process. NMR data indicated an equilibrium between free and bound OA, which shifts towards free OA as ELOA is progressively diluted, indicating that OA is relatively loosely bound. Activity measurements together with fluorescence spectroscopy and circular dichroism suggested a conversion of ELOA towards a more native-like state on interaction with lipid membranes, although complete refolding was not observed. Altogether, these results suggest that ELOA may act as an OA carrier and facilitate OA transfer to the membrane. ELOA's properties illustrate that protein folding variants may possess specific functional properties distinct from the native protein.     

Male Body Size and Mating Success and Their Relation to Larval Host Plant History in the Moth Rothschildia lebeau in Costa Rican Dry Forest

The moth Rothschildia lebeau uses three tree species as its primary larval hosts in the tropical dry forest of northwestern Costa Rica. These hosts were shown previously to have different relative effects on caterpillar performance, resulting in an apparent host-related life history trade-off between large adult body size on the one hand but low offspring survival on the other. To further assess the potential ecological and evolutionary importance of this trade-off, an observational field study of the relationship between male body size and mating success was conducted. Across mating trials, larger males had a higher probability of being observed mating. Independent of the effect of size, the amount of wing damage an individual had sustained (a measure of relative age) was negatively correlated with the probability a male was observed mating. Within mating trials, the mated male tended to be larger than the average unmated male, but there was no difference in wing damage. Overall, results of this study were consistent with a positive effect of male body size on mating success, consistent with the idea that larval host plant history and its effects on adult body size matters in terms of adult male fitness. However, all sized males were observed mating over the course of the study, and the size advantage did not appear to be particularly strong.     

A phylogeographic study of the cosmopolitan genus Phragmites (Poaceae) based on AFLPs

Within the genus Phragmites (Poaceae), the species P. australis (the common reed) is virtually cosmopolitan, and shows considerable variation in ploidy level and morphology. Genetic variation in Phragmites was studied using AFLPs, and analysed with parsimony and distance methods. Groups of P. australis strongly supported in the analyses include one that comprises all South American clones, a distinct group from the US Gulf Coast, and a group of E. Asian and Australian octoploids. Among the other species, the paleotropical P. vallatoria is supported as monophyletic and most closely related to the paraphyletic P. mauritianus and to the Gulf Coast and S. American groups. The E. Asian species P. japonicus is closely related to a group of P. australis clones mostly from central North America. Tetraploidy predominates in the genus, and optimisation of chromosome numbers onto the phylogeny shows that higher ploidy levels have evolved many times.     

大熊猫肠道纤维素分解菌的分离鉴定及产酶性质

【目的】从健康大熊猫新鲜粪便中分离具有纤维素酶活性的菌株,并对其进行菌种鉴定及产酶性质研究。【方法】利用羧甲基纤维素钠培养基分离纯化具有较高纤维素酶活性的菌株,根据形态学特征、生理生化特性以及16S rDNA分析对其进行分类鉴定,研究影响该菌株纤维素酶的产酶条件,以及对不同纤维素底物的降解情况。【结果】分离得到一株纤维素酶产生菌株P2,该菌株为好氧的革兰氏阳性细菌,生长温度范围20-50℃(最适温度37℃),pH范围6.0-9.0(最适pH7.0),NaCl浓度范围0%-15%(最适2%NaCl),培养24h达到产酶高峰。16S rDNA基因序列分析显示,菌株P2与解淀粉芽胞杆菌(Bacillusamyloliquefaciens)NBRC15535相似性为99.66%。该菌株对四种纤维素底物(滤纸、脱脂棉、秸秆、竹纤维)均有不同程度的降解,内切葡聚糖酶、外切葡聚糖酶、β-葡萄糖苷酶和总酶活具有不同的酶活变化。【结论】本研究首次从大熊猫粪便中分离出了好氧纤维素分解菌,并鉴定为解淀粉芽胞杆菌,对上述四种纤维结构均有一定的破坏和分解作用,为进一步研究大熊猫竹纤维消化机制提供了菌源。     

Intercellular communication via the endo-lysosomal system: Translocation of granzymes through membrane barriers

Cytotoxic lymphocytes (CLs) are responsible for the clearance of virally infected or neoplastic cells. CLs possess specialised lysosome-related organelles called granules which contain the granzyme family of serine proteases and perforin. Granzymes may induce apoptosis in the target cell when delivered by the pore forming protein, perforin. Here we follow the perforin-granzyme pathway from synthesis and storage in the granule, to exocytosis and finally delivery into the target cell. This review focuses on the controversial subject of perforin-mediated translocation of granzymes into the target cell cytoplasm. It remains unclear whether this occurs at the cell surface with granzymes moving through a perforin pore in the plasma membrane, or if it involves internalisation of perforin and granzymes and subsequent release from an endocytic compartment. The latter mechanism would represent an example of cross talk between the endo-lysosomal pathways of individual cells. This article is part of a Special Issue entitled: Proteolysis 50 years after the discovery of lysosome.     

Isotope signatures in winter moulted feathers predict malaria prevalence in a breeding avian host

It is widely accepted that animal distribution and migration strategy might have co-evolved in relation to selection pressures exerted by parasites. Here, we first determined the prevalence and types of malaria blood parasites in a breeding population of great reed warblers Acrocephalus arundinaceus using PCR. Secondly, we tested for differences in individual feather stable isotope signatures (delta (13)C, delta (15)N, deltaD and delta (34)S) to investigate whether malaria infected and non-infected birds had occupied different areas in winter. We show that birds moulting in Afro-tropical habitats with significantly higher delta (13)C and delta (15)N but lower deltaD and delta(34)S values were more frequently infected with malaria parasites. Based on established patterns of isotopic distributions, our results indicate that moulting sites with higher incidence of malaria are generally drier and situated further to the north in West Africa than sites with lower incidence of malaria. Our findings are pertinent to the general hypothesis that animal distribution and particularly avian migration strategy might evolve in response to selection pressures exerted by parasites at different geographic scales. Tradeoffs between investment in energy demanding life history traits (e.g. migration and winter moult) and immune function are suggested to contribute to the particular choice of habitat during migration and at wintering sites.     

Parasite Threat to Panda Conservation

The giant panda is a global symbol of wildlife conservation that is threatened by historic and current habitat loss. Despite a great deal of research on the physiology, reproductive biology, and diet of pandas in the wild and in captivity, there is little information on wild panda mortality. Here we integrate previously unavailable data on the mortality of wild pandas. We report on three recent phases of panda mortality: deaths due to bamboo flowering in the 1970s and 1980s, surprisingly extensive poaching in the 1980s and 1990s, and a parasitic infection over the past few years. Our analyses suggest that the current most significant threat to wild panda survival is disease due to extraintestinal migration (visceral larval migrans) by an ascarid nematode. We demonstrate that the probability of death of wild pandas being caused by this disease increased significantly between 1971 and 2005 and discuss the possible factors leading to the emergence of this disease. Electronic Supplementary Material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Characterization of eight polymorphic microsatellite loci for the giant grouper (Epinephelus lanceolatus Bloch)

Eight polymorphic microsatellite loci were isolated and characterized using a small insert genomic DNA library for the giant grouper (Epinephelus lanceolatus Bloch, 1790), a commercially valuable marine fish in tropical waters. They showed polymorphism information content ranging from 0.177 to 0.775, allele numbers ranging from two to 10, effective allele numbers ranging from 1.227 to 5.012, and observed and expected heterozygosities from 0.2 to 0.733 and from 0.185 to 0.801, respectively, which we anticipate will be useful for population genetic studies of the giant grouper.     

Ultrastructure of glial cells in the nervous system of <Emphasis Type="Italic">Grillotia erinaceus</Emphasis>

Until now, there has been no answer to the question of whether specialized glial cells exist in the nervous system of platyhelminths. The identification of these cells in parasitic flatworms is difficult due to their organization as parenchymal animals. The goal of this study was to reveal and describe structural elements corresponding to the term glia in the CNS of the parasitic flatworm Grillotia erinaceus (Cestoda: Trypanorhyncha). Three types of glial cells are revealed. The first type consists of fibroblast-like cells located in the cerebral ganglia that contain fibrils and excrete onto the surface fibrillar material and possess desmosomes; the presumable function of fibroblast-like glial cells is the isolation and support of ganglionar neurons. Glial cells of the second type form a myelin-like envelope of giant axons and bulbar nerves of the scolex and have laminar cytoplasm; they are numerous and exceed the number of neurons in the composition of nerves. Glial cells of the third type form multilayer envelopes in the main nerve cords and make contacts with the excretory epithelium; however, specialized junctions with neurons were not found. The existence of glia in other free living and parasitic flatworms is discussed.     

Membrane binding of oligomeric alpha-synuclein depends on bilayer charge and packing

Membrane disruption by oligomeric α-synuclein (αS) is considered a likely mechanism of cytotoxicity in Parkinson’s disease (PD). However, the mechanism of oligomer binding and the relation between binding and membrane disruption is not known. We have visualized αS oligomer-lipid binding by fluorescence microscopy and have measured membrane disruption using a dye release assay. The data reveal that oligomeric αS selectively binds to membranes containing anionic lipids and preferentially accumulates into liquid disordered (Ld) domains. Furthermore, we show that binding of oligomers to the membrane and disruption of the membrane require different lipid properties. Thus membrane-bound oligomeric αS does not always cause bilayer disruption.