Concordant phylogeography and cryptic speciation in two Western Palaearctic oak gall parasitoid species complexes

Little is known about the evolutionary history of most complex multi‐trophic insect communities. Widespread species from different trophic levels might evolve in parallel, showing similar spatial patterns and either congruent temporal patterns (Contemporary Host‐tracking) or later divergence in higher trophic levels (Delayed Host‐tracking). Alternatively, host shifts by natural enemies among communities centred on different host resources could disrupt any common community phylogeographic pattern. We examined these alternative models using two Megastigmus parasitoid morphospecies associated with oak cynipid galls sampled throughout their Western Palaearctic distributions. Based on existing host cynipid data, a parallel evolution model predicts that eastern regions of the Western Palaearctic should contain ancestral populations with range expansions across Europe about 1.6 million years ago and deeper species‐level divergence at both 8–9 and 4–5 million years ago. Sequence data from mitochondrial cytochrome b and multiple nuclear genes showed similar phylogenetic patterns and revealed cryptic genetic species within both morphospecies, indicating greater diversity in these communities than previously thought. Phylogeographic divergence was apparent in most cryptic species between relatively stable, diverse, putatively ancestral populations in Asia Minor and the Middle East, and genetically depauperate, rapidly expanding populations in Europe, paralleling patterns in host gallwasp species. Mitochondrial and nuclear data also suggested that Europe may have been colonized multiple times from eastern source populations since the late Miocene. Temporal patterns of lineage divergence were congruent within and across trophic levels, supporting the Contemporary Host‐tracking Hypothesis for community evolution.     

苯肼对红细胞在体衰老过程中微观流变特性的影响

在Brunara等人用苯肼使动物造成急性溶血性贫血的方法基础上,建立一种由急性溶血性贫血后,而诱发家兔幼红细胞增多的非正常生理状态的红细胞在体衰老模型,继而研究新生红细胞从产生到死亡死亡过程,即衰老过程的流变学特性的变化规律。通过对新生红细胞的压积、变形、取向及与之相应的全血的粘度、血沉等指标的连续60多天的监测,发现红细胞在衰老过程中的微观流变学特性确实有明显改变。红细胞在体衰老过程中微观流变特性逐渐变差。     

Specificity and Structure of a High Affinity Activin Receptor-like Kinase 1 (ALK1) Signaling Complex

Activin receptor-like kinase 1 (ALK1), an endothelial cell-specific type I receptor of the TGF-β superfamily, is an important regulator of normal blood vessel development as well as pathological tumor angiogenesis. As such, ALK1 is an important therapeutic target. Thus, several ALK1-directed agents are currently in clinical trials as anti-angiogenic cancer therapeutics. Given the biological and clinical importance of the ALK1 signaling pathway, we sought to elucidate the biophysical and structural basis underlying ALK1 signaling. The TGF-β family ligands BMP9 and BMP10 as well as the three type II TGF-β family receptors ActRIIA, ActRIIB, and BMPRII have been implicated in ALK1 signaling. Here, we provide a kinetic and thermodynamic analysis of BMP9 and BMP10 interactions with ALK1 and type II receptors. Our data show that BMP9 displays a significant discrimination in type II receptor binding, whereas BMP10 does not. We also report the crystal structure of a fully assembled ternary complex of BMP9 with the extracellular domains of ALK1 and ActRIIB. The structure reveals that the high specificity of ALK1 for BMP9/10 is determined by a novel orientation of ALK1 with respect to BMP9, which leads to a unique set of receptor-ligand interactions. In addition, the structure explains how BMP9 discriminates between low and high affinity type II receptors. Taken together, our findings provide structural and mechanistic insights into ALK1 signaling that could serve as a basis for novel anti-angiogenic therapies.     

The ultrastructure of MCF-10A acini

MCF-10A human mammary epithelial cells cultured inside reconstituted basement membrane form acini that resemble the acinar structures of mammary lobules. This three-dimensional culture system has been used for identifying and characterizing the signal transduction pathways controlling cell proliferation and death, and for studying their disregulation in malignant progression. We have compared the ultrastructure of MCF-10A acini, MCF-10A cells grown in monolayer, and the acinar structures of human breast lobules. The tissue architecture of MCF-10A acini was formed by hemidesmosomes connected to a basement membrane and by abundant desmosomes between acinar cells. Intermediate filaments that joined into large and abundant filament bundles connected hemidesmosomes and desmosomes to sites at the nuclear surface. Fewer and thinner bundles of filaments were observed in monolayer MCF-10A cells and even fewer in breast tissue. Tight junctions were observed between cells in breast tissue but missing in MCF-10A acini. The cytoplasm of MCF-10A acinar cells had a polar organization similar to that observed in breast tissue, with centrosomes and the Golgi apparatus on the apical side of the nucleus. MCF-10A acinar nuclei had an irregular, frequently invaginated surface and had a single nucleolus. The distribution of heterochromatin was similar to that in the epithelial cells of breast tissue. The nuclei of monolayer MCF-10A cells had multiple nucleoli, a more regular profile, and less heterochromatin. Electron microscopy has the resolution required to survey features of MCF-10A cell and acinus architecture that may change with manipulations designed to induce malignant phenotypes.     

Holocephalan (Chondrichthyes) dental plates with hypermineralized dentine as a substitute for missing teeth through developmental plasticity

All extant holocephalans (Chimaeroidei) have lost the ability to make individual teeth, as tooth germs are not part of the embryonic development of the dental plates or of their continuous growth. Instead, a hypermineralized dentine with a unique mineral, whitlockin, is specifically distributed within a dentine framework into structures that give the dental plates their distinctive, species-specific morphology. Control of the regulation of this distribution must be cellular, with a dental epithelium initiating the first outer dentine, and via contact with ectomesenchymal tissue as the only embryonic cell type that can make dentine. Chimaeroids have three pairs of dental plates within their mouth, two in the upper jaw and one in the lower. In the genera Chimaera, Hydrolagus and Harriotta, the morphology and distribution of this whitlockin within each dental plate differs both between different plates in the same species and between species. Whitlockin structures include ovoids, rods and tritoral pads, with substantial developmental changes between these. For example, rods appear before the ovoids and result from a change in the surrounding trabecular dentine. In Harriotta, ovoids form separately from the tritoral pads, but also contribute to tritor development, while in Chimaera and Hydrolagus, tritoral pads develop from rods that later are perforated to accommodate the vasculature. Nevertheless, the position of these structures, secreted by the specialized odontoblasts (whitloblasts), appears highly regulated in all three species. These distinct morphologies are established at the aboral margin of the dental plate, with proposed involvement of the outer dentine. We observe that this outer layer forms into serially added lingual ridges, occurring on the anterior plate only. We propose that positional, structural specificity must be contained within the ectomesenchymal populations, as stem cells below the dental epithelium, and a coincidental occurrence of each lingual, serial ridge with the whitlockin structures that contribute to the wear-resistant oral surface.     

Properties of phosphofructokinase from rat liver and their relation to the control of glycolysis and gluconeogenesis

1. Phosphofructokinase from rat liver has been partially purified by ammonium sulphate precipitation so as to remove enzymes that interfere in one assay for phosphofructokinase. The properties of this enzyme were found to be similar to those of the same enzyme from other tissues (e.g. cardiac muscle, skeletal muscle and brain) that were previously investigated by other workers. 2. Low concentrations of ATP inhibited phosphofructokinase activity by decreasing the affinity of the enzyme for the other substrate, fructose 6-phosphate. Citrate, and other intermediates of the tricarboxylic acid cycle, also inhibited the activity of phosphofructokinase. 3. This inhibition was relieved by either AMP or fructose 1,6-diphosphate; however, higher concentrations of ATP decreased and finally removed the effect of these activators. 4. Ammonium sulphate protected the enzyme from inactivation, and increased the activity by relieving the inhibition due to ATP. The latter effect was similar to that of AMP. 5. Phosphofructokinase was found in the same cellular compartment as fructose 1,6-diphosphatase, namely the soluble cytoplasm. 6. The properties of phosphofructokinase and fructose 1,6-diphosphatase are compared and a theory is proposed that affords dual control of both enzymes in the liver. The relation of this to the control of glycolysis and gluconeogenesis is discussed.     

Diatom-derived carbohydrates as factors affecting bacterial community composition in estuarine sediments

Microphytobenthic biofilms in estuaries, dominated by epipelic diatoms, are sites of high primary productivity. These diatoms exude large quantities of extracellular polymeric substances (EPS) comprising polysaccharides and glycoproteins, providing a substantial pool of organic carbon available to heterotrophs within the sediment. In this study, sediment slurry microcosms were enriched with either colloidal carbohydrates or colloidal EPS (cEPS) or left unamended. Over 10 days, the fate of these carbohydrates and changes in beta-glucosidase activity were monitored. Terminal restriction fragment length polymorphism (T-RFLP), DNA sequencing, and quantitative PCR (Q-PCR) analysis of 16S rRNA sequences were used to determine whether sediment bacterial communities exhibited compositional shifts in response to the different available carbon sources. Initial heterotrophic activity led to reductions in carbohydrate concentrations in all three microcosms from day 0 to day 2, with some increases in beta-glucosidase activity. During this period, treatment-specific shifts in bacterial community composition were not observed. However, by days 4 and 10, the bacterial community in the cEPS-enriched sediment diverged from those in colloid-enriched and unamended sediments, with Q-PCR analysis showing elevated bacterial numbers in the cEPS-enriched sediment at day 4. Community shifts were attributed to changes in cEPS concentrations and increased beta-glucosidase activity. T-RFLP and sequencing analyses suggested that this shift was not due to a total community response but rather to large increases in the relative abundance of members of the gamma-proteobacteria, particularly Acinetobacter-related bacteria. These experiments suggest that taxon- and substrate-specific responses within the bacterial community are involved in the degradation of diatom-derived extracellular carbohydrates.     

Copper induced oxidation of serotonin: analysis of products and toxicity

Serotonin is a major neurotransmitter that controls many functions, ranging from mood and behaviour through to sleep and motor functions. The non-enzymatic oxidation of serotonin is of significant importance as some oxidation products are considered to be neurotoxic. An interaction between copper and serotonin has been suggested by symptoms observed in a number of neurodegenerative diseases such as Wilson's and Prion diseases. Using PC12 cells as a model of neuronal cells, we show that the interaction between copper and serotonin is toxic to undifferentiated cells. The toxicity is largely due to reactive oxygen species as cell death is significantly reduced in the presence of the antioxidant mannitol. Differentiation of the PC12 cells also confers resistance to the oxidative process. In vitro oxidation of serotonin by copper results in the eventual formation of a coloured pigment, thought to be a melanin-like polymeric species. Using spectroscopic methods we provide evidence for the formation of a single intermediate product. This dimeric intermediate was identified and characterized as 5,5'-dihydroxy-4,4'-bitryptamine. These results indicate that copper structurally alters serotonin and this process may play a role in copper related neurodegenerative diseases.     

Role of plant stomata in bacterial invasion

Stomata are microscopic pores in the epidermis of the aerial parts of terrestrial plants. These pores are essential for photosynthesis, as they allow CO(2) to diffuse into the plant. The size of the stomatal pore changes in response to environmental conditions, such as light intensity, air humidity and CO(2) concentrations, as part of the plant's adaptation to maximize photosynthetic efficiency and, at the same time, to minimize water loss. Historically, stomata have been considered as passive portal of entry for plant pathogenic bacteria. However, recent studies suggest that stomata can play an active role in restricting bacterial invasion as part of the plant innate immune system. Some plant pathogens have evolved specific virulence factors to overcome stomata-based defence. Interestingly, many bacterial disease outbreaks require high humidity, rain, or frost damage, which could promote stomatal opening and/or bypass stomatal defence by creating wounds as alternative entry sites. Further studies on microbial and environmental regulation of stomata-based defence should fill gaps in our understanding of bacterial pathogenesis, disease epidemiology and phyllosphere microbiology.