Ultrastructure of a magnetotactic spirillum.

The ultrastructure of a magnetotactic bacterium (strain MS-1) was examined by transmission, scanning, and scanning-transmission electron microscopy. The organism resembled other spirilla in general cell morphology, although some differences were detected at the ultrastructural level. Electron-dense particles within magnetotactic cells were shown by energy-dispersive X-ray analysis to be localizations containing iron. A non-magnetotactic variant of strain MS-1 lacked these novel bacterial inclusion bodies. A chain of these particles traversed each magnetotactic cell in a specific arrangement that was consistent from cell to cell, seemingly associated with the inner surface of the cytoplasmic membrane. Each particle was surrounded by an electron-dense layer separated from the particle surface by an electron-transparent region. The term "magnetosome" is proposed for the electron-dense particles with their enveloping layer(s) as found in this and other magnetotactic bacteria.     

The role of apolipoprotein E in Alzheimer's disease: pharmacogenomic target selection

The association of inheritance of different apolipoprotein E (APOE, gene; apoE, protein) alleles with the risk and rate of onset of Alzheimer's disease (AD) is now well established and widely confirmed. While there are now a collection of hypotheses concerning the specific relationship of APOE polymorphisms to various phenotypic manifestations of AD, no single compelling theory has been tested and universally accepted. The only clear fact emerging during the past 6 years is that differences in APOE genotype affect the average rate of disease onset as a predictable function of the inheritance of this polymorphic gene. Methods now exist to enable experimental designs to study the metabolic effects of inheriting different APOE alleles, addressing what differences that may be present for many years, perhaps over the entire lifetime, can lead to earlier or later manifestations of the disease and are therapeutically tractable. This review summarizes part of an experimental approach to identify biological pathways influenced by the different APOE polymorphisms that are relevant to the pathogenesis of AD.     

Comparative assessment of passive surveillance in disease-free and endemic situation: Example of <Emphasis Type="Italic">Brucella melitensis</Emphasis> surveillance in Switzerland and in Bosnia and Herzegovina

Background

Globalization and subsequent growth in international trade in animals and animal products has increased the importance of international disease reporting. Efficient and reliable surveillance systems are needed in order to document the disease status of a population at a given time. In this context, passive surveillance plays an important role in early warning systems. However, it is not yet routinely integrated in the assessment of disease surveillance systems because different factors like the disease awareness (DA) of people reporting suspect cases influence the detection performance of passive surveillance. In this paper, we used scenario tree methodology in order to evaluate and compare the quality and benefit of abortion testing (ABT) for Brucella melitensis (Bm) between the disease free situation in Switzerland (CH) and a hypothetical disease free situation in Bosnia and Herzegovina (BH), taking into account DA levels assumed for the current endemic situation in BH.

Results

The structure and input parameters of the scenario tree were identical for CH and BH with the exception of population data in small ruminants and the DA in farmers and veterinarians. The sensitivity analysis of the stochastic scenario tree model showed that the small ruminant population structure and the DA of farmers were important influential parameters with regard to the unit sensitivity of ABT in both CH and BH. The DA of both farmers and veterinarians was assumed to be higher in BH than in CH due to the current endemic situation in BH. Although the same DA cannot necessarily be assumed for the modelled hypothetical disease free situation as for the actual endemic situation, it shows the importance of the higher vigilance of people reporting suspect cases on the probability that an average unit processed in the ABT-component would test positive.

Conclusion

The actual sensitivity of passive surveillance approaches heavily depends on the context in which they are applied. Scenario tree modelling allows for the evaluation of such passive surveillance system components under assumed disease free situation. Despite data gaps, this is a real opportunity to compare different situations and to explore consequences of changes that could be made.

     

Redox Cycling of Iron Supports Growth and Magnetite Synthesis by Aquaspirillum magnetotacticum

Under anaerobic conditions and in the absence of alternative electron acceptors, growth of the magnetic bacterium Aquaspirillum magnetotacticum MSI was iron concentration dependent. Weak chelation of the iron (with quinate, oxalate, or 2,3-dihydroxybenzoate) enhanced growth, whereas strong chelation (with EDTA, citrate, or nitrilotriacetic acid) retarded the growth of strain MSI relative to that of controls lacking chelators. Growth was proportional to the percentage of unchelated iron in medium containing EDTA in various molar ratios to iron. Addition of the respiratory inhibitors antimycin A (5 μM), NaCN (10 mM), and NaN₃ (10 mM) inhibited growth with Fe(III) or NO₃^- as the terminal electron acceptor. Growth with O₂ and NO₃^- was inhibited by 2-heptyl-4-hydroxyquinolone-N-oxide (HOQNO) but not with 2 mM Fe(III). Under strongly reducing conditions, strain MS1 survived but grew poorly and became irreversibly nonmagnetic. Growth and iron reduction in anaerobic cultures were stimulated by the provision of small amounts of O₂ or H₂O₂. Slow infusion of air to cultures which had reduced virtually all of the Fe(III) in the medium (2 mM) supported a high rate of iron reoxidation (relative to killed controls) and growth in proportion to the amount of iron reoxidized. Oxygen consumption by iron-reducing cultures was predominantly biological, since NaCN and HOQNO both inhibited consumption. Inhibition of oxygen consumption (and iron reoxidation) by the addition of ferrozine and the inhibition of iron oxidation (and oxygen consumption) by the addition of HOQNO suggest that iron oxidation by strain MS1 is an aerobic respiratory process, perhaps tied to energy conservation. Iron oxidation was also necessary for magnetite synthesis, since in microaerobic denitrifying cultures, sequestration of reduced iron by ferrozine present in 10-fold molar excess to the available iron resulted in loss of magnetism and a severe drop in the average magnetosome number of the cells.     

Magnetite and magnetotaxis in microorganisms

Magnetotactic bacteria from freshwater and marine sediments orient and navigate along geomagnetic field lines. Their magnetotactic response is based on intracellular, single magnetic domains of ferrimagnetic magnetite, which impart a permanent magnetic dipole moment to the cell.     

Small deletion variants have stable breakpoints commonly associated with alu elements

Copy number variants (CNVs) contribute significantly to human genomic variation, with over 5000 loci reported, covering more than 18% of the euchromatic human genome. Little is known, however, about the origin and stability of variants of different size and complexity. We investigated the breakpoints of 20 small, common deletions, representing a subset of those originally identified by array CGH, using Agilent microarrays, in 50 healthy French Caucasian subjects. By sequencing PCR products amplified using primers designed to span the deleted regions, we determined the exact size and genomic position of the deletions in all affected samples. For each deletion studied, all individuals carrying the deletion share identical upstream and downstream breakpoints at the sequence level, suggesting that the deletion event occurred just once and later became common in the population. This is supported by linkage disequilibrium (LD) analysis, which has revealed that most of the deletions studied are in moderate to strong LD with surrounding SNPs, and have conserved long-range haplotypes. Analysis of the sequences flanking the deletion breakpoints revealed an enrichment of microhomology at the breakpoint junctions. More significantly, we found an enrichment of Alu repeat elements, the overwhelming majority of which intersected deletion breakpoints at their poly-A tails. We found no enrichment of LINE elements or segmental duplications, in contrast to other reports. Sequence analysis revealed enrichment of a conserved motif in the sequences surrounding the deletion breakpoints, although whether this motif has any mechanistic role in the formation of some deletions has yet to be determined. Considered together with existing information on more complex inherited variant regions, and reports of de novo variants associated with autism, these data support the presence of different subgroups of CNV in the genome which may have originated through different mechanisms.     

1-Amido-1-phenyl-3-piperidinylbutanes — CCR5 antagonists for the treatment of HIV. Part 1

The development of a new class of CCR5 antagonist replacing the tropane core of maraviroc by piperidine with a branched N-substituent is described. Compound 15h shows good whole cell antiviral activity together with microsomal stability and only weak activity at the hERG ion channel.     

1-Amido-1-phenyl-3-piperidinylbutanes – CCR5 antagonists for the treatment of HIV: Part 2

Optimisation of a series of 4-piperidinyltriazoles led to the identification of compound 28a which showed good whole cell antiviral activity, excellent selectivity over the hERG ion channel and complete oral absorption.     

Microbial Transport, Survival, and Succession in a Sequence of Buried Sediments

Abstract Two chronosequences of unsaturated, buried loess sediments, ranging in age from <10,000 years to >1 million years, were investigated to reconstruct patterns of microbial ecological succession that have occurred since sediment burial. The relative importance of microbial transport and survival to succession was inferred from sediment ages, porewater ages, patterns of abundance (measured by direct counts, counts of culturable cells, and total phospholipid fatty acids), activities (measured by radiotracer and enzyme assays), and community composition (measured by phospholipid fatty acid patterns and Biolog substrate usage). Core samples were collected at two sites 40 km apart in the Palouse region of eastern Washington State, near the towns of Washtucna and Winona. The Washtucna site was flooded multiple times during the Pleistocene by glacial outburst floods; the Winona site elevation is above flood stage. Sediments at the Washtucna site were collected from near surface to 14.9 m depth, where the sediment age was approximately 250 ka and the porewater age was 3700 years; sample intervals at the Winona site ranged from near surface to 38 m (sediment age: approximately 1 Ma; porewater age: 1200 years). Microbial abundance and activities declined with depth at both sites; however, even the deepest, oldest sediments showed evidence of viable microorganisms. Same-age sediments had equal quantities of microorganisms, but different community types. Differences in community makeup between the two sites can be attributed to differences in groundwater recharge and paleoflooding. Estimates of the microbial community age can be constrained by porewater and sediment ages. In the shallower sediments (<9 m at Washtucna, <12 m at Winona), the microbial communities are likely similar in age to the groundwater; thus, microbial succession has been influenced by recent transport of microorganisms from the surface. In the deeper sediments, the populations may be considerably older than the porewater ages, since microbial transport is severely restricted in unsaturated sediments. This is particularly true at the Winona site, which was never flooded.