How does hydroxyl introduction influence the double helical structure: the stabilization of an altritol nucleic acid:ribonucleic acid duplex

Altritol nucleic acids (ANAs) are a promising new tool in the development of artificial small interfering ribonucleic acids (siRNAs) for therapeutical applications. To mimic the siRNA:messenger RNA (mRNA) interactions, the crystal structure of the ANA:RNA construct a(CCGUAAUGCC-P):r(GGCAUUACGG) was determined to 1.96?? resolution which revealed the hybrid to form an A-type helix. As this A-form is a major requirement in the RNAi process, this crystal structure confirms the potential of altritol-modified siRNAs. Moreover, in the ANA strands, a new type of intrastrand interactions was found between the O2' hydroxyl group of one residue and the sugar ring O4' atom of the next residue. These interactions were further investigated by quantum chemical methods. Besides hydration effects, these intrastrand hydrogen bonds may also contribute to the stability of ANA:RNA duplexes.     

Temporal variability of top-down forces and their role in host choice evolution of phytophagous arthropods

The role of top-down forces in host choice evolution of phytophagous arthropods is the subject of a vividly animated debate. Empirical evidence for the evolutionary role of top-down forces comes from studies showing that phytophagous arthropods prefer hosts that entail enemy-free space. The aim of this paper is to draw the attention of plant–arthropod researchers to the potentially, temporally variable nature of third trophic level effects. We show that this aspect is largely neglected in studies on enemy-free space, despite the fact that relative enemy impact varies seasonally among plants in at least some studies. We conclude that rigorous testing of the enemy-free space hypothesis can only be performed when within and between season variation in higher trophic level effects is taken into account.     

Opiate receptor blockade in man reduces 2-deoxy-d-glucose-induced food intake but not hunger,thirst, and hypothermia

Opioid peptides may act as neuromodulators in the central nervous system to conserve energy stores and water in mammals. To examine this hypothesis in man, the effect of opiate receptor blockade with naloxone on the hunger, thirst, and hypothermic response to 2-deoxy-D-glucose-induced glucoprivic stress was assessed. Opiate receptor blockade decreased stress-induced food intake but did not reduce marked increases in hunger produced by glucoprivation. Naloxone infusions did not change the hypercortisolemic, polydipsic, hypothermic, and thermogenic response to 2-deoxy-D-glucose. While these results do not suggest a major role for a β-endorphin modulation of stress-induced hunger, hypothermia and water conservation, the reduction of food intake could be due to augmented satiety, perhaps associated with retardation of gastric emptying during opiate receptor blockade.     

Isoform-Specific Attachment of Osteoprogenitors to Laminins: Mapping to the Short Arms of Laminin-1

The recruitment of osteoblast progenitors involves their migration and attachment to the sites of bone formation through interactions with matrix proteins. In a time-limited cell attachment assay, coated laminin-1 inhibits the adhesion of most rat calvaria cells but attaches specifically to osteoprogenitors, as quantified by the number of bone colonies (nodules) formed in the cultures. In order to determine the molecular mechanisms involved in osteoprogenitor attachment to laminin-1, we investigated the effects of laminin-5, a N-truncated laminin variant. In contrast to laminin-1, laminin-5 increased (1.5-fold) rat calvaria cell attachment and did not display any specific affinity for osteoprogenitors. In competition experiments on laminin-5, blocking antibodies directed against either the integrin chain beta1 or the C-terminal portion of laminin-5, as well as thermic denaturation of the protein at 80 degrees C, inhibited rat calvaria cell attachment, suggesting the implication of integrin alpha3beta1 binding to the conformation-dependent C-terminal end of laminin-5. Stepwise thermic denaturation did not suppress the anti-adhesive activity of laminin-1, while osteoprogenitor recruitment was abolished after denaturation above 60 degrees C, suggesting that different domains are involved in these two effects. The anti-beta1 antibody further decreased RC cell attachment to laminin-1, providing evidence for concomitant anti-adhesive and beta1-dependent cell attachment activities. Blocking of beta1 integrin subunit did not, however, reduce osteoprogenitor recruitment. Finally, purified elastase digestion fragment E1+, encompassing the N-terminal short arms of laminin-1, reproduced the effects of the complete molecule in the assay, while C-terminal fragment E8 did not display any cell attachment or osteoprogenitor recruitment properties. In conclusion, the anti-adhesive and osteoprogenitor-selective effects of laminin-1 on rat calvaria cell populations are distinct, beta1-integrin-independent properties mapping to the short arms of the molecule and thus not displayed by the truncated laminin-5.     

Development of a selective and sensitive polymerase chain reaction assay for the detection of Mycoplasma pirum

Abstract A new assay using the polymerase chain reaction to amplify a 173-nucleotide DNA fragment within the 16S ribosomal RNA gene of Mycoplasma pirum has been developed. The assay selectively amplified DNA from all strains of M. pirum tested with a high level of sensitivity, even in a context of human DNA. DNA from other mollicute species, including those closely related to M. pirum , from bacteria phylogenetically close to mollicutes ( Clostridium innocuum, C. ramosum and Bacillus subtilis ), from Escherichia coli and from human peripheral blood mononuclear cells, did not produce the amplified DNA product specific for M. pirum .     

Estimation of Vaccine Efficacy in Non-Randomly Mixing Populations

A deterministic model for the transmission of an acute infectious disease in a heterogeneous, nonrandomly mixing population is developed. This model facilitates the estimation of transmission probabilities from the observed attack rates. If some of the members of the population are vaccinated, then the vaccine efficacy (VE), defined as the relative reduction in the transmission probability due to vaccination, can be estimated. We provide several estimators of VE, depending on the amount of information available on the mixing pattern and on the action of the vaccine. We show that if vaccinated persons increase the frequency of their contacts with infectious persons, then estimators ignoring this change in behavior may substantially underestimate the VE.     

Analysis of splicing patterns by pyrosequencing

Several different mRNAs can be produced from a given pre-mRNA by regulated alternative splicing, or as the result of deregulations that may lead to pathological states. Analysing splicing patterns is therefore of importance to describe and understand developmental programs, cellular responses to internal or external cues, or human diseases. We describe here a method, Pyrosequencing Analysis of Splicing Patterns (PASP), that combines RT–PCR and pyrosequencing of PCR products. We demonstrated that: (i) Ratios of two pure RNAs mixed in various proportions were accurately measured by PASP; (ii) PASP can be adapted to virtually any splicing event, including mutually exclusive exons, complex patterns of exon skipping or inclusion, and alternative 3′ terminal exons; (iii) In extracts from different organs, the proportions of RNA isoforms measured by PASP reflected those measured by other methods. The PASP method is therefore reliable for analysing splicing patterns. All steps are done in 96-wells microplates, without gel electrophoresis, opening the way to high-throughput comparisons of RNA from several sources.