Exploring the effect of aminoglycoside guanidinylation on ligands for Tau exon 10 splicing regulatory element RNA

We describe the effect of guanidinylation of the aminoglycoside moiety on acridine-neamine-containing ligands for the stem-loop structure located at the exon 10-5′-intron junction of Tau pre-mRNA, an important regulatory element of tau gene alternative splicing. On the basis of dynamic combinatorial chemistry experiments, ligands that combine guanidinoneamine and two different acridines were synthesized and their RNA-binding properties were compared with those of their amino precursors. Fluorescence titration experiments and UV-monitored melting curves revealed that guanidinylation has a positive effect both on the binding affinity and specificity of the ligands for the stemloop RNA, as well as on the stabilization of all RNA sequences evaluated, particularly some mutated sequences associated with the development of FTDP-17 tauopathy. However, this correlation between binding affinity and stabilization due to guanidinylation was only found in ligands containing a longer spacer between the acridine and guanidinoneamine moieties, since a shorter spacer produced the opposite effect (e.g. lower binding affinity and lower stabilization). Furthermore, spectroscopic studies suggest that ligand binding does not significantly change the overall RNA structure upon binding (circular dichroism) and that the acridine moiety might intercalate near the bulged region of the stem->loop structure (UV-Vis and NMR spectroscopy).

Combined intermittent hypoxia and surface muscle electrostimulation as a method to increase peripheral blood progenitor cell concentration.

Background: Our goal was to determine whether short-term intermittent hypoxia exposure, at a level well tolerated by healthy humans and previously shown by our group to increase EPO and erythropoiesis, could mobilizehematopoietic stem cells (HSC) and increase their presence in peripheral circulation. Methods: Four healthy male subjects were subjected to three different protocols: one with only a hypoxic stimulus (OH), another with a hypoxic stimulus plus muscle electrostimulation (HME) and the third with only muscle electrostimulation (OME). Intermittent hypobaric hypoxia exposureconsisted of only three sessions of three hours at barometric pressure 540 hPa (equivalent to an altitude of 5000 m) for three consecutive days, whereas muscular electrostimulation was performed in two separate periods of 25 min in each session. Blood samples were obtained from an antecubital vein on three consecutive days immediately before the experiment and 24 h, 48 h, 4 days and 7 days after the last day of hypoxic exposure. Results: There was a clear increase in the number of circulating CD34+ cells after combined hypobaric hypoxia and muscular electrostimulation. This response was not observed after the isolated application of the same stimuli. Conclusion: Our results open a new application field for hypobaric systems as a way to increase efficiency in peripheral HSC collection.

Combined intermittent hypoxia and surface muscle electrostimulation as a method to increase peripheral blood progenitor cell concentration.

Background: Our goal was to determine whether short-term intermittent hypoxia exposure, at a level well tolerated by healthy humans and previously shown by our group to increase EPO and erythropoiesis, could mobilizehematopoietic stem cells (HSC) and increase their presence in peripheral circulation. Methods: Four healthy male subjects were subjected to three different protocols: one with only a hypoxic stimulus (OH), another with a hypoxic stimulus plus muscle electrostimulation (HME) and the third with only muscle electrostimulation (OME). Intermittent hypobaric hypoxia exposureconsisted of only three sessions of three hours at barometric pressure 540 hPa (equivalent to an altitude of 5000 m) for three consecutive days, whereas muscular electrostimulation was performed in two separate periods of 25 min in each session. Blood samples were obtained from an antecubital vein on three consecutive days immediately before the experiment and 24 h, 48 h, 4 days and 7 days after the last day of hypoxic exposure. Results: There was a clear increase in the number of circulating CD34+ cells after combined hypobaric hypoxia and muscular electrostimulation. This response was not observed after the isolated application of the same stimuli. Conclusion: Our results open a new application field for hypobaric systems as a way to increase efficiency in peripheral HSC collection.

The clc element of Pseudomonas sp. strain B13, a genomic island with various catabolic properties.

Pseudomonas sp. strain B13 is a bacterium known to degrade chloroaromatic compounds. The properties to use 3- and 4-chlorocatechol are determined by a self-transferable DNA element, the clc element, which normally resides at two locations in the cell's chromosome. Here we report the complete nucleotide sequence of the clc element, demonstrating the unique catabolic properties while showing its relatedness to genomic islands and integrative and conjugative elements rather than to other known catabolic plasmids. As far as catabolic functions, the clc element harbored, in addition to the genes for chlorocatechol degradation, a complete functional operon for 2-aminophenol degradation and genes for a putative aromatic compound transport protein and for a multicomponent aromatic ring dioxygenase similar to anthranilate hydroxylase. The genes for catabolic functions were inducible under various conditions, suggesting a network of catabolic pathway induction. For about half of the open reading frames (ORFs) on the clc element, no clear functional prediction could be given, although some indications were found for functions that were similar to plasmid conjugation. The region in which these ORFs were situated displayed a high overall conservation of nucleotide sequence and gene order to genomic regions in other recently completed bacterial genomes or to other genomic islands. Most notably, except for two discrete regions, the clc element was almost 100% identical over the whole length to a chromosomal region in Burkholderia xenovorans LB400. This indicates the dynamic evolution of this type of element and the continued transition between elements with a more pathogenic character and those with catabolic properties.

Muscle moment-arms: a key element in muscle-force estimation.

A clear and rigorous definition of muscle moment-arms in the context of musculoskeletal systems modelling is presented, using classical mechanics and screw theory. The definition provides an alternative to the tendon excursion method, which can lead to incorrect moment-arms if used inappropriately due to its dependency on the choice of joint coordinates. The definition of moment-arms, and the presented construction method, apply to musculoskeletal models in which the bones are modelled as rigid bodies, the joints are modelled as ideal mechanical joints and the muscles are modelled as massless, frictionless cables wrapping over the bony protrusions, approximated using geometric surfaces. In this context, the definition is independent of any coordinate choice. It is then used to solve a muscle-force estimation problem for a simple 2D conceptual model and compared with an incorrect application of the tendon excursion method. The relative errors between the two solutions vary between 0% and 100%.

Organic acids in the rhizosphere and phytoavailability of sewage sludge-borne trace elements

The aim of this work was to quantify low molecular weight organic acids in the rhizosphere of plants grown in a sewage sludge-treated media, and to assess the correlation between the release of the acids and the concentrations of trace-elements in the shoots of the plants. The species utilized in the experiment were cultivated in sand and sewage sludge-treated sand. The acetic, citric, lactic, and oxalic acids, were identified and quantified by high performance liquid chromatography in samples collected from a hydroponics system. Averages obtained from each treatment, concentration of trace elements in shoots and concentration of organic acids in the rhizosphere, were compared by Tukey test, at 5% of probability. Linear correlation analysis was applied to verify an association between the concentrations of organic acids and of trace elements. The average composition of organic acids for all plants was: 43.2, 31.1, 20.4 and 5.3% for acetic, citric, lactic, and oxalic acids, respectively. All organic acids evaluated, except for the citric acid, showed a close statistical agreement with the concentrations of Cd, Cu, Ni, and Zn found in the shoots. There is a positive relationship between organic acids present in the rhizosphere and trace element phytoavailability.

Electron microscopic visualization of protein-DNA interactions at the estrogen responsive element and in the first intron of the Xenopus laevis vitellogenin gene.

Stable protein-DNA complexes can be assembled in vitro at the 5' end of Xenopus laevis vitellogenin genes using extracts of nuclei from estrogen-induced frog liver and visualized by electron microscopy. Complexes at the three following sites can be identified on the gene B2: the transcription initiation site, the estrogen responsive element (ERE) and in the first intron. The complex at the transcription initiation site is stabilized by dinucleotides and thus represents a ternary transcription complex. The formation of the complexes at the two other sites is enhanced by estrogen and is reduced by tamoxifen, an antagonist of estrogen, while this latter effect is reversed by adding an excess of hormone. No sequence homology is apparent between the site containing the ERE and the binding site in intron I and functional tests in MCF-7 cells suggest that these two sites are not equivalent. Finally, we made use of previously characterized deletion mutants of the 5' flanking region of the gene B1, a close relative of the gene B2, to demonstrate that the 13-bp palindromic core element of the ERE is involved in the formation of the complexes observed upstream of the transcription initiation site.

Drug concentration response relationships in normal volunteers after oral administration of losartan, an angiotensin II receptor antagonist.

The aim of this study was to investigate the relationships between plasma concentrations of losartan, an orally active angiotensin II inhibitor, its active metabolite EXP3174, and angiotensin II blockade. Six healthy subjects received single oral doses of 40, 80, or 120 mg losartan and placebo at 1-week intervals in a crossover study. Angiotensin II blockade was assessed by the blood pressure response to exogenous angiotensin II before and after losartan administration. EXP3174 reached higher plasma concentrations and was eliminated more slowly than its parent compound; its levels paralleled the profile of angiotensin II blockade closer than losartan. Inhibition of the pressure response was dose dependent. The Hill-shaped relationship between response and EXP3174 concentration (or time-integrated variables) approached a plateau with 80 mg. The dose-dependent increase in plasma renin and angiotensin II exhibited a considerable individual scatter. We conclude that losartan produces a dose-dependent, effective angiotensin II blockade that is largely determined by the active metabolite EXP3174.

The clc element and related genomic islands in Proteobacteria

Genomic islands are large DNA segments, present in most bacterial genome, that are acquired via horizontal gene transfer and contribute to the rapid bacterial evolution and adaptation of the host cell. Here we focus on the clc element (or ICEclc), a 103‑kb genomic island first discovered in Pseudomonas knackmussii B13, as a model of this diverse group of mobile genetic elements. ICEclc is normally integrated in the host bacterial chromosome but can excise and transfer to a new host by conjugation. In this chapter we review the basic features of ICEclc, the mechanisms of its life‑style as well as evolutionary relationships with other known and unknown elements in a variety of Proteobacteria.

Trace element distribution among rock-forming minerals from metamorphosed to partially molten basic igneous rocks in a contact aureole (Fuerteventura, Canaries)

Low pressure partial melting of basanitic and ankaramitic dykes gave rise to unusual, zebra-like migmatites, in the contact aureole of a layered pyroxenite-gabbro intrusion, in the root zone of an ocean island (Basal Complex, Fuerteventura, Canary Islands). These migmatites are characterised by a dense network of closely spaced, millimetre-wide leucocratic segregations. Their mineralogy consists of plagioclase (An(32-36)), diopside, biotite, oxides (magnetite, ilmenite), +/-amphibole, dominated by plagioclase in the leucosome and diopside in the melanosome. The melanosome is almost completely recrystallised, with the preservation of large, relict igneous diopside phenocrysts in dyke centres. Comparison of whole-rock and mineral major- and trace-element data allowed us to assess the redistribution of elements between different mineral phases and generations during contact metamorphism and partial melting. Dykes within and outside the thermal aureole behaved like closed chemical systems. Nevertheless, Zr, Hf, Y and REEs were internally redistributed, as deduced by comparing the trace element contents of the various diopside generations. Neocrystallised diopside - in the melanosome, leucosome and as epitaxial phenocryst rims - from the migmatite zone, are all enriched in Zr, Hf, Y and REEs compared to relict phenocrysts. This has been assigned to the liberation of trace elements on the breakdown of enriched primary minerals, kaersutite and sphene, on entering the thermal aureole. Major and trace element compositions of minerals in migmatite melanosomes and leucosomes are almost identical, pointing to a syn- or post-solidus reequilibration on the cooling of the migmatite terrain i.e. mineral-melt equilibria were reset to mineral-mineral equilibria. (C) 2007 Elsevier B.V. All rights reserved.