Structural changes in thermoelectric SnSe at high pressures.

The crystal structure of the thermoelectric material tin selenide has been investigated with angle-dispersive synchrotron x-ray powder diffraction under hydrostatic pressure up to 27 GPa. With increasing pressure, a continuous evolution of the crystal structure from the GeS type to the higher-symmetry TlI type was observed, with a critical pressure of 10.5(3) GPa. The orthorhombic high-pressure modification, ß'-SnSe, is closely related to the pseudo-tetragonal high-temperature modification at ambient pressure. The similarity between the changes of the crystal structure at elevated temperatures and at high pressures suggests the possibility that strained thin films of SnSe may provide a route to overcoming the problem of the limited thermal stability of ß-SnSe at high temperatures.

Enhanced thermoelectric performance in TiNiSn-based half-Heuslers.

Thermoelectric figures of merit, ZT > 0.5, have been obtained in arc-melted TiNiSn-based ingots. This promising conversion efficiency is due to a low lattice thermal conductivity, which is attributed to excess nickel in the half-Heusler structure.

Iron spin-reorientation transition in NdFeAsO.

The low-temperature magnetic structure of NdFeAsO has been revisited using neutron powder diffraction and symmetry analysis using the Sarah representational analysis program. Four magnetic models with one magnetic variable for each of the Nd and Fe sublattices were tested. The best fit was obtained using a model with Fe moments pointing along the c-direction, and Nd moments along the a-direction. This signals a significant interplay between rare-earth and transition metal magnetism, which results in a spin-reorientation of the Fe sublattice upon ordering of the Nd moments. All models that fit the data well, including collinear models with more than one magnetic variable per sublattice, were found to have an Fe moment of 0.5 µ(B) and a Nd moment of 0.9 µ(B), demonstrating that the low-temperature Fe moment is not substantially enhanced compared to the spin-density wave state.

Valence bond glass on an fcc lattice in the double Perovskite Ba2YMoO6.

We report on the unconventional magnetism in the cubic B-site ordered double perovskite Ba2YMoO6, using ac and dc magnetic susceptibility, heat capacity and muon spin rotation. No magnetic order is observed down to 2 K while the Weiss temperature is approximately -160 K. This is ascribed to the geometric frustration in the lattice of edge-sharing tetrahedra with orbitally degenerate Mo5+ s=1/2 spins. Our experimental results point to a gradual freezing of the spins into a disordered pattern of spin singlets, quenching the orbital degeneracy while leaving the global cubic symmetry unaffected, and providing a rare example of a valence bond glass.

Reintroduction of Riva-Rocci measurements to determine systolic blood pressure?

INTRODUCTION: In 1896, Riva-Rocci introduced the upper arm cuff to measure systolic blood pressure. In 1905, Nicolai Sergeivich Korotkoff added the auscultatory technique, allowing measurement of both systolic and diastolic blood pressure. Both methods have, to our knowledge, never been formally tested against each other. In this study, we want to fill this gap in history. METHODS: We measured systolic blood pressure by the Korotkoff sound technique and approximated the Riva-Rocci technique by measuring cuff pressure at the moment that the first pulsation became visible in Finapres readings, at the finger. This proxy of the Riva-Rocci technique allows an objective, offline, analysis. Measurements were performed simultaneously on the same arm in 57 subjects. RESULTS: Systolic blood pressure measured by the Korotkoff sound technique was 167+/-30 mmHg (mean +/-SD ). Systolic blood pressure according to the Riva-Rocci technique was 165+/-32 mmHg. The Riva-Rocci technique underestimated measurements with the Korotkoff technique by 1.8+/-4.4 mmHg (NS, p=0.79). CONCLUSION: Riva-Rocci measurements of systolic blood pressure may be as good as the traditionally used Korotkoff measurements.

Bactericidal effects of a fusion protein of llama heavy-chain antibodies coupled to glucose oxidase on oral bacteria.

Enzymes such as lactoperoxidase and glucose oxidase (GOx) are used as antimicrobial agents in oral care products. Their low specificities and substantiveness can be reduced by covalent coupling of antimicrobial molecules to antibodies. Variable domains (V(HH)) derived from llama heavy-chain antibodies are particularly suited for such an approach. The antibodies are composed solely of heavy-chain dimers; therefore, production of active fusion proteins by using molecular biology-based techniques is less complicated than production by use of conventional antibodies. In this study, a fusion protein consisting of V(HH) and GOx was constructed and expressed by Saccharomyces cerevisiae. A llama was immunized with Streptococcus mutans strain HG982. Subsequently, B lymphocytes were isolated and cDNA fragments encoding the V(HH) fragments were obtained by reverse transcription-PCR. After construction of a V(HH) library in Escherichia coli and screening of the library against mutans group streptococci and Streptococcus sanguinis strains, we found two V(HH) fragments with high specificities for S. mutans strains. A GOx gene was linked to the two V(HH) genes and cloned into S. cerevisiae yeasts. The yeasts expressed and secreted the recombinant proteins into the growth medium. The test of binding of fusion proteins to oral bacteria through their V(HH) fragments showed that S. mutans had been specifically targeted by GOx-S120, one of the fusion protein constructs. A low concentration of the fusion protein was also able to selectively kill S. mutans within 20 min in the presence of lactoperoxidase and potassium iodide. These findings demonstrate that the fusion protein GOx-V(HH) is potentially valuable in the selective killing of target bacteria such as S. mutans.

Benefits of high altitude allergen avoidance in atopic adolescents with moderate to severe asthma, over and above treatment with high dose inhaled steroids.

Some patients with severe asthma cannot be controlled with high doses of inhaled steroids (ICS), which may be related to ongoing environmental allergen exposure. We investigated whether 10 weeks of high altitude allergen avoidance leads to sustained benefits regarding clinical and inflammatory markers of disease control in adolescents with persistent asthma despite treatment with high dose ICS. Eighteen atopic asthmatic adolescents (12-18 yr, 500-2000 microg ICS daily) with established house dust mite allergy, participated in a parallel-group study. Quality of life (PAQL), lung function, bronchial hyperresponsiveness (BHR) to adenosine and histamine, induced sputum and urine samples were collected repeatedly from 10 patients during a 10-week admission period to the Swiss Alps (alt. 1560 m) and at 6 weeks after return to sea level. Results were compared with those in eight patients, studied in their home environment at sea level for a similar time period. Throughout the study, asthma medication remained unchanged in both groups. During admission to high altitude, PAQL, lung function, BHR to adenosine and histamine, and urinary levels of eosinophil protein X (U-EPX), leukotriene E4 (U-LTE4) and 9alpha11beta prostaglandin F2 (U-9alpha11beta PGF2) improved significantly (P < 0.05), with a similar tendency for sputum eosinophils (P < 0.07). Furthermore, the changes in PAQL and BHR to adenosine and histamine were greater in the altitude than in the control group (P < 0.05). At 6 weeks after renewed allergen exposure at sea level, the improvements in PAQL (P < 0.05), BHR to adenosine (P < 0.07) and histamine (P < 0.05), as well as U-EPX (P < 0.05) and U-LTE4 (P < 0.05) were maintained. A short period of high altitude allergen avoidance, on top of regular treatment with ICS and long-acting beta2-agonists, results in improvement of asthma, as assessed by clinical and inflammatory markers of disease severity. These findings indicate that short-term, rigorous allergen avoidance can improve the long-term control of severe asthma over and above what can be achieved even by high doses of inhaled steroids.

Isolation of antigen specific llama VHH antibody fragments and their high level secretion by Saccharomyces cerevisiae.

Recently the existence of 'heavy chain' immunoglobulins in Camelidae has been described. However, as yet there is no data on the binding of this type of antibody to haptens. In addition, it was not a priori predictable whether the binding domains (VHH) of these antibodies could be produced and secreted by the lower eukaryotic micro-organism Saccharomyces cerevisiae. In the present study these questions are addressed. Heavy chain immunoglobulins directed against two hapten molecules, the azo-dyes RR6 and RR120 as well as the (proteinaceous) human pregnancy hormone, have been raised in Lama glama. We were able to select specific VHH fragments for all three antigens by direct screening of Escherichia coli or yeast libraries, even without prior enrichment via bio-panning. This is the first example of the isolation of llama anti-hapten VHH domains. Surprisingly, the affinities of the llama VHHs for the RR6 hapten obtained in this way are in the low nM range. Furthermore, some of the antigen specific VHHs were secreted by S. cerevisiae at levels over 100 mg l-1 in shake flask cultures. These two findings extend the possible application areas for the llama VHH fragments significantly.

Induced sputum in adolescents with severe stable asthma. Safety and the relationship of cell counts and eosinophil cationic protein to clinical severity.

This study examined the safety of sputum induction and the relation between sputum cell counts and clinical parameters in adolescents with severe persistent asthma. Within 5 days, induced sputum and reversibility in forced expiratory volume in one second (FEV1), quality of life, provocative concentration causing a 20% fall in FEV1 (PC20) of adenosine monophosphate and histamine, exercise-induced bronchoconstriction, overall asthma severity index, and blood eosinophils were collected in 20 atopic adolescents with moderate-to-severe persistent asthma (12-18 yrs of age, FEV1 65-110% of predicted, on 500-2,000 microg inhaled steroids daily). FEV1 was reversible by 13.3-2.3% pred. After sputum induction, FEV1 was still increased by 9.0+/-2.6% pred as compared to the pre-salbutamol baseline. Sputum contained, median (range): 12.4 (0.4-59.5)% squamous cells, 47.3 (6.8-84.0)% macrophages, 39.0 (4.6-84.8)% neutrophils, 4.8 (1.0-12.4)% lymphocytes, 0.4 (0-10.8)% eosinophils and 3.6 (0-23.4)% bronchial epithelial cells. Sputum eosinophils showed a trend towards a significant association with the overall asthma severity index (r=0.46, p=0.06) and correlated inversely with baseline FEV1 (r=-0.51, p=0.03). In conclusion, sputum can be induced safely in adolescents with moderate-to-severe persistent asthma, if pretreated with beta2-agonists. Despite relatively low sputum eosinophil counts in these patients on inhaled steroids, the association of eosinophil numbers with baseline forced expiratory volume in one second and asthma severity index favours a role of induced sputum in monitoring adolescents with severe asthma.

Differences in the effect of allergen avoidance on bronchial hyperresponsiveness as measured by methacholine, adenosine 5'-monophosphate, and exercise in asthmatic children.

Asthma is now considered as an inflammatory airway disease. There is evidence that allergen avoidance reduces clinical symptoms in atopic asthma. We investigated the effect of a month's stay in the hypoallergenic environment of Davos, Switzerland (1560 m) which is relatively free of house dust mite (HDM) on changes in bronchial hyperresponsiveness (BHR), using the challenge tests of adenosine 5'-monophosphate (AMP), exercise and methacholine to test for BHR. Thirteen asthmatic children with an allergy to HDM participated in the study. We measured BHR on admission to the Davos Asthma Center and after 1 month in the house dust-free environment. The medications used by the patients at the time of admission were kept unchanged during this month. No significant difference in BHR was found to methacholine challenge after a 1-month stay at high altitude (P > 0.05). By contrast, the response to AMP was significantly different as indicated by displacement of the dose-response curve to the right by 2.15 doubling concentrations (P = 0.005). We also observed a significant difference in response to exercise (P = 0.03). These results indicate that a month's stay in a hypoallergenic environment caused a reduction in BHR to AMP and exercise, but not to methacholine. In addition, the results support the concept of differences in trigger mechanisms for BHR, and that responses to a methacholine challenge are not the same as responses to an exercise challenge. The observed reduction in BHR in asthmatic children to the indirect bronchial stimuli of AMP and exercise suggest reduced airway inflammation following avoidance of house dust aeroallergens. AMP and exercise challenges may therefore be better indicators of asthmatic airway inflammation than the direct stimulus of methacholine.

Effect of allergen avoidance at high altitude on direct and indirect bronchial hyperresponsiveness and markers of inflammation in children with allergic asthma.

BACKGROUND: Improvement of allergic asthma is seen at high altitude partly because of low concentrations of allergen, especially house dust mite. To investigate the effect of a hypoallergenic environment (Davos, 1560 m) on airways inflammation, the changes in bronchial hyperresponsiveness measured with methacholine and adenosine 5'-monophosphate (AMP), blood eosinophils, eosinophil cationic protein (ECP), and serum IgE were studied. METHODS: In 16 allergic asthmatic children tests were performed on admission and after one month. Medication was kept unchanged during the month of investigation and the patients performed peak expiratory flow (PEF) measurements twice daily. RESULTS: After one month at high altitude a considerable improvement was seen in the provocative concentration of AMP causing a 20% fall in forced expiratory volume in one second (PC20 AMP), but not with methacholine. There was also a reduction in total blood eosinophils and ECP. No change in serum IgE was observed. Peak flow variability decreased. CONCLUSIONS: After one month at high altitude a reduction in airways inflammation occurs. The results indicate that AMP responsiveness is a more accurate marker of disease activity in relation to inflammation in asthma than methacholine. The benefits of allergen avoidance at high altitude have important clinical implications for children with allergic asthma.

An accessory gene, lipB, required for the production of active Pseudomonas glumae lipase.

Pseudomonas glumae PG1 is able to secrete lipase into the extracellular medium. The lipase is produced as a precursor protein, with an N-terminal signal sequence. A second open reading frame (ORF) was found immediately downstream of the lipase structural gene, lipA, a situation found for the lipases of some other Pseudomonas species. Inactivation of this ORF resulted in a lipase-negative phenotype, indicating its importance in the production of active extracellular lipase. The ORF, lipB, potentially encodes a protein of 353-amino-acid residues, having a hydrophobic N-terminal (amino acids 1 to 90) and a hydrophilic C-terminal part. As a first step in determining the role of LipB, its subcellular location was determined. The protein was found to fractionate with the inner membranes. The expression of fusions of lipB fragments with phoA revealed an N(in)-C(out) topology for the LipB protein, which was confirmed by protease accessibility studies on EDTA-permeabilized cells and on inverted inner membrane vesicles. These and other results indicate that most of the LipB polypeptide is located in the periplasm and anchored to the inner membrane by an N-terminal transmembrane helix, located between amino acids 19 and 40.

Isolation of a salt-inducible gene from rice and its molecular cloning.

The genomic sequences of a salt inducible gene of rice have been isolated from both Indica and Japonica varieties of rice. The cDNA of this gene, SalT, characterized earlier shows sequence identity with both the genomic sequences. Approximately 750 base pairs of intervening sequence is present in the 1.2kb genomic sequence, obtained by PCR. There is a high degree of homology between the Indica and Japonica SalT genes except for the presence of an extra HindIII site in the former. A genomic library of Indica rice was screened and a phage clone of the SalT gene was partially characterized. Different species of monocot and dicot plant DNA showed sequence homology with SalT gene.

Cloning of the Pseudomonas glumae lipase gene and determination of the active site residues.

The lipA gene encoding the extracellular lipase produced by Pseudomonas glumae PG1 was cloned and characterized. A sequence analysis revealed an open reading frame of 358 codons encoding the mature lipase (319 amino acids) preceded by a rather long signal sequence of 39 amino acids. As a first step in structure-function analysis, we determined the Ser-Asp-His triad which makes up the catalytic site of this lipase. On the basis of primary sequence homology with other known Pseudomonas lipases, a number of putative active site residues located in conserved areas were found. To determine the residues actually involved in catalysis, we constructed a number of substitution mutants for conserved Ser, Asp, and His residues. These mutant lipases were produced by using P. glumae PG3, from which the wild-type lipase gene was deleted by gene replacement. By following this approach, we showed that Ser-87, Asp-241, and His-285 make up the catalytic triad of the P. glumae lipase. This knowledge, together with information on the catalytic mechanism and on the three-dimensional structure, should facilitate the selection of specific modifications for tailoring this lipase for specific industrial applications.

Molecular cloning and characterization of a gene coding for methanol oxidase in Hansenula polymorpha.

The structural gene and the regulatory DNA sequence of the yeast Hansenula polymorpha methanol oxidase have been isolated. According to the nucleotide sequence data obtained, the structural gene encodes a 664 amino acids long protein, contains no intervening sequences, and the 5'- and 3'-non-coding region contains several sequences implicated in transcription initiation and termination in the yeast Saccharomyces cerevisiae. Although the methanol oxidase is translocated to the peroxisomes, no cleavable signal sequence was found at the N-terminus of the protein.