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Biomedical subjects

G Wagner

Publications and source records attributed to G Wagner.

At least 55 records · Page 3Linked to original sources
PubMed2001

[2 + 3] cycloaddition of nitrones to platinum-bound organonitriles: effect of metal oxidation state and of nitrile substituent.

The ligated benzonitriles in the platinum(II) complex [PtCl2(PhCN)2] undergo metal-mediated [2 + 3] cycloaddition with nitrones -ON+(R3)=C(R1)(R2) [R1/R2/R3 = H/Ph/Me, H/p-MeC6H4/Me, H/Ph/CH2Ph] to give delta 4-1,2,4-oxadiazoline complexes, [PtCl2(N=C(Ph)O-N(R3)-C(R1)(R2))2] (2a, 4a, 6a), as a 1:1 mixture of two diastereoisomers, in 60-75% yields, while [PtCl2(MeCN)2] is inactive toward the addition. However, a strong activation of acetonitrile was reached by application of the platinum(IV) complex [PtCl4(MeCN)2] and both [PtCl4(RCN)2] (R = Me, Ph) react smoothly with various nitrones to give [PtCl4(N=C(R)O-N(R3)-C(R1)(R2))2] (1b-6b). The latter were reduced to the corresponding platinum(II) complexes [PtCl2(N=C(R)O-N(R3)-C(R1)(R2))2] (1a-6a) by treatment with PhCH2NHOH, while the reverse reaction, i.e. conversion of 1a-6a to 1b-6b, was achieved by chlorination with Cl2. The diastereoisomers of [PtCl2(N=C(R)O-N(R3)-C(R1)(R2))2] (1a-6a) exhibit different kinetic labilities, and liberation of the delta 4-1,2,4-oxadiazolines by substitution with 1,2-bis(diphenylphosphino)ethane (dppe) in CDCl3 proceeds at different reaction rates to give free N=C(R)O-N(R3)-C(R1)(R2) and [PtCl2(dppe)] in almost quantitative NMR yield. All prepared compounds were characterized by elemental analyses, FAB mass spectrometry, and IR and 1H, 13C(1H), and 195Pt (metal complexes) NMR spectroscopies; X-ray structure determination of the first (delta 4-1,2,4-oxadiazoline)Pt(II) complexes was performed for (S,S)/(R,R)-rac-[PtCl2(N=C(Me)O-N(Me)-C(H)Ph)2] (1a) (a = 9.3562(4), b = 9.8046(3), c = 13.1146(5) A; alpha = 76.155(2), beta = 83.421(2), gamma = 73.285(2) degrees; V = 1117.39(7) A3; triclinic, P1, Z = 2), (R,S)-meso-[PtCl2(N=C(Ph)O-N(Me)-C(H)Ph)2] (2a) (a = 8.9689(9), b = 9.1365(5), c = 10.1846(10) A; alpha = 64.328(6), beta = 72.532(4), gamma = 67.744(6) degrees; V = 686.82(11) A3; triclinic, P1, Z = 1), (S,S)/(R,R)-rac-[PtCl2(N=C(Me)O-N(Me)-C(H)(p-C6H4Me))2] (3a) (a = 11.6378(2), b = 19.0767(7), c = 11.5782(4) A; beta = 111.062(2) degrees; V = 2398.76(13) A3; monoclinic, P2(1)/c, Z = 4), and (S,S)/(R,R)-rac-[PtCl2(N=C(Me)O-N(CH2Ph)-C(H)Ph2] (5a) (a = 10.664(2), b = 10.879(2), c = 14.388(3) A; alpha = 73.11(3), beta = 78.30(3), gamma = 88.88(3) degrees; V = 1562.6(6) A3; triclinic, P1, Z = 2).

Journal Article↗
PubMed2001

Description of the test area and reference sampling at Dornach.

The selected test area for the comparative evaluation of European methods on sampling and sample preparation of soils (CEEM Soil) at Dornach near Basel (Switzerland) is located at approximately 400 m a.S.l. on the north-west rolling footslope of the Jura mountain chain that has a temperate climate. The area is known to be airborne polluted by emissions of a non-ferrous metal recycling plant. The geology is dominated by Jurassic limestone and (decarbonated) loess loam. The land use is deciduous forest (beech, oak) in the upper part and traditional cherry orchards with permanent grassland which have mostly been converted into arable land. The detailed soil survey distinguishes four different soil mapping units in the test area of 0.61 ha. The reference sampling was performed in a 190-m-long and 20-40 m large transect area following four devices: (1) composite samples (0-10 cm and 0-20 cm), each from 25 stratified single samples of 61 squares of 10 x 10 m; (2) hypotheses and soil horizon-based composite samples at nine locations; (3) horizon-related samples from the four described soil profiles representing the mapping units; and (4) three soil cores with 5-cm interval samples taken in the major land use units. Altogether 301 reference soil samples were taken.

Environmental Monitoring↗
PubMed2001

Analytical aspects of the CEEM soil project.

In the past, exercises aiming at an assessment of data uncertainty in environmental analysis were usually restricted to the analysis step, while sampling and pre-analytical sample treatment was largely ignored. Collaborative studies on the quantification of sampling errors require, besides a suitable and well characterized test site, the availability of a reference laboratory for the analysis of all of the samples taken in the context of the study by all participants and also test methods which do not contribute large and variable uncertainties due to long and complex analytical methodologies. Here we summarize the major analytical aspects of a European project on the identification and quantification of sampling influences on the determination of lead, cadmium, copper and zinc in soil. The participant group included the leading soil analysis laboratories in Europe; the test site at Dornach (CH) was well suited for the purpose and showed high metal gradients and differentiated land use. The analytical methods (wavelength-dispersive X-ray fluorescence spectrometry and solid-state Zeeman AAS) used in the study showed stable performance characteristics within the confidence interval of the certified reference materials used for the measurement quality control over the entire project period. Additionally, double-blind tests on split samples showed agreement of data in very narrow limits thus demonstrating the reliability of the reference database.

Databases, Factual↗
PubMed2001

European soil sampling guidelines for soil pollution studies.

The soil sampling guidelines used in European countries (ESSG), as kindly provided by the national institutions which participated in the project, have been recorded, studied, evaluated and presented in this paper. The aim has been to ascertain what soil sampling guidelines exist in Europe; to detect similarities and differences (comparable results), advantages and deficiencies; to identify incompatible strategies and evaluate how methodologies might affect data quality; to investigate sources of deviations or uncertainties; to improve comparability and representativeness of soil sampling; to investigate the need for harmonised sampling guidelines; and to develop suggestions for standard operating procedures (SOP). Soil sampling guidelines throughout Europe differ as to whether they are applied by law, or used throughout the country. In some countries these are ISO/DIS related or based (ISO 10381-1, 1995; ISO 10381-2, 1995), or are produced by a scientific society or a standardisation body. As far as sampling strategy is concerned, not all sampling guidelines clearly describe the sampling scale, the specifications for contamination risk precautions, the sampling plan and protocol structure and the pre-analysis treatment of the soil samples. The purpose for sampling, in descending order of frequency, is soil pollution, soil fertilisation, general soil monitoring, background risk assessment, or else it is not specified. The majority of countries do not sample the top organic matter separately. Sampling depth is either related to the morphogenetic horizon or to ad hoc sampling depth, which is not specified in all cases. They suggest mass- and volume-related soil sampling, while the sampling pattern is not presented in all national guidelines. The criteria for area, site, unit, sub-unit, and point selection are mainly based on pedology and land use, following the history and pre-screening information or geology, or is site related. Some guidelines suggest the division of sampling units into sub-units. The sampling pattern is mainly grid sampling, grid and random sampling, or not mentioned. Sampling density inside the sampling unit either varies greatly or it is not mentioned, while the size of the sampling unit varies widely. Most guidelines require the collection of composite instead of simple samples, while some prefer sampling soil profiles. In the European SSG many technical details and steps are either not defined or vary, while in the pre-analysis treatment quality assurance (QA) and quality control (QC) approaches are used either both in the lab and in the field, or only in the field, or are not mentioned. The common points and the points in which harmonisation could be started or achieved are discussed.

Agriculture↗
PubMed2001

Comparative soil sampling in the Dornach site (Switzerland) for soil three-dimensional pollution description.

Fifteen institutions from 13 European countries and Switzerland participated in a comparative test sampling at the Dornach site, near Basel in Switzerland. They received the site description and were asked to develop their own sampling plans, based on their national guidelines for a three-dimensional description of the Pb, Zn, Cu and Cd pollution, with a maximum of 15 samples. The comparative sampling test took place in late August 1997. The sampling plans and records, provided by the participants, were compared and evaluated in terms of sampling strategy throughout the site, the sampling strategy inside the sampling unit, strategy at the sampling point and last minute alteration of the sampling plans in the field. The object of this was to define the similarities and the differences in the sampling plans and identify the crucial steps inducing error or uncertainty which should be harmonized throughout Europe. The number of the total composite samples varied from 4 to 16, while the number of sampling points varied from 4 to 224 and the sampling density varied from 0.25 to 16 single samples per 100 m2. The number of 10 x 10 m2 quadrats from which samples were taken varied from 3 to 56, out of the total 61. The number of sampling units varied between 3 and 12. The criteria in descending order of frequency were: both land use and pedology, land use, pedology. The majority of the national participants divided the sampling units into two or three sub-units, while seven participants collected replicate composite samples from the same sampling unit. Only one sampled from the existing profiles, eight national representatives ignored the plough depth. The sampling pattern inside the sampling unit was in descending order of frequency: random, point sampling, regular, 'W' and 'X' shaped sampling. The number of single samples in the composite varied from 1 to 20. Most of the national participants sampled to pre-defined (ad-hoc) sampling depths, while others sampled soil horizons and others both. The maximum soil depth sampled also varied from 20 to 117 cm. Most participants mixed in the top organic matter horizon while others sampled it separately. Most sampled separately the top Ah horizon in the forest while the rest mixed it with the underlying soil horizon. The last-minute sampling plan alterations were in: the sampling depth (nine), the movement of sampling points (five), the reduction of sub-samples in the composite sample (four), changes in the number of sampling units (three), ignoring the bottom sample (three), not sampling the L/H layer (three) although this was planned, unplanned sampling of the L/H layer (two) and changing the number of planned samples (two). This study has highlighted the need for soil sampling harmonization throughout Europe for pollution and soil quality determination.

Environmental Monitoring↗
PubMed2001

Quantitative evaluation of the CEEM soil sampling intercomparison.

The aim of the CEEM soil project was to compare and to test the soil sampling and sample preparation guidelines used in the member states of the European Union and Switzerland for investigations of background and large-scale contamination of soils, soil monitoring and environmental risk assessments. The results of the comparative evaluation of the sampling guidelines demonstrated that, in soil contamination studies carried out with different sampling strategies and methods, comparable results can hardly be expected. Therefore, a reference database (RDB) was established by the organisers, which acted as a basis for the quantitative comparison of the participants' results. The detected deviations were related to the methodological details of the individual strategies. The comparative evaluation concept consisted of three steps: The first step was a comparison of the participants' samples (which were both centrally and individually analysed) between each other, as well as with the reference data base (RDB) and some given soil quality standards on the level of concentrations present. The comparison was made using the example of the metals cadmium, copper, lead and zinc. As a second step, the absolute and relative deviations between the reference database and the participants' results (both centrally analysed under repeatability conditions) were calculated. The comparability of the samples with the RDB was categorised on four levels. Methods of exploratory statistical analysis were applied to estimate the differential method bias among the participants. The levels of error caused by sampling and sample preparation were compared with those caused by the analytical procedures. As a third step, the methodological profiles of the participants were compiled to concisely describe the different procedures used. They were related to the results to find out the main factors leading to their incomparability. The outcome of this evaluation process was a list of strategies and methods, which are problematic with respect to comparability, and should be standardised and/or specified in order to arrive at representative and comparable results in soil contamination studies throughout Europe. Pre-normative recommendations for harmonising European soil sampling guidelines and standard operating procedures have been outlined in Wagner G, Desules A, Muntau H, Theocharopoulos S. Comparative Evaluation of European Methods for Sampling and Sample Preparation of Soils for Inorganic Analysis (CEEM Soil). Final Report of the Contract SMT4-CT96-2085, Sci Total Environ 2001;264:181-186. Wagner G, Desaules A, Munatu H. Theocharopolous S, Quevauvaller Ph. Suggestions for harmonising sampling and sample pre-treatment procedures and improving quality assurance in pre-analytical steps of soil contamination studies. Paper 1.7 Sci Total Environ 2001b;264:103-118.

Environmental Monitoring↗
PubMed2001

Harmonisation and quality assurance in pre-analytical steps of soil contamination studies--conclusions and recommendations of the CEEM Soil project.

The paper summarises the project's results and consequences including expert's statements. Based on sampling strategies and methodological details which have been recognised to be critical for the comparability of the results of soil contamination studies, recommendations are given towards harmonisation of soil sampling guidelines, improvement of quality assurance of pre-analytical steps and inclusion of soil sampling into accreditation systems. Recommended approaches to improve QA and QC in soil sampling are: harmonised guidelines; specified SOPs; written sampling (strategy) plans; defined qualification and experience of sampling personnel; sampling records; regular interlaboratory comparisons (proficency tests) for sampling; and inclusion of sampling and sample preparation into accreditation procedures. Needs for further research in the field of pre-analytical phases of soil contamination studies are outlined and further R&D projects are encouraged.

Accreditation↗
PubMed2001

Effect of dimethyl sulfoxide on the electron transfer reactivity of hemoglobin.

Hemoglobin, after being treated with dimethyl sulfoxide, exhibits a direct electrochemical response at a pyrolytic graphite electrode. The apparent standard potential (E degrees ') of hemoglobin is -0.119 V (vs. NHE). Meanwhile, since no electrochemical mediator is required for its direct electrochemistry, this work provides a convenient way to perform electrochemical research on this protein.

Dimethyl Sulfoxide↗
PubMed2001

A small domain of CBP/p300 binds diverse proteins: solution structure and functional studies.

The transcriptional coactivators CBP and p300 are critical regulators of metazoan gene expression. They associate with many different DNA-bound transcription factors through small, conserved domains. We have identified a compactly folded 46 residue domain in CBP and p300, the IRF-3 binding domain (IBiD), and we have determined its structure by NMR. It has a helical framework containing an apparently flexible polyglutamine loop that participates in ligand binding. Spectroscopic data indicate that induced folding accompanies association of IBiD with its partners, which exhibit no evident sequence similarities. We demonstrate the significance both in vitro and in vivo of interactions between IBiD and a number of diverse partners. Thus, IBiD is an important contributor to signal integration by CBP and p300.

Amino Acid Sequence↗
PubMed2001

Prevalence of short-segment Barrett's epithelium.

BACKGROUND/AIMS: The incidence of adenocarcinoma of the oesophagus has increased. Its major risk factor is Barrett's epithelium of which the sine qua non is microscopically diagnosed intestinal metaplasia. Short segment Barrett's epithelium may often be overlooked during routine endoscopy. In routine biopsies taken from normal-appearing mucosa of the distal oesophagus, the reported rates of short segment Barrett's epithelium in the distal oesophagus reached 36%. We compared these rates with the results obtained in a community hospital in Israel. METHODS: Consecutive patients undergoing oesophagogastroduodenoscopy were enrolled. Biopsy specimens taken from cardia, oesophagogastric junction and 2 cm above the oesophagogastric junction were stained with haematoxylin & eosin and Alcian blue. RESULTS: There were 112 study patients (mean age +/- SD 48. 9+/-18.3 years, 51.8% males). Nine (8.04%) patients had intestinal metaplasia (according to specimen from 2 cm above oesophagogastric junction), and symptoms of gastro-oesophageal reflux were found in only four (44.4%) of them. Of these nine patients, six (6.66%) had normal-appearing mucosa and three (3.33%) had macroscopic Barrett's epithelium. Alcian blue staining revealed two patients with intestinal metaplasia that haematoxylin & eosin staining had missed. CONCLUSION: We found an 8% prevalence of intestinal metaplasia compared to 18-36% reported in the literature. We also determined that the added advantage of routine biopsy was 5.4%.

Adenocarcinoma↗
PubMed2001

A solubility-enhancement tag (SET) for NMR studies of poorly behaving proteins.

Protein-fusion constructs have been used with great success for enhancing expression of soluble recombinant protein and as tags for affinity purification. Unfortunately the most popular tags, such as GST and MBP, are large, which hinders direct NMR studies of the fusion proteins. Cleavage of the fusion proteins often re-introduces problems with solubility and stability. Here we describe the use of N-terminally fused protein G (B1 domain) as a non-cleavable solubility-enhancement tag (SET) for structure determination of a dimeric protein complex. The SET enhances the solubility and stability of the fusion product dramatically while not interacting directly with the protein of interest. This approach can be used for structural characterization of poorly behaving protein systems, and would be especially useful for structural genomics studies.

Algorithms↗
PubMed2001

Identification of small-molecule inhibitors of interaction between the BH3 domain and Bcl-xL.

To study the role of the BH3 domain in mediating pro-apoptotic and anti-apoptotic activities of Bcl-2 family members, we identified a series of novel small molecules (BH3Is) that inhibit the binding of the Bak BH3 peptide to Bcl-xL. NMR analyses revealed that BH3Is target the BH3-binding pocket of Bcl-xL. Inhibitors specifically block the BH3-domain-mediated heterodimerization between Bcl-2 family members in vitro and in vivo and induce apoptosis. Our results indicate that BH3-dependent heterodimerization is the key function of anti-apoptotic Bcl-2 family members and is required for the maintenance of cellular homeostasis.

Apoptosis↗
PubMed2001

Effects of diabetes on neurotransmission in rat vaginal smooth muscle.

The aim of this work was to characterize the effect of experimental diabetes on neurotransmission in rat vagina. Female Sprague-Dawley rats were divided into two groups: non-diabetic controls (NDM, n=38) and diabetics (DM, n=38). DM was produced by intraperitoneal injection of streptozotocin. Eight weeks later the animals were killed, the distal part of the vagina was removed, and smooth muscle strips were prepared for functional organ bath experiments and for measurement of nitric oxide synthase (NOS) activity. In DM preparations, the EC(50) value for noradrenaline (NA) was significantly increased (P<0.05) and the maximal contractile response decreased (P=0.001). In preparations precontracted with NA, the NO donor SNAP and calcitonin gene-related peptide (CGRP) caused concentration-dependent relaxations, which were significantly decreased (P<0.001) in the DM group. Electrical stimulation of nerves (EFS) caused frequency-dependent contractions, which were significantly lower in DM than in NDM strips (P<0.001). SNAP and CGRP concentration-dependently inhibited EFS evoked contractions in both NDM and DM preparations. The inhibition was significantly lower (P<0.05) in the DM group. In NDM preparations precontracted with NA, EFS evoked frequency-dependent relaxations; such relaxations were inhibited or reduced in DM. Treatment with the NOS inhibitor, L-NOARG 0.1 mM, abolished relaxations in all preparations or produced contraction in DM preparations. Calcium-dependent NOS activity was not significantly different in the DM and NDM groups. However, the DM animals showed a small but significant increase in calcium-independent NOS-activity (P<0.05). Diabetes interferes with adrenergic-, cholinergic- and NANC-neurotransmitter mechanisms in the smooth muscle of the rat vagina. The changes in the nitrergic neurotransmission are not due to reduction in NOS-activity, but seem to be due to interference with later steps in the L-arginine/NO/guanylate cyclase/cGMP system.

Animals↗
PubMed2001

An unmediated hydrogen peroxide biosensor based on hemoglobin incorporated in a montmorillonite membrane.

Hemoglobin was incorporated in a montmorillonite membrane. Electrochemical and spectroscopic studies revealed that the electron transfer reactivity and peroxidase activity of the protein were both enhanced. Nevertheless, its structure was still maintained native-like in the membrane. An unmediated hydrogen peroxide biosensor was accordingly prepared. The calibration plot of this H202 sensor was linear in the range of 1.0 x 10(-6)-6.0 x 10(-4) mol L(-1). The relative standard deviation was 3.1% for six successive determinations at a concentration of 1.0 x 10(-4) mol L(-1). The detection limit was 6.0 x 10(-7) mol L(-1). Possible interferences in real sample analyses are discussed.

Animals↗
PubMed2001

Accessory liver in an infant with congenital diaphragmatic hernia.

Incidence of congenital diaphragmatic hernia (CDH) ranges from 1 in 2,400 to one in 5,000 live births. Associated anomalies in CDH are approximately 30% to 35%. The authors report on an infant with CDH and an accessory supradiaphragmatic liver with separate vascularization from the thoracic aorta. The pathogenesis of this malformation is discussed. The postoperative course and the follow-up of the child over 5 years was completely uneventful.

Abnormalities, Multiple↗