[Thrombotic occlusion of the extracorporeal circulation during hepatic chemosaturation despite targeted anticoagulation : A case report]. / Thrombotischer Verschluss der extrakorporalen Zirkulation während hepatischer Chemosaturation trotz zielgerechter Antikoagulation : Ein Fallbericht.

Percutaneous hepatic chemosaturation is a treatment option for unresectable primary or secondary liver tumors. In this procedure the part of the inferior vena cava (VCI) that collects blood from the hepatic veins is isolated using a double balloon catheter. Like this, systemic distribution of the chemotherapeutic agent melphalan which is administered via the hepatic artery can be prevented. After passage through the liver and drainage from the retrohepatic VCI, the chemosaturated blood passes through two extracorporeal filters. Subsequently, the filtered blood is returned via the jugular vein. The procedure is often accompanied by severe hemodynamic instability, the cause of which is still not completely understood. In addition, coagulation management of extracorporeal circulation is often challenging. The authors report a case in which a thrombus formed in the returning leg of the extracorporeal circulation despite sufficient activated clotting time (ACT). Targeted problem search and resolution were necessary simultaneously to hemodynamic stabilization and interdisciplinary collaboration to successfully perform the intervention and provide the patient with safe treatment.

Maximum likelihood estimation of recombination rates from population data.

We describe a method for co-estimating r = C/mu (where C is the per-site recombination rate and mu is the per-site neutral mutation rate) and Theta = 4N(e)mu (where N(e) is the effective population size) from a population sample of molecular data. The technique is Metropolis-Hastings sampling: we explore a large number of possible reconstructions of the recombinant genealogy, weighting according to their posterior probability with regard to the data and working values of the parameters. Different relative rates of recombination at different locations can be accommodated if they are known from external evidence, but the algorithm cannot itself estimate rate differences. The estimates of Theta are accurate and apparently unbiased for a wide range of parameter values. However, when both Theta and r are relatively low, very long sequences are needed to estimate r accurately, and the estimates tend to be biased upward. We apply this method to data from the human lipoprotein lipase locus.

Sampling among haplotype resolutions in a coalescent-based genealogy sampler.

Analysis of the coalescent structure of a population may provide information useful in mapping disease loci. Current coalescent-based genealogy samplers require haplotyped data, but haplotypes are not always available, and it is not practical to sum over all haplotype assignments for large data sets. We describe a method of adding haplotype re-evaluation to the sampler, so that it samples not only among genealogies explaining a given haplotype configuration, but also among different haplotype configurations. Several different haplotype-rearrangement strategies are considered, but the simplest-inverting the phase of a single site in a single individual-appears to be the most successful. The straightforward haplotype sampler does not mix well; heating approaches can greatly improve its performance.

Usefulness of single nucleotide polymorphism data for estimating population parameters.

Single nucleotide polymorphism (SNP) data can be used for parameter estimation via maximum likelihood methods as long as the way in which the SNPs were determined is known, so that an appropriate likelihood formula can be constructed. We present such likelihoods for several sampling methods. As a test of these approaches, we consider use of SNPs to estimate the parameter Theta = 4N(e)micro (the scaled product of effective population size and per-site mutation rate), which is related to the branch lengths of the reconstructed genealogy. With infinite amounts of data, ML models using SNP data are expected to produce consistent estimates of Theta. With finite amounts of data the estimates are accurate when Theta is high, but tend to be biased upward when Theta is low. If recombination is present and not allowed for in the analysis, the results are additionally biased upward, but this effect can be removed by incorporating recombination into the analysis. SNPs defined as sites that are polymorphic in the actual sample under consideration (sample SNPs) are somewhat more accurate for estimation of Theta than SNPs defined by their polymorphism in a panel chosen from the same population (panel SNPs). Misrepresenting panel SNPs as sample SNPs leads to large errors in the maximum likelihood estimate of Theta. Researchers collecting SNPs should collect and preserve information about the method of ascertainment so that the data can be accurately analyzed.

[Detection of airborne cultivatable microorganisms from compost sites--emissions and imissions]. / Erfassung von luftgetragenen kultivierbaren Mikroorganismen aus Kompostierungsanlagen--Emission und Immission.

The statement presented here gives an overview and assessment of the procedures and concepts currently used for the collection and determination of airborne, culturable microorganisms at sources of emission within composting plants and in their near vicinity. The paper focuses on "classical" methods, which involve cultivation as an intermediate step for the determination of viable, airborne microorganisms. The theoretical and practical requirements on such methods are discussed. Results and experiences from recent investigations are described.

['Microbial air pollutants'. Emission sources and preventive measures]. / 'Mikrobielle Luftverunreinigungen'. Emissionsquellen und -minderungsmassnahmen.

Already in the planning or monitoring phase, measures have to be realized for the reduction in emissions of bio-aerosols in biological waste treatment plants. For this purpose, operation-related measures (in open and partially closed plants) and technology-related measures (in closed plants with automatic ventilation) can be taken. A survey on the currently feasible measures for reduction is submitted. The realization has to be adapted to the individual site and type of plant. An enormous demand for examinations is envisaged in order to enable a qualified assessment of the emission behaviour of diverse waste air systems or process steps.

Maximum likelihood estimation of population growth rates based on the coalescent.

We describe a method for co-estimating 4Nemu (four times the product of effective population size and neutral mutation rate) and population growth rate from sequence samples using Metropolis-Hastings sampling. Population growth (or decline) is assumed to be exponential. The estimates of growth rate are biased upwards, especially when 4Nemu is low; there is also a slight upwards bias in the estimate of 4Nemu itself due to correlation between the parameters. This bias cannot be attributed solely to Metropolis-Hastings sampling but appears to be an inherent property of the estimator and is expected to appear in any approach which estimates growth rate from genealogy structure. Sampling additional unlinked loci is much more effective in reducing the bias than increasing the number or length of sequences from the same locus.

Functionalisation of Si/SiO2 and glass surfaces with ultrathin dextran films and deposition of lipid bilayers.

Dextran with molecular weight of 500 kDalton was covalently coupled to glass and Si/SiO2-surfaces by epoxy functionalisation or by photo reactive functionalisation of the solid surface. With the described methods we can control the deposited mass density between 0.3 and 4.8 ng/m2 corresponding to mean film thicknesses of a dry dextran film between 2 A and 30 A. We studied the structural properties (thickness, density) of ultrathin dextran layers coupled to silicon wafers of glass surfaces in humid atmosphere and under water by ellipsometry and reflection interference contrast microscopy (RICM) and developed a new method to measure the interfacial forces in ultrathin films. We demonstrate, that these hydrophilic polymer films from soft cushions which can be reversibly swollen both under water and in humidified air. In water the films swell up to thicknesses of about 600 to 800 A as measured by reflection interference contrast microscopy (RICM) and ellipsometry. The interaction of the polymer films with Si/SiO2-surfaces in contact with humidified air was studied by ellipsometry. We measured the thickness of the polymer layers as a function of the relative humidity of the atmosphere surrounding the sample in a hydration chamber. Depending on the humidity of the surrounding air and induced by the hydration the film thickness changes by about a factor of 10. Coupling of N-hydroxysuccinimide to dextran enables the functionalisation of the dextran cushions with a broad range of different specific binding molecules for various detection tasks. The possibility of soft hydrated dextran films as a cushion for the deposition of self healing lipid bilayers is shown.

Estimating effective population size and mutation rate from sequence data using Metropolis-Hastings sampling.

We present a new way to make a maximum likelihood estimate of the parameter 4N mu (effective population size times mutation rate per site, or theta) based on a population sample of molecular sequences. We use a Metropolis-Hastings Markov chain Monte Carlo method to sample genealogies in proportion to the product of their likelihood with respect to the data and their prior probability with respect to a coalescent distribution. A specific value of theta must be chosen to generate the coalescent distribution, but the resulting trees can be used to evaluate the likelihood at other values of theta, generating a likelihood curve. This procedure concentrates sampling on those genealogies that contribute most of the likelihood, allowing estimation of meaningful likelihood curves based on relatively small samples. The method can potentially be extended to cases involving varying population size, recombination, and migration.

Lipid mono- and bilayer supported on polymer films: composite polymer-lipid films on solid substrates.

We report the deposition of lipid monolayers and bilayers on polyacrylamide films deposited by radical chain reaction onto solid substrates in aqueous solutions. Polymer films of various degrees of monomer density and cross-linking are prepared. Lateral diffusion and fluorescent probe permeation measurements yield insight into the continuity of the lipid layers and show that monolayers exposed to air are much less sensitive towards polymer heterogeneities than bilayers below water, which is explained in terms of the wetting laws. The diffusion studies of lipid and lipopeptide probes yield absolute values of the frictional coefficients between the lipid layer and the polymer films and allow one to estimate the surface viscosity of the polymer film. The potential applications of supported membranes on soft thin polymer films for the preparation of biofunctionalized surfaces or biocompatible receptive surfaces for biosensors are discussed.

A simulation comparison of phylogeny algorithms under equal and unequal evolutionary rates.

Using simulated data, we compared five methods of phylogenetic tree estimation: parsimony, compatibility, maximum likelihood, Fitch-Margoliash, and neighbor joining. For each combination of substitution rates and sequence length, 100 data sets were generated for each of 50 trees, for a total of 5,000 replications per condition. Accuracy was measured by two measures of the distance between the true tree and the estimate of the tree, one measure sensitive to accuracy of branch lengths and the other not. The distance-matrix methods (Fitch-Margoliash and neighbor joining) performed best when they were constrained from estimating negative branch lengths; all comparisons with other methods used this constraint. Parsimony and compatibility had similar results, with compatibility generally inferior; Fitch-Margoliash and neighbor joining had similar results, with neighbor joining generally slightly inferior. Maximum likelihood was the most successful method overall, although for short sequences Fitch-Margoliash and neighbor joining were sometimes better. Bias of the estimates was inferred by measuring whether the independent estimates of a tree for different data sets were closer to the true tree than to each other. Parsimony and compatibility had particular difficulty with inaccuracy and bias when substitution rates varied among different branches. When rates of evolution varied among different sites, all methods showed signs of inaccuracy and bias.

Relative effectiveness of various alternating frequencies of a power toothbrush.

The influence on plaque-removing efficiency of the alternating frequency of a powered brush has never been established. In the present study, a mechanical brush was tested at various alternations per minute (F1 = 2100, F2 = 2500, F3 = 3500). A double-blind, randomized, triple crossover design was applied. After a plaque growth phase, the test brushes were used under supervision for 90 s and the remaining plaque scored. A ridit analysis yielded significant differences between F2 and F1/F3. Odds ratios and frequency distributions demonstrated a clinically meaningful advantage for F2. Subjective evaluation by the participants confirmed the positive performance of F2. The results can be generalized in 3 ways: (1) the alternating frequency of a power brush influences its effectiveness, (2) high frequencies are not generally superior, (3) the test brush has its optimal cleaning efficiency at F2, which does not necessarily need to be true for other brands. It seems imperative to determine the optimal frequency for any new brush in a controlled study.

Genetic exchange in the evolution of the human MHC class II loci.

A total of 61 DNA sequences from human major histocompatibility class II loci were searched for statistical evidence of past genetic exchange (gene conversion or recombination). Among the 12 A-locus sequences (derived from DPA1 and DQA1), 4 clusters indicating potential exchange events were found. Among the 49 B-locus sequences (derived from DOB, DPB1, DPB2, DQB1, DRB1, DRB3, DRB4 and DRB5), 15 clusters were found. The clusters suggested short exchanges (less than 100 bp) within and between loci, and were concentrated in exon 2 (coding for the antigen binding site). The most striking feature of the results was the presence of an approximately 200-bp region in the middle of B-locus exon 2 which contained almost no locus-specific substitutions, which were abundant elsewhere. This suggests either strong selection for locus specificity in the other regions of the gene or a history of frequent between-locus exchange in this part of exon 2, which is involved in forming the antigen binding site.

Gene conversion in the evolution of the human and chimpanzee MHC class I loci.

Sixty-five DNA sequences from human and chimpanzee major histocompatibility complex class I loci were searched for statistical evidence of past gene conversion. Twenty-four potential conversions were detected; they were distributed across both variable and conserved portions of the gene, and involved both classical and non-classical loci. The majority spanned less than 100 bp, comparable in length to the conversions observed in spontaneous mutations in mice. Both within-locus and between-locus conversions were observed. Certain areas of the antigen recognition site appear to have been the target for multiple conversion events. The implications of these findings for the evolution of the class I multigene family are discussed.

[Sensitivity of pocket diagnosis as a function of numbers of probings]. / Sensitivität der Taschendiagnostik in Abhängigkeit von der Anzahl der Sondierungen.

Probing depth (PD) is measured at 2, 4 or 6 sites per tooth. We sought to ascertain whether or not more measurements increase the sensitivity of assessing the severity of periodontitis. 2 probings compared with 4 probings per tooth resulted in 68% sensitivity for PD greater than 2 mm and 77% for PD greater than 4 mm. The mesio-buccal PD explains only 16% of the variance of the buccal/oral PD. Comprehensive examination of pockets should consist of a minimum of 4 probings per tooth.

Gene conversion in the evolution of both the H-2 and Qa class I genes of the murine major histocompatibility complex.

In order to better understand the role of gene conversion in the evolution of the class I gene family of the major histocompatibility complex (MHC), we have used a computer algorithm to detect clustered sequence similarities among 24 class I DNA sequences from the H-2, Qa, and Tla regions of the murine MHC. Thirty-four statistically significant clusters were detected; individual analysis of the clusters suggested at least 25 past gene conversion or recombination events. These clusters are comparable in size to the conversions observed in the spontaneously occurring H-2Kbm and H-2Kkm2 mutations, and are distributed throughout all exons of the class I gene. Thus, gene conversion does not appear to be restricted to the regions of the class I gene encoding their antigen-presentation function. Moreover, both the highly polymorphic H-2 loci and the relatively monomorphic Qa and Tla loci appear to have participated as donors and recipients in conversion events. If gene conversion is not limited to the highly polymorphic loci of the MHC, then another factor, presumably natural selection, must be responsible for maintaining the observed differences in level of variation.