Antibodies to Core Lipopolysaccharide Determinants: Absence of Cross-reactivity with Heterologous Lipopolysaccharides

Using monoclonal antibodies directed against defined epitopes of endotoxin core, this study demonstrated that the presentation of lipopolysaccharide (LPS) to antibodies is critical for measuring the specific binding of antibodies to LPS structures. False cross-reactive reactions apparently were observed when free core LPS or lipid A were used as antigens in ELISA, whereas coating with complexes of high-density lipoproteins with core LPS increased both the sensitivity and the specificity of the test compared with coating with free core LPS, so that nonspecific binding of antibodies was largely avoided. Using this technique, it was not possible to find broadly cross-reactive core LPS antibodies after immunization of rabbits and humans with rough mutants of gram-negative bacteria. These observations underscore the need for careful evaluation of the potential for cross-reactivity of antisera and of monoclonal antibodies directed against endotoxin cor

Exact Solution of an Evolutionary Model without Ageing

We introduce an age-structured asexual population model containing all the relevant features of evolutionary ageing theories. Beneficial as well as deleterious mutations, heredity and arbitrary fecundity are present and managed by natural selection. An exact solution without ageing is found. We show that fertility is associated with generalized forms of the Fibonacci sequence, while mutations and natural selection are merged into an integral equation which is solved by Fourier series. Average survival probabilities and Malthusian growth exponents are calculated indicating that the system may exhibit mutational meltdown. The relevance of the model in the context of fissile reproduction groups as many protozoa and coelenterates is discussed.Comment: LaTeX file, 15 pages, 2 ps figures, to appear in Phys. Rev.

Attributing scientific and technical progress: the case of holography

Holography, the three-dimensional imaging technology, was portrayed widely as a paradigm of progress during its decade of explosive expansion 1964–73, and during its subsequent consolidation for commercial and artistic uses up to the mid 1980s. An unusually seductive and prolific subject, holography successively spawned scientific insights, putative applications and new constituencies of practitioners and consumers. Waves of forecasts, associated with different sponsors and user communities, cast holography as a field on the verge of success—but with the dimensions of success repeatedly refashioned. This retargeting of the subject represented a degree of cynical marketeering, but was underpinned by implicit confidence in philosophical positivism and faith in technological progressivism. Each of its communities defined success in terms of expansion, and anticipated continual progressive increase. This paper discusses the contrasting definitions of progress in holography, and how they were fashioned in changing contexts. Focusing equally on reputed ‘failures’ of some aspects of the subject, it explores the varied attributes by which success and failure were linked with progress by different technical communities. This important case illuminates the peculiar post-World War II environment that melded the military, commercial and popular engagement with scientific and technological subjects, and the competing criteria by which they assessed the products of science

500,000 Years of Environmental History in Eastern Anatolia: The PALEOVAN Drilling Project

International Continental Scientific Drilling Program (ICDP) drilled a complete succession of the lacustrine sediment sequence deposited during the last ~500,000 years in Lake Van, Eastern Anatolia (Turkey). Based on a detailed seismic site survey, two sites at a water depth of up to 360 m were drilled in summer 2010, and cores were retrieved from sub-lake-floor depths of 140 m (Northern Basin) and 220 m (Ahlat Ridge). To obtain a complete sedimentary section, the two sites were multiple-cored in order to investigate the paleoclimate history of a sensitive semi-arid region between the Black, Caspian, and Mediterranean seas. Further scientific goals of the PALEOVAN project are the reconstruction of earthquake activity, as well as the temporal, spatial, and compositional evolution of volcanism as reflected in the deposition of tephra layers. The sediments host organic matter from different sources and hence composition, which will be unravelled using biomarkers. Pathways for migration of continental and mantle-derived noble gases will be analyzed in pore waters. Preliminary 40Ar/39Ar single crystal dating of tephra layers and pollen analyses suggest that the Ahlat Ridge record encompasses more than half a million years of paleoclimate and volcanic/geodynamic history, providing the longest continental record in the entire Near East to date

Direct determination of trace elements in powdered samples by in-cell isotope dilution femtosecond laser ablation ICPMS

A method has been developed for the direct and simultaneous multielement determination of Cu, Zn, Sn, and Pb in soil and sediment samples using femtosecond laser ablation inductively coupled plasma mass spectrometry (fs-LA-ICPMS) in combination with isotope dilution mass spectrometry (IDMS). The in-cell isotope dilution fs-LA-ICPMS method proposed in this work was based on the quasi-simultaneous ablation of the natural abundance sample and the isotopically enriched solid spike, which was performed using a high repetition rate laser and a fast scanning beam device in a combined manner. Both the sample preparation procedure and the total analysis time have been drastically reduced, in comparison with previous approaches, since a unique multielement isotopically enriched solid spike was employed to analyze different powdered samples. Numerous experimental parameters were carefully selected (e.g., carrier gas flow rate, inlet diameter of the ablation cell, sample translation speed, scanner speed, etc.) in order to ensure the complete mixing between the sample and the solid spike aerosols. The proposed in-cell fs-LA-ICP-IDMS method was tested for the analysis of two soil (CRM 142R, GBW-07405) and two sediment (PACS-2, IAEA-405) reference materials, and the analysis of Cu, Zn, Sn, and Pb yielded good agreement of usually not more than 10% deviation from the certified values and precisions of less than 15% relative standard deviation. Furthermore, the concentrations were in agreement not only with the certified values but also with those obtained by ICP-IDMS after the microwave-assisted digestion of the solid samples, demonstrating therefore that in-cell fs-LA-ICP-IDMS opens the possibility for accurate and precise determinations of trace elements in powdered samples reducing the total sample preparation time to less than 5 min. Additionally, scanning electron microscope measurements showed that the aerosol generated by in-cell fs-LA-ICP-IDMS predominantly consisted of linear agglomerates of small particles (in the order of few tens of nanometers) and a few large spherical particles with diameters below 225 nm

Antibodies to core lipopolysaccharide determinants: absence of cross-reactivity with heterologous lipopolysaccharides

Using monoclonal antibodies directed against defined epitopes of endotoxin core, this study demonstrated that the presentation of lipopolysaccharide (LPS) to antibodies is critical for measuring the specific binding of antibodies to LPS structures. False cross-reactive reactions apparently were observed when free core LPS or lipid A were used as antigens in ELISA, whereas coating with complexes of high-density lipoproteins with core LPS increased both the sensitivity and the specificity of the test compared with coating with free core LPS, so that nonspecific binding of antibodies was largely avoided. Using this technique, it was not possible to find broadly cross-reactive core LPS antibodies after immunization of rabbits and humans with rough mutants of gram-negative bacteria. These observations underscore the need for careful evaluation of the potential for cross-reactivity of antisera and of monoclonal antibodies directed against endotoxin core

The Cuprous-Cupric Complex in Hydrochloric Acid Solution

In the process described by Diehl and Brouns (1) for the direct determination of copper in bronze by electrodeposition from hydrochloric acid solution using hydroxylammonium chloride as anodic depolarizer and controlling the cathode potential automatically (3), the sample of bronze is dissolved in hydrochloric acid by the dropwise addition of nitric acid or of hydrogen peroxide. Subsequently the solution is diluted and electrolyzed, the cathode reaction being· first the reduction of cupric ion to the chlorocuprous ion, CuCl3==, and then the deposition of copper. The time of electrolysis can be materially shortened if the first reduction is effected chemically, by the addition of hydrocxylammonium chloride or of stannous chloride. If the reducing agent be added to the solution before it is diluted, that is, to a fairly concentrated hydrochloric acid solution, the solution turns dark brown or black, the color being due to some material in solution which disappears on dilution. It became of interest to learn more of this dark colored solution, particularly since it was observed that a small amount of antimony did or did not deposit with the copper depending on whether the reduction was made before or after the dilution