Biochemical screening for chromosomal disorders and neural tube defects (NTD): is adjustment of maternal alpha-fetoprotein (AFP) still appropriate in insulin-dependent diabetes mellitus (IDDM)?

Maternal serum alpha-fetoprotein (AFP) has been reported to be decreased in insulin-dependent diabetes mellitus (IDDM). The objective of the present study was to reinvestigate this finding in detail. Maternal serum levels of AFP, human chorionic gonadotropin (hCG), and unconjugated estriol (uE3) in 114 diabetic women, of whom 84 had IDDM, were compared to those of 19,251 control pregnancies in the second trimester (15th to 20th gestational weeks). The mean body weight at the date of sampling was 73.7 kg in all diabetic women, 72.7 kg in women with IDDM and 68.3 kg in non-diabetic women, respectively. Body weights were significantly (p<0.001) elevated in all diabetic pregnancies. Using weight-adjusted MoM (multiple of the median) values no statistical difference of serum levels in diabetic and non-diabetic pregnant women was found. Median MoM levels were 1.01 (hCG), 1.01 (uE3), 1.06 (AFP) in all diabetic women, and 0.95 (hCG), 0.96 (uE3), 0.96 (AFP) in women with IDDM, respectively. Ignoring adjustment for maternal weight leads to a reduction of all serum parameters in diabetic pregnancies. However, median MoM values of all three analytes are not statistically different when compared to non-diabetic pregnancies. This finding is contrary to the results of former studies from the 1970s and 1980s. It is concluded that progress in insulin adjustment and blood glucose surveillance of diabetic patients on the whole has balanced out serum levels. Therefore adjustment of serum AFP values for diabetic status no longer seems reasonable. Copyright © 2001 John Wiley & Sons, Ltd.     

Amphimixis and the individual in evolving populations: does Weismann’s Doctrine apply to all,most or a few organisms?

The German biologist August Weismann (1834–1914) proposed that amphimixis (sexual reproduction) creates variability for natural selection to act upon, and hence he became one of the founders of the Neo-Darwinian theory of biological evolution. He is perhaps best known for what is called “Weismann’s Doctrine” or “Weismann’s Barrier” (i.e. the irreversible separation of somatic and germ cell functionalities early during ontogeny in multicellular organisms). This concept provided an unassailable argument against “soft inheritance” sensu Lamarck and informed subsequent theorists that the only “individual” in the context of evolution is the mature, reproductive organism. Herein, we review representative model organisms whose embryology conforms to Weismann’s Doctrine (e.g. flies and mammals) and those that do not (e.g. freshwater hydroids and plants) based on this survey and the Five Kingdoms of Life scheme; we point out that most species (notably bacteria, fungi, protists and plants) are “non-Weismannian” in ways that make a canonical definition of the “individual” problematic if not impossible. We also review critical life history functional traits that allow us to create a matrix of all theoretically conceivable life cycles (for eukaryotic algae, embryophytes, fungi and animals), which permits us to establish where this scheme Weismann’s Doctrine holds true and where it does not. In addition, we argue that bacteria, the dominant organisms of the biosphere, exist in super-cellular biofilms but rarely as single (planktonic) microbes. Our analysis attempts to show that competition among genomic variants in cell lineages played a critical part in the evolution of multicellularity and life cycle diversity. This feature was largely ignored during the formulation of the synthetic theory of biological evolution and its subsequent elaborations.     

Investigations into the influence of dustiness on dust explosions

A new safety characteristic the “dustiness” according to VDI 2263 – part 9 (Verein Deutscher Ingenieure, 2008) is investigated. Dustiness means the tendency of a dust to form clouds. The paper deals with the influence of the dustiness on vented dust explosions. In order to look into the effects of the dustiness on dust cloud formation and explosion properties experiments and simulations in a vertical dust dispersion glass tube apparatus were carried out.Preliminary explosion experiments showed that the dustiness has an influence on the reduced explosion pressure in a vented 75 L test apparatus. Dusts with comparable p_max and K_St values and different dustiness were tested. Dusts with higher dustiness produced higher overpressures, despite comparable safety characteristics. In order to verify the results for applications in the process industries further tests with different settings are planned as well as industrial scale experiments. Characteristics of the dust such as particle size, density, specific surface area and particle shape, which influence the dispersibility, have been determined experimentally.The Euler/Lagrange and the Euler/Euler approaches are compared for simulating an exemplary dust/air mixture. Especially sedimentation and the ability of the approaches to simulate the tendency of dust to stay airborne were investigated. The Euler/Lagrange approach is better suited for simulating local dust concentrations, particle size distributions and particle forces. It could be used to point out regions of high dust concentrations in a vessel. With the Euler/Euler method it is possible to achieve fast solutions for one specified diameter, but the simulated dust/air mixtures are always more homogenous than in reality. ANSYS CFX version 13 was used in all simulations.     

Consumer-resource body-size relationships in natural food webs

It has been suggested that differences in body size between consumer and resource species may have important implications for interaction strengths, population dynamics, and eventually food web structure, function, and evolution. Still, the general distribution of consumer-'resource body-size ratios in real ecosystems, and whether they vary systematically among habitats or broad taxonomic groups, is poorly understood. Using a unique global database on consumer and resource body sizes, we show that the mean body-size ratios of aquatic herbivorous and detritivorous consumers are several orders of magnitude larger than those of carnivorous predators. Carnivorous predator-prey body-size ratios vary across different habitats and predator and prey types (invertebrates, ectotherm, and endotherm vertebrates). Predator-prey body-size ratios are on average significantly higher (1) in freshwater habitats than in marine or terrestrial habitats, (2) for vertebrate than for invertebrate predators, and (3) for invertebrate than for ectotherm vertebrate prey. If recent studies that relate body-size ratios to interaction strengths are general, our results suggest that mean consumer-resource interaction strengths may vary systematically across different habitat categories and consumer types.