QUANTITATIVE GENETICS OF RESPONSE TO COMPETITORS IN NEMOPHILA MENZIESII: A GREENHOUSE STUDY

To determine the potential for adaptation to a local biotic environment, we examined the magnitude and nature of genetic variation in response to neighboring plants within a natural population of the native California annual, Nemophila menziesii. A total of 22 plants from a natural population were crossed in three reciprocal factorials. The progeny were grown in a greenhouse in nine treatments that varied in conspecific density and in the density of a naturally co-occurring grass species, Bromus diandrus. Increasing the density of each species significantly reduced individual survival, fruit number, and dry weight. Among survivors, we found small to moderate heritability of dry weight within treatments. Additive genetic correlations (r_A) of dry weight between competitive regimes were generally large and positive. In no case were they significantly different from 1, as expected under the null hypothesis that the relative performance of the genotypes under consideration is the same in all environments. On the basis of these results, we cannot conclude that the structure of genetic covariation within this population would promote genetic differentiation in response to locally varying conditions of density of these two species. Aspects of the experiment that may have compromised our ability to detect r_A differing from 1 are discussed.     

Until death do us part? In-depth insights into Dutch consumers’ considerations about product lifetimes and lifetime extension

Long-lasting electronic products contribute to a sustainable society; however, both expected and actual lifetimes are in decline. This research provides in-depth insights into consumers’ considerations about product lifetimes, barriers to extending lifetimes, and responses to a product lifetime label. Results of interviews (n = 22) with Dutch consumers suggest a positive view on long-lasting products. Nevertheless, their products’ value depreciated during their lifetimes. Consumers consider themselves unable to estimate how long products should last, which can be detrimental as low expectations tend to negatively influence actual lifetimes. Also, use intensity and consumers’ care(less) behavior influence the lifetime. To extend product lifetimes, consumers often disregard the option of repairing malfunctioning products. They have limited knowledge and ability, and believe repair provides poor value for money. Lifetime extension can also be hindered by market-related factors, such as convenient replacement services, new technological developments, and (attractive) deals. We suggest a product lifetime label should contain relevant and reliable information; furthermore, we recommend including (extended) warranty information. When information about repairability is included, potential negative responses should be considered. Finally, raising awareness about the environmental impact of short-lived products via a label may have a positive effect but requires more research attention.     

Higher-order interactions of Bcr-Abl can broaden chronic myeloid leukemia (CML) drug repertoire

Bcr-Abl, a nonreceptor tyrosine kinase, is associated with leukemias, especially chronic myeloid leukemia (CML). Deletion of Abl's N-terminal region, to which myristoyl is linked, renders the Bcr-Abl fusion oncoprotein constitutively active. The substitution of Abl's N-terminal region by Bcr enables Bcr-Abl oligomerization. Oligomerization is critical: it promotes clustering on the membrane, which is essential for potent MAPK signaling and cell proliferation. Here we decipher the Bcr-Abl specific, step-by-step oligomerization process, identify a specific packing surface, determine exactly how the process is structured and identify its key elements. Bcr's coiled coil (CC) domain at the N-terminal controls Bcr-Abl oligomerization. Crystallography validated oligomerization via Bcr-Abl dimerization between two Bcr CC domains, with tetramerization via tight packing between two binary assemblies. However, the structural principles guiding Bcr CC domain oligomerization are unknown, hindering mechanistic understanding and drugs exploiting it. Using molecular dynamics (MD) simulations, we determine that the binary complex of the Bcr CC domain serves as a basic unit in the quaternary complex providing a specific surface for dimer–dimer packing and higher-order oligomerization. We discover that the small α1-helix is the key. In the binary assembly, the helix forms interchain aromatic dimeric packing, and in the quaternary assembly, it contributes to the specific dimer–dimer packing. Our mechanism is supported by the experimental literature. It offers the key elements controlling this process which can expand the drug discovery strategy, including by Bcr CC-derived peptides, and candidate residues for small covalent drugs, toward quenching oligomerization, supplementing competitive and allosteric tyrosine kinase inhibitors.     

Transmission of poly(dT60) single-stranded DNA through polycarbonate track-etched ultrafiltration membranes

The objective of this study was to examine membrane filtration of a single stranded DNA (ssDNA) with 60 thymine nucleotides, and to elucidate the variables controlling its transmission across track-etched porous membranes. Dead end filtration measurements were performed using different pore size membranes (10, 15, and 30 nm) at different transmembrane pressures in solutions with ionic strength ranging from 0 to 1000 mM NaCl. The diffusivity of the ssDNA was determined using fluorescence recovery after photobleaching, yielding hydrodynamic radii ranging from 1.6 to 2.8 nm, with values decreasing with increasing solution ionic strength. Despite the small ssDNA/membrane pore size, nearly 100% rejection was observed for measurements performed with the 10 and 15 nm pore size membranes under low-ionic strength conditions. These high rejections can be attributed to strong repulsive electrostatic ssDNA-membrane interactions. With increasing ionic strength, electrostatic interactions as well as the effective size of the ssDNA decreases and the flexibility of the ssDNA increases, leading to a reduction in ssDNA rejection. A design of experiments approach was used to plan filtration experiments that adequately covered the variable space with a manageable number of experiments. The results yielded an empirical expression relating ssDNA rejection to pore size, solution ionic strength and transmembrane pressure. There was evidence of flow induced elongation at high-transmembrane pressures in the 30 nm pore size membranes, but not in the smaller pore size membranes. These results are consistent with critical flux estimates developed using a free draining model for the ssDNA.     

Beiträge zur Entwicklungsgeschichte vonSphaerularia bombi Dufour 1837

Ohne ZusammenfassungDiese Arbeit wurde durchgeführt mit freundlicher Unterstützung der Gesellschaft von Freunden und Förderern der Universität Bonn (Geffrub)     

THE COMPARISON OF QUANTITATIVE GENETIC PARAMETERS BETWEEN POPULATIONS

A statistical method for comparing matrices of genetic variation and covariation between groups (e.g., species, populations, a single population grown in distinct environments) is proposed. This maximum-likelihood method provides a test of the overall null hypothesis that two covariance component matrices are identical. Moreover, when the overall null hypothesis is rejected, the method provides a framework for isolating the particular components that differ significantly between the groups. Simulation studies reveal that discouragingly large experiments are necessary to obtain acceptable power for comparing genetic covariance component matrices. For example, even in cases of a single trait measured on 900 individuals in a nested design of 100 sires and three dams per sire in each population, the power was only about 0.5 when additive genetic variance differed by a factor of 2.5. Nevertheless, this flexible method makes valid comparison of covariance component matrices possible.     

Ingestion of Salmonella enterica Serotype Poona by a Free-Living Nematode, Caenorhabditis elegans, and Protection against Inactivation by Produce Sanitizers

Free-living nematodes are known to ingest food-borne pathogens and may serve as vectors to contaminate preharvest fruits and vegetables. Caenorhabditis elegans was selected as a model to study the effectiveness of sanitizers in killing Salmonella enterica serotype Poona ingested by free-living nematodes. Aqueous suspensions of adult worms that had fed on S. enterica serotype Poona were treated with produce sanitizers. Treatment with 20 μg of free chlorine/ml significantly (α = 0.05) reduced the population of S. enterica serotype Poona compared to results for treating worms with water (control). However, there was no significant difference in the number of S. enterica serotype Poona cells surviving treatments with 20 to 500 μg of chlorine/ml, suggesting that reductions caused by treatment with 20 μg of chlorine/ml resulted from inactivation of S. enterica serotype Poona on the surface of C. elegans but not cells protected by the worm cuticle after ingestion. Treatment with Sanova (850 or 1,200 μg/ml), an acidified sodium chlorite sanitizer, caused reductions of 5.74 and 6.34 log₁₀ CFU/worm, respectively, compared to reductions from treating worms with water. Treatment with 20 or 40 μg of Tsunami 200/ml, a peroxyacetic acid-based sanitizer, resulted in reductions of 4.83 and 5.34 log₁₀ CFU/worm, respectively, compared to numbers detected on or in worms treated with water. Among the organic acids evaluated at a concentration of 2%, acetic acid was the least effective in killing S. enterica serotype Poona and lactic acid was the most effective. Treatment with up to 500 μg of chlorine/ml, 1% hydrogen peroxide, 2,550 μg of Sanova/ml, 40 μg of Tsunami 200/ml, or 2% acetic, citric, or lactic acid had no effect on the viability or reproductive behavior of C. elegans. Treatments were also applied to cantaloupe rind and lettuce inoculated with S. enterica serotype Poona or C. elegans that had ingested S. enterica serotype Poona. Protection of ingested S. enterica serotype Poona against sanitizers applied to cantaloupe was not evident; however, ingestion afforded protection of the pathogen on lettuce. These results indicate that S. enterica serotype Poona ingested by C. elegans may be protected against treatment with chlorine and other sanitizers, although the basis for this protection remains unclear.