Evolutionary stability conditions for signaling games with costly signals

The paper investigates the class of signaling games with the following properties: (a) the interests of sender and receiver coincide, (b) different signals incur differential costs, and (c) different events (meanings/types) have different probabilities. Necessary and sufficient conditions are presented for a profile to be evolutionarily stable and neutrally stable, and for a set of profiles to be an evolutionarily stable set.The main finding is that a profile belongs to some evolutionarily stable set if and only if a maximal number of events can be reliably communicated. Furthermore, it is shown that under the replicator dynamics, a set of states with a positive measure is attracted to “sub-optimal” equilibria that do not belong to any asymptotically stable set.     

The Duisburg birth cohort study: influence of the prenatal exposure to PCDD/Fs and dioxin-like PCBs on thyroid hormone status in newborns and neurodevelopment of infants until the age of 24 months

Prenatal exposure to polychlorinated biphenyls (PCBs) and polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) can affect neurobehavioral development of infants and children. This effect may be mediated through disruption of thyroid hormone homeostasis. However, epidemiological studies reveal no consistent influence of PCDD/Fs and PCBs on thyroid status and neurodevelopment at environmental background levels. The effects may resolve with time of further decreasing exposure to these compounds. The aim of this study was to find out if there are still effects related to prenatal PCDD/F and PCB observable at the meanwhile decreased levels of exposure by using the same methods which have been applied in similar studies during the last 10 years in Europe. The birth cohort study was initiated in the year 2000 in the industrialized city of Duisburg, Germany. 232 healthy mother-infant pairs were recruited between 2000 and 2002. Dioxins, dioxin-like PCBs and six indicator PCBs were analyzed in maternal blood during pregnancy and in maternal milk following extraction and sample clean-up by HRGC/HRMS. Thyroid stimulating hormone (TSH), total thyroxine (T4), total triiodothyronine (T3), free thyroxine (FT4) and free triiodothyronine (FT3) were measured in serum samples of the pregnant women and in cord serum samples by chemiluminescent immunometric assay. Neurological examinations were performed at ages 2 weeks and 18 months using the neurological optimality score (NOS), mental and motor development were assessed using the Bayley Scales of Infant Development (BSID) at ages 12 and 24 months. Multiple linear regression analysis was used to describe the association of PCDD/F and PCB in maternal blood or milk with the outcome measurements after adjustment for confounding. Blood levels (n=182) of WHO 2005 toxic equivalents (TEQ) (PCDD/F+PCB) were in the range of 3.8-58.4 pg/glipid base (median: 19.3 pg/glipid base). The corresponding data for human milk (n=149) were 2.6-52.4 pg/glipid base (median: 19.7 pg/glipid base). Multiple regression analysis showed no decrease of thyroid hormones related to WHO 2005 TEQ in blood and milk of mothers and their newborns. Furthermore, no associations between exposure and neurological and developmental measures were observed. This study supports the view that the current decreased exposure to PCDD/Fs and PCBs does not impair thyroid function of newborns and neurodevelopment of infants until the age of 24 months.     

Ectopic expression of Arabidopsis thaliana plasma membrane intrinsic protein 2 aquaporins in lily pollen increases the plasma membrane water permeability of grain but not of tube protoplasts

To investigate the role of aquaporin-mediated water transport during pollen grain germination and tube growth, Arabidopsis thaliana plasma membrane intrinsic proteins (PIPs) were expressed in pollen of Lilium longiflorum (lily). Successful expression of AtPIPs in particle-bombarded lily pollen grains was monitored by co-expression with fluorescent proteins and single-cell RT-PCR, and by measuring the water permeability coefficient (P(os)) in swelling assays using protoplasts prepared from transformed pollen grains and tubes. Expression of AtPIP1;1 and AtPIP1;2 in pollen grains resulted in P(os) values similar to those measured in nontransformed pollen grain protoplasts (6.65 +/- 2.41 microm s(-1)), whereas expression of AtPIP2 significantly increased P(os) (AtPIP2;1, 13.79 +/- 6.38; AtPIP2;2, 10.16 +/- 3.30 microm s(-1)). Transformation with combinations of AtPIP1 and AtPIP2 did not further enhance P(os). Native pollen tube protoplasts showed higher P(os) values (13.23 +/- 4.14 microm s(-1)) than pollen grain protoplasts but expression of AtPIP2;1 (18.85 +/- 7.60 microm s(-1)) did not significantly increase their P(os) values. Expression of none of the tested PIPs had any effect on pollen tube growth rates. The ectopic expression of AtPIP2s in lily pollen increased the water permeability of the plasma membrane in pollen grains, but not in pollen tubes. The measured endogenous water permeability does not limit water uptake during tube growth, but has to be regulated to prevent tube bursting.     

A preliminary study for identifying olfactory markers of fear in the rat

In stressful situations, many animals release alarm pheromones to warn conspecifics of impending danger. The authors sought to establish experimental conditions for a larger study aimed at identifying alarm pheromones emitted by the rat. They placed rats in a specially designed chamber and exposed them to aversive tactile, visual and acoustic stimuli over the course of a few days. The researchers observed rats' behavior and analyzed air samples taken from their immediate environment under the following conditions: (i) when rats were unstressed; (ii) immediately after rats were exposed to aversive stimuli; and (iii) when rats were left alone in the chamber after being conditioned to fear imminent aversive stimuli. Stressed rats emitted several substances that are known to function as alarm pheromones in insects. When previously unstressed control rats were exposed to these same substances, they had a distinct behavioral fear response.     

NCAM-induced focal adhesion assembly: a functional switch upon loss of E-cadherin

Loss of expression of the cell-cell adhesion molecule E-cadherin is a hallmark of epithelial-mesenchymal transition (EMT) in development and in the progression from epithelial tumours to invasive and metastatic cancers. Here, we demonstrate that the loss of E-cadherin function upregulates expression of the neuronal cell adhesion molecule (NCAM). Subsequently, a subset of NCAM translocates from fibroblast growth factor receptor (FGFR) complexes outside lipid rafts into lipid rafts where it stimulates the non-receptor tyrosine kinase p59(Fyn) leading to the phosphorylation and activation of focal adhesion kinase and the assembly of integrin-mediated focal adhesions. Ablation of NCAM expression during EMT inhibits focal adhesion assembly, cell spreading and EMT. Conversely, forced expression of NCAM induces epithelial cell delamination and migration, and high NCAM expression correlates with tumour invasion. These results establish a mechanistic link between the loss of E-cadherin expression, NCAM function, focal adhesion assembly and cell migration and invasion.     

Lotus japonicus CASTOR and POLLUX Are Ion Channels Essential for Perinuclear Calcium Spiking in Legume Root Endosymbiosis

The mechanism underlying perinuclear calcium spiking induced during legume root endosymbioses is largely unknown. Lotus japonicus symbiosis-defective castor and pollux mutants are impaired in perinuclear calcium spiking. Homology modeling suggested that the related proteins CASTOR and POLLUX might be ion channels. Here, we show that CASTOR and POLLUX form two independent homocomplexes in planta. CASTOR reconstituted in planar lipid bilayers exhibited ion channel activity, and the channel characteristics were altered in a symbiosis-defective mutant carrying an amino acid replacement close to the selectivity filter. Permeability ratio determination and competition experiments reveled a weak preference of CASTOR for cations such as potassium over anions. POLLUX has an identical selectivity filter region and complemented a potassium transport–deficient yeast mutant, suggesting that POLLUX is also a potassium-permeable channel. Immunogold labeling localized the endogenous CASTOR protein to the nuclear envelope of Lotus root cells. Our data are consistent with a role of CASTOR and POLLUX in modulating the nuclear envelope membrane potential. They could either trigger the opening of calcium release channels or compensate the charge release during the calcium efflux as counter ion channels.     

Molecular profiling of yeasts isolated during spontaneous fermentations of Austrian wines

The aim of the present study was to evaluate the autochthonous yeast population during spontaneous fermentations of grape musts in Austrian wine-producing areas. Investigation of genomic and genetic variations among wine yeasts was a first step towards a long-term goal of selecting strains with valuable enological properties typical for this geographical region. An approach, combining sequences of the D1/D2 domain of the 26S rRNA gene and random amplified polymorphic DNA fingerprinting, was used to characterize yeasts at the species level, whereas the differentiation of Saccharomyces strains was accomplished by amplified fragment length polymorphism fingerprinting. At the beginning of fermentation, representatives of nine genera were identified, with Hanseniaspora and Metschnikowia species characterized most frequently. Saccharomyces cerevisiae and Saccharomyces bayanus var. uvarum strains, which were identified throughout the entire fermentation process, showed a high level of genetic diversity. A number of S. cerevisiae strains were common at multiple wineries, but a wide range of strains with characteristic profiles were characterized at individual locations. This biodiversity survey represents a contribution to the investigation and preservation of genetic diversity of biotechnologically relevant yeasts in Austrian wine-making areas.     

Acetogenic anthraquinones: biosynthetic convergence and chemical evidence of enzymatic cooperation in nature

Phenylanthraquinones belong to the quite rare class of fully unsymmetric biaryls, consisting of two different molecular portions, an anthraquinone part, chrysophanol, and a phenyl part, 2,4-dihydroxy-6-methoxyacetophenone, linked together by phenol-oxidative coupling. The biosynthesis of these two moieties, from eight and four acetate units, respectively, bears some unique features: Chrysophanol is the first example of an acetogenic natural product that is, in an organism-specific manner, formed via more than one folding mode: In eukaryotes, like, e.g., in fungi, in higher plants, and in insects, it is formed via folding mode F, while in prokaryotes it originates through mode S. It has, more recently, even been found to be synthesized by a third pathway, which we have named mode S′. It is thus the first example of biosynthetic convergence in polyketide biosynthesis. The monocyclic “southern” portion of the molecule, which is much simpler (arising from only four acetate units and without decarboxylation), unexpectedly does not show the anticipated randomization of the C₂-labeling in the aromatic ring, but has clearly localized C₂ units, excluding any symmetric intermediate like, e.g., 2,4,6-trihydroxyacetophenone. This is confirmed by competitive feeding experiments with specifically ¹³C₂-labeled acetophenones, showing the O-methylation to be the decisive symmetry-preventing step, which hints at a close collaboration of the participating enzymes. The results make knipholone an instructive example of structure, function, and evolution of polyketide synthases and O-methyltransferases, and their cooperation.

High-impact sulfur compounds: constitutional and configurational assignment of sulfur-containing heterocycles

To unambiguously identify their structures and to evaluate their organoleptic properties, several constitutional und configurational isomers of dialkyl-tetrathianes and dialkyl-pentathiepanes were synthesized by two different synthetic protocols, and separated by preparative gas chromatography. Raman and NMR spectroscopy were used to differentiate between the constitutional 3,6-dialkyl-1,2,4,5-tetrathiane and the 4,6-dialkyl-1,2,3,5-tetrathiane isomers. Furthermore, cis- and trans-isomers of 3,6-dialkyl-1,2,4,5-tetrathianes were distinguished by temperature-dependent NMR experiments. Static, quantum-chemical simulations of the NMR spectra for these cis- and trans-isomers were calculated in the gas layer in order to confirm our experimental assignments. In addition, the assignment of 4,7-alkyl-1,2,3,5,6-pentathiepanes were deducted from their Raman spectra. Dialkyl-tetrathianes and dialkyl-pentathiepanes are interesting components to be used in flavor applications due to their unique olfactory impact and facets.