A model of triploid endosperm evolution driven by parent-offspring conflict

The parental investment in angiosperms comprises the endosperm, a nutrient reserve that is used during seed development. The endosperm contains genes from both parents. The most common endosperm form is the 3n Polygonum -type with more maternal genetic influence than paternal, i.e. with two maternal nuclei and one paternal nucleus. The evolutionary original state is thought to be a diploid endosperm with equal influence of the parents. We focus on the evolution of the triploid endosperm and show that a gene for triploid endosperm would have an initial advantage in a population of diploid endosperm type plants, and increase to fixation. We assume that endosperm amount is controlled by endosperm genes. Then a gene causing triploid endosperm will increase the influence of the mother plant on parental investment. The production of endosperm with two copies of the maternal genes will modify the inheritance of endosperm amount and cause an increased production of seeds.     

Iron prevents ascorbic acid (vitamin C) induced hydrogen peroxide accumulation in copper contaminated drinking water

Ascorbic acid (vitamin C) induced hydrogen peroxide (H₂O₂) formation was measured in household drinking water and metal supplemented Milli-Q water by using the FOX assay. Here we show that ascorbic acid readily induces H₂O₂ formation in Cu(II) supplemented Milli-Q water and poorly buffered household drinking water. In contrast to Cu(II), iron was not capable to support ascorbic acid induced H₂O₂ formation during acidic conditions (pH: 3.5-5). In 12 out of the 48 drinking water samples incubated with 2 mM ascorbic acid, the H₂O₂ concentration exceeded 400 μM. However, when trace amounts of Fe(III) (0.2 mg/l) was present during incubation, the ascorbic acid/Cu(II)-induced H₂O₂ accumulation was totally blocked. Of the other common divalent or trivalent metal ions tested, that are normally present in drinking water (calcium, magnesium, zinc, cobalt, manganese or aluminum), only calcium and magnesium displayed a modest inhibitory activity on the ascorbic acid/Cu(II)-induced H₂O₂ formation. Oxalic acid, one of the degradation products from ascorbic acid, was confirmed to actively participate in the iron induced degradation of H₂O₂. Ascorbic acid/Cu(II)-induced H₂O₂ formation during acidic conditions, as demonstrated here in poorly buffered drinking water, could be of importance in host defense against bacterial infections. In addition, our findings might explain the mechanism for the protective effect of iron against vitamin C induced cell toxicity.     

A theoretical framework for quantitative analysis of the molecular basis of costimulation

We present a theoretical framework for simulating the synaptic accumulation of the costimulatory molecules CD28, CTLA-4, B7-1, and B7-2, based on a system of mean-field, ordinary differential equations, and rigorous biophysical and expression data. The simulations show that binding affinity, stoichiometric properties, expression levels, and, in particular, competition effects all profoundly influence complex formation at cellular interfaces. B7-2 engages 33-fold more CD28 than CTLA-4 at the synapse in contrast to B7-1, which ligates approximately 7-fold more CTLA-4 than CD28. Although B7-1 completely dominates interactions with CTLA-4, forming linear arrays of 7-18 receptor-ligand pairs, CTLA-4 is fully engaged by B7-2 when B7-1 is absent. Additional simulations reveal the sensitivity of CD28 interactions to modeled transport processes. The results support the concept that B7-2 and B7-1 are the dominant ligands of CD28 and CTLA-4, respectively, and indicate that the inability of B7-2 to recruit CTLA-4 to the synapse cannot be due to the differential binding properties of B7-1 and B7-2 only. We discuss the apparent redundancy of B7-1 in the context of a potentially dynamic synaptic microenvironment, and in light of functions other than the direct enhancement of T cell inhibition by CTLA-4.     

Efficient fractionation and improved protein identification by peptide OFFGEL electrophoresis

The sample fractionation steps conducted prior to mass detection are critically important for the comprehensive analysis of complex protein mixtures. This paper illustrates the effectiveness of OFFGEL electrophoresis with the Agilent 3100 OFFGEL Fractionator for the fractionation of peptides. An Escherichia coli tryptic digest was separated in 24 fractions, and peptides were identified by reversed-phase liquid chromatography on a microfluidic device with mass spectrometric detection. About 90% of the identified individual peptides were found in only one or two fractions. The distribution of the calculated isoelectric points for the peptides identified in each fraction was especially narrow in the acidic pH range. Standard deviations approached the size of the pH segment covered by the respective fraction. The experimental peptide isoelectric point measured by OFFGEL electrophoresis was used as an additional filter for validation of peptide identifications.     

Binding of calcium to anticoagulant protein S: role of the fourth EGF module

Protein S is an anticoagulant protein containing a Gla (enclosing gamma-carboxyglutamic acids) module, a TSR (thrombin sensitive region) module, four EGF (epidermal growth factor)-like modules, and a SHBG (sex hormone binding globulin)-like region. Protein S is a cofactor to activated protein C (APC) in the degradation of coagulation factors Va and VIIIa but also has APC-independent activities. The function of the fourth EGF module (EGF4) in protein S has so far not been clear. We have now investigated this module through studies of recombinant wild-type protein S and a naturally occurring mutant (Asn217Ser). The mutant has essentially normal APC anticoagulant activity and a previously reported secretion defect. In the wild-type protein, Asn217 is normally beta-hydroxylated. The binding of calcium to wild-type protein S is characterized by four high-affinity binding sites with K(D) values ranging from 10(-)(7) to 10(-)(9) M. Three of these binding sites are located in EGF modules. Using surface plasmon resonance, competition with a calcium chelator, and antibody-based methods, we found that one high-affinity binding site for calcium was lost in protein S Asn217Ser but that the mutation also affected the calcium-dependent conformation of EGF1. We conclude that binding of calcium to EGF4 of protein S, involving Asn217, is important for the maintenance of the structure of protein S. Also, the abolition of binding of calcium to EGF4, related to Asn217, impairs both the structure and function of EGF1.     

Herbivory limits the yellow water lily in an overgrown lake and in flowing water

Aquatic macrophytes with floating leaves are often key ecological species that affect entire aquatic ecosystems. Here we describe an investigation of the importance of insect herbivory for population growth and leaf senescence in the yellow water lily (Nuphar lutea). In order to gain a general picture of the importance of herbivory under different conditions, we experimentally manipulated herbivory in a large lily population in natural still water and observed the natural development of 32 smaller populations in flowing water. Herbivory drastically increased leaf senescence, reducing leaf density. In the still water, over one summer, leaf density increased by a factor of 1.23 in the presence of water lily leaf beetles and 1.61 when herbivory was eliminated. In flowing water, population growth was restricted mainly by leaf crowdedness, which limited large dense populations. Herbivory by water lily leaf beetles also had a limiting effect on yellow water lily, again mainly in large dense populations. Small populations supported a lower density of beetles. Previous studies have not addressed population-level responses of vascular plants with floating leaves. Our results suggest that herbivory can result in greater light penetration into the water and reduce “enemy-free space” for aquatic species that find such space in water lily stands. We suggest that the water lily leaf beetle should be considered an “ecological engineer.”     

Resource Needs for Adolescent Friendly Health Services: Estimates for 74 Low- and Middle-Income Countries

Background

In order to achieve Millennium Development Goals 4, 5 and 6, it is essential to address adolescents’ health.

Objective

To estimate the additional resources required to scale up adolescent friendly health service interventions with the objective to reduce mortality and morbidity among individuals aged 10 to 19 years in 74 low- and middle- income countries.

Methods

A costing model was developed to estimate the financial resources needed to scale-up delivery of a set of interventions including contraception, maternity care, management of sexually transmitted infections, HIV testing and counseling, safe abortion services, HIV harm reduction, HIV care and treatment and care of injuries due to intimate partner physical and sexual violence. Financial costs were estimated for each intervention, country and year using a bottom-up ingredients approach, defining costs at different levels of delivery (i.e., community, health centre, and hospital level). Programme activity costs to improve quality of care were also estimated, including activities undertaken at national-, district- and facility level in order to improve adolescents’ use of health services (i.e., to render health services adolescent friendly).

Results

Costs of achieving universal coverage are estimated at an additional US$ 15.41 billion for the period 2011–2015, increasing from US$ 1.86 billion in 2011 to US$ 4,31 billion in 2015. This corresponds to approximately US$ 1.02 per adolescent in 2011, increasing to 4.70 in 2015. On average, for all 74 countries, an annual additional expenditure per capita ranging from of US$ 0.38 in 2011 to US$ 0.82 in 2015, would be required to support the scale-up of key adolescent friendly health services.

Conclusion

The estimated costs show a substantial investment gap and are indicative of the additional investments required to scale up health service delivery to adolescents towards universal coverage by 2015.     

Multiblock Copolymers with Highly Sulfonated Blocks Containing Di‐ and Tetrasulfonated Arylene Sulfone Segments for Proton Exchange Membrane Fuel Cell Applications

Multiblock copoly(arylene ether sulfone)s with different block lengths and ionic contents are tailored for durable and proton‐conducting electrolyte membranes. Two series of fully aromatic copolymers are prepared by coupling reactions between non‐sulfonated hydrophobic precursor blocks and highly sulfonated hydrophilic precursor blocks containing either fully disulfonated diarylsulfone or fully tetrasulfonated tetraaryldisulfone segments. The sulfonic acid groups are exclusively introduced in ortho positions to the sulfone bridges to impede desulfonation reactions and give the blocks ion exchange capacities (IECs) of 4.1 and 4.6 meq. g^?1, respectively. Solvent cast block copolymer membranes show well‐connected hydrophilic nanophase domains for proton transport and high decomposition temperatures above 310 °C under air. Despite higher IEC values, membranes containing tetrasulfonated tetraaryldisulfone segments display a markedly lower water uptake than the corresponding ones with disulfonated diarylsulfone segments when immersed in water at 100 °C, presumably because of the much higher chain stiffness and glass transition temperature of the former segments. The former membranes have proton conductivities in level of a perfluorosulfonic acid membrane (NRE212) under fully humidified conditions. A membrane with an IEC of 1.83 meq. g^?1 reaches above 6 mS cm^?1 under 30% relative humidity at 80 °C, to be compared with 10 mS cm^?1 for NRE212 under the same conditions.