Probing the 3D Structure and Function of a Cation/H+ Exchanger in Plant Reproduction

Maintaining intracellular pH and K+ homeostasis are necessary for a cell to divide, grow, and communicate with other cell types. How a cell responds to stimuli and subsequently regulates intracellular pH and K+ content are largely unknown. Ion transporters, including cation/H+ exchangers are one potential determinant of intracellular pH and K+ content. A novel family of CHX transporters, predicted to exchange a cation for a H+, is found in all land plants, though their functions in the plant and the mode of transport are mostly unknown. What is the mode of transport of Arabidopsis thaliana CHX17? Model structures of the CHX17 transmembrane domain were built from two crystallized bacterial Na+/H+ antiporters. Based on protein architecture and homology, residues were selected for mutagenesis and CHX17 activity was tested in yeast. Thr170 and Lys383 in the discontinuous α-helices of transmembrane 4 and 11, and Asp201 and Lys355 in the middle of transmembranes 5 and 10 are necessary for CHX17 activity. Results suggest these are core residues that participate in cation binding and/or catalysis. Glu111 near the cytosolic surface of CHX17 was necessary for activity, suggesting CHX17 could be regulated by cytosolic pH. Thus the protein fold and mode of transport of Arabidopsis CHX17 resemble a K+/H+ exchanger. What roles do K+/H+ exchangers play in plant reproduction? chx17/18/19 mutant plants showed a 56%-77% reduction in seed set though the biological basis was unknown. Reciprocal crosses showed reduced seed set was primarily caused by defects in the male gametophyte. Mutant chx17/18/19 pollen grains developed normally and pollen tubes grew and reached most ovules. However, half the ovules receiving a mutant pollen tube failed to develop. Wild-type pistils that received chx17/18/19 pollen showed unfertilized ovules, ovules with single fertilizations, and some embryos that developed similarly to wild-type. Thus, some triple mutant pollen showed failure to complete fertilization. When fertilization was successful, embryos from self-fertilized chx17/18/19 pods showed delays in development. Our findings suggest maintenance of pH and K+ homeostasis in endomembrane compartments by CHX17 and its homologs could regulate membrane trafficking events necessary for pollen tube growth, male gamete fusion, and embryo development

Time variability of accretion flows: effects of the adiabatic index and gas temperature

We report on next phase of our study of rotating accretion flows onto black holes. We consider hydrodynamical (HD) accretion flows with a spherically symmetric density distribution at the outer boundary but with spherical symmetry broken by the introduction of a small, latitude-dependent angular momentum. We study accretion flows by means of numerical two-dimensional, axisymmetric, HD simulations for variety of the adiabatic index, $\gamma$ and the gas temperature at infinity, $c_\infty$. Our work is an extension of work done by Proga & Begelman who consider models for only $\gamma=5/3$. Our main result is that the flow properties such as the topology of the sonic surface and time behavior strongly depend on $\gamma$ but little on $c_\infty$. In particular, for $1 < \gamma < 5/3$, the mass accretion rate shows large amplitude, slow time-variability which is a result of mixing between slow and fast rotating gas. This temporal behavior differs significantly from that in models with \gamma\simless 5/3 where the accretion rate is relatively constant and from that in models with \gamma\simgreat 1 where the accretion exhibits small amplitude quasi-periodic oscillations. The key parameter responsible for the differences is the sound speed of the accretion flow which in turn determines whether the flow is dominated by gas pressure, radiation pressure or rotation. Despite these differences the time-averaged mass accretion rate in units of the corresponding Bondi rate is a weak function of $\gamma$ and $c_\infty$.Comment: 31 pages, 14 figures, accepted for publication in ApJ, for full resolution version goto http://users.camk.edu.pl/mmosc/ms.pd

Thermochronological Evidence for Late Proterozoic (Vendian) Cooling in Southwest Wedel Jarlsberg Land, Spitsbergen

Two Proterozoic terranes with different metamorphic histories are distinguished from geological mapping in southwestern Wedel Jarlsberg Land: a northern greenschist facies terrane and a southern amphibolite facies terrane which has been overprinted by greenschist facies metamorphism. To better characterize the tectonothermal history of these terranes we have obtained new Ar-40/Ar-39 mineral dates from this area. A muscovite separate from the northern terrane yielded a Caledonian plateau age of 432 +/- 7 Ma. The southern terrane yielded significantly older Ar-40/Ar-39 ages with three muscovite plateau dates of 584 +/- 14 Ma, 575 +/- 15 Ma, and 459 +/- 9 Ma, a 484 +/- 5 Ma biotite plateau date, and a 616 +/- 17 Ma hornblende plateau date. The oldest thermochronological dates are over 300 Ma younger than the age of amphibolite facies metamorphism and therefore probably do not represent uplift-related cooling. Instead, the Vendian dates correlate well with a regionally widespread magmatic and metamorphic/thermal resetting event recognized within Caledonian complexes of northwestern Spitsbergen and Nordaustlandet. The apparent Ordovician dates are interpreted to represent partial resetting, suggesting that late Caledonian greenschist facies overprinting of the southern terrane was of variable intensity

The influence of bicuspid aortic valves on the dynamic pressure distribution in the ascending aorta: a porcine ex vivo model †

OBJECTIVES The aim of the study was to simulate the effect of different bicuspid aortic valve configurations on the dynamic pressure distribution in the ascending aorta. METHODS Aortic specimens were harvested from adult domestic pigs. In Group 1, bicuspidalization was created by a running suture between the left and the right coronary leaflets (n = 6) and in Group 2 by a running suture between the left and the non-coronary leaflets (n = 6). Eleven tricuspid specimens served as controls. Two intraluminal pressure catheters were positioned at the concavity and the convexity of the ascending aorta. The specimens were connected to a mock circulation (heart rate: 60 bpm, target pressure: 95 mmHg). A comparison of the different conditions was also done in a numerical simulation. RESULTS At a distal mean aortic pressure of 94 ± 10 mmHg, a mean flow rate of 5.2 ± 0.3 l/min was achieved. The difference of maximal dynamic pressure values (which occurred in systole) between locations at the convexity and the concavity was 7.8 ± 2.9 mmHg for the bicuspid and 1.0 ± 0.9 mmHg for the tricuspid specimens (P < 0.001). The numerical simulation revealed an even higher pressure difference between convexity and concavity for bicuspid formation. CONCLUSIONS In this hydrodynamic mock circulation model, we were able to demonstrate that bicuspid aortic valves are associated with significant pressure differences in different locations within the ascending aorta compared with tricuspid aortic valves. These altered pressure distributions and flow patterns may further add to the understanding of aneurismal development in patients with bicuspid aortic valves and might serve to anticipate adverse aortic events due to a better knowledge of the underlying mechanism

The economic value of additional airport departure capacity

This article presents a model for the economic value of extra capacity at an airport. The model is based on a series of functional relationships linking the benefits of extra capacity and the associated costs. It takes into account the cost of delay for airlines and its indirect consequences on the airport, through the loss or gain of aeronautical and non-aeronautical revenues. The model is highly data-driven and to this end a number of data sources have been used. In particular, special care has been used to take into account the full distribution of delay at the airports rather than its average only. The results with the simple version of the model show the existence of a unique maximum for the operating profit of the airport in terms of capacity. The position of this maximum is clearly dependent on the airport and also has an interesting behaviour with the average number of passenger per aircraft at the airport and the predictability of the flight departure times. In addition, we also show that there exists an important trade-off between an increased predictability and the punctuality at the airport. Finally, it is shown that a more complex behavioural model for passengers can introduce several local maxima in the airport profit and thus drive the airport towards suboptimal decisions

Fitting the integrated Spectral Energy Distributions of Galaxies

Fitting the spectral energy distributions (SEDs) of galaxies is an almost universally used technique that has matured significantly in the last decade. Model predictions and fitting procedures have improved significantly over this time, attempting to keep up with the vastly increased volume and quality of available data. We review here the field of SED fitting, describing the modelling of ultraviolet to infrared galaxy SEDs, the creation of multiwavelength data sets, and the methods used to fit model SEDs to observed galaxy data sets. We touch upon the achievements and challenges in the major ingredients of SED fitting, with a special emphasis on describing the interplay between the quality of the available data, the quality of the available models, and the best fitting technique to use in order to obtain a realistic measurement as well as realistic uncertainties. We conclude that SED fitting can be used effectively to derive a range of physical properties of galaxies, such as redshift, stellar masses, star formation rates, dust masses, and metallicities, with care taken not to over-interpret the available data. Yet there still exist many issues such as estimating the age of the oldest stars in a galaxy, finer details ofdust properties and dust-star geometry, and the influences of poorly understood, luminous stellar types and phases. The challenge for the coming years will be to improve both the models and the observational data sets to resolve these uncertainties. The present review will be made available on an interactive, moderated web page (sedfitting.org), where the community can access and change the text. The intention is to expand the text and keep it up to date over the coming years.Comment: 54 pages, 26 figures, Accepted for publication in Astrophysics & Space Scienc

Data standards for transcatheter aortic valve implantation: the European Unified Registries for Heart Care Evaluation and Randomised Trials (EuroHeart)

Funding: European Society of Cardiology.publishersversionepub_ahead_of_prin

Genomic Expression Libraries for the Identification of Cross-Reactive Orthopoxvirus Antigens

Increasing numbers of human cowpox virus infections that are being observed and that particularly affect young non-vaccinated persons have renewed interest in this zoonotic disease. Usually causing a self-limiting local infection, human cowpox can in fact be fatal for immunocompromised individuals. Conventional smallpox vaccination presumably protects an individual from infections with other Orthopoxviruses, including cowpox virus. However, available live vaccines are causing severe adverse reactions especially in individuals with impaired immunity. Because of a decrease in protective immunity against Orthopoxviruses and a coincident increase in the proportion of immunodeficient individuals in today's population, safer vaccines need to be developed. Recombinant subunit vaccines containing cross-reactive antigens are promising candidates, which avoid the application of infectious virus. However, subunit vaccines should contain carefully selected antigens to confer a solid cross-protection against different Orthopoxvirus species. Little is known about the cross-reactivity of antibodies elicited to cowpox virus proteins. Here, we first identified 21 immunogenic proteins of cowpox and vaccinia virus by serological screenings of genomic Orthopoxvirus expression libraries. Screenings were performed using sera from vaccinated humans and animals as well as clinical sera from patients and animals with a naturally acquired cowpox virus infection. We further analyzed the cross-reactivity of the identified immunogenic proteins. Out of 21 identified proteins 16 were found to be cross-reactive between cowpox and vaccinia virus. The presented findings provide important indications for the design of new-generation recombinant subunit vaccines