Water use efficiency of twenty-five co-existing Patagonian species growing under different soil water availability

The variation of plant water use efficiency (WUE) with water availability has two interacting components: a plastic response, evident when individuals of the same genotype are compared (e.g. wet versus dry years), and an interspecific response, evident when different species living in habitats with different water availability are compared. We analysed the WUE of 25 Patagonian species that belong to four life forms (grasses, shrubs, annual herbs and perennial herbs) in relation to the climatic conditions of 2 years and the mean historic water availability experienced by each species. To estimate water availability, we calculated the effective soil water potential (EWP) of each species, based on available information about soil water dynamics, phenology and root system structure. To estimate WUE, we used isotopic discrimination of leaf C (Δ¹³C) and mean annual water vapour difference between leaves and atmosphere (Δe) measured in situ. For the plastic response, for every species and life form, WUE increased from the dry to the wet year. We hypothesize that photosynthesis was less nutrient limited in the wet than in the dry year, facilitating higher net photosynthesis rates per unit of stomatal conductance in the wet year. For the interspecific response, WUE was lower in species native to drier habitats than in species native to wetter habitats. This response was mostly accounted for by a decrease in Δe with EWP. Annual herbs, which avoid drought in time (they have the earliest growth cycle), and shrubs, which avoid drought in space (they have the deepest roots), showed the highest EWP and WUE. We conclude that the conventional wisdom which states that the highest WUE occurs within a species during the driest years, and among species in the driest habitats, does not always hold true, and that co-existing life forms drastically differ in water availability and water economy.     

Enantioseparation of phenylglycinol in chiral-modified zeolite HY: a molecular simulation study

A mechanism has been proposed for the separation of valinol enantiomers using a chiral-modified zeolite HY (i.e., zeolite HY containing (+)-(1R;2R)-hydrobenzoin) Molecular modeling of chiral-modified zeolite HY employed in enantioselective separation. Jirapongphan SS, Warzywoda J, Budil DE, Sacco A Jr. Chirality 2007; in press, which accurately predicted the experimentally measured enantioseparation. This methodology has been applied to predict the separation of an enantiomeric pair of phenylglycinol molecules (a precursor in the synthesis of HIV-1 protease inhibitors) using the modified zeolite HY as a CSP. Phenylglycinol and valinol molecules are similar in terms of the presence of polar (i.e., amine and hydroxyl) groups. These functional groups are important in the proposed chiral discrimination. Supercage-based docking simulations yielded an enantioselectivity of 1.3 with (+)-(S)-phenylglycinol molecule better retained in the zeolite. Also, the simulations predicted two binding modes that were the same as those in the valinol system. This suggests that specific structural features (i.e., number and type of polar groups), which generate the hypothesized binding modes, are required in an enantioseparation utilizing the chiral-modified zeolite HY.     

Olfactory performance of rats after selective deafferentation of the olfactory bulb by 3-methyl indole

Rats trained to detect propyl acetate and valeric acid and to discriminate between propyl acetate and amyl acetate and between valeric acid and butyric acid were injected with a low dose of 3-methyl indole, a treatment that produces well-defined and selective deafferentation of the olfactory bulbs. Treatment completely deafferented most but not all bulbar loci for aliphatic acids and at least disrupted those for propyl and amyl acetate. In posttreatment tests, experimental rats performed somewhat but not significantly more poorly than controls and about as well on the acid detection and discrimination tasks as on the corresponding acetate tests.     

Exploring disparities between global HIV/AIDS funding and recent tsunami relief efforts: an ethical analysis

Objective: To contrast relief efforts for the 26 December 2004 tsunami with current global HIV/AIDS relief efforts and analyse possible reasons for the disparity. Methods: Literature review and ethical analysis. Results: Just over 273,000 people died in the tsunami, resulting in relief efforts of more than US$10 bn, which is sufficient to achieve the United Nation’s long‐term recovery plan for South East Asia. In contrast, 14 times more people died from HIV/AIDS in 2004, with UNAIDS predicting a US$8 bn funding gap for HIV/AIDS in developing nations between now and 2007. This disparity raises two important ethical questions. First, what is it that motivates a more empathic response to the victims of the tsunami than to those affected by HIV/AIDS? Second, is there a morally relevant difference between the two tragedies that justifies the difference in the international response? The principle of justice requires that two cases similarly situated be treated similarly. For the difference in the international response to the tsunami and HIV/AIDS to be justified, the tragedies have to be shown to be dissimilar in some relevant respect. Are the tragedies of the tsunami disaster and the HIV/AIDS pandemic sufficiently different, in relevant respects, to justify the difference in scope of the response by the international community? Conclusion: We detected no morally relevant distinction between the tsunami and the HIV/AIDS pandemic that justifies the disparity. Therefore, we must conclude that the international response to HIV/AIDS violates the fundamental principles of justice and fairness.     

Receiver bias for exaggerated signals in honeybees and its implications for the evolution of floral displays

Mechanistic models of animal signals posit the occurrence of biases on the part of receivers that could be potentially exploited by signallers. Such biases are most obvious when animals are confronted with exaggerated versions of signals they normally encounter. Signalling systems operating in plant-pollinator interactions are among the most highly coevolved, with plants using a variety of floral signals to attract pollinators. A number of observations suggest that pollinators preferentially visit larger floral displays although the benefit of this to either the plant or the pollinator is not always clear. We use a standard dual-choice experimental protocol to show that honeybees display a receiver bias for exaggerated size and colour contrast--two important components of floral signals--even when such signals do not indicate quality. We discuss the implications of this receiver bias for the evolution of floral displays and its possible exploitation by invading alien plants.     

The fallacy of the Principle of Procreative Beneficence

The claim that we have a moral obligation, where a choice can be made, to bring to birth the 'best' child possible, has been highly controversial for a number of decades. More recently Savulescu has labelled this claim the Principle of Procreative Beneficence. It has been argued that this Principle is problematic in both its reasoning and its implications, most notably in that it places lower moral value on the disabled. Relentless criticism of this proposed moral obligation, however, has been unable, thus far, to discredit this Principle convincingly and as a result its influence shows no sign of abating. I will argue that while criticisms of the implications and detail of the reasoning behind it are well founded, they are unlikely to produce an argument that will ultimately discredit the obligation that the Principle of Procreative Beneficence represents. I believe that what is needed finally and convincingly to reveal the fallacy of this Principle is a critique of its ultimate theoretical foundation, the notion of impersonal harm. In this paper I argue that while the notion of impersonal harm is intuitively very appealing, its plausibility is based entirely on this intuitive appeal and not on sound moral reasoning. I show that there is another plausible explanation for our intuitive response and I believe that this, in conjunction with the other theoretical criticisms that I and others have levelled at this Principle, shows that the Principle of Procreative Beneficence should be rejected.     

Does Bienertia cycloptera with the single-cell system of C(4) photosynthesis exhibit a seasonal pattern of delta (13)C values in nature similar to co-existing C (4) Chenopodiaceae having the dual-cell (Kranz) system?

Family Chenopodiaceae is an intriguing lineage, having the largest number of C₄ species among dicots, including a number of anatomical variants of Kranz anatomy and three single-cell C₄ functioning species. In some previous studies, during the culture of Bienertia cycloptera Bunge ex Boiss., carbon isotope values (δ¹³C values) of leaves deviated from C₄ to C₃−C₄ intermediate type, raising questions as to its mode of photosynthesis during growth in natural environments. This species usually co-occurs with several Kranz type C₄ annuals. The development of B. cycloptera morphologically and δ¹³C values derived from plant samples (cotyledons, leaves, bracts, shoots) were analyzed over a complete growing season in a salt flat in north central Iran, along with eight Kranz type C₄ species and one C₃ species. For a number of species, plants were greenhouse-grown from seeds collected from the site, in order to examine leaf anatomy and C₄ biochemical subtype. Among the nine C₄ species, the cotyledons of B. cycloptera, and of the Suaeda spp. have the same respective forms of C₄ anatomy occurring in leaves, while cotyledons of members of tribe Caroxyloneae lack Kranz anatomy, which is reflected in the δ¹³C values found in plants grown in the natural habitat. The nine C₄ species had average seasonal δ¹³C values of −13.9‰ (with a range between species from −11.3 to −15.9‰). The measurements of δ¹³C values over a complete growing season show that B. cycloptera performs C₄ photosynthesis during its life cycle in nature, similar to Kranz type species, with a seasonal average δ¹³C value of −15.2‰. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Allostery in pharmacology: thermodynamics, evolution and design

This review focuses on basic models of allostery, the ambiguous application of the allosteric term in pharmacology illustrated by receptors, the role of thermodynamics in allosteric mechanisms, evolution and design of allostery. The initial step of ligand activation is closure of the agonist-binding cavity. Large entropy increases accompany the agonist-elicited conformational changes of pentameric ligand-gated ion channels due to cavity closure and rearrangement of transmembrane helices. The effects of point mutations on thermodynamic parameters of binding and function can reveal energetic coupling of neighbouring (and distant) amino acid residues in activation. High-order double-mutant cycle analysis and rate-equilibrium linear free-energy relationships can identify the trajectory and conformational spread of activation.Protein assembly and allostery can be deduced from colocalization and physicochemical principles. Molecular evolution has led from homooligomerization of protomers to heterotropic cooperativity and to allosteric regulation. Examples are discussed such as similar paths of protein (dis)assembly and evolution, irreversible evolution, statistical analysis of sequence homology revealing coevolution, different impacts of adaptation and evolution on hemoglobin, and the flagellar motor switch of bacteria. The driving force of dynamic allostery is associated with funnel-like free energy landscapes of protein binding and shifts in conformational fluctuations upon binding. Allostery can be designed based on our increasing knowledge of natural allosteric mechanisms and evolution. The allosteric principle has been applied for various bio/macro/molecular and signal transduction systems as well as in cognitive sciences.     

Multivariate analysis of bacterial volatile compound profiles for discrimination between selected species and strains in vitro

Volatile compounds (VCs) are produced by all microorganisms as part of their normal metabolism. The aim of this study was to determine whether bacterial VC profiles could be used to discriminate between selected bacterial species and strains in vitro.Selected Ion Flow Tube Mass Spectrometry (SIFT-MS) was used to quantify the concentration of 23 microbial VCs within the head-space of various bacterial monocultures, during both the logarithmic and stationary growth phases. In comparison with existing techniques, SIFT-MS enables quantitative, high throughput, real-time head-space analysis to be performed, without need for sample preparation. The results show that most VCs were produced by > 1 bacterial species or strain, and some were produced by all strains tested. Multivariate analysis using similarity matrices, cluster analysis and multidimensional scaling (MDS) was used to determine whether there was a characteristic VC profile at either the species or strain level. Significant discrimination of all bacterial species and strains was achieved by analysing the VC profiles, and the relative similarity of VC profiles could be differentiated in 2 or 3 dimensional space. This study has shown that there are significant differences in the volatile profiles obtained from various bacterial monocultures grown in vitro, and that the analysis techniques herein employed have the potential to differentiate samples at the strain level.     

Tracking of food quantity by coyotes (Canis latrans)

Previous studies have demonstrated that Weber's Law mediates quantitative discrimination abilities across various species. Here, we tested coyotes’ (Canis latrans) ability to discriminate between various quantities of food and investigated whether this ability conforms to predictions of Weber's Law. We demonstrate herein that coyotes are capable of reliably discriminating large versus small quantities of discrete food items. As predicted by Weber's Law, coyotes’ quantitative discrimination abilities are mediated by the ratio between the large and small quantities of food and exhibit scalar variability. Furthermore, in this task coyotes were not discriminating large versus small quantities based on olfactory cues alone.