What Makes a Difference in Exercise-Induced Bronchoconstriction: An 8 Year Retrospective Analysis

Background

Exercise-induced bronchoconstriction (EIB) was recently classified into EIB alone and EIB with asthma, based on the presence of concurrent asthma.

Objective

Differences between EIB alone and EIB with asthma have not been fully described.

Methods

We retrospectively reviewed who visited an allergy clinic for respiratory symptoms after exercise and underwent exercise bronchial provocation testing. More than a 15% decrease of forced expiratory volume in 1 second (FEV1) from baseline to the end of a 6 min free-running challenge test was interpreted as positive EIB.

Results

EIB was observed in 66.9% of the study subjects (89/133). EIB-positive subjects showed higher positivity to methacholine provocation testing (61.4% vs. 18.9%, p<0.001) compared with EIB-negative subjects. In addition, sputum eosinophilia was more frequently observed in EIB-positive subjects than in EIB-negative subjects (56% vs. 23.5%, p = 0.037). The temperature and relative humidity on exercise test day were significantly related with the EIB-positive rate. Positive EIB status was correlated with both temperature (p = 0.001) and relative humidity (p = 0.038) in the methacholine-negative EIB group while such a correlation was not observed in the methacholine-positive EIB group. In the methacholine-positive EIB group the time to reach a 15% decrease in FEV1 during exercise was significantly shorter than that in the methacholine-negative EIB group (3.2±0.7 min vs. 8.6±1.6 min, p = 0.004).

Conclusions

EIB alone may be a distinct clinical entity from EIB with asthma. Conditions such as temperature and humidity should be considered when performing exercise tests, especially in subjects with EIB alone.     

Quantification of Hordeins by ELISA: The Correct Standard Makes a Magnitude of Difference

Background

Coeliacs require a life-long gluten-free diet supported by accurate measurement of gluten (hordein) in gluten-free food. The gluten-free food industry, with a value in excess of $6 billion in 2011, currently depends on two ELISA protocols calibrated against standards that may not be representative of the sample being assayed.

Aim

The factors affecting the accuracy of ELISA analysis of hordeins in beer were examined.

Results

A simple alcohol-dithiothreitol extraction protocol successfully extracts the majority of hordeins from barley flour and malt. Primary hordein standards were purified by FPLC. ELISA detected different classes of purified hordeins with vastly different sensitivity. The dissociation constant (Kd) for a given ELISA reaction with different hordeins varied by three orders of magnitude. The Kd of the same hordein determined by ELISA using different antibodies varied by up to two orders of magnitude. The choice of either ELISA kit or hordein standard may bias the results and confound interpretation.

Conclusions

Accurate determination of hordein requires that the hordein standard used to calibrate the ELISA reaction be identical in composition to the hordeins present in the test substance. In practice it is not feasible to isolate a representative hordein standard from each test food. We suggest that mass spectrometry is more reliable than ELISA, as ELISA enumerates only the concentration of particular amino-acid epitopes which may vary between different hordeins and may not be related to the absolute hordein concentration. MS quantification is undertaken using peptides that are specific and unique enabling the quantification of individual hordein isoforms.     

What a Difference a Dalton Makes: Bacterial Virulence Factors Modulate Eukaryotic Host Cell Signaling Systems via Deamidation

SUMMARY

Pathogenic bacteria commonly deploy enzymes to promote virulence. These enzymes can modulate the functions of host cell targets. While the actions of some enzymes can be very obvious (e.g., digesting plant cell walls), others have more subtle activities. Depending on the lifestyle of the bacteria, these subtle modifications can be crucially important for pathogenesis. In particular, if bacteria rely on a living host, subtle mechanisms to alter host cellular function are likely to dominate. Several bacterial virulence factors have evolved to use enzymatic deamidation as a subtle posttranslational mechanism to modify the functions of host protein targets. Deamidation is the irreversible conversion of the amino acids glutamine and asparagine to glutamic acid and aspartic acid, respectively. Interestingly, all currently characterized bacterial deamidases affect the function of the target protein by modifying a single glutamine residue in the sequence. Deamidation of target host proteins can disrupt host signaling and downstream processes by either activating or inactivating the target. Despite the subtlety of this modification, it has been shown to cause dramatic, context-dependent effects on host cells. Several crystal structures of bacterial deamidases have been solved. All are members of the papain-like superfamily and display a cysteine-based catalytic triad. However, these proteins form distinct structural subfamilies and feature combinations of modular domains of various functions. Based on the diverse pathogens that use deamidation as a mechanism to promote virulence and the recent identification of multiple deamidases, it is clear that this enzymatic activity is emerging as an important and widespread feature in bacterial pathogenesis.     

The Difference that Diaspora Makes: Thinking through the Anthropology of Immigrant Education in the United States

In this article, I examine the possibility of a productive dialogue between diaspora studies and the anthropology of immigrant education in the United States. Arguing that their respective views on the nation-state is a key source for their different orientations toward migrant social and cultural worlds, I nevertheless argue that an engagement between these two fields of study will yield more critical understandings of nationalism, the category of the "immigrant," and multiculturalism within both these areas of scholarship.     

Moonlight Makes Owls More Chatty

Background

Lunar cycles seem to affect many of the rhythms, temporal patterns and behaviors of living things on Earth. Ambient light is known to affect visual communication in animals, with the conspicuousness of visual signals being largely determined by the light available for reflection by the sender. Although most previous studies in this context have focused on diurnal light, moonlight should not be neglected from the perspective of visual communication among nocturnal species. We recently discovered that eagle owls Bubo bubo communicate with conspecifics using a patch of white throat plumage that is repeatedly exposed during each call and is only visible during vocal displays.

Methodology/Principal Findings

Here we provide evidence that this species uses moonlight to increase the conspicuousness of this visual signal during call displays. We found that call displays are directly influenced by the amount of moonlight, with silent nights being more frequent during periods with no-moonlight than moonlight. Furthermore, high numbers of calling bouts were more frequent at moonlight. Finally, call posts were located on higher positions on moonlit nights.

Conclusions/Significance

Our results support the idea that moon phase affects the visual signaling behavior of this species, and provide a starting point for examination of this method of communication by nocturnal species.     

Stereoscopic Offset Makes Objects Easier to Recognize

Binocular vision is obviously useful for depth perception, but it might also enhance other components of visual processing, such as image segmentation. We used naturalistic images to determine whether giving an object a stereoscopic offset of 15-120 arcmin of crossed disparity relative to its background would make the object easier to recognize in briefly presented (33-133 ms), temporally masked displays. Disparity had a beneficial effect across a wide range of disparities and display durations. Most of this benefit occurred whether or not the stereoscopic contour agreed with the object’s luminance contour. We attribute this benefit to an orienting of spatial attention that selected the object and its local background for enhanced 2D pattern processing. At longer display durations, contour agreement provided an additional benefit, and a separate experiment using random-dot stimuli confirmed that stereoscopic contours plausibly contributed to recognition at the longer display durations in our experiment. We conclude that in real-world situations binocular vision confers an advantage not only for depth perception, but also for recognizing objects from their luminance patterns and bounding contours.     

What Makes a Good Pore Former: A Study of Synthetic Melittin Derivatives

Pore formation by membrane-active peptides, naturally encountered in innate immunity and infection, could have important medical and technological applications. Recently, the well-studied lytic peptide melittin has formed the basis for the development of combinatorial libraries from which potent pore-forming peptides have been derived, optimized to work under different conditions. We investigate three such peptides, macrolittin70, which is most active at neutral pH; pHD15, which is active only at low pH; and MelP5_Δ6, which was rationally designed to be active at low pH but formed only small pores. There are three, six, and six acidic residues in macrolittin70, pHD15, and MelP5_Δ6, respectively. We perform multi-microsecond simulations in 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) of hexamers of these peptides starting from transmembrane orientations at neutral pH (all residues at standard protonation), low pH (acidic residues and His protonated), and highly acidic environments in which C-termini are also protonated. Previous simulations of the parent peptides melittin and MelP5 in 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) are repeated in POPC. We find that the most potent pore-forming peptides exhibit strong interpeptide interactions, including salt bridges, H-bonds, and polar interactions. Protonation of the C-terminus promotes helicity and pore size. The proximity of the peptides allows fewer lipid headgroups to line the pores than in previous simulations, making the pores intermediate between barrel stave and toroidal. Based on these structures and geometrical arguments, we attempt to rationalize the factors that under different conditions can increase or decrease pore stability and propose mutations that could be tested experimentally.     

An Assembly Funnel Makes Biomolecular Complex Assembly Efficient

Like protein folding and crystallization, the self-assembly of complexes is a fundamental form of biomolecular organization. While the number of methods for creating synthetic complexes is growing rapidly, most require empirical tuning of assembly conditions and/or produce low yields. We use coarse-grained simulations of the assembly kinetics of complexes to identify generic limitations on yields that arise because of the many simultaneous interactions allowed between the components and intermediates of a complex. Efficient assembly occurs when nucleation is fast and growth pathways are few, i.e. when there is an assembly “funnel”. For typical complexes, an assembly funnel occurs in a narrow window of conditions whose location is highly complex specific. However, by redesigning the components this window can be drastically broadened, so that complexes can form quickly across many conditions. The generality of this approach suggests assembly funnel design as a foundational strategy for robust biomolecular complex synthesis.