Effects of anthropogenic disturbance and climate on patterns of bat fly parasitism

Environmental conditions, including anthropogenic disturbance, can significantly alter host and parasite communities. Yet, our current knowledge is based mainly on endoparasites, while ectoparasites remain little studied. We studied the indirect effects of anthropogenic disturbance (human population density) and climate (temperature, precipitation and elevation) on abundance of highly host-specific bat flies in four Neotropical bat species across 43 localities in Venezuela. We formulated a set of 11 a priori hypotheses that included a combination of the two effectors and host species. Statistically, each of these hypotheses was represented by a zero-inflated negative binomial mixture model, allowing us to control for excess zeros in the data. The best model was selected using Akaike's information criteria. Fly abundance was affected by anthropogenic disturbance in Artibeus planirostris, Carollia perspicillata and Pteronotus parnellii, but not Desmodus rotundus. Climate affected fly abundance in all bat species, suggesting mediation of these effects via the host or by direct effects on flies. We conclude that human disturbance may play a role in shaping bat-bat fly interactions. Different processes could determine fly abundance in the different bat species.     

Inverse association between Helicobacter pylori and pediatric asthma in a high-prevalence population

Background: Helicobacter pylori‐associated disease has led to aggressive diagnostic and eradication protocols that are partially responsible for the decrease in prevalence of H. pylori carriage. Recent evidence indicates that in low‐prevalence populations, H. pylori may have protective effects on allergic diseases. The aim of this study was to explore the relationship between pediatric asthma and H. pylori infection in a population with high prevalence of H. pylori infection. Materials and Methods: A national referral laboratory was screened for all ¹³C urea breath tests performed in children aged 5–18 years between 2007 and 2008, for patient demographics and physician‐diagnosed asthma. Data concerning asthma‐associated medication usage were extracted from electronic medical records and databases. Data were analyzed using a stepwise logistic regression model. Results: During the study period, 6959 patients underwent urea breath testing (average age 12.4 ± 3.5 years). Of these, 3175/6959 (45.6%) were positive for H. pylori, and 578/6959 (8.3%) had asthma. Rates of asthma in H. pylori‐positive and H. pylori‐negative children were 7.3 and 9.1%, respectively (odds ratio 0.82; 95% confidence interval (CI) 0.69–0.98; p = .032). We also confirmed that male gender, urban residence, and age are associated with childhood asthma. Conclusions: We demonstrate an inverse association between H. pylori and pediatric asthma in a population with a high prevalence of H. pylori.     

A multilocus model of the genetic architecture of autoimmune thyroid disorder, with clinical implications

We report here a preliminary model of the genetic architecture of Autoimmune Thyroid Disorder (AITD). Using a flexible class of mathematical modeling techniques, applied to an established set of data and supplemented with information both from candidate-gene and genome-wide-association studies and from basic bioinformatics, we find strong statistical support for a model in which AITD is the result of "hits" along three distinct genetic pathways: affected individuals have (1) a genetic susceptibility to clinical AITD, along with (2) a separate predisposition to develop the autoantibodies characteristic of AITD, and they also have (3) a predisposition to develop high levels of autoantibodies once they occur. Genes underlying each of these factors then appear to interact with one another to cause clinical AITD. We also find that a genetic variant in CTLA4 that increases risk for AITD in some people might actually protect against AITD in others, depending on which additional risk variants an individual carries. Our data show that the use of statistical methods for the incorporation of information from multiple sources, combined with careful modeling of distinct intermediate phenotypes, can provide insights into the genetic architecture of complex diseases. This model has several clinical implications, which we believe will prove relevant to other complex diseases as well.     

Thickness distribution of actin bundles in vitro

Bundles of filamentous actin form the primary building blocks of a broad range of cytoskeletal structures, including filopodia, stereocilia and microvilli. In each case, the cell uses specific associated proteins to tailor the dynamics, dimensions and mechanical properties of the bundles to suit a specific cellular function. While the length distribution of actin bundles was extensively studied, almost nothing is known about the thickness distribution. Here, we use high-resolution cryo-TEM to measure the thickness distribution of actin/fascin bundles, in vitro. We find that the thickness distribution has a prominent peak, with an exponential tail, supporting a scenario of an initial fast formation of a disc-like nucleus of short actin filaments, which only later elongates. The bundle thicknesses at steady state are found to follow the distribution of the initial nuclei indicating that no lateral coalescence occurs. Our results show that the distribution of bundles thicknesses can be controlled by monitoring the initial nucleation process. In vivo, this is done by using specific regulatory proteins complexes. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

The influence of ethanol on feeding in the frugivorous yellow-vented bulbul (Pycnonotus xanthopygos)

The sugars in fleshy fruits provide a rich source of energy to frugivorous animals. However, these carbohydrates also serve as a substrate for alcoholic fermentation by yeasts, ethanol being the main by-product of this process. Ethanol ingestion via frugivory thus occurs in a diverse assemblage of invertebrate and vertebrate taxa, including numerous species of birds. We tested the roles of ethanol as an odor cue for resource location by adult yellow-vented bulbuls (Pycnonotus xanthopygos) and as a possible appetite stimulant in feeding trials with artificial food. We hypothesized (1) that the odor of ethanol does not serve as a food-locating cue in diurnal frugivorous passerine birds, and predicted that the choice of food source and the mass of food eaten by such birds will not be influenced by the odor of ethanol. We further hypothesized (2) that food intake in passerine birds is affected by ingestion of ethanol according to its concentration [EtOH], and predicted that food intake will follow a bell-shaped curve in relation to [EtOH]. In accord with hypothesis (1) and its prediction, we found that the odor of ethanol did not affect food preferences, in either ethanol-naïve or ethanol-experienced yellow-vented bulbuls, when presented at concentrations found in naturally ripe fruit (0.0–1.0%); this suggests that the odor of ethanol is not a food-locating cue for the bulbuls. Hypothesis (2) was partially supported, namely at low [EtOH] (0–3%), food intake was constant and at high [EtOH] (3%) food intake decreased, following only the right half of the predicted bell-shaped response. Ethanol-naïve birds showed no preference towards any [EtOH] presented in two-way choice trials. However, daily food intake in ethanol-experienced bulbuls in single option trials decreased by an average of 36% when the artificial food contained the highest tested concentration of ethanol (3.0%). We suggest that decreasing food intake when food ethanol concentration is relatively high may be a means of avoiding intoxication and is related to the ethanol-metabolizing ability of the bird.     

Helicobacter pylori recurrence in developed and developing countries: meta-analysis of 13C-urea breath test follow-up after eradication

Objective: Recurrence of Helicobacter pylori infection after eradication is rare in developed countries and more frequent in developing countries. Most recurrent cases are attributed to recrudescence (recolonization of the same strain within 12 months) rather than to reinfection (colonization with a new strain after more than 12 months). The aim of the study was to analyze recurrence rates in developed and developing countries and to deduce the relative roles of recrudescence and reinfection. Methods: The PubMed database was searched up to January 31, 2007 using the keywords “Helicobacter pylori” or “H. pylori” and “recurrence” or “recrudescence,” or “reinfection.” Only prospective case studies in adults that used the ¹³C‐urea breath test (¹³CUBT) were included. Meta‐analyses were performed with statdirect Statistical software, version 2.6.1, StatsDirect Ltd, Chesire, UK. Results: The literature search yielded 10 studies of H. pylori recurrence in developed countries (3014 patients followed for 24–60 months) and 7 studies in developing countries (2071 patients followed for 12–60 months). The calculated annual recurrence rates were 2.67% and 13.00%, respectively. Nested meta‐analysis of cases with a longer follow‐up after eradication revealed an annual recurrence rate of 1.45% (RR 0.54) in developed countries and 12.00% (RR 0.92) in developing countries. Conclusions: The similarity of the annual recurrence rates during the first year after eradication and the annual recurrence rates in the second year after successful eradication in developing countries supports reinfection as the main cause in the second period. Therefore, a different approach for follow‐up of H. pylori eradication may be needed between developed and developing countries.     

Helicobacter pylori and Non-malignant Diseases

In 2007 Helicobacter pylori research continued to deal with some controversies raised in the last decade. The main problems remain unsolved: peptic ulcer disease negative for H. pylori , synergism of H. pylori infection and aspirin and other nonsteroidal anti-inflammatory drugs or cyclooxygenase 2 specific inhibitors, the role of H. pylori eradication in uninvestigated and nonulcer dyspepsia, and the possible protective effect of H. pylori infection against gastroesophageal reflux disease and its complications such as Barrett's esophagus and adenocarcinoma. The incidence and prevalence of peptic ulcer disease as well as ulcer-related mortality are continuing to decline all over the world. The increasing consumption of anti-inflammatory and antisecretory drugs was not found to change the trend over the last period and therefore H. pylori was considered the key factor in causing ulcer-related mortality. Some progress has been achieved in understanding H. pylori -induced immunological processes, and attack mechanisms, as well as specific pathogenesis in uremic and cirrhotic patients. There is still a lot to learn about the bacterium and host factors related to H. pylori infection and its complications.