Protists have divergent effects on bacterial diversity along a productivity gradient

Productivity and predation are thought to be crucial drivers of bacterial diversity. We tested how the productivity–diversity of a natural bacterial community is modified by the presence of protist predators with different feeding preferences. In the absence of predators, there was a unimodal relationship between bacterial diversity and productivity. We found that three protist species (Bodo, Spumella and Cyclidium) had widely divergent effects on bacterial diversity across the productivity gradient. Bodo and Cyclidium had little effect on the shape of the productivity–diversity gradient, while Spumella flattened the relationship. We explain these results in terms of the feeding preferences of these predators.     

Cth2 Protein Mediates Early Adaptation of Yeast Cells to Oxidative Stress Conditions

Cth2 is an mRNA-binding protein that participates in remodeling yeast cell metabolism in iron starvation conditions by promoting decay of the targeted molecules, in order to avoid excess iron consumption. This study shows that in the absence of Cth2 immediate upregulation of expression of several of the iron regulon genes (involved in high affinity iron uptake and intracellular iron redistribution) upon oxidative stress by hydroperoxide is more intense than in wild type conditions where Cth2 is present. The oxidative stress provokes a temporary increase in the levels of Cth2 (itself a member of the iron regulon). In such conditions Cth2 molecules accumulate at P bodies-like structures when the constitutive mRNA decay machinery is compromised. In addition, a null Δcth2 mutant shows defects, in comparison to CTH2 wild type cells, in exit from α factor-induced arrest at the G1 stage of the cell cycle when hydroperoxide treatment is applied. The cell cycle defects are rescued in conditions that compromise uptake of external iron into the cytosol. The observations support a role of Cth2 in modulating expression of diverse iron regulon genes, excluding those specifically involved in the reductive branch of the high-affinity transport. This would result in immediate adaptation of the yeast cells to an oxidative stress, by controlling uptake of oxidant-promoting iron cations.     

Guidelines on appropriate indications for upper gastrointestinal endoscopy. Working Party of the Joint Committee of the Royal College of Physicians of London,Royal College of Surgeons of England,Royal College of Anaesthetists,Association of Surgeons,the British Society of Gastroenterology,and the Thoracic Society of Great Britain.

Upper gastrointestinal endoscopy is a valuable diagnostic tool, but for an endoscopy service to be effective it is essential that it is not overloaded with inappropriately referred patients. A joint working party in Britain has considered the available literature on indications for endoscopy, assessed standard practice through a questionnaire, and audited randomly selected cases using an independent panel of experts and an American database system. They used these data to produce guidelines on the appropriate and inappropriate indications for referral for endoscopy, although they emphasise that under certain circumstances there may be reasons to deviate from the advice given. The need for endoscopy is most difficult to judge in patients with dyspepsia, and this aspect is discussed in detail. Early endoscopy will often prove more cost effective than delaying until the indications are clearer.     

Dissociating Two Stages of Preparation in the Stop Signal Task Using fMRI

Often we must balance being prepared to act quickly with being prepared to suddenly stop. The stop signal task (SST) is widely used to study inhibitory control, and provides a measure of the speed of the stop process that is robust to changes in subjects’ response strategy. Previous studies have shown that preparation affects inhibition. We used fMRI to separate activity that occurs after a brief (500 ms) warning stimulus (warning-phase) from activity that occurs during responses that follow (response-phase). Both of these phases could contribute to the preparedness to stop because they both precede stop signals. Warning stimuli activated posterior networks that signal the need for top-down control, whereas response phases engaged prefrontal and subcortical networks that implement top-down control. Regression analyses revealed that both of these phases affect inhibitory control in different ways. Warning-phase activity in the cerebellum and posterior cingulate predicted stop latency and accuracy, respectively. By contrast, response-phase activity in fronto-temporal areas and left striatum predicted go speed and stop accuracy, in pre-supplementary motor area affected stop accuracy, and in right striatum predicted stop latency and accuracy. The ability to separate hidden contributions to inhibitory control during warning-phases from those during response-phases can aid in the study of models of preparation and inhibitory control, and of disorders marked by poor top-down control.     

Evolutionary history of Scinax treefrogs on land‐bridge islands in south‐eastern Brazil

Aim We investigated how Pleistocene refugia and recent (c. 12,000 years ago) sea level incursions shaped genetic differentiation in mainland and island populations of the Scinax perpusillus treefrog group. Location Brazilian Atlantic Forest, São Paulo state, south‐eastern Brazil. Methods Using mitochondrial and microsatellite loci, we examined population structure and genetic diversity in three species from the S. perpusillus group, sampled from three land‐bridge islands and five mainland populations, in order to understand the roles of Pleistocene forest fragmentation and sea level incursions on genetic differentiation. We calculated metrics of relatedness and genetic diversity to assess whether island populations exhibit signatures of genetic drift and isolation. Two of the three island populations in this study have previously been described as new species based on a combination of distinct morphological and behavioural characters, thus we used the molecular datasets to determine whether phenotypic change is consistent with genetic differentiation. Results Our analyses recovered three distinct lineages or demes composed of northern mainland São Paulo populations, southern mainland São Paulo populations, and one divergent island population. The two remaining island populations clustered with samples from adjacent mainland populations. Estimates of allelic richness were significantly lower, and estimates of relatedness were significantly higher, in island populations relative to their mainland counterparts. Main conclusions Fine‐scale genetic structure across mainland populations indicates the possible existence of local refugia within São Paulo state, underscoring the small geographic scale at which populations diverge in this species‐rich region of the Atlantic Coastal Forest. Variation in genetic signatures across the three islands indicates that the populations experienced different demographic processes after marine incursions fragmented the distribution of the S. perpusillus group. Genetic signatures of inbreeding and drift in some island populations indicate that small population sizes, coupled with strong ecological selection, may be important evolutionary forces driving speciation on land‐bridge islands.     

Toxic shock syndrome in a patient with systemic lupus erythematosus.

A case is presented of toxic shock syndrome in a patient with systemic lupus erythematosus. Toxic shock syndrome is rarely reported in patients who are immunosuppressed, perhaps because such patients are often treated vigorously with antibiotics at the earliest sign of infection. The association in this case may have been coincidental.     

Effects of exercise and thermal stress on caffeine pharmacokinetics in men and eumenorrheic women.

The influence of gender, exercise, and thermal stress on caffeine pharmacokinetics is unclear. We hypothesized that these factors would not have an effect on the metabolism of caffeine. Eight women participated in four 8-h trials and six men participated in two 8-h trials after the ingestion of 6 mg/kg caffeine. The women performed two resting trials (1 in the follicular phase and 1 in the luteal phase of the menstrual cycle) and two exercise trials (90 min of cycling exercise at 65% of maximal O(2) uptake, 1 h after caffeine ingestion) in the follicular phase (1 without and 1 with an additional thermal stress). The men performed one exercise and one resting trial. Menstrual cycle, gender, and exercise, with or without an additional thermal stress, had no effect on the pharmacokinetic measurements or urine caffeine. There was a trend for higher plasma caffeine and lower plasma paraxanthine concentrations in the women. These results confirm that gender, exercise, and thermal stress have no effect on caffeine pharmacokinetics in men and women.