Challenging the trade-off model for the evolution of virulence: is virulence management feasible?

Progress in understanding the evolution of infectious diseases has inspired proposals to manage the evolution of pathogen (including parasite) virulence. A common view is that social interventions that lower pathogen transmission will indirectly select lower virulence because of a trade-off between transmission and virulence. Here, we argue that there is little theoretical justification and no empirical evidence for this plan. Although a trade-off model might apply to some pathogens, the mechanism appears too weak for rapid selection of substantial changes in virulence. Direct selection against virulence itself might be a more rewarding approach to managing the evolution of virulence.     

Chromosome number variability in central european members of the<Emphasis Type="Italic">Festuca ovina</Emphasis> and<Emphasis Type="Italic">F. pallens</Emphasis> groups (sect.<Emphasis Type="Italic">Festuca</Emphasis>)

Chromosome numbers for 98 plants ofF. pallens, 19 ofF. psammophila, F. belensis andF. vaginata, and 44 ofF. ovina (originating from Austria, the Czech Republic, Germany, Slovakia and Latvia) are given. In addition to theF. ovina andF. pallens groups, chromosome counts for the following taxa are also reported:F. alpestris (2n=14) reported for the first time in this work,F. amethystina subsp.amethystina (2n=28),F. brevipila (2n=42),F. cinerea (2n=28),F. rupicola subsp.rupicola (2n=42) andF. versicolor subsp.versicolor (2n=14).InF. pallens, two ploidy levels (2n=2x=14+0-1B, 2n=4x=28+0-1B) as well as two natural triploid plants (2n=21+0-1B), were found. In addition to the fourF. pallens types that have been distinguished in Austria, one new tetraploid type (F. pallens “scabrifolia”) from the Czech Republic and Germany is reported and its taxonomy is discussed. The distributions of the Oberösterreich-Niederösterreich and Pannonisches-HügellandF. pallens types outside of Austria are documented.Only the diploid chromosome number (2n=14) was found inF. psammophila andF. vaginata. Chromosome numbers forF. psammophila subsp.muellerstollii andF. belensis (both 2n=14) were determined here for the first time. Two ploidy levels, 2n=14+0-5B corresponding toF. ovina subsp.ovina and 2n=28 corresponding toF. ovina subsp.guestphalica andF. cf.duernsteinensis were confirmed inF. ovina. Differences in chromosome structure (simple and multiple secondary constrictions) betweenF. pallens as opposed toF. psammophila andF. vaginata are discussed. A complete survey of published chromosome counts for Central European species from theF. ovina andF. pallens groups is included.     

A possible role for atrial fibroblasts in postinfarction bradycardia

Atrial fibroblasts are considered to modulate the contractile activity of the heart in response to mechanical stretch. In this study we examined whether atrial fibroblasts are possibly involved in bradyarrhythmia, which is a severe complication after myocardial infarction. For this purpose, transmembrane electrical potentials were recorded in cardiac fibroblasts near the sinoatrial node from sham-operated rats and from rats with myocardial infarction. Twenty days after infarction due to coronary artery ligation, the right atrial tissue weights and the sensitivity of the fibroblast membrane potential to mechanical stretch correlated positively with the infarct size. Cardiac growth was enhanced, but the stretch sensitivity and the resting membrane potential of the atrial fibroblasts declined between 8 and 30 days after infarction. The frequency of spontaneous atrial contractions was significantly reduced 8 days after myocardial infarction and recovered in parallel with the membrane potential of the fibroblasts. These findings suggest that changes in the susceptibility of atrial fibroblasts to mechanical stretch may contribute to bradyarrhythmia during postinfarct remodeling of the heart.     

Are you looking at me? Accuracy in processing line-of-sight in Turner syndrome.

The behavioural phenotype of women with Turner syndrome (X-monosomy, 45,X) is poorly understood, but includes reports of some social development anomalies. With this in mind, accuracy of direction of gaze detection was investigated in women with Turner syndrome. Two simple experimental tasks were used to test the prediction that the ability to ascertain gaze direction from face photographs showing small lateral angular gaze deviations would be impaired in this syndrome, compared with a control population of men and women. The prediction was confirmed and was found to affect both the detection of egocentric gaze from the eyes (''is the face looking at me?'') and the detection of allocentric gaze, where the eyes in a photographed face inspected one of a number of locations of attention (''where is she looking?''). We suggest that dosage-sensitive X-linked genes contribute to the development of gaze-monitoring abilities.     

Multi-pronged inhibition of airway hyper-responsiveness and inflammation by lipoxin A(4)

The prevalence of asthma continues to increase and its optimal treatment remains a challenge. Here, we investigated the actions of lipoxin A(4) (LXA(4)) and its leukocyte receptor in pulmonary inflammation using a murine model of asthma. Allergen challenge initiated airway biosynthesis of LXA(4) and increased expression of its receptor. Administration of a stable analog of LXA(4) blocked both airway hyper-responsiveness and pulmonary inflammation, as shown by decreased leukocytes and mediators, including interleukin-5, interleukin-13, eotaxin, prostanoids and cysteinyl leukotrienes. Moreover, transgenic expression of human LXA(4) receptors in murine leukocytes led to significant inhibition of pulmonary inflammation and eicosanoid-initiated eosinophil tissue infiltration. Inhibition of airway hyper-responsiveness and allergic airway inflammation with a stable LXA(4) analog highlights a unique counter-regulatory profile for the LXA(4) system and its leukocyte receptor in airway responses. Moreover, our findings suggest that lipoxin and related pathways offer novel multi-pronged therapeutic approaches for human asthma.     

Preconception cystic fibrosis carrier couple screening: impact,understanding, and satisfaction

The impact, understanding of test-results, and satisfaction among participating couples in a preconception cystic fibrosis (CF) carrier screening project were assessed 6 months after testing. Questionnaire data were obtained from 17/18 identified carriers, 15 partners of carriers with negative test results, and 794 (73%) other participants. None of the carriers changed their reproductive plans because of their test results. Eight participants were worried about their results, including four carriers. Those who attended a general practitioner (GP) consultation for pretest education were less worried than those who attended an educational session. Seven carriers felt less healthy. Predictors of a correct understanding of test results (correct in 62% of participants) were: positive test results, high level of knowledge of CF, high level of education, attending an educational session, and previously heard of CF. All participants who reported that they were worried, all carriers, and 95% of the other participants said that they would make the same decision to be tested again. Although couples who were educated during a GP consultation were less worried, the results of the study suggest that understanding is more correct in couples attending an educational session. The results further suggest that since satisfaction with the screening was high, worries and feeling less healthy due to the test results are probably not a great burden.     

Dereplication for biotechnology screening: PyMS analysis and PCR–RFLP–SSCP (PRS) profiling of 16S rRNA genes of marine and terrestrial actinomycetes

The search for exploitable biology is a major task for biotechnology-based industries. In this context, discrimination between previously tested or recovered micro-organisms (dereplication) is imperative, in order to reduce screening costs by sorting large collections of isolates, which are then subjected to further detailed evaluation. Pyrolysis mass spectrometry (PyMS) is a whole-cell fingerprinting technique that enables the rapid and reproducible sorting of micro-organisms, uses small samples and has the advantage of being fully automated. In this study, we compare chemometric fingerprinting with a ribotyping fingerprinting method, in order to investigate the extent to which pyrogroups formed by PyMS analysis relate to genetic diversity, using polymerase chain reaction-restriction fragment length polymorphism-single-strand conformational polymorphism (PRS). A mixture of environmental strains of mycolic acid containing actinomycetes was used to mimic the selection of colonies from primary isolation plates. The congruence found between the clusters defined by the chemometric and molecular fingerprinting techniques was very high and demonstrated the effectiveness of PyMS as a rapid sorting and dereplicating procedure for putatively novel strains, criteria that are critical for biotechnological screens. Moreover, PyMS analysis revealed significant variation within pyrogroups that contained strains with the same genotypic (PRS) characteristics, thus emphasising its discriminatory capacity at the infraspecies level.