Environmental stresses inhibit splicing in the aquatic fungus Blastocladiella emersonii

Background  

Exposure of cells to environmental stress conditions can lead to the interruption of several intracellular processes, in particular those performed by macromolecular complexes such as the spliceosome.     

Effect of tetracyclines on the dynamics of formation and destructuration of beta2-microglobulin amyloid fibrils

The discovery of methods suitable for the conversion in vitro of native proteins into amyloid fibrils has shed light on the molecular basis of amyloidosis and has provided fundamental tools for drug discovery. We have studied the capacity of a small library of tetracycline analogues to modulate the formation or destructuration of β2-microglobulin fibrils. The inhibition of fibrillogenesis of the wild type protein was first established in the presence of 20% trifluoroethanol and confirmed under a more physiologic environment including heparin and collagen. The latter conditions were also used to study the highly amyloidogenic variant, P32G. The NMR analysis showed that doxycycline inhibits β2-microglobulin self-association and stabilizes the native-like species through fast exchange interactions involving specific regions of the protein. Cell viability assays demonstrated that the drug abolishes the natural cytotoxic activity of soluble β2-microglobulin, further strengthening a possible in vivo therapeutic exploitation of this drug. Doxycycline can disassemble preformed fibrils, but the IC(50) is 5-fold higher than that necessary for the inhibition of fibrillogenesis. Fibril destructuration is a dynamic and time-dependent process characterized by the early formation of cytotoxic protein aggregates that, in a few hours, convert into non-toxic insoluble material. The efficacy of doxycycline as a drug against dialysis-related amyloidosis would benefit from the ability of the drug to accumulate just in the skeletal system where amyloid is formed. In these tissues, the doxycycline concentration reaches values several folds higher than those resulting in inhibition of amyloidogenesis and amyloid destructuration in vitro.     

Evening exposure to a light-emitting diodes (LED)-backlit computer screen affects circadian physiology and cognitive performance

Many people spend an increasing amount of time in front of computer screens equipped with light-emitting diodes (LED) with a short wavelength (blue range). Thus we investigated the repercussions on melatonin (a marker of the circadian clock), alertness, and cognitive performance levels in 13 young male volunteers under controlled laboratory conditions in a balanced crossover design. A 5-h evening exposure to a white LED-backlit screen with more than twice as much 464 nm light emission {irradiance of 0,241 Watt/(steradian × m(2)) [W/(sr × m(2))], 2.1 × 10(13) photons/(cm(2) × s), in the wavelength range of 454 and 474 nm} than a white non-LED-backlit screen [irradiance of 0,099 W/(sr × m(2)), 0.7 × 10(13) photons/(cm(2) × s), in the wavelength range of 454 and 474 nm] elicited a significant suppression of the evening rise in endogenous melatonin and subjective as well as objective sleepiness, as indexed by a reduced incidence of slow eye movements and EEG low-frequency activity (1-7 Hz) in frontal brain regions. Concomitantly, sustained attention, as determined by the GO/NOGO task; working memory/attention, as assessed by "explicit timing"; and declarative memory performance in a word-learning paradigm were significantly enhanced in the LED-backlit screen compared with the non-LED condition. Screen quality and visual comfort were rated the same in both screen conditions, whereas the non-LED screen tended to be considered brighter. Our data indicate that the spectral profile of light emitted by computer screens impacts on circadian physiology, alertness, and cognitive performance levels. The challenge will be to design a computer screen with a spectral profile that can be individually programmed to add timed, essential light information to the circadian system in humans.     

Comparison of morphological and genetic analyses reveals cryptic divergence and morphological plasticity in Stylophora (Cnidaria, Scleractinia)

A combined morphological and genetic study of the coral genus Stylophora investigated species boundaries in the Gulf of Aden, Yemen. Two mitochondrial regions, including the hypervariable IGS9 spacer and the control region, and a fragment of rDNA were used for phylogenetic analysis. Results were compared by multivariate analysis on the basis of branch morphology and corallite morphometry. Two species were clearly discriminated by both approaches. The first species was characterised by small corallites and a low morphological variability and was ascribed to a new geographical record of Stylophora madagascarensis on the basis of its phylogenetic distinction and its morphological similarity to the type material. The second species was characterised by larger corallite size and greater morphological variability and was ascribed to Stylophora pistillata. The analysis was extended to the intrageneric level for other S. pistillata populations from the Red Sea and the Pacific Ocean. Strong internal divergence was evident in the genus Stylophora. S. pistillata populations were split into two highly divergent Red Sea/Gulf of Aden and western Pacific lineages with significant morphological overlap, which suggests they represent two distinct cryptic species. The combined use of morphological and molecular approaches, so far proved to be a powerful tool for the re-delineation of species boundaries in corals, provided novel evidence of cryptic divergence in this group of marine metazoans.     

The gene encoding pyolysin,the pore-forming toxin of Arcanobacterium pyogenes,resides within a genomic islet flanked by essential genes

The plo gene, encoding the Arcanobacterium pyogenes cholesterol-dependent cytolysin, pyolysin (PLO), was localized to a 2.7-kb genomic islet of reduced %G+C content and alternate codon usage frequency. This islet, conserved among isolates from diverse hosts and geographical locations, separated the housekeeping genes smc and ftsY, which are found adjacent in many prokaryotes. The ftsY and ffh genes, located downstream of the plo islet, encode components of the signal recognition particle. Mutational analysis suggested that these genes were essential for viability in A. pyogenes. The A. pyogenes ffh gene was unable to complement a conditional ffh mutant of Escherichia coli and its overexpression was toxic in E. coli. Mutagenesis of the islet-encoded orf121 did not affect plo expression, indicating that it may not be involved directly in the regulation of plo expression. Regardless, the presence of the plo gene as part of a genomic islet inserted between genes essential for normal growth may provide selective pressure for the retention of this important virulence factor.     

Phenotypic and Genotypic Characterization of Daptomycin-Resistant Methicillin-Resistant Staphylococcus aureus Strains: Relative Roles of mprF and dlt Operons

Development of in vivo daptomycin resistance (DAP-R) among Staphylococcus aureus clinical isolates, in association with clinical treatment failures, has become a major therapeutic problem. This issue is especially relevant to methicillin-resistant S. aureus (MRSA) strains in the context of invasive endovascular infections. In the current study, we used three well-characterized and clinically-derived DAP-susceptible (DAP-S) vs. resistant (DAP-R) MRSA strain-pairs to elucidate potential genotypic mechanisms of the DAP-R phenotype. In comparison to the DAP-S parental strains, DAP-R isolates demonstrated (i) altered expression of two key determinants of net positive surface charge, either during exponential or stationary growth phases (i.e., dysregulation of dltA and mprF), (ii) a significant increase in the D-alanylated wall teichoic acid (WTA) content in DAP-R strains, reflecting DltA gain-in-function; (iii) heightened elaboration of lysinylated-phosphatidylglyderol (L-PG) in DAP-R strains, reflecting MprF gain-in-function; (iv) increased cell membrane (CM) fluidity, and (v) significantly reduced susceptibility to prototypic cationic host defense peptides of platelet and leukocyte origins. In the tested DAP-R strains, genes conferring positive surface charge were dysregulated, and their functionality altered. However, there were no correlations between relative surface positive charge or cell wall thickness and the observed DAP-R phenotype. Thus, charge repulsion mechanisms via altered surface charge may not be sufficient to explain the DAP-R outcome. Instead, changes in the compositional or biophysical order of the DAP CM target of such DAP-R strains (i.e., increased fluidity) may be essential to this phenotype. Taken together, DAP-R in S. aureus appears to involve multi-factorial and strain-specific adaptive mechanisms.     

Resistance Training Improves Hemodynamic Function,Collagen Deposition and Inflammatory Profiles: Experimental Model of Heart Failure

The role of resistance training on collagen deposition, the inflammatory profile and muscle weakness in heart failure remains unclear. Therefore, this study evaluated the influence of a resistance training program on hemodynamic function, maximum strength gain, collagen deposition and inflammatory profile in chronic heart failure rats. Thirty-two male Wistar rats submitted to myocardial infarction by coronary artery ligation or sham surgery were assigned into four groups: sedentary sham (S-Sham, n = 8); trained sham (T-Sham, n = 8); sedentary chronic heart failure (S-CHF, n = 8) and trained chronic heart failure (T-CHF, n = 8). The maximum strength capacity was evaluated by the one maximum repetition test. Trained groups were submitted to an 8-week resistance training program (4 days/week, 4 sets of 10–12 repetitions/session, at 65% to 75% of one maximum repetition). After 8 weeks of the resistance training program, the T-CHF group showed lower left ventricular end diastolic pressure (P<0.001), higher left ventricular systolic pressure (P<0.05), higher systolic blood pressure (P<0.05), an improvement in the maximal positive derivative of ventricular pressure (P<0.05) and maximal negative derivative of ventricular pressure (P<0.05) when compared to the S-CHF group; no differences were observed when compared to Sham groups. In addition, resistance training was able to reduce myocardial hypertrophy (P<0.05), left ventricular total collagen volume fraction (P<0.01), IL-6 (P<0.05), and TNF-α/IL-10 ratio (P<0.05), as well as increasing IL-10 (P<0.05) in chronic heart failure rats when compared to the S-CHF group. Eight weeks of resistance training promotes an improvement of cardiac function, strength gain, collagen deposition and inflammatory profile in chronic heart failure rats.     

Evaluation of a rapid and inexpensive liquid culture system for the detection of Mycobacterium avium subsp. paratuberculosis in bovine faeces

Mycobacterium avium subsp. paratuberculosis (MAP) is the etiologic agent of paratuberculosis, a chronic granulomatous enteric disease of ruminants. MAP detection by faecal culture provides the definitive diagnosis of the infection. Automated liquid systems for MAP culture are more sensitive and rapid than culture on solid media, but they are expensive and require specialised equipment. In this study, a non-automated culture method using a modified Middlebrook 7H9 liquid medium (7H9+) was compared with Herrold's solid medium (HEYM) and direct real-time PCR on dairy cattle faeces. MAP growth in 7H9+ was monitored weekly by real-time PCR until the 12th week post-inoculation. The analytical sensitivity of the three methods was evaluated using faecal samples from a healthy cow spiked with ten-fold dilutions of MAP organisms (10⁴-10^− 1) and naturally MAP-infected faeces serially diluted 1 to 10 in negative faecal samples. The limits of detection of the solid culture and direct real-time PCR were 10² and 10³ MAP/g, respectively. In comparison, the 7H9+ culture revealed as few as 1 MAP/g. A marked reduction in time to detection of the pathogen, compared with HEYM culture, was obtained. In addition, the three methods were applied to environmental faecal samples collected from a high- and a low-prevalence herd. The culture in 7H9+ showed to be the most sensitive test in the low-prevalence herd and provided faster results than HEYM. In the high-prevalence herd the three methods showed the same sensitivity and the real-time PCR had the shortest turnaround time. In conclusion, the use of 7H9+ for MAP-detection from cattle faeces maximizes diagnostic sensitivity and reduces turnaround time and, therefore, could replace culture in solid medium. Hence, we propose a two-step protocol for the assessment of MAP faecal excretion based on: 1) direct real-time PCR on all samples; and 2) inoculation of negative samples into 7H9+ and analysis after 3 and, if necessary, 6 weeks by real-time PCR.     

Carbonate facies dominated by syndepositional cements: a key component of Middle Triassic platforms. The Marmolada case history (Dolomites, Italy)

Summary This article deals with the discussion of the role of the syndepositional cementation for the growth of the Middle Triassic pre-volcanic carbonate platforms of the Dolomites (Southern Alps, Northern Italy). The study is concentrated on the Marmolada Buildup, which escaped the facies destroying dolomitization which affected many surrounding platforms. The investigations took place within an almost isochronous uppermost Anisian palcogeographic transect, ranging from the platform-top to the margin and the upper slope. Methods used include geological mapping, sedimentological and paleontological studies, evaluation of the microfacies, as well as SEM and EDS epifluorescence analyses. The well bedded platform-top succession consists of intra-bioclast calcarenites and calcirudites, interbedded with subordinate boundstones, and organized in shallowing upward, meter scale depositional cycles, sometimes capped by subaerial surfaces. The platform margin belt is rich in boundstones and lacks a primary framework formed by organisms; metazoan skeletons form less then 5% of the rock volume. The outer margin and the uppermost slope are characterized by decimeter-scale boundstone blocks, coated and linked to each other by huge amounts of radiaxial fibrous calcite cements, arranged in concentric crusts. These cements (“evinospongiac”) represent the main component of the margin and upper slope facies. Epifluorescence analyses suggest the existence of abundant organic residual matter associated not only with the bioclasts and peloids, but also with the syndepositional cements. Organic matter likely played a significant role in carbonate cementation and was a key factor for the early lithification of the platform as well as for the sediment production. Minor element microanalyses reveal an uniform Mg content in different calcite types (2–4 Mole % MgCO₃), independently from the primary nature of the components. Late diagenetic sparry calcites exhibit similar Mg values but no iron. These data point to a homogenization of minor element distribution, probably associated with a slow but long-lasting semi-closed fluid circulation, possibly related with the Neogene uplifting of the Dolomite Mountains.