Structural insight into repair of alkylated DNA by a new superfamily of DNA glycosylases comprising HEAT-like repeats

3-methyladenine DNA glycosylases initiate repair of cytotoxic and promutagenic alkylated bases in DNA. We demonstrate by comparative modelling that Bacillus cereus AlkD belongs to a new, fifth, structural superfamily of DNA glycosylases with an alpha–alpha superhelix fold comprising six HEAT-like repeats. The structure reveals a wide, positively charged groove, including a putative base recognition pocket. This groove appears to be suitable for the accommodation of double-stranded DNA with a flipped-out alkylated base. Site-specific mutagenesis within the recognition pocket identified several residues essential for enzyme activity. The results suggest that the aromatic side chain of a tryptophan residue recognizes electron-deficient alkylated bases through stacking interactions, while an interacting aspartate–arginine pair is essential for removal of the damaged base. A structural model of AlkD bound to DNA with a flipped-out purine moiety gives insight into the catalytic machinery for this new class of DNA glycosylases

Chronic CaMKII inhibition blunts the cardiac contractile response to exercise training

Activation of the multifunctional Ca2+/calmodulin-dependent protein kinase II (CaMKII) plays a critical role modulating cardiac function in both health and disease. Here, we determined the effect of chronic CaMKII inhibition during an exercise training program in healthy mice. CaMKII was inhibited by KN-93 injections. Mice were randomized to the following groups: sham sedentary, sham exercise, KN-93 sedentary, and KN-93 exercise. Cardiorespiratory function was evaluated by ergospirometry during treadmill running, echocardiography, and cardiomyocyte fractional shortening and calcium handling. The results revealed that KN-93 alone had no effect on exercise capacity or fractional shortening. In sham animals, exercise training increased maximal oxygen uptake by 8% (p < 0.05) compared to a 22% (p < 0.05) increase after exercise in KN-93 treated mice (group difference p < 0.01). In contrast, in vivo fractional shortening evaluated by echocardiography improved after exercise in sham animals only: from 25 to 32% (p < 0.02). In inactive mice, KN-93 reduced rates of diastolic cardiomyocyte re-lengthening (by 25%, p < 0.05) as well as Ca2+ transient decay (by 16%, p < 0.05), whereas no such effect was observed after exercise training. KN-93 blunted exercise training response on cardiomyocyte fractional shortening (63% sham vs. 18% KN-93; p < 0.01 and p < 0.05, respectively). These effects could not be solely explained by the Ca2+ transient amplitude, as KN-93 reduced it by 20% (p < 0.05) and response to exercise training was equal (64% sham and 47% KN-93; both p < 0.01). We concluded that chronic CaMKII inhibition increased time to 50% re-lengthening which were recovered by exercise training, but paradoxically led to a greater increase in maximal oxygen uptake compared to sham mice. Thus, the effect of chronic CaMKII inhibition is multifaceted and of a complex nature

Road traffic noise and children's inattention

BACKGROUND: An increasing number of children are exposed to road traffic noise levels that may lead to adverse effects on health and daily functioning. Childhood is a period of intense growth and brain maturation, and children may therefore be especially vulnerable to road traffic noise. The objective of the present study was to examine whether road traffic noise was associated with reported inattention symptoms in children, and whether this association was mediated by sleep duration. METHODS: This study was based on the Norwegian Mother and Child Cohort Study conducted by the Norwegian Institute of Public Health. Parental reports of children's inattention at age 8 were linked to modelled levels of residential road traffic noise. We investigated the association between inattention and noise exposure during pregnancy (n = 1934), noise exposure averaged over 5 years (age 3 to 8 years; n = 1384) and noise exposure at age 8 years (n = 1384), using fractional logit response models. The participants were children from Oslo, Norway. RESULTS: An association with inattention at age 8 years was found for road traffic noise exposure at age 8 years (coef = .0083, CI = [.0012, .0154]; 1.2% point increase in inattention score per 10 dB increase in noise level), road traffic noise exposure average for the last 5 years (coef = .0090, CI = [.0016, .0164]; 1.3% point increase/10 dB), and for pregnancy road traffic noise exposure for boys (coef = .0091, CI = [.0010, .0171]), but not girls (coef = -.0021, CI = [-.0094, .0053]). Criteria for doing mediation analyses were not fulfilled. CONCLUSION: Results indicate that road traffic noise has a negative impact on children's inattention. We found no mediation by sleep duration

Acute exercise is not cardioprotective and may induce apoptotic signalling in heart surgery: a randomized controlled trial

During open-heart surgery, the myocardium experiences ischaemia-reperfusion injury. A single bout of moderate, 30-min exercise induces preconditioning and protects the heart from ischaemia-reperfusion injury in rats, but this has never been investigated in humans. We aimed to investigate whether 1 bout of moderate exercise 24 h prior to surgery protects against mitochondrial and cardiac damage.Patients scheduled for elective coronary artery bypass were eligible for this pilot study. Twenty were included and randomized to the treadmill exercise group (the EX group, n = 10) 24 h preoperatively or to standard presurgical procedures (control n = 10). Right atrial (RA) and left ventricular (LV) biopsies were collected immediately before and as long as possible after aortic cross-clamping to assess the primary outcome of mitochondrial respiration by respirometry, in addition to reactive oxygen species production by fluorometry and apoptotic transcripts. Cardiac troponin T and creatine kinase myocardial brain were measured in plasma at arrival, before surgery and 6 and 24 h postoperatively.Mitochondrial respiration was lower in the EX group after surgery in the LV (Complex I -22%, P

Structural model with proposed active site and lesion recognition pocket of AlkD

<p><b>Copyright information:</b></p><p>Taken from "Structural insight into repair of alkylated DNA by a new superfamily of DNA glycosylases comprising HEAT-like repeats"</p><p></p><p>Nucleic Acids Research 2007;35(7):2451-2459.</p><p>Published online 29 Mar 2007</p><p>PMCID:PMC1874660.</p><p>© 2007 The Author(s)</p> The model contains residues 11 through to 226 and is lacking α-helix α1 and the 11 C-terminal residues (predicted to be disordered). () Cartoon rendering of the protein which comprises 13 α-helices contributing to the six repeats in . () APBS () calculated electrostatic potential mapped onto the protein surface (red = negative, white = neutral and blue = positive) showing the 20–25 Å wide, positively charged, putative DNA binding groove. () Amino acid residue conservation in 43 AlkD homologs mapped onto the space filling representation of the model generated with ConSurf (). The scale extends from magenta (highly conserved), through white to cyan (highly variable). There is a nest of conserved residues in the putative DNA binding groove, and several conserved basic amino acid residues (Arg and Lys) are sited along the upper and lower edge of the groove. () Stereo view of a close-up of the highly conserved nest shows the eight conserved residues that were mutated by site-directed mutagenesis. The catalytic activity and MMS sensitivity of the resulting mutants were determined (). The eight conserved residues have identical geometry in the experimental structure 2B6C. The orientation of the protein in space is identical in all panels. The model is also available as Supplementary Video 1 online

Spatial and temporal variations of Norwegian geohazards in a changing climate, the GeoExtreme Project

Various types of slope processes, mainly landslides and avalanches (snow, rock, clay and debris) pose together with floods the main geohazards in Norway. Landslides and avalanches have caused more than 2000 casualties and considerable damage to infrastructure over the last 150 years. The interdisciplinary research project &quot;GeoExtreme&quot; focuses on investigating the coupling between meteorological factors and landslides and avalanches, extrapolating this into the near future with a changing climate and estimating the socioeconomic implications. The main objective of the project is to predict future geohazard changes in a changing climate. A database consisting of more than 20 000 recorded historical events have been coupled with a meteorological database to assess the predictability of landslides and avalanches caused by meteorological conditions. Present day climate and near future climate scenarios are modelled with a global climate model on a stretched grid, focusing on extreme weather events in Norway. The effects of climate change on landslides and avalanche activity are studied in four selected areas covering the most important climatic regions in Norway. The statistical analysis of historical landslide and avalanche events versus weather observations shows strong regional differences in the country. Avalanches show the best correlation with weather events while landslides and rockfalls are less correlated. The new climate modelling approach applying spectral nudging to achieve a regional downscaling for Norway proves to reproduce extreme events of precipitation much better than conventional modelling approaches. Detailed studies of slope stabilities in one of the selected study area show a high sensitivity of slope stability in a changed precipitation regime. The value of elements at risk was estimated in one study area using a GIS based approach that includes an estimation of the values within given present state hazard zones. The ongoing project will apply the future climate scenarios to predict the changes in geohazard levels, as well as an evaluation of the resulting socioeconomic effects on the Norwegian society in the coming 50 years