Efficacy of mechanical postconditioning following warm, global ischaemia depends on circulating fatty acid levels in an isolated, working rat heart model

Gebiet: Chirurgie Abstract: OBJECTIVES: – The number of heart transplantations is limited by donor organ availability. Donation after circulatory determination of death (DCDD) could significantly improve graft availability, however, organs undergo warm ischaemia followed by reperfusion, leading to tissue damage. Laboratory studies suggest that mechanical postconditioning [(MPC), brief, intermittent periods of ischaemia at the onset of reperfusion] can limit reperfusion injury, however, clinical translation has been disappointing. We hypothesized that MPC-induced cardioprotection depends on fatty acid levels at reperfusion. – – METHODS: – Experiments were performed with an isolated rat heart model of DCDD. Hearts of male Wistar rats (n = 42) underwent working-mode perfusion for 20 min (baseline), 27 min of global ischaemia and 60 min reperfusion with or without MPC (two cycles of 30 s reperfusion/30 s ischaemia) in the presence or absence of high fat [(HF), 1.2 mM palmitate]. Haemodynamic parameters, necrosis factors and oxygen consumption (O2C) were assessed. Recovery rate was calculated as the value at 60 min reperfusion expressed as a percentage of the mean baseline value. The Kruskal-Wallis test was used to provide an overview of differences between experimental groups, and pairwise comparisons were performed to compare specific time points of interest for parameters with significant overall results. – – RESULTS: – Percent recovery of left ventricular (LV) work [developed pressure (DP)-heart rate product] at 60 min reperfusion was higher in hearts reperfused without fat versus with fat (58 ± 8 vs 23 ± 26%, P < 0.01) in the absence of MPC. In the absence of fat, MPC did not affect post-ischaemic haemodynamic recovery. Among the hearts reperfused with HF, two significantly different subgroups emerged according to recovery of LV work: low recovery (LoR) and high recovery (HiR) subgroups. At 60 min reperfusion, recovery was increased with MPC versus no MPC for LV work (79 ± 6 vs 55 ± 7, respectively, P < 0.05) in HiR subgroups and for DP (40 ± 27 vs 4 ± 2%), dP/dtmax (37 ± 24 vs 5 ± 3%) and dP/dtmin (33 ± 21 vs 5 ± 4%, P < 0.01 for all) in LoR subgroups. – – CONCLUSIONS: – Effects of MPC depend on energy substrate availability, MPC increased recovery of LV work in the presence, but not in the absence, of HF. Controlled reperfusion may be useful for therapeutic strategies aimed at improving post-ischaemic recovery of cardiac DCDD grafts, and ultimately in increasing donor heart availability.

Diagnostic performance of a new red light LED device for approximal caries detection

The aim of this study was to test a newly developed LED-based fluorescence device for approximal caries detection in vitro. We assembled 120 extracted molars without frank cavitations or fillings pairwise in order to create contact areas. The teeth were independently assessed by two examiners using visual caries detection (International Caries Detection and Assessment System, ICDAS), bitewing radiography (BW), laser fluorescence (LFpen), and LED fluorescence (Midwest Caries I.D., MW). The measurements were repeated at least 1 week later. The diagnostic performance was calculated with Bayesian analyses. Post-test probabilities were calculated in order to judge the diagnostic performance of combined methods. Reliability analyses were performed using kappa statistics for nominal data and intraclass correlation (ICC) for absolute data. Histology served as the gold standard. Sensitivities/specificities at the enamel threshold were 0.33/0.84 for ICDAS, 0.23/0.86 for BW, 0.47/0.78 for LFpen, and 0.32/0.87 for MW. Sensitivities/specificities at the dentine threshold were 0.04/0.89 for ICDAS, 0.27/0.94 for BW, 0.39/0.84 for LFpen, and 0.07/0.96 for MW. Reliability data were fair to moderate for MW and good for BW and LFpen. The combination of ICDAS and radiography yielded the best diagnostic performance (post-test probability of 0.73 at the dentine threshold). The newly developed LED device is not able to be recommended for approximal caries detection. There might be too much signal loss during signal transduction from the occlusal aspect to the proximal lesion site and the reverse.

Genetic diversity and differentiation follow secondary succession in a multi-species study on woody plants from subtropical China

Aims: Species diversity and genetic diversity may be affected in parallel by similar environmental drivers. However, genetic diversity may also be affected independently by habitat characteristics. We aim at disentangling relationships between genetic diversity, species diversity and habitat characteristics of woody species in subtropical forest. Methods: We studied 11 dominant tree and shrub species in 27 plots in Gutianshan, China, and assessed their genetic diversity (Ar) and population differentiation (F’ST) with microsatellite markers. We tested if Ar and population specific F’ST were correlated to local species diversity and plot characteristics. Multi-model inference and model averaging were used to determine the relative importance of each predictor. Additionally we tested for isolation-by-distance and isolation-by-elevation by regressing pairwise F’ST against pairwise spatial and elevational distances. Important findings: Genetic diversity was not related to species diversity for any of the study species. Thus, our results do not support joint effects of habitat characteristics on these two levels of biodiversity. Instead, genetic diversity in two understory shrubs, Rhododendron simsii and Vaccinium carlesii, was affected by plot age with decreasing genetic diversity in successionally older plots. Population differentiation increased with plot age in Rhododendron simsii and Lithocarpus glaber. This shows that succession can reduce genetic diversity within, and increase genetic diversity between populations. Furthermore, we found four cases of isolation-by-distance and two cases of isolation-by-elevation. The former indicates inefficient pollen and seed dispersal by animals whereas the latter might be due to phenological asynchronies. These patterns indicate that succession can affect genetic diversity without parallel effects on species diversity and that gene flow in a continuous subtropical forest can be restricted even at a local scale.