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

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.

AMS-C14 analysis of graphite obtained with an Automated Graphitization Equipment (AGE III) from aerosol collected on quartz filters

AMS-14C applications often require the analysis of small samples. Such is the case of atmospheric aerosols where frequently only a small amount of sample is available. The ion beam physics group at the ETH, Zurich, has designed an Automated Graphitization Equipment (AGE III) for routine graphite production for AMS analysis from organic samples of approximately 1 mg. In this study, we explore the potential use of the AGE III for graphitization of particulate carbon collected in quartz filters. In order to test the methodology, samples of reference materials and blanks with different sizes were prepared in the AGE III and the graphite was analyzed in a MICADAS AMS (ETH) system. The graphite samples prepared in the AGE III showed recovery yields higher than 80% and reproducible 14C values for masses ranging from 50 to 300 lg. Also, reproducible radiocarbon values were obtained for aerosol filters of small sizes that had been graphitized in the AGE III. As a study case, the tested methodology was applied to PM10 samples collected in two urban cities in Mexico in order to compare the source apportionment of biomass and fossil fuel combustion. The obtained 14C data showed that carbonaceous aerosols from Mexico City have much lower biogenic signature than the smaller city of Cuernavaca.

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.