The blood oxygen level dependent (BOLD) effect of in-vitro myoglobin and hemoglobin.

The presence of deoxygenated hemoglobin (Hb) results in a drop in T2 and T2* in magnetic resonance imaging (MRI), known as the blood oxygenation level-dependent (BOLD-)effect. The purpose of this study was to investigate if deoxygenated myoglobin (Mb) exerts a BOLD-like effect. Equine Met-Mb powder was dissolved and converted to oxygenated Mb. T1, T2, T2*-maps and BOLD-bSSFP images at 3Tesla were used to scan 22 Mb samples and 12 Hb samples at room air, deoxygenation, reoxygenation and after chemical reduction. In Mb, T2 and T2* mapping showed a significant decrease after deoxygenation (- 25% and - 12%, p < 0.01), increase after subsequent reoxygenation (+ 17% and 0% vs. room air, p < 0.01), and finally a decrease in T2 after chemical reduction (- 28%, p < 0.01). An opposite trend was observed with T1 for each stage, while chemical reduction reduced BOLD-bSSFP signal (- 3%, p < 0.01). Similar deflections were seen at oxygenation changes in Hb. The T1 changes suggests that the oxygen content has been changed in the specimen. The shortening of transverse relaxation times in T2 and T2*-mapping after deoxygenation in Mb specimens are highly indicative of a BOLD-like effect

Cardioprotective reperfusion strategies differentially affect mitochondria: Studies in an isolated rat heart model of donation after circulatory death (DCD)

International audienceDonation after circulatory death (DCD) holds great promise for improving cardiac graft availability; however, concerns persist regarding injury following warm ischemia, after donor circulatory arrest, and subsequent reperfusion. Application of preischemic treatments is limited for ethical reasons; thus, cardioprotective strategies applied at graft procurement (reperfusion) are of particular importance in optimizing graft quality. Given the key role of mitochondria in cardiac ischemia-reperfusion injury, we hypothesize that 3 reperfusion strategies-mild hypothermia, mechanical postconditioning, and hypoxia, when briefly applied at reperfusion onset-provoke mitochondrial changes that may underlie their cardioprotective effects. Using an isolated, working rat heart model of DCD, we demonstrate that all 3 strategies improve oxygen-consumption-cardiac-work coupling and increase tissue adenosine triphosphate content, in parallel with increased functional recovery. These reperfusion strategies, however, differentially affect mitochondria; mild hypothermia also increases phosphocreatine content, while mechanical postconditioning stimulates mitochondrial complex I activity and reduces cytochrome c release (marker of mitochondrial damage), whereas hypoxia upregulates the expression of peroxisome proliferator-activated receptor-gamma coactivator (regulator of mitochondrial biogenesis). Characterization of the role of mitochondria in cardioprotective reperfusion strategies should aid in the identification of new, mitochondrial-based therapeutic targets and the development of effective reperfusion strategies that could ultimately facilitate DCD heart transplantation

Cardioprotective reperfusion strategies differentially affect mitochondria:studies in an isolated rat heart model of donation after circulatory death (DCD).

Donation after circulatory death (DCD) holds great promise for improving cardiac graft availability, however concerns persist regarding injury following warm ischemia, after donor circulatory arrest, and subsequent reperfusion. Application of pre-ischemic treatments is limited for ethical reasons, thus cardioprotective strategies applied at graft procurement (reperfusion) are of particular importance in optimizing graft quality. Given the key role of mitochondria in cardiac ischemia-reperfusion injury, we hypothesize that three reperfusion strategies: mild hypothermia, mechanical post-conditioning and hypoxia, when briefly applied at reperfusion onset, provoke mitochondrial changes that may underlie their cardioprotective effects. Using an isolated, working rat heart model of DCD, we demonstrate that all three strategies improve oxygen-consumption-cardiac-work coupling and increase tissue ATP content, in parallel with increased functional recovery. These reperfusion strategies, however, differentially affect mitochondria; mild hypothermia also increases phosphocreatine content, while mechanical post-conditioning stimulates mitochondrial complex I activity and reduces cytochrome c release (marker of mitochondrial damage), whereas hypoxia up-regulates the expression of Pgc-1α (regulator of mitochondrial biogenesis). Characterisation of the role of mitochondria in cardioprotective reperfusion strategies should aid in the identification of new, mitochochondrial-based therapeutic targets and the development of effective reperfusion strategies that could ultimately facilitate DCD heart transplantation. This article is protected by copyright. All rights reserved