Given a passage, construct a question on the basis of the information present in the passage. Construct the question in such a way that (i) it is unambiguous, (ii) it is answerable from the passage, (iii) its answer is unique (iv) it answer uses text phrases from the passage. Avoid creating questions that (i) can't be answered correctly without actually understanding the passage and (ii) uses the same words or phrases given in the passage.

Mitochondrial permeability transition pore (mPTP) opening is a terminal event leading to mitochondrial dysfunction and cell death under conditions of oxidative stress (OS). However, mPTP blockade with cyclosporine A (CsA) has shown variable efficacy in limiting post-ischemic dysfunction and arrhythmias. We hypothesized that strong feedback between energy dissipating (mPTP) and cardioprotective (mKATP) channels determine vulnerability to OS.', 'Guinea pig hearts (N = 61) were challenged with H2O2 (200 μM) to elicit mitochondrial membrane potential (ΔΨm) depolarization. High-resolution optical mapping was used to measure ΔΨm or action potentials (AP) across the intact heart. Hearts were treated with CsA (0.1 μM) under conditions that altered the activity of mKATP channels either directly or indirectly via its regulation by protein kinase C. mPTP blockade with CsA markedly blunted (P < 0.01) OS-induced ΔΨm depolarization and delayed loss of LV pressure (LVP), but did not affect arrhythmia propensity. Surprisingly, prevention of mKATP activation with the chemical phosphatase BDM reversed the protective effect of CsA, paradoxically exacerbating OS-induced ΔΨm depolarization and accelerating arrhythmia onset in CsA treated compared to untreated hearts (P < 0.05). To elucidate the putative molecular mechanisms, mPTP inhibition by CsA was tested during conditions of selective PKC inhibition or direct mKATP channel activation or blockade. Similar to BDM, the specific PKC inhibitor, CHE (10 μM) did not alter OS-induced ΔΨm depolarization directly. However, it completely abrogated CsA-mediated protection against OS. Direct pharmacological blockade of mKATP, a mitochondrial target of PKC signaling, equally abolished the protective effect of CsA on ΔΨm depolarization, whereas channel activation with 30 μM Diazoxide protected against ΔΨm depolarization (P < 0.0001). Conditions that prevented mKATP activation either directly or indirectly via PKC inhibition led to accelerated ΔΨm depolarization and early onset of VF in response to OS. Investigation of the electrophysiological substrate revealed accelerated APD shortening in response to OS in arrhythmia-prone hearts.
Do functional crosstalk between the mitochondrial PTP and KATP channels determine arrhythmic vulnerability to oxidative stress?

Renal ischemia-reperfusion (I/R) injury may occur after renal transplantation, thoracoabdominal aortic surgery, and renal artery interventions.', 'To investigate the therapeutic effects of aprotinin on tissue protection against I/R injury in a rat model. N-acetylcysteine (NAC), a potent antioxidant, was also tested to assess the experimental model.', 'Twenty-four rats were categorized into 3 groups of 8 rats each: those receiving isotonic sodium chloride solution (control group); NAC, 150 mg/kg; and aprotinin, 40,000 KIU/kg. The animals underwent unilateral nephrectomy after 60 minutes of warm ischemia and 60 minutes of reperfusion of the kidney. Malondialdehyde, a lipid peroxidation marker, and antioxidant glutathione levels were measured in the kidney parenchyma. Tissue samples were obtained for histologic analysis.', 'Compared with the control group, the NAC group demonstrated significantly low levels of malondialdehyde (P = .04) and high levels of glutathione (P = .01). At histopathologic analysis, less acute tubular necrosis (ATN) and cellular swelling was noted in the NAC group (P = .002 and P = .005, respectively). In the aprotinin group, histopathologic analysis revealed less tissue damage in terms of ATN (P < .001, cellular swelling (P < .001), and vacuolysis (P = .002). Compared with the NAC group, ATN (P = .01), vacuolysis (P = .04), and congestion (P = .05) were significantly less in the aprotinin group.
Does serine protease inhibitor aprotinin ameliorate renal injury in a rat model of ischemia-perfusion injury?

To study the effect of dexamethasone on postextubation stridor (PS) incidence and reintubation rate due to PS in a high-risk paediatric intensive care population.', 'All children aged between 4 wk and 6 y, who were intubated for at least 24 h and extubated between August 1999 and May 2002, were retrospectively included (n=60). Medical records of the included patients were studied; records of patients treated with dexamethasone prior to and following extubation (n=23) were compared with control patients who had not received prophylactic medication (n=37).', 'Nine patients in the control group developed significant postextubation stridor, necessitating nebulized epinephrine or glucocorticosteroids. In six of these children, reintubation as a result of postextubation stridor was indicated. None of the patients treated with dexamethasone developed severe postextubation stridor or required reintubation.

Does dexamethasone reduce reintubation rate due to postextubation stridor in a high-risk paediatric population?