Given a passage with a context and an answer, 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.

Ex Input:
Context: To date, cardiac catheterization and endomyocardial biopsy have been considered the "gold standard" for rejection surveillance after heart transplantation. Factors such as patient size (i.e., infant transplantation), loss of vascular access after repeated catheterizations, and anesthesia requirements all present unique problems and risks related to pediatric rejection surveillance. Therefore, additional methods to monitor for rejection in a non-invasive, reliable and frequent manner have been sought. We studied the utility of echocardiographic measurement of the left ventricular myocardial performance index (LVMPI), a reproducible measure of combined systolic and diastolic performance, in pediatric heart transplant recipients as a method of identifying acute rejection.', 'Two-dimensional/Doppler echocardiographic studies (n = 36) were performed on 21 cardiac transplant patients (ages 6.2 to 21.9 years) at the time of endomyocardial biopsy. The LVMPI, the sum of the isovolumic contraction time and isovolumic relaxation time divided by aortic ejection time, was determined at each study, as well as other echocardiographic measures of systolic and diastolic function. Patients were grouped by concurrent histologic rejection grade and the results compared between groups.', 'Significant differences in LVMPI (p < 0.001) were noted between patients with no rejection (Grade 0; n = 23) and those with moderate to severe rejection (Grade 3; n = 5), as well as between those with no rejection and those with focal moderate (Grade 2; n = 8) rejection (p < 0.05). The LVMPI was 0.42 +/- 0.03 (mean +/- SEM) for the group without rejection, 0.57 +/- 0.06 for those with Grade 2 rejection and 0.73 +/- 0.05 for those with Grade 3 rejection. Although 9 of the 23 studies in the non-rejection group had LVMPI values exceeding 0.44 (upper threshold value), 12 of 13 patients in the rejection groups exceeded this threshold. LVMPI >or= 0.64 was associated with significant rejection in all cases in this study (n = 7). No significant differences were noted between groups for left ventricular ejection fraction or shortening fraction, percent septal or posterior wall thickening, left ventricular mass index or mitral valve deceleration time. In addition, for those individual patients with multiple studies, the LVMPI consistently increased with higher rejection grades and decreased after therapy.
Answer: In this series, increased LVMPI correlated with biopsy-proven rejection, and frequent serial assessments using this technique may provide a relatively sensitive non-invasive means of rejection surveillance after pediatric cardiac transplantation. False positive results may be encountered, likely due to alterations in diastolic function that have been previously observed in transplant recipients.

Ex Output:
Does increased myocardial performance index correlate with biopsy-proven rejection in pediatric heart transplant recipients?


Ex Input:
Context: This study was designed to investigate the effects of simvastatin in a rat model of acute myocardial infarction.', 'Male Wistar rats were anesthetized (thiopentone sodium 120 mg/kg). After a thoracotomy, the left-anterior-descending coronary artery (LAD) was occluded (for 25 min) and reperfused (for 120 min). Area at risk (AR) was determined with Evans Blue dye and infarct size after staining of the area at risk with nitroblue tetrazolium.', 'In rats, which received the vehicle for simvastatin (10% DMSO, 1 ml/kg i.v. at 1 h prior to the occlusion of the LAD), occlusion of the LAD for 25 min followed by reperfusion for 2 hours resulted in an infarct size of 54 +/- 4% (n=7) of the AR. When compared with vehicle, administration of simvastatin (1 mg/kg i.v. bolus administration at 1 h prior to the onset of myocardial ischemia) caused a significant reduction in myocardial infarct size of 39%. LAD-occlusion and reperfusion caused a progressive fall in mean arterial blood pressure (when compared with sham-operated animals). Simvastatin had no significant effect on blood pressure.
Answer: The result indicates that simvastatin, an inhibitor of HMG-CoA reductase and a ligand of PPAR-a and PPAR-g, reduces the tissue necrosis associated with acute myocardial infarction. We propose that statins may be useful in conditions associated with ischemia-reperfusion of the heart and other organs.

Ex Output:
Does simvastatin reduce infarct size in a model of acute myocardial ischemia and reperfusion in the rat?


Ex Input:
Context: To determine whether increased sequence variation occurs in regions of endogenous HIV-1 targeted by HIV-1-specific CD4 T cells. The presence of increased variation would be suggestive of immune evasion by HIV-1.', 'We performed a cross-sectional study of untreated HIV-1-infected subjects measuring HIV-1-specific interferon (IFN)-gamma-secreting CD4 T-cell responses against epitopes in Gag p17 and p24 and concurrent endogenous plasma HIV-1 RNA epitope sequence variation.', 'CD8- depleted IFNgamma enzyme-linked immunospot assays were used to identify regions of HIV-1 Gag recognized by CD4 T cells. Reverse transcriptase polymerase chain reaction and TA cloning were used to sequence endogenous plasma HIV-1 virus and identify variants.', 'CD4 T-cell epitopes in Gag p17 and p24 were identified in 5 individuals, and concurrent sequence information on endogenous HIV-1 was obtained in 4 of these individuals. Endogenous plasma HIV-1 RNA sequencing revealed no intrapatient amino acid sequence variation through identified epitopes.
Answer: In these chronically infected viremic subjects, circulating IFNgamma-secreting CD4 T-cell responses were directed against epitope sequences found in the predominant strain of endogenous circulating plasma HIV-1, suggesting that escape from CD4 T-cell responses is not a common process in vivo.

Ex Output:

Do hIV-1-specific CD4+ T-cell responses are not associated with significant viral epitope variation in persons with persistent plasma viremia?