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: Low-level vagus nerve stimulation (LL-VNS) has been demonstrated to protect myocardium against acute ischemia/reperfusion (I/R) injury. However, the underlying mechanism of this protective effect remains unknown.', 'This study aimed to test the hypothesis that LL-VNS exerts cardioprotective effect on acute I/R injury in canines via antioxidative stress and antiapoptosis reactions.', 'Thirty anesthetized mongrel dogs were randomly divided into three groups: I/R group (N = 12, the left anterior descending coronary artery was occluded for 1 hour following by 1 hour reperfusion), LL-VNS group (N = 9, I/R plus LL-VNS), and sham group (N = 9, sham surgery without LL-VNS). The voltage threshold was set at 80% of the voltage required to slow the sinus rate. Infarct size was assessed with Evans Blue and triphenyltetrazolium chloride. Activity assays, TUNEL staining, and western blotting were performed to determine markers of oxidative stress and apoptosis.', 'LL-VNS significantly decreased the incidence of ventricular arrhythmias, increased vagal tone, as confirmed by heart rate viability, and reduced infarct size compared with the I/R group. This improvement was associated with a reduction in myocardial neutrophil infiltration, the inhibition of oxidative stress, and the suppression in cardiomyocyte apoptosis. In contrast, the lack of LL-VNS in the I/R group induced the opposite effect compared with the sham group.
Answer: LL-VNS exerts protective effects on myocardial I/R injury. Its potential mechanisms involve the suppression of oxidative stress and cellular apoptosis.

Ex Output:
Does low-Level Vagus Nerve Stimulation attenuate Myocardial Ischemic Reperfusion Injury by Antioxidative Stress and Antiapoptosis Reactions in Canines?

Ex Input:
Context: Although the presence of perineural invasion has been recognized as a poor prognostic factor in extrahepatic cholangiocarcinoma, the molecular mechanisms of perineural invasion in extrahepatic cholangiocarcinoma remain unclear. Nerve growth factor has been reported to be a candidate predictive biomarker of perineural invasion in some cancers.', 'To investigate the impact of intratumoral nerve growth factor expression in resected extrahepatic cholangiocarcinoma on survival.', 'Intratumoral nerve growth factor expression was investigated immunohistochemically in 112 patients with resected extrahepatic cholangiocarcinoma. Associations between nerve growth factor expression and clinicopathological factors were statistically evaluated, and risk factors for poor survival were analyzed using univariate and multivariate analyses.', 'High and low nerve growth factor expression was observed in 62 (55%) and 50 (45%) patients, respectively. For all 112 patients, no significant correlation was found between nerve growth factor expression and presence of perineural invasion (P = 0.942). Moreover, nerve growth factor expression was not associated with recurrence-free survival (P = 0.861) and overall survival (P = 0.973). In multivariate analysis, lymph node metastasis (P = 0.004) was identified as an independent risk factor for early recurrence and the presence of perineural invasion (P = 0.002) and lymph node metastasis (P < 0.001) was identified as independent risk factors for poor survival.
Answer: Intratumoral nerve growth factor expression is not associated with perineural invasion or recurrence-free and overall survival in patients with resected extrahepatic cholangiocarcinoma.

Ex Output:
Is nerve Growth Factor Expression Associated with Perineural Invasion in Extrahepatic Cholangiocarcinoma?

Ex Input:
Context: The purpose of this study is to determine whether chiropractic manipulation is associated with any measurable changes in the difference between the arterial blood pressures on the left and right before and after treatment in normotensive subjects.', 'A nonrandomized, matched pair, controlled clinical trial, with the treatment (manipulation) group and control (resting) group matched for age and sex, was performed in chiropractic student clinics in London, UK. The treatment group consisted of 35 new patients presenting to a single student chiropractor between the start of April 2003 and the end of August 2003. The control group consisted of 35 nonpatients matched for sex and age. The intervention was chiropractic manipulation. Preintervention and postintervention systolic and diastolic blood pressures were recorded in both arms through the use of a digital oscillometric sphygmomanometer.', "A significant difference was found between the pre- and posttreatment blood pressure differences for systolic pressures (P = .01), but no significant difference was found in either set of control data or the treatment diastolic values. A significant difference was also found between the treatment and control group's preintervention systolic differences (P = .002), but not between the groups at any other time.
Answer: Chiropractic treatment appears to have an effect on the difference in systolic blood pressure between the arms, which is not shown in the control group or the diastolic treatment group values. This may be attributable to a difference between the 2 groups' preintervention systolic values; however, there was no significant difference between the 2 groups after intervention.

Ex Output:
Does chiropractic manipulation affect the difference between arterial systolic blood pressures on the left and right in normotensive subjects?