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.

[Q]: It has already been demonstrated that the rat esophagus produces retinoic acid from retinol. In this study, this process is further characterized and the effect of acetaldehyde examined to elucidate the possible mechanisms behind the epidemiological evidence that the incidence of esophageal cancer is higher in alcoholics.', 'Rat esophageal samples were incubated with all-trans retinal and newly formed all-trans retinoic acid (ATRA) was quantified using high-performance liquid chromatography (HPLC). Furthermore, beta-nicotinamide adenine dinucleotide (NAD)-dependent acetaldehyde oxidation by the rat esophagus was examined by tracing NAD reduction using a spectrophotometer.', 'Rat esophageal samples produced ATRA from all-trans retinal in a NAD-dependent manner and the potential was significantly attenuated by phenetyl isothiocynate, an ALDH inhibitor, or acetaldehyde depending on the concentration used. Rat esophageal samples also oxidized acetaldehyde of various concentrations NAD dependently. The ATRA formation potential that was temporarily inhibited by acetaldehyde was recovered to the control level by dialysis when the specimen was incubated with up to 50 microM of acetaldehyde.
[A]: Does acetaldehyde inhibit the formation of retinoic acid from retinal in the rat esophagus?

[Q]: Pulmonary hypertension (PH) is prognosti- cally important in chronic obstructive pulmonary disease (COPD). Since PH only weakly correlates with hypoxemia, other factors must play a role.', 'To investigate whether polymorphisms of the serotonin transporter (5HTT), serotonin-2a receptor (5HTR2a) and endothelial nitric oxide synthetase (eNOS) are related to PH in COPD.', 'In 59 COPD patients who underwent right heart catheterization, 6-min walking distance, NYHA functional class, pulmonary function tests, blood gases and 5HTT, 5HTR2a and eNOS (4ab and T298C) polymorphisms were determined.', 'Forty-nine COPD patients in NYHA functional class III-IV were included. Ten were excluded due to comorbid causes of PH (mainly chronic thromboembolic). PH (mPAP > or =25 mm Hg) was present in 55% and usually mild, but out of proportion (mPAP > or =40 mm Hg) in 12%. Patients with PH had significantly higher frequencies of the 5HTT-L-allele (52%) compared to individuals without PH (36%), and LL homozygote patients had more severe PH. In patients with out-of-proportion PH, the L-allelic frequency was even 75%. We found no association of 5HTR2a and eNOS polymorphism with PH in COPD.
[A]: Are genetic polymorphisms of the serotonin transporter , but not the 2a receptor or nitric oxide synthetase , associated with pulmonary hypertension in chronic obstructive pulmonary disease?

[Q]: Liraglutide improves the metabolic control of diabetic animals after islet transplantation. However, the mechanisms underlying this effect remain unknown. The objective of this study was to evaluate the anti-inflammatory and anti-oxidative properties of liraglutide on rat pancreatic islets in vitro and in vivo.', 'In vitro, rat islets were incubated with 10molL', 'Islet viability and function were preserved and enhanced with liraglutide treatment. Liraglutide decreased CCL2 and IL-6 secretion and macrophage activation after 12h of culture, while IL-10 secretion was unchanged. However, intracellular levels of ROS were increased with liraglutide treatment at 12h. This result was correlated with an increase of anti-oxidative capacity. In vivo, liraglutide decreased macrophage infiltration and reduced fasting blood glucose in transplanted rats.
[A]:
Is improvement of islet graft function using liraglutide correlated with its anti-inflammatory properties?