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 Q]: Context: Oxidative stress has been considered to play a primary role in the pathogenesis of stress-induced gastric damage. The aim of this study was to investigate the effects of melatonin, ascorbic acid and β-carotene on stress-induced gastric mucosal damage.', 'Fifty-six male Wistar albino rats were divided into control, stress, stress + standard diet, stress + saline, stress + melatonin, stress + ascorbic acid and stress + β-carotene groups. The rats from stress groups were exposed to starvation, immobilization and cold by immobilizing for 8 h at +4°C following 72-hour food restriction. Following stress application, melatonin, ascorbic acid and β-carotene were administered for 7 days. Specimens of gastric tissue were prepared for microscopic and biochemical examinations.', 'Mean histopathological damage scores and mean tissue malondialdehyde levels were significantly decreased but mean tissue glutathione levels and glutathione peroxidase and superoxide dismutase activities were increased in treatment groups vs. stress groups in general. Mean histopathological damage scores of the stress + Mel group was lower than those of stress + D, stress + S, stress + β-car (p < 0.05) and stress + Asc groups (p < 0.005). Additionally, mean tissue catalase activity of the stress + Mel group was higher than that of stress + S (p < 0.005), stress + D (p < 0.05) and stress + β-car groups (p < 0.05).
Answer: Melatonin is more effective than ascorbic acid and β-carotene in improvement of gastric damage induced by intensive stress. We suggest that as well as the direct antioxidant and free radical scavenging potency of melatonin, its indirect effect via the brain-gut axis might account for its greater beneficial action against stress-induced gastric damage.
[EX A]: Is melatonin more effective than ascorbic acid and β-carotene in improvement of gastric mucosal damage induced by intensive stress?

[EX Q]: Context: Concomitant thyroid nodules are the most common reason for false-positive ultrasonography (US) results in primary hyperparathyroidism. The aims of this prospective clinical study were to evaluate false-positive US results according to the characteristics of concomitant thyroid nodules and to determine which characteristics of thyroid nodules are important.', 'This prospective study included 120 consecutive patients with primary hyperparathyroidism. The patients were divided into 2 groups according to preoperative US results. Group 1 consisted of 32 patients with false-positive US results and group 2 consisted of 88 patients with true-positive US results.', 'The risk for false-positive US result was increased 25-fold for patients with parathyroid adenoma weight of more than 500 mg (odds ratio [OR], 25; 95% confidence interval [CI], 8.6-74.5), 75-fold for more than 1 posteriorly located thyroid (OR, 75; 95% CI, 19.3-293.4), 358-fold for the presence of exophytic thyroid nodules (OR, 358; 95% CI, 42.3-3036), and 423-fold for the presence of posteriorly located thyroid nodules (OR, 423; 95% CI, 49-3662).
Answer: Although there was no particular characteristic of concomitant thyroid nodules that contributes to false-positive US results, the posteriorly located thyroid nodules were the strongest correlate for the false-positive US results to other features.
[EX A]: Do the characteristics of concomitant thyroid nodules cause false-positive ultrasonography results in primary hyperparathyroidism?

[EX Q]: Context: To investigate the alteration of the retinal nerve fiber thickness (NFLT) before and after vitreous surgery for a macular hole in cases with or without visual field defects.', 'The NFLT of 23 eyes with idiopathic macular hole was measured with scanning laser polarimeter upto 12 months after surgery. The NFLT was divided into superior, inferior, nasal, and temporal quadrants. The mean NFLT of each quadrant was analyzed statistically and compared to the results of visual field tests.', 'In all cases, the NFLT decreased significantly upto 3 months after surgery, but increased gradually upto 12 months. In cases with visual field loss, the thickness of the nerve fiber layer that corresponds to the visual field defect diminished strongly, in contrast with other quadrants. Even in cases without visual field loss, the NFLT decreased significantly a month after surgery, especially in the nasal and inferior quadrants.
Answer: This study demonstrates that the thickness of retinal nerve fiber layer decreases at least one month after surgery, even in cases without visual field defect. This fact may suggest the existence of a subclinical complication of vitreous surgery.
[EX A]:
Does [ Thickness of retinal nerve fiber layer decrease after vitreous surgery for idiopathic macular hole ]?