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.
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Question: 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.

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


Question: Context: Preconditioning neurons with noninjurious hypoxia (hypoxic preconditioning, HPC) or the anesthetic isoflurane (APC) induces tolerance of severe ischemic stress. The mechanisms of both types of preconditioning in the hippocampus require moderate increases in intracellular Ca and activation of protein kinase signaling. The authors hypothesized that the expression of signal transduction genes would be similar after APC and HPC.', 'Hippocampal slice cultures prepared from 9-day-old rats were preconditioned with hypoxia (5 min of 95% nitrogen/5% carbon dioxide) or 1% isoflurane in air/5% carbon dioxide for 1 h. A day later, cultures were subjected to 10 min oxygen and glucose deprivation (simulated ischemia). Intracellular Ca, measured in CA1 neurons at the completion of preconditioning, and cell death in CA1, CA3, and dentate regions was assessed 48 h after simulated ischemia. Message RNA encoding 119 signal transduction genes was quantified with rat complimentary DNA microarrays from pre-oxygen-glucose deprivation samples.', 'Both APC and HPC increased intracellular Ca approximately 50 nm and decreased CA1, CA3, and dentate neuron death by about 50% after simulated ischemia. Many signaling genes were increased after preconditioning, with hypoxia increasing more apoptosis/survival genes (8 of 10) than isoflurane (0 of 10). In contrast, isoflurane increased more cell cycle/development/growth genes than did hypoxia (8 of 14 genes, vs. 1 of 14).
Answer: Despite sharing similar upstream signaling and neuroprotective outcomes, the genomic response to APC and HPC is different. Increased expression of antiapoptosis genes after HPC and cell development genes after APC has implications both for neuroprotection and long-term effects of anesthetics.

Answer: Does expression of signal transduction genes differ after hypoxic or isoflurane preconditioning of rat hippocampal slice cultures?


Question: Context: We evaluated the associations between dual energy X-ray absorptiometry (DXA) and histologically determined cancellous and cortical bone volume by controlling for vascular calcifications and demographic variables in hemodialysis (HD) patients. Femoral bone mineral density (f-BMD) was associated with cortical porosity.', 'Assessment of bone mass in chronic kidney disease patients is of clinical importance because of the association between low bone volume, fractures, and vascular calcifications. DXA is used for noninvasive assessment of bone mass whereby vertebral results reflect mainly cancellous bone and femoral results reflect mainly cortical bone. Bone histology allows direct measurements of cancellous and cortical bone volume. The present study evaluates the association between DXA and histologically determined cancellous and cortical bone volumes in HD patients.', 'In 38 HD patients, DXA was performed for assessment of bone mass, anterior iliac crest bone biopsies for bone volume, and multislice computed tomography for vascular calcifications.', 'While lumbar bone mineral density (l-BMD) by DXA was not associated with histologically measured cancellous bone volume, coronary Agatson score showed a borderline statistically significant association (P = 0.055). When controlled for age and dialysis duration, f-BMD by DXA was associated with cortical porosity determined by histology (P = 0.005).
Answer: The usefulness of l-BMD for predicting bone volume is limited most probably because of interference by soft tissue calcifications. In contrast, f-BMD shows significant association with cortical porosity.

Answer:
Does femoral bone mineral density reflect histologically determined cortical bone volume in hemodialysis patients?