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: Guanidinoacetic acid (GAA) is an experimental dietary additive that might act as a creatine source in tissues with high-energy requirements. In this case study, we evaluated brain levels of creatine in white matter, gray matter, cerebellum, and thalamus during 8\xa0wk oral GAA administration in five healthy men and monitored the prevalence and severity of side effects of the intervention.', 'Volunteers were supplemented daily with 36\xa0mg/kg body weight (BW) of GAA for the first 4\xa0wk of the intervention; afterward GAA dosage was titrated ≤60\xa0mg/kg BW of GAA daily. At baseline, 4, and 8\xa0wk, the participants underwent brain magnetic resonance spectroscopy, clinical chemistry studies, and open-ended questionnaire for side-effect prevalence and severity.', 'Brain creatine levels increased in similar fashion in cerebellum, and white and gray matter after GAA supplementation, with an initial increase of 10.7% reported after 4\xa0wk, and additional upsurge (7.7%) from the weeks 4 to 8 follow-up (P\xa0<\xa00.05). Thalamus creatine levels decreased after 4\xa0wk for 6.5% (P\xa0=\xa00.02), and increased nonsignificantly after 8\xa0wk for 8% (P\xa0=\xa00.09). GAA induced an increase in N-acetylaspartate levels at 8-wk follow-up in all brain areas evaluated (P\xa0<\xa00.05). No participants reported any neurologic adverse event (e.g., seizures, tingling, convulsions) during the intervention.
Answer: Supplemental GAA led to a region-dependent increase of the creatine pool in the human brain. This might be relevant for restoring cellular bioenergetics in disorders characterized by low brain creatine and functional enzymatic machinery for creatine synthesis, including neurodegenerative diseases, brain tumors, or cerebrovascular disease.
[EX A]: Does dietary guanidinoacetic acid increase brain creatine levels in healthy men?

[EX Q]: Context: Spinal anesthesia can be challenging in patients undergoing total joint arthroplasty because of poorly palpable surface landmarks and age-related changes in the lumbar spine. We hypothesized that pre-procedural ultrasound imaging would be effective in identifying the lumbar intervertebral spaces and would provide an accurate measure of the depth to the intrathecal space.', "Fifty patients undergoing elective total joint arthroplasty were recruited in this prospective descriptive study. Using a curved-array 2-5 MHz transducer, the lumbar spine was imaged in two views, i.e., longitudinal parasagittal (LP) and transverse midline (TM). The intervertebral levels were identified by counting upwards from the sacrum. The locations of the interlaminar spaces were identified by visualizing the ligamentum flavum-dura mater complex and the posterior aspect of the vertebral body. The needle insertion point for a midline approach was determined from the ultrasound examination and was marked on the skin of the patient's back.", 'The mean patient age was 67 +/- 10 yr, and 46% of the patients had a body mass index >30 kg . m(-2). Surface landmarks were difficult or impossible to palpate in 38% of the patients. The scan quality on the LP and TM views was adequate or better in 100 and 98% of the patients, respectively. Dural puncture was achieved with one needle insertion attempt and within two needle insertion attempts in 84% and 98% of the patients, respectively. The ultrasound-measured depth to the intrathecal space correlated well with the actual needle insertion depth (concordance correlation coefficient = 0.82, accuracy 0.95, precision 0.86), with a tendency to overestimate the depth by just 2.1 +/- 5.4 mm.
Answer: Ultrasound imaging of the lumbar spine provides clinically useful information that can facilitate spinal anesthesia in the older orthopedic patient population.
[EX A]: Does an ultrasound-assisted approach facilitate spinal anesthesia for total joint arthroplasty?

[EX Q]: Context: The ability of CD8(+) T-cells to induce prostate inflammation was examined using a prostate ovalbumin expressing transgenic mouse (POET) and/or adoptive transfer of T-cell receptor (TCR) transgenic T-cells (OT-I) that specifically recognize ovalbumin. Localization of inflammatory cells to prostate tissue was examined following T-cell activation via endogenous prostatic antigen, recombinant type 5 adenovirus carrying the gene coding ovalbumin (Ad5-mOVA), or adoptive transfer of in vitro antigen stimulated OT-I cells.', 'Ovalbumin specific OT-I cells were activated by autologous prostate antigen and trafficked to the prostate, but did not induce inflammation unless present in overwhelming numbers ( approximately 65% of CD8(+) T-cells). Activation of antigen specific CD8(+) T-cells in vitro (peptide pulsed antigen presenting cells) or in vivo (Ad5-mOVA) induced transitory prostate inflammation, without induction of prostate pathology, regardless of CD4(+) T-cell availability. Inflammation also was observed in OT-I x POET mice but again, pathological effects were not observed.
Answer: T lymphocytes specific for a prostate antigen are capable of inducing inflammatory infiltration of prostatic tissue rapidly following activation, but do not produce pathological prostate injury.
[EX A]:
Is t-cell recognition of a prostate specific antigen sufficient to induce prostate tissue destruction?