instruction:
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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Context: The endosteum of the bone marrow provides a specialized hypoxic niche that may serve to preserve the integrity, pluripotency, longevity and stemness of resident mesenchymal stem cells (MSCs). To explore the molecular genetic consequences of such a niche we subjected human (h) MSCs to a pO2 of 4 mmHg and analyzed global gene expression and alternative splicing (AS) by genome-exon microarray and RT-qPCR, and phenotype by western blot and immunostaining.', 'Out of 446 genes differentially regulated by >2.5-fold, down-regulated genes outnumbered up-regulated genes by 243:203. Exon analyses revealed 60 hypoxia-regulated AS events with splice indices (SI) >1.0 from 53 genes and a correlation between high SI and degree of transcript regulation. Parallel analyses of a publicly available AS study on human umbilical vein endothelial cells (HUVECs) showed that there was a strong cell-specific component with only 11 genes commonly regulated in hMSCs and HUVECs and 17 common differentially spliced genes. Only 3 genes were differentially responsive to hypoxia at the gene (>2.0) and AS levels in both cell types. Functional assignments revealed unique profiles of gene expression with complex regulation of differentiation, extracellular matrix, intermediate filament and metabolic marker genes. Antioxidant genes, striated muscle genes and insulin/IGF-1 signaling intermediates were down-regulated. There was a coordinate induction of 9 out of 12 acidic keratins that along with other epithelial and cell adhesion markers implies a partial mesenchymal to epithelial transition.
Answer: We conclude that severe hypoxia confers a quiescent phenotype in hMSCs that is reflected by both the transcriptome profile and gene-specific changes of splicosome actions. The results reveal that severe hypoxia imposes markedly different patterns of gene regulation of MSCs compared with more moderate hypoxia. This is the first study to report hypoxia-regulation of AS in stem/progenitor cells and the first molecular genetic characterization of MSC in a hypoxia-induced quiescent immobile state.
answer:
Does severe hypoxia exert parallel and cell-specific regulation of gene expression and alternative splicing in human mesenchymal stem cells?


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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.
answer:
Does an ultrasound-assisted approach facilitate spinal anesthesia for total joint arthroplasty?


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Context: Lynch syndrome (LS) is clinically defined by the Amsterdam criteria (AC) and by germline mutations in mismatch-repair (MMR) genes leading to microsatellite instability (MSI) at the molecular level. Patients who do not fulfil AC are considered suspected-Lynch according to the less stringent Bethesda guidelines (BG) and should be tested for MSI and MMR germline mutations. BRAF mutations have been proposed as a marker to exclude LS because they are generally absent in LS patients and present in sporadic colorectal cancer (sCRC) with MSI due to promoter hypermethylation of the MLH1 gene. Our aim was to verify whether BRAF mutations may improve the criteria to select patients for germline MMR mutation assessment.', 'We analyzed 303 formalin-fixed paraffin-embedded CRC samples including 174 sCRC, 28 patients fulfilling AC, and 101 suspected-Lynch patients fulfilling BG. We analyzed MSI and BRAF mutations in all CRC samples. MLH1, MSH2 and MSH6 germline mutations were investigated in MSI patients fulfilling AC or BG.', 'sCRC samples showed MSI in 20/174 (11%) cases. BRAF mutations were detected in 10/174 (6%) sCRC cases and were significantly correlated with MSI (P = 0.002). MSI was observed in 24/28 (86%) Amsterdam cases which were BRAF wild-type. MMR gene mutation was detected in 22/26 (85%) AC cases, all showing MSI. Suspected-Lynch cases carried MSI in 41/101 (40%) and BRAF mutations in 7/101 (7%) cases. MMR gene mutation was detected in 13/28 (46%) evaluable MSI patients of this group and only in cases characterized by a wild-type BRAF gene.
Answer: The prevalence of BRAF mutations in CRC patients is not high but extremely correlated with MSI and risk categories as BG, whereas they are absent in LS patients. BRAF mutation detection can reduce the need for MMR gene analysis in a small (but not negligible) proportion of MSI patients (7%), with a positive impact on the financial and psychological costs of unnecessary tests.
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Is bRAF mutation analysis a valid tool to implement in Lynch syndrome diagnosis in patients classified according to the Bethesda guidelines?