Given a context passage, generate a question from the passage such that its answer is shortest continous span from the passage.

Ex Input:
Precursor cells have been shown to be affected by oxidative stress, in vivo and vitro, but little is known about the expression of antioxidant mechanisms in neuronal/glial differentiation. We have characterized the expression of Cu/Zn superoxide dismutase (Cu/Zn SOD), one of the main antioxidant proteins involved in the breakdown of superoxide, in the immature rat dorsolateral subventricular zone (SVZ), rostral migratory stream (RMS) and hippocampal subgranular zone (SGZ). Progenitor cells were identified immunohistochemically on cryostat sections by 5'Bromodeoxyuridine (BrdU) incorporation and expressing cells were further characterized using double labeling for progenitor markers. In the SVZ, only a subpopulation of BrdU+ cells, mostly found in the medial SVZ, expressed Cu/Zn SOD. These cells were mostly nestin+ and some were also vimentin+. In contrast, in the lateral SVZ few Cu/Zn SOD+/BrdU+ cells were found. These were primarily nestin+, vimentin-, showed some PSA-NCAM expression, but only a few were NG2+. In the RMS and SGZ virtually all BrdU+ progenitors were Cu/Zn SOD+ and expressed nestin and vimentin. Some RMS cells were also PSA-NCAM+. These findings show a heterogeneous expression of Cu/Zn SOD in restricted cell types in the germinative zones and suggest a role for antioxidant Cu/Zn SOD in progenitor cells of the immature rat brain.

Ex Output:
Which intermediate filament (IF) protein can be used as a non-specific marker of the neuronal precursor cells of the subventricular zone?

Ex Input:
Change in gene expression associated with pancreatic cancer could be attributed to the variation in histone posttranslational modifications leading to subsequent remodeling of the chromatin template during transcription. However, the interconnected network of molecules involved in regulating such processes remains elusive. hPaf1/PD2, a subunit of the human PAF-complex, involved in the regulation of transcriptional elongation has oncogenic potential. Our study explores the possibility that regulation of histone methylation by hPaf1 can contribute towards alteration in gene expression by nucleosomal rearrangement. Here, we show that knockdown of hPaf1/PD2 leads to decreased di- and tri-methylation at histone H3 lysine 4 residues in pancreatic cancer cells. Interestingly, hPaf1/PD2 colocalizes with MLL1 (Mixed Lineage Leukemia 1), a histone methyltransferase that methylates H3K4 residues. Also, a reduction in hPaf1 level resulted in reduced MLL1 expression and a corresponding decrease in the level of CHD1 (Chromohelicase DNA-binding protein 1), an ATPase dependent chromatin remodeling enzyme that specifically binds to H3K4 di and trimethyl marks. hPaf1/PD2 was also found to interact and colocalize with CHD1 in both cytoplasmic and nuclear extracts of pancreatic cancer cells. Further, reduced level of CHD1 localization in the nucleus in hPaf1/PD2 Knockdown cells could be rescued by ectopic expression of hPaf1/PD2. Micrococcal nuclease digestion showed an altered chromatin structure in hPaf1/PD2-KD cells. Overall, our results suggest that hPaf1/PD2 in association with MLL1 regulates methylation of H3K4 residues, as well as interacts and regulates nuclear shuttling of chromatin remodeling protein CHD1, facilitating its function in pancreatic cancer cells.

Ex Output:
Which is the histone residue methylated by MLL1?

Ex Input:
A blinded, retrospective study was performed to determine the value of supine abdominal radiographs in diagnosing pneumoperitoneum. Supine films from 44 cases of pneumoperitoneum were randomly interspersed among supine films from 87 control subjects without free air, and the films were reviewed for the presence or absence of various signs of pneumoperitoneum, including Rigler's sign (gas on both sides of the bowel wall), the falciform ligament sign (gas outlining the falciform ligament), the football sign (gas outlining the peritoneal cavity), the inverted-V sign (gas outlining the medial umbilical folds), and the right-upper-quadrant gas sign (localized gas in the right upper quadrant). One or more of these signs were present in 26 cases (59%) of pneumoperitoneum, including the right-upper-quadrant gas sign in 18 cases (41%), Rigler's sign in 14 cases (32%), and the falciform ligament and football signs in one case each (2%). Unfortunately, there were frequent errors in the interpretation of the right-upper-quadrant gas sign and Rigler's sign, with a total of 11 false-positive cases (13%). Further analysis of the true-positive right-upper-quadrant gas signs showed that these gas collections were always triangular or linear with an inferolateral to superomedial orientation and, if triangular, a concave superolateral border. In the true-positive Rigler's signs, the bowel wall thickness ranged from 1 to 8 mm, whereas the false positives all had a bowel wall thickness of 1 mm or less. Proper interpretation of the various signs of pneumoperitoneum on supine films should lead to more accurate diagnosis of this condition.

Ex Output:
Falciform ligament sign is characteristic to which disease?