TASK DEFINITION: In this task, you are given a passage which has a question and the context. You have to generate an answer to the question based on the information present in the context.
PROBLEM: Context: High arginase-1 (Arg) expression by myeloid-derived suppressor cells (MDSC) is known to inhibit antitumor T-cell responses through depletion of l-arginine. We have previously shown that nitric oxide (NO), an immune mediator produced from l-arginine, is a potent radiosensitizer of hypoxic tumor cells. This study therefore examines whether Arg(+) overexpressing MDSC may confer radioresistance through depleting the substrate for NO synthesis.', 'MDSC and Arg expression were studied in preclinical mouse CT26 and 4T1 tumor models and further validated in rectal cancer patients in comparison with healthy donors. The radioprotective effect of MDSC was analyzed in hypoxic tumor cells with regard to l-arginine depletion.', 'In both mouse tumors and cancer patients, MDSC expansion was associated with Arg activation causing accelerated l-arginine consumption. l-Arginine depletion in turn profoundly suppressed the capacity of classically activated macrophages to synthesize NO resulting in impaired tumor cell radiosensitivity. In advanced cT3-4 rectal cancer, circulating neutrophils revealed Arg overexpression approaching that in MDSC, therefore mounting a protumor compartment wherein Arg(+) neutrophils increased from 17% to over 90%.\Question: Do myeloid-derived suppressor cells reveal radioprotective properties through arginase-induced l-arginine depletion?

SOLUTION: Protumor Arg(+) MDSC reveal a unique ability to radioprotect tumor cells through l-arginine depletion, a common mechanism behind both T-cell and macrophage inhibition.

PROBLEM: Context: Our previous work demonstrated altered messenger RNA expression of integrin -5 and -8, using an in silico analysis of publically available data from patients with biliary atresia (BA); however, we were unable to demonstrate statistically significant differences in protein expression because of sample size. In the present study, we repeated the analysis of liver fibrosis and protein expression of the integrins in a larger cohort of patients with BA and compared them with patients undergoing liver biopsy for other diagnoses, with the hypothesis that 1 of the integrins would be differentially expressed.', 'Liver specimens were obtained at 2 collaborating institutions. Samples from infants with BA (n = 23) were compared with samples from those who underwent liver biopsy for neonatal hepatitis (n = 9). All of the specimens were analyzed by 2 pathologists (C.R. and R.A.), who were blinded to the diagnoses. Standard Ishak scoring was performed to evaluate fibrosis and inflammation, and immunohistochemical (IHC) positivity was graded from 0 to 4. Comparisons between the IHC positivity and Ishak scoring for the BA and control groups were performed using the Student t test with P < 0.01 considered significant because of the multiple comparisons. Interobserver variability was assessed by intraclass correlation (ICC).', 'Pooled analysis from specimens from patients with BA showed significantly more fibrosis than controls based on Ishak scores (3.21 1.82 vs 1.17 1.00, P < 0.005). IHC evaluation showed increased integrin 8 protein expression when compared with controls (2.67 0.81 vs 1.72 0.62, P < 0.005); however, there were no significant differences in integrin 5 (1.93 0.84 vs 1.50 0.90, P = 0.23) or integrin 6 (0.85 1.20 vs 0.94 0.85, P = 0.82) expression. These data were confirmed on individual analysis. Interobserver agreement was fair for integrin 5 (ICC 0.52), good for integrin 6 (ICC 0.72), and excellent for integrin 8 (ICC 0.79) and fibrosis (ICC 0.89).\Question: Is integrin -8 , but not -5 or -6 , protein expression increased in livers of children with biliary atresia?

SOLUTION: Our data show that integrin 8, but not integrin 5 or integrin 6, protein expression is increased in liver specimens of patients with BA. These data support the mounting evidence that transforming growth factor- (TGF-) activation is responsible for the fibrosis found in BA. Anti-integrin 8 or more global integrin blocking strategies may be therapeutic options in BA, but further work is clearly needed.

PROBLEM: Context: Cerebral embolism from cardiac source is an important cause of stroke, specially in patients younger than 45 years old.', 'To describe the transesophageal echocardiography (TEE) findings in young and non-young stroke patients without any prior evidence of cardiac source for cerebral embolism.', 'Transversal study: 523 patients (267 men and 256 women) with ischemic stroke, without any evidence of cardiac abnormality, underwent to TEE.', 'Ten percent were aged 45 years; or less. Left ventricle hypertrophy, left atrial enlargement, spontaneous contrast in aorta, interatrial septum aneurysm, mitral and aortic valve calcification, aortic valve regurgitation, and atherosclerotic plaques in aorta were significantly more frequent in patients aged more than 45 years; 2.8% of non-young patients had thrombus in left heart.\Question: Does transesophageal echocardiography disclose unexpected cardiac sources of embolus in stroke patients aged more than 45 years?

SOLUTION:
TEE is widely used to diagnose cardiac source of cerebral embolism in young patients, but it seems to be as useful for older ones, in whom cerebral embolism risk is underestimated; atherogenic and cardioembolic causes may actually coexist, and both should be treated.