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.

Context: Impaired neurodevelopmental outcome represents a major morbidity for survivors of infant heart surgery for congenital heart defects. Previous studies in these neonates have reported preoperative microcephaly, periventricular leukomalacia, and other findings. The hypothesis of this study is that preoperative cerebral blood flow is substantially diminished and might relate to preoperative neurologic conditions.', 'Preoperative brain magnetic resonance imaging was performed. Cerebral blood flow measurements in infants with congenital heart defects were obtained by using a novel noninvasive magnetic resonance imaging technique, pulsed arterial spin-label perfusion magnetic resonance imaging. Cerebral blood flow was measured before the operation under standard ventilation and repeated after increased carbon dioxide.', 'A total of 25 term infants were studied. The average age at the time of the operation was 4.4 +/- 4.6 days. Congenital heart defects varied widely. Microcephaly occurred in 24% (6/25). Baseline cerebral blood flow was 19.7 +/- 9.2 mL . 100 g -1 . min -1 (8.0-42.2 mL . 100 g -1 . min -1 ). Five patients had cerebral blood flow measurements of less than 10 mL . 100 g -1 . min -1 . Mean hypercarbic cerebral blood flow increased to 40.1 +/- 20.3 mL . 100 g -1 . min -1 (11.4-94.0 mL . 100 g -1 . min -1 , P < .001). Pairwise analyses found that low hemoglobin levels were associated with higher baseline cerebral blood flow values ( P = .04). Periventricular leukomalacia occurred in 28% (7/25) and was associated with decreased baseline cerebral blood flow values ( P = .05) and a smaller change in cerebral blood flow with hypercarbia ( P = .003).
Answer: Structural brain abnormalities are common in these neonates before surgical intervention. Preoperative cerebral blood flow for this cohort was low and drastically reduced in some patients. Low cerebral blood flow values were associated with periventricular leukomalacia. Carbon dioxide reactivity was preserved but might be compromised by some aspects of the cardiac anatomy. The full spectrum of cerebral blood flow measurements with this technique in congenital heart defects and their long-term significance require continued investigation.
Is preoperative cerebral blood flow diminished in neonates with severe congenital heart defects?

Context: Prostaglandin D2 (PGD2) and cysteinyl leukotrienes (cysLTs) are lipid mediators derived from mast cells, which activate TH2 cells. The combination of PGD2 and cysLTs (notably cysteinyl leukotriene E4 [LTE4]) enhances TH2 cytokine production. However, the synergistic interaction of cysLTs with PGD2 in promoting TH2 cell activation is still poorly understood. The receptors for these mediators are drug targets in the treatment of allergic diseases, and hence understanding their interaction is likely to have clinical implications.', 'We aimed to comprehensively define the roles of PGD2, LTE4, and their combination in activating human TH2 cells and how such activation might allow the TH2 cells to engage downstream effectors, such as neutrophils, which contribute to the pathology of allergic responses.', 'The effects of PGD2, LTE4, and their combination on human TH2 cell gene expression were defined by using a microarray, and changes in specific inflammatory pathways were confirmed by means of PCR array, quantitative RT-PCR, ELISA, Luminex, flow cytometry, and functional assays, including analysis of downstream neutrophil activation. Blockade of PGD2 and LTE4 was tested by using TM30089, an antagonist of chemoattractant receptor-homologous molecule expressed on TH2 cells, and montelukast, an antagonist of cysteinyl leukotriene receptor 1.', 'PGD2 and LTE4 altered the transcription of a wide range of genes and induced diverse functional responses in TH2 cells, including cell adhesion, migration, and survival and cytokine production. The combination of these lipids synergistically or additively enhanced TH2 responses and, strikingly, induced marked production of diverse nonclassical TH2 inflammatory mediators, including IL-22, IL-8, and GM-CSF, at concentrations sufficient to affect neutrophil activation.
Answer: PGD2 and LTE4 activate TH2 cells through different pathways but act synergistically to promote multiple downstream effector functions, including neutrophil migration and survival. Combined inhibition of both PGD2 and LTE4 pathways might provide an effective therapeutic strategy for allergic responses, particularly those involving interaction between TH2 cells and neutrophils, such as in patients with severe asthma.
Do prostaglandin D2 and leukotriene E4 synergize to stimulate diverse TH2 functions and TH2 cell/neutrophil crosstalk?

Context: To determine if oligosaccharides of hyaluronan (o-HA) promotes wound recovery by accelerating angiogenesis and to study the mechanisms by which o-HA stimulates endothelial cell (EC) proliferation.', 'Using hyaluronidase digestion, we prepared a mixture of hyaluronan (HA) fragments sizesd 2 to 10 disaccharides units, and studied their effects on EC growth and migration in mimicking wound recovery in vitro. The effects of o-HA on EC growth in vitro were studied by counting cell numbers. The roles of 2 hyaluronan receptors on EC cells, CD44 and RHAMM (Receptor for HA-Mediated Motility), were studied in initiating signaling cascades, using immunoblot assay. Signal transduction was determined by blocking antibodies to CD44 and RHAMM. An in vitro wound healing model was prepared by scratching the cellular layer of cultured EC, and movement of cells into the denuded area was quantified.', 'o-HA was a strong stimulator to EC proliferation at low concentration 10microg/ml compared with native high molecular weight HA (n-HA) (P < 0.01). Signal transduction may be initiated by o-HA via RHAMM receptor on EC membrane, but not CD44. In the in vitro model, the lesion area was nearly completely recovered when the EC layer was exposed to o-HA 40hrs post-injury, whereas the wound area remained half recovered pretreated with native undegraded large HA and control medium.(P < 0.05 from 24 to 40hrs).
Answer: Hyaluronan oligosaccharides may play a role in wound healing by increasing angiogenesis. o-HA-RHAMM binding dependent signal transduction pathway may be important in the regulation of angiogenesis associated with EC proliferation.

Are hyaluronan oligosaccharides potential stimulators to angiogenesis via RHAMM mediated signal pathway in wound healing?