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.

[EX Q]: Context: Infection of human immunodeficiency virus (HIV) has been associated with several chronic diseases, including pulmonary artery hypertension and atherosclerosis. However, the underlying mechanisms of these vascular complications are largely unknown. The objective of this study was to test a novel hypothesis that HIV Nef, an accessory HIV protein, may directly affect endothelial functions and gene expression in pulmonary arteries.', 'Fresh porcine pulmonary artery rings and human pulmonary artery endothelial cells (HPAECs) were treated with HIV Nef for 24 h. With a myograph device, vasomotor function was determined with thromboxane A2 analog, U46619, for contraction, bradykinin, and sodium nitroprusside for relaxation. The expression of endothelial nitric oxide synthase (eNOS) was determined with real-time PCR and immunohistochemistry. Nitric oxide (NO) production was determined by Calorimetric Nitric Oxide Assay kit. Superoxide anion levels were detected with lucigenin-enhanced chemiluminescence assay and dihydroethidium (DHE) staining.', 'The endothelium-dependent vasorelaxation in response to bradykinin was significantly reduced in HIV Nef-treated porcine pulmonary artery rings in a concentration-dependent manner. In response to bradykinin (10(-8) mol/L), HIV Nef (10 ng/mL) significantly reduced vasorelaxation by 32% compared with untreated controls (P < 0.05). In addition, HIV Nef significantly decreased eNOS expression in the vessels and HPAECs. HIV Nef at 10 ng/mL significantly decreased NO production in HPAECs by 21% compared with controls (P < 0.05). Furthermore, HIV Nef significantly increased superoxide anion production in porcine pulmonary arteries and HPAECs compared with controls (P < 0.05). Consequently, Mn (III) tetrakis porphyrin, a superoxide dismutase mimic, effectively blocked HIV Nef-induced vasomotor dysfunction and superoxide anion production. The specificity of HIV Nef action was confirmed by anti-Nef antibody blocking and Nef heat inactivation.\Question: Does hIV Nef protein cause endothelial dysfunction in porcine pulmonary arteries and human pulmonary artery endothelial cells?
[EX A]: HIV Nef protein significantly decreases endothelium-dependent vasorelaxation in porcine pulmonary arteries. It also reduces eNOS expression and induces oxidative stress in both porcine pulmonary arteries and HPAECs. This study demonstrates a new mechanism of HIV Nef, which causes endothelial dysfunction and may contribute to the human pulmonary artery disease in HIV-infected patients.

[EX Q]: Context: Elevated blood lead levels (BLL) and malaria carry an important burden of disease in West Africa. Both diseases might cause anemia and they might entail long-term consequences for the development and the health status of the child. Albeit the significant impact of malaria on lead levels described in Nigeria, no evaluation of the effect of elevated BLL on malaria risk has been investigated so far.', 'Between 2010 and 2012, blood lead levels of 203 Beninese infants from Allada, a semi-rural area 50km North from Cotonou, were assessed at 12 months of age. To assess lead levels, blood samples were analyzed by mass spectrometry. In parallel, clinical, microbiological and hematological data were collected. More precisely, hemoglobin, serum ferritin, CRP, vitamin B12, folate levels, and Plasmodium falciparum parasitemia were assessed and stool samples were also analyzed.', 'At 12 months, the mean BLL of infants was 7.41 μg/dL (CI: 65.2; 83), and 128 infants (63%) had elevated blood lead levels, defined by the CDC as BLL>5 μg/dL. Lead poisoning, defined as BLL>10 μg/dL, was found in 39 infants (19%). Twenty-five infants (12.5%) had a positive blood smear at 12 months and 144 infants were anemic (71%, hemoglobin<110 g/L). Elevated blood lead levels were significantly associated with reduced risk of a positive blood smear (AOR = 0.38, P-value = 0.048) and P. falciparum parasite density (beta-estimate = -1.42, P-value = 0.03) in logistic and negative binomial regression multivariate models, respectively, adjusted on clinical and environmental indicators.\Question: Do elevated Blood Lead Levels Are Associated with Reduced Risk of Malaria in Beninese Infants?
[EX A]: Our study shows for the first time that BLL are negatively associated with malarial risk considering other risk factors. Malaria is one of the main causes of morbidity and mortality in infants under 5 years worldwide, and lead poisoning is the 6th most important contributor to the global burden of diseases measured in disability adjusted life years (DALYs) according to the Institute of Health Metrics. In conclusion, due to the high prevalence of elevated BLL, health interventions should look forward to minimize the exposure to lead to better protect the population in West Africa.

[EX Q]: Context: Cirrhotic patients undergoing transjugular intrahepatic portosystemic shunt (TIPS) for refractory ascites or recurrent variceal bleeding are at risk for decompensation and death. This study examined whether a new model for end stage liver disease (MELD), which incorporates serum sodium (MELDNa), is a better predictor of death or transplant after TIPS than the original MELD.', "One hundred forty-eight consecutive patients undergoing nonemergent TIPS for refractory ascites or recurrent variceal bleeding from 1997 to 2006 at a single center were evaluated retrospectively. Cox model analysis was performed with death or transplant within 6 months as the end point. The models were compared using the Harrell's C index. Recursive partitioning determined the optimal MELDNa cutoff to maximize the risk:benefit ratio of TIPS.", 'The predictive ability of MELDNa was superior to MELD, particularly in patients with low MELD scores. The C indices (95% confidence interval [CI]) for MELDNa and MELD were 0.65 (95% CI, 0.55-0.71) and 0.58 (95% CI, 0.51-0.67) using a cut-off score of 18, and 0.72 (95% CI, 0.60-0.85) and 0.62 (95% CI, 0.49-0.74) using a cut-off score of 15. Using a MELDNa >15, 22% of patients were reclassified to a higher risk with an event rate of 44% compared with 10% when the score was <or=15.\Question: Does new model for end stage liver disease improve prognostic capability after transjugular intrahepatic portosystemic shunt?
[EX A]:
MELDNa performed better than MELD in predicting death or transplant after non-emergent TIPS, especially in patients with low MELD scores. A MELD score <or=18 can provide a false positive prognosis; a MELDNa score <or=15 provides a more accurate risk prediction.