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: Surfactant protein A (SP-A) is a C-type lectin involved in surfactant homeostasis as well as host defense in the lung. We have recently demonstrated that SP-A enhances the killing of bacillus Calmette-Guerin (BCG) by rat macrophages through a nitric oxide-dependent pathway. In the current study we have investigated the role of tyrosine kinases and the downstream mitogen-activated protein kinase (MAPK) family, and the transcription factor NFkappaB in mediating the enhanced signaling in response to BCG in the presence of SP-A.', 'Human SP-A was prepared from alveolar proteinosis fluid, and primary macrophages were obtained by maturation of cells from whole rat bone marrow. BCG-SP-A complexes were routinely prepared by incubation of a ratio of 20 microg of SP-A to 5 x 105 BCG for 30 min at 37 degrees C. Cells were incubated with PBS, SP-A, BCG, or SP-A-BCG complexes for the times indicated. BCG killing was assessed using a 3H-uracil incorporation assay. Phosphorylated protein levels, enzyme assays, and secreted mediator assays were conducted using standard immunoblot and biochemical methods as outlined.', 'Involvement of tyrosine kinases was demonstrated by herbimycin A-mediated inhibition of the SP-A-enhanced nitric oxide production and BCG killing. Following infection of macrophages with BCG, the MAPK family members ERK1 and ERK2 were activated as evidence by increased tyrosine phosphorylation and enzymatic activity, and this activation was enhanced when the BCG were opsonized with SP-A. An inhibitor of upstream kinases required for ERK activation inhibited BCG- and SP-A-BCG-enhanced production of nitric oxide by approximately 35%. Macrophages isolated from transgenic mice expressing a NFkappaB-responsive luciferase gene showed increased luciferase activity following infection with BCG, and this activity was enhanced two-fold in the presence of SP-A. Finally, lactacystin, an inhibitor of IkappaB degradation, reduced BCG- and SP-A-BCG-induced nitric oxide production by 60% and 80% respectively.
Answer: These results demonstrate that BCG and SP-A-BCG ingestion by macrophages is accompanied by activation of signaling pathways involving the MAP kinase pathway and NFkappaB.
Are mitogen-activated protein kinases and NFkappaB involved in SP-A-enhanced responses of macrophages to mycobacteria?

Context: DNA methylation is an important biological form of epigenetic modification, playing key roles in plant development and environmental responses.', 'In this study, we examined single-base resolution methylomes of Populus under control and drought stress conditions using high-throughput bisulfite sequencing for the first time. Our data showed methylation levels of methylated cytosines, upstream 2 kp, downstream 2kb, and repeatitive sequences significantly increased after drought treatment in Populus. Interestingly, methylation in 100 bp upstream of the transcriptional start site (TSS) repressed gene expression, while methylations in 100-2000 bp upstream of TSS and within the gene body were positively associated with gene expression. Integrated with the transcriptomic data, we found that all cis-splicing genes were non-methylated, suggesting that DNA methylation may not associate with cis-splicing. However, our results showed that 80% of trans-splicing genes were methylated. Moreover, we found 1156 transcription factors (TFs) with reduced methylation and expression levels and 690 TFs with increased methylation and expression levels after drought treatment. These TFs may play important roles in Populus drought stress responses through the changes of DNA methylation.
Answer: These findings may provide valuable new insight into our understanding of the interaction between gene expression and methylation of drought responses in Populus.
Do single-base-resolution methylomes of Populus trichocarpa reveal the association between DNA methylation and drought stress?

Context: Tobacco smoking is a public health issue and has been implicated in adverse reproductive outcomes including semen quality. Available data however provides conflicting findings. The objective of this study was to evaluate the effect of tobacco smoking on semen quality among men in Ghana.', 'In this study, a total of 140 subjects were recruited, comprising 95 smokers and 45 non-smokers. Smokers were further categorized into mild, moderate and heavy smokers. Semen parameters such as sperm concentration, motility, viability and normal morphology were measured according to the World Health Organisation criteria.', 'The study showed that smokers had significantly lower semen volume, sperm concentration, sperm motility, total sperm count, sperm morphology, free testosterone and follicle stimulating hormone (p <0.05 respectively), compared with non-smokers. Smokers were at a higher risk of developing oligospermia, asthenozoospermia and teratozoospermia (OR\u2009=\u20093.1, 4.2 and, 4.7; p <0.05) than non-smokers.
Answer: Results demonstrated a decline in semen quality in a dose dependent tobacco smoking manner.

Is tobacco smoking associated with decreased semen quality?