instruction:
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.
question:
Context: Nonviral vectors based on polyethylenimine (PEI) usually contain an excess of PEI that is not complexed to DNA. Since unbound PEI contributes to cellular and systemic toxicity, purification of polyplexes from unbound PEI is desirable.', 'Size exclusion chromatography (SEC) was used to purify PEI polyplexes of free PEI. Transfection properties of purified polyplexes and the effect of free PEI on gene delivery were studied in vitro and in vivo after systemic application into mice.', 'SEC did not change the size and zeta-potential of polyplexes. Independent of the amount of PEI used for complex formation, purified PEI polyplexes had the same final PEI nitrogen/DNA phosphate ratio of 2.5. Notably, purified PEI polyplexes demonstrated low cellular and systemic toxicity. High transfection efficiency was achieved with purified polyplexes at high DNA concentrations (8-15 microg/ml). At low DNA concentrations (2-4 microg/ml) gene transfer with purified particles was less efficient than with polyplexes containing free PEI both in vitro and in vivo. Mechanistic studies showed that free PEI partly blocked cellular association of DNA complexes but was essential for the following intracellular gene delivery. Adding free PEI to cells treated with purified particles with a delay of up to 4 h resulted in significantly enhanced transfection efficiency compared with non-purified particles or purified particles without free PEI.
Answer: This study presents an efficient method to remove free PEI from PEI polyplexes by SEC. Our results from transfection experiments demonstrate that free PEI substantially contributes to efficient gene expression but also mediates toxic effects in a dose-dependent manner. Purified polyplexes without free PEI have to be applied at increased concentrations to achieve high transfection levels, but exhibit a greatly improved toxicity profile.
answer:
Does purification of polyethylenimine polyplexes highlight the role of free polycations in gene transfer?

question:
Context: Current views on the control of cell development are anchored on the notion that phenotypes are defined by networks of transcriptional activity. The large amounts of information brought about by transcriptomics should allow the definition of these networks through the analysis of cell-specific transcriptional signatures. Here we test this principle by applying an analogue to comparative anatomy at the cellular level, searching for conserved transcriptional signatures, or conserved small gene-regulatory networks (GRNs) on root hairs (RH) and pollen tubes (PT), two filamentous apical growing cells that are a striking example of conservation of structure and function in plants.', 'We developed a new method for isolation of growing and mature root hair cells, analysed their transcriptome by microarray analysis, and further compared it with pollen and other single cell transcriptomics data. Principal component analysis shows a statistical relation between the datasets of RHs and PTs which is suggestive of a common transcriptional profile pattern for the apical growing cells in a plant, with overlapping profiles and clear similarities at the level of small GTPases, vesicle-mediated transport and various specific metabolic responses. Furthermore, cis-regulatory element analysis of co-regulated genes between RHs and PTs revealed conserved binding sequences that are likely required for the expression of genes comprising the apical signature. This included a significant occurrence of motifs associated to a defined transcriptional response upon anaerobiosis.
Answer: Our results suggest that maintaining apical growth mechanisms synchronized with energy yielding might require a combinatorial network of transcriptional regulation. We propose that this study should constitute the foundation for further genetic and physiological dissection of the mechanisms underlying apical growth of plant cells.
answer:
Does transcriptional profiling of Arabidopsis root hairs and pollen define an apical cell growth signature?

question:
Context: The timing of CEA for symptomatic internal carotid artery (ICA) stenosis remains a matter of controversy. Recent registry data showed a significantly increased risk, especially in the very early days after the onset of symptoms. In this study the outcome of CEA in the hyperacute phase has been investigated.', 'The outcome of CEA for symptomatic ICA stenosis between January 2004 and December 2013 has been retrospectively analyzed. Patients were divided into four timing groups: surgery within 0 and 2 days, between 3 and 7 days, 8 and 14 days, and thereafter. The post-operative 30 day stroke and death rates were assessed.', 'A total of 761 symptomatic patients (40.1% with transient ischemic attack [TIA], 21.3% with amaurosis fugax, and 38.6% with ischemic stroke) were included, with an overall peri-operative stroke and death rate of 3.3%. A stroke and death rate of 4.4% (9/206) for surgery within 0 and 2 days, 1.8% (4/219) between 3 and 7 days, 4.4% (6/136) between 8 and 14 days, and 2.5% (5/200) in the period thereafter (p=.25 for the difference between the groups) was observed. The timing of surgery did not influence the peri-operative outcome in a multivariate regression analysis (OR 0.93 [0.63-1.36], p=.71).
Answer: These data show that very urgent surgery in symptomatic patients can be performed without increased procedural risk. Given the fact that ruptured plaques with neurological symptoms carry the highest risk of a recurrent ischemic event in the first 2 days, treating patients as soon as possible to offer the highest benefit in stroke prevention is recommended.
answer:
Does very urgent carotid endarterectomy increase the procedural risk?