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.

Ex Input:
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.

Ex Output:
Does purification of polyethylenimine polyplexes highlight the role of free polycations in gene transfer?

Ex Input:
Context: Nonasthmatic eosinophilic bronchitis (EB) has emerged as a useful tool to study the structural and inflammatory mechanisms of airway hyperresponsiveness (AHR) in asthma. We have previously shown that vascular remodeling and reticular basement membrane (RBM) thickening are present in EB. However, it is not known whether other features of structural remodeling including increased airway smooth muscle (ASM) mass, matrix deposition, and glandular hyperplasia are also present in EB.', 'We sought to determine whether structural remodeling occurs in EB and is associated with AHR and airflow limitation.', 'Forty-two patients with asthma, 21 patients with EB, and 19 healthy volunteers were recruited. ASM area, RBM thickness, collagen 3 deposition, glandular area, mast cells, and granulocytes were assessed in bronchial biopsy samples.', 'Nonasthmatic eosinophilic bronchitis and asthma were associated with a significant increase in ASM mass and RBM thickness compared with healthy subjects. In contrast, we did not observe any significant differences in collagen 3 deposition in the lamina propria and ASM or the % area of glands in the lamina propria. Univariate analysis demonstrated that mast cell numbers in the ASM were the only feature of remodeling associated with AHR (beta = -0.51; P = .004). Stepwise linear regression revealed that a combination of mast cell numbers in the ASM (beta = -0.43) and disease duration (beta = -0.25; model-adjusted R(2) = 0.26; P = .027) best modeled AHR.
Answer: Mast cell localization to the ASM bundle, but not structural remodeling of the airway wall, is associated with AHR in asthma.

Ex Output:
Is airway hyperresponsiveness dissociated from airway wall structural remodeling?

Ex Input:
Context: All treatment in Crohn's disease, although palliative, aims at restoring full health. The objective of this study was to compare health-related quality of life and psychosocial conditions in patients with Crohn's proctocolitis with a general population.", "One hundred and twenty-seven patients with Crohn's proctocolitis (median age 44 years, 44.1% men) were compared with 266 controls (median age 45 years, 50.7% men). A questionnaire consisting of the Short Form-36 (SF-36), the Psychological General Well-Being Index (PGWB) and a visual analogue scale (VAS) evaluating general health as well as questions regarding psychosocial conditions was used. Disease activity was evaluated by Best's modification of the classical Crohn's Disease Activity Index.", 'Patients in remission had a health related quality of life similar to controls according to the SF-36 apart from general health where scores were lower (P < 0.01). Patients with active disease scored lower in all aspects of the SF-36 (P < 0.001 or P < 0.0001) as well as the PGWB (P < 0.0001). In a model for multiple regression including age, gender, concomitant small bowel disease, permanent stoma, previous colonic surgery, disease activity, duration, and aggressiveness, disease activity was the only variable negatively predicting all 8 domains of the SF-36 in the patient group (P < 0.001). The mean annual sick-leave for patients and controls were 33.9 and 9.5 days (P < 0.0001), respectively. Sixty-eight percent of the patients and 78.4% of the controls (P = 0.04) were married or cohabited, 67.7% and 78.0% (P = 0.04), respectively, had children.
Answer: The health related quality of life for patients with Crohn's proctocolitis in remission does not differ from the general population. The disease has, however, a negative impact on parenthood, family life and professional performance.

Ex Output:
Does health related quality of life in Crohn 's proctocolitis differ from a general population when in remission?