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.

Context: Although the echolucent plaque in carotid stenosis is associated with future ischemic stroke, the predictive value of echogenicity in small and medium size carotid plaques on vascular events has not been thoroughly examined. Thus, we prospectively tested the hypothesis that plaque echogenicity of carotid atheroma can predict the future total cardiovascular events in patients with vascular risk factors.', 'Ultrasound assessment of carotid intima-media complex thickness (IMT) and plaque echogenicity using integrated backscatter (IBS) analysis was performed in 596 patients aged 40 or more, with any history of vascular events or with at least 1 risk factor, who were enrolled between 2001 and 2006 in the Osaka Follow-up Study for Carotid Atherosclerosis, part 2 (OSACA2). We followed the incidence of total cardiovascular events including cerebrovascular events, coronary heart disease (CHD), and peripheral artery disease (PAD) for 6.4 years. We divided the patients into two groups according to the IBS index above (echorich plaques) and under (echolucent plaque) the median value, and calculated the hazard ratios (HR) of the echolucent group compared with the echogenic group in the risk of cardiovascular events.', 'Among 596 patients, carotid stenosis was found only in 87 patients. During the follow-up period, we observed 121 cardiovascular events including 63 cerebrovascular events, 45 CHD cases, and 13 PAD cases. The patients with incident cardiovascular events had larger plaque thickness and lower IBS index than those without incident vascular events. The relative risk of vascular events for echolucent versus echorich plaques was 1.45 (95% confidence interval [CI] 0.99-2.13, p = 0.058) after adjustment for risk factors and plaque thickness. In patients with plaque size above the median value (>2.1 mm), the relative risk of vascular events for echolucent plaques was 1.72 (95% CI 1.06-2.85, p = 0.029), but this association was not observed in patients with plaque size <2.0 mm.\Question: Does echogenicity of medium-to-large carotid plaques predict future vascular events?
The association between echogenicity of carotid plaque and incident vascular events is dependent on the plaque size. Echolucent medium-to-large plaques, but not small plaques, are associated with the risk of future total cardiovascular events. This finding suggests that measurement of echolucency in medium-to-large carotid plaques may improve selection of patients at high risk for total vascular events.

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.\Question: Does purification of polyethylenimine polyplexes highlight the role of free polycations in gene transfer?
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.

Context: Adults and children affected by human immunodeficiency virus type-1 (HIV-1) infection show bone demineralization. Little is known about skeletal status using a quantitative high-frequency ultrasound (QUS) technique in these patients.', 'To evaluate the bone quality and assess the role of the IGF system in the bone metabolism and skeletal status of HIV-1 perinatally infected children.', 'Serum free and total IGF-I, IGFBP-3, serum osteocalcin level, urinary deoxypyridinoline concentration, spontaneous interleukin-6 (IL-6) release and broadband ultrasound attenuation (BUA) were evaluated in 44 prepubertal children who had perinatal HIV-1 infection. The patients were divided into two groups depending on the severity of their clinical condition: group 1 (23 children with no or mild clinical symptoms, mean age 8.0 +/- 2.9 years) and group 2 (21 children with severe clinical symptoms, mean age 8.58 +/- 2.47 years). Fifty-five healthy age- and sex-matched controls were analysed for comparison.', 'Compared with group 1 and the controls, group 2 patients showed a significantly reduced BUA Z-score (P < 0.001), and significantly reduced concentrations of serum osteocalcin (P < 0.001) and urinary deoxypyridinoline (P < 0.001 and P < 0.05, respectively). Group 2 patients also showed significantly reduced serum free IGF-I (P < 0.001) and total IGF-I (P < 0.05) levels compared with the controls, but not with group 1. No statistically significant differences were found between the three groups with regard to IGFBP-3. Group 2 patients showed significantly higher spontaneous IL-6 release than group 1 patients and controls (P < 0.001). BUA Z-scores displayed a significant correlation with free IGF-I in group 2 (r = 0.96; P < 0.001), group 1 (r = 0.56; P = 0.005) and controls (r = 0.50; P < 0.001).\Question: Is changed bone status in human immunodeficiency virus type 1 ( HIV-1 ) perinatally infected children related to low serum free IGF-I?

Our study shows that only patients affected by perinatal HIV-1 infection with severe clinical manifestations present significant changes in bone quality and bone metabolism. Our data also show that impairment of skeletal status is related to reduction in serum total and free IGF-I. Children with perinatal HIV-1 infection, because of a considerable improvement in life expectancy, seem at great risk of not obtaining an optimal bone mass. A possible therapeutic approach should be considered in these children.