instruction:
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.
question:
Context: Symptomatic patients with severe aortic stenosis (AS) demonstrate abnormal left ventricular (LV) mechanics. The aim of this study was to compare mechanics in asymptomatic and symptomatic patients with severe AS using two-dimensional myocardial strain imaging.', 'One hundred fifty-four patients with severe AS (aortic valve area 1.0 cm(2)) referred to a heart valve clinic from 2004 to 2011 were studied. Thirty patients were asymptomatic, with normal LV ejection fractions ( 55%), without other significant valvular disease or wall motion abnormalities. Thirty-two symptomatic patients who underwent early aortic valve replacement, with similar age, gender, LV ejection fraction, and aortic valve area, were selected for comparison. Both groups were also compared with 32 healthy subjects with similar age and gender distributions and normal echocardiographic results who served as controls. LV longitudinal and circumferential strain and rotation were measured using speckle-tracking software applied to archived echocardiographic studies. Conventional echocardiographic and myocardial mechanical parameters were compared among the study subgroups.', 'Patients with asymptomatic severe AS demonstrated smaller reductions in longitudinal strain, higher (supernormal) apical circumferential strain (-38 6% vs -35 4%, P < .05), and extreme (supernormal) apical rotation (12.2 4.9 vs 2.9 1.7, P < .0005) compared with symptomatic patients. Apical rotation < 6 was the single significant predictor of symptoms in logistic regression analysis of clinical, echocardiographic, and mechanical parameters. Twelve asymptomatic patients underwent eventual aortic valve replacement and showed decreases in strain and apical rotation compared with baseline values.\Question: Are symptoms in severe aortic stenosis associated with decreased compensatory circumferential myocardial mechanics?
answer:
Longitudinal strain was uniformly low in patients with severe AS and lower in those with symptoms. Compensatory circumferential myocardial mechanics (increased apical circumferential strain and rotation) were absent in symptomatic patients. Thus, myocardial mechanics may help in the follow-up of patients with severe AS and timing of valve surgery.

question:
Context: HBV covalently closed circular DNA (cccDNA), the replicative intermediate responsible for persistent HBV infection of hepatocytes, is the template for transcription of all viral mRNAs. Nuclear cccDNA accumulates as a stable episome organized into minichromosomes by histone and nonhistone proteins. In this study we investigated, by a newly developed sensitive and specific assay, the relationship between viral replication and HBV chromatin assembly, transcription, and interaction with viral and cellular regulatory proteins.', 'To achieve this aim we coupled a quantitative chromatin immunoprecipitation (ChIP) technique to an established method that allows the amplification of virion-encapsidated HBV genomes after transfection of linear HBV DNA into human hepatoma HuH7 cells. The cccDNA-ChIP technique was also applied to study HBV minichromosome transcriptional regulation in liver tissue from HBV-infected patients.', 'The use of anti-acetyl-H4/-H3 specific antibodies to immunoprecipitate transcriptionally active chromatin revealed that HBV replication is regulated by the acetylation status of the cccDNA-bound H3/H4 histones. Class I histone deacetylases inhibitors induced an evident increase of both cccDNA-bound acetylated H4 and HBV replication. Finally, histones hypoacetylation and histone deacetylase 1 recruitment onto the cccDNA in liver tissue correlated with low HBV viremia in hepatitis B patients.\Question: Is hepatitis B virus replication regulated by the acetylation status of hepatitis B virus cccDNA-bound H3 and H4 histones?
answer:
We developed a ChIP-based assay to analyze, in vitro and ex vivo, the transcriptional regulation of HBV cccDNA minichromosome. Our results provide new insights on the regulation of HBV replication and identify the enzymatic activities that modulate the acetylation of cccDNA-bound histones as new therapeutic targets for anti-HBV drugs.

question:
Context: To test the relationships among particular motives for smoking cessation, stage of readiness to quit (preparation or contemplation), and sociodemographic characteristics.', 'A cross-sectional study to examine attitudes toward and use of health promotion at the worksite, using a self-administered questionnaire.', 'Two German metal companies.', 'Of 1641 responding employees (response rate 65% in company A and 44% in company B), 360 smokers who intended to quit immediately (n = 105) or in the near future (n = 255) were analyzed.', "The questionnaire comprised of sociodemographic characteristics, smoking behavior, smoking history, readiness to quit smoking, motives to quit, such as coworkers' complaints and health-related or financial concerns. Chi-squared tests and multiple logistic regression analyses were performed.", "Health-related reasons (94%) predominated financial (27%) or image-related (14%) reasons for smoking cessation. Participants in the cessation preparation group were more likely to report an awareness of being addicted (79.6% vs. 58.2%; p < .001) and the negative public image (22.5% vs. 11.6%; p < .01) as reasons for quitting compared with those in the contemplation group. In multivariable regression models, the motives for smoking cessation, including reduced performance, family's and coworkers' complaints, pregnancy/children, and negative public image, but not health-related and financial concerns, differed significantly by gender, age, marital status, education, and occupational status.\Question: Are motives for smoking cessation associated with stage of readiness to quit smoking and sociodemographics among German industrial employees?
answer:
Motives for smoking cessation vary according to the individual's level of readiness to quit and sociodemographic background.