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.

Q: Context: Chromatin epigenetics participate in control of gene expression during metazoan development. DNA methylation and post-translational modifications (PTMs) of histones have been extensively characterised in cell types present in, or derived from, mouse embryos. In embryonic stem cells (ESCs) derived from blastocysts, factors involved in deposition of epigenetic marks regulate properties related to self-renewal and pluripotency. In the germ lineage, changes in histone PTMs and DNA demethylation occur during formation of the primordial germ cells (PGCs) to reset the epigenome of the future gametes. Trimethylation of histone H3 on lysine 27 (H3K27me3) by Polycomb group proteins is involved in several epigenome-remodelling steps, but it remains unclear whether these epigenetic features are conserved in non-mammalian vertebrates. To investigate this question, we compared the abundance and nuclear distribution of the main histone PTMs, 5-methylcytosine (5mC) and 5-hydroxymethylcytosine (5hmC) in chicken ESCs, PGCs and blastodermal cells (BCs) with differentiated chicken ESCs and embryonic fibroblasts. In addition, we analysed the expression of chromatin modifier genes to better understand the establishment and dynamics of chromatin epigenetic profiles.', 'The nuclear distributions of most PTMs and 5hmC in chicken stem cells were similar to what has been described for mammalian cells. However, unlike mouse pericentric heterochromatin (PCH), chicken ESC PCH contained high levels of trimethylated histone H3 on lysine 27 (H3K27me3). In differentiated chicken cells, PCH was less enriched in H3K27me3 relative to chromatin overall. In PGCs, the H3K27me3 global level was greatly reduced, whereas the H3K9me3 level was elevated. Most chromatin modifier genes known in mammals were expressed in chicken ESCs, PGCs and BCs. Genes presumably involved in de novo DNA methylation were very highly expressed. DNMT3B and HELLS/SMARCA6 were highly expressed in chicken ESCs, PGCs and BCs compared to differentiated chicken ESCs and embryonic fibroblasts, and DNMT3A was strongly expressed in ESCs, differentiated ESCs and BCs.\Question: Do chicken embryonic stem cells and primordial germ cells display different heterochromatic histone marks than their mammalian counterparts?

A: Chicken ESCs and PGCs differ from their mammalian counterparts with respect to H3K27 methylation. High enrichment of H3K27me3 at PCH is specific to pluripotent cells in chicken. Our results demonstrate that the dynamics in chromatin constitution described during mouse development is not universal to all vertebrate species.
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Q: Context: To assist in the development of preventive strategies, we studied whether the neighbourhood environment or modifiable behavioural parameters, including cardiorespiratory fitness (CRF) and physical activity (PA), are independently associated with obesity and metabolic risk markers in children.', 'We carried out a cross-sectional analysis of 502 randomly selected first and fifth grade urban and rural Swiss schoolchildren with regard to CRF, PA and the neighbourhood (rural vs urban) environment. Outcome measures included BMI, sum of four skinfold thicknesses, homeostasis model assessment of insulin resistance (HOMA-IR) and a standardised clustered metabolic risk score.', 'CRF and PA (especially total PA, but also the time spent engaged in light and in moderate and vigorous intensity PA) were inversely associated with measures of obesity, HOMA-IR and the metabolic risk score, independently of each other, and of sociodemographic and nutritional parameters, media use, sleep duration, BMI and the neighbourhood environment (all p < 0.05). Children living in a rural environment were more physically active and had higher CRF values and reduced HOMA-IR and metabolic risk scores compared with children living in an urban environment (all p < 0.05). These differences in cardiovascular risk factors persisted after adjustment for CRF, total PA and BMI.\Question: Are reduced cardiorespiratory fitness , low physical activity and an urban environment independently associated with increased cardiovascular risk in children?

A: Reduced CRF, low PA and an urban environment are independently associated with an increase in metabolic risk markers in children.
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Q: Context: Accumulation in the brain of small aggregates of amyloid beta-protein 42 (Abeta42) is the major pathogenic event of Alzheimer disease (AD). In familial early-onset AD this event is likely the result of Abeta42 overproduction; in the most common sporadic late-onset form of the disease the mechanisms of Abeta42 accumulation are unknown.', 'To address this issue the authors analyzed plasma levels of Abeta42 in 88 elderly patients with amnestic mild cognitive impairment (MCI), chosen as paradigm of preclinical sporadic AD.', 'The authors found a significant increase of Abeta42 plasma levels in women with MCI, in comparison to the affected men and 72 cognitively normal age-matched subjects. The levels were independent of variables in education, apolipoprotein E genotype, cholesterol, and creatinine plasma concentrations, as well as hemoglobin content.\Question: Are plasma levels of amyloid beta-protein 42 increased in women with mild cognitive impairment?

A:
The elevation of Abeta42 plasma levels in women with MCI may represent a biologic explanation for the sex-dependent increased incidence of late-onset AD in women identified by epidemiologic studies.
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