Chromatin-remodeling complexes can translocate nucleosomes along the DNA in an ATP-coupled reaction. This process is an important regulator of all DNA-dependent processes because it determines whether certain DNA sequences are found in regions between nucleosomes with increased accessibility for other factors or wrapped around the histone octamer complex. In a comparison of seven different chromatin-remodeling machines (ACF, ISWI, Snf2H, Chd1, Mi-2, Brg1, and NURF), it is demonstrated that these complexes can read out DNA sequence features to establish specific nucleosome-positioning patterns. For one of the remodelers, ACF, we identified a 40-bp DNA sequence element that directs nucleosome positioning. Furthermore, we show that nucleosome positioning by the remodelers ACF and Chd1 is determined by a reduced affinity to the end product of the translocation reaction. The results suggest that the linkage of differential remodeling activities with the intrinsic binding preferences of nucleosomes can result in establishing distinct chromatin structures that depend on the DNA sequence and define the DNA accessibility for other protein factors.
The plain radiographic features of gout are well known; however, the sensitivity
of plain radiographs alone for the detection of signs of gout is poor in acute
disease. Radiographic abnormalities do not manifest until late in the disease
process, after significant joint and soft tissue damage has already occurred.
The advent of dual-energy computed tomography (DECT) has enabled the
non-invasive diagnosis and quantification of gout by accurately confirming the
presence and extent of urate crystals in joints and soft tissues, without the
need for painful and often unreliable soft tissue biopsy or joint aspiration.
Specific ultrasound findings have been identified and may also be used to aid
diagnosis. Both ultrasound and magnetic resonance imaging (MRI) may be used for
the measurement of disease extent, monitoring of disease activity or treatment
response, although MRI findings are nonspecific. In this article we summarize
the imaging findings and diagnostic utility of plain radiographs, ultrasound,
DECT, MRI and nuclear medicine studies in the assessment as well as the
implications and utility these tools have for measuring disease burden and
therapeutic response.
Varicocele embolisation is successful with a low complications rate. Neck and groin access are equally successful with no significant difference in screening time.
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