High resolution imaging reveals heterogeneity in chromatin states between cells that is not inherited through cell division

BACKGROUND: Genomes of eukaryotes exist as chromatin, and it is known that different chromatin states can influence gene regulation. Chromatin is not a static structure, but is known to be dynamic and vary between cells. In order to monitor the organisation of chromatin in live cells we have engineered fluorescent fusion proteins which recognize specific operator sequences to tag pairs of syntenic gene loci. The separation of these loci was then tracked in three dimensions over time using fluorescence microscopy. RESULTS: We established a work flow for measuring the distance between two fluorescently tagged, syntenic gene loci with a mean measurement error of 63 nm. In general, physical separation was observed to increase with increasing genomic separations. However, the extent to which chromatin is compressed varies for different genomic regions. No correlation was observed between compaction and the distribution of chromatin markers from genomic datasets or with contacts identified using capture based approaches. Variation in spatial separation was also observed within cells over time and between cells. Differences in the conformation of individual loci can persist for minutes in individual cells. Separation of reporter loci was found to be similar in related and unrelated daughter cell pairs. CONCLUSIONS: The directly observed physical separation of reporter loci in live cells is highly dynamic both over time and from cell to cell. However, consistent differences in separation are observed over some chromosomal regions that do not correlate with factors known to influence chromatin states. We conclude that as yet unidentified parameters influence chromatin configuration. We also find that while heterogeneity in chromatin states can be maintained for minutes between cells, it is not inherited through cell division. This may contribute to cell-to-cell transcriptional heterogeneity. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s12860-016-0111-y) contains supplementary material, which is available to authorized users

Iron Behaving Badly: Inappropriate Iron Chelation as a Major Contributor to the Aetiology of Vascular and Other Progressive Inflammatory and Degenerative Diseases

The production of peroxide and superoxide is an inevitable consequence of aerobic metabolism, and while these particular "reactive oxygen species" (ROSs) can exhibit a number of biological effects, they are not of themselves excessively reactive and thus they are not especially damaging at physiological concentrations. However, their reactions with poorly liganded iron species can lead to the catalytic production of the very reactive and dangerous hydroxyl radical, which is exceptionally damaging, and a major cause of chronic inflammation. We review the considerable and wide-ranging evidence for the involvement of this combination of (su)peroxide and poorly liganded iron in a large number of physiological and indeed pathological processes and inflammatory disorders, especially those involving the progressive degradation of cellular and organismal performance. These diseases share a great many similarities and thus might be considered to have a common cause (i.e. iron-catalysed free radical and especially hydroxyl radical generation). The studies reviewed include those focused on a series of cardiovascular, metabolic and neurological diseases, where iron can be found at the sites of plaques and lesions, as well as studies showing the significance of iron to aging and longevity. The effective chelation of iron by natural or synthetic ligands is thus of major physiological (and potentially therapeutic) importance. As systems properties, we need to recognise that physiological observables have multiple molecular causes, and studying them in isolation leads to inconsistent patterns of apparent causality when it is the simultaneous combination of multiple factors that is responsible. This explains, for instance, the decidedly mixed effects of antioxidants that have been observed, etc...Comment: 159 pages, including 9 Figs and 2184 reference

IS RESISTIN A LINK BETWEEN HIGHLY ACTIVE ANTIRETROVIRAL THERAPY AND FAT REDISTRIBUTION IN HIV-INFECTED CHILDREN?

OBJECTIVES: To assess the features of fat redistribution, detected by clinical and ultrasound (US) methods, and the presence of metabolic disorders in HIV-infected children undergoing antiretroviral therapy. To evaluate if serum levels of resistin, a hormone produced only by visceral adipose tissue, are a marker of fat redistribution in these patients. DESIGN AND METHODS: Forty-five consecutive symptomatic HIVinfected children were considered for inclusion in the study. Patients were enrolled if treated for at least 6 months with antiretroviral therapy with or without protease inhibitor (PI) and if compliant to the study protocol. Patients were evaluated for: anthropometric measures, fat redistribution by clinical and US methods, serum lipids, parameters of insulin resistance by homeostasis model assessment for insulin resistance, serum resistin levels by an enzyme-linked immunosorbent assay. RESULTS: Eighteen children fulfilled the inclusion criteria and were enrolled in the study. Twelve (66%) children had clinical and/or US evidence of fat redistribution; 9 (75%) of them were on PI therapy; only 3 of 6 children without fat redistribution were on PI therapy (p<0.05). Serum lipids and insulin resistance parameters did not differ between children with or without fat redistribution. There was a highly significant linear correlation between visceral fat detected by US and circulating resistin levels (r=0.87; p<0.0001). CONCLUSIONS: Fat redistribution occurred in most HIV-infected children undergoing PI therapy. Because serum resistin levels reflect the amount of visceral fat, they could be considered a sensitive marker of fat redistribution in HIV-infected children

Acute necrotizing encephalopathy: a relapsing case in a European adult

Acute necrotizing encephalopathy: a relapsing case in a European adult

Selection of sucrose concentration depends on the effort required to obtain it: studies using tetrabenazine, D₁, D₂, and D₃ receptor antagonists

RationaleLow doses of dopamine (DA) antagonists and accumbens DA depletions reduce food-reinforced instrumental behavior but do not impair primary food motivation, causing animals to reallocate behavior away from food-reinforced tasks with high response requirements and select less effortful alternatives. However, it is uncertain if this same pattern of effects would occur if sucrose was used as the reinforcer. Objectives These experiments studied the impact of DA depletion and antagonism on performance of an effort-related choice task using sucrose as the reinforcer, as well as sucrose consumption, preference, and taste reactivity tests. Methods The effects of DA manipulations were assessed using a task in which rats chose between lever pressing on a fixed ratio 7 schedule for 5.0 % sucrose versus freely consuming a less concentrated solution (0.3 %). Results The DA depleting agent tetrabenazine shifted effort-related choice, decreasing lever pressing for 5.0 % sucrose but increasing intake of the concurrently available 0.3 % sucrose. Tetrabenazine did not affect sucrose appetitive taste reactivity, or sucrose consumption or preference, in free consumption tests. The D1 antagonist ecopipam and the D2 antagonist haloperidol also shifted choice behavior at doses that did not alter sucrose consumption or preference. In contrast, sucrose pre-exposure reduced consumption across all conditions. D3 antagonism had no effects. Conclusions D1 and D2 receptor blockade and DA depletion reduce the tendency to work for sucrose under conditions that leave fundamental aspects of sucrose motivation (intake, preference, hedonic reactivity) intact. These findings have implications for studies employing sucrose intake or preference in animal models of depression