[Radiographic implications of procedures involving cardiac implantable electronic devices (CIEDs) - Selected aspects]. / Implikacje radiologiczne zabiegów stalej elektroterapii serca (CIED) ­ wybrane aspekty.

BACKGROUND: Some cardiac implantable electronic device (CIED) implantation procedures require the use of X-rays, which is reflected by such parameters as total fluoroscopy time (TFT) and dose-area product (DAP - defined as the absorbed dose multiplied by the area irradiated). MATERIAL AND METHODS: This retrospective study evaluated 522 CIED implantation (424 de novo and 98 device upgrade and new lead placement) procedures in 176 women and 346 men (mean age 75±11 years) over the period 2012-2015. The recorded procedure-related parameters TFT and DAP were evaluated in the subgroups specified below. The group of 424 de novo procedures included 203 pacemaker (PM) and 171 implantable cardioverter-defibrillator (ICD) implantation procedures, separately stratified by single-chamber and dual-chamber systems. Another subgroup of de novo procedures involved 50 cardiac resynchronization therapy (CRT) devices. The evaluated parameters in the group of 98 upgrade procedures were compared between 2 subgroups: CRT only and combined PM and ICD implantation procedures. RESULTS: We observed differences in TFT and DAP values between procedure types, with PM-related procedures showing the lowest, ICD - intermediate (with values for single-chamber considerably lower than those for dual-chamber systems) and CRT implantation procedures - highest X-ray exposure. Upgrades to CRT were associated with 4 times higher TFT and DAP values in comparison to those during other upgrade procedures. Cardiac resynchronization therapy de novo implantation procedures and upgrades to CRT showed similar mean values of these evaluated parameters. CONCLUSIONS: Total fluoroscopy time and DAP values correlated progressively with CIED implantation procedure complexity, with CRT-related procedures showing the highest values of both parameters. Med Pr 2017;68(3):363-374.

A Specialized Histone H1 Variant Is Required for Adaptive Responses to Complex Abiotic Stress and Related DNA Methylation in Arabidopsis.

Linker (H1) histones play critical roles in chromatin compaction in higher eukaryotes. They are also the most variable of the histones, with numerous nonallelic variants cooccurring in the same cell. Plants contain a distinct subclass of minor H1 variants that are induced by drought and abscisic acid and have been implicated in mediating adaptive responses to stress. However, how these variants facilitate adaptation remains poorly understood. Here, we show that the single Arabidopsis (Arabidopsis thaliana) stress-inducible variant H1.3 occurs in plants in two separate and most likely autonomous pools: a constitutive guard cell-specific pool and a facultative environmentally controlled pool localized in other tissues. Physiological and transcriptomic analyses of h1.3 null mutants demonstrate that H1.3 is required for both proper stomatal functioning under normal growth conditions and adaptive developmental responses to combined light and water deficiency. Using fluorescence recovery after photobleaching analysis, we show that H1.3 has superfast chromatin dynamics, and in contrast to the main Arabidopsis H1 variants H1.1 and H1.2, it has no stable bound fraction. The results of global occupancy studies demonstrate that, while H1.3 has the same overall binding properties as the main H1 variants, including predominant heterochromatin localization, it differs from them in its preferences for chromatin regions with epigenetic signatures of active and repressed transcription. We also show that H1.3 is required for a substantial part of DNA methylation associated with environmental stress, suggesting that the likely mechanism underlying H1.3 function may be the facilitation of chromatin accessibility by direct competition with the main H1 variants.