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We recently reported that when low doses of ionizing radiation induce low numbers of DNA double-strand breaks (DSBs) in G 2 -phase cells, about 50 % of them are repaired by homologous recombination (HR) and the remaining by classical non-homologous end-joining (c-NHEJ). However, with increasing DSB-load, the contribution of HR drops to undetectable (at ∼10 Gy) as c-NHEJ dominates. It remains unknown whether the approximately equal shunting of DSBs between HR and c-NHEJ at low radiation doses and the predominant shunting to c-NHEJ at high doses, applies to every DSB, or whether the individual characteristics of each DSB generate processing preferences. When G 2 -phase cells are irradiated, only about 10 % of the induced DSBs break the chromatids. This breakage allows analysis of the processing of this specific subset of DSBs using cytogenetic methods. Notably, at low radiation doses, these DSBs are almost exclusively processed by HR, suggesting that chromatin characteristics awaiting characterization underpin chromatid breakage and determine the preferential engagement of HR. Strikingly, we also discovered that with increasing radiation dose, a pathway switch to c-NHEJ occurs in the processing of this subset of DSBs. Here, we confirm and substantially extend our initial observations using additional methodologies. Wild-type cells, as well as HR and c-NHEJ mutants, are exposed to a broad spectrum of radiation doses and their response analyzed specifically in G 2 phase. Our results further consolidate the observation that at doses <2 Gy, HR is the main option in the processing of the subset of DSBs generating chromatid breaks and that a pathway switch at doses between 4-6 Gy allows the progressive engagement of c-NHEJ. PARP1 inhibition, irrespective of radiation dose, leaves chromatid break repair unaffected suggesting that the contribution of alternative end-joining is undetectable under these experimental conditions., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Mitral annular disjunction is a structural abnormality of the mitral annulus fibrosus, which has been described by pathologists to be associated with mitral leaflet prolapse. Mitral annular disjunction is a common finding in patients with myxomatous mitral valve diseases. The prevalence of mitral annular disjunction should be checked routinely during presurgical imaging. Otherwise, mitral annular disjunction itself might be an arrhythmogenic entity, irrespective of the presence of mitral valve prolapse (MVP). Therefore, we should check echocardiography keeping in mind mitral annular disjunction. Further prospective studies are needed to address whether a causative mechanistic link exists between mitral annular disjunction and arrhythmic MVP., Competing Interests: Disclosure All authors have nothing to disclose., (Copyright © 2021 Elsevier Inc. All rights reserved.)

Four repair pathways process DNA double-strand breaks (DSBs). Among these pathways the homologous recombination repair (HRR) subpathway of gene conversion (GC) affords error-free processing, but functions only in S- and G 2 -phases of the cell cycle. Classical non-homologous end-joining (c-NHEJ) operates throughout the cell cycle, but causes small deletions and translocations. Similar deficiencies in exaggerated form, combined with reduced efficiency, are associated with alternative end-joining (alt-EJ). Finally, single-strand annealing (SSA) causes large deletions and possibly translocations. Thus, processing of a DSB by any pathway, except GC, poses significant risks to the genome, making the mechanisms navigating pathway-engagement critical to genome stability. Logically, the cell ought to attempt engagement of the pathway ensuring preservation of the genome, while accommodating necessities generated by the types of DSBs induced. Thereby, inception of DNA end-resection will be key determinant for GC, SSA and alt-EJ engagement. We reported that during G 2 -phase, where all pathways are active, GC engages in the processing of almost 50 % of DSBs, at low DSB-loads in the genome, and that this contribution rapidly drops to nearly zero with increasing DSB-loads. At the transition between these two extremes, SSA and alt-EJ compensate, but at extremely high DSB-loads resection-dependent pathways are suppressed and c-NHEJ remains mainly active. We inquired whether in this processing framework all DSBs have similar fates. Here, we analyze in G 2 -phase the processing of a subset of DSBs defined by their ability to break chromosomes. Our results reveal an absolute requirement for GC in the processing of chromatid breaks at doses in the range of 1 Gy. Defects in c-NHEJ delay significantly the inception of processing by GC, but leave processing kinetics unchanged. These results delineate the essential role of GC in chromatid break repair before mitosis and classify DSBs that underpin this breakage as the exclusive substrate of GC., Competing Interests: Declaration of Competing Interest Authors declare no conflict of interest., (Copyright © 2020 Elsevier B.V. All rights reserved.)

The classical G 2 -assay is widely used to assess cell-radiosensitivity and cancer phenotype: Cells are exposed to low doses of ionizing-radiation (IR) and collected for cytogenetic- analysis ˜1.5 h later. In this way, chromosome-damage is measured in cells irradiated in G 2 -phase, without retrieving information regarding kinetics of chromosome-break-repair. Modification of the assay to include analysis at multiple time-points after IR, has enabled kinetic-analysis of chromatid-break-repair and assessment of damage in a larger proportion of G 2 -phase cells. This modification, however, increases the probability that at later time points not only cells irradiated in G 2 -phase, but also cells irradiated in S-phase will reach metaphase. However, the response of cells irradiated in G 2 -phase can be mechanistically different from that of cells irradiated in S-phase. Therefore, indiscriminate analysis may confound the interpretation of experiments designed to elucidate mechanisms of chromosome-break-repair and the contributions of the different DSB-repair-pathways in this response. Here we report an EdU based modification of the assay that enables S- and G 2 -phase specific analysis of chromatid break repair. Our results show that the majority of metaphases captured during the first 2 h after IR originate from cells irradiated in G 2 -phase (EdU - metaphases) in both rodent and human cells. Metaphases originating from cells irradiated in S-phase (EdU + metaphases) start appearing at 2 h and 4 h after IR in rodent and human cells, respectively. The kinetics of chromatid-break-repair are similar in cells irradiated in G 2 - and S-phase of the cell-cycle, both in rodent and human cells. The protocol is applicable to classical-cytogenetic experiments and allows the cell-cycle specific analysis of chromosomal-aberrations. Finally, the protocol can be applied to the kinetic analysis of chromosome-breaks in prematurely-condensed-chromosomes of G 2 -phase cells. In summary, the developed protocol provides means to enhance the analysis of IR-induced-cytogenetic-damage by providing information on the cell-cycle phase where DNA damage is inflicted., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Objectives: Visual assessment of the ejection fraction (EF) is often used in clinical practice, but is subjective and requires training and experience. The auto EF method has been newly developed for automated detection of the left ventricular (LV) endocardial border throughout the cardiac cycle. The clinical feasibility was assessed of the auto EF method for measuring LV volumes and EF in patients. Manually traced EF measured by the biplane modified Simpson's rule was used as the reference standard., Methods: The study population consisted of 30 consecutive patients with normal sinus rhythm. All patients underwent two-dimensional echocardiography. The auto EF method incorporated pattern and shape recognition to automatically locate the LV, track the endocardium, and calculate EF from routine digital images. LV end-diastolic and end-systolic volumes and EF measured by the auto EF method were compared those by the manually traced method. LVEF by the Auto EF method was also compared with visual EF determined by nonattending physicians., Results: Auto EF was more reproducible than visual EF by the expert reader. LVEF by the auto EF method had excellent correlation and close limits of agreement with manually traced EF compared with visual EF(4-chamber view: y = 1.10 x - 4.28, r = 0.94, bias = 1.6%, 2-chamber view: y = 0.88 x + 7.25, r = 0.90, bias = 0.4%). LV volumes by the auto EF method underestimated those by manually traced EF (end-diastolic volume by 4-chamber view: y = 0.72 x + 8.92, r = 0.93, bias = - 16.7 ml, end-systolic volume by 4-chamber view: y = 0.82 x - 0.97, r = 0.98, bias = - 8.5 ml, end-diastolic volume by 2-chamber view: y = 0.73 x + 12.4, r = 0.82, bias = - 12.3 ml, end-systolic volume by 2-chamber view: y = 0.65 x + 6.94, r = 0.90, bias = - 6.8 ml)., Conclusions: The auto EF method is a clinically useful tool for the measurement of LV volumes and EF.

Objectives: This study evaluated the accuracy of the directional color power Doppler (DCPD) and continuous wave Doppler (CWD) methods incorporated in the new hand-carried SonoSite 180PLUS ultrasound device., Methods: The hand-held ultrasound system with 2.5 MHz transducer and SONOS 5500 was used as a standard ultrasound system with a 2 to 4 MHz wideband transducer. The experimental study used a Doppler wire phantom to evaluate the influence of target wire speed and angle of transducer on DCPD imaging. The clinical study included 48 consecutive patients. DCPD assessment of valvular regurgitation measured the distances of DCPD signals of mitral, aortic and tricuspid valve regurgitation using the apical four-chamber view for comparison with standard echocardiography. CWD assessment measured the peak velocities of the aortic flow and tricuspid valve regurgitant flow for comparison with standard echocardiography., Results: In the experimental study, DCPD signals were not influenced by target wire speed changes and transducer incident angles. In the clinical study, agreements for mitral, aortic and tricuspid regurgitation between the two methods were 89.6%, 81.8% and 78.7%, respectively. The distances of DCPD valve regurgitant signals by the hand-carried ultrasound device showed good correlation (mitral regurgitation: y = 0.84x + 0.55; r = 0.93, aortic regurgitation: y = 0.95x + 0.27; r = 0.94, tricuspid regurgitation: y = 0.86x + 0.61; r = 0.90) with those by standard echocardiography. Evaluation of CWD velocity measurements showed good agreement for the lower flow velocities (< 2.0 m/sec). However, underestimation occurred for the high flow velocities (> 2.0 m/sec) compared with those by standard echocardiography (aortic flow: y = 0.80x + 0.11; r = 0.95, tricuspid regurgitation: y = 1.00x - 0.23; r = 0.90)., Conclusions: The new hand-carried ultrasound device (SonoSite 180PLUS equipped with DCPD and CWD) is clinically useful for evaluating valvular regurgitations and flow velocities. Further studies are needed to determine the mechanism of the underestimation of high flow velocities by CWD.

Objectives: Hand-held ultrasound devices are becoming available for clinical examination, but the accuracy and precision of such devices are unclear. This study compared the accuracy of a hand-held echo device to a standard echo system., Methods: Twenty-two patients were examined with the OptiGo (Phillips Medial Systems) hand-held ultrasound system with a 2.5 MHz transducer and SONOS 5500 (Phillips Medial Systems) standard ultrasound system with a 2 to 4 MHz wideband transducer. Patients with cardiac arrhythmia and tachycardia were excluded. Image quality, chamber size (left ventricle, left atrium), global and regional left ventricular function, valve morphology and severity of valve regurgitation were assessed., Results: There was good agreement between the two imaging devices for image quality (77.3%), left ventricular ejection fraction (90.5%), regional wall motion score (> 90%), valve morphology (> 90%), severity of valve regurgitation (> 81.0%) and there was good correlation and agreement for left ventricular and left atrial size., Conclusions: Although the OptiGo has limitations, the hand-held examination appropriately estimates global and regional left ventricular function, valve morphology, valve regurgitation and chamber size.

Serum and dialysate boron levels in 17 patients with long term hemodialysis (HD) were determined by inductively coupled plasma emission spectrometry (ICPES). Serum boron level was compared with the value of age matched 467 healthy controls and the relationship between serum and dialysate boron level was analyzed. The results showed that serum boron level was significantly higher at the beginning of HD, and lower at the completion of HD in comparison with controls. Although the dialysate was contaminated with trace boron, HD resulted in an excessive decrease of serum boron, rather than boron exposure from the dialysate. Boron hemodialyzability was almost proportional to the gradient of the boron level at the beginning of HD and it could be controlled by the adjustment of the gradient. In conclusion, the serum boron level was very much disturbed in long term HD patients. If boron excess in serum at the beginning of HD, or deficiency at the completion of HD may contribute to the complications of HD patients, fine adjustment and close surveillance of the gradient should be taken into account.