Exercise Testing and Stress Imaging in Valvular Heart Disease

The role of exercise testing and stress imaging in the management of patients with valvular heart disease (VHD) is reviewed in this article. The American College of Cardiology/American Heart Association and the European Society of Cardiology/European Association of Cardiothoracic Surgery have recently put emphasis on the role of exercise testing to clarify symptom status and the use of stress imaging to assess the dynamic component of valvular abnormalities and unmask subclinical myocardial dysfunction that could be missed at rest. Recent studies have demonstrated the incremental prognostic value of exercise echocardiography for asymptomatic patients with severe aortic stenosis, moderate-severe mitral stenosis, and severe primary mitral regurgitation. In patients with low-flow, low-gradient aortic stenosis, dobutamine stress echocardiography is recommended to differentiate true severe from pseudosevere aortic stenosis. Data on the prognostic value of stress echocardiography in aortic regurgitation and functional mitral regurgitation are less robust. Data are sparse on the use of stress imaging in right-sided VHD, however recent studies using stress cardiovascular magnetic resonance imaging offer some prognostic information. Although the strongest recommendations for surgical treatment continue to be based on symptom status and resting left ventricular repercussions, stress imaging can be useful to optimize risk stratification and timing of surgery in VHD. Randomized clinical trials are required to confirm that clinical decision-making based on stress imaging can lead to improved outcomes.     

Domain within the helicase subunit Mcm4 integrates multiple kinase signals to control DNA replication initiation and fork progression

Eukaryotic DNA synthesis initiates from multiple replication origins and progresses through bidirectional replication forks to ensure efficient duplication of the genome. Temporal control of initiation from origins and regulation of replication fork functions are important aspects for maintaining genome stability. Multiple kinase-signaling pathways are involved in these processes. The Dbf4-dependent Cdc7 kinase (DDK), cyclin-dependent kinase (CDK), and Mec1, the yeast Ataxia telangiectasia mutated/Ataxia telangiectasia mutated Rad3-related checkpoint regulator, all target the structurally disordered N-terminal serine/threonine-rich domain (NSD) of mini-chromosome maintenance subunit 4 (Mcm4), a subunit of the mini-chromosome maintenance (MCM) replicative helicase complex. Using whole-genome replication profile analysis and single-molecule DNA fiber analysis, we show that under replication stress the temporal pattern of origin activation and DNA replication fork progression are altered in cells with mutations within two separate segments of the Mcm4 NSD. The proximal segment of the NSD residing next to the DDK-docking domain mediates repression of late-origin firing by checkpoint signals because in its absence late origins become active despite an elevated DNA damage-checkpoint response. In contrast, the distal segment of the NSD at the N terminus plays no role in the temporal pattern of origin firing but has a strong influence on replication fork progression and on checkpoint signaling. Both fork progression and checkpoint response are regulated by the phosphorylation of the canonical CDK sites at the distal NSD. Together, our data suggest that the eukaryotic MCM helicase contains an intrinsic regulatory domain that integrates multiple signals to coordinate origin activation and replication fork progression under stress conditions.Eukaryotic DNA replication initiates from multiple replication origins within each chromosome to duplicate the large genome efficiently. To ensure DNA synthesis occurs once and only once across the genome, cells adopt a two-step process to activate replication origins during two separate stages of the cell-division cycle. The first step is licensing of replication origins, which occurs only when cyclin-dependent kinase (CDK) activity is low. In Saccharomyces cerevisiae, origins of DNA replication are licensed in G1 by the formation of a prereplicative complex (pre-RC). The process begins with the origin recognition complex binding to replication origins and recruiting the licensing factor Cdc6, which facilitates loading of the Cdt1-bound minichromosome maintenance (MCM) complex composed of Mcm2–Mcm7 (Mcm2–7). The hexameric Mcm2–7 is the core of the replicative helicase that unwinds DNA during replication. Within the pre-RC Mcm2–7 is loaded as an inactive double hexamer. The next step, activation of licensed origins (origin firing), occurs throughout the S phase and requires the continuous presence of two kinases, the S phase CDKs and the Dbf4-dependent Cdc7 kinase (DDK). CDK phosphorylates Sld2 and Sld3 to allow their binding to Dpb11 (1, 2), facilitating recruitment of Cdc45 and GINS (composed of protein subunits Sld5, Psf1, Psf2 and Psf3; Go, Ichi, Nii, and San stand for five, one, two, and three in Japanese, respectively) to Mcm2–7 to create an active helicase. DDK phosphorylates Mcm2–7 and blocks an intrinsic initiation inhibitory activity residing in the N terminus of the Mcm4 subunit (3). The concerted action of these S-phase kinases transforms the inactive Mcm2–7 double hexamer into the active helicase complex composed of Cdc45, Mcm2-7, and GINS (the CMG complex) (4–6). Upon initiation, DNA polymerases and other components of the replication machinery are recruited to form replisomes and establish replication forks, where DNA synthesis ensues.Kinase-signaling pathways target various components of the replication machinery. Both CDK and DDK target replication proteins in addition to their essential targets described above. Furthermore, Ataxia telangiectasia mutated/Ataxia telangiectasia mutated Rad3-related (ATM/ATR) signaling targets components of the CMG helicase complex under replication stress (7–10). In the yeast S. cerevisiae, DNA damage activates the checkpoint kinase Rad53, which phosphorylates both Sld3 and Dbf4 to inhibit late origin firing (11, 12). The yeast ATM/ATR homolog Mec1 also targets Mcm4 (13). The stress-activated protein kinase Hog1 targets an auxiliary replisome component Mrc1 to regulate both origin firing and fork progression (14). Although we now have a better understanding of the essential functions of protein kinases in controlling the initiation of replication, we do not completely understand how the separate kinase signaling pathways are coordinated to regulate both initiation and replication fork progression.The structurally disordered N-terminal serine/threonine-rich domain (NSD) of Mcm4 is a target of multiple kinases, including DDK, CDK, and Mec1 (3, 13, 15, 16). Within this region we have identified two functionally distinct domains that exert different functions and are regulated by different kinase systems even though they overlap extensively in primary amino acid sequences. The segment of the Mcm4 NSD proximal to the DDK-docking domain (DDD) (15), and hence termed “proximal NSD,” blocks initiation until it is phosphorylated by DDK. In contrast, the distal segment of the NSD at the N terminus, away from the DDD, is targeted by additional kinases and contributes positively to promote S-phase progression. In this study we present a comprehensive analysis of the pattern of origin activation, replication fork progression, and the checkpoint response in cells under replication stress caused by the inhibition of ribonucleotide reductase (RNR). We show that the distal and proximal NSD segments contribute differently to origin activation and DNA replication fork progression. Furthermore, they exert opposing effects on checkpoint signaling under replication stress. All these effects are regulated by phosphorylation. We suggest that the Mcm4 NSD, a regulatory domain intrinsic to the replicative helicase, mediates the control of multiple aspects of DNA replication. Our data reveal a sophisticated mechanism to fine-tune S-phase progression in response to changing environments.     

Epidemiology,clinical picture and long-term outcomes of FIP1L1-PDGFRA-positive myeloid neoplasm with eosinophilia: Data from 151 patients

FIP1L1-PDGFRA-positive myeloid neoplasm with eosinophilia (F/P+ MN-eo) is a rare disease: robust epidemiological data are lacking and reported issues are scarce, of low sample-size and limited follow-up. Imatinib mesylate (IM) is highly efficient but no predictive factor of relapse after discontinuation has yet been identified. One hundred and fifty-one patients with F/P+ MN-eo (143 males; mean age at diagnosis 49 years; mean annual incidence: 0.18 case per million population) were included in this retrospective nationwide study involving all French laboratories who perform the search of F/P fusion gene (study period: 2003-2019). The main organs involved included the spleen (44%), skin (32%), lungs (30%), heart (19%) and central nervous system (9%). Serum vitamin B12 and tryptase levels were elevated in 74/79 (94%) and 45/57 (79%) patients, respectively, and none of the 31 patients initially treated with corticosteroids achieved complete hematologic remission. All 148 (98%) IM-treated patients achieved complete hematologic and molecular (when tested, n = 84) responses. Forty-six patients eventually discontinued IM, among whom 20 (57%) relapsed. In multivariate analysis, time to IM initiation (continuous HR: 1,01 [0.99-1,03]; P = .05) and duration of IM treatment (continuous HR: 0,97 [0,95-0,99]; P = .004) were independent factors of relapse after discontinuation of IM. After a mean follow-up of 80 (56) months, the 1, 5- and 10-year overall survival rates in IM-treated patients were 99%, 95% and 84% respectively. In F/P+ MN-eo, prompt initiation of IM and longer treatment durations may prevent relapses after discontinuation of IM.     

A heavy metal baseline score predicts outcome in acute myeloid leukemia

Despite abundant epidemiological data linking metals to leukemia and other cancers, baseline values of toxic and essential metals in patients with leukemia and the clinical impact of these metals remain unknown. Thus, we sought to quantify metal values in untreated patients with acute myeloid leukemia (AML) and controls and determine the impact of metal values on AML patients' survival. Serum samples from patients with untreated AML and controls at Hospices Civils de Lyon were analyzed and compared for trace metals and copper isotopic abundance ratios with inductively coupled plasma mass spectrometry. Survival analysis was performed as a function of metal values, and a multi-metal score was developed for patients with AML. Serum samples were collected from 67 patients with untreated AML and 94 controls. Most patients had intermediate-risk cytogenetics (63.1%) without FLT3 internal tandem duplication mutations (75.6%) or NPM1 mutations (68.1%). Most metal values differed significantly between AML and control groups. Patients with lower magnesium and higher cadmium values had the worst survival rates, with only 36% surviving at 6 months (P = .001). The adverse prognostic effect of this combination was maintained on multivariate analysis. Based on this, we developed a novel metal score, which accounts for multiple relative abnormalities in the values of five toxic and five essential metals. Patients with a higher metal score had significantly worse survival, which was maintained on multivariate analysis (P = .03). This baseline metal scoring system was also prognostic when we applied it to a separate population of front-line AML patients.     

A chasing dead-end case report: a fatal lead intoxication following an attempted homicide

Forensic Toxicology - In developed countries, lead intoxication is decreasing in adults as sources of contamination were considerably reduced. Hence, cases of lead encephalopathy have become...     

18F-FDG PET/CT in bone sarcoidosis: an observational study

Clinical Rheumatology - Bone sarcoidosis is usually rare. Imaging procedures such as fluorine-18 fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) can reveal bone...     

Fetuin-A and thyroxin binding globulin predict rituximab response in rheumatoid arthritis patients with insufficient response to anti-TNFα

Clinical Rheumatology - Rheumatoid arthritis (RA) is a debilitating disease, but patient management and treatment have been revolutionized since the advent of bDMARDs. However, about one third of...