Quadruplex DNA: sequence, topology and structure.

G-quadruplexes are higher-order DNA and RNA structures formed from G-rich sequences that are built around tetrads of hydrogen-bonded guanine bases. Potential quadruplex sequences have been identified in G-rich eukaryotic telomeres, and more recently in non-telomeric genomic DNA, e.g. in nuclease-hypersensitive promoter regions. The natural role and biological validation of these structures is starting to be explored, and there is particular interest in them as targets for therapeutic intervention. This survey focuses on the folding and structural features on quadruplexes formed from telomeric and non-telomeric DNA sequences, and examines fundamental aspects of topology and the emerging relationships with sequence. Emphasis is placed on information from the high-resolution methods of X-ray crystallography and NMR, and their scope and current limitations are discussed. Such information, together with biological insights, will be important for the discovery of drugs targeting quadruplexes from particular genes

Characterization of a K+-induced conformational switch in a human telomeric DNA oligonucleotide using 2-aminopurine fluorescence

Human telomeric DNA consists of tandem repeats of the DNA sequence d(GGGTTA). Oligodeoxynucletotide telomere models such as d[A(GGGTTA)(3)GGG] (Tel22) fold in a cation-dependent manner into quadruplex structures consisting of stacked G-quartets linked by d(TTA) loops. NMR has shown that in Na(+) solutions Tel22 forms a ‘basket’ topology of four antiparallel strands; in contrast, Tel22 in K(+) solutions consists of a mixture of unknown topologies. Our previous studies on the mechanism of folding of Tel22 and similar telomere analogs utilized changes in UV absorption between 270 and 325 nm that report primarily on G-quartet formation and stacking showed that quadruplex formation occurs within milliseconds upon mixing with an appropriate cation. In the current study, we assessed the dynamics and equilibria of folding of specific loops by using Tel22 derivatives in which the dA residues were serially substituted with the fluorescent reporter base, 2-aminopurine (2-AP). Tel22 folding induced by Na(+) or K(+) assessed by changes in 2-AP fluorescence consists of at least three kinetic steps with time constants spanning a range of ms to several hundred seconds. Na(+)-dependent equilibrium titrations of Tel22 folding could be approximated as a cooperative two-state process. In contrast, K(+)-dependent folding curves were biphasic, revealing that different conformational ensembles are present in 1 mM and 30 mM K(+). This conclusion was confirmed by (1)H NMR. Molecular dynamics simulations revealed a K(+) binding pocket in Tel22 located near dA1 that is specific for the so-called hybrid-1 conformation in which strand 1 is in a parallel arrangement. The possible presence of this topologically specific binding site suggests that K(+) may play an allosteric role in regulating telomere conformation and function by modulating quadruplex tertiary structure

Temporal changes in the epidemiology, management, and outcome from acute respiratory distress syndrome in European intensive care units: a comparison of two large cohorts

Background: Mortality rates for patients with ARDS remain high. We assessed temporal changes in the epidemiology and management of ARDS patients requiring invasive mechanical ventilation in European ICUs. We also investigated the association between ventilatory settings and outcome in these patients. Methods: This was a post hoc analysis of two cohorts of adult ICU patients admitted between May 1–15, 2002 (SOAP study, n = 3147), and May 8–18, 2012 (ICON audit, n = 4601 admitted to ICUs in the same 24 countries as the SOAP study). ARDS was defined retrospectively using the Berlin definitions. Values of tidal volume, PEEP, plateau pressure, and FiO2 corresponding to the most abnormal value of arterial PO2 were recorded prospectively every 24 h. In both studies, patients were followed for outcome until death, hospital discharge or for 60 days. Results: The frequency of ARDS requiring mechanical ventilation during the ICU stay was similar in SOAP and ICON (327[10.4%] vs. 494[10.7%], p = 0.793). The diagnosis of ARDS was established at a median of 3 (IQ: 1–7) days after admission in SOAP and 2 (1–6) days in ICON. Within 24 h of diagnosis, ARDS was mild in 244 (29.7%), moderate in 388 (47.3%), and severe in 189 (23.0%) patients. In patients with ARDS, tidal volumes were lower in the later (ICON) than in the earlier (SOAP) cohort. Plateau and driving pressures were also lower in ICON than in SOAP. ICU (134[41.1%] vs 179[36.9%]) and hospital (151[46.2%] vs 212[44.4%]) mortality rates in patients with ARDS were similar in SOAP and ICON. High plateau pressure (> 29 cmH2O) and driving pressure (> 14 cmH2O) on the first day of mechanical ventilation but not tidal volume (> 8 ml/kg predicted body weight [PBW]) were independently associated with a higher risk of in-hospital death. Conclusion: The frequency of and outcome from ARDS remained relatively stable between 2002 and 2012. Plateau pressure > 29 cmH2O and driving pressure > 14 cmH2O on the first day of mechanical ventilation but not tidal volume > 8 ml/kg PBW were independently associated with a higher risk of death. These data highlight the continued burden of ARDS and provide hypothesis-generating data for the design of future studies

Factors influencing arrival of patients with acute myocardial infarction at emergency departments: Implications for community nursing interventions

xanthos t., pantazopoulos i., vlachos i., stroumpoulis k., barouxis d., kitsou v., marathias k., karabinis a. & papadimitriou l. (2010) Factors influencing arrival of patients with acute myocardial infarction at emergency departments: implications for community nursing interventions. Journal of Advanced Nursing 66(7), 1469-1477. Title.: Factors influencing arrival of patients with acute myocardial infarction at emergency departments: implications for community nursing interventions. Aim.: This paper identifies the characteristics of Greek patients with acute myocardinal infraction who have long prehospital delays and identifies the factors that are specifically associated with these delays. Background.: The time between the first appearance of symptoms until the hospitalization of the patient with myocardial infarction correlates statistically significantly with in-hospital and long-term mortality. Methods.: The study took place in two Greek coronary care units from 1 June 2007 to 31 July 2008. From 232 consecutive patients with myocardial infarction, 160 were enrolled. Data were collected by a trained hospital staff nurse, who interviewed all patients within 48 hours of hospital admission. Results.: Smokers arrived statistically significantly sooner at the hospital than non-smokers [smokers' prehospital time delay: 78·9 (sd = 3·2) minutes vs. non-smokers' prehospital time delay: 98·2 (sd = 4·1) minutes, Mann-Whitney U-test, Z = -2·5, P < 0·05]. Patients with hyperlipidaemia arrived with a mean delay of 13 minutes less than normolipidaemic patients. Those with inferior ST segment elevation myocardial infarction exhibited statistically significantly shorter delay times than those with anterior or lateral (inferior vs. anterior, P = 0·003, inferior vs. lateral, P = 0·024, anova with Bonferroni-Holm post hoc test, F = 7·5, P = 0·001). Conclusion.: Community nurses should educate all patients about myocardial infarction, not only those at high risk but also those without known risk factors for ischaemic heart disease. © 2010 The Authors. Journal compilation © 2010 Blackwell Publishing Ltd

Nurses are more efficient than doctors in teaching basic life support and automated external defibrillator in nurses

Background: Cardiac arrest (CA) is a leading cause of death worldwide. The European Resuscitation Council (ERC) has developed basic life support/automated external defibrillation (BLS/AED) courses for uniform training in out-of-hospital CA. Objective: The present study compares the resuscitation skills of two groups of nursing staff, one taught by newly trained ERC nurse-instructors and the other by newly trained doctor-instructors. Method: Eighteen doctors and 18 nurses were asked to teach a total of 108 nurses in a (BLS/AED) course. One month after its completion, all 108 nurses were asked to be re-evaluated, with the use of the objective structured clinical examination. Conclusions: No statistical significant difference between the two groups was noted in the written test, in contrast with data collected from the practice skills check-list. Nurses in group A could easily identify the patient in cardiac arrest but had difficulties concerning chest compressions and handling the AED. Nurses in group B were more focused during the performances, used AED more accurately and continued cardiopulmonary resuscitation with no delays. Nurses prove to be more efficient in training nurses. © 2008 Elsevier Ltd. All rights reserved