Conformational flexibility of RNA polymerase III during transcriptional elongation

RNA polymerase (Pol) III is responsible for the transcription of genes encoding small RNAs, including tRNA, 5S rRNA and U6 RNA. Here, we report the electron cryomicroscopy structures of yeast Pol III at 9.9 Å resolution and its elongation complex at 16.5 Å resolution. Particle sub-classification reveals prominent EM densities for the two Pol III-specific subcomplexes, C31/C82/C34 and C37/C53, that can be interpreted using homology models. While the winged-helix-containing C31/C82/C34 subcomplex initiates transcription from one side of the DNA-binding cleft, the C37/C53 subcomplex accesses the transcription bubble from the opposite side of this cleft. The transcribing Pol III enzyme structure not only shows the complete incoming DNA duplex, but also reveals the exit path of newly synthesized RNA. During transcriptional elongation, the Pol III-specific subcomplexes tightly enclose the incoming DNA duplex, which likely increases processivity and provides structural insights into the conformational switch between Pol III-mediated initiation and elongation

Verwendung der Nahinfrarotspektroskopie zur Kontrolle der Extremitätenperfusion unter venoarterieller ECMO-Therapie

Patients undergoing peripheral venoarterial extracorporeal membrane oxygenation have a high risk of lower limb ischemia. In general, regular controls are carried out based on clinical and laboratory parameters in order to quickly detect and treat complications. These controls are challenging due to states of shock, nonpulsatile flow and vasopressor therapy. As additional monitoring the use of near-infrared spectroscopy (NIRS) is described in the literature as being very successful in detecting ischemia. The present article describes the use and possible limitations of NIRS for the diagnostics of peripheral ischemia

Postoperative acute respiratory dysfunction and the influence of antibiotics after acute type A aortic dissection surgery: A retrospective analysis

Objectives Surgery for acute type A aortic dissection is associated with several perioperative complications, such as acute respiratory dysfunction (ARD). The aim of this study was to investigate perioperative risk factors involved in the development of ARD and whether antibiotic treatment has an impact. Methods 243 patients underwent surgery for acute type A aortic dissection between 2008 and 2017. The patients were retrospectively divided into the ARD and NON-ARD group. ARD was defined as PaO2/FiO2 ≤ 200 mmHg (PF ratio) within 48 hours after surgery. All patients received either narrow- or broad-spectrum antibiotics. Results After the exclusion of 42 patients, 201 patients were analyzed. The PF ratio of the ARD group was significantly lower than of the NON-ARD group within the first 7 days. ARD patients (n = 111) were significantly older (p = .031) and had a higher body mass index (BMI) (p = .017). ARD patients required longer postoperative ventilation (2493 vs. 4695 [min], p = .006) and spent more days in the intensive care unit (7.0 vs. 8.9 [days], p = .043) compared to NON-ARD. The mortality was significantly lower for ARD than for NON-ARD patients (p = .030). The incidence of pneumonia was independent of the antibiotic treatment regime (p = .391). Renal and neurological complication rate was higher in patients treated with broad-spectrum antibiotic. Conclusion ARD is the main complication (55%) that occurs approximately 24 hours after surgery for acute type A aortic dissection. The preoperative risk factors for ARD were higher age and increased BMI. Patients on broad-spectrum antibiotics did not show an improved postoperative outcome compared to patients with narrow-spectrum antibiotics

The novel CaMKII inhibitor GS-680 reduces diastolic SR Ca leak and prevents CaMKII-dependent pro-arrhythmic activity

Rationale: Ca/calmodulin-dependent protein kinase II (CaMKII) was shown to increase diastolic sarcoplasmic reticulum (SR) Ca leak, which can result in delayed afterdepolarizations and triggered arrhythmias Since increased CaMKII expression and activity has been mechanistically linked to arrhythmias in human heart failure (HF) and atrial fibrillation (AF), specific strategies aimed at CaMKII inhibition may have therapeutic potential, Objective: We tested the antiarrhythmic and inotropic effects of a novel selective and ATP-competitive CaMKII inhibitor (GS-680). Methods and results: Trabeculae were isolated from right atrial appendage biopsies of patients undergoing cardiac surgery. Premature atrial contractions (PACs) were induced by stimulation with isoproterenol (ISO, 100 nM) at increased [Ca](o) (3.5 mM). Interestingly, compared to vehicle, PACs were significantly inhibited by exposure to GS-680 (at 100 and 300 nM). GS-680 also significantly decreased early and delayed afterdepolarizations in isolated human atrial myocytes. Moreover, GS-680 (at 100 or 300 nM) significantly inhibited diastolic SR Ca leak, measured as frequency of spontaneous SR Ca release events (Ca sparks) in isolated human atrial myocytes (Fluo-4 loaded) similar to the well-established peptide CaMKII inhibitor AIP. In accordance, GS 680 significantly reduced CaMKII autophosphorylation (Western blot) but enhanced developed tension after 10 or 30 s pause of electrical stimulation (post-rest behavior). Surprisingly, we found a strong negative inotropic effect of GS-680 in atrial trabeculae at 1 Hz stimulation rate, which was not observed at 4 Hz and abolished by beta-adrenergic stimulation. In contrast, GS-680 did not impair systolic force of isolated ventricular trabeculae from explanted hearts of heart transplant recipients at 1 Hz, blunted the negative force-frequency relationship (1-3 Hz) and significantly increased the Ca transient amplitude. Conclusion: The novel ATP-competitive and selective CaMKII inhibitor GS-680 inhibits pro-arrhythmic activity in human atrium and improves contractility in failing human ventricle, which may have therapeutic implications