OBJECTIVES: Acute intestinal ischemia is a severe complication of abdominal aortic surgery that is difficult to diagnose early and therefore to treat adequately and timely. In this study the perioperative kinetics of d-lactate and ischemia-modified albumin (IMA) are described and the predictive value of these markers for the early diagnosis of acute intestinal ischemia is assessed. DESIGN & METHODS: This non-randomised, single-centre cohort study enrolled 50 patients with abdominal aortic aneurysm (AAA) and 30 patients with aortoiliac occlusive disease (AOID). Serum d-lactate and IMA were assessed pre-, intra-, and postoperatively at eight defined time points. RESULTS: The highest serum d-lactate was at 6 h after complete declamping of the vascular graft. The highest predictive power of d-lactate was at 3 h after complete declamping (AUC 0.857). IMA was found to be higher in the AAA group in ischemic patients 10 min after complete declamping than in the AOID group. The highest predictive values of IMA were at 1 h after aortic cross-clamping (AUC 0.758) and 3 and 6 h after complete declamping (0.745 and 0.721, respectively). Moreover, the multivariate model with both markers at 3 h after complete declamping improved the detection of intestinal ischemia (AUC 0.894). CONCLUSIONS: Serum levels of IMA and d-lactate seem to be influential predictive markers for postoperative intestinal ischemia, especially after 3 h from complete declamping of vascular reconstruction.
- MeSH
- aneurysma břišní aorty * chirurgie komplikace MeSH
- biologické markery MeSH
- ischemie diagnóza etiologie MeSH
- kohortové studie MeSH
- kyselina mléčná * MeSH
- lidé MeSH
- sérový albumin MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
Cytosine-rich DNA regions can form four-stranded structures based on hemi-protonated C.C+ pairs, called i-motifs (iMs). Using CD, UV absorption, NMR spectroscopy, and DSC calorimetry, we show that model (CnT3)3Cn (Cn) sequences adopt iM under neutral or slightly alkaline conditions for n > 3. However, the iMs are formed with long-lasting kinetics under these conditions and melt with significant hysteresis. Sequences with n > 6 melt in two or more separate steps, indicating the presence of different iM species, the proportion of which is dependent on temperature and incubation time. At ambient temperature, kinetically favored iMs of low stability are formed, most likely consisting of short C.C+ blocks. These species act as kinetic traps and prevent the assembly of thermodynamically favored, fully C.C+ paired iMs. A higher temperature is necessary to unfold the kinetic forms and enable their substitution by a slowly developing thermodynamic structure. This complicated kinetic partitioning process considerably slows down iM folding, making it much slower than the timeframes of biological reactions and, therefore, unlikely to have any biological relevance. Our data suggest kinetically driven iM species as more likely to be biologically relevant than thermodynamically most stable iM forms.
Toxic dipeptide-repeat (DPR) proteins are produced from expanded G4C2 repeats in the C9ORF72 gene, the most common genetic cause of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). Two DPR proteins, poly-PR and poly-GR, repress cellular translation but the molecular mechanism remains unknown. Here we show that poly-PR and poly-GR of ≥20 repeats inhibit the ribosome's peptidyl-transferase activity at nanomolar concentrations, comparable to specific translation inhibitors. High-resolution cryogenic electron microscopy (cryo-EM) reveals that poly-PR and poly-GR block the polypeptide tunnel of the ribosome, extending into the peptidyl-transferase center (PTC). Consistent with these findings, the macrolide erythromycin, which binds in the tunnel, competes with poly-PR and restores peptidyl-transferase activity. Our results demonstrate that strong and specific binding of poly-PR and poly-GR in the ribosomal tunnel blocks translation, revealing the structural basis of their toxicity in C9ORF72-ALS/FTD.
- MeSH
- amyotrofická laterální skleróza * genetika metabolismus MeSH
- dipeptidy metabolismus MeSH
- elektronová kryomikroskopie MeSH
- frontotemporální demence * genetika metabolismus MeSH
- lidé MeSH
- protein C9orf72 genetika metabolismus MeSH
- proteiny genetika metabolismus MeSH
- ribozomy metabolismus MeSH
- transferasy MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Research Support, N.I.H., Extramural MeSH
During translation, a conserved GTPase elongation factor-EF-G in bacteria or eEF2 in eukaryotes-translocates tRNA and mRNA through the ribosome. EF-G has been proposed to act as a flexible motor that propels tRNA and mRNA movement, as a rigid pawl that biases unidirectional translocation resulting from ribosome rearrangements, or by various combinations of motor- and pawl-like mechanisms. Using time-resolved cryo-EM, we visualized GTP-catalyzed translocation without inhibitors, capturing elusive structures of ribosome•EF-G intermediates at near-atomic resolution. Prior to translocation, EF-G binds near peptidyl-tRNA, while the rotated 30S subunit stabilizes the EF-G GTPase center. Reverse 30S rotation releases Pi and translocates peptidyl-tRNA and EF-G by ~20 Å. An additional 4-Å translocation initiates EF-G dissociation from a transient ribosome state with highly swiveled 30S head. The structures visualize how nearly rigid EF-G rectifies inherent and spontaneous ribosomal dynamics into tRNA-mRNA translocation, whereas GTP hydrolysis and Pi release drive EF-G dissociation.
- MeSH
- aminoacyl-tRNA metabolismus MeSH
- elektronová kryomikroskopie * MeSH
- elongační faktor G chemie metabolismus MeSH
- Escherichia coli chemie metabolismus MeSH
- fosfáty metabolismus MeSH
- guanosintrifosfát chemie metabolismus MeSH
- malé podjednotky ribozomu bakteriální chemie metabolismus MeSH
- messenger RNA metabolismus MeSH
- proteosyntéza MeSH
- ribozomy chemie metabolismus MeSH
- RNA transferová metabolismus MeSH
- vazba proteinů MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Research Support, N.I.H., Extramural MeSH
Viruses from the genus Enterovirus are important human pathogens. Receptor binding or exposure to acidic pH in endosomes converts enterovirus particles to an activated state that is required for genome release. However, the mechanism of enterovirus uncoating is not well understood. Here, we use cryo-electron microscopy to visualize virions of human echovirus 18 in the process of genome release. We discover that the exit of the RNA from the particle of echovirus 18 results in a loss of one, two, or three adjacent capsid-protein pentamers. The opening in the capsid, which is more than 120 Å in diameter, enables the release of the genome without the need to unwind its putative double-stranded RNA segments. We also detect capsids lacking pentamers during genome release from echovirus 30. Thus, our findings uncover a mechanism of enterovirus genome release that could become target for antiviral drugs.
- MeSH
- Cercopithecus aethiops MeSH
- dvouvláknová RNA chemie genetika MeSH
- elektronová kryomikroskopie MeSH
- enterovirus B lidský genetika ultrastruktura MeSH
- epitelové buňky ultrastruktura virologie MeSH
- genom virový * MeSH
- kapsida chemie ultrastruktura MeSH
- koncentrace vodíkových iontů MeSH
- lidé MeSH
- RNA virová chemie genetika MeSH
- simulace molekulární dynamiky MeSH
- svlékání virového obalu genetika MeSH
- virion genetika ultrastruktura MeSH
- zvířata MeSH
- Check Tag
- lidé MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
Esophageal cancer is a malignant disease with poor prognosis, increasing incidence, and ineffective treatment options. MicroRNAs are post-transcriptional regulators of gene expression involved in many biological processes including carcinogenesis. We determined miR-205 expression levels in tumor/non-tumor tissues of 45 esophageal cancer patients using qPCR and found that decreased level of miR-205 in tumor tissue correlates with poor overall survival in esophageal adenocarcinoma patients. Further, we observed significantly higher levels of miR-205 in tumor tissue of esophageal squamous cell carcinoma. Ectopic overexpression of miR-205 in adenocarcinoma cell line SK-GT-4 led to decreased cell proliferation, cell cycle arrest in G1, and decreased migration ability. Conversely, in squamous cell line KYSE-150, same effects like inhibition of proliferation, migration, and colony-forming potential and cell cycle arrest in G2 were observed after silencing of miR-205. We performed global gene expression profiling and revealed that suppressive functioning of miR-205 in adenocarcinoma could be realized through regulation of epithelial-mesenchymal transition (EMT), whereas oncogenic in squamous cell carcinoma by regulation of metalloproteinase 10. Our results suggest that miR-205 could serve as biomarker in esophageal cancer and acts as a tumor suppressor in esophageal adenocarcinoma and oncogene in esophageal squamous cell carcinoma.
- MeSH
- adenokarcinom genetika metabolismus patologie MeSH
- apoptóza genetika MeSH
- buněčný cyklus genetika MeSH
- dospělí MeSH
- epitelo-mezenchymální tranzice genetika MeSH
- kvantitativní polymerázová řetězová reakce MeSH
- lidé středního věku MeSH
- lidé MeSH
- mikro RNA fyziologie MeSH
- míra přežití MeSH
- nádorové buněčné linie MeSH
- nádory jícnu genetika metabolismus patologie MeSH
- onkogeny genetika MeSH
- pohyb buněk genetika MeSH
- proliferace buněk genetika MeSH
- regulace genové exprese u nádorů fyziologie MeSH
- senioři MeSH
- spinocelulární karcinom genetika metabolismus patologie MeSH
- stanovení celkové genové exprese MeSH
- tumor supresorové geny MeSH
- Check Tag
- dospělí MeSH
- lidé středního věku MeSH
- lidé MeSH
- mužské pohlaví MeSH
- senioři MeSH
- ženské pohlaví MeSH
- Publikační typ
- časopisecké články MeSH
