Neurohumoral mechanisms of the rat heart adaptation to overload

The present study confirms involvement of the sympathicoadrenal system in adaptation of heart to overload. Besides, at formation of chronic heart failure (CHF) there have been revealed a rise of the histamine and serotonin levels in blood plasma and myocardium as well as glucocorticoid hyperactivation.     

Functional Profiling Reveals Critical Role for miRNA in Differentiation of Human Mesenchymal Stem Cells

Background

Mesenchymal stem (MS) cells are excellent candidates for cell-based therapeutic strategies to regenerate injured tissue. Although human MS cells can be isolated from bone marrow and directed to differentiate by means of an osteogenic pathway, the regulation of cell-fate determination is not well understood. Recent reports identify critical roles for microRNAs (miRNAs), regulators of gene expression either by inhibiting the translation or by stimulating the degradation of target mRNAs.

Methodology/Principal Findings

In this study, we employed a library of miRNA inhibitors to evaluate the role of miRNAs in early osteogenic differentiation of human MS cells. We discovered that miR-148b, -27a and -489 are essential for the regulation of osteogenesis: miR-27a and miR-489 down-regulate while miR-148b up-regulates differentiation. Modulation of these miRNAs induced osteogenesis in the absence of other external differentiation cues and restored osteogenic potential in high passage number human MS cells.

Conclusions/Significance

Overall, we have demonstrated the utility of the functional profiling strategy for unraveling complex miRNA pathways. Our findings indicate that miRNAs regulate early osteogenic differentiation in human MS cells: miR-148b, -27a, and -489 were found to play a critical role in osteogenesis.     

Elucidation of the substrate binding site of Siah ubiquitin ligase

The Siah family of RING proteins function as ubiquitin ligase components, contributing to the degradation of multiple targets involved in cell growth, differentiation, angiogenesis, oncogenesis, and inflammation. Previously, a binding motif (degron) was recognized in many of the Siah degradation targets, suggesting that Siah itself may facilitate substrate recognition. We report the crystal structure of the Siah in complex with a peptide containing the degron motif. Binding is within a groove formed in part by the zinc fingers and the first two beta strands of the TRAF-C domain of Siah. We show that residues in the degron, previously described to facilitate binding to Siah, interact with the protein. Mutagenesis of Siah at sites of interaction also abrogates both in vitro peptide binding and destabilization of a known Siah target.     

Two immunologically distinct types of protofilaments can be identified in Natrialba magadii flagella

A rabbit antiserum to the 15-kDa acetylcholinesterase toxin neutralised the lethal effect of the 15-kDa toxin of Aeromonas hydrophila when injected into trout. However, immunisation of fish with the 15-kDa toxoid failed to induce an antibody response, and a higher molecular mass form of this toxin was purified from the extracellular products with the aim of inducing an immune response in fish. The optimal conditions for production of extracellular products by A. hydrophila strain B32 were studied to increase the concentration of this protoxin. The extracellular products were fractionated by molecular exclusion chromatography to yield a purified protoxin with an estimated molecular mass of 45 kDa by SDS-PAGE and which gave a positive reaction in Western blotting with the rabbit anti-15-kDa toxin serum. Since the 45-kDa protoxin showed lower specific acetylcholinesterase activity than the active 15-kDa toxin, the behaviour of the active site was studied using specific inhibitors. This 45-kDa protoxin was 13.3-fold less toxic than the 15-kDa toxin and induced antibody production in fish.     

Haloarcula marismortui archaellin genes as ecoparalogs

The genome of haloarchaeon Haloarcula marismortui contains two archaellin genes—flaA2 and flaB. Earlier we isolated and characterized two H. marismortui strains in that archaella consisting of FlaA2 archaellin (with a minor FlaB fraction) or of FlaB only. Both the FlaA2 and FlaB strains were motile and produced functional helical archaella. Thus, it may seem that the FlaA2 archaellin is redundant. In this study we investigated the biological roles of archaellin redundancy and demonstrated that FlaA2 archaellin is better adapted to more severe conditions of high temperature/low salinity, while FlaB has an advantage with increasing salinity. We used the thermodynamic data and bioinformatics sequence analysis to demonstrate that archaella formed by FlaA2 are more stable than those formed by FlaB. Our combined data indicate that the monomer FlaA2 archaellin is more flexible and leads to more compact and stable formation of filamentous structures. The difference in response to environmental stress indicates that FlaA2 and FlaB replace each other under different environmental conditions and can be considered as ecoparalogs.     

Calcium-Activated Potassium Current Modulates Ventricular Repolarization in Chronic Heart Failure

The role of I_KCa in cardiac repolarization remains controversial and varies across species. The relevance of the current as a therapeutic target is therefore undefined. We examined the cellular electrophysiologic effects of I_KCa blockade in controls, chronic heart failure (HF) and HF with sustained atrial fibrillation. We used perforated patch action potential recordings to maintain intrinsic calcium cycling. The I_KCa blocker (apamin 100 nM) was used to examine the role of the current in atrial and ventricular myocytes. A canine tachypacing induced model of HF (1 and 4 months, n = 5 per group) was used, and compared to a group of 4 month HF with 6 weeks of superimposed atrial fibrillation (n = 7). A group of age-matched canine controls were used (n = 8). Human atrial and ventricular myocytes were isolated from explanted end-stage failing hearts which were obtained from transplant recipients, and studied in parallel. Atrial myocyte action potentials were unchanged by I_KCa blockade in all of the groups studied. I_KCa blockade did not affect ventricular myocyte repolarization in controls. HF caused prolongation of ventricular myocyte action potential repolarization. I_KCa blockade caused further prolongation of ventricular repolarization in HF and also caused repolarization instability and early afterdepolarizations. SK2 and SK3 expression in the atria and SK3 in the ventricle were increased in canine heart failure. We conclude that during HF, I_KCa blockade in ventricular myocytes results in cellular arrhythmias. Furthermore, our data suggest an important role for I_KCa in the maintenance of ventricular repolarization stability during chronic heart failure. Our findings suggest that novel antiarrhythmic therapies should have safety and efficacy evaluated in both atria and ventricles.     

Variations of Dynamic Contrast-Enhanced Magnetic Resonance Imaging in Evaluation of Breast Cancer Therapy Response: A Multicenter Data Analysis Challenge

Pharmacokinetic analysis of dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) time-course data allows estimation of quantitative parameters such as K^trans (rate constant for plasma/interstitium contrast agent transfer), v_e (extravascular extracellular volume fraction), and v_p (plasma volume fraction). A plethora of factors in DCE-MRI data acquisition and analysis can affect accuracy and precision of these parameters and, consequently, the utility of quantitative DCE-MRI for assessing therapy response. In this multicenter data analysis challenge, DCE-MRI data acquired at one center from 10 patients with breast cancer before and after the first cycle of neoadjuvant chemotherapy were shared and processed with 12 software tools based on the Tofts model (TM), extended TM, and Shutter-Speed model. Inputs of tumor region of interest definition, pre-contrast T₁, and arterial input function were controlled to focus on the variations in parameter value and response prediction capability caused by differences in models and associated algorithms. Considerable parameter variations were observed with the within-subject coefficient of variation (wCV) values for K^trans and v_p being as high as 0.59 and 0.82, respectively. Parameter agreement improved when only algorithms based on the same model were compared, e.g., the K^trans intraclass correlation coefficient increased to as high as 0.84. Agreement in parameter percentage change was much better than that in absolute parameter value, e.g., the pairwise concordance correlation coefficient improved from 0.047 (for K^trans) to 0.92 (for K^trans percentage change) in comparing two TM algorithms. Nearly all algorithms provided good to excellent (univariate logistic regression c-statistic value ranging from 0.8 to 1.0) early prediction of therapy response using the metrics of mean tumor K^trans and k_ep (= K^trans/v_e, intravasation rate constant) after the first therapy cycle and the corresponding percentage changes. The results suggest that the interalgorithm parameter variations are largely systematic, which are not likely to significantly affect the utility of DCE-MRI for assessment of therapy response.