Serum Cardiac Troponin-I is Superior to Troponin-T as a Marker for Left Ventricular Dysfunction in Clinically Stable Patients with End-Stage Renal Disease

Background

Serum troponin assays, widely used to detect acute cardiac ischemia, might be useful biomarkers to detect chronic cardiovascular disease (CVD). Cardiac-specific troponin-I (cTnI) and troponin-T (cTnT) generally detect myocardial necrosis equally well. In dialysis patients however, serum cTnT levels are often elevated, unlike cTnI levels. The present study aims to elucidate the associations of cTnI and cTnT with CVD in clinically stable dialysis patients.

Methods

Troponin levels were measured using 5^th generation hs-cTnT assays (Roche) and STAT hs-cTnI assays (Abbott) in a cohort of dialysis patients. Serum troponin levels were divided into tertiles with the lowest tertile as a reference value. Serum troponins were associated with indicators of CVD such as left ventricular mass index (LVMI), left ventricular ejection fraction (LVEF) and the presence of coronary artery disease (CAD). Associations were explored using regression analysis.

Results

We included 154 consecutive patients, 68±7 years old, 77% male, 70% hemodialysis. Median serum cTnT was 51ng/L (exceeding the 99^th percentile of the healthy population in 98%) and median serum cTnI was 13ng/L (elevated in 20%). A high cTnI (T3) was significantly associated with a higher LVMI (Beta 31.60; p=0.001) and LVEF (Beta -4.78; p=0.005) after adjusting for confounders whereas a high serum cTnT was not. CAD was significantly associated with a high cTnT (OR 4.70 p=0.02) but not with a high cTnI. Unlike cTnI, cTnT was associated with residual renal function (Beta:-0.09; p=0.006).

Conclusion

In the present cohort, serum cTnI levels showed a stronger association with LVMI and LVEF than cTnT. However, cTnT was significantly associated with CAD and residual renal function, unlike cTnI. Therefore, cTnI seems to be superior to cTnT as a marker of left ventricular dysfunction in asymptomatic dialysis patients, while cTnT might be better suited to detect CAD in these patients.     

Protein interactions between surface annexin A2 and S100A10 mediate adhesion of breast cancer cells to microvascular endothelial cells

Annexin A2 (AnxA2) and S100A10 are known to form a molecular complex. Using fluorescence-based binding assays, we show that both proteins are localised on the cell surface, in a molecular form that allows mutual interaction. We hypothesized that binding between these proteins could facilitate cell–cell interactions. For cells that express surface S100A10 and surface annexin A2, cell–cell interactions can be blocked by competing with the interaction between these proteins. Thus an annexin A2-S100A10 molecular bridge participates in cell–cell interactions, revealing a hitherto unexplored function of this protein interaction.     

Structural characterization of the cell wall D-glucans isolated from the mycelium of Botryosphaeria rhodina MAMB-05

Three D-glucans were isolated from the mycelium of the fungus Botryosphaeria rhodina MAMB-05 by sequential extraction with hot-water and hot aqueous KOH (2% w/v) followed by ethanol precipitation. Following their purification by gel permeation chromatography on Sepharose CL-4B, the structural characteristics of the D-glucans were determined by FT-IR and 13C NMR spectroscopy and, after methylation, by GC-MS. The hot-water extract produced a fraction designated Q1A that was a beta-(1-->6)-D-glucan with the following structure: [Formula: see text] The alkaline extract, when subjected to repeated freeze-thawing, yielded two fractions: K1P (insoluble) that comprised a beta-(1-->3)-D-glucan with beta-D-glucose branches at C-6 with the structure: [Formula: see text] and K1SA (soluble) consisting of a backbone chain of alpha-(1-->4)-linked D-glucopyranosyl residues substituted at O-6 with alpha-D-glucopyranosyl residues: [Formula: see text]     

Fluorescent human RAD51 reveals multiple nucleation sites and filament segments tightly associated along a single DNA molecule

The DNA strand-exchange reactions defining homologous recombination involve transient, nonuniform allosteric interactions between recombinase proteins and their DNA substrates. To study these mechanistic aspects of homologous recombination, we produced functional fluorescent human RAD51 recombinase and visualized recombinase interactions with single DNA molecules in both static and dynamic conditions. We observe that RAD51 nucleates filament formation at multiple sites on double-stranded DNA. This avid nucleation results in multiple RAD51 filament segments along a DNA molecule. Analysis of fluorescent filament patch size and filament kinks from scanning force microscopy (SFM) images indicate nucleation occurs minimally once every 500 bp. Filament segments did not rearrange along DNA, indicating tight association of the ATP-bound protein. The kinetics of filament disassembly was defined by activating ATP hydrolysis and following individual filaments in real time.     

Single-molecule studies of nucleic acid motors

Nucleic acid motors comprise a variety of structurally, mechanistically and functionally very different enzymes. These motor proteins have in common the ability to directionally move DNA or RNA, or to move along DNA or RNA using a chemical energy source such as ATP. Recently, it became possible to study the action of a single motor on single DNA or RNA molecules in real time; this has provided unprecedented insight into the behavior and mechanism of these motors. As a result, the past few years have witnessed an enormous increase in such single-molecule studies of a variety of different motor systems. Particular highlights have included the investigation of the sequence-dependent behavior and helical tracking of motors, and the attainment of the ultimate (i.e. single base pair) resolution, which enables the detection of individual single base motor steps.     

Conservation by trans-border cooperation: population genetic structure and diversity of geoffroy’s bat (Myotis emarginatus) at its north-western european range edge

Biodiversity and Conservation - In the European Union, all bat species are strictly protected and member states must ensure their conservation. However, if populations are genetically structured,...     

G-protein coupled receptor solubilization and purification for biophysical analysis and functional studies,in the total absence of detergent

G-protein coupled receptors (GPCRs) constitute the largest class of membrane proteins and are a major drug target. A serious obstacle to studying GPCR structure/function characteristics is the requirement to extract the receptors from their native environment in the plasma membrane, coupled with the inherent instability of GPCRs in the detergents required for their solubilization. In the present study, we report the first solubilization and purification of a functional GPCR [human adenosine A_2A receptor (A_2AR)], in the total absence of detergent at any stage, by exploiting spontaneous encapsulation by styrene maleic acid (SMA) co-polymer direct from the membrane into a nanoscale SMA lipid particle (SMALP). Furthermore, the A_2AR–SMALP, generated from yeast (Pichia pastoris) or mammalian cells, exhibited increased thermostability (∼5°C) compared with detergent [DDM (n-dodecyl-β-D-maltopyranoside)]-solubilized A_2AR controls. The A_2AR–SMALP was also stable when stored for prolonged periods at 4°C and was resistant to multiple freeze-thaw cycles, in marked contrast with the detergent-solubilized receptor. These properties establish the potential for using GPCR–SMALP in receptor-based drug discovery assays. Moreover, in contrast with nanodiscs stabilized by scaffold proteins, the non-proteinaceous nature of the SMA polymer allowed unobscured biophysical characterization of the embedded receptor. Consequently, CD spectroscopy was used to relate changes in secondary structure to loss of ligand binding ([³H]ZM241385) capability. SMALP-solubilization of GPCRs, retaining the annular lipid environment, will enable a wide range of therapeutic targets to be prepared in native-like state to aid drug discovery and understanding of GPCR molecular mechanisms.     

Lack of evidence of a beneficial effect of azathioprine in dogs treated with prednisolone for idiopathic immune-mediated hemolytic anemia: a retrospective cohort study

Background  

Azathioprine is used as an immunosuppressant in canine immune-mediated hemolytic anemia (IMHA), but this potentially toxic and carcinogenic drug has not been proven to be beneficial. The aim of this study was to determine the difference in outcome and survival of dogs with idiopathic IMHA treated with a protocol that included azathioprine and prednisolone versus a protocol that included prednisolone alone.     

Structural analysis of hyperperiodic DNA from Caenorhabditis elegans

Several bioinformatics studies have identified an unexpected but remarkably prevalent ~10 bp periodicity of AA/TT dinucleotides (hyperperiodicity) in certain regions of the Caenorhabditis elegans genome. Although the relevant C.elegans DNA segments share certain sequence characteristics with bent DNAs from other sources (e.g. trypanosome mitochondria), the nematode sequences exhibit a much more extensive and defined hyperperiodicity. Given the presence of hyperperiodic structures in a number of critical C.elegans genes, the physical characteristics of hyperperiodic DNA are of considerable interest. In this work, we demonstrate that several hyperperiodic DNA segments from C.elegans exhibit structural anomalies using high-resolution atomic force microscopy (AFM) and gel electrophoresis. Our quantitative analysis of AFM images reveals that hyperperiodic DNA adopts a significantly smaller mean square end-to-end distance, hence a more compact coil structure, compared with non-periodic DNA of similar length. While molecules remain capable of adopting both bent and straight (rod-like) configurations, indicating that their flexibility is still retained, examination of the local curvatures along the DNA contour length reveals that the decreased mean square end-to-end distance can be attributed to the presence of long-scale intrinsic bending in hyperperiodic DNA. Such bending is not detected in non-periodic DNA. Similar studies of shorter, nucleosome-length DNAs that survived micrococcal nuclease digestion show that sequence hyperperiodicity in short segments can likewise induce strong intrinsic bending. It appears, therefore, that regions of the C.elegans genome display a significant correlation between DNA sequence and unusual mechanical properties.