Influence of psoas muscle area on mortality following elective abdominal aortic aneurysm repair

The total psoas muscle area (TPMA), as a measure of sarcopenia and frailty, has been demonstrated previously to be a potential method of risk stratification in surgical patients. In this study, TPMA did not appear to be associated with mortality and morbidity in patients undergoing elective abdominal aortic aneurysm intervention. Therefore TPMA may not be a suitable method of risk stratification for routine clinical practice.

Not predictive

Background

The effect of sarcopenia based on the total psoas muscle area (TPMA) on CT is inconclusive in patients undergoing abdominal aortic aneurysm (AAA) intervention. The aim of this prospective cohort study was to evaluate morphometric sarcopenia as a method of risk stratification in patients undergoing elective AAA intervention.

Methods

TPMA was measured on preintervention CT images of patients undergoing elective endovascular aneurysm repair (EVAR) or open aneurysm repair. Mortality was assessed in relation to preintervention TPMA using Cox regression analysis, with calculation of hazard ratios at 30 days, 1 year and 4 years. Postintervention morbidity was evaluated in terms of postintervention care, duration of hospital stay and 30‐day readmission. Changes in TPMA on surveillance EVAR imaging were also evaluated.

Results

In total, 382 patient images acquired between March 2008 and December 2016 were analysed. There were no significant intraobserver and interobserver differences in measurements of TPMA. Preintervention TPMA failed to predict morbidity and mortality at all time points. The mean(s.d.) interval between preintervention and surveillance imaging was 361·3(111·2) days. A significant reduction in TPMA was observed in men on surveillance imaging after EVAR (mean reduction 0·63(1·43) cm² per m²; P < 0·001). However, this was not associated with mortality (adjusted hazard ratio 1·00, 95 per cent c.i. 0·99 to 1·01; P = 0·935).

Conclusion

TPMA is not a suitable risk stratification tool for patients undergoing effective intervention for AAA.

http://bit.ly/2TrsbZ5

A cholesterol analogue induces an oligomeric reorganization of VDAC

The oligomeric organization of the voltage-dependent anion-selective channel (VDAC) and its interactions with hexokinase play integral roles in mitochondrially mediated apoptotic signaling. Various small to large assemblies of VDAC are observed in mitochondrial outer membranes but they do not predominate in detergent solubilized VDAC samples. In this study, a cholesterol analogue, cholesteryl-hemisuccinate (CHS), was shown induce the formation of detergent soluble VDAC multimers. The various oligomeric states of VDAC induced by the addition of CHS were deciphered through an integrated biophysics approach using microscale thermophoresis, analytical ultracentrifugation and size exclusion chromatography-small angle X-ray scattering.

http://bit.ly/2G2Yr1T

Nanomechanics of diaminopurine-substituted DNA

2,6-diaminopurine (DAP) is a nucleobase analog of adenine. When incorporated into double-stranded DNA, it forms three hydrogen bonds with thymine. Rare in nature, DAP-substitution alters the physical characteristics of a DNA molecule without sacrificing sequence specificity. Here we show that in addition to stabilizing double-strand hybridization, DAP-substitution also changes the mechanical and conformational properties of dsDNA. Thermal melting experiments reveal that DAP-substitution raises melting temperatures without diminishing sequence-dependent effects.

http://bit.ly/2G0z7cM

Solvatochromic modeling of Laurdan for multiple polarity analysis of dihydro-sphingomyelin bilayer

The hydration properties of the interface between lipid bilayers and bulk water are important for determining membrane characteristics. Here, the emission properties of a solvent-sensitive fluorescence probe, 6-lauroyl-2-dimethylamino naphthalene (Laurdan), were evaluated in lipid bilayer systems composed of the sphingolipids, D-erythro-N-palmitoyl-sphingosylphosphorylcholine (PSM) and D-erythro-N-palmitoyl-dihydrosphingomyelin (DHPSM). The glycerophospholipids, 1-palmitoyl-2-palmitoyl-sn-glycero-3-phosphocholine (DPPC) and 1-oleoyl-2-oleoyl-sn-glycero-3-phosphocholine (DOPC), were used as controls.

http://bit.ly/2GggelA

Synaptobrevin-2 C-terminal Flexible Region Regulates the Discharge of Catecholamine Through the Fusion Pore

The discharge of catecholamine molecules through the fusion pore is a regulated process, and understanding the role of the SNARE proteins during this process has been of great interest. These proteins facilitate the formation of the fusion pore, but it has been unclear whether their transmembrane domains regulate the flux of discharged catecholamines through direct interactions. Here, it is shown, using mutagenesis studies, that the transmembrane domain of the vesicular SNARE protein, synaptobrevin-2, does not directly interact with the discharged catecholamine, however it is suggested that synaptobrevin-2 transmembrane domain indirectly modulates the flux of catecholamine by interacting with the vesicle membrane.

http://bit.ly/2GkB4QP

The role of early bioelectric signals in the regeneration of planarian anterior/posterior polarity

Axial patterning during planarian regeneration relies on a transcriptional circuit that confers distinct positional information on the two ends of an amputated fragment. The earliest known elements of this system begin demarcating differences between anterior and posterior wounds by 6 hours post-amputation. However, it is still unknown what upstream events break the axial symmetry, allowing a mutual repressor system to establish invariant, distinct biochemical states at the anterior and posterior ends.

http://bit.ly/2G2uWwT

CcdB at pH 4 forms a partially unfolded state with a dry core

pH is an important factor that affects the protein structure, stability and activity. Here we probe the nature of the low pH structural form of the homodimeric CcdB protein (Controller of Cell Death B). Characterization of CcdB protein at pH 4 and 300K using circular dichroism spectroscopy, ANS binding and Trp solvation studies suggests that it forms a partially unfolded state with a dry core at equilibrium under these conditions. CcdB remains dimeric at pH 4 as shown by multiple techniques, such as SEC-MALS, analytical ultra-centrifugation and electron paramagnetic resonance.

http://bit.ly/2GclTJ4