Augmentation index assessed by applanation tonometry is elevated in Marfan Syndrome

<p>Abstract</p> <p>Background</p> <p>To examine whether augmentation index (AIx) is increased in Marfan syndrome (MFS) and associated with increased aortic root size, and whether a peripheral-to-central generalised transfer function (GTF) can be applied usefully in MFS.</p> <p>Methods</p> <p>10 MFS patients and 10 healthy controls (matched for sex, age and height) were studied before and after 400 μg sub-lingual GTN. Arterial waveforms were recorded using applanation tonometry. AIx and pulse pressure (PP) were determined for the radial and carotid arteries. Pulse wave velocity (PWV) was measured between carotid and femoral arteries. GTFs were generated to examine the relationship between radial and carotid waveforms.</p> <p>Results</p> <p>AIx was greater in MFS compared to controls at radial (mean -31.4 (SD 14.3)% v -50.2(15.6)%, p = 0.003) and carotid (-7.6(11.2)% v -23.7(12.7)%, p = 0.004) sites. Baseline PP at all measurement sites, and PWV, did not differ between subject groups. Multivariate analysis demonstrated that PWV and carotid AIx were positively correlated with aortic root size (p < 0.001 and p = 0.012 respectively), independent of the presence of MFS. PP was not associated with aortic root size. GTN caused similar decreases in AIx in both controls and patients. Significant differences were found in GTFs between MFS and control subjects, which changed following GTN administration. However, when an independent GTF was used to derive carotid waves from radial waves, no differences were found in the degree of error between MFS and controls.</p> <p>Conclusion</p> <p>AIx is sensitive to the vascular abnormalities present in MFS, and may have a role as an adjunct to measurement of central PP and PWV. Differences between MFS and controls in the nature of the peripheral-to-central GTF are present, although have little effect on the pulse contour.</p

Sequence Effect of Self-Assembling Peptides on the Complexation and In Vitro Delivery of the Hydrophobic Anticancer Drug Ellipticine

A special class of self-assembling peptides has been found to be capable of stabilizing the hydrophobic anticancer agent ellipticine in aqueous solution. Here we study the effect of peptide sequence on the complex formation and its anticancer activity in vitro. Three peptides, EAK16-II, EAK16-IV and EFK16-II, were selected to have either a different charge distribution (EAK16-II vs. EAK16-IV) or a varying hydrophobicity (EAK16-II vs. EFK16-II). Results on their complexation with ellipticine revealed that EAK16-II and EAK16-IV were able to stabilize protonated ellipticine or ellipticine microcrystals depending on the peptide concentration; EFK16-II could stabilize neutral ellipticine molecules and ellipticine microcrystals. These different molecular states of ellipticine were expected to affect ellipticine delivery. The anticancer activity of these complexes was tested against two cancer cell lines: A549 and MCF-7, and related to the cell viability. The viability results showed that the complexes with protonated ellipticine were effective in eradicating both cancer cells (viability <0.05), but their dilutions in water were not stable, leading to a fast decrease in their toxicity. In contrast, the complexes formulated with EFK16-II were relatively stable upon dilution, but their original toxicity was relatively low compared to that with protonated ellipticine. Overall, the charge distribution of the peptides seemed not to affect the complex formation and its therapeutic efficacy in vitro; however, the increase in hydrophobicity of the peptides significantly altered the state of stabilized ellipticine and increased the stability of the complexes. This work provides essential information for peptide sequence design in the development of self-assembling peptide-based delivery of hydrophobic anticancer drugs

Nanomechanical properties of α-synuclein amyloid fibrils: a comparative study by nanoindentation, harmonic force microscopy, and Peakforce QNM

We report on the use of three different atomic force spectroscopy modalities to determine the nanomechanical properties of amyloid fibrils of the human α-synuclein protein. α-Synuclein forms fibrillar nanostructures of approximately 10 nm diameter and lengths ranging from 100 nm to several microns, which have been associated with Parkinson's disease. Atomic force microscopy (AFM) has been used to image the morphology of these protein fibrils deposited on a flat surface. For nanomechanical measurements, we used single-point nanoindentation, in which the AFM tip as the indenter is moved vertically to the fibril surface and back while the force is being recorded. We also used two recently developed AFM surface property mapping techniques: Harmonic force microscopy (HarmoniX) and Peakforce QNM. These modalities allow extraction of mechanical parameters of the surface with a lateral resolution and speed comparable to tapping-mode AFM imaging. Based on this phenomenological study, the elastic moduli of the α-synuclein fibrils determined using these three different modalities are within the range 1.3-2.1 GPa. We discuss the relative merits of these three methods for the determination of the elastic properties of protein fibrils, particularly considering the differences and difficulties of each method

Injectable Materials for the Treatment of Myocardial Infarction and Heart Failure: The Promise of Decellularized Matrices

Cardiovascular disease continues to be the leading cause of death, suggesting that new therapies are needed to treat the progression of heart failure post-myocardial infarction. As cardiac tissue has a limited ability to regenerate itself, experimental biomaterial therapies have focused on the replacement of necrotic cardiomyocytes and repair of the damaged extracellular matrix. While acellular and cellular cardiac patches are applied surgically to the epicardial surface of the heart, injectable materials offer the prospective advantage of minimally invasive delivery directly into the myocardium to either replace the damaged extracellular matrix or to act as a scaffold for cell delivery. Cardiac-specific decellularized matrices offer the further advantage of being biomimetic of the native biochemical and structural matrix composition, as well as the potential to be autologous therapies. This review will focus on the requirements of an ideal scaffold for catheter-based delivery as well as highlight the promise of decellularized matrices as injectable materials for cardiac repair

Plasmid-based transient human stromal cell-derived factor-1 gene transfer improves cardiac function in chronic heart failure

We previously demonstrated that transient stromal cell-derived factor-1 alpha (SDF-1) improved cardiac function when delivered via cell therapy in ischemic cardiomyopathy at a time remote from acute myocardial infarction (MI) rats. We hypothesized that non-viral gene transfer of naked plasmid DNA-expressing hSDF-1 could similarly improve cardiac function. To optimize plasmid delivery, we tested SDF-1 and luciferase plasmids driven by the cytomegalovirus (CMV) promoter with (pCMVe) or without (pCMV) translational enhancers or α myosin heavy chain (pMHC) promoter in a rodent model of heart failure. In vivo expression of pCMVe was 10-fold greater than pCMV and pMHC expression and continued over 30 days. We directly injected rat hearts with SDF-1 plasmid 1 month after MI and assessed heart function. At 4 weeks after plasmid injection, we observed a 35.97 and 32.65% decline in fractional shortening (FS) in control (saline) animals and pMHC-hSDF1 animals, respectively, which was sustained to 8 weeks. In contrast, we observed a significant 24.97% increase in animals injected with the pCMVe-hSDF1 vector. Immunohistochemistry of cardiac tissue revealed a significant increase in vessel density in the hSDF-1-treated animals compared with control animals. Increasing SDF-1 expression promoted angiogenesis and improved cardiac function in rats with ischemic heart failure along with evidence of scar remodeling with a trend toward decreased myocardial fibrosis. These data demonstrate that stand-alone non-viral hSDF-1 gene transfer is a strategy for improving cardiac function in ischemic cardiomyopathy

Dose dense 1 week on/1 week off temozolomide in recurrent glioma: a retrospective study

Alternative temozolomide regimens have been proposed to overcome O6-methylguanine-DNA methyltransferase mediated resistance. We investigated the efficacy and tolerability of 1 week on/1 week off temozolomide (ddTMZ) regimen in a cohort of patients treated with ddTMZ between 2005 and 2011 for the progression of a glioblastoma during or after chemo-radiation with temozolomide or a recurrence of another type of glioma after radiotherapy and at least one line of chemotherapy. Patients received ddTMZ at 100–150 mg/m2/d (days 1–7 and 15–21 in cycles of 28-days). All patients had a contrast enhancing lesion on MRI and the response was assessed by MRI using the RANO criteria; complete and partial responses were considered objective responses. Fifty-three patients were included. The median number of cycles of ddTMZ was 4 (range 1–12). Eight patients discontinued chemotherapy because of toxicity. Two of 24 patients with a progressive glioblastoma had an objective response; progression free survival at 6 months (PFS-6) in glioblastoma was 29%. Three of the 16 patients with a recurrent WHO grade 2 or 3 astrocytoma or oligodendroglioma or oligo-astrocytoma without combined 1p and 19q loss had an objective response and PFS-6 in these patients was 38%. Four out of the 12 evaluable patients with a recurrent WHO grade 2 or 3 oligodendroglioma or oligo-astrocytoma with combined 1p and 19q loss had an objective response; PFS-6 in these patients was 62%. This study indicates that ddTMZ is safe and effective in recurrent glioma, despite previous temozolomide and/or nitrosourea chemotherapy. Our data do not suggest superior efficacy of this schedule as compared to the standard day 1–5 every 4 weeks schedule

The mechanism of impact of summative assessment on medical students’ learning

It has become axiomatic that assessment impacts powerfully on student learning, but there is a surprising dearth of research on how. This study explored the mechanism of impact of summative assessment on the process of learning of theory in higher education. Individual, in-depth interviews were conducted with medical students and analyzed qualitatively. The impact of assessment on learning was mediated through various determinants of action. Respondents’ learning behaviour was influenced by: appraising the impact of assessment; appraising their learning response; their perceptions of agency; and contextual factors. This study adds to scant extant evidence and proposes a mechanism to explain this impact. It should help enhance the use of assessment as a tool to augment learning

Influence of the central-to-peripheral arterial stiffness gradient on the timing and amplitude of wave reflections

In individuals with compliant aortas, peripheral muscular artery stiffness exceeds central elastic artery stiffness. With ageing, central stiffness increases, with little change in peripheral stiffness, resulting in a reversal of the normal stiffness gradient. This reversal may reduce wave reflection amplitude, due to movement of the major “effective” reflection site further from the heart. To test this, we investigated the relationship among arterial stiffness gradients (normal and reversed), wave reflection amplitude and reflection site distance. Subjects aged ≥50years were recruited from the Anglo-Cardiff Collaborative Trial. Central stiffness was assessed by carotid-femoral pulse wave velocity (cfPWV). In study 1, peripheral PWV was also measured in the arm (carotid-radial, crPWV), and in study 2 in the leg (femoral- dorsalis pedis, fpPWV). Reflection site distance was calculated from cfPWV and reflected wave travel time. Subjects were dichotomized into those with a normal stiffness gradient (peripheral>central PWV), or a reversed gradient (peripheral<central PWV). In study 1, reflection site distance was greater in subjects with a reversed gradient (P<0.01), whereas time to reflection was lower (P<0.001). Both augmentation pressure (P<0.001) and augmentation index (P<0.05) were greater in subjects with a reversed gradient. In study 2, augmentation pressure, augmentation index and reflection site distance were greater in subjects with a reversed stiffness gradient (P<0.01, P<0.05 and P<0.01, respectively), and time to reflection was not different between groups. A reversed arterial stiffness gradient is associated with increased reflection site distance and a paradoxical increase in reflected wave amplitude, and augmentation index