Ascending aorta curvature and flow displacement are associated with accelerated aortic growth at long-term follow-up: A MRI study in Marfan and thoracic aortic aneurysm patients.

BACKGROUND: Aortic aneurysm formation is associated with increased risk of aortic dissection. Current diagnostic strategies are focused on diameter growth, the predictive value of aortic morphology and function remains underinvestigated. We aimed to assess the long-term prognostic value of ascending aorta (AA) curvature radius, regional pulse wave velocity (PWV) and flow displacement (FD) on aortic dilatation/elongation and evaluated adverse outcomes (proximal aortic surgery, dissection/rupture, death) in Marfan and non-syndromic thoracic aortic aneurysm (NTAA) patients. METHODS: Long-term magnetic resonance imaging (MRI) and clinical follow-up of two previous studies consisting of 21 Marfan and 40 NTAA patients were collected. Baseline regional PWV, AA curvature radius and normalized FD were assessed as well as diameter and length growth rate at follow-up. Multivariate linear regression was performed to evaluate whether baseline predictors were associated with aortic growth.=. RESULTS: Of the 61 patients, 49 patients were included with MRI follow-up (n = 44) and/or adverse aortic events (n = 7). Six had undergone aortic surgery, no dissection/rupture occurred and one patient died during follow-up. During 8.0 [7.3-10.7] years of follow-up, AA growth rate was 0.40 ± 0.31 mm/year. After correction for confounders, AA curvature radius (p = 0.01), but not FD or PWV, was a predictor of AA dilatation. Only FD was associated with AA elongation (p = 0.01). CONCLUSION: In Marfan and non-syndromic thoracic aortic aneurysm patients, ascending aorta curvature radius and flow displacement are associated with accelerated aortic growth at long-term follow-up. These markers may aid in the risk stratification of ascending aorta elongation and aneurysm formation.

Hierarchical bioinspired adhesive surfaces-a review.

The extraordinary adherence and climbing agility of geckos on rough surfaces has been attributed to the multiscale hierarchical structures on their feet. Hundreds of thousands of elastic hairs called setae, each of which split into several spatulae, create a large number of contact points that generate substantial adhesion through van der Waals interactions. The hierarchical architecture provides increased structural compliance on surfaces with roughness features ranging from micrometers to millimeters. We review synthetic adhesion surfaces that mimic the naturally occurring hierarchy with an emphasis on microfabrication strategies, material choice and the adhesive performance achieved.

Coupling between MRI-assessed regional aortic pulse wave velocity and diameters in patients with thoracic aortic aneurysm: a feasibility study.

AIMS: Thoracic aortic aneurysm (TAA) is potentially life-threatening and requires close follow-up to prevent aortic dissection. Aortic stiffness and size are considered to be coupled. Regional aortic stiffness in patients with TAA is unknown. We aimed to evaluate coupling between regional pulse wave velocity (PWV), a marker of vascular stiffness, and aortic diameter in TAA patients. METHODS: In 40 TAA patients (59 ± 13 years, 28 male), regional aortic diameters and regional PWV were assessed by 1.5 T MRI. The incidence of increased diameter and PWV were determined for five aortic segments (S1, ascending aorta; S2, aortic arch; S3, thoracic descending aorta; S4, suprarenal and S5, infrarenal abdominal aorta). In addition, coupling between regional PWV testing and aortic dilatation was evaluated and specificity and sensitivity were assessed. RESULTS: Aortic diameter was 44 ± 5 mm for the aortic root and 39 ± 5 mm for the ascending aorta. PWV was increased in 36 (19 %) aortic segments. Aortic diameter was increased in 28 (14 %) segments. Specificity of regional PWV testing for the prediction of increased regional diameter was ≥ 84 % in the descending thoracic to abdominal aorta and ≥ 68 % in the ascending aorta and aortic arch. CONCLUSION: Normal regional PWV is related to absence of increased diameter, with high specificity in the descending thoracic to abdominal aorta and moderate results in the ascending aorta and aortic arch.

Morphological and functional carotid vessel wall properties in relation to cerebral white matter lesions in myocardial infarction patients.

OBJECTIVE: Atherosclerotic large vessel disease is potentially involved in the pathogenesis of cerebral small vessel disease related to occurrence of white matter lesions (WMLs) in the brain. We aimed to assess morphological and functional carotid vessel wall properties in relation to WML using magnetic resonance imaging (MRI) in myocardial infarction (MI) patients. MATERIALS AND METHODS: A total of 20 MI patients (90 % male, 61 ± 11 years) underwent carotid artery and brain MRI. Carotid vessel wall thickness (VWT) was assessed, by detecting lumen and outer wall contours. Carotid pulse wave velocity (PWV), a measure of elasticity, was determined using the transit-time method. Patients were divided according to the median VWT into two groups. Brain MRI allowed for the WML score. RESULTS: Mean VWT was 1.41 ± 0.29 mm and mean carotid PWV was 7.0 ± 2.2 m/s. A significant correlation (Pearson r = 0.45, p = 0.046) between VWT and PWV was observed. Furthermore, in the group of high VWT, the median WML score was higher as compared with the group with lower VWT (4.0 vs 3.0, p = 0.035). CONCLUSIONS: Carotid artery morphological and functional alterations are correlated in MI patients. Patients with high VWT showed a higher amount of periventricular WMLs. These findings support the hypothesis that atherosclerotic large vessel disease is potentially involved in the pathogenesis of cerebral small vessel disease.

Fabrication of metal nanoparticle arrays by controlled decomposition of polymer particles.

We report a novel fabrication method for ordered arrays of metal nanoparticles that exploits the uniform arrangement of polymer beads deposited as close-packed monolayers. In contrast to colloidal lithography that applies particles as masks, we used thermal decomposition of the metal-covered particles to precisely define metal structures. Large arrays of noble metal (Au, Ag, Pt) nanoparticles were produced in a three-step process on silicon, fused silica and sapphire substrates, demonstrating the generality of this approach. Polystyrene spheres with diameters ranging between 110 nm and 1 µm were convectively assembled into crystalline monolayers, coated with metal and annealed in a resistive furnace or using an ethanol flame. The thermal decomposition of the polymer microspheres converted the metal layer into particles arranged in hexagonal arrays that preserved the order of the original monolayer. Both the particle size and the interparticle distance were adjusted via the thickness of the metal coating and the sphere diameter, respectively.

High field carotid vessel wall imaging: a study on reproducibility.

PURPOSE: Currently, a multi-contrast protocol, including a combination of five MR-sequences is used as reference standard for morphologic imaging and quantitative measurements of the carotid artery vessel wall. The purpose of this study is to investigate the scan-rescan reproducibility together with intra- and inter-observer reproducibility of each of the five MR-sequences. METHODS: Twenty healthy volunteers (55% male, mean age=26 years) underwent repeated MR-examinations (3T-Philips-MRI) of the left carotid artery vessel wall with five sequences; T1-TFE, T2-TSE, PD-TSE, T1-TSE and 3D TOF. A standard phased-array coil with two flexible elements of 14cm×17cm was used to obtain nine transverse imaging sections of the left carotid artery with identical in-plane resolution (0.46mm×0.46mm). Reproducibility analysis was performed in 3 slices of the common carotid artery for all sequences. RESULTS: For, scan-rescan reproducibility, intra class correlation coefficients (ICC) were excellent for all sequences and ranged from 0.79 to 0.95. The intra-observer ICC ranged from 0.89 to 0.98 and the inter-observer ICC ranged from 0.84 to 0.96, for both lumen and vessel wall assessment. CONCLUSIONS: By high field MR imaging, vessel wall and lumen area of the carotid artery can be assessed with excellent scan-rescan, intra- and inter-observer reproducibility for all five sequences.

Note: An adhesion measurement setup for bioinspired fibrillar surfaces using flat probes.

Current adhesion measurement setups designed for experiments on bioinspired fibrillar surfaces, either commercial or constructed in-house, do not allow adhesion measurements with in situ visualization, high resolution, high force range, and controlled alignment at the same time. In this paper a new adhesion tester is presented, which enables contact experiments with controlled tilt angle (accuracy of ±0.02°). This allows the use of flat probes and thus greatly simplifies the determination of experimental parameters such as pull-off strength or Young's modulus. The deflection of a double-clamped glass beam is measured by laser interferometry with an accuracy of ±60 nm, which yields a precise force measurement over three orders of magnitude force range without changing the glass beam. Contact formation and detachment events can be visualized in situ. The current adhesion tester is designed for force measurements in the range of 1 µN to 1 N and fills the gap between macroscopic tests and atomic force microscopy measurements.

In vitro adhesion measurements between skin and micropatterned poly(dimethylsiloxane) surfaces.

Micropatterned adhesive surfaces may have potential in reconstructive surgery. The adhesion performance of mice ear skin to micropatterned poly(dimethylsiloxane) (PDMS) was investigated, under in vitro conditions, and compared to flat substrates. No significant difference in separation force F was observed between flat substrates and micropatterned surfaces with pillar arrays. However, the energy necessary for separation of the substrate from the skin was sensitive to the topography. Furthermore, our results show that the force-displacement curves depended on the wetness of the skin: Highest force values were obtained for fresh skin while the forces decreased as the skin dried out. The results are encouraging for further studies on the potential of patterned PDMS in biomedical applications.

Subcellular fractionation of bone marrow-derived macrophages: localization of phospholipase A1 and A2 and acyl-CoA:1-acylglycero-3-phosphorylcholine-0-acyltransferase.

Analysis of the subcellular distribution of lipid-metabolizing enzymes was carried out in bone marrow-derived macrophages with special respect to a comparison of the subcellular localisation of phospholipase A1 and A2 and to acyl-CoA:1-1-acylglycero-3-phosphorylcholine-0-acetyltransferase. After cell disruption differential centrifugation was followed by additional sucrose gradient purification of three main fractions. Satisfactory enrichment factors were obtained by this method for the following marker enzymes. The plasma-membrane enzyme alkaline phosphodiesterase I was enriched up to 25-fold and the acyl-CoA:1-acylglycero-3-phosphorylcholine-0-acyltransferase was enriched up to 30-fold. The marker enzyme for the endoplasmic reticulum, NADPH-cytochrome c reductase showed a similar enrichment and distribution as the acyltransferase. Therefore it was concluded that the acyl-CoA:1-acylglycero-3-phosphorylcholine-0-acyltransferase of bone marrow-derived macrophages is mainly located in the endoplasmic reticulum. Phospholipase A1 and A2 occurred in a high proportion together with the lysosomal marker enzyme N-acetyl-beta-glucosaminidase in the soluble supernatant and in the gradient fractions. In the endoplasmic reticulum phospholipase A2 occurred only in trace activities whereas phospholipase A1 was maximally enriched in this subcellular fraction. No subcellular fraction could be obtained where phospholipase A2 was enriched exclusively. However, it can be concluded that the two enzymes which are responsible for the balance of fatty acid liberation and re-acylation are located in two different cellular compartments. Furthermore it can be claimed that in the cell there has to exist an exchange of substrates and products between these compartments to achieve a complete metabolic cycle of the de- and re-acylation reaction of phospholipids in bone marrow-derived macrophages.

Control of arachidonic acid accumulation in bone marrow-derived macrophages by acyltransferases.

The turnover of phospholipid fatty acid moieties of bone marrow-derived macrophages was analyzed by separate determination of degrading and acylating activities. Acylating activities were followed in intact cells by incubation with excess arachidonic acid and degradation of phospholipids was followed in cells prelabeled with fatty acids. Significant phospholipase A2 activity was detectable only if the reutilization of liberated fatty acid was inhibited , e.g. by p-chloromercuribenzoate. It was of interest that the divalent cation ionophore A 23187 and various antiphlogistic drugs like indomethacin, diclofenac, and acetylsalicylic acid were found to inhibit the acylation reaction. These compounds led to increased levels of free arachidonic acid in stimulated, as well as in unstimulated cells. Increased activities of phospholipase A2 were achieved by treatment with the bivalent cation ionophore A 23187 and with zymosan. The effect of zymosan obtained from various sources was found to be exclusively due to contamination of tee zymosan particles with phospholipase A2 activity. Even when the cellular phospholipase activity was increased by the addition of exogenous phospholipase activity contained in the zymosan particles, degradation of cellular phospholipids was not measurable unless the reacylation was inhibited. These results suggest that in the cells studied, the level of free arachidonic acid is mainly controlled by the activity of the lysophosphatide acyltransferase.

Release of prostaglandins by small intestinal tissue of man and rat in vitro and the effect of endotoxin in the rat in vivo.

Rat jejunal tissue in vitro synthesizes large amounts of prostaglandin (PG) D2 and smaller amounts of 6-keto-PGF1 alpha and PGE2, whereas human small intestinal mucosa synthesizes much smaller amounts of the three PG determined with about equal amounts of PGE2 and PGD2. Intraperitoneal administration of bacterial endotoxin to rats induce fluid accumulation in the small intestine and increases significantly the release of PGD2, PGE2 and 6-keto-PGF1 alpha into the small intestinal lumen in vivo. Endotoxin-induced stimulation of PG release is particularly pronounced for PGD2. Fluid accumulation and PG output are inhibited by indomethacin. It seems possible that the different total amounts of PG synthesized by small intestinal tissue of man and rat as well as the different pattern of PG released might contribute to species-specific responses of the gastrointestinal tract to various pathophysiological stimuli.

On the metabolism of prostaglandins by rat brain homogenate.

Using radio-immuno assays for prostaglandins and prostaglandin metabolites, three prostaglandin metabolizing enzymes were found in the 100,000 X g supernatant of rat brain, 15-hydroxy-prostaglandin-dehydrogenase, delta13-reductase and prostaglandin E-9-keto-reductase. Specific activity of the latter enzyme was highest in striatum and midbrain and lowest in cortex, cerebellum and spinal cord.