Luminal Dimensions Research Articles

In Vivo Biomechanical Assessment of Anterior Rabbit Urethra After Repair of Surgically Created Hypospadias

We studied the in vivo biomechanical properties of the anterior urethra in a rabbit hypospadias simulation model at long-term followup after urethroplasty. A total of 38, 9-week-old white New Zealand male rabbits were randomized into active treatment and control groups. The active treatment group included hypospadias-like simulation and acute repair (sham, mobilization and advancement, tubularized incised posterior urethral plate). After 23 weeks all groups underwent biomechanical investigation using impedance planimetry. Cross-sectional area pressure measurements during bag distention were conducted at 3 different positions along the urethra, and biomechanical (tension-strain) relations were computed. The biomechanical parameters studied were urethral luminal dimension (cross-sectional area pressure relation) and its deformability to luminal pressure (tension-strain relation). The urethral cross-sectional area was significantly larger in the mobilization and advancement group compared to the tubularized incised plate group (p <0.001), shams and controls at the distal distention site (p <0.05), and other groups at the intermediate distention site (p <0.05). The strain-tension curves were not significantly different between the groups. All groups showed a nonlinear cross-sectional area pressure and circumferential wall tension-strain relationships in the 3 distention sites. The urethras exhibited a decreasing ability to be distended with increasing pressures, indicating self-protection against damage. At long-term followup no differences in tension-strain relations were found between groups, despite the fact that the mobilization and advancement group had enlarged urethras. Our hypospadias simulation animal model could be useful to test commonly used or new urethroplasty techniques and their functional (biomechanical) long-term results before clinical use.

Life‐long caloric restriction confers pronounced AMPK‐dependent cardioprotection

AIMSTo determine whether myocardial resistance to ischemia/reperfusion (I/R) injury is enhanced in the senescent heart after life‐long caloric restriction, and whether AMP‐activated protein kinase (AMPK) plays a role in that phenotype.METHODS AND RESULTSHearts from ad libitum fed (AL) and life‐long calorically restricted (LCR, 40% restriction) B6D2F1 mice were examined by echocardiography, and 25/90 minute global I/R. AMPK inhibition (AraA) was applied to both groups (AL+AraA, LCR+AraA) prior to I/R. LCR hearts were smaller (AL, 270 ± 7 mg vs. LCR, 185 ± 5 mg, p &lt; 0.001), and had thinner posterior walls (PWTd: AL, 1.07 ± 0.05 mm vs. LCR, 0.84 ± 0.05 mm, p &lt; 0.05), but similar in vivo luminal dimension (LVIDd; LVIDs: AL, 3.8 ± 0.14; 2.0 ± 0.19 mm vs. LCR, 3.5 ± 0.18; 1.8 ± 0.17 mm, both p &gt; 0.2). LCR hearts were protected from infarction (Infarct Size: AL, 28 ± 4 % vs. LCR, 10 ± 1 %, p &lt; 0.01) and post‐ischemic functional deficit (LVDP recovery: AL, 65 ± 8 % vs. LCR, 93 ± 7 %, p &lt; 0.01), and both effects were abolished by AraA (Infarct size: LCR+AraA, 22 ± 4 %; LVDP recovery: LCR+AraA, 82 ± 9 %, both p vs. AL &gt; 0.1). LCR dramatically increased AMPKα phosphorylation (AL, 1.30 ± 0.03 vs. LCR, 1.55 ± 0.03, ratio units, p &lt; 0.001), but not expression (AL, 1.21 ± 0.07 vs. LCR, 1.19 ± 0.01, ratio units, p = 0.8).CONCLUSIONSLife‐long caloric restriction induces powerful AMPK‐dependent I/R resistance, and involves elevated AMPKα phosphorylation.

Improved Classification of Coronary Artery Abnormalities Based Only on Coronary Artery z-Scores After Kawasaki Disease

Competing definitions and classifications of coronary artery abnormalities (CAAs) after Kawasaki disease (KD) have been arbitrarily defined based on clinical experience. We sought to propose a classification system for CAAs based only on coronary artery z-scores. All echocardiograms performed between 1990 and 2007 on patients with a previous history of KD were reviewed. Coronary artery luminal dimensions were converted to body-surface-area-adjusted z-scores and compared to current classification systems. A total of 1356 patients with a previous history of KD underwent 4379 echocardiograms. There was important overlap in the distributions of coronary artery z-scores between the different CAA classes as defined by the American Heart Association (AHA). The AHA classification underestimated the severity of CAAs in 19-32% of small CAAs and 35-78% of medium CAAs. We determined the optimal definition of CAA to be small if the z-score is >or=2.5 to <5.0, large if the z-score is >or=5.0 to <10.0, and giant if the z-score is >or=10.0. This classification seems to appropriately apply to the circumflex branch despite a lack of normal values for this branch. The current AHA classification might not accurately classify CAAs in KD patients. Accurate classification is important for defining management and prognosis consistently across patient age and size.

Accuracy of Computed Tomographic Angiography for Stenosis Quantification Using Quantitative Coronary Angiography or Intravascular Ultrasound as the Gold Standard

Computed tomographic angiography (CTA) is considered to have limited accuracy for quantifying exact percent diameter stenosis in coronary arteries. However, most studies evaluating CTA use quantitative coronary angiography (QCA) as the gold standard, a technique with its own limitations. We sought to determine whether CTA measurements of stenosis severity correlate better with intravascular ultrasound (IVUS) than with QCA. Luminal dimensions of 67 de novo coronary lesions were measured by CTA, IVUS, and QCA. IVUS was performed when lesion severity by angiography was equivocal. Mean percent diameter stenosis by QCA was 51 +/- 9.8% and mean IVUS minimal luminal area was 3.8 +/- 1.8 mm(2). There was a moderate correlation between CTA minimal luminal area and IVUS minimal luminal area (r(2) = 0.41, p <0.001), but no relation between CTA and QCA measurements of minimal luminal diameter (r(2) = 0.01, p = 0.57) or diameter stenosis (r(2) = 0.02, p = 0.31). There was also no relation between IVUS minimal luminal area and QCA diameter stenosis (r(2) = 0.01, p = 0.50). When lesions with moderate or severe calcification were excluded, the correlation between CTA minimal luminal area and IVUS minimal luminal area was good (r(2) = 0.68, p <0.001). In conclusion, in this cohort of patients with intermediate-grade lesions on cardiac catheterization, absolute measurements of stenosis severity on CTA correlated with IVUS but not with QCA. Our findings suggest that limitations of quantitative coronary angiography as a gold standard need to be considered in studies evaluating the accuracy of coronary CTA.

On the Inappropriateness of Noninvasive Multidetector Computed Tomography Coronary Angiography to Trigger Coronary Revascularization: A Comparison With Invasive Angiography

Our purpose was to evaluate the appropriateness of multidetector computed tomography angiography (MDCTA) as an anatomical standard for decision making in patients with known or suspected coronary artery disease. Although correlative studies between MDCTA and coronary angiography (CA) show good agreement, MDCTA visualizes plaque burden and calcifications well before luminal dimensions are encroached. Pressure-derived fractional flow reserve (FFR) was obtained in 81 patients (116 vessels) who underwent both CA and MDCTA. Segments were visually graded for stenosis severity as: G0 = normal, G1 = nonobstructive (<50% diameter reduction), and G2 = obstructive (> or =50% diameter reduction). Concordance between segmental severity scores by MDCTA and CA was good (k = 0.74; 95% confidence interval: 0.56 to 0.92). Diagnostic performance of MDCTA for detection of functionally significant stenosis based on FFR was low (sensitivity 79%; specificity 64%; positive likelihood ratio 2.2; negative likelihood ratio 0.3). Revascularization was considered appropriate in the presence of reduced FFR (< or =0.75). Decision making based on MDCTA guidance would result in revascularization in the absence of ischemia in 22% of patients (18 of 81) and inappropriate deferral in 7% (6 of 81), while revascularization in the absence of ischemia would be 16% (13 of 81) and inappropriate deferral 12% (10 of 81) with decisions guided by CA. Combined evaluation of stenosis severity using both anatomy (with either CA or MDCTA) and function (with FFR) yields the highest proportion of appropriate decisions: 90% and 91%, respectively (p = 0.0001 vs. CA only, p = 0.0001 vs. MDCTA only). Similar to CA, anatomical assessment of coronary stenosis severity by MDCTA does not reliably predict its functional significance.

Comparison between Three‐Dimensional Angiographic Reconstruction and Intravascular Ultrasound Imaging for the Measurement of Cross‐Sectional Luminal Dimensions in Intermediate Coronary Lesions

Intravascular ultrasound (IVUS) has enabled the measurement of minimal luminal area of coronary stenoses. We evaluated the hypothesis that angiographic three-dimensional reconstruction of luminal dimensions may be able to provide similar measurements to IVUS in intermediate coronary lesions. We retrospectively enrolled patients undergoing invasive coronary angiography and IVUS for the assessment of angiographically intermediate coronary lesions (50-70%) at a high-volume tertiary care hospital between July 1, 2006, and May 20, 2008. IVUS (Boston Scientific, Natick Massachusetts, USA) minimal cross-sectional area (CSA) and minimal luminal diameters (MLD) were compared with the measurements obtained using a sophisticated three-dimensional angiographic reconstruction software (CardiOP-B, Paieon, Inc., Rosh Ha'ayin, Israel), with orthogonal angiographic views used to reconstruct and calculate lesion dimensions. Data were obtained from 34 patients with 35 lesions. The lesions were assessed in the left main (n = 2), left anterior descending artery (n = 15), left circumflex/marginal artery (n = 7), and right coronary artery (n = 11). Using IVUS, the mean minimal CSA was 3.78 +/- 1.60 mm(2), and MLD was 1.88 +/- 0.43 mm. Three-dimensional reconstruction measurements of minimal CSA (3.42 +/- 1.66 mm(2)) highly correlated in a linear fashion with the measurements by IVUS (R = 0.88, P < 0.0001). A three-dimensional angiographic measurement of coronary minimal CSA is highly correlated with the measurements using IVUS. This new software technology may be a promising imaging modality to measure CSAs in coronary lesions.

How to Compare Apples and Oranges: Infants' Object Identification Tested With Equally Salient Shape, Luminance and Color Changes.

What kind of featural information do infants rely on when they are trying to recognize a previously seen object? The question of whether infants use certain features (e.g. shape or color) more than others (e. g. luminance), can only be studied legitimately if visual salience is controlled, since the magnitude of feature values - how noticeable and interesting they are - will affect results. We employed a novel methodology, 'Interdimensional Salience Mapping', that allowed us to quantify and calibrate salience changes along shape, luminance and color feature dimensions. We then compared 9-month-old infants' identification of objects, employing feature changes that were equally salient. These results show that infants more readily identify objects on the basis of color and shape than luminance. Additionally, we show that relative salience changes rapidly in infancy - in particular, we found significantly higher salience thresholds for color in younger (6.5-month-old) infants - but that individual differences within an age group are remarkably modest.

Circulation: Clinical Summaries

<i>Circulation:</i> Clinical Summaries

Attenuated Plaque Detected by Intravascular Ultrasound: Clinical, Angiographic, and Morphologic Features and Post-Percutaneous Coronary Intervention Complications in Patients With Acute Coronary Syndromes

We evaluated the clinical significance of attenuated plaque (hypoechoic plaque with deep ultrasound attenuation). Attenuated plaques are unusual intravascular ultrasound (IVUS) findings in patients with acute coronary syndrome (ACS). We reviewed clinical presentations and angiographic and pre-intervention IVUS findings in 293 ACS patients undergoing percutaneous coronary intervention (PCI) without a distal protection device: 187 with non-ST-segment elevation myocardial infarction (NSTEMI) and 106 with ST-segment elevation myocardial infarction (STEMI). Attenuated plaque was observed in 75 patients (25.6%): 39.6% of STEMI versus 17.6% of NSTEMI (p < 0.001). (We also reviewed 100 randomly selected patients with stable angina and pre-intervention IVUS; none had attenuated plaque.) Overall, in ACS patients with attenuated plaques: 1) the level of C-reactive protein was higher; 2) angiographic thrombus and initial coronary flow Thrombolysis In Myocardial Infarction flow grade <2 were more common; and 3) IVUS lesion site plaque burden and remodeling index were significantly greater, lesion site luminal dimensions significantly smaller, and thrombus, positive remodeling, and plaque rupture were more common. No-reflow (26.7% vs. 4.6%, p < 0.001) and deteriorated post-PCI coronary blood flow (8.0% vs. 2.8%, p = 0.001) were higher. In ACS patients with normal coronary blood flow at baseline, deterioration in the coronary blood flow post-PCI was more common in lesions with attenuated plaque. Attenuated plaque was more common in ACS patients with STEMI than NSTEMI. Attenuated plaque in ACS patients was associated with a higher C-reactive protein level, more severe and complex lesion morphology, reduced coronary blood flow before PCI, and especially no-reflow after PCI.

Response to Letters Regarding Article, “Effect of Rosuvastatin Therapy on Coronary Artery Stenoses Assessed by Quantitative Coronary Angiography: A Study to Evaluate the Effect of Rosuvastatin on Intravascular Ultrasound–Derived Coronary Atheroma Burden”

We thank Dr Kaneda and Drs Sutton, Blumenthal, and Kapur for their interest and commentaries on our analysis.1 In response to Dr Kaneda’s request for sensitivity analyses, we applied the same conservative assumptions employed in the intravascular ultrasound (IVUS) analysis2 to all noncompleters and to those with ischemic events and found that statistically significant regression occurred in both percentage diameter stenosis (%DS) and minimum lumen diameter. With regard to the assessment of disease progression, as in previous quantitative coronary angiography (QCA) studies that we referenced,3 the prespecified outcome variable was the change in baseline stenoses >25%. This is very reasonable because some studies have shown that only progression of stenoses present at baseline was predictive of coronary events.4 In A Study to Evaluate the Effect of Rosuvastatin on Intravascular Ultrasound–Derived Coronary Atheroma Burden (ASTEROID), 379 of the 507 randomized patients (75%) had both a baseline and a follow-up QCA study. Sixteen of these patients (4.2%) developed a new lesion of >25% stenosis that represented an increase of at least 20% from baseline. Of those 379 patients, the 292 (77%) with baseline …

Neural mechanisms of chromatic and achromatic vision

AbstractBuilding upon electrophysiological recordings from the lateral geniculate nucleus (LGN) of the macaque monkey, we describe a model for neural processing of color and brightness/lightness information that starts in the cone receptors and continues in the opponent cells of the retina, LGN, and visual cortex. The excitation of the three cone types to direct stimulation by light is modified in accordance with a hyperbolic response function before providing inputs to retinal ganglion cells. Using weighted differences of such cone outputs, we simulate the responses of common types of opponent ganglion and geniculate cells to light modulation along the chromatic and luminance dimensions. Extrapolating the results of the simulation, we suggest a way in which the brain might combine inputs from the geniculate to obtain correlates of chromatic and achromatic color vision and of brightness/lightness perception. In particular, we demonstrate for the first time how combinations of “L–M” and “M–L” parvocellular ON‐ and OFF‐opponent‐cells may lead to a quantitative account of brightness and blackness scaling. © 2008 Wiley Periodicals, Inc. Col Res Appl, 33, 433–443, 2008

Quantitative multi-modality imaging analysis of a bioabsorbable poly-L-lactic acid stent design in the acute phase: a comparison between 2- and 3D-QCA, QCU and QMSCT-CA

To investigate if three-dimensional (3D) based quantitative techniques are comparable to each other and to explore possible differences with respect to the reference method of 2D-QCA in the acute phase and to study whether non-invasive MSCT could potentially be applied to quantify luminal dimensions of a stented coronary segment with a novel bioabsorable drug-eluting stent made of poly-l-lactic-acid (PLLA). Quantitative imaging data derived from 16 patients enrolled at our institution in a first-in-man trial (ABSORB) receiving a biodegradable stent and who were imaged with standard coronary angiography and intravascular ultrasound were compared. Shortly, after stenting the patients also underwent a MSCT procedure. Standard 2D-QCA showed significant smaller stent lengths (p < 0.01). Although, the absolute measured stent diameters and areas by 2D-QCA tend to be smaller, the differences failed to be statistically different when compared to the 3D based quantitative modalities. Measurements made by non-invasive QMSCT-CA of implanted PLLA stents appeared to be comparable to the other 3D modalities without significant differences. Three-dimensional based quantitative analyses showed similar results quantifying luminal dimensions as compared to 2D-QCA during an evaluation of a new bioabsorbable coronary stent design in the acute phase. Furthermore, in biodegradable stents made of PLLA, non-invasive QMSCT-CA can be used to quantify luminal dimensions.

Comparison of Quantitative Coronary Angiography with Intracoronary Ultrasound. Can Quantitative Coronary Angiography Accurately Estimate the Severity of a Luminal Stenosis?

In this study we investigated the accuracy of monoplane and biplane quantitative coronary angiography in estimating the luminal dimensions, using intracoronary ultrasound as gold standard. Biplane angiography and intracoronary ultrasound were performed in 24 arterial segments. The end-diastolic intracoronary ultrasound frames were manually selected and segmented. In 2 end-diastolic X ray projections, quantitative coronary angiography was performed and a novel methodology was applied to register the segmented frames onto the processed angiographic images. The luminal areas determined by quantitative coronary angiography in 1 (monoplane) and 2 projections (mean) were compared with those determined by intracoronary ultrasound. The obtained correlation coefficients for the monoplane and mean estimations were 0.69 +/- 0.12 and 0.77 +/- 0.08, respectively. It would appear that by increasing the angle between the biplane projections, the correlation between intracoronary ultrasound and mean estimations improves. Our results provide evidence that orthogonal biplane angiography is more reliable and should be preferred to assess luminal dimensions.

Angiographically uncertain left main coronary artery narrowings: correlation with multidetector computed tomography and intravascular ultrasound

Angiographic assessment of left main coronary artery (LMCA) stenosis is often difficult and unreliable. To date, intravascular ultrasound (IVUS) is used to determine the significance of lesions in patients with LMCA stenosis of uncertain significance. We aimed to prospectively show the ability of multidetector computed tomography (MDCT) to assess LMCA luminal and plaque dimensions, and to characterize atherosclerotic plaque, as compared to IVUS and quantitative coronary angiography (QCA), in patients with angiographically uncertain LMCA stenosis. Twenty patients, with angiographically uncertain LMCA stenosis, underwent coronary evaluation with IVUS, QCA and 16-slice MDCT. Minimal lumen diameter (MLD), minimal lumen area (MLA), lumen area stenosis (LAS) and plaque burden (PB) were assessed. The MLD (median [interquartile range]) was 3.2 mm (2.5-3.7) by IVUS, 2.8 mm (2.3-3.3) by QCA (r=0.52, P<0.05), and 2.8 mm (2.5-3.8) by MDCT (r=0.77, P<0.01). MDCT estimated MLA as 10.7 mm(2) (7.1-12.6) Vs. 9.9 mm(2) (6.5-13.5) by IVUS (r=0.93, P<0.01). Very high correlations were observed between MDCT and IVUS in assessing LAS (mean +/- SD) (25.8+/-19.1% and 29.0+/-24.9% respectively, r=0.83, P<0.01), and PB (49.2+/-15.8% and 49.2+/-19.7% respectively, r=0.94, P<0.01). MDCT assigned plaque as being non-calcified with a sensitivity of 100%, while calcified plaques with a sensitivity of 75%. A high degree of correlation was found between MDCT and IVUS regarding the assessment of minimal lumen diameter and area, lumen area stenosis and plaque burden as well as plaque characterization in patients with angiographically borderline LMCA stenosis. Therefore, in patients selected for non-invasive coronary tree evaluation, MDCT may provide a valuable tool for the assessment, decision-making and follow-up of patients with uncertain LMCA disease.

Response to Letter Regarding Article, “Stent Thrombosis Late After Implantation of First-Generation Drug-Eluting Stents: A Cause for Concern”

We are grateful for the thorough comments by Agostoni et al and Kereiakes et al, which give us the opportunity to clarify our position. As Agostoni et al point out, important limitations exist in the measurements of luminal dimensions that may be magnified when the change in those dimensions are assessed by measurement of late loss (LL). Furthermore, there is variation in absolute quantitative coronary angiography (QCA) values according to core laboratories, which makes comparison of QCA data problematic.1 Regardless of these facts, QCA of lumen dimensions has long been the backbone of clinical studies in the field of restenosis.2 It has now become crucial to go beyond luminal measurements and to focus on both events that matter to the patient and their …

Coronary stent assessment on multidetector computed tomography: Source and predictors of image distortion

Background Metallic stent struts cause imaging artifacts on multidetector computed tomography (MDCT) which interfere with the assessment of in-stent coronary restenosis. We examined the degree of image distortion of implanted coronary stents on MDCT, comparing different stent types, sizes and orientation. Methods We quantified stent dimensions and image distortion of 151 non-opacified coronary stents in 89 patients (81% men, age 65 ± 10 years) who underwent MDCT with a 40 slice MDCT scanner. Stent dimension by MDCT was compared with measurements obtained from quantitative coronary angiographic (QCA) in the immediate post-implantation angiogram and with manufacturers' data. Results Stent image quality was good for 107 stents (71%), moderate for 38 (25%) and poor in 6 (4%), 2 (< 1%) of which were not assessable. Blooming artifact resulted in a mean MDCT luminal (inner) diameter 30 ± 14% smaller than QCA diameter (2.0 ± 0.5 vs 2.9 ± 0.3 mm, p < 0.001) and a mean outer diameter exceeding QCA by 31 ± 14% (3.8 ± 0.5 vs 2.9 ± 0.3 mm, p < 0.001). MDCT luminal stent diameter was unrelated to strut thickness or the vessel stented but appeared to be smaller for vertically orientated stents ( p = 0.017), cobalt alloy (vs stainless steel) ( p = 0.011) and also for different stent types ( p = 0.006). Conclusion The luminal dimension of implanted coronary stents, as visualized with 40 slice MDCT, was one third smaller than on invasive angiography. This decrease in visualized stent luminal diameter forms the basis for the difficulty in accurate assessment of in-stent restenosis by MDCT.

Efficacy of reduced‐dose sirolimus‐eluting stents in the human coronary artery: Serial IVUS analysis of neointimal hyperplasia and luminal dimension

Using serial intravascular ultrasound (IVUS), the efficacy of reduced-dose sirolimus-eluting stents (SESs) in the prevention of neointimal hyperplasia (NH) and maintenance of luminal patency in human coronary arteries was evaluated. In the animal model, a broad therapeutic window regarding sirolimus doses in suppressing NH has been reported. Serial cross-sectional and volumetric IVUS analyses were performed in 44 patients treated with SES that contained lower sirolimus doses (either 45% or 70%) than standard SES. For cross-sectional analysis, minimum lumen area (MLA) was measured. Percent (%) NH volumetric obstruction was calculated as 100 x NH volume/stent volume. IVUS measurements were similar between the two drug-dose groups. At 12 months follow-up, only one case developed late incomplete stent apposition. Between 4 and 12 months, a slight increase of in-stent % area loss and % NH obstruction was noted (3.5% +/- 10.4% to 6.7% +/- 10.7% and 1.9% +/- 5.0% to 4.4% +/- 8.0%, respectively). The majority of studied cases, however, sustained less than a 10% volumetric (93% of studied cases) and area loss (75% of studied cases) in the stented segment up to 12 months. At 12 months, % area loss within the stented segments and 5-mm reference segments were comparable (7.0% +/- 19.6% versus 6.7% +/- 10.7%). Although slight increases of NH were noted, SESs, delivering two reduced drug doses, appeared to be effective for maintaining luminal patency during 12 months follow-up.

Intravascular imaging of atherosclerotic human coronaries in a porcine model: a feasibility study

To perform intravascular imaging of atherosclerotic human coronary conduits in an animal model under conditions of flow and cardiac motion that approximate those encountered in vivo. Given the lack of animal models of vulnerable plaque, a model which would allow imaging of human disease and simulate coronary motion and blood flow could advance the development of emerging technologies to detect vulnerable plaques. Human coronary segments from adult cadaver hearts were prepared as xenografts. In anesthetized Yorkshire pigs (45-50 kg) the chest was opened and the exposed aorta and right atrium were cannulated and attached in an end-to-end fashion to the human coronary xenograft, forming an aorto-atrial conduit. The xenograft was fixed to the anterior wall of the heart to simulate motion. Angiography and intravascular ultrasound (IVUS) of each graft were performed. Twelve human coronary grafts (10 from right coronary segments) were prepared and implanted successfully in seven animals. All animals tolerated the procedure. The average graft length was 39 +/- 2.3 mm. Blood flow rates distal to the graft were >100 ml/min in nine grafts. IVUS was performed in all 12 grafts and documented expansion of arterial (6.9%) and luminal (9.3%) dimensions during the cardiac cycle (P < 0.001 for both). There was a wide range of coronary atherosclerotic pathology within the grafts, including intimal thickening, fibrocalcific plaque, and deep lipid pools. This human-to-porcine coronary xenograft model allows intravascular imaging of human coronary pathology under conditions of blood flow and motion, and may be used to develop technologies aimed at identifying high-risk plaques.

Chromatic tuning of contour-shape mechanisms revealed through the shape-frequency and shape-amplitude after-effects

We investigated whether contour-shape processing mechanisms are selective for color direction using the shape-frequency and shape-amplitude after-effects, or SFAE and SAAE [Gheorghiu, E. & Kingdom, F. A. A. (2006). Luminance-contrast properties of contour-shape processing revealed through the shape-frequency after-effect. Vision Research, 46(21), 3603–3615. Gheorghiu, E. & Kingdom, F. A. A. (2007). The spatial feature underlying the shape-frequency and shape-amplitude after-effects. Vision Research, 47(6), 834–844]. All contours were defined along the ‘red-green’, ‘blue-yellow’ and ‘luminance’ axes of cardinal color space. Adapting and test contours were defined along the same or along opposite polarities within a cardinal axis, and along the same or along different cardinal axes. We found (i) little transfer of the after-effects across different within-axis polarities, for all cardinal axes and for both even-symmetric and odd-symmetric contours; (ii) little transfer between the red–green and blue–yellow cardinal axes; (iii) little transfer between the chromatic and luminance cardinal directions for the SAAE; (iv) large transfer between the chromatic and luminance cardinal directions for the SFAE. We conclude that contour-shape mechanisms are selective for within-cardinal axis polarity and for the chromatic axes within the isoluminant plane. However for certain types of contour-shape processing they are poorly selective along the chromatic versus luminance dimension. Overall our results suggest that contour-shape encoding mechanisms are selective for color direction and that color is important for contour-shape processing.

Comparison of Polyester Scaffolds for Bioengineered Intestinal Mucosa

Introduction: Biodegradable polyester scaffolds have proven useful for growing neointestinal tissue equivalents both in vitro and in vivo. These scaffolds allow cells to attach and grow in a 3-dimensional space while nutrient flow is maintained throughout the matrix. The purpose of this study was to evaluate different biopolymer constructs and to determine mucosal engraftment rates and mucosal morphology. Hypothesis: We hypothesized that different biopolymer constructs may vary in their ability to provide a good scaffolding onto which intestinal stem cell organoids may be engrafted. Study Design: Eight different microporous biodegradable polymer tubes composed of polyglycolic acid (PGA), polylactic acid, or a combination of both, using different fabrication techniques were seeded with intestinal stem cell clusters obtained from neonatal rats. Three different seeded polymer constructs were subsequently placed into the omentum of syngeneic adult recipient rats (n = 8). Neointestinal grafts were harvested 4 weeks after implantation. Polymers were microscopically evaluated for the presence of mucosal growth, morphology, scar formation and residual polymer. Results: Mucosal engraftment was observed in 7 out of 8 of the polymer constructs. A maximal surface area engraftment of 36% (range 5–36%) was seen on nonwoven, randomly entangled, small fiber PGA mesh coated with aerosolized 5% poly-L-lactic acid. Villous and crypt development, morphology and created surface area were best on PGA nonwoven mesh constructs treated with poly-L-lactic acid. Electrospun microfiber PGA had poor overall engraftment with little or no crypt or villous formation. Conclusion: Intestinal organoids can be engrafted onto biodegradable polyester scaffoldings with restitution of an intestinal mucosal layer. Variability in polymer composition, processing techniques and material properties (fiber size, luminal dimensions and pore size) affect engraftment success. Future material refinements should lead to improvements in the development of a tissue-engineered intestine.