Low WSS Induces Intimal Thickening,while Large WSS Variation and Inflammation Induce Medial Thinning,in an Animal Model of Atherosclerosis

Objective

Atherosclerotic plaque development in the arterial wall is the result of complex interaction between the wall’s endothelial layer and blood hemodynamics. However, the interaction between hemodynamic parameters and inflammation in plaque evolution is not yet fully understood. The aim of the present study was to investigate the relation between wall shear stress (WSS) and vessel wall inflammation during atherosclerotic plaque development in a minipig model of carotid stenosis.

Methods

A surgical procedure was performed to create left common carotid artery stenosis by placement of a perivascular cuff in minipigs under atherogenic diet. Animals were followed up on 3T MRI, 1 week after surgery and 3, 6, and 8 months after initiation of the diet. Computational fluid dynamics simulation estimated WSS distribution for the first imaging point. Vascular geometries were co-registered for direct comparison of plaque development and features (Gadolinium- and USPIO-Contrast Enhanced MRI, for permeability and inflammation respectively) with the initial WSS. Histological analysis was performed and sections were matched to MR images, based on spatial landmarks.

Results

Vessel wall thickening, permeability and inflammation were observed distally from the stenosis. They were eccentric and facing regions of normal wall thickness. Histological analysis confirmed eccentric plaque formation with lipid infiltration, intimal thickening and medial degradation. High phagocytic activity in the stenosis region was co-localized with high WSS, corresponding to intense medial degradation observed on histology samples.

Conclusion

Lower WSS promotes atherosclerotic plaque development distal to an induced stenosis. Vascular and perivascular inflammation locations were predominant in the high WSS stenosis segment, where medial thinning was the major consequence.     

A reliable method for assessing rotational power

Rotational core training is said to be beneficial for rotational power athletes. Currently, there has been no method proposed for the reliable assessment of rotational power. Therefore, our purpose was to determine the test-retest reliability of kinetic and kinematic rotational characteristics of a pulley system when performing a rotational exercise of the axial skeleton in the transverse plane to find out if this would be a reliable tool for evaluating rotational power. Healthy, college-aged men (n = 8) and women (n = 15) reported for 3 testing sessions. The participants were seated on a box, and they held the handle with both arms extended in front of their body, starting their motion with their torso rotated toward the machine. All the participants rotated their torso forcefully until they reached 180° of rotation, and they then slowly returned to the starting position, 3 times per trial, with 3 loads: 9% body weight (BW), 12% BW, and 15% BW. The repetition with the greatest power for each trial for each load was analyzed. The mean peak power repetition (watts) for all the subjects was 20.09 ± 7.16 (9% BW), 26.17 ± 8.6 (12% BW), and 30.74 ± 11.022 (15% BW) in the first training session and 22.3 ± 8.087 (9% BW), 28.7 ± 11.295 (12% BW), and 33.52 ± 12.965 (15% BW) in the second training session with intraclass correlation coefficients of 0.97 (9%BW), 0.94 (12%BW), and 0.95 (15%BW). When the participants were separated by sex, there were no significant differences between groups. Based on these results, it was found that a pulley system and an external dynamometer can be used together as a reliable research tool to assess rotational power.     

Microfluidic technologies for studying synthetic circuits

Advances in synthetic biology have augmented the available toolkit of biomolecular modules, allowing engineering and manipulation of signaling in a variety of organisms, ranging in complexity from single bacteria and eukaryotic cells to multi-cellular systems. The richness of synthetic circuit outputs can be dramatically enhanced by sophisticated environmental control systems designed to precisely pattern spatial-temporally heterogeneous environmental stimuli controlling these circuits. Moreover, the performance of the synthetic modules and 'blocks' needed to assemble more complicated networks requires more complete characterization as a function of arbitrarily complex environmental inputs. Microfluidic technologies are poised to meet these needs through a variety of innovative designs capitalizing on the unique benefits of manipulating fluids on the micro-scales and nano-scales. This review discusses the utility of microfluidics for the study of synthetic circuits and highlights recent work in the area.     

Dissociation of Learned Helplessness and Fear Conditioning in Mice: A Mouse Model of Depression

The state of being helpless is regarded as a central aspect of depression, and therefore the learned helplessness paradigm in rodents is commonly used as an animal model of depression. The term ‘learned helplessness’ refers to a deficit in escaping from an aversive situation after an animal is exposed to uncontrollable stress specifically, with a control/comparison group having been exposed to an equivalent amount of controllable stress. A key feature of learned helplessness is the transferability of helplessness to different situations, a phenomenon called ‘trans-situationality’. However, most studies in mice use learned helplessness protocols in which training and testing occur in the same environment and with the same type of stressor. Consequently, failures to escape may reflect conditioned fear of a particular environment, not a general change of the helpless state of an animal. For mice, there is no established learned helplessness protocol that includes the trans-situationality feature. Here we describe a simple and reliable learned helplessness protocol for mice, in which training and testing are carried out in different environments and with different types of stressors. We show that with our protocol approximately 50% of mice develop learned helplessness that is not attributable to fear conditioning.     

In vivo measurement of coronary circulation angiotensin-converting enzyme activity in humans

Angiotensin-converting enzyme (ACE) is present on the luminal surface of the coronary vessels, mostly on capillary endothelium. ACE is also expressed on coronary smooth muscle cells and on plaque lipid-laden macrophages. Excessive coronary circulation (CC)-ACE activity might be linked to plaque progression. Here we used the biologically inactive ACE substrate (3)H-labeled benzoyl-Phe-Ala-Pro ([(3)H]BPAP) to quantify CC-ACE activity in 10 patients by means of the indicator-dilution technique. The results were compared with atherosclerotic burden determined by coronary angiography. There was a wide range of CC-ACE activity as revealed by percent [(3)H]BPAP hydrolysis (30-74%). The atherosclerotic extent scores ranged from 0.0 to 66.97, and the plaque area scores ranged from 0 to 80 mm(2). CC-ACE activity per unit extracellular space (V(max)/K(m)V(i)), an index of metabolically active vascular surface area, was correlated with myocardial blood flow (r = 0.738; P = 0.03) but not with measures of the atherosclerotic burden. These results show that CC-ACE activity can be safely measured in humans and that it is a good marker of the vascular area of the perfused myocardium. It does not, however, reflect epicardial atherosclerotic burden, suggesting that local tissue ACE may be more important in plaque development.     

Interaction of asymmetric ABCC9-encoded nucleotide binding domains determines KATP channel SUR2A catalytic activity

Nucleotide binding domains (NBDs) secure ATP-binding cassette (ABC) transporter function. Distinct from traditional ABC transporters, ABCC9-encoded sulfonylurea receptors (SUR2A) form, with Kir6.2 potassium channels, ATP-sensitive K+ (K ATP) channel complexes. SUR2A contains ATPase activity harbored within NBD2 and, to a lesser degree, NBD1, with catalytically driven conformations exerting determinate linkage on the Kir6.2 channel pore. While homodomain interactions typify NBDs of conventional ABC transporters, heterodomain NBD interactions and their functional consequence have not been resolved for the atypical SUR2A protein. Here, nanoscale protein topography mapped assembly of monodisperse purified recombinant SUR2A NBD1/NBD2 domains, precharacterized by dynamic light scattering. Heterodomain interaction produced conformational rearrangements inferred by secondary structural change in circular dichroism, and validated by atomic force and transmission electron microscopy. Physical engagement of NBD1 with NBD2 translated into enhanced intrinsic ATPase activity. Molecular modeling delineated a complemental asymmetry of NBD1/NBD2 ATP-binding sites. Mutation in the predicted catalytic base residue, D834E of NBD1, altered NBD1 ATPase activity disrupting potentiation of catalytic behavior in the NBD1/NBD2 interactome. Thus, NBD1/NBD2 assembly, resolved by a panel of proteomic approaches, provides a molecular substrate that determines the optimal catalytic activity in SUR2A, establishing a paradigm for the structure-function relationship within the K ATP channel complex.     

Population estimation of human embryonic stem cell cultures

Traditionally, the population of human embryonic stem cell (hESC) culture is estimated through haemacytometer counts, which include harvesting the cells and manually analyzing a fraction of an entire population. Obviously, through this highly invasive method, it is not possible to preserve any spatial information on the cell population. The goal of this study is to identify a fast and consistent method for in situ automated hESC population estimation to quantitatively estimate the cell growth. Therefore, cell cultures were fixed, stained, and their nuclei imaged through high‐resolution microscopy, and the images were processed with different image analysis techniques. The proposed method first identifies signal and background by computing an image specific threshold for image segmentation. By applying a morphological operator (watershed), we split most physically overlapping nuclei, leading to a pixel area distribution of isolated signal areas on the image. On the basis of this distribution, we derive a nucleus area model, describing the distribution of the area of cell debris, single nuclei, and small groups of connected nuclei. Through the model, we can give a quantitative estimation of the population. The focus of this study is on low‐density human embryonic stem cell populations; hence cultures were measured at days 2–3 after seeding. Compared with manual cell counts, the automatic method achieved higher accuracy with <6% error. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2010