Effect of through‐plane motion on left ventricular rotation: A study using slice‐following harmonic phase imaging

Noninvasive quantification of regional left ventricular rotation may improve understanding of cardiac function. Current methods used to quantify rotation typically acquire data on a set of prescribed short‐axis slices, neglecting effects due to through‐plane myocardial motion. We combine principles of slice‐following tagged imaging with harmonic phase analysis methods to account for through‐plane motion in regional rotation measurements. We compare rotation and torsion measurements obtained using our method to those obtained from imaging datasets acquired without slice‐following. Our results in normal volunteers demonstrate differences in the general trends of average and regional rotation‐time plots in midbasal slices and the rotation versus circumferential strain loops. We observe substantial errors in measured peak average rotation of the order of 58% for basal slices (due to change in the pattern of the curve), ?6.6% for midventricular slices, and ?8.5% for apical slices; and an average error in base‐to‐apex torsion of 19% when through‐plane motion is not considered. This study concludes that due to an inherent base‐to‐apex gradient in rotation that exists in the left ventricular, accounting for through‐plane motion is critical to the accuracy of left ventricular rotation quantification. Magn Reson Med, 2013. © 2011 Wiley Periodicals, Inc.     

Twist、Snail蛋白在喉鳞状细胞癌中的表达及其临床意义

目的 探讨Twist、Snail蛋白在喉鳞状细胞癌（喉鳞癌）组织中的表达及其临床意义.方法 应用免疫组织化学法检测60例喉鳞癌组织、30例癌旁组织中Twist、Snail蛋白的表达情况.结果 喉鳞癌组织中Twist的阳性表达为68.3％（41/60）,Snail的阳性表达为71.7％ （43/60）,均显著高于癌旁组织中的表达率;在喉鳞癌组织中Twist、Snail蛋白的表达之间存在显著正相关,相关系数（r）为0.529（P ＜0.01）.结论 喉鳞癌组织中存在Twist、Snail蛋白的高表达,两者的联合表达能增加肿瘤细胞侵袭力,促进喉鳞癌的浸润、转移.     

Intraobserver reliability of two-dimensional ultrasound derived strain imaging in the assessment of the left ventricle, right ventricle, and left atrium of healthy human hearts

Aims: To determine the intraobserver reproducibility of peak and temporal values for myocardial strain (?) and strain rate (SR) using a speckle tracking technique in the left ventricle (LV), right ventricle (RV), and left atrium (LA). Methods and Results: Myocardial speckle tracking echocardiograms of the LV, RV, and LA were obtained on 20 healthy adults to provide indices of longitudinal, radial, circumferential ?, and SR as well as LV rotation and twist. Each participant had two separate acquisitions approximately 30 minutes apart. No systematic bias was present in ? data. LV ? across all planes provided “good” to “very good” intraclass correlation coefficient (ICC) values (0.714–0.807), however radial ? was inferior in terms of coefficients of variation (CoV) (19%). SR data were more variable than ? with LV radial SR performing least favorably. RV and LA ? demonstrated excellent reproducibility (ICCs of 0.834, 0.959, and CoVs of 7% and 6%, respectively). RV and LA SR were again more variable but generally acceptable ICC > 0.6 and CoV < 15%. Peak basal and apical rotation demonstrated quite high variability while derived torsion had low variability and excellent agreement (ICC = 0.940, CoV = 10%). Time‐to‐peak values demonstrated acceptable agreement with the exception of systolic SR from all chambers. Conclusion: Good reproducibility was obtained for peak ? indices although radial ? performs less favorably. Intraobserver variation of peak ? appears superior to values obtained for peak SR. Time‐to‐peak values demonstrate very good intraobserver reproducibility across all planes of contraction with exception of (time‐to‐peak) systolic strain rate (SRS).     

From the Cover: Archaeal actin from a hyperthermophile forms a single-stranded filament

The prokaryotic origins of the actin cytoskeleton have been firmly established, but it has become clear that the bacterial actins form a wide variety of different filaments, different both from each other and from eukaryotic F-actin. We have used electron cryomicroscopy (cryo-EM) to examine the filaments formed by the protein crenactin (a crenarchaeal actin) from Pyrobaculum calidifontis, an organism that grows optimally at 90 °C. Although this protein only has ∼20% sequence identity with eukaryotic actin, phylogenetic analyses have placed it much closer to eukaryotic actin than any of the bacterial homologs. It has been assumed that the crenactin filament is double-stranded, like F-actin, in part because it would be hard to imagine how a single-stranded filament would be stable at such high temperatures. We show that not only is the crenactin filament single-stranded, but that it is remarkably similar to each of the two strands in F-actin. A large insertion in the crenactin sequence would prevent the formation of an F-actin-like double-stranded filament. Further, analysis of two existing crystal structures reveals six different subunit–subunit interfaces that are filament-like, but each is different from the others in terms of significant rotations. This variability in the subunit–subunit interface, seen at atomic resolution in crystals, can explain the large variability in the crenactin filaments observed by cryo-EM and helps to explain the variability in twist that has been observed for eukaryotic actin filaments.Actin is one of the most highly conserved as well as abundant eukaryotic proteins. From chickens to humans, an evolutionary separation of ∼350 million years, there are no amino acid changes in the skeletal muscle isoform of actin (1). There are at least six different mammalian isoforms that are quite similar to each other, and all seem to have diverged from a common ancestral actin gene (2). In contrast, we now know that bacteria have actin-like proteins that share a common fold (3–5) but have vanishingly little sequence similarity both among themselves and to eukaryotic actin (6).Two recent crystal structures of a crenarchaeal actin, crenactin (7, 8), raise interesting questions about the structure of the crenactin filament and its evolutionary relationship to F-actin. In both crystals (with two different space groups) crenactin forms a single-stranded filament with eight subunits per ∼420-Å right-handed turn, with a rise and rotation per subunit, therefore, of ∼53 Å and 45°, respectively. In contrast, in F-actin there is a rise and rotation of ∼55 Å and ∼27° along each of the two long-pitch right-handed strands. It was stated (9) that outside of the crystal the crenactin filaments are double-stranded, based upon the suggestion (8) that a single-stranded filament would unlikely be stable and that power spectra from crenactin filaments showed a strong layer line at ∼1/(210 Å), half of the repeat in the crystals.We have been able to image and reconstruct at low resolution the filaments formed by crenactin. Surprisingly, these filaments contain only a single strand, as opposed to the two strands present in F-actin and in the filaments formed by a number of bacterial actin-like proteins (9–13). We show that the crenactin filament is consistent with the single strand seen in crystals (7, 8), and that this strand is quite similar to each of the two strands within F-actin. This supports arguments about the close phylogenetic proximity between eukaryotic actin and archaeal actin (14, 15) and highlights the substantial divergence that has taken place between the bacterial actin-like proteins and eukaryotic actin (6).     

Effects of an over-ground exoskeleton on external knee moments during stance phase of gait in healthy adults

Background

Physical activity and exercise is central to conservative management of knee osteoarthritis (KOA), but is often difficult for patients with KOA to maintain over the decade or more prior to surgical management. Better approaches are needed for maintaining physical function and health in this population that can also address the patho-biomechanics of the osteoarthritic knee.The objective of the study is to quantify how a lower-extremity robotic exoskeleton (dermoskeleton) modifies the external knee moments during over-ground walking in a sample of healthy adults, and to evaluate these biomechanical modifications in the context of the osteoarthritic knee.

左心室扭转运动在心脏再同步治疗中的价值

<正>大量的循证医学证据表明,心脏再同步治疗(cardiac resynchronization therapy,CRT)能有效改善慢性心力衰竭患者的症状、提高生活质量、降低心力衰竭住院率和全因死亡率[1-2],已成为合并心脏不同步者的一线治疗手段。在CRT的发展过程中,超声心动检查发挥着不可或缺的作用。虽然在传统超声的基础上,组织多普勒、三维超声等新技术有了较大的发展,但目前仍缺乏有效的指标来预测CRT疗效。超声检测心脏扭转是近年来发展起来的新技术,因其独特的