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Hyporheic flow path response to hydraulic jumps at river steps: Flume and hydrodynamic models

WATER RESOURCES RESEARCH 2011年第2期47卷 W02517.1-W02517.10页

作者： Endreny, T. Lautz, L. Siegel, D. I. SUNY Sch Environm Sci & Forestry Baker Labs 423 Dept Environm Resources Engn Syracuse NY 13210 USA Syracuse Univ Dept Earth Sci Heroy Geol Labs 204 Syracuse NY 13210 USA

The conceptual model of hyporheic exchange below river steps may oversimplify exchange flow paths if it depicts a uniform pattern of downstream-directed upwelling. This research used nonmobile, porous bed flume experiments and hydrodynamic simulation (CFD) to characterize hyporheic flow paths below a river step with a hydraulic jump. Bed slope was 1%, step height was 4 cm, downstream flow depth was 4 cm, substrate was 1 cm median diameter gravel, and hydraulic jump length was 25 cm in the flume and CFD experiments. With the hydraulic jump, flow paths changed to include downwelling beneath the water plunging into the pool and upstream-directed upwelling at the base of the step and beneath the length of jump. Failure to represent the influence of static and dynamic pressures associated with hydraulic jumps leads to erroneous prediction of subsurface flow paths in 75% of the streambed beneath the jump. A refined conceptual model for hyporheic flow paths below a step with a hydraulic jump includes reversed hyporheic circulation cells, in which downwelling water moves upstream and then upwells, and flow reversals, in which the larger flow net of downstream-directed upwelling encounters a nested flow path of upstream-directed upwelling. Heterogeneity in hyporheic flow paths at hydraulic jumps has the potential to explain field-observed mosaics in streambed redox patterns and expand structure-function relationships used in river management and restoration.

关键词： dynamic pressure FLOW PATH Upwelling structure-function relationships downwelling River management Streambeds Hydraulic jump insertion depth

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Biological parametric mapping with robust and non-parametric statistics

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NEUROIMAGE 2011年第2期57卷 423-430页

作者： Yang, Xue Beason-Held, Lori Resnick, Susan M. Landman, Bennett A. Vanderbilt Univ Nashville TN 37235 USA NIA NIH Baltimore MD 21224 USA Johns Hopkins Univ Baltimore MD 21218 USA

Mapping the quantitative relationship between structure and function in the human brain is an important and challenging problem. Numerous volumetric, surface, regions of interest and voxelwise image processing techniques have been developed to statistically assess potential correlations between imaging and non-imaging metrices. Recently, biological parametric mapping has extended the widely popular statistical parametric mapping approach to enable application of the general linear model to multiple image modalities (both for regressors and regressands) along with scalar valued observations. This approach offers great promise for direct, voxelwise assessment of structural and functional relationships with multiple imaging modalities. However, as presented, the biological parametric mapping approach is not robust to outliers and may lead to invalid inferences (e.g., artifactual low p-values) due to slight mis-registration or variation in anatomy between subjects. To enable widespread application of this approach, we introduce robust regression and non-parametric regression in the neuroimaging context of application of the general linear model. Through simulation and empirical studies, we demonstrate that our robust approach reduces sensitivity to outliers without substantial degradation in power. The robust approach and associated software package provide a reliable way to quantitatively assess voxelwise correlations between structural and functional neuroimaging modalities. (C) 2011 Elsevier Inc. All rights reserved.

关键词： structure-function relationships Statistical parametric mapping Biological parametric mapping Robust regression Non-parametric regression

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Gerstmann Meets Geschwind: A Crossing (or Kissing) Variant of a Subcortical Disconnection Syndrome?

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NEUROSCIENTIST 2011年第6期17卷 633-644页

作者： Kleinschmidt, Andreas Rusconi, Elena Univ Parma Dept Neurosci Physiol Sect I-43100 Parma Italy INSERM U992 F-91191 Gif Sur Yvette France CEA I2BM DSV F-91191 Gif Sur Yvette France UCL Dept Secur & Crime Sci London England

That disconnection causes clinical symptoms is a very influential concept in behavioral neurology. Criteria for subcortical disconnection usually are symptoms that are distinct from those following cortical lesions and damage to a single, long-range fiber tract. Yet, a recent study combining functional magnetic resonance imaging and fiber tracking concluded that a focal lesion in left parietal white matter provides the only tenable explanation for pure Gerstmann's syndrome, an enigmatic tetrad of acalculia, agraphia, finger agnosia, and left-right disorientation. Such a lesion would affect not only a single fiber tract but crossing or "kissing" of different fiber tracts and hence disconnect separate cortical networks. As fiber crossing is prominent in the cerebral white matter, the authors propose an extension to the subcortical disconnection framework that opens the door to ascribing a more diversified clinical phenomenology to white matter damage and ensuing disconnection than has been the case so far.

关键词： functional and clinical neuroanatomy structure-function relationships functional neuroimaging diffusion tensor imaging tractography human brain

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Disease-Specific Kidney Imaging: Introduction

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SEMINARS IN NEPHROLOGY 2011年第3期31卷 235-236页

作者： Molitoris, Bruce A. Indiana Univ Sch Med Div Nephrol Indianapolis IN 46202 USA

The kidney is an extremely complex structural organ consisting of vascular and epithelial components functioning in a highly coordinated fashion that allows for the regulation of a myriad of interdependent cellular processes. Over the years talented and creative individuals have developed novel and imaginative imaging approaches that allow for understanding and integrating the unique structure-function relationships that occur. The goal of imaging in clinical nephrology has been to translate these observations and provide information on the structure and/or the function of kidney disease.

关键词： Kidney Diseases Talent information structure structure-function relationships Nephrology Cellular processes Kidney kidney imaging

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Dynamic culture enhances stem cell infiltration and modulates extracellular matrix production on aligned electrospun nanofibrous scaffolds

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ACTA BIOMATERIALIA 2011年第2期7卷 485-491页

作者： Nerurkar, Nandan L. Sen, Sounok Baker, Brendon M. Elliott, Dawn M. Mauck, Robert L. Univ Penn McKay Orthopaed Res Lab Dept Orthopaed Surg Philadelphia PA 19104 USA Univ Penn Dept Mech Engn & Appl Mech Philadelphia PA 19104 USA Univ Penn Dept Bioengn Philadelphia PA 19104 USA

Electrospun nanofibrous scaffolds have become widely investigated for tissue engineering applications, owing to their ability to replicate the scale and organization of many fiber-reinforced soft tissues such as the knee meniscus, the annulus fibrosus of the intervertebral disc, tendon, and cartilage. However, due to their small pore size and dense packing of fibers, cellular ingress into electrospun scaffolds is limited. Progress in the application of electrospun scaffolds has therefore been hampered, as limited cell infiltration results in heterogeneous deposition of extracellular matrix and mechanical properties that remain below native benchmarks. In the present study, dynamic culture conditions dramatically improved the infiltration of mesenchymal stem cells into aligned nanofibrous scaffolds. While dynamic culture resulted in a reduction of glycosaminoglycan content, removal from dynamic culture to free-swelling conditions after 6 weeks resulted recovery of glycosaminoglycan content. Dynamic culture significantly increased collagen content, and collagen was more uniformly distributed throughout the scaffold thickness. While mechanical function was assessed and tensile modulus increased with culture duration, dynamic culture did not result in any additional improvement beyond free-swelling culture. Transient dynamic (6 weeks dynamic followed by 6 weeks free-swelling) culture significantly enhanced cell infiltration while permitting GAG accumulation. In this study, we demonstrated that a simple modification to standard in vitro culture conditions effectively improves cellular ingress into electrospun scaffolds, resolving a challenge which has until now limited the utility of these materials for various tissue engineering applications. (C) 2010 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

关键词： Electrospinning functional tissue engineering Dynamic culture Stem cells structure-function relationships

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Mutagenesis analyses explore residues responsible for the neurotoxic and anticoagulant activities of Trimucrotoxin, a pit-viper venom Asn⁶-phospholipase A₂

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BIOCHIMIE 2011年第2期93卷 277-285页

作者： Tsai, Inn-Ho Wang, Ying-Ming Hseu, Ming-Jhy Acad Sinica Inst Biol Chem Taipei Taiwan Natl Taiwan Univ Inst Biochem Sci Taipei Taiwan

Trimucrotoxin (TmCT) is an Asn(6)-containing phospholipase A(2) (FLA(2)) from Protobothrops mucrosquamatus (pit-viper) venom. In an attempt to characterize the amino acid residues responsible for the neurotoxic and anticoagulant activities of TmCT, the recombinant fusion proteins of TmCT wild type and mutants were expressed in Escherichia coli. Correct refolding and processing of 37 TmCT mutants were confirmed by their HPLC retention times, circular dichroism spectra, and masses obtained from ESI-MS spectrometry. Each mutant was assayed by pH-stat titration using zwitterionic as well as anionic micelle substrates, and the neurotoxicity was evaluated by using the contractile responses of chick biventer cervicis muscles. The results demonstrated that the residues Asn(1), Asn(6), Lys(7), Ile(11), Met(12), Gly(53), Thr(79), His(108) and Met(118) are important to TmCT neurotoxicity. Through various tests, we also confirmed that enzymatic activity, as opposed to binding to Factor Xa, was a necessary part of TmCT's anticoagulant effect. In addition, pulldown assays of the WT and selected mutants revealed that TmCT's in vitro binding to crotoxin acidic subunit may involve a broad surface area. We conclude that the hot spot mutations at specific positions 53, 79, 108, and 118 during the pit-viper Asn(6)-PLA(2) evolution regulate their neurotoxicities, and that many of the neurotoxic site residues and the anticoagulant mechanism of TmCT are different from those of ammodytoxin A (a true-viper venom neurotoxic PLA(2)). (C) 2010 Elsevier Masson SAS. All rights reserved.

关键词： Pit-viper venom presynaptic neurotoxin Anticoagulant phospholipase Mutagenesis structure-function relationships Protobothrops mucrosquamatus venom

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Regional variation in the mechanical role of knee meniscus glycosaminoglycans

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JOURNAL OF APPLIED PHYSIOLOGY 2011年第6期111卷 1590-1596页

作者： Sanchez-Adams, Johannah Willard, Vincent P. Athanasiou, Kyriacos A. Univ Calif Davis Dept Biomed Engn Davis CA 95616 USA Rice Univ Dept Bioengn Houston TX USA

Sanchez-Adams J, Willard VP, Athanasiou KA. Regional variation in the mechanical role of knee meniscus glycosaminoglycans. J Appl Physiol 111: 1590-1596, 2011. First published September 8, 2011;doi:10.1152/japplphysiol.00848.2011.-High compressive properties of cartilaginous tissues are commonly attributed to the sulfated glycosaminoglycan (GAG) fraction of the extracellular matrix (ECM), but this relationship has not been directly measured in the knee meniscus, which shows regional variation in GAG content. In this study, biopsies from each meniscus region (outer, middle, and inner) were either subjected to chondroitinase ABC (CABC) to remove all sulfated GAGs or not. Compressive testing revealed that GAG depletion in the inner and middle meniscus regions caused a significant decrease in modulus of relaxation (58% and 41% decreases, respectively, at 20% strain), and all regions exhibited a significant decrease in viscosity (outer: 29%;middle: 58%;inner: 62% decrease). Tensile properties following CABC treatment were unaffected for outer and middle meniscus specimens, but the inner meniscus displayed significant increases in Young's modulus (41% increase) and ultimate tensile stress (40% increase) following GAG depletion. These findings suggest that, in the outer meniscus, GAGs contribute to increasing tissue viscosity, whereas in the middle and inner meniscus, where GAGs are most abundant, these molecules also enhance the tissue's ability to withstand compressive loads. GAGs in the inner meniscus also contribute to reducing the circumferential tensile properties of the tissue, perhaps due to the pre-stress on the collagen network from increased hydration of the ECM. Understanding the mechanical role of GAGs in each region of the knee meniscus is important for understanding meniscus structure-function relationships and creating design criteria for functional meniscus tissue engineering efforts.

关键词： structure-function relationships cartilage chondroitinase abc musculoskeletal

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Quantitative characterization of postnatal growth trends in proximal pulmonary arteries in rats by phase-contrast magnetic resonance imaging

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AMERICAN JOURNAL OF PHYSIOLOGY-LUNG CELLULAR AND MOLECULAR PHYSIOLOGY 2011年第3期301卷 L368-L379页

作者： Razavi, Hedi Zarafshar, Shahrzad Y. Sawada, Hirofumi Taylor, Charles A. Feinstein, Jeffrey A. Stanford Univ Dept Bioengn Clark Ctr Rm S165 Stanford CA 94305 USA Stanford Univ Dept Mech Engn Stanford CA 94305 USA Stanford Univ Dept Pediat Stanford CA 94305 USA Stanford Univ Dept Surg Stanford CA 94305 USA

Razavi H, Zarafshar SY, Sawada H, Taylor CA, Feinstein JA. Quantitative characterization of postnatal growth trends in proximal pulmonary arteries in rats by phase-contrast magnetic resonance imaging. Am J Physiol Lung Cell Mol Physiol 301: L368-L379, 2011. First published June 10, 2011;doi:10.1152/ajplung.00069.2011.-Malformations of the pulmonary arteries can increase right heart workload and result in morbidity, heart failure, and death. With the increased use of murine models to study these malformations, there is a pressing need for an accurate and noninvasive experimental technique that is capable of characterizing pulmonary arterial hemodynamics in these animals. We describe the growth trends of pulmonary arteries in 13 male Sprague-Dawley rats at 20, 36, 52, 100, and 160 days of age with the introduction of phase-contrast MRI as such a technique. PCMRI results correlated closely with cardiac output measurements by ultrasound echocardiography and with fluorescent microspheres in right-left lung flow split (flow partition). Mean flow, average cross-sectional area, distensibility, and shear rates for the right and left pulmonary arteries (RPA and LPA) were calculated. The RPA was larger and received more flow at all times than the LPA (P < 0.0001). Right-left flow split did not change significantly with age, and arterial distensibility was not significantly different between RPA and LPA, except at 160 days (P < 0.01). Shear rates were much higher for the LPA than the RPA (P < 0.0001) throughout development. The RPA and LPA showed different structure-function relationships but obeyed similar allometric scaling laws, with scaling exponents comparable to those of the main pulmonary artery. This study is the first to quantitatively describe changes in RPA and LPA flows and sizes with development and to apply phase-contrast MRI techniques to pulmonary arteries in rats.

关键词： hemodynamics lungs wall shear structure-function relationships allometric scaling power laws

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Design, synthesis and characterization of a peptide able to bind proteins of the KCTD family: implications for KCTD - cullin 3 recognition

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JOURNAL OF PEPTIDE SCIENCE 2011年第5期17卷 373-376页

作者： Pirone, Luciano Correale, Stefania de Paola, Ivan Zaccaro, Laura De Simone, Giuseppina Vitagliano, Luigi Pedone, Emilia Di Gaetano, Sonia CNR Inst Biostruct & Bioimaging I-80134 Naples Italy Univ Naples Federico 2 Dept Biol Sci I-80134 Naples Italy

Pox virus Zinc/Bric-a-brac, Tramtrack and Broad (POZ/BTB) is a widespread domain detected in proteins involved in a variety of biological processes. Human genome analyses have unveiled the presence of POZ/BTB domain in a class of proteins (KCTD) whose role as important players in crucial biological processes is emerging. The development of new molecular entities able to interact with these proteins and to modulate their activity is a field of relevant interest. By using molecular modeling and literature mutagenesis analyses, we here designed and characterized a peptide that is able to interact with submicromolar affinities with two different members (KCTD11 and KCTD5) of this family. This finding suggests that the tetrameric KCTD11 and the pentameric KCTD5 are endowed with a similar cavity at the subunit-subunit interface deputed to the Cul3 binding, despite their different oligomeric states. Copyright (C) 2011 European Peptide Society and John Wiley & Sons, Ltd.

关键词： protein-protein recognition structure-function relationships ubiquitination POZ/BTB domains

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Anatomical and molecular mapping of the left and right ventricular His-Purkinje conduction networks

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JOURNAL OF MOLECULAR AND CELLULAR CARDIOLOGY 2011年第5期51卷 689-701页

作者： Atkinson, Andrew Inada, Shin Li, Jue Tellez, James O. Yanni, Joseph Sleiman, Rakan Abd Allah, Eman Anderson, Robert H. Zhang, Henggui Boyett, Mark R. Dobrzynski, Halina Univ Manchester Fac Med & Human Sci Core Technol Facil Manchester M13 9NT Lancs England

functioning of the cardiac conduction system depends critically on its structure and its complement of ion channels. Therefore, the aim of this study was to document both the structure and ion channel expression of the left and right ventricular His-Purkinje networks, as we have previously done for the sinoatrial and atrioventricular nodes. A three-dimensional (3D) anatomical computer model of the His-Purkinje network of the rabbit heart was constructed after staining the network by immunoenzyme labelling of a marker protein, middle neurofilament. The bundle of His is a ribbon-like structure and the architecture of the His-Purkinje network differs between the left and right ventricles. The 3D model is able to explain the breakthrough points of the action potential on the ventricular epicardium during sinus rhythm. Using quantitative PCR, the expression levels of the major ion channels were measured in the free running left and right Purkinje fibres of the rabbit heart. Expression of ion channels differs from that of the working myocardium and can explain the specialised electrical activity of the Purkinje fibres as suggested by computer simulations;the expression profile of the left Purkinje fibres is more specialised than that of the right Purkinje fibres. The structure and ion channel expression of the Purkinje fibres are highly specialised and tailored to the functioning of the system. The His-Purkinje network in the left ventricle is more developed than that in the right ventricle and this may explain its greater clinical importance. (C) 2011 Elsevier Ltd. All rights reserved.

关键词： Cardiac conduction system Bundle branches Purkinje fibres structure-function relationships Ion channels Computer modelling

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