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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Pure and applied geophysics 151 (1998), S. 463-475 
    ISSN: 1420-9136
    Keywords: Key words: Anisotropy, mantle flow, subduction zones, shear-wave splitting.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract —We have obtained constraints on the strength and orientation of anisotropy in the mantle beneath the Tonga, southern Kuril, Japan, and Izu-Bonin subduction zones using shear-wave splitting in S phases from local earthquakes and in teleseismic core phases such as SKS. The observed splitting in all four subduction zones is consistent with a model in which the lower transition zone (520–660 km) and lower mantle are isotropic, and in which significant anisotropy occurs in the back-arc upper mantle. The upper transition zone (410–520 km) beneath the southern Kurils appears to contain weak anisotropy. The observed fast directions indicate that the geometry of back-arc strain in the upper mantle varies systematically across the western Pacific rim. Beneath Izu-Bonin and Tonga, fast directions are aligned with the azimuth of subducting Pacific plate motion and are parallel or sub-parallel to overriding plate extension. However, fast directions beneath the Japan Sea, western Honshu, and Sakhalin Island are highly oblique to subducting plate motion and parallel to present or past overriding plate shearing. Models of back-arc mantle flow that are driven by viscous coupling to local plate motions can reproduce the splitting observed in Tonga and Izu-Bonin, but further three-dimensional flow modeling is required to ascertain whether viscous plate coupling can explain the splitting observed in the southern Kurils and Japan. The fast directions in the southern Kurils and Japan may require strain in the back-arc mantle that is driven by regional or global patterns of mantle flow.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-1335
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung T- und B-Zellzählungen, Bestimmungen der Fluidität von Ig-Rezeptoren und der Grad der Virusantigen-Expression wurden korreliert mit histologischen Befunden während der Latenzzeit und Tumorbildung von virusinduzierten Lymphomen der Maus. Zur Untersuchung kamen BALB/c Mäuse nach Infektion mit dem stark onkogenen Moloney Leukämievirus (MLV), dem mittelgradig bei der BALB/c Maus onkogenen Gross Passage A virus (GLV-A) und dem praktisch nicht onkogenen Gross 3T3 Zellkulturvirus (GLV-T). Die Methodik schloß ein: Immunfluoreszenzmikroskopie mit Antiseren gegen T-Zellen, B-Zellen und MLV-intaktem Virus, Histologie und Elektronenmikroskopie. Folgender Ablauf von Veränderungen wurde beobachtet bei MLV- und GLV-A infizierten Mäusen, jedoch nicht bei GLV-T infizierten Tieren: Eine signifikante Abnahme der Fluidität von Ig-Rezeptoren und eine erhebliche Expression von Virusantigen wurden bereits bei der ersten Untersuchung, d. i. 2 Wochen nach der Infektion, beobachtet. Es folgte 5–8 Wochen später eine signifikante Herabsetzung der Prozent-T-Zellen, begleitet von einer histologisch verifizierbaren Thymusatrophie und Atrophie der thymusabhängigen Partien des lymphatischen Gewebes. Weitere 2–8 Wochen später wurden die ersten Lymphomherde histologisch im atrophischen Thymus diagnostiziert. Klinisch feststellbare und generalisierte Lymphome waren dann 20–30 Wochen nach Virusinfektion zu erheben. Ultrastrukturell fanden sich Veränderungen in Anordnung und Quantität cytoplasmatischer Mikrofilamente in proliferierenden Lymphoblasten und Lymphomzellen. Es wird geschlossen, daß die beobachteten Veränderungen auf die onkogene Wirksamkeit von Typ C Mäuse-RNS-Viren zurückzuführen ist und nicht auf eine Virusinfektion per se.
    Notes: Summary T- and B-cell counts, estimation of Ig receptor fluidity, and expression of virus-coded antigens were correlated with histological findings during the development of virus-induced mouse lymphoma. Tested were BALB/c mice after infection with the strongly oncogenic Moloney leukemia virus (MLV), the moderately oncogenic (in BALB/c mice) Gross passage A virus (GLV-A), and the essentially non-oncogenic Gross 3T3 tissue culture virus (GLV-T). Methods included immunofluorescence microscopy with antisera against T-cells, B-cells and MLV intact virus, routine histology, and electron microscopy. Following time sequence of changes was observed in mice with oncogenic MLV- and GLV-A infection but not in GLV-T infection: Significant decrease of Ig receptor fluidity and expression of virus antigen were observed already at the initial investigation,i.e. 2 weeks post virus infection. This was followed by significant decreases in percent T-cells 5–8 weeks later, accompanied by histologic atrophy of the thymus and of thymus-dependent regions of lymphatic tissues. Another 2–8 weeks after the decrease in percent T-cells occurred, the first lymphomatous foci became obvious in the thymus. Clinically overt and generalized lymphoma was diagnosed at 20–30 weeks post virus infection. Ultrastructurally, some changes in the arrangement and quantity of cytoplasmic microfilaments were noted in proliferating lymphoblasts and in lymphoma cells. It is concluded, that the described changes were related to the oncogenic potential of mouse C-type RNA viruses and not just to virus infection per se.
    Type of Medium: Electronic Resource
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  • 3
    Publication Date: 2013-06-21
    Description: Myeloid cell leukemia-1 (MCL-1) is an anti-apoptotic BCL-2 protein that is up-regulated in several human cancers. MCL-1 is also highly expressed in myocardium, but its function in myocytes has not been investigated. We generated inducible, cardiomyocyte-specific Mcl-1 knockout mice and found that ablation of Mcl-1 in the adult heart led to rapid cardiomyopathy and death. Although MCL-1 is known to inhibit apoptosis, this process was not activated in MCL-1-deficient hearts. Ultrastructural analysis revealed disorganized sarcomeres and swollen mitochondria in myocytes. Mitochondria isolated from MCL-1-deficient hearts exhibited reduced respiration and limited Ca 2+ -mediated swelling, consistent with opening of the mitochondrial permeability transition pore (mPTP). Double-knockout mice lacking MCL-1 and cyclophilin D, an essential regulator of the mPTP, exhibited delayed progression to heart failure and extended survival. Autophagy is normally induced by myocardial stress, but induction of autophagy was impaired in MCL-1-deficient hearts. These data demonstrate that MCL-1 is essential for mitochondrial homeostasis and induction of autophagy in the heart. This study also raises concerns about potential cardiotoxicity for chemotherapeutics that target MCL-1.
    Print ISSN: 0890-9369
    Topics: Biology
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  • 4
    Publication Date: 2020-10-26
    Description: Resolving flow geometry in the mantle wedge is central to understanding the thermal and chemical structure of subduction zones, subducting plate dehydration, and melting that leads to arc volcanism, which can threaten large populations and alter climate through gas and particle emission. Here we show that isotope geochemistry and seismic velocity anisotropy provide strong evidence for trench-parallel flow in the mantle wedge beneath Costa Rica and Nicaragua. This finding contradicts classical models, which predict trench-normal flow owing to the overlying wedge mantle being dragged downwards by the subducting plate. The isotopic signature of central Costa Rican volcanic rocks is not consistent with its derivation from the mantle wedge1, 2, 3 or eroded fore-arc complexes4 but instead from seamounts of the Galapagos hotspot track on the subducting Cocos plate. This isotopic signature decreases continuously from central Costa Rica to northwestern Nicaragua. As the age of the isotopic signature beneath Costa Rica can be constrained and its transport distance is known, minimum northwestward flow rates can be estimated (63–190 mm yr-1) and are comparable to the magnitude of subducting Cocos plate motion (approx85 mm yr-1). Trench-parallel flow needs to be taken into account in models evaluating thermal and chemical structure and melt generation in subduction zones.
    Type: Article , PeerReviewed
    Format: text
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  • 5
    Publication Date: 2015-04-25
    Description: Polarities and amplitudes of intracrustal P-SV conversions (P waves converted to vertically polarized shear waves) in receiver functions from the Southeastern Suture of the Appalachian Margin Experiment array and USArray Transportable Array provide new constraints on the origin of seismic reflectivity delineating the Alleghanian detachment in the southern Appalachians(eastern United States). Forward modeling of receiver functions is consistent with a 3.5-km-thick, high shear-wave velocity (Vs = 3.9 km/s) section of deformed Paleozoic platform metasedimentary rocks beneath the Blue Ridge at 3–6.5 km depth. In the Inner Piedmont, conversions from the top and base of a low-Vs zone (3.1 km/s) at depths of 5–9 km are interpreted as a package of metasedimentary rocks or a shear zone characterized by radial anisotropy. The detachment continues to the southeast beneath the Carolina terrane, where high-amplitude negative conversions at 10–13 km depth are consistent with arc rocks (Vs = 4.0 km/s) overlying sheared rocks with lower Vs (3.2 km/s). Southeast-dipping conversions at 5–10 km depth mark the boundary between the Inner Piedmont and Carolina terrane. This study demonstrates that relatively high-frequency receiver functions (up to ~3 Hz), though still lower in frequency than P-wave energy analyzed for reflection profiling (〉20 Hz), can provide important links between surface geology and active-source experiments to better constrain models of crustal structure.
    Print ISSN: 0091-7613
    Electronic ISSN: 1943-2682
    Topics: Geosciences
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  • 6
    Publication Date: 2014-03-15
    Description: Seismic images of the base of the lithosphere across the San Andreas fault system (California, USA) yield new constraints on the distribution of deformation in the deep lithosphere beneath this strike-slip plate boundary. We show that conversions of shear to compressional waves (Sp) across the base of the lithosphere are systematically weaker on the western side of the plate boundary, indicating that the drop in seismic shear-wave velocity from lithosphere to asthenosphere is either smaller or occurs over a larger depth range. In central and northern California, the lithosphere-asthenosphere boundary changes character across a distance of 〈50 km, and does so directly beneath the San Andreas fault along its simple central segment, and beneath the Calaveras–Green Valley–Bartlett Springs faults to the north. Given the absolute velocities of the North America and Pacific plates, and low viscosities inferred for the asthenosphere, these results indicate the juxtaposition of mantle lithospheres with different properties across these faults. The spatial correlation between the central San Andreas fault and the laterally abrupt change in the velocity structure of the deepest mantle lithosphere points to the accommodation of relative plate motion on a narrow shear zone (〈50 km in width), and a rheology that enables strain localization throughout the thickness of the lithosphere.
    Print ISSN: 0091-7613
    Electronic ISSN: 1943-2682
    Topics: Geosciences
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  • 7
    Publication Date: 2014-04-16
    Description: Observed seismic anisotropy and geochemical anomalies indicate the presence of 3-D flow around and above subducting slabs. To investigate how slab geometry and velocity affect mantle flow, we conducted a set of experiments using a subduction apparatus in a fluid-filled tank. Our models comprise two independently adjustable, continuous belts to represent discrete sections of subducting slabs that kinematically drive flow in the surrounding glucose syrup that represents the upper mantle. We analyse how slab dip (ranging from 30° to 80°), slab dip difference between slab segments (ranging from 20° to 50°), rates of subduction (4–8 cm yr –1 ) and slab/trench rollback (0–3 cm yr –1 ) affect mantle flow. Whiskers were used to approximate mineral alignment induced by the flow, as well as to predict directions of seismic anisotropy. We find that dip variations between slab segments generate 3-D flow in the mantle wedge, where the path lines of trenchward moving mantle material above the slab are deflected towards the slab segment with the shallower dip. The degree of path line deflection increases as the difference in slab dip between the segments increases, and, for a fixed dip difference, as slab dip decreases. In cases of slab rollback and large slab dip differences, we observe intrusion of subslab material through the gap and into the wedge. Flow through the gap remains largely horizontal before eventual downward entrainment. Whisker alignment in the wedge flow is largely trench-normal, except near the lateral edges of the slab where toroidal flow dominates. In addition, whisker azimuths located above the slab gap deviate most strongly from trench-normal orientations when slab rollback does not occur. Such flow field complexities are likely sufficient to affect deep melt production and shallow melt delivery. However, none of the experiments produced flow fields that explain the trench-parallel shear wave splitting fast directions observed over broad arc and backarc regions in many subduction zones.
    Print ISSN: 0956-540X
    Electronic ISSN: 1365-246X
    Topics: Geosciences
    Published by Oxford University Press on behalf of The Deutsche Geophysikalische Gesellschaft (DGG) and the Royal Astronomical Society (RAS).
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  • 8
    Publication Date: 2015-05-30
    Description: Human cardiac progenitor cells (hCPC) improve heart function after autologous transfer in heart failure patients. Regenerative potential of hCPCs is severely limited with age, requiring genetic modification to enhance therapeutic potential. A legacy of work from our laboratory with Pim1 kinase reveals effects on proliferation, survival, metabolism, and rejuvenation of hCPCs in vitro and in vivo. We demonstrate that subcellular targeting of Pim1 bolsters the distinct cardioprotective effects of this kinase in hCPCs to increase proliferation and survival, and antagonize cellular senescence. Adult hCPCs isolated from patients undergoing left ventricular assist device implantation were engineered to overexpress Pim1 throughout the cell (PimWT) or targeted to either mitochondrial (Mito-Pim1) or nuclear (Nuc-Pim1) compartments. Nuc-Pim1 enhances stem cell youthfulness associated with decreased senescence-associated β-galactosidase activity, preserved telomere length, reduced expression of p16 and p53, and up-regulation of nucleostemin relative to PimWT hCPCs. Alternately, Mito-Pim1 enhances survival by increasing expression of Bcl-2 and Bcl-XL and decreasing cell death after H2O2 treatment, thereby preserving mitochondrial integrity superior to PimWT. Mito-Pim1 increases the proliferation rate by up-regulation of cell cycle modulators Cyclin D, CDK4, and phospho-Rb. Optimal stem cell traits such as proliferation, survival, and increased youthful properties of aged hCPCs are enhanced after targeted Pim1 localization to mitochondrial or nuclear compartments. Targeted Pim1 overexpression in hCPCs allows for selection of the desired phenotypic properties to overcome patient variability and improve specific stem cell characteristics.
    Print ISSN: 0021-9258
    Electronic ISSN: 1083-351X
    Topics: Biology , Chemistry and Pharmacology
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  • 9
    Publication Date: 2016-12-21
    Description: In contrast to crustal deformation observed in the actively forming Himalayas, where shallowly dipping crustal detachments extend over hundreds of kilometers, prior work on the Paleozoic southern Appalachian orogeny inferred that the final continental collision occurred on a steeply dipping crustal suture, permitting collision models that are dominated by strike-slip motion. Here, we use scattered seismic phases to instead reveal the Appalachian (Alleghanian) crustal suture as a low-angle (〈~15°) southward-dipping interface that soles into a flat-lying mid-crustal detachment. The observed suture geometry implies more than 300 km of head-on shortening across a plate boundary structure similar to the Himalayan mid-crustal detachment, indicating that this mode of deformation has been fundamental in continental collisions over hundreds of millions of years.
    Print ISSN: 0091-7613
    Electronic ISSN: 1943-2682
    Topics: Geosciences
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  • 10
    Publication Date: 2012-06-22
    Description: Rationale: Bone marrow–derived cells to treat myocardial injury improve cardiac function and support beneficial cardiac remodeling. However, survival of stem cells is limited due to low proliferation of transferred cells. Objective: To demonstrate long-term potential of c-kit + bone marrow stem cells (BMCs) enhanced with Pim-1 kinase to promote positive cardiac remodeling. Methods and Results: Lentiviral modification of c-kit + BMCs to express Pim-1 (BMCeP) increases proliferation and expression of prosurvival proteins relative to BMCs expressing green fluorescent protein (BMCe). Intramyocardial delivery of BMCeP at time of infarction supports improvements in anterior wall dimensions and prevents left ventricle dilation compared with hearts treated with vehicle alone. Reduction of the akinetic left ventricular wall was observed in BMCeP-treated hearts at 4 and 12 weeks after infarction. Early recovery of cardiac function in BMCeP-injected hearts facilitated modest improvements in hemodynamic function up to 12 weeks after infarction between cell-treated groups. Persistence of BMCeP is improved relative to BMCe within the infarct together with increased recruitment of endogenous c-kit + cells. Delivery of BMC populations promotes cellular hypertrophy in the border and infarcted regions coupled with an upregulation of hypertrophic genes. Thus, BMCeP treatment yields improved structural remodeling of infarcted myocardium compared with control BMCs. Conclusions: Genetic modification of BMCs with Pim-1 may serve as a therapeutic approach to promote recovery of myocardial structure. Future approaches may take advantage of salutary BMC actions in conjunction with other stem cell types to increase efficacy of cellular therapy and improve myocardial performance in the injured myocardium.
    Keywords: Structure, Growth factors/cytokines, Gene therapy
    Print ISSN: 0009-7330
    Electronic ISSN: 1524-4571
    Topics: Medicine
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