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  • 1
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: This study examines the angiotensin II (Ang II) regulation of intracellular free calcium concentration ([Ca2+]i) in astroglia cultured from the hypothalamus and brainstem of the adult rat. Bath perfusion or rapid puffer application of angiotensin II (Ang II) (1–100 nM) increased [Ca2+]i in both polygonal and stellate astroglia when measured using fura-2 imaging fluorescence microscopy. Ang II increased [Ca2+]i in 96.1 and 95.6% of the polygonal and stellate glial cells, respectively. In normal Tyrode's solution (containing 2 mM CaCl2), the Ang II-stimulated increase in [Ca2+]i characteristically showed a biphasic response, i.e., an initial rapid transient peak followed by a sustained, steady-state plateau of free Ca2+. In both cell types, the selective Ang II type 1 receptor subtype (AT1) antagonist losartan (1 µM) inhibited the Ang II-stimulated increase in [Ca2+]i. The selective AT2 antagonist PD 123319 (1 µM) did not inhibit the Ang II-stimulated increase in [Ca2+]i in either cell type. To define the sources of Ca2+ that participate in the Ang II-stimulated increase in [Ca2+]i in astroglia, experiments were performed in a nominally Ca2+-free Tyrode's solution. In either cell type, this resulted in only an initial transient increase of Ca2+ and no sustained plateau of Ca2+ when challenged with Ang II. Thapsigargin (5 µM), cyclopiazonic acid (10 µM), and ryanodine (10 µM), but not caffeine (1–10 mM), inhibited the initial rise in [Ca2+]i. The plateau increase of [Ca2+]i caused by Ang II (100 nM) was reversibly inhibited by both cadmium (100 µM) and nifedipine (10 µM); in contrast, gadolinium (100 µM) had no effect on the plateau increase of [Ca2+]i. These results indicate that Ang II, in physiological concentrations, can activate AT1 receptors to stimulate both Ca2+ release from intracellular stores and Ca2+ influx from the extracellular space to increase [Ca2+]i of polygonal and stellate astroglia.
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  • 2
    ISSN: 1540-8191
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract The role of estrogens in providing atheroprotection has been well documented in both epidemiologic and experimental studies. This phenomenon has traditionally been attributed to the beneficial lipid-modifying effects of estrogens. Yet lipid alterations may not be the sole mechanism of estrogen-mediated cardiovascular protection. Previous studies have utilized models of either diet- or injury-induced atherosclerosis. As such, the interrelationship between estrogens, lipids, and atherosclerosis remains unclear. The purpose of this study was to determine the effect of ovariectomy with or without estrogen replacement on the development of aortic intimal hyperplasia. Although we acknowledge the influence of estrogens on the lipid profile, we hypothesized that estrogens are atheroprotective independent of changes in serum lipids. Twelve Warhill ewes (7–11 years old) were randomized to sham (2 sheep) operation, ovariectomy (OVx-5 sheep), or ovariectomy with 17β-estradiol replacement (OVxE-5 sheep). Serum cholesterol and triglyceride levels were measured at 0, 6, and 12 months. Necropsy was performed at 6 and 12 months with histologic morphometric analysis of the aortoiliac bifurcation. Ovariectomy resulted in intimal thickening in comparison to the sham (p 〈 0.0001) and hormone replacement group (p 〈 0.0001). Serum cholesterol and triglyceride levels were similar and normal (40–60 mg/dl) among all groups. Estradiol abrogates aortic intimal hyperplasia following ovariectomy independent of the hormone's effects on lipid metabolism.
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Ground water monitoring & remediation 19 (1999), S. 0 
    ISSN: 1745-6592
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Geosciences
    Notes: Characterizing mass transfer during in situ air sparging requires knowledge of the size, shape, and interfacial area of air channels. These characteristics were determined by analysis of digital images of air channels passing through submerged glass beads having particle size in the sand range. Pore-scale channeling occurred in all cases. The analysis showed that the air channels were narrower, more tortuous, more closely spaced, and moved nearly vertically through the coarser media. In the finer media, air channels had larger diameter, were spaced further apart, and passed nearly horizontally through the media. The mean diameter of the channels varied between 2.8 and 8.1 mm, and the mean spacing varied between 8.3 and 19.4 mm. Estimates of the area of the air-water interface per unit volume of soil (a0), computed using data from the digital images and an assumed arrangement of channels, ranged from 0.02 to 0.2 mm2/mm3. Larger a0 were obtained for coarser media and uniformly graded media. These estimates of a0 compare well with published values for common packed-column materials and for unsaturated soils.
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  • 4
    Electronic Resource
    Electronic Resource
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Earth and Planetary Sciences 27 (1999), S. 417-462 
    ISSN: 0084-6597
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Geosciences , Physics
    Notes: Abstract Cenozoic extension in the western United States presents a complex interrelation of extension, volcanism, and plate boundary tectonics that defeats simple notions of "active" or "passive" rifting. Forces driving extension can originate at plate boundaries, through basal traction, basal normal forces, or from buoyancy forces internal to the crust and lithospheric mantle. The latter two are most responsible for driving extension where it is observed in the Basin and Range. The complex evolution of the northern Basin and Range probably represents removal or alteration of mantle lithosphere interacting with buoyancy stored in the crust. In contrast, crustal buoyancy forces combined with a divergent plate boundary between about 28 and 16 Ma to drive extension in the southern Basin and Range. The central Basin and Range most likely extended as a result of boundary forces external to itself but arising from buoyancy forces elsewhere in the western United States.
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  • 5
    ISSN: 1600-065X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Summary: T-cell development is a complex and ordered process that is regulated in part by the progressive assembly and expression of antigen receptor genes. T cells can be divided into two lineages based on expression of either an αβ or γδ T-cell antigen receptor (TCR), The genes that encode the TCR β and y chains lie in distinct loci, whereas the genes that encode the TCR a and S chains he in a single locos (TCR α/δ locus). Assembly of TCR variable region genes is mediated by a site-specific recombination process that is common among all lymphocytes. Despite the common nature of this process, recombination of TCR genes is tightly regulated within the context of the developing T cell. TCR β, γ and δ variable region genes are assembled prior to TCR α variable region genes. Furthermore, assembly of TCR β variable region genes is regulated within the context of allelic exclusion. The regulation of rearrangement arid expression of genes within the TCR α/δ locus presents a complicated problem. TCR α and δ variable region genes are assembled at different stages of T-cell development, and fully assembled TCR α and δ variable region genes must be expressed in distinct hneages of T cells, αβ and γδ. respectively We have developed several experimental approaches lo assess the role of cis-acting elements in regulating recombination and expression of TCR genes. Here we describe these approaches and discuss our analyses of the regulation of accessibility of the TCR β and TCR α/δ foci during T-cell development.
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  • 6
    ISSN: 1546-1718
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Medicine
    Notes: [Auszug] Clones containing the complete human UCP2 coding sequence were obtained by PCR amplification of lung and skeletal muscle cDNA using primers designed based on EST sequences from human UCP2 clones in the IMAGE consortium library. The amino acid sequence of human UCP2 is 59% identical to human UCP1 ...
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  • 7
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] When a female mammal makes the transition from virginity to motherhood, she is forced to refocus her activities dramatically. She must adapt to a multitude of new demands by her offspring or risk losing a significant metabolic and genetic investment. She needs to find and remember the location of ...
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  • 8
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Ground water monitoring & remediation 17 (1997), S. 0 
    ISSN: 1745-6592
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Geosciences
    Notes: Field tests were conducted in three boreholes using an ultrasonic testing method to evaluate its ability to assess contact between the seal and riser (casing). The ultrasonic method is used inside the riser without disturbing the riser, seal, or formation soil. The risers were 50-mm-diameter (2-inch) Schedule 40 steel pipes that are used for ground water monitoring wells. Different types of seals were placed around the risers and defects were purposely introduced in the seals to test the ultrasonic method. The ultrasonic response changed as the neat-cement seals cured or hydration of the bentonite seals changed. When adequate moisture was not available, the bentonite seals deteriorated, losing contact with the riser. When adequate moisture was available, however, the seals swelled into contact with the riser. Both conditions were detected with the ultrasonic method. The method also detected the intentional defects, as well as defects that were not intended. The boreholes were excavated to compare results of the ultrasonic tests with the actual condition of the seals. The condition of the seals agreed well with the results of the ultrasonic tests.
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  • 9
    ISSN: 1572-977X
    Keywords: culverts ; culvert trap ; mosquito impoundment ; seine ; fish
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Fish population dynamics in a 24.3 ha mangrove-dominated mosquito impoundment in east-central Florida were examined by seining and culvert traps before and after installation of culverts that established estuarine connection for the first time in 39 years. In a 27-day period following the culvert opening, fish species increased from 9 to 21, while total number of fish in the impoundment decreased. Movement of fishes through culverts in both directions commenced immediately following culvert opening. Recruitment of transient species into the impoundment appeared to key on a single wind-driven high tide event. Such short-term events may be important cues for fish movement into and out of impounded salt marshes.
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  • 10
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 381 (1996), S. 37-41 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] In orogenic belts, intrinsic (buoyancy) and extrinsic (boundary) forces act on the continental lithosphere; determining the relative importance of these forces is fundamental to understanding the dynamics of continental deformation. In the western United States, estimates of gravitational ...
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