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  • 1
    ISSN: 1573-0581
    Keywords: volcanology ; hotspot ; Pacific ; Macdonald ; petrology ; Austral Islands
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The southeastern extension of the Austral Islands volcanic chain terminates near 29°S, 140°W at the active Macdonald Seamount. The ‘hotspot’ region near Macdonald consists of at least five other volcanic edifices each more than 500 m high, included in an area about 50–100 km in diameter. On the basis of the sea-floor topography, the southeastern limit of the hotspot area is located about 20 km east of the base of Macdonald, where it is defined by the 3950 m isobath. At the edge of the hotspot area, there is a marked deepening of the seafloor from c.3900 m down to 4000–4300 m. The deeper sea-floor is faulted and heavily sedimented. The Macdonald volcano itself stands 3760 m above the surrounding seafloor, and has a basal diameter of 45 km. Its summit in January 1987 was 39 m below sea level, and it seems likely that Macdonald will emerge at the surface in the near future. Recent (March and November 1986) phreatic explosions on Macdonald Seamount erupted fragments of ultramafic and mafic plutonic blocks together with basic lapilli (volcaniclastic sand). The plutonic blocks have been variably altered and metamorphosed, and in some cases show signs of mineralisation (disseminated sulphides). The blocks presumably come from deeper levels in the volcanic system. The volcanics so far dredged from Macdonald consist of olivine and clinopyroxene cumulus-enriched basalts, evolved basalts, and mugearite. On the basis of incompatible element variations, simple crystal fractionation seems to be controlling the chemical evolution of Macdonald magmas.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The binding of iodinated basic fibroblast growth factor (bFGF) to low-density heparan sulfate proteoglycan purified from the Engelbreth Holm Swarm (EHS) sarcoma was investigated using different techniques. The tumor clearly contained bFGF, the level being comparable to that found in other tissues such as human or bovine brain. 125I bFGF strongly bound to the basement membrane-like matrix of EHS frozen sections as revealed by autoradiography. Iodinated bFGF bound to purified heparan sulfate proteoglycan but not to laminin or collagen type IV, three components isolated from the same tumor. In contrast, acidic fibroblast growth factor (aFGF) displayed negligible binding to heparan sulfate proteoglycan. Binding of bFGF to frozen sections and to purified proteoglycan could be strongly inhibited by heparin and was displaced by an excess of unlabeled factor and completely suppressed after heparitinase and heparinase treatments. Binding was a function of the salt concentration and was abolished at 0.6 M NaCl. Scatchard analysis indicated the affinity site had a Kd of about 30 nM, a value 10-15 higher than that recently reported by Moscatelli (J. Cell. Physiol., 131:123-130, 1987) in the case of the low-affinity binding sites present on the surface of baby hamster kidney (BHK) cells.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The human omentum contains a potent, not yet identified angiogenic activity. The omentum is very vascularized. Therefore, we investigated whether human omental microvascular endothelial cells (HOME cells) express the angiogenic peptide basic fibroblast growth factor (bFGF). Cytosol prepared from HOME cells stimulated DNA synthesis in bovine epithelial lens cells (BEL cells). The mitogenic activity could be neutralized by an anti-bFGF antibody. Basic FGF-like material from the HOME cell cytosol was bound onto a heparin-Sepharose column at 0.6 M and was eluted at 3 M NaCl. The 3 M NaCl eluted material reacted with the specific anti-bFGF antibody in an ELISA and stimulated DNA synthesis. It did not react with a specific anti-acidic fibroblast growth factor (aFGF) antibody. Western blotting experiments using the same bFGF antibody showed the presence of a major band of 17 Kd and a doublet of 20-22 Kd. Northern blotting of nonstimulated HOME cells using a specific 1.4 kb bFGF probe showed the presence of 5 molecular species of 6.6, 3.7, 2.2, 2.0, and 1.0kb. No aFGF mRNA was detected with a specific previously characterized 4.04 kb probe. 12-O-tetradecanoylphorbol 13-acetate (TPA) did not influence significantly the expression of bFGF at the protein and mRNA level in HOME cells. Thus, protein kinase C activation by TPA did not appear to modulate significantly the expression of bFGF for that cell type. Contrastingly, human umbilical vein endothelial cells (HUVE cells), which expressed no bFGF and aFGF mRNA at a basal level, were induced to express bFGF but not aFGF mRNA when stimulated by TPA. These results suggest that the described angiogenic activity could be the bFGF-like mitogen contained in HOME cells and that these cells are different from endothelial cells derived from large vessels (HUVE cells) regarding the expression of bFGF.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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