40 resultados para amph


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Studies were made of the glacial geology and provenance of erratic in the Shackleton Range during the German geological expedition GEISHA in 1987/88, especially in the southern and northwestern parts of the range. Evidence that the entire Shackleton Range was once overrun by ice from a southerly to southeasterly direction was provided by subglacial erosional forms (e.g. striations, crescentic gouges, roches moutonnées) and erratics which probably orriginated in the region of the Whichaway Nunataks and the Pensacola Mountains in the southern part of the range. This probably happened during the last major expansion of the Anarctic polar ice sheet, which, on the basis of evidence from other parts of the continent, occurred towards the end of the Miocene. Till and an area of scattered erratics were mapped in the northwestern part of the range. These were deposited during a period of expansion of the Slessor Glacier in the Weichselian (Wisconsian) glacial stage earlier. This expansion was caused by blockage of the glacier by an expanded Filchner ice shelf which resulted from the sinking of the sea level during the Pleistocene, as demonstrated by geological studies in the Weddell Sea and along the coast of the Ross Sea. Studies of the erratics at the edges of glaciers provided information about rock concealed by the glacier.

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The first part of this thesis includes some topics of a non-geochemical nature but which are of importance in interpreting the geochemistry of nodules. The points covered include their distribution, petrography, structure, mineralogy and internal compositional variations. Part Two includes the geochemistry of both nodules and that of their surrounding sediments, This geochemical study has been divided into firstly, a general geochemical study of both nodules and sediments using a statistical approach to the interpretation of the data, secondly, the regional geochemistry of Pacific and Indian Ocean nodules and sediments, the latter entirely uninvestigated in the past, and thirdly, local variations in the composition of nodules. Throughout, emphasis has been placed on the geochemistry of nodules in terms of their environment of formation.

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Amphiphysin (Amph) is a src homology 3 domain-containing protein that has been implicated in synaptic vesicle endocytosis as a result of its interaction with dynamin. In a screen for novel members of the amphiphysin family, we identified Amph2, an isoform 49% identical to the previously characterized Amph1 protein. The subcellular distribution of this isoform parallels Amph1, both being enriched in nerve terminals. Like Amph1, a role in endocytosis at the nerve terminal is supported by the rapid dephosphorylation of Amph2 on depolarization. Importantly, the two isoforms can be coimmunoprecipitated from the brain as an equimolar complex, suggesting that the two isoforms act in concert. As determined by cross-linking of brain extracts, the Amph1–Amph2 complex is a 220- to 250-kDa heterodimer. COS cells transfected with either Amph1 or Amph2 show greatly reduced transferrin uptake, but coexpression of the two proteins rescues this defect, supporting a role for the heterodimer in clathrin-mediated endocytosis. Although the src homology 3 domains of both isoforms interact with dynamin, the heterodimer can associate with multiple dynamin molecules in vitro and activates dynamin’s GTPase activity. We propose that it is an amphiphysin heterodimer that drives the recruitment of dynamin to clathrin-coated pits in endocytosing nerve terminals.

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The cores described in this report were taken on AMPHITRITE Expedition in Decenber 1963 - February 1964 by Scripps Institution of Oceanography from, the R/V Argo. A total of 148 cores were recovered and are available at Scripps for sampling and study. The coring sites, all in the tropical central Pacific. The AMPHITRITE cores are here briefly described to identify visually distinct units based on lithology, color, texture, or other characteristic unique to an interval of sediment. For determination of lithology, the slides prepared from samples of the cores were examined microscopically in conjuction with the visual examination.