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481.
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483.
We sampled the mussels of the Pearl River along the eastern border of Louisiana, USA, in 1997 and 2007. Hurricane Katrina
followed the pathway of the river in August 2005, and we were interested in detecting any resulting decreases in mussel abundance
or diversity. The mussel assemblage was relatively stable, despite the hurricane and a drought in the Pearl River Basin in
2006 and 2007. We detected no change in average species richness per site, and the total number of mussels collected per site
(e.g., collection per unit effort) actually increased in 2007. Species importance curves comparing the two studies did, however,
suggest a reduction from 29 to 23 species. Monte Carlo simulations and comparisons of assemblage similarity also suggested
that Glebula rotundata increased at the expense of Potamilus purpuratus and Villosa lienosa, possibly because it was more tolerant of salt water intrusion. Eight of 13 mussels with adequate sample sizes had different
adult size structures in the two surveys, either increasing or decreasing in mean shell length during the 10 years. Large
individuals were rare for the two species that decreased in relative abundance in 2007. Semi-quantitative sampling appeared
adequate here to compare relatively long-term changes in mussel diversity and adult size structure. However, more research
on natural variation in assemblage structure and mussel size distributions is needed to understand the importance of disturbances
like hurricanes or droughts. 相似文献
484.
I. Suzanna C. de Wit Siegfried W. de Laat Gerry T. Snoek Karel W. A. Wirtz 《Development, growth & differentiation》1995,37(1):99-109
Phosphatidylinositol transfer protein (PI-TP) was studied in P19 embryonal carcinoma (EC) cells at different stages of retinoic acid (RA) induced differentiation. Western blot analysis indicated an increased expression of PI-TP (35 kDa) during differentiation. Western blots of isoelectric focusing gels showed that the 35 kDa band consisted of the PI-carrying form of PI-TP (pl 5.5) and of a novel, more acidic form of PI-TP (pl 5.4), levels of both of which increased during differentiation. These increased levels were not reflected in the in vitro PI-transfer activity of the cytosolic fraction nor in the mRNA levels as analyzed by northern blotting. By using indirect immunofluorescence it was shown that PI-TP is localized in the cytoplasm and associated with perinuclear Golgi structures and that this distribution is slightly affected during RA-induced differentiation. Immunoprecipitation of PI-TP from [32 P]Pi labeled cells demonstrated that the level of phosphorylation of PI-TP is high in undifferentiated P19 EC cells and low after 5 days of RA-induced differentiation. These results strongly suggest that changes in the levels of PI-TP are intimately connected with changes in the growth characteristics of P19 EC cells during RA-induced differentiation. It remains to be established to what extent this connection is governed by the recent finding that PI-TP is an essential cytosolic factor in stimulating phospholipase C activity. 相似文献
485.
Gerry Shaw 《BioEssays : news and reviews in molecular, cellular and developmental biology》1996,18(1):35-46
Pleckstrin homology (PH) domains are a family of compact protein modules defined by sequences of roughly 100 amino acids. These domains are common in vertebrate, Drosophila, C. elegans and yeast proteins, suggesting an early origin and fundamental importance to eukaryotic biology. Many enzymes which have important regulatory functions contain PH domains, and mutant forms of several such proteins are implicated in oncogenesis and developmental disorders. Numerous recent studies show that PH domains bind various proteins and inositolphosphates. Here I discuss PH domains in detail and conclude that they form a versatile family of membrane binding and protein localization modules. 相似文献
486.
Superoxide dismutase (SOD) is known to protect cells from the lethal effects of ionizing radiation by the dismutation of oxygen radicals. Diethyldithiocarbamate (DDC) is known inhibitor of SOD and may therefore be useful as a radiosensitizer. DDC however, is also a thinly radio protector due to its ability to scavenge radiation induced free radicals. We have shown that DDC. if administered to turnours 1 hour prior to x-irradiation exerts a protective effect, whereas if administered 4 hours prior to irradiation, it radiosensitizes. This time modulation effect is not apparent after neutron irradiation where DDC protects in both situations. We have also examined the effect of DPC on the LD50/30 in mice after total body irradiation. 相似文献