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41.
N Rakieten B S Gordon A Beaty R W Bates P S Schein F G Standaert 《Proceedings of the Society for Experimental Biology and Medicine. Society for Experimental Biology and Medicine (New York, N.Y.)》1976,151(3):632-635
Hypoglycemic rats bearing insulin-secreting islet-cell adenomas produced by the combined action of streptozotocin and nicotinamide were treated with streptozotocin. Antitumor response was demonstrated by elevation of blood glucose, reduction in plasma and tumor IRI, and histopathologic changes in the beta-cell neoplasm. The rodent tumor model may serve as a predictive system for selection and investigation of mechanisms of action of future antitumor agents to be used in the treatment of malignant insulinoma in man. 相似文献
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43.
Christophe Piscart Alain Manach Gordon H. Copp Pierre Marmonier 《Journal of Biogeography》2007,34(3):524-533
Aim To assess temporal changes in gammarid distribution in Brittany and microhabitat-use overlap between the endangered endemic Gammarus duebeni celticus Stock & Pinkster, 1970 , the expanding natives G. pulex (Linnaeus, 1758) and Echinogammarus berilloni (Catta, 1878), and the introduced G. tigrinus Sexton, 1939.
Location Brittany and adjacent regions in western France.
Methods The spatial and temporal patterns in distribution of gammarids at the scale of Brittany were studied using 351 sites. Longitudinal distributions (from the source to the estuary of the river) and microhabitat-use (substratum type and water velocity) were also considered in selected rivers.
Results At the regional scale, all species occurred together less often than expected statistically, with significant deviations from expected for G. pulex vs. both G. duebeni celticus and G. tigrinus , and for E. berilloni vs. both G. duebeni celticus and G. tigrinus . However, at the microhabitat scale, E. berilloni occurred significantly more often than expected with the endemic G. duebeni celticus , and this appears to be due to similar substratum and water velocity preferences, although at both the regional and microhabitat scales E. berilloni prefers wider streams than G. duebeni celticus . This study reveals a decline in the endangered G. duebeni celticus since 1970.
Main conclusions The longitudinal and local distributions of G. duebeni celticus , and the higher-than-expected co-occurrence of the species with G. pulex , suggest that the decline of the endemic species may be due to changes in the environment and/or interference from native G. pulex , which is expanding its range in Brittany. The results are discussed as regards to the consequences for regional biodiversity. 相似文献
Location Brittany and adjacent regions in western France.
Methods The spatial and temporal patterns in distribution of gammarids at the scale of Brittany were studied using 351 sites. Longitudinal distributions (from the source to the estuary of the river) and microhabitat-use (substratum type and water velocity) were also considered in selected rivers.
Results At the regional scale, all species occurred together less often than expected statistically, with significant deviations from expected for G. pulex vs. both G. duebeni celticus and G. tigrinus , and for E. berilloni vs. both G. duebeni celticus and G. tigrinus . However, at the microhabitat scale, E. berilloni occurred significantly more often than expected with the endemic G. duebeni celticus , and this appears to be due to similar substratum and water velocity preferences, although at both the regional and microhabitat scales E. berilloni prefers wider streams than G. duebeni celticus . This study reveals a decline in the endangered G. duebeni celticus since 1970.
Main conclusions The longitudinal and local distributions of G. duebeni celticus , and the higher-than-expected co-occurrence of the species with G. pulex , suggest that the decline of the endemic species may be due to changes in the environment and/or interference from native G. pulex , which is expanding its range in Brittany. The results are discussed as regards to the consequences for regional biodiversity. 相似文献
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45.
Regulated trafficking of neurotransmitter receptors in excitable cells may play an important role in synaptic plasticity. In addition, agonist-induced endocytosis of nicotinic acetylcholine receptors (nAChRs) in particular might be involved in nicotine tolerance and addiction. The existing evidence concerning regulated internalization of cell-surface nAChRs is indirect and equivocal, however. In the present study, radioligand binding and fluorescence microscopy were used to show that agonists cause substantial endocytosis of nAChRs on cultured myotubes. Exposure to carbachol or nicotine caused a decrease in the intensity of fluorescent labeling of clusters of cell-surface nAChRs that was blocked by low temperature. Overall, myotubes exposed to carbachol or nicotine bound 50-70% less [(125)I]-alpha-bungarotoxin on the cell surface than untreated cells. The effect of carbachol was significant within 5 min, increased progressively for at least 4 h, and had a sensitivity of 100 nM or less. Exposure to carbachol caused the appearance or dramatic expansion of an intracellular pool of nAChRs, which were localized to discrete, largely perinuclear structures. A pulse-chase labeling protocol allowed the selective labeling and localization of nAChRs that had been internalized from the cell surface. In untreated cells, very little internalization of nAChRs occurred over a period of 3 h, indicating that constitutive endocytosis of receptors over this period was minimal. Exposure to carbachol, however, caused a dramatic increase in the endocytosis of nAChRs. These results provide direct evidence that agonists, including the tobacco alkaloid nicotine, can cause substantial endocytosis of cell-surface nAChRs. 相似文献
46.
John D.M. Gordon 《Global Ecology and Biogeography》2001,10(3):333-334
47.
48.
Angela Gordon 《American anthropologist》2002,104(2):676-677
Fleeting Identities: Perishable Material Culture in Archaeological Research. Penelope Ballard Drooker. ed. Carbondale, 1L: Center for Archaeological Investigations, 2001.410 pp. 相似文献
49.
50.
Barry M. Gordon 《Biological trace element research》1987,12(1):153-159
Information concerning the chemical state of trace elements in biological systems generally has not been available. Such information
for toxic elements and metals in metalloproteins could prove extremely valuable in the elucidation of their metabolism and
other biological processes. The shielding of core electrons by binding electrons affect the energy required for creating inner-shell
holes. Furthermore, the molecular binding and symmetry of the local environment of an atom affect the absorption spectrum
in the neighborhood of the absorption edge. X-ray absorption near-edge structure (XANES) using synchrotron radiation excitation
can be used to provide chemical speciation information for trace elements at concentrations as low as 10 ppm. The structure
and position of the absorption curve in the region of an edge can yield vital data about the local structure and oxidation
state of the trace element in question. Data are most easily interpreted by comparing the observed edge structure and position
with those of model compounds of the element covering the entire range of possible oxidation states. Examples of such analyses
will be reviewed. 相似文献