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Manuel Macías Germaine Escames Josefa Leon Ana Coto Younes Sbihi Antonio Osuna Darío Acu?a-Castroviejo 《European journal of biochemistry》2003,270(5):832-840
Increasing evidence suggests that melatonin can exert some effect at nuclear level. Previous experiments using binding techniques clearly showed the existence of specific melatonin binding sites in cell nucleus of rat liver. To further identify these sites, nuclear extracts from rat hepatocytes were treated with different percentages of ammonium sulfate and purified by affinity chromatography. Subsequent ligand blot analysis shows the presence of two polypeptides of approximately 60 and approximately 74 kDa that bind specifically to melatonin. N-Terminal sequence analysis showed that the 60 kDa protein shares a high homology with rat calreticulin, whereas the 74 kDa protein shows no homology with any known protein. The binding of melatonin to calreticulin was further characterized incubating 2-[125I]melatonin with recombinant calreticulin. Binding kinetics show a Kd = 1.08 +/- 0.2 nm and Bmax = 290 +/- 34 fmol.mg protein-1, compatible with other binding sites of melatonin in the cell. The presence of calreticulin was further identified by Western blot analysis, and the lack of endoplasmic reticulum contamination in our material was assessed by Western blot and immunostaining with anti-calnexin Ig. The results suggest that calreticulin may represent a new class of high-affinity melatonin binding sites involved in some functions of the indoleamine including genomic regulation. 相似文献
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A S Perelson 《Biophysical journal》1975,15(7):667-685
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The nucleotide sequence of a 550 base pairs long segment, located between map positions 21 and 22.5 in the adenovirus type 2 genome has been determined. S1 nuclease mapping and sequence analysis of cDNA copies of adenovirus mRNA demonstrated that the established sequence includes the i-leader which is spliced to the 5'-end of certain adenovirus mRNAs (1). The i-leader which is 440 nucleotides long contains an open translational reading frame which is preceded by an AUG triplet and which terminates in the third segment of the tripartite leader. A polypeptide with the same molecular weight as predicted from the DNA sequence was identified by in vitro translation of mRNA which had been selected by hybridization to DNA fragments, containing sequences from the i-leader. The results thus suggest that the i-leader, unlike other adenovirus leader segments, is used for translation. 相似文献
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D Elder 《Differentiation; research in biological diversity》1979,14(3):119-122
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A ward has been set up for adolescents, who, being neither children nor adults, have special needs. It provides a pleasant and enthusiastic atmosphere that allows the patients to mix together socially alties is important, but not more than 20% should be long-stay patients. Those needing intensive care or specialised investigations and those likely to be a disruptive influence are excluded. No serious sexual problems have been encountered. 相似文献
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An investigation of non-steady-state algal growth. I. An experimental model ecosystem 总被引:3,自引:0,他引:3
In order to test rigorously the transient behaviour of mathematical models
of algal growth, detailed laboratory data sets with good temporal
resolution are required. A series of algal growth experiments was conducted
in transient conditions. Monoculture growth of, and competition for
nutrients between, three contrasting species of phytoplankton (the diatom
Thalassiosira pseudonana, the harmful flagellate
Heterosigma carterae and the toxic dinoflagellate
Alexandrium minutum) were investigated in different
temperature, light and nutrient regimes. Although growth dynamics were
qualitatively similar in batch culture, quantitative differences were
evident in the growth response of the different species when grown in
single yield-limiting nutrient conditions in identical physical conditions.
Quantities such as the carbon:nitrogen (C:N) ratio and C and N per cell
varied between species and within species under different growth
conditions. Such results have particular significance to the development of
mathematical models, which commonly represent algal populations as a single
homogeneous group using a single currency such as numbers, C or N. Changes
in light and temperature regime influenced algal growth:
Alexandrium failed to grow at low temperatures, while
specific growth rates of Thalassiosira were more
sensitive to changes in temperature than those of
Heterosigma. Changes in the dominant organism(s)
and/or its size or nutrient status may influence the transfer of nutrients
within the food web. Commonly, mathematical models make cell growth a
function of a single yield-limiting nutrient. Decreased growth rates and
high residual nutrient concentrations in competition experiments indicate
that this approach is unlikely to be successful in conditions of limited
supply of more than one nutrient, where multiple nutrient stresses will be
significant.
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