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  • 1
    ISSN: 1573-5117
    Keywords: tropical zooplankton ; bioenergetics ; assimilation efficiency
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Measurements of body mass, carbon content, respiration, growth, and egestion are combined in a model of secondary production by the tropical freshwater shrimp Caridina. The model is developed to permit its direct application to empirical data for abundances and size frequency distributions of field populations. Model calculations combined with population data for offshore Lake Victoria over a period of two years indicate that Caridina consume the equivalent of 2.2% of annual lake primary production. Present net annual secondary production by the shrimp is an order of magnitude greater than the present fishery yield of the lake. Detritus-fed experimental organisms evidently had assimilation efficiencies as low as 10% by model calculation.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 49 (1992), S. 366-377 
    ISSN: 0730-2312
    Keywords: Murine embryonal carcinoma ; Interferon ; F9 cells ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Murine embryonal carcinoma (EC) F9 cells do not produce interferon (IFN) at the protein or RNA level in response to inducing agents, while retinoic acid differentiated F9 cells do produce IFN. A probe was constructed spanning positions -104 to -39 of the human β-IFN upstream regulatory region to examine this developmental control at the level of a transcriptional regulatory mechanism. Gel mobility shift analyses were used to examine this molecular mechanism to determine whether the differential expression of positive or negative trans-acting factors may act to control β-IFN expression in undifferentiated EC cells. These analyses showed that while nuclear extracts from poly-l,C induced L929 cells, in the IFN producing cell line, showed two shifted bands, nuclear extracts from both induced and uninduced F9 cells showed only one shifted band using the -104/ -39 probe. While this single shifted band co-migrated with the faster migrating species of L929 cell extracts, competition analysis revealed differences between the two complexes. An oligonucleotide representing the positive regulatory domain PRDII competed efficiently for the probe when induced F9 cell extracts were examined, but failed to compete when induced L929 cell extracts were examined. In contrast, an oligonucleotide representing the positive regulatory domain PRDI competed very well when induced L929 cell extracts were examined but had only a minimal effect when induced F9 cell extracts were examined. These data suggest the involvement of developmentally regulated transcriptional factors(s) which have yet to be characterized.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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