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921.
Cláudia Fileto Marlene S. Arcifa Aloysio S. Ferrão-Filho Lúcia Helena S. Silva 《Aquatic Ecology》2004,38(4):503-514
The influence of two seston fractions, < 20 μm (nanoplankton) and ≥ 20 μm (microplankton), on growth and reproduction of cladoceran species with different sizes, from Lake Monte Alegre, was evaluated through individual growth and life table experiments. Size, shape and other features of the algae in the fractions were described. The procedure of filtering lake water through a 20 μm net for seston fractionation caused mutual contamination. The smallest cladoceran species, Ceriodaphnia cornuta Sars and Moina micrura Kurz, produced larger clutch sizes and exhibited higher intrinsic rates of population growth (r) in the nanoplankton, despite contamination of their food by inedible algae. The largest species, Simocephalus mixtus Sars, produced larger clutch sizes in the microplankton. There were no differences in juvenile biomass growth between treatments for M. micrura and Daphnia gessneri Herbst, but lower value of the exponential growth rate (g) in the microplankton was significant for M. micrura. Fecundity (eggs/total female) of M. micrura was significantly lower in the microplankton, while D. gessneri did not reproduce in this fraction, at the end of growth experiments. Spines, colonies, cenobium, filaments, hard cell wall, and gelatinous sheaths, represented constraints to cladoceran reproductive performance, besides algae size. Microplankton contamination by nanoplanktonic algae, in the experiments, probably minimized the negative effect of inedible algae. Nanoplankton was more suitable for the smallest species and microplankton for the largest one. 相似文献
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925.
Calcium channels: Molecular pharmacology,structure and regulation 总被引:27,自引:0,他引:27
926.
A high performance liquid chromatographic (HPLC) method was developed for the qualitative and quantitative determination of L-tyrosine and six common tetrahydroisoquinoline alkaloids (papaverine, noscapine, sanguinarine, morphine, codeine and thebaine) of Papaver somniferum. The reversed phase HPLC method yields baseline separation of the alkaloids in 20 min and is achieved using a simple H2O: MeOH linear gradient. Silanol effects commonly associated with the separation of such strongly basic compounds were minimized by the addition of the amine modifier, triethylamine, to the mobile phase. 相似文献
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Phosphate extraction of heart mitochondria results in the release of creatine kinase. Under appropriate conditions phosphate-extracted mitochondria are able to rebind the creatine kinase, either from crude extracts or as the purified enzyme. Heart mitochondria are able to bind up to sevenfold more creatine kinase than they originally contained. The association is specific since the cytoplasmic isozyme from heart (MM) does not bind, and does not interfere with the binding of the mitochondrial isozyme even when MM is present in large excess. It is interesting that although liver mitochondria do not contain the mitochondrial isozyme of creatine kinase they are able to bind approximately the same amount of the enzyme as the heart mitochondria. 相似文献
929.
Patrick O''Connor Susan Fremont Joanne Schneider Heather Dowty Marlene Jaeger Glenn Talaska David Warshawsky 《Journal of chromatography. B, Analytical technologies in the biomedical and life sciences》1997,700(1-2):49-57
7H-Dibenzo[c,g]carbazole, DBC, is a potent environmental liver carcinogen. Liver DNA from mice treated with DBC exhibited seven distinct DBC-DNA adducts as detected by 32P-postlabeling using multidimensional TLC. To improve quantitation and chemically characterize the adducts, DNA samples were hydrlyzed, 32P-postlabeled and the adducts were separated from the unadducted normal nucleotides on TLC using a D1 solvent, 0.65 M sodium phosphate (pH 6.8). Adducts were eluted from the TLC plates with 4.0 M pyridinium formate, concentrated, resuspended in 50% aqueous methanol and injected onto the HPLC; five individual adduct peaks were resolved and collected by this method. This approach will prove useful to decrease analysis time and improve chemical characterization of tightly clustered DNA adducts generated in vivo. 相似文献
930.
Measurements of photosynthetically active radiation through clear freshwater ice 154–158 cm thick varied from 14.8 to 24.8% depending, in this case, primarily on the amount of flocullent material trapped within the ice. Transmittance in one area dropped to less than 1% with the presence of a 3 cm thick snow cover. Extinction coefficients varied from 0.014 to 0.010 cm–1. 相似文献