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Within- and between-species patterns of allocation to pulp and seed in vertebrate dispersed plants 总被引:1,自引:0,他引:1
Will Edwards 《Oikos》2005,110(1):109-114
Non-uniform scaling of pulp and seed mass has been shown to alter dispersal probabilities in vertebrate dispersed species. Since dispersal in tropical forests is strongly linked to establishment success, processes determining allocation to pulp and seed are likely to impact on parental fitness, and therefore should be under the control of natural selection. In this study I examine size-dependent dry mass allocation pattern to pulp and seed mass both among and within 20 fruit-producing plant species of tropical rainforest in northeast Queensland, Australia. Reduced major axis analyses using mean values for each species showed significant isometry, indicating that at the community level, plant species that employ vertebrates as a means of seed dispersal tend to allocate an equivalent mean relative proportion of the overall dry weight investment in fruit to pulp. However, identical analyses conducted for each species separately revealed that relationships within individual species do not reflect the inter-specific relationship. These results imply two influences on dry mass allocation to fruit components; the first (within-species allometry) determines how fruits vary within each species. The second (between-species allometry) operates in a similar manner across species to produce equal ratios of mean pulp and seed mass independent of within-species allometries. 相似文献
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5'-Nucleotidase, assayed as 5'-AMPase, has been extensively characterized and established as a stable, quantitative plasma membrane marker in HeLa S3 cells. The membrane 5'-AMPase has a Km of 7.0 microM. Relative affinities of the other 5'-mononucleotides for the enzyme are 5'-GMP > 5'-TMP > 5'-UMP > 5'-CMP. There are activity optima at pH7 and 10; the latter is Mg(2+)-dependent. The membrane preparations have a small amount of acid phosphatase activity that is distinct from 5'-AMPase activity but no alkaline phosphatase. AOPCP, ADP, and ATP are strongly inhibitory. Mg2+, Ca2+, or Co2+ additions do not affect the pH 7.0 activity; Mn2+ activates slightly, whereas Zn2+, Cu2+, and Ni2+ are inhibitory. EDTA slowly inactivates, but removal of the EDTA without the addition of divalent cations restores activity. The inactivation is also substantially reversed by Co2+ or Mn2+, but reactivability by divalent cations decreases with time in EDTA. ConA strongly inhibits, and alpha-methyl-D-mannoside or glucose (the latter much less efficiently) relieves the inhibition, indicating that the 5'-AMPase is a glycoprotein. Histidine is also inhibitory. Ouabain, phloretin, cytochalasin B, cysteine, phenyl-alanine, MalNEt, and IAA are without effect. 5'-AMPase activity codistributes with pulse-bound [3H]ouabain when either of two cell fractionation procedures are used. The 5'-AMPase activity per cell is constant at different cell densities in exponentially growing cells, and activity per unit cell volume remains constant throughout the cell cycle. These properties, together with its absence in other organelles, its stability to storage, its insensitivity to certain experimental manipulations, and its general insensitivity to inhibitors of specific transport systems, make 5'-AMPase a useful quantitative marker in studies on the regulation of HeLa membrane transport systems. Key Words: HeLa, 5'-nucleotidase, plasma membrane marker, non-specific phosphatases, divalent ions, ConA, AOPCP, cell cycle, mitochondria, transport inhibitors. 相似文献
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H H Guldner C Szostecki T Gr?tzinger H Will 《Journal of immunology (Baltimore, Md. : 1950)》1992,149(12):4067-4073
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Differential effect of three-repeat and four-repeat tau on mitochondrial axonal transport 总被引:1,自引:0,他引:1
Will Stoothoff† Phillip B. Jones Tara L. Spires-Jones Daniel Joyner Ekta Chhabra Kathryn Bercury‡ Zhanyun Fan Hong Xie Brian Bacskai Jon Edd§ Daniel Irimia§ Bradley T. Hyman 《Journal of neurochemistry》2009,111(2):417-427
Tau protein is present in six different splice forms in the human brain and interacts with microtubules via either 3 or 4 microtubule binding repeats. An increased ratio of 3 repeat to 4 repeat isoforms is associated with neurodegeneration in inherited forms of frontotemporal dementia. Tau over-expression diminishes axonal transport in several systems, but differential effects of 3 repeat and 4 repeat isoforms have not been studied. We examined the effects of tau on mitochondrial transport and found that both 3 repeat and 4 repeat tau change normal mitochondrial distribution within the cell body and reduce mitochondrial localization to axons; 4 repeat tau has a greater effect than 3 repeat tau. Further, we observed that the 3 repeat and 4 repeat tau cause different alterations in retrograde and anterograde transport dynamics with 3 repeat tau having a slightly stronger effect on axon transport dynamics. Our results indicate that tau-induced changes in axonal transport may be an underlying theme in neurodegenerative diseases associated with isoform specific changes in tau's interaction with microtubules. 相似文献
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AbstractPropylene oxide (PO) is an important industrial compound and a directly acting mutagen. Human exposure to PO can be monitored by the determination of haemoglobin adducts. An immunoassay that quantifies the N-terminal adduct N-(2-hydroxypropyl)valine in whole haemoglobin was developed and its potential usefulness as a tool for biologically monitoring occupational exposure was demonstrated. Analytical reliability was confirmed in a comparative study with GC-MS (range 3.7–992 nmol g?1 haemoglobin (Hb), correlation coefficient 0.99, n=10). The assay has been configured as a competitive enzyme-linked immunosorbent assay to facilitate the rapid throughput of samples. The assay employs a whole blood matrix and has a working range of 2–250 pmol g?1 Hb. It does not appear to be affected by structurally similar metabolites and has been used to determine adducts in human blood samples. The first results in potentially exposed workers indicate the assay's high potential usefulness in routine occupational biomonitoring of exposure to PO. 相似文献
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Ethylene oxide (EO) is an important industrial compound and a directly acting mutagen. Human exposure to it can be monitored by the determination of haemoglobin (Hb) adducts. An immunoassay that quantifies the N-terminal adduct N-(2-hydroxyethyl)valine in whole blood was developed and its potential usefulness as a tool for biologically monitoring occupational exposure demonstrated. Analytical reliability was confirmed in a comparative study with gas chromatography-mass spectrometry (range 0.040-589 nmol g-1 Hb, correlation coefficient 0.98, n=10). The assay was configured as a competitive enzyme-linked immunosorbent assay to facilitate the rapid throughput of samples. The assay uses a whole blood matrix and has a working range of 10-10 000 pmol N-(2-hydroxethyl)valine g-1 Hb. The assay does not appear to be affected by structurally similar metabolites and has been used to determine adducts in human blood samples. The first results from potentially exposed workers indicate the assay might be a powerful tool for the routine occupational biomonitoring of EO exposure. 相似文献