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381.
J.S. Eklf M. Gullstrm M. Bjrk M.E. Asplund L. Hammar A. Dahlgren M.C.
hman 《Aquatic Botany》2008,89(3):337-340
Seagrass grazing is an intrinsic disturbance in primarily tropical and subtropical areas. While there is a general parabolic response in seagrass growth to grazing intensity, there is less knowledge on the role of grazing frequency, as well as potential interactions between grazing intensity and frequency. This study experimentally investigated physiological responses in Thalassia hemprichii to simulated (leaf cutting) grazing regimes with different intensities (25% vs. 75%) and frequencies (1 times vs. 3 times) over 35 days in Chwaka Bay (Zanzibar, Tanzania). The results showed that the two high-intensity treatments (75% removal) had 37–41% lower growth rate than the low-intensity/low-frequency treatment, and rhizome sugar and starch content were both affected in a similar way. A 36% lower starch content in the simulated low-intensity/high-frequency regime (25% × 3) compared to the one of low-intensity/low-frequency (25% × 1) also shows an interaction between grazing intensity and frequency. This suggests that high-intensity (and to some extent frequency) grazing regimes, in comparison to low-intensity regimes, could negatively affect T. hemprichii growth, energy reserves, and thereby the ability to deal with additional stress like light limitation or grazing. 相似文献
382.
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384.
Willem C. Hülsmann Marie-Louise Dubelaar L. Elly A. De Wit Niek L. M. Persoon 《Molecular and cellular biochemistry》1988,79(2):137-145
Summary Lipopolysaccharide (LPS), the active principle of certain endotoxins, protein-free perfused in rat hearts leads in 3 h to
a considerable loss of lipoprotein lipase (LPL) activity. In the presence of albumin LPS has virtually no effect. Tumor necrosis
factor (TNF) added instead of LPS had no effects on LPL activity during 3 hin vitro perfusion.
LPS injected into rats intravenously leads within 3 h to severe toxic phenomena amongst which increased capillary permeability.
This was visualized as increased rate of interstitial fluid formation in Langendorff hearts mounted 3 h after rats had been
treated with LPS. LPL activity did not decline in 3 h lasting endotoxemia. Six hours after LPS injection, however, cardiac
LPL activity was considerably lowered, although immunoblotting and immunohistochemistry still showed LPL protein to be present.
These date indicate the presence of a considerable pool of inactive LPL protein in addition to active LPL, that can be released
in the presence of heparin. The LPL activity is lowered by LPS injection after a lag phase of at least 3 h, while capillary
endothelial cells are influenced more rapidly. The relatively late expression of TNF toxicity in cardiomyocytes of the intact
heart is discussed. 相似文献
385.
Summary Tumor Necrosis Factor (TNF) inhibits lipoprotein lipase activity in cultured myocytes and in the Langendorff rat heart after
3 h perfusion with TNF of glucocorticoid-pretreated rats. TNF acutely stimulates glyc(ogen)olysis and concomitantly endogenous
lipolysis. The latter was significantly increased only when rats had been pretreated with glucocorticoid or fed a trierucate-rich
diet. Under these conditions, contractile activity of the Langendorff hearts was acutely increased by TNF The mechanism of
the actue increase of contractile function and the accompanying increased glycolytic and lipolytic activities, by TNF, may
be explained by increased cytosolic Ca2+ and cAMP levels. 相似文献
386.
387.
Marie-Louise Kann Jean-Pierre Fouquet 《Biology of the cell / under the auspices of the European Cell Biology Organization》1993,77(3):311-313
Summary— In hamster and mouse spermatozoa a spectrin immunogold labeling was found under the plasma membrane in the principal piece of the flagellum. During spermatid differentiation, the spectrin labeling was associated with the manchette, a transient microtubular network involved in nuclear shaping and organelle translocation. 相似文献