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871.
Eutrophication of the Dutch Wadden Sea: External nutrient loadings of the Marsdiep and Vliestroom basin 总被引:1,自引:0,他引:1
Henk W. van der Veer Wim van Raaphorst Magda J. N. Bergman 《Helgoland Marine Research》1989,43(3-4):501-515
The increasing P and N content in the two main tidal basins in the western Dutch Wadden Sea, the Marsdiep and the Vliestroom
basin, has been reconstructed from the 50s onwards. The area is enriched with nutrients by two sources both originating from
the river Rhine, one being the discharge from Lake IJssel and the other the exchange with the coastal zone of the North Sea.
Due to a buffering by Lake IJssel for about 15–20 years, the eutrophication of the western Wadden Sea showed a time lag compared
with the continuously increasing nutrient concentrations in the river Rhine and the coastal zone of the North Sea. At present,
the primary production in part of the area still seems to be nutrient limited in summer, while loadings have already been
decreasing in recent years. So far, no severe, negative effects on the ecosystem have been reported. Some remarks are made
on the eutrophication in other parts of the Dutch' Wadden Sea in relation to the hydrographic characteristics of these areas.
Presented at the VI International Wadden Sea Symposium (Biologische Anstalt Helgoland, Wattenmeerstation Sylt, D-2282 List,
FRG, 1–4 November 1988)
Publication No. 18 of the project “Ecological Research of the North Sea and Wadden Sea” (EON) 相似文献
872.
G J Smith S M Le Mesurier M L de Montfort A W Lykke 《Cell biology international reports》1984,8(2):161-169
Epithelial cell strains, designated NAL, have been established from normal lungs of adult female Balb/c mice. The ultrastructural characteristics, effect of dexamethasone on cellular morphology and proliferation rate, and the cytoskeletal protein pattern of NAL suggests that these cell strains may be related to a urethane-induced mouse lung adenoma cell strain NUL and to a metastasizing mouse lung tumour cell line CMT. NAL exhibited no anchorage-independent growth under normal conditions, however extensive passaging in the presence of 5 X 10(-6)M dexamethasone resulted in a colony forming efficiency in soft agar of 8.4% at passage number 30. 相似文献
873.
874.
Summary Clinical, cytogenetic, autoradiographic, fluorescence microscopic and dermatoglyphic data of a boy with 48,XYY,21+ karyotype are reported. The child had some clinical anomalies common in Down's syndrome. DNA replication of the 2 Y chromosomes was synchronous in all labelled metaphases. It was possible to distinguish the two Y's from the pairs No. 21-22 under the fluorescence microscope and single as well as double Y bodies were demonstrated in buccal mucosa cells. Dermatoglyphic investigation revealed some features typical for mongolism. 相似文献
875.
Magda A. El-Meleigy 《Biological trace element research》1992,34(2):177-183
The presence of copper in the growth medium induces the biosynthesis of several low-mol-wt copper ogano-chelators in Aspergillus fumigatus and Penicillium chrysogenum. By use of P. chrysogenum, we were able to prepare several low-mol-wt metallothionein chelators, as well as several short-chain copper chelatins. The amino acid composition of a chelatin of mol wt approx 799 Da revealed the presence of cysteine, glutamic acid, glycine, and leucine. Use of A. fumigatus led to fewer copper chelators and one very short-chain peptide: a chelatin of mol wt approx 624 Da. composed of four amino acids, asparagine, glutamic acid, cysteine, and glycine. These results may confirm our assumption that fungi detoxify the deleterious action of toxic elements by producing high levels of heavy metal chelators/chelatins. 相似文献
876.
R Pérez-Tamayo I Montfort E Tello A Olivos 《International journal for parasitology》1992,22(1):125-129
In experimental acute amebic liver abscess, produced in hamsters by the intraportal inoculation of 1 x 10(6) axenic trophozoites of Entamoeba histolytica strain HM-1, we examined the blood perfusion of the lesions 5, 10, 24 and 72 h after injection of the parasites. India ink introduced into the portal circulation filled all liver vessels but was systematically excluded from even the earlier amebic lesions. The absence of serum proteinase inhibitors from the lesions may allow the participation of amebic proteinases in the causation of tissue necrosis. 相似文献
877.
No Zwaig Rosa Nagel de Zwaig Toms Istúriz Magda Wecksler 《Journal of bacteriology》1973,114(2):469-473
A spontaneously arising regulatory mutant of the gluconate system in Escherichia coli was isolated. This mutant became constitutive, probably in one step, for gluconate high-affinity transport, gluconokinase, and gluconate-6-P dehydrase. The mutation involved (gntR18) is cotransducible with asd. Pseudorevertants, derived from a mutant (M2) that shows a long lag for growth on gluconate mineral medium, were also isolated and characterized. They give constitutive levels of gluconokinase and gluconate-6-P dehydrase but lack high-affinity transport function. Genetic experiments performed with one of these pseudorevertants (M4) indicate that it carries a secondary mutation in the gntR gene. The M4 phenotype is thus the result of the interaction of expression of a constitutive mutation (gntR4) with the mutation of strain M2 (gntM2). 相似文献
878.
Angelo C. Pinto Paul M. Baker Benjamin Gilbert Richard Pinchin Francisco A.M. Reis Magda S. Waineraich Dorothea H.T. Zocher 《Phytochemistry》1980,19(11):2486-2487
The isolation of (20R)-20-hydroxy-24-methylenedammar-3-one from Vellozia stipitata is described. 相似文献
879.
Hydrogels that mimic the natural extracellular matrix (ECM) are used in three-dimensional cell culture, cell therapy, and tissue engineering. A semi-synthetic ECM based on cross-linked hyaluronana offers experimental control of both composition and gel stiffness. The mechanical properties of the ECM in part determine the ultimate cell phenotype. We now describe a rheological study of synthetic ECM hydrogels with storage shear moduli that span three orders of magnitude, from 11 to 3 500 Pa, a range important for engineering of soft tissues. The concentration of the chemically modified HA and the cross-linking density were the main determinants of gel stiffness. Increase in the ratio of thiol-modified gelatin reduced gel stiffness by diluting the effective concentration of the HA component. 相似文献
880.