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61.
Teresa Vegas-Vilarrúbia 《Hydrobiologia》1995,310(1):33-46
The distribution of phytoplankton species of a tropical blackwater reservoir is discussed on the basis of spatial differences in water composition and of species abundance and diversity. Spatial heterogeneity in water composition identified three different environments within the reservoir itself: (1) strongly colored waters, high turbidity and iron concentrations at the inflow; (2) calcium enriched, nearly uncolored waters at El Pao Bay; (3) lightly colored water, higher transparency and a higher ratio monovalent to divalent cations in the main body of the reservoir. Three corresponding phytoplankton associations were found. Principal Component Analysis helped to explore the relationship of particular species with the abiotic factors. Among them, water color, turbidity, and mineralization proved to be determinant in habitat diversification. 相似文献
62.
宋光江 李桂信 李启清 孙安堂 宋兴军 杜克明 刘京升SONG Guang-Jiang LI Gui-Xin LI Qi-Qing SUN An-Tang SONG Xing-Jun DU Ke-Ming LIU Jiang-Sheng 《遗传》1995,17(4):1-3
CT所见肝脏肿大占据左右上腹,纠正了既往把肝左叶当做脾大的结论;B超发现前所没有报道的二尖瓣赘生物将给患者终生致残;标准品DS行双向电泳,首次发现其分离为DS1与GS2两个斑点;杂合子、患者尿GAG均出现DS1斑点,而正常人则不出现。实验显示,DS1的出现在杂合子检出和患者确诊上有重要意义。 相似文献
63.
Thomas J. Thekkumkara Jing Du John C. Zwaagstra Kathleen M. Conrad John Krupinski Kenneth M. Baker 《Molecular and cellular biochemistry》1995,152(1):77-86
G-protein coupled Angiotensin II receptors (AT1A), mediate cellular responses through multiple signal transduction pathways. In AT1A receptor-transfected CHO-K1 cells (T3CHO/AT1A), angiotensin II (AII) stimulated a dose-dependent (EC50=3.3 nM) increase in cAMP accumulation, which was inhibited by the selective AT1, nonpeptide receptor antagonist EXP3174. Activation of protein kinase C, or increasing intracellular Ca2+ with ATP, the calcium ionophore A23187 or ionomycin failed to stimulate cAMP accumulation. Thus, AII-induced cAMP accumulation was not secondary to activation of a protein kinase C- or Ca2+/calmodulin-dependent pathway. Since cAMP has an established role in cellular growth responses, we investigated the effect of the AII-mediated increase in cAMP on cell number and [3H]thymidine incorporation in T3CHOA/AT1A cells. AII (1 M) significantly inhibited cell number (51% at 96 h) and [3H]thymidine incorporation (68% at 24 h) compared to vehicle controls. These effects were blocked by EXP3174, confirming that these responses were mediated through the AT1 receptor. Forskolin (10 M) and the cAMP analog dibutyryl-cAMP (1 mM) also inhibited [3H]thymidine incorporation by 55 and 25% respectively. We extended our investigation on the effect of AII-stimulated increases in cAMP, to determine the role for established growth related signaling events, i.e., mitogen-activated protein kinase activity and tyrosine phosphorylation of cellular proteins. AII-stimulated mitogen-activated protein kinase activity and phosphorylation of the 42 and 44 kD forms. These events were unaffected by forskolin stimulated increases in cAMP, thus the AII-stimulated mitogen-activated protein kinase activity was independent of cAMP in these cells. AII also stimulated tyrosine phosphorylation of a number of cellular proteins in T3CHO/AT1A cells, in particular a 127 kD protein. The phosphorylation of the 127 kD protein was transient, reaching a maximum at 1 min, and returning to basal levels within 10 min. The dephosphorylation of this protein was blocked by a selective inhibitor of cAMP dependent protein kinase A, H89-dihydrochloride and preexposure to forskolin prevented the AII-induced transient tyrosine phosphorylation of the 127 kD protein. These data suggest that cAMP, and therefore protein kinase A can contribute to AII-mediated growth inhibition by stimulating the dephosphorylation of substrates that are tyrosine phosphorylated in response to AII. 相似文献
64.
Offshore fluxes of Cu, Zn, Cd, Pb and Hg were calculated based onresidual flow patterns and salinity gradients along the Belgian
coast. Theresidual flow lines along the Belgian coast are more or less parallel to thecoast except in the area where the north-easterly
flowing watermass comingfrom the Channel encounters the south-westerly-oriented Scheldt outflow,forming a residual hydrodynamical
front. From the steady-state salinitypattern, diffusion coefficients perpendicular to the residual flow werededuced; they
ranged from 21 to 108 m2 s-1.
Offshore fluxes of dissolved and particulate trace metals based on diffusiveand mixing processes are calculated. The steady
state profiles of dissolvedmetals show a dilution effect in the coastal waters, reaching an almostconstant concentration in
the marine watermass in the 1981–1983dataset. The ratios of the Scheldt input of trace metals to the totaldissolved offshore
flux vary from 38 to 55% (1981–1983),depending on the kind of metal, and from 55 to 91% (1995–1996).The ratio of the Scheldt
input to the dissolved metal flow parallel to thecoast, is in both periods (1981–1983 and 1995–1996), smallerthan 1%. The
steady-state concentration profiles of particular metalsversus salinity are fairly constant in the coastal-estuarine and marinewatermasses,
but decrease very abruptly from the first to the secondwatermass. Assuming a conservative behaviour of the particular metals,offshore
fluxes and the resulting concentration increases agree fairly wellwith the observed values. The ratios of the Scheldt input
to the particulatetrace metal offshore flux vary between 30 to 46% (1981–1983)and 13 to 37% (1995–1996). The contribution
of the Scheldtestuary to the flows parallel to the coast ranges from 1.6 to 2.9%(1981–1983) and from 0.6 to 1.6% (1995).
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
65.
Previous work in our laboratory led to the isolation of a cadmium (Cd)-resistant variant (Cdr2C10) of the line CHO Chinese Hamster cell having a 10-fold greater resistance to the cytotoxic action of Cd2+ compared with the CHO cell. This resistance was attributed to an increased capacity of the Cd2+-resistant Cdr2C10 subline to induce synthesis of the Cd2+- and Zn2+-binding protein(s), metallothionein(s) (MT). Evidence that Cd2+ behaves as an analog of the essential trace metal, Zn2+, especially as an inducer of MT synthesis, suggested that the Cdr and CHO cell types could be employed to investigate cellular Zn2+ metabolism. In the present study, measurements were made to compare CHO and Cdr cell types for (a) growth as a function of the level of ZnCl2 added to the culture medium, (b) uptake and subcellular distribution of Zn2+, and (c) capacity to induce MT synthesis. The results of these measurements indicated that (a) both CHO and Cdr cell types grew normally (T
d≊16–18 h) during exposures to Zn2+ at levels up to 100 μM added to the growth medium, but displayed abrupt growth inhibition at higher Zn2+ levels, (b) Cdr cells incorporate fourfold more Zn2+ during a 24-h exposure to the maximal subtoxic level of Zn2+ and (c) the CHO cell lacks the capacity to induce MT synethesis while the Cdr cell is proficient in this response during exposure to the maximal subtoxic Zn2+ level. These findings suggest that (a) the CHO and Cdr cell systems will be useful in further studies of cellular Zn2+ metabolism, especially in comparisons of Zn2+ metabolism in the presence and absence of induction of the Zn2+-sequestering MT and (b) a relationship exists between cellular capacity to induce MT synthesis and capacity for cellular
Zn2+ uptake. 相似文献
66.
Modification of oligosaccharide-lipid synthesis and protein glycosylation in glucose-deprived cells 总被引:9,自引:0,他引:9
S J Turco 《Archives of biochemistry and biophysics》1980,205(2):330-339
Incubation of vesicular stomatitis virus-infected glucose-starved baby hamster kidney cells with [35S]methionine results in the synthesis of all viral proteins. However, as judged by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and tryptic peptide mapping, the G protein is abnormally glycosylated. Metabolic labeling of the oligosaccharide-lipid precursors with [3H]mannose for 15 min, followed by Chromatographic and enzymatic analysis, indicates that the radiolabeled lipid-linked oligosaccharides are devoid of glucose in contrast to the glucosylated oligosaccharide-lipids synthesized by cells grown in the presence of glucose. Also, in contrast to control cells, examination of the glycopeptide fraction reveals the presence of [3H]mannose-labeled glycopeptides which are resistant to erado-β-N-acetylglucos-aminidase H and are smaller in size than glycopeptides from mature vesicular stomatitis virus. In order to observe these effects, a minimum time of 5 h of glucose deprivation is necessary and the addition of 55 μm glucose or mannose to the medium reverses these effects. These results indicate that vesicular stomatitis virus-infected BHK cells deprived of glucose are unable to glucosylate the oligosaccharide-lipid intermediates and, consequently, are unable to glycosylate the G protein normally. 相似文献
67.
Margit M.K. Nass 《Gene》1983,21(3):249-255
A precise physical map, containing the structurally and operationally defined D-loop origin, terminal region, and direction of heavy-strand replication, has been constructed for mitochondrial DNA (mtDNA) from ovary (CHO-KI) and lung cells of Chinese hamster (Cricetulus griseus 2 N = 22), and compared with our previously established genome coordinates for mtDNA from Syrian hamster ( Mesocricetus auratus 2 N = 44). All four HpaI sites in Cricetulus are conserved in Mesocricetus (8 sites). Extensive variation exists for hexanucleotides cleaved by EcoRI HindIII PstI. KpnI and BamHI. Sequence divergence between Chinese and Syrian hamster mtDNAs, as reflected from analysis of the mapped recognition sites for these six endonucleases, is estimated as 5–9% base substitutions. mtDNAs from both hamster and several other mammalian species contain a commonly conserved HpaI site in the region of light strand initiation. 相似文献
68.
69.
四种中草药对大鼠半乳糖性白内障氧化还原物质及糖类含量的影响 总被引:1,自引:0,他引:1
对正常和半乳糖性白内障及给中草药的大鼠晶状体中某些吡啶核苷酸成分、糖类、非蛋白质巯基的含量进行了比较。结果表明,在白内障晶状体中,NADPH及非蛋白质巯基的含量明显低于正常晶状体的,而NADP、半乳糖及半乳糖醇的含量明显高于正常晶状体的;当注射半乳糖的同时分别用黄岑、石斛、菟丝子及玉蝴蝶四种中草药水煎剂灌胃,上述变化为基本恢复至正常晶状体的水平。表明四种中草药对晶状体中的异常生化变化具有阻止及纠正作用。 相似文献
70.