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61.
Spanish salt lakes: Their chemistry and biota 总被引:9,自引:9,他引:0
A large number of small saline lakes are distributed throughout Spain. Four main lake districts occur from sea level to 1000 m.a.s.l. Most lakes are temporary because of the arid conditions in the Spanish endorheic areas. Many lakes are situated in Tertiary depressions in NE. and S. Spain. Lake basins were formed in karstic areas by hydrologic and aeolian erosion. Saline lakes in NE. Spain occupy areas isolated between river basins. The major ions encountered in these lakes are usually sodium-chloride and magnesium-sulphate; sodium carbonate or sodium-sulphate rich waters also occur.The biota of Spanish salt lakes is related to that of a larger biogeographical region which includes the Mediterranean countries. The main types of salt lakes in Spain include: (1) temporarily mineralized but not highly saline lakes, salinity is less than 7 g l-1. Chara canescens, C. aspera, Zanichellia palustris, Daphnia atkinsoni, Mixodiaptomus incrassatus and Arctodiaptomus wierzejskii are the most characteristic organisms. (2) Temporary salt lakes, salinity fluctuates between 7 and 300 g l-1. Chara galioides, Lamprothamnion papulosum, Daphnia mediterranea, Arctodiaptomus salinus and Cletocamptus retrogressus are the most common species. (3) Permanent salt lakes, Ruppia maritima, Najas marina and Artemia salina are the characteristic organisms. 相似文献
62.
James V. Moroney N. E. Tolbert Barbara B. Sears 《Molecular & general genetics : MGG》1986,204(2):199-203
Summary Six independently isolated mutants of Chlamydomonas reinhardtii that require elevated CO2 for photoautotrophic growth were tested by complementation analysis. These mutants are likely to be defective in some aspect of the algal concentrating mechanism for inorganic carbon as they exhibit CO2 fixation and inorganic carbon accumulation properties different from the wild-type. Four of the six mutants defined a single complementation group and appear to be defective in an intracellular carbonic anhydrase. The other two mutations represent two additional complementation groups.Abbreviations HS
high salt medium which has 13 mM phosphate at pH 6.8
- HSA
high salt plus 36 mM acetate medium
- YA
high salt medium with 4 g yeast extract per L and 36mM acetate
- Arg
arginine
- cia-
CO2 accumulation mutants that cannot grow on low CO2
- Ci
inorganic carbon (CO2+HCO
-
3
)
- CA
carbonic anhydrase
- mt
mating type
Supported in part by the McKnight Foundation and by NSF grant PCM 8005917 and published as journal article 11924 from the Michigan State Agriculatural Experiment Station 相似文献
63.
Summary A pot experiment with lettuce involving three N forms each at six application levels, showed that lettuce can be grown satisfactorily
with a very low nitrate content when supplied with ammonium sulphate and a nitrification inhibitor. For plants growing on
nitrate N, the optimum midrib sap nitrate concentration as maturity approached was about 1400 mg/1 NO3-N. Large losses of mineral N were observed from the peat medium, even in the absence of plants.
A relationship is presented which would enable a lettuce grower to estimate whole-shoot nitrate concentration from a quick
test of midrib sapi.e. NO3-N (mg/kg in fresh shoot) =0.14×NO3-N (mg/l in sap).
Tipburn was worst at intermediate levels of applied N, and was less serious with pure ammonium nutrition than with nitrate. 相似文献
64.
Human blood was sheared between rotating polyethylene disks and plasma hemoglobin measured at intervals to produce kinetic
hemolysis curves (KHC), plotted as free hemoglobin concentration vs time. The KHC produced by blood samples incubated in the
presence of penicillin, streptomycin, gentamicin, and amikacin lie always below those for control samples, indicating a reduction
in hemolysis; this reduction was greater as the drug concentration was increased. Explanations in terms of alterations in
red cell structure were sought by several characterization tests of amikacin-loaded blood samples. Drug-localization studies
demonstrated that significant fractions of the total dosage were associated with the red-cell membrane. Resistive pulse spectroscopy
was used to show how amikacin affected cell size, deformability, and osmotic fragility; results were sensitive to storage
age of the blood. In all cases, the effect of shearing was to reduce cell size, deformability, and osmotic fragility. Mechanisms
for hemolytic protection by drugs are proposed. 相似文献
65.
Claude Vallet-Strouve Charles Tellier Serge Poignant Philippe Boucrot 《The Journal of membrane biology》1985,84(1):73-79
Summary The effect of biliary salts and fatty acids on the bilayer structure of rabbit intestinal brush-border membranes was studied using the nonperturbing probe31P NMR. The broad. asymmetric lineshape of the31P NMR spectrum of isolated brush-border vesicles demostrates that their component phospholipids are organized in extended bilayers. These membranes are not significantly perturbed by incubation with physiological concentrations of biliary salts (3, 9, 18mm), demonstrating that the vesicles are highly stable, corresponding to their biological function. However, the emergence of a narrow peak superimposed on the broad lineshape indicates that a small proportion of the membrane phospholipids has reached isotropic motion, which may correspond to external or internal micellar structures. Incubation with mixed micelles of fatty acids and taurochlorate show that long-chain fatty acids enhance the membrane-perturbing effect of taurocholate while short-chain, watersoluble fatty acids do not, suggesting a difference in the absorption mechanisms. 相似文献
66.
67.
Magnus Appelberg 《Hydrobiologia》1985,121(1):19-25
During exposure to soft water, acidified to pH 4.0, the haemolymph concentrations of Na+, K+, and Cl– decreased whereas the Ca2+ concentration fluctuated in Astacus astacus. The haemocyte content of K+ decreased from 9% to 2% of the total haemolymph K+ content after exposure to pH 3.7 for 3 days. Within 14 days, 250 µg Al3+ l–1, as Al2(SO4)3 at pH 5.0, reduced the haemolymph Na+ content in Astacus astacus and Pacifastacus leniusculus, however, the effects were less pronounced than earlier reported for fish. Disturbed ion regulation, mainly depending on low pH, is thought to contribute to the absence of these species in acid waters. 相似文献
68.
In Mono Lake (California), a large saline lake, chlorophyll concentrations in the euphotic zone increased from 4 to 45 µg l–1 between July and October 1979. These seasonal changes in chlorophyll are detectable on imagery obtained with the multispectral scanner on Landsat. Computer-compatible tapes of Landsat images were normalized for solar zenith and corrected for atmospheric scatter and absorption to obtain Landsat band 4 emittances (W m–2 str–1) of 13.4 ± 0.5 when chlorophyll was 4 µg l–1 and 4.6 ± 0.3 when chlorophyll was 45 µg l–1. Lake wide, spatial heterogeneity of chlorophyll of 2 µg l–1 in July and 8 µg l–1 in October was not detectable on the Landsat imagery. 相似文献
69.
Osmotic potentials and individual epidermal cell turgor pressures were measured in the leaves of seedlings of Suaeda maritima growing over a range of salinities. Leaf osmotic potentials were lower (more negative) the higher the salt concentration of the solution and were lowest in the youngest leaves and stem apices, producing a gradient of osmotic potential towards the apex of the plant. Epidermal cell turgor pressures were of the order of 0.25 to 0.3 MPa in the youngest leaves measured, decreasing to under 0.05 MPa for the oldest leaves. This pattern of turgor pressure was largely unaffected by external salinity. Calculation of leaf water potential indicated that the gradient between young leaves and the external medium was not altered by salinity, but with older leaves, however, this gradient diminished from being the same as that for young leaves in the absence of NaCl, to under 30% of this value at 400 mM NaCl. These results are discussed in relation to the growth response of S. maritima. 相似文献
70.
C L Wood M S O'Dorisio L M Vassalo W B Malarkey T M O'Dorisio 《Regulatory peptides》1985,12(3):237-248
The vasoactive intestinal polypeptide (VIP) receptor was characterized on the GH3 rat pituitary tumor cell line using competitive binding studies with peptides having sequence homology with VIP. Further studies investigated receptor coupling to the adenylate cyclase complex by measurement of cAMP levels. Finally, the molecular weight of the receptor was estimated by affinity labeling techniques. Studies using 125I-VIP and unlabeled competing peptides revealed a single class of high affinity binding sites with a dissociation constant (KD) of 17 +/- 2 nM (mean +/- S.E.M.) for VIP, 275 +/- 46 nM for peptide histidine isoleucine (PHI), and 1380 +/- 800 nM for human pancreatic growth hormone releasing factor (GHRF). VIP and PHI each stimulated intracellular cAMP accumulation in a dose-dependent manner; both peptides demonstrated synergism with forskolin. In contrast, GHRF neither stimulated accumulation of cAMP nor demonstrated synergism with forskolin. VIP plus PHI (1 microM each) caused no significant increase in cAMP over either VIP or PHI alone, implying that the two peptides act through the same receptor. Covalent crosslinking of 125I-VIP to its binding site using either disuccinimidyl suberate (DSS) or ethylene glycol bis(succinimidyl succinate) (EGS) was followed by SDS-PAGE and autoradiography. The result is consistent with an Mr 47 000 VIP-binding subunit comprising or being associated with the VIP receptor of GH3 pituitary tumor cells. 相似文献