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1.
在温室条件下,采用盆栽根箱培养的方法研究盐胁迫下I 69杨(PopulusdeltoidesBartr.cv.'Lux')和NL 1381杨〔PopulusdeltoidesBartr.cv.'Lux'×P.euramericana(Dode)GeninierCL'I 45 51'〕根际、非根际土壤盐分分布特征。盐处理浓度共设3个水平:CK(NaCl0g kg)、处理A(NaCl1g kg)和处理B(NaCl2g kg),采用完全随机设计。结果表明,2个杨树无性系根际水溶性K+亏缺,水溶性Na+、Ca2+和Mg2+富集。K+的亏缺率及Na+的富集率随NaCl处理浓度的增大而减小,Ca2+和Mg2+的富集率在非盐渍条件下最低,处理A达最高,处理B较处理A略有下降。在盐胁迫下,无性系NL 1381杨根际土壤Na+的浓度和电导率均低于无性系I 69杨,可以有效减轻盐分对根系的渗透胁迫,相对而言具有较强的抗盐性。  相似文献   

2.
Two microanalytical techniques were used to investigate the inorganic cation content and distributions in birch (Betula verrucosa Ehrh.) pollen. With intact pollen grains. X-ray microanalysis (EDX) could only give a mean ionic composition. Secondary Ion Microscopy and Spectrometry (SIMS) appeared to be a more suitable technique to image ion distributions in the different pollen structures. This was carried out with samples prepared using a new vapour phase technique designed to improve ion retention. Transmission electron microscopy (TEM)showed good structural preservation of the samples. Monovalent ion (K+, Na+) distribution showed features different from those of the divalent cations (Ca2+, Mg2+). In the vegetative cell, the alkaline cations were mainly distributed in the most internal part of the cytoplasm and they were probably associated with starch grains or concentrated in dry vacuoles. Calcium distribution correlated well with the areas in the cytoplasm of the vegetative cell containing a dense network of mitochondria and endoplasmic reticulum. Within the pollen grain, the sperm cell appeared to contain the most calcium. Calcium was also abundant in the sporoderm. These results reveal the potential of SIMS for pollen studies that include germination, the monitoring of air pollutants and the allergens-ion interactions.  相似文献   

3.
Intracellular Mg2+ concentration ([Mg2+]i) was measured in rat ventricular myocytes with the fluorescent indicator furaptra (25 degrees C). After the myocytes were loaded with Mg2+, the initial rate of decrease in [Mg2+]i (initial Delta[Mg2+]i/Deltat) was estimated upon introduction of extracellular Na+, as an index of the rate of Na+-dependent Mg2+ efflux. The initial Delta[Mg2+]i/Deltat values with 140 mM [Na+]o were essentially unchanged by the addition of extracellular Ca2+ up to 1 mM (107.3+/-8.7% of the control value measured at 0 mM [Ca2+]o in the presence of 0.1 mM EGTA, n=5). Intracellular loading of a Ca2+ chelator, either BAPTA or dimethyl BAPTA, by incubation with its acetoxymethyl ester form (5 microM for 3.5 h) did not significantly change the initial Delta[Mg2+]i/Deltat: 115.2+/-7.5% (seven BAPTA-loaded cells) and 109.5+/-10.9% (four dimethyl BAPTA loaded cells) of the control values measured in the absence of an intracellular chelator. Extracellular and/or intracellular concentrations of K+ and Cl- were modified under constant [Na+]o (70 mM), [Ca2+]o (0 mM with 0.1 mM EGTA), and membrane potential (-13 mV with the amphotericin-B-perforated patch-clamp technique). None of the following conditions significantly changed the initial Delta[Mg2+]i/Deltat: 1), changes in [K+]o between 0 mM and 75 mM (65.6+/-5.0% (n=11) and 79.0+/-6.0% (n=8), respectively, of the control values measured at 140 mM [Na+]o without any modification of extracellular and intracellular K+ and Cl-); 2), intracellular perfusion with K+-free (Cs+-substituted) solution from the patch pipette in combination with removal of extracellular K+ (77.7+/-8.2%, n=8); and 3), extracellular and intracellular perfusion with K+-free and Cl--free solutions (71.6+/-5.1%, n=5). These results suggest that Mg2+ is transported in exchange with Na+, but not with Ca2+, K+, or Cl-, in cardiac myocytes.  相似文献   

4.
F Noel  R S Pardon 《Life sciences》1989,44(22):1677-1683
Vanadate inhibitory effects on Na+, K+-ATPases from carcass of Schistosoma mansoni and from lamb kidney outer medulla were compared in the presence of various concentrations of Na+, K+ and Mg2+. Depending on the ionic conditions, the schistosomal Na+, K+-ATPase was 2.4- to 175-fold less sensitive to vanadate than the lamb kidney enzyme. In 100 mM Na+, 3 mM K+ and 3 mM Mg2+, schistosomal Na+, K+-ATPase was surprisingly resistant to vanadate (I50 = 944 microM). The difference in vanadate sensitivity between schistosomal and lamb Na+, K+-ATPases may be due to a species difference in the efficacy of Na+, K+ and Mg2+ in promoting conformational changes between E1 and E2 forms of the enzyme.  相似文献   

5.
M Bijak 《Folia biologica》1989,37(1-2):3-11
Daily changes in Na+, K+, Ca2+ and Mg2+ contents in the cingulate cortex of mice housed under controlled light/dark (LD) conditions were investigated for a 24-hour period in spring, summer, autumn and winter. The total ion content in the mineralized tissue was evaluated by absorption/emission flame spectrophotometry. In nearly all the tested cation contents significant daily concentration changes were found with a maximum in the dark phase of the LD cycle. The differences in wave form and mean cingulate cortex ion contents throughout the year suggest that the rhythms undergo seasonal variations. The functional importance of daily and anual fluctuations in the brain cation concentrations has been discussed.  相似文献   

6.
K+-dependent phosphatase and Mg2+, Na+, K+-ATPase were studied under the activating effect of surfactant homologs of the alkyl sulphate series with the hydrocarbon radical long chain C4-C15. The homologs are shown to activate the enzymes when they are in the molecular-disperse but not in micellar state. A clear regularity is observed in the effect of these surfactants on K+-phosphatase depending on the length of the hydrocarbon radical chain: the degree of the activating effect rises with the chain lengthening, reaching the maximum value when the number of carbon atoms is 12. The lower and upper bounds of the alkyl sulphate hydrocarbon radical chain length necessary for manifestation of the activating effect shift somewhat for K+-dependent phosphatase as compared with Mg2+, Na+, K+-ATPase. The data obtained evidence for a stronger stability of the phosphatase to a destructive effect of the surfactants as compared with transport ATPase.  相似文献   

7.
A current state of researches on mechanisms of ion homeostasis regulation in the specific conditions of the uncontrolled malignant tumor growth (mainly in carcinomas) concerning the contribution of Na+,K+-ATPase, plasma membrane and sarco(endo)plasmic reticulum Ca2+-ATPases has been reviewed. Particular attention has been focused on the molecular and biochemical links providing the redistribution of the transporting ATPases isozyme pattern for the regulatory requirements of the cell signaling pathways at stable proliferation and viability in malignancy.  相似文献   

8.
Transport of H+, K+, Na+ and Ca++ in Streptococcus   总被引:6,自引:0,他引:6  
Summary The streptococci differ from other bacteria in that cation translocations (with the possible exception of one of the K+ uptake systems) occur by primary transport systems, i.e., by cation pumps which use directly the free energy released during hydrolysis of chemical bonds to power transport. Transport systems in other bacteria, especially for Na+ and Ca++, are often secondary, using the free energy of another ion gradient to drive cation transport. In streptococci H+ efflux occurs via the F1F0-ATPase. This enzyme is composed of eight distinct subunits. Three of the subunits are embedded in the membrane and form a H+ channel; this is called the F0 portion of the enzyme. The other five subunits form the catalytic part of the enzyme, called F1, which faces the cytoplasm and can easily be stripped from the membrane. Physiologically, this enzyme functions as a H+-ATPase, pumping protons out of the cell to form an electrochemical proton gradient, . The F1F0-ATPase, however, is fully reversible and if supplied with Pi, ADP and a + of sufficient magnitude (ca –200 mv) catalyzes the synthesis of ATP. Streptococcus faecalis can accumulate K+ and establish a gradient of 50 000:1 (in>out) under some conditions. Uptake occurs by two transport systems. The dominant, constitutive system requires both an electrochemical proton gradient and ATP to operate. The minor, inducible K+ transport system, which has many similarities to the K+-ATPase of the Kdp transport system found in Escherichia coli, requires only ATP to power K+ uptake.Sodium extrusion occurs by a Na+/H+-ATPase. Exchange is electroneutral and there is no requirement for a . The possibility that the Na+/H+-ATPase may consist of two parts, a catalytic subunit and a Na+/H+ antiport subunit, is suggested by the finding that damage to the Na+ transport system either through mutation or protease action leads to the appearance of -requiring Na+/H+ antiporter activity.Ca++ like Na+ is extruded from metabolizing, intact cells. Transport requires no but does require ATP. Reconstitution of Ca++ transport activity with accompanying Ca++-stimulated ATPase activity into proteoliposomes suggests that Ca++ is transported by a Ca++-translocating ATPase.Where respiring organelles and bacteria use secondary transport systems the streptococci have developed cation pumps. The streptococci, which are predominantly glycolyzing bacteria, generate a much inferior to that of respiring organisms and organelles. The cation pumps may have developed simply in response to an inadequate .Abbreviations electrochemical potential of protons - membrane potential - pH pH gradient - p proton-motive force - DCCD N,Na1-dicyclohexlcarbodiimide - TCS tetrachlorosalicylanilide - FCCP carbonylcyanide-p-trifluoromethylphenylhydrazone - CCCP carbonylcyanie-m-chlorophenylhydrazone - TPMP+ triphenylmethyl phosphonium ion - DDA+ dibenzyldimethylammonium ion - Hepes 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid - EGTA ethyleneglycol-bis (amino-ethyl-ether)-N,N-tetraacetic acid  相似文献   

9.
Summary A theory for Na+, K+ and Ca2+ competitive adsorption to a charged membrane is used to explain a number of experimental observations in smooth muscle. Adsorption is described by Langmuir isotherms for mono- and divalent cations which in turn are coupled in a self-consistent way to the bulk solution through the diffuse double layer theory and the Boltzman equations. We found that the dissociation constants for binding of Na+, K+ and Ca2+ in guinea pig taenia coli areca. 0.009, 1.0, and 4×10–8 m, respectively. Furthermore, the effect of a Ca2+ pump that maintains free surface Ca2+ concentration constant is investigated. A decrease in intracellular Na+ content results in an increased Ca2+ uptake; part of this uptake is due to an increase in surface-bound Ca2+ in an intracellular compartment which is in contact with the myofilaments. Variations in the amount of charge available to bind Ca2+ and the surface charge density are studied and their effect interpreted in terms of different pharmacological agents.  相似文献   

10.
Na+-ATPase activity of a dog kidney (Na+ + K+)-ATPase enzyme preparation was inhibited by a high concentration of NaCl (100 mM) in the presence of 30 microM ATP and 50 microM MgCl2, but stimulated by 100 mM NaCl in the presence of 30 microM ATP and 3 mM MgCl2. The K0.5 for the effect of MgCl2 was near 0.5 mM. Treatment of the enzyme with the organic mercurial thimerosal had little effect on Na+ -ATPase activity with 10 mM NaCl but lessened inhibition by 100 mM NaCl in the presence of 50 microM MgCl2. Similar thimerosal treatment reduced (Na+ + K+)-ATPase activity by half but did not appreciably affect the K0.5 for activation by either Na+ or K+, although it reduced inhibition by high Na+ concentrations. These data are interpreted in terms of two classes of extracellularly-available low-affinity sites for Na+: Na+-discharge sites at which Na+-binding can drive E2-P back to E1-P, thereby inhibiting Na+-ATPase activity, and sites activating E2-P hydrolysis and thereby stimulating Na+-ATPase activity, corresponding to the K+-acceptance sites. Since these two classes of sites cannot be identical, the data favor co-existing Na+-discharge and K+-acceptance sites. Mg2+ may stimulate Na+-ATPase activity by favoring E2-P over E1-P, through occupying intracellular sites distinct from the phosphorylation site or Na+-acceptance sites, perhaps at a coexisting low-affinity substrate site. Among other effects, thimerosal treatment appears to stimulate the Na+-ATPase reaction and lessen Na+-inhibition of the (Na+ + K+)-ATPase reaction by increasing the efficacy of Na+ in activating E2-P hydrolysis.  相似文献   

11.
12.
The concentration variability of Ca, Mg, Na, K ions in the haemolymph and urine has been analyzed in Procambarus clarkii during interecdysis instar, the animals having been kept under several temperature conditions (10, 15, 20, 25, 30 degrees C) during two different periods of time (48 h and 7 days). The environmental temperature did not affect the concentration of sodium and calcium in the haemolymph. Nevertheless the above parameter had an effect on the concentration of potassium and magnesium in the haemolymph as well as on the concentration of the four cations considered in the urine of Procambarus clarkii. No significant differences have been found in relation to the time of exposure.  相似文献   

13.
M Roux  M Bloom 《Biochemistry》1990,29(30):7077-7089
The binding of calcium, magnesium, lithium, potassium, and sodium to membrane bilayers of 5 to 1 (M/M) 1-palmitoyl-2-oleoylphosphatidylcholine (POPC) and 1-palmitoyl- 2-oleoylphosphatidylserine (POPS) was investigated by using deuterium nuclear magnetic resonance (2H NMR). Both lipids were deuteriated on their polar headgroups, and spectra were obtained at 25 degrees C in the liquid-crystalline phase as a function of salt concentration. The spectra obtained with calcium were correlated with 45CaCl2 binding studies to determine the effective membrane-bound calcium at low calcium binding, up to 0.78 calcium per POPS. Deuterium quadrupolar splittings of both POPC and POPS headgroups were shown to be very sensitive to calcium binding. The behavior of these two headgroups over a wide range of CaCl2 concentrations suggests that Ca2+ binding occurs in at least two steps, the first step being achieved with 0.5 M CaCl2, with a stoichiometry of 0.5 Ca2+ per POPS. Correlations of the deuterium Ca2+ binding data with related data obtained after incorporation of a cationic integral peptide showed that the effects of these two cationic molecules of the POPS headgroup are qualitatively similar, and provided further support for two-step Ca2+ binding to the POPC/POPS 5:1 membranes. The corresponding data obtained with magnesium, lithium, and potassium indicate that these cations interact with both the choline and serine headgroups. The amplitudes of headgroup perturbations could be partly correlated to the relative affinities of the metallic cations for the lipid membrane. The two-step binding described with Ca2+ appears to be relevant to the Mg2+ data, and in certain limits to the Li+ data. The data were interpreted in terms of conformational changes of the lipid headgroups induced by an electric field due to the charges of the membrane-bound metallic cations. A conformational change of the serine headgroup induced by the membrane-bound charges is proposed. We propose that the metallic cations can be differentiated on the basis of their respective spatial distribution functions relative to the choline and serine headgroups. According to this interpretation, the divalent cations Ca2+ and Mg2+ are more deeply buried in the membrane than monovalent Na+ and K+, the case of Li+ being intermediate of the latter two. This conclusion is discussed in relation to fundamental theories of the spatial distribution of ions near the interface between water and smooth charged solid surfaces.  相似文献   

14.
The accumulation ratio of a permeant cation under steady-state conditions after active uptake, is defined as: ({cati}{cat0})1z, where Z is the valence of the cation, and {cati} and {cat0} are the internal and external cation activities, respectively. The electrogenic proton pump predicts that the accumulation ratio should be independent of (i) the chemical structure of the cation and (ii) the degree of permeability of the membrane to cations. Furthermore the accumulation ratio should be the same for all permeant cation species simultaneously present. In the present study it is found that under steady-state conditions: (i) the accumulation ratio is not the same for potassium in the presence of valinomycin, for tetrapropylammonium in the presence of tetraphenylboron, and for calcium in the presence of acetate; (ii) the accumulation ratio is not identical for two cations such as potassium and sodium present simultaneously in the presence of gramicidin; (iii) the accumulation ratio is dependent on the external carrier concentration, such as valinomycin or tetraphenylboron. It is concluded that the cation distribution ratios under steady-state conditions are not compatible with the predictions of the electrogenic proton pump model.  相似文献   

15.
The relationship between Pb2+ accumulation and cation (K+, Mg2+, Ca2+) release in Saccharomyces cerevisiae was extensively investigated. As Pb2+ accumulation proceeded, the release of cellular metal ions such as K+, Mg2+ and Ca2+ was concomitantly released within 24 h, thereafter Pb2+ penetrated into the inner cellular parts and consequently plasmolysis of the cell was observed by TEM analysis. Pb2+ accumulation process in S. cerevisiae after 24 h was metabolism-independent because of the absence of cell viability. As the cell storage time was prolonged, the released amount of K+ was markedly increased, while the amount of accumulated Pb2+ was nearly constant regardless of cell storage time and the time required to reach an equilibrium state was shortened. The autoclaved cells had less Pb2+ accumulation capacity than the untreated cells, and the amounts of released K+ and Mg2+ were very low due to the denaturation of cell surface and cell membrane.  相似文献   

16.
17.
A method for the determination of nanomole amounts of P and major cations in samples of dried plant tissue is described. Samples weighing 2-7 mg were digested by refluxing tissue in a mixture of perchloric and nitric acids, under conditions which minimized the hazards associated with perchloric acid digestion. In most tissues analyzed, reproducibility between triplicate samples was less than +/- 5%. However, where the amount of P in the tissue was very low (samples contained about 50 nmol P each), the variation between triplicates was greater.  相似文献   

18.
Purified myometrium cells plasma membrane Ca2+, Mg(2+)-ATPase was reconstitute in liposomes in functionally active state by the method of cholate dialysis: it showed ATP-hydrolase activity increased by 0.8 microM A23187 average 4 times and it showed Mg2+, ATP-dependent Ca(2+)-transporting activity. Reconstituted system transported Ca2+ at an initial rate of 114.4 +/- 16.3 nmol.min-1.mg-1 with the stoichiometry Ca2+: ATP = 1: (3.2-3.7). Calmodulin increased by 30% the initial rate of Ca(2+)-accumulation by the proteoliposomes with reconstituted Ca2+, Mg(2+)-ATPase; 0.1 mM orthovanadate decreased by 80% Ca(2+)-accumulation by this system. Ca2+, Mg(2+)-ATPase reconstituted in liposomes is just Ca(2+)-transporting ATPase of the plasma membrane. Obtained enzyme preparate can be utilised for study of the properties of this important energy-dependent Ca(2+)-transporting system of smooth muscle cell.  相似文献   

19.
20.
Summary In an artificial system, the ionophore A23187, which transports Ca2+ but not Na+, is able to mediate the uphill translocation of Ca2+ from one aqueous medium to another across an organic immiscible phase, provided that a Na+, Li+ or H+ gradient is imposed on the system. Therefore, in the process known as Na-Ca countertransport, the downhill influx of Na+ may not be necessary for causing Ca2+ extrusion against its electrochemical gradient.  相似文献   

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