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1.
Uptake and distribution of calcium, magnesium and potassium in cucumber of different age 总被引:1,自引:0,他引:1
Uptake and distribution of Ca+ , Mg2+ and K2+ were investigated in plants of cucumber ( Cucumis sativus L. var. Cila) which had been cultivated for 12, 19, 32, or 53 days in complete nutrient solution with 1.0 m M Ca2+ , 2.0 m M Mg2+ and 2.0 m M K+ . The + concentration was about the same in roots and shoots, while the Ca2+ and Mg2+ concentrations were low in roots compared to shoots. The K+ concentration decreased with increasing leaf age, while the Ca2+ and Mg2+ concentrations increased, except in older plants with flowers and fruits, where an increased concentration was found in the youngest leaves. This is discussed in connection with increased indoleacetic acid (IAA) synthesis in the shoot. Excision of leaves at different levels from 21-day-old plants, followed by uptake for 24 h from the nutrient solution on days 22 and 23, resulted in no immediate reduction in Ca2+ (45 Ca) uptake. Transport of Ca2+ increased to leaves above and below the excision point and total Ca2+ uptake remained at the same level as for the intact plant. It is suggested that regulation of Ca2+ uptake is primarily achieved in the root while the distribution in the shoot is regulated by the accessability of negative binding sites. 相似文献
2.
Bert P. Stok Otto Gy. Tànczos Monika Kähr C. E. E. Stuiver ers Kylin Pieter J. C. Kuiper 《Physiologia plantarum》1981,52(1):115-123
Mg2+ - and Ca2+ -uptake was measured in dark-grown oat seedlings ( Avena sativa L. cv. Brighton) cultivated at two levels of mineral nutrition. In addition the stimulation of the ATPase activity of the microsomal fraction of the roots by Mg2+ was measured. Ca2+ -uptake by the roots was mainly passive. Mg2+ -uptake mainly active; the passive component of Mg2+ -uptake was accompanied by Ca2+ -efflux up to 60% of the Ca2+ present in the roots.
In general Mg2+ -uptake of oat roots was biphasic. The affinity of the second phase correspond well with that of the Mg2+ -stimulation of the ATPase activity, in low-salt roots as well as in high-salt roots and in roots of plants switched to the other nutritional condition. Linear relationships were observed when [phase 2] Mg2+ -uptake was plotted against Mg2+ -stimulation of the ATPase activity of the microsomal fraction of the roots. In 5 days old high-salt plants 1 ATP (hydrolysed in the presence of Mg2+ J corresponded with active uptake of a single Mg2+ ion, but in older high-salt roots and in low-salt roots more ATP was hydrolysed per net uptake of a Mg2+ ion. The results are discussed against the background of regulation of the Mg2+ -level of the cytoplasm of root cells by transport of Mg2+ by a Mg2+ -ATPase to the vacuole, to the xylem vessels, and possibly outwards. 相似文献
In general Mg
3.
Abstract: The association of Mg2+ ions with mitochondria isolated from guinea pig cerebral cortex is investigated and resolved into two components, that bound to the surface of both the outer and the inner membranes and that transported into the mitochondrial matrix. When rotenone-treated mitochondria are preincubated in a Mg2+ -containing medium, Mg2+ binding can be measured and actual Mg2+ transport determined after the addition of succinate. Mg2+ uptake as well as retention within mitochondria is an energy-dependent process linked to substrate oxidation. EGTA completely prevents Mg2+ uptake, while the Ca2+ uniporter inhibitor Ruthenium Red, along with prevention of Mg2+ uptake, induces a slow efflux of accumulated Mg2+ ions. These findings suggest that both inward and outward Mg2+ movements follow Ca2+ fluxes across the mitochondrial membrane. Modulation of Mg2+ movements by mitochondria is therefore suggested to occur within nerve terminals. 相似文献
4.
Pb and Cd uptake in rice roots 总被引:9,自引:0,他引:9
Pb and Cd are heavy metal pollutants that inhibit plant growth. Using a cultivated rice variety (Dongjin, Oryza sativa L.), we studied how the transport and toxicity of Pb2+ and Cd2+ are affected by the presence of K+ , Ca2+ or Mg2+ . K+ had a little effect on uptake or toxicity of Pb2+ and Cd2+ . Ca2+ or Mg2+ blocked both Cd2+ transport into rice roots and Cd2+ toxicity on root growth, which suggested that their detoxification effect is directly related to their blocking of entry of the heavy metals. Similarly, Ca2+ blocked both Pb2+ transport into the root and Pb2+ toxicity on root growth. The protective effect of Ca2+ on Pb2+ toxicity may be related to its inhibition of the heavy metal accumulation in the root tip, a potential target site of Pb2+ toxicity. Mg2+ did not ameliorate the Pb2+ toxicity on root growth as much as Ca2+ did, although it decreased Pb2+ uptake into roots similarly as Ca2+ did. These results suggest that the protective effect of Ca2+ on Pb2+ toxicity may involve multiple mechanisms including competition at the entry level, and that Pb2+ and Cd2+ may compete with divalent cations for transport into roots of rice plants. 相似文献
5.
The effect of Ca2+ , Mg3+ and Ni2+ on root elongation was studied in Alyssum bertolonii Desv., a nickel-accumulating and serpentine endemic species. The results confirm the detoxifying action of Ca2+ which reduces the toxic effect of Mg2+ and Ni2+ on root development. In addition, Ca2+ and Mg2+ interact positively in depressing Ni2+ uptake. The combined effect of these two ions is of relevance for the mechanism of nickel tolerance in A. bertolonii. 相似文献
6.
Six cultivars of barley ( Hordeum vulgare L., cvs Salve, Nürnberg II, Bomi, Risø 1508, Mona and Sv 73 608) were exposed for three weeks to combinations of high and low mineral supply and differential root/shoot temperature. For all the parameters tested [fresh and dry weights, contents and levels of N, K+ , Ca2+ and Mg2+ , and influx of Rb+ (86 Rb)] the cultivar differences were influenced by the mineral supply, the root temperature and the age of the plants.
The cultivar differences in N nutrition of three-week-old plants could partly be attributed to variation in root size, uptake of N and in use-efficiency of the element. The cultivar variation in root-shoot partitioning of N was small, except when low mineral supply was combined with a low root temperature. Similarly, cultivar differences in contents of K+ , Ca2+ and Mg2+ were influenced by variation in uptake, use-efficiency and root/shoot partitioning of the elements. Low root temperature increased cultivar variation in K+ , Ca2+ and Mg2+ partitioning.
The modern cultivar Salve was compared with Nürnberg II, which is derived from a German land race. Nürnberg II performed better than Salve when low root temperature and restricted mineral supply were combined. Otherwise Salve grew better, partly due to a more efficient use of N.
Two high-lysine lines, Risø 1508 and Sv 73 608, were compared with their mother lines Bomi and Mona. The differences obtained revealed no general effect of the high-lysine genes on growth and mineral nutrition of up to three-week-old barley plants. 相似文献
The cultivar differences in N nutrition of three-week-old plants could partly be attributed to variation in root size, uptake of N and in use-efficiency of the element. The cultivar variation in root-shoot partitioning of N was small, except when low mineral supply was combined with a low root temperature. Similarly, cultivar differences in contents of K
The modern cultivar Salve was compared with Nürnberg II, which is derived from a German land race. Nürnberg II performed better than Salve when low root temperature and restricted mineral supply were combined. Otherwise Salve grew better, partly due to a more efficient use of N.
Two high-lysine lines, Risø 1508 and Sv 73 608, were compared with their mother lines Bomi and Mona. The differences obtained revealed no general effect of the high-lysine genes on growth and mineral nutrition of up to three-week-old barley plants. 相似文献
7.
S.-S. Yen S.-H. Chen-Yen R. L. Klein 《Differentiation; research in biological diversity》1974,2(6):351-356
The Ca++ and Mg+ + contents of embryonic chick heart were studied by atomic absorption spectrophotometry during a period from 48 h of foetal development until 2-3 days post-hatching. The hearts were isolated and incubated for 40 min at 22°C in three different media aerated with 95% 02 -5% C02 . The media included: normal Ringer's; Ca+ -free Ringer's with 3 mM EGTA; and Ca++ -free Ringer's with 3 mM EDTA. At 48 h, the tubular myocardium contained 7-3 mM Ca++ per wet weight which decreased rapidly to 1-2 mM by 10 days of development and remained between 0-9 and 1-1 mM until hatching. The Ca++ content paralleled the changes in Na+ content reported earlier. Treatment with excess chelators, EGTA or EDTA, resulted in removal of 65-75% of the Ca++ content throughout development until the time of hatching, when 50% of the Ca++ became firmly bound. In contrast to the results with Ca++ , myocardial Mg++ content rose rapidly from an initial value of 3.2 mM at 48 h to 6.7 mM by the 5th day of development, and then gradually declined throughout the remaining foetal development to 4.8 mM 2-3 days post-hatching. The Mg++ contents closely paralleled changes in K+ content during development, which were reported earlier. Treatment with EGTA and EDTA removed 13-22% and 19-28% of the myocardial Mg++ , respectively, during development until just prior to hatching, when only 10-12% could be removed by chelation. 相似文献
8.
Low-K+ , high-Na+ cells of strain RL21a of Neurospora crassa , in steady state with 25 m M Na+ , were used to study K+ /Na+ exchanges in the presence or absence of Ca2+ and Mg2+ . In the presence of Ca2+ and Mg2+ , a low concentration of K+ (0.3 m M ) triggered a rapid exchange, but in the absence of the divalents, a high K+ concentration (30 m M ) was required to initiate the exchange at a rapid rate. In the absence of Ca2+ and Mg2+ , K+ uptake did not occur at low K+ concentration, internal K+ did not regulate Na+ influx in the presence of external K+ , and the efflux of Na+ proceeded at maximum activity at very low-K+ contents. 相似文献
9.
The Mg2+ requirement in fertilization was investigated in sea urchins. It was found that when sea urchin eggs were inseminated in sea water free of Mg2+ , little fertilization took place. Even when spermatozoa pre-treated with dissolved egg-jelly to induce the acrosome reaction, which needs Ca2+ , were used, the fertilization rate remained quite low in the absence of Mg2+ . In Strongylo-centrotus intermedius , the lowest concentration of Mg2+ required for 50% fertilization was 0.05 mM in the presence of 10 mM Ca2+ , whereas that of calcium was 3 mM in the presence of 49 mM Mg2+ . These critical concentrations increased when the concentration of the other ion decreased. Removal of Mg2+ or Ca2+ or both from the suspending medium had little adverse effect on sperm motility. The elevation of the fertilization membrane was also induced by butyric acid independent of the presence or absence of Mg2+ and/or Ca2+ . These results indicate that Mg2+ are required at least in some process(es) between acrosome reaction and fertilization membrane elevation, such as sperm penetration or membrane fusion. 相似文献
10.
Ischemia-Induced Inhibition of Calcium Uptake into Rat Brain Microsomes Mediated by Mg2+ /Ca2+ ATPase
Abstract: It is well established that ischemia is associated with prolonged increases in neuronal intracellular free calcium levels. Recent data suggest that regulation of calcium uptake and release from the endoplasmic reticulum is important in maintaining calcium homeostasis. The endoplasmic reticulum Mg2+ /Ca2+ ATPase is the major mechanism for sequestering calcium in this organelle. Inhibition of this enzyme may play a causal role in the loss of calcium homeostasis. In order to investigate the effect of ischemia on calcium sequestration into the endoplasmic reticulum, microsomes were isolated from control and ischemic whole brain homogenates by differential centrifugation. Calcium uptake was measured by radioactive calcium (45 Ca2+ ) accumulation in the microsomes mediated by Mg2+ /Ca2+ ATPase. Ischemia caused a statistically significant inhibition of presteady-state and steady-state calcium uptake. Duration of ischemia was directly proportional to the degree of inhibition. Decreased calcium uptake was shown not to be the result of increased calcium release from ischemic compared with control microsomes nor the result of selective isolation of ischemic microsomes from the homogenate with a decreased capacity for calcium uptake. The data demonstrate that ischemia inhibits the ability of brain microsomes to sequester calcium and suggest that loss of calcium homeostasis is due, in part, to ischemia-induced inhibition of endoplasmic reticulum Mg2+ /Ca2+ ATPase. 相似文献
11.
Uptake of metals by bacterial polysaccharides 总被引:3,自引:1,他引:2
J.L. GEDDIE AND I.W. SUTHERLAND. 1993. The binding of cations by a range of bacterial polysaccharides was examined. Comparison of native and deacetylated polymers indicated the influence of polysaccharide acetylation on ion uptake and selectivity. The effects of temperature and pH on ion uptake were also examined. Metal ion uptake was carried out by dialysis and samples were analysed using ion chromatography. The native acetylated polymers showed a selectivity for Ca2+ > Mg2+ > monovalent cations, whereas samples lacking acetyl groups showed a selectivity for monovalent cations > Mg2+ > Ca2+ . Increased temperatures reduced the capacity for several of the polymers to bind the cations; The Zoogloea ramigera polymer appeared least affected. The pH value also affected uptake. 相似文献
12.
ROLE OF MALATE TRANSPORT IN REGULATING METABOLISM IN MITOCHONDRIA ISOLATED FROM RABBIT BRAIN 总被引:2,自引:2,他引:0
Abstract— Partly purified chromaffin granules were incubated in vitro with Ca2+ (with trace amounts of 45 Ca2+ ) in concentrations ranging from 4 μm to 1 mm. After incubation the granules were washed with media containing EDTA and then subjected to density gradient centrifugation (1.3 to 2.0 m-sucrose solutions) in order to characterize the particles which had taken up 45 Ca2+ . By using marker enzymes and various inhibitors of Ca2+ uptake into such cell particles as mitochondria it was established that under the conditions of the experiments chromaffin granules took up Ca2+ from the incubation medium. To characterize this uptake a simplified density gradient procedure was tested and found to be suitable. The uptake of Ca2+ into chromaffin granules was strongly dependent on temperature. It was not activated by ATP. The uptake was linear up to 10 min. At high calcium concentrations (above 200 μm) the rate of uptake levelled off. The uptake at 37°C was 1 nmol Ca2+ /mg protein/min at a Ca2+ concentration of 500 μm. Mg2+ had no influence on Ca2+ uptake, whereas Sr2+ (1 mm) inhibited it. The methods established in this study should prove useful for a further characterization of this Ca2+ uptake into chromaffin granules which is likely to represent a useful model for the Ca2+ uptake occurring in the intact gland. 相似文献
13.
The uptake of Cd2+ by excised roots of Tamarix aphylla (L.) Karst, was investigated using roots of hydroponically grown plants. The concentration isotherm of Cd2+ uptake approached saturation with a single phase hyperbola. The time course of Cd2+ absorption was generally hyperbolic, with an apparent linear section between 2 and 30 min. The temperature response varied among different temperature ranges: a Q10 of approximately 1.9 was found between 10 and 20°C, but at higher and lower temperatures Q10 values were only 1–1.3. It is concluded that Cd2+ uptake by the roots of T. aphylla at moderate temperatures is mediated by a metabolic process, combined with a passive influx component that becomes dominant at higher and lower temperatures. The distribution of the absorption sites for Cd2+ and for Fe2+ along the roots of T. aphylla was also investigated. Cadmium uptake showed no apparent pattern, whereas a distinct pattern of uptake was observed for Fe2+ , with the highest rates at the root tip. Iron absorption was stimulated in the presence of nutrients, whereas that of Cd2+ was inhibited. Adsorption and absorption of Cd2+ were strongly inhibited by Ca2+ and by Mg2+ , but were unaffected by Fe2+ . Monovalent ions (Na+ , K+ , Li+ ) also reduced Cd2+ absorption, but to a lesser extent than Ca2+ and Mg2+ . Uptake of Cd+ was reduced at lower pH of the medium. The importance of interfering cations for Cd2+ tolerance of T. aphylla is emphasized. 相似文献
14.
Abstract: Nations were found to inhibit the uptake of L-tryptophan into synaptosomes with a shallow dose-response curve. Almost maximal inhibition was obtained with 10 mM-Na+ . The divalent cations Ca2+ and Mg2+ were shown to be responsible for the increased uptake of L-tryptophan in the absence of Na+ ions. Other divalent cations also promoted tryptophan uptake under this condition (Ca2+ < Mg2+ < Mn2+ < Fe2+ < Zn2+ < Cu2+ ). It was concluded that monovalent chelate complexes were responsible for this enhancing effect. The measured L-tryptophan uptake was the net product of membrane bound and unbound tryptophan. Both bound and unbound tryptophan were increased in the presence of divalent cations. If no divalent cations were added to the incubation medium, Na+ ions decreased the unbound tryptophan but were without effect on bound tryptophan. Under these circumstances D-tryptophan had no effect on binding of the L-isomer and affected the transport of 1.-tryptophan only at very high does (100 x conc. L-tryptophan). These results suggest that I -tryptophan binds to a stereospecific transport carrier located in the synaptosomal membrane and that Na+ ions prevent the translocation of this carrier amino acid complex from the outer to the inner site of the neuronal membrane. 相似文献
15.
Martin G. Klotz Alajos Bérczi László Erdei Bernd Liebermann 《Physiologia plantarum》1989,75(3):405-410
Purified plasmalemma vesicles were isolated in the presence of 250 m M sucrose from roots of 14-day-old seedlings of winter wheat ( Triticum aestivum L. Martonvásári-8) by phase partitioning of salt-washed microsomal fractions in a Dextran-polyethylene glycol two-phase system, and both Mg2+ - and Ca2+ -ATPase activities were detected. Orthovanadate-sensitive Mg2+ -ATPase activity associated with the inside of right side-out plasmalemma (PM) vesicles (latency 98%) was inhibited 76% by 0.3 m M Ca2+ , Ca2+ -dependent ATPase activity located partly on the inside and partly on the outside of plasmalemma vesicles (latency 47%) was not affected by Mg2+ .
Mg2+ -ATPase activity was inhibited by 68% and inhibition of Mg2+ activation by 0.3 m M Ca2+ partly disappeared in the presence of 10 p M tentoxin, a fungal phytotoxin. Mg2+ -ATPase activity remained inhibited up to 10 n M tentoxin while at 1 μ M tentoxin Mg2+ activation was as high as without tentoxin. K+ -stimulation and vanadate inhibition was increased and decreased, respectively, by 100 p M -10 n M tentoxin. Ca2+ -dependent ATPase activity was continuously increased by 1 p M -10 n M tentoxin, but at 1 μ M tentoxin the stimulation disappeared. The effects of p M tentoxin on plasma-lemma Mg2+ -ATPase are discussed in relation to its influence on K+ transport in wheat seedlings. 相似文献
Mg
16.
Abstract: The activities mediated by the N -methyl-D-aspartate (NMDA) receptor were studied in cultured rat cerebellar granule cells. Micromolar concentrations of the metal binding compounds, EDTA, cysteine, and histidine, as well as serum albumin strongly potentiated receptor activity in the presence of millimolar concentrations of Ca2+ and Mg2+ . The findings indicated that these agents remove an endogenous metal, probably Zn2+ , which attenuates NMDA receptor-mediated 45 Ca uptake and toxicity. Several added metal ions were therefore tested at low micromolar concentrations. Zn2+ was found to be the most potent inhibitor of NMDA-induced 45 Ca uptake, followed by Cu2+ and Fe2+ . Co2+ , Cd2+ , Fe3+ , and AI3+ had no significant effect, whereas Ni2+ potentiated the 45 Ca uptake but inhibited at much higher concentrations. The potentiating agents that remove the endogenous metal had a particularly dramatic effect in the presence of Mg2+ , the voltage-dependent suppressor of the NMDA receptor. Mg2+ also played an important role in the inhibitory effect of added Zn2+ . Much lower concentrations of Zn2+ were needed to achieve inhibition of NMDA-induced 45 Ca uptake in the presence of Mg2+ . Under a variety of conditions, a very good correlation was found between NMDA receptor-mediated 45 Ca uptake and the magnitude of acute neurotoxicity. 相似文献
17.
KIYOTA GOSHIMA HACHIRO YAMANAKA GORO EGUCHI SHIGEO YOSHINO 《Development, growth & differentiation》1978,20(2):191-204
Increase in the extracellular Ca2+ concentration from low (≤ 10−7 M) to normal (10−3 M) caused morphological changes of cultured myocardial cells obtained from fetal mouse heart. The extracellular Na+ and K+ concentrations of the normal medium (10−3 M Ca2+ ) did not significantly affect the genesis of these morphological changes. Like Ca2+ , Ba2+ and Sr2+ , but not Mg2+ , Co2+ or Ni2+ , could induce morphological changes. Increase in the extracellular Ca2+ concentration from 10−8 M to 10−3 M also caused excess uptake of 45 Ca2+ by cultured myocardial cells. B–16CW 1 cells, which did not show these morphological changes, did not take up excess 45 Ca2+ on this treatment. Treatments, such as addition of verapamil or incubation at pH 6.3, which reduced the genesis of morphological changes, reduced the rate of 45 Ca2+ uptake by myocardial cells. These facts show that the morphological changes of myocardial cells induced by increasing the extracellular Ca2+ concentration from low to normal are due to excess uptake of Ca2+ by the myocardial cells.
The morphological changes of cultured myocardial cells induced by increasing the extracellular Ca2+ concentration from low to normal were reversed on further incubation of the cells in medium with or without Ca2+ . 相似文献
The morphological changes of cultured myocardial cells induced by increasing the extracellular Ca
18.
Sidedness of (Calcium, Magnesium) Adenosine Triphosphatase of Purified Torpedo Synaptic Vesicles 总被引:10,自引:7,他引:3
Abstract: Purified Torpedo synaptic vesicles contain ouabain-insensitive Mg2+ τ and Ca2+ -stimulated ATPase activity. The sidedness of the ATPase on the vesicular membranes was investigated. Addition of ATP and Mg2+ or Ca2+ to intact vesicles results in activation of the ATPase. Exposure of the vesicles to low concentrations of Lubrol-PX and Triton X-100, which do not solubilize the activity, results in the concurrent release of the vesicular contents and in an increase of the Mg2+ -ATPase activity, whereas the Ca2+ -dependent activity is drastically decreased. p -Chloromercuribenzene sulphonate (PCMBS) almost completely inhibits the activity of detergent-treated vesicles whereas that of the native material is only slightly affected. Tryptic digestion of intact vesicles and of vesicular ghosts results in partial reduction of the ATPase activity. These results suggest that the vesicles contain an outward oriented Ca2+ /Mg2+ ATPase activity which can be modulated by detergents. 相似文献
19.
Abstract. An increase in egg size with embryonic development in stoneflies is believed to result from the uptake of water by osmosis. The present study aims to investigate whether a selective ion transport through egg membranes exists before hatching, and whether ions are released after hatching. Viable and nonviable egg masses are incubated in Petri dishes filled with water, and the concentrations of the ions F− , Cl− , SO4 2− , NO3 − , Na+ , K− , Mg2+ and Ca2+ in the water are determined. The ion transport of an egg mass before and after hatching and a nonviable egg mass is then calculated. Before hatching, Cl− , SO4 2− , NO3 − , Na+ , Mg2+ and Ca2+ are taken up from the surrounding water into the inner egg. These ions are selectively taken into the egg. After hatching, Cl− , SO4 2− , Na+ , Mg2+ and Ca2+ are released into the surrounding water. The amount of these ions released after hatching is lower than the amount taken up before hatching. Ions that are not released after hatching are considered to be used in embryonic development. 相似文献
20.
K. A. Hartnett A. K. Stout S. Rajdev †P. A. Rosenberg I. J. Reynolds E. Aizenman 《Journal of neurochemistry》1997,68(5):1836-1845
Abstract: Accumulation of intracellular Ca2+ is known to be critically important for the expression of NMDA receptor-mediated glutamate neurotoxicity. We have observed, however, that glutamate can also increase the neuronal intracellular Mg2+ concentration on activation of NMDA receptors. Here, we used conditions that elevate intracellular Mg2+ content independently of Ca2+ to investigate the potential role of Mg2+ in excitotoxicity in rat cortical neurons in vitro. In Ca2+ -free solutions in which the Na+ was replaced by N -methyl- d -glucamine or Tris (but not choline), which also contained 9 m M Mg2+ , exposure to 100 µ M glutamate or 200 µ M NMDA for 20 min produced delayed neuronal cell death. Neurotoxicity was correlated to the extracellular Mg2+ concentration and could be blocked by addition of NMDA receptor antagonists during, but not immediately following, agonist exposure. Finally, we observed that rat cortical neurons grown under different serum conditions develop an altered sensitivity to Mg2+ -dependent NMDA receptor-mediated toxicity. Thus, the increase in intracellular Mg2+ concentration following NMDA receptor stimulation may be an underestimated component critical for the expression of certain forms of excitotoxic injury. 相似文献