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1.
The respiration rate of leaves and mesophyll protoplasts of pea (Pisum sativum L.), from plants which were previously kept in darkness for 24 h was doubled following a period of photosynthesis at ambient
level of O2 (21 %), whereas the low level of O2 (1 % and 4 % for leaves and protoplasts, respectively) reduced this light-enhanced dark respiration (LEDR) to the rate as
noted before the illumination. Similarly to respiration rate, the oxygen at used concentrations had no effect on the ATP/ADP
ratio in the dark-treated leaves. However, the ATP/ADP ratio in leaves photosynthesizing at 21 % O2 was higher (up to 40 %, dependence on CO2 concentration in the range 40–1600 1 dm−3) than in those photosynthesizing at 1 % O2 or darkened at air (21 % O2). Also, at 1 % O2 the accumulation of malate was suppressed (by about 40 %), to a value noted for leaves darkened at 21 % O2. The dark-treatment of leaves reduced the ability of isolated mitochondria to oxidize glycine (by about twofold) and succinate,
but not malate. Mitochondria from both the light- and dark-treated leaves did not differ in qualitative composition of free
amino acids, however, there were significant quantitative differences especially with respect to aspartate, alanine, glutamate
and major intermediates of the photorespiratory pathway (glycine, serine). Our results suggest that accumulation of photorespiratory
and respiratory metabolites in pea leaves during photosynthesis at 1 % O2 is reduced, hence the suppression of postillumination respiration rate. 相似文献
2.
The effect of lead on photosynthesis and respiration in detached leaves and in mesophyll protoplasts of Pisum sativum 总被引:2,自引:0,他引:2
Eugeniusz Parys Elżbieta Romanowska Maria Siedlecka Jerzy W. Poskuta 《Acta Physiologiae Plantarum》1998,20(3):313-322
Photosynthesis and transpiration rate of detached leaves of pea (Pisum sativum L. cv. Iłowiecki) exposed to solution of Pb(NO3)2 at 1 or 5 mmol·dm−3 concentrations were inhibited. The higher concentration of this toxicant decreased photosynthesis and transpiration rates
2 and 3 times respectively, and increased respiration by about 20 %, as measured after 24 hours of treatment. Similarly to
Pb(NO3)2, glyceraldehyde solution, an inhibitor of phosphoribulokinase, at 50 mmol·dm−3 concentration decreased the rates of photosynthesis and transpiration during introduction into pea leaves. The rate of dark
respiration, however, remained unchanged during 2 hours of experiment.
The potential photochemical efficiency of PS II (Fv/Fm) and the activity of Rubisco (EC 4.1.1.39) at 5 mmol·dm−3 of Pb(NO3)2 were lowered by 10 % and 20 % respectively, after 24 hours. Neither changes in the activity of PEPC (EC 4.1.1.31) or protein
and pigment contents were noted in Pb-treated leaves. The photosynthetic activity of protoplasts isolated from leaves treated
for 24 or 48 hours with Pb(NO3)2 at 5 mmol·dm−3 concentration was decreased 10 % or 25 %, whereas, the rate of dark respiration was stimulated by about 40 % and 75 %, respectively.
The content of abscisic acid, a hormone responsible for stomatal closure, in detached pea leaves treated for 24 h with 5 mmol·dm−3 of Pb(NO3)2 solution was increased by about 3 times; a longer (48h) treatment led to further increase (by about 7 times) in the amount
of this hormone. The results of our experiments provide evidences that CO2 fixation in detached pea leaves, at least up to 24 hours of Pb(NO3)2 treatment, was restricted mainly by stomatal closure. 相似文献
3.
In the absence of exogenous Ca2+ and Mg2+ and in the presence of EGTA, which favours the release of endogenous Ca2+, the polyamine spermine is able to stimulate the activity of pyruvate dehydrogenase complex (PDC) of energized rat liver
mitochondria (RLM). This stimulation exhibits a gradual concentration-dependent trend, which is maximum, about 140%, at 0.5 mM
concentration, after 30 min of incubation. At concentrations higher than 0.5 mM, spermine still stimulates PDC, when compared
with the control, but shows a slight dose-dependent decrease. Changes in PDC stimulation are very close to the phosphorylation
level of the E1α subunit of PDC, which regulates the activity of the complex, but it is also the target of spermine. In other words, progressive
dephosphorylation gradually enhances the stimulation of RLM and progressive phosphorylation slightly decreases it. These results
provide the first evidence that, when transported in RLM, spermine can interact in various ways with PDC, showing dose-dependent
behaviour. The interaction most probably takes place directly on a specific site for spermine on one of the regulatory enzymes
of PDC, i.e. pyruvate dehydrogenase phosphatase (PDP). The interaction of spermine with PDC may also involve activation of
another regulatory enzyme, pyruvate dehydrogenase kinase (PDK), resulting in an increase in E1α phosphorylation and consequently reduced stimulation of PDC at high polyamine concentrations. The different effects of spermine
in RLM are discussed, considering the different activities of PDP and PDK isoenzymes. It is suggested that the polyamine at
low concentrations stimulates the isoenzyme PDP2 and at high concentrations it stimulates PDK2. 相似文献
4.
The anoxia-dependent elevation of cytosolic Ca2+ concentration, [Ca2+]cyt, was investigated in plants differing in tolerance to hypoxia. The [Ca2+]cyt was measured by fluorescence microscopy in single protoplasts loaded with the calcium-fluoroprobe Fura 2-AM. Imposition of
anoxia led to a fast (within 3 min) significant elevation of [Ca2+]cyt in rice leaf protoplasts. A tenfold drop in the external Ca2+ concentration (to 0.1 mM) resulted in considerable decrease of the [Ca2+]cyt shift. Rice root protoplasts reacted upon anoxia with higher amplitude. Addition of plasma membrane (verapamil, La3+ and EGTA) and intracellular membrane Ca2+-channel antagonists (Li+, ruthenium red and cyclosporine A) reduced the anoxic Ca2+-accumulation in rice. Wheat protoplasts responded to anoxia by smaller changes of [Ca2+]cyt. In wheat leaf protoplasts, the amplitude of the Ca2+-shift little depended on the external level of Ca2+. Wheat root protoplasts were characterized by a small shift of [Ca2+]cyt under anoxia. Plasmalemma Ca2+-channel blockers had little effect on the elevation of cytosolic Ca2+ in wheat protoplasts. Intact rice seedlings absorbed Ca2+ from the external medium under anoxic treatment. On the contrary, wheat seedlings were characterized by leakage of Ca2+. Verapamil abolished the Ca2+ influx in rice roots and Ca2+ efflux from wheat roots. Anoxia-induced [Ca2+]cyt elevation was high particularly in rice, a hypoxia-tolerant species. In conclusion, both external and internal Ca2+ stores are important for anoxic [Ca2+]cyt elevation in rice, whereas the hypoxia-intolerant wheat does not require external sources for [Ca2+]cyt rise. Leaf and root protoplasts similarly responded to anoxia, independent of their organ origin. 相似文献
5.
Removal of heavy metals (Pb2+, Zn2+) from aqueous solution by dried biomass of Spirulina sp. was investigated. Spirulina rapidly adsorbed appreciable amount of lead and zinc from the aqueous solutions within 15 min of initial contact with the
metal solution and exhibited high sequestration of lead and zinc at low equilibrium concentrations. The specific adsorption
of both Pb2+ and Zn2+ increased at low concentration and decreased when biomass concentration exceeded 0.1 g l−1. The binding of lead followed Freundlich model of kinetics where as zinc supported Langmuir isotherm for adsorption with
their r
2
values of 0.9659 and 0.8723 respectively. The adsorption was strongly pH dependent as the maximum lead biosorption occurred
at pH 4 and 10 whereas Zn2+ adsorption was at pH 8 and 10. 相似文献
6.
7.
J. Z. Hu G. X. Shi Q. S. Xu X. Wang Q. H. Yuan K. H. Du 《Russian Journal of Plant Physiology》2007,54(3):414-419
The effects of various concentrations of Pb2+ on the antioxidant enzyme activities and the ultrastructure in Potamogeton crispus leaves were studied. Peroxidase (POD) activity and malondialdehyde (MDA) content peaks were observed with an increase in
Pb2+ concentration, whereas superoxide dismutase (SOD) and catalase (CAT) activities decreased firstly and then rose. Meantime,
the chlorophyll content declined with increasing Pb2+ concentration. Simultaneously, high concentrations of Pb2+ aggravated ultrastructural damage to the leaf cells including swelling of chloroplasts, disruption and disappearance of chloroplast
envelopes; swelling of mitochondrial cristae, deformation and vacuolation of mitochondria; condensation of chromatin, dispersion
of nucleoli, and disruption of nuclear membrane. Changes in antioxidant enzyme activities and damage to fine structure are
the results of lead-induced ROS accumulation. The estimated lethal concentration to P. crispus ranged from 10 to 15 mg/l lead.
Published in Russian in Fiziologiya Rastenii, 2007, Vol. 54, No. 3, pp. 469–474.
The text was submitted by the authors in English. 相似文献
8.
Yuri N. Antonenko Tatyana I. Rokitskaya Arthur J. L. Cooper Boris F. Krasnikov 《Journal of bioenergetics and biomembranes》2010,42(2):151-163
Minocycline (an anti-inflammatory drug approved by the FDA) has been reported to be effective in mouse models of amyotrophic
lateral sclerosis and Huntington disease. It has been suggested that the beneficial effects of minocycline are related to
its ability to influence mitochondrial functioning. We tested the hypothesis that minocycline directly inhibits the Ca2+-induced permeability transition in rat liver mitochondria. Our data show that minocycline does not directly inhibit the mitochondrial
permeability transition. However, minocycline has multiple effects on mitochondrial functioning. First, this drug chelates
Ca2+ ions. Secondly, minocycline, in a Ca2+-dependent manner, binds to mitochondrial membranes. Thirdly, minocycline decreases the proton-motive force by forming ion
channels in the inner mitochondrial membrane. Channel formation was confirmed with two bilayer lipid membrane models. We show
that minocycline, in the presence of Ca2+, induces selective permeability for small ions. We suggest that the beneficial action of minocycline is related to the Ca2+-dependent partial uncoupling of mitochondria, which indirectly prevents induction of the mitochondrial permeability transition. 相似文献
9.
The effects of Т1+ ions on the dynamics of intracellular Cа2+ in neonatal rat cardiomyocytes have been studied. It was shown for the first time that application of Т1+ led to an uncontrolled increase in [Cа2+]i in cells. Moreover, the ability of Т1+ to increase [Cа2+]i depended on the Т1+ concentration used and the time of exposure to the cells. The increase in [Cа2+]i was related to the entry of Cа2+ from the extracellular medium. Thallium did not release Cа2+ from intracellular stores. The thallium-induced increase in [Cа2+]i was not inhibited by nifedipine. It is possible that L-channels do not participate in the processes of thalliuminduced increase in [Cа2+]i. It is assumed that the thallium ions-induced calcium overload in cardiomyocytes may contribute to the toxic effect of Т1+ on the myocardium. 相似文献
10.
The toxic effect of Pb2+ has been studied in eukaryotic cells by using Tetrahymena as a target. The maximum power (P
m) and the growth rate constant (k) were determined, which showed that values of P
m and k were linked to the concentration (C) of Pb2+. The addition of Pb2+ caused a decrease of the maximum heat production and growth rate constant, indicating that Tetrahymena growth was inhibited in the presence of Pb2+, and Pb2+ took part in the metabolism of cells. From micrographs, morphological changes of Tetrahymena were observed with addition of Pb2+, indicating that the toxic effect of Pb2+ derived from destroying the membrane of surface of Tetrahymena. According to the thermogenic curves and photos of Tetrahymena under different conditions, it is clear that metabolic mechanism of Halobacterium halobium R1 growth has been changed with the addition of Pb2+. 相似文献
11.
Ca2+ has been well accepted as a signal that coordinates changes in cytosolic workload with mitochondrial energy metabolism in
cardiomyocytes. During increased work, Ca2+ is accumulated in mitochondria and stimulates ATP production to match energy supply and demand. The kinetics of mitochondrial
Ca2+ ([Ca2+]m) uptake remains unclear, and we review the debate on this subject in this article. [Ca2+]m has multiple targets in oxidative phosphorylation including the F1/FO ATPase, the adenine nucleotide translocase, and Ca2+-sensitive dehydrogenases (CaDH) of the tricarboxylic acid (TCA) cycle. The well established effect of [Ca2+]m is to activate CaDHs of the TCA cycle to increase NADH production. Maintaining NADH level is not only critical to keep a
high oxidative phosphorylation rate during increased cardiac work, but is also necessary for the reducing system of the cell
to maintain its reactive oxygen species (ROS) —scavenging capacity. Further, we review recent data demonstrating the deleterious
effects of elevated Na+ in cardiac pathology by blunting [Ca2+]m accumulation. 相似文献
12.
Methods of quantum chemistry have been applied to double-charged complexes involving the transition metals Ni2+, Cu2+ and Zn2+ with the aromatic amino acids (AAA) phenylalanine, tyrosine and tryptophan. The effect of hydration on the relative stability
and geometry of the individual species studied has been evaluated within the supermolecule approach. The interaction enthalpies,
entropies and Gibbs energies of nine complexes Phe•M, Tyr•M, Trp•M, (M = Ni2+, Cu2+ and Zn2+) were determined at the Becke3LYP density functional level of theory. Of the transition metals studied the bivalent copper
cation forms the strongest complexes with AAAs. For Ni2+and Cu2+ the most stable species are the NO coordinated cations in the AAA metal complexes, Zn2+cation prefers a binding to the aromatic part of the AAA (complex II). Some complexes energetically unfavored in the gas-phase are stabilized upon microsolvation. 相似文献
13.
The evidence of possible involvement of the mitochondrial cyclosporin A-insensitive palmitate/Ca2+-activated pore in palmitate-induced apoptosis is presented. It has been established that the opening of the palmitate/Ca2+-activated pore results in the high-amplitude swelling of mitochondria and the release of the apoptosis-inducing factor from organelles. These processes are accompanied by a short-term slight decrease of membrane potential, which recovers in 1 min. The possible role of the palmitate/Ca2+-activated pore in the induction of palmitate-induced apoptosis is discussed. 相似文献
14.
Ohashi W Inouye S Yamazaki T Doi-Katayama Y Yokoyama S Hirota H 《Journal of biomolecular NMR》2005,31(4):375-376
15.
16.
The effects induced by lead ions on the short-circuit current (SCC) and on the potential difference (V) of the toad Pleurodema thaul skin were investigated. Pb2+ applied to the outer (mucosal) surface increased SCC and V and when applied to the inner (serosal) surface decreased both parameters. The stimulatory effect, but not the inhibitory action, was reversible after washout of the metal ion. The amiloride test showed that the increase was due principally to stimulation of the driving potential for Na+ (V-ENa+) and that inhibition was accompanied by a reduction in the V-ENa+ and also by a significant decrease in skin resistance indicating possible disruption of membrane and/or cell integrity. The effect of noradrenaline was increased by outer and decreased by inner administration of Pb2+. The results suggest that mucosal Pb2+ activates toad skin ion transport by stimulating the V-ENa+ and that serosal Pb2+, with easier access to membrane and cellular constituents, inactivates this mechanism, revealing greater toxicity when applied to the inner surface of the skin.
Abbreviations: SCC – short-circuit current; V – potential difference; V-ENa+– driving potential for Na+; ENaC – epithelial sodium channel; RNa+– active sodium resistance; RS – passive or shunt resistance; GNa– active sodium conductance; GS – passive or shunt conductance; Gmax – total conductance; EC50– half-maximal excitatory concentration; IC50– half maximal inhibitory concentration; NA – noradrenaline. 相似文献
17.
Mechanism of luminal Ca<Superscript>2+</Superscript> and Mg<Superscript>2+</Superscript> action on the vacuolar slowly activating channels 总被引:2,自引:0,他引:2
The non-selective slow vacuolar (SV) channel can dominate tonoplast conductance, making it necessary to tightly control its activity. Applying the patch-clamp technique to vacuoles from sugar beet (Beta vulgaris L.) taproots we studied the effect of divalent cations on the vacuolar side of the SV channel. Our results show that the SV channel has two independent binding sites for vacuolar divalent cations, (i) a less selective one, inside the channel pore, binding to which impedes channel conductance, and (ii) a Ca2+-selective one outside the membrane-spanning part of the channel protein, binding to which stabilizes the channels closed conformations. Vacuolar Ca2+ and Mg2+ almost indiscriminately blocked ion fluxes through the open channel pore, decreasing measured single-channel current amplitudes. This low-affinity block displays marked voltage dependence, characteristic of a permeable blocker. Vacuolar Ca2+—with a much higher affinity than Mg2+—slows down SV channel activation and shifts the voltage dependence to more (cytosol) positive potentials. A quantitative analysis results in a model that exactly describes the Ca2+-specific effects on the SV channel activation kinetics and voltage gating. According to this model, multiple (approximately three) divalent cations bind with a high affinity at the luminal interface of the membrane to the channel protein, favoring the occupancy of one of the SV channels closed states (C2). Transition to another closed state (C1) diminishes the effective number of bound cations, probably due to mutual repulsion, and channel opening is accompanied by a decrease of binding affinity. Hence, the open state (O) is destabilized with respect to the two closed states, C1 and C2, in the presence of Ca2+ at the vacuolar side. The specificity for Ca2+ compared to Mg2+ is explained in terms of different binding affinities for these cations. In this study we demonstrate that vacuolar Ca2+ is a crucial regulator to restrict SV channel activity to a physiologically meaningful range, which is less than 0.1% of maximum SV channel activity.Abbreviation SV Slow vacuolar 相似文献
18.
S. M. Korotkov K. V. Sobol I. V. Shemarova V. V. Furaev A. R. Shumakov V. P. Nesterov 《Biophysics》2016,61(5):733-740
The inotropic effect of Pr3+ and La3+ ions on the heart muscle of frog Rana ridibunda, as well as the influence of the ions on respiration, swelling, and the potential (ΔΨmito) on the inner membrane of Ca2+- loaded rat heart mitochondria, energized by glutamate and malate or succinate in the presence of rotenone were studied. It was found that 2 mM Pr3+ in Ringer’s solution reduces the force of spontaneous contractions and those induced by electrical stimulation in the heart; it had a negative chronotropic effect, decreasing the frequency of spontaneous contractions. Pr3+ and La3+ prevented a decrease in the 2,4-dinitrophenol (DNP)- uncoupled respiration of energized rat heart mitochondria, swelling of these organelles in salt media, and a reduction in ΔΨmito on the inner mitochondrial membrane that were induced by Ca2+ ions. Retardation by Pr3+ and La3+ ions of these calcium-induced effects may suggest that in the inner mitochondrial membrane these metals inhibit the opening of the mitochondrial permeability transition pore caused by Ca2+ overload of mitochondria. The data we obtained are important for a better understanding of the mechanisms of the damaging action of rare-earth elements on Ca2+-dependent processes in the vertebrate myocardium. 相似文献
19.
I. Yu. Subota A. Sh. Arziev L. P. Senzhenko V. I. Tarasenko G. A. Nevinskii Yu. M. Konstantinov 《Russian Journal of Plant Physiology》2010,57(1):37-44
The effect of common intracellular signals (Ca2+ and cAMP) on the activity of protein phosphorylation in mitochondria was investigated in coleoptiles of maize (Zea mays L.). Treatment of isolated mitochondria with 2 mM CaCl2 brought about an increase in the level of phosphorylation of proteins with mol ws of 74, 60, and 33 kD but considerably reduced
phosphorylation of the protein with a mol wt of 51.5 kD. In the presence of Ca2+, phosphorylation of polypeptides with mol wts of 59 and 66 kD was also detected. cAMP considerably reduced phosphorylation
of essentially all the investigated proteins in isolated mitochondria, which could be explained by activation of their dephosphorylation.
Phosphorylation of mitochondrial proteins involves a polypeptide of about 94 kD showing kinase activity, which may be proper
protein kinase or one of the subunits of a compound structure. In maize mitochondria, PP1A phosphatases were found. A hypothesis
was advanced that redox-dependent phosphorylation/dephosphorylation of mitochondrial proteins plays an important role in mitochondrial
signaling in higher plants. 相似文献
20.
Electrocytes from the electric organ of Electrophorus electricus exhibited sodium action potentials that have been proposed to be repolarized by leak currents and not by outward voltage-gated potassium currents. However, patch-clamp recordings have suggested that electrocytes may contain a very low density of voltage-gated K+ channels. We report here the cloning of a K+ channel from an eel electric organ cDNA library, which, when expressed in mammalian tissue culture cells, displayed delayed-rectifier K+ channel characteristics. The amino-acid sequence of the eel K+ channel had the highest identity to Kv1.1 potassium channels. However, different important functional regions of eel Kv1.1 had higher amino-acid identity to other Kv1 members, for example, the eel Kv1.1 S4-S5 region was identical to Kv1.5 and Kv1.6. Northern blot analysis indicated that eel Kv1.1 mRNA was expressed at appreciable levels in the electric organ but it was not detected in eel brain, muscle, or cardiac tissue. Because electrocytes do not express robust outward voltage-gated potassium currents we speculate that eel Kv1.1 channels are chronically inhibited in the electric organ and may be functionally recruited by an unknown mechanism. 相似文献