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1.
The activity of dehydrogenase in Saccharomyces cerevisiae was estimated by reduction of 2,3,5-triphenyltetrazolium chloride. By the adaptation of yeast to cadmium, the high activity of dehydrogenase was observed. Furthermore, the activity of dehydrogenase in Cd-resistant cells was increased by growing in medium containing CdSO4. However, the activity of dehydrogenase was inhibited by the addition of CdSO4 to the reaction mixture. The activity of dehydrogenase in Cd-sensitive cells was increased slightly by incubation with low concentrations of CdSO4. High activity of dehydrogenase in Cd-resistant cells was completely negated by the addition of cycloheximide to the incubation medium. The increase of dehydrogenase activity is due partly to de novo synthesis of protein. 相似文献
2.
In vitro and in vivo cadmium toxicity studies focus almost exclusively on CdCl 2 effects. Only a few studies have used adrenocortical cells and tissue to determine cadmium salt effects during stress of adrenocorticotropin stimulation. Because several biologically relevant water-soluble cadmium salts exist, this study extended work with CdCl 2 to evaluate the acute adrenocortical cell steroid secretory responses to non-lethal cadmium acetate (CdAc 2) and CdSO 4
4 concentrations. Control or ACTH-stimulated cultured Y-1 mouse adrenal tumor cells (ATCC) which secrete 20-dihydroprogesterone (20-DHP) were incubated for 0.5 h in serum-free medium (FMEM) with or without 0.5, 1.0, 5.0, 10.0, 50.0, 100.0, 500.0 and 1000.0 µg CdAc 2 or CdSO 4/ml FMEM (1.9, 3.8, 19.0, 38.0, 190.0, 380.0 and 1900.0 µmol/L, respectively). For each salt, cell viability was measured at the end of the incubation using live cell trypan blue exclusion. In addition, cumulative CdAc 2 effects during 4 h incubations and effect reversibility were determined for control and stimulated cells. After each experimental incubation, the 20-DHP secreted into the medium was determined by radioimmunoassay. Over 80% of all control or ACTH-stimulated cells were viable after incubation in the presence or absence of various CdAc 2 or CdSO 4 concentrations. Cadmium acetate and sulfate inhibited basal and ACTH-stimulated steroid secretion in a dose-dependent manner. For basal steroid secretion the CdAc 2 concentration that first significantly inhibited was 0.5 µg/ml medium (1.9 µmol/L); stimulated secretion was significantly inhibited beginning at 5.0 µg/ml (19.0 µmol/L) and the concentration reducing stimulated 20-DHP secretion by 50% (IC 50) was 5.6 µg/ml (21.3 µmol/L). Similarly, the first CdSO 4 concentration to significantly inhibit basal and ACTH-stimulated steroid secretion was 10.0 µg/ml medium (39.0 µmol/L); the IC 50 was 7.8 µg/ml (29.8 µmol/L). Except that basally secreting Cd 2+
2+-treated cells almost doubled 20-DHP secretion after Cd 2+ removal and subsequent incubation with ACTH, all basal and ACTH-stimulated steroid secretion was irreversibly inhibited by every CdAc 2 concentration. All CdAc 2 concentrations initiated and maintained cumulative inhibitory effects on basal and ACTH-stimulated steroid secretion over a 4 h period. Reversibility and cumulative CdSO 4 treatment studies were not conducted. Based on the results from the present studies, both CdAc 2 and CdSO 4 appeared to incrementally inhibit control and ACTH-stimulated steroidogenesis without affecting cell viability and to be more potent inhibitors of adrenocortical cell steroid secretion than CdCl 2. Finally, CdAc 2 effects on control and stimulated cells were cumulative and irreversible. 相似文献
3.
Segments of oat ( Avena sativa L.) roots which had been exposed to 1 millimolar CdSO 4 in quarter-strength Hoagland No. 1 solution exhibited decreased respiratory rates, ATP levels, membrane-bound ATPase activity, and reduced K + fluxes. Respiration and ATP levels were decreased after a 2-hour treatment with 1 millimolar CdSO 4 to 65 and 75%, respectively, of control rates. A membrane-bound, Mg 2+-dependent, K +-stimulated acid ATPase was rapidly inhibited to 12% of control activity in the presence of 1 millimolar CdSO 4. Potassium uptake into root segments was inhibited to 80% of control values after 30 minutes in the presence of CdSO 4. A 2-hour pretreatment of root segments with CdSO 4 inhibited K + uptake to 15% of control values. Cytoplasmic K + efflux was inhibited with 1 millimolar CdSO 4. The rates and the degree of Cd2+ inhibition of the parameters listed above suggest that one of the first sites of Cd2+ action is the plasmalemma K+ carrier (ATPase) in oat roots. 相似文献
4.
The effect of pargyline on the uptake of acetaldehyde (in the presence of pyrazole) by isolated rat liver cells was studied after incubating the liver cells for 0, 10, 30, 45, and 60 min with 0.40, 1.30, and 2.6 mm pargyline. Without any incubation period, pargyline had no effect on acetaldehyde uptake. With increasing time of incubation, there was a progressive increase in the extent of inhibition of acetaldehyde uptake by pargyline. This suggests the possibility that pargyline is metabolized to the effective inhibitor or the incubation period allows pargyline to reach its site(s) of action. Pargyline was also a more effective inhibitor of the uptake of lower concentrations of acetaldehyde, e.g., 0.167 mm, than of higher concentrations (1.0 mm) of acetaldehyde, especially after short incubation periods or when pyrazole was omitted from the reaction medium. After a 20- to 30-min incubation period, pargyline inhibited the control rate of ethanol oxidation by the liver cells, as well as the accelerated rate of ethanol oxidation found in the presence of pyruvate or an uncoupling agent. Pargyline had no effect on hepatic oxygen consumption. During ethanol oxidation, a time-dependent release of acetaldehyde into the medium was observed. Pyruvate, by increasing the rate of ethanol oxidation, increased the output of acetaldehyde five- to tenfold. Pargyline increased the output of acetaldehyde two- to threefold, despite decreasing the rate of ethanol metabolism by the liver cells. These data indicate that pargyline inhibits the low Km aldehyde dehydrogenase in intact rat liver cells and that this enzyme plays the major role in oxidizing the acetaldehyde which arises during the metabolism of ethanol. Although most of the acetaldehyde generated during the oxidation of ethanol is removed by the liver cells in an effective manner, changes in the activity of aldehyde dehydrogenase or the rate of acetaldehyde generation significantly alter the hepatic output of acetaldehyde. 相似文献
5.
Repeated cultivations (4 passages) of salmonellæ (18 strains) resistant to cadmium, streptomycin and β-lactam antibiotics in Müller-Hinton Broth (MHB) and Mac-Conkey Broth (MCB) without and with CdSO 4 (2, 20 and 100 mg/L) showed a higher toxic effect of cadmium in MCB. The strains survived at CdSO 4 100 mg/L in MHB for four transfers, in MCB only a single transfer. In dependence on the medium used and amount of metal added, the increase of resistance to antibiotics was different. In MHB, the same levels of resistance to carbenicillin and streptomycin were induced by CdSO 4 (20 and 100 mg/L), in MCB it was by 2 and 20 mg/L. Simultaneous stop of the growth of a control culture S. typhimurium with chromosomal resistance to streptomycin, isolates with and without plasmid in MCB which contained CdSO 4 100 mg/L, and the results of conjugal transfer of resistance suggest that changes of resistance to antibiotics were not medated by determinants of resistance to antibiotics. The binding of cadmium to outer membrane protein can cause a decreased permeability to these antibiotics as a resistance mechanism. 相似文献
6.
In a medium containing a trace element solution and 10 -4 M ferrous ions the growth yield of Clostridium formicoaceticum on fructose was 5.5 g of weight per l; in the absence of metal ion solution it was 1 g per l. The specific activity of methyl viologen dependent formate dehydrogenase under both conditions was 0.28 and 0.03 units per mg of protein, respectively. It could be increased to 9.75 units when the growth medium contained 10 -4 M tungstate and 10 -5 M selenite in addition. Molybdate was only about 40% as effective as tungstate. Tungstate or molybdate could not be replaced by vanadate, selenite not by sulfide. The formate dehydrogenase catalyzed also the reduction of CO 2 to formate. The highest rate of formate synthesis was observed when pyruvate served as the reductant. No pyruvate: formate exchange but rapid pyruvate: CO 2 exchange could be observed with cell-free extracts of C. formicoaceticum. Pyruvate is fermented by C. formicoaceticum to yield up to 1.16 mole acetate per mole of pyruvate. Resting cells accumulated some formate in addition to acetate. 相似文献
7.
Summary Various nitrogen compounds were tested for their ability to alleviate the reduced nitrogen requirement of soybean cells growing in defined liquid medium containing nitrate as the alternative nitrogen source. Either l-glutamine, l-alanine, putrescine or NH 4
+ satisfied this requirement. Addition of l-glutamate resulted in poor growth. Where growth was stimulated, nitrate reductase (NR) activity increased whereas glutamate dehydrogenase activity in the cells showed no such correlation. In all fresh media which supported rapid growth, NR activity first decreased rapidly to a low value. Subsequent dry weight increases occurred concommitantly with an increase in NR activity. When 2,4-dichlorophenoxyacetic acid was omitted from the medium the growth was slow and the NR activity did not increase. During the first 40 h of incubation in medium containing NH 4
+ plus NO 3
- the cells produced a growth-enhancing factor(s). This factor(s) was present in the cells and in the medium and eliminated the requirement for reduced nitrogen.This work was supported by a grant in aid of research from the National Research Council of Canada to one of us (J. K.). NRCC No. 12520 相似文献
8.
The use of phosphate solubilizing plant growth-promoting microorganisms as inoculants assists in the hydrolysis of insoluble forms of phosphorus leading to increased plant growth. Pseudomonas putida PCI2 was evaluated for phosphatase activity and solubilization of AlPO 4 and FePO 4. The effect of different incubation temperatures, concentrations of NaCl and different pH on growth of PCI2 and P solubilization was studied. PCI2 proved to be positive for phosphatase activity, solubilized AlPO 4 and hydrolyzed Ca 3(PO 4) 2 even in medium with 5 % NaCl. In addition, PCI2 produced 45 % units of siderophores. The production of IAA by PCI2 was stimulated in vitro by the addition of different concentrations of L-tryptophan to the culture medium. Assays with tomato seedlings showed that the length of the root was reduced as the concentration of IAA increased. On the other hand, inoculation with PCI2 caused a clear growth-promoting effect on shoot growth in the presence of L-tryptophan. P. putida PCI2 is adapted to different environmental conditions and has potential to be developed and used as an inoculant for increasing the growth of tomato plants. 相似文献
9.
The tannins chebulinic acid or tara tannin were added to an incubation system in which GA 3 induces enzyme synthesis in endosperm half seeds of barley ( Hordeum vulgare L.). The activity of amylase and acid phosphatase in the incubation medium was reduced compared to the activity in the medium after incubation with GA 3 alone. When embryo half seeds of barley were incubated with chebulinic acid or tara tannin in the absence of added GA 3, the enzyme activity of the incubation medium was also reduced. The activity of preformed enzymes obtained from endosperm half seeds previously induced with GA 3 was not reduced by the addition of tannin. Comparisons were made of the amount of enzyme activity from breis of aleurone layers incubated with GA 3 in the presence and absence of tannins. The amounts of activity were relatively small and approximately equal in both cases, indicating that secretion from the aleurone was not blocked by the tannins. The reduction of enzyme activity caused by tannins in both endosperm and embryo half seeds could be completely reversed by the addition of GA 3. 相似文献
10.
The effect of ammonium addition (6.5, 58, and 395 μg of NH 4+-N g [dry weight] of soil −1) on soil microbial communities was explored. For medium and high ammonium concentrations, increased N 2O release rates and a shift toward a higher contribution of nitrification to N 2O release occurred after incubation for 5 days at 4°C. Communities of ammonia oxidizers were assayed after 4 weeks of incubation by denaturant gradient gel electrophoresis (DGGE) of the amoA gene coding for the small subunit of ammonia monooxygenase. The DGGE fingerprints were invariably the same whether the soil was untreated or incubated with low, medium, or high ammonium concentrations. Phylogenetic analysis of cloned PCR products from excised DGGE bands detected amoA sequences which probably belonged to Nitrosospira 16S rRNA clusters 3 and 4. Additional clones clustered with Nitrosospira sp. strains Ka3 and Ka4 and within an amoA cluster from unknown species. A Nitrosomonas-like amoA gene was detected in only one clone. In agreement with the amoA results, community profiles of total bacteria analyzed by terminal restriction fragment length polymorphism (T-RFLP) showed only minor differences. However, a community shift occurred for denitrifier populations based on T-RFLP analysis of nirK genes encoding copper-containing nitrite reductase with incubation at medium and high ammonia concentrations. Major terminal restriction fragments observed in environmental samples were further described by correspondence to cloned nirK genes from the same soil. Phylogenetic analysis grouped these clones into clusters of soil nirK genes. However, some clones were also closely related to genes from known denitrifiers. The shift in the denitrifier community was probably the consequence of the increased supply of oxidized nitrogen through nitrification. Nitrification activity increased upon addition of ammonium, but the community structure of ammonium oxidizers did not change. 相似文献
11.
The formation of the nicotinamide adenine dinucleotide phosphate-dependent formate dehydrogenase in Clostridium thermoaceticum is stimulated by the presence of molybdate and selenite in the growth medium. The highest formate dehydrogenase activity was obtained with 2.5 × 10 −4 M Na 2MoO 4 and 5 × 10 −5 Na 2SeO 3. Tungstate but not vanadate could replace molybdate and stimulate the formation of formate dehydrogenase. Tungstate stimulated activity more than molybdate, and in combination with molybdate the stimulation of formation of formate dehydrogenase was additive. Formate dehydrogenase was isolated from cells grown in the presence of Na 275SeO 2, and a correlation was observed between bound 75Se and enzyme activity. 相似文献
12.
A substance capable of stimulating the activities of pyruvate dehydrogenase and low Km cyclic AMP phosphodiesterase was prepared from H4-II-EC3′ hepatoma cells by acid extraction and partially purified by molecular exclusion chromatography. The material thus prepared by gel chromatography was found to stimulate the activities of these enzymes in a concentration-dependent manner. The amount or activity of the pyruvate dehydrogenase stimulating factor was increased in cells which had been treated with physiological concentrations of insulin (0.2 mU/ml). Increasing the concentration of insulin increased the amount or activity of the factor generated. High concentrations of insulin did not cause a reversal of the effects of insulin. The stimulation of pyruvate dehydrogenase activity by the factor was eliminated when sodium fluoride (75 mm) was present in the enzyme assay, implying that activation was mediated by the pyruvate dehydrogenase phosphatase. The enzyme-stimulating factor isolated from hepatoma cells shares a number of important characteristics with the putative second messenger of insulin prepared from other cell types: (1) it is heat and acid stable, (2) it has a similar apparent molecular weight, (3) it is generated in an insulin-dependent manner, (4) it stimulates the activity of pyruvate dehydrogenase by a fluoride-sensitive mechanism, and (5) it elutes from the anion-exchange resin AG 1-X8 at an ionic strength of 0.4 m. These findings suggest that the stimulator of pyruvate dehydrogenase and of low Km cyclic AMP phosphodiesterase isolated from hepatoma cells has chemical properties identical with those of the putative second messenger of insulin action isolated from a number of other insulin-sensitive tissues. 相似文献
13.
Sex steroid and cortisol levels were compared in Leibovitz’s L-15 cultural medium after incubation of tissue samples from the intact female and male sterlet ( Acipenser rhutenus L.) and from the fishes exposed to hormonal stimulation of sexual maturation by a superactive analog of mammalian gonadotropin-releasing hormone (LH-RH-A). A higher level of 17,20β,21-trihydroxy-4-pregnen-3-one (20βS) was revealed in the cultural medium following incubation of ovarian follicles isolated from females 5 h after LH-RH-A stimulation, as compared to the data obtained for intact females. The addition of 1 μM progesterone (P 4) to the cultural medium before incubation of ovarian follicles also led to an increase in the 20βS level in the incubates by the end of the experiment. Cortisol and testosterone levels in the incubates exhibited the same tendency. The blood cortisol level significantly increased in females 5 h after their hormonal stimulation. In males, showing high levels of androgens (testosterone and 11-ketotestosterone) in the blood serum before hormonal stimulation, high levels of these hormones were also detected in the cultural medium after incubation of testicular and liver tissue samples. The addition of P 4 to the medium before incubation stimulated the production of sex steroids and cortisol by the gonadal fragments. Upon addition of P 4 to the incubation mixture, containing liver tissue samples, the 20βS level increased. 相似文献
14.
Partially purified intact chloroplasts were prepared from batch cultures of both wild type ( Wt) and a mutant strain of Chlamydomonas reinhardtii. Protoplasts were generated from log phase cultures of Wt (137c) and the phosphoribulokinase-deficient mutant F60 by incubation of the cells in autolysine. These protoplasts were suspended in an osmoticum, cooled, and then subjected to a 40 pounds per square inch pressure shock using a Yeda pressure bomb. The resulting preparation was fractionated on a Percoll step gradient which separated the intact chloroplasts from both broken chloroplasts and protoplasts. The chloroplast preparation was not significantly contaminated with the cytoplasmic enzyme activity phosphoenolpyruvate carboxylase (>5%), and contained (100%) stromal enzyme activity ribulose-1,5-bisphosphate carboxylase. The chloroplast preparation is significantly contaminated by mitochondria, as determined by succinate dehydrogenase activity. Chloroplasts prepared from Wt cells retained CO2-dependent O2 photoevolution at rates in excess of 60 micromoles per milligram chlorophyll per hour, an activity which is severely inhibited by the addition of 10 millimolar KH2PO4. The chloroplasts are osmotically sensitive as determined by ferricyanide-dependent O2 photoevolution. 相似文献
15.
The ammonium uptake by cucumber seedlings was estimated from ammonium ions depletion in an uptake solution. The uptake of
NH
4
+
was decreased by about 60 % after one hour and by about 90 % after two hours of 100 μM Cu 2+ treatment. On the contrary the accumulation of ammonium in roots of Cu 2+-treated seedlings at the same time was higher than in the control. Cu 2+ in the concentration inhibiting NH
4
+
absorption during one hour inhibited also glutamine synthetase (GS) (EC 6.3.1.2) and NADH-glutamate dehydrogenase (NADH-GDH)
(EC 1.4.1.2) activities both localized in the roots of seedlings. After one hour and at least up to the 4th hour Cu 2+ accumulated mainly in roots (95 %). It was probably the reason of the GS activity in cotyledons of seedling treated with
Cu 2+ that it was at the same level as in the control. NADH-GDH activity in cotylcdons after one hour of the Cu 2+ treatment was lower than in the control but the influence of Cu 2+ action on the activity of this enzyme in roots was by far stronger. 100 μM Cu 2+ did not affect the activities of both enzymes in in vitro experiments. Copper added into the incubation medium in 1000 μM concentration decreased GS activity, but still did not change
NADH-GDH activity. These results suggested the indirect Cu 2+ action on the investigated enzymes in in vivo experiments. However, no substantial effect on enzyme activities extracted from control plants was observed after the addition
of the extract from Cu 2+-treated plants into the incubation medium.
The data suggest that the influence of Cu 2+ on uptake and assimilation of ammonium may be connected not only with changes of plasma membrane properties in the root cells
of Cu 2+ treated seedlings but also with Cu 2+ action on two major enzymes involved in NH
4
+
assimilation: glutamate synthetase and NADH-glutamate dehydrogenase. 相似文献
16.
Incubation of rat liver parenchymal cells with 10 ?5m epinephrine or norepinephrine resulted in a rapid incorporation of 32P into pyruvate kinase. Inclusion of α-adrenergic blocking agents (phenoxybenzamine or phentolamine) in the hepatocyte incubation medium prior to addition of epinephrine suppressed the subsequent phosphorylation of pyruvate kinase. On the other hand, inclusion of the β-adrenergic antagonist, propranolol, in the hepatocyte incubation medium prior to addition of epinephrine did not suppress the epinephrine-elicited phosphorylation of pyruvate kinase. Exogenous addition of either cyclic AMP or cyclic GMP to the hepatocyte incubation medium also resulted in increased phosphorylation of pyruvate kinase. To investigate whether the same amino acid residue(s) of liver pyruvate kinase was being phosphorylated in each instance, 32P-labeled pyruvate kinase was isolated from hepatocytes after incubation in the presence or absence of either glucagon or epinephrine. In addition, purified liver pyruvate kinase was phosphorylated in vitro with a rat liver cyclic AMP-dependent protein kinase. Each 32P-labeled pyruvate kinase was then subjected to tryptic digestion, two-dimensional thin-layer peptide mapping, and autoradiography. Each 32P-labeled pyruvate kinase sample yielded 44 to 48 tryptic peptides upon staining with ninhydrin and 4 peptides that contain 32P as detected by autoradiography. Furthermore, the same 4 peptides of pyruvate kinase were radiolabeled in each instance. Thus phosphorylation of pyruvate kinase in vitro with [γ- 32P]ATP or upon addition of either glucagon or epinephrine to hepatocytes incubated with 32Pi resulted in phosphorylation of the same amino acid residues. 相似文献
17.
This communication describes the isolation and characterization of mutants of Rhizobium trifolii which can induce nitrogenase activity in defined liquid medium. Two procedures were used for the isolation of these mutants from R. trifolii strain DT-6: (1) following chemical mutagenesis, slow growin mutants were selected which were unable to utilize NH 4+ as sole source of nitrogen; (2) as spontaneous mutants resistant to the glutamate analogue L-methionine-DL-sulfoximine.Mutants (DT-71, DT-125) isolated by these procedures induced nitrogenase activity in the free-living state, whereas the parent strain lacked this property. Induction of nitrogenase activity in these mutants occurred during the late exponential phase of growth when the rate of protein synthesis was decreasing. The addition of NH 4+ to a medium containing glutamate as the nitrogen-source resulted in a 50–70% reduction (repression?) of nitrogenase activity; in contrast, the rate of protein synthesis or the rate of respiration was not influenced by exogenous NH 4+.Biochemistry analysis showed that these mutants (strains DT-71 and DT-125) have defects in both nitrogen and carbon metabolism. The levels of glutamate synthase (both NADP +-and NAD +-dependent activities) and glutamate dehydrogenase (NAD +-dependent activity) were markedly lower. In addition, the mutants were found to have no detectable ribitol dehydrogenase or β-galactosidase activity. These findings are discussed in relation to a mechanism of regulation of symbiotic nitrogen fixation. 相似文献
18.
The aim of this study was to investigate the mechanism of inhibition of mitochondrial aldehyde dehydrogenase (ALDH2) by carbon tetrachloride (CCl 4). CCl 4 administration caused marked hepatocyte ballooning and necrosis in the pericentral region. CCl 4 also inhibited hepatic ALDH2 activity in a time-dependent manner without altering the protein level, suggesting ALDH2 inhibition through covalent modifications such as phosphorylation by JNK. To demonstrate phosphorylation, the isoelectric point (p I) of ALDH2 in CCl 4-exposed rats was compared to that of untreated controls. Immunoblot analysis revealed that immunoreactive ALDH2 bands in CCl 4-exposed rats were shifted to acidic p I ranges on two-dimensional electrophoresis (2-DE) gels. Incubation with alkaline phosphatase significantly restored the suppressed ALDH2 activity with a concurrent alkaline p I shift of the ALDH2 spots. Both JNK and activated JNK were translocated to mitochondria after CCl 4 exposure. In addition, incubation with catalytically active JNK led to significant inhibition of ALDH2 activity, with an acidic p I shift on 2-DE gels. Furthermore, immunoprecipitation followed by immunoblot analysis with anti-phospho-Ser–Pro antibody revealed phosphorylation of a Ser residue(s) of ALDH2. These results collectively indicate a novel underlying mechanism by which CCl 4 exposure activates JNK, which translocates to mitochondria and phosphorylates ALDH2, contributing to inhibition of ALDH2 activity accompanied by decreased cellular defense capacity and increased lipid peroxidation. 相似文献
19.
Soluble and stable insulin-dextran complex was prepared. Pyruvate dehydrogenase activity, as assayed by 14CO 2 formation from [1- 14C]-pyruvate in crude mitochondria of mouse adipose tissue, was increased after incubation of fat pads with native insulin or insulin-dextran. The direct addition of insulin or insulin-dextran to mitochondria was without effect. At submaximal stimulation, insulin-dextran was 10 times less effective than native insulin but the degree of maximal stimulation and the time course of activation by insulin and insulin-dextran were similar. The results favor the concept that the activation of pyruvate dehydrogenase in fat cells does not need the entry of insulin into cells. 相似文献
20.
Callus cultures of two parental clones of Populus nigra L., Poli and 58-861, originating from contrasting environments, were exposed to different cadmium concentrations (0, 150
and 250 μM CdSO 4). Clones showed different growth responses to cadmium, evaluated by the tolerance index (Ti), with Poli being more tolerant
to the metal at both concentrations. The cadmium concentration at the end of the treatment was very similar between clones
at 150 μM CdSO 4, while a higher value in 58-861 compared to Poli was detected at 250 μM CdSO 4. The bioconcentration factor evidenced the lowest value in Poli at 250 μM CdSO 4. Unlike 58-861, cadmium provoked a strong induction of thiols and phytochelatins in clone Poli. In both clones, organic acid
concentration differed notably in untreated calli and cadmium treatment induced a general lowering of these compounds. A notably
higher antioxidant enzyme activity (ascorbate peroxidase, APX; catalase, CAT; guaiacol peroxidase, GPX) was measured in control
calli of clone Poli compared to 58-861. Cadmium induced a remarkable enhancement of APX and CAT, but not GPX, activity at
150 μM CdSO 4 in Poli. Conversely, in 58-861 at 150 μM CdSO 4, and in both clones at 250 μM CdSO 4, a decrease in the antioxidant activity occurred. This investigation provided evidence that these two contrasting genotypes
of P. nigra are characterised by a different response to cadmium in callus cultures. In particular, in Poli, the higher tolerance to
cadmium is associated with a higher activity of antioxidative enzymes and the ability to strongly increase thiol and PC concentration
in response to metal exposure. 相似文献
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