Inhibitory Effects Of Cadmium Research Articles

Multiple invivo Effects of Cadmium on Photosynthetic Electron Transport in Pea Plants.

The inhibitory effects of cadmium (CdSO4 ) on the primary photosynthetic processes were studied invivo in Pisum sativum by using Multi-function Plant Efficiency Analyser (M-PEA-2). Photosynthetic parameters related to photosystem (PS) II, PS I and intersystem electron carriers were calculated from the light-induced kinetics of prompt chlorophyll a fluorescence (OJIP transient), delayed chlorophyll a fluorescence (DF), and 820 nm modulated reflection (MR). Low-dose exposure to cadmium (20 μm CdSO4 for 48 h) reduced probability of electron transfer from plastoquinones to the terminal electron acceptors of PSI (δRo ) accompanied by a decrease in the rate of P700 + and PC reduction (Vred ) and the magnitude of the I2 step on the DF kinetics. Electron transport through PSI remained unaltered. The obtained results allowed us to propose existence of the potential site of inhibition of photosynthetic electron flow by cadmium between PSII and PSI. We propose to use parameters δRo , Vred , and I2 /I1 as sensitive indicators of an early contamination by heavy metals.

Improved ethanol production in the presence of cadmium ions by a Saccharomyces cerevisiae transformed with a novel cadmium-resistance gene DvCRP1

ABSTRACTThe DvCRP1 gene obtained from Dunaliella viridis is a cadmium-resistance gene that induces cadmium accumulation in microbial and plant cells. In the present study, Saccharomyces cerevisiae was used as a model system to investigate the effect of DvCRP1 on both cadmium detoxification and ethanol production. Inhibitory effects of cadmium (50–300 µmol/L) on growth (29–92%), glucose consumption (23–89%), and ethanol production (17–92%) were observed at 24 h by S. cerevisiae. DvCRP1 alleviated the inhibitory effect of cadmium, with increase in the ethanol production. The established mathematical model showed that the initial inoculation concentration, cadmium concentration, and transformation of DvCRP1 were the most important factors for cell growth, glucose consumption, and ethanol production. Cadmium detoxification of yeast was also enhanced by increasing the initial concentration of yeast cells. Transforming with DvCRP1 further enhanced detoxification, especially at high cadmium concentrations. Transforming with DvCRP1 further enhanced detoxification, especially at high cadmium concentrations (200 µmol/L). The present results evidenced the potential of the insertion of the DvCRP1 gene into yeast for use in bio-refineries during fermentation of heavy metals-contaminated substrates. In addition, this is a promising method for phytoremediation of agricultural soils highly contaminated by heavy metals.

Cadmium inhibits the differentiation of 3T3-L1 preadipocyte through the C/EBPα and PPARγ pathways

Cadmium, a well-known toxic heavy metal, affects cellular physiology by disturbing cellular signaling pathways. We investigate the effect of cadmium on cellular differentiation using 3T3-L1 preadipocyte cell lines as an in vitro model. Here, it was shown that cadmium (3 μM) significantly decreased both glycerol-3-phosphate dehydrogenase (GPDH) activity and lipid accumulation of differentiating 3T3-L1 cells in a dose-dependent manner. In addition, inhibitory action of cadmium on differentiating 3T3-L1 cells was effective only at the initial stage of 3T3-L1 preadipocyte differentiation. Western blot analysis revealed that cadmium suppressed the expression of CCAAT/enhancer-binding protein alpha (C/EBPα) and peroxisome proliferator-activator receptor gamma (PPARγ) proteins, key transcriptional activators for adipogenesis, in a dose-dependent manner. These results suggest that the inhibitory effects of cadmium on 3T3-L1 preadipocyte differentiation, as indicated by a decrease in GPDH activity and lipid accumulation, a marker of adipogenesis, appeared to be mediated through the downregulated expression of C/EBPα and PPARγ proteins.

Evaluation of inoculation of plant growth-promoting rhizobacteria on cadmium and lead uptake by canola and barley

Plant growth promoting bacteria are important for plant growth and heavy metal uptake of metal-polluted soils. In this study, to isolate (cadmium and lead) Cd and Pb-resistant bacteria, seven strains of Pseudomonas putida and Pseudomonas i¬‚uorescens were plated onto Tryptone Soya Broth supplemented with different concentrations of Pb(No3)2and CdCl2 (0, 30, 60 mg L-1). Three heavy metals resistant isolated strains included P. putida strain 11 (P.p.11), P. putida strain 4 (P.p.4) and P. fluorescens strain 169 (P.f.169)were investigated. The bacteria were able to produce indole-3-acetic acid (IAA), siderophores and 1-aminocyclopropane-1-carboxylic deaminase (ACCD). They were inoculated to canola and barly seeds in a soil artificially contaminated with Cd (10 and 20 mg kg-1) and Pb (300 and 600 mg kg-1) in a pot experiment. Results showed that the inoculation with these PGPR increased shoot dry matter of canola. An increase in Cd and Pb uptake was observed in canola inoculated with P.p.11 and P.f.169. Translocation factor indicated that inoculated canola with P.f.169 and barley with all of the three strains had abilities of Cd and Pb phytoextraction in the contaminated soil respectively. The bacterial strains protected the plants against the inhibitory effects of cadmium and lead probably due to production of IAA, siderophore and ACCD activity. Key words: 1-aminocyclopropane-1-carboxylic deaminase (ACC deaminase), canola, heavy metals, phytoextraction, Pseudomonas.

Improvement of Brassica napus growth under cadmium stress by cadmium-resistant rhizobacteria

This study focuses on the characterization of four bacterial isolates from heavy metal-polluted rhizosphere in order to examine their plant growth promoting (PGP) activity. The PGP activity on the canola ( Brassica napus) of the strains which showed cadmium resistance and multiple PGP traits was assessed in the presence and in the absence of Cd 2+. The strains, Pseudomonas tolaasii ACC23, Pseudomonas fluorescens ACC9, Alcaligenes sp. ZN4 and Mycobacterium sp. ACC14 showed 1-aminocyclopropane-1-carboxylate deaminase (ACCD) activity. They also synthesized ACCD enzyme in vitro when 0.4 mM Cd 2+ was added to the growth medium. The presence of the metal, however, reduced the ACCD activity in Alcaligenes sp. ZN4 and Mycobacterium sp. ACC14, while it did not affect the ACCD activity of P. tolaasii ACC23 and P. fluorescens ACC9. ACC9 and ACC23 produced indole acetic acid (IAA) and siderophores, while ACC14 produced only IAA. IAA and siderophores were produced more actively under Cd-stress. Root elongation assays conducted on B. napus under gnotobiotic conditions demonstrated increases (from 34% up to 97%) in root elongation of inoculated canola seedlings compared to the control plants. Subsequently, the effect of inoculation with these strains on growth and uptake of Cd 2+ in roots and shoots of canola was studied in pot experiments using Cd-free and Cd-treated (15 μg Cd 2+ g −1 dw) soil. Inoculation with P. tolaasii ACC23, P. fluorescens ACC9 and Mycobacterium sp. ACC14 promoted the growth of plants at concentrations of 0 and 15 μg Cd 2+ g −1 soil. The maximum growth was observed in the plants inoculated with P. tolaasii ACC23. The strains did not influence the specific accumulation of cadmium in the root and shoot systems, but all increased the plant biomass and consequently the total cadmium accumulation. The present observations showed that the bacterial strains used in this study protect the plants against the inhibitory effects of cadmium, probably due to the production of IAA, siderophores and ACCD activity.

EFFECTS OF METALS AND ORGANIC CONTAMINANTS ON THE RECOVERY OF BIOLUMINESCENCE IN THE MARINE DINOFLAGELLATE PYROCYSTIS LUNULA (DINOPHYCEAE)1

Pyrocystis lunula Schutt is a unicellular photoautotrophic dinoflagellate, commonly found in marine environments, displaying circadian-controlled bioluminescence. Because of this species' characteristics, effects of pollutants on bioluminescence in P. lunula may make for an easy and simple bioassay that would be valuable for toxicity testing and the protection of coastal resources. This study therefore investigated the short-term effects of metals and organic pollutants on the recovery of the bioluminescent potential in P. lunula. Recovery of bioluminescence was strongly inhibited in a dose-dependent manner by all reference contaminants tested, the system being most sensitive to copper and cadmium (4-h IC50 s 0.96 and 1.18 muM, respectively), followed by phenanthrene, lead, SDS, and nickel (4-h IC50 s 1.64, 12.8, 15.6, and 73.1 muM, respectively), whereas relatively high concentrations of phenol were needed to elicit a response (4-h IC50 1.64 mM). Except for exposure to lead and nickel, the inhibitory effects of cadmium, copper, and all organic pollutants were reversible, with P. lunula recovering 80%-100% of its bioluminescence potential after a period of 72 h in uncontaminated medium. Our results show that the restoration of bioluminescence in P. lunula is sensitive to the reference contaminants tested and obtains highly reproducible results.

Fate of copper and cadmium in a sediment‐water system, and effect on chitin degrading bacteria

AbstractFate and effect of copper and cadmium on the degradation of chitin were studied in sediment microcosms. Artificial sediment was spiked with metals, and metal partitioning between sediment components, overlying water and bacteria was described. Most of the added metals were bound to sediment particles. Remarkable metal enrichments were found on Fe‐oxide, Mn‐oxide, and chitin. In sediments containing the nominal concentration of 100 mg/kg Cu, the chitin‐degrading bacteria Cytophaga johnsonae showed a significant decrease in N‐acetylglucoseaminidase activity. Toxicity of copper was attributed to free ions in the overlying water. The bacteria were more sensitive to copper than to cadmium. Inhibitory effects of cadmium were primarily caused by sediment‐associated cadmium.

Inhibitory effects of cadmium on in vitro calcification of a clonal osteogenic cell, MC3T3-E1

To examine an inhibitory mechanism of Cd on bone formation, the effects of Cd on calcification were investigated in a culture of a clonal osteogenic cell line, MC3T3-E1. At 3 days after inoculation, Cd was added to the medium containing 7 m m β-glycerophosphate, and culture was continued for 8 days. Cd at 1.78 μ m and above caused a significant decrease in 45Ca accumulation. The decrease in mineralization by Cd was similar to that in collagen content or alkaline phosphatase (ALP) activity. Histologically, the cell density and the mineralization degree were lower than those of the controls. Ultrastructurally, degenerated cells were observed with undifferentiated cells which had fewer rough-surfaced endoplasmic reticulum and many mitochondria. This suggests that Cd may inhibit the differentiation into osteoblasts as well as the cell function. On the other hand, calcification of cells at 8 days after inoculation was inhibited by Cd at 1.78 μ m and above. The decrease in collagen content and ALP activity by Cd was much lower than that in calcification. Cd-treated cells were well differentiated into osteoblasts morphologically, but the mineralization degree was lower than that of the controls. Ultrastructurally, cell damage was not recognized so strongly compared with long-term Cd treatment. The mineralization of osteoblasts was also inhibited by Zn levels which left both collagen content and ALP activity unaffected. From these results, it was suggested that the inhibitory effect of Cd on in vitro calcification of MC3T3-E1 cells may be due to both a depression of cell-mediated calcification and a decrease in physicochemical mineral deposition.

Short- and long-term effects of heavy metals on urease activity in soils

The inhibitory effects of cadmium, chromium, copper, lead, nickel and zinc on urease activity of five different soils during two different periods were investigated, in order to obtain information on the change in heavy metal toxicity with time. The results are presented graphically as logistic dose-response curves. When the ecological dose range was used as a measure of toxicity this value decreased significantly only for copper in the sandy soil. Considering toxicity as the ecological dose-50% (ED50) value, toxicity tended to increase over 1 1/2 years for cadmium, copper and zinc. For nickel and lead, however, the toxicity stabilized in all soils, except in sand and clay. The average ED 50 value of zinc varied between 100 and 300 mg kg−1 and its toxicity was highest. It is emphasized that these data may help to set limits for the heavy-metal pollution of soils.

Evidence for stimulatory and inhibitory effects of cadmium on the [ 3H] thymidine incorporation into various organs of the mouse

The effects of cadmium chloride on the DNA turnover in various organs of the mouse were evaluated by measuring the incorporation of intraperitoneally injected [6- 3H] thymidine. This approach is considered to be a useful complement to other short-term in vivo tests in the screening for genotoxic properties of chemicals. A moderate amount of CdCl 2 (1 mg/kg body wt) lacked inhibitory effects on the incorporation of [ 3H]thymidine, but produced a significantly increased uptake of the DNA precursor into the liver. Whereas the genotoxic polycyclic aromatic hydrocarbon 3-methylcholanthrene suppressed the [ 3H]tthymidine incorporation into several organs when given in a dose of 30 mg/kg body wt, cadmium chloride was inhibitory only when injected in a sublethal dose (4 mg/kg body wt). When the injected amount of CdCl 2 was 4 mg/kg, an initial and transient inhibition of the [ 3H] thymidine incorporation was observed in several organs. After extending the time between the injection of cadmium and sacrifice to 72 h, such a high dose of cadmium produced potent stimulatory effects on the [ 3H]- thymidine incorporation not only into the liver but also into the pancreas, kidney, small intestine, and testis. The mechanism behind the cadmium-induced stimulation of the DNA synthesis remains obscure but may be due to an increased biosynthesis of the cytoplasmatic protein metallothionein. The stimulatory effects of cadmium on the incorporation of [ 3H] thymidine correlate well both with reported sites of extensive accumulation of the heavy metal and the presence of high concentrations of cadmium-induced metallothionein.

Effect of cadmium on the isolated vas deferens from guinea-pig.

The effects of cadmium on the responses to the agonists, K, acetylcholine, noradrenaline, Ba and Ca were investigated in the isolated vas deferens from guinea pig. 1. The low concentration of cadmium enhanced the effects of tested agonists, and the enhancement was larger in order of K, Ba, Ca, noradrenaline=acetylcholine. 2. The high concentration of cadmium inhibited the effects of tested agonists with a dose-dependent manner. The inhibitory effect was weaker against the contraction by K and was stronger against the contractions by Ba, Ca, acetylcholine and noradrenaline. 3. The inhibitory effects of cadmium against the contractions by acetylcholine and noradrenaline were almost the same. 4. On the shape of contraction by K, cadmium showed the stronger inhibition against the tonic contraction than the phasic contraction. 5. The above mentioned results were mainly discussed on the Ca mobilization and the receptor selectivity.

Inhibitory Effects of Cadmium on the Release of Acetylcholine from Cardiac Nerve Terminals

The effect of stimulation of the vagaosympathetic trunk or the vagal nerve on the cardiac interval of the spontaneously beating heart of the bullfrog was studied in the presence and absence of Cd. The prolongation of the cardiac interval following the nerve stimulation was abolished by Cd (5 micrometer). Such an effect of Cd was completely antagonized by increasing the external Ca to 10 times the normal concentration. Cd (10 micrometer) did not alter the compound action potential of the nerve trunk, nor did it affect the pacemaker activity of the heart. Bioassay of acetylcholine in the effluent from the heart after cardiac nerve stimulation showed that Cd reduced the acetylcholine release from the cardiac nerve. It is concluded that Cd may act on the cardiac nerve terminals where Cd suppresses the release of acetycholine.

Reductions in the Toxicity of Cadmium to Microorganisms by Clay Minerals

The clay minerals montmorillonite and kaolinite protected bacteria, including actinomycetes, and filamentous fungi from the inhibitory effects of cadmium (Cd). Montmorillonite provided greater protection than did equivalent concentrations of kaolinite. The protective ability of the clays was correlated with their cation exchange capacity (CEC). The greater the CEC, the greater the absorbancy of exogenous Cd by the exchange complex and the greater the protection. The greater protection afforded by montmorillonite, as compared to kaolinite, was correlated with its higher CEC. Clays homoionic to Cd did not protect against exogenous Cd, as the exchange complex was already saturated with Cd. Montmorillonite homoionic to Cd was more detrimental to microbial growth than was kaolinite homoionic to Cd, as more Cd was present on and apparently desorbed from the montmorillonite.

Sulphydryl groups in photosynthetic energy conservation III. Inhibition of photophosphorylation in spinach chloroplasts by CdCl 2

Low concentrations of CdCl 2 inhibited cyclic and non-cyclic photophosphorylation in spinach chloroplasts and depressed coupled electron transport to the basal level. The basal electron transport and the electron flow stimulated by several uncouplers, except arsenate, were not affected. The inhibitory effects of cadmium were reversed by dithiols like dithioerythritol or 2,3-dimercaptopropanol. The light-induced pH rise of chloroplast suspensions and the trypsin-activated Ca-ATPase were not affected by cadmium at the concentrations that inhibited ATP synthesis but the latter was affected by higher concentrations.