Accumulation of cadmium in rat liver cadmium binding protein following single and repeated cadmium administration.

The accumulation of cadmium in rat liver cadmium binding protein induced by single and repeated intraperitoneal injections of CdCl2 and the de novo biosynthesis of CdBP were studied by using 109Cd to measure cadmium binding in the CdBP and 35S incorporation as indicator of protein synthesis. The biosynthesis of CdBP is controlled by the cadmium concentrations. For single doses up to 1 mg Cd2+/Kg b.w. about 50% of the cadmium is present in the soluble fraction of liver bound to CdBP and the incorporation of 35S-cysteine is linear with the cadmium concentration. When single doses ranging from 1 to 3 mg Cd2+/Kg b.w. are administered the fractions of both 35S-cysteine and cadmium incorporated into de novo synthesized CdBP gradually decrease. For single doses higher than 3 mg Cd2+/Kg b.w. the biosynthesis capability is maximum and 20 mug Cd/g liver can be incorporated into the de novo biosynthesized CdBP. When rats are treated every day with amounts of cadmium of about 0.8 mg Cd2+/Kg b.w. for up to 8 days a dose-proportional increase in both Cd incorporation and CdBP biosynthesis are observed. This shows a cumulative incorporation of cadmium in the de novo biosynthesized CdBP. Experiments carried out by injecting 65ZnCl2 and 203HgCl2 every day showed that they are not accumulated like cadmium and do not induce the biosynthesis of rat liver CdBP after repeated administration over 7 days.     

Variation in cadmium accumulation potential and tissue distribution of cadmium in tobacco

Variation in Cd accumulation between Nicotiana species but not varieties has been observed in seedlings grown in solution culture with moderate-to-low levels of Cd. Nicotiana tabacum has been characterized as a leaf and root accumulator while Nicotiana rustica is shown to be primarily a root accumulator, having about half the leaf Cd per gram dry weight of N. tabacum. This phenotype is retained in the mature N. rustica plant. To characterize these two species which differ in their modes of Cd accumulation, tissue Cd distribution, partitioning of metal in soluble and insoluble fractions and the contribution of soluble Cd-binding proteins (peptides) to total plant Cd was assessed using mature solution cultured plants. Metal accumulation was highest in the most mature leaves and in young roots. The preponderance of young roots in N. rustica may, in part, account for low leaf/high root Cd accumulation in this species. While Cd-binding peptides appear to be a principal form of Cd in leaves and roots of seedlings and these also occur in mature leaves, Cd is equally distributed between soluble (about 80% as Cd-binding peptide) and uncharacterized insoluble forms in mature plant roots.     

Antioxidant capacity and cadmium accumulation in parsley seedlings exposed to cadmium stress

Parsley (Petroselinum hortense L.) plants cultivated under controlled conditions were exposed to different doses of cadmium to investigate the antioxidant capacity and cadmium accumulation in the samples. Two-months-old parsley seedlings were treated with four different concentrations of CdCl₂ (0, 75, 150, and 300 μM) for fifteen days. Cadmium level in leaves increased significantly by increasing the Cd contamination in the soil. Total chlorophyll and carotenoid content declined considerably with Cd concentration. Cd treatment caused a significant increase lipid peroxidation in tissue of leaf. Superoxide dismutase activity (SOD, EC 1.15.1.1) increased partially at 75 and 150 μM CdCl₂ concentrations whereas the activity decreased at 300 μM CdCl₂. Catalase (CAT, EC 1.11.1.6) and ascorbate peroxidase (APX, EC 1.11.1.11) activities were reduced by Cd application. Total phenolic compound amount increased significantly with increasing Cd concentration, as ferric reduction power, superoxide anion radical, and DPPH˙ free radical scavenging activities elevated slightly by the concentration. These results suggest that antioxidant enzymes activities were repressed depending on accumulation of cadmium in leaves of parsley while the non-enzymatic antioxidant activities slightly increased.     

Antioxidant defense system and cadmium uptake in barley genotypes differing in cadmium tolerance

Using two barley (Hordeum vulgare) cultivars (cvs. Tokak and Hamidiye) nutrient solution experiments were conducted in order to study the genotypic variation in tolerance to Cd toxicity based on (i) development of leaf symptoms, (ii) decreases in dry matter production, (iii) Cd concentration and (iv) changes in antioxidative defense system in leaves (i.e., superoxide dismutase, ascorbate peroxidase, glutathione reductase, catalase, ascorbic acid and non-protein SH-groups). Plants were grown in nutrient solution under controlled environmental conditions, and subjected to increasing concentrations of Cd (0, 15, 30, 60 and 120 micromol/L Cd) for different time periods. Of the barley cultivars Hamidiye was particularly sensitive to Cd as judged by the severity and earlier development of Cd toxicity symptoms on leaves. Within 48 h of Cd application Hamidiye rapidly developed severe leaf Cd toxicity symptoms whereas in Tokak the leaf symptoms appeared only slightly. Hamidiye also tended to show more decrease in growth caused by Cd supply when compared to Tokak. The differences in sensitivity to Cd between Tokak and Hamidiye were not related to Cd concentrations in roots and shoots or Cd accumulation per plant. With the exception of catalase, activities of the enzymes involved in detoxification of reactive oxygen species (ROS) were markedly enhanced in Hamidiye by increasing Cd supply. By contrast, in Tokak there was either only a slight increase or no change in the activities of the antioxidative enzymes. Similarly, levels of ascorbic acid and especially non-protein SH-groups were increased in Hamidiye by Cd supply, but not affected in Tokak. The results indicate the existence of a large genotypic variation between barley cultivars for Cd tolerance. The differential Cd tolerance found in the barley cultivars was not related to uptake or accumulation of Cd in plants, indicating importance of internal mechanisms in expression of differential Cd tolerance in barley. As a response to increasing Cd supply particular increases in antioxidative mechanisms in the Cd-sensitive barley cultivar Hamidiye suggest that the high Cd sensitivity of Hamidiye is related to enhanced production and oxidative damage of ROS.     

Phytochelatin and cadmium accumulation in wheat

Cadmium (Cd) is a nonessential heavy metal that can be harmful at low concentrations in organisms. Therefore, it is necessary to decrease Cd accumulation in the grains of wheats aimed for human consumption. In response to Cd, higher plants synthesize sulphur-rich peptides, phytochelatins (PCs). PC–heavy metal complexes have been reported to accumulate in the vacuole. Retention of Cd in the root cell vacuoles might influence the symplastic radial Cd transport to the xylem and further transport to the shoot, resulting in genotypic differences in grain Cd accumulation. We have studied PC accumulation in 12-day-old seedlings of two cultivars of spring bread wheat (Triticum aestivum), and two spring durum wheat cultivars (Triticum turgidum var. durum) with different degrees of Cd accumulation in the grains. Shoots and roots were analysed for dry weight, Cd and PC accumulation. There were no significant differences between the species or the varieties in the growth response to Cd, nor in the distributions of PC chain lengths or PC isoforms. At 1 μM external Cd, durum wheat had a higher total Cd uptake than bread wheat, however, the shoot-to-root Cd concentration ratio was higher in bread wheat. When comparing varieties within a species, the high grain Cd accumulators exhibited lower rates of root Cd accumulation, shoot Cd accumulation, and root PC accumulation, but higher shoot-to-root Cd concentration ratios. Intraspecific variation in grain Cd accumulation is apparently not only explained by differential Cd accumulation as such, but rather by a differential plant-internal Cd allocation pattern. However, the higher average grain Cd accumulation in the durum wheats, as compared to the bread wheats, is associated with a higher total Cd accumulation in the plant, rather than with differential plant-internal Cd allocation. The root-internal PC chain length distributions and PC–thiol-to-Cd molar ratios did not significantly differ between species or varieties, suggesting that differential grain Cd accumulation is not due to differential PC-based Cd sequestration in the roots.     

Incorporation of cadmium into proteins in a cadmium tolerant fungi

Aspergillus carbonarius and a strain of Penicillium, a cadmium tolerant fungi, are able to metabolize cadmium chloride up to 2% (w/v). Their amino acids analysis on cadmium free and cadmium chloride containing media indicated certain disorders in their metabolic activities. Cystathionine was only detected in both fungi in the presence of cadmium chloride. However, cadmium was incorporated into several types of low and high molecular weight proteins. The amino acids hydrolyzates of a cadmium containing protein are characterized by the presence of high levels of sulfur amino acids; cysteine and methionine. Ethylasparagine was detected in the hydrolyzate of that cadmium containing protein as well.     

Characterization of cadmium desorption in soils and its relationship to plant uptake and cadmium leaching

Experiments on Cd desorption were conducted with a range of water-to-soil ratios to assess the desorption characteristics of Cd in soils and the availability of Cd for absorption by plant roots and leaching to groundwater, Soil samples were collected from sites contaminated by a former Pb and Zn smelter, by sewage irrigation, or with artificial additions of Cd and sewage sludge. Glasshouse pot experiments were conducted in which the yield and Cd uptake of crop plants were determined. Cadmium leached from soil columns was also studied using soil lysimeters. The soil solution Cd concentration decreased with increasing solution-to-soil ratio and followed a negative power function. Two constants obtained from logarithmic linear regression were identified. The intercept (C₁) was Cd concentration in the soil solution where the solution/soil ratio was equal to 1 and this constant was the intensity factor of the initial element supply in the soil. The slope (a) showed a decreasing trend for Cd concentration in the soil solution which was related to the soil buffering capacity. A corrected concentration (C₁/a) is proposed for expressing soil desorption ability. This combined index was significantly correlated with Cd uptake by plants and also with Cd leached from soil columns.     

镉胁迫下春小麦中镉的分布、富集及转移规律

采用盆栽试验,研究了镉胁迫下重金属镉(Cd)在春小麦中的分布、富集及转移规律。结果表明:Cd胁迫下,小麦根、茎、叶和籽粒中Cd积累量随外源Cd的增加而增加,小麦不同部位Cd积累量为根叶茎籽粒;籽粒中Cd含量与土壤中Cd显著相关;小麦不同部位对Cd的富集能力差异显著,且随外源Cd处理浓度的增加,各部位富集系数逐渐降低,低Cd浓度时各部位更易富集Cd;小麦植株地上部的转移系数亦呈递减趋势为茎、叶籽粒;在春小麦全生育期,土壤中Cd含量无明显变化,根对外源Cd的富集吸收于生育期70d左右达峰值,小麦植株中的Cd也在80d左右达到峰值后逐步减少,表明植株中的Cd,随籽粒的成熟逐步转移至籽粒。     

Exogenous spermidine elevating cadmium tolerance in Salix matsudana involves cadmium detoxification and antioxidant defense

In this study, exogenous spermidine role on Salix matsudana tolerance to cadmium was evaluated. Spermidine and cadmium presented antagonistic effects on the biomass, copper and zinc concentrations in S. matsudana. cadmium mainly distributed in the cell wall of subcellular fraction; 46.97%–60.43% of cadmium existed in a sodium chloride-extracted form. Cadmium contents in roots, leaves, and twigs ranged from 2002.67 to 3961.00, 111.59 to 229.72, and 102.56 to 221.27?mg/kg, respectively. Spermidine application elevated cadmium concentrations in the roots, cuttings, and cell wall and the ratio of deionized water-extracted cadmium, but decreased cadmium levels in the twigs and leaves and the fractions of cadmium extracted by ethanol and sodium chloride, respectively. Putrescine and malondialdehyde were important indicators of cadmium-induced oxidative damage. Exogenous spermidine alleviated the accumulation of superoxide anion, hydrogen peroxide, malondialdehyde via promoting the levels of spermidine, soluble protein, superoxide dismutase, reductive ascorbate, glutathione reductase, and glutathione peroxidase in S. matsudana leaves under the corresponding cadmium stress. The results indicated that S. matsudana was a candidate for cadmium rhizoremediation and extraction in leaves; the spermidine application enhanced the cadmium tolerance of S. matsudana through promoting cadmium accumulation in roots, cell wall, and less bioactive chemical forms and the antioxidative ability.     

Jasmonic acid alleviates cadmium toxicity in Arabidopsis via suppression of cadmium uptake and translocation

Jasmonic acid(JA) is thought to be involved in plant responses to cadmium(Cd) stress, but the underlying molecular mechanisms are poorly understood. Here, we show that Cd treatment rapidly induces the expression of genes promoting endogenous JA synthesis, and subsequently increases the JA concentration in Arabidopsis roots. Furthermore, exogenous methyl jasmonate(MeJA)alleviates Cd-generated chlorosis of new leaves by decreasing the Cd concentration in root cell sap and shoot, and decreasing the expression of the AtIRT1,AtHMA2 and AtHMA4 genes promoting Cd uptake and long-distance translocation, respectively. In contrast,mutation of a key JA synthesis gene, At AOS, greatly enhances the expression of AtIRT1, AtHMA2 and AtHMA4,increases Cd concentration in both roots and shoots, and confers increased sensitivity to Cd. Exogenous Me JA recovers the enhanced Cd-sensitivity of the ataos mutant,but not of atcoi1, a JA receptor mutant. In addition,exogenous Me JA reduces NO levels in Cd-stressed Arabidopsis root tips. Taken together, our results suggest that Cd-induced JA acts via the JA signaling pathway and its effects on NO levels to positively restrict Cd accumulation and alleviates Cd toxicity in Arabidopsis via suppression of the expression of genes promoting Cd uptake and long-distance translocation.     

Distribution of cadmium in leaves of cadmium tolerant and sensitive ecotypes of Silene vulgaris

It has been postulated that vacuolar compartmentation might play an important role in naturally selected cadmium tolerance in Silene vulgaris (Moench.) Garcke (Bladder campion). Additionally, a tendency of heavy metals to accumulate in the epidermis has been reported. Since these factors would affect the distribution of cadmium in leaves, we determined the distribution of cadmium in leaves of cadmium tolerant and sensitive ecotypes of Silene vulgaris at different levels of exposure and at different time intervals. Cadmium concentrations were higher in leaves of sensitive plants than in those of cadmium tolerant ones after identical exposure to cadmium for a period of 8 days. The highest cadmium concentrations were found in the lower epidermis of plants of both ecotypes. The amount of cadmium located at the lower epidermis was highest for sensitive plants, although the stomatal density was lower in the sensitive ecotype than in the tolerant one. A possible explanation for this phenomenon is the weak relationship between transpiration (water flow) and element allocation. Our results support the hypothesis that vacuolar storage of cadmium plays an important role in the mechanism of cadmium tolerance in Silene vulgaris .     

土壤镉胁迫对田七体内镉分布及富集特性影响

田七(Panax notoginseng)是我国的一种传统珍贵的草本药用植物,其重金属污染问题已经引起广泛关注。为了分析田七不同部位对镉毒害的响应,明确不同浓度镉污染对田七体内镉分布的基本特征以及不同部位的富集特性,以揭示镉胁迫对田七不同部位的影响机制及富集转移特性。该研究在"田七之乡"广西靖西市田七园以3年生田七为材料,土培条件下以不施镉处理为空白对照,设置6个镉浓度(5、10、20、30、40、50 mg·kg~(-1))梯度,研究了在不同浓度镉胁迫下田七不同部位镉积累特征以及转移特性。结果表明:在不同器官(叶、茎、剪口、须根、主根)随着镉浓度的增加各器官镉的积累量均显著(P0.05)增加,呈现出正相关关系。田七不同部位镉含量的分布特征表现:空白对照下田七各器官镉累积分布表现为须根剪口主根茎叶;当镉浓度为5、10、20、30、40、50 mg·kg~(-1)时,田七镉分布表现为剪口主根须根茎叶;地下部的镉含量显著高于地上部的镉含量;随着镉浓度的增加,无论地下部生物富集系数还是地上部生物富集系数均表现为逐渐降低的趋势。     

Characterization of cadmium uptake in Lactobacillus plantarum and isolation of cadmium and manganese uptake mutants.

Two different Cd(2+) uptake systems were identified in Lactobacillus plantarum. One is a high-affinity, high-velocity Mn(2+) uptake system which also takes up Cd(2+) and is induced by Mn(2+) starvation. The calculated K(m) and V(max) are 0.26 microM and 3.6 micromol g of dry cell(-1) min(-1), respectively. Unlike Mn(2+) uptake, which is facilitated by citrate and related tricarboxylic acids, Cd(2+) uptake is weakly inhibited by citrate. Cd(2+) and Mn(2+) are competitive inhibitors of each other, and the affinity of the system for Cd(2+) is higher than that for Mn(2+). The other Cd(2+) uptake system is expressed in Mn(2+)-sufficient cells, and no K(m) can be calculated for it because uptake is nonsaturable. Mn(2+) does not compete for transport through this system, nor does any other tested cation, i.e., Zn(2+), Cu(2+), Co(2+), Mg(2+), Ca(2+), Fe(2+), or Ni(2+). Both systems require energy, since uncouplers completely inhibit their activities. Two Mn(2+)-dependent L. plantarum mutants were isolated by chemical mutagenesis and ampicillin enrichment. They required more than 5,000 times as much Mn(2+) for growth as the parental strain. Mn(2+) starvation-induced Cd(2+) uptake in both mutants was less than 5% the wild-type rate. The low level of long-term Mn(2+) or Cd(2+) accumulation by the mutant strains also shows that the mutations eliminate the high-affinity Mn(2+) and Cd(2+) uptake system.     

镉胁迫下金银花的生长反应及积累特性

采用水培试验方法,研究了藤本植物金银花在不同浓度镉（Cd）胁迫下的生长反应和积累特 性,结果表明,Cd对金银花生长未造成显著影响,甚至低浓度(5和10 mg·L^-1) Cd具有一定的生长促进作用,表现为植物的株高和叶绿素含量有所增加。当Cd处理浓度达到50 mg·L^-1时,植物的株高和根长虽有所降低,但与对照相比并无显著差异,且耐性系数均＞0.8,表明金银花对Cd具有较强的耐性。当Cd处理浓度为25 mg·L^-1时,金银花地上部中Cd含量达到286.12 μg·g^-1,而富集系数均＞1,说明金银花具备Cd超富集植物的特征,对Cd污染土壤的修复具有很大的应用潜力。     

水稻镉安全材料的镉吸收动力学特征

采用水培试验,以前期筛选出的水稻Cd安全材料D62B为试验材料,普通材料泸恢17为对照材料,在不同Cd浓度和时间处理下,研究水稻Cd安全材料的Cd吸收动力学特性.结果表明: 在不同Cd处理时间下,D62B根系对Cd的吸收总量均低于泸恢17,且随吸收时间的延长,差异逐渐增大.当吸收时间达到72 h,泸恢17体内积累的Cd总量为D62B的1.3倍.两种水稻材料Cd吸收动力学符合米氏方程,米氏方程常数(K_m)值差异不大,但泸恢17的最大吸收速率(V_max)是D62B的2倍.当Cd处理时间大于48 h,D62B根系对Cd的转移系数低于泸恢17,且其根部Cd分配比例明显大于泸恢17,即D62B根系对Cd的固持能力大于泸恢17.D62B的Cd吸收能力较弱,且其向地上部转移Cd的能力显著低于泸恢17.     

Cd污染地草坪草中Cd分布特征及化学形态的研究

对种植在沈阳西郊Cd污染地上草坪草中Cd的分布及化学形态进行了分析研究。结果表明,Cd主要分布于草的根系中,而且在不同草种中的分布特征存在较大差异。有些草对土壤中的Cd无明显的富集作用,具有抗Cd能力;而有些草对Cd有较强的富集能力,通过研究不同溶剂对不同草种的浸提效能,探明了草中Cd以酸溶态为最多,约占总量的63.3%;水溶态和有机态Cd均很少,在迁移转化过程中酸溶态Cd具有较大活性,水溶态Cd随时间和温度的变化而呈一定的规律性,有机态Cd随介质极性的增强而活性加大。     

Smoking habits and cadmium intake in Turkey

Tobacco was estimated to account over 4 million annual deaths in 1998 and deaths attributable to tobacco usage will rise to 8.4 million in 2020 (http://tobacco.who.int/en/advocacy/wntdzoola.html.) In Turkey, 74% of the males and 29% of the females are smoking, and each year, 150,000 deaths are associated with cigaret smoking. There are 4700 chemical compounds in cigaret smoke, including 43 carcinogens. Cadmium (Cd) is only one of these harmful chemicals in the cigaret. The level of cadmium in whole blood is a reliable index of extent of recent metal uptake. In this study, cadmium concentrations in fasting whole-blood samples, from 119 healthy subjects (58 males and 61 females), ranging in age from 17 to 77 yr, who were not occupationally exposed to cadmium were measured by graphite furnace atomic absorption spectrometry, which is the most widely used technique for the measurement of cadmium concentrations in the whole blood. The blood cadmium concentration of nonsmokers, ex-smokers, and smokers were compared. The blood cadmium concentration of female smokers were found to be highest (mean: 2.62±0.72; median: 0.90 ng/mL Cd) and that of nonsmokers lowest (mean: 0.67±0.57; median: 0.44 ng/mL Cd). For smokers, an analysis of smoking history exhibited significant correlations between the number of daily cigarets smoked and the blood cadmium concentration (r=0.54, p=0.001) and years of smoking and blood cadmium concentration (r=0.51, p<0.001). Cadmium intake from cigaret smoking was found to be higher that the intake from air and diet.     

Renal function in the freshwater rainbow trout after dietary cadmium acclimation and waterborne cadmium challenge

Renal function was examined in adult rainbow trout (Oncorhynchus mykiss) after chronic exposure to a sublethal level of dietary Cd (500 mg/kg diet) for 52 d and during a subsequent challenge to waterborne Cd (10 microg/L) for 72 h. Dietary Cd had no major effects on UFR (urine flow rate) and GFR (glomerular filtration rate) but caused increased renal excretion of glucose, protein, and major ions (Mg(2+), Zn(2+), K(+), Na(+), Cl(-) but Ca(2+)). However, dietary Cd did not affect any plasma ions except Na(+) which was significantly elevated in the Cd-acclimated trout. Plasma glucose and ammonia levels fell by 25% and 36% respectively, but neither plasma nor urine urea was affected in Cd-acclimated fish. Dietary Cd exposure resulted in a remarkable increase of Cd load in the plasma (48-fold, approximately 22 ng/mL) and urine (60-fold, 8.9 ng/mL), but Cd excretion via the kidney was negligible on a mass-balance basis. Clearance ratio analysis indicates that all ions, Cd, and metabolites were reabsorbed strongly (58-100%) in both na?ve and dietary Cd exposed fish, except ammonia which was secreted in both groups. Mg(2+), Na(+), Cl(-) and K(+) reabsorption decreased significantly (3-15%) in the Cd-exposed fish relative to the control. Following waterborne Cd challenge, GFR and UFR were affected transiently, and only Mg(2+) and protein excretion remained elevated with no recovery with time in Cd-acclimated trout. Urinary Ca(2+) and Zn(2+) excretion rates dropped with an indication of renal compensation towards plasma declines of both ions. Cadmium challenge did not cause any notable effects on urinary excretion rates of metabolites. However, a significant decrease in Mg(2+) reabsorption but an increase in total ammonia secretion was observed in the Cd-acclimated fish. The study suggests that dietary Cd acclimation involves physiological costs in terms of renal dysfunction and elevated urinary losses.