Growth inhibition and intracellular distribution of Pb ions by the white-rot fungus Abortiporus biennis

When Abortiporus biennis was grown on PbO-amended media, Pb (II) ions accumulated near fungal membrane structures, in the cell wall, and in the cytoplasm of the fungal cells, and their presence caused cell vacuolization. Increased concentration of PbO in the growth media caused a decline in fungal accumulation capacity. Neither PbO solubilization nor an increased level of organic acids underneath the mycelium was found.     

紫茉莉对铅胁迫生理响应的FTIR研究

铅是一种毒性强的重金属元素,一旦进入环境将很难修复,进而通过食物链危及人类健康。傅里叶变换红外光谱法(FTIR)具有准确度好、简便快捷、分辨率高的特点,是一种探讨植物重金属耐性机理的可行方法。紫茉莉是一种生长快的多年生草本植物,有应用于铅污染土壤植物稳定的前景。通过温室培养,研究不同铅处理条件下(0,50,100,200,500,1000μmol/L),紫茉莉不同组织器官(根、茎、叶)的傅立叶红外光谱(FTIR)图谱变化,结果发现,生长介质铅处理浓度低于500μmol/L时对紫茉莉的生长基本没有影响,当Pb处理浓度达到1000μmol/L时,生物量略显降低,但是各处理浓度间生物量差异性不显著。紫茉莉根组织在3420,2920,1610,1060 cm^-1 等处峰高先上升后下降,反映蛋白质、氨基酸、糖类、羧酸等物质在低铅处理条件下往往作为渗透性调节物质出现, 有机物含量升高,但随着铅含量的升高, 其合成和运输受限, 有机物含量逐渐下降;茎组织在2920,1630,1380,1060 cm^-1 等处峰高无明显变化;叶组织在1650 cm^-1 处峰高随铅处理浓度升高而升高,这可能与紫茉莉叶中蛋白质和氨基酸等物质含量升高有关。这表明,紫茉莉通过根系有机物含量的变化,将植物吸收的Pb大部分积累在根部,阻止Pb向地上部分运输,有效的保护了植物地上部分。     

Pb hyperaccumulation and tolerance in common buckwheat (Fagopyrum esculentum Moench)

Common buckwheat grown in Pb-contaminated soil was found to accumulate a large amount of Pb in its leaves (8,000 mg/kg DW), stem (2,000 mg/kg DW), and roots (3,300 mg/kg DW), without significant damage. This indicates that buckwheat is a newly recognized Pb hyperaccumulator, which is defined as a plant containing over 1,000 mg/kg of Pb in its shoots on a dry-weight basis. Moreover, it was shown that application of the biodegradable chelator methylglycinediacetic acid trisodium salt at concentrations of up to 20 mmol/kg resulted in a more than five times higher concentration of Pb in the shoot without notable growth inhibitation at up to 10 mmol/kg. These results indicate that buckwheat is a potential phytoremediator of Pb-contaminated soils.     

Lead tolerance and accumulation in the gametophytes of the fern Athyrium yokoscense

The fern Athyrium yokoscense is known to be highly tolerant to lead toxicity, and is a lead hyperaccumulator that can accumulate over 1,000 g g^–1 of lead in its dry matter. In this work, we examined whether the gametophytic generation of A. yokoscense also resists lead toxicity like the sporophytic generation. Spore germination in A. yokoscense was more tolerant to Pb²⁺, compared to that in other fern species, such as Pteridium aquilinum, Lygodium japonicum and Pteris vittata. In addition, the early gametophyte development of A. yokoscense was not much affected by 10 M Pb²⁺, as evaluated from the prothallial growth and rhizoid development. We also showed that Athyrium gametophytes could accumulate more than 10,000 g g^–1 of lead, and that the lead was localized in the cytosol and vacuole of rhizoidal cells, as determined by a transmission electron micrograph. These results indicate that Athyrium gametophytes have the ability to accumulate lead in the rhizoids. Furthermore, the gametophytes were found to include a large amount of proanthocyanidins (condensed tannins). Because proanthocyanidins have a latent ability to complex with lead ions, the possible roles of proanthocyanidins in the lead tolerance and accumulation of Athyrium gametophytes are discussed.     

The improvement of sensitivity in lead and cadmium determinations using flame atomic absorption spectrometry

Various designs of quartz tubes of the slotted tube atom trap were examined to improve the sensitivity of flame atomic absorption spectrophotometry. The studied designs include the diameter length and the length of the upper slot of quartz tubes. Tubes having a diameter of 5 and 6 mm and an upper slot length of 2.3 cm produce the best sensitivity—as high as 6- and 10-fold enhancement for lead (Pb) and cadmium (Cd), respectively. The limits of quantitation were found to be 35 and 4 ng ml⁻¹ for Pb and Cd, respectively, by the optimized method. The achieved technique was applied to determine the concentrations of Pb and Cd in cancerous (malign) and noncancerous (adenoma) human thyroid tissues.     

Syntheses, characterizations and crystal structures of two lead(II) diphosphonates: Pb2[NH(CH2PO3)2] · 2H2O and Pb3[HO2C(CH2)3NH(CH2PO3)2]2 · 2H2O

Hydrothermal reactions of lead(II) acetate and HO₂C(CH₂)₃N(CH₂PO₃H₂)₂ at 170 and 140 °C, respectively, resulted in two different lead diphosphonates, namely, Pb₂[NH(CH₂PO₃)₂] · 2H₂O (1), in which the butyric acid moiety of the HO₂C(CH₂)₃N(CH₂PO₃H₂)₂ has been cleaved and a novel layered compound, Pb₃[HO₂C(CH₂)₃NH(CH₂PO₃)₂]₂ · 2H₂O (2). Their crystal structures have been determined by single crystal X-ray diffraction. In compound 1, the interconnection of the lead(II) ions by bridging amino-diphosphonate ligands leads to the formation of a 3D network. Compound 2 features an unusual triple-layer structure with the non-coordinated butyric acid moieties as pendant groups between the layers.     

An early- and late-stage convolution model for disease natural history

The standard convolution model of disease natural history posits an asymptomatic (preclinical) and a symptomatic (clinical) state. An augmented model includes, in both the preclinical and clinical states, an early and late stage of disease. In the case of cancer, the early stage would generally correspond to the organ-confined stages before there is evidence of cancer spread. We compute the number of screen-detected (preclinical) and clinical cases in the early and late stages expected under a given screening program and show how the model can be fit to data from a screening trial using maximum likelihood. We also develop expressions for sojourn time, lead time, and overdiagnosis in the context of the model, where each of the above concepts incorporates disease stage. As an example, we fit the model to data from the Mayo Lung Cancer Screening trial.     

Low level lead (Pb) exposure during gestation and lactation: assessment of effects on pubertal development in Fisher 344 and Sprague-Dawley female rats

Studies using both Fisher 344 and Sprague-Dawley (SD) rat lines have shown that gestational and/or lactational maternal lead (Pb) exposure causes delayed reproductive maturation in their respective female offspring. Because these studies utilized different experimental regimens for dosing and for monitoring Pb levels, it has not been possible to determine which rat line provides the best model for low level Pb toxicity studies. This study was designed to address this issue. Adult Fisher and SD female rats were dosed with either a solution of PbAc containing 12 mg of Pb/ml or sodium acetate (NaAc) for controls. Dosing began 30 days prior to breeding and continued until their pups were weaned at 21 days of age. At the time of breeding and through weaning the blood lead (BPb) levels in the Fisher dams averaged 37.3 microg/dl and the SD dams averaged 29.9 microg/dl. Pb delayed the timing of puberty (p < 0.01) in Fisher offspring, and suppressed serum levels of luteinizing hormone (LH, p < 0.001) and estradiol (E2, p < 0.01). These effects did not occur in the SD offspring. Doubling the dose given to the SD rats increased their BPb levels to 62.6 microg/dl, yet there were still no effects noted. These results indicate that Fisher offspring are more sensitive to maternal Pb exposure with regard to puberty related insults than are SD rats, suggesting that the Fisher line may be a more reliable rodent model to study the effects of low level Pb toxicity.     

Synthesis and structural characterisation of the lead-platinum sulfido aggregates [Pt2(μ-S)2(PPh3)4PbX2] (X = Br, I); promotion of rare tetrahedral geometry for lead(II)

The reactions of [Pt₂(μ-S)₂(PPh₃)₄] with excess PbBr₂ or PbI₂ in methanolic suspension result in the formation of the neutral lead(II) halide adducts [Pt₂(μ-S)₂(PPh₃)₄PbX₂] (X = Br, I). The X-ray structure determination of the lead iodide adduct reveals an essentially tetrahedral lead(II) centre, which is a rare coordination geometry for lead(II), which almost invariably is hemidirected, with a stereochemically active lone pair. In contrast, the structure of the PbBr₂ adduct, although suffering from some disorder, shows a more typical, distorted arrangement of ligands; these results are discussed in terms of the tendency for soft, bulky ligands to promote symmetric, holodirected geometries. The ESI mass spectra of the adducts are reported, and yield [M−halide]⁺ ions.     

Sonochemical syntheses of strawberry-like nano-structure mixed-ligand lead(II) coordination polymer: Thermal, structural and X-ray powder diffraction studies

Nano-structure of a new Pb(II) two-dimensional coordination polymer, {[Pb(2-pyc)(N₃)(H₂O)]_n (1), 2-Hpyc = 2-pyridinecarboxylic acid} was synthesized by a sonochemical method. The new nano-structure was characterized by scanning electron microscopy, X-ray powder diffraction, IR spectroscopy and elemental analyses. Compound 1 was structurally characterized by single crystal X-ray diffraction and consists of two-dimensional polymeric units. The thermal stability of compound 1 was studied by thermal gravimetric and differential thermal analyses and compared. PbO nano-powder was obtained by calcination of the nano-structure of compound 1 at 400 °C. This study demonstrates the coordination polymers may be suitable precursors for the preparation of nano-scale materials and dependent on their packing they may produce different and interesting morphologies.