Accumulated forms of thallium and cadmium in Lemna minor. II. Relationship between duration of exposure and metal-protein binding

Abstract

Gel filtration chromatography (with Sephadex G25, G50 and G100) was used to separate the different forms of thallium (Tl) and cadmium (Cd) in the cytosol fraction of Lemna minor and to examine the influence of the duration of metal exposure on the speciation of the two elements. A major proportion of Cd in the soluble phase was found to be bound to three groups of proteinaceous and polypeptide fractions; two of these, the high molecular weight protein fraction (Mr > 150,000) and the low polypeptide sized moieties of about M_r 1,500 or less were constitutive entities, whereas the intermediate sized fraction (Mr 7,000 - 8,000) could only be detected in plants previously exposed to Cd. After 12 days of exposure to Cd this fraction accounted for the greatest part of the bound Cd in Lemna tissues. Extending the period of exposure from 18 hours to 12 days resulted in a shift in the distribution of Cd between the low and intermediate fractions. Evidence for Tl-protein binding was limited and confined to the high molecular weight fraction, and most of the Tl in the soluble phase was present in a form closely allied to the free ion. The contrasting behaviour between the two elements has been interpreted in terms of the differences in their physicochemical properties.     

环境因子对奇异虉草和小子虉草种子萌发的影响

在室内条件下考察了环境因子温度、pH、盐分、土壤含水量以及种子埋深对外来入侵植物奇异虉草和小子虉草种子萌发和幼苗生长的影响,并与小麦进行对比研究.结果显示;(1)当温度为5℃、NaCl浓度为0.25 mol/L以及种子埋藏深度达到30 mm时,奇异虉草和小子虉草的种子完全不能萌发,而同等条件下小麦种子的发芽率分别依次为89.33%、53.33%和95.00%.(2)在pH 4.0～10.0和土壤含水量10.0%～25.0%条件下,奇异虉草和小子虉草的种子均能萌发;但pH在4.0和10.0以及土壤含水量低于15%时,其发芽率受到显著抑制;当土壤含水量为10%时奇异虉草和小子虉草的种子发芽率分别为19.33%和16.67%,而小麦种子的萌发完全受到抑制.(3)奇异虉草和小子虉草的幼苗最适生长环境为,温度25℃～30℃、pH为6.0～9.0、NaCl浓度0～0.05 mol/L以及种子埋藏深度为0～5 mm.研究表明温度、盐分和种子埋藏深度是影响奇异虉草和小子虉草种子萌发的关键因素,而偏碱性环境更有利于其种子萌发,其种子萌发对干旱胁迫的耐受性强于小麦.     

Crystal structure of the read-through domain from bacteriophage Qβ A1 protein

Bacteriophage Qβ is a small RNA virus that infects Escherichia coli. The virus particle contains a few copies of the minor coat protein A1, a C‐terminally prolonged version of the coat protein, which is formed when ribosomes occasionally read‐through the leaky stop codon of the coat protein. The crystal structure of the read‐through domain from bacteriophage Qβ A1 protein was determined at a resolution of 1.8 Å. The domain consists of a heavily deformed five‐stranded β‐barrel on one side of the protein and a β‐hairpin and a three‐stranded β‐sheet on the other. Several short helices and well‐ordered loops are also present throughout the protein. The N‐terminal part of the read‐through domain contains a prominent polyproline type II helix. The overall fold of the domain is not similar to any published structure in the Protein Data Bank.     

Growth rate based dose-response relationships and EC-values of ten heavy metals using the duckweed growth inhibition test (ISO 20079) with Lemna minor L. clone St

The duckweed Lemna minor L. clone St was used to investigate the effect of 10 heavy metals under the standardised test conditions of the ISO protocol 20079. By using growth rates derived from frond number (FN), fresh weight (FW), dry weight (DW), chlorophyll and carotenoid (Car) contents, concentration–response curves for all heavy metals and all growth parameters were classified. In addition, all data were fitted to obtain the inhibitions of growth rates (E_rC_x) at the level of 10%, 20% and 50% (E_rC₁₀, E_rC₂₀ and E_rC₅₀, respectively) then used to evaluate the phytotoxicity of the different heavy metals. On the basis of the E_rC₅₀ values (average ranking of all five growth parameters), the following series of phytotoxicity was detected by using molar concentrations: Ag⁺>Cd²⁺>Hg²⁺>Tl⁺>Cu²⁺>Ni²⁺>Zn²⁺>Co²⁺>Cr(VI)>As(III)>As(V).     

Revised Crystal Structure of Human Adenovirus Reveals the Limits on Protein IX Quasi-Equivalence and on Analyzing Large Macromolecular Complexes

We report the revised crystal structure of a pseudo-typed human adenovirus at 3.8-Å resolution that is consistent with the atomic models of minor proteins determined by cryo-electron microscopy. The diffraction data from multiple crystals were rescaled and merged to increase the data completeness. The densities for the minor proteins were initially identified in the phase-refined omit maps that were further improved by the phases from docked poly-alanine models to build atomic structures. While the trimeric fiber molecules are disordered due to flexibility and imposition of 5-fold symmetry, the remaining major capsid proteins hexon and penton base are clearly ordered, with the exception of hypervariable region 1 of hexons, the RGD containing loop, and the N-termini of the penton base. The exterior minor protein IX together with the interior minor proteins IIIa and VIII stabilizes the adenovirus virion. A segment of N-terminal pro-peptide of VI is found in the interior cavities of peripentonal hexons, and the rest of VI is disordered. While the triskelion substructures formed by the N-termini of IX conform to excellent quasi 3-fold symmetry, the tetrameric coiled-coils formed by the C-termini and organized in parallel and anti-parallel arrangement do not exhibit any quasi-symmetry. This observation also conveys the pitfalls of using the quasi-equivalence as validation criteria for the structural analysis of extended (non-modular) capsid proteins such as IX. Together, these results remedy certain discrepancies in the previous X-ray model in agreement with the cryo-electron microscopy models.     

Sex-specific association between X-linked Toll-like receptor 7 with the outcomes of hepatitis C virus infection

Toll-like receptor 7 (TLR7) senses hepatitis C virus (HCV) infection and drives the host specific innate and adaptive immune response. The aim of this study was to estimate the distributions of TLR7 single nucleotide polymorphisms (SNPs), including rs179019 and rs3853839, as well as the effect of TLR7 gene variants on TLR7 mRNA expression and cytokine production in response to TLR7 agonist in vitro. TLR7 SNP genotyping was performed among a Chinese sample population of 418 patients with persistent HCV infection, 317 patients with HCV spontaneous clearance, and 989 healthy controls. TLR7 mRNA expression and TLR7-specific IFN-α and IL-6 secretion in peripheral blood mononuclear cells, derived from 60 healthy individuals in vitro, were then quantified. We identified the association of TLR7 rs3853839C allele, haplotype CC and haplotype AC (rs179019/rs3853839) with protection against HCV persistence in Chinese females (OR = 0.49, 95% CI = 0.29–0.81, P = 0.01 for rs3853839 GC; OR = 0.29, 95% CI = 0.11–0.75, P = 0.01 for rs3853839 CC; OR = 0.51, 95% CI = 0.38–0.77, P < 0.01 for haplotype CC; OR = 0.29, 95% CI = 0.10–0.88, P = 0.03 for haplotype AC). In addition, the rs3853839 CC genotype among female carriers had significantly low TLR7 mRNA expression (P = 0.006 for GG vs. CC, P = 0.021 for GC vs. CC), along with decreased IFN-α (P = 0.002 for GG vs. CC, P = 0.021 for GC vs. CC) and increased antiviral IL-6 production (P = 0.002 for GG vs. CC, P = 0.030 for GC vs. CC), after treatment with Imiquimod in vitro. The cytokine profile among rs3853839 CC genotype female carriers may indicate a pronounced protective effect against persistent HCV infection. The functional polymorphism of TLR7 rs3853839C allele was found to be sex-specific and associated with protection against HCV persistence among Chinese females, which may be due to specific IFN-α and IL-6 secretion profiles.     

Genetic association of interleukin-10 promoter polymorphisms and susceptibility to diffuse large B-cell lymphoma: A meta-analysis

Published data on the association between interleukin-10 (IL-10) gene polymorphisms and diffuse large B-cell lymphoma (DLBCL) risk are inconclusive. To derive a more precise estimation of the relationship, a meta-analysis was performed, focusing on four major IL-10 gene variants in the promoter region: –3575T/A, –1082A/G, –819C/T and –592C/A. We applied the false discovery rate (FDR) method to adjust for multiple testing. A significant association between IL-10 –3575T/A polymorphism and the risk of DLBCL was observed in the pooled 10 case–control studies (A vs. T: OR = 1.16, 95% CI = 1.08–1.25, P < 0.0001; AA + TA vs. TT: OR = 1.20, 95% CI = 1.08–1.33, P = 0.0009; AA vs. TA + TT: OR = 1.25, 95% CI = 1.09–1.44, P = 0.001). The results indicated that carriers of –1082G allele (–1082GG/GA genotypes) had a nearly 30% increased risk of DLBCL, as compared with carriers of –1082AA genotype (GG + GA vs. AA: OR = 1.30, 95% CI = 1.08–1.57, P = 0.005). When P-values were not adjusted for multiple testing, the risk was significantly decreased among people with –592AA genotype (AA vs. AC + CC: OR = 0.63, 95% CI = 0.43–0.94, P = 0.02), while carriers with –819TT genotype also modestly weakened the DLBCL susceptibility at a marginal level of significance (TT vs. CT + CC: OR = 0.59, 95% CI = 0.35–0.99, P = 0.05). However, these associations were not significant after correction for multiple testing. This meta-analysis suggests that IL-10 –3575A allele confers a greater risk to DLBCL susceptibility, while –1082A/G polymorphism also has significant association with DLBCL risk. These results may help to further clarify the malignancy-risk gene signature of DLBCL, and thus have prognostic and predictive value especially for early-stage DLBCL.     

我国鼎湖山的担子菌类——Ⅰ.多孔菌科的种

广东鼎湖山自然保护区内的大型真菌比较丰富和复杂。本文报道该地区有关多孔菌科的4个新种和14个新纪录,其中小多孔菌Polyporus minor Bi et G.Y.Zheng sp.nov.,近莲座多孔菌Polyporus subfloriformis Bi et Zheng sp. nov.,近软多孔菌Polyporus submollis Bi etZheng sp.nov.和近多年生多孔菌Polyporus subperennis Bi et Zheng sp.nov.,等为新种。     

Trichinella spiralis: genetic basis for differential expression of phase-specific intestinal immunity in inbred mice

Responsiveness of mouse strains after phase-specific immunization with Trichinella spiralis is compared. Two strains ($\text{NFR}\text{N, NFS/N}$) showed strong overall responsiveness. The response type could be characterized in phase-specific terms as: strongly anti-adult, weakly to moderately anti-preadult, and strongly antifecundity. By comparison, congenic mice of the C₅₇B1 $\text{10}\text{Sn}$ background (B10·A, B10·D₂, B10·S, B10·Q) displayed poor total responses that could be characterized as: weakly anti-adult, very weakly anti-preadult, weakly anti-fecundity after preadult immunization, and mixed (weak and strong) after adult immunization. The $\text{C}{}_3\text{H}\text{HeJ}$ mouse appeared to be intermediate between the B10·BR and the $\text{NFR}\text{N}$ strains in overall responsiveness. Genetic determinants of anti-preadult or anti-adult responses of $\text{NFR}\text{N}$ strain mice were dominant over their B10 congenic counterparts as shown in F₁, crosses of $\text{NFR}\text{N}$ × B1O·BR mice. Since the $\text{NFR}\text{N}$ (predominantly H-2^q) and the $\text{NFS}\text{N}$ (H-2^S) are both strong responders, while the B10·Q(H-2^q) and B10·S (H-2^S) are weak, it is suggested that the major genes controlling anti-preadult and anti-adult responses are not linked to the major histocompatibility complex. However, variations in anti-adult immunity and anti-fecundity in the B10 congenic mice (B10·Q and B10·S are the strongest responders) suggest that minor genes linked to the MHC exert some control over these responses. Some evidence was obtained for gene complementation as the F₁ cross of $\text{NFR}\text{N}$ and $\text{NFS}\text{N}$ mice responded more vigorously than the parental lines. We conclude that multiple genes determine anti-T. spiralis intestinal responses in mice. The major genes are unlinked to the major histocompatibility complex whereas several minor genes are linked.     

Chromosomal microarray analysis for pregnancies with abnormal maternal serum screening who undergo invasive prenatal testing

Recently, chromosomal microarray analysis (CMA) has been implemented as a first-tier test in pregnancies with ultrasound anomalies. However, its application for pregnancies with abnormal maternal serum screening (AMSS) only is not widespread. This study evaluated the value of CMA compared to traditional karyotyping in pregnancies with increased risk following first- or second-trimester maternal serum screening. Data from 3973 pregnancies with referral for invasive prenatal testing following AMSS were obtained from April 2016 to May 2020. Routine karyotyping was performed and single nucleotide polymorphism array was recommended. The foetuses were categorized according to the indications as AMSS only (group A) and AMSS with ultrasound anomalies (group B). CMA was performed on 713 prenatal samples. The proportion of women opting for CMA testing in both groups increased over the years. The incremental yield of clinically significant findings for pregnancies with high risk of screening results was similar to that for the foetuses with ultrasound soft markers (P > 0.05), but significantly lower than that for the foetuses with structural anomalies (P < 0.05). The total frequencies of variants of unknown significance in groups A and B showed no significant difference (P > 0.05). CMA should be performed for pregnant women undergoing prenatal invasive testing due to AMSS, especially with high-risk results, regardless of ultrasound findings.