Ni uptake by a green alga. 2. Validation of equilibrium models for competition effects

It is generally admitted that the presence of major cations and H+ can attenuate trace metal uptake. Recent models such as the biotic ligand model (BLM) aim to quantify and predict this effect by determining stability constants for each of the major competitors for any given interaction of a trace metal with a biological organism. In this study, short-term Ni internalization fluxes (J(int)) were used to quantitatively assess the binding of H+, Mg2+, Ca2+ (K(H-Rs), K(Mg-Rs), K(Ca-Rs)), and trace metals to transport sites (R(s)) leading to Ni biouptake by Chlamydomonas reinhardtii. H+ and Mg2+ are shown to compete directly for the entry of Ni with affinity constants that are of the same order of magnitude (K(Mg-Rs) = 10(5.1) M(-1); K(H-Rs) = 10(5.3) M(-1)) as that measured for Ni (K(Ni-Rs) = 10(5.1) M(-1)). The Ni internalization fluxes were also strongly linked to the Mg cell status. In contrast, the role of Ca2+ could not be explained by a simple competitive equilibrium with the Ni transport sites. Aluminum (K(Al-Rs) = 10(8) M(-1)), Zn (K(Zn-Rs) = 10(6.5) M(-1)), and Cu (K(Cu-Rs) = 10(6.6) M(-1)) were all shown to compete strongly with Ni for uptake. In addition to the determination of uptake constants, these studies provide insight into the transport mechanisms of Ni by the green alga, C. reinhardtii.     

Cadmium uptake by a green alga can be predicted by equilibrium modelling

Short-term uptake of cadmium by a wild-type (2137) and a cell wall-less strain (CW-2) of Chlamydomonas reinhardtii was examined as a function of Cd speciation in a well-defined, aqueous medium. Internalization fluxes were determined for free cadmium concentrations ranging from 5 x 10(-10) M to 5 x 10(-4) M in the presence of ligands forming both labile and inert hydrophilic complexes. A first-order biological internalization, as predicted by the free ion activity model (FIAM), was observed for both strains. The maximum Cd internalization flux, Jmax, for the wild-type strain was 5-fold higher (1.3 x 10(-11) mol cm(-2) min(-1)) than for the CW-2 strain (2.3 x 10(-12) mol cm(-2) min(-1)) and was not influenced by the presence of competitors such as Ca in the experimental solution. The conditional stability constant for the adsorption of Cd to transport sites of the CW-2 strain was 5-fold higher (10(6.7) M(-1)) than for the wild-type strain (10(6) M(-1)). Competition experiments demonstrated that Mo, Mn, Cu, Co, Zn, Ni, Ca, and Pb inhibited, at least partially, Cd uptake, while no inhibition was observed for similar concentrations of Mg and Fe. The stability constant for the competitive binding of Ca to the Cd transport site was determined to be 10(4.5) M(-1). Cu and Zn competed with Cd uptake sites with stability constants of 10(5.6) and 10(5.2) M(-1), respectively. Protons also appeared to compete with Cd uptake sites as uptake could generally be predicted quantitatively in their presence. Finally, in the presence of low concentrations (<20 mg L(-1)) of Suwannee River fulvic acid, Cd internalization fluxes could be predicted from [Cd2+], in accordance with the FIAM.     

绿藻晶饮料适宜工艺条件的研究

介绍了绿藻晶饮料的制作方法,采用正交实验法确定绿藻最佳的提取工艺条件,研究结果表明,提取工艺的最佳条件为提取温度100℃;提取时间为3h;柠檬酸为0.08g/kg。同时添加与绿藻有协同功用的药食兼用的植物成分,制成绿藻晶饮料。     

小球藻(Chlorella zofingiensis)生物合成虾青素的应用前景

虾青素是一种具有超强抗氧化特性的酮式类胡萝卜素,在食品和医药领域有着极广阔的应用前景。小球藻(Chlorella zofingiensis)的虾青素合成能力被报道后,倍受国内外学者关注。本文综述了近年来国内外在C.zofingiensis虾青素生物合成方面的研究进展,包括虾青素合成有关的诱导条件、虾青素合成过程中的生理变化、虾青素合成途径以及合成酶表达的分子调控等方面,并对小球藻C.zofingiensis的产业化前景进行了展望。     

Enhancement of human fibroblast growth and other dermatological effects induced by cell extract from heat-shocked blue green alga (Cyanobacteria)

It has been known that high amounts of 'heat shock proteins (HSPs)' are produced under heat and other environmental stresses in cells. Recently, it was reported that HSP could also be accumulated in some dermal cells to protect the cellular proteins from damage caused by ultraviolet radiation. Here, the authors have focused on thermophilic cyanobacteria and the heat shock treatment. Thermophilic cyanobacteria are known to thrive under extreme environmental conditions, and produce distinctively high amounts of HSP when exposed to higher temperatures. We tested cell extract from heat-shocked cyanobacterial cells on a number of skin-related biological activities and found it significantly effective. The cyanobacterial cells, originally collected from a spa as hot as 55 °C, were cultivated in the laboratory at 50 °C and broken by a freeze-fracture method. The extract thus obtained had a superoxide dismutase (SOD)-like activity and inhibited lipid peroxide formation. We found that the extract obtained from the heat-shocked (at 63 °C) cells showed a much stronger SOD-like activity, while the inhibitory effect on lipid peroxide formation remained almost the same. Furthermore, the SOD-like activity could withstand heat up to 70 °C for as long as 1 h. Most remarkably, supplementing this heat-shocked extract strongly promoted the proliferation of human dermal fibroblast culture. Extracts from the cells grown at a regular temperature (50 °C) did not promote the proliferation of the fibroblasts. The heat-shocked extract was fractionated by ultrafiltration for further analysis. A fraction (molecular weight: 10 000–30 000) has shown the strongest activity so far. These results indicate that the heat-shocked cyanobacterial extract with its increased amounts of HSPs is a promising potent ingredient for anti-aging cosmetic materials.     

Strong induction of phytochelatin synthesis by zinc in marine green alga, Dunaliella tertiolecta

Synthesis of phytochelatins (PCs), heavy-metal-sequestering peptides, in the marine green alga, Dunaliella tertiolecta, was evaluated under various conditions of exposure to heavy metals. To investigate the effect of heavy metals on both PC synthesis and their upstream biosynthetic reactions, an ion-pair-HPLC system was developed in this study, by which PCs and their biosynthetic intermediates, cysteine (Cys), gamma-glutamylcysteine (gammaEC) and glutathione (GSH), could be determined simultaneously with high sensitivity. When the cells were exposed to Zn2+, the level of PCs was maximal at 200 microM and significantly higher than that obtained after exposure to 400 microM Cd2+, which is the strongest inducer of PC synthesis in higher plants in vivo and in vitro as well as in microalgae. The predominant PC subtype was PC4, followed by PC3 and PC5, whereas PC2, which is generally abundant in higher plants, has the lowest level among PC2 to PC5. These results suggest that the characteristics of PC synthase in D. tertiolecta including the requirement of heavy metals for its catalysis and substrate specificity towards GSH and PC(n) are considerably different from those in higher plants and other algae. While PC synthesis proceeded in the heavy-metal-treated cells, the level of GSH did not appreciably change. To maintain the same size of the GSH pool, GSH must be newly synthesized to balance the amount consumed for PC synthesis.     

Microscale investigations of Ni uptake by cement using a combination of scanning electron microscopy and synchrotron-based techniques

Cement is used to condition waste materials and for the construction and backfilling of repositories for low-and intermediate-level radioactive waste. In this study, Ni uptake by hardened cement paste has been investigated with the aim of improving our understanding of the immobilization process of Ni(ll) in cement on the microscale. Information on the cement microstructure, Ni distribution, Ni concentration, and speciation of the Ni phases formed in the cement system and their association with specific cement minerals has been gained by using scanning electron microscopy (SEM) and synchrotron-based micro-X-ray fluorescence (micro-XRF) and micro-X-ray absorption spectroscopy (micro-XAS). The Ni-doped samples were prepared at a water/cement ratio of 0.4 using a sulfate-resisting Portland cement and were hydrated for 30 days. The metal loadings of the system were varied from 50 up to 5000 mg/kg. SEM investigations show that for all metal loadings the Ni phases form rims around inner-calcium silicate hydrates, suggesting a direct association with this cement phase. The micro-XAS measurements further reveal that a mixture of Ni phases form at Ni-enriched regions. Data analysis indicates that Ni(ll) is predominantly immobilized in a layered double hydroxide-type phase (Ni-Al LDH) and only to a minor extent precipitates as Ni-hydroxides (alpha-Ni(OH)2 and beta-Ni(OH)2). At 50 mg/kg Ni loading, however, the p-XAS measurements suggest the presence of an additional Ni species. In the latter system Ni-Al LDH is found in Ni-rich regions, whereas at Ni-poor regions an unknown species is formed.     

Validation of test-day models for genetic evaluation of dairy goats in Norway

Test-day data for daily milk yield and fat, protein, and lactose content were sampled from the years 1988 to 2003 in 17 flocks belonging to 2 genetically well-tied buck circles. In total, records from 2,111 to 2,215 goats for content traits and 2,371 goats for daily milk yield were included in the analysis, averaging 2.6 and 4.8 observations per goat for the 2 groups of traits, respectively. The data were analyzed by using 4 test-day models with different modeling of fixed effects. Model [0] (the reference model) contained a fixed effect of year-season of kidding with regression on Ali-Schaeffer polynomials nested within the year-season classes, and a random effect of flock test-day. In model [1], the lactation curve effect from model [0] was replaced by a fixed effect of days in milk (in 3-d periods), the same for all year-seasons of kidding. Models [2] and [3] were obtained from model [1] by removing the fixed year-season of kidding effect and considering the flock test-day effect as either fixed or random, respectively. The models were compared by using 2 criteria: mean-squared error of prediction and a test of bias affecting the genetic trend. The first criterion indicated a preference for model [3], whereas the second criterion preferred model [1]. Mean-squared error of prediction is based on model fit, whereas the second criterion tests the ability of the model to produce unbiased genetic evaluation (i.e., its capability of separating environmental and genetic time trends). Thus, a fixed structure with year (year, year-season, or possibly flock-year) was indicated to appropriately separate time trends. Heritability estimates for daily milk yield and milk content were 0.26 and 0.24 to 0.27, respectively.     

Lactation curve models for estimating gene effects over a timeline

The effects of genes are commonly estimated using random regression models based on test-day data and only give a general gene effect. Alternatively, lactation curve models can be used to estimate biological and environmental effects, or to predict missing test-day data and perform breeding value estimation. This study combines lactation curve models and estimation of gene effects to represent gene effects in different stages of lactation. The lactation curve models used were based on the Wood, Wilmink, and Ali and Schaeffer models. A random regression test-day model was used to compare estimated gene effects with the results of commonly used models. The well-characterized DGAT1 gene with known effects on milk yield, milk fat, and milk protein production was chosen to test this new approach in a Holstein-Friesian dairy cattle population. The K232A polymorphism and the promoter VNTR (variable number of tandem repeats) of the DGAT1 gene were used. All lactation curve models predicted the production curves sufficiently. Nevertheless, for predicting genotype effects, the Wilmink curve indicated the closest fit to the data. This study shows that the characteristic gene effects for DGAT1 genotypes occur after lactation d 40, which might be explained by a link to other genes affecting metabolic traits. Furthermore, allele substitution effects of allele K of the K232A locus showed that the typical effect of low milk and protein yield is due mainly to a lower overall production level, whereas the higher fat and protein content is reached by increased production toward its peak and fat yield is increased because of a higher production after this peak. Predicting gene effects with production curves gives better insight into the timeline of gene effects. This can be used to form genetic groups, in addition to feeding groups, for managing livestock populations in a more effective way.     

Analysis of a chiral aroma compound by complexation gas chromatography

Summary Complexation gas chromatography with Ni(II)-bis[3-heptafluorobutyryl-(1R)-camphorate] as a chiral stationary phase is an efficient analytical method to resolve some racemic 1,3-oxathianes quantitatively into their enantiomers without derivatization. Configurations of 1,3-oxathiane enantiomers were assigned by optically pure reference substances.

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Analyse eines chiralen Aromastoffs mittels Komplexierungsgaschromatographie

Zusammenfassung Durch Komplexierungs-Gaschromatographie an. Ni(II)-bis [3-heptafluorbutyryl-(1R)-campherat] als chiraler stationärer Phase werden die racemischen Gemische einiger 1,3-Oxathiane ohne Derivatisierung quantitativ getrennt. Die Konfiguration der getrennten 1,3-Oxathiarl-Enantiomere wird mittels optisch reiner Vergleichssubstanzen zugeordnet.

     

Bioavailability models for predicting copper toxicity to freshwater green microalgae as a function of water chemistry

We investigated whether an earlier-developed bioavailability model for predicting copper toxicity to growth rate of the freshwater alga Pseudokirchneriella subcapitata could be extrapolated to other species and toxicological effects (endpoints). Hardness and dissolved organic carbon did not significantly affect the toxicity of the free Cu2+ ion to P. subcapitata (earlier study) and Chlorella vulgaris(this study), but a higher pH resulted in an increased toxicity for both species. Regression analysis showed significant linear relationships between ECxpCu (= "effect concentration" that produces x% adverse effect, expressed as pCu = -log of the Cu2+ activity) and pH. By linking these regression models with a geochemical metal speciation model, dissolved copper concentrations that elicit a given adverse effect (EC(X)dissolved) can be predicted. Within the pH range investigated (5.5-8.7), slopes of the linear EC(X)pCu vs pH regression models varied between 1.301 and 1.472 depending on the species and the effect level (10% or 50%) considered. In a statistical sense these slopes were all significantly different from one another (p < 0.05), suggesting that this empirical regression model does not yet capture the full complexity of toxicological copper bioavailability to algae. However, we demonstrated that regression models with an "average" slope of 1.354 had predictive power very similar to those of regression models with species and effect-specific slopes. Additionally, the "average" regression model was further successfully validated for other species (Chlamydomonas reinhardtii and Scenedesmus quadricauda) and for different toxicological effects/endpoints (growth rate, biomass yield, and phosphorus uptake rate). For all these toxicity datasets effect concentrations of copper could be predicted with this "average" model by errors of less than a factor of 2 in 94-100% of the cases. The success of this "average" model suggests the possibility that the pH-based linear regression model may form a sound conceptual basis for modeling the toxicological bioavailability of copper to green algae in regulatory assessments, although a full mechanistic understanding is lacking and should be the focus of future studies.     

Towards a Comprehensive Validation of ELISA Kits for Food Allergens: Case 1—Egg

There are several enzyme-linked immunosorbent assay (ELISA) kits in the market that have been proven to be useful for the determination of egg in foods. However, inconsistent results that are obtained when different kits are used make the selection of one kit over another very difficult. Two different approaches were used to help understand why results vary among kits. Different kits were used to analyze spiked egg material [NIST reference material (RM) 8445] in wheat flour (raw ingredients) and cookies containing egg as an ingredient baked for different periods of time (processed food). These results were compared with immunoblotting using conjugated antibodies from the commercial kits to determine the antibody specificity and sample extraction efficiency. ELISA results can be difficult to compare because reporting units differ among kits. Results from both ELISA and immunoblotting are in agreement regarding the decreased detection of proteins in baked cookie extracts. Moreover, immunoblotting showed that this reduction is due to reduced protein content in these extracts. However, a properly selected extraction solution may help improve the solubility of certain egg proteins in processed foods. Harmonization of the reporting unit system along with the use of a common reference material is recommended as the path forward in the standardization of detection methods for food allergens. This would assist the end user in making an informed decision regarding the selection of the most appropriate kit for his or her purpose.     

一类恒化器模型正平衡解的稳定性

在齐次Neumann条件下研究一类具有能量维持扩散的恒化器模型的稳定性.首先利用最大值原理和Harnack不等式给出平衡态方程正解的先验估计;其次利用谱分析和特征值理论证明正常数平衡解的一致渐近稳定性;最后借助构造Lyapunov函数来证明正常数平衡解的全局渐近稳定性.     

Validation of single-step genomic BLUP random regression test-day models and SNP effects analysis on milk yield in French Saanen goats

The shape of the lactation curve is linked to an animal's health, feed requirements, and milk production throughout the year. Random regression models (RRM) are widely used for genetic evaluation of total milk production throughout the lactation and for milk yield persistency. Genomic information used with the single-step genomic BLUP method (ssGBLUP) substantially improves the accuracy of genomic prediction of breeding values in the main dairy cattle breeds. The aim of this study was to implement an RRM using ssGBLUP for milk yield in Saanen dairy goats in France. The data set consisted of 7,904,246 test-day records from 1,308,307 lactations of Saanen goats collected in France between 2000 and 2017. The performance of this type of evaluation was assessed by applying a validation step with data targeting candidate bucks. The model was compared with a nongenomic evaluation and a traditional evaluation that use cumulated performance throughout the lactation model (LM). The incorporation of genomic information increased correlations between daughter yield deviations (DYD) and estimated breeding values (EBV) obtained with a partial data set for candidate bucks. The LM and the RRM had similar correlation between DYD and EBV. However, the RRM reduced overestimation of EBV and improved the slope of the regression of DYD on EBV obtained at birth. This study shows that a genomic evaluation from a ssGBLUP RRM is possible in dairy goats in France and that RRM performance is comparable to a LM but with the additional benefit of a genomic evaluation of persistency. Variance of adjacent SNPs was studied with LM and RRM following the ssGBLUP. Both approaches converged on approximately the same regions explaining more than 1% of total variance. Regions associated with persistency were also found.     

Heavy metal uptake by lignin: comparison of biotic ligand models with an ion-exchange process

Metal uptake by kraft lignin, hereafter referred to as lignin, occurs by displacement of protons or bound metals with equilibrium constants K(ex)H and K(ex), respectively. Values calculated for wide ranges of initial concentrations are reasonably constant, thereby demonstrating the validity of these displacement processes and proving that uptake in these systems is not simple adsorption. It was found that the stoichiometry for Sr and Cd uptake by Ca-loaded lignin is 1 mol of metal for 1 mol of Ca released. This observation for metals of very different binding strengths is difficult to rationalize with the biotic ligand model as generally applied but is in complete agreement with an ion-exchange process. Binding strengths to lignin, which contains only oxygen ligands, follow the order Pb > Cu > Zn > Cd > Ca (strongest to weakest). For proton displacement, only more tightly bound metals such as Pb, Cu, Zn, and Cd can compete with protons for anion-binding sites at low pH, but at high pH, uptake of Ca, Sr, and Li can occur. An observed logarithmic decrease of K(ex)H with pH can be explained by having only weaker acids available for proton displacement under more basic conditions. The advantages and disadvantages of using adsorption and biotic ligand models for an ion-exchange process are discussed.     

Comparison of predictive models for growth of parent and green fluorescent protein-producing strains of Salmonella

The green fluorescent protein (GFP) from the jellyfish Aequorea victoria can be expressed in, and used to follow the fate of, Salmonella in microbiologically complex ecosystems such as food. As a first step in the evaluation of GFP as a tool for the development of predictive models for naturally contaminated food, the present study was undertaken to compare the growth kinetics of parent and GFP-producing strains of Salmonella. A previously established sterile chicken burger model system was used to compare the growth kinetics of stationary-phase cells of parent and GFP strains of Salmonella Enteritidis, Salmonella Typhimurium, and Salmonella Dublin. Growth curves for constant temperatures from 10 to 48 degrees C were fit to a two- or three-phase linear model to determine lag time, specific growth rate, and maximum population density. Secondary models for the growth parameters as a function of temperature were generated and compared between the parent and GFP strain pairs. The effects of GFP on the three growth parameters were significant and were affected by serotype and incubation temperature. The expression of GFP reduced specific growth rate and maximum population density while having only a small effect on the lag times of the three serotypes. The results of this study indicate that the growth kinetics of the GFP strains tested were different from those of the parent strains and thus would not be good marker strains for the development of predictive models for naturally contaminated food.