Fluxes of mercury through biota in the LG-2 reservoir after flooding

The purpose of this study was to estimate the temporal fluxes of mercury (Hg) among the diverse biotic components of the aquatic ecosystem of the LG-2 reservoir before and shortly after flooding, and to compare the relative magnitudes of these fluxes. Flooding took place from autumn 1978 to autumn 1979. The basic food chain considered was: Phytoplankton ? Zooplankton ? Prey Fish ? Predatory Fish.     

Modeling the transport and fate of mercury in an urban lake (Onondaga Lake,NY)

A mass balance model was developed to simulate mercury (Hg) cycling in Onondaga Lake, New York. MERC4, a U.S. Environmental Protection Agency model of the physical and biogeochemical transport and transformation of Hg, was modified by the addition of input from two supporting models (Fish Bioenergetics Model 2 and a lake eutrophication model) to model the transport of Hg into and out of plankton and fish. The model calculates the concentrations of total Hg, methylmercury, elemental Hg, and ionic Hg in both dissolved and particulate forms in the water column. The model was calibrated to an extensive data set of temporally and spatially variable Hg concentrations in Onondaga Lake in 1992. In addition to standard transport processes of advection and dispersion included in MERC4, the Onondaga Lake Mercury Model includes remineralization to simulate release of Hg from settling particulates before incorporation into sediment. The model provides an analytical framework for understanding and predicting the behavior of Hg in Onondaga Lake and has potential use in evaluating the relative impact of different source control and remedial alternatives.     

Controls on microbial mercury transformations in contaminated sediments downstream of the Idrija mercury mine (West Slovenia) to the Gulf of Trieste (northern Adriatic)

Purpose

Concentrations and transformations of mercury were measured in river, estuarine, and marine sediments to determine factors affecting the fate of mercury entering the northern Adriatic Sea.

Materials and methods

Radiotracer methodology was used to compare rates of mercury methylation (²⁰³Hg), MeHg demethylation (¹⁴C), and sulfate reduction (³⁵S) in sediment depth profiles to concentrations of total and dissolved mercury species in the lower freshwater region of the Isonzo River, the coastal lagoons, and in the Gulf of Trieste, northern Adriatic Sea.

Results and discussion

Mercury was readily methylated and demethylated in all sediments, but the relative activity of these processes varied greatly with location. Methylation activity increased greatly from freshwater to the marine regions; however, demethylation was extremely high in the estuarine and lagoon sites. Ratios of methylation to demethylation were low in these coastal sites but increased further offshore in the gulf, which agreed with increased ratios of MeHg to total Hg (%MeHg) in gulf sediments. Comparisons of microbial activities indicated that sulfate reduction strongly controlled both methylation and demethylation. However, Hg methylation in coastal lagoon sediments was controlled by rapid demethylation and the bioavailability of Hg that was affected by Hg adsorption and precipitation. Methylation in offshore marine sites correlated with sulfate reduction but not the partitioning of Hg between pore water and solid phases. The decrease in sulfide production offshore exacerbated Hg methylation.

Conclusions

The freshwater to marine gradient in the Idrija/So?a/Isonzo/Adriatic region is dynamic, exhibiting horizontally variable rates of microbial activities and Hg transformations that create “hot spots” of MeHg accumulation that are controlled differently in each region.

     

Total mercury and methylmercury mass balance in an alkaline,hypereutrophic urban lake (Onondaga Lake,NY)

A total mercury (total Hg) and methylmercury (CH₃Hg) mass balance was developed for Onondaga Lake, NY, based on sampling of tributaries, sediments, water column, and biota in 1992. Thein situ flux of total Hg and CH₃Hg from sediments to the overlying water and the rate of net CH₃Hg production in the water column were determined experimentally. Fluxes from atmospheric deposition, groundwater, and volatilization were estimated from limited field data and the literature. Ultraclean sampling and analytical techniques developed specifically for Hg were used. Results indicate that tributaries contribute the majority of total Hg entering the lake (13.6 kg in 1992). Other sources of total Hg included groundwater flux (0.02 kg), atmospheric deposition (0.44 kg), and flux from sediments (0.056 kg). Net sedimentation (11.1 kg), outflow (2.8 kg), and volatilization (0.016 kg) were sinks for total Hg. The two major sources of CH3_Hg were tributaries (0.26 kg) and net CH₃Hg production in the water column (0.60 kg). Flux from sediments accounted for only 0.017 kg CH₃Hg. Net sedimentation (0.47 kg), outflow (0.24 kg), and net uptake, by fish (0.20 kg) were sinks for CH₃Hg. Gross sedimentation of CH₃Hg exceeded net sedimentation by 90%, suggesting that release of CH₃Hg from settling particles is a significant process.     

Benthic fluxes of mercury during redox changes in pristine coastal marine sediments from the Gulf of Trieste (northern Adriatic Sea)

Purpose

The Gulf of Trieste (northern Adriatic Sea) is an example of a coastal environment contaminated with mercury (Hg). Contamination is a consequence of nearly 500?years of activity at the Idrija Mine (western Slovenia), which is the second largest Hg mine in the world. Oxygen depletion can be common in the Gulf of Trieste due to late summer stratification of the water column and accumulation of labile organic matter. Since changing redox conditions can have an impact on Hg transformations, we studied the effect of oxygen depletion, in parallel with sulphide, iron (Fe), manganese (Mn), fluorescent dissolved organic matter (FDOM) and nitrogen (N) and phosphorus (P) availability, on total Hg and methylmercury (MeHg) fluxes from sediments.

Materials and methods

Pore water concentrations and benthic fluxes of total dissolved Hg and MeHg were studied in situ and in microcosm laboratory experiments using flux chambers encompassing three different stages: oxic, anoxic and reoxidation.

Results and discussion

Our experiments showed that in the oxic stage there were small effluxes of MeHg to the water column, which increased in the anoxic stage and dropped rapidly in a subsequent reoxic stage, showing influx. Our results support the hypothesis that MeHg desorption from reduced metal hydroxides under anoxic conditions, and co-precipitation with Fe-oxides and MeHg demethylation in the reoxidation stage, may play a major role in determining MeHg benthic fluxes. For Hg and MeHg, it appears that there is little relationship between their pore water distribution and flux and that of FDOM, i.e. humics.

Conclusions

The results indicate that there was no significant difference in Hg and MeHg pore water levels and their benthic fluxes between the contaminated northern and central parts of the Gulf of Trieste and the pristine southern part. This suggests that shallow and stratified coastal marine environments, in general, represent areas with a risk of high benthic release of toxic MeHg.     

Historical sedimentary trends of mercury and other trace elements from two saltmarshes of the Marano and Grado lagoon (northern Adriatic Sea)

Purpose

Previous research conducted in the Marano and Grado lagoon (northern Adriatic Sea) has shown that this environment has been affected by trace metal contamination, especially by mercury (Hg), from both industrial (the chlor-alkali plant) and mining activities (Idrija mine, Slovenia). Sediment cores were collected from two different saltmarshes of this lagoon environment to evaluate the degree of the anthropogenic enrichments and the geochronology of Hg accumulation.

Materials and methods

Core subsampling was performed by cutting 1-cm thick slices at discrete intervals. Mercury determination was done differently from the other parameters in that the two long cores were subsampled at 1-cm intervals to obtain continuous concentration profiles. Samples were completely decomposed, using a mixture of mineral acids in a closed microwave system before being analysed for trace metal content using ICP-OES. Total Hg content in the solid phase was determined by DMA-80. ¹³⁷Cs was measured via gamma spectrometry. ²¹⁰Pb activity was measured via alpha-counting of its daughter, ²¹⁰Po, assuming secular equilibrium between the two isotopes.

Results and discussion

In saltmarsh sediments, Fe, Co, Li, Sc and V show no enrichment at both sites thus suggesting that they are essentially lithogenic elements. Conversely, enrichments are minimal (EF = <2) for As, Cd, Cr, Ni, Pb and Zn and moderate (EF = 2–5) for Cu and Mn and also for Pb and Zn but only in some levels of the sedimentary sequences. An exception is Hg, as expected due to the long-term input proceeding from the historical mining activity which has especially affected the eastern sector of the lagoon.

Conclusions

The core collected from the saltmarsh in the eastern lagoon (Grado) displays a better time resolution during the last century although the Hg background level has not been reached. Conversely, the core collected in the western sector (Marano) has recorded a longer and more complete history of Hg contamination, from the beginning of the peak of Hg extraction activity at the Idrija mine (1850). Both saltmarshes still receive Hg inputs and the sediment accumulation rates in the upper section appear to have increased over the last 10–20 years (from 0.30 to 0.45 cm year^?1 at Marano and from 0.30 to 0.74 cm year^?1 at Grado). Many of these morphological structures suffer erosive processes thus representing a potential source of contaminants associated with sediments, in particular Hg. Conservation and monitoring of saltmarshes should be taken into consideration also from this environmental point of view.

     

Fundamental roles of biological barriers in mercury accumulation and transfer in freshwater ecosystems (analysis at organism,organ, cell and molecular levels)

In the framework of an ecotoxicological approach to the processes of bioaccumulation and transfer of Hg in freshwater systems, we present a synthesis of our experimental studies concerning the interactions between inorganic Hg and MeHg and biological barriers

- at organism and organ levels : three biological models are selected: fish (Salmo gairdneri), burrowing mayfly nymphs (Hexagenia rigida) and rooted macrophytes (Elodea densa, Ludwigia natans). Results show strong specificities of the biological barriers (gills, intestine, roots, ...) towards metal fixation and absorption, closely related to the chemical form of the metal, the contamination sources (water, sediments or food) and the physico-chemical characteristics of the medium ;

- at cell and molecular levels : biophysical study of Hg fixation on membrane reveals a new binding site on the phospholipids, the primary amine group on serine and ethanolamine polar heads, jointly with the SH groups of proteins ; Hg(II) induces a strong rigidification of the phospholipidic bilayers. Inorganic Hg and MeHg transports through model membranes (BLM) are essentially due to diffusion of neutral chloride species. These interactions between Hg compounds and membranes are strongly dependent on Hg chemical speciation (pH and pCl effects).

     

Changes in the levels of polymethoxyflavones and flavanones as part of the defense mechanism of Citrus sinensis (cv. Valencia Late) fruits against Phytophthora citrophthora

Phytophthora citrophthora causes serious losses in Citrus fruits through brown rot lesion. The effect of infection with P. citrophthora on Citrus sinensis (cv. Valencia Late) fruits was studied, with particular reference to the levels of the flavanones hesperidin and isonaringin and the polymethoxyflavones sinensetin, nobiletin, tangeretin, and heptamethoxyflavone, because flavonoids are most probably involved as natural defense or resistance mechanisms in this genus. Changes in the levels of these flavonoids were detected after infection. The hesperidin and isonaringin contents fell by 13 and 67%, respectively, whereas the contents of their corresponding aglycons, hesperetin and naringenin, increased, suggesting the hydrolyzing effect of this fungus on the glycosylated flavanones. The heptamethoxyflavone, nobiletin, sinensetin, and tangeretin levels increased by 48, 28, 26, and 24%, respectively. The in vitro study revealed that these compounds acted as antifungal agents, the most active being the aglycons (naringenin and hesperetin), followed by the polymethoxyflavones and flavanone glycosides. The participation of these flavonoids in the defense mechanism of this Citrus species is discussed.     

Soil properties and plant community relationship in a saltmarsh of the Grado and Marano lagoon (northern Italy)

Purpose

The relationship between soil properties and plant communities was investigated in a saltmarsh of the Grado and Marano lagoon (northern Italy), where hydrology and micromorphology strongly influence the features of the ecosystem. A multidisciplinary approach was used to assess the change of soil properties and plant communities in relation to the submergence of soil.

Materials and methods

The plant community and soil profile surveys were both carried out along a transect in six sampling sites of the Gran Chiusa saltmarsh (Grado and Marano lagoon). The morphological and physicochemical parameters of soil profiles were investigated, and soils were classified according to Soil Taxonomy. The concentration of macronutrients in both soils and plants was analysed by inductively coupled plasma-optical emission spectrometry. Cluster and linear discriminant analysis were used to assist the interpretation of the data of plant communities and soil properties, respectively. The bioconcentration factor explored the macronutrient relationship between plant community and soil.

Results and discussion

A high, middle and low zone were identified by clustering the different plant communities along the studied transect. Discriminant analysis showed how the increase in soil submergence supported the accumulation of S and Ca content and depletion of Fe and Na. The development of different plant communities was linked to both soil water saturation and to the capacity of halophytes to tolerate anoxic conditions or salinity, by extrusion or bioconcentration strategies.

Conclusions

This study demonstrates that tide level plays an important role in the pedological development and chemical transformations along a soil hydrosequence. The micromosaic vegetation pattern may therefore represent a useful index of the hydrological and nutritional status of the underlying soils and could be used to predict changes in coastal ecosystems.

     

Soils and the soil cover of the taiga zone in the northern Urals (upper reaches of the Pechora River)

The territory in the upper reaches of the Pechora River is characterized by the predominance of Al-Fe-humus and metamorphic soils with gley features developing under the middle taiga fir-spruce forests rather than gley-podzolic soils as had been considered before. Some of the described soil profiles represent intergrades between brown taiga soils (burozems) and gleysols; these soils are absent in the new Russian soil classification system. General regularities of the soil cover are controlled by the geomorphic position of the soils on slopes and by the conditions of ground moistening and lateral soil water flows. The development of modern soil cover patterns is determined by the impact of herbaceous and woody vegetation, bioturbation of the soils by windfalls, the presence of dead tree trunks on the soil surface, and other factors.     

脂联素(A dipoQ)及其受体基因(A dipoR1and A dipoR2)在猪背最长肌和腰大肌中的表达差异

脂联素(AdipoQ)是脂肪组织分泌的一种细胞因子,通过血液循环系统到达靶器官与其受体1和2(AdipoR1和AdipoR2)结合,参与脂质和能量代谢及胰岛素敏感性调节方面的生物学过程.利用荧光定量PCR技术检测了210日龄长白猪和荣昌猪的背最长肌和腰大肌组织中Adip0Q、AdipoR1和AdipoR2基因mRNA丰度的表达差异,并分析了基因相对表达量与猪肥胖指数(porcine obesityindex,POI)、肌内脂肪(intramuscular fat,IMF)含量和背最长肌横截面面积的相关性.结果表明,在不同性别的长白猪和荣昌猪的两种肌肉组织中均检测到AdipoQ、AdipoR1和AdipoR2的表达,但表达量在品种、性别和组织间存在明显差异.AdipoQ和AdipoR1基因表达量与POI和IMF含量呈负相关,与背最长肌横截面面积呈正相关,但均未达到显著水平(P＞0.05),A dipoR2基因表达量与IMF含量呈显著负相关(P＜0.05).研究结果提示,AdipoQ、AdipoR1和AdipoR2表达量与脂肪沉积性状呈负相关,与肌肉生长性状呈正相关,这与其增加脂肪酸氧化,减少脂肪沉积的功能相符.     

2,4-Dihydroxy-7-methoxy-1,4-benzoxazin-3-one (DIMBOA) and 6-methoxy-benzoxazolin-2-one (MBOA) levels in the wheat rhizosphere and their effect on the soil microbial community structure

Despite increasing knowledge of 2,4-dihydroxy-7-methoxy-1,4-benzoxazin-3-one (DIMBOA) and 6-methoxy-benzoxazolin-2-one (MBOA) as allelochemicals involved in the defense of wheat against pests, relatively little is known about their levels in the rhizosphere and interactions with the soil microbial community. This study quantified DIMBOA and MBOA in the wheat rhizosphere and analyzed the soil microbial community structure. MBOA rather than DIMBAO was found in the wheat rhizosphere, and its concentration varied with cultivars, plant densities, and growth conditions. Wheat could detect the presence of competing weeds and respond by increased MBOA in the rhizosphere. There was a linear positive relationship between the MBOA level in the wheat rhizosphere and soil fungi/bacteria. When DIMBOA was applied to soil, yielding MBOA increased soil fungi. There were different phospholipid fatty acid (PLFA) patterns in soil incubated with DIMBOA and MBOA. These results suggested that DIMBOA and MBOA could affect the soil microbial community structure to their advantage through the change in fungi populations.     

Iron and sulfate reduction in the sediments of acidic mine lake 116 (Brandenburg,Germany): Rates and geochemical evaluation

A combination of rate measurements of iron(III)oxide and sulfate reduction, thermodynamic data, and pore-water and solid phase analyses was used to evaluate the relative significance of iron and sulfate reduction in the sediments of an acidic strip mining lake (Lake 116, Brandenburg, Germany). The rate of sulfate reduction was determined using a 35S-radiotracer method. Rates of iron turnover were quantified by mass balances based on pore-water concentration profiles. The differences in Gibbs free energy yield from reduction of iron and sulfate and from methanogenesis were calculated from individual redox couples and concentrations of reactants to account for the influence of high Fe2+ concentrations and differing mineral phases. Integrated (O-20 cm) mean rates of sulfate reduction were 1.2 (pelagial), respectively 5.2 (littoral) mmol (m2d)-1. Based on electron equivalents, the estimated iron reduction rates reached between about 50 % (pelagial) and 75 % (littoral) of the sulfate reduction rates. Compared to conditions usually assumed in the literature, in the sediments Gibbs free energy advantage of iron reduction over sulfate reduction was reduced frmm +11 KJeq-1 to a range of about +7 KJeq-1 (ferrihydrite, "reactive iron") to -6 KJeq-1 (goethite). This indicates that iron reduction was thermodynamically favored to sulfate reduction only if amorphous iron(III)oxides were available and is in accordance to the high competitiveness of sulfate reducers in the sediment. While total iron concentration in the sediments was high (up to 80% of the dryweight), reactive iron only accounted for 11-38% and was absolutely and relatively diminished in the zone of iron reduction. Pore-water concentration gradients and 137CS profiles indicated that little or no bioturbation occurred in the sediments, probably inhibiting the renewal of reactive iron. We further hypothesize that the reactivity of the iron oxide surfaces was reduced due to adsorption of DOM, suggested by IR spectra of the DOM and by a surface coverage estimate using literature data. Pelagial and littoral sediments displayed different dynamics. At the littoral relative iron reduction rate estimates were higher, iron sulfides were not accumulated and residence times of iron oxides were short compared to the pelagial. At the littoral site reoxidation of iron sulfides probably resulted in the renewal of reactive iron(III)oxides, possibly allowing for higher relative rates of iron reduction.     

Effect of lithological substrate on microbial biomass and enzyme activity in brown soil profiles in the northern Apennines (Italy)

The aim of the present study was to investigate the microbial activity along forest brown soil profiles sequence developed on different lithological substrates (carbonate or non-carbonated cement in sandstone formations) at different altitudes. The main question posed was: does carbonate affect the biochemical activity of brown soil profiles at different altitudes? For the purpose of this study, four soil profiles with different amounts and compositions of SOM developed on different lithological substrates were selected: two with carbonate (MB and MZ) and the other two with non-carbonated cement in the sandstone formations (MF1 and MF2). Chemical and biochemical properties of soil were analysed along soil profiles in order to assess the SOM quantity and quality, namely total organic C (C_org), water extractable organic C (WEOC) and humification indices (HI, DH, HR). Microbial biomass (C_mic and N_mic) content, as well as the specific activities of acid phosphatase, β-glucosidase and chitinase enzymes were chosen as indicators of biochemical activity. The soil biochemical properties provided evidence of better conditions for microorganisms in MB than in MF1, MF2 and MZ soil profiles, since patterns of microbial biomass content and activity might be expected in response to the amount and quality of organic substances. The different lithological substrates did not show any clear effect on soil microbial biomass content, since similar values were obtained in MF1, MF2 (with non-carbonated cement) and MZ (with carbonate). However, the specific activities of acid phosphatase (per unit of C_org and per unit of C_mic) were higher in soils with no carbonate (MF1 and MF2) than in soils with carbonate (MB and MZ). In conclusion, the biochemical activity along brown soil profiles was mainly regulated by different soil organic matter content and quality, while the two different lithological substrates (with carbonate or non-carbonated cement in the sandstone formations) did not show any direct effect on microbial biomass and its activity. However, the activity of acid phosphatase per unit of C was particularly enhanced in soil with non-carbonate cement in the sandstone formations.     

Changes in polyamines and ethylene during the development and ripening of eggplant fruits (Solanum melongena)

The levels of free polyamines in the endocarpium of eggplants (Solanum melongena) cv. Black Nite were studied during fruit growth and ripening. Other parameters such as weight and volume variation, respiratory intensity, ethylene production, and sugar content were determined. The polyamines found were putrescine and spermidine, with a higher amount of the former. No spermine, agmatine, or cadaverine were found during the development and ripening period of eggplant. At the beginning of fruit development, the levels of putrescine and spermidine observed were 1.67 nmol/g of fresh tissue. Putrescine levels peaked at 17.4 nmol/g of fresh tissue on the ninth day after petal fall, decreasing later to the initial levels. No significant changes in spermidine were observed during the growth period of the fruit. Beginning 9 days after petal fall, there was a rapid increase in fruit weight and volume, which coincided with the maximum content of free polyamines. At the same growth stage, total sugar content was maximum. Ethylene production decreased rapidly from 14.23 to 1.5 microL/kg.h and remained low during the whole growth period.     

Density and activity patterns of ocelots (Leopardus pardalis) in northern Peru and the impact of oil exploration activities

The western Amazon is experiencing unprecedented levels of oil and gas exploration, a trend of particular concern given the high levels of biodiversity found in this relatively pristine and unstudied region. Despite the widespread use of seismic reflection technology for exploration, no studies have investigated the response of wildlife populations to this disturbance in the tropics. We conducted a trail camera survey inside a large oil concession (Block 39) in the Peruvian Amazon near the Ecuador border with ongoing 2D seismic explorations to investigate its effects on ocelot (Leopardus pardalis) activity and abundance. The estimated size of the ocelot population within our 22 km² study area was the same before (control period: 34 ± 6.9 ocelots) and during exploration operations (disturbance period; 34 ± 4.6 ocelots) and we detected no change in activity patterns between the two periods. Ocelot capture rate was unaffected by the presence of seismic crews, and distance to the nearest seismic line was not correlated with capture rate at individual stations. Our density estimates (ocelots/100 km²) from the control (75.2) and disturbance period (94.7) include the highest reported for the species, and represent the first ocelot density estimates from the northwest Amazon forest. These high values conform to recent research showing a positive association between ocelot density, annual rainfall, and proximity to the equator (this study: >2500 mm annual rainfall; <200 km from equator). We discuss the potential short- and long-term environmental impacts of seismic operations, particularly as they relate to large mammal populations.     

Changes in nesting behavior and lipid content of a marine amphipod (Amphithoe valida) to the toxicity of a no. 2 fuel oil

Laboratory cultured amphipods, Amphithoe valida, were exposed to the water soluble fractions (WSF) of a No. 2 fuel oil for 6 days, and then transferred to clean sea water for one week. Survival and nesting behavior were observed daily, and the lipid contents were checked at the end of exposure and at the end of depuration. Survival of amphipods during exposure was high at all concentrations of WSF tested (0 to 25%). A delayed toxicity was observed; mortality was high in concentrations ? 15% WSF during depuration. The number of nests decreased with increasing concentration of WSF and length of exposure. Recovery of nest building activity in clean sea water was either lacking or small, indicating some damage to their nesting capability. The lipid contents of amphipods were close to the expected range (except at 25% WSF) following the exposure, but dropped to about 1 % following recovery compared with an expected value of 3.3%. Impairments of the chemosensory and locomotory systems may occur during exposure, which prevent amphipods from constructing nests for protection and food reserves, and eventually lead animals to use their stored energy of lipid for survival. Of the three biological parameters studied, nesting behavior and lipid content as a percentage of dry weight were better indicators of the sublethal stress of WSF than the response of survival; significant alterations of the former two parameters were found at the concentrations ? 5% WSF.     

Correlates of abundance and breeding success in the globally threatened Hinde's babbler (Turdoides hindei) and its congener, northern pied babbler (T. hypoleucus)

We investigated the relationship between habitat quality, abundance, group size and breeding success in the threatened Kenyan endemic Hinde's babbler (Turdoides hindei; Family Timaliidae), a co-operative breeder mainly associated with riverine thickets in cultivated areas. At two intensively cultivated sites, significantly more Hinde's babbler groups occurred in areas retaining at least 3% thicket cover, while breeding outcome improved where cover exceeded 9%. Despite previous concerns over low breeding success, the percentage of young birds present (17%, n=424 birds aged) was similar to that of a sympatric congener, the northern pied babbler (T. hypoleucus) (12%, n=162), and comparable with that of two other African congeners. Although breeding outcome was positively correlated with adult group size, there was no evidence that larger groups monopolised more favourable habitat or defended larger territories. Group density showed a positive, non-linear relationship with adjacent cover, levelling out where this exceeded 15-20%. Our findings suggest that even a modest increase in thicket cover may significantly raise the density and productivity of Hinde's babblers at these sites.     

猪细小病毒VLPs供外源蛋白插入的候选位点发现及其重组PCV2-ORF2的病毒样颗粒构建

先将猪细小病毒(PPV)SC-1株VP2基因扩增产物克隆到pMD18-T载体构建质粒pMD-VP2;设计两对引物(分别引入Hind Ⅲ和Sac Ⅰ两个酶切位点)扩增猪圆环病毒二型(PCV2)SC株ORF2基因,构建了pMD-ORF2.A和pMD-ORF2.B两质粒;经相应内切酶酶切后回收目的片段,插入PPV SC-1株VP2基因的Hind Ⅲ和Sac Ⅰ两个特异限制酶切位点处(分别对应于PPV VP2蛋白N端和C端1/3处),得到重组质粒pPVP2-ORF2.A和pPVP2-ORF2.B.经鉴定后的质粒pPVP2-ORF2.A和pPVP2-ORF2.B用Kpn Ⅰ、BamH Ⅰ和ApaL Ⅰ三酶切,回收含VP2和ORF2基因的目的片段克隆至真核表达载体(pEGFP-C1),得到重组质粒pEGFP.VO.A和pEGFP.VO.B.脂质体法转染重组质粒于Cos7细胞后,采用荧光显微镜和电镜观察基因表达情况,结果仅在转染pEGFP.VO.A的样品中观察到了病毒样颗粒(VLPs).纯化VLPs免疫小鼠,结果显不能产生较好的细胞免疫和针对PPV和PCV2的特异性体液免疫,该结果表明研究中获得了PCV VP1-PCV2ORF2重组VLPs,同时也揭示PPV VPLs的N端1/3适于外源蛋白插入构建重组VLPs     

Changes of the volatile profile and artifact formation in Daidai (Citrus aurantium) cold-pressed peel oil on storage

The chemical changes and artifact formation in daidai (Citrus aurantium L. var. Cyathifera Y. Tanaka) cold-pressed peel oil upon storage at 20, 5, and -21 degrees C for 3, 6, and 12 months were investigated using capillary gas chromatography (GC) and GC-MS. Major changes occurred in the oil stored at 20 and 5 degrees C. No changes were found at -21 degrees C. Monoterpene hydrocarbons decreased from 98.0 to 66.4% upon 12 months at 20 degrees C, while sesquiterpene hydrocarbons and alcohols increased from 0.1 to 2.4% and from 0.3 to 7.9%, respectively. Notable decreases of germacrene D, myrcene, linalyl acetate, and limonene occurred. Prominent increases of cis-carveol, trans-beta-farnesene, trans-p-2,8-menthadien-1-ol, linalool, and beta-caryophyllene were found. Thirty-four artifact compounds constituting 17.0% of the total volatile compounds were formed upon 12 months at 20 degrees C. The artifacts consisted of 13 alcohols (6.0%), five carbonyl compounds (5.3%), seven esters (4.9%), three epoxides (0.4%), four hydrocarbons (0.3%), and two unidentified. The prominent artifact compounds were (+)-carvone, trans,trans-farnesyl acetate, sabinene hydrate, 1-octen-3-ol, cis,cis-farnesyl acetate, and dihydrocarveol acetate. The results could be applied for monitoring and control of the flavor quality of daidai essential oil and related products.