Temporal variations of manganese in the haemolymph and tissues of the Norway lobster, Nephrops norvegicus (L.)

The Norway lobster, Nephrops norvegicus, lives on sediments rich in manganese (Mn) and any dissolved Mn(2+) can readily be taken up by the animal. To investigate temporal fluctuations of bioavailable Mn, a N. norvegicus fishing ground on the Swedish west coast was repeatedly sampled every 2 months from September 1992 to November 1994. The lobsters collected contained on average 91.7 μg Mn g(-1) dry wt. (S.E. 4.2, n=156). The oxygen saturation of the bottom water proved to be negatively correlated with both the temperature of the water and the Mn (concentration and total content) of the animal's haemolymph. The temporal fluctuations in animal Mn load were however, small compared to spatial differences found in an earlier study. There was an increase in the Mn concentration of the lobster exoskeleton (from 56 to 340 μg Mn g(-1) dry wt. exoskeleton) and gills (from 34 to 160 μg Mn g(-1) dry wt. gill) in postmoult animals compared to premoult. The Mn concentrations of the lobsters' hepatopancreas and muscle tissue remained relatively constant throughout the moult cycle and appear to be more conservative in their Mn concentration and less affected by exposure to Mn.     

Bioaccumulation of cadmium in an experimental aquatic food chain involving phytoplankton (Chlorella vulgaris), zooplankton (Moina macrocopa), and the predatory catfish Clarias macrocephalus x C. gariepinus

The accumulation of cadmium (Cd) was studied in an experimental aquatic food chain involving the phytoplankton Chlorella vulgaris as the primary producer, the zooplankton Moina macrocopa as the primary consumer, and the catfish Clarias macrocephalus x Clarias gariepinus as the secondary consumer. C. vulgaris was first exposed to Cd solutions at 0.00, 0.35, and 3.50 mg l(-1), referred to as control group and experimental groups 1 and 2, respectively. Subsequently, each group was fed to three corresponding groups of M. macrocopa. Finally, three groups of catfish were fed these corresponding groups of M. macrocopa. After C. vulgaris was exposed to 3.50 mg l(-1) Cd (experimental group 2), the residual Cd in solution was only 4.01 microg l(-1), lower than the maximum allowable limit of Cd in natural water sources (5 microg l(-1)). Cd concentrations in C. vulgaris were 0.01+/-0.00 microg g(-1) (dry wt) in the control group, 194+/-1.80 microg g(-1) (dry wt) in experimental group 1, and 1140+/-20.06 microg g(-1) (dry wt) in experimental group 2. The Cd concentrations in M. macrocopa were 0.01+/-0.00 microg g(-1) (dry wt) in the control group, 16.48+/-2.23 microg g(-1) (dry wt) in experimental group 1, and 56.6+/-3.23 microg g(-1) (dry wt) in experimental group 2. The Cd concentrations in catfish muscle increased with increasing Cd concentrations in the food. After 60 days of fish culture, the mean concentrations of Cd in fish muscle were 0.01+/-0.00 microg g(-1) (dry wt) in the control group, 0.61+/-0.02 microg g(-1) (dry wt) in experimental group 1 and 1.04+/-0.06 microg g(-1) (dry wt) in experimental group 2. Cd concentration in fish muscle of experimental group 2 was equal to the permissible limit. Cd accumulation affected fish growth: at the end of the study, the mean fresh weight (12.81 g) of catfish in the control group, was significantly higher than those experimental group 1 (10.43 g) and experimental group 2 (10.00 g). The results showed that the measurement of Cd concentration in water does not necessarily give a measure of the safety of aquatic organisms as human food. Hence, heavy metal contamination is a matter for concern when organisms are harvested, for fish and human consumption, from natural water sources.     

Intra- and interpopulation variability in maternal transfer of mercury to eggs of walleye (Stizostedion vitreum)

Mercury concentrations were determined for unfertilized eggs from seven walleye populations and for muscle and liver tissue from three of these seven populations in Canada and the United States. Female walleye transferred very little of their body methylmercury burden to their eggs. Methylmercury concentrations in eggs were 1.1-12% of those in muscle, and methylmercury burdens in eggs represented only 0.2-2.1% of the total body burden. Egg methylmercury as a percentage of total mercury increased with maternal length across populations. Percent methylmercury also increased with egg total mercury concentration but the slope of this relationship varied among populations. Egg methylmercury concentration increased with female age, and both muscle and liver methylmercury concentrations. Egg methylmercury concentration was also affected by female length at age but the effect of this relationship varied among populations. Mean predicted egg methylmercury concentrations (ng g(-1) dry) of 8-year-old, 550-mm females for the seven populations were as follows: Clay Lake, 796; Lake Superior, 24.3; Lake Winnipeg, 16.3; Lake Erie, 11.8; Primrose Lake, 8.76; Lake Manitoba, 7.32; Waconda Lake, 6.69.     

Reproductive impairment in Japanese quail (<Emphasis Type="Italic">Coturnix japonica</Emphasis>) after in ovo exposure to o,p'-DDT

We have previously described various effects in adult Japanese quail consequent on treatment with oestrogenic compounds in ovo. In the present study, the environmental contaminant o,p'-DDT [1-(2-chlorophenyl)-1-(4-chlorophenyl)-2,2,2-trichloroethane] was administered to quail eggs to further evaluate test endpoints for oestrogenic effects related to reproduction in the Japanese quail. Exposure to 2 mg o,p'-DDT/egg (150 micro g/g egg) resulted in impaired sexual behaviour, reduced cloacal gland area and lowered plasma testosterone concentration in males. Females displayed oviductal abnormalities, including retained right oviduct, decreased length of left oviduct, alterations in shell gland morphology and disrupted distribution of carbonic anhydrase in the shell gland. Egg laying was severely impaired. Consequently, a number of endpoints in adult quail may be useful for demonstrating an oestrogen-like mode of action by environmental contaminants during embryonic development.     

Maternal transfer of trace elements in the Atlantic horseshoe crab (<Emphasis Type="Italic">Limulus polyphemus</Emphasis>)

The maternal transfer of trace elements is a process by which offspring may accumulate trace elements from their maternal parent. Although maternal transfer has been assessed in many vertebrates, there is little understanding of this process in invertebrate species. This study investigated the maternal transfer of 13 trace elements (Ag, As, Cd, Co, Cr, Cu, Fe, Hg, Mn, Ni, Pb, Se, and Zn) in Atlantic horseshoe crab (Limulus polyphemus) eggs and compared concentrations to those in adult leg and gill tissue. For the majority of individuals, all trace elements were transferred, with the exception of Cr, from the female to the eggs. The greatest concentrations on average transferred to egg tissue were Zn (140?µg/g), Cu (47.8?µg/g), and Fe (38.6?µg/g) for essential elements and As (10.9?µg/g) and Ag (1.23?µg/g) for nonessential elements. For elements that were maternally transferred, correlation analyses were run to assess if the concentration in the eggs were similar to that of adult tissue that is completely internalized (leg) or a boundary to the external environment (gill). Positive correlations between egg and leg tissue were found for As, Hg, Se, Mn, Pb, and Ni. Mercury, Mn, Ni, and Se were the only elements correlated between egg and gill tissue. Although, many trace elements were in low concentration in the eggs, we speculate that the higher transfer of essential elements is related to their potential benefit during early development versus nonessential trace elements, which are known to be toxic. We conclude that maternal transfer as a source of trace elements to horseshoe crabs should not be overlooked and warrants further investigation.     

Effect of p-p′-DDE Administered in Vivo and in Vitro on Ca2+ Binding and Ca2+-Mg2+-ATPase Activity in Egg Shell Gland Mucosa of Ducks

Abstract: Thinning of the egg shell is produced by p-p′-DDT and DDE in several species of birds. A study was made of the effect of DDE administered in vitro and in vivo on the Ca²⁺ binding and Ca²⁺-Mg²⁺-activated ATPase of a homogenate of the egg shell gland of ducks (Anas platyrhynchos var.). The concentration of Ca²⁺ was 1×10^?4 and that of MgATP 1×10^?3M. In vitro, DDE in concentrations of 2–16 μg/ml of incubation medium inhibited the Ca²⁺-Mg²⁺-activated ATPase in a concentration-dependent manner, whereas Mg²⁺-activated ATPase was not affected by these concentrations. The Ca²⁺ binding by the homogenate was reduced by DDE in the same concentrations. The sodium azide sensitive Ca²⁺ binding was most sensitive. In vivo, DDE administered in a concentration of 40 mg/kg dry weight of the food for 45 days reduced the egg shell index by 18% in comparison to controls. After 45 days of treatment the DDE concentration in the egg shell gland mucosa was 1.20±0.16 μg/g of wet weight, while no DDE was detected in the controls. The Ca²⁺-Mg²⁺-activated ATPase was reduced by 32%, whereas the Mg²⁺-ATPase was not changed. The Ca²⁺ binding by the homogenate was reduced by 29%, the sodium azide sensitive part being most vulnerable. DDE increased the total Ca content of the egg shell gland mucosa by 44%. Since Ca is transported against a concentration gradient between blood plasma and the lumen of the shell gland, it is suggested that DDE, by inhibiting the Ca²⁺-Mg²⁺-activated ATPase, decreased the Ca translocation over the egg shell gland mucosa.     

Manganese induced apoptosis in haematopoietic cells of Nephrops norvegicus (L.)

Manganese (Mn) is highly abundant as MnO2 in marine sediments. During hypoxia in bottom waters, the reduced bioavailable fraction of manganese, Mn2+, increases. Thereby, Norway lobster, Nephrops norvegicus, can experience concentrations up to 1000 times normoxic levels. A previous study has shown that exposure to a realistic concentration of 20 mg l(-1) of Mn for 10 days reduced the number of circulating haemocytes in N. norvegicus significantly. Here we aimed to investigate if apoptosis contributes to the Mn-induced haemocytopenia, with the overall hypothesis that Mn induces apoptosis in a time and concentration dependent manner. N. norvegicus were exposed to Mn (0, 5, 10 and 20 mg l(-1)) for 5 and 10 days. After 5 days of exposure the total haemocyte counts were not affected. However, after 10 days there was a gradual decrease in cell numbers, reaching a reduction by 44% when the animals were exposed to 20 mg Mn l(-1). Apoptosis in cells, released from the haematopoietic tissue, was investigated by using TUNEL assay, which detects specific DNA strand breaks. The fraction of apoptotic cells gradually increased from 2.5% in un-exposed lobsters to 15% in those exposed to 20 mg l(-1) but there was no difference related to the exposure time. A gradual increase of apoptosis was further confirmed by electrophoretic DNA-ladder formation, however to a lower extent in lobsters exposed during 5 days. Cell viability, determined by metabolic activity and cell membrane integrity, was not reduced, indicating that apoptosis rather than necrosis caused reduced number of haemocytes. It was concluded that apoptosis seemed to increase already after 5 days of 5 mg l(-1) of Mn-exposure, although exposure for 10 days was required before it was reflected in the haemocyte numbers. Reduced numbers of haemocytes may increase the prevalence for infections in N. norvegicus in their natural habitat.     

Synthesis and characterization of metal oxide based ion exchanger from chicken egg shell biomass for the removal of arsenic from water

A new metal oxided-based high capacity biosorbent for As(III) was designed and synthesized from egg shell biomass and characterized using FTIR, FE-SEM, EDX, XRD, chemical analysis. For this, raw egg shell (RES) powder was first dissolved with HCl and mixed with ZrOCl₂18H₂O solution then precipitated to obtain hydrated double oxide precipitate (HDOP), which was employed for As(III) removal. As(III) biosorption onto HDOP is fast, depends on pH and As(III) concentration. Pseudo second order kinetics and Langmuir isotherm models successfully described the As(III) biosorption mechanism. HDOP provided exchangeable hydroxide/or chloride ligands for improved biosorption of As(III). Maximum biosorption capacity of HDOP for As(III) from Langmuir isotherm modelling was found to be 40 mg g^?1 at optimum pH 10. Chloride and nitrate cause negligible interference whereas sulphate and phosphate significantly reduced As(III) biosorption capacity of HDOP. HDOP completely removed arsenic from contaminated ground water and the remaining concentration was reached below the safe drinking water standard (10 μg L^?1) set by WHO. Moreover, HDOP exhibited effective regeneration and high stability with As(III) removal up to 8 cycles. Thus, HDOP synthesized from egg shell biomass can be used as a low cost, environmentally benign and high capacity biosorbent for the treatment of arsenic polluted water.     

油茶的粕、果皮和叶的抗肿瘤活性研究

目的比较油茶粕、果皮和叶提取物对多种肿瘤细胞增殖抑制的作用。方法常规传代培养5种肿瘤细胞,采用噻唑蓝(MTT)法和乳酸脱氢酶(LDH)法测定细胞活性。结果 30～90μg.mL-1油茶粕总皂苷、31.25～500μg.mL-1油茶果皮乙酸乙酯提取物30%乙醇洗脱物、62.5～500μg.mL-1油茶叶95%乙醇提取物乙酸乙酯萃取物呈剂量依赖性地抑制多种肿瘤细胞增殖。体外增殖抑制作用强弱为油茶粕总皂苷>油茶果皮乙酸乙酯捏取物30%乙醇洗脱物>油茶叶95%乙醇提取物乙酸乙酯萃取物。进一步确定了油茶粕总皂苷对人乳腺癌细胞(MCF-7)产生的明显抑制作用是通过破坏细胞膜而发挥作用的。结论分析比较后,分别确定了油茶粕、果皮和叶抗肿瘤的有效部位,填补了油茶粕总皂苷在肿瘤治疗领域的空白。     

Mucoadhesive fenretinide patches for site-specific chemoprevention of oral cancer: enhancement of oral mucosal permeation of fenretinide by coincorporation of propylene glycol and menthol

The objective of this study was to enhance oral mucosal permeation of fenretinide by coincorporation of propylene glycol (PG) and menthol in fenretinide/Eudragit RL PO mucoadhesive patches. Fenretinide is an extremely hydrophobic chemopreventive compound with poor tissue permeability. Coincorporation of 5-10 wt % PG (mean J(s) = 16-23 μg cm?2 h?1; 158-171 μg of fenretinide/g of tissue) or 1-10 wt % PG + 5 wt % menthol (mean J(s) = 18-40 μg cm?2 h?1; 172-241 μg of fenretinide/g of tissue) in fenretinide/Eudragit RL PO patches led to significant ex vivo fenretinide permeation enhancement (p < 0.001). Addition of PG above 2.5 wt % in the patch resulted in significant cellular swelling in the buccal mucosal tissues. These alterations were ameliorated by combining both enhancers and reducing PG level. After buccal administration of patches in rabbits, in vivo permeation of fenretinide across the oral mucosa was greater (～43 μg fenretinide/g tissue) from patches that contained optimized permeation enhancer content (2.5 wt % PG + 5 wt % menthol) relative to permeation obtained from enhancer-free patch (～17 μg fenretinide/g tissue) (p < 0.001). In vitro and in vivo release of fenretinide from patch was not significantly increased by coincorporation of permeation enhancers, indicating that mass transfer across the tissue, and not the patch, largely determined the permeation rate control in vivo. As a result of its improved permeation and its lack of deleterious local effects, the mucoadhesive fenretinide patch coincorporated with 2.5 wt % PG + 5 wt % menthol represents an important step in the further preclinical evaluation of oral site-specific chemoprevention strategies with fenretinide.     

Manganese induced immune suppression of the lobster, Nephrops norvegicus

Manganese (Mn) is one of the most abundant elements on earth, particularly in the soft bottom sediments of the oceans. As a micronutrient Mn is essential in the metabolic processes of organisms. However, at high concentrations the metal becomes a neurotoxin with well-documented effects. As a consequence of euthrophication, manganese is released from bottom sediments of coastal areas and the Norway lobsters, Nephrops norvegicus, can experience high levels of bioavailable Mn(2+). Here, we present the first report showing that Mn also affects several fundamental processes in the mobilisation and activation of immunoactive haemocytes. When N. norvegicus was exposed to a realistic [Mn(2+)] of 20 mg l(-1) for 10 days 24.1 microg ml(-1) was recorded in the haemolymph. At this concentration the total haemocyte count was reduced by ca. 60%. By using BrdU as a tracer for cell division, it was shown that the proliferation rate in the haematopoietic tissue did not increase, despite the haemocytepenia. A gene coding for a Runt-domain protein, known to be involved in maturation of immune active haemocytes in a variety of organisms, was identified also in haemocytes of N. norvegicus. The expression of this gene was >40% lower in the Mn-exposed lobsters as judged by using a cDNA probe and the in situ hybridisation technique. In response to non-self molecules, like lipopolysaccharide (LPS), the granular haemocytes of arthropods are known to degranulate and thereby release and activate the prophenoloxidase system, necessary for their immune defence. A degranulation assay, tested on isolated granular haemocytes, showed about 75% lower activity in the Mn-exposed lobsters than that for the unexposed. Furthermore, using an enzymatic assay, the activation per se of prophenoloxidase by LPS was found blocked in the Mn-exposed lobsters. Taken together, these results show that Mn exposure suppressed fundamental immune mechanisms of Norway lobsters. This identifies a potential harm that also exists for other organisms and should be considered when increasing the distribution of bioavailable Mn, as has been done through recently introduced applications of the metal.     

Effects of injected methylmercury on the hatching of common loon (Gavia immer) eggs

To determine the level of in ovo methylmercury (MeHg) exposure that results in detrimental effects on fitness and survival of loon embryos and hatched chicks, we conducted a field study in which we injected eggs with various doses of MeHg on day 4 of incubation. Eggs were collected following about 23 days of natural incubation and artificially incubated to observe hatching. Reduced embryo survival was evident in eggs injected at a rate of ≥1.3 μg Hg/g wet-mass. When maternally deposited Hg and injected Hg were considered together, the median lethal concentration of Hg (LC₅₀) was estimated to be 1.78 μg Hg/g wet-mass. Organ mass patterns from eggs of chicks injected at a rate of 2.9 μg Hg/g differed from that of controls and chicks from the 0.5 μg Hg/g treatment, largely related to a negative relation between yolk sac mass and egg mercury concentration. Chicks from eggs in the 2.9 μg Hg/g treatment were also less responsive to a frightening stimulus than controls and chicks from the 0.5 μg Hg/g treatment. We also found that the length of incubation period increased with increasing egg mercury concentration. Tissue Hg concentrations were strongly associated (r ² ≥ 0.80) with egg Hg concentration.     

Effects of an acute silver challenge on survival, silver distribution and ionoregulation within developing rainbow trout eggs (Oncorhynchus mykiss)

Rainbow trout eggs were acutely challenged with silver (as AgNO(3)) at different stages of development from fertilization through to hatch in moderately hard water (120 mg CaCO(3) l(-1), 0.70 mM (25 mg l(-1)) Cl(-), 1.3 mg l(-1) DOC, 12.3+/-0.1 degrees C) at measured total silver concentrations of 0.11+/-0.004, 1.55+/-0.15, and 14.15+/-1.52 microg l(-1). Four separate acute challenges were conducted, each consisting of 5 days exposure to the respective silver concentration, followed by 4 days recovery after transfer to silver-free water (series 1, 1-10 days post-fertilization; series 2, 8-17 days post-fertilization; series 3, 16-25 days post-fertilization; series 4, 23-32 days post-fertilization). Mortality was not significantly different from control during exposure to 0.11, 1.55, and 14.15 microg l(-1) total silver in series 2, 3 and 4 (mortality for series 1 data could not be calculated for technical reasons). In the four days of recovery following silver exposure, however, there was significant mortality at 14.15 microg l(-1) total silver reaching 100, 31 and 72% in series 2, 3 and 4, respectively, indicating eggs are more sensitive in the period of 8-17 and 23-32 days post-fertilization at this temperature. Mortality following silver exposure was associated with ionoregulatory impairment in series 3 and 4, where up to 60% of whole egg [Na(+)] and [Cl(-)] was lost relative to controls at 14.15 microg l(-1) total silver. Significant but smaller reductions in egg [Na(+)] and/or [Cl(-)] were also observed at 0.11 and 1.55 microg l(-1) total silver. The greatest accumulation of silver in whole eggs and chorions occurred in series 4, reaching concentrations of 0.53 microg g(-1) (eggs) and 15.5 microg g(-1) (chorions) in the 14.15 microg l(-1) treatment. The accumulation of silver in the whole eggs and chorions of the 0.11 microg l(-1) treatment was not different from controls throughout embryonic development. Of the total silver content, only a small proportion of silver was found in the embryos (1-17%), indicating that the chorion is a protective barrier during acute silver exposure.     

CHANGES IN EGG COMPOSITION OF AMERICAN KESTRELS EXPOSED TO DIETARY POLYCHLORINATED BIPHENYLS

Changes in the quality of eggs of birds exposed to polychlorinated biphenyls (PCBs) have been described, but have never been directly attributed to PCBs. Polychlorinated biphenyl residues in eggs have been associated with reduced reproductive success and embryonic deformities in wild birds. Egg size and composition, specifically the amount of albumen, yolk, and water in an egg, also influence the growth and viability of embryos and hatchlings, and consequently the reproductive success of birds. To deter mine whether PCB exposure of adult birds affected the size and composition of their eggs, 25 pairs of captive American kestrels (Falco sparverius) were fed a mixture of PCB-spiked (1248:1254:1260) food to give an approximate exposure of 7 mg/kg body weight/d, beginning 1 mo prior to pairing, and continuing throughout the courtship, egg-laying, and incubation periods. This dietary level in the adult female kestrels resulted in mean total PCB residues in the eggs of 34.1 µg/g wet weight (geometric mean), which is environmentally relevant. PCB residues in eggs increased with the time of female exposure to the contaminated diet and laying date. Variation in egg size within PCB clutches was significantly greater than within control clutches, although absolute egg mass and volume did not differ markedly by treatment. Only infertile eggs and only one egg per clutch were used for egg composition analysis. Yolks in the PCB-contaminated eggs were heavier, with less wet and dry albumen relative to control eggs. Water content and eggshell thickness were not significantly affected by PCB exposure. These results suggest that eggs from the PCB treatment have relatively more lipid and less protein available for embryonic development. Changes in egg composition were not associated with egg size, lay date, ambient temperature, humidity, or precipitation, which are factors known to affect these variables in bird eggs. The PCB-induced changes in egg composition described here provide insight into possible mechanisms contributing to reduced reproductive performance in wild birds exposed to PCBs.     

Metabotropic glutamate receptor 5 antagonist 2-methyl-6-(phenylethynyl)pyridine (MPEP) microinfusions into the nucleus accumbens shell or ventral tegmental area attenuate the reinforcing effects of nicotine in rats

Systemic administration of the mGlu5 receptor antagonist 2-methyl-6-(phenylethynyl)-pyridine (MPEP) was previously shown to selectively attenuate nicotine self-administration without affecting food-maintained responding in rats. Glutamatergic neurotransmission in the ventral tegmental area (VTA) and nucleus accumbens (NAcc) shell plays an important role in the reinforcing effects of nicotine. To determine the brain sites that may mediate the systemic effects of MPEP on nicotine self-administration, the present study investigated the effects of MPEP microinfusions into the VTA or the NAcc shell on nicotine and food self-administration in separate groups of rats. Administration of low MPEP doses (0, 0.5, 1, and 2 μg/0.5 μl/side) microinfused into the NAcc shell had no effect on nicotine self-administration, whereas higher MPEP doses (0, 10, 20, and 40 μg/0.5 μl/side) microinfused into the NAcc shell dose-dependently attenuated nicotine self-administration without affecting food-maintained responding. Microinfusions of MPEP into the VTA (0, 10, 20, and 40 μg/0.5 μl/side) significantly decreased both nicotine and food self-administration at 20 μg/0.5 μl/side but did not affect responding for either reinforcer at 40 μg/0.5 μl/side. This lack of effect of 40 μg/0.5 μl/side MPEP on either nicotine or food self-administration when administered into the VTA may be attributable either to actions of MPEP at presynaptic mGlu5 receptors or at targets other than mGlu5 receptors. Importantly, anatomical control injections 2 mm above the NAcc shell or the VTA using the most effective MPEP dose in the two regions did not result in attenuation of nicotine self-administration. In conclusion, MPEP microinfusions in the VTA or NAcc shell attenuates the reinforcing effects of nicotine possibly via blockade of mGlu5 receptors located in these regions.     

顶空-气相色谱法测定蛋黄卵磷脂的溶剂残留量

目的建立顶空毛细管气相色谱法同时测定蛋黄卵磷脂中乙醇、丙酮残留量的分析方法。方法采用顶空进样毛细管气相色谱法,以正丙醇为内标,键合聚乙二醇（Phenomenex ZB-FFAP）石英毛细管色谱柱;柱升温程序,初始35℃,保持10 min,以25℃/min升至180℃,保持5 min;进样口温度220℃;检测器温度250℃;氮气为载气,流速：1 m L/min;分流进样,分流比5∶1;顶空温度80℃,平衡时间45 min。结果丙酮在25.104-2 510.4μg/m L浓度范围线性关系良好,r^2=0.999 7,最低检测限为20 ng,加样回收率为94.0%-97.7%;乙醇在23.7-2 370μg/m L浓度范围线性关系良好,r^2=0.999 3,最低检测限为0.001 6μg,加样回收率为97.3%-102.9%。结论该方法简便、快速、结果准确,适用于测定蛋黄卵磷脂中丙酮、乙醇残留量。     

Effects of TCDD and its Congeners 3,3′,4,4′-Tetraehloroazoxybenzene and 3,3′,4,4′-Tetrachlorobiphenyl on Lymphoid Development in the Thymus of Avian Embryos

Abstract: Thymus anlagen from 11-day-old chick and 14-day-old turkey and duck embryos were cultured in media containing 2, 3, 7, 8-tetrachlorodibenzo-p-dioxin (TCDD) for 5 days. The maximal TCDD-induced decrease in lymphoid cell number of chick embryo thymus (to about 60% of the control number) occured at concentrations of 10^?10 M and above. To produce the same effect on lymphoid cell number in the cultures of thymus anlagen from turkey and duck embryos, about a 100-fold higher concentration of TCDD was needed. The toxicity of the TCDD congeners 3,3′4,4′-tetrachloroazoxybenzene (TCAOB) and 3,3′,4,4′-tetrachlorobiphenyl (TCB) to embryonic chicken thymus was tested in vitro and in ovo. In chick embryo thymus cultures, TCAOB and TCB were about two orders of magnitude less toxic than TCDD. Injection of TCAOB and TCB into chicken eggs preincubated for 11 days resulted in a dose-dependent decrease in thymic lymphoid cell number 5 days later, declining to about 14% of the controls at 10 μg TCAOB/kg egg. The ED₅₀ value was estimated to be 3.6 and 60 μg/kg egg for TCAOB and TCB, respectively.     

Response of spinach (Spinacea oleracea) to the added fluoride in an alkaline soil

The influence of soil contamination by inorganic fluoride (NaF) on the uptake and accumulation of fluoride in the shoot and root of spinach (Spinacea oleracea) was investigated in pot experiment under controlled conditions. The soluble fluoride in soil varied between 2.57mgkg(-1) soil and 16.44mgkg(-1) soil in the treatment range of 0-800mgNaFkg(-1) soil. It was found that the concentration of the total fluoride in shoot and root varied between 23.5mgkg(-1) dry wt. (control) and 219.8mgkg(-1) dry wt. (at 800mgNaFkg(-1) soil). The fluoride concentration in shoot and root showed a linear trend. At the added fluoride concentration beyond 200mgNaFkg(-1) of soil, the spinach root retained more fluoride than shoot. In the treatment range 0-800mgNaFkg(-1) soil, the water labile fluoride in the juice varied from 0.32 to 0.78ppm in shoot and 1.03 to 2.79ppm in the root. No visible symptom of phyto-toxicity was noticed with the treatment from 0 to 800mgNaFkg(-1) soil. It was inferred from this study that spinach (S. oleracea) accumulates fluoride at tissues level and has a distinct mechanism of partitioning of water labile fluoride and total fluoride in the tissues.     

Liposomes as an alternative delivery system for investigating dietary metal toxicity to Daphnia magna

Dietary metal toxicity studies with invertebrates such as Daphnia magna are often performed using metal-contaminated algae as a food source. A drawback of this approach is that it is difficult to distinguish between the direct toxicity of the metal and indirect effects caused by a reduced essential nutrient content in the metal-contaminated diet, due to prior exposure of the algae to the metal. This hampers the study of the mechanisms of dietary metal toxicity in filter-feeding freshwater invertebrates. The aim of the present study was to develop a technique for producing metal-contaminated liposomes as an alternative delivery system of dietary metals. These liposomes are not vulnerable to metal-induced shifts in nutrient quality. Liposomes were prepared by the hydration of phosphatidylcholine in media containing either 0 (control) or 50mg Ni/L. The liposomes had average diameters of 19.31 (control) and 10.48 μm (Ni-laden), i.e., a size appropriate for ingestion by D. magna. The liposome particles were then mixed with uncontaminated green algae in a 1/10 ratio (on a dry wt. basis) to make up two diets that differed in Ni content (i.e., 2.0 μg Ni/g dry wt. in the control and 144.2 μg Ni/g dry wt. in the Ni-contaminated diet, respectively). This diet was then fed to D. magna during a 21-day chronic bioassay. The experiment showed that the Ni content and the size distribution of the liposomes were stable for at least 7 days. Also the use of phosphatidylcholine as a liposome component did not affect the reproduction of the daphnids. Exposure to increased level of dietary Ni resulted in 100% mortality after 14 days of exposure and in an increased whole-body Ni concentration in D. magna of 14.9 and 20.4 μg Ni/g dry wt. after 7 and 14 days of exposure, respectively. The Ni-exposed daphnids also exhibited a reduced size (i.e., 30% smaller than the control) after 7 days and a completely halted growth between day 7 and day 14. In terms of reproduction, the size of the first brood (number of juveniles) of the Ni-exposed daphnids was significantly reduced (by 85%) compared to the control. None of the Ni-exposed individuals were able to produce a second brood before dying. The algal ingestion rate - after correction for the indirect effect of a reduced size - was increased (by 68%) by dietary Ni after 6 days of exposure compared to the control, but was severely reduced (by 80% compared to the control) after 13 days. These data suggest that an inhibition of the ingestion process may have contributed to the observed effects of dietary Ni on growth and reproduction beyond 6 days of exposure, although the involvement of other mechanisms cannot be excluded. The mechanism(s) which led to the reduced growth during the first week of exposure remain unclear, although inhibition of the ingestion process can likely be excluded here as an explanation. Overall, this paper demonstrates, using this new method of delivering dietary Ni via liposome carriers and thus excluding potential diet quality shifts, that dietary Ni can indeed induce toxic effects in D. magna. This method may therefore be a promising tool to help further elucidate the mechanisms of dietary metal toxicity to filter-feeding invertebrates.     

Selenium accumulation and reproduction in birds breeding downstream of a uranium mill in northern Saskatchewan, Canada

Selenium (Se) concentrations in aquatic invertebrates and bird eggs collected along the treated effluent receiving environment of the Key Lake uranium mill in northern Saskatchewan were significantly greater than from nearby reference areas, and in some cases (e.g., eggs of common loons—Gavia immer) were higher than commonly used thresholds for adverse reproductive effects in birds (i.e., 5 μg/g dry weight in diet; 12–15 μg/g dry weight in eggs). Mean Se concentrations in tree swallow (Tachycineta bicolor) eggs reached a maximum of 13.3 μg/g dry weight at the point of treated effluent discharge and exhibited a gradient of decreasing Se concentrations with increasing distance from the effluent discharge, probably reflecting both effluent dilution and local site fidelity by nesting swallows. In some cases, high intra-clutch variability in Se concentrations in mallard (Anas platyrhynchos) and tree swallow eggs was observed in high-Se sites, suggesting that a single egg randomly sampled from a nest in an area of higher Se exposure may not be representative of Se concentrations in other eggs from the same nest. Overall, tree swallow reproductive success was similar in both exposed and reference areas.