Bioenergetic and pharmacokinetic model for exposure of common loon (Gavia immer) chicks to methylmercury

A bioenergetics model was used to predict food intake of common loon (Gavia immer) chicks as a function of body mass during development, and a pharmacokinetics model, based on first-order kinetics in a single compartment, was used to predict blood Hg level as a function of food intake rate, food Hg content, body mass, and Hg absorption and elimination. Predictions were tested in captive growing chicks fed trout (Salmo gairdneri) with average MeHg concentrations of 0.02 (control), 0.4, and 1.2 microg/g wet mass (delivered as CH3HgCl). Predicted food intake matched observed intake through 50 d of age but then exceeded observed intake by an amount that grew progressively larger with age, reaching a significant overestimate of 28% by the end of the trial. Respiration in older, nongrowing birds probably was overestimated by using rates measured in younger, growing birds. Close agreement was found between simulations and measured blood Hg, which varied significantly with dietary Hg and age. Although chicks may hatch with different blood Hg levels, their blood level is determined mainly by dietary Hg level beyond approximately two weeks of age. The model also may be useful for predicting Hg levels in adults and in the eggs that they lay, but its accuracy in both chicks and adults needs to be tested in free-living birds.     

Derivation of screening benchmarks for dietary methylmercury exposure for the common loon (Gavia immer): Rationale for use in ecological risk assessment

The current understanding of methylmercury (MeHg) toxicity to avian species has improved considerably in recent years and indicates that exposure to environmentally relevant concentrations of MeHg through the diet can adversely affect various aspects of avian health, reproduction, and survival. Because fish-eating birds are at particular risk for elevated MeHg exposure, the authors surveyed the available primary and secondary literature to summarize the effects of dietary MeHg on the common loon (Gavia immer) and to derive ecologically relevant toxic thresholds for dietary exposure to MeHg in fish prey. After considering the available data, the authors propose three screening benchmarks of 0.1, 0.18, and 0.4?μg?g(-1) wet weight MeHg in prey fish. The lowest benchmark (0.1?μg?g(-1) wet wt) is the threshold for adverse behavioral impacts in adult loons and is close to the empirically determined no observed adverse effects level for subclinical effects observed in captive loon chicks. The remaining benchmarks (0.18 and 0.4?μg?g(-1) wet wt) correspond to MeHg levels in prey fish associated with significant reproductive impairment and reproductive failure in wild adult loons. Overall, these benchmarks incorporate recent findings and reviews of MeHg toxicity in aquatic fish-eating birds and provide the basis for a national ecological risk assessment for Hg and loons in Canada. Environ. Toxicol. Chem. 2012; 31: 2399-2407. ? 2012 SETAC.     

Distribution and accumulation of mercury in tissues of captive-reared common loon (Gavia immer) chicks

We determined the distribution and accumulation of Hg in tissues of common loon (Gavia immer) chicks maintained for up to 15 weeks on either a control diet with no added methylmercury chloride (MeHgCl) or one containing either 0.4 or 1.2 microg Hg (as MeHgCl)/g wet-weight food. Total Hg and MeHg tissue concentrations were strongly positively correlated (r2 > 0.95) with the amount of Hg delivered to individual chicks throughout the course of the experiment. The pattern of differential Hg concentration in internal tissues was consistent within each treatment: Liver > kidney > muscle > carcass > brain. Feather Hg concentrations were consistently higher than those of internal tissues and represented an important route of Hg elimination. Feather mass accounted for 4.3% +/- 0.1% (average +/- standard error) of body mass, yet 27.3% +/- 2.6% of total Hg intake was excreted into feathers. Our calculations indicate that 26.7% +/- 4.9% of ingested Hg was not accounted for and, thus, either was never absorbed or was absorbed and subsequently eliminated in feces. With the additional excretion into feathers, 54% of ingested Hg was excreted. Demethylation was evident in the liver at all treatment levels and in the kidneys of chicks dosed at 1.2 microg Hg/g. Mercury concentrations were strongly positively correlated (r2 > or = 0.95) among internal tissues and with blood Hg concentration. Mercury concentrations of secondary feathers were moderately correlated (r2 = 0.82-0.93) with internal tissues. We supply regression models that may be used to provide perspective and a useful means of interpreting the variety of measures of Hg exposure reported in the literature.     

Mercury and Selenium Concentrations in Livers and Eggs of Common Loons (Gavia immer) from Minnesota

Mercury and selenium act as mutual antagonists in mature birds, but their toxicity is additive or synergistic in avian embryos and immature birds. Twenty eggs and livers from 18 mature and 9 immature common loon carcasses found in Minnesota were collected. Livers and eggs were analyzed for mercury and selenium by atomic emission and atomic absorption spectroscopy. Liver mercury concentrations were significantly higher in mature loons compared to those of immature loons and eggs. Liver selenium concentrations were significantly higher in mature loons than those of immature loons, and selenium concentrations in immature loon livers were significantly higher than levels in eggs. There was a significant positive correlation between mercury and selenium in loon livers. There was a negative correlation between mercury and selenium in eggs. Received: 2 February 2001/Accepted: 28 May 2001     

混合稀土硝酸盐对仔鼠免疫功能的影响

目的：了解混合稀土硝酸盐[RE(NO3)3]能否经胎盘进入仔鼠体内及RE（NO3）3对仔鼠免疫功能的影响。方法：小鼠妊娠7－8d开始经口灌胃，分别给予2，20，200mg/kgRE（NO3）3，对照组给与蒸馏水，直至生下仔鼠。采用电感耦合等离子体质谱法（ICP－MS）检测F1代仔鼠体内稀土元素镧（La）、铈（Ce）、镨（Pr）、钕（Nd）的含量；分别测定刚离乳及离乳3周仔鼠免疫器官重量、脾抗体形成细胞数（IgM-PFC／脾）、迟发型变态反应（DTH）和巨噬细胞功能。结果：妊娠期母鼠经口灌胃RE（NO3）3后，20．0mg/kg组F1代仔鼠刚出生时体内稀土元素La高于对照组（P＜0．05）；200．0mg/kg组F1代仔鼠刚出生时体内稀土元素La、Ce、Pr、Nd含量均明显高于对照组（P＜0．05）。F1代仔鼠刚离乳时，20．0mg/kg组仔鼠脾脏重量明显高于对照组（P＜0．05）；2．0mg/kg RE(NO3)3可明显增加IgM-PFC/脾（升高82．2％）；2．0，20．0mg/kg组碳粒廓清指数K值和吞噬指数α值均明显高于对照组（P＜0．01，P＜0．05）；2．0mg/kg RE（NO3）3对DTH有明显升高作用（P＜0．05）。F1代仔鼠离乳后3周各剂量组仔鼠脾脏重及其脏体比均明显高于对照组（P＜0．05）；200．0mg/kg RE（NO3）3对IgM-PFC／脾有明显的抑制作用（抑制率为36．9％），且对碳粒廓清指数K值和吞噬指数α也有明显的抑制作用（P＜0．05）。各剂量组DTH未见有明显改变。结论：RE（NO3）3可经胎盘转运进入仔鼠体内，且可对仔鼠免疫功能产生一定的影响，这些影响可能是RE（NO3）3经胎盘转运进入仔鼠体内的结果。     

Toxic effects of dietary methylmercury on immune function and hematology in American kestrels (Falco sparverius)

Fifty-nine adult male American kestrels (Falco sparverius) were assigned to one of three diet formulations including 0 (control), 0.6, and 3.9?μg/g (dry wt) methylmercury (MeHg). Kestrels received their diets daily for 13 weeks to assess the effects of dietary MeHg on immunocompetence. Immunotoxic endpoints included assessment of cell-mediated immunity (CMI) using the phytohemagglutinin (PHA) skin-swelling assay and primary and secondary antibody-mediated immune responses (IR) via the sheep red blood cell (SRBC) hemagglutination assay. Select hematology and histology parameters were evaluated to corroborate the results of functional assays and to assess immunosuppression of T and B cell-dependent components in spleen tissue. Kestrels in the 0.6 and 3.9?μg/g MeHg groups exhibited suppression of CMI, including lower PHA stimulation indexes (p?=?0.019) and a 42 to 45% depletion of T cell-dependent splenic lymphoid tissue (p?=?0.006). Kestrels in the 0.6?μg/g group exhibited suppression of the primary IR to SRBCs (p?=?0.014). MeHg did not have a noticeable effect on the secondary IR (p?=?0.166). Elevation of absolute heterophil counts (p?相似文献   

Effects of methylmercury and spatial complexity on foraging behavior and foraging efficiency in juvenile white ibises (Eudocimus albus)

Methylmercury is a globally distributed neurotoxin, endocrine disruptor, and teratogen, the effects of which on wildlife at environmentally relevant levels are largely unknown. In birds, foraging efficiency and learning may be sensitive endpoints for sublethal methylmercury toxicity, and these endpoints also may be biologically relevant at the population level. In the present study, groups of wild-caught, prefledgling white ibises (Eudocimus albus) were raised in a free-flight, open-air aviary on diets that approximated the measured range of methylmercury exposure in the Everglades ecosystem (0, 0.05, 0.1, and 0.3 mg/kg/d). The effect of methylmercury exposure on group foraging efficiency was examined by allowing birds to forage on 200 fathead minnows (Pimephales promelas) in artificial ponds for 15 min by straining the arenas' contents through a seine net and counting all remaining prey. Additionally, we varied the difficulty of foraging by these tactile feeding birds by adding multiple levels of structural complexity (e.g., increased vegetation and prey refugia) to the pond. Structural complexity affected both foraging efficiency and the rate of increase in efficiency over time (improvement). Methylmercury exposure affected foraging efficiency (p = 0.03). It did not affect foraging improvement in the face of increasingly challenging environments, however, and the dose-response relationship was nonlinear (e.g., the control and high-exposure groups were the least efficient foragers). Evidence for an effect of methylmercury on foraging efficiency therefore was inconclusive because of unpredicted results and no interaction with time or habitat complexity. These data suggest a nonlinear dose-response relationship at low levels of methylmercury exposure; future research is needed to verify this hypothesis. This appears to be the first experimental demonstration of the effects of habitat complexity on foraging efficiency in long-legged wading birds.     

燃煤砷污染对人体免疫功能影响

目的进一步了解燃煤砷污染对人体免疫功能的远期影响,为燃煤型砷中毒的预防和干预提供科学依据。方法采用碱性磷酸酶抗碱性磷酸酶桥联酶标法（APAAP）测定燃煤型砷中毒患者外周T淋巴细胞亚群CD3^＋、CD4^＋、CD8^＋细胞的变异情况,并比较1998年与2005年各项指标的变化。免疫比浊法测定患者血清中免疫球蛋白IgGI、gMI、gM及补体C3、C4的含量。结果燃煤型砷中毒患者T淋巴细胞亚群CD3^＋、CD4^＋细胞和CD4^＋/CD8^＋比值显著低对照组（P〈0.01）,1998年与2005年比较差异无统计学意义（P〉0.05）;患者血清中IgG和C4分别显著高于和低于对照组（P〈0.01）,其余指标差异无统计学意义（P〉0.05）。结论燃煤砷污染所致人体免疫球蛋白及补体改变以及T淋巴细胞亚群免疫功能的持久性损害,不仅可能是砷中毒的促发原因之一,还可能是该病病情持续发展的原因之一,采取针对性提高免疫功能的防治策略有助于砷中毒的预防和干预。     

Cellular immune responses of nutritionally stressed juvenile cotton rats (Sigmodon hispidus) during acute benzene exposure

Wild juvenile cotton rats (Sigmodon hispidus) were used in this study to examine the effects of exposure to cyclophosphamide (CY) or differing levels of benzene on selected measures of cellular immunity following dietary protein restriction. Benzene caused marginal immunotoxicity as indicated by suppressed splenocyte proliferation and total circulating neutrophils. Cyclophosphamide and also crude protein restriction induced severe immune lesions manifested as thymus and spleen atrophy, depressed delayed hypersensitivity response, reduced proliferative capacity of splenocytes, and reduced numbers of total leukocytes, lymphocytes, and splenocytes. Although severe immune modulation resulted from the individual effects of CY exposure and dietary protein restriction, there was little statistically significant toxicant-diet interaction.     

Effect of copper exposure during embryonic development on chemosensory function of juvenile fathead minnows (Pimephales promelas)

Fish rely on chemosensation to alert them of nearby predators. Recent evidence suggests that metals disrupt this chemical communication system. Our objective was to determine the chemical alarm response of juvenile fathead minnows after embryonic copper (Cu) exposure. Embryos were randomly assigned to one of two treatments: clean water or water containing 10 microg/L Cu. Once hatched, half of the Cu-exposed embryos were transferred to clean water (after hatch), while the other half remained in the Cu-contaminated water. Fish were tested using a triumvirate maze at the age of 84-96 d post-hatch. Fish reared in clean water significantly avoided the alarm cue. However, fish reared under continuous Cu exposure and those that were only exposed to Cu during embryonic development were unable to respond to the chemical alarm stimulus. Fish from all treatments did not respond to two control stimuli. Results from this study suggest that fish exposed to elevated Cu concentrations during embryonic development is sufficient to impair chemosensory function during later life stages. This could result in an inability to detect nearby predators by olfaction, which could lead to important ecological perturbations in populations inhabiting metal-contaminated systems.     

Subclinical effects of prenatal methylmercury exposure on cardiac autonomic function in Japanese children

Objectives: The subclinical effects of prenatal exposure to methylmercury from fish consumption on the cardiac autonomic function were assessed in 136 Japanese 7-year-old children recruited for this study. Methods: Samples of child’s hair and dry umbilical cord preserved were collected, and hair mercury and cord tissue methylmercury concentrations were determined as current and prenatal exposure biomarkers, respectively. Cardiac autonomic indicators of parasympathetic and sympathetic activities were calculated from the electrocardiographic RR intervals measured. Results: In the children, the cord tissue methylmercury (0.017–0.367, median 0.089 μg/g) was not significantly correlated with the hair mercury (0.43–6.32, median 1.66 μg/g). The cord tissue methylmercury was related negatively to parasympathetic components of cardiac autonomic indicators (P<0.05) and positively to sympathovagal indices (P<0.05), even after correction for possible confounders such as age and sex, although the hair mercury was not significantly correlated with any cardiac autonomic indicators. Conclusions: Despite the potential limitations involved in the retrospective study, these findings suggest that prenatal methylmercury exposure (median of estimated maternal hair mercury at parturition, 2.24 μg/g) may be associated with reduced parasympathetic activity and/or sympathovagal shift.     

Effects of sodium dichromate exposure on the immune responses of juvenile coho salmon,Oncorhynchus kisutch,againstVibrio anguillarum

Sublethal exposure of juvenile coho salmon (Oncorhynchus kisutch) to Cr (as sodium dichromate) in freshwater decreased their disease resistance and serum agglutinin production againstVibrio anguillarum. Duplicate disease resistance experiments, in which groups of salmon were exposed to 0.0 or 0.5 mg Cr/L for two weeks and then injected in subgroups with one of four tenfold dilutions of liveV. anguillarum (ca. 3–4 × 10^2–5 bacteria/.1 ml dose), showed that disease mortality increased with dose and was significantly greater in Cr-exposed fish. Serum agglutinin production, measured in fish which were injected withV. anguillarum bacterin and then exposed to 0.0 or 0.5 mg Cr/L for two weeks, was significantly inhibited in Cr-exposed salmon by six weeks after immunization. It is suggested that measurement of disease resistance and agglutinin production may be sensitive and ecologically realistic indicators of sublethal toxicity in aquatic animals.     

孕期壬基酚暴露对雄性仔鼠免疫功能影响

目的 探讨孕期壬基酚暴露(NP)对雄性仔鼠免疫功能的影响.方法 母鼠孕14~19 d灌胃NP(0,20,40,80,200 mg/kg),仔一代(F1)雄性仔鼠于60 d龄剖杀取脾脏、胸腺、血清,测免疫功能相关各项指标.结果 NP80、200 mg/kg组脾脏、胸腺重量及脏器系数显著低于阴性对照组(P<0.05),且脾脏重量、脏器系数与染毒剂量呈负相关(r=-0.884);NP200 mg/kg组仔鼠血清γ-干扰素(IFN-γ)、白细胞介素6(IL-6)的水平与阴性对照组比较显著降低(P<0.05),且血清IFN-γ与染毒剂量呈负相关(r=-0.980);NP200 mg/kg组脾淋巴细胞的增殖能力较阴性对照组低(P<0.05),脾、胸腺内淋巴细胞显著减少,出现灶状坏死.结论 壬基酚可通过胎盘屏障,200 mg/kg对雄性仔鼠免疫功能有抑制作用.     

甲基汞暴露对子代生长发育的影响——基于DNA甲基化研究

目的 本研究基于DNA甲基化,探讨甲基汞（Me Hg）暴露对子代生长发育的影响。方法 通过面对面问卷调查获取研究对象基本信息,系统采集万山汞矿区114位分娩母亲的静脉血、新生儿脐带血和生长发育指标。将24只妊娠SD大鼠随机分为对照组（生理盐水）、低（0.6 mg/kg）、中（1.2 mg/kg）、高（2.4 mg/kg）剂量Me Hg染毒组,自受孕第5天灌胃染毒至子代仔鼠出生第21天（PND21）,适应性喂养至PND60天。利用液相色谱-串联质谱法测量新生儿脐带血和仔鼠血5-甲基胞嘧啶（5m C）和5-羟甲基胞嘧啶（5hm C）水平。结果 暴露组新生儿的体重（t=2.025,P=0.045）和双顶径（t=2.382,P=0.019）均显著低于对照组。与对照组相比,暴露组脐带血5m C(t=2.615,P=0.010)和5hm C(t=3.640,P<0.001)均显著下降。脐带血5m C与新生儿股骨长之间呈显著正相关（r=0.197,P=0.035）。动物实验结果显示,各剂量染毒组仔鼠体重组间差异有统计学意义（F=11.327,P<0.001）;与对照组相比,低、中、高剂量...     

谷氨酰胺双肽对全胃切除术后病人免疫功能的影响

目的 :观察添加谷氨酰胺双肽的肠外营养对全胃切除术后病人免疫功能的影响。　方法 :6 8例行全胃切除的胃癌病人 ,随机分为对照组 (n =34)和实验组 (n =34)。两组病人均接受等氮、等热量的肠外营养 1周 ,实验组同时补充谷氨酰胺双肽 ,相当于谷氨酰胺 0 .34g/(kg·d)。在术前和术后第 1、8天取外周血测定IgM、IgG、IgA、CD3、CD4、CD8、CD4 /CD8比值。　结果 :术后第 8天 ,实验组IgG、IgA、CD4、CD4 /CD8均显著高于对照组。　 结论 :含谷氨酰胺双肽的肠外营养可改善全胃切除术后病人的免疫功能     

运动对PM2.5所致小鼠细胞免疫功能改变的影响

【目的】本研究旨在探讨运动对细颗粒物(PM_(2.5))所致小鼠细胞免疫功能改变的影响。【方法】将24只雄性C57BL/6小鼠随机分为过滤空气组(n=6)、浓缩PM_(2.5)组(n=6)、运动后暴露过滤空气组(n=6)和运动后暴露浓缩PM_(2.5)组(n=6)。运动组小鼠每天在小鼠跑步机上运动1 h后,休息1 h,然后运动组和非运动组小鼠均暴露于浓缩PM_(2.5)或过滤空气。运动暴露24周后,使用流式细胞仪技术检测小鼠脾脏CD3~+CD4~+CD8a~+T细胞、CD18~+T细胞和CD154~+T细胞的数量。【结果】暴露仓、对照仓和室外空气中PM_(2.5)浓度的中位数分别为49.24、12.18、32.25μg/m~3。PM_(2.5)暴露导致CD3~+CD4~+CD8a~+T细胞数量增加,CD154~+T细胞数量降低(P<0.05),而跑步运动明显降低CD3~+CD4~+CD8a~+T细胞数量(P<0.05),提高CD154~+T细胞数量(P<0.05)。【结论】PM_(2.5)暴露破坏机体免疫系统稳态,有规律的跑步运动能够维持免疫系统平衡,增强机体对PM_(2.5)的抵抗能力。     

Effects of aging on immune function

A variety of changes are observed in the immune system in both animals and humans with increasing age. There is a decline in the functional capacity of the cell populations that mount generalized and focused immune responses, and decreasing production and response of these cells to regulatory signals and proteins. These changes translate into less effective innate and adaptive immune responses, increased reactivity against self-antigens in vivo, and an increased incidence of infection. There may also be an increased risk of mortality. The mechanisms underlying age-related changes in immune function are not fully understood, but are likely to be multifactorial, including environmental and behavioral factors that affect over-all immune function from the molecular level to that of the entire organism.     

铅暴露对猪免疫功能影响

目的 探讨饲料中添加不同剂量铅对猪免疫功能的影响.方法 将24头14～17kg仔猪随机分为4组,用正常饲料和分别添加5,15,45mg/kg(分别为低、中、高剂量组,均按含铅量计)醋酸铅的饲料对其进行90d攻毒饲养试验.测定猪血液中白细胞数量(WBC)、血清中免疫球蛋白(IgM、IgG、IgA)、和补体(C3,C4)含量,并使用四甲基偶氮噻唑盐(MTT)法检测血液中T淋巴细胞活力.结果 低剂量组T淋巴细胞活力降低29.3%,与对照组比较差异有统计学意义(P<0.05);中剂量组IgA含量下降0.12g/L,T淋巴细胞活力降低25.2%,与对照组比较差异均有统计学意义(P<0.05);高剂量组的白细胞(WBC).IgM、IgG、IgA、C3含量分别下降4.3×109,1.48,0.13,0.14,0.31g/L,T淋巴细胞活力下降37.4%,与对照组比较差异均有统计学意义(P<0.05).结论 饲料中含铅量达到5mg/kg时影响猪免疫功能,高于45mg/kg时可导致猪免疫力显著降低.