Prolonged exposure to low doses of ozone: short- and long-term changes in behavioral performance in mice

Two separate experiments were designed to assess the effects of ozone exposure on outbred CD-1 mice. In the first experiment, adult males were exposed continuously to O3 at 0, 0.3, or 0.6 ppm for 30 days and their behavior was assessed in a 5-min open-field test on exposure days 4 and 19 and on day 3 after the end of the exposure phase. In addition, mice performed a Morris water maze task from exposure day 24 to 28. In the second experiment, adult females were exposed from 30 days prior to the formation of breeding pairs until gestational day 17 to the same doses used in the first experiment. Litters were fostered at birth to untreated dams and neurobehavioral development of the offspring was investigated until adulthood. Specifically, somatic and sensorimotor development [postnatal day (PND) 2-20], homing performance (PND 12), motor activity (PND 21), passive avoidance (PND 22-23), water maze performances (PND 70-74), and response to a nociceptive stimulus (PND 100) were assessed. Results from both experiments confirm that exposure to O3 slightly but selectively affected neurobehavioral performance in rodents. Exposure to O3 did not grossly affect neurobehavioral development, whereas it consistently impaired reversal learning in the Morris water maze test in both prenatally and adult exposed mice. Moreover, longer latency to step-through in the first trial of the passive avoidance test and a decrease in wall rearing in the hot-plate test were recorded in O3 prenatally exposed mice. Except for the first open-field test, altered responses were observed only in animals exposed at the intermediate concentration of the gas. Adaptation and/or onset of compensatory mechanisms might be responsible for the lack of linear dose-response relationships.     

Effects of a high protein diet on bone formation and calcium metabolism in rats

The effects of a high protein diet on bone formation and calcium (Ca) metabolism were evaluated in rats using an ectopic endochondral bone induction model. A control diet (18% casein) or a high protein diet (18% casein + 20% lactalbumin) was given to 50-day-old rats. Ten days after the feeding of the experimental diet, rats were intramuscularly implanted with demineralized bone powder (day 0). On day 14 and day 21, the implanted bone powder was harvested, and blood and urine samples were also obtained. Urinary Ca excretion was not increased on day 12-14; however, it was elevated on day 19-21 in rats fed the high protein diet compared with rats fed the control diet. The high protein diet remarkably stimulated urinary sulfate excretion in both sampling periods, which reflected dietary sulfur-containing amino acids contents. Also, rats fed the high protein diet exhibited a decrease in serum Ca concentrations. There was little difference in Ca contents and the activities of alkaline phosphatase and acid phosphatase in the implants between control group and high protein diet group on day 14 and day 21. Histological examination in the implanted demineralized bone powder on day 14 indicated only cartilage in rats fed the high protein diet in contrast to the occurrences of osteogenesis and remodeling in those fed the control diet. Retarded bone formation in rats fed the high protein diet might be owing to, in part at least, a restricted amount of Ca utilized at the stage of cartilage calcification.     

两种矽肺造模方法比较

目的 比较两种矽肺造模方法的优劣,并探讨一次性气管滴注法造模的最佳时间。方法 口鼻暴露染尘小鼠20只,气管滴注染尘小鼠20只,分别于染尘后第7、14、21、28天处死;对照组小鼠5只,正常饲养28d处死。检测各时间节点小鼠肺湿重、脏器系数、肺组织羟脯氨酸(hydroxyproline,HYP)含量,并观察肺组织病理改变。结果 口鼻暴露法染尘21、28d小鼠肺湿重及脏器系数,7、14、21、28d小鼠肺纤维化评分,与对照组比较差异有统计学意义(P<0.05),染尘28d小鼠肺组织形成矽结节;气管滴注染尘后第14、21、28天小鼠肺湿重、脏器系数,第28天小鼠HYP含量,第7、14、21、28天小鼠肺纤维化评分,与对照组比较差异有统计学意义(P<0.05),染尘后第21天形成多个矽结节,第28天矽结节融合成大片状。结论 暴露法染尘28d小鼠开始形成矽结节,滴注法染尘后第21天小鼠即可完成矽肺造模。     

Interactions in Developmental Toxicology: Effects of Concurrent Exposure to Lead, Organic Mercury, and Arsenic in Pregnant Mice

The development toxicity of lead nitrate (25 mg/kg, SC), methylmercury chloride (12.5 mg/kg, PO), and sodium arsenite (6 mg/kg, SC) was assessed in CD1 mice following administration on gestation day 10 of these chemicals separately or in their binary and ternary combinations. Cesarean sections were performed on day 18 of gestation, and fetuses were examined for malformations and variations. Three fetuses from each dam were used for whole-body analyses of Pb, Hg, and As. Maternal toxic effects were more remarkable in the group concurrently exposed to Pb, Hg, and As than in those given binary combinations of the elements. In turn, maternal toxicity was more notable in these groups than in those given separately the test compounds. With regard to developmental toxicity, the most relevant effects (decreased fetal weight, cleft palate) corresponded to the Hg-treated groups. It is in agreement with the finding that in all experimental groups the levels of Pb and As in whole fetuses were under their respective detection limits. In general terms, the present data suggests that at the current doses, the interactive effects of Pb and As on Hg-induced developmental toxicity were not greater than additive. In contrast, exposure of pregnant mice to Pb and As at doses that were practically nontoxic to dams, concurrently with organic Hg at a toxic dose, caused supra-additive interactions in maternal toxicity. Received: 26 March 2001/Accepted: 15 July 2001     

Bone, blood and semen lead in men with environmental and moderate occupational exposure

Lead (Pb) in blood, bone, and semen was measured in 162 to 186 environmentally exposed men from Mexico City, aged 19- 48. Semen Pb was measured by inductively coupled plasma mass spectrometry, blood Pb by atomic absorption spectrometry and bone Pb by K X-ray fluorescence. Mean Pb levels in blood, semen, tibia (cortical) and patella (trabecular) bone were 12 microg/dl, 2.7 microg/l, 13 microg/g, and 20 microg/g, respectively. Semen Pb was determined by blood Pb and patella Pb. Determinants of higher tibia Pb were age, living near industry in which Pb is used, and a high occupational Pb exposure index. Higher patella Pb was predicted by age, higher traffic density near home, a high index of occupational exposure to Pb and a greater number of cigarettes smoked per day in the year prior to the study. Blood and bone Pb results are consistent with findings in other populations. Semen results provide new information on the semen-bone Pb relationship. Bone, especially trabecular one, proved to be a significant endogenous lead source for blood and semen burdens in reproductive aged men.     

Impact of occupational exposure on lead levels in women

In 1994, 207 women participated in a study designed to examine the effects of occupational exposure and various lifestyle factors on bone and blood lead levels. In vivo measurements of Pb concentrations in tibia were performed by X-ray fluorescence. All 108 former smelter employees and 99 referents provided blood samples and answered a questionnaire on lifestyle characteristics and the relevant medical history. Lead concentrations in tibia and blood were significantly higher in the exposed group. The difference in mean bone Pb concentrations of the two groups is markedly greater than the difference in the mean blood Pb concentrations, supporting the view that bone Pb measurements are a more reliable determinant of Pb body burden. Chronic exposure did not result in any statistically significant differences in adverse pregnancy outcomes. A significantly lower age at the onset of menopause in occupationally exposed women may suggest that Pb causes adverse changes in the pattern of estrus and menses. The exposed women had lower bone Pb concentrations than those found in most studies on predominantly male workers. Blood Pb concentrations remain increased in women long after the cessation of occupational exposure, reflecting the importance of the endogenous exposure. The endogenous exposure relation found for postmenopausal exposed women is consistent with data on male smelter workers, whereas the relation found for premenopausal women is significantly lower. This suggests that sex plays an important role in the metabolism of lead, and current models of exposure extrapolated from male data may be inappropriate for use on women.     

Effects of dietary Pb(II) and tributyltin on neotropical fish, Hoplias malabaricus: histopathological and biochemical findings

Trahira (Hoplias malabaricus) used to investigate the effects of successive Pb(II) or tributyltin (TBT) dietary doses. After 70 days of acclimation, individuals were exposed to 21 microg Pbg(-1) or 0.3 microg TBTg(-1) (5-day intervals, 14 doses). Two experiments were conducted to investigate the histopathological effects (liver and kidney) and measure the cholinesterase activity (muscle and brain) after Pb(II) or TBT dietary doses. A number of morphological effects were observed in liver, including cytoskeleton disturbance, microautophagy of mitochondria, nuclear damage, and cell death. In kidney, necrosis area, increasing of the neutrophils cell number, changes in melano-macrophage centers, and free macrophages were frequently registered after both Pb(II) and TBT exposures. The cholinesterase activity was inhibited in muscle after 14 doses of Pb(II), but no effects were found in individuals exposed to TBT. In summary, this work is the first to report detailed in vivo toxic effects in tropical fish, H. malabaricus, after dietary sublethal exposure to Pb(II) and TBT.     

大鼠骨折骨痂中血管内皮生长因子的表达

目的探讨大鼠股骨骨折愈合中骨痂内血管内皮生长因子vascular endothelial growth factor，VEGF）的表达规律。方法取12周雌性SD大鼠32只，体重（280±25）g，随机分成4组，每组8只。A组为骨折1周组，B组为骨折2周组。C组为骨折3周组，D组为骨折4周组。制作股骨骨折模型。各组截取骨痂后行HE染色观察骨痂生长情况及其组织形态，免疫组织化学染色测定VEGF表达，原位杂交法测定VEGFmRNA表达。结果HE染色观察A组骨折间隙可见成纤维细胞，夹杂有少量的早期软骨细胞。B组有少量软骨骨痂形成。C组骨折端可见软骨骨痂增多和少量编织骨痂。D组骨折端编织骨痂增多，并出现板层骨。免疫组织化学和原位杂交方法检测可见术后1～4周的骨折部位，不同时间有多种组织细胞参与VEGF及VEGFmRNA的表达。骨痂中VEGF及VEGFmRNA平均阳性细胞百分率：创伤后7d骨折位点均表达增强，14d、21d仍保持高水平表达，28d骨折位点表达降低。结论VEGF在骨折修复过程中具有重要作用，并作为一种重要细胞因子参与和调节了骨折修复过程。     

脱氧雪腐镰刀菌烯醇致幼鼠成年鼠骨及关节软骨损伤差异的实验研究

目的观察脱氧雪腐镰刀菌烯醇(DON)致Wistar幼鼠、成年鼠膝关节骨与软骨损伤的异同。方法 24只健康雄性Wistar幼鼠(20日龄)和24只健康雄性Wistar成鼠(60日龄),分别随机分为正常对照组、DON低剂量组、DON高剂量组,每组各8只,共6组;幼鼠和成鼠的低剂量组和高剂量组均通过灌胃的方式隔日染毒,低剂量灌胃剂量为0.06 mg/kg,高剂量灌胃剂量为0.25 mg/kg;对照组使用相同体积的生理盐水。作用80 d后,取双侧膝关节,进行光镜和电镜病理形态学观测。结果对照组关节软骨基质较均匀、致密,骺板软骨从骨骺到干骺端结构完好,软骨基质呈弱嗜酸性,细胞排列保持良好的层次;幼鼠低剂量组可见软骨细胞变性,坏死,排列紊乱。高剂量组可见软骨细胞溶解、甚至消失。健康细胞与受损细胞交互排列,呈现DLD现象。骨小梁数目减少,且骨小梁变细、连接中断,立体网状结构破坏,且随剂量的增加骨小梁的破坏也愈加严重,甚至骨小梁大片消失;成年鼠可见软骨细胞变性坏死,高剂量组有的细胞核溶解、消失。电镜可见基质内有较小的、大小均匀的、电子密度高的颗粒状物质,线粒体肿胀和固缩兼有,并见大小不等的空泡,脊破坏或消失。高剂量情况下,细胞核形态不规则、固缩,染色质边聚,关节软骨胶原网络结构破坏。结论 DON可导致Wistar大鼠骨和软骨损伤,其损伤结局与骨的发育阶段有关:在干骺闭合前,DON除可致软骨损伤外,还可致骨发育障碍,甚至停滞;在干骺闭合以后其损伤仅表现在软骨上,提示DON可能是大骨节病和骨关节炎等骨关节病的原因。     

Enzymatic inhibition and morphological changes in Hoplias malabaricus from dietary exposure to lead(II) or methylmercury

Neotropical fish traíra (Hoplias malabaricus) were used to investigate the effects of dietary doses of metals through individual exposures to either inorganic lead(II) or methylmercury, respectively, 21 microg Pb2+g(-1) w.w. and 75 ng H(3)C-Hg+g(-1) w.w., every 5 days, for 70 days (14 doses). The erythrocyte delta-aminolevulinic acid dehydratase (ALAd) activity was inhibited after 14 doses of Pb2+ and H(3)C-Hg+. The muscle cholinesterase (ChE) activity was inhibited after 14 doses of H(3)C-Hg+. Damage in cytoskeleton and nuclei were observed after exposure to inorganic lead. Individuals exposed to H(3)C-Hg+ showed the presence of atypical granules and vesicles, cytoplasm disorganization, and mitochondria damages in hepatocytes also after 14 doses. The present results demonstrate that erythrocyte ALAd and muscle ChE activities can be used as long-term biomarkers of sublethal, subchronic, and trophic exposures to Pb2+, and H(3)C-Hg+ in fish. Also the morphological aspects described in the present work confirm the toxicity of both studied metals.     

硝酸镧染毒对小鼠骨髓细胞微核率的影响

目的研究硝酸镧染毒对小鼠骨髓细胞微核率的影响。方法将21日龄昆明种小鼠随机分为9组,每组12只,分别腹部皮下注射不同剂量的硝酸镧溶液(10、50、100、200、300、400、500mg/kg),阴性对照组给予蒸馏水,阳性对照组给予环磷酰胺,每天1次,连续7d,观察小鼠骨髓细胞微核率及小鼠体重。结果300、400、500mg/kg组小鼠增重低于阴性对照组,差异有显著性(P<0.05)。100、200、300、400、500mg/kg组小鼠骨髓细胞微核率高于阴性对照组(P<0.05)。随染毒剂量增加,小鼠骨髓细胞微核率呈上升趋势(r=0.9223P<0.05)。结论硝酸镧具有一定遗传毒性。     

Hematological findings in neotropical fish Hoplias malabaricus exposed to subchronic and dietary doses of methylmercury, inorganic lead, and tributyltin chloride

Hematological indices are gaining general acceptance as valuable tools in monitoring various aspects the health of fish exposed to contaminants. In this work some effects of methyl mercury (MeHg), inorganic lead (Pb2+), and tributyltin (TBT) in a tropical fish species were evaluated by hematological methods after a trophic exposition at a subchronic level. Forty-two mature individuals of the freshwater top predator fish Hoplias malabaricus were exposed to trophic doses (each 5 days) of MeHg (0.075 microg g(-1)), Pb2+ (21 microg g(-1)), and TBT (0.3 microg g(-1)) using young fish Astyanax sp. as prey vehicle. After 14 successive doses over 70 days, blood was sampled from exposed and control groups to evaluate hematological effects of metals on erythrocytes, total leukocytes and differential leukocytes counts, hematocrit, hemoglobin concentration, and red blood cell indices mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH), and mean corpuscular hemoglobin concentration (MCHC). Transmission electron microscopy and image analysis of erythrocytes were also used to investigate some morphometric parameters. Results show no significant effects in MCH and MCHC for all tested metals, but differences were found in erythrocytes, hemoglobin, hematocrit, MCV, and white blood cells counts. The number of leukocytes was increased in the presence of MeHg, suggesting effects on the immune system. Also the MCV increased in individuals exposed to MeHg. No ultrastructural damages were observed in red blood cells but the image analysis using light microscopy revealed differences in area, elongation, and roundness of erythrocytes from individuals exposed to Pb2+ and TBT but not in the group exposed to MeHg. The present work shows that changes in hematological and blood indices could highlight some barely detectable metal effects in fish after laboratory exposure to contaminated food, but their application in field biomonitoring using H. malabaricus will need more detailed studies and a careful consideration of environmental parameters.     

Comparison of local and systemic immunity after intratracheal, intraperitoneal, and intravenous immunization of mice exposed to either aerosolized or ingested lead

The humoral immunity of newborn mice exposed for 28 days to 2.5 mg/m3 aerosolized Pb(NO3)2 (Pb28-aero) or of 2-week-old mice similarly exposed for 14 days (Pb14-aero) was compared with that of both 2-week-old mice given 125 micrograms Pb(NO3)2/day by gastric intubation for 14 days (Pb14-oral) and of 4-week-old nonexposed controls. Mice from each group were immunized with 10(8) sheep red blood cells by intravenous (i.v.), intraperitoneal (ip), or intratracheal (it) routes of immunization. Immunity was assessed by both hemagglutination and the enumeration of antibody-forming cells from the spleen and thoracic lymph nodes. All treatment groups had decreased thymus/body weight and spleen/body weight ratios whereas only Pbaero groups had enlarged livers. The most significant immunosuppression occurred in the ip-immunized Pb28-aero group. A significant suppression of humoral immunity was also observed in thoracic lymph node samples from Pbaero groups immunized it or iv. There was no apparent immunosuppression in any treatment group after iv immunization. These results indicate that aerosolized lead is more immunosuppressive than equivalent amounts of ingested lead. This is most likely due to the greater absorption of inhaled lead and the subsequent cytotoxicity of lead for cells in the draining lymph nodes.     

Perinatally Administered Bisphenol A as a Potential Mammary Gland Carcinogen in Rats

Background: Environmental exposure to bisphenol A (BPA) affects mammary gland development in rodents and primates. Prenatal exposure to environmentally relevant doses of BPA increased the number of intraductal hyperplasias and ductal carcinomas in situ by 50 days of age in Wistar-Furth rats.Objective: We aimed to determine whether BPA exposure of dams during gestation only or throughout lactation affects the incidence of mammary gland neoplasia in female offspring.Methods: We treated pregnant Sprague-Dawley rats with BPA at 0, 0.25, 2.5, 25, or 250 μg BPA/kg BW/day from gestational day (GD) 9 to birth and from GD9 to postnatal day (PND) 21. Mammary glands from BPA-exposed offspring were examined at four time points for preneoplastic and neoplastic lesions. To assess circulating BPA levels, we exposed pregnant rats to vehicle or 250 μg BPA/kg BW/day during gestation only or during gestation/lactation and analyzed sera from dams, fetuses, and nursing pups for total and unconjugated BPA.Results: Total and unconjugated BPA were detected in sera from 100% of dams and fetuses and 33% of pups exposed to 250 μg BPA/kg BW/day. Unconjugated BPA levels in exposed dams and fetuses (gestational) and in exposed dams and pups (gestational/lactational) were within levels found in humans. Preneoplastic lesions developed in BPA-exposed female offspring across all doses as early as PND50. Unexpectedly, mammary gland adenocarcinomas developed in BPA-exposed offspring by PND90.Conclusions: Our findings suggest that developmental exposure to environmentally relevant levels of BPA during gestation and lactation induces mammary gland neoplasms in the absence of any additional carcinogenic treatment. Thus, BPA may act as a complete mammary gland carcinogen.Citation: Acevedo N, Davis B, Schaeberle CM, Sonnenschein C, Soto AM. 2013. Perinatally administered bisphenol A acts as a mammary gland carcinogen in rats. Environ Health Perspect 121:1040–1046; http://dx.doi.org/10.1289/ehp.1306734     

Effects of local and whole body irradiation on appearance of osteoclasts during wound healing of tooth extraction sockets in rats

We examined effects of local and whole body irradiation before tooth extraction on appearance and differentiation of osteoclasts in the alveolar bone of rat maxillary first molars. Wistar rats weighting 100 g were divided into three groups: non-irradiation group, local irradiation group, and whole body irradiation group. In the local irradiation group, a field made with lead blocks was placed over the maxillary left first molar tooth. In the whole body irradiation group, the animals were irradiated in cages. Both groups were irradiated at 8 Gy. The number of osteoclasts around the interradicular alveolar bone showed chronological changes common to non-irradiated and irradiated animals. Several osteoclasts appeared one day after tooth extraction, and the maximal peak was observed 3 days after extraction. Local irradiation had no difference from non-irradiated controls. In animals receiving whole body irradiation, tooth extraction one day after irradiation caused smaller number of osteoclasts than that 7 day after irradiation during the experimental period. Whole body-irradiated rats had small osteoclasts with only a few nuclei and narrow resorption lacunae, indicating deficiency of radioresistant osteoclast precursor cells. Injection of intact bone marrow cells to whole body-irradiated animals immediately after tooth extraction recovered to some content the number of osteoclasts. These findings suggest that bone resorption in the wound healing of alveolar socket requires radioresistant, postmitotic osteoclast precursor cells from hematopoietic organs, but not from local sources around the alveolar socket, at the initial phase of wound healing.     

骨髓间充质干细胞促小鼠皮肤烫伤修复研究

  目的  探讨骨髓间充质干细胞(bone marrow mesenchymal stem cells,BMSCs)对小鼠皮肤烫伤的促修复作用,为临床采用BMSCs治疗烫伤提供依据。
  方法  以3周龄C57BL/6J小鼠的骨髓细胞悬液体外扩增培养BMSCs。将36只10周龄C57BL/6J小鼠随机分为局部细胞移植组、尾静脉细胞移植组和平行对照组(每组12只),建立皮肤烫伤模型。小鼠皮肤烫伤损伤模型建立成功1 h后,将BMSCs通过皮下和尾静脉分别注射到两个细胞移植组中,平行对照组注射生理盐水。观察动物创面变化,计算21 d后的创面愈合率、检测炎症因子变化和皮肤形态学变化。
  结果  分离培养的BMSCs增殖旺盛,能够多向分化为成骨细胞、成软骨细胞和成脂细胞。局部细胞移植组和尾静脉细胞移植组的创面愈合率在21 d后达到98.2%和99.0%,其差异无统计学意义(P > 0.05);而平行对照组愈合率在7 d后明显低于两个细胞移植组(P < 0.05)。BMSCs移植后,在第3天和第7天后,两个细胞移植组白细胞和白细胞介素-6(IL-6)水平明显低于平行对照组(P < 0.05);在3 d、7 d和14 d后,两个细胞移植组C反应蛋白和肿瘤坏死因子-α(TNF-α)水平明显低于平行对照组(P < 0.05);但21 d后各炎症因子水平在各组间差异无统计学意义(P > 0.05)。两个细胞移植组的皮肤形态学在21 d后胶原纤维丰富,皮肤组织结构清晰,而平行对照组可见炎性细胞浸润、胶原排列紊乱和充血现象。
  结论  皮肤烫伤模型移植BMSCs后,后者可提高宿主C57BL/6J小鼠的皮肤烫伤恢复能力。
     

Damage of genetic material in somatic cells of mice exposed to low doses of X-rays

Pzh:SFIS mice were exposed during 8 weeks, 5 days per week to doses of 0.05 Gy; 0.10 Gy; 0.20 Gy of X-rays. Samples were taken at 24 h and at 72 h after the end of irradiation for micronucleus test, in the case of estimation induction of DNA damages also at 24 h and at 1, 4 and 8 weeks. Subchronic exposure of mice to low doses of ionizing radiation induced damages of genetic material of theirs somatic cells. The enhanced frequency of micronuclei were observed in reticulocytes and polychromatic erythrocytes of bone marrow after each of dose. Subchronic exposure to X-rays induced also DNA single strand breaks in bone marrow lymphocytes. Damage were observed up to 8 weeks after the end of exposure. Results obtained in this study confirmed sensitivity of bone marrow cells to low doses of X-rays.     

Benzene hematotoxicity and leukemogenesis

Eight-to-twelve-week-old male and female C57B1/6 BNL mice were exposed to air or benzene vapor in air at a concentration of 10, 25, 100, 300, or 400 ppm. Benzene at concentrations of 100 ppm or higher for 10 exposures of 6 hours per day 5 days a week produced a reduction in bone marrow cellularity and the number of pluripotent stem cells in the bone marrow. The fraction of stem cells in DNA synthesis was also increased. Exposure to 300 ppm 6 hours a day 5 days a week for 2, 4, 8, and 16 weeks produced a diminution in the stem cell levels in bone marrow which returned to those of controls 2 weeks after benzene exposure for 2 and 4 weeks, 16 weeks after exposure for 8 weeks, and to 92% of controls 25 weeks after 16 weeks of exposure. There was a more rapid return of blood lymphocytes to the control level. Mice exposed to 300 ppm for 6 hours/day, 5 days per week for 16 weeks began dying at 330 days of age, whereas no deaths were observed in sham-exposed mice until 440 days of age. The benzene-exposed mice died in two waves: the first was from 330-390 days of age, with a second wave commencing at 570 days of age. The first wave of mortality was due primarily to thymic lymphomata. The second wave was due to a mixture of nonthymic lymphomata and solid tumors.     

Estrogenic compounds affect development of harpacticoid copepod Tigriopus japonicus

The aim of this investigation was to evaluate the impact of estrogenic compounds on the harpacticoid copepod Tigriopus japonicus after continuous exposure to environmentally relevant concentrations. Natural estrogen (17beta-estradiol), three known estrogenic compounds in vertebrates (bisphenol A, 4-nonylphenol, p-t-octylphenol), and an invertebrate molting hormone (20-hydroxyecdysone) were tested for their effects on development and reproductive characters in two successive generations of T. japonicus. Less than 24-h-old nauplii (parentals) were exposed to four sublethal concentrations of these compounds for 21 d at 25 degrees C. The first brood of nauplii (F1) produced was monitored further under the same culture conditions and exposures to test compounds. Results showed that all estrogenic compounds affected development (both in number of days to reach copepodid stage and sexual maturity) in the parental generation. Similar effects were apparent in the F1; however, fecundity, sex ratio, and survival were not significantly affected, even at concentrations as high as 10 microg/L (nominal concentration). The invertebrate molting hormone 20-hyroxyecdysone had no detectable effect on any of the endpoints tested but gave the lowest 48-h 50% lethal concentration (LC50) value. The results suggest that endocrine disruption could occur in copepods following exposure to environmentally relevant concentrations of estrogenic compounds, especially if they are exposed starting from embryonic development.     

Aggressive behavior and serum testosterone concentration during the maturation process of male mice: the effects of fetal exposure to bisphenol A

The relationship between exposure to endocrine-disrupting chemicals (EDs) and risk to reproductive organs is well documented, but the influence of EDs on behavioral development has not been studied. In this study we evaluated the effect of fetal exposure to bisphenol A, which mimics estrogenic activity, on aggressive behavior and hormonal change in male mice. On gestation days 11-17, female mice were fed bisphenol A at 2 ng/g or 20 ng/g of body weight (environmentally relevant concentration). Aggression rating and blood sampling of the offspring were done at 8, 12, and 16 weeks of age. Aggression scores increased significantly (p < 0.01) at 8 weeks of age in male mice exposed to bisphenol A at both the 2 ng/g and 20 ng/g concentrations compared with a control group, but no difference was found after 12 weeks. Relative testis weight (per gram of body weight) was significantly lower at 8 and 12 weeks in mice treated with 2 ng/g than in controls (p < 0.05) and was significantly lower at 12 weeks in mice treated with 20 ng/g than in controls (p < 0.01). The serum testosterone concentration in treated mice was not significantly different from that in controls. These results demonstrate that bisphenol A temporarily activated aggressive behavior in mice at 8 weeks of age and that low doses of bisphenol A interfered with the normal development of reproductive organs. The mechanism activating this aggressive behavior was not elevated testosterone concentration.