Search

By mimicking the info-chemicals emitted by grazers, the common anionic surfactant sodium dodecyl sulfate (SDS) can induce colony formation in the green algal genus Scenedesmus at environmentally relevant concentrations. The morphogenetic effects can hinder the feeding efficiency of grazers, reducing energy flow along the pelagic food chain from Scenedesmus to consumers. Despite this potential ecological risk, few studies exist on whether the SDS-triggered induction of colonies is common in other species of the family Scenedesmaceae. Here, we investigated the effects of SDS on the growth and morphology of three species of Scenedesmaceae (Desmodesmus subspicatus, Scenedesmus acutus, and Tetradesmus dimorphus) and on the clearance rates of Daphnia galeata grazing on the SDS-induced colonies. SDS triggered colony formation in all algal species at concentrations nonlethal to them; however, the induction levels of colony formation were generally lower than for those in the Daphnia culture medium. We also found that the SDS-induced colonial algae reduced D. galeata clearance rates. Our results highlight the potential effect of SDS on the Daphnia–Scenedesmaceae system by evoking the morphological response of Scenedesmaceae at concentrations below those that exert toxicity. Such disruptive effects of pollutants on predator–prey interactions should be considered within the framework of ecological risk assessments.

Neonicotinoid insecticides, the most widely used category of insecticides for 20 years and candidate risk of neurodevelopment, have been detected in human urine and in hair. If the former reflecting dietary contamination over short periods and the latter total exposure over longer periods is not known. We quantified and compared the concentrations in spot urine by LC-MS/MS and in hair by UHPLC-MS/MS.In the first study, samples from an international group of scientists in Italy in 2016 (M/F=12/7),detection rate in urine and in hair was 0% vs 85.0% for imidacloprid; 0% vs 52.5% for thiacloprid; 0% vs 45.0% for acetamiprid; 0% vs 25.0% for thiamethoxam; and 0% vs 17.5% for clothianidin.In the second study, samples from 99 volunteers in three islands of the Philippines in 2017,detection rate in urine and in hair was 48.5% vs 60.6% for imidacloprid; 1.0% vs 8.1% for thiacloprid; 10.1% vs 13.1% for acetamiprid; 31.3% vs 30.3% for thiamethoxam; and 14.1% vs 45.5% for clothianidin. In the Philippine, concentrations were negatively correlated between urine and hair for thiamethoxam (r = -0.70, p = 0.016), but not for clothianidin or imidacloprid. Both analyses of urine and hair are complementary to assess human neonicotinoid exposure.

To evaluate whether microbial stoichiometries of biomass and enzyme activity could vary in response to changes in nutrient availability in an arable soil during the crop growth period, temporal variation in nutrient availability, soil enzyme activities associated with carbon (C), nitrogen (N), phosphorus (P), and sulfur (S) acquisition, and microbial biomass C, N, and P were measured in an Allophanic Andosol amended with chemical fertilizer and cow manure. The ratio of l -asparaginase to β- d -glucosidase activities had a significant negative correlation with potentially mineralizable N. In addition, the ratio of arylsulfatase to β- d -glucosidase activities showed a significant negative correlation with available S. Thus, it seems plausible that microorganisms in the soil would allocate their resources to synthesis of N - and S-acquiring enzymes in response to variation in the nutrient availability caused by fertilization and over time. Also, the ratio of microbial biomass C/P had a significant negative correlation with available P, suggesting that this stoichiometry could reflect P availability in the soil. These results imply that microbial biomass and ecoenzymatic stoichiometries are useful for evaluating nutrient availability in soils.

Methane ( $$\mathrm {CH}_{4}$$ ) is known to be emitted from lakes to the atmosphere via processes such as diffusion and ebullition (i.e., bubble emission). We developed a practical method for partitioning eddy-covariance $$\mathrm {CH}_{4}$$ fluxes from a shallow lake into diffusive and ebullitive fluxes using a wavelet analysis based on local scalar similarity between the $$\mathrm {CH}_{4}$$ concentration and other reference scalars, such as the air temperature or water vapour concentration, in the wavelet time-scale domain, with the hypothesis that similar and dissimilar fluctuation components are related to diffusive and ebullitive $$\mathrm {CH}_{4}$$ fluxes, respectively. Our method is applied to approximately two weeks of data obtained at a shallow mid-latitude lake. The partitioned diffusive flux has a physically sound relationship with wind speed, supporting the validity of the method. The ratio of the diffusive flux to the total flux is typically 0.11 with flow from an area of steady bubble emission, but otherwise 0.36. Further validation is required using a larger dataset and data from other lakes. The proposed method can be easily applied to historical data because it requires only 10-Hz data of $$\mathrm {CH}_{4}$$ concentration and other reference scalars, along with an empirical parameter.

The mineralization of organic phosphorus (P) in soil is mainly driven by extracellular phosphatases secreted by soil microbes. Previous studies have suggested that microbial phosphatase production is regulated by soil nutrient stoichiometry and, thus, promoted by carbon and nitrogen (CN) amendment. However, the mechanism leading to increased phosphatase activity after nutrient amendment to soil is unclear, and it is not known how long the effect of the nutrient amendment lasts. To address these questions, we performed a 24-day time-series analysis of full-factorial soil microcosms with CN amendment. Phosphatase activity as well as that expressed per unit of β- d -glucosidase activity, increased sharply and significantly in response to the CN amendment. This suggests that the microbial community shifted their resource allocation after the nutrient amendment and preferentially produced phosphatases rather than β- d -glucosidase. This shifted resource allocation pattern was maintained throughout the 24-day incubation period, and copiotrophic microbes dominated soils that received CN amendment. These results indicate that the effect of the CN amendment on soil microbial resource allocation lasted for >24 days. Together, our results highlight the importance of high-resolution time-series observations that complement long-term studies for which frequent observation is often difficult.

We estimated acute toxicity of benzo[a]pyrene (B[a]P) using two cladoceran species, Ceriodaphnia reticulata and Daphnia magna, and also analyzed its impact on zooplankton community throughout an exposure experiment using small-scale mesocosms. LC(50) of B[a]P for C. reticulata and D. magna was 4.3 and 4.7 µg/l, respectively. However, individuals fed with Chlorella showed higher LC(50), 6.1 µg/l for C. reticulata and 8.0 µg/l for D. magna. In the exposure experiment, we examined the impact of B[a]P on zooplankton community using conceivable concentrations in the environment (5 and 10 µg/l) using typical zooplankton community in eutrophicated systems. Despite the residence time of B[a]P in the water column was short as < 4 days, application of B[a]P induced decrease of zooplankton abundance. However, the recovery pattern was different among cladocerans and rotifers. Consequently, B[a]P showed insecticide-like impacts, suppressing cladoceran populations and inducing the dominance of rotifers particularly under high concentration (10 µg/l). Results have suggested that, even such short duration of B[a]P in the water body can have impact on zooplankton abundance and community structure. Since B[a]P easily precipitate to the bottom and rapidly disappears from the water body, careful monitoring and further assessment of the potential toxicity of polycyclic aromatic hydrocarbons are necessary.

The methylthiotriazine herbicide, simetryn, is commonly used in Japan, and its concentration in surface water is often high enough to affect natural phytoplankton. To estimate how the plankton community in eutrophic systems respond to short-term exposure of realistic concentrations of simetryn, we collected plankton from a eutrophic lake and exposed them to low (20 μg l−1) and high (100 μg l−1) concentrations of simetryn for 12 days in microcosm tanks (50 l). High concentrations significantly lowered total phytoplankton biomass, particularly green algal density. Consequently, the species composition was severely modified by simetryn application. However, there was no apparent impact of simetryn on microbial food-web components, bacteria, heterotrophic nanoflagellates (HNF), and ciliates. Despite the decreased abundance of algal food, the zooplankton community showed subtle changes with simetryn application. The results indicate that the direct impact of simetryn on planktonic organisms other than phytoplankton, particularly on microbial food-web components, is weak. The indirect impact of simetryn on zooplankton through the change of food quality and quantity was also small. It has been suggested that the persistence of microorganisms, alternative food for zooplankton, probably dilutes the indirect impact of simetryn on zooplankton by compensating for the loss of food phytoplankton. Consequently, the plankton community in eutrophicated systems is resistant to the herbicide at a feasible concentration for a short period of time.

Concentration of the herbicides in water was investigated between 2003 and 2007 at Lake Suwa. Concentration of each herbicide in Lake Suwa was lower than half effective concentration of green algae, so we concluded that these herbicides hardly affected the phytoplankton that lived in Lake Suwa. Herbicides were detected for several months in the lake. When water exchange rate was high in summer due to large amount of rainfall, concentration of herbicides in lake water was reduced.Concentration and composition of herbicides were different between center of the lake and shore of the lake in 2007. When large amount of herbicides flowed into the lake from rivers, concentration of herbicides at shore of the lake was higher than center of the lake. This result showed that herbicides at the shore of lake were affected by rivers more than center of the lake.

The fate of chemicals in a lake environment has a close relationship with hydraulic events. Animate and inanimate as water quality affect one another in the lake. Accordingly, water movement is an important issue for understanding the material cycle and effects of environmental pollutants in the lake.In this paper, three methods for investigation in Lake Suwa were introduced. First is the continuous observation of water temperature by using temperature logger. And its results showed that the formation and destruction of thermal stratification were repeated in summer season. Second is our routine water quality observation data as Secchi disk transparency. Recently, transparency has improved in summer season, as a result of decrease of phosphorus amount in the lake water. Third is the analysis of dioxins in the sediment. The major source was impurities of chemical herbicides (PCP and CNP). And large amounts of dioxins flowed into the lake in flood stage compared to normal stage.

諏訪湖では，現在までに水質・底質に関する化学・生物的な研究は多くみられるが，物質循環を議論するうえで不可欠な「湖水の動き」に関する現地観測はあまりみられなかった．そこで本研究では，ADCPを用いて，「湖水の動き」を考える上で不可欠な因子である（１）主要流出入河川の流量，（２）沿岸に繁茂する水草帯内外の流れ場，（３）唯一の流出口である釜口水門付近の流れ場の現地観測を行った．得られた結果は以下の通りである．（１）主要流入河川の上川・宮川・砥川において，観測結果と長野県発表の流量データには大きい差があったが，流出河川の天竜川においては，観測結果と県データの差が小さかった．（２）水草帯内外で流れ場の構造は異なっていた．また，水草の存在が水平方向流速を小さくし，乱れ成分が支配的な流れ場特性を作り出していた．（３）諏訪湖唯一の流出口である釜口水門付近における流出傾向は，北東部からの方が南西部からに比べて卓越していた．

The impact of eutrophication on aquatic ecosystems remains an important topic in aquatic ecology; however, recent successes in water quality restoration in highly eutrophicated water bodies present new research potential regarding re-oligotrophication. Successfully reducing nutrient loading from sewage treatment through restoration activities, induces large changes in phytoplankton composition and biomass, particularly replacement of cyanobacterial dominance. In Lake Suwa, a shallow eutrophic lake in central Japan, recovery has occurred due to water quality restoration efforts since the 1970s. The improvement of lake trophic state from hypertrophic to mesotrophic is accompanied by various changes, such as rapid decreases in biomass of phytoplankton, benthic invertebrates and planktivorous pond smelt, and increases in biomass of aquatic vegetation, mainly floating leaved plants. During re-oligotrophication, zooplankton are important because they are major secondary producers in lake ecosystems. In Lake Suwa, the Research and Education Center for Inland Water Environment, Shinshu University has collected bi-weekly zooplankton samples and analyzed species composition since 1996, when the lake was in a hypertrophic state with serious Microcystis blooms. Lake Suwa is one representative lake for re-oligotrophication in a shallow eutrophic system, and our zooplankton dataset can be used to understand the changes in ecosystem structure and function.

In the present study, we investigated the Polycyclic Aromatic Hydrocarbons (PAHs) at the representative eutrophic lake “Lake Suwa”, which has drastically eutrophicated since 1960s by inflow of domestic and industrial effluents. We also investigated PAHs in river sediments, road dusts, suspended solids and air particles of the catchment area of Lake Suwa.We showed that the concentrations of Σ17PAHs in the lake sediments and river sediments were 364±129 ng/g-dry and 157±194 ng/g-dry, respectively. On the other hand, the concentrations of Σ17PAHs in sediments were relatively high in the northeast part of Lake Suwa.One of the major PAHs in the sediment of Lake Suwa was perylene. It would be mainly produced from precursor substances (such as perylenequinone) in anoxic lake sediment. On the other hand, the major sources of other PAHs (except perylene) were considered to be both petrogenic and pyrogenic source as diesel exhaust matter and asphalt. They entered the Lake Suwa through rivers and finally precipitated to lake sediment.

In the present study, we estimated inflow and effluent load of Polycyclic Aromatic Hydrocarbons (PAHs) in Lake Suwa, Japan. Estimation of PAHs inflow and effluent load were performed by measuring changes in stream flow and concentration of suspended solids (SS) in the lake and river water. Results showed that the concentration of SS increased with stream flow. Annual (March 2004 to February 2005) inflow and effluent load of SS at the lake were calculated as 8.9×106 kg and 7.6×106 kg, respectively. The mass balance between inflow and effluent load indicated that 1.3×106 kg of SS were sedimentated to the lake. The total amount of Σ9PAHs (Phenanthrene, Pyrene, Chrysene, Benzo[e]pyrene, Benzo[b]fluoranthene, Benzo[k]fluoranthene, Benzo[a]pyrene, Dibenz[a,h]anthracene, Benzo[ghi]perylene) in lake SS varied by 230±120 g/lake (average±SD); the maximum amount exceeded 500 g/lake, which was observed in May and October 2004. Specifically, for Benzo[a]pyrene the total amount in lake SS was 14±7 g/lake. Estimation of total Σ9PAHs flowing into Lake Suwa and out through Kamaguchi Gate indicated Σ9PAHs values of 8.6 and 3.5 kg/yr, respectively. The mass balance between Σ9PAHs inflow and outflow indicated that approximately 5.1 kg/yr of Σ9PAHs were sedimentated with SS to the lake. The annual flux of PAHs in Lake Suwa calculated in the present study agreed with the deposition flux of PAHs in a previous study estimated from sediment cores (4 kg/yr) (Ikenaka et al.: Environ. Pollut., 138, 530-538 (2005)). Inflow loads of PAHs markedly increased in May 21, October 9, and October 21 when heavy rains occurred, occupying approximately 27 % of the annual inflow. These results indicated that large quantities of PAHs flowed into the lake when river flow increased by heavy rain.

The aquatic crustacean Daphnia magna is an important species for ecotoxicological study, and is often used as a test organism for environmental risk assessment. However, the mechanism of xenobiotic metabolism by this species has not been studied in detail. In the present study, pyrene was used as model substance to investigate the mechanism of xenobiotic metabolism in D. magna. The results of 24-h exposure experiments showed that D. magna could metabolize pyrene and biotransform it into water-soluble metabolites. On the other hand, the metabolism of pyrene was significantly inhibited by SKF-525A as the cytochrome P450 (CYP) inhibitor. These observations indicated that oxidation by CYP participated in the biotransformation of pyrene by D. magna. We also identified the pyrene metabolites formed by D. magna by HPLC with an electrospray ionization triple quadrupole mass spectrometry detector (LC/ESIMS/MS) and de-conjugation by sulfatase, beta-glucuronidase, and beta-glucosidase. One of the metabolites was ionized in ESI negative mode and formed a dominant mass of m/z 297 (MS) with the product ion of m/z 217 (MS2). Furthermore, this metabolite formed 1-hydroxypyrene on treatment with sulfatase. This metabolite was considered to be a sulfate conjugate of oxidized pyrene (1-hydroxypyrenesulfate). Furthermore, we quantified the deconjugated 1-hydroxypyrene formed by the above enzyme treatment. It showed that 52% of the total metabolized pyrene was biotransformed into 1-hydroxypyrene-sulfate, and more than 73% was biotransformed into oxidized pyrene conjugate. These results indicated that CYP and several conjugation enzymes participate in its biotransformation, and sulfation is important in D. magna for metabolism and elimination of xenobiotics.

Wind has an important role in the behavior of lake current. In this study, the field measurement of wind and currentdistribution was performed simultaneouslyin Lake Suwa. The results proved the spatially nonuniformity of winddistribution over the lakeand counterclockwise horizontal water circulation in the lake when the strong north-west wind was observed. It was examined the effect of spatially non-uniform wind on the lake currentusing a quasi 3-D numerical model by comparingwith the calculation result when the spatially uniform wind allover the lake was assumed. In result, the horizontal water circulation obtained by the fieldmeasurement was recognized byconsideringthe measured wind distribution. This showed that spatially nonuniformity of wind distribution had a great influence on the movement of lake current.

Article, Enviromental Pollution. 138(3): 529-537 (2005)

Dioxin-like polychlorinated biphenyls (PCBs) exert their toxicities by activating the arylhydrocarbon receptor (AhR), a ligand-dependent transcription factor, in a similar manner to the most toxic dioxin, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). In the present study, we re-evaluated the relative potency (REP) of the toxic members of dioxin-like PCBs, PCB126 (toxic equivalency factor, TEF 0.1) and PCB169 (TEF 0.01) relative to TCDD, focusing our attention on their effects on the immune reactions of mice immunized with ovalbumin (OVA). Thymus involution, IgM production, and IL-5 produced by the splenocytes were examined in addition to CYP1A1 induction, the established index of AhR-activation, in the spleen. PCB126 had an REP value of 0.1 because of its effects on thymus, IgM, IL-5, and CYP1A1 induction in the spleen, although its effect on IgG1 production was weaker. On the other hand, PCB169 had a smaller REP value estimated at less than 0.01 with regard to CYP1A1 induction in the spleen and all examined immunological effects, except for IgM production. The tissue concentrations of PCB169 and TCDD could not explain the reason for the smaller potency of PCB169, since the spleen contained a higher proportion of PCB169 to TCDD than dosed. These results indicate that dioxin-like PCBs, especially PCB169, shows deviating REPs against immune reactions, and also suggest that PCB169-liganded AhR behaves differently from TCDD-liganded AhR in immune cells.

Dioxin and its related compounds are suspected to cause neurological and nueroendocrinological disruption in human and laboratory animal offspring upon in utero and lactational exposure during growth and development. We tested the hypothesis by utilizing Long-Evans Hooded rats that perinatal exposure to dioxins affects the neocortical function and expression of sexual behavior in adulthood. In the sexual behavior test, perinatal exposure to TCDD significantly reduced the number of mounts and intromissions. The mRNA semi-quantification in in situ hybridization showed that the mating stimulus in control males induced c-fos mRNA expression in the preoptic area (POA) and the brain derived neurotrophic factor (BDNF) mRNA upregulation in the frontal cortex. In contrast, perinatal exposure to TCDD lowered the upregulation of BDNF mRNA in the frontal cortex but not that of c-fos mRNA in the POA. The volume of the sexually dimorphic nucleus of the preoptic area (SDN-POA) was not affected. The results suggest that perinatal TCDD affects the neocortical function independently from the brain sexual differentiation and alters the expression of sexual behavior.

The present study was conducted to clarify the involvement of mast cells in the exacerbating effect of diesel exhaust particles (DEP) toward allergic airway inflammation and airway hyperresponsiveness (AHR). Airway inflammation by the infiltration of cosinophils with goblet cell proliferation and AHR, as well as by the production of antigen-specific IgG1 and IgE, in plasma were examined using mast cell-deficient mice (W/W(v)) and normal mice (W/W(+)). Both groups of mice received ovalbumin (OVA) or OVA+DEP intratracheally. The eosinophilic airway inflammation and goblet cell proliferation promoted by OVA were significantly greater in W/W(+) than in W/W(v). A similar result was observed in AHR, but was not significant among both groups of mice. DEP enhanced OVA induced-allergic airway inflammation, goblet cell proliferation, and development of AHR in W/W(v), but not in W/W(+). DEP decreased production of antigen-specific IgG1 and IgE in both groups of mice. Mast cells were observed in the submucosal layer of the main bronchus in W/W(v). The number of mast cells was significantly decreased by OVA treatment. The results indicate that mast cells are not necessary to enhance airway damage and development of AHR in W/W(v) by DEP. However, mast cells may be required for the OVA-induced cosinophilic inflammation, airway damage with goblet cell proliferation, and AHR in W/W(+).

Concentrations of polychlorinated dibenzo-p-dioxins (PCDDs), dibenzofurans (PCDFs) and coplanar biphenyls (Co-PCBs) were determined in Japanese human adipose tissues. Temporal trends were assessed by comparing data collected during 1970-1971, 1994-1996 and 2000. Mean TEQ levels of PCDD/Fs in human adipose tissue showed a significant decrease from 31.6 +/- 9.2 pg-TEQ/g fat wt in 1970-1971 to 11.9 +/- 7.4 pg-TEQ/g fat wt in 2000, and coplanar PCBs decreased from 35.4 +/- 21.9 pg-TEQ/g fat wt in 1970-1971 to 15.3 +/- 8.2 pg-TEQ/g fat wt in 2000. However, some PCB congener concentrations did not change during this time. A comparison of data using the latest PCB-TEQ showed no significant changes. Therefore, research on source characterization and monitoring of short-term temporal trends on these compounds should be carried out continuously.

We have investigated how a low dose of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) affects thyroid hormone regulation, especially in relation to the localization of thyroid stimulating hormone (TSH) in the pituitary and that of thyroxin (T4) of the thyroid in the rat. Female Sprague-Dawley rats were given a single oral administration of TCDD ranging from 1.0 to 4.0 microg/kg body weight (bw), and then tissue specimens were removed on day 7 post-administration. Thyroid hormone concentrations were measured in serum, and the expression of the TCDD-responsive genes, UDP-glucuronosyltransferase-1 (UGT1) and cytochrome P4501A1 (CYP1A1) were examined in the liver. TCDD administration resulted in an increase in both immunostaining intensity and the number of TSH-positive cells in the anterior pituitary. T4 was found to localize only in the follicular lumen of the thyroid in vehicle-treated control rats, while TCDD administration caused a foamy change in the colloid of some follicles, an indication of accelerating the biosynthesis of T4 in the thyroid. By morphometrical analysis, the ratio of parenchymal/lumenal area of the thyroid was found to increase in response to TCDD. TCDD treatment as low as 2.0 microg TCDD/kg bw induced a significant decrease in both serum total T4 (TT4) and free T4 (FT4) concentrations in the rats, with a significant increase in serum TSH levels in the 4.0 microg TCDD/kg bw rats. Serum total triiodothyronine (TT3) level was unchanged in all groups. The UGT1 gene was significantly induced at a TCDD dose as low as 1.0 microg/kg bw in a dose-dependent manner. TCDD concentrations in the serum, liver and adipose tissues were detected in a dose-related fashion. The present immunohistochemical results clearly support the earlier biochemical findings on the perturbation of the thyroid-pituitary axis by TCDD and suggest that UGT1 is an immediate target of a low TCDD exposure that triggers the perturbation.

Vehicle exhaust particles from gasoline and diesel engine cars were analyzed for PCDDs and PCDFs. The congener patterns of PCDDs and PCDFs in exhaust particles were different between gasoline and diesel engine cars. Suspended particulate matter from electrostatic precipitator connected to a highway tunnel was also analyzed for PCDDs and PCDFs. The congener pattern of suspended particular matter was different from both of gasoline and diesel engine cars. Total amounts of PCDDs/PCDFs sum concentrations in gasoline, diesel and suspended particulate matter were 0.21, 0.87 and 26.0 ng/g, respectively. The I-TEQs levels in gasoline, diesel and suspended particulate matter were 4.2, 11 and 242 pg/g, respectively.

We have previously shown that intratracheal instillation of suspension of diesel exhaust particles enhances allergen-related eosinophilic airway inflammation, airway hyperresponsiveness, and local expression of interleukin (IL)-5 and granulocyte macrophage-colony stimulating factor (GM-CSF) in mice. The present study was designed to elucidate the effects of daily inhalation of diesel exhaust (DE) on the allergen-related respiratory disease. ICR mice were exposed for 40 weeks to clean air or DE at a soot concentration of 0.3, 1.0, or 3.0 mg/m3 with aerosol allergen challenges (1% ovalbumin in isotonic saline for 6 min) at 3-week intervals during the last 24 weeks of exposures. Exposure to DE enhanced allergen-related eosinophil recruitment to the submucosal layers of the airways and to the bronchoalveolar space, and increased protein levels of GM-CSF and IL-5 in the lung in a dose-dependent manner compared to exposure to clean air. There were strong correlations between the number of eosinophils in bronchoalveolar lavage (BAL) fluid and IL-5 concentrations in BAL supernatants and lung tissue supernatants. In addition, the increases in eosinophil recruitment and local cytokine expression were accompanied by goblet cell proliferation in the bronchial epithelium and airway hyperresponsiveness to inhaled acetylcholine. In contrast, the control mice exposed for 40 weeks to clean air or DE at a soot concentration of 0.3, 1.0, or 3.0 mg/m3 without allergen provocation showed no eosinophil recruitment to the submucosal layers of the airways nor to the bronchoalveolar space and few goblet cells in the bronchial epithelium. The present study provides experimental evidence that daily inhalation of DE can enhance allergen-related respiratory diseases such as allergic asthma. This effect may be mediated by the enhanced local expression of IL-5 and GM-CSF. Increased ambient levels of DE may be implicated in the increasing prevalence of bronchial asthma in recent years.

We previously reported that the intratracheal instillation of diesel exhaust particles enhances allergic airway inflammation and hyperresponsiveness in mice. However, it is not known whether the effects of such instillation differ from those obtained with the daily inhalation of diesel exhaust. We therefore examined whether the inhalation of diesel exhaust would also enhance allergic reactions. Mice were exposed to diesel exhaust or clean air for 5 wk. After the first week, the animals were sensitized to ovalbumin by intraperitoneal injection. At the end of the exposure period, they underwent an ovalbumin challenge. Control animals received saline instead of ovalbumin. Independently of ovalbumin sensitization, diesel exhaust caused an increase in the numbers of neutrophils and macrophages in bronchoalveolar lavage fluid, whereas a significant increase in eosinophil numbers occurred only after antigen challenge combined with diesel exhaust exposure. Furthermore, ovalbumin alone caused an increase in eosinophil numbers in lung tissue, and this was enhanced by diesel exhaust. Exposure to diesel exhaust combined with ovalbumin sensitization, but not diesel exhaust inhalation alone, enhanced the number of goblet cells in lung tissue, respiratory resistance, production of ovalbumin-specific immunoglobulin E and G1 in the serum, and expression of interleukin-5 in lung tissue.

We have previously reported that intratracheal instillation of diesel exhaust particles (DEP) enhances allergen-induced eosinophilic airway inflammation, local expression of interleukin-5 and granulocyte macrophage-colony stimulating factor, and allergen-specific production of IgE and IgG in mice. The present study was undertaken to elucidate the effects of DEP on airway hyperresponsiveness as another characteristic feature of allergic asthma. The animals were randomized into four experimental groups that received intratracheal instillation with vehicle, ovalbumin (OVA), DEP, or the combination of OVA and DEP on a weekly basis for 6 weeks. Respiratory resistance (Rrs) was measured 24 h after the last instillation. An increase in Rrs in animals that inhaled acetylcholine was significantly greater in the combined treatment with OVA and DEP than in the other treatments. The present study indicates that DEP can enhance airway responsiveness associated with allergen exposure, and provides experimental evidence that DEP may deteriorate the pathophysiology of allergen-related respiratory disease such as allergic asthma.

To clarify the relationship between the manifestations of allergic airway inflammation modulated by diesel exhaust particles (DEP) and immunoglobulin production in response to an antigen, airway inflammation characterized by the infiltration of eosinophils, goblet cell proliferation, and antigen-specific immunoglobulin (Ig) production was investigated in five strains of mice after immunization with ovalbumin (OA). Mice were injected intratracheally with OA (1 microg) or OA (1 microg) + DEP (50 microg) four times at 3-week intervals. The order of antigen-specific IgG1 production in plasma of mouse strains treated with OA alone was CBA/2NBDF/1C57BL/6ICRC3H/He. The adjuvant effect of DEP on IgG1 production was observed in CBA/2N, BDF/1, ICR, and C57BL/6 mice. The immune activity in BDF/1 mice was significantly elevated (P0.01). The OA-specific IgE in plasma was unaffected by antigen challenge with or without DEP in any strain. The degree of eosinophilic inflammation and goblet cell proliferation in the airway induced by OA alone or OA + DEP corresponded well with the antigen-specific IgG1 production. These results suggest that the manifestations of allergic airway inflammation modulated by DEP were closely related to the immunoglobulin production response to OA, especially with regard to enhanced IgG1 production.

A large amount of i-urobilin is present in the bottom sediment of urban rivers, and the value of distribution ratio (sediment/water) increase along the river, being higher at the river mouth. The adsorption equilibrium of i-urobilin is important to estimate the movement of i-urobilin as a fecal pollution indicator in the aquatic environment. A model adsorption experiment was carried out to determine the factors affecting the uptake of i-urobilin by the bottom sediment. The particle size of sediment affected the adsorption of i-urobilin. Furthermore, the content of i-urobilin in sediment agreed with the model adsorption experiment. It was reported previously that the content of i-urobilin and suspended solids in river water increased after rainfall. These indicated that i-urobilin moved with suspended solids, which would precipitate at the river mouth. These results suggested that sediment samples should be collected at the mouth of the river, where i-urobilin was concentrated.

牛込濠の湖水,植物プランクトン及び標品のフォスファターゼ活性に及ぼす五種のテトラピロール化合物の影響について観察した。三試料のアルカリフォスファターゼ活性は,使用したビリルビン,ビリベルジン,メソポルフィリン,ウロビリンにより阻害されたが,阻害強度は化合物によって異なる。酸フォスファターゼはウロビリンを除く4種のテトラピロール化合物により阻害を受けた。これらの化合物によるアルカリフォスファターゼ,及び酸フォスファターゼの阻害形式は,Line-weaver-Burk plotにより解析された。さらに,アルカリフォスファターゼに対するウロビリンの影響を調べるために,両者を混合させた溶液のゲルクロマトグラフィーを行った結果,アルカリフォスファターゼの活性中心である亜鉛がウロビリンとキレートを形成し,脱離する可能性が示唆された。従って,テトラピロール化合物のフォスファターゼ阻害は,テトラピロール化合物のキレート形成によるものと推察された。

We found that aquatic crustaceans, decapoda; atyidae (Caridina multidentata, Neocaridina denticulate, and Paratya compressa), metabolize pyrene to a new conjugation product. The results of deconjugation treatments indicated that glucose and sulfate combined with 1-hydroxypyrene. Further analysis by LC/ESI-MS/MS showed that the molecular weight of the product was 460 (m/z 459; deprotonated ion), and that it has a glucose-sulfate moiety (m/z 241; fragment ion). These results indicated that the new metabolite was the glucose-sulfate conjugate of 1-hydroxypyrene. The glucose-sulfate conjugate is a phase II product that has not been reported previously from any organism. Several studies have demonstrated that sulfation is an important pathway for metabolism of xenobiotics in aquatic invertebrates. Thus, glucose-sulfate conjugates may add an important signal for excretion or sequestration of xenobiotics for aquatic invertebrates.

This article reports the organ distribution and bioaccumulation of hepatotoxic microcystins (MCs) in freshwater fishes at different trophic levels from the large, shallow, eutrophic Lake Chaohu in September 2003, when there were heavy surface blooms of toxic cyanobacteria. Among all fish, intestines and blood had the highest average content of MC-RR + MC-LR (22.0 and 14.5 microg g(-1) DW, respectively), followed by liver, bile, and kidney (7.77, 6.32, and 5.81 microg g(-1) DW, respectively), whereas muscle had the least (1.81 microg g(-1) DW). MC content in muscle was highest in carnivorous fish (Culter ilishaeformis, 2.22 microg g(-1) DW) and omnivorous fish (Carassius auratus, 1.96 microg g(-1) DW) and was lowest in phytoplanktivorous fish (Hypophthalmichthys molitrix, 1.65 microg g(-1) DW) and herbivorous fish (Parabramis pekinensis 0.660 microg g(-1) DW). However, the amount of MC in the gut of H. molitrix (137 microg g(-1) DW) was more than 20 times that in the other fish (6.50 microg g(-1) DW). The MCs showed a tendency to accumulate up the food chain, and piscivorous fish at the top of the food chain were at high risk of exposure to MCs in Lake Chaohu. Our study is the first to report MC concentrations in the bile and blood of wild fish. One hundred grams of fish muscle would contain 2.64-49.7 microg of MC-LR equivalent, or about 1.3-25 times the recommended tolerable daily intake of MC-LR by humans, indicating that fish are already severely contaminated by MCs and that the local authorities should warn the public of the risk of poisoning by eating the contaminated fish.

To determine whether the disruption of thyroid hormone and retinoid homeostasis that occurs after exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) can be mediated by the arylhydrocarbon receptor (AhR), pregnant AhR-heterozygous (AhR+/-) mice were administered a single oral dose of 10 microg kg(-1) TCDD at gestation day 12.5. Serum and liver were collected on postnatal day 21 from vehicle-treated control or TCDD-treated AhR+/- and AhR-null (AhR-/-) mouse pups. Whereas TCDD exposure resulted in a marked reduction of total thyroxin (TT4) and free T4 (FT4) levels in the serum of AhR+/- mice, TCDD had no effects on AhR-/- mice. Gene expression of UDP-glucuronosyltransferase (UGT)1A6, cytochrome P450 (CYP)1A1, and CYP1A2 in the liver was induced markedly by TCDD in AhR+/- but not AhR-/- mice. Induction of CYP1A1 in response to TCDD was confirmed by immunohistochemical evidence in that CYP1A1 protein was conspicuously localized in the cytoplasm of hepatocytes in the centrilobular region. Levels of retinyl palmitate were greatly reduced in the liver of TCDD-exposed AhR+/- mice, but not in vehicle-treated AhR+/- mice. No effects of TCDD on retinoid levels in the liver were found in AhR-/- mice. We conclude that disruption of thyroid hormone and retinoid homeostasis is mediated entirely via AhR. Induction of UGT1A6 is thought to be responsible at least partly for reduced serum thyroid hormone levels in TCDD-exposed mice.

Effects of gestational and lactational exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) on thyroid function of offspring were investigated in the rat. Pregnant Holtzman rats, TCDD-sensitive strain, were given a single oral dose of 200 ng or 800 ng TCDD/kg on gestational day 15. Parameters related to the thyroid functions were examined on postnatal days (PNDs) 21 and 49. Serum T(4) levels in offspring decreased significantly on PND21 in the two TCDD-exposed groups but increased on PND 49 only in the high-dose group. A dose of 800 ng TCDD/kg exerted a more than 2-fold increase in serum TSH level in male offspring on PNDs 21 and 49. A significant induction of uridine diphosphate-glucuronosyltransferase-1 gene by TCDD was observed on PND 21 but returned to basal levels on PND 49. Gene expression of cytochrome P4501A1 was markedly induced in the liver treated with TCDD. Even a single oral perinatal exposure to 800 ng TCDD/kg resulted in hyperplasia of the thyroid gland of offspring on PND 49. Proliferating cell nuclear antigen immunocytochemistry also supported this finding. Thus, gestational and lactational exposure to TCDD was found to disrupt thyroid hormone homeostasis, which results in a sustained excessive secretion of TSH, followed by the hyperplasia of thyroid follicular cells.

Exposure to a relatively low dose of 2,3,7,8-tetrachlorodebenzo- p-dioxin (TCDD) during mid-gestation induces a reduction of ventral prostate weight in rat offspring. Recently we reported that a single administration of TCDD (12.5- 800 ng/kg body weight) to pregnant Holtzman rats on gestational day (GD) 15 caused a decrease in androgen receptor (AR) mRNA level in the ventral prostate during the prepubertal period, and we proposed that this reduction of AR mRNA is one of the most sensitive adverse endpoints due to perinatal exposure to TCDD (S. Ohsako et al., 2001, Toxicol. Sci. 60, 132-143). In the present study, to investi- gate the mechanism of a decrease in AR mRNA level, we admin- istered TCDD to rats at other developmental stages and compared possible alterations of the male reproductive system. Pregnant Sprague-Dawley rats were given a single oral dose of 1 mg TCDD/kg body weight on GD 15 or GD 18, or male pups born from untreated dams were subcutaneously given a single dose of 1 mg TCDD/kg body weight on postnatal day 2 (PND 2). Offspring exposed on GD 15, GD 18, and PND 2 were sacrificed on PND 70. TCDD exposure on GD 15 resulted in significant decreases in the urogenital complex and ventral prostate weights and urogenital- glans penis length of male rat offspring, but not on GD 18 and PND 2. Testicular and epididymal weights were also lower than control group only in the TCDD-exposed GD 15 group. Anogeni- tal distance was significantly reduced in the TCDD-exposed GD 15 and GD 18 groups, but not in the TCDD-exposed PND 2 group. Semiquantitative RT-PCR analysis showed that AR mRNA levels were decreased in the TCDD-exposed GD 15 group only, and that the constitutive level of cytochrome P450 1A1 (CYP1A1) mRNA in the ventral prostate was not changed by TCDD in any of the exposed groups. No changes in AR mRNA level were detected in the testis or brain in any of the TCDD-exposed groups. These results suggest the presence of a critical window during develop- ment with regard to impairments of male reproductive organs by in utero and lactational exposure to a low dose of TCDD.

Exposure to a low dose of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) produces a variety of toxic manifestations, including fetal death. In order to evaluate the effects of low-dose TCDD on placental function in this study, pregnant Holtzman rats were given a single oral dose of 800 or 1600 ng TCDD/kg body wt or an equivalent volume of vehicle (control) on gestation day (GD) 15 and the results were observed on GD16 and GD20. The number of fetal deaths increased in the animals exposed to TCDD. Although fetal and placental weight did not differ significantly between the control group and the TCDD groups, histological differences from the control rats were clearly observed in the junctional zone (JZ) of the placentas of the TCDD-exposed rats. In the control placenta, glycogen cells occupied the majority of the JZ on GD16, but then decreased in number and almost disappeared by GD20, whereas on GD20 the placenta of the TCDD-exposed rats exhibited a larger area occupied by the glycogen cells and cysts filled with eosinophilic material surrounded by glycogen cells in the JZ than that of the control group. Glycogen assay revealed that the glycogen content of the placentas from the TCDD-exposed rats was higher than in the control rats. Semiquantitative RT-PCR analysis was performed to assess the expression of glucose transporter 1 (GLUT1) and GLUT3, the two major placental glucose transporter isoforms. On GD20 the level of expression of GLUT1 mRNA in the placentas was not different between the control and TCDD groups, whereas the level of expression of GLUT3 mRNA approximately doubled in both the 800 and 1600 ng/kg TCDD groups. GLUT3 mRNA expression was restricted to the labyrinth zone of placenta, where zone-specific expression of mRNA arylhydrocarbon receptor and induction of cytochrome P450 1A1 mRNA by TCDD were observed, and none was detected in the JZ. These results, including the increase of glycogen content and GLUT3 mRNA level in TCDD-exposed placentas, provide the first evidence of alteration of glucose kinetics in the placenta by TCDD.

Metallothioneins (MTs) are cysteine-rich metal-binding proteins that exert cytoprotective effects against metal toxicity and external stimuli including ionizing or ultraviolet B irradiation. Since 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) is known to cause an exaggerated oxidative stress response in animals and in different organs, we have studied possible involvement of MT in the oxidative responses induced by TCDD. Female Sprague-Dawley (SD) rats (6-week old) were administered a single oral dose of TCDD that varied from 1.0 to 4.0 microg/kg body weight. The serum and tissues were collected 7 days after dosing. Indicators of oxidative damage were assessed. Significant increases in serum 8-hydroxydeoxyguanosine (8-OHdG) levels were observed in the rats dosed with 2.0 and 4.0 microg TCDD/kg bw. Only 4.0 microg TCDD/kg bw produced a decrease in reduced glutathione concentration in the liver. Immunohistochemical staining revealed a TCDD-induced increase in heme oxygenase-1 (HO-1) expression in the hepatic macrophages (Kupffer cells). Under these conditions, MT protein as well as the mRNAs of MT-I and MT-II, were dose-dependently induced in the liver by TCDD doses from 1.0 microg/kg bw. TCDD-induced MT was found to localize in the parenchymal cells of the liver. Serum concentrations of cytokines (TNF-alpha, IL-1beta and IL-6) were not affected by TCDD. The hepatic concentrations of Cu, Zn and Fe were all increased significantly by TCDD administration. Our results suggest that MT levels are increased in the liver upon exposure to TCDD, perhaps by TCDD-generated reactive oxygen species, and that it may play a protective role in TCDD-induced oxidative stress responses as an antioxidant.