The complete mitochondrial genome of the non-biting midge Chironomus yoshimatsui (Diptera: Chironomidae).

A non-biting midge Chironomus yoshimatsui has been widely used in ecotoxicology and chemical risk assessments. In this study, the complete mitochondrial genome (mitogenome) sequence of C. yoshimatsui was determined using short-read next-generation sequencing technologies. The mitogenome was 15,734 bp in length and consisted of 13 protein coding genes, 2 ribosomal RNAs, and 22 transfer RNAs. The A + T content was 77.8%. The gene order was identical to the pattern conserved across Diptera. The mitocgenome sequence obtained in this study provides a useful resource for further evolutionary and ecological studies.

Predicted no effect concentration derivation as a significant source of variability in environmental hazard assessments of chemicals in aquatic systems: an international analysis.

Environmental hazard assessments for chemicals are carried out to define an environmentally "safe" level at which, theoretically, the chemical will not negatively affect any exposed biota. Despite this common goal, the methodologies in use are very diverse across different countries and jurisdictions. This becomes particularly obvious when international scientists work together on documents with global scope, e.g., in the World Health Organization (WHO) International Program on Chemical Safety. In this article, we present a study that describes the extent of such variability and analyze the reasons that lead to different outcomes in deriving a "safe level" (termed the predicted no effect concentration [PNEC] throughout this article). For this purpose, we chose 5 chemicals to represent well-known substances for which sufficient high-quality aquatic effects data were available: ethylene glycol, trichloroethylene, nonylphenol, hexachlorobenzene, and copper (Cu). From these data, 2 data sets for each chemical were compiled: the full data set, that contained all information from selected peer-review sources, and the base data set, a subsample of the full set simulating limited data. Scientists from the European Union (EU), United States, Canada, Japan, and Australia independently carried out hazard assessments for each of these chemicals using the same data sets. Their reasoning for key study selection, use of assessment factors, or use of probabilistic methods was comprehensively documented. The observed variation in the PNECs for all chemicals was up to 3 orders of magnitude, and this was not simply due to obvious factors such as the size of the data set or the methodology used. Rather, this was due to individual decisions of the assessors within the scope of the methodology used, especially key study selection, acute versus chronic definitions, and size of assessment factors. Awareness of these factors, together with transparency of the decision-making process, would be necessary to minimize confusion and uncertainty related to different hazard assessment outcomes, particularly in international documents. The development of a "guideline on transparency in decision-making" ensuring the decision-making process is science-based, understandable, and transparent, may therefore be a promising way forward.

Utility of delayed fluorescence as endpoint for rapid estimation of effect concentration on the green alga Pseudokirchneriella subcapitata.

Algal growth inhibition tests for environmental risk assessment require improved efficiency to evaluate large numbers of chemicals. As an endpoint for rapid estimation of the effect concentration of test chemicals, we propose the delayed fluorescence (DF) measurement from an alga 24 h after exposure. Eight chemicals (bifenox, bromoxynil, bensulfuronmethyl, diuron, diflufenican, thiobencarb, m-chlorophenylhydrazone and 2,5-dibromo-3-methyl-6-isopropyl-p-benzoquinone) were tested. The EC50 values from the 24 h DF measurement were similar to those from the conventional 72 h growth test for seven tested chemicals excepting thiobencarb. We conclude that 24 h DF measurement is a possible endpoint for rapid estimation of the EC50 values obtained in the 72 h growth test for those seven chemicals.

Induction profile of HSP70-cognate genes by environmental pollutants in Chironomidae.

Several species of invertebrates have been studied to examine the toxicological effects of chemicals that include insecticides and heavy metals. We characterized heat-shock protein (hsp) genes from the ubiquitous midge, Chironomidae. More than 70 fold induction of hsp70 expression was detected by quantitative PCR after 37°C treatment in the midge. Expression of hsp70 was induced not only by heat but also by exposure to insecticides and heavy metals such as cadmium and copper. Expression time courses for hsp70 were highly specific to each chemical. When midges were exposed to sub-lethal level of a pyrethroid insecticide, ethofenprox, hsp70 expression was increased over 20 fold with a transient peak at 1.5h. Heavy metal exposure led to delayed hsp70 up regulation of 7 fold at 6-7h. Expression of another hsp70-cognate gene (hsc70) was also characterized. Using these genes we propose a novel system for biomonitoring of heavy metals and other pollutants.

Stage-dependent differences in effects of carbaryl on population growth rate in Japanese medaka (Oryzias latipes).

Fish embryo toxicology is important because embryos are considered more susceptible than adult fish to the effects of toxic chemicals. Recently, fish embryo bioassay was proposed to replace the conventional fish acute toxicity chemical test of the Organization for Economic Cooperation and Development guidelines because it offers the advantages of fewer reagents, easy handling, and efficient data production. To accelerate the establishment of a chemical toxicity database for the protection of environmental and human health, we need to determine whether the conventional toxicity test can safely be replaced by such fish embryo toxicity tests. For instance, it is unclear how the presence of the chorion moderates the toxic effects of some chemicals. If such chemical toxicities do differ between embryos and, for example, the larval stage, then different toxic effects should appear in later life. We tested the later-life effects of the neurotoxic insecticide carbaryl at sublethal concentrations (0 [control] and 5 and 10 mg/L) in embryos and posthatch larvae of the freshwater fish medaka, Oryzias latipes. Although embryos exposed until hatching showed multiple developmental malformations and reductions in subsequent survival rates over three months, no significant reduction was observed in tolerance to starvation for 7 d and in intrinsic population growth rate (r). Exposure of larvae for 96 h resulted in dose-responsive vertebral fracture, significant reduction in tolerance to starvation for 7 d, and reduced three-month survival rate; r was reduced significantly and consistently. These results suggested that posthatch larvae were more susceptible than embryos to carbaryl exposure and that the toxic cascades may differ between larvae and embryos. The influences of carbaryl exposure on population growth rate differed significantly with developmental stage.

Estrogenic modulation of CYP3A38, CYP3A40, and CYP19 in mature male medaka (Oryzias latipes).

We examined cytochrome P450 production and activity and circulating hormone concentrations in male medaka exposed to 17beta-estradiol (E2) or 17alpha-ethinylestradiol (EE2). Intraperitoneal injection of E2 at 1, 10, or 100 microg/g-fish completely suppressed CYP3A38 protein production and suppressed CYP3A40 protein levels by 89%, 52%, or 47%, respectively. CYP3A38 and CYP3A40 mRNA expression was unaltered, and CYP3A enzymatic activity initially increased and then decreased with increasing E2 dose. Males co-cultured with females were exposed to a markedly high concentration (43 ng/L) of E2 secreted by females. CYP3A protein levels in co-cultured males were suppressed. Serum testosterone (TE) and 11keto-testosterone levels in co-cultured males were downregulated to 40% of pre-exposure levels. Serum E2 levels increased in co-cultured males or males exposed to EE2. Testicular CYP19, which converts TE to E2, increased by 9.5 times in males exposed to 50 ng/L EE2 and by 21.5 times in those exposed to 100 ng/L EE2. Male medaka exposed to EE2 showed increased serum Vtg levels. Estrogenic exposure induced Vtg production, suppressed CYP3A protein production, downregulated TE metabolism, and enhanced CYP19 activity. Serum E2 endogenously induced by CYP19 could contribute to Vtg induction in male medaka.

[Progress on OECD Chemicals Programme (13)--SIAM 22 in Paris, 2006].

The 22nd Screening Information Data Set (SIDS) Initial Assessment Meeting (SIAM 22) was held at the Organisation for Economic Co-operation and Development (OECD) headquarters in Paris, France. The initial assessment documents of five substances (CAS numbers: 75-59-2, 80-51-3, 101-83-7, 103-24-2, 27813-02-1) sponsored by Japan were all agreed at the meeting. In this report, the documents of these substances are introduced.

[Progress on OECD chemicals programme (11)--SIAM 19 in Berlin, 2004].

The 19th Screening Information Data Set (SIDS) Initial Assessment Meeting (SIAM 19) was held in Berlin, Germany, hosted by the Germen Federal Agency for the Environment. The initial assessment documents of four substances (CAS numbers: 92-70-6, 126-33-0,131-17-9, 7580-85-0) and one category (High Molecular Weight Phthalate Esters) at SIAM 19 were submitted by the Japanese Government with or without the International Council of Chemical Associations (ICCA) and all of them were agreed at the meeting. In this report, the documents of these substances are introduced.

Activation of a stress-induced gene by insecticides in the midge, Chironomus yoshimatsui.

Stress proteins (heat shock proteins, HSPs) have been proposed as general biomarkers for environmental monitoring. In the present study, we evaluated the environmental stress-burden on the aquatic midge Chironomus yoshimatsui using hsp70 expression. Larvae collected from streams receiving polluted runoff (field strain) were resistant to the organophosphorus insecticide, fenitrothion (F), and the synthetic pyrethroid, ethofenprox (E), whereas a strain originally collected from an unpolluted area (susceptible strain) showed low resistance to insecticide exposure. To examine the expression of an HSP70 gene in C. yoshimatsui, an hsp70 cDNA probe was prepared using RNA obtained from the field strain larvae and used for Northern blot analyses. The expression of this HSP70 gene in larvae collected from two field sites in May about 1 week after insecticide spraying in the fields was 2.3 (p = 0.018) to 3.3 fold higher than that in the susceptible strain and was also 4.6 and 1.4 (p = 0.033) fold higher than those collected in November 3 months after the cessation of insecticide spraying. In order to identify potential inducers of the HSP70 gene of the field strain, larvae of the susceptible strain were exposed to F or E for 24 h and hsp70 mRNA levels determined. Exposures to F at 0.4 microg/L and E at 1.1 microg/L increased hsp70 mRNA levels 2.7 (p = 0.049) and 4.4 (p = 0.043) fold over controls, respectively. These results suggest that larvae collected from polluted areas are burdened by environmental stressors and the tested insecticides are potential inducers of HSP70. The results also support the suggestion that HSP70 gene expression is a sensitive indicator of low level (nonlethal) exposures to certain insecticides.