Effects of Tributyltin-Contaminated Aquatic Environments and Remediated Water on Early Development of Sea Urchin (Hemisentrotus pulcherrimus).

In this study, gametotoxicity and embryotoxicity experiments were performed using Hemicentrotus pulcherrimus to investigate the toxic effects of tributyltin (TBT). The effects of TBT on fertilization and embryogenesis were assessed at various concentrations (0, 0.02, 0.05, 0.09, 0.16, 0.43, 0.73, 4.68, and 9.22 ppb). The fertilization rates decreased in a concentration-dependent manner, with significant reduction following treatment with TBT at 0.05 ppb. Embryos exhibited developmental impairment after TBT exposure at each tested concentration. The frequency of developmental inhibition delay that treatment with TBT delayed embryonic development in a dose-dependent manner, with 100% of embryos exhibiting developmental impairment at 4.68 ppb. During developmental recovery tests, embryos cultured in fresh media without TBT showed advanced embryonic development. Although the observed normal development after transferring the developmentally delayed embryos to fresh media without TBT offers prospects for the restoration of contaminated environments, embryonic development remained incomplete. These results suggest that TBT adversely affects the early embryonic development of H. pulcherrimus.

Review of cadmium toxicity effects on fish: Oxidative stress and immune responses.

Cadmium (Cd) in aquatic environments can cause environmental toxicity to fish and induce oxidative stress owing to an excessive production of reactive oxygen species in fish bodies. Fish have developed various antioxidant systems to protect themselves from reactive oxygen species; thus, a change in antioxidant responses in fish can be a criterion for evaluating oxidative stress resulting from Cd exposure. Because Cd exposure may be recognized as an exogenous substance by a fish body, it may lead to the stimulation or suppression of its immune system. Various immune responses can be assessed to evaluate Cd toxicity in fish. This review aimed to identify the impacts of Cd exposure on oxidative stress and immunotoxicity in fish as well as identify accurate indicators of Cd toxicity in aquatic ecosystems.

Toxic Effects on Oxidative Stress, Neurotoxicity, Stress, and Immune Responses in Juvenile Olive Flounder, Paralichthys olivaceus, Exposed to Waterborne Hexavalent Chromium.

Juvenile Paralichthys olivaceus were exposed to waterborne hexavalent chromium at various concentrations (0, 0.5, 1.0, and 2.0 mg/L) for 10 days. After chromium exposure, the activities of superoxide dismutase and glutathione S-transferase, which are oxidative stress indicators, were significantly increased; however, the glutathione level was significantly reduced. Acetylcholinesterase activity as a neurotoxicity marker was significantly inhibited upon chromium exposure. Other stress indicators, including plasma cortisol and heat shock protein 70, were significantly increased. The immune response markers (lysozyme and immunoglobulin M) were significantly decreased after chromium exposure. These results suggest that exposure to environmental toxicity in the form of waterborne chromium at concentrations higher than 1.0 mg/L causes significant alterations in antioxidant responses, neurotransmitters, stress, and immune responses in juvenile olive flounders. This study will provide a basis for an accurate assessment of the toxic effects of hexavalent chromium on aquatic organisms.

Ingestion and egestion of polystyrene microplastic fragments by the Pacific oyster, Crassostrea gigas.

Marine microplastics (MPs) pose a risk to human health through accumulation in maricultural organisms, particularly bivalves. Various studies have reported the presence of MP particles in Pacific oysters (Crasostrea gigas). In this study, we investigated the size-specific ingestion and egestion of polystyrene (PS) MPs by Pacific oysters. The cultivation density of C. gigas was maintained at 1 L of filtered seawater per oyster (n = 5) during the MP ingestion and egestion experiments. On exposure to 300 n/L of PS MP fragments for 7 d, 60.4% of the PS was ingested within 6 h (7.25 × 102 ± 1.36 × 102 n/indv.), and the ingestion was saturated at 12 h (1.2 × 103 ± 2.2 × 102 n/indv.) in C. gigas. The maximum MP ingestion capacity (Igmax) of a single Pacific oyster was 73.0 ± 16.3 n/g wet weight. Further, 62.9% of the PS MP particles were egested for 7 d from the saturated single C. gigas. Ingestion and egestion varied according to the PS MP size. In the case of <50 µm PS MP, ingestion rate was low but MP amount and net-ingestion efficiency was significantly higher than other PS MP sizes. In addition, egestion, egestion rate, and net-egestion efficiency for <50 µm PS MPs were significantly higher than other PS MP sizes. Therefore, smaller MPs (<50 µm) normally exhibit the highest ingestion and egestion rates; therefore, the 50-300 µm size fraction exhibited the highest residual possibility (particles >1000 µm were excluded). Additionally, considering the net-egestion efficiency, the most economical and efficient depuration period was 24 h. This study clarifies the size-specific MP accumulation in oysters, and the egestion results suggest that the potential risk of MPs to human health through the intake of maricultural products could be reduced by depuration.

Toxic effects of lead exposure on bioaccumulation, oxidative stress, neurotoxicity, and immune responses in fish: A review.

Lead (Pb) is a highly toxic metal in aquatic environments. Fish are at the top of the food chain in most aquatic environments, and are the most susceptible to the toxic effects of Pb exposure. In addition, fish are one of the most abundant vertebrates, and they can directly affect humans through food intake; therefore, fish can be used to assess the extent of environmental pollution in an aquatic environment. Pb-induced toxicity in fish exposed to toxicants is primarily induced by bioaccumulation in specific tissues, and the accumulation mechanisms vary depending on water habitat (freshwater or seawater) and pathway (waterborne or dietary exposure). Pb accumulation in fish tissues causes oxidative stress due to excessive ROS production. Oxidative stress by Pb exposure induces synaptic damage and neurotransmitter malfunction in fish as neurotoxicity. Moreover, Pb exposure influences immune responses in fish as an immune-toxicant. Therefore, the purpose of this review was to examine the various toxic effects of Pb exposure, including bioaccumulation, oxidative stress, neurotoxicity, and immune responses, and to identify indicators to evaluate the extent of Pb toxicity by based on the level of Pb exposure.

Microscopic evidence of a new 9R-AgI polytype heterostructure.

The extraordinary high ionic conductivity and the phase transition with large thermal hysteresis of AgI:Al2O3 nanocomposites can be ascribed to the presence of unusual polytype 7H and 9R modification of AgI as mesoscopic heterostructures. In addition to the 7H AgI phase in the composites previously identified by a Rietveld analysis of X-ray diffraction, a new 9R AgI polytype with a characteristic three-fold contrast was directly evidenced by high resolution transmission electron microscopy. The epitaxial intergrowth of various polytypes was also microscopically evidenced which is in accordance with the Rietveld analysis.

Ambient pressure syntheses of size-controlled corundum-type In2O3 nanocubes.

Hydrolysis of In(O-iPr)3 by 10 molar excess of water at 90 degrees C in a surfactant/solvent mixture of oleylamine/oleic acid/trioctylamine provides very small nanoparticles (<5 nm in diameter) of In(O)(OH). Subsequent in situ thermolysis of the formed In(O)(OH) nanoparticles at 350 degrees C and ambient pressure produces monodisperse h-In2O3 nanocubes, which can form an extended two-dimensional array on a flat surface. The size of the In2O3 nanocubes (8, 10, and 12 nm) could be easily controlled by the simple change in the amounts of employed surfactants. The h-In2O3 nanocube samples show blue PL emissions at room temperature due to, presumably, systematic oxygen vacancy.