Bioaccumulation and toxicodynamics of cadmium to freshwater planarian and the protective effect of N-acetylcysteine.

Although toxic responses of freshwater planarians after exposure to environmental toxicants can be observed through external toxicological end points, physiological responses inside the bodies of treated planarians have rarely been investigated. The present study was designed, using cadmium (Cd) as a reference toxicant, to determine its bioaccumulation and toxicodynamics in the freshwater planarian, Dugesia japonica, after acute toxicity was obtained. Accumulated Cd concentrations, metallothionein levels, and the oxidative status in planarians were determined after exposure to Cd. Furthermore, we hypothesized that the acute death of Cd-treated planarians was associated with increased oxidative stress. After Cd-treated planarians were coexposed to antioxidant, N-acetylcysteine (NAC), we found that NAC protected planarians from Cd lethality by maintaining the oxidative status and decreasing the bioaccumulation of Cd. The results of the present study support planarians being used as a practical model for toxicological studies of environmental contaminants in the future.

Evaluation of the estrogenic effects of bisphenol-A on male freshwater prawn Macrobrachium asperulum.

Bisphenol-A(BPA), a known endocrine-disrupting chemical that is distributed world wide, is extensively employed in industry, dentistry and consumer household products. This study was conducted to explore the estrogenic effects of BA on the male freshwater prawn, Macrobrachium asperulum, by examining the daily survival rate, molting frequency, hepatosomatic index (HSI), and levels of vitellogenin-like protein. Results revealed that BPAcan elicitthe expression of vitellogenin-like protein (0.09 and 0.09 microg P x (mg protein))-1), respectively) in male organisms exposed to 0.1 and 1 ng l(-1) BPA at day 7. Moreover, prawns were perceived to be sensitive to estrogenic compounds. Hence, it can be concluded that M. asperulum can be used as a species for biomonitoring, and levels of vitellogenin-like protein in males are a useful biomarker for detecting estrogenic contaminations.

Reproduction obstacles for the female green neon shrimp (Neocaridina denticulata) after exposure to chlordane and lindane.

The purpose of this study was to investigate the effects of chlordane and lindane on reproduction obstacles and endocrine disruption in female green neon shrimp (Neocaridina denticulata). Individuals of N. denticulata, a common inhabitant of freshwater systems in Taiwan, was exposed to different levels of chlordane (1 and 10 ngl(-1)) and lindane (0.1 and 1 microgl(-1)). The reproductive ability and reproductive hormone levels were observed after exposure. According to our findings, an increase in estrogen, induction of a vitellogenin-like protein, and changes in reproductive performance were observed in both chlordane- and lindane-treated shrimp. Thus, it was concluded that chlordane and lindane may cause some reproduction obstacles and disruption of endocrine functions in N. denticulata.

Herpes-like virus infection causing mortality of cultured abalone Haliotis diversicolor supertexta in Taiwan.

A herpes-like virus is demonstrated for the first time to be associated with high mortality rates in maricultured abalone Haliotis diversicolor supertexta in Taiwan. Histopathology of moribund abalone indicated that the nerve system was the primary target tissue. The lesions were characterised by tissue necrosis accompanied with infiltration of haemocytes. Electron microscopic examination demonstrated viral particles within the degenerated cerebral ganglion cells. The viruses were hexagonal, approximately 100 nm in diameter and had a single coat. Some viral particles contained a dense nucleoid, while others were empty. The ultrastructure and morphogenesis of the virus particles were consistent with those of the herpesvirus described from the oyster Crassostrea virginica. Experimental infection using supernatant collected from minced visceral organs and muscle of moribund abalone induced 100 % mortality through both intramuscular injection and bath treatments.

Effects of cadmium and zinc on oxygen consumption, ammonium excretion, and osmoregulation of white shrimp (Litopenaeus vannamei).

White shrimp, Litopenaeus vannamei, a globally important cultured prawn species, is an ideal animal for studying the impairment caused by the effects of heavy metals that are often detected in coastal areas. The main purpose of the present study was to detect the acute toxicity of Cd and Zn to L. vannamei, and to investigate their effects on gill functions, which have not been carried out in this species before, hoping to obtain some important significance. First of all, we examined the acute toxicity of cadmium (Cd) and zinc (Zn) to L. vannamei and obtained 24-, 48-, 72-, and 96-h medium lethal concentration (LC50) values of 2.58, 1.30, 1.14, and 1.07 mgCd l(-1) and 3.98, 2.14, 1.75, and 1.35 mgZn l(-1), respectively. Furthermore, we also found that exposure of shrimp to Cd or Zn caused an inhibition in oxygen consumption of 91.3% and 75.9% lower than that of the control. However, after separate exposure to Cd or Zn, elevations in ammonium excretion were obtained, which were 153.7% and 144.1%, respectively, higher than the control. It is most likely that elevations in ammonium excretion were related to decreased osmotic pressure of shrimp blood. Finally, the distribution of Cd and Zn within gills was also determined.

Effects of gallium on common carp (Cyprinus carpio): acute test, serum biochemistry, and erythrocyte morphology.

Gallium (Ga) is one of the intermetallic elements that are increasingly being used in making high-speed semiconductors such as gallium arsenide. The purposes of this study were to investigate the effects of gallium on acute toxicity, on serum biochemical variables as well as on erythrocyte morphological changes in the blood stream of common carp (Cyprinus carpio). Median lethal concentrations were determined in acute tests. The 96-h LC50 value was 19.78 (18.49-21.16) mgl(-1). Common carp were exposed to different gallium concentrations (2.0, 4.0, and 8.0 mgl(-1)) for 28 days in laboratory toxicity tests. Means of the measured serum biochemistry parameters (including glucose, blood urea nitrogen, creatinine, cholesterol, and triglyceride) of these exposed groups significantly differed from those of the untreated group. Deformation of erythrocytes suggest disturbance of respiration as an additional indicator of Ga exposure. Our results suggest that 2.0 mgl(-1) is proposed as a biologically safe concentration which can be used for establishing tentative water quality criteria concerning of same size common carp. In addition, serum biochemical parameters as well as erythrocyte morphological changes are promising clinical diagnostic tools for assessing the effects of gallium compounds on common carp.

Effects of the endocrine disrupter chemicals chlordane and lindane on the male green neon shrimp (Neocaridina denticulata).

The purpose of this study was to investigate the effect of chlordane and lindane on morphological changes and endocrine disruption in male Green neon shrimp (Neocaridina denticulata). In this experiment, individuals of N. denticulata, a common inhabitant of freshwater systems in Taiwan, were exposed to chlordane (1 and 10 ng/l and lindane (0.1 and 1 microg/l morphological changes and reproductive hormone levels were observed following four weeks exposure. According to our findings, an increase in estrogen, a reduction in testosterone, and morphological alternations of the masculine appendage were observed in both chlordane- and lindane-treated shrimp, while induction of a vitellogenin-like protein appeared only in shrimp treated with 10 ng/l chlordane. An endocrine disruption effect on N. denticulata was demonstrated, and may apply to other organochlorine pesticides or endocrine disruption chemicals.

The preferential accumulation of cadmium in the head portion of the freshwater planarian, Dugesia japonica (Platyhelminthes: Turbellaria).

Free-living freshwater planarians are considered to have the potential for development as an experimental model for toxicological studies on xenobiotics, including metals. However, little was known about the distribution patterns of metals in the body of treated planarians. This study was conducted to determine the tissue distribution patterns of cadmium (Cd) in different body portions of the treated planarian, Dugesia japonica. Results showed that Cd accumulated in the head of planarians at a significantly higher concentration than in the tail. After examining the level of metallothionein (MT), we suggested that the tissue distribution pattern of Cd might be related to MT induction patterns. In contrast, in planarians treated with copper (Cu), neither the tissue accumulation of Cu nor the multiples of induction of MTs significantly differed between different portions. Furthermore, a higher Cd accumulation rate in the head of planarians caused more-severe oxidative stress to appear in this portion and also a higher susceptibility to a lethal concentration of Cd. Finally, both in vitro and in vivo acetylcholinesterase activities in both body portions of planarians were inhibited by Cd. The present study provides the first report that different metals are distributed in various body portions with different patterns in the planarian.

Histopathological and biochemical evidence of hepatopancreatic toxicity caused by cadmium and zinc in the white shrimp, Litopenaeus vannamei.

The white shrimp, Litopenaeus vannamei, a globally important cultured prawn species, is an ideal animal for studying the impairment caused by the effects of heavy metals that are often detected in coastal areas. In this study, L. vannamei was exposed to different concentrations of cadmium (Cd) and zinc (Zn) for up to 28 d. Histopathological alterations in the hepatopancreas were observed in L. vannamei after long-term exposure to Cd and Zn. Hepatopancreatic injury was further confirmed by the inductions of two biochemical markers, hemolymphatic glutamate-oxalacetate transaminase (GOT) and glutamate-pyruvate transaminase (GPT). It was notable that L. vannamei was able to repair its hepatopancreas from the damage caused by Zn, which was evidenced by the results of the histopathological observations, determinations of tissue metal concentrations, and examination of GOT and GPT levels.

Metallothionein induction and heavy metal accumulation in white shrimp Litopenaeus vannamei exposed to cadmium and zinc.

Metallothioneins (MTs) have been widely considered for their potential use as specific biomarkers to reflect the existence of heavy metal pollution, because their induction has been observed to be obviously elevated after heavy metal exposure in a large number organism studied. However, relatively fewer efforts have been made in MT-related studies of prawn species, such as the white shrimp Litopenaeus vannamei, a globally important aquaculture species. With the results from gel filtration chromatography, we demonstrate the existence of MTs or MT-like proteins in L.vannamei. We further studied the relationship between MT induction and metals accumulation after long-term exposure to the heavy metals Cd and Zn. From our results, it is very clear that the response of L. vannamei to Cd differs from that to Zn, and this should be considered when using MTs in field applications to monitor metals contamination.

Effects of chlordane and lindane on testosterone and vitellogenin levels in green neon shrimp (Neocaridina denticulata).

The purpose of this study was to investigate the acute toxicity of chlordane and lindane as well as their endocrine disruption effect on green neon shrimp (Neocaridina denticulata), a common habitant in freshwater system of eastern Asia and Hawaii. First, the organisms were exposed to chlordane and lindane to estimate the 96-h LC(50)(96-h median lethal concentration). Then, levels of testosterone and vitellogenin in hemolymph of N. denticulata after exposure to sublethal concentrations of chlordane (1 ng/L and 10 ng/L) and lindane (0.1 microg/L and 1 microg/L) were also examined. The 96-h LC(50) values obtained from the results of acute exposure were 127.03 (130.11-122.35) ng/L and 9.36 (8.00-10.96) microg/L for chlordane and lindane, respectively. Furthermore, reductions of testosterone concentration were observed in both chlordane- and lindane-treated shrimps, whereas induction of vitellogenin-like protein was only apparent in chlordane-treated shrimps. Thus, it is concluded that chlordane and lindane may probably show some disruption endocrine functions on N. denticulata.