The use of freshwater planarians in environmental toxicology studies: Advantages and potential.

Regarding the humane use of animals in scientific research, invertebrates are often recommended in toxicological studies. "Freshwater planarians" refers to numerous free-living freshwater members of the Class "Turbellaria" of the phylum Platyhelminthes. This group of invertebrates has received extensive attention from biologists for many years because of their unique biological characteristics, such as the primitive form of the central nervous system and notable capability to regenerate tissues. Using freshwater planarians as test animals in chemical toxicity studies has grown in popularity since the 1960s. Results from various toxicological experiments have collectively suggested that freshwater planarians can serve as not only alternative models for chemical toxicity screenings in laboratories but also as potential bioindicators for the quality of freshwater environments. However, thus far, no standardized battery of tests for conducting toxicological studies that includes freshwater planarians has been proposed. This paper comprehensively reviews the toxicological information obtained from chemically exposed planarians and proposes practical factors for consideration in toxicity experiments with freshwater planarians as test organisms.

Inhibitory effects of pain relief drugs on neurological enzymes: implications on their potential neurotoxicity to aquatic animals.

Pain relief medications commonly occur in the aquatic environment at measurable levels. While the neurotoxicity of pain relievers to higher vertebrates is currently known, little is known about their effects on aquatic animals. This study investigated the neurotoxicity of pain relievers to aquatic animals. We used three neurological enzymes, cholinesterase (ChE), adenosine triphosphatase (ATPase), and monoamine oxidase (MAO), from a freshwater planarian (Dugesia japonica) and green neon shrimp (Neocaridina denticulata) as biomarkers to examine the effects of pain relievers on in vitro activity. The activity of MAO and ChE, but not ATPase, was significantly inhibited by acetaminophen, but not by other pain relievers examined. It was likely that the inhibitory effects of acetaminophen on shrimp neurological enzymes were more severe than on the planarian. These findings suggest that acetaminophen is potentially neurotoxic to aquatic animals, at least in terms of neurotransmission disturbance.

Disturbances to neurotransmitter levels and their metabolic enzyme activity in a freshwater planarian exposed to cadmium.

Using specific neurobehaviors as endpoints, previous studies suggested that planarian neurotransmission systems could be targets of Cd neurotoxicity. However, direct evidence for disturbed neurotransmission systems by Cd in treated planarians is still lacking. In planarians, dopamine (DA) and serotonin (5-HT) play critical roles in neuromuscular function, but little is known about their metabolic degradation. Therefore, in this study, we attempted to determine the appearances of DA, 5-HT, and their metabolic products in the freshwater planarian Dugesia japonica, characterize the activity of enzymes involved in their metabolism, and investigate the effects of Cd on planarian 5-HTergic and DAergic neurotransmission systems. Only DA, 5-HT, and 5-hydroxyindole-3-acetic acid (5-HIAA) were found in planarian tissues. Further enzymatic study revealed the activity of planarian monoamine oxidase (MAO) but not catechol-O-methyl transferase (COMT). These findings suggest that planarian MAO catalyzes the metabolism of 5-HT into 5-HIAA. However, DA metabolites from the MAO-involved metabolic pathway were not found, which might be due to a lack of COMT activity. Finally, in Cd-treated planarians, tissue levels of 5-HT and DA were decreased and MAO activity altered, suggesting that planarian neurotransmission systems are disturbed following Cd treatment.

Alterations of biochemical indicators in hepatopancreas of the golden apple snail, Pomacea canaliculata, from paddy fields in Taiwan.

The freshwater golden apple snail, Pomacea canaliculata, is one of the world's 100 worst invasive alien species. The snails' wide distribution, high abundance, and sensitivity to environmental pollution make them a potential bioindicator for environmental contamination. In this study, the biochemical status of golden apple snails collected from paddy fields throughout the island of Taiwan was examined. This study found that the biochemical status of apple snails collected from paddy fields differed from that of animals bred and maintained in the laboratory. Furthermore, certain biochemical endpoints of the snails collected from the paddy fields before and after agricultural activities were also different-hemolymphatic vitellogenin protein was induced in male snail after exposure to estrogen-like chemicals, the hepatic monooxygenase (1.97 +/- 0.50 deltaA(650mm) 30 min(-1) mg(-1) protein in control group) and glutathione S transferase (0.02 +/- 0.01 delta A(340mm) 30 min(-1) mg(-1) protein in control group) snails exposed to pesticides, as well as the hepatopancreatic levels of aspartate aminotransferase (450.00 +/- 59.40 U mg(-1) mg(-1) protein in control group) and alanine aminotransferase (233.27 +/- 42.09 U mg(-1) mg(-1) protein in control group) decreased the indicating that xenobiotics destroyed hepatopancreatic. The above findings reveal that apple snail could be used as a practical bioindicator to monitor anthropogenic environmental pollution.

Cadmium neurotoxicity to a freshwater planarian.

Although freshwater planarians are evolutionarily primitive, they are some of the simplest bilateral animals possessing integrated neural networks similar to those in vertebrates. We attempted to develop planarian Dugesia japonica as a model for investigating the neurotoxicity of environmental pollutants such as cadmium (Cd). This study was therefore designed to study the effects of Cd on the locomotor activity, neurobehavior, and neurological enzymes of D. japonica. After planarians were exposed to Cd at high concentrations, altered neurobehavior was observed that exhibited concentration-dependent patterns. Morphological alterations in Cd-treated planarians included irregular shape, body elongation, screw-like hyperkinesia, and bridge-like position. To study the direct effects of Cd on neurological enzymes, tissue homogenates of planarians were incubated in vitro with Cd before their activity was measured. Results showed that acetylcholinesterase (AChE), adenosine triphosphatase (ATPase), and monoamine oxidase A (MAO-A) activities were inhibited in a concentration-dependent manner. MAO-B activity was significantly induced by Cd at low concentrations and inhibited at high concentrations. Changes in the in vivo activity of AChE and ATPase were also found after planarians were treated with Cd at a sublethal concentration (5.56 µM). These observations indicate that neurotransmission systems in planarians are disturbed after Cd exposure.

Photonic generation of ultra-wide-band doublet pulse through monolithic integration of tapered directional coupler and quantum well waveguide.

We proposed and demonstrated a novel scheme of photonic ultra-wide-band (UWB) doublet pulse based on monolithic integration of tapered optical-direction coupler (TODC) and multiple-quantum-well (MQW) waveguide. TODC is formed by a top tapered MQW waveguide vertically integrating with an underneath passive waveguide. Through simultaneous field-driven optical index- and absorption- change in MQW, the partial optical coupling in TODC can be used to get a valley-shaped of optical transmission against voltage. Therefore, doublet-enveloped optical pulse can be realized by high-speed and high-efficient conversion of input electrical pulse. By just adjusting bias through MQW, 1530 nm photonic UWB doublet optical pulse with 75-ps pulse width, below -41.3 dBm power, 125% fractional bandwidth, and 7.5 GHz of -10 dB bandwidth has been demonstrated, fitted into FCC requirement (3.1 GHz~10.6 GHz). Doublet-pulse data transmission generated in optical fiber is also performed for further characterization, exhibiting a successful 1.25 Gb/s error-free transmission. It suggests such optoelectronic integration template can be applied for photonic UWB generation in fiber-based communications.

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.

Broadband multiple-cascaded integration of electroabsorption modulators and high impedance transmission lines by lowering standing-wave effect.

Standing wave effect of applied electrical field on optical modulation in multiple-cascaded integration (CI) electroabsorption modulator (EAM) and high-impedance transmission line (HITL) has been investigated in this paper. As modulation frequency is increased to the scale that electrical wavelength is in the order of optical modulator length, multiple electrical reflection and self-interference on impedance-mismatch boundaries becomes significant, leading to strong position-dependent field distribution and degrading modulation bandwidth. Sharp bandwidth roll of electrical-optical (EO) conversion by standing wave has been found experimentally in CI structure, consistent with simulation results. By comparing different segment number and length of CI- structure, larger section number of design can overcome such problem to get more flatten bandwidth response. Such simple CI for 300µm long EAM has been demonstrated with flat EO response of -3dB drop 45GHz and -10dB microwave reflection (up to 65GHz) in 6-segement device, suggesting this scheme design is quite useful for efficient broad band modulation.

In vivo and in vitro metabolism of tobacco-specific nitrosamine, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), by the freshwater planarian, Dugesia japonica.

Cigarette smoke is a risk factor for human health, and many studies were conducted to investigate its adverse effects on humans and other mammals. However, since large amounts of cigarette products are produced and consumed, it is possible that tobacco chemicals can end up in aquatic environments through several routes, thus influencing aquatic organisms. In this study, the presence of tobacco-specific nitrosamine (TSNA), 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), in aquatic environment was demonstrated. Since toxic effects on and distribution patterns of tobacco chemicals in aquatic organisms were rarely studied, after results of an acute toxicity pretest were obtained, experiment was conducted to investigate the bioaccumulation pattern of NNK and distribution patterns of its metabolites, mainly 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL), in NNK-treated freshwater planarians, Dugesia japonica. Results from in vivo and in vitro studies showed that NNK was readily converted to NNAL through the carbonyl reduction in bodies of NNK-treated planarians. Tissue concentrations of both chemicals increased in time- and dose-dependent manners. Furthermore, we examined the end products of NNK/NNAL α-hydroxylation in NNK-treated planarians, but only 1-(3-pyridyl)-1,4-butanediol was detected, suggesting that NNK metabolism in planarians partially differs from that in mammalian systems. This is the first report on NNK metabolism in an aquatic organism and can be used as a foundation for developing freshwater planarians as a new in vivo model for the study of NNK toxicology in the future.

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.

Alterations of biochemical parameters in malformed Indian rice frogs, Rana limnocharis from Southern Taiwan.

The purpose of this study is to investigate the factors that cause malformed frogs in upstream Kaoping river (KP site) and Tungkang river (T site) of Southern Taiwan. In this experiment, the activities of monooxygenase (MO), glutathione-S-transferase (GST), acetylcholinesterase (AchE) as well as the concentration of vitellogenin (Vg) in the liver were measured. Results show that activities of MO, GST and AchE, and Vg levels in normal frogs (male/female) were 0.09 +/- 0.02/0.09+/-0.01 deltaA min(-1) mg(-1) protein, 0.12 +/- 0.04/0.13 +/- 0.04 deltaA min(-1) mg(-1) protein, 6.13 +/- 2.69/6.01 +/- 2.09 U mg(-1) protein and 0.87 +/- 0.42/2.18 +/- 0.50 microg mg(-1) protein, respectively. Activities of MO, GST and AchE, and Vg levels in malformed frogs (male/female) were 0.15 +/- 0.04/0.21 +/- 0.07 deltaA min(-1) mg(-1) protein, 0.27 +/- 0.08/0.30 +/- 0.12 deltaA min(-1) mg(-1) protein, 4.59 +/- 2.71/5.19 +/- 3.74 U mg(-1) protein and 1.46 +/- 0.61/3.15 +/- 0.88 microg mg(-1) protein, respectively in KP site, and were 0.16 +/- 0.69/0.1 +/- 80.07 deltaA min(-1) mg(-1) protein, 0.21 +/- 0.07/0.24 +/- 0.08 deltaA min(-1) mg(-1) protein, 5.13 +/- 4.58/3.94 +/- 1.33 U mg(-1) protein and 2.23 +/- 1.47/4.11 +/- 1.63 microg mg(-1) protein, respectively in T site. These results indicate that male and female malformed frogs in both rivers upstream are found with higher activities. No significant difference in AchE activity was found between normal and malformed frogs in this investigation. It is therefore reasonable to speculate that the organic chemicals released from agricultural activities are presumable the main factors that lead to the malformation of frogs.

Comparative tissue distributions of cadmium chloride and cadmium-based quantum dot 705 in mice: Safety implications and applications.

Cadmium (Cd) is a component in quantum dot 705 (QD705). Whether QD705 behaves similar to Cd in vivo is of great concern. We compared the distributional kinetics of cadmium chloride (CdCl(2)) and QD705 in mice after intravenous injection. QD705 showed a longer plasma and body retention than CdCl(2) and could be detected in the brain during early exposure. While both the liver and spleen demonstrated a constant Cd concentration for 28 days after QD705 injection, it is likely that this represents intact QD705 stored in mononuclear phagocytes. The kidneys showed a time-dependent accumulation of Cd in the QD705-exposed animals. By day 28, Cd in the kidneys from QD705 was 3-fold that of CdCl(2). QD705 and CdCl(2) have very different kinetics in distribution and metabolism. The long body retention of QD705 in the kidneys may mean that QD705 has even more renal toxicity than CdCl(2).

Field-driven all-optical wavelength converter using novel InGaAsP/InAlGaAs quantum wells.

A new type of semiconductor quantum well (QW) for high-speed all optical wavelength converter (AOWC) is proposed and demonstrated in this work. Based on InGaAsP (well)/InGaAlAs (barrier) multiple QW, large electron band offset ratio relative to heavy hole can be attained to shorten sweep rate of photocarrier driven by electric field, realizing high-speed efficient AOWC through cross absorption modulation (XAM). By such QWs, an optical waveguide with high-speed electrode connection is fabricated. A -3dB bandwidth of 38 GHz with 8V bias in time-varying photocurrent and all optical response is observed. The corresponding sweep time is less than 10ps, consistent with calculated tunneling rate of QW and thus confirming high sweep rate through field-driven tunneling processing. All-optical conversion with error-free 40Gb/s data transmission and -11dB of conversion efficiency in system performance is also attained in this device, suggesting that such AOWC has potential for 100Gb/s application.

Novel ultra-wideband (UWB) photonic generation through photodetection and cross-absorption modulation in a single electroabsorption modulator.

We propose and demonstrate, by proof of concept, a novel method of ultra-wide band (UWB) photonic generation using photodetection and cross-absorption modulation (XAM) of multiple quantum wells (MQW) in a single short-terminated electroabsorption modulator (SEAM). As an optical pump pulse excite the MQWs of SEAM waveguide, the probe light pulse with the same polarity can be generated through XAM, simultaneously creating photocurrent pulse propagating along the waveguide. Using the short termination of SEAM accompanied by the delayed microwave line, the photocurrent pulse can be reversed in polarity and re-modulated the waveguide, forming a monocycle UWB optical pulse. An 89 ps cycle of monocycle pulse with 114% fractional bandwidth is obtained, where the electrical power spectrum centered at 4 GHz of frequency ranges from 0.1 GHz to 8 GHz for -10 dB drops. Meanwhile, the generation processing is also confirmed by observing the same cycle of monocycle electrical pulse from the photodetection of SEAM. The whole optical processing is performed inside a compact semiconductor device, suggesting the optoelectronic integration template has a potential for the application of UWB photonic generation.

Involvement of oxidative stress and activation of aryl hydrocarbon receptor in elevation of CYP1A1 expression and activity in lung cells and tissues by arsenic: an in vitro and in vivo study.

Epidemiological evidence indicated that there was a synergistic interaction between arsenic and cigarette smoke on enhancement of lung cancer risk. Benzo[a]pyrene (B[a]P), a component in cigarette smoke, is one of the most carcinogenic compounds known. Animal studies have demonstrated that there were increased benzo[a]pyrene-7,8-diol-9,10-epoxide (BPDE) adduct formation and lung tumorigenesis in animals when they were coexposed to B[a]P and arsenic. Since BPDE adduct is a by-product of B[a]P metabolism, elevation of B[a]P metabolism by arsenic is suspected. However, the effects of arsenic on cytochrome P450 1A1 (CYP1A1) status (expression and activity), which is essential for B[a]P metabolism, either in lung cells or in lung tissues, are never demonstrated. We hypothesized that arsenic would enhance aryl hydrocarbon receptor (AhR) activation leading to CYP1A1 expression and activity in lung cells. Indeed, our present study successfully demonstrated the elevation of CYP1A1 messenger RNA expression in H1355 cells, a human lung adenocarcinoma cell line, as well as CYP1A1 expression and activity in lung tissues of arsenic-exposed mice. We further demonstrated that this elevation of CYP1A1 expression could be effectively blocked with AhR antagonist, 3',4'-dimethoxyflavone, indicating that the arsenic-induced CYP1A1 expression and activity were via AhR activation. Furthermore, we found that arsenic-induced AhR activation and -enhanced CYP1A1 expression can be further increased by a prooxidant, buthionine-(S,R)-sulfoximine, and suppressed by antioxidants, such as N-acetylcysteine and catalase. Our findings provided clear evidence that arsenic can enhance CYP1A1 expression and activity via AhR activation, and the arsenic-induced AhR activation is probably triggered by oxidative stress.

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.

Computational and ultrastructural toxicology of a nanoparticle, Quantum Dot 705, in mice.

We conducted pharmacokinetic and toxicology studies on Quantum Dot 705 (QD705) in male ICR mice for up to 6 months after a single intravenous dose. Time-course sacrifices were carried out at 1, 4, and 24 h; 3, 7, 14, and 28 days; and 6 months on groups of six mice per time point. Mass balance studies were also carried out at 24 h, 28 days, and 6 months. Using inductively coupled plasma mass spectrometry, various tissues, urine, and feces were analyzed for cadmium (Cd111), which is a major (46%) component of QD705. On the basis of these experimental studies, a physiologically based pharmacokinetic computer simulation model was developed with excellent predictive capability for the time-dependent kinetic and distributional changes of QD705 in tissues. QD705 persisted and accumulated in the spleen, liver, and kidneys for at least 28 days with little or no disposition but was gradually and partially eliminated by 6 months. Although histological alterations of the spleen, liver, and kidney by light microscopy are unremarkable, investigation using electron microscopy on numerous renal samples revealed definitive mitochondrial alterations in renal tubular epithelial cells at 28 days and 6 months postdosing. Health implications and potential beneficial applications of QD705 are suggested.

Enhancements of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) metabolism and carcinogenic risk via NNK/arsenic interaction.

Epidemiological studies indicated an enhancement of cigarette smoke-induced carcinogenicity, including hepatocellular carcinoma, by arsenic. We believe that arsenic will enhance the expression of hepatic CYP2A enzyme and NNK metabolism (a cigarette smoke component), thus its metabolites, and carcinogenic DNA adducts. Male ICR mice were exposed to NNK (0.5 mg/mouse) and sodium arsenite (0, 10, or 20 mg/kg) daily via gavaging for 10 days and their urine was collected at day 10 for NNK metabolite analysis. Liver samples were also obtained for CYP2A enzyme and DNA adducts evaluations. Both the cyp2a4/5 mRNA levels and the CYP2A enzyme activity were significantly elevated in arsenic-treated mice liver. Furthermore, urinary NNK metabolites in NNK/arsenic co-treated mice also increased compared to those treated with NNK alone. Concomitantly, DNA adducts (N(7)-methylguanine and O(6)-methylguanine) were significantly elevated in the livers of mice co-treated with NNK and arsenic. Our findings provide clear evidence that arsenic increased NNK metabolism by up-regulation of CYP2A expression and activity leading to an increased NNK metabolism and DNA adducts (N(7)-methylguanine and O(6)-methylguanine). These findings suggest that in the presence of arsenic, NNK could induce greater DNA adducts formation in hepatic tissues resulting in higher carcinogenic potential.

Persistent tissue kinetics and redistribution of nanoparticles, quantum dot 705, in mice: ICP-MS quantitative assessment.

BACKGROUND: Quantum dots (QDs) are autofluorescent semiconductor nanocrystals that can be used for in vivo biomedical imaging. However, we know little about their in vivo disposition and health consequences. OBJECTIVES: We assessed the tissue disposition and pharmacokinetics of QD705 in mice. METHODS: We determined quantitatively the blood and tissue kinetics of QD705 in mice after single intravenous (iv) injection at the dose of 40 pmol for up to 28 days. Inductively coupled plasma-mass spectrometry (ICP-MS) measurement of cadmium was the primary method of quantification of QD705. Fluorescence light microscopy revealed the localization of QD705 in tissues. RESULTS: Plasma half-life of QD705 in mice was short (18.5 hr), but ICP-MS analyses revealed QD705 persisted and even continued to increase in the spleen, liver, and kidney 28 days after an iv dose. Considerable time-dependent redistribution from body mass to liver and kidney was apparent between 1 and 28 days postdosing. The recoveries at both time points were near 100%; all QD705s reside in the body. Neither fecal nor urinary excretion of QD705 was detected appreciably in 28 days postdosing. Fluorescence microscopy demonstrated deposition of QD705 in the liver, spleen, and kidneys. CONCLUSION: Judging from the continued increase in the liver (29-42% of the administered dose), kidney (1.5-9.2%), and spleen (4.8-5.2%) between 1 and 28 days without any appreciable excretion, QD705 has a very long half-life, potentially weeks or even months, in the body and its health consequences deserve serious consideration.

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.