Effects of perfluorooctane sulfonate (PFOS) on swimming behavior and membrane potential of paramecium caudatum
ABSTRACT Persistent perfluorinated organic compounds such as perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA) were distributed widely in the global. PFOS (15 microM or higher) caused backward swimming of paramecia. The Triton-extracted paramecia, where the membrane was disrupted and the externally applied chemicals are freely accessible to the ciliary apparatus, showed forward swimming up to 0.1 microM Ca2+ in the medium and backward swimming at about 0.2 microM and higher. PFOS (0.1 mM) did not change the relationship between the swimming directions and free Ca2+ concentrations. Effects of various surfactants including PFOS and PFOA on the swimming direction of paramecia were compared with the hemolysis of mouse erythrocytes as an indicator of surfactant activities. The hemolysis did not correlate with their swimming behavior. PFOS caused triphasic membrane potential changes both in the wild-type paramecia and caudatum non-reversal (CNR) mutants, the latter is defective in voltage-gated Ca2+ channels. An action potential of the wild-type specimen was induced at lower current intensity when PFOS was present in the medium. Voltage-clamp study indicated that PFOS had no effect on the depolarization-induced Ca2+ influx responsible for the action potential. The membrane potential responses obtained were similar to those obtained by the application of some bitter substances such as quinine that activate chemoreceptors of paramecia. Since the CNR specimens did not exhibit PFOS-induced backward swimming at concentrations examined, the backward swimming is attributable to the influx of Ca2+ into the cilia through voltage-gated Ca2+ channels. The Ca2+ channels are most probably activated by the depolarizing receptor potentials resulted from the PFOS-induced activation of chemoreceptors.
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ABSTRACT: Experiments were conducted to evaluate the toxic effects ofmonocrotophos in ciliate models Paramecium caudatum and Oxytricha fallax. In acute toxicity studies higherconcentrations of monocrotophos caused marked increase in mobility of cells exhibiting rocking movements within two mins of exposure but were decreased after 30 mins. LC50 value by mortality curve for 3 hr acute toxicity test of Oxytricha fallax and Paramecium caudatum was found 307.744 +/- 33.27 mg l(-1) and 332.284 +/- 57.52 mg l(-1) respectively. Oxytricha fallax was found sensitive than Paramecium caudatum to monocrotophos. In acute exposure cells showed deformities such as swelling, oval shaped deformity and in higher concentrations shortening of longitudinal axis with blackening of cytoplasm occurred. The length of paramecia was reduced prominently. Similarly enlargement of contractile vacuole and stress egestion of food vacuoles was also observed. The morphological studies showed the changes in shape, size, colour and width of Paramecia and Oxytricha. Frequencies of macronuclear aberrations were significant showing deformities such as rod shaped, elongation, fragmentation, diffusion and total absence of nucleus and were concentration dependent. The data provided in the present study on interaction of pesticides with nuclear structure can be of immense value because most of these pesticides have been reported to have carcinogenic, mutagenic and teratogenic properties.Journal of Environmental Biology 09/2010; 31(5):603-7. · 0.55 Impact Factor
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ABSTRACT: Perfluorooctane sulfonate (PFOS) is one of the persistent organic pollutants distributed widely in the global environment. We have found that a single oral administration of PFOS induced tonic convulsion in mice and rats when a brief ultrasonic stimulus was applied to the animals. The aim of this study is to examine whether the neurotoxicity is caused by subchronic dietary exposure to PFOS. Rats were treated with dietary PFOS at 0, 2, 8, 32 and 128 ppm for 13 weeks. Animals were carefully observed for pharmacotoxic signs and responses to the ultrasonic stimulus applied biweekly. PFOS increased liver weight and decreased food consumption and body weight. PFOS concentrations in the serum, brain, liver and kidney were increased almost proportional to its total dose, although the ratios of PFOS concentrations in tissues to total doses in the group treated with the highest concentration were a little lower. The ranges of relative concentrations in the brain, liver and kidney to serum concentration were 0.13 to 0.24, 2.7 to 6.3 and 0.82 to 1.6, respectively. PFOS alone did not cause any neurotoxic symptoms; however, 5 rats out of 6 showed tonic convulsion in the 6th week when ultrasonic stimulus was applied to the 128 ppm rats with the total PFOS dose of 338 mg/kg. The ultrasonic stimulus did not cause convulsion in the other groups. Histopathological examination including electron microscopic examination could not detect any abnormality in the brain. Because the acute oral dose of PFOS causing the convulsion was 250 mg/kg (Sato et al., 2009), the convulsion induced by PFOS seemed to depend on its total dose regardless of treatment schedule.The Journal of Toxicological Sciences 02/2011; 36(1):55-62. DOI:10.2131/jts.36.55 · 1.38 Impact Factor
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ABSTRACT: Persistent perfluorinated organic compounds such as perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA) are distributed widely in the global environment including wildlife and human. In this study, we investigated the genotoxicity of PFOS and PFOA using the novel in vivo comet assay developed for Paramecium caudatum. For the comet assay, large nuclei squeezed out of the paramecia with 0.25 M sucrose containing 0.6% Triton X-100 were embedded in a layer of agarose gel placed over the slide glass. N-methyl-N´-nitro-N-nitrosoguanidine (MNNG) and 2-aminoanthracene (2-AA) were successfully used for positive controls. Productions of 8-hydroxydeoxyguanosine (8-OH-dG) and intracellular reactive oxygen species (ROS) were also measured in paramecia. PFOS did not cause DNA damage on any conditions examined. On the other hand, 12 and 24 hr exposure to PFOA (100 µM) increased DNA migration in electrophoresis condition at pH 13, but not at pH 12.1, suggesting that the DNA damage may be alkali labile site (such as apurinic/apyrimidinic (AP) site). Exposure of paramecia to 100 µM PFOA for 1, 3 and 24 hr and to 10 µM PFOA for 24 hr significantly increased intracellular ROS. Under the same condition, however, 8-OH-dG level was not affected by PFOA. The PFOA-induced DNA damage was not abolished by the application of 100 µM GSH which completely inhibited the increase of intracellular ROS. In conclusion, the PFOA-induced in vivo DNA damage was first shown in paramecia, and the DNA damage might not be directly attributable to increase in intracellular ROS.The Journal of Toxicological Sciences 12/2010; 35(6):835-41. DOI:10.2131/jts.35.835 · 1.38 Impact Factor