The Experts below are selected from a list of 1491 Experts worldwide ranked by ideXlab platform
Jussi V. K. Kukkonen - One of the best experts on this subject based on the ideXlab platform.
-
Effects of activated carbon ageing in three PCB contaminated sediments: Sorption efficiency and secondary effects on Lumbriculus variegatus
Water research, 2015Co-Authors: Inna Nybom, Jussi V. K. Kukkonen, David Werner, Matti T. Leppänen, Kimmo Mäenpää, Greta C. Waissi-leinonen, Jarkko AkkanenAbstract:The sorption efficiency and possible secondary effects of activated carbon (AC) (o 63-200 μm) was studied with Lumbriculus variegatus in three PCB contaminated sediments applying long AC-sediment contact time (3 years). AC amendment efficiently reduced PCB bioavailability as determined with both, L. variegatus bioaccumulation test and passive samplers. However, dose related secondary effects of AC on egestion rate and biomass were observed (applied doses 0.25% and 2.5% sediment dry weight). The sorption capacity and secondary effects remained similar when the experiments were repeated after three years of AC-sediment contact time. Further, transmission electron microscopy (TEM) samples revealed morphological changes in the L. variegatus gut wall microvilli layer. Sediment properties affected both sorption efficiency and secondary effects, but 2.5% AC addition had significant effects regardless of the sediment. In, conclusion, AC is an efficient and stable sorbent to decrease the bioavailability of PCBs. However, sediment dwelling organisms, such as Oligochaete worms in this study, may be sensitive to the carbon amendments. The secondary effects and possible morphological changes in benthic organisms should not be overlooked as in many cases they form the basis of the aquatic food webs.
-
Multixenobiotic resistance efflux activity in Daphnia magna and Lumbriculus variegatus
Chemosphere, 2014Co-Authors: Eeva-riikka Vehniäinen, Jussi V. K. KukkonenAbstract:Abstract Multixenobiotic resistance is a phenomenon in which ATP-binding cassette (ABC) family proteins transfer harmful compounds out of cells. Daphnia magna and Lumbriculus variegatus are model species in aquatic ecotoxicology, but the presence and activity of ABC proteins have not been well described in these species. The aim of this work was to study the presence, activity, and inhibition of ABC transport proteins in D. magna and L. variegatus . The presence of abcb1 and abcc transcripts in 8–9-day-old D. magna was investigated by qRT-PCR. The activity of MXR in D. magna and L. variegatus was explored by influx of the fluorescent ABC protein substrates rhodamine B and calcein-AM, with and without the model inhibitors verapamil (unspecific ABC inhibitor), reversin 205 (ABCB1 inhibitor) and MK571 (ABCC inhibitor). Juvenile D. magna possessed all examined abcb and abcc transcripts, but only reversin 205 inhibited MXR activity. The MXR activity in L. variegatus was inhibited by MK571, and to a lesser extent by verapamil, whereas reversin 205 seemed to stimulate the transport activity. Whereas calcein-AM worked better as an MXR substrate in D. magna , rhodamine B was a better substrate for L. variegatus MXR activity measurements. This is the first report on MXR activity in the order Lumbriculida , subclass Oligochaeta , and class Clitellata .
-
Changes in Lumbriculus variegatus metabolites under hypoxic exposure to benzo(a)pyrene, chlorpyrifos and pentachlorophenol: consequences on biotransformation.
Chemosphere, 2013Co-Authors: Stanley O. Agbo, Matti T. Leppänen, Jarkko Akkanen, Juha Lemmetyinen, Markku Keinänen, Sarita Keski-saari, Philipp Mayer, Jussi V. K. KukkonenAbstract:Abstract The regulation of endogenous metabolites is still not fully understood in aquatic invertebrates exposed concurrently to toxicants and hypoxia. Despite the prevalence of hypoxia in the aquatic environment, toxicity estimations seldom account for multiple stressors thereby differing from natural conditions. In this study, we examined the influence of hypoxia ( 2 ) on contaminant uptake and the composition of intracellular metabolites in Lumbriculus variegatus exposed to benzo(a)pyrene (B(a)P, 3 μg L −1 ), chlorpyrifos (CPF, 100 μg L −1 ) or pentachlorophenol (PCP, 100 μg L −1 ). Tissue extracts of worms were analyzed for 123 metabolites by gas chromatography–mass spectrometry and metabolite levels were then related to treatments and exposure time. Hypoxia markedly increased the accumulation of B(a)P and CPF, which underlines the significance of oxygen in chemical uptake. The oxygen effect on PCP uptake was less pronounced. Succinate and glycerol-3-phosphate increased significantly ( p
-
Bioconcentration of benzo[a]pyrene in Chironomus riparius and Lumbriculus variegatus in relation to dissolved organic matter and biotransformation
Aquatic Ecosystem Health & Management, 2013Co-Authors: Stanley O. Agbo, Jarkko Akkanen, Matti T. Leppänen, Jussi V. K. KukkonenAbstract:The relative health of benthic invertebrate populations is threatened by both dissolved and strongly-bound contaminants. Sediment-bound contaminants can be mobilized and metabolized in the guts of deposit-feeders and may lead to even more potent derivatives. For this reason, measures of parent substance concentrations in organisms are not a suitable exposure indicator when substantial biotransformation can occur. In this study, we assessed the concentration of waterborne 14C-benzo[a]pyrene (BaP) in Chironomus riparius larvae and in the oligochaete Lumbriculus variegatus at different levels of dissolved organic carbon (DOC). These two species have different biotransformation capabilities. Polydimethylsiloxane (PDMS) fiber was used to assess the freely-dissolved concentrations for the prediction of uptake and elimination kinetics. Exposure concentrations decreased due to the presence of DOC. Radioactivity that corresponded to the metabolites exceeded 90% of total extractable fractions in C. riparius, and su...
-
Response of Lumbriculus variegatus transcriptome and metabolites to model chemical contaminants.
Comparative biochemistry and physiology. Toxicology & pharmacology : CBP, 2012Co-Authors: Stanley O. Agbo, Matti T. Leppänen, Jarkko Akkanen, Juha Lemmetyinen, Markku Keinänen, Sarita Keski-saari, Zhixin Wang, Hailin Wang, David A. Price, Jussi V. K. KukkonenAbstract:Assessment of the underlying molecular events leading to xenobiotic toxicity is challenging especially when techniques are applied in isolation. We examined transcriptional and metabolic changes in Lumbriculus variegatus exposed to benzo(a)pyrene (B(a)P), cadmium (Cd) or pentachlorophenol (PCP) by DNA microarrays (7422 ESTs) and gas chromatography-mass spectrometry (GC-MS), respectively. In addition, the DNA damage response of worms exposed to B(a)P was assessed by a capillary electrophoresis laser induced fluorescence (CE-LIF) immunoassay. We found elevated expression of oxidative stress responsive genes, which correlated positively with the changes in antioxidant vitamin precursors including alpha-tocopherol and cholecalciferol. Other genes with strong differential expressions were mostly involved in actin related processes and proteolysis, despite an apparent delayed Cd response. Phosphates, sugars and fatty acids were effectively reduced and suggested that chemical treatments may have interfered with energy metabolism. The increased amount of B(a)P diol-epoxide (BPDE)-DNA adducts in exposed worms appeared to correlate with the variability in uridine, inosine and xanthine, which are key components of nucleoside metabolism. This suggests that DNA damage was imminent or peaked within 6h. The results conformed to transcriptional changes in B(a)P exposed worms and compliment other approaches to elucidate underlying molecular changes.
Matti T. Leppänen - One of the best experts on this subject based on the ideXlab platform.
-
Effects of activated carbon ageing in three PCB contaminated sediments: Sorption efficiency and secondary effects on Lumbriculus variegatus
Water research, 2015Co-Authors: Inna Nybom, Jussi V. K. Kukkonen, David Werner, Matti T. Leppänen, Kimmo Mäenpää, Greta C. Waissi-leinonen, Jarkko AkkanenAbstract:The sorption efficiency and possible secondary effects of activated carbon (AC) (o 63-200 μm) was studied with Lumbriculus variegatus in three PCB contaminated sediments applying long AC-sediment contact time (3 years). AC amendment efficiently reduced PCB bioavailability as determined with both, L. variegatus bioaccumulation test and passive samplers. However, dose related secondary effects of AC on egestion rate and biomass were observed (applied doses 0.25% and 2.5% sediment dry weight). The sorption capacity and secondary effects remained similar when the experiments were repeated after three years of AC-sediment contact time. Further, transmission electron microscopy (TEM) samples revealed morphological changes in the L. variegatus gut wall microvilli layer. Sediment properties affected both sorption efficiency and secondary effects, but 2.5% AC addition had significant effects regardless of the sediment. In, conclusion, AC is an efficient and stable sorbent to decrease the bioavailability of PCBs. However, sediment dwelling organisms, such as Oligochaete worms in this study, may be sensitive to the carbon amendments. The secondary effects and possible morphological changes in benthic organisms should not be overlooked as in many cases they form the basis of the aquatic food webs.
-
Changes in Lumbriculus variegatus metabolites under hypoxic exposure to benzo(a)pyrene, chlorpyrifos and pentachlorophenol: consequences on biotransformation.
Chemosphere, 2013Co-Authors: Stanley O. Agbo, Matti T. Leppänen, Jarkko Akkanen, Juha Lemmetyinen, Markku Keinänen, Sarita Keski-saari, Philipp Mayer, Jussi V. K. KukkonenAbstract:Abstract The regulation of endogenous metabolites is still not fully understood in aquatic invertebrates exposed concurrently to toxicants and hypoxia. Despite the prevalence of hypoxia in the aquatic environment, toxicity estimations seldom account for multiple stressors thereby differing from natural conditions. In this study, we examined the influence of hypoxia ( 2 ) on contaminant uptake and the composition of intracellular metabolites in Lumbriculus variegatus exposed to benzo(a)pyrene (B(a)P, 3 μg L −1 ), chlorpyrifos (CPF, 100 μg L −1 ) or pentachlorophenol (PCP, 100 μg L −1 ). Tissue extracts of worms were analyzed for 123 metabolites by gas chromatography–mass spectrometry and metabolite levels were then related to treatments and exposure time. Hypoxia markedly increased the accumulation of B(a)P and CPF, which underlines the significance of oxygen in chemical uptake. The oxygen effect on PCP uptake was less pronounced. Succinate and glycerol-3-phosphate increased significantly ( p
-
Bioconcentration of benzo[a]pyrene in Chironomus riparius and Lumbriculus variegatus in relation to dissolved organic matter and biotransformation
Aquatic Ecosystem Health & Management, 2013Co-Authors: Stanley O. Agbo, Jarkko Akkanen, Matti T. Leppänen, Jussi V. K. KukkonenAbstract:The relative health of benthic invertebrate populations is threatened by both dissolved and strongly-bound contaminants. Sediment-bound contaminants can be mobilized and metabolized in the guts of deposit-feeders and may lead to even more potent derivatives. For this reason, measures of parent substance concentrations in organisms are not a suitable exposure indicator when substantial biotransformation can occur. In this study, we assessed the concentration of waterborne 14C-benzo[a]pyrene (BaP) in Chironomus riparius larvae and in the oligochaete Lumbriculus variegatus at different levels of dissolved organic carbon (DOC). These two species have different biotransformation capabilities. Polydimethylsiloxane (PDMS) fiber was used to assess the freely-dissolved concentrations for the prediction of uptake and elimination kinetics. Exposure concentrations decreased due to the presence of DOC. Radioactivity that corresponded to the metabolites exceeded 90% of total extractable fractions in C. riparius, and su...
-
Response of Lumbriculus variegatus transcriptome and metabolites to model chemical contaminants.
Comparative biochemistry and physiology. Toxicology & pharmacology : CBP, 2012Co-Authors: Stanley O. Agbo, Matti T. Leppänen, Jarkko Akkanen, Juha Lemmetyinen, Markku Keinänen, Sarita Keski-saari, Zhixin Wang, Hailin Wang, David A. Price, Jussi V. K. KukkonenAbstract:Assessment of the underlying molecular events leading to xenobiotic toxicity is challenging especially when techniques are applied in isolation. We examined transcriptional and metabolic changes in Lumbriculus variegatus exposed to benzo(a)pyrene (B(a)P), cadmium (Cd) or pentachlorophenol (PCP) by DNA microarrays (7422 ESTs) and gas chromatography-mass spectrometry (GC-MS), respectively. In addition, the DNA damage response of worms exposed to B(a)P was assessed by a capillary electrophoresis laser induced fluorescence (CE-LIF) immunoassay. We found elevated expression of oxidative stress responsive genes, which correlated positively with the changes in antioxidant vitamin precursors including alpha-tocopherol and cholecalciferol. Other genes with strong differential expressions were mostly involved in actin related processes and proteolysis, despite an apparent delayed Cd response. Phosphates, sugars and fatty acids were effectively reduced and suggested that chemical treatments may have interfered with energy metabolism. The increased amount of B(a)P diol-epoxide (BPDE)-DNA adducts in exposed worms appeared to correlate with the variability in uridine, inosine and xanthine, which are key components of nucleoside metabolism. This suggests that DNA damage was imminent or peaked within 6h. The results conformed to transcriptional changes in B(a)P exposed worms and compliment other approaches to elucidate underlying molecular changes.
-
Responses of Lumbriculus variegatus to activated carbon amendments in uncontaminated sediments.
Environmental science & technology, 2012Co-Authors: Inna Nybom, Jussi V. K. Kukkonen, David Werner, Matti T. Leppänen, George Siavalas, Kimon Christanis, Hrissi K. Karapanagioti, Jarkko AkkanenAbstract:Activated carbon (AC) amendment is a recently developed sediment remediation method. The strong hydrophobic organic contaminant sorption efficiency of AC has been shown in several studies, but effects on benthic organisms require more investigation. The AC induced effects on egestion rate, growth and reproduction of Lumbriculus variegatus were studied by applying bituminous coal based AC in three different particle size fractions, namely
Almut Gerhardt - One of the best experts on this subject based on the ideXlab platform.
-
Effect of the exposure to metal lead on the regenerative ability of Lumbriculus variegatus (Oligochaeta).
Environmental toxicology and pharmacology, 2010Co-Authors: Ana Margarida Sardo, Almut Gerhardt, Lourdes Pereira, Amadeu M.v.m. SoaresAbstract:Lumbriculus variegatus is a recommended species for use in sediment toxicity tests and is known to have a remarkable power of segmental regeneration. Here, we tested the effects of a chemical stressor on the regenerative ability of L. variegatus and investigated the potential of regenerative ability as an additional new parameter in standard toxicity tests. The worms were cut into two equal segments, and exposed to various concentrations of lead. Two assays were performed: one with sediment spiked with lead and the other with water spiked with lead. The endpoints were segmental regeneration, survival and behaviour. Regenerative ability was clearly affected by exposure to lead-contaminated sediment and lead-contaminated water. Organisms exposed to lead grew more slowly than those not exposed; worms exposed to contaminated water showed higher mortalities than those exposed to contaminated sediment. Results showed that L. variegatus’ regenerative ability, as a developmental test parameter, is more sensitive than mortality.
-
importance of exposure route for behavioural responses in Lumbriculus variegatus muller oligochaeta lumbriculida in short term exposures to pb
Environmental Science and Pollution Research, 2007Co-Authors: Almut GerhardtAbstract:Goal, Scope and Background Lumbriculus variegatus Muller (Oligochaeta), a common freshwater sediment-dweller, has frequently been used in toxicokinetic studies, although has been less used in ecotoxicity tests.
-
Behavior, Growth, and Reproduction of Lumbriculus variegatus (Oligochaetae) in Different Sediment Types
Human and Ecological Risk Assessment: An International Journal, 2007Co-Authors: A. M. Sardo, Amadeu M.v.m. Soares, Almut GerhardtAbstract:Lumbriculus variegatus is an oligochaete widely used in sediment toxicity tests. The locomotory behavior of adults from a normal and a clone population was studied in the Multispecies Freshwater Biomonitor™ along with growth and reproduction to determine how different sediment types may affect this worm and forced clones during testing. Four different sand size classes were established by sieving: fine ( 2 mm), and whole sediment. Locomotory activity was highest in fine and then in coarse sediment, while in whole and medium sediment size classes worms grew and reproduced less, and had lower locomotory activity levels. Fine sediment (< 1 mm) should be used as the negative control in L. variegatus whole sediment toxicity tests. A clone population, generated by cutting all worms over six generations, showed lower locomotory activity levels than normal worms. Artificial cloning is not recommended for obtaining additional test organisms.
Peter F. Landrum - One of the best experts on this subject based on the ideXlab platform.
-
Uptake and depuration of nonionic organic contaminants from sediment by the oligochaete, Lumbriculus variegatus
Environmental toxicology and chemistry, 2003Co-Authors: Christopher G. Ingersoll, David R. Mount, Gerald T. Ankley, Eric L. Brunson, Ning Wang, F. James Dwyer, James N. Huckins, Jim D. Petty, Peter F. LandrumAbstract:Uptake of sediment-associated contaminants by the oligochaete Lumbriculus variegatus was evaluated after 1, 3, 7, 14, 28, and 56 d of exposure to a field-collected sediment contaminated with DDT and its metabolites, dichlorodiphenyldichloroethane (DDD) and dichlorodiphenyldichloroethylene (DDE), or to a field-collected sediment contaminated with polycyclic aromatic hydrocarbons (PAHs). Depuration of contaminants by oligochaetes in a control sediment or in water was also evaluated over a 7-d period after 28 d of exposure to the field-collected sediments. Accumulation of PAHs with a log octanol-water partitioning coefficient (log Kow) 5.6 or DDD and DDE typically exhibited a steady increase from day 1 to about day 14 or 28, followed by a plateau. Therefore, exposures conducted for a minimum of 14 to 28 d better reflected steady-state concentrations for DDT and its metabolites and for PAHs. Depuration rates for DDT and its metabolites and high-Kow PAHs were much higher in organisms held in clean sediment relative to both water-only depuration and model predictions. This suggests that depuration in clean sediment may artificially accelerate depuration of hydrophobic compounds. Comparisons between laboratory-exposed L. variegatus and oligochaetes collected in the field from these sediments indicate that results of laboratory tests can be extrapolated to the field with a reasonable degree of certainty.
-
Biological responses of Lumbriculus variegatus exposed to fluoranthene-spiked sediment.
Archives of environmental contamination and toxicology, 2002Co-Authors: Peter F. Landrum, M. L. Gedeon, G. A. Burton, Marc S. Greenberg, Carolyn D. RowlandAbstract:Lumbriculus variegatus was used as a bioassay organism to examine the impact of the sediment-associated polycyclic aromatic hydrocarbon (PAH) fluoranthene on be- havior, reproduction, and toxicokinetics. The number of worms increased between the beginning and end of the experiment at 59 gg 1 fluoranthene, but at the next higher treatment (108 gg 1 ) the number of worms found was lower and not different from the control. Worms exposed to 95 gg 1 also exhibited increased reproduction when fed a yeast-cerophyl- trout chow mixture. On a total biomass basis, only the 95 g g 1 exposure with food exhibited a statistically significant increase over the nonfed control. Evaluation of reproduction at the two highest treatments was compromised by a brief aera- tion failure 2 days before the end of the experiment. The behavioral responses were followed as changes in biological burial rate (sediment reworking rate) of a 137 Cs-labeled marker layer. The biological burial rate increased toward a plateau as the concentration increased from the control (3.9 gg 1 dry weight total PAH) to 355 gg 1 dry weight fluoranthene in sediment. The aeration failure had minimal impact on the determination of reworking rate because all the data for the rate determination were collected prior to the aeration failure. Up- take and elimination rates declined with increasing treatment concentration across the range of fluoranthene concentrations, 59 -355 gg 1 dry weight sediment. The disconnect between the increasing biological burial rates and the decreasing toxicokinetics rates with increasing exposure concentration demonstrates that the toxicokinetic processes are dominated by uptake and elimination to interstitial water. The bioaccumulation factor (concentration in the organisms on a wet weight basis divided by the concentration in sediment on a dry weight basis) ranged from 0.92 to 1.88 on day 10 and declined to a range of 0.52 to 0.99 on day 28 with the lowest value at the highest dose.
-
Lethal and sublethal body residues for PCB intoxication in the oligochaete, Lumbriculus variegatus
Aquatic Toxicology, 1999Co-Authors: Susan W. Fisher, Stephen W. Chordas, Peter F. LandrumAbstract:The oligochaete, Lumbriculus variegatus, was used to examine the utility of critical body residues in describing lethal and sublethal chronic endpoints during polychlorinated biphenyls (PCB) exposure. L. variegatus was exposed to four 14C-PCB congeners and 2,2-bis-(p-chlorophenyl)-1,1-dichloroethylene (DDE) on algal cells. Accumulation and resulting effects were monitored in 10-day acute and 35-day chronic exposures. L. variegatus was resistant to the acute lethal narcotic effects of these contaminants and no mortality was obtained in 10-day exposures. However, mortality that was significantly different from unexposed controls occurred for four compounds in 35-day assays; average body residues for chronic mortality were consistent among contaminants (0.88–1.35 mmol kg−1). Kinetic studies showed that failure to generate mortality in some exposures was due to rapid elimination. Mono-2-chlorobiphenyl, for instance, had a Kd of 0.22 h−1 which was seven to 44 times faster than for the other contaminants. Sublethal reductions in body mass and reproduction occurred at lower body residues than were needed to produce mortality (0.34–0.56 mmol kg−1). The consistency of the sublethal data suggests that they may offer a means of interpreting residue data for PCBs in the environment.
-
effects of sediment bound polydimethylsiloxane on the bioavailability and distribution of benzo a pyrene in lake sediment to Lumbriculus variegatus
Environmental Toxicology and Chemistry, 1995Co-Authors: Jussi V. K. Kukkonen, Peter F. LandrumAbstract:Oligochaetes, Lumbriculus variegatus, were exposed to Lake Michigan sediment spiked in the laboratory with polydimethylsiloxane (PDMS) at two different concentrations. Additionally, these sediment samples and one without PDMS were spiked with benzo[a]pyrene (BaP). The accumulation of PDMS and BaP, survival, wet weight, and defecation of the animals were monitored. Lumbriculus variegatus accumulated sediment-associated BaP rapidly and achieved steady state within 96 to 168 h. The BaP uptake clearances were 0.069, 0.060, and 0.056 for BaP only, BaP with low-dose PDMS, and BaP with high-dose PDMS exposures, respectively. The BaP bioaccumulation factor was reduced by PDMS in the sediment. Only very low concentrations of PDMS were found associated with the worms, which suggests some surface sorption or association with material in the gut. Elimination of BaP in clean sediment was rapid, but elimination in water was much slower. Elimination rate constants for BaP, k{sub c}, were 0.0229 {+-} 0.0011 h{sup {minus}1} for sediment and 0.0004 {+-} 0.0004 h{sup {minus}1} water-only depuration. The PDMS was excreted within 10 h both in sediment and water-only depuration exposures, indicating that most of the measured body burden was due to the sediment-associated material inside the organisms` gut. Animals were not purged before analyses, and severalmore » approaches were investigated for estimating the contribution of the intestinal contents. Based on both measurements and calculations, sediment-associated BaP in the gut contributes less than 10% of total body burden. Thus, a 10-h water-only purge was found to be the most appropriate method for eliminating the gut-content influence on the body burden.« less
-
Effects of sediment‐bound polydimethylsiloxane on the bioavailability and distribution of benzo[a]pyrene in lake sediment to Lumbriculus variegatus
Environmental Toxicology and Chemistry, 1995Co-Authors: Jussi V. K. Kukkonen, Peter F. LandrumAbstract:Oligochaetes, Lumbriculus variegatus, were exposed to Lake Michigan sediment spiked in the laboratory with polydimethylsiloxane (PDMS) at two different concentrations. Additionally, these sediment samples and one without PDMS were spiked with benzo[a]pyrene (BaP). The accumulation of PDMS and BaP, survival, wet weight, and defecation of the animals were monitored. Lumbriculus variegatus accumulated sediment-associated BaP rapidly and achieved steady state within 96 to 168 h. The BaP uptake clearances were 0.069, 0.060, and 0.056 for BaP only, BaP with low-dose PDMS, and BaP with high-dose PDMS exposures, respectively. The BaP bioaccumulation factor was reduced by PDMS in the sediment. Only very low concentrations of PDMS were found associated with the worms, which suggests some surface sorption or association with material in the gut. Elimination of BaP in clean sediment was rapid, but elimination in water was much slower. Elimination rate constants for BaP, k{sub c}, were 0.0229 {+-} 0.0011 h{sup {minus}1} for sediment and 0.0004 {+-} 0.0004 h{sup {minus}1} water-only depuration. The PDMS was excreted within 10 h both in sediment and water-only depuration exposures, indicating that most of the measured body burden was due to the sediment-associated material inside the organisms` gut. Animals were not purged before analyses, and severalmore » approaches were investigated for estimating the contribution of the intestinal contents. Based on both measurements and calculations, sediment-associated BaP in the gut contributes less than 10% of total body burden. Thus, a 10-h water-only purge was found to be the most appropriate method for eliminating the gut-content influence on the body burden.« less
Charles D. Drewes - One of the best experts on this subject based on the ideXlab platform.
-
Behavioral effects of ivermectin in a freshwater oligochaete, Lumbriculus variegatus.
Environmental toxicology and chemistry, 2001Co-Authors: Jing Ding, Charles D. Drewes, Walter H. HsuAbstract:Ivermectin is a potent antiparasitic drug against nematode and arthropod parasites. In this study, we examined the lethal and sublethal effects of ivermectin in a freshwater oligochaete, Lumbriculus variegatus. The median lethal concentration (LC50) at 72 h after ivermectin exposure was 560 nM. Sublethal endpoints focused on several stimulus-evoked locomotor behaviors: escape reflexes controlled by giant interneuron pathways, swimming and reversal, and crawling. Swimming, reversal, and crawling are controlled by nongiant interneuron pathways. Ivermectin inhibited swimming, reversal, crawling frequency, and crawling speed in a time- and concentration-dependent manner with a mean inhibitory concentration (IC50) at 3 h of 1.1, 16, 91, and 51nM, respectively. Ivermectin at 0.3 nM also significantly decreased the frequency of helical swimming waves. Picrotoxin, a Cl− channel blocker, antagonized the ivermectin-induced decrease in swimming frequency, crawling frequency, and crawling speed. There were no adverse effects on escape reflex 3 h after exposure to 300 nM ivermectin. Electrophysiological recordings showed that ivermectin had no effects on the conduction velocity of giant fiber systems. The results indicated that locomotor behaviors controlled by nongiant locomotor pathways were more sensitive to ivermectin than pathways controlled by giant interneurons and that Cl− channels may be involved in mediating ivermectin's inhibitory effects.
-
Autotomy reflex in a freshwater oligochaete, Lumbriculus variegatus (Clitellata: Lumbriculidae)
Aquatic Oligochaetes, 1999Co-Authors: Nalena M. Lesiuk, Charles D. DrewesAbstract:A novel apparatus was developed that induced segmental autotomy in the freshwater oligochaete, Lumbriculus variegatus. The apparatus delivered a quantifiable amount of focal compression to the dorsal body surface at a selected site along the worm. This resulted in a rapid and stereotyped autotomy sequence, beginning with formation of a lateral fissure in the body just anterior to the compression site. Formation of the fissure usually occurred 100– 200 ms after the onset of compression. Autotomy readily occurred in the absence of significant longitudinal tension at the autotomy site and in the absence of direct laceration of the body wall. Autotomy culminated in a complete, transverse separation and sealing of anterior and posterior body fragments with no apparent blood loss from either end. There was a direct relationship between the amount of compression and the probability of autotomy in both midbody and tail regions. However, there was a consistently greater probability of autotomy in tail versus midbody regions. Autotomy did not occur if the duration of compression was less than 77 ms. Autotomy responses were suppressed in dose-dependent manner by a 15 min treatment with nicotine prior to compression. In instances where compression just failed to induce autotomy there was no evidence of disruption of impulse conduction in giant nerve fibers. Rapid and clear-cut autotomy, in combination with this worm’s significant capacity for regeneration of lost segments, are adaptively significant strategies for surviving predatory attack.
-
Helical swimming and body reversal behaviors in Lumbriculus variegatus (Annelida: Clitellata: Lumbriculidae)
Aquatic Oligochaetes, 1999Co-Authors: Charles D. DrewesAbstract:Two unusual locomotor behaviors (body reversal and helical swimming) are described and related to postembryonic body size in the freshwater oligochaete, Lumbriculus variegatus (Annelida: Clitellata: Lumbriculidae). Both behaviors occur as responses to tactile stimulation when worms are on smooth substrates that offer little or no traction or protection. Body reversal, evoked by touch to anterior segments, involves a stereotyped sequence of bending movements that effectively reverse head and tail positions in about 0.4 s in newly hatched worms and 0.6 s in juvenile and adult worms. Though little net shift in the body center occurs, reversal may optimize body positioning in preparation for swimming away from predatory threat. In contrast to reversal, swimming is evoked by touch to posterior segments and consists of a rapid, rhythmic sequence of helical body waves (frequency ≈9–11 Hz). Waves alternate between clockwise and counterclockwise helical orientations, with posterior passage of each wave providing forward thrust. Swim velocity and wave velocity increase with body size. Though total distance and duration of each swim episode is short (≈1–2 body lengths in < 2 s), swimming may be an important means of predator avoidance in the littoral environment of these worms.
-
Assessing sublethal neurotoxicity effects in the freshwater oligochaete, Lumbriculus variegatus
Aquatic Toxicology, 1993Co-Authors: Richard W. Rogge, Charles D. DrewesAbstract:Abstract The sublethal neurotoxic and behavioral effects of five chemicals (4-aminopyridine, cadmium chloride, carbofuran, chloroform and diazinon) were examined in the freshwater oligochaete, Lumbriculus variegatus (Family Lumbriculidae), following short-term exposure by immersion. Noninvasive electrophysiological recordings of touch-evoked medial giant nerve fiber (MGF) spikes were obtained, before and after exposure, using printed circuit board recording grids. Neurotoxic effects included substantial, and reversible, decreases in MGF conduction velocity following exposure to all chemicals, except CdCl 2 . Reversible losses of MGF touch sensitivity occurred with exposure to chloroform and CdCl 2 . Hypersensitivity of the MGF to touch, accompanied by high-frequency spike trains and rebound spikes, occurred with exposure to 4-aminopyridine. Our approach provides a rapid and sensitive means of detecting and differentiating sublethal neurotoxic effects, in vivo, in this cosmopolitan benthic oligochaete.
-
Morphallaxis in an aquatic oligochaete, Lumbriculus variegatus: reorganization of escape reflexes in regenerating body fragments.
Developmental biology, 1990Co-Authors: Charles D. Drewes, Charles R. FourtnerAbstract:We describe functional and anatomical correlates of the reorganization of giant nerve fiber-mediated escape reflexes in body fragments of an aquatic oligochaete, Lumbriculus variegatus, a species that reproduces asexually by fragmentation. Since fragments from any axial position always regenerate short heads (seven or eight segments long) and much longer tail sections, segments originating from posterior fragments become transposed along the longitudinal axis and acquire, by morphallaxis, features of escape reflex organization that conform to their new anterior position. Using noninvasive electrophysiological recordings we have quantified, on a day-to-day and a segment-by-segment basis, the reorganization that occurs in sensory field arrangements of the medial (MGF) and lateral (LGF) giant nerve fibers, as well as changes in giant fiber conduction velocity and morphometry. Our results show that (1) posterior fragments, originally subserved by the LGF sensory field gradually become subserved by the MGF sensory field; (2) appropriate increases in the ratio of MGF:LGF cross-sectional area, perimeter, and conduction velocity accompany the reorganization in giant fiber sensory fields; and (3) sensory field reorganization can be repeatedly reversed by additional amputations. These results demonstrate that the functional organization of escape reflexes is highly plastic and that morphallaxis may result from the counterbalance of morphogenic influences localized within the anterior and posterior ends of regenerating body fragments.
