Home About us Contact
|
Home About us Contact | ||
|
|
||
Feeding Inhibition (feeding + inhibition)
Selected AbstractsToxicity of short-chain alcohols to the nematode Caenorhabditis elegans: A comparison of endpointsJOURNAL OF BIOCHEMICAL AND MOLECULAR TOXICOLOGY, Issue 2 2005Grace Thompson Abstract The toxicities of 4 short-chain alcohols,namely methanol, ethanol, iso -propanol and iso -butanol,were compared in the nematode Caenorhabditis elegans using several different ecotoxicological endpoints. Range-finding tests were conducted using transgenic PC161 worms carrying a double reporter construct (GFP plus lacZ) linked to the stress-inducible hsp16-1 promoter. These tests showed little response from the GFP reporter, but gave good dose,response curves for the lacZ reporter,showing clear induction at 0.5% v/v ethanol in an overnight assay, but only at 4% in a shorter 6-h assay. Comparison of the short-term dose,response curves shows a confusing pattern of differences between the four alcohols tested, although dose-dependence is evident across at least part of the concentration range. Feeding inhibition assays are somewhat inconclusive with regard to alcohol type, although iso -butanol and iso -propanol appear more toxic than ethanol, while methanol is least toxic. To resolve some of the remaining ambiguities, we also used a fecundity assay to show that iso -propanol is more toxic than ethanol, and a lethality assay to show that iso -butanol is more toxic than iso -propanol. Most of the endpoints studied are consistent with the following order of toxicity: iso -butanol > iso -propanol > ethanol , methanol. © 2005 Wiley Periodicals, Inc. J Biochem Mol Toxicol 19:87,95, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/jbt.20060 [source] Effects of insecticide exposure on feeding inhibition in mayflies and oligochaetesENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 8 2007Alexa C. Alexander Abstract The present study examined the effects of pulse exposures of the insecticide imidacloprid on the mayfly, Epeorus longimanus Eaton (Family Heptageniidae), and on an aquatic oligochaete, Lumbriculus variegatus Müller (Family Lumbriculidae). Pulse exposures of imidacloprid are particularly relevant for examination, because this insecticide is relatively soluble (510 mg/L) and is most likely to be at effect concentrations during runoff events. Experiments examined the recovery of organisms after a 24-h pulse exposure to imidacloprid over an environmentally realistic range of concentrations (0, 0.1, 0.5, 1, 5, and 10 ,g/L). Effects on feeding were measured by quantifying the algal biomass consumed by mayflies or foodstuffs egested by oligochaetes. Imidacloprid was highly toxic, with low 24-h median lethal concentrations (LC50s) in early mayfly instars (24-h LC50, 2.1 ± 0.8 ,g/L) and larger, later mayfly instars (24-h LC50, 2.1 ± 0.5 ,g/L; 96-h LC50, 0.65 ± 0.15 ,g/L). Short (24-h) pulses of imidacloprid in excess of 1 ,g/L caused feeding inhibition, whereas recovery (4 d) varied, depending on the number of days after contaminant exposure. In contrast to mayflies, oligochaetes were relatively insensitive to imidacloprid during the short (24-h) pulse; however, immobility of oligochaetes was observed during a 4-d, continuous-exposure experiment, with 96-h median effective concentrations of 6.2 ± 1.4 ,g/L. Overall, imidacloprid reduced the survivorship, feeding, and egestion of mayflies and oligochaetes at concentrations greater than 0.5 but less than 10 ,g/L. Inhibited feeding and egestion indicate physiological and behavioral responses to this insecticide. [source] Postexposure feeding depression: A new toxicity endpoint for use in laboratory studies with Daphnia magnaENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 6 2002Ruth A. McWilliam Abstract In situ bioassays with daphnids currently employ lethality as an endpoint, and although sublethal responses (reproduction and feeding rate) can be measured in the field, such endpoints pose major practical challenges. Previous studies have indicated that Daphnia magna exposed to toxic substances can exhibit delayed recovery in feeding behavior (postexposure feeding depression). This simple, robust response has the potential to be an ecologically relevant and potentially diagnostic endpoint. This study developed and tested the use of postexposure feeding depression as a toxicity endpoint in the laboratory environment. First, replicate numbers were manipulated to produce statistically reliable results. Second, postexposure feeding depression in D. magna was studied under laboratory conditions, by employing toxic substances with differing modes of action. Although most substances caused feeding inhibition during direct exposure, not all substances produced postexposure feeding depression. However, the use of lethality as a supplementary endpoint provided an alternative measure when no feeding depression was apparent after exposure. In combination, these endpoints offer a potentially more sensitive, ecologically relevant alternative to the use of lethality alone for in situ bioassay studies. [source] Acotiamide (Z-338) as a possible candidate for the treatment of functional dyspepsiaNEUROGASTROENTEROLOGY & MOTILITY, Issue 6 2010H. Suzuki Abstract Acotiamide hydrochloride is a novel upper gastrointestinal (GI) motility modulator and stress regulator currently being developed for the treatment of functional dyspepsia (FD). The mechanism underlying the enhancement of GI motility by this agent has been proposed to be based on its muscarinic antagonism and inhibitory effects on acetylcholinesterase activity. Pathophysiological studies showed that acotiamide significantly improved both delayed gastric emptying and feeding inhibition in restraint stress-induced model, but did not affect both normal gastric emptying and feeding in intact animals, indicating that acotiamide exerted effects only on the impaired gastric emptying and feeding behavior. According to the clinical pilot study in Europe, acotiamide, at the dose of 100 mg t.i.d., showed to improve the symptoms and quality of life of patients with FD, indicating the need for larger scale symptomatic studies on the efficacy of acotiamide in patients with FD. The recent phase II studies conducted in Japan presented in this issue of the journal also confirmed that acotiamide, at the optimal dose of 100 mg, has potential therapeutic efficacy, especially for meal-related FD symptoms. Although a phase III study is on going, acotiamide is now expected as a novel treatment option for FD. [source] Acotiamide hydrochloride (Z-338), a novel prokinetic agent, restores delayed gastric emptying and feeding inhibition induced by restraint stress in ratsNEUROGASTROENTEROLOGY & MOTILITY, Issue 9 2008K. Seto Abstract, Acotiamide hydrochloride (Z-338) is a member of new class prokinetic agents currently being developed for the treatment of functional dyspepsia (FD). DNA microarray analysis showed that acotiamide altered the expressions of stress-related genes such as , -aminobutyric acid (GABA) receptors, GABA transporters and neuromedin U (NmU) in the medulla oblongata or hypothalamus after administration of acotiamide. Therefore, effects of acotiamide on stress-related symptoms, delayed gastric emptying and feeding inhibition, in rats were examined. Acotiamide significantly improved both delayed gastric emptying and feeding inhibition in restraint stress-induced model, but did not affect both basal gastric emptying and feeding in intact rats, indicating that acotiamide exerted effects only on gastric emptying and feeding impaired by the stress. On the other hand, mosapride showed significant acceleration of gastric emptying in intact and restraint stress-induced model, and itopride showed no effect on restraint stress-induced delayed gastric emptying. In addition, gene expression of NmU increased by restraint stress was suppressed by administration of acotiamide, while acotiamide had no effect on delayed gastric emptying induced by an intracerebroventricular administration of NmU, suggesting that the suppressive effect of acotiamide on gene expression of NmU might be important to restore delayed gastric emptying or feeding inhibition induced by restraint stress. These findings suggest that acotiamide might play an important role in regulation of stress response. As stress is considered to be a major contributing factor in the development of FD, the observed effects may be relevant for symptom improvement in FD. [source] Effects on litter-dwelling earthworms and microbial decomposition of soil-applied imidacloprid for control of wood-boring insectsPEST MANAGEMENT SCIENCE (FORMERLY: PESTICIDE SCIENCE), Issue 2 2008David P Kreutzweiser Abstract BACKGROUND: Imidacloprid is an effective, systemic insecticide for the control of wood-boring insect pests in trees. Systemic applications to trees are often made by soil injections or drenches, and the resulting imidacloprid concentrations in soil or litter may pose a risk of harm to natural decomposer organisms. The authors tested effects of imidacloprid on survival and weight gain or loss of the earthworms Eisenia fetida (Savigny) and Dendrobaena octaedra (Savigny), on leaf consumption rates and cocoon production by D. octaedra and on microbial decomposition activity in laboratory microcosms containing natural forest litter. RESULTS:Dendrobaena octaedra was the most sensitive of the two earthworm species, with an LC50 of 5.7 mg kg,1, an LC10 of about 2 mg kg,1 and significant weight losses among survivors at 3 mg kg,1. Weight losses resulted from a physiological effect rather than from feeding inhibition. There were no effects on cocoon production among survivors at 3 mg kg,1. The LC50 for E. fetida was 25 mg kg,1, with significant weight losses at 14 mg kg,1. There were no significant effects on microbial decomposition of leaf material at the maximum test concentration of 1400 mg kg,1. CONCLUSION: The results indicate that, when imidacloprid is applied as a systemic insecticide to the soil around trees, it is likely to cause adverse effects on litter-dwelling earthworms if concentrations in the litter reach or exceed about 3 mg kg,1. Copyright © 2007 Her Majesty the Queen in the Right of Canada, Canadian Forest Service. Published by John Wiley & Sons, Ltd. [source] Susceptibility of the pine processionary caterpillar Thaumetopoea pityocampa (Lepidoptera: Thaumetopoeidae) toward ,-endotoxins of Bacillus thuringiensis under laboratory conditionsANNALS OF APPLIED BIOLOGY, Issue 3 2001A B SHEVELEV Summary A series of natural crystal proteins from B. thuringiensis subsp. Alesti 12,25, caucasicus, galleriae 11,67, galleriae 6,96, kenyae, and shondungensis and spore-crystal preparations from finitimus 11,66 and from a recombinant strain of B. thuringiensis subsp. kurstaki expressing Cry 1 Ga1 only, were assessed as a toxic agent for the pine processionary caterpillar, Thaumetopoea pityocampa. Some preparations had a thoroughly investigated composition and contained Cry1Aa, Cry1Ab2, Cry1Ab7, Cry1D, Cry1F, Cry 1 Ga1, Cry9Aa, Cry26 crystal proteins, whereas crystals of B. thuringiensis subsp. caucasicus, kenyae, and shondungensis harboured predominantly unidentified toxins distant from commonly used prototypes. Bioassays were based on the simultaneous assignment of each treatment to groups of 20 full sibling first-instar larvae, obtained from broods of a population from North-western Italy. The toxin was applied to pine needles by the leaf dipping method and the effect was registered in both feeding inhibition and mortality. B. thuringiensis subsp. caucasicus, kenyae, galleriae 6,96, alesti, and galleriae 11,67 gave the best results in terms of both feeding inhibition and larval mortality. Broods tested in B. thuringiensis bioassays showed a substantial variation in susceptibility to the toxins, suggesting the potential development of resistance in the population. [source] | |||||||||||||