Concentrations of metallothionein-like proteins and heavy metals in the freshwater snail Lymnaea stagnalis exposed to different levels of waterborne cadmium.
Explore the source record for details and available documents.
Animals↗
Biomedical subjects
J W Lewis
Publications and source records attributed to J W Lewis.
Fish macroparasites as indicators of heavy metal pollution in river sites in Austria.
This paper describes two approaches to evaluate the use of fish macroparasites as bioindicators of heavy metal pollution at selected river stretches in Austria. Firstly changes in the diversity and richness of endoparasites of the cyprinid barbel, Barbrus barbuls (L.), were tested in relation to heavy metal contents in the aquatic system. Secondly, the bioaccumulation potential of cadmium, lead and zinc was assessed in the acanthocephalan, Pomphorhynchus laevis (Miller, 1776), and compared with that in the muscle, liver and intestine of its barbel host. The present results indicated that in order to validate the role of parasite community patterns related to heavy metal pollution, more investigations on food web dynamics, interelationships between parasites and the presence/absence of intermediate hosts will be essential. Heavy metal concentrations differed significantly between the organs of barbel and P. laevis (P=0.001) with levels up to 2860 fold in the parasite. The high level of heavy metal accumulation in P. laevis compared with that in its barbel host, suggests that despite variability in the parasite infrapopulation, host mobility and feeding behaviour, P. laevis is a most sensitive indicator of heavy metals in aquatic ecosystems.
Acanthocephala↗
Pollution toxicity to the transmission of larval digeneans through their molluscan hosts.
The increased occurrence of pollutants in ecosystems is a continuing area of concern. It is known that numerous diseases of wild aquatic animals can occur with decreased or increased prevalences in areas associated with high or chronic levels of pollution. This may have serious implications for environmental health. There has consequently been an increasing number of laboratory and field studies on disease transmission under polluted conditions, especially focusing on digeneans of medical or economic importance. The effect of pollutants to the transmission of larval digeneans (miracidia, cercariae, metacercariae) and snail-digenean interactions is therefore considered. An overview and interpretation of the published literature on laboratory and field studies is provided. It is apparent from these studies that the influence of pollutants on digenean transmission is highly complex with much of the observed effects in the laboratory often masked by a complexity of other factors in the field. Future studies would benefit from a standardisation of experimental procedures, increasing the number of combined laboratory and field studies, and increasing the complexity of the experiments undertaken.
Animals↗
Inflammatory interactions in fish exposed to pollutants and parasites: a role for apoptosis and C reactive protein.
Although previous studies have highlighted the inflammatory responses of fish infected with parasites and exposed to pollutants, very little is known about how these two stressors interact within the fish. In this review, which also contains original data, the effect of these two parameters on the fish inflammatory response is assessed and, in particular, the role of apoptosis and the acute phase protein, C reactive protein, is evaluated. In Cyprinus carpio exposed to 0.5 mg NH4+ l(-1) or 0.1 mg Cd2+ l(-1) and experimentally infected with the blood fluke, Sanguinicola inermis, the pollutant type and the order in which the fish experiences the parasite and toxicant, significantly affects the ultrastructural appearance and cellular content of the pronephros and thymus. This is reflected in the intensity of infection where the pollutant appears to have less effect on an established infection. Both stressors, pollutant and infection, may mediate their effects via the endocrine system. Studies have revealed that cortisol at 100 ng ml(-1) is able to induce apoptosis in pronephric cells of carp and that an increase in apoptosis is associated with an increase in phagocytosis in this immune organ. In addition, C reactive protein, which is used as a biomarker of the inflammatory response in humans and other mammals, is evaluated as a possible indicator of physiological states in fish exposed to pathogens and pollutants.
Ammonia↗
Parasite infracommunity diversity in eels: a reflection of local component community diversity.
The intestinal macroparasite communities of freshwater eels (Anguilla anguilla) captured in the south of England from Windsor (River Thames) during August 2001, and Leckford (River Test) during late June/July 2000, are reported for the first time. Parasite component communities were among the most species rich and diverse recorded from European eels. A total of 13 intestinal macroparasite species were encountered during the study, 8 from each eel host population with 3 being common to both. Acanthocephalans, nematodes and cestodes were recovered from each host population. Eels from Windsor additionally harboured Nicolla gallica (Digenea), which was also the most prevalent and abundant macroparasite species in these hosts. Each component community followed a log normal rank abundance distribution and demonstrated reduced species dominance and increased species equitability compared with previous studies. As such, the study component communities were suitable for testing the hypothesis of low infracommunity diversity in European eel hosts. Specifically, this hypothesis predicts that the intestinal macroparasite infracommunities of European eels are species-poor, displaying low density and diversity with high dominance, irrespective of component community diversity, and that this may be more pronounced in UK host populations. This hypothesis was not upheld; study findings demonstrate that higher infracommunity diversity in eel hosts is possible, and suggest that infracommunity diversity in individual eel hosts may be a simple, stochastic reflection of component community diversity.
Anguilla↗
Toxicity of cadmium and zinc to the decaudised cercarial life-span of Diplostomum spathaceum (Trematoda: Diplostomidae).
The toxicity of cadmium and zinc at concentrations ranging from 0.1 to 10000 microg/l to the life-span of decaudised cercarial bodies (cercariae that have shed their tails) of Diplostomum spathaceum was investigated. The effects of metal exposure at 3 temperatures (12, 20, and 25 degrees C) and 3 levels of water hardness (distilled water, soft water and hard water) were studied. In general, under most experimental conditions increasing metal concentrations reduced the life-span of decaudised cercariae. Increasing water hardness and decreasing water temperature caused an increase in the life-span of both control and metal exposed decaudised cercariae. However, at certain isolated metal concentrations, associated with a specific level of water hardness and temperature, increased survival above controls occurred. Differences in the relative toxicity of cadmium and zinc were dependent on the environmental conditions of exposure. The decaudised cercarial life-span under metal exposure was found to be generally independent of the overall cercarial survival and tail loss in most experimental conditions. Prolonged exposure to cadmium and zinc caused changes in the decaudised cercarial life-span when compared to individuals decaudised during the initial 24 h exposure period to those which were decaudised during the final 24 h period of cercarial survival. The validity of studying the decaudised cercarial life-span as an indicator of 'fitness' of larvae to migrate through the tissues of the target fish host, in terms of glycogen utilization, was assessed for those cercariae decaudised during the initial 24 h exposure period only. A limited reduction in the decaudised cercarial life-span during this period compared to controls was recorded, which may possibly indicate a reduced penetration 'fitness' of cercariae exposed to cadmium and zinc. The importance and relevance of these findings to parasite migration and establishment in the fish host are discussed.
Animals↗
Cadmium toxicity and snail-digenean interactions in a population of Lymnaea spp.
The toxicity of cadmium to a population of Lymnaea peregra and L. stagnalis naturally infected with a range of digeneans and collected from a number of sites in the lower Thames Valley, UK was investigated. Lymnaeid snails were exposed to 100 microg l-1 cadmium and the effects on host survival and emergence of cercariae recorded. Overwintered L. peregra, but not L. stagnalis, showed significantly reduced survival compared to seasonally infected snails, i.e. snails which have acquired an infection during the spring or summer. A significant increase in survival with increasing snail size was demonstrated for L. stagnalis and for seasonally infected L. peregra only. Only L. stagnalis infected with Diplostomum spathaceum and L. peregra infected individually with D. spathaceum, Sanguinicola inermis, Echinoparyphium recurvatum and Notocotylus attenuatus demonstrated a significantly reduced survival compared to laboratory-bred controls. The exposure of L. stagnalis to cadmium resulted in a significant reduction in the emergence of D. spathaceum over a 5-day period but cadmium-exposed L. peregra showed no difference in the emergence of E. recurvatum cercariae over a 3-day exposure period. The mechanisms and importance of metal toxicity to snail-digenean interactions are discussed.
Animals↗
Cadmium-induced cellular and immunological responses in Cyprinus carpio infected with the blood parasite, Sanguinicola inermis.
Little is known about immune responses in teleosts as linked to the aetiology of pollutants and parasitic diseases and in particular their combined effects on the host. Cadmium(Cd)-mediated immunological responses in the thymus and pronephros of juvenile carp (Cyprinus carpio), experimentally infected with the blood parasite, Sanguinicola inermis (Trematoda: Sanguinicolidae) for 30 days followed by an exposure to 0.1 mg Cd2+ l(-1) for 48 or 168 h were investigated. Differential organ-specific changes occurred in both organs examined. In carp exposed to Cd, intracelluar spaces, vacuolation in the eosinophils, dissociation of cell membranes together with the formation of concentric whorls occurred. The thymus of infected carp exposed to Cd had a granular cytosol which contained vesicles with electron-dense inclusions, swollen mitochondria with distended cristae and condensed nuclei in the erythrocytes. Cell counts on the two organs revealed a differential response to cadmium exposure in S. inermis infected carp compared to control infected fish. A significant increase in the neutrophil, eosinophil and thrombocyte components occurred in the thymus in contrast to a significant decrease in pronephric neutrophils. In addition, there was a differential blastogenesis response in infected and Cd-exposed infected carp fry exposed to cercarial antigens and the mitogens, concanavalin A and pokeweed mitogen.
Animals↗
Toxicity of cadmium and zinc to encystment of Notocotylus attenuatus (Trematoda: Notocotylidae) cercariae.
The toxicity of cadmium, zinc, and cadmium/zinc mixtures at concentration ranging from 100 to 10,000 microg/L was investigated against the encystment strategy of free-living metacercarial stages of the parasitic fluke Notocotylus attenuatus. Exposure of encysting cercariae caused a reduction in encystment by all metals at concentrations of 1000 microg/L or higher. The formation of cyst associations was reduced in all metal-polluted test solutions. In addition, there was an increase in the number of floating metacercariae (cysts formed when not in contact with any surface) at low metal concentrations. The effects of metal toxicity to encystment strategy and its influence on transmission to the target host are briefly discussed.
Animals↗
Toxicity of cadmium and zinc mixtures to Diplostomum spathaceum (Trematoda: Diplostomidae) cercarial survival.
The toxicity of cadmium and zinc mixtures at concentrations ranging from 0.1 to 10,000 microg/L was investigated against the survival of the free-living cercarial stage of the parasitic fluke Diplostomum spathaceum. Cercariae were exposed to metal mixtures of equal concentration, metal mixtures of unequal concentration, and low-dose pretreatment followed by high-dose exposure mixtures. Under all exposures cercarial survival was increased compared to that achieved with single metals. At exposures with metal mixture of equal concentration in the range 0.1-100 microg/L survival was increased compared to that achieved by controls. The mechanism of metal toxicity and their effects on cercarial survival are discussed.
Animals↗
The osmotic relationship of the swimbladder nematode Anguillicola crassus with seawater eels.
The study was designed to test the hypothesis that the majority of individuals in a population of Anguillicola crassus can tolerate seawater by osmoconformation with the blood plasma of the eel host. The osmolality of the pseudocoelomic fluid of pre-adult and adult A. crassus was compared to the osmolality of eel plasma after eels were maintained in laboratory freshwater for 2 weeks (short-term transfer) or 3 months (long-term transfer) or in natural seawater for 2 h (acute transfer), 2 weeks or 3 months. The majority of A. crassus (at least 90% of the tested population) osmoconform with their hosts in seawater within +/-30 mOsm/kg of host osmolality. Some pre-adults and adults (15-21% of the total population) were unable to withstand osmotic stress resulting in vacuolation of the hypodermis and intestinal wall, and cuticular detachment. The reasons for variation in the tissue tolerance of A. crassus to increased osmolality of host plasma are unknown and are not related to maturity, sex or conditions in the swimbladder. Osmoconformation in the majority of the population, however, enables parasites to survive and reproduce for long periods in seawater eels. The adaptation of A. crassus to its euryhaline host has played an important part in the rapid spread of the swimbladder nematode in populations of the European eel.
Air Sacs↗
Toxicity of cadmium and zinc to cercarial tail loss in Diplostomum spathaceum (Trematoda: Diplostomidae).
The effect of cadmium and zinc at concentrations ranging from 0.1 to 10,000 microg/l on tail loss in cercariae of Diplostomum spathaceum was investigated at 3 temperatures (12, 20 and 25 degrees C) and 3 levels of water hardness (distilled water, soft water and hard water). Increasing tail loss over time was found to be linked with a parallel decrease in cercarial survival in controls. Exposure to the heavy metals induced, especially at high concentrations, a change in the relationship between cercarial tail loss and survival, causing either stimulation or inhibition of tail loss dependent on the individual toxic exposure. Under most environmental conditions the rate of tail loss over time was reduced by increasing metal concentrations. Inhibition of tail loss occurred in a limited number of both control and metal-exposed cercariae, with a number of low metal concentrations inducing greater inhibition than in controls. Stimulation of tail loss causing an increased tail loss rate above controls also occurred at certain high metal concentrations. Increasing water hardness and decreasing water temperature caused a reduced tail loss rate over time in both control and metal-exposed cercariae. However, with decreasing temperature a reduced rate of tail loss over time in metal-exposed cercariae compared to controls occurred at some low metal concentrations. When tail loss was compared against cercarial death of the experimental population toxic exposure induced changes in the parallel relationship of these parameters, dependent on individual metal concentration, water temperature and hardness. Differences in the relative effects of cadmium and zinc on cercariae were dependent on the environmental conditions of exposure. Both metals showed limited effects during the period of maximum cercarial infectivity (0-5 h). The mechanisms and importance of metal toxicity to cercarial tail loss are discussed.
Animals↗
Toxic effects of cadmium and zinc on the transmission of Echinoparyphium recurvatum cercariae.
The toxicity of cadmium, zinc and Cd/Zn mixtures to the transmission of Echinoparyphium recurvatum (Digenea: Echinostomatidae) cercariae into the snail second intermediate hosts was investigated at concentrations ranging from 100 microg l-1 to 10 000 microg l-1 in both soft and hard water. A differential response in the infectivity of metal-exposed cercariae into Lymnaea peregra and Physa fontinalis was demonstrated which was dependent on the snail species being infected. Exposure of L. peregra, P. fontinalis, and L. stagnalis to heavy metals caused a differing susceptibility to E. recurvatum cercariae depending on the snail species being exposed. The mechanism and effects of metal toxicity, together with the importance of the parasite/host strain on cercarial transmission are discussed.
Animals↗
Steric barrier to bathorhodopsin decay in 5-demethyl and mesityl analogues of rhodopsin.
Absorbance difference spectra were recorded from 20 ns to 1 micros after 20 degrees C photoexcitation of artificial visual pigments derived either from 5-demethylretinal or from a mesityl analogue of retinal. Both pigments produced an early photointermediate similar to bovine bathorhodopsin (Batho). In both cases the Batho analogue decayed to a lumirhodopsin (Lumi) analogue via a blue-shifted intermediate, BSI, which formed an equilibrium with the Batho analogue. The stability of 5-demethyl Batho, even though the C8-hydrogen of the polyene chain cannot interact with a ring C5-methyl group to provide a barrier to Batho decay, raises the possibility that the 5-demethylretinal ring binds oppositely from normal to form a pigment with a 6-s-trans ring-chain conformation. If 6-s-trans binding occurred, the ring C1-methyls could replace the C5-methyl in its interaction with the chain C8-hydrogen to preserve the steric barrier to Batho decay, consistent with the kinetic results. The possibility of 6-s-trans binding for 5-demethylretinal also could account for the unexpected blue shift of 5-demethyl visual pigments and could explain why 5-demethyl artificial pigments regenerate so slowly. Although the mesityl analogue BSI's absorption spectrum was blue-shifted relative to its pigment spectrum, the blue shift was much smaller than for rhodopsin's or 5-demethylisorhodopsin's BSI. This suggests that increased C6-C7 torsion may be responsible for some of BSI's blue shift, which is not the case for mesityl analogue BSI either because of reduced spectral sensitivity to C6-C7 torsion or because the symmetry of the mesityl retinal analogue precludes having 6-s-cis and 6-s-trans conformers. The similarity of the mesityl analogue BSI and native BSI lambda(max) values supports the idea that BSI has a 6-s angle near 90 degrees, a condition which could disconnect the chain (and BSI's spectrum) from the double bond specifics of the ring.
Animals↗
beta-carboline binding to imidazoline receptors.
A series of beta-carbolines were prepared and their affinities for imidazoline (I(1) and I(2)) sites evaluated. Selected compounds were also examined at alpha(2)-adrenoceptors. Some of the beta-carbolines were found to bind with high affinity to I(2)-sites and this affinity was dependent on both the planarity of the molecule and the presence of the aryl ring substituents. Good I(1)-affinity was observed with two of the compounds but none of the tested compounds bound to alpha(2)-adrenoceptors. The hallucinogenic properties of beta-carbolines have been linked to activity at 5-HT receptors, in particular 5-HT(2), however, it is apparent from this study that many of these compounds display substantially higher affinity for the imidazoline sites. This finding, and those showing modulation of some behavioural effects of morphine by I(2)-ligands, suggests that imidazoline sites may be interesting new targets in drug abuse research.
Animals↗
Characterization of opiates, neuroleptics, and synthetic analogs at ORL1 and opioid receptors.
Nociceptin/orphanin FQ (N/OFQ) was recently identified as the endogenous ligand for the opioid-receptor like (ORL1) receptor. Although the ORL1 receptor shows sequence homology with the opioid receptors, the nociceptin/ORL1 ligand-receptor system has very distinct pharmacological actions compared to the opioid receptor system. Recently, several small-molecule ORLI receptor ligands were reported by pharmaceutical companies. Most of these ligands had close structural similarities with known neuroleptics and opiates. In this study, we screened several available neuroleptics and opiates for their binding affinity and functional activity at ORL1 and the opioid receptors. We also synthesized several analogs of known opiates with modified piperidine N-substituents in order to characterize the ORL1 receptor ligand binding pocket. Substitution with the large, lipophilic cyclooctylmethyl moiety increased ORL1 receptor affinity and decreased mu receptor affinity and efficacy in the fentanyl series of ligands but had a different effect in the oripavine class of opiate ligands. Our results indicate that opiates and neuroleptics may be good starting points for ORL1 receptor ligand design, and the selectivity may be modulated by appropriate structural modifications.
Animals↗
The photocycle of a flavin-binding domain of the blue light photoreceptor phototropin.
The plant blue light receptor, phot1, a member of the phototropin family, is a plasma membrane-associated flavoprotein that contains two ( approximately 110 amino acids) flavin-binding domains, LOV1 and LOV2, within its N terminus and a typical serine-threonine protein kinase domain at its C terminus. The LOV (light, oxygen, and voltage) domains belong to the PAS domain superfamily of sensor proteins. In response to blue light, phototropins undergo autophosphorylation. E. coli-expressed LOV domains bind riboflavin-5'-monophosphate, are photochemically active, and have major absorption peaks at 360 and 450 nm, with the 450 nm peak having vibronic structure at 425 and 475 nm. These spectral features correspond to the action spectrum for phototropism in higher plants. Blue light excitation of the LOV2 domain generates, in less than 30 ns, a transient approximately 660 nm-absorbing species that spectroscopically resembles a flavin triplet state. This putative triplet state subsequently decays with a 4-micros time constant into a 390 nm-absorbing metastable form. The LOV2 domain (450 nm) recovers spontaneously with half-times of approximately 50 s. It has been shown that the metastable species is likely a flavin-cysteine (Cys(39) thiol) adduct at the flavin C(4a) position. A LOV2C39A mutant generates the early photoproduct but not the adduct. Titrations of LOV2 using chromophore fluorescence as an indicator suggest that Cys(39) exists as a thiolate.
Cell Membrane↗
Selective delta-opioid receptor ligands: potential PET ligands based on naltrindole.
Two series of delta-selective ligands related to the prototypic delta-antagonist naltrindole have been prepared and evaluated in opioid binding assays with the aim of developing new PET ligands for the delta-opioid receptor. One compound (5d) had significantly higher selectivity than naltrindole, but with substantially reduced binding affinity. For those compounds retaining similar affinity to naltrindole, those having ethyl and fluoroethyl substituents afforded the highest levels of selectivity. However, none of the compounds combined the high level of affinity and selectivity ideally suited to the development of an imaging agent.
Diagnostic Imaging↗