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L Maltby

Publications and source records attributed to L Maltby.

9 recordsLinked to original sources
PubMed1997

The effects of motorway runoff on freshwater ecosystems: 3. Toxicant confirmation.

Previous studies have demonstrated that small streams receiving road runoff have reduced water and sediment quality. These changes in quality are associated with alterations in the structure and functioning of stream communities. Laboratory studies have indicated that the community changes are due to sediment-associated contaminants, and toxicant identification evaluations have shown that the major toxicants are contained probably in a fraction of sediment extract that contains polycyclic aromatic hydrocarbons (PAHs). The aim of the present study was to determine whether PAHs were indeed the major toxicants in sediment extracts. Toxicity tests were performed with PAH mixtures, the toxic fraction of an extract of runoff-contaminated sediment, and a whole sediment extract. These indicated that three PAHs accounted for the toxicity of a sediment extract: pyrene, fluoranthene, and phenanthrene. The possibility of spatial or temporal variation in major toxicants was also investigated and tests on a number of sediment extracts obtained from a number of sites at different times demonstrated that the three PAHs accounted for 30.8 to 120% of an extract's toxicity. When the PAHs were considered individually, pyrene was shown to account for most of the toxicity (44.9%), followed by fluoranthene (16%) and phenanthrene (3.5%).

Animals↗
PubMed1995

Development of a monoclonal antibody-based immunoassay for the detection and quantification of Anguillospora longissima colonizing leaf material.

Monoclonal antibodies (MAbs) to the aquatic hyphomycete Anguillospora longissima were raised in mice by using a coimmunization program. A cell line was raised that produced a MAb of the immunoglobulin M class that was specific for A. longissima both in an enzyme-linked immunosorbent assay (ELISA) and by immunofluorescence but that did not recognize other members of the aquatic hyphomycetes. This MAb (AL-HH8c) was used to develop a quantitative ELISA in vitro. The antigen recognized by AL-HH8c is produced throughout the mycelium, irrespective of mycelial age and culture conditions. By using this MAb, mycelium of A. longissima colonizing leaf material can be detected by ELISA, immunofluorescence, and immunoenzymatic staining methods.

Animals↗
PubMed1994

Responses of Gammarus pulex (Amphipoda, Crustacea) to metalliferous effluents: identification of toxic components and the importance of interpopulation variation.

This study was designed to evaluate the ability of an in-situ bioassay to assess the impact of complex effluents on freshwaters and to identify toxic components. Reductions in the feeding rate of Gammarus pulex proved to be a sensitive indicator of the impact of metalliferous effluents on receiving water quality. The effluents contained a mixture of five potentially toxic metals. By combining information on feeding rates with bioaccumulation data, two metals, iron and manganese, were identified as the probable toxic agents. Laboratory experiments validated the conclusions reached from the field study and confirmed that iron was a major toxicant. The sensitivities of Gammarus pulex from a metal-contaminated site and a clean site were compared during both the field and laboratory studies. Interpopulation differences in the response of G. pulex to toxicants were detected in the field study but not in the laboratory experiments. Possible reasons for this are discussed.

Journal Article↗
PubMed1994

Conserved cis-elements bind a protein complex that regulates Drosophila ras2/rop bidirectional expression.

The Drosophila ras2 promoter region exhibits bidirectional activity, as has been demonstrated for the human c-Ha-ras1 and the mouse c-Ki-ras. Here we address a unique case of ras regulation, as Drosophila ras2 provides the only example to date in which the flanking gene (rop) and its product have been isolated. A linking mechanism of control suggests a mutual interaction between the two gene products. Our studies indicate that the Drosophila ras2 promoter region shares with the human c-Ha-ras1 promoter a CACCC box and an AP-1-like sequence. A 14 bp promoter fragment which holds a CACCC element is demonstrated to interact with a specific transcription factor (factor B). This CACCC promoter element represents a stretch of imperfect palindrome. We present evidence that this factor can form a complex with another specific DNA-binding protein (factor A). The binding sites (A + B) for these protein factors are essential for 95% expression of both genes flanking the promoter (ras2 and rop). Region A consists of four overlapping consensus sequences: a TATA-like element, a DSE-like motif (the core sequence of the serum response element), a DRE octamer, which has been shown to play a role in cell proliferation, and a 5 bp direct repeat representing the GATA consensus sequence. Factor A has a very weak affinity to the full promoter region, but when complexed with factor B binding efficiency is enhanced. We also show that alterations of DNA-protein binding specificities can be achieved by supplementing the growth media with different sera.

Animals↗
PubMed1992

Cadmium resistance in Gammarus pulex (L.).

The ability of Gammarus pulex to develop cadmium resistance through physiological acclimation was investigated. Organisms were found to be significantly more tolerant to acute cadmium toxicity after pre-exposure to sublethal concentrations of cadmium and zinc. The induced elevation in cadmium tolerance was shown to be associated with an increase in the body concentration of a metallothionein-like protein. Pre-exposure had no apparent effect on cadmium uptake, although it did influence the distribution of cadmium within the organisms. Whereas pre-exposure to low levels of zinc and cadmium increased cadmium tolerances in acute tests, it had no observable effects on sublethal responses measured during chronic exposure.

Animals↗
PubMed1990

Effect of stress on a freshwater benthic detritivore: scope for growth in Gammarus pulex.

Scope for growth (SfG), a measure of energy balance (between food intake and metabolic output) within animals, has been used as an indicator of pollution stress in marine systems. However, it has not been used commonly in freshwater systems and here we investigate the sensitivity of SfG in Gammarus pulex, a benthic freshwater crustacean, under conditions often associated with pollution. The effects of four specific substances were investigated; a metal (zinc), an organic (3,4-dichloroaniline), and two dissolved gases (oxygen and ammonia). In all cases SfG was reduced by the stress, primarily due to a depression in energy intake. Only with ammonia was energy output (respiration) significantly affected.

Ammonia↗
PubMed1990

Field deployment of a scope for growth assay involving Gammarus pulex, a freshwater benthic invertebrate.

Scope for growth (SfG) is a measure of the energy balance of an animal (i.e., the difference between energy intake and metabolic output). The SfG of marine invertebrates, particularly the mussel Mytilus edulis, has been successfully used as the basis of a field bioassay to detect a range of stresses both natural (temperature, food, salinity) and anthropogenic (hydrocarbons, sewage sludge). SfG of the freshwater amphipod Gammarus pulex was found to be a sensitive indicator of stress under laboratory conditions and here we describe the field deployment of this technique and present data from three field trials. In every case, SfG was reduced at the downstream polluted site compared with that at an upstream reference site. This reduction in SfG was the result of a decrease in energy intake (absorption) rather than an increase in energy expenditure (respiration).

Animals↗
PubMed1987

Acute toxicity tests on the freshwater isopod, Asellus aquaticus using FeSO4. 7H2O, with special reference to techniques and the possibility of intraspecific variation.

Techniques are described for assessing the toxicity of Fe(II), an important component of the effluent from mines, to the freshwater isopod, Asellus aquaticus. These techniques either involve buffer systems or working at low pH. Both techniques indicate that A. aquaticus is very tolerant of Fe(II). Furthermore, the low-pH technique suggests that animals from sites exposed to mine-waste pollution are more tolerant than those from sites not so exposed. This difference is masked in the buffer experiments, possibly due to the formation of less toxic buffer-Fe(II) complexes.

Journal Article↗