A QSAR for Measuring Sublethal Responses in the Marine Macroalga Enteromorpha intestinalis

Abstract

Two methods for measuring the effect of organic toxicants on the marine macroalga Enteromorpha intestinalis were compared. EC₅₀ data for the effect of C₁?C₈ n?alcohols on neutral red dye retention and ion leakage were used to construct QSARs with log K_ow as the only physicochemical parameter. The two QSARs were statistically indistinguishable suggesting that both procedures reflect the same non-specific narcotic effect on membrane integrity. The effect on ion leakage of compounds with more specific modes of action was also investigated. The herbicides diuron and diquat had no effect at concentrations which inhibit photosynthesis, the uncoupler 2,4-dichlorophenol was no more toxic than a narcotic of similar polarity, but the known high toxicity of the antifouling compound tributyltin was clearly reflected by the ion leakage response.     

On the Existence of Auslander–Reiten Sequences of Group Representations. III

This is the third and final part of our study of the existence of Auslander–Reiten sequences ofgroup representations. In Part I we considered representations of group schemes in characteristic 0.In Part II we considered representations of group schemes in characteristic p. In this partwe give applications to representations of abstract groups and Lie algebras.     

On the Existence of Auslander–Reiten Sequences of Group Representations. I

This is the first part of our study of the existence ofAuslander–Reiten sequences of group representations. In this part weconsider representations of group schemes in characteristic 0; in Part II weconsider representations of group schemes in characteristic p; andin Part III we give applications to representations of groups and Liealgebras.     

Symmetric and Exterior Powers, Linear Source Modules and Representations of Schur Superalgebras

We study modules for the general linear group (over an infinitefield of arbitrary characteristic) which are direct summandsof tensor products of exterior powers and symmetric powers ofthe natural module. These modules, which we call listing modules,include the tilting modules and the injective modules for Schuralgebras. The modules are studied via their relationship tolinear source modules for symmetric groups on the one hand,and simple modules for Schur superalgebras on the other. Listingmodules are parametrized by certain pairs of partitions. Theyare used to describe, by generators and relations, the Grothendieckring of polynomial functors generated by the symmetric and exteriorpowers. We also (continuing work of J. Grabmeier) describe thevertices and sources of linear source modules for symmetricgroups. 2000 Mathematical Subject Classification: 20G05, 20C30.     

Application of steam distillation in the determination of petroleum hydrocarbons in water and mussels (Mytilus edulis) from dosing experiments with crude oil

Steam distillation is shown to provide recoveries in excess of 80% for petroleum hydrocarbons in the volatility range encompassed by toluene and pyrene from water and mussel tissues. These recoveries were achieved with an apparatus based on Dean and Stark water estimators which are commercially available at low cost. Saponification is shown to aid hydrocarbon recovery from mussel tissue. The steam distillates derived from tissues were analysed by u.v. spectrophotometry after clean-up on alumina, or directly by gas-liquid chromatography or normal- and reverse-phase high-performance liquid chromatography (h.p.l.c.). Steam distillates of water did not require prior clean-up. Normal-phase h.p.l.c. of steam distillates on an amino-cyano phase provided a particularly convenient method for petroleum-derived aromatic hydrocarbons. These techniques were examined extensively in laboratory experiments with crude oil, but preliminary results suggest that they may be used also in environmental monitoring of hydrocarbons.     

The development and evaluation of Freeze-Fracture/Cytoplasmic maceration for the SEM to investigate algal ultrastructure

Freeze-fracture/cytoplasmic maceration (FF/CM) to expose chloroplast ultrastructure for the SEM was developed for the green alga Enteromorpha intestinalis (Linnaeus) Link, and the results were compared with conventional TEM preparation. Preliminary investigations showed that the method used for higher plants was inadequate to expose algal chloroplast membrane detail, but, by decreasing the molarity of the buffer during maceration to make it more hypotonic relative to the tissue, sufficient cytoplasmic extraction was accomplished in 7 days using osmium tetroxide at a lower concentration than suggested in previous work. Post-maceration in tannic acid was omitted from the processing after the preliminary study to assess its effects on the final images, and consequently preparation time was shortened drammatically and now compares favourably with the time take to prepare material for the TEM. Ultrastructural integrity is preserved and is consistent with normal TEM preparations.