Abstract-Pulp mill effluents contain a myriad of chemicals that have the potential to cause deleterious effects on aquatic biota in receiving waters. Some of these chemicals evoke an acute lethal response of exposed biota while others evoke sublethal responses. One such sublethal response is the induction of mixed-function oxygenases (MFO) in fish, specifically the CYP1A1 enzyme ethoxyresorufin-o-deethylase (EROD). We followed the partitioning of the inducing chemicals in pulp mill effluent fractions by Toxicity Identification Evaluation (TIE), or bioassay-driven chemical analysis. This procedure was eventually modified to a more direct technique involving centrifugation, filtration, cleanup procedures, and C 18 solid-phase adsorption. The extracts from the fractionation of two pulp mill effluents after secondary treatment were tested for EROD-inducing activity in a 4-d rainbow trout bioassay. The methanol extracts of particulates/colloids showed significant inducing capacity in Mill A effluent but not in Mill B effluent. The C 18 methanol extracts induced activity from both effluents, with extracts from Mill A causing the greatest response. The particulate/colloidal extract (Mill A) was used as the source material for chemicals which caused EROD induction. The fraction was purified by solid-phase extraction techniques and reverse-phase high-performance liquid chromatography. The majority of the EROD activity was found in the moderately nonpolar region of the chromatogram (K ow ϭ 4.6 to 5.1).

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Glycoprotein gB is the most highly conserved glycoprotein in the herpesvirus family and plays a critical role in virus entry and fusion. Glycoprotein gB of herpes simplex virus type 1 contains a hydrophobic stretch of 69 aa near the carboxy terminus that is essential for its biological activity. To determine the role(s) of specific amino acids in the carboxy-terminal hydrophobic region, a number of amino acids were mutagenized that are highly conserved in this region within the gB homologues of the family Herpesviridae. Three conserved residues in the membrane anchor domain, namely A786, A790 and A791, as well as amino acids G743, G746, G766, G770 and P774, that are non-variant in Herpesviridae, were mutagenized. The ability of the mutant proteins to rescue the infectivity of the gB-null virus, K082, in trans was measured by a complementation assay. All of the mutant proteins formed dimers and were incorporated in virion particles produced in the complementation assay. Mutants G746N, G766N, F770S and P774L showed negligible complementation of K082, whereas mutant G743R showed a reduced activity. Virion particles containing these four mutant glycoproteins also showed a markedly reduced rate of entry compared to the wild-type. The results suggest that non-variant residues in the carboxy-terminal hydrophobic region of the gB protein may be important in virus infectivity.

Within bleached kraft mills, the main sources of compounds inducing the mixed function oxygenase (MFO) activities of fish are waste cooking liquor, black liquor, and effluents from the first stages of the bleaching process. We measured the potency for MFO induction in rainbow trout (Oncorhynchus mykiss) of black liquors from pulp mills using kraft pulping and either softwood or hardwood furnish. Concentrations causing induction ranged from 0.0032 to 0.2%(v/v), and below critical thresholds, concentration‐response relationships were linear. Above threshold concentrations, activity declined, and lethality occurred at concentrations greater than 0.1% (v/v) black liquor during 4‐d exposures. Hardwood pulping generated black liquor that was less potent than that from softwood, but much of the difference was due to a higher water content; hardwood black liquor was more dilute as indicated by normalizing results to dissolved organic carbon. Compounds inducing MFO activity may be natural wood extractives associated with wood resins, or compounds created by the digestion of lignin. A high potency of black liquor from alcohol pulping supports the hypothesis of a natural compound because alcohol extraction does not chemically alter lignin to the same extent as kraft pulping; inducing compounds can also be extracted from wood chips with dichloromethane. The high potency of black liquor compared to bleaching or extraction‐stage effluents suggests that control of black liquor losses may be very important in limiting exposure of fish to inducing compounds.