Free-living nematodes-Panagrellus sp., Turbatrix aceti, Caenorhabditis elegans and C.hriggsae-were each fed to the fish Danio sp. and the process of their digestion, in the fish alimentary canal, was studied by light and electron microscope.Almost no identifiable nematodes were found in the fish gut when the digestion period was 3 h or more, except for buccal capsules of the four studied species, males' spicules of Panagrellus sp. and Turbatrix aceti and egg-capsules of the Caenorhabditis species. These structures could serve as indicators that the nematodes had been preyed on and digested by the fish.Differences in the mode of digestion were noticed between the various species of nematodes studied, after a period of0.5-I h, in the fish gut. In Panagrellus sp. and T. aceti disintegration of the soft inner tissues occurred mostly at the anterior or posterior ends of the nematode's body, while in Caenorhabditis the majority of digested nematodes were affected at both ends or evenly along the entire body. Digestion seemed to be initiated mostly at the nematodes' body apertures: mouth, anus or cloaca, and vulva which could be due to a more vulnerable cuticle around those areas. Disintegration proceeded from the soft inner parts to the more resistant cuticle that was finally disintegrated. Ofthe three layers of cuticle the most resistant were the external cortex and the basal layers.

In previous studies with luminous bacteria of all different species it has been reported that the synthesis of luciferase is autoinducible: during growth at low cell densities synthesis is effectively repressed while after induction, at higher cell densities, the rate of synthesis of enzyme is up to five times the growth rate. In this paper we report on newly isolated strains of Photobacterium leiognathi which show continued luciferase synthesis irrespective of the cell density. The specific synthesis rate may nevertheless differ from the rate of growth and depends on the luciferase content of the inoculated cells. A ratio of 1 was established for cells having a maximum luciferase content varying to a ratio of about 2 for cells that contained only 1% of the maximum.

Radioiodinated, native and denatured bovine serum albumin (albumin) P-lactoglobulin and cytochrome c were introduced into hepatoma tissue culture cells by erythrocyte-ghost-mediated microinjection, and their rates of degradation were compared. Denatured albumin was degraded at 20% of the rate of undenatured albumin, denatured 8-lactoglobulin was degraded three times faster than undenatured p-lactoglobulin, while denatured and undenatured cytochrome c were degraded at the same rate. Thus, denaturation does not affect the rates of intracellular breakdown of microinjected proteins in a simple predictable way. Exhaustive methylation did not inhibit the degradation of denatured P-lactoglobulin or albumin, indicating that, like their undenatured counterparts, they are not degraded via the ubiquitin pathway.In reticulocyte lysates, in the presence of ATP, denatured albumin and P-lactoglobulin were broken down at slightly slower rates than the parent proteins. Exhaustive methylation of both denatured and undenatured proteins completely abolished their ATP-dependent breakdown. This inhibition is consistent with the hypothesis that free -NH2 groups are required for the attachment of ubiquitin prior to degradation in this system.Removal of an ammonium sulfate fraction from reticulocyte lysates produces a proteolytic system markedly different from the whole lysate [Speiser, S. & Etlinger, J. D. (1983) Proc. Natl Acad. Sci. USA 80, 3577-35801. In this system both denatured and undenatured albumin and P-lactoglobulin were degraded essentially independently of ATP. Methylation only slightly decreased the breakdown of denatured proteins, suggesting that they are not degraded via the ubiquitin pathway. A possible explanation of these results is that removal of the ammonium sulfate fraction unmasks an ATP-independent proteolytic system unrelated to the ubiquitin pathway.

Toxicity tests have not been widely used to assess the performance of urban‐runoff treatment facilities. In the present study, Ceriodaphnia dubia toxicity tests were used to quantify toxicity of urban runoff at Crandall Creek and the downstream Demonstration Urban Stormwater Treatment (DUST) March in Fremont, California. Acute toxicity, expressed as the median time to lethality (LT50) for C. dubia, was used to compare the relative intensities of toxicity in the system. During or shortly after storm events, horizontal and vertical gradients in LT50 and electrical conductivity were observed, with high correlation between the two parameters. Toxicity diminished as time passed after the storm. The performance of the DUST Marsh as a treatment facility was evaluated for three aspects: detention, dilution, and toxicity removal. We found that toxic storm water generated by small‐ to medium‐sized storms (5 to 25 mm rain) was contained in the marsh. Toxicity was greatly reduced upon dilution of storm water with pre‐existing marsh water, and mixing of the water column increased the rate of toxicity diminution. Toxicity reduction, above and beyond that attributable to dilution, was evident in the marsh. Results of this study demonstrate the potential use of toxicity assessments as an integral component of marsh design and management.