The biosynthesis of pyrimidines in Pseudomonas putida was investigated. In this study, pyrimidine requiring mutants were isolated by conventional mutagenesis and enrichment. The strains required exogenously supplied pyrimidines for growth and were found by enzyme assays to be deficient for the product of the pyrB gene encoding the enzyme aspartate transcarbamoylase. None of the intermediates of the pathway could supply the auxotrophic requirement of the strain; only preformed pyrimidines, metabolized via salvage pathways could suffice. Pyrimidine limitation in the mutant caused a slight but significant fifty per cent increase in expression of all the de novo biosynthetic enzymes. Pyrimidine starvation's effect on nucleotide pool levels was examined in the mutant and caused a marked swelling of the purine nucleotide pools.

The phylogenetics of eight species of the Peromyscus truei and P. boylii species groups from 15 populations were analyzed based on mitochondrial DNA sequence differentiation, using 13 hexanucleotide specific restriction enzymes. P. difficilis, P. nasutus, and P. attwateri were found to be members of the same clade. P. leucopus was not found to be closely related to any of the species of the boylii or truei species groups. Phylogenetic interpretations for the remaining species differed based on Wagner and Dollo parsimony analyses. P. true appears to be most closely related to P. gratus based on Wagner parsimony and the phenetic analysis, while the relationship of P. gratus to other species could not be resolved based on Dollo parsimony.

Using a rat model, the effects of a single dose or six to twelve months of daily oral administration of ethanol on the immune system were determined. The rats were challenged with sheep red blood cells after the various dosing periods to elicit an immune response. Immune system responsiveness was determined by means of white blood cell counts and differentials, antibody titers, and T-cell numbers. No deleterious effects of the ethanol on the immune response were seen, while the female alcohol-fed rats showed a significant increase in T-Cell numbers, white blood cell counts, and lymphocytes over the sham group.

The 96-hr LC50 of cyfluthrin in Pimephales promelas ata temperature of 23*C and a pH of 8 was 1.08 g/L. The toxicity of cyfluthrin was inversely related to temperature and pH. A temperature of 10*C and a pH of 6 significantly decreased the 96-hr LC50 to 0.009 gg/L. Likewise, sublethal exposures to cyfluthrin significantly affected the fathead minnow's ability to tolerate high and low temperatures. Cyfluthrin compromised the fathead minnow's lower temperature tolerance (CTMin) by 60C and the upper temperature tolerance (CTMax) by 20C. Although cyfluthrin may not be present in the environment in large amounts due to its physical and chemical properties, small concentrations ( g/L) may adversely affect fish populations.

Research estimated toxicity of refuse-derived fuel fly ash (RDF-FA) on two earthworms species, Lumbricus terrestris and Eisenia foetida. Specific objectives were to: (1) Compare their 14-day LC50s under light and dark conditions; (2) separate toxicity due to osmotic, pH and physical factors from that of heavy metal contaminants; (3) compare relative differences of artificial soil and commercial soil as exposure media for evaluating toxicity to earthworms. The 14-d LC50s for L. terrestris in dark and light were 57.0 and 48.34 % RDF-FA, and 59.25 and 41.00 % RDF-FA for E. foetida using artificial soil. All of the toxicity resulted from heavy metals within the RDF-FA. Using L. terrestris, the LC50s for artificial soil and commercial soil were 52.30 and 64.34%.

Concurrent outdoor aquatic 1950 L microcosm and 0.04 ha mesocosm experiments with bluegill sunfish evaluated the ecological impact of cyfluthrin. Cyfluthrin effects were not observed on mesocosm bluegill; a slight decrease in growth was observed in the microcosm bluegill. Otolith weight to length relationships between bluegill size-classes from microcosms, local streams, and a fish hatchery revealed no differences. Our results indicated bluegill predation impacts were slight on benthic invertebrates. Extensive predation on emerging insects was observed. Microcosm bluegill impacts on zooplankton populations followed expected predation effects, resulting in larger populations of smaller taxa. Bluegill functioned as "keystone" predators for microcosm taxa and improved taxa richness for benthic colonizing invertebrates and zooplankton.

Six sites within the Denton and Hickory Creek watersheds were sampled over three years to assess the impact of seasonal intermittent stream conditions on the ichthyofauna. An integrated approach using field and laboratory techniques was employed to evaluate the responses of the fishes.

Objectives were to: (1) assess toxicity of polychlorinated biphenyls on Eisenia foetida, in terms of survival (LC5O/LD5O), and suppression of coelomocytes to form secretory (SR) and erythrocyte rosettes (ER) with, and to phagocytize rabbit erythrocytes; and (2) compare results with those of Lumbricus terrestris to assess relative sensitivities to PCB. Using 5-d filter paper contact exposure protocol, LC50 and LD50 were 30.4 cg/cm2 and 4450 cg/g dry mass, respectively. Nominal PCB exposure concentrations of 5.0 and 10.0 pg/cm2 resulted in tissue levels of 1389 and 2895 pg/g dry mass causing a significant reduction in SR formation by 18 and 52%, respectively. ER formation and phagocytosis were reduced significantly (52 and 61%) only at the higher tissue concentration. Compared to reported data on lethality and immunomodulation in L. terrestris, E. foetida appears to be more resistant.

Metabolic differences in the strategies used for pyrimidine base and nucleoside salvage were studied in the pseudomonads and enteric bacteria. Fluoro--analogs were used to select mutant strains of E. coli, S. typhimurium, P. putida, and P. aeruginosa blocked in one or more of the uracil and uridine salvage enzymes. HPLC analysis of cell-free extracts from wild-type and mutant strains examined the effectiveness of the selections. Evidence was found for cytidine kinase in Pseudomonas and for an activity that converted uracil compounds to cytosine compounds. Using media supplemented with 150 μg of orotic acid per ml, P. putida SOC 1, a Pyr, upp mutant which utilizes orotic acid as a pyrimidine source was isolated for the first time in any study.

Serotonin (5-hydroxytryptamine, 5-HT) has been shown to activate carbohydrate metabolism in adult female Ascaris suum. Serotonin may be either absorbed directly from the environment or synthesized de novo from the absorbed L-tryptophan in adult female A. suum. The enzymes necessary for the synthesis of 5-HT have been identified in both intestine and muscle tissues. The serotonin absorbed from the environment is obtained either from the host's gastrointestinal contents or from the 5-HT producing bacteria in the intestine of A. suum. Numerous 5-HT producing bacteria were identified in the intestinal microflora. The physiological contributions of 5-HT producing bacteria to the 5-HT level, turnover and binding sites in the intestinal tissue of A. suum were investigated.

Ten bacteria capable of growth on the metal-cyano complex, tetracyanonickelate (II) {K2 [Ni(CN)J } (TCN), supplied as the sole nitrogen source, were isolated. Seven isolates were identified as pseudomonads while the remaining three were classified as Klebsiella species. In addition to TCN, all isolates were able to utilize KCN although it was significantly more toxic. The degradation of TCN was most complete when supplied at growth-limiting concentrations, did not occur when ammonia was present, and resulted in the formation of nickel cyanide [Ni(CN)2] as a degradation product.