The Trinity River flows through the Dallas-Ft. Worth Metroplex in north central Texas where it receives effluents from numerous point sources including seven large regional wastewater treatment facilities. Historically, the Trinity River has been impacted by massive wastewater loadings which often constitute > 80% of the total river discharge during low flow periods. Normally, high mass loadings correspond to the summer months, compounding the effects of a naturally stressful period, characterized by high temperatures and low dissolved oxygen concentrations. Samples from 12 stations were collected quarterly over an 18 month period from the Trinity River and two tributaries. Water samples were analyzed for a variety of water quality variables, including metals, priority pollutants, pesticides, and general water quality parameters. Water samples were also tested for acute and subchronic effects with several test species. Fish were collected at each station and assemblages were characterized using traditional classification techniques and the Index of Biotic Integrity. In addition, sediment samples were assessed for toxic effects which could have adversely impacted fish recruitment and in situ biomonitoring experiments were performed. Quantitative habitat characterization analyses were performed to gain additional information that could possibly explains differences in fish assemblage structure related to habitat variability. Data …

Aspartate transcarbamoylase (ATCase; encoded by pyrBI genes) is one of the most studied regulatory enzymes in bacteria. It is feedback inhibited by cytidine triphosphate (CTP) and activated by adenosine triphosphate (ATP). Much is known about the catalytic site of the enzyme, not nearly as much about the regulatory site, to which CTP binds. Until now a positive selection for feedback-modified mutants was not available. The selection we have developed involves the use of a pyrA deletion in S. typhimurium. This strain lacks carbamoylphosphate and requires both a pyrimidine and arginine for growth. In this strain citrulline is used to satisfy the pyrimidine and arginine requirements. The minimal flow through the pyrimidine pathway from the citrulline-produced carbamoylphosphate is exquisitely sensitive to feedback control of ATCase by CTP. By elevating the CTP pool, via exogenous cytidine, in a strain that also contains a cytidine deaminase mutant (cdd) growth can be stopped completely, indicating 100% inhibition. It was therefore possible to measure in vivo feedback inhibition of ATCase among the citrulline users and to isolate a family of ATCase regulatory mutants with either modified or no response to effectors.

The necessity for a functional user friendly laboratory data management program has become evident as the quantity of information required for modern scientific research has increased to to titanic proportions. The required union of strong computer power, ease of operation, and adaptability have until recently been outside the realm of most research laboratories. Previous systems, in addition to their high cost, are necessarily complex and require software experts in order to effect any changes that the end user might deem necessary. This study examines the Apple Macintosh computer program Hypercard as an interactive laboratory information system that is user-friendly, cost effective, and adaptable to the changing demands within a modern molecular or microbiology.

This research project deals with the characterization of self-replicating Kirsten murine viral DNA. The replication of this viral DNA and tetracycline resistance conferred to bacteria by this viral DNA will be studied. The restriction endonuclease and Southern blot analysis revealed a fragment of pBR322 from the Hind III and Pst I site that is located in the 3' end of the MLV-K:E molecule. Single stranded sequencing of the two terminal ends of this fragment verified that the 3' end of MLV-K:E contains identical sequence homology to pBR322. The presence of this pBR322 fragment explains the unusual properties of the MLV-K:E molecule. However, tetracycline resistance is less in E. Coli containing MLV-K:E than E. coli containing pBR322 as determined by zone of inhibition assay. This may be due to alteration in the promoter region of the tetracycline gene.

This study had two objectives: to achieve suspension cultivation of Sf1Ep cells and to develop procedures for achieving the replication of T. pallidum in those cell cultures. Sf1Ep cells have been the sole cell line used for the in vitro cultivation of T. pallidum. A study was undertaken to determine if other cell lines can support growth of T. pallidum. Rabbit skin fibroblasts (RAB-9), nude mouse ear (NME) cells, and normal rebbit testis fibroblasts (RT) were compared to Sf1Ep cells for their ability to support in vitro multiplication of T. pallidum. RAB-9 cells supported multiplication of treponemes equal to that of Sf1Ep cells. NME and RT cells also supported growth but to a lesser extent than Sf1Ep cells. Utilization of alternative cell lines may lead to improved in vitro growth of T. pallidum including possible serial passage.