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Repression of the Escherichia coli araBAD promoter, PBAD, was studied using a mutant PBAD promoter (cip-5) that is expressed in the absence of the two proteins required for PBAD induction, AraC protein and the cyclic AMP receptor protein (CRP-cAMP). Like the wild type promoter, cip-5 was repressed by AraC protein, and this repression required a site well upstream of the transcriptional start site. cip-5 was used to determine whether repression results from interference with the functioning of either AraC protein at araI and/or CRP-cAMP. Repression of cip-5 was eliminated by a point mutation within the AraC protein binding site araI but was not affected in the absence of CRP-cAMP. These results suggest that repression involves an interaction between two AraC protein binding sites located over 200 nucleotides apart. Our results also suggest that the majority of the CRP requirement for PBAD is a result of PBAD repression. When repression was abolished by deletion of the araO2 site, the requirement for CRP-cAMP in PBAD induction was greatly reduced.

The marriage of the delivery and insurance mechanisms is key to the managed care, preferred provider concept, for it holds potential for cost-effective optimization of delivery and marketing efforts. It is, however, necessary to understand each component of the marriage, if the benefits are to be enjoyed. This article explores the five major benefit plan financing arrangements in use today and examines their implications for risk-reward sharing arrangements in a managed care environment.

Access to accurate cost information is integral to product line development and management. It is also necessary under the PPS system which reimburses hospitals at a fixed rate for the provision of health care and puts hospitals at risk for their costs. The following case study presents a methodology for identifying and analyzing the costs of providing central processing services.

Fall-lambing western range ewes were fed either a high-or low-energy ration the last two months of gestation and were fed protein and energy in excess postpartum. GnRH was infused for 10 hours on day 5 or 26 postpartum. Blood samples were collected at 20-minute intervals during infusion and radioimmunoassayed for LH. Net weight change from day 60 prepartum to day 1 postpartum was 0.67 +/- 1 kg vs. -6.9 +/- 1.5 kg (mean +/- SE) for the high-and low-energy groups, respectively (P < 0.05). Nutritional treatment had no effect on LH response at either day 5 or day 26 postpartum, althoughthe day 26 LH response to GnRH was greater (P < 0.05) than the day 5 LH response. LH response was greater (P < 0.05) in ewes that gained weight prepartum vs. ewes that lost weight prepartum, but only in ewes infused on day 5 postpartum.

Rat serine dehydratase cDNA clones were isolated from a lambda gt11 cDNA library on the basis of their reactivity with monospecific immunoglobulin to the purified enzyme. Using the cDNA insert from a clone that encoded the serine dehydratase subunit as a probe, additional clones were isolated from the same library by plaque hybridization. Nucleotide sequence analysis of the largest clone obtained showed that it has 1444 base pairs with an open reading frame consisting of 1089 base pairs. The deduced amino acid sequence contained sequences of several portions of the serine dehydratase protein, as determined by Edman degradation. Rat liver serine dehydratase mRNA virtually disappeared from livers of rats fed a protein-free diet for 5 days. Several genomic clones were isolated from two libraries. Determinations of the transcription start site and the structure of the 3' flanking region of the gene indicated that the coded mRNA is 1504 nucleotides long. The 5' promoter region contained a variety of sequences similar to several consensus sequences believed to be important for the regulation of specific gene expression.

The reversible stage of tumor promotion, which follows the stage of initiation and precedes that of progression in multistage carcinogenesis, is a unique example of reversible toxicity in biological systems. In order to study the molecular mechanisms involved in the action of promoting agents during this stage, the regulation of the expression of genes for two enzymes of glutathione metabolism, gamma-glutamyl transpeptidase (GGT) and the placental isozyme of glutathione S-transferase (GST-P), was studied under several different conditions of promotion during multistage hepatocarcinogenesis in the rat. Promotion by phenobarbital caused an increased expression of both of these genes in altered hepatic focal lesions, although this was somewhat more variable in the case of the GGT gene. C.I. Solvent Yellow 14, an industrial dye, served as an effective promoting agent. Feeding this dye resulted in a dramatic increase in the expression of GST-P, but not that of GGT in altered hepatic foci. Factors in crude, cereal-based diets inhibited the stage of promotion by diethylnitrosamine, but enhanced promotion by phenobarbital in a synergistic manner. In contrast, at least one purified diet had the converse effect during this stage. The mRNA levels of GST-P were uniformly elevated dramatically in reversible nodules and neoplasms of rat liver that had been induced by diethylnitrosamine and phenobarbital promotion. In contrast, the level of GGT mRNA was somewhat variable, with an occasional neoplasm exhibiting almost a background level of expression of this gene. Therefore, the altered regulation of multiple genes in hepatocytes during the stage of promotion can vary with the promoting agent itself; this process may be related to the heterogeneous gene expression seen in hepatic neoplasms. A possible role for specific DNA sequences in the 5' flanking regions of such genes is considered. In addition, a cDNA clone to the mRNA of human liver GGT was isolated and sequenced. The homology of the coding sequence of the human liver GGT mRNA to that of rat kidney GGT mRNA was striking.