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Extensive studies indicate that both genetic and epigenetic (physiological and biomechanical) factors play a role in the development of twist state which must correspond to the establishment of cell surface conformational state at the level of cell wall assembly. Therefore, in order to identify the unknown factors that control the macrofiber production, twist states and hand inversion, genetic studies concerning regulation of macrofiber production and macrofiber structural states seemed to be appropriate. Genetic studies were carried out by using an insertional mutagenesis method. Bank(s) of insertions were obtained that carry the Tn917 transposon at random locations in the genome. Selected isolates were characterized with respect to macrofiber production and twist, and helix hand inversion stimulated by various physiological factors. The bank(s) of insertional mutants were searched for those defective or impaired in response to ion-induced hand inversion. None were found to exhibit the desired phenotype. Clones with altered static state were not rare. Another approach was to take advantage of the transposon "lac system" and to use the bank of insertion mutants to study regulation of gene expression. The chromogenic substrate for β-galactosidase, X-gal, made possible the search for factors governing gene expression during macrofiber morphogenesis in a manner similar to the way in which developmental biologists study regulation of gene expression during embryogenesis. First, insertion strains were screened for lac-Z expression on TBAB (Tryptose Blood Agar Base) X-gal plates. Isolates were then characterized by growth in fluid media. One strain (3:1) was found that expressed the E. coli lac-Z structural gene when grown on solid media (TBAB X-gal), but not when grown in fluid media. These observations led us to an examination of the role the medium may play in the regulation of gene expression. Evidence was obtained indicating that a number of insertion strains respond to growth in viscous media by expression of lac-Z+ indicating that different host gene promoters can be regulated by a physical component of the environment. The degree of expression moreover was positively correlated with the degree of viscosity. Environmental physical forces applied to the "body" of a bacterial cell must therefore play a role in gene expression. In at least one strain, 5:7Oring, gene expression was found only in right-handed structures suggesting that either specific genes are involved in the twist state and hand determination or that helix hand itself may govern gene expression. Finally, the 5:7Oring strain shows also the presence of a probable intercellular signalling through a diffusible chemical that causes gene expression to occur only in certain cells found at specific locations within the population.

A new approach has been introduced to characterize the epidermal growth factor receptors and their relation to the mechanism of cell growth control using hybrid cells made between human EGF responsive cells and mouse A9 cells incapable of EGF binding. BALBc mice were immunized with human carcinoma A431 cells carrying an extraordinary high number of EGF receptors; antisera were used to identify the human nature of EGF receptors in these hybrid cells. One of the hybrid lines, C2B5, that retains only one human chromosome, an X/7 translocation, and a nearly complete mouse parental genome was used to analyze the relationship of the binding ability and certain post-receptor functions to the cellular mitogenic response. It was shown that the ability to bind, internalize and degrade the ligand and/or its receptor is not sufficient for cells to respond to the mitogen. Spleen cells from mice immunized with A431 cells were fused with mouse myeloma P3NP cells. One of the isolated hybridoma lines, B4G7, secreted a monoclonal antibody of the IgG class which inhibits the binding of ¹²⁵I-EGF to A431 and human fibroblasts, but not of mouse 3T3 cells. This inhibition was partial (65-70%) and Scatchard analysis of the binding data suggested that antibody preferentially interacts with a low affinity class of EGf receptors. The antibody specifically precipitated EGF receptor from radiolabeled cells. This monoclonal antibody was crosslinked to subunit A of toxic ricin through a disulfide bond. The resulting conjugate inhibited protein synthesis of A431 cells at 4 x 10⁻¹¹M and exhibited substantial cell killing. Using this conjugate we isolated a variant of A431 cells, designated C1-B7, with approximately 30 times less EGF binding capacity. Contrary to the parental A431, this variant is resistant to EGF-induced suppression of cell growth and appears to have lost most of the low affinity receptors. The high affinity type EGF receptors retained by the variant are 170,000 Mr and susceptible to EGF-induced phosphorylation, presumably on tyrosine residues. In membrane prepared from this variant, besides the EGF receptor, a low molecular weight component of as yet unknown nature is highly phosphorylated in an EGF-independent manner.

This dissertation focuses on the welfare implications of different government policies aimed to diminish the consumption of energy produced from fossil fuels in the United States. The first of these policies, taxation on gasoline consumption, diminishes consumption by increasing the cost per mile traveled. However, this policy measure has not been favored by policy-makers, and instead, the Corporate Average Fuel Economy standards, CAFEs, were put in place since the seventies. This policy consists of a pre-established threshold of fuel-efficiency, measured in miles per gallon, that car manufacturers selling cars in the United States are subject to each year. For each manufacturer, the CAFE is calculated, which weights the fuel-efficiency of each car model by the number of units sold of that car model. If the CAFE for a given manufacturer lies below the pre-established standard for that year, the manufacturer is subject to a fine. I exploit the manufacturers' past behavior in setting prices for their car models to estimate structural demand and supply parameters that characterize the car industry facing these policies. With those parameters, I can estimate the welfare impacts of tightening the CAFE standard to the new threshold set by the Obama administration and compare those impacts to the ones from raising gasoline taxes to obtain the same gasoline reduction in consumption. The findings are that in the short run, taxation is a less costly policy than tightening the CAFE standard. The second and third essays study the consequences of adopting renewable sources for electricity production. These technologies bring reductions in emissions of pollutants to the atmosphere, but not at no cost. They are expensive and their introduction to already existing electricity systems requires modifications to the usual scheduling of power plants because of the intermittent nature of the renewable sources, such as solar. We compute the equilibrium effects of this policy finding that if the environmental benefits are not taken into account, these policies are welfare decreasing with the amount of renewable sources. Some lower levels of penetration are more cost efficient if we take into account dynamic considerations in the scheduling of the plants.

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