Lawrence C. Davis

Combined Chemotherapy and Radiotherapy Compared with Radiotherapy Alone in Patients with Cancer of the Esophagus

BACKGROUND The efficacy of conventional treatment with surgery and radiation for cancer of the esophagus is limited. The median survival is less than 10 months, and less than 10 percent of patients survive for 5 years. Recent studies have suggested that combined chemotherapy and radiation therapy may result in improved survival. METHODS This phase III prospective, randomized, and stratified trial was undertaken to evaluate the efficacy of four courses of combined fluorouracil (1000 mg per square meter of body-surface area daily for four days) and cisplatin (75 mg per square meter on the first day) plus 5000 cGy of radiation therapy, as compared with 6400 cGy of radiation therapy alone, in patients with squamous-cell carcinoma or adenocarcinoma of the thoracic esophagus. The trial was stopped after the accumulated results in 121 patients demonstrated a significant advantage for survival in the patients who received chemotherapy and radiation therapy. RESULTS The median survival was 8.9 months in the radiation-treated patients, as compared with 12.5 months in the patients treated with chemotherapy and radiation therapy. In the former group, the survival rates at 12 and 24 months were 33 percent and 10 percent, respectively, whereas they were 50 percent and 38 percent in the patients receiving combined therapy (P less than 0.001). Seven patients in the radiotherapy group and 25 in the combined-therapy group were alive at the time of the analysis. The patients who received combined treatment had fewer local (P less than 0.02) and fewer distant (P less than 0.01) recurrences. Severe and life-threatening side effects occurred in 44 percent and 20 percent, respectively, of the patients who received combined therapy, as compared with 25 percent and 3 percent of those treated with radiation alone. CONCLUSIONS Concurrent therapy with cisplatin and fluorouracil and radiation is superior to radiation therapy alone in patients with localized carcinoma of the esophagus, as measured by control of local tumors, distant metastases, and survival, but at the cost of increased side effects.

Beneficial effects of plants in the remediation of soil and groundwater contaminated with organic materials

Abstract The use of plants in remediation of soil and unconfined groundwater contaminated with organic materials is appealing for a variety of reasons: (1) plants provide a remediation strategy that utilizes solar energy; (2) vegetation is aesthetically pleasing; (3) plant samples can be harvested and tested as indicators of the level of remediation; (4) plants help contain the region of contamination by removing water from soil; (5) rhizosphere microbial communities are able to biodegrade a wide variety of organic contaminants; and (6) many plants have mechanisms for transporting oxygen to the rhizosphere. However, before effective plant remediation strategies can be developed, an understanding is needed of the physical, biological, and chemical relationships that determine the fate of each organic contaminant in the rhizosphere. This review presents an overview of some factors required to understand and model the complex processes that determine the fate of the organic contaminants in plant remediation ...

Nitrogenase. I. Repression and derepression of the iron-molybdenum and iron proteins of nitrogenase in Azotobacter vinelandii

Abstract Evidence is presented that the dilution effect on nitrogenase from Azotobacter vinelandii can be overcome by the addition of an optimal amount of Component I (iron-molybdenum protein) or Component II (iron protein); and this optimized activity parallels the activity obtained by applying the dilution-factor correction. The synthesis of both of the nitrogenase components, after exhaustion of ammonia from the medium, seems to be coordinate. The degradation of both of the nitrogenase components after repression was found to be coordinate and neither component was found to be in excess at any time after repression. For the initial one-half generation the nitrogenase activity falls at approximately the same rate as the increase in cell mass, suggesting simple dilution. After this point, however, activity falls more rapidly and more than 95 % of the activity is lost in two generations.

Nitrogenase. III. Nitrogenaseless mutants of Azotobacter vinelandii: Activities, cross-reactions and epr spectra

Abstract Mutant strains of Azotobacter vinelandii that are unable to fix nitrogen were analyzed for their ability to reduce acetylene and oxidize dithionite. The activities of Components I (Fe-Mo-protein) and II (Fe-protein), the presence of antibody cross-reacting material to each of the components and the electron paramagnetic resonance (EPR) intensities at g = 3.65 also were examined in these strains. All mutant strains so far studied that are unable to reduce nitrogen, are also incapable of reducing acetylene or oxidizing dithionite. Representatives of various nitrogenaseless mutants have been characterized. Based on activity measurements they fall into three classes: those lacking both components (I − II − ), those lacking Component I (I − II + ) and those lacking Component II (I + II − ). Many strains have extremely low levels of activity for either component, but in some of these strains, cross-reacting material is made for one or both of the components. The EPR at g = 3.65 correlates well with the activity for Component I in several of these mutant strains, but in four of the mutants there appears to be 10-20-fold higher amounts of paramagnetic center than the nitrogen-fixing activity in in vitro tests would indicate.

Benefits of vegetation for soils with organic contaminants

Referee: Dr. Paul E. Olson, Colorado State University, Department of Biology, E414 Anatomy/Zoology Building, Fort Collins, CO 80523-1878 Plants have many beneficial effects on contaminated soils, including direct metabolism of some organic compounds, stimulation of microbial activity in the root zone, extraction of water, reduction of infiltration, improved aeration of the soil and stabilization against wind and water erosion. Some of these benefits have been explored and exploited in the newly named field of phytoremediation, whereas others remain largely in the domain of agronomy and ecology. This review attempts an assessment of the major environmental impacts of plants in general, recently termed phytotechnology, while including some case studies where particular species have been shown to have impacts on certain contaminants, more specifically termed phytoremediation. There is growing evidence that plants can have significant benefits in phytoremediating a range of complex organic molecules, including pesticides, solvents, explosives, and industrial byproducts.

Use of Infrared Microspectroscopy in Plant Growth and Development

Abstract Infrared microspectroscopy (IMS) has emerged as a key technique for the study of plant growth and development. The combination of IMS and synchrotron radiation has enabled researchers to analyze plant development at a cellular level. The spatial distribution of functional groups in plant tissue can be determined by the “chemical imaging” ability of IMS. Attenuated total reflectance (ATR) and polarized IR spectroscopies in combination with IMS makes sampling rapid and easy, providing direct analysis in situ. This review covers applications of IMS to study cell wall architecture and the major cell wall components: lignin, cellulose, and polysaccharides; applications for agricultural and feed products; and changes to plant structure due to biotic and abiotic stressors.

Nitrogenase II. Changes in the EPR signal of Component I (iron-molybdenum protein) of Azotobacter vinelandii nitrogenase during repression and derepression

Abstract The purified, native iron-molybdenum protein (Component I) of Azotobacter vinelandii nitrogenase shows EPR signals at g values of 4.32, 3.65, and 2.01, when observed below 40° K. The resonances near g = 4.32 and 3.65 are unobscured when whole nitrogen-fixing cells are observed, and we have compared the appearance and disappearance of these resonances with nitrogenase activity as well as Component I protein determined immunochemically, during derepression and repression of nitrogenase. The characteristic resonances are absent in cells grown on ammonium salts. During derepression the activity, EPR signal, and cross-reacting material appear and pass through a maximum in parallel. During repression the immunochemically-detectable protein decays inversely with cell growth, while the activity and signal are depressed considerably more rapidly. This suggests that a short-term control mechanism, including the substantial alteration of the paramagnetic center of Component I without elimination of the antigenic moiety, is responsible for rapid repression of nitrogenase by ammonia. EPR signals similar to those of Component I in Azotobacter were also observed at low temperatures in nitrogen-fixing cells of Clostridium pasteurianum, Klebsiella pneumoniae, and Bacillus polymyxa, suggesting that in vivo studies of Component I of nitrogenase may be feasible generally.

Potential for Plant-Based Remediation of Pesticide-Contaminated Soil and Water using Nontarget Plants such as Trees, Shrubs, and Grasses

Appropriate environmental management of pesticides includes their proper application, use of filter strips and riparian buffers to contain pesticides in runoff from fields, prompt cleanup of spills, and treatment processes for wastewater associated with manufacturing and equipment usage. Plants have beneficial effects in the management of pesticide-contaminated soil and water, including direct metabolism of many pesticides, stimulation of microbial activity in the root zone, extraction of contaminated water, and reduction of infiltrating contaminated water. In this work, we review the literature on nontarget plants that can grow in pesticide-contaminated soil and water, and the fate of pesticides in filter strips, riparian buffers, and vegetated remediation environments. Past research indicates that there are significant differences in the tolerance of plants to pesticides present in soil and water, and that some plants are more effective than others in the remediation of pesticide-contaminated soil and water. Thus, there is value in the identification of tolerant plants and favorable plant-based remediation technologies for management of pesticides and contaminated sites.

Fate of volatile chlorinated organic compounds in a laboratory chamber with alfalfa plants.

The fate of two volatile organo chlorinated compounds, 1,1,1-trichloroethane (TCA) and trichloroethylene (TCE), was studied in rhizosphere soil. Laboratory experiments were performed with alfalfa (Medicago sativa) growing in sandy silt soil fed continuously with groundwater contaminated with TCA and TCE at 50 and 200 μL/L, respectively. Methane generated in the groundwater provided evidence for anaerobic biodegradation. Groundwater samples indicated that the concentration of TCE decreased with axial position during the steady-state period. The flow rate of the effluent was significantly less than the inlet flow because of active evapotranspiration. Thus, a significant fraction of TCA and TCE disappeared. Headspace analysis of the gas in the enclosed chamber using a FT-IR spectrophotometer showed that small quantities of TCA and TCE migrated into the gas phase above the alfalfa plants ; no chlorinated intermediates or methane were found in this gas phase.

Nitrogenase: VII. Effect of component ratio, ATP and H2, on the distribution of electrons to alternative substrates

Some kinetic properties of purified component I (Mo-Fe protein) and component II (Fe protein) of nitrogenase (EC 1.7.99.2) from Azotobacter vinelandii have been examined. The apparent Km values for reducible substrates (0.1 atm for N2, 0.01 atm for acetylene) and dithionite (0.5 mM) are similar for osmotically shocked cell lysates and purified components. However, the ATP dependence of acetylene and N2 reduction varies sigmoidally with ATP concentration and as a function of the relative and absolute concentration of components I and II in the assay. Acetylene is reduced in preference to N2 in competitive assays when component I is in relative excess. Acetylene reduction is not as dependent upon ATP concentration as is N2 reduction, so that acetylene is also a preferred substrate at lower ATP levels. Hydrogen specifically inhibits N2 reduction, diverting electrons to acetylene when both substrates are present in the assay. We propose a model of the enzyme activity, in which the substrates for reduction are bound to component I with electrons being activated by component II. ATP may be involved in activating electrons and in maintaining the appropriate conformation or reduction state of components to allow effective reduction of substrates. The relative rate of reduction of alternative substrates is dependent on the concentration of the particular state(s) capable of reacting with each substrate. The concentration of a particular state of component I is a function of components I, II and ATPL