Virucidal Effect of Transient Electric Arcs in Aqueous Systems

Bacterial and animal viruses were inactivated by high voltage electrical discharges in water. The sensitivity of phages to the immediate component of this effect was correlated to the sensitivity to ultraviolet radiation. Transient electrical arcs in weak electrolytes also generated chemical compounds which were virucidal against phages T3, T5, and varphiX174 but were only slightly virucidal against phages T2 and T4.     

Influence of the Conductivity of the Discharge Liquid on the Microbicidal Effect of Transient Electric Arcs in Aqueous Systems

The microbicidal effect of electrical discharges on microorganisms suspended in the discharge liquid was reduced when the liquid contained high concentrations of inorganic salts (conductivity k >/= 5 mmho/cm). A higher discharge voltage and a smaller distance between the submerged electrodes counteracted this reduction. The decrease in the microbicidal effect was accompanied by a change in the electrical current and by a decreased yield of microbicidal photons from the electric discharge.     

Bactericidal Effect of Various Combinations of Gamma Radiation and Chloramine on Aqueous Suspensions of Escherichia coli

Methods of combining gamma radiation with chloramine to disinfect aqueous suspensions of Escherichia coli were investigated. Logarithmically grown cells were exposed to the bactericidal agents sequentially (i.e., radiation followed by chloramine, and chloramine followed by radiation) and simultaneously. Regardless of which combination was used, the bactericidal effect was always less than additive. During the phase of work involving the simultaneous addition of both agents, it was observed that chloramine was destroyed more rapidly by radiation than were the organisms. Since an increase in the bactericidal effectiveness of either disinfectant by prior or simultaneous treatment of the cells with the other disinfectant was not achieved in buffered distilled water, it was concluded that disinfection of wastewater effluents by combining ionizing radiation with chloramine would not be economically feasible.     

Growth and Secondary Metabolite Production by Hairy Roots of Tagetes Patula in Aqueous Two-Phase Systems

Hairy roots of Tagetes patula have been grown in aqueous two-phase systems. After selecting suitable polymers from single-phase experiments (in which salt phases were unable to support growth in the desired concentrations) several two-phase systems were tested for their influence on cell growth and thiophene production. Cell growth occurred in all aqueous two-phase systems, but the highest growth rate was achieved in normal medium. There was no difference in thiophene production between medium and aqueous two-phase systems. The partition of thiophenes favoured slightly the more hydrophobic top phase in most cases, while the cells were confined to the bottom phase. One aqueous two-phase system (15% polyethyleneglycol 10,000 and 15% Reppal PES 200) was tested in a stirred tank reactor with normal medium as a control. The growth rate in medium was higher than in the aqueous two-phase system, while the thiophene production per unit cell weight was in the same range for both systems. The excretion of thiophenes in the reactor with the aqueous two-phase system was about ten times as high as in the control reactor. The amount excreted was however still not more than 3% of the total production.     

Growth and Secondary Metabolite Production by Hairy Roots of Tagetes Patula in Aqueous Two-Phase Systems

Hairy roots of Tagetes patula have been grown in aqueous two-phase systems. After selecting suitable polymers from single-phase experiments (in which salt phases were unable to support growth in the desired concentrations) several two-phase systems were tested for their influence on cell growth and thiophene production. Cell growth occurred in all aqueous two-phase systems, but the highest growth rate was achieved in normal medium. There was no difference in thiophene production between medium and aqueous two-phase systems. The partition of thiophenes favoured slightly the more hydrophobic top phase in most cases, while the cells were confined to the bottom phase. One aqueous two-phase system (15% polyethyleneglycol 10,000 and 15% Reppal PES 200) was tested in a stirred tank reactor with normal medium as a control. The growth rate in medium was higher than in the aqueous two-phase system, while the thiophene production per unit cell weight was in the same range for both systems. The excretion of thiophenes in the reactor with the aqueous two-phase system was about ten times as high as in the control reactor. The amount excreted was however still not more than 3% of the total production.     

Enhancement of the Bactericidal Effect of Antibiotics by Inhibition of Enzymes Involved in Production of Hydrogen Sulfide in Bacteria

Molecular Biology - Counteraction of the origin and distribution of multidrug-resistant pathogens responsible for intra-hospital infections is a worldwide issue in medicine. In this brief review,...     

Rapid High-Level Production of Functional HIV Broadly Neutralizing Monoclonal Antibodies in Transient Plant Expression Systems

Passive immunotherapy using anti-HIV broadly neutralizing monoclonal antibodies (mAbs) has shown promise as an HIV treatment, reducing mother-to-child-transmission (MTCT) of simian/human immunodeficiency virus (SHIV) in non-human primates and decreasing viral rebound in patients who ceased receiving anti-viral drugs. In addition, a cocktail of potent mAbs may be useful as mucosal microbicides and provide an effective therapy for post-exposure prophylaxis. However, even highly neutralizing HIV mAbs used today may lose their effectiveness if resistance occurs, requiring the rapid production of new or engineered mAbs on an ongoing basis in order to counteract the viral resistance or the spread of a certain HIV-1 clade in a particular region or patient. Plant-based expression systems are fast, inexpensive and scalable and are becoming increasingly popular for the production of proteins and monoclonal antibodies. In the present study, Agrobacterium-mediated transient transfection of plants, utilizing two species of Nicotiana, have been tested to rapidly produce high levels of an HIV 89.6PΔ140env and several well-studied anti-HIV neutralizing monoclonal antibodies (b12, 2G12, 2F5, 4E10, m43, VRC01) or a single chain antibody construct (m9), for evaluation in cell-based viral inhibition assays. The protein-A purified plant-derived antibodies were intact, efficiently bound HIV envelope, and were equivalent to, or in one case better than, their counterparts produced in mammalian CHO or HEK-293 cells in both neutralization and antibody dependent viral inhibition assays. These data indicate that transient plant-based transient expression systems are very adaptable and could rapidly generate high levels of newly identified functional recombinant HIV neutralizing antibodies when required. In addition, they warrant detailed cost-benefit analysis of prolonged incubation in plants to further increase mAb production.     

Computer Simulation of Aqueous Biomolecular Systems

Abstract

Computer simulation techniques are increasingly being used to predict structural and thermodynamic properties of large heterogeneous macromolecule and solvent assemblies. We discuss, with examples from our own studies, some problems we and others have experienced in using these techniques, which were originally devised for simple liquids. In particular, we consider the problems which arise from the large size and heterogeneity of macromolecule water systems, comparisons with experimental data and equilibration and sampling procedures.     

Biodegradation of N-Nitrosodimethylamine in Aqueous and Soil Systems

N-Nitrosodimethylamine (NDMA) was mineralized by microorganisms in aqueous and soil systems. Initial rates of mineralization (micrograms per milliliter per day) were calculated for a wide range of initial concentrations of NDMA (micrograms per milliliter to picograms per milliliter). Log-log plots of the data were fitted with both linear and nonlinear least-squares analyses; however, linear models provided better fits for the kinetic data in all cases. The slopes of the linear fits were not significantly different than 1.0 (P < 0.05); thus, first-order reaction kinetics were in effect over the range of concentrations tested, and saturation kinetics were not achieved. Rate constants (day⁻¹) and total percent mineralized increased with decreasing initial concentrations of NDMA. Rates of mineralization were reduced in aqueous systems when supplemental carbon was available, whereas in soils, percentages of organic matter and supplemental carbon had little effect on rates of mineralization. Implications of these results for predictions of rates and threshold limits of mineralization activity in natural systems are discussed. A laboratory scale simulated trickling filter containing an activated charcoal bed provided a suitable environment for mineralization of NDMA at concentrations of 50 and 100 μg/ml on a continuous basis. NDMA was not toxic to natural populations of microorganisms at concentrations up to 10 mg/ml. Using high-pressure liquid chromatography coupled with radioactivity detection, we identified formaldehyde and methylamine as intermediates produced during the biodegradation of NDMA.     

Transient Potentials in Dendritic Systems of Arbitrary Geometry

A simple graphical calculus is developed that generates analytic solutions for membrane potential transforms at any point on the dendritic tree of neurons with arbitrary dendritic geometries, in response to synaptic “current” inputs. Such solutions permit the computation of transients in neurons with arbitrary geometry and may facilitate analysis of the role of dendrites in such cells.     

Transient Responses to Spatial Perturbations in Advective Systems

We study the transient dynamics, following a spatially-extended perturbation of models describing populations residing in advective media such as streams and rivers. Our analyses emphasize metrics that are independent of initial perturbations—resilience, reactivity, and the amplification envelope—and relate them to component spatial wavelengths of the perturbation using spatial Fourier transforms of the state variables. This approach offers a powerful way of understanding the influence of spatial scale on the initial dynamics of a population following a spatially variable environmental perturbation, an important property in determining the ecological implications of transient dynamics in advective systems. We find that asymptotically stable systems may exhibit transient amplification of perturbations (i.e., have positive reactivity) for some spatial wavelengths and not others. Furthermore, the degree and duration of amplification varies strongly with spatial wavelength. For two single-population models, there is a relationship between transient dynamics and the response length that characterizes the steady state response to spatial perturbations: a long response length implies that peak amplification of perturbations is small and occurs fast. This relationship holds less generally in a specialist consumer-resource model, likely due to the model’s tendency for flow-induced instabilities at an alternative characteristic spatial scale.     

The Blue Arcs of the Retina

Around a dim light viewed in a dark room can be seen faint blue-gray arcs which occupy that part of the visual field corresponding to the retina where the arcuate nerve fiber bundle passes from macular ganglion cell bodies to the optic nerve. These blue arcs of the retina are an entoptic phenomenon in which action potentials of the arcuate nerve fiber bundle presumably excite adjacent neurons. The experiments here described show that the light stimulus initially evoking the blue arcs excites cones and not rods as has been generally believed until now. Another commonly held idea is that the blue arcs are produced by bioluminescence or fluorescence associated with the action potentials in the arcuate nerve fiber bundle. The experiments described here disprove this hypothesis.     

Bactericidal Effect of Hydrogen Peroxide on Spacecraft Isolates

Solutions of 3, 10, and 15% hydrogen peroxide were found to have pronounced bactericidal effects, as a function of time of exposure, on sporeformers and non-sporeformers isolated from spacecraft.     

Systems of Production and Social Discourse: The Skipper Effect Revisited

We have argued that differences in success in Icelandic fishing are statistically explained more by technical and ecological factors than by personal qualities of skippers, the "skipper effect." Research by other scholars has reopened the discussion of the skipper effect. We assess some of the statistical arguments, pointing out that while there may be a strong skipper effect in some societies, in other societies it is weak or negligible. We suggest that it is important to distinguish between the statistical reality of the skipper effect and its sociology and that the concept of skipper effect is of limited utility in comparative studies, since different researchers using it have not always been talking about the same phenomena and fishing success is conceived differently in different societies. The discussion of the skipper effect echoes debates on resource management and the authenticity of folk models, as well as larger debates in social theory on the relationship between the symbolic and the real and the role of history and agency. Folk theories of production, we argue, are best regarded as cultural accounts constructed in social discourse, in the context of production systems.