The role of environmental factors in asthma. (1/15)

Although the everyday experience of asthmatic patients provides ample anecdotal evidence that environmental exposures provoke bronchospasm, it has proved more difficult to assess the impact of air quality on the timing of asthma attacks and the prevalence of asthma in populations. Spectacular 'asthma epidemic days' are sometimes attributable to exceptional outdoor aero-allergen exposures. By comparison, effects of inorganic particles and gaseous pollutants in outdoor air on the incidence of asthma attacks are subtle and poorly quantified. Environmental tobacco smoke and mould growth are the indoor factors most consistently associated with respiratory morbidity, but their roles in initiating allergic asthma remain uncertain. Evidence relating asthma risk to fumes from gas cooking, and to allergens from dust mites and household pets remains confused and controversial. It is unlikely that trends in either outdoor or indoor air pollution have contributed substantially to the rise in prevalence of asthma and allergic disease in recent decades.  (+info)

Laboratory-scale evidence for lightning-mediated gene transfer in soil. (2/15)

Electrical fields and current can permeabilize bacterial membranes, allowing for the penetration of naked DNA. Given that the environment is subjected to regular thunderstorms and lightning discharges that induce enormous electrical perturbations, the possibility of natural electrotransformation of bacteria was investigated. We demonstrated with soil microcosm experiments that the transformation of added bacteria could be increased locally via lightning-mediated current injection. The incorporation of three genes coding for antibiotic resistance (plasmid pBR328) into the Escherichia coli strain DH10B recipient previously added to soil was observed only after the soil had been subjected to laboratory-scale lightning. Laboratory-scale lightning had an electrical field gradient (700 versus 600 kV m(-1)) and current density (2.5 versus 12.6 kA m(-2)) similar to those of full-scale lightning. Controls handled identically except for not being subjected to lightning produced no detectable antibiotic-resistant clones. In addition, simulated storm cloud electrical fields (in the absence of current) did not produce detectable clones (transformation detection limit, 10(-9)). Natural electrotransformation might be a mechanism involved in bacterial evolution.  (+info)

Asthma admissions and thunderstorms: a study of pollen, fungal spores, rainfall, and ozone. (3/15)

Asthma admissions have been reported to increase during thunderstorms. In some cases, this has been attributed to rises in pollen or fungal spore counts occurring alone or in combination with rainfall. We tested the hypothesis that thunderstorms in general are associated with asthma admissions, and investigated the possible roles of pollen, fungal spores, ozone, and other meteorological factors. We obtained data on multiple pollen and fungal spore counts, rainfall, temperature, ambient ozone concentrations, and asthma admissions for 32 dates when lightning strikes were recorded in the Cardiff/Newport area, and 64 matched dates in previous and subsequent years. Poisson regression models were used to investigate associations between admissions and proposed causative environmental factors. The number of asthma admissions was greater on days with thunderstorms than on control days (p<0.001). There were no associations or interactions between admissions and any pollen or fungal spore counts or rainfall. After adjusting for thunderstorms, there was an independent association between increasing ozone concentration, when temperature was included in the model, and increasing admissions (p=0.02). Asthma admissions are increased during thunderstorms. The effect is more marked in warmer weather, and is not explained by increases in grass pollen, total pollen or fungal spore counts, nor by an interaction between these and rainfall. There was an independent, positive association between ozone concentrations and asthma admissions.  (+info)

Corona chemistry in Titan. (4/15)

The atmosphere of Titan is constantly bombarded by galactic cosmic rays and Saturnian magnetospheric electrons causing the formation of free electrons and primary ions, which are then stabilized by ion cluster formation and charging of aerosols. These charged particles accumulate in drops in cloud regions of the troposphere. Their abundance can substantially increase by friction, fragmentation or collisions during convective activity. Charge separation occurs with help of convection and gravitational settling leading to development of electric fields within the cloud and between the cloud and the ground. Neutralization of these charged particles leads to corona discharges which are characterized by low current densities. We have therefore, experimentally studied the corona discharge of a simulated Titan's atmosphere (10% methane and 2% argon in nitrogen) at 500 Torr and 298 K by GC-FTIR-MS techniques. The main products have been identified as hydrocarbons (ethane, ethyne, ethene, propane, propene+propyne, cyclopropane, butane, 2-methylpropane, 2-methylpropene, n-butane, 2-butene, 2,2-dimethylpropane, 2-methylbutane, 2-methylbutene, n-pentane, 2,2-dimethylbutane, 2-methylpentane, 3-methylpentane, n-hexane, 2,2-dimethylhexane, 2,2-dimethylpentane, 2,2,3-trimethylbutane, 2,3-dimethylpentane and n-heptane), nitriles (hydrogen cyanide, cyanogen, ethanenitrile, propanenitrile, 2-methylpropanenitrile and butanenitrile) and a highly branched hydrocarbon deposit. We present the trends of hydrocarbons and nitriles formation as a function of discharge time in an ample interval and have derived their initial yields of formation. The results clearly demonstrate that a complex organic chemistry can be initiated by corona processes in the lower atmosphere. Although photochemistry and charged particle chemistry occurring in the stratosphere can account for many of the observed hydrocarbon species in Titan, the predicted abundance of ethene is too low by a factor of 10 to 40. While some ethene will be produced by charged-particle chemistry, the production of ethene by corona processes and its subsequent diffusion into the stratosphere appears to be an adequate source. Because little UV penetrates to the lower atmosphere to destroy the molecules formed there, the corona-produced species may be long-lived and contribute significantly to the composition of the lower atmosphere and surface.  (+info)

A preliminary study on the relation between thunderstorms and mortality of in-patients. (5/15)

BACKGROUND: The aim of this study was to investigate the association between thunderstorms and mortality of in-patients. METHODS: Data for in-patients and deaths in internal medicine departments from four hospitals in Shanghai were collected and grouped according to meteorological conditions. RESULTS: Weekly mortality of in-patients was significantly higher on days with thunderstorms than on fine days. This effect was significant for patients in respiratory, cardiovascular and neurology wards but not in the wards of other specialties.  (+info)

Isolation of lightning-competent soil bacteria. (6/15)

Artificial transformation is typically performed in the laboratory by using either a chemical (CaCl(2)) or an electrical (electroporation) method. However, laboratory-scale lightning has been shown recently to electrotransform Escherichia coli strain DH10B in soil. In this paper, we report on the isolation of two "lightning-competent" soil bacteria after direct electroporation of the Nycodenz bacterial ring extracted from prairie soil in the presence of the pBHCRec plasmid (Tc(r), Sp(r), Sm(r)). The electrotransformability of the isolated bacteria was measured both in vitro (by electroporation cuvette) and in situ (by lightning in soil microcosm) and then compared to those of E. coli DH10B and Pseudomonas fluorescens C7R12. The electrotransformation frequencies measured reached 10(-3) to 10(-4) by electroporation and 10(-4) to 10(-5) by simulated lightning, while no transformation was observed in the absence of electrical current. Two of the isolated lightning-competent soil bacteria were identified as Pseudomonas sp. strains.  (+info)

Natural Pseudomonas sp. strain N3 in artificial soil microcosms. (7/15)

The lightning-competent Pseudomonas sp. strain N3, recently isolated from soil, has been used to study the extent of natural electrotransformation (NET) or lightning transformation as a horizontal gene transfer mechanism in soil. The variation of electrical fields applied to the soil with a laboratory-scale lightning system provides an estimate of the volume of soil affected by NET. Based on the range of the electric field that induces NET of Pseudomonas strain N3, the volume of soil, where NET could occur, ranges from 2 to 950 m(3) per lightning strike. The influence of DNA parameters (amount, size, and purity) and DNA soil residence time were also investigated. NET frequencies (electrotransformants/recipient cells) ranged from 10(-8) for cell lysate after 1 day of residence in soil to 4 x 10(-7) with a purified plasmid added immediately before the lightning. The electrical field gradient (in kilovolts per cm) also played a role as NET frequencies ranging from 1 x 10(-5) at 2.3 kV/cm to 1.7 x 10(-4) at 6.5 kV/cm.  (+info)

Phosphorus in prebiotic chemistry. (8/15)

The prebiotic synthesis of phosphorus-containing compounds-such as nucleotides and polynucleotides-would require both a geologically plausible source of the element and pathways for its incorporation into chemical systems on the primitive Earth. The mineral apatite, which is the only significant source of phosphate on Earth, has long been thought to be problematical in this respect due to its low solubility and reactivity. However, in the last decade or so, at least two pathways have been demonstrated which would circumvent these perceived problems. In addition, recent results would seem to suggest an additional, extraterrestrial source of reactive phosphorus. It appears that the 'phosphorus problem' is no longer the stumbling block which it was once thought to be.  (+info)