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PubMed1999

Dissection of the ozone-induced calcium signature.

The cellular responses of plants to numerous extracellular stimuli are mediated by transient elevations in the concentration of cytosolic free calcium ([Ca2+]cyt). We have addressed the question of how cells can use this apparently ubiquitous system to initiate so many specific and appropriate end responses. We show that the pollutant gas ozone elicits a biphasic Ca2+ response in intact Arabidopsis plants and a subsequent increase in expression of the gene encoding the antioxidant defence enzyme glutathione-S-transferase (GST). The second of the two [Ca2+]cyt peaks, but not the first, could be eliminated either by pre-treatment of plants with lanthanum chloride, or by reducing the duration of ozone fumigation. Under these conditions, ozone-induced GST expression was abolished. These data provide a functional dissection of the ozone Ca2+ signalling pathway and indicate that the second ozone-induced [Ca2+]cyt peak provides the necessary information to direct expression of GST.

Arabidopsis↗
PubMed1999

Enterobacter aerogenes outbreak in a neonatal intensive care unit.

BACKGROUND: Enterobacter aerogenes, a Gram-negative bacterium, is an important, although infrequent, cause of nosocomial bacteremia in the hospitalized pediatric and neonatal population. Enterobacter aerogenes was isolated for the first time in our neonatal intensive care unit (NICU) from blood culture of a 5-day-old neonate; 12 more cases were discovered in the next 70 days. The present report summarizes the clinico-bacteriological spectrum and outcome of the affected neonates. Efforts made to find the source of infection and curb the outbreak are also presented. METHODS AND RESULTS: Thirteen newborns, including seven preterms, acquired E. aerogenes septicemia. Perinatal risk factors were present in all the neonates. The mean birthweight of affected infants was 1880 +/- 540 g. Symptoms appeared at a mean age of 3.5 +/- 1.5 days (range 3-8 days). The clinical presentation was indistinguishable from septicemia caused by other Gram-negative organisms. Complications encountered included sclerema, bleeding diathesis, meningitis and shock. The organism, isolated from blood in all and from the cerebrospinal fluid in two cases, was found to be resistant to all antibiotics in the first five cases, but turned sensitive to gentamicin, cefotaxime and amikacin during the latter half of the epidemic. The bacterium in the last case (no. 13) was again found to be resistant to all the antibiotics. Overall mortality was 46.2%; the mean interval between onset of symptoms and death being 2.3 +/- 1.8 days. The organism was traced to the rubber pipe attached to a foot-operated suction machine in the NICU. The neonatal unit was temporarily closed, fumigated and reopened with strict instructions to follow proper hand washing protocol and ensure cohort nursing of infected infants. CONCLUSIONS: Enterobacter aerogenes is capable of causing nosocomial outbreaks of septicemia in NICU. Low birthweight infants with associated perinatal risk factors appear to be predisposed. The sensitivity patterns of the isolates highlight the capability of E. aerogenes to acquire or lose resistance to antibiotics rapidly during treatment. A high mortality rate coupled with a short interval between onset of symptoms and death, suggested high virulence of the strain.

Cross Infection↗
PubMed2003

Fungicidal and anti-aflatoxigenic effects of the essential oil of Cymbopogon citratus (DC.) Stapf. (lemongrass) against Aspergillus flavus Link. isolated from stored rice.

AIMS: To develop a natural fungicide against aflatoxigenic fungi, to protect stored rice, using the essential oil of lemongrass. METHODS AND RESULTS: Aspergillus flavus Link. was isolated from stored rice and identified as an aflatoxigenic strain. Lemongrass oil was tested against A. flavus and the test oil was fungistatic and fungicidal against the test pathogen at 0.6 and 1.0 mg ml(-1), respectively. Aflatoxin production was completely inhibited at 0.1 mg ml(-1). The results obtained from the thin layer chromatographic bioassay and gas chromatography indicated citral a and b as the fungicidal constituents in lemongrass oil. During the fumigant toxicity assay of lemongrass oil, the sporulation and the mycelial growth of the test pathogen were inhibited at the concentrations of 2.80 and 3.46 mg ml(-1), respectively. CONCLUSION: Lemongrass oil could be used to manage aflatoxin formation and fungal growth of A. flavus in stored rice. SIGNIFICANCE AND IMPACT OF THE STUDY: Currently, fungicides are not used to control fungal pests or mycotoxin production on stored rice. Rice treated with the essential oil of lemongrass could be used to manage fungal pests as well as the insect pests in stored rice. The essential oil is chemically safe and acceptable to consumers, as synthetic chemical fungicides can cause adverse health effects to consumers.

Aflatoxins↗
PubMed2005

Beech leaf colonization by the endophyte Apiognomonia errabunda dramatically depends on light exposure and climatic conditions.

Ozone and light effects on endophytic colonization by Apiognomonia errabunda of adult beech trees (Fagus sylvatica) and their putative mediation by internal defence compounds were studied at the Kranzberg Forest free-air ozone fumigation site. A. errabunda colonization was quantified by "real-time PCR" (QPCR). A. errabunda-specific primers allowed detection without interference by DNA from European beech and several species of common genera of plant pathogenic fungi, such as Mycosphaerella, Alternaria, Botrytis, and Fusarium. Colonization levels of sun and shade leaves of European beech trees exposed either to ambient or twice ambient ozone regimes were determined. Colonization was significantly higher in shade compared to sun leaves. Ozone exhibited a marginally inhibitory effect on fungal colonization only in young leaves in 2002. The hot and dry summer of 2003 reduced fungal colonization dramatically, being more pronounced than ozone treatment or sun exposure. Levels of soluble and cell wall-bound phenolic compounds were approximately twice as high in sun than in shade leaves. Acylated flavonol 3- O-glycosides with putatively high UV-B shielding effect were very low in shade canopy leaves. Ozone had only a minor influence on secondary metabolites in sun leaves. It slightly increased kaempferol 3- O-glucoside levels exclusively in shade leaves. The frequently prominent hydroxycinnamic acid derivative, chlorogenic acid, was tested for its growth inhibiting activity against Apiognomonia and showed an IC50 of approximately 8 mM. Appearance of Apiognomonia-related necroses strongly correlated with the occurrence of the stress metabolite, 3,3',4,4'-tetramethoxybiphenyl. Infection success of Apiognomonia was highly dependent on light exposure, presumably affected by the endogenous levels of constitutive phenolic compounds. Ozone exerted only minor modulating effects, whereas climatic factors, such as pronounced heat periods and drought, were dramatically overriding.

Ascomycota↗
PubMed2005

Short term effects of ozone on the plant-rhizosphere-bulk soil system of young beech trees.

Plant growth largely depends on microbial community structure and function in the rhizosphere. In turn, microbial communities in the rhizosphere rely on carbohydrates provided by the host plant. This paper presents the first study on ozone effects in the plant-rhizosphere-bulk soil system of 4-year-old beech trees using outdoor lysimeters as a research platform. The lysimeters were filled with homogenized soil from the corresponding horizons of a forest site, thus minimizing field heterogeneity. Four lysimeters were treated with ambient ozone (1 x O3) and four with double ambient ozone concentrations (2 x O3; restricted to 150 ppb). In contrast to senescence, which was almost unaffected by ozone treatment, both the photochemical quantum yield of photosystem II (PSII) and leaf gas exchange were reduced (11 - 45 %) under the elevated O3 regime. However, due to large variation between the plants, no statistically significant O3 effect was found. Even though the amount of primary metabolites, such as sugar and starch, was not influenced by elevated O3 concentrations, the reduced photosynthetic performance was reflected in leaf biochemistry in the form of a reduction in soluble phenolic metabolites. The rhizosphere microbial community also responded to the O3 treatment. Both community structure and function were affected, with a tendency towards a lower diversity and a significant reduction in the potential nutrient turnover. In contrast, litter degradation was unaffected by the fumigation, indicating that in situ microbial functionality of the bulk soil did not change.

Carbohydrate Metabolism↗
PubMed2006

Chlorophyll a fluorescence imaging of ozone-stressed Brassica napus L. plants differing in glucosinolate concentrations.

Brassicaceae are characterised by glucosinolates (GS), which appear to be involved not only in biotic but also in abiotic stress responses of plants. We investigated the effect of O (3) stress on leaf GS concentrations in two lines of BRASSICA NAPUS L., differing in GS content. Ozone fumigation decreased GS concentrations in leaves of B. NAPUS of one line. In control conditions, chlorophyll content, rates of saturating photosynthesis, and quantum yield of photosystem 2 differed between the two BRASSICA lines, but differences were smaller in O (3)-stress conditions, suggesting that the relationship between leaf GS concentration and sensitivity to abiotic stress merits further research. In agreement with other ecophysiological measurements, chlorophyll fluorescence imaging clearly distinguished both lines and in some cases also treatments. A method for analysis of fluorescence images accounting for the two-dimensional leaf heterogeneity is presented.

Brassica napus↗
PubMed1997

Ethical aspects and dilemmas of fertility control of unwanted wildlife: an animal welfarist's perspective.

Proposals to manipulate the fertility of wild, free-living animals extend the domination humans already exercise over domesticated animals. Current lethal methods for population control include poisoning, trapping, hunting, dogging, shooting, explosives, fumigants, and deliberately introduced disease. Animal welfare interests are based on individual animal suffering, but those interests are often overshadowed by labelling of groups of animals as pests, resource species, national emblem or endangered species. Public concern for animal welfare and acceptance of new population control methods will be influenced by such labels. The animal welfare implications of new population control technology must be balanced against the existing inhumane lethal methods used. It will be difficult to resolve the dilemma of a mechanism for disseminating a fertility control agent that will cause some animal suffering (e.g. a genetically-manipulated myxoma virus for European rabbits), yet may reduce future rabbit populations and therefore the number suffering from lethal methods. An Animal Impact Statement is proposed as a tool to assist debate during development of fertility control methods and for decision making prior to their use. A comprehensive and objective Animal Impact Statement may introduce an ethic that moves the pendulum from attitudes that allow sentient animals to be destroyed by any and all available means, towards a more objective selection of the most effective and humane methods.

Animal Welfare↗
PubMed2006

Combinatorially selected defense peptides protect plant roots from pathogen infection.

Agricultural productivity and sustainability are continually challenged by emerging and indigenous pathogens. Currently, many pathogens can be combatted only with biocides or environmentally dangerous fumigants. Here, we report a rapid and pathogen-specific strategy to reduce infection by organisms that target plant roots. Combinatorially selected defense peptides, previously shown to effect premature encystment of Phytophthora capsici zoospores, were fused to maize cytokinin oxidase/dehydrogenase as a display scaffold. When expressed in tomato roots, the peptide-scaffold constructs were secreted and accumulated to sufficient concentrations in the rhizosphere to induce zoospore encystment and thereby deter taxis to the root surface. Pathogen infection was significantly inhibited in roots expressing bioactive peptides fused to the maize cytokinin oxidase/dehydrogenase scaffold. This peptide-delivery technology is broadly applicable for rapid development of plant defense attributes against plant pathogens.

Combinatorial Chemistry Techniques↗
PubMed1980

Ambient air concentration of sulfur dioxide affects flight activity in bees.

Three long-term (16-29 days) low-level (0.14-0.28 ppm) sulfur dioxide fumigations showed that exposure to this gas has deleterious effects on male sweat bees (Lasioglossum zephrum). Although effects on mortality were equivocal, flight activity was definitely reduced. Because flight is necessary for successful mating behavior, the results suggest that sulfur dioxide air pollution could adversely affect this and doubtless other terrestrial insects.

Journal Article↗
PubMed1995

Molecular mechanisms of defense by rhizobacteria against root disease.

Genetic resistance in plants to root diseases is rare, and agriculture depends instead on practices such as crop rotation and soil fumigation to control these diseases. "Induced suppression" is a natural phenomenon whereby a soil due to microbiological changes converts from conducive to suppressive to a soilborne pathogen during prolonged monoculture of the susceptible host. Our studies have focused on the wheat root disease "take-all," caused by the fungus Gaeumannomyces graminis var. tritici, and the role of bacteria in the wheat rhizosphere (rhizobacteria) in a well-documented induced suppression (take-all decline) that occurs in response to the disease and continued monoculture of wheat. The results summarized herein show that antibiotic production plays a significant role in both plant defense by and ecological competence of rhizobacteria. Production of phenazine and phloroglucinol antibiotics, as examples, account for most of the natural defense provided by fluorescent Pseudomonas strains isolated from among the diversity of rhizobacteria associated with take-all decline. There appear to be at least three levels of regulation of genes for antibiotic biosynthesis: environmental sensing, global regulation that ties antibiotic production to cellular metabolism, and regulatory loci linked to genes for pathway enzymes. Plant defense by rhizobacteria producing antibiotics on roots and as cohabitants with pathogens in infected tissues is analogous to defense by the plant's production of phytoalexins, even to the extent that an enzyme of the same chalcone/stilbene synthase family used to produce phytoalexins is used to produce 2,4-diacetylphloroglucinol. The defense strategy favored by selection pressure imposed on plants by soilborne pathogens may well be the ability of plants to support and respond to rhizosphere microorganisms antagonistic to these pathogens.

Journal Article↗
PubMed1996

Environmental stress sensitivity of an ascorbic acid-deficient Arabidopsis mutant.

L-ascorbic acid (vitamin C) is a powerful reducing agent found in millimolar concentrations in plants, and is proposed to play an important role in scavenging free radicals in plants and animals. However, surprisingly little is known about the role of this antioxidant in plant environmental stress adaptation or ascorbate biosynthesis. We report the isolation of soz1, a semi-dominant ozone-sensitive mutant that accumulates only 30% of the normal ascorbate concentration. The results of genetic approaches and feeding studies show that the ascorbate concentration affects foliar resistance to the oxidizing gas ozone. Consistent with the proposed role for ascorbate in reactive oxygen species detoxification, lipid peroxides are elevated in soz1, but not in wild type following ozone fumigation. We show that the soz1 mutant is hypersensitive to both sulfur dioxide and ultraviolet B irradiation, thus implicating ascorbate in defense against varied environmental stresses. In addition to defining the first ascorbate deficient mutant in plants, these results indicate that screening for ozone-sensitive mutants is a powerful method for identifying physiologically important antioxidant mechanisms and signal transduction pathways. Analysis of soz1 should lead to more information about the physiological roles and metabolism of ascorbate.

Arabidopsis↗
PubMed2004

Gliomas and farm pesticide exposure in men: the upper midwest health study.

The National Institute for Occupational Safety and Health evaluated farm pesticide exposure and glioma risk in a study that included 457 glioma cases and 648 population-based controls, all adult men (18-80 yr old) and nonmetropolitan residents of Iowa, Michigan, Minnesota, and Wisconsin. Multiple logistic regressions were used to control for farm residence, age, age group, education, and exposure to other pesticides. No associations were found between glioma and 12 specific pesticides. We estimated adjusted odds ratios (ORs) and 95% confidence intervals (CIs) and found reduced glioma risk for insecticides (OR = 0.53, CI = 0.37-0.77), fumigants (OR = 0.57, CI = 0.34-0.95), and organochlorines (OR = 0.66, CI = 0.47-0.94). In analyses excluding proxy respondents (47% of cases) most CIs included 1.0. No positive association of farm pesticide exposure and glioma was found. Other farm exposures may explain the excess brain cancer risk seen in previous studies.

Adolescent↗
PubMed1980

The occurrence of salmonellae during the rearing of broiler birds.

1. The incidence of salmonellae was studied in two broiler houses at each of two commercial sites in an integrated commercial enterprise. 2. Salmonellae were not isolated from the empty, cleaned and fumigated houses and only on one occasion from the foodstuffs. 3. Salmonellae were isolated from the environment of the chicks and spasmodically from the litter, water troughs and dust. 4. The incidence of infection of the chicks did not influence the number of isolations of salmonellae from the environment of the birds during rearing. 5. Water in the water troughs rather than foodstuffs appeared to be the major oral route of infection or re-infection of birds during rearing.

Animals↗
PubMedDate not supplied

Food irradiation: is it an alternative to chemical preservatives?

Generalizations about effects of irradiation may be misleading if the dose and commodities are not specified. Irradiation could be used for inhibition of sprouting, disinfestation, destruction of parasites in meat, to delay maturation of fruit and for pasteurization and sterilization. In some applications it could replace chemical sprout inhibitors, fumigants and chemical preservatives; in other cases it may have unique advantages e.g. in eradication of non-spore-forming pathogens in dry or frozen foods. Toxicological and nutritional evaluation has repeatedly confirmed the safety of irradiated foods. Effects on nutritional quality are frequently comparable with heat treatment and sometimes more conservative, particularly if oxygen is excluded. While food irradiation could be an alternative to chemical preservatives, misinformation has led to uncertainties as to its future.

Food↗
PubMed1988

Perceived causes and traditional treatment of diarrhoea by mothers in Eastern Sudan.

Mothers of Eastern Sudan seek or practice traditional treatment for diarrhoeal disease in their children based on their perception of causation. Fifty-six mother groups from 39 villages and 17 urban centres were surveyed in this study. The collected data were grouped by definition of diarrhoea, its perceived causes and practiced treatment thought to be appropriate. Differences were shown between the urban and rural groups. A longer list of perceived causes was obtained from rural mothers. Fumigation and use of rice water and custard were the preferred managements of urban mothers, while cautery, use of mihaya and goat's milk prevailed in rural areas. The importance of having the definition of diarrhoea cited in future studies is discussed and recommended.

Diarrhea, Infantile↗
PubMed1986

Automatic headspace sampling for determination of ethylene dibromide residues in cereals.

The possibility was investigated to apply a commercially available automatic head-space sampler in trace analysis of ethylene dibromide (EDB, 1,2-dibromoethane), in cereals. Samples of rice and wheat flour were thermostatted in closed vials at 70 degrees C for 30 min. The top gas was then automatically introduced into a gas chromatograph equipped with an electron capture detector. Quantitation was performed using external standards (untreated samples spiked with solutions of EDB in N,N'-dimethylacetamide). The relative standard deviation of the method was 3.4% for rice and 4.5% for wheat flour, at a residue level of 0.008 mg/kg. The detection limit was 0.001 mg/kg (the official EC residue tolerance is 0.01 mg/kg). Preliminary experiments with other fumigants were carried out as well. The headspace technique in question has the following advantages over other methods for determining EDB residues in cereals: 1. No sample pre-treatment like extraction, steam distillation, purge and trap etc.; 2. Automated sample handling; 3. "Clean" chromatograms.

Autoanalysis↗
PubMed1980

Evaluation pf methodology for determining 1,2-dibromoethane (EDB) in ambient air.

EDB (ethylene dibromide) is of regulatory interest because it has cancer inducing properties and is a causative agent of aspermia. Methodology used in determining the extent of exposure of workers to EDB in a citrus fumigation facility was evaluated. The purpose of this effort was to develop and/or evaluate the methodology. A number of solid adsorbents were evaluated for trapping EDB. Charcoal was found to be the most efficient for this application. The influence of a number of factors, e.g., humidity, biphenyl concentration and solvents, on trapping and elution efficiency was determined. The level of sensitivity attained in these studies exceeds that necessary to monitor the proposed standard of a maximum of 1 mg/m3 for a 15 min occupational exposure.

Adsorption↗
PubMed1980

Consideration of the possible carcinogenicity of some pesticides.

The sophistication, sensitivity, and the predictability of carcinogenesis bioassays using small rodents is reviewed. Bioassays were conducted using both sexes of mice (B6C3F1:C57BL/6xC3H F1 hybrid) and rats (Osborne-Mendel or Fisher 344). Chemicals tested included three acaracides, two fungicides, two fumigants, four herbicides, twelve chlorinated insecticides, and five organo-phosphorus insecticides. The tumor response of each test strain and sex to the above chemicals is discussed, as well as the spontaneous tumor incidence of each strain. The results suggest caution when interpreting the data from bioassays.

Animals↗