Chlamydiosis in workers at a duck farm and processing plant   总被引：4，自引：0，他引：4  

DG HINTON  A. SHIPLEY†  JW GALVIN‡  JT HARKIN‡  RA BRUNTON† 《Australian veterinary journal》1993,70(5):174-176

SUMMARY An outbreak of chlamydiosis was Investigated in workers at a duck farm and processing plant during winter 1989. Chlamydia psittaci was isolated from ducks, but there was little evidence of clinical chlamydiosis in the ducks. Serological tests showed that 76% of workers had been exposed to Infection, 12% recently, 16% had not been exposed and 8% had inconclusive test results. There was a strong association (P < 0.05) between years of employment and exposure to Infection. Infection appeared to be contracted during the first year of employment. Measures were Implemented to reduce shed contamination and control rodents and wild birds. At the same time, ducks were medicated, the processing plant was modified, work practices were altered and workers were advised about chlamydiosis to reduce the risk of human infection.  相似文献   

Production of phenolic metabolites by a soil pseudomonad     

David A. Bencini  Charles R. Howell  James R. Wild 《Soil biology & biochemistry》1983,15(4):491-492

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Toxicity of (+)- and (-)-gossypol to the plant pathogen,Rhizoctonia solani     

Puckhaber LS  Dowd MK  Stipanovic RD  Howell CR 《Journal of agricultural and food chemistry》2002,50(24):7017-7021

The dimeric sesquiterpene gossypol occurs naturally in cottonseed and other parts of the cotton plant. Gossypol exists as enantiomers because of the restricted rotation around the central binaphthyl bond. The (-)-enantiomer is toxic to nonruminant animals while the (+)-enantiomer exhibits little, if any, toxicity to these animals. Developing cotton plants with low levels of the (-)-gossypol could expand the use of cottonseed as a feed source. Gossypol also may play a role in protecting the plant from pathogens. The relative toxicity of (+)- and (-)-gossypol to plant pathogens has not been reported. We measured the concentration of (+)- and (-)-gossypol in roots from cotton seedlings that were treated with the biocontrol agent Trichoderma virens that induces biosynthesis of gossypol and related terpenoids in cotton roots. (-)-Gossypol was the minor enantiomer in control and treated roots, but levels were slightly higher in roots from T. virens-treated seed. We also determined the toxicity of the gossypol enantiomers and the racemate to the seedling disease pathogen Rhizoctonia solani. The (+)- and (-)-enantiomers of gossypol and the racemate are equally effective in inhibiting growth of this pathogen. The lethal doses of the gossypols required to kill the pathogen appeared to be similar, but their toxicities are significantly less than those of related cotton and kenaf sesquiterpenes. The results indicate that altering the enantiomeric ratio in cotton roots will not adversely affect the resistance of seedlings to the seedling pathogen R. solani.  相似文献   

Fayette County Meteorite     

Ward H  Howell H 《Science (New York, N.Y.)》1888,11(278):266

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Functional role of aspartic acid-27 in dihydrofolate reductase revealed by mutagenesis   总被引：12，自引：0，他引：12  

E E Howell  J E Villafranca  M S Warren  S J Oatley  J Kraut 《Science (New York, N.Y.)》1986,231(4742):1123-1128

The crystal structures and enzymic properties of two mutant dihydrofolate reductases (Escherichia coli) were studied in order to clarify the functional role of an invariant carboxylic acid (aspartic acid at position 27) at the substrate binding site. One mutation, constructed by oligonucleotide-directed mutagenesis, replaces Asp27 with asparagine; the other is a primary-site revertant to Ser27. The only structural perturbations involve two internally bound water molecules. Both mutants have low but readily measurable activity, which increases rapidly with decreasing pH. The mutant enzymes were also characterized with respect to relative folate: dihydrofolate activities and kinetic deuterium isotope effects. It is concluded that Asp27 participates in protonation of the substrate but not in electrostatic stabilization of a positively charged, protonated transition state.  相似文献   

Turnover of ribosomal RNA in rat liver   总被引：14，自引：0，他引：14  

J N Loeb  R R Howell  G M Tomkins 《Science (New York, N.Y.)》1965,149(688):1093-1095

After a single injection of radioactive orotic acid and a "chase" of nonradioactive precursor, the specific activity of ribosomal RNA in rat liver decreases logarithmically at a rate corresponding to a half-life of about S days. The possible significance of this result is discussed with regard to control of protein synthesis.  相似文献   

Spatial characterization of acidification related parameters in sensitive regions of Atlantic Canada     

S. R. Esterby  A. H. El-Shaarawi  G. D. Howell  T. A. Clair 《Water, air, and soil pollution》1989,46(1-4):289-303

Many lakes in eastern Canada are sensitive to long range transport of atmospheric pollutants because of their low buffering capacity. Thus, it is important to assess long term changes in water quality. Due to the large number of lakes, a method was needed for choosing a subset of lakes to monitor regularly. Preliminary surveys were conducted in Nova Scotia and Newfoundland in which water quality parameters connected with acidification were measured in a set of lakes in each region. This paper describes the division of each set of lakes into several groups, with lakes in a group having similar water quality parameter values, by means of cluster analysis and principal component ordination. The characteristics of the groups are shown by graphical procedures and summary statistics, and this characterization is used to both determine the number of groups and describe the final choice. The membership of the groups was subsequently assessed in terms of the influences of terrestrial weathering, marine aerosols, anthropogenically derived mineral acids and natural organic acids.  相似文献   

Elucidation of protein-lipid interactions in a lysozyme-corn oil system by Fourier transform Raman spectroscopy     

Howell NK  Herman H  Li-Chan EC 《Journal of agricultural and food chemistry》2001,49(3):1529-1533

Lysozyme (25% in D2O, corn oil, and their emulsions (10% w/w oil/D2O solution) were examined by Fourier transform Raman spectroscopy. Emulsions showed three layers, namely, top oil, middle cream, and bottom aqueous layers. Raman spectral analysis revealed hydrophobic interactions involving both protein and lipid components. Compared to lysozyme in D2O, the difference spectrum obtained after subtraction of oil from the cream layer spectrum showed reduced intensity of tryptophan bands at 760, 1013, 1340, and 1360 cm(-)(1), reduced intensity ratio of the tyrosine doublet at 850 and 830 cm(-)(1), and increased intensity of the C-H bending band at 1455 cm(-)(1). Compared to corn oil, the difference spectrum after subtraction of lysozyme from the cream layer spectrum indicated decreased intensity at 2855 cm(-)(1) (lipid CH(2) symmetric stretch) and 3011 cm(-)(1) (unsaturated fatty acid hydrocarbon chain =C-H stretch) and a higher intensity ratio of the C-H stretching band at 2900 cm(-)(1) to bands at 2885 and 2933 cm(-)(1). Spectra of the top and bottom layers resembled corn oil and lysozyme, respectively, except for changes in the D2O band. Raman spectroscopy can be used to detect structural changes in proteins, lipids, and D2O due to protein-lipid interactions.  相似文献   

Large-scale vermicomposting: emission of nitrous oxide and effects of temperature on earthworm populations: The 7th international symposium on earthworm ecology · Cardiff · Wales · 2002   总被引：1，自引：0，他引：1  

James Frederickson  Graham Howell 《Pedobiologia》2003,47(5-6):724-730

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The Effect of Temperature on First Feeding, Growth, and Survival of Larval Witch Flounder Glyptocephalus cynoglossus     

Deborah A.  Bidwell W. Huntting  Howell 《Journal of the World Aquaculture Society》2001,32(4):373-384

Witch flounder Glyptocephalus cynoglossus has recently been identified as a candidate species for aquaculture in the northeastern United States and the Canadian Atlantic Provinces. This study investigated the optimal temperatures for witch flounder larval first feeding and for long term larval culture from hatching through metamorphosis. Maximum first feeding occurred between 15.0 and 16.2 C. Larvae did not survive beyond first feeding when reared at mean temperatures of 5.1, 10.4, or 19.5 C and were unable to initiate feeding at mean rearing temperatures below 6.0 C. At a rearing temperature of 15.0 C in 16-L tanks, mean larval survival to 60 days post hatch (dph) was 14.1%. Mean overall length-specific growth rate for larvae reared to 60 dph at 15.0 C was 3.5%/d and mean absolute growth was 0.62 mm/d. Subsequent larval growth at 15.6 C began to taper off towards 70 dph at the onset of weaning which overlapped with larval metamorphosis. Growth plateaued at 85 dph, followed by a rebound between 90 and 95 dph. Survival was 100% when weaning onto a dry, pelleted diet was initiated at 70 dph with a 10-d live diet co-feeding period. These results are favorable and encourage the further pursuit of commercial witch flounder culture.  相似文献