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A trematode from the family Nasitrematidae Yamaguti 1951 was found adhered to the round window in the inner ear of a Bottlenosed Dolphin (Tursiops truncatus). The possibility that parasites could be responsible for changes in acoustic behavior and hearing loss is discussed. 相似文献
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Phosphatidylethanolamine (PE) N-methyltransferase catalyzes the synthesis of phosphatidylcholine by the stepwise transfer of methyl groups from S-adenosylmethionine to the amino head group of PE. PE N-methyltransferase was solubilized from a microsomal membrane fraction of rat liver using the nonionic detergent Triton X-100 and purified to apparent homogeneity. Specific activities of PE N-methyltransferase with PE, phosphatidyl-N-monomethylethanolamine (PMME), and phosphatidyl-N,N-dimethylethanolamine (PDME) as substrates were 0.63, 8.59, and 3.75 mumol/min/mg protein, respectively. The purified enzyme was composed of a single subunit with a molecular mass of 18.3 kDa as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Methylation activities dependent on the presence of PE, PMME, and PDME and the 18.3-kDa protein co-eluted when purified PE N-methyltransferase was subjected to gel filtration on Sephacryl S-300 in the presence of 0.1% Triton X-100. All three methylation activities eluted with a Stokes radius 2.1 A greater than that determined for pure Triton micelles (molecular mass difference of 27.4 kDa). Two-dimensional analysis of PE N-methyltransferase employing nonequilibrium pH gradient gel electrophoresis and sodium dodecyl sulfate-polyacrylamide gel electrophoresis indicates that the enzyme is composed of a single isoform. Analysis of enzyme activity using PE, PMME, and PDME at various Triton X-100 concentrations indicated the enzyme follows the "surface dilution" model proposed for other enzymes that act at the surface of mixed micelle substrates. Initial velocity data for all three lipid substrates (at fixed concentrations of Triton X-100) were highly cooperative in nature. Hill numbers for PMME and PDME ranged from 3 at 0.5 mM Triton to 6 at 2.0 mM Triton. All three methylation activities had a pH optimum of 10. These results provide evidence that a single membrane-bound enzyme catalyzes all three methylation steps for the conversion of PE to phosphatidylcholine. 相似文献
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A wide variety of animals have been utilized in an attempt to provide the information necessary to bring scrub typhus to the point where it is no longer a threat to man. The laboratory mouse is usually the animal of choice for the study of this disease. The discovery that certain strains of inbred mice are genetically resistant to Rickettsia tsutsugamushi, the agent of scrub typhus, has opened new avenues in the study of the immune response to the disease. The cynomolgus monkey, Macaca fascicularis, appears to be the best animal model for the study of scrub typhus as it occurs in humans and should be useful in the development of an efficacious vaccine. 相似文献
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An evaluation was made of the efficiency of five classes of chemical cleaning agents for removing biofilm from spirally wound cellulose acetate reverse-osmosis membranes receiving influent with high or low levels of combined chlorine. Each cleaning regimen utilized one or more of the following types of chemical: (i) surfactants and detergents, (ii) chaotropic agents, (iii) bactericidal agents, (iv) enzymes, and (v) antiprecipitants. Cleaning efficiency was tested in the laboratory on membrane material removed from operations at various intervals (2 to 74 days). Cleaning effectiveness was evaluated against nontreated control membranes and was scored by scanning electron microscopy and enumeration of surviving bacteria after treatment of the membranes. The combinations of classes which were most effective in biofilm removal were the anionic and chaotropic agent combination and combinations involving enzyme-containing preparations. Membranes receiving influent with high levels of combined chlorine were easier to clean but more susceptible to structural damage from prolonged exposure to combined chlorine. No treatment or combination of treatments was completely effective or effective at all stages of biofilm development. 相似文献
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A C Keat R N Maini G C Nkwazi G D Pegrum G L Ridgway J T Scott 《BMJ (Clinical research ed.)》1978,1(6113):605-607
Inflammatory arthritis, tendinitis, and fasciitis after non-specific urethritis ("sexually acquired reactive arthritis" (SARA)) was studied prospectively in 531 men with non-specific urethritis, with particular reference to the frequency of isolation of Chlamydia trachomatis and the presence of HLA-B27. Satisfactory cultures were obtained from the urethral swabs from 384 patients; and HLA typing was performed on 482, of whom 30 (6%) were HLA-B27-positive. Arthritis developed in 16 patients, and five of the 14 (36%) with satisfactory cultures were positive for C trachomatis; 135 of the patients without arthritis were also positive for C trachomatis, an identical proportion. Seven of the 15 patients (40%) with arthritis who were HLA-typed were HLA-B27-positive. Six of the 30 patients with HLA-B27 developed peripheral arthritis in contrast to only nine of the 452 patients lacking the antigen, suggesting a tenfold increase susceptibility. C trachomatis, however, was no more prevalent in cultures from HLA-B27-positive men than from the others. Thus carriage of C trachomatis is unlikely to be influenced by HLA-B27. C trachomatis may be an important pathogen in some cases of SARA but does not appear to be an exclusive trigger factor for this condition. 相似文献
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Aequorin is a photoprotein which emits light in response to changes in free calcium concentration. When aequorin was microinjected into plasmodia of Physarum polycephalum, light emission varied in synchrony with the motile oscillations of the organisms. Therefore, movement is correlated which changes in the concentration of free calcium. 相似文献