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51.
Vaccinia virus recombinants expressing either the measles virus fusion or hemagglutinin glycoprotein protect dogs against canine distemper virus challenge. 总被引:12,自引:9,他引:3 下载免费PDF全文
J Taylor S Pincus J Tartaglia C Richardson G Alkhatib D Briedis M Appel E Norton E Paoletti 《Journal of virology》1991,65(8):4263-4274
cDNA clones of the genes encoding either the hemagglutinin (HA) or fusion (F) proteins of the Edmonston strain of measles virus (MV) were expressed in vaccinia virus recombinants. Immunofluorescence analysis detected both proteins on the plasma membranes of unfixed cells as well as internally in fixed cells. Immunoprecipitation of metabolically radiolabeled infected-cell extracts by using specific sera demonstrated a 76-kDa HA polypeptide and gene products of 60, 44, and 23 kDa which correspond to a MV F precursor and cleavage products F0, F1, and F2, respectively. Neither recombinant induced cell fusion of Vero cells when inoculated individually, but efficient cell fusion was readily observed upon coinfection of cells with both recombinants. Inoculation of dogs with the vaccinia virus-MV F recombinant (VV-MVF) did not give rise to detectable MV-neutralizing antibody. Inoculation of dogs with the vaccinia virus-MV HA recombinant (VV-MVHA) or coinoculation with both recombinants (VV-MVF and VV-MVHA) induced significant MV-neutralizing titers that were increased following a booster inoculation. Inoculation of dogs with the vaccinia virus recombinants or with MV failed to induce canine distemper virus (CDV)-neutralizing antibodies. Upon challenge with a lethal dose of virulent CDV, signs of infection were observed in dogs inoculated with (VV-MVF). No symptoms of disease were observed in dogs that had been vaccinated with VV-MVHA or with VV-MVHA and VV-MVF and then challenged with CDV. All dogs vaccinated with the recombinant viruses as well as those inoculated with MV or a vaccine strain of CDV survived CDV challenge. 相似文献
52.
Bovine serum albumin (BSA), a relatively impure protein, is routinely used as a component of embryo culture media. Since media containing BSA are chemically undefined, it would be desirable to replace BSA with substitutes of similar activity which are either chemically better defined and/or better standardized than BSA. Two commercial products, Ultroser((R)) G (USG) and Solcoseryl((R)) (SOL), were evaluated as replacements for BSA in culture with respect to the development of ovine embryos in vitro. A total of 126 late 8-cell and early 16-cell embryos were distributed among modified Brinster's medium for ovum culture (BMOC-2) containing either 1.5% BSA, 2.0% USG or 2.0% SOL. All three culture media supported development of ovine embryos. Results indicate that 8- and 16-cell embryos will develop into blastocysts in a BSA-free medium containing either USG or SOL. A higher number of embryos developed into blastocysts in media containing BSA than in media containing USG or SOL, and more blastocysts hatched in media containing BSA. Although the overall degree of embryonic development was more advanced in BSA-supplemented media, the concentrations of USG and SOL that were used in this study may not have been optimal for ovine embryo culture. 相似文献
53.
P Payment E Franco L Richardson J Siemiatycki 《Applied and environmental microbiology》1991,57(4):945-948
During a prospective epidemiological study of gastrointestinal health effects associated with the consumption of drinking water produced by reverse-osmosis domestic units, a correlation was demonstrated between the bacterial counts on R2A medium incubated at 35 degrees C and the reported gastrointestinal symptoms in families who used these units. A univariate correlation was found with bacterial counts on R2A medium at 20 degrees C but was confounded by the bacterial counts at 35 degrees C. Other variables, such as family size and amount of water consumed, were not independently explanatory of the rate of illness. These observations raise concerns for the possibility of increased disease associated with certain point-of-use treatment devices for domestic use when high levels of bacterial growth occur. 相似文献
54.
55.
Nonlinear mechanical responses of mouse cochlear hair bundles. 总被引:8,自引:0,他引:8
I J Russell M K?ssl G P Richardson 《Proceedings. Biological sciences / The Royal Society》1992,250(1329):217-227
The stiffness of sensory hair bundles of both inner (IHC) and outer (OHC) hair cells was measured with calibrated silica fibres in mouse cochlear cultures to test the hypothesis that the mechanical properties of the hair bundle reflect processes underlying mechanotransduction. For OHCs, the displacement of the hair bundle relaxed with time constants of 6 ms for displacements which open transducer channels and 4 ms for displacements which close the channels. The corresponding values of the time constants for IHCs were 10 ms and 8 ms, respectively. A displacement-dependent change in the stiffness of the hair bundle was not observed when the bundle was displaced orthogonally to the direction of excitation. The stiffness of the hair bundle as a function of nanometre displacements from the resting position was remarkably nonlinear. The stiffness declined to a minimum from the resting stiffness by about 12% for OHCs and 20% for IHCs when the hair bundle was displaced by about 20 nm in the excitatory direction, and it increased by a similar amount when the bundle was displaced by 20 nm in the inhibitory direction. The displacement at which the stiffness reached a minimum was within the most sensitive region of the hair-cell transducer function (receptor potential as a function of hair-bundle displacement), and the displacement at which the stiffness reached a maximum was at the point of saturation of the transducer function in the inhibitory direction. The nonlinear displacement-dependent compliance change is reversibly abolished, and the time constant of relaxation of the bundle for excitatory displacements is reversibly reduced, when mechanotransduction is blocked by the addition of either neomycin sulphate or cobalt chloride to the solution bathing the hair cells. The displacement-dependent compliance change was not apparently reduced when the receptor potential was attenuated through the substitution of sodium in the bathing solution with a less permeant cation, tetraethylammonium. These findings suggest that the nonlinear mechanical properties of the hair bundle are associated with aspects of the hair-cell mechanotransducer process. The mechanical properties of the hair bundle are discussed in relation to the 'gating-spring' hypothesis of hair-cell transduction. 相似文献
56.
57.
The diets of larval Rhyacophilidae (Rhyacophila inculta), Polycentropodidae (Polycentropus variegatus) and Arctopsychidae (Parapsyche almota and P. elsis) from five streams in the University of British Columbia Research Forest, British Columbia (Canada), are recorded and related
to feeding mode/constructional activities and prey representation in the habitat. Particular attention was paid to the extent
of dietary overlap and the degree of intraspecific dietary variations between streams.
An overall similarity of the diets of the study species was notable and all commonly consumed chironomid (Diptera) larvae,
Simulium (Diptera) and Zapada (Plecoptera), although there was interspecific variation in the relative importance of these items. Polycentropus variegatus and Parapsyche spp. ate Baetis and Paraleptophlebia, the latter predators also consuming Hydrachnellae (Acarina). Other prey were generally of minor importance and consequently
interspecific dietary overlaps were high.
Differences in the range of prey consumed by predaceous Trichoptera were apparent. Free-foraging R. inculta which selectively consumed sedentary simuliid larvae had the narrowest niche breadth. Parapsyche spp. and Polycentropus variegatus foreguts generally contained an over-representation of chironomid larvae compared to their proportionate occurrence in the
benthos, and these caddisflies exhibited high niche overlap. The relative importance of chironomids as food for Parapsyche spp. and Polycentropus variegatus is attributed to prey behaviour, i.e. drift, and poorly developed escape responses when they are caught on the predator's
net. 相似文献
58.
Effect of the novel ionophore tetronasin (ICI 139603) on ruminal microorganisms. 总被引:6,自引:4,他引:2 下载免费PDF全文
The antimicrobial activity of the novel ionophore tetronasin (formerly ICI 139603) was compared with that of monensin for the growth of ruminal bacteria, protozoa, and an anaerobic fungus. The potency of tetronasin toward most bacteria and the fungus was an order of magnitude or more greater than that of monensin. Lactobacillus casei was 55 times more sensitive to tetronasin than to monensin, indicating a potential role for tetronasin in reversing lactic acidosis. Bacteria with a gram-positive ultrastructure were generally sensitive to the ionophores and unable to adapt to grow in their presence. The exception was the cellulolytic Ruminococcus flavefaciens, which adapted during successive cultivation on media with increasing ionophore concentrations to grow at 100-fold higher concentrations of tetronasin than were initially lethal to the organism. Gram-negative bacteria were more resistant and generally able to adapt to grow in the presence of both ionophores. An in vivo trial with cattle and in vitro growth experiments indicated that the effect of tetronasin on ciliate protozoa was minor. In vitro experiments measuring hydrogen production by Neocallimastix frontalis suggested that this fungus would be unable to survive in ruminants receiving tetronasin. 相似文献
59.
Acrosin was extracted from turkey spermatozoa by use of urea together with sonication and freezing, and purified approximately 18-fold by sequential use of chromatofocusing and affinity chromatography. The use of chromatofocusing for the initial purification step proved to be superior to preparative isoelectric focusing. Similar to acrosin from many mammalian species, turkey acrosin was found to be a glycoprotein possessing characteristics of serine proteases. Polyacrylamide gel electrophoresis (PAGE) of the enzyme indicated the presence of two isozymes. Sodium-dodecyl sulfate PAGE under reducing conditions revealed three subunits with approximate molecular weights of 11,700, 13,900, and 15,900. 相似文献
60.