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101.
Wendy L. Picking Jennifer A. Mertz Mary E. Marquart William D. Picking 《Protein expression and purification》1996,8(4):401-408
Shigella flexneriand related enteropathogenic bacteria are important agents of bacillary dysentery, a potentially life-threatening illness for children in underdeveloped regions of the world. Onset of shigellosis stems fromS. flexneriinvasion of colonic epithelial cells, leading to localized cell death and inflammation. Invasion plasmid antigens (Ipa) B, C, and D are three secreted proteins encoded by the large virulence plasmid ofS. flexnerithat have been implicated as essential effectors of this cell invasion process. These proteins are expressed as part of theipaoperon and are among the major targets of the host immune response to shigellosis. Biochemical characterization of the Ipa invasins has been complicated by the fact they have not been purified in the quantities needed for detailedin vitroanalysis. Here we describe the first cloning, expression, and extensive purification of IpaB and IpaC fusion proteins fromEscherichia colifor use in dissecting of the protein biochemistry ofS. flexneripathogenesis. A variety of approaches were used to prepare significant quantities of these proteins in their soluble forms, including the use of different host cell lines, modification of bacterial growth conditions, and the use of alternative plasmid expression vectors. Now that these Ipa proteins are available in a highly pure form, it will be possible to initiate studies on their important biological and immunological properties as well as their recruitment into high-molecular-weight protein complexes. Together with IpaD (purified as part of a previous study), these purified proteins will be useful for: (a) exploring properties of the host immune response toS. flexneriinvasion, (b) elucidating the specific biochemical properties that lead to pathogen internalization, (c) analyzing the importance of specific Ipa protein complexes in host cell invasion, and (d) monitoring, or perhaps even augmenting, the efficacy of live oral vaccines in human trials. 相似文献
102.
A spontaneous melanotic ependymoma was observed in the brain of an adult female Goeldi's marmoset (Callimico goeldii). The mass completely occupied the left lateral ventricle, rupturing the fornix and corpus callosum, and compressing the adjacent neuropil. Special histochemical techniques, including melanin bleach, periodic acid-Schiff, Perls iron and phosphotungstic acid hematoxylin, demonstrated the neoplasms to be an ependymoma with a rare melanotic differentiation. 相似文献
103.
Richard Karban Gregory English-Loeb M. Andrew Walker Jennifer Thaler 《Experimental & applied acarology》1995,19(4):189-197
We observed the number of predatory mites (Phytoseiidae:Typhlodromus caudiglans) on the foliage of 20 North American species of grapes (Vitis spp) plus the domesticated EuropeanVitis vinifera, all grown in a common garden. We found relatively few phytophagous mites. The numbers of phytophagous mites were not correlated with the plant characteristics that we measured. We found approximately five times as many predatory mites as phytophagous mites and the numbers of these phytoseiid predators were not affected by the availability of prey. Similarly, numbers of phytoseiids were unaffected by plant gender and, hence, the availability of pollen, another source of food. The numbers of phytoseiids were not clustered according to the taxonomic grouping of the tested plant species. Leaf surface characteristics explained over 25% of the variance in the numbers of phytoseiids. Numbers of phytoseiids were positively associated with the density of vein hairs, the density of bristles in leaf axils, and the presence of leaf domatia. These results suggest that sheltered habitats rather than food availability may limit the numbers of phytoseiid mites on grapevines. 相似文献
104.
Comparative chromosome painting between two marsupials: origins of an XX/XY1Y2 sex chromosome system
Roland Toder Rachel J. W. O’Neill Johannes Wienberg Patricia C. M. O’Brien Lucille Voullaire Jennifer A. Marshall-Graves 《Mammalian genome》1997,8(6):418-422
Cross-species chromosome painting was used to investigate genome rearrangements between tammar wallaby Macropus eugenii (2n = 16) and the swamp wallaby Wallabia bicolor (2n = 10♀/11♂), which diverged about 6 million years ago. The swamp wallaby has an XX female:XY1Y2 male sex chromosome system thought to have resulted from a fusion between an autosome and the small original X, not involving
the Y. Thus, the small Y1 should represent the original Y and the large Y2 the original autosome. DNA paints were prepared from flow-sorted and microdissected chromosomes from the tammar wallaby.
Painting swamp wallaby spreads with each tammar chromosome-specific probe gave extremely strong and clear signals in single-,
two-, and three-color FISH. These showed that two tammar wallaby autosomes are represented unchanged in the swamp wallaby,
two are represented by different centric fusions, and one by a tandem fusion to make the very long arms of swamp wallaby Chromosome
(Chr) 1. The large swamp wallaby X comprises the tammar X as its short arm, and a tandemly fused 7 and 2 as the long arm.
The acrocentric swamp wallaby Y2 is a 2/7 fusion, homologous with the long arm of the X. The small swamp wallaby Y1 is confirmed as the original Y by its painting with the tammar Y. However, the presence of sequences shared between the microdissected
tammar Xp and Y on the swamp wallaby Y2 implies that the formation of the compound sex chromosomes involved addition of autosome(s) to both the original X and Y.
We propose that this involved fusion with an ancient pseudoautosomal region followed by fission proximal to this shared region.
Received: 16 October 1996/Accepted: 30 January 1997 相似文献
105.
KATP channels were reconstituted in COSm6 cells by coexpression of the sulfonylurea receptor SUR1 and the inward rectifier potassium channel Kir6.2. The role of the two nucleotide binding folds of SUR1 in regulation of KATP channel activity by nucleotides and diazoxide was investigated. Mutations in the linker region and the Walker B motif (Walker, J.E., M.J. Saraste, M.J. Runswick, and N.J. Gay. 1982. EMBO [Eur. Mol. Biol. Organ.] J. 1:945–951) of the second nucleotide binding fold, including G1479D, G1479R, G1485D, G1485R, Q1486H, and D1506A, all abolished stimulation by MgADP and diazoxide, with the exception of G1479R, which showed a small stimulatory response to diazoxide. Analogous mutations in the first nucleotide binding fold, including G827D, G827R, and Q834H, were still stimulated by diazoxide and MgADP, but with altered kinetics compared with the wild-type channel. None of the mutations altered the sensitivity of the channel to inhibition by ATP4−. We propose a model in which SUR1 sensitizes the KATP channel to ATP inhibition, and nucleotide hydrolysis at the nucleotide binding folds blocks this effect. MgADP and diazoxide are proposed to stabilize this desensitized state of the channel, and mutations at the nucleotide binding folds alter the response of channels to MgADP and diazoxide by altering nucleotide hydrolysis rates or the coupling of hydrolysis to channel activation. 相似文献
106.
107.
Cloning and molecular characterization of two genes encoding adhesion proteins involved in Trichomonas vaginalis cytoadherence 总被引:11,自引:2,他引:9
108.
A strain of Escherichia coli with a deletion of the penicillin-binding protein 6 gene (dacC) has been constructed. The properties of this strain establish that the complete lack of penicillin-binding protein 6 has no marked effect on the growth of E. coli. 相似文献
109.
Summary A maternal de novo reciprocal translocation between the short arms of chromosomes 9 and 13 is reported. Using C-, Q- or G-banding, it was not possible to determine the precise breakpoint on 13, but a combination of silver staining and in situ hybridisation was used to do so on the two chromosomes, and it was demonstrated that the break on chromosome 13 had occurred within the NOR. 相似文献
110.
The hallucinogen analog -2-(2,5-dimethoxy-4-methylphenyl)-cyclopropylamine (DMCPA) was resolved into its two optical isomers. Examination of selected behavioral profiles in mice and cats clearly showed that the levorotatory isomer of DMCPA possesses stereoselective activity when compared with the dextro isomer. The results parallel those obtained using the isomers of the known hallucinogen, DOM (STP) in the same animal models. Comparison of the optical rotatory dispersion (ORD) curves for the N-(5-bromosalicylidene) derivatives of DMCPA and -2-phenylcyclopropylamine (tranylcypromine) of known absolute configuration established the configuration of DMCPA to be (-)-1R,2S. This stereoselective activity and proof of absolute configuration lend strong support to a new model of the hallucinogen receptor. The proposed model suggests possible structural similarities between LSD and phenethylamine hallucinogens. 相似文献