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881.
Enhancement of human immunodeficiency virus type 1 envelope-mediated fusion by a CD4-gp120 complex-specific monoclonal antibody.
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S Lee K Peden D S Dimitrov C C Broder J Manischewitz G Denisova J M Gershoni H Golding 《Journal of virology》1997,71(8):6037-6043
The entry of human immunodeficiency virus type 1 (HIV-1) into cells is initiated by binding of the viral glycoprotein gp120-gp41 to its cellular receptor CD4. The gp120-CD4 complex formed at the cell surface undergoes conformational changes that may allow its association with an additional membrane component(s) and the eventual formation of the fusion complex. These conformational rearrangements are accompanied by immunological changes manifested by altered reactivity with monoclonal antibodies specific for the individual components and presentation of new epitopes unique to the postbinding complex. In order to analyze the structure and function of the gp120-CD4 complex, monoclonal antibodies were generated from splenocytes of BALB/c mice immunized with soluble CD4-gp120 (IIIB) molecules (J. M. Gershoni, G. Denisova, D. Raviv, N. I. Smorodinsky, and D. Buyaner, FASEB J. 7:1185-1187 1993). One of those monoclonal antibodies, CG10, was found to be strictly complex specific. Here we demonstrate that this monoclonal antibody can significantly enhance the fusion of CD4+ cells with effector cells expressing multiple HIV-1 envelopes. Both T-cell-line-tropic and macrophage-tropic envelope-mediated cell fusion were enhanced, albeit at different optimal doses. Furthermore, infection of HeLa CD4+ (MAGI) cells by HIV-1 LAI, ELI1, and ELI2 strains was increased two- to fourfold in the presence of CG10 monoclonal antibodies, suggesting an effect on viral entry. These findings indicate the existence of a novel, conserved CD4-gp120 intermediate structure that plays an important role in HIV-1 cell fusion. 相似文献
882.
Characterization of humoral and CD4+ cellular responses after genetic immunization with retroviral vectors expressing different forms of the hepatitis B virus core and e antigens.
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M Sllberg K Townsend M Chen J O'Dea T Banks D J Jolly S M Chang W T Lee D R Milich 《Journal of virology》1997,71(7):5295-5303
The humoral and CD4+ cellular immune responses in mice following genetic immunization with three retroviral vectors encoding different forms of hepatitis B virus core antigen (HBcAg) and e antigen (HBeAg) were analyzed. The retroviral vectors induced expression of intracellular HBcAg (HBc[3A4]), secreted HBeAg (HBe[5A2]), or an intracellular HBcAg-neomycin phosphoryltransferase fusion protein (HBc-NEO[6A3]). Specific antibody levels and immunoglobulin G isotype restriction were highly dependent on both the host major histocompatibility complex and the transferred gene. Humoral and CD4+ cellular HBcAg and/or HBeAg (HBc/eAg)-specific immune responses following retroviral vector immunization were of a lower magnitude but followed the same characteristics compared with those after immunization with HBc/eAg in adjuvant. Two factors influenced the humoral responses. First, in vivo depletion of CD8+ cells in HBc-NEO[6A3]-immunized H-2k mice abrogated both HBcAg-specific antibodies and in vitro-detectable cytotoxic T lymphocytes. Second, priming of H-2b mice with an HBc/eAg-derived T-helper (Th) peptide in adjuvant prior to retroviral vector immunization greatly enhanced the HBc/eAg-specific humoral responses to all three vectors, suggesting that insufficient HBc/eAg-specific CD4+ Th-cell priming limits the humoral responses. In conclusion, direct injection of retroviral vectors seems to be effective in priming HBc/eAg-specific CD8+ but comparatively inefficient in priming CD4+ Th cells and subsequently specific antibodies. However, the limited HBc/eAg-specific CD4+ cell priming can effectively be circumvented by prior administration of a recombinant or synthetic form of HBc/eAg in adjuvant. 相似文献
883.
Hybertson Brooks M.; Bursten Stuart L.; Leff Jonathan A.; Lee Young M.; Jepson Eric K.; Dewitt Chris R.; Zagorski John; Cho Hyun G.; Repine John E. 《Journal of applied physiology》1997,82(1):226-232
Hybertson, Brooks M., Stuart L. Bursten, Jonathan A. Leff,Young M. Lee, Eric K. Jepson, Chris R. Dewitt, John Zagorski, Hyun G. Cho, and John E. Repine. Lisofylline prevents leak, but not neutrophil accumulation, in lungs of rats given IL-1intratracheally. J. Appl. Physiol.82(1): 226-232, 1997.Interleukin-1 (IL-1) is increased in lunglavages from patients with the acute respiratory distress syndrome, andadministering IL-1 intratracheally causes neutrophil accumulation and aneutrophil-dependent oxidative leak in lungs of rats. In the presentstudy, we found that rats pretreated intraperitoneally with lisofylline[(R)-1-(5-hydroxyhexyl)-3,7-dimethylxanthine (LSF)], an inhibitor of lysophosphatidic acid acyl transferase, which reduces the production of unsaturated phosphatidic acid species,did not develop the lung leak or the related ultrastructural abnormalities that occur after intratracheal administration of IL-1.However, rats pretreated with LSF and then given IL-1 intratracheally did develop the same elevations of lung lavage cytokine-induced neutrophil chemoattractant (CINC) levels and the same increased numbersof lung lavage neutrophils as rats given IL-1 intratracheally. Lungs ofrats given IL-1 intratracheally also had increased unsaturated phosphatidic acid and free acyl (linoleate, linolenate) concentrations compared with untreated rats, and these lipid responses were prevented by pretreatment with LSF. Our results reveal that LSF decreases lungleak and lung lipid alterations without decreasing neutrophil accumulation or lung lavage CINC increases in rats given IL-1 intratracheally. 相似文献
884.
Jeffrey K. McKee J. Francis Thackeray Lee R. Berger 《American journal of physical anthropology》1995,96(3):235-250
Fossil assemblages from the Pliocene and Pleistocene of southern Africa were seriated in order to give a better idea of their relative chronology. Time-sensitive mammals were selected for calculation of the Faunal Resemblance Index among 17 site units. On the basis of a logistical seriation and subsequent site analysis, the following sequence of sites was deemed most probable: Makapansgat Member 3, Makapansgat Member 4, Taung Dart deposits, Sterkfontein Member 4 and Taung Hrdli?ka deposits, Sterkfontein Member 5 (in part) and Kromdraai B, Kromdraai A and Swartkrans Member 1, Swartkrans Member 2, Swartkrans Member 3, Plovers Lake, Cornelia, Elandsfontein Main Site, Cave of Hearths Acheulian levels, Florisbad and Equus Cave and Klasies River Mouth. © 1995 Wiley-Liss, Inc. 相似文献
885.
Identification of a yeast artificial chromosome clone spanning a translocation breakpoint at 7q32.1 in a Smith-Lemli-Opitz syndrome patient. 总被引:2,自引:0,他引:2
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T L Alley B A Gray S H Lee S W Scherer L C Tsui G S Tint C A Williams R Zori M R Wallace 《American journal of human genetics》1995,56(6):1411-1416
Smith-Lemli-Opitz syndrome (SLOS) is a mental retardation/multiple congenital anomaly syndrome. The gene(s) involved has not been mapped or cloned, but, recently, a biochemical abnormality in cholesterol biosynthesis has been shown to occur in most SLOS patients. The defect is suspected to occur in the penultimate step of the cholesterol pathway, involving the enzyme 7-dehydrocholesterol reductase, which has not been isolated. On the basis of the hypothesis that a de novo balanced translocation [t(7;20)(q32.1;q13.2)] in an SLOS patient directly interrupts the SLOS gene, positional cloning techniques are being employed to localize and identify the SLOS gene. We report the identification of a chromosome 7-specific YAC that spans the translocation breakpoint, as detected by FISH. This is the first study narrowing a candidate SLOS region and placing it on physical and genetic maps of the human genome. 相似文献
886.
887.
Combination of the tod and the tol pathways in redesigning a metabolic route of Pseudomonas putida for the mineralization of a benzene, toluene, and p-xylene mixture.
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Construction of a hybrid strain which is capable of mineralizing components of a benzene, toluene, and p-xylene mixture simultaneously was attempted by redesigning the metabolic pathway of Pseudomonas putida. Genetic and biochemical analyses of the tod and the tol pathways revealed that dihydrodiols formed from benzene, toluene, and p-xylene by toluene dioxygenase in the tod pathway could be channeled into the tol pathway by the action of cis-p-toluate-dihydrodiol dehydrogenase, leading to complete mineralization of a benzene, toluene, and p-xylene mixture. Consequently, a hybrid strain was constructed by cloning todC1C2BA genes encoding toluene dioxygenase on RSF1010 and introducing the resulting plasmid into P. putida mt-2. The hybrid strain of P. putida TB105 was found to mineralize a benzene, toluene, and p-xylene mixture without accumulation of any metabolic intermediate. 相似文献
888.
Positive selection is a general phenomenon in the evolution of abalone sperm lysin 总被引:36,自引:21,他引:15
Lysin is a 16kDa acrosomal protein used by abalone sperm to create a hole
in the egg vitelline envelope (VE). The interaction of lysin with the VE is
species-selective and is one step in the multistep fertilization process
that restricts heterospecific (cross-species) fertilization. For this
reason, the evolution of lysin could play a role in establishing prezygotic
reproductive isolation between species. Previously, we sequenced sperm
lysin cDNAs from seven California abalone species and showed that positive
Darwinian selection promotes their divergence. In this paper an additional
13 lysin sequences are presented representing species from Japan, Taiwan,
Australia, New Zealand, South Africa, and Europe. The total of 20 sequences
represents the most extensive analysis of a fertilization protein to date.
The phylogenetic analysis divides the sequences into two major clades, one
composed of species from the northern Pacific (California and Japan) and
the other composed of species from other parts of the world. Analysis of
nucleotide substitution demonstrates that positive selection is a general
process in the evolution of this fertilization protein. Analysis of
nucleotide and codon usage bias shows that neither parameter can account
for the robust data supporting positive selection. The selection pressure
responsible for the positive selection on lysin remains unknown.
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889.
In vivo analyses of the internal control region in the 5S rRNA gene from Saccharomyces cerevisiae. 总被引:1,自引:0,他引:1
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The internal control region of the Saccharomyces cerevisiae 5S rRNA gene has been characterized in vivo by genomic DNase I footprinting and by mutational analyses using base substitutions, deletions or insertions. A high copy shuttle vector was used to efficiently express mutant 5S rRNA genes in vivo and isotope labelling kinetics were used to distinguish impeded gene expression from nascent RNA degradation. In contrast to mutational studies in reconstituted systems, the analyses describe promoter elements which closely resemble the three distinct sequence elements that have been observed in Xenopus laevis 5S rRNA. The results indicate a more highly conserved structure than previously reported with reconstituted systems and suggest that the saturated conditions which are used in reconstitution studies mask sequence dependence which may be physiologically significant. Footprint analyses support the extended region of protein interaction which has recently been observed in some reconstituted systems, but mutational analyses indicate that these interactions are not sequence specific. Periodicity in the footprint provides further detail regarding the in vivo topology of the interacting protein. 相似文献
890.
Efficient gene activation in mammalian cells by using recombinant adenovirus expressing site-specific Cre recombinase. 总被引:36,自引:2,他引:34
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Y Kanegae G Lee Y Sato M Tanaka M Nakai T Sakaki S Sugano I Saito 《Nucleic acids research》1995,23(19):3816-3821
A recombinant adenovirus (Ad) expressing Cre recombinase derived from bacteriophage P1 was constructed. To assay the Cre activity in mammalian cells, another recombinant Ad bearing an on/off-switching reporter unit, where a LacZ-expression unit can be activated by the Cre-mediated excisional deletion of an interposed stuffer DNA, was also constructed. Co-infection experiments together with the Cre-expressing and the reporter recombinant Ads showed that the Cre-mediated switching of gene expression was detected in nearly 100% of cultured CV1, HeLa and Jurkat cells. These results suggest that the recombinant Ad efficiently expressed functional Cre and offers a basis for establishing a powerful on/off switching strategy of gene expression in cultured mammalian cells and presumably in transgenic animals. The method is also applicable to construction of recombinant Ad bearing a gene the expression of which is deleterious to propagation of recombinant Ad. 相似文献