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排序方式: 共有272条查询结果,搜索用时 15 毫秒
1.
Heinz W. Kunz Andrea L. Cortese Hassett Tetsuo Inomata D. N. Misra Thomas J. Gill III 《Immunogenetics》1989,30(3):181-187
A new antigenic system in the rat homologous to theQa/TL antigen system in the mouse has been characterized. It was detected by antibodies raised in donor-recipient combinations
that were matched for theRT1. A, B, D, E loci in the major histocompatibility complex (MHC): (R11×BN)F1 anti-BN.1L(LEW), (R18×BN)F1 anti-BN.1L, and BN.1LV1(F344) anti-BN.1L. Absorption analyses using these antisera and a variety of inbred, congenic and
recombinant strains identified three alleles,RT1.G
a
,G
b
,G
c
, of whichG
c
is a null allele. The strain distribution of these alleles was determined, using 37 strains of rats representative of all
of the prototypic haplotypes and a number of congenic and recombinant strains. The use of the congenic and recombinant strains
showed that theRT1.G locus was linked to the MHC and that the most probable gene order wasA-E-G. Testcross analysis showed that the map distance betweenA andG was 1.4 cM(4/285 recombinants). The RT1.G antigen has a heavy chain ofM
r 46 000 and is present on both T and B cells. 相似文献
2.
Vladimir Vincek Felipe Figueroa Thomas J. Gill III Andrea L. Cortese Hassett Jan Klein 《Immunogenetics》1990,32(4):293-295
Offprint requests: J. Klein. 相似文献
3.
Regulated copper uptake in Chlamydomonas reinhardtii in response to copper availability. 总被引:1,自引:0,他引:1 下载免费PDF全文
A saturable and temperature-dependent copper uptake pathway has been identified in Chlamydomonas reinhardtii. The uptake system has a high affinity for copper ions (Km approximately 0.2 microM) and is more active in cells that are adapted to copper deficiency than to cells grown in a medium containing physiological (submicromolar to micromolar) copper ion concentrations. The maximum velocity of copper uptake by copper-deficient cells (169 pmol h-1 10(6) cells-1 or 62 ng min-1 mg-1 chlorophyll) is up to 20-fold greater than that of fully copper-supplemented cells, and the Km (approximately 2 x 10(2) nM) is unaffected. Thus, the same uptake system appears to operate in both copper-replete and copper-deficient cells, but its expression or activity must be induced under copper-deficient conditions. A cupric reductase activity is also increased in copper-deficient compared with copper-sufficient cells. The physiological characteristics of the regulation of this cupric reductase are compatible with its involvement in the uptake pathway. Despite the operation of the uptake pathway under both copper-replete and copper-deficient conditions, C. reinhardtii cells maintained in fully copper-supplemented cells do not accumulate copper in excess of their metabolic need. These results provide evidence for a homeostatic mechanism for copper metabolism in C. reinhardtii. 相似文献
4.
The ATP-binding-cassette transmembrane transporters (ABC transporters)
known from vertebrates belong to four major subfamilies: (1) the P-
glycoproteins (Pgp); (2) the cystic fibrosis transmembrane conductance
regulators (CFTR); (3) the Tap proteins encoded with the major
histocompatibility complex of mammals; and (4) the peroxisomal membrane
proteins. Both Pgp and CFTR have a structure suggesting a past internal
gene duplication; a phylogenetic analysis indicated that these duplications
occurred independently, while an independent tandem gene duplication
occurred in the case of the Tap family. Both the Pgp and Tap proteins show
evidence of relationship to bacterial ABC transporters lacking internal
duplication, and both are significantly more closely related to the HlyB
and MsbA families of transporters from purple bacteria than they are to ABC
transporters from nonpurple bacteria. The simplest hypothesis to explain
this observation is that eukaryotic Pgp and Tap genes are descended from a
mitochondrial gene or genes that were subsequently translocated to the
nuclear genome. The Pgp genes of eukaryotes are characterized by a
remarkable degree of convergent evolution between the ATP-binding cassettes
of their N- terminal and C-terminal halves, whereas no such convergence is
seen between the two halves of CFTR genes or between the duplicated Tap
genes. Exon 13 of the CFTR gene, which encodes a putative regulatory domain
not found in other ABC transporters apart from CFTR, showed high levels of
both synonymous and nonsynonymous difference in comparisons among different
mammalian species, suggesting that this region is a mutational hot spot.
相似文献
5.
6.
X Xiao G Hintermann AL Demanin J Piret 《Journal of industrial microbiology & biotechnology》1996,16(4):261-262
Streptomyces glaucescens is shown to possess -lactamase activity which is inhibitable by clavulanate. This is important in regard to its use as a cloning host for enzymes of \-lactam biosynthesis. 相似文献
7.
Cloning and characterization of the katB gene of Pseudomonas aeruginosa encoding a hydrogen peroxide-inducible catalase: purification of KatB, cellular localization, and demonstration that it is essential for optimal resistance to hydrogen peroxide. 下载免费PDF全文
S M Brown M L Howell M L Vasil A J Anderson D J Hassett 《Journal of bacteriology》1995,177(22):6536-6544
Pseudomonas aeruginosa is an obligate aerobe that is virtually ubiquitous in the environment. During aerobic respiration, the metabolism of dioxygen can lead to the production of reactive oxygen intermediates, one of which includes hydrogen peroxide. To counteract the potentially toxic effects of this compound, P. aeruginosa possesses two heme-containing catalases which detoxify hydrogen peroxide. In this study, we have cloned katB, encoding one catalase gene of P. aeruginosa. The gene was cloned on a 5.4-kb EcoRI fragment and is composed of 1,539 bp, encoding 513 amino acids. The amino acid sequence of the P. aeruginosa katB was approximately 65% identical to that of a catalase from a related species, Pseudomonas syringae. The katB gene was mapped to the 71- to 75-min region of the P. aeruginosa chromosome, the identical region which harbors both sodA and sodB genes encoding both manganese and iron superoxide dismutases. When cloned into a catalase-deficient mutant of Escherichia coli (UM255), the recombinant P. aeruginosa KatB was expressed (229 U/mg) and afforded this strain resistance to hydrogen peroxide nearly equivalent to that of the wild-type E. coli strain (HB101). The KatB protein was purified to homogeneity and determined to be a tetramer of approximately 228 kDa, which was in good agreement with the predicted protein size derived from the translated katB gene. Interestingly, KatB was not produced during the normal P. aeruginosa growth cycle, and catalase activity was greater in nonmucoid than in mucoid, alginate-producing organisms. When exposed to hydrogen peroxide and, to a greater extent, paraquat, total catalase activity was elevated 7- to 16-fold, respectively. In addition, an increase in KatB activity caused a marked increase in resistance to hydrogen peroxide. KatB was localized to the cytoplasm, while KatA, the "housekeeping" enzyme, was detected in both cytoplasmic and periplasmic extracts. A P. aeruginosa katB mutant demonstrated 50% greater sensitivity to hydrogen peroxide than wild-type bacteria, suggesting that KatB is essential for optimal resistance of P. aeroginosa to exogenous hydrogen peroxide. 相似文献
8.
Neonatal DNA immunization with a plasmid encoding an internal viral protein is effective in the presence of maternal antibodies and protects against subsequent viral challenge. 总被引:2,自引:0,他引:2 下载免费PDF全文
Conventional vaccines are remarkably effective in adults but are much less successful in the very young, who are less able to initiate a mature immune response and who may carry maternal antibodies which inactivate standard vaccines. We set out to determine whether DNA immunization might circumvent these problems. We have previously shown that intramuscular injection of plasmid DNA encoding the nucleoprotein (NP) gene of lymphocytic choriomeningitis virus (LCMV) is capable of inducing immune responses and protecting 50% of adult mice against lethal and sublethal challenge with LCMV. Here we demonstrate that mouse pups injected with the same plasmid hours or days after birth produce major histocompatibility complex-restricted, NP-specific cytotoxic T lymphocytes (CTL) that persist into adulthood; 48% of vaccinated pups responded to subsequent sublethal viral challenge by the accelerated production of anti-NP LCMV-specific CTL, indicating that these animals had been successfully immunized by the plasmid DNA. In addition, these mice showed a >95% reduction in splenic viral titers 4 days postinfection compared to control mice, demonstrating a more rapid control of infection in vivo. Furthermore, pups born of and suckled on LCMV-immune dams (and therefore containing passively acquired anti-LCMV antibodies at the time of DNA inoculation) responded to the DNA vaccine in a similar manner, showing that maternally derived anti-LCMV antibodies do not significantly inhibit the generation of protective immune responses following DNA vaccination. These findings suggest that, at least in this model system, DNA immunization circumvents many of the problems associated with neonatal immunization. 相似文献
9.
Neisseria gonorrhoeae cells defective in the biosynthesis of the recA gene product are no more sensitive to hydrogen peroxide than wild-type cells. Although gonococci possess nearly 100-fold-greater catalase levels than Escherichia coli, they are more susceptible to hydrogen peroxide than this organism. The natural niche of gonococci undoubtedly results in exposure to oxidant stress; however, they do not demonstrate particularly efficient antioxidant defense systems. 相似文献
10.
ERIC S. BONO PATRICK SMOLINSKI AL CASAGRANDA JUNDE XU 《Computer methods in biomechanics and biomedical engineering》2013,16(2):125-131
The Shear-slip Mesh Update Method (SSMUM) is being used in flow simulations involving large but regular displacements of one or more boundaries of the computational domain. We follow up the earlier discussion of the method with notes on practical implementation aspects. In order to establish a benchmark problem for this class of flow problems, we define and report results from a two-dimensional viscous flow around a rotating stirrer in a square chamber. The application potential of the method is demonstrated in the context of biomedical design problem, as we perform an analysis of blood flow in a centrifugal left ventricular assist device, or blood pump, which involves a rotating impeller in a non-axisymmetric housing. 相似文献