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排序方式: 共有380条查询结果,搜索用时 125 毫秒
1.
2.
M Ogata H Lorberboum-Galski D FitzGerald I Pastan 《Journal of immunology (Baltimore, Md. : 1950)》1988,141(12):4224-4228
IL-2-PE40 is a chimeric molecule in which IL-2 is attached to the amino end of modified Pseudomonas exotoxin molecule lacking cell recognition domain. This molecule was extremely toxic for Con A-stimulated spleen cells from mice. Moreover, IL-2-PE40 has suppressive effect against Ag-activated cells; it inhibits the generation of cytotoxic T lymphocyte activity in a MLC. IL-2-PE40 could be a useful agent in IL-2R targeting therapy including immunosuppressive therapy for allograft rejection or some autoimmune diseases. 相似文献
3.
Radiosensitivity of human bone marrow granulocyte-macrophage progenitor cells and stromal colony-forming cells: effect of dose rate 总被引:1,自引:0,他引:1
T J FitzGerald M McKenna L Rothstein C Daugherty K Kase J S Greenberger 《Radiation research》1986,107(2):205-215
Study of the radiation biology of human bone marrow hematopoietic cells has been difficult since unseparated bone marrow cell preparations also contain other nonhematopoietic stromal cells. We tested the clonogenic survival after 0.05 or 2 Gy/min X irradiation using as target cells either fresh human bone marrow or nonadherent hematopoietic cells separated from stromal cells by the method of long-term bone marrow culture (LTBMC). Sequential nonadherent cell populations removed from LTBMC were enriched for hematopoietic progenitors forming granulocyte-macrophage colony-forming unit culture (GM-CFUc) that form colonies at Day 7, termed GM-CFUc7, or Day 14 termed GM-CFUc14. The results demonstrated no effect of dose rate on the D0 or n of fresh marrow GM-CFUc (colonies greater than or equal to 50 cells) after plating in a source of their obligatory growth factor, colony-stimulating factor (CSF) (GM-CFUc7 irradiated at 2 Gy/min, D0 = 1.02 +/- 0.05, n = 1.59 +/- 0.21; at 0.05 Gy/min, D0 = 1.07 +/- 0.03, n = 1.50 +/- 0.04; GM-CFUc14 at 2 Gy/min, D0 = 1.13 +/- 0.03, n = 1.43 +/- 0.03; at 0.05 Gy/min, D0 = 1.16 +/- 0.04, n = 1.34 +/- 0.05). There was a decrease in the radiosensitivity of GM-CFUc7 and GM-CFUc14 derived from nonadherent cells of long-term bone marrow cultures compared to fresh marrow that was observed at both dose rates. In contrast, adherent stromal cells irradiated at low compared to high dose rate showed a significantly greater radioresistance (Day 19 colonies of greater than or equal to 50 cells; at 2 Gy/min, D0 = 0.99 Gy, n = 1.03; at 0.05 Gy/min D0 = 1.46 Gy, n = 2.00). These data provide strong evidence for a difference in the radiosensitivity of human marrow hematopoietic progenitor compared to adherent stromal cells. 相似文献
4.
Isolation and characterization of a large,neurite-associated glycoconjugate from neuroblastoma cells 下载免费PDF全文
A high molecular weight glycoconjugate has been isolated from neurite-producing neuronal tumor cells in culture and has been designated as I(0) based on its elution characteristics in gel filtration chromatography. This molecule cannot be found in a variety of nonneuronal cells. I(0) is found in the substratum-attached material or cell fraction of neurite-producing neuroblastoma cells, depending upon culture conditions. It is found in the substratum-bound fraction of B104 rat neuroblastoma cells during serum starvation and in the EGTA-detached cell fraction of B104 cells grown in chemically defined N2 medium. It occurs only in the cell fraction of the human neuroblastoma line Platt. Examination of behavioral variants of the B104 rat line further strengthens the association of I(0) with neurite production; the constitutive neurite-producing E(R)B9 variant contains I(0) while the non-neurite-producing E(R)A11 variant does not. I(0) is large, eluting in the void volume of sepharose-CL2B columns. Radioiodination of intact cells with lactoperoxidase shows I(0) to be a cell surface component. Metabolic radiolabeling studies show that it contains a high proportion of polysaccharide to protein, does not contain mannose, and is unsulfated. Alkaline borohydride reduction release two size classes of large polysaccharide chain. The alkaline reduction results, along with the mannose incorporation studies, show the presence of O-glycosidic linkages and few, if any, N-linkages. Resistance to nitrous acid deamination, insensitivity to glycosaminoglycan lyases, and the absence of sulfation, indicate that I(0) does not contain the glycosaminoglycans hyaluronic acid, chondroitin-, dermatan-, or heparin- sulfates. Affinity column chromatography reveals high binding affinity of I(0) to polyornithine and no binding to gelatin (collagen) or the glycosaminoglycans hyaluronate and heparin. These studies describe a unique high molecular weight glycoconjugate on the surface of neurite-producing neuroblastoma cell lines from two species. 相似文献
5.
D. R. Gamble M. L. Kinsley M. G. FitzGerald R. Bolton K. W. Taylor 《BMJ (Clinical research ed.)》1969,3(5671):627-630
Sera from 123 patients with diabetes mellitus of recent onset, 155 patients with diabetes of more than two years'' duration, and 250 normal persons were collected over a period of two and a half years. All sera were tested for neutralizing antibody to Coxsackie virus types B1–6, and a sample was tested for complement-fixing antibody to a number of viral, rickettsial, and mycoplasmal antigens.In diabetics of recent onset no evidence was found of any excess of antibodies to mumps virus or some common respiratory viruses. Insulin-dependent diabetes within three months of onset were found to have higher antibody titres to Coxsackie B virus, particularly of type B4, than either normal subjects or patients with diabetes of longer duration. 相似文献
6.
Domain II mutants of Pseudomonas exotoxin deficient in translocation 总被引:16,自引:0,他引:16
Y Jinno M Ogata V K Chaudhary M C Willingham S Adhya D FitzGerald I Pastan 《The Journal of biological chemistry》1989,264(27):15953-15959
Pseudomonas exotoxin (PE) kills mammalian cells in a complex process that involves cell surface binding, internalization by endocytosis, translocation to the cytosol, and ADP-ribosylation of elongation factor 2. PE is a three-domain protein in which domain I binds to the cell surface, domain II promotes translocation into the cytosol, and domain III carries out ADP-ribosylation. To determine how translocation occurs, we have mutated all the arginine residues in domain II and found that mutations at positions 276 and 279 greatly diminished the cytotoxicity of PE and mutations 330 and 337 substantially reduced cytotoxicity. Biochemical studies indicate that after internalization into an endocytic compartment, the PE molecule undergoes a specific and saturable intracellular interaction, and this interaction is deficient in an Arg276----Gly mutant. Our data suggest that the translocation process of PE involves a specific interaction of Arg276 (and possibly Arg279, Arg330, and Arg337) with components of an intracellular compartment. 相似文献
7.
Pseudomonas exotoxin: chimeric toxins 总被引:17,自引:0,他引:17
Pseudomonas exotoxin binds to and enters cells by receptor-mediated endocytosis. Within the cell it requires exposure to low pH to enable it to translocate to the cell cytoplasm where it inhibits protein synthesis by ADP-ribosylating elongation factor 2. The toxin has three main structural domains whose functions are: Ia, cell binding; II, translocation; and III, ADP-ribosylation. Key amino acids have been identified within each domain that are required for the function of the toxin. Chimeric toxins were made originally by using chemical cross-linking reagents to couple Pseudomonas exotoxin (or other toxins) to cell-binding proteins. More recently, a variety of Pseudomonas exotoxin-related chimeric toxins have been made by gene fusion technology. These chimeric toxins may be useful clinically for treating various diseases and experimentally for understanding receptor function. 相似文献
8.
Relative apparent synapomorphy analysis (RASA). I: The statistical measurement of phylogenetic signal 总被引:10,自引:9,他引:1
We have developed a new approach to the measurement of phylogenetic signal
in character state matrices called relative apparent synapomorphy analysis
(RASA). RASA provides a deterministic, statistical measure of natural
cladistic hierarchy (phylogenetic signal) in character state matrices. The
method works by determining whether a measure of the rate of increase of
cladistic similarity among pairs of taxa as a function of phenetic
similarity is greater than a null equiprobable rate of increase. Our
investigation of the utility and limitations of RASA using simulated and
bacteriophage T7 data sets indicates that the method has numerous
advantages over existing measures of signal. A first advantage is
computational efficiency. A second advantage is that RASA employs known
methods of statistical inference, providing measurable sensitivity and
power. The performance of RASA is examined under various conditions of
branching evolution as the number of characters, character states per
character, and mutations per branch length are varied. RASA appears to
provide an unbiased and reliable measure of phylogenetic signal, and the
general approach promises to be useful in the development of new techniques
that should increase the rigor and reliability of phylogenetic estimates.
相似文献
9.
Molecular evolution of voltage-sensitive ion channel genes: on the origins of electrical excitability 总被引:14,自引:0,他引:14
We have analyzed nucleic acid and amino acid sequence alignments of a
variety of voltage-sensitive ion channels, using several methods for
phylogenetic tree reconstruction. Ancient duplications within this family
gave rise to three distantly related groups, one consisting of the Na+ and
Ca++ channels, another the K+ channels, and a third including the cyclic
nucleotide-binding channels. A series of gene duplications produced at
least seven mammalian homologues of the Drosophila Shaker K+ channel;
clones of only three of these genes are available from all three mammalian
species examined (mouse, rat, and human), pointing to specific genes that
have yet to be recovered in one or another of these species. The
Shaw-related K+ channels and the Na+ channel family have also undergone
considerable expansion in mammals, relative to flies. These expansions
presumably reflect the needs of the high degree of physiological and
neuronal complexity of mammals. Analysis of the separate domains of the
four-domain channels (Ca++ and Na+) supports their having evolved by two
sequential gene duplications and implies the historical existence of a
functional two-domain channel.
相似文献
10.
mtDNA diversity in rhesus monkeys reveals overestimates of divergence time and paraphyly with neighboring species 总被引:4,自引:0,他引:4
Reconstructions of the human-African great ape phylogeny by using
mitochondrial DNA (mtDNA) have been subject to considerable debate. One
confounding factor may be the lack of data on intraspecific variation. To
test this hypothesis, we examined the effect of intraspecific mtDNA
diversity on the phylogenetic reconstruction of another Plio- Pleistocene
radiation of higher primates, the fascicularis group of macaque (Macaca)
monkey species. Fifteen endonucleases were used to identify 10 haplotypes
of 40-47 restriction sites in M. mulatta, which were compared with similar
data for the other members of this species group. Interpopulational,
intraspecific mtDNA diversity was large (0.5%- 4.5%), and estimates of
divergence time and branching order incorporating this variation were
substantially different from those based on single representatives of each
species. We conclude that intraspecific mtDNA diversity is substantial in
at least some primate species. Consequently, without prior information on
the extent of genetic diversity within a particular species, intraspecific
variation must be assessed and accounted for when reconstructing primate
phylogenies. Further, we question the reliability of hominoid mtDNA
phylogenies, based as they are on one or a few representatives of each
species, in an already depauperate superfamily of primates.
相似文献