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排序方式: 共有340条查询结果,搜索用时 15 毫秒
1.
Summary Conditioned culture medium from Daudi cells was used as a source of soluble H-Y antigen. Concentrated culture medium was labeled with 125I and then fractionated by gel filtration. Column fractions were assayed for the presence of H-Y antigen by urease-ELISA. H-Y antigen-containing fractions were then pooled and subjected to an improved immunoprecipitation protocol. Three predominant H-Y antigenic proteins were identified with estimated molecular weights of above 200,000, 50,000, and 20,000. 相似文献
2.
K W Adolph 《Archives of biochemistry and biophysics》1987,253(1):176-188
Fundamental differences were previously discovered in the ADP-ribosylation of proteins from metaphase chromosomes and interphase nuclei of HeLa cells. The number of modified nonhistone species was found to be dramatically reduced for metaphase chromosomes. An investigation has therefore been made of factors which could influence, and therefore be responsible for, this change in ADP-ribosylation during the cell cycle. Modified proteins were detected by autoradiography of sodium dodecyl sulfate-polyacrylamide gels containing mitotic and interphase samples from permeabilized cells that had been incubated with [32P]NAD. Whole cells showed a difference between interphase and metaphase similar to that for isolated nuclei and chromosomes. Chromosome expansion, disruption of chromosomes or nuclei, DNA nicking, and cellular growth activity significantly changed the incorporation of 32P label. Inhibitors of protein, RNA, and DNA synthesis did not, however, greatly affect ADP-ribosylation. The pattern of labeled species was not altered by the presence of nonradioactive NAD, though the extent of labeling declined. The results were not artifactually due to the procedure used to arrest cells in mitosis. Similar results were found with Novikoff rat hepatoma cells, demonstrating that the difference between metaphase and interphase is not confined to HeLa cells. 相似文献
3.
Evidence that replication initiates at only some of the potential origins in each oligomeric form of bovine papillomavirus type 1 DNA. 总被引:16,自引:3,他引:13 下载免费PDF全文
J B Schvartzman S Adolph L Martín-Parras C L Schildkraut 《Molecular and cellular biology》1990,10(6):3078-3086
In a subclone of ID13 mouse fibroblasts latently infected with bovine papillomavirus type 1 (BPV-1) DNA, the viral genome occurred as a mixture of extrachromosomal circular monomers and oligomers. Multiple copies were also associated with the host cell genome, predominantly at a single site in a head-to-tail tandem array. We examined the replicative intermediates of extrachromosomal forms of BPV-1 DNA by using two-dimensional gel electrophoresis. The results obtained indicate that initiation of DNA replication occurred near the center of the EcoRI-BamHI 5.6-kilobase fragment. In some molecules, however, this fragment was replicated from one end to the other by means of a single fork initiated elsewhere. Termination also occurred within this fragment. The EcoRI-BamHI 2.3-kilobase fragment replicated as a DNA molecule containing a termination site for DNA replication and also by means of a single fork traversing the fragment from one end to the other. Thus, replication forks proceeded through these fragments in different manners, apparently depending on whether they were part of a monomer, a dimer, a trimer, or higher oligomers. These observations lead to the conclusion that initiation of DNA replication in BPV-1 DNA takes place at or close to plasmid maintenance sequence 1. From this point, replication proceeds bidirectionally and termination occurs approximately 180 degrees opposite the origin. The results obtained are consistent with one or more replication origins being quiescent in BPV-1 DNA oligomers. 相似文献
4.
Variations in ADP-ribosylation of nuclear scaffold proteins during the HeLa cell cycle 总被引:1,自引:0,他引:1
Cell cycle variations in ADP-ribosylation of nuclear scaffold proteins were determined. Nuclei of synchronized cells were isolated and labeled with [32P]NAD before nuclear scaffolds were obtained by digestion of DNA with DNase I and extraction of proteins with 2M NaCl. Autoradiograms revealed the three groups of "lamins" and a species identified as poly (ADP-ribose) polymerase to be the primary ADP-ribosylated proteins. The patterns of modification of nuclear scaffold proteins displayed similar features through the cell cycle. Radioactivity in the lamins increased from 20% in early-S phase to 40% in G1 phase of the next cell cycle. 相似文献
5.
Hardies SC; Martin SL; Voliva CF; Hutchison CA d; Edgell MH 《Molecular biology and evolution》1986,3(2):109-125
6.
We examined the nature of the diphtheria toxin fragment A recognition site in the protein synthesis translocating factor present in cell-free preparations from the archaebacteria Thermoplasma acidophilum and Halobacterium halobium. In agreement with earlier work (M. Kessel and F. Klink, Nature (London) 287:250-251, 1980), we found that extracts from these organisms contain a protein factor which is a substrate for the ADP-ribosylation reaction catalyzed by diphtheria toxin fragment A. However, the rate of the reaction was approximately 1,000 times slower than that typically observed with eucaryotic elongation factor 2. We also demonstrated the presence of diphthine (the deamidated form of diphthamide, i.e., 2-[3-carboxyamide-3-(trimethylammonio)propyl]histidine) in acid hydrolysates of H. halobium protein in amounts comparable to those found in hydrolysates of similar preparations from eucaryotic cells (Saccharomyces cerevisiae and HeLa). Diphthine could not be detected in hydrolysates of protein from the eubacterium Escherichia coli. Whereas both archaebacterial and eucaryotic elongation factors contain diphthamide, they differ importantly in other respects. 相似文献
7.
Flow through a Collapsible Tube: Experimental Analysis and Mathematical Model 总被引:2,自引:0,他引:2 下载免费PDF全文
Flow through thin-wall axisymmetric tubes has long been of interest to physiologists. Analysis is complicated by the fact that such tubes will collapse when the transmural pressure (internal minus external pressure) is near zero. Because of the absence of any body of related knowledge in other sciences or engineering, previous workers have directed their efforts towards experimental studies of flow in collapsible tubes. More recently, some attention has been given towards analytical studies. Results of an extensive series of experiments show that the significant system parameter is transmural pressure. The cross-sectional area of the tube depends upon the transmural pressure, and changes in cross-section in turn affect the flow geometry. Based on experimental studies, a lumped parameter system model is proposed for the collapsible tube. The mathematical model is simulated on a hybrid computer. Experimental data were used to define the functional relationship between cross-sectional area and transmural pressure as well as the relation between the energy loss coefficient and cross-sectional area. Computer results confirm the validity of the model for both steady and transient flow conditions. 相似文献
8.
Conditions were investigated for the production of a new gum by the yeast Cryptococcus laurentii var. flavescens NRRL Y-1401 in shaken flasks and 20-liter fermentors. The most suitable medium contained 6% commercial glucose, 0.25% autolyzed brewer's yeast, and 0.001% MnSO4 and had an initial pH of 6.5. Polysaccharide yields, as measured by the dry weight of the alcohol precipitates, were in the range of 30 to 35% based on initial glucose. 相似文献
9.
George E. Milo G. Adolph Ackerman Ronald L. Sanders 《In vitro cellular & developmental biology. Plant》1984,20(12):899-911
Summary Human lung epithelial cells have been isolated and maintained in pure culture and characterized during their time in culture.
Any residual fibroblasts were removed by selective trypsinization within the first 48 h in culture and the residual epithelial
cells from the primary culture grew to confluent density. The epithelial cells at Passage 2 or greater were serially subpassaged
when cultures reached ca. 80% confluency. This procedure permitted us to conduct biochemical and structural studies of starting
materials and subsequent population doublings.
Electron microscope evaluation of both initial monolayers and cell suspensions showed cultures to be composed of a single
cell type. These cells had microvilli on their free or apical surface. Subsequent population doubling level 1 up to 5 exhibited
the same structures. They contained lamellar inclusions, which are typical of Type II alveolar epithelial cells. Fetal lung
(age 18 to 20 wk) cell suspensions processed for electron microscopy before culturing showed cells to be undifferentiated,
epithelial-like with small microvilli along cell borders, and with desmosomes at cell junctions. Lamellar inclusions were
not observed in these cells. Ultrastructural studies of the cultured epithelial cells demonstrated that the lamellar inclusions
had a slightly positive reaction when tested for acid phosphatase. Phospholipid analysis of these lung epithelial cells showed
a phospholipid composition consistent with that found in surfactant-containing Type II cells. Cultured epithelial cells stained
with phosphine 3-R demonstrated a green fluorescent cytoplasm and nucleus with brightly fluorescent yellow-orange perinuclear
particles. The preceding characterization of these cells leads us to conclude that they exhibit structural and biochemical
features commensurate with Type II epithelial cells from human lung. Moreover, these selection techniques applied to the isolation
of human lung Type II cells from the tissue permit us to study the differentiative function of these cells routinely under
conditions of growth in vitro.
This work was supported in part by grants from EPA, R 806638-01 and 131-640-1599A1 相似文献
10.
Conservation of interphase chromatin nonhistone antigens as components of metaphase chromosomes 总被引:1,自引:0,他引:1
K W Adolph 《FEBS letters》1984,165(2):211-215
The degree of conservation of HeLa interphase chromatin nonhistone antigens among the nonhistones of isolated metaphase chromosomes was determined with immunological procedures. Proteins were separated on SDS-polyacrylamide gels and electrophoretically transferred to diazophenylthioether (DPT)-paper, which was then overlaid with antiserum to chromatin from interphase nuclei. The bound antibodies were detected with 125I-labeled protein A. Alternatively, polyacrylamide gels were directly overlaid with antiserum and with 125I-protein A. Densitometry of autoradiograms and stained gels revealed the degree of conservation of nonhistone antigenic determinants from interphase to metaphase to be over 90% for chromatin. 相似文献