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31.
The addition of phleomycin (25 mug) to primary mouse embryo cells infected with polyoma virus was found to cause 96% inhibition of the synthesis of infectious virus. When ribonucleic acid and protein synthesis was investigated in these cells by use of isotope incorporation, it was found that neither was inhibited drastically. Immunofluorescent staining studies with the use of antibody directed to the viral structural proteins showed that proteins were synthesized in the presence of the antibiotic. However, when deoxyribonucleic acid (DNA) synthesis was investigated, it was found that DNA synthesis in uninfected cells was completely inhibited within the initial 10 hr of phleomycin addition, whereas DNA synthesis in infected cells proceeded at a reduced rate. Selective DNA extraction (Hirt method) of phleomycin-treated infected cells demonstrated that synthesized viral DNA was salt-extractable, similar to that in infected control cells lacking phleomycin. This extracted DNA was further fractionated by ethidium bromide-cesium chloride density gradient equilibrium centrifugation. The phleomycin-treated preparations revealed twice as much component II (circular nicked and linear) as component I (supercoiled) DNA, whereas the DNA from normally infected control cells showed the reverse picture. It was also demonstrated that viral particles synthesized in the presence of phleomycin did not contain component I DNA. This packaged DNA was found to consist of fragments of both the host and viral types. Cells that were prelabeled with (3)H-thymidine and then treated with phleomycin demonstrated host DNA degradation. However, fragments formed from prelabeled host DNA were not encapsidated into viral particles. 相似文献
32.
Separation of the Polypeptides of Chlamydia and Its Cell Walls by Polyacrylamide Gel Electrophoresis 总被引:6,自引:3,他引:3
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The polypeptide composition of Chlamydia was examined by acrylamide gel electrophoresis. When the polypeptide patterns of purified infectious elementary bodies (EB) of C. psittaci meningopneumonitis strain, 6BC strain, and C. trachomatis T'ang strain were compared, no significant differences were observed. The polypeptide patterns of whole EB and reticulate bodies (RB) appeared to overlap, but differences were found. In EB cell walls, nine main and several minor bands of polypeptides were observed in gels containing sodium lauryl sulfate, and the eighth main band from the top of the gel stained positive with periodic acid-Schiff reagent. On the other hand, the polypeptides in bands 3, 6, and 8 in EB cell walls were missing or minor in RB cell walls, and the ninth band was clearly stained by PAS. Band 8 was also stained slightly. Purified subunits, which occur as a lattice structure on the inside layer of EB cell walls but are largely missing in RB cell walls, contained bands 4, 6, and 8, and band 8 was PAS positive. These results indicate that significant polypeptide synthesis or reorganization in the cell walls occurs during the growth cycle. 相似文献
33.
Summary Changes in the chord conductanceG and the membrane electromotive forceE
m
in the so-called breakdown region of large negative potential of theChara plasmalemma were analyzed in more detail. In addition to the increase inG, the voltage sensitivity of the change inG increased, which was the cause of marked inductive current in the breakdown region. The breakdown potential, defined as a critical potential at which both low and high slope conductances of theI–V
m
relationship cross, almost coincided with the potential at which an inductive current began to appear. This breakdown potential level changed with pH
o
in a range between 5 and 9. TheChara plasmalemma was electrically most tolerant around pH
o
7.In some cellsE
m
shifted to a positive level as large as +50+70 mV during the breakdown phenomenon. Such a large positive shift ofE
m
is caused mainly by the increase in conductance of Cl– and partly Ca2+ and K+. 相似文献
34.
Y Tsukada K Ohkawa N Hibi K Tsuzuki K Oguma H Satoh 《Cancer biochemistry biophysics》1989,10(3):247-256
A monoclonal mouse antibody (MoHG) was produced using in vitro cultured AH66R tumor cells treated with cholesteryl hemisuccinate as an immunogen. The antibody identified a 90 kd membrane glycoprotein (HG-90) which is expressed on in vitro cultured hepatoma cell lines AH66 and AH66R. A monoclonal antibody was prepared to the anthracycline drug daunomycin, and it also reacted with adriamycin. A fusion was made of the hybridoma HG-90 with the hybridoma which recognized daunomycin/adriamycin. This bispecific hybridoma A8C recognized both determinants. We studied the therapeutic effect of the A8C bispecific antibody with adriamycin treatment and compared it to the effect of the bispecific antibody to which adriamycin had been conjugated via an albumin (Alb) bridge. The therapy model used was the tumor AH66R in Donryu rats. Tumor bearing rats had their subcutaneous tumors resected on day 10, a time when distant metastases were present. After the surgical resection of the tumor the rats were injected intravenously for two cycles with the bispecific antibodies, followed by the administration of adriamycin (ADR) or MoHG.Alb.ADR conjugates. A slight therapeutic effect occurred with either MoHG or ADR alone but treatment with the bispecific antibody followed by the administration of ADR or with the MoHG.Alb.ADR conjugates significantly prolonged survival, with 60% of the treated animals being "tumor free" when sacrificed on day 80. Lower serum concentrations of alphafetoprotein were observed with the bispecific antibody and drug treatment. This suggests that the bispecific antibody/drug treatment is potentially more beneficial in the suppression of distant metastases than the MoHG.Alb.ADR conjugate. This may be due to an increase in the local drug concentration of unmodified adriamycin. 相似文献
35.
M Okishio S Ohkawa Y Ichimori K Kondo 《Biochemical and biophysical research communications》1992,183(2):849-855
S-Nitrosothiols (S-nitrosocysteine, S-nitrosoglutathione and S-nitroso-N-acetylpenicillamine), which belong to the group of endothelium-derived relaxing factors (EDRFs), caused decreases of cytosolic free Ca2+ concentrations ([Ca2+]i) in cultured rat vascular smooth muscle cells (VSMCs). The endothelin-1 (ET-1)-induced sustained increase of [Ca2+]i in rat VSMCs was completely abolished by preaddition of at least an equal molar quantity of S-nitrosocysteine (Cys-SNO). Also exposure of VSMCs to a mixture of Cys-SNO and ET-1 at the same time resulted in the transient increase only. These results suggest that S-nitrosothiols may have no significant effect on ET-1-induced Ca2+ release from intracellular stores via inositol 1,4,5-triphosphate production but do affect Ca2+ influx through Ca2+ channels in the plasma membrane. 相似文献
36.
In vitro development of one-cell embryos from outbred mice: Influence of culture medium composition 总被引:2,自引:0,他引:2
Akiko Spindle 《In vitro cellular & developmental biology. Plant》1990,26(2):151-156
Summary One-cell embryos from outbred mice (CF1, CD-1, and Dub:ICR) were cultured in various modifications of egg culture medium (ECM).
The best development was observed in medium in which inorganic salts of modified T6 medium (mT6) replaced those of ECM. In
this modification (TE), 66% of one-cell CF1 embryos developed into blastocysts, comared to 46 and 43% for ECM and mT6, respectively.
Moreover, the cell numbers of blastocysts developing in TE (74.9±3.3) were higher than the cell numbers of those developing
in ECM (55.1±2.4). The culture requirements of embryos varied between different stocks of mice: Fewer CF1 embryos developed
to the blastocyst stage than either Dub:ICR embryos (90%) or CD-1 embryos (84%). Lowering the osmolarity of the medium from
300 to 280 mOsm, increasing the concentration of KC1 from 1.42 to 25 mM, or omitting lactate from the medium during Day 1 of culture did not further improve development of embryos, in contrast
to previous reports. However, the time at which embryos were transferred to outgrowth medium influenced their postblastocyst
development. The best development was observed when embryos were transferred on Day 4 of culture at the late morula-early
blastocyst stage.
This work was supported by the Office of Health and Environmental Research, U.S. Department of Energy, Washington, DC, contract
DE-AC03-76-SF01012. 相似文献
37.
Maruyama Akiko; Yoshiyama Makoto; Adachi Yasuhiro; Tani Akinobu; Hasegawa Ryo; Esashi Yohji 《Plant & cell physiology》1996,37(8):1054-1058
The effects of allyl, sulfur and cyanogenic compounds on thegermination of upper cocklebur (Xanthium pennsylvanicum Wallr.)seeds were examined. Mercaptoethanol and methylmercaptan aswell as KCN, substrates for rßcyanoalanine synthase(CAS), and H2S and thiocyanate, the products of the CAS catalyzingreaction, were effective in promoting germination, suggestingthe involvement of CAS in germination. Most of allyl compounds, especially allylthiourea, as well asethylene which activated CAS [Hasegawa et al. (1994) Physiol.Plant. 91: 141], promoted the germination in an abnormal typewhich occurred by the predominant growth of cotyledons as didC2H4 [Katoh and Esashi (1975) Plant Cell Physiol. 16: 687].However, they failed to activate CAS unlike ethylene, and toliberate free ethylene during an incubation period. It was thuspossible that an C2H4-like double bond within allyl compoundscan act to promote seed germination. (Received June 10, 1996; Accepted August 21, 1996) 相似文献
38.
39.
Binding of nonamer peptides to three HLA-B51 molecules which differ by a single amino acid substitution in the A-pocket 总被引:2,自引:2,他引:0
Akiko Kikuchi Takashi Sakaguchi Kiyoshi Miwa Yuji Takamiya Hans-Georg Rammensee Yutaro Kaneko Masafumi Takiguchi 《Immunogenetics》1996,43(5):268-276
The interaction between 9-mer peptides and HLA-B51 molecules was investigated by quantitative peptide binding assay using
RMA-S cell expressing human β2-microglobulin and HLA-B51 molecules. Of 147 chemically synthesized 9-mer peptides possessing
two anchor residues corresponding to the motif of HLA-B*5101 binding self-peptides, 27 paptides bound to HLA-B*5101 molecules. Pro and Ala at position 2 as well as Ile at position 9 were confirmed to be main anchor residues, while Gly
at position 2 as well as Val, Leu, and Met at position 9 were weak anchor residues for HLA-B*5101. The A-pocket is suspected to have a critical role in peptide binding to MHC class I molecules because this pocket corresponds
to the N-terminus of peptides and has a strong hydrogen bond formed by conserved Tyr residues. Further analysis of peptide
binding to HLA-B*5102 and B*5103 molecules showed that a single amino acid substitution of Tyor for His at residue 171(B*5102) and that of Gly for Trp at residue 167 (B*5103) has a minimum effect in HLA-B51-peptide binding. Since previous studies showed that some HLA-B51 alloreactive CTL clones
failed to kill the cells expressing HLA-B*5102 or HLA-B*5103, these results imply that the structural change of the A-pocket among HLA-B51 subtypes causes a critical conformational
change of the epitope for TCR recognition rather than influences the interaction between peptides and MHC class I molecules. 相似文献
40.
Tissue-specific expression of an anti-ras ribozyme inhibits proliferation of human malignant melanoma cells. 总被引:4,自引:0,他引:4
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In this study, we have compared the efficacy of a tissue-specific promoter (tyrosinase promoter) with a viral promoter to express anti-ras ribozyme RNA in human melanoma cells. The retroviral vector containing the tyrosinase promoter was superior in its ability to suppress the human melanoma phenotype in vitro as characterized by changes in growth, melanin synthesis, morphology and H-ras gene expression. These data support the use of tissue-specific expression of anti-oncogene ribozymes as a rational therapeutic strategy in human cancers. 相似文献