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Query: UMLS:C0027651 (tumor)
 685,946 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Lipid content and composition of DNA, histone and nonhistone proteins of Ehrlich ascites tumor cell chromatin were investigated. All fractions contained varying amounts of lipids, mostly neutral lipids, with different quantitative distribution. The DNA fraction was characterized by elevated total cholesterol level (37%); the histone fraction by high glycerol ester content (62%); and the nonhistone protein fraction by high percentage of glycerol ethers (22%). The results suggest that neutral lipids are integral parts of tumor cell nucleoproteins.
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PMID:Neutral lipids in DNA, histone and nonhistone fractions of Ehrlich ascites tumor cell chromatin. 55 6

The tumor promoter 12-O-tetradecanoyl-phorbol-13-acetate (TPA) induces discrete waves of proliferation and differentiation when applied to mouse epidermis. The aim of this study was to elucidate the temporal relationship between histone phosphorylation and synthesis of DNA and RNA in mouse epidermis during the process of tumor promotion. This investigation as facilitated by choosing a low but nevertheless strongly tumor-promoting dose of TPA (0.002 micronmole/mouse), which induced the epidermal cells to go through only one round of DNA synthesis and cell division. Histones were isolated from mouse epidermis, and the rates of phosphorylation of the individual histone species were determined at different times after treatment with TPA. The results demonstrated that the phosphorylation of H1 histone was initiated at about the same time as the synthesis of DNA but continued past the S phase and reached a maximum simultaneously with the maximum in the epidermal mitotic rate. The only other histone that phosphorylated to any significant extent was Histone H2A. From the results obtained, it was concluded that histone phosphorylation in the epidermis is related to the processes of DNA replication and mitosis after stimulation with TPA. Positive evidence for the activation of specific genes, which has been proposed by other authors to be important in the promotion of epidermal tumors, was not found in this investigation.
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PMID:Histone phosphorylation and synthesis of DNA and RNA during phases of proliferation and differentiation induced in mouse epidermis by the tumor promoter 12-O-tetradecanoyl-phorbol-13-acetate. 85 63

Topical application of 17 nmoles of the potent tumor promoter, 12-O-tetradecanoylphorbol-13-acetate, resulted in a stimulation of the incorporation of [(3)H]lysine into epidermal histones. Maximum incorporation occurred 24 hr after treatment, concurrent with maximum DNA synthesis. The effects of phorbol and two phorbol esters on histone synthesis were related to their tumor-promoting activities. Treatment with hydroxyurea partially prevented the phorbol ester-induced stimulation of both DNA and histone synthesis, although it had no effect on the stimulation of protein synthesis. These findings are consistent with the likelihood that phorbol ester-induced epidermal histone synthesis is the result of a coupling between DNA synthesis and histone synthesis.
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PMID:Stimulation of the synthesis of mouse epidermal histones by tumor-promoting agents. 92 41

A potent immunosuppressive principle was isolated in a soluble form from the nuclei of Ehrlich ascites tumor cells. DNA-free preparation, obtained from the purified nuclei by homogenizing in 2M NaCl-5M urea solution and removing the dissociated DNA with LaCl3-precipitation, revealed strong activity to suppress the development of helper thymus-derived lymphocyte activity in mice. Moreover, almost all of the immunosuppressive activity originally found in the nuclear residue fraction after extraction with sodium citrate solution was recovered in 0.25 N HCl extract which mainly contains proteins. The nuclear components of tumor cells were also detected in the body fluid of tumor-bearing animals, as examined by the reactivity with a rabbit antiserum specific for some nuclear component of Ehrlich tumor cells. These results suggest that the immunosuppressive principle in the nuclei of Ehrlich tumor cells is a histone-like substance, and liberated into the body fluid from tumor cell nuclei in the tumor-bearing state.
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PMID:Isolation of soluble immunosuppressive substance(s) from Ehrlich ascites tumor cell nuclei. 102 53

The loosely bound chromatin proteins of Ehrlich ascites hyperdiploid cells have been prepared by extraction of chromatin with 0.35 M NaCl. Sodium dodecyl sulfate gel electrophoresis of the 0.35 M NaCl-soluble chromatin proteins reveals high heterogeneity with a molecular weight range of 10,000 to 170,000. The 0.35 M NaCl-soluble chromatin proteins contain many components similar to the more tightly bound non-histone chromatin proteins complex with the loosely bound chromatin proteins by gradient dialysis, the inhibitory effect of histones on transcription of DNA in vitro was reduced. The reconstituted complex manifested a level of template activity similar to that of native chromatin as measured in an Ehrlich ascites tumor RNA polymerase reaction. The loosely bound chromatin proteins contain RNA as well as phosphoproteins. Phenol extraction or DNA affinity chromatography of these proteins yielded fractions enhanced 25- to 30-fold in phosphorus which were capable of stimulating DNA-templated RNA synthesis in vitro. The stimulation of transcription from DNA was template-specific, effective only with a DNA template prepared from Ehrlich ascites tumor, but not from rat liver, calf thymus, or chicken erythrocytes. In addition, the stimulatory effect of the specific DNA-binding proteins appears to be RNA polymerase-specific, the stimulation being manifested with Ehrlich ascites tumor nucleoplasmic RNA polymerase and not with Micrococcus luteus RNA polymerase. Thus, the loosely bound chromosomal proteins from Ehrlich ascites tumor contain a fraction that specifically binds to Ehrlich ascites tumor DNA and exhibits a template- and RNA polymerase-specific stimulatory effect on transcription from DNA.
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PMID:Study of the loosely bound non-histone chromatin proteins. Stimulation of deoxyribonucleic acid-templated ribonucleic acid synthesis by a specific deoxyribonucleic acid-binding phosphoprotein fraction. 111 17

Newly synthesized polysomal messenger RNAs from cleavage stage embryos of the sea urchin Arbacia punctulata and Lytechinus pictus that contain putative histone mRNAs have been fractionated on 6% polyacrylamide slab gels. At least 8 RNA species with unique electrophoretic mobilities have been recognized. The complex of RNAs has been eluted from the gels in three groups, A, B, and C, in increasing order of mobility. The template activity of the three fractions and the unfractionated starting material was examined in the mouse Krebs II ascites tumor cell-free protein synthesizing system. The unfractionated messenger complex programs the synthesis of proteins that co-electrophorese exclusively with sea urchin histones in both sodium dodecyl sulfate and acid urea gel systems. The products of in vitro protein systhesis stimulated by the individual polyacrylamide gel RNA fractions were similarly examined. Each stimulated protein synthesis and was enriched for specific histone templates. We conclude that RNA fraction A is template for histone f1, C is template for histone f2a1, and B serves as template for f2b, f2a2, and f3 histones. A minor degree of contamination of the A and B RNA fractions was obvious from the production of other histones by each template. The co-electrophoresis of specific template activity with specific radiolabeled RNAs supports the concept that most or all of the labeled RNAs are indeed themselves the histone mRNAs.
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PMID:Individual histone messenger RNAs: identification by template activity. 112 55

The appearance of methylated lysines in newly synthesized histones from Ehrlich ascites tumor cells was measured during one generation time. Newly synthesized histones were pulse-labeled in vivo by L-[3H]lysine, and the time course of the uptake of label into monomethyl, dimethyl and trimethyllysine from gel-electrophoretically isolated histones F2a1 (H4) and F3 (H3) was followed. Methylation starts immediately after histone biosynthesis. It proceeds, however, more slowly than histone synthesis. Both the rate of methylation and the mechanism of methylation in F3 and F2a1 histones differ. F3 methylation can be described by a first-order reaction, i.e. the reaction rate depends only on the concentration of free methylation sites available. Rate constants of approximately 0.21 h-1 were found for all three methylation steps. Methylation in the F2a1 histone proceeds more slowly than in F3. The dimethylation step in this fraction can be described by a zero-order reaction with a rate constant which is the reciprocal of the duration of the DNA synthesis phase. Alternatively this step could be correlated with the transition of the cells from the S phase into the G2 phase. By the end of one generation time all methylation sites in all F2a1 and F3 molecules are occupied by methyl groups at a ratio of about 1:3:1 for monomethyl, dimethyl and trimethyllysine in the F3 histone. In the F2a1 molecule the methyllysines consist mainly of dimethyllysine.
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PMID:Kinetics of histone methylation in vivo and its relation to the cell cycle in Ehrlich ascites tumor cells. 114 43

The complement of nuclear non-histone proteins in epithelial cells of the colon is progressively altered during the course of carcinogenesis induced by 1, 2-dimethylhydrazine, until finally the nuclear proteins of tumor cells are easily distinguishable from those of the surrounding normal tissue. These changes in nuclear protein compostion reflect earlier differences in the rates of synthesis of individual protein species. Radioisotopic double-labeling experiments show that the synthesis of nuclear proteins of molecular weights 44,000 and 62,000 is selectively accelerated within 4 weeks after administration of the carcinogen, long before any morphological indications of malignancy appear.
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PMID:Selective synthesis and accumulation of nuclear non-histone proteins during carcinogenesis of the colon induced by 1, 2-dimethylhydrazine. 121 54

A striking similarity exists between the pathogenetic properties of group A streptococci and those of activated mammalian professional phagocytes (neutrophils, macrophages). Both types of cells are endowed by the ability to adhere to target cells; to elaborate oxidants, hydrolases, and membrane-active agents (hemolysins, phospholipases); and to freely invade tissues and destroy cells. From the evolutionary point of view, streptococci might justifiably be considered the forefathers of "modern" leukocytes. Our earlier findings that synergy between a streptococcal hemolysin (streptolysin S, SLS) and a streptococcal thiol-dependent proteinase and between cytotoxic antibodies+complement and streptokinase-activated plasmin readily killed tumor cells, led us to hypothesize that by analogy to the pathogenetic mechanisms of streptococci, the mechanisms of tissue destruction initiated by activated leukocytes in inflammatory sites, as well as in tissues undergoing episodes of ischemia and reperfusion, might also be the result of the synergistic effects among leukocyte-derived oxidants, phospholipases, proteinases, cytokines, and cationic proteins. The current report extends our previous synergy studies with endothelial cells to two additional cell types--monkey kidney epithelial cells and rat beating heart cells. Monolayers of 51Cr-labeled cells that had been treated by combinations of sublytic amounts of hydrogen peroxide (generated either by glucose oxidase, xanthine-xanthine oxidase, or by paraquat) and with sublytic amounts of a variety of membrane-active agents (streptolysin S, phospholipases A2 and C, lysophosphatides, histone, chlorhexidine) were killed in a synergistic manner (double synergy). Crystalline trypsin markedly enhanced cell killing by combinations of oxidant and the membrane-active agents (triple synergy). Injury to the cells was characterized by the appearance of large membrane blebs that detached from the cells and floated freely in the media, looking like lipid droplets. Cytotoxicity induced by the various combinations of agonists was depressed, to a large extent, by scavengers of hydrogen peroxide (catalase, dimethyl thiourea, and by Mn2+) but not by SOD or by deferoxamine. When cationic agents were employed together with hydrogen peroxide, polyanions (heparin, polyanethole sulfonate) were also found to inhibit cell killing. It is proposed that in order to effectively combat the deleterious toxic effects of leukocyte-derived agonists on cells and tissues, antagonistic "cocktails" comprised of cationized catalase, cationized SOD, dimethylthiourea, Mn(2+)+glycine, proteinase inhibitors, putative inhibitors of phospholipases, and polyanions might be concocted. The current literature on synergistic phenomena pertaining to mechanisms of cell and tissue injury in inflammation is selectively reviewed.
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PMID:Synergism among oxidants, proteinases, phospholipases, microbial hemolysins, cationic proteins, and cytokines. 142 26

This paper describes a simple and direct procedure for assaying Ca(2+)-dependent protein kinase C (PKC) activity in membrane fractions isolated from purified murine B lymphocytes (B cells) treated with phorbol 12-myristate 13-acetate (PMA). The results indicate that membrane-bound PKC in B cells, treated with PMA, can be measured directly in the presence of 0.5% Brij 58 by assaying the transfer of 32P from [gamma-32P]ATP to histone type III-S. This method obviates the need for partial purification of the protein kinase by ion-exchange chromatography prior to assaying PKC activity. The properties of membrane-associated PKC activity in B cells have been characterized, and the kinetics of PMA-induced translocation of PKC in cultured murine B cells, the rat glial tumor clone C6, and primary neonatal osteoblastic cells have been defined by this direct assay. The results obtained with B cells and the other cell lines indicate that this direct assay procedure could be useful for studies on the factors controlling PKC translocation in a variety of cultured mammalian cells.
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PMID:Direct assay of membrane-associated protein kinase C activity in B lymphocytes in the presence of Brij 58. 148 85


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