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Query: UMLS:C0011570 (depression)
 172,036 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Using our new method for assaying DNases with radioactively labeled DNA bound to wells of plastic depression plates as substrate, we could distinguish between endonucleases and exonucleases and between haplotomic and diplotomic endonucleases. Oligonucleotides smaller than 30 detach from the DNA binding sites of the well into the reaction mixture. Thus, a lag period was evident before endonucleases produced small soluble oligonucleotides, while exonucleases released mononucleotides or short oligonucleotides without any lag period. Haplotomic and diplotomic endonucleases were detected because of the different rates in which they produce small soluble oligonucleotides which were expressed in different lag periods. Under conditions in which the haplotomic DNase 1 changes its mode of action to become a diplotomic enzyme, the shift was clearly detected by a change in the lag period in the well assay.
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PMID:Differentiation between exonucleases and endonucleases and between haplotomic and diplotomic endonucleases using 3-h-dna-coated wells of plastic depression plates as substrate. 16 56

Incubation of HeLa cells with the anticancer agent N-methyl-N-nitrosourea (MNU) results in: (a) depression of intracellular nicotinamide adenine dinucleotide levels; (b) stimulation of the chromatin-associated, chromosomal protein-modifying enzyme polyadenosine diphosphoribose [poly(ADP-ribose)] polymerase, which uses nicotinamide adenine dinucleotide as substrate; and (c) some fragmentation of cellular DNA. DNase treatment of HeLa nuclei in vitro also stimulates poly(ADP-ribose) polymerase activity, but not in nuclei derived from MNU-treated cells unless they have been subsequently incubated to allow for recovery from MNU damage. DNA polymerase activity is stimulated in vitro by poly(ADP) ribosylation of nuclear proteins. By using intact nuclei derived from MNU-treated HeLa cells, the repair via elongation of single-strand DNA breaks is demonstrated in vitro. This repair is dependent on DNA polymerase activity and is enhanced by adenosine diphosphate ribosylation of histones. Inhibition of poly(ADP-ribose) polymerase with nicotinamide results in extensive degradation of MNU-damaged DNA. Taken as a whole, these results suggest that poly(ADP-ribose) polymerase may play a role in the repair of alkylation damage to cellular DNA and that the inhibition of this enzyme in vivo might be exploited to potentiate the antitumor and carcinogenic activities of MNU.
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PMID:A putative role for nicotinamide adenine dinucleotide-promoted nuclear protein modification in the antitumor activity of N-methyl-N-nitrosourea. 19 15

Temperature-sensitive "leaky" mutants of phage MS2 having white dense ring around negative colonies are described. As these mutants are used for quantitative genetic studies, the white ring presents interest. Typical mutant 40 is used as a model for investigation. Light microscopy has shown, that cells from white ring zone have spore-like inclusions, which determine the characteristic structure of surrounding mutant negative colonies. Cytochemical reactions for the presence of glicogen, lipids, volutin, nuclear material and spores were negative. Electrone microscopy of negatively stained samples and ultrathin sections has revealed that cells from white ring zone, unlike phage-infected wild type cells, have two types of electron dense inclusions: 1) crystalline structures formed with great number of closely packed mature phage particles, and 2) large amorphic bodies. Electrone microscope-cytochemical data showed that inclusions remain intact under treatment of ultrathin sections of white zone ring with DNase and perchloric acid, while nuclear material was completely destroyed. Amorphic bodied were completely destructed after the treatment with RNase, while nuclear material and crystalline phage aggregated remained unchanged. Therefore, amorphic bodies consist of RNA, which has not been used to form virions. Single cycle of the development of mutant 40 at 37 degrees and 43 degrees C and under the temperature of incubation 37 degrees leads to 43 degrees C and 43 degrees leads to 37 degrees C in the course of intracellular reproduction is investigated. Influence of the phage on growth on infected culture is studied. The data obtained draw to a conclusion that the impaired function belongs to cystron protein of the phage membrane. As certain mutations in this cystrone of RNA-containing phage result in the depression of cystrone RNA polymerase, it is supposed that the formation of RNA containing bodies in infected cells, determining the formation of white rings in NA, together with cristalline aggregates of cells, is a result of mutation damage of cystrone protein of the phage MS2 membrane.
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PMID:[Effect of mutagens on RNA-containing phages and its infectious RNA. VII. Genetic nature of morphologic mutants of RNA-containing phage MS2]. 99 65

Most genetic characteristics of T4 recombination (the effects of chromosomal termini on recombination, heterozygosity, high negative interference, base mismatch repair, polarized segregation, and the stimulation or depression of recombination in response to phage mutations or external perturbations) can be expressed adequately in terms of our present understanding of the molecular events of T4 infection cycles. T4 DNA replication begins and ends with linear chromosomes and does not require a circular intermediate. Replication is bi-directional, possibly from multiple origins. Two phases of replication are distinguishable: (a) an early mode during which about 20 progeny copies of infecting chromosomes are made prior to (b) a recombination-dependent mode during which progeny molecules associate to form covalently joined linear concatemers. Further replication is generally arrested if concatemerization is prevented. T4 DNA recombination depends on the production of single-stranded gaps and termini. If replication is inhibited, the single-stranded regions are produced by deoxyribonuclease activities. In contrast, during partial replication of damaged chromosomes, during slow replication when enzymes or subtrates are limited, and during normal replication, they are formed by strand-displacement DNA polymerization. As a rule, any agents or perturbations that cause an accumulation of single-stranded regions stimulate recombination, whereas efficient repair of such regions depresses it. Both the preservation and pairing of single-stranded regions are facilitated by the gene-32 single-stranded DNA binding protein. Covalent repair of strand interruptions between recombined DNA segments requires polymerases or nucleases as well as ligases.
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PMID:Molecular and genetic recombination of bacteriophage T4. 110 66

Serum levels of IgM, IgG and IgG-antibody subclasses directed against cell envelopes, lipopolysaccharides and cytoplasmic fractions from Capnocytophaga sputigena, C. gingivalis and C. ochracea were examined in age-, race- and sex-matched periodontally healthy (n = 25) subjects and subjects with adult periodontitis (n = 25). The envelopes and cytoplasmic fractions were obtained by ballistic disintegration of the cells and ultracentrifugation. Cell envelopes were treated with DNase, RNase and lysozyme. Lipopolysaccharides were obtained by hot phenol-water extraction and treated with DNase and RNase. The relative levels of the antibodies in response to the cell fractions were measured by the streptavidinbiotin micro enzyme-linked immunosorbent assay. Both groups showed IgM and IgG antibodies to each fraction of the three Capnocytophaga species, but the frequency of positive IgG subclass responses varied. The IgG4 responses were lower than the other subclasses. There were no significant differences between the IgM antibody levels of the two groups. However, the adult periodontitis group had significantly lower IgG antibody titres to the cell envelopes and cytoplasmic fractions of C. gingivalis and C. ochracea, and lipopolysaccharide of C. gingivalis. These results were reflected in the depressed levels of IgG1 and/or IgG2 to these cellular fractions from the same bacterial species. The adult periodontitis group also showed a lower level of IgG1 to the cytoplasmic fractions of C. sputigena without any depression in the total IgG antibody level. There were no significant differences between the groups in IgG3 and IgG4 antibody levels to any of the cellular fractions.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Serum antibody responses in human periodontitis to cellular components of Capnocytophaga. 141 21

We have recently shown that phosphorothioate (PS) oligodeoxynucleotide (ODN) analogs, unlike their normal congeners, exhibit significant anti-HIV activity (Matsukura et al., (1987) Proc. Natl. Acad. Sci. USA 84, 7706-7710). We now report the syntheses, melting temperatures (Tm), and nuclease susceptibilities of a series of phosphorothioate ODN analogs. These include all-PS duplexes, duplexes with one normal chain and the other chain either all-PS, or end-capped with several PS groups at both 3' and 5' ends. The DNase susceptibilities of the S-ODNs are much less than the normal phosphodiesters, but by contrast duplexes of poly-rA with S-dT40 are much more susceptible to RNase H digestion. The Tm's for AT base pairs of S-ODNs are significantly depressed relative to normals, while GC base pairs show much less Tm depression. The Tm's of S-dT oligomers with poly-rA are reduced relative to the duplexes with normal dA oligomers. These results have significance for the biological properties of these analogs as anti-message inhibitors of gene expression, and provide a rational basis for the S-dC/G sequences as potential effective anti-AIDS agents.
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PMID:Physicochemical properties of phosphorothioate oligodeoxynucleotides. 283 90

A tumor-derived factor that inhibits cellular DNA synthesis was identified. The factor was extractable from a small-cell lung carcinoma cell line grown in either chemically defined medium or nu/nu mice and inhibited tritiated thymidine ([3H]dThd) incorporation by tumor cell lines of autologous, allogeneic, and xenogeneic origins. The viability of nonproliferating cells from normal tissue was not affected. Tumor extract inhibitory activity was trypsin labile but was resistant to other proteases, neuraminidase, lipase, DNase, RNase, glucosidase, extremes of pH-temperature, and reducing conditions. Inhibitory activity was reversibly bound to helix pomatia lectin but not to lentil, wheat germ, or concanavalin A lectins. Purification by size-exclusion high-performance liquid chromatography yielded a bioactive unimodal 12-kilodalton (kd) peak. The bioactive 12-kd moiety could be eluted from sodium dodecyl sulfate-polyacrylamide gels. Redosing of populations of the T-lymphoblastoid cell line CEM achieved an early (24 hr) sustained depression of pulse [3H]dThd incorporation and ultimately led to decreased population density of factor-treated populations. DNA histogram analysis demonstrated no change in cell cycle phase distribution after factor treatment. 5-Bromo-2'-deoxyuridine (BrdUrd) vs. propidium iodide with the two-parameter Fluorescence-Activated Cell Sorter analysis showed relative inhibition of non-S-phase BrdUrd uptake at 24 hours. A cell-free DNA polymerase assay demonstrated significant inhibition of non-alpha-polymerase-associated DNA synthesis in factor-treated cells. These studies suggest that this tumor-derived inhibitor of DNA synthesis represents a class of cellular products involved in the autoregulation of growth by regulation of DNA synthetic activity.
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PMID:Inhibition of DNA synthesis by a small-cell lung carcinoma-derived protein. 302 Mar 1

The sea urchin embryo nuclei which retained their ability to maintain the DNA synthesis in an in vitro system were isolated. The DNA synthesis isolated nuclei was shown to be an ATP-dependent process which is inhibited by low concentrations of actinomycin D, a polymerase alpha araCTP inhibitor. The newly synthesized DNA is represented by short fragments of about 4S. After addition of Ca2+, Mg2+-dependent DNAase to sea urchin embryo nuclei, the synthesis of short DNA fragments is enhanced. This stimulating effect of Ca2+, Mg2+-dependent DNAase is ATP-dependent and is observed only within a narrow range of enzyme concentrations (of the order of 1-5 units of DNAase activity per ml of incubation sample). The increase in the enzyme concentration to 10 or more units of activity results in the depression of DNA synthesis. It is concluded that DNA replication in sea urchin embryo nuclei depends on the presence of active DNAases as well as on the number of accessible initiation sites of DNA replication.
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PMID:[Effect of Ca2+, Mg2+-dependent deoxyribonuclease on DNA synthesis in cell nuclei from embryos of the sea urchin Strongylocentrotus intermedius]. 344 31

Tumours produce substances that inhibit the expression of cell-mediated immunity, in the form of delayed-type hypersensitivity in mice. Phenol-saline extracts of bovine ocular squamous cell carcinoma (BOSCC) which have immunotherapeutic activity in cattle were able to immunize mice against this depressive effect. Such immunization was effective against products of BOSCC, a spontaneous rat tumour, three of four human tumour cell lines and (in other experiments) mouse tumours. Phenol-saline extracts of mouse tumour cell lines were immunogenic (protective against depression of delayed-type hypersensitivity) in mice. Fractions of BOSCC phenol-saline extracts which were immunotherapeutically active in cattle were generally also protective in mice. The protective activity was lost after treatment with proteinase K, and was present in the supernatant after precipitation with 55% ammonium sulphate. It was not affected by treatment with RNase or DNase or by heating to 50 degrees C for 2 h. It was present in gel filtration fractions with an apparent molecular weight of 10,000-37,000 daltons. The immunogenic factor in mice and the immunotherapeutic factor in cattle may be related to each other.
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PMID:Depression of cell-mediated immunity by tumour cell products: induction of resistance by immunotherapeutically active extracts of bovine ocular squamous cell carcinoma. 359 86

Physicochemical and immunological techniques have been used in an attempt to characterize a filterable agent, separated from the intestines of mice raised under ordinary conditions of husbandry, which produces a lasting depression of weight in specific pathogen-free (SPF) mice when administered to them orally shortly after birth. Although this agent has not yet been identified, it will be tentatively designated here as enterovirus. The mouse enterovirus can be readily sedimented by ultracentrifugation and by precipitation at pH 4.3; it does not pass through cellophane membranes. Its infective power is completely destroyed by ultraviolet radiation, but is resistant to heating at 56 degrees C, exposure to ether, treatment with trypsin, ribonuclease, and deoxyribonuclease. Dialysis and treatment with ether and nucleases greatly increase the infective activity of the intestinal filtrates containing the enterovirus, a finding which suggests that these procedures eliminate or destroy some inhibitory substance(s). The mouse enterovirus causes hemagglutination of mouse red blood cells. When injected into rabbits, it elicits in them an immune response that renders their serum capable of neutralizing its weight-depressing activity. As measured by inhibition of hemagglutination or complement fixation, the sera of infected mice do not exhibit any significant activity against usual mouse viruses. Centrifugation of the mouse enterovirus in 50%-20% sucrose gradient gave almost complete recovery of the infectivity and of hemagglutinating activity in the same fraction. In contrast, the protein content of the material was distributed through the various fractions. Consequently, this procedure resulted in a marked increase of specific activity.
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PMID:Lasting biological effects of early environmental influences. IV. Notes on the physicochemical and immunological characteristics of an enterovirus that depresses the growth of mice. 431 May 4


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