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Query: UMLS:C0009443 (cold)
 92,137 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We have investigated three aspects of RNA turmor virus replication and cell transformation: (1) the properties of the purified avian and mammalian viral RNA-directed DNA polumerase, (2) some characteristics of the viral 60-70S RNA genome, 30-40S RNA subunits and intracellular viral RNA species, and (3) the interaction of the viral DNA polymerase with its RNA template early during infection and cell transformation by the murine sarcoma-leukemia virus (MSV[MLV]). Avian myeloblastosis virus (AMV) contains two forms of RNA-directed DNA polymerase, alpha, consisting of a single polypeptide of molecular weight 65,000, and alphabeta, consisting of two polypeptides of molecular weights 65,000 and 105,000. The alpha and alphabeta forms of AMV DNA polymerase both possess RNase H activity that requires free end termini on the ribopolymer and can degrade the RNA of the RNA-DNA hybrid in the 3' to 5' and 5' to 3' directions. But, alpha and alphabeta possess a different mode of exoribonuclease activity. While alphabeta RNase H is a processive exoribonuclease that degrades the polynucleotide chain to a core residue before attacking a second chain, alpha RNase H is a random exoribonuclease that releases the polynucleotide after each scission. Highly purified Moloney-MSV(MLV) DNA polymerase has both RNase H activity and the ability to read viral 60-70S RNA. These activities comigrate through five different steps of purification and are present at levels comparable to those found in purified AMV DNA polymerase. The MSV(MLV) 60-70S RNA genome and 35S RNA subunits were shown by periodate oxidationtritiated borohydride reduction to contain adenosine as the major 3'-terminal nucleoside. Poly (A) segments were isolated from viral 60-70S and 35S RNA by treatment with RNase A or RNase T1 and purified by afinity chromatography and gel electrophoresis. Viral poly(A) was shown to be present at the 3' terminus as -G(C,U)A190AOH. The similar sequence reported for poly(A) present in mammalian mRNA suggests that similar mechanisma are involved in the transcription and processing of both cellular and viral DNA sequences. Within transformed cells replicating MSV(MLV), viral 35S and 20S RNA were found in membrane-bound polyribosomes, whereas only 35S RNA was detected in free polyribosomes. The origin and function of 20S RNA is unknown. The early events during rapid infection and cell transformation of mouse 3T6 cells by the Harvey strain of MSV(MLV) were studied. By both autoradiographic analysis and molecular hybridization, viral DNA synthesis was detected in the cytoplasm by 1 hour after infection, reached a maximum at 2 hours, and subsequently decreased. Cytological chase experiments produced evidence that cytoplasmic viral DNA was transported to the nucleus. In situ hybridization experiments using radioactive viral DNA product as a probe demonstrated the rapid association of viral DNA sequences with the chromocenters of interphase nuclei and with the centromeric heterochromatin regions of some chromosomes.
Cold Spring Harb Symp Quant Biol 1975
PMID:Properties of oncornavirus RNA-directed DNA polymerase, the RNA template, and the intracellular products formed early during infection and cell transformation. 5 Sep 2

Ribonucleic acid-containing polyadenylic acid [poly(A)+-RNA] was studied in lysates from an osmotic-sensitive mutant of Saccharomyces cerevisiae characterized by low nuclease activity. The poly(A)+-RNA fraction, analyzed by electrophoresis in polyacrylamide-formamide gels, constitutes a heterogeneous population of molecules, with molecular weights ranging from 0.2 X 10(6) to 3 X 10(6) and having an average of 1.2 X 10(6). The turnover rate of poly(A)+-RNA was determined by the decay of radioactivity after a cold uracil chase, and the observed half-life of 21 min corresponds to about 10% of the cell doubling time. Poly(A)+-RNA was analyzed by gel electrophoresis under denaturing and non-denaturing conditions. A correlation was established between the apparent secondary structure and the turnover rate of poly(A)+-RNA species.
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PMID:Size and turnover of polyadenylic acid-containing ribonucleic acids in a fragile mutant of Saccharomyces cerevisiae. 31 49

CHO cells and cs-4-D3 cells were used to investigate the association between poly(ADP-rib) synthesis and the cessation of DNA synthesis and DNA fragmentation. The cs4-D3 cells are cold-sensitive DNA synthesis arrest mutants of CHO cells. Upon incubation at 33 degrees C, DNA synthesis in the cs4-D3 cells stops and the cells enter a prolonged G1 or G0 phase. The events that occurred when cs4 cells were incubated at 33 degrees C were similar to those that occurred when wild-type CHO cells grew to high density. (1) In both cases, DNA synthesis and cell growth stopped. (2) The NAD+ concentration/cell was 20-25% lower in growth-arrested cells than in logarithmically growing cells. (3) Poly(ADP-rib) synthesis was 3-4 fold higher in growth-arrested cells than in logarithmically growing cells. (4) The growth-inhibited cells developed DNA strand breaks which resulted in large percentages of their DNA appearing in the low molecular weight range of alkaline sucrose gradients. (5) Both the increased rate of poly(ADP-rib) synthesis and the development of DNA strand breaks appears to be characteristic of the G1 phase of the cell cycle. (6) When growth-inhibited cells were restored to conditions favorable for DNA synthesis and cell growth, the DNA strand breaks were repaired. (7) Prolonged incubation under growth-restrictive conditions resulted in the accumulation of more DNA strand breaks than the cells could repair. This was followed by cell death when the cells were restored to conditions favorable for cell growth.
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PMID:Association of poly(ADP-rib) synthesis with cessation of DNA synthesis and DNA fragmentation. 53 44

Poly(A)+RNA was isolated from brown adipose tissue of cold acclimated rats and a fraction enriched for uncoupling protein mRNA was used to generate a cDNA library in pBR 322. Immunological screening of 1,500 colonies with an affinity-purified antiserum against the uncoupling protein yielded five positive clones, pUCPrat1-5. Clone pUCPrat2 encoded the C-terminal 54 amino acids of rat uncoupling protein and exhibited 90% amino acid homology with the hamster protein. Clones pUCPrat3-5 encoded only the C-terminal 11 amino acids suggesting that an antigenic determinant lies within this sequence.
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PMID:Immunological detection of cDNA clones encoding the uncoupling protein of brown adipose tissue: evidence for an antigenic determinant within the C-terminal eleven amino acids. 242

Myeloperoxidase (MPO) is a major protein present in myeloid cells and is used by these cells to help kill microbes. The human promyelocytic HL-60 line can be induced to differentiate to granulocytes or macrophagelike cells. Poly (A) containing RNA was isolated from HL-60 granulocytes, HL-60 macrophages, HL-60 blasts, and normal human granulocytes. The mRNA was translated in a reticulocyte lysate system in the presence of 35S-methionine. The MPO was precipitated from the lysate with rabbit IgG antiserum to human MPO. The resulting precipitate from HL-60 blasts gave a major band of radioactivity of approximately 77,000 daltons and another band at approximately 46,000 daltons on sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The MPO identity of the labeled bands was confirmed by cold competition. The relative mRNA activity expressed as a percentage of radioactivity incorporated into MPO (77,000-dalton band) as compared with total trichloracetic acid (TCA) precipitable radioactivity was 0.2%. Negligible mRNA activity for MPO was present in HL-60 granulocytes, HL-60 macrophages, and normal human granulocytes. Pulse-chase experiments showed that MPO was an approximate 75,000-dalton major band and 77,000-dalton minor band of radioactivity after HL-60 blasts were labeled for 1/2 hour with 35S-methionine and the cell lysate immunoprecipitated and subjected to SDS-PAGE. The chase experiments (one to 24 hours) showed that the 77,000- and 75,000-dalton bands of radioactivity were replaced with two major bands (55,000 and 15,000 daltons) and one minor band (approximately 39,000 daltons) of radioactivity. Six-hour 35S-methionine labeling experiments showed that the relative rate of MPO synthesis compared with total TCA precipitable radioactivity was 0.5% in HL-60 blasts and almost negligible in HL-60 macrophages and granulocytes, normal human granulocytes, and B-lymphocytes. The KG-1 myeloblasts and KG-1a early myeloblasts synthesized a small amount of the 75,000-dalton MPO protein. Although HL-60 cells no longer synthesized MPO after differentiation, HL-60 granulocytes and HL-60 macrophages continued to contain MPO as measured by enzyme activity.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Myeloperoxidase: its structure and expression during myeloid differentiation. 298 91

We used embryonic chick pelvic cartilage as a model to study the mechanism by which cyclic AMP increases RNA synthesis. Isolated nuclei were incubated with [32P]-8-azidoadenosine 3,5'-monophosphate ([32P]N3cAMP) with no resultant specific nuclear binding. However, in the presence of cytosol proteins, nuclear binding of [32P]N3cAMP was demonstrable that was specific, time dependent, and dependent on a heat-labile cytosol factor. The possible biological significance of the nuclear binding of the cyclic AMP-protein complex was identified by incubating isolating nuclei with either cyclic AMP or cytosol cyclic AMP-binding proteins prepared by batch elution DEAE cellulose chromatography (DEAE peak cytosol protein), or both, in the presence of cold nucleotides and [3H]uridine 5'-triphosphate. Poly(A) RNA production occurred only in nuclei incubated with cyclic AMP and the DEAE peak cytosol protein preparation. Actinomycin D inhibited the incorporation of [3H]uridine 5'-monophosphate into poly(A) RNA. The newly synthesized poly(A) RNA had a sedimentation constant of 23S. Characterization of the cytosol cyclic AMP binding proteins using [32P]N3-cAMP with photoaffinity labeling three major cAMP-binding complexes (41,000, 51,000, and 55,000 daltons). The 51,000 and 55,000 dalton cyclic AMP binding proteins were further purified by DNA-cellulose chromatography. In the presence of cyclic AMP they stimulated poly(A) RNA synthesis in isolated nuclei. The 51,000-dalton cyclic AMP-binding protein was the predominant one that bound to the nuclei. While cyclic AMP-dependent protein kinsae activity was present in the cytosol and DEAE peak cytosol proteins, it was not present in the DNA-cellulose-bound, cyclic AMP-binding proteins. We conclude that one possible mechanism by which cyclic AMP increases RNA synthesis is by complexing to a 51,000-dalton cytosol cyclic AMP-binding protein and being subsequently translocated to the nucleus, where it is specifically bound and associated with induction of poly(A) RNA synthesis.
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PMID:Specific nuclear binding of adenosine 3',5'-monophosphate-binding protein complex with subsequent poly(A) RNA synthesis in embryonic chick cartilage. 615 54

The aim of this work was to develop sustained local release systems for radioiodinated iodo-2'-deoxyuridine (125IUdR) from biodegradable polymeric microspheres to facilitate the controlled delivery of 125IUdR to brain tumours. The selective uptake of IUdR into the cell nucleus results in cell disruption over the short range of the low energy Auger electrons. The biodegradable microspheres can be precisely implanted in the brain by stereotactic techniques and the IUdR within the microspheres is protected from degradation and thus a sustained source of radiolabelled IUdR is available in the vicinity of the residual tumour cells. Poly(lactic-co-glycolic acid), PLGA (85:15), microspheres containing cold IUdR and the Auger-electron emitter 125I, as 125IUdR were prepared using the O/W, O/O and W/O/W emulsion-solvent evaporation methods. The W/O/W emulsion method was most effective in achieving good drug loading with the use of bovine plasma in the internal water phase. Also effective in improving the drug loading was the use of 20% acetone in the dichloromethane and the presence of Span 40 in the organic phase. Electrolytes (NaCl and IUdR) in the external aqueous phase also improved drug loading. After an initial rapid release from the microspheres, a sustained release was observed over 15 days for the 'cold' IUdR. The sustained release portions of the release curves showed Higuchi (t1/2), diffusion controlled release kinetics. The radiolabelled IUdR microspheres showed a burst release effect of 30-40% followed by a sustained release over 35 days.
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PMID:Iodo-2'-deoxyuridine (IUdR) and 125IUdR loaded biodegradable microspheres for controlled delivery to the brain. 981 56

Poly-N-isopropylacrylamide (PNIPAM) is a chemical isomer of poly-leucine, having the polar peptide group in the side-chain rather than in the backbone. It has been demonstrated experimentally that PNIPAM dissolved in aqueous solution undergoes a collapse transition from coil to globule on increasing temperature above the θ-point. By a careful reviewing of existing experimental data, we emphasize that such coil to globule collapse has to be considered an intramolecular first-order transition, analogous to the cold renaturation of small globular proteins. The main theoretical approaches to the coil to globule collapse in homopolymers are discussed briefly, and a critical comparison between the existing models is performed. We point out that, as a general result, the coil to globule collapse is expected to be a first-order transition for rigid and semi-rigid macromolecules. Finally, taking advantage of the analogy between the coil to globule collapse of PNIPAM and the cold renaturation of small globular proteins, we try to clarify some important and intriguing aspects of protein thermodynamics. This leads to the conclusion that the amphiphilic nature of polypeptide chain plays the fundamental role for the existence of two temperature-induced conformational transitions.
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PMID:On the temperature-induced coil to globule transition of poly-N-isopropylacrylamide in dilute aqueous solutions. 1070 90

Poly(3-hydroxybutyrate-co-3-hydroxyoctanoate), PHBO, represents a class of PHA copolymers that contain both short-chain-length and medium-chain-length repeat units. Radiolabeled and cold PHBO, containing 90 mol % 3-hydroxybutyrate and 10 mol % 3-hydroxyoctanoate were chemically synthesized using a new difunctional alkoxyzinc initiator. (14)C-PHBO was incubated with samples of anaerobic digester sludge, septage, freshwater sediment, and marine sediment under conditions resembling those in situ. In addition, it was incubated in laboratory-scale landfill reactors. (14)C-PCL (poly-epsilon-caprolactone) was incubated with anaerobic digester sludge and in landfill reactors. Biodegradation was determined by measuring generation of (14)CO(2) and (14)CH(4) resulting from mineralization of the radiolabeled polymers. PHBO was extensively mineralized in digester sludge, septage sediments, and the landfill reactors, with half-lives less than 30 days. PCL was not significantly mineralized in digester sludge over 122 days. In the landfill reactors, PCL mineralization was slow and was preceded by a long lag period (>200 days), suggesting that PCL mineralization is limited by its rate of hydrolysis. The results indicate that PHBO is practically biodegradable in the major anaerobic habitats that it may enter. In contrast, anaerobic biodegradation of PCL is less ubiquitous and much slower.
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PMID:Anaerobic biodegradation of aliphatic polyesters: poly(3-hydroxybutyrate-co-3-hydroxyoctanoate) and poly(epsilon-caprolactone). 1209 27

The extent of the phase-selective solubility of poly(N-alkylacrylamide)s was studied by UV-vis and fluorescence spectroscopy using poly(N-isopropylacrylamide) and poly(N-octadecylacrylamide) as representative polar and nonpolar poly(N-alkylacrylamide)s in a mixture of polar and nonpolar thermomorphic solvents. Phase-selective solubilities of greater than 10000:1 were seen with each labeled polymer in polar and nonpolar solvents such as heptane and DMF or heptane and 90% EtOH-H(2)O. Using a poly(N-acryloxysuccinimide) as a common precursor, a pool-split synthesis was devised to prepare a library of poly(N-alkylacrylamide)s whose members varied only in the size of their N-alkyl substituent. The solubilities of these library members were measured in both the polar and nonpolar phases of a thermomorphic heptane/90% EtOH-H(2)O mixture at 25 degrees C. Such solvent mixtures are miscible hot (70 degrees C) and biphasic cold (25 degrees C). The results show that poly(N-pentylacrylamide) is selectively soluble (>99.5%) in the polar EtOH-rich phase at rest. Poly(N-alkylacrylamide)s with larger N-alkyl groups are predominantly (C(6), 85%; C(7), 95%) or exclusively (>C(8), >99.5%) in the heptane-rich phase at rest.
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PMID:Phase-selective solubility of poly(N-alkylacrylamide)s. 1283 95


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