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  • Canadian Science Publishing  (4)
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  • Canadian Science Publishing  (4)
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  • 1
    Online Resource
    Online Resource
    DNA Polymerase Activity in the Nuclei of Developing Rat Brain and Liver
    Canadian Science Publishing ; 1972
    In:  Canadian Journal of Biochemistry Vol. 50, No. 2 ( 1972-02-01), p. 186-189
    Details
    In: Canadian Journal of Biochemistry, Canadian Science Publishing, Vol. 50, No. 2 ( 1972-02-01), p. 186-189
    Abstract: The level of DNA polymerase activity per tissue in the soluble fraction (NS) of rat brain nuclei underwent a twofold increase during the first 2 weeks after birth and then declined steeply over the next 10 weeks to a value only one-third ofthat in the newborn. In contrast to brain, the enzyme activity per liver increased continuously from birth up to 12 weeks of age (10-fold). The DNA contents of these tissues appear to be quantitatively related to the DNA polymerase activities in the respective NS fractions. These preparations did not phosphorylate thymidylate to TTP, but could convert the other three complementary deoxynucleotides to the triphosphate level. This latter activity was highest in the NS fraction of the newborn rat brain and decreased drastically with growth. In the corresponding fraction of liver, the activity remained relatively stable throughout the growth period tested.
    Type of Medium: Online Resource
    ISSN: 0008-4018
    URL: Article
    DOI: 10.1139/o72-025
    Language: English
    Publisher: Canadian Science Publishing
    Publication Date: 1972
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  • 2
    Online Resource
    Online Resource
    Depolymerization of polyadenylic acid by subcellular fractions of rat brain and liver
    Canadian Science Publishing ; 1969
    In:  Canadian Journal of Biochemistry Vol. 47, No. 3 ( 1969-03-01), p. 283-289
    Details
    In: Canadian Journal of Biochemistry, Canadian Science Publishing, Vol. 47, No. 3 ( 1969-03-01), p. 283-289
    Abstract: Rat brain and liver homogenates depolymerized polyadenylic acid when added to a reaction mixture containing this polynucleotide. The activity in the homogenate declined progressively with the age of the tissues. This was reflected in a parallel reduction in the activity of the soluble fraction. In brain, the activity in the nuclear fraction also declined in the adult to half the level of the newborn. In contrast, liver nuclei had approximately the same activity at all stages of growth.With advancement in age, an increasingly greater proportion of the total activity of the tissues was contained in the nuclear fraction, while at the same time the proportion of activity in the soluble fraction decreased. The proportion of activity contained in the mitochondrial–microsomal fraction also increased with growth in brain, with the maximum increment in activity occurring after 8 weeks of age. In liver, there was actually a decrease of activity in this fraction during the same period. At all ages, the mitochondrial–microsomal fraction of brain contained a higher proportion of activity and the nuclear fraction of brain contained a lower proportion of activity compared to corresponding fractions of liver. The presence of polyadenylic acid degrading activity in these fractions and its relative increase with age may indicate a changing emphasis in the pattern of RNA metabolism during growth; for example, a higher rate of RNA synthesis in the young and a higher rate of RNA turnover in the adult.When the soluble fraction of rat brain was dialyzed, the polyadenylic acid degrading activity of this fraction was stimulated by the addition of inorganic orthophosphate. Brain and liver homogenates also mediated an ADP – inorganic phosphate exchange reaction which was highest in the newborn and decreased rapidly with age. These observations indicate that at least a part of the polyadenylic acid degrading activity in brain and liver extracts may be due to phosphorolytic action.
    Type of Medium: Online Resource
    ISSN: 0008-4018
    URL: Article
    DOI: 10.1139/o69-043
    Language: English
    Publisher: Canadian Science Publishing
    Publication Date: 1969
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  • 3
    Online Resource
    Online Resource
    Subcellular Distribution of DNA Polymerase Activity in Newborn Rat Brain and Liver
    Canadian Science Publishing ; 1971
    In:  Canadian Journal of Biochemistry Vol. 49, No. 12 ( 1971-12-01), p. 1285-1291
    Details
    In: Canadian Journal of Biochemistry, Canadian Science Publishing, Vol. 49, No. 12 ( 1971-12-01), p. 1285-1291
    Abstract: DNA polymerase activities were determined in the cytoplasmic soluble, the nuclear soluble, and the nuclear particulate fractions of newborn rat brain and liver. The results indicate that a majority of the brain nuclear enzyme may be bound to particulate material while a majority of the liver nuclear enzyme may be free or only loosely bound. Although the subcellular distributions of DNA polymerase activity are widely different in newborn brain and liver, the enzyme activity in any given subcellular fraction is higher in liver than in brain.
    Type of Medium: Online Resource
    ISSN: 0008-4018
    URL: Article
    DOI: 10.1139/o71-186
    Language: English
    Publisher: Canadian Science Publishing
    Publication Date: 1971
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  • 4
    Online Resource
    Online Resource
    DNA Polymerases of Newborn Rat Brain and Liver
    Canadian Science Publishing ; 1971
    In:  Canadian Journal of Biochemistry Vol. 49, No. 8 ( 1971-08-01), p. 978-986
    Details
    In: Canadian Journal of Biochemistry, Canadian Science Publishing, Vol. 49, No. 8 ( 1971-08-01), p. 978-986
    Abstract: DNA polymerase activity was found to be present in appreciable quantities in the extracts of whole tissue (TS) as well as of nuclei (NS) isolated from newborn rat brain and liver. The NS fractions of either of the two tissues exhibited a higher specific activity per unit protein than the corresponding TS fractions. The optimum pH requirements as well as the ability to support DNA synthesis over a long period indicate that the NS fractions were also comparatively less contaminated by interfering substances than the TS fractions.The reaction requirements for the incorporation of TMP residues into DNA by the NS fractions of newborn rat brain and liver and the effect of various inhibitors and hydrolytic enzymes on this reaction were also investigated. These extracts resembled preparations from other mammalian tissues in that they exhibited absolute requirements for the primer DNA, the four complimentary deoxynucleoside triphosphates, and Mg 2+ ions. When three of the four deoxynucleoside triphosphates were omitted and only TTP-2- 14 C was added to the reaction mixture, a limited incorporation of TMP-2- 14 C into DNA occurred. Other investigations such as the effect of actinomycin and of sulfhydryl compounds revealed that a large part of incorporation by the TS and NS fractions of newborn brain and liver was due to the replicative DNA nucleotidyltransferase enzyme.
    Type of Medium: Online Resource
    ISSN: 0008-4018
    URL: Article
    DOI: 10.1139/o71-142
    Language: English
    Publisher: Canadian Science Publishing
    Publication Date: 1971
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