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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 56 (1991), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: “Bound’ and “free’ RNA polymerase activities were assessed in the nuclear fraction of cerebral cortical, neuronal, astroglial, and oligodendroglial cells obtained from rats of young, adult, and old ages. Significant decreases in both the bound and free polymerase II activities were noticed in old brain, as compared to adult brain, in neuronal and oligodendroglial nuclei. In astroglia, only the free polymerase II was found to be affected. No effect of aging could be seen on the activity of bound RNA polymerase I + III. The free RNA polymerase I + III activity was increased from adult to old age in neuronal nuclei, but unchanged in oligodendroglial and astroglial nuclei. The age-dependent reduction in RNA polymerase II was maximum in oligodendroglial cells, whereas it was least, although still significant, in neuronal cells. DNA isolated from old brain was unable to enhance the transcriptional activity when added to chromatin preparations obtained from rat brains of any of the above ages, and the “old’ chromatin was unable to accept even the “young’ DNA as additional exogenous template. It is concluded that the reduced gene expression noticed in old brain nuclei is due to both altered chromatin/DNA structure and inadequate levels of free RNA polymerase II.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 45 (1985), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: Neurons do not divide during adult life and thus they provide a unique system to study the effects of age-accumulated damage to DNA in the absence of DNA replication. We have analyzed DNA polymerase activity in neurons isolated from young adult and very aged mice. The predominant catalytic activity is DNA polymerase-β and it is present in similar amounts in neurons from young and old mice. This polymerase is highly errorprone in copying φX174 DNA, the error frequency being about 1/7,000 and not significantly different when obtained from young and old animals. This high infidelity is considered with respect to DNA repair and the protein synthesis error catastrophe theory of aging.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science Ltd
    Journal of neurochemistry 67 (1996), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: Two biochemical strategies using nick translation-type of incubation and terminal transferase-catalyzed reaction were used to assess single- (SSB) and double-strand (DSB) breaks in DNA of permeabilized neurons isolated from young, adult, and old rat cerebral cortex. Both SSBs and DSBs accumulate with age. On prior treatment of neuronal cells with 1 mM glutamate or 50 µMN-methyl-N′-nitro-N-nitrosoguanidine (MNNG), more extensive damage was seen at all ages, with the old neurons suffering maximal damage. When neuronal DNA was subjected to agarose electrophoresis, increasingly diffused bands were seen with age in normally aging neurons. However, a typical nucleosomal ladder, characteristic of apoptosis, was seen only when the cells were exposed to either glutamate or MNNG irrespective of the age of the neurons. Furthermore, this apoptotic fragmentation of DNA was prevented by prior treatment of the cells with either cycloheximide or aurintricarboxylic acid, indicating that both glutamate and MNNG induce programmed cell death. Fluorescence microscopic observation of glutamate- and MNNG-treated neurons after acridine orange staining revealed a high degree of staining and marked condensation of nuclear DNA. On the other hand, no such phenomenon was observed in normally aging neurons either histologically or in biochemical assays of damage. It is concluded that both glutamate and MNNG induce programmed cell death in neurons independent of age and that accumulation of DNA damage in naturally aging neurons occurs through a process other than that of apoptosis.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 22 (1974), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Different regions of the brains of babies born with low birth weights for the gestational age (small-for-date infants) were analysed for various chemical constituents. The brains of small-for-date babies were reduced in size. On a percentage basis, cerebellum and medulla oblongata were more affected than cerebrum. Cellularity, estimated by DNA content, was affected only in the cerebrum. However, the cell size and the concentrations of various constituents (proteins, lipids, different classes of lipids) studied in different regions of the brains of small-for-date infants remained unaffected compared to those found in the normal brains.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Oxford UK : Blackwell Science Ltd
    Journal of neurochemistry 74 (2000), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: Apoptosis is now recognized as a normal feature in the development of the nervous system and may also play a role in neurodegenerative diseases and aging. This phenomenon has been investigated intensively during the last 6-7 years, and the progress made in this field is reviewed here. Besides a few in vivo studies, a variety of neuronal preparations from various parts of the brain, the majority of which were primary cultures, and some cell lines have been investigated. Several apoptosis-inducing agents have been identified, and these include lack of neurotrophic support, neurotransmitters, neurotoxicants, modulators of protein phosphorylation and calcium homeostasis, DNA-damaging agents, oxidative stress, nitric oxide, and ceramides. The precise signaling cascade is not well established, and there are lacunae in many suggested pathways. However, it appears certain that the Bcl family of proteins is involved in the apoptotic pathway, and these proteins in turn affect the processing of interleukin-1β converting enzyme (ICE)/caspases. The available evidence suggests that there may be several apoptotic pathways that may depend on the cell type and the inducing agent, and most of the pathways may converge at the ICE/caspases step.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Molecular and cellular biochemistry 137 (1994), S. 109-116 
    ISSN: 1573-4919
    Keywords: DNase ; DNA-repair ; aging ; rat brain
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract A deoxyribonuclease has been purified to electrophoretic homogeneity from young and old rat brain. The enzyme is an endonuclease, with an optimum pH 5.0. Divalent cations are not needed for the activity. The DNase showed highest activity towards Native DNA either as such or UV irradiated with little activity on denatured DNA, apurinic DNA or DNA pretreated with mitomycin C or actinomycin D. The enzyme hydrolyzes double stranded poly (dA-dT)·(dA-dT) but not other homologous or heterologous synthetic polynucleotides. The enzyme does not excise pyrimidine dimers preferentially but acts at a site away from the dimer. The DNase was partially purified from nuclei also and both the nuclear and extra nuclear enzymes showed similar properties. The specific activity of brain DNase decreases markedly with age. DNase preparations from both young and old rats showed similar apparent molecular weight (62KD) and many other properties like elution profiles and the N-terminal amino acid. However the old enzyme was more susceptible to temperature and proteolytic digestion. These results are taken to indicate a possible role for this enzyme in recognizing conformational distortions in DNA and that altered molecules of this enzyme accumulate in aging brain.
    Type of Medium: Electronic Resource
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