Nuclear DNA

About: Nuclear DNA is a research topic. Over the lifetime, 3933 publications have been published within this topic receiving 185830 citations.

Nuclear DNA fragmentation in Creutzfeldt-Jakob disease: does a mere positive in situ nuclear end-labeling indicate apoptosis?

Abstract: The method of in situ end-labeling of nuclear DNA fragmentation was used in the study of ten patients (two biopsies, eight autopsies) with sporadic Creutzfeldt-Jakob disease (CJD). All the patients had the typical morphological lesions including neuron loss, spongiform change and astrocytosis. Four of them also showed prion protein (PrP) deposits in the cerebral cortex, and two of them kuru-like plaques in the cerebellum. A few cells with DNA breaks were found in the two biopsy cases; one of them, suffering from a panencephalopathic form of the disease, showed positive nuclei not only in the cerebral cortex but also in the subcortical white matter. Variable numbers of positive nuclei were observed in the gray and white matter in the eight autopsy cases, in which, although the distribution of positive cells roughly correlated with the distribution of neuron loss, no clear relationship was found as regards the distribution and degree of cell labeling and the degree of neuron loss. Furthermore, large numbers of positive cells were concentrated in a particular area, whereas a few cells were seen in a neighboring equally affected area. Positive glial cells in the plexiform layer of the CA1 area of the hippocampus, and in the frontal white matter were frequently encountered. Staining of the cytoplasm in a minority of cells was interpreted as the result of nuclear DNA leakage. None of the stained cells had the typical morphology of apoptosis; most particularly, peripheral chromatin condensation and formation of apoptotic bodies were not seen in any case. PrP deposits did not result in an increase of nuclear DNA breaks either within the area or in adjacent regions. Although positive cells were also observed in autopsy cases of controls which were processed in the same way, positive labeling as a whole was higher in CJD than in age-matched controls. These results show that brain nuclear DNA is vulnerable in CJD, and suggest that increased DNA vulnerability has a role in cell death and neuron loss. Since nuclear shrinkage and positive nuclear staining with the method of in situ end-labeling of nuclear DNA fragmentation are not exclusive to apoptosis, further information is needed to categorize cell death in CJD as apoptosis. Necrosis or other forms of cell death, as well as increased DNA vulnerability to agonal changes of the individuals, and to postmortem delay in the fixation of the tissues, may account for additional positive staining in cases examined at autopsy.

Nuclear DNA content and chromosome numbers throughout the life cycle of the Colonia strain of the myxomycete, Physarum polycephalum

Abstract: Nuclear DNA content and ploidy have been determined at different stages of the life cycle of the Colonia strain of the myxomycete Physarum polycephalum. Analyses at the plasmodial stage showed that (a) Burton and Fuelgen DNA analyses agreed within 15% with strains which ranged from 0-6 to 3-6 pg of DNA per nucleus; (b) S-phase in Colonia is during the early part of interphase as in the Wisconsin strain; (c) in heterothallic and heterothallic x Colonia crossed strains there are 1-0-1-2 pg of DNA and 70 chromosomes per nucleus and in Colonia 0-6 pg of DNA and 40 chromosomes. Germinating spores of all strains contained one population of cells with about 0-5 pg of DNA and 40 chromosomes and another of larger cells with up to 2-5 pg of DNA and 200 chromosomes. The polyploid nuclei comprised 2-20% of the total in heterothallic strains, 2-65% in heterothallic x Colonia crosses and 25-75% in Colonia. A method was devised for making chromosome spreads of amoebae grown on bacterial lawns. Cells were first exposed to dilute formaldehyde at 26 degrees C for 30 min, then spread on slides with hot lactic acid and strained. Such spreads of CLd (Colonia) and RSD4 (heterothallic) amoebae both contained about 40 chromosomes. The data are consistent with the view that Colonia is haploid throughout its life cycle and that chromosome number is neither halved during sporulation nor doubled during plasmoidal formation. However, the possibility exists that an alternance of ploidy occurs by way of the few diploid nuclei present in the plasmodium.

Intraspecific variation of nuclear DNA content in plant species

Abstract: SUMMARYIn recent years, wide DNA changes have been described among and within plant species. As to intraspecific DNA variations, they have been reported in a number of species, namely, Linum usitatissimum, Mtcroseris douglasii, M. bigelovii, Zea mays, Heliantbus annuus and others. DNA changes have been detected mostly by Feulgen cytophometry, that, if experiments follow some general rules, may be adequate for quantitative analyses. Biochemical analyses have, in some cases, confirmed the cytophotometric findings; it is generally accepted that DNA variations involve loss or increase of repeated DNA sequences (including rDNA). Concerning the origin and inheritance of DNA changes, a marked deviation from normal segregation rates are found in different species, and genome size seems to change following precise mechanisms. The functional significance of DNA changes is discussed: in many (but not all) cases a relationship has been established between DNA changes and adaptation to different environments, through ...

Incorporation of [3H]Thymidine into Nuclear and Mitochondrial DNA in Synchronized Mammalian Cells

Abstract: Human liver cells (Chang) were synchronized by cold shock. The second generation was scanned with two-hour pulses of [3H]thymidine. The incorporation of [3H]thymidine into nuclear and mitochondrial DNA during each pulse was determined. Maximal incorporation into the nuclear DNA occurred during S-phase (6 hours long) and to a smaller extent during and shortly after cytokinesis. The mitochondrial DNA was most highly labeled between S-phase and cytokinesis. The nuclear DNA's had a buoyant density in caesium chloride of 1.699 g/ml, whereas the mitochondrial DNA banded at a density of 1.688 g/ml.