Showing papers on "Nuclear DNA published in 1970"
TL;DR: It is concluded that the intact mitochondrial DNA of S. carlsbergensis and S. cerevisiae consists of a circular molecule with a contour length of approx.
200 citations
TL;DR: The preferential alkylation of the mitochondrial DNA by N-methyl-N-nitrosourea in situ is discussed in connexion with the cytoplasmic-mutation hypothesis of carcinogenesis.
Abstract: The reaction of the carcinogen N-methyl-N-nitrosourea with mitochondrial DNA from various rat tissues was examined in vivo and in vitro. After incubation of isolated mitochondria or cell nuclei with N[14C]-methyl-N-nitrosourea in vitro and subsequent isolation and purification of the DNA the specific radioactivity of the mitochondrial DNA was 3–7 times that of the nuclear DNA. The incorporation of 14C into embryonic mitochondrial DNA in vitro was about twice that into the liver mitochondrial DNA. Identical incorporation rates, however, were found for the reaction of isolated mitochondrial DNA or nuclear DNA respectively with N[14C]-methyl-N-nitrosourea. After intraperitoneal injection of 43.3–58.5mg of N[14C]-methyl-N-nitrosourea/kg body wt. to adult rats the labelling of the mitochondrial DNA was on average 5 times that of the nuclear DNA. A smaller specific labelling was observed for the ribosomal RNA, transfer RNA, and mitochondrial RNA as well as for the mitochondrial protein as compared with the mitochondrial DNA. After hydrolysis of the alkylated nucleic acids with hydrochloric acid, fractionation was carried out on Dowex 50 cation-exchange columns. In most experiments 70–80% of the input 14C radioactivity was eluted in the 7-methylguanine fraction. The preferential alkylation of the mitochondrial DNA by N-methyl-N-nitrosourea in situ is discussed in connexion with the cytoplasmic-mutation hypothesis of carcinogenesis.
133 citations
TL;DR: Autoradiography demonstrates that only half of the cells are labelled with [ 3 H]thymidine, and that many of the Cells showing cytoplasmic labelling have disintegrated nuclei, consistent with a hypothesis that in this system the DNA isolated from the cy toplasm is a degradation product of nuclear DNA.
128 citations
TL;DR: Nuclei isolated from rat liver in the absence of Ca2+ incorporate deoxyribonucleotides into added poly d(A-T) but not into their nuclear DNA, which is of high molecular weight.
128 citations
TL;DR: Results indicated that, compared to total nuclear DNA, the DNA replicated early in this period has a higher average buoyant density and hence, higher average G + C content.
125 citations
TL;DR: The purified Deoxyribonucleic acid polymerase has been purified 3550-fold from rat liver mitochondria, which computes to 14,000-fold based on whole liver as the starting material.
124 citations
TL;DR: There appears to be a relationship between the degree of repair synthesis and on the other hand frequency of cells entering S-phase, incidence of metaphase plates with chromatid breaks, flow of cells from G2 into pro-metaphase and “uncoiling” of metaphases chromosomes or heterochromatic segments of interphase nuclei.
Abstract: The oncogenic and mutagenic 4-nitroquinoline 1-oxide (4NQO) induces DNA-repair synthesis (unscheduled DNA synthesis) in diploid, aneuploid, normal and neoplastic human and Syrian-hamster cells. DNA-repair synthesis occurs in nuclei at G1, G2 and S-phase and in metaphase chromosomes of Syrian-hamster cells exposed to 4NQO. DNA-repair synthesis was separated from DNA-replication synthesis associated with chromosome replication at S-phase by arginine deprivation. The degree of [ 3 H]TdR incorporation into nuclear DNA is dependent on the dose of 4NQO (5·10 −8 to 1·10 −5 M ) and on the amount of DNA per cell. The time course of DNA-repair synthesis induced by 4NQO or UV was examined on non-dividing cells which were arrested by an arginine-deficient culture medium: an early occurring peak is followed by an abrupt decline at about 8 h post-treatment which is succeeded by a prolonged low level incorporation of [ 3 H]TdR. The effect of a completed and uncompleted repair synthesis on the flow of cells into S-phase and on the frequency of chromosome anomalies was studied on cells arrested by arginine deprivation and triggered to divide by addition of arginine. There appears to be a relationship between the degree of repair synthesis and on the other hand frequency of cells entering S-phase, incidence of metaphase plates with chromatid breaks, flow of cells from G2 into pro-metaphase and “uncoiling” of metaphase chromosomes or heterochromatic segments of interphase nuclei.
120 citations
TL;DR: Treatment of cultured mouse fibroblasts and hamster kidney cells with ethidium bromide was found to inhibit the incorporation of [(3)H]thymidine into mitochondrial closed-circular DNA, but not into nuclear DNA.
Abstract: Treatment of cultured mouse fibroblasts (L-cells) and hamster kidney cells with ethidium bromide was found to inhibit the incorporation of [(3)H]thymidine into mitochondrial closed-circular DNA, but not into nuclear DNA. The specific activity of nuclear DNA in treated cells was higher than in control cells. Treatment also led to breakdown of closed-circular mitochondrial DNA, greatly enlarged mitochondrial profiles with few or no cristae, and a higher yield of mitochondrial protein per cell.A significant increase in the content of circular DNA dimers and oligomers of mitochondria was observed after treatment of L-cells with cycloheximide and puromycin or treatment of chick fibroblasts with cycloheximide, and in hamster kidney cells transformed with polyoma virus. Little or no effects on dimer and oligomer content were found in L-cells treated with vinblastine, colcemid, rifampicin, chloramphenicol, or mengovirus, in Rous-transformed hamster cells, or in cuprizone-induced giant mitochondria of rat liver.
92 citations
TL;DR: The activities of thymidine kinase and DNA polymerase of adrenal glands were concomitantly increased following adrenocorticotropic hormone treatment, indicating an induction of DNA synthesis.
86 citations
TL;DR: An evaluation of mitochondrial and microsomal contamination involving chemical, enzymatic and ultrastructural analysis indicated only slight contamination in both nuclear and nuclear membrane fractions.
76 citations
TL;DR: These two evolutionary phenomena are closely linked and result from common causes, and are likely to be related to the evolution of cell size and nuclear DNA.
Abstract: THE pronounced differences in the DNA content of cell nuclei of vertebrates have recently been discussed1–3, but these articles did not mention the possible correlations between the evolution of nuclear DNA with the evolution of cell size which was simultaneously reviewed4. I now suggest that these two evolutionary phenomena are closely linked and result from common causes.
TL;DR: The oocyte therefore contains about 24 haploid equivalents of ribosomal DNA, which are localized presumably in its single large nucleolus.
TL;DR: Study of sequence homology of mitochondrial and cytoplasmic aminoacyl-tRNA's with mitochondrial DNA of rat liver shows that at least four mitochondrial tRNA's are potentially transcribed from mitochondrial DNA, and some species of mitochondrial t RNA may be transcribed in vivo from one strand and others from the complementary strand of mitochondrial DNA.
TL;DR: Whether the gain or loss of nuclear DNA associated with the evolution of these Allium species is random with respect to base ratio or, conversely, biased and restricted to DNA of particular base composition is questioned.
Abstract: IN living organisms genetic information is stored in the form of DNA. Differences in genetic information result from changes in the sequence of bases in the polynucleotide chains. Gross changes in the base sequence are usually, although not always, accompanied by changes in the overall base composition. Organisms which are genetically very closely related will have much the same DNA base composition. Organisms which are distantly related or quite unrelated may, or on the other hand may not, have widely different base compositions. Between species of micro-organisms the base composition varies widely. In bacteria, for example, the GC content ranges from 25 to 75 per cent. (Belozersky and Spirin, 1960; Sueoka, 1961). A correspondence between genetic relationship and base composition has proved useful in the taxonomy of this group. Between species of higher plants the base composition, in sharp contrast, shows a much narrower range, with GC values of from 35 to 49 per cent. (Belozersky, 1961). There is no indication as yet that base composition will prove as useful in higher plant taxonomy as in bacteria. The range in base composition is, perhaps, too narrow. However, information on base composition in higher plants is limited. Further investigations may reveal a wider range in base ratios than the 14 per cent. established to date. The following is an account of measurements of nuclear DNA base composition in twenty Alliurn species and of a few species in other genera of the same family, the Liliaceae. The measurements are based on a method which gives substantially greater accuracy than was previously possible (Kirk, 1967). The purpose of the survey was, first, to determine to what extent species within the genus A Ilium vary in respect of their nuclear DNA base composition. Second, to ascertain whether differences in base composition are correlated with differences in nuclear DNA amount. The latter is of special interest because in A Ilium, as in other Angiosperm genera, the nuclear DNA amount varies considerably between species (Rees, Cameron Hazarika and Jones, 1966; Jones and Rees, 1969). The question arises, therefore, as to whether the gain or loss of nuclear DNA associated with the evolution of these Allium species is random with respect to base ratio or, conversely, biased and restricted to DNA of particular base composition.
TL;DR: The results strongly suggest that variation in chromosome size indicates a corresponding change in the rate of cell metabolism and may well reflect change in genetic activity.
Abstract: The natural variation in chromosome size in root-tip and shoot apex meristems of Vicia faba has been studied. Chromosomes in main root-tips of one week old plants are 2–3 times larger than those in small lateral root-tips of 3 week old plants. While the nuclear DNA content remains constant, the nuclear RNA and nuclear histone contents show a positive linear correlation with chromosome volume. The DNA: histone ratio varies and is lowest in cells with large chromosomes. Nuclear volume and chromosome volume are not linearly related and changes in nuclear density therefore seem likely. A positive linear relationship between chromosome volume and mitotic index in colchicined squashes is demonstrated. The results strongly suggest that variation in chromosome size indicates a corresponding change in the rate of cell metabolism and may well reflect change in genetic activity.
TL;DR: Mitochondrial DNA from Tetrahymena pyriformis strain T has a buoyant density (rho) of 1.685 compared with rho1.688 for whole cell DNA, implying a complexity of approx.
Abstract: 1. Mitochondrial DNA from Tetrahymena pyriformis strain T has a buoyant density (rho) of 1.685 compared with rho1.688 for whole cell DNA. Mitochondrial preparations from T. pyriformis strain W show an enrichment of a light satellite (rho1.686), although this is not obtained free from nuclear DNA (rho1.692). 2. T. pyriformis mitochondrial DNA renatures rapidly and the kinetics of this process indicate a complexity of approx. 3x10(7) daltons. 3. The base-pairing in the renaturation product is of a precise nature, since the ;melting' temperature (80.5 degrees C) is indistinguishable from that of the native DNA (80.5 degrees C). 4. Centrifugation of mitochondrial DNA in an alkaline caesium chloride density gradient gives two bands, implying the separation of the complementary strands.
TL;DR: Methylation of major nuclear DNA-cytosine was found to occur throughout the mitotic cycle of Physarum polycephalum, during the period of DNA synthesis (S), as well as during the remainder of interphase (G2) when essentially no synthesis de novo of the major nuclearDNA takes place.
TL;DR: A negative correlation was found between histone and total nuclear protein and hist one and nuclear RNA amounts and Histone protein was found to increase as the number of B's went up, and in this case the values were disproportionately high for odd numbered B-classes.
Abstract: The nuclear basis of B-chromosome genetic activity in rye has been investigated using quantitative cytochemical techniques on isolated root tip nuclei. Nuclear DNA amount was found to be directly proportional to B-chromosome number. Relative amounts of total nuclear protein and nuclear RNA however, decreased with increasing numbers of B's but not in a strictly linear fashion. The values were disproportionately low for odd numbered B-classes of plants. Histone protein was found to increase as the number of B's went up, and in this case the values were disproportionately high for odd numbered B-classes. A negative correlation was found between histone and total nuclear protein and histone and nuclear RNA amounts.
TL;DR: It was found that isolated 3 H-thymidine-labelled metaphase chromosomes can penetrate into mammalian cells in vitro and the progressive changes in the cellular labelling patterns with time indicate that, in most cases, the ingested chromosome is degraded in the cytoplasm of the recipient cell and the chromosomal DNA is integrated into the host nuclear DNA.
TL;DR: The hypothesis that homologous chromosomes or genomes require similar duration for their DNA synthesis and suggest that the structures of chromosomes are involved in temporal control of the DNA synthesis in cells is supported.
Abstract: The relative amounts of nuclear DNA of root meristematic cells of two related diploid Avena species, A. strigosa 2x and A. pilosa, which have different karyotypes, and an autotetraploid of one, A. strigosa 4x, were measured by Feulgen microspectrophotometry. The durations of various periods of their mitotic cycles were studied by autoradiography of cells pulse-labeled with tritiated thymidine. The results show that the autotetraploid, with twice the amount of nuclear DNA of its diploid, has the same duration of S period as the diploid, while A. pilosa, with intermediate nuclear DNA content, has a longer S period. These results support the hypothesis that homologous chromosomes or genomes require similar duration for their DNA synthesis and suggest that the structures of chromosomes are involved in temporal control of the DNA synthesis in cells.
TL;DR: The results suggest that continuous protein synthesis is required for nuclear DNA replication in chlorella pyrenoidosa.
TL;DR: The mitochondrial DNA was shown to be free of nuclear DNA by its renaturation properties and by its banding pattern in an alkaline cesium chloride equilibrium buoyant-density gradient.
TL;DR: Estimates of the absolute DNA amounts of twelve species of Bufo are presented, highest and lowest DNA amounts found in species with 22 chromosomes relate as 1.6∶1; one species with 20 chromosomes shows the lowest DNA amount determined to date.
Abstract: Specific nuclear DNA amounts were determined by Feulgen and gallocyanin chromalum cytophotometry in nine species of Bufo. These were compared with published data on DNA amounts and chromosome numbers. Together, estimates of the absolute DNA amounts of twelve species of Bufo are presented. Highest and lowest DNA amounts found in species with 22 chromosomes relate as 1.6∶1; one species with 20 chromosomes shows the lowest DNA amount determined to date.
TL;DR: Measurements of the initial slope of the Feulgen hydrolysis curve allow the precise determination of specific nuclear DNA amounts for sixteen salamander species because of the low stain densities involved.
Abstract: Measurements of the initial slope of the Feulgen hydrolysis curve allow the precise determination of specific nuclear DNA amounts. The low stain densities involved preclude density-dependent systematic error. Best estimates of the nuclear DNA amount for sixteen salamander species are presented.
TL;DR: It is concluded that “I-DNA” is not a separate entity from nuclear DNA but may be an artefact derived from it.
Abstract: On the basis of double radioactive labelling and buoyant density studies, it is concluded that “I-DNA” is not a separate entity from nuclear DNA but may be an artefact derived from it.
TL;DR: The result is interpreted as showing that mitochondria contain both mitochondrial and nuclear DNA transcripts, with a very low degree of homology which is at the limit of significance.
Abstract: RNA was isolated from mitochondrial fractions of various respiratory sufficient and deficient yeast strains. The RNA hybridizes in vitro with mitochondrial DNA as well as with nuclear DNA. The result is interpreted as showing that mitochondria contain both mitochondrial and nuclear DNA transcripts. RNA was separated from the hybrids, and by its re-hybridization with either nuclear or mitochondrial DNA, the sequence homology between these two classes of DNA was examined. A very low degree of homology was found which is at the limit of significance. Other reports on the sequence homology between nuclear and mitochondrial DNA are discussed critically.
TL;DR: In view of the continuing interest in mammalian DNA polymerase, its distribution in fractionated rat liver nuclei and especially its relationship to the nuclei active in vivo in DNA synthesis are investigated.
TL;DR: It is shown that during the early cleavage stages of sea urchin embryos, the number of nuclei doubles in 2 h or less and the DNA doubles in about 10–12 min at 16° C1.
Abstract: DURING the early cleavage stages of sea urchin embryos, the number of nuclei doubles in 2 h or less and the DNA doubles in about 10–12 min at 16° C1. A special relationship between nuclear DNA and DNA polymerase is suggested by the constant ratio of polymerase activity to DNA2,3. Evidence suggests that this proportionality is maintained by the translocation of the stored polymerase from the cytoplasm to the nucleus4.
TL;DR: The relationship between DNA synthesis and protein accumulation in cell nucleus and cytoplasm has been investigated by the use of a combination of ultramicrointerferometric and Ultramicrospectrophotometric methods.
Abstract: The relationship between DNA synthesis and protein accumulation in cell nucleus and cytoplasm has been investigated by the use of a combination of ultramicrointerferometric and ultramicrospectrophotometric methods.
5-Fluoro-2'-deoxyuridine (FUdR) inhibited DNA synthesis, resulting in inhibition of cell proliferation in G-1 and early S-phase. However, synthesis and accumulation of protein continued in the presence of FUdR, as indicated by a 54% increase in the average dry mass value per individual cell during 18-hour exposure to FUdR; due primarily to protein accumulation in the cytoplasm, the average cytoplasmic dry mass increased by as much as 85%, while the dry mass of the nucleus increased by only 21%.
The dry mass values of individual nuclei were well-correlated to the nuclear DNA content throughout the period of exposure to FUdR. In contrast to the continued accumulation of protein in the cytoplasm during inhibition of DNA synthesis, protein accumulation in the nucleus was inhibited. When cells were released from inhibition of DNA synthesis by the addition of 2'-deoxythymidine, the nuclear DNA content and nuclear dry mass increased in near-synchrony, there being some evidence that DNA synthesis was initiated somewhat prior to initiation of increase in nuclear dry mass.
Thus, it appears that DNA synthesis (or an increase in nuclear DNA content) is intimately related to the regulation of protein accumulation in the nucleus.