DNA Base composition and repetitious DNA in several conifers

Coniferous DNA was analyzed by ultraoentrifugation and thermal denaturation and renaturation to determine base composition and the presence of repetitive sequences. The percent quanine plus cytosine values among species were constant and independent of DNA quantity per cell, whereas the proportion of repetitive DNA per genome was greatest in those species that had the highest DNA content.     

Different response of cellular DNA content to cardiac hypertrophy in human and rat heart myocytes

1. Rat and human heart myocytes adapt to overload-induced hypertrophy differently. 2. Human myocyte nuclei respond with polyploidization and multinucleation, thus increasing the DNA content per myocyte from 20 to 40 pg. As a result, nuclear DNA content per 10,000 microns3 of cell volume decreases from 12 to 10 pg. 3. In rat hearts with aortic constriction nuclear DNA content remains constant (13 pg), and the DNA content per 10,000 microns3 of myocyte volume falls from 9 to 6 pg. 4. We hypothesize that "dilution" of nuclear DNA in the hypertrophied rat heart myocyte limits the capacity to hypertrophy (much less than 100%). 5. The human heart myocyte, which is able to compensate for dilution of nuclear DNA, may increase in size more than three-fold. 6. The lower limit of DNA content per unit of myocyte volume is 6 pg/10,000 microns3 in both species.     

DNA values in the genus Phalaris (Gramineae)

In the genus Phalaris diploid species with 2n=12 have approximately twice the DNA content per cell found in species with 2n=14; i. e. the first group has chromosomes about twice the size of the other group. DNA content per unit length suggests that the difference is reflected more in the diameter of the metaphase chromosome than in the lengths. The trend in evolution seems to be towards increase in DNA content.     

DNA content of micronuclei in human lymphocytes

We have calculated the distribution of DNA contents in micronuclei (MN) induced by ionizing radiation in human lymphocytes on two assumptions: the MN arise from acentric chromosome fragments (ACF), and the ACF result from the random breakage and rejoining of chromosomes. Measurements show that about 80 per cent of MN have a DNA content in the range of 0.5-6 per cent of the G1 nucleus. This group is consistent with the model and shows little dependence on radiation dose over the dose range of 0.5-4 Gy, or on lymphocyte culture time, varying from 48 to 76 hours. The MN with DNA content from 6 to 20 per cent of the G1 nucleus are probably the result both of spindle defects and of DNA synthesis in MN.     

DNA and protein content relationship in the cells of mature cotyledons ofPisum sativum

Summary The relationship between the DNA and reserve protein contents have been investigated in the cells of mature cotyledons ofPisum sativum. The study was made on two seeds chosen, on preliminary analysis, as having a markedly different protein content per cotyledon. The seed with the higher protein content was of theCameor variety, the other was of theAmino variety. The DNA content per cell was measured with a scanning microspectrophotometer and the protein content per cell using morphometric methods. In both seeds, nuclei of the storage parenchyma were polyploid in a range from 8 to 64 C levels, but the average DNA content per cell was higher in the Cameor specimen. The protein content also, whether expressed per unit of protoplasm or per cell, was always higher in the Cameor seed. The greater protein content of this seed was due to a higher content of protein per cell. In both seeds the level of ploidy and the reserve protein content per cell increased in the same way from the peripheral zone to the centre of the cotyledon. A high positive correlation was found for the two seeds between the DNA content and the protein content per cell.     

Reduction of Chloroplast DNA Content in Solanum nigrum Suspension Cells by Treatment with Chloroplast DNA Synthesis Inhibitors

Suspension cell cultures of Solanum nigrum were grown in the presence of six different chloroplast DNA synthesis inhibitors in order to determine whether the pool size of chloroplast DNA (cpDNA) could be selectively reduced relative to the nuclear DNA content. One of the effects of the inhibitors was a reduction in cell growth and viability. Cell growth (fresh weight) was reduced 50% (in 8 day cultures) by: 100 micromolar bisbenzimide, 8 micromolar ethidium bromide, 0.3 micromolar 5-fluordeoxyuridine (Fudr), 200 micromolar nalidixic acid, 30 micromolar novobiocin, or 10 micrograms per milliliter rifampicin. At these concentrations, three of the inhibitors, ethidium bromide, Fudr, and rifampicin, also substantially reduced the viability of the cultures. Analyses of the chloroplast and nuclear DNA content per gram fresh weight by dot blot hybridizations indicated that the reduction of cpDNA content was greatest at inhibitor concentrations which reduced cell growth by more than 50% but this depended on the culture conditions. For example, the two DNA gyrase inhibitors, nalidixic acid and novobiocin, were more effective in lowering cpDNA content in cultures which were transferred (2 × 4 days) once during the eight day incubation. Because several inhibitors were toxic to cell growth, the DNA content of treated cells was also determined on the basis of cell (protoplasts) number. Analyses of nuclear and cpDNA content per cell for each treatment indicated that only the DNA gyrase inhibitors, nalidixic acid, and novobiocin reduced cpDNA content. Neither inhibitor reduced nuclear DNA content. These results suggest that DNA gyrases participate in cpDNA replication. The selective reduction of cpDNA content in regeneratable cultures may facilitate the generation and selection of cpDNA mutants or transformants from higher plants.     

Influence of formamide on the thermal stability of DNA

The utility of formamide in the denaturation and renaturation of DNA has been examined. The melting temperature of duplex DNA is lowered by 0·6°C per per cent formamide. The depression of melting temperature is independent of the GC content. Formamide also increases the width of the thermal transition. Upto 30%, it does not affect the rate of DNA reassociation     

Preferential degradation of plastid DNA with preservation of mitochondrial DNA in the sperm cells ofPelargonium zonale during pollen development

Summary In the present study, we studied changes in organellar DNA in the sperm cells of maturing pollen ofPelargonium zonale, a plant typical to exhibit biparental inheritance, by fluorescence microscopy after staining with 4,6-diamidino-2-phenylindole (DAPI) and by immunogold electron microscopy using anti-DNA antibody. Fluorescence intensities of DAPI-stained plastid nuclei in generative and sperm cells at various developmental stages were quantified with a video-intensified microscope photon counting system (VIMPCS). Results indicated that the amount of DNA per plastid in generative cells increased gradually during pollen development and reached a maximum value (about 70 T per plastid; 1 T represents the amount of DNA in a particle of T4 phage) in young sperm cells at 5 days before flowering. However, the DNA content of plastids was subsequently reduced to about 20% of the maximum value on the day of flowering. Moreover, the DNA content of the plastid further decreased to 4% of the maximum value when pollen grains were cultured for 6 h in germination medium. In contrast, the amount of DNA per mitochondrion did not decrease significantly around the flowering day. Similar results were also obtained by immunogold electron microscopy using anti-DNA antibody. The density of gold particles on plastids decreased during pollen maturation whereas labelling density on mitochondria remained relatively constant. The number of plastids and mitochondria per generative cell or per pair of sperm cells did not change significantly, indicating that the segregation of DNA by plastid division was not responsible for the decrease in the amount of DNA per plastid. These results indicate that the plastid DNA is preferentially degraded, but the mitochondrial DNA is preserved, in the sperm cells ofP. zonale. While the plastid DNA of the sperm cells decreased before fertilization, it was also suggested that the low DNA contents that remain in the plastids of the sperm cells are enough to account for the biparental inheritance of plastids inP. zonale.Abbreviations DAPI 4,6-diamidino-2-phenylindole - VIMPCS video-intensified microscope photon counting system     

豌豆种子发育过程中DNA和RNA的变化

实验结果表明：豌豆种子发育过程中单粒鲜重、ＤＮＡ和ＲＮＡ含量都随开花后日数增加而增加。其中豌豆开花第２１天,ＲＮＡ含量达最高峰,拖尾现象消失而趋于单一带区,ＤＮＡ的迁移率也降到最低,从而确定出豌豆开花后第２１天是基因转录活动降低的转折点,为种子蛋白质基因工程研究提供参考。     

Mitochondrial DNA content of human spermatozoa

Sperm mitochondria play an important role in spermatozoa because of the high ATP demand of these cells. Different mitochondrial DNA (mtDNA) mutations and haplogroups influence sperm function. The mtDNA dose also contributes to genetic variability and pathology in different tissues and organs, but nothing is known about its relevance in the performance of spermatozoa. We estimated the variability in mtDNA content within a population of men. Different mtDNA:nuclear DNA ratios were characteristic of progressive and nonprogressive spermatozoa, confirming the influence of mtDNA content on sperm functionality. We also estimated that the absolute content of mtDNA was 700 and 1200 mtDNA copies per cell in progressive and nonprogressive human spermatozoa, respectively. These results suggest that a marked increase of mtDNA copy number per cell volume takes place during spermatogenesis.     

Cellular content of chloroplast DNA and chloroplast ribosomal RNA genes in Euglena gracilis during chloroplast development.

The cellular content of chloroplast DNA in Euglena gracilis has been quantitatively determined. DNA was extracted from Euglena cells at various stages of chloroplast development and renatured in the presence of trace amounts of 3H-labeled chloroplast DNA. From the kinetics of renaturation of the 3H-labeled chloroplast DNA, compared with the kinetics of renaturation of excess nonradioactive chloroplast DNA, the fraction of cellular DNA represented by chloroplast DNA was calculated. The content of chloroplast DNA was found to increase from 4.9 to 14.6% of cellular DNA during light-induced chloroplast development. Correcting for the change in DNA mass per cell, the number of copies of chloroplast DNA is found to vary from 1400 to 2900 per cell. During this developmental transition, the cellular content of the chloroplast ribosomal RNA genes varies from 1900 to 5200 copies per cell. The ratio of the number of copies of rRNA genes to chloroplast genomes per cell remains in the range of 1-2 throughout chloroplast development, ruling out selective amplification of chloroplast rRNA genes as a means of regulation of rRNA gene expression. Direct measurement of the number of rRNA cistrons per 9.2 X 10(7) dalton genome yields a value of 1 or 2.     

DNA content of spermatozoa in different genetic lines of turkeys

The variability of DNA content in turkey spermatozoa of four different lines and its correlation with body weight and sperm concentration were studied. In lines selected for lower body weight the DNA content was 2.034 and 2.036 pg per spermatozoon. In lines selected for higher body weight the DNA content was 2.267 and 2.370 pg per spermatozoon. Sperm concentration in 1 mm³ of semen, however, was higher in lines with a lower body weight (6.08–6.21 million) in comparison with lines selected for higher body weight (5.46–5.67 million). The correlations between the DNA content and sperm concentration were negative (r ranged from ?.457 to ?.860).     

A method to estimate the DNA content of whole nuclei from measurements made on thin tissue sections

A microdensitometry method that allows estimation of the distribution of the DNA content of nuclei in thin tissue sections is described. The method is based on a theoretical model of Feulgen-stained spherical nuclei, of different sizes, in each of which the DNA is present as a homogeneous solution. In thin sections of nuclei of different sizes, the fraction of DNA per section is inversely proportional to the radius of the nucleus. Histograms of the product of DNA content and radius per nuclear section are independent of nuclear size but depend on total DNA content. The distribution of the total DNA content of nuclei in a section can be estimated from such a histogram. The results of the measurements of a Feulgen-stained rat liver section are described.     

DNA content, kinetic complexity, and the ploidy question in Candida albicans.

Candida albicans is a dimorphic fungus that is pathogenic for humans. No sexual cycle has been reported for this fungus, and earlier reports have differed on whether typical strains of C. albicans are haploid or diploid. Previous estimates of the DNA content of C. albicans varied by one order of magnitude. We used three independent methods to measure the kinetic complexity of the single-copy DNA from a typical strain of C. albicans (strain H317) to determine the DNA content per haploid genote; we obtained values of 15 and 20 fg per cell by using S1 nuclease and hydroxyapatite assays, respectively. Optical assays for DNA reassociation kinetics, although not definitive in themselves, yielded values in this range. Chemical measurements of the DNA content of several typical strains, including strain H317, yielded values clustered about a mean of 37 fg per cell. We concluded that these strains are diploid.     

Changes in the structure of DNA molecules and the amount of DNA per plastid during chloroplast development in maize

We examined the DNA from chloroplasts obtained from different tissues of juvenile maize seedlings (from eight to 16 days old) and adult plants (50-58 days old). During plastid development, we found a striking progression from complex multigenomic DNA molecules to simple subgenomic molecules. The decrease in molecular size and complexity of the DNA paralleled a progressive decrease in DNA content per plastid. Most surprising, we were unable to detect DNA of any size in most chloroplasts from mature leaves, long before the onset of leaf senescence. Thus, the DNA content per plastid is not constant but varies during development from hundreds of genome copies in the proplastid to undetectable levels in the mature chloroplast. This loss of DNA from isolated, mature chloroplasts was monitored by three independent methods: staining intact chloroplasts with 4',6-diamidino-2-phenylindole (DAPI); staining at the single-molecule level with ethidium bromide after exhaustive deproteinization of lysed chloroplasts; and blot-hybridization after standard DNA isolation procedures. We propose a mechanism for the production of multigenomic chloroplast chromosomes that begins at paired DNA replication origins on linear molecules to generate a head-to-tail linear concatemer, followed by recombination-dependent replication.     

Endoreduplication of nuclear DNA in the developing maize endosperm

Multiparametric flow cytometry was used to analyze the development of the endosperm in Zea mays L. during the period from 8 to 20 days after pollination (dap). Nuclear size, DNA content per nucleus, and frequencies of nuclei with varying properties were measured in preparations that included all of the endosperm nuclei of single kernels of the inbred strain Al88. Characteristics of nuclear populations from different kernels on the same ear showed minimal variation. The dynamic changes of non-mitotic cells involved in endosperm development consisted of alternating periods of DNA replication with non-replication. Seven rounds of DNA replication had occurred in some nuclei in the later developmental stages with the rate averaging approximately one round per 24-hour period. Analysis of the DNA levels in the nuclei showed an exact doubling pattern indicating an endoreduplication process, that is, replication of the entire genome during each round. The loosely organized polytenization of the chromatin occurred to varying extents among the nuclei within an endosperm. A weak positive correlation existed between DNA content and size of nuclei suggesting that DNA increases and nuclear growth may not be highly coordinated in this tissue. Increased proportions of the larger nuclei occurred in the later stages of endosperm development. Considering the entire endosperm, the average DNA content per nucleus at the 15-dap peak level was approximately 12.8 C constituting a 2.7-fold overall increase from 8 dap.     

Repetitious DNA in some Anemone Species

The DNA from several Anemone species, which contain different amounts of heterochromatin as revealed by Giemsa staining, was analysed by ultra-centrifugation and renaturation. No satellite band was observed in any of the samples centrifuged in cesium chloride gradients. Renaturation studies showed the presence of repetitive sequences. The proportion of repetitive DNA per genome varied from 53% to 67% and did not correlate with either the DNA content per cell or the relative amount of heterochromatin.     

Plant Genome Size Measurement with DNA Image Cytometry

To test the reliability of DNA image cytometry for the measurement of nuclear DNA content in plant material, we conducted independent experiments in two laboratories using different image analysis instruments for densitometric measurement of nuclear DNA amount in Feulgen-stained squash preparations of root tips. The 2C nuclear DNA content of the nine species studied spanned a 100-fold range (approx. 0.3–33 pg). The estimates of nuclear DNA content measured with image cytometry methods were comparable to values obtained previously using both photometric cytometry and flow cytometry. Image cytometry methods showed little variation among repeated experiments within each laboratory or among different operators using the same instrument. Furthermore, the interphase-peak method (measurement of several hundred interphase nuclei per slide) was comparable to the classical prophase/telophase approach (measurement of ten early prophase and ten late telophase nuclei per slide). Hence, DNA image cytometry gives accurate and reproducible results and may be used as an alternative to photometric cytometry in plant nuclear DNA content measurements. In the present study, we propose that two standards for quality control of nuclear DNA content measurement are used in plant DNA image cytometry: (1) the coefficient of variation of the peak should be lower than 6%, and (2) the 4C/2C ratio should be between 1.9 and 2.1.     

Effect of exogenous DNA on the content and biosynthesis of endogenous DNA in rat bone marrow]

The influence of exogenous DNA on the content of endogenous DNA and the rate of biosynthesis was studied in rat bone marrow. After the injection of highly-polymerized homologous DNA to intact rats the content of rat DNA per 1 gm of the bone marrow decreased within the first 3 days (the most marked fall occurred in 3 days--by 36%), and returned to the normal by the 6th day. The rate of DNA biosynthesis in rat bone marrow increased in 18 hours (doublled in comparison with control), remained elevated within 6 days (by 58%) and approached the normal level from 1 to 3 days after the DNA injection.     

Cell Production and DNA Accumulation in the Wheat Endosperm, and their Association with Grain Weight

Nuclear DNA content was measured in developing endosperm cellsof two wheat varieties, Chinese Spring and Spica. 3C, 6C, 12Cand 24C nuclei were detected, indicating that some form of endoreduplicationand/or endopolyploidization was occurring. The total amountof DNA in the endosperm continued to increase until 24 dayspost anthesis. This accumulation of DNA resulted both from productionof new nuclei and also from increases in the DNA content ofexisting nuclei. Estimates of endosperm cell numbers were made from the totalDNA content per endosperm and the mean DNA content per endospermnucleus for a range of genotypes differing in mature grain weight.Endosperm DNA content and cell number were both positively associatedwith mature grain weight among the genotypes examined. However,not all of the variation in grain weight could be attributedto variation in cell number because of differences in mean dryweight per endosperm cell. The large-grained variety, Spica, had a greater mean weightper endosperm cell than Chinese Spring and this difference aroseafter cell production in the endosperm had ceased. Triticum aestivum, grain weight, cell size, cell number, DNA content