Distribution Of DNA Values Research Articles

Genome-size variation in bivalve molluscs determined by flow cytometry

The nuclear DNA content (2 C value) of 200 individuals representing 10 species of bivalve molluscs belonging to the families Pectinidae (Chlamys opercularis and Pecten maximus), Ostreidae (Ostrea edulis), Mytilidae (Mytilus edulis and M. galloprovincialis), Mactridae (Spisula solidissima), Cardiidae (Cerastoderma edule), and Veneridae (Venerupis rhomboideus, V. pullastra, and Ruditapes decussatus) have been analyzed by measuring the fluorescent signal of ethidium bromidestained gill cells using flow cytometry Mean genome sizes ranged from 2.23 pg per diploid nucleus in Chlamys opercularis to 3.84 pg in M. galloprovincialis. The distribution of DNA values among all species was continuous and overlapping. There was significant heterogeneity in mean genome size between individuals within species as well as among the different species. A high per cent of the total genome size-variation was allocated at the species level (92%), and 7% at the level of individuals within species. The data suggest that a significant fraction of the bivalve genome, on average ≃0.17 pg or 7%, is free to vary among individuals of the same species without phenotypic or biological consequence. The correlation between the 2 C value and chromosome number was low, suggesting some variation in the amount of DNA per chromosome. Within the subclass Pteriomorphia, the species of Pectinidae, Ostreidae and Mytilidae have shown high genome size-differences correlating with their evolutionary distance.

Densitometric evaluation of DNA content in colorectal cancer

The aim of the present study was to provide information on the DNA content in colorectal tumours using densitometric techniques on histological samples and correlating the findings with age, sex, histological grade, stage, presence or absence of lymph-node metastasis and survival time. The distribution of DNA values was significantly related with the histological grade, Dukes' stage and infiltration of the peritumoral lymph-nodes. The distribution of DNA values was not significantly correlated with age and sex. From the data obtained in this study it can be concluded that evaluation of DNA content in colorectal adenocarcinoma can be used as a prognostic test that is complementary to histological investigation. The ploidy can provide information for classifying the degree of malignancy and can also be used to determine which tumours are biologically most aggressive.

DNS-Ploidie und Proliferationsverhalten beim metastasierten Neuroblastom*

Nuclear DNA contents of tumor cells were measures by fluorescence cytophotometry in bone marrow and touch preparations of 26 children with neuroblastoma, registered in the NBL79 study of the German Pediatric Oncology society. In all cases tumor cells were found to have a higher DNA-content as compared to the normal diploid (2c) DNA-value of granulocytes in the same preparation. Average ploidy values of the histograms of bone marrow metastases were in the tetra- to hypertetraploid (4c-5c) range and showed unimodal distribution in the majority of cases. In the primary tumors there was also a wide distribution of DNA-values in the aneuploid range. A bimodal distribution with stemlines at 2,5c and 5c was found in a stage I, grade I, differentiated primary tumor. Various ploidy patterns found at different sites in the large tumor mass of a newborn might be interpreted as an expression of different degrees of differentiation within the same tumor. In 2 of 4 patients where primary tumor and metastatic lesions could be examined there was a higher ploidy in the 5c to 6c, or even in the 8c range in the metastatic cell population. It appears, thus, that clonal evolution of tumor cells occurs during growth and spread of neuroblastoma.

Etude de la teneur en DNA nucléaire dans le méristème apical des tiges du Celosia cristata (Amarantacées) en fonction de la photopériode

Two samples of plants of Celosia cristata, a quantitative short-day plant, were grown in an 8-h or a 16-h day. The shoot apices were collected at 11, 15, 18, and 28 days in order to carry out a cytophotometric study of the nuclear DNA in the corpus. This distribution of the DNA values was analyzed statistically using the χ2 test. At the beginning of development, for both 8-h day and 16-h day plants, the DNA content of the majority of the nuclei is at the 2C level. Then the percentage 2C–4C or 4C nuclei increases, slowly for the plants grown under a 16-h photoperiod and quickly for the others. At the 28th day, the Gaussian distribution of DNA values indicates that the state reached by the meristems is quite different. Between the 18th day and the 28th day of culture, ontogenesis of the shoot apex goes through a critical period. At the end of this period, shoot apices of the plants grown under a 16-h photoperiod are in the intermediate phase with a majority of nuclei in the synthetic phase (S) or in the postsynthetic phase (G2). Simultaneously, structural modifications of the axial zone give rise to a central zone characteristic of the fasciation of the shoot apex. In plants grown with an 8-h photoperiod, the shoot apex goes through the prefloral phase with more numerous nuclei in the presynthetic phase (G1) or in the synthetic one (S). For each sample the nuclei clustered in a particular phase of the cell cycle indicate that a certain synchronism of the cell cycles in the corpus takes place. These results are compared with those recently obtained by other authors working with different plants.

Morphometric and cytophotometric investigations of lobular neoplasia of the breast with ductal involvement.

The two different types, A and B, of in situ lobular neoplasia of the breast can be distinguished by cytomorphological means. DNA-measurements of type A are preponderantly diploid while those of type B vary from diploidy to hyperteraploidy with a maximum in the hyperdiploid range. The results indicate a higher potential of malignancy in type B. Homogenous ductular cell proliferations in the immediate neighbourhood of a lobular neoplasia display virtually the same distribution of DNA-values. Such evidence suggests that ductular changes and concomitant intralobular lesions have a common genesis, showing also a similar tendency towards malignant changes.

The influence of non-cytotoxic concentrations of the herbicide 2,4-dichlorophenoxyacetic acid on the DNA synthesis in cultured vertebrate cells.

The influence of the herbicide 2,4-Dichlorophenoxyacetic acid on the growth of cultured chicken muscle cells was studied by observing morphological changes and by cytophotometric measurement of the DNA content of individual cells. DNA-synthesis curves were derived from the distribution of DNA values. No marked effects were observed at a concentration of 60 mug per liter. In contrast, doses of 600 mug per liter caused a loss in cell differentiation consisting of a partial lack of polar orientation, diminished formation of fibers, and an increase of the N/C ratio. The nuclear matrix of desoxyribonucleoprotein (DNP) changed to a more heteropycnotic structure. Isolated cell necroses were found after 44 hrs of exposure. When compared to the controls, the relative DNA synthesis time was found to be prolonged 1.5-fold. The number of cells in the G2 phase decreased during 44 hrs of exposure. It is concluded from these results that the dosedependent growth inhibition of 2,4-D on vertebrate cells in culture takes effect during DNA synthesis. The morphological changes of the nuclear structure suggests that 2,4-D directly affects the template activity of the DNP matrix.

Induced DNA synthesis in orchid mycorrhiza

The distribution of DNA values in the cortex of mycorrhizal and non-mycorrhizal roots of Dactylorhiza purpurella and Spathoglottis plicata has been studied by Feulgen microdensitometry. Endoreduplication occurs during differentiation of cortical parenchyma. Nuclei with two or four times the normal DNA content are present in infected and adjacent uninfected cells. Autoradiography following (3)H-thymidine incorporation showed that DNA synthesis is induced in fully differentiated cortical cells of S. plicata during infection by Tulasnella calospora.

DNA values in somatic tissues of Dermestes (dermestidae: coleoptera). I. Abdominal fat body and testis wall of the adult.

The distribution of DNA values in some somatic tissues of seven Dermestes species has been investigated. In all cases the DNA values are distributed as members of a doubling series. Distributions are found to be similar between species and sexes for the same tissue but different between tissues in the same species. Species DNA values derived from somatic tissues agree with DNA values previously determined for spermatids. These data are discussed in relation to the range of species DNA values (2.7 x) and the process of differentiation.