Genome size expansion and the relationship between nuclear DNA content and spore size in the Asplenium monanthes fern complex (Aspleniaceae)

BACKGROUND

Homosporous ferns are distinctive amongst the land plant lineages for their high chromosome numbers and enigmatic genomes. Genome size measurements are an under exploited tool in homosporous ferns and show great potential to provide an overview of the mechanisms that define genome evolution in these ferns. The aim of this study is to investigate the evolution of genome size and the relationship between genome size and spore size within the apomictic Asplenium monanthes fern complex and related lineages.

RESULTS

Comparative analyses to test for a relationship between spore size and genome size show that they are not correlated. The data do however provide evidence for marked genome size variation between species in this group. These results indicate that Asplenium monanthes has undergone a two-fold expansion in genome size.

CONCLUSIONS

Our findings challenge the widely held assumption that spore size can be used to infer ploidy levels within apomictic fern complexes. We argue that the observed genome size variation is likely to have arisen via increases in both chromosome number due to polyploidy and chromosome size due to amplification of repetitive DNA (e.g. transposable elements, especially retrotransposons). However, to date the latter has not been considered to be an important process of genome evolution within homosporous ferns. We infer that genome evolution, at least in some homosporous fern lineages, is a more dynamic process than existing studies would suggest.

Genome size variation in wild and cultivated maize along altitudinal gradients

It is still an open question as to whether genome size (GS) variation is shaped by natural selection. One approach to address this question is a population-level survey that assesses both the variation in GS and the relationship of GS to ecological variants. We assessed GS in Zea mays, a species that includes the cultivated crop, maize, and its closest wild relatives, the teosintes. We measured GS in five plants of each of 22 maize landraces and 21 teosinte populations from Mexico sampled from parallel altitudinal gradients. GS was significantly smaller in landraces than in teosintes, but the largest component of GS variation was among landraces and among populations. In maize, GS correlated negatively with altitude; more generally, the best GS predictors were linked to geography. By contrast, GS variation in teosintes was best explained by temperature and precipitation. Overall, our results further document the size flexibility of the Zea genome, but also point to a drastic shift in patterns of GS variation since domestication. We argue that such patterns may reflect the indirect action of selection on GS, through a multiplicity of phenotypes and life-history traits.

Evolution of genome size in Carex (Cyperaceae) in relation to chromosome number and genomic base composition

BACKGROUND AND AIMS

The genus Carex exhibits karyological peculiarities related to holocentrism, specifically extremely broad and almost continual variation in chromosome number. However, the effect of these peculiarities on the evolution of the genome (genome size, base composition) remains unknown. While in monocentrics, determining the arithmetic relationship between the chromosome numbers of related species is usually sufficient for the detection of particular modes of karyotype evolution (i.e. polyploidy and dysploidy), in holocentrics where chromosomal fission and fusion occur such detection requires knowledge of the DNA content.

METHODS

The genome size and GC content were estimated in 157 taxa using flow cytometry. The exact chromosome numbers were known for 96 measured samples and were taken from the available literature for other taxa. All relationships were tested in a phylogenetic framework using the ITS tree of 105 species.

KEY RESULTS

The 1C genome size varied between 0·24 and 1·64 pg in Carex secalina and C. cuspidata, respectively. The genomic GC content varied from 34·8 % to 40·6 % from C. secalina to C. firma. Both genomic parameters were positively correlated. Seven polyploid and two potentially polyploid taxa were detected in the core Carex clade. A strong negative correlation between genome size and chromosome number was documented in non-polyploid taxa. Non-polyploid taxa of the core Carex clade exhibited a higher rate of genome-size evolution compared with the Vignea clade. Three dioecious taxa exhibited larger genomes, larger chromosomes, and a higher GC content than their hermaphrodite relatives.

CONCLUSIONS

Genomes of Carex are relatively small and very GC-poor compared with other angiosperms. We conclude that the evolution of genome and karyotype in Carex is promoted by frequent chromosomal fissions/fusions, rare polyploidy and common repetitive DNA proliferation/removal.

Cytogeography and genome size variation in the Claytonia perfoliata (Portulacaceae) polyploid complex

BACKGROUND AND AIMS

Genome duplication is a central process in plant evolution and contributes to patterns of variation in genome size within and among lineages. Studies that combine cytogeography with genome size measurements contribute to our basic knowledge of cytotype distributions and their associations with variation in genome size.

METHODS

Ploidy and genome size were assessed with direct chromosome counts and flow cytometry for 78 populations within the Claytonia perfoliata complex, comprised of three diploid taxa with numerous polyploids that range to the decaploid level. The relationship between genome size and temperature and precipitation was investigated within and across cytotypes to test for associations between environmental factors and nuclear DNA content.

KEY RESULTS

A euploid series (n = 6) of diploids to octoploids was documented through chromosome counts, and decaploids were suggested by flow cytometry. Increased variation in genome size among populations was found at higher ploidy levels, potentially associated with differential contributions of diploid parental genomes, variation in rates of genomic loss or gain, or undetected hybridization. Several accessions were detected with atypical genome sizes, including a diploid population of C. parviflora ssp. grandiflora with an 18 % smaller genome than typical, and hexaploids of C. perfoliata and C. parviflora with genomes 30 % larger than typical. There was a slight but significant association of larger genome sizes with colder winter temperature across the C. perfoliata complex as a whole, and a strong association between lower winter temperatures and large genome size for tetraploid C. parviflora.

CONCLUSIONS

The C. perfoliata complex is characterized by polyploids ranging from tetraploid to decaploid, with large magnitude variation in genome size at higher ploidy levels, associated in part with environmental variation in temperature.

Flow cytometric determination of genome size in European sunbleak Leucaspius delineatus (Heckel, 1843)

The aim of this study was to compare DNA content in hepatocyte and erythrocyte nuclei of the European sunbleak, Leucaspius delineatus, in relation to nuclear and cell size by means of flow cytometry and fluorescence microscopy. The DNA standards, chicken and rainbow trout erythrocytes, were prepared in parallel with both cell types, with initial separation of liver cells in pepsin solution followed by cell filtering. Standards and investigated cells were stained with a mixture of propidium iodide, citric acid, and Nonidet P40 in the presence of RNAse, and fluorescence of at least 50,000 nuclei was analyzed by flow cytometry. Average cell size was determined by flow cytometry, using fresh cell suspension in relation to latex beads of known diameter. The size of nuclei was examined on the basis of digital micrographs obtained by fluorescence microscopy after nuclei staining with DAPI. The sunbleak's erythrocyte nuclei contain 2.25 ± 0.06 pg of DNA, whereas the hepatocyte nuclei contain 2.46 ± 0.06 pg of DNA. This difference in DNA content was determined spectroscopically using isolated DNA from the two cell types. The modal diameters of the erythrocytes and hepatocytes were estimated to be 5.1 ± 0.2 and 22.3 ± 5.0 μm, respectively, and the corresponding modal dimensions of their nuclei (measured as surface area) were 15.2 and 21.4 μm(2), respectively. The nucleoplasmic index, as calculated from diameters estimated from surface area of nuclear profiles, was 2.51 for the erythrocytes compared with 0.08 for hepatocytes.

Flow cytometric methods to investigate culture heterogeneities for plant metabolic engineering

Plant cell cultures provide an important method for production and supply of a variety of natural products, where conditions can be easily controlled, manipulated, and optimized. Development and optimization of plant cell culture processes require both bioprocess engineering and metabolic engineering approaches. Cultures are generally highly heterogeneous, with significant variability amongst cells in terms of growth, metabolism, and productivity of key metabolites. Taxus cultures produce the important anti-cancer agent Taxol((R)) (i.e., paclitaxel) and have demonstrated significant variability amongst cell populations in culture with regard to paclitaxel accumulation, cell cycle participation, and protein synthesis. To fully understand the link between cellular metabolism and culture behavior and to enable targeted metabolic engineering approaches, cultures need to be studied at a single cell level. This chapter describes the application of plant cell flow cytometric techniques to investigate culture heterogeneity at the single cell level, in order to optimize culture performance through targeted metabolic engineering. Flow cytometric analytical methods are described to study Taxus single cells, protoplasts, and nuclei suspensions with respect to secondary metabolite accumulation, DNA content, cell size, and complexity. Reproducible methods to isolate these single particle suspensions from aggregated Taxus cultures are discussed. Methods to stain both fixed and live cells for a variety of biological markers are provided to enable characterization of cell phenotypes. Fluorescence-activated cell sorting (FACS) methods are also presented to facilitate isolation of certain plant cell culture populations for both analysis and propagation of superior cell lines for use in bioprocesses.

Genome size variation in the genus Carthamus (Asteraceae, Cardueae): systematic implications and additive changes during allopolyploidization

BACKGROUND AND AIMS

Plant genome size is an important biological characteristic, with relationships to systematics, ecology and distribution. Currently, there is no information regarding nuclear DNA content for any Carthamus species. In addition to improving the knowledge base, this research focuses on interspecific variation and its implications for the infrageneric classification of this genus. Genome size variation in the process of allopolyploid formation is also addressed.

METHODS

Nuclear DNA samples from 34 populations of 16 species of the genus Carthamus were assessed by flow cytometry using propidium iodide.

KEY RESULTS

The 2C values ranged from 2.26 pg for C. leucocaulos to 7.46 pg for C. turkestanicus, and monoploid genome size (1Cx-value) ranged from 1.13 pg in C. leucocaulos to 1.53 pg in C. alexandrinus. Mean genome sizes differed significantly, based on sectional classification. Both allopolyploid species (C. creticus and C. turkestanicus) exhibited nuclear DNA contents in accordance with the sum of the putative parental C-values (in one case with a slight reduction, frequent in polyploids), supporting their hybrid origin.

CONCLUSIONS

Genome size represents a useful tool in elucidating systematic relationships between closely related species. A considerable reduction in monoploid genome size, possibly due to the hybrid formation, is also reported within these taxa.

Estimation of the nuclear DNA content of gossypium species

BACKGROUND AND AIMS

Gossypium is an economically important, globally distributed taxon comprising more than 50 species. DNA content estimates from about half of the species indicate over a 3-fold variation exists. However, the nine DNA content estimates for G. hirsutum reveal over a 2-fold difference for this species alone. Recent reports have shown that several plant compounds can bias DNA content estimates obtained by commonly used methods. The purpose of this research was to examine the standardization procedures used for DNA content determinations with flow cytometry as applied to Gossypium, and generate revised DNA content estimates for all available Gossypium species using best-standard practices.

METHODS

Flow cytometry was used to measure fluorescence of isolated Gossypium nuclei stained with propidium iodide. Fluorescence values were converted to DNA content estimates based on the nuclear fluorescence of standard genotypes of barley, corn and rice. Various combinations of nuclei preparations relative to the standards were evaluated for their influence on the estimates.

KEY RESULTS

Both external standardization and internal standardization with Oryza sativa 'IR36' yielded statistically similar DNA content estimates for Gossypium. Internal standardization with Hordeum vulgare 'Sultan' resulted in a high estimate of DNA content. Nuclear DNA content estimates were generated for 37 Gossypium species using external standardization. Estimates of ancestral genome sizes reveal that both increases and decreases in nuclear DNA content have occurred. Variation in intraspecific and intragenomic DNA content was low, and the allopolyploid AD-genome size was nearly the additive of its progenitor genomes.

CONCLUSIONS

Due to unknown factors, internal standardization with H. vulgare 'Sultan' may not be appropriate for DNA content determinations of Gossypium. The current DNA content estimates support accepted cytogenetic divisions of the genus. Gossypium is a genus that exhibits genome constancy both through speciation within genomic groups and allopolyploidization.

Evolution of genome size in Brassicaceae

BACKGROUND AND AIMS

Brassicaceae, with nearly 340 genera and more than 3350 species, anchors the low range of angiosperm genome sizes. The relatively narrow range of DNA content (0.16 pg < 1C < 1.95 pg) was maintained in spite of extensive chromosomal change. The aim of this study was to erect a cytological and molecular phylogenetic framework for a selected subset of the Brassicacae, and use this as a template to examine genome size evolution in Brassicaceae.

METHODS

DNA contents were determined by flow cytometry and chromosomes were counted for 34 species of the family Brassicaceae and for ten Arabidopsis thaliana ecotypes. The amplified and sequenced ITS region for 23 taxa (plus six other taxa with known ITS sequences) were aligned and used to infer evolutionary relationship by parsimony analysis.

KEY RESULTS

DNA content in the species studied ranged over 8-fold (1C = 0.16-1.31 pg), and 4.4-fold (1C = 0.16-0.71 pg) excluding allotetraploid Brassica species. The 1C DNA contents of ten Arabidopsis thaliana ecotypes showed little variation, ranging from 0.16 pg to 0.17 pg.

CONCLUSIONS

The tree roots at an ancestral genome size of approximately 1x = 0.2 pg. Arabidopsis thaliana (1C = 0.16 pg; approximately 157 Mbp) has the smallest genome size in Brassicaceae studied here and apparently represents an evolutionary decrease in genome size. Two other branches that represent probable evolutionary decreases in genome size terminate in Lepidium virginicum and Brassica rapa. Branches in the phylogenetic tree that represent probable evolutionary increases in genome size terminate in Arabidopsis halleri, A. lyrata, Arabis hirsuta, Capsella rubella, Caulanthus heterophyllus, Crucihimalaya, Lepidium sativum, Sisymbrium and Thlaspi arvense. Branches within one clade containing Brassica were identified that represent two ancient ploidy events (2x to 4x and 4x to 6x) that were predicted from published comparative mapping studies.

Genome evolution in the genus Sorghum (Poaceae)

BACKGROUND AND AIMS

The roles of variation in DNA content in plant evolution and adaptation remain a major biological enigma. Chromosome number and 2C DNA content were determined for 21 of the 25 species of the genus Sorghum and analysed from a phylogenetic perspective.

METHODS

DNA content was determined by flow cytometry. A Sorghum phylogeny was constructed based on combined nuclear ITS and chloroplast ndhF DNA sequences.

KEY RESULTS

Chromosome counts (2n = 10, 20, 30, 40) were, with few exceptions, concordant with published numbers. New chromosome numbers were obtained for S. amplum (2n = 30) and S. leiocladum (2n = 10). 2C DNA content varies 8.1-fold (1.27-10.30 pg) among the 21 Sorghum species. 2C DNA content varies 3.6-fold from 1.27 pg to 4.60 pg among the 2n = 10 species and 5.8-fold (1.52-8.79 pg) among the 2n = 20 species. The x = 5 genome size varies over an 8.8-fold range from 0.26 pg to 2.30 pg. The mean 2C DNA content of perennial species (6.20 pg) is significantly greater than the mean (2.92 pg) of the annuals. Among the 21 species studied, the mean x = 5 genome size of annuals (1.15 pg) and of perennials (1.29 pg) is not significantly different. Statistical analysis of Australian species showed: (a) mean 2C DNA content of annual (2.89 pg) and perennial (7.73 pg) species is significantly different; (b) mean x = 5 genome size of perennials (1.66 pg) is significantly greater than that of the annuals (1.09 pg); (c) the mean maximum latitude at which perennial species grow (-25.4 degrees) is significantly greater than the mean maximum latitude (-17.6) at which annual species grow.

CONCLUSIONS

The DNA sequence phylogeny splits Sorghum into two lineages, one comprising the 2n = 10 species with large genomes and their polyploid relatives, and the other with the 2n = 20, 40 species with relatively small genomes. An apparent phylogenetic reduction in genome size has occurred in the 2n = 10 lineage. Genome size evolution in the genus Sorghum apparently did not involve a 'one way ticket to genomic obesity' as has been proposed for the grasses.

The C-value enigma in plants and animals: a review of parallels and an appeal for partnership

AIMS

Plants and animals represent the first two kingdoms recognized, and remain the two best-studied groups in terms of nuclear DNA content variation. Unfortunately, the traditional chasm between botanists and zoologists has done much to prevent an integrated approach to resolving the C-value enigma, the long-standing puzzle surrounding the evolution of genome size. This grand division is both unnecessary and counterproductive, and the present review aims to illustrate the numerous links between the patterns and processes found in plants and animals so that a stronger unity can be developed in the future.

SCOPE

This review discusses the numerous parallels that exist in genome size evolution between plants and animals, including (i) the construction of large databases, (ii) the patterns of DNA content variation among taxa, (iii) the cytological, morphological, physiological and evolutionary impacts of genome size, (iv) the mechanisms by which genomes change in size, and (v) the development of new methodologies for estimating DNA contents.

CONCLUSIONS

The fundamental questions of the C-value enigma clearly transcend taxonomic boundaries, and increased communication is therefore urged among those who study genome size evolution, whether in plants, animals or other organisms.

The origin, evolution and proposed stabilization of the terms 'genome size' and 'C-value' to describe nuclear DNA contents

BACKGROUND

Perusing the literature on nuclear 'genome size' shows that the term is not stabilized, but applied with different meanings. It is used for the DNA content of the complete chromosome complement (with chromosome number n), for which others use 'C-value', but also for the DNA content of the monoploid chromosome set only (with chromosome number x). Reconsideration of the terminology is required.

AIM

Our purpose is to discuss the currently unstable usage of the terms 'genome size' and 'C-value', and to propose a new unified terminology which can describe nuclear DNA contents with ease and without ambiguity.

PROPOSALS

We argue that there is a need to maintain the term genome size in a broad sense as a covering term, because it is widely understood, short and phonetically pleasing. Proposals are made for a unified and consensual terminology. In this, 'genome size' should mean the DNA content based on chromosome number x and n, and should be used mainly in a general sense. The necessary distinction of the kinds of genome sizes is made by the adjectives 'monoploid' and the neology 'holoploid'. 'Holoploid genome size' is a shortcut for the DNA content of the whole chromosome complement characteristic for the individual (and by generalization for the population, species, etc.) irrespective of the degree of generative polyploidy, aneuploidies, etc. This term was lacking in the terminology and is for reasons of linguistic consistency indispensable. The abbreviated terms for monoploid and holoploid genome size are, respectively, Cx-value and C-value. Quantitative data on genome size should always indicate the C-level by a numerical prefix, such as 1C, 1Cx, 2C, etc. The proposed conventions cover general fundamental aspects relating to genome size in plants and animals, but do not treat in detail cytogenetic particularities (e.g. haploids, hybrids, etc.) which will need minor extensions of the present scheme in a future paper.

Genome size variation and evolution in Veronica

BACKGROUND AND AIMS

The amount of DNA per chromosome set is known to be a fairly constant characteristic of a species. Its interspecific variation is enormous, but the biological significance of this variation is little understood. Some of the characters believed to be correlated with DNA amount are alpine habitat, life history and breeding system. In the present study, the aim is to distinguish between direct causal connections and chance correlation of the amount of DNA in the genus Veronica.

METHODS

Estimates of DNA amount were analysed for 42 members of Veroniceae in connection with results from a phylogenetic analysis of plastid trnL-F DNA sequences and tested correlations using standard statistical tests, phylogenetically independent contrasts and a model-based generalized least squares method to distinguish the phylogenetic effect on the results.

KEY RESULTS

There appears to be a lower upper limit for DNA amount in annuals than in perennials. Most DNAC-values in Veroniceae are below the mean DNA C-value for annuals in angiosperms as a whole. However, the long-debated correlation of low genome size with annual life history is not significant (P = 0.12) using either standard statistical tests or independent contrasts, but it is significant with the generalized least squares method (P < 0.01).

CONCLUSIONS

The correlation of annual life history and low genome size found in earlier studies could be due to the association of annual life history and selfing, which is significantly correlated with low genome size using any of the three tests applied. This correlation can be explained by models showing a reduction in transposable elements in selfers. A significant correlation of higher genome sizes with alpine habitats was also detected.

Genome size variation in Central European species of Cirsium (Compositae) and their natural hybrids

BACKGROUND AND AIMS

Nuclear DNA amounts of 12 diploid and one tetraploid taxa and 12 natural interspecific hybrids of Cirsium from 102 populations in the Czech Republic, Austria, Slovakia and Hungary were estimated.

METHODS

DAPI and PI flow cytometry were used.

KEY RESULTS

2C-values of diploid (2n = 34) species varied from 2.14 pg in C. heterophyllum to 3.60 pg in C. eriophorum (1.68-fold difference); the 2C value for the tetraploid C. vulgare was estimated at 5.54 pg. The DNA contents of hybrids were located between the values of their putative parents, although usually closer to the species with the smaller genome. Biennial species of Cirsium possessed larger nuclear DNA amounts than their perennial relatives. Genome size was negatively correlated with Ellenberg's indicator values for continentality and moisture and with eastern limits of distribution. A negative relationship was also detected between the genome size and the tendency to form natural interspecific hybrids. On the contrary, C-values positively corresponded with the spinyness (degree of spinosity). AT frequency ranged from 48.38 % in C. eriophorum to 51.75 % in C. arvense. Significant intraspecific DNA content variation in DAPI sessions was detected in C. acaule (probably due to the presence of B-chromosomes), and in tetraploid C. vulgare. Only the diploid level was confirmed for the Pannonian C. brachycephalum, generally considered to be tetraploid. In addition, triploidy was discovered for the first time in C. rivulare.

CONCLUSIONS

Considerable differences in nuclear DNA content exist among Central European species of Cirsium on the diploid level. Perennial soft spiny Cirsium species of wet habitats and continental distributions generally have smaller genomes. The hybrids of diploid species remain diploid, and their DNA content is smaller than the mean of the parents. Species with smaller genomes produce interspecific hybrids more frequently.

Microgeographic genome size differentiation of the carob tree, Ceratonia siliqua, at 'Evolution Canyon', Israel

BACKGROUND AND AIMS

We tested whether the local differences in genome size recorded earlier in the wild barley, Hordeum spontaneum, at 'Evolution Canyon', Mount Carmel, Israel, can also be found in other organisms. As a model species for our test we chose the evergreen carob tree, Ceratonia siliqua.

METHODS

Genome size was measured by means of DAPI flow cytometry.

KEY RESULTS

In adults, significantly more DNA was recorded in trees growing on the more illuminated, warmer, drier, microclimatically more fluctuating 'African' south-facing slope than in trees on the opposite, less illuminated, cooler and more humid, 'European' north-facing slope in spite of an interslope distance of only 100 m at the canyon bottom and 400 m at the top. The amount of DNA was significantly negatively correlated with leaf length and tree circumference. In seedlings, interslope differences in the amount of genome DNA were not found. In addition, the first cases of triploidy and tetraploidy were found in C. siliqua.

CONCLUSIONS

The data on C. siliqua at 'Evolution Canyon' showed that local variability in the C-value exists in this species and that ecological stress might be a strong evolutionary driving force in shaping the amount of DNA.

Biological characterisation of superficial bladder cancer by bivariate cytokeratin 7/DNA analysis, flow cytometric assessment of MIB- 1, and an immunohistochemical study

A total of 238 cases of bladder carcinoma stages Ta, Tis, T1 were submitted prospectively to multiparameter flow cytometry and immunohistochemical study in order to determine the biological aggressiveness of the tumour. DNA index (DI), S-phase fraction (SPF) obtained by bivariate cytokeratin 7/DNA analyses, and the immunohistochemical evaluation of p53 and MIB-1 were studied in relation to the traditional prognostic factors in bladder cancer (stage and grade). the variance analysis results showed that DNA aneuploidy was significantly associated with high stage (p = 0.0001), high grade (p = 0.0001), high SPF value > or = 5.5% (p = 0.0001), MIB-1 positivity > or = 31% (p = 0.0001) and high expression of p53 (staining involving > 50% of cells, p = 0.0001). Even if there was no statistical significance the hypotetraploid class (1.70 < DI < 1.89) showed poor prognostic biomarkers more frequently than the other aneuploid classes. Out of 238 cases, 101 were also submitted to flow cytometric measurement of MIB-1 (fMIB-1) to study the correlation between cell proliferation and DNA content. Data obtained from fresh, 3:1 methanol/acetone fixed samples were compared with values obtained from both cell cycle analysis methods and routine application of the MIB-1 immunostaining in histological sections. fMIB-1 values were positively correlated with SPF values (r = 0.801, p < 0.01) and S+G2M fraction (percentage of cells in S and in G2M phases) (r = 0.763, p < 0.01) but no correlation with paraffin sections was found. A fMIB-1 value > 7% was strongly associated with aneuploidy (p = 0.0001). The determination of DNA content coupled with the study of the epithelial (cytokeratin 7) and proliferative (MIB-1) markers could be useful in providing important information on the biological behaviour of superficial bladder tumours.

Colchicine therapy for hepatic murine schistosomal fibrosis: image analysis and serological study

Colchicine in a dose of 200 micrograms kg body weight/day (5 days/week) was administered to groups of Schistosoma mansoni infected mice 12 weeks post infection, either alone or following previous praziquantel therapy at the 8th week of infection. Certain groups received colchicine for 6 weeks and others received it for 10 weeks. Colchicine alone did not significantly change the light microscopic appearance of schistosomal liver fibrosis, or hepatic collagen content estimated histomorphometrically, and did not reduce the elevated IL-2 serum level. Colchicine induced hepatic injury consisted of intense inflammatory reaction in granuloma and portal tracts, hepatocytic degeneration, and elevation of serum AST and ALT levels. Colchicine seemed to postpone granulomatous reaction healing and collagen deposition rather than inhibiting collagen formation or degrading it. Colchicine inhibited proliferation of hepatocytes of infected mice by expanding G2-M phases of cell cycle, thus reduced Ag NOR count and raised cell ploidy and cyclic AMP serum level. Subsidence of schistosomal infection by praziquantel prior to colchicine therapy greatly reduced inflammatory cellular reaction, significantly diminished hepatic collagen deposition and serum IL-2 level, minimized the elevated nuclear ploidy and cyclic AMP serum level that followed colchicine therapy when administered alone.

Ha-ras oncogene effect on DNA content and chromatin supraorganization in benzo[a]pyrene-transformed human breast epithelial cells

When transfected to benzo[a]pyrene (BP)-transformed MCF-10F human breast epithelial cells (BP1 cell line) the c-Ha-ras oncogene has proven to enhance the neoplastic changes initiated by exposure to BP, giving rise to an aggressive tumorigenic cell line, BP1-Tras. We have previously demonstrated by image analysis that BP affects the DNA content and the chromatin supraorganization of MCF-10F cells. Here Feulgen-stained BP1-Tras cells were studied by image analysis in order to evaluate possible additional changes in DNA content and chromatin texture induced by insertion of the ras oncogene. A high variability in DNA content also including polyploidy or near-polyploidy, and an increase in the packing states of the chromatin which became still condensed in BP1 cells were found in BP1-Tras cells. The results differed from those reported for the BP1-E1 cell line which is also an aggressive tumorigenic cell line, but was attained through progressive passages of BP-transformed cells. It was demonstrated that different patterns of changes in DNA content and chromatin organization may be involved in equally aggressive tumorigenic BP-transformed cell lines originated from the same cell line by different mechanisms.

Heterogeneity of DNA distribution in diploid cells: a new predictive discriminant factor for solid tumour behaviour

Spatial nuclear DNA heterogeneity distribution of Feulgen-stained DNA diploid cells was studied by image cytometry in voided urine of 119 patients without bladder tumour (n = 20) and with initial (n = 23) or previous (n = 76) diagnosed bladder tumour. For each patient, repetitive DNA measurements were performed during 1-4 years of follow up. Only cells of diploid DNA histograms and diploid subpopulations of aneuploid DNA histograms were used for analysis. DNA heterogeneity distribution of these diploid cells was quantified by statistical parameters of each nuclear optical density distribution. Discriminant analysis was performed on three groups of DNA histograms. Group A (n = 44): aneuploid DNA histograms of patients with bladder tumour. Group D (n = 55): 38 diploid DNA histograms of the 20 patients without bladder tumour (subgroup D1) and 17 diploid DNA histograms of patients with a non-recurrent bladder tumour (subgroup D2). Group R (n = 27): diploid DNA histograms of patients with bladder tumour recurrence. No statistically significant discriminant function was found to separate D1 and D2. However, the first canonical discriminant function C1 differentiated diploid cells of diploid DNA histograms (group D and group R) from diploid cell subpopulations of aneuploid DNA histograms (group A). Mean C1 values were 1.06, 0.84 and -1.45 for groups R, D and A, respectively. The second canonical discriminant function C2 differentiated diploid DNA histograms of patients with bladder tumour recurrence (group R) from diploid DNA histograms of patients without bladder tumour or without bladder tumour recurrence (group D). Mean C2 values were 1.78 and -0.76 for groups R and D, respectively. In 95% confidence limit, the rate of rediscrimination using the two first canonical discriminant functions C1 and C2 were 86.4, 74.5 and 74.1% for groups A, D and R, respectively. Percent of "grouped" cases correctly classified was 78.6%. Thus spatial DNA heterogeneity distribution of diploid cells seems to quantitate probable genetic instability as a function of clinical evolution such as tumour recurrence, and suggests the possible presence of aneuploid stemlines in a heterogeneous tumour, even if a diploid DNA histogram is observed in a single sample. From standardized C1 and C2 canonical discriminant function coefficients, a DNA heterogeneity index (2c-HI) is proposed to characterize diploid cells providing a descriptive and predictive discriminant factor for solid tumour behaviour.

DNA measurement of overlapping cell nuclei in thick tissue sections

The paper describes an improved image analysis procedure for measuring the DNA content of cell nuclei in thick sections of liver tissue by absorption densitometry. Whereas previous methods only permitted the analysis of isolated nuclei, the new technique enables both isolated and overlapping nuclei to be measured. A 3D segmentation procedure determines whether each object is an isolated nucleus or a pair of overlapping nuclei; in the latter case the combined optical density is redistributed to the individual nuclei. A selection procedure ensures that only complete nuclei are measured. The method has been tested on specially-prepared Feulgen-stained 20micro sections of normal liver tissue. The overall distribution of the nuclear DNA measurements shows well-defined diploid and tetraploid peaks, with coefficient of variations of less than 10%. Similar distributions were obtained from both the isolated nuclei and overlapped nuclei sub-populations.

First Cytogenetic Investigation in Populations of Acacia heterophylla, Endemic from La Reunion Island, with Reference to A. melanoxylon

Five populations of tetraploid Acacia heterophylla, endemic from La Réunion island, were compared together and with their Australian diploid relative A. melanoxylon for cytogenetic and DNA characteristics. A. melanoxylon (2n = 26) had 1·59 pg nuclear DNA; A. heterophylla (2n = 4x = 52) had double this value (3·19 pg), and there was no difference between populations within species. Both species had 39 % GC. Interchromosome connections were evident at metaphase and mitotic irregularities at anaphase were twice as frequent in A. heterophylla as in A. melanoxylon, again with no difference between populations within species. These results argue for a recent autotetraploid origin of A. heterophylla from A. melanoxylon. Yet, fluorochrome banding showed that in some A. heterophylla populations, GC-rich bands had slightly changed from the supposed ancestral pattern, probably by means of translocations involving parts of nuclear organizer areas. No clear relation was found between banding patterns and ecological factors.