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PubMed1993

[Hepatocyte polyploidization in chronic liver diseases in man].

Levels of hepatocyte ploidy were investigated in patients with chronic viral hepatitis, alcohol hepatitis, and liver cirrhosis. It was shown that in spite of some decrease in the share of mononucleate diploid hepatocytes these cells equally make the main part of hepatocyte population (about 80% on the average) both during chronic liver diseases and in the norm. In chronic hepatitis and cirrhosis processes of polyploidization in the human liver, unlike those in livers of laboratory animals (rats and mice), are accomplished with much lower rates and characterized by accumulation of binucleate diploid cells. These processes differ from those occurring under ageing. Reparative regeneration of human liver under chronic hepatitis and cirrhosis is accomplished on the whole by proliferation of mononucleate diploid hepatocytes but processes of polyploidization in the liver of some patients can play a significant role in reparative liver growth.

Adolescent↗
PubMed1997

[Genome multiplication mechanisms in the development of albumen gland polyploid cells of Succinea lauta (Gastropoda:Pulmonata). VI. Ultrastructural research of endomitotic structure].

This ultrastructural study of endomitosis in polyploid albumen gland cells of succineid snail. S. lauta was made to extend the previous research (Anisimov, 1997). The investigation was prosecuted on ultrathin sections by means of transmission electron microscopy. The insertion of 3H-thymidine and 3H-uridine into the nuclei and the light microscopy control of nuclear ploidy allowed to identify glands on early and intensive polyploidization stages and to ignore pseudoendomitotic terminally differentiated cells. Considering ultrastructural qualities and information about the cell population kinetics enabled us to discriminate between predifferentiation (2-4c), protodifferentiation (4-8c) and promoted differentiation (8-16c) cell stages. The endomitotic cycle was observed synchronously with the development of cytoplasmatic structures and secretion production in differentiating cells of ploidy levels 4-8-16c. According to morphological condition of the chromatin and chromosomes, G1-, S- and G2-interphase periods can be determined, such as successive stages of endomitosis (endopro-, meta-, ana-, and telophase). The following main features of endomitosis are accentuated: the normal (mitotic) chromosome cycle with total compaction in endometaphase and differential decompaction in interphase; the absence of the mitotic spindle; integrity of the nuclear envelope, nucleolus and contacts between them and chromosomes; part of chromosomes split nonsimultaneously and incompletely in the endoanaphase, or endomitosis with diplochromosomes rarely occurs. Chromosome nondisjunction is a temporary process that does not lead to a permanent chromosome endoreduplication (polyteny). It is emphasized that the normal chromosome cycle is combined with a complete block of cytoplasmic structures. Possible reasons of mitotic cycle reduction during the transition of differentiating cells to endomitotic polyploidy are discussed.

Animals↗
PubMed1997

[Genome multiplication mechanisms in the development of albumen gland polyploid cell of Succinea lauta (Gastropoda:Pulmonata). VIII. Pseudomitosis in the terminally differentiated cells].

Using a mature albumen gland of Succinea lauta, a study was made of the chromatin structure and RNA synthesis activity in polyploid nuclei (16c-32c-64c) of terminally differentiated cells, by means of electron microscopy and 3H-uridine radioautography of squash preparations. No 3H-thymidine incorporation in these cells was observed, which suggested the absence of DNA synthesis and endomitotic cycles at the examined functional stage of gland development. Some different stages of secretory cells could be distinguished: a resting period of the terminally differentiated cells, with the least 3H-uridine incorporation; a phase of intense heterosynthetic transcription, with the highest 3H-uridine incorporation; intervals in daily cycles; nuclear degeneration in ageing cells. At all these states the nuclei demonstrated some morphological features of endomitosis. This may be possible, because in the course of terminal cell differentiation the main chromatin mass is compacting like chromatids or chromocentres with thin euchromatinous filaments, which can be covered with perichromatinous granules. Since the true endomitosis is deliberately excluded at this stage, the above described morphological state of polyploid nuclei is regarded as postendomitotic and is designated as pseudoendomitosis. The view of the existence of "two fundamentally different types of endomitosis", one of which is "endomitosis in general", and the other "shows up as stationary" (Therman et al., 1983), is accepted as groundless.

Animals↗
PubMed1998

Human herpesvirus 7 infection induces profound cell cycle perturbations coupled to disregulation of cdc2 and cyclin B and polyploidization of CD4(+) T cells.

Human herpesvirus 7 (HHV-7) infection of both primary CD4(+) T lymphocytes and SupT1 lymphoblastoid T-cell line induced a progressive accumulation of cells exibiting a gap 2/mitosis (G2/M) and polyploid content coupled to an increased cell size. The expression of both cyclin-dependent kinase cdc2 and cyclin B was increased in HHV-7-infected cells with respect to the uninfected ones. Moreover, the simultaneous flow cytometric analysis of cyclin B and DNA content showed that cyclin B expression was not only increased but also unscheduled with respect to its usual cell cycle pattern. However, the levels of kinase activity associated to cdc2 were decreased in HHV-7-infected cells with respect to uninfected cultures. To elucidate the origin of the enlarged HHV-7-infected cells, extensive electron and confocal microscopy analyses were performed. Membrane fusion events associated to cytoplasmic bridges, which characterize the formation of syncytia, were never observed. On the other hand, analysis of serial sections of the same cells strongly suggested that enlarged HHV-7-infected cells contained a single polylobated nucleus. This was confirmed by flow cytometry analysis performed on nuclei isolated from HHV-7-infected cells, which showed multiple peaks with a DNA content >4n. Taken together, these data indicate that giant cells, which represent the hallmark of in vitro HHV-7 infection, arise from single CD4(+) T cells undergoing a process of polyploidization.

CD4-Positive T-Lymphocytes↗
PubMed1999

Rapid structural and epigenetic changes in polyploid and aneuploid genomes.

Recent work with plants has demonstrated that genome instability can be triggered by a change in chromosome number arising from either whole genome duplications (polyploidy) or loss/gain of individual chromosomes (aneuploidy). This genome instability is manifested as rapid structural and epigenetic alterations that can occur somatically or meiotically within a few generations after heteroploid formation. The intrinsic instability of newly formed polyploid and aneuploid genomes has relevance for genome evolution and human carcinogenesis, and points toward recombinational and epigenetic mechanisms that sense and respond to chromosome numerical changes.

Aneuploidy↗
PubMedDate not supplied

Fra(X) prenatal diagnosis: are endoreduplicated and polyploid cells useful diagnostic criteria?

Cytogenetic and molecular protocols for prenatal ascertainment of the fragile X syndrome and the associated fragile site at Xq27.3 are relatively reliable. Any new diagnostic method which becomes available still elicits much interest. Kimchi-Sarfaty et al. [1991] reported an increase in frequency of endoreduplication and polyploidy in fra(X) lymphoblasts and amniocytes when cultured with methotrexate (MTX) or fluorodeoxyuridine. Recently we analyzed the endoreduplication/polyploidy system using amniotic fluid, chorionic villus, and fibroblasts from fra(X) positive abortus cell cultures and from control samples. We observed no increased expression of endoreduplicated or polyploid cells in fra(X) positive amniocytes after exposure to MTX. The data presented here clearly dispute the value of endoreduplication/polyploid scoring as a diagnostic aid in prenatal fra(X) analysis.

Chromosome Aberrations↗
PubMed1988

Specific nuclear elimination in polyploid plasmodia of the slime mold Physarum polycephalum.

In growing plasmodia of the myxomycete Physarum polycephalum (G2-phase), three distinct classes of nuclei with a relative DNA content of 1x, 2x, and 4x are observed in the presumed haploid strain CL. The 2x and 4x species comprise up to 35% and 5% of the nuclei. Quantitative cytofluorometric studies of nuclei isolated in either G2- or S-phase or after FUDR treatment (G1 arrest) show that the three nuclear populations undergo a synchronous mitotic cycle and that the relative DNA content of the nuclear fractions in G-2 phase reflects the 2c, 4c, and 8c state. The heterogeneity of the nuclear population does, however, seem to be restricted to the growth phase. During a starvation period of 4 days that always preceeds sporulation (and also meiosis), the 4c nuclear population is reduced to 7%, 8c nuclei are no longer detected. These results suggest that a mechanism exists in Physarum for the selective detection and elimination of polyploid nuclei.

Cell Nucleus↗
PubMed1984

Control of DNA synthesis in polyploid mammalian cells.

To test the hypothesis that the duration of DNA synthesis is an inverse function of nuclear size or DNA content, the S phase was calculated from PLM analysis for pseudodiploid, tetraploid, and octaploid lines of Chinese hamster cells growing as a monolayer or in suspension. S phase times were found not to be significantly different between polyploid lines and the diploid lines from which they were derived, regardless of the conformation of the nucleus. There is no evidence, therefore, that would implicate the nuclear membrane, or nuclear surface area/volume relationships, in the control of DNA synthesis.

Animals↗
PubMed1992

Mitotically unstable polyploids in the yeast Pichia guilliermondii.

Attempts to obtain triploids or tetraploids of P. guilliermondii by sexual hybridization led to mitotically stable hybrids. However, their DNA content per cell was not higher than in diploids. The results of random spore analysis demonstrate that these hybrids were in fact aneuploids which obviously suffered drastic chromosome losses immediately after mating. This phenomenon could have been caused either by aneuploidy already present in the parental strains or it might have been due to a general inability of P. guilliermondii to maintain a polyploid genome.

Aneuploidy↗
PubMed1998

Adhesion of mature polyploid megakaryocytes to fibronectin is mediated by beta 1 integrins and leads to cell damage.

Human CD34+ bone marrow cells were committed to the megakaryocytic lineage in serum-free liquid cultures by the following cytokines: thrombopoietin, erythropoietin, and IL-6. Megakaryocyte maturation has been described as being regulated by the extracellular matrix. These cells express receptors for laminin, collagen, and vitronectin, but they selectively adhere to and spread on fibronectin, a major component of the bone marrow environment. Function-perturbing antibodies against beta 1 integrins totally abolished the adhesion of megakaryocytes on fibronectin, whereas antibodies to beta 3 did not, suggesting that beta 1 integrins were responsible for the adhesive phenotype of these polyploid cells. beta 1-positive clusters were visualized in close contact with the extremities of stress fibers at the cell surface. In the course of cell spreading, we observed morphological modifications such as the disorganization of the compact nuclei structure and the appearance of holes in the cytoplasm leading to the release of alpha IIb beta 3-positive cellular fragments. This process appeared to be a specific feature of megakaryocytes and is correlated neither to apoptosis nor to integrin signaling.

Actin Cytoskeleton↗
PubMed2001

Inferring the history of the polyploid Silene aegaea (Caryophyllaceae) using plastid and homoeologous nuclear DNA sequences.

The origin of the rare allotetraploid Silene aegaea was inferred from plastid rps16 intron sequences, homoeologous copies of nuclear ribosomal internal transcribed spacer (ITS) sequences, and an intron from the nuclear gene coding for the second largest subunit of RNA polymerase II (RPB2). The nuclear DNA regions support the S. sedoides and S. pentelica lineages as most closely related to the two S. aegaea paralogues. A few recombinant ITS sequences were found, but as PCR recombination could be demonstrated, no true recombination could be demonstrated. No recombination was found in the RPB2 sequences. Plastid rps16 intron sequences strongly support S. pentelica as the maternal lineage. The strength of the approach of using homoeologous sequences of several loci is demonstrated, and its usefulness for the study of phylogenies of groups including polyploids is emphasized.

Base Sequence↗
PubMed1980

Multinucleation and polyploidization of aging human cells in culture.

In conclusion, evidence has been presented to show that multinucleation and polyploidization are common, if not ubiquitous, phenomena observable both in proliferating human cell populations in culture, and in cell populations which have already passed through their proliferative phase in culture. A hypothetical model is presented, the essence of which postulates the existence of a regularly controlled cell life, including DNA synthesis, out of cell cycle.

Cell Nucleus↗
PubMed1987

Recombination between several polyploid loci.

The population genetics of polyploids classified at several loci studied in terms of the probabilistic mechanism of crossing over and segregation. The methods of genetic algebra are used.

Genetic Linkage↗
PubMed1987

Chromosome organisation in polyploid mouse trophoblast nuclei.

At least one-third of mouse trophoblast cells undergo endoreduplication during the first half of gestation. It has been suggested that the endoreduplicated chromosomes may be polytenised. Here it is shown, using in situ hybridisation to the alpha-1 antitrypsin genes, which map at a unique site, that while there is a tendency for duplicated chromosomes to cluster, this does not involve the complete fusion of replicated chromatids found in fully polytene chromosomes, and in a substantial proportion of homologues the sites on the chromosome arms corresponding to these genes are widely separated. The centromeres do not fuse into a single chromocentre but the possibility is not ruled out that individual chromosomes may be polytenised in the centromeric region. Evidence is also presented showing that endoreduplication in trophoblast nuclei is not accompanied by the formation of new prekinetochore structures, in contrast to the situation in polyploid mouse liver and C127 cells.

Animals↗
PubMed1979

Proportional polyploidization of 5S RNA genes in the ovary of Drosophila melanogaster mutants containing three 5S RNA gene loci.

The 5S RNA gene content of polyploid cells of the ovary of Drosophila melanogaster has been compared in animals with two or three gene clusters. The amount of 5S RNA genes is exactly proportional to the number of gene clusters as determined by DNA-RNA filter hybridization. In contrast, the number of rDNA genes in endomitotic cells remains constant regardless of different numbers of nucleolus organizer regions (Spear, 1974).

Animals↗
PubMed1987

Polyploidization of G2M phase cells separated from aerobically and anaerobically grown Ehrlich ascites tumor cells.

G2-enriched fractions of Ehrlich ascites tumor cells (up to 80%-85% G2 cells) separated from anaerobically and aerobically cultured asynchronous populations by centrifugal elutriation revealed the same growth characteristics after recultivation under standard conditions: a significant proportion of cells with increased DNA (DNA content greater than 4C) emerged. Interruption of DNA synthesis by deprivation of oxygen may account for polyploidization (over-replication) of DNA but other mechanisms must be taken into consideration.

Aerobiosis↗
PubMed1981

Focal necroses, fatty degeneration and subendocardial nuclear polyploidization of the myocardium in newborns after beta-sympathicomimetic suppression of premature labor.

It has been well documented in laboratory animals that beta-sympathicomimetics, such as isoprenalin, can cause myocardial lesions. Other so called "beta2-selective" symphaticomimetic drugs, which nevertheless induce beta1-cardiostimulatory side effects, are now widely used for suppression of premature labor. We examined the hearts of 25 newborns whose mothers had been treated with beta-sympathicomimetics for various lengths of time (24h to 8 weeks). Three types of lesions were detected: (1) focal subendocardial necroses (3 cases), similar to isoprenalin-induced myocardial necroses in animal experiments, (2) diffuse fatty degeneration of myocardial cells (3 cases), and (3) nuclear polyploidization in the subendocardial layer of the right ventricular wall (14 cases). However, the immediate causes of death could not be directly related to the tocolytic treatment in any of the cases.

Adrenergic beta-Agonists↗
PubMed1986

Polyploidization and localisation of poly(A)+ RNA in the different cell types of the vitellogenic meroistic ovary of the fleshfly, Sarcophaga bullata.

The degree of polyploidization, the level of transcriptional activity and the volume of the different cell types present in the meroistic ovary of Sarcophaga bullata were measured during different vitellogenic stages. The nurse cells and the germinal vesicle exhibited very pronounced differences with regard to DNA content and mRNA synthesis, even though they are genetically identical. During the 4C stage (late vitellogenesis), we observed different degrees of polyploidy in follicle cells adjacent to the oocyte and those surrounding the nurse cells. Although the chromatin of the germinal vesicle is condensed into a karyosome, in situ hybridisation revealed the presence of transcriptional activity. The volume of the germinal vesicle, which contains only 4C DNA, is big enough to contain 2048C DNA. The meroistic ovary is a highly polarized differentiating system. Our results are discussed in the light of the fact that the polytrophic ovary is a miniature electrophoresis chamber.

Animals↗