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PubMedDate not supplied

[Polyploidization of cardiac myocytes as a programmed event of ontogenesis].

The pieces of ventricles of newborn rats, which consist of diploid myocytes in more than 95%, were transplanted under the renal capsule of a syngeneic adult rat. Within 35 days the transplants contained 40 to 60% of the cells with the double or even greater DNA content in the mononuclear and binuclear classes. The composition of the classes was similar unlike the number of the cells of a certain class in the transplant and in the heart of a 35 day old rat. A conclusion has been drawn that the polyploidization is programmed and the realization of this programme depends on the growth, work, and other factors but is expressed even at their minimal action in the transplant. The growth of the transplanted myocytes was weaker than in the heart. It is supposed that, unlike the polyploidization, the growth of the myocytes outside the cycle is, predominantly, functional-dependent.

Animals↗

PubMed1986

[Analysis of the polyploidization kinetics of the parenchymal cells in the rat liver].

Methodological approaches to kinetics of cell polyploidization in the rat liver parenchyma are discussed. Different ways of hepatocyte polyploidization in the course of postnatal liver growth have been assessed. The intensities of hepatocyte transitions from one ploidy class to another were determined. On the basis of literary experimental data the following is summarized: With the increase in the animal age, there is a decrease in hepatocyte transition from one ploidy class to and ther; in young animals the intensity of formation of tetraploid hepatocytes through the stage of binuclear cells (2c----2c X 2----4c) is 0.39-0.55 within two weeks, the intensity of direct transitions (2c----4c) being 0.00-0.19 within the same time. The intensity of entering to DNA synthesis is reduced with the increase in hepatocyte ploidy levels; in this case the coefficient of the reducing of mitotic activity is calculated as 0.10-0.22, and 0.01-0.05 for 4c- and 8c-hepatocytes, resp. The factors stimulating proliferation in the liver increase the intensity of the direct cell transition (2c----4c) by several times which can exceed the intensity of transition through the binuclear cell stage.

Aging↗

PubMedDate not supplied

Growth arrest and polyploidization induced by metahalone microtubule inhibitors on rat glioma cells in culture.

Two pyrimidine analogs (metahalones) NY 3163, NY 3170 have been tested for their effects on the growth of rat glioma cells in monolayer and in spheroid culture. Both substances have earlier been found to inhibit the microtubule system in malignant cells. In glioma cells, arrest of mitosis was accompanied by repeated cycles of DNA synthesis, leading to different levels of polyploidization up to 16 and 32 ploid cells. The effect was not reversible through a culture period of 4 days. Reduced ability of directional migration of cells on a plastic surface was seen for 16 days after exposure. The reaction to microtubule inhibitors seems to differ depending on the type of tumour cells, where some malignant cells have earlier been reported to escape mitotic arrest and proceed to the next G1 phase, in contrast to the present glioma cells which undergo polyploidization.

Animals↗

PubMed1978

Cell kinetics of mouse urinary bladder epithelium. III. A histologic and ultrastructural study of bladder epithelium during regeneration after a single dose of cyclophosphamide, with special reference to the mechanism by which polyploid cells are formed.

In order to see whether the polyploid cells lining the mouse urinary bladder are formed by nuclear fusion, such epithelium was studied under the light and electron microscope forty-eight hours after an injection of cyclophosphamide when the bladder epithelium regenerates with rapid formation of many diploid, tetraploid and octoploid cells. The probability of seing fusion, if it occurs, ought then to be high. Serial sections of many specimens from four mice revealed no signs of fusion. Thus we found no support for the theory that polyploid cells are formed by nuclear fusion.

Animals↗

PubMed1984

Induction of polyploid nuclei in the plasmodium of Physarum polycephalum by platinum antitumor compounds.

The intranuclear mitosis of the plasmodial nuclei of myxomycetes permits the observation of defects in chromosomal repartition which would probably be lethal in other eukaryotic cells with open mitosis. We found that antitumoral platinum-amine compounds perturbed late mitotic events and induced the formation of giant nuclei which were polyploid in plasmodia of Physarum polycephalum. Using 26 platinum-amine complexes, we have shown that all antitumoral compounds induced the formation of polyploid nuclei for drug concentrations at least three times lower than the amount necessary to block the overall plasmodial growth, whereas platinum compounds without antitumor activity did not behave this way. DNA replication appeared to be quantitatively normal during formation of giant nuclei by antitumoral compounds. These observations suggest that platinum-amine compounds exert their antitumor activity by interfering with mitosis rather than by a gross inhibition of DNA synthesis.

Cell Nucleolus↗

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↗

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↗

PubMed2026

Genome-wide cyclin gene evolution in Arabidopsis and Brassica reveals polyploidization-driven duplication and flowering-time associations.

Cyclin genes are plant cell cycle regulators that play essential roles in growth, development, and reproduction. However, the evolutionary dynamics and genomic organization of cyclin genes across the Brassicaceae family remain poorly understood, particularly in the context of allotetraploid genome evolution. Here, we investigated the diversity, expansion mechanisms, and potential functional diversification of cyclin genes across ten Brassicaceae genomes, including four Arabidopsis and six Brassica species. A total of 1087 cyclin genes representing 23 cyclin types were identified. Comparative genomic analyses revealed that cyclin gene expansion was strongly influenced by polyploidization in Brassica species, with 1845 duplication events involving 1063 genes. Whole-genome duplication was the predominant mechanism driving expansion, while both inter- and intra-genomic duplications contributed to gene retention in tetraploid Brassica species, with the highest duplication frequency observed in Brassica juncea. Across genomes, 120 physical gene clusters were identified, including homogeneous and heterogeneous types. Ortholog analysis between progenitor and allotetraploid species identified 852 orthologous pairs involving 366 genes, indicating extensive conservation following allotetraploid formation. Phylogenetic analysis resolved cyclins into three major clades, while expression-based clustering in Brassica napus grouped genes into four major clusters, suggesting functional diversification. Integration of pan-genomic and flowering-time QTL analyses further identified two cyclin genes, Bna21cycA2 and Bna113cycD4, which contain amino acid polymorphisms and represent putative candidate variations potentially associated with flowering-time variation across multiple genomes. These findings provide new insights into the evolutionary expansion, retention, and potential functional divergence of cyclin genes in Brassicaceae and highlight candidate loci for future functional studies and crop improvement.

Evolution, Molecular↗

PubMed1987

Angiotensin evokes in polyploid rat glioma cells hyperpolarization-depolarization responses and cross-desensitization with bradykinin.

Angiotensins I, II and III induced a hyperpolarizing response of up to 1 min duration followed by a depolarizing response of up to 4 min when applied by pressure pulses or iontophoresis to polyploid rat glioma cells C6-4-2. The hyperpolarization (depolarization) was associated with a 50% decrease (no measurable change) in membrane resistance. The reversal potential (ca.-90 mV) of the hyperpolarization most likely points to an increase K+ conductance. Cells desensitized to angiotensins on application of high doses of either angiotensins or bradykinin.

Angiotensin II↗

PubMed1990

Cytogenetic and molecular approaches of polyploidization in colorectal adenocarcinomas.

We present the cytogenetic analysis of 23 cases of polyploid colorectal adenocarcinomas. We took advantage of the high intratumoral heterogeneity of the karyotypes to identify clones, subclones, and cell-to-cell variations. This allowed us to reconstruct the chromosomal evolution of each tumor and to propose a schema of the chromosomal changes in relation to the endoreduplication process. All but one case were characterized by a relative deficiency of chromosomes 17p and 18. Other deficiencies affecting the late-replicating X, and to a lesser degree, 1p, 5q, 14, 15, 8p, 10, 21, and 4, and excesses affecting the early-replicating X, 8q, 13, 16, 17q, and 11 were frequently associated. This pattern of imbalances is very similar to that of the monosomic type previously described in near-diploid tumors. The pattern of the 23rd tumor corresponded to those of the trisomic type tumors. These data largely confirm the existence of two distinct processes of chromosomal evolution in colorectal adenocarcinomas, with a strong tendency to undergo endoreduplication for the monosomic type near-diploid tumors. To correlate cytogenetic and molecular data, allelic losses analyses were investigated for probes of chromosomes 17p and 18. In all 12 informative tumors, a loss of heterozygosity for probes of the short arm of chromosome 17 indicated the occurrence of a rearrangement of chromosome 17 before the endoreduplication. The same was true for allelic losses for probes of chromosome 18 found in 11 of 12 informative tumors. The correlation between cytogenetic and molecular data is thus excellent and indicates that losses of 17p and 18 are early events in the tumor process.

Adenocarcinoma↗