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PubMed1979

[Regenerative reactions of myocardiocyte nuclei in ischemic heart disease].

The ploidy of myocardiocytes nuclei in the left ventricle was determined stereometrically and microspectrophotometrically in 20 cases of ischemic heart disease (IHD) and 9 control cases. An increase in the number of nuclei and the degree of their ploidy and their correlation with the myocardium mass were established. The number of polyploid nuclei was particularly high in the periphery of postinfarction scars. These data indirectly indicate the participation of polyploidization and amitosis of myocardiocytes nuclei in the development of myocardial regenerative hypertrophy.

Adult↗
PubMedDate not supplied

[Comparison of inactivated rabies vaccines obtained from diploid and polyploid heterologous cells (Hak, BHK, and Vero)].

Homologous or heterologous diploid or polyploid cells have been established as good producers of virus. In this study we present three types of experimental inactivated antirabies vaccines obtained under identical conditions from three types of cells. The study concerns the following characteristics of the vaccines: protecting powers, rabies antigens and major polypeptidic components; this study was performed on supernatants of tissue cultures and concentrated and purified vaccines. Moreover, some cellular and serum contaminants as well as minor rabies proteins were analysed in the viral solutions. It, thus, appears that all these types of vaccines have a similar protecting power (Number of 50% protective doses/micrograms viral protein).

Animals↗
PubMed2001

Kinetics of endomitosis in primary murine megakaryocytes.

Megakaryocytes (MKs) develop from diploid progenitor cells via successive rounds of DNA synthesis in the absence of cell division, a process termed endomitosis (EnM). While the mechanism underlying EnM is not known, studies in yeast and leukemic cell lines have suggested that it may be due to reduced levels of cyclin B1 or cdc2, leading to a decrease in mitotic kinase activity. Using flow cytometry to study EnM highly purified marrow-derived MK precursors, we found that: (1) on average, 36% of 8N-32N MKs expressed abundant cyclin B during G2/M. The percentage of cells in G2/M decreased in >64N MKs, suggesting the limit of EnM, (2) the level of cyclin B per G2/M MK increased linearly with ploidy, (3) cyclin B expression oscillated normally in polyploid MKs, (4) MPM-2, a phosphoepitope created by the action of mitotic kinases and specific to M-phase cells, was expressed in a significant fraction of polyploid MKs, and (5) there was an apparent increase of cyclin B in G1-phase in polyploid MKs. This study provides the first qualitative kinetic data regarding the cell cycle status of MKs within individual ploidy classes. It also demonstrates the feasibility of using anti-cyclin B antibody and flow cytometry to resolve G1 from G2/M populations in polyploid MKs. Finally, these findings establish that neither a relative nor absolute deficiency of mitotic kinase components is responsible for EnM, suggesting that the departure from normal cell division kinetics seen in polyploid MKs is likely due to alterations in other cell cycle regulators.

Animals↗
PubMed2000

Ectopic expression of cyclin E allows non-endomitotic megakaryoblastic K562 cells to establish re-replication cycles.

Megakaryocytes become polyploid by entering a truncated cell cycle, consisting of alternate S phases and abortive mitoses. We have investigated the regulation of the G1/S transition by comparing two megakaryoblastic cell lines, HEL and K562, which respectively do or do not become polyploid in response to phorbol esters. A pronounced downregulation of cyclin A, and to a lesser extent of cyclin E, occurred in K562 cells during the first 24 h after TPA treatment, in contrast with re-replicating HEL cells, in which both cyclins were present in individual G2/M cells. Transactivation experiments suggested that the absence of cyclin A in differentiated K562 cells could be due to a TPA-mediated inhibition of its transcription. To investigate the potential role of cyclin E in the establishment of re-replication cycles, we isolated K562 clones constitutively expressing cyclin E. The resulting clones, and also K562 cells transiently expressing cyclin E, entered re-replication cycles when treated with TPA. The transcriptional activity of the cyclin A promoter was not inhibited after TPA treatment, and although the levels of cyclin A fluctuated during further re-replication cycles, they never decreased below S phase levels. We conclude that the presence of cyclin E in megakaryoblastic G2/M cells determines cyclin A expression and allows the entrance into an extra S phase.

Bone Marrow Cells↗
PubMed1999

Cytogeography and chromosome evolution of subgenus Tridentatae of Artemisia (Asteraceae).

The subgenus Tridentatae of Artemisia (Asteraceae: Anthemideae) is composed of 11 species of various taxonomic and geographic complexities. It is centered on Artemisia tridentata with its three widespread common subspecies and two more geographically confined ones. Meiotic chromosome counts on pollen mother cells and mitotic chromosome counts on root tips were made on 364 populations ( = 3.1 plants per population). These population counts are ∼60% of all Tridentatae counts. Some are first records for taxa. The Tridentatae are a polyploid complex (x = 9) with ploidy levels from 2x to 8x, but mostly 2x (48%) and 4x (46%). Polyploidy occurs in nine of the 11 species and in many subspecies as well. Supernumerary or b chromosomes are present only at a low frequency. In the principal species, A. tridentata, 2x plants are larger than 4x ones, which are adapted to drier conditions, probably in consequence of their slower growth rates. Gigas diploidy is a phenomenon shared by some other woody genera, but is in contrast to the gigas polyploid nature of many herbaceous genera. Polyploidy occurs within populations and is essentially autoploid. Hybridization sometimes occurs at taxa interfaces in stable hybrid zones. Stable Tridentatae hybrid zones coupled with the group's inherent propensity for polyploidization has led to the establishment of a geographically and numerically large and successful complex of species.

Journal Article↗
PubMed1987

Significance of polyploidy in megakaryocytes and other cells in health and tumor disease.

Polyploidy--the doubling of chromosome sets of cells caused by a stop of mitosis at different levels of the mitotic cycle--is a phenomenon widely observed in plants, protozoa, metazoa, and animals. In man obligate polyploid tissues are found in liver parenchyma, heart muscle cells, and bone marrow megakaryocytes. Polyploidy occurs mostly in stable and highly differentiated cells and tissues. Besides age, stimulation of proliferation and increased metabolic function lead to polyploidization in these organs. Aneuploidy, however, is exclusively found in tumor cells. Megakaryocyte differentiation and polyploidy are controlled by thrombopoietin-like activities, of which the loci of production are still unknown. Megakaryocytes are unique among polyploid mammal cells. On the precursor level they maintain their proliferative activity independently of the mammal's age. Once having entered the incomplete mitotic cycle they stop cytokinesis and develop into highly polyploid cells. Polyploidization of megakaryocytes is the basic requirement for establishing highly effective hemostasis in mammals, which exhibit blood circulation based on high blood pressures. Every polyploidization results in increased production of membrane materials with which the platelet becomes endowed. By shedding cytoplasmic fragments approximately 3000 platelets are set free from a 32c megakaryocyte, compared with only 16 nucleated thrombocytes by mitotic division. There is further evidence that the heterogeneity of platelets mostly depends on the different polyploidy classes of the megakaryocytes from which they are derived. Changes in the polyploidy pattern of megakaryocytes could therefore have consequences for hemostatic disorders in several human diseases, particularly in malignancy.

Humans↗
PubMed2002

Megakaryocyte polyploidization is associated with a functional gene amplification.

It is believed that polyploidy induces an orchestrated increase in gene expression. To know whether all alleles remain functional during megakaryocyte polyploidization, we used a well-established fluorescence in situ hybridization technique which allows one to simultaneously detect pre-mRNAs and assess ploidy level in a single cell. All alleles of GPIIb, GPIIIa, VWF, beta-actin, hsp70, c-mpl, Fli-1, and FOG-1 genes are transcriptionally active in megakaryocytes from 4N to 32N. All X chromosomes in male cells are transcriptionally active but only half of them are transcriptionally active in female megakaryocytes, as revealed by the transcriptional activity of the GATA-1 gene. Nuclear untranslated XIST RNA accumulates on the inactivated X chromosomes, indicating that they are subjected to a normal inactivation process. Altogether, our results demonstrate that megakaryocyte polyploidization results in a functional gene amplification whose likely function is an increase in protein synthesis parallel with cell enlargement.

Alleles↗
PubMed2001

Heterologous expression of the transcriptional regulator escargot inhibits megakaryocytic endomitosis.

Certain cell types escape the strict mechanisms imposed on the majority of somatic cells to ensure the faithful inheritance of parental DNA content. This is the case in many embryonic tissues and certain adult cells such as mammalian hepatocytes and megakaryocytes. Megakaryocytic endomitosis is characterized by repeated S phases followed by abortive mitoses, resulting in mononucleated polyploid cells. Several cell cycle regulators have been proposed to play an active role in megakaryocytic polyploidization; however, little is known about upstream factors that could control endomitosis. Here we show that ectopic expression of the transcriptional repressor escargot interferes with the establishment of megakaryocytic endomitosis. Phorbol ester-induced polyploidization was inhibited in stably transfected megakaryoblastic HEL cells constitutively expressing escargot. Analysis of the expression and activity of different cell cycle factors revealed that Escargot affects the G(1)/S transition by influencing Cdk2 activity and cyclin A transcription. Nuclear proteins that specifically bind the Escargot-binding element were detected in endomitotic and non-endomitotic megakaryoblastic cells, but down-regulation occurred only during differentiation of cells that become polyploid. As Escargot was originally implicated in ploidy maintenance of Drosophila embryonic and larval cells, our results suggest that polyploidization in megakaryocytes might respond to mechanisms conserved from early development to adult cells that need to escape normal control of the diploid state.

CDC2-CDC28 Kinases↗
PubMed2004

Wilms tumors develop through two distinct karyotypic pathways.

Wilms tumor is an embryonic neoplasm characterized by a large variation in histologic patterns. Cytogenetic investigations have identified nonrandom chromosomal changes characteristic for this tumor type, of which numerical changes, mostly trisomies for chromosomes 7, 8, and 12, are particularly frequent. Despite the abundance of cytogenetic information, with more than 350 published karyotypes, very little is known about the mode of karyotypic evolution. In this investigation, we have used 355 karyotypes of Wilms tumor to identify frequent imbalances. The most frequent were +1q, +6, +7q, +8, +12, +13, -11, and -16. Tumor cases were then classified with respect to the presence or absence of these imbalances and statistically analyzed to assess the order of appearance of chromosomal imbalances, as well as possible karyotypic pathways. We show that Wilms tumors develop through one major mode of karyotypic evolution, common to both low- and high-complex tumors, and that polyploid cases are relatively rare. We also establish a temporal order by which the different imbalances occur and show that at least two cytogenetic pathways exist, one dominated by gains and another by losses. We also show that these pathways are well separated and do not share a common set of late imbalances.

Biological Evolution↗
PubMed2006

Regulation of growth by ploidy in Caenorhabditis elegans.

Some animals, such as the larvae of Drosophila melanogaster, the larvae of the Appendicularian chordate Oikopleura, and the adults of the nematode Caenorhabditis elegans, are unusual in that they grow largely by increases in cell size. The giant cells of such species are highly polyploid, having undergone repeated rounds of endoreduplication. Since germline polyploid strains tend to have large cells, it is often assumed that endoreduplication drives cell growth, but this remains controversial. We have previously shown that adult growth in C. elegans is associated with the endoreduplication of nuclei in the epidermal syncitium, hyp 7. We show here that this relationship is causal. Manipulation of somatic ploidy both upwards and downwards increases and decreases, respectively, adult body size. We also establish a quantitative relationship between ploidy and body size. Finally, we find that TGF-beta (DBL-1) and cyclin E (CYE-1) regulate body size via endoreduplication. To our knowledge, this is the first experimental evidence establishing a cause-and-effect relationship between somatic polyploidization and body size in a metazoan.

Animals↗
PubMed2001

Apomixis in Tripsacum: comparative mapping of a multigene phenomenon.

A relationship has been established between the expression of apomixis in natural polyploids of Tripsacum dactyloides and fertility as measured by percent seed set. Thus, fertility may be reliably used as a defining phenotype for apomixis when scoring the progeny from diploid (2n = 2x = 36) x tetraploid (2n = 4x = 72) crosses in Tripsacum. By exploiting the relationship between apomixis and fertility, as defined by seed set, analyses were performed on a set of related second-generation triploid populations segregating for apomixis. These populations were derived from sexual (diploid) x apomictic (tetraploid) crosses. Six out of 25 genome-dispersed restriction fragment length polymorphism (RFLP) markers co-segregate with fertility. Five of these markers were previously reported and include: php20855, tda48, tda53, umc62, and umc83, and are linked to Tripsacum genetic linkage groups F, I, H, L, and A, respectively. Significantly, we report here the syntenic relationships of the maize chromosome intervals to Tripsacum that segregate for numerous meiosis-specific and fertility-associated genes. Utilizing RFLP locus comparative mapping based on conservation of chromosome (genic) regions between related species, it may be concluded that the genes controlling fertility have been preserved in both Tripsacum and maize. A sixth marker, umc166, has also been shown to co-segregate with fertility and is conserved in both grass species. Specifically, umc166 is linked to Tripsacum linkage group D and, by syntenic comparison, to the short arm of maize chromosome 5. Encoded within this marked interval is the gene Ameiotic1 (Am1) whose function is required for the initiation of meiosis in both micro- and megaspore mother cells and whose absence of expression in the female is, in all likelihood, a prerequisite for the expression of apomixis.

Chromosome Mapping↗
PubMed2001

Polyploidy associated with oxidative injury attenuates proliferative potential of cells.

Polyploid cells are encountered ubiquitously but the biological significance of polyploidy is unclear. In view of their extensive capacity for regeneration, hepatocytes offer excellent systems for analyzing growth control mechanisms. We isolated hepatocytes from adult rats with and without two-third partial hepatectomy, which induces hepatic polyploidy. Polyploid hepatocytes showed evidence for oxidative injury with antioxidant depletion, lipid peroxidation and 8-hydroxy-adducts of guanine in nuclear DNA. Liver repopulation assays in intact animals showed markedly decreased replication capacity in polyploid hepatocytes. Recapitulation of polyploidy in cultured hepatocytes established that mitogenic stimulation in the presence of oxidative DNA injury was capable of inducing polyploidy. The findings provide novel frameworks in the context of polyploidy for understanding tissue development, regeneration and oncogenesis.

Animals↗
PubMed1995

Angiotensin converting enzyme inhibition prevents polyploidization of cardiomyocytes in spontaneously hypertensive rats with left ventricular hypertrophy.

Polyploidization of cardiomyocyte nuclei is a physiological phenomenon that increases in pathological conditions such as myocardial hypertrophy. The purpose of this study was to evaluate the potential benefit of the angiotensin converting enzyme (ACE) inhibitor quinapril in reversing the polyploidization of cardiomyocyte nuclei in spontaneously hypertensive rats (SHR) with established left ventricular hypertrophy (LVH). Sixteen week-old male SHR were treated with oral quinapril (average dose 10 mg/kg per day) for 20 weeks. Sixteen- and 36-week-old untreated SHR and 16- and 36-week-old normotensive Wistar-Kyoto (WKY) rats were used as controls. Nuclear polyploidization was determined by DNA flow cytometry of frozen tissues from the left ventricle, at least 20,000 nuclei being measured in each sample. The rates of tetraploidy in the 16- and 36-week-old SHR groups were 2.8 per cent (range 2.16-3 per cent) and 5.4 per cent (range 4.9-5.9 per cent), respectively. Treated SHR had a similar rate of DNA tetraploidy to the 16- and 36-week-old WKY rat groups: 1.8 per cent (range 1.5-2.3 per cent), 1.55 per cent (range 1.5-1.6 per cent), and 1.5 per cent (range 1.4-1.6 per cent), respectively. The differences in the percentage of tetraploid cardiomyocytes between the SHR untreated groups and the SHR treated group were statistically significant (P < 0.05). Regression of LVH and normalization of blood pressure were observed in treated rats. These results indicate that DNA tetraploidy in the myocardium of SHR increases with hypertrophy and decreases on quinapril treatment. It is suggested that ACE inhibition modifies nuclear processes involved in myocyte growth in arterial hypertension.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1993

Polyploidization by means of endoduplication in a human breast cancer cell line.

Near DNA diploid human adult solid tumors are often associated with certain near-tetraploid cells. In an established human breast cancer cell line, Hs578T, with a DNA index in the hyperdiploid region, polyploid cells appeared during exponential growth. Among clones generated from single cells and analyzed by the video time lapse technique, an intraclonal interdivision time (IDT) heterogeneity is presented that renders endoduplication a plausible explanation for the generation of the polyploid cells observed. This conclusion, drawn from our IDT analysis, is supported by curves drawn from counting grain-positive cells during continuous labeling with [3H]-thymidine. Our results are compared with a parallel analysis of the aneuploid human breast cancer cell line MDA-231, generating intraclonal IDT heterogeneity, due mainly to the mitotic instability of that line, as we reported previously.

Breast Neoplasms↗
PubMed1981

[Biorhythm changes in DNA synthesis in hepatocytes exposed to organophosphates and strontium-89].

The authors irradiated albino rats with I microc/gr strontium89 with previously modelled liver injury by FOS (Agria 1050). A temporary inhibition of the methodical activity was established as well as aberrant mitoses and strongly manifested polyploidity of the hepatic cells. Those phenomena faded quickly (within 8 days), with the exception of polyploidity, which as a sign of physiological regeneration the authors admit to be adaptive reaction directed to the restoration of the functional level of the liver on account of the hepatocytes preserved. Prior to the onset of tissue regeneration, the cellular one should be terminated, due to which, the mytotic activity was highly inhibited on the 3rd day of the irradiation, the DNA-synthesis cycle being lengthened and mainly on account of tgi, i.e. during the reparative biosynthesis the cell is incapable/of developing in the mitotic phase. After the presynthetic period is over the hepatocytes rapidly overcome the inhibition, tgi is considerably shortened and from presynthesis they almost immediately enter the period of mitosis. That requires an additional protein synthesis, manifested by the changes in serum protein. S and G1 proved to be most sensitive to DNA-synthesis blocking. The presynthetic period is essentially lengthened due to lesions of the cellular structures, synthesizing substances, necessary for entering S - i.e. the hepatocytes pass T, equal to the inhibition between G1 and S, its duration being proportional to the degree of the lesion of the organ.

Animals↗
PubMed1999

Maintenance of near-diploid karyotype of PA-1 human ovarian teratocarcinoma cells due to death of polyploid cells by chromosome fragmentation/pulverization.

Chromosome instability (polyploidy or aneuploidy) is one of the characteristics of malignant tumors. Human teratocarcinoma cell line PA-1, which was established more than 10 years ago, consists of a majority of near-diploid cells and a minority of polyploid cells, indicating that it is karyologically very stable. In the present study we investigated this genomic stability from the view point of cytogenetics. Cleavages and breaks in the chromosome were found in the metaphase of PA-1 polyploid cells, accompanied by the formation of polynucleosomal DNA fragments. These findings were absent in the near-diploid cells. In addition, polyploid cells did not show colony-formation ability by in situ analysis of cytogenetics in each colony. Thus, the maintenance of the near-diploid karyotype in PA-1 cells may be due to a blockage in the M-phase of the polyploid cells by functional mitotic checkpoints, if any, leading to cell death due to inability to enter the next cell cycle.

Chromosome Banding↗
PubMed1975

Underreplication of satellite dnas in polyploid ovarian tissue of Drosophila virilis.

The satellite DNAs of Drosophila virilis have been examined in diploid and polyploid tissues by isopycnic ultracentrifugation and thermal denaturation experiments. Previous work has established that the satellite DNAs are underreplicated in the polytene chromosomes of the salivary glands of D. virilis. The results of the present experiments demonstrate that this underreplication also takes place in the ovaries which contain nurse cells and follicle cells. These tissues are polyploid but do not show polytene chromosomes.

Animals↗
PubMed1994

[The rate of polyploid fertilization of ovocytes in in vitro fertilization in patients with an increased ovarian response].

Polyploid fertilization is a common cause of human embryo's early loss in in vivo (1-2%) and in in vitro fertilization (3-5%) as well. Cause of increased rate of polypoid fertilization in in vitro fertilization is multifactorial. The aim of this paper was to establish if high ovarian response to exogenous hormone stimulation of ovaries can be one of the causes of increased incidence of polyploid fertilization. The research included 125 patients from whom 568 ovocytes were obtained by ultrasound aspiratory punction of ovarian follicles. The gathered results point to the fact that exogenous ovarian stimulation and the degree of ovarian response have a significant influence on increase of polyploid fertilization's rate. Thus, in the group of patients from whom 11 or more ovocytes were obtained, the rate of polyploid fertilization amounted to 11.3%, whereas it is statistically significantly higher (p < 0.01) in regard to those in whom less important difference in the rate of polyploid fertilization considering applied schemes of ovulation's stimulation (p > 0.1) was not established nor was it established considering the age of patients (p > 0.05). Despite the fact that the rate of polyploid fertilization in in vitro conditions is higher that in the natural conception, this method of treating marital infertility opens a unique possibility to identify all irregularities considering fertilization and prevent development of such embryos on time as it happens at the very beginning of the preimplantational stage of ovum's fertilization in laboratory conditions.

Adult↗