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PubMedDate not supplied

Induction of megakaryocytic characteristics in human leukemic cell line K562: polyploidy, inducers, and secretion of mitogenic activity.

Because of the rarity of megakaryocytes in the bone marrow, a cell line inducible for megakaryocytic characteristics provides a valuable model for study. When cultured with phorbol esters, the human multipotent hematopoietic leukemic cell line K562 can be induced to develop many megakaryocytic characteristics, viz. increased cell size, reduced growth rate, megakaryocytic antigens, and expression of the sis proto-oncogene, the structural gene for the B-chain of platelet-derived growth factor. Further aspects of this process are here presented. First, it induces the release of mitogenic activity into the medium. Second, phorbol dibutyrate induces polyploidy, a feature of normal megakaryocyte development. Third, mezerein and teleocidin, nonphorbol ester tumor promotors, also induce development of multinuclearity and polyploidy.

Cell Division↗
PubMed1999

Polyploidy: recurrent formation and genome evolution.

Polyploidy has played a major role in the evolution of many eukaryotes. Recent studies have dramatically reshaped views of polyploid evolution, demonstrating that most polyploid species examined, both plant and animal, have formed recurrently from different populations of their progenitors. Populations of independent origin can subsequently come into contact and hybridize, generating new genotypes. Because of the frequency of polyploidy in plants, many recognized species are probably polyphyletic. Extensive and rapid genome restructuring can occur after polyploidization. Such changes can be mediated by transposons. Polyploidization could represent a period of transilience, during which genomic changes occur, potentially producing new gene complexes and facilitating rapid evolution.

Journal Article↗
PubMed2002

Growth retardation, polyploidy, and multinucleation induced by Clast3, a novel cell cycle-regulated protein.

We have identified a novel gene, Clast3, by subtraction of cDNAs derived from activated and naive B lymphocytes. Clast3 expression is elevated in cycling cells and down-regulated in cells undergoing growth arrest, indicating that its expression is controlled in a cell cycle-dependent manner. The deduced amino acid sequence of Clast3 cDNA exhibits no significant homology to the known proteins in mammalian and other species. Immunofluorescence staining revealed that Clast3 localizes into discrete nuclear foci. Forced expression of Clast3 results in growth retardation, polyploidy, and generation of multinucleated cells. Treatment of Clast3 transfectants with nocodazole, a spindle-damaging agent, greatly enhances the incidence of the multinucleated cells, suggesting that Clast3 overexpression impairs the same checkpoint activated by nocodazole. Down-regulation of Clast3 expression by antisense oligonucleotides results in a decrease of cells at G(2)-M phase and a concomitant increase of apoptotic cells. These findings indicate that Clast3 is a novel cell cycle-regulated protein and that its constitutive overexpression induces polyploidy and multinucleation by interfering with the mitotic spindle checkpoint.

3T3 Cells↗
PubMed2005

Polyploidy and cellular mechanisms changing leaf size: comparison of diploid and autotetraploid populations in two species of Lolium.

BACKGROUND AND AIMS: Growth and development of plant organs, including leaves, depend on cell division and expansion. Leaf size is increased by greater cell ploidy, but the mechanism of this effect is poorly understood. Therefore, in this study, the role of cell division and expansion in the increase of leaf size caused by polyploidy was examined by comparing various cell parameters of the mesophyll layer of developing leaves of diploid and autotetraploid cultivars of two grass species, Lolium perenne and L. multiflorum. METHODS: Three cultivars of each ploidy level of both species were grown under pot conditions in a controlled growth chamber, and leaf elongation rate and the cell length profile at the leaf base were measured on six plants in each cultivar. Cell parameters related to division and elongation activities were calculated by a kinematic method. KEY RESULTS: Tetraploid cultivars had faster leaf elongation rates than did diploid cultivars in both species, resulting in longer leaves, mainly due to their longer mature cells. Epidermal and mesophyll cells differed 20-fold in length, but were both greater in the tetraploid cultivars of both species. The increase in cell length of the tetraploid cultivars was caused by a faster cell elongation rate, not by a longer period of cell elongation. There were no significant differences between cell division parameters, such as cell production rate and cell cycle time, in the diploid and tetraploid cultivars. CONCLUSION: The results demonstrated clearly that polyploidy increases leaf size mainly by increasing the cell elongation rate, but not the duration of the period of elongation, and thus increases final cell size.

Body Size↗
PubMed1995

Vascular smooth muscle polyploidy in genetic hypertension: the role of angiotensin II.

Flow cytometry DNA analysis has been used to measure the percentage of aortic vascular smooth muscle cells in G2 + M phase of the cell cycle in mature stroke-prone spontaneously hypertensive rats (SHRSP). The effects of three different pharmacological interventions on the cell cycle parameters have also been studied. Vascular smooth muscle cells isolated from SHRSP have significantly elevated G2 + M phase of the cell cycle compared with cells from the normotensive reference strain, Wistar-Kyoto (WKY). This observation reflects an increased tetraploid and octaploid cell populations in vivo. Treatment with a combination of hydralazine and hydrochlorothiazide had no effect on the percentage of cells in G2 + M phase of the cell cycle. Treatments with angiotensin converting enzyme inhibitor, perindopril or AT1 receptor antagonist, losartan, resulted in an equivalent blood pressure-lowering effect to that obtained with hydralazine/hydrochlorothiazide. In contrast to hydralazine/hydrochlorothiazide, these two treatments resulted in a highly significant regression of vascular smooth muscle polyploidy in the SHRSP. We hypothesise that angiotensin II plays an important role in cell cycle regulation in that, alone or in conjunction with one of the inhibitory proteins, it is able to stop the cell cycle progression after endoduplication but before the cytoplasmic division. Pharmacological interventions which remove an excess of angiotensin II may allow the cells to re-enter the cell cycle thus resulting in the regression of vascular smooth muscle polyploidy and improved arterial compliance.

Angiotensin II↗
PubMed2006

High-throughput analysis of chromosome abnormality in spontaneous miscarriage using an MLPA subtelomere assay with an ancillary FISH test for polyploidy.

Chromosome analysis of spontaneous miscarriages is clinically important but is hampered by frequent tissue culture failure and relatively low-resolution analysis. We have investigated replacement of conventional karyotype analysis with a quantitative subtelomere assay performed on uncultured tissue samples, which is based on Multiplex Ligation-Dependent Probe Amplification. This assay is suitable for this purpose as approximately 98% of all observed karyotype abnormalities in spontaneous miscarriages involve copy-number change to one or more subtelomere regions. A pilot study has compared karyotyping and subtelomere analysis on 78 samples. Extensive tissue necrosis accounted for failure of both karyotyping and subtelomere testing in four (5.1%) samples. Excluding these, there were no (0/74) subtelomere test failures compared to 9.5% (7/74) karyotype failures. Twenty-two (30%) whole chromosome aneuploidies and five (6.8%) structural abnormalities were detected using the subtelomere assay. With the exception of three cases of triploidy, all karyotype abnormalities were detected by the subtelomere assay. Following on from this study, a further 100 samples were tested using the subtelomere assay in conjunction with a simple ancillary FISH test using uncultured cells to exclude polyploidy in the event of a normal subtelomere assay result. Except for three necrotic samples, tests results were obtained for all cases revealing 18 abnormalities including one case of triploidy. Taking into consideration the high success rate for the combined MLPA and FISH test results, and the very significant additional advantages of cost-effective, high-throughput batching, and automated, objective analysis, this approach greatly facilitates routine investigation of chromosome abnormalities in spontaneous miscarriage.

Abortion, Spontaneous↗
PubMed1975

Colcemid-induced polyploidy and aneuploidy in normal and tumour cells in vitro.

The frequency of colcemid-induced genome mutations (aneuploidy and polyploidy) in normal and SV40-transformed cultures of Djungarian hamster embryonic cells was studied. Genome mutations were easily induced by the drug in transformed but not in normal cultures. Elevation of colcemid concentration and prolongation of the incubation period did not substantially increase the frequency of genome mutations in normal cells. An attempt was made to study the causes of the differences in sensitivity to colcemid-mutagenicity of normal and transformed cells. Transformed cells did not include more 3H-colchicine than normal cells, and binding of the drug to cell homogenates was similar in both kinds of cultures. According to these data the higher sensitivity of transformed cells to colcemid is not connected either with increased permeability of the cell to the drug or with changes in its binding to tubulin.

Aneuploidy↗
PubMed1990

Polyploidy in differentiation and evolution.

Somatic and generative (germ-line) polyploidy are more widely spread phenomena among living organisms than generally thought. The occurrence of polyploidization and related events in normal and pathological differentiation, their recognized main functions, as well as the structural specificities of polyploid nuclei are reviewed, and the relationship between ontogenetic and phylogenetic events is discussed. The mechanisms leading to the polyploid state, as well as other processes resulting in a genomic condition different from the diploid one (such as DNA under-replication, gene amplification, and chromatin elimination), are briefly sketched. The various changes in chromosomal DNA described are, in conclusion, seen as evidence supporting the paradigm of a "fluid" or dynamic organization of the eukaryotic genome, as being part of a cybernetic feedback regulation system of gene expression. A model is proposed that unifies the aspects of DNA variation, chromatin structure, and diversification in ontogenesis and phylogenesis.

Animals↗
PubMed1990

Megakaryocyte polyploidy as a grouped geometric distribution obeying the log-normal population law.

Discrete nuclear lobe scores and flow- or image-cytometry DNA values of classically identified megakaryocytes behave as a grouped geometric distribution. This model is fully specified by a geometric mean and standard deviation (GM and GSD), the latter typically being ca 1.16 for volumes of diploid blood cell populations. Via log-normal probability paper, the 30 to 50 megakaryocytes in clinical marrow smears readily yield the ploidy model's GM and GSD which are named MPM and MPD for megakaryocyte polyploidy median and dispersion. In euthrombopoietic outbred mammals, MPMs are ca 12N ploidy units, and MPDs approximate a factor of 1.41. Both are unitless criteria. Thus, the thrombon is characterized by three populations exhibiting the high size dispersion which unmasks canonical operation of the log-normal population law: picoliter megakaryothrombocytes with their MPD ca 1.41, femtoliter thrombocytes with a volume GSD ca 1.74, and the end product of locally delivered pieces of subattoliter platelet dust with a volume GSD ca. 2.0.

Animals↗
PubMed1979

Polyploidy in insect evolution.

Of all living organisms insects are the group with the highest number of existing species. It is, of course, true that a fraction of the total number of insects has been cytologically studied. Polyploid forms are rare exceptions among them. Polyploidy in insects is always associated with the parthenogenetic mode of reproduction. The cytologically verified cases are described. As for the geographic distribution of polyploid insects, they have successfully colonized vast land areas. Their distributions are, in general, northern and montane. The polyploid races are in general far more widespread than their diploid bisexual ancestors. The possible models of origin of polyploid insects are covered as well as data on their gaenetic variability. There are apparent environmental correlations in the distribution of certain forms. Most polyploid insects have life cycles extending over two (or more) years. They are also in general flightless forms. Hypotheses on the relation between heterozygosity in polyploids as well as the consequences of mutations in polyploid lineages are also presented.

Animals↗
PubMed1979

Polyploidy, plants, and electrophoresis.

Investigations of polyploidy using electrophoresis are at present severely limited by several areas of difficulty which limit all applications of this technique. The technical problems inherent in electrophoresis of plants, namely extraction of active extracts and maximizing resolution of electrophoretic variants through investigation of gel and especially assay conditions, have never been addressed explicitly. No rationale for initiating work on a new species is available. Analytical approaches to defining the conditions which limit resolution are rare. Gel-to-gel variation is poorly controlled, seldom monitored. The individual nature of electrophoretic investigations limits the comparability of data among labs. In short, "hit-and-miss" approaches predominate, and these limit investigation. Techniques are now available which one can hope will greatly improve the experimental situation.

Animal Population Groups↗
PubMed1979

Polyploidy in algae.

The green algae and the charophytes represent the most widely studied groups of algae in respect to their ploidy levels. In some genera increased size accompanies ploidy level changes as well as certain morphological modifications, but in other genera no evident obvious changes can be discerned. In the other major groups of algae, namely the Rhodophycophyta and Phaeophycophyta, few cases of polyploidy have been documented adequately. In the remaining groups, unusual nuclear phenomena and/or behavior have hampered studies and few species have adequately been studied in regard to their polidy levels.

Eukaryota↗
PubMed1979

Polyploidy in fungi.

There is evidence supporting a concept of polyploid evolution in a number of groups of fungi. These typically have dominant diploid phases in their life-histories. There are a number of reports of suspected polyploidy in other fungi, but these should be considered speculative at this time.

Ascomycota↗
PubMed1993

Polyploidies in abortion material decrease with maternal age.

Among 639 spontaneous abortions between the 8th and 14th week of gestation 342 (53.5%) revealed an abnormal karyotype. While the rate of trisomies distinctly increased with advancing maternal age, a decrease in the rate of 45,X conceptuses and polyploidies was observed among abortions from older women. The overall relation of XXXX:XXYY among the tetraploidies was 14:11 and that of XXX:XXY:XYY among the triploidies was 26:36:1. However, when the latter was related to maternal age, a reversal of the XXX:XXY ratio of 1:2 in the younger to 2:1 in the older age groups became evident. Furthermore a decrease in the rate of "paternally" derived partial hydatidiform moles was found among the triploid abortion specimens from older women. From these observations we conclude that digyny plays a major role in the origin of triploidy in the increased maternal age groups, while diandry related to immaturity of oocytes and impairment of oocyte cortical function is more frequent in triploid abortions from younger women.

Abortion, Spontaneous↗
PubMed1980

Polyploidy in mammalian urothelial cells.

The mitotic indices and the extent of polyploidy in urothelial cells of baboons, dogs and swine were studied. All three species had very low mitotic activity in vivo but short-term culturing of these cells in vitro stimulated mitosis thus enabling chromosome counts. Tetraploid cells were found in the urothelium of all three species, and higher ploidies also in dog and swine. There were substantial differences in the proportions of diploidy and higher ploidies among the three species and among individuals within each species. Dog urothelial cells were predominantly tetraploid (70%) while more swine cells were diploid (68%). Baboon urothelial cells had only two ploidy classes and 92% were diploid.

Animals↗
PubMed1980

Polyploidy in the australian leptodactylid frog genus Neobatrachus.

Karyotypic analysis of six species of the Australian leptodactylid frog genus Neobatrachus showed that N. pictus, N. centralis, N. pelobatoides and N. wilsmorei are diploid (2n = 24) while N. sudelli and N. sutor are tetraploid (4n = 48). Polyploidy has not been reported previously among Australian anurans. Idiograms of the six species indicate that they are similar to the other Australian leptodactylids so far discribed. DNA values of the tetraploids are approximately double the values for diploids. Tetraploid nuclear and cell sizes are greater compared with diploids but total body size shows no increase. At diakinesis in primary spermatocytes of tetraploids, mainly tetravalents together with a few bivalents are present. Silver straining of metaphase spreads clearly demonstrates the location of NORs at the secondary constrictions and their frequent association in the tetraploid N. sutor. Nucleolar number in interphase nuclei provides a reliable guide for distinguishing tetraploid from diploid frogs in the absence of chromosome analysis and can be determined for both living and preserved specimens. The possible origins and relationships of the tetraploid species are discussed.

Animals↗
PubMed1977

Rapid determination of polyploidy in human chorionic tissue sections.

Chromosomal analysis from aborted tissue has become an important diagnostic aid. However, the necessary cultures are frequently unsuccessful due to the condition of the aborted tissue. Polyploidy, in particular triploidy, in the conceptus is a common cause of early pregnancy loss and unlike aneuploidy does not appear to be associated with an increased recurrence risk. The necessity to monitor a subsequent pregnancy with amniocentesis is therefore eliminated. Therefore, in cases where a chromosomal anomaly is probable, a fast simple method of identification of a polyploid karyotype would be valuable. In this presentation, we describe a method using a scanning light microscope and histologic tissue preparations. This method can accurately determine the ploidy of the aborted material in 5 days.

Abortion, Spontaneous↗
PubMed1976

Polyploidy in the pancreas of the normal and diabetic mutant mouse.

The DNA content of endocrine and exocrine pancreatic nuclei of normal C57BL/KsJ and diabetic mutant C57BL/Ks-db/db mice was measured by Feulgen microdensitometry. The exocrine and endocrine pancreatic nuclei of the 4-week-old normal, 12-week-old normal, and 4-week-old (prehyperglycaemic) diabetic mutant mice contained diploid and tetraploid cells, while the 12-week-old (established hyperglycaemic) mutant contained diploid, tetraploid, and octaploid nuclei. The polyploidy in the endocrine pancreas of all these mice was confined to the B-cells, while the A-cells were always diploid.

Age Factors↗