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Results for “polyploidization”

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At least 163 records · Page 9Linked to original sources
PubMed1984

Polyploid cells in ageing hamster fibroblasts in vitro: possible implication of the centrosome.

Fibroblasts from hamster embryos cultivated in vitro present the typical ageing process of other fibroblastic lines, but they also suddenly give rise to giant non dividing cells which could be considered to represent terminally differentiated cells [36]. We investigated the latter mechanism, first by showing that microtubules in these cells depolymerized from the centrosome and not from the cell periphery as in other cells; secondly we analysed the structure of the centrosome on serial sections and found a diminished pericentriolar material; finally time lapse sequence studies of cell division confirmed that this process sometimes aborts giving rise to these giant polyploid cells. As a consequence, what first appeared as a differentiation process is in fact the result of an environmental deterioration which probably reaches a critical level thus creating a catastrophic consequence for the cell.

Animals↗
PubMed1982

[Formation of aberrant polyploid hepatocytes in exposure to the alkylating preparation dipin and to stimulation of proliferation].

One month after the treatment of mice with the alkylating drug Dipin followed by partial hepatectomy 4.7--35.1% of hepatocytes with micronuclei and nuclear bridges in liver were registered. The ploidy level sharply increased. Aberrant cells were the most polyploid ones (16c, 32c). The DNA-fuchsin content in these aberrant polypolid cells decreased by 10--15% due to degrading and non-replication of DNA in the micronuclei.

Alkylating Agents↗
PubMedDate not supplied

[Effect of carbon and nitrogen sources on pullulan biosynthesis by polyploid strains of Pullularia pullulans].

The effect of eight carbohydrates and three nitrogen sources on the activity of pullulan accumulation was studied with a haploid strain, a diploid strain and a tetraploid strain of Pullularia pullulans. The rate of pullulan biosynthesis was found to be the highest in media containing glucose, sucrose and maltose. In this case, the activity of the polysaccharide synthesis in the polyploid strains exceeded that in the haploid strain by 21-80% depending on the carbon source in the medium. The pullulan synthesizing activity of the tetraploid strain depended on the nature of these carbohydrates to a lesser extent than in the case of the haploid and diploid strains. The activity of pullulan synthesis was influenced noticeably by the source of nitrogen in the medium. The greatest amounts of pullulan were accumulated by the three strains in a medium with sodium nitrate.

Carbon↗
PubMed1980

Polyploidization of extraembryonic tissues during mouse embryogenesis.

It has recently been shown that visceral yolk-sac endoderm is derived from the primitive endoderm of the 4.5-day mouse blastocyst (Gardner & Papaioannou, 1975; Gardner & Rossant, 1979). During development, primitive endodermal cells acquire nuclei with more than four times the haploid amount of DNA. The finding of metaphases with multiple sets of chromosomes suggests that the diploid precursors of such endodermal giant cells become truly polyploid. Amniotic cells also contain giant nuclei but the mechanism by which these arise is uncertain. The giant-cell transformation therefore appears to be a general feature of mouse extraembryonic development rather than a phenomenon restricted solely to trophoblast. The basis and significance of these findings are discussed in relation to the development of other extraembryonic membranes both of plant and animal origin.

Animals↗
PubMed1981

Some flow cytofluorimetric studies of the nuclear ploidy of mouse hepatocytes. II. Early changes in nuclear ploidy of mouse hepatocytes following carbon tetrachloride administration: evidence for polyploid nuclei arrested in telophase.

Mature mice have a large proportion of their hepatocyte nuclei in polyploid states (tetraploid and octaploid), and this is more prominent in females. We measured nuclear ploidy distribution cytometrically using ethidium bromide-stained hepatocyte nuclei liberated by in situ collagenase perfusion of the liver via the portal vein. After s.c. administration of 0.2 ml carbon tetrachloride the ploidy distributions of 8-month-old female mice changed from a control of 35% 2N, 45% 4N, and 20% 8N to 54% 2N, 45% 4N and 1% 8N at 6 h, and 65% 2N, 35% 4N and 0% 8N at 24 h. By 72 h 92% of the nuclei were diploid. These changes preceded any changes in mitotic index and S-phase index (3H-TdR autoradiographs). Histology confirmed the loss of higher-ploid nuclei but without mitotic figures or selective cell necrosis to account for the observations. Cleaved nuclei were prominent in sections of liver examined 3 h after CCl4 administration and suggested division of polypoid nuclei that had undergone prior segregation of chromatids and had presumably been arrested in telophase.

Animals↗
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↗
PubMed1980

[Fragmentation of polyploid nuclei in rat trophoblast giant cells. II. Formation of deep folds in the nuclear envelope--the beginning of fragmentation].

Using light and electron microscopy, the nuclear envelope (NE) of the trophoblast giant cells has been examined at the beginning of the spontaneous fragmentation of nuclei on the last days of pregnancy (not long before their degeneration). In the course of the polyploid nucleus division, deep and narrow invaginations appear in the NE, frequently running through the whole nucleus, from one pole towards the other, and separating it into fragments. Short finger-like outgrowings are seen extending from the long invaginations perperdicularly or at a certain angel. Both the nuclear membrances, having numerous nuclear pores, are involved in the formation of these invaginations and shorter extentions. Local enlargements are seen produced in the perinuclear space, mainly in the area of NE invaginations. Narrow folds, separating the giant nucleus into fragments, are filled with the cytoplasm rich in ribosomes. In the nuclear fragments so produced, association between the earlier dispersed chromatin and the NE becomes stronger. Large accumulations of the condensed chromatin are mainly distributed under the NE, only a few minute chromatin blocks being found in the center of the nucleus filled up with diffuse chromatin.

Animals↗
PubMedDate not supplied

[Frequency of formation of mutants resistant to nystatin in polyploid strains of Candida scottii].

Polyploid strains of Candida scottii differ by their susceptibility to the action of nistatin. Haploid strain is most resistant, diploid strain is less resistant than haploid strain, and triploid strain is more susceptible than diploid strain. UV-treatment resulted in mutants which were 1.5--2 times more resistant to the action of nistatin than parent forms. The frequency of nistatin-resistant mutants increases with the ploidity of the cultures and with the doses of UV-irradiation.

Candida↗
PubMed2026

Ancient polyploidization waves as evolutionary shields for angiosperms.

Chen et al. identified 132 whole-genome duplications (WGDs) clustered around environmental crises. We highlight how, over longer evolutionary timescales, ancient WGDs convergently retained MADS-box, MYB, WRKY and HSF transcription factors, building stress-adaptation networks. These insights guide climate-resilient crop improvement through comparative genomics and CRISPR engineering.

MADS-box↗
PubMed1988

MCA/MR syndrome in a female infant with tetraploidy mosaicism: review of the human polyploid phenotype.

We report on a 3-month-old girl with unusual facial appearance, short neck with low posterior hairline, wide chest, valvular pulmonic stenosis, abnormal fingernails, and diploid-tetraploid mosaicism (46,XX/92,XXXX in 7.2% of peripheral leucocytes and in 29% of skin fibroblasts). Comparison with 11 previously reported cases with mosaic or complete tetraploidy does not establish an easily recognizable syndrome. However, a malformation pattern is apparent when tetraploidy patients are compared with 14 cases of triploid mosaicism and 44 previously reported cases of nonmosaic triploidy. A history of sex hormone exposure was present in 5 of 11 pregnancies resulting in tetraploidy; this exposure may correlate with the occurrence of tetraploidy in polycystic ovary syndrome and in tumors of the female reproductive tract. The mechanism of dysmorphogenesis involved in polyploidy is considered, including hypotheses of altered nuclear/cytoplasmic ratio, of trophoblastic alteration, of delayed cell division, or of altered autosome/active X chromosome ratio.

Abnormalities, Multiple↗
PubMed1977

Accumulation of polyploid cells and G2-phase cells during ascites tumor growth.

Ehrlich ascites tumor cells from the plateau phase of growth were transplanted into new hosts, pulse-labeled with tritiated thymidine and blocked with repeated injections of vinblastine. When unlabeled cells were analyzed for their cellular DNA content utilizing a cytophotometric technique it was found that in relation to the total number of cells (labeled plus unlabeled), 13% had a 2C DNA content, 36% a 4C DNA content and 5% and 8C DNA content at 0.5 hours after tranplantation. By 24 hours the distributions changed dramatically: the initally unlabeled 2C cells were now 4C, the 36% of the cells that were initially 4C partitioned into 24% that were still 4C and 12% that progressed to 8C, and the initial 8C cells remained 8C. These studies indicate that the accumulation of 4C cells during the plateau phase of growth is due to a combination of G2 diploid and G1 tetraploid cells.

Animals↗
PubMed1978

Spontaneous mutation rate to thioguanine resistance is decreased in polyploid hamster cells.

The mutation rate to thioguanine resistance was 3.11 X 10(-6) in a near diploid V79 hamster cell line and 7.58 X 10(-8) in a near tetraploid derivative produced with colchicine. The specific activities of glucose-6-phosphate dehydrogenase and phosphoglycerate kinase of the tetraploid line were greater than that of the diploid which suggests that twice the number of active X chromosomes were present in the tetraploid. These results are compatible with the hypothesis that spontaneous variants resistant to thioguanine arise through mutation and chromosomal segregation, as has been suggested for induced mutations in tetraploid hamster cells.

Cell Line↗
PubMed1989

Sexing the human fetus and identification of polyploid nuclei by DNA-DNA in situ hybridisation in interphase nuclei.

Samples of human adult lymphocytes, fetal lymphocytes, amniotic fluid cells, and chorionic villus cells were sexed independently by cytogenetics and DNA-DNA in situ hybridisation to a tritiated Y probe. For the in situ hybridisation analysis, the presence of Y bodies (hybridisation bodies) in 100 interphase nuclei were scored after autoradiography. In all, 82/83 samples were sexed in this way (one technical failure) and 78/82 were sexed by both in situ hybridisation and cytogenetics. There was complete agreement between the two methods. There was a considerable variation (40-100%) in the percentage of interphase nuclei with a hybridisation body among the male samples, but very few nuclei from female samples showed significant hybridisation. In situ hybridisation could be used to sex the conceptus when males but not females are at risk for various X-linked genetic disorders and may also be useful for detecting 45,X/46,XY mosaicism or polyploid/diploid mosaicism. This would be particularly useful for direct preparations of chorionic villus samples, which often prove difficult to analyse cytogenetically but offer the best means of avoiding maternal contamination. Some interphase nuclei had more than one hybridisation body, and this was most commonly found among amniotic fluid cells. Comparison of sizes of nuclei with one or two hybridisation bodies strongly suggested that most of the amniotic fluid cell nuclei with two hybridisation bodies were tetraploid.

Adult↗
PubMed1988

Polyploid fragile strains of Saccharomyces cerevisiae--a novel source of proteins for nutritional purposes.

A series of prototrophic fragile strains of different ploidy (2n, 3n and 4n) has been genetically constructed on the basis of haploid srb1 containing segregants of the fragile Saccharomyces cerevisiae mutant VY 1160. The strains have been characterized by several criteria. In regard to generation time, biomass yield, and nucleic acids content of the cells, the tetraploid srb1 homozygous hybrid is indistinguishable from an industrial strain of S. cerevisiae. However, it is characterized by a higher protein content. Unlike any other laboratory or industrial strains, the original mutant and these hybrids possess an ability for lysis upon suspension in hypotonic solutions. The dependence of the percentage of lysed cells on the growth phase and concentration of osmotic stabilizer in the medium has been investigated. The quantity of proteins in the soluble and insoluble fractions obtained after lysis of these strains by osmotic shock has been determined. These hybrids can be considered as a potential industrial source of proteins for nutritional purposes.

Culture Media↗