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Results for “polyploidization”

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PubMedDate not supplied

[Polyploidization of rat hepatocytes induced by x-ray radiation at different periods of the cell cycle].

As determined by the yield of polyploid hepatocytes after X-irradiation of rats with a dose of 6 Gy the S-stage of the cell cycle was most radiosensitive; as to the yield of cells with chromosome aberrations the middle of the G1-stage was the most radiosensitive period of the cell cycle. The differences in the radiosensitivity of the cell cycle stages indicated that although primary lesions were similar molecular mechanisms leading to tre final effect were essentially different.

Animals↗
PubMed1979

Polyploidization and hemiploidization induced by PUVA in vivo.

To obtain additional information on the in vivo injury induced by PUVA treatment, primary cultures were initiated from biopsies of the uninvolved skin of 15 PUVA-treated psoriatic patients, and the cells generated were analysed for morphological and chromosomal modifications. Three biopsies were obtained from each patient, the first one before commencing PUVA therapy (control) and the other two during the course of therapy. It was found that PUVA treatment has diverse effects on the mitotic activity, mitotic mechanisms and chromosomes of the cutaneous cells: (1) an inhibition of cell proliferation during the early stages of therapy followed by a reversion to normal proliferation as the PUVA treatments were continued; the production of (2) cells with more than one nucleus, (3) macrocells, (4) cells with micronuclei, (5) polyploid cells, (6) haploid cells, (7) cells with 13 chromosomes denoting a twofold reduction in the normal number of metaphase chromosomes, (8) end-associations of the chromosomes as in the pachytene phase of meiosis (9) diplotene chromosomes, and (10) chromosomal translocations.

Cell Division↗
PubMed1979

[Intranuclear and cytoplasmic annulate lamellae in the polyploid giant cells of the trophoblast].

Intranuclear and cytoplasmic annulate lamellae in polyploid giant cells of the trophoblast have been studied in rat placenta on days 12--17 of development. The annulate lamellae are present in the cytoplasm within a limited time, being visible on day 12 only. These are arranged in bundles near the nucleus to be moving then to the cytoplasm. The end parts of annulate lamellae are broadened to make cisterns of rough endoplasmic reticulum. Unlike the cytoplasmic annulate lamellae, those found within the nucleus are seen in part of the nuclei investigated throughout the whole period examined to look as single structures (not gathered in bundles), they can be branching, separating closed spaces within the nucleus (making local swellings in the loci of branching; the latter having electron dense or transparent vesicles). Association with nuclear chromatin in some regions is a peculiar feature of the intranuclear annulate lamellae. This association is especially obvious at endoprophase in the cycle ofthe polytene nucleus during the somatic conjugation--chromonemes unite in a bundle and condense. Ultrastructural changes of the annulate lamellae is noted throughout the polytene nucleus cycle and during the cell differentiation. It is supposed that in the case of temporary labile chromosome polyteny in the nuclear cycle, which is characteristic of mammalian trophoblasts, annulate lamellae can well compare, in their function, with the synaptonemal complex--these prevent from too tight associations of homologues in the course of somatic conjugation of chromosomes.

Animals↗
PubMed1979

[Plication of the nuclear membrane and its derivatives in the polyploid cell nuclei of the rat trophoblast].

Folding pattern of the nucleus envelope and intranuclear membrane structures in trophoblast giant cells and in trophoblast of the intermediate region of the rat placenta have been studied. Cells of the intermediate region of the placenta demonstrate deep invaginations resulting in the appearance of lobulated nuclei. Invaginations of the nuclear envelope pass on a narrow fold made by an inner nuclear membrane. The polyploid nuclei of trophoblast giant cells have superficial folds and deeper finger-like invaginations in their envelopes. Such folding trophoblast nuclei in two populations examined are met throughout the whole ontogenesis of the cell. In the giant cells, individual intranuclear tubes or their accumulations are seen. The tubes are made by a unit membrane and are surrounded with a matrix. The nuclear chromatin, diffuse or condenced, is in association with the tube surface. The tubes are met near the nucleolus and on its surface, where these are surrounded with the granular component of the nucleolus. In the trophoblast of the intermediate region of the placenta, intranuclear concentric membranes have been found; made of paired membranes, intramembranous space being filled with electron dense matrix. The concentric membranes lie separately in the karyoplasm, not being associated with the chromatin.

Animals↗
PubMed1978

[Effect of experimental arrest of eye growth on the proliferation and polyploidization of the retinal pigment epithelium in rats].

Following the lens removal from the left eye of the newborn rats, animals were obtained with one normal (control) and another microphtalmic eye. The animals were sacrificed on the 2nd, 3rd, 5th, 7th and 9th days of postnatal development after four injections of 3H-thymidine during 19 hrs. The number of labelled nuclei and mono- and binuclear cells in the central zone of the eye fundus was counted on the autographs. After the initial increase of the index of labelled nuclei in the operated eyes (on the 2nd, 3rd and 5th days) it fell below the control level (on the 7th and 9th days). The number of binuclear cells in the operated eyes, as well as in the control, attains on the 5th day 50% of the total number of cells and remains at this level up to the end of the experiment, whereas in the control eyes the number of binuclear cells increases up to 60% on the 7th and 80% on the 9th day. The results obtained have shown that in rats the factors of total eye growth participate in the control of proliferative activity and polyploidization of the pigment epithelium cells in the retina.

Age Factors↗
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↗
PubMed1994

Mode of inheritance of the higher degree of megakaryocyte polyploidization in C3H mice. I. Evidence for a role of genomic imprinting in megakaryocyte polyploidy determination.

C3H mice have higher average ploidy megakaryocytes than all other mouse strains tested, but the mode of inheritance of this anomaly is unknown. Therefore, to clarify the genetics of high ploidy megakaryocytes in C3H mice, we measured megakaryocyte DNA content from both male and female offspring from F1, as well as backcross matings. In all, offspring from seven different matings of mice were studied: (1) C57BL X C57BL (the first strain listed is the male parent in each case), (2) B6C3F1 (offspring from C57BL X C3H mating) X C57BL, (3) C57BL X B6C3F1, (4) C57BL X C3H, (5) C3H X B6C3F1, (6) B6C3F1 X C3H, and (7) C3H X C3H. The polyploid megakaryocyte DNA content distributions of the offspring from these matings show that C3H mice have higher percentages of high ploidy megakaryocytes than did all other mice. Also, male mice had significantly higher percentages of high ploidy (32N and 64N) megakaryocytes than did female mice for all matings, except backcross mating no. 6. The megakaryocyte DNA content for individual offspring of a given backcross appeared to form a single, continuous distribution, rather than segregate into two distinct groups, suggesting that the higher megakaryocyte DNA content of C3H mice is caused by involvement of multiple allelles. This conclusion is further supported by our finding that the frequency of high ploidy megakaryocytes among offspring of the various matings was related to the proportion of C3H genotype contributed by the parents, ie, average megakaryocyte DNA content increased linearly (r2 = .88 for male mice and .84 for female mice. P < .0001) with increasing C3H gene dosage; the correlations for both male and female mice were essentially parallel (slope = 0.08 and 0.09, respectively). In addition, we found an effect of genomic imprinting on megakaryocyte DNA content in backcross offspring. The genetic imprinting was characterized by the female parent having a greater influence on the offspring's megakaryocyte DNA content than the male parent, ie, although the overall genetic makeup was the same, female offspring from backcross no. 6 (in which the female was C3H) had higher average megakaryocyte ploidy values than those from backcross no. 5 (in which the female was B6C3F1).(ABSTRACT TRUNCATED AT 400 WORDS)

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↗
PubMed1996

The role of p53 in the induction of polyploidity of myelomonocytic leukemic M1/2 cells.

p53 was shown to play a central role in the maintenance of genomic integrity. The present experiments suggest that p53 is involved in the control of cell ploidity. Using a p53 non-producer cell line, M1/2, that was reconstituted to express either wild type or mutant p53 protein, by infection with the temperature sensitive (Ts) p53Val135 virus, it was found that both loss of wild type p53 or overexpression of mutant p53, may be associated with the generation of cell polyploidity. Overexpression of mutant p53 protein enhanced the appearance of giant cells that further accumulated following gamma-irradiation. Expression of wild type p53 reduced the level of giant cells which accumulated in the parental M1/2 p53 non-producer cells following gamma-irradiation. This activity of the wild type p53 seems to be mediated by either the reduction in the rate of giant cell generation, as observed in M1/2 derived cell lines expressing low levels of wild type p53 protein or by facilitating their apoptosis, as observed in wild type p53 high-producer cells. The latter conclusion is further supported by the observation that isolated giant cells are directly induced to undergo apoptosis following wild type p53 expression.

Animals↗
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↗
PubMed1996

Increased stringency of the 1,25-dihydroxyvitamin D3-induced G1 to S phase block in polyploid HL60 cells.

Treatment of mammalian cells with 1,25-dihydroxyvitamin D3 (1,25D3) produces a G1 to S (G1/S) phase cell cycle block. In addition, it has been noted that a smaller proportion of cells accumulates in the G2/M compartment in 1,25D3-treated cultures. Since cyclins have a major influence on the regulation of cell cycle progression, we determined the expression of cyclins A and B as markers of the G2 phase and of cyclin E as the marker of G1/S transition. No increase in the steady-state levels of cyclin A or cyclin B mRNA was detected in the total cell population or in the cyclin B1 protein in the G2/M cell cycle compartment. In contrast, immunodetectable cyclin E protein was increased in cell cultures as a whole and specifically in the G2/M compartment cells. Determination of BrdU incorporation into DNA by flow cytometry showed marked inhibition of DNA replication in cells with DNA content higher than 4C, and autoradiography of 3H-TdR-pulsed cells showed that polynucleated cells did not replicate DNA after 96 h of treatment with 1,25D3 or analogs. Taken together, these experiments show that at least a portion of the G2/M compartment in 1,25D3-arrested cultures of HL60 cells represents G1 cells at a higher ploidy level, which are blocked from entering the high ploidy S phase.

Calcitriol↗