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Results for “polyploidization”

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PubMed1975

The recognition and incidence of haploid and polyploid spermatozoa in man, rabbit and mouse.

The existence of polyploid mammalian spermatozoa has been inferred from studies of Feulgen-DNA absorption. Rabbit spermatozoa fell into two discrete groups with mean absorptions close to a 1:2 ratio (inferred to be haploids and diploids respectively); simple visual appraisal of the size of the head or nucleus gave an identical classification. The incidences of ploidy classes were 98-94% haploid, 1-06% diploid, 0-00% higher than diploid (N = 3010; from DNA measurements and visual appraisal of the size in a rabbit chosen to have a high incidence of diploids) and, correspondingly, 99-691%, 0-308%, 0-001% (N = 138001; from sixty-nine unselected rabbits, scored by visual appraisal of the size of the sperm head). In man also, virtually discrete groups with absorptions close to a 1:2 ratio existed and were inferred to be haploids and diploids respectively. A few human spermatozoa were found with absorptions corresponding to a ploidy of three and/or four. Visual appraisal of the size of the human sperm nucleus as Small, Medium or Large was only a partial guide to ploidy. All Small human spermatozoa measured for DNA absorption were found to be haploid. About two-thirds of Medium human spermatozoa were found, however, to be haploid, and some Large spermatozoa were haploid or diploid. The incidences of ploidy classes in the human were 99-37% haploid, 0-56% diploid, 0-07% higher than diploid (N = 5554; with consistency between duplicate slides and between two subjects; from DNA measurements and visual appraisal of nuclear size). The estimated incidence of diploid human spermatozoa is consistent with the known incidence oftriploid fetuses. In a mouse with a putatively high incidence of diploids, all 1000 DNA measurements were nevertheless within the haploid range, with one diploid encountered outside the main sampling.

Animals↗
PubMed1975

[Basic factors in the polyploidization of cerebellar Purkinfe cells in chick embryogenesis. III. Kinetics of RNA and DNA in Purkinje cell nuclei].

The content and concentration of RNA and DNA in the nuclei of the Purkinje cells of cerebellum of chick embryos (10-21 day-old) were determined by cytospectrophotometry. The RNA concentration shows a dayly rhythm, its content significantly increasing. The periods of the increase of RNA synthesis coincide with the periodicity of protein synthesis, the morphogenesis of the Purkinje cells and with the embryo's development as a whole. The DNA concentration remaining constant, its content increases sharply with the onset of the specific functional activity of cells and of the intensive growth of axons and dendrites. The variability of the mean values of this growth increases which is conditioned by the appearance of cells with hyperdiploid, tetraploid and hypertetraploid DNA contents in their nuclei. The Purkinje cells do not divide, their increased DNA content may be regarded as the expression of polyploidization or polytenization (which are functionaly equivalent) of a part of the nuclei. It is not excluded that in this case a differential gene amplification may take place. The increase of DNA content is associated with the onset of morphofunctional maturity of cells and may be due to a continuously increasing intensity of protein synthesis secured by the matrix material.

Animals↗
PubMedDate not supplied

[Changes in the content of different nuclear proteins and DNA from diploid and polyploid hepatocytes in regenerating liver of mice].

The content of 4 fractions of nuclear proteins (histones, acid chromatin protein, globulins and chromatin-free acid protein) in diploid and polyploid hepatocytes from intact and regenerating liver of mice is studied. These types of nuclei are found to differ in the protein content and in the protein/DNA ratio. Synthesis of all classes of nuclear proteins was intensified at the G1-stage, and synthesis of DNP non-histone proteins at the end of S- and G2-stage. Possible role of different nuclear proteins in the regulation of cell multiplication is discussed.

Animals↗
PubMedDate not supplied

[More active synthesis of the polysaccharide, pullulan, by polyploid cultures of Pullularia pullulans].

The polyploid strains of Pullularia pullulans differ from each other and from the haploid strain in the amount of the polysaccharide pullulan liberated into the cultural broth. The highest pullulan synthesizing activity (per unit of the assimilated carbon source and the synthesized biomass) was manifested by the diploid strain of P. pullulans 1125(13) whose cells produced more pullulan (by 75%) within three days of growth than the cells of the haploid culture. The content of pullulan calculated per unit area of the cell surface increased with the level of ploidy: 1.5-1.8 times in the diploid cultures and 3.4 times in the tetraploid culture cf. the parent haploid culture. Apparently, the polyploidy of the P. pullulans culture was accompanied with mutations involved in the synthesis of the extracellular polysaccharide.

Culture Media↗
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↗
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↗
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↗
PubMed1975

Differential replication of satellite DNA in polyploid tissues of Drosophila virilis.

Satellite DNA amounts were examined in adult tissues of Drosophila virilis, a species whose DNA contains three prominent satellites. Satellite amounts in DNA from six of the seven tissues were lower than in DNA from diploid (adult brain) tissue. Satellite amounts in adult ovary DNA, however, were equivalent to or greater than diploid levels. When DNA from pupal ovaries was examined, a 30% increase in satellite amounts over diploid levels was found. An RNA-DNA hybridization experiment showed that the ribosomal RNA genes in pupal ovary DNA were under-replicated relative to diploid DNA levels.

Animals↗