Polyploidy: The chromosomal constitution of a cell containing multiples of the normal number of CHROMOSOMES; includes triploidy (symbol: 3N), tetraploidy (symbol: 4N), etc.Ploidies: The degree of replication of the chromosome set in the karyotype.Genome, Plant: The genetic complement of a plant (PLANTS) as represented in its DNA.Triploidy: Polyploidy with three sets of chromosomes. Triploidy in humans are 69XXX, 69XXY, and 69XYY. It is associated with HOLOPROSENCEPHALY; ABNORMALITIES, MULTIPLE; PARTIAL HYDATIDIFORM MOLE; and MISCARRAGES.Diploidy: The chromosomal constitution of cells, in which each type of CHROMOSOME is represented twice. Symbol: 2N or 2X.Ferns: Seedless nonflowering plants of the class Filicinae. They reproduce by spores that appear as dots on the underside of feathery fronds. In earlier classifications the Pteridophyta included the club mosses, horsetails, ferns, and various fossil groups. In more recent classifications, pteridophytes and spermatophytes (seed-bearing plants) are classified in the Subkingdom Tracheobionta (also known as Tracheophyta).Chromosomes, Plant: Complex nucleoprotein structures which contain the genomic DNA and are part of the CELL NUCLEUS of PLANTS.Tetraploidy: The presence of four sets of chromosomes. It is associated with ABNORMALITIES, MULTIPLE; and MISCARRAGES.DNA, Plant: Deoxyribonucleic acid that makes up the genetic material of plants.Genome Size: The amount of DNA (or RNA) in one copy of a genome.Gene Duplication: Processes occurring in various organisms by which new genes are copied. Gene duplication may result in a MULTIGENE FAMILY; supergenes or PSEUDOGENES.Noscapine: A naturally occurring opium alkaloid that is a centrally acting antitussive agent.Achillea: A plant genus of the family ASTERACEAE that has long been used in folk medicine for treating wounds.Thalictrum: A plant genus of the family RANUNCULACEAE. Members contain isoquinoline alkaloids and triterpene glycosides.Cleome: A plant genus of the family CAPPARACEAE that contains cleogynol and 15alpha-acetoxycleomblynol (dammaranes) and 1-epibrachyacarpone (a triterpene), and ISOTHIOCYANATES.Endoreduplication: A type of nuclear polyploidization in which multiple cycles of DNA REPLICATION occur in the absence of CELL DIVISION and result in a POLYPLOID CELL.Evolution, Molecular: The process of cumulative change at the level of DNA; RNA; and PROTEINS, over successive generations.Gossypium: A plant genus of the family MALVACEAE. It is the source of COTTON FIBER; COTTONSEED OIL, which is used for cooking, and GOSSYPOL. The economically important cotton crop is a major user of agricultural PESTICIDES.Angiosperms: Members of the group of vascular plants which bear flowers. They are differentiated from GYMNOSPERMS by their production of seeds within a closed chamber (OVARY, PLANT). The Angiosperms division is composed of two classes, the monocotyledons (Liliopsida) and dicotyledons (Magnoliopsida). Angiosperms represent approximately 80% of all known living plants.Mitosis: A type of CELL NUCLEUS division by means of which the two daughter nuclei normally receive identical complements of the number of CHROMOSOMES of the somatic cells of the species.Genes, Duplicate: Two identical genes showing the same phenotypic action but localized in different regions of a chromosome or on different chromosomes. (From Rieger et al., Glossary of Genetics: Classical and Molecular, 5th ed)Hybridization, Genetic: The genetic process of crossbreeding between genetically dissimilar parents to produce a hybrid.Genes, Chloroplast: Those nucleic acid sequences that function as units of heredity which are located within the CHLOROPLAST DNA.Aneuploidy: The chromosomal constitution of cells which deviate from the normal by the addition or subtraction of CHROMOSOMES, chromosome pairs, or chromosome fragments. In a normally diploid cell (DIPLOIDY) the loss of a chromosome pair is termed nullisomy (symbol: 2N-2), the loss of a single chromosome is MONOSOMY (symbol: 2N-1), the addition of a chromosome pair is tetrasomy (symbol: 2N+2), the addition of a single chromosome is TRISOMY (symbol: 2N+1).Portulacaceae: A plant family of the order Caryophyllales, subclass Caryophyllidae, class Magnoliopsida. There are no true petals; each flower has two to six sepals. They produce betacyanin and betaxanthin pigments and lack anthocyanins.Tragopogon: A plant genus of the family ASTERACEAE. The root and shoots have been used for food.Nocodazole: Nocodazole is an antineoplastic agent which exerts its effect by depolymerizing microtubules.Genes, Plant: The functional hereditary units of PLANTS.Phylogeny: The relationships of groups of organisms as reflected by their genetic makeup.Aurora Kinases: A family of highly conserved serine-threonine kinases that are involved in the regulation of MITOSIS. They are involved in many aspects of cell division, including centrosome duplication, SPINDLE APPARATUS formation, chromosome alignment, attachment to the spindle, checkpoint activation, and CYTOKINESIS.Aurora Kinase B: An aurora kinase that is a component of the chromosomal passenger protein complex and is involved in the regulation of MITOSIS. It mediates proper CHROMOSOME SEGREGATION and contractile ring function during CYTOKINESIS.Apomixis: Asexual reproduction resulting in the formation of viable seeds from FLOWERS without fertlization (i.e. use of POLLEN). Progeny plants produced from apomictic seeds are perfect clones of the parent.Onagraceae: The evening primrose plant family of the order Myrtales, subclass Rosidae, class Magnoliopsida. Flower parts are mostly in fours and the ovary is inferior.Aneugens: Agents which affect CELL DIVISION and the MITOTIC SPINDLE APPARATUS resulting in the loss or gain of whole CHROMOSOMES, thereby inducing an ANEUPLOIDY.Reproductive Isolation: Mechanisms that prevent different populations from exchanging genes (GENE FLOW), resulting in or maintaining GENETIC SPECIATION. It can either prevent mating to take place or ensure that any offspring produced is either inviable or sterile, thereby preventing further REPRODUCTION.Reproduction, Asexual: Reproduction without fusion of two types of cells, mostly found in ALGAE; FUNGI; and PLANTS. Asexual reproduction occurs in several ways, such as budding, fission, or splitting from "parent" cells. Only few groups of ANIMALS reproduce asexually or unisexually (PARTHENOGENESIS).Megakaryocytes: Very large BONE MARROW CELLS which release mature BLOOD PLATELETS.Gametogenesis, Plant: The process of germ cell development in plants, from the primordial PLANT GERM CELLS to the mature haploid PLANT GAMETES.Genomic Instability: An increased tendency of the GENOME to acquire MUTATIONS when various processes involved in maintaining and replicating the genome are dysfunctional.Acanthaceae: A plant family of the order Lamiales. It is characterized by simple leaves in opposite pairs, cystoliths (enlarged cells containing crystals of calcium carbonate), and bilaterally symmetrical and bisexual flowers that are usually crowded together. The common name for Ruellia of wild petunia is easily confused with PETUNIA.Rosa: A plant genus in the family ROSACEAE and order Rosales. This should not be confused with the genus RHODIOLA which is sometimes called roseroot.Cytokinesis: The process by which the CYTOPLASM of a cell is divided.Dipsacaceae: A plant family of the order Dipsacales, subclass Asteridae, class Magnoliopsida. It is sometimes called the teasel family.Solanaceae: A plant family of the order Solanales, subclass Asteridae. Among the most important are POTATOES; TOMATOES; CAPSICUM (green and red peppers); TOBACCO; and BELLADONNA.Biological Evolution: The process of cumulative change over successive generations through which organisms acquire their distinguishing morphological and physiological characteristics.Ecotype: Geographic variety, population, or race, within a species, that is genetically adapted to a particular habitat. An ecotype typically exhibits phenotypic differences but is capable of interbreeding with other ecotypes.Synteny: The presence of two or more genetic loci on the same chromosome. Extensions of this original definition refer to the similarity in content and organization between chromosomes, of different species for example.Genetic Speciation: The splitting of an ancestral species into daughter species that coexist in time (King, Dictionary of Genetics, 6th ed). Causal factors may include geographic isolation, HABITAT geometry, migration, REPRODUCTIVE ISOLATION, random GENETIC DRIFT and MUTATION.Cell Cycle: The complex series of phenomena, occurring between the end of one CELL DIVISION and the end of the next, by which cellular material is duplicated and then divided between two daughter cells. The cell cycle includes INTERPHASE, which includes G0 PHASE; G1 PHASE; S PHASE; and G2 PHASE, and CELL DIVISION PHASE.Brassica rapa: A plant species cultivated for the seed used as animal feed and as a source of canola cooking oil.Spindle Apparatus: A microtubule structure that forms during CELL DIVISION. It consists of two SPINDLE POLES, and sets of MICROTUBULES that may include the astral microtubules, the polar microtubules, and the kinetochore microtubules.In Situ Hybridization, Fluorescence: A type of IN SITU HYBRIDIZATION in which target sequences are stained with fluorescent dye so their location and size can be determined using fluorescence microscopy. This staining is sufficiently distinct that the hybridization signal can be seen both in metaphase spreads and in interphase nuclei.Contig Mapping: Overlapping of cloned or sequenced DNA to construct a continuous region of a gene, chromosome or genome.Chromosomes, Artificial, Bacterial: DNA constructs that are composed of, at least, a REPLICATION ORIGIN, for successful replication, propagation to and maintenance as an extra chromosome in bacteria. In addition, they can carry large amounts (about 200 kilobases) of other sequence for a variety of bioengineering purposes.Panicum: A plant genus of the family POACEAE. The seed is one of the EDIBLE GRAINS used in millet cereals and in feed for birds and livestock (ANIMAL FEED). It contains diosgenin (SAPONINS).Plants: Multicellular, eukaryotic life forms of kingdom Plantae (sensu lato), comprising the VIRIDIPLANTAE; RHODOPHYTA; and GLAUCOPHYTA; all of which acquired chloroplasts by direct endosymbiosis of CYANOBACTERIA. They are characterized by a mainly photosynthetic mode of nutrition; essentially unlimited growth at localized regions of cell divisions (MERISTEMS); cellulose within cells providing rigidity; the absence of organs of locomotion; absence of nervous and sensory systems; and an alternation of haploid and diploid generations.Cyclin D3: A broadly expressed type D cyclin. Experiments using KNOCKOUT MICE suggest a role for cyclin D3 in LYMPHOCYTE development.Organophosphates: Carbon-containing phosphoric acid derivatives. Included under this heading are compounds that have CARBON atoms bound to one or more OXYGEN atoms of the P(=O)(O)3 structure. Note that several specific classes of endogenous phosphorus-containing compounds such as NUCLEOTIDES; PHOSPHOLIPIDS; and PHOSPHOPROTEINS are listed elsewhere.Genetic Variation: Genotypic differences observed among individuals in a population.Thysanoptera: An order of very small, fringed-wing INSECTS including many agricultural pests.Brassica napus: A plant species of the family BRASSICACEAE best known for the edible roots.Chromosomal Instability: An increased tendency to acquire CHROMOSOME ABERRATIONS when various processes involved in chromosome replication, repair, or segregation are dysfunctional.Gene Dosage: The number of copies of a given gene present in the cell of an organism. An increase in gene dosage (by GENE DUPLICATION for example) can result in higher levels of gene product formation. GENE DOSAGE COMPENSATION mechanisms result in adjustments to the level GENE EXPRESSION when there are changes or differences in gene dosage.

*  Is sugar water good for plants? | Reference.com

What are the advantages of polyploidy in plants?. * Q: What are some good cottage garden plants?. ...

*  Genetic and epigenetic reprogramming of the wheat genome upon allopolyploidization - LEVY - 2004 - Biological Journal of the...

In the past few years we have analysed alterations in genome structure and expression that occur in wheat upon allopolyploidization. Our major findings in natural and synthetic allopolyploid wheat are reviewed here. It was found that allopolyploidization brings about rapid genome evolution through the instantaneous generation of a variety of cardinal genetic and epigenetic alterations comprising: (1) non-random elimination of coding and non-coding DNA sequences, (2) epigenetic changes such as DNA methylation of coding and non-coding DNA leading, among others, to gene silencing, and (3) activation of retroelements, which in turn alters the expression of adjacent genes. These changes were reproducible, occurring in the F1 hybrids or in the first generation(s) of a series of nascent allopolyploids corresponding to various interspecific and intergeneric combinations. Moreover, these changes were similar to those that occurred twice in nature: first, at the transition from diploid to tetraploid wheat ...

*  HHMI Scientists Search Results | Howard Hughes Medical Institute (HHMI)

Aneuploidy, Polyploidy, and Cancer Dana-Farber Cancer Institute Boston, MA Paul Modrich, PhD Investigator DNA Mismatch Repair ...

*  HHMI Scientists Search Results | Howard Hughes Medical Institute (HHMI)

Aneuploidy, Polyploidy, and Cancer Dana-Farber Cancer Institute Boston, MA Daniel Haber, MD, PhD Investigator Genetic Markers ...

*  HHMI Scientists Search Results | Howard Hughes Medical Institute (HHMI)

Aneuploidy, Polyploidy, and Cancer Dana-Farber Cancer Institute Boston, MA Michael Rape, PhD Investigator Ubiquitin-dependent ...

*  HHMI Scientists Search Results | Howard Hughes Medical Institute (HHMI)

Aneuploidy, Polyploidy, and Cancer Dana-Farber Cancer Institute Boston, MA Robert Tjian, PhD Investigator Mechanisms of Gene ...

*  HHMI Scientists Search Results | Howard Hughes Medical Institute (HHMI)

Aneuploidy, Polyploidy, and Cancer Dana-Farber Cancer Institute Boston, MA Sue Biggins, PhD Investigator Structure and Function ...

*  Myc increases self-renewal in neural progenitor cells through Miz-1 | Journal of Cell Science

Myc may cause polyploidy in NPCs but it does not increase apoptosis. Our analysis of the DNA content of the Myc NPC populations ... Myc may cause polyploidy in NPCs but it does not increase apoptosis. (A) Tetraploid Myc NPCs were found in one of the three ...

*  JCI - The insulin/Akt pathway controls a specific cell division program that leads to generation of binucleated tetraploid...

From polyploidy to aneuploidy, genome instability and cancer. Nat. Rev. Mol. Cell Biol. 5:45-54. View this article via: ... Hepatic polyploidy and liver growth control. Semin. Cancer Biol. 10:161-171. View this article via: CrossRef PubMed Google ... Cell polyploidy: its relation to tissue growth and function. Int. Rev. Cytol. 50:275-332. View this article via: CrossRef ... Polyploidy in the human myometrium. Z. Mikrosk. Anat. Forsch. 89:18-26. View this article via: PubMed Google Scholar ...

*  Hs 578Bst ATCC ® HTB-125™ Homo sapiens mammary gland; breast

Polyploidy occurred at 6.9%. Both X chromosomes were normal. The chromosome N9 pair was heteromorphic for the centromeric ...

*  Taimed - Vikipeedia, vaba entsüklopeedia

2011). Ancestral polyploidy in seedplants and angiosperms. Nature 473, 97-100. *↑ Newman, T., de Bruijn, F.J., Green, P. et al ...

*  Integration of Insulin receptor/Foxo signaling and dMyc activity during muscle growth regulates body size in Drosophila |...

Brodsky, W. Y. and Uryvaeva, I. V. (1977). Cell polyploidy: its relation to tissue growth and function. Int. Rev. Cytol. 50,275 ...

*  Antievolution.org - Antievolution.org Discussion Board -Topic::Blood-clotting, evolution, and Behe

Polyploidy is where the cell nucleus contains multiple sets of chromosomes. Humans are diploid meaning we have two copies of ... One way that genome duplication can occur is through polyploidy and subsequent degeneration back to a lower ploidy state. ( ...

*  Transcriptome-wide profiling and expression ana...

The transcript assembly represents the first such assembly in the highly polyploidy, facultative apomictic Kentucky bluegrass. ... reduces problems caused by the genome complexity and polyploidy, but the repeat content still hampers the sequence assembly. ...

*  PPT - Chapter 13: Genetic Engineering PowerPoint Presentation - ID:2647686

EX: Polyploidy (3N or 4N) plants have resulted from this - larger & hardier ...

*  Plus it

Continuous exposure of tumour cells to the inhibitor causes multipolar spindle formation, chromosome misalignment, polyploidy ...

*  Various Characteristics of Hybrid between River Puffer, Takifugu obscurus and Tiger Puffer, T. rubripes, and Their Hybrid...

Ploidy manipulation has been extended to exploit polyploidy production methods in aquaculture (Scheerer & Thorgaard, 1983; ...

*  Z-138 ATCC ® CRL-3001™ Homo sapiens Mantle cell lymphoma (B

This is a hyperdiploid human cell line of male origin with a modal chromosome number of 49 and a 4% polyploidy rate. Most of ...

*  ORBi: Browsing ORBi

Polyploidy would have occurred between 7 and 9.4 million years in the evolutionary history of the genus. In addition, Bayesian ...

*  JoVE | Peer Reviewed Scientific Video Journal - Methods and Protocols

Stathmin1 overexpression associated with polyploidy, tumor-cell invasion, early recurrence, and poor prognosis in human ... Overexpression of STMN1 promoted polyploidy formation, tumor-cell invasion, and intrahepatic metastasis, suggesting that STMN1 ... while ectopic expression of STMN1 enhanced cell invasion and caused polyploidy of cells. In conclusion, STMN1 overexpression ...

*  June 2011 ISEH Newsletter - International Society for Experimental Hematology

Moreover, the combination of CXCL12 and TPO results in increased polyploidy in megakaryocytes generated from human progenitor ...

*  Annexe 3

In: International Conference on Polyploidy, Hybridization and Biodiversity, 17-20/05/2009, Saint-Malo, France. (Co-author) ...

*  Is there any experiment that proves the increase of genetic reserve? (Page 1) - Evolution - Ask a Biologist Q&A

Recent occurrences of polyploidy are well documented in many plant systems (see examples in wiki page) and some fish groups (e. ...

*  Penguin First Editions :: Early First Edition Penguin Books :: penguinfirsteditions.com

POLYPLOIDY AND PLANT BREEDING by M. S. Swaminathan * THE ANALYSIS OF HUMAN SKILL by R. C. Oldfield * THE THYROID GLAND - A ...

*  The Biologist Is In: February 2015

This system is referred to as "permanent odd polyploidy". It even works with extra uneven chromosome copies. The extras form ...

PaleopolyploidyJason WintersLygodiumGene duplication: Gene duplication (or chromosomal duplication or gene amplification) is a major mechanism through which new genetic material is generated during molecular evolution. It can be defined as any duplication of a region of DNA that contains a gene.NoscapineYarrow oilThalictrum heliophilum: Thalictrum heliophilum is a species of flowering plant in the buttercup family known by the common names sun-loving meadowrue and Cathedral Bluff meadow-rue. It is endemic to Colorado in the United States, where it is known from three counties.Cleome platycarpa: Cleome platycarpa is a species of flowering plant in the cleome family known by the common names golden bee plant and golden spiderflower. It is native to the western United States from northeastern California to Idaho, including the Modoc Plateau, where it grows on clay and volcanic soils in the sagebrush.Gig (carriage): A gig, also called chair or chaise, is a light, two-wheeled sprung cart pulled by one horse.Molecular evolution: Molecular evolution is a change in the sequence composition of cellular molecules such as DNA, RNA, and proteins across generations. The field of molecular evolution uses principles of evolutionary biology and population genetics to explain patterns in these changes.Gossypium herbaceum: Gossypium herbaceum, commonly known as Levant cotton, is a species of cotton native to the semi-arid regions of sub-Saharan Africa and Arabia where it still grows in the wild as a perennial shrub. It is a sister-species of Gossypium arboreum.AmborellaBookmarking: Bookmarking (also "gene bookmarking" or "mitotic bookmarking") refers to a potential mechanism of transmission of gene expression programs through cell division.Hybrid inviability: Hybrid inviability is a post-zygotic barrier, which reduces a hybrid's capacity to mature into a healthy, fit adult.Hybrid inviability.Claytonia megarhiza: Claytonia megarhiza is a species of wildflower in the purslane family known by the common names fell-fields claytonia and alpine springbeauty. It is native to western North America from northwestern Canada to New Mexico, where it grows in talus habitats in subalpine and alpine climates.NocodazoleBranching order of bacterial phyla (Gupta, 2001): There are several models of the Branching order of bacterial phyla, one of these was proposed in 2001 by Gupta based on conserved indels or protein, termed "protein signatures", an alternative approach to molecular phylogeny. Some problematic exceptions and conflicts are present to these conserved indels, however, they are in agreement with several groupings of classes and phyla.Aurora inhibitorHesperadinAphelandra: Aphelandra is a genus of about 170 species of flowering plants in the family Acanthaceae, native to tropical regions of the Americas.Rosa canina: Rosa canina, commonly known as the dog-rose, is a variable climbing wild rose species native to Europe, northwest Africa and western Asia.Cytokinesis: Cytokinesis (from the Greek κύτος, "container" and κίνησις, "motion") is the process during cell division in which the cytoplasm of a single eukaryotic cell is divided to form two daughter cells. It usually initiates during the early stages of mitosis, and sometimes meiosis, splitting a mitotic cell in two, to ensure that chromosome number is maintained from one generation to the next.Dipsacus: Dipsacus is a genus of flowering plant in the family Caprifoliaceae. The members of this genus are known as teasel, teazel or teazle.Brunfelsia: Brunfelsia is a genus of flowering plants in the family Solanaceae, the nightshades. There are about 50 species described.Start point (yeast): The Start checkpoint is a major cell cycle checkpoint in yeast. The Start checkpoint ensures irreversible cell-cycle entry even if conditions later become unfavorable.Spindle apparatus: In cell biology, the spindle apparatus refers to the subcellular structure of eukaryotic cells that separates chromosomes between daughter cells during cell division. It is also referred to as the mitotic spindle during mitosis, a process that produces genetically identical daughter cells, or the meiotic spindle during meiosis, a process that produces gametes with half the number of chromosomes of the parent cell.Panicum coloratum: Panicum coloratum is a species of grass known by the common names kleingrass, blue panicgrassPanicum coloratum. Tropical Forages.FosfluconazoleGenetic variation: right|thumbAeolothripidae: The Aeolothripidae are a family of thrips. They are particularly common in the holarctic region, although several occur in the drier parts of the subtropics, including dozens in Australia.Copy number analysis: Copy number analysis usually refers to the process of analyzing data produced by a test for DNA copy number variation in patient's sample. Such analysis helps detect chromosomal copy number variation that may cause or may increase risks of various critical disorders.

(1/1578) C-myc overexpression and p53 loss cooperate to promote genomic instability.

p53 monitors genomic integrity at the G1 and G2/M cell cycle checkpoints. Cells lacking p53 may show gene amplification as well as the polyploidy or aneuploidy typical of many tumors. The pathways through which this develops, however, are not well defined. We demonstrate here that the combination of p53 inactivation and c-myc overexpression in diploid cells markedly accelerates the spontaneous development of tetraploidy. This is not seen with either N-myc or L-myc. Tetraploidy is accompanied by significantly higher levels of cyclin B and its associated cdc2 kinase activity. Mitotic spindle poisons accelerate the appearance of tetraploidy in cells either lacking functional p53 or overexpressing c-myc whereas the combination is additive. Restoration of p53 function in cells overexpressing c-myc causing rapid apoptosis, indicating that cells yet to become tetraploid have nonetheless suffered irreversible genomic and/or mitotic spindle damage. In the face of normal p53 function, such damage would either be repaired or trigger apoptotis. We propose that loss of p53 and overexpression of c-myc permits the emergence and survival of cells with increasingly severe damage and the eventual development of tetraploidy.  (+info)

(2/1578) The modulation of DNA content: proximate causes and ultimate consequences.

The forces responsible for modulating the large-scale features of the genome remain one of the most difficult issues confronting evolutionary biology. Although diversity in chromosomal architecture, nucleotide composition, and genome size has been well documented, there is little understanding of either the evolutionary origins or impact of much of this variation. The 80,000-fold divergence in genome sizes among eukaryotes represents perhaps the greatest challenge for genomic holists. Although some researchers continue to characterize much variation in genome size as a mere by-product of an intragenomic selfish DNA "free-for-all" there is increasing evidence for the primacy of selection in molding genome sizes via impacts on cell size and division rates. Moreover, processes inducing quantum or doubling series variation in gametic or somatic genome sizes are common. These abrupt shifts have broad effects on phenotypic attributes at both cellular and organismal levels and may play an important role in explaining episodes of rapid-or even saltational-character state evolution.  (+info)

(3/1578) Cell cycle arrest mediated by hepatitis delta antigen.

Hepatitis delta antigen (HDAg) is the only viral-encoded protein of the hepatitis delta virus (HDV). This protein has been extensively characterized with respect to its biochemical and functional properties. However, the molecular mechanism responsible for persistent HDV infection is not yet clear. Previously, we reported that overexpression of HDAg protects insect cells from baculovirus-induced cytolysis [Hwang, S.B. Park, K.-J. and Kim, Y.S. (1998) Biochem. Biophys. Res. Commun. 244, 652-658]. Here we report that HDAg mediates cell cycle arrest when overexpressed in recombinant baculovirus-infected insect cells. Flow cytometry analysis has shown that HDAg expression in Spodoptera frugiperda cells causes an accumulation of substantial amounts of polyploid DNA in the absence of cell division. This phenomenon may be partly responsible for the persistent infection of chronic HDV patients.  (+info)

(4/1578) Partial hepatectomy-induced polyploidy attenuates hepatocyte replication and activates cell aging events.

In understanding mechanisms of liver repopulation with transplanted hepatocytes, we studied the consequences of hepatic polyploidization in the two-thirds partial hepatectomy model of liver regeneration. Liver repopulation studies using genetically marked rodent hepatocytes showed that the number of previously transplanted hepatocytes did not increase in the liver with subsequential partial hepatectomy. In contrast, recipients undergoing partial hepatectomy before cells were transplanted showed proliferation in transplanted hepatocytes, with kinetics of DNA synthesis differing in transplanted and host hepatocytes. Also, partial hepatectomy caused multiple changes in the rat liver, including accumulation of polyploid hepatocytes along with prolonged depletion of diploid hepatocytes, as well as increased senescence-associated beta-galactosidase and p21 expression. Remnant hepatocytes in the partially hepatectomized liver showed increased autofluorescence and cytoplasmic complexity on flow cytometry, which are associated with lipofuscin accumulation during cell aging, and underwent apoptosis more frequently. Moreover, hepatocytes from the partially hepatectomized liver showed attenuated proliferative capacity in cell culture. These findings were compatible with decreased proliferative potential of hepatocytes experiencing partial hepatectomy compared with hepatocytes from the unperturbed liver. Attenuation of proliferative capacity and other changes in hepatocytes experiencing partial hepatectomy offer novel perspectives concerning liver regeneration in the context of cell ploidy.  (+info)

(5/1578) Elimination and rearrangement of parental rDNA in the allotetraploid Nicotiana tabacum.

Origin and rearrangement of ribosomal DNA repeats in natural allotetraploid Nicotiana tabacum are described. Comparative sequence analysis of the intergenic spacer (IGS) regions of Nicotiana tomentosiformis (the paternal diploid progenitor) and Nicotiana sylvestris (the maternal diploid progenitor) showed species-specific molecular features. These markers allowed us to trace the molecular evolution of parental rDNA in the allopolyploid genome of N. tabacum; at least the majority of tobacco rDNA repeats originated from N. tomentosiformis, which endured reconstruction of subrepeated regions in the IGS. We infer that after hybridization of the parental diploid species, rDNA with a longer IGS, donated by N. tomentosiformis, dominated over the rDNA with a shorter IGS from N. sylvestris; the latter was then eliminated from the allopolyploid genome. Thus, repeated sequences in allopolyploid genomes are targets for molecular rearrangement, demonstrating the dynamic nature of allopolyploid genomes.  (+info)

(6/1578) Low levels of nucleotide diversity at homoeologous Adh loci in allotetraploid cotton (Gossypium L.).

Levels of genetic diversity within and among populations and species are shaped by both external (population-level) and internal (genomic and genic) evolutionary forces. To address the effect of internal pressures, we estimated nucleotide diversity for a pair of homoeologous Adh loci in an allotetraploid species, Gossypium hirsutum. These data represent the first such estimates for a pair of homoeologous nuclear loci in plants. Estimates of nucleotide diversity for AdhA in Gossypium are lower than those for any plant nuclear gene yet described. This low diversity appears to reflect primarily a history of repeated, severe genetic bottlenecks associated with both speciation and recent domestication, supplemented by an unusually slow nucleotide substitution rate and an autogamous breeding system. While not statistically supportable, the sum of the observations also suggest differential evolutionary dynamics at each of the homoeologous loci.  (+info)

(7/1578) Clinical details, cytogenic studies,and cellular physiology of a 69, XXX fetus, with comments on the biological effect of triploidy in man.

A triploid fetus, 69, XXX, aborted spontaneously at 26 weeks' gestation. It had multiple abnormalities including syndactyly of the hands and feet single palmar creases, hypoplasia of the adrenals and ovaries, hypertrophy of thigh muscles, and abnormalities of the brain. The placenta was large and showed hydatidiform degeneration. The pregnancy had been complicated by acute dyspnoea, pre-eclampsia, and postpartum haemorrhage. Detailed cytogenetic studies, using banding and fluorescence techniques, were performed on fetus and parents. Meiotic studies were made on the fetal ovaries. Muscle cell differentiation and electrophysiological relationships of cultured skin fibriblasts were examined in an attempt to study the way in which the extra haploid set of chromosomes exerts its effect on the phenotype. The antenatal diagnosis of late triploidy is discussed. The finding that 25 per cent of late triploids have spina bifida is further evidence that meningomyelocele has a genetic component and strongly suggests that this results from chromosomal imbalance or a regulatory gene disturbance.  (+info)

(8/1578) P53-dependent effects of RAS oncogene on chromosome stability and cell cycle checkpoints.

Mutations activating the function of ras proto-oncogenes are often observed in human tumors. Their oncogenic potential is mainly due to permanent stimulation of cellular proliferation and dramatic changes in morphogenic reactions of the cell. To learn more on the role of ras activation in cancerogenesis we studied its effects on chromosome stability and cell cycle checkpoints. Since the ability of ras oncogenes to cause cell transformation may be dependent on activity of the p53 tumor-suppressor the cells with different p53 state were analysed. Ectopic expression of N-ras(asp12) caused in p53-deficient MDAH041 cell line an augmentation in the number of chromosome breaks in mitogenic cells, significant increase in the frequency of metaphases showing chromosome endoreduplication and accumulation of polyploid cells. Similar effects were induced by different exogenous ras genes (N-ras(asp12), H-ras(leu12), N-ras proto-oncogene) in Rat1 and Rat2 cells which have a defect in p53-upstream pathways. In contrast, in REF52 and human LIM1215 cells showing ras-induced p53 up-regulation, ras expression caused only slight increase in the number of chromosome breaks and did not enhance the frequency of endoreduplication and polyploidy. Inactivation in these cells of p53 function by transduction of dominant-negative C-terminal p53 fragment (genetic suppressor element #22, GSE22) or mutant p53s significantly increased the frequency of both spontaneous and ras-induced karyotypic changes. In concordance with these observations we have found that expression of ras oncogene caused in p53-defective cells further mitigation of ethyl-metansulphonate-induced G1 and G2 cell cycle arrest, but did not abrogate G1 and G2 cell cycle checkpoints in cells with normal p53 function. These data indicate that along with stimulation of cell proliferation and morphological transformation ras activation can contribute to cancerogenesis by increasing genetic instability.  (+info)



chromosome

  • Continuous exposure of tumour cells to the inhibitor causes multipolar spindle formation, chromosome misalignment, polyploidy and apoptosis. (aacrjournals.org)
  • This is a hyperdiploid human cell line of male origin with a modal chromosome number of 49 and a 4% polyploidy rate. (atcc.org)

cells

  • Although it is less common in mammals, some tissues - including heart muscle cells, platelet progenitor megakaryocytes, and liver parenchyma - develop a certain degree of polyploidy during their normal life cycle. (jci.org)

plants