A CYTOGEOGRAPHIC STUDY OF ERIOPHYLLUM LANATUM (COMPOSITAE,HELENIEAE)

Analysis of 368 plants derived from 239 natural populations showed that this taxonomically perplexing and wide-ranging species-complex consists of diploids (n = 8), tetraploids, hexaploids and octoploids. Microsporocytes were the source of most of the chromosome counts. Meiosis was basically regular. Multivalent formation was uncommon, but 11 % of all the plants examined had one or more full-sized extra chromosomes. The frequency of plants with extra chromosomes varied significantly among the taxa, from 0 (five varieties) to over 20 % (two varieties). Except in one instance, where one population yielded a diploid and a triploid, different ploidy levels were not found in the same population. The frequency of diploid, tetraploid, hexaploid and octoploid populations was, respectively, 71, 22, 4 and 2%. Variety obovatum appears to be exclusively diploid, and var. aphanactis exclusively tetraploid. Diploids and one or more polyploid levels occurred in the other taxa. No correlation was found between polyploidy and geological history, soils, topography or climate, nor were the polyploids more widely distributed than the diploids. Some of the polyploid populations seem to have been derived from inter-varietal hybridizations, but others do not. The complex has a “pillar” structure in which 10 diploid taxa support a three-level polyploid superstructure. The available evidence suggests that the major role of polyploidy here has been to stabilize the products of intra- and inter-varietal hybridizations.     

Cytogenetic activities of tobacco particulate matter (TPM) derived from a low to middle tar British cigarette

Tobacco particulate matter (TPM) derived from an experimental low to middle tar cigarette was tested for its cytogenetic activity upon a low passage number Chinese hamster pulmonary cell line. Examination of the mitotic profiles (after one cell cycle) revealed no interference by the agent with mitotic spindle formation and/or function. However, complete chromosomes (or parts of them) were seen to dislocate from the mitotic spindles. Such an event was probably the result of the chromosome aberrations, substantial numbers of which were observed in second division cells, or through a process of centromere inactivation. In second division cells there was a reduction in the number of diploid cells accompanied by an increase in both hypodiploidy and polyploidy and there was also a non-dose-related increase in endoreduplication. The results demonstrate that TPM was capable of inducing both structural and numerical chromosome aberrations in cultured mammalian cells.     

Ploidy of somatic embryos and the ability to regenerate plantlets in melon (Cucumis melo L.)

Summary The number of chromosomes in cells of callus, somatic embryos and regenerated plantlets during somatic embryogenesis were examined in two cultivars of melon (Cucumis melo L.). Somatic embryos were diploid (50.0%/32.1%), tetraploid (38.5%/57.5%) and octoploid (11.5%/10.4%) whereas in callus cells diploidy (41.9%/43.3%), tetraploidy (27.9%/25.8%), octoploidy (11.6%/15.5%) and a low frequency of other types of ploidy and aneuploidy were observed. Mixoploid somatic embryos were not observed. These results suggest that the somatic embryos were selectively differentiated from diploid, tetraploid and octoploid cells, and that endopolyploidization of cultured cells occurred before the start of cell division leading to somatic embryogenesis. The ratio of diploid to tetraploid (1.30/0.55) in somatic embryos was less than that in callus cells (1.50/1.68) while ratios of diploid to octoploid (4.35/3.09) and tetraploid to octoploid (3.35/5.52) in somatic embryos were greater than those in callus cells (3.61/2.80 and 2.40/1.67). Therefore, it appears that the ability of callus cell to differentiate into somatic embryos increases in the following order: octoploid < diploid < tetraploid. Regenerated plantlets were diploid (65.5%/55.1%) and tetraploid (34.5%/44.9%). No octoploid plantlets were observed. The ratio of diploid to tetraploid in regenerated plantlets (1.72/1.23) was greater than that in somatic embryos. Therefore, it appears that the ability of somatic embryos to develop into plantlets increases in the following order: octoploid < tetraploid < diploid.     

Barriers to interbreeding in the Eriophyllum lanatum (Asteraceae, Helenieae) species complex

Sampling 426 plants from 271 populations of Eriophyllum lanatum, a western North American species complex, revealed 195 diploid (x = 8), 61 tetraploid, ten hexaploid, and five octoploid populations. Polyploids were ～400% more frequent in taxonomic intermediates. One to four supernumerary chromosomes were found in 13% of the populations. Artificial hybridizations were made in 58 of the 65 possible diploid-level combinations involving the ten varieties of E. lanatum and E. confertiflorum var. confertiflorum. Aberrations, mostly failure to pair normally, were observed in diakinesis or M(1) cells of progeny in 23 of 99 crosses. Studies of pollen stainability in cotton blue-lactophenol and other fertility indicators in 886 F(1)'s from 191 crosses involving 81 populations showed that strong (22-40% pollen stainability) to weak (60-76% pollen stainability) barriers to interbreeding existed among diploids of the E. lanatum varieties and among them and E. confertiflorum var. confertiflorum. Pollen stainability was much higher in progenies of tetraploid, hexaploid, and octoploid intra- and interspecific crosses involving E. confertiflorum var. tanacetiflorum, E. jepsonii, and E. latilobum than in diploid ones, supporting the hypothesis that polyploidy has mainly served to stabilize the products of intervarietal and interspecific hybridizations.     

Origin of triploidy and tetraploidy in man: 11 cases with chromosomes markers

Sixteen triploid and one tetraploid human abortuses were studied for the origin of polyploidy using a sequential Q- and R-banding technique. Ten triploid abortuses provided informative data: one originated in the maternal first meiotic division; five apparently resulted from dispermy; two derived from an error during either the paternal second meiotic division or the first mitotic division; and the last two were of paternal origin. The results indicate that paternal factors, especially dispermy, are the predominant sources of triploidy in man. The tetraploid abortus showed duplication of both the maternal and paternal haploid sets, suggesting normal division of chromosomes and suppression of cytoplasmic cleavage at the first mitotic division. No correlation was found between the origin of polyploidy and the phenotype of the triploid abortuses, nor between the origin of polyploidy and the maternal use of oral contraceptives.     

Arrangement of spindle apparatus in mitoses of different ploidy

In non-hypotonically treated mitoses from tissue cultures of Microtus agrestis, both the constitutive heterochromatin of the sex chromosomes and the spindle apparatus were stained by the Giemsa C-banding technique. By means of counting the heterochromatic chromosomes, we determined the cell ploidy and studied the number of centrioles and the spindle arrangement of diploid, triploid, tetraploid and octoploid mitoses. Diploid and triploid prophases contained 2 centrioles in most cases, tetraploid prophases 4, binucleate cells with 2 diploid nuclei likewise 4 and binucleate cells with 2 tetraploid nuclei 8 centrioles. Nearly 99% of diploid and triploid metaphases were bipolar. Of the tetraploid metaphases only 45% were bipolar, 29.5% tripolar, 7.5% quadripolar and 18% formed as a parallel mitosis. In all examined binucleate cells that had had an asynchronous DNA synthesis, a multipolar mitosis was found.     

Formation of bipolar spindles with two centrosomes in tetraploid cells established from normal human fibroblasts

Tetraploid cells with unstable chromosomes frequently arise as an early step in tumorigenesis and lead to the formation of aneuploid cells. The mechanisms responsible for the chromosome instability of polyploid cells are not fully understood, although the supernumerary centrosomes in polyploid cells have been considered the major cause of chromosomal instability. The aim of this study was to examine the integrity of mitotic spindles and centrosomes in proliferative polyploid cells established from normal human fibroblasts. TIG-1 human fibroblasts were treated with demecolcine (DC) for 4?days to induce polyploidy, and the change in DNA content was monitored. Localization of centrosomes and mitotic spindles in polyploid mitotic cells was examined by immunohistochemistry and laser scanning cytometry. TIG-1 cells treated with DC became almost completely tetraploid at 2?weeks after treatment and grew at the same rate as untreated diploid cells. Most mitotic cells with 8C DNA content had only two centrosomes with bipolar spindles in established tetraploid cells, although they had four or more centrosomes with multipolar spindles at 3?days after DC treatment. The frequency of aneuploid cells increased as established tetraploid cells were propagated. These results indicate that tetraploid cells that form bipolar spindles with two centrosomes in mitosis can proliferate as diploid cells. These cells may serve as a useful model for studying the chromosome instability of polyploid cells.     

Is There a Relationship between Infection by Rhizobia and Occurrence of Disomatic Nuclei in Nodules of Alfalfa (Medicago sativa L.)?

Cytological examination of nodules from diploid, tetraploid, and octoploid alfalfa (Medicago sativa L.) plants revealed that the proportion of nodule cells infected by rhizobia was not significantly affected by nuclear ploidy of the host plant. Flow cytometry was used to determine the influence of host plant nuclear ploidy on the nuclear ploidy of infected cells. In nodules from diploid plants, most of the nuclei were tetraploid, whereas in nodules from tetraploid plants, about half of the nodule nuclei were tetraploid and half were octoploid; in octoploid plants, most of the nodule nuclei were octoploid. The occurrence of disomatic nuclei was independent of infection of nodule cells by rhizobia, because diploid plants had mostly disomatic nodule nuclei, and octoploid plants had mostly monosomatic nodule nuclei, whereas all nodules maintained a constant proportion of infected to uninfected cells. These results do not support the earlier hypothesis that infected nodule cells contain disomatic nuclei.     

狗尾草属野生近缘种的染色体鉴定

对来自多个国家和地区的10个种(青狗尾草S.viridis,法氏狗尾草S.faberii,轮生狗尾草S.verticillata、S.verticillifor-mis,金色狗尾草S.glauca、S.pumila、S.grisebachii、S.leucopila、S.parviflora、S.queenslandica等)50份狗尾草材料进行了染色体计数及倍性鉴定。发现狗尾草属中的青狗尾草均为二倍体,金色狗尾草S.glauca有四倍体和八倍体,轮生狗尾草S.verticillata有二倍体和四倍体,法氏狗尾草S.faberii为四倍体,S.pumila有二倍体和四倍体,S.grisebachii为二倍体,S.leucopila为二倍体,S.queenslandica为四倍体。本研究中对S.grisebachii、S.leucopila、S.queenslandica3个种是首次染色体倍性观察。发掘近缘种的有益基因是作物育种的重要途径之一,本研究搜集的谷子近缘野生种对谷子远缘杂交育种和谷子起源进化分析有重要意义。     

Human diploid fibroblast cells in senescence; Cycling through polyploidy to mitotic cells

Summary Previously, it was found that senescent cells can undergo a modified cell cycle with mitotic cells as the end results. The major cycling events started with polyploidization, followed by depolyploidization to multinucleated cells (MNCs). These latter cells produced mononuclear offspring cells that could express mitotic cell divisions. In this report the emphasis is on late senescent fibroblasts that exhibited the senescence-associated change in cell morphology to large flat cells. Prior to live cell photography, flat cell cultures were maintained for months in the same culture flasks and therefore judged to be in a late senescent phase. All of the cellular events outlined above were present in these old cell cultures. Time lapse pictures showed movements of mitotic daughter cells away from each other and alignment of the chromosomes on the metaphase plate was visible in other mitotic cells. These data challenge the common view that cell senescence is irreversible and, therefore, an antitumor mechanism. A new finding was that the spike in polyploid cells in the near senescent phase consisted of cells with pairs of sister chromosomes from endoreduplication of DNA (two rounds of DNA synthesis and no mitosis). The lack of cells with 92 single chromosomes (e.g., G2 tetraploid cells) suggested that these polyploid cells also went through a changed cell cycle. The question now is whether these atypical polyploid cells are a subpopulation in senescence that can undergo the cycling from polyploidy to genome-reduced mitotic cells.     

Regain of sex determination system and sexual reproduction ability in a synthetic octoploid male fish

Polyploids in vertebrates are generally associated with unisexual reproduction, but the direct consequences of polyploidy on sex determination system and reproduction mode remain unknown. Here, we synthesized a group of artificial octoploids between unisexual gynogenetic hexaploid Carassius gibelio and sexual tetraploid Carassius auratus. The synthetic octoploids were revealed to have more than 200 chromosomes, in which 50 chromosomes including the X/Y sex determination system were identified to transfer from sexual tetraploid C. auratus into the unisexual gynogenetic hexaploid C. gibelio. Significantly, a few synthetic octoploid males were found to be fertile, and one octoploid male was confirmed to regain sexual reproduction ability,which exhibits characteristics that are the same to sexual reproduction tetraploid males, such as 1:1 sex ratio occurrence, meiosis completion and euploid sperm formation in spermatogenesis, as well as normal embryo development and gene expression pattern during embryogenesis. Therefore, the current finding provides a unique case to explore the effect of sex determination system incorporation on reproduction mode transition from unisexual gynogenesis to sexual reproduction along with genome synthesis of recurrent polyploidy in vertebrates.     

Contributions to the cytotaxonomy of the Commelinaceae. Chromosome evolution in Tradescantia section Cymbispatha

The five species of Tradescantia section Cymbispatha studied, including one species T. poelliae D. R. Hunt, have chromosome numbers of In = 12, 14, 16, 22, 28, 30 and 36 and karyotypes of acrocentric, metacentric or telocentric chromosomes, or mixtures of both acrocentric and metacentric chromosomes. The numbers of major chromosome arms of these cytotypes give a nombre fondamentaP series of 14, 28, 42 and 56 which, in combination with meiotic analyses, indicates plants which, in genetical terms at least, are diploid, tetraploid, hexaploid and octoploid. This series has evolved from a 2 n = 14 acrocentric or telocentric karyotype by a combination of Robertsonian fusion and polyploidy. Pseudo-iso-chromosomes are sometimes formed in this evolutionary development and can persist as stable members of normal complements.     

Contributions to the cytotaxonomy of the Commelinaceae. Chromosome evolution in Tradescantia section Cymbispatha

The five species of Tradescantia section Cymbispatha studied, including one species T. poelliae D. R. Hunt, have chromosome numbers of In = 12, 14, 16, 22, 28, 30 and 36 and karyotypes of acrocentric, metacentric or telocentric chromosomes, or mixtures of both acrocentric and metacentric chromosomes. The numbers of major chromosome arms of these cytotypes give a nombre fondamentaP series of 14, 28, 42 and 56 which, in combination with meiotic analyses, indicates plants which, in genetical terms at least, are diploid, tetraploid, hexaploid and octoploid. This series has evolved from a 2 n = 14 acrocentric or telocentric karyotype by a combination of Robertsonian fusion and polyploidy. Pseudo-iso-chromosomes are sometimes formed in this evolutionary development and can persist as stable members of normal complements.     

Microspectrophotometry of cell nuclei stained with the Feulgen reaction. IV. Formation of tetraploid nuclei in rat liver cells during postnatal growth

1. DNA contents of the individual parenchymal nuclei of rat livers during postnatal growth were estimated by microspectrophotometric apparatus, and different ploidy classes of nuclei were classified by their DNA contents. With the same material the total number of parenchymal nuclei in the liver was counted microscopically. 2. If the DNA content of nuclei encountered most frequently in several tissues represents the diploid class, the ploidy classes of the rat liver cell nuclei correspond to di-, tri-, tetra-, and octoploid, with the di- and tetraploid ones predominating considerably. 3. In suckling rats (below 25 gm. of body weight) the liver parenchyma is composed almost exclusively of cells with diploid nuclei, whereas in young rats (above 80 gm.), of tetraploid nuclei. In the growth stage between 25 and 80 gm., there is a remarkable replacement of the diploid nuclei by the tetraploid ones. However, in the liver of adult rats weighing more than 150 gm., any increase or decrease in the frequency of diploid and tetraploid nuclei is hardly observable. In such rats, the nuclear population of the liver parenchyma seems to reach a cell-ecological equilibrium which is considered to be a stable one. 4. It is shown that such nuclear populations and the total number of nuclei in a liver are controlled by the growth state, and not by the age. 5. The decrease in the total number of diploid nuclei and the increase in tetraploid nuclei in the growing livers of rats weighing from 40 up to 130 gm. can both be explained by the hypothesis that the tetraploid nuclei originate from the interphase diploid nuclei without involving mitosis. This hypothesis implies that mitosis is confined to the reproduction of diploid cells alone. 6. It is suggested that, in general, the synthesis of DNA does not necessarily result in the formation of visible mitotic chromosomes. 7. Mitotic time and generation time of diploid nuclei and the percentage of the tetraploidization from diploid nuclei are calculated and discussed.     

MICROSPECTROPHOTOMETRY OF CELL NUCLEI STAINED WITH THE FEULGEN REACTION : IV. FORMATION OF TETRAPLOID NUCLEI IN RAT LIVER CELLS DURING POSTNATAL GROWTH

1. DNA contents of the individual parenchymal nuclei of rat livers during postnatal growth were estimated by microspectrophotometric apparatus, and different ploidy classes of nuclei were classified by their DNA contents. With the same material the total number of parenchymal nuclei in the liver was counted microscopically. 2. If the DNA content of nuclei encountered most frequently in several tissues represents the diploid class, the ploidy classes of the rat liver cell nuclei correspond to di-, tri-, tetra-, and octoploid, with the di- and tetraploid ones predominating considerably. 3. In suckling rats (below 25 gm. of body weight) the liver parenchyma is composed almost exclusively of cells with diploid nuclei, whereas in young rats (above 80 gm.), of tetraploid nuclei. In the growth stage between 25 and 80 gm., there is a remarkable replacement of the diploid nuclei by the tetraploid ones. However, in the liver of adult rats weighing more than 150 gm., any increase or decrease in the frequency of diploid and tetraploid nuclei is hardly observable. In such rats, the nuclear population of the liver parenchyma seems to reach a cell-ecological equilibrium which is considered to be a stable one. 4. It is shown that such nuclear populations and the total number of nuclei in a liver are controlled by the growth state, and not by the age. 5. The decrease in the total number of diploid nuclei and the increase in tetraploid nuclei in the growing livers of rats weighing from 40 up to 130 gm. can both be explained by the hypothesis that the tetraploid nuclei originate from the interphase diploid nuclei without involving mitosis. This hypothesis implies that mitosis is confined to the reproduction of diploid cells alone. 6. It is suggested that, in general, the synthesis of DNA does not necessarily result in the formation of visible mitotic chromosomes. 7. Mitotic time and generation time of diploid nuclei and the percentage of the tetraploidization from diploid nuclei are calculated and discussed.     

Factors affecting the frequency of tetraploid cells in a predominantly diploid suspension culture ofDaucus carota

Summary Tetraploid clones were isolated from a predominantly diploid culture line ofDaucus carota by plating alone or after colchicine treatment. Although individually these tetraploid clones had similar growth rates to the diploid culture, they were progressively eliminated from mixtures with the diploid line. As the diploid culture line always contained a low frequency of tetraploids, the selective elimination of tetraploids must have been balanced by their continuous production. The frequency of endoreduplication detected was too low to maintain the equilibrium frequency of tetraploids and it is proposed that polyploidisation also occurred by endomitosis. The mean frequency of tetraploid metaphases within the diploid culture line was reduced by shortening the interval between subcultures from 14 to 7 days. This 7-day regime also eliminated linear growth and stationary phase periods, but did not alter the maximum growth rate or mitotic index of the culture. It is argued that the change in mean tetraploid metaphase frequency is indicative of a change in the number of tetraploid cells within the culture, brought about by an alteration in the equilibrium between production and elimination of tetraploid cells.     

Mitotic disturbances associated with inversion 9qh. A case report

A 25-year-old female with history of spontaneous abortion and subsequent birth of Down syndrome child was referred for chromosome analysis. Her karyotype revealed 46, XX with pericentric inversion of 9 qh, while her husband was normal with 46, XY chromosomes. Metaphase analysis of the female showed 20.5% cells with premature centromere division, 4% with endoreduplication, 2% with polyploidy and 9.33% aneuploidy. These frequencies were considerably higher as compared to a normal control. These observations suggest that inv (9qh) might have some interchromosomal effect leading to higher incidence of mitotic disturbances, finally resulting in aneuploidy. This predisposition is evident by spontaneous abortion and later birth of a Down syndrome child.     

Biochemical,morphological and flow cytometric evaluation of the effects of hexachlorobenzene on rat liver

This study investigated the ability of HCB (0.1% in the diet for 15 days) to cause early changes in the cellular ploidy of rat liver. Treatment caused marked hepatomegaly, increase of microsomal proteins and cytochrome P-450 content and reduction of hepatocyte microviscosity. Microscopic examination showed that the hepatocytes were enlarged, with hyaline cytoplasm and vacuoles. The size distribution of the isolated hepatocytes showed a larger percentage of bigger cells. Flow-cytometric DNA/protein analysis was performed on whole (fixed) cells and on nuclei. From the combined results of both analyses it was possible to exclude significant changes in the percentages of diploid, mononucleated tetraploid, binucleated tetraploid and octoploid hepatocytes. The DNA and protein content of each subpopulation remained unchanged. Our results suggest that HCB does not cause early diploidization of liver cells and that hepatomegaly and cytochrome P-450 induction seem not to be correlated with effects on total DNA and total protein contents.Abbreviations HCB hexachlorobenzene - PI propidium iodide - FITC fluorescein isothiocyanate - DN diploid nuclei - SN 2N-4N nuclei in S-phase - TN tetraploid nuclei - DC diploid cells - SDC 2N-4N diploid cells in S-phase - TC tetraploid cells - STC 4N-8N tetraploid cells in S-phase - OC octoploid cells - MDC mononucleated diploid cells - SMDC mononucleated diploid cells in S-phase - BOC binucleated octoploid cells - SBTC binucleated tetraploid cells in S-phase - BTC binucleated tetraploid cells - MTC mononucleated tetraploid cells.     

Decaploidy in Fragaria iturupensis (Rosaceae)

The strawberry genus, Fragaria (Rosaceae), has a base chromosome number of x = 7. Cultivated strawberries (F. ×ananassa nothosubsp. ananassa) are octoploid (2n = 8x = 56) and first hybridized from F. chiloensis subsp. chiloensis forma chiloensis × F. virginiana subsp. virginiana. Europe has no known native octoploid species, and only one Asian octoploid species has been reported: F. iturupensis, from Iturup Island. Our objective was to examine the chromosomes of F. iturupensis. Ploidy levels of wild strawberry species, include diploid (2n = 2x = 14), tetraploid (2n = 4x = 28), pentaploid (2n = 5x = 35), hexaploid (2n = 6x = 42), octoploid (2n = 8x = 56), and nonaploid (2n = 9x = 63). Artificial triploid (2n = 3x = 21), tetraploid, pentaploid, octoploid, decaploid (2n = 10x = 70), 16-ploid, and 32-ploid plants have been constructed and cultivated. Surprisingly, chromosome counts and flow cytometry revealed that F. iturupensis includes natural decaploid genotypes with 2n = 10x = 70 chromosomes. This report is the first of a naturally occurring decaploid strawberry species. Further research on F. iturupensis and exploration on northern Pacific islands is warranted to ascertain the phylogeny and development of American octoploid species.     

Morphological Variability and Levels of Nuclear Ploidy in Neurons of the Central Nervous System of Bivalves Relative to the Problem of Somatic Polyploidy

Ploidy of neurons was assessed by the method of nuclear DNA cytophotometry in ganglia of the central nervous system (CNS) in 28 species of Bivalvia belonging to 5 existing subclasses and having various bio-ecological characteristics. A significant variation in the nucleus size and chromatin structure was revealed on crush preparations and slides; however, almost all nuclei were diploid. Some species had nuclei with tetraploid DNA value (from 0.2 up to 1%) and with condensed chromosomes, the probable mitotic fraction of cells. It was concluded that variation in the sizes of neurons and of their nuclei in the given instance was of a functional character, and polyploidy was untypical for the nervous system of bivalves. Apparently, the polyploidy, as an evolutionary strategy of neuron growth, had no anatomical prerequisites in bivalves, which is similar to CNS oligomerization in higher gastropods, as they are devoid of any functional adaptive sense.