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Results for “polyploidy”

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PubMed1995

Induction of polyploidy in human lymphocytes in vitro by excess adenine, but not by adenosine.

It is known that high levels of DNA precursors can be both clastogenic and mutagenic in cultured cell lines and in vivo. The purpose of the present study was to examine at an observational level the cytogenetic effects of adenine and adenosine in primary human cell cultures. Human peripheral blood lymphocytes from four donors were cultured and treated with a range of concentrations of adenine and adenosine. Although no increase in sister chromatid exchange (SCE) frequency was observed with either compound, there was a statistically significant, dose-related increase in the proportion of polyploid cells in cultures treated with adenine, but not in those treated with adenosine. Some of the polyploid metaphases found after adenine treatment contained diplochromosomes, suggesting that endoreduplication might have been involved in polyploid formation in these cells. It is concluded that a high level of adenine can cause genetic changes in human lymphocytes by interfering with mitosis, perhaps by disturbing the balance of DNA precursor pools.

Adenine↗
PubMed1985

Growth and aging in the rat: changes in total protein, cellularity, and polyploidy in various organs.

The objectives of this study were to determine the influence of growth and aging on ploidy, cell number, and protein content of various organs. Tissue homogenates were prepared at 3, 8, 25, 50, and 100 weeks of age. Samples were analyzed for DNA per nucleus (by flow cytofluorometry), nuclei number, and protein content. Livers of 8- and 100-week-old animals were also perfused with collagenase and the released cells separated into parenchymal and nonparenchymal populations by unit gravity sedimentation. Nuclei of these cells were also analyzed for DNA. In all four zones of the kidney and in thyroid, 4n nuclei diminished in percentage between 3 and 50 weeks and increased at 100 weeks. In the growth phase these probably are cycling cells and after 50 weeks represent an increasing population of nuclei arrested after synthesis of DNA. Constant levels of ploidy were found in brain, heart, rectus abdominis, and adrenal throughout the 3-100 weeks. A dramatic increase in 4n nuclei occurred between 3 and 8 weeks in liver with little change occurring thereafter. Ploidy is a property of only parenchymal cells in liver and this probably is also true in other organs. The 4n nuclei that remain in constant proportion to the total population are established early in life and are not related to aging. They are probably tetraploid and replicate into 4n daughter cells during growth. Cerebrum shows no changes in nuclei number but exhibits a 70% increase in protein between 3 and 100 weeks. Although kidney, liver and adrenal show large increases in number of nuclei (approximately equal to fourfold) with growth, these are not as great as increases in body weight (approximately equal to 11-fold). With regard to organ protein, only liver shows increases approximating those in body weight. Increases in organ nuclei appear to occur in concert for adrenal, kidney, and liver whereas increases in organ protein bear no relationship to each other. Protein content remains at stable levels in organs of 100-week-old animals and little (adrenal, liver) or no (brain, kidney) diminution occurs in nuclei numbers.

Aging↗
PubMed1979

Polyploidy and domestication: the origin and survival of polyploids in cytotype mixtures.

The origin and survival of a polyploid in a mixture of this polyploid and its parent(s) is reviewed. With several examples a picture is drawn of the interference of cytotypes in a mixture of cytotypes. Some natural polyploids, both wild and domesticated, are very successful. They, like bread wheat and banana, largely replaced their parents. The same is true for some artificial polyploids like autotriploid hybride sugar beet in Europe and autotetraploid perennial ryegrass. But when grown together with their parents for several generations they will disappear from this misture. Although in South America under primitive conditions, diploid, triploid, and tetraploid potatoes are grown, elsewhere only the tetraploids have survived. Various causes are presented to explain why the diploids and triploids succumbed. Autotetraploids of maize, rye, barley, and rice cannot maintain themselves in diploid/tetraploid mixtures. The maintenance of diploid or tetraploid rye varieties is less difficult as both are "self-cleaning" with respect to the other. Only two haploid cultivars exist but they can only maintain themselves with the help of man. It is concluded that the survival chances of a polyploid after its origination is low. Firstly, under conditions of random sampling a rare type has a very small chance of occurring in the next generation. Furthermore, seedset of triploids and tetraploids is often low which limits their survival. In addition, in mixtures of cross-fertilizing diploid and autotetraploids the n gamete has an advantage over the 2n gamete. This limits the survival of the autotetraploids again. It is concluded that our knowledge of the the mutual interference of cytotypes in a cytotype mixture is quite limited. Much more research is needed and some proposals concerning this research are made.

Agriculture↗