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691.
692.
Eleni Mantikou Kai Mee Wong Sjoerd Repping Sebastiaan Mastenbroek 《生物化学与生物物理学报:疾病的分子基础》2012,1822(12):1921-1930
Mitotic errors are common in human preimplantation embryos. The occurrence of mitotic errors is highest during the first three cleavages after fertilization and as a result about three quarters of human preimplantation embryos show aneuploidies and are chromosomally mosaic at day three of development. The origin of these preimplantation mitotic aneuploidies and the molecular mechanisms involved are being discussed in this review.At later developmental stages the mitotic aneuploidy rate is lower. Mechanisms such as cell arrest, apoptosis, active correction of the aneuploidies and preferential allocation of the aneuploid cells to the extra-embryonic tissues could underlie this lower rate.Understanding the mechanisms that cause mitotic aneuploidies in human preimplantation embryos and the way human preimplantation embryos deal with these aneuploidies might lead to ways to limit the occurrence of aneuploidies, in order to ultimately increase the quality of embryos and with that the likelihood of a successful pregnancy in IVF/ICSI. This article is part of a Special Issue entitled: Molecular Genetics of Human Reproductive Failure. 相似文献
693.
Byeong Mee Min 《Journal of Plant Biology》2005,48(4):411-421
A natural, tidal-flat population ofSuaeda japonica was studied to determine how air temperatures early in the growing season affected population formation. Changes in germination
rates, density, standing crop (amount of biomass aboveground), and plant heights and weights were monitored from February
1999 to September 2000. Seed germination occurred between mid-February and early May in 1999, and from mid-February to mid-April
in 2000. The daily mean air temperature fluctuated below and over 0°C through the end of March in 1999 and until mid-March
in 2000. Seedling losses due to freezing were greater in 1999 than in 2000. Densities in 1999 and 2000 were 790 and 2201 plants/m2 in the early growing season, and 578 and 803 plants/m2 later on, respectively. Therefore, the density and mortality ofS. japonica was higher in 2000 than in 1999. Values of correlation were low between density and standing crop, but diverse between density
and height. The variation in standing crops was remarkable but that of height was small among sites. Frequencies of size classes,
based on height, followed normal distribution curves over time, but those based on weight were very great in the lower classes
over the entire growing season. 相似文献
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695.
Chromosome numbers of five Saccharum species hybrids and their cell suspension cultures were determined. The chromosome number was stable in four parental clones (2n = 122, 114, 114, and 112), but was variable in another (2n = 108-128). The cell suspension cultures have been maintained in a yeast extract-enriched nutrient medium for more than 6 years. These cultures were variable in chromosome number for all clones, with a partial aneuploid series at the haploid and/or polyploid level. Each clone had different chromosomal population modes after 6 years of culture. The loss of chromosomes over a period of time would have an effect on the genetic makeup of a cell population. This has implications in the use and interpretation of data from pathological, cytogenetical, biochemical, and physiological studies using cell cultures and is probably a partial explanation for the loss of totipotency in 6-year-old sugarcane tissue and suspension cultures. 相似文献
696.