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951.
哺乳动物体细胞核移植中供体细胞的研究进展 总被引:2,自引:0,他引:2
在哺乳动物体细胞核移植中,供体细胞是影响其效率的主要因素之一。供体细胞的类型、细胞周期、细胞的培养代数、冷藏与冷冻处理,以及供体动物的性别、年龄等都可能影响核移植胚胎的发育。根据现有资料,简要综述了在哺乳动物体细胞核移植中有关供体细胞的研究进展。 相似文献
952.
953.
Summary Investigations into the mechanisms of somatic embryogenesis (SE) have largely focused on the hormonal regulation of the process
and a repertoire of strategies has been developed to regenerate many species via SE. However, the genes that regulate the
induction and development of somatic embryos have not been defined. In the recent times, regeneration via overexpression of
genes, such as WUSCHEL or LEAFY COTYLEDON, in Arabidopsis has started to provide a basis for understanding the genes involved in SE. This has gone hand in hand with the availability
of genome sequence information and the availability of mutants in model plants such as Arabidopsis and Medicago. An improved understanding of zygotic embryogenesis and the maintenance and differentiation of stem cells in the shoot meristem
also helps to provide novel insights into the mechanisms of SE. This review examines the current understanding of the genetic
regulation of SE in the context of current molecular understanding of plant development. 相似文献
954.
Wan-Jun Zhang Jiang-Li Dong Ben-Guo Liang Yong-Sheng Jin Tao Wang 《In vitro cellular & developmental biology. Plant》2006,42(2):114-118
Summary We report a protocol for efficient plant regeneration of four tall fescue (Festuca arundinacea Schreb.) cultivars (‘Surpro’, ‘Coronado’, ‘Summer Lawn’, and ‘Fawn’) via somatic embryogenesis. Calli were initiated from
mature seeds grown on modified Murashige and Skoog (MMS) medium supplemented with 7.0mgl−1 (31.7μM) 2,4-dichlorophenoxyacetic acid (2,4-D) and 0.05 mgl−1 (0.23 μM) kinetin (Kin). Calli were maintained and proliferated by subculture at monthly intervals on MMS medium containing 4.5 mgl−1 (20.4 μM) 2,4-D and 0.2mgl−1 (0.9 μM) Kin. Somatic embryos (SE) were induced from seed-derived calli on SE-induction medium (MMS supplemented with 2.0 mgl−1 2,4-D and 0.2mgl−1 Kin). Plantlets were regenerated from somatic embryogenic calli grown on modified SH medium supplemented with 2 mgl−1 Kin. Using this optimized protocol, 78.6–82.3% of mature seeds of all four cultivars produced SE clusters, of which 93.5–95.3%
regenerated into plants within 10 wk. The regenerants showed no phenotypic abnormalities. 相似文献
955.
Hamako Sasamoto Yohichi Wakita Shinso Yokota Nobuo Yoshizawa Toshio Katsuki Yoshihiko Nishiyama Toshitaka Yokoyama Mitsue Fukui 《In vitro cellular & developmental biology. Plant》2006,42(2):174-178
Summary This study reports the characterization of 11 plants regenerated from electrically fused protoplasts between Populus alba and Alnus firma. Growth characteristics of five regenerated plants (AP-1-AP-5) in terms of shoot height and leaf color showed small differences
compared with those of P. alba grown, in pots, and showed no difference in shoot height and diameter compared with those grown in nursery field. There was
also no difference in the RAPD pattern between the plants regenerated from interfamilial protoplast fusion and P. alba. In contrast, the lately regenerated plants (AP-6-AP-11) grown in pots showed a marked difference in leaf morphology and
RAPD pattern. There was a variation in the ratio of longitudinal to transverse length of leaves among the 11 plants from interfamilial
fusions compared with that of protoclones and intraspecific fused protoplasts of P. alba. 相似文献
956.
We studied the rate of oxygen consumption by the Lymnaea stagnalis embryos. The rate of oxygen consumption increased consistently during embryogenesis. The volume specific rate of oxygen consumption increased initially from the early cleavage stages until the gastrula stage and then decreased gradually to the eclosion of snails. There are three periods in embryogenesis of L. stagnalis, which differ in the coefficients of allometric dependence between the rate of oxygen consumption and volume of embryos: (1) early embryogenesis, when the increase in the rate of oxygen consumption is not accompanied by the growth of volume of the embryos; (2) larval period (trochophore and veliger stages; exponential coefficient k = 0.514), and (3) postlarval period (exponential coefficient k = 0.206). 相似文献
957.
Fuchs M 《The journal of gene medicine》2006,8(11):1358-1362
From early on, the possibility of genetic intervention in humans has been the subject of philosophical and ethical reflection in the scientific community. It became the object of public debate and parliamentary decision‐making under the rule of law even before the first authorized trials on human subjects could start. This article explains why the debate on germ‐line intervention and genetic enhancement is still ongoing. The focus is on somatic gene therapy. There is a political and academic consensus that it represents an adequate tool for a high‐ranking end if some points are considered and taken into account. But where do we stand and what are the ethical conclusions we can draw from recent clinical experiences? Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
958.
Fahrenkrug SC Clark KJ Dahlquist MO Hackett PB 《Marine biotechnology (New York, N.Y.)》1999,1(6):552-561
Internal ribosome entry sites (IRESs) allow ribosomal access to messenger RNA without a requirement for cap recognition and
subsequent scanning to an initiator AUG. Hence, IRESs have been adapted into dicistronic vectors for the expression of more
than one gene from a single mRNA. Dicistronic vectors have been used for many applications in mammalian tissue culture and
transgenesis. However, whether the IRESs from mammalian viruses function without temporal or spatial restrictions in nonmammalian
organisms like zebra fish (Danio rerio) is unknown. Therefore, we have examined the expression capabilities of the encephalomyocarditis virus (EMCV) IRES during
zebrafish embryogenesis. We determined that the EMCV IRES was sufficient to permit detectable expression of several second
cistron reporters during zebrafish embryogenesis, including luciferase and green fluorescent protein. This suggests that our
dicistronic vectors are suitable for general use in any vertebrate system, from fish to humans.
Received March 26, 1999; accepted June 14, 1999. 相似文献
959.
J. B. M. Custers S. C. H. J. Snepvangers H. J. Jansen L. Zhang M. M. van Lookeren Campagne 《Protoplasma》1999,208(1-4):257-264
Summary The cauliflower mosaic virus 35S (35S-CaMV) promoter, which is generally used as a constitutive promoter in plants, is known to be silent during microspore and pollen development. Here we analyzed whether the 35S-CaMV promoter fused to thegus (-glucuronidase) gene can be used as a marker for early sporophytic development in embryogenic microspore cultures of tobacco andBrassica napus. In microspore culture ofB. napus, the 35S-CaMV promoter remained off from the start of embryogenic culture up to the mid-cotyledonary embryo stage. 35S-CaMV promoter activity was only present in those microspores that initiated sporophytic development, but failed to enter embryogenic development. Similar results were also obtained with shed-microspore cultures of tobacco, in which rapid, direct embryogenesis takes place. In isolated-microspore cultures, in which embryogenesis is delayed, an intermitting period of sporophytic development was observed, characterized by extensive 35S-CaMV promoter activity. Therefore, the 35S-CaMV promoter discriminates between two classes of sporophytic development: it is activated in microspores which change fate from gametophytic into (temporarily) nonembryogenic sporophytic development, whereas the promoter is silent in sporophytic microspores that enter embryogenic development directly. This mirrors our observation that the 35S-CaMV promoter is also silent in young zygotic embryos. 相似文献
960.
Oli MK 《Theoretical population biology》1999,56(3):293-300
An important biological feature of cyclic populations of voles and lemmings is phase-related changes in average body mass, with adults in high-density phases being 20-30% heavier than those in low-density phases of a cycle. This observation, called the "Chitty effect," is considered to be a ubiquitous feature of cyclic populations. It has been argued that understanding the Chitty effect is fundamental to unraveling the enigma of population cycles. However, there exists no agreement among biologists regarding the causes of the Chitty effect. Here, I propose a simple hypothesis to explain the Chitty effect, based on phase-related, dynamic allocation of energy between reproductive and somatic effort. The essence of the hypothesis is that: (1) reproduction is suppressed in animals born or raised in the later part of the increase phase by environmental factors, including social influences; (2) suppression of reproduction limits the amount of energy that is diverted for reproductive effort, and forces a disproportionately greater amount of surplus power (the energy left after the energetic costs of standard and active metabolism are met) to be allocated for somatic effort; (3) the surplus energy, above and beyond what is required for routine biological activities, will allow continuous growth and deposition of additional body mass, which causes an increase in body mass; and (4) animals grow to a larger size as a population enters the peak density phase, causing an increase in the average body mass. The Chitty effect is predicted to be most pronounced at the late increase or peak phase of a population cycle. Possible causes of reproductive suppression include direct or indirect influences of the environmental factors. The Chitty effect may be a consequence, not a cause, of population cycles in small mammals. 相似文献