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11.
12.
Antisense genes in plants: an overview 总被引:18,自引:0,他引:18
Plants are the first multicellular higher eukaryotic organisms in which artificial antisense genes have been shown to down-regulate target gene expression. Manipulations with an antisense gene can serve as a tool to study the effect of a particular plant gene inactivation, the interaction of gene products whose genes are coordinately expressed, or the functional analysis of cryptic genes. Transgenic plants harbouring an antisense gene already gave rise to patentable new characteristics, showing that the technique has great scientific and economic value. 相似文献
13.
Ronald E. Koes Cornelis E. Spelt Jos N. M. Mol Anton G. M. Gerats 《Plant molecular biology》1988,10(4):375-385
Chalcone synthase (CHS) genes in Petunia hybrida comprise a multigene family containing at least 7 complete members in the strain Violet 30 (V30). Based on a high sequence homology in both coding and non-coding sequence, a number of CHS genes can be placed into two subfamilies. By restriction fragment length polymorphism (RFLP) analysis it was shown that both chromosomes II and V carry one of these subfamilies, in addition to the other CHS genes identified so far. Members of a subfamily were found to be closely linked genetically. Analysis of the Petunia species that contributed to the hybrid nature of P. hybrida (P. axillaris, P. parodii, P. inflata and P. violacea) shows that none of the CHS gene clusters is specific for either one of the parents and therefore did not arise as a consequence of the hybridization. The number of CHS genes within a subfamily varies considerably among these Petunia species. From this we infer that the CHS subfamilies arose from very recent gene duplications. 相似文献
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蚤数量与宿主数量关系 总被引:9,自引:5,他引:4
无论在自然条件下或在人为条件下,蚤指数和染蚤率的高低与宿主密度的高低是一致的.宿主密度的升降,会导致其寄生蚤指数和染蚤率的升降. 本文讨论了宿主数量下降导致其寄生蚤数量下降的原因,仅是分析推测,提出几方面的看法. 相似文献
16.
Klaas J. Lusthof Nicolaas J. del Mol Wilma Richter Lambert H.M. Janssen John Butler Brigid M. Hoey Willem Verboom David N. Reinhoudt 《Free radical biology & medicine》1992,13(6):599-608
The formation of reactive oxygen intermediates (ROI) during redox cycling of newly synthesized potential antitumor 2,5-bis (1-aziridinyl)-1,4-benzoquinone (BABQ) derivatives has been studied by assaying the production of ROI (superoxide, hydroxyl radical, and hydrogen peroxide) by xanthine oxidase in the presence of BABQ derivatives. At low concentrations (< 10 microM) some BABQ derivatives turned out to inhibit the production of superoxide and hydroxyl radicals by xanthine oxidase, while the effect on the xanthine-oxidase-induced production of hydrogen peroxide was much less pronounced. Induction of DNA strand breaks by reactive oxygen species generated by xanthine oxidase was also inhibited by BABQ derivatives. The DNA damage was comparable to the amount of hydroxyl radicals produced. The inhibiting effect on hydroxyl radical production can be explained as a consequence of the lowered level of superoxide, which disrupts the Haber-Weiss reaction sequence. The inhibitory effect of BABQ derivatives on superoxide formation correlated with their one-electron reduction potentials: BABQ derivatives with a high reduction potential scavenge superoxide anion radicals produced by xanthine oxidase, leading to reduced BABQ species and production of hydrogen peroxide from reoxidation of reduced BABQ. This study, using a unique series of BABQ derivatives with an extended range of reduction potentials, demonstrates that the formation of superoxide and hydroxyl radicals by bioreductively activated antitumor quinones can in principle be uncoupled from alkylating activity. 相似文献
17.
本文报导四川省西部鱼类寄生粘孢子虫粘体虫属六新种,即异型粘体虫,新种Myxosoma disparis sp.nov.,四川粘体虫,新种Myxosoma sichuanensis sp.nov.,光唇粘体虫,新种Myxosoma acrossochilusi sp.nov.鳅粘体虫,新种Myxosoma nemachilusi sp.nov.斜囊粘体虫,新种Myxosoma obliqua sp.nov.,雅安粘体虫,新种Myxosoma yaanensis sp.nov.。 相似文献
18.
Abstract The vitellogenic period of gypsy moth ovarian development starts on day 3 of the pupal stage and continues through adulthood. During this period, rapid increases occur in follicle size, protein content, and wet weight of the ovary. Patency is observed on day 3 of the pupal stage.
Pre-vitellogenic follicles are formed in the last larval stadium. Newly formed follicles detach from the germarium on day 4, and increase rapidly to 140 per ovariole at the end of the last larval stadium. The pre-vitellogenic follicles are uniformly around 50 um in diameter. No vitellogenin is incorporated into the oocytes until the pupal stage.
Polyacrylamide gel electrophosesis (PAGE) in the presence of sodium dodecylsulphate (SDS) analysis of male and female haemolymph samples and vitellogenic ovaries demonstrates the presence of two female-specific subunits of vitellogenin of 180 kD and 160 kD. These proteins are detected only in haemolymph and ovarian extracts of vitellogenic females. The molecular weight of the native protein determined by size exclusion chromatography is approximately 400–420 kD.
A highly sensitive double antibody sandwich enzyme-linked immunosorbent assay (ELISA) was developed to monitor the temporal changes in vitellogenin titre in haemolymph. Vitellogenin production starts on day 2 of the last larval stadium, reaching a maximum level by day 6 of the last larval stadium, and decreasing in the late pupal stage as vitellogenin was internalized into the oocytes. This is the first report of vitellogenin production occurring in the larval stage of a holometabolous insect. The fact that vitellogenin production and uptake occur during different stages of development in the gypsy moth, opens up some interesting questions concerning the underlying regulatory mechanisms controlling each process. 相似文献
Pre-vitellogenic follicles are formed in the last larval stadium. Newly formed follicles detach from the germarium on day 4, and increase rapidly to 140 per ovariole at the end of the last larval stadium. The pre-vitellogenic follicles are uniformly around 50 um in diameter. No vitellogenin is incorporated into the oocytes until the pupal stage.
Polyacrylamide gel electrophosesis (PAGE) in the presence of sodium dodecylsulphate (SDS) analysis of male and female haemolymph samples and vitellogenic ovaries demonstrates the presence of two female-specific subunits of vitellogenin of 180 kD and 160 kD. These proteins are detected only in haemolymph and ovarian extracts of vitellogenic females. The molecular weight of the native protein determined by size exclusion chromatography is approximately 400–420 kD.
A highly sensitive double antibody sandwich enzyme-linked immunosorbent assay (ELISA) was developed to monitor the temporal changes in vitellogenin titre in haemolymph. Vitellogenin production starts on day 2 of the last larval stadium, reaching a maximum level by day 6 of the last larval stadium, and decreasing in the late pupal stage as vitellogenin was internalized into the oocytes. This is the first report of vitellogenin production occurring in the larval stage of a holometabolous insect. The fact that vitellogenin production and uptake occur during different stages of development in the gypsy moth, opens up some interesting questions concerning the underlying regulatory mechanisms controlling each process. 相似文献
19.
20.
A Boodhoo C D Mol J S Lee W F Anderson 《The Journal of biological chemistry》1988,263(34):18578-18581
The purification and crystallization of Fab fragments of two mouse monoclonal immunoglobulins specific for different DNA structures are described. In each case, papain digestion of the immunoglobulins produced a mixture of Fab species differing in their isoelectric points. Purification of one of these species was required to obtain suitable crystals. One of these antibodies, Jel 72, is specific for right-handed duplex poly(dG).poly(dC). An Fab fragment of Jel 72 with a pI of 8.8 was purified by anion-exchange chromatography and used to obtain crystals from 56% saturated ammonium sulfate and 50 mM sodium acetate, pH 4.2, that diffract to 2.6-A resolution. They belong to the orthorhombic space group P2(1)2(1)2(1), with cell dimensions of a = 94.6, b = 102.6, c = 92.4 A. The other antibody, Jel 318, binds triple-stranded DNA poly[d(Tm5C)].poly[d(GA)].poly[d(m5C + T)]. Jel 318 Fab fragments with isoelectric points of 7.6 and 7.8 were also purified by anion-exchange chromatography, and crystals were obtained from 12% polyethylene glycol 8000, 50 mM NaCl, and 10 mM Tris.HCl, pH 7.8. These crystals diffract to about 2.4-A resolution and also belong to the orthorhombic space group P2(1)2(1)2(1), with cell dimensions of a = 82.4, b = 139.5, and c = 42.0 A. For both Fab fragments, crystal size and quality improved dramatically upon purification of an individual isoelectric species. 相似文献