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991.
992.
青海藏族青少年骨龄与生长发育关系研究 总被引:1,自引:0,他引:1
本文报告了青海省境内,世居在海拔3000-4000米地区的728名7-18岁健康藏族青少年学生的手、腕部骨骼发育情况,对骨化中心出现和骨骺愈合求出了50%出现年龄,并对骨龄与青春期身高突增的关系及与月经初衬潮的关系进行了分析。 相似文献
993.
Progesterone interacts with P-glycoprotein in multidrug-resistant cells and in the endometrium of gravid uterus 总被引:8,自引:0,他引:8
C P Yang S G DePinho L M Greenberger R J Arceci S B Horwitz 《The Journal of biological chemistry》1989,264(2):782-788
P-Glycoprotein (P-GP) plays a pivotal role in maintaining the multidrug-resistant (MDR) phenotype. This membrane glycoprotein is overproduced in MDR cells and the endometrium of the mouse gravid uterus (Arceci, R.J., Croop, J.M., Horwitz, S.B., and Housman, D. (1988) Proc. Natl. Acad. Sci. U.S.A. 85, 4350-4354). This latter observation and an interest in endogenous substrates for P-GP led to a study of the interaction of steroids with P-GP found in the endometrium of the mouse gravid uterus and in MDR cells derived from the murine macrophage-like cell J774.2. [3H]Azidopine labeling of P-GP from these two sources was inhibited by various steroids, particularly progesterone. Progesterone also markedly inhibited [3H]vinblastine binding to membrane vesicles prepared from MDR cells, enhanced vinblastine accumulation in MDR cells, and increased the sensitivity of MDR cells to vinblastine. In addition, we have demonstrated that the hydrophobicity of a steroid is important in determining its effect on inhibition of drug binding to P-GP. It is concluded that progesterone, a relatively nontoxic endogenous steroid, interacts with P-GP and is capable of reversing drug resistance in MDR cells. 相似文献
994.
Michael F. Dowe Jr. Gregg W. Roman Anita S. Klein 《Molecular & general genetics : MGG》1990,221(3):475-485
Summary The regulatory mutation bronze mutable 4 Derivative 6856 (bz-m4 D6856) contains a complex 6.7 kb Dissociation (Ds) element tagged with a duplication of low copy bz 3 flanking sequences (Klein et al. 1988). This creates a unique opportunity to study the transposition of a single member of the repetitive family of Ds elements. Eighteen full purple revertants (Bz alleles) of bz-m4 were characterized enzymatically and by genomic mapping. For 17 of the Bz alleles, reversion to a wild-type phenotype was caused by excision of the 6.7 kb Ds transposon. Nine of these Bz alleles retained the transposon somewhere in their genome. In this study we show that like Ac (Schwartz 1989; Dooner and Belachew 1989), the 6.7 kb Ds element can transpose within a short physical distance, both proximal and distal to its original position. Additional bz sequences have been mapped immediately distal to the mutant locus in bz-m4 D6856; genetic evidence suggests these are flanked by two additional Ds elements. The remaining Bz revertant, Bz :107, arose from excision of a more complex 13 kb Ds element. 相似文献
995.
Uwe-G. Maier Klaus D. Grasser Michael M. Haa? Günter Feix 《Molecular & general genetics : MGG》1990,221(2):164-170
Summary A 216 by promoter fragment of the 19 kDa protein zein gene pMS1, containing the CCAAT and TATA boxes, was analysed by a variety of techniques for in vitro interactions with nuclear proteins from endosperm tissue. HMG proteins were found to form stable complexes with these A/T-rich promoter sequences and several specific DNA-binding proteins appear to be involved in the formation of DNA-protein complexes with this fragment. A 29 bp region spanning the two CCAAT boxes was protected from DNase I digestion in footprinting experiments. 相似文献
996.
Ji-Liang Tang Clare L. Gough Michael J. Daniels 《Molecular & general genetics : MGG》1990,222(1):157-160
Summary A recombinant plasmid pIJ3079 contains DNA sequences from Xanthomonas campestris pv campestris involved in coordinate negative regulation of production of the extracellular enzymes protease, endoglucanase, amylase and polygalacturonate lyase, and extracellular polysaccharide (EPS). Wild-type bacteria harbouring pIJ3079 and therefore carrying extra copies of the gene(s) therein showed reduced enzyme and EPS production and reduced aggresiveness to plants. Localised Tn5 mutagenesis of the corresponding region of the genome gave mutants producing higher levels of enzymes and EPS than the wild type, suggesting that the gene(s) may negatively regulate production in the normal cell. Enzyme and EPS production in the mutants was still dependent on previously characterised positive regulatory genes. 相似文献
997.
Thievery,home ranges,and nestmate recognition inEctatomma ruidum 总被引:1,自引:0,他引:1
Summary Thievery of food items among colonies of a ponerine ant,Ectatomma ruidum was common; nonnestmates in colonies or near the colony entrances receive incoming food items and carry them to their own
colony. In our study area 7 of 10 colonies were victimized by thief ants. Colonies have discrete home ranges and home range
size is correlated with the number of workers in the colony. Worker ants discriminate nestmates from non-nestmates when non-nestmates
are presented at colony entrances, but individuals from different colonies were not observed to engage in agonistic interactions
away from nest entrances. Non-nestmates gain entrance to colonies when the entrance is unguarded. Many instances of non-nestmates
being removed from colonies by residents were observed. The costs and benefits of theft under these circumstances are considered. 相似文献
998.
Photoaffinity labeling with [32P] 8-azidoadenosine 5-triphosphate (8-N3ATP) was used to identify putative binding sites on tobacco (Nicotiana tabacum L. and N. rustica L.) leaf ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBPCase, EC 4.1.1.39). Incorporation of 32P was observed in polypeptides corresponding to both RuBPCase subunits when desalted leaf and chloroplast extracts, and purified RuBPCase were irradiated with ultraviolet light in the presence of [32P] 8-N3ATP. 32P-labeling was dependent upon ultraviolet irradiation and occurred with [32P] 8-N3ATP labeled in the -position, indicating covalent incorporation of the photoprobe. Both [32P] 8-N3ATP and [32P] 8-N3GTP were incorporated to a similar extent into the 53-kilodalton (kDa) large subunit (LSu), but incorporation of [32P] 8-N3GTP into the 14-kDa small subunit (SSu) of RuBPCase was <5% of that measured with [32P] 8-N3ATP. Distinct binding sites for 8-N3ATP on the two subunits were indicated by different apparent K
D
values, 3 and 18 M for the SSu and LSu, respectively, and differences in the response of photoaffinity labeling to Mg2+, anions and enzyme activation. Active-site-directed compounds, including the non-gaseous substrate ribulose 1,5-bisphosphate, the reaction intermediate analog 2-carboxyarabinitol-1,5-bisphosphate and several phosphorylated effectors afforded protection to the LSu site against photoincorporation but provided almost no protection to the SSu. These results indicate that 8-N3ATP binds to the active-site region of the LSu and a distinct site on the SSu of RuBPCase. Experiments conducted with intact pea (Pisum sativum L.) and tobacco chloroplasts showed that the SSu was not photolabeled with [32P] 8-N3ATP in organello or in undesalted chloroplast lysates but was photolabeled when lysates were ultrafiltered or desalted. These results indicate that 8-N3ATP binds to a site on the SSu that has physiological significance.Abbreviations kDa
kilodalton
- LSu
large subunit
- 8-N3ATP
8-azidoadenosine 5-triphosphate
- RuBP
ribulose-1,5-bisphosphate
- RuBPCase
ribulose-1,5-bisphosphate carboxylase/oxygenase
- SSu
small subunit
Kentucky Agricultural Experiment Station Journal Article No. 89-3-150The authors acknowledge the technical assistance of J.C. Anderson. This work was supported in part by National Institute of Health grant GM 35766 to B.E.H. 相似文献
999.
Ethylene Binding and Action in Rice Seedlings 总被引:1,自引:0,他引:1
Sanders Ian O.; Ishizawa Kimiharu; Smith Aileen R.; Hall Michael A. 《Plant & cell physiology》1990,31(8):1091-1099
The existence of at least two saturable, high affinity bindingsites for ethylene is demonstrated in rice seedlings. The sitesdiffer markedly in their rates of association and dissociation.Suppression of endogenous ethylene biosynthesis leads to a significantenhancement of the [14C]ethylene binding observed. Norbornadieneinhibits ethylene binding and promotion of growth by ethylene.Carbon dioxide and hypoxia promote growth but neither affectsethylene binding. (Received June 25, 1990; Accepted August 24, 1990) 相似文献
1000.
Polysaccharide Fraction from Higher Plants which Strongly Interacts with the Cytosolic Phosphorylase Isozyme : I. Isolation and Characterization 总被引:2,自引:1,他引:1 下载免费PDF全文
From leaves of Spinacia oleracea L. or from Pisum sativum L. and from cotyledons of germinating pea seeds a high molecular weight polysaccharide fraction was isolated. The apparent size of the fraction, as determined by gel filtration, was similar to that of dextran blue. Following acid hydrolysis the monomer content of the polysaccharide preparation was studied using high pressure liquid and thin layer chromatography. Glucose, galactose, arabinose, and ribose were the main monosaccharide compounds. The native polysaccharide preparation interacted strongly with the cytosolic isozyme of phosphorylase (EC 2.4.1.1). Interaction with the plastidic phosphorylase isozyme(s) was by far weaker. Interaction with the cytosolic isozyme was demonstrated by affinity electrophoresis, kinetic measurements, and by 14C-labeling experiments in which the glucosyl transfer from [14C]glucose 1-phosphate to the polysaccharide preparation was monitored. 相似文献