首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 15 毫秒
1.
Two new analogues of 1-D-1-O-(2-acetamido-2-deoxy-alpha-D-glucopyranosyl)-myo-inositol, a biosynthetic intermediate in the production of mycothiol in the Mycobacteria have been synthesized. Both the 2-deoxy-2-C-(2'-hydroxypropyl)-D-glucoside 5, and the 2-deoxy-2-C-(2'-oxopropyl)-D-glucoside 6, are derived from fully benzylated 1-D-1-O-(2-C-allyl-2-deoxy)-D-glucopyranosyl)-myo-inositol 20, readily assembled via a protected 2-C-allyl-2-deoxyglucosyl fluoride. Both 5 and 6 inhibit the incorporation of [3H]inositol by whole cells of Mycobacterium smegmatis into a number of metabolites which contain inositol.  相似文献   

2.
Human BST-2 (hBST-2) has been identified as a cellular antiviral factor that blocks the release of various enveloped viruses. Orthologues of BST-2 have been identified in several species, including human, monkeys, pig, mouse, cat and sheep. All have been reported to possess antiviral activity. Duplication of the BST-2 gene has been observed in sheep and the paralogues are referred to as ovine BST-2A and BST2-B, although only a single gene corresponding to BST-2 has been identified in most species. In this study, we identified three isoforms of bovine BST-2, named bBST-2A1, bBST-2A2 and bBST-2B, in bovine cells treated with type I interferon, but not in untreated cells. Both bBST-2A1 and bBST-2A2 are posttranslationally modified by N-linked glycosylation and a GPI-anchor as well as hBST-2, while bBST-2B has neither of these modifications. Exogenous expression of bBST-2A1 or bBST-2A2 markedly reduced the production of bovine leukemia virus and vesicular stomatitis virus from cells, while the antiviral activity of bBST-2B was much weaker than those of bBST-2A1 and bBST-2A2. Our data suggest that bBST-2A1 and bBST-2A2 function as part of IFN-induced innate immunity against virus infection. On the other hand, bBST-2B may have a different physiological function from bBST-2A1 and bBST-2A2.  相似文献   

3.
4.
NELL2 is a neuron-specific secreted glycoprotein containing an N-terminal thrombospondin I-like domain (TSP-N). In this study, we describe NELL2-Tsp, a novel alternative splice variant of rat NELL2. NELL2-Tsp uses an alternate stop codon resulting in a C-terminal truncated form of NELL2, containing a signal peptide and a TSP-N domain. NELL2-Tsp is a glycosylated protein specifically expressed in brain tissue. NELL2-Tsp and NELL2 are secreted, likely due to the putative signal peptide. However, due to the truncation, the secreted portion of NELL2-Tsp is smaller than that of NELL2. Immunoprecipitation analysis confirmed that NELL2-Tsp was able to associate with NELL2 and with itself. In addition, expression of NELL2-Tsp notably reduced secretion of NELL2 and inhibited NELL2-mediated neurite outgrowth. These results suggest that NELL2-Tsp may act as a negative regulator of wild-type NELL2.  相似文献   

5.
重金属对油菜种子萌发和胚根生长的影响   总被引:5,自引:0,他引:5  
分析了Hg2 、Cd2 、Ni2 、Co2 、Zn2 5种重金属离子对油菜种子萌发和胚根伸长的影响,以及金属离子K 、Mg2 和Ca2 与重金属的交互作用。结果表明:(1)重金属对油菜种子萌发的抑制作用依次为Hg2 >Cd2 和Co2 >Ni2 >Zn2 ,而对胚根生长的毒害作用依次为Hg2 >Cd2 >Co2 >Ni2 >Zn2 。(2)萌发率为40%以上时,K 和Ca2 可以提高Ni2 、Zn2 和Co2 胁迫下油菜种子的萌发率,却进一步降低了Hg2 、Cd2 胁迫下种子的萌发;Mg2 可以提高Ni2 、Zn2 、Cd2 和Co2 胁迫下种子的萌发率,但对Hg2 毒害却没有缓解。(3)胚根伸长率达到60%以上时,K 和Mg2 增强了Ni2 、Hg2 、Cd2 和Co2 对胚根生长的抑制,而Ca2 则缓解了Zn2 、Ni2 和Co2 对胚根生长的抑制作用。研究结果对于重金属复合污染土壤中植物种子的萌发和定植具有理论和实践意义。  相似文献   

6.
Shoc2 is a positive regulator of signaling to extracellular signal-regulated protein kinases 1 and 2 (ERK1/2). Shoc2 is also proposed to interact with RAS and Raf-1 in order to accelerate ERK1/2 activity. To understand the mechanisms by which Shoc2 regulates ERK1/2 activation by the epidermal growth factor receptor (EGFR), we dissected the role of Shoc2 structural domains in binding to its signaling partners and its role in regulating ERK1/2 activity. Shoc2 is comprised of two main domains: the 21 leucine rich repeats (LRRs) core and the N-terminal non-LRR domain. We demonstrated that the N-terminal domain mediates Shoc2 binding to both M-Ras and Raf-1, while the C-terminal part of Shoc2 contains a late endosomal targeting motif. We found that M-Ras binding to Shoc2 is independent of its GTPase activity. While overexpression of Shoc2 did not change kinetics of ERK1/2 activity, both the N-terminal and the LRR-core domain were able to rescue ERK1/2 activity in cells depleted of Shoc2, suggesting that these Shoc2 domains are involved in modulating ERK1/2 activity.  相似文献   

7.
We have employed a new scale for characterizing chromosomal forms in the karyotypes of four species of Bipalium from five localities in Japan. Specimens of Bipalium nobile Kawakatsu et Makino, 1982, from Yokohama had a diploid chromosome number of 2x = 10 (2m + 2sm + 2sm + st & sm + 2sm); specimens of the same species from Toyonaka had this number as well but with slightly different chromosomal form (2m + 2sm + sm & st + 2st + m & sm). An undescribed species from Sanjô, Bipalium sp. 2, with two dorsal stripes and a yellow head crescent, had 2x = 10 (2m + 2sm + 2sm + 2sm + 2m); and another undescribed species from Chichijima Island, Bipalium sp. 3, with five dorsal stripes, had 2x = 10 (2m + 2sm + 2sm + 2sm + 2m). A non-sexual bipaliid tentatively identified as Bipalium kewense Moseley, 1878, from Chichijima Island had 2x = 18 (2m + 2m + 2m + 2sm + 2st + 2sm + 2sm + 2sm + 2sm).  相似文献   

8.
The initial rate and final extent of polymerization of both bovine brain tubulin and sea urchin egg tubulin were enhanced in the presence of 2H2O. The yields were increased in association with the elevation of the 2H2O concentration. 2H2O also reduced the critical concentration for polymerization of brain tubulin. Thermodynamic analysis was attempted using the temperature dependence of the critical concentration for polymerization in the presence of 2H2O. We obtained linear van 't Hoff plots and calculated thermodynamic parameters which were positive and were increased with the elevation of the 2H2O concentration. The enhancement of the polymerization of tubulin by 2H2O could, therefore, be the result of the strengthening of intra- and/or inter-molecular hydrophobic interactions of the tubulin molecules. We believe that the increase in length and number of microtubules of the mitotic spindles in the dividing cells of the eukaryotes with 2H2O may be caused by the direct involvement of 2H2O in the polymerization of tubulin.  相似文献   

9.
车前属两种植物的核型研究   总被引:2,自引:0,他引:2  
张华宣   《广西植物》1998,18(2):119-122
本文对我国两种车前属Plantago植物的核型进行了分析。2个种的染色体数目均为2n=2x=12。它们的核型是:海滨车前P.camtschaticaLink,Enum.2n=2x=12=8m+4sm;毛车前P.jehohlensisKoidz.2n=2x=12=6m+4sm+2st。它们的核型均属“2A”型。由12条染色体组成。  相似文献   

10.
IKx is a voltage-dependent K+ current in the inner segment of rod photoreceptors that shows many similarities to M-current. The depression of IKx by external Ba2+ was studied with whole-cell voltage clamp. Ba2+ reduced the conductance and voltage sensitivity of IKx tail currents and shifted the voltage range over which they appeared to more positive potentials. These effects showed different sensitivities to Ba2+: conductance was the least sensitive (K0.5 = 7.6 mM), voltage dependence intermediate (K0.5 = 2.4 mM) and voltage sensitivity the most sensitive (K0.5 = 0.2 mM). Ca2+, Co2+, Mn2+, Sr2+, and Zn2+ did not have actions comparable to Ba2+ on the voltage dependence or the voltage sensitivity of IKx tail currents. In high K+ (100 mM), the voltage range of activation of IKx was shifted 20 mV negative, as was the tau-voltage relation. High K+ did not prevent the effect of Ba2+ on conductance, but abolished its ability to affect voltage dependence and voltage sensitivity. Ba2+ also altered the apparent time-course of activation and deactivation of IKx. Low Ba2+ (0.2 mM) slowed both deactivation and activation, with most effect on deactivation; at higher concentrations (1-25 mM), deactivation and activation time courses were equally affected, and at the highest concentrations, 5 and 25 mM Ba2+, the time course became faster than control. Rapid application of 5 mM Ba2+ suggested that the time dependent currents in Ba2+ reflect in part the slow voltage-dependent block and unblock of IKx channels by Ba2+. This blocking action of Ba2+ was steeply voltage- dependent with an apparent electrical distance of 1.07. Ba2+ appears to interact with IKx channels at multiple sites. A model which assumes that Ba2+ has a voltage-independent and a voltage-dependent blocking action on open or closed IKx channels reproduced many aspects of the data; the voltage-dependent component could account for both the Ba(2+)- induced shift in voltage dependence and reduction in voltage sensitivity of IKx tail currents.  相似文献   

11.
It was shown that IgGs purified from the sera of healthy Wistar rats contain several different bound Me2+ ions and oxidize 3,3'-diaminobenzidine through a H2O2-dependent peroxidase and H2O2-independent oxidoreductase activity. IgGs have lost these activities after removing the internal metal ions by dialysis against EDTA. External Cu2+ or Fe2+ activated significantly both activities of non-dialysed IgGs containing different internal metals (Fe > or = Pb > or = Zn > or = Cu > or = Al > or = Ca > or = Ni > or = Mn > Co > or = Mg) showing pronounced biphasic dependencies corresponding to approximately 0.1-2 and approximately 2-5 mM of Me2+, while the curves for Mn2+ were nearly linear. Cu2+ alone significantly stimulated both the peroxidase and oxidoreductase activities of dialysed IgGs only at high concentration (> or = 2 mM), while Mn2+ weakly activated peroxidase activity at concentration >3 mM but was active in the oxidoreductase oxidation at a low concentration (<1 mM). Fe2+-dependent peroxidase activity of dialysed IgGs was observed at 0.1-5 mM, but Fe2+ was completely inactive in the oxidoreductase reaction. Mg2+, Ca2+, Zn2+, Al2+ and especially Co2+ and Ni2+ were not able to activate dialysed IgGs, but slightly activated non-dialysed IgGs. The use of the combinations of Cu2+ + Mn2+, Cu2+ + Zn2+, Fe2+ + Mn2+, Fe2+ + Zn2+ led to a conversion of the biphasic curves to hyperbolic ones and in parallel to a significant increase in the activity as compared with Cu2+, Fe2+ or Mn2+ ions taken separately; the rates of the oxidation reactions, catalysed by non-dialysed and dialysed IgGs, became comparable. Mg2+, Co2+ and Ni2+ markedly activated the Cu2+-dependent oxidation reactions catalysed by dialysed IgGs, while Ca2+ inhibited these reactions. A possible role of the second metal in the oxidation reactions is discussed.  相似文献   

12.
A series of derivatives of the 2-deoxy analogue of beta-KDO (2,6-anhydro-3-deoxy-D-glycero-D-talo-octonic acid; ammonium salt, 2) has been synthesised as potential inhibitors of CMP-KDO synthetase, starting from methyl 2,6-anhydro-3-deoxy-4,5:7,8-di-O-isopropylidene-D-glycero-D-talo- octonate and replacing the CO2Me group attached to C-2 variously by CONH2, CONHOH, CH2OH, CH2PO(OH)(O-NH4+), COCH2PO(OH)(O-H3N+pheny), CH2CO2-NH4+, CON-HCH2CO2-NH4+, CONHBn, CONHHexyl, CO2Bn, and CO2Hexyl. Of these derivatives, the hydroxamic acid (CONHOH) was the best inhibitor of CMP-KDO synthetase, but was less potent than 2.  相似文献   

13.
Chinen A  Hamaoka T  Yamada Y  Kawamura S 《Genetics》2003,163(2):663-675
Zebrafish is becoming a powerful animal model for the study of vision but the genomic organization and variation of its visual opsins have not been fully characterized. We show here that zebrafish has two red (LWS-1 and LWS-2), four green (RH2-1, RH2-2, RH2-3, and RH2-4), and single blue (SWS2) and ultraviolet (SWS1) opsin genes in the genome, among which LWS-2, RH2-2, and RH2-3 are novel. SWS2, LWS-1, and LWS-2 are located in tandem and RH2-1, RH2-2, RH2-3, and RH2-4 form another tandem gene cluster. The peak absorption spectra (lambdamax) of the reconstituted photopigments from the opsin cDNAs differed markedly among them: 558 nm (LWS-1), 548 nm (LWS-2), 467 nm (RH2-1), 476 nm (RH2-2), 488 nm (RH2-3), 505 nm (RH2-4), 355 nm (SWS1), 416 nm (SWS2), and 501 nm (RH1, rod opsin). The quantitative RT-PCR revealed a considerable difference among the opsin genes in the expression level in the retina. The expression of the two red opsin genes and of three green opsin genes, RH2-1, RH2-3, and RH2-4, is significantly lower than that of RH2-2, SWS1, and SWS2. These findings must contribute to our comprehensive understanding of visual capabilities of zebrafish and the evolution of the fish visual system and should become a basis of further studies on expression and developmental regulation of the opsin genes.  相似文献   

14.
The capacity of PGE2 to inhibit human T cell responses was examined by investigating its effect on mitogen-induced IL-2 production and proliferation of highly purified CD4+ T cells. PGE2 inhibited both PHA and anti-CD3 induced proliferation and IL-2 production by an action directly on the responding T cell. Inhibition of IL-2 production reflected decreased accumulation of mRNA for IL-2. A variety of other cAMP elevating agents exerted similar inhibitory effects. Inhibition of proliferation could be overcome by supplemental IL-2, PMA, or the anti-CD28 mAb 9.3. Although PMA and 9.3 markedly increased the amount of IL-2 produced by mitogen-stimulated T cells, the percentage inhibition of IL-2 secretion caused by PGE2 and other cAMP elevating agents remained comparable in these costimulated cultures. Rescue of T cell DNA synthesis by these agents appeared to reflect the finding that, although PGE2 markedly inhibited IL-2 production, the absolute amount of IL-2 produced was increased sufficiently to sustain mitogen-induced proliferation. As anticipated, PGE2, forskolin, and cholera toxin increased T cell cAMP levels. The quantity of cellular cAMP generated in response to PGE2, cholera toxin, and forskolin could be inhibited by PMA or 2',5'-dideoxyadenosine. Using these reagents, the inhibitory effects of PGE2 were found to reflect intracellular cAMP levels, but only within a very narrow range. The results indicate that by elevating cAMP levels, PGE2 inhibits human T cell IL-2 production at a point that is common to both the CD3 and CD28 signaling pathways.  相似文献   

15.
We previously reported that zebrafish have four tandemly duplicated green (RH2) opsin genes (RH2-1, RH2-2, RH2-3, and RH2-4). Absorption spectra vary widely among the four photopigments reconstituted with 11-cis retinal, with their peak absorption spectra (lambda(max)) being 467, 476, 488, and 505 nm, respectively. In this study, we inferred the ancestral amino acid (aa) sequences of the zebrafish RH2 opsins by likelihood-based Bayesian statistics and reconstituted the ancestral opsins by site-directed mutagenesis. The ancestral pigment (A1) to the four zebrafish RH2 pigments and that (A3) to RH2-3 and RH2-4 showed lambda(max) at 506 nm, while that (A2) to RH2-1 and RH2-2 showed a lambda(max) at 474 nm, indicating that a spectral shift had occurred toward the shorter wavelength on the evolutionary lineages A1 to A2 by 32 nm, A2 to RH2-1 by 7 nm, and A3 to RH2-3 by 18 nm. Pigment chimeras and site-directed mutagenesis revealed a large contribution (approximately 15 nm) of glutamic acid to glutamine substitution at residue 122 (E122Q) to the A1 to A2 and A3 to RH2-3 spectral shifts. However, the remaining spectral differences appeared to result from complex interactive effects of a number of aa replacements, each of which has only a minor spectral contribution (1-3 nm). The four zebrafish RH2 pigments cover nearly an entire range of lambda(max) distribution among vertebrate RH2 pigments and provide an excellent model to study spectral tuning mechanisms of RH2 in vertebrates.  相似文献   

16.
Oxidation of ferrous iron during peroxidation of lipid substrates   总被引:3,自引:0,他引:3  
Oxidation of Fe2+ in solution was dependent upon medium composition and the presence of lipid. The complete oxidation of Fe2+ in 0.9% saline was markedly accelerated in the presence of phosphate or EDTA and the ferrous oxidation product formed was readily recoverable as Fe2+ by ascorbate reduction. In contrast, in the presence of either brain synaptosomal membranes, phospholipid liposomes, fatty acid micelles or H2O2, less than 50% of the Fe2+ oxidized during an incubation could be recovered as Fe2+ via reduction with ascorbate. In the presence of unsaturated lipid, oxidation of Fe2+ was associated with peroxidation of lipid, as assessed by the uptake of O2 and formation of thiobarbituric acid-reactive products during incubations. Although relatively little Fe2+ oxidation or lipid peroxidation occurred in saline with synaptosomes or linoleic acid micelles during an incubation with Fe2+ alone, significant Fe2+ oxidation and lipid peroxidation occurred in incubations containing a 1:1 ratio of Fe2+ and Fe3+. Extensive Fe2+ oxidation and lipid peroxidation also occurred with Fe2+ alone in saline incubations with either linolenic or arachidonic acid acid micelles or liposomes prepared from dilinoleoylphosphatidylcholine. While a 1:1 ratio of Fe2+ and Fe3+ enhanced thiobarbituric acid-reactive product formation in incubations containing linolenic or arachidonic micelles, it reduced the rate of O2 consumption as compared with Fe2+ alone. The results demonstrate that oxidation of Fe2+ in incubations containing lipid substrates is linked to and accelerated by peroxidation of those substrates. Furthermore, the results suggest that oxidation of Fe2+ in the presence of lipid or H2O2 creates forms of iron which differ from those formed during simple Fe2+ autoxidation.  相似文献   

17.
The role of Mg2+ in the activation of phosphoenzyme hydrolysis has been investigated with the (Ca2+, Mg2+)-ATPase of sarcoplasmic reticulum vesicles. The enzyme of the native and solubilized vesicles was phosphorylated with ATP at 0 degrees C, pH 7.0, in the presence of Ca2+ and Mg2+. When Ca2+ and Mg2+ in the medium were chelated, phosphoenzyme hydrolysis continued for about 15 s and then ceased. The extent of this hydrolysis increased with increasing concentrations of Mg2+ added before the start of phosphorylation. This shows that the hydrolysis was activated by the Mg2+ added. The Mg2+ which activated phosphoenzyme hydrolysis was distinct from Mg2+ derived from MgATP bound to the substrate site. The Mg2+ site at which Mg2+ combined to activate phosphoenzyme hydrolysis was located on the outer surface of the vesicular membranes. During the catalytic cycle, Mg2+ combined with the Mg2+ site before Ca2+ dissociated from the Ca2+ transport site of the ADP-sensitive phosphoenzyme with bound Ca2+. This Mg2+ did not activate hydrolysis of the ADP-sensitive phosphoenzyme with bound Ca2+, but markedly activated hydrolysis of the ADP-insensitive phosphoenzyme without bound Ca2+. It is concluded that during the catalytic cycle, Mg2+ activates phosphoenzyme hydrolysis only after Ca2+ has dissociated from the Ca2+ transport site of phosphoenzyme.  相似文献   

18.
国产8种蜘蛛抱属植物的核型研究   总被引:3,自引:0,他引:3  
首次报道了8种蜘蛛抱属植物的核型,其中6种的染色体数目为首次报道,结果如下:峨边蜘蛛抱蛋A.ebianensis,2n=2x=36=18m 2sm(2sat) 16st;盈江蜘蛛抱蛋A.yingjiangensis,2n=2x=36=14m 6sm(2sat) 16st;海南蜘蛛抱蛋A.hainensis,2n=2x=36=20m(2sat) 14st 2t;石山蜘蛛抱蛋A.saxicola,2n=2x=36=16m 4sm(2sat) 16st;要蜘蛛抱蛋白A.muricata,2n=2x=36=18m 2sm(2sat) 16st);啮边蛛抱蛋A.marginella,2n=2x=38=22m 4sm(2sat) 12st;西林蜘蛛抱蛋A.xillinensis,2n=4x=76=48m(4sat) 2sm 26st;十字蜘蛛抱蛋A.cruciformis,2n=4x=76=46m(4sat) 12sm 18st。核型类型都为2C型。首次在中国发现了A.cruciformis和A.xilinensis的野生四倍体。根据外部形态性及已有的38种植物的核型资料分析,认为该属染色体的原始基数可能为x=18,核型向对称性增强的方向演化,其主要表现在中部着丝粒染色体数目的增多,这种演化趋似与其花部结构的进化密切相关。  相似文献   

19.
The conversion of [3H]estradiol to 2-hydroxyestradiol (2-OH-E2) by homogenates of porcine ovarian follicles was assayed in vitro in the presence and absence of 10 and 100 microM concentrations of the following potential substrates or inhibitors of estrogen-2/4-hydroxylase (E-2/4-H): (1) estrogens; estrone (E1), estriol (E3) and 17 alpha-estradiol (17 alpha-E2), (2) catecholestrogens; 2-hydroxyestradiol (2-OH-E2), 4-hydroxyestradiol (4-OH-E2) and 2-hydroxyestrone (2-OH-E1); (3) 2-methoxyestradiol (2-MeO-E2); (4) halogenated estrogens; 2-bromoestradiol, (2-Bromo-E2) 4-bromoestradiol and 2,4-dibromoestradiol; (5) androgens; testosterone (T), dihydrotestosterone (DHT) and androstenedione; (6) progesterone; (7) epinephrine; (8) inhibitors of steroid aromatase; aminoglutethimide and 4-hydroxyandrostenedione and (9) SKF 525A, an inhibitor of cytochrome P-450. Progesterone and 2-Bromo-E2 were the two most effective inhibitors (2-OH-E2 formation = 4 and 5% of control at 100 microM and 29.6 and 17.4% at 10 microM of progesterone and 2-Bromo-E2, respectively). 2-MeO-E2 at 100 microM was nearly as effective as progesterone in inhibiting E-2/4-H activity but only caused about 50% inhibition at 10 microM. The three catecholestrogens reduced 2-OH-E2 formation to about the same degree (21-23% of control at 100 microM). The 2,4-dibromo-E2 was equipotent with the catecholestrogens while 4-bromo-E2 was about half as effective. The phenolic estrogens, potential substrates for the enzyme, reduced 2-OH-E2 formation to different degrees, with E3 being the most effective. Among the androgens, DHT was almost as effective an inhibitor as the catecholestrogens, T was about half as effective while androstenedione had no effect. Epinephrine and the two inhibitors of aromatase did not inhibit E-2/4-H activity. SKF 525A inhibited E-2/4-H activity but with a potency only about 1/10th that reported for liver.  相似文献   

20.
Hydrogenphosphonate method was used for synthesis of 4-nitrophenyl 2-acetamido-3- and 4-nitrophenyl 2-acetamido-4-(2-acetamido-2-deoxy-alpha-D-glucopyranosyl phosphate)-2-deoxy-beta-D-glucopyranosides. The glycosides, phosphate diester fragments of the title bacteria capsular antigens, were obtained by H-phosphorylation of the suitably protected 2-acetamido-2-deoxy-beta-D-glucopyranosides with 2-acetamido-3,4,6-tri-O-benzoyl-2-deoxy-alpha-D-glucopyranosyl H-phosphonate in the presence of trimethylacetyl chloride followed by oxidation and deprotection.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号