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1.
Bi2Se3 nanorods have been synthesized through a simple hydrothermal reduction approach. The nanorods formed were ≈50 nm in average diameter and ≈4 μm nm in length. XRD characterization suggested that the product consisted of the rhombohedral phase of pure Bi2Se3. The products were also characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and thermo gravimetric analysis. The synthesis procedure is simple and uses less toxic reagents than the previously reported methods. The results showed that the capping agent CTAB plays a crucial role in the process. Other factors, such as the reaction time, the different capping agent and the sort of reductant also have influence on the morphology of the final products to some extent. 相似文献
2.
Phosphate homeostasis is controlled in part by absorption from the intestine, and reabsorption in the kidney. While the effect of Vitamin D metabolites on enterocytes is well documented, in the current study we assess selected responses in primary cultures of kidney cells. Time course studies revealed a rapid stimulation of phosphate uptake in cells treated with 1,25(OH)(2)D(3), relative to controls. Dose-response studies indicated a biphasic curve with optimal stimulation at 300 pM 1,25(OH)(2)D(3) and inhibition at 600 pM seco-steroid. Antibody 099--against the 1,25D(3)-MARRS receptor - abolished stimulation by the steroid hormone. Moreover, phosphate uptake was mediated by the protein kinase C pathway. The metabolite 24,25(OH)(2)D(3), which was found to inhibit the rapid stimulation of phosphate uptake in intestinal cells, had a parallel effect in cultured kidney cells. Finally, the 24,25(OH)(2)D(3) binding protein, catalase, was assessed for longer term down regulation. In both intestinal epithelial cells and kidney cells incubated with 24,25(OH)(2)D(3) for 5-24h, both the specific activity of the enzyme and protein levels were decreased relative to controls, while 1,25(OH)(2)D(3) increased both parameters over the same time periods. We conclude that the Vitamin D metabolites have similar effects in both kidney and intestine, and that 24,25(OH)(2)D(3) may have effects at the level of gene expression. 相似文献
3.
Although the activation of phospholipase A2 (PLA2) in ras-transformed cells has been well documented, the mechanisms underlying this activation are poorly understood. In this study we tried to elucidate whether the membrane phospholipid composition and physical state influence the activity of membrane-associated PLA2 in ras-transformed fibroblasts. For this purpose membranes from non-transfected and ras-transfected NIH 3T3 fibroblasts were enriched with different phospholipids by the aid of partially purified lipid transfer protein. The results showed that of all tested phospholipids only phosphatidylcholine (PC) increased PLA2 activity in the control cells, whereas in their transformed counterparts both PC and phosphatidic acid (PA) induced such effect. Further we investigated whether the activatory effect was due only to the polar head of these phospholipids, or if it was also related to their acyl chain composition. The results demonstrated that the arachidonic acid-containing PC and PA molecules induced a more pronounced increase of membrane-associated PLA2 activity in ras-transformed cells compared to the corresponding palmitatestearate- or oleate- containing molecular species. However, we did not observe any specific effect of the phospholipid fatty acid composition in non-transformed NIH 3T3 fibroblasts. In ras-transformed cells incubated with increasing concentrations of arachidonic acid, PLA2 activity was altered in parallel with the changes of the cellular content of this fatty acid. The role of phosphatidic and arachidonic acids as specific activators of PLA2 in ras-transformed cells is discussed with respect to their possible role in the signal transduction pathways as well as in the processes of malignant transformation of cells. 相似文献
4.
Synthesis of a series of monoorganobismuth dithiocarboxylate complexes, [RBi(S2CAr)2] (R = Me, Ph, tol; Ar = Ph, tol), has been reported. They have been characterized by elemental analyses and spectroscopic methods. Molecular structures of [RBi(S2Ctol)2] (R = Me or Ph) have been established by single crystal X-ray diffraction studies. The bismuth atom in these complexes adopts a square pyramidal configuration with the R group at the apical position. In the solid state, these complexes show supra-molecular association devoid of Bi?S secondary interactions. Thermolysis of [RBi(S2Ctol)2] (R = Me or Ph) in refluxing diphenylether yielded Bi2S3 nanocrystals which were characterized by XRD, EDAX and SEM. The complex [PhBi(S2Ctol)2] has been employed for deposition of thin films of Bi2S3 by AACVD. 相似文献
5.
Based on an understanding of atomic layer deposition (ALD) from prior experimental and computational results, all-atom molecular dynamics (MD) simulations are used to model the Al2O3 film structure and composition during ALD processing. By separating the large time-scale surface reactions from the small time-scale structural relaxation, we have focused on the growth dynamics of amorphous Al2O3 films at the atomic scale. The simulations are able to reproduce some important properties and growth mechanisms of Al2O3 ALD films, and hence provide a bridge between atomic-level information and experimental measurements. Information about the evolution of the microscopic structures of the Al2O3 films is generated, and the influence of operation parameters on the Al2O3 ALD process. The simulations predict a strong influence of the initial surface composition and process temperature on the surface roughness, growth rate and growth mode of the deposited films. 相似文献
6.
Adenosine 5-triphosphate receptors are known to be involved in fast excitatory postsynaptic currents in myenteric neurons of the digestive tract. In the present study, the distribution of P2X2 and P2X3 receptor mRNA was examined by in situ hybridisation while P2X2 and P2X3 receptor protein was localised by immunohistochemical methods. In addition, P2X2 and P2X3 receptors were colocalised with calbindin and calretinin in the myenteric and submucosal plexus. P2X2- and P2X3-immunoreactive neurons were found in the myenteric and submucosal plexuses throughout the entire length of the rat digestive tract from the stomach to the colon. Approximately 60%, 70% and 50% of the ganglion cells in the myenteric plexus of the gastric corpus, ileum and distal colon, and 56% and 45% in the submucosal plexus of the ileum and distal colon, respectively, showed positive immunoreactivity to the P2X2 receptor. Approximately 10%, 2% and 15% of the ganglion cells in the myenteric plexus of the gastric corpus, ileum and distal colon, and 62% and 40% in the submucosal plexus of the ileum and distal colon, respectively, showed positive immunoreactivity to the P2X3 receptor. Double-labelling studies showed that about 10–25% of the neurons with P2X2 immunoreactivity in myenteric plexus and 30–50% in the submucosal plexus were found to express calbindin or calretinin. About 80% of the neurons with P2X3 receptor immunoreactivity in the myenteric plexus and about 40% in the submucosal plexus expressed calretinin. Approximately 30–75% of the neurons with P2X3 receptor immunoreactivity in the submucosal plexus expressed calbindin, while none of them were found to express calbindin in the myenteric plexus. 相似文献
7.
Selective and per-O-acylation of carbohydrate derivatives using acyl chlorides and Al2O3, a solid support reagent, is reported. This protocol does not require the addition of any base or activator. This methodology has been further extended to the selective acylation of carbohydrate diols and the one-pot preparation of acetylated glycosyl chlorides direct from free reducing sugars. The yields obtained in most of the cases are excellent. 相似文献
8.
A peptide constrained to a conformation of second extracellular loop of human prostaglandin-E(2) (PGE(2)) receptor subtype3 (hEP3) was synthesized. The contacts between the peptide residues at S211 and R214, and PGE(2) were first identified by NMR spectroscopy. The results were used as a guide for site-directed mutagenesis of the hEP3 protein. The S211L and R214L mutants expressed in HEK293 cells lost binding to [(3)H]PGE(2). This study found that the non-conserved S211 and R214 of the hEP3 are involved in PGE(2) recognition, and implied that the corresponding residues in other subtype receptors could be important to distinguish the different configurations of PGE(2) ligand recognition sites. 相似文献
9.
Daisuke Sawada Tomoyuki Katayama Yuya Tsukuda Nozomi Saito Masashi Takano Hiroshi Saito Ken-ichiro Takagi Eiji Ochiai Seiichi Ishizuka Kazuya Takenouchi Atsushi Kittaka 《Bioorganic & medicinal chemistry letters》2009,19(18):5397-5400
We synthesized and isolated 2α-substituted analogs of 14-epi-previtamin D3 after thermal isomerization at 80 °C for the first time. The VDR binding affinity and transactivation activity of osteocalcin promoter in HOS cells were evaluated, and the 2α-methyl-substituted analog was found to have greater genomic activity than 14-epi-previtamin D3. 相似文献
10.
Miura D Norman AW Mizwicki MT Fujishima T Konno K Kittaka A Takayama H Ishizuka S 《The Journal of steroid biochemistry and molecular biology》2005,94(5):469-479
We synthesized all eight possible A-ring diastereomers of 2-methyl substituted analogs of 1alpha,25-dihydroxyvitamin D3 [1alpha,25(OH)2D3] and also all eight A-ring diastereomers of 2-methyl-20-epi-1alpha,25(OH)2D3. Their biological activities, especially the antagonistic effect on non-genomic pathway-mediated responses induced by 1alpha,25(OH)2D3 or its 6-s-cis-conformer analog, 1alpha,25(OH)2-lumisterol3, were assessed using an NB4 cell differentiation system. Antagonistic activity was observed for the 1beta-hydroxyl diastereomers, including 2beta-methyl-1beta,25(OH)2D3 and 2beta-methyl-3-epi-1beta,25(OH)2D3. Very interestingly, 2beta-methyl-3-epi-1alpha,25(OH)2D3 also antagonized the non-genomic pathway, despite its 1alpha-hydroxyl group. Other 1alpha-hydroxyl diastereomers did not show antagonistic activity. 20-epimerization diminished the antagonistic effect of all of these analogs on the non-genomic pathway. These findings suggested that the combination of the 2-methyl substitution of the A-ring and 20-epimerization of the side chain could alter the biological activities in terms of antagonism of non-genomic pathway-mediated biological response. Based on a previous report, 2-methyl substitution alters the equilibrium of the A-ring conformation between the alpha- and beta-chair conformers. The 2beta-methyl diastereomers, which exhibited antagonism on non-genomic pathway-mediated response, were considered to prefer the beta-conformer. Further examination to elucidate the relationship between the altered ligand shape and receptors interaction will be important for molecular level understanding of the mechanism of antagonism of the non-genomic pathway. 相似文献
11.
Taketani Y Nomoto M Yamamoto H Isshiki M Morita K Arai H Miyamoto K Kato S Takeda E 《Biochemical and biophysical research communications》2003,305(2):287-291
The mechanisms by which Pi depletion rapidly regulates gene expression and cellular function have not been clarified. Here, we found a rapid increase in intracellular ionized calcium [Ca(2+)](i) by phosphate depletion in LLC-PK(1) cells using confocal microscopy with the green-fluorescence protein based calcium indicator "yellow cameleon 2.1." The increase of [Ca(2+)](i) was observed in the presence or absence of extracellular Ca(2+). At the same time, an approximately twofold increase in intracellular inositol 1,4,5-triphosphate (IP(3)) occurred in response to the acute Pi depletion in the medium. Furthermore, 2-aminoethoxydiphenyl borate completely blocked the [Ca(2+)](i) increase induced by Pi depletion. These results suggest that Pi depletion causes IP(3)-mediated release of Ca(2+) from intracellular Ca(2+) pools and rapidly increases [Ca(2+)](i) in LLC-PK(1) cells. 相似文献
12.
Atsuko Takeuchi Yuki Ishida Hiroko Sekimoto Sonoko Masuda Toshio Okano Soroku Nishiyama Ichiro Matsuda Tadashi Kobayashi 《Journal of chromatography. B, Analytical technologies in the biomedical and life sciences》1997,691(2):1987
A simplified method for the determination of 25-hydroxy and 1α,25-dihydroxy metabolites of vitamins D2 and D3 in human plasma was developed. Plasma samples were deproteinizated and applied to a Bond Elut C18 OH cartridge to separate 25-hydroxyvitamin D (25-OH-D) and 1α-25-dihydroxyvitamin D [1,25(OH)2D] fractions. The 25-OH-D fraction was purified by a Bond Elut C18 cartridge and 25-OH-D2 and 25-OH-D3 were assayed by HPLC using a Zorbax SIL column. The 1,25(OH)2D fraction obtained above was subsequently applied to HPLC using a Zorbax SIL column to separate 1,25(OH)2D2 and 1,25(OH)2D3 fractions which were determined by a radioreceptor assay (RRA) using calf thymus receptor. The method was applied to nutritional studies. 相似文献
13.
The organotin complex [Ph3SnS(CH2)3SSnPh3] (1) was synthesized by PdCl2 catalyzed reaction between Ph3SnCl and disodium-1,3-propanedithiolate which in turn was prepared from 1,2-propanedithiol and sodium in refluxing THF. Reaction of 1 with Ru3(CO)12 in refluxing THF affords the mononuclear complex trans-[Ru(CO)4(SnPh3)2] (2) and the dinuclear complex [Ru2(CO)6(μ-κ2-SCH2CH2CH2S)] (3) in 20 and 11% yields, respectively, formed by cleavage of Sn-S bond of the ligand and Ru-Ru bonds of the cluster. Treatment of pymSSnPPh3 (pymS = pyrimidine-2-thiolate) with Ru3(CO)12 at 55-60 °C also gives 2 in 38% yield. Both 1 and 2 have been characterized by a combination of spectroscopic data and single crystal X-ray diffraction analysis. 相似文献
14.
Akhter S Kutuzova GD Christakos S DeLuca HF 《Archives of biochemistry and biophysics》2007,460(2):227-232
The exact role of calbindin D9k in vitamin D-mediated calcium absorption has been debated but remains unsettled. In 129/OlaHsd mice, calbindin D9k was found highest in duodenum (36-50%) and kidney (24-34%) followed by stomach, lung and uterus. Age does not affect the relative distribution of calbindin D9k but it does decline with age in duodenum of both male and female 129/Ola mice. Recently, we produced a null calbindin D9k mutant 129/OlaHsd mouse; this mouse proved to be indistinguishable from the wild-type in phenotype and in a serum calcium level regardless of age or gender. We have now examined directly whether the mutant mouse can absorb calcium from the intestine in response to the active form of vitamin D. The calbindin D9k null mutant mouse is fully able to absorb calcium from the intestine in response to 1,25-dihydroxyvitamin D3. It is, therefore, clear that calbindin D9k is not required for vitamin D-induced intestinal calcium absorption. 相似文献
15.
Yunhui Cheng Natalia Makarova Ryoko Tsukahara Huazhang Guo E Shuyu Patricia Farrar Louisa Balazs Chunxiang Zhang Gabor Tigyi 《Cellular signalling》2009,21(12):1874-1884
Lysophosphatidic acid (LPA) and its ether analog alkyl-glycerophosphate (AGP) elicit arterial wall remodeling when applied intralumenally into the uninjured carotid artery. LPA is the ligand of eight GPCRs and the peroxisome proliferator-activated receptor γ (PPARγ). We pursued a gene knockout strategy to identify the LPA receptor subtypes necessary for the neointimal response in a non-injury model of carotid remodeling and also compared the effects of AGP and the PPARγ agonist rosiglitazone (ROSI) on balloon injury-elicited neointima development. In the balloon injury model AGP significantly increased neointima; however, rosiglitazone application attenuated it. AGP and ROSI were also applied intralumenally for 1 h without injury into the carotid arteries of LPA1, LPA2, LPA1&2 double knockout, and Mx1Cre-inducible conditional PPARγ knockout mice targeted to vascular smooth muscle cells, macrophages, and endothelial cells. The neointima was quantified and also stained for CD31, CD68, CD11b, and α-smooth muscle actin markers. In LPA1, LPA2, LPA1&2 GPCR knockout, Mx1Cre transgenic, PPARγfl/−, and uninduced Mx1Cre × PPARγfl/− mice AGP- and ROSI-elicited neointima was indistinguishable in its progression and cytological features from that of WT C57BL/6 mice. In PPARγ−/− knockout mice, generated by activation of Mx1Cre-mediated recombination, AGP and ROSI failed to elicit neointima and vascular wall remodeling. Our findings point to a difference in the effects of AGP and ROSI between the balloon injury- and the non-injury chemically-induced neointima. The present data provide genetic evidence for the requirement of PPARγ in AGP- and ROSI-elicited neointimal thickening in the non-injury model and reveal that the overwhelming majority of the cells in the neointimal layer express α-smooth muscle actin. 相似文献
16.
Hui Sun Yuqi Ding Jinzhao Duan Qijun Zhang Zhiyong Wang Hui Lou Xiaoming Zheng 《Bioresource technology》2010,101(3):953-958
ZrO2 supported La2O3 catalyst prepared by impregnation method was examined in the transesterification reaction of sunflower oil with methanol to produce biodiesel. It was found that the catalyst with 21 wt% loaded La2O3 and calcined at 600 °C showed the optimum activity. The basic property of the catalyst was studied by CO2-TPD, and the results showed that the fatty acid methyl ester (FAME) yield was related to their basicity. The catalyst was also characterized by TG–DTA, XRD, FTIR, SEM and TEM, and the mechanism for the formation of basic sites was discussed. It was also found that the crystallite size of support ZrO2 decreased by loading of La2O3, and the model of the solid-state reaction on the surface of La2O3/ZrO2 catalyst was proposed. Besides, the influence of various reaction variables on the conversion was investigated. 相似文献
17.
The interaction of Ca(2+), with dipalmitoyl phosphatidylcholine (DPPC) model membranes was studied in the presence and absence of vitamin D(2) by using Fourier transform infrared spectroscopy. Addition of vitamin D(2) and/or Ca(2+) into pure DPPC liposomes shifts the phase transition to higher temperature, orders and decreases the dynamics of the acyl chains in both phases and does not induce hydrogen bond formation in the interfacial region. Moreover, the dynamics of the head group of the phospholipid decreases in both phases. The addition of vitamin D(2) into DPPC liposomes containing Ca(2+), decreases the effect of Ca(2+) at all the functional groups under investigation. Similarly, the effect of vitamin D(2) also decreases in the presence of Ca(2+). This behavior is dominant at high Ca(2+) concentrations. Our results show how simultaneous presence of vitamin D(2) and Ca(2+) alter the behavior of each other, which is reflected as a decrease in the interactions between the ions and vitamin D(2) within the membrane. 相似文献
18.
1alpha,25(OH)(2)D(3) activates protein kinase C (PKC) in rat growth plate chondrocytes via mechanisms involving phosphatidylinositol-specific phospholipase C (PI-PLC) and phospholipase A(2) (PLA(2)). The purpose of this study was to determine if 1alpha,25(OH)(2)D(3) activates PI-PLC directly or through a PLA(2)-dependent mechanism. We determined which PLC isoforms are present in the growth plate chondrocytes, and determined which isoform(s) of PLC is(are) regulated by 1alpha,25(OH)(2)D(3). Inhibitors and activators of PLA(2) were used to assess the inter-relationship between these two phospholipid-signaling pathways. PI-PLC activity in lysates of prehypertrophic and upper hypertrophic zone (growth zone) cells that were incubated with 1alpha,25(OH)(2)D(3), was increased within 30s with peak activity at 1-3 min. PI-PLC activity in resting zone cells was unaffected by 1alpha,25(OH)(2)D(3). 1beta,25(OH)(2)D(3), 24R,25(OH)(2)D(3), actinomycin D and cycloheximide had no effect on PLC in lysates of growth zone cells. Thus, 1alpha,25(OH)(2)D(3) regulation of PI-PLC enzyme activity is stereospecific, cell maturation-dependent, and nongenomic. PLA(2)-activation (mastoparan or melittin) increased PI-PLC activity to the same extent as 1alpha,25(OH)(2)D(3); PLA(2)-inhibition (quinacrine, oleyloxyethylphosphorylcholine (OEPC), or AACOCF(3)) reduced the effect of 1alpha,25(OH)(2)D(3). Neither arachidonic acid (AA) nor its metabolites affected PI-PLC. In contrast, lysophosphatidylcholine (LPC) and lysophosphatidylethanolamine (LPE) activated PI-PLC (LPE>LPC). 1alpha,25(OH)(2)D(3) stimulated PI-PLC and PKC activities via Gq; GDPbetaS inhibited activity, but pertussis toxin did not. RT-PCR showed that the cells express PLC-beta1a, PLC-beta1b, PLC-beta3 and PLC-gamma1 mRNA. Antibodies to PLC-beta1 and PLC-beta3 blocked the 1alpha,25(OH)(2)D(3) effect; antibodies to PLC-delta and PLC-gamma did not. Thus, 1alpha,25(OH)(2)D(3) regulates PLC-beta through PLA(2)-dependent production of lysophospholipid. 相似文献
19.
Susumi Hatakeyama Satoshi Nagashima Naoko Imai Keisuke Takahashi Jun Ishihara Atsuko Sugita Takeshi Nihei Hitoshi Saito Fumiaki Takahashi Noboru Kubodera 《The Journal of steroid biochemistry and molecular biology》2007,103(3-5):222
1α,25-Dihydroxy-2β-(3-hydroxypropoxy)vitamin D3 (ED-71), an analog of active vitamin D3, 1α,25-dihydroxyvitamin D3 [1,25(OH)2D3], possesses a hydroxypropoxy substituent at the 2β-position of 1,25(OH)2D3. ED-71 has potent biological effects on bone and is currently under phase III clinical studies for bone fracture prevention. It is well-known that the synthesis and secretion of parathyroid hormone (PTH) is regulated by 1,25(OH)2D3. Interestingly, during clinical development of ED-71, serum intact PTH in osteoporotic patients did not change significantly upon treatment with ED-71. The reason remains unclear, however. Brown et al. reported that 3-epi-1,25(OH)2D3, an epimer of 1,25(OH)2D3 at the 3-position, shows equipotent and prolonged activity compared to 1,25(OH)2D3 at suppressing PTH secretion. Since ED-71 has a bulky hydroxypropoxy substituent at the 2-position, epimerization at the adjacent and sterically hindered 3-position might be prevented, which may account for its weak potency in PTH suppression observed in clinical studies. We have significant interest in ED-71 epimerization at the 3-position and the biological potency of 3-epi-ED-71 in suppressing PTH secretion. In the present studies, synthesis of 3-epi-ED-71 and investigations of in vitro suppression of PTH using bovine parathyroid cells are described. The inhibitory potency of vitamin D3 analogs were found to be 1,25(OH)2D3 > ED-71 ≥ 3-epi-1,25(OH)2D3 3-epi-ED-71. ED-71 and 3-epi-ED-71 showed weak activity towards PTH suppression in our assays. 相似文献
20.
Alexander Grote Zsolt Boldogkoi Alexander Grote Zsolt Boldogkoi Andreas Zimmer Christian Steinhäuser 《Molecular membrane biology》2013,30(6):497-506
P2X receptor function in the CNS is poorly understood, and currently available data are partly inconsistent. In the presented study, we investigated P2X3 receptors stably expressed in HEK293 cells. Non-stationary noise analysis of whole cell currents and rapid ATP application through flash photolysis allowed for assessing the single channel conductance (6.6?pS) and the fast activation kinetics of the receptor (20?ms). The characteristics of channel desensitization and pharmacological properties matched previous findings. The properties of wild type receptors were compared with P2X3 constructs carrying a fluorescent tag (ECFP or DsRed2) at the C-terminus. These fluorescently labeled subunits formed functional receptors, with neither the affinity of the ligand binding site nor channel properties (ion selectivity, gating kinetics, single channel conductance) differing from wild type. We conclude that both fusion proteins tested here are suitable for generating transgenic mice, which can be expected to promote understanding of the physiological role of P2X3 receptors in CNS signaling. 相似文献