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排序方式: 共有847条查询结果,搜索用时 218 毫秒
171.
Indene Compounds Synthetically Derived from Vitamin D Have Selective Antibacterial Action on Helicobacter pylori 下载免费PDF全文
Kiyofumi Wanibuchi Kouichi Hosoda Masato Ihara Kentaro Tajiri Yuki Sakai Hisashi Masui Takashi Takahashi Yoshikazu Hirai Hirofumi Shimomura 《Lipids》2018,53(4):393-401
Helicobacter pylori infects the human stomach and is closely linked with the development of gastric cancer. When detected, this pathogen can be eradicated from the human stomach using wide‐spectrum antibiotics. However, year by year, H. pylori strains resistant to the antibacterial action of antibiotics have been increasing. The development of new antibacterial substances effective against drug‐resistant H. pylori is urgently required. Our group has recently identified extremely selective bactericidal effects against H. pylori in (1R,3aR,7aR)‐1‐[(1R)‐1,5‐dimethylhexyl]octahydro‐7a‐methyl‐4H‐inden‐4‐one (VDP1) (otherwise known as Grundmann's ketone), an indene compound derived from the decomposition of vitamin D3 and proposed the antibacterial mechanism whereby VDP1 induces the bacteriolysis by interacting at least with PtdEtn (dimyristoyl‐phosphatidylethanolamine [di‐14:0 PtdEtn]) retaining two 14:0 fatty acids of the membrane lipid constituents. In this study, we synthesized new indene compounds ((1R,3aR,7aR)‐1‐((2R,E)‐5,6‐dimethylhept‐3‐en‐2‐yl)‐7a‐methyloctahydro‐4H‐inden‐4‐one [VD2‐1], (1R,3aR,7aR)‐1‐((S)‐1‐hydroxypropan‐2‐yl)‐7a‐methyloctahydro‐1H‐inden‐4‐ol [VD2‐2], and (1R,3aR,7aR)‐7a‐methyl‐1‐((R)‐6‐methylheptan‐2‐yl)octahydro‐1H‐inden‐4‐ol [VD3‐1]) using either vitamin D2 or vitamin D3 as materials. VD2‐1 and VD3‐1 selectively disrupted the di‐14:0 PtdEtn vesicles without destructing the vesicles of PtdEtn (dipalmitoyl‐phosphatidylethanolamine) retaining two 16:0 fatty acids. In contrast, VD2‐2, an indene compound lacking an alkyl group, had no influence on the structural stability of both PtdEtn vesicles. In addition, VD2‐1 and VD3‐1 exerted extremely selective bactericidal action against H. pylori without affecting the viability of commonplace bacteria. Meanwhile, VD2‐2 almost forfeited the bactericidal effects on H. pylori. These results suggest that the alkyl group of the indene compounds has a crucial conformation to interact with di‐14:0 PtdEtn of H. pylori membrane lipid constituents whereby the bacteriolysis is ultimately induced. 相似文献
172.
Okawa Maya Iwata Tomoharu Tanaka Yusuke Kurashima Takeshi Toda Hiroyuki Kashima Hisashi 《Machine Learning》2022,111(8):2929-2950
Machine Learning - Massive spatio-temporal event data sets are now available that cover events such as disease outbreaks, armed conflicts and crimes. Predicting such events and revealing the... 相似文献
173.
Hisashi Kajiura Houjin HuangShigemitsu Tsutsui Yousuke MurakamiMitsuaki Miyakoshi 《Carbon》2002,40(13):2423-2428
A brittle porous deposit consisting of high-purity fibrous carbon products with a diameter of 25-100 nm was obtained on a heated anode surface in hydrogen DC arc-discharge. Hydrogen arc plasma was generated between a graphite cathode and a carbon/metal composite anode consisting of 1.0 at.% Fe, 0.6 at.% Co, 2.4 at.% Ni, and 0.4 at.% FeS. X-ray diffraction analysis revealed that the fibrous products had a turbostratic carbon structure, with an interlayer spacing of 0.346 nm. Elemental analysis showed that the fibrous products were composed of 98.4 mass% of carbon. Three types of nano-structured fibrous products were observed using transmission electron microscopy, (1) with a bamboo structure, (2) with a hollow core, and (3) without a hollow core. The formation of fibrous products was initiated by arc-generated metal particles with a diameter of 5-75 nm, then carbon for further growth was supplied by the decomposition of polycyclic aromatic hydrocarbons that were created by interactions between arc-generated carbon clusters and atomic hydrogen. The nano-structure of the fibrous products is thought to depend on the size and morphology of the catalytic metal particles. The synthesis conditions, microstructural characterization and the growth mechanism of the fibrous carbon products are reported. 相似文献
174.
Yasushi Kawakami Hisako Kojima Kazuo Nakamura Minoru Suzuki Akihiko Uchida Yoshihiko Murata Yoichi Tamai 《Lipids》1995,30(4):333-337
The occurrence of glycosphingolipids with unique carbohydrate structures in different species of cestode, Platyhelminth, which
had been shown, previously, prompted us to study the molecular species of the monohexosylceramides (cerebrosides) in the pseudophyllidean
cestode,Spirometra erinacei. The purpose of the study was to obtain a basis for future investigations of the physiological role of glycolipids in parasitism.
Cerebrosides were isolated froms. erinacei at two growth stages, i.e., from the larval form (plerocercoid) and from the adult tapeworms (intestinal form). The cerebrosides
were separated into four subfractions by silica gel column chromatography, and their constituents were analyzed by gasliquid
chromatography, gas chromatography/mass spectrometry, and high-performance liquid chromatography/mass spectrometry. The hexoses
of the cerebrosides consisted primarily of galactose in both growth stages, while only a small amount of glucose was detected.
The ceramides were composed of sphinganine (d18∶0) and phytosphingosine (t18∶0) as sphingoid bases, and of nonhydroxy fatty
acids ranging from C16 to C30 and hydroxy stearic acid (18h∶0). The cerebrosides of adult tapeworms contained more 18h∶0 than those of plerocercoids. The
combination of hexoses and ceramides in the cerebroside molecules was slightly different in the two growth stages: the glucocerebrosides
of plerocercoids contained only d18∶0-nonhydroxy fatty acids in their ceramide moieties, whereas those of adult tapeworms
contained varying ceramide moieties. Our data indicate that the molecular species of glycolipids present were essentially
homeostatic throughout growth in spite of the entirely different environmental conditions, although there were slight differences
in the hexose distribution in the two growth stages. 相似文献
175.
1-Octen-3-ol together with geosmin: new secretion compounds from a polydesmid millipede,Niponia nodulosa 总被引:1,自引:0,他引:1
The small millipede Niponia nodulosa (Polydesmida: Cryptodesmidae) emits an earthy smell when disturbed. This smell was obtained from hexane extracts from both sexes at the sixth and seventh instars and adult stages, and was found by GC/MS analyses to be composed of two compounds, 1-octen-3-ol as the major component and geosmin as the minor component. This is the first report of these compounds in secreted substances from millipedes. As they showed little repellent activity against foraging ants in bioassays, their biological function as defensive allomones was not clearly elucidated. However, both compounds provoked negative chemotaxis of conspecific millipedes in a Y-tube olfactometer, especially 1-octen-3-ol, which was active at a dose equivalent to the content of a single millipede. Such biological activity suggests that this compound is involved in intraspecific communication in this millipede and may play a role as an alarm pheromone. 相似文献
176.
Shin-Yubari coal was impregnated with several catalysts of different chemical types during pulverization. The resultant system was more homogeneous and reactive than systems prepared by impregnation of coarse coal. The relative activities of the catalysts were determined as a function of gasification temperature, catalyst loading and gasifying agent. The activity sequence in steam was K ? Ba ? Ni ? Fe ? coal ash. Each catalyst had a unique reaction profile. For example, using steam the specific rate or the rate per remaining fixed-carbon weight decreased with time for the iron-catalysed reaction, whereas it increased for the potassium-catalysed reaction. A similar order of activity was observed in carbon dioxide, but a different sequence was noted for the hydrogenation reaction. Transition metal catalysts were the most active. The hydrogenation reaction profiles were different from the oxidation profiles. 相似文献
177.
Semielliptical surface flaws of different sizes were introduced into Al2 O3 by Knoop microhardness indentation. The specimens were fractured by four-point bending and the profiles of the indentation flaws were determined by observing the fracture surfaces with a scanning electron microscope. The relation between the indentation flaw size and the fracture strength could be well explained by applying the fracture-mechanics analysis for semielliptical surface flaw in bending. The calculated values of the as-indented critical stress intensity factor, KIC , were lower than previously reported presumably because of the influence of the residual stresses produced by the indenter. 相似文献
178.
Hisashi Kato-Noguchi Seiji Kosemura Shosuke Yamamura Junya Mizutani Koji Hasegawa 《Journal of chemical ecology》1994,20(2):309-314
The allelopathic potential of oat (Avena sativa L.) extracts was investigated under laboratory conditions. The ethyl ether-, acetone-, and water-soluble fractions obtained from the extract of oat shoots inhibited the germination and growth of roots and hypocotyls of lettuce (Lactuca sativa L.). The inhibitory activity of the water-soluble fraction was maximum, followed by that of ethyl ether-soluble and acetone-soluble fraction. An active principle of the water-soluble fraction was isolated and its structure was determined by spectral data asl-tryptophan.l-Tryptophan inhibited the growth of hypocotyls and roots of lettuce seedlings at concentrations greater than 0.03 and 0.1 mM, respectively. These results suggested thatl-tryptophan may be an allelochemical which affects the growth or germination of different plant species. 相似文献
179.
Donald J. Progar Terry L. St. Clair Akihiro Yamaguchi Shoji Tamai 《The Journal of Adhesion》1995,54(1):103-114
The poly(keto-imide), LARCTM-TPI, was developed in the late 1970's and has proven to be remarkable stable as a high temperature adhesives. Thermal aging results that were generated at both NASA Langley Research Center and at Boeing Aerospace Company proved this material to be stable in adhesive bond form for at least 60,000 hours at 232°C. A commercial form of LARCTM-TPI was made available in the mid-to-late 1980's by Mitsui Toatsu Chemicals, Inc. (MTC). Since that time, MTC has optimized the process for manufacturing LARCTM-TPI with the major improvements being in molecular weight control. Most recently, MTC synthesized a derivatized version of LARCTM-TPI which contains pendant phenoxy moieties. This material is soluble in a number of organic solvents and it exhibits outstanding melt-flow properties which make it attractive as a hot-melt-processable polyimide adhesive. The synthesis and characterization of this novel material is the subject of this research paper. 相似文献
180.
Masayuki Fujimoto Hiroshi Koyama Yuji Nishi Toshimasa Suzuki Shinji Kobayashi Yukio Tamai Nobuyoshi Awaya 《Journal of the American Ceramic Society》2007,90(7):2205-2209
We characterized the structure of the crystallographic domain of a (Pr0.7 Ca0.3 )MnO3 (PCMO ( x =0.3)) thin film epitaxially grown on a (001)SrTiO3 (STO) single-crystal substrate. We found that the domain structure exhibited an atomically smooth coherent interface with the STO substrate with no misfit dislocations. The crystallographic relationships between the domains and the substrate in their planes were interpreted to be PCMO ( x =0.3)[110][001]//STO[100][010] and PCMO ( x =0.3)[001][1-10]//STO[100][010]. The domain structure of PCMO ( x =0.3)[110][1-10]//STO[100][010] has less possibility of having the larger anisotropic strain energy found in a monoclinically distorted pseudo-cubic perovskite unit cell of PCMO ( x =0.3). This epitaxial growth structure is totally different from the previously reported PCMO ( x =0.5) epitaxial thin-film structure on STO substrate. Our observations suggested that an x value change strongly influences the structure of epitaxial PCMO thin films. 相似文献