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排序方式: 共有36条查询结果,搜索用时 15 毫秒
1.
Deniz Caylioglu Rieke Johanna Meyer Dana Hellmold Carolin Kubelt Michael Synowitz Janka Held-Feindt 《International journal of molecular sciences》2021,22(7)
Glioblastoma (GBM) is a barely treatable disease due to its profound chemoresistance. A distinct inter- and intratumoral heterogeneity reflected by specialized microenvironmental niches and different tumor cell subpopulations allows GBMs to evade therapy regimens. Thus, there is an urgent need to develop alternative treatment strategies. A promising candidate for the treatment of GBMs is AT101, the R(-) enantiomer of gossypol. The present study evaluates the effects of AT101, alone or in combination with temozolomide (TMZ), in a microenvironmental glioma stem cell niche model of two GBM cell lines (U251MG and U87MG). AT101 was found to induce strong cytotoxic effects on U251MG and U87MG stem-like cells in comparison to the respective native cells. Moreover, a higher sensitivity against treatment with AT101 was observed upon incubation of native cells with a stem-like cell-conditioned medium. This higher sensitivity was reflected by a specific inhibitory influence on the p-p42/44 signaling pathway. Further, the expression of CXCR7 and the interleukin-6 receptor was significantly regulated upon these stimulatory conditions. Since tumor stem-like cells are known to mediate the development of tumor recurrences and were observed to strongly respond to the AT101 treatment, this might represent a promising approach to prevent the development of GBM recurrences. 相似文献
2.
The surface of polyethylene was derivatized with ester, carboxylate, amino, hydroxyl, and phosphate functional groups. α, ω bifunctional alkanes, containing on one end a primary amine, were coupled to oxidized polyethylene through an amide linkage. Polyethylene was first oxidized with chromic acid, the carboxylate groups were converted to the acyl chloride with phosphorus pentachloride, and then reacted with a primary amine to give the covalently bound amide. The copposing ends of the bifunctional alkanes were the methyl, tertiary amine, ester, and hydroxyl groups. The ester was converted to the carboxylate by acid cleavage and the hydroxyl group converted to the phosphate by treatment first with phosphorus oxychloride and then aqueous base. Attenuated total reflection FTIR, XPS, and pH-dependent contact angle wetting were used to characterize the surfaces. The FTIR data were used to confirm the formation of the amide and to detect an undesired carboxylate/ammonium ion complex formed in the presence of trace amounts of water. XPS data were used to confirm expected changes in elemental composition and to provide quantitative estimates of the yields. Oxidation of the polyethylene introduced 5 × 1014 carboxylate groups/cm2 in the 25 Å XPS sampling depth. Of these, up to 98% could be converted to the amide. The advancing contact angle data confirmed the acid/base behavior of the functional groups. 相似文献
3.
Zusammenfassung OpenSocial definiert eine Menge von Programmierschnittstellen für Anwendungen von Drittanbietern im Kontext sozialer Netzwerke.
Unter der Verwendung von Standardtechnologien wie HTML und JavaScript k?nnen Entwickler interoperable Anwendungen erstellen,
die auf den sozialen Graphen des jeweiligen Netzwerks zugreifen. 相似文献
4.
Rieke C Mormann F Andrzejak RG Kreuz T David P Elger CE Lehnertz K 《IEEE transactions on bio-medical engineering》2003,50(5):634-639
A number of recent studies indicate that nonlinear electroencephalogram (EEG) analyses allow to define a state predictive of an impending epileptic seizure. In this paper, we combine a method for detecting nonlinear determinism with a novel test for stationarity to characterize EEG recordings from both the seizure-free interval and the preseizure phase. We discuss differences between these periods, particularly an increased occurrence of stationary, nonlinear segments prior to seizures. These differences seem most prominent for recording sites within the seizure-generating area and for EEG segments less than one minute's length. 相似文献
5.
Katayama M Sutovsky P Yang BS Cantley T Rieke A Farwell R Oko R Day BN 《Reproduction (Cambridge, England)》2005,130(6):907-916
The effects of sperm-immobilization methods on decondensation of sperm chromatin and retention of subacrosomal sperm perinuclear theca (SAR-PT) after intracytoplasmic sperm injection (ICSI) were examined in pigs. Sperm membrane damage caused by different immobilization methods by rubbing with a micropipette without piezo pulses (R), or with a low (L) or high (H) intensity of piezo pulses while rubbing, was assessed by the time required for staining of sperm heads with eosin Y solution. The average time for staining of sperm heads immobilized by the R, L or H treatments was 76, 41 or 26 s, respectively. The fertilization rate following ICSI was increased by sperm immobilization by piezo pulses compared with R, but increased intensity of pulses from L to H did not cause further improvements (29, 48 and 47%, respectively). An immunofluorescence study revealed that H immobilization promoted the dissociation of SAR-PT from sperm chromatin compared with L and R, and it increased the frequency of male pronuclear formation in which chromatin appeared uniformly decondensed. With in vitro fertilization (IVF), SAR-PT disassembled coordinately with sperm chromatin decondensation and it was not detectable around male pronuclei. This was different from most of the oocytes after ICSI in which remnants SAR-PT were detected adjacent to male pronuclei. We concluded that increased damage on the sperm plasma membrane at immobilization improved fertilization rates and decondensation of sperm chromatin after ICSI due to the accelerated dissociation of SAR-PT from the sperm nucleus. Also, the behavior of SAR-PT after ICSI was different from that observed in oocytes after IVF. 相似文献
6.
7.
Rieke Himstedt Dr. Silke Wagner Dr. Robert J. R. Jaeger Dr. Michèle-Laure Lieunang Watat Dr. Jana Backenköhler Dr. Zeljka Rupcic Prof. Dr. Marc Stadler Prof. Dr. Peter Spiteller 《Chembiochem : a European journal of chemical biology》2020,21(11):1613-1620
Mycenarubin C, a previously unknown red pyrroloquinoline alkaloid, was isolated from fruiting bodies of the mushroom Mycena rosea and its structure was elucidated mainly by NMR spectroscopy and mass spectrometry. Unlike mycenarubin A, the major pyrroloquinoline alkaloid in fruiting bodies of M. rosea, mycenarubin C, contains an eight-membered ring with an additional C1 unit that is hitherto unprecedented for pyrroloquinoline alkaloids known in nature. Incubation of mycenarubin A with an excess of formaldehyde revealed that mycenarubin C was generated nearly quantitatively from mycenarubin A. An investigation into the formaldehyde content of fresh fruiting bodies of M. rosea showed the presence of considerable amounts of formaldehyde, with values of 5 μg per gram of fresh weight in fresh fruiting bodies. Although mycenarubin C did not show bioactivity against selected bacteria and fungi, formaldehyde inhibits the growth of the mycoparasite Spinellus fusiger at concentrations present in fruiting bodies of M. rosea. Therefore, formaldehyde might play an ecological role in the chemical defence of M. rosea against S. fusiger. In turn, S. fusiger produces gallic acid—presumably to detoxify formaldehyde by reaction of this aldehyde with amino acids and gallic acid to Mannich adducts. 相似文献
8.
The composite‐crosslinked poly(N‐isopropylacrylamide) (PNIPAAm) gels were prepared by grafting N‐isopropylacrylamide on the surface of glass plates modified by organosilanes. The glass plates as the substrate increase the mechanical strength of composite PNIPAAm gel layers. We investigated the effects of a series of organosilanes and the reaction time of organosilanes on surface characteristics, such as the static contact angle and the layer thickness. We discuss the equilibrium swelling ratio and the water release behavior of the gel layers in terms of the crosslinking density of the composite gels. The composite gels exhibit not only the characteristics of remarkable water release but also the reversed hydrophilic–hydrophobic surface properties. The gel layers are hydrophilic under 25°C and change to hydrophobic above 40°C. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 1–11, 1999 相似文献
9.
Ross D. Rieke Deepak S. Thakur Brian D. Roberts Geoffrey T. White 《Journal of the American Oil Chemists' Society》1997,74(4):341-345
Fatty alcohols are produced by hydrogenating fatty methyl esters in slurry phase in the presence of copper chromite catalyst
at temperatures of 250–300°C and hydrogen pressures of 2000–3000 psi. The fatty methyl ester, catalyst, and hydrogen are fed
to the reactor cocurrently. The product slurry is passed through gas-liquid separators and then through a continuous filtration
system for removal of the catalyst. A portion of the used catalyst in crude alcohol is recycled to the hydrogenator. The overall
efficiency of the process depends upon the intrinsic activity, life, and filterability of the catalyst. The fatty alcohol
producer therefore requires a catalyst with high activity, long life, and good separation properties. The main goal of the
present laboratory investigation was to develop a superior copper chromite catalyst for the slurry-phase process. Two copper
chromite catalysts, prepared by different procedures, were tested for methyl ester hydrogenolysis activity, reusability, and
filtration characteristics. The reaction was carried out in a batch autoclave at 280°C and 2000–3000 psi hydrogen pressure.
The reaction rates were calculated by assuming a kinetic mechanism that was first-order in methyl ester concentration. The
catalyst with the narrower particle size distribution was 30% more active, filtered faster, and maintained activity for several
more uses than the catalyst with the broader particle size distribution. X-ray photoelectron spectroscopy data showed higher
surface copper concentrations for the former catalyst. 相似文献
10.
Fatty methyl ester hydrogenation to fatty alcohol part I: Correlation between catalyst properties and activity/selectivity 总被引:1,自引:3,他引:1
Ross D. Rieke Deepak S. Thakur Brian D. Roberts Geoffrey T. White 《Journal of the American Oil Chemists' Society》1997,74(4):333-339
Fatty alcohols, derived from natural sources, are commercially produced by hydrogenation of fatty acids or methyl esters in
slurry-phase or fixed-bed reactors. One slurry-phase hydrogenation of methyl ester process flows methyl esters and powdered
copper chromite catalyst into tubular reactors under high hydrogen pressure and elevated temperature. In the present investigation,
slurry-phase hydrogenations of C12 methyl ester were carried out in semi-batch reactions at nonoptimal conditions (i.e., low hydrogen pressure and elevated
temperature). These conditions were used to accentuate the host of side reactions that occur during the hydrogenation. Some
14 side reaction routes are outlined. As an extension of this study, copper chromite catalyst was produced under a number
of varying calcination temperatures. Differences in catalytic activity and selectivity were determined by closely following
side reaction products. Both activity and selectivity correlate well with the crystallinity of the copper chromite surface;
they increase with decreasing crystallinity. The ability to follow the wide variety of side reactions may well provide an
additional tool for the optimized design of hydrogenation catalysts. 相似文献