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排序方式: 共有96条查询结果,搜索用时 62 毫秒
11.
Tziveleka LA Kontoyianni C Sideratou Z Tsiourvas D Paleos CM 《Macromolecular bioscience》2006,6(2):161-169
Multifunctional hyperbranched polyether polyols bearing protective poly(ethylene glycol) (PEG) chains with or without the folate targeting ligand at their end have been prepared. Solubilization in these polymers of a fluorescent probe, pyrene, and an anticancer drug, tamoxifen, was physicochemically investigated. It was found that PEG chains attached at the surface of these hyperbranched polymers, in addition to their well-established protective role, enhance the encapsulation efficiency of the polymers. The release of pyrene and tamoxifen observed upon addition of sodium chloride is, in most of the cases, significant only at concentrations exceeding the physiological extracellular concentration. Thus, a significant amount of the probe or drug remains solubilized inside the carriers, which is an encouraging result if the polymers are to be used for drug delivery. 相似文献
12.
Natwalinkhol Settapramote Niramon Utama-ang Touchwin Petiwathayakorn Kornvipa Settakorn Saovaros Svasti Somdet Srichairatanakool Pimpisid Koonyosying 《Molecules (Basel, Switzerland)》2021,26(16)
Redox-active iron generates reactive oxygen species that can cause oxidative organ dysfunction. Thus, the anti-oxidative systems in the body and certain dietary antioxidants, such as anthocyanins, are needed to control oxidative stress. We aimed to investigate the effects of dielectric barrier discharge (DBD) plasma technology in the preparation of Riceberry™ rice flour (PRBF) on iron-induced oxidative stress in mice. PRBF using plasma technology was rich in anthocyanins, mainly cyanidine-3-glucoside and peonidine-3-glucoside. PRBF (5 mg AE/mg) lowered WBC numbers in iron dextran (FeDex)-loaded mice and served as evidence of the reversal of erythrocyte superoxide dismutase activity, plasma total antioxidant capacity, and plasma and liver thiobarbituric acid-reactive substances in the loading mice. Consequently, the PRBF treatment was observed to be more effective than NAC treatment. PRBF would be a powerful supplementary and therapeutic antioxidant product that is understood to be more potent than NAC in ameliorating the effects of iron-induced oxidative stress. 相似文献
13.
Junhong Feng Xuran Zhang Qing Ruan Yuhao Jiang Junbo Zhang 《Molecules (Basel, Switzerland)》2021,26(15)
In order to seek novel technetium-99m folate receptor-targeting agents, two folate derivatives (CN5FA and CNPFA) were synthesized and radiolabeled to obtain [99mTc]Tc-CN5FA and [99mTc]Tc-CNPFA complexes, which exhibited high radiochemical purity (>95%) without purification, hydrophilicity, and good stability in vitro. The KB cell competitive binding experiments indicated that [99mTc]Tc-CN5FA and [99mTc]Tc-CNPFA had specificity to folate receptor. Biodistribution studies in KB tumor-bearing mice illustrated that [99mTc]Tc-CN5FA and [99mTc]Tc-CNPFA had specific tumor uptake. Compared with [99mTc]Tc-CN5FA, the tumor/muscle ratios of [99mTc]Tc-CNPFA were higher, resulting in a better SPECT/CT imaging background. According to the results, the two 99mTc complexes have potential as tumor imaging agents to target folate receptors. 相似文献
14.
Taft F Harmrolfs K Nickeleit I Heutling A Kiene M Malek N Sasse F Kirschning A 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(3):880-886
Access of four new tumor specific folic acid/ansamitocin conjugates is reported that relies on a synthetic strategy based on the combination of mutasynthesis and semisynthesis. Two bromo‐ansamitocin derivatives were prepared by mutasynthesis or by a modified fermentation protocol, respectively, that served as starting point for the semisynthetic introduction of an allyl amine linker under Stille conditions. A sequence of standard coupling steps introduced the pteroic acid/glutamic acid/cysteine unit to the modified ansamitocins. All new derivatives, including those that are expected to be generated after internalization of the folic acid/ansamitocin conjugates into the cancer cell and reductive cleavage of the disulfide linkage showed good to strong antiproliferative activity (IC50 <10 nM ) for different cancer cell lines. Finally, the four conjugates were exposed to two cancer cell lines [cervix carcinoma, KB‐3‐1 (FR+) and lung carcinoma, A‐459 (FR?)], the latter devoid of the membrane‐bound folic acid receptor (FR?). All four conjugates showed strong antiproliferative activity for the FR+ cancer cell line but were inactive against the FR? cell line. The synthetic strategy pursued is based on the combination of mutasynthesis and semisynthesis and proved to be powerful for accessing new ansamitocin derivatives that are difficult to prepare by total synthesis. 相似文献
15.
《Analytical letters》2012,45(14):2280-2292
Abstract Cervical cancer is the second most common cancer in women worldwide with 80% of cases arising in the developing world, following cancer of the breast. The mortality associated with cervical cancer can be reduced if this disease is detected in a timely fashion. In this study, a folate conjugated fluorescent nanoparticle (FCFN) probe was used to detect cervical cancer cells. Fluorescent nanoparticles (FNs), with excellent characteristics such as nontoxicity and photostability, were first synthesized with a simple, cost-effective, and environmentally friendly modified St?ber synthesis method and then successfully modified with folate. This kind of fluorescence probe based on FCFNs has been used to detect cervical cancer cells with fluorescence microscopy imaging technology. The experimental results demonstrate that the FCFNs can effectively recognize cervical cancer cells and exhibit good sensitivity and exceptional photostability; they would provide a novel way for the diagnosis and curative effect observation of cervical cancer cells and offer a new method in detecting folate receptors (FR). 相似文献
16.
17.
G.A. Harmain 《Theoretical and Applied Fracture Mechanics》2010,53(1):80-37
Many engineering components are subjected to variable amplitude loading history. It is well known that retardation in fatigue crack growth occurs due to application of single overloads in a constant amplitude loading block. Many models have been proposed to capture this counter intuitive phenomenon which has resulted in improved understanding of retardation effect following tensile overloads and consequently resulting in better life prediction models. The proposed study is focused on to evaluation of retardation in fatigue life due to application of a single overload. A model for prediction of crack growth and crack growth rate following single overloads is presented. Several modifications to Wheeler’s growth idea are proposed, which incorporate a consideration for effective stress intensity factor, based on Elber’s concept of crack closure, relationship between overload ratio and the Wheeler’s exponent, and fatigue growth rate calculations. The results presented here show that plastic zone interaction following overload and the consideration of crack closure explain retardation effect following a single overload. Correlation between analysis and experimental data obtained from several sources in literature show that the scheme, is robust and provides an insight into the nonlinear aspect of crack growth results. The model has been tested for 2024-T3 aluminum alloy and 6061-T6 aluminum alloy and thorough calibrations performed, established the fidelity of the program. 相似文献
18.
The performance of various organizational structures is an essential parameter in the reengineering of organizations, particularly in the current rapidly changing, competitive and information technology-dependent environment. This situation has generally resulted in a smaller workforce confronted with voluminous information-processing requirements. Naturally, the focus has been on the design of organzations that will support effective and efficient learning processes. This specific study is on the contingency modely by Ouksel et al. (1997) on the impact of organizational structure on organizational learning and performance. It expands the empirical evaluation of the model to test its robustness. This is done by conducting extensive simulations with (a) a larger number of variables in the decision tasks, and (b) a larger set of numbers for each of the numeric variables, than has been used in the past. Overall, the validity of previous results achieved has been confirmed, but the selection of the most appropriate design, that which will indeed improve learning, is even more nuanced than past studies have concluded. 相似文献
19.
Jiaying Yu Xiaowei Liu Jing Guo Jinhui Zhao Ying Li Changhao Sun Liyan Liu 《Biomedical chromatography : BMC》2020,34(3):e4765
The aim of the present study was to develop a novel ultrasound-assisted derivatization method for analysis of urine that can be used for preliminary screening and monitoring of metabolic disorders. Here we describe an ultrasound-assisted derivatization method followed by GC–MS analysis to quantify 26 organic acids in urine. The optimum levels of the variables affecting the yield of derivatization were investigated, including urease doses, derivatization reagents and derivatization conditions (duration time, reaction temperature and sonic power). The method exhibited the best results with 80 μl urease. The optimal reaction conditions were 100 μl BSTFA, 80% ultrasound power, 70°C and 40 min. This method showed satisfactory linearity, good reproducibility and an acceptable limit of detection and accuracy. Therefore, it could potentially be used to as a standard method to enable comparisons between laboratories. Finally, we applied our method to urine samples from pregnant rats administered 2 or 10 mg/kg folic acid supplementation. 相似文献
20.
We develop deterministic fluid approximations to describe the recovery from rare congestion events in a large multi-server
system in which customer holding times have a general distribution. There are two cases, depending on whether or not we exploit
the age distribution (the distribution of elapsed holding times of customers in service). If we do not exploit the age distribution,
then the rare congestion event is a large number of customers present. If we do exploit the age distribution, then the rare
event is an unusual age distribution, possibly accompanied by a large number of customers present. As an approximation, we
represent the large multi-server system as an M/G/∞ model. We prove that, under regularity conditions, the fluid approximations are asymptotically correct as the arrival rate
increases. The fluid approximations show the impact upon the recovery time of the holding-time distribution beyond its mean.
The recovery time may or not be affected by the holding-time distribution having a long tail, depending on the precise definition
of recovery. The fluid approximations can be used to analyze various overload control schemes, such as reducing the arrival
rate or interrupting services in progress. We also establish large deviations principles to show that the two kinds of rare
events have the same exponentially small order. We give numerical examples showing the effect of the holding-time distribution
and the age distribution, focusing especially on the consequences of long-tail distributions.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献