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排序方式: 共有142条查询结果,搜索用时 31 毫秒
1.
W.J Loos A Sparreboom J Verweij K Nooter G Stoter J.H.M Schellens 《Journal of chromatography. B, Analytical technologies in the biomedical and life sciences》1997,694(2):745
Two sensitive reversed-phase high-performance liquid chromatographic fluorescence methods, with simple sample handling at the site of the patient, are described for the determination of the lactone and lactone plus carboxylate forms of 9-aminocamptothecin (9AC). For 9AC lactone, the sample preparation was a liquid–liquid extraction with acetonitrile–n-butyl chloride (1:4, v/v), whereas the sample preparation for 9AC total (lactone plus carboxylate) was a simple deproteinization with 5% perchloric acid–methanol (1:1, v/v), which results in the conversion of the carboxylate into the lactone form. The lower limits of quantitation were 50 pg/ml and 100 pg/ml for 9AC lactone and 9AC total, respectively. The within-run precisions at four tested concentrations were ≤6.3% for 9AC lactone and ≤5.3% for 9AC total. The between-run precisions were ≤8.9% and ≤5.6%, respectively. The assays were developed to enable pharmacological analysis of 9AC in a bioavailability and oral phase I study in patients with solid tumors. 相似文献
2.
Hepatic autophagy and intracellular ATP. A morphometric study 总被引:1,自引:0,他引:1
J P Schellens H Vreeling-Sindelárová P J Plomp A J Meijer 《Experimental cell research》1988,177(1):103-108
In order to estimate the sensitivity of macroautophagy in liver toward changes in ATP we have analyzed the volume density of the autophagic/lysosomal system in isolated rat hepatocytes, incubated under conditions where intracellular ATP was partially depleted. (a) It appeared that reduction of the intracellular ATP concentration by 30-50% decreased the volume density of autophagic vacuoles by 70%. (b) Partial ATP depletion did not involve significant changes in the volume density of dense bodies. Together with studies showing that the rate of overall proteolysis via macroautophagy decreases with decreasing ATP concentration (P.J.A.M. Plomp, E.J. Wolvetang, A.K. Groen, A.J. Meijer, P.B. Gordon, and P.O. Seglen (1987) Eur. J. Biochem. 164, 197-203) our data indicate that changes in intracellular ATP primarily affect early steps in the autophagic/proteolytic pathway. 相似文献
3.
E. J. de Waal H. Vreeling-Sindelárová J. P. M. Schellens J. M. Houtkooper J. James 《Cell and tissue research》1986,243(3):641-648
Summary Ultrastructural morphometric analysis was used to study time-dependent variations in macro and microautophagy in rat hepatocytes. Except during periods of shortterm starvation for up to 24 h, animals were kept under standardized conditions of food intake.In hepatocytes of meal-fed rats the volume fraction of macroautophagic vacuoles is significantly higher at 23:00 h, i.e., immediately before food intake, compared to 11:00 h, i.e., 12 h following feeding. During fasting, macroautophagy drops to a low level.Microautophagic vacuoles in hepatocytes of meal-fed rats, sacrificed at 11:00 or 23:00 h respectively, do not show any significant quantitative differences. However, during 12 h of starvation, the volume fraction of microautophagic vacuoles rises significantly, whereas the numerical density remains constant. Subsequently, during the second 12-h period of fasting, the volume fraction of microautophagic vacuoles remains unchanged, but the numerical density increases. Over a period of 24 h of starvation the volume fraction of the total lysosomal system does not change significantly, whereas the numerical density rises.The time-dependent changes of the macroautophagic vacuolar system correlate with the circadian, food-related variations in the protein content of individual hepatocytes from meal-fed animals. The increase in volume fraction and thereafter in number of microautophagic vacuoles, as observed during starvation, coincides with a large decrease in protein content of individual hepatocytes. 相似文献
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Detecting non-neutral heterogeneity across a region of DNA sequence in the ratio of polymorphism to divergence 总被引:11,自引:4,他引:7
Natural selection, in the form of balancing selection or selective sweeps,
can result in a decoupling of the amounts of molecular polymorphism and
divergence. Thus natural selection can cause some areas of DNA sequence to
have greater silent polymorphism, relative to divergence between species,
than other areas. It would be useful to have a statistical test for
heterogeneity in the polymorphism to divergence ratio across a region of
DNA sequence, one that could identify heterogeneity greater than that
expected from the neutral processes of mutation, drift, and recombination.
The only currently available test requires that a region be arbitrarily
divided into sections that are compared with each other, and the
subjectivity of this division could be problematic. Here a test is proposed
in which runs of polymorphic and fixed sites are counted, where a "run" is
a set of one or more sites of one type preceded and followed by the other
type. The number of runs is smaller than otherwise expected if
polymorphisms are clumped together. By simulating neutral evolution and
comparing the observed number of runs to the simulations, a statistical
test is possible which does not require any a priori decisions about
subdivision.
相似文献
6.
J P Schellens W M Frederiks C J Van Noorden H Vreeling-Sindelárová F Marx P J McMillan 《The journal of histochemistry and cytochemistry》1992,40(12):1975-1979
Unfixed cryostat sections of rat liver were incubated to demonstrate D-amino acid oxidase activity at the ultrastructural level. Incubation was performed by mounting the sections on a semipermeable membrane which was stretched over a gelled incubation medium containing D-proline as substrate and cerium ions as capture reagent for hydrogen peroxide. After an incubation period of 30 min, ultrastructural morphology was retained to such an extent that the final reaction product could be localized in peroxisomes, whereas the crystalline core remained unstained. Control incubations were performed in the absence of substrate; the lack of final reaction product in peroxisomes indicated the specificity of the reaction. We conclude that the semipermeable membrane technique opens new perspectives for localization of enzyme activities at the ultrastructural level without prior tissue fixation, thus enabling localization of the activity of soluble and/or labile enzymes. 相似文献
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9.
Janine JH Oosterhof G Jolanda Elving Ietse Stokroos Arie van nieuw Amerongen Henny C van der Mei Henk J Busscher 《Biofouling》2013,29(6):347-353
The integrity of biofilms on voice prostheses used to rehabilitate speech in laryngectomized patients causes unwanted increases in airflow resistance, impeding speech. Biofilm integrity is ensured by extracellular polymeric substances (EPS). This study aimed to determine whether synthetic salivary peptides or mucolytics, including N-acetylcysteine and ascorbic acid, influence the integrity of voice prosthetic biofilms. Biofilms were grown on voice prostheses in an artificial throat model and exposed to synthetic salivary peptides, mucolytics and two different antiseptics (chlorhexidine and Triclosan). Synthetic salivary peptides did not reduce the air flow resistance of voice prostheses after biofilm formation. Although both chlorhexidine and Triclosan reduced microbial numbers on the prostheses, only the Triclosan-containing positive control reduced the air flow resistance. Unlike ascorbic acid, the mucolytic N-acetylcysteine removed most EPS from the biofilms and induced a decrease in air flow resistance. 相似文献
10.