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The ultrastructure of aggregates formed by mixtures of pig erythrocyte lecithin, cholesterol and globoside in aqueous systems was studied by electron microscopy and X-ray diffraction. Globoside and lecithin in up to equimolar amounts formed a lamellar mesophase, although the structure of the lamellae was perturbed. Mixtures containing excess globoside formed complex tubular or reticular aggregates. Cholesterol appeared to promote mixing of lecithin and globoside. The flexibility gradient of the hydrocarbon (hc) region of the lipid bilayers was studied using electron spin resonance (esr) spectroscopy of various nitroxide-labelled stearic acid probes. Globoside in equimolar amounts greatly perturbed the order parameters of lecithin bilayers, reducing the fluidity of the hc region and flattening the flexibility gradient near the polar (p) surface. The effect of globoside on lecithin-cholesterol bilayers was not so pronounced, since the latter was already more ordered than lecithin bilayers. A phase transition of pure globoside at 55 degrees C, involving 'melting' of the hc chains was also detected using X-ray and esr spectroscopic techniques. The interbilayer spacing, dw, of equimolar lecithin-globoside lamellar phase increased by 42% from that of lecithin bilayers, indicating that the glycolipid p group may increase the net repulsive force between bilayers, as was previously predicted theoretically. 相似文献
164.
M. T. Stephen Hsia 《Cell biology and toxicology》1987,3(2):127-142
The induction of unscheduled DNA synthesis has been considered as a suitable endpoint for the screening of genotoxic agents. Experimentally, unscheduled DNA synthesis is most frequently measured by autoradiography. The purpose of this report was to examine the usefulness of the liquid scintillation counting technique in measuring unscheduled DNA synthesis response in isolated rat hepatocytes. The various liquid scintillation counting-based unscheduled DNA synthesis assay procedures were examined according to the following groupings: (1) procedures based on the acid precipitation of cellular macromolecules, (2) procedures based on isopycnic gradient centrifugation of solubilized cells, (3) procedures based on nuclei isolation in conjunction with other DNA purification methods, and (4) procedures based on the selective retention of hepatocellular DNA. Limited cases in which test chemicals gave positive unscheduled DNA synthesis response in liquid scintillation counting-based assays and negative unscheduled DNA synthesis response in autoradiography-based assays are presented. It is concluded that liquid scintillation counting-based unscheduled DNA synthesis assays represent an appropriate system for inclusion in carcinogenicity and mutagenicity testing programs.Abbreviations 2-AAF
2-acetylaminofluorene
- 2-AF
2-aminofluorene
- AFB1
aflatoxin B1
- ARG
autoradiography
- DMN
dimethylnitrosamine
- LSC
liquid scintillation counting
- MMS
methyl methanesulfonate
- MNNG
N-methyl-N-nitro-N-nitrosoguanidine
- 4-NQO
4-nitroquinoline-1-oxide
- PCA
perchloric acid
- TCA
trichloroacetic acid
- UDS
unscheduled DNA synthesis 相似文献
165.
Yih-Juh?Shiau Satish?Manohar?Nalawade Chi-Ni?Hsia Vanisree?Mulabagal Hsin-Sheng?TsayEmail author 《In vitro cellular & developmental biology. Plant》2005,41(5):666-670
Summary
Dendrobium candidum Wall. Ex Lindl. is an important species used in the formulation of Shih-hu, a Chinese traditional medicine. An efficient
protocol for in vitro propagation of D. candidum using the axenic nodal segments of the shoots, originated from the in vitro germinated seedlings, was developed. The seeds from 120-d-old capsules after pollination were first germinated on half-strength
Murashige and Skoog (MS) basal medium supplemented with 30 g l−1 sucrose. After 4 mo., the seedlings were subcultured on a similar medium supplemented with 1 ml l−1 HYPONeX, 80 g l−1 potato homogenate and 2 g l−1 activated charcoal for further growth. Axenic nodal segments excised from 9-mo.-old seedlings were cultured on the medium
in the presence of 2 mg l−1 benzyladenine (BA) and 0.1 mg l−1 naphthaleneacetic acid (NAA). After 75 d, 73.2% of the explants gave rise to buds/shoots. The elongated shoots were rooted
on the medium containing 0.2 mg l−1 NAA and the plantlets were successfully acclimatized in soil. 相似文献
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Mutation of a nitrate transporter, AtNRT1:4, results in a reduced petiole nitrate content and altered leaf development 总被引:3,自引:0,他引:3
Unlike nitrate uptake of plant roots, less is known at the molecular level about how nitrate is distributed in various plant tissues. In the present study, characterization of the nitrate transporter, AtNRT1:4, revealed a special role of petiole in nitrate homeostasis. Electrophysiological studies using Xenopus oocytes showed that AtNRT1:4 was a low-affinity nitrate transporter. Whole-mount in situ hybridization and RT-PCR demonstrated that AtNRT1:4 was expressed in the leaf petiole. In the wild type, the leaf petiole had low nitrate reductase activity, but a high nitrate content, indicating that it is the storage site for nitrate, whereas, in the atnrt1:4 mutant, the petiole nitrate content was reduced to 50-64% of the wild-type level. Moreover, atnrt1:4 mutant leaves were wider than wild-type leaves. This study revealed a critical role of AtNRT1:4 in regulating leaf nitrate homeostasis, and the deficiency of AtNRT1:4 can alter leaf development. 相似文献
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Norcantharidin,a clinical used chemotherapeutic agent,acts as a powerful inhibitor by interfering with fibrinogen–integrin αIIbβ3 binding in human platelets 下载免费PDF全文
Chih‐Hsuan Hsia Wan‐Jung Lu Kuan‐Hung Lin Duen‐Suey Chou Pitchairaj Geraldine Thanasekaran Jayakuma Nen‐Chung Chang Joen‐Rong Sheu 《Journal of cellular and molecular medicine》2018,22(4):2142-2152
During platelet activation, fibrinogen binds to its specific platelet receptor, integrin αIIbβ3, thus completing the final common pathway for platelet aggregation. Norcantharidin (NCTD) is a promising anticancer agent in China from medicinal insect blister beetle. In this study, we provided the evidence to demonstrate NCTD (0.1–1.0 μM) possesses very powerful antiplatelet activity in human platelets; nevertheless, it had no effects on surface P‐selectin expression and only slight inhibition on ATP‐release reaction in activated platelets. Moreover, NCTD markedly hindered integrin αIIbβ3 activation by interfering with the binding of FITC‐labelled PAC‐1. It also markedly reduced the number of adherent platelets and the single platelet spreading area on immobilized fibrinogen as well as clot retraction. Additionally, NCTD attenuated phosphorylation of proteins such as integrin β3, Src and FAK in platelets spreading on immobilized fibrinogen. These results indicate that NCTD restricts integrin αIIbβ3‐mediated outside‐in signalling in human platelets. Besides, NCTD substantially prolonged the closure time in human whole blood and increased the occlusion time of thrombotic platelet plug formation and prolonged the bleeding time in mice. In conclusion, NCTD has dual activities, it can be a chemotherapeutic agent for cancer treatment, and the other side it possesses powerful antiplatelet activity for treating thromboembolic disorders. 相似文献