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41.
We have previously shown that pH-sensitive immunoliposomes can mediate a target-specific delivery of plasmid DNA to tumor cells grown in a mouse model [Wang, C.-Y., & Huang, L. (1987) Proc. Natl. Acad. Sci. U.S.A. 84, 7851-7855]. The efficiency of delivery in terms of the target cell transformation frequency has now been characterized for both short- and long-term gene expression in a tissue culture system. Herpes simplex virus thymidine kinase (TK) gene was used as a reporter gene. It was placed under the control of the promoter for the rat phosphoenolpyruvate carboxykinase gene, which contains a cAMP regulatory element. Therefore, the expression of the exogenous gene in the target cell, mouse Ltk- cells, can be regulated by cAMP drugs. The plasmid DNA was encapsulated in liposomes using a detergent dialysis method. The efficiency of gene delivery was optimized with respect to the time course and dose of liposome-associated DNA. The existence of antibody of the liposomes was essential for the maximal level of DNA delivery. Delivery was also dependent on the lipid composition of the liposome. The pH-sensitive lipid composition gave 8-fold higher efficiency than the corresponding pH-insensitive composition. The transformation efficiency of the target cell also depended on the regulation of gene expression; cells incubated with dibutyryl-cAMP and theophylline showed a much higher level of transformation frequency than cells incubated without the drugs. When all liposome and incubation parameters are optimized, the Ltk- cells showed a 47% efficiency for the short-term transformation, and 2% for the long-term transformation.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
42.
Y Hashimoto K Chida M Huang M Katayama T Nishihira T Kuroki 《Biochemical and biophysical research communications》1989,163(1):406-411
The protein kinase C (PKC) activities of tumor tissue and adjacent normal mucosa of human cancers of the esophagus (8 cases), stomach (1 case) and colon (3 cases) were measured. Considerable variations were found in the activity of PKC and in its subcellular distribution in these cancers. The PKC activities of the membrane and cytosolic fractions of the eight esophageal cancers were, however, similar to those of the adjacent normal mucosa: the average PKC activities of the tumor tissues and normal mucosa were 7.5 and 8.3 pmol/min/mg protein, respectively, in their membrane fractions and 7.9 and 7.8 pmol/min/mg protein, respectively, in their cytosolic fractions. 相似文献
43.
Immunoliposomes with different acid sensitivities as probes for the cellular endocytic pathway 总被引:1,自引:0,他引:1
By combining dioleoylphosphatidylethanolamine (DOPE) with oleic acid (OA), palmitoylhomocysteine (PHC) or dipalmitoylsuccinylglycerol (DPSG) we have prepared pH-sensitive liposomes with different acid sensitivities. DOPE/OA liposomes are the most acid sensitive, while DOPE/DPSG liposomes are the least acid sensitive. Incubation of DOPE/OA liposomes with mouse L929 cells reduces the pH-sensitivity of these liposomes by altering the lipid composition. Using diphtheria toxin fragment A as a marker for cytoplasmic delivery, we find that the delivery kinetics of pH-sensitive immunoliposomes closely correlates with the modified acid sensitivities of the liposomes. Immunoliposomes encounter pH 6-6.2 with a t1/2 of 5-15 min after internalization. By contrast, acidification of the endosomes to pH 5.0 takes longer (t1/2 approximately 25 min). We also used a whole cell null point technique (Yamishiro and Maxfield (1987) J. Cell Biol. 105, 2713-2721) to directly determine the average pH encountered by the endocytosed immunoliposomes. We find that acidification determined by the null point method proceeds less rapidly than that estimated from DTA delivery data. This is likely due to the fact that the measured DTA delivery is done by those liposomes which first arrive at the endosomes with sufficient acidity. Our data suggests that DOPE/PHC immunoliposomes deliver at the early endosome while DOPE/DPSG immunoliposomes deliver at the late endosomes. The DOPE/OA immunoliposomes, with the altered composition and acid sensitivity, deliver with a kinetics intermediate between the other two immunoliposomes. Thus, pH-sensitive liposomes represent useful probes for studying the kinetics of endosome acidification. 相似文献
44.
45.
传入C纤维的兴奋在中电针“足三里”激活中缝大核中的作用 总被引:6,自引:0,他引:6
The purpose of the present work is to study whether the analgesia of "Zusanli" EA was mainly produced by its noxious effect. The antidromic C waves on N. peroneus communis innervating the area of "Zusanli" point were recorded. When "Zusanli" point was stimulated by trains of stimuli, the amplitude of the antidromic C wave was obviously decreased due to collision with the orthodromic stimulation. It was suggested that EA of "Zusanli" could excite some C fibers. It was observed that when the stimulation intensity reached the threshold of C fiber, the NRM neurons were obviously activated, and when it reached or exceeded the intensity for producing the maximal C wave, the NRM neurons were highly activated. Therefore, EA analgesia is probably produced mainly by its noxious stimulus component, especially carried by C fibers, via a negative feedback mechanism in modulating pain. 相似文献
46.
Plants contain highly divergent actin isovariants 总被引:5,自引:0,他引:5
B G McLean S R Huang E C McKinney R B Meagher 《Cell motility and the cytoskeleton》1990,17(4):276-290
Actin protein isovariants have been identified in animals with distinct cytoplasmic or muscle specific patterns of expression. Analysis of vascular plant actin gene sequences suggests that an even greater diversity should exist within the plant actin protein families, but previous studies on plant proteins have not demonstrated the presence of multiple actin isovariants. Antibodies recognizing a conserved amino-terminal plant actin peptide, a family of plant actin peptides from a variable region, and two monoclonal antibodies to conserved epitopes within animal actins were used to identify isovariants of soybean actin resolved by two-dimensional isoelectric focusing (IEF) sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Approximately six to eight actin isovariants with pI values ranging from 5.1 to 5.8 have been identified from soybean hypocotyls, stems, leaves, and roots with varying amounts of most isovariants present in all four organs. Acidic isovariants were present in much higher levels in leaves and stems. Antisera with lambda-class actin specificity detected a subset of three isovariants in all organs examined. One monoclonal and one antipeptide antisera are shown to react well with a wide variety of plant actin isovariants. Similar patterns of actin isovariants were detected in the distant angiosperms, Arabidopsis, petunia, and maize. It is likely that many of these diverse classes of isovariants have been preserved throughout vascular plant evolution and reflect the ancient diversity within plant actin gene families. The extreme difference among isovariants implies the presence of a complex actin-based cytoskeletal system in plants. 相似文献
47.
48.
不同季节银木叶精油化学成分的研究 总被引:1,自引:0,他引:1
黄远征;温鸣章;肖顺昌;赵蕙;任维俭 《武汉植物学研究》1988,6(3):253-259
用毛细管气相色谱-质谱-计算机联用技术、毛细管气相色谱双柱保留指数法和双柱标准品叠加法分析了不同季节银木叶精油化学成分。从分离出来的207—250个色谱峰中,初步鉴定出59个成分,被鉴定成分的总量占精油总组成的94.45—98.92%,其主要成分随采油季节不同而有所不同。 相似文献
49.
J. M. White D. D. Jones D. Huang J. J. Gauthier 《Journal of industrial microbiology & biotechnology》1988,3(5):263-272
Summary A cyanide-degrading pseudomonad was isolated by selective enrichment in a chemostat inoculated with coke-plant activated sludge and maintained at a dilution rate of 0.042/h for 60 days with a feed of 10 mg/l cyanide. The isolate, a facultative methylotroph capable of growth on methanol and methylamine, degraded cyanide to formate and ammonia; it could utilize the released ammonia as a nitrogen source but did not further metabolize formate under the experimental conditions employed. Both cyanide-degrading enzyme activity and respiratory resistance to cyanide were inducible and were enhanced by repeated exposure to the compound. Cell-free extracts stoichiometrically converted cyanide to formate and ammonia in a reaction that did not require oxygen. Enzyme activity, lost upon dialysis, was restored by less than equimolar ratios of NAD(P)H or ascorbate to cyanide, indicating that the reductants did not function directly as co-enzymes. 相似文献
50.
R. J. de Antueno R. C. Cantrill Y. -S. Huang S. K. Raha M. Elliot D. F. Horrobin 《Molecular and cellular biochemistry》1992,116(2):153-161
The present study examines the time dependent effects of n-6 and n-3 polyunsaturated fatty acids on liver microsomal lipid metabolism in FVB mice fed a diet supplemented with a mixture of free fatty acids (mainly 18:3n-6 and 20:5n-3) at 25 mg/g diet. Significant changes in the fatty acid composition of total liver and microsomal lipids were observed after 7 days on the diets. Thereafter, some animals remained on the same diet while others were fed a diet supplemented with hydrogenated coconut oil (HCO). With the exception of 20:5n-3 which showed a slower recovery, establishment of the HCO pattern was rapid indicating that the diet-induced changes could be easily reversed. The unsaturation index, the cholesterol/phospholipid ratio and the microviscosity of the microsomal membranes were not affected by these dietary manipulations. Unsaturated fatty acid supplementation reduced the activity of 9 desaturase by 50%. Feeding the HCO diet to mice previously fed the EPA/GLA diet led to a progressive increase in 9 desaturase activity, reaching 80% of the day zero values after 14 days. The monoene content of hepatic total lipids reflected, in most cases, the changes in enzyme activity. This study shows that a low dose of a n-3 and n-6 free fatty acid mixture increases the quantities of members of the n-3 family, without loss of n-6 fatty acids in microsomal membranes and modifies the activity of 9 desaturase without altering the microsome physicochemical parameters. 相似文献