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21.
Jochen Tittgen Jürgen Hermans Johannes Steppuhn Thomas Jansen Christer Jansson Bertil Andersson Rachel Nechushtai Nathan Nelson Reinhold G. Herrmann 《Molecular & general genetics : MGG》1986,204(2):258-265
Summary Spinach cDNA libraries, made from polyadenylated seedling RNA, have been constructed in pBR322 and the expression vector gt11. Recombinant plasmids or phage for 14 intrinsic and peripheral thylakoid membrane proteins and one stromal protein have been identified. They encode components containing antigenic determinants against the lysine-rich 34 kd, the 23 kd and 16 kd proteins all associated with the water-splitting apparatus of the photosystem II reaction center, the ATP synthase subunits gamma, delta and CFo-II, the Rieske Fe/S protein of the cytochrome b/f complex, subunits 2, 3, 5 and 6 of the photosystem I reaction center, plastocyanin, ferredoxin oxidoreductase, chlorophyll a/b-binding apoproteins of the lightharvesting complex associated with photosystem II, and the small subunit of the stromal enzyme ribulose bisphosphate corboxylase/oxygenase. The cDNA inserts lack complementarity to plastid DNA but hybridize to restricted nuclear DNA as well as to discrete poly A+-mRNA species. The precursor products obtained after translation of hybrid selected RNA fractions in a wheat germ assay are imported and processed by isolated unbroken spinach chloroplasts. The imported components comigrate with the respective authentic proteins. 相似文献
22.
Summary The deffects of a purified homologue of tunicamycin (B2-tunicamycin) on the biosynthesis of lipid-linked intermediates participating in protein glycosylation in normal embryonic fibroblasts, 3T3 and virally transformed (simian virus 40 and polyoma virus) mouse fibroblasts grown in culture were investigated. Long incubations (20 h) with the antibiotic caused a higher degree of inhibition of sugar incorporation into glycoproteins in transformed cells. However, the formation of lipid-linked intermediates was inhibited to a similar level in both cell types. When time dependent inhibition experiments were carried out using transformed cells, an earlier and stronger inhibition of the formation of lipid-oligosaccharides occurred (70% inhibition at 30 min). In 3T3 cells, prolonged incubation (6–8 h) was necessary in order to reach a similar degree of inhibition. Formation of lipid-sugar was also inhibited to a greater extent by B2-tunicamycin in transformed cells. This inhibition was not clearly time dependent. Analysis of the newly synthesized glycolipids in 3T3 and in transformed cells after B2-tunicamycin treatment have shown reduction in dolichyl-P-P-sugars as well as in other glycolipids. Dimethylsulfoxide (10%) and linoleic acid (0.5 mg/ml) markedly increased the level of tunicamycin activity in 3T3 cells while phosphatidylcholine (2 mg/ml) partially reversed it. The stronger and faster inhibition of the formation of lipid intermediates of the dolichyl-phosphate cycle caused by B2-tunicamycin in transformed cells, described here for the first time, may therefore be due to differences in penetration of the antibiotic into these cells.Abbreviations DMEM
Dulbecco's modified Eagle's medium
- DMSO
dimethylsulfoxide
- MF
mouse fibroblasts from Balb/c mouse embryos
- 3T3
Balb/3T3 mouse fibroblastic line
- SV40
Simian virus 40
- PY
polyoma virus
- TLC
thin layer chromatography 相似文献
23.
Summary The effect of treatment with melphalan in vitro on the activity of spleen cells from BALB/c mice was investigated. Incubation of spleen cells with 1.5–5 g melphalan/1×107 inhibited subsequent mitogenic stimulation by ConA or PHA and the allogeneic response of BALB/c spleen cells against C57B1 target spleen cells. Incubation of spleen cells with ConA led to induction of suppressor T cells which when added to fresh cultures inhibited the allogeneic response. Preincubation of spleen cells with melphalan even at low concentrations (0.15–0.5 g 1×107 cells) which do not directly affect mitogenic stimulation or allogeneic response partially inhibited the generation of suppressor T cells by ConA. Treatment with melphalan had no effect on already induced suppressor T cells as shown by incubation of spleen cells with melphalan (0.15–5 g/1×107 cells) after incubation with ConA. Addition of cells treated with melphalan alone (without ConA) to fresh cultures led to an increase in the allogeneic response. 相似文献
24.
13C NMR resonances of 15 simple tetrahydroisoquinolines have been assigned on the basis of chemical shift theory, 13C-1H coupling constants 相似文献
25.
Chloroplast and cytoplasmic low-molecular-weight ribonucleic acid components of the leaf of Vicia faba L 总被引:5,自引:3,他引:2 下载免费PDF全文
1. A method for the extraction of plant nucleic acids and their separation on methylated-serum-albumin-kieselguhr columns is described. It is demonstrated that the characteristics of the elution profiles of material from the same source are consistently reproducible. 2. Major dissimilarities were found in the elution profiles of nucleic acids from root and from leaves of Vicia faba L. These dissimilarities were confirmed by polyacrylamide-gel electrophoresis. 3. Four distinct types of low-molecular-weight RNA were demonstrated to be present in leaves, clearly distinguished by their behaviour when chromatographed on methylated-serum-albumin-kieselguhr columns. (a) Both cytoplasmic and chloroplast ribosomes contained a low-molecular-weight RNA, and these components were distinct from each other. (b) The chloroplast possessed a unique ;soluble' RNA (i.e. RNA that is not precipitated by centrifugal forces that sediment ribosomes) which was not present in the rest of the cell. (c) A soluble component, probably transfer RNA, was found in both the chloroplasts and in the cytoplasm. 4. The components distinguishable by methylated-serum-albumin-kieselguhr column chromatography could not be distinguished by sucrose-density-gradient centrifugation. 相似文献
26.
27.
Yasmin H. Neggers Mary B. Dubard Robert L. Goldenberg Tsunenobu Tamura Kelley E. Johnston Rachel L. Copper John C. Hauth 《Biological trace element research》1996,55(1-2):127-135
Plasma zinc (Zn) concentrations were measured in 4376 indigent women (86% African-American), at a mean (±SD) gestational age
of 15 (±7.8) wk to determine the relationship between various maternal characteristics and plasma Zn levels during pregnancy.
Mean plasma Zn levels were lower in African-American women than in Caucasian women, in multiparous women than in primiparous
women, and in women with body weight >69.9 kg than in those with body weight ≤69.9 kg (p≤0.001 for each comparison). There were no significant differences related to maternal age, marital status, education, or
smoking habit. Multiple regression analysis, including maternal prepregnancy weight, race, age, parity, smoking habit, education,
and marital status indicated that race, parity, and pregnancy weight were significantly associated with maternal plasma Zn
levels, adjusted for gestational age. Maternal race was the best predictor of plasma Zn concentrations among the population
of pregnant women studied A significant proportion of variance in maternal plasma Zn levels remained unexplained after taking
into account various maternal characteristics. The reasons for lower plasma Zn levels in African-American women, compared
to Caucasian women, during pregnancy are unknown. 相似文献
28.
Rachel Y. Reams H. Leon Thacker Daniel D. Harrington Meliton N. Novilla Billie Wilson 《Mycopathologia》1996,135(2):115-118
Aspergillus flavus Link ex Fries and A. parasiticus Speare can invade peanut kernels and under certain environmental conditions produce unacceptable levels of the mycotoxin aflatoxin. A concerted effort is underway to reduce aflatoxin contamination in peanut and peanut products. A potentially effective method of control in peanut is the discovery and use of genes for resistance to either fungal invasion or aflatoxin formation. The objective of the present experimental study was to develop an effective and efficient procedure for screening individual plants or pods of single plants for resistance to invasion by the aflatoxigenic fungi and subsequent aflatoxin production. Methods of obtaining adequate drought-stress and fungal infection were developed through this series of experiments. By completely isolating the pods from the root zone and imposing drought-stress only on pegs and pods, high levels of fungal infection were observed. High amounts of preharvest aflatoxin accumulation were also produced by completely isolating the pods from the root zone. Mid-bloom inoculation with A. parasiticus-contaminated cracked corn and drought-stress periods of 40 to 60 days were the most effective procedures. This technique was used to assess peanut genotypes previously identified as being partially resistant to A. parasiticus infection or aflatoxin contamination, and segregating populations from four crosses. Variability in aflatoxin contamination was found among the 11 genotypes evaluated, however, none were significantly lower than the standard cultivars. Broad-sense heritability of four crosses was estimated through evaluation of seed from individual plants in the F2 generation. The heritability estimates of crosses GFA-2 × NC-V11 and Tifton-8 × NC-V11 were 0.46 and 0.29, respectively, but mean aflatoxin contamination levels were high (73,295 and 27,305 ppb). This greenhouse screening method could be an effective tool when genes for superior aflatoxin resistance are identified.Cooperative investigation of the USDA-ARS and the University of Georgia, College of Agriculture. 相似文献
29.
Measures of geographic range size: the effects of sample size 总被引:2,自引:0,他引:2
A number of methods have been used for quantifying the sizes of the geographic ranges of species. The consequences of different levels of sampling (the proportion of actual spatial occurrences) are explored for eight of these, using data on the occurrences of butterfly species on a 10 × 10 km grid across Britain. For all methods, the percentage error of estimation (PEE) decreases with the number of 10 × 10 km squares which a species occupies, most rapidly for extent measures, and more rapidly for area measures than for measures of numbers of units occupied. The rate of decline in PEE itself falls as sampling effort increases. At a given sampling level, rank correlations between range sizes measured by different methods are generally high, but there is no consistent change in the magnitude of these correlations as the level of sampling increases. The composition of the set of species with the smallest range sizes changes with the level of sampling. 相似文献
30.
Christon J. Hurst Janet C. Blannon Rachel L. Hardaway Wesley C. Jackson 《Applied microbiology》1994,60(9):3462-3465
This study examined whether the practice of incorporating either tetrazolium red or tetrazolium violet dye into plaque assay medium deleteriously influences plaque assay titers. Representative members of six different virus families were studied: Cystoviridae (ϕ6), Leviviridae (MS2), Microviridae (ϕX174), Myoviridae (T2), Podoviridae (P22), and Siphoviridae (Denver, T1, and VD13). Each of the members of the Podoviridae and Siphoviridae families appeared to be suppressed by either one or both dyes at a 300-μg/ml concentration. The chosen representatives of the other bacteriophage families were not suppressed by either dye at a 300-μg/ml concentration. Subsequent trials revealed no suppression of Podoviridae or Siphoviridae plaque assay titers when members of these virus families were tested with the same two dyes at the lower concentrations of 150 and 50 μg/ml. Interestingly, the bacteriophage families whose members were affected by the dyes have additional commonality in that they are the two bacteriophage families whose members possess both double-stranded DNA genomes and noncontractile tails. 相似文献