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31.
JoAnne S. Richards Gerard J. Hickey Shiuan Chen John E. Shively Peter F. Hall Dana Gaddy-Kurten Richard Kurten 《Steroids》1987,50(4-6):393-409
To determine the molecular basis for changes in aromatase (P450arom) activity in rat ovarian follicles and corpora lutea, seven clones for rat P450arom cDNA have been identified and isolated from a rat granulosa cell λgtll cDNA expression library using a 62 mer deoxyoligonucleotide probe (derived from an amino acid sequence of purified human placental aromatase) and a human placental P450arom cDNA probe. One of the rat P450arom cDNA clones contained an insert 1.2 kb in size. Both the human 1.8 kb cDNA and the rat 1.2 kb cDNA probes hybridized to a single species of P450arom mRNA that was 2.6 kb in size. Northern blot analysis revealed that corpora lutea isolated on day 15 of pregnancy contained high amounts of P450arom mRNA, whereas granulosa cells of antral follicles of hormonally primed, hypophysectomized rats (i.e., those from which mRNA was isolated to construct the cDNA library) contained only low amounts of P450arom mRNA. The lower amounts of P450arom in granulosa cells of preovulatory follicles in the estradiol-follicle-stimulating hormone primed hypophysectomized rats were unexpected because follicles incubated in medium containing testosterone substrate produce more estradiol than do corpora lutea isolated on day 15 of pregnancy and incubated under similar conditions. Additional studies will determine the hormonal events responsible for the elevated amounts and constitutive maintenance of P450arom mRNA and aromatase activity in luteal cells in vivo and in vitro. 相似文献
32.
The asymmetric distribution of phospholipids in bovine endothelial-cell membranes was probed with 2,4,6-trinitrobenzenesulphonate and purified phospholipase A2. The data suggest that phosphotidylethanolamine is primarily located in the inner lipid bilayer, as reported for other cell types. Stearic acid is taken up by the endothelial cells and is randomly distributed among the membrane phospholipids. In contrast, the polyunsaturated fatty acids (arachidonic, eicosatrienoic and eicosapentaenoic acids) have initial incorporation into the phosphatidylcholine fraction. These fatty acids then undergo a time-dependent transfer from phosphatidylcholine to phosphatidylethanolamine. Thus we propose that endothelial cells possess a mechanism for the selective internalization of polyunsaturated fatty acids. 相似文献
33.
34.
Functional genes for cellobiose utilization in natural isolates of Escherichia coli. 总被引:3,自引:1,他引:2 下载免费PDF全文
The genes for utilization of cellobiose are normally cryptic in both laboratory strains and natural isolates of Escherichia coli. A survey of natural isolates of E. coli reveals that functional genes for cellobiose utilization, while rare, are present. The fraction of E. coli that utilized cellobiose ranged from less than 0.01% in human fecal samples to 7% in fecal samples obtained from horses. Samples obtained from sheep, cows, dogs, and pigs contained 0.1 to 0.5% cellobiose-positive E. coli. Neither the previously identified cel genes nor the bgl genes from E. coli K-12 were expressed during growth on cellobiose by any of the 14 naturally occurring Cel+ isolates that were tested. All of the naturally occurring Cel+ isolates possessed a cel operon, but all were deleted for the major portion of the bgl operon. The functional cel+ genes from these natural isolates differed from the mutationally activated cel+ genes obtained in earlier studies in that (i) the mutationally activated cel+ genes were temperature sensitive, while the functional genes were not, and (ii) transport of cellobiose was inducible in the strains carrying functional cel+ genes, while it was expressed constitutively in strains carrying mutationally activated genes. 相似文献
35.
Signal sequence mutations that alter coupling of secretion and translation of an Escherichia coli outer membrane protein. 总被引:3,自引:2,他引:1 下载免费PDF全文
The lamB701-708 signal sequence mutation reduces expression of LamB, an outer membrane protein of Escherichia coli. To investigate the possibility that synthesis and export of LamB are coupled, as suggested by the expression defect of the lamB701-708 mutation, we isolated intragenic suppressors of the lamB701-708 mutation. The expression defect imposed by the lamB701-708 mutation is suppressed by an export-defective signal sequence mutation, suggesting that translation and export are coupled. The additional observation that not all export-defective signal sequence mutations suppressed the lamB701-708 expression defect suggests that translational arrest can be uncoupled from export. 相似文献
36.
J Hall M Ayres X H Zha P O'Brien B Durham D Knaff F Millett 《The Journal of biological chemistry》1987,262(23):11046-11051
In order to define the interaction domain on Rhodospirillum rubrum cytochrome c2 for the photosynthetic reaction center, positively charged lysine amino groups on cytochrome c2 were modified to form negatively charged carboxydinitrophenyl lysines. The reaction mixture was separated into six different fractions by ion exchange chromatography on carboxymethylcellulose and sulfopropyl-Sepharose. Peptide mapping studies indicated that fraction A consisted of a mixture of singly labeled derivatives modified at lysines 58, 81, and 109 on the back of cytochrome c2. Fractions C1, C2, C3, and C4 were found to be mixtures of singly labeled derivatives modified at lysines 9, 13, 75, 86, and 88 on the front of cytochrome c2 surrounding the heme crevice. The photooxidation of the carboxydinitrophenyl-cytochrome c2 derivatives by reaction centers purified from R. rubrum was measured following excitation with a laser pulse. The second-order rate constant of fraction A modified at backside lysines was found to be 2.3 X 10(7) M-1 s-1, nearly the same as that of native cytochrome c2, 2.6 X 10(7) M-1 s-1. However, the rate constants of fractions C1-C4 were found to be 6 to 12-fold smaller than that of native cytochrome c2. These results indicate that lysines surrounding the heme crevice of cytochrome c2 are involved in electrostatic interactions with carboxylate groups at the binding site of the reaction center. The reaction rates of horse heart cytochrome c derivatives modified at single lysine amino groups with trifluoroacetyl or trifluoromethylphenylcarbamoyl were also measured. Modification of lysines 8, 13, 25, 27, 72, 79, or 87 surrounding the heme crevice was found to significantly lower the rate of reaction, while modification of lysines in other regions had no effect. This indicates that the reaction of horse heart cytochrome c with the reaction center also involves the heme crevice domain. 相似文献
37.
As a model system for analysing interactions between chlamydiae and myeloid cells and their precursors, we have studied binding, ingestion and destruction of Chlamydia trachomatis (L2 serovar) by the human promyelocytic cell line HL-60. HL-60 cells were induced by phorbol myristate acetate (PMA) and dimethyl sulphoxide (DMSO) to differentiate along either the macrophage or the granulocyte pathway, respectively. Using an immunofluorescence assay and electron microscopy, we have shown that induced (differentiated) HL-60 cells, but not uninduced (undifferentiated) HL-60 or other cell lines treated with PMA or DMSO, exhibit increased binding, ingestion and elimination of C. trachomatis; these activities are associated with specific histochemical and antigenic markers of myeloid differentiation. These results suggest that myeloid cells acquire the ability to interact with and kill chlamydiae during cell development. 相似文献
38.
Thomas K. C. Leung Christine Hall Clinton Monfries Louis Lim 《Journal of neurochemistry》1987,49(1):232-238
Neurone-specific enolase (NSE) and the brain form of creatine phosphokinase (CPK-BB) were previously found to be present in rat synaptosomal plasma membranes (SPM) using two-dimensional gel (2-D gel) and peptide analysis; enzymatic activities of these and of pyruvate kinase (PK), all involved in ATP generation, were shown to be "cryptic" unless the SPM were treated with Triton X-100. We now show that enzymatic activation also occurs when the SPM are treated with trifluoperazine (TFP). TFP activation occurred even when the enzymes were membrane associated, showing that solubilization was not responsible for "unmasking" the enzyme activities. When TFP treatment was performed at alkaline instead of neutral pH, NSE and CPK-BB were released as well as PK, nonneuronal enolase, and aldolase which were identified by 2-D gel and tryptic peptide analysis. Other proteins released included calmodulin, actin, and the 70-kilodalton heat-shock cognate protein. Tubulin, synapsin I, and a 35-kilodalton basic protein were largely unaffected. The latter was identified as the glycolytic enzyme glyceraldehyde-3-phosphate dehydrogenase on the basis of 2-D gel and peptide analyses and subsequent partial sequencing of a rat brain cDNA coding for the same protein. TFP treatment is thus useful for activating latent enzymes as well as for distinguishing enzymes that have a different disposition on the membrane. 相似文献
39.
Hall ER 《Biotechnology advances》1987,5(2):257-269
Attached biofilm reactors provide the means for implementing energy-efficient anaerobic wastewater treatment at full scale. Progress has been made in the development of fixed, expanded and fluidized bed anaerobic processes by addressing fundamental reactor design issues. Several new biofilm reactor concepts have evolved from recent studies. 相似文献
40.
Prognostic significance of DNA ploidy and morphometric analyses of adenocarcinoma of the uterine cervix 总被引:1,自引:0,他引:1
Y S Fu T L Hall J S Berek N F Hacker J W Reagen 《Analytical and quantitative cytology and histology / the International Academy of Cytology [and] American Society of Cytology》1987,9(1):17-24
In an effort to improve the prognostic accuracy of the histologic criteria used for cervical adenocarcinomas, the nuclear DNA ploidy levels, means and standard deviations of nuclear areas and amounts of lumen and neoplastic tissue were quantitated. Useful thresholds in discriminating recurrent disease, as identified by logistic regression analysis, included a DNA ploidy level of 3.0 N, a percent of lumen of 34.6% and nuclear area mean and standard deviation of 53.1 sq micron and 20.1 sq micron, respectively. These parameters should provide useful guidelines in the visual assessment of histologic features that have prognostic significance. 相似文献