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31.
32.
To provide more information on satellite nucleoli, these nuclear structures were studied by means of cytochemical and immunofluorescence procedures in rat and mouse hepatocytes without and following experimental inhibition of the RNA synthesis. The immuno-staining specific for nucleoli or B23 as well as C23 proteins demonstrated that satellite nucleoli and characteristic nucleoli exhibit the same fluorescence. The number of satellite nucleoli decreased after inhibition of nucleolar RNA synthesis in a similar way to the number of silver-stained granules (SSGs) of characteristic nucleoli. Inhibition of RNA synthesis also reduced the number of hepatocytes containing satellite nucleoli. Thus, satellite nucleoli seem to be real nucleoli from single NORs which did not fuse in the formation of a characteristic nucleolus. 相似文献
33.
Glucuronic acid conjugates of bilirubin-IXα in normal bile compared with post-obstructive bile. Transformation of the 1-O-acylglucuronide into 2-, 3-, and 4-O-acylglucuronides 总被引:7,自引:2,他引:5
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Frans Compernolle Gustaaf P. Van Hees Norbert Blanckaert Karel P. M. Heirwegh 《The Biochemical journal》1978,171(1):185-201
Structures have been determined for bilirubin-IXalpha conjugates in freshly collected bile of normal rats, dogs and man and in post-obstructive bile of man and rats. The originally secreted conjugate has been characterized as azopigment (I), i.e. a 1-O-acyl-beta-d-glucopyranuronic acid glycoside. Conversion of the acetylated methyl ester of azopigment (I) into methyl 2,3,4-tri-O-acetyl-1-bromo-1-deoxy-beta-d-glucopyranuronate (V) indicates the pyranose ring structure for the carbohydrate and a C-1 attachment for the bilirubin-IXalpha acyl group. Alternative procedures for deconjugation of azopigment (I) and its derivatives are also described. In post-obstructive bile, the 1-O-acylglucuronide is converted into 2-, 3- and 4-O-acylglucuronides via sequential intramolecular migrations of the bilirubin acyl group. The following approach was utilized. (1) The tetrapyrrole conjugates were cleaved to dipyrrolic aniline and ethyl anthranilate azopigments, and the azopigments were separated as the acids or methyl esters. (2) The isomeric methyl esters were characterized by mass spectral analysis of the acetates and silyl ethers. (3) The free glycosidic function was demonstrated by 1-oxime and 1-methoxime derivative formation. (4) The position of the dipyrrolic O-acyl group was determined for the methyl esters by protecting the free hydroxyl groups of the glucuronic acid moieties as the acetals formed with ethyl vinyl ether and by further conversion of the carbohydrates into partially methylated alditol acetates. These were analysed by using g.l.c.-mass spectrometry. The relevance of the present results with regard to previous reports on disaccharidic conjugates is discussed. Details of procedures for the formation of chemical derivatives for g.l.c. and mass spectrometry have been deposited as Supplementary Publication SUP 50081 (15 pages) at the British Library Lending Division, Boston Spa, West Yorkshire LS23 7BQ, U.K., from whom copies can be obtained on the terms indicated in Biochem. J. (1978), 169, 5. 相似文献
34.
Summary The presence of 1% agar in the fixation and substrate solutions for the histochemical demonstration of thiamine pyrophosphatase (4.4 mM TPP; 3.6 mM Pb2+; 0.025 Tris-maleate buffer, pH 7.2) clearly facilitates the localization of the enzyme in Golgi apparatus in cold microtome sections prepared from unfixed specimens. 相似文献
35.
Rabbit antibodies to the nuclear Tris extract of HeLa cells which have been shown by the indirect immunofluorescence technique to localize in nucleoli of a variety of human malignant tumors but not in a number of nontumor tissues also produced bright fluorescence in nucleoli of tumor cells in several hematological malignancies. The tumors studied included Hodgkins malignant lymphoma, non-Hodgkins malignant lymphoma, acute myeloid and acute myelomonocytic leukemia, chronic lymphatic and chronic myeloid leukemia. In contrast, none of the corresponding normal cell lines in the bone marrow exhibited bright nucleolar fluorescence. In addition, neither the cells of patients with acute infectious mononucleosis nor lymphoid hyperplasia exhibited bright nucleolar fluorescence. These studies suggest that antibodies to HeLa cell nucleolar antigens may be useful in immunodiagnosis of human malignancies. 相似文献
36.
A simple simulation model of the secondary shrub succession has been elaborated on the grounds of primary field data from abandoned fields of different ages in the area of Bohemian Karst. The model describes vegetational dynamics using adaptedVolterra-Lotka equations for competing species. Carrying capacities and growth rates are expressed as a function of the depth of the soil. 相似文献
37.
Escherichia coli cells were immobilized and grown in hollow-fiber reactors allowing simultaneous NMR spectroscopy and perfusion with nutrient medium. The extent to which the cells were starved due to inadequate mass transfer was predicted using a mathematical model of reaction and diffusion. Reactors were experimentally characterized using (35)S autoradiography to visualize spatial variations in protein synthesis rates and transmission electron microscopy to indicate spatial variations in cell morphology. Mass transfer limitations in reactors operated at 37 degrees C were shown to be severe, with regions of starved cells occupying up to 80% of the cell-containing region. Phosphorus-31 nuclear magnetic resonance (NMR) spectra of the immobilized, perfused cells revealed abnormally low volume-averaged concentrations of sugar phosphates, NTP, and ratios of NTP/NDP in these reactors. Intracellular pH was also depressed in the cells. In order to overcome mass transfer limitations in the cell layer, the reactor growth temperature was decreased. Sulfur-35 autoradiographs of a reactor operated at 16 degrees C did not indicate the presence of starved cells. The NMR spectra obtained from this reactor showed near-normal intracellular pH, metabolite concentrations, and NTP/NDP ratios. The presence of significant mass transfer limitations in a perfused cell sample during NMR spectroscopy is generally undesirable since the resulting spectra can be ambiguous and difficult to interpret. The strategy adopted in this work, namely estimation of the relative rates of reaction and diffusion in the cell mass and appropriate changes in reactor design and operating parameters, should prove generally applicable for the design of perfused cell samples for NMR spectroscopic experiments. 相似文献
38.
Food and water samples from an Ethiopian community were screened for the presence of enterotoxin-producing bacteria. Using the Chinese hamster ovary cell assay, 40 of 213 isolates (18.8%) produced heat-labile (LT) enterotoxin. These LT-producing isolates comprised 33 of 177 (18.6%) strains from 24 of 68 food samples (35.3%) and 7 of 36 (19.4%) isolates of 4 of 17 water samples (23.5%). One LT-producing strain each of Salmonella emek and of Shigella dysenteriae was found. Three pseudomonads, all LT producers, produced heat-stable enterotoxin as gauged by the suckling mouse test. Two strains of LT-enterotoxigenic Escherichia coli O68 were found in water samples. No enterotoxigenic E. coli were isolated from food samples, but 13 of the LT-producing strains were Enterobacter, Klebsiella, Serratia, and Proteus species, and 7 food samples yielded more than one species of enterotoxigenic bacterium. Of the enterotoxigenic isolates from food, 15 were oxidase-positive strains of the genera Aeromonas, Pseudomonas, Achromobacter, Flavobacterium, and Vibrio. LT-enterotoxigenic Enterobacter, Acinetobacter, Klebsiella, Proteus, Providencia, and Serratia species represented 20 of the food and water isolates. Culture supernatant fluids of representative strains of oxidase-positive and oxidase-negative species giving positive reactions in Chinese hamster ovary cell tests induced fluid accumulation in rabbit ileal loops. Eight of the food samples and two of the water samples contained more than one isolate or species of enterotoxigenic bacterium. The stability of the LT production by oxidase-positive bacteria and non-E. coli strains was assessed by the rabbit skin and adrenal cell tests after 9 months and 1 year of storage, respectively, in Trypticase soy broth with glycerol at −70°C. Only 33% of the oxidase-positive strains were still LT enterotoxigenic. Of the oxidase-negative strains, 50 and 33% were LT producing at 9 months and 1 year, respectively. None of the E. coli isolates, both enterotoxigenic and nonenterotoxigenic, possessed K88, K99, or colonization factor antigen. The survey demonstrates the presence in food and water of enterotoxigenic bacteria of the same species as those isolated from cases of infantile diarrhea in the same community, although a correlation between these sources and infantile diarrhea remains to be established. 相似文献
39.
40.
The molecular mechanisms of protein inactivation, i.e. aggregation, thiol-disulphide exchange, alteration of the primary structure, dissociation of cofactor molecules from the active centre, dissociation of the oligomeric proteins into subunits and conformational changes have been analysed. All these mechanisms are closely interrelated during inactivation of proteins. However, in many cases, the conformational changes accompany and trigger other inactivation processes. Reactivation of irreversibly inactivated proteins is·discussed. Reactivation can be successful when inactivation has been caused by aggregation, modification of SH-groups (or S-S bonds) or as a consequence of irreversible conformational changes. 相似文献