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91.
Isolated melanophores of the angelfish, Pterophyllum scalare, have been used in a morphometric analysis and a quantitative study of their microtubule system. Using transverse sections spaced at regular intervals, the changes associated with the process of pigment aggregation have been determined. Upon the concentration of pigment granules in the central cell region, almost half of the cytoplasmic portion is also withdrawn from the peripheral cell regions. Counts of microtubules within a cell sector in cells with pigment aggregated and dispersed, respectively, reveal (a) a constancy of the number of microtubules in this sector regardless of the distance from the cell center, and (b) a reduction of microtubule number in cells with pigment aggregated by about 58%. On the basis of these counts, the total number of microtubules has been calculated. In the dispersed state, about 2,400 microtubules extend between the center and the periphery of the cell, while their number is about 1,000 in the aggregated state. Using a 13-protofilament model of a microtubule and relevant data on size and molecular weight of microtubule subunits, the amount of tubulin present as microtubules is calculated. In the average, the cells contain 1.95·108 monomers corresponding to 1.78·10?8 mg tubulin. A tentative estimation of the concentration of tubulin inside a melanophore yields values of 6.1 mg/ml for the whole cell and 16.5 mg/ml for the cytoplasm alone (excluding membrane-bound organelles). Based on this estimation, a comparison, with microtubule assembly in vitro is made. 相似文献
92.
93.
Noemi Luknar-Gabor Ursula Fenger Christoph Wagener Heinz Breuer 《Biochemical and biophysical research communications》1982,109(4):1270-1275
A variant of the carcinoembryonic antigen (CEA) with lower molecular weight than a CEA reference preparation has been separated from CEA. Using a polyclonal, spleen absorbed anti-CEA antiserum, the variant crossreacts with reference CEA in immunodiffusion. The CEA-activity of the variant has been demonstrated using an enzyme-immunoassay with monoclonal CEA specific antibodies. There is sufficient immunological evidence that this variant is a distinct antigen different from the crossreactive antigens described so far. The reactivity of the polyclonal anti-CEA antiserum with the CEA variant was abolished by absorption against the immobilized variant. 相似文献
94.
Jürgen Bachmann Monika Feldmer Ursula Ganten Günter Stock Detlev Ganten 《The Journal of steroid biochemistry and molecular biology》1991,40(4-6):511-515
The prevalence of hypertension in men is higher than in women and the onset of this disease is earlier in male than in female subjects. In spontaneously hypertensive rats, males also have higher blood pressures than females. Evidence from epidemiological, physiological, molecular biological and morphological studies concerning this sexual dimorphism is reviewed. We demonstrate that the gonadal steroids testosterone and estrogen have important effects on the gene regulation of the renin-angiotensin system. This may in part contribute to the sexual dimorphism in blood pressure control. The direct effect of steroid hormones on genes related to hypertension provides a suitable paradigm to improve our understanding of molecular and cellular mechanisms of cardiovascular control. 相似文献
95.
Daniel V. Santi Ursula Edman Svetlana Minkin Patricia J. Greene 《Protein expression and purification》1991,2(5-6)
Gatalytically active Pneumocystis carinii thymidylate synthase is expressed to the extent of about 4% of the soluble protein in Escherichia coli χ2913 harboring plasmid pUETS-1.8 (U. Edman, J. C. Edman, B. Lundgren, and D. V. Santi, Proc. Natl. Acad. Sci. USA 86, 6503–6507, 1989). Ion-exchange, affinity, hydrophobic, and reactive dye agarose chromatography steps were explored to devise a large-scale purification protocol for P. carinii thymidylate synthase. Sequential DE52, Q-Sepharose, phenyl-Sepharose, and Cibacron Blue F3GA chromatography yielded enzyme that was homogeneous by SDS-PAGE in a yield of over 50%. The sequence of the first 10 amino acid residues of the purified protein was in accord with that predicted from the DNA sequence. Isoelectric focusing gave a pI of 6.2. Kinetic analysis of the purified enzyme revealed that the the Km values were 4.7 ± 1.3 μM for dUMP and 15.7 ± 4.3 μM for 5,10-methylenetetrahydrofolate, similar to those of many other thymidylate synthases; the κcat of the most active preparation was 0.8 s−1. The enzyme is stable for at least 2 months when stored at −80°C in the presence of 40% glycerol, Tris-HCl, and thiol. 相似文献
96.
Mathias Schwanstecher Ursula Schaupp Stefan Löser Uwe Panten 《Journal of neurochemistry》1992,59(4):1325-1335
Glibenclamide closes an ATP-sensitive K+ channel (K-ATP channel) by interaction with the sulfonylurea receptor in the plasma membrane of pancreatic B cells and thereby initiates insulin release. Previous studies demonstrated that the Mg2+ complex of ATP decreases glibenclamide binding to the sulfonylurea receptor from pancreatic islets. The aim of the present study was to examine the effect of adenine and guanine nucleotides on binding of sulfonyl-ureas to the cerebral sulfonylurea receptor. For this purpose, binding properties of the particulate and solubilized site from rat or pig cerebral cortex were analyzed. Maximum recovery of receptors in detergent extracts amounted to 40-50%. Specific binding of [3H]glibenclamide to the solubilized receptors corresponded well to specific binding to microsomes. In microsomes and detergent extracts, the Mg2+ complexes of ATP, ADP, GTP, and GDP inhibited binding of [3H]glibenclamide. These effects were not observed in the absence of Mg2+. In detergent extracts, Mg-ATP (300 microM) reduced the number of high-affinity sites for [3H]-glibenclamide by 52% and increased the dissociation constant for [3H]glibenclamide by eightfold; Mg-ATP was half-maximally effective at 41 microM. Alkaline phosphatase accelerated the reversal of Mg-ATP-induced inhibition of [3H]glibenclamide binding. The data suggest similar control of the sulfonylurea receptor from brain and pancreatic islets by protein phosphorylation. 相似文献
97.
Marc Mercken† Mark Vandermeeren† Ursula Lübke‡ Jan Six Jef Boons† Eugène Vanmechelen re Van De Voorde Jan Gheuens† 《Journal of neurochemistry》1992,58(2):548-553
Immunoaffinity chromatography with a monoclonal antibody produced against bovine tau protein was used to purify tau proteins from human brain. Fifty grams of brain tissue yielded approximately 2 mg of pure tau proteins. The affinity-purified human tau was used to produce a high-titered rabbit anti-human tau serum. The monoclonal anti-tau antibody and the polyclonal rabbit anti-tau serum were then used to construct a sandwich enzyme-linked immunosorbent assay for detection of human tau proteins, with a sensitivity of 1 ng/ml. 相似文献
98.
Silke Ruppel Charlotte Hecht-Buchholz Rainer Remus Ursula Ortmann Rita Schmelzer 《Plant and Soil》1992,145(2):261-273
The aim of this study was to investigate the ability of Pantoea agglomerans, a plant growth-promoting bacterium, to colonize various regions and tissues of the wheat plant (Triticum aestivum L.) by using different inoculation methods and inoculum concentrations. In addition, the enzyme-linked immunosorbent assay
(ELISA) and transmission electron microscopy (TEM) were used to determine: (a) the ability of the bacterial cells to grow
and survive both on the surface and within internal tissue of the plant and (b) the response of the plant to bacterial infection.
After inoculation, cells of the diazotrophic bacterial strain P. agglomerans were found to be located in roots, stems and leaves. Colony development of bacterial cells was only detected within intercellular
spaces of the root and on the root surface. However, single bacterial cells were observed in leaves and stems on the surface
of the epidermis, in the vicinity to stomatal cells, within intercellular spaces of the mesophyll and within xylem vessels.
Inoculated bacterial cells were found to be able to enter host tissues, to multiply in the plant and to maintain a delicate
relationship between endophyte and host. The density of bacterial settlement in the plant in all experiments was about 106 to 107 cells per mL root or shoot sap. Establishment was confirmed by a low coefficient of variation of ELISA means at these concentrations. 相似文献
99.
Cell-wall acidification and electrical reactions (depolarization and hyperpolarization) are typical auxin responses in maize (Zea mays L.) coleoptiles. In an attempt to test the role of the outer epidermis in these responses, they have been measured and compared in intact and peeled coleoptile fragments. To exclude interactions between parenchymal and epidermal cells, the coleoptile pieces were completely stripped of their outer epidermis. This preparation was monitored by means of a scanning electron microscope. When externally applied indole-3-acetic acid was tested, we found that neither cell-wall acidification nor the electrical membrane responses depended on the presence of intact epidermal cells.Abbreviations IAA
Indole-3-acetic acid
- MES
2-[N morpholino-ethane-sulfonic acid
- TRIS
2-Amino-2-hydroxymethyl-1,3-propanediol
We thank Kuki Kaethner for her excellent technical assistance. This work was supported by the Hessische Graduiertenförderung and the Deutsche Forschungsgemeinschaft. 相似文献
100.
R. Rodney Howell Amir I. Arbisser David S. Parsons Charles I. Scott Ursula Fraustadt William R. Collie Robert N. Marshall Oscar Cavazos Ibarra 《American journal of human genetics》1981,33(6):957-967
We have defined a new autosomal recessive disorder in patients stemming from a small community in northern Mexico. Diagnosable at birth, its major symptoms include brittle hair, mental retardation, and nail dysplasia. Structural hair abnormalities are seen by both light and electron microscopy. Hair cystine content is reduced while the copper/zinc ratio in hair is increased. 相似文献