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91.
Endogenous ligands complicate radioligand-binding assays of high-affinity binding proteins by obscuring binding sites or by diluting the labeled ligand. We have developed a mathematical model for such systems where radioligand and endogenous ligand are structurally identical. Data which relate radioligand binding at equilibrium as a function of sample volume can be plotted such that the concentrations of endogenous ligand and binder are graphically determined; however, a more precise determination may be done by nonlinear regression with the aid of a microcomputer. The method is demonstrated for the assay of biotin-binding proteins in the presence of a range of endogenous biotin concentrations below and above that required to saturate the binding sites. 相似文献
92.
The effect of experimental hyperthyroidism on renal and adrenal weight increase in mice. 总被引:1,自引:0,他引:1
P D Broulík J Marek V Schreiber 《Physiological research / Academia Scientiarum Bohemoslovaca》1991,40(5):527-532
The mouse kidneys are enlarged after the administration of thyroxine and this influence is not mediated through androgens. The administration of thyroxine increased the weight of the adrenals and the level of plasma corticosterone. Besides the direct effect of the thyroid hormones on the kidney, our findings indicate that the excess of triiodothyronine and thyroxine stimulates the activity of adrenals indirectly and evokes hyperadrenocorticism which could be related to the action of adrenal steroids on kidney function and kidney growth. In accordance with the above mentioned hypothesis it has been shown that aminoglutethimide, a potent blocker of adrenal steroidogenesis, decreases the level of plasma corticosterone and inhibits the enlargement of the kidney in hyperthyroid mice in spite of the high serum thyroxine values. 相似文献
93.
Characterization and expression of the human leukocyte-common antigen (CD45) gene contained in yeast artificial chromosomes. 总被引:3,自引:0,他引:3
J L Fernandez-Luna R J Matthews B H Brownstein R D Schreiber M L Thomas 《Genomics》1991,10(3):756-764
The leukocyte-common antigen (CD45) is a transmembrane protein tyrosine phosphatase expressed uniquely by cells of hematopoietic origin. There are multiple isoforms of CD45 that are generated by the variable use of three exons (exons 4-6). The use of the variable exons results in changes near the amino-terminus of the mature glycoprotein. The gene is located on chromosome 1 for both human and mouse in a region that is homologous between these two species. This conserved linkage group contains a number of genes of immunological interest, such as the genes for complement regulatory proteins and the FCG2 receptor. Yeast artificial chromosomes provide a vector system in which large fragments of foreign DNA can be isolated and are suited to long-range physical mapping. To this end, three yeast artificial chromosomes containing the human CD45 gene have been isolated and characterized. They overlap to span 475 kb, establishing the largest physical map for DNA within the conserved linkage group. The CD45 gene is entirely encoded within one yeast artificial chromosome clone as determined by mapping with cDNA probes. A mouse B cell line transfected with this YAC clone expressed the low-molecular-weight isoform of the protein into the cell surface. The size of the human CD45 gene was determined to be approximately 120 +/- 10 kb. 相似文献
94.
Summary Four enhanced carbonyl carbon resonances were observed whenStreptomyces subtilisin inhibitor (SSI) was labeled by incorporating specifically labeled [1-13C]Cys. The13C signals were assigned by the15N,13C double-labeling method along with site-specific mutagenesis. Changes in the spectrum of the labeled protein ([C]SSI) were induced by reducing the disulfide bonds with various amounts of dithiothreitol (DTT). The results indicate that, in the absence of denaturant, the Cys71-Cys101 disulfide bond of each SSI subunit can be reduced selectively. This disulfide bond, which is in the vicinity of the reactive site scissile bond Met73-Val74, is more accessible to solvent than the other disulfide bond. Cys35-Cys50, which is embedded in the interior of SSI. This half-reduced SSI had 65% of the inhibitory activity of native SSI and maintained a conformation similar to that of the fully oxidized SSI. Reoxidation of the half reduced-folded SSI by air regenerates fully active SSI which is indistinguishable with intact SSI by NMR. In the presence of 3 M guanidine hydrochloride (GuHCl), however, both disulfide bonds of each SSI subunit were readily reduced by DTT. The fully reduced-unfolded SSI spontaneously refolded into a native-like structure (fully reduced-folded state), as evidenced by the Cys carbonyl carbon chemical shifts, upon removing GuHCl and DTT from the reaction mixture. The time course of disulfide bond regeneration from this state by air oxidation was monitored by following the NMR spectral changes and the results indicated that the disulfide bond between Cys71 and Cys101 regenerates at a much faster rate than that between Cys35 and Cys50.Nomenclature of the various states of SSI that are observed in the present study
Fully oxidized-folded
native or intact (without GuHCl or DTT)
-
half reduced-folded
(Cys71-Cys101 reduced; DTT without GuHCl)
-
inversely half reduced-folded
(Cys35-Cys50 reduced; a reoxidation intermediate from fully reduced-folded state)
-
fully reduced-unfolded
(reduced by DTT in the presence of GuHCl)
-
fully reduced-folded
(an intermediate state obtained by removing DTT and GuHCl from the fully reduced-unfolded SSI reaction mixture) 相似文献
95.
Dr. Yoko Kameda 《Cell and tissue research》1982,225(3):693-697
Summary Small follicles composed solely of C cells were occasionally observed in large C cell groups of dog thyroid glands. The lumina of C-cell follicles were filled with, or contained peripheral depositions of PAS-positive amorphous material, which was similar in ultrastructural features to thyroglobulin-containing colloid in typical thyroid follicles. This indicates that C cells, in addition to secreting calcitonin, produce a glycoprotein that can be stored in the lumina of the follicles. 相似文献
96.
Akitane Mori Masayuki Akagi Yasuto Katayama Yoko Watanabe 《Journal of neurochemistry》1980,35(3):603-605
: Guanidino compounds in the cobalt-induced epileptogenic cerebral cortex of cats were fluorometrically analysed by a JASCO G-520 guanidino compounds analyser, and an unknown high peak was observed in the chromatogram that was identical to the peak of authentic α-guanidinoglutaric acid. In another experiment, the substance was extracted from the cobalt focus tissue, converted into dimethylpyrimidyl derivative-butylester, and analysed by a GC/MS technique. The mass spectrum of the substance was identical to the dimethylpyrimidyl derivative of α-guanidinoglutaric acid butylester (M+= 365). 相似文献
97.
W E Schreiber R Gentry E H Fischer 《Biochemical and biophysical research communications》1981,100(3):1415-1421
Calmodulin and cyclic nucleotide phosphodiesterase activities were measured in hemolysates prepared from 18 normal and 17 schizophrenic subjects. No significant difference between groups was found for either activity. The results suggest that calmodulin is present in normal amounts in patients with schizophrenia. This is compatible with the idea that the interaction of calmodulin with antipsychotic agents is structurally non-specific. 相似文献
98.
Alain B. Schreiber Johan Hoebeke Bernard Vray A. Donny Strosberg 《Experimental cell research》1981,132(2)
The association and dissociation mechanisms of lectin membrane receptor microclustering on HeLa cells have been studied by measuring resonance energy transfer between fluoresceinated and rhodaminated lentil lectin. Compounds known to affect membrane receptor mobility, such as Ca2+ ions, methylamine, cytochalasin D and nocodazole, did not modify the association kinetics nor the maximal energy transfer values at 4 and 37 °C. Dissociation of the membrane receptor microclusters was followed by measuring the temporal decrease in energy transfer values at 4 °C after preincubation for different time intervals at 37 °C. The rate of dissociation of the lectin receptors decreased in the presence of Ca2+ ions (10−3 M) and after cross-linking with anti-lectin antibodies. An increase was observed in the presence of cytochalasin D (10−6 M) and, to a lesser extent, of methylamine (10−2 M). When cytochalasin D and methylamine were combined at subliminal concentrations, a partial synergistic effect was observed. Nocodazole (10−6 M) had no effect. The results suggest that the association of lectin membrane receptors in microclusters is mediated only by physicochemical parameters. Ca2+ ions, cytochalasin D (microfilaments) and methylamine (transglutaminase)-sensitive components appear, however, to play an important role in the stabilization of the receptor microclusters. 相似文献
99.
U. Schreiber 《BBA》1980,591(2):361-371
Phycobilin fluorescence of Anacystis nidulans grown at 28°C increases substantially upon cooling below 10°C. A maximal increase is found around ?5°C and amounts to 300%, with almost complete reversibility upon re-warming. Illumination with actinic light leads to considerable stimulation of the cold-induced phycobilin fluorescence increase. Analysis of the light stimulation phenomenon reveals: (1) Actinic illumination shifts the fluorescence-temperature characteristic by about 3°C upwards on the T-axis. At temperatures below 5°C the light stimulating effect becomes smaller again and fluorescence-temperature characteristics measured at high and low light intensity converge around ?5°C. (2) In the 13-8°C region a large (up to 100%) light-induced phycobilin fluorescence increase is observed, while only negligible changes occur in the dark. (3) 3-(3,4-Dichlorophenyl)-1,1-dimethyl urea (DCMU) as well as uncouplers inhibit the light stimulation, which hence depends on coupled electron transport.In agreement with previous work (Schreiber, U. (1979) FEBS Lett. 107, 4–9) it is concluded that illumination enhances cold-induced phycobilisome detachment by increasing the net negative charge at the outer surface of the thylakoid membrane. The possible role of a fluid → ordered transition of membrane lipids (Murata, N. and Fork, D.C. (1975) Plant Physiol. 56, 791–796) is discussed. 相似文献
100.