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971.
Liposomes composed of soybean phosphatidylcholine were peroxidized using the reagent sodium hypochlorite or the myeloperoxidase-hydrogen peroxide-Cl- system. Linoleic acid hydroperoxide previously prepared from linoleic acid by means of lipoxidase was incorporated into liposomes. The yield of thiobarbituric acid reactive substances (TBARS) continuously increased with higher amounts of hydroperoxide groups after the initiation of lipid peroxidation by hypochlorous acid producing systems. The accumulation of TBARS was inhibited by scavengers of free radicals such as butylated hydroxytoluene and by the scavengers of hypochlorous acid, taurine and methionine. Lipid peroxidation was also prevented by sodium azide or chloride free medium in the myeloperoxidase-hydrogen peroxide-Cl- system. Here we show for the first time that the reaction of hypochlorous acid with a biologically relevant hydroperoxide yields free radicals able to cause further oxidation of lipid molecules. 相似文献
972.
The potential physiological impact of morphological changes in the active dendritic spines, which are believed to be associated
with altered synaptic efficacy, was investigated in a computer simulation study using the NEURON package [1]. A compartmental
model of a simplified neuron was built, which included 30 complex spines (neck, head, and active zone) and accommodating AMPA-type
synaptic inputs with alpha-function conductances. Hodgkin-Huxley type excitable membranes were inserted into the spine heads.
It was shown that arranging spines in dense clusters, as opposed to a uniformly random spine distribution, has a negligible
effect on the synaptic signal transfer (other model conditions, including synaptic input and spine density, remained unchanged).
However, if a proportion (e.g., 3–20%) of the spines partly fuse with their neighbors forming branched spines, this could
increase dramatically the cell response to the unchanged synaptic input. Results of this pilot study provide the basis for
a more detailed investigation of the relationship between the spine arrangement and synaptic function, considering dual-component
synaptic currents and mechanisms controlling ion fluxes in the dendritic compartments. 相似文献
973.
J. Kelley Bentley Peter W. Reed 《Biochimica et Biophysica Acta (BBA)/General Subjects》1981,678(2):238-244
All of the common cytochalasins activate superoxide anion release and exocytosis of β-N-acetylglucosaminidase and lysozyme from guinea-pig polymorphonuclear leukocytes (neutrophils) incubated in a buffered sucrose medium. Half-maximal activation of both processes is produced by approx. 2 μM cytochalasin A, C >μM cytochalasin B ? 4–5 μM cytochalasin D, E. While maximal rates of O2? release and extents of exocytosis require extracellular calcium (1–2 mM), replacing sucrose with monovalent cation chlorides is inhibitory to neutrophil activation by cytochalasins. Na+, K+ or choline inhibited either cytochalasin B- or E-stimulated O2? production with IC50 values of 5–10 mM and inhibition occurs whether Cl?, NO3? or SCN? is the anion added with Na+ or K+. Release of β-N-acetylglucosaminidase in control or cytochalasin B-stimulated cells is inhibited by NaCl (IC50 ≈ 10 mM), while cytochalasin E-stimulated exocytosis is reduced less and K+ or choline chloride are ineffective in inhibiting either cytochalasin B- or E-stimulated exocytosis. Release of β-glucuronidase, myeloperoxidase or acid phosphatase from neutrophils incubated in buffered sucrose is not stimulated by cytochalasin B. Stimulation of either O2? or β-N-acetylglucosaminidase release by low concentrations of cytochalasin A is followed by inhibition of each at higher concentrations. It appears that all cytochalasins can activate both NAD(P)H oxidase and selective degranulation of neutrophils incubated in salt-restricted media and that differential inhibition of these two processes by monovalent cations and/or anions is produced at some step(s) subsequent to cytochalasin interaction with the cell. 相似文献
974.
975.
Structural studies of a human gamma 3 myeloma protein (Jir) bearing the allotypic marker Gm(st) 总被引:2,自引:0,他引:2
H Matsumoto S Ito T Miyazaki T Ohta 《Journal of immunology (Baltimore, Md. : 1950)》1983,131(4):1865-1870
The authors established the amino acid substitutions determining G3m(s) and G3m(t) specificities, which characterize Mongoloid populations, by sequence analysis of the Fc region of a myeloma protein (Jir). By comparing the amino acid sequences of the IgG3 (Jir) and the other IgG subclasses analyzed to date, it was found that G3m(s) was an isoallotype specified by an amino acid substitution at position 435; i.e., whereas the subclasses IgG1, IgG2, and IgG4 had histidine in common, G3m(s-) had arginine in this position. This was also confirmed by the observation that the Fc fragment in question bound to protein A. It was also established that the amino acid at position 379 of G3m(t-) IgG3 and the other subclasses was valine, whereas methionine in this position was specific for G3m(t+). In addition, the amino acids at position 339 of G3m(u-) IgG3 Jir was threonine, and at position 296 of G3m(g-) IgG3 Jir was tyrosine. These findings are not in accord with the hitherto postulated relations of alanine and phenylalanine to G3m(u-) and G3m(g-), respectively. Finally, this study showed that a large number of substitutions occurred at positions 384 through 389, which suggests that many specificities of the G3m(b) group occur on IgG3 proteins. 相似文献
976.
977.
978.
Holly A. Ingraham Mehran Goulian 《Biochemical and biophysical research communications》1982,109(3):746-752
Deoxyuridine triphosphatase has been purified from cultured human lymphoid cells in high yield and stable form by a relatively simple procedure. The properties differed somewhat from those reported previously, e.g. apparent Km, molecular weight, and effects of divalent metals. No other naturally occurring dNTP or NTP serves as substrate, however, the enzyme may be an important site of interaction with intracellular derivatives of analogues of dUrd. It is shown here that deoxyuridine triphosphatase acts on araUTP, 6-azadUTP, 2′-FdUTP, and 2′,3′-dideoxyUTP, but the enzyme has no effect on 5-C1dUTP, 5-BrdUTP, 5-HgdUTP and dUrd-5′[α-thio]triphosphate. For the preparation of one of the analogues, the enzyme, trans-N-deoxyribosylase, from Lactobacillus, was used to prepare the deoxynucleoside from the base, a procedure that may have general usefulness. 相似文献
979.
980.
R. J. Kemble 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1987,73(3):364-370
Summary An assay is described whereby Eco RI restriction fragment length polymorphisms of mitochondrial and chloroplast DNAs can definitively identify cytoplasms of interest in Brassica crop development. Restrictable mitochondrial and chloroplast DNA is extracted from as little as 2–3 g and 0.5 g leaf tissue, respectively, and the donor plants are able to continue to develop in a normal manner. An unknown cytoplasm can be identified in three days, which is a considerable saving in time and labor compared to the several years required by traditional methods. The assay is very inexpensive and should be established as a routine procedure in laboratories involved in sexual or somatic Brassica hybrid production. 相似文献