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841.
842.
P Marynen F Van Leuven J J Cassiman H Van den Berghe 《Biochimica et biophysica acta》1984,799(2):187-193
alpha 2-Macroglobulin complexed to proteinases activated during clotting of cystic fibrosis and control sera was quantitated with the complex-specific monoclonal antibody F2B2 . Similar amounts of alpha 2-macroglobulin complexes (between 40 and 90 micrograms/ml) were generated in cystic fibrosis and control sera. Endocytosis of the complexes by normal human fibroblasts was compared to the amount of complexes detected by the F2B2 -radioimmunoassay. Normal uptake was observed with 13 out of 14 cystic fibrosis sera. One cystic fibrosis serum showed strongly reduced endocytosis of the complexes. Complexes isolated from this serum on immobilized F2B2 failed to inhibit binding of purified alpha 2-macroglobulin-trypsin to its receptor, demonstrating deficient receptor-binding of these complexes. The low uptake complexes could not be distinguished from complexes isolated from control or other cystic fibrosis sera by isoelectric focusing, rate electrophoresis or SDS-polyacrylamide gel electrophoresis. 相似文献
843.
Rat pups, 3 weeks old, were injected i.p. with combinations of 3H2O and either [3-14C]acetoacetate or [14C]glucose. 3H/14C incorporation ratios were measured in lipid fractions of homogenates and myelin prepared from whole brain and spinal cord. Spinal cord synthesized at least twice as much fatty acids and 3-fold more sterols than whole brain. Both tissues used acetoacetate preferentially for sterol synthesis, whereas label from [14C]glucose was distributed between fatty acids and sterols in the same way as 3H from 3H2O. The relative contributions of acetoacetate to sterol synthesis in whole tissue and in the purified myelin fraction were about the same, both for the cerebrum and for the spinal cord. 相似文献
844.
Determination of nonspecific lipid transfer protein in rat tissues and Morris hepatomas by enzyme immunoassay 总被引:2,自引:0,他引:2
T Teerlink T P Van der Krift G P van Heusden K W Wirtz 《Biochimica et biophysica acta》1984,793(2):251-259
Rat tissues contain a nonspecific transfer protein which in vitro mediates the transfer of diacylphospholipids as well as cholesterol between membranes. This protein appears identical to sterol carrier protein. A specific enzyme immunoassay for this protein was developed using antibodies raised in rabbits, against a homogeneous protein from rat liver. This assay was based on the very high affinity of the nonspecific lipid transfer protein for polyvinyl surfaces. A reproducible adsorption was achieved by presenting the protein to the surface in the presence of a large excess of bovine serum albumin. The adsorbed protein was detected with specific immunoglobulin (IgG) isolated by antigen-linked affinity chromatography and a goat anti-rabbit IgG-enzyme conjugate. Adsorption was proportional to the amount of protein present, giving rise to a linear standard curve. The enzyme immunoassay measured transfer protein levels in the range 0.2-2 ng. The highest concentrations of transfer protein were found in liver and intestinal mucosa. Levels in other tissues including brain, lung, kidney, spleen, heart, adrenals, ovary and testis were 5-10-fold lower than in liver. In the fast-growing Morris hepatoma 7777 the concentration of nonspecific lipid transfer protein was approximately one-tenth of that measured in the host liver, whereas a reduction of 65% was observed in the slow-growing Morris hepatomas 7787 and 9633. Subcellular distribution studies showed that approx. 70% of the transfer protein was present in the soluble supernatant fraction. 相似文献
845.
DNA circles with cruciforms from Isospora (Toxoplasma) gondii 总被引:4,自引:0,他引:4
P Borst J P Overdulve P J Weijers F Fase-Fowler M Van den Berg 《Biochimica et biophysica acta》1984,781(1-2):100-111
We have isolated a closed circular duplex DNA fraction from the unicellular parasite Isospora (Toxoplasma) gondii and examined the purified DNA by electron microscopy. A major part of this circular DNA consists of 12-micron circles containing a cruciform with 0.5-micron tails. We also found 23-micron circles with the properties expected of head-to-tail dimers of the 12-micron circles. Some of these dimers have two cruciforms with 0.4-micron tails, some have one cruciform with 0.8-micron tails. When ethidium bromide was diffused into the DNA solution, circles with tails were replaced by twisted circles without tails. Direct mixing of the DNA with high ethidium bromide concentrations (5 micrograms/ml) gave rise to highly twisted circles with tails. This proves that the tailed circles are covalently continuous and indicates that ethidium bromide blocks branch migration. The 0.5-micron tails are part of a 1.7-micron palindrome, which was visualized by spreading denatured DNA under snap-back conditions. We argue that the cruciform is not present in vivo and that the 12-micron circles may represent the mitochondrial DNA of Toxoplasma. 相似文献
846.
Gemma A.J. Kuijpers Irene G.P. Van Nooy Jan Joep H.H.M. De Pont Sjoerd L. Bonting 《生物化学与生物物理学报:生物膜》1984,774(2):269-276
The isolated rabbit pancreas secretes a fluid containing chloride and bicarbonate in about equal concentrations. Replacement of bicarbonate by acetate, phosphate or isethionate, replacement of Na+ by Li+ and addition of ouabain to the bathing medium of the pancreas inhibit the secretion of fluid, chloride and bicarbonate in a similar fashion and by maximally 100%. Replacement of chloride by isethionate inhibits fluid secretion by maximally 50%, chloride secretion by 90% and bicarbonate secretion by 20%. It is concluded that fluid secretion is based on a Na+-gradient-dependent bicarbonate influx or proton efflux in the ductular cell, and that the secretion of chloride is secondary to that of bicarbonate. 相似文献
847.
Fons A.L.J. Peters Ron H.M. Van Der Pal Robert L.A. Peters Wim J. Vredenberg Ruud Kraayenhof 《BBA》1984,766(1):169-178
This work aimed at the resolution of the multi-component electric potential changes induced by single-turnover flash illumination of Photosystem-I-enriched subchloroplast vesicles. If supplemented with ferredoxin and under carefully adjusted redox poising, these vesicles show a pronounced slow-rising and -decaying electric potential component, as monitored by endogenous and exogenous field-sensitive probes, carotenoids and oxonol VI, respectively. The fast and slow potential components can be easily discriminated without the need for computer-assisted deconvolution after selective presaturation of the slow component by preillumination or a transmembrane ΔpH, after selective suppression of the slow component by low valinomycin or uncoupler concentrations or in the absence of ferredoxin. The slow electric potential component, as compared to the fast one, is relatively sensitive to low concentrations of ionophores and uncouplers, detergent, ageing and lower temperatures (4–12°C), is associated with electrogenic proton displacements and is interpreted to respond to a field that is more located on the membrane-bulk interface. Temperature effects show transition temperatures around 20°C for both the rise and decay of the slow potential component. The results provide further evidence that the carotenoids and oxonol VI sense the same (slow) electric field, but may be differently located in the thylakoid membrane. 相似文献
848.
Fons A.L.J. Peters Guus A.B. Smit Arie T.M. Van Diepen Klaas Krab Ruud Kraayenhof 《BBA》1984,766(1):179-187
Cytochrome redox changes and electric potential generation are kinetically compared during cyclic electron transfer in Photosystem-I-enriched and Photosystem-II-depleted subchloroplast vesicles (i.e., stroma lamellae membrane vesicles) supplemented with ferredoxin using a suitable electron donating system. In response to a single-turnover flash, the sequence of events is: (1) fast reduction of cytochrome b-563 (t0.5 ≈ 0.5 ms) (2) oxidation of cytochrome c-554 (t0.5 ≈ 2 ms), (3) slower reduction of cytochrome b-563 (t0.5 ≈ 4 ms), (4) generation of the ‘slow’ electric potential component (t0.5 ≈ 15–20 ms), (5) re-reduction of cytochrome c-554 (t0.5 ≈ 30 ms) and (6) reoxidation of cytochrome b-563t0.5 ≈ 90 ms). Per flash two cytochrome b-563 species turn over for one cytochrome c-554. These b-563 cytochromes are reduced with different kinetics via different pathways. The fast reductive pathway proceeds probably via ferredoxin, is insensitive to DNP-INT, DBMIB and HQNO and is independent on the dark redox state of the electron transfer chain. In contrast, the slow reductive pathway is sensitive to DNP-INT and DBMIB, is strongly delayed at suboptimal redox poising (i.e., low ratio) and is possibly coupled to the reduction of cytochrome c-554. Each reductive pathway seems obligatory for the generation of about 50% of the slow electric potential component. Also cytochrome c-559LP (LP, low potential) is involved in Photosystem-I-associated cyclic electron flow, but its flash-induced turnover is only observed at low preestablished electron pressure on the electron-transfer chain. Data suggest that cyclic electron flow around Photosystem I only proceeds if cytochrome b-559LP is in the reduced state before the flash, and a tentative model is presented for electron transfer through the cyclic system. 相似文献
849.
A.C. Van Bochove T. Swarthoff H. Kingma R.M. Hof R. Van Grondelle L.N.M. Duysens J. Amesz 《BBA》1984,764(3):343-346
A reaction-center pigment-protein complex of the green bacterium Prosthecochloris aestuarii was studied by means of nanosecond-flash spectroscopy. In this complex electron transfer between the primary and secondary acceptor is blocked. The spectra and kinetics of the absorption changes induced by a short flash indicated the formation of the radical pair P-840+I?, which decayed in 20–35 ns, mainly to the triplet state of the primary electron donor P-840. The absorption difference spectrum of the initial absorption change indicated that the primary acceptor I is either bacteriopheophytin c or another pigment with absorption maximum at 665 nm. 相似文献
850.
The conditions used in some immunoblot procedures can fail to detect calmodulin, S100 proteins, and other proteins with similar physical properties. We describe here some of the basis of this difficulty, and provide an immunoblot protocol that allows the rapid and reproducible detection of calmodulin and S100 beta in crude biological samples. These proteins are rapidly transferred from sodium dodecyl sulfate-polyacrylamide gels to membrane matrices, and retention on the matrix is enhanced by a glutaraldehyde fixation step. Either nitrocellulose or a positively charged membrane filter (ZetaProbe) can be used as the immobilizing matrix. By combining microslab gel electrophoresis, 30 min electrophoretic transfer, and glutaraldehyde fixation of nitrocellulose paper, an immunoblot analysis can be done in an 8-hr day. 相似文献