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71.
U Krzych A V Fowler A Miller E E Sercarz 《Journal of immunology (Baltimore, Md. : 1950)》1982,128(4):1529-1534
The proliferative and helper T cell repertoires were compared in the CBA/J mouse for the response to the large protein antigen, tetrameric beta-galactosidase (GZ = 1021 a.a/monomer). The systems assessed the ability of cyanogen bromide (CB) peptides of GZ to: 1) prime for a T cell proliferative response to GZ; or 2) generate T cell help, measured by the production of anti-FITC PFC in the in vitro response to GZ-FITC. Priming for in vitro proliferation was attempted with 11 CB peptides comprising 70% of the GZ molecule. Strong priming was found with five peptides and intermediate priming was found with four other peptides; two peptides were without effect (CB-20 = a.a 767-862, and CB-4 = a.a. 188-202). Despite this indication of generally dispersed recognition of GZ epitopes, only two CB peptides, CB-2 (a.a. 3-92) and CB-10 (a.a. 378-418) were able to induce a T helper cell response. The surprising dearth of helper T cell-inducing epitopes may be peculiar to the limited fluorescein (FITC) substitution on GZ-FITC (17-25 FITC residues per tetramer) or it may reflect the constraints involved in T cell recognition required for T-B collaboration. Also considered was the possibility that the helper T cell repertoire might be distinct from the proliferative repertoire, the latter reflecting DNA synthesis and recruitment by other functional T cell subpopulations. 相似文献
72.
Mechanism of Linolenic Acid-induced Inhibition of Photosynthetic Electron Transport 总被引:3,自引:2,他引:1
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The effect of linolenic acid on photosynthetic electron transport reactions in chloroplasts has been localized at a site on the donor side of photosystem I and at two functionally distinct sites in photosystem II. 相似文献
73.
Two successful cases of replantation of part of an ear are presented; both were done by simple suture. The larger of these replants consisted of a 13 x 43 mm segment of the superior helix and concha. Both were vascularized beofre 48 hours. The greatest problem was venous congestion. In the larger replant we made multiple puncture wounds daily on both sides of the graft with an 18-gauge needle to help relieve this. 相似文献
74.
A. C. Fowler 《Journal of mathematical biology》1981,13(1):23-45
A model of the humoral immune response, proposed by Dibrov, Livshits and Volkenstein (1977b), in which the antibody production by a constant target cell population depends on the antigenic stimulation at earlier times, is considered from an analytic standpoint. A method of approximation based on a consideration of the asymptotic limit of large delay in the antibody response is shown to be applicable, and to give results similar to those obtained numerically by the above authors. The relevance of this type of approximation to other systems exhibiting outbreak phenomena is discussed. 相似文献
75.
Fine, almost single cell, suspensions were produced from both existing suspension cultures containing large cell clumps and
from chopped callus pieces by immobilizing the cells in 4–5 mm diameter calcium alginate beads. The immobilized cells continued
to divide inside the beads and at the bead surface, and after 2–3 weeks' culture, fine cell suspensions were formed as a result
of loss of the surface cells into the medium. After removal of the cell suspensions by filtration, subsequent culture of the
beads in fresh medium resulted in the further production of homogeneous cell suspensions after 1–2 weeks. In this way an almost
continuous supply of fine cell suspensions could be obtained from cultures containing large clumps of cells. The cells produced
by this method remained in this state for at least one culture period, although in some instances repeated subculture resulted
in an increase in the size of cell groups. The technique has been successfully applied to the production of fine cell suspensions
ofCatharanthus roseus, Nicotiana tabacum andDaucus carota. 相似文献
76.
The amino acid sequence in the 8 cyanogen bromide peptides comprising the central segment of beta-galactosidase is presented. This portion of the molecule, about 27% of the protein, contains over 40% of the lysine and tyrosine residues and has a slight excess of basic amino acids. 相似文献
77.
Interactions between spectrin and the inner surface of the human erythrocyte membrane have been implicated in the control of lateral mobility of the integral membrane proteins. We report here that incubation of “leaky” erythrocytes with a water-soluble proteolytic fragment containing the membrane attachment site for spectrin achieves a selective and controlled dissociation of spectrin from the membrane, and increases the rate of lateral mobility of fluorescein isothiocyanate-labeled integral membrane proteins (> 70% of label in band 3 and PAS-1). Mobility of membrane proteins is measured as an increase in the percentage of uniformly fluorescent cells with time after fusion of fluorescent with nonfluorescent erythrocytes by Sendai virus. The cells are permeable to macromolecules since virus-fused erythrocytes lose most of their hemoglobin. The membrane attachment site for spectrin has been solubilized by limited proteolysis of inside-out erythrocyte vesicles and has been purified (V). Bennett, J Biol Chem 253:2292 (1978). This 72,000-dalton fragment binds to spectrin in solution, competitively inhibits association of 32P-spectrin with inside-out vesicles with a Ki of 10?7M, and causes rapid dissociation of 32P-spectrin from vesicles. Both acid-treated 72,000-dalton fragment and the 45,000 dalton-cytoplasmic portion of band 3, which also was isolated from the proteolytic digest, have no effect on spectrin binding, release, or membrane protein mobility. The enhancement of membrane protein lateral mobility by the same polypeptide that inhibits binding of spectrin to inverted vesicles and displaces spectrin from these vesicles provides direct evidence that the interaction of spectrin with protein components in the membrane restricts the lateral mobility of integral membrane proteins in the erythrocyte. 相似文献
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80.
A method is described for the removal of the carbohydrate sequences of glycoproteins, and their covalent attachment to hydrocarbon chains. These synthetic membrane components may then be incorporated into liposome and cell membranes. Pronase-liberated glycopeptides derived from fetuin were linked by a reduced Schiff's base linkage to tetradecyl aldehyde. The resulting glycolipid was incorporated by external addition, into phosphatidylcholine liposomes. Glycolipid transfer to these liposomes rendered them suseptible to agglutination by wheat germ lectin, which binds N-acetylneuraminic acid, the terminal carbohydrate of the high molecular weight fetuin sugar sequence. Sequential removal of the terminal sugars, and subsequent agglutination behaviour towards various lectins, suggests that the carbohydrate sequence had been transfered intact. The glycolipid was incorporated into plant protoplast membranes by incubation with glycolipid-containing liposomes for 2 h at 37°C. These synthetic glycolipids may find a use in the study of carbohydrate-based recognition systems in animal and plant membranes. In addition they may prove useful in the development of cell and membrane tagging and handling techniques, by the insertion of sugar groups not normally present in these membranes. 相似文献