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1.
Proteolytically modified human beta 2-microglobulin augments the specific cytotoxic activity in murine mixed lymphocyte culture 总被引:1,自引:0,他引:1
A proteolytically modified form of beta 2-microglobulin (beta 2-m) present in the serum of patients suffering from autoimmune, immunodeficient diseases and cancer has been reported in the literature. In the present study we show that human beta 2-m as well as the proteolytically modified human form (M-beta 2-m) bind to murine lymphocytes expressing H-2 class I antigens; M-beta 2-m, when added at day 0 and 1 of culture in nanomolar concentrations to a one-way murine allogeneic mixed lymphocyte culture (MLC) augments the generation of specific cytotoxic T lymphocytes; M-beta 2-m increases the endogenous production of interleukin 2 in the MLC culture; monoclonal antibody which reacts with both the native beta 2-m and M-beta 2-m molecule blocks the augmentation of cytotoxic T lymphocyte production induced by M-beta 2-m; murine as well as human MLC responder cells can proteolytically modify native human beta 2-m; and the modifying activity of murine MLC responder cells was blocked in an intermediary step by an alloantibody, which reacts specifically with murine major histocompatibility complex, class I-associated beta 2-m. These findings suggest that the modification process is preceded by an association of human beta 2-m with the cell surface of the responder cells. Our data indicate that the modification of beta 2-m might reflect early events in allospecific responder cell activation. 相似文献
2.
A modified form of beta-2-microglobulin (beta-2-m) has previously been described to be present in serum from patients suffering from autoimmune diseases, acquired immune deficiency syndrome and small-cell lung cancer [Plesner, T. and Wiik, A. (1979) Scand. J. Immunol. 9, 247-254; Bhalla et al. (1985) Clin. Chem. 31, 1411-1412; Nissen et al. (1984) Clin. Chim. Acta 141, 41-50]. In the present study we describe the purification and characterization of this modified human serum beta-2-m from patients with small-cell lung cancer. Purified urinary beta-2-m was added to the serum samples incubated at 20 degrees C for five days to obtain a higher yield of modified beta-2-m (m-beta-2-m). m-beta-2-m was then purified from serum by gel filtration followed by chromatofocusing of the fractions containing beta-2-m. m-beta-2-m was found to have an apparent molecular mass of 15 kDa and a pI of 5.3 when analyzed by sodium dodecyl sulphate/polyacrylamide gel electrophoresis and analytical isoelectric focusing respectively. Amino acid analysis of m-beta-2-m revealed that the protein is missing one lysine residue compared to the composition deduced from the cDNA sequence of beta-2-m. Amino acid sequence analysis showed that m-beta-2-m consists of two polypeptide chains produced by a proteolytic cleavage of beta-2-m in the disulphide loop. After reduction and alkylation of m-beta-2-m the two chains were separated by reverse-phase high-pressure liquid chromatography. By amino acid sequencing, amino acid residues 1-56 and 59-99 were identified in the A and B chains respectively. By comparison of the amino acid composition of m-beta-2-m with the known sequence of beta-2-m it was possible to deduce the existence of a Ser-57 in the A chain. Thus proteolytic cleavage of beta-2-m in the intrachain disulphide loop releases the amino acid Lys-58, which results in a modified form of beta-2-m with a molecular mass of 11,620 Da as determined by amino acid analysis. 相似文献
3.
Dose responses of gibberellins 总被引:4,自引:0,他引:4
Per Nissen 《Physiologia plantarum》1988,72(1):197-203
To determine the response type, published data for the most widely used bioassays for gibberellins have been analyzed by means of a computer program for estimating sensitivity parameters, or by interpolation. The dose response data are almost uniformly subsensitive, i. e. more than an 81-fold increase in external gibberellin concentration is required for a change from 10 to 90% of maximal response (S90 /S10 ). Data for the interaction of gibberellins with artificial membranes are, in contrast, markedly ultrasensitive (S90 /S10 ± 10). This difference further strengthens the view that lipid structures do not function as receptors for gibberellins. Most of the subsensitive dose responses for gibberellins can be quite precisely represented by cooperative isotherms. However, available data are insufficiently detailed for an unequivocal choice among cooperative, multiphasic or more complex kinetics. 相似文献
4.
The chemically induced barley (Hordeum vulgare L.) mutation, agr, was found to be a simple recessive trait resulting in agravitropic roots and normal gravitropic shoots. The total seedling root growth was similar for mutant and wild-type roots, although the mutant had fewer roots per seed and greater elongation per root. Although the concentration of exogenous indole-3-acetic acid (IAA) required to reduce root growth by 50% (GR50) was 12 times greater for the agravitropic mutant, agravitropic and gravitropic roots were equally sensitive to exogenous applications of 2,4-dichlorophenoxyacetic acid (2,4-D) and naphthalene acetic acid (NAA). Root IAA contents, determined by high-pressure liquid chromatography (HPLC), were not different for gravitropes and agravitropes. The greater root elongation rates, lack of sensitivity to exogenous IAA, and normal endogenous IAA levels indicate that auxin-controlled growth regulation may be altered in the mutant. 相似文献
5.
J. A. Magnuson E. R. Pandolfino G. R. Munske A. E. Namen M. S. Nissen 《Journal of biosciences》1983,5(1):83-91
Two lectins, a tetramer designated LBL4 and an octamer LBL8 designated have been purified from the lima beanPhaseolus lunatus. The tetramer appears to be nonmitogenic for human lymphocytes and is a weak mitogen for bovine cells. The octamer and a chemically cross-linked form of the tetramer are good mitogens. The lima bean lectin binds to only certain sub-populations of human lymphocytes. The primary class which does not bind appears to be a sub-population ofT-lymphocytes. Comparisons of cell binding with other lectins which bind to 2-acetamido-2-deoxy-D-galactose have been carried out. Quantitative analysis of the binding to human erythrocytes is co-operative but binding to lymphocytes is non-co-operative. These results show that there may not be a direct correlation between mitogenic stimulation and cooperative binding to membrane receptors. 相似文献
6.
Cysteamine (2-aminoethanethiol) inhibited cell division in synchronously dividing cultures of Euglena gracilis at relatively low concentrations (0.005 M), Cystamine (2,2′-dithiobis(ethylamine). however, was only partially inhibitory at high concentrations (0.1 M). This differential inhibition may reflect certain unique features of nuclear division in euglenoid flagellates. 相似文献
7.
The role of indole-3-butyric acid (IBA) in adventitious root formation was studied by analyzing the uptake and subsequent metabolism of IBA in shoots of M.26 apple (Malus pumila Mill.) rootstock grown in vitro. Roots were induced by exposing shoots to 4 M IBA and [3H]IBA for 5 days in the dark and then transferring them to plant growth regulator (PGR)-free medium in the light until roots formed. Approximately 50% of the total radioactivity applied was taken up from the agar medium by the shoots during the 5-day incubation period in IBA. Indole-3-butyric acid metabolism was studied by extraction and high-performance liquid chromatographic (HPLC) separation of [3H]IBA and metabolites from the basal sections of treated shoots. The major [3H]IBA metabolite co-eluted with authentic [14C]indole-3-acetic acid (IAA) suggesting that IBA was converted to IAA in the shoots. The proportion of newly synthesized IAA present as conjugates was higher at the end of the 5-day IBA treatment period than after 13 days in PGR-free medium. There appeared to be no conjugation of IBA at any time. 相似文献
8.
The refined crystal structure of the ternary complex of yeast Phe-tRNAPhe, Thermus aquaticus elongation factor EF-Tu and the non-hydrolyzable GTP analog, GDPNP, revelas many details of the EF-Tu recognition of aminoacylated tRNA (aa-tRNA). EF-Tu-GTP recognizes the aminoacyl bond and one side of the backbone fold of the acceptor helix and has a high affinity for all ordinary elongator aa-tRNAs by binding to this aa-tRNA motif. Yet, the binding of deacylated tRNA, initiator tRNA, and selenocysteine-specific tRNA (tRNASec) is effectively discriminated against. Subtle rearrangements of the binding pocket may occur to optimize the fit to any side chain of the aminoacyl group and interactions with EF-Tu stabilize the 3′-aminoacyl isomer of aa-tRNA. A general complementarity is observed in the location of the binding sites in tRNA for synthetases and for EF-Tu. The complex formation is highly specific for the GTP-bound conformation of EF-Tu, which can explain the effects of various mutants. 相似文献
9.
Inhibition by 2,4-D of somatic embryogenesis in carrot as explored by its reversal by difluoromethylornithine 总被引:1,自引:0,他引:1
The development of somatic embryos is, in many plants, inhibited by 2,4-dichlorophenoxyacetic acid (2,4-D) and other auxins. The finding that difluoromethylornithine (DFMO) can counteract this inhibition has been used to test some of the hypotheses for the mechanism of inhibition.
Inhibition of somatic embryogenesis in carrot ( Daucus carota L.) by exogenous ethylene (from ethephon), antioxidants (ascorbic acid and glutathione), ethanol/acetaldehyde and abscisic acid was not counteracted by DFMO, indicating that the inhibitory effect of 2,4-D is not manifest through the formation of these compounds. Embryogenesis was abolished by micromolar concentrations of the polar auxin transport inhibitors 2, 3, 5-triiodobenzoic acid (TIBA), N-1-naphthylphthalamic acid (NPA) and 9-hydroxyfluorene-9-carboxylic acid (HFCA). This inhibition was counteracted to a considerable extent by DFMO. Inhibition by relatively high concentrations of the antiauxin 2-( p -chlorophenoxy)-isobutyric acid (CPIB), which does not affect polar auxin transport, was in contrast not counteracted by DFMO. These findings indicate that exogenous auxins may inhibit embryogenesis by interfering with the ability of postglobular embryos to set up internal auxin gradients necessary for polarized growth. 相似文献
Inhibition of somatic embryogenesis in carrot ( Daucus carota L.) by exogenous ethylene (from ethephon), antioxidants (ascorbic acid and glutathione), ethanol/acetaldehyde and abscisic acid was not counteracted by DFMO, indicating that the inhibitory effect of 2,4-D is not manifest through the formation of these compounds. Embryogenesis was abolished by micromolar concentrations of the polar auxin transport inhibitors 2, 3, 5-triiodobenzoic acid (TIBA), N-1-naphthylphthalamic acid (NPA) and 9-hydroxyfluorene-9-carboxylic acid (HFCA). This inhibition was counteracted to a considerable extent by DFMO. Inhibition by relatively high concentrations of the antiauxin 2-( p -chlorophenoxy)-isobutyric acid (CPIB), which does not affect polar auxin transport, was in contrast not counteracted by DFMO. These findings indicate that exogenous auxins may inhibit embryogenesis by interfering with the ability of postglobular embryos to set up internal auxin gradients necessary for polarized growth. 相似文献
10.
Sinlan Poo Ana Karen Candia Kristina L. Cohen Francesca T. Erickson Sara A. Mason Bradley D. Nissen Adair F. McNear Jonathon J. Reinig Joseph S. Sherrock Ashley R. Aguiluz Letitia L. Jacques Hanna E. R. Jenkins Anne Devan-Song 《Biotropica》2023,55(4):806-815
Environmentally cued hatching has been well-documented in amphibians in response to a wide range of abiotic and biotic factors. The hatching of terrestrial amphibian eggs in response to flooding may be basal within the group, but amphibian lineages in tropical Asia and sub-Saharan Africa have not received as much attention as their Neotropical counterparts. We investigated submergence-induced hatching in Feihyla hansenae, a Rhacophorid tree frog with terrestrial eggs. We quantified natural rates of clutch submergence at our study site in Thailand. Using submergence experiments, we found that embryos are capable of hatching early to escape flooding, and that failure to hatch results in mortality. Among the embryos that were able to hatch early, only the earliest, youngest hatchlings experienced a trade-off in body size that persisted for 6 days, while later, older hatchlings were not significantly smaller than spontaneous hatchlings under control conditions. By incorporating our natural and experimental data into Monte Carlo methods to simulate and compare survival probabilities with and without hatching plasticity, we found an overall 3.1% increase in submergence survival due to hatching plasticity. Our findings support the idea that flooding-induced hatching is widespread across amphibians with terrestrial eggs and highlight the importance of researching understudied tropical regions. As climate change is projected to affect rainfall patterns, the ability of embryos to escape abiotic egg-stage threats may be an indicator of species' ability to flexibly navigate a changing environment. 相似文献