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1.
Bruno Jirgensons 《Journal of Protein Chemistry》1982,1(1):71-84
The factors determining the onset and extent of reconstructive denaturation of proteins were considered by comparing circular dichroism (CD) data of seven proteins and previously published findings. The effects of sodium dodecyl sulfate (SDS) on the conformation of the following proteins were tested: lysozyme, the mitogens fromPhytolacca americana (fractions Pa2 and Pa4), lectin fromWistaria floribunda, ovine lutropin, a Bence Jones protein, and histone H2B. While the helix content of lysozyme was raised by SDS slightly, in the Bence Jones protein andW. floribunda lectin it increased from near zero to about 25–30%. In histone H2B the helix content was raised by SDS even to about 48%. However, no clear indication of helix formation could be observed in the mitogens and lutropin, even at low pH or 2.0–2.5. The tertiary structure of the proteins was perturbed by SDS. It was concluded that the reorganization of secondary structure of the proteins was favored by the following factors: (1) presence of helicogenic amino acid sequences in the protein, (2) availability of positively charged sites of the basic amino acids for interactions with the dodecyl ion, (3) absence of a large surplus of negatively charged sites on the surface of protein, and (4) absence of extensive disulfide cross-linking within the macromolecule. Both hydrophobic and electrostatic interactions occur in reconstructive denaturation, and the newly formed helices are stabilized by hydrophobic shielding by the alkyl chains of the alkyl sulfate. 相似文献
2.
The DNP derivative of sonicate antigens of the H37Ra strain ofMycobacterium tuberculosis (Ra-DNP) is known to induce marked B-cell proliferation. In order to understand whether B-cell proliferation in response
to Ra-DNP was antigen driven or represented a non-specific mitogenic effect of Ra-DNP, the effect of Ra-DNP was compared with
that of lipopolysaccharide a potent B-cell mitogen. Parameters used for comparison were (i) thymidine incorporation, (ii)
viable cell counts, (iii) amount of lg secreted, (iv) isotype profile of Ig released and (v) cell cycling pattern of B-cells
in culture. Overall the effect of Ra-DNP was found to be essentially similar to that of lipopolysaccharide for all parameters
examined. Yet quantitatively, the effect of the former was always relatively poorer. At optimal doses, the effect of Ra-DNP
ranged from 50 to 70% of the lipopolysaccharide effect in different assays. These results suggest that Ra-DNP may have a B-cell
mitogenic effect similar to the effect of lipopolysaccharide, but all B-cells may not respond to Ra-DNP. 相似文献
3.
Robert L. Vender 《In vitro cellular & developmental biology. Animal》1992,28(6):403-409
Summary The development of pulmonary hypertension in a wide variety of human disease states and experimental animal models characterized
by chronic alveolar hypoxia is mediated by two pathologic vascular processes, a) vasoconstriction and b) vasoconstruction
(structural remodeling). The anatomic changes seen within the pulmonary circulation include a) increased deposition of collagen
and elastin in the adventitial layer and b) aberrant pulmonary vascular smooth muscle cell proliferation and maturation in
the medial segments. Despite the demonstrated ability of pharmacologic manipulation in the experimental animal to ameliorate
both the structural and hemodynamic changes, the actual etiologic mechanisms are only beginning to be explored. Using the
cell culture technique of co-cultivation, we have investigated the potential role of bovine pulmonary arterial endothelial
cell-derived factors in mediating abnormal bovine smooth muscle cell growth under conditions of reduced oxygen tension. We
have demonstrated that these cultured endothelial cells exposed in vitro to reduced levels of atmospheric oxygen concentrations
of 5.0% and 2.5% O2 for durations of 24 to 72 h produce and secrete soluble growth factor(s) which stimulate smooth muscle cell proliferation
when compared to cells maintained under standard tissue culture oxygen conditions of 95% room air. This growth-stimulatory
effect required the concomitant presence of serum factors (0.5% fetal bovine serum), was inhibited by heparin, was distinct
from platelet-derived growth factor, and seemed to have a molecular weight greater than 14 000 Da. We conclude that reduced
levels of oxygen tension in vitro can selectively induce pulmonary arterial endothelial cells to release mitogen(s) which
can stimulate vascular smooth muscle replication. Furthermore, we speculate that this in vitro finding may be of importance
as an etiologic mechanism to explain the accelerated smooth muscle cell growth characteristic of hypoxic pulmonary arteriopathy. 相似文献
4.
Human platelet lysate contains growth factor activities for established cell lines derived from various tissues of several species 总被引:3,自引:0,他引:3
Caroline T. Eastment David A. Sirbasku 《In vitro cellular & developmental biology. Plant》1980,16(8):694-705
Summary Factors have been studied from human platelets that promote the growth of a hormone-responsive rat mammary adenocarcinoma
cell line MTW9/PL, the BALB/c 3T3 mouse embryo fibroblasts, and numerous other established cell lines. A wide variety of the
commonly employed cell lines, including lines of human, mouse, monkey, chicken, rat, Chinese hamster, and Syrian hamster origin,
were tested for their growth response to a standard concentration of 200 μg/ml human platelet lysate, and the lysate was found
to contain mitogenic activity for 24 of the 29 different lines assayed. A comparison was made between the platelet growth
activity for the MTW9/PL cells and the well characterized platelet mitogen for the BALB/c 3T3 cells, platelet-derived growth
factor (PDGF). When the platelet lysate was subjected to digestion by highly purified trypsin, the mitogenic activity for
the MTW9/PL cells was not affected whereas that for the BALB/c 3T3 cells was essentially destroyed. Crude PDGF was prepared
by heating the human platelet lysates at 100°C for 2 min followed by clarification, dialysis, lyophilization, and reconstitution.
This PDGF material had no apparent growth activity for MTW9/PL cells, although chromatography of this material on Biogel P-100
revealed a high molecular weight (approximately 40,000 daltons) activity for the BALB/c 3T3 cells (presumably PDGF) and two
growth activities for the MTW9/PL cells, one high molecular weight activity and a second activity of molecular weight less
than 10,000. These studies demonstrated a form of epithelial tumor cell growth activity separable from the 3T3 type PDGF in
crude heated extracts.
This work was supported by American Cancer Society Grant BC-255B and NIH Grant CA 26617. 相似文献
5.
6.
Assessment of biological activity of synthetic fragments of transforming growth factor-alpha 总被引:2,自引:0,他引:2
K Darlak G Franklin P Woost E Sonnenfeld D Twardzik A Spatola G Schultz 《Journal of cellular biochemistry》1988,36(4):341-352
Transforming growth factor-alpha (TGF-alpha) is a single chain polypeptide hormone of 50 amino acids that stimulates growth of some human cancer cells via an autocrine mechanism. The domain(s) of TGF-alpha that bind and activate its receptor have not been reported. Hydrophilicity plots of TGF-alpha indicate three discrete sequences that are theoretically exposed on the hormone's surface and thus potentially able to interact with the TGF-alpha receptor. Fragments of TGF-alpha encompassing these hydrophilic domains were prepared by using solid-phase peptide synthesis (SPPS) techniques and purified by use of high performance liquid chromotography (HPLC). Assessment of biological activity of the TGF-alpha fragments indicated that none of the fragments significantly inhibited binding of EGF to the receptor, stimulated DNA synthesis of cells, inhibited EGF-induced DNA synthesis of cells, stimulated growth of cells in soft agar, or induced phosphorylation of the receptor or p35 protein. These results indicate that the receptor binding domain of TGF-alpha is not totally encompassed by any of the separate fragments tested and probably is formed by multiple separate regions of TGF-alpha. 相似文献
7.
Myelin basic protein (MBP) and two peptides derived from MBP (MBP1–44 and MBP152–167) stimulated Schwann cell (SC) proliferation in a cAMP-mediated process. The two mitogenic regions of MBP did not compete with one another for binding to SC suggesting a distinctive SC receptor for each mitogenic peptide. Neutralizing antibodies to the fibroblast growth factor receptor blocked the mitogenic effect of the myelin-related SC mitogen found in the supernatant of myelin-fed macrophages. The binding of 125I-MBP to Schwann cells was specifically inhibited by basic fibroblast growth factor (bFGF) and conversely the binding of 125I-bFGF was competitively inhibited by MBP. These data suggested that the mitogenic effect of one MBP peptide was mediated by a bFGF receptor. The binding of MBP to ganglioside GM1 and the ability of MBP peptides containing homology to the B subunit of cholera toxin (which binds ganglioside GM1) to compete for the binding of a mitogenic peptide (MBP1–44) to SC, identified ganglioside GM1 as a second SC receptor. Based on these results, we conclude that MBP1–44 and MBP152–167 associate with ganglioside GM1 and the bFGF receptor respectively to stimulate SC mitosis. 相似文献
8.
The effect of ethylenediaminetetraacetate (EDTA) on the mitogen response of porcine lymphocytes and the role of metal ions
in reversal of the inhibitory effect of EDTA were determined. Porcine lymphocyte responses to mitogens were totally suppressed
when serum used to supplement Ca2+, Mg2+-free minimum essential medium (MEM) was dialyzed against saline or saline with 0.2 or 0.60 mM EDTA, but the responses were only partially reduced when the same serum was added to RPMI-1640 medium. The inhibition observed
in MEM could be reversed by adding 1×10−3
M Ca2+ and 1×10−3
M Mg2+ to the dialyzed serum. Serum treated directly with 0.60 mM EDTA completely suppressed blastogenesis in lymphocyte cultures maintained in RPMI-1640 or Ca2+, Mg2+ free MEM. The inhibitory effect of EDTA-treated serum could be completely reversed by adding Zn2+ or a combination of Zn2+ with other cationic ions, or partially reversed by adding Ni2+ or Fe3+. Zn2+ was the most effective ion, in that it was the only ion that, when alone added to the serum, could completely restore lymphocyte
responses to phytohemagglutinin (PHA) or pokeweed mitogen (PWM). 相似文献
9.
Growth and phenotypic characterization of porcine coronary artery smooth muscle cells 总被引:6,自引:0,他引:6
M. C. Lavigne P. W. Ramwell R. Clarke 《In vitro cellular & developmental biology. Animal》1999,35(3):136-143
Summary Vascular smooth muscle cell (VSMC) proliferation significantly contributes to atherosclerotic plaque formation and limits
the success rate of percutaneous transluminal coronary angioplasty. We derived a population of porcine coronary artery SMCs
to characterize VSMC proliferation and phenotype in preparation to study the molecular actions of VSMC mitogens and antiproliferative
agents. Growth assays were designed to minimize the estrogen content in the culture medium, since this steroid hormone significantly
influences VSMC growth and the expression of VSMC mitogens and their receptors. Culture conditions were identified such that
this criterion was achieved while maintaining a significant VSMC growth rate. Cells cultured in serum-free medium, regardless
of growth factor supplements, did not remain adherent to a plastic culture substrate, nor did they proliferate. Dextran-coated
charcoal (DCC)-treated sera, including fetal bovine, calf, and porcine, supported VSMC adhesion, but not growth. Whole fetal
bovine serum (FBS) produced the best proliferative response. A type-I collagen-coated culture surface significantly enhanced
VSMC growth, but only in culture medium containing non-DCC-treated FBS. Flow cytometry analyses confirmed the mitogenic effects
of this substrate. The VSMCs exhibited a morphological change on type-I collagen, but this was not accompanied by a change
in VSMC phenotype. Our data indicate that culture of these porcine coronary artery SMCs in 2.5% FBS plus 10 ng platelet-derived
growth factor-BB per ml in phenol red-free medium on type-I collagen may be the optimal conditions for studying the molecular
aspects of VSMC mitogens and antiproliferative agents. 相似文献
10.
Ruiz-Bravo A Bujalance C Romero F Moreno E Jimenez-Valera M 《FEMS immunology and medical microbiology》2003,39(3):229-233
This study compared the immunomodulating properties of viable and killed Yersinia enterocolitica O9 in BALB/c mice. At 10 days after infection by the intragastric route, ex vivo assays showed a suppression of spleen cell proliferation in response to Salmonella lipopolysaccharide, concanavalin A and heat-killed yersiniae. Mice infected with Y. enterocolitica O9 for 10 days resisted the challenge with a lethal dose of Listeria monocytogenes. In contrast, intravenous administration of heat-killed yersiniae did not modify the ability of spleen cells to proliferate in response to lipopolysaccharide or concanavalin A, and proliferation in response to killed yersiniae was significantly increased. By 3 days after administration of a single dose of heat-killed yersiniae, the resistance of mice to L. monocytogenes challenge was significantly increased. Our findings show profound differences in immunomodulation by viable and heat-killed yersiniae, but suggest that killed yersiniae retain interesting immunomodulating properties. 相似文献