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1.
Michael S. Lipkowitz Edgar Leal-Pinto B. Eleazar Cohen Ruth G. Abramson 《Glycoconjugate journal》2002,19(7-9):491-498
UAT, also designated galectin 9, is a multifunctional protein that can function as a urate channel/transporter, a regulator of thymocyte-epithelial cell interactions, a tumor antigen, an eosinophil chemotactic factor, and a mediator of apoptosis. We review the evidence that UAT is a transmembrane protein that transports urate, describe our molecular model for this protein, and discuss the evidence from epitope tag and lipid bilayer studies that support this model of the transporter. The properties of recombinant UAT are compared with those of urate transport into membrane vesicles derived from proximal tubule cells in rat kidney cortex. In addition, we review channel functions predicted by our molecular model that resulted in the novel finding that the urate channel activity is regulated by sugars and adenosine. Finally, the presence and possible functions of at least 4 isoforms of UAT and a closely related gene hUAT2 are discussed. Published in 2004. 相似文献
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Motor neurons isolated from 6-day-old embryonic chick spinal cords require muscle extract for survival in culture; however, it was found, that some motor neurons, identified by retrograde labeling with rhodamine, will survive in mixed spinal cell cultures in the absence of the extract. The motor neuron survival-promoting activity produced by spinal cells is soluble and differs from the factor present in muscle extract, the two activities acting in a synergistic manner: the spinal cell activity potentiated that of muscle to decrease its ED50 by an order of magnitude, the motor neuronal survival (30%) seen in the presence of both factors being more than the sum of their individual activities. This synergism was shown to be restricted to the action of the spinal cell factor on motor neurons, no effect of the factor being noted with sympathetic neurons. As a series of defined growth and survival factors present in the central nervous system (nerve growth factor, brain-derived neurotrophic factor, acidic and basic fibroblast growth factors) had no effect on motor neuron survival, we conclude that the molecule responsible for the motor neuron survival-promoting activity of the spinal cells is a previously undefined factor. 相似文献
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The cellular interactions of laminin fragments. Cell adhesion correlates with two fragment-specific high affinity binding sites 总被引:26,自引:0,他引:26
M Aumailley V Nurcombe D Edgar M Paulsson R Timpl 《The Journal of biological chemistry》1987,262(24):11532-11538
The molecular interactions of laminin with several tumor cell lines and skin fibroblasts were investigated by radioligand binding studies and cell attachment assays using laminin, the laminin-nidogen complex, and laminin fragments as substrates and also domain-specific antibodies as inhibitors of cell attachment. The majority of cells showed a dual binding pattern for fragments 1 and 8 which originate from short-arm or long-arm structures of laminin, respectively. Both of these fragments in solution bind to suspended cells with high affinity (KD = 1-10 nM), with the receptor numbers for each fragment depending on the cell type. Competition studies and independent variation of receptor numbers demonstrated that the cell-binding structures on each fragment are different, implicating the existence of two distinct cellular receptors for laminin. The ability of these fragments to act as substrates for cell adhesion correlated with the presence of high affinity binding sites on the cells. However, only antibodies to fragment 8 were able to block cell adhesion to laminin, despite the presence of binding sites for fragment 1. A few cells had very low numbers of high affinity receptors for either fragment 1 or 8. The latter cell type was used to demonstrate that complex formation between laminin and nidogen, which binds to fragment 1 structures, reduces the potential of laminin for cell binding. 相似文献
6.
Bruce F. Cooper Johanna K. Krontiris-Litowitz Edgar T. Walters 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1989,159(2):225-235
1. Preliminary, general chemical characteristics of substances in artificial sea water (ASW) washed through stimulated body wall (SBW) and in hemolymph taken from noxiously stimulated animals (SHL) were consistent with those of classical neurotransmitters, amino acids, and small- to medium-sized peptides. 2. 5-Hydroxytryptamine (5HT) and acetylcholine (ACh), unlike SBW and SHL, caused relaxation when perfused into isolated body wall. FMRFamide produced a biphasic response--brief contraction followed by prolonged relaxation. 3. Small cardioactive peptide (SCPB) caused body wall contractions similar to those produced by SBW and SHL, except that SCPB contractions displayed more desensitization and were completely blocked by 30 mM CoCl2. SCPB and SBW contractions were synergistic. 4. Dopamine caused persistent body wall contractions similar to those of SBW and SHL. Dopamine contractions were reduced but not blocked by 30 mM CoCl2. Unlike SBW activity, dopamine activity was reduced by alkalinization. 5. Glutamate and taurine produced strong but usually short-lasting body wall contractions. Adenosine, octopamine, arginine vasotocin, and cholecystokinin (CCK-8) caused weak or variable contractions. Met-enkephalin and somatostatin caused no obvious body wall responses. 6. When superfused over the fully sheathed abdominal ganglion, FMRFamide, met-enkephalin, glutamate, aspartate, and taurine reduced the magnitude of the gill-withdrawal reflex elicited by siphon nerve stimulation. 7. Taken together with earlier results, these data suggest a preliminary framework for trauma signal pathways. It is proposed that stress hormones (perhaps including FMRFamide, SCPs, 5HT, and dopamine) are released into hemolymph from neuroendocrine cells. Effective amounts of active intracellular solutes such as amino acids may also be released by extensive cellular rupture. Various humoral signals produce slow effects that contribute to hemostasis, balling up, increased cardiac output, and reflex suppression. 相似文献
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Summary CommercialViscum album extract Helixor-M contains a dialysable oligosaccharide (HM-BP) that activates natural killer (NK) cytotoxicity against K562 tumour cells when preincubated with human peripheral blood mononuclear cells (PBMC) for 72 h. The activated effector cells were exclusively found in the monocyte/macrophage subpopulation. However, when peripheral non-adherent cells (PNAC) were preincubated with HM-BP for 72 h the NK cytotoxicity of CD56+CD3– NK cells was activated. This discrepancy was found to be due to the release of prostaglandin E2 from activated monocytes/macrophages, which blocked activation of the cytotoxicity of NK cells. Analysis of the supernatant culture medium after 72 h preincubation demonstrated that HM-BP induced release of interferon (IFN) from T cells (preferentially from CD3+CD4+ cells) and of tumour necrosis factor (TNF) from monocytes/macrophages. Release of IFN was the crucial step for activation of NK cytotoxicity since enhancement of NK cytotoxicity during pretreatment of PBMC or PNAC with HM-BP was completely blocked in the presence of anti-IFN antibodies. Anti-interleukin-2, anti-TNF or anti-IFN antibodies had no effect on the HM-BP-induced enhancement of NK cytotoxicity. The activation of the NK cytotoxicity of nonadherent cells by interleukin-2 treatment was found to be synergistic to the enhancement of NK cytotoxicity by treatment with HM-BP. 相似文献
8.
Jose L. Vega Vicki L. Holmberg Edgar C. Clausen James L. Gaddy 《Archives of microbiology》1988,151(1):65-70
Intrinsic growth and substrate uptake parameters were obtained for Peptostreptococcus productus, strain U-1, using carbon monoxide as the limiting substrate. A modified Monod model with substrate inhibition was used for modeling. In addition, a product yield of 0.25 mol acetate/mol CO and a cell yield of 0.034 g cells/g CO were obtained. While CO was found to be the primary substrate, P. productus is able to produce acetate from CO2 and H2, although this substrate could not sustain growth. Yeast extract was found to also be a growth substrate. A yield of 0.017 g cell/g yeast extract and a product yield of 0.14 g acetate/g yeast extract were obtained. In the presence of acetate, the maximum specific CO uptake rate was increased by 40% compared to the maximum without acetate present. Cell replication was inhibited at acetate concentrations of 30 g/l. Methionine was found to be an essential nutrient for growth and CO uptake by P. productus. A minimum amount of a complex medium such as yeast extract (0.01%) is, however, required. 相似文献
9.
Laminin increases both levels and activity of tyrosine hydroxylase in calf adrenal chromaffin cells 总被引:8,自引:5,他引:3
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We have investigated the effects of substrate-bound laminin on levels of enzymes of the catecholamine biosynthetic pathway in primary cultures of calf adrenal chromaffin cells. Laminin increases the levels of the enzymes tyrosine hydroxylase, dopamine-beta-hydroxylase, and phenylethanolamine-N-methyl-transferase. This effect is selective, in that levels of other enzymes (lactate dehydrogenase, aromatic amino acid decarboxylase, and acetylcholinesterase) are not increased. The effect of laminin can be blocked by antibodies directed against a fragment of the heparin-binding domain of the molecule, whereas antibodies directed against other fragments do not block the increase in tyrosine hydroxylase. Thus the laminin domain involved in enzyme regulation in chromaffin cells is apparently the same as that previously implicated in laminin's interactions with neurons to potentiate survival and stimulate neurite outgrowth (Edgar, D., R. Timpl, and H. Thoenen, 1984, EMBO (Eur. Mol. Biol. Organ.) J., 3:1463-1468). The increase in chromaffin cell tyrosine hydroxylase levels is preceded by an activation of the enzyme in which the Vmax (but not the Km) is altered. The effects of laminin appear to be developmentally regulated, since neither activation nor increased levels of tyrosine hydroxylase occur in adult adrenal chromaffin cells exposed to laminin. 相似文献
10.
The effects of chronic nerve growth factor administration on the development of neuropeptides in the embryonic chick peripheral nervous system were quantitated by radioimmunoassays. Starting at embryonic Day 3.5, daily doses of 20 micrograms of nerve growth factor (NGF) increased the substance P content of lumbosacral spinal sensory ganglia at all ages studied (Days 10-14), while having no effect on substance P levels of thoracic sensory ganglia. In contrast, the contents of somatostatin were increased in both thoracic and lumbosacral ganglia, but only at comparatively late time points (Day 14). Nerve growth factor administration was also found to decrease the somatostatin contents of lumbosacral paravertebral sympathetic ganglia at early time points (Day 8) while increasing levels at later stages (Day 14), thus acting to accelerate the normally occurring developmental changes in level of this peptide. These changes were shown to be specific for somatostatin by demonstrating that NGF increased tyrosine hydroxylase levels in sympathetic neurons at Day 8, and had no effect on sympathetic vasoactive intestinal polypeptide levels at Day 14. It has been concluded that exogenous NGF does not simply act to increase or prolong the expression of neuron-specific phenotypes in the chick, but rather its action is time and location dependent to accelerate development. 相似文献