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91.
H D Gresham L T Clement J E Volanakis E J Brown 《Journal of immunology (Baltimore, Md. : 1950)》1987,139(12):4159-4166
Data presented in this paper indicate that polymorphonuclear leukocyte (PMN) Fc receptor-mediated phagocytosis can be markedly augmented and that this augmentation is under regulatory control. Stimulation of PMN with either a low m.w., heat-labile cytokine(s) (the culture supernatant effluent from a YM-10 Centricon unit, YM-10E), phorbol esters (phorbol dibutyrate), or the polyene antibiotic, amphotericin B, enhances Fc-mediated ingestion in a dose-dependent manner. YM-10 effluent- and amphotericin B-stimulated ingestion is completely abrogated by treating the PMN with either pertussis toxin (PT), cholera toxin (CT), or a monoclonal antibody (mAb), 1C2. However, neither toxin nor mAb 1C2 affects nonstimulated ingestion or phagocytosis stimulated by phorbol esters or synthetic diacylglycerol. Increasing intracellular cyclic adenosine monophosphate levels by stimulation with prostaglandin E1 and the phosphodiesterase inhibitor, isobutylmethylxanthine, does not mimic the effect of either toxin or mAb 1C2. In addition, toxin-mediated inhibition is not due to loss of either the Fc receptor recognized by mAb 3G8 or the antigen recognized by mAb 1C2. These data indicate that both CT and PT regulate the phagocytic response of PMN, in a manner like mAb 1C2, probably by affecting a guanosine 5'-triphosphate-binding protein distinct from those that regulate adenylate cyclase. Since phorbol ester-stimulated ingestion is not inhibited by either PT, CT, or mAb 1C2 and phorbol esters activate protein kinase C directly, phagocytosis amplification regulated by PT, CT, and mAb 1C2 may involve protein kinase C activation. 相似文献
92.
We present molecular dynamics simulations on the active site region of dimeric triose phosphate isomerase (TIM) using the co-ordinates of native chicken muscle TIM as a starting point and performing simulations with no substrate, with dihydroxyacetone phosphate (DHAP), the natural substrate, and with dihydroxyacetone sulfate (DHAS), a substrate analog. Whereas most of the protein moves less than 1 A during the simulation, some residues in the active site loop move more than 8 A during the 10.5 picoseconds of dynamics for each of the simulations. Most interestingly, the nature of the loop motion depends on the substrate, with the largest motion found in the presence of DHAP, and only in the presence of DHAP does the loop move to "close off" the active site pocket. The final structure found for the DHAP-chicken TIM complex is qualitatively similar to that described by Alber et al. for DHAP-yeast TIM. Simulations on the monomeric protein gives insight into why the molecule is active only as a dimer. 相似文献
93.
94.
Microdissection and microcloning from the proximal region of mouse chromosome 7: isolation of clones genetically linked to the pudgy locus 总被引:1,自引:0,他引:1
Microdissection and microcloning have been utilized in order to create a bank of clones from the proximal region of mouse chromosome 7. Several important loci map to this area, including the albino locus (c), pink-eye dilution (p), and the developmental mutant, pudgy (pu). By use of interspecific crosses between Mus musculus domesticus and Mus spretus, we have generated backcross progeny segregating for the mutations chinchilla (cch) and pink-eye dilution (p). Exploiting the evolutionary divergence between the two species, we have analyzed the inheritance of restriction fragment length variants of three microclones and their linkage to the two markers cch and p, respectively. All three clones studied map to the dissected region, and as such also show genetic linkage to the pudgy locus. This bank of chromosome 7-derived microclones should provide molecular start points for the isolation of a variety of developmental loci of unknown gene product, including the pudgy locus. 相似文献
95.
Reconstitution of somatostatin and muscarinic receptor mediated stimulation of K+ channels by isolated GK protein in clonal rat anterior pituitary cell membranes 总被引:10,自引:0,他引:10
A Yatani J Codina R D Sekura L Birnbaumer A M Brown 《Molecular endocrinology (Baltimore, Md.)》1987,1(4):283-289
Somatostatin (SS) inhibits secretion from many cells, including clonal GH3 pituitary cells, by a complex mechanism that involves a pertussis toxin (PTX)-sensitive step and is not limited to its cAMP lowering effect, since secretion induced by cAMP analogs and K+ depolarization are also inhibited. SS also causes membrane hyperpolarization which may lead to decreases in intracellular Ca2+ need for secretion. Using patch clamp techniques we now demonstrate: 1) that both (SS) and acetylcholine applied through the patch pipette to the extracellular face of a patch activate a 55-picosiemens K+ channel without using a soluble second messenger; 2) that, after patch excision, the active state of the ligand-stimulated channel is dependent on GTP in the bath, is abolished by treatment of the cytoplasmic face of the patch with activated PTX and NAD+, and after inactivation by PTX, is restored in a GTP-dependent manner by addition of a nonactivated human erythrocyte PTX-sensitive G protein, and 3) that the 55-picosiemens K+ channel can also be activated in a ligand-independent manner with guanosine [gamma-thio] triphosphate (GTP gamma S) or with Mg2+/GTP gamma S-activated erythrocyte G protein. We call this protein GK. It is an alpha-beta-gamma trimer of which we have previously shown that the alpha-subunit is the substrate for PTX and that it dissociates on activation with Mg2+/GTP gamma S into alpha-GTP gamma S plus beta-gamma. A similarly activated and dissociated preparation of GS, the stimulatory regulatory component of adenylyl cyclase, having a different alpha-subunit but the same beta-gamma-dimer, was unable to cause K+ opening.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
96.
Mammalian DNA polymerase alpha: a replication-competent holoenzyme form from calf thymus 总被引:1,自引:0,他引:1
U Hübscher M Gassmann S Spadari N C Brown E Ferrari H J Buhk 《Philosophical transactions of the Royal Society of London. Series B, Biological sciences》1987,317(1187):421-428
Calf thymus DNA polymerase alpha, like the replication-specific DNA polymerase III holoenzyme of Escherichia coli, can be isolated as a distinct complex. A specific multiprotein form of the polymerase alpha, a form designated replication-competent (RC) holoenzyme, consists of a complex of a polymerase-primase core and at least six other polypeptides. The RC holoenzyme can efficiently replicate several naturally occurring templates, including the genomic DNA of the porcine circovirus (PCV). The DNA of this virion consists of a single-stranded circle with a defined replication origin, and its replication requires the cellular DNA replication machinery. It might therefore provide an invaluable opportunity to investigate chromosomal replication mechanisms, analogous to the way that studies on E. coli bacteriophage DNA replication elucidated host DNA replication mechanisms. Calf RC holoenzyme alpha selectively initiates PCV DNA replication in vitro at a site that possibly represents a consensus sequence of cellular DNA replication origins. The cell-free PCV replication system will be exploited for the in vitro dissection and reconstitution of the RC holoenzyme and the functional analysis of its component polypeptides. 相似文献
97.
Extensive degradation of Aroclors and environmentally transformed polychlorinated biphenyls by Alcaligenes eutrophus H850. 总被引:14,自引:8,他引:6
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D L Bedard R E Wagner M J Brennan M L Haberl J F Brown Jr 《Applied microbiology》1987,53(5):1094-1102
We have isolated and characterized a strain of Alcaligenes eurtrophus, designated H850, that rapidly degrades a broad and unusual spectrum of polychlorinated biphenyls (PCBs) including many tetra- and pentachlorobiphenyls and several hexachlorobiphenyls. This strain, which was isolated from PCB-containing dredge spoils by enrichment on biphenyl, grows well on biphenyl and 2-chlorobiphenyl but poorly on 3- and 4-chlorobiphenyl. Capillary gas-chromatographic analysis showed that biphenyl-grown resting cells of H850 degraded the components of 38 of the 41 largest peaks of Aroclor 1242 and 15 of the 44 largest peaks of Aroclor 1254, resulting in an overall reduction of PCBs by 81% for Aroclor 1242 (10 ppm) and 35% for Aroclor 1254 (10 ppm) in 2 days. Furthermore, H850 metabolized the predominantly ortho-substituted PCB congeners that resulted from the environmental transformation of the more highly chlorinated congeners of Aroclor 1242 by the upper Hudson River anaerobic meta-, para-dechlorination agent system C (J. F. Brown, R. E. Wagner, Jr., D. L. Bedard, M. J. Brennan, J. C. Carnahan, R. J. May, and J. J. Tofflemire, Northeast Environ. Sci. 3:167-179, 1984). The congener selectivity patterns indicate that a two-step process consisting of anaerobic dechlorination followed by oxidation by H850 can effectively degrade all of the congeners in Aroclor 1242 and possibly all those in Aroclor 1254. 相似文献
98.
Light induces a rapid and transient increase in inositol-trisphosphate in toad rod outer segments 总被引:1,自引:0,他引:1
J E Brown C Blazynski A I Cohen 《Biochemical and biophysical research communications》1987,146(3):1392-1396
The sub-second time course of changes in the content of [3H]inositol-1,4,5-trisphosphate was determined in rod outer segments from very rapidly frozen Bufo retinas that had been incubated with [3H]inositol. Rod outer segments were cut off frozen specimens with a cryostat microtome and the water soluble extracts were analyzed. The content of [3H]inositol-1,4,5-trisphosphate rose after approximately 250 msec of bright illumination, but returned to the unstimulated level after 1 sec, whether the stimulus remained on or not. That is, there was rapid but transient change in the content of [3H]inositol-1,4,5-trisphosphate after the onset of stimulation. 相似文献
99.
100.
M J Engle M Dooley D J Brown 《Biochemical and biophysical research communications》1987,145(1):397-401
Fetal rabbit lungs from 23 day gestation animals were used to investigate the potential role of lactate as a substrate for fetal lung glycogen synthesis. Fetal lactate dehydrogenase activity was approximately twice that found in the adult lung, while the activity of phosphoenolpyruvate carboxykinase was elevated fourfold over the adult value. Pyruvate carboxylase activities were similar in both fetal and adult lungs. Studies employing fetal lung explants in organ culture indicated that the presence of both glucose and lactate may be necessary for glycogen accumulation in the developing fetal lung. These data support the hypothesis that lactate is an important precursor for fetal lung glycogen. 相似文献