995 resultados para Binding constant


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OBJECTIVE: Inflammatory bowel diseases (IBDs), Crohn's disease, and ulcerative colitis (UC), are multifactorial disorders, characterized by chronic inflammation of the intestine. A number of genetic components have been proposed to contribute to IBD pathogenesis. In this case-control study, we investigated the association between two common vitamin D-binding protein (DBP) genetic variants and IBD susceptibility. These two single nucleotide polymorphisms (SNPs) in exon 11 of the DBP gene, at codons 416 (GAT>GAG; Asp>Glu) and 420 (ACG>AAG; Thr>Lys), have been previously suggested to play roles in the etiology of other autoimmune diseases. METHODS: Using TaqMan SNP technology, we have genotyped 884 individuals (636 IBD cases and 248 non-IBD controls) for the two DBP variants. RESULTS: On statistical analysis, we observed that the DBP 420 variant Lys is less frequent in IBD cases than in non-IBD controls (allele frequencies, P=0.034; homozygous carrier genotype frequencies, P=0.006). This inverse association between the DBP 420 Lys and the disease remained significant, when non-IBD participants were compared with UC (homozygous carrier genotype frequencies, P=0.022) or Crohn's disease (homozygous carrier genotype frequencies, P=0.016) patients separately. Although the DBP position 416 alone was not found to be significantly associated with IBD, the haplotype DBP_2, consisting of 416 Asp and 420 Lys, was more frequent in the non-IBD population, particularly notably when compared with the UC group (Odds ratio, 4.390). CONCLUSION: Our study adds DBP to the list of potential genes that contribute to the complex genetic etiology of IBD, and further emphasizes the association between vitamin D homeostasis and intestinal inflammation.

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Spermatogenesis is a temporally regulated developmental process by which the gonadotropin-responsive somatic Sertoli and Leydig cells act interdependently to direct the maturation of the germinal cells. The metabolism of Sertoli and Leydig cells is regulated by the pituitary gonadotropins FSH and LH, which, in turn, activate adenylate cyclase. Because the cAMP-second messenger pathway is activated by FSH and LH, we postulated that the cAMP-responsive element-binding protein (CREB) plays a physiological role in Sertoli and Leydig cells, respectively. Immunocytochemical analyses of rat testicular sections show a remarkably high expression of CREB in the haploid round spermatids and, to some extent, in pachytene spermatocytes and Sertoli cells. Although most of the CREB antigen is detected in the nuclei, some CREB antigen is also present in the cytoplasm. Remarkably, the cytoplasmic CREB results from the translation of a unique alternatively spliced transcript of the CREB gene that incorporates an exon containing multiple stop codons inserted immediately up-stream of the exons encoding the DNA-binding domain of CREB. Thus, the RNA containing the alternatively spliced exon encodes a truncated transcriptional transactivator protein lacking both the DNA-binding domain and nuclear translocation signal of CREB. Most of the CREB transcripts detected in the germinal cells contain the alternatively spliced exon, suggesting a function of the exon to modulate the synthesis of CREB. In the Sertoli cells we observed a striking cyclical (12-day periodicity) increase in the levels of CREB mRNA that coincides with the splicing out of the restrictive exon containing the stop codons. Because earlier studies established that FSH-stimulated cAMP levels in Sertoli cells are also cyclical, and the CREB gene promoter contains cAMP-responsive enhancers, we suggest that the alternative RNA splicing controls a positive autoregulation of CREB gene expression mediated by cAMP.

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A recombinant baculovirus encoding a single-chain murine major histocompatibility complex class I molecule in which the first three domains of H-2Kd are fused to beta 2-microglobulin (beta 2-m) via a 15-amino acid linker has been isolated and used to infect lepidopteran cells. A soluble, 391-amino acid single-chain H-2Kd (SC-Kd) molecule of 48 kDa was synthesized and glycosylated in insect cells and could be purified in the absence of detergents by affinity chromatography using the anti-H-2Kd monoclonal antibody SF1.1.1.1. We tested the ability of SC-Kd to bind antigenic peptides using a direct binding assay based on photoaffinity labeling. The photoreactive derivative was prepared from the H-2Kd-restricted Plasmodium berghei circumsporozoite protein (P.b. CS) peptide 253-260 (YIPSAEKI), a probe that we had previously shown to be unable to bind to the H-2Kd heavy chain in infected cells in the absence of co-expressed beta 2-microglobulin. SC-Kd expressed in insect cells did not require additional mouse beta 2-m to bind the photoprobe, indicating that the covalently attached beta 2-m could substitute for the free molecule. Similarly, binding of the P.b. CS photoaffinity probe to the purified SC-Kd molecule was unaffected by the addition of exogenous beta 2-m. This is in contrast to H-2KdQ10, a soluble H-2Kd molecule in which beta 2-m is noncovalently bound to the soluble heavy chain, whose ability to bind the photoaffinity probe is greatly enhanced in the presence of an excess of exogenous beta 2-m. The binding of the probe to SC-Kd was allele-specific, since labeling was selectively inhibited only by antigenic peptides known to be presented by the H-2Kd molecule.

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Vibrio vulnificus and Vibrio cholerae are Gram-negative pathogens that cause serious infectious disease in humans. The beta form of pro-IL-1 is thought to be involved in inflammatory responses and disease development during infection with these pathogens, but the mechanism of beta form of pro-IL-1 production remains poorly defined. In this study, we demonstrate that infection of mouse macrophages with two pathogenic Vibrio triggers the activation of caspase-1 via the NLRP3 inflammasome. Activation of the NLRP3 inflammasome was mediated by hemolysins and multifunctional repeat-in-toxins produced by the pathogenic bacteria. NLRP3 activation in response to V. vulnificus infection required NF-kappaB activation, which was mediated via TLR signaling. V. cholerae-induced NLRP3 activation also required NF-kappaB activation but was independent of TLR stimulation. Studies with purified V. cholerae hemolysin revealed that toxin-stimulated NLRP3 activation was induced by TLR and nucleotide-binding oligomerization domain 1/2 ligand-mediated NF-kappaB activation. Our results identify the NLRP3 inflammasome as a sensor of Vibrio infections through the action of bacterial cytotoxins and differential activation of innate signaling pathways acting upstream of NF-kappaB.

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Researchers have used stylized facts on asset prices and trading volumein stock markets (in particular, the mean reversion of asset returnsand the correlations between trading volume, price changes and pricelevels) to support theories where agents are not rational expected utilitymaximizers. This paper shows that this empirical evidence is in factconsistent with a standard infite horizon perfect information expectedutility economy where some agents face leverage constraints similar tothose found in todays financial markets. In addition, and in sharpcontrast to the theories above, we explain some qualitative differencesthat are observed in the price-volume relation on stock and on futuresmarkets. We consider a continuous-time economy where agents maximize theintegral of their discounted utility from consumption under both budgetand leverage con-straints. Building on the work by Vila and Zariphopoulou(1997), we find a closed form solution, up to a negative constant, for theequilibrium prices and demands in the region of the state space where theconstraint is non-binding. We show that, at the equilibrium, stock holdingsvolatility as well as its ratio to stock price volatility are increasingfunctions of the stock price and interpret this finding in terms of theprice-volume relation.