Resumptive pronouns are often regarded as a last-resort strategy for rescuing illicit long-distance dependencies. Previous work has demonstrated a facilitative role for resumptive pronouns in ...production as well as in comprehension, though not a grammatical option in the languages. This study examined whether the same pattern is found in Cantonese, a language that allows resumption as a legitimate relativization strategy. Young Cantonese monolingual children were tested for both comprehension and production of object relative clauses using different relativization strategies (the gap strategy vs. the resumptive pronoun strategy). Although children did not perform better on either strategy in comprehension, and never employed resumptive pronouns in their production, resumption did prevent misanalysis of prenominal relative clauses as matrix clauses, suggesting that these elements help reveal the full structure of the relative clause to the processor. The study also showed better performance on subject than on object relative clauses, suggesting that the widely observed subject–object asymmetry also applies to Cantonese.
The question of whether there exists a universal subject preference in relativization has stimulated research in a wide range of languages and across different domains, yielding an extensive body of ...literature in relative clause acquisition and processing. In this article, we aim at consolidating the efforts of existing research in order to inform further exploration of the universality of the subject preference with a comprehensive analysis of relevant work (including journal articles on empirical studies, dissertations, and conference proceedings). We present an overview of the proposals regarding the source(s) of the subject-object asymmetry from a cross-linguistic perspective and discuss commonly used methodologies in this research area, and we survey the research on relative clause processing and acquisition of different linguistic communities, including native speakers, second language learners, clinical populations, and heritage speakers.
RNA-guided CRISPR-Cas9 endonucleases are widely used for genome engineering, but our understanding of Cas9 specificity remains incomplete. Here, we developed a biochemical method (SITE-Seq), using ...Cas9 programmed with single-guide RNAs (sgRNAs), to identify the sequence of cut sites within genomic DNA. Cells edited with the same Cas9-sgRNA complexes are then assayed for mutations at each cut site using amplicon sequencing. We used SITE-Seq to examine Cas9 specificity with sgRNAs targeting the human genome. The number of sites identified depended on sgRNA sequence and nuclease concentration. Sites identified at lower concentrations showed a higher propensity for off-target mutations in cells. The list of off-target sites showing activity in cells was influenced by sgRNP delivery, cell type and duration of exposure to the nuclease. Collectively, our results underscore the utility of combining comprehensive biochemical identification of off-target sites with independent cell-based measurements of activity at those sites when assessing nuclease activity and specificity.
Differences in the ability of opioid drugs to promote regulated endocytosis of μ-opioid receptors are related to their tendency to produce drug tolerance and dependence. Here we show that ...drug-specific differences in receptor internalization are determined by a conserved, 10-residue sequence in the receptor's carboxyl-terminal cytoplasmic tail. Diverse opioids induce receptor phosphorylation at serine (S)375, present in the middle of this sequence, but opioids differ markedly in their ability to drive higher-order phosphorylation on flanking residues threonine (T)370, T376, and T379. Multi-phosphorylation is required for the endocytosis-promoting activity of this sequence and occurs both sequentially and hierarchically, with S375 representing the initiating site. Higher-order phosphorylation involving T370, T376, and T379 specifically requires GRK2/3 isoforms, and the same sequence controls opioid receptor internalization in neurons. These results reveal a biochemical mechanism differentiating the endocytic activity of opioid drugs.
Impact of LL-37 on anti-infective immunity Bowdish, Dawn M. E.; Davidson, Donald J.; Lau, Y. Elaine ...
Journal of leukocyte biology,
April 2005, Letnik:
77, Številka:
4
Journal Article
Recenzirano
Host defense peptides (often called cationic antimicrobial peptides) have pleiotropic immunomodulatory functions. The human host defense peptide LL‐37 is up‐regulated at sites of infection and has ...little or no antimicrobial activity in tissue‐culture media but under the same conditions, demonstrates immunomodulatory effects on epithelial cells, monocytes, and dendritic cells (DC). These effects include the induction of chemokine production in a mitogen‐activated protein kinase‐dependent manner in epithelial cell lines and monocytes and profound alterations of DC differentiation, resulting in the capacity to enhance a T helper cell type 1 response. Although the exact mechanisms of interaction between LL‐37 and these cell types have not been elucidated, there is evidence for specific (i.e., receptor‐mediated) and nonspecific interactions. The relative significance of the direct antimicrobial activities and immunomodulatory properties of LL‐37 and other cationic host defense peptides in host defense remains unresolved. To demonstrate that antimicrobial activity was not necessarily required for protection in vivo, model peptides were synthesized and tested for antimicrobial and immunomodulatory activities. A peptide with no antimicrobial activity was found to be protective in animal models of Staphylococcus aureus and Salmonella infection, implying that a host defense peptide can protect by exerting immunomodulatory properties.
Chronic treatment with morphine results in a decrease in μ-opioid receptor sensitivity, an increase in acute desensitization, and a reduction in the recovery from acute desensitization in locus ...ceruleus neurons. With acute administration, morphine is unlike many other opioid agonists in that it does not mediate robust acute desensitization or induce receptor trafficking. This study compares μ-opioid receptor desensitization and trafficking in brain slices taken from rats treated for 6-7 d with a range of doses of morphine (60, 30, and 15 mg · kg(-1) · d(-1)) and methadone (60, 30, and 5 mg · kg(-1) · d(-1)) applied by subcutaneous implantation of osmotic minipumps. Mice were treated with 45 mg · kg(-1) · d(-1). In morphine-treated animals, recovery from acute Met(5)enkephalin-induced desensitization and receptor recycling was diminished. In contrast, recovery and recycling were unchanged in slices from methadone-treated animals. Remarkably the reduced recovery from desensitization and receptor recycling found in slices from morphine-treated animals were not observed in animals lacking β-arrestin-2. Furthermore, pharmacological inhibition of G-protein receptor kinase 2 (GRK2), although not affecting the ability of Met(5)enkephalin to induce desensitization, acutely reversed the delay in recovery from desensitization produced by chronic morphine treatment. These results characterize a previously unidentified function of the GRK/arrestin system in mediating opioid regulation in response to chronic morphine administration. They also suggest that the GRK/arrestin system, rather than serving as a primary mediator of acute desensitization, controls recovery from desensitization by regulating receptor reinsertion to the plasma membrane after chronic treatment with morphine. The sustained GRK/arrestin-dependent desensitization is another way in which morphine and methadone are distinguished.
During organogenesis, immunosurveillance, and inflammation, chemokines selectively recruit leukocytes by activating seven-transmembrane-spanning receptors. It has been suggested that an important ...component of this process is the formation of a haptotactic gradient by immobilization of chemokines on cell surface glycosaminoglycans (GAGs). However, this hypothesis has not been experimentally demonstrated in vivo. In the present study we investigated the effect of mutations in the GAG binding sites of three chemokines, monocyte chemoattractant protein-1/CC chemokine ligand (CCL)2, macrophage-inflammatory protein-1β/CCL4, and RANTES/CCL5, on their ability to recruit cells in vivo. These mutant chemokines retain chemotactic activity in vitro, but they are unable to recruit cells when administered intraperitoneally. Additionally, monomeric variants, although fully active in vitro, are devoid of activity in vivo. These data demonstrate that both GAG binding and the ability to form higher-order oligomers are essential for the activity of particular chemokines in vivo, although they are not required for receptor activation in vitro. Thus, quaternary structure of chemokines and their interaction with GAGs may significantly contribute to the localization of leukocytes beyond migration patterns defined by chemokine receptor interactions.
The human cathelicidin LL‐37 is a cationic host defense peptide (antimicrobial peptide) expressed primarily by neutrophils and epithelial cells. This peptide, up‐regulated under conditions of ...inflammation, has immunomodulatory and antimicrobial functions. We demonstrate that LL‐37 is a potent inhibitor of human neutrophil apoptosis, signaling through P2X7 receptors and G‐protein‐coupled receptors other than the formyl peptide receptor‐like‐1 molecule. This process involved modulation of Mcl‐1 expression, inhibition of BID and procaspase‐3 cleavage, and the activation of phosphatidylinositol‐3 kinase but not the extracellular signal‐regulated kinase 1/2 mitogen‐activated protein kinase pathway. In contrast to the inhibition of neutrophil apoptosis, LL‐37 induced apoptosis in primary airway epithelial cells, demonstrating alternate consequences of LL‐37‐mediated modulation of apoptotic pathways in different human primary cells. We propose that these novel immunomodulatory properties of LL‐37 contribute to peptide‐mediated enhancement of innate host defenses against acute infection and are of considerable significance in the development of such peptides and their synthetic analogs as potential therapeutics for use against multiple antibiotic‐resistant infectious diseases.
Social patterning of disease is pervasive and persistent. Disease patterns change with economic development and the attendant epidemiological transition. It is becoming evident that social patterns ...of disease are epidemiologically stage specific. In a population with a recent history of rapid economic development we examined social patterns of all-cause and cause-specific mortality over time to elucidate how economic development impacts disparities in health. We used concentration indices to provide a summary measure of disparities by income in potential years of life lost (PYLL) for the Hong Kong population from 1976 to 2006. For all-cause mortality and for each of the specific causes considered the concentration curve in 2006 dominated the 1976 concentration curve. The concentration index for all-cause PYLL was negligible in 1976, but increased over the period. PYLL attributable to injury and poisoning was fairly consistently associated with lower income, but PYLL attributable to cardiovascular diseases and cancer reversed from an association with higher income in 1976 to an association with lower income in 2006. Social disparities in health are not universal or homogeneous in origin. Attention should be focused on disease-specific causes of disparities, so that contextually specific prevention strategies can be implemented. This is of particular relevance to China and other emerging economies where there may be a window of opportunity to prevent disparities in cancer and cardiovascular diseases occurring.
In comparison to endogenous ligands of seven-transmembrane receptors, which typically act as full agonists, many drugs act as partial agonists. Partial agonism is best described as a "macroscopic" ...property that is manifest at the level of physiological systems or cell populations; however, whether partial agonists also encode discrete regulatory information at the "microscopic" level of individual receptors is not known. Here, we addressed this question by focusing on morphine, a partial agonist drug for μ-type opioid peptide receptors (MORs), and by combining quantitative mass spectrometry with cell biological analysis to investigate the reduced efficacy of morphine, compared to that of a peptide full agonist, in promoting receptor endocytosis. We showed that these chemically distinct ligands produced a complex and qualitatively similar mixture of phosphorylated opioid receptor forms in intact cells. Quantitatively, however, the different agonists promoted disproportionate multisite phosphorylation of a specific serine and threonine motif, and we found that modification at more than one residue was essential for the efficient recruitment of the adaptor protein β-arrestin that mediated subsequent endocytosis of MORs. Thus, quantitative encoding of agonist-selective endocytosis at the level of individual opioid receptors was based on the conserved biochemical principles of multisite phosphorylation and threshold detection.
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