Search

Rationally-engineered functional biomaterials offer the opportunity to interface with complex biology in a predictive, precise, yet dynamic way to reprogram their behaviour and correct shortcomings. Success here may lead to a desired therapeutic effect against life-threatening diseases, such as cancer. Here, we engineered "Crab"-like artificial ribonucleases through coupling of peptide and nucleic acid building blocks, capable of operating alongside and synergistically with intracellular enzymes (RNase H and AGO2) for potent destruction of oncogenic microRNAs. "Crab"-like configuration of two catalytic peptides ("pincers") flanking the recognition oligonucleotide was instrumental here in providing increased catalytic turnover, leading to ≈30-fold decrease in miRNA half-life as compared with that for " single-pincer" conjugates. Dynamic modeling of miRNA cleavage illustrated how such design enabled "Crabs" to drive catalytic turnover through simultaneous attacks at different locations of the RNA-DNA heteroduplex, presumably by producing smaller cleavage products and by providing toeholds for competitive displacement by intact miRNA strands. miRNA cleavage at the 5′-site, spreading further into double-stranded region, likely provided a synergy for RNase H1 through demolition of its loading region, thus facilitating enzyme turnover. Such synergy was critical for sustaining persistent disposal of continually-emerging oncogenic miRNAs. A single exposure to the best structural variant (Crab-p-21) prior to transplantation into mice suppressed their malignant properties and reduced primary tumor volume (by 85 %) in MCF-7 murine xenograft models. [Display omitted] [ABSTRACT FROM AUTHOR]

Abstract Little is known about the exact genes that confer vulnerability or resilience to environmental stressors during early neurodevelopment. Partial genetic deletion of neuregulin 1 (Nrg1) moderates the neurobehavioural effects of stressors applied in adolescence and adulthood, however, no study has yet examined its impact on prenatal stress. Here we examined whether Nrg1 deficiency in mice modulated the impact of prenatal stress on various behaviours in adulthood. Male heterozygous Nrg1 mice were mated with wild-type female mice who then underwent daily restraint stress from days 13 to 19 of gestation. Surprisingly, prenatal stress had overall beneficial effects by facilitating sensorimotor gating, increasing sociability, decreasing depressive-like behaviour, and improving spatial memory in adulthood. Such benefits were not due to any increase in maternal care, as prenatal stress decreased nurturing of the offspring. Nrg1 deficiency negated the beneficial behavioural effects of prenatal stress on all measures except sociability. However, Nrg1 deficiency interacted with prenatal stress to trigger locomotor hyperactivity. Nrg1 deficiency, prenatal stress or their combination failed to alter acute stress-induced plasma corticosterone concentrations. Collectively these results demonstrate that Nrg1 deficiency moderates the effects of prenatal stress on adult behaviour, but it does so in a complex, domain-specific fashion. Highlights • Prenatal stress (PS) had a beneficial effect on various behaviours in adult mice. • PS improved sensorimotor gating, sociability, spatial memory and stress coping. • Nrg1 deficiency reduced all the benefits of PS except for enhanced sociability. • Nrg1 deficiency and prenatal stress combined to trigger locomotor hyperactivity. [ABSTRACT FROM AUTHOR]

The endocannabinoid system is dysregulated in schizophrenia. Mice with heterozygous deletion of neuregulin 1 ( Nrg1 HET mice) provide a well-characterised animal model of schizophrenia, and display enhanced sensitivity to stress and cannabinoids during adolescence. However, no study has yet determined whether these mice have altered brain endocannabinoid concentrations. Nrg1 application to hippocampal slices decreased 2-arachidonoylglycerol (2-AG) signalling and disrupted long-term depression, a form of synaptic plasticity critical to spatial learning. Therefore we specifically aimed to examine whether Nrg1 HET mice exhibit increased 2-AG concentrations and disruption of spatial learning. As chronic stress influences brain endocannabinoids, we also sought to examine whether Nrg1 deficiency moderates adolescent stress-induced alterations in brain endocannabinoids. Adolescent Nrg1 HET and wild-type (WT) mice were submitted to chronic restraint stress and brain endocannabinoid concentrations were analysed. A separate cohort of WT and Nrg1 HET mice was also assessed for spatial learning performance in the Morris Water Maze. Partial genetic deletion of Nrg1 increased anandamide concentrations in the amygdala and decreased 2-AG concentrations in the hypothalamus. Further, Nrg1 HET mice exhibited increased 2-AG concentrations in the hippocampus and impaired spatial learning performance. Chronic adolescent stress increased anandamide concentrations in the amygdala, however, Nrg1 disruption did not influence this stress-induced change. These results demonstrate for the first time in vivo interplay between Nrg1 and endocannabinoids in the brain. Our results demonstrate that aberrant Nrg1 and endocannabinoid signalling may cooperate in the hippocampus to impair cognition, and that Nrg1 deficiency alters endocannabinoid signalling in brain stress circuitry. [ABSTRACT FROM AUTHOR]

Summary: Aims: Although the use of portfolios is widespread within healthcare education, agreement on their purpose, content, assessment and value is still debated. The objective of this study was to achieve consensus on quality criteria for clinical practice portfolios that would act as guidance for students and lecturers. Methods: A Delphi survey was undertaken to seek consensus on the opinions of 23 ‘expert participants’ through a series of rounds of structured questionnaires. The Delphi tool was produced as an on-line survey questionnaire and panel experts were invited to score statements using a discrete 7 point visual analogue scale. The statements were written as quality criteria relating to portfolio development which had been identified from the literature and by the research team. The survey employed three rounds of feedback and consensus was measured as 80% agreement for each quality criteria scoring 5 and above. Results: Consensus was reached on 31 quality criteria which were categorised into 4 areas: structured collection of labelled evidence; nature of evidence; critical reflection; and assessment and judgement. Mean scores for the final wording of the quality criteria ranged from 5.3 to 6.8 with the standard deviation for all of the mean scores being below 1.5. There was consensus that these quality criteria were relevant to health and social care professionals involved in developing clinical practice portfolios. Conclusions: The Delphi process facilitated exchange of ideas amongst panel ‘experts’ about the content and evaluation of clinical practice portfolios, with most debate relating to judgement of competence and rewarding originality and creativity. These issues illustrate the tensions between educational values and professional constraints. The Delphi process proved to be an effective method for achieving consensus on quality criteria for clinical practice portfolios and enabled the development of validated guidelines. [Copyright &y& Elsevier]

β-Defensins are important in mammalian immunity displaying both antimicrobial and chemoattractant activities. Three canonical disulfide intramolecular bonds are believed to be dispensable for antimicrobial activity but eβential for chemoattractant ability. However, here we show that HBD3 (human β-defensin 3) alkylated with iodoactemide and devoid of any disulfide bonds is still a potent chemoattractant. Furthermore, when the canonical six cysteine residues are replaced with alanine, the peptide is no longer active as a chemoattractant. These findings are replicated by the murine ortholog Defb14. We restore the chemoattractant activity of Defb14 and HBD3 by introduction of a single cysteine in the fifth position (CysV) of the β-defensin six cysteine motif. In contrast, a peptide with a single cysteine at the first position (CysI) is inactive. Moreover, a range of overlapping linear fragments of Defb14 do not act as chemoattractants, suggesting that the chemotactic activity of this peptide is not dependent solely on an epitope surrounding CysV. Full-length peptides either with alkylated cysteine residues or with cysteine residues replaced with alanine are still strongly antimicrobial. Defb14 peptide fragments were also tested for antimicrobial activity, and peptides derived from the N-terminal region display potent antimicrobial activity. Thus, the chemoattractant and antimicrobial activities of β-defensins can be separated, and both of these functions are independent of intramolecular disulfide bonds. These findings are important for further understanding of the mechanism of action of defensins and for therapeutic design. [ABSTRACT FROM AUTHOR]

Defensins are cationic antimicrobial peptides that have a characteristic six-cysteine motif and are important components of the innate immune system. We recently described a β-defensin-related peptide (Defr1) that had potent antimicrobial activity despite having only five cysteines. Here we report a relationship between the structure and activity of Defr1 through a comparative study with its six cysteine-containing analogue (Defr1 Y5C). Against a panel of pathogens, we found that oxidized Deft1 had significantly higher activity than its reduced form and the oxidized and reduced forms of Defr1 Y5C. Furthermore, Defr1 displayed activity against Pseudomonas aeruginosa in the presence of 150 mM NaCl, whereas Defr1 Y5C was inactive. By using nondenaturing gel electrophoresis and Fourier transform ion cyclotron resonance mass spectrometry, we observed Defr1 and Defr1 Y5C dimers. Two complementary fragmentation techniques (collision-induced dissociation and electron capture dissociation) revealed that Defr1 Y5C dimers form by noncovalent, weak association of monomers that contain three intramolecular disulfide bonds. In contrast, Defr1 dimers are resistant to collision-induced dissociation and are only dissociated into monomers by reduction using electron capture. This is indicative of Defr1 dimerization being mediated by an intermolecular disulfide bond. Proteolysis and peptide mass mapping revealed that Defr1 Y5C monomers have β-defensin disulfide bond connectivity, whereas oxidized Defr1 is a complex mixture of dimeric isoforms with as yet unknown inter- and intramolecular connectivities. Each isoform contains one intermolecular and four intramolecular disulfide bonds, but because we were unable to resolve the isoforms by reverse phase chromatography, we could not assign each isoform with a specific antimicrobial activity. We conclude that the enhanced activity and stability of this mixture of Defr1 dimeric isoforms are due to the presence of an intermolecular disulfide bond. This first description of a covalently cross-linked member of the defensin family provides further evidence that the antimicrobial activity of a defensin is linked to its ability to form stable higher order structures. [ABSTRACT FROM AUTHOR]

Summary: Aims: The aims of this study were to evaluate whether the introduction of new evidence based portfolio guidelines helped students and assessors to understand the expectations for completion of a clinical practice portfolio, and whether this understanding resulted in the submission of evidence consistent with the guidelines. Methods: New evidence based portfolio guidelines were introduced to an undergraduate BSc (Hons) Radiography (Diagnostic) programme. A total of 134 students completed 12 item questionnaires relating to using the portfolio guidelines. Semi-structured interviews were undertaken with 12 students and 5 lecturer practitioners. Documentary analysis was undertaken on 26 portfolios. Results: Survey data indicated that the new guidelines increased students'' understanding of portfolio evidence requirements. Statistically significant increases in scores were evident for only two out of 12 questions; these related to understanding the need for critical reflection and which elements of the portfolio would be rewarded in assessment. Survey data also indicated some dissatisfaction with the role of lecturer practitioners and clinical assessors in relation to portfolio development. Interviews provided more mixed perceptions of the contribution of enhanced guidelines and identified some reasons for dissatisfaction with the lecturer practitioner and clinical assessor role. Documentary analysis indicated that whilst the guidelines improved students'' and lecturers'' understanding of evidence requirements, this did not translate into portfolio evidence which matched guideline expectations. Portfolio evidence was restricted to meeting the minimum profession specific task requirements and often indicated a mis-match between guideline expectations and assessor assessment judgements. Conclusions: New evidence based guidelines improved understanding of evidence and presentation requirements for clinical practice portfolios. Consistent interpretation of portfolio guidelines however requires structured preparation and ongoing support of students, assessors and lecturers if the pedagogic aims for clinical portfolio use are to become an integral part of providing evidence of meeting professional competence requirements. [Copyright &y& Elsevier]

Bacterial pathogens either hide from or modulate the host''s immune response to ensure their survival. Photorhabdus is a potent insect pathogenic bacterium that uses entomopathogenic nematodes as vectors in a system that represents a useful tool for probing the molecular basis of immunity. During the course of infection, Photorhabdus multiplies rapidly within the insect, producing a range of toxins that inhibit phagocytosis of the invading bacteria and eventually kill the insect host. Photorhabdus bacteria have recently been established as a tool for investigating immune recognition and defense mechanisms in model hosts such as Manduca and Drosophila. Such studies pave the way for investigations of gene interactions between pathogen virulence factors and host immune genes, which ultimately could lead to an understanding of how some Photorhabdus species have made the leap to becoming human pathogens. [Copyright &y& Elsevier]

This paper describes an Experience-based Co-design (EBCD) project that aimed to increase patient activity within an acute stroke unit. We apply the concept of liminality to explore ways in which the EBCD process, a form of Participatory Action Research, may dilute or even dissolve social hierarchies and challenge assumptions about practices and constraints in this care setting, thereby opening up possibilities for transformation that enhances the therapeutic value of the space for patients and care providers alike. By occasioning a liminal phase of possibility for change, the work of one co-design group explored in detail here suggests that, in this process, the sociomaterial interactions involving patients, family members, staff, and the physical space are refashioned and re-inscribed in transformed 'emplaced' relationships of care. [ABSTRACT FROM AUTHOR]

Abstract: The Rcs phosphorelay is composed of the sensor kinase, RcsC, the HPt-domain protein RcsD and the response regulator, RcsB. In this review we discuss the role of the Rcs phosphorelay in the Enterobacteriaceae, highlighting the observation that the Rcs phosphorelay appears to play a key role in the temporal regulation of biofilm formation and pathogenicity. [Copyright &y& Elsevier]

Photorhabdus is a genus of insect-pathogenic bacteria that also maintains a mutualistic interaction with Heterorhabditid nematodes. Bacteria in this genus are members of the family Enterobacteriaceae and are, therefore, closely related to many important mammalian pathogens. This bacteria–nematode complex has been exploited as a biocontrol agent that is active against several insect pests. However, this model system is also uniquely placed to address important fundamental questions about pathogenicity and mutualism. Indeed, recent genetic studies have suggested that there is a significant overlap in the genetic requirements of Photorhabdus for these contrasting interactions. In addition, the identification of key regulators of pathogenicity and symbiosis only serves to highlight the similarities between Photorhabdus, a genus of bacteria that infects invertebrate hosts, and closely related mammalian enteric pathogens. [Copyright &y& Elsevier]

Encapsulated ferritins belong to the universally distributed ferritin superfamily, whose members function as iron detoxification and storage systems. Encapsulated ferritins have a distinct annular structure and must associate with an encapsulin nanocage to forma competent iron store that is capable of holding significantly more iron than classical ferritins. The catalytic mechanism of iron oxidation in the ferritin family is still an open question because of the differences in organization of the ferroxidase catalytic site and neighboring secondary metalbinding sites. We have previously identified a putative metalbinding site on the inner surface of the Rhodospirillum rubrum encapsulated ferritin at the interface between the two-helix subunits and proximal to the ferroxidase center. Here we present a comprehensive structural and functional study to investigate the functional relevance of this putative iron-entry site by means of enzymatic assays, MS, and X-ray crystallography. We show that catalysis occurs in the ferroxidase center and suggest a dual role for the secondary site, which both serves to attract metal ions to the ferroxidase center and acts as a flow-restricting valve to limit the activity of the ferroxidase center. Moreover, confinement of encapsulated ferritins within the encapsulin nanocage, although enhancing the ability of the encapsulated ferritin to undergo catalysis, does not influence the function of the secondary site. Our study demonstrates a novel molecular mechanism by which substrate flux to the ferroxidase center is controlled, potentially to ensure that iron oxidation is productively coupled to mineralization. [ABSTRACT FROM AUTHOR]

In student collaboration, purposeful peer interaction crucial for success on the task. Such collaboration requires adequate and purposeful student agency. Theoretically, the between-individual complementarity of agency behaviors enhances purposeful interaction. However, the level of agency of group members can disrupt the collaborative interactions. We conducted a case study of collaborative mathematical problem solving, where one student's behaviors of noncomplementary agency characterized the group interaction. We examined the video recording of the group by continuous quantitative coding of students' agency behaviors and segmented the interaction process into four phases. We analyzed qualitatively these phases based on the verbal transcript. We found that the target student's agency grew in relation to the other students despite her lack of mathematical competence. The findings provide us with a new perspective to understand the role of the situational individual agency in collaborative learning that underlines the tolerance of noncomplementarity of agency in student collaboration. • A case of student group work was found to contradict interpersonal theory. • Continuous coding can capture momentary agency behaviors in the group level. • Noncomplementary interpersonal behaviors can lead to successful collaboration. • Theoretically, situational and structural agency are in relation to each other. [ABSTRACT FROM AUTHOR]

Potent cytolytic peptides with specific tethering and cloaking sites have been synthesised and used to release payload from liposomes in a quantitative manner. A functionally located cloaking site has been modified specifically by simple conjugation without adversely affecting the cytolytic properties of the peptide. The cytolytic activity of modified peptides was then efficiently (>98%) cloaked and uncloaked by ligand–protein or hapten–antibody interactions. The principle of a dual response peptide has been demonstrated using an avidin-cloaked pH-sensitive peptide. Biospecific cloaking/uncloaking provided a new sensitive (∼12 pmol) homogeneous diagnostic and also appears potentially suited to bioresponsively targeted release of antimicrobial, anticancer and other drugs now delivered using liposomes. [Copyright &y& Elsevier]