Meta-Synthesis of Qualitative Case Studies: An Approach to Theory Building

The purpose of this article is to provide the research design of a meta-synthesis of qualitative case studies. The meta-synthesis aims at building theory out of primary qualitative case studies that have not been planned as part of a unified multisite effect. By drawing on an understanding of research synthesis as the interpretation of qualitative evidence from a postpositivistic perspective, this article proposes eight steps of synthesizing existing qualitative case study findings to build theory. An illustration of the application of this method in the field of dynamic capabilities is provided. After enumerating the options available to meta-synthesis researchers, the potential challenges as well as the prospects of this research design are discussed. © The Author(s) 2013

Macro-iterativity : a qualitative multi-arc design for studying complex issues and big questions

The impact and relevance of our discipline's research is determined by its ability to engage the big questions of the grand challenges we face today. Our central argument is that we need innovative methods that engage large-scope phenomena, not least because these phenomena benefit from going beyond individual study design. We introduce the concept of macro-iterativity which involves multiple iterations that move between, and link across, a set of research cycles. We offer a multi-arc research design that comprises the discovery arc and extension arc and three extension logics through which scholars can combine these arcs of inquiry in a coherent way. Based on this research design, we develop a roadmap that guides scholars through the four steps of how to engage in multi-arc research along with the main techniques and outputs. We argue that a multi-arc design supports the move toward more generative theorizing that is required for researching problems dealing with the complex issues and big questions of our time.PostprintPeer reviewe

Multi-theoretic approaches to understanding the science classroom

Multi-camera on-site video technology and post-lesson video stimulated interviews were used in a purposefully inclusive research design to generate a complex data set amenable to parallel analyses from several complementary theoretical perspectives. The symposium reports the results of parallel analyses employing positioning theory, systemic functional linguistics, distributed cognition and representational analysis of the same nine-lesson sequence in a single science classroom during the teaching of a single topic: States of Matter. Without contesting the coherence and value of a well-constructed mono-theoretic research study, the argument is made that all such studies present an inevitably partial account of a setting as complex as the science classroom: privileging some aspects and ignoring others. In this symposium, the first presentation examined the rationale for multi-theoretic research designs, highlighting the dangers of the circular amplification of those constructs predetermined by the choice of theory and outlining the intended benefits of multi-theoretic designs that offer less partial accounts of classroom practice. The second and third presentations reported the results of analyses of the same lesson sequence on the topic “states of matter” using the analytical perspectives of positioning theory and systemic functional linguistics. The final presentation reported the comparative analysis of student learning of density over the same three lessons from distributed cognition and representational perspectives. The research design promoted a form of reciprocal interrogation, where the analyses provided insights into classroom practice and the comparison of the analyses facilitated the reflexive interrogation of the selected theories, while also optimally anticipating the subsequent synthesis of the interpretive accounts generated by each analysis of the same setting for the purpose of informing instructional advocacy

Site-specific covalent labeling of His-tag fused proteins with N-acyl-N-alkyl sulfonamide reagent

The ability to incorporate a desired functionality into proteins of interest in a site-specific manner can provide powerful tools for investigating biological systems and creating therapeutic conjugates. However, there are not any universal methods that can be applied to all proteins, and it is thus important to explore the chemical strategy for protein modification. In this paper, we developed a new reactive peptide tag/probe pair system for site-specific covalent protein labeling. This method relies on the recognition-driven reaction of a peptide tag and a molecular probe, which comprises the lysine-containing short histidine tag (KH6 or H6K) and a binuclear nickel (II)- nitrilotriacetic acid (Ni²⁺-NTA) complex probe containing a lysine-reactive N-acyl-N-alkyl sulfonamide (NASA) group. The selective interaction of the His-tag and Ni²⁺–NTA propeles a rapid nucleophilic reaction between a lysine residue of the tag and the electrophilic NASA group of the probe by the proximity effect, resulting in the tag-site-specific functionalization of proteins. We characterized the reactive profile and site-specificity of this method using model peptides and proteins in vitro, and demonstrated the general utility for production of a nanobody-chemical probe conjugate without compromising its binding ability

Genome sequence of Desulfitobacterium hafniense DCB-2, a Gram-positive anaerobe capable of dehalogenation and metal reduction

<p>Abstract</p> <p>Background</p> <p>The genome of the Gram-positive, metal-reducing, dehalorespiring <it>Desulfitobacterium hafniense </it>DCB-2 was sequenced in order to gain insights into its metabolic capacities, adaptive physiology, and regulatory machineries, and to compare with that of <it>Desulfitobacterium hafniense </it>Y51, the phylogenetically closest strain among the species with a sequenced genome.</p> <p>Results</p> <p>The genome of <it>Desulfitobacterium hafniense </it>DCB-2 is composed of a 5,279,134-bp circular chromosome with 5,042 predicted genes. Genome content and parallel physiological studies support the cell's ability to fix N₂and CO₂, form spores and biofilms, reduce metals, and use a variety of electron acceptors in respiration, including halogenated organic compounds. The genome contained seven reductive dehalogenase genes and four nitrogenase gene homologs but lacked the Nar respiratory nitrate reductase system. The <it>D. hafniense </it>DCB-2 genome contained genes for 43 RNA polymerase sigma factors including 27 sigma-24 subunits, 59 two-component signal transduction systems, and about 730 transporter proteins. In addition, it contained genes for 53 molybdopterin-binding oxidoreductases, 19 flavoprotein paralogs of the fumarate reductase, and many other FAD/FMN-binding oxidoreductases, proving the cell's versatility in both adaptive and reductive capacities. Together with the ability to form spores, the presence of the CO₂-fixing Wood-Ljungdahl pathway and the genes associated with oxygen tolerance add flexibility to the cell's options for survival under stress.</p> <p>Conclusions</p> <p><it>D. hafniense </it>DCB-2's genome contains genes consistent with its abilities for dehalogenation, metal reduction, N₂and CO₂fixation, anaerobic respiration, oxygen tolerance, spore formation, and biofilm formation which make this organism a potential candidate for bioremediation at contaminated sites.</p

Pancreas-Targeted NIR Fluorophores for Dual-Channel Image-Guided Abdominal Surgery

Objective: Pancreas-related complications are some of the most serious ones in abdominal surgery. The goal of this study was to develop and validate novel near-infrared (NIR) fluorophores that would enable real-time pancreas imaging to avoid the intraoperative pancreatic injury. Design: After initial screening of a large NIR fluorophore library, the performance of 3 selected pancreas-targeted 700 nm NIR fluorophores, T700-H, T700-F, and MB, were quantified in mice, rats, and pigs. Dose ranging using 25 and 100 nmol, and 2.5 μmol of T700-F, and its imaging kinetics over a 4 h period were tested in each species. Three different 800 nm NIR fluorophores were employed for dual-channel FLARE™ imaging in pigs: 2 μmol of ZW800-1 for vessels and kidney, 1 μmol of ZW800-3C for lymph nodes, and 2 μmol of ESNF31 for adrenal glands. Results: T700-F demonstrated the highest signal to background ratio (SBR), with peak SBR at 4 h postinjection in mice. In pigs, T700-F produced an SBR ≥ 2 against muscle, spleen, and lymph nodes for up to 8 h after a single intravenous injection. The combination of T700-F with each 800 nm NIR fluorophore provided simultaneous dual-channel intraoperative imaging of pancreas with surrounding organs in real time. Conclusion: Pancreas-targeted NIR fluorophores combined with the FLARE dual-channel imaging system enable the real-time intraoperative pancreas imaging which helps surgeons perform safer and more curative abdominal surgeries

Microcarrier-Based Expansion of Adult Murine Side Population Stem Cells

The lack of reliable methods to efficiently isolate and propagate stem cell populations is a significant obstacle to the advancement of cell-based therapies for human diseases. One isolation technique is based on efflux of the fluorophore Hoechst 33342. Using fluorescence-activated cell sorting (FACS), a sub-population containing adult stem cells has been identified in a multitude of tissues in every mammalian species examined. These rare cells are referred to as the ‘side population’ or SP due to a distinctive FACS profile that results from weak staining by Hoechst dye. Although the SP contains multi-potent cells capable of differentiating toward hematopoietic and mesenchymal lineages; there is currently no method to efficiently expand them. Here, we describe a spinner-flask culture system containing C2C12 myoblasts attached to spherical microcarriers that act to support the growth of non-adherent, post-natal murine skeletal muscle and bone marrow SP cells. Using FACS and hemocytometry, we show expansion of unfractionated EGFP+ SP cells over 6 wks. A significant number of these cells retain characteristics of freshly-isolated, unfractionated SP cells with respect to protein expression and dye efflux capacity. Expansion of the SP will permit further study of these heterogeneous cells and determine their therapeutic potential for regenerative and reparative therapies

Comparison of the New-Generation Self-Expanding NAVITOR Transcatheter Heart Valve with Its Predecessor, the PORTICO, in Severe Native Aortic Valve Stenosis

Background Third-generation transcatheter heart valves (THVs) are designed to improve outcomes. Data on the new intra-annular self-expanding NAVITOR are scarce. Aims The aim of this analysis was to compare outcomes between the PORTICO and the NAVITOR systems. Methods Data from 782 patients with severe native aortic stenosis treated with PORTICO (n = 645) or NAVITOR (n = 137) from 05/2012 to 09/2022 were evaluated. The clinical and hemodynamic outcomes of 276 patients (PORTICO, n = 139; NAVITOR, n = 137) were evaluated according to VARC-3 recommendations. Results Rates of postprocedural more-than-mild paravalvular leakage (PVL) were significantly lower for NAVITOR than for PORTICO (7.2% vs. 1.5%, p = 0.041). In addition, severe bleeding rates (27.3% vs. 13.1%, p = 0.005) and major vascular complications (5.8% vs. 0.7%, p = 0.036) were lower in the NAVITOR group. The mean gradients (7 vs. 8 mmHg, p = 0.121) and calculated aortic valve areas (1.90 cm2 vs. 1.99 cm2, p = 0.235) were comparable. Rates of PPI were similarly high in both groups (15.3 vs. 21.6, p = 0.299). Conclusions The NAVITOR demonstrated favorable in-hospital procedural outcome data, with lower rates of relevant PVL, major vascular complications, and severe bleeding than its predecessor the PORTICO and preserved favorable hemodynamic outcomes

Transcriptome analysis of controlled and therapy-resistant childhood asthma reveals distinct gene expression profiles

Background: Children with problematic severe asthma have poor disease control despite high doses of inhaled corticosteroids and additional therapy, leading to personal suffering, early deterioration of lung function, and significant consumption of health care resources. If no exacerbating factors, such as smoking or allergies, are found after extensive investigation, these children are given a diagnosis of therapy-resistant (or therapy-refractory) asthma (SA). Objective: We sought to deepen our understanding of childhood SA by analyzing gene expression and modeling the underlying regulatory transcription factor networks in peripheral blood leukocytes. Methods: Gene expression was analyzed by using Cap Analysis of Gene Expression in children with SA (n = 13), children with controlled persistent asthma (n = 15), and age-matched healthy control subjects (n = 9). Cap Analysis of Gene Expression sequencing detects the transcription start sites of known and novel mRNAs and noncoding RNAs. Results: Sample groups could be separated by hierarchical clustering on 1305 differentially expressed transcription start sites, including 816 known genes and several novel transcripts. Ten of 13 tested novel transcripts were validated by means of RT-PCR and Sanger sequencing. Expression of RAR-related orphan receptor A (RORA), which has been linked to asthma in genome-wide association studies, was significantly upregulated in patients with SA. Gene network modeling revealed decreased glucocorticoid receptor signaling and increased activity of the mitogen-activated protein kinase and Jun kinase cascades in patients with SA. Conclusion: Circulating leukocytes from children with controlled asthma and those with SA have distinct gene expression profiles, demonstrating the possible development of specific molecular biomarkers and supporting the need for novel therapeutic approaches.Peer reviewe

Divergent Serpentoviruses in Free-Ranging Invasive Pythons and Native Colubrids in Southern Florida, United States

Burmese python (Python bivittatus) is an invasive snake that has significantly affected ecosystems in southern Florida, United States. Aside from direct predation and competition, invasive species can also introduce nonnative pathogens that can adversely affect native species. The subfamily Serpentovirinae (order Nidovirales) is composed of positive-sense RNA viruses primarily found in reptiles. Some serpentoviruses, such as shingleback nidovirus, are associated with mortalities in wild populations, while others, including ball python nidovirus and green tree python nidovirus can be a major cause of disease and mortality in captive animals. To determine if serpentoviruses were present in invasive Burmese pythons in southern Florida, oral swabs were collected from both free-ranging and long-term captive snakes. Swabs were screened for the presence of serpentovirus by reverse transcription PCR and sequenced. A total serpentovirus prevalence of 27.8% was detected in 318 python samples. Of the initial swabs from 172 free-ranging pythons, 42 (24.4%) were positive for multiple divergent viral sequences comprising four clades across the sampling range. Both sex and snout-vent length were statistically significant factors in virus prevalence, with larger male snakes having the highest prevalence. Sampling location was statistically significant in circulating virus sequence. Mild clinical signs and lesions consistent with serpentovirus infection were observed in a subset of sampled pythons. Testing of native snakes (n = 219, 18 species) in part of the python range found no evidence of python virus spillover; however, five individual native snakes (2.3%) representing three species were PCR positive for unique, divergent serpentoviruses. Calculated pairwise uncorrected distance analysis indicated the newly discovered virus sequences likely represent three novel genera in the subfamily Serpentovirinae. This study is the first to characterize serpentovirus in wild free-ranging pythons or in any free-ranging North America reptile. Though the risk these viruses pose to the invasive and native species is unknown, the potential for spillover to native herpetofauna warrants further investigation