Association of dexmedetomidine use with haemodynamics, postoperative recovery, and cost in paediatric anaesthesia: a hospital registry study.

BACKGROUND: Dexmedetomidine utilisation in paediatric patients is increasing. We hypothesised that intraoperative use of dexmedetomidine in children is associated with longer postanaesthesia care unit length of stay, higher healthcare costs, and side-effects. METHODS: We analysed data from paediatric patients (aged 0-12 yr) between 2016 and 2021 in the Bronx, NY, USA. We matched our cohort with the Healthcare Cost and Utilization Project-Kids' Inpatient Database (HCUP-KID). RESULTS: Among 18 104 paediatric patients, intraoperative dexmedetomidine utilisation increased from 51.7% to 85.7% between 2016 and 2021 (P<0.001). Dexmedetomidine was dose-dependently associated with a longer postanaesthesia care unit length of stay (adjusted absolute difference [ADadj] 19.7 min; 95% confidence interval [CI]: 18.0-21.4 min; P<0.001, median length of stay of 122 vs 98 min). The association was magnified in children aged ≤2 yr undergoing short (≤60 min) ambulatory procedures (ADadj 33.3 min; 95% CI: 26.3-40.7 min; P<0.001; P-for-interaction <0.001). Dexmedetomidine was associated with higher total hospital costs of USD 1311 (95% CI: USD 835-1800), higher odds of intraoperative mean arterial blood pressure below 55 mm Hg (adjusted odds ratio [ORadj] 1.27; 95% CI: 1.16-1.39; P<0.001), and higher odds of heart rate below 100 beats min-1 (ORadj 1.32; 95% CI: 1.21-1.45; P<0.001), with no preventive effects on emergence delirium requiring postanaesthesia i.v. sedatives (ORadj 1.67; 95% CI: 1.04-2.68; P=0.034). CONCLUSIONS: Intraoperative use of dexmedetomidine is associated with unwarranted haemodynamic effects, longer postanaesthesia care unit length of stay, and higher costs, without preventive effects on emergence delirium.

Lysozyme-Sucrose Interactions in the Solid State: Glass Transition, Denaturation, and the Effect of Residual Water.

The freeze-drying of proteins, along with excipients, offers a solution for increasing the shelf-life of protein pharmaceuticals. Using differential scanning calorimetry, thermogravimetric analysis, sorption calorimetry, and synchrotron small-angle X-ray scattering (SAXS), we have characterized the properties at low (re)hydration levels of the protein lysozyme, which was freeze-dried together with the excipient sucrose. We observe that the residual moisture content in these samples increases with the addition of lysozyme. This results from an increase in equilibrium water content with lysozyme concentration at constant water activity. Furthermore, we also observed an increase in the glass transition temperature (Tg) of the mixtures with increasing lysozyme concentration. Analysis of the heat capacity step of the mixtures indicates that lysozyme does not participate in the glass transition of the sucrose matrix; as a result, the observed increase in the Tg of the mixtures is the consequence of the confinement of the amorphous sucrose domains in the interstitial space between the lysozyme molecules. Sorption calorimetry experiments demonstrate that the hydration behavior of this formulation is similar to that of the pure amorphous sucrose, while the presence of lysozyme only shifts the sucrose transitions. SAXS analysis of amorphous lysozyme-sucrose mixtures and unfolding of lysozyme in this environment show that prior to unfolding, the size and shape of lysozyme in a solid sucrose matrix are consistent with its native state in an aqueous solution. The results obtained from our study will provide a better understanding of the low hydration behavior of protein-excipient mixtures and support the improved formulation of biologics.

Preoperative Treatment of Severe Diabetes Mellitus and Hypertension Mitigates Healthcare Disparities and Prevents Adverse Postoperative Discharge to a Nursing Home.

OBJECTIVE: To evaluate whether patients of Black race are at higher risk of adverse postoperative discharge to a nursing home, and if a higher prevalence of severe diabetes mellitus and hypertension are contributing. BACKGROUND: It is unclear whether a patient's race predicts adverse discharge to a nursing home after surgery, and if preexisting diseases are contributing. METHODS: A total of 368,360 adults undergoing surgery between 2007 and 2020 across 2 academic healthcare networks in New England were included. Patients of self-identified Black or White race were compared. The primary outcome was postoperative discharge to a nursing facility. Mediation analysis was used to examine the impact of preexisting severe diabetes mellitus and hypertension on the primary association. RESULTS: In all, 10.3% (38,010/368,360) of patients were Black and 26,434 (7.2%) patients were discharged to a nursing home. Black patients were at increased risk of postoperative discharge to a nursing facility (adjusted absolute risk difference: 1.9%; 95% confidence interval: 1.6%-2.2%; P <0.001). A higher prevalence of preexisting severe diabetes mellitus and hypertension in Black patients mediated 30.2% and 15.6% of this association. Preoperative medication-based treatment adherent to guidelines in patients with severe diabetes mellitus or hypertension mitigated the primary association ( P -for-interaction <0.001). The same pattern of effect mitigation by pharmacotherapy was observed for the endpoint 30-day readmission. CONCLUSIONS: Black race was associated with postoperative discharge to a nursing facility compared to White race. Optimized preoperative assessment and treatment of diabetes mellitus and hypertension improves surgical outcomes and provides an opportunity to the surgeon to help eliminate healthcare disparities.

Artificial Intelligence in Fracture Detection: A Systematic Review and Meta-Analysis.

Background Patients with fractures are a common emergency presentation and may be misdiagnosed at radiologic imaging. An increasing number of studies apply artificial intelligence (AI) techniques to fracture detection as an adjunct to clinician diagnosis. Purpose To perform a systematic review and meta-analysis comparing the diagnostic performance in fracture detection between AI and clinicians in peer-reviewed publications and the gray literature (ie, articles published on preprint repositories). Materials and Methods A search of multiple electronic databases between January 2018 and July 2020 (updated June 2021) was performed that included any primary research studies that developed and/or validated AI for the purposes of fracture detection at any imaging modality and excluded studies that evaluated image segmentation algorithms. Meta-analysis with a hierarchical model to calculate pooled sensitivity and specificity was used. Risk of bias was assessed by using a modified Prediction Model Study Risk of Bias Assessment Tool, or PROBAST, checklist. Results Included for analysis were 42 studies, with 115 contingency tables extracted from 32 studies (55 061 images). Thirty-seven studies identified fractures on radiographs and five studies identified fractures on CT images. For internal validation test sets, the pooled sensitivity was 92% (95% CI: 88, 93) for AI and 91% (95% CI: 85, 95) for clinicians, and the pooled specificity was 91% (95% CI: 88, 93) for AI and 92% (95% CI: 89, 92) for clinicians. For external validation test sets, the pooled sensitivity was 91% (95% CI: 84, 95) for AI and 94% (95% CI: 90, 96) for clinicians, and the pooled specificity was 91% (95% CI: 81, 95) for AI and 94% (95% CI: 91, 95) for clinicians. There were no statistically significant differences between clinician and AI performance. There were 22 of 42 (52%) studies that were judged to have high risk of bias. Meta-regression identified multiple sources of heterogeneity in the data, including risk of bias and fracture type. Conclusion Artificial intelligence (AI) and clinicians had comparable reported diagnostic performance in fracture detection, suggesting that AI technology holds promise as a diagnostic adjunct in future clinical practice. Clinical trial registration no. CRD42020186641 © RSNA, 2022 Online supplemental material is available for this article. See also the editorial by Cohen and McInnes in this issue.

A setup for millisecond time-resolved X-ray solution scattering experiments at the CoSAXS beamline at the MAX†IV Laboratory.

The function of biomolecules is tightly linked to their structure, and changes therein. Time-resolved X-ray solution scattering has proven a powerful technique for interrogating structural changes and signal transduction in photoreceptor proteins. However, these only represent a small fraction of the biological macromolecules of interest. More recently, laser-induced temperature jumps have been introduced as a more general means of initiating structural changes in biomolecules. Here we present the development of a setup for millisecond time-resolved X-ray solution scattering experiments at the CoSAXS beamline, primarily using infrared laser light to trigger a temperature increase, and structural changes. We present results that highlight the characteristics of this setup along with data showing structural changes in lysozyme caused by a temperature jump. Further developments and applications of the setup are also discussed.

Assessment of humoral and cellular immune responses to SARS CoV-2 vaccination (BNT162b2) in immunocompromised renal allograft recipients.

BACKGROUND: Assessing the composition of immune responses to SARS-CoV-2 vaccines is critical for our understanding of protective immunity, especially for immune compromised patients. The Pfizer (BNT162b2) vaccination showed >90% efficacy in protecting individuals from infection. However, these studies did not examine responses in immunocompromised kidney transplant patients (KT). Subsequent reports in KT have shown severe deficiencies in Spike-specific immunoglobin G (IgG) responses prompting booster vaccinations, but a broader understanding of T-cell immunity to vaccinating is lacking. METHODS: We examined SARS-CoV-2 Spike IgG and CD4+/CD8+ Spike-specific T-cell responses in 61 KT patients maintained on different immunosuppressive protocols (ISP) (Tac + mycophenolate mofetil + prednisone) versus (belatacept + MMF + prednisone) and compared to 41 healthy controls. We also examined cytomegalovirus-cytotoxic T-cell responses (CMV-Tc) in both groups to assess T-cell memory. RESULTS: Our data confirmed poor Spike IgG responses in vaccinated KT patients with both ISP (21% demonstrating Spike IgG 1M post-second dose of BNT162b2 vs. 93% in controls). However, 35% of Spike IgG (-) patients demonstrated CD4+ and/or CD8+ T-cell responses. All but one CMV-IgG+ patient demonstrated good CMV-Tc responses. No differences in T-cell immunity by ISP were seen. CONCLUSION: Immunocompromised KT recipients showed severe defects in humoral and T-cell immune response after vaccination. No differences in immune responses to SARS-CoV-2 Spike peptides were observed in KT patients by ISP post-vaccination. The detection of Spike-specific T-cell immunity in the absence of Spike IgG suggests that vaccination in immunocompromised KT patients may provide partial immunity, although not preventing infection, T-cell immunity may limit its severity.

The Throat Pack Debate: A Review of Current Practice in UK and Ireland Cleft Centers.

INTRODUCTION: The use of throat packs during oropharyngeal surgery has long been a topic of debate among cleft surgeons. The advantage of inserting an absorbent tulle within the pharynx must be weighed against the risk of unintended retention postoperatively. Despite safety check mechanisms in place, retention may occur with potentially life-threatening consequences. We present a comprehensive review of throat pack use in all cleft units within the United Kingdom and Ireland. METHODS: All 20 cleft surgery units in the United Kingdom and Ireland were surveyed on their use of throat packs in children aged 6 months to 2 years undergoing elective cleft palate surgery. RESULTS: The response rate to the survey was 100%. Seventy-five percent of units currently use throat packs; in 40%, they are used in addition to cuffed endotracheal tubes (ETTs). Inclusion of the throat pack in the surgical swab count was perceived as the safest mechanism employed to avoid retention. 26.1% of respondents were aware of at least 1 incident of pack retention in their unit. DISCUSSION/CONCLUSION: The reported UK and Irish experience demonstrates that three-quarters of units routinely use packs. Notably, a quarter of respondents to the survey have experience of an incident of throat pack retention. Nevertheless, the majority of respondents considered the perceived risk of retaining a pack to be low. The growing use of microcuffed ETTs in UK cleft units paired with a low incidence of perioperative complications when a throat pack is not introduced might prompt cleft surgeons to review routine pharyngeal packing.

Measurement of the coherent beam properties at the CoSAXS beamline.

The CoSAXS beamline at the MAX IV Laboratory is a modern multi-purpose (coherent) small-angle X-ray scattering (CoSAXS) instrument, designed to provide intense and optionally coherent illumination at the sample position, enabling coherent imaging and speckle contrast techniques. X-ray tracing simulations used to design the beamline optics have predicted a total photon flux of 1012-1013 photons s-1 and a degree of coherence of up to 10% at 7.1 keV. The normalized degree of coherence and the coherent flux of this instrument were experimentally determined using the separability of a ptychographic reconstruction into multiple mutually incoherent modes and thus the Coherence in the name CoSAXS was verified. How the beamline can be used both for coherent imaging and XPCS measurements, which both heavily rely on the degree of coherence of the beam, was demonstrated. These results are the first experimental quantification of coherence properties in a SAXS instrument at a fourth-generation synchrotron light source.

Hydration-Induced Structural Changes in the Solid State of Protein: A SAXS/WAXS Study on Lysozyme.

The stability of biologically produced pharmaceuticals is the limiting factor to various applications, which can be improved by formulation in solid-state forms, mostly via lyophilization. Knowledge about the protein structure at the molecular level in the solid state and its transition upon rehydration is however scarce, and yet it most likely affects the physical and chemical stability of the biological drug. In this work, synchrotron small- and wide-angle X-ray scattering (SWAXS) are used to characterize the structure of a model protein, lysozyme, in the solid state and its structural transition upon rehydration to the liquid state. The results show that the protein undergoes distortion upon drying to adopt structures that can continuously fill the space to remove the protein-air interface that may be formed upon dehydration. Above a hydration threshold of 35 wt %, the native structure of the protein is recovered. The evolution of SWAXS peaks as a function of water content in a broad range of concentrations is discussed in relation to the structural changes in the protein. The findings presented here can be used for the design and optimization of solid-state formulations of proteins with improved stability.

Structural Diversity of Native Major Ampullate, Minor Ampullate, Cylindriform, and Flagelliform Silk Proteins in Solution.

The foundations of silk spinning, the structure, storage, and activation of silk proteins, remain highly debated. By combining solution small-angle neutron and X-ray scattering (SANS and SAXS) alongside circular dichroism (CD), we reveal a shape anisotropy of the four principal native spider silk feedstocks from Nephila edulis. We show that these proteins behave in solution like elongated semiflexible polymers with locally rigid sections. We demonstrated that minor ampullate and cylindriform proteins adopt a monomeric conformation, while major ampullate and flagelliform proteins have a preference for dimerization. From an evolutionary perspective, we propose that such dimerization arose to help the processing of disordered silk proteins. Collectively, our results provide insights into the molecular-scale processing of silk, uncovering a degree of evolutionary convergence in protein structures and chemistry that supports the macroscale micellar/pseudo liquid crystalline spinning mechanisms proposed by the community.

On the Structure of Solid Lipid Nanoparticles.

Solid lipid nanoparticles (SLNs) have a crystalline lipid core which is stabilized by interfacial surfactants. SLNs are considered favorable candidates for drug delivery vehicles since their ability to store and release organic molecules can be tailored through the identity of the lipids and surfactants used. When stored, polymorphic transitions in the core of drug-loaded SLNs lead to the premature release of drug molecules. Significant experimental studies have been conducted with the aim of investigating the physicochemical properties of SLNs, however, no molecular scale investigations have been reported on the behaviors that drive SLN formation and their polymorphic transitions. A combination of small angle neutron scattering and all-atom molecular dynamics simulations is therefore used to yield a detailed atomistic description of the internal structure of an SLN comprising triglyceride, tripalmitin, and the nonionic surfactant, Brij O10 (C18:1 E10 ). The molecular scale mechanisms by which the surfactants stabilize the crystalline structure of the SLN lipid core are uncovered. By comparing these results to simulated liquid and solid aggregates of tripalmitin lipids, how the morphology of the lipids vary between these systems is demonstrated providing further insight into the mechanisms that control drug encapsulation and release from SLNs.

Dose-dependent acute liver injury with hypersensitivity features in humans due to a novel microsomal prostaglandin E synthase 1 inhibitor.

AIMS: LY3031207, a novel microsomal prostaglandin E synthase 1 inhibitor, was evaluated in a multiple ascending dose study after nonclinical toxicology studies and a single ascending dose study demonstrated an acceptable toxicity, safety and tolerability profile. METHODS: Healthy subjects were randomized to receive LY3031207 (25, 75 and 275 mg), placebo or celecoxib (400 mg) once daily for 28 days. The safety, tolerability and pharmacokinetic and pharmacodynamic profiles of LY3031207 were evaluated. RESULTS: The study was terminated when two subjects experienced drug-induced liver injury (DILI) after they had received 225 mg LY3031207 for 19 days. Liver biopsy from these subjects revealed acute liver injury with eosinophilic infiltration. Four additional DILI cases were identified after LY3031207 dosing had been stopped. All six DILI cases shared unique presentations of hepatocellular injury with hypersensitivity features and demonstrated a steep dose-dependent trend. Prompt discontinuation of the study drug and supportive medical care resulted in full recovery. Metabolites from metabolic activation of the imidazole ring were observed in plasma and urine samples from all subjects randomized to LY3031207 dosing. CONCLUSIONS: This study emphasized the importance of careful safety monitoring and serious adverse events management in phase I trials. Metabolic activation of the imidazole ring may be involved in the development of hepatotoxicity of LY3031207.

Neonatal Outcome of Babies Born to Women 40 Years and over at the University Hospital of the West Indies 2012-2013.

AIM: This article aims to determine neonatal outcome of babies born to women ≥40 years at the University Hospital of the West Indies. METHODS: This was a matched retrospective cohort study looking at the outcome of all babies born to women ≥40 years and control babies born to women aged 20-30 years at the University Hospital of the West Indies over a 2-year period. Maternal and neonatal demographic data and course of admission for admitted neonates were recorded. Descriptive analyses were performed. RESULTS: One hundred and ninety-eight neonates were born to women ≥40 years and 208 to their younger counterparts, M:F 1:1.2. There was no difference in the number of preterm or low birth weight infants, the number of neonates with a low 5 min Apgar score <7, the number of neonates admitted or the number of neonates who died between women ≥40 years and their younger counterparts (p > 0.05). CONCLUSION: No difference in adverse neonatal outcome was noted between women ≥40 years and their younger counterparts.

Rapid Identification of a Cooling Tower-Associated Legionnaires' Disease Outbreak Supported by Polymerase Chain Reaction Testing of Environmental Samples, New York City, 2014-2015.

We investigated an outbreak of eight Legionnaires' disease cases among persons living in an urban residential community of 60,000 people. Possible environmental sources included two active cooling towers (air-conditioning units for large buildings) <1 km from patient residences, a market misting system, a community-wide water system used for heating and cooling, and potable water. To support a timely public health response, we used real-time polymerase chain reaction (PCR) to identify Legionella DNA in environmental samples within hours of specimen collection. We detected L. pneumophila serogroup 1 DNA only at a power plant cooling tower, supporting the decision to order remediation before culture results were available. An isolate from a power plant cooling tower sample was indistinguishable from a patient isolate by pulsed-field gel electrophoresis, suggesting the cooling tower was the outbreak source. PCR results were available <1 day after sample collection, and culture results were available as early as 5 days after plating. PCR is a valuable tool for identifying Legionella DNA in environmental samples in outbreak settings.

TSLP or IL-7 provide an IL-7Rα signal that is critical for human B lymphopoiesis.

Thymic stromal lymphopoietin (TSLP) and IL-7 are cytokines that signal via the IL-7 receptor alpha (IL-7Rα) to exert both overlapping and unique functions during early stages of mouse B-cell development. In human B lymphopoiesis, the requirement for IL-7Rα signaling is controversial and the roles of IL-7 and TSLP are less clear. Here, we evaluated human B-cell production using novel in vitro and xenograft models of human B-cell development that provide selective IL-7 and human TSLP (hTSLP) stimulation. We show that in vitro human B-cell production is almost completely blocked in the absence of IL-7Rα stimulation, and that either TSLP or IL-7 can provide a signal critical for the production and proliferation of human CD19(+) PAX5(+) pro-B cells. Analysis of primary human bone marrow stromal cells shows that they express both IL-7 and TSLP, providing an in vivo source of these cytokines. We further show that the in vivo production of human pro-B cells under the influence of mouse IL-7 in a xenograft scenario is reduced by anti-IL-7 neutralizing antibodies, and that this loss can be restored by hTSLP at physiological levels. These data establish the importance of IL-7Rα mediated signals for normal human B-cell production.

Differences in the phenotypic effects of mutations in homologous MrpA and MrpD subunits of the multi-subunit Mrp-type Na+/H+ antiporter.

Mrp antiporters are the sole antiporters in the Cation/Proton Antiporter 3 family of transporter databases because of their unusual structural complexity, 6-7 hydrophobic proteins that function as a hetero-oligomeric complex. The two largest and homologous subunits, MrpA and MrpD, are essential for antiport activity and have direct roles in ion transport. They also show striking homology with proton-conducting, membrane-embedded Nuo subunits of respiratory chain complex I of bacteria, e.g., Escherichia coli. MrpA has the closest homology to the complex I NuoL subunit and MrpD has the closest homology to the complex I NuoM and N subunits. Here, introduction of mutations in MrpD, in residues that are also present in MrpA, led to defects in antiport function and/or complex formation. No significant phenotypes were detected in strains with mutations in corresponding residues of MrpA, but site-directed changes in the C-terminal region of MrpA had profound effects, showing that the MrpA C-terminal region has indispensable roles in antiport function. The results are consistent with a divergence in adaptations that support the roles of MrpA and MrpD in secondary antiport, as compared to later adaptations supporting homologs in primary proton pumping by the respiratory chain complex I.

FIRE - Flyby of Io with Repeat Encounter: A conceptual design for a New Frontiers mission to Io.

A conceptual design is presented for a low complexity, heritage-based flyby mission to Io, Jupiter's innermost Galilean satellite and the most volcanically active body in the Solar System. The design addresses the 2011 Decadal Surveys recommendation for a New Frontiers class mission to Io and is based upon the result of the June 2012 NASA-JPL Planetary Science Summer School. A science payload is proposed to investigate the link between the structure of Io's interior, it's volcanic activity, it's surface composition, and it's tectonics. A study of Io's atmospheric processes and Io's role in the Jovian magnetosphere is also planned. The instrument suite includes a visible/near IR imager, a magnetic field and plasma suite, a dust analyzer and a gimbaled high gain antenna to perform radio science investigations. Payload activity and spacecraft operations would be powered by three Advanced Stirling Radioisotope Generators (ASRG). The primary mission includes 10 flybys with close-encounter altitudes as low as 100 km. The mission risks are mitigated by ensuring that relevant components are radiation tolerant and by using redundancy and flight-proven parts in the design. The spacecraft would be launched on an Atlas V rocket with a delta-v of 1.3 km/s. Three gravity assists (Venus, Earth, Earth) would be used to reach the Jupiter system in a 6-year cruise. The resulting concept demonstrates the rich scientific return of a flyby mission to Io.

Identification of a Hematopoietic Cell Dedifferentiation-Inducing Factor.

It has long been realized that hematopoietic cells may have the capacity to trans-differentiate into non-lymphohematopoietic cells under specific conditions. However, the mechanisms and the factors for hematopoietic cell trans-differentiation remain unknown. In an in vitro culture system, we found that using a conditioned medium from proliferating fibroblasts can induce a subset of hematopoietic cells to become adherent fibroblast-like cells (FLCs). FLCs are not fibroblasts nor other mesenchymal stromal cells, based on their expression of type-1 collagen, and other stromal cell marker genes. To identify the active factors in the conditioned medium, we cultured fibroblasts in a serum-free medium and collected it for further purification. Using the fractions from filter devices of different molecular weight cut-offs, and ammonium sulfate precipitation collected from the medium, we found the active fraction is a protein. We then purified this fraction by using fast protein liquid chromatography (FPLC) and identified it by mass spectrometer as macrophage colony-stimulating factor (M-CSF). The mechanisms of M-CSF-inducing trans-differentiation of hematopoietic cells seem to involve a tyrosine kinase signalling pathway and its known receptor. The FLCs express a number of stem cell markers including SSEA-1 and -3, OCT3/4, NANOG, and SOX2. Spontaneous and induced differentiation experiments confirmed that FLCs can be further differentiated into cell types of three germ layers. These data indicate that hematopoietic cells can be induced by M-CSF to dedifferentiate to multipotent stem cells. This study also provides a simple method to generate multipotent stem cells for clinical applications.

A novel xenograft model to study the role of TSLP-induced CRLF2 signals in normal and malignant human B lymphopoiesis.

Thymic stromal lymphopoietin (TSLP) stimulates in-vitro proliferation of human fetal B-cell precursors. However, its in-vivo role during normal human B lymphopoiesis is unknown. Genetic alterations that cause overexpression of its receptor component, cytokine receptor-like factor 2 (CRLF2), lead to high-risk B-cell acute lymphoblastic leukemia implicating this signaling pathway in leukemogenesis. We show that mouse thymic stromal lymphopoietin does not stimulate the downstream pathways (JAK/STAT5 and PI3K/AKT/mTOR) activated by the human cytokine in primary high-risk leukemia with overexpression of the receptor component. Thus, the utility of classic patient-derived xenografts for in-vivo studies of this pathway is limited. We engineered xenograft mice to produce human thymic stromal lymphopoietin (+T mice) by injection with stromal cells transduced to express the cytokine. Control (-T) mice were produced using stroma transduced with control vector. Normal levels of human thymic stromal lymphopoietin were achieved in sera of +T mice, but were undetectable in -T mice. Patient-derived xenografts generated from +T as compared to -T mice showed a 3-6-fold increase in normal human B-cell precursors that was maintained through later stages of B-cell development. Gene expression profiles in high-risk B-cell acute lymphoblastic leukemia expanded in +T mice indicate increased mTOR pathway activation and are more similar to the original patient sample than those from -T mice. +T/-T xenografts provide a novel pre-clinical model for understanding this pathway in B lymphopoiesis and identifying treatments for high-risk B-cell acute lymphoblastic leukemia with overexpression of cytokine-like factor receptor 2.

Charge-Mediated Localization of Conjugated Polythiophenes in Zwitterionic Model Cell Membranes.

The selective engineering of conjugated polyelectrolyte (CPE)-phospholipid interfaces is poised to play a key role in the design of advanced biomedical and biotechnological devices. Herein, we report a strategic study to investigate the relationship between the charge of the CPE side group and their association with zwitterionic phospholipid bilayers. The interaction of dipalmitoylphosphatidylcholine (DPPC) phospholipid vesicles with a series of poly(thiophene)s bearing zwitterionic, cationic, or anionic terminal groups (P3Zwit, P3TMAHT and P3Anionic, respectively) has been probed. Although all CPEs showed an affinity for the zwitterionic vesicles, the calculated partition coefficients determined using photoluminescence spectroscopy suggested preferential incorporation within the lipid bilayer in the order P3Zwit > P3Anionic ≫ P3TMAHT. The polarity probe Prodan was used to further qualify the position of the CPE inside the vesicle bilayers via Förster resonance energy transfer (FRET) studies. The varying proximity of the CPEs to Prodan was reflected in the Stern-Volmer quenching constants and decreased in the order P3Anionic > P3TMAHT ≫ P3Zwit. Dynamic light scattering measurements showed an increase in the hydrodynamic diameter of the DPPC vesicles upon addition of each poly(thiophene), but to the greatest extent for P3Anionic. Small-angle neutron scattering studies also revealed that P3Anionic specifically increased the thickness of the headgroup region of the phospholipid bilayer. Epifluorescence and atomic force microscopy imaging showed that P3TMAHT formed amorphous agglomerates on the vesicle surface, P3Zwit was buried throughout the bilayer, and P3Anionic formed a shell of protruding chains around the surface, which promoted vesicle fusion. The global data indicate three distinctive modes of interaction for the poly(thiophene)s within DPPC vesicles, whereby the nature of the association is ultimately controlled by the pendant charge group on each CPE chain. Our results suggest that charge-mediated self-assembly may provide a simple and effective route to design luminescent CPE probes capable of specific localization within phospholipid membranes.