Substrate mineralization stimulates focal adhesion contact redistribution and cell motility of bone marrow stromal cells

Understanding the mechanisms of substrate based control of cell function is critical to the design of biomaterials. Cells interact with their extracellular matrix through cell adhesion contacts. We have previously described the self assembly of bone-like mineral onto an organic template and have shown that these biomimetic surfaces lead to an increased volume fraction of bone regenerated in vivo . In the present study, we compared the distribution of cell adhesion contacts, cell spreading, and cell motility of murine bone marrow stromal cells (BMSC) on mineralized vs. nonmineralized substrates. We developed a new approach for quantification of cell-material interactions and demonstrated that cell adhesion contacts on mineralized substrates were distributed throughout the cell surface contacting the substrate, whereas on nonmineralized substrates cell adhesion contacts were present near the cell periphery. We propose that mineralized substrates stimulate the predominant expression of fibrillar contacts, and nonmineralized substrates stimulate expression of focal adhesion contacts. Cell motility assays with colloidal gold demonstrated a statistically significant decrease in the average phagokinetic index of migrating cells on mineralized vs. nonmineralized substrates after 90 min of cell seeding. We propose that the physical–chemical properties of the substrate, altered by mineralization, cause expression of specific types of cell contacts and, as a result, modify molecular mechanisms responsible for cell spreading, motility, and possibly differentiation. © 2006 Wiley Periodicals, Inc. J Biomed Mater Res, 2006Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/55848/1/30786_ftp.pd

Association of hydrophobically-modified poly(ethylene glycol) with fusogenic liposomes

AbstractWe present results on using cooperative interactions to shield liposomes by incorporating multiple hydrophobic anchoring sites on polyethylene glycol (PEG) polymers. The hydrophobically-modified PEGs (HMPEGs) are comb-graft polymers with strictly alternating monodisperse PEG blocks (Mw=6, 12, or 35 kDa) bonded to C18 stearylamide hydrophobes. Cooperativity is varied by changing the degree of oligomerization at a constant ratio of PEG to stearylamide. Fusogenic liposomes prepared from N-C12-DOPE:DOPC 7:3 (mol:mol) were equilibrated with HMPEGs. Affinity for polymer association to liposomes increases with the degree of oligomerization; equilibrium constants (given as surface coverage per equilibrium concentration of free polymer) for 6 kDa PEG increased from 6.1±0.8 (mg/m2)/(mg/ml) for 2.5 loops to 78.1±12.2 (mg/m2)/(mg/ml) for 13 loops. In contrast, the equilibrium constant for distearoylphosphatidylethanolamine-poly(ethylene glycol) (DSPE-PEG5k) was 0.4±0.1 (mg/m2)/(mg/ml).The multi-loop HMPEGs demonstrate higher levels of protection from complement binding than DSPE-PEG5k. Greater protection does not correlate with binding strength alone. The best shielding was by HMPEG6k-DP3 (with three 6 kDa PEG loops), suggesting that PEG chains with adequate surface mobility provide optimal protection from complement opsonization. Complement binding at 30 min and 12 h demonstrates that protection by multi-looped PEGs is constant whereas DSPE-PEG5k initially protects but presumably partitions off of the surface at longer times

WAVELET ESTIMATION USING BAYESIAN BASIS SELECTION AND BASIS AVERAGING

Wavelet shrinkage methods are widely recognized as a useful tool for non-parametric regression and signal recovery, while Bayesian approaches to choosing the shrinkage method in wavelet smoothing are known to be effective. In this paper we extend the Bayesian methodology to include choice among wavelet bases (and the Fourier basis), and averaging of the regression function estimates over different bases. This results in improved function estimates

Creating New β-Globin-Expressing Lentiviral Vectors by High-Resolution Mapping of Locus Control Region Enhancer Sequences.

Hematopoietic stem cell gene therapy is a promising approach for treating disorders of the hematopoietic system. Identifying combinations of cis-regulatory elements that do not impede packaging or transduction efficiency when included in lentiviral vectors has proven challenging. In this study, we deploy LV-MPRA (lentiviral vector-based, massively parallel reporter assay), an approach that simultaneously analyzes thousands of synthetic DNA fragments in parallel to identify sequence-intrinsic and lineage-specific enhancer function at near-base-pair resolution. We demonstrate the power of LV-MPRA in elucidating the boundaries of previously unknown intrinsic enhancer sequences of the human β-globin locus control region. Our approach facilitated the rapid assembly of novel therapeutic βAS3-globin lentiviral vectors harboring strong lineage-specific recombinant control elements capable of correcting a mouse model of sickle cell disease. LV-MPRA can be used to map any genomic locus for enhancer activity and facilitates the rapid development of therapeutic vectors for treating disorders of the hematopoietic system or other specific tissues and cell types

Pollution Abatement and International Self-Sufficiency

Dorfman (1973) anticipates increases in international trade when pollution abatement reduces damage to polluted industries. We simulate the effect of abatement with a Heckscher-Ohlin-Samuelson model of a production on production externality. Both countries are Pigouvian and two levels of abatement effectiveness are endogenized. Although more effective pollution abatement increases total world production of both goods, trade decreases as a proportion of total world production. Our results with possibly greater pollution abatement by larger countries are useful in explaining Rose's (1991) findings that post-1973 increases in real output for large countries are associated with declines in international trade.International TRade; Trade

A Truly Robust Signal Temporal Logic: Monitoring Safety Properties of Interacting Cyber-Physical Systems under Uncertain Observation

Signal Temporal Logic is a linear-time temporal logic designed for classifying the time-dependent signals originating from continuous-state or hybrid-state dynamical systems according to formal specifications. It has been conceived as a tool for systematizing the monitoring of cyber-physical systems, supporting the automatic translation of complex safety specifications into monitoring algorithms, faithfully representing their semantics. Almost all algorithms hitherto suggested do, however, assume perfect identity between the sensor readings, informing the monitor about the system state and the actual ground truth. Only recently have Visconti et al. addressed the issue of inexact measurements, taking up the simple model of interval-bounded per-sample error that is unrelated, in the sense of chosen afresh, across samples. We expand their analysis by decomposing the error into an unknown yet fixed offset and an independent per-sample error and show that in this setting, monitoring of temporal properties no longer coincides with collecting Boolean combinations of state predicates evaluated in each time instant over best-possible per-sample state estimates, but can be genuinely more informative in that it infers determinate truth values for monitoring conditions that interval-based evaluation remains inconclusive about. For the model-free as well as for the linear model-based case, we provide optimal evaluation algorithms based on affine arithmetic and SAT modulo theory, solving over linear arithmetic. The resulting algorithms provide conclusive monitoring verdicts in many cases where state estimations inherently remain inconclusive. In their model-based variants, they can simultaneously address the issues of uncertain sensing and partial observation

Parental strategies used in the family meal session of Family-Based Treatment adolescent anorexia nervosa : links with treatment outcomes

Examine relationships between parental mealtime strategies used in the family meal session of Family-Based Treatment (FBT) and adolescent outcomes at EOT (session 20). Method: Eighteen families with an adolescent receiving FBT-AN participated. Parental strategies during videoed family meals were assessed using a family mealtime coding system. Change scores were calculated for both adolescent %EBW and EDE scores. Results: Increased use of parental direct and non-direct eating prompts during the family meal was associated with greater adolescent weight gain at EOT. Use of parental mealtime strategies was not associated with any significant change in adolescent eating psychopathology at EOT. Discussion: Parental verbal eating prompts during the family meal may be effective in promoting short-term weight gain. During the family meal session, parents should be encouraged to maintain a direct focus on their adolescent child’s eating behaviour which may assist their child with food consumption and potential weight gain. Further research examining food-based interactions among parents and their adolescent child with AN is needed