STARTING VALUES FOR PROC MIXED WITH REPEATED MEASURES DATA

A major advantage of PROC MIXED for repeated measures data is that one could choose from many different correlated error models. However, MIXED uses default starting values that may cause difficulty obtaining REML estimates of the covariance parameters for several of the models available. This can take the form of excessively long run times or even failure to converge. We have written a program to obtain initial covariance parameter estimates that result in greatly improved performance of the REML algorithm. We will use two covariance models frequently of interest in animal health experiments, the first-order ante-dependence model [ANTE(l)] and the Toeplitz model with heterogeneous variances [TOEPH], to illustrate the use of our procedure

Retinal tissue engineering using mouse retinal progenitor cells and a novel biodegradable, thin-film poly(e-caprolactone) nanowire scaffold

Retinal progenitor cells (RPCs) can be combined with nanostructured polymer scaffolds to generate composite grafts in culture. One strategy for repair of diseased retinal tissue involves implantation of composite grafts of this type in the subretinal space. In the present study, mouse retinal progenitor cells (RPCs) were cultured on laminin-coated novel nanowire poly(e-caprolactone)(PCL) scaffolds, and the survival, differentiation, and migration of these cells into the retina of C57bl/6 and rhodospsin −/− mouse retinal explants and transplant recipients were analyzed. RPCs were cultured on smooth PCL and both short (2.5 μm) and long (27 μm) nanowire PCL scaffolds. Scaffolds with adherent mRPCs were then either co-cultured with, or transplanted to, wild-type and rhodopsin −/− mouse retina. Robust RPC proliferation on each type of PCL scaffold was observed. Immunohistochemistry revealed that RPCs cultured on nanowire scaffolds increased expression of mature bipolar and photoreceptor markers. Reverse transcription polymerase chain reaction revealed down-regulation of several early progenitor markers. PCL-delivered RPCs migrated into the retina of both wild-type and rhodopsin knockout mice. The results provide evidence that RPCs proliferate and express mature retinal proteins in response to interactions with nanowire scaffolds. These composite grafts allow for the migration and differentiation of new cells into normal and degenerated retina

Control of Neural Stem Cell Survival by Electroactive Polymer Substrates

Stem cell function is regulated by intrinsic as well as microenvironmental factors, including chemical and mechanical signals. Conducting polymer-based cell culture substrates provide a powerful tool to control both chemical and physical stimuli sensed by stem cells. Here we show that polypyrrole (PPy), a commonly used conducting polymer, can be tailored to modulate survival and maintenance of rat fetal neural stem cells (NSCs). NSCs cultured on PPy substrates containing different counter ions, dodecylbenzenesulfonate (DBS), tosylate (TsO), perchlorate (ClO4) and chloride (Cl), showed a distinct correlation between PPy counter ion and cell viability. Specifically, NSC viability was high on PPy(DBS) but low on PPy containing TsO, ClO4 and Cl. On PPy(DBS), NSC proliferation and differentiation was comparable to standard NSC culture on tissue culture polystyrene. Electrical reduction of PPy(DBS) created a switch for neural stem cell viability, with widespread cell death upon polymer reduction. Coating the PPy(DBS) films with a gel layer composed of a basement membrane matrix efficiently prevented loss of cell viability upon polymer reduction. Here we have defined conditions for the biocompatibility of PPy substrates with NSC culture, critical for the development of devices based on conducting polymers interfacing with NSCs

Biophysical mechanisms of single-cell interactions with microtopographical cues

Biophysical cues encoded in the extracellular matrix (ECM) are increasingly being explored to control cell behavior in tissue engineering applications. Recently, we showed that cell adhesion to microtopographical structures (“micropegs”) can suppress proliferation in a manner that may be blunted by inhibiting cellular contractility, suggesting that this effect is related to altered cell-scaffold mechanotransduction. We now directly investigate this possibility at the microscale through a combination of live-cell imaging, single-cell mechanics methods, and analysis of gene expression. Using time-lapse imaging, we show that when cells break adhesive contacts with micropegs, they form F-actin-filled tethers that extend and then rupture at a maximum, critical length that is greater than trailing-edge tethers observed on topographically flat substrates. This critical tether length depends on myosin activation, with inhibition of Rho-associated kinase abolishing topography-dependent differences in tether length. Using cellular de-adhesion and atomic force microscopy indentation measurements, we show that the micropegs enhance cell-scaffold adhesive interactions without changing whole-cell elasticity. Moreover, micropeg adhesion increases expression of specific mechanotransductive genes, including RhoA GTPase and myosin heavy chain II, and, in myoblasts, the functional marker connexin 43. Together, our data support a model in which microtopographical cues alter the local mechanical microenvironment of cells by modulating adhesion and adhesion-dependent mechanotransductive signaling

Treatment with acetaminophen/paracetamol or ibuprofen alleviates post-dose symptoms related to intravenous infusion with zoledronic acid 5 mg

Summary: Patients treated with intravenous zoledronic acid 5 mg for osteoporosis may experience post-dose influenza-like symptoms. Oral acetaminophen/paracetamol or ibuprofen administered 4 h post-infusion reduced the proportion of patients with increased oral temperature and worsening post-infusion symptom scores vs. placebo, thus providing an effective strategy for the treatment of such symptoms. Introduction: Once-yearly intravenous zoledronic acid 5 mg is a safe and effective treatment for postmenopausal osteoporosis. This study assessed whether transient influenza-like post-dose symptoms associated with intravenous infusion of zoledronic acid can be reduced by post-dose administration of acetaminophen/paracetamol or ibuprofen. Methods: In an international, multicenter, randomized, double-blind, double-dummy parallel-group study, bisphosphonate-naïve postmenopausal women with osteopenia (n = 481) were randomized to receive zoledronic acid 5 mg + acetaminophen/paracetamol (n = 135), ibuprofen (n = 137) or placebo (n = 137), or placebo + placebo (n = 72). Acetaminophen/paracetamol and ibuprofen were administered every 6 h for 3 days beginning 4 h post-infusion. Results: The proportion of patients with increased oral temperature (≥1°C above 37.5°C) and with worsening post-infusion symptom scores over 3 days was significantly lower in patients receiving ibuprofen (36.8% and 48.5%) or acetaminophen/paracetamol (37.3% and 46.3%) vs. those receiving placebo (63.5% and 75.9%, respectively; all p < 0.0001) compared with background rates of 11.1% and 16.7%, respectively, in the absence of any active treatment. Overall incidence of adverse events was comparable for patients receiving acetaminophen/paracetamol or ibuprofen. Conclusion: Oral acetaminophen/ paracetamol or ibuprofen effectively managed the transient influenza-like symptoms associated with zoledronic acid 5 mg. © 2011 International Osteoporosis Foundation and National Osteoporosis Foundation

Evolution of subject characteristics in FREEDOM and its extension for up to 8 years

Diabetes mellitus: pathophysiological changes and therap