Material Composition and Implantation Site Affect in vivo Device Degradation Rate.

Successful tissue engineering requires biomedical devices that initially stabilize wounds, then degrade as tissue is regenerated. However, the material degradation rates reported in literature are often conflicting. Incorporation of in situ monitoring functionality into implanted devices would allow real time assessment of degradation and potential failure. This necessitates introduction of contrast agent as most biomedical devices are composed of polymeric materials with no inherent contrast in medical imaging modalities. In the present study, computed tomography (CT)-visible radiopaque composites were created by adding 5-20wt% tantalum oxide (TaOx) nanoparticles into polymers with distinct degradation profiles: polycaprolactone (PCL), poly(lactide-co-glycolide) (PLGA) 85:15 and PLGA 50:50, representing slow, medium and fast degrading materials respectively. Radiopaque phantoms, mimicking porous tissue engineering devices, were implanted into mice intramuscularly or intraperitoneally, and monitored via CT over 20 weeks. Changes in phantom volume, including collapse and swelling, were visualized over time. Phantom degradation profile was determined by polymer matrix, regardless of nanoparticle addition and foreign body response was dictated by the implant site. In addition, degradation kinetics were significantly affected in mid-degrading materials, transitioning from linear degradation intramuscularly to exponential degradation intraperitoneally, due to differences in inflammatory responses and fluid flow. Nanoparticle excretion from degraded phantoms lagged behind polymer, and future studies will modulate nanoparticle clearance. Utilizing in situ monitoring, this study seeks to unify literature and facilitate better tissue engineering devices, by highlighting the relative effect of composition and implant site on important materials properties.

A comparison of smartphone and infrasound microphone data from a fuel air explosive and a high explosive.

For prompt detection of large (>1 kt) above-ground explosions, infrasound microphone networks and arrays are deployed at surveyed locations across the world. Denser regional and local networks are deployed for smaller explosions, however, they are limited in number and are often deployed temporarily for experiments. With the expanded interest in smaller yield explosions targeted at vulnerable areas such as population centers and key infrastructures, the need for more dense microphone networks has increased. An "attritable" (affordable, reusable, and replaceable) and flexible alternative can be provided by smartphone networks. Explosion signals from a fuel air explosive (thermobaric bomb) and a high explosive with trinitrotoluene equivalent yields of 6.35 and 3.63 kg, respectively, were captured on both an infrasound microphone and a network of smartphones. The resulting waveforms were compared in time, frequency, and time-frequency domains. The acoustic waveforms collected on smartphones produced a filtered explosion pulse due to the smartphone's diminishing frequency response at infrasound frequencies (<20 Hz) and was found difficult to be used with explosion characterization methods utilizing waveform features (peak overpressure, impulse, etc.). However, the similarities in time frequency representations and additional sensor inputs are promising for other explosion signal identification and analysis. As an example, a method utilizing the relative acoustic amplitudes for source localization using the smartphone sensor network is presented.

Discrimination of phosgene from cyanogen chloride in recovered chemical munitions using tagged neutron interrogation with high-resolution gamma-ray spectroscopy.

The associated particle (AP) technique has recently been used with a high-purity germanium γ-ray spectrometer to assess its capability to improve field identification of recovered chemical warfare (CW) materiel through prompt gamma-ray neutron activation analysis (PGNAA) measurements. A particularly challenging pair of CW agents commonly found in recovered munitions are phosgene (CG) and cyanogen chloride (CK), which have two of three elements in common, i.e. chlorine and carbon, but differ in the third being either oxygen or nitrogen. The detection of both latter elements is complicated by high oxygen concentration in the field environment which interferes with the small signal produced from the chemical agents. The matter is further complicated by the precautionary field practice of overpacking recovered munitions with vermiculite in larger steel multiple round containers (MRCs), which places additional oxygen-rich material in contact with the munition while further attenuating an already weak signal emitted from the munition center. This work reports quantitative results from realistic field measurements of CG and CK simulants in mock 4.2-inch (11 cm) mortar rounds overpacked with vermiculite in a large MRC. Results obtained with the AP technique are compared to those obtained with the traditional PGNAA approach for both overpacked- and bare-munition measurements. The AP technique is shown to provide a much more confident discrimination between the two chemicals, particularly for the more challenging field-relevant overpacked measurements, where a significant gain in sensitivity to all the key elements (chlorine, carbon, nitrogen and oxygen) is achieved.

Validation of a rapid enzyme immunoassay for the quantitation of retinol-binding protein to assess vitamin A status within populations.

OBJECTIVE: To compare the prevalence of vitamin A deficiency (VAD) among Cambodian preschool children as determined by the retinol-binding protein-enzyme immunoassay (RBP-EIA) and direct measurement of serum retinol by high-performance liquid chromatography (HPLC). SETTING AND SUBJECTS: Sera from 359 children were randomly selected from archived specimens collected in a national VAD prevalence survey in Cambodia. METHODS: Sera were first analyzed for retinol content by HPLC and then subjected to analysis using RBP-EIA to determine serum RBP concentrations. National Institute of Standards and Technology and control sera were used to ensure quality and accuracy for each set of analyses. To classify VAD, the same cutoff point of <0.70 micromol/l was employed for each indicator. RESULTS: Overall, the prevalence of VAD based on serum retinol was 22.3% (95% confidence interval (CI): 18.0, 26.6), whereas the RBP-EIA indicated a VAD prevalence of 20.9% (95% CI: 16.7, 25.1). A simple linear regression model indicated an R2 of 0.79, and a receiver operating curve analysis revealed an area under the curve of 0.92. CONCLUSIONS: We found no significant difference between the results of RBP-EIA compared to retinol analyzed by HPLC in estimating the prevalence of VAD. Use of the test could enable public health authorities to assess the extent of VAD and track progress in control programs in resource-poor settings.

Transplantation of porcine umbilical cord matrix cells into the rat brain.

Immune rejection of transplanted material is a potential complication of organ donation. In response to tissue transplantation, immune rejection has two components: a host defense directed against the grafted tissue and an immune response from the grafted tissue against the host (graft vs host disease). To treat immune rejection, transplant recipients are typically put on immunosuppression therapy. Complications may arise from immune suppression or from secondary effects of immunosuppression drugs. Our preliminary work indicated that stem cells may be xenotransplanted without immunosuppression therapy. Here, we investigated the survival of pig stem cells derived from umbilical cord mucous connective tissue (UCM) after transplantation into rats. Our data demonstrate that UCM cells survive at least 6 weeks without immune suppression of the host animals after transplantation into either the brain or the periphery. In the first experiment, UCM cells were transplanted into the rat brain and recovered in that tissue 2-6 weeks posttransplantation. At 4 weeks posttransplantation, the UCM cells engrafted into the brain along the injection tract. The cells were small and roughly spherical. The transplanted cells were positively immunostained using a pig-specific antibody for neuronal filament 70 (NF70). In contrast, 6 weeks posttransplantation, about 10% of the UCM cells that were recovered had migrated away from the injection site into the region just ventral to the corpus callosum; these cells also stained positively for NF70. In our second experiment, UCM cells that were engineered to constitutively express enhanced green fluorescent protein (eGFP) were transplanted. These cells were recovered 2-4 weeks after brain transplantation. Engrafted cells expressing eGFP and positively staining for NF70 were recovered. This finding indicates a potential for gene therapy. In the third experiment, to determine whether depositing the graft into the brain protected UCM cells from immune detection/clearance, UCM cells were injected into the tail vein and/or the semitendinosis muscle in a group of animals. UCM cells were recovered from the muscle or within the kidney 3 weeks posttransplantation. In control experiments, rat brains were injected with PKH 26-labeled UCM cells that had been lysed by repeated sonic disruption. One and 2 weeks following injection, no PKH 26-labeled neurons or glia were observed. Taken together, these data indicate that UCM cells can survive xenotransplantation and that a subset of the UCM cells respond to local signals to differentiate along a neural lineage.

The relationship between cemental caries, oral hygiene status and fermentable carbohydrate intake.

Two groups of patients were evaluated for the presence of active, restored, and recurrent root surface caries. One group of 120 subjects had received treatment for moderate to severe periodontitis. The second group consisted of 124 subjects who were affected by moderate to severe periodontitis but had received no treatment. The two groups were also evaluated for amounts of recession, pocket depth, and the presence of bacterial plaque. In addition, each subject was asked to compile a record of his/her dietary intake for a seven-day period. The treated group was found to brush and floss more frequently than the untreated group and had a lower mean plaque score (45.8), than the untreated group (61.4). There was no difference in the mean plaque scores for the subgroups with and without root surface caries within either the treated groups. The prevalence of root surface caries increased through age 59 in the treated group, then diminished after age 60. In the untreated group the prevalence increased steadily with age. Analysis of the data from the dietary hisories revealed that the subjects in both the treated and the untreated groups who were affected with root surface caries had a significantly higher (P less than 0.01) number of fermentable carbohydrate exposures per week.