Combined space environment on spacecraft engineering materials

Spacecraft structures and surface materials exposed to the space environment for extended periods, up to thirty years, have increased potential for damage from long term exposure to the combined space environment including solar ultraviolet radiation, electrons, and protons and orbiting space debris. The space environment in which the Space Station Freedom and other space platforms will orbit is truly a hostile environment. For example, the currently estimated integral fluence for electrons above 1 Mev at 2000 nautical miles is above 2 x 10(exp 10) electrons/cm(sup 2)/day and the proton integral fluence is above 1 x 10(exp 9) protons/cm(sup 2)/day. At the 200 - 400 nautical miles, which is more representative of the altitude which will provide the environment for the Space Station, each of these fluences will be proportionately less; however, the data indicates that the radiation environment will obviously have an effect on structural materials exposed to the environment for long durations. The effects of ultraviolet radiation, particularly in the vacuum ultraviolet (less than 200 nm wavelength) is more difficult to characterize at this time. Very little data is available in the literature which can be used for determining the life cycle of a material placed in space for extended durations of time. In order to obtain critical data for planning and designing of spacecraft systems, use of a small vacuum system at the Environmental Effects Facility at MSFC, which can be used for these purposes was used. A special effort was made to build up this capability during the course of this research effort and perform a variety of experiments on materials proposed for the Space Station. A description of the apparatus and the procedure devised to process potential spacecraft materials is included

Phase A design study of microgravity fluoride fiber puller

Improved transmission properties for fluoride fibers due to space processing has great potential for commercial benefits. Phase A design study will determine conceptual feasibility and provide initial definition of the technical requirements and design issues for space

MUTZ-3 derived Langerhans cells in human skin equivalents show differential migration and phenotypic plasticity after allergen or irritant exposure

AbstractAfter allergen or irritant exposure, Langerhans cells (LC) undergo phenotypic changes and exit the epidermis. In this study we describe the unique ability of MUTZ-3 derived Langerhans cells (MUTZ-LC) to display similar phenotypic plasticity as their primary counterparts when incorporated into a physiologically relevant full-thickness skin equivalent model (SE-LC). We describe differences and similarities in the mechanisms regulating LC migration and plasticity upon allergen or irritant exposure. The skin equivalent consisted of a reconstructed epidermis containing primary differentiated keratinocytes and CD1a+ MUTZ-LC on a primary fibroblast-populated dermis. Skin equivalents were exposed to a panel of allergens and irritants. Topical exposure to sub-toxic concentrations of allergens (nickel sulfate, resorcinol, cinnamaldehyde) and irritants (Triton X-100, SDS, Tween 80) resulted in LC migration out of the epidermis and into the dermis. Neutralizing antibody to CXCL12 blocked allergen-induced migration, whereas anti-CCL5 blocked irritant-induced migration. In contrast to allergen exposure, irritant exposure resulted in cells within the dermis becoming CD1a−/CD14+/CD68+ which is characteristic of a phenotypic switch of MUTZ-LC to a macrophage-like cell in the dermis. This phenotypic switch was blocked with anti-IL-10. Mechanisms previously identified as being involved in LC activation and migration in native human skin could thus be reproduced in the in vitro constructed skin equivalent model containing functional LC. This model therefore provides a unique and relevant research tool to study human LC biology in situ under controlled in vitro conditions, and will provide a powerful tool for hazard identification, testing novel therapeutics and identifying new drug targets

Phenotypic analysis of migratory dendritic cell (DC) subsets from skin and gingiva.

<p>Chemotaxis, maturation and differentiation-associated marker expression on DC subsets 1–5 from skin vs. gingiva, shown per indicated subset (*P<0.05, n = 4–9 for skin and gingiva). Explants (6mm diameter) from skin and gingiva were taken and cultured floating in medium for 48h, after which they were discarded and migrated DC harvested, stained and analysed by flowcytometry.</p

Comparison of cell density between full-thickness skin and gingiva (per 100μm tissue cross-section).

<p>Comparison of cell density between full-thickness skin and gingiva (per 100μm tissue cross-section).</p

Dendritic cell (DC) subset definition and distribution.

<p>Dendritic cell (DC) subset definition and distribution according to CD1a and CD14 expression in CD11c^hi DC migrated from human skin or gingiva. Explants (6mm diameter) from skin and gingiva were taken and cultured floating in medium for 48h, after which they were discarded and migrated DC harvested, stained and analysed by flowcytometry. (A) Flow cytometry dot plots with gates denoting five migrated DC subsets (numbered 1 to 5) in skin and gingiva. (B) Frequency distribution of the five subsets among migrated DC (n = 9).</p