Impact of 60 days of head-down bed rest on large arteries.

BACKGROUND: The long-term cardiovascular consequences of microgravity on large arteries are a threat for long-term space missions. We hypothesized that changes in arterial properties differ according to the arterial territory (upper or lower body), and arterial structure (elastic vs. muscular arteries), in response to 60-day head-down bed rest (HDBR). METHOD: Twenty healthy male volunteers were included and received a daily multivitamin supplementation in a double-blind fashion. At baseline, 29 and 52 days during strict HDBR, then 12 and 30 days after HDBR, aortic stiffness was measured using carotid-to-femoral pulse wave velocity (cf-PWV) and aortic MRI. Carotid, femoral, brachial and popliteal arteries were studied by ultrasound echo tracking, central blood pressure (BP) by tonometry and endothelial function by flow-mediated dilatation. RESULTS: Cf-PWV increased during HDBR (+0.8 and +1.1m/s, at D29 and D52, respectively, P = 0.004), corresponding to an increase in vascular age up to +11 years (P = 0.003). Changes were similar to those observed on MRI (+0.8 m/s at D52, P < 0.01) and were independent of BP and heart rate changes. After HDBR, cf-PWV showed a substantial recovery at R12 but still remained higher than baseline at R30 (+0.8 m/s, P = 0.018), corresponding to +6.5 years of vascular aging (P = 0.018). Thoracic aorta diameter increased significantly (+6%, P = 0.0008). During HDBR, femoral and popliteal arteries showed dimensional changes, leading to femoral inward hypotrophic remodeling (femoral diameter: -12%, P < 0.05; wall cross-sectional area: -25%, P = 0.014) and popliteal inward eutrophic remodeling (popliteal diameter: -25%, P < 0.05; wall cross-sectional area: -3%, P = 0.51). After HDBR, both arterial territories of the leg recovered. We did not observe any significant changes for carotid arteries nor for endothelial function during and after HDBR. Multivitamin supplementation did not affect vascular changes. HDBR was associated with an important increase in aortic stiffness, which did not completely recover 1 month after the end of HDBR. The thoracic aorta and the lower body muscular arteries underwent significant changes in dimensions whereas the common carotid arteries were preserved. CONCLUSION: These results should raise caution for those exposed to microgravity, real or simulated.

Photochemical Stability of a Cotton Fabric Surface Dyed with a Reactive Triphenodioxazine Dye.

The paper describes the photochemical stability of a commercial triphenodioxazine dye (Reactive Blue_204) linked onto a cotton fabric. Preliminary studies have shown that as a result of irradiation, the dye and its photodegradation products can pass directly onto the skin under conditions that mimic human perspiration and cause side-effects. The cotton dyed fabric was photo irradiated at different time intervals. Standard methods were employed to evaluate the color strength at various levels of pH, temperature, dyeing contact time, and salt concentration. The influence of UV radiation at different doses (λ > 300 nm) on the structural and color modifications of the dyed cotton fabrics was studied. Structural modifications before and after irradiation were compared by applying FTIR, UV-Vis, and near infrared chemical imaging (NIR-CI) techniques. Color modifications were investigated with the CIELAB system. Color differences significantly increased with the irradiation dose. High irradiation doses caused changes in the dye structure.

Incorporating 4D into Bioprinting: Real-Time Magnetically Directed Collagen Fiber Alignment for Generating Complex Multilayered Tissues.

In vitro multilayered tissues with mimetic architectures resembling native tissues are valuable tools for application in medical research. In this study, an advanced bioprinting strategy is presented for aligning collagen fibers contained in functional bioinks. Streptavidin-coated iron nanoparticles are embedded in printable bioinks with varying concentrations of low gelling temperature agarose and type I collagen. By applying a straightforward magnetic-based mechanism in hydrogels during bioprinting, it is possible to align collagen fibers in less concentrated hydrogel blends with a maximum agarose concentration of 0.5 w/v%. Conversely, more elevated concentrations of agarose in printable blends show random collagen fiber distribution. Interestingly, hydrogel blends with unidirectionally aligned collagen fibers show significantly higher compression moduli compared to hydrogel blends including random fibers. Considering its application in the field of cartilage tissue engineering, bioprinted constructs with alternating layers of aligned and random fibers are fabricated. After 21 days of culture, cell-loaded constructs with alternating layers of aligned and random fibers express markedly more collagen II in comparison to solely randomly oriented fiber constructs. These encouraging results translate the importance of the structure and architecture of bioinks used in bioprinting in light of their use for tissue engineering and personalized medical applications.