RELATIONSHIPS BETWEEN LARVAL MORPHOMETRICS AND SETTING EFFICIENCY IN THE EASTERN OYSTER, CRASSOSTREA VIRGINICA

In oyster hatcheries, the decision to move larvae from rearing tanks to setting tanks is based on physical and behavioral characteristics. These criteria can suggest conflicting action and a more reliable method may result in higher spat production. I observed hatchery reared Crassostrea virginica larvae, beginning with larvae retained on a 200 µm sieve. Aliquots of larvae were measured or placed in a setting vessel, and the remaining were returned to the culture cone daily. Each day had an associated setting efficiency, loss, and set of larval morphometrics, including shell height and length and eyespot diameter. Day was most strongly correlated with setting efficiency. Eyespot diameter was moderately correlated with setting efficiency, and shell morphometrics were weakly correlated with setting efficiency. I estimated daily spat production, which peaked on day 2. These results suggest spat production may be increased by altering current hatchery methods to consider eyespot diameter or days past retention on a 200 µm sieve when deciding to place larvae in setting tanks

A Versatile Open-Source Printhead for Low-Cost 3D Microextrusion-Based Bioprinting

Three-dimensional (3D) bioprinting promises to be essential in tissue engineering for solving the rising demand for organs and tissues. Some bioprinters are commercially available, but their impact on the field of Tissue engineering (TE) is still limited due to their cost or difficulty to tune. Herein, we present a low-cost easy-to-build printhead for microextrusion-based bioprinting (MEBB) that can be installed in many desktop 3D printers to transform them into 3D bioprinters. We can extrude bioinks with precise control of print temperature between 2–60 °C. We validated the versatility of the printhead, by assembling it in three low-cost open-source desktop 3D printers. Multiple units of the printhead can also be easily put together in a single printer carriage for building a multi-material 3D bioprinter. Print resolution was evaluated by creating representative calibration models at different temperatures using natural hydrogels such as gelatin and alginate, and synthetic ones like poloxamer. Using one of the three modified low-cost 3D printers, we successfully printed cell-laden lattice constructs with cell viabilities higher than 90% after 24-h post printing. Controlling temperature and pressure according to the rheological properties of the bioinks was essential in achieving optimal printability and great cell viability. The cost per unit of our device, which can be used with syringes of different volume, is less expensive than any other commercially available product. These data demonstrate an affordable open-source printhead with the potential to become a reliable alternative to commercial bioprinters for any laboratory

Publications of the NASA space biology program for 1980 - 1984

A listing of 562 publications supported by the NASA Space Biology Program for the years 1980 to 1984 is presented. References are arranged under the headings which are plant gravitational research, animal gravitational research, and general. Keyword title indexes and a principal investigator listing are also included

A Versatile Open-Source Printhead for Low-Cost 3D Microextrusion-Based Bioprinting

Three-dimensional (3D) bioprinting promises to be essential in tissue engineering for solving the rising demand for organs and tissues. Some bioprinters are commercially available, but their impact on the field of Tissue engineering (TE) is still limited due to their cost or difficulty to tune. Herein, we present a low-cost easy-to-build printhead for microextrusion-based bioprinting (MEBB) that can be installed in many desktop 3D printers to transform them into 3D bioprinters. We can extrude bioinks with precise control of print temperature between 2–60 °C. We validated the versatility of the printhead, by assembling it in three low-cost open-source desktop 3D printers. Multiple units of the printhead can also be easily put together in a single printer carriage for building a multi-material 3D bioprinter. Print resolution was evaluated by creating representative calibration models at different temperatures using natural hydrogels such as gelatin and alginate, and synthetic ones like poloxamer. Using one of the three modified low-cost 3D printers, we successfully printed cell-laden lattice constructs with cell viabilities higher than 90% after 24-h post printing. Controlling temperature and pressure according to the rheological properties of the bioinks was essential in achieving optimal printability and great cell viability. The cost per unit of our device, which can be used with syringes of different volume, is less expensive than any other commercially available product. These data demonstrate an affordable open-source printhead with the potential to become a reliable alternative to commercial bioprinters for any laboratory

Aerospace medicine and biology: A continuing bibliography with indexes (supplement 335)

This bibliography lists 143 reports, articles and other documents introduced into the NASA Scientific and Technical Information System during March, 1990. Subject coverage includes: aerospace medicine and psychology, life support systems and controlled environments, safety equipment, exobiology and extraterrestrial life, and flight crew behavior and performance

Development of hybrid coatings for osseointegration improvement of metal dental implants

Los implantes de titanio presentan comprobada biocompatibilidad no obstante carecen de propiedades osteoinductoras. Las estrategias actuales de modificación superficial de los implantes no resultan plenamente efectivas en casos particulares de baja calidad del hueso receptor. La presente tesis doctoral plantea una nueva estrategia basada en recubrimientos superficiales bioabsorbibles de base silicio para mejorar el éxito de dichos implantes. Para alcanzar dicho objetivo se han sintetizado vía sol-gel diversos recubrimientos a partir de los precursores de silicio trimetoximetilsilano (MTMOS), 3-glicidoxipropiltrimetoxisilano (GPTMS) y tetraetoxisilano (TEOS). Se ha realizado una detallada caracterización de los recubrimientos, especialmente en lo que a sus propiedades físicas, químicas y biológicas se refiere. Los resultados obtenidos muestran que todos los recubrimientos se encuentran bien adheridos a la superfície metálica, además, el prototipo final ha demostrado ser claramente biocompatible con los tejidos vivos sin mermar las propiedades osteoconductivas de los implantes de titanio comerciales.Titanium dental implants have proved biocompatibility, nevertheless, they lack of osteoinductive properties. The usual strategy of modifying titanium dental implants' surfaces is not fully effective in the special situations of poor bone quality. THis work focuses on a new strategy that consists on developing synthetic and biologically absorbable silica-based external coatings to improve these implants' success. In order to achieve this purpose, sol-gel technology was used to synthesize several coatings based on the precursors trimethoxymethylsilane (MTMOS), 3-glycidyloxypropylsilane (GPTMS) and tetraethoxysilane (TEOS). The coatings were thoroughly characterized, specifically focusing on their physical and chemical properties as well as on their biological performance. Resukts show taht all the synthesized coatings were well adhered to the metal surface and the final prototype shows clear biocompatibility with living tissues without affecting the osteoconductive properties of the commercial titanium dental implants

Spatial analysis of topography for glacier mapping in the Western Himalaya

Understanding climate change requires accurate assessment of the Earths cryosphere, as glacier fluctuations directly and indirectly reflect changes in radiative forcing and temperature and precipitation patterns. Direct assessment of alpine glaciers in high-mountains is notoriously difficult, and assessment from space represents the only practical alternative for assessing regional and global ice-fluctuation patterns. The mapping of debris-covered glaciers is especially problematic, as glacier surfaces exhibit spectral reflectance patterns similar to surrounding rock and sediment. Therefore, multispectral analysis of satellite imagery does not permit accurate delineation. Consequently, the use of satellite-derived topographic information and spatial analysis were evaluated for mapping the Raikot and Sachen Glaciers at Nanga Parbat mountain in the Pakistan Himalaya. Geomorphometric analyses were used to generate first- and secondorder topographic parameters. These were utilized to generate homogeneous elemental-form objects, which were evaluated for glacier mapping. Topo-sequence information was also examined and represents the slope-angle altitude function within slope facet objects. The results indicate that it is difficult to characterize the hierarchical topographic organization of glaciers using topographic parameters and elemental form objects. Even though only one level of the topographic hierarchy was attempted, elemental form objects appear to be more useful than topographic parameters, as they represent a combination of topographic information. In addition, elemental-form objects can be used to identify and map selected glacial features without further aggregation to another level in the hierarchy. Toposequence information was found to be of value in differentiating glacier versus non-glacier surfaces. Collectively these results indicate that spatial analysis of the topography can be used for glacier mapping, although accurate digital elevation models are required, along with more sophisticated approaches for quantitatively characterizing the topography. It is suggested that specific topographic primitives and glacier landforms be individually characterized and integrated into a landscape topographic hierarchy in order to accurately characterize and map debris-covered glaciers. Finally, special attention to the concept of scale must be formally accounted for in analysis procedures

Inkjet bioprinting and 3D culture of human MSC-laden binary starPEG-heparin hydrogels for cartilage tissue engineering

Articular cartilage is a highly specialized, hierarchically organized tissue covering the articular surfaces of diarthrodial joints that absorbs and distributes forces upon mechanical loading and enables low-friction movement between opposing bone ends. Despite a strong resilience towards mechanical stress, once damaged cartilage is generally not regenerated due to a limited repair potential of the residing cells (chondrocytes) and the local absence of vascularized blood vessels and nerves. Eventually, this may lead to osteoarthritis, a chronic degenerative disorder of the synovial joints which has a strongly growing prevalence worldwide. Modern regenerative therapies that aim to rebuild cartilage tissue in vivo and in vitro using chondrocyte- and stem cell-based methods are still not able to produce tissue constructs with desired biomechanical properties and organization for long-term repair. Therefore, cartilage tissue engineering seeks for new ways to solve these problems. In this regard, the application of hydrogel-based scaffolding materials as artificial matrix environments to support the chondrogenesis of embedded cells and the implementation of appropriate biofabrication techniques that help to reconstitute the zonal structure of articular cartilage are considered as promising strategies for sophisticated cartilage regeneration approaches. In this thesis, a modular starPEG-heparin hydrogel platform as cell-instructive hydrogel scaffold was used in combination with a custom-designed 3D inkjet bioprinting method with the intention to develop a printable 3D in vitro culture system that promotes the chondrogenic differentiation of human mesenchymal stromal cells (hMSC) in printed cell-laden hydrogels with layered architectures in order to fabricate cartilage-like tissue constructs with hierarchical organization. Firstly, the successful bioprinting of horizontally and vertically structured, cell-free and -laden hydrogel scaffolds that exhibit layer thicknesses in the range of the superficial zone, the thinnest articular cartilage layer is demonstrated. The long-term integrity of the printed constructs and the cellular functionality of the plotted cells that generally had a high viability after the printing process are shown by a successful PDGF-BB-mediated hMSC migration assay in a printed multilayered hydrogel construct over a culture period of 4 weeks. Secondly, when the established printing procedures were applied for the chondrogenic differentiation of hMSCs, it was found that the printed cell-laden constructs showed a limited potential for in vitro chondrogenesis as indicated by a weaker immunostaining for cartilage-specific markers compared to casted hydrogel controls. In order to increase the post-printing cell density to tackle the limited printable cell concentration which was regarded as the primary reason for the impaired performance of the printed scaffolds, different conditions with varying culture medium and hydrogel compositions were tested to stimulate 3D cell proliferation. However, a significant 3D cell number increase could not be achieved which ultimately resulted in shifting the further focus to casted hMSC-laden starPEG-heparin hydrogels. Thirdly, the chondrogenic differentiation of hMSCs in casted hydrogels proved to be successful which was indicated by a uniform deposition of cartilage-specific ECM molecules comparable with the outcomes of scaffold-free MSC micromass cultures used as reference system. However, the quantitative analysis of biochemical and physical properties of the engineered hydrogel constructs yielded still significant lower values in relation to native articular cartilage tissue. Fourthly, in order to improve these properties and to enhance the chondrogenesis in starPEGheparin hydrogels, a dualistic strategy was followed. In the first part, specific externally supplied stimulatory cues including a triple growth factor supply strategy and macromolecular crowding were applied. As second part, intrinsic properties of the modular hydrogel system such as the crosslinking degree, the enzymatic degradability and the heparin content were systematically and independently altered. It was found that while the external cues showed no supportive benefits for the chondrogenic differentiation, the reduction of the heparin content in the hydrogel proved to be a key trigger that resulted in a significantly increased cartilage-like ECM deposition and gel stiffness of engineered constructs with low and no heparin content. In conclusion, this work yielded important experiences with regards to the application of inkjet bioprinting for hMSC-based cartilage tissue engineering approaches. Furthermore, the obtained data provided valuable insights into the interaction of MSCs and a surrounding hydrogel-based microenvironment that can be used for the further development of chondrosupportive scaffolding materials which may facilitate the fabrication of cartilage-like tissue constructs

Mimicking bone microenvironment : 2D and 3D in vitro models of human osteoblasts

Understanding the in vitro biology and behavior of human osteoblasts is crucial for developing research models that reproduce closely the bone structure, its functions, and the cell-cell and cell-matrix interactions that occurs in vivo. Mimicking bone microenvironment is challenging, but necessary, to ensure the clinical translation of novel medicines to treat more reliable different bone pathologies. Currently, bone tissue engineering is moving from 2D cell culture models such as traditional culture, sandwich culture, micro-patterning, and altered substrate stiffness, towards more complex 3D models including spheroids, scaffolds, cell sheets, hydrogels, bioreactors, and microfluidics chips. There are many different factors, such cell line type, cell culture media, substrate roughness and stiffness that need consideration when developing in vitro models as they affect significantly the microenvironment and hence, the final outcome of the in vitro assay. Advanced technologies, such as 3D bioprinting and microfluidics, have allowed the development of more complex structures, bridging the gap between in vitro and in vivo models. In this review, past and current 2D and 3D in vitro models for human osteoblasts will be described in detail, highlighting the culture conditions and outcomes achieved, as well as the challenges and limitations of each model, offering a widen perspective on how these models can closely mimic the bone microenvironment and for which applications have shown more successful results