The Microfluidic Probe: Operation and Use for Localized Surface Processing

Microfluidic devices allow assays to be performed using minute amounts of sample and have recently been used to control the microenvironment of cells. Microfluidics is commonly associated with closed microchannels which limit their use to samples that can be introduced, and cultured in the case of cells, within a confined volume. On the other hand, micropipetting system have been used to locally perfuse cells and surfaces, notably using push-pull setups where one pipette acts as source and the other one as sink, but the confinement of the flow is difficult in three dimensions. Furthermore, pipettes are fragile and difficult to position and hence are used in static configuration only. The microfluidic probe (MFP) circumvents the constraints imposed by the construction of closed microfluidic channels and instead of enclosing the sample into the microfluidic system, the microfluidic flow can be directly delivered onto the sample, and scanned across the sample, using the MFP. . The injection and aspiration openings are located within a few tens of micrometers of one another so that a microjet injected into the gap is confined by the hydrodynamic forces of the surrounding liquid and entirely aspirated back into the other opening. The microjet can be flushed across the substrate surface and provides a precise tool for localized deposition/delivery of reagents which can be used over large areas by scanning the probe across the surface. In this video we present the microfluidic probe (MFP). We explain in detail how to assemble the MFP, mount it atop an inverted microscope, and align it relative to the substrate surface, and finally show how to use it to process a substrate surface immersed in a buffer

Virus-Inspired Membrane Encapsulation of DNA Nanostructures To Achieve In Vivo Stability

DNA nanotechnology enables engineering of molecular-scale devices with exquisite control over geometry and site-specific functionalization. This capability promises compelling advantages in advancing nanomedicine; nevertheless, instability in biological environments and innate immune activation remain as obstacles for in vivo application. Natural particle systems (i.e., viruses) have evolved mechanisms to maintain structural integrity and avoid immune recognition during infection, including encapsulation of their genome and protein capsid shell in a lipid envelope. Here we introduce virus-inspired enveloped DNA nanostructures as a design strategy for biomedical applications. Achieving a high yield of tightly wrapped unilamellar nanostructures, mimicking the morphology of enveloped virus particles, required precise control over the density of attached lipid conjugates and was achieved at 1 per ∼180 nm2. Envelopment of DNA nanostructures in PEGylated lipid bilayers conferred protection against nuclease digestion. Immune activation was decreased 2 orders of magnitude below controls, and pharmacokinetic bioavailability improved by a factor of 17. By establishing a design strategy suitable for biomedical applications, we have provided a platform for the engineering of sophisticated, translation-ready DNA nanodevices

In Vitro Bone Cell Models: Impact of Fluid Shear Stress on Bone Formation.

This review describes the role of bone cells and their surrounding matrix in maintaining bone strength through the process of bone remodeling. Subsequently, this work focusses on how bone formation is guided by mechanical forces and fluid shear stress in particular. It has been demonstrated that mechanical stimulation is an important regulator of bone metabolism. Shear stress generated by interstitial fluid flow in the lacunar-canalicular network influences maintenance and healing of bone tissue. Fluid flow is primarily caused by compressive loading of bone as a result of physical activity. Changes in loading, e.g., due to extended periods of bed rest or microgravity in space are associated with altered bone remodeling and formation in vivo. In vitro, it has been reported that bone cells respond to fluid shear stress by releasing osteogenic signaling factors, such as nitric oxide, and prostaglandins. This work focusses on the application of in vitro models to study the effects of fluid flow on bone cell signaling, collagen deposition, and matrix mineralization. Particular attention is given to in vitro set-ups, which allow long-term cell culture and the application of low fluid shear stress. In addition, this review explores what mechanisms influence the orientation of collagen fibers, which determine the anisotropic properties of bone. A better understanding of these mechanisms could facilitate the design of improved tissue-engineered bone implants or more effective bone disease models

Metaphoric coherence: Distinguishing verbal metaphor from `anomaly\u27

Theories and computational models of metaphor comprehension generally circumvent the question of metaphor versus “anomaly” in favor of a treatment of metaphor versus literal language. Making the distinction between metaphoric and “anomalous” expressions is subject to wide variation in judgment, yet humans agree that some potentially metaphoric expressions are much more comprehensible than others. In the context of a program which interprets simple isolated sentences that are potential instances of cross‐modal and other verbal metaphor, I consider some possible coherence criteria which must be satisfied for an expression to be “conceivable” metaphorically. Metaphoric constraints on object nominals are represented as abstracted or extended along with the invariant structural components of the verb meaning in a metaphor. This approach distinguishes what is preserved in metaphoric extension from that which is “violated”, thus referring to both “similarity” and “dissimilarity” views of metaphor. The role and potential limits of represented abstracted properties and constraints is discussed as they relate to the recognition of incoherent semantic combinations and the rejection or adjustment of metaphoric interpretations

Exploring Science Identity: The Lived Experiences of Underserved Students in a University Supplemental Science Program

Underserved students attending under-resourced schools experience limited opportunities to engage in advanced science. An exploration into the influence a supplemental science program has on underserved students’ acquisition of science knowledge and skills to increase their pursuit of science was conducted to help explain science identity formation in students. The proliferation of supplemental science programs have emerged as a result of limited exposure and resources in science for underserved students, thus prompting further investigation into the influence supplemental science programs have on underserved students interest and motivation in science, attainment of science knowledge and skills, and confidence in science to promote science identities in students. Using a phenomenological qualitative approach, this study examined science identity formation in high school students participating in a university supplemental environmental health science program. The study explored high school students’ perceptions of their lived experiences in science supplemental activities, research, and field experiences and the influences these experiences have in relation to their science identity development. The university supplemental science program was an eight-week summer program in which students interacted with a diverse group of peers from various high schools, through engaging in environmental health science rotations, field experiences, and research with faculty advisors and graduate student mentors. Data collection included existing program evaluation data including, weekly journals and exit interviews, as well as follow-up interviews conducted several months after the program concluded. The study findings from a three step coding process of the follow-up interview transcripts provided six emerging themes as follows: (1) promoting interest and motivation to pursue new areas of science, (2) mechanisms in the acquisition of science knowledge and skills in scientific practice, (3) confidence in science knowledge and abilities, (4) understanding and applying science in the world, (5) emerging relationships with peers and mentors in science, and (6) aspirations to be a science person in the scientific community. This research study informs other supplemental science programs, has implications for improved science curricula and instruction in K12 schools, as well as explains how exposure to science experiences can help students gain identities in science

The Photoreceptor Cell-Specific Nuclear Receptor Gene (PNR ) Accounts for Retinitis Pigmentosa in the Crypto-Jews from Portugal (Marranos), Survivors from the Spanish Inquisition

The last Crypto-Jews (Marranos) are the survivors of Spanish Jews who were persecuted in the late fifteenth century, escaped to Portugal and were forced to convert to save their lives. Isolated groups still exist in mountainous areas such as Belmonte in the Beira-Baixa province of Portugal. We report here the genetic study of a highly consanguineous endogamic population of Crypto-Jews of Belmonte affected with autosomal recessive retinitis pigmentosa (RP). A genome-wide search for homozygosity allowed us to localize the disease gene to chromosome 15q22-q24 (Zmax=2.95 at θ=0 at the D15S131 locus). Interestingly, the photoreceptor cell-specific nuclear receptor (PNR) gene, the expression of which is restricted to the outer nuclear layer of retinal photoreceptor cells, was found to map to the YAC contig encompassing the disease locus. A search for mutations allowed us to ascribe the RP of Crypto-Jews of Belmonte to a homozygous missense mutation in the PNR gene. Preliminary haplotype studies support the view that this mutation is relatively ancient but probably occurred after the population settled in Belmonte

Conversation acts in task-oriented spoken dialogue

A linguistic form\u27s compositional, timeless meaning can be surrounded or even contradicted by various social, aesthetic, or analogistic companion meanings. This paper addresses a series of problems in the structure of spoken language discourse, including turn-taking and grounding. It views these processes as composed of fine-grained actions, which resemble speech acts both in resulting from a computational mechanism of planning and in having a rich relationship to the specific linguistic features which serve to indicate their presence. The resulting notion of Conversation Acts is more general than speech act theory, encompassing not only the traditional speech acts but turn-taking, grounding, and higher-level argumentation acts as well. Furthermore, the traditional speech acts in this scheme become fully joint actions, whose successful performance requires full listener participation. This paper presents a detailed analysis of spoken language dialogue. It shows the role of each class of conversation acts in discourse structure, and discusses how members of each class can be recognized in conversation. Conversation acts, it will be seen, better account for the success of conversation than speech act theory alone

Stiffness of cell micro-environment guides long term cell growth in cell seeded collagen microspheres

Mesenchymal stem cells are widely implicated as a cell source for tissue engineering of skeletal tissue in cell-based therapy. Physical and mechanical cues are potent controlling factors in cell differentiation and can be implemented as a guide to study cellular response, matrix production and tissue regeneration. Microspheres were produced by gelation of bovine collagen type I with concentration of 2 mg/mL and 1,000-2,000 cells per droplet. Short and long term cell viability of human embryonic stem cell-derived mesenchymal progenitors (hES-MPs) and MG-63 osteoblastic cells as well as collagen microstructure and contraction were monitored during 28 days post encapsulation (pc). Results indicated that collagen concentration, hence mechanical properties of cell’s extracellular micro-environment are important in cell proliferation and differentiation. Contraction of cell-embedded microspheres was found to be vital in cell adaptation and the remodelling of their new environment. It was also found that collagen concentration of 2 mg/mL supports proliferation of hES-MPs while higher collagen concentration promoted the viability of MG-63s. Results of hES-MPs characterization in 3D soft environment and mechanically stimulated hES-MPs collagen microspheres can be used in cells/therapeutic carriers, implants in bone and cartilage healing applications. The microspheres developed in this study can also be used as a tool to build more optimised construct to transfer mechanically stimulated stem cells to the specific area of a defective bone which would add significant benefit to the field of bone regeneration

Nanoethics, science communication, and a fourth model for public engagement

This paper develops a fourth model of public engagement with science, grounded in the principle of nurturing scientific agency through online participatory bioethics. It argues that social media is an effective device through which to enable such engagement, as it has the capacity to empower users and transforms audiences into co-producers of knowledge, rather than consumers of content, the value of which is recognised within the citizen science movement. Social media also fosters greater engagement with the political and legal implications of science, thus promoting the value of scientific citizenship through the acquisition of science capital. This argument is explored by considering the case of nanoscience and nanotechnology, as an exemplar for how emerging technologies may be handled by the scientific community and science policy makers, and as a technology that has defined a second era of science communication

Relative frequencies of inherited retinal dystrophies and optic neuropathies in Southern France: assessment of 21-year data management

PURPOSE: Inherited retinal dystrophies (IRDs) and inherited optic neuropathies (IONs) are rare diseases defined by specific clinical and molecular features. The relative prevalence of these conditions was determined in Southern France. METHODS: Patients recruited from a specialized outpatient clinic over a 21-year period underwent extensive clinical investigations and 107 genes were screened by polymerase chain reaction/sequencing. RESULTS: There were 1957 IRD cases (1481 families) distributed in 70% of pigmentary retinopathy cases (56% non-syndromic, 14% syndromic), 20% maculopathies and 7% stationary conditions. Patients with retinitis pigmentosa were the most frequent (47%) followed by Usher syndrome (10.8%). Among non-syndromic pigmentary retinopathy patients, 84% had rod-cone dystrophy, 8% cone-rod dystrophy and 5% Leber congenital amaurosis. Macular dystrophies were encountered in 398 cases (30% had Stargardt disease and 11% had Best disease). There were 184 ION cases (127 families) distributed in 51% with dominant optic neuropathies, 33% with recessive/sporadic forms and 16% with Leber hereditary optic neuropathy. Positive molecular results were obtained in 417/609 families with IRDs (68.5%) and in 27/58 with IONs (46.5%). The sequencing of 5 genes (ABCA4, USH2A, MYO7A, RPGR and PRPH2) provided a positive molecular result in 48% of 417 families with IRDs. Except for autosomal retinitis pigmentosa, in which less than half the families had positive molecular results, about 75% of families with other forms of retinal conditions had a positive molecular diagnosis. CONCLUSIONS: Although gene discovery considerably improved molecular diagnosis in many subgroups of IRDs and IONs, retinitis pigmentosa, accounting for almost half of IRDs, remains only partly molecularly defined