Understanding Needs Embodiment: A Theory-Guided Reanalysis of the Role of Metaphors and Analogies in Understanding Science

Many authors stress the importance of basing teaching on students' prior knowledge. To build a bridge between students' everyday knowledge and scientific concepts, the role of metaphors and analogies came into the focus of the science education community during the past two decades. Approaches using metaphor-based teaching strategies often regard metaphors and analogies as teaching tools that can be adopted by a teacher. On the basis of the theoretical framework of experientialism, we argue that not only teaching but also thinking about and understanding science without metaphors and analogies is not possible. An analysis of studies dealing with metaphors and analogies in science education shows that instructional analogies and metaphors are often not understood as intended or not used by students in their own explanations. By reanalyzing 199 instructional metaphors and analogies on the basis of a metaphor analysis, we show that it takes more than making a connection to everyday life to communicate science fruitfully. We show that good instructional metaphors and analogies need embodied sources. These embodied sources are everyday experiences conceptualized in, for example, schemata such as containers, paths, balances, and up and down. For the analysis, we introduce the concept of conceptual metaphors for analyzing metaphors as well as analogies

Intercellular Transport of Oct4 in Mammalian Cells: A Basic Principle to Expand a Stem Cell Niche?

Background: The octamer-binding transcription factor 4 (Oct4) was originally described as a marker of embryonic stem cells. Recently, the role of Oct4 as a key regulator in pluripotency was shown by its ability to reprogram somatic cells in vitro, either alone or in concert with other factors. While artificial induction of pluripotency using transcription factors is possible in mammalian cell culture, it remains unknown whether a potential natural transfer mechanism might be of functional relevance in vivo. The stem cell based regeneration of deer antlers is a unique model for rapid and complete tissue regeneration in mammals and therefore most suitable to study such mechanisms. Here, the transfer of pluripotency factors from resident stem cell niche cells to differentiated cells could recruit more stem cells and start rapid tissue regeneration. Methodology/Principal Findings: We report on the ability of STRO-1 + deer antlerogenic mesenchymal stem cells (DaMSCs) to transport Oct4 via direct cell-to-cell connections. Upon cultivation in stem cell expansion medium, we observed nuclear Oct4 expression in nearly all cells. A number of these cells exhibit Oct4 expression not only in the nucleus, but also with perinuclear localisation and within far-ranging intercellular connections. Furthermore, many cells showed intercellular connections containing both F-actin and a-tubulin and through which transport could be observed. To proof that intercellular Oct4-transfer has functional consequences in recipient cells we used a co-culture approach with STRO-1 + DaMSCs and a murine embryonic fibroblast indicator cell line (Oct4-GFP MEF). In this cell line a reporter gene (GFP) unde

Localization and Characterization of STRO-1+ Cells in the Deer Pedicle and Regenerating Antler

The annual regeneration of deer antlers is a unique developmental event in mammals, which as a rule possess only a very limited capacity to regenerate lost appendages. Studying antler regeneration can therefore provide a deeper insight into the mechanisms that prevent limb regeneration in humans and other mammals, and, with regard to medical treatments, may possibly even show ways how to overcome these limitations. Traditionally, antler regeneration has been characterized as a process involving the formation of a blastema from de-differentiated cells. More recently it has, however, been hypothesized that antler regeneration is a stem cell-based process. Thus far, direct evidence for the presence of stem cells in primary or regenerating antlers was lacking. Here we demonstrate the presence of cells positive for the mesenchymal stem cell marker STRO-1 in the chondrogenic growth zone and the perivascular tissue of the cartilaginous zone in primary and regenerating antlers as well as in the pedicle of fallow deer (Dama dama). In addition, cells positive for the stem cell/progenitor cell markers STRO-1, CD133 and CD271 (LNGFR) were isolated from the growth zones of regenerating fallow deer antlers as well as the pedicle periosteum and cultivated for extended periods of time. We found evidence that STRO-1+ cells isolated from the different locations are able to differentiate in vitro along the osteogenic and adipogenic lineages. Our results support the view that the annual process of antler regeneration might depend on the periodic activation of mesenchymal progenitor cells located in the pedicle periosteum. The findings of the present study indicate that not only limited tissue regeneration, but also extensive appendage regeneration in a postnatal mammal can occur as a stem cell-based process

Expression and Function of Serotonin 2A and 2B Receptors in the Mammalian Respiratory Network

Neurons of the respiratory network in the lower brainstem express a variety of serotonin receptors (5-HTRs) that act primarily through adenylyl cyclase. However, there is one receptor family including 5-HT2A, 5-HT2B, and 5-HT2C receptors that are directed towards protein kinase C (PKC). In contrast to 5-HT2ARs, expression and function of 5-HT2BRs within the respiratory network are still unclear. 5-HT2BR utilizes a Gq-mediated signaling cascade involving calcium and leading to activation of phospholipase C and IP3/DAG pathways. Based on previous studies, this signal pathway appears to mediate excitatory actions on respiration. In the present study, we analyzed receptor expression in pontine and medullary regions of the respiratory network both at the transcriptional and translational level using quantitative RT-PCR and self-made as well as commercially available antibodies, respectively. In addition we measured effects of selective agonists and antagonists for 5-HT2ARs and 5-HT2BRs given intra-arterially on phrenic nerve discharges in juvenile rats using the perfused brainstem preparation. The drugs caused significant changes in discharge activity. Co-administration of both agonists revealed a dominance of the 5-HT2BR. Given the nature of the signaling pathways, we investigated whether intracellular calcium may explain effects observed in the respiratory network. Taken together, the results of this study suggest a significant role of both receptors in respiratory network modulation

Lernen im Museum - Nachhaltiges Lernen durch Führungen? [Abstract]

Härting J, Wilde M. Lernen im Museum - Nachhaltiges Lernen durch Führungen? [Abstract]. In: Riemeier T, Niebert K, Krüger D, eds. 10. Internationale Frühjahrsschule der Fachsektion Didaktik der Biologie im vbio. 2008: 26-27

Systematic studies on the formation of DNA-LDH-nanocomplexes and their application as gene carriers

Over the last decade nanometre-sized layered double hydroxides (LDH) have been successfully explored as cellular delivery agents for various drugs [1, 2] and bio-active molecules such as peptides or DNA [3-5]. Despite its intrinsic promising properties such as good biocompatibility, low cytotoxicity [6, 7], high loading of anionic/polar molecules, pH controllable release, protection of guest molecules in the interlayer [6] and controllable particle size [3, 6, 8], initial transfection experiments showed disappointing performance of LDH compared to commercially available carriers. Therefore synthesis of DNA-LDH-nanocomplexes (LDH) and transfection protocols for mammalian cell lines were optimized, resulting in high transfection efficiencies of up to 60-70 % positive cells. We found that working at fairly high temperatures for DNA-intercalation with much diluted DNA solutions respective LDH suspensions at slightly acidic pH provides the best environment for high DNA uptake. Incubation time and DNA shape (plasmid/linearized) hardly affect the amount of intercalated DNA, whereas the size of DNA fragments seems to have major impact, with smaller plasmids being intercalated at five-fold higher rates than larger ones. Transfection and expression of various GFP plasmids in mammalian cell lines (HEK 293T, NIH 3T3, COS7) gave positive cells with DNA levels as low as 0.5 μg/well (Ø 35 mm). Production of LDH nanoparticles is less costly than for liposome based commercial competitors while showing similar efficiency, providing an alternative transfection agent with superior cost-performance-ratio

Controlled preparation of layered double hydroxide nanoparticles and their application as gene delivery vehicles

Layered double hydroxides (LDHs) have been known for many decades as catalyst and ceramic precursors, traps for anionic pollutants, catalysts, and additives for polymers, but they recently attracted attention as potential nano-sized carriers for therapeutic/bio-active molecules and genes. Among the many different nanoparticles that have been shown to facilitate gene and/or drug delivery, LDH nanoparticles are particularly well suited for this purpose due to their many desirable properties. In this research Mg2Al(OH)(6)NO3 LDH nanoparticles of varying lateral sizes were synthesized by altering the synthesis conditions. The synthesis conditions particularly influencing the particle size distribution of the LDH suspensions are (a) the temperature during the co-precipitation step and (b) the duration and the temperature of the hydrothermal treatment The association of these nanoparticles with plasmid DNA was studied and it was established that-in contrast to previously published reports-for the plasmid sizes used no significant intercalation occurs. The plasmids wrap around individual particles instead and aggregation of particles is observed. However, due to the observed strong interaction between LDH nanoparticles and DNA, the particles were nonetheless evaluated as transfection agents for mammalian cells. Considerable transfection efficiencies when transfecting adherent cell lines (i.e., HEK293T, NIH 3T3, COS-7, and CHO-K1) were observed, while the transfection of suspension CHO-S cells remained unsuccessful. This is attributed to the formation of aggregates upon DNA-LDH complex formation which settle on top of adherent cells but due to the constant agitation of suspension cultures not on the surface of e.g., CHO-S cells. (C) 2009 Elsevier B.V. All rights reserved