Purpose: To study the anatomical relationships involving the intrinsic and extrinsic myofiber populations of the human tongue employing diffusion tensor imaging (DTI) with tractography. Materials and Methods:Images of the human tongue in vivo were obtained using a twice-refocused spin echo DTI pulse sequence at 1.5T, isotropic 3 ϫ 3 ϫ 3 mm 3 voxels, b-value 500 seconds/mm 2 , and 90 different diffusion sensitizing gradient directions. Multivoxel tracts were generated along the vectors of maximal diffusion in each voxel. The data was visualized using custom fiber tracking software and images compared with known anatomy.Results: DTI tractography depicts the complete three-dimensional (3D) myoarchitecture of the human tongue, specifically demonstrating the geometric relationships between the intrinsic and extrinsic myofiber populations. These results define the manner in which key extrinsic fiber populations merge with the longitudinally-, transversely-, and vertically-aligned intrinsic fibers. Conclusion:The current results display for the first time the use of DTI tractography in vivo to visualize the complete structural anatomy of the human tongue and allow us to consider fundamental structure-function relationships.
SUMMARY The mammalian tongue is believed to fall into a class of organs known as muscular hydrostats, organs for which muscle contraction both generates and provides the skeletal support for motion. We propose that the myoarchitecture of the tongue, consisting of intricate arrays of muscular fibers, forms the structural basis for hydrostatic deformation. Owing to the fact that maximal diffusion of the ubiquitous water molecule occurs orthogonal to the short axis of most fiber-type cells, diffusion-weighted magnetic resonance imaging (MRI)measurements can be used to derive information regarding 3-D fiber orientation in situ. Image data obtained in this manner suggest that the tongue consists of a complex juxtaposition of muscle fibers oriented in orthogonal arrays, which provide the basis for multidirectional contraction and isovolemic deformation. From a mechanical perspective, the lingual tissue may be considered as set of continuous coupled units of compression and expansion from which 3-D strain maps may be derived. Such functional data demonstrate that during physiological movements, such as protrusion, bending and swallowing, hydrostatic deformation occurs via synergistic contractions of orthogonally aligned intrinsic and extrinsic fibers. Lingual deformation can thus be represented in terms of models demonstrating that synergistic contraction of fibers at orthogonal or near-orthogonal directions to each other is a necessary condition for volume-conserving deformation. Evidence is provided in support of the supposition that hydrostatic deformation is based on the contraction of orthogonally aligned intramural fibers functioning as a mechanical continuum.
Microfluidic cell culture is a promising technology for applications in the drug screening industry. Key benefits include improved biological function, higher quality cell-based data, reduced reagent consumption, and lower cost. In this work, we demonstrate how a microfluidic cell culture design was adapted to be compatible with the standard 96-well plate format. Key design features include the elimination of tubing and connectors, the ability to maintain long term continuous perfusion cell culture using a passive gravity driven pump, and direct analysis on the outlet wells of the microfluidic plate. A single microfluidic culture plate contained 8 independent flow units, each with 10(4) cells at a flow rate of 50 μl/day (6 minute residence time). The cytotoxicity of the anti-cancer drug etoposide was measured on HeLa cells cultured in this format, using a commercial lactate dehydrogenase (LDH) plate reader assay. The integration of microfluidic cell culture methods with commercial automation capabilities offers an exciting opportunity for improved cell-based screening.
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