Both normal cell turnover and healing of laryngeal and tracheal injuries involve cell migration and mitosis. The proteins that regulate normal cell turnover and wound healing in the larynx and trachea have not been established. It is possible that peptide growth factors, such as transforming growth factor-alpha (TGF alpha) acting through its receptor (EGF/TGF alpha-R), participate in the regulation of these processes. To investigate this hypothesis, we analyzed laryngotracheal cells for TGF alpha protein and receptor in normal and postwounding conditions. TGF alpha protein was detected by immunohistochemical analysis in normal ferret laryngeal and tracheal mucosa. Specific binding to the EGF/TGF alpha receptor in membrane homogenates of ferret larynx and trachea reached saturation after 60 minutes at 37 degrees C, and was effectively displaced by unlabeled epidermal growth factor (EGF) or TGF alpha, but not by unlabeled insulin, angiotensin II, or basic fibroblast growth factor. Scatchard analysis of the specific binding indicated the presence of high-affinity (Kd = 117 pmol) and low-affinity (Kd = 40 nmol) binding sites. The maximum number of available binding sites was 73 fmol/mg protein. Localization of the EGF/TGF alpha receptor by autoradiographic analysis of 125I-EGF binding to sections of normal ferret larynx and trachea revealed EGF/TGF alpha receptors throughout the epithelium, with the highest grain density in the basal layers. Quantitative analysis of autoradiographic grain density between normal, intubated, and extubated animals revealed no significant differences. The presence of TGF alpha protein and its receptor in normal and wounded larynx and trachea supports the hypothesis that these proteins are involved in regulating physiologic responses of laryngotracheal cells.

The field of mechanobiology is aimed at understanding the role the mechanical environment plays in directing cell and tissue development, function and disease. The empirical aspect of the field requires the development of accurate, reproducible and reliable loading platforms that can apply microprecision mechanical load. In this study we designed, fabricated and characterized a pure uniaxial loading platform capable of testing small synthetic and organic specimens along a horizontal axis. The major motivation for platform development was in stimulating bone cells seeded on elastomeric substrates and soft tissue loading. The biological uses required the development of culturing fixtures and environmental chamber. The device utilizes commercial microactuators, load cells and a rail/carriage block system. Following fabrication, acceptable performance was verified by suture tensile testing.

In terms of accurate and precise mechanical testing, machines run the continuum. Whereas commercial platforms offer excellent accuracy, they can be cost-prohibitive, often priced in the $100,000-$200,000 price range. At the other extreme are stand-alone manual devices that often lack repeatability and accuracy (e.g., a manual crank device). However, if a single use is indicated, it is over-engineering to design and machine something overly elaborate. Nonetheless, there are occasions where machines are designed and built in-house to accomplish a motion not attainable with the existing machines in the laboratory. Described in detail here is one such device. It is a loading platform that enables pure uniaxial loading. Standard loading machines typically are biaxial in that linear loading occurs along the axis and rotary loading occurs about the axis. During testing with these machines, a load is applied to one end of the specimen while the other end remains fixed. These systems are not capable of conducting pure axial testing in which tension/compression is applied equally to the specimen ends. The platform developed in this paper enables the equal and opposite loading of specimens. While it can be used for compression, here the focus is on its use in pure tensile loading. The device incorporates commercial load cells and actuators (movers) and, as is the case with machines built in-house, a frame is machined to hold the commercial parts and fixtures for testing.

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