Transmittance and diffuse reflectance measurements were recently performed over a range from 800 to 2200 nm for previously frozen and fresh native porcine stomach cardiac and pyloric mucosa sections of 1.2-1.6 mm thickness. Mucosa consists of moist epithelium and the connective tissue immediately beneath it. Mucosal structure is somewhat identical to skin with cell epidermal and fibrous dermal layers. The absence of the dead cell layer, such as the SC of skin, makes normal mucosa more permeable for chemical agents. Immersion solutions (glycerol/DMSO/water) of different concentrations were topically applied onto the epithelium surface of the sample and then spectra were acquired at time intervals of 5, 10, 20, and 30 min. The difference in apparent absorbance (extracted from the diffuse reflectance) between two wavelengths, 1936 nm and 1100 nm, was used to estimate water content. Some results are presented in Fig. 42. It can be seen from Figs. 42(a) and 42(b) that, over the whole wavelength range investigated, the transmittance was increased with time, and diffuse reflectance was decreased over the range of 800-1370 nm. The greatest increase in transmittance was at 1278 nm, and the greatest decrease in reflectance was at 1066 nm.
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