Locating Iodine in Tissues Autographically, Especially after Fixation by Freezing and Drying

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Abstract
The ability of radioactive elements to affect photographic emulsions enables the detection of radioactive iodine in the thyroid. By placing unstained histological sections of a thyroid (from an animal treated with radioactive iodine) in contact with the gelatin side of medium lantern slide plates, each accumulation of radioactive iodine in the section affects the photographic plate. After exposures prolonged for several days to several weeks depending on the amount of radioactivity in the tissues, the plate is developed and fixed by routine photographic methods. The histological section is stained and may be compared under the microscope to the reactions on the plate or “autographs”. In an attempt to detect the location of the inorganic iodine which is displaced during fixation and embedding by ordinary methods because of its solubility, a simplified freezing-drying technic for fixation was devised which, at least with the thyroid, yielded well fixed sections. The quick freezing was obtained with acetone-dry-ice mixtures; and the drying was performed at -25° to -30° C. Preliminary addition of paraffin to the tube in which the drying was performed made possible the inclusion in vacuum by heating the tube when drying was completed. The tissue could then be sectioned at 10ju on the microtome. The slides were placed on photographic plates for detection of radioactive iodine as indicated above. Before staining, the sections were treated with absolute alcohol for denaturation of the proteins.

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