Abstract
Vitamin A reveals a green fluorescence in ultraviolet light which disappears rapidly during irradiation. 1 This was observed under the fluorescence microscope using dilute aqueous emulsions of vitamin A concentrates. The striking green of the droplets fades during the observation. The same behavior is noted in some animal tissues and may be attributed to the presence of vitamin A. Querner, 2 describing inclusions in epithelial cells of liver and adrenal, and Jancso 3 demonstrating fluorescence of the pigment epithelium of the eye, made this assumption. The assumption that such a fluorescence is due to vitamin A can be supported now by the following facts. We found this fading fluorescence always located in lipoids of the body and absent after treatment of the tissue with alcohol or acetone. Its distribution in the body agrees with that of vitamin A as determined chemically. Animal experiments, as those reported later and a few briefly mentioned by Querner offer evidence that this particular fluorescence is due to the presence of vitamin A.
Thin pieces of tissue were fixed in excess of 10% formalin and frozen sections made within 24 hours after fixation and examined under the fluorescence microscope. Inadequate and prolonged fixation must be avoided because the fatty bodies acquire a disturbing bluish fluorescence due to oxidation.
The observation of the spontaneous fluorescence of vitamin A could be supported by staining with fluorescing dyes (fluorochromy). Fats give a bluish fluorescence with methylene blue which in presence of vitamin A is surpassed by the fading green fluorescence. By changing the ultraviolet to a ground glass filter one can observe the blue stained slide in visible light and exactly localize the fluorescing inclusions. In addition, the carrier substances (lipoids) can be demonstrated by fluorescing dyes.
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