SELENIUM-the
N E W ENIGMA
L. L.WOODS St. Augustine's College, Raleigh, North Camlina
S
ELENIUM researches have had a new impetus during the past decade resulting in many new uses, and bizarre compounds. Some of the recently developed uses are the manufacture of photoelectric cells, fire-proof cable coverings, abrasive resistant rubber, and as a dehydrogenating agent. Organic compounds of selenium have been prepared from this element which are truly unusual in both character and odor. A comprehensive review of these compounds by W. F. Bradt (1)reveals that although a great deal of work has been done in this direction we are in need of some thoroughgoing research really to understand the chemistry of selenium when held in organic union. In this article we will not attempt to survey the inorganic or organic chemistry of this element; but we will review a small segment of the biological researches which, we believe, are quite significant. Indeed, medical men have, as a result of these researches, come to suspect that the disease pellagra is nothing more than selenium poisoning. Selenium poisoning of animals has been known as "alkali poisoning" or "blind staggers." This disease seems to be purely a local occurrence in the North Central and Great Plains States; in Kansas the disease was described by Mayo (2) as early as 1890-1891. Studies by Hurd-Kmer (3) on the effect of vegetation grown in seleniferous soils on animals have cleared the situation a great deal. Her researches prove that plants grown in soils containing one ,to two parts per million of selenium (as selenate; for the selenites are reduced by the plant, and red selenium &ay be seen in root tissue) have all the vigor and height of the normal species, but when fed to rats are deadedly toxic; analysis on these plants shows as much as three hundred twenty-five to three hundred thirty parts per million of selenium in the leafy tissue. However, when the same plants were grown in the same type of seleniferous soils, but made rich with sulfur, no ill effects were noticed. Hurd-Kmer, therefore, suggests a seleniumsulfur relationship to the effect that vegetation (cabbage, broccoli, mustard, and cauliflower) which requires a large amount of sulfur, when grown in soils which are low in sulfur content will take up selenium to compensate for the deficiency even to the extent of becoming toxic. Plants which require little sulfur, such as grasses, may be grown in sulfur-poor soil and will not be toxic unless the selenium content (as selenate) of the soil is exceptionally high. An interesting item is the fact that i t appears to be young plants which absorb the most selenium, and toward maturity the content of this element in the leafy tissue is appreciably
decreased; this is true especially in the case of wheat. Young wheat growing in soil containing thirty parts per million sodium selenate had as high as 1120 parts per million in the leafy tissue. However, upon maturity the same plants had only two hundred twenty parts per million. Another interesting fact is that when wheat is infested with plant lice, and the roots are treated with sodium selenate solution, the lice immediately decamp. Wheat is one of the cereals which is particularly susceptible to selenium poisoning. Indeed, Robinson (4) is of the opinion that no wheat is absolutely free of this substance. His researches indicate that commercial wheat contains from one to nineteen parts per million, and that most of the element is concentrated in the gluten of the cereal. A sample of flour purchased in New York had a content as high as twenty-six parts per million, which was definitely harmful; for he sets sixteen parts per million as the maximum amount of selenium which can occur in a substance without hannful results to the human body. The symptomology of animals which have been poisoned by selenized vegetation is described (5) as: (1) Necrosis and regeneration of hepatic parenchyma w$th periportal fibrosis and&resultingcirrhosis combined with hemorrhages and secondary inflammatoryreaction of lungs and kidneys. (2) Reduced selenium is found in the liver and spleen, and compounds of selenium are found in all tissues, secretions, and excretions. (3) Cattle, sheep, horses, and pigs show erosions on the ends of the weight-hearing hones, along with haof abnormalities which impair locomotion, malaise, anorexia, stunted growth, loss of hair, loss of weight and emaciation, impairment of reproductive power, and severe anemia to be followed by exhaustion, toxemia, and death. (4) Chickens (6) show a decided impairment of fertility; if the eggs hatch, the young do not live long, and monstrosities occur among them frequently.
Known cases of human poisoning by seleniferous foods have been studied by Smith, Franke, and Westfall (7). These cases were one hundred eleven families of the Wyoming, South Dakota, and Nebraska area; and their observations on the symptomology of selenium toxicosis were almost identical with the symptomology of pellagra as set forth by Rohan De Barondes (8) in his study of selenium poisoning, which are: (1) Gastra-intestinal disturbances and nervous and mental disorders that often terminate in complete dementia. (2) On exposure to the bright light of sun during summer months, skin manifestations present themselves in the form of vesiculations and actinic dermatitis. The other symptoms present become more aggravated, and it is at this time that the mortality is highest. (3) During the fall months the skin commences to desquamate, and by wintertimeatrophicand pigmented areas resembling vitiligo make their appearance.
(4) Patients of pellagra complain of a garlic-like odor, or a n arsenic-like odor in the mouth and breath. A similar odor is noted on and about selenium poisoned animals.
chemistry, and i t is not only an enigma to the inorganic and organic chemist, but also to the physician and the agricultural chemist.
De Barondes elaborates upon his study of selenium DEFINITIONS O F SOME O F THE MEDICAL TERMS poisoning to remark that selenium alkalis and oxides are toxic, but the oxides if taken orally in small quanti(1) Necrosis.-Death of more or less extensive groups of ties seem to contribute to the oxidation of body sulfur. cells with regenerative changes. of liver, may be (2) Hepatic Parenchyma.-Idammation It is used for this reason in the treatment of cancec. acute yellow atrophy of organ. A comparison of the symptoms of pellagra have been (3) PeriPortel Fibrosis.-Fibrosis of tissue around the liver; observed in alcoholic patients who drink cheap bever- fibrosis-forming of fibers. ages made of corn, probably containing much sele(4) Cirrhosis.-A degeneration or atrophy of parenchyma nium. The proper treatment for selenium toxicosis is a cells of an organ. (5) Malaise.-Discomfort, out-of-sorts feeling. sulfur-rich diet and dried yeast. W. H. Sebrell (9) (6) Anorezia.-Loss of appetite. gives as the proper diet for pellagra, dried yeast, lean (7) Vesicu1ations.-Inflation4. inflamed swollen spots. meats, wheat-germ containing foods, and sulfur-bear(8) Actinic Dermatitir.-Inflammation of skin due to effects ing green vegetables. Again, there is a similarity, of sunlight. (9) Desquamation.-Shredding, peeling, or scaling of skin. even in the treatment for the two diseases. (10) Atrophic.-Wasted areas. These few excerpts from biological researches make (11) Regeneration.-Reproduction. or repair of injured the selenium problem very personal to all branches of tissue. LITERATURE ClTED
(1) BRADT, J. CEEM.EDUC.,12,363-6 (1933).
(6) FRANKE andothers, Anat. Record, 65,118 (Apr., 1936). (2) MAYO,~ u l l c t i n24, Kansas Agricultural Experiment Station (7) SMITH,FRANKE,AND WESTFALL, Pcblic Health Re&, 51, (1891). 1489-1532 (Oct., 1936). (3) H ~ D - K A R ~ ESclcnium R, Absorption by Plants and Their BARONDES, Am.; I. Digestive Diseases Nutrition. 3, 330 Resulting Tozidty to ~ ~Ann, R ept. i I ~~~~~~~~i~~ ~ ~ (8) DE ~(July, ~ 1936). Inst.. 28'3302 (1935). DE BARONDES, Presse Med., 45, 188 (Feb., 1937). (4) ROBINSON, Ind. Eng. C h m . , 28,736 (June, 1936). 5. Am. Med. Asroc., 107,968 (1936)(9) SEBRELL, Am. J. Nursing, 38,507-10 (May, 1938). (5) EDITORIAL,
