鉛中毒症状の診断的価値に関する実験的研究
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概要
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An experimental study concerning the diagnostic evaluation of symptoms due to lead poisoning was made with rabbits which were exposed to lead oxide dusts of different concentrations. Symptoms such as stippling, polychromasia, reticulocytosis, hemoglobin decrease and urinary coproporphyrin increase were estimated and also analysis of serum protein fraction was carried out by the paper electrophoretic method. A chamber for exposure which was equipped with the Wright's dust feed mechanism was tpecially designed for the rabbits allowing to inhale lead dusts. The experiment lasted over a period of one and half years from autumn 1957 so spring 1959. Maximum length of exposure was limited to 4 hours each day, and to 3 days each week. During the course of the experiment, cessation of lead inhalation for 2 month was inserted in order to observe how soon these symptoms disappear after the cessation of exposure. Principal results obtained were as follows. 1) The urinary coproporphyrin level and the stippled cell counts were increased before anemia developed. Besides, it was noted that the increase of stippled cells was not shown until four to five months after the urinary porphyrin became positive. The decrease of hemoglobin amount occured immediately after the definite rise of the stippled cell counts. From these facts, it would appear doubtful that the increased excretion of urinary coprophrin is merely due to the blocking by lead of entrance of iron into the protoporphyrin ring. The increased urinary coproporphyrin in the earlier stage of lead absorption must be due to other mechanism than this hypothesis which explains the decreased hemoglobin amount. 2) Urinary coproporphyrin, stippled cell counts and reduction of hemoglobin were increased parallel with the lead amount inhaled. However, the reticulocyte counts, polychromasia as well as changes of the serum protein' namely the elevation of α_2 and γ-globulin levels and the decrease of the albumin level had no relation with the degree of lead absorption, as far as the experimental animals were concerned. 3) Reduced hemoglobin and increased stippled cells by lead exposure returned rapidly to the normal value after the cessation of inhalation. On the other hand, urinary coproporphyrin delayed to become normal, in spite of the prompt recovery of those symptoms mentioned above.
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