does not show changes in association with early or minimal lesions of cancer.
)Since antitrypsin values appear to be closely rlelated to the growth of seminoma of the testis, it sugfgested that the test may have unique prognostic value in the study of this condition.2 ) The test may aid in excluding the diagnosis of advanced but non-terminal malignancy, or in the discovery of these lesions when they present themselves in obscure form. Received L%ust 3J 1949. P.S.E.B.M., 1949J 7%The method of assay for vitamin B12 herein described was developed using a diet based on purified casein. The diet was made to contain 0.05% iodinated casein (Protamone) as a metabolic stimulant and 0.5% sulfaguanidine [to inhibit bacterial synthesis of vitamins. Weanling rats, depleted on this diet for about 7 days, show a depression of growth rate which is counteracted by administratilon of vitamin BIZ. The rate of response within a critical range is proportional to the amount of vitamin Bl2 administered, either as the purified viitamin or as concentrates of the vitamin, such as liver extract.It is well known that liver extract and vit. B12 show much higher activity by injection than by oral administration in the pernicious anemia patient. We were interested in the present study to dsetermine whether a difference could be shown between the effects of oral and intramuscular administration of the vitamin. We were interested also to determine the comparative effects of single doses at the beginning of the assay period versus divided doses throughout the assay period. Following completion of thlese studies, Emer-son1 reported that vitamin BIZ is equally active by either the oral or subcutaneous route in daily doses ranging from 0.0625 to 0.5 pg per rat day, somewhat higher than the range we have studied.Register, Ruegamer and Elvehjem* reported 1Emerson, G. A., P m . SOC. Em. Bmb. AND MED., 1949, 7.0, 392. a quantitative response in rat growth in their assay in the range of 0.025 to 0.1 U.S.P. units per rat day in the form of commercial liver extract. Direct comparison with vit. B12activity was not made in the Wisconsin report.We were interested to determine with a sampIe liver extract whether 1 pg of vit. B12 would correspond fairly closely by rat assay to I U.S.P. unit, a figure previously suggested by Rickes et al.P to be in approximately the correot range. Experimental. Weanling rats, 35-45 g, of mixed sex were placed on a vitamin B12 low diet for depletion. The B12 depletion diet has the composition shown in Table I. In preliminary assays S.M.,4 vitamin test casein was further purified by the method of solution and reprecipitation of Novak and Hauge? Later we found that vitamin test casein gave s t i sfactory results without further purification.The rate of weight gain is about 12-15 g during the second week on the depletion diet and diminishes to about one-half this rate during the third week of depletion. The depletion period used ranged from 7 to 14 days.The 7-day period is preferred because of the increased mortality wh'ich occurs o...
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