An adrenal corticoid which has an α-ketolic grouping at C17, a ketone or β-hydroxyl at C11, a ketone at C3, and a double bond in the 4,5 position is able to involute the thymus gland of the weanling rat. The thymolytic activity of an 11-oxycorticosteroid is increased approximately 3 to 3.5 times by the addition of an α-hydroxyl at C17. The ability of a 17-hydroxycorticosteroid to cause thymic atrophy is enhanced 1.2 times by acetylation at C21, 1.5 times by replacement of a ketone at C11 with β-hydroxyl group, 4 to 5 times by the formation of a 1,2 double bond, and 8 to 10 times by the introduction of a fluorine atom in the α position at C9. The potency of Δ1-11-oxycorticosteroids relative to naturally occurring corticoids is significantly greater when the steroids are injected in an aqueous medium than when they are given in corn oil. The relative activities of adrenal corticoids as determined by the thymus involution method do not differ significantly from those obtained by other glucocorticoid bio-assays.
A conventional quantal response assay procedure was employed to determine the LD50 of shellfish extracts. The slope of the log dose – response line obtained with butter clam extracts was not significantly different from that found with scallop liver extracts. When kept in a dry, cold state, a lyophilized extract of scallop liver was stable throughout a test period of nearly three years. Such a preparation could be used as a reference standard for the bio-assay of shellfish toxin. Female mice were more susceptible to the paralytic poison than male mice. The LD50 per mouse was related directly to the average body weight of the test animals. The volume of the injection medium had no effect on either the magnitude of the LD50 or the slope of the probit regression line. A highly significant inverse relationship was demonstrated between the toxicity measured in mouse units, a procedure based on the mean death time of the test animals, and the LD50 per kgm. of mouse determined by an assay with an all-or-none response.
A method is described for preparing a 19 S thyroglobulin component from a saline beef thyroid extract by chromatographic fractionation on Sephadex G-200. By employing Sephadex G-200 it was possible to separate a saline extract of minced beef thyroid gland into several fractions, the first of which (fraction I) contained approximately 60% of the protein and 96% of the iodine. Spectrophotometric, ultracentrifugal, and immunochemical methods revealed that fraction I possessed, in addition to the 19 S thyroglobulin protein, a 25 S component as well as serum proteins. A narrow band of fraction I appeared to be free of both the 25 S component and the serum proteins. The material in this subfraction had a sedimentation constant of S20,w = 19.1 and contained 1.2 mg of iodine per 100 mg of protein.
A commercial insulin preparation was stored for 2 years, its normal shelf-life, at temperatures from 2" to 36". Full potency was retained for 2 years when the sample was kept at 2". However, the activity of the insulin decreased with time as the storage temperature was increased. After one year at room temperature (20" to 25") the activity of the insulin sample was 20 per cent below that stated on the label. Between 2" and 20" there was a consistent but not significant drop in activity. In the initial period the loss in potency may be essentially a reaction of zero order. THE stability of commercial insulin preparations is important, not only to the manufacturer, but also to the physician and in particular to the diabetic patient. Krogh and Hemmingsenl were the first to make a systematic study of the relation between temperature, time, and the destruction of amorphous insulin in a sterile aqueous solution. Their results suggested that the inactivation of insulin at a constant temperature followed a first order reaction, the rate of destruction at any moment being proportional to the concentration. In addition, it was reported that the optimal stability of an aqueous solution of insulin occurred between pH 2 and 4. Sahyun, Goodell and Nixon2, working with a low-ash insulin preparation, revealed that the addition of Zn++ to the aqueous medium improved the stability significantly. However, Lens3 could not confirm this stabilising effect of Zn++, and reported that the stability of crystalline insulin in aqueous solution was unpredictable. Lens concluded that the inactivation was not due to hydrolysis of the insulin, but could be attributed to denaturation or heat precipitation which was usually followed by an irreversible oxidative process.These inve~tigationsl-~ were carried out for short periods at elevated temperatures. There is a scarcity of information about the stability of commercial insulin preparations when kept at temperatures encountered under ordinary storage conditions for the expected shelf-life of the product. Consequently an experiment was designed to determine the rate at which insulin made from zinc insulin crystals loses activity when stored for a period of two years at temperatures of 2" to 36". MATERIALS AND METHODSInsulin Toronto, made from zinc insulin crystals, Lot 942-1, 40 International Units per ml., was used in this study, and was prepared from
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