Cloned cDNA of human interleukin 2 (IL-2) was expressed in Escherichia coli cells in which IL-2 formed insoluble inclusion bodies. Human IL-2 has three Cys residues, namely, Cys-58, Cys-105, and Cys-125, and native IL-2 has an intramolecular disulfide bond between Cys-58 and Cys-105. Since the formation of inclusion bodies was thought to be due to disorder in the oxidation state of these Cys residues, all intramolecular disulfide bond isomers of IL-2 were prepared by denaturation of native IL-2 to characterize the state of a disulfide bond in IL-2 in the inclusion bodies. These isomers can be separated from native IL-2, reduced IL-2, and IL-2's with intermolecular disulfide bonds by means of reversed-phase high-performance liquid chromatography. Human IL-2 produced in inclusion bodies in E. coli carrying a recombinant DNA was analyzed by HPLC and was proved to be a fully reduced form with no intra- and intermolecular disulfide bonds. Refolding of reduced IL-2 in the presence of reduced and oxidized glutathione and a low concentration of guanidine hydrochloride resulted in the formation of the biologically active IL-2 quantitatively. Further purification provided a practically pure IL-2 preparation without contamination of any disulfide bond isomers.

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The present experiment was conducted to investigate the optimum length of the preliminary and collection periods when the chromic oxide-powder, chromic oxide-paper and 4 N-HCl insoluble ash (AIA) are used as indicators in digestion trials with pigs, and to compare the digestibility of total feces collection method with that of those indicator methods. Rations consisted of the following 3 diets: (A) commercial diet for young pigs; (B) diet generally used for the performance test for meat production in Japan; (C) diet B with 20% beet-pulp. Eight Landrace barrows were divided equally into two groups: pigs of one group were given diets A, B and C for 10, 14 and 14 days, respectively; and pigs of the other group were given diets A, C and B for 10, 14 and 14 days, respectively, in serial order. Four animals of each group were split into two lots. A pair of them was given the diet added chromic oxide-powder and another chromic oxide-paper contained approximately 40% chromic oxide, in which 0.2% of either chromic oxide-powder or chromic oxide-paper had been added to formula feed of diet B or diet C. The chromic oxide component in the feces for chromic oxide-powder or chromic oxide-paper method attained a steady state within 4 days after the ration was replaced. The days needed for a steady state of the AIA component in the feces was 4 days after the ration was replaced by diet B. By contrast, feeding diet C a case was observed that the AIA component in the feces did not come into equilibrium in less than 14 days. The coefficients of variation of apparent digestibility for each component in total collection method after 4 days preliminary feeding period decreased greatly during the first 3 to 4 days, but those of the indicator methods decreased slightly and there was little advantage with the extension of the length of collection period. This suggested that the collection periods of 1-2 days is enough for digestion trial by indicator method. Feeding diet B and C the fecal recoveries of the chromic oxide-powder were 95.9 and 95.1%, and those of the chromic oxide-paper were 94.3 and 96.5%, respectively. The digestibilities of dry matter, crude protein and energy determined by those two indicator methods were about 1% lower than those determined by the total collection method and an error of this size should probably be acceptable to most investigators. Feeding diet B the fecal recovery of AIA was 99% and the digestibilities determined by this method were practically identical to those obtained by the total collection method. But the fecal recovery of AIA was poor by feeding diet C.Jpn. J. Zootech. Sci., 55 (12) : [924][925][926][927][928][929] 1984 Jpn. J. Zootech. Sci., 55 (12): 924-929 929 1984

The present experiment was conducted to investigate the optimum length of the preliminary and collection periods in digestion trials by the conventional total collection method with pigs.Eight Landrace barrows weighing 45 to 54kg at the beginning of the experiment were used.Each pig was kept in a metabolism cage throughout the experiment. Rations consisted of the following 3 diets; A, commercial diet for young pigs, B, diet generally used for the performance test for meat production in Japan and C, diet B with 20% beet-pulp.The pigs were divided into two groups; pigs of one group were given diets A, B and C for 10, 14 and 14 days, respectively, and pigs of the other group were given diets A, C and B for 10, 14 and 14 days, respectively, in serial order. The pigs were given 35g/kg body-weight of either diet A or diet B, or 30g/kg body-weight of diet C per day. Feces were collected quantitatively during the last 32 days (days 7-38).The components in the feces attained a steady state within 3 to 4 days after the ration was replaced. This suggests that at least 4 days are necessary for a preliminary feeding period. The coefficients of variation of apparent digestibility for each component after 4 days preliminary feeding period decreased with lengthening collection period. The decreas in the coefficient was great during the first 3 to 4 days, but slight after that. These results indicate that 4 days are necessary for the preliminary and collection periods in the digestion trials by the total collection method. Jpn.