Purification to apparent homogeneity of a thymocyte specific growth factor from calf thymus

New Preparative Schedule and Further Characterization of a Thymocyte Specific Growth Factor from Calf Thymus

“…Ninhydrin-cadmium reaction was performed ac cording to Heilmann et al [6] with slight modifications (5). Incor poration of 'H-dT into DNA of guinea pig thymocytes in 5-hour cultures [3] was estimated by liquid scintillation and used as assay. The results were expressed as mean counts per minute (cpm) of du plicate cultures in percent of controls.…”

“…3.4.21.1, 15 h, 37°C), pronase (protease from Streptomyces griseus , 5 h, 37°C), 2-mercaptoethanol (I % 2-ME, 5 h, 20°C) and cyanogen bromide (20 mM in 70% formic acid, 24 h, 20°C) and then lyophilized and redissolved twice and assayed in thymocyte cultures. Appropriate control material as described earlier [3] was assayed simultaneously.…”

“…Based on previous data [3] on physicochemical properties of the growth-stimulating thymic factor, a refined extraction schedule was designed (see below). The method is modified from a peptide extraction schedule of Mutt [8].…”

“…In previous papers, we have reported on a growth factor obtained from calf thymus, with effect on immature cycling thymocytes but without any ef fect on immunologically mature thymocytes, periph eral lymphocytes, bone marrow cells and liver cells [2][3][4]. The growth stimulating activity was resident in ac idic, heat stable material with Mr of 1,000-2,000 [3,5]. Extended studies on the chemical structure and bio logical effects of the factor required higher amounts of purified material.…”

“…Extended studies on the chemical structure and bio logical effects of the factor required higher amounts of purified material. Based on the physicochemical properties of the material [3], a new purification sche dule was designed and is presented in this paper to gether with a further characterization of the growth factor.…”