Isolation and separation of nucleic acids from Streptomyces hydrogenans (author's transl)]

Different methods for homogenization of cells of Streptomyces hydrogenans, for extraction of nucleic acids and for fractionation of the RNA and DNA obtained were critically examined. The only way to prepare high molecular weight rapidly labelled RNA and polysomes was to grind freeze-dried cells together with kieselguhr with a mortar and pestle. The best results for extraction of nucleic acids from the cell homogenate were obtained in the presence of diethyl pyrocarbonate (diethyl oxydiformate), yielding nucleic acids of considerable purity in a minimal amount of time. The best resolution of extracted nucleic acids was achieved by electrophoresis in 2% agarose acrylamide gels. This technique proved that during the cell homogenization and extraction procedure the bulk of nucliec acids was not degraded to low molecular weight material. An improved device for the registration of the profile of the absorption after gel electrophoresis is described.     

Thyroxine Treatment and Chicken (Gallus gallus) Embryo Duodenum in vitro

To study direct action of thyroxine (T₄) on duodenal development in chicken embryos, duodena from stage 42 White Leghorn (strain Hyline 934F) Gallus gallus embryos were cultured, cut into quarter segments and slit open on grids. L-T₄ was added to McCoy's 5A medium to concentrations of 14 ng/ml or 14 ng/100 ml. To control for possible physicochemical effects, D-T₄ was added to other media in the same concentrations, and saline vehicle was added to control media. Bovine serum albumin (BSA) was added to a duplicate set of cultures (0.2% w/vol) as a nutritive supplement. After 48 h alkaline phosphatase (E.C. 3.1.3.1) specific activity was significantly elevated (p < 0.05) in segments cultured with 14 ng L-T₄/100 ml (non-BSA) compared to saline control cultures. With 14 ng L-T₄/ml (BSA) phosphatase activity had increased significantly compared to segments treated with 14 ng L-T₄/100 ml (BSA), while those cultured with D-T₄ (BSA) had significantly lower activities than all other BSA-treated groups including controls. Total protein content was significantly elevated in all D-T₄ treated segments, both non-BSA and BSA-treated, compared to protein values of all other treatment groups. Following 48 h of culture the fine structure of epithelial mucosal cells usually showed condensed cytoplasm, while goblet cells were well developed, structural features appearing in all segments regardless of treatment. The responses after treatment further support a direct role for T₄ in duodenal development.