Search PubMed⌕ Search

Biomedical subjects

C A Edwards

Publications and source records attributed to C A Edwards.

118 records · Page 7Linked to original sources
PubMed1979

Phosphorylation of T-antigen and control T-antigen expression in cells transformed by wild-type and tsA mutants of simian virus 40.

Chinese hamster lung (CHL) cells transformed by wild-type simian virus 40 (cell line CHLWT15) or transformed by the simian virus 40 mutants tsA30 (cell lines CHLA30L1 and CHLA30L2) or tsA239 (cell line CHLA239L1) were used to determine the rates of turnover and synthesis of the T-antigen protein and the rate of turnover of the phosphate group(s) attached to the T-antigen at both the permissive and restrictive temperatures. The phosphate group turned over several times within the lifetime of the protein to which it was attached, with the exception of the phosphate group in the tsA transformants at 40 degrees C, which turned over at the same rate as the T-antigen protein. The steady-state levels of the T-antigens (molecular weights, 92,000 [92K] and 17K) and the amount of simian virus 40-specific RNA was also determined in each of the lines. The CHLA30L1 line contained two to three times more early simian virus 40 RNA than the CHLA30L2 line; although neither line formed colonies in agar at 40 degrees C, CHLA30L1 overgrew a normal monolayer at 40 degrees C. The rate of 92K-T-antigen synthesis was 1.5 times faster in CHLA30L1 than in CHLA30L2 at 33 degrees C and 4 times faster at 40 degrees C. The different phenotype of these two presumably isogenic cell lines seem to be related to the levels of the T-antigens. The ratios of the 92K T-antigen to the 17K T-antigens were similar in the two lines. Transformed CHL cell lines, unlike transformed mouse 3T3 cell lines, were found to contain very small amounts of the 56K T-antigen.

Animals↗
PubMed1979

Roles of the simian virus 40 tumor antigens in transformation of Chinese hamster lung cells: studies with simian virus 40 double mutants.

Simian virus 40 mutants containing both a tsA mutation (rendering the 90,000 molecular weight [90K] T-antigen thermolabile) and a deletion between 0.54 and 0.59 map units (reducing the size and the amount of the 20K t-antigen) were used to transform Chinese hamster lung cells. The frequencies of transformation by the double mutants were comparable to that of the tsA mutant alone by both the focus and agar assays except when the cells were serum depleted before infection. Growth-arrested cells were transformed (using the agar assay) by the deletion mutants at less than 2% the frequency found when the 20K t-antigen was normal. Growth arrest had very little effect on the temperature sensitivity of the resultant transformed cell lines whether or not the deletion was present.

Animals↗
PubMed1978

Comparison of the 3alpha-and 20beta-hydroxysteroid dehydrogenase activities of the cortisone reductase of Streptomyces hydrogenans.

The 3alpha- and 20beta-hydroxysteroid dehydrogenase (HSD) activities of cortisone reductase in Streptomyces hydrogenans have been examined to determine whether both activities are due to one enzyme. This question was raised when changes in the commercial preparations of the enzyme reduced the 3alpha-HSD activity to 5% of its original level while retaining full 20beta-HSD activity. In our experiments, the enzyme was purified to crystallinity and partially characterized. The 3alpha- and 20beta-HSD activities were both coinduced and copurified. The 3alpha- and 20beta-HSD activities were compared using the crystalline enzyme for studies of substrate competition, thermal inactivation at 52 degrees C, loss of activity with three haloacetoxysteroids, and the effects of Me2SO and temperature on the reaction rate. These studies support the conclusion that the 3alpha- and 20beta-HSD activities are due to the same enzyme molecule. In addition, it appears that the binding sites for the two activities do not act independently.

20-Hydroxysteroid Dehydrogenases↗
PubMedDate not supplied

Dentin bonding: SEM comparison of the dentin surface in primary and permanent teeth.

The literature suggest differences between primary and permanent teeth regarding the composition and morphology of the dentin. The purpose of this study was to compare the effect of two dentin conditioners on the micromorphology of the dentin surface of primary and permanent teeth. Human extracted and noncarious molars were divided into four groups and conditioned with either 10% phosphoric acid (All-Bond 2) or 10% maleic acid (Scotchbond Multi-Purpose) for different time periods. SEM photomicrographs (1500x) were taken from the conditioned dentin and evaluated blindly by three calibrated examiners. The results indicate that the smear layer was removed more easily from primary teeth than from permanent teeth (P = 0.0001), which suggests greater reactivity to acidic dentin conditioners. We also found that the longer the time of application of dentin conditioner the more smear layer is removed (P = 0.0094). In comparing primary and permanent dentin, the results of this study indicate that less time is required for appropriate acid conditioning of primary dentin surfaces. Such a differentiated protocol for bonding to primary tooth dentin results in surface morphological characteristics similar to those found in conditioned permanent teeth.

Acid Etching, Dental↗