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Biomedical subjects

M Yee

Publications and source records attributed to M Yee.

23 records · Page 2Linked to original sources
PubMed1980

Effect of copper on Menkes' and normal cultured skin fibroblasts.

Skin fibroblasts from normal subjects and from patients with Menkes' disease did not demonstrate any significant differences in morphologic or growth characteristics when cultured in medium without added copper. Addition of CuCl2 to the medium caused a reduction in the growth rate of the fibroblasts. Menkes' fibroblasts were more sensitive to copper than normal cells. Concentrations greater than 50 micrograms CuCl2/ml of medium caused extensive cell death especially in the mutant cells. The rate of DNA synthesis in Menkes' fibroblasts was reduced in the presence of 2--100 micrograms CuCl2/ml. Normal cells showed a reduction in DNA synthesis at CuCl2 concentrations greater than 50 micrograms/ml, whereas at concentrations between 2 and 30 micrograms/ml the rate of DNA synthesis was increased. These findings indicate that CuCl2 is more toxic to Menkes' than to normal fibroblasts and suggest that a similar response of neuronal cells may occur in the patients in vivo.

Brain Diseases, Metabolic↗
PubMed1979

Nuclear actin and histones from the myxomycete Physarum flavicomum.

A method was established for the isolation and purification of nuclei in high yield from the microplasmodia of Physarum flavicomum. Purified nuclei was resistant to breakage by methods commonly employed for isolated plant and animal nuclei. Incubation of nuclei with 5 mM dithiothreitol at pH 9.2 was found to be the simplest and most effective method for breaking the nuclei. Several methods for the extraction of nuclear protein were compared. Incubation of nuclear lysates with either 2 M NaCl, with or without 5 M urea, or 1 M CaCl2 resulted in the extraction of nuclear actin together with histones. The histones were chemically fractionated into the five basic groups common to other eucaryotic tissue. Amino acid analyses of the total histone were also performed. Nuclear actin was found to have a molecular weight of 41,000 +/- 4,000 daltons as determined by SDS polyacrylamide gel electrophoresis. The amino acid composition of the nuclear actin was established.

Actins↗
PubMedDate not supplied

Novel crystalline sheets of Na,K-ATPase induced by phospholipase A2.

Treatment of purified preparations of Na,K-ATPase by phospholipase A2 has led to the formation of two-dimensional crystals of the protein. Control tests with another phospholipase and two detergents have shown that crystallization occurs as the result of hydrolysis and/or solubilization of the phospholipids in the enzyme vesicles. Experimentation with various buffer systems has indicated that reduction in the amount of phospholipids alone is sufficient for inducing the formation of crystalline sheets. Inclusion of crystal inducing ions in the buffer facilitates the crystallization process, resulting in more extensive arrays. The new crystalline sheets are exclusively dimeric with average unit cell dimensions: a = 15.8 +/- 0.4 nm, b = 4.9 +/- 0.2 nm, and gamma = 64 +/- 3 degrees. Examination of the micrographs shows that the initial intermolecular interaction leading to the formation of sheets is between the alpha subunits. Results from this study suggest that removal and/or modification of phospholipids by phospholipases could prove successful in crystallizing those membrane proteins in which excess lipid is the main barrier to the formation of two-dimensional arrays.

Crystallization↗