Search PubMed⌕ Search

Biomedical subjects

R G Ham

Publications and source records attributed to R G Ham.

49 records · Page 3Linked to original sources
PubMed1977

Improved medium for clonal growth of human diploid fibroblasts at low concentrations of serum protein.

A new medium (MCDB 104) has been developed which will support clonal growth of WI-38 cells at concentrations of serum protein as low as 25 micrograms per ml (equivalent to 0.05% serum). The principal factors responsible for reduction of the protein requirement are: (a) adjustment of all nutrient concentrations in medium F12 to experimentally determined optimum values for WI-38 cells; (b) supplementation with trace elements; (c) replacement of hypoxanthine and folic acid with adenine and folinic acid; and (d) coating of the culture surface with polylysine. Individually, many of these modifications exert only a small effect on cellular growth at reduced protein concentrations, but collectively their effect has been very substantial. Other strains of fibroblast-like human diploid cells from amniotic fluid, fetal lung and newborn foreskin also will grow at reduced concentrations of serum protein in the new medium.

Adenine↗
PubMed1977

Critical adjustment of cysteine and glutamine concentrations for improved clonal growth of WI-38 cells.

Clonal growth of WI-38 cells with a plating efficiency of 45% has been achieved in a synthetic nutrient mixture (MCDB 102) supplemented with either whole or dialyzed fetal bovine serum precisely. Deviation by a factor of three in either direction from the optimum concentration (9.0 x 10(-5) M) eliminates essentially all clonal growth. A high concentration of glutamine (2.5 x 10(-3) M) is also needed for optimum clonal growth.

Blood↗
PubMed1977

Clonal growth of chinese hamster cell lines in protein-free media.

A protein-free synthetic medium, MCDB 301, has been developed for clonal growth of Chinese hamster ovary cell lines. Medium F12 was developed originally for that purpose, but later failed to support good growth without small amounts of serum protein. Growth was restored by the addition of nonphysiological amounts of commercially prepared thyroxine or smaller amounts of the trace element selenium. The thyroxine preparation was shown to contain sufficient selenium to account for all of its growth-promoting activity. MCDB 301 contains increased concentrations of calcium chloride and glutamine, and a smaller amount of cysteine than medium F12. It also has been supplemented with 19 inorganic ions, in addition to selenium and those in medium F12, in order to insure against possible future deficiencies as chemicals are purified further. A Chinese hamster lung line which will not grow in MCDB 301 alone will grow when the medium is supplemented either with methylcellulose or with insulin. The growth-promoting activity is thought to be an impurity shared in common by both substances. The probable "essential" role of impurities in cellular growth in most synthetic media and the problems involved in attempting to develop a truly "defined" medium are discussed.

Animals↗
PubMed1976

Selenium is an essential trace nutrient for growth of WI-38 diploid human fibroblasts.

The trace element selenium is essential for clonal growth of diploid fibroblasts from human fetal lung (WI-38) in media containing small amounts of serum protein. Maximum growth stimulation is obtained when 30 nM neutralized selenious acid is added to a synthetic medium containing 1.5 mg/ml of dialyzed fetal bovine serum protein (equivalent to a 3% serum concentration). Serum appears to be a source of selenium in most culture media, since higher concentrations of serum protein or whole serum mask the selenium requirement of WI-38 cells. Selenium is also required by a Chinese hamster cell line that can be grown in a protein-free synthetic culture medium.

Cell Line↗
PubMed1976

Stimulation of clonal growth of normal fibroblasts with substrata coated with basic polymers.

Improved media have reduced the amount of serum protein required for clonal growth of normal human and chicken fibroblast-like cells. In the presence of limiting amounts of serum protein, attachment of colonies to tissue culture plastic surfaces is weak. Treatment of the culture surface with polylysine or other basic polymers causes the cells to adhere much more tightly. Growth is also improved on the surfaces treated with basic polymers, and further reductions in the concentration of serum as possible. At sufficiently low protein concentrations, growth of some types of cells is totally dependent on the use of a treated surface. Several different types of normal human and chicken fibroblast-like cells show improved growth on polylysine-coated surfaces, but no improvement was obtained in growth of a line of SV-40 transformed WI-38 cells. Acidic and neutral polymers are generally inactive. Collagen and gelatin improve growth slightly, but the effect is much less than that obtained with basic polymers. Both natural and synthetic polymers with an excess of basic groups are active, including histone, polyarginine, polyhistidine, polylysine, polyornithine, and protamine. The only critical requirement appears to be a polymer that carries a positive charge at a physiological pH.

Blood Proteins↗
PubMedDate not supplied

Methods for reducing the serum requirement for growth in vitro of nontransformed diploid fibroblasts.

The amount of serum protein required for clonal growth of normal diploid human and chicken fibroblasts has been reduced more than 90% by development of improved synthetic media and culture conditions. The following has contributed significantly to the reduction: (1) replacement of specific serum proteins with defined small molecular nutrients; (2) precise quantitative balance of all defined nutrients for optimal growth of single cells of each type under consideration; (3) modification of the culture substrate; (4) improvement of the cell harvesting technique. By combining these improvements, optimal growth of human fibroblasts (fetal lung, newborn foreskin, amniotic fluid) and chicken embryo fibroblasts occurs in synthetic media supplemented with 500 microgram/ml dialyzed fetal bovine serum protein [equivalent to 1% (v/v) whole serum]. The human fibroblasts form large colonies at a suboptimum rate at 25 microgram/ml dialyzed serum protein [equivalent to 0.05% (v/v) whole serum] and several divisions can be obtained in the complete absence of serum protein. Human and chicken fibroblasts differ both in their quantitative requirements for defined nutrients, and in the type and number of incompletely characterized serum components that they continue to require under the improved growth conditions. The improved systems provide a sensitive assay for the remaining undefined growth-promoting components of serum and other biological extracts.

Animals↗