Quantitative changes in gene copy number are found frequently in biology. They range from
polytenization of chromosomes to generation of polyploid cells to selective gene …

… Berlin & Schimke (29 ) have shown that glucocorticoid administration results in the
accumulation of enzyme activity along very different time courses for tyrosine transaminase, …

Methotrexate-resistant Leishmania tropica contain two separate regions of DNA amplification,
one encoding the bifunctional thymidylate synthetase-dihydrofolate reductase (TS-DHFR) …

The rate of dihydrofolate reductase synthesis in the AT-3000 line of methotrexate-resistant
murine Sarcoma 180 cells is approximately 200-to 250-fold greater than that of the sensitive, …

(a) Male Osborne Mendel rats reared on Purina Rat Chow were given the experimental diets
for 14 days; some were young rats of initial weight 50 to 60 g, others older and weighing …

Results.-Figure 1 illustrates typical starch gel electrophoretic patterns of the hexokinases
from 104,000 X g supernatants of tissues of an adult rat. Four distinct bands of enzyme …

Rat tissues contain four hexokinases including both the liver-specific high K m glucokinase
and three low K m hexo-kinases present in differing proportions in the various tissues. Each …

… Nunberg, and RT Schimke, unpublished data. I Parental cells from the stable or unstable
L5178Y line gave similar results. However, the data presented here are from the L5178Y line …

Methotrexate-resistant Chinese hamster ovary cells selected for high resistance by progressive
increments of methotrexate in the culture medium have levels of dihydrofolate reductase (…

Using multiparameter flow cytometric analysis, we find that senescent cells accumulate in a
unique cell-cycle compartment characterized in cell-cycle arrest in G1 and a significantly …