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Biomedical subjects

L Levine

Publications and source records attributed to L Levine.

At least 343 records · Page 19Linked to original sources
PubMed1970

Production of both prolactin and growth hormone by clonal strains of rat pituitary tumor cells. Differential effects of hydrocortisone and tissue extracts.

Several established clonal strains of rat pituitary cells which produce growth hormone in culture have been shown to secrete a second protein hormone, prolactin. Prolactin was measured immunologically in culture medium and within cells by complement fixation. Rates of prolactin production varied from 6.6 to 12 microg/mg cell protein per 24 hr in four different cell strains. In these cultures ratios of production of prolactin to growth hormone varied from 1.0 to 4.1. A fifth clonal strain produced growth hormone but no detectable prolactin. Intracellular prolactin was equivalent to the amount secreted into medium in a period of about 1-2 hr. Both cycloheximide and puromycin suppressed prolactin production by at least 94%. Hydrocortisone (3 x 10(-6)M), which stimulated the production of growth hormone 4- to 8-fold in most of the cell strains, reduced the rate of prolactin production to less than 25% of that in control cultures. Conversely, addition of simple acid extracts of several tissues, including hypothalamus, to the medium of all strains increased the rate of production of prolactin six to nine times and decreased growth hormone production by about 50%. We conclude that multifunctional rat pituitary cells in culture show unusual promise for further studies of the control of expression of organ-specific activities in mammalian cells.

Animals↗
PubMed1969

Tetanus.

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Humans↗
PubMed1969

Establishment of a clonal strain of hepatoma cells which secrete albumin.

A clonal strain of epithelial cells (designated MH(1)C(1)) has been established from the transplantable Morris hepatoma No. 7795. The cells have maintained distinctive morphology throughout more than 20 subcultures (split 1:5) at 2- to 4-week intervals in supplemented Ham's F 10 medium. They contain many highly refractile, round, cytoplasmic bodies which stain bright red with Oil Red O. The population doubling time was 2 wk when the clonal strain was first established. It has gradually decreased to 1 wk. The cells synthesize rat serum albumin and secrete it into the culture medium as determined immunologically by microcomplement fixation and double diffusion. Albumin secretion (3-6 microg albumin/mg cell nitrogen/24 hr) occurs throughout the logarithmic phase of cell proliferation and has not diminished during serial propagation since the strain was initiated 15 months ago.

Animals↗
PubMed1969

Control of growth hormone production by a clonal strain of rat pituitary cells. Stimulation by hydrocortisone.

Addition of hydrocortisone to the medium of a clonal strain of rat pituitary cells (GH(3)) stimulated the rate of production of growth hormone. The stimulation had a lag period of about 24 hr, reached a maximum at 70-100 hr, and was observed at a hydrocortisone concentration as low as 5 x 10(-8)M. Cells maximally stimulated with 3 x 10(-6)M hydrocortisone produced 50-160 microg growth hormone/mg cell protein/24 hr. These rates were four to eight times those observed in control cells. At maximum stimulation, intracellular levels of growth hormone in both stimulated and control cells were equal to the amount secreted into the medium in about 15 min. Removal of hydrocortisone from the medium of GH(3) cells caused a return of the rate of growth hormone production to that in control cells. Addition of hydrocortisone to the medium of cells growing exponentially with a population-doubling time of 60 hr caused both an increase in the doubling time to 90 hr and a stimulation of growth hormone production. Cycloheximide (3.6 x 10(-5)M) and puromycin (3.7 x 10(-4)M) suppressed incorporation of labeled amino acids into protein by 93 and 98%, respectively, and suppressed growth hormone production by stimulated and control cells by at least 94%.

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