L.E. Gerschenson

Tyrosine transaminase induction by dexamethasone in a new rat liver cell line.

A cell line derived from normal, adult rat liver has been established; the cells are similar to hepatocytes, as shown by electron microscopy. The addition of dexamethasone to the culture medium induced a three- to sixfold increase in the specific activity of tyrosine α-ketoglutarate transaminase; this increase was inhibited by the simultaneous addition of cycloheximide or actinomycin D. The latter, when added to cells given prior treatment with dexamethasone, further enhanced the transaminase activity. Contact-inhibited cells showed a lower response to dexamethasone than exponentially growing cells.

Fine structural and growth characteristics of cultured rat liver cells: Insulin effects

Abstract The structural characteristics of an established epithelial cell line (RLC), derived from adult rat liver are described. Some similarities with hepatocytes were found. This cell line can be adapted to grow in serum-free medium provided insulin is added to the medium. Besides having a growth effect insulin also induced the formation of polyribosomes. The cells grown in serum-free medium have a fibroblastic morphology which reverts to an epithelial one upon the addition of medium plus serum.

Studies on the effects of essential fatty acids on growth rate, fatty acid composition, oxidative phosphorylation and respiratory control of HeLa cells in culture

Abstract 1. Mammalian cells in culture provide a simple model to study the function of polyunsaturated fatty acids. 2. HeLa S 3 cells cultured in a lipid-deficient medium showed a pattern of essential fatty acid deficiency represented by an increase in 18:1 and a decrease in 20:4 and 18:2, a lack of growth and impaired mitochondrial function. 3. Addition of albumin-bound linoleic or arachidonic acid partially or totally prevented these changes.

Studies in vitro on single beating rat-heart cells X. The effect of linoleic and palmitic acids on beating and mitochondrial phosphorylation

Abstract 1. Beating rat-heart cells cultured in a lipid-deficient medium showed: (a) lack of growth; (b) decrease and later a cessation of the beating; (c) impairment of oxidative phosphorylation and a decrease in the respiratory control; (d) a pattern of fatty acid deficiency as shown by the analysis using gas-liquid chromatography. 2. The addition of albumin-bound linoleic acid or arachidonic acids prevented partially or totally the effects of the lipid deficiency on the mitochondrial function and the fatty acid composition, but did not promote growth and did not improve the beating. 3. Medium supplemented with albumin-bound palmitic acid maintained the beating, but did not promote growth and did not affect the impairment of the mitochondrial function.

REGULATION OF THE PYRUVATE KINASE OF AN ESTABLISHED RAT LIVER CELL LINE (RLC) IN CULTURE BY INSULIN, GLUCOSE, AND SERUM

Summary The PK of RLC cells appears to be under the influence of hormonal and nutritional regulatory mechanisms similar to those modulating the enzyme in rat liver. The insulin effect appears to be dependent upon de novo RNA synthesis, while the serum effect is not. The stimulation of the PK activity by glucose appears to be totally independent of protein synthesis. The addition of glucose or lactic acid to the culture medium inhibited the insulin effect.

[73] The isolation and culture of liver cells

Publisher Summary The use of isolated or cultured cells provides a simpler experimental system in which the environment can be easily controlled; in addition, the possibility of obtaining recombinational systems by hybridization provides an important tool for the analysis of genetic regulatory mechanisms. The chapter outlines only some of the more simple techniques used lately in the laboratory to dissociate and to culture isolated rat liver cells, especially parenchymal cells.

Histodifferentiation and cytodifferentiation in rabbit endometrium. A comparison of the effects of progesterone and various progesterone metabolites.

Abstract The effects of progesterone, 20α-hydroxy-pregn-4-en-3-one, (20α-OH-P) 17 α hydroxyprogesterone (17α-OH-P) and 5α-pregnan-3, 20-dione (5α-P) on endometrium of ovariectomized rabbits have been examined. Progesterone, at 5 mg/kg/day and at 1.7 mg/kg/day increased the number of mitotic figures observed in luminal and glandular epithelium after 5 days of treatment and induced considerable arborization. None of the other compounds induced significant arborization and only 10 mg/kg/day of 20α-OH-P increased the mitotic index in luminal and glandular epithelium. Administrations of 20α-OH-P, 17α-OH-P or 5α-P resulted in the appearance of very large, pale cells in the luminal epithelium which were not present in progesterone treated rabbits. Cytochemical techniques revealed no specific staining in these cells for polysaccharides (PAS, Alcian blue), lipid (Oil Red O) or for blastokinin, a progesterone-inducible, uterine protein, examined by the fluoroscein isothiocyanate labeled antibody technique. The possibility of an apparent dissociation between histodifferentiation and cytodifferentiation is discussed.

Hormonal regulation of cultured rabbit endometrial cells

A technique for culturing primary explants of rabbit endometrial cells in chemically defined medium has been developed. Diethylstilbestrol and natural estrogens were found to increase the rate of DNA initiation while progesterone had the opposite effect. Ultrastructural studies revealed that with estrogens, the cultures had the appearance of rapidly dividing cells having large euchromatic nuclei and prominent nucleoli, with aboundant free ribosomes in the cytoplasm. On the other hand, progesterone induced the formation of large multinucleated cells and also converted the cells to a more secretory type. When the cultures appear secretory, a protein called blastokinin (uteroglobin) is believed secreted. We have found that cultured cells synthesize blastokinin and progesterone is necessary for its continuous synthesis. The cultures were found to have receptors for the ovarian hormones and these receptors exhibited saturation kinetics. The dissociation constants for the receptors were also determined. A hypothetical model for the hormonal regulation of cell proliferation and differentiation is proposed.

Triacetylated insulin: biologic activity and resistance to degradation.

Tritiated N-hydroxysuccinimide acetate was prepared with specific activities up to 5 Ci/mmole and utilized to prepare tritiated triacetyl insulin. Binding of triacetyl insulin to liver plasma membranes was measured by its capacity to displace 125I-monoiodoinsulin. At low concentrations, less than 10 ng/ml triacetyl insulin appears to be as effective as native insulin in reducing the binding of 125I-monoiodoinsulin to plasma membranes. At concentrations of 20 ng/ml and higher, triacetyl insulin is significantly less effective than native insulin in displacing binding of 125I-monoiodoinsulin to plasma membranes. The properties of triacetyl insulin in this system are not ascribable to deacetylation and conversion of the substituted product to native insulin. Biologic activity of triacetylated insulin was studied in two other in vitro systmes. A comparison was made of the capacity of native beef insulin and its triacetyl derivative to stimulate glucose oxidation by epididymal fat pads. At all three concentrations tested (2, 6, and 18 ng/ml), triacetyl insulin exerted considerable activity, although its potency was significantly less than that of native insulin. Similar effects were observed when biologic activity was measured by induction of tyrosine-alpha-ketoglutarate transaminase in a cultured liver cell system where significant activity of triacetyl insulin was found at concentrations of 10(-9)-10(-7) M. In all systems tested, the activity of triacetylated insulin could not be accounted for by deacetylation and conversion to native insulin. In all systems studied, triacetyl insulin was more resistant to degradation than was monoiodoinsulin.