Suppression of DNA synthesis in hepatoma cells exposed to glucocorticoid hormone in vitro

Effect of hydrocortisone on the production and glycosylation of an Fc-fusion protein in CHO cell cultures

Glucocorticoids are known to modulate various cellular functions such as cell proliferation, metabolism, glycosylation, and secretion of many proteins. We tested the effect of hydrocortisone (HC) on cell growth, viability, metabolism, protein production, and glycosylation of an Fc-protein expressing Chinese hamster ovary (CHO) cell culture. HC extended cell viability but impaired cell growth. The inhibitory effect on cell growth was dose-dependent and decreased when the glucocorticoid addition was delayed. When HC was added after 2 or 3 days of culture, an increase in glutamate consumption was observed, which was reversed by the glucocorticoid receptor antagonist mifepristone (Mif). Titer and specific productivity increased in the presence of HC. The increase in titer was only slightly reversed by Mif. On the other hand, Mif by itself induced an increase in titer to a level comparable to or higher than HC. Protein glycosylation was altered by the glucocorticoid in a dose- and time-dependent manner, with a shift to more acidic bands, which correlated with an increase in sialic acid moieties. This increase, which was not linked to a decrease in extracellular sialidase activity in HC-treated cultures, was reversed by Mif. Predictive models based on design of experiments enabled the definition of optimal conditions for process performance in terms of viability and titer and for the quality of the Fc-fusion protein in terms of glycosylation. The data obtained suggest a use of glucocorticoids for commercial production of Fc-fusion proteins expressed in CHO cells.

Dexamethasone modulates ErbB tyrosine kinase expression and signaling through multiple and redundant mechanisms in cultured rat hepatocytes

Glucocorticoids paradoxically exert both stimulatory and inhibitory effects on the proliferation of cultured rat hepatocytes. We studied the effects of dexamethasone, a synthetic glucocorticoid, on the proliferation of cultured rat hepatocytes. The timing of growth factor addition modified the action of high-dose dexamethasone (10(-6) M) on DNA synthesis. When we added transforming growth factor-alpha at the time of plating, 10(-6) M dexamethasone weakly stimulated DNA synthesis by 26% relative to cells cultured in dexamethasone-free media. When we delayed growth factor addition until 24-48 h after plating, 10(-6) M dexamethasone inhibited DNA synthesis by 50%. Using immunological methods, we analyzed the expression and signaling patterns of the ErbB kinases in dexamethasone-treated cells. High-dose dexamethasone stabilized the expression of epidermal growth factor receptor (EGFr) and ErbB3, and it suppressed the de novo expression of ErbB2 that occurs during the third and fourth day of culture in 10(-8) M dexamethasone. High-dose dexamethasone by 72 h suppressed basal and EGF-associated phosphorylation of ERK and Akt. The reduction in ERK1/2 phosphorylation correlated with suppression of a culture-dependent increase in Son-of sevenless 1 (Sos1) and ERK1/2 expression. High-dose dexamethasone in hepatocytes stabilized or upregulated several inhibitory effectors of EGFr/ErbB2 and ERK, including receptor-associated late transducer (RALT) and MKP-1, respectively. Thus 10(-6) M dexamethasone exerts a time-dependent and redundant inhibitory effect on EGFr-mediated proliferative signaling in hepatocytes, targeting not only the ErbB proteins but also their various positive and negative effectors.

Annexin expressions are temporally and spatially regulated during rat hepatocyte differentiation

Annexin (Anx) 1, 2, 5, and 6 expressions were determined at the transcriptional and translational levels in the rat hepatocytes from gestational day 15 to postnatal day 17. Dramatic shifts were observed in Anx 1 and 2 levels, which peaked at day 1 and gestational day 20, respectively, and reached low levels thereafter. However, Anx 5 and 6 rates were more constant. Prenatal administration of dexamethasone (dex) resulted in a decrease of Anx 1 mRNA levels, and a strong increase in Anx 2 mRNA contents. In adult hepatocytes cultured in the presence of EGF or HGF, Anx 1 and 2 expressions resumed. By immunohistochemistry, Anx 1 was detected only in the cytoplasm of hepatocytes of 1- to 3-day-old rats, Anx 2 and 6 both exhibited a redistribution from the cytoplasm toward the plasma membrane, and Anx 5 was present in the nucleus, cytoplasm, and plasma membrane. Thus, Anx 1, 2, 5, and 6 have individual modes of expression and localization in the differentiating hepatocytes, where they might play unique roles at well defined phases of liver ontogeny.

Dose-related opposite effects of hydrocortisone on hepatocyte proliferation in the rat

To evaluate the role of glucocorticoids in the regulation of hepatocyte proliferation, high doses (6.25 mg/kg or more) and low doses (1.25 mg/kg or less) of hydrocortisone were injected into various categories of rats which had very different levels of proliferation. We used: (a) suckling rats whose stable unsynchronized proliferation can be stimulated and synchronized by acute inflammation or cyproterone feeding; (b) adult rats with a low level of proliferation, and (c) 2/3 hepatectomized rats during the first period of synchronized proliferation or during the second period of lower and unsynchronized proliferation. The kinetics of the labelling index and mitotic index were observed after hydrocortisone injection. High doses inhibited proliferation, as already found by many investigators. This effect was observed in suckling and hepatectomized rats and during acute inflammation in suckling or adult rats. Low doses had no inhibitory activities and, on the contrary, stimulated proliferation in some situations. The highest stimulations were observed during the early period after 2/3 hepatectomy or in combination with acute inflammation either in suckling rats or in 2/3 hepatectomized rats during the late period of regeneration. In all these situations hydrocortisone was a cofactor active during the early G1-phase. In contrast, in normal suckling rats a slight stimulation was observed due to an action at the G0-G1 transition. No such effect was found in adult rats. Our data show that doses of hydrocortisone in the therapeutic range or close to physiological values do not inhibit and, on the contrary, can stimulate hepatocyte proliferation.

N-terminal peptide fragments of lipocortin-1 inhibit A549 cell growth and block EGF-induced stimulation of proliferation

Lipocortin-1 mediates growth inhibition of glucocorticoids in A549 cells by suppressing the release of PGE2 necessary for their proliferation. We now show that 2 peptide fragments derived from the N-terminal portion of lipocortin-1 corresponding to amino-acids 13-25 and 21-33 also inhibited A549 cell growth and suppressed release of PGE2, whereas peptides 1-12 and 13-25 (Phe21; in which the tyrosine at position 21 was replaced by a phenylalanine residue) were inactive. Similarly, peptide 21-33 (Phe21) and a scrambled sequence of 13-25 failed to inhibit cell growth. Moreover, the EGF-induced stimulation of cell proliferation and PGE2 release in these cells was blocked by peptides 13-25 and 21-33, and also by peptides 1-12, 13-25 (Phe21) and 21-33 (Phe21), but not by a scrambled sequence of peptide 13-25.

Lipocortin 1 mediates dexamethasone-induced growth arrest of the A549 lung adenocarcinoma cell line

The synthetic glucocorticoid dexamethasone (1 microM to 1 pM) strongly (maximum greater than 80%) inhibits proliferation of the A549 human lung adenocarcinoma line (EC50 greater than 1 nM) and leads to the appearance, or a further increase (approximately 3-fold) in the expression on the cell surface, of the calcium and phospholipid binding protein lipocortin (annexin) 1. Both these effects, which are shared by hydrocortisone (1 microM) but not by progesterone or aldosterone (1 microM), are inhibited by the antiglucocorticoids RU38486 and RU43044 (1 microM). The nonsteroidal antiinflammatory drugs indomethacin (1 microM) and naproxen (10 microM) and human recombinant lipocortin 1 (0.05-5.0 micrograms/ml) also produce growth arrest in this cell line. During proliferation A549 cells spontaneously release prostaglandin E2 [10-20 ng (28-57 pmol) per ml per 5-day period] into the growth medium. In concentrations that cause growth-arrest, dexamethasone, indomethacin, and lipocortin 1 abolish the generation of this eicosanoid by A549 cells. Prostaglandin E2 itself (0.01-1 pM) stimulates cell growth and partially reverses (approximately 50%) the inhibition of growth caused by dexamethasone and indomethacin. Addition of the neutralizing anti-lipocortin 1 monoclonal antibody 1A (5 micrograms/ml), but not the nonneutralizing anti-lipocortin monoclonal antibody 1B, substantially reversed (greater than 80%) the inhibitory activity of dexamethasone on both growth and prostaglandin E2 synthesis. The generation of prostaglandin E2 by A549 cells seems to be an important regulator of cell proliferation in vitro and the dexamethasone-induced suppression of proliferation in this model is attributable to eicosanoid inhibition caused by lipocortin 1.

Effects of postnatal dexamethasone treatment on development of alveoli in adult rats

We compared the effects of dexamethasone given to rats from age 4 to 14 days, on alveolar development at age 99 days. Judged by similar nose-to-tail length and body weight, somatic growth was not altered by dexamethasone treatment. Lung volumes in both air- and saline-filled lungs and mean chord length (Lm) were increased, whereas alveolar surface area (Sa) and surface-to-volume ratio (S/V) were diminished in dexamethasone-treated adult rats. These changes were associated with a significant reduction in DNA content and concentration but larger protein/DNA and RNA/DNA ratios in the lungs of treated rats. We conclude that dexamethasone treatment during the critical period of septation in rats impairs alveolar formation, which persists until adulthood and leads to larger and less complex gas-exchange regions. Inhibition of DNA synthesis due to dexamethasone may be responsible for its effects on alveolar development. Larger lung volumes in treated rats are, most likely, related to larger air space dimensions.

Glucocorticoid receptor-dependent inhibition of cellular proliferation in dexamethasone-resistant and hypersensitive rat hepatoma cell variants

Exposure of the Fu5 rat hepatoma cell line to glucocorticoids, such as dexamethasone and hydrocortisone, suppressed the growth rate and final density of cells grown in the presence of serum. This hormonal effect was proportional to receptor occupancy and affinity and, in addition, the glucocorticoid antagonist RU38486 prevented this response. Two classes of dexamethasone-resistant variants that failed to be growth inhibited were recovered from ethyl methylsulfonate-mutagenized populations by continuous culture in the presence of 1 microM dexamethasone. The first class, represented by the EDR3 subclone, was completely glucocorticoid unresponsive and failed to express receptor transcripts. The second class, represented by the EDR1, EDR5, and EDR7 subclones, possessed significant levels of glucocorticoid receptor but were only partially glucocorticoid responsive when stimulated with saturating levels of hormone. Introduction of functional glucocorticoid receptor genes into both classes of dexamethasone-resistant variants by a recombinant retrovirus expression vector restored glucocorticoid responsiveness and suppression of cell growth. A hypersensitive variant (BDS1), recovered by bromodeoxyuridine selection, was fully glucocorticoid responsive, and its inhibition of proliferation was more acutely regulated by dexamethasone. Taken together, our results established that the inhibition of proliferation in Fu5 rat hepatoma cells represents a new glucocorticoid response that requires the expression of a functional glucocorticoid receptor.

Glucocorticoid receptor-dependent inhibition of cellular proliferation in dexamethasone-resistant and hypersensitive rat hepatoma cell variants

Exposure of the Fu5 rat hepatoma cell line to glucocorticoids, such as dexamethasone and hydrocortisone, suppressed the growth rate and final density of cells grown in the presence of serum. This hormonal effect was proportional to receptor occupancy and affinity and, in addition, the glucocorticoid antagonist RU38486 prevented this response. Two classes of dexamethasone-resistant variants that failed to be growth inhibited were recovered from ethyl methylsulfonate-mutagenized populations by continuous culture in the presence of 1 microM dexamethasone. The first class, represented by the EDR3 subclone, was completely glucocorticoid unresponsive and failed to express receptor transcripts. The second class, represented by the EDR1, EDR5, and EDR7 subclones, possessed significant levels of glucocorticoid receptor but were only partially glucocorticoid responsive when stimulated with saturating levels of hormone. Introduction of functional glucocorticoid receptor genes into both classes of dexamethasone-resistant variants by a recombinant retrovirus expression vector restored glucocorticoid responsiveness and suppression of cell growth. A hypersensitive variant (BDS1), recovered by bromodeoxyuridine selection, was fully glucocorticoid responsive, and its inhibition of proliferation was more acutely regulated by dexamethasone. Taken together, our results established that the inhibition of proliferation in Fu5 rat hepatoma cells represents a new glucocorticoid response that requires the expression of a functional glucocorticoid receptor.

The uncoupling of macromolecular synthesis from cell division in SV3T3 cells by glucocorticoids: the imposition of a G2 block

Through a receptor-mediated process glucocorticosteroids block cell division by 20-45 hours in SV40-transformed 3T3 (SV3T3) mouse fibroblasts growing in a low calf serum (0.30% v/v) medium containing biotin. However, the rate of DNA synthesis, determined at various times after dexamethasone addition by the incorporation of radioactive thymidine into acid-insoluble material, is not inhibited by this steroid as late as 66 hours. A modest decrease is observable by 91 hours. There is also no reduction in the uptake of exogenous thymidine into acid-soluble cellular pools. Similarly, RNA synthesis and the uptake of radioactive uridine are not affected by the glucocorticoid up to 69 hours. Measurements of the amounts of cellular DNA (by the fluorescent dye, 4', 6-diamidino-2-phenylindole) and protein revealed that both macromolecules are present in elevated quantities in steroid-treated cells. (The constancy of the protein content in the nonproliferative stage suggests that protein synthesis and degradation are occurring at equal rates.) If the steroid is removed and fresh 10% calf serum medium added, cell division commences (even if nearly 90% of protein synthesis is inhibited by cycloheximide) as early as 45 minutes later such that by 2 hours the viable cell count increases by as much as 70%. Since the growth curve after recovery resembles a step function, it appears that the cells are partially synchronized by the glucocorticoid. These results demonstrate that the glucocorticoid cytostatic effect in SV3T3 cells is the result of a block not in G1, as previously thought, but in G2.

Glucocorticoids inhibit the stimulatory effect of epidermal growth factor on the initiation of DNA synthesis

Confluent, quiescent Swiss 3T3 cells in culture can be stimulated to initiate DNA synthesis and divide by addition of growth factors to the culture medium. Here we show that hydrocortisone and other steroids which have glucocorticoid activity inhibit the stimulation of these cells by epidermal growth factor (EGF) in contrast to their reported enhancement of stimulation by fibroblast growth factor (FGF). Binding studies using [3H]-triamcinolone acetonide show that Swiss 3T3 cells contain a single class of glucocorticoid receptor of uniform affinity (KD = 2.0 nM), and about 34,000 receptor sites per cell. Those steroids which displace bound [3H]-triamcinolone acetonide are also effective in inhibiting the stimulation of DNA synthesis by EGF in the presence or absence of insulin, and the concentration of triamcinolone acetonide required for one-half maximal biological effect is in the same range as the KD. A similar concentration is required for one-half maximal enhancement of the effect of FGF. These results suggest that both the inhibitory and stimulatory effects of glucocorticoids may be mediated via these receptors, the different effects thus being due to differences in the intracellular events triggered by each growth factor.

The effects of retinoids on proliferative capacities and macromolecular synthesis in human breast cancer MCF-7 cells

The effects of various retinoids on the proliferative capacities and on the synthesis of DNA, RNA, and protein have been investigated in MCF-7 mammary carcinoma cells in culture. Of the various retinoids tested, retinoic acid revealed maximum activity in inhibiting cell proliferation and thymidine incorporation. The degree of inhibition of cell proliferation by the various retinoids paralleled their capacity to inhibit thymidine incorporation, suggesting suppression of DNA synthesis as a primary cause of restriction of cell growth by these compounds. Two nonepithelial human cell lines were tested for sensitivity to retinoids, and showed diminished responses compared with MCF-7 cells. This suggests a correlation between the ability of retinoids to exert control of differentiation and cell proliferation for a given cell type. Reversibility of the effect of retinoid treatment, high cell viability, and lack of retinoid-induced lysosomal enzyme release, as shown in our studies, indicate that cytotoxicity may be excluded as a cause of decreased cell proliferation and inhibition of thymidine incorporation by retinoids.

Neonatal macrosomia in maternal diabetes

In order to determine the effect of maternal diabetes on the somatic growth of the rat fetus and to elucidate mechanisms underlying the control of fetal growth, concentrations of DNA and proteins and DNA polymerase-alpha activities in neonates were examined. The maternal status was classified as normal (no urinary glucose excretion), mildly diabetic (0.01-0.99 g/day urinary glucose), and severely diabetic (1.00 g/day or more urinary glucose). The total DNA contents in mg/neonate were 26.8 +/- 2.2 (mean +/- SEM), 31.3 +/- 2.5, and 29.4 +/- 2.7 for neonates from normal, mildly diabetic and severely diabetic mothers, respectively. The DNA polymerase activities in (cpm/g neonate) X 10(-3) for the same groups of neonates were 432 +/- 58, 1,008 +/- 74, and 888 +/- 118, respectively. These results indicate that the neonatal macrosomia disappears as the severity of maternal diabetes increases. Furthermore, DNA polymerase is one of possible biochemical sites through which macrosomia is manifested in diabetic pregnancies.

Effect of steroid hormones on liver cells in culture

A variety of liver and hepatoma cell lines were incubated in the presence of corticosterone. DNA synthesis was inhibited in some but not all cell lines. One of them, the Fu 5a clone of the Reuber hepatoma cell line, was subjected to corticosterone for 48 h. Incorporation of labeled thymidine into DNA was inhibited up to 10%. Afterward, corticosterone was removed. DNA synthesis then increased 16-fold relative to controls. It was concluded that corticosterone blocks these cells in late G1 phase of the cell cycle and thus leads to synchronization.

Selection of a dexamethasone-resistant H-4-IIE-C3 rat hepatoma tissue-culture line

Exposure of H-4-IIE-C3 rat hepatoma cell cultures to the synthetic glucocorticoid, dexamethasone, results in an inhibition of cellular proliferation which is not the result of steroid-induced cytolysis. A significant decrease in both the rate of DNA synthesis and DNA content precedes a detectable effect on cell number. Continuous culture of H-IIE-C3 cells in medium containing 10(-5) M dexamethasone results in the selection of a steroid-resistant cell population that has the growth characteristics of unselected sensitive cultures and shows normal steroid induction of tryosine transaminase. Selection is a slow process requiring 24 to 36 months to obtain a phenotypically stable resistant cell line, and can be subdivided into three phases--a sensitive phase, adaptation and resistance. A comparison of the karyotypes of unselected and resistant cultures shows that the selection process enriches for a dexamethasone-resistant subpopulation.

Elevation of HeLa cell 3-hydroxy-3-methylglutaryl coenzyme A reductase activity by glucocorticoids: possible relationship to the cell cycle

Elevation of 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMG-CoA reductase, EC 1.1.1.34) activity by glucocorticoids was shown to be dependent on the concentration of hormone in the medium over a range of 5 X 10(-10) to 1 X 10(-8) M, although the presence of steroid in the assay at 10(-5) M elicited no increase in activity. There was a demonstrated time dependence for the addition of dexamethasone i.e., from zero to six hours after serum removal, addition of hormone resulted in the same peak acitvity; addition at 12 hours gave slight elevation but resulted in an extended maintenance of the peak level of activity; addition at 24 hours showed no effect. When cycloheximide was added to the above times, subsequent kinetics showed identical decay of the enzyme activities from control and treated cultures at 6 and 24 hours, but at 12 hours the activity from dexamethasone treated cells exhibited an extended lag before the onset of decay, which then proceeded at the same rate as the control. The continuous presence of the hormone was not necessary for the induction to continue and the addition of Actinomycin D to cultures incubated in the presence of hormone resulted in an immediate decay of catalytic activity without evidence of "superinduction." The addition of progesterone at the same time as dexamethasone resulted in a concentration-dependent inhibition of the augmentation, suggesting the involvement of the glucocorticoid receptor in the elevation of HMG-CoA reductase activity. Flow microfluorometric (FMF) analysis of hormone treated cells indicated a delayed entrance into the DNA synthesis (S) phase of the cell cycle. The temporal relationships between this cell cycle perturbation and HMG-CoA reductase elevation are discussed.

Inhibition of growth in vitro by glucocorticoids in mouse embryonic facial mesenchyme cells

The growth of primary embryonic facial mesenchyme cells established from cleft palate sensitive A/J and resistant C57BL/6J (C57) mice is inhibited by glucocorticoid treatment. A reduction in cell number in both A/J and C57 culture is accompanied by a significant decrease in [3H] thymidine incorporation into both acid soluble and insoluble material. No significant changes in total cellular protein or [14C] leucine incorporation were observed in either cell type. A greater reduction in [3H] thymidine incorporation occurs in cells undergoing exponential growth following steroid exposure than in cells approaching stationary growth. In both A/J and C57 cultures the reduction in cell number exhibits a dose-dependent response to dexamethasone; is specific for glucocorticoids; and is dependent upon the concentration of serum in which the cells are maintained. A/J cells show a greater sensitivity to the inhibitory effect of dexamethasone on cell number and thymidine incorporation than comparably treated C57 cells. Specific, high affinity, saturable cytoplasmic receptors for [3H] dexamethasone are present in the maxillary cytosols from which the primary cultures were established. These receptors exhibit binding specificity for glucocorticoids, and have properties which are similar to glucocorticoid receptors identified in other systems. In both cell types, a correlation exists between the degree of growth inhibition or reduction of [3H] thymidine incorporation and the level of glucocorticoid receptors. These results provide evidence for a receptor-mediated set of responses to glucocorticoids in these cells.

Growth dependence of phosphoglyceric acid dehydrogenase activity in cultured rat liver cells

Rat liver epithelial cells in culture (WIRL-3C) have the enzymes that synthesize serine from 3-phophoglyceric acid. Both phosphoglyceric acid dehydrogenase (PGAD) and serine-phosphate (serine-P) forming activities fluctuate with time after subculture and are higher in growing than confluent cells. This activity pattern was not common for other dehydrogenases in WIRL-3C cells, nor was it common for PGAD activity in other cultured cells. At time of subculture, cells are removed from spent medium, treated with trypsin, and fed fresh medium. None of these parameters causes the rise in activity; in contrast, reduction in cell density and the accompanying stimulation of growth do. PGAD activity decreases when growth is slowed either as the cells progress to the end of the culture cycle, when cells are treated with dexamethasone-phosphate (Dx-P) or dibutyryl cyclic AMP(cAMP) and theophylline or when the serum concentration of the medium is reduced to 0.2%. Under these conditions, decreased PGAD activity is paralleled by a decline in growth and DNA accumulation. PGAD activity in WIRL-3C cells is regulated in a manner closely resembling what has been observed previously in rat liver from the whole animal. The possible use of this system in studying regulation of gene expression in mammalian cells is discussed.

The effects of glucocorticoids on cultured human endothelial cells

The effects of hydrocortisone, dexamethasone and prednisone on the morphology, replication, DNA synthesis, cell protein content and protein synthesis of cultured, human endothelial cells were evaluated. After culturing the cells with these glucocorticoids for 24-48 h, the cells covered a greater portion of the culture surface area. The mean surface area of the individual endothelial cell treated with glucocorticoids was 1.53 times greater than that of the untreated control endothelial cell. When compared with controls, the endothelial cover provided by the cells treated with glucocorticoids was more extensive and in many instances covered the entire culture surface. The change in morphology was associated with an increase in protein synthesis and protein content of the cells without an increase in DNA synthesis or cellular replication. Dexamethasone was approximately 10-fold more effective than hydrocortisone, while prednisone was the least effective. Aldosterone, DOCA, testosterone, progesterone, oestradiol and oestriol were ineffective. These studies indicate that glucocorticoids can alter the morphology and biochemistry of cultured endothelial cells and may have implications for the effects of steroids in the treatment of thrombocytopenic states and vascular disorders in man.

Vascular and lymphatic tumors in infancy, childhood and adulthood: challenge of diagnosis and treatment

The essential features of the major benign and malignant vascular tumors affecting infants, children and adults have been presented. Major emphasis has been placed upon the classification and treatment of hemangiomas, although malignant vascular tumors are discussed, and extensive and selected references are cited. The classification system of hemangiomas presented in this monograph is based upon the clinical prognosis of the angioma. The principles of treatment for hemangiomas based upon our clinical classification are discussed and may be summarized as follows: 1. The diagnostic features and prognosis vary with the variety of the angioma. 2. Spontaneous regression occurs only with juvenile hemangiomas, and the major involution occurs before age 5. 3. Patients with rapidly growing capillary cavernous hemangiomas should be treated with steroids. 4. Treatment modalities that increase scarring of the surface epithelium are contraindicated. 5. Intradermal and cirsoid angiomas do not spontaneously regress. 6. Congenital A-V fistulas require aggressive surgery. 7. The ultimate deformity resulting from angiomas may be greatly reduced by plastic surgical techniques. 8. Radiation therapy is never indicated for the treatment of hemangiomas. 9. The psychologic impact of the congenital deformity on patients is generally more detrimental than comparable postsurgical or traumatic deformities.

Steroid hormone alteration of herpes simplex virus type 1 replication

The effect of steroid hormones on herpes simplex virus type 1 replication was examined. Virus replication studies revealed that various concentrations of prednisolone, hydrocortisone, dexamethasone, or progesterone could decrease virus yields up to a maximum of 99%. Using isopycnic centrifugation in CsCl to separate viral from cell DNA, it was found that virus-specific DNA synthesis was decreased by 30 to 100% depending on the hormone and concentration used. Cell-specific DNA synthesis was also adversely affected, but this did not alter cell viability or plating efficiency.

Glucocorticoids modulate the in vitro development of the embryonic rat pancreas

The effect of the glucocorticoid analogue, dexamethasone, on the development of the embryonic pancreas was studied in tissue culture. It specifically enhances the accumulation of exocrine enzymes without altering the level of general cell proteins. The enhancement, however, is not symmetrical: the cellular levels of the two major exocrine products, amylase and chymotrypsinogen, are increased about 10- and 2-fold, respectively. Two other zymogens that are present in minor quantities, procarboxypeptidases A and B, are also increased, whereas no effect is seen on lipase A. Coordinate with these effects on synthesis, there is a dramatic change in the morphology of dexamethasone-stimulated acinar cells. Their number of zymogen granules is higher and crystalline arrays are found in the rough endoplasmic reticulum. Dexamethasone also inhibits cell replication, perhaps by selectively inhibiting the last cell divisions of the culture period. At the same time, there is a disproportionate reduction in the insulin content of cultured rudiments. We find that pancreatic development is normal in the absence of dexamethasone and that this glucocorticoid does not precociously induce the appearance of the specific secretory products, but rather enhances by a constant degree their synthesis and accumulation. Therefore, we conclude that glucocorticoids may play a modulatory but not an inductive role in pancreatic development.

The diverse effects of 5'-bromodeoxyuridine on enzyme activities in cultured H35 hepatoma cells

Reuber (H35) hepatoma cells were grown in medium containing 10(-5)M bromodeoxyuridine (BrdU), which was incorporated into their DNA. Cell growth rate was unaffected by BrdU for the first two generations, after which it was reduced by about 50%. The effect of BrdU incorporation on the activities of several enzymes with rapid turnover rates was examined to test the hypothesis that the synthesis of such enzymes will be preferentially inhibited by BrdU. Tyrosine amino-transferase (TAT) activity decreased by 70% within two generations whereas thymidine kinase activity remained at control values. PEP carboxykinase activity was unchanged during the first generation in BrdU-containing medium but, during the second, its activity increased by at least 30%. Ornithine decarboxylase levels decreased by about 50% only after two generations in the presence of BrdU. There appeared to be no simple relationship between turnover rates and the effect of BrdU on enzyme activity. Incorporation of BrdU was found to inhibit the induction of both TAT and PEP carboxykinase by dexamethasone and to enhance the inhibition of cell growth by this steroid. These results are discussed with respect to possible mechanisms of gene expression and development in both normal and neoplastic cells.

The dexamethasone receptor in the Novikoff Hepatoma. Characterization and changes in concentration and nuclear uptake during glucocorticoid therapy

Novikoff hepatoma ascites cells, grown intraperitoneally in rats, are shown to possess a high-affinity, low-capacity dexamethasone-binding protein. The receptor protein has an intracellular localization and concentration, association constant (Ka), glucocorticoid specificity and nuclear uptake in the presence of dexamethasone comparable with those of the G-protein of rat liver. During therapy of the tumour-bearing animal with cortisol, marked cyclic variations were observed in the concentration and nuclear uptake of the putative G-protein in the tumor cells; more transient variations were also observed in the Ka value of the receptor protein.