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Biomedical subjects

R I Grove

Publications and source records attributed to R I Grove.

32 records · Page 2Linked to original sources
PubMed1985

Beta-epidermal growth factor is the des-asparaginyl form of the polypeptide.

Reversed-phase high performance liquid chromatography of mouse epidermal growth factor (EGF) yielded two major forms, alpha- and beta-EGF, and a minor component, gamma-EGF. All three forms exhibited receptor-binding activity. Analysis of native alpha- and beta-EGF by mass spectrometry and partial Edman degradation led us to propose that alpha-EGF has a primary structure equivalent to that originally reported for EGF and that beta-EGF is the des-asparaginyl form of the polypeptide. When the purified alpha- and beta-polypeptides were cultured with human embryonic palatal mesenchymal cells stimulation of cell proliferation was observed at concentrations as low as 0.01 ng/ml with maximal stimulation occurring at about 1 ng/ml. Essentially no difference was noted in the mitogenic potency of the two forms. This suggests that the NH2-terminal region of EGF is not critical for mitogenic activity.

Amino Acid Sequence↗
PubMed1985

Inhibition of arachidonic acid metabolism is not involved in dexamethasone-induced growth inhibition in embryonic palatal development.

Previous studies have shown that glucocorticoids induce cleft palate in susceptible strains of mice and inhibit proliferation of palatal mesenchyme cells in vivo and in culture. The present study shows that the synthetic glucocorticoid, dexamethasone (DEX), inhibits serum-stimulated arachidonic acid release in cultured mouse palatal mesenchyme cells. Arachidonic acid could neither prevent the DEX effect on cell proliferation when added in culture nor prevent glucocorticoid-induced cleft palate when administered in vivo. Furthermore, the time course for DEX-induced inhibition of arachidonic acid release (maximal by 5h) is markedly different from the time courses for both inhibition of cell proliferation in culture and cleft palate induction in vivo (3 to 4 days). These results suggest that both DEX-induced cleft palate formation and inhibition of palatal cell proliferation arise from some mechanism other than a DEX-induced inhibition of arachidonic acid metabolism.

Animals↗
PubMed1984

Influence of epidermal growth factor and cyclic AMP on growth and differentiation of palatal epithelial cells in culture.

A serum-free, hormonally defined medium was developed which supports growth and differentiation in primary culture of epithelial cells from prefusion embryonic mouse palatal shelves. Using this culture system, medial epithelial programmed cell death was investigated. In the absence of EGF, medial epithelial cells undergo cell death and detach from the substratum by 24 hr of culture. The addition of EGF alone or in combination with various agents which increase intracellular cyclic AMP levels prevented medial epithelial cell death in both cell and organ culture. EGF appeared to exert its most dramatic effect in cell culture on growth and differentiation of the squamous oral epithelial cells. In addition, EGF and agents such as 8-bromo-cyclic AMP, dibutyryl cyclic AMP, or cholera toxin synergistically stimulated the appearance of a long-lived, rapidly proliferating cell type by Day 4 of culture. Our results suggest that both EGF and cyclic AMP together may be important in regulating proliferation of embryonic palatal epithelial cells.

Animals↗
PubMed1984

Role of glucocorticoids and epidermal growth factor in normal and abnormal palatal development.

The purpose of this chapter has been to discuss glucocorticoid and EGF involvement in normal and abnormal palatal development. It is to be hoped that we have made clear the important point that these hormone/growth factors and their receptors are present during normal embryonic palatal development to provide for regulation of growth and cellular differentiation. When these hormone/growth factors are administered in pharmacological or large doses that result in teratogenesis, these potent chemicals and their receptors then become inducers of cleft palate. The primary reason for this is that the hormone/growth factor receptors have unique and special areas of localizations in target (embryonic and fetal) tissues, e.g., glucocorticoids in the palate. Therefore, large amounts of these chemicals are specifically bound to receptors in these target tissues and these high levels of hormone/growth factor-receptor complexes result in aberrant development, e.g., glucocorticoids cause inhibition of palatal mesenchymal cell growth. These effects are distinct from the interactions of physiological levels of these hormone/growth factors with their receptors in these target tissues during development, e.g., glucocorticoids cause induction of key enzymes and modulation of EGF receptor levels. The exact molecular mechanism(s) by which high levels of hormone/growth factors--receptor complexes exert harmful effects on embryos or fetuses is (are) unknown and remain(s) a challenge for the future. Interaction of hormone/growth factors and their receptors certainly cannot provide an explanation for the mechanism of all types of craniofacial teratogenesis, but this concept certainly appears capable of providing important information relating to the mechanisms of many animal and human teratogens. The fact that these chemicals and their receptors are involved in normal development makes them all the more important since subtle alterations in their levels or activities could result in teratogenesis without an exposure to pharmacological levels of these hormone/growth factors. It seems that progress in this area will develop quickly since the techniques of recombinant DNA research are available in conjunction with responsive in vitro cell systems such as the established line of human embryonic palatal mesenchymal cells. Clearly, the future looks very exciting for understanding the role that these hormone/growth factors and their receptors play in normal and abnormal palate development.

Animals↗
PubMed1983

Dexamethasone affects phosphatidylinositol synthesis and degradation in cultured human embryonic cells.

Dexamethasone (DEX), a glucocorticoid which induces cleft palate, causes marked alterations in the synthesis and degradation of phosphatidylinositol (PI) but not phosphatidylcholine in an established fibroblastic cell line derived from a human embryonic palate. Incorporation of radiolabeled inositol into phosphatidylinositol as well as degradation of prelabeled phosphatidylinositol is stimulated by DEX. The dose-response curves for the DEX-induced effect on PI synthesis and DEX-induced inhibition of cell proliferation are nearly identical, with the maximal responses occurring at 10(-8)M DEX. Our results suggest that DEX-induced inhibition of human embryonic palatal mesenchyme cell proliferation and alterations in synthesis and degradation of phosphatidylinositol are related.

Cell Division↗
PubMed1983

Growth and differentiation of embryonic mouse palatal epithelial cells in primary culture.

The study of both normal and abnormal mammalian palatal development would be greatly enhanced by the advent of a cell culture system for the palatal epithelium in the absence of its mesenchyme. We have developed such a method for the primary culture of the secondary palatal epithelium from the embryonic mouse which allows for both epithelial cell proliferation and differentiation into the three cell types normally found in vivo. These include the terminally differentiated medial epithelial cells and the appearance of the nasal epithelial cell phenotype (ciliated pseudostratified), as well as the oral epithelial cell phenotype (stratified squamous). The most successful culture medium tested consisted of a 1:1 mixture of DMEM/F-12 basal medium supplemented with fetal bovine serum and epidermal growth factor (EGF). Epithelial cell attachment, DNA synthesis and differentiation are greatly stimulated by the presence of EGF and by an extracellular matrix (ECM) substratum. Our results have demonstrated for the first time the feasibility of culturing embryonic palatal epithelial cells in primary culture in the absence of any mesenchymal tissue.

Animals↗
PubMed1982

Effects of 12-O-tetradecanoylphorbol 13-acetate on glycerolipid metabolism in cultured myoblasts.

We recently reported that treatment of differentiated chick embryo myoblasts in culture with the potent tumor promoter 12-O-tetradecanoylphorbol 13-acetate (TPA) caused a 2-fold increase in the level of 1,2-diacylglycerol in the plasma membrane fraction within 15-30 min (Grove, R.I. and Schimmel, S.D. (1981) Biochem. Biophys. Res. Commun. 102, 158-164). This system has been characterized further and the metabolic origin and fate of the stimulated diacylglycerol have been investigated. The stimulation of 1,2-diacylglycerol was insensitive to alterations of Ca2+ concentration in the medium and to the presence of inhibitors of Ca2+ flux, protein synthesis and prostaglandin synthesis. The fatty acid composition of the newly formed diacylglycerol was similar to that of phosphatidylcholine. In addition, the glycerol moiety of the diacylglycerol was shown to be derived from a lipid with metabolic turnover similar to that of phosphatidylcholine. The tumor promoter was also found to stimulate rapidly synthesis of phosphatidic acid, phosphatidylinositol and phosphatidylcholine. A possible model is proposed, therefore, in which the tumor promoter stimulates a membrane-associated phospholipase C which generates 1,2-diacylglycerol via the hydrolysis of phosphatidylcholine. The newly formed diacylglycerol is then metabolized back to phosphatidylcholine or to phosphatidic acid and phosphatidylinositol.

Animals↗
PubMed1982

Prescreening for environmental teratogens using cultured mesenchymal cells from the human embryonic palate.

Mesenchymal cells from the prefusion human embryonic palate have been established in culture and can be grown in either a serum-free hormone-supplemented medium or a serum-containing medium. The growth of these cells is quite rapid in culture and inhibited in a dose-dependent manner by most teratogens thus far tested, such as dexamethasone. These cells are highly sensitive to a variety of DNA synthetic and mitotic inhibitors. The responses of these cells are complementary to the ovarian tumor cell attachment assay of Braun et al [1, and in this volume]. When used in conjunction with the tumor cells, the overall reliability is greater than 90% with only one false-negative, allopurinol.

Cells, Cultured↗
PubMed1981

Effect of Ca++ on triphosphoinositide extraction in fusing myoblasts.

Ca++-dependent degradation of triphosphoinositide has been postulated to regulate levels of membrane-bound Ca++ and to generate a 1,2-diacylglycerol fusogen in cell fusion. Triphosphoinositide metabolism was therefore studied during Ca++-induced fusion of cultured chick embryo myoblasts. Using a frequently cited extraction procedure, it was found that apparent Ca++-dependent triphosphoinositide degradation was actually due to inhibition of extraction. A new procedure using the ion-pairing reagent tetrabutylammonium sulfate was developed which was unaffected by Ca++ and gave 2- to 20-fold greater extraction of triphosphoinositide than existing procedures. With this procedure, no changes in triphosphoinositide metabolism were found during myoblast fusion.

Animals↗
PubMed1980

Binding of phorbol-12-myristate-13-acetate to cultured myoblasts.

The tumor promoter phorbol 12-myristate 13-acetate (PMA) binds in a rapid (maximal at 30 min), reversible, and non-saturable manner to cultured embryonic chick myoblasts. Serum was not required for binding although it promoted the release of PMA from the cells. This appears to be due to PMA binding to serum proteins. At any concentration tested, approx. 10% of the total PMA was bound at 5 min and 30% was bound at 30 min. It is estimated that a PMA concentration in the cell membrane of only 1 molecule of PMA/5000 molecules of membrane lipid elicits maximal biological responses in these cells.

Animals↗