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Biomedical subjects

S Adamo

Publications and source records attributed to S Adamo.

At least 55 records · Page 3Linked to original sources
PubMed1984

Phosphorylation of specific polypeptides induced by 12-O-tetradecanoylphorbol-13-acetate in chick embryo fibroblasts.

The tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA) induces, in cultured chick embryo fibroblasts, a generalised increase of the incorporation of labelled inorganic phosphate, and stimulates the phosphorylation of at least two polypeptide bands, 26 K and 65 K. Stimulation of the phosphorylation of 26 K and 65 K occurs within minutes of the addition of TPA to the culture medium of chick embryo fibroblasts, but it can also be evidenced at later times. Removal of TPA from the culture medium causes reversion of this effect. Stimulation of the phosphorylation of 26 K is also induced by the Ca2+-ionophore A23187, but the calmodulin inhibitor trifluoperazine does not inhibit the TPA induced stimulation of polypeptide phosphorylation. Agents increasing the intracellular cAMP concentration do not stimulate the phosphorylation of 26 K and 65 K. The results obtained suggest that the phosphorylation of specific polypeptides, probably induced by TPA through a Ca2+-phospholipid dependent mechanism, may represent an early regulative event which may be relevant for the pleiotropic effect of TPA in cultured normal cells.

Animals↗
PubMed1983

Studies on the mechanism of retinoid-induced adhesion of spontaneously transformed mouse fibroblasts.

Transformed cells (Balb/c, 3T12-3), induced to increase their adhesion to the substrate by treatment with retinoic acid, display higher incorporation of (2-(3)H)-mannose into both lipids and glycoproteins than untreated controls. Stimulation of (2-(3)H)-mannose incorporation into manno-lipids is evident 8 hr after exposing the cells to retinoic acid, and stimulation of tritiated mannose incorporation into glycoproteins occurs slightly later. SDS-PAGE of (2-(3)H)-mannose labelled glycoproteins indicates that both retinoic acid and retinol treatments stimulate the incorporation of the radiolabelled sugar into a glycoprotein with subunit MW 180,000 (Gp 180) and, to a lesser extent, into other glycoproteins. 3H-leucine incorporation into a protein banding at the same position as the 3H-mannose labelled Gp 180 does not appear to be affected by retinoid treatment. A retinoic acid induced increase in the amount of Gp 180 can also be shown by lactoperoxidase catalyzed radioiodination of cultured 3T12 cells, and controlled trypsin digestion experiments indicate that Gp 180 is a component of the cell surface. On the contrary, the increased cell adhesion to the substrate induced by retinoic acid is not accompanied, in this system, by an increase in the amount of fibronectin, as judged by iodination of the cell surface components followed by SDS-PAGE.

Animals↗
PubMed1982

Glycopeptide alterations induced by 12-O-tetradecanoyl phorbol-13-acetate in chick embryo cultured myotubes.

The tumor promoter 12-O-tetradecanoyl phorbol-13-acetate (TPA) specifically inhibits the expression of differentiative traits in cultured chick embryo myotubes, without inducing them to reenter the cell cycle. We evaluated the effect of TPA on glycoconjugate synthesis in cultured myotubes under various experimental conditions. Radioactively labelled glycoconjugates were obtained by labelling control and TPA treated cultured myotubes with radioactive monosaccharides. After chloroform-methanol extraction and extensive pronase digestion, the glycoconjugates were separated on the basis of size on Sephadex G 50 columns. A relative enrichment in larger glycopeptides was induced by TPA treatment of myotubes for 24 or 48 h. Glycopeptide groups were further analyzed by affinity chromatography on ConA Sepharose columns. A marked and reproducible decrease in the affinity of medium size glycopeptides for ConA was observed as a result of TPA treatment of cultured myotubes. These modifications are reversible upon removal of the tumor promoter from the culture medium of pretreated myotubes. The reported effects of TPA, closely resembling those occurring in transformed cells, appear to be due to structural modifications of glycopeptides whose mechanism and role in transformation and modulation of differentiation are discussed.

Animals↗
PubMed1982

TPA-induced inhibition of the expression of differentiative traits in cultured myotubes: dependence on protein synthesis.

The tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA) dramatically modifies the differentiative program of myotubes, developed in culture from chick embryo skeletal myogenic cells. In fact TPA selectively decreases the expression of differentiative parameters with a lag of 8-10 h from its administration to the cultures. We have tested whether the reported effect of TPA depends on the synthesis of specific products during the lag phase of TPA action. The data presented indicate that inhibition of protein synthesis by the use of cycloheximide prevents the appearance of TPA induced inhibition of the expression of differentiative products, such as creatine phosphokinase (CPK) activity and acetylcholine receptors (AChR). Following removal of cycloheximide and reinitiation of normal protein synthesis, the TPA induced inhibitory effect on CPK and AChR appears after a delay of about the same length as the time lag of TPA action. Our results indicate that inhibition of protein synthesis during the lag phase of TPA action prevents the effect of this tumor promoter on myotube differentiative parameters, and suggest that the expression of differentiative traits in cultured myotubes is affected by TPA via a regulatory step implying protein synthesis.

Animals↗
PubMed1980

Retinoid metabolism and mode of action.

Vitamin A and its derivaties (retinoids) are necessary for the maintenance of normal phenotypic expression. An attempt at understanding the biochemical role of vitamin A had led to the demonstration of a new pathway for retinol. In this pathway, vitamin A is phosphorylated to retinylphosphate (RP), which is then glycosylated to retinylphosphatemannose (MRP). These two derivatives have been found in a variety of tissues in vivo and in vitro and appear to be ubiquitous components of cellular membranes. The suggestion has been made that MRP may mediate specific cellular interactions by functioning as a lipid intermediate in the biosynthesis of specific glycoconjugates. A study on spontaneously-transformed mouse fibroblasts (Balb/c 3T12-3 cells) has shown that retinoids are active in increasing the adhesive properties of these cells as measured in an EDTA-mediated detachment assay. Various retinoids were tested for their activity in the adhesion test, and this activity was found to correlate well with their biological activity in maintaining the expression of normal epithelial differentiation in other systems. Retinoic acid, 5,6-epoxyretinol, and 5,6-epoxyretinoic acid were the most active compounds. Retinoids without biological activity in other systems were also inactive in inducihg adhesive properties of 3T12-3 cells. Among these were the synthetic derivatives of retinol, anhydroretinol, and 4,5-monoeneperhydroretinol, and the phenyl derivative of retinoic acid. Beta-Ionone, abscisic acid, and juvenile hormone, which are devoid of vitamin A activity in other systems, were also inactive in this system. Retinoid-induced changes in cell surface proteins were investigated but no difference in 125I-fibronectin (MW 220,000) was detectable between retinoid-treated and untreated cells. However, these cells synthesized retinylphosphatemannose and the incorporation of 2-3H-mannose into a specific glycoprotein (gp 180) was found to be enhanced specifically by retinoid treatment. Investigations of the involvement of gp 180 in adhesion are in progress.

Animals↗
PubMed1979

Retinoid metabolism in spontaneously transformed mouse fibroblasts (Balb/c 3T12-3 cells): enzymatic conversion of retinol to anhydroretinol.

Spontaneously transformed mouse fibroblasts (Balb/c 3T12-3 cells) displayed an increased adhesion when cultured in the presence of 10(-6) M all-trans retinol and acquired morphological characteristics of the normal phenotype. Thus it was of interest to investigate the metabolism of [15-(14)C]retinol in this system. Within 24 hours of culture, approximately 4.25% of the [(14)C]retinol was taken up by the cells. The hydrocarbon [(14)C]anhydroretinol was a major metabolic product and was identified by gas-liquid chromatography and by its typical ultraviolet absorption spectrum with maxima at 386, 364, and 346 nm. At 24 and 40 hours anhydroretinol represented 27% and 55%, respectively, of the total nonpolar metabolites or approximately 16% and 30% of the total radioactive products. Formalin-fixed fibroblasts or cultured intestinal mucosal cells did not convert retinol into anhydroretinol. A more polar product with a UV absorption maximum at 310 nm was also found. The time course of the synthesis of this product by 3T12 cells suggested a precursor-product relationship with anhydroretinol. A microsomal preparation from 3T12 cells was also active in synthesizing [(14)C]anhydroretinol and [(14)C]metabolite-310 from [(14)C]retinol. Moreover incubation of metabolite-310 with the 3T12 microsomes yielded anhydroretinol (40% conversion in 30 minutes), suggesting that metabolite-310 is an intermediate in the synthesis of anhydroretinol by these cells. Anhydroretinol appears to be an end product of the metabolism of retinol in 3T12-3 cells, as suggested by the finding that over 90% of [(14)C]anhydroretinol incubated for 30 hours with 3T12-3 cells was recovered unaltered, without the formation of detectable retroretinol, retinol, or retinoic acid.-Bhat, P. V., L. M. De Luca, S. Adamo, I. Akalovsky, C. S. Silverman-Jones, and G. L. Peck. Retinoid metabolism in spontaneously transformed mouse fibroblasts (Balb/c 3T12-3 cells): enzymatic conversion of retinol to anhydroretinol.

Animals↗
PubMed1979

Hereditary pancreatitis: morphological pictures (ERCP) in the youngest member of a family.

Endoscopic retrograde cholangiopancreatography (ERCP) pictures of the pancreatic duct and of the biliary tract are described in the youngest member of a family with hereditary pancreatitis. The endoscopic changes are very similar to those usually observed in patients affected by chronic relapsing pancreatitis. Morphological changes were particularly marked in the body and tail of the pancreas. However, no abnormal changes were observed in the biliary tract.

Child↗
PubMed1978

Biosynthetic changes in myosin heavy subunit during myogenesis in culture.

In primary culture of chick embryo muscle cells myosin synthesis is detected in mononucleated cells and increased at the onset of fusion with a maximal increment of 20-fold per plate in differentiated myotube. The possibility that the myosin synthetized by duplicating myoblast could be different from that present in post-mitotic myoblast and myotube was evaluated by investigating the regulation of its synthesis and the turnover of the molecule. Following Actinomycin D treatment (0.05 microgram/ml, 8 h), myosin synthesis is partially affected (about 50% inhibition) in pre-fusion myoblast while the synthesis is more sensitive to the drug at the onset of fusion (80% inhibition). With the progress of the differentiative stage the half-life of the molecule increases from 30 h in duplicating myoblasts to 200 h in fibers. The half-life of myosin synthetized by duplicating myoblasts in the explanted embryonic muscle, is 12 h. These data show different features of myosin heavy chains related to specific stages of differentiation and suggest the possibility that modulative changes of the molecule could induce its functional maturation during myogenesis.

Animals↗
PubMed1976

Expression of differentiative traits in the absence of cell fusion during myogenesis in culture.

Fusion of myoblasts is inhibited in cultures at low Ca++ concentration (0.44 mM); yet creatine phosphokinase and myokinase activities as well as myosin synthesis and the appearance of post-mitotic myoblasts do not significantly differ from those of control cultures (grown at 1.04 mM Ca++) which undergo cell fusion. When Ca++ concentration is increased to the control value after the second day of culture, fusion occurs very rapidly and it is not inhibited by actinomycin D or cycloheximide. Treatment with 0.06 mM bromodeoxyuridine strongly inhibits creatine phosphokinase activity and myotubes formation. The study of the kinetics of reversal of cell fusion and of creatine phosphokinase activity after removal of the analog, shows that this process is slower than the decrease of the relative content of bromodeoxyuridine incorporated into DNA. The result obtained support the following conclusions: a) the expression of the differentiative characters examined does not require cell fusion; b) the process of myotube formation seems to imply two subsequent stages consisting first of a slow maturative process, which is followed by the actual fusion of cell membranes; the former is Ca++ independent, the latter is Ca++ dependent and does not require RNA or protein synthesis.

Adenylate Kinase↗
PubMedDate not supplied

[PCBs cause necrosis of L6C5 myoblasts].

Polychlorinated biphenyls (PCBs) are structurally related to dioxins, widely used in the past in various industrial applications and daily used products. Although PCBs production was discontinued more than twenty years ago, their chemical stability and high lipophilicity make them persistent pollutants and dangerous occupational contaminants. Skeletal muscle is an important site of PCB accumulation. Our previous results about the effects of PCBs on L6C5 myoblasts, showed that "low concentrations" (< 10 microg/ml) of these compounds inhibit in vitro myogenic differentiation in a concentration-dependent fashion, while toxic effects only begin to be evident at PCB concentrations > or = 10 microg/ml. In the present paper we wondered if the observed cell mortality is due to necrosis or if it depends on the activation of programmed cell death mechanisms (apoptosis). Using different methods of analysis, we have observed that PCBs cause necrosis of myogenic cells and that such effect is related to the employed concentrations and to the time of exposure (EC50 approximately = 50 microg/ml). Our results may help to explain the creatin kinase elevation, observed in the blood of patients acutely exposed to high concentrations of PCBs, as the consequence of a necrotic damage of the skeletal muscle. It will be therefore interesting to evaluate the presence of muscular damages in the chronic exposures to PCBs.

Animals↗