PubMed Health⌕ Search

Biomedical subjects

S Adamo

Publications and source records attributed to S Adamo.

At least 37 records · Page 2Linked to original sources
PubMed1990

12-O-tetradecanoylphorbol-13-acetate-induced differentiation of a human rhabdomyosarcoma cell line.

The effect of 12-O-tetradecanoyl phorbol-13-acetate (TPA) on proliferation and differentiation of the human embryonal rhabdomyosarcoma cell line RD was investigated. The proliferation of RD cells is drastically and reversibly inhibited by 100 nM TPA. The effect is evident after 24 h of treatment and is maximal after 50-70 h. The reduction of proliferation in treated cells is followed by increased expression of differentiative characters such as a large increase in muscle myosin expression and in the binding of 125I-alpha-bungarotoxin. Moreover TPA induces the appearance of myotube-like structures, which contain bundles of thick and thin myofilaments along with Z bodies. The described effects are not observed if the TPA-containing medium is replaced daily, thus suggesting that these effects might be related to substances secreted by treated cells. The phosphorylation of three proteins is significantly stimulated by TPA within minutes of its administration to RD cells. Although with a different pattern, the stimulation of protein phosphorylation is still clearly detectable after 6 days of incubation with TPA. These results on human rhabdomyosarcoma cells are, to our knowledge, the first evidence for a growth-inhibiting and a differentiative effect of TPA on a solid tumor of mesodermal origin.

Cell Differentiation↗
PubMed1989

Effects of protein kinase C (PK-C) activators and inhibitors on human large granular lymphocytes (LGL): role of PK-C on natural killer (NK) activity.

The role of protein kinase C (PK-C) in the early metabolic events involved in human natural killer (NK) cell activation has been studied through the action of PK-C-specific activators and inhibitors. Highly purified human large granular lymphocytes (LGL) were treated for 1 hr with the diacylglycerol analog 1-oleoyl-2-acetyl glycerol (OAG) (10(-4)-10(-5) g/ml) or with 12-O-tetradecanoylphorbol-13-acetate (TPA) (10(-8)-10(-10) g/ml), both specific activators of PK-C. Both these agents consistently increased NK activity against K562 target cells. Suboptimal doses of either OAG or TPA also synergized with Ca2+ ionophores to augment spontaneous cytotoxic activity. Pretreatment of LGL with 1-(5-isoquinolinesulfonyl)-2-methylpiperazine dihydrocloride (H7) (5-40 microM), a potent PK-C inhibitor, greatly reduced NK activity in a time- and dose-dependent fashion. By contrast, N-(2-guanidinoethyl)-5-isoquinolinesulfonamide hydrochloride (HA 1004), a potent cAMP- and cGMP-dependent PK inhibitor with almost no effect on PK-C, marginally reduced NK activity. Moreover, almost complete NK activity inhibition was observed when H7 (10 microM), but not HA 1004 (50 microM), was present in the NK assay. Finally, 48 hr stimulation of LGL with TPA (10(-6) g/ml), a treatment able to inactivate most of the PK-C cellular pool, almost completely abrogated NK activity. This functional evidence was supported by phosphorylation of several endogenous substrates which occurs within 5 min in TPA-treated LGL. Two proteins of 70 and 56 kDa have been identified as major PK-C substrates, together with other phosphorylated proteins with MW ranging from 177 to 43 kDa. H7, but not HA 1004, almost completely inhibited the TPA-induced phosphorylation of all of these proteins in the NK cells. These data strongly suggest that selective activation of PK-C plays an essential role in the mechanisms of NK cell activation.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed1989

Signal transduction in the Sertoli cell: serum modulation of the response to FSH.

Immature Sertoli cells of the testicular seminiferous tubule maintain the expression of their differentiated phenotype when cultured in unsupplemented medium. In preliminary experiments we observed that foetal bovine serum (FBS) stimulates polyphosphoinositides (PI) hydrolysis in Sertoli cells. We then evaluated the effect of serum on the function of the immature Sertoli cell in culture, in terms of cAMP and estrogen production. Treatment of Sertoli cells for 30 min with 1-10% FBS had no effect on basal cAMP accumulation but abolished the response to FSH. The serum concentration producing half-maximal inhibition of the FSH-dependent cAMP accumulation was 0.5-1%. Comparison of the FSH-dose-response in the absence or presence of serum showed a decreased maximal response when serum was present. Sertoli cells exposed to serum were also less responsive to the beta-adrenergic agonist isoproterenol, to cholera toxin, and to forskolin. The serum inhibition was rapidly reversed upon removal of serum or incubating the cells with the phosphodiesterase inhibitor MIX (methyl-isobutyl-xanthine). Similarly to what observed with cAMP, serum affected androgen aromatization stimulated by FSH, isoproterenol, cholera toxin, forskolin and dibutyryl cAMP. These data indicate that factors present in serum can act as modulators of the Sertoli cell function in vitro by rapidly and reversibly inhibiting the cAMP and steroidogenic response of the Sertoli cell to FSH.

Animals↗
PubMed1989

Activity and regulation of calcium-, phospholipid-dependent protein kinase in differentiating chick myogenic cells.

The activity of calcium-, phospholipid-dependent protein kinase (PKc) was measured in (a) total extracts, (b) crude membrane, and (c) cytosolic fractions of chick embryo myogenic cells differentiating in culture. Total PKc activity slowly declines during the course of terminal myogenesis in contrast to the activity of cAMP-dependent protein kinase, which was also measured in the same cells. Myogenic cells at day 1 of culture possess high particulate and low soluble PKc activity. A dramatic decline of particulate PKc activity occurs during myogenic cell differentiation and is accompanied, through day 4, by a striking rise of the soluble activity. The difference in the subcellular distribution of PKc between replicating myoblasts and myotubes is confirmed by phosphorylation studies conducted in intact cells. These studies demonstrate that four polypeptides whose phosphorylation is stimulated by the tumor promoter 12-O-tetradecanoyl phorbol 13-acetate in myotubes, are spontaneously phosphorylated in control myoblasts. Phosphoinositide turnover under basal conditions in [3H]inositol-labeled cells is faster in myoblasts than in myotubes, a finding that may in part explain the different distribution of PKc observed during the course of myogenic differentiation.

Animals↗
PubMed1989

Validity of high-dose ranitidine treatment (300 mg b.i.d.) in clinical practice: an open study in 68 consecutive cases of severe peptic disease.

Ranitidine, at doses of 300 mg b.i.d., brings about a pronounced inhibition of both daytime and nocturnal acid secretion. The aim of the present open study, conducted in 68 patients with peptic lesions of the upper gastrointestinal tract, was to assess whether or not ranitidine at 300 mg b.i.d. for 4 weeks was capable of healing these lesions, which had failed to respond to treatment with H2-antagonists at standard doses, even when administered over fairly lengthy periods (greater than 8 weeks). The results obtained show that the 300 mg b.i.d. regimen yields a marked gain in terms of healing of lesions and relief of symptoms (achieved in roughly 80% of cases), accompanied by excellent tolerance. It is concluded that a double dose of ranitidine is clinically justified in particular cases.

Female↗
PubMed1988

Effect of L-carnitine on ethanol and acetate plasma levels after oral administration of ethanol in humans.

In a randomized double-blind, cross-over experiment, 0.5 g/kg of ethanol in the form of white wine and 3 g of L-carnitine by intravenous infusion were administered to 15 healthy volunteers. Ethanol and acetate plasma levels and the urine concentrations of acetylcarnitine were determined. Administration of ethanol induced a significant increase of both plasma ethanol and acetate, lasting 6-8 hr. The concomitant administration of carnitine resulted in a significant decrease of plasma acetate, whereas plasma ethanol levels remained unmodified. Urinary acetylcarnitine content significantly increased following administration of ethanol plus carnitine, but not when L-carnitine alone was administered. The resulting conclusion is that administered L-carnitine might trap excess acetyls derived both from free acetate, formed by ethanol oxidation, and from acetyl coenzyme A, accumulated as a result of the ethanol-induced decrease in the Krebs cycle flux.

Acetates↗
PubMed1988

Follicle-stimulating hormone modulation of phosphoinositide turnover in the immature rat Sertoli cell in culture.

The possibility that FSH modulates the Ca++-, phospholipid-dependent pathway was studied in cultured rat Sertoli cells. Cells were metabolically labeled with [3H]myoinositol, and accumulation of [3H]inositol phosphates [( 3H]inositol mono-, di-, and trisphosphates) was measured by extraction and fractionation on ion exchange chromatography. Fetal bovine serum increased Sertoli cell phosphoinositide (PI) turnover in a time and concentration-dependent manner (ED50 = 2-3% vol/vol). FSH by itself had no significant effect on the accumulation of inositol phosphates. On the other hand, FSH inhibited, in a concentration-dependent manner, the serum-stimulated accumulation of inositol phosphates by more than 50%. HPLC ion exchange chromatography of the inositol phosphates showed that all isomers present in serum-stimulated extracts were reduced to the same extent after treatment with FSH. The treatment of the cells with either forskolin, the beta-adrenergic agonist isoproterenol, or (Bu)2cAMP also inhibited the PI turnover stimulated by fetal bovine serum. FSH inhibition was not detected in mature Sertoli cells, in which FSH no longer stimulates cAMP accumulation. These results demonstrate that FSH, via formation of cAMP, exerts inhibitory effects on the PI turnover of the Sertoli cell. Thus, while stimulating the cAMP-dependent pathway, at the same time FSH inhibits the Ca++-, phospholipid-dependent pathway.

Animals↗
PubMed1987

Acetylcholine may regulate its own nicotinic receptor-channel through the C-kinase system.

Acetylcholine (ACh)-activated channel properties were examined on an aneural culture of chick embryo myotubes by using patch-clamp techniques. Changes in conductance, open time and closed time were induced by the selective activator of the calcium- and phospholipid-dependent C-kinase (PKc), 12-O-tetradecanoylphorbol-13-acetate (TPA). The action of TPA was mimicked by exogenous phospholipase C and was blocked by the PKc inhibitor, 1-(5-isoquinolinylsulphonyl)-2-methyl-piperazine. In addition to its gating action, ACh was shown to stimulate phosphoinositide turnover and to translocate PKc from the cytosol to the cell membrane. Both these ACh-induced effects were inhibited by curare and not substantially affected by atropine. Bath-applied ACh outside the patch-pipette in the cell-attached patch-clamp mode, had a strong effect on the ACh-activated channels in the patch membrane, in a way that resembled the action of TPA. These findings raise the possibility that ACh regulates its own nicotinic receptors through the C-kinase system.

Acetylcholine↗
PubMed1986

Altered distribution of protein kinase C in dystrophic muscle cells and its modulation by liposome-delivered phospholipids.

The activity and subcellular distribution of the calcium-phospholipid dependent protein kinase (protein kinase C) were studied in normal and dystrophic muscle cells in vitro. Clonal strains of satellite cells, isolated from normal and dystrophic (C57BL/6J/dydy) mice, differentiate in vitro at a comparable level (over 80% of fusion). Differentiated myotubes were homogenized and separated into a soluble and a particulate fraction. The activity of protein kinase C was assayed in both fractions, and was found to be mainly in the cytosol of normal cells, whereas it was mainly associated to the membrane fraction of dystrophic cells. This altered distribution of the enzyme was likely consequent to alterations in the phospholipid composition of the dystrophic cell membrane, since it was possible to partially revert the situation by modifying the membranes with liposome-delivered phospholipids. Splenic lymphocytes from dystrophic mice showed an altered distribution of protein kinase C similar to that observed in muscle cells. The possible biochemical basis and the functional consequences of this altered distribution of the enzyme in the dystrophic cells are discussed.

Animals↗
PubMed1986

Proliferating and quiescent cells exhibit different subcellular distribution of protein kinase C activity.

The activity of calcium, phospholipid-dependent protein kinase (PKc), which is thought to play an important role in cell proliferation, has been measured in the particulate and soluble fractions of cultured cells, under different proliferative conditions. Our results indicate that proliferating cells display higher PKc activity than quiescent cells. Furthermore, in both normal and transformed cells, PKc is preferentially associated with the particulate fraction when the cells are proliferating, while in mitotically quiescent cells the majority of the enzyme activity is found in the soluble fraction. These data suggest tha PKc activity and subcellular distribution undergo spontaneous changes according to the proliferative state of the cells.

Animals↗
PubMed1986

Calcium-, phospholipid-dependent protein kinase activity of cultured rat Sertoli cells and its modifications by vitamin A.

The activity of the calcium-, phospholipid-dependent protein kinase (PKc) was partially characterized in Sertoli cell cultures prepared from 20-day-old rats. The calcium dependency, the requirements for phosphatidylserine and diolein, as well as the Km for ATP and for the tumor promoter TPA, were determined in total cell extracts. The specific activity of PKc was almost 3-fold higher in the soluble than in the particulate fraction of Sertoli cells. Treatment of cultured Sertoli cells with retinol inhibited, within 1 h of treatment, both the soluble and the particulate fraction-associated PKc activity, with an IC50 of 0.1 microM. Partial inhibition of PKc activity was obtained treating Sertoli cell cultures with FSH, while testosterone was ineffective. However, both FSH and testosterone potentiated the inhibitory effect of retinol. Less differentiated Sertoli cells, obtained from 8-day-old rats, displayed higher PKc activity and a pattern of subcellular distribution of the enzyme opposite to that of Sertoli cells obtained from 20-day-old rats. These data suggest that the actual PKc activity of rat Sertoli cells be negatively regulated by retinol and, spontaneously, during the progression of Sertoli cell differentiation.

Animals↗
PubMed1986

A double-blind controlled trial of ranitidine 300 mg nocte and ranitidine 150 mg b.i.d. in the short-term treatment of gastric ulcer.

A multi-center study was carried out to compare the healing rates of ranitidine 300 mg nocte and 150 mg b.i.d. in the short-term treatment of gastric ulcers and to assess the side-effect liability of ranitidine 300 mg given in a single daily dose. Forty-five outpatients suffering from endoscopically and bioptically proven uncomplicated benign gastric ulcer were selected for the study. The patients were treated, for 4 weeks, on the basis of a double-blind randomized design. An endoscopic examination was repeated within 4 days after the end of the treatments. The patients who did not demonstrate complete healing were treated for an additional 4-week period. Clinical controls were performed to evaluate symptoms, antacid consumption, compliance with trial tablet consumption; hematological and biochemical tests were also carried out at the end of the 4 and 8-week periods. No differences were observed between the healing rate induced by 300 mg nocte and 150 mg b.i.d., after 4 weeks of treatment (76% and 79% respectively) and after 8 weeks (100% in both groups). Similar results were obtained as far as symptoms, antacid consumption and compliance are concerned. Neither treatment regimen induced appreciable side-effects.

Adult↗
PubMed1985

Acetylcholine stimulates phosphatidylinositol turnover at nicotinic receptors of cultured myotubes.

Acetylcholine treatment of [3H]inositol pre-labelled cultured chick embryo myotubes results in the stimulation of phosphatidylinositol breakdown, as shown by the measurement of inositol-1-phosphate accumulating in the presence of lithium. The described effect is dependent on agonist concentration and incubation time, and is inhibited by tubocurarine and alpha-bungarotoxin. The activation of phosphatidylinositol breakdown by acetylcholine at extrajunctional nicotinic receptors is likely to be involved in the modulation of the functional activity of the receptor.

Acetylcholine↗
PubMed1985

[Pentoxifylline and arterial hypertension in diabetes mellitus: long-term results in randomized groups].

This follow-up study concerns the use of pentoxifylline (PTX) as antihypertensive drug in randomized diabetic groups. A significant reduction of systolic and diastolic arterial blood pressure has been obtained in diabetic patients treated with PTX alone or with PTX associated to conventional antihypertensive therapy. The normalization of arterial blood pressure was associated to an improvement of erythrocyte filterability and to a reduction of proteinuria. Therefore, pentoxifylline can be considered a good pharmacological approach in the treatment of diabetic hypertension and in the prevention of diabetic renal disease.

Diabetes Complications↗