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Biomedical subjects

E Chiosi

Publications and source records attributed to E Chiosi.

18 recordsLinked to original sources
PubMed2004

Differentiation of H9c2 cardiomyoblasts: The role of adenylate cyclase system.

The adenylate cyclase (AC)/cAMP/cAMP-dependent protein kinase pathway controls many biological phenomena. The molecular mechanisms by which cAMP induces alternative commitment towards differentiation or proliferation are not still completely known. The differentiation of myoblast cell lines into myocytes/myotubes represents a well-established model of skeletal muscle differentiation. We analyzed the AC/cAMP pathway during terminal differentiation of H9c2 myoblasts. When cultured in low-serum containing medium, H9c2 myoblasts exit the cell cycle and differentiate into myocytes/myotubes. A key step of this process is the expression of myogenin, an essential transcription factor for the terminal differentiation into myocytes. During this phenomenon we observed a decrease in both cAMP levels and AC activity, which suggests a functional negative role of cAMP on the differentiation process of H9c2 cells. 8-Br-cAMP and other cAMP-elevating agents, such as forskolin, IBMX, and isoproterenol, negatively affected skeletal muscle differentiation of H9c2 myoblasts. Both AC activity down-regulation and intracellular cAMP reduction were accompanied by significant variations in the levels of membrane proteins belonging to the AC system (AC catalytic subunit, G(alphai-1), G(alphas)). The functional relationship between intracellular cAMP content and protein levels of AC system is discussed.

Adenylyl Cyclases↗
PubMed2000

Treatment of v-Ki-ras-transformed SVC1 cells with low retinoic acid induces malignancy reversion associated with ras p21 down-regulation.

The effect of nontoxic, low concentrations (10(-8) M) of retinoic acid (RA) for a relatively long time (28 days) on a Kirsten ras-virus transformed cell line (Ki-SVC1), derived from the rat seminal vesicle epithelium, was investigated. In these experimental conditions, the cell treatment with RA induced a decrease of the proliferation rate, apoptosis and a marked reduction of both anchorage-independent growth and tumorigenicity. These biological responses were either preceded or associated with important changes in adenylate cyclase/protein kinase C signaling pathways, the activation of important apoptosis-linked genes and a marked decrease of the v-Ki-ras p21 protein. The significance of these findings is discussed.

Adenylyl Cyclases↗
PubMed1999

GTPase and transglutaminase are associated in the secretion of the rat anterior prostate.

We have found that in the secretion of rat anterior prostate, a hydrolyzing activity on GTP is present with a high affinity for the substrate; ATP, GDP, and ADP are not substrates for enzymatic activity. At the same time we have shown that GTP is a negative modulator for the well-known type IV transglutaminase activity present in the prostatic secretion. The hydrolyzing activity on GTP appears to be due to two molecular species: a high-molecular-weight GTPase, having electrophoretical mobility higher than 100 kDa, and a low-molecular-weight GTPase, of about 30 kDa. The two enzymatic activities are associated in the prostatic secretion with the transglutaminase (type IV). We describe an experimental procedure to separate them.

Animals↗
PubMed1997

tTGase/G alpha h protein expression inhibits adenylate cyclase activity in Balb-C 3T3 fibroblasts membranes.

Stably transfected Balb-C 3T3 fibroblasts (clone 5), overexpressing a catalytically active tissue transglutaminase, showed a basal adenylate cyclase activity lower than control cells (clone 1). Several modulators of the adenylate cyclase activity (forskolin, Mn2+ and pertussis toxin) showed the existence of a marked negative control on the adenylate cyclase activity present in clone 5 cells. Very interestingly, this same marked negative control was also found in a Balb-C 3T3 fibroblast clone stably transfected with a mutagenized human tissue transglutaminase (mut277 cys > ser) virtually devoid of transglutaminase catalytic activity (clone Ser). Conversely, a significant increase of the adenylate cyclase activity was observed in bovine aortic endothelial cells after the lowering of tissue transglutaminase expression levels by the transfection of an eukaryotic expression vector containing the gene for tissue transglutaminase in antisense orientation. All these findings suggest a possible role for type II tissue transglutaminase as a negative modulator of the adenylate cyclase activity in different cell types, beside its transglutaminase enzyme activity.

3T3 Cells↗
PubMed1993

ras oncogene-induced transformation of a rat seminal vesicle epithelial cell line produces a marked increase of adenylate cyclase and protein kinase C activities.

Cells transformed by Kirsten murine sarcoma virus (Ki-MSV) have basal adenylate cyclase activity (AC) higher than control cells and comparable level of forskolin-stimulated AC activity. Moreover, a higher protein kinase C (PKC) activity was found to be present in the transformed cells. The molecular mechanism underlying the increase of AC activity was investigated. Our findings strongly suggest that this biochemical event is due to a marked decrease of the alpha i negative control of the enzyme, even though the alpha i of transformed cells appears to possess fully functional domains interacting with both the effector enzyme and the agonist-activated receptor.

Adenosine Diphosphate Ribose↗
PubMed1993

Role of calcium in chloride secretion mediated by cAMP pathway activation in rabbit distal colon mucosa.

Effects of Ca2+ on adenosine 3',5'-cyclic monophosphate (cAMP)-mediated Cl- secretion were investigated in intact mucosa and isolated crypt cells of rabbit descending colon. Addition of 10 microM prostaglandin (PG)E2 or forskolin to tissues incubated in Ca(2+)-free medium increased the size of short-circuit current (Isc) and Cl- secretion as estimated by unidirectional 36Cl flux measurements (net flux = -2.31 +/- 0.24 vs. -1.22 +/- 0.10 mueq.h-1.cm-2, n = 4, P < 0.001). Addition of 10 microM PGE2 to tissues incubated in 1.2 mM Ca2+ Ringer induced a 7-fold increase in mean cAMP level, whereas it produced an 11-fold increase in tissues exposed to Ca(2+)-free medium. Membrane preparations from whole mucosa incubated in Ca(2+)-free medium displayed a cyclic nucleotide phosphodiesterase activity significantly lower than controls (18.76 +/- 0.54 vs. 31.20 +/- 0.39 pmol cAMP. mg protein-1.min-1, means +/- SE, n = 4, P < 0.001). Ca2+ removal also affected adenylate cyclase (AC) responsiveness to agonists; AC activity increased in controls by 54 and 226% after stimulation with 10 microM PGE2 and forskolin, respectively, but it increased more (77 and 325%, respectively) after incubation in Ca(2+)-free solutions.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenylyl Cyclases↗
PubMed1988

Protein kinase C activities are increased in rat thyroid epithelial cells expressing v-ras genes.

Both cytoplasmic and membrane-bound protein kinase C activities are increased in: Harvey-Sarcoma Virus, infected thyroid epithelial cells. The cytoplasmic kinase C increase is found in the chromatographic fraction eluted at lower salt concentration (100 mM NaCl-S100), while the more acidic protein fraction eluted at higher salt concentration (35 mM NaCl-S350) is virtually absent. Although the cytoplasmic S100 fraction from the control and ras-virus infected cells display a comparable PBt2 binding activity, they are different in the Ca+2-dependence and the TPA down regulation. In addition, the membranes from the control and ras-virus infected cells are different phosphate acceptors in place of the H1 histones.

Animals↗
PubMed1986

Inheritance of Brown's syndrome.

Two families are described with members affected by Brown's syndrome. Another case of Brown's syndrome is described in a dizygotic twin. The authors suggest a hypothesis for the influence of heredity in Brown's syndrome.

Child↗
PubMed1983

Low insulin concentrations stimulate in vitro the soluble guanylate cyclase activity of rat liver.

The soluble guanylate cyclase activity of rat liver appears to be stimulated in VITRO by insulin at pMolar concentrations, while proinsulin, denaturated insulin or desoctapeptide insulin, are not able to stimulate the studied enzymic activity. Corresponding concentrations of other peptide hormones such as corticotropin (ACTH) or glucagon, either in the absence or in the presence of bacitracin, do not show any effect on the investigated enzymic system. Insulin stimulation of the soluble guanylate cyclase is characterized by a significant increase in the Vmax together with a decrease of the apparent Km. Insulin at low concentrations doesn't affect the cyclic GMP hydrolyzing activity; conversely higher concentrations of the hormone, while exerting a less marked effect on the guanylate cyclase activity, inhibit the cyclic GMP hydrolyzing activity.

Animals↗
PubMed1983

A stimulating effect of guanyl nucleotides on the rat-liver soluble cyclic GMP high-affinity phosphodiesterase activity.

The high affinity (low Km) cyclic GMP phosphodiesterase (PDE) is activated by GTP, while the cyclic AMP PDE is not. GTP and its hydrolysis-resistant analogue, guanylylimidodiphosphate (GppNHp), display a half-maximal stimulating effect at almost the same concentration (5 X 10(-6) M). The GTP stimulating effect is not observed when the socalled cyclic GMP low affinity (high Km) PDE is operative. GTP cooperates with the increase of the substrate concentration on removing the IBMX inhibitory effect. The isolation through a classical chromatographic procedure on a DEAE-cellulose column, of a PDE fraction specific for cyclic GMP, results in the loss of the GTP stimulating effect.

1-Methyl-3-isobutylxanthine↗
PubMed1983

Relationship between the fluidity of the membrane lipids and the activity of the membrane-bound proteins: the effects of lidocaine on the adenylate cyclase activity of rat myocardium.

The lidocaine effects on the basal adenylate cyclase activity of the studied membranes depend on the substrate concentration: the drug has an inhibiting effect on non-saturating ATP concentrations, but displays a stimulating effect on the saturating ones. In the presence of maximally stimulating NaF concentrations, lidocaine further stimulates the adenylate cyclase activity through all the ATP concentrations used. In the presence of ATP saturating concentrations, the adenylate cyclase activity stimulated by various Gpp(NH)p concentrations, is inhibited in the presence of lidocaine as well as the enzymic activity stimulated by several l-isoproterenol concentrations in the presence of a fixed Gpp(NH)p concentration.

Adenylyl Cyclases↗
PubMed1982

Hydrolyzing activities on cAMP in E. coli B cells incubated in the presence of polyamines.

1. Hydrolyzing activities on cAMP were investigated in E. coli B cells incubated in the presence or absence of 10(-5) M spermine, spermidine or putrescine. 2. Bacterial cells incubated in the presence of each of the investigated polyamines show an increase in the PDE (phosphodiesterase) activities already evident after 3 min of incubation, reaching the maximum between 5 and 10 min. disappearing between 15 and 25 min. 3. The stimulating effect is higher in the presence of lower (10(-6) M) substrate concentration (high affinity PDE activities). 4. Kinetic analyses carried out for the "high affinity" PDE activity, indicate that spermidine and putrescine are the most effective on increasing both the Vmax or the apparent Km. 5. Kinetic analysis carried out for the "low affinity" PDE activity, indicate that putrescine is the most active on increasing either the Vmax or the apparent Km and that spermine and spermidine have both quantitatively and qualitatively comparable effects. 6. Analyses, by TLC, of the products of the hydrolytic activities on cyclic AMP (5'-adenosine monophosphate (5'-AMP), adenosine, inosine) indicate that the incubation in the presence of each of three polyamines, results in an increase also of the 5' nucleotidase and adenosine deaminase activity.

Cyclic AMP↗
PubMedDate not supplied

[Brown's syndrome].

Having observed a very tight adhesion between the trochlea and the tendon of the obliquus superior bulbi muscle or an increase in tendon thickness posterior to the trochlea in operated patients, the author tried to correct this abnormality using partial trochleotomy and the lysis of the adhesions, followed by the application of Scott-Knapp sutures. The morphological basis of Brown's syndrome, consisting of an obstruction at the level of the trochlea, was demonstrated experimentally by means of an eye motion simulator.

Humans↗