Biomedical subjects

S Mele

Publications and source records attributed to S Mele.

14 recordsLinked to original sources

PubMed2004

Biocompatible lipidic formulations: phase behavior and microstructure.

Biocompatible systems formulated for use in the food, cosmetic, and pharmaceutical fields are characterized. Ternary phase diagrams of mixtures of natural lipids (glycerol trioleate, glycerol monooleate, diglycerol monooleate, and lecithin) and water were investigated by means of optical microscopy in polarized light and by multinuclear NMR spectroscopy. All systems showed a microemulsion region at high oil content and a large area of coexistence of two liquid crystalline (hexagonal and lamellar) phases. 1H and 13C NMR self-diffusion measurements were used to characterize microstructural features of the microemulsions. On water dilution, the two-phase liquid crystalline region transforms into a creamy emulsion area where the droplets of water are stabilized by both the lamellar and the hexagonal phases, as indicated by 2H NMR measurements. Due to the very effective dispersing action of the two liquid crystalline phases, these emulsions show a high stability toward phase separation.

Biocompatible Materials↗

PubMed1999

The p66shc adaptor protein controls oxidative stress response and life span in mammals.

Gene mutations in invertebrates have been identified that extend life span and enhance resistance to environmental stresses such as ultraviolet light or reactive oxygen species. In mammals, the mechanisms that regulate stress response are poorly understood and no genes are known to increase individual life span. Here we report that targeted mutation of the mouse p66shc gene induces stress resistance and prolongs life span. p66shc is a splice variant of p52shc/p46shc (ref. 2), a cytoplasmic signal transducer involved in the transmission of mitogenic signals from activated receptors to Ras. We show that: (1) p66shc is serine phosphorylated upon treatment with hydrogen peroxide (H2O2) or irradiation with ultraviolet light; (2) ablation of p66shc enhances cellular resistance to apoptosis induced by H2O2 or ultraviolet light; (3) a serine-phosphorylation defective mutant of p66shc cannot restore the normal stress response in p66shc-/- cells; (4) the p53 and p21 stress response is impaired in p66shc-/- cells; (5) p66shc-/- mice have increased resistance to paraquat and a 30% increase in life span. We propose that p66shc is part of a signal transduction pathway that regulates stress apoptotic responses and life span in mammals.

Adaptor Proteins, Signal Transducing↗

PubMed1997

Opposite effects of the p52shc/p46shc and p66shc splicing isoforms on the EGF receptor-MAP kinase-fos signalling pathway.

Shc proteins are targets of activated tyrosine kinases and are implicated in the transmission of activation signals to Ras. The p46shc and p52shc isoforms share a C-terminal SH2 domain, a proline- and glycine-rich region (collagen homologous region 1; CH1) and a N-terminal PTB domain. We have isolated cDNAs encoding for a third Shc isoform, p66shc. The predicted amino acid sequence of p66shc overlaps that of p52shc and contains a unique N-terminal region which is also rich in glycines and prolines (CH2). p52shc/p46shc is found in every cell type with invariant reciprocal relationship, whereas p66shc expression varies from cell type to cell type. p66shc differs from p52shc/p46shc in its inability to transform mouse fibroblasts in vitro. Like p52shc/p46shc, p66shc is tyrosine-phosphorylated upon epidermal growth factor (EGF) stimulation, binds to activated EGF receptors (EGFRs) and forms stable complexes with Grb2. However, unlike p52shc/p46shc it does not increase EGF activation of MAP kinases, but inhibits fos promoter activation. The isolated CH2 domain retains the inhibitory effect of p66shc on the fos promoter. p52shc/p46shc and p66shc, therefore, appear to exert different effects on the EGFR-MAP kinase and other signalling pathways that control fos promoter activity. Regulation of p66shc expression might, therefore, influence the cellular response to growth factors.

3T3 Cells↗

PubMed1997

Etiology and therapy of community-acquired pneumonia.

The Authors report the data of a retrospective study performed on 520 patients admitted to the Institute of Respiratory Diseases, University of Sassari, Italy, for community acquired pneumonia (CAP) from 1980 to 1995. The aim of this study was to investigate: the frequency of risk factors and their impact on severity of pneumonia; the frequency of pathogens and their correlation with the severity of the illness; antibiotic treatments. One or more risk factors were found in 86% of patients, while 14% had none. In 286 patients (55%) no etiological diagnosis was possible, while in 234 patients (45%) the pathogen was identified. Of the latter, 73% suffered from pneumonia caused by Gram-negative bacilli, 24% by Gram-positive organisms, 0.8% by Mycoplasma pneumoniae and 1.7% by respiratory viruses and endemic fungi. The mortality rate found was 2.69%. In this study, pneumonia caused by Gram-negative bacilli showed a plurilobar and often bilateral involvement, frequent resistance to the most common antibiotics, which required longer hospitalization (> 30 days). The high prevalence of pneumonia caused by Gram-negative bacilli can be explained by the presence in most of the patients, of serious and numerous risk factors.

Adolescent↗

PubMed1996

A family of Shc related proteins with conserved PTB, CH1 and SH2 regions.

Shc proteins are targets of activated tyrosine kinases and have been implicated in the transmission of activation signals to Ras. Upon phosphorylation, Shc proteins form stable complexes with cellular tyrosine-phosphorylated proteins and with the Grb2 adaptor protein. Two Shc isoforms of 52 and 46 kDa have been characterized. They share a C-terminal SH2 domain, a proline- and glycine-rich region (collagen homologous region 1; CH1) and a N-terminal phospho-tyrosine binding domain (PTB). We report her ethe initial characterization of two Shc related human cDNAs: ShcB and ShcC. The ShcB and ShcC cDNAs code for proteins that are highly similar and share the same modular organization as Shc. PTB and SH2 domains of ShcB and ShcC have similar binding specificities in vitro and bind to activated EGFR in a phosphotyrosine-dependent manner. Based on these findings we propose to rename Shc as ShcA. Anti-ShcB and anti-ShcC antibodies recognize specific polypeptides of 52, 47 kDa (ShcB) and 54 kDa (ShcC) in mammalian cells. Since these two genes are predominantly expressed in specific brain tissues, these Shc family members may be involved in cell type-specific signaling, in the nervous system.

Adaptor Proteins, Signal Transducing↗

PubMed1995

Constitutive phosphorylation of Shc proteins in human tumors.

The Shc gene encodes three overlapping proteins which all contain a carboxy-terminal SH2 domain. Shc proteins are ubiquitously expressed and are downstream targets and effectors of activated tyrosine kinases (TK). We investigated tyrosine-phosphorylation of Shc proteins in normal and transformed cells. In tumor cells with known TK gene alterations Shc proteins were constitutively phosphorylated and complexed with the activated TK. No constitutive Shc phosphorylation was found in primary cell cultures and normal tissues. In 14 of 27 tumor cell lines with no reported TK alterations, Shc proteins were constitutively phosphorylated and formed stable complexes with novel tyrosine-phosphorylated polypeptides. Ten distinct Shc-associated phosphoproteins were identified with molecular weights ranging from 30 to 200 kDa. In a subset of carcinoma cell lines, phosphorylated Shc proteins complexed with a p175 phosphoprotein that was identified as the constitutively activated EGFR. In one glioblastoma cell line, a Shc-associated p190 was identified as the activated PDGFR. In 13 of 14 acute leukemia samples phosphorylated Shc proteins were constitutively complexed with a p140 phosphoprotein. Some of the Shc-associated phosphoproteins (EGFR, PDGFR, erbB-2, Met, bcr-abl, H4-ret) bound both the Shc- and Grb2-SH2 domains in vitro; others (p175; p70-p80) only the Shc-SH2 domain and yet others (p140) only the Grb2-SH3 domains. These results indicate that Shc proteins are common substrates of constitutively activated TKs and that the analysis of Shc phosphorylation allow the identification of tumors with constitutive TK activation.

Adaptor Proteins, Signal Transducing↗

PubMed1987

D1 dopamine receptors in the rat retina: effect of dark adaptation and chronic blockade by SCH 23390.

Chronic administration of SCH 23390 (0.03 mg/kg s.c., three times daily), a selective D1 dopamine (DA) receptor blocker, markedly increased the [3H]SCH 23390 binding in the rat retina. As revealed by the Scatchard plot analysis of saturation data from retinal homogenates, chronic SCH 23390 increased the total number of binding sites by 34% when compared to tissue from solvent-treated rats but failed to change the apparent affinity of [3H]SCH 23390 for its binding sites. The up-regulation of [3H]SCH 23390 binding sites was paralleled by an increase in the sensitivity of retina DA-sensitive adenylate cyclase. In fact, DA (5 X 10(-6) M to 10(-4) M) produced a higher accumulation of cyclic AMP (from 58 to 128%) in the retina of SCH 23390-treated rats as compared to the accumulation (from 35 to 80%) found in tissue from solvent-treated rats. Since dark adaptation decreases dopaminergic function in the rat retina, the influence of environmental lighting on [3H]SCH 23390 binding and DA-sensitive adenylate cyclase activity was studied. After 4 h of dark adaptation the density of [3H]SCH 23390 binding sites was higher (32%) than that from light-adapted rats. On the other hand, dark adaptation failed to change the apparent affinity of [3H]SCH 23390 for its binding sites. Moreover, DA elicited a greater stimulation of adenylate cyclase activity in homogenates of retina from dark-adapted rats. Thus, the maximum adenylate cyclase response to DA resulted higher in the retina of dark-adapted rats (152%) than that found in the retina of light-adapted animals (97%).(ABSTRACT TRUNCATED AT 250 WORDS)

Adaptation, Physiological↗

PubMed1987

6-Hydroxydopamine-induced degeneration of nigral dopamine neurons: differential effect on nigral and striatal D-1 dopamine receptors.

Dopamine-sensitive adenylate cyclase and 3H-SCH 23390 binding parameters were measured in the rat substantia nigra and striatum 15 days after the injection of 6-hydroxydopamine into the medial forebrain bundle. The activity of nigral dopamine-sensitive adenylate cyclase and the binding of 3H-SCH 23390 to rat nigral D-1 dopamine receptors were markedly decreased after the lesion. On the contrary, 6-hydroxydopamine-induced degeneration of the nigrostriatal dopamine pathway enhanced both adenylate cyclase activity and the density of 3H-SCH 23390 binding sites in striatal membrane preparations. The changes in 3H-SCH 23390 binding found in both nigral and striatal membrane preparations were associated with changes in the total number of binding sites with no modifications in their apparent affinity. The results indicate that: within the substantia nigra a fraction (30%) of D-1 dopamine receptors coupled to the adenylate cyclase is located on cell bodies and/or dendrites of dopaminergic neurons; striatal D-1 dopamine receptors are tonically innervated by nigrostriatal afferent fibers.

Adenylyl Cyclases↗

PubMed1987

Foot shock stress decreases chloride efflux from rat brain synaptoneurosomes.

Foot shock stress delivered continuously for 20 min decreased the 36Cl- efflux from cerebral cortex synaptoneurosomes of handling-habituated (unstressed) rats but failed to have the same effect on the synaptoneurosomes of naive (stressed) rats. The presence of pentobarbital (500 microM), GABA (100 microM) or muscimol (50 microM in the dilution buffer reversed the stress-induced decrease of 36Cl- efflux from synaptoneurosomes of unstressed rats. Moreover, these drugs also stimulated 36Cl- efflux from cortical synaptoneurosomes of naive stressed rats. The results indicate that stress decreases the function of Cl- channels coupled to the GABA/barbiturate receptor complex.

Animals↗

PubMed1987

Developmental and age-related changes in D1-dopamine receptors and dopamine content in the rat striatum.

The relationship between the postnatal development of dopaminergic (DAergic) nerve endings and the maturation of D1 DA receptors in the rat striatum was analyzed by measuring the content of DA and dihydroxyphenylacetic acid (DOPAC), two biochemical markers of DAergic nerve terminal proliferation, and the ontogenetic changes in [3H]SCH 23390 binding sites. DA-stimulated adenylate cyclase (AC) activity was also measured in order to characterize the coupling of [3H]SCH 23390 binding sites to the responses mediated by the activation of D1 DA receptors. Striatal levels of DA and DOPAC, as well as the density and affinity of [3H]SCH 23390 binding sites and DA-stimulated AC activity were also measured in senescent rats. The striatal content of DA increased slowly after birth, reaching adult levels by postnatal day 60 and remaining constant through adulthood and senescence (up to 20 months of age). The density of [3H]SCH 23390 binding sites increased 14-fold from birth to postnatal day 35, when a peak value was reached, whereas a significant decrease was observed in the striatum of aged rats. In contrast, the affinity of D1 DA receptors for [3H]SCH 23390 remained unchanged from birth through senescence. The stimulation of cyclic AMP formation induced by 100 microM DA increased 4-fold from birth to postnatal day 14, when the maximal responsiveness to DA was observed and then returned to adult levels. No significant alterations were observed in the Km values during development, whereas the stimulatory effect of 100 microM DA on AC activity was significantly decreased in senescent rats.(ABSTRACT TRUNCATED AT 250 WORDS)

3,4-Dihydroxyphenylacetic Acid↗

PubMed1987

Changes in GABAergic transmission induced by stress, anxiogenic and anxiolytic beta-carbolines.

The cerebral cortex of unstressed (handling-habituated) rats has a higher number of low affinity GABA receptors than stressed (naive) rats. Foot shock stress delivered to unstressed rats decreases the density of cortical low affinity GABA receptors to the level found in the naive animals. The effect of stress on GABA receptors is mimicked by anxiogenic beta-carbolines, both after in vitro addition (10(-6) M) to cortical membrane preparations or after the in vivo administration (20 mg/kg IP) to unstressed rats. Vice versa, benzodiazepines or anxiolytic beta-carbolines (ZK 93423, 10(-5) M) added to membranes from naive rats increase GABA binding to the level of unstressed rats and remove the decrease in the density of GABA receptors elicited by anxiogenic beta-carbolines. Rats chronically treated with the anxiogenic beta-carboline, FG 7142 (15 mg/kg IP twice a day for 10 consecutive days) have an enhanced sensitivity to punishment at 5 and 15 days after the last treatment. The behavioural effect is paralleled by a marked decrease in the total number of cortical low affinity GABA receptors. Both biochemical and behavioural effects elicited by chronic FG 7142 are prevented by the concurrent administration of the benzodiazepine antagonist Ro15-1788. These results suggest that (a) anxiolytic beta-carbolines, like benzodiazepines, increase the GABAergic transmission, (b) acute and chronic anxiogenic beta-carboline administration, like stress, decreases GABAergic transmission. Since all these effects are antagonized by the benzodiazepine receptor blocker Ro15-1788, it is tempting to speculate that stress releases an endogenous ligand for benzodiazepine recognition sites.

Animals↗

PubMed1987

Enhanced sensitivity to beta-carboline inverse agonists in rats chronically treated with FG 7142.

The biochemical and behavioural effects of the chronic administration of the beta-carboline inverse agonist FG 7142 were studied in the rat. Repeated administration of FG 7142 (15 mg/kg IP, twice daily for 10 consecutive days) induced sensitization to the effects of this drug, which from proconvulsant became a full convulsant. Thus, myoclonic seizures were observed in 30% and 80% of the animals by the third and the eighth day of treatment, respectively. The sensitization to the convulsant effect of FG 7142 persisted for up to 50 days after withdrawal and was completely prevented by the concurrent administration of the benzodiazepine receptor antagonist Ro15-1788 (15 mg/kg IP, twice a day for 10 days). Moreover, four to twelve days after withdrawal from chronic treatment with FG 7142, an increased sensitivity to the proconvulsant beta CCE and to the convulsant DMCM was observed. In addition, convulsions induced by isoniazid (350 mg/kg, SC) were potentiated in rats chronically treated with FG 7142 at 5 and 20 days after withdrawal. These pharmacological effects were paralleled by a decrease in the density of low affinity GABA receptors in the cerebral cortex and cerebellum. These results are consistent with the view that repeated administration of FG 7142 induces a long-lasting down-regulation of the GABAergic function which results in an increased sensitivity to beta-carboline inverse agonists and isoniazid. The possibility that a concomitant decrease in the responsiveness to benzodiazepines and Ro15-1788 takes place after chronic treatment with FG 7142 is also discussed.

Animals↗

PubMed1986

3H-SCH 23390 binding sites in the rat substantia nigra: evidence for a presynaptic localization and innervation by dopamine.

Chronic treatment with SCH 23390, a selective D-1 dopamine receptor antagonist, elicited a 32% increase in the density of 3H-SCH 23390 binding sites in nigral membrane preparations but failed to change the apparent KD of the ligand for its binding sites. Haloperidol, a D-2 dopamine receptor antagonist which blocks the dopamine-sensitive adenylate cyclase and (-) sulpiride, a selective D-2 dopamine receptor blocker, which does not block the dopamine-sensitive adenylate cyclase, failed to change both the Bmax and KD of 3H-SCH 23390 binding. Finally, the intrastriatal injection of kainic acid produced a marked decrease of both GAD activity and GABA content and 3H-SCH 23390 binding sites (65%) in the homolateral substantia nigra. The results show that in the rat substantia nigra most of the 3H-SCH 23390 binding sites have a presynaptic localization on the striato-nigral GABAergic afferent terminals and suggest that dopamine released from nigral dendrites exerts a tonic influence on these presynaptic D-1 dopamine receptors.

Animals↗

PubMed1984

Evidence for the presence of benzodiazepine receptor subclasses in different areas of the human brain.

The kinetic characteristics of [3H]flunitrazepam ([3H]FNT) and [3H]ethyl-beta-carboline-3-carboxylate ([3H]beta-CCE) were compared in three different areas of the human brain. As revealed by the Scatchard plot analysis the total number of binding sites labelled by [3H]beta-CCE was markedly lower than that labelled by [3H]FNT. In fact, only 50% of the binding sites for [3H]FNT were also available for [3H]beta-CCE. This finding indicates that in the cerebral cortex, hippocampus and cerebellum of the human brain at least 50% of the benzodiazepine recognition sites are that of Type II. This conclusion is further supported by the evidence that CL-218872 (5 X 10(-6) M), a specific ligand for Type I benzodiazepine recognition site, inhibited [3H]FNT binding by 50% in membranes from the above brain areas. The results suggest that two distinct types of benzodiazepines recognition sites are present in different areas of the human brain.

Adult↗