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C Usai

Publications and source records attributed to C Usai.

At least 19 recordsLinked to original sources
PubMed2005

Differences in suicide behaviour in the elderly: a study in two provinces of Northern Italy.

BACKGROUND: to investigate the suicide phenomenon among the elderly (people aged 65 and over) in the Italian provinces of Novara and Verbania, in the time span between January 1990 and December 2000, in order to evaluate if the characteristics of the suicide behaviour correlate to the place of living with particular attention to the psychosocial factors. METHODS: the information was collected from the Republic Procuration of the two provinces. Frequencies and contingency tables were evaluated to compare the data found in the two provinces. Standardised Mortality Ratios (SMRs) with their confidential intervals (95% confidence intervals) were calculated in comparison with the average suicide rates in North West Italy in the same period and in the same age group. RESULTS: One hundred and eighty-four suicides were committed from the elderly, with an average rate of 14.07 per 100 000 inhabitants in Novara and 25.56 in Verbania. The most common methods used to commit suicide were hanging and jumping from height. The factors chiefly related to suicide were mental disease, followed by organic illness. The analysis of SMRs point out that the incidence of suicide in the province of Verbania is higher than in North West Italy while in Novara it is lower. CONCLUSION: the evaluation of the suicide risk in the elderly in a diagnostic and preventive framework must take into consideration the psychosocial factors that vary with the place of living.

Age Factors↗
PubMed2003

[Suicidal behaviour in young people. An epidemiological study in the Verbano-Cusio-Ossola Province (years 1988-2000)].

BACKGROUND: The aim of the present study is to investigate the suicide and attempted suicide phenomenon among young people (<25 years old) in the Verbano-Cusio-Ossola province from January 1988 to December 2000. METHODS: This epidemiological-descriptive survey is based on the acquisition of data through the examination of model 45 registered at the Verbania Public Prosecutor's office. The data obtained were analysed with SPSS 8.0 software for Windows. The significance of the differences between the rates observed in our group and those observed in Italy in the same period was estimated by calculating SMR and SIR (Standardized Mortality Rates and Standardized Incidence Rates respectively). RESULTS: In the period considered in our study, 13 suicides and 62 attempted suicides were notified to the Court, with a rate of 2.55 and 12.18 per 100,000 inhabitants, respectively. The analysis of SMR and SIR points out that the incidence of suicide and attempted suicide among young people is higher in this province than in Italy. The most frequently used methods to commit suicide are hanging and carbon monoxide poisoning, while drug intoxication prevails in attempted suicide. The most common reasons are disagreements, followed by mental illness, psychosocial factors, loss of a relative and toxic dependence. CONCLUSIONS: The present study means to provide a description of suicide behaviour among young people in a geographic and cultural context, in order to point out its problems and to provide useful information for the diagnosis and prevention.

Adolescent↗
PubMed2001

The temperature-signaling cascade in sponges involves a heat-gated cation channel, abscisic acid, and cyclic ADP-ribose.

Sponges (phylum Porifera) are the phylogenetically oldest metazoan animals, their evolution dating back to 600 million years ago. Here we demonstrate that sponges express ADP-ribosyl cyclase activity, which converts NAD(+) into cyclic ADP-ribose, a potent and universal intracellular Ca(2+) mobilizer. In Axinella polypoides (Demospongiae, Axinellidae), ADP-ribosyl cyclase was activated by temperature increases by means of an abscisic acid-induced, protein kinase A-dependent mechanism. The thermosensor triggering this signaling cascade was a heat-activated cation channel. Elucidation of the complete thermosensing pathway in sponges highlights a number of features conserved in higher organisms: (i) the cation channel thermoreceptor, sensitive to heat, mechanical stress, phosphorylation, and anesthetics, shares all of the functional characteristics of the mammalian heat-activated background K(+) channel responsible for central and peripheral thermosensing; (ii) involvement of the phytohormone abscisic acid and cyclic ADP-ribose as its second messenger is reminiscent of the drought stress signaling pathway in plants. These results suggest an ancient evolutionary origin of this stress-signaling cascade in a common precursor of modern Metazoa and Metaphyta.

ADP-ribosyl Cyclase↗
PubMed2001

A self-restricted CD38-connexin 43 cross-talk affects NAD+ and cyclic ADP-ribose metabolism and regulates intracellular calcium in 3T3 fibroblasts.

Connexin 43 (Cx43) hexameric hemichannels, recently demonstrated to mediate NAD(+) transport, functionally interact in the plasma membrane of several cells with the ectoenzyme CD38 that converts NAD(+) to the universal calcium mobilizer cyclic ADP-ribose (cADPR). Here we demonstrate that functional uncoupling between CD38 and Cx43 in CD38-transfected 3T3 murine fibroblasts is paralleled by decreased [Ca(2+)](i) levels as a result of reduced intracellular conversion of NAD(+) to cADPR. A sharp inverse correlation emerged between [Ca(2+)](i) levels and NAD(+) transport (measured as influx into cells and as efflux therefrom), both in the CD38(+) cells (high [Ca(2+)](i), low transport) and in the CD38(-) fibroblasts (low [Ca(2+)](i), high transport). These differences were correlated with distinctive extents of Cx43 phosphorylation in the two cell populations, a lower phosphorylation with high NAD(+) transport (CD38(-) cells) and vice versa (CD38(+) cells). Conversion of NAD(+)-permeable Cx43 to the phosphorylated, NAD(+)-impermeable form occurs via Ca(2+)-stimulated protein kinase C (PKC). Thus, a self-regulatory loop emerged in CD38(+) fibroblasts whereby high [Ca(2+)](i) restricts further Ca(2+) mobilization by cADPR via PKC-mediated disruption of the Cx43-CD38 cross-talk. This mechanism may avoid: (i) leakage of NAD(+) from cells; (ii) depletion of intracellular NAD(+) by CD38; (iii) overproduction of intracellular cADPR resulting in potentially cytotoxic [Ca(2+)](i).

3T3 Cells↗
PubMed2001

Paracrine roles of NAD+ and cyclic ADP-ribose in increasing intracellular calcium and enhancing cell proliferation of 3T3 fibroblasts.

CD38 is a bifunctional ectoenzyme synthesizing from NAD(+) (ADP-ribosyl cyclase) and degrading (hydrolase) cyclic ADP-ribose (cADPR), a powerful universal calcium mobilizer from intracellular stores. Recently, hexameric connexin 43 (Cx43) hemichannels have been shown to release cytosolic NAD(+) from isolated murine fibroblasts (Bruzzone, S., Guida, L., Zocchi, E., Franco, L. and De Flora, A. (2001) FASEB J. 15, 10-12), making this dinucleotide available to the ectocellular active site of CD38. Here we investigated transwell co-cultures of CD38(+) (transfected) and CD38(-) 3T3 cells in order to establish the role of extracellular NAD(+) and cADPR on [Ca(2+)](i) levels and on proliferation of the CD38(-) target cells. CD38(+), but not CD38(-), feeder cells induced a [Ca(2+)](i) increase in the CD38(-) target cells which was comparable to that observed with extracellular cADPR alone and inhibitable by NAD(+)-glycohydrolase or by the cADPR antagonist 8-NH(2)-cADPR. Addition of recombinant ADP-ribosyl cyclase to the medium of CD38(-) feeders induced sustained [Ca(2+)](i) increases in CD38(-) target cells. Co-culture on CD38(+) feeders enhanced the proliferation of CD38(-) target cells over control values and significantly shortened the S phase of cell cycle. These results demonstrate a paracrine process based on Cx43-mediated release of NAD(+), its CD38-catalyzed conversion to extracellular cADPR, and influx of this nucleotide into responsive cells to increase [Ca(2+)](i) and stimulate cell proliferation.

3T3 Cells↗
PubMed2001

Extracellular cyclic ADP-ribose potentiates ACh-induced contraction in bovine tracheal smooth muscle.

Cyclic ADP-ribose (cADPR), a universal calcium releaser, is generated from NAD(+) by an ADP-ribosyl cyclase and is degraded to ADP-ribose by a cADPR hydrolase. In mammals, both activities are expressed as ectoenzymes by the transmembrane glycoprotein CD38. CD38 was identified in both epithelial cells and smooth myocytes isolated from bovine trachea. Intact tracheal smooth myocytes (TSMs) responded to extracellular cADPR (100 microM) with an increase in intracellular calcium concentration ([Ca(2+)](i)) both at baseline and after acetylcholine (ACh) stimulation. The nonhydrolyzable analog 3-deaza-cADPR (10 nM) elicited the same effects as cADPR, whereas the cADPR antagonist 8-NH(2)-cADPR (10 microM) inhibited both basal and ACh-stimulated [Ca(2+)](i) levels. Extracellular cADPR or 3-deaza-cADPR caused a significant increase of ACh-induced contraction in tracheal smooth muscle strips, whereas 8-NH(2)-cADPR decreased it. Tracheal mucosa strips, by releasing NAD(+), enhanced [Ca(2+)](i) in isolated TSMs, and this increase was abrogated by either NAD(+)-ase or 8-NH(2)-cADPR. These data suggest the existence of a paracrine mechanism whereby mucosa-released extracellular NAD(+) plays a hormonelike function and cADPR behaves as second messenger regulating calcium-related contractility in TSMs.

ADP-ribosyl Cyclase↗
PubMed2000

Extracellular cyclic ADP-ribose increases intracellular free calcium concentration and stimulates proliferation of human hemopoietic progenitors.

Cyclic ADP-ribose (cADPR) is a universal second messenger that regulates many calcium-related cellular events by releasing calcium from intracellular stores. Since these events include enhanced cell proliferation and since the bone marrow harbors both ectoenzymes that generate cADPR from NAD(+) (CD38 and BST-1), we investigated the effects of extracellular cADPR on human hemopoietic progenitors (HP). Exposure of HP to 100 microM cADPR for 24 h induced a significant increase in colony output (P<0.01) and colony size (P<0.003). A horizontal expansion of HP, as demonstrated by a markedly increased replating efficiency in semisolid medium (up to 700 times compared to controls), was also observed, indicating that cADPR priming can affect cell growth for multiple generations over several weeks after exposure. Influx of extracellular cADPR into the cells was demonstrated, and a causal relationship between the functional effects and the increase of intracellular free calcium concentration induced by cADPR on HP was established through the use of specific antagonists. Similar effects on HP were produced by nanomolar concentrations of the nonhydrolyzable cADPR analog 3-deaza-cADPR. These data demonstrate that extracellular cADPR behaves as a cytokine enhancing the proliferation of human HP, a finding that may have biomedical applications for the ex vivo expansion of hemopoietic cells.

Adenosine Diphosphate Ribose↗
PubMed2000

Topology of CD38.

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ADP-ribosyl Cyclase↗
PubMed1999

Pathways of cadmium influx in mammalian neurons.

The influx of the toxic cation Cd2+ was studied in fura 2-loaded rat cerebellar granule neurons. In cells depolarized with Ca2(+)-free, high-KCI solutions, the fluorescence emission ratio (R) increased in the presence of 100 microM Cd2(+). This increase was fully reversed by the Cd2+ chelator tetrakis(2-pyridylmethyl)ethylenediamine, indicating a cadmium influx into the cell. The rate of increase, dR/dt, was greatly reduced (67+/-5%) by 1 microM nimodipine and enhanced by 1 microM Bay K 8644. Concurrent application of nimodipine and omega-agatoxin IVA (200 nM) blocked Cd2+ permeation almost completely (88+/-5%), whereas omega-conotoxin MVIIC (2 microM) reduced dR/dt by 24+/-8%. These results indicate a primary role of voltage-dependent calcium channels in Cd2+ permeation. Stimulation with glutamate or NMDA and glycine also caused a rise of R in external Cd2+. Simultaneous application of nimodipine and omega-agatoxin IVA moderately reduced dR/dt (25+/-3%). NMDA-driven Cd2(+) entry was almost completely prevented by 1 mM Mg2+, 50 microM memantine, and 10 microM 5,7-dichlorokynurenic acid, suggesting a major contribution of NMDA-gated channels in glutamate-stimulated Cd2+ influx. Moreover, perfusion with alpha-amino-3-hydroxy-5-methylisoxazole-4-propionate caused a slow increase of R. These results suggest that Cd2+ permeates the cell membrane mainly through the same pathways of Ca2+ influx.

Animals↗
PubMed1999

Ligand-induced internalization of CD38 results in intracellular Ca2+ mobilization: role of NAD+ transport across cell membranes.

CD38, a transmembrane glycoprotein widely expressed in vertebrate cells, is a bifunctional ectoenzyme catalyzing the synthesis and hydrolysis of cyclic ADP-ribose (cADPR). cADPR is a universal second messenger that releases calcium from intracellular stores. Since cADPR is generated by CD38 at the outer surface of many cells, where it acts intracellularly, increasing attention is paid to addressing this topological paradox. Recently, we demonstrated that CD38 is a catalytically active, unidirectional transmembrane transporter of cADPR, which then reaches its receptor-operated intracellular calcium stores. Moreover, CD38 was reported to undergo a selective and extensive internalization through non clathrin-coated endocytotic vesicles upon incubating CD38(+) cells with either NAD+ or thiol compounds: these endocytotic vesicles can convert cytosolic NAD into cADPR despite an asymmetric unfavorable orientation that makes the active site of CD38 intravesicular. Here we demonstrate that the cADPR-generating activity of the endocytotic vesicles results in remarkable and sustained increases of intracellular free calcium concentration in different cells exposed to either NAD+, or GSH, or N-acetylcysteine. This effect of CD38-internalizing ligands on intracellular calcium levels was found to involve a two-step mechanism: 1) influx of cytosolic NAD+ into the endocytotic vesicles, mediated by a hitherto unrecognized dinucleotide transport system that is saturable, bidirectional, inhibitable by 8-N3-NAD+, and characterized by poor dinucleotide specificity, low affinity, and high efficiency; 2) intravesicular CD38-catalyzed conversion of NAD+ to cADPR, followed by outpumping of the cyclic nucleotide into the cytosol and subsequent release of calcium from thapsigargin-sensitive stores. This unknown intracellular trafficking of NAD+ and cADPR based on two distinctive and specific transmembrane carriers for either nucleotide can affect the intracellular calcium homeostasis in CD38(+) cells.

3T3 Cells↗
PubMed1998

Expression of CD38 increases intracellular calcium concentration and reduces doubling time in HeLa and 3T3 cells.

CD38 is a bifunctional ectoenzyme, predominantly expressed on hematopoietic cells during differentiation, that catalyzes the synthesis (cyclase) and the degradation (hydrolase) of cyclic ADP-ribose (cADPR), a powerful calcium mobilizer from intracellular stores. Due to the well established role of calcium levels in the regulation of apoptosis, proliferation, and differentiation, the CD38/cADPR system seems to be a likely candidate involved in the control of these fundamental processes. The ectocellular localization of the cyclase activity, however, contrasts with the intracellular site of action of cADPR. Here we demonstrate that ectocellular expression of human CD38 in CD38(-) HeLa and 3T3 cells results in intracellular CD38 substrate (NAD+ + NADH) consumption and product (cADPR) accumulation. Furthermore, a causal relationship is established between presence of intracellular cADPR, partial depletion of thapsigargin-sensitive calcium stores, increase in basal free cytoplasmic calcium concentration, and decrease of cell doubling time. The significant shortening of the S phase in CD38(+) HeLa cells, as compared with controls, demonstrates an effect of intracellular cADPR on the mammalian cell cycle.

3T3 Cells↗
PubMed1998

The transmembrane glycoprotein CD38 is a catalytically active transporter responsible for generation and influx of the second messenger cyclic ADP-ribose across membranes.

CD38 is a type II transmembrane glycoprotein expressed in many vertebrate cells. It is a bifunctional ectoenzyme that catalyzes both the synthesis of Cyclic ADP-ribose (cADPR) from NAD+ and the degradation of cADPR to ADP-ribose by means of its ADP-ribosyl cyclase and cADPR-hydrolase activities, respectively. The cyclase also converts NGD+ to cyclic GDP-ribose (cGDPR), which is refractory to cADPR-hydrolase. cADPR, but not cGDPR, is a potent calcium mobilizer from intracellular stores. It has been demonstrated to be a new second messenger involved in the regulation of calcium homeostasis in many cell types, from plants to mammals. The number of physiological processes shown to be regulated by cADPR is steadily increasing. A topological paradox exists because ectocellularly generated cADPR acts intracellularly. Here we demonstrate that the catalytic functioning of CD38 is accompanied by a cADPR (cGDPR) -transporting activity across natural and artificial membranes. In resealed membranes from CD38(+) human erythrocytes, transport of catalytically generated cADPR or cGDPR was saturation dependent and occurred against a concentration gradient. Likewise, CD38-reconstituted proteoliposomes were active in concentrating NAD+ (NGD+) -derived cADPR (cGDPR) inside the vesicle compartment. Moreover, the cADPR-transporting activity in CD38 proteoliposomes prevented the hydrolase-catalyzed degradation to ADPR that occurs conversely with detergent-solubilized CD38, resulting in selective influx of cADPR. In the CD38 proteoliposomes, catalytically active CD38 exhibited monomeric, dimeric, and tetrameric structures. In CD38 sense- but not in antisense-transfected HeLa cells, externally added NAD+ resulted in significant, transient increases in cytosolic calcium. These data suggest that transmembrane juxtaposition of two or four CD38 monomers can generate a catalytically active channel for selective formation and influx of cADPR (cGDPR) to reach cADPR-responsive intracellular calcium stores.

ADP-ribosyl Cyclase↗
PubMed1996

Ectocellular in vitro and in vivo metabolism of cADP-ribose in cerebellum.

CD38, a type II transmembrane glycoprotein predominantly expressed in blood cells, is a bifunctional ectoenzyme directly involved in the metabolism of cADP-ribose (cADPR). This is a potent Ca2+ mobilizer in several types of cells. The relationship between the ectocellular site of cADPR production and its intracellular calcium-related functions is poorly understood. Cultured rat cerebellar granule cells showed both enzymic activities of CD38, ADP-ribosyl cyclase and cADPR hydrolase, at a ratio of 16 to 1 respectively, and were immunostained by the anti-(human CD38) monoclonal antibody IB4. In these cells externally added cADPR and beta-NAD+ (the precursor of cADPR), but not alpha-NAD+ or ADP-ribose, enhanced the peak of the depolarization-induced rise in intracellular Ca2+ concentration. This effect was inhibited by 1 microM ryanodine, suggesting a potentiation of calcium-induced calcium release by cADPR. CD38 ectoenzyme activities, ADP-ribosyl cyclase and cADPR hydrolase, were also demonstrated in vivo by microdialysis of adult rat cerebellum, where IB4 bound to granule neurons selectively. Trace amounts (11.5 +/- 3.8 nM) of NAD+ were detected by microdialysis sampling and sensitive assays in the basal interstitial fluid of the cerebellum. These results provide a link between ectocellular cADPR turnover and intracellular calcium mobilization in cerebellum.

ADP-ribosyl Cyclase↗
PubMed1996

High affinity block by nimodipine of the internal calcium elevation in chronically depolarized rat cerebellar granule neurons.

Chronic depolarization enhances survival of cultured rat cerebellar granule neurons by elevating the internal calcium concentration ([Ca2+]i). In Fura2-loaded cells maintained in 25 mM KCl, [Ca2+]i was close to 150 nM and decreased to approximately 50 nM when KCl was lowered to 5.4 mM. The effect of nimodipine (IC50 = 0.45 nM) was similar to depolarization removal, while agatoxin IVA (up to 500 nM) was ineffective. In whole-cell-clamp experiments, the IC50 for current inhibition was 57 nM, while with transient, KCl-induced depolarizations, the dose dependence of nimodipine inhibition had a 'double-affinity' shape, with IC50(1) = 0.30 nM and IC50(2) = 71 nM. We concluded that L-type calcium channels are the main responsible of the elevated internal calcium level necessary for survival in these neurons. These channels do not inactivate and bind nimodipine with different affinity, depending on their state.

Animals↗
PubMed1996

Role of external and internal calcium on heterocarrier-mediated transmitter release.

Release-regulating heterocarriers exist on brain nerve endings. We have investigated in this study the mechanisms involved in the neurotransmitter release evoked by GABA heterocarrier activation. GABA increased the basal release of [3H]acetylcholine and [3H]noradrenaline from rat hippocampal synaptosomes and of [3H]dopamine from striatal synaptosomes. These GABA effects, insensitive to GABA receptor antagonists, were prevented by inhibiting GABA uptake but not by blocking noradrenaline, choline, or dopamine transport. Lack of extracellular Ca2+ or addition of tetrodotoxin selectively abolished the GABA-evoked release of [3H]noradrenaline, leaving unaffected that of [3H]acetylcholine or [3H]dopamine. 1,2-Bis(2-aminophenoxyl)-ethane-N,N,N',N'-tetraacetic acid acetoxymethyl ester (BAPTA-AM) or vesamicol attenuated the release of [3H]acetylcholine elicited by GABA. Reserpine, but not BAPTA-AM, prevented the effect of GABA on [3H] dopamine release. Autoreceptor activation inhibited the GABA-evoked release of [3H]noradrenaline but not that of [3H]acetylcholine or [3H]dopamine. It is concluded that (a) the release of [3H]noradrenaline consequent to activation of GABA heterocarriers sited on noradrenergic terminals meets the criteria of a conventional exocytotic process, (b) the extracellular [Ca2+]-independent releases of [3H]acetylcholine and [3H]dopamine appear to occur from vesicles possibly through involvement of intraterminal Ca2+, and (c) autoreceptor activation only affects heterocarrier-mediated vesicular release linked to entry of extracellular Ca2+.

Acetylcholine↗
PubMed1995

Functional characterization of the effect of nimodipine on the calcium current in rat cerebellar granule cells.

1. We investigated the effect of nimodipine on the calcium current in dissociated cerebellar granule cells from 8-day-old rats. We measured the whole cell current and the depolarization-induced internal calcium elevation in Fura2-loaded cells exposed to high-potassium solutions. 2. Nimodipine maximally depressed the peak calcium current from holding potential (Vh) = -80 mV by 25% and the inactivation resistant residual current from Vh = -50 mV by 44%. The nimodipine-sensitive current had the same amplitude under both conditions and the half-maximal inhibition concentration (IC50) was close to 50 nM. 3. In contrast to other components of the calcium current, the nimodipine-sensitive current did not inactivate significantly during 1-s depolarization and it was weakly sensitive to the holding potential and to depolarizing conditioning prepulses. The effect of nimodipine was higher on the current elicited by small depolarizations and the current at -30 mV was depressed by < or = 70%. Depolarizing prepulses enhanced the effect of 1 nM (but not that of 1 microM) nimodipine. 4. In Fura2-loaded cells, nimodipine strongly antagonized the internal calcium rise due to superfusion with 15-75 mM potassium. The effect was significantly more potent on the internal calcium rise determined by lower depolarizations, with 80% inhibition of the peak response to 25 mM KCl. The dose dependence of this depression was best approximated by a two-site curve with IC50(1) = 0.27 nM and IC50(2) = 65 nM. The time course of recovery was dependent on the duration of treatment, suggesting a close interaction between nimodipine and the lipid membrane. 5. The effect of 1 microM nimodipine was not influenced by predepolarizations determined by treatments with calcium-free elevated potassium solutions, but when doses as low as 1 nM were applied the fast decay of the calcium level suggested a voltage dependence of the effect. Nimodipine also depressed < or = 90% of the plateau phase of the depolarization-induced internal calcium rise at different depolarizations. 6. Incubation in omega-conotoxin, fraction GVIA (5 microM) did not cause any significant decrease in the calcium response, whereas omega-agatoxin, fraction IVA (0.5 microM) depressed the calcium peak by 40-60% and its effect was additive with that of nimodipine. 7. We conclude that the nimodipine-sensitive current is a persistent, inactivation-resistant current that activates at a membrane potential lower than the other components and is likely to be responsible for the elevation of calcium determined by nonovershooting, prolonged depolarizations in these cells.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗