Showing papers by "University of Cagliari published in 1990"

Blockade of the noradrenaline carrier increases extracellular dopamine concentrations in the prefrontal cortex: evidence that dopamine is taken up in vivo by noradrenergic terminals.

Abstract: The effect of systemic administration of desmethylimipramine (DMI) and oxaproptiline (OXA), two inhibitors of the noradrenaline (NA) reuptake carrier, on the in vivo extracellular concentrations of dopamine (DA) was studied by transcerebral dialysis in the prefrontal cortex and in the dorsal caudate of freely moving rats. In the NA-rich prefrontal cortex, either drug increased extracellular DA concentrations whereas in the dorsal caudate neither was effective. Haloperidol increased extracellular DA concentrations more effectively in the dorsal caudate than in the prefrontal cortex. Pre-treatment with DMI or OXA. which failed to modify the effect of haloperidol in the dorsal caudate, potentiated its action in the prefrontal cortex. 6-Hydroxydopamine lesioning of the dorsal NA bundle prevented the ability of OXA to increase DA concentrations. The results suggest that reuptake into NA terminals is an important mechanism by which DA is cleared from the extracellular space in a NA-rich area such as the prefrontal cortex. The elevated extracellular concentrations of DA resulting from blockade of such mechanism by tricyclic antidepressants may play a role in the therapeutic effects of these drugs.

A case-control study of gastric cancer and diet in Italy: II. Association with nutrients

Abstract: A case-control study involving interviews with 1,016 gastric cancer (GC) patients and 1,159 population-based controls in high- and low-risk areas was conducted to evaluate dietary factors and their contribution to the marked geographic variation in mortality from this cancer within Italy. Risks of GC were found to vary significantly with estimated nutrient intake. Risk rose with increasing consumption of nitrites and protein, and decreased in proportion to intake of ascorbic acid, beta-carotene, alpha-tocopherol, and vegetable fat. The associations with nitrite and beta-carotene tended to fade, however, in multivariate analyses adjusting for intake of other nutrients. Ascorbic acid showed the strongest geographic gradient, with highest consumption in low-risk areas. The findings suggest that the protective effects we previously reported for consumption of fresh fruit, fresh vegetables and olive oil may be linked to the vitamins C and E contained in these foods. The findings are consistent with the hypothesis that N-nitroso compounds are involved in GC risks, since elevated risks were apparent for agents (nitrites, protein) that promote nitrosation, while decreased risks were found for nutrients (ascorbic acid and alpha-tocopherol) which inhibit the process.

Decrease in the Function of the γ-Aminobutyric Acid-Coupled Chloride Channel Produced by the Repeated Administration of Pentylenetetrazol to Rats

Abstract: The acute administration of pentylenetetrazol (PTZ; 25-75 mg/kg i.p.) failed to modify the specific binding of t-[35S]butylbicyclophosphorothionate ([35S]TBPS) to membrane preparations from the cerebral cortex of the rat. In contrast, the repeated administration of PTZ (30 mg/kg i.p., three times a week for 12 weeks) reduced by 26% the density of [35S]TBPS binding sites without modifying the dissociation constant. This effect was observed 3 days after the last PTZ administration. A parallel reduction of gamma-aminobutyric acid (GABA)-stimulated 36Cl- uptake was measured in the cerebral cortex of PTZ-treated rats 3 days after the last injection. The repeated administration of PTZ produced sensitization to the drug, or chemical kindling. In fact, no convulsions were observed in the first week of treatment, but all the animals became sensitized to PTZ by the 12th week. The results are consistent with the hypothesis that chronic treatment with PTZ at a subconvulsant dose causes a decrease in GABA-coupled chloride channel activity that may be related to the chemical kindling produced by this compound.

The General Anesthetic Propofol Enhances the Function of γ‐Aminobutyric Acid‐Coupled Chloride Channel in the Rat Cerebral Cortex

Abstract: The effect of the general anesthetic propofol on t-[35S]butylbicyclophosphorothionate ([35S]TBPS) binding to unwashed membrane preparations from rat cerebral cortex was studied and compared to that of other general anesthetics (pentobarbital, alphaxalone) which are known to enhance GABAergic transmission. Propofol produced a concentration-dependent complete inhibition of [35S]TBPS binding, an effect similar to that induced by pentobarbital and alphaxalone, although these agents differ markedly in potency (alphaxalone greater than propofol greater than pentobarbital). The concomitant addition of propofol either with alphaxalone or pentobarbital produced an additive inhibition of [35S]TBPS binding, suggesting separate sites of action or different mechanisms of these drugs. Moreover, although bicuculline (0.1 microM) completely antagonized the propofol-induced inhibition of [35S]TBPS binding, the effect of this anesthetic was not due to a direct interaction with the gamma-aminobutyric acidA (GABAA) recognition site. In fact, propofol, like alphaxalone and pentobarbital, markedly enhanced [3H]GABA binding in the rat cerebral cortex. Finally, propofol was able to enhance [3H]GABA binding in membranes previously incubated with the specific chloride channel blocker picrotoxin. Taken together these data strongly suggest that propofol, like other anesthetics and positive modulators of GABAergic transmission, might exert its pharmacological effects by enhancing the function of the GABA-activated chloride channel.

Presence and synthesis of inhibin subunits in human decidua

Abstract: A growing number of studies provided the evidence that human decidua is a pregnancy-related tissue capable of hormone production and metabolism. The aim of the present study was to evaluate the possible presence of inhibin subunits in human decidua. Tissue samples were collected in pregnant women during the first (8 weeks) and second trimester (18 weeks) of gestation and at term (40 weeks). Immunohistochemical data were obtained using affinity purified polyclonal antisera raised in rabbit against porcine alpha, beta A, or beta B subunits. Levels of the respective inhibin subunits were evaluated by Northern blot analysis using cDNA probes encoding sequences corresponding to each subunit. The present results indicated that human decidua contains and synthesizes inhibin alpha, beta A, and beta B subunits. The immunohistochemical data showed that decidual cells were stained with both inhibin alpha and beta B antisera, showing a similar localization. On the other hand, cells stained with inhibin beta A antisera were sparse and followed a distribution pattern different from that of cells stained with alpha or beta B antisera. The first inhibin alpha and beta B subunit mRNAs were both expressed in first trimester of pregnancy, and those mRNA levels showed a gestational related increase. The beta A subunit mRNA was expressed at very low levels at term and could not be detected earlier during pregnancy. The present data showed that human decidua actively produces inhibin subunits with a gestational-related profile. The results suggest that decidua may be a further source of inhibin-related proteins during pregnancy and emphasize the endocrine competence of human decidua.

Cell proliferation and promotion of rat liver carcinogenesis: different effect of hepatic regeneration and mitogen induced hyperplasia on the development of enzyme-altered foci.

Abstract: A series of experiments was performed to investigate the effect of different types of cell proliferation on the development of enzyme-altered preneoplastic hepatic foci in male Wistar rats. Animals were given a single dose of diethylnitrosamine (100 mg/kg body weight). After a 2-week recovery period liver cell proliferation was repeatedly induced by four or eight necrogenic doses of carbon tetrachloride (compensatory cell proliferation), or by four or eight treatments with three different liver mitogens, namely lead nitrate, ethylene dibromide and nafenopin (direct hyperplasia). The carcinogen altered hepatocytes were monitored as gamma-glutamyltransferase positive or adenosine triphosphatase negative foci. The results indicate that compensatory cell proliferation induced by both four and eight carbon tetrachloride treatments enhanced the growth of diethylnitrosamine-initiated hepatocytes to enzyme-altered foci. On the contrary, repeated waves of cell proliferation induced by liver mitogens did not result in any significant number of enzyme-altered foci.

Structural and electronic properties of narrow-band-gap semiconductors: InP, InAs, and InSb.

Abstract: Cette etude est realisee selon la methode lineaire de l'onde plane amelioree de potentiel entier et par des pseudopotentiels ab initio a conservation de norme. Dans l'approximation de la densite locale, InAs et InSb ont un caractere metallique, tandis que InP conserve ses proprietes semiconductrices. La comparaison des resultats obtenus par les 2 methodes met en avant le role du «semicœur» peu profond In 4d

Results of prototype studies for a spaghetti calorimeter

Abstract: In the framework of the LAA project, prototypes for a new type of calorimeter, intended for the detection of both electromagnetic (em) and hadronic showers, muons and missing energy (eg neutrinos) at high-luminosity multi-TeV pp colliders, were tested The detector consists of scintillating plastic fibres embedded in a lead matrix at a volume ratio 1:4, such as to achieve compensation The optimization of the construction of the detector modules is described, as well as the performance concerning em shower and muon detection and e/π separation We used electron, pion and muon beams in the energy range 10–150 GeV for this purpose For the energy resolution of electrons we found 13%/trE, with a constant term of 1% The signal uniformity was better than 3% over the total surface of projective modules The signal linearity for em shower detection was better than 1%, and the e/π separation was better than 5 × 10−4 for isolated particles Channeling effects are negligible, provided that the angle between the incoming particles and the fibre axis is larger than 2°

Structural properties of lead-iron phosphate glasses by X-ray diffraction☆

Abstract: The structural properties of lead-iron phosphate glasses have been investigated by X-ray diffraction in an attempt to understand the chemical and mechanical characteristics presented by lead metaphosphate glass as the result of the addition of iron oxide. Information on FeO bond lengths and coordination numbers was obtained by a comparison of radial distribution functions of glass samples containing iron oxide and of the iron-free glass matrix. Stable structural arrangements around Fe(III) atoms were detected, which could be responsible for the stabilizing effect of Fe2O3 on lead metaphosphate glass.

Covariant first-order Lagrangians, energy-density and superpotentials in general relativity

Abstract: A class of covariant first-order Lagrangians for General Relativity interacting with external matter fields is considered. These Lagrangians depend on the choice of a background connection which has no dynamics. The Poincare-Cartan form, energy density flows and energy-momentum tensors are derived for this class of Lagrangians by applying standard methods, and the results are compared with those appearing in current literature. We obtain new results concerning superpotentials and covariant conservation laws. As an example, these are applied to calculate the mass and angular momentum for the Schwarzschild and Kerr black-holes.

Temperature, composition, and f O2 effects on intersite distribution of Mg and Fe 2+ in olivines

Abstract: Single-crystal X-ray structure refinement of natural olivines equilibrated at high temperature under controlled oxygen fugacity (fO2) conditions, coupled with a structure-energy model were used to establish the influence of T, fO2 and bulk chemistry on intracrystalline disorder.

Pollen and mold allergy: aerobiologic survey in the atmosphere of Cagliari, Italy (1986-1988).

Abstract: The occurrence of pollens and molds in the atmosphere of Cagliari, Italy over a 3-year period (1986-88) is reported. Pollen grains are present in the air from February to July, with a maximum in May. Urticaceae and Cupressaceae were the major contributors to the total pollen airspora, followed by Graminaceae, Oleaceae, Pinaceae, Cheno-Amaranthaceae, and Fagaceae. Fungal spores showed two periods of high sporulation, from April to June and in September-October, and two marked decreases, during winter and August. Cladosporium was by far the most abundant spore identified, followed by Basidiomycetes, Alternaria, and Fusarium.

Stereospecific blockade of N-methyl-D-aspartate transmission by MK 801 prevents priming of SKF 38393-induced turning.

Abstract: In rats unilaterally lesioned with 6-hydroxydopamine, the D-1 agonist SKF 38393 (3 mg/kg SC) induced contralateral turning only after priming with a dopaminergic agonist such as apomorphine. Administration of the N-methyl-d-aspartate receptor antagonist (+) MK 801 (0.1 mg/kg IP) 15 min before apomorphine (0.1 mg/kg SC) prevented the ability of apomorphine to act as a primer while potentiating its acute contralateral turning effects. The inactive isomer (−) MK 801 was without effect. The results indicate that the N-methyl-d-aspartate receptor exerts a permissive role on priming.

Effects of dopamine, D-1 and D-2 dopaminergic agonists on the excitability of hippocampal CA1 pyramidal cells in guinea pig.

Abstract: In hippocampal pyramidal cells (HPCs), Dopamine (DA) application (1 μM) produced, in 50% of recorded cells, an hyperpolarization of the resting membrane potential (r.m.p.) and an increase of the afterhyperpolarization (AHP) amplitude and duration in 79% of recorded cells. DA-induced effects on both the r.m.p. and AHP were mimicked by bath application of a D-l selective agonist, SKF 38393 (20 μM). In addition, we have observed that a D-l selective antagonist such as SCH 23390 (1 μ,M) abolished the action of both DA and SKF 38393. In contrast, the activation of D-2 receptors through LY 171555 (10 μm) produced, in 50% of cells, a depolarization of the r.m.p. and a depression of the AHP in 67% of recorded cells. These results suggest that the effects observed in hippocampal pyramidal neurons after DA application of micromolar concentration are mediated by D-1 subtype of receptors.

Patterns of digestion of human chromosomes by restriction endonucleases demonstrated by in situ nick translation.

Abstract: A restriction enzyme-nick translation procedure has been developed for localizing sites of restriction endonuclease action on chromosomes. This method involves digestion of fixed chromosome preparations with a restriction enzyme, nick translation with DNA polymerase I in the presence of biotinylated-dUTP, detection of the incorporated biotin label with streptavidinalkaline phosphatase, and finally staining for alkaline phosphatase. Results obtained on human chromosomes using a wide variety of restriction enzymes are described, and compared with results of Giemsa and Feulgen staining after restriction enzyme digestion. Results of nick translation are not in general the opposite of those obtained with Giemsa staining, as might have been expected. Although the nick translation procedure is believed to give a more accurate picture of the distribution of restriction enzyme recognition sites on chromosomes than Giemsa staining, it is clear that the results of the nick translation experiments are affected by accessibility to the enzymes of the chromosomal DNA, as well as by the extractability of the DNA.