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M Giorgetti

Publications and source records attributed to M Giorgetti.

At least 19 recordsLinked to original sources
PubMed2006

In vitro estrogenic activity of Achillea millefolium L.

Isolation and biological characterization of pure compounds was used to identify and characterize estrogenic activity and estrogen receptors (ER) preference in chemical components of Achillea millefolium. This medicinal plant is used in folk medicine as an emmenagogue. In vitro assay, based on recombinant MCF-7 cells, showed estrogenic activity in a crude extract of the aerial parts of A. millefolium. After fractionation of the crude extract with increasing polar solvents, estrogenic activity was found in the methanol/water fraction. Nine compounds were isolated and characterized by HR-MS spectra and 1D- and 2D-NMR techniques. In particular, dihydrodehydrodiconiferyl alcohol 9-O-beta-D-glucopyranoside - a glycosyl-neolignan - was isolated for the first time from the genus Achillea in addition to six flavone derivatives, apigenin, apigenin-7-O-beta-D-glucopyranoside, luteolin, luteolin-7-O-beta-D-glucopyranoside, luteolin-4'-O-beta-D-glucopyranoside, rutin, and two caffeic acid derivatives, 3,5-dicaffeoylquinic acid and chlorogenic acid. Apigenin and luteolin, the most important estrogenic compounds among those tested, were studied for their ability to activate alpha or beta estrogen receptors (ERalpha, ERbeta) using transiently transfected cells. Our results suggest that isolation and biological characterization of estrogenic compounds in traditionally used medicinal plants could be a first step in better assessing further (e.g. in vivo) tests of nutraceutical and pharmacological strategies based on phytoestrogens.

Achillea↗
PubMed2002

In vivo modulation of ventral tegmental area dopamine and glutamate efflux by local GABA(B) receptors is altered after repeated amphetamine treatment.

The activity of dopamine neurons in the ventral tegmental area is modulated by excitatory (glutamatergic) and inhibitory (GABAergic) afferents. GABA, released by intrinsic neurons and by projection neurons originating in the nucleus accumbens and other regions, inhibits dopamine neurons via activation of GABA(A) and GABA(B) receptor subtypes. Using in vivo microdialysis in freely moving rats, we investigated the role of ventral tegmental area GABA(B) receptors in modulating levels of dopamine and glutamate within the ventral tegmental area, both in naive rats and in rats treated repeatedly with saline or amphetamine (5 mg/kg i.p., for 5 days). In naive rats, administration of a potent and selective GABA(B) receptor antagonist (CGP 55845A) into the ventral tegmental area elicited a concentration-dependent increase in dopamine levels, but did not alter glutamate levels. In rats tested 3 days after discontinuing repeated amphetamine administration, 50 microM CGP 55845A increased dopamine levels to a greater extent than in saline controls. This difference was no longer present in rats tested 10-14 days after discontinuing repeated amphetamine injections. CGP 55845A (50 microM) had no effect on glutamate levels in the ventral tegmental area of saline-treated rats. However, it produced a robust increase in glutamate levels in rats tested 3 days, but not 10-14 days, after discontinuing repeated amphetamine injections. These results suggest that somatodendritic dopamine release is normally under strong tonic inhibitory control by GABA(B) receptors. Repeated amphetamine administration enhances GABA(B) receptor transmission in the ventral tegmental area during the early withdrawal period, increasing inhibitory tone on both dopamine and glutamate levels. This is the first demonstration, in an intact animal, that drugs of abuse alter GABA(B) receptor transmission in the ventral tegmental area.

Amphetamine↗
PubMed2001

Amphetamine-induced plasticity of AMPA receptors in the ventral tegmental area: effects on extracellular levels of dopamine and glutamate in freely moving rats.

Previous electrophysiological studies suggested that the initiation of behavioral sensitization to cocaine and amphetamine involves a transient increase in AMPA receptor responsiveness in the ventral tegmental area (VTA). To test this, we used in vivo microdialysis to examine the effects of intra-VTA administration of AMPA (10 microm) and NMDA (100 microm) on dopamine (DA) and glutamate efflux in the VTA and the nucleus accumbens (NAC), an important target of VTA DA neurons. We compared rats treated for 5 d with saline or 5 mg/kg amphetamine and withdrawn for 3 or 10-14 d. After 3 d of withdrawal, intra-VTA AMPA increased both NAC and VTA DA levels to a greater extent in the amphetamine group, whereas NMDA produced similar effects in the saline and amphetamine groups. This enhanced responsiveness to AMPA was no longer evident in rats tested 10-14 d after the last injection. In addition, intra-VTA AMPA but not NMDA increased both VTA and NAC glutamate levels in rats tested 3 d after the last injection of amphetamine but not in saline controls. After 10-14 d, the responsiveness of glutamate levels to AMPA was no longer evident in the NAC but persisted in the VTA. Additional studies indicated that the glutamate effect in the NAC may involve increased responsiveness of DA receptors within the NAC. These findings establish an in vivo animal model with which to explore the consequences of repeated drug administration for AMPA receptor plasticity in the VTA. They also indicate that repeated amphetamine leads to potentiated interactions between DA and glutamate transmission.

Amphetamine↗
PubMed2001

Nickel hexacyanoferrate membrane as a coated wire cation-selective electrode.

Nickel hexacyanoferrates containing alkali metal cations as counter ions were used to prepare ion-selective electrodes for potentiometric sensing of intercalated species in the coated wire electrode (CWE) configuration. All the electrodes developed display a quasi-Nernstian response towards potassium ion, whereas the highest sensitivity is generally achieved when Cs+ is the counter cation in the sensing material. The selectivity constants of the electrodes were calculated by the matched potential method considering K+ as the primary ion. The selectivity order is Cs+ > K+ > Na+ > Li+ and reflects the effective dimension of the hydrated cations.

Journal Article↗
PubMed2001

Alterations in behaviour and glutamate transmission following presentation of stimuli previously associated with cocaine exposure.

To study the role of glutamate in cocaine-conditioned responses, we developed a rat model in which conditioned locomotion is produced by repeated pairing of cocaine with discrete stimuli (flashing light and metronome). "Paired" subjects received cocaine (15 mg/kg) prior to six exposures to stimuli for 30 min in the test environment. "Unpaired" subjects received equivalent presentations of the stimuli yet received cocaine in home cages. Tests with the stimuli alone demonstrated that the conditioned locomotion displayed by Paired subjects was evident at 3 or 10 days post-training and resistant to two sessions of testing. The degree of conditioned locomotion was not correlated with the subjects' response to novelty or cocaine. Administration of the noncompetitive AMPA receptor antagonist GYKI 52466 (2.5 mg/kg, a dose without effect on spontaneous activity) attenuated the expression of conditioned activity. In vivo microdialysis revealed that Paired subjects had significantly lower basal glutamate levels in the nucleus accumbens (NAc) than did Unpaired subjects when no stimuli were presented. Presentation of the conditioned stimuli resulted in significant increases in glutamate levels in the NAc in the Paired group whilst glutamate levels in the Unpaired group remained unchanged. The associative control of glutamate levels in the NAc by stimuli formerly paired with a drug of abuse is an unprecedented finding. It is likely to reflect the convergence of excitatory inputs that the NAc receives from limbic structures.

Animals↗
PubMed2001

Expanded polytetrafluoroethylene as tendon replacement: an experimental study in chickens.

We designed an experimental animal model (in chickens) to assess the potential applications, above all in hand surgery, of an expanded polytetrafluoroethylene (e-PTFE) graft as a replacement for a natural tendon. The results of macroscopic, histological, and functional observations made five weeks, and three, four, five, and six months after implantation showed that the e-PTFE seemed to be a good replacement for tendons, because it integrated well with surrounding tissue and permitted good functional recovery within a reasonable time period.

Animals↗
PubMed2000

Chronic cocaine treatment induces dysregulation in the circadian pattern of rats' feeding behavior.

The effects of protracted cocaine administration (15 mg/kg i.p., twice a day for 9 days) on the circadian pattern of feeding behavior was studied in individually housed male Sprague-Dawley rats, maintained under a 12:12 light:dark cycle. Water and food were available ad libitum and food intake was measured twice a day before, during and after withdrawal of cocaine (or saline) treatment. Neither total 24-h food intake, nor body mass at the end of the experiment, was significantly different between cocaine-treated and control animals. However, cocaine administration affected the temporal distribution of food consumption. During the dark (activity) phase, rats receiving cocaine injections consumed significantly less food than control animals, and this effect persisted for up to 3 days of cocaine withdrawal. During the light (rest) phase, cocaine administration promoted food consumption and a significantly higher food intake was also observed during the first five cocaine withdrawal days. Continuous monitoring of locomotor activity did not reveal significant changes in the circadian pattern of activity between the two experimental groups during different treatment periods, except for an acute increase in locomotion within an hour after daytime cocaine injection. The results of this study demonstrate that sub-chronic cocaine administration alters the circadian pattern of rats' feeding behavior.

Animals↗
PubMed2000

Evidence of bilayer structure in V2O5 xerogel.

Polarized X-ray absorption spectroscopy has been used to study the short-range structure of deposited films of V2O5 xerogel. The material is characterized by a layer of VO5 units with the V-O apical bond perpendicular to the basal (xy) plane. We have focused our attention along the z axis. Experiments were carried out by extended X-ray absorption fine structure (EXAFS) spectroscopy in a grazing incidence geometry and showed evidence for close interactions between neighboring layers of V2O5. The structure is described by two sheets of V2O5 facing each other. Fitting of the EXAFS data has confirmed the existence of a vanadium-vanadium interaction between two different V2O5 layers and an oxygen bridge between them.

Journal Article↗
PubMed2000

In situ X-ray absorption spectroelectrochemical study of hydroxocobalamin.

An in situ X-ray absorption spectroscopy (XAS) spectroelectrochemical study of aquocobalamin (system B12a-B12r-B12s) has been carried out in aqueous solutions buffered at different pH values. To the best of our knowledge, this is the first structural study of aquocobalamin at room temperature under controlled oxidation conditions. Most of the previous work was in fact performed using frozen samples chemically treated to produce the species. The spectroelectrochemical approach offers several advantages: (1) the reduction products may be studied without poisoning the system with chemical reductive reagents and (2) any possible variation of the oxidation state owing to the electrons produced by the incident beam is avoided as the electrode, under potentiostatic control, acts as a scavenger. The spectroelectrochemical approach, together with more careful data analysis, has led to an improved interpretation of the XAS data. These conditions were not met in previous works where the oxidation state was not controlled and multiple scattering contributions were not taken into account. The general shape of the XAS spectra of the different species is not greatly affected by pH. A signature for the base-off square-planar coordination has been evidenced for the Co(II) compound at basic pH. A new signature for Co(I), indicating square-planar coordination, has been identified on the experimental spectra and simulated in theoretical X-ray absorption near-edge structure (XANES) studies. The flexibility of the electrochemical approach, that permits to unambiguously establish the formal oxidation state, has led to very reliable values for energy shift and peak intensity variations. The experimental XANES and extended X-ray absorption fine structure (EXAFS) spectra with a very good signal-to-noise ratio have been processed using the GNXAS package that takes into account multiple scattering contributions. EXAFS and XANES independent analysis result in the same structural model. The reduction from Co(III) to Co(II) produces the most significant structural changes: the cobalt coordination number decreases from six to five, and the edge position shifts by 2.4 +/- 0.3 eV. In addition, the XANES spectra are strongly modified. The reduction from Co(II) to Co(I) produces mainly electronic effects with no apparent change of the coordination number. A discussion of the limits and potentialities of EXAFS in this type of study has also been included.

Absorptiometry, Photon↗
PubMed2000

Local GABAergic modulation of acetylcholine release from the cortex of freely moving rats.

Cortical perfusion with GABA agonists and antagonists modulates the spontaneous release of cortical acetylcholine and GABA in freely moving rats. Twenty-four hours after implantation of a dialysis fibre, cerebral cortex spontaneously released acetylcholine (3.8 +/- 0.2 pmol/10 min) and GABA (6.6 +/- 0.4 pmol/10 min) at a stable rate. Local administration of GABA (1 or 5 mM) or the GABAA agonist muscimol (25 or 50 microM) had no effect on the spontaneous release of acetylcholine. However, bicuculline (1-25 microM), a GABAA antagonist, added to the dialysis perfusate, elicited a concentration-dependent increase of acetylcholine release to approximately double that of control. This effect of bicuculline (25 microM) was completely prevented by coperfusion with muscimol (50 microM). Local administration of the GABAB receptor agonist baclofen (10 or 50 microM) elicited a concentration-dependent increase in spontaneous acetylcholine release with a maximal increase of about 60%. Intracortical administration of baclofen also decreased the spontaneous release of GABA. The GABAB receptor antagonist CGP 35348 (1 mM), administered alone for 20 min through the dialysis fibre, was without effect on spontaneous acetylcholine release; however, it completely blocked both the baclofen-induced increase in acetylcholine release and the decrease in GABA release. These results suggest that cortically released GABA exerts a tonic influence on cholinergic activity.

Acetylcholine↗
PubMed1998

The Verbalizer-Visualizer Questionnaire: a review.

The psychometric properties of Richardson's 1977 Verbalizer-Visualizer Questionnaire have been studied by analyzing papers in which this questionnaire was employed. Such review showed that the Verbalizer-Visualizer Questionnaire does not measure a unidimensional construct and does not predict the actual use of mental imagery in thinking. Further, a lack of long-term reliability of the questionnaire emerged. In conclusion, use of the questionnaire to assess the verbal-visual cognitive style appears questionable.

Eye Movements↗
PubMed1998

Imidazenil, a positive allosteric GABAA receptor modulator, inhibits the effects of cocaine on locomotor activity and extracellular dopamine in the nucleus accumbens shell without tolerance liability.

Imidazenil, a benzodiazepine recognition site ligand that acts as partial positive allosteric modulator of gamma-aminobutyric acid (GABA) action at GABAA receptors, inhibits in a dose-dependent manner (0.56-2.5 micromol/kg i.p. to rats) the cocaine-induced increase in dopamine (DA) content in the dialysates of the nucleus accumbens shell and striatum and also inhibits cocaine-induced locomotor activity. Diazepam, a full allosteric modulator of GABA action at GABAA receptors, in a dose of 4.4 micromol/kg i.p. also attenuates the cocaine-induced increase in DA content in the dialysates of nucleus accumbens shell, and striatum and the cocaine-induced locomotor activity. However, imidazenil (2.5 micromol/kg i.p.) fails to reduce spontaneous locomotor activity, whereas diazepam (4.4 micromol/kg i.p.) elicits sedation and ataxia and clearly impairs spontaneous locomotor activity. When added in vitro, both imidazenil and diazepam potentiate the GABA-mediated reduction of the ventral tegmental area DA neuron firing rate. After protracted treatment (14 days/three times a day with an increasing-dose schedule), the inhibitory actions of imidazenil fail to develop tolerance, whereas the actions of diazepam exhibit high tolerance liability. We conclude that imidazenil is devoid of tolerance liability and that, via a GABAA-mediated reduction in the extracellular DA in nucleus accumbens shell, it might reduce the psychomotor activity and reinforcing properties of cocaine.

Allosteric Regulation↗
PubMed1997

Increased incidence of preeclampsia in pregnancies complicated by fetal malformation.

There seems to be a correlation between preeclampsia and congenital abnormalities, but whether it is positive or negative is a matter of controversy. Since it has been demonstrated that reduced perfusion of the trophoblast, which is an early feature of preeclampsia, can also represent a cause of fetal malformation, a positive correlation between the two conditions should be found. In the search for such a correlation we retrospectively examined 8,894 cases collected until 1994 by the IMER group (Indagine Malformazioni Emilia-Romagna). In the presence of malformation a higher incidence of preeclampsia was found (4.60 versus 3.47) with an odds ratio of 1.34 (95% CI = 1.08-1.67). Furthermore multivariate analysis showed that malformations of the male genital apparatus and those named 'multiple congenital abnormalities' can be considered as risk factors for preeclampsia. Since it is known that the development of male genitalia occurs under the influence of androgens, it can be hypothesized that hypoxia could act by favoring low end organ responsiveness. In our opinion the positive correlation with fetal malformations should be interpreted as clinical evidence of the early onset of the physiopathologic mechanism of preeclampsia.

Abnormalities, Multiple↗