Biomedical subjects

M Amici

Publications and source records attributed to M Amici.

At least 19 recordsLinked to original sources

PubMed2006

Anomalous levels of Cl- transporters in the hippocampal subiculum from temporal lobe epilepsy patients make GABA excitatory.

The mRNA levels of NKCC1, an inwardly directed Na(+), K(+)-2Cl(-) cotransporter that facilitates the accumulation of intracellular Cl(-), and of KCC2, an outwardly directed K(+)-Cl(-) cotransporter that extrudes Cl(-), were studied in surgically resected brain specimens from drug-resistant temporal lobe (TL) epilepsy (TLE) patients. Quantitative RT-PCR analyses of the mRNAs extracted from the human TLE-associated brain regions revealed an up-regulation of NKCC1 mRNA and a down-regulation of KCC2 mRNA in the hippocampal subiculum, compared with the hippocampus proper or the TL neocortex, suggesting an abnormal transcription of Cl(-) transporters in the TLE subiculum. In parallel experiments, cell membranes isolated from the same TLE-associated brain regions were injected into Xenopus oocytes that rapidly incorporated human GABA(A) receptors into their surface membrane. The GABA currents elicited in oocytes injected with membranes from the subiculum had a more depolarized reversal potential (E(GABA)) compared with the hippocampus proper or the neocortex. The NKCC1 blocker bumetanide or a temperature decrease of 10 degrees C shifted the GABA-current E(GABA) more negative in oocytes injected with membranes from TLE hippocampal subiculum, matching the E(GABA) of TL neocortex-injected oocytes. We conclude that the anomalous expression of both Cl(-) transporters, NKCC1 and KCC2 [corrected] in TLE hippocampal subiculum probably causes altered Cl(-) transport in the "epileptic" neurons, as revealed in the microtransplanted Xenopus oocytes, and renders GABA aberrantly "exciting," a feature that may contribute to the precipitation of epileptic seizures.

Animals↗

PubMed2005

Rundown of GABA type A receptors is a dysfunction associated with human drug-resistant mesial temporal lobe epilepsy.

Pharmacotherapeutic strategies have been difficult to develop for several forms of temporal lobe epilepsy, which are consequently treated by surgical resection. To examine this problem, we have studied the properties of transmitter receptors of tissues removed during surgical treatment. We find that when cell membranes, isolated from the temporal neocortex of patients afflicted with drug-resistant mesial temporal lobe epilepsy (TLE), are injected into frog oocytes they acquire GABA type A receptors (GABA(A)-receptors) that display a marked rundown during repetitive applications of GABA. In contrast, GABA(A)-receptor function is stable in oocytes injected with cell membranes isolated from the temporal lobe of TLE patients afflicted with neoplastic, dysgenetic, traumatic, or ischemic temporal lesions (lesional TLE, LTLE). Use-dependent GABA(A)-receptor rundown is also found in the pyramidal neurons of TLE neocortical slices and is antagonized by BDNF. Pyramidal neurons in cortical slices of a traumatic LTLE patient did not show GABA(A)-receptor rundown. However, the apparent affinity of GABA(A)-receptor in oocytes microtransplanted with membranes from all of the epileptic patients studied was smaller than the affinity of receptors transplanted from the nonepileptic brain. We conclude that the use-dependent rundown of neocortical GABA(A)-receptor represents a TLE-specific dysfunction, whereas the reduced affinity may be a general feature of brains of both TLE and LTLE patients, and we speculate that our findings may help to develop new treatments for TLE and LTLE.

Adolescent↗

PubMed2004

Radiometric characterisation of more representative natural building materials in the province of Rome.

Natural building materials, characterised by middle-low-activity concentrations of primordial radionuclides ((40)K, (232)Th and (238)U series) are widely used in Italy. Since natural materials reflect the geological variability of their sites of origin, a systematic study was carried out in the province of Rome and the results are reported in this paper. In the present work, in order to evaluate average, minimum and maximum contents of primordial radionuclides, more representative lithologies outcropping on the territory of the province of Rome were identified and around 150 samples were collected. Also, these lithologies were characterised from a radioprotection point of view, by means of the evaluation of the index, I, when they are used as building materials. The results confirm the high-primordial radionuclide content within some materials used in Latium (central Italy). Although the study was carried out in a limited area, the results confirm considerable variation in the primordial radionuclide content depending on the sites of origin.

Background Radiation↗

PubMed2002

Ultrasound extraction and thin layer chromatography-flame ionization detection analysis of the lipid fraction in marine mucilage samples.

This paper reports an analytical procedure based on ultrasound to extract lipids in marine mucilage samples. The experimental conditions of the ultrasound procedure (solvent and time) were identified by a FT-IR study performed on different standard samples of lipids and of a standard humic sample, before and after the sonication treatment. This study showed that diethyl ether was a more suitable solvent than methanol for the ultrasonic extraction of lipids from environmental samples because it allowed to minimize the possible oxidative modifications of lipids due to the acoustic cavitation phenomena. The optimized conditions were applied to the extraction of total lipid amount in marine mucilage samples and TLC-flame ionization detection analysis was used to identify the relevant lipid sub-fractions present in samples.

Chromatography, Thin Layer↗

PubMed2002

Effect of neurotoxic metal ions on the proteolytic activities of the 20S proteasome from bovine brain.

The effect of oxidative stress induced by neurotoxic metal ions on the properties of the brain 20S proteasome or multicatalytic proteinase complex (MPC) has been studied. Exposure of the 20S proteasome to increasing amounts of Fe(III), Fe(II), Cu(II) or Zn(II) affects its main hydrolytic activities: trypsin-like (T-L), chymotrypsin-like (ChT-L), peptidylglutamyl-peptide hydrolase (PGPH), branched-chain amino acid preferring (BrAAP) and caseinolytic activities, although in different ways. T-L activity showed gradual activation by both iron ions but inhibition by Cu(II) and Zn(II). ChT-L and PGPH activities were inhibited whereas BrAAP activity was widely activated by all the tested metal salts except for zinc ions. Moreover, the exposure to ferrous salt increased the degradation rate of casein. The functional effects appear to be linked to oxidation-induced modifications, as demonstrated by an increase of carbonyl groups following the exposure to metal ions. In addition, modifications induced by ferrous salt on the catalytic subunits were also supported by western blot analyses performed using anti-X, anti-Y and anti-Z antibodies. The results obtained clearly indicate that metal-catalyzed oxidation strongly affects the functions of the brain 20S proteasome, even though the catalytic subunits seem to be differently influenced by oxidative phenomena.

Alzheimer Disease↗

PubMed2002

An ultrasound assisted extraction of the available humic substance from marine sediments.

In this paper an ultrasound assisted procedure for the extraction of the bio-available fraction of humic substance in marine sediments is described. The proposed method is based on a preliminary 24 h 8 M HCl treatment already proposed in a previous paper [M. Mecozzi, E. Pietrantonio, M. Amici, Fres. Environ. Bull. 7 (1998) 605], followed by consecutive extractions by 0.5 M NaOH coupling to an ultrasonic treatment. The main advantages of the ultrasound procedure are the reduced times of extraction which take 30 min in contrast to the 24 h required by shaking method and the possibility to perform also the quantitative estimation of the extractable fraction of humic substance present in marine samples.

Carbohydrates↗

PubMed2001

Structure--function relationships in bovine thymus 20S proteasome: a fluorimetric study.

The structure--function relationships occurring on the bovine thymus 20S proteasome, which exhibits the features of an immunoproteasome, have been studied. The investigation has been performed, essentially, using a fluorimetric approach, taking advantage either of the sensitivity of the complex to sodium dodecil sulfate and chaotropic agents (urea and guanidine hydrochloride) or of the presence, on the molecule, of a high number of tryptophan residues. The results obtained indicate that the perturbation or the oxidation of these residues affect the catalytic events taking place on the thymus proteasome and that the functional effects determined by SDS and chaotropic agents most likely occur through a series of progressive structural modifications leading to an inactive molecule. The presence of structural intermediates in the proteasome inactivation process suggests that thymus proteasome is a molecule characterized, at the same time, by structural flexibility (modulation of active sites) and structural stability (maintaining of the quaternary structure) in agreement with its crucial role in the cell life cycle.

Animals↗

PubMed2001

Characterization of mucilage aggregates in Adriatic and Tyrrhenian Sea: structure similarities between mucilage samples and the insoluble fractions of marine humic substance.

The appearance of gelatinous aggregates called mucilages causes serious damages to tourism and fishery industries of the Adriatic Sea. So, many studies have been planned and some of them are still in progress to clarify the origin and causes of the phenomenon. The scientific research has showed that mucilages are produced by several marine organisms when peculiar climatic and trophic conditions occur. Moreover, as far as the mucilage composition is concerned, although it is well known that polysaccharides give a high contribution, knowledge of the structural characteristics of mucilages and their relationship with the natural organic matter of the marine environment has not been clarified yet. In this paper a study on the characterization of the marine mucilage samples collected in the Adriatic and Tyrrhenian Seas is described. The study was performed by spectroscopic (infrared and colorimetric) techniques, and elemental analysis. The results showed that mucilage samples have chemical and structural similarities with the insoluble fraction of the marine humic substance (humin). According to experimental evidences it is possible to establish the relationship between mucilages and the dissolved organic matter (DOM) in the marine environment in order to identify the most likely pathways of mucilage formation.

Adhesives↗

PubMed2001

Determination of carbonate in marine solid samples by FTIR-ATR spectroscopy.

A method for detecting carbonate in marine solid samples (sediments, corals) by Fourier transform infrared spectroscopy (FTIR) coupled to the total attenuated reflectance (ATR) technique is described. Compared to other techniques, the proposed method is not based on the measurement of CO2 evolved by combustion or acidification of the sample, but on the direct measurement of carbonate present in the sample. For this reason, the method by FTIR-ATR spectroscopy does not require any chemical pre-treatment. The proposed method allows determination of carbonate in the range 6-100% (w/w) as Na2CO3 and gives comparable results with the determination of inorganic carbon by elemental analysis.

Animals↗

PubMed1999

Ultrasound-assisted analysis of total carbohydrates in environmental and food samples.

Analytical methods to determine total carbohydrates in environmental and food samples usually require a preliminary chemical hydrolytic procedure to convert polysaccharides into monosaccharides prior to detection by colorimetric or chromatographic techniques. In this paper, an alternative hydrolytic procedure is presented. The method for hydrolysis of polysaccharides is based on the application of ultrasound at room temperature. The advantages of the method proposed here are reduced time required for analysis (4-5 h) and the improvement of the analytical accuracy due to the absence of the most common reactions of oxidation. The proposed method was applied to the determination of total carbohydrates in several environmental samples (seawater and marine mucilage) and starchy food samples. Results for total carbohydrate obtained using the ultrasound procedure for hydrolysis of samples agreed with those found when applying other published procedures.

Adhesives↗

PubMed1994