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A Amato

Publications and source records attributed to A Amato.

At least 19 recordsLinked to original sources
PubMed2006

Direct evidence for a dynamical ground state in the highly frustrated Tb(2)Sn(2)O(7) pyrochlore.

mSR experiments have been performed on a powder sample of the "ordered spin ice" Tb(2)Sn(2)O(7) pyrochlore. At base temperature (T=35 mK), the muon relaxation is found to be of dynamical nature, which demonstrates that strong fluctuations persist below the ferromagnetic transition (T(C)=0.87 K). Hints of long-range ordering appear as oscillations of the muon polarization when an external field is applied and also as a hysteretic behavior below T(C). We propose that dynamics results from fluctuations of clusters of correlated spins with the ordered spin ice structure.

Journal Article↗
PubMed2006

Muon spin relaxation studies of superconductivity in a crystalline array of weakly coupled metal nanoparticles.

We report muon-spin-relaxation studies in weak transverse fields of the superconductivity in the metal cluster compound, Ga84[N(SiMe3)2]20-Li6Br2(thf)20.2 toluene. The temperature and field dependence of the muon-spin-relaxation rate and Knight shift clearly evidence type II bulk superconductivity below Tc approximately 7.8 K, with Bc1 approximately 0.06 T, Bc2 approximately 0.26 T, kappa approximately 2, and weak flux pinning. The data are well described by the s-wave BCS model with weak electron-phonon coupling in the clean limit. A qualitative explanation for the conduction mechanism in this novel type of narrow-band superconductor is presented.

Journal Article↗
PubMed2006

Evidence of two dimensionality in quasi-one-dimensional cobalt oxides.

The quasi-one-dimensional (Q1D) cobalt oxides A(N + 2)Co(n + 1)O(3n + 3) (A = Ca, Sr, and Ba, n = 1 - infinity) were investigated by muon-spin spectroscopy under applied pressures of up to 1.1 GPa. The relationship between the onset Néel temperature T(on)(N) and the interchain distance (d(ic)), which increases monotonically with n, is well fitted by the formula T(N)/T(N,0) = (1 - d(ic)/d(ic,o)(beta), here for T(on)(N) approximately 100 K for Ca(3)Co(2)O(6) (n = 1) and approximately 15 for BaCoCoO(3) (n = infinity at ambient P. The T(on)(N) - d(ic) curve also predicts a large dependence of Y(N) for the compounds with n > or = 5, i.e., in the vicinity of , while the compounds show only a very small effect. Indeed, our high-pressure mu(+) results show that of BaCoO(3) is enhanced by with a slope of 2.2 K(Gpa), whereas no detectable changes by P for both Ca(3)Co(2)O(6) and Sr(4)Co(3)O(9) (n = 2). This clearly confirms the role of the 2D-antiferromagnetic interaction on T(on)(N) in the Q1D cobalt oxides.

Journal Article↗
PubMed2006

Spin dynamics and magnetic order in magnetically frustrated Tb2Sn2O7.

We report a study of the geometrically frustrated magnetic material Tb2Sn2O7 by the positive muon-spin relaxation technique. No signature of a static magnetically ordered state is detected while neutron magnetic reflections are observed in agreement with a published report. This is explained by the dynamical nature of the ground state of Tb2Sn2O7: the Tb3+ magnetic moment characteristic fluctuation time is approximately 10(-10) s. The strong effect of the magnetic field on the muon-spin-lattice relaxation rate at low fields indicates a large field-induced increase of the magnetic density of states of the collective excitations at low energy.

Journal Article↗
PubMed2006

Adefovir dipivoxil-associated thrombocytopenia in a patient with chronic hepatitis B.

A 56-year-old male patient received adefovir dipivoxil (10 mg/day) for chronic hepatitis B resistant to lamivudine. On the fifth week of treatment, the platelet count dropped to 26 x 10(3) mm(-3); anti-platelet antibodies were detectable in serum. The drug was discontinued and the platelet count improved spontaneously. A re-challenge with adefovir caused a new episode of thrombocytopenia, again after a five-week treatment period. To date, thrombocytopenia has not been described after adefovir therapy for chronic hepatitis B and seems to be a rare event.

Adenine↗
PubMed2006

Static magnetic order in metallic K0.49CoO2.

By means of muon-spin spectroscopy, we have found that K0.49CoO2 crystals undergo successive magnetic transitions from a high-T paramagnetic state to a magnetic ordered state below 60 K and then to a second ordered state below 16 K, even though K0.49CoO2 is metallic at least down to 4 K. An isotropic magnetic behavior and wide internal-field distributions suggest the formation of a commensurate helical spin density wave (SDW) state below 16 K, while a linear SDW state is likely to exist above 16 K. It was also found that exhibits a further transition at 150 K presumably due to a change in the spin state of the Co ions. Since the dependence of the internal-field below 60 K was similar to that for Na0.5CoO2, this suggests that magnetic order is more strongly affected by the Co valence than by the interlayer distance or interaction and/or the charge ordering.

Journal Article↗
PubMed2006

Perioperative blood transfusions for the recurrence of colorectal cancer.

BACKGROUND: The improvement of renal allograft survival by pre-transplantation transfusions alerted the medical community to the potential detrimental effect of transfusions in patients being treated for cancer. OBJECTIVES: The present meta-analysis aims to evaluate the role of perioperative blood transfusions (PBT) on colorectal cancer recurrence. This is accomplished by validating the results of a previously published meta-analysis (Amato 1998); and by updating it to December 2004. SEARCH STRATEGY: Published papers were retrieved using Medline, EMBASE, the Cochrane Library, controlled trials web-based registries, or the CCG Trial Database. The search strategy used was: {colon OR rectal OR colorectal} WITH {cancer OR tumor OR neoplasm} AND transfusion. The tendency not to publish negative trials was balanced by inspecting the proceedings of international congresses. SELECTION CRITERIA: Patients undergoing curative resection of colorectal cancer (classified either as Dukes stages A-C, Astler-Coller stages A-C2, or TNM stages T1-3a/N0-1/M0) were included if they had received any amount of blood products within one month of surgery. Excluded were patients with distant metastases at surgery, and studies with short follow-up or with no data. DATA COLLECTION AND ANALYSIS: A specific form was developed for data collection. Data extraction was cross-checked, using the most recent publication in case of repetitive ones. Papers' quality was ranked using the method by Evans and Pollock. Odds ratios (OR, with 95% confidence intervals) were computed for each study, and pooled estimates were generated by RevMan (version 4.2). When available, data were stratified for risk factors of cancer recurrence. MAIN RESULTS: The findings of the 1998 meta-analysis were confirmed, with small variations in some estimates. Updating it through December 2004 led to the identification of 237 references. Two-hundred and one of them were excluded because they analyzed survival (n=22), were repetitive (n=26), letters/reviews (n=66) or had no data (n=87). Thirty-six studies on 12,127 patients were included: 23 showed a detrimental effect of PBT; 22 used also multivariable analyses, and 14 found PBT to be an independent prognostic factor. Pooled estimates of PBT effect on colorectal cancer recurrence yielded overall OR of 1.42 (95% CI, 1.20 to 1.67) against transfused patients in randomized controlled studies. Stratified meta-analyses confirmed these findings, also when stratifying patients by site and stage of disease. The PBT effect was observed regardless of timing, type, and in a dose-related fashion, although heterogeneity was detected. Data on surgical techniques was not available for further analysis. AUTHORS' CONCLUSIONS: This updated meta-analysis confirms the previous findings. All analyses support the hypothesis that PBT have a detrimental effect on the recurrence of curable colorectal cancers. However, since heterogeneity was detected and conclusions on the effect of surgical technique could not be drawn, a causal relationship cannot still be claimed. Carefully restricted indications for PBT seems necessary.

Colorectal Neoplasms↗
PubMed2006

Weight loss in obese children carrying the proopiomelanocortin R236G variant.

To acquire more information relative to the course of obesity in conditions of food restriction in subjects carrying mutations in the melanocortin signaling pathway, 710 obese children (mean age: 9.5+/-2.1 yr; mean z-score body mass index: 3.63+/-1.6) were genotyped for the proopiomelanocortin (POMC) R236G substitution, a variant which has been associated to early onset obesity, by restriction fragment length polymorphism (RFLP) analysis. Three children were heterozygotes for the R236G variant (0.4%). One of them had the metabolic syndrome. This variant was not found in 400 controls. The 3 probands followed a hypocaloric balanced diet and, after about 12 months, normalized their weight as well as fat mass and insulin resistance. The patient with the metabolic syndrome reversed this condition. These results show that a) the R236G substitution of POMC gene, although not a major cause of obesity among Italian obese children and adolescents, is associated with early onset obesity, and that b) inherited alterations of the melanocortin signaling pathway, independently of the degree of obesity, do not preclude the possibility to lose weight in mutated individuals following a hypocaloric diet.

Adolescent↗
PubMed2006

Evidence for a role of inducible nitric oxide synthase in gastric relaxation of mdx mice.

Alterations of gastric mechanical activity have been reported in mdx mouse, animal model for Duchenne muscular dystrophy. This study examined if alterations in the vasoactive intestinal polypeptide (VIP) system are present in mdx stomach. Gastric mechanical activity was recorded in vitro as changes of endoluminal pressure and neurally or pharmacologically evoked relaxations were analysed in mdxvs normal stomach. Reverse-transcription polymerase chain reaction was used to detect inducible nitric oxide synthase (iNOS) expression. Relaxations to sodium nitroprusside in mdx stomach showed no difference in comparison with normal preparations. In normal stomach, VIP produced relaxation, which was reduced by VIP6-28, antagonist of VIP receptors, but was not modified by Nomega-nitro-L-arginine methyl ester (L-NAME), 1-H-oxodiazol-[1,2,4]-[4,3-a]quinoxaline-1-one (ODQ) or by N-(3-(aminomethyl)-benzyl)acetamidine (1400W) and aminoguanidine, inhibitors of iNOS. In contrast, in mdx stomach VIP responses were antagonized not only by VIP6-28, but also by L-NAME, ODQ, 1400W or aminoguanidine. In normal stomach, the slow relaxation evoked by stimulation at high frequency was reduced by VIP6-28, but it was unaffected by 1400W or aminoguanidine. In mdx stomach, it was reduced by VIP6-28 or 1400W, which did not show additive effects. iNOS mRNA was expressed only in mdx stomach. The results suggest that in mdx gastric preparations, iNOS is functionally expressed, being involved in the slow relaxation induced by VIP.

Animals↗
PubMed2006

Altered tachykinergic influence on gastric mechanical activity in mdx mice.

This study investigated whether alterations in gastric activity in dystrophic mdx mouse can be attributed to dysfunctions of tachykinins. Endoluminal pressure was recorded and the expression of neuronal nitric oxide synthase (nNOS), NK1 and NK2 neurokinin receptors was investigated by immunohistochemistry. SR48968, NK2 receptor antagonist, but not SR140333, NK1 receptor antagonist, decreased the tone only in mdx gastric preparations. In the presence of N(omega)-nitro-l-arginine methyl ester (l-NAME), inhibitor of NOS, SR48968 reduced the tone also in normal stomach. [Sar(9), Met(O(2))(11)]-SP, agonist of NK1 receptors, caused tetrodotoxin-sensitive relaxations, antagonized by SR140333 or l-NAME, with no difference in the potency or efficacy between normal and mdx preparations. [beta-Ala(8)]-NKA(4-10), an NK2 receptor agonist, induced SR48968-sensitive contractions in both types of preparations, although the maximal response of mdx tissues was significantly lower than normal preparations. Immunohistochemistry demonstrated a consistent reduction of nNOS and NK2 receptor expression in mdx stomach smooth muscle cells and no change in nNOS and NK1 receptor expression in neurones. In conclusion, in mdx stomach the activation of NK2 receptors plays a role in the development of the tone, associated with a reduced NO production by muscular nNOS. The hypo-responsiveness to NK2 receptors could depend on the reduced expression of these receptors.

Animals↗
PubMed2006

Effect of tramadol on Bispectral Index during intravenous anaesthesia with propofol and remifentanil.

The aim of this study was to investigate the effects of tramadol on the Bispectral Index (BIS) during total intravenous propofol-remifentanil anaesthesia. Forty-four adult ASA Physical status I-II patients, scheduled for elective general surgical procedures were included in a prospective observational randomized study. Doses for anaesthetics and opioids were adjusted to keep the BIS value at 50 +/- 5. After 20 minutes of stable anaesthesia, the subjects were randomly allocated to receive intravenous saline (control group) or tramadol 1.5 mg/kg (tramadol group). BIS values, mean arterial pressure, and heart rate were recorded every five minutes for 20 minutes. Mean BIS values after tramadol administration were not significantly different from those following saline, throughout the observation period (P > 0.05). There were no patients in whom BIS values were more than 60 or who presented explicit recall of events under anaesthesia. There were no significant changes in mean arterial pressure, SpO2, or heart rate (P > 0.05). The results indicate that the administration of tramadol during stable total intravenous anaesthesia with propofol-remifentanil does not affect BIS values. The clinical relevance is that tramadol can be safely administered pre- and intraoperatively as pre-emptive or preventive analgesia without modification of the depth of anaesthesia.

Aged↗
PubMed2005

Ageing, hormonal behaviour and cyclin D1 in ductal breast carcinomas.

Owing to the gradual modification of breast tissue in postmenopausal women, there can be differential effects on local oestrogen receptor (ER) expression, with potential impingement on the biological behaviour of cancer cells in the ageing. A series of 45 ductal carcinoma (DC) cases were selected in postmenopausal women who were not being treated with HRT. Immunohistochemical analyses were performed for hormone receptors and Ki67 expression. Fluorescence in situ hybridisation (FISH) analysis was carried out to study CCND1 amplification. The selected population was subdivided into three groups by age and was subjected to statistical studies: linear model analysis, estimation of relative incidence (RI), multivariate analysis, and nonparametric tests were performed to investigate whether there were any links between age and molecular variables in DCs. The results show a low rate of proliferation and high ER expression in the oldest age group. In the same group a close correlation was found between high ER expression and CCN in the older age group D1 amplification (P=0.000), as was a more advanced phenotype in terms of tumour size and presence of positive lymph nodes than in the other age groups considered. The results suggest that ductal breast cancer has a favourable molecular prognosis, especially in extreme old age. In particular, there is an inverse correlation between ageing and proliferation rate despite the presence of an accentuated proliferation stimulus (high ER with CCD1 amplifications) in the oldest group relative to the other groups considered.

Adult↗
PubMed2005

Cascade of bulk magnetic phase transitions in NaxCoO2 as studied by muon spin rotation.

Using muon spin rotation, well-defined bulk approximately 100% magnetic phases in NaxCoO2 are revealed. A novel magnetic phase is detected for x=0.85 with the highest transition temperature ever observed for x>or=0.75. This stresses the diversity of x>or=0.75 magnetic phases and the link between magnetic and structural degrees of freedom. For the charge-ordered x=0.50 compound, a cascade of transitions is observed below 85 K. From a detailed analysis of our data, we conclude that the ordered moment varies continuously with temperature and suggest that the two secondary transitions at 48 and 29 K correspond to a moderate reorientation of antiferromagnetically coupled moments.

Journal Article↗
PubMed2005

Drugs of anesthesia acting on central cholinergic system may cause post-operative cognitive dysfunction and delirium.

Given the progressive and constant increase of average life expectancy, an increasing number of elderly patients undergo surgery. After surgery, elderly patients often exhibit a transient reversible state of cerebral cognitive alterations. Among these cognitive dysfunctions, a state of delirium may develop. Delirium is an aetiologically non-specific syndrome characterised by concurrent disturbances of consciousness and attention, perception, thinking, memory, psychomotor behaviour and the sleep-wake cycle. Delirium appears to occur in 10-26% of general medical patients over 65, and is frequently associated with a significant increase in morbidity and mortality. During hospitalization, mortality rates have been estimated to be 10-26% of patients who developed post-operative delirium, and 22-76% during the following months. Over the last few decades, post-operative delirium has been associated with several pre-operative predictor factors, as well as age (50 years and older), alcohol abuse, poor cognitive and functional status, electrolyses or glucose abnormalities, and type of surgery. The uncertain pathogenesis of post-operative cognitive dysfunctions and delirium has not permitted a causal approach to developing an effective treatment. General anesthesia affects brain function at all levels, including neuronal membranes, receptors, ion channels, neurotransmitters, cerebral blood flow and metabolism. The functional equivalents of these impairments involve mood, memory, and motor function behavioural changes. These dysfunctions are much more evident in the occurrence of stress-regulating transmission and in the alteration of intra-cellular signal transduction systems. In addition, more essential cellular processes, that play an important role in neurotransmitter synthesis and release, such as intra-neuronal signal transduction and second messenger system, may be altered. Keeping in mind the functions of the central muscarinic cholinergic system and its multiple interactions with drugs of anesthesia, it seems possible to hypothesize that the inhibition of muscarinic cholinergic receptors could have a pivotal role in the pathogenesis not only of post-operative delirium but also the more complex phenomena of post-operative cognitive dysfunction.

Anesthetics, General↗
PubMed2005

Distribution of the mutated delta 32 allele of the CCR5 gene in a Sicilian population.

The CCR5 gene encodes a cell-surface chemokine receptor molecule that serves as a co-receptor for macrophage-tropic strains of human immunodeficiency virus type 1 (HIV-1). A mutation in this gene may alter the expression or the function of the protein product, thereby altering chemokine binding and/or signalling or HIV-1 infection of cells that normally express CCR5 protein. Individuals homozygous for a 32-bp deletion allele of CCR5 (CCR5 delta32), heritable as a Mendelian trait, are relatively resistant to HIV-1 infection. The CCR5 delta32 mutation is present in the Caucasian population at different frequencies. The aim of this study was to investigate the frequency of truncated alleles of the CCR5 delta32 gene in a Sicilian population, as the interpopulation variation in CCR5 delta32 frequency may be a significant factor in the prediction of AIDS endemicity in future studies. We examined 901 healthy individuals from several Sicilian provinces. We found a mean (+/- standard deviation) delta32 allele frequency (fr) of 0.04 +/- 0.012. The highest value was observed in the province of Messina, with a mean delta32 allele frequency of 0.06 +/- 0.024, where we collected samples from a cohort of 114 HIV-1-infected individuals. The observed frequency amongst these patients was quite low (fr = 0.03 +/- 0.031) compared to the healthy population, although the difference was not statistically significant.

Adolescent↗
PubMed2004

Effect of two gaps on the flux-lattice internal field distribution: evidence of two length scales in Mg(1-x)AlxB2 from muSR.

We have measured the transverse field muon spin precession in the flux-lattice (FL) state of the two-gap superconductor MgB2 and of the electron doped compounds Mg(1-x)AlxB2 in magnetic fields up to 2.8 T. We show the effect of the two gaps on the internal field distribution in the FL, from which we determine two coherence length parameters and the doping dependence of the London penetration depth. This is an independent determination of the complex vortex structure already suggested by the STM observation of large vortices in a MgB2 single crystal. Our data agree quantitatively with STM and we thus validate a new phenomenological model for the internal fields.

Journal Article↗
PubMed2004

muSR study of the quantum dynamics in the frustrated S=3/2 kagomé bilayers.

We present muSR experiments in the S=3/2 kagomé bilayer compound Ba(2)Sn(2)ZnGa(10-7p)Cr(7p)O22 [BSZCGO(p)] and compare it to the isostructural SrCr(9p)Ga(12-9p)O19 [SCGO(p)], including for the latter new results for p > or =0.89. Quantum-dynamical low energy magnetic excitations are evidenced in this novel compound. We study the evolution of the muon relaxation rate with p, T, and field. A phenomenological model for the muon relaxation based on sporadic dynamics due to spin excitations in a singlet sea proposed by Uemura et al. is extended to all fields and T range. Its connection to the RVB picture is discussed, and we argue that such coherent states might mediate the interactions between "impurities" which induce the spin glass freezing.

Journal Article↗