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Biomedical subjects

A Marcelli

Publications and source records attributed to A Marcelli.

At least 19 recordsLinked to original sources
PubMed2006

Far-infrared absorption of La1-xCaxMnO3-y at high pressure.

The first far-infrared absorption spectra of manganite samples at pressures P up to 10 GPa were obtained on La1-xCaxMnO3-y by use of synchrotron radiation. For x=0.25 and 0.20 (y=0), P promotes partial metallization at room temperature through a strong reduction of the insulating gap. An x=0.20 sample with y=0.08 does not show any charge delocalization effect up to 10 GPa. An Urbach-like model of disordered Jahn-Teller wells is shown to well fit the far-infrared band edge and allows one to obtain a reliable pressure dependence of the energy gap.

Journal Article↗
PubMed2001

Symmetry role on the preedge X-ray absorption fine structure at the metal K edge.

The preedge features in a system with "even" symmetry, apart from quadrupolar transition contribution, are mainly dipolar in character, associated with the existence of unoccupied states made up of mixed cation-4p with higher-neighboring cation-3d orbitals, and reflect the density of states due to the medium-range order of the system. In "odd" symmetry materials these preedge features are the result of a transition from the 1s to a final density of states of p symmetry due to an unsymmetrical mixing of the ligand wave functions with the central cation 3d orbitals, similar to atetrahedral configuration. These results are validated for Fe as a photoabsorber by comparing XAS spectra of Fe2SiO4 (fayalite) to ab initio full multiple scattering calculations at the Fe K edge, but pertain to all systems containing sixfold-coordinated cations.

Journal Article↗
PubMed2001

Local atomic and electronic structure of Al90FexCe10-x alloys: XAFS analysis.

X-ray absorption fine structure (XAFS) above the Fe K-edge and the Ce L3-edge in amorphous Al90Fe(x)Ce10-x (x = 3, 5, and 7) alloys have been measured and analyzed. Quantitative analyses of the Fe K-edge and Ce L3-edge EXAFS spectra are limited to local structure parameters of the first coordination sphere. Using a theoretical multiple scattering (MS) approach, we show that the Fe and Ce XANES are sensitive to the structure of coordination spheres, which extend up to nearly 4.5 A. Comparison of experimental XANES spectra with theoretical MS results allows one to determine the local structure around the iron and cerium sites up to at least the third shell of atoms.

Journal Article↗
PubMed2001

Oxygen 1s ELNES study of perovskites (Ca,Sr,Ba)TiO3.

The O K-edge spectra of perovskites XTiO3 with X=Ca, Sr and Ba have been measured using electron energy-loss spectroscopy (EELS) and are analyzed using the ab initio full multiple-scattering (MS) calculations. The near-edge structures arise mainly from covalency by direct and/or indirect interaction between oxygen and metal. The coordination number of the cation and the site symmetry also influence the spectral shape and structures. Comparison of full MS simulations of different clusters around the excited atom allows to interpret and correlate the features present in the spectra of each compound to its specific atomic arrangement and electronic structure.

Journal Article↗
PubMed1999

A prospective study of the influence of HIV status on the seroreversion of serological tests for syphilis.

UNLABELLED: The evolution of serological tests for syphilis (STSs) after therapy in HIV+ patients is a major point of controversy, with possible seroreactivation and illicit seroreversion in these patients. The aim of our study was to evaluate the long-term outcome of STSs in a cohort of HIV+ male homosexuals with a history of treated syphilis as compared with HIV- controls. PATIENTS AND METHODS: Sixty-nine HIV+ male homosexuals with a documented history of treated syphilis and positive baseline treponemal tests were prospectively studied between 1986 and 1993. A medical examination, HIV staging, CD4+ cell count, VDRL, FTA-Abs tests and TPHA were performed every 6 months. Controls consisted of 49 HIV- patients with similar inclusion criteria over the same period. Comparisons between subgroups were based on chi(2) and Kruskal-Wallis tests. Analysis of negativation of the STS used the failure data methods (Kaplan-Meier, log-rank and Cox's model). RESULTS: Patients had a mean age of 38 years, a baseline CD4+ cell count of 578/mm(3), elapsed time since last syphilis of 7.5 years and a median follow-up of 4.3 years. Controls had a mean age of 42 years, elapsed time since last syphilis of 5.3 years and a median follow-up of 4.7 years. Time to seroreversion was shorter in HIV+ patients for TPHA (p = 0.009, log-rank test) and FTA-Abs test (p = 0.001, log-rank test), even after adjustment for stage of syphilis, age and time since the last episode of syphilis. The decrease in VDRL titres was not different between the 2 groups (p = 0.053, log-rank test). Seroreversion of the TPHA, FTA-Abs test and VDRL test was not significantly related to stage of syphilis, time elapsed since the last episode of syphilis, age or history of STDs in both groups. Seroreversion of the TPHA and VDRL test was not related to baseline CD4+ cell count. However, seroreversion of the FTA-Abs test was related to a low baseline CD4+ cell count (p = 0. 003). In HIV+ patients, a significant decrease in titres was noticed for TPHA, FTA-Abs test and VDRL test over time, but this time effect remained only for TPHA titres after adjustment for the CD4+ cell count. CONCLUSION: TPHA may serorevert in HIV+ patients. Thus, a non-reactive TPHA does not exclude a past syphilis infection in such patients. Evolution of the VDRL test after therapy is regular in HIV+ patients. The VDRL test remains adequate for controlling the efficacy of treatment in these patients.

Adult↗
PubMed1998

SINBAD, a brilliant IR source from the DAPhiNE storage ring.

SINBAD is the Italian IR synchrotron radiation beamline, designed to work at wavelengths greater than 10 micro m. It is being installed on DAPhiNE, a new collider that is designed to work at 0.51 GeV with a beam current up to 5 A. Due to such a high current, the IR extracted from a bending magnet will be more brilliant than that of a black body at 2000 K by two orders of magnitude at 100 micro m. The beamline optical system, projected by ray-tracing simulation, consists of six mirrors that first focus the radiation on a wedged CVD diamond-film window and then transfer the collimated beam to the experimental area where a Michelson interferometer will be installed.

Journal Article↗
PubMed1997

Tissue suspension agglutination: a simple method to screen species-specific and organ-specific reactions.

Agglutination tests with preparations of parenchymatous organs were developed. The tissue suspensions were dried at room temperature after they had been spread as a very thin layer on a glass plate, or otherwise, they were lyophilized. The dried preparations were pulverized and then prepared as stable suspensions in saline. The agglutination test was conducted on a slide by mixing one drop of the tested serum at a convenient dilution with one drop of tissue powder suspension. Agglutination in the form of readily discernible clumps could be assessed after 1-10 min. By means of this procedure, species-specific reactions were studied using suspensions of kidneys of various species. Organ-specific reactions were noted with suspensions of brain and thyroid. Agglutination of thyroid powder was observed with rabbit anti-rabbit thyroid sera as well as with many, albeit not all, sera of patients with Hashimoto's disease.

Agglutination Tests↗
PubMed1996

Antiphosphatidylethanolamine antibodies as the only antiphospholipid antibodies. I. Association with thrombosis and vascular cutaneous diseases.

OBJECTIVE: To detect antiphosphatidylethanolamine antibodies (aPE) as the only antiphospholipid antibodies (aPL) in 122 patients we investigated for aPL and to correlate the presence of aPL with clinical manifestations. METHODS: Patients with autoimmune diseases (n = 41), thromboembolic episodes (TEE) (n = 34), livedo reticularis (LR) without (n = 17) or with (n = 14) thrombosis or recurrent fetal losses (RFL), systemic vasculitides (n = 10), and miscellaneous disorders (n = 6) were investigated for antibodies directed against 4 anionic phospholipids (PL) (cardiolipin, phosphatidylserine, inositol, phosphatidic acid) and lupus anticoagulant (LAC) and then for aPE by modified ELISA. RESULTS: 15 patients had aPE and no antibodies to anionic PL including LAC. 7 had IgM, 4 had IgG plus IgM, and 4 had IgG. These aPE were significantly more often associated with TEE alone, with TEE and LR, or with LR alone (p = 0.004) than with autoimmune diseases. CONCLUSION: The detection of aPE as the sole aPL in one patient with mesenteric infarcts and RFL led to the diagnosis of primary antiphospholipid syndrome. Followup of 3 patients showed that aPE cannot be considered as transient autoantibodies. Therefore, patients whose clinical symptoms suggest antiphospholipid syndrome but whose sera are negative for antibodies to cardiolipin or another anionic PL should be screened for aPE, particularly patients with thrombosis, RFL, and/or LR.

Adolescent↗
PubMed1996

[Glomerular nephropathies and exposure to organic solvents--a case-control study].

Several studies have suggested that exposure to organic solvents is associated with glomerular nephropathies (GN), but this relationship remains controversial. A case-control study of 298 biopsy-proven cases and 298 hospital controls, matched for year of birth, sex, origin, and place of residence, was conducted between 1989 and 1991 in five hospitals in the Paris area : 82 cases of membranous glomerulopathy were included ; 100, nephrotic syndrome with either minimal change nephropathy or focal and segmental hyalinosis (MCN/FSH); and 116, IgA nephropathy (IgA N). Subjects were interviewed about their lifelong occupational and non-occupational activities. Type, level, and duration of solvent exposure were assessed blind with respect to case-control status by two industrial hygienists. HLA phenotypes were determined. Among males, a clear association, which was not explained by social class, was observed between chronic renal failure and high exposure to solvents for both MCN/FSH (OR = 7.7, 95% CI 1.4-41.6) and IgA N (OR = 3.5, 95% CI 1.0-11.8). The odds ratios increased with duration of exposure. No relationship was observed between such exposure and GN cases with normal renal function. No evidence was found that the HLA phenotype plays a role in the solvent exposure-disease association. These results support the hypothesis of a causal relationship between high solvent exposure, which concerned 15% of the males in this study, and the development of GN with chronic renal failure.

Adult↗
PubMed1995

Organic solvent exposure may increase the risk of glomerular nephropathies with chronic renal failure.

BACKGROUND: Several studies have suggested that exposure to organic solvents is associated with glomerular nephropathies (GN), but this relationship remains controversial. METHODS: A case-control study of 298 biopsy-proven cases and 298 hospital controls, matched for year of birth, sex, origin, and place of residence, was conducted between 1989 and 1991 in five hospitals in the Paris area: 82 cases of membranous glomerulopathy were included; 100, nephrotic syndrome with either minimal change nephropathy or focal and segmental hyalinosis (MCN/FSH); and 116, IgA nephropathy (IgA N). Subjects were interviewed about their lifelong occupational and non-occupational activities. A 'blind' assessment of type, level, and duration of solvent exposure was carried out by two industrial hygienists. Human leucocyte antigen (HLA) phenotypes were determined. RESULTS: Among males, a clear association, which was not explained by social class, was observed between chronic renal failure and high exposure to solvents for both MCN/FSH (OR = 7.7, 95% CI: 1.4-41.6) and IgA N (OR = 3.5, 95% CI: 1.0-11.8). The odds ratios increased with duration of exposure. No relationship was observed between such exposure and GN cases with normal renal function. No evidence was found that the HLA phenotype plays a role in the association between solvent exposure and the disease. CONCLUSIONS: These results support the hypothesis of a causal relationship between high solvent exposure, which concerned 15% of the males in this study, and the development of GN with chronic renal failure.

Adult↗
PubMed1992

Regulation of IL-2 beta receptor expression and beta-chain mRNA by human thymocytes.

The high affinity form of the human IL-2 receptor (IL-2R) has two known components, the IL-2R alpha (p55) and the IL-2R beta chain (p75). We have previously shown that recombinant IL-2 (rIL-2) could induce the expression of the alpha-chain (p55) on T cells and thymocytes, and increase this expression following suboptimal activation with concanavalin A (Con A) in combination with IL-2. An increase in the accumulation of IL-2R alpha-specific mRNA induced by rIL-2 in T cells and thymocytes had also been documented. We report here that the expression of IL-2R beta on the cell surface can be demonstrated on human thymocytes by the binding of Mik beta1, a MoAb directed against an epitope of the beta-chain. The IL-2R beta chain is constitutively expressed on freshly isolated thymocytes; this expression can be increased in thymocytes activated with Con A in combination with IL-2 or tetradecanoylphorbol 13-acetate (TPA). Blocking the formation of high affinity receptors with a MoAb directed against the alpha-chain of the receptor results in an increase in the display of IL-2R beta as evidenced by binding of MoAb Mik beta1. The accumulation of IL-2R-beta-specific mRNA is observed in freshly isolated thymocytes and it is increased in thymocytes cultured with rIL-2 alone, with Con A, and further enhanced by the addition of rIL-2 in combination with Con A or with TPA. Cyclosporine (CsA), which inhibits the accumulation of lymphokine-specific mRNA of thymocytes, does not inhibit the induction of the accumulation of IL-2R beta-specific mRNA. This is analogous to its effect on the expression of the alpha-chain (p55), and the accumulation of alpha-chain-specific mRNA.

Animals↗