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M Duc

Publications and source records attributed to M Duc.

At least 19 recordsLinked to original sources
PubMed2006

Influence of kinetics on the determination of the surface reactivity of oxide suspensions by acid-base titration.

The effect of acid-base titration protocol and speed on pH measurement and surface charge calculation was studied on suspensions of gamma-alumina, hematite, goethite, and silica, whose size and porosity have been well characterized. The titration protocol has an important effect on surface charge calculation as well as on acid-base constants obtained by fitting of the titration curves. Variations of pH versus time after addition of acid or base to the suspension were interpreted as diffusion processes. Resulting apparent diffusion coefficients depend on the nature of the oxide and on its porosity.

Aluminum Oxide↗
PubMed2006

Sorption of selenite ions on hematite.

The sorption of selenite from aqueous solutions onto hematite was investigated as a function of pH (2-12), ionic strength (0.01-0.1 M), and concentration of selenium (10(-7)-10(-2) M). The sorption may proceed according to two processes: surface complexation, followed by the precipitation of ferric selenite starting at approximate [Se] = 4 x 10(-4) M (surface coverage>ca. 2 at nm(-2)). The sorption isotherms have been fitted by a Tempkin equation. A surface complexation model (2-pK/Constant Capacitance Model) was used to fit the sorption data. The nature of the surface species of selenite cannot be determined by modeling since monodentate >FeOSe(O)O- or >FeOSe(O)OH and bidentate (>FeO)2SeO surface complexes are both able to fit the experimental data. The reversibility and kinetics of sorption were also studied. The affinity of selenite ions toward hematite, expressed as the distribution coefficient with respect to the surface area (K(D) in L m(-2)), was compared with results published for other ferric oxides (goethite and amorphous ferric oxide). It was found that the reactivity toward selenite is similar, contrary to acid-base properties which depend on the nature of the oxide and its level of purity.

Journal Article↗
PubMed2004

Effect of solubility on the determination of the protonable surface site density of oxyhydroxides.

The impact of the dissolved quantity of aluminum on the calculation of surface charge from titration experiments of hydrated gamma-alumina was investigated. Two methods were developed to correct this effect: direct determination of aluminum in solution in batch titration experiments and application of a dissolution rate model in continuous titration experiments. There is a large effect of dissolution on surface charge determination for pH>10 and pH < 4.5. Application of these correction methods to these pH ranges lead to apparent saturation surface charges of 1.3 and 2.3 at nm(-2), respectively. The last value seems to be the real proton-active site density, while the hydroxyl-active site density cannot be reached for easily achievable basic pH values.

Journal Article↗
PubMed2001

Serology of typhoid fever in an area of endemicity and its relevance to diagnosis.

Currently, the laboratory diagnosis of typhoid fever is dependent upon either the isolation of Salmonella enterica subsp. enterica serotype Typhi from a clinical sample or the detection of raised titers of agglutinating serum antibodies against the lipopolysaccharide (LPS) (O) or flagellum (H) antigens of serotype Typhi (the Widal test). In this study, the serum antibody responses to the LPS and flagellum antigens of serotype Typhi were investigated with individuals from a region of Vietnam in which typhoid is endemic, and their usefulness for the diagnosis of typhoid fever was evaluated. The antibody responses to both antigens were highly variable among individuals infected with serotype Typhi, and elevated antibody titers were also detected in a high proportion of serum samples from healthy subjects from the community. In-house enzyme-linked immunosorbent assays (ELISAs) for the detection of specific classes of anti-LPS and antiflagellum antibodies were compared with other serologically based tests for the diagnosis of typhoid fever (Widal TO and TH, anti-serotype Typhi immunoglobulin M [IgM] dipstick, and IDeaL TUBEX). At a specificity of > or =0.93, the sensitivities of the different tests were 0.75, 0.55, and 0.52 for the anti-LPS IgM, IgG, and IgA ELISAs, respectively; 0.28 for the antiflagellum IgG ELISA; 0.47 and 0.32 for the Widal TO and TH tests, respectively; and 0.77 for the anti-serotype Typhi IgM dipstick assay. The specificity of the IDeaL TUBEX was below 0.90 (sensitivity, 0.87; specificity, 0.76). The serological assays based on the detection of IgM antibodies against either serotype Typhi LPS (ELISA) or whole bacteria (dipstick) had a significantly higher sensitivity than the Widal TO test when used with a single acute-phase serum sample (P < or = 0.007). These tests could be of use for the diagnosis of typhoid fever in patients who have clinical typhoid fever but are culture negative or in regions where bacterial culturing facilities are not available.

Adolescent↗
PubMed2000

Neural substrates of spatial and temporal disorientation in Alzheimer's disease.

To examine the neuroanatomical correlates of spatial and temporal disorientation in Alzheimer's disease (AD), we performed an anterograde clinicopathological study of 29 patients with clinically and neuropathologically confirmed AD. Spatial and temporal disorientation was assessed using the locational orientation subtests of the Mini Mental State Examination and the Benton's test for temporal orientation. Quantitative analysis of neurofibrillary tangles and senile plaques were performed in the CA1 field of the hippocampus, layers II and V of the entorhinal cortex, and layers II-III and V-VI of areas 9, 7, 39, 19, 37, 20 and 23 in the right hemisphere. Forward stepwise logistic regression was used to assess the relationship between lesion densities and the presence of either spatial or temporal disorientation; severity scores and brain weight were included as covariants. A statistically significant relationship was found between neurofibrillary tangle densities in Brodmann's areas 7, 23 and the CA1 field of hippocampus and both spatial and temporal disorientation. Senile plaque counts did not correlate with any of the neuropsychological parameters. Both temporal and spatial disorientation in AD are related to the degeneration of the same pathways linking the hippocampus with the superior parietal and posterior cingulate cortex in the right hemisphere. These observations are discussed with respect to the notion of global corticocortical disconnection in AD.

Aged↗
PubMed1999

Neuroanatomic correlates of visual agnosia in Alzheimer's disease: a clinicopathologic study.

OBJECTIVE: To examine the neuroanatomic correlates of visual agnosia in AD. METHODS: The authors performed an anterograde clinicopathologic study of 23 patients with clinically and neuropathologically confirmed AD in a 305-bed acute care geriatric hospital and a 165-bed acute care psychiatric hospital. The presence of apperceptive visual agnosia was assessed using the Ghent's overlapping figure test and the Gottschaldt's hidden figure test. Associative visual agnosia was examined using the conceptual items of the Columbia Mental Maturity Test. Correlations between neurofibrillary tangle (NFT) and senile plaque (SP) densities and visual agnosia were studied using forward stepwise logistic regression. RESULTS: A statistically significant relation was found between NFT densities in Brodmann's areas 18, 19, and 37, and associative visual agnosia, whereas NFT densities in the areas studied did not correlate with the presence of apperceptive visual agnosia. Senile plaque counts did not correlate with any of the neuropsychological parameters. CONCLUSIONS: These results support the existence of a dichotomy between associative and apperceptive agnosia, and show that only the former is related to the damage of secondary and high-order visual association areas in AD. In addition, the results suggest that SP densities do not represent a valuable pathologic correlate of visual agnosia in this disorder.

Aged↗
PubMed1999

Mobilization of lead from bone in end-stage renal failure patients with secondary hyperparathyroidism.

BACKGROUND: It is now recognized that long-term exposure to even low levels of lead may increase bone lead content. Lead can then be released in toxicologically significant amounts during critical states of increased bone turnover. METHODS: Two patients with end-stage renal failure, one on haemodialysis and the other on continuous ambulatory peritoneal dialysis (CAPD), had been exposed to lead and developed secondary hyperparathyroidism. An edetate calcium disodium (EDTA) test was performed in combination with haemofiltration or CAPD before and after parathyroidectomy. RESULTS: Before parathyroidectomy, both patients had low delta aminolaevulinic acid dehydrase (ALA-D) and high concentrations of chelated lead. After parathyroidectomy, there was a dramatic decrease in chelated lead and the ALA-D returned to normal. CONCLUSION: Secondary hyperparathyroidism increases mobilization of bone lead in dialysis patients with an elevated lead burden. This may cause toxic effects.

Aged↗
PubMed1998

Pathologic correlates of apraxia in Alzheimer disease.

OBJECTIVE: To examine the neuroanatomical correlates of apraxia in Alzheimer disease. PATIENTS: Twenty-three patients with clinically overt Alzheimer disease. DESIGN: Anterograde study and neuropathologic case series. Clinical severity was assessed using the Global Deterioration Scale. Ideomotor praxis was examined on transitive and intransitive movements and meaningless gestures, and dressing ability was evaluated clinically. Constructive praxis was tested using a 3-dimensional figure copying task. Correlations between neurofibrillary tangle and senile plaque densities and praxis test performance were studied using stepwise logistic regression models. SETTING: Studies were conducted at the Psychiatric and Geriatric Hospitals of the University of Geneva School of Medicine, Geneva, Switzerland. MAIN OUTCOME MEASURES: Odds ratios to estimate the associations between neurofibrillary tangle and senile plaque densities in each neocortical area and the presence of ideomotor, dressing, and constructional apraxia. RESULTS: Statistically significant relationships were found between neurofibrillary tangle densities in the anterior cingulate cortex and ideomotor and dressing apraxia and between neurofibrillary tangle densities in the superior parietal, posterior cingulate, and occipital cortex and constructional apraxia. Senile plaque counts did not correlate with praxic performance. CONCLUSIONS: These results suggest that ideomotor and dressing apraxia are associated with mild damage of the anterior cingulate cortex, whereas constructional apraxia is related to the disruption of cortical pathways mediating visuospatial cognition in Alzheimer disease. Senile plaque densities do not represent a valuable pathologic correlate of apraxia in this disorder.

Aged↗
PubMed1998

Enzyme replacement therapy decreases hypergammaglobulinemia in Gaucher's disease.

We report the effects of enzyme replacement therapy in a patient with Gaucher's disease associated with a monoclonal gammopathy. Alglucerase induces a linear decline in immunoglobulin and beta 2-microglobulin levels. This observation suggests that this treatment decreases the chronic antigenic stimulation commonly found in Gaucher's disease.

Adult↗
PubMed1998

[Nervous system borreliosis with pseudo-lymphoma cells in cerebrospinal fluid].

We report the case of a 44-year-old woman, who experienced acute back pains, leg paraesthesia, and diplopia. Analysis of the cerebrospinal fluid revealed, in addition to increased protein and decreased glucose levels, an elevated number of large atypical cells, resembling lymphoma cells. Magnetic resonance imaging of the brain and spine was normal. High levels of antibodies against Borrelia burgdorferi were found in both serum and cerebrospinal fluid. The patient completely recovered with ceftriaxone therapy.

Adult↗
PubMed1995

[Gaucher's disease: current aspects].

Gaucher's disease is an autosomal recessive inherited disorder, characterized by genetic deficiency of lysosomial glucocerebrosidase. Its substrate (glycosylceramide) subsequently accumulates in cells of monocyte/macrophage origin, resulting in enlargement of the spleen and liver, skeletal lesions, and, in the most severe phenotypes, in neurological disorders. Thirty-six mutations have been at present documented in the gene encoding for the glucocerebrosidase, but four of them (N370S, L444P, 84GG and IVS2+1) are really frequent, particularly in ashkenaze population. Gaucher's disease is diagnosed by the presence of Gaucher cells, especially in bone marrow aspirate, and by assessing the glucocerebrosidase activity. The prognosis has been considerably improved by enzyme replacement therapy.

Gaucher Disease↗
PubMed1995

Elevated body lead burden from drinking water in end-stage chronic renal failure.

Delta aminolaevulinic acid dehydratase (ALA-D) who assayed in 66 patients with end-stage renal failure who live in a region where there is a high risk of lead poisoning from drinking water (Vosges mountains). Sixty patients received dialysis and six underwent renal transplantation. Results were compared to those obtained in 366 control subjects with normal renal function hospitalized in a department of Internal Medicine and living in the same geographical area. The ALA-D level was significantly lower in dialysed patients (0.40 +/- 20) than in controls (0.57 +/- 0.31) (P = 0.0014). Transplant recipients had ALA-D levels comparable to subjects with normal renal function (0.59 +/- 0.37). In this high-risk population an EDTA test was performed in 74 subjects (with normal renal function and 17 dialysis patients in combination with haemofiltration for the latter patients. In the two study groups a negative correlation was found between ALA-D and the amount of lead chelated during the 24 h following administration of EDTA (r = -0.77 and -0.88 respectively). In subjects who live in an area of endemic lead poisoning, the incidence of elevated body lead burden from drinking water was similar in the group with normal renal function and in the group of dialysed patients (18.6 and 8.3% respectively). This study shows (i) that in dialysis patients, measurement of ALA-D represents an accurate screening test for lead overload, provided that the lower threshold of normal is lowered from 0.40 to 0.20, and (ii) that diagnosis and treatment are possible by administering EDTA in conjunction with haemofiltration or CAPD.

Aged↗
PubMed1994

[Lead poisoning in pregnancy].

Endemic areas of lead poisoning have recently been rediscovered raising an important public health problem, particularly for pregnant women and their offspring. Theoretically, pregnant women can no longer be exposed to occupational sources with the application of public health regulations but other sources including water contamination, wall paint, industrial wastes and automobile exhaust fumes cannot be ignored. The placental barrier is permeable to free serum lead and levels in cord blood reaches 5 to 10% of the maternal blood level. In addition, lead may be released from maternal bone reserves during pregnancy and thus become a major source of intoxication for the fetus. Lead content in fetal organs increases with gestational age and may affect the nervous system and calcium dependent organs. Moderate lead levels of 100 micrograms/L can inhibit fetal haeme and erythropoiesis. Besides the classical signs of lead poisoning, pregnant women risk spontaneous abortion and increased blood pressure. Manifestations in the fetus and newborn include prematurity, fetal hypotrophy and malformations. Other manifestations are not seen until several years after birth and include retarded mental development and muscular and behaviour disorders. Diagnosis is based on screening tests which should be used in cases of suspected accidental or environmental intoxication. Tests should include assay of zinc protoporphyrins and aminolevulinic acid dehydrase. A search for the source of the contamination should be undertaken when blood levels above 250 micrograms/L are observed. Treatment with metal chelators is not recommendable (except in extreme life-threatening cases) during pregnancy due to their teratogenic effect. Prevention is the only adequate treatment.

Bone and Bones↗
PubMed1994

[Current diagnosis and treatment of lead poisoning].

Lead may be an industrial and an environmental hazard which becomes of greater importance every year. Classical symptoms of plumbism are rare, whenever minor clinical signs increase in frequency. Erythrocyte zinc protoporphyrin and delta-aminolaevulinic acid dehydratase are reliable indicators of the importance of the lead poisoning in individuals. The concentration of lead in blood is also a suitable biological indicator as is EDTA mobilization test. The treatment is based on the use of chelating agents such as calcium EDTA or DMSA, but the only solution is reduction or removal of the sources of lead exposure.

Accidents↗
PubMed1994

Muscle bioenergetics in obese Zucker rats.

The purpose of this study was to investigate the energetic metabolism in obese Zucker rats, using phosphorus nuclear magnetic resonance spectroscopy at rest and during a 2-Hz muscle stimulation and subsequent recovery. Animals were anesthetized with ketamine (150 mg/kg ip). Fed obese rats and 2-day-fasted obese rats were compared with their normally fed and 2-day-fasted lean litter mates. No differences were found between the two groups for ATP, total creatine, phosphocreatine (PCr), and intracellular pH. Starvation in lean rats resulted in a significant fall in inorganic phosphate (Pi), increased resting ADP level, and decreased PCr and ADP recovery after stimulation. The obese rats exhibited a decreased PCr/Pi and increased ADP at rest and a decreased PCr resynthesis and ADP metabolization rate after stimulation. Muscle stimulation in fasted obese rats induced higher PCr depletion and more pronounced acidosis. These results suggest an in vivo mitochondrial metabolism dysfunction in fasted lean as well as in fed and fasted obese rats.

Adenosine Diphosphate↗
PubMed1994

Sarcoid reactions in cystic duct carcinoma.

A diagnosis of sarcoidosis was evoked in a 61-year-old man on clinical and histologic bases. Nevertheless, a bile duct carcinoma was disclosed in association with the discovery of generalized sarcoid-like granulomas. This is only the third time that such an association has been described. HLA-B8, DR3, and DRw52 antigens were found, suggesting that altered immunologic mechanisms could play a role in the pathogenesis of this sarcoid-like reaction.

Bile Duct Neoplasms↗