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Biomedical subjects

M Ben Ali

Publications and source records attributed to M Ben Ali.

6 recordsLinked to original sources
PubMed2006

Formaldehyde-sensitive sensor based on recombinant formaldehyde dehydrogenase using capacitance versus voltage measurements.

A new formaldehyde-selective biosensor was constructed using NAD(+)- and glutathione-dependent recombinant formaldehyde dehydrogenase as a bio-recognition element immobilised on the surface of Si/SiO(2)/Si(3)N(4) structure. Sensor's response to formaldehyde was evaluated by capacitance measurements. The calibration curves obtained for formaldehyde concentration range from 10 microM to 20mM showed a broad linear response with a sensitivity of 31 mV/decade and a detection limit about 10 microM. It has been shown that the output signal decreases with the increase of borate buffer concentration and the best sensitivity is observed in 2.5mM borate buffer, pH 8.40. The response of the created formaldehyde-sensitive biosensor has also been examined in 2.5mM Tris-HCl buffer, and the shift to the positive bias of the C(V) curves along with the potential axis has been observed, but the sensitivity of the biosensor in this buffer is decreased dramatically to the value of 2.4 mV/decade.

Aldehyde Oxidoreductases↗
PubMed2006

Formaldehyde assay by capacitance versus voltage and impedance measurements using bi-layer bio-recognition membrane.

A novel formaldehyde sensitive biosensor based on bacterial formaldehyde dehydrogenase (FDH) as a bio-recognition element has been developed. The bio-recognition membrane had bi-layer architecture and consisted of FDH, cross-linked with albumin, and of the cofactor NAD at a high concentration level (first layer). The second layer was a negatively charged Nafion membrane, which prevented a leakage of negatively charged NAD molecules from the bio-membrane. As transducers, gold electrodes SiO(2)/Si/SiO(2)/Ti/Au and electrolyte-insulator-semiconductor Si/SiO(2) (EIS) structures have been used. Changes in capacitance and impedance properties of the bio-recognition membrane have been used for monitoring formaldehyde concentration in a bulk solution. It has been shown that formaldehyde can be detected within a concentration range from 1 microM to 20mM depending on the type of transduction used, with a detection limit of 1 and 100 microM for gold-based and EIS-based transducers, respectively.

Aldehyde Oxidoreductases↗
PubMed2006

[NK/T-Cell lymphoma of nasopharynx].

OBJECTIVE: Discussion of the clinical and paraclinical features of a rare tumor in the nasopharynx, the NK/T-cell lymphoma, with an emphasis on the implications of Epstein Barr Virus (EBV) in its pathogenesis and prognosis. CASES REPORT: We report the cases of a woman and a man aged 34 and 48, respectively. Clinical presentation was non-specific and diagnosis was established with deep biopsies under general anesthesia. Immunochemistry and in situ hybridization were positive for Epstein Barr virus in tumor cells in both cases. The patients were first treated with chemotherapy (CHOP regimen), then underwent radiotherapy. The first patient achieved complete response at twenty months follow-up. The second patient presented two recurrences which were treated by chemotherapy. He died from acute renal failure during treatment of the second recurrence. CONCLUSION: Diagnosis of NK/T-cell lymphoma may be delayed in the event of non-specific symptoms. Deep biopsies outside necrotic tissue must be obtained. Search for EBV is important as its presence is a factor of poor prognosis.

Adult↗
PubMed2001

Purification and sequence analysis of the atypical maltohexaose-forming alpha-amylase of the B. stearothermophilus US100.

The maltohexaose-forming alpha-amylase, of B. stearothermophilus US100, was purified to homogeneity by a combination of osmotic shock, starch adsorption and anion exchange chromatography. This enzyme has a relative molecular mass of 59 kDa. The analysis of the nucleotide sequence, of the corresponding gene, allowed the identification of a single open reading frame encoding a 549 amino acid protein, exhibiting a large homology to the other B. stearothermophilus alpha-amylases. This homology reaches a maximum with those of DY-5 and DN1792 strains with respectively 3 and 4 aa different over 549. The relatively small differences, between Amy US100 and that of DN1792 strain, take in more importance since we have demonstrated that these enzymes differ essentially by their starch hydrolysis pattern.

Journal Article↗
PubMed2001

[Submandibular lithiasis. Report of 48 cases].

This retrospective study concerned 48 patients treated surgically for sub mandibular lithiasis. Results of medical imaging (plain films, sialography, ultrasonography) are confronted with operative findings. The surgical indications are analysed according to lithiasis localisation.

Adult↗