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Biomedical subjects

S Ammar

Publications and source records attributed to S Ammar.

At least 19 recordsLinked to original sources
PubMed2001

Conducting-polymer electrochemical switching as an easy means for control of the molecular properties of grafted transition metal complexes.

Copper(II) 3',4'-bis(N,N'-oxamato)terthiophene has been synthesized and electropolymerized. The copper(II)-complex centers are not affected by the polymerization process, which involves coupling between Calpha carbon atoms of the terthiophene units and leads to a new conjugated polymer consisting of polythiophene chains bearing bis(oxamato)-Cu(II) groups regioregularly grafted onto the polymer backbone. The polymer is stable with respect to polythiophene electroactivity, and no demetallation or modification of the Cu oxidation state occurs over a large potential range. In this material, the two moieties exhibit direct electronic interaction, which makes it possible to use the conductive polymer backbone as a molecular wire or a nanocontact capable of inputting to the bis(oxamato)-Cu(II) groups through the polythiophene-switching reaction. FTIR, XPS, and XAS spectroscopies have been used to study the effect of the state of the conducting polymer upon the properties of the copper(II) center (electron density, ligand field strength, size of cavity, force constants of some bonds). These properties can be controlled to some extent by the potential applied to this device. From the point of view of the copper(II) center, this effect is similar to the grafting of substituents with various electronic properties.

Journal Article↗
PubMed2001

Tablet fluoridation influences the calcification of primary tooth pulp.

This study was conducted to determine the influence of long-term tablet fluoridation on primary pulp calcification by light microscopy. Twenty-four caries-free primary molars (after continuous postpartally initiated 1- to 10-year tablet fluoridation) were compared to 17 primary molars of children without fluoride prophylaxis. Pulp calcification in children with tablet fluoridation was significantly more frequent and more pronounced than in untreated children (p = 0.001). Besides the known pulp stones, the prophylaxis group evidenced a special form of calcification consisting of fibrodentin-like hard tissue not observed in the untreated children. These hard tissue bodies developed "intramurally" on the pulp floor and the inside of the dental roots with an irregular extramural spread into the coronal and radicular pulp by displacement and fibrotization of the pulp tissue. Moreover, some of the teeth had more or less extensive areas of interglobular dentin. The affected teeth were ankylosed in the area of the bi- and trifurcation and on the inside of the roots and were thus infra-occluded. Although the duration of tablet fluoridation has no statistically significant influence on pulp calcification, there is a correlation between extensive pulp calcification, postnatally initiated fluoride prophylaxis and the infraocclusion of primary molars.

Child↗
PubMed2001

Root growth and lignification of two wheat species differing in their sensitivity to NaCl, in response to salt stress.

Application of a 100-mM NaCl salt stress to wheat seedlings of a salt-tolerant (Triticum durum var. Ben Béchir) and a salt-sensitive (Triticum aestivum var. Tanit) species decreases the fresh and dry weights of roots especially in the salt-sensitive species, and slightly increases the ratio of dry to fresh weight, especially in the salt-resistant species. All peroxidase activities are increased by salt stress, the water-soluble peroxidase activity being increased much more in the salt-sensitive than in the salt-tolerant species, while the opposite result is observed with the cell-wall peroxidase activity. Some water-soluble peroxidases have been hypothesised to have auxin oxidase activity (which might explain the effect observed on the root biomass), while the cell-wall peroxidases would be involved in lignification. Histochemical observation confirms a more intense lignification in the root cells of the salt-tolerant species compared to the sensitive species, under the effect of NaCl.

Kinetics↗
PubMed1998

Modelling behavioral syndromes using Bayesian networks.

In this paper Bayesian networks modelling is applied to a multidimensional model of depression. The characterization of the probabilistic model exploits expert knowledge to associate latent concentrations of neurotransmitters and symptoms. An evolution perspective is also considered. Specific criteria are introduced to detect the influence of the latent variable on the observation of symptoms. The Bayesian analysis is carried out using Gibbs sampling technique which is implemented in the BUGS software. The estimation phase leads to the selection of symptoms entering into the definition of behavioral syndromes. Results on real data are discussed. The last section deals with simulation experiments. Simulation results confirm our methodological choices. Results of the paper can enlarge to the central problem of the management of latent variables in Bayesian networks modelling.

Artificial Intelligence↗
PubMed1998

Ibn Al Jazzar and the Kairouan medical school of the tenth century AD.

This brief account of the Tunisian physician Ibn Al Jazzar heralds the Congress of the International Society for the History of Medicine to be held in his native country in September 1998. His life work reveals him as a pioneer in distinguishing the art of medicine and pharmacy.

Arab World↗
PubMed1996

Genital Chlamydia trachomatis infection in Egyptian women: incidence among different clinical risk groups.

OBJECTIVE: To investigate genital Chlamydial infection incidence among high risk clinical conditions in Egyptian women. METHODS: A case control study in Ain Shams University Hospital involving 501 patients with cervicitis (n = 58), abnormal cervical smear (n = 256), tubal infertility (n = 85), ectopic pregnancy (n = 22), preterm labour (n = 80) and 192 controls. Active cervical Chlamydial infection was diagnosed using direct immunofluorescent technique. Data were analyzed by Chi-square (chi 2) and Z tests. RESULTS: Significant increase of Chlamydial infection among different clinical conditions compared to controls. The percentage of positive chlamydial infection was 79.3% among cervicitis group, 33.3% among subjects with inflammatory smear, 75.2% among those with cervical condyloma, 82.6% among those with cervical intraepithelial neoplasia, 51.8% among tubal infertility subjects, 77.2% among ectopic patients and 56.3% among subjects with preterm labour. CONCLUSION: The incidence of Chlamydial infection in these high risk Egyptian patients is relatively high. Emperical treatment is recommended as the diagnosis is costly and usually not available.

Case-Control Studies↗
PubMed1992

Theoretical considerations and perspectives on the onset of action of moclobemide.

The aim of this paper is to focus on methodological problems related to clinical studies on the onset of action of antidepressants, especially moclobemide. The methodological discussion proposed focuses on: --global efficacy as a function of time; --proposals for a specific approach to the study of the onset of action; --quality of the response and onset of action; --the dimensional level and the onset of action.

Antidepressive Agents↗