Biomedical subjects

S Abdallah

Publications and source records attributed to S Abdallah.

11 recordsLinked to original sources

PubMed2005

Non-tuberculous mycobacteria in patients with bronchiectasis.

BACKGROUND: Non-tuberculous mycobacteria (NTM) are ubiquitous environmental organisms. Patients with pre-existing lung damage are susceptible to NTM, but their prevalence in bronchiectasis is unknown. Distinguishing between lung colonisation and disease can be difficult. METHODS: A prospective study of 100 patients with bronchiectasis was undertaken to evaluate the prevalence of NTM in sputum, and a retrospective analysis of clinical, microbiological, lung function and radiology data of our clinic patients with NTM sputum isolates over 11 years was performed. RESULTS: The prevalence of NTM in this population of patients with bronchiectasis was 2%. Patients in the retrospective study were divided into three groups: bronchiectasis+multiple NTM isolates (n=25), bronchiectasis+single isolates (n=23), and non-bronchiectasis+multiple isolates (n=22). Mycobacterium avium complex (MAC) species predominated in patients with bronchiectasis compared with non-bronchiectasis lung disease (72% v 9%, p<0.0001). Single isolates were also frequently MAC (45.5%). Multiple isolates in bronchiectasis were more often smear positive on first sample than single isolates (p<0.0001). NTM were identified on routine screening samples or because of suggestive radiology. No particular bronchiectasis aetiology was associated with an NTM. Pseudomonas aeruginosa and Staphylococcus aureus were frequently co-cultured. Six (25%) of multiple NTM patients had cavities of which five were due to MAC. Half the patients with multiple isolates were treated, mostly due to progressive radiology. CONCLUSIONS: NTM are uncommon in non-cystic fibrosis bronchiectasis. Routine screening identifies otherwise unsuspected patients. MAC is the most frequent NTM isolated.

Adult↗

PubMed2005

Selecting among competing alternatives: selection and retrieval in the left inferior frontal gyrus.

It has been widely argued that the left inferior frontal gyrus (LIFG) is involved in the control of retrieval of information from long-term memory. Recent claims that the LIFG is involved in selecting among semantic alternatives have been challenged on the grounds that the manipulation of selection demands may have been confounded with controlled retrieval. The current study used an event-related functional magnetic resonance paradigm to re-examine the possibility that LIFG activation is involved in selection processes. In order to minimize potential confounding effects of controlled retrieval, we used an automatic retrieval task (picture naming) and held retrieval demands constant, while varying selection demands by way of competitor priming from earlier semantically related trials. We found significant activation in LIFG as a function of increased selection demands; activation centred on two peaks, one in anterior LIFG and a second more superior and posterior region. These data support the view that LIFG plays a role in selection among semantic information, even in the absence of controlled retrieval processes.

Adult↗

PubMed2005

[Pseudotumoral form of abdominal tuberculosis: report of four cases].

PURPOSE: To report the imaging features of four cases of pseudo-tumoral abdominal tuberculosis in order to demonstrate diagnostic difficulties, even in endemic areas, despite expanding imaging modalities. MATERIAL AND METHODS: We have retrospectively reviewed four cases investigated in our hospital between 1998 and 2002. The first case concerned a 2 year and 6 month old boy admitted for a right iliac fossa mass. The other patients were 43 and 48 year old women admitted for epigastric mass and persistent epigastric pain with past history of treated tuberculosis respectively. The last was an 86 year old man investigated because progressive worsening of general health. Sonography (US) and computed tomography (CT) were performed in all four cases. RESULTS: Involvement of the ileocaecal region was noted in three cases. Large intestinal hypervascular mass in the pediatric case, heterogeneous mass with porta hepatis lymph node in the patient with past history of treated tuberculosis, pseudotumoral caecal wall thickening in the third case. The multiloculated pattern of the epigastric mass and its location initially suggested a diagnosis of pancreatic tumor. CONCLUSION: Abdominal tuberculosis is rare even in endemic areas. This diagnosis must be considered when imaging modalities depict a hypervascular soft tissue mass on Doppler examination with peripheral enhancement on CT scan.

Abdomen↗

PubMed2004

Processing objects at different levels of specificity.

How objects are represented and processed in the brain is a central topic in cognitive neuroscience. Previous studies have shown that knowledge of objects is represented in a feature-based distributed neural system primarily involving occipital and temporal cortical regions. Research with nonhuman primates suggest that these features are structured in a hierarchical system with posterior neurons in the inferior temporal cortex representing simple features and anterior neurons in the perirhinal cortex representing complex conjunctions of features (Bussey & Saksida, 2002; Murray & Bussey, 1999). On this account, the perirhinal cortex plays a crucial role in object identification by integrating information from different sensory systems into more complex polymodal feature conjunctions. We tested the implications of these claims for human object processing in an event-related fMRI study in which we presented colored pictures of common objects for 19 subjects to name at two levels of specificity - basic and domain. We reasoned that domain-level naming requires access to a coarser-grained representation of objects, thus involving only posterior regions of the inferior temporal cortex. In contrast, basic-level naming requires finer-grained discrimination to differentiate between similar objects, and thus should involve anterior temporal regions, including the perirhinal cortex. We found that object processing always activated the fusiform gyrus bilaterally, irrespective of the task, whereas the perirhinal cortex was only activated when the task required finer-grained discriminations. These results suggest that the same kind of hierarchical structure, which has been proposed for object processing in the monkey temporal cortex, functions in the human.

Adult↗

PubMed1996

Synthesis and antiplatelet activity of 1-tert-butylamino-3-(3-thienyloxy)-2-propanols.

The synthesis of new 1-tert-butylamino-3-(3-thienyloxy)-2-propanols by two alternative methods is described. Their initial antiplatelet activity evaluation against ADP, adrenaline, and collagen is reported, and the preliminary structure-activity relationships are established. The appropriateness of further pharmacological investigations, especially for the best compound of the series 1f, is indicated.

1-Propanol↗

PubMed1995

Anticonvulsant activity of aryl and hetarylsulfonylhydrazones.

A series of aryl and hetarylsulfonylhydrazones of aromatic aldehydes were tested for acute toxicity and anticonvulsant activity in mice. Some of these compounds were effective in the MES, pentetrazol and strychnine tests. Thiophene derivatives were the most active terms of the series.

Animals↗

PubMed1994

Numerical simulation of unsteady laminar flow through a tilting disk heart valve: prediction of vortex shedding.

Heart valves induce flow disturbances which play a role in blood cell activation and damage, but questions of the magnitude and spatial distribution of fluid stresses (wall shear stress and turbulent stress) cannot be readily addressed with current experimental techniques. Therefore, a numerical simulation procedure for flow through artificial heart valves is presented. The algorithm employed is based on the Navier-Stokes equations in generalized curvilinear coordinates with artificial compressibility for coupling of velocity and pressure. The algorithm applies a finite-difference technique on a body-conforming composite grid around the heart valve disk on which the numerical simulations are performed. Steady laminar flow over a backward-facing step and unsteady laminar flow inside a square driven cavity are computed to validate the algorithm. Two-dimensional, time-accurate simulation of flow through a tilting disk valve with a steady upstream Reynolds number as high as 1000 reveals the complex behavior of 'vortex shedding'. By scaling the results at the Reynolds number of 1000 to peak systolic flow conditions, the maximum value of shear stress on the valve disk is estimated to be 770 dyn cm-2. The 'apparent' Reynolds stress associated with vortex shedding is estimated to be as high as 3900 dyn cm-2 with a vortex shedding frequency of about 26 Hz. The 'apparent' Reynolds stress value is of similar magnitude as reported in experiments but would not be expected to damage blood cells because the spatial scales associated with vortex shedding are much larger than blood cell dimensions.

Algorithms↗

PubMed1994

Homodimeric murine interleukin-3 agonists indicate that ligand dimerization is important for high-affinity receptor complex formation.

Homodimeric murine interleukin 3 (mIL-3) agonists were generated by intermolecular cystine-bonding. Steady-state binding assays and association kinetics performed at 4 degrees C using these agonists revealed specific binding to both the high- and low-affinity receptor. DSS-mediated crosslinking studies performed at 4 degrees C with agonist concentrations compatible with high-affinity receptor complex formation allowed to detect protein complexes of the alpha chain, the beta chain(s) and the high-affinity receptor complex migrating with apparent molecular weights of 90 kDa, 140 kDa, and above 180 kDa, respectively. In contrast, monomeric mIL-3 was crosslinked to the alpha chain receptor only unless high concentrations were used. Binding studies performed at 4 degrees C revealed a positive cooperative interaction of monomeric mIL-3 with the low-affinity receptor. Proliferation studies and association kinetics performed at 37 degrees C showed that under physiological conditions these agonists were at least 2- to 3-fold more potent than monomeric mIL-3. We therefore propose that dimerization of mIL-3 may be involved in high-affinity receptor complex formation.

Animals↗

PubMed1992

Intermolecular cystine-bonding of murine interleukin 2 indicates that ligand dimerization is important for the formation of the high-affinity receptor complex.

Interleukin 2 is thought to be active as a monomeric protein. As the nonessential Cys-140 of murine interleukin 2 (mIL2) is located in the hydrophobic interface of the amphiphilic F domain it was successfully used to stabilize hydrophobic amino acid contacts between two mIL2 cores yielding biologically active cystine-bonded dimeric mIL2. (3H) thymidine incorporation assays with intermolecular cystine-bonded or monomeric mIL2 revealed almost identical median effective concentrations (EC50) and high-affinity dissociation constants (Kdh), respectively. Comparative binding and internalization assays suggest that one cystine-bonded dimeric or two monomeric mIL2 molecules bind to the high-affinity receptor complex. Furthermore, DSS concentration-dependent crosslinking studies using monomeric mIL2 revealed four membrane-derived protein-complexes with apparent molecular weights of about 70 kDa, 85 kDa, 95 kDa and 100 kDa, respectively, showing that both mIL2 receptor chains may be crosslinked to a monomeric or dimeric ligand molecule, respectively. We therefore propose that dimerization of murine interleukin 2 occurring either in solution at concentrations above the low-affinity dissociation constant or at the low-affinity receptor is important for regulation of high-affinity complex formation and signal transduction.

Amino Acid Sequence↗

PubMed1990

The effect of fasting on the activation in vivo of the insulin receptor kinase.

Fasting causes insulin resistance in liver and fat, and increases insulin sensitivity in muscle. We studied the response in vitro and in vivo to insulin of the insulin receptor tyrosine kinase in muscle and liver from 72 h fasted and control rats. Insulin was injected intraperitoneally together with glucose, and blood and tissue samples were obtained 0, 5, 15 and 30 min later. Basal serum glucose and insulin levels were significantly higher in control than in fasting rats. Serum glucose rose to approximately 300 mg/dl at 5 min and then progressively declined without hypoglycaemia. Receptors were prepared from whole tissue by wheat germ lectin affinity chromatography. 125I-insulin binding to purified receptors was increased by fasting in both muscle (18%) and liver (50%). In untreated fasting and control animals, muscle and liver insulin receptor tyrosine kinase activity was stimulated to similar levels by insulin added in vitro. With only insulin treatment in vivo, muscle receptor tyrosine kinase behaved similarly in fasting and control animals with maximal activation at 15 min post injection. In liver, insulin in vivo stimulated receptor tyrosine kinase activity maximally at 5 min post injection in both fasting and control, but in fasting animals the treatment in vivo caused a significantly larger and more prolonged activation of the enzymic activity, possibly due to a decrease in the rate of dephosphorylation and deactivation of the beta subunits.

Animals↗

PubMed1985

Twice or four times daily beclomethasone dipropionate in mild stable asthma?

A double-blind cross-over study lasting 16 weeks was conducted to establish if a twice daily regimen of beclomethasone dipropionate (BDP) was as effective in controlling asthma as a four times daily regimen. The patient's need for inhaled steroids (100 mcg BDP qds) was confirmed prior to entering the study by deterioration of peak expiratory flow rates and/or increased bronchodilator usage during a single-blind placebo period of 6 weeks. Thirty six asthmatics were eligible to enter the study and completed both treatment periods. Daily record cards of symptom scores, four times daily peak expiratory flow rate measurements and inhaled bronchodilator usage were recorded throughout the study. There was no significant difference between the mean PEFR measurements taken four times each day and the variability in PEFR, between the two treatment groups. Symptom scores for cough, wheeze, breathlessness and overall disability also showed no significant difference. Symptomatic inhaler usage for the two groups was similar. Lung function measurements of FEV1, FVC and VC were almost identical; FEV1 being 2.1 l on twice daily regimen and 2.2 l on four times daily regimen. A slight variation was observed in PEFR taken at the end of each treatment period at the clinic visits, being 361 l/min on twice daily and 380 l/min on four times daily drug dosage. In stable asthmatics, the control of asthma measured both symptomatically and by daily lung function was independent of dosing schedule, but twice daily treatment may well lead to better compliance.

Adult↗