Biomedical subjects

I Ali

Publications and source records attributed to I Ali.

At least 19 recordsLinked to original sources

PubMed2006

Polymer packaging and ejection in viral capsids: shape matters.

We use a mesoscale simulation approach to explore the impact of different capsid geometries on the packaging and ejection dynamics of polymers of different flexibility. We find that both packing and ejection times are faster for flexible polymers. For such polymers a sphere packs more quickly and ejects more slowly than an ellipsoid. For semiflexible polymers, however, the case relevant to DNA, a sphere both packs and ejects more easily. We interpret our results by considering both the thermodynamics and the relaxational dynamics of the polymers. The predictions could be tested with biomimetic experiments with synthetic polymers inside artificial vesicles. Our results suggest that phages may have evolved to be roughly spherical in shape to optimize the speed of genome ejection, which is the first stage in infection.

Capsid↗

PubMed2005

Polymer translocation: the effect of backflow.

We investigate the effect of backflow on the translocation dynamics of short, flexible polymer chains threading through a small hole in a wall. We find that hydrodynamic interactions between polymer beads play an important role in determining the translocation time distribution: as a monomer moves through the hole it sets up a flow field which transfers momentum to neighboring monomers, thus helping them to move in the same direction. Translocation times are calculated by using the velocity-Verlet algorithm to solve the equations of motion of a polymer which moves in a fluid described by the stochastic rotation algorithm, a particle-based Navier-Stokes solver.

Algorithms↗

PubMed2005

Hemolysis of human red blood cells by riboflavin-Cu(II) system: enhancement by azide.

Photoactivated riboflavin in the presence of Cu(II) generates reactive oxygen species (ROS) which can hemolyze human red blood cells (RBC). In the present work we examined the effect of sodium azide (NaN3) on RBC in the presence of riboflavin and Cu(II). The addition of NaN3 to the riboflavin-Cu(II) system enhanced K+ loss and hemolysis. The extent of K+ loss and hemolysis were time and concentration dependent. Bathocuproine, a Cu(I)-sequestering agent, inhibited the hemolysis completely. Among various free radical scavengers used to identify the major ROS involved in the reaction, thiourea was found to be the most effective scavenger. Thiourea caused almost 85% inhibition of hemolysis suggesting that *OH is the major ROS involved in the reaction. Using spectral studies and other observations, we propose that when NaN3 is added to the riboflavin-Cu(II) system, it inhibits the photodegradation of riboflavin resulting in increased *OH generation. Also, the possibility of azide radical formation and its involvement in the reaction could not be ruled out.

Azides↗

PubMed2005

Dependence of radiochromic film response kinetics on fractionated doses.

Because the rate and magnitude of the post-exposure growth of the MD-55 radiochromic film (RCF) dosimeter response depends significantly on total dose, we have investigated the influence of fractionation and protracted dose delivery on optical density (OD) as a function of total dose and the exposure-to-densitometry time interval for a 633-nm scanning laser densitometer. Both measurements and models demonstrate that fractionation induces transient OD over responses, which can be as large as 20%, but rapidly dissipate within 24 h. However, the superposition model predicts 2-5% over responses that persist as long as 700 h.

Brachytherapy↗

PubMed2005

Decreased antioxidant enzyme expression and increased oxidative damage in erosive lichen planus of the vulva.

The aim of this study was to investigate whether increased oxidative stress occurs in erosive lichen planus of the vulva. Skin biopsies from six patients with untreated, histologically confirmed erosive lichen planus of the vulva were examined immunohistochemically using antibodies against antioxidant enzymes. The protein-bound lipid peroxidation products malondialdehyde (MDA) and 4-hydroxynonenale (4-HNE) and the oxidative DNA damage marker 8-hydroxy-2'-deoxyguanosine (8-OHdG) were investigated. Protein carbonyls as markers of protein oxidation were visualised using the dinitrophenylhydrazone (DNPH) method. Normal vulval tissues from 12 subjects served as controls. In vulval lichen planus tissue the enzymatic antioxidant defence was found to be significantly decreased in the epidermal layers. Furthermore, a significant increase of lipid peroxidation products and oxidative DNA damage was found within the epidermis. Protein oxidation occurred predominantly in the papillary dermis. This is the first study to demonstrate a decreased antioxidant defence and increased oxidative damage to lipids, DNA and proteins in lichen planus. These oxidative modifications point to pathophysiological alterations mainly within the basal cell layers of the epidermis and at the dermoepidermal junction. Further studies are warranted to investigate the potential role of oxidative stress in the development of autoimmunity in this disease.

8-Hydroxy-2'-Deoxyguanosine↗

PubMed2004

Dynamics of polymer packaging.

We use the stochastic rotation dynamics algorithm to investigate the packaging of flexible and semiflexible polymers into a capsid that is permeable to solvent molecules. The model takes into account hydrodynamic interactions arising due to local flow. The flexible chain maintains a random configuration as it is being fed into the capsid, in contrast to the semiflexible chain, whose configuration is initially spool-like, becoming more random at high packing. We measure the packing rate, which is found to decrease with the percentage of the chain packed and highlight the difference between the flexible and semiflexible chains. Reflecting experiments, we find pauses in the packing process for individual chains as the motor loses grip of the fluctuating beads. We also find that hydrodynamics is important, in that the packaging rate is faster when flow is included.

Journal Article↗

PubMed2004

Removal of chlorophenols from wastewater using red mud: an aluminum industry waste.

Removal of toxic substances from wastewaters using low-cost alternatives to activated carbon is an important area in environmental sciences. Efforts have been made to convert red mud, an aluminum industry waste, into a low-cost potential adsorbent, and the final material has been used for the removal of phenol, 2-chlorophenol, 4-chlorophenol, and 2,4-dichlorophenol from wastewater. It is pertinent to mention that phenol and chlorophenols are highly carcinogenic and an priority class of pollutants which needs to be removed from effluents before discharge into water bodies. 2,4-Dichlorophenol and 4-chlorophenol are sorbed by the developed adsorbent up to 94-97%, while the removal of 2-chlorophenol and phenol was up to 50-81%. The removal of phenols and its derivatives was achieved up to 98% by column experiments at a flow rate of 0.5 mL/min. The order of removal was 2,4-dichlorophenol > 4-chlorophenol > 2-chlorophenol > phenol, and the removal takes place through a particle diffusion mechanism. The adsorption was found to be endothermic in nature and follows both Langmuir and Freundlich models. Estimation of the phenols was carried out by capillary electrophoresis, and the adsorbent has been successfully tried for the removal of chlorophenols from a wastewater. The developed process is very useful, economic, rapid, and reproducible for the removal of phenols.

Adsorption↗

PubMed2004

Thermodynamic properties of He-H2 fluid mixtures over a wide range of temperatures and pressures.

The effect of pressure P and temperature T on the properties of mixing of helium-hydrogen (He-H2 ) fluid mixture is studied based on statistical mechanical perturbation theory. The constituent species are considered to be interacting via a pair potential consisting of short range repulsion and a long range attraction which has been included through a double Yukawa (DY) potential. He and H2 are the lightest elements; therefore, the quantum effect is included via first-order quantum correction in the framework of Wigner-Kirkwood expansion. The dimerization of the H2 molecule is treated as a hard convex body fluid for which the equation of state (EOS) can be derived from hard sphere system based on scaled particle theory. An advanced and most recent EOS has been used for our investigation. The use of the DY potential, which can readily be simulated to empirical potentials, has enabled us to obtain analytical expressions for attractive and quantum energy contributions in terms of Laplace transforms. With a view to ensure internal consistency of the various thermodynamic functions to extract information on segregation and order in the mixture, different functions, such as compressibility factor, Gibbs free energy of mixing, entropy of mixing, and concentration fluctuations in the long wavelength limit, have been calculated as functions of composition of the mixture over an extended region of P and T. The results suggest that segregation, heterocoordination, or both may occur in the He-H2 mixture depending upon its composition, pressure, and temperature.

Journal Article↗

PubMed2004

Oxidative stress is implicated in the pathogenesis of lichen sclerosus.

BACKGROUND: Lichen sclerosus (LS) is a chronic inflammatory skin disease of unknown aetiology which can be associated with secondary malignancies. Recent evidence supports an autoimmune basis for this disorder, as demonstrated by autoantibodies to extracellular matrix protein 1 (ECM-1). The pathophysiological mechanisms leading to autoimmunity and carcinogenesis are poorly understood. OBJECTIVES: We hypothesized that oxidative stress, which has been demonstrated to be involved in the pathogenesis of several autoimmune and malignant disorders, contributes to these processes in LS. METHODS: Skin biopsies from 16 patients with untreated, histologically confirmed vulval LS were examined immunohistochemically using antibodies against the lipid peroxidation products malondialdehyde and 4-hydroxynonenale and against the oxidative DNA damage marker 8-hydroxy-2'-deoxyguanosine. Protein carbonyls as markers of protein oxidation were visualized using the dinitrophenylhydrazone method. Expression of antioxidant enzymes was investigated. Normal vulval tissue from 16 subjects served as control. RESULTS: In vulval LS tissue a significant increase of lipid peroxidation products was found particularly within the basal cell layers of the epidermis, thus colocalizing with ECM-1. Oxidative DNA damage was detected throughout LS biopsies. Intriguingly, protein oxidation was significantly increased within the dermis of LS lesions, indicating oxidative protein damage in the areas of sclerosis and inflammation. The enzymatic antioxidant defence in LS was found to be significantly disturbed. CONCLUSIONS: This is the first study to demonstrate oxidative damage to lipids, DNA and proteins in LS, revealing a novel pathophysiological mechanism which may contribute to sclerosis, autoimmunity and carcinogenesis. Therapeutic strategies using antioxidants might be a useful new approach in the treatment of LS and could also help to prevent secondary malignancies.

Aged↗

PubMed2004

Comparison of the OptiMAL rapid antigen test with field microscopy for the detection of Plasmodium vivax and P. falciparum: considerations for the application of the rapid test in Afghanistan.

To establish the sensitivity and specificity of a batch of 'OptiMAL 48' rapid antigen tests procured by the World Health Organization in Afghanistan, a sample was tested, in parallel with routine, microscopical diagnosis, at basic health units (BHU) within Afghan refugee camps in Pakistan. The results of both methods of field diagnosis were compared with those of cross-checking microscopy at a reference laboratory, which were taken as the 'gold standard'. Out of 499 patients examined, 36% were diagnosed as malaria cases by field microscopy and 34% by the rapid test. For the OptiMAL 48 test, cross-checking of the corresponding smears at the reference laboratory gave a sensitivity of 79.3% and a specificity of 99.7% for Plasmodium falciparum and corresponding values of 86.1% and 98.7% for P. vivax infections. The performance of the field microscopy was better, with a sensitivity and specificity of 85.2% and 99.7% for P. falciparum, and 90.4% and 98.7% for P. vivax, respectively. These results show that the performance of OptiMAL 48 is adequate for acute- and post-emergency situations when the alternative is just clinical diagnosis. However, in the developing health system of Afghanistan, the main focus should be on the expansion of the existing network for microscopical diagnosis and quality control, to meet the needs of a stable situation. Rapid antigen tests are more suited to investigations of outbreaks in remote situations, where health services are deficient or absent.

Afghanistan↗

PubMed2004

Enantiomeric separation of glutethimide derivatives using a Ceramospher RU-2 column.

The enantiomeric resolution of p-acetylaminoglutethimide and p-nitroglutethimide was achieved on a Ceramospher RU-2 column using methanol as the mobile phase. The flow rates of the mobile phase were 1.0 and 0.5 mL/min for p-acetylaminoglutethimide and p-nitroglutethimide, respectively, with UV detection at 254 nm. The values of alpha of the resolved enantiomers of p-acetylaminoglutethimide and p-nitroglutethimide were 1.63 and 1.24 while the values of Rs were 1.44 and 0.86 respectively. The possible chiral mechanism was the formation of transient diastereomeric intermediates between the enantiomers and the chiral selector (1,10-phenanthroline) ruthenium II complex which was stabilized by pi-pi interactions.

Anticonvulsants↗

PubMed2003

Equilibrium uptake and sorption dynamics for the removal of a basic dye (basic red) using low-cost adsorbents.

Waste carbon slurries (generated in fertilizer plants) and blast furnace slag (generated in steel plants) have been converted into low-cost potential adsorbents. The adsorbents have been characterized and tried for the removal of the dye basic red from wastewater. Studies were performed at different pH to find the pH at which maximum adsorption occurs. Equilibrium isotherms were determined to assess the maximum adsorption capacity of the adsorbents. Adsorption capacities are compared for activated carbon developed from fertilizer waste and activated slag developed from blast furnace waste. The adsorption data are correlated with Freundlich and Langmuir isotherms in each system. The kinetics of adsorption depends on the adsorbate concentration and the physical and chemical characteristics of the adsorbent. Studies were conducted to delineate the effect of pH, temperature, initial absorbate concentration, particle size of the adsorbent, and solid-to-liquid ratio. The adsorption of basic red was found to be endothermic and first-order in nature.

Journal Article↗

PubMed2003

Dependence of radiochromic film optical density post-exposure kinetics on dose and dose fractionation.

Radiochromic film (RCF) has been shown to be a precise and accurate secondary planar dosimeter for acute exposure radiation fields. However, its application to low dose-rate brachytherapy has been questioned because of possible dose-rate effects. To address this concern, we have measured the optical density (OD) of Model 55-2 RCF as a function of time (interval between the completion of irradiation and densitometry using a 633 nm laser scanner) following exposure (from less than 1 hour to 90 days) for single and split doses from 1 Gy to 100 Gy. Our work demonstrates that film darkening as a function of post-irradiation time depends significantly on total dose, with films exposed to lower doses developing faster than films given higher doses. At 1 Gy, the OD 90 days after exposure is 200% larger than that measured 1 h after exposure compared to a 20% increase over 90 days for doses larger than 20 Gy. An empirical model with time-independent, fast and slow growth terms was used to fit single exposure data. The dependence of the resulting best-fit parameters on dose was investigated. Splitting the dose into two fractions (20 Gy followed by doses of 1-80 Gy 24 h later) results in modest post-irradiation time-dependent changes in the total optical density (at most 15% at small doses), which dissipates within 20 hours following the second exposure. This experimental finding is consistent with the predictions of a simple cumulative dose superposition model. Overall, both experimental and empirical modeling suggest that dose-rate effects may be relatively small despite the strong dependence of film darkening kinetics on total dose. However, more experimental evaluation of radiochromic film response dependence on dose rate and dose-time-fractionation patterns is needed.

Brachytherapy↗

PubMed2003

Mucous membrane pemphigoid: nasal and laryngeal manifestations.

Mucous membrane pemphigoid (MMP) is a sub-epithelial blistering disease that primarily involves mucosal surfaces but may also involve the skin. Clinically, it appears as vesiculobullous lesions of the oral cavity and eyes, but other tissues such as the nasopharyngeal and laryngeal mucosa can also be affected. Ultimately, scarring and airway stenosis may occur. The condition should be managed by a multidisciplinary team led by a dermatologist. Immunosuppressive therapy forms the mainstay of treatment, with surgery having both a diagnostic role and a use in the treatment of complications such as airway obstruction. There must be a low threshold of suspicion for laryngeal involvement in this group of patients, so that prompt action can be taken. Once laryngeal stenosis has occurred repeated endoscopic laser excision of scar tissue can be used to maintain an adequate airway. Adjuvant use of mitomycin-C can be used beneficially in the treatment of laryngeal complications of MMP.

Adjuvants, Immunologic↗

PubMed2002

Bupropion (Zyban) toxicity.

Bupropion is a monocyclic antidepressant structurally related to amphetamine. Zyban, a sustained-release formulation of bupropion hydrochloride, was recently released in Ireland, as a smoking cessation aid. In the initial 6 months since it's introduction, 12 overdose cases have been reported to The National Poisons Information Centre. 8 patients developed symptoms of toxicity. Common features included tachycardia, drowsiness, hallucinations and convulsions. Two patients developed severe cardiac arrhythmias, including one patient who was resuscitated following a cardiac arrest. All patients recovered without sequelae. We report a case of a 31 year old female who required admission to the Intensive Care Unit for ventilation and full supportive therapy, following ingestion of 13.5g bupropion. Recurrent seizures were treated with diazepam and broad complex tachycardia was successfully treated with adenosine. Zyban caused significant neurological and cardiovascular toxicity in overdose. The potential toxic effects should be considered when prescribing it as a smoking cessation aid.

Adult↗

PubMed2002

Thermodynamic study of the enantiomeric resolution of flurbiprofen by HPLC using Chiralpak AD-RH column.

The chiral resolution of (+/-)-flurbiprofen was achieved using water-acetonitrile (60:40, v/v) containing 0.1% acetic acid on a Chiralpak AD-RH column at 20 degrees C. The enantio-resolution was studied with different percentages of acetonitrile. Thermodynamic parameters (enthalpy, entropy and free energy) were calculated by carrying out the enantio-resolution experiments at 0 to 60 degrees C. The enantio-resolution was found to be exothermic in nature. Attempts have been made to explain the mechanism of chiral resolution of flurbiprofen on the Chiralpak AD-RH column.

Chromatography, High Pressure Liquid↗

PubMed2001

Photoelectron diffraction mapping: molecules illuminated from within.

We demonstrate the use of a multiparticle coincidence technique to image the diffraction of an electron wave whose source is placed at a specific site in a free molecule. Core-level photoelectrons are used to illuminate the molecule from within. By measuring the vector momenta of two molecular fragments and the photoelectron, a richly structured electron diffraction pattern is obtained in a body-fixed frame of the randomly oriented molecule in the gas phase. We illustrate this technique for CO, creating a photoelectron from the C(1s) shell and scanning its energy from zero to 30 eV.

Journal Article↗

PubMed2001

Environmental exposure of the pediatric age groups in Cairo City and its suburbs to cadmium pollution.

In a trial to assess the exposure of subjects in the pediatric age group to cadmium (Cd) pollution, serum Cd was estimated by atomic absorption spectrometry in 405 subjects, birth-18 years old, from Cairo City and its suburbs. Serum Cd mean concentrations were: 0.92 microg/l in 32 neonates (birth-4 weeks); 1.33 microg/l in 70 infants (4 weeks-2 years); 1.11 microg/l in 100 children in the preschool period (2-6 years); 1.34 microg/l in 103 primary school children (6-12 years); and 1.24 microg/l in 100 adolescents (12-18 years). In neonates, serum Cd was higher in babies with weights and heights that remained below the 5th percentile for age. Breast-fed infants had a serum Cd geometric mean level (1.25 microg/l) that was not in accordance to that of their mothers' milk (0.52 microg/l, P < 0.001), suggesting alternative routes of exposure. Environmental tobacco-smoke exposure was the most important determinant of Cd status in the school-aged children, the geometric mean being 1.42 microg/l in passive smokers vs. 1.2 microg/l in non-exposed children (P < 0.05). Moreover, adolescents who were active smokers had a significantly higher serum Cd level (1.7 microg/l) as compared to non-smokers (1.2 microg/l). Gender did influence the Cd status in adolescents, being higher among males, probably related to smoking, or to the difference in lifestyle of adolescents according to gender in the community. Alpha-1-microglobulinuria was accompanied by a higher serum Cd concentration in the group of adolescents only, suggesting a subclinical renal effect after several years of cumulative exposure. The residential classification, whether urban or suburban, did not influence the serum Cd status; neither did the present or past history of bronchial asthma. These findings certainly justify further evaluation of the problem of Cd pollution among Cairene individuals, knowing the long-term consequences of exposure to it. Systematic efforts for the proper disposal of Cd wastes and prevention of smoking in public places are recommended.

Adolescent↗