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Search Results: 1 - 10 of 374 matches for " Usama Ramadan Abdelmohsen "
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Antioxidant and Anti-Protease Activities of Diazepinomicin from the Sponge-Associated Micromonospora Strain RV115
Usama Ramadan Abdelmohsen,Matthias Szesny,Eman Maher Othman,Tanja Schirmeister,Stephanie Grond,Helga Stopper,Ute Hentschel
Marine Drugs , 2012, DOI: 10.3390/md10102208
Abstract: Diazepinomicin is a dibenzodiazepine alkaloid with an unusual structure among the known microbial metabolites discovered so far. Diazepinomicin was isolated from the marine sponge-associated strain Micromonospora sp. RV115 and was identified by spectroscopic analysis and by comparison to literature data. In addition to its interesting preclinical broad-spectrum antitumor potential, we report here new antioxidant and anti-protease activities for this compound. Using the ferric reducing antioxidant power (FRAP) assay, a strong antioxidant potential of diazepinomicin was demonstrated. Moreover, diazepinomicin showed a significant antioxidant and protective capacity from genomic damage induced by the reactive oxygen species hydrogen peroxide in human kidney (HK-2) and human promyelocytic (HL-60) cell lines. Additionally, diazepinomicin inhibited the proteases rhodesain and cathepsin L at an IC 50 of 70–90 μM. It also showed antiparasitic activity against trypomastigote forms of Trypanosoma brucei with an IC 50 of 13.5 μM. These results showed unprecedented antioxidant and anti-protease activities of diazepinomicin, thus further highlighting its potential as a future drug candidate.
Isolation, Phylogenetic Analysis and Anti-infective Activity Screening of Marine Sponge-Associated Actinomycetes
Usama Ramadan Abdelmohsen,Sheila M. Pimentel-Elardo,Amro Hanora,Mona Radwan,Soad H. Abou-El-Ela,Safwat Ahmed,Ute Hentschel
Marine Drugs , 2010, DOI: 10.3390/md8030399
Abstract: Terrestrial actinomycetes are noteworthy producers of a multitude of antibiotics, however the marine representatives are much less studied in this regard. In this study, 90 actinomycetes were isolated from 11 different species of marine sponges that had been collected from offshore Ras Mohamed (Egypt) and from Rovinj (Croatia). Phylogenetic characterization of the isolates based on 16S rRNA gene sequencing supported their assignment to 18 different actinomycete genera representing seven different suborders. Fourteen putatively novel species were identified based on sequence similarity values below 98.2% to other strains in the NCBI database. A putative new genus related to Rubrobacter was isolated on M1 agar that had been amended with sponge extract, thus highlighting the need for innovative cultivation protocols. Testing for anti-infective activities was performed against clinically relevant, Gram-positive ( Enterococcus faecalis, Staphylococcus aureus) and Gram-negative ( Escherichia coli, Pseudomonas aeruginosa) bacteria, fungi ( Candida albicans) and human parasites ( Leishmania major, Trypanosoma brucei). Bioactivities against these pathogens were documented for 10 actinomycete isolates. These results show a high diversity of actinomycetes associated with marine sponges as well as highlight their potential to produce anti-infective agents.
Manufacturing and in vivo inner ear visualization of MRI traceable liposome nanoparticles encapsulating gadolinium
Jing Zou, Rohit Sood, Sanjeev Ranjan, Dennis Poe, Usama A Ramadan, Paavo KJ Kinnunen, Ilmari Pyykk?
Journal of Nanobiotechnology , 2010, DOI: 10.1186/1477-3155-8-32
Abstract: Measurements of relaxivities (r1 and r2) showed that LPS+Gd-DOTA had efficient visible signal characteristics for MRI. In vivo studies demonstrated that LPS+Gd-DOTA with 130 nm size were efficiently taken up by the inner ear at 3 h after transtympanic injection and disappeared after 24 h. With intracochlear injection, LPS+Gd-DOTA were visualized to distribute throughout the inner ear, including the cochlea and vestibule with fast dynamics depending on the status of the perilymph circulation.Novel LPS+Gd-DOTA were visible by MRI in the inner ear in vivo demonstrating transport from the middle ear to the inner ear and with dynamics that correlated to the status of the perilymph circulation.Treatments of inner ear diseases with traditional strategies have had limited success and the goal of sensory organ and nerve repair or regeneration has yet to be achieved. One of the greatest challenges has been the limitations to passage through the blood-inner ear barriers and uncontrollable delivery of treatment agents after either intravenous or oral administration (Figure 1) [1]. Multifunctional nanoparticles (MFNPs) are a promising new means for the delivery of gene or drug to the inner ear for the treatment of inner ear diseases including sensorineural hearing loss (SNHL) and Meniere's disease. Eight types of MFNPs are currently under development within the European Union consortium, Nanoear [2] with the intention that they can be applied with an intratympanic, minimally-invasive approach in the clinic. MFNPs can be functionalized with the application of surface ligands to improve cellular or nuclear internalization to improve the targeted delivery of therapeutic agent. In some of our preliminary studies lipid nanocapsules were shown using confocal microscopy to become distributed in different cochlear cell populations and liposome nanoparticles functionalized with TrkB ligand were internalized into cochlear cells after round window membrane permeation [3,4].In the process o
Flat Panel Solar Thermoelectric System Size Optimisation at Different Vacuum Levels  [PDF]
Kazuz Ramadan
Open Journal of Energy Efficiency (OJEE) , 2015, DOI: 10.4236/ojee.2015.44006

A systematic experimental investigation to understand the effect of heat loss and the thermoelectric aspect ratio (cross sectional area and length) on a flat plate solar thermoelectric system performance was carried out. The investigation involved a series of experiments on systems with 4 different sizes of thermoelectric generators, and it was tested in 5 different vacuum levels during the steady-state. The detailed experimental investigation provided a substantial amount of data, which revealed that the system performance of both heat and electricity power were improved when the heat lost was minimised. The system’s performance strongly depended on the aspect ratio of the thermoelectric generators. This finding might have a significant impact on the cost of the system by saving the user’s and the manufacturer’s time in examining different TEGs with different aspect ratios in order to get the optimum size optimisation of the hybrid system, as well as reduce the manufacturing cost.

Microstructural Evolution of Cast Hyper-Eutectic Al-18% Si Alloy during Cyclic Semi-Solid Heat Treatment  [PDF]
Mohamed Ramadan
Journal of Minerals and Materials Characterization and Engineering (JMMCE) , 2015, DOI: 10.4236/jmmce.2015.35041
Abstract: The cyclic semi-solid heat treatment represents a promising technique for improving microstructure and mechanical properties of a wide range of metallic alloys. In the current research the influence of cyclic semi-solid heat treatment on microstructure of Al-18% Si alloy containing 0.8% Fe has been studied. All specimens were heated in an electrically heated resistance furnace with heating rate of 10°C·min-1 to 585°C. For a complete one cycle heat treatment (5 min heating time), samples after 5 min holding at 585°C were cooled to a temperature of 550°C in still air cooling and the samples were taken out immediately for water quenching. It was found that heat treatment cycles should be limited to 3 cycles or less in order to maintain fine grain size and globular structure without agglomeration and coalescence. Cyclic semi-solid heat treatment changes morphology of iron-rich intermetallics phases to be plate-like and fine plate iron-rich intermetallics phases, in stead of needle-like iron-rich intermetallics phases that are observed in as-cast samples. Cyclic heating shows a relatively higher hardness for all heating cycles compared with as-cast one due to its finer and globular structure. Cyclic semi-solid heat treatment technique results in lower coarsening rate constant compared with isothermal heat treatment one due to coarsening discontinuous effect.
Optimized Mouse Model for the Imaging of Tumor Metastasis upon Experimental Therapy
Sergio Lavilla-Alonso, Usama Abo-Ramadan, Juha Halavaara, Sophie Escutenaire, Turgut Tatlisumak, Kalle Saksela, Anna Kanerva, Akseli Hemminki, Sari Pesonen
PLOS ONE , 2011, DOI: 10.1371/journal.pone.0026810
Abstract: Development of new cancer treatments focuses increasingly on the relation of cancer tissue with its microenvironment. A major obstacle for the development of new anti-cancer therapies has been the lack of relevant animal models that would reproduce all the events involved in disease progression from the early-stage primary tumor until the development of mature metastatic tissue. To this end, we have developed a readily imageable mouse model of colorectal cancer featuring highly reproducible formation of spontaneous liver metastases derived from intrasplenic primary tumors. We optimized several experimental variables, and found that the correct choice of cell line and the genetic background, as well as the age of the recipient mice, were critical for establishing a useful model system. Among a panel of colorectal cancer cell lines tested, the epithelial carcinoma HT29 line was found to be the most suitable in terms of producing homogeneous tumor growth and metastases. In our hands, SCID mice at the age of 125 days or older were the most suitable in supporting consistent HT29 tumor growth after splenic implantation followed by reproducible metastasis to the liver. A magnetic resonance imaging (MRI) protocol was optimized for use with this mouse model, and demonstrated to be a powerful method for analyzing the antitumor effects of an experimental therapy. Specifically, we used this system to with success to verify by MRI monitoring the efficacy of an intrasplenically administered oncolytic adenovirus therapy in reducing visceral tumor load and development of liver metastases. In summary, we have developed a highly optimized mouse model for liver metastasis of colorectal cancer, which allows detection of the tumor load at the whole body level and enables an accurate timing of therapeutic interventions to target different stages of cancer progression and metastatic development.
Adenoviruses with an αvβ integrin targeting moiety in the fiber shaft or the HI-loop increase tumor specificity without compromising antitumor efficacy in magnetic resonance imaging of colorectal cancer metastases
Sergio Lavilla-Alonso, Gerd Bauerschmitz, Usama Abo-Ramadan, Juha Halavaara, Sophie Escutenaire, Iulia Diaconu, Turgut Tatlisumak, Anna Kanerva, Akseli Hemminki, Sari Pesonen
Journal of Translational Medicine , 2010, DOI: 10.1186/1479-5876-8-80
Abstract: Here, the utility of αvβ integrin targeting moiety Arg-Gly-Asp (RGD) in the Lys-Lys-Thr-Lys (KKTK) domain of the fiber shaft or in the HI-loop of adenovirus serotype 5 for increased tumor targeting and antitumor efficacy was evaluated. To this end, novel spleen-to-liver metastatic colorectal cancer mouse model was used and the antitumor efficacy was evaluated with magnetic resonance imaging (MRI).Both modifications (RGD in the HI-loop or in the fiber shaft) increased gene transfer efficacy in colorectal cancer cell lines and improved tumor-to-normal ratio in systemic administration of the vector.Antitumor potency was not compromised with RGD modified viruses suggesting increased safety profile and tumor specificity.Colorectal cancer is the fourth most common type of cancer in men and the third most common in women worldwide and more than one million people are diagnosed with colorectal cancer every year. Incidence rates have increased during past decades, while 5-year survival rates have improved but remain between 60 to 40% in different countries[1,2]. Metastatic disseminated disease can be cured only rarely and even though early detection and prevention strategies play a key role in improving colorectal cancer statistics, also new therapeutic options are needed. To this end, gene therapy has been of interest to cancer researchers for a few decades and modalities based on adenovirus serotype 5 vectors are one of the most studied strategies. Safety data for adenovirus 5 has been excellent[3-6] and some recent clinical studies have shown some evidence of efficacy for many types of cancer[3-8] including colorectal cancer[9,10]. However, the main disadvantage of the current adenoviral therapies is that the efficacy of tumor transduction limits the efficacy of treatment. In particular, intravenous administration of the vector does not usually allow transduction levels compatible with clinical responses[11,12].Thus, for successful cancer gene therapy, tumor transduction
Influence of Solar Cycle Variations on Solar Spectral Radiation  [PDF]
Usama Ali Rahoma, Rabab Helal
Atmospheric and Climate Sciences (ACS) , 2013, DOI: 10.4236/acs.2013.31007

The climatic changes associated with solar variability are largely caused by variations in total solar irradiance and solar spectral irradiance with solar activity. Thus the spectral composition of solar radiation is crucial in determining atomspheric structure. The variations in solar spectrum depend on the varied solar spots. Recently, evidence for a strong effect of solar activity on terrestrial isolation on ground-based measurements carried out by the National Research Institute of Astronomy and Geophysics (NRIAG), Helwan, Egypt (lat. 29?52'N and long. 31?20'E) during (1990-2000) were presented. Specifically, a strong increase of terrestrial isolation with sunspot number as well as a decline of the solar spectrum with solar activity was reported. Daily measurements of the solar radiation between 280 nm and 2800 nm were made by Eppley Pyranometer and Pyrheliometer instruments. The decreasing at the range 280 - 530 nm and 530 - 630 nm are represented less than 50% of direct solar radiation and the stability of at the range 630 - 695 nm and 695 - 2800 nm it mean that; some of difference radiation is appear in diffused radiation which allow to height of the temperature as much as the largest associated with significance as it appears from the curves of relative humidity.

Low Power Wideband Sensing for One-Bit Quantized Cognitive Radio Systems
Abdelmohsen Ali,Walaa Hamouda
Computer Science , 2015,
Abstract: We proposes an ultra low power wideband spectrum sensing architecture by utilizing a one-bit quantization at the cognitive radio (CR) receiver. The impact of this aggressive quantization is quantified and it is shown that the proposed method is robust to low signal-to-noise ratios (SNR). We derive closed-form expressions for both false alarm and detection probabilities. The sensing performance and the analytical results are assessed through comparisons with respective results from computer simulations. The results indicate that the proposed method provides significant saving in power, complexity, and sensing period on the account of an acceptable range of performance degradation.
Spectrum Monitoring Using Energy Ratio Algorithm For OFDM-Based Cognitive Radio Networks
Abdelmohsen Ali,Walaa Hamouda
Computer Science , 2015,
Abstract: This paper presents a spectrum monitoring algorithm for Orthogonal Frequency Division Multiplexing (OFDM) based cognitive radios by which the primary user reappearance can be detected during the secondary user transmission. The proposed technique reduces the frequency with which spectrum sensing must be performed and greatly decreases the elapsed time between the start of a primary transmission and its detection by the secondary network. This is done by sensing the change in signal strength over a number of reserved OFDM sub-carriers so that the reappearance of the primary user is quickly detected. Moreover, the OFDM impairments such as power leakage, Narrow Band Interference (NBI), and Inter-Carrier Interference (ICI) are investigated and their impact on the proposed technique is studied. Both analysis and simulation show that the \emph{energy ratio} algorithm can effectively and accurately detect the appearance of the primary user. Furthermore, our method achieves high immunity to frequency-selective fading channels for both single and multiple receive antenna systems, with a complexity that is approximately twice that of a conventional energy detector.
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