Abstracts of Talks
Georges Al Makdessi
Advisor: Dr Malek Tabbal, Physics, FAS.
Development and characterization of a low-pressure
plasma system for surface modification of materials.
Abstract :
Low pressure plasmas (below 1 Torr) are extensively investigated because of their broad range of applications in high-impact technological fields. For example, such plasmas are used for improving adhesion between surfaces by enhancing bondability on substrates such as glass or polymers through the control of surface energies. Oxygen plasmas are among the most attractive for these applications. They are used for surface cleaning of biomaterials that come in contact with blood or proteins and require special surface treatments to induce biocompatibility. Oxygen plasmas are also utilized in the growth of oxide materials that play a central role in the semiconductor and opto-electronic industry. Remote plasma processing allows for the possibility of oxidizing a material by exposing it to an oxygen reactive species generated by the plasma. A remote plasma is formed when the excited species of the plasma diffuse and expand at low pressure beyond the plasma volume thereby making the process scalable and applicable to large surfaces. One of the most important type of species present in the remote plasmas are the free radicals that have a high chemical reactivity and promote compound formation at temperatures much lower than those required by purely thermal reactions. In addition, remote plasmas have a low thermal budget since they induce little heating of the treated material; this factor is very important because it allows independent control of plasma conditions and substrate temperature. Another important property of remote plasma processing is that it allows surface specific oxidation of materials.
The aim of this work is to characterize the oxygen plasma generated by a microwave source that is being used for thin film growth and oxidation. The study consists in evaluating the oxygen atomic density by optical emission spectroscopy and determining the electron density and electron temperature in the remote plasma using Langmuir probes.
Tests of oxidation of pure metallic films through thermal treatment in the oxygen remote plasma have also been performed. A parametric study as a function operating conditions, namely microwave power, flow rate, chamber pressure, plasma source-substrate distance, and substrate temperature, has been achieved in order to optimize the oxidation process and correlate it to plasma operating conditions.
Wassim Kassem
Advisor: Dr Malek Tabbal, Physics, FAS.
Pulsed Laser Deposition of Tungsten Thin Films for Magnetic Fusion Applications.
Abstract:
The ASDEX upgrade utilized Tungsten as a first wall material for its plasma facing components in fusion reactors. Coatings of Tungsten on CFC tiles were done by several techniques and evaluated at the Max-Planck-Institut für Plasmaphysik. The investigation of these coatings is of prime importance for the efficiency of the plasma generated inside the reactors and more so for the case of Tungsten, so improvement in the production of these wall materials is an ongoing process. PLD is one such technique that has yet to be fully tried out.
Thin coatings of Tungsten were deposited on Graphite by ablating a 99.99% Tungsten target using a 20 ns KrF excimer laser (λ=248nm). Two types of substrates were used. The main body of work so far was done on substrates fabricated by pre-depositing Graphite on Si(100) substrates. The other substrate used is a Graphite (CFC) pucks donated by the Max-Planck institute matching specifically those already used in fusion reactors. The two substrates have different properties in terms of crystalline structure, roughness, thickness, as well as other physical properties.
The effect of background gas pressure, substrate temperature, laser fluency, and substrate properties is studied using several techniques including x-ray diffraction, AFM, surface profileometry, and RBS. The key goal is to assess the quality of the Tungsten thin films in terms of adherence, coverage, and overall quality.
Early results show films ranging in thickness between 360 and 10 nm. A sputtering effect has been detected during deposition of the thin films due to highly energetic species in the nascent plume hindering film growth. However, all samples show excellent coverage with a mirror-like finish under the naked eye. Even the very rough donated CFC substrate with very tall features in the µm range show very good coverage. All samples -tested- exhibited a crystal structure of varying quality vis-à-vis deposition conditions.
Maya Saade
Advisor: Dr Elie Barbour, Animal and Veterinary Sciences, FAFS
Optimization of Sperm Separation and Gene Characterization in Animals.
Abstract
In intensive farming systems, there is a desire to control the sex ratio of animals; furthermore, recent trends emphasize the use of specific marker genes in selection for better animals. The research objectives are to optimize a flowcytometric method to separate goat male and female spermatozoa, and to standardize different Polymerase Chain Reaction (PCR) methods to detect genes of selection interest, namely those responsible for production, immunity and disease resistance. The work was performed on semen of Lebanese local low production goats and imported high production Saanen goats. Optimization of sperm sexing was done using flowcytometry using increasing amounts of fluorophore labelling, incubation time, and number of sperm washings. The PCR was adopted to verify sperm sorting, and to optimize detection protocols for genes of interest with varying primers concentrations. Successfully amplified αS1-Casein and MHC-class IIDRB were subjected to restriction endonucleases. Optimized Flowcytometry showed 2 distinct peaks relative to X and Y spermatozoa at 22.4µM fluorophore concentration, 30 minutes incubation time and 3 times sperm-washing. Growth Hormone, α-Lactalbumin, αS1-Casein, MHC-classIIDRB, Scrapie prion were successfully amplified at 4µl (5pmol/µl), 1.2µl (100pmol/µl), 0.5µl (100pmol/µl), 4µl (5pmol/µl) and 4µl (5pmol/µl) primers level respectively. PCR for selected genes revealed similarity between local and imported Saanen sperms, in relation to amplicons of each of Growth Hormone gene (435.4 and 110bp), α-Lactalbumin (190.5bp), αS1-Casein (230.6bp) and MHC-classIIDRB (285bp). Various banding patterns were obtained following the endonucleases activity on amplicons, patterns that could be related in the future to targeted traits for selection. As for the prion gene, a common 811bp band was obtained in most sperms; the sequencing of the prion amplicon will help in future selection of goats that are resistant to scrapie disease, causing variant-CJD in humans. In conclusion, Lebanese local goats showed a genetic potential for selection for the studied traits; however, further trials should be done to finalize sperm sexing protocols. Future research will target genes responsible for higher prolificacy in animals.
Dr Hala Gali-Muhtasib, Biology, FAS.
Thymoquinone: a promising plant derived anticancer drug.
Abstract:
There has been growing interest in naturally occurring compounds with anti-cancer potential. Black seed is one of the most extensively studied plants. This annual herb grows in countries bordering the Mediterranean Sea and India. Thymoquinone (TQ) is the bioactive constituent of the volatile oil of black seed. It has been shown to exert anti-neoplastic and anti-inflammatory effects. The molecular pathways of TQ action are not fully understood. Nevertheless, TQ is known to induce apoptosis by p53-dependent and p53-independent pathways in cancer cell lines. Growth inhibition is associated with induction of cell cycle arrest. TQ also acts on the immune system by modulating the levels of inflammatory mediators. To date, the chemotherapeutic potential of TQ in the clinic has not been tested, but numerous studies have shown its promising anti-cancer effects in animal models. The combination of TQ with clinically used anti-cancer drugs has led to improvements in their therapeutic index, and prevents non-tumor tissues from sustaining chemotherapy-induced damage.
Eileen Dergarabetian
Advisor: Dr Hala Gali-Muhtasib, Biology, FAS.
Thymoquinone induces cell death in T cell leukemia through caspase-dependent mechanisms.
Thymoquinone induces cell death in T cell leukemia through caspase-dependent mechanisms.
Abstract:
HTLV-I associated adult T-cell leukemia (ATL) and HTLV-I-negative peripheral T-cell lymphomas are associated with poor prognosis. Using increasing concentrations of Thymoquinone (TQ); a black seed extract, we demonstrate inhibition of cell proliferation and induction of apoptosis in HTLV-I transformed and HTLV-I negative malignant T cells, while normal resting or activated T lymphocytes were resistant. TQ-induced apoptosis was associated with the dissipation of mitochondrial membrane potential in both HTLV-I negative and positive malignant T cells and the subsequent release of cytchrome c and decrease in the protein expression levels of Bcl-2. Such loss of mitochondrial membrane integrity was associated with caspases-3, -8 and -9 activation. Treatment of cells with caspase inhibitors suppressed TQ-induced cell death, suggesting that caspases are partially involved in cell death mechanisms by TQ. Our data suggest that TQ treatment affects multiple pathways critical for the survival of HTLV-I positive and negative malignant T cells supporting a potential role for TQ in the treatment of ATL and HTLV-I-negative T-cell leukemias.
Khaled Ghattass
Advisor: Dr Hala Gali-Muhtasib, Biology, FAS.
Cell death by the quinoxaline dioxide DCQ in human colon cancer cells is enhanced under hypoxia and is independent of p53 and p21.
Abstract:
The radio sensitizer DCQ has been shown by our group to enhance sensitivity of HCT116 human colon cancer cells to hypoxia. Here we used HCT116 that are either wildtype for p53 and p21, null for p53 or null for p21 to understand the role of these genes in cellular response to DCQ under normoxia or hypoxia. DCQ decreased colony forming ability and viability of all HCT116 cells to a greater extent under hypoxia than normoxia and the p21-/-cell line was most sensitive. Cells had different HIF-1α responses to hypoxia and/or drug treatment. Higher DCQ doses induced PreG1-phase increase and apoptosis, however, lower doses caused mitotic catastrophe. In p53+/+ cells, apoptosis correlated with the increased expression of the pro-apoptotic caspase-2 and inhibition of the pro-survival protein PIDD-C. Exposure of p53+/+ cells to 5 or 10μM DCQ induced single strand breaks and triggered the activation of the nuclear kinase ATM by phosphorylation at Ser1981 in all phases of the cell cycle. On the other hand, no drug toxicity to normal FHs74 Int human intestinal cell line was observed. The ability of DCQ to induce apoptosis independently of p53 or p21 and in more than one colon cancer cell line makes it an interesting molecule with potential anticancer activities.
Chirine El-Baba
Advisor: Dr Hala Gali-Muhtasib, Biology, FAS.
The sage components linalyl acetate and α-terpeniol enhance cell death through inhibition of nuclear factor kappa-B signaling.
Abstract:
Linalyl acetate (Ly) and α-terpineol (Te), two monoterpenes derived from Lebanese sage, exhibit synergistic anti-proliferative effects when combined together through mechanisms that are not fully understood. Here, we investigated the effect of Ly and Te on the NF-κB signaling pathway in HCT-116 human colon cancer cells. The drug combination dose-dependently inhibited the proliferation of HCT-116 at non-cytotoxic concentrations. Treatment with Ly+Te at 0.6mM or 1mM induced 30% and 60% respective increases in the PreG1 population and the mechanism was found to be due to apoptosis and necrosis. DNA binding assays revealed that Ly and Te combinations suppressed both basal and TNFα-induced NF-κB activation. The suppression of NF-κB activation correlated with the inhibition of p65 nuclear translocation and IκBα degradation. Ly and Te combination also downregulated the expression of NF-κB-regulated antiapoptotic (cIAP1, cIAP2, Bcl-2, Bcl-iixL) and proliferative (cyclin D1, c-Myc) gene products. Separate treatments and drug combinations significantly decreased the DNA binding activity of NF-κB as early as 3hrs. Overall, our results indicate that the anticancer activities of Ly and Te are mediated in part through the suppression of NF-κB activation, suggesting that these sage components may be used in combination with chemotherapeutic agents to induce apoptosis.
Akram Ghantous
Advisor: Dr Nadine Darwiche, Biology, FAS
Chemopreventive Properties of Parthenolide in EpidermalCarcinogenesis: Role of NF-KB Signaling.
Abstract:
Parthenolide, the major sesquiterpene lactone and bioactive molecule from the medicinal plant feverfew (Tanacetum parthenium), demonstrates
specificity towards tumor cells and is currently in clinical trials.
It is among the most promising anticancer drugs and the only small molecule, to date, that kills cancer stem cells while sparing normal ones. We investigated the chemopreventive properties of parthenolide
in skin cancer using an in vitro model of epidermal carcinogenesis.
This model is suited for chemoprevention studies and depicts the multistep process of cancer. Skin cancer incidence is on the rise, and it has been increasing in Lebanon as evidenced from the AmericanUniversity of Beirut Medical Center Tumor Registry in 2006.
At low micromolar concentrations, parthenolide selectively inhibited the growth of neoplastic keratinocytes while sparing normal ones. At these concentrations, promoter-induced cell proliferation was inhibited, and cells were blocked in the S and G2/M phases. Cyclin proteins were reduced while key differentiation markers were upregulated. Elevated NF-?B signaling is essential for keratinocyte malignant transformation. Importantly, parthenolide prevented promoter-induced anchorage-independent growth, a hallmark of transformation, and inhibited promoter-induced NF-?B DNA binding and transcriptional activities.
Our studies highlight chemopreventive and therapeutic properties of parthenolide in skin cancer. Since tumor promotion is epigenetically regulated, we are currently testing for the ability of parthenolide to epigenetically inhibit epidermal carcinogenesis by modulating NF-?B target genes.
Gilbert Rahme
Advisor: Dr Rabih Talhouk, Biology, FAS
Connexin-43 Expression Reduces the Tumor Phenotype of Breast Adenocarcinoma Cell Lines in a Pathway Dependent on β-Catenin Signaling.
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Abstract:
Gap junction intercellular communication (GJIC) is crucial for tissue homeostasis, differentiation and development. Connexins (Cx), the gap junction proteins, are tumor suppressors, and Cx43 expression is often down regulated in breast tumors. Furthermore, Cx43, among others, regulates mammary tissue differentiation. We sought to study the effect of exogenous Cx43 fused to eGFP in the construct P-eGFP-N1 when transfected into the human breast adenocarcinoma cells, MDA-MB-231 cells, exhibiting a high invasive phenotype, and MCF-7 cells, exhibiting a less invasive phenotype. MCF-7 cells transfected with Cx43-eGFP showed a 56% decrease in total cell number by day 6 in culture, when grown in 2D on plastic, in comparison to a sham transfected (empty plasmid), and to untransfected cells which showed comparable total cell numbers. Similarly, MCF-7 Cx43 transfected cells showed an 80% reduction in total cell number at day 8 when grown in 3D cultures (on reconstituted basement membrane), and demonstrated a significantly higher amount of small sized spherical clusters. Exogenous Cx43-eGFP expression decreased the extravasative ability and cellular motility of MCF-7 cells by 60% and 70% respectively. On the other hand, MDA-MB-231 cells did not show any difference in total cell number when grown in 2D cultures on plastic, but exhibited a 35% reduction in proliferation when grown in 3D cultures. Remarkably, MDA-MB-231 cells showed stellate growth cluster morphology in 3D. This phenotype was decreased by 20% in cells transfected with exogenous Cx43-eGFP, and showed spherical clusters instead of stellate ones. The association of Cx43-eGFP with α-,β-catenin and ZO-2 was noted in MCF-7 cells in both 2D and 3D cultures, in contrast to no complex assembly in MDA-MB-231 cells in 2D cultures. Interestingly, nuclear levels of β-catenin were shown to decrease in 2D and 3D cultures of MCF-7 cells in conjunction with gap junction assembly and tumor suppression, in contrast to decreased nuclear β-catenin only in 3D cultures of MDA-MB-231 cells, where tumor suppressive effects are only noted. This comparative study suggested that the assembly of the gap junction complex with α-,β-catenin and ZO-2 may be partly involved in reduced growth rate, invasiveness, and change in morphology of MCF-7 in 2D and 3D cultures, and MDA-MB-231 cells in 3D cultures. In conclusion, and in addition to having a crucial role in mammary differentiation (Talhouk et al. 2008), the assembly of the GJ complex could possibly have a role in reverting mammary tumorigenesis, to a state of partial re-differentiation. Lastly, 3D studies suggest that Cx43 expression exerts a context dependent effect, particularly in the higher invasive cell line, MDA-MB-231. Moreover, our laboratory has initiated a study aiming to elucidate the significance of Cx43 gap junction complexes, particularly with β-catenin, in maintaining the “normal” phenotype of MCF-10A cells.
Hassan Yassine
Advisor: Dr Mike Osta, Biology, FAS
Two C-Type Lectins Cooperate to Defend Anopheles Gambiae Against Gram-Negative Bacteria.
Abstract:
Insect C-type lectins (CTLs) have been shown to mediate immune effector responses in vitro, however, the relative contribution of these CTLs to immune defenses in vivo is still poorly understood. Here, we report that two C-type lectin-like molecules, CTL4 and CTLMA2, which were shown previously to inhibit Plasmodium berghei ookinete melanization in the malaria vector Anopheles gambiae, are required for the clearance of Escherichia coli, but not Staphylococcus aureus, from adult female mosquitoes. Silencing either CTL by RNA interference dramatically reduces mosquito survival to Gram-negative but not to Gram-positive bacterial infections, suggesting a role in defense against Gram-negative bacteria. Further, molecular characterization reveals that both CTLs are secreted into the mosquito hemolymph mainly in the form of a disulfide-linked heterodimer. This association explains the similar roles of these CTLs in bacterial defense as well as in the melanization response to P. berghei ookinetes. Apparently, CTL4 and CTLMA2 serve pleiotropic functions in the innate immune response of A. gambiae.
Myriam Khawand
Advisor: Dr Colin Smith, Biology, FAS
The Microbial Biodiversity of Jeita Grotto: A UniqueLebanese Habitat.
Abstract:
Subterranean microbial ecologies are important and poorly understood. The identification and characterization of microbes in these ecologies are interesting because they reside in starved environments with no sunlight and limited organic input. They participate in elemental cycles, including the carbon cycle, and they pass to drinking water. The most accessible subterranean habitats are caves, yet very few have been studied worldwide, and none have been described in Lebanon. This study aims to identify the diverse bacteria residing in Jeita Grotto at two different seasons: high flow during spring and low flow in autumn. 16S rDNA analysis identified bacteria belonging to the phyla Proteobacteria, Bacteroidetes, Actinobacteria, and Acidobacteria. Of these, Proteobacteria is the most abundant phylum with Beta Proteobacteria most common. Preliminary results suggest the presence of a complex metabolic network consisting of heterotrophs, such as Flavobacteria and Acidobacteria, and chemoautotrophs, such as Variovorax sp. and nitrite-oxidizing bacteria. That heterotrophs outnumber the autotrophs suggests that there is organic input. The identification of five coliform bacteria suggests sewage could be a source of organic input.