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Search Results: 1 - 10 of 153 matches for " Ghassan Dbaibo "
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p53 and Ceramide as Collaborators in the Stress Response
Rouba Hage-Sleiman,Maria O. Esmerian,Hadile Kobeissy,Ghassan Dbaibo
International Journal of Molecular Sciences , 2013, DOI: 10.3390/ijms14034982
Abstract: The sphingolipid ceramide mediates various cellular processes in response to several extracellular stimuli. Some genotoxic stresses are able to induce p53-dependent ceramide accumulation leading to cell death. However, in other cases, in the absence of the tumor suppressor protein p53, apoptosis proceeds partly due to the activity of this “tumor suppressor lipid”, ceramide. In the current review, we describe ceramide and its roles in signaling pathways such as cell cycle arrest, hypoxia, hyperoxia, cell death, and cancer. In a specific manner, we are elaborating on the role of ceramide in mitochondrial apoptotic cell death signaling. Furthermore, after highlighting the role and mechanism of action of p53 in apoptosis, we review the association of ceramide and p53 with respect to apoptosis. Strikingly, the hypothesis for a direct interaction between ceramide and p53 is less favored. Recent data suggest that ceramide can act either upstream or downstream of p53 protein through posttranscriptional regulation or through many potential mediators, respectively.
IL-1 stimulates ceramide accumulation without inducing apoptosis in intestinal epithelial cells
Fadia R. Homaidan,Marwan E. El-Sabban,Iman Chakroun,Mirvat El-Sibai,Ghassan S. Dbaibo
Mediators of Inflammation , 2002, DOI: 10.1080/09629350210313
Abstract: Background: In inflammatory bowel disease (IBD), cytokine levels (such as interleukin-1 (IL-1)) are elevated. We have shown previously that IL-1 activates phospholipid signaling pathways in intestinal epithelial cells (IEC), leading to increased ceramide levels.
Evidence of Infection with H4 and H11 Avian Influenza Viruses among Lebanese Chicken Growers
Ghazi Kayali, Elie Barbour, Ghassan Dbaibo, Carelle Tabet, Maya Saade, Houssam A. Shaib, Jennifer Debeauchamp, Richard J. Webby
PLOS ONE , 2011, DOI: 10.1371/journal.pone.0026818
Abstract: Human infections with H5, H7, and H9 avian influenza viruses are well documented. Exposure to poultry is the most important risk factor for humans becoming infected with these viruses. Data on human infection with other low pathogenicity avian influenza viruses is sparse but suggests that such infections may occur. Lebanon is a Mediterranean country lying under two major migratory birds flyways and is home to many wild and domestic bird species. Previous reports from this country demonstrated that low pathogenicity avian influenza viruses are in circulation but highly pathogenic H5N1 viruses were not reported. In order to study the extent of human infection with avian influenza viruses in Lebanon, we carried out a seroprevalence cross-sectional study into which 200 poultry-exposed individuals and 50 non-exposed controls were enrolled. We obtained their sera and tested it for the presence of antibodies against avian influenza viruses types H4 through H16 and used a questionnaire to collect exposure data. Our microneutralization assay results suggested that backyard poultry growers may have been previously infected with H4 and H11 avian influenza viruses. We confirmed these results by using a horse red blood cells hemagglutination inhibition assay. Our data also showed that farmers with antibodies against each virus type clustered in a small geographic area suggesting that unrecognized outbreaks among birds may have led to these human infections. In conclusion, this study suggests that occupational exposure to chicken is a risk factor for infection with avian influenza especially among backyard growers and that H4 and H11 influenza viruses may possess the ability to cross the species barrier to infect humans.
Temporally distinct roles for tumor suppressor pathways in cell cycle arrest and cellular senescence in Cyclin D1-driven tumor
Hasan Zalzali, Mohammad Harajly, Lina Abdul-Latif, Nader El Chaar, Ghassan Dbaibo, Stephen X Skapek, Raya Saab
Molecular Cancer , 2012, DOI: 10.1186/1476-4598-11-28
Abstract: Senescence evolved over a period of weeks, with initial hyperproliferation followed by cell cycle arrest due to ROS production leading to activation of a DNA damage response and the p53 pathway. Interestingly, cell cycle exit was associated with repression of the Cyclin-dependent kinase Cdk2. This was followed days later by formation of heterochromatin foci correlating with RB protein hypophosphorylation. In the absence of the Cdk4-inhibitor p18Ink4c, cell cycle exit was delayed but most cells eventually showed a senescent phenotype. However, tumors later arose from this premalignant, largely senescent lesion. We found that the p53 pathway was intact in tumors arising in a p18Ink4c-/- background, indicating that the two genes represent distinct tumor suppressor pathways. Upon tumor progression, both p18Ink4c-/- and p53-/- tumors showed increased Cdk2 expression. Inhibition of Cdk2 in cultured pre-tumorigenic and tumor cells of both backgrounds resulted in decreased proliferation and evidence of senescence.Our findings indicate that the p53 and the RB pathways play temporally distinct roles in senescence induction in Cyclin D1-expressing cells, and that Cdk2 inhibition plays a role in tumor suppression, and may be a useful therapeutic target.
Apoptosis and the activity of ceramide, Bax and Bcl-2 in the lungs of neonatal rats exposed to limited and prolonged hyperoxia
Ahmad W Husari, Ghassan S Dbaibo, Hala Bitar, Aline Khayat, Shoghag Panjarian, Michel Nasser, Fadi F Bitar, Marwan El-Sabban, Ghazi Zaatari, Salman M Mroueh
Respiratory Research , 2006, DOI: 10.1186/1465-9921-7-100
Abstract: Newborn rats were placed in chambers containing room air or oxygen above 90% for 7 days. The rats were sacrificed at 3, 7 or 14 days and their lungs removed. Sections were fixed, subjected to TUNEL, Hoechst, and E-Cadherin Staining. Sections were also incubated with anti-Bcl-2 and anti-Bax antisera. Bcl-2 and Bax were quantitated by immunohistochemistry. Lipids were extracted, and ceramide measured through a modified diacylglycerol kinase assay. RT-PCR was utilized to assess IL-1β expression.TUNEL staining showed significant apoptosis in the hyperoxia-exposed lungs at 3 days only. Co-staining of the apoptotic cells with Hoechst, and E-Cadherin indicated that apoptotic cells were mainly epithelial cells. The expression of Bax and ceramide was significantly higher in the hyperoxia-exposed lungs at 3 and 14 days of age, but not at 7 days. Bcl-2 was significantly elevated in the hyperoxia-exposed lungs at 3 and 14 days. IL-1β expression was significantly increased at 14 days.Exposure of neonatal rat lung to hyperoxia results in early apoptosis documented by TUNEL assay. The early rise in Bax and ceramide appears to overcome the anti-apoptotic activity of Bcl-2. Further exposure did not result in late apoptotic changes. This suggests that apoptotic response to hyperoxia is time sensitive. Prolonged hyperoxia results in acute lung injury and the shifting balance of ceramide, Bax and Bcl-2 may be related to the evolution of the inflammatory process.Oxygen supplement is used in different therapeutic interventions. Respiratory diseases in neonates such as hyaline membrane disease and persistent pulmonary hypertension often require high concentrations of supplemental oxygen. Such concentrations are known to cause cellular damage and death in lungs and other organs as well. Cell death secondary to hyperoxia occurs via two mechanisms: cell necrosis and apoptosis [1,2].Cell necrosis is a mode of cell death that occurs exclusively in environmental disruption under nonphysiologica
Genotypes and serotype distribution of macrolide resistant invasive and non- invasive Streptococcus pneumoniae isolates from Lebanon
Nedal Taha, George F Araj, Rima H Wakim, Souha S Kanj, Zeina A Kanafani, Ahmad Sabra, Marie-Therese Khairallah, Farah J Nassar, Marwa Shehab, Maysa Baroud, Ghassan Dbaibo, Ghassan M Matar
Annals of Clinical Microbiology and Antimicrobials , 2012, DOI: 10.1186/1476-0711-11-2
Abstract: Forty four macrolide resistant and 21 macrolide susceptible S. pneumoniae clinical isolates were tested for antimicrobial susceptibility according to CLSI guidelines (2008) and underwent molecular characterization. Serotyping of these isolates was performed by Multiplex PCR-based serotype deduction using CDC protocols. PCR amplification of macrolide resistant erm (encoding methylase) and mef (encoding macrolide efflux pump protein) genes was carried out.Among 44 isolates resistant to erythromycin, 35 were resistant to penicillin and 18 to ceftriaxone. Examination of 44 macrolide resistant isolates by PCR showed that 16 isolates harbored the erm(B) gene, 8 isolates harbored the mef gene, and 14 isolates harbored both the erm(B) and mef genes. There was no amplification by PCR of the erm(B) or mef genes in 6 isolates. Seven different capsular serotypes 2, 9V/9A,12F, 14,19A, 19F, and 23, were detected by multiplex PCR serotype deduction in 35 of 44 macrolide resistant isolates, with 19F being the most prevalent serotype. With the exception of serotype 2, all serotypes were invasive. Isolates belonging to the invasive serotypes 14 and 19F harbored both erm(B) and mef genes. Nine of the 44 macrolide resistant isolates were non-serotypable by our protocols.Macrolide resistance in S. pneumoniae in Lebanon is mainly through target site modification but is also mediated through efflux pumps, with serotype 19F having dual resistance and being the most prevalent and invasive.Streptococcus pneumoniae continues to be a major cause of morbidity and mortality in humans. It is one of the most significant bacterial pathogens causing community acquired infections, most notably pneumonia, otitis media, bacteremia, and meningitis [1,2]. Treatment of pneumococcal infections is becoming difficult due to the high prevalence of penicillin-resistant strains and to the rapid development of resistance to other antimicrobials including macrolides. These drugs are extensively used for the treat
Upper Cervical Spine Infection. Complication of Hypopharyngeal Injury  [PDF]
Ghassan Skaf, Elias Elias
International Journal of Otolaryngology and Head & Neck Surgery (IJOHNS) , 2016, DOI: 10.4236/ijohns.2016.52016
Abstract: Background: We describe a rare case of Candida albicans retropharyngeal infection with upper cervical spondylodiscitis associated with epidural abscess triggered by ingestion of a chicken bone. Case Description: A 63-year-old woman presented with posterior neck and bilateral shoulders pain three weeks after choking on a 2-centimeter chicken bone. Magnetic resonance imaging (MRI) revealed spondylodiscitis and epidural abscess with significant spinal cord compression at C2 and C3 levels. A Barium swallow showed a focal disruption of the posterior wall of the esophagus. A posterior upper cervical fixation (C2-C5) was initially performed. One week later an anterior decompressive procedure was carried out followed by iliac crest bony fusion, and repair of the esophageal defect. Intra-operative cultures showed heavy growth of Candida albicans. After a transitory post-operative neurologic worsening, and after six weeks of appropriate antifungal therapy, the patient achieved a full clinical and radiologic recovery. Conclusion: Prompt surgical debridement, fusion and stabilization combined with adequate antimicrobial agents are necessary to guarantee a good outcome and reverse the neurological deficits.
Wind-Solar Hybrid Electrical Power Production to Support National Grid: Case Study - Jordan  [PDF]
Ghassan HALASA, Johnson A. ASUMADU
Energy and Power Engineering (EPE) , 2009, DOI: 10.4236/epe.2009.12011
Abstract: The paper presents the next generation of power energy systems using solar- and wind-energy systems for the country of Jordan. Presently with the oil prices are on the rise, the cost of electrical power production is very high. The opportunity of a large wind and solar hybrid power production is being explored. Sights are chosen to produce electricity using the wind in the Mountains in Northern Jordan and the sun in the Eastern Desert. It is found that the cost of windmill farm to produce 100 - 150 MW is US$290 million while solar power station to produce 100 MW costs US$560 million. The electrical power costs US$0.02/kWh for the wind power and US$0.077 for the solar power. The feasibility for using wind and solar energies is now when the price oil reaches US$ 100.00 per barrel. The paper also discusses different power electronics circuits and control methods to link the renewable energy to the national grid. This paper also looks at some of the modern power electronics converters and electrical generators, which have improved significantly solar and wind energy technologies.
Warring Societies (and Intellectuals)
Ghassan Hage
Transforming Cultures , 2006,
Abstract: I’m going to talk about warring societies and the role of academics in them. I’m trying to describe a logic of colonial settler states, which have always conceived themselves to be besieged by uncivilised others and which structure themselves defensively and legitimise these structures in the sense that they have to protect themselves from the uncivilised others surrounding them.
Ghassan Samara
International Journal of Cyber-Security and Digital Forensics , 2012,
Abstract: Vehicular Ad hoc Network security is one of the hottest topics of research in the field of network security. One of the ultimate goals in the design of such networking is to resist various malicious abuses and security attacks. In this research new security mechanism is proposed to reduce the channel load resulted from frequent warning broadcasting happened in the adversary discovery process a€“ Accusation Report (AR) - which produces a heavy channel load from all the vehicles in the road to report about any new adversary disovery. Furthermore, this mechanism will replace the Certificate Revocation List (CRL), which cause long delay and high load on the channel with Local Revocation List (LRL) which will make it fast and easy in the adversary discovery process.
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