634 resultados para Epstein, AbrahamEpstein, AbrahamAbrahamEpstein


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Due to the clinical success of left ventricular assist devices (LVADs) used for short term "bridge to transplant" and the limited availability of donor organs, heart assist devices are being considered for long term implantation as an alternative to heart transplantation. In an effort to improve biocompatibility, a nonthrombogenic cellular lining was developed from genetically engineered smooth muscle cells (GE-SMC) for the Thermocardiosystems Heartmate$\sp{\rm TM}$ LVAD. SMCs have been transduced with the genes for endothelial nitric oxide synthase (NOS III) and GTP cyclohydrolase (GTPCH) with subsequent stable expression of the NOS III protein via an Epstein Barr based DNA expression vector. Transduced SMCs produce nitric oxide at concentrations that reduce platelet deposition and smooth muscle cell proliferation when tested in vitro. In addition, the adhesive capabilities of GE-SMC linings were also examined, and optimized in physical environments mimicking typical in vivo LVAD operation. Preliminary investigations examining cell adhesion during constant shear stress exposure demonstrated an acute phase of cell loss corresponding to cytoskeletal F-actin rearrangement. Subsequently, an in vitro circulatory loop was designed to expose cell lined LVADs to in vivo operating conditions. Cumulative cell loss from cell lined LVADs was less than 10% after 24 hours of flow. Using a protocol for "preconditioning" the cell lining within the mock circulatory loop, the first implantation of an LVAD containing a genetically engineered SMC lining was successfully implemented in a bovine model. Results from this 24 hour study indicate that the flow-conditioned cellular lining remained intact with no evidence of thromboembolization and only minimal changes in coagulation studies. ^

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To quantify species- specific relationships between bivalve carbonate isotope geochemistry ( delta O-18(c)) and water conditions ( temperature and salinity, related to water isotopic composition [delta O-18(w)]), an aquaculture-based methodology was developed and applied to Mytilus edulis ( blue mussel). The four- by- three factorial design consisted of four circulating temperature baths ( 7, 11, 15, and 19 degrees C) and three salinity ranges ( 23, 28, and 32 parts per thousand ( ppt); monitored for delta O-18(w) weekly). In mid- July of 2003, 4800 juvenile mussels were collected in Salt Bay, Damariscotta, Maine, and were placed in each configuration. The size distribution of harvested mussels, based on 105 specimens, ranged from 10.9 mm to 29.5 mm with a mean size of 19.8 mm. The mussels were grown in controlled conditions for up to 8.5 months, and a paleotemperature relationship based on juvenile M. edulis from Maine was developed from animals harvested at months 4, 5, and 8.5. This relationship [ T degrees C = 16.19 (+/- 0.14) - 4.69 (+/- 0.21) {delta O-18(c) VPBD - delta O-18(w) VSMOW} + 0.17 (+/- 0.13) {delta O-18(c) VPBD - delta O-18(w) VSMOW}(2); r(2) = 0.99; N = 105; P < 0.0001] is nearly identical to the Kim and O'Neil ( 1997) abiogenic calcite equation over the entire temperature range ( 7 - 19 degrees C), and it closely resembles the commonly used paleotemperature equations of Epstein et al. ( 1953) and Horibe and Oba ( 1972). Further, the comparison of the M. edulis paleotemperature equation with the Kim and O'Neil ( 1997) equilibrium- based equation indicates that M. edulis specimens used in this study precipitated their shell in isotopic equilibrium with ambient water within the experimental uncertainties of both studies. The aquaculture- based methodology described here allows similar species- specific isotope paleothermometer calibrations to be performed with other bivalve species and thus provides improved quantitative paleoenvironmental reconstructions.

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The causes of a greening trend detected in the Arctic using the normalized difference vegetation index (NDVI) are still poorly understood. Changes in NDVI are a result of multiple ecological and social factors that affect tundra net primary productivity. Here we use a 25 year time series of AVHRR-derived NDVI data (AVHRR: advanced very high resolution radiometer), climate analysis, a global geographic information database and ground-based studies to examine the spatial and temporal patterns of vegetation greenness on the Yamal Peninsula, Russia. We assess the effects of climate change, gas-field development, reindeer grazing and permafrost degradation. In contrast to the case for Arctic North America, there has not been a significant trend in summer temperature or NDVI, and much of the pattern of NDVI in this region is due to disturbances. There has been a 37% change in early-summer coastal sea-ice concentration, a 4% increase in summer land temperatures and a 7% change in the average time-integrated NDVI over the length of the satellite observations. Gas-field infrastructure is not currently extensive enough to affect regional NDVI patterns. The effect of reindeer is difficult to quantitatively assess because of the lack of control areas where reindeer are excluded. Many of the greenest landscapes on the Yamal are associated with landslides and drainage networks that have resulted from ongoing rapid permafrost degradation. A warming climate and enhanced winter snow are likely to exacerbate positive feedbacks between climate and permafrost thawing. We present a diagram that summarizes the social and ecological factors that influence Arctic NDVI. The NDVI should be viewed as a powerful monitoring tool that integrates the cumulative effect of a multitude of factors affecting Arctic land-cover change.

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Recently several novel and previously reported non-protein-coding RNAs (ncRNAs) have been identified to be upregulated upon Epstein-Barr virus (EBV) infection in human B-lymphocytes. A group of these significantly upregulated ncRNAs are called vault RNAs (vtRNAs). ,b Only about 5% of the total cellular vtRNAs are connected to the vault particle, the largest known ribonucleoprotein particle (RNP) in eukaryotic cells. However the function of this ncRNA family and moreover of the vault particle remains still rather unclear. Our previous findings suggest a link between EBV infection and vtRNA expression. Consequently we are interested which part of the viral genome is responsible for the upregulation and moreover which function the vtRNAs might possess during virus propagation. To address this question we have separately overexpressed specific EBV-encoded, latently expressed proteins in BL2-cells to determine the influence on the vault RNA levels. Thereby we identified one EBV-encoded protein, called Latent Membrane Protein 1 (LMP1), which significantly contributes to the vtRNA upregulation. We used LMP1 mutants to characterize the region of the protein and the responsible pathway for triggering the elevated vtRNA expression. Our results suggest that the NFkB- pathway might be involved in this process. To investigate a possible functional connection between the vtRNA and EBV infection, we have overexpressed vtRNA1-1 in BL41, a cell line usually not expressing this vault RNA. We show that overexpression of vtRNA1-1 leads to a better viral establishment and markedly protects cells from undergoing apoptosis. Knock-down of the major vault protein, the main component of the vault particle, had no effect on EBV infection and apoptosis resistance. Thus these results support the view that the observed phenotype is caused by the vtRNA rather than the vault particle.

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by Louis M. Epstein

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PURPOSE To compare the occurrence rate and depth of the demarcation line and topographical outcome after corneal cross-linking (CXL) for keratoconus using two different treatment protocols. METHODS A retrospective analysis of 131 eyes with progressive keratoconus treated with CXL using riboflavin and UV-A was performed. Eyes were treated either with the standard Dresden protocol (30 minutes irradiation, 3 mW/cm(2), UV-XTM 1000) or a rapid protocol (10 minutes irradiation, 9 mW/cm(2), UV-XTM 2000). The presence and depth of the corneal demarcation line was assessed with an anterior segment optical coherence tomography device 1 month after CXL by a masked observer. Corneal topography and tomography was performed at baseline and at 12-month follow-up with Pentacam and the TMS (Topographic Modeling System) device. RESULTS In the standard protocol group, 76.5% (62/81) of treated corneas revealed a demarcation line 1 month after CXL, whereas such a demarcation line was observed in only 22% (11/50) of eyes treated with the rapid protocol (P < 0.0001). The demarcation line was significantly more superficial in the rapid protocol group (P = 0.004). Corneal topography values between baseline and 12 months after CXL showed a mean change of -0.76 diopters (D) in Kmax (SD ± 2.7) in the standard protocol group versus a mean change of +0.72 D in Kmax (SD ± 1.5) in the rapid protocol (P = 0.007). CONCLUSIONS The rapid CXL protocol negatively influences the occurrence and depth of the demarcation line 1 month after CXL. Our results show a negative effect on the topographical outcome 1 year after CXL.

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PURPOSE To analyse the influence of corneal cross-linking (CXL) with ultraviolet-A (UV-A) and riboflavin on drug permeability in human subjects. METHODS Keratoconus patients (n = 23; mean age 26.9 ± 5.8 years) undergoing a standard CXL procedure with UV-A (5.4 J/cm(2) , 30 min) and riboflavin in one eye were included in the study. The pupillary diameter, measured before and every 3 min for 30 min after the topical application of one drop of 2% pilocarpine, was used as an indirect measure of the corneal permeability. The pupillary diameter was measured with an infrared pupillometer device before (baseline) and 4 months after CXL. RESULTS Prior to pilocarpine application, no significant difference in the pupillary diameter was detected before CXL and 4 months later. The mean decrease in the pupillary diameter after the application of pilocarpine was similar at baseline and the 4-month follow-up visit: mean decreases of 3.9 and 3.7 mm were observed 30 min after pilocarpine application, respectively (p > 0.05). CONCLUSIONS No significant influence of CXL on the corneal penetration of topically applied pilocarpine was observed in this clinical study.

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Non-protein-coding RNAs are a functionally versatile class of transcripts found in all domains of life exerting their biological role at the RNA level. Recently, we demonstrated that the vault-associated RNAs (vtRNAs) were significantly up-regulated in human B cells upon Epstein-Barr virus (EBV) infection [1,2]. vtRNAs are an integral part of the vault complex, a huge and evolutionarily conserved cytoplasmic ribonucleoprotein complex. The major vault protein (MVP) is the main structural component of the complex while vtRNA accounts for only 5% of its mass. Very little is known about the function(s) of the vtRNAs or the vault complex. In particular the role and significance of the previously observed vtRNA up-regulation upon EBV infection remained unclear. We individually expressed EBV-encoded genes in B cells and found the latent membrane protein 1 (LMP1) as trigger for vtRNA up-regulation. To unravel a putative functional interconnection between vtRNA expression and EBV infection, we ectopically expressed vtRNA1-1 in human B cells and observed an improved viral establishment. Furthermore, expression of vtRNA1-1 but not of the other vtRNA paralogs protected cells from undergoing apoptosis. Knock-down of MVP had no effect on these phenotypes thus revealing the vtRNA and not the vault complex to contribute to the enhanced EBV establishment and apoptosis resistance. Mutational analysis highlighted the central domain of the vtRNA to be involved in the anti-apoptotic effect. Ongoing research aims at characterizing the target of vtRNA1-1 in the apoptotic pathway. In summary, our data reveal a crucial cellular function for the so far elusive RNA biology of the vtRNAs.

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von Hannah Meyer-Breuer

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von Simon Stern