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Selected AbstractsMagnetic Resonance Imaging in the Study of the Lithium,Pilocarpine Model of Temporal Lobe Epilepsy in Adult RatsEPILEPSIA, Issue 4 2002Catherine Roch Summary: ,Purpose: In temporal lobe epilepsy, it remains to be clarified whether hippocampal sclerosis is the cause or the consequence of epilepsy. We studied the temporal evolution of the lesions in the lithium,pilocarpine model of epilepsy in the rat with magnetic resonance imaging (MRI) to determine the progressive morphologic changes occurring before the appearance of chronic epilepsy. Methods: MRI was performed on an MR scanner operating at 4.7 T. We followed the evolution of lesions using T2 - and T1 -weighted sequences before and after the injection of gadolinium from 2 h to 9 weeks. Results: At 2 h after status epilepticus (SE), a blood,brain barrier breakdown could be observed only in the thalamus; it had disappeared by 6 h. At 24 h after SE, edema was present in the amygdala and the piriform and entorhinal cortices together with extensive neuronal loss; it disappeared progressively over a 5-day period. During the chronic phase, a cortical signal reappeared in all animals; this signal corresponded to gliosis, which appeared on glial fibrillary acidic protein (GFAP) immunohistochemically stained sections as hypertrophic astrocytes with thickened processes. In the hippocampus, the correlation between histopathology and T2 -weighted signal underscored the progressive constitution of atrophy and sclerosis, starting 2 days after SE. Conclusions: These data show the reactivity of the cortex that characterizes the initial step leading to the development of epilepsy and the late gliosis that could result from the spontaneous seizures. Moreover, it appears that hippocampal sclerosis progressively worsened and could be both the cause and the consequence of epileptic activity. [source] Unscheduled DNA replication origin activation at inserted HPV 18 sequences in a HPV -18/MYC ampliconGENES, CHROMOSOMES AND CANCER, Issue 8 2007Chiara Conti Oncogene amplification is a critical step leading to tumorigenesis, but the underlying mechanisms are still poorly understood. Despite data suggesting that DNA replication is a major source of genomic instability, little is known about replication origin usage and replication fork progression in rearranged regions. Using a single DNA molecule approach, we provide here the first study of replication kinetics on a previously characterized MYC/papillomavirus (HPV18) amplicon in a cervical cancer. Using this amplicon as a model, we investigated the role DNA replication control plays in generating amplifications in human cancers. The data reveal severely perturbed DNA replication kinetics in the amplified region when compared with other regions of the same genome. It was found that DNA replication is initiated from both genomic and viral sequences, resulting in a higher median frequency of origin firings. In addition, it was found that the higher initiation frequency was associated with an equivalent increase in the number of stalled replication forks. These observations raise the intriguing possibility that unscheduled replication origin activation at inserted HPV -18 viral DNA sequences triggers DNA amplification in this cancer cell line and the subsequent overexpression of the MYC oncogene. This article contains Supplementary Material available at http://www.interscience.wiley.com/jpages/1045-2257/suppmat. © 2007 Wiley-Liss, Inc. [source] Monoclonal antibodies against a 62 kDa proteinase of Trichomonas vaginalis decrease parasite cytoadherence to epithelial cells and confer protection in micePARASITE IMMUNOLOGY, Issue 3 2004H. Hernández SUMMARY Trichomonas vaginalis infects the epithelium of the genital tract. The mechanism by which it invades the tissue leading to the disease is not thoroughly understood. However, results of several studies seem to agree that parasite adhesion to epithelium cells is the initial step leading to infection in women. T. vaginalis is associated with high levels of proteolytic activity. The role of some of these proteinases in the development of infection has been demonstrated. The current study establishes the role of a 62 kDa excretion,secretion proteinase in parasite cytoadherence. Monoclonal antibodies (MAbs) against this enzyme were tested for their ability to inhibit this process. Three stable hybrid producers of IgG1class MAbs (4D8, 1A8, 3C11) against the 62 kDa proteinase were obtained. Two of them (4D8 and 1A8) showed parasite recognition by immunofluorescence. Parasite cytoadherence to a monolayer of HeLa cells was inhibited by the 4D8, 1A8 and 3C11 antibodies. MAb 4D8 administered 24 h before a challenge with T. vaginalis by the intraperitoneal route was able to protect the majority of mice. Nitric oxide levels in the serum of animals inoculated with MAb 4D8 and challenged with the parasite were significantly different from those recorded in mice treated with an unrelated MAb. These studies show that an appropriate antibody against 62 kDa proteinase can help the host resist a challenge by the intraperitoneal route with T. vaginalis. [source] Reduced endothelin-3 expression in sporadic Hirschsprung diseaseBRITISH JOURNAL OF SURGERY (NOW INCLUDES EUROPEAN JOURNAL OF SURGERY), Issue 5 2000S. E. Kenny Background: Enteric aganglionosis in Hirschsprung disease has been linked to genes coding for endothelin-3 (EDN3) and the endothelin B receptor (EDNRB), but there is no such linkage in most patients with sporadic Hirschsprung disease. However, the similarity between the distal colonic aganglionosis in Hirschsprung disease and that due to EDN3 or EDNRB mutations led to the hypothesis that levels of expression of these genes might be affected in the absence of mutation, thus causing the Hirschsprung disease phenotype. The aim of this study was to determine EDN3 and EDNRB messenger RNA (mRNA) levels in tissue samples from patients with sporadic Hirschsprung disease. Methods: RNA and DNA were isolated from the ganglionic and aganglionic colonic segments of ten children with sporadic Hirschsprung disease, and from the colon of ten age-matched controls. The DNA was analysed for mutations in the genes coding for endothelin-3 (ET-3) and endothelin B receptor (ET-B) proteins. Relative levels of EDN3 and EDNRB mRNA were determined by semi-quantitative transcriptase,polymerase chain reaction. Results: Three children had sequence variants in EDN3 and EDNRB. In the remaining seven patients, EDN3 mRNA levels were reduced in both the ganglionic and aganglionic colon compared with levels in controls; there was no difference in expression of EDNRB between groups. Conclusion: In the absence of mutation, EDN3 is downregulated in short-segment Hirschsprung disease, suggesting that this may be a common step leading to aganglionosis. © 2000 British Journal of Surgery Society Ltd [source] Computational Investigations on the General Reaction Profile and Diastereoselectivity in Sulfur Ylide Promoted AziridinationCHEMISTRY - A EUROPEAN JOURNAL, Issue 17 2007Deepa Janardanan Abstract Mechanism and diastereoselectivity of sulfur ylide promoted aziridination reactions were studied by density functional theory with inclusion of solvent effects through the continuum solvation model. The general reaction pathway was modeled for the addition of substituted sulfur ylides (Me2S+CH,R) to an aldimine ((E)-methyl ethylidenecarbamate, MeHCNCO2Me). The nature of the substituents on the ylidic carbon atom substantially affects the reaction profile. The stabilized (R=COMe) and semistabilized (R=Ph) ylides follow a cisoid addition mode leading to trans aziridines via anti betaine intermediates. The simplest model ylide (unstabilized, R=H) underwent cisoid addition in a similar fashion. In the case of stabilized ylides product diastereoselectivity is controlled by the barriers of the elimination step leading to the 2,3- trans aziridine, whereas it is decided in the addition step in the case of semistabilized ylides. The importance of steric and electronic factors in diastereoselective addition (2 and 5) and elimination (5) transition states was established. Comparison of results obtained with the gas-phase optimized geometries and with the fully optimized solvent-phase geometries reveals that the inclusion of solvent effects does not bring about any dramatic changes in the reaction profiles for all three kinds of ylides. In particular, diastereoselectivity for both kinds of ylides was found to be nearly the same in both these approaches. [source] EARLY ACTIVATION OF INTERNAL MEDIAL SMOOTH MUSCLE CELLS IN THE RABBIT AORTA AFTER MECHANICAL INJURY: RELATIONSHIP WITH INTIMAL THICKENING AND PHARMACOLOGICAL APPLICATIONSCLINICAL AND EXPERIMENTAL PHARMACOLOGY AND PHYSIOLOGY, Issue 1-2 2006Huguette Louis SUMMARY 1Smooth muscle cells (SMC) participate in both inflammatory and dedifferentiation processes during atherosclerosis, as well as during mechanical injury following angioplasty. In the latter, we studied medial SMC differentiation and inflammation processes implicated early after de-endothelialization in relation to mechanical stresses. We hypothesized that activation of a subpopulation of SMC within the media plays a crucial role in the early phase of neointimal formation. 2For this purpose, we used a rabbit model of balloon injury to study activation and differentiation of medial SMC in the early time after denudation and just before neointima thickening. Inflammation was evaluated by the expression of vascular cell adhesion molecule (VCAM)-1, integrin a4b1 and nuclear factor (NF)-kB. Myosin isoforms and 2P1A2 antigen, a membrane protein expressed by rabbit dedifferentiated SMC, were used as markers of differentiation. 3On day 2 after de-endothelialization, VCAM-1, a4b1 and NF-kB were coexpressed by a well-defined subpopulation of SMC of the internal part of the media, in the vicinity of the blood stream. At the same time, the majority of SMC throughout the media expressed non-muscle myosin heavy chain-B (nm-MHC-B) and 2P1A2 antigen. On day 7, when intimal thickening appeared, SMC of the media were no longer activated, whereas some intimal SMC expressed the activation markers. Thus, after de-endothelialization, early dedifferentiation occurs in most of the medial SMC, whereas activation concerned only a subpopulation of SMC located in the internal media. Using the T-type voltage-operated calcium channel blocker mibefradil (0.1,1 mmol/L) in SMC culture, we showed that this agent exhibited an antiproliferative effect in a dose-dependant manner only on undifferentiated cells. 4In conclusion, the results suggest that the activated SMC represent cells that are potentially able to migrate and participate in the intimal thickening process. Thus, the medial SMC inflammatory process, without any contribution of inflammatory cells, may represent a major mechanism underlying the development of intimal thickening following mechanical stress. In humans, inhibition of T-type calcium channels may be a tool to prevent the early proliferation step leading to neointimal formation. [source] Visualization and microscopic modeling of phase inversion during compoundingPOLYMER ENGINEERING & SCIENCE, Issue 8 2001R. Ratnagiri A detailed description of the sequence of deformation steps leading to phase inversion during compounding in a low-viscosity-ratio co-polyester/polyethylene blend is presented. Visualization using a glass window and sampling of the blend at different mixing times enabled identification of the intermediate morphologies of the major component en route to phase inversion. Based on these observations, a theoretical model is developed to predict the time to phase inversion. The model incorporates a simplified flow-field approximation and the calculation of strain imparted to the major component domains. A strain-based criterion for phase inversion is then proposed, which, in conjunction with the model, yields an explicit expression for the time to phase inversion during compounding, tP.I.. The model predictions are seen to be in good agreement with the increase of tP.I., on scaleup between two mixing bowls. The correct functional dependence of tP.I. on the nominal maximum-shear-rate is predicted. Using combination of pure drag and planar extensional flow, the model predictions are shown to be consistent with the observed dependence of tP.I. on the volume fraction of the minor component and the blend viscosity ratio. [source] Enzyme-Triggered and Self-Cleaving Fragrant Alcohol PrecursorsCHEMISTRY & BIODIVERSITY, Issue 6 2008Felix Flachsmann Abstract The high volatility and water solubility of many natural perfumery alcohols leads to their rapid loss in fabric-care and personal-care applications. A dramatically enhanced substantivity is achieved by the use of fragrance precursors as controlled-release systems. In the first part of this article, we present multi-odorant precursors, in which the enzymatic cleavage of esters or carbonates of fragrant alcohols triggers subsequent steps leading to the release of fragrant ketones, lactones, and additional fragrant alcohols. In the second part, a study on oligocarbonates of fragrant alcohols is presented. Therein, the outstanding enzyme-independent performance of gluconolactone oligocarbonate 27 for the long-lasting release of (Z)-hex-3-en-1-ol is highlighted. We show that these polyfunctional compounds undergo complex rearrangements and intramolecular substitution reactions which lead to the observed release kinetics. [source] | |||||||||||||