985 resultados para Ptolemaios son of Chairemon (see also O.Mich. I, 650)


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NK cells can kill MHC-different or MHC-deficient but not syngeneic MHC-expressing target cells. This MHC class I-specific tolerance is acquired during NK cell development. MHC recognition by murine NK cells largely depends on clonally distributed Ly49 family receptors, which inhibit NK cell function upon ligand engagement. We investigated whether these receptors play a role for the development of NK cells and provide evidence that the expression of a Ly49 receptor transgene on developing NK cells endowed these cells with a significant developmental advantage over NK cells lacking such a receptor, but only if the relevant MHC ligand was present in the environment. The data suggest that the transgenic Ly49 receptor accelerates and/or rescues the development of NK cells which would otherwise fail to acquire sufficient numbers of self-MHC-specific receptors. Interestingly, the positive effect on NK cell development is most prominent when the MHC ligand is simultaneously present on both hemopoietic and nonhemopoietic cells. These findings correlate with functional data showing that MHC class I ligand on all cells is required to generate functionally mature NK cells capable of reacting to cells lacking the respective MHC ligand. We conclude that the engagement of inhibitory MHC receptors during NK cell development provides signals that are important for further NK cell differentiation and/or maturation.

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Glutaric aciduria type I (GA-I) is a cerebral organic aciduria caused by deficiency of glutaryl-Co-A dehydrogenase (GCDH). GCDH deficiency leads to accumulation of glutaric acid (GA) and 3-hydroxyglutaric acid (3-OHGA), two metabolites that are believed to be neurotoxic, in brain and body fluids. The disorder usually becomes clinically manifest during a catabolic state (e.g. intercurrent illness) with an acute encephalopathic crisis that results in striatal necrosis and in a permanent dystonic-dyskinetic movement disorder. The results of numerous in vitro and in vivo studies have pointed to three main mechanisms involved in the metabolite-mediated neuronal damage: excitotoxicity, impairment of energy metabolism and oxidative stress. There is evidence that during a metabolic crisis GA and its metabolites are produced endogenously in the CNS and accumulate because of limiting transport mechanisms across the blood-brain barrier. Despite extensive experimental work, the relative contribution of the proposed pathogenic mechanisms remains unclear and specific therapeutic approaches have yet to be developed. Here, we review the experimental evidence and try to delineate possible pathogenetic models and approaches for future studies.

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In recent years, the nighttime wet pavement retroreflectivity of pavement markings has become an important issue. In a effort to continue research in this area, the Iowa Department of Transportation evaluated the effectiveness of Visibeads in the Des Moines metropolitan area. Visibeads are three to four times larger in diameter then conventional glass beads. This larger size provides for better retroreflectivity under nighttime wet pavement conditions. The areas chosen for evaluation do not have roadway lighting, therefore, making them a good choice for Visibeads. Although the DOT has tested Visibeads in the past with moderate success, it is believed that using Visibeads with longer life markings such as epoxy will improve their performance.

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BACKGROUND: Prognostic models have been developed to predict survival of patients with newly diagnosed glioblastoma (GBM). To improve predictions, models should be updated with information at the recurrence. We performed a pooled analysis of European Organization for Research and Treatment of Cancer (EORTC) trials on recurrent glioblastoma to validate existing clinical prognostic factors, identify new markers, and derive new predictions for overall survival (OS) and progression free survival (PFS).¦METHODS: Data from 300 patients with recurrent GBM recruited in eight phase I or II trials conducted by the EORTC Brain Tumour Group were used to evaluate patient's age, sex, World Health Organisation (WHO) performance status (PS), presence of neurological deficits, disease history, use of steroids or anti-epileptics and disease characteristics to predict PFS and OS. Prognostic calculators were developed in patients initially treated by chemoradiation with temozolomide.¦RESULTS: Poor PS and more than one target lesion had a significant negative prognostic impact for both PFS and OS. Patients with large tumours measured by the maximum diameter of the largest lesion (⩾42mm) and treated with steroids at baseline had shorter OS. Tumours with predominant frontal location had better survival. Age and sex did not show independent prognostic values for PFS or OS.¦CONCLUSIONS: This analysis confirms performance status but not age as a major prognostic factor for PFS and OS in recurrent GBM. Patients with multiple and large lesions have an increased risk of death. With these data prognostic calculators with confidence intervals for both medians and fixed time probabilities of survival were derived.

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Well developed experimental procedures currently exist for retrieving and analyzing particle evidence from hands of individuals suspected of being associated with the discharge of a firearm. Although analytical approaches (e.g. automated Scanning Electron Microscopy with Energy Dispersive X-ray (SEM-EDS) microanalysis) allow the determination of the presence of elements typically found in gunshot residue (GSR) particles, such analyses provide no information about a given particle's actual source. Possible origins for which scientists may need to account for are a primary exposure to the discharge of a firearm or a secondary transfer due to a contaminated environment. In order to approach such sources of uncertainty in the context of evidential assessment, this paper studies the construction and practical implementation of graphical probability models (i.e. Bayesian networks). These can assist forensic scientists in making the issue tractable within a probabilistic perspective. The proposed models focus on likelihood ratio calculations at various levels of detail as well as case pre-assessment.

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The major objective of this project is to evaluate image analysis for characterizing air voids in Portland cement contract (PCC) and asphalt concrete (AC) and aggregate gradation in asphalt concrete. Phase 1 of this project has concentrated on evaluation and refinement of sample preparation techniques, evaluation of methods and instruments for conducting image analysis, and finally, analysis and comparison of a select portion of samples. Preliminary results suggest a strong correlation between the results obtained from the linear traverse method and image analysis methods for determining percent air voids in concrete. Preliminary work with asphalt samples has shown that damage caused by a high vacuum of the conventional scanning electron microscope (SEM) may too disruptive. Alternative solutions have been explored, including confocal microscopy and low vacuum electron microscopy. Additionally, a conventional high vacuum SEM operating at a marginal operating vacuum may suffice.