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  • 1
    ISSN: 1432-2323
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Résumé Le but d'un système de dépistage primaire est de détecter des lésions pré-malignes et malignes susceptibles d'être traitées chirurgicalement de façon “curative.” Bien qu'un certain nombre de marqueurs tumoraux “classiques” soient utiles dans la surveillance du traitement, aucun ne s'est encore montré capable de servir pour le diagnostic ou dépistage précoce. En ce qui concerne le cancer colorectal, la valeur de l'antigène carcinoembryonnaire (ACE), de l'antigène gastrointestinal (CA19-9), et d'autres “marqueurs biochimiques” plus récents, est virtuellement non-existante, même chez des patients à haut risque. Des progrès nouveaux ont été accomplis, en génétique cellulaire somatique et en chimie moléculaire. Comme pour d'autres épithéliomes, des perturbations de l'expression oncogénique ont été mis en évidence dans les cancers colorectaux, et reflètent probablement un événement important dans la transformation maligne. Cependant, les études d'expression oncogène n'ont pas encore fourni de renseignement cliniquement utiles. Récemment, une étude de recherche pour mettre en évidence des anomalies génétiques et chromosomiques spécifiques dans le syndrome de cancer colique familial a amené à découvrir le gène de la polypose familiale (GPF) au niveau du duodénum (5q21–q22). La perte d'allèles du chromosome 5 a été observée dans les cellules tumorales chez au moins 20% des patients présentant un cancer colique sporadique. Le type d'association, c'est à dire, entre un changement génétique constitutionnel et un changement acquis, rappelle ce que l'on observe dans d'autres cancers (par exemple rétinoblastome et tumeur de Wilms). La découverte d'un GPF peut éventuellement servir de base au diagnostic pré-symptomatique ou pré-natal pour cette maladie, voire même pour quelques cas sporadiques. Cependant, on pense que d'autres marqueurs liés au cancer colorectal seront découverts et auront une plus large application dans le dépistage précoce présymptomatique.
    Abstract: Resumen El propósito de un sistema primario de tamizaje para detección de cáncer es identificar las lesiones premalignas y los carcinomas susceptibles de cirugía “curativa.” Aunque algunos de los marcadores tumorales “clásicos” han logrado reconocida aplicación en el manejo clínico, ninguno es de utilidad para propósitos de diagnóstico en la fase presintomática o para tamizaje. En el caso del carcinoma colorrectal, la capacidad de tamizaje del antígeno carcinoembriónico (ACE), del antígeno relacionado con cáncer gastrointestinal, CA19-9, y de otros “marcadores bioquímicos” recientemente identificados es virtualmente nula, aún en pacientes con alto riesgo de desarrollar enfermedad. Algunas perspectivas promisorias han comenzado a emerger a partir de enfoques de biología molecular y genética. Como fenómeno común con otros neoplasmas epiteliales, se han demostrado alteraciones en la expresión oncogénica de los cánceres colorrectales que probablemente son reflejo de eventos importantes en el proceso de transformación maligna y progresión de la enfermedad. Sin embargo, los estudios de expresión oncogénica aún no aportan información que sea de utilidad clínica. Recientemente una investigación intensa en búsqueda de alteraciones cromosónicas y genéticas en los sindromes de cáncer colónico hereditario ha logrado establecer la ubicación del gen de la poliposis adenomatosa familiar en el cromosoma 5q21–q22. Como un hecho significante, la pérdida de alelas en el cromosoma 5 tambien ha sido observado en las células tumorales de por lo menos 20% de los pacientes con cáncer de colonesporádico. Este tipo de asociación entre el cambio genético constitucional y la aberración en las células de los tumores esporádicos es reminiscente de otras enfermedades neoplásicas con componente genético (por ejemplo, el retinoblastoma y el tumor de Wilms). El descubrimiento del gen de la poliposis adenomatosa familiar provee un fundamento para el diagnóstico presintomático o prenatal de esta entidad, así como de ciertas formas de cáncer colorrectal esporádico. Sin embargo, se puede predecir que otros marcadores ligados a los genes de susceptibilidad del cáncer colorrectal, con una más amplia capacidad de aplicación en el diagnóstico presintomático y en el tamizaje, habrán de ser eventualmente descubiertos.
    Notes: Abstract The aim of a primary screening system is to detect premalignant lesions and carcinomas when amenable to “curative” surgery. Although a number of “classical” tumor markers have acquired potential for clinical management, none is presently adequate for presymptomatic diagnosis or screening. In colorectal carcinoma, the screening potential of carcinoembryonic antigen (CEA), the gastrointestinal-related antigen, CA19-9, and other more recently characterized “biochemical markers” is virtually nonexistent, even in patients at high risk to develop the disease. Promising new leads are beginning to emerge from somatic cell genetic and molecular biological approaches. In common with other epithelial neoplasms, perturbations in oncogene expression have been demonstrated in colorectal cancers, and probably reflect important events in malignant transformation and progression. Studies of oncogene expression have, however, not yet yielded clinically useful information. Recently, an intensive search for specific chromosomal and gene abnormalities in the hereditary colon cancer syndromes led to the location of the familial adenomatous polyposis (FAP) gene at chromosome 5q21–q22. Significant is that the loss of alleles on chromosome 5 has also been observed in the tumor cells of at least 20% of sporadic colon cancer patients. This type of association between constitutional genetic change and genetic aberration in the cells of sporadic tumors is reminiscent of other malignant diseases with a genetic component (e.g., retinoblastoma and Wilms' tumor). The disclosure of the FAP gene might ultimately provide a basis for the presymptomatic or prenatal diagnosis of FAP as well as some forms of sporadic colorectal cancer; however, it can be anticipated that other markers linked to colorectal cancer susceptibility genes will eventually be discovered, with potentially wider application in presymptomatic diagnosis and screening.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 34 (1980), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We report on the synchronization of two commercial picosecond Ti:sapphire lasers with unprecedented low temporal jitter between the pulse trains. Pulse jitter is reduced from a few picoseconds to 20 fs with a stability of several hours. The technology enabling the tight pulse synchronization is reviewed in this article. We demonstrate the usefulness of the synchronization scheme by applying the technique to coherent anti-Stokes Raman scattering (CARS) microscopy. It is shown that CARS images can be acquired with a significant improvement in signal-to-noise ratio. This level of performance brings the fluctuations of the CARS signal down to the fundamental photon shot-noise limit. We present detailed statistical analysis of the pulse jitter and CARS noise along with enhanced CARS vibrational images of polymer beads. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Organometallics 5 (1986), S. 456-460 
    ISSN: 1520-6041
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 5
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: The effects of dibutyryl cyclic AMP (dbcAMP) and dibutyryl cyclic GMP (db-cGMP) were tested on Ca2+-ATPase, Mg2+-ATPase, and (Ca2++ Mg2+)-ATPase activities in lysed synaptosomes prepared from whole rat brains (minus cerebellum). At concentrations from 0.1 to 2.0 mM, db-cGMP produced a selective, concentration-dependent increase in Ca2+-ATPase activity. Both db-cGMP and db-cAMP slightly reduced Mg2+-ATPase activity, whereas neither compound had concentration-dependent effects on (Ca2++ Mg2+)-ATPase activity. These findings suggest that the Mg2+-independent, Ca2+-ATPase activity in rat brain is regulated by a cyclic GMP-dependent process. Further, the data provide evidence that the Ca2+-ATPase activity in lysed synaptosomal membranes represents an enzyme that is distinguishable from both the Mg2+- and (Ca2++ Mg2+-ATPase.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The optical properties of alpha-Al2O3 have been determined by two independent methods, vacuum ultraviolet (VUV) spectroscopy and electron energy-loss spectroscopy (EELS) over the energy range from 6 to 142 eV. For each experimental method two sets of high-quality data have been measured and analyzed from alpha-Al2O3. The evolution of the differences between the data for each experimental method and its associated analytical method indicate the reliability of the results, and the comparison between the methods emphasizes the relative advantages of each. VUV spectroscopy offers a higher energy resolution, resolving sharper features in the spectra, whereas EELS significantly extends the energy range, which has been exploited here to 140 eV but can be extended even further. Good overall consistency is found, but there are pronounced differences in the valence region from 10 to 30 eV, where strong absorptions are present, increasing the relative variability of the analysis. This demonstrates that accuracy estimates of the optical properties are meaningful only when supplied as a function of energy, because both strong intrinsic absorptions and weak experimental signals make accurate determinations difficult. Moreover, variations in the optical properties are observed most easily in the interband transition strength, Jcv, and are less evident when the optical properties are represented as the complex index of refraction. Because the optical properties can change with specimen origin and preparation and because of the details of data acquisition and numerical analysis procedures, assessing the contributions of each of these methods to our accurate knowledge of the optical constants is essential.
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