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  • Polymer and Materials Science  (9)
  • Diterpene  (3)
  • Magnetic resonance imaging  (3)
  • 1
    ISSN: 1433-0407
    Keywords: Schlüsselwörter Intrazerebrale Blutung ; Magnetresonanztomographie ; Hämosiderin ; Key words Intracerebral hematome ; Magnetic resonance imaging ; Hemosiderin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary Increased use of gradient echo T2*- weighted gradient echo sequences in magnetic resonance imaging (MRI) of patients suffering from primary ICH called attention to foci of signal loss which were suggested to represent remnants of cerebral microbleeds. In a post mortem correlative MR and histopathological study we provide support for this notion. We found areas of signal loss on gradient echo T2*-weighted sequences in 7 out of 11 brains of patients who had died of intracerebral hematoma. Histopathologically, these areas represented hemosiderin deposits indicating previous extravasation of blood. To provide data about the prevalence of these MRI findings in a healthy elderly population a subgroup of participants of the Austrian Stroke Prevention Study was analyzed. We detected foci of signal loss on gradient echo T2*-weighted sequences in 18 out of 280 volunteers (6,4%). MR-based evidence of previous microbleeds may indicate a potentially higher risk of suffering from intracerebral bleeding which could have therapeutic implications for the treatment of acute stroke and for secondary prevention. This hypothesis will have to be tested in future prospective trials.
    Notes: Zusammenfassung Vermehrte Anwendung T2*-gewichteter Gradienten-Echo-Sequenzen bei Magnetresonanztomographie- (MRT-) Untersuchungen von Patienten nach einem intrazerebralen Hämatom machte auf kleine, hypointense Areale aufmerksam, von denen bisher nur angenommen wurde, daß sie abgelaufene Mikroblutungen darstellen. In einer Post-mortem-Studie mit MRT und vergleichenden histopathologischen Untersuchungen zeigen wir Daten, die diese Hypothese stützen. Bei 7 von 11 Patienten, die an primärem intrazerebralem Hämatom verstorben waren, fanden sich hypointense Areale in T2*-Gradienten-Echo-Sequenzen. Histopathologisch zeigten diese Areale Hämosiderin-Ablagerungen, welche auf abgelaufene Blutungen hinweisen. Um Aussagen über die Prävalenz dieser MRT-Befunde in einem Kollektiv klinisch unauffälliger Probanden mittleren Alters machen zu können, wurden Teilnehmer derÖsterreichischen Schlaganfall-Vorsorge-Studie untersucht. Bei 18 von 280 Probanden (6,4%) fanden sich Signalhypointensitäten in T2*-Gradienten-Echo-Sequenzen. Der MR-tomographische Nachweis abgelaufener Mikroblutungen könnte ein Hinweis auf ein erhöhtes zerebrales Blutungsrisiko sein, was therapeutische Konsequenzen für die primäre Therapie und Sekundärprophylaxe beim Schlaganfall haben könnte. Hierzu sind noch weitere prospektive Studien notwendig.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Neuroradiology 40 (1998), S. 675-683 
    ISSN: 1432-1920
    Keywords: Key words Cortical dysplasia ; focal ; Magnetic resonance imaging ; Magnetic resonance spectroscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We studied nine cases of focal cortical dysplasia (FCD) by MRI, with surface-rendered 3D reconstructions. One case was also examined using single-voxel proton MR spectroscopy (MRS). The histological features were reviewed and correlated with the MRI findings. The gyri affected by FCD were enlarged and the signal of the cortex was slightly increased on T1-weighted images. The gray-white junction was indistinct. Signal from the subcortical white matter was decreased on T1- and increased on T2-weighted images in most cases. Contrast enhancement was seen in two cases. Proton MRS showed a spectrum identical to that of normal brain.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-1920
    Keywords: Magnetic resonance imaging ; Superficial siderosis ; Central nervous system
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We reviewed a 7-year series of brain MRI examinations to determine the frequency and clinical significance of superficial siderosis of the central nervous system (SS). SS was defined by widespread bilateral signal loss at the surfaces of the cerebral or cerebellar hemispheres, the brain stem and the spinal cord on T2-weighted images. Clinical data comprised a neurological examination of identified patients and a review of their case notes. Among 8843 consecutive studies we identified 13 (0.15 %) patients with MRI evidence of SS. Only 2 had symptoms or signs characteristic of SS, such as cerebellar ataxia, hearing loss, myelopathy and dementia. Haemosiderin deposition was most widespread in both symptomatic individuals. A definite cause for SS was detected in 9 patients (69 %). None of them had a full clinical picture of SS. These data indicate SS per se to be much more frequent than may be assumed from the literature. It appears to become symptomatic only with extensive amounts of widespread iron deposition which develop preferentially with cryptic or unidentified causes of bleeding.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1432-1335
    Keywords: Tumorpromoter ; Phorbol ; Diterpene ; Leukemogenesis cocarcinogens ; Tumorpromotor ; Cocarcinogene ; Phorbol ; Diterpen ; Leukämogenese
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung Phorbol und sechs strukturverwandte Substanzen, die die polyfunktionellen Diterpene des Tiglian-, Ingenan- und Lathyrantyps repräsentieren, wurden an SWR-Mäusen auf systemische promovierende und leukämogene Wirkung geprüft. Zur systemischen Initiation wurde kurz nach Geburt 15 μg Dimethylnitrosamin (DMN) s.c. injiziert. Die Diterpene wurden i.p. entweder mit oder ohne vorhergehende Initiation mit DMN gegeben. Systemische Promotion für Leber zeigten alle geprüften Diterpene mit der Entstehung von Adenomen. Einige der Diterpene erwiesen sich wirksamer als Phorbol. Die relativ hohe Dosis von DMN, die als Initiator verwendet wurde, machte eine Auswertung bezüglich promovierender Wirkung auf die Lunge unmöglich. Die leukämogene Wirkung von Phorbol bei SWR Mäusen wurde für drei verschiedene Dosen bestätigt. Die übrigen Diterpene zeigten mit der jeweils geprüften Dosis keine signifikante leukämogene Wirkung. Die leukämogene Wirkung des Phorbols wurde durch vorausgehende DMN-Injektion vollständig verhindert. Die fehlende Korrelation zwischen promovierender Wirkung an Haut, systemischer promovierender Wirkung an Leber und leukämogener Wirkung der getesteten Diterpene wird diskutiert.
    Notes: Summary Phorbol and six structurally related compounds representing the polyfunctional diterpenes of the tigliane, ingenane, and lathyrane types were tested for systemic promoting and leukemogenic activity in SWR mice. For systemic initiation soon after birth, 15 μg dimethylnitrosamine (DMN) was injected s.c. The diterpenes were administered i.p. either with or without prior systemic initiation with DMN. Systemic promotion was expressed for liver by induction of adenomas with all the diterpenes tested, some of them being more potent than phorbol. The relatively high dose of DMN used as initiator prevented an evaluation of promoting action in relation to lung carcinogenesis. The leukemogenic effect of phorbol in SWR mice was confirmed at three different dose levels. The other diterpenes tested had no significant leukemogenic activity. The leukemogenic action of phorbol was totally inhibited by prior DMN injection. The lack of correlation between promoting action in skin, systemic promoting action in liver and leukemogenic action, among the diterpenes tested, is discussed.
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  • 5
    ISSN: 1432-1335
    Keywords: Diterpene ; Tumorpromoter ; Plasminogen-Aktivator ; Blutplättchen-Aggregation ; Diterpene ; Tumor promoter ; Plasminogen activator ; Platelet aggregation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary Phorbol and eight of its derivatives were investigated for their ability to stimulate the synthesis of the enzyme plasminogen activator in cultured chick embryo fibroblasts and to aggregate human blood platelets and have been assayed for tumor, promoting and skin, irritant activities. Over a range of concentrations, elevation in the levels of plasminogen activator activity induced by phorbol derivatives correlates well with their promoting and irritant properties. In the platelet aggregation assay however, the parallelism between the activities measured in different biological assays was less complete. While strong promoters, such as TPA, are potent aggregating agents, and weak promoters, such as PDA, are poor or ineffective inducers of aggregation, two derivatives, PDD and PDB, deviate from this general result. Platelets must be exposed to PDD in relatively high concentrations before they will aggregate, and PDB was found to be the most potent aggregating agent of all the derivatives tested.
    Notes: Zusammenfassung Phorbol und acht seiner Derivate wurden auf ihre Fähigkeit untersucht, die Synthese von Plasminogen-Aktivator in Zellkulturen von Hühnerembryo-Fibroblasten zu stimulieren und die Aggregation von Blutplättchen zu induzieren und auf ihre tumorpromovierende und hautirritierende Wirkung getestet. Die Erhöhung der Plasminogen-Aktivator Aktivität durch Phorbolderivate korreliert gut mit ihren irritierenden und promovierenden Eigenschaften. Im Test auf Blutplättchen-Aggregation ist die Korrelation nicht eindeutig: Sie gilt für starke Promotoren (wie TPA), die auch hochwirksame Induktoren der Aggregation sind, sowie für schwache Promotoren (wie PDA), die nur gering oder nicht induzieren; Ausnahmen sind PDD und PDB: PDD, ein starker Promoter, ist nur schwach wirksam, PDB, ein schwacher Promotor, ist dagegen das am stärksten aggregationsstimulierende Derivat.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Journal of cancer research and clinical oncology 103 (1982), S. 17-29 
    ISSN: 1432-1335
    Keywords: Diterpene ; Tumor promoter ; Differentiation ; Leukemia cells
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary 12-O-Tetradecanoylphorbol-13-acetate (TPA), the prototype polyfunctional diterpene ester tumor promoter of two-step carcinogenesis in mouse skin, induced differentiation of human promyelocytic leukemia cells (HL-60) in culture. Differentiation of HL-60 cells was characterized by increased phagocytosis, increased lysozyme activity (EC 3.2.1.17) in the growth medium, and changes in morphology to those characteristics of more mature cells resembling macrophages. Many of the cells treated with TPA became aggregated, attaching firmly to culture flasks. The average intracellular myeloperoxidase activity (EC 1.11.1.7) per cell decreased during induction of differentiation by TPA. It was also found that TPA enhanced, rather than inhibited, differentiation of HL-60 cells induced by DMSO. In addition to TPA, several polyfunctional diterpene esters of the tigliane, ingenane, and daphnane type have been tested for their ability to induce morphological and functional changes of HL-60 cells. The activities of the compounds to induce these changes correlated well with their activities as tumor promoters in two-step carcinogenesis in mouse skin. In particular, half the concentrations required for induction of adhesion of the cells to flasks were roughly correlated to the potency of these compounds as tumor promoters. Among the compounds tested, phorbol-12,13-didecanoate (PDD), ingenol-3-hexadecanoate, Pimelea factor P1 and Pimelea factor P2 were as active as TPA, while 4-O-methyl-TPA and 4α-PDD were much less active. Phorbol and ingenol were totally inactive up to a concentrations 10,000-fold higher than that of TPA.
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  • 7
    Electronic Resource
    Electronic Resource
    Weinheim [u.a.] : Wiley-Blackwell
    Materials and Corrosion/Werkstoffe und Korrosion 45 (1994), S. 21-28 
    ISSN: 0947-5117
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Description / Table of Contents: Microbial deterioration of materials - fundamentals: Mathematical modelling of destruction mechanismsModern trends in materials science require novel methods and strategies. The general aim is to describe by models the reactions occurring at the surface and within a solid. At the present time, however, it is only possible to derive, from the experimental work, mathematical relations, and this is not sufficient for a prediction of materials behaviour. On the basis of the three steps involved in the description of materials behaviour, i. e. rules of thumb, statistical evaluation of experimental data (including models developed for the presentation of reaction kinetics), and development of physical models (among others Monte Carlo simulations), these three steps and, in particular, the preliminary step of biocorrosion, i. e. biofilm formation, are discussed. Only physical models allow a prediction of reactions, although a prediction independent from experiment is not possible because of the unknown distributions of the acting energies and their possible fluctuations. Beyond that an outline is given of the description of corrosion reactions and crack propagation. A general problem, in particular in connection with biological reactions, is the lack of interdisciplinary education of scientists and engineers.
    Notes: Die moderne Entwicklung der Werkstoffwissenschaft bedingt einen Wandel in den Methoden und Strategien. Es wird angestrebt, die an und im Festkörper ablaufenden Reaktionen in Form von Modellen zu beschreiben. Gegenwärtig gelingt es aber nur, aus experimentellen Untersuchungen mathematische Zusammenhänge abzuleiten, womit eine Vorhersage des Werkstoffverhaltens mit theoretischen Mitteln nicht gelingt.Ausgehend von den drei Erkenntnisstufen zur Beschreibung des Werkstoffverhaltens, den Faustregeln, einer Auswertung von Experimenten mit statistischen Methoden, hierzu gehören auch reaktionskinetische Modellansätze, und der Entwicklung physikalischer Modelle, u.a. Monte-Carlo-Simulationen, werden diese insbesondere für die „Vorstufe“ der biokorrosiven Schädigung vorgestellt, der Biofilmbildng. Nur physikalische Modelle ermöglichen die „Voraussage“ von Reaktionsabläufen, wobei infolge der Unkenntnis der Verteilungen für die wirkenden Energien und deren möglichen Fluktuationen eine vom Experiment getrennte Voraussage nicht möglich ist.In einem Überblick wird darüber hinaus auch auf die Beschreibung von Korrosionsreaktionen und das Rißwachstum eingegangen. Ein generelles Problem, insbesondere im Zusammenhang mit biologischen Reaktionsabläufen, stellt die nicht fachgrenzenübergreifende Ausbildung von Naturwissenschaftlern and Ingenieuren dar.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Weinheim [u.a.] : Wiley-Blackwell
    Materials and Corrosion/Werkstoffe und Korrosion 47 (1996), S. 716-717 
    ISSN: 0947-5117
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Biopolymers 16 (1977), S. 317-326 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Intensity-fluctuation laser-light-scattering spectroscopy has been used to characterize the temperature dependence of the translational diffusion coefficient through the helix-coil region for the DNA isolated from bacteriophage N1. The diffusion coefficient does not change smoothly, but exhibits fine structure detail similar to that seen in the uv absorption hyperchromicity. These changes are related to the heterogeneous distribution of bases along the N1-DNA chain.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Biopolymers 16 (1977), S. 327-340 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Intensity-fluctuation laser-scattering spectroscopy measurements have been reported for the DNA isolated from bacteriophage φ29. The cumulant method of data analysis gives well-defined weighted average decay frequencies. Available theoretical models are shown to yield good values for the diffusion coefficient and longest intramolecular relaxation time for low-molecular-weight DNA's but not for higher molecular weight species. The temperature dependence of the apparent diffusion coefficient exhibits drastic oscillations in the helix-coil transition region. The number of these oscillations is consistent with independent measurements of uv hyperchromicity measurements and suggests that φ29-DNA is composed of at least three regions of differing G + C content.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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