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  • 1
    ISSN: 1433-0407
    Keywords: Schlüsselwörter ALS ; Neurogenetik ; Exzitatorische Aminosäuren ; Cu/Zn-SOD ; Key words Amyotrophic lateral sclerosis ; Neurogenetics ; Excitatory amino acids ; Cu/Zn SOD
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary At presently, the etiology and pathogenesis of amyotrophic lateral sclerosis (ALS) are unknown. In recent years, the genetic background of hereditary motor neuron diseases has been partly defined. In particular, these advances represent an opportunity to improve our understanding of the pathogenesis of the familial and sporadic forms of ALS and thus provide a basis for rational therapeutic approaches. In this article, recent findings on the pathogenesis of the familial form of ALS and their implications for the sporadic form are discussed.
    Notes: Zusammenfassung Die Ätiologie und Pathogenese der amyotrophen Lateralsklerose (ALS) bleibt weitgehend ungeklärt. In den zurückliegenden Jahren sind bei den genetisch bedingten Varianten dieser Erkrankung wichtige Fortschritte bei der Identifizierung ihrer molekularbiologischen Grundlagen gemacht worden. Diese Fortschritte berechtigen zu der Hoffnung, daß es in Zukunft gelingt, die Pathogenese der familiären, aber auch der sporadischen Formen der Erkrankung zu erhellen und damit rationalen Therapieansätzen weiter den Weg zu bereiten. Im Rahmen dieser Übersichtsarbeit soll sowohl auf die vorliegenden Befunde bei der familiären Form der ALS (fALS) als auch auf die mögliche Bedeutung dieser Befunde für pathogenetische Vorstellungen bei der sporadischen Form der ALS (sALS) eingegangen werden.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-0533
    Keywords: Key words Motor neuron disease ; Vertical gaze palsy ; Progressive supranuclear palsy ; Multiple system atrophy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The case of a 38-year-old patient with rapidly progressing motor neuron disease, complicated by major dysfunction of the extrapyramidal system and of vertical gaze is described. Neuropathological examination revealed a degenerative process that severely affected the lower motor neurons, as well as the neurons of the pars compacta of the substantia nigra, the nucleus of Darkschewitsch, the nucleus interstitialis of Cajal, the colliculi superiores, and the pallidum. The long tracts were unaffected at all levels of the brain stem and spinal cord. There was no convincing evidence for the presence of a multiple system atrophy or progressive supranuclear palsy; the results rather revealed a pattern of vulnerability characteristic of a variant of motor neuron disease.
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  • 3
    ISSN: 1439-6327
    Keywords: Lactate threshold ; Ventilatory threshold ; prior exercise
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary To determine if blood lactate (LA) is the stimulus responsible for ‘breakaway’ ventilation (VE), the lactate (LT) and ventilation (VT) thresholds were monitored during one-legged cycling exercise. Ten healthy volunteer male subjects (Mean 2-legged $$\dot V_{O_{2\max } } $$ =4.27 l·min−1) performed prior exercise (PE) to reduce muscle glycogen stores by cycling at 75–85% of maximal heart rate (HR max) for 60–75 min, followed by a 30 h low carbohydrate diet. Pre- and post- LT and VT tests were performed on a cycle ergometer employing a continuous protocol with increments of 16 W every 3 min. Muscle biopsies were taken from the vastus lateralis muscle before the PE ride, prior to the threshold test 24 h later, and before testing the non-exercised (NE) leg. An I.V. catheter placed in the antecubital vein was used for serial blood samples taken at rest, and during the final 30 s of each progressive load. Gas analysis was calculated every 30 s (Beckman Metabolic Measurement Cart). Biopsies (N=3) showed that the exercise and diet regimen elicited glycogen reduction which significantly (p〈0.05) reduced R and the blood LA concentration in both the PE (2.62 to 1.99 mmol·l−1) and NE (2.87 to 2.26 mmol·l−1) legs at LT. At VT, LA concentrations were also significantly reduced in the PE (3.35 to 2.56 mmol·l−1) and NE (3.59 to 2.74 mmol·−1) legs. $$\dot V_{O_2 } $$ and VE, however, were similar between pre- and post- tests. Results of this study suggest that plasma LA accumulation is not responsible for ‘breakaway’ ventilation during progressive exercise and that LT and VT are not a cause and effect relationship.
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  • 4
    ISSN: 1435-1536
    Keywords: NMR field-cycling relaxation spectroscopy ; transverse relaxation ; self-diffusion ; NMR field-gradient method ; zero-shear viscosity ; defect diffusion ; reptation ; tube renewal ; contour length fluctuation ; critical molecular weight ; matrix effects ; amorphous polymers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Molecular weight and frequency dependences, respectively, of the nuclear magnetic relaxation times and the self-diffusion coefficient of polyethylene and polystyrene have been investigated over several orders of magnitude. The relation to viscous behaviour is established. A closed concept is developed. Conclusions are: a) Theγ-process in amorphous polyethylene can be described by the aid of the limited defect diffusion model. b) Theβ-process in the same material is interpreted as limited reptation. The intensity function of this process depends on the amorphous content. c) The three-component description of chain fluctuations already presented in previous papers has been modified in order to account for the precise molecular weight dependences, which now have been measured. Especially we distinguish between internal and whole-chain reptation. A correlation function is derived, which predicts the right limiting behaviour inspite of its semi-empirical character. The three components can be identified by the frequency and molecular weight dependences of the nuclear magnetic relaxation times. d) The molecular weight dependences are subdivided by 3 (spin lattice relaxation), 2 (transverse relaxation), 1 (zero-shear viscosity) and 0 (self-diffusion coefficient) characteristic molecular weights (M C, MBC, MAB). All of them can be derived as dynamic case transitions. Especially the classical critical molecular weight of the viscosity can be explained by the transition between tube fluctuations governed by internal and wholechain reptation, respectively. The assumption of a structural transition is unnecessary. e) A semi-empirical expression for the zero-shear viscosity is derived for the whole range of chain lengths. The analysis of the molecular weight dependences of the NMR relaxation times straightforwardly leads to those of the zero-shear viscosity. f) Using a NMR field-gradient method, it is shown again that the self-diffusion coefficients of both melt examples obeyD ∼M w −2.0 . g) Matrix effects predominantly are due to changes in the free volume.
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