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  • 1
    ISSN: 1432-1106
    Keywords: Harmaline tremor ; Cerebellum ; Inferior olive ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Purkinje cells were recorded extracellularly and mapped in the cerebellar cortex of the rat under tremogenic doses of harmaline. Four différent types of responses were encountered, of which two were considered as being responsible for the harmaline tremor. The latter had a regular firing pattern of complex spikes at 5 to 10 Hz and were mostly found in the vermis. Their number decreased in the more lateral region of the cerebellar cortex until they eventually disappeared. Horseradish peroxidase was injected into all the areas of the cerebellar cortex containing Purkinje cells with harmaline-induced activity. Labeled neurons were in all cases traced to the medial accessory olive. The metabolic activity of the inferior olive under harmaline was measured with 2-deoxyglucose. Increased labeling was only found in the medial accessory olive. Such an increase was demonstrated as being due to a direct effect of the drug on the inferior olivary neurons, indicating that the medial accessory olive is responsible for the harmaline tremor in the rat. Our results point out that, in the rat, there is an inverse relationship between serotoninergic innervation of a region in the inferior olivary nucleus and that with harmaline sensitivity, therefore a serotoninergic mechanism hypothesis for the harmaline tremor needs further investigation.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-1106
    Keywords: Cerebellum ; Fastigial nucleus, [14C]-2-deoxyglucose ; Unit activity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The cerebellar output function was studied using cerebellopetal proprioceptive stimulation hich produces simple and complex excitatory discharges as well as inhibitory activity in the Purkinje cells. The activity of the intracerebellar nuclei (and of the entire brain stem) was measured by the energy consumption as revealed with the [14C]-2-deoxyglucose method. The stimulations consisted of repetitive (1–20 c/s) electrical excitation of the nerve leading to the inferior oblique, to the masseteric and to the gastrocnemius soleus muscle. Compared to a group of non-stimulated controls, heavy bilateral labeling was obtained in the posterior pole of the fastigial nucleus. This was not observed with stimulation of the vibrissal pad which, however, produced a clear increase of [14C]-2-deoxy glucose uptake in the secondary trigeminal complex. Labeling of the posterior part of the fastigial nuclei was suppressed by ablation or pharmacologic inactivation of the overlying cerebellar cortex which suppresses the inhibitory activity of the Purkinje cells into the nuclear cells. Labeling of the posterior fastigial nuclei was also decreased in animals not stimulated but with ablation or pharmacologic inactivation of the overlying cerebellar ortex. The hypothesis proposed is that the marking results are the consequence of an increased activity in the Purkinje cell terminals. The activity of the Purkinje cells was also recorded extracellulary both before and during repetitive stimulation of a muscle nerve. The discharge activity of those in the cerebellar vermis and giving axons to the posterior fastigial nucleus was increased by the stimulation, whereas the activity of those of the hemispheral parts remained unchanged. Units in the fastigial nucleus were also recorded. Their activity was found to be deeply depressed so that only a few units were encountered and no further decrease of their discharge could be detected with the stimulation of a muscle nerve. Nevertheless, using the present data and those previously obtained, the conclusion is advanced that the cerebellar output function is actually decreased during afferent cerebellar stimulation.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Journal of statistical physics 57 (1989), S. 1069-1098 
    ISSN: 1572-9613
    Keywords: Block copolymers ; generating function ; Polya's theorem ; gelation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We determine the statistical properties of block copolymer complexes in solution. These complexes are assumed to have the topological structure of (i) a tree or of (ii) a line-dressed tree. In case the structure is that of a tree, the system is shown to undergo a gelation transition at sufficiently high polymer concentration. However, if the structure is that of a line-dressed tree, this transition is absent. Hence, we show the assumption about the topological structure to be relevant for the statistical properties of the system. We determine the average size of the complexes and calculate the viscosity of the system under the assumption that the complexes geometrically can be treated as porous spheres.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Journal of statistical physics 57 (1989), S. 1099-1122 
    ISSN: 1572-9613
    Keywords: Block copolymers ; generating function method ; Polya's theorem ; gelation ; nonnested structures
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We determine the statistical properties of block copolymers in solution. These complexes are assumed to have the topological structure of connected graphs with “nonnested” loops and cycles. The generating function method is used to determine the number of topologically different complexes containing a given number of block copolymers. It is shown that at sufficiently high concentration the system undergoes a transition to a gel phase. Furthermore, the average number of polymers per complex is calculated. Finally, the relative increase in viscosity is found under the assumption that the complexes can be treated as porous spheres.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    BioEssays 19 (1997), S. 747-750 
    ISSN: 0265-9247
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Although the precise function of utrophin at the postsynaptic membrane of the neuromuscular junction still remains unclear, despite recent genetic ‘knockout’ experiments(1,2), a separate study in a transgenic mouse model system for Duchenne muscular dystrophy (DMD) has nonetheless shown that overexpression of utrophin into extrasynaptic regions of muscle fibers can functionally compensate for the lack of dystrophin and alleviate the muscle pathology(3). In this context, the next step is to identify the mechanisms presiding over expression of utrophin at the neuromuscular synapse in attempts to induce its expression throughout DMD muscle fibers. In fact, additional studies have shown that an important DNA element contained with the utrophin promoter may confer synapse-specific expression to the utrophin gene(4,5). Identification of the events culminating in the transaction of the utrophin gene within synaptic myonuclei should provide important cues for the development of an effective therapeutic strategy for DMD.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 0736-0266
    Keywords: Sulfate ; Cartilage ; Glycosaminoglycans ; Mouse ; Articular ; Life and Medical Sciences
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: We have studied the effect of environmental sulfate concentration on the glycosaminoglycan synthesis of anatomically intact patellar cartilage of the mouse in vitro. Incubation of mouse patellae in medium with sulfate concentrations below 0.5 mM resulted in a diminished incorporation of sulfate but in unaltered incorporation of glucosamine. This suggested the synthesis of undersulfated glycosaminoglycans under these conditions. We characterized glycosaminoglycans synthesized at three different sulfate concentrations: a sulfate concentration physiological for the mouse (1.0 mM), a sulfate concentration in the range where sulfate incorporation was strongly diminished (0.1 mM), and an extremely low sulfate concentration (10 nM). Analysis of glycosaminoglycan disaccharides and DEAE anion chromatography of the glycosaminoglycans could not confirm the synthesis of undersulfated glycosaminoglycans at 0.1 mM. The chromatogram of glycosaminoglycans synthesized in medium containing 10 nM showed the presence of a very low sulfated glycosaminoglycan pool not observed at higher medium sulfate concentrations. Intermediately sulfated glycosaminoglycans were also synthesized during incubation with 10 nM sulfate. So, our data indicate that only very low sulfate concentrations in the medium lead to the synthesis of undersulfated glycosaminoglycans and that the sulfation mechanism of murine patellar cartilage chondrocytes does not seem to fit completely in an “all-or-nothing” pattern.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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