985 resultados para ReJeX-iT7 TP-40


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Collection : Le siècle ; 1-46

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A four page, semi-weekly paper that was published from 1803 to 1814.

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A four page, semi-weekly paper that was published from 1803 to 1814.

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The cholesterol chelating agent, methyl-b-cyclodextrin (MbCD), alters synaptic function in many systems. At crayfish neuromuscular junctions, MbCD is reported to reduce excitatory junctional potentials (EJPs) by impairing impulse propagation to synaptic terminals, and to have no postsynaptic effects. We examined the degree to which physiological effects of MbCD correlate with its ability to reduce cholesterol, and used thermal acclimatization as an alternative method to modify cholesterol levels. MbCD impaired impulse propagation and decreased EJP amplitude by 40% (P,0.05) in preparations from crayfish acclimatized to 14uC but not from those acclimatized to 21uC. The reduction in EJP amplitude in the cold-acclimatized group was associated with a 49% reduction in quantal content (P,0.05). MbCD had no effect on input resistance in muscle fibers but decreased sensitivity to the neurotransmitter L-glutamate in both warm- and coldacclimatized groups. This effect was less pronounced and reversible in the warm-acclimatized group (90% reduction in cold, P,0.05; 50% reduction in warm, P,0.05). MbCD reduced cholesterol in isolated nerve and muscle from cold- and warmacclimatized groups by comparable amounts (nerve: 29% cold, 25% warm; muscle: 20% cold, 18% warm; P,0.05). This effect was reversed by cholesterol loading, but only in the warm-acclimatized group. Thus, effects of MbCD on glutamatesensitivity correlated with its ability to reduce cholesterol, but effects on impulse propagation and resulting EJP amplitude did not. Our results indicate that MbCD can affect both presynaptic and postsynaptic properties, and that some effects of MbCD are unrelated to cholesterol chelation.

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Dark brown sediment with sub-angular to sub-rounded clasts. Rotation structures and lineations are common. Clasts ranging from small to large in size. Many large grains are fractured. Minor amounts of grain stacking and crushing can be seen. A few clay and organic rich domains can be seen.

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Coarse grained sample with sub-angular to sub-rounded clasts ranging from small-large in size. Rotation structures, grain crushing and lineations were seen throughout the sample.

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Coarse grained sample with clasts ranging from small to medium. Clast shape ranges from angular to sub-angular. Lineations and rotation structures seen. Clay material and fine grained domains (darker colour) also seen.

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This is a coarse grained sample with some very fine grained domains throughout the sample. The clast shape and size range from small to large, as well as angular to sub-rounded. Grain crushing is the most prevalent in this sample. It also contains some rotation structures and minor necking structures. Lineations and grain stacking can also be seen.