ISSN:
1615-6102
Schlagwort(e):
Axoplasmic transport
;
Force generating mechanism
;
Microtubules
;
Nerve cell
;
Saltatory movement
;
Viscosity
Quelle:
Springer Online Journal Archives 1860-2000
Thema:
Biologie
Notizen:
Summary In this article the mode of force generation of axoplasmic transport is examined on theoretical grounds. We use as criteria the experimental evidence available, the biophysical boundary conditions, energetical feasibility, and earlier theoretical treatments of this topic. The following results are obtained: 1. Comparison of the energy available and the energy required to move organelles through the viscous cytoplasm shows that the viscosities reported preclude such movement of larger vesicles or mitochondria. This suggests that transport should occur in microregions of low viscosity. 2. For ultrastructural, pharmacological, and biochemical reasons such low viscosity regions are expected to be located around microtubules. 3. Out of the 11 theoretical possibilities to generate the driving force we had to rule out four because of obvious violations of verified data. Four other modes of force generation would require one or several additional transport mechanisms to explain the entire phenomenon. Models which imply streaming of low viscosity axonal regions are found to be in good agreement with the experimental findings. 4. The comparison of intracellular sites for the location of the force generating mechanism suggests that they are located at the microtubular surface. We have shown that the properties of axoplasmic transport fit most easily the concept that the proposed low viscosity domains be located around microtubules and microtubule bundles and that these domains represent streaming regions of cytoplasm. This concept is found to be in agreement with the presented list of criteria any hypothesis of axoplasmic transport must satisfy.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1007/BF01283700
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