Chemotropism mechanism

Commissural axons from the embryonic rat spinal cord extend preferentially toward floorplate explants in a manner suggestive of a chemotropic mechanism (Tessier-Lavigne et al., 1988 Placzek et al., 1990). Recently, two closely-related proteins isolated from embryonic chick brains, netrin-1 and netrin-2, have been shown to possess chemotropic activity in this spinal cord assay system (Serafini et al., 1994 Kennedy et al., 1994). 

The property of chemotropicity testifies to the balance of the redox layer system with respect to the vertical fluxes of the oxidants and reductants supplied. This should be the well-defined sequence of changes with depth of the favorability of the potential redox reactions [ 17,75] that can be realized by the bacterial community. The development of bacteria in this case should affect the distributions of nutrients. By modern estimation [79] the chemosynthetic production is comparable with photosynthetic production, and that should in the same manner affect the consumption of inorganic nutrients and production of their organic forms. Besides this the possible abiotic chemical reactions and the sedimentation of particulate matter of different densities should also play their roles in this mechanism. 

Yaginuma, H. and Oppenheim, R.W. (1991). An experimental analysis of in vivo guidance cues used by axons of spinal intemeurons in the chick embryo evidence for chemotropism and related guidance mechanisms, y. Neurosci. 11, 2598-2613. Yuan, S.S., Cox, L.A., Dasika, G.K. and Lee, E.Y. (1999). Cloning and functional... 

Since the chemistry of the chemotropic factor is unknown, the mechanism of the chemotropic response can be explained only in anatomical terms. It is from this point of view that we will consider the meager speculations to be found in the literature. First, however, it is necessary to recognize the fact that a pollen tube grows at its extreme tip. According to Iwanami... 

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