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Jaffe & Créton | Calcium Waves |
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Jaffe & Créton | Calcium Waves |
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An early demonstration of electrical currents through polarizing fucus eggs (Jaffe, 1966; perhaps 6 mA/cm2) suggested the idea of self-electrophoresis as a localizing mechanism during development. This led to the development of the so-called vibrating probe to map and measure steady transcellular or transorganismal currents (Fig. 1).
Fig. 1 - A vibrating probe in front of a growing embryo of Pelvetia , a fucoid alga. From Nuccitelli & Jaffe, 1974.
This device then led to the discovery that steady electrical currents commonly traverse developing and regenerating systems and that these can be remarkably large. Thus 100 mamp/cm2 leaves the developing chick's primitive streak; up to 500 mA/cm2 enters the rhizoid of photosynthesizing and developing Acetabularia cells; while about 1000 mA/cm2 or 1 mA/cm2(!) crosses the cytoplasmic bridges between Cecropia nurse and oocyte cells. Such results and the circumstances in which such currents could lead to self-electrophoresis were reviewed and considered in (Jaffe, 1985).
The idea of self-electrophoresis also led to the idea that charged macromolecules floating in the plasma membrane are important targets of self-electrophoresis. A mathematical analysis of this process later indicated that a steady voltage difference of one millivolt or less across a cell should suffice to segregate such molecules against the unavoidable counteraction of diffusion (Jaffe, 1977). This provides an explanation of the fact that voltage drops of a millivolt or less per cell commonly do suffice to polarize the growth or direct the movement of various plant and animal cells (Jaffe & Nuccitelli, 1977; see Robinson, 1985 below ). We last contributed to this field in a study of developing Drosophila . It indicated voltages across the nurse cell/oocyte bridges of about 10 mV and along the perivitelline space of the embryo of at least 4 mV. These are surely large enough to segregate critical macromolecules by self-electrophoresis (Overall & Jaffe, 1985).
Subsequent work on or pertinent to self-electrophoresis has come from other laboratories, particularly those of Ken Robinson and of Richard Borgens at Purdue, Richard Nuccitelli at UC Davis, Dick Woodruff in Philadelphia, Colin McCaig and Iain Baikie in Aberdeen, as well as Bill Theurkauf at the University of Massachusetts medical center in Worchester (See references below.)
However, we now plan - in Lionel's second childhood - to return to self-electrophoresis, particularly in Drosophila .
References:
Baikie, ID et al (1999) Multitip scanning bio-Kelvin probe. Rev. Sc. Instrum. 70: 1842-1850.
Jenkins, LS, Duerstock, BS & Borgens, RB (1996) Reduction of the current of injury leaving the amputation inhibits limb regeneration in the red spotted newt. Dev. Biol. 178: 251-262.
McCaig, CD & Erskine, L (1996) Nerve growth and nerve guidance in a physiological electric field. In Nerve Growth and Guidance (CD McCaig, Ed.) Portland Press, London pp.151-170.
Nishimura, KY, Isseroff, RR & Nuccitelli, R. (1996) Human keratinocytes migrate to the negative pole in direct current electric fields comparable to those measured in mammalian wounds. J. Cell Sc. 109: 199-207.
Robinson, KR (1985) The Responses of Cells to Electrical Fields: A Review. J. Cell Biol. 101: 2023-2027.
Robinson, KR & Messerli, MA (1996) Electric embryos: the embryonic epithelium as a generator of developmental information. In Nerve Growth and Guidance (CD McCaig, Ed.) Portland Press, London pp.131-150.
Theurkauf, WE & Hazelrigg, TI (1998) In vivo analyses of cytoplasmic transport and cytoskeletal organization during Drosophila oogenesis. Development 125: 3655-3666.
Singleton, K & Woodruff, RI (1994) The osmolarity of adult Drosophila hemolymph and its effect on oocyte-nurse cell electrical polarity. Dev. Biol. 161: 154-167.