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First published online February 4, 2005
Journal of Experimental Biology 208, 603-610 (2005)
Published by The Company of Biologists 2005
doi: 10.1242/jeb.01422

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Analysis of Na⁺, Cl^-, K⁺, H⁺ and NH₄⁺ concentration gradients adjacent to the surface of anal papillae of the mosquito Aedes aegypti: application of self-referencing ion-selective microelectrodes

Andrew Donini^* and Michael J. O'Donnell

Department of Biology, McMaster University, Life Sciences Building, 1280 Main Street West, Hamilton, Ontario, Canada, L8S 4K1

View larger version (82K): [in a new window]   Fig. 1. Representative example of SeRIS microelectrode measurements showing calculated ion fluxes along the surface of the anal papillae in vivo. The length of the arrows and the arrowheads indicate the magnitude and direction of flux, respectively. The papillae were arbitrarily divided into quarters such that regions 1 and 2 comprised the proximal half of the papillae and regions 3 and 4 the distal portion of the papillae. (A) H+ flux. H+ is released by the papillae into the bathing medium. Note that H+ flux is higher in the proximal regions of the papillae. Vertical scale bar, 6.5 pmol cm-2 s-1; horizontal scale bar, 90 µm. (B) Cl- flux. Cl- is taken up by the papillae from the bathing medium. The papillae that measurements were taken from was positioned approximately 500 µm below the other papilla that is seen in the field of view. Vertical scale bar, 42 pmol cm-2 s-1, horizontal scale bar, 54 µm.

View larger version (20K): [in a new window]   Fig. 2. Summary of ion fluxes in the four regions of the anal papilla in vivo. Negative values denote influx of ions from the bathing medium into papilla, and positive values denote efflux of ions from the papilla into the bathing medium. H+ and K+ fluxes were significantly higher in region 1 (asterisks; K+ flux: ANOVA P<0.01; Tukey-Kramer P<0.05; H+ flux: ANOVA P<0.05; Dunn's test P<0.05). There were no regional differences in Na+, Cl- and NH4+ fluxes. Values are mean + S.E.M. (Na+, N=5; Cl-, N=7; H+, N=6; K+, N=5; NH4+, N=7).

View larger version (35K): [in a new window]   Fig. 3. H+ flux along the length of a papilla in vitro. The papilla was removed from the larva and sealed at the open end with Vaseline. Note that in comparison with Fig. 2A there were no regional differences in H+ flux. Vertical scale bar, 7 pmol cm-2 s-1; horizontal scale bar, 115 µm.

View larger version (21K): [in a new window]   Fig. 4. Summary of ion fluxes in the four regions of the anal papilla in vitro. There were no regional differences in ion fluxes. Values are mean + S.E.M. (Na+, N=6; Cl-, N=7; H+, N=9; K+, N=9).