QUICK SEARCH:   [advanced] Author: Keyword(s):
Home     Help     Feedback     Subscriptions     Archive     Search     Table of Contents

First published online May 8, 2007
Journal of Experimental Biology 210, 1726-1734 (2007)
Published by The Company of Biologists 2007
doi: 10.1242/jeb.02766

This Article Summary Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Tracy, C. R. Articles by Karasov, W. H. Search for Related Content PubMed PubMed Citation Articles by Tracy, C. R. Articles by Karasov, W. H.

Absorption of sugars in the Egyptian fruit bat (Rousettus aegyptiacus): a paradox explained

Christopher R. Tracy^1,2,*, Todd J. McWhorter^3,4, Carmi Korine¹, Michal S. Wojciechowski^1,5, Berry Pinshow¹ and William H. Karasov³

¹ Mitrani Department of Desert Ecology, Jacob Blaustein Institutes for Desert Research, Ben-Gurion University of the Negev, 84990 Midreshet Ben-Gurion, Israel
² School of Science, Charles Darwin University, Darwin, NT 0909, Australia
³ Department of Wildlife Ecology, University of Wisconsin, Madison, WI 53706, USA
⁴ Department of Veterinary Biology & Biomedical Science, Murdoch University, Murdoch, WA 6150, Australia
⁵ Department of Animal Physiology, Institute of General and Molecular Biology, Nicolas Copernicus University, Torun, Poland

View larger version (10K): [in this window] [in a new window]   Fig. 1. Plots of mean (± s.e.m.) plasma L-rhamnose concentration versus time since its oral or injected administration into Egyptian fruit bats (N=11). Each concentration (ng mg–1 plasma) was normalized to the dose administered to the bat. The inset shows the mean values on a semi-log plot. The line through points from the injection trial is the nonlinear fit to the biexponential model: Ct=Ae–t + Be–ßt (see Materials and methods, and Table 2 for derived parameters). The line is extrapolated beyond the data to permit visual comparison with the data from the oral administration trial.

View larger version (9K): [in this window] [in a new window]   Fig. 2. Plots of mean (± s.e.m.) plasma cellobiose concentration versus time since its oral or injected administration into Egyptian fruit bats (N=11). Each concentration (ng mg–1 plasma) was normalized to the dose administered to the bat. The inset displays the mean values on a semi-log plot. The line through points from the injection trial is the nonlinear fit to the biexponential model: Ct=Ae–t + Be–ßt (see Materials and methods, and Table 1 for derived parameters). The line is extrapolated beyond the data to permit visual comparison with the data from the oral administration trial.

View larger version (10K): [in this window] [in a new window]   Fig. 3. Plots of mean (± s.e.m.) plasma 3-O-methyl-D-glucose concentration versus time since its oral or injected administration into Egyptian fruit bats (N=11). Each concentration (ng mg–1 plasma) was normalized to the dose administered to the Egyptian fruit bat. The inset displays the mean values on a semi-log plot. The line through points from the injection trial is the nonlinear fit to the biexponential model: Ct=Ae–t + Be–ßt (see Materials and methods, and Table 1 for derived parameters). The line is extrapolated beyond the data to permit visual comparison with the data from the oral administration trial.

View larger version (6K): [in this window] [in a new window]   Fig. 4. The fractional absorptions of three carbohydrate probes in Egyptian fruit bats, Rousettus aegyptiacus (circles, N=11) and Sprague-Dawley laboratory rats [squares, N=6; rat data from Lavin et al. (Lavin et al., 2004)]. 3-OMD-glucose (194 Da; closed symbols) is absorbed both actively and passively; L-rhamnose (164 Da) and cellobiose (342 Da) are absorbed passively (open symbols). For rats, lactulose (342 Da), an isomer of cellobiose, was used as a probe instead, and was assumed to behave similarly to cellobiose. Asterisks indicate statistically significant differences (P<0.05) between rats and R. aegyptiacus (see main text); error bars are ±1 s.e.m. (some error bars are smaller than the symbols). Both species show high absorption of 3-OMD-glucose, and both show decreasing absorption of the passively absorbed probes as probe size increases; however, passive absorption by R. aegyptiacus was significantly higher than that by rats for both passively absorbed probes.

View larger version (11K): [in this window] [in a new window]   Fig. 5. (A) Cumulative absorption versus time since ingestion of 3-O-methyl-D-glucose (3OMD-glucose; open circles, solid line), cellobiose (open triangle, broken line) and L-rhamnose (open square, dotted line) by Egyptian fruit bats. (B) The ratios of apparent absorption of L-rhamnose and 3OMD-glucose were calculated from the cumulative amounts absorbed in Fig. 5A. Assuming that absorption of L-rhamnose is passive, whereas the absorption of 3OMD-glucose represents the sum of passive plus mediated absorption, the ratio of the apparent absorption (L-rhamnose/3OMD-glucose) indicates the proportion of 3OMD-glucose absorption that occurs via the passive pathway. These data suggest that at least 60% of 3OMD-glucose absorption was passive, whatever time point one chooses to use in calculating apparent absorption rate (i.e. from zero to 5 min or zero to 2 h).