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Cope's gray tree frog Hyla chrysoscelis accumulates glycerol during cold acclimation. We hypothesized that, during this process, gray tree frogs adjust renal filtration and/or reabsorption rates to retain accumulated glycerol. During cold acclimation, plasma concentrations of glycerol rose >200-fold, to 51 mmol/l. Although fractional water reabsorption decreased, glomerular filtration rate (GFR) and, consequently, urine flow were <5% of warm levels, and fractional glycerol reabsorption increased. In contrast, dehydrated frogs increased fractional water reabsorption, decreased GFR, and did not accumulate glycerol. We hypothesized that expression of proteins from the aquaporin (AQP)/glyceroporin (GLP) family was associated with changing patterns of water and glycerol movement. We cloned the cDNA for three such proteins, quantified mRNA expression in nine tissues using real-time quantitative PCR, and functionally characterized them using a Xenopus oocyte expression system. HC-1, an AQP1-like water channel conferring low glycerol permeability, is expressed ubiquitously in warm- and cold-acclimated tissues. HC-2, a water channel most similar to AQP2, is primarily expressed in organs of osmoregulation. HC-3, which is most similar to AQP3, is functionally characterized as a GLP, with low permeability to water but high permeability to glycerol. Aspects of expression levels and functional characteristics varied between cold and warm conditions for each of the three AQPs, suggesting a complex pattern of involvement in osmoregulation related to thermal acclimation.

Investigated problem-solving ability and reported regimen adherence among children, early adolescents, and middle adolescents with IDDM in response to hypothetical social situations where a choice between diabetes regimen adherence and peer desires must be made. Sixty-seven 8- to 17-year-olds with IDDM from two distinct U.S. geographical areas participated. Results indicated that compared to children with IDDM, adolescents with IDDM had better problem-solving abilities in response to social pressure situations, possibly reflecting their greater cognitive maturity. However, adolescents were also more likely to choose behaviors that are less regimen adherent. Differences in levels of problem-solving ability and adherence between the two regional subsamples were also found. Similar developmental patterns were found in both groups, showing the robust nature of the observed age-related trend of decreasing adherence in social situations despite increasing problem-solving abilities. Findings were interpreted in the context of normal adolescent development. Results are conceptually important for those interested in the transaction between peer and social influences and adherence for children and adolescents with IDDM, as well as other health behaviors.

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