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438 results on '"Walters, J. R."'

1. Seasonal body weight variation in five species of woodpeckers

Author

Koenig, W D, Walters, E L, Walters, J R, Kellam, J S, Michalek, K G, and Schrader, M S

Subjects
body mass, body weight, fat storage, food storage, Piciformes, seasonality, woodpeckers
Abstract

We investigated patterns of seasonal variation in body weight in six populations of five resident species of temperate-zone woodpeckers: Acorn Woodpecker (Melanerpes formicivorus), Red-bellied Woodpecker (M. carolinus), Red-cockaded Woodpecker (Picoides borealis), Downy Woodpecker (P. pubescens), and Great Spotted Woodpecker (Dendrocopos major). After controlling for time of day and overall body size, annual variation in body weight was small and generally not statistically significant. However, analysis revealed evidence of significant "winter fattening," comparable in magnitude to other temperate-zone resident species, in three of the species. The degree of winter fattening did not correlate with either the size of the acorn crop (for the Acorn Woodpecker) or latitude, two variables potentially related to predictability of food resources. However, the smaller species exhibited significantly greater winter fattening than the larger species, as predicted by the hypothesis that energy storage should be more important for small-bodied species. Furthermore, the food-storing Acorn Woodpecker exhibited considerably less winter fattening than the nonfood-storing species, supporting the hypothesis that food storage provides an ecological alternative to winter fattening.

Published
2005

33. Liver Biopsy

Author

Walters, J. R. F. and Paton, A.

Published
1980

40. Glucagon-like peptide-2 increases sucrase-isomaltase but not caudal-related homeobox protein-2 gene expression

Author

KITCHEN, P. A., FITZGERALD, A. J., GOODLAD, R. A., BARLEY, N. F., GHATEI, M. A., LEGON, S., BLOOM, S. R., PRICE, A., WALTERS, J. R. F., and FORBES, A.

Subjects
Peptides -- Analysis, Gene expression -- Analysis, Cell proliferation -- Analysis, Jejunum -- Evaluation, Ileum -- Evaluation, Biological sciences
Abstract

Kitchen, P. A., A. J. Fitzgerald, R. A. Goodlad, N. F. Barley, M. A. Ghatei, S. Legon, S. R. Bloom, A. Price, J. R. F. Walters, and A. Forbes. Glucagon-like peptide-2 increases sucrase-isomaltase but not caudal-related homeobox protein-2 gene expression. Am. J. Physiol. Gastrointest. Liver Physiol. 278: G425-G428, 2000.--To determine the effect of glucagon-like peptide-2 (GLP-2) on sucrase-isomaltase and caudal-related homeobox protein-2 (Cdx-2) gene expression, male Wistar rats were divided into total parenteral nutrition (TPN)-fed and GLP-2-treated, TPN-fed groups. TPN was given via a jugular line, inserted under anesthesia, for 7 days. The treatment group received 40 [micro]/day of GLP-2 intravenously with the TPN diet. The small intestine and colon were weighed and measured. Tissue was obtained from the jejunum, terminal ileum, and midcolon. RNA analysis, morphometry, and microdissection were performed. The weight of the small intestine of GLP-2-treated rats was greater than that of TPN-fed rats (P [is less than] 0.001). GLP-2 increased the mean metaphase arrests/crypt in both the jejunum and ileum (P [is less than] 0.001). Ileal expression of sucrase-isomaltase was increased by 1.6-fold (P [is less than] 0.05). Jejunal expression was increased by a similar amount, although not significantly (P = 0.08). There was no change in Cdx-2 gene expression. Thus GLP-2 can maintain small intestinal morphology and function, but effects on gene expression are not mediated by gross changes in the level of the mRNA for the homeobox protein Cdx-2. total parenteral nutrition; cellular proliferation; jejunum; ileum.

Published
2000

44. Seasonal body weight variation in five species of woodpeckers

Author

Koenig, W. D., Walter Koenig, Walters, J. R., Kellam, J. S., Michalek, K. G., and Schrader, M. S.

Subjects
body weight, seasonality, woodpeckers, Piciformes, fat storage, body mass, food storage
Abstract

We investigated patterns of seasonal variation in body weight in six populations of five resident species of temperate-zone woodpeckers: Acorn Woodpecker (Melanerpes formicivorus), Red-bellied Woodpecker (M. carolinus), Red-cockaded Woodpecker (Picoides borealis), Downy Woodpecker (P. pubescens), and Great Spotted Woodpecker (Dendrocopos major). After controlling for time of day and overall body size, annual variation in body weight was small and generally not statistically significant. However, analysis revealed evidence of significant "winter fattening," comparable in magnitude to other temperate-zone resident species, in three of the species. The degree of winter fattening did not correlate with either the size of the acorn crop (for the Acorn Woodpecker) or latitude, two variables potentially related to predictability of food resources. However, the smaller species exhibited significantly greater winter fattening than the larger species, as predicted by the hypothesis that energy storage should be more important for small-bodied species. Furthermore, the food-storing Acorn Woodpecker exhibited considerably less winter fattening than the nonfood-storing species, supporting the hypothesis that food storage provides an ecological alternative to winter fattening.

Published
2005

48. Inbreeding and experience affect response to climate change by endangered woodpeckers

Author

Schiegg, K, Pasinelli, G, Walters, J R, Daniels, S J, University of Zurich, and Schiegg, K

Subjects
10127alt Institute of Zoology (former), 2300 General Environmental Science, 1300 General Biochemistry, Genetics and Molecular Biology, 2400 General Immunology and Microbiology, 570 Life sciences, biology, 590 Animals (Zoology), 1100 General Agricultural and Biological Sciences
Published
2002

50. Can we improve estimates of juvenile dispersal distance and survival?

Author

Biological Sciences, Cooper, C. B., Daniels, Susan J., Walters, J. R., Biological Sciences, Cooper, C. B., Daniels, Susan J., and Walters, J. R.

Abstract

Estimates of distributions of natal dispersal distances and juvenile recruitment rates in open populations are strongly influenced by the extent and shape of the areas sampled. Techniques to improve biased dispersal and survival estimates include area-ratio methods based on weighting observations by sampling effort, the extent and shape of the area sampled, and the amount and distribution of preferred habitat surrounding the area sampled. We partitioned territories within the boundaries of a large, almost geographically closed, population of individually marked Red-cockaded Woodpeckers (Picoides borealis) and estimated dispersal and survival parameters from hypothetical smaller study areas (sampling areas) of varying sizes and shapes in order to examine whether an area-ratio method provides accurate or improved estimates of juvenile dispersal distance and survival. Non-aggregated sampling areas resulted in the detection of fewer dispersal events, but because of their large spatial extent, produced unbiased dispersal estimates. The use of aggregated sampling areas (circular or linear) resulted in the detection of higher numbers of dispersal events, but produced biased dispersal estimates that were generally improved by the area-ratio method. Area-ratio corrections usually provided better estimates of median dispersal distance than uncorrected estimates. Survival to breeding was usually underestimated and often not improved by the area-ratio method, regardless of extent and shape of the sampling area. Estimates of juvenile survival to breeding were improved by assuming that rates of emigration were equivalent to immigration, and correcting survival estimates accordingly. Small, local studies should use an area-ratio method to improve their estimates of median dispersal distance. Because the correction method estimates relative, but not absolute, numbers of individuals dispersing across distance categories, the area-ratio method should not be used for estimating surviv

Published
2008

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