Rachel M Borthwell

University of California, Davis, Davis, California, United States

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Publications (5)8.96 Total impact

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    ABSTRACT: Hummingbirds present a unique combination between extremely high life costs and a number of efficient adaptations to fuel these demands. In addition to cognitive abilities, territorial hummingbirds display aggressive behaviors that allow for access to better food resources. In year-round territorial species, male-male territorial aggression is similar between breeding and non-breeding seasons; however, the endocrine mechanisms underlying control of territoriality during these distinct seasonal periods may differ. In many species, testosterone (T) triggers increased aggression during the breeding season whereas territoriality in the non-breeding season can be regulated by circulating the biologically inert sex steroid precursor dehydroepiandrosterone (DHEA) and converting it to T in target tissues. The seasonal hormonal regulation of hummingbird territorial behavior has heretofore been unknown. Our goal was to assess seasonal changes in sex steroids, territorial aggression levels, and body condition during reproductive and non-reproductive seasons in hummingbirds. To validate the use of cloacal fluid (CF) for the study of sex steroids, steroid levels in plasma and CF were correlated in Sephanoides sephaniodes. During the reproductive season, Calypte. anna, Archilochus alexandri, and Selasphorus rufus males showed high levels of T that were positively correlated with aggression, but the relationship between T and body condition was not consistent across species. As expected, T levels in females were significantly lower than in males in all seasons, however still detectable. During the non-reproductive season, CF DHEA of Calypte anna was high and positively correlated with aggressive behaviors and body condition. Our results suggest that hummingbirds display aggressive behaviors that could be linked to different hormones during the breeding and non-breeding seasons.
    10/2014; 155(4):1017-1025. DOI:10.1007/s10336-014-1088-y
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    ABSTRACT: A transgenic ferret model of cystic fibrosis has recently been generated. It is probable that malfunction of airway mucous glands contributes significantly to the airway pathology of this disease. The usefulness of the ferret model may therefore depend in part on how closely the airway glands of ferrets resemble those of humans. Here, we show that in the ferret trachea glands are commonest in its most ventral aspect and disappear about half way up the lateral walls; they are virtually absent from the dorsal membranous portion. Further, the aggregate volume of glands per unit mucosal surface declines progressively by about 60% between the larynx and the carina. The average frequency of glands openings for the ferret trachea as a whole is only about one-fifth that in humans (where gland openings are found at approximately the same frequency throughout the trachea). Glands in the ferret trachea are on average about one-third the size of those in the human. Therefore, the aggregate volume of tracheal glands (per unit mucosal surface area) in the ferret is only about 6% that in humans. As in other mammalian species, airway glands in the ferret disappear at an airway internal diameter of ∼1 mm, corresponding approximately in this species to airway generation 6. Anat Rec, 2013. © 2013 Wiley Periodicals, Inc.
    The Anatomical Record Advances in Integrative Anatomy and Evolutionary Biology 11/2013; 296(11). DOI:10.1002/ar.22783 · 1.53 Impact Factor
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    ABSTRACT: The fragile X premutation is a tandem CGG trinucleotide repeat expansion in the fragile X mental retardation 1 (FMR1) gene between 55 and 200 repeats in length. A CGG knock-in (CGG KI) mouse has been developed that models the neuropathology and cognitive deficits reported in fragile X premutation carriers. It has been suggested that carriers of the premutation demonstrate a spatiotemporal hypergranularity, or reduced resolution of spatial and temporal processing. A temporal ordering of spatial locations task was used to evaluate the ability of CGG KI mice to process temporal and spatial information with either high or low levels of spatial interference. The results indicate that CGG KI mice showed difficulty performing a spatial novelty detection task when there were high levels of spatial interference, but were able to perform the novelty detection task when there was low spatial interference. These data suggest that CGG KI mice show reduced spatial and temporal resolution that are modulated by the dosage of the Fmr1 gene mutation, such that when behavioral tasks require mice to overcome high levels of either spatial or temporal interference, the CGG KI mice perform increasingly poorly as the CGG repeat length increases.
    Behavioural brain research 04/2012; 233(1):29-34. DOI:10.1016/j.bbr.2012.04.029 · 3.39 Impact Factor
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    ABSTRACT: Malfunction of airway submucosal glands contributes to the pathology of cystic fibrosis (CF), and cell cultures of CF human airway glands show defects in Cl(-) and water transport. Recently, a transgenic pig model of CF (the CF pig) has been developed. Accordingly, we have developed cell cultures of pig airway gland epithelium for use in investigating alterations in gland function in CF. Our cultures form tight junctions (as evidenced by high transepithelial electrical resistance) and show high levels of active anion secretion (measured as amiloride-insensitive short-circuit current). In agreement with recent results on human airway glands, neurohumoral agents that elevate intracellular Ca(2+) potently stimulated anion secretion, while elevation of cAMP was comparatively ineffective. Our cultures express lactoferrin and lysozyme (serous gland cell markers) and MUC5B (the main mucin of airway glands). They are, therefore, potentially useful in determining if CF-related alterations in anion transport result in altered secretion of serous cell antimicrobial agents or mucus.
    AJP Lung Cellular and Molecular Physiology 02/2012; 302(10):L1098-106. DOI:10.1152/ajplung.00253.2011 · 4.04 Impact Factor
  • American Thoracic Society 2011 International Conference, May 13-18, 2011 • Denver Colorado; 05/2011

Publication Stats

11 Citations
8.96 Total Impact Points


  • 2013–2014
    • University of California, Davis
      • • Department of Neurobiology, Physiology and Behavior
      • • Department of Physiology and Membrane Biology
      Davis, California, United States