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Description
Reproduction is energetically costly and seasonal breeding has evolved to capitalize on predictable increases in food availability. The synchronization of breeding with periods of peak food availability is especially important for small birds, most of which do not store an extensive amount of energy. The annual change in photoperiod is the primary environmental cue regulating reproductive development, but must be integrated with supplementary cues relating to local energetic conditions. Photoperiodic regulation of the reproductive neuroendocrine system is well described in seasonally breeding birds, but the mechanisms that these animals use to integrate supplementary cues remain unclear. I hypothesized that (a) environmental cues that negatively affect energy balance inhibit reproductive development by acting at multiple levels along the reproductive endocrine axis including the hypothalamus (b) that the availability of metabolic fuels conveys alterations in energy balance to the reproductive system. I investigated these hypotheses in male house finches, Haemorhous mexicanus, caught in the wild and brought into captivity. I first experimentally reduced body condition through food restriction and found that gonadal development and function are inhibited and these changes are associated with changes in hypothalamic gonadotropin-releasing hormone (GnRH). I then investigated this neuroendocrine integration and found that finches maintain reproductive flexibility through modifying the release of accumulated GnRH stores in response to energetic conditions. Lastly, I investigated the role of metabolic fuels in coordinating reproductive responses under two different models of negative energy balance, decreased energy intake (food restriction) and increased energy expenditure (high temperatures). Exposure to high temperatures lowered body condition and reduced food intake. Reproductive development was inhibited under both energy challenges, and occurred with decreased gonadal gene expression of enzymes involved in steroid synthesis. Minor changes in fuel utilization occurred under food restriction but not high temperatures. My results support the hypothesis that negative energy balance inhibits reproductive development through multilevel effects on the hypothalamus and gonads. These studies are among the first to demonstrate a negative effect of high temperatures on reproductive development in a wild bird. Overall, the above findings provide important foundations for investigations into adaptive responses of breeding in energetically variable environments.
ContributorsValle, Shelley (Author) / Deviche, Pierre (Thesis advisor) / McGraw, Kevin (Committee member) / Orchinik, Miles (Committee member) / Propper, Catherine (Committee member) / Sweazea, Karen (Committee member) / Arizona State University (Publisher)
Created2018
Description
Objectives. The role of parents and caregivers is vital in promoting healthy eating habits among Hispanic adolescents. However, there are inconsistent findings on whether parental feeding practices are beneficial to their diet quality. The purpose of this study was to assess the effect of parental feeding practices on adolescent dietary outcomes post-parenting intervention among Hispanic dyads. The present study is a secondary analysis using data from a randomized controlled trial testing the effect of a parenting intervention, Families Preparing the New Generation Plus (FPNG+), on adolescent dietary and substance use outcomes among sixth to seventh grade Hispanic students. Methods. A subsample of dyads (n=78) completed surveys to collect information on parental feeding practices and adolescent dietary outcomes at baseline (T1) and immediately post-FPNG+ intervention (T2). Parents (mean age of 39.7 years; 84.6% female) self-reported their use of parental control, pressure to eat, and food restriction parenting practices at T1. Adolescents (mean age of 12.3 years; 68.2% male) self-reported their consumption of fruits, vegetables, and sugar sweetened beverage (SSB) intake at both T1 and T2. Repeated measures ANOVA were employed to compare changes in adolescent dietary outcomes by each of the three parental feeding practices assessed. Results. Findings showed significant differences in changes in vegetable consumption between adolescents of parents who reported use of control (-0.69 cup equivalents/day; p = 0.018), compared to virtually unchanged vegetable intake among those of parents who reported not using control. There were also significant differences in vegetable intake by food restriction, with a decrease in intake among adolescents whose parents reported not using restriction (-0.65 cup equivalents per day; p = 0.021), compared to a virtually unchanged vegetable intake among the use of restriction group. Dietary outcomes of fruit and sugar from SSB intake were not statistically significant by use of any of the parental feeding practices studied. Conclusion. Findings showed that adolescents whose parents used control and food restriction did not have less favorable changes in vegetable intake compared to those of parents who did not use these practices. More research is needed to determine whether the use of parental feeding practices may be advantageous on the intake of fruits, vegetables, and SSBs among adolescents to advise effective parenting interventions and establish lasting healthy eating habits of Hispanic youth.
ContributorsHannoona, Oryana (Author) / Vega-Lopez, Sonia (Thesis advisor) / Campos, Ana P (Committee member) / McCoy, Maureen (Committee member) / Arizona State University (Publisher)
Created2023