Mark A. Chappell - US grants

This is a request to obtain funds to acquire an infrared thermal imaging system. The equipment will be used by five investigators as part of several ongoing studies of plant and animal physiology. The specific projects described in this proposal utilize thermal imaging to monitor cutaneous vasomotor changes in dogs, rats and rabbits with respect to heat, exercise and hydration; to study thermo regulation in desert insects and Adelie penguins; to study heat and pollutant effects on gas exchange in plants; to measure the influence of solar radiation on amphibian thermal regulation.

Adelie penguins, Pygoscelis adeliae, are the most abundant of the Antarctic penguins and are important components of the Antarctic marine ecosystem. The breeding ecology, behavior, and thermal physiology of Adelies have been extensively studied by a variety of investigators, but many aspects of their ecological and reproductive energetics have not been described. In previous NSF- funded research, the effects of temperature and weather (e.g., wind and sunlight) on the energy costs of thermoregulation in breeding Adelies and their chicks were determined. The purpose of this research is to measure rates of energy consumption and changes in body composition in breeding Adelies, and to simultaneously study their foraging behavior. This will enable us to determine reproductive effort. The isotopic technique of doubly labeled water (DLW) will be used to determine both energy flux and body composition, at various times throughout the breeding season. The behavior, physiology, and energetics of diving during foraging trips will be studied with computerized time-depth recorders (TDR). Simultaneous DLW and TDR studies will provide information on foraging costs and foraging efficiency. Stomach content analysis will reveal what the birds are eating. Diet information combined with DLW measurements will allow calculation of rates of food consumption, and, hence, the trophic impact of breeding Adelies on the surrounding marine ecosystem.

0111604 Hammond & Chappell

Life at high altitude poses a dual challenge to mammals. First, energy demands are greater because environmental temperatures are generally lower than at low altitudes in the same latitudinal range. At the same time, however, low oxygen availability (hypoxia) limits an individual's capacity for energy expenditure. One of the physiological mechanisms animals use to cope with the low oxygen availability at high altitudes is to increase the amount of oxygen that can be carried from the lungs to the cells by increasing hemoglobin oxygen binding capacity (hemoglobin oxygen affinity). These changes can occur within the lifetime of an individual, but there are also known genetic differences between animals, within a species, for hemoglobin / oxygen binding ability. Alternatively, many animals are known to have the capacity to reversibly increase the size and functional capacity of various organ systems (including the cardiovascular system) in the face of increased demand (phenotypic plasticity) and some animals use this plasticity to cope with both low temperatures and hypoxia at high altitudes.

A model animal for the study of hemoglobin genetics is the deer mouse (Peromyscus maniculatus) which has been shown, in classic studies, to have genetic differences in hemoglobin type that are strongly correlated with native altitude, affect oxygen binding, and positively influence short-term exercise performance. Deer mice have also been shown to display increases in the size of the lungs, heart and digestive tract at high altitudes. One limitation of the work to date on both deer mice hemoglobins and organ phenotypic plasticity, is that it did not incorporate the influence of the site of gestational development and maturation (birth site), because it was performed on animals that were born and allowed to mature at low altitudes before they were moved to high altitude. It is known, however, that the gestational environment can be crucial to determining the anatomical and physiological capacity of adult animals. Thus the first goal of this research is to determine how energy expenditure (aerobic performance) is affected by gestational development at specific altitudes and if the hemoglobin genetics are still significant in determining the individual's physiological capacity to cope with life at high altitudes after accounting for plasticity of organ size. To test this, aerobic performance trials will be performed on mice with different hemoglobin genotypes born and reared at either high or low altitude.

Another unanswered question is the effect of hemoglobin genetics on long-term energy expenditure (i.e., over periods of days or weeks). This is an important issue new research has shown that sustainable energy demands of mice living at high altitudes can be nearly as high as previous measures of short term aerobic capacity. Young animals face an even greater challenge. Newly weaned juveniles are smaller than adults but have correspondingly higher mass-specific energy demands. Therefore it seems reasonable to expect that growth rates might be influenced by hemoglobin genotype and site of gestational development. Accordingly, the second goal of this research is to determine if hemoglobin genotype influences growth rates and sustainable metabolic rate under conditions of cold exposure and high-altitude hypoxia. To test this, mice with specific hemoglobin genotypes will be reared in semi-natural conditions at high and low test altitudes. We expect that mice with the appropriate hemoglobin genotype for a given test altitude will have the highest rates of sustainable metabolic output (measured as food consumption) and growth.

DESCRIPTION (provided by applicant): Fatherhood can influence health and longevity in men. The mechanisms underlying these effects are unknown; however, as human and other mammalian fathers undergo predictable changes in several metabolically important hormones, one possibility is that these endocrine profiles influence energy homeostasis, metabolism, and body composition, which in turn can affect health and longevity. The proposed studies will characterize the effects of fatherhood in the California mouse (Peromyscus californicus), a monogamous rodent in which fathers invest extensively in their offspring and undergo systematic changes in hormone levels and body mass. Specifically, this research will test the hypotheses that fatherhood alters: plasma levels of metabolically important hormones (Aim 1); energy homeostasis, metabolism, body mass, and body fat (Aim 2); behaviors that may contribute to these energetic and metabolic effects (Aim 3); and that these consequences of fatherhood are modulated by paternal parity/age, offspring age, and stress. Experiment 1 will use a longitudinal design to characterize the effects of fatherhood on physical (body mass, body composition), energetic (resting and maximal metabolic rates, daily energy expenditure), hormonal (corticosterone, testosterone), and behavioral (ingestive behavior, activity levels) measures. Data will be collected at five time points, spanning approximately a 9-month period, from fathers (housed with a mate and pups) and nonbreeding males (housed with an ovariectomized female). Half of the mice in each group will be exposed to a chronic, intermittent noise stressor, and the other half will be maintained under standard laboratory conditions. Experiment 2 will use a cross-sectional approach to further characterize possible hormonal, metabolic, and behavioral mechanisms underlying the anticipated effects of fatherhood on body mass, body composition, and energetics. Specifically, it will characterize 1) circulating levels of the metabolic hormones leptin, adiponectin, triiodothyronine, and thyroxine; 2) blood triglyceride, cholesterol, and glucose levels; 3) the propensity to ingest high-fat and high-sucrose substances; and 4) organ masses and distribution of fat stores, in nonbreeding males, new fathers, and experienced fathers. Depending on the results of Experiment 1, half of the mice in each group may again be exposed to a chronic, intermittent noise stressor. These studies are expected to demonstrate that fatherhood in P. californicus alters metabolic hormone levels, energy homeostasis, metabolism, body composition, and behavior. They will also clarify how these effects are modulated by paternal age/parity, offspring age, and chronic stress. The results will provide unique insights into the biology of mammalian fatherhood and may eventually lead to an improved understanding of the effects of fatherhood on health and longevity in men, as well as health outcomes in their offspring.

Reproduction is an energetically expensive process and therefore can lead to impairments in health and survival. In mammals the costs and tradeoffs, including reduced growth, impaired immune function, and lower life expectancy, have been mainly studies and associated with females and maternal care. In some mammals, including humans, males/fathers also provide extensive care for their offspring; however, the consequences for fathers of providing paternal care has not been well studied. Therefore, this research will investigate the effects of fatherhood on blood hormone levels, body composition (fat and lean mass), energy utilization, exercise performance, and immune function in the California mouse, a monogamous rodent in which both parents engage in extensive parental behavior. Behavioral, morphological, and physiological measures will be compared between males housed with a breeding female and males housed with a female that has been surgically neutered. Because the consequences of fatherhood might be exacerbated by stress, half of the animals will be housed under standard laboratory conditions and the other half under cold conditions. The results will identify the effects of parenthood on behavior, morphology and physiology in fathers, and will further indicate whether such effects differ with the animals' age, reproductive experience, or stress. These results will provide novel insights into the biology of paternal care and may have important implications for understanding parenting in humans. In addition, this research will contribute to the training of numerous graduate and undergraduate students, a substantial number of whom will be underrepresented minorities and/or socioeconomically disadvantaged.