• Development Of Human Adaptation To Cold

      Marshall, Henry Crawford, Jr. (1970)
    • Ecological And Physiological Adaptations Of The Porcupine To Winter Alaska

      Coltrane, Jessica A.; Barboza, Perry; Spalinger, Donald E.; Farley, Sean; Barnes, Brian M. (2012)
      Understanding the ecology and physiology of wildlife is paramount to conservation and management of species. North American porcupines (Erethizon dorsatum) are mammalian herbivores that occupy a diverse array of habitats across a broad geographical range. However, few studies have explored the ecology and physiology of porcupines. I used captive and free ranging porcupines to 1) identify the physiological abilities that enable them to survive on low quality winter forage when thermoregulatory demands are high, 2) determine responses of porcupines to winter conditions, and 3) determine how winter conditions influence habitat selection and home range size at the northern limits of their range. My research revealed that the persistence of porcupines at the northern limits of their range is due to plasticity of food intake, as well as physiological tolerance of low-quality diets and low ambient temperatures. Captive porcupines gained mass when high quality diets were available. However, porcupines decreased their dry matter intake throughout winter, indicating a seasonal decrease in metabolic rate. Low requirements for energy and nitrogen minimized the loss of body mass when intakes were low, while plant toxins increased urinary losses of energy and nitrogen. Free-ranging porcupines conserved lean body mass in winter by catabolizing fat stores. Proportional fat loss was correlated positively with total fat mass at the start of winter. Fat losses were minimized by lowering rates of energy expenditure. Water turnovers were slow in wild porcupines and body temperatures were not reduced to save energy. In order to survive winter on a low quality diet of white spruce (Picea glauca ) needles and cambium and paper birch (Betula papyrifera ) cambium, porcupines maintained large home ranges comprised primarily of mixed conifer/hardwood forests. Occupying a mixed forest habitat allowed porcupine to switch their diet between two forage tree species, potentially alleviating saturated detoxification pathways. Overall, porcupines possess the physiological abilities of a specialist herbivore during winter; however, they rely on abundant high quality summer forages to replenish their stores of fat and protein for reproduction and survival in the subsequent winter.
    • An ecological-physiology perspective on seabird responses to contemporary and historic environmental change

      Will, Alexis P.; Kitaysky, Alexander; Breed, Greg; Powell, Abby; Springer, Alan (2017-05)
      The chapters included in this dissertation implement an ecological-physiology approach to understanding how long-lived marine organisms, using seabirds as a model, respond to changes in the environment. Many seabird populations are governed by bottom-up processes, yet efforts to connect prey dynamics and parameters such as breeding performance often yield mixed results. Here I examined how individual foraging behavior and nutritional status change at the inter-annual, decadal, and multi-decadal scale. I validated that the concentration of the avian stress hormone in seabird feathers is indicative of their exposure to nutritional stress. I then used this technique to show that young seabirds (Rhinoceros auklets, Cerorhinca monocerata) that experience variable foraging conditions during their prolonged nestling period incurred higher nutritional stress when provisioned with prey that was relatively low in energy content. On the other hand, when examining adult foraging behavior, a signal of environmental variability was lost in the noise of changing diets. Foraging behavior of adults appeared to be highly flexible and less informative in regard to detecting an environmental change. I used stable isotope analysis to re-construct the isotopic niche dynamics (where and at what trophic level seabirds were obtaining prey) and partitioning of food resources for three abundant seabirds (common and thick-billed murres, Uria aalge, and U. lomvia, respectively; and black-legged kittiwakes, Rissa tridactyla) breeding in the southeastern Bering Sea under cold and warm states of the ecosystem. Access to diverse habitat reversed how seabirds partitioned prey during food shortages: seabirds with access to multiple habitats contracted their isotopic niche during food-limited conditions in contrast to the expansion of the isotopic niche observed for seabirds with access to only one type of habitat. Finally, I measured nutritional stress and stable isotope signatures (carbon and nitrogen) in contemporary and historic red-legged kittiwake (Rissa brevirostris) feather samples to examine how birds breeding on St. George Island have responded to changes in summer and winter conditions in the Bering Sea over time. Red-legged kittiwakes were less nutritionally stressed during warm summers and winters. It is not clear, however, whether all seabirds would do well if the Bering Sea were to break with its pattern of oscillating between warm and cold conditions. Prey for these birds may either be negatively affected by continuously warm conditions (murres and black-legged kittiwakes feeding on juvenile pollock, Gadus chalcogrammus) or the conditions that are most beneficial to the prey are not known (red-legged kittiwakes feeding on myctophids). With this work I suggest that measuring nutritional stress in feathers and using stable isotope analysis to characterize foraging niches may document more dynamic responses to changes in the environment than population level parameters such as breeding performance. To do so, however, requires a better understanding of the relationship between these individual-level responses and fitness.
    • Endocrine And Immune Profiles Of Immature Pinnipeds

      Keogh, Mandy Jean; Atkinson, Shannon; Castellini, Michael; Hellman, Tuula; Ortiz, Rudy; Runstadler, Jonathan (2011)
      There is increasing interest in assessing the health of individuals and populations of pinnipeds found in the North Pacific, primarily due to population declines leading to conservation concerns. This study assessed the "health" of animals by quantifying hormones associated with fat mass (leptin), lipid and water metabolism (cortisol and aldosterone), and growth and metabolism (thyroxine and triiodothyronine) as well as circulating total and differential leukocyte counts and in vitro proliferation of peripheral blood mononuclear cells (PBMC). Body mass and condition are influenced by an individual's disease and nutritional state. Glucocorticoids are known to affect the immune system and may be stimulated by a multitude of factors. I hypothesized that age or body mass would influence leukocyte counts, PBMC proliferation, and hormone concentrations in Steller sea lion (Eumetopias jubatus) pups and that the response of cortisol to an acute stressor would impact immune parameters in juvenile harbor seals (Phoca vitulina ). Further, given the inherent requirements of disturbance and animal handling necessary for sampling pinnipeds, the impact of these activities on endocrine and immune profiles was assessed. Total white blood cell (WBC) counts, neutrophil counts and T cell proliferation decreased with increasing age in Steller sea lion pups. However, no relationship between body condition index and circulating concentration of hormones quantified was detected. Circulating concentrations of cortisol, thyroxine, and triiodothyronine were influenced by the rookery disturbance. However, the variation attributed to the disturbance was low and did not alter total or differential WBC counts or in vitro proliferation of PBMC. In harbor seals, cortisol and aldosterone concentrations increased following an acute stressor which resulted in a stress leukogram. Total WBC decreased driven primarily by the decrease in neutrophil counts with simultaneous increase in lymphocytes leading to an overall decrease in neutrophil to lymphocyte ratio. These findings highlight the endocrine system's influence on the immune system in immature pinnipeds.
    • Resistance To Multi Organ Failure And Metabolic Alterations After Global Ischemia/Reperfusion In The Arctic Ground Squirrel

      Bogren, Lori Kristine; Drew, Kelly; Green, Thomas; Harris, Michael; O'Brien, Kristin (2013)
      Cardiac arrest (CA) and hemorrhagic shock (HS) are two clinically relevant situations where the body undergoes global ischemia/reperfusion (I/R). Hibernating animals such as ground squirrels have been shown to be resistant to I/R injury in various tissues. The present study compared physiological and metabolic changes occurring during global I/R in an I/R-injury prone animal, the rat, to that of I/R injury resistant animals, arctic ground squirrels (AGS). We sought to determine if AGS are protected from multi organ failure after global I/R and if any protection is dependent upon their hibernation season or the ability to maintain a stable metabolic profile during I/R. For CA, rats and euthermic AGS were asphyxiated for 8 min, inducing CA. For HS, rats, euthermic AGS, and interbout arousal AGS were subject to HS by withdrawing blood to achieve a MAP of 35 mm Hg for 20 min before reperfusion. For both I/R models, the animals' temperature was maintained at 36.5-37.5�C. After reperfusion, animals were monitored for 3 hours (HS) or 7 days (CA), then tissues and blood were collected for histopathology, clinical chemistries, cytokine level analysis (HS only), and 1H-NMR metabolomics of hydrophobic and hydrophilic metabolites (HS only). For the HS studies, a group of rats and AGS were monitored for three days after HS to access survival and physiological impairment. Regardless of season AGS showed no physiological deficit 12 hours after HS or CA. Blood chemistries and circulating cytokine levels indicated liver damage and systemic inflammation in the rats while AGS showed no signs of organ damage or inflammation. In addition, rats had a shift in their hydrophilic metabolic fingerprint and alterations in several metabolite concentrations during HS-induced I/R, indicative of metabolic adjustments and organ damage. In contrast, AGS, regardless of season, were able to maintain a 1H-NMR metabolic profile with few changes in quantified metabolites during I/R. These data demonstrate that AGS are resistant to systemic inflammation and organ damage/failure after I/R and this resistance is not dependent on their ability to become hypothermic during insult but may stem from an intrinsic resistance to disruptions in their metabolic processes during I/R.
    • Serotonergic And Hypocretinergic Systems Modulate Ventilation And Hypercapnic Ventilatory Responses

      Corcoran, Andrea E. (2009)
      Serotonergic (5-HT) cells of the medullary raphe are putative central chemoreceptors, one of multiple chemoreceptive sites in the brainstem that interact to produce the respiratory chemoreflex. This role is debated, and the importance of 5-HT neurons as chemoreceptors in relatively intact systems is unclear. The main focus of this dissertation is to provide further physiological evidence for the involvement and modulation of 5-HT neurons in CO2 chemosensitivity. This is of interest as a large number of Sudden Infant Death Syndrome (SIDS) cases report dysfunction in the 5-HT system, and CO2 may be an exogenous stressor leading to SIDS when in combination with this underlying vulnerability. Also, since SIDS occurs primarily during sleep, I also focus on the potential functional interaction between the 5-HT and hypocretinergic systems, as hypocretins play a role in arousal and also potentially in chemosensitivity. I confirm the hypothesis that the serotonergic and hypocretinergic systems modulate ventilation and hypercapnic ventilatory responses. Using the in situ preparation derived from juvenile rats and the in vitro medullary slice preparation from mice, I verify that 5-HT neurons are critical in generating a response to CO2, primarily via facilitation of the respiratory rhythm through 5-HT2 receptors. I also find evidence to support the hypothesis that hypocretins play a significant role in the neuroventilatory response to CO2 through activation of hypocretin receptors type 1. By comparing results from rhythmic medullary slice preparations from wildtype (normal 5-HT function) and Lmx1bf/f/p (lack central 5-HT neurons) neonatal mice, I attempt to identify whether changes in hypoglossal nerve output in response to acidosis are affected by hypocretin receptors, and whether this is dependent on the presence of 5-HT neurons. Frequency results from such studies are inconclusive; however, hypocretins do appear to mediate the burst duration response via serotonergic mechanisms. I also find that hypocretins facilitate baseline neural ventilatory output in part through 5-HT neurons. Thus, both the 5-HT and hypocretinergic systems are involved in modulating ventilation and hypercapnic ventilatory responses.
    • The Seasonality Of Reproduction, Body Composition, And Energy Expenditure In Northern Red-Backed Voles (Myodes Rutilus)

      Stevenson, Kalb Thayer (2009)
      Arvicoline rodents (voles and lemmings) inhabit high-latitude environments and undergo pronounced seasonal changes in their physiology and behavior. They are an important prey resource in circumpolar regions, and their population numbers can affect the survival and reproductive fitness of many predator and secondary prey species. I studied the effects of seasonality and environmental factors on reproduction and energy allocation in the northern red-backed vole (Myodes rutilus), an arvicoline rodent in Alaska known to have bred in winter. My overall aim was to measure the effects of season and environmental factors on the reproductive axis, body composition, and energy expenditure of this animal. I validated a dual-energy X-ray absorptiometry (DXA) apparatus for use in determining fat and lean tissue, body water, protein, and mineral content in M. rutilus (R2 = 0.65 to 0.98, p < 0.001 for all parameters). Absolute fat, but not percentage fat changed seasonally. Reproductive organ masses reached peak levels in spring (females) and early summer (males), and significant co-variates were photoperiod, temperature, snow cover, body mass, and percent fat (depending on breeding period and gender). I found one instance of late-summer male non-responsiveness, but no winter breeding. However, 28.2% of captive, lab-raised male voles were non-responsive to short days (ad lib. food and water at 20�C), which was within the 20-40% frequency range known for lower latitude species. Differences were found at the gonadal level and pituitary level (testosterone and luteinizing hormone (LH) either varied by group and/or were correlated with testis mass), while differences at the hypothalamic level (gonadotropin-releasing hormone immunoreactivity (GnRH-ir) and gonadotropin-inhibiting hormone (GnIH)-ir cell counts) were inconclusive. Body composition and relative visceral organ mass changed seasonally, and significant covariates were photoperiod (mass, %protein, %mineral), gender (intestines), and temperature (heart). Field metabolic rate did not differ by breeding period, but was significantly correlated with temperature. Bone mineral density (BMD) of voles was highest in early summer and lowest in winter, whereas the BMD of two hibernating mammals did not change during winter torpor. These findings could help to identify the mechanisms underpinning arvicoline rodent population cycling and to predict physiological and ecological responses of small mammals to different climate change scenarios.
    • Vitamin D, cognitive function, and oxidative stress: clues to overtraining syndrome?

      Jerome, Scott P.; Reynolds, Arleigh J.; Duffy, Lawrence K.; Sheppard, Dani K.; Watts, Phillip B. (2018-05)
      Overtraining syndrome (OTS) is characterized by an unexplainable drop in athletic performance. It affects primarily elite, endurance athletes, though sub-elite athletes are also affected. Although the deterioration in performance is often the most pronounced and troublesome symptoms for athletes, others range from severe fatigue and insomnia to depression and lack of mental concentration. There is no known diagnostic tool except for ruling out all other possible explanations for the abnormal performance. The only known remedy for OTS is rest. Some recover within months while others take a year or more. Some athletes never fully recovery and never return to pre-OTS performance levels. The exact mechanism behind OTS is unknown. Consensus has been reached among exercise science professionals that 1) an imbalance between stress load and recovery leads to OTS; 2) OTS exists on a spectrum of possible outcomes from different exercise/rest ratios; and 3) exercise is only one part of systemic stress that can lead to OTS. In addition to physical exercise, other factors such as environmental conditions, family dynamics, schoolwork, job stressors, and social pressures all contribute to the total stress load on the body. A severe and sustained imbalance between stress and rest is a likely contributor to OTS in athletes. I investigated biomarkers and psychological markers that, in concert, could be used to identify athletes who are at the greatest risk for developing OTS before the onset of symptoms. I examined vitamin D, cognitive function, and oxidative stress status in university cross country skiers in addition to athletic performance status during the competitive ski season. This study's results support three primary conclusions. First, collegiate endurance athletes are more prone to vitamin D insufficiency and deficiency than their sedentary counterparts. Second, collegiate cross country ski racers in the circumpolar North are unlikely to maintain adequate vitamin D during a competition season. Furthermore, vitamin D levels are likely to drop in the post-season, recovery period. Third, cognitive function is likely to be significantly higher in the post-season than during the competition season. Fourth, those who experienced a drop in performance during the competition season are more likely to show signs of oxidative stress. These findings may help to produce a screening tool for OTS.