• Assessing The Health Of Harbor Seals In Alaska

      Trumble, Stephen John; Castellini, Michael (2003)
      Declining populations of pinnipeds in the Gulf of Alaska, possibly resulting from changes in prey quality, prompted research to determine the population health status of harbor seals (Phoca vitulina) using blood chemistry and digestive constraints. Blood chemistry and morphology reference range values between two harbor seal pup populations in Alaska, one population in continued decline, Prince William Sound, and another in recent increase, Tugidak Island, offered clues that blood values can vary on the population scale and that health assessment must utilize an appropriate set of reference values for valid comparisons. Subsequently, a captive study involving harbor seals yielded changes in ten blood chemistry or hematology values as a function of season and diet. These data provided evidence that populations may have distinct "identities" based on blood chemistry values. The "metabolic identity" of a population provides evidence of the relationship between environmental stressors and the genetic capacity of the animal to respond to metabolic demands. This made it possible to better understand population level differentiation in plasma chemistry values and thus assess the health of animals occupying the outlier regions of populations, since these regions are often suggestive of poor health. A captive study involving harbor seals, which are known to consume the low quality prey (pollock) implicated in the declines of many species of birds and mammals in the Gulf of Alaska, yielded consistent dry matter digestibility resulting in greater gut fill from pollock than from herring. Digestible energy intakes from pollock were greater than from either herring or the mixed diet. Lipid digestibility of herring declined from 90% to 50% when lipid intake exceeded 60 g kg -0.75 d-1. Results of this study imply that a flexible digestive system for harbor seals can compensate for ingesting a prey of low energy density by increasing gut fill and enhancing protein and lipid assimilation, to sustain digestible energy intake. In other words, harbor seals can offset differences in prey quality if prey availability and abundance does not limit the physiological plasticity of their digestive system to maintain their supply of energy and nutrients.
    • Cecal Function In Ptarmigan

      Gasaway, William Clifton (1974)
    • Daily Meal Patterns, Voluntary Food Intake And Fattening Of Reindeer During Winter And Responses To Insulin

      Stimmelmayr, Raphaela; White, R. G.; Drew, K. L. (2001)
      I determined the effect of insulin injections on daily feeding behavior and voluntary food intake (VFI) in reindeer (Rangifer tarandus t. ) fed a concentrate ration during winter. Food intake in the absence of insulin injections was down regulated and characterized by small, regular meals during daylight and irregular and sometimes large nighttime meals. Each large nighttime meal was associated with a long post-meal interval. Daytime meal size could be predicted from an estimate of the energy deficit incurred since the previous meal; however, the occasional oversized nighttime meals were not predicted from energy deficit and suggested that appetite may be deregulated at night. I hypothesized that a low daily dose of long acting insulin (1.0 IU/kg BW, s.c.) would result in regular feeding day and night, which should result in reduced VFI. Changes in serum insulin concentration could not be detected following insulin treatment, however exogenous insulin resulted in a loss of daytime and nighttime differences in meal size and intermeal interval length and a decrease in mean daily meal size. Over a 21 d treatment period, exogenous insulin prevented an increase in VFI during a warming trend and tended to counter a linear decline in body mass and backfat depth (measured by ultra-sound) typified by control animals (given Lactate Ringer 0.005 ml/kg BW, s.c.). The influence of insulin over fat retention suggests that reindeer are capable of lipogenesis in winter. A combination of rhythmic variation in satiety response to meals during daylight and decoupling of meal size and frequency at night is suggested as an endocrine model underlying daily appetite regulation in the reindeer.
    • Ecological and physiological aspects of caribou activity and responses to aircraft overflights

      Maier, Julie Ann Kitchens (1996)
      I investigated the use of remote-sensing of caribou (Rangifer tarandus) activity to assess disturbance of low-altitude overflights by jet aircraft. Resource management agencies are concerned about the potential effects of these overflights on important species of ungulates. I hypothesized that low-altitude overflights would affect activity and movements of caribou, and thereby constitute a disturbance with negative consequences on energetics. I used caribou of the Delta Herd (DCH) and captive animals at the Large Animal Research Station (LARS) to address the hypotheses: caribou (1) exhibit equal activity day and night; (2) do not time activity to light; and (3) activity patterns do not change seasonally in response to daylength. Caribou were nychthemeral and exhibited uniform activity with no apparent timing to light. DCH caribou responded to seasonal changes in the environment by modifying activity (increased activity in response to insect harassment), whereas LARS caribou altered activity in response to fluctuating physiological variables (increased activity during rut). Changes in daylength did not affect activity. Data on activity from LARS and DCH caribou were compared with extant data on caribou of the Denali and Porcupine herds. Poor quality forage in winter was inferred from long resting bouts, and low availability of forage was inferred from long active bouts of post-calving caribou of the DCH. In midsummer, caribou of the DCH exhibited significantly longer active and shorter resting bouts than did LARS caribou, consistent with a moderate level of insect harassment. Responses of caribou to overflights were mild in late winter and, thus, overflights did not constitute a disturbance. Post-calving caribou responded to overflights by increasing daily activity, linear movements, incremental energy cost, and average daily metabolic rate. Energetic responses and movements were significantly related to the loudest overflight of the day. In the insect season, activity levels increased significantly in response to overflights but with no corresponding increase in linear movements or energetics. My recommendations are to prohibit aircraft overflights of caribou during calving and post-calving periods and during key feeding times in insect harassment seasons. Research indicates the possibility of more severe effects in nutritionally stressed animals.
    • Investigations of health status and body condition of harbor seals (Phoca vitulina) in the Gulf of Alaska

      Fadely, Brian Scott; Castellini, Michael A. (1997)
      Harbor seal (Phoca vitulina) declines during the past 20 years in the Kodiak Island and Prince William Sound regions contrast with stable or slightly increasing populations in southeastern areas of Alaska. Aspects of health status and body condition were investigated to test the hypothesis that these declines were driven by nutritional limitation, and to determine whether recent differential population trajectories among Kodiak Island, Prince William Sound, and southeast Alaska could have health-related components. For comparisons between 1992-96, three aspects of health status were examined; blood chemistry, blubber distribution and quantity; and blubber quality. Clinical ranges of plasma chemistries and hematologies were established for free-ranging seals in the Gulf of Alaska. Significant handling, individual, and seasonal effects were found on many blood parameters that could bias interannual and interregional comparisons if not incorporated in models. Based on statistical modeling, some seals showed more clinically aberrant values than expected by chance, but these were not clumped among regions or years. Differences existed in interannual blood chemistry and hematology patterns between juveniles and adults. Likewise, there were regional differences in blood chemistries of unknown significance. Morphometric indices were poor indicators of condition defined as size-at-age or blubber content. This was related to patterns of blubber distribution and variability, which differed between males and females. Blubber quality, measured as lipid content, did not substantially vary seasonally or between geographic regions, but blubber from Prince William Sound was less hydrated than blubber from non-declining areas. There were no detectable differences in body condition of seals from the Gulf of Alaska sampled during 1963/64 (pre-decline), 1976-78 (during decline) and 1995-96. However, sample sizes were small and patchily distributed throughout locations and years. Thus, the likelihood of detecting body condition changes in response to environmental conditions was poor. Body condition was not substantially different among seals from Prince William Sound, Kodiak Island and southeast Alaska measured during 1993-96. However, interannual blood chemistry and body condition patterns were evident among Prince William Sound seals that may have been associated with environmental conditions.
    • Molecular Mechanisms Of Metabolic Control In The Arctic Ground Squirrel

      Barger, Jamie Louis; Boyer, Bert (2002)
      The annual cycle of the arctic ground squirrel (Spermophilus parryii) is characterized by periods of intense energy deposition and utilization, and therefore this species an attractive model for investigating the molecular mechanisms of metabolic control in mammals. In late summer, animals become hyperphagic and undergo intense fattening prior to hibernation. Leptin, a hormone produced by white adipose tissue, reverses obesity in rodent genetic models, but the effects of leptin on outbred rodent strains and wild species is modest. Similarly, administration of mouse recombinant leptin did not affect food intake or adiposity during prehibernation fattening in arctic ground squirrels. These results suggest that either prehibernation fattening is insensitive to negative feedback from leptin or that animals in general lack a negative feedback system controlling adiposity. At the terminus of prehibernation fattening, arctic ground squirrels commence hibernation, during which time nonshivering thermogenesis is invoked to maintain a high body temperature relative to sub-freezing ambient conditions. Thermogenesis occurs primarily by uncoupling oxidative phosphorylation and is catalyzed by mitochondrial membrane transport proteins. I compared the expression patterns of an established and a putative uncoupling protein gene (Ucp1 and Ucp3, respectively) in arctic ground squirrels as a function of temperature, hibernation, or fasting. As expected, levels of brown adipose tissue Ucp1 mRNA and protein were increased by cold exposure and hibernation and decreased by fasting. In contrast, levels of Ucp3 mRNA in skeletal muscle were not increased by cold or hibernation, but were paradoxically increased by fasting. Furthermore, I describe two independent studies that show that increases in the amount of UCP3 do not uncouple oxidative phosphorylation in vitro, suggesting that UCP3 does not mediate thermogenesis in skeletal muscle. Finally, I measured several parameters of mitochondrial bioenergetics in active and hibernating arctic ground squirrels to investigate if the reduced metabolic rate during hibernation is attributable to active suppression of metabolic rate or is instead a secondary consequence of the effects of low body temperature on enzyme kinetics. I show that mitochondrial substrate oxidation is depressed during hibernation, supporting the hypothesis that the reduced metabolic rate during hibernation is a partial consequence of active metabolic depression.
    • Pathophysiology of infections by the gastric trichostrongylid Obeliscoides in a rabbit model system

      Nielsen, Carol A.; White, Robert G.; Dieterich, Robert A. (1991)
      The gastric trichostrongylid parasite Obeliscoides sp. was isolated from Alaskan snowshoe hares (Lepus americanus) and passaged 3 times in laboratory rabbits (Oryctolagus cuniculus). Despite its low fertility, the isolate persisted, often as occult infections, for up to 45 weeks and produced physiologic effects in clinically normal rabbits. Prominent eosinophilic and hyperplastic lesions of the gastric mucosa occurred during post-inoculation weeks (PIW) 2-15, while mononuclear aggregations were seen in older infections. Gastric lesion severity was directly related to size of the Obeliscoides population, which declined over time and was smaller in secondary infections. Anorexia occurred within 3 weeks of infective larval inoculation in 12 (of 21) primary and 2 (of 10) secondary infections. Serum total protein, albumin, and the A/G ratio were significantly reduced in anorectic infected rabbits compared to fasted uninfected rabbits. Fecal N excretion was significantly increased between PIW 1 and 5 in rabbits with primary infections, and during PIW 1 and 2 for those with secondary infections. Nitrogen absorption was enhanced during PIW 5-15 of primary infection. Serum gastrin concentrations, determined for the first time in Obeliscoides-infected rabbits by radioimmunoassay, were significantly elevated in primary infections during PIW 6 and 7, while hypokalemia was apparent during PIW 5. Hypermagnesemia occurred in both primary and secondary infections between PIW 8 and 15. Other serum constituents and concentrations of N, Ca and P in the gastrointestinal tract and feces remained largely unchanged. Total mean retention time (TMRT), 31.8 h, and GI turnover time (GITT), 26.3 h, of the fiber component (determined with Ce-141-marked fiber $>$355 microns) were significantly prolonged in secondary infections during PIW 16 to 26. TMRT (53.0 h) and GITT (57.0 h) of the liquid component (using Cr-51 EDTA), were determined for the first time in rabbits, and were not significantly changed by Obeliscoides infection. Persisting populations of this Obeliscoides isolate caused physiologic and pathologic alterations in clinically healthy rabbits. Because these effects were similar to those seen in ruminant Ostertagia spp. infections, this laboratory model could be useful in understanding the pathophysiology of costly production losses that occur in parasitized commercial livestock.
    • Physiological and ecological implications of hemorheological variations in marine and terrestrial mammals

      Wickham, Lori Lee (1988)
      The possible significance of variations in interspecific hemorheological properties related to diving behavior was studied in eight species of marine mammals with humans and pigs as terrestrial controls. Diving duration was positively correlated with elevated blood hemoglobin, oxygen capacity and viscosity among animals of the same class. No acclimatization response to activity was evident from studies of blood drawn from newly-captured northern elephant seals and sea otters and those in captivity for extended periods which justified the use of captive animals for rheological studies. Adaptations of marine mammals to diving were evident from comparisons of phocid seal and pig hemorheology. Seals had increased oxygen storage (six times) with less viscosity-dependent reductions in oxygen transport ($-$22%) when compared to pigs at equal packed cell volume. Phocid seal blood samples were compared with those of pigs and humans for erythrocyte aggregation and blood viscoelasticity to study the mechanics of viscometric variations. Viscous and elastic components of seal blood viscosity were 20 to 73% lower than those of pigs due to decreased aggregation extent and rate (P $<$ 0.05). Lower plasma fibrinogen and increased erythrocyte electrophoretic mobility are believed to contribute to lowered seal blood aggregation. Comparisons of the in vivo effects of blood viscosity on whole body and myocardial oxygen consumption by manipulation of whole body hematocrit in seals and pigs revealed that optimal hematocrit ranges for seals were shifted to the right of those from pigs (SEALS: 25%-55%; PIGS: 25%-45%; P $<$ 0.05). Seals showed significantly less viscosity-dependence in total body oxygen transport and oxygen consumption than did pigs. Myocardial oxygen consumption data were variable and showed no statistically significant differences among seals and pigs. The seals' lower erythrocyte aggregation, decreased low-shear viscosity and a greater ability to compensate for viscosity changes may represent adaptations to reduce the stress necessary to reinitiate flow in stagnant venous sinuses thereby reducing blood-flow resistance during dive-recovery. These adaptations may help maintain circulatory perfusion to vital organs, while flow is restricted to less oxygen-dependent tissues during underwater submergence without sacrificing the advantage of increased blood oxygen storage.
    • Physiology of the endocrine, cardiorespiratory and nervous systems in pinnipeds: Integrative approach and biomedical considerations

      Zenteno-Savin, Tania; Castellini, Michael A. (1997)
      This thesis explored several aspects of the hormonal and cardiovascular physiology in pinnipeds (seals and sea lions). Plasma concentrations of the vasoactive hormones angiotensin II (Ang II), arginine vasopressin (AVP, the antidiuretic hormone) and atrial natriuretic peptide (ANP) were studied in six species of seals and sea lions. Resting levels of AVP, ANP and Ang II in these pinnipeds were similar to those reported for other vertebrate species, including humans. Age-related differences were found in the concentrations of these hormones in seals and sea lions. Geographic differences in hormone concentrations were found in Steller sea lions and harbor seals. To address the endocrine and cardiovascular responses to breath-holding (apnea) in marine mammals, heart rates and plasma levels of Ang II, AVP and ANP were studied in Weddell seal (Leptonychotes weddellii) and northern elephant seal (Mirounga angustirostris) pups during periods of spontaneous breathing (eupnea) and apnea. Ang II, AVP, and ANP, as well as the autonomic nervous system, were found to contribute differently to the control of heart rate in seal pups, depending whether the respiratory system was in eupnea or apnea. Because of changes in seals of different ages, it appeared that the integration of cardiorespiratory and hormonal function is not fully mature at birth, but develops post-natally, probably simultaneously to the development of diving behavior. These studies also suggested that the factors affecting cardiorespiratory function, including hormones, may differ by species. Plasma concentrations of AVP, ANP and Ang II were measured during food limitation and fasting in captive Steller sea lions (Eumetopias jubatus) and compared to levels in free-ranging conspecifics. The results suggest that Steller sea lions have a remarkable capacity to maintain hydrosmotic and endocrine balance during short-term food limitation and fasting. Hormonal studies did not provide conclusive evidence that Steller sea lions in Alaskan waters are currently affected by long-term food limitation.
    • Prolonged fasting in pinnipeds

      Rea, Lorrie Darlene; Castellini, Michael A. (1995)
      Marine mammals are capable of fasting for extremely long periods at different stages of their life cycle. The first objective of this thesis was to determine how plasma chemistry changed during fasting in large free-ranging phocids, northern elephant seal pups. Next, elephant seals of very low (LWM) and very high weaning mass (HWM) were examined to address how weaning mass impacts fasting chemistry. In the third section, blood chemistry was utilized to study the transition from suckling to weaning in Weddell seal pups, because behavioral verification of weaning is difficult in this species. Lastly, blood chemistry and body morphology of Steller sea lion pups were examined for indications of possible nutritional deficiency that could be associated with apparent declines in juvenile survival of sea lions in Alaska. In average mass (AWM) elephant seals, changes in blood urea nitrogen (BUN), non-esterified fatty acid (NEFA) and beta-hydroxybutyrate ($\beta$-HBA) concentrations provide strong evidence that the pups effectively minimize protein loss through increased reliance on lipid metabolism and ketone body production early in the fast. Elephant seals maintain this phase of protein sparing for up to 11 weeks. Size of elephant seal pups at weaning influenced how stored fuels were utilized during the fast. LWM pups showed higher NEFA and $\beta$-HBA levels than average or HWM pups but showed no indication of increasing protein mobilization before they left the beach. HWM pups showed evidence that they may be able spare more protein than average pups. Plasma metabolite levels and the accompanying rates of mass change suggest that Weddell seal pups typically fast after weaning. High $\beta$-HBA concentrations seen within 1 to 3 weeks of weaning are similar to levels seen during the first 3 weeks of fasting in other phocid species. Blood chemistry and body morphology data collected from 168 Steller sea lion pups showed no indication that young pups from areas of population decline were nutritionally compromised. The clinical plasma chemistry profiles showed no indication of general poor health in any of the areas studied.
    • Structure-Function Relationship Of The Developing Acetylcholine Receptor In Amphibians

      Sullivan, Michael Patrick; Duffy, Larry (2001)
      The nicotinic acetylcholine receptor is responsible for the transfer of signals from the peripheral nervous system to skeletal muscle, resulting in movement. Despite the importance of the acetylcholine receptor, many questions remain unanswered about the relationship between the structure and function of the receptor. The purpose of our research was to explain certain features of the relationship between the amino acid sequence and the function of the amphibian nicotinic acetylcholine receptor. We focused on describing the structural elements underlying the physiologic changes that occur during development and re-innervation of damaged mature muscle. We used molecular biological techniques to alter the amino acid sequence of the receptor and then studied the effects of these alterations using the electrophysiological technique of single channel recording. Our research resulted in the discovery of critical residues involved in two important characteristics of receptor function, the conductance and open time of the ion channel. These results offer new molecular insights into the classic observation that synaptic currents become briefer in duration during the course of muscle development in vertebrates.
    • Temperature Regulation: Central Neurology And The Role Of Gamma-Aminobutyric Acid (Sheep)

      Smullin, David Hyam (1986)
      This thesis investigates the hypothesis that thermoregulation may depend upon opposing responses of hot and cold temperature sensors with reciprocal inhibition between the efferent signals to the heat loss and heat production effectors, rather than upon comparison of a regulated variable with a temperature insensitive reference signal. A physical model was built to demonstrate that temperature regulation can work on this principle, and intracerebroventricular injections (ICV) of synaptically active substances were made into sheep to investigate the role of gamma-aminobutyric acid (GABA) as a neurotransmitter of reciprocal inhibition in thermoregulation. The model consisted of two inversely-related temperature-dependent signal generators connected to opposing correction effectors which served to heat and cool a plexiglass chamber. Reciprocal inhibition between the efferent pathways created a thermoregulatory null-zone which could be varied by manipulating signals converging onto either pathway to qualitatively simulate physiological responses to fever, hibernation and ICV injections of synaptically active substances. ICV injections of GABA or its agonist muscimol inhibited heat loss in the heat and heat production in the cold in sheep. An ICV injection of a GABA blocker prior to the ICV injection of an excitatory transmitter of either the heat production pathway in the heat or the heat loss pathway in the cold activated both heat production and heat loss effectors simultaneously. These results support the hypotheses that thermoregulation may depend upon opposing responses of sensor signals with reciprocal inhibition between the signals to opposing effectors and that GABA acts as the neurotransmitter of reciprocal inhibition.
    • The development of diving behavior and physiology in juvenile Weddell seals (Leptonychotes weddellii) in McMurdo Sound, Antarctica

      Burns, Jennifer Moss; Castellini, Michael (1997)
      The development of diving behavior and physiology in juvenile Weddell seals (Leptonychotes weddellii) in McMurdo Sound, Antarctica was studied in order to determine the effects of age, body size, and condition on diving ability. During the austral summers of 1992, 1993, and 1994, the diving behavior of 39 pups and 15 yearlings was monitored using time depth recorders (TDRs). In addition, 26 pups were equipped with satellite-linked time depth recorders (SLTDRs) to track fall and winter diving behavior. Blood samples and morphological measurements were taken at each handling. Pups began to dive within two weeks of birth, and the mean dive depth, duration, and number of dives per day increased significantly over the next 10 weeks. During this period, the ability of pups to regulate physiological processes related to diving increased, as did their aerobic dive limit (ADL). Whereas diving behavior was determined primarily by age rather than mass in young pups, age had little effect on the diving behavior of pups older than 2 months (as determined from SLTDR records). Because seals were not handled after SLTDR deployment, the effects of mass could not be directly modeled in these pups. However, in yearlings, the ADL, and approximately 50% of the variation in dive behavior could be explained by differences in body size. Most dive parameters differed by time of day, and deeper and longer dives were more frequent in the afternoon period. The diel pattern was consistent with the hypothesis that pups were foraging throughout the day on vertically migrating prey species. In yearlings, dive patterns suggested that large individuals foraged primarily on shallow water prey, while smaller animals concentrated on deeper prey such as Antarctic silverfish. Tracking studies revealed that juveniles were capable of long distance movements, but suggested that they remained closer to the coastline than adults. The absence of obvious differences in dive behavior between regions suggested that juveniles were foraging on similar prey throughout the Ross Sea. While scat analyses confirmed this hypothesis, tissue stable isotope ratios suggested that some juveniles were feeding on different prey, or in different areas than adults.