The Experts below are selected from a list of 291 Experts worldwide ranked by ideXlab platform

Daniel P Costa - One of the best experts on this subject based on the ideXlab platform.

  • terrestrial locomotion of the Northern Elephant Seal mirounga angustirostris limitation of large aquatically adapted Seals on land
    The Journal of Experimental Biology, 2018
    Co-Authors: Kelsey A Tennett, Daniel P Costa, Anthony J Nicastro, Frank E Fish
    Abstract:

    ABSTRACT The aquatic specializations of phocid Seals have restricted their ability to locomote on land. The amphibious Northern Elephant Seal, Mirounga angustirostris , is the second largest phocid Seal in the world, with males reaching 2700 kg. Although Elephant Seals are proficient swimmers and deep divers, their extreme size and aquatic specializations limit terrestrial movement. The kinematics of terrestrial locomotion in Northern Elephant Seals were analyzed from video recordings of animals observed on the beach of Ano Nuevo State Reserve, CA, USA. The Seals moved using a series of rhythmic undulations produced by dorsoventral spinal flexion. The traveling spinal wave moved anteriorly along the dorsal margin of the body with the chest, pelvic region and foreflippers serving as the main points of contact with the ground. The hindflippers were not used. The spinal wave and foreflippers were used to lift the chest off the ground as the body was pushed forward from the pelvis as the foreflippers were retracted to pull the body forward. Seals moved over land at 0.41–2.56 m s −1 (0.12–0.71 body lengths s −1 ). The frequency and amplitude of spinal flexions both displayed a direct increase with increasing speed. The duty factor for the pelvic region decreased with increasing velocity while the duty factor of the foreflipper remained constant. Kinematic data for Elephant Seals and other phocids were used in a biomechanical model to calculate the mechanical energy expended during terrestrial locomotion. The Elephant Seals were found to expend more energy when traveling over land for their size than smaller phocids. The unique method of terrestrial movement also exhibited greater energy expenditure on land than values for large quadrupeds. The trade-off for the Northern Elephant Seal is that its massive size and morphology have well adapted it to an aquatic existence but limited its locomotor performance (i.e. speed, endurance) on land.

  • effects of maternal age and mass on foraging behaviour and foraging success in the Northern Elephant Seal
    Functional Ecology, 2013
    Co-Authors: Jason L Hassrick, Daniel E Crocker, Daniel P Costa
    Abstract:

    Summary 1. Animals that show indeterminate growth and put relatively constant proportions of stored body reserves towards annual reproductive effort are confronted with a problem of meeting ever-increasing energetic demands in unpredictable environments. 2. We examined how intrinsic traits, mass and age, as well as extrinsic environmental features impact diving and movement behaviour in a marine capital breeder, the Northern Elephant Seal, Mirounga angustirostris. We assessed the impact of this behavioural variation on foraging success, measured as energy gained at sea. 3. We used principal component analysis to reduce behavioural variables into three principal components that described time in foraging zones (PC1), foraging distance (PC2) and bout structure of dive shapes (PC3). 4. Both intrinsic traits and extrinsic environmental features influenced behaviour and foraging success. Body mass was the sole predictor of residence time in foraging zones (PC1), which, in turn, was the strongest behavioural predictor of foraging efficiency and success over the short postbreeding season. Foraging distance (PC2) significantly varied with year. Since foraging distance is an index of the horizontal and vertical distances Seals travel while foraging, we suggest that it was impacted by inter-annual variation in marine prey distribution. Age had a negligible impact on most aspects of behaviour, except for the structure of dive shapes on the postmoult foraging trip. 5. All principal components significantly impacted rates of energy gain for postbreeding foraging trips when maternal body stores must be recovered quickly before returning to shore to moult. Age impacted the bout structure of dives in pregnant females in a way that influenced success, suggesting a role for previous experience during the long postmoult foraging migration. 6. Strong impacts of body mass on diving ability, foraging success and reproductive effort suggest a proximate mechanism for trade-offs in the cost of reproduction. Mass lost to current investment in offspring impacts a mother’s ability to accrue resources for future offspring.

  • a profile of carbohydrate metabolites in the fasting Northern Elephant Seal
    Comparative Biochemistry and Physiology Part D: Genomics and Proteomics, 2013
    Co-Authors: Cory D Champagne, Daniel P Costa, Dorian S Houser, Melinda A Fowler, Segal M Boaz, Daniel E Crocker
    Abstract:

    Abstract Northern Elephant Seals endure prolonged periods of food deprivation at multiple life-history stages and simultaneous with energetically costly activities—including reproduction and development. Most mammals decrease their energy expenditure while fasting, with simultaneous reductions in gluconeogenesis and circulating glucose concentration. Paradoxically, Elephant Seals maintain high rates of both energy expenditure and gluconeogenesis, and high blood glucose concentrations throughout fasting. We therefore characterized the suite of changes that occur in carbohydrate metabolites during fasting in Northern Elephant Seals. Using a broad-based metabolomics platform we investigated fasting during two states—lactation in adult females and the post-weaning developmental period in pups. A total of 227 metabolites were detected in Seal plasma; 31 associated with carbohydrate metabolism were analyzed in the present study. Several compounds showed similar responses during lactation and the post-weaning fast (e.g. glycerol and mesaconate) whereas other compounds displayed quite different abundances between groups (e.g. citrate and pyruvate). This work found that, while the changes that occur with fasting were frequently similar in lactating females and developing pups, the relative abundance of compounds often varied markedly. These differences suggest that the metabolic strategies used to endure prolonged fasts are influenced by life-history or nutrient constraints.

  • foraging behavior and success of a mesopelagic predator in the northeast pacific ocean insights from a data rich species the Northern Elephant Seal
    PLOS ONE, 2012
    Co-Authors: Patrick W Robinson, Daniel E Crocker, Cory D Champagne, Daniel P Costa, Melinda A Fowler, Juan Pablo Galloreynoso, Chandra Goetsch, Kimberly T Goetz, Jason L Hassrick, Luis A Huckstadt
    Abstract:

    The mesopelagic zone of the northeast Pacific Ocean is an important foraging habitat for many predators, yet few studies have addressed the factors driving basin-scale predator distributions or inter-annual variability in foraging and breeding success. Understanding these processes is critical to reveal how conditions at sea cascade to population-level effects. To begin addressing these challenging questions, we collected diving, tracking, foraging success, and natality data for 297 adult female Northern Elephant Seal migrations from 2004 to 2010. During the longer post-molting migration, individual energy gain rates were significant predictors of pregnancy. At sea, Seals focused their foraging effort along a narrow band corresponding to the boundary between the sub-arctic and sub-tropical gyres. In contrast to shallow-diving predators, Elephant Seals target the gyre-gyre boundary throughout the year rather than follow the southward winter migration of surface features, such as the Transition Zone Chlorophyll Front. We also assessed the impact of added transit costs by studying Seals at a colony near the southern extent of the species’ range, 1,150 km to the south. A much larger proportion of Seals foraged locally, implying plasticity in foraging strategies and possibly prey type. While these findings are derived from a single species, the results may provide insight to the foraging patterns of many other meso-pelagic predators in the northeast Pacific Ocean.

  • environmental perturbations behavioral change and population response in a long term Northern Elephant Seal study
    2011
    Co-Authors: Daniel P Costa
    Abstract:

    Abstract : A major challenge in marine mammal conservation and management is to understand how behavioral responses affect populations. To address this challenge, the National Research Council established the Committee on Characterizing Biologically Significant Marine Mammal Behavior. This committee developed a framework for analyzing the population consequences of acoustic disturbance, or PCAD (NRC 2005). The PCAD framework defines a series of transfer functions which describe how behavioral responses to sound affect life functions, how life functions are linked to vital population rates, and how changes in vital rates cause population change (Fig. 1). The U.S. Navy included the PCAD framework in the U.S. Navy Living Marine Resource Sound Research Requirements, specifically within the Response to Naval Sounds requirement #5: Determine biologically significant behavioral responses from Navy sound sources on individuals representing marine mammal species of concern with respect to ... determining long-term effects of behavioral responses and how individual vital rates may affect the population. This requirement was given the highest priority under the Navy's requirements. Implementing the concepts of transfer functions which link behavior to population change, however, requires substantial long-term data on individual animals and population size, and there are few marine mammal populations where quantifying the functions is plausible. Funding from this grant has allowed us to extend and improve a four-decade study of Northern Elephant Seal populations in California, aiming specifically to quantify key linkages within the PCAD model. Since 1968, several thousand individual Seals have been tagged and tracked for their lifetimes, and several hundred of those have been weighed or outfitted with telemetry devices in order to document pelagic foraging behavior and body condition.

Daniel E Crocker - One of the best experts on this subject based on the ideXlab platform.

  • mobilisation of blubber fatty acids of Northern Elephant Seal pups mirounga angustirostris during the post weaning fast
    Comparative Biochemistry and Physiology A-molecular & Integrative Physiology, 2015
    Co-Authors: Caroline Louis, Daniel E Crocker, Laurent Perdaens, Stephanie Suciu, Stephen K Tavoni, Cathy Debier
    Abstract:

    Northern Elephant Seal pups were longitudinally sampled at Ano Nuevo State Reserve during the post-weaning fast, in order to evaluate the changes of fatty acid (FA) profiles in serum as well as in the inner and outer layers of blubber. The major FAs of inner and outer blubber layers were broadly similar to those found in NES maternal milk previously measured, suggesting a direct deposit of dietary FAs in the blubber during the suckling period. The outer blubber layer contained more medium-chain monounsaturated FAs that contribute in keeping the fluidity of this tissue at cold temperatures. It was compensated by higher proportions of saturated FAs in the inner blubber layer. The FA signature of inner blubber, the layer that is mainly mobilised during energy deprivation, slightly differed from the signature of serum. There were greater proportions of medium-chain saturated FAs and ω-6 polyunsaturated FAs, and lower proportions of long-chain saturated FAs, medium-chain monounsaturated FAs and long-chain monounsaturated FAs in serum as compared to inner blubber. We also demonstrated that lipophilicity is the main factor governing the mobilisation of FAs from blubber. The least lipophilic FAs were preferentially hydrolysed from blubber, leading to an enrichment of the more lipophilic FAs in this tissue with the progression of the fast. The expression levels of HSL and ATGL, which are two enzymes involved in the lipolytic process, remained stable during the post-weaning fast. This suggests that the pups have developed the enzymatic mechanisms for an efficient lipolysis as soon as the first week of fast.

  • transcriptome analysis of Northern Elephant Seal mirounga angustirostris muscle tissue provides a novel molecular resource and physiological insights
    BMC Genomics, 2015
    Co-Authors: Jane Khudyakov, Rudy M Ortiz, Likit Preeyanon, Cory D Champagne, Daniel E Crocker
    Abstract:

    Background The Northern Elephant Seal, Mirounga angustirostris, is a valuable animal model of fasting adaptation and hypoxic stress tolerance. However, no reference sequence is currently available for this and many other marine mammal study systems, hindering molecular understanding of marine adaptations and unique physiology.

  • elevated carboxyhemoglobin in a marine mammal the Northern Elephant Seal
    The Journal of Experimental Biology, 2014
    Co-Authors: Paul J Ponganis, Michael S Tift, Daniel E Crocker
    Abstract:

    Low concentrations of endogenous carbon monoxide (CO), generated primarily through degradation of heme from heme-proteins, have been shown to maintain physiological function of organs and to exert cytoprotective effects. However, high concentrations of carboxyhemoglobin (COHb), formed by CO binding to hemoglobin, potentially prevent adequate O2 delivery to tissues by lowering arterial O2 content. Elevated heme-protein concentrations, as found in marine mammals, are likely associated with greater heme degradation, more endogenous CO production and, consequently, elevated COHb concentrations. Therefore, we measured COHb in Elephant Seals, a species with large blood volumes and elevated hemoglobin and myoglobin concentrations. The levels of COHb were positively related to the total hemoglobin concentration. The maximum COHb value was 10.4% of total hemoglobin concentration. The mean (±s.e.m.) value in adult Seals was 8.7±0.3% (N=6), while juveniles and pups (with lower heme-protein contents) had lower mean COHb values of 7.6±0.2% and 7.1±0.3%, respectively (N=9 and N=9, respectively). Serial samples over several hours revealed little to no fluctuation in COHb values. This consistent elevation in COHb suggests that the magnitude and/or rate of heme-protein turnover is much higher than in terrestrial mammals. The maximum COHb values from this study decrease total body O2 stores by 7%, thereby reducing the calculated aerobic dive limit for this species. However, the constant presence of elevated CO in blood may also protect against potential ischemia–reperfusion injury associated with the extreme breath-holds of Elephant Seals. We suggest the Elephant Seal represents an ideal model for understanding the potential cytoprotective effects, mechanisms of action and evolutionary adaptation associated with chronically elevated concentrations of endogenously produced CO.

  • development enhances hypometabolism in Northern Elephant Seal pups mirounga angustirostris
    Functional Ecology, 2013
    Co-Authors: Michael S Tift, Rudy M Ortiz, Dorian S Houser, Elizabeth C Ranalli, Daniel E Crocker
    Abstract:

    Summary Investigation into the development of oxygen storage capacity in air-breathing marine predators has been performed, but little is known about the development of regulatory factors that influence oxygen utilization. Strategies for efficiently using oxygen stores should enable marine predators to optimize time spent foraging underwater. We describe the developmental patterns of oxygen use during voluntary breath-holds in Northern Elephant Seals (Mirounga angustirostris) at 2 and 7 weeks postweaning. We measured (i) changes in oxygen consumption (VO2) and (ii) changes in venous pH, partial pressure of oxygen (pO2), haemoglobin saturation (sO2), oxygen content (O2ct), partial pressure of carbon dioxide (pCO2), haematocrit (Hct) and total haemoglobin (tHb). To examine the effect of the dive response on the development of oxygen utilization, voluntary breath-hold experiments were conducted in and out of water. Suppression of VO2 during voluntary breath-holds increased significantly between 2 and 7 weeks postweaning, reaching a maximum suppression of 53% below resting metabolic rate and 56% below Kleiber's standard metabolic rate. From 2 to 7 weeks postweaning, breath-hold VO2 was reduced by 52%. Between the two age classes, this equates to a mean breath-hold VO2 reduction of 16% from resting VO2. Breath-hold VO2 also declined with increasing breath-hold duration, but there was no direct effect of voluntary submergence on reducing VO2. Age did not influence rates of venous pO2 depletion during breath-holds. However, voluntary submergence did result in slower pO2 depletion rates when compared with voluntary terrestrial apnoeas. The differences in whole-body VO2 during breath-holds (measured at recovery) and venous pO2 (reflective of tissue O2-use measured during breath-holds) likely reflect metabolic suppression in hypoxic, vasoconstricted tissues. Consistent pCO2 values at the end of all voluntary breath-holds (59·0 ± 0·7 mmHg) suggest the physiological cue for stimulating respiration in Northern Elephant Seal pups is the accumulation of CO2. Oxygen storage capacity and metabolic suppression directly limit diving capabilities and may influence foraging success in low-weaning weight Seals forced to depart to sea prior to achieving full developmental diving capacity.

  • prolonged fasting activates hypoxia inducible factors 1α 2α and 3α in a tissue specific manner in Northern Elephant Seal pups
    Gene, 2013
    Co-Authors: Jose G Sonanezorganis, Jose Pablo Vazquezmedina, Daniel E Crocker, Rudy M Ortiz
    Abstract:

    Abstract Hypoxia inducible factors (HIFs) are important regulators of energy homeostasis and cellular adaptation to low oxygen conditions. Northern Elephant Seals are naturally adapted to prolonged periods (1–2 months) of food deprivation (fasting) which result in metabolic changes that may activate HIF-1. However, the effects of prolonged fasting on HIFs are not well defined. We obtained the full-length cDNAs of HIF-1α and HIF-2α, and partial cDNA of HIF-3α in Northern Elephant Seal pups. We also measured mRNA and nuclear protein content of HIF-1α, -2α, -3α in muscle and adipose during prolonged fasting (1, 3, 5 & 7 weeks), along with mRNA expression of HIF-mediated genes, LDH and VEGF. HIF-1α, -2α and -3α are 2595, 2852 and 1842 bp and encode proteins of 823, 864 and 586 amino acid residues with conserved domains needed for their function (bHLH and PAS) and regulation (ODD and TAD). HIF-1α and -2α mRNA expression increased 3- to 5-fold after 7 weeks of fasting in adipose and muscle, whereas HIF-3α increased 5-fold after 7 weeks of fasting in adipose. HIF-2α protein expression was detected in nuclear fractions from adipose and muscle, increasing approximately 2-fold, respectively with fasting. Expression of VEGF increased 3-fold after 7 weeks in adipose and muscle, whereas LDH mRNA expression increased 12-fold after 7 weeks in adipose. While the 3 HIFα genes are expressed in muscle and adipose, only HIF-2α protein was detectable in the nucleus suggesting that HIF-2α may contribute more significantly in the up-regulation of genes involved in the metabolic adaptation during fasting in the Elephant Seal.

Rudy M Ortiz - One of the best experts on this subject based on the ideXlab platform.

  • transcriptome analysis of Northern Elephant Seal mirounga angustirostris muscle tissue provides a novel molecular resource and physiological insights
    BMC Genomics, 2015
    Co-Authors: Jane Khudyakov, Rudy M Ortiz, Likit Preeyanon, Cory D Champagne, Daniel E Crocker
    Abstract:

    Background The Northern Elephant Seal, Mirounga angustirostris, is a valuable animal model of fasting adaptation and hypoxic stress tolerance. However, no reference sequence is currently available for this and many other marine mammal study systems, hindering molecular understanding of marine adaptations and unique physiology.

  • development enhances hypometabolism in Northern Elephant Seal pups mirounga angustirostris
    Functional Ecology, 2013
    Co-Authors: Michael S Tift, Rudy M Ortiz, Dorian S Houser, Elizabeth C Ranalli, Daniel E Crocker
    Abstract:

    Summary Investigation into the development of oxygen storage capacity in air-breathing marine predators has been performed, but little is known about the development of regulatory factors that influence oxygen utilization. Strategies for efficiently using oxygen stores should enable marine predators to optimize time spent foraging underwater. We describe the developmental patterns of oxygen use during voluntary breath-holds in Northern Elephant Seals (Mirounga angustirostris) at 2 and 7 weeks postweaning. We measured (i) changes in oxygen consumption (VO2) and (ii) changes in venous pH, partial pressure of oxygen (pO2), haemoglobin saturation (sO2), oxygen content (O2ct), partial pressure of carbon dioxide (pCO2), haematocrit (Hct) and total haemoglobin (tHb). To examine the effect of the dive response on the development of oxygen utilization, voluntary breath-hold experiments were conducted in and out of water. Suppression of VO2 during voluntary breath-holds increased significantly between 2 and 7 weeks postweaning, reaching a maximum suppression of 53% below resting metabolic rate and 56% below Kleiber's standard metabolic rate. From 2 to 7 weeks postweaning, breath-hold VO2 was reduced by 52%. Between the two age classes, this equates to a mean breath-hold VO2 reduction of 16% from resting VO2. Breath-hold VO2 also declined with increasing breath-hold duration, but there was no direct effect of voluntary submergence on reducing VO2. Age did not influence rates of venous pO2 depletion during breath-holds. However, voluntary submergence did result in slower pO2 depletion rates when compared with voluntary terrestrial apnoeas. The differences in whole-body VO2 during breath-holds (measured at recovery) and venous pO2 (reflective of tissue O2-use measured during breath-holds) likely reflect metabolic suppression in hypoxic, vasoconstricted tissues. Consistent pCO2 values at the end of all voluntary breath-holds (59·0 ± 0·7 mmHg) suggest the physiological cue for stimulating respiration in Northern Elephant Seal pups is the accumulation of CO2. Oxygen storage capacity and metabolic suppression directly limit diving capabilities and may influence foraging success in low-weaning weight Seals forced to depart to sea prior to achieving full developmental diving capacity.

  • prolonged fasting activates hypoxia inducible factors 1α 2α and 3α in a tissue specific manner in Northern Elephant Seal pups
    Gene, 2013
    Co-Authors: Jose G Sonanezorganis, Jose Pablo Vazquezmedina, Daniel E Crocker, Rudy M Ortiz
    Abstract:

    Abstract Hypoxia inducible factors (HIFs) are important regulators of energy homeostasis and cellular adaptation to low oxygen conditions. Northern Elephant Seals are naturally adapted to prolonged periods (1–2 months) of food deprivation (fasting) which result in metabolic changes that may activate HIF-1. However, the effects of prolonged fasting on HIFs are not well defined. We obtained the full-length cDNAs of HIF-1α and HIF-2α, and partial cDNA of HIF-3α in Northern Elephant Seal pups. We also measured mRNA and nuclear protein content of HIF-1α, -2α, -3α in muscle and adipose during prolonged fasting (1, 3, 5 & 7 weeks), along with mRNA expression of HIF-mediated genes, LDH and VEGF. HIF-1α, -2α and -3α are 2595, 2852 and 1842 bp and encode proteins of 823, 864 and 586 amino acid residues with conserved domains needed for their function (bHLH and PAS) and regulation (ODD and TAD). HIF-1α and -2α mRNA expression increased 3- to 5-fold after 7 weeks of fasting in adipose and muscle, whereas HIF-3α increased 5-fold after 7 weeks of fasting in adipose. HIF-2α protein expression was detected in nuclear fractions from adipose and muscle, increasing approximately 2-fold, respectively with fasting. Expression of VEGF increased 3-fold after 7 weeks in adipose and muscle, whereas LDH mRNA expression increased 12-fold after 7 weeks in adipose. While the 3 HIFα genes are expressed in muscle and adipose, only HIF-2α protein was detectable in the nucleus suggesting that HIF-2α may contribute more significantly in the up-regulation of genes involved in the metabolic adaptation during fasting in the Elephant Seal.

  • activation of systemic but not local renin angiotensin system is associated with upregulation of tnf α during prolonged fasting in Northern Elephant Seal pups
    The Journal of Experimental Biology, 2013
    Co-Authors: Daniel E Crocker, Jose A Viscarra, Jose Pablo Vazquezmedina, Jose G Sonanezorganis, Miwa Suzuki, Rudy M Ortiz
    Abstract:

    Northern Elephant Seal pups naturally endure a 2–3 month post-weaning fast that is associated with activation of systemic renin–angiotensin system (RAS), a decrease in plasma adiponectin (Acrp30), and insulin resistance (IR)-like conditions. Angiotensin II (Ang II) and tumor necrosis factor-alpha (TNF-α) are potential causal factors of IR, while Acrp30 may improve insulin signaling. However, the effects of fasting-induced activation of RAS on IR-like conditions in Seals are not well described. To assess the effects of prolonged food deprivation on systemic and local RAS, and their potential contribution to TNF-α as they relate to an IR condition, the mRNA expressions of adipose and muscle RAS components and immuno-relevant molecules were measured along with plasma RAS components. Mean plasma renin activity and Ang II concentrations increased by 89 and 1658%, respectively, while plasma angiotensinogen (AGT) decreased by 49% over the fast, indicative of systemic RAS activation. Prolonged fasting was associated with decreases in adipose and muscle AGT mRNA expressions of 69 and 68%, respectively, corresponding with decreases in tissue protein content, suggesting suppression of local AGT production. Muscle TNF-α mRNA and protein increased by 239 and 314%, whereas those of adipose Acrp30 decreased by 32 and 98%, respectively. Collectively, this study suggests that prolonged fasting activates a systemic RAS, which contributes to an increase in muscle TNF-α and suppression of adipose Acrp30. This targeted and tissue-specific regulation of TNF-α and Acrp30 is likely coordinated to synergistically contribute to the development of an IR-like condition, independent of local RAS activity. These data enhance our understanding of the adaptive mechanisms evolved by Elephant Seals to tolerate potentially detrimental conditions.

  • decreased expression of adipose cd36 and fatp1 are associated with increased plasma non esterified fatty acids during prolonged fasting in Northern Elephant Seal pups mirounga angustirostris
    The Journal of Experimental Biology, 2012
    Co-Authors: Jose A Viscarra, Daniel E Crocker, Cory D Champagne, Sean H Adams, Jose Pablo Vazquezmedina, Ruben Rodriguez, Rudy M Ortiz
    Abstract:

    SUMMARY The Northern Elephant Seal pup ( Mirounga angustirostris ) undergoes a 2–3 month post-weaning fast, during which it depends primarily on the oxidation of fatty acids to meet its energetic demands. The concentration of non-esterified fatty acids (NEFAs) increases and is associated with the development of insulin resistance in late-fasted pups. Furthermore, plasma NEFA concentrations respond differentially to an intravenous glucose tolerance test (ivGTT) depending on fasting duration, suggesting that the effects of glucose on lipid metabolism are altered. However, elucidation of the lipolytic mechanisms including lipase activity during prolonged fasting in mammals is scarce. To assess the impact of fasting and glucose on the regulation of lipid metabolism, adipose tissue and plasma samples were collected before and after ivGTTs performed on early (2 weeks, N =5) and late (6–8 weeks; N =8) fasted pups. Glucose administration increased plasma triglycerides and NEFA concentrations in late-fasted Seals, but not plasma glycerol. Fasting decreased basal adipose lipase activity by 50%. Fasting also increased plasma lipase activity twofold and decreased the expressions of CD36, FAS, FATP1 and PEPCK-C by 22–43% in adipose tissue. Plasma acylcarnitine profiling indicated that late-fasted Seals display higher incomplete LCFA β-oxidation. Results suggest that long-term fasting induces shifts in the regulation of lipolysis and lipid metabolism associated with the onset of insulin resistance in Northern Elephant Seal pups. Delineation of the mechanisms responsible for this shift in regulation during fasting can contribute to a more thorough understanding of the changes in lipid metabolism associated with dyslipidemia and insulin resistance in mammals.

Dorian S Houser - One of the best experts on this subject based on the ideXlab platform.

  • development enhances hypometabolism in Northern Elephant Seal pups mirounga angustirostris
    Functional Ecology, 2013
    Co-Authors: Michael S Tift, Rudy M Ortiz, Dorian S Houser, Elizabeth C Ranalli, Daniel E Crocker
    Abstract:

    Summary Investigation into the development of oxygen storage capacity in air-breathing marine predators has been performed, but little is known about the development of regulatory factors that influence oxygen utilization. Strategies for efficiently using oxygen stores should enable marine predators to optimize time spent foraging underwater. We describe the developmental patterns of oxygen use during voluntary breath-holds in Northern Elephant Seals (Mirounga angustirostris) at 2 and 7 weeks postweaning. We measured (i) changes in oxygen consumption (VO2) and (ii) changes in venous pH, partial pressure of oxygen (pO2), haemoglobin saturation (sO2), oxygen content (O2ct), partial pressure of carbon dioxide (pCO2), haematocrit (Hct) and total haemoglobin (tHb). To examine the effect of the dive response on the development of oxygen utilization, voluntary breath-hold experiments were conducted in and out of water. Suppression of VO2 during voluntary breath-holds increased significantly between 2 and 7 weeks postweaning, reaching a maximum suppression of 53% below resting metabolic rate and 56% below Kleiber's standard metabolic rate. From 2 to 7 weeks postweaning, breath-hold VO2 was reduced by 52%. Between the two age classes, this equates to a mean breath-hold VO2 reduction of 16% from resting VO2. Breath-hold VO2 also declined with increasing breath-hold duration, but there was no direct effect of voluntary submergence on reducing VO2. Age did not influence rates of venous pO2 depletion during breath-holds. However, voluntary submergence did result in slower pO2 depletion rates when compared with voluntary terrestrial apnoeas. The differences in whole-body VO2 during breath-holds (measured at recovery) and venous pO2 (reflective of tissue O2-use measured during breath-holds) likely reflect metabolic suppression in hypoxic, vasoconstricted tissues. Consistent pCO2 values at the end of all voluntary breath-holds (59·0 ± 0·7 mmHg) suggest the physiological cue for stimulating respiration in Northern Elephant Seal pups is the accumulation of CO2. Oxygen storage capacity and metabolic suppression directly limit diving capabilities and may influence foraging success in low-weaning weight Seals forced to depart to sea prior to achieving full developmental diving capacity.

  • a profile of carbohydrate metabolites in the fasting Northern Elephant Seal
    Comparative Biochemistry and Physiology Part D: Genomics and Proteomics, 2013
    Co-Authors: Cory D Champagne, Daniel P Costa, Dorian S Houser, Melinda A Fowler, Segal M Boaz, Daniel E Crocker
    Abstract:

    Abstract Northern Elephant Seals endure prolonged periods of food deprivation at multiple life-history stages and simultaneous with energetically costly activities—including reproduction and development. Most mammals decrease their energy expenditure while fasting, with simultaneous reductions in gluconeogenesis and circulating glucose concentration. Paradoxically, Elephant Seals maintain high rates of both energy expenditure and gluconeogenesis, and high blood glucose concentrations throughout fasting. We therefore characterized the suite of changes that occur in carbohydrate metabolites during fasting in Northern Elephant Seals. Using a broad-based metabolomics platform we investigated fasting during two states—lactation in adult females and the post-weaning developmental period in pups. A total of 227 metabolites were detected in Seal plasma; 31 associated with carbohydrate metabolism were analyzed in the present study. Several compounds showed similar responses during lactation and the post-weaning fast (e.g. glycerol and mesaconate) whereas other compounds displayed quite different abundances between groups (e.g. citrate and pyruvate). This work found that, while the changes that occur with fasting were frequently similar in lactating females and developing pups, the relative abundance of compounds often varied markedly. These differences suggest that the metabolic strategies used to endure prolonged fasts are influenced by life-history or nutrient constraints.

  • differential changes of fat soluble vitamins and pollutants during lactation in Northern Elephant Seal mother pup pairs
    Comparative Biochemistry and Physiology A-molecular & Integrative Physiology, 2012
    Co-Authors: Cathy Debier, Daniel E Crocker, Dorian S Houser, Marie Vanden Berghe, Melinda A Fowler, Eric Mignolet, Tanguy De Tillesse, Jeanfrancois Rees, Jeanpierre Thome, Yvan Larondelle
    Abstract:

    We investigated the changes of vitamins A and E as well as PCBs and DDTs during lactation in Northern Elephant Seal (Mirounga angustirostris) mother-pup pairs. On average, milk vitamin A concentrations were 6 times higher during late lactation than during early lactation, a pattern that differs dramatically from terrestrial mammals. Vitamin A concentrations also significantly increased in the inner blubber throughout lactation, whereas they remained constant in the outer blubber. Similar dynamics were observed for PCBs and DDTs in maternal blubber and milk. Blubber appears to be an important storage site for vitamin A and organochlorines in Seals and a direct transfer of those molecules to the mammary gland may occur. The dynamics of vitamin A, PCBs and DDTs differed from those of vitamin E. There was a significant drop in milk vitamin E concentrations between early and late lactation, which is the usual pattern observed in terrestrial mammals. The dynamics of vitamin E in the blubber layers also differed from those of vitamin A, suggesting different mechanisms of mobilization and transfer into the milk.

  • air and bone conduction evoked potential audiometry in the Northern Elephant Seal
    Journal of the Acoustical Society of America, 2008
    Co-Authors: Dorian S Houser, Daniel E Crocker, James J Finneran
    Abstract:

    Elephant Seals (Mirounga angustirostris) are the largest and most aquatic of the pinnipeds, spending up to eight months of the year at sea diving to depths as great as 1600 m. The pinna is absent in the Elephant Seal and the middle ear cavity and auditory canal are lined with a cavernous tissue, both of which are likely adaptations to deep diving. Elephant Seals demonstrate a greater sensitivity to low frequency sounds than do other pinnipeds and an overall greater sensitivity to underwater sound than to airborne sound. The relative importance of sound conduction pathways in the Elephant Seal is undetermined, although it has been speculated that bone conduction pathways are important to underwater hearing in this species. To compare the sensitivity of the Elephant Seal to both air and bone conducted stimuli, auditory evoked responses were recorded in Seals exposed to signals presented through headphones and via a bone vibrator. In comparison to airborne stimuli, bone conduction methods provide an opportun...

  • click and tone pip auditory evoked potentials in a large marine mammal the Northern Elephant Seal
    Journal of the Acoustical Society of America, 2006
    Co-Authors: Dorian S Houser, James J Finneran
    Abstract:

    The use of auditory‐evoked potentials (AEPs) to study the hearing of mysticete whales is challenged by access to animals, their large size, and proportionately smaller brain relative to odontocetes. One means by which AEP techniques can be adapted to these larger animals is by application to more readily available proxy species. The Northern Elephant Seal (Mirounga angustirostris) is a large pinniped, potentially in excess of 2000 kg, with a thick dermis, large skull, relatively small auditory nerve, and a low‐frequency vocal communication system. AEP collection in Elephant Seals provides similar challenges to those of the mysticetes but at a scale that provides a greater opportunity for success. AEP tests were conducted on Northern Elephant Seals at Ano Nuevo State Reserve, the natural haul‐out site of the Elephant Seal. Subjects were chemically immobilized with tiletamine/zolazepam and chemical restraint was maintained with bolus injections of ketamine. Click‐evoked potentials were collected from four w...

Robert L Delong - One of the best experts on this subject based on the ideXlab platform.