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Daniel E Crocker - One of the best experts on this subject based on the ideXlab platform.
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adipose transcriptome analysis provides novel insights into molecular regulation of prolonged fasting in northern elephant seal pups
Physiological Genomics, 2018Co-Authors: Bridget Martinez, Jane Khudyakov, Daniel E Crocker, Kim Rutherford, Neil J Gemmell, Rudy M. OrtizAbstract:The physiological and cellular adaptations to extreme fasting in northern elephant seals (Mirounga angustirostris, NES) are remarkable and may help to elucidate endocrine mechanisms that regulate l...
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lipophilicity of pcbs and fatty acids determines their mobilisation from blubber of weaned northern elephant seal pups
Science of The Total Environment, 2016Co-Authors: Caroline Louis, Daniel E Crocker, Adrian Covaci, Cathy DebierAbstract:Polychlorinated biphenyls (PCBs) exhibit lipophilic properties that lead to their bioaccumulation in adipose tissue. Following PCB exposition, northern elephant seals (Mirounga angustirostris) concentrate high amounts of these pollutants in their large adipose tissue stores. During lipolytic periods such as the post-weaning fast, fatty acids (FAs), which form triglycerides, and PCBs are both mobilised from adipose tissue. Our results showed that the degree of lipophilicity of FAs and PCBs impacted their release: the more lipophilic FAs and PCBs tended to be more conserved in blubber over the fast than the less lipophilic ones. This led to an enrichment of more lipophilic compounds within adipocytes with the progression of the fast. Life history patterns that include fasting may thus influence the profile of blubber lipids and contaminants.
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transcriptome analysis of northern elephant seal Mirounga angustirostris muscle tissue provides a novel molecular resource and physiological insights
BMC Genomics, 2015Co-Authors: Jane Khudyakov, Likit Preeyanon, Rudy M. Ortiz, Cory D. Champagne, Daniel E CrockerAbstract: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.
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transcriptome analysis of northern elephant seal Mirounga angustirostris muscle tissue provides a novel molecular resource and physiological insights
BMC Genomics, 2015Co-Authors: Jane I Khudyakov, Likit Preeyanon, Rudy M. Ortiz, Cory D. Champagne, Daniel E CrockerAbstract: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. We sequenced a transcriptome of M. angustirostris derived from muscle sampled during an acute stress challenge experiment to identify species-specific markers of stress axis activation and recovery. De novo assembly generated 164,966 contigs and a total of 522,699 transcripts, of which 68.70% were annotated using mouse, human, and domestic dog reference protein sequences. To reduce transcript redundancy, we removed highly similar isoforms in large gene families and produced a filtered assembly containing 336,657 transcripts. We found that a large number of annotated genes are associated with metabolic signaling, immune and stress responses, and muscle function. Preliminary differential expression analysis suggests a limited transcriptional response to acute stress involving alterations in metabolic and immune pathways and muscle tissue maintenance, potentially driven by early response transcription factors such as Cebpd. We present the first reference sequence for Mirounga angustirostris produced by RNA sequencing of muscle tissue and cloud-based de novo transcriptome assembly. We annotated 395,102 transcripts, some of which may be novel isoforms, and have identified thousands of genes involved in key physiological processes. This resource provides elephant seal-specific gene sequences, complementing existing metabolite and protein expression studies and enabling future work on molecular pathways regulating adaptations such as fasting, hypoxia, and environmental stress responses in marine mammals.
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development enhances hypometabolism in northern elephant seal pups Mirounga angustirostris
Functional Ecology, 2013Co-Authors: Michael S Tift, Elizabeth C Ranalli, Rudy M. Ortiz, Dorian S Houser, Daniel E CrockerAbstract: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.
Daniel P. Costa - One of the best experts on this subject based on the ideXlab platform.
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the extra burden of motherhood reduced dive duration associated with pregnancy status in a deep diving mammal the northern elephant seal
Biology Letters, 2018Co-Authors: Luis A Huckstadt, Michael S Tift, Rachel R Holser, Daniel P. CostaAbstract:The cost of pregnancy is hard to study in marine mammals, particularly in species that undergo pregnancy while diving continuously at sea such as elephant seals (genus Mirounga). We analysed the diving behaviour of confirmed pregnant and non-pregnant northern elephant seals (M. angustirostris, n = 172) and showed that after an initial continuous increase in dive duration, dives of pregnant females become shorter after week 17. The reasons for this reduction in dive duration remain unknown, but we hypothesize that increased fetal demand for oxygen could be the cause. Our findings reveal an opportunity to explore the use of biologging data to investigate pregnancy status of free-ranging marine mammals and factors that could affect pregnancy success.
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Parasitological examination for presence of hookworms ( Uncinaria spp.) in northern elephant seals ( Mirounga angustirostris ) at Año Nuevo State Reserve, California (2012)
Parasitology Research, 2012Co-Authors: Eugene T. Lyons, Terry R Spraker, Tatiana A Kuzmina, Daniel P. Costa, Daniel E Crocker, N. Jaggi, Sharon C. Tolliver, Michael S TiftAbstract:Northern elephant seals (Mirounga angustirostris Gill, 1866), inhabiting rookeries on the mainland of Ano Nuevo State Reserve in central California, were investigated in 2012 for presence of hookworms (Uncinaria spp.). Material collected and examined for hookworms included: blubber (n = 15), stomach and intestines (n = 21) from dead pups; feces from the rectum of weaned pups (n = 23); sand containing apparent feces in areas of weaned pups (n = 28) and sand without apparent feces in areas of weaned pups (n = 54); milk from females (n =23) at 5 days and about 23 to 26 days postpartum; and placenta from one female. Evidence of hookworm presence was not detected in any of the samples examined. Possible reasons why hookworms were not found in northern elephant seals on the mainland of Ano Nuevo State Reserve are discussed.
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Pattern and depth of dives in Northern elephant seals, Mirounga angustirostris
Journal of Zoology, 2009Co-Authors: Burney J Leboeuf, Anthony C Huntley, Daniel P. Costa, Gerald L Kooyman, Randall W DavisAbstract:A time-depth recorder was attached to a female Northern elephant seal at the end of her lactation fast before she entered the sea to feed. The animal dived continuously during its first 11 days at sea, the period recorded for a total of 653 dives. Mean dive time was 21 min, with the longest submersion lasting 32 min. Mean surface interval between dives was 3 min, resulting in a total surface time of 11 %. Mean dive depth was 333 m and the deepest dive was 630 m, the deepest ever recorded for a pinniped. A depth histogram recorder attached to another female yielded a similar frequency distribution of dive depths.
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water conservation in fasting northern elephant seals Mirounga angustirostris
The Journal of Experimental Biology, 2006Co-Authors: Christopher W Lester, Daniel P. CostaAbstract:SUMMARY Prolonged terrestrial fasting is a key element in the life history of elephant seals. While on land seals typically fast without access to fresh water, and thus must maintain positive water balance by reductions in water loss such that they can subsist primarily on metabolic water production (MWP). The terrestrial apnea demonstrated by seals may reduce respiratory evaporative water loss (REWL) to levels that allow seals to make a net gain of water from MWP. We empirically measured REWL in 13 fasting northern elephant seal pups and determined the effects on water conservation of a breathing mode that incorporates a regular pattern of apneas, of ≥1 min in duration, followed by eupneic recovery, compared with a breathing mode with no apneas longer than 20 s and resembling typical breathing patterns in other mammals (normative breathing). Overall REWL fell 41% from 0.075±0.013 g min -1 (mean ± s.d.) during normative breathing to 0.044±0.006 g min -1 during apneic breathing. The decline in REWL is attributed to a decrease in overall ventilation rate, made possible by a decline in metabolic rate along with an increase in oxygen extraction that would occur during apneic breathing. Data on the range of ambient humidity conditions at the local breeding site were collected and used to bound the range of environmental conditions used in laboratory measurements. Our data showed that the observed variations in ambient humidity had no significant effect on REWL. A combination of apneic breathing and the complex nasal turbinates allows fasting elephant seals to reduce REWL well below the rate of MWP so that they can maintain water balance during the fast.
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renal responses to plasma volume expansion and hyperosmolality in fasting seal pups
American Journal of Physiology-regulatory Integrative and Comparative Physiology, 2002Co-Authors: Daniel P. Costa, Rudy M. Ortiz, Charles E. Wade, Leo C OrtizAbstract:Renal responses were quantified in northern elephant seal (Mirounga angustirostris) pups during their postweaning fast to examine their excretory capabilities. Pups were infused with either isotoni...
Rudy M. Ortiz - One of the best experts on this subject based on the ideXlab platform.
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adipose transcriptome analysis provides novel insights into molecular regulation of prolonged fasting in northern elephant seal pups
Physiological Genomics, 2018Co-Authors: Bridget Martinez, Jane Khudyakov, Daniel E Crocker, Kim Rutherford, Neil J Gemmell, Rudy M. OrtizAbstract:The physiological and cellular adaptations to extreme fasting in northern elephant seals (Mirounga angustirostris, NES) are remarkable and may help to elucidate endocrine mechanisms that regulate l...
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transcriptome analysis of northern elephant seal Mirounga angustirostris muscle tissue provides a novel molecular resource and physiological insights
BMC Genomics, 2015Co-Authors: Jane Khudyakov, Likit Preeyanon, Rudy M. Ortiz, Cory D. Champagne, Daniel E CrockerAbstract: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.
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transcriptome analysis of northern elephant seal Mirounga angustirostris muscle tissue provides a novel molecular resource and physiological insights
BMC Genomics, 2015Co-Authors: Jane I Khudyakov, Likit Preeyanon, Rudy M. Ortiz, Cory D. Champagne, Daniel E CrockerAbstract: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. We sequenced a transcriptome of M. angustirostris derived from muscle sampled during an acute stress challenge experiment to identify species-specific markers of stress axis activation and recovery. De novo assembly generated 164,966 contigs and a total of 522,699 transcripts, of which 68.70% were annotated using mouse, human, and domestic dog reference protein sequences. To reduce transcript redundancy, we removed highly similar isoforms in large gene families and produced a filtered assembly containing 336,657 transcripts. We found that a large number of annotated genes are associated with metabolic signaling, immune and stress responses, and muscle function. Preliminary differential expression analysis suggests a limited transcriptional response to acute stress involving alterations in metabolic and immune pathways and muscle tissue maintenance, potentially driven by early response transcription factors such as Cebpd. We present the first reference sequence for Mirounga angustirostris produced by RNA sequencing of muscle tissue and cloud-based de novo transcriptome assembly. We annotated 395,102 transcripts, some of which may be novel isoforms, and have identified thousands of genes involved in key physiological processes. This resource provides elephant seal-specific gene sequences, complementing existing metabolite and protein expression studies and enabling future work on molecular pathways regulating adaptations such as fasting, hypoxia, and environmental stress responses in marine mammals.
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development enhances hypometabolism in northern elephant seal pups Mirounga angustirostris
Functional Ecology, 2013Co-Authors: Michael S Tift, Elizabeth C Ranalli, Rudy M. Ortiz, Dorian S Houser, Daniel E CrockerAbstract: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.
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Angiotensin II and Aldosterone Increase with Fasting in Breeding Adult Male Northern Elephant Seals (Mirounga angustirostris)
Physiological and Biochemical Zoology, 2006Co-Authors: Rudy M. Ortiz, Dorian S Houser, Daniel E Crocker, Paul WebbAbstract:Abstract The renin‐angiotensin‐aldosterone system (RAAS) appears to contribute significantly to osmoregulation of fasting northern elephant seal (Mirounga angustirostris) pups; however, RAAS has not been characterized in fasting adult seals. Therefore, this study examined the contribution of RAAS to water turnover rates in fasting adult male northern elephant seals. Blood samples were obtained twice during their breeding fast at an interval of 6.5 wk, and water efflux rate was estimated by isotopic dilution during the same period. Serum electrolytes (Na+, K+, Cl−) and osmolality were unaltered between the two sampling periods, indicating ionic and osmotic homeostasis during the fast. Despite the lack of an increase in vasopressin, serum angiotensin II and aldosterone were increased and were significantly and positively correlated. Changes in aldosterone concentration and water efflux rate were significantly and negatively correlated, suggesting that the greater the increase in aldosterone, the smaller the...
Dorian S Houser - One of the best experts on this subject based on the ideXlab platform.
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development enhances hypometabolism in northern elephant seal pups Mirounga angustirostris
Functional Ecology, 2013Co-Authors: Michael S Tift, Elizabeth C Ranalli, Rudy M. Ortiz, Dorian S Houser, Daniel E CrockerAbstract: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.
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Lactate flux and gluconeogenesis in fasting, weaned northern elephant seals (Mirounga angustirostris)
Journal of Comparative Physiology B, 2013Co-Authors: Stephen K. Tavoni, Cory D. Champagne, Dorian S Houser, Daniel E CrockerAbstract:Elephant seals maintain rates of endogenous glucose production (EGP) typical of post-absorptive mammals despite enduring prolonged periods of food deprivation concurrent with low rates of glucose oxidation. These high rates of EGP suggest extensive glucose recycling during fasting. We investigated lactate metabolism in fasting elephant seals to assess its role in glucose recycling. Whole-animal glucose and lactate fluxes were measured as the rates of appearance of glucose and lactate ( Ra _gluc and Ra _lac, respectively) using a primed constant infusion of [U-^14C] lactate and [6-^3H] glucose, and we calculated the minimum contribution of lactate to gluconeogenesis ( GNG _lac). Ra _lac was high compared to resting values in other species (3.21 ± 0.71 mmol min^−1* kg^−1), did not change between 14 ± 1 and 31 ± 8 days of fasting and varied directly with Ra _glu. The minimum GNG _lac was 44.6 ± 6.0 % of EGP, varied directly with plasma lactate levels, and did not change over the fast. Ra _ lac and Ra _ glu both varied directly with plasma insulin concentrations. These data suggest that lactate is the predominant gluconeogenic precursor in fasting elephant seals and that high rates of glucose recycling through Cori cycle activity contribute to the maintenance of EGP during fasting. High levels of Cori cycle activity and EGP may be important components of metabolic adaptations that maintain glucose production while avoiding ketosis during extended fasting or are related to sustained metabolic alterations associated with extended breath-holds in elephant seals.
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Assessment of gestation, lactation and fasting on stable isotope ratios in northern elephant seals (Mirounga angustirostris)
Marine Mammal Science, 2010Co-Authors: Sarah Habran, Dorian S Houser, Daniel E Crocker, Cathy Debier, Gilles Lepoint, Jean-marie BouquegneauAbstract:Effects of physiological processes such as gestation, lactation and nutritional stress on stable isotope ratios remain poorly understood. To determine their impact, we investigated these processes in simultaneously fasting and lactating northern elephant seals (Mirounga angustirostris). Stable carbon and nitrogen isotope values were measured in blood and milk of 10 mother-pup pairs on days 5 and 22 of lactation. As long- and short-term integrators of diet, blood cells and serum may reflect foraging data or energy reserves from late gestation and lactation, respectively. Limited changes in isotopic signatures of maternal blood over the lactating period were highlighted. Nitrogen isotope fractionation associated with mother-to-offspring
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Hormonal regulation of glucose clearance in lactating northern elephant seals (Mirounga angustirostris).
The Journal of Experimental Biology, 2008Co-Authors: Melinda A. Fowler, Cory D. Champagne, Dorian S Houser, Daniel E CrockerAbstract:SUMMARY Northern elephant seals exhibit the rare strategy of fasting and lactating concomitantly. We investigated hormonal regulation of glucose clearance in northern elephant seals using glucose tolerance tests (GTT) performed early in lactation and again just prior to weaning. For comparison, identical measurements were made on separate females late in the molt fast. Serial blood samples were used to assess glucose clearance and hormone responses for 3 h post glucose injection. Plasma glucose remained elevated at the end of the sampling period in all groups. Glucose clearance rates were not significantly different among test groups. A significant insulin response was observed in early lactation, no significant response was observed late in lactation and an intermediate response was observed late in the molt fast. The insulin response to a glucose load decreased with adipose tissue proportions. Plasma glucagon decreased significantly following GTT in early and late lactation, although the magnitude of the depression was small in comparison to other species. Hypoinsulemia may be critical to facilitate net lipolysis late in lactation. Consistently low glucose clearance among test groups suggests insulin insensitivity within peripheral tissues. Glucagon suppression independent of insulin release suggests modification of the typical insulin–glucagon counter-regulation. These findings suggest that metabolic features of diabetic-like conditions may be adaptive in the context of long-term fasting.
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click evoked potentials in a large marine mammal the adult male northern elephant seal Mirounga angustirostris
Journal of the Acoustical Society of America, 2008Co-Authors: Dorian S Houser, Daniel E Crocker, James J FinneranAbstract:Auditory evoked potential (AEP) hearing studies in marine mammals should consider an expected size-dependent reduction in AEP amplitude. This study is the first to measure the click-evoked response in a large marine mammal, the adult male elephant seal (Mirounga angustirostris). Click stimuli were presented at peak-peak equivalent sound pressure levels of 117–118dB re: 20μPa. Three positive peaks (P1–P3) and two negative peaks (N4 and N5) were observed in the AEP. Response latencies were longer than previously observed in a 1.8yr old seal and the maximum peak-peak amplitude was comparatively reduced by more than 60%. The inverse relationship between size and AEP amplitude will likely require increased averaging with larger subjects and possibly modifications to electrode placement and design in order to increase the quality of recorded evoked responses.
Dawn P. Noren - One of the best experts on this subject based on the ideXlab platform.
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estradiol and testosterone concentrations increase with fasting in weaned pups of the northern elephant seal Mirounga angustirostris
Physiological and Biochemical Zoology, 2005Co-Authors: R A Shermancooney, L Pagarigan, Dawn P. Noren, Rudy M. Ortiz, C. L. Ortiz, Frank TalamantesAbstract:ABSTRACT Although neonatal development is generally associated with increased levels of circulating testosterone (T) and estradiol (E2), food deprivation may inhibit steroidogenesis. Therefore, these potentially conflicting stimuli were examined in fasting weaned northern elephant seal (Mirounga angustirostris) pups by measuring serum concentrations of T, E2, progesterone (P4), and luteinizing hormone (LH) by either radioimmunoassay (P4, LH) or enzymeimmunoassay (T, E2). Blood samples were obtained from 20 male and 20 female pups at both early (<1 wk postweaning) and late (6–8 wk postweaning) periods during their natural postweaning fast. T in males (early: \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage[OT2,OT1]{fontenc} \newcommand\cyr{ \renewcommand\rmdefault{wncyr} \renewcommand\sfdefault{wncyss...
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thermoregulation of weaned northern elephant seal Mirounga angustirostris pups in air and water
Physiological and Biochemical Zoology, 2002Co-Authors: Dawn P. NorenAbstract:Abstract Fasting weaned northern elephant seal pups (Mirounga angustirostris) experience diverse environmental conditions on land and in water on a daily basis. Each environment undoubtedly induces distinct energetic costs that may vary for pups of differing body condition. To determine the energetic costs associated with different environmental conditions and whether costs vary between individuals, body mass, surface area, volume, body composition, resting metabolic rate, and core body temperature were determined for 17 weaned northern elephant seal pups from Ano Nuevo, California. Metabolic rate and body temperature were measured for pups resting in air ( \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage[OT2,OT1]{fontenc} \newcommand\cyr{ \renewcommand\rmdefault{wncyr} \renewcommand\sfdefault{wncyss...
