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Arctic Ground Squirrels Limit Bone Loss during the Prolonged Physical Inactivity Associated with Hibernation.

https://arctichealth.org/en/permalink/ahliterature271927
Source
Physiol Biochem Zool. 2016 Jan-Feb;89(1):72-80
Publication Type
Article
Author
Samantha J Wojda
Richard A Gridley
Meghan E McGee-Lawrence
Thomas D Drummer
Ann Hess
Franziska Kohl
Brian M Barnes
Seth W Donahue
Source
Physiol Biochem Zool. 2016 Jan-Feb;89(1):72-80
Language
English
Publication Type
Article
Abstract
Prolonged disuse (e.g., physical inactivity) typically results in increased bone porosity, decreased mineral density, and decreased bone strength, leading to increased fracture risk in many mammals. However, bears, marmots, and two species of ground squirrels have been shown to preserve macrostructural bone properties and bone strength during long seasons of hibernation while they remain mostly inactive. Some small hibernators (e.g., 13-lined ground squirrels) show microstructural bone loss (i.e., osteocytic osteolysis) during hibernation, which is not seen in larger hibernators (e.g., bears and marmots). Arctic ground squirrels (Urocitellus parryii) are intermediate in size between 13-lined ground squirrels and marmots and are perhaps the most extreme rodent hibernator, hibernating for up to 8 mo annually with body temperatures below freezing. The goal of this study was to quantify the effects of hibernation and inactivity on cortical and trabecular bone properties in arctic ground squirrels. Cortical bone geometrical properties (i.e., thickness, cross-sectional area, and moment of inertia) at the midshaft of the femur were not different in animals sampled over the hibernation and active seasons. Femoral ultimate stress tended to be lower in hibernators than in summer animals, but toughness was not affected by hibernation. The area of osteocyte lacunae was not different between active and hibernating animals. There was an increase in osteocytic lacunar porosity in the hibernation group due to increased lacunar density. Trabecular bone volume fraction in the proximal tibia was unexpectedly greater in the hibernation group than in the active group. This study shows that, similar to other hibernators, arctic ground squirrels are able to preserve many bone properties during hibernation despite being physically inactive for up to 8 mo.
PubMed ID
27082526 View in PubMed
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Clock Gene Expression in the Suprachiasmatic Nucleus of Hibernating Arctic Ground Squirrels.

https://arctichealth.org/en/permalink/ahliterature290083
Source
J Biol Rhythms. 2017 06; 32(3):246-256
Publication Type
Journal Article
Research Support, U.S. Gov't, Non-P.H.S.
Date
06-2017
Author
Tomoko Ikeno
Cory T Williams
C Loren Buck
Brian M Barnes
Lily Yan
Author Affiliation
Department of Psychology, Michigan State University, East Lansing, Michigan.
Source
J Biol Rhythms. 2017 06; 32(3):246-256
Date
06-2017
Language
English
Publication Type
Journal Article
Research Support, U.S. Gov't, Non-P.H.S.
Keywords
ARNTL Transcription Factors - genetics
Animals
Arctic Regions
Body temperature
Circadian Clocks - genetics
Circadian Rhythm - physiology
Hibernation - genetics
Light
Period Circadian Proteins - genetics
Photoperiod
Proto-Oncogene Proteins c-fos - genetics
Sciuridae - genetics - physiology
Seasons
Suprachiasmatic Nucleus - physiology
Abstract
Most organisms have a circadian system, entrained to daily light-dark cycles, that regulates 24-h rhythms of physiology and behavior. It is unclear, however, how circadian systems function in animals that exhibit seasonal metabolic suppression, particularly when this coincides with the long-term absence of a day-night cycle. The arctic ground squirrel, Urocytellus parryii, is a medium-sized, semi-fossorial rodent that appears above-ground daily during its short active season in spring and summer before re-entering a constantly dark burrow for 6 to 9 months of hibernation. This hibernation consists of multiple week-long torpor bouts interrupted by short (
PubMed ID
28452286 View in PubMed
Less detail

Clock Gene Expression in the Suprachiasmatic Nucleus of Hibernating Arctic Ground Squirrels.

https://arctichealth.org/en/permalink/ahliterature282215
Source
J Biol Rhythms. 2017 Apr 01;:748730417702246
Publication Type
Article
Date
Apr-01-2017
Author
Tomoko Ikeno
Cory T Williams
C Loren Buck
Brian M Barnes
Lily Yan
Source
J Biol Rhythms. 2017 Apr 01;:748730417702246
Date
Apr-01-2017
Language
English
Publication Type
Article
Abstract
Most organisms have a circadian system, entrained to daily light-dark cycles, that regulates 24-h rhythms of physiology and behavior. It is unclear, however, how circadian systems function in animals that exhibit seasonal metabolic suppression, particularly when this coincides with the long-term absence of a day-night cycle. The arctic ground squirrel, Urocytellus parryii, is a medium-sized, semi-fossorial rodent that appears above-ground daily during its short active season in spring and summer before re-entering a constantly dark burrow for 6 to 9 months of hibernation. This hibernation consists of multiple week-long torpor bouts interrupted by short (
PubMed ID
28452286 View in PubMed
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Comparative functional genomics of adaptation to muscular disuse in hibernating mammals.

https://arctichealth.org/en/permalink/ahliterature257282
Source
Mol Ecol. 2014 Oct 14;
Publication Type
Article
Date
Oct-14-2014
Author
Vadim B Fedorov
Anna V Goropashnaya
Nathan C Stewart
Oivind Tøien
Celia Chang
Haifang Wang
Jun Yan
Louise C Showe
Michael K Showe
Brian M Barnes
Author Affiliation
Institute of Arctic Biology, University of Alaska Fairbanks, Fairbanks, AK, 99775, USA.
Source
Mol Ecol. 2014 Oct 14;
Date
Oct-14-2014
Language
English
Publication Type
Article
Abstract
Hibernation is an energy saving adaptation that involves a profound suppression of physical activity that can continue for 6-8 months in highly seasonal environments. While immobility and disuse generate muscle loss in most mammalian species, in contrast, hibernating bears and ground squirrels demonstrate limited muscle atrophy over the prolonged periods of physical inactivity during winter suggesting that hibernating mammals have adaptive mechanisms to prevent disuse muscle atrophy. To identify common transcriptional programs that underlie molecular mechanisms preventing muscle loss, we conducted a large-scale gene expression screen in hind limb muscles comparing hibernating and summer active black bears and arctic ground squirrels using custom 9,600 probe cDNA microarrays. A molecular pathway analysis showed an elevated proportion of over-expressed genes involved in all stages of protein biosynthesis and ribosome biogenesis in muscle of both species during torpor of hibernation that suggests induction of translation at different hibernation states. The induction of protein biosynthesis likely contributes to attenuation of disuse muscle atrophy through the prolonged periods of immobility of hibernation. The lack of directional changes in genes of protein catabolic pathways does not support the importance of metabolic suppression for preserving muscle mass during winter. Coordinated reduction of multiple genes involved in oxidation reduction and glucose metabolism detected in both species is consistent with metabolic suppression and lower energy demand in skeletal muscle during inactivity of hibernation. This article is protected by copyright. All rights reserved.
PubMed ID
25314618 View in PubMed
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Coping with differences in snow cover: the impact on the condition, physiology and fitness of an arctic hibernator.

https://arctichealth.org/en/permalink/ahliterature287444
Source
Conserv Physiol. 2017;5(1):cox065
Publication Type
Article
Date
2017
Author
Michael J Sheriff
Rudy Boonstra
Rupert Palme
C Loren Buck
Brian M Barnes
Source
Conserv Physiol. 2017;5(1):cox065
Date
2017
Language
English
Publication Type
Article
Abstract
The Earth's climate is changing at an unprecedented rate and, as ecologists, we are challenged with the difficult task of predicting how individuals and populations will respond to climate-induced changes to local and global ecosystems. Although we are beginning to understand some of the responses to changing seasonality, the physiological mechanisms that may drive these responses remain unknown. Using long-term data comparing two nearby populations (
Notes
Cites: Science. 2000 Sep 22;289(5487):2068-7411000103
Cites: Integr Comp Biol. 2013 Dec;53(6):960-423933811
Cites: Ann N Y Acad Sci. 2005 Apr;1040:162-7115891021
Cites: Vet Res Commun. 2002 Feb;26(2):127-3911922482
Cites: Nature. 2003 Jan 2;421(6918):37-4212511946
Cites: Science. 1989 Jun 30;244(4912):1593-52740905
Cites: Trends Ecol Evol. 2006 Jan;21(1):38-4616701468
Cites: Gen Comp Endocrinol. 2010 May 1;166(3):614-920051245
Cites: Philos Trans R Soc Lond B Biol Sci. 2017 Jun 19;372(1723):28483870
Cites: Am Nat. 2017 Dec;190(6):854-85929166160
Cites: Proc Biol Sci. 2011 Mar 22;278(1707):835-4220861045
Cites: Physiol Biochem Zool. 2017 May/Jun;90(3):370-38228384423
Cites: Nature. 2010 Jul 22;466(7305):482-520651690
Cites: Proc Biol Sci. 2011 Aug 7;278(1716):2369-7521177687
Cites: Trends Mol Med. 2007 Jul;13(7):269-7717544850
Cites: Proc Natl Acad Sci U S A. 2000 Feb 15;97(4):1630-310677510
Cites: Philos Trans R Soc Lond B Biol Sci. 2013 Jul 08;368(1624):2012048023836786
Cites: Nature. 2012 Sep 27;489(7417):554-722878721
Cites: J Anim Ecol. 2009 Nov;78(6):1249-5819426257
Cites: Conserv Physiol. 2014 Jun 27;2(1):cou02327293644
Cites: Gen Comp Endocrinol. 2007 Feb;150(3):430-617161400
Cites: Nature. 2006 May 4;441(7089):81-316672969
Cites: Integr Comp Biol. 2017 Sep 1;57(3):437-44928957523
Cites: Endocr Rev. 2000 Feb;21(1):55-8910696570
Cites: Trends Ecol Evol. 2004 May;19(5):249-5516701264
Cites: Trends Ecol Evol. 2009 Nov;24(11):634-4219679371
Cites: Gen Comp Endocrinol. 2008 Jul;157(3):288-9518602555
Cites: Gen Comp Endocrinol. 2008 Jul;157(3):207-1618558405
Cites: Proc Biol Sci. 2010 Apr 22;277(1685):1259-6620018784
Cites: Philos Trans R Soc Lond B Biol Sci. 2012 Jun 19;367(1596):1647-6422566673
Cites: Gen Comp Endocrinol. 2016 Oct 1;237:10-1827449342
Cites: Integr Comp Biol. 2004 Apr;44(2):95-10821680490
Cites: Oecologia. 2011 Aug;166(4):869-8721344254
Cites: Horm Behav. 2005 Jun;48(1):44-5215919384
Cites: Gen Comp Endocrinol. 2000 Apr;118(1):113-2210753573
Cites: Philos Trans R Soc Lond B Biol Sci. 2008 Jul 12;363(1501):2369-7518006410
Cites: Science. 2008 Oct 31;322(5902):690-218974339
PubMed ID
29218224 View in PubMed
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Cryoprotectant Production in Freeze-Tolerant Wood Frogs Is Augmented by Multiple Freeze-Thaw Cycles.

https://arctichealth.org/en/permalink/ahliterature280828
Source
Physiol Biochem Zool. 2016 Jul-Aug;89(4):340-6
Publication Type
Article
Author
Don J Larson
Brian M Barnes
Source
Physiol Biochem Zool. 2016 Jul-Aug;89(4):340-6
Language
English
Publication Type
Article
Keywords
Adaptation, physiological - physiology
Alaska
Animals
Cryoprotective Agents - metabolism
Freezing
Glucose - metabolism
Hibernation
Liver - metabolism
Male
Muscle, Skeletal - metabolism
Myocardium - metabolism
Ranidae - physiology
Seasons
Time Factors
Abstract
Ice nucleation across the skin of wood frogs (Lithobates sylvaticus) rapidly induces endogenous production of glucose, a cryoprotectant necessary for freeze tolerance. In laboratory studies of freeze tolerance, wood frogs are cooled slowly, often at -0.05°C h(-1), to facilitate high cryoprotectant production and survival. Under natural conditions in Alaska, however, wood frogs accumulate maximal tissue glucose concentrations while cooling at much faster rates, -0.35° to -1.6°C h(-1), and in addition undergo multiple successive freeze-thaw cycles before remaining frozen for the winter. We examined whether simulating these ecologically relevant cooling rates and repeated freeze-thaw events in captive wood frogs results in the high glucose concentrations found in naturally frozen wood frogs. We found that over successive freezing and thawing events, glucose concentrations increased stepwise in all measured tissues. Short thawing periods did not result in a statistically significant decline of glucose concentrations. Wood frogs that experienced three freeze-thaw events had fresh weight glucose concentrations that approached values found in tissues of wood frogs frozen in natural conditions. Laboratory wood frogs survive frozen for 2 mo, while wood frogs frozen under natural conditions survive frozen for up to 7 mo at temperatures below -18°C. We hypothesize that repeated freeze-thaw cycles with rapid cooling and warming rates allow for greater survival in Alaskan wood frogs through enhanced cryoprotectant production.
PubMed ID
27327184 View in PubMed
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Energy regulation in context: Free-living female arctic ground squirrels modulate the relationship between thyroid hormones and activity among life history stages.

https://arctichealth.org/en/permalink/ahliterature266574
Source
Horm Behav. 2015 Sep 28;75:111-119
Publication Type
Article
Date
Sep-28-2015
Author
Kathryn Wilsterman
C Loren Buck
Brian M Barnes
Cory T Williams
Source
Horm Behav. 2015 Sep 28;75:111-119
Date
Sep-28-2015
Language
English
Publication Type
Article
Abstract
Thyroid hormones (THs), key regulators of lipid and carbohydrate metabolism, are likely modulators of energy allocation within and among animal life history stages. Despite their role in modulating metabolism, few studies have investigated whether THs vary among life history stages in free-living animals or if they exhibit stage-specific relationships to total energy expenditure and activity levels. We measured plasma total triiodothyronine (tT3) and thyroxine (tT4) at four, discrete life history stages of female arctic ground squirrels from two different populations in northern Alaska to test whether plasma THs correlate with life history stage-specific changes in metabolic rate and energy demand. We also tested whether THs explained individual variation in aboveground activity levels within life history stages. T3 peaked during lactation and was lowest during pre-hibernation fattening, consistent with known changes in basal metabolism and core body temperature. In contrast, T4 was elevated shortly after terminating hibernation but remained low and stable across other life-history stages in the active season. THs were consistently higher in the population that spent more time above-ground but the relationship between THs and activity varied among life history stages. T3 was positively correlated with activity only during lactation (r(2)=0.50) whereas T4 was positively correlated with activity immediately following lactation (r(2)=0.48) and during fattening (r(2)=0.53). Our results support the hypothesis that THs are an important modulator of basal metabolism but also suggest that the relationship between THs and activity varies among life history stages.
PubMed ID
26416501 View in PubMed
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Entraining to the polar day: circadian rhythms in arctic ground squirrels.

https://arctichealth.org/en/permalink/ahliterature283389
Source
J Exp Biol. 2017 Jun 16;
Publication Type
Article
Date
Jun-16-2017
Author
Cory T Williams
Brian M Barnes
Lily Yan
C Loren Buck
Source
J Exp Biol. 2017 Jun 16;
Date
Jun-16-2017
Language
English
Publication Type
Article
Abstract
Circadian systems are principally entrained to 24h light/dark cycles, but this cue is seasonally absent in polar environments. Although some resident polar vertebrates have weak circadian clocks and are seasonally arrhythmic, the arctic ground squirrel (AGS) maintains daily rhythms of physiology and behavior throughout the summer, which includes six weeks of constant daylight. Here, we show that persistent daily rhythms in AGS are maintained through a circadian system that readily entrains to the polar day yet remains insensitive to entrainment by rapid light-dark transitions, which AGS generate naturally due to their semi-fossorial behavior. Additionally, AGS do not show 'jet lag', the slow realignment of circadian rhythms induced by the inertia of an intrinsically stable master circadian clock in the suprachiasmatic nucleus (SCN). We suggest this is due to the low expression of arginine vasopressin in the SCN of AGS, since vasopressin is associated with inter-neuronal coupling and robust rhythmicity.
PubMed ID
28623226 View in PubMed
Less detail

Entraining to the polar day: circadian rhythms in arctic ground squirrels.

https://arctichealth.org/en/permalink/ahliterature291310
Source
J Exp Biol. 2017 09 01; 220(Pt 17):3095-3102
Publication Type
Journal Article
Research Support, U.S. Gov't, Non-P.H.S.
Date
09-01-2017
Author
Cory T Williams
Brian M Barnes
Lily Yan
C Loren Buck
Author Affiliation
Department of Biological Sciences and Center for Bioengineering Innovation, Northern Arizona University, Flagstaff, AZ 86011, USA ctwilliams@alaska.edu.
Source
J Exp Biol. 2017 09 01; 220(Pt 17):3095-3102
Date
09-01-2017
Language
English
Publication Type
Journal Article
Research Support, U.S. Gov't, Non-P.H.S.
Keywords
Animals
Arctic Regions
Arginine Vasopressin - metabolism
Circadian Rhythm
Male
Photoperiod
Sciuridae - physiology
Abstract
Circadian systems are principally entrained to 24 h light-dark cycles, but this cue is seasonally absent in polar environments. Although some resident polar vertebrates have weak circadian clocks and are seasonally arrhythmic, the arctic ground squirrel (AGS) maintains daily rhythms of physiology and behavior throughout the summer, which includes 6 weeks of constant daylight. Here, we show that persistent daily rhythms in AGS are maintained through a circadian system that readily entrains to the polar day yet remains insensitive to entrainment by rapid light-dark transitions, which AGS generate naturally as a consequence of their semi-fossorial behavior. Additionally, AGS do not show 'jet lag', the slow realignment of circadian rhythms induced by the inertia of an intrinsically stable master circadian clock in the suprachiasmatic nucleus (SCN). We suggest this is due to the low expression of arginine vasopressin in the SCN of AGS, as vasopressin is associated with inter-neuronal coupling and robust rhythmicity.
PubMed ID
28623226 View in PubMed
Less detail

Genomic analysis of expressed sequence tags in American black bear Ursus americanus.

https://arctichealth.org/en/permalink/ahliterature97574
Source
BMC Genomics. 2010;11:201
Publication Type
Article
Date
2010
Author
Sen Zhao
Chunxuan Shao
Anna V Goropashnaya
Nathan C Stewart
Yichi Xu
Øivind Tøien
Brian M Barnes
Vadim B Fedorov
Jun Yan
Author Affiliation
CAS-MPG Partner Institute for Computational Biology, Shanghai Institutes of Biological Sciences, 320 Yue Yang Road, Shanghai, 200031, China.
Source
BMC Genomics. 2010;11:201
Date
2010
Language
English
Publication Type
Article
Keywords
Alaska
Alternative Splicing
Amino Acid Sequence
Animals
Evolution, Molecular
Expressed Sequence Tags
Gene Expression Profiling
Gene Expression Regulation
Genome - genetics
Humans
Models, Molecular
Molecular Sequence Data
Organ Specificity
Phylogeny
Protein Structure, Tertiary
Sequence Alignment
Ursidae - genetics
Abstract
BACKGROUND: Species of the bear family (Ursidae) are important organisms for research in molecular evolution, comparative physiology and conservation biology, but relatively little genetic sequence information is available for this group. Here we report the development and analyses of the first large scale Expressed Sequence Tag (EST) resource for the American black bear (Ursus americanus). RESULTS: Comprehensive analyses of molecular functions, alternative splicing, and tissue-specific expression of 38,757 black bear EST sequences were conducted using the dog genome as a reference. We identified 18 genes, involved in functions such as lipid catabolism, cell cycle, and vesicle-mediated transport, that are showing rapid evolution in the bear lineage Three genes, Phospholamban (PLN), cysteine glycine-rich protein 3 (CSRP3) and Troponin I type 3 (TNNI3), are related to heart contraction, and defects in these genes in humans lead to heart disease. Two genes, biphenyl hydrolase-like (BPHL) and CSRP3, contain positively selected sites in bear. Global analysis of evolution rates of hibernation-related genes in bear showed that they are largely conserved and slowly evolving genes, rather than novel and fast-evolving genes. CONCLUSION: We provide a genomic resource for an important mammalian organism and our study sheds new light on the possible functions and evolution of bear genes.
PubMed ID
20338065 View in PubMed
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27 records – page 1 of 3.