Metabolism of bears before, during, and after winter sleep

Nelson, R. A.; Hw, Wahner; Jd, Jones; Rd, Ellefson; Pe, Zollman

doi:10.1152/ajplegacy.1973.224.2.491

Cited by 211 publications

(130 citation statements)

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“…Most mammals, including the confamilial harbor seal, consistently demonstrate a postprandial hyperfiltration and a reduction in filtration associated with the cessa-Ž tion of food and water consumption Hiatt and Hiatt, 1942;Pullman et al, 1954;Brown et al, 1971;Nelson et al, 1973;Hladky and Rink, 1986;. Boim and Schor, 1992;Bosch, 1995 . In this study, the broad variability in GFR and mass-specific GFR, independent of food and water abstention or consumption, defines neither a postprandial hyperfiltration, nor a hypofiltration due to fasting or water abstention.…”

Section: Discussionmentioning

confidence: 99%

Renal function in suckling and fasting pups of the northern elephant seal

Houser

Crocker

Webb

et al. 2001

Comparative Biochemistry and Physiology Part A: Molecular &

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Elephant seals fast for prolonged periods without access to water. This is made possible, in part, by reductions in urine production. However, the mechanisms involved in reducing urine production are not understood. In this study, Ž . Ž . glomerular filtration rate GFR was measured in five northern elephant seal pups Mirounga angustirostris via the inulin clearance technique. Measurements were made during day 9 and day 18᎐22 of nursing and the second and eighth week of the postweaning fast. Plasma aldosterone and cortisol concentrations, quantified by radioimmunoassay, were measured in eight other weanlings during the second and eighth week of the fast. Mean GFR was 79.3" 29.3 mlrmin during the early suckling period and 78.2" 17.1, 89.8" 52.7, and 80.4" 12.2 mlrmin during the late suckling, early fasting and late fasting periods, respectively. Differences between nursing and fasting were insignificant, possibly because reduced protein oxidation during suckling and rapid recruitment of protein for tissue synthesis obviated the need for postprandial hyperfiltration. Alternatively, maintenance of GFR during fasting may facilitate urea concentration by compensating for reductions in the fractional excretion of urea. It is further hypothesized that aldosterone is primarily responsible for mediating renal water reabsorption in this system. ᮊ

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Section: Discussionmentioning

confidence: 99%

Renal function in suckling and fasting pups of the northern elephant seal

Houser

Crocker

Webb

et al. 2001

Comparative Biochemistry and Physiology Part A: Molecular &

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“…Unlike small hibernators such as ground squirrels (Ͻ1 kg) that enter deep levels of torpor with body temperatures near 0°C, hibernating black bears (30 -150 kg) remain aware and capable of moving throughout hibernation (25). Although bears neither eat, drink, defecate, nor urinate during a 3-6 mo hibernation season (28), their core body temperature decreases to only 30 -36°C (3). Metabolic rate in hibernating bears is reduced by 20 -50%, and it takes 2-3 wk after emergence and a return to normal body temperature for resting metabolic rate to recover to normal levels (40).…”

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confidence: 99%

Elevated expression of protein biosynthesis genes in liver and muscle of hibernating black bears (Ursus americanus)

Fedorov

Goropashnaya

Tøien

et al. 2009

Physiological Genomics

125

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We conducted a large-scale gene expression screen using the 3,200 cDNA probe microarray developed specifically for Ursus americanus to detect expression differences in liver and skeletal muscle that occur during winter hibernation compared with animals sampled during summer. The expression of 12 genes, including RNA binding protein motif 3 (Rbm3), that are mostly involved in protein biosynthesis, was induced during hibernation in both liver and muscle. The Gene Ontology and Gene Set Enrichment analysis consistently showed a highly significant enrichment of the protein biosynthesis category by overexpressed genes in both liver and skeletal muscle during hibernation. Coordinated induction in transcriptional level of genes involved in protein biosynthesis is a distinctive feature of the transcriptome in hibernating black bears. This finding implies induction of translation and suggests an adaptive mechanism that contributes to a unique ability to reduce muscle atrophy over prolonged periods of immobility during hibernation. Comparing expression profiles in bears to small mammalian hibernators shows a general trend during hibernation of transcriptional changes that include induction of genes involved in lipid metabolism and carbohydrate synthesis as well as depression of genes involved in the urea cycle and detoxification function in liver. gene expression; hibernation; translation; RNA binding protein motif 3 MAMMALIAN HIBERNATION IS a physiological and behavioral adaptation involving a coordinated suppression of heat production and body temperature wherein whole body metabolism and energy demand are significantly reduced over several days to several months. During hibernation, heart and respiration rates, blood flow, and oxygen consumption decrease dramatically to Ͻ10% of normal or basal rates (2, 4). These physiological changes do not represent a loss of homeostasis but instead are precisely controlled and spontaneously reversible, and they allow individual animals to survive highly seasonal or unpredictable environments where food availability becomes lacking (7, 12). The molecular and genetic basis of hibernation in small mammals has only recently begun to be described, and little is known about its evolutionary history. Hibernating species have been found in diverse families among seven orders of mammals (26), however, and the interspersed phylogenetic distribution of hibernating and nonhibernating species has led to the hypothesis that rather than requiring the creation of novel gene products, hibernation results from the differential expression of genes that exist widely among mammals (35).Microarray technology provides powerful means for the unbiased detection of differences in expression of thousands of genes in a single hybridization experiment (14). In contrast to single-gene expression analysis, the genome-wide approach also allows for identification of coordinated transcriptional changes in functional groups of regulatory genes within metabolic and signaling pathways. Recent studies of differential gen...

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“…Bears are believed to remain active prior to denning until a negative energy balance occurs (Schooley et al 1994). During hibernation, metabolic rates of bears are reduced substantially and they do not normally eat, drink, urinate or defecate (Folk et al 1972;Nelson et al 1973;Nelson and Beck 1984). Parturition and early maternal care occurs in dens, and lack of adequate den sites may result in litter loss or complete reproductive failure (Hamilton and Marchinton 1980;Alt 1984;Smith 1985;Weaver and Pelton 1994).…”

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Black Bear, <em>Ursus americanus</em>, Denning Chronology and Den Site Selection in the Northeastern Cascades of Washington

Gaines

2003

Can Field Nat

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I studied Black Bear denning chronology and den site selection during 1995-1998 in the northeastern Cascade Mountains of Washington. Male Black Bears entered dens between 22 October and 19 November and emerged between 4 April and 7 May. Females entered dens somewhat sooner, between 15 October and 19 November, and emerged later than males, 4 April and 22 May. These den entry and emergence dates were similar to those reported at similar lattitudes in northwestern Montana. Roads had an important influence on den site selection by Black Bears in this study area. Bears selected dens in areas with no open roads >200 ha in size, >500 m from the nearest open road, and 1500-2000 m in elevation. The combination of information on denning chronology and site characterstics should allow managers to coordinate human activities to reduce the potential for disturbance to denning Black Bears.

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Metabolism of bears before, during, and after winter sleep

Cited by 211 publications

References 0 publications

Renal function in suckling and fasting pups of the northern elephant seal

Renal function in suckling and fasting pups of the northern elephant seal

Elevated expression of protein biosynthesis genes in liver and muscle of hibernating black bears (Ursus americanus)

Black Bear, <em>Ursus americanus</em>, Denning Chronology and Den Site Selection in the Northeastern Cascades of Washington

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