| the primary structure of the hemoglobin alpha-chain of the arctic ground squirrel. | the amino acid sequence of the alpha-chain from the arctic ground squirrel citellus parryii) is reported. the tryptic peptides prepared from the hemoglobin were isolated by reverse phase hplc and sequenced. data from the tryptic peptides were supported by that from cyanogen bromide peptides and acid cleavage peptides which were partially sequenced. comparison with other rodent alpha-chains shows 15 differences with mouse, 20 with rat, 25 with muskrat, 16 with mole rat, 33 with the guinea-pig and ... | 1987 | 3608432 |
| transneuronal transport in the vestibular and auditory systems of the squirrel monkey and the arctic ground squirrel. i. vestibular system. | transneuronal transport of [3h]proline, [3h]fucose, and [3h]leucine in various combinations from pledgets implanted in the ampulla of a single semicircular duct was studied in the squirrel monkey and arctic ground squirrel after long survival periods. tritiated amino acids implanted in any single ampulla resulted in labeling of nearly all vestibular and auditory receptors, nearly all cells of the vestibular and spiral ganglia and central transport via nearly all root fibers of both nerves. prima ... | 1985 | 4075118 |
| transneuronal transport in the vestibular and auditory systems of the squirrel monkey and the arctic ground squirrel. ii. auditory system. | transneuronal transport in the auditory system of the squirrel monkey and the arctic ground squirrel was studied after implantation of tritiated protein or glycoprotein precursors into the ampulla of a single semicircular duct. in both species, essentially the same pattern of transneuronal transport extended beyond the cochlear nuclei to the central nucleus of the inferior colliculus (cnic), after survival periods ranging from 9 to 33 days. animals displayed dense labeling over nearly all audito ... | 1985 | 4075119 |
| experimental infections by brucella suis type 4 in alaskan rodents. | the susceptibility of nine species of rodents and one species of lagomorph to brucella suis type 4 was studied experimentally. the rodent species included: guinea pig (cavia porcellus), scandinavian lemming (lemmus lemmus), brown lemming (l. sibiricus), northern red-backed vole (clethrionomys rutilis), varying lemmings (dicrostonyx stevensoni and d. rubricatus), yellow-cheeked vole (microtus xanthognathus), flying squirrel (glaucomys sabrinus) and ground squirrel (citellus parryii). the lagomorp ... | 1980 | 7463596 |
| [the effect of different types of species-specific acoustic signals on the rate of mammalian cardiac contractions]. | experiments with rodents and even-toed ungulates show that significant changes in the heart rate (hr) in response to administration of species-specific sound stimuli occur only under conditions of deficiency of useful information. cardiac response depends mainly upon the type of the signal, ecology and physiology of the animal-recipient. in mammals living in colonies and herds in the open (ground squirrels, reindeer) hr changes become conspicuous only under conditions excluding acquirement of vi ... | 1995 | 7597827 |
| a new hepadnavirus endemic in arctic ground squirrels in alaska. | we present evidence for a novel member of the hepadnavirus family that is endemic in wild arctic ground squirrels (spermophylus parryi kennicotti) in alaska. this virus, designated arctic squirrel hepatitis virus (ashv), was initially detected in the livers of animals bearing large hepatic nodules by nucleic acid hybridization with hepadnavirus probes and in plasma by cross-reactivity with antibodies to hepadnavirus surface and core antigens. the complete nucleotide sequence of the 3,302-bp-long ... | 1996 | 8676441 |
| evaluation of the safety of two attenuated oral rabies vaccines, sag1 and sag2, in six arctic mammals. | the safety of two attenuated oral rabies vaccines was evaluated in mink and in five species of rodents which occur in the arctic. a 0.03 ml sample of liquid vaccine was installed directly into the mouth of voles and lemmings and 0.1 ml into the mouth of arctic ground squirrels and mink. animals were euthanized at 36 and 46 days postexposure; brain tissue was analyzed by fat and serum by rffit. no rabies deaths occurred in 47 animals tested. four animals representing three rodent species seroconv ... | 1996 | 8744551 |
| leptin inhibits prehibernation hyperphagia and reduces body weight in arctic ground squirrels. | the ob gene product leptin is thought to play a physiological role in the fine tuning of a homeostatic mechanism regulating satiety and adiposity. mouse recombinant leptin was administered to seasonally hyperphagic arctic ground squirrels as a first step in demonstrating the evolutionary conservation of leptin function and the potential involvement of leptin in the seasonal regulation of adiposity in hibernators. continuous infusion of leptin for 3 wk via miniosmotic pumps resulted in a reductio ... | 1996 | 8997382 |
| leptin prevents posthibernation weight gain but does not reduce energy expenditure in arctic ground squirrels. | in mammals, leptin reduces energy intake and may increase energy expenditure as a means to maintain body weight and/or adiposity at an appropriate level. hibernating mammals seasonally alter body mass, food intake, and body composition and, therefore, represent an attractive model for investigating the physiological regulation of changing body mass and adiposity. previous experiments in our laboratory demonstrated that administration of mouse recombinant leptin reduces food intake and body weigh ... | 1997 | 9467893 |
| microbial origin of glutamate, hibernation and tissue trauma: an in vivo microdialysis study. | using quantitative microdialysis in hibernating arctic ground squirrels (ags), striatal glutamate concentrations ([glu](dia)) progressively increased to approximately 200 microm after 3 days of microdialysis in euthermic but not hibernating ground squirrels. initially, the progressive increase in [glu](dia) was thought to be related to greater tissue response in euthermic animals. alternatively, given the vastly different body temperatures between the two groups (37 vs. 3 degrees c), glutamate m ... | 2002 | 12323415 |
| the effect of temperature on myocardial adenine nucleotide levels and the activity of various oxidases in rabbits and arctic ground squirrels. | | 1959 | 14399550 |
| absence of cellular stress in brain after hypoxia induced by arousal from hibernation in arctic ground squirrels. | although hypoxia tolerance in heterothermic mammals is well established, it is unclear whether the adaptive significance stems from hypoxia or other cellular challenge associated with euthermy, hibernation, or arousal. in the present study, blood gases, hemoglobin o2 saturation (s(o2), and indexes of cellular and physiological stress were measured during hibernation and euthermy and after arousal thermogenesis. results show that arterial o2 tension (pa(o2)) and s(o2) are severely diminished duri ... | 2005 | 15976308 |
| spatial and temporal trends of contaminants in terrestrial biota from the canadian arctic. | contaminants in the canadian arctic have been studied over the last twelve years under the guidance of the northern contaminants program. this paper summarizes results from that program from 1998 to 2003 with respect to terrestrial animals in the canadian arctic. the arctic terrestrial environment has few significant contaminant issues, particularly when compared with freshwater and marine environments. both current and historical industrial activities in the north may have a continuing effect o ... | 2005 | 16109438 |
| persistent tolerance to oxygen and nutrient deprivation and n-methyl-d-aspartate in cultured hippocampal slices from hibernating arctic ground squirrel. | hibernating arctic ground squirrel (hags), spermophilus parryii, survive profound decreases in cerebral perfusion during torpor and return to normal blood flow during intermittent rewarming periods without neurologic damage. hibernating ags tolerate traumatic brain injury in vivo, and acute hippocampal slices from hibernating animals tolerate oxygen and glucose deprivation. it remains unclear, however, if neuroprotection results from intrinsic tissue properties or from differences in response to ... | 2006 | 16395285 |
| detection of differential gene expression in brown adipose tissue of hibernating arctic ground squirrels with mouse microarrays. | hibernation is an energy-saving strategy adopted by a wide range of mammals to survive highly seasonal or unpredictable environments. arctic ground squirrels living in alaska provide an extreme example, with 6- to 9-mo-long hibernation seasons when body temperature alternates between levels near 0 degrees c during torpor and 37 degrees c during arousal episodes. heat production during hibernation is provided, in part, by nonshivering thermogenesis that occurs in large deposits of brown adipose t ... | 2006 | 16464973 |
| the arctic ground squirrel brain is resistant to injury from cardiac arrest during euthermia. | hetereothermic mammals tolerate hypoxia during euthermy and torpor, and evidence suggests this tolerance may extend beyond hypoxia to cerebral ischemia. during hibernation, ca1 hippocampal neurons endure extreme fluctuations in cerebral blood flow during transitions into and out of torpor as well as reductions in cerebral blood flow during torpor. in vitro studies likewise show evidence of ischemia tolerance in hippocampal slices harvested from euthermic ground squirrels; however, no studies hav ... | 2006 | 16574920 |
| decreased nr1 phosphorylation and decreased nmdar function in hibernating arctic ground squirrels. | heterothermic mammals such as ground squirrels tolerate ischemia and n-methyl-d-aspartate (nmda) better than homeothermic mammals such as rats both in vivo and in vitro, and this tolerance is enhanced in the hibernating state. however, the cellular mechanisms underlying this tolerance remain unclear. nmda receptors (nmdar) play a key role in excitotoxicity. the purpose of the current study was therefore to test the hypothesis that nmdar are down-regulated in hibernating arctic ground squirrels ( ... | 2006 | 16676330 |
| phf-like tau phosphorylation in mammalian hibernation is not associated with p25-formation. | in alzheimer's disease and related disorders, hyperphosphorylation of tau is associated with an increased activity of cyclin dependent kinase 5 (cdk5). elevated cdk5 activity is thought to be due to the formation of p25 and thereby represents a critical element in the dysregulation of tau phosphorylation under pathological conditions. however, there is still a controversy regarding the correlation of p25 generation and tau pathology. recently, we demonstrated physiological, paired helical filame ... | 2009 | 19184336 |
| protein kinase c epsilon activation delays neuronal depolarization during cardiac arrest in the euthermic arctic ground squirrel. | during the pre-hibernation season, arctic ground squirrels (ags) can tolerate 8 min of asphyxial cardiac arrest (ca) without detectable brain pathology. better understanding of the mechanisms regulating innate ischemia tolerance in ags has the potential to facilitate the development of novel prophylactic agents to induce ischemic tolerance in patients at risk of stroke or ca. we hypothesized that neuroprotection in ags involves robust maintenance of ion homeostasis similar to anoxia-tolerant tur ... | 2009 | 19493168 |
| adaptive response of brain tissue oxygenation to environmental hypoxia in non-sedated, non-anesthetized arctic ground squirrels. | the present study examined the physiological mechanisms of the responses of brain tissue oxygen partial pressure (p(t)o(2)), brain temperature (t(brain)), global oxygen consumption (v(o2)), and respiratory frequency (f(r)) to hypoxia in non-sedated and non-anesthetized arctic ground squirrels (spermophilus parryii, ags) and rats. we found that (1) in contrast to oxygen partial pressure in blood (p(a)o(2)), the baseline value of p(t)o(2) in summer euthermic ags is significantly higher than in rat ... | 2009 | 19559806 |
| the physiological link between metabolic rate depression and tau phosphorylation in mammalian hibernation. | abnormal phosphorylation and aggregation of tau protein are hallmarks of a variety of neurological disorders, including alzheimer's disease (ad). increased tau phosphorylation is assumed to represent an early event in pathogenesis and a pivotal aspect for aggregation and formation of neurofibrillary tangles. however, the regulation of tau phosphorylation in vivo and the causes for its increased stage of phosphorylation in ad are still not well understood, a fact that is primarily based on the la ... | 2011 | 21267079 |
| daily body temperature rhythms persist under the midnight sun but are absent during hibernation in free-living arctic ground squirrels. | in indigenous arctic reindeer and ptarmigan, circadian rhythms are not expressed during the constant light of summer or constant dark of winter, and it has been hypothesized that a seasonal absence of circadian rhythms is common to all vertebrate residents of polar regions. here, we show that, while free-living arctic ground squirrels do not express circadian rhythms during the heterothermic and pre-emergent euthermic intervals of hibernation, they display entrained daily rhythms of body tempera ... | 2011 | 21752811 |
| resistance of california ground squirrels (spermophilus beecheyi) to the venom of the northern pacific rattlesnake (crotalus viridis oreganus): a study of adaptive variation. | recent studies have documented natural resistance to snake venom in a number of diverse mammalian species. the present paper documents for the first time variation in such resistance within one single species, the california ground squirrel (spermophilus beecheyi). this species is a frequent prey of the northern pacific rattlesnake (crotalus viridis oreganus) in certain habitats. venom resistance was tested directly in two populations of ground squirrels by injection of 1-40 mg/kg venom doses. o ... | 2012 | 3672545 |
| patterns of hibernation in the arctic ground squirrel. | | 1989 | 1203818 |
| freeze avoidance in a mammal: body temperatures below 0 degree c in an arctic hibernator. | hibernating arctic ground squirrels, spermophilus parryii, were able to adopt and spontaneously arouse from core body temperatures as low as -2.9 degrees c without freezing. abdominal body temperatures of ground squirrels hibernating in outdoor burrows were recorded with temperature-sensitive radiotransmitter implants. body temperatures and soil temperatures at hibernaculum depth reached average minima during february of -1.9 degrees and -6 degrees c, respectively. laboratory-housed ground squir ... | 2009 | 2740905 |
| no oxygen? no problem! intrinsic brain tolerance to hypoxia in vertebrates. | many vertebrates are challenged by either chronic or acute episodes of low oxygen availability in their natural environments. brain function is especially vulnerable to the effects of hypoxia and can be irreversibly impaired by even brief periods of low oxygen supply. this review describes recent research on physiological mechanisms that have evolved in certain vertebrate species to cope with brain hypoxia. four model systems are considered: freshwater turtles that can survive for months trapped ... | 0 | 24671961 |
| thermogenic capacity at subzero temperatures: how low can a hibernator go? | abstract hibernation in mammals is a physiological and behavioral adaptation to survive intervals of low resource availability through profound decreases in metabolic rate (mr), core body temperature (tb), and activity. most small mammalian hibernators thermoconform, with tb approximating ambient temperature (ta); arctic species are an exception, since they must actively defend what can be large thermal gradients between tb and ta. here we compare the thermogenic capacity of the arctic ground sq ... | 2015 | 25590595 |
| tissue hypoxia during ischemic stroke: adaptive clues from hypoxia-tolerant animal models. | the treatment and prevention of hypoxic/ischemic brain injury in stroke patients remain a severe and global medical issue. numerous clinical studies have resulted in a failure to develop chemical neuroprotection for acute, ischemic stroke. over 150 estimated clinical trials of ischemic stroke treatments have been done, and more than 200 drugs and combinations of drugs for ischemic and hemorrhagic strokes have been developed. billions of dollars have been invested for new scientific breakthroughs ... | 2015 | 25738761 |
| eimeria yukonensis n. sp. (protozoa: eimeriidae) from the arctic ground squirrel spermophilus undulatus. | | 1969 | 5817318 |
| eimeria species (apicomplexa: eimeriidae) from arctic ground squirrels (spermophilus parryii) and red squirrels (tamiasciurus hudsonicus) in alaska and in siberia, russia. | fecal samples from arctic ground squirrels (spermophilus parryii) collected in alaska (n = 90) and russia (n = 46) and from red squirrels (tamiasciurus hudsonicus) in alaska (n = 35) were examined for the presence of eimeria spp. (apicomplexa: eimeriidae). four species were recovered from arctic ground squirrels, including eimeria callospermophili (prevalence = 18%), eimeria cynomysis (23.5%), eimeria lateralis (19%), and eimeria morainensis (77%). a single species, eimeria tamiasciuri (91%), wa ... | 2005 | 17089755 |
| effects of season and host physiological state on the diversity, density, and activity of the arctic ground squirrel cecal microbiota. | we examined the seasonal changes of the cecal microbiota of captive arctic ground squirrels (urocitellus parryii) by measuring microbial diversity and composition, total bacterial density and viability, and short-chain fatty acid concentrations at four sample periods (summer, torpor, interbout arousal, and posthibernation). abundance of firmicutes was lower, whereas abundances of bacteroidetes, verrucomicrobia, and proteobacteria were higher during torpor and interbout arousal than in summer. ba ... | 2014 | 25002417 |
| comparative phylogeography highlights the double-edged sword of climate change faced by arctic- and alpine-adapted mammals. | recent studies suggest that alpine and arctic organisms may have distinctly different phylogeographic histories from temperate or tropical taxa, with recent range contraction into interglacial refugia as opposed to post-glacial expansion out of refugia. we use a combination of phylogeographic inference, demographic reconstructions, and hierarchical approximate bayesian computation to test for phylodemographic concordance among five species of alpine-adapted small mammals in eastern beringia. the ... | 2015 | 25734275 |
| lipid emulsion enhances cardiac performance after ischemia-reperfusion in isolated hearts from summer-active arctic ground squirrels. | hibernating mammals, like the arctic ground squirrel (ags), exhibit robust resistance to myocardial ischemia/reperfusion (ir) injury. regulated preference for lipid over glucose to fuel metabolism may play an important role. we tested whether providing lipid in an emulsion protects hearts from summer-active ags better than hearts from brown norway (bn) rats against normothermic ir injury. langendorff-prepared ags and bn rat hearts were perfused with krebs solution containing 7.5 mm glucose with ... | 2017 | 28364393 |
| preparing for winter: divergence in the summer-autumn hematological profiles from representative species of the squirrel family. | we examined hematological parameters in four related sciurid species in the late summer-autumn to assess the role of habitat, elevation, body size, and behavior in shaping these parameters. red squirrels (tamiasciurus hudsonicus) and arctic ground squirrels (spermophilus parryii) were sampled in southwestern yukon, yellow-pine chipmunks (tamias amoenus) in southern alberta, and the eastern grey squirrel (sciurus carolinensis) in southern ontario. we obtained whole blood samples from each species ... | 2005 | 16111907 |
| managing anabolic steroids in pre-hibernating arctic ground squirrels: obtaining their benefits and avoiding their costs. | androgens have benefits, such as promoting muscle growth, but also significant costs, including suppression of immune function. in many species, these trade-offs in androgen action are reflected in regulated androgen production, which is typically highest only in reproductive males. however, all non-reproductive arctic ground squirrels, irrespective of age and sex, have high levels of androgens prior to hibernating at sub-zero temperatures. androgens appear to be required to make muscle in summe ... | 2014 | 25376801 |
| evolutionary relationships among colonies of columbian ground squirrels as shown by mitochondrial dna. | mitochondrial dna (mtdna) from 71 columbian ground squirrels (spermophilus columbianus) collected in 12 locations in western canada were assayed for restriction-site variation with 10 endonucleases. five of these endonucleases revealed variant patterns, and the composite genotypes were used to develop a linear transformation series among the mtdna genotypes. two of the four clones had a wide distribution, while the remaining two clones were geographically restricted. the mtdna of columbian groun ... | 1987 | 28564362 |
| coping with differences in snow cover: the impact on the condition, physiology and fitness of an arctic hibernator. | 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 (<20 km apart) of free-living arctic ground sq ... | 2017 | 29218224 |
| the impact of rewilding, species introductions and climate change on the structure and function of the yukon boreal forest ecosystem. | community and ecosystem changes are happening in the pristine boreal forest ecosystem of the yukon for two reasons. first, climate change is affecting the abiotic environment (temperature, rainfall, growing season) and driving changes in plant productivity and predator-prey interactions. secondly, simultaneously change is occurring because of mammal species reintroductions and rewilding. the key ecological question is the impact these faunal changes will have on trophic dynamics. primary product ... | 2017 | 29168615 |
| sex-dependent phenological plasticity in an arctic hibernator. | hibernation provides a means of escaping the metabolic challenges associated with seasonality, yet the ability of mammals to prolong or reenter seasonal dormancy in response to extreme weather events is unclear. here, we show that arctic ground squirrels in northern alaska exhibited sex-dependent plasticity in the physiology and phenology of hibernation in response to a series of late spring snowstorms in 2013 that resulted in the latest snowmelt on record. females and nonreproductive males resp ... | 2017 | 29166160 |
| arctic ground squirrel resist peroxynitrite-mediated cell death in response to oxygen glucose deprivation. | cerebral ischemia-reperfusion (i/r) injury initiates a cascade of events, generating nitric oxide (no) and superoxide(o2•-) to form peroxynitrite (onoo-), a potent oxidant. arctic ground squirrels (ags; urocitellus parryii) show high tolerance to i/r injury. however, the underlying mechanism remains elusive. we hypothesize that tolerance to i/r modeled in an acute hippocampal slice preparation in ags is modulated by reduced oxidative and nitrative stress. hippocampal slices (400µm) from rat and ... | 2017 | 28962873 |
| entraining to the polar day: circadian rhythms in arctic ground squirrels. | 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 ... | 2017 | 28623226 |
| a new insight into the ability to resist ischemic brain injury: does hibernation matter?: an editorial comment for 'arctic ground squirrel hippocampus tolerates oxygen glucose deprivation independent of hibernation season even when not hibernating and after atp depletion, acidosis and glutamate efflux'. | read the commented article 'arctic ground squirrel hippocampus tolerates oxygen glucose deprivation independent of hibernation season even when not hibernating and after atp depletion, acidosis and glutamate efflux' on doi: 10.1111/jnc.13996. | 2017 | 28542925 |
| clock gene expression in the suprachiasmatic nucleus of hibernating arctic ground squirrels. | 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 ... | 2017 | 28452286 |
| stable isotope analysis of co2 in breath indicates metabolic fuel shifts in torpid arctic ground squirrels. | stable carbon isotope ratios (δ13c) in breath show promise as an indicator of immediate metabolic fuel utilization in animals because tissue lipids have a lower δ13c value than carbohydrates and proteins. metabolic fuel consumption is often estimated using the respiratory exchange ratio (rer), which has lipid and carbohydrate boundaries, but does not differentiate between protein and mixed fuel catabolism at intermediate values. because lipids have relatively low δ13c values, measurements of sta ... | 2017 | 28396263 |
| central activation of the a1 adenosine receptor in fed mice recapitulates only some of the attributes of daily torpor. | mice enter bouts of daily torpor, drastically reducing metabolic rate, core body temperature (t b), and heart rate (hr), in response to reduced caloric intake. because central adenosine activation has been shown to induce a torpor-like state in the arctic ground squirrel, and blocking the adenosine-1 (a1) receptor prevents daily torpor, we hypothesized that central activation of the a1 adenosine receptors would induce a bout of natural torpor in mice. to test the hypothesis, mice were subjected ... | 2017 | 28378088 |
| seasonal loss and resumption of circadian rhythms in hibernating arctic ground squirrels. | circadian clocks are near universal among organisms and play a key role in coordinating physiological and metabolic functions to anticipate or coincide with predictable daily changes in the physical and social environment. however, whether circadian rhythms persist and are functionally important during hibernation in all mammals is currently unclear. we examined whether circadian rhythms of body temperature (t b) persist during multi-day, steady-state torpor and investigated the association betw ... | 2017 | 28332018 |
| diet affects arctic ground squirrel gut microbial metatranscriptome independent of community structure. | we examined the effect of diet on pre-hibernation fattening and the gut microbiota of captive arctic ground squirrels (urocitellus parryii). we measured body composition across time and gut microbiota density, diversity and function prior to and after five-weeks on control, high-fat, low-fat (18%, 40% and 10% energy from fat, respectively), or restricted calorie (50% of control) diets. squirrels fattened at the same rate and to the same degree on all diets. additionally, we found no differences ... | 2017 | 28251799 |
| arctic ground squirrel hippocampus tolerates oxygen glucose deprivation independent of hibernation season even when not hibernating and after atp depletion, acidosis, and glutamate efflux. | cerebral ischemia/reperfusion (i/r) triggers a cascade of uncontrolled cellular processes that perturb cell homeostasis. the arctic ground squirrel (ags), a seasonal hibernator resists brain damage following cerebral i/r caused by cardiac arrest and resuscitation. however, it remains unclear if tolerance to i/r injury in ags depends on the hibernation season. moreover, it is also not clear if events such as depletion of atp, acidosis, and glutamate efflux that are associated with anoxic depolari ... | 2017 | 28222226 |
| dna analysis of a 30,000-year-old urocitellus glacialis from northeastern siberia reveals phylogenetic relationships between ancient and present-day arctic ground squirrels. | in contrast to the abundant fossil record of arctic ground squirrels, urocitellus parryii, from eastern beringia, only a limited number of fossils is known from its western part. in 1946, unnamed gulag prisoners discovered a nest with three mummified carcasses of arctic ground squirrels in the permafrost sediments of the el'ga river, yakutia, russia, that were later attributed to a new species, citellus (urocitellus) glacialis vinogr. to verify this assignment and to explore phylogenetic relatio ... | 2017 | 28205612 |
| the influence of androgens on hibernation phenology of free-living male arctic ground squirrels. | free-living ground squirrel species are sexually dimorphic in hibernation phenology. the underlying causes of these differences are not yet known. androgens, testosterone (t) in particular, inhibit hibernation. to determine the influence of endogenous androgens on annual timing of hibernation we first measured circulating levels of t and dehydroepiandrosterone (dhea), an adrenal androgen implicated in non-mating season aggression in other species, in free-living male arctic ground squirrels (uro ... | 2017 | 27986541 |
| neural signaling metabolites may modulate energy use in hibernation. | despite an epidemic in obesity and metabolic syndrome limited means exist to effect adiposity or metabolic rate other than life style changes. here we review evidence that neural signaling metabolites may modulate thermoregulatory pathways and offer novel means to fine tune energy use. we extend prior reviews on mechanisms that regulate thermogenesis and energy use in hibernation by focusing primarily on the neural signaling metabolites adenosine, amp and glutamate. | 2017 | 27878659 |
| integrating archaeology and ancient dna analysis to address invasive species colonization in the gulf of alaska. | the intentional and unintentional movement of plants and animals by humans has transformed ecosystems and landscapes globally. assessing when and how a species was introduced are central to managing these transformed landscapes, particularly in island environments. in the gulf of alaska, there is considerable interest in the history of mammal introductions and rehabilitating gulf of alaska island environments by eradicating mammals classified as invasive species. the arctic ground squirrel (uroc ... | 2017 | 27859602 |
| the secret life of ground squirrels: accelerometry reveals sex-dependent plasticity in above-ground activity. | the sexes differ in how and when they allocate energy towards reproduction, but how this influences phenotypic plasticity in daily activity patterns is unclear. here, we use collar-mounted light loggers and triaxial accelerometers to examine factors that affect time spent above ground and overall dynamic body acceleration (odba), an index of activity-specific energy expenditure, across the active season of free-living, semi-fossorial arctic ground squirrels (urocitellus parryii). we found high d ... | 2016 | 27703706 |
| you can hide but you can't run: apparent competition, predator responses and the decline of arctic ground squirrels in boreal forests of the southwest yukon. | throughout much of north america's boreal forest, the cyclical fluctuations of snowshoe hare populations (lepus americanus) may cause other herbivores to become entrained in similar cycles. alternating apparent competition via prey switching followed by positive indirect effects are the mechanisms behind this interaction. our purpose is to document a change in the role of indirect interactions between sympatric populations of hares and arctic ground squirrels (urocitellus parryii plesius), and t ... | 2016 | 27635312 |
| seasonal programming, not competition or testosterone, drives stress-axis changes in a partially-semelparous mammal. | animals must make tradeoffs between reproduction and longevity. this is particularly pronounced in male arctic ground squirrels (urocitellus parryii), that compete aggressively for territories and mates during a three-week breeding season. breeding males have high rates of severe wounding, high mortality rates, and high free cortisol levels, along with downstream consequences of chronic stress (weight loss, reduced immune function) that appear to contribute to their early death. the elevated cor ... | 2016 | 27561227 |
| future approaches to therapeutic hypothermia: a symposium report. | | 2017 | 27227020 |
| the effects of hibernation and forced disuse (neurectomy) on bone properties in arctic ground squirrels. | bone loss is a well-known medical consequence of disuse such as in long-term space flight. immobilization in many animals mimics the effects of space flight on bone mineral density. decreases in metabolism are also thought to contribute to a loss of skeletal mass. hibernating mammals provide a natural model of disuse and metabolic suppression. hibernating ground squirrels have been shown to maintain bone strength despite long periods of disuse and decreased metabolism during torpor. this study e ... | 2016 | 27225624 |
| proteomic profiling reveals adaptive responses to surgical myocardial ischemia-reperfusion in hibernating arctic ground squirrels compared to rats. | hibernation is an adaptation to extreme environments known to provide organ protection against ischemia-reperfusion (i/r) injury. an unbiased systems approach was utilized to investigate hibernation-induced changes that are characteristic of the hibernator cardioprotective phenotype, by comparing the myocardial proteome of winter hibernating arctic ground squirrels (ags), summer active ags, and rats subjected to i/r, and further correlating with targeted metabolic changes. | 2016 | 27187119 |
| integrating physiology, behavior, and energetics: biologging in a free-living arctic hibernator. | the use of animal-borne instruments (abis), including biologgers and biotransmitters, has played an integral role in advancing our understanding of adjustments made by animals in their physiology and behavior across their annual and daily cycles and in response to weather and environmental change. here, we review our research employing body temperature (tb), light, and acceleration biologgers to measure patterns of physiology and behavior of a free-living, semi-fossorial hibernator, the arctic g ... | 2016 | 27139082 |
| arctic ground squirrels limit bone loss during the prolonged physical inactivity associated with hibernation. | 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 ... | 2016 | 27082526 |
| arctic ground squirrel neuronal progenitor cells resist oxygen and glucose deprivation-induced death. | to investigate the influence of ischemia/reperfusion on arctic ground squirrel (ags) neuronal progenitor cells (npcs), we subjected these cultured cells to oxygen and glucose deprivation. | 2016 | 26981205 |
| coping with pregnancy after 9months in the dark: post-hibernation buffering of high maternal stress in arctic ground squirrels. | pregnancy and lactation are key times in the life of female mammals when energetic resources must be brought to bear to produce and nurture offspring. changes in glucocorticoid (gc) levels are central to this objective, due to their roles in modulating development and physiology and in mediating energetic tradeoffs. we examined gc changes over reproduction in a species living in a harsh seasonal environment: the arctic ground squirrel (urocitellus parryii). females become pregnant immediately af ... | 2016 | 26555380 |
| energy regulation in context: free-living female arctic ground squirrels modulate the relationship between thyroid hormones and activity among life history stages. | 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 histor ... | 2015 | 26416501 |
| how will the greening of the arctic affect an important prey species and disturbance agent? vegetation effects on arctic ground squirrels. | increases in terrestrial primary productivity across the arctic and northern alpine ecosystems are leading to altered vegetation composition and stature. changes in vegetation stature may affect predator-prey interactions via changes in the prey's ability to detect predators, changes in predation pressure, predator identity and predator foraging strategy. changes in productivity and vegetation composition may also affect herbivores via effects on forage availability and quality. we investigated ... | 2015 | 25666700 |
| comparative functional genomics of adaptation to muscular disuse in hibernating mammals. | 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 identif ... | 2014 | 25314618 |
| 1h-nmr metabolomic biomarkers of poor outcome after hemorrhagic shock are absent in hibernators. | hemorrhagic shock (hs) following trauma is a leading cause of death among persons under the age of 40. during hs the body undergoes systemic warm ischemia followed by reperfusion during medical intervention. ischemia/reperfusion (i/r) results in a disruption of cellular metabolic processes that ultimately lead to tissue and organ dysfunction or failure. resistance to i/r injury is a characteristic of hibernating mammals. the present study sought to identify circulating metabolites in the rat as ... | 2014 | 25211248 |
| habituation of arctic ground squirrels (urocitellus parryii) to handling and movement during torpor to prevent artificial arousal. | hibernation is a unique physiological adaptation characterized by periods of torpor that consist of repeated, reversible, and dramatic reductions of body temperature, metabolism, and blood flow. external and internal triggers can induce arousal from torpor in the hibernator. studies of hibernating animals often require that animals be handled or moved prior to sampling or euthanasia but this movement can induce changes in the hibernation status of the animal. in fact, it has been demonstrated th ... | 2014 | 24847278 |
| temporal dynamics of the cecal gut microbiota of juvenile arctic ground squirrels: a strong litter effect across the first active season. | arctic ground squirrels (urocitellus parryii) are active for a scant 3 to 5 months of the year. during the active season, adult squirrels compete for mates, reproduce, and fatten in preparation for hibernation, while juvenile squirrels, weaned in early july, must grow and acquire sufficient fat to survive their first hibernation season. during hibernation, the gut microbial community is altered in diversity, abundance, and activity. to date, no studies have examined the gut microbiota of hiberna ... | 2014 | 24795380 |
| resistance to systemic inflammation and multi organ damage after global ischemia/reperfusion in the arctic ground squirrel. | cardiac arrest (ca) and hemorrhagic shock (hs) are two clinically relevant situations where the body undergoes global ischemia as blood pressure drops below the threshold necessary for adequate organ perfusion. resistance to ischemia/reperfusion (i/r) injury is a characteristic of hibernating mammals. the present study sought to determine if arctic ground squirrels (ags) are protected from systemic inflammation and multi organ damage after ca- or hs-induced global i/r and if, for hs, this protec ... | 2014 | 24728042 |
| metabolic rate and prehibernation fattening in free-living arctic ground squirrels. | hibernating mammals become sequestered and cease foraging during prolonged seasonal periods of reduced or unpredictable food availability and instead rely on cached food and/or endogenous reserves of fat and protein accumulated during the previous active season. the gain in weight is due to increased food consumption, but it also has been hypothesized that hibernators maximize rates of fattening by decreasing costs of maintenance before weight gain, reflected in reduced resting metabolic rate (r ... | 2013 | 23995482 |
| molecular signatures of mammalian hibernation: comparisons with alternative phenotypes. | mammalian hibernators display phenotypes similar to physiological responses to calorie restriction and fasting, sleep, cold exposure, and ischemia-reperfusion in non-hibernating species. whether biochemical changes evident during hibernation have parallels in non-hibernating systems on molecular and genetic levels is unclear. | 2013 | 23957789 |
| changing seasonality and phenological responses of free-living male arctic ground squirrels: the importance of sex. | many studies have addressed the effects of climate change on species as a whole; however, few have examined the possibility of sex-specific differences. to understand better the impact that changing patterns of snow-cover have on an important resident arctic mammal, we investigated the long-term (13 years) phenology of hibernating male arctic ground squirrels living at two nearby sites in northern alaska that experience significantly different snow-cover regimes. previously, we demonstrated that ... | 2013 | 23836786 |
| circannual rhythm in body temperature, torpor, and sensitivity to a₁ adenosine receptor agonist in arctic ground squirrels. | a₁ adenosine receptor (a₁ar) activation within the central nervous system induces torpor, but in obligate hibernators such as the arctic ground squirrel (ags; urocitellus parryii), a₁ar stimulation induces torpor only during the hibernation season, suggesting a seasonal increase in sensitivity to a₁ar signaling. the purpose of this research was to investigate the relationship between body temperature (tb) and sensitivity to an adenosine a1 receptor agonist in ags. we tested the hypothesis that i ... | 2013 | 23735499 |
| lipids of liver membrane structures during hibernation of the arctic ground squirrel spermophilus undulatus. | | 2017 | 23478979 |
| a test of alternative models for increased tissue nitrogen isotope ratios during fasting in hibernating arctic ground squirrels. | we describe two models explaining the increase in tissue nitrogen isotope ratios (δ(15)n) that occurs during fasting in animals. the catabolic model posits that protein breakdown selectively removes the lighter isotope of nitrogen ((14)n) from catabolized tissues, causing an increase in the proportion of heavy nitrogen isotope ((15)n). the anabolic model posits that protein synthesis during fasting results in elevated δ(15)n values, as the unreplaced loss of (14)n to urea results in a higher pro ... | 2012 | 22735347 |
| hibernation and circadian rhythms of body temperature in free-living arctic ground squirrels. | in mammals, the circadian master clock generates daily rhythms of body temperature (t(b)) that act to entrain rhythms in peripheral circadian oscillators. the persistence and function of circadian rhythms during mammalian hibernation is contentious, and the factors that contribute to the reestablishment of rhythms after hibernation are unclear. we collected regular measures of core t(b) (every 34 min) and ambient light conditions (every 30 s) before, during, and following hibernation in free-liv ... | 2012 | 22705489 |
| inhibition of nmda-type glutamate receptors induces arousal from torpor in hibernating arctic ground squirrels (urocitellus parryii). | hibernation is an adaptation to overcome periods of resource limitation often associated with extreme climatic conditions. the hibernation season consists of prolonged bouts of torpor that are interrupted by brief interbout arousals. physiological mechanisms regulating spontaneous arousals are poorly understood, but may be related to a need for gluconeogenesis or elimination of metabolic wastes. glutamate is derived from glutamine through the glutamate-glutamine cycle and from glucose via the py ... | 2012 | 22697356 |
| thermoregulatory changes anticipate hibernation onset by 45 days: data from free-living arctic ground squirrels. | hibernation is a strategy of reducing energy expenditure, body temperature (t(b)) and activity used by endotherms to escape unpredictable or seasonally reduced food availability. despite extensive research on thermoregulatory adjustments during hibernation, less is known about transitions in thermoregulatory state, particularly under natural conditions. laboratory studies on hibernating ground squirrels have demonstrated that thermoregulatory adjustments may occur over short intervals when anima ... | 2012 | 22526260 |
| estimating lean mass over a wide range of body composition: a calibration of deuterium dilution in the arctic ground squirrel. | calculating body water through isotope dilution has become a useful way to nondestructively estimate body composition in many species. the most accurate estimates using this method require calibration against proximate chemical analysis of body composition for individual species, but no studies to our knowledge have calibrated this method on a hibernating mammal that seasonally undergoes dramatic changes in body composition. we use deuterium oxide to estimate total body water in captive arctic g ... | 2011 | 22095496 |
| inducing hibernation in the arctic ground squirrel. | | 2011 | 21857633 |
| season primes the brain in an arctic hibernator to facilitate entrance into torpor mediated by adenosine a(1) receptors. | torpor in hibernating mammals defines the nadir in mammalian metabolic demand and body temperature that accommodates seasonal periods of reduced energy availability. the mechanism of metabolic suppression during torpor onset is unknown, although the cns is a key regulator of torpor. seasonal hibernators, such as the arctic ground squirrel (ags), display torpor only during the winter, hibernation season. the seasonal character of hibernation thus provides a clue to its regulation. in the present ... | 2011 | 21795527 |
| coping with intense reproductive aggression in male arctic ground squirrels: the stress axis and its signature tell divergent stories. | we tested the adaptive stress hypothesis that male arctic ground squirrels (urocitellus parryii) exhibit a stress response over the course of the breeding season that is characterized by increasing free cortisol concentrations, increasing mobilization of stored energy, and decreasing physical condition. we assessed the functioning of the hypothalamic-pituitary-adrenal axis by measuring cortisol levels in response to the stress of capture and in response to a hormone challenge protocol (dexametha ... | 2013 | 21743255 |
| diversity and demography in beringia: multilocus tests of paleodistribution models reveal the complex history of arctic ground squirrels. | to assess effects of historical climate change on northern species, we quantified the population history of the arctic ground squirrel (spermophilus parryii), an arctic-adapted rodent that evolved in beringia and was strongly influenced by climatic oscillations of the quaternary. competing hypotheses for the species' population history were derived from patterns of mitochondrial (mtdna) structure and a bioclimatic envelope model (bem). hypotheses invoked (1) sequential isolation of regional popu ... | 2011 | 21729045 |
| data logging of body temperatures provides precise information on phenology of reproductive events in a free-living arctic hibernator. | precise measures of phenology are critical to understanding how animals organize their annual cycles and how individuals and populations respond to climate-induced changes in physical and ecological stressors. we show that patterns of core body temperature (t (b)) can be used to precisely determine the timing of key seasonal events including hibernation, mating and parturition, and immergence and emergence from the hibernacula in free-living arctic ground squirrels (urocitellus parryii). using t ... | 2011 | 21691770 |
| hibernating above the permafrost: effects of ambient temperature and season on expression of metabolic genes in liver and brown adipose tissue of arctic ground squirrels. | hibernating arctic ground squirrels (urocitellus parryii), overwintering in frozen soils, maintain large gradients between ambient temperature (t(a)) and body temperature (t(b)) by substantially increasing metabolic rate during torpor while maintaining a subzero t(b). we used quantitative reverse-transcription pcr (qrt-pcr) to determine how the expression of 56 metabolic genes was affected by season (active in summer vs hibernating), metabolic load during torpor (imposed by differences in t(a): ... | 2011 | 21430207 |
| growth and differentiation of adult hippocampal arctic ground squirrel neural stem cells. | arctic ground squirrels (urocitellus parryii, ags) are unique in their ability to hibernate with a core body temperature near or below freezing. these animals also resist ischemic injury to the brain in vivo and oxygen-glucose deprivation in vitro. these unique qualities provided the impetus to isolate ags neurons to examine inherent neuronal characteristics that could account for the capacity of ags neurons to resist injury and cell death caused by ischemia and extremely cold temperatures. iden ... | 2011 | 21248701 |
| phenological variation in annual timing of hibernation and breeding in nearby populations of arctic ground squirrels. | ecologists need an empirical understanding of physiological and behavioural adjustments that animals can make in response to seasonal and long-term variations in environmental conditions. because many species experience trade-offs between timing and duration of one seasonal event versus another and because interacting species may also shift phenologies at different rates, it is possible that, in aggregate, phenological shifts could result in mismatches that disrupt ecological communities. we inv ... | 2011 | 21177687 |
| mitochondrial metabolites in tissues as indicators of metabolic alterations during hibernation. | the decrease in metabolism is one of mechanisms for hibernating animals to resist hypoxia and oxidative stress. assuming that the inhibition of mitochondria; respiration in torpor and its activation upon arousal are accompanied by changes in the content of mitochondrial substrates, we estimated the levels of endogenous metabolites of the tricarboxylic acid (tca) cycle in the liver, brown adipose tissue, and the brain of the arctic ground squirrels as possible indicators of mitochondrial processe ... | 2013 | 21042654 |
| genomic analysis of mirnas in an extreme mammalian hibernator, the arctic ground squirrel. | micrornas (mirnas) are 19- to 25-nucleotide-long small and noncoding rnas now well-known for their regulatory roles in gene expression through posttranscriptional and translational controls. mammalian hibernation is a physiological process involving profound changes in set-points for food consumption, body mass and growth, body temperature, and metabolic rate in which mirnas may play important regulatory roles. in an initial study, we analyzed mirnas in the liver of an extreme hibernating specie ... | 2010 | 20442247 |
| shotgun proteomics analysis of hibernating arctic ground squirrels. | mammalian hibernation involves complex mechanisms of metabolic reprogramming and tissue protection. previous gene expression studies of hibernation have mainly focused on changes at the mrna level. large scale proteomics studies on hibernation have lagged behind largely because of the lack of an adequate protein database specific for hibernating species. we constructed a ground squirrel protein database for protein identification and used a label-free shotgun proteomics approach to analyze prote ... | 2010 | 19955082 |
| energetics of arousal episodes in hibernating arctic ground squirrels. | arctic ground squirrels overwintering in northern alaska experience average soil temperature of -10 degrees c. to examine energetic costs of arousing from hibernation under arctic compared to temperate conditions, captive ground squirrels were maintained in ambient temperatures (t(a)) of 2, -5 and -12 degrees c. rates of oxygen consumption and carbon dioxide production were used to estimate metabolic rate and fuel use during the three phases of arousal episodes: rewarming, euthermia, and recooli ... | 2009 | 19277682 |
| physiological oxidative stress after arousal from hibernation in arctic ground squirrel. | hibernation in arctic ground squirrels (ags), spermophilus parryii, is characterized by a profound decrease in oxygen consumption and metabolic demand during torpor that is punctuated by periodic rewarming episodes, during which oxygen consumption increases dramatically. the extreme physiology of torpor or the surge in oxygen consumption during arousal may increase production of reactive oxygen species, making hibernation an injurious process for ags. to determine if ags tissues experience cellu ... | 2009 | 19233307 |
| impact of live trapping on stress profiles of richardson's ground squirrel (spermophilus richardsonii). | researching the physiological ecology of natural populations requires an understanding of the impact of capture-induced stress because of its numerous effects on physiological processes. in many cases, initial blood samples to which comparisons are made are obtained well after capture and may differ markedly from free-ranging conditions. we examined the extent to which stress profiles of male richardson's ground squirrels (spermophilus richardsonii) were affected by short-term responses to live ... | 2009 | 19059261 |
| simultaneous measurement of brain tissue oxygen partial pressure, temperature, and global oxygen consumption during hibernation, arousal, and euthermy in non-sedated and non-anesthetized arctic ground squirrels. | this study reports an online temperature correction method for determining tissue oxygen partial pressure p(to2) in the striatum and a novel simultaneous measurement of brain p(to2) and temperature (t(brain)) in conjunction with global oxygen consumption v(o2) in non-sedated and non-anesthetized freely moving arctic ground squirrels (ags, spermophilus parryii). this method fills an important research gap-the lack of a suitable method for physiologic studies of tissue p(o2) in hibernating or othe ... | 2008 | 18722471 |
| dietary fatty acid composition and the hibernation patterns in free-ranging arctic ground squirrels. | laboratory experiments have demonstrated that the amount of polyunsaturated fatty acids (pufas) in the diet before hibernation influences patterns of mammalian torpor. the hibernation ability of ground squirrels is greatest (longest torpor bouts, greatest number of animals entering torpor) when the pufa content of their fall diets is 33-74 mg/g, under laboratory conditions. the extent to which natural fall diets both (a) vary in pufa content and (b) influence the torpor patterns of free-ranging ... | 2008 | 18513150 |
| arctic ground squirrel (spermophilus parryii) hippocampal neurons tolerate prolonged oxygen-glucose deprivation and maintain baseline erk1/2 and jnk activation despite drastic atp loss. | oxygen-glucose deprivation (ogd) initiates a cascade of intracellular responses that culminates in cell death in sensitive species. neurons from arctic ground squirrels (ags), a hibernating species, tolerate ogd in vitro and global ischemia in vivo independent of temperature or torpor. regulation of energy stores and activation of mitogen-activated protein kinase (mapk) signaling pathways can regulate neuronal survival. we used acute hippocampal slices to investigate the role of atp stores and e ... | 2008 | 18398417 |
| physiological regulation of tau phosphorylation during hibernation. | the microtubule-associated protein tau is abnormally hyperphosphorylated in the brains of individuals with alzheimer disease and other tauopathies, and is believed to play a critical role in the pathogenesis of these diseases. while the mechanisms leading to abnormal tau phosphorylation remain elusive, the recent demonstration of reversible tau phosphorylation during hibernation provides an ideal physiological model to study this critical process in vivo. in this study, arctic ground squirrels ( ... | 2008 | 18284615 |
| modulation of gene expression in hibernating arctic ground squirrels. | we performed a broadscale screening of differential gene expression using both high-throughput bead-array technology and real-time pcr assay in brown adipose tissue, liver, heart, hypothalamus, and skeletal muscle in hibernating arctic ground squirrels, comparing animals sampled after two durations of steady-state torpor, during two stages of spontaneous arousal episodes, and in animals after they ended hibernation. significant seasonal and torpor-arousal cycle differences of gene expression wer ... | 2008 | 17925484 |
| enantioseparation and stacking of cyanobenz[f]isoindole-amino acids by reverse polarity capillary electrophoresis and sulfated beta-cyclodextrin. | a capillary electrophoresis method with laser-induced fluorescence detection for the chiral separation of cyanobenz[f]isoindole (cbi) derivatives of amino acids was developed and optimized. the enantioseparations are accomplished with sulfated beta-cd (s-beta-cd) as chiral selector at low ph and reverse polarity. bge conditions were optimized for cbi-serine and then applied to other cbi-amino acids. baseline resolution of 13 cbi-amino acids was achieved using a single bge formulation of 2 wt % s ... | 2007 | 17222044 |
| distribution of nmda receptor subunit nr1 in arctic ground squirrel central nervous system. | hibernation is a natural model of neuroprotection and adult synaptic plasticity. nmda receptors (nmdar), which play key roles in excitotoxicity and synaptic plasticity, have not been characterized in a hibernating species. tolerance to excitotoxicity and cognitive enhancement in arctic ground squirrels (ags, spermophilus parryii) suggests that nmdar expression may decrease in hibernation and increase upon arousal. nmdar consist of at least one nmdar1 (nr1) subunit, which is required for receptor ... | 2006 | 17097266 |