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Seasonal patterns in the physiology of the European brown bear (Ursus arctos arctos) in Finland
Abstract
The physiological indicators such as body temperature, blood chemistry and hematology of seven European brown bears (Ursus arctos arctos) were used in the present study. They were kept in either the Zoological Garden of University of Oulu (65 degrees N, 25 degrees 24'E) or the Ranua Zoological Garden approx. 150 km NE of Oulu. Transmitters with a temperature-dependent pulse rate were implanted subcutaneously or into the abdominal cavity under anesthesia. Our data indicate that the body temperature of the bear decreases during the winter sleep to 4-5 degrees C below the normal level (37.0-37.5 degrees C). The lowest values, 33.1-33.3 degrees C, were measured several times in midwinter. Hematocrit, hemoglobin and erythrocyte counts seem to be higher, and the leucocyte count lower during the denning period than in the awake bear. Plasma N-wastes were lower during the winter sleep than before or after it. The analysed blood parameters showed that plasma catecholamines and thyroid hormones decreased in the fall.
... Regulations of the thyroid hormone levels in hibernating bears have previously been described [14][15][16][17][18], but to our awareness, this is the first study using paired free-ranging (wild) bears. Additionally, the knowledge of thyroid hormone function in humans has greatly expanded since the previous studies on bears were published, enabling us to discuss the biological effects of the thyroid hormone differences observed in bears in an updated context. ...
... We found that the thyroid hormones, T 4 (the most abundant) and T 3 (the most potent), decreased during hibernation in Scandinavian brown bears in agreement with the results from most previous publications, which generally report decreases in both total and free thyroid hormone levels [14][15][16][17][18]. One study, however, found increased thyroid hormone levels in wild hibernating bears [20]. ...
... Hypothyroidism in humans is typically associated with decreased basal metabolic rate, bradycardia (slower heart rate), hypothermia, constipation, and fatigue [7], and severe hypothyroidism in humans has been reported to lower the total body energy expenditure by as much as 50% [6]. A similar physiology is seen in hibernating bears with a metabolic rate reduced to 25% of that in the active state [1], slower heart rate [26,27], decreased body temperature [4,16], and no defecation [1]. Based on this similarity, we suggest that hypothyroidism is a key regulator of hibernation physiology in bears (Fig. 3). ...
Brown bears hibernate throughout half of the year as a survival strategy to reduce energy consumption during prolonged periods with scarcity of food and water. Thyroid hormones are the major endocrine regulators of basal metabolic rate in humans. Therefore, we aimed to determine regulations in serum thyroid hormone levels in hibernation compared to the active state to investigate if these are involved in the adaptions for hibernation.
We used electrochemiluminescence immunoassay to quantify total triiodothyronine (T3) and thyroxine (T4) levels in hibernation and active state in paired serum samples from six subadult Scandinavian brown bears. Additionally, we determined regulations in the liver mRNA levels of three major thyroid hormone-binding proteins; thyroxine-binding globulin (TBG), transthyretin (TTR), and albumin, by analysis of previously published grizzly bear RNA sequencing data.
We found that bears were hypothyroid when hibernating with T4 levels reduced to less than 44% (P = 0.008) and T3 levels reduced to less than 36% (P = 0.016) of those measured in the active state. In hibernation, mRNA levels of TBG and albumin increased to 449% (P = 0.031) and 121% (P = 0.031), respectively, of those measured in the active state. TTR mRNA levels did not change.
Hibernating bears are hypothyroid and share physiologic features with hypothyroid humans, including decreased basal metabolic rate, bradycardia, hypothermia, and fatigue. We speculate that decreased thyroid hormone signaling is a key mediator of hibernation physiology in bears. Our findings shed light on the translational potential of bear hibernation physiology to humans for whom a similar hypometabolic state could be of interest in specific conditions.
... Multiple lineages of mammals, including ground squirrels [1][2][3], bears [4][5][6], and even several primates [7,8], hibernate annually, during which metabolism is depressed, body temperature decreases to varying extents, and a suite of cellular and physiological changes culminate in the ability to survive periods of food scarcity [4,5,[9][10][11]. Understanding how organisms both Here, we present an unprecedented transcriptomic dataset for 26 samples collected from 13 tissues of two hibernating brown bears (Table 1). ...
... Multiple lineages of mammals, including ground squirrels [1][2][3], bears [4][5][6], and even several primates [7,8], hibernate annually, during which metabolism is depressed, body temperature decreases to varying extents, and a suite of cellular and physiological changes culminate in the ability to survive periods of food scarcity [4,5,[9][10][11]. Understanding how organisms both Here, we present an unprecedented transcriptomic dataset for 26 samples collected from 13 tissues of two hibernating brown bears (Table 1). ...
Objectives
Complex physiological adaptations often involve the coordination of molecular responses across multiple tissues. Establishing transcriptomic resources for non-traditional model organisms with phenotypes of interest can provide a foundation for understanding the genomic basis of these phenotypes, and the degree to which these resemble, or contrast, those of traditional model organisms. Here, we present a one-of-a-kind gene expression dataset generated from multiple tissues of two hibernating brown bears ( Ursus arctos ).
Data description
This dataset is comprised of 26 samples collected from 13 tissues of two hibernating brown bears. These samples were collected opportunistically and are typically not possible to attain, resulting in a highly unique and valuable gene expression dataset. In combination with previously published datasets, this new transcriptomic resource will facilitate detailed investigation of hibernation physiology in bears, and the potential to translate aspects of this biology to treat human disease.
... During deep torpor, metabolic rate often plummets to as low as 2% of basal metabolic rate or 0.01 mL O 2 /g/h (Geiser 1988;Buck & Barnes 2000), a remarkable shift that is accompanied by major changes in vital signs; for example, in ground squirrels this includes reductions in heart rate (from 350-400 beats/min to as low as 5-10 beats/min), breathing rate (from >40 breaths/min to <1 breath/min), organ perfusion rates (<10% of euthermic values), and core body temperature (from euthermic values of 35-38°C to near-ambient levels during torpor, often <5°C) that ultimately reduce the animal's energy expenditure (Wang 1979;Carey et al. 2003). Large hibernators such as black bears are an exception and show a different pattern in their metabolic adaptations, with body temperature cooling only to 30-36°C during torpor (Hissa et al. 1994;Tøien et al. 2011). Overall, by hibernating, mammals can conserve up to 90% of the energy that it would otherwise take to remain euthermic over the winter months (Wang & Lee 1996). ...
... Instead, they change position on a daily basis and display multiday cycles of T b between 30 to 36°C (Tøien et al. 2011). However, in line with the modest drop of T b (Hissa et al. 1994;Tøien et al. 2011), the drop of leukocyte counts is also modest in hibernating brown bears (~40% vs. ~90% in small hibernators), while lymphocyte counts were unchanged between hibernation and active periods (Sahdo et al. 2013). Metabolic suppression in bears during hibernation was suggested to be independent of T b , indicating that processes of hibernation may occur, at least in part, in a temperature-independent matter (Tøien et al. 2011). ...
... Blood parameters have been reported in several bear species, including the American black bear (Ursus americanus) (Matula et al., 1980;Nelson et al., 1984;Schroeder, 1987;Karen and David, 1992;Hellgren et al., 1993;LeBlanc et al., 2001;Lohuis et al., 2005), brown bear (Ursus arctos) (Robert, 1985;Hissa et al., 1994;Huber et al., 1997;Graesli et al., 2014;Graesli et al., 2015), polar bear (Ursus maritimus) (Derocher et al., 1990;Tryland et al., 2002;Sandala et al., 2004;Thiemann et al., 2008;Bytingsvik et al., 2012) Andean bear (Tremarctos ornatus) (Castellanos et al., 2010;Castellanos et al., 2013), sloth bear (Melursus ursinus) (Veeraselvam et al., 2014(Veeraselvam et al., , 2018 and Malayan sun bear (Helarctos malayanus) (Azlan et al., 2011). The specific parameters assessed vary between studies based on their with drop lines to help locate the points in the x, y plane (axis 1 score and axis 2 score are the same as the point and axis 3 score = 0). ...
Physiological indexes like blood parameters have been widely used to monitor the health of free-roaming animals. Attempts to reintroduce one of China’s most endangered species, the giant panda (Ailuropoda melanoleuca), have been hampered by a lack of data on its ecology and physiology. We examined three giant pandas’ hematological and blood chemistry parameters in a soft release program and 30 captive giant pandas as controls and determined the reference intervals (RIs) for those blood parameters in the captive animals. Elevation, captivity status and the interaction of those factors were statistically significant for hematologic measures. Release pandas had significantly higher hemoglobin and hematocrit values after they moved to high elevation locations. We also found significant difference in the enzyme parameters between high and low elevation pandas such as higher aspartate aminotransferase, alanine aminotransferase, creatinine kinase, amylase and lower lactate dehydrogenase and alkaline phosphatase. Release pandas also had higher nutrition parameter values such as higher albumin, globulin and creatinine. The RI for blood parameters in our study provides a baseline to monitor the health of captive animals and forms the basis for assessing the health of free-roaming giant pandas in future reintroduction efforts.
... Smaller bears had higher T b in summer and lower T b in winter, in line with the principles of thermodynamics and surface-to-volume ratios. The large dataset available here allowed us to conduct comparisons across a range of sizes of free-ranging brown bears, where the relationship between environment and physiology were not altered, as is often the case for captive bears [67]. We conclude that the smallest bears hibernated more deeply and longer than large bears, likely from a combined effect of basic thermodynamics (high thermal conductance, due to a high surface-to-body-mass ratio), the higher need for energy savings, and a lower cost of warming up a smaller body. ...
Background:
Despite centuries of research, debate remains on the scaling of metabolic rate to mass especially for intraspecific cases. The high variation of body mass within brown bears presents a unique opportunity to study the intraspecific effects of body mass on physiological variables. The amplitude of metabolic rate reduction in hibernators is dependent on body mass of the species. Small hibernators have high metabolic rates when euthermic but experience a drastic decrease in body temperature during torpor, which is necessary to reach a very low metabolic rate. Conversely, large hibernators, such as the brown bear (Ursus arctos), show a moderate decrease in temperature during hibernation, thought to be related to the bear's large size. We studied body mass, abdominal body temperature, heart rate, and accelerometer-derived activity from 63 free-ranging brown bears (1-15 years old, 15-233 kg). We tested for relationships between body mass and body temperature, heart rate, and hibernation duration.
Results:
The smallest individuals maintained lower body temperatures during hibernation, hibernated longer, and ended hibernation later than large bears. Unlike body temperature, winter heart rates were not associated with body mass. In summer, the opposite pattern was found, with smaller individuals having higher body temperature and daytime heart rates. Body mass was associated with body temperature in the winter hypometabolic state, even in a large hibernating mammal. Smaller bears, which are known to have higher thermal conductance, reached lower body temperatures during hibernation. During summer, smaller bears had higher body temperatures and daytime heart rates, a phenomenon not previously documented within a single mammalian species.
Conclusion:
We conclude that the smallest bears hibernated more deeply and longer than large bears, likely from a combined effect of basic thermodynamics, the higher need for energy savings, and a lower cost of warming up a smaller body.
... Hibernation in bears involves annual shifts in metabolism and physiology that enable bears to survive food-scarce winters (1)(2)(3)(4). Notably, multiple tissues become insulin resistant during hibernation, only to have insulin sensitivity restored at the completion of the hibernation season (5)(6)(7). Recent studies of gene expression (8), differential isoform usage (9,10), and cell culture experiments (7,11) have made progress in identifying cellular and molecular mechanisms that drive key features of hibernation. ...
Hibernation in bears involves a suite of metabolic and physiological changes, including the onset of insulin resistance, that are driven in part by sweeping changes in gene expression in multiple tissues. Feeding bears glucose during hibernation partially restores active season physiological phenotypes, including partial re-sensitization to insulin, but the molecular mechanisms underlying this transition remain poorly understood. Here, we analyze tissue-level gene expression in adipose, liver, and muscle to identify genes that respond to mid-hibernation glucose feeding and thus potentially drive post-feeding metabolic and physiological shifts. We show that mid-hibernation feeding stimulates differential expression in all analyzed tissues of hibernating bears, and that a subset of these genes respond specifically by shifting expression towards levels typical of the active season. Inferences of upstream regulatory molecules potentially driving these post-feeding responses implicate PPARG and other known regulators of insulin sensitivity, providing new insight into high-level regulatory mechanisms involved in shifting metabolic phenotypes between hibernation and active states.
... Hibernation is one of the most efficient energy-saving mechanisms, which is regularly activated early in advance of the beginning of winter (Nelson 1973). In contrast to other hibernating species, the body temperature of bears drops only 2 to 6 °C below the summer core temperature of 37-38 °C, (French 1986, Hissa et al. 1994, Tøien et al. 2011. Heart rate during hibernation can be as low as 8-10 beats per minute (bpm), compared to the heart rate of 30-50 bpm of sleeping bears in summer (Folk et al. 1972, Folk et al. 1976, Folk et al. 1980, Nelson et al. 2003, Folk et al. 2008. ...
Abstract
This is a report about the second year of collaboration between Biosphere Expeditions and Björn & Vildmark with the overall purpose of researching the behaviour of free ranging brown bears (Ursus arctos) in central Sweden for the Scandinavian Brown Bear Research Project (SBBRP). This collaboration investigates, amongst other topics, how climate change as well as human activities affect the brown bear behaviour and population, and provides managers in Sweden with solid, science-based knowledge to manage brown bears.
From 28 May to 4 June 2022, six citizen scientists collected data on bear denning behaviour and feeding ecology by investigating the 2021/2022 hibernation season den sites of GPS-marked brown bears and by collecting fresh scats from day bed sites. All field work was performed in the northern boreal forest zone in Dalarna and Gävleborg counties, south-central Sweden, which is the southern study area of the SBBRP. After two days of field work training, citizen scientists were divided into three to four sub-teams each day. All study positions were provided by the expedition scientist and only data and samples from radio-marked bears with a VHF or GPS transmitter were collected.
Citizen scientists defined den types (anthill den, soil den, rock den, basket den or uprooted tree den), recorded bed material thickness, size and content, as well as all tracks and signs around the den sites to elucidate whether a female had given birth to cubs during hibernation. All first scats after hibernation and hair samples from the bed were collected, and the habitat type around the den and the visibility of the den site were described.
Twenty-six winter positions of 21 different bears were investigated. Two bears shifted their dens at least once during the hibernation season. In total, the expedition found 23 dens; two soil dens, eight anthill dens, one anthill/soil den, one stone/rock den, four dens under uprooted trees and seven basket dens. Unusually, one pregnant female that gave birth to three cubs during winter, and four females that hibernated together with dependent offspring spent the winter in basket dens. Normally basket dens are mainly used by large males.
Excavated bear dens had an average outer length of 2.0 m, an outer width of 2.2 m, and an outer height of 0.8 m. The entrance on average comprised 28% of the open area. The inner length of the den was on average 1.3 m and the inner width was 1.1 m. The inner height of the dens was on average 0.6 m. Bears that hibernated in covered dens used mainly mosses (47%), field layer shrubs (36%) and branches (14%) as nest material, which reflected the composition of the field layer and ground layer that was present at the den site. However, bears that hibernated in open dens such as basket dens, preferred branches (43%) followed by grass (26%); mosses (19%) and field shrubs (12%) as nest material. The expedition found two first post-hibernation bear scats at the den sites.
Ten bears selected their den sites in older forests, and eleven bears in younger forests, only two bears hibernated in very young forest. The habitat around the dens was dominated by spruce (Picea abies) 37%, scots pine (Pinus sylvestris) 35% and birch (Betula pendula, Betula pubescens) 27%.
As part of its intensive data collection activities, the expedition investigated about half of all winter den positions that the SBBRP recorded in 2021/2022 and collected 64 scats at cluster positions, which represents all scat samples that the SBBRP normally collects during a time period of 14 days. A detailed food item analysis will be performed in 2025 and the data will be published.
It appears that climate change is altering bear denning behaviour and may reduce food resources that bears need for fat production. Overharvesting (hunting) of bears and habitat destruction are the major reasons why brown bear populations have declined or have become fragmented in much of their range. In Scandinavia, human activity around den sites has been suggested as the main reason why bears abandon their dens. This can reduce the reproductive success of pregnant female brown bears and increases the chance of human/bear conflict. Understanding denning behaviour is critical for effective bear conservation. Further research is needed to determine whether good denning strategies help bears avoid being disturbed. Additionally, enclosed dens offer protection and insulation from inclement weather. A continued fragmentation of present bear ranges, inhibiting dispersal, together with an increasing bear population, might lead to bears denning closer to human activities than at present, thereby increasing human/bear conflict. The dens that were investigated by the expedition were visible from 22 m on average. Cover opportunities and terrain types not preferred by humans are thereby presumably important for bears that are denning relatively close to human activities, but further research needs to be done to validate this theory.
Through all of the above, the expedition made a very significant contribution to the SBBRP’s field work in a showcase of how citizen science can supplement existing research projects run by professional scientists.
Sammandrag
Detta är en rapport om det andra året av samarbete mellan Biosphere Expeditions och Björn & Vildmark med det övergripande syftet att forska om beteendet hos vild levande brunbjörnar (Ursus arctos) i mellansverige för det skandinaviska björnforskningsprojektet (SBBRP). Samarbetet undersöker bland annat hur klimatförändringar och mänsklig aktivitet påverkar brunbjörnens beteende och population, och ger myndigheter i Sverige gedigen, vetenskapligt baserad kunskap för att förvalta brunbjörnstammen.
Från den 28 maj till den 4 juni 2022 samlade sju expeditionsdeltagare in data om björnens idesval och födoval. De undersökte idesplatserna där björnar har legat i vintersömnen under säsongen 2021-2022 och de samlade samla färsk spillning från daglegor från GPS-märkta brunbjörnar.
Allt fältarbete utfördes i norra boreala skogszonen i Dalarna och Gävleborgs län, södra mellersta Sverige, som är SBBRP:s södra studieområde.
Efter två dagars utbildning inom fältarbete delades expeditionsdeltagaren in i tre till fyra grupper. Alla studiepositioner tillhandahölls av expeditionsforskaren och endast data och prover från radiomärkta björnar med en VHF- eller GPS-sändare samlades in.
Expeditionsdeltagaren definierade idestyper (myrstackide, jordiden, steniden, korgiden eller iden under en rotvälta), och undersökte bäddmaterialet i idet, samt alla spår och tecken runt iden för att ta reda på om en hona hade född ungar under vintern. Alla första spillningar samlades in samt och hårprover från bäddmaterialed. Dessutom beskrevs habitatet och hur dold idet var placerad i terrängen.
26 vinterpositioner för 21 olika björnar undersöktes. Två björnar flyttade från sina iden minst en gång under vintersömnen. Totalt hittade expeditionsdeltagaren 23 iden; två jordiden, åtta myrstackiden, ett myrstackide / jordide, ett steniden, fyra iden under en rotvälta och sju korgiden. Ovanligt nog övervintrade en dräktig björnhona ett korgide där hon födde sina ungar under vintern. Dessutom övervintrade fyra honor med ungar i olika korgiden. Vanligtvis är det framförallt hanbjörnar som använder korgiden.
Utgrävda björniden hade en genomsnittlig yttre längd på 2,0 och yttre bredd på 2,2 m och en yttre höjd av 0,8 m. Ingången utgjorde i genomsnitt 28% av det öppna yta. Den inre längden på idet var i genomsnitt 1,3 m och den inre bredden 1,1 m. Den inre höjden på idena var i genomsnitt 0,6 m. Björnar använde främst grenar (43%), gräs (26%) bärris (12%) och mossor (19%) som bäddmaterial, vilket återspeglade sammansättningen av fältskiktet och jordskiktet som fanns vid idesplatsen. Expeditionsdeltagare hittade två första björnspillningar efter vintersömnen.
Tio björnar valde bygga sina iden i äldre skogar, elva i yngre skogar och två björnar övervintrade i väldigt ung skog. Habitatet runt idesplatsen dominerades av tall (Pinus sylvestris) 35%, gran (Picea abies) 37%, och björk (Betula pendula, Betula pubescens) 27%.
Expeditionen undersökte ungefär hälften av alla vinterpositioner som SBBRP registrerade under 2021/2022 och samlade in 63 spillningar på klusterpositioner, vilket motsvarar alla av de spillnings-prover som björnprojektet normalt samlar in under en tidsperiod på 14 dagar. En detaljerad spillnings analys kommer att genomföras under 2025 och uppgifterna kommer att publiceras efteråt.
Genom allt ovanstående gav expeditionen ett mycket viktigt bidrag till SBBRP: s fältarbete som visade hur expeditionsdeltagare kan komplettera befintliga forskningsprojekt som drivs av professionella forskare. Klimatförändringar förändrar björnens beteende och kan minska födotillgången. Intensiv björnjakt och förstörelse av habitat är de främsta orsakerna till att populationer av brunbjörnar har minskat eller blivit fragmenterade i stora delar av världen. I Skandinavien är mänsklig aktivitet kring idesplatser troligtvis det främsta skälet varför björnar byta iden. Detta kan minska reproduktionen bland dräktiga björnhonor och ökar risken för konflikt mellan människor och björnar. Förståelse av vinterbeteende är avgörande för effektiv bevarande av björnen. Ytterligare forskning behövs för att avgöra om goda vinterstrategier hjälper björnar att undvika störningar. Dessutom erbjuder väl isolerade ide skydd från dåligt väder. En fortsatt fragmentering av nuvarande björnstammen, som hämmar spridning, tillsammans med en ökande björnpopulation, kan leda till att björnar kommer närmare mänsklig bebyggelse, vilket ökar konflikterna mellan människa och björnar. De iden som undersöktes av expeditionen var synliga från 22 m i genomsnitt. Täta terrängtyper som inte föredras av människor är därmed förmodligen viktiga för björnar som bygger sina iden relativt nära mänsklig bebyggelse, men ytterligare forskning måste göras för att validera denna teori.
The American black bear (Ursus americanus) is an opportunistic and adaptable species with high rehabilitation success rates. Injured, ill, and orphaned bears across the southeastern United States are examined and treated at the University of Tennessee College of Veterinary Medicine followed by rehabilitation at Appalachian Bear Rescue (ABR). Hematology and biochemistry reference ranges exist for healthy adult black bears; however, most bears presenting to ABR are young and of variable health status. Thus, further investigation into the difference of blood values at varying ages and presentations is warranted. ABR records from 1996 to 2022 included 106 bears with completed hematology and plasma biochemistry panels (22 paired samples at intake and release, 84 at intake only). Intake-only samples consisted of 12 neonates (<3 mon old), 64 cubs (3–12 mon), and 30 yearlings (1–2 yr). Bears presented as orphaned neonates (22%), orphaned cubs (45%), malnourished yearlings (24%), and injured/ill (9%) during fall (16%), winter (13%), spring (32%), and summer (39%). Changes in hematology and plasma biochemistry results between intake and release included an increase in hematocrit and glucose. Injured/ill bears presented with higher total leukocyte count (WBC), absolute neutrophils (ABS segs), alanine aminotransferase (ALT), aspartate aminotransferase (AST), and creatine kinase (P < 0.05). Positive correlation between ALT, AST, proteins, and blood urea nitrogen and negative correlation between absolute lymphocytes and alkaline phosphatase were noted with age. Both WBC and ABS segs were lower during winter (P < 0.05). Understanding what factors affect juvenile black bear blood values improves clinical expectations and evaluation upon intake, clinical evaluation, and treatment.
Thermal physiological research in Germany over the past 70 years has endeavoured to “illuminate” normal homoeothermic temperature regulation—and fever, hyperthermia, and hypothermia as abnormal states—“at all levels of biological organisation”. The topics of this research have ranged from humans and whole animal models to their organismic, cellular, and molecular levels. The approaches of comparative and behavioural physiology have been used extensively to elucidate the principles underlying the functional cytoarchitecture of central nervous control of body temperature. Studies of the ontogeny of homoeothermic temperature regulation have assisted in clarifying the principles of temperature regulation as a hierarchically organised system of multiple sensors, controllers, and effectors. The inherent redundancy of the system accounts for the high degree of stability of homoeothermic temperature regulation in the face of disturbances of thermal homoeostasis in conditions in which competing demands are imposed on its effectors by nervous and endocrine control of non-thermoregulatory systems essential for body homoeostasis. Perhaps a suitable summary of thermoregulatory research in Germany might be a slight modification of the name of one of the sections, which we often cite, of the American Journal of Physiology, viz., Regulatory, Integrative and Comparative Physiology of Temperature Regulation!
The development of science has been closely tied to universities. In Finland, the University of Turku was founded in 1640, as the Royal Academy of Turku, by Kristina, the Queen of Sweden. At that time, Finland was a part of Sweden, together with the Baltic countries and northern parts of present Germany. Queen Kristina (1626–1689) was a daughter of the Swedish king, Gustavus Adolphus the Great (1594–1632, known in English as Gustav II Adolf), who modernised his kingdom in many ways. He ratified the foundation, in 1632, of the University of Tartu, now Estonia’s leading university. The universities in Turku and Tartu have promoted science and education in Finland and Estonia, endorsing the close tie between the development of science and our universities.
Blood samples from 22 brown bears (Ursus arctos) were assayed for calcium, phosphorus, glucose, urea, creatinine, uric acid, cholesterol, total protein, albumin, total bilirubin, alkaline phosphatase, lactic dehydrogenase, glutamic–oxaloacetic acid transaminase, sodium, potassium, and chloride.Statistically significant seasonal changes in brown bears included a spring-to-summer decrease of calcium, urea, creatinine, and uric acid and concurrent increases of glucose and potassium. These changes may be related to renal function and seasonal variations in the bear's diet. The only sexual difference was the higher uric acid levels in male brown bears than in females.The blood chemistry of four black bears (Ursus americanus) was similar to that of brown bears except for slightly higher levels of phosphorus, creatinine, uric acid, glutamic–oxaloacetic acid transaminase, sodium, and chloride. Our limited sample of black bears did not allow an investigation of seasonal changes.
Neuro-endocrine influences are evident in hibernating Ursus americanus such as hypothermia, bradycardia, anorexia, decreased metabolic rate, sleep position and prolonged sleeping period. Both a catabolic state (similar to anorexia nervosa and starvation) and an anabolic state (similar to pregnancy and growth) are present simultaneously. The bear balances these states perfectly so that it successfully hibernates for 7 months without food or water at a near normal body temperature with no toxic waste accumulation. To succeed, the bear recycles N from recently formed urea back into amino acids at a rate exceeding urea formation. This process appears to be a result of neuro-endocrine interaction with metabolic processes. This neuro-endocrine-metabolic state required for hibernation in the bear is operative weeks prior to actual denning.-from Authors
Blood samples were collected from 220 adult and 78 subadult black bears (Ursus americanus) from fall 1977 through summer 1985 on the Kenai Peninsula, Alaska. The samples were analyzed for 24 biochemical and 2 hematological parameters. Discriminant analysis was used to select useful blood parameters for assessing the condition of black bears based upon the dynamic spring to fall physical condition change. Parameters found to be most useful for females were hemoglobin (Hb), alpha 1 globulin (A1G), and calcium (Ca). The parameters most useful for males were globulin (G), packed cell volume (PCV), albumin/globulin ratio (A/G), sodium (Na), calcium/phosphorus ratio (Ca/P), and Hb. We recommend using Hb and PCV to determine the condition of black bears in the field. Blood profile changes in denning bears were detected for nearly all parameters. The urea/creatinine (U/C) mean was 8.9 for denning bears (n = 48).
During 1956 and 1957, four black bears (Ursus americanus) were held captive in northern Michigan. They were dormant in winter quarters from approximately 25 December to 17 April, during which time all lost weight. Four times over a 9-month period the bears were anesthetized and various physiological and hematological values were obtained.