The brown bear as a translational model for sedentary lifestyle-related diseases.

Sedentary lifestyle accelerates biological ageing, is a major risk factor for developing metabolic syndrome and is associated with cardiovascular disease, diabetes mellitus, kidney failure, sarcopenia and osteoporosis. In contrast to the linear path to worsening health in humans with metabolic syndrome, brown bears have developed a circular metabolic plasticity enabling these animals to tolerate obesity and a 'sedentary lifestyle' during hibernation and exit the den metabolically healthy in spring. Bears are close to humans physiology wise, much closer than rodents, the preferred experimental animals in medical research, and may better serve as translational model to develop treatments for lifestyle-related diseases. In this review, aspects of brown bear hibernation survival strategies are outlined and conceivable experimental strategies to learn from bears are described.

Drivers of hibernation in the brown bear.

BACKGROUND: Hibernation has been a key area of research for several decades, essentially in small mammals in the laboratory, yet we know very little about what triggers or ends it in the wild. Do climatic factors, an internal biological clock, or physiological processes dominate? Using state-of-the-art tracking and monitoring technology on fourteen free-ranging brown bears over three winters, we recorded movement, heart rate (HR), heart rate variability (HRV), body temperature (Tb), physical activity, ambient temperature (TA), and snow depth to identify the drivers of the start and end of hibernation. We used behavioral change point analyses to estimate the start and end of hibernation and convergent cross mapping to identify the causal interactions between the ecological and physiological variables over time. RESULTS: To our knowledge, we have built the first chronology of both ecological and physiological events from before the start to the end of hibernation in the field. Activity, HR, and Tb started to drop slowly several weeks before den entry. Bears entered the den when snow arrived and when ambient temperature reached 0 °C. HRV, taken as a proxy of sympathetic nervous system activity, dropped dramatically once the bear entered the den. This indirectly suggests that denning is tightly coupled to metabolic suppression. During arousal, the unexpected early rise in Tb (two months before den exit) was driven by TA, but was independent of HRV. The difference between Tb and TA decreased gradually suggesting that bears were not thermoconforming. HRV increased only three weeks before exit, indicating that late activation of the sympathetic nervous system likely finalized restoration of euthermic metabolism. Interestingly, it was not until TA reached the presumed lower critical temperature, likely indicating that the bears were seeking thermoneutrality, that they exited the den. CONCLUSIONS: We conclude that brown bear hibernation was initiated primarily by environmental cues, but terminated by physiological cues.

Seroprevalence of Neospora caninum in gray wolves in Scandinavia.

Transmission of the protozoan parasite Neospora caninum between wild and domestic animals has gained some interest during recent years. Because of the close relationship between gray wolf (Canis lupus) and dog it has been suggested that gray wolf is a definitive host for the parasite. The aim of this study was to estimate the seroprevalence of N. caninum in Scandinavian gray wolves and to investigate any geographical patterns of the infection. The investigation was based on blood samples collected from 109 wolves between 1998 and 2009 within the Scandinavian wolf project Skandulv. They were analysed by N. caninum iscom ELISA and those with absorbance values exceeding 0.20 were also analysed by immunoblotting. Samples that were positive in both tests were deemed positive. Four (3.7%) wolves were positive at the first sampling. They were all sampled 2005 at different locations, and were both females and males. From one male wolf three samples were collected over a 7-year period. No antibodies were detected at the first sampling in 1998 when he was approximately 8 months old but when he was sampled again 5 and 7 years later the ELISA and immunoblotting were positive. The results indicate that N. caninum infection is present in Scandinavian wolves. It is unclear how the wolves acquired the infection.

Dental and periodontal health in free-ranging Swedish brown bears (Ursus arctos).

Dental data from 22 Swedish brown bears (Ursus arctos) were collected during April and May 2008, during the annual capture of free-ranging brown bears in Dalarna County, Sweden by the Scandinavian Brown Bear Research Project. The bears were of different genders and ages. All animals were weighed and subjected to physical examination and all were found to be in good condition. The oral cavity was inspected and photographed and abnormalities were recorded on a dental chart. One bear had mild class II malocclusion. All yearlings had varying numbers of incompletely erupted permanent teeth. All adult bears were missing one or more premolars. Tooth wear increased with age; the most affected teeth were the incisors followed by the canines, premolars and molars. Complicated fractures most commonly affected the canines. Fifteen animals had gross evidence of enamel defects, but the aetiology of these was not determined. There was a low prevalence of calculus and periodontal disease and none of the bears had caries infections. The mean pH of saliva collected from these animals was 9.75. Further studies, based on a larger sample size followed over time, will be required in order to evaluate the progression of dental disease in brown bears.

Reversible anaesthesia of free-ranging lions (Panthera leo) in Zimbabwe.

The combination of medetomidine-zolazepam-tiletamine with subsequent antagonism by atipamezole was evaluated for reversible anaesthesia of free-ranging lions (Panthera leo). Twenty-one anaesthetic events of 17 free-ranging lions (5 males and 12 females, body weight 105-211 kg) were studied in Zimbabwe. Medetomidine at 0.027-0.055 mg/kg (total dose 4-11 mg) and zolazepam-tiletamine at 0.38-1.32 mg/kg (total dose 50-275 mg) were administered i.m. by dart injection. The doses were gradually decreased to improve recovery. Respiratory and heart rates, rectal temperature and relative haemoglobin oxygen saturation (SpO2) were recorded every 15 min. Arterial blood samples were collected from 5 lions for analysis of blood gases and acid-base status. For anaesthetic reversal, atipamezole was administered i.m. at 2.5 or 5 times the medetomidine dose. Induction was smooth and all lions were anaesthetised with good muscle relaxation within 3.4-9.5 min after darting. The predictable working time was a minimum of 1 h and no additional drug doses were needed. Respiratory and heart rates and SpO2 were stable throughout anaesthesia, whereas rectal temperature changed significantly over time. Atipamezole at 2.5 times the medetomidine dose was sufficient for reversal and recoveries were smooth and calm in all lions independent of the atipamezole dose. First sign of recovery was observed 3-27 min after reversal. The animals were up walking 8-26 min after reversal when zolazepam-tiletamine doses < 1 mg/kg were used. In practice, a total dose of 6 mg medetomidine and 80 mg zolazepam-tiletamine and reversal with 15 mg atipamezole can be used for either sex of an adult or subadult lion. The drugs and doses used in this study provided a reliable, safe and reversible anaesthesia protocol for free-ranging lions.

Clinical evaluation of established optimal immobilizing doses of medetomidine-ketamine in captive reindeer (Rangifer tarandus tarandus).

OBJECTIVE: To evaluate clinical effects and repeatability of clinical effects for an optimal immobilizing dose of a combination of medetomidine hydrochloride (MED) and ketamine hydrochloride (KET) in reindeer (Rangifer tarandus tarandus). ANIMALS: 12 healthy 6- to 8-month old reindeer. PROCEDURE: Each reindeer was immobilized once with an initial dose (combination of 0.06 mg of MED/kg of body weight and 0.3 mg KET/kg) and twice with an optimal dose of MED-KET. Reversal was achieved with 5 mg of atipamezole/mg of MED injected 45 minutes after MED-KET administration. Observational variables were recorded. Oxygen saturation of arterial hemoglobin measured by pulse oximetry (Spo2), respiratory rate (RR), heart rate (HR), and rectal temperature (RT) were recorded 10, 25, and 40 minutes after immobilization. RESULTS: Mean time to first sign of sedation and time until a recumbent animal lifted its head were significantly reduced for reindeer given the optimal dose, compared with the initial dose. Mean Spo2 remained > 90% during initial immobilization; this value was significantly lower for the optimal dose, but increased during immobilization from 85 to 89%. At all doses, RR increased significantly throughout the recorded period; however, RT and HR were constant. Except for time until reindeer stood, all time variables, Spo2, RR, RT, and HR were repeatable. CONCLUSION AND CLINICAL RELEVANCE: mmobilization of captive reindeer achieved by use of the optimal dose established here is clinically acceptable, although Spo2 should be carefully monitored. Administration of the optimal dose produced the same clinical effect during repeated immobilization of the same reindeer.

Determination of optimal immobilizing doses of a medetomidine hydrochloride and ketamine hydrochloride combination in captive reindeer.

OBJECTIVE: To establish optimal immobilizing doses of medetomidine hydrochloride (MED) with ketamine hydrochloride (KET) for hand- and dart-administered injections in captive reindeer. ANIMALS: 12 healthy 6- to 9-month-old reindeer (Rangifer tarandus tarandus). Procedure An optimal dose was defined as a dose resulting in an induction time of 150 to 210 seconds, measured from the time of IM injection until recumbency. Initially, each stalled reindeer was immobilized by hand-administered injection. If the induction time was > 210 seconds, the dose was doubled for the next immobilization procedure. If it was < 150 seconds, the dose was halved for the next immobilization procedure. This iteration procedure was continued for each reindeer until an optimal dose was found. Later the reindeer was placed in a paddock and darted with its optimal dose as determined by hand-administered injection. Adjusting to a linear relationship between dose and induction time, optimal darting doses for each reindeer were predicted and later verified. RESULTS: The established mean optimal hand- and dart-administered doses were 0.10 mg of MED/kg of body mass with 0.50 mg of KET/kg, and 0.15 mg of MED/kg with 0.75 mg of KET/kg, producing mean induction times of 171 seconds and 215 seconds, respectively. The mean induction time after darting was 5 seconds greater than the upper limit of the predefined time interval. CONCLUSIONS AND CLINICAL RELEVANCE: The higher dose requirement of MED-KET administration outdoors, compared with indoors, was explained by factors inherent in the darting technique and the different confinements. The iteration and the prediction methods seem applicable for determination of optimal doses of MED-KET in reindeer. The iteration and the prediction procedures may be used to reduce the number of experimental animals in dose-response studies in other species.

The effects of medetomidine and its reversal with atipamezole on plasma glucose, cortisol and noradrenaline in cattle and sheep.

In the present study, we report the effect of medetomidine followed by atipamezole on plasma glucose, cortisol and noradrenaline in calves, cows and sheep. Eight calves, eight lactating dairy cows and eight adult female sheep were included in a crossover trial. The animals were injected i.v. with medetomidine (40 microg/kg), followed 60 min later by atipamezole i.v. (200 microg/kg) or saline. The wash-out period between experiments was 1 or 2 weeks. In every animal, medetomidine induced a marked hyperglycaemia, which was reversed by atipamezole. Cortisol levels increased significantly in cows and sheep, reaching levels 4-8-fold higher than the baseline levels 25-45 min after injection of medetomidine. Atipamezole did not affect the cortisol levels, except in sheep where an increase was observed. Plasma levels of noradrenaline decreased in cows and sheep after medetomidine injection, reflecting the inhibition of sympathetic activity by the drug. After injection of the antagonist, there was a large increase in noradrenaline levels. In conclusion, a high dose of medetomidine does not seem to reduce the overall endocrine stress response in cattle and sheep, which has previously been reported in other species.

A pharmacokinetic study including some relevant clinical effect of medetomidine and atipamezole in lactating dairy cows.

Medetomidine is the most potent and selective alpha2-agonist used in veterinary medicine and its effects can be antagonized by the alpha2-antagonist atipamezole. The pharmacokinetics of medetomidine and atipamezole were studied in a cross-over trial in eight lactating dairy cows. The animals were injected intravenously (i.v.) with medetomidine (40 microg/kg) followed by atipamezole i.v. (200 microg/kg) or saline i.v. after 60 min. Drug concentrations in plasma were measured by HPLC. After the injection of atipamezole, the concentration of medetomidine in plasma increased slightly, the mean increment being 2.7 ng/mL and the mean duration 12.1 min. However, atipamezole did not alter the pharmacokinetics of medetomidine. It is likely that the increase in medetomidine concentration is caused by displacement of medetomidine by atipamezole in highly perfused tissues. The volume of distribution at steady state (Vss) for medetomidine followed by saline and medetomidine followed by atipamezole was 1.21 and 1.32 L/kg, respectively, whereas the total clearance (Cl) values were 24.2 and 25.8 mL/min x kg. Vss and Cl values for atipamezole were 1.77 mL/kg and 48.1 mL/min x kg, respectively. Clinically, medetomidine significantly reduced heart rate and increased rectal temperature for 45 min. Atipamezole reversed the sedative effects of medetomidine. However, all the animals, except one, relapsed into sedation at an average of 80 min after injection of the antagonist.

Antibodies against orthopoxviruses in wild carnivores from Fennoscandia.

Two hundred and three sera obtained in 1993-96 from red foxes (Vulpes vulpes), lynx (Lynx lynx), brown bears (Ursus arctos) and wolverines (Gulo gulo) in Fennoscandia (Norway, Sweden, and Finland) were examined for the presence of anti-orthopoxvirus antibodies by a competition enzyme linked immunosorbent assay (ELISA). High prevalences were found for the red foxes in Norway (7/62, 11%) and Finland (7/14, 50%). While only one of 73 (1%) lynx from Finland had anti-orthopoxvirus antibodies, a high prevalence was found in sera from the Sarek National Park in Sweden (5/17, 29%). In addition, anti-orthopoxvirus antibodies were found in one brown bear from the same area (1/45, 2%), whereas none of the 14 wolverines were seropositive. This is the first report of anti-orthopoxvirus antibodies in the brown bear and the lynx, and the first screening for such antibodies in Sweden and Finland. These results indicate that orthopoxviruses are distributed in Sweden and Finland as well as in Norway, and that the red fox and the European lynx may serve as indicator species for the presence of orthopoxviruses in the local populations of small mammals.

Pharmacokinetics of medetomidine and atipamezole in dairy calves: an agonist-antagonist interaction.

Medetomidine and atipamezole are licensed for use in dogs and cats in several countries and are highly selective and specific alpha2-adrenoceptor agents. The pharmacokinetics of the agonist medetomidine and the antagonist atipamezole were studied in a cross-over trial in eight dairy calves. The animals were injected intravenously (i.v.) with medetomidine (40 microg/kg i.v.), followed by atipamezole (200 microg/kg i.v.) or saline after 60 min. The wash-out period between experiments was 1 week. Drug concentrations in plasma were determined using HPLC. Atipamezole significantly (P < 0.05) increased the AUMC and MRT of medetomidine due to an increase in the medetomidine concentration when atipamezole was injected i.v. The mean increment in medetomidine concentration was 6.4 ng/mL, increased levels having a mean duration of 39.4 min. Other pharmacokinetic parameters of medetomidine were not significantly altered by atipamezole. Sedative effects of the agonist, and the effectiveness of the antagonist were recorded. All the animals relapsed into sedation on average 80 min after reversal with atipamezole. It is likely that the increase in medetomidine concentration after the injection of atipamezole i.v. results from displacement of medetomidine from alpha2-adrenoceptors in highly perfused tissues.

Reversal of medetomidine-induced sedation in reindeer (Rangifer tarandus tarandus) with atipamezole increases the medetomidine concentration in plasma.

The pharmacokinetics of two potent alpha 2-adrenoceptor agents that can be used for immobilization (medetomidine) and reversal (atipamezole) of the sedation in mammals, were studied in three reindeer (Rangifer tarandus tarandus) in winter and again in summer. Medetomidine (60 micrograms/kg) was injected intravenously (i.v.), followed by atipamezole (300 micrograms/kg) intravenously 60 min later. Drug concentrations in plasma were measured by HPLC. The administration of atipamezole resulted in an immediate 2.5-3.5 fold increase in the medetomidine concentration in plasma. Clearance for medetomidine (median 19.3 mL/min.kg) was lower than clearance for atipamezole (median 31.0 mL/min.kg). The median elimination half-lives of medetomidine and atipamezole in plasma were 76.1 and 59.9 min, respectively. The animals became resedated 0.5-1 h after the reversal with atipamezole. Resedation may be explained by the longer elimination half-life of medetomidine compared to atipamezole.

Xylazine-induced sedation in axis deer (Axis axis) and its reversal by atipamezole.

Eight free-ranging axis deer (Axis axis) were captured in drive nets and injected with xylazine (3.4 +/- 0.1 mg/kg; mean +/- SEM) intramuscularly using a hand-held syringe. Xylazine induced complete immobilization and sedation in three animals, heavy sedation in three, and moderate sedation in two. The mean induction time was 10.4 +/- 1.0 min. The mean rectal temperature, heart and respiratory rates of immobilized animals were 39.2 +/- 0.4 degrees C, 75.5 +/- 6.5 beats/min and 62.1 +/- 4.2 breaths/min, respectively. All the animals were given atipamezole intravenously for reversal. The mean time from injection of xylazine to administration of atipamezole was 37.8 +/- 4.6 min. A dose ratio (w/w) for xylazine:atipamezole-HCl of 10:1 was used. The mean time from injection of atipamezole to mobility was 2.41 +/- 0.58 min. Atipamezole given intravenously effectively antagonized xylazine-induced sedation in axis deer. Only one animal showed signs of overalertness after reversal and no cases of resedation were observed.