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Hair cortisol concentration (HCC) is being used increasingly to evaluate long‐term stress in many mammalian species. Most of the cortisol is assumed to passively diffuse from circulating blood into hair follicles and gradually accumulate in growing hair. However, our research with free‐ranging grizzly bears (Ursus arctos) suggests HCC increases significantly within several hours following capture, a time too brief to be explained by this mechanism alone. In this study with captive grizzly bears, we sought to determine if a brief spike in blood cortisol concentration, thus mimicking a single stressful event, would cause an increase in HCC over a 7‐day period. To do this, we administered a single intravenous dose (5 μg/kg) of cosyntropin to three captive unanaesthetised adult female grizzly bears on two occasions, during April when hair growth was arrested and during August when hair was growing. In both trials, the cosyntropin caused a two‐fold or greater increase in serum cortisol levels within 1 hr but did not appear to influence HCC at 1, 48, and 168 hr following cosyntropin administration. We conclude the cosyntropin‐induced cortisol spike was likely insignificant when compared to the adrenocortical response that occurs in free‐ranging bears when captured. We suggest further study with a larger sample of captive bears to evaluate the combined effects of anaesthesia and multiple doses of cosyntropin administered over several hours would better simulate the adrenocortical response of free‐ranging grizzly bears during capture., Administration of cosyntropin to captive grizzly bears caused increased serum cortisol levels within 1 hr. However, cosyntropin did not influence hair cortisol concentration at 1, 48, and 168 hr following administration. Cosyntropin‐induced hair cortisol levels were insignificant compared to free‐ranging bears during capture.

In contrast to most industrialized countries, maternal mortality in the USA is rising. Cardiovascular disease, both acquired heart disease (e.g. coronary disease, arrhythmias, and heart failure), as well as congenital heart disease survivors, are all potentially important factors in explaining this worrisome trend. Increase in acquired cardiac disease is likely attributable to greater rates of obesity, diabetes, hypertension, and an increase in the incidence of advanced maternal age, while congenital heart disease in pregnancy is increasing due to advances in pediatric cardiovascular surgery. Despite the growing cardiovascular risk of pregnant women, most obstetricians and cardiologists have limited experience in caring for women with heart disease. Accordingly, management is largely guided by expert opinion likely to vary greatly across centers. To address these challenges, a multidisciplinary approach to care that includes both cardiologists and obstetricians could leverage the knowledge of both specialties and support streamlined communication between the patient and her providers. Our experience highlights the necessary components and essential infrastructure for building a center of excellence in treating pregnant women with heart disease.Condensation: A guide for creating a center of excellence for prenatal care for women with cardiovascular disease.The problem: Cardiac disease is the leading cause of maternal mortality, and pregnancies affected by cardiac disease continue to rise, both congenital and acquired.The solution: Maternal fetal medicine, obstetricians, and cardiologists can join together in tertiary facilities to create Maternal Cardiac Centers of Excellence to provide multidisciplinary, structured care for these high-risk patients.

Purpose of review Cardiovascular disease (CVD) is the number one cause of maternal mortality in the USA. There are many cardiac conditions which pose significant risk to maternal health, and these women should be offered options to avoid unwanted pregnancies. Individualized contraceptive counseling focusing on woman’s desire for future pregnancy, comorbid conditions, and desire for hormone or non-hormonal (contraceptive) options is paramount to avoid adverse or unwanted side effects. The purpose of this review is to give general guidance on prescribing both hormonal and non-hormonal contraceptives for providers caring for women with heart disease. Recent findings Specific recommendation for the use of either non-hormonal or hormonal contraception requires knowledge of the types of contraceptive options available, cost, failure rates, and contraindications to use. Newer progestin-only options have become available and should be considered first-line therapy for women with cardiovascular disease. Summary The physiologic burden of pregnancy on the cardiovascular system can cause significant maternal morbidity and mortality for women with underlying CVD. These women should be offered safe and effective options for birth control, and both cardiology and obstetrical providers alike should possess fundamental knowledge of appropriate options.

Revealing the mechanisms underlying the reversible physiology of hibernation could have applications to both human and animal health as hibernation is often associated with disease-like states. The present study uses RNA-sequencing to reveal the tissue and seasonal transcriptional changes occurring in grizzly bears (

Across China and Southeast Asia, over 17,000 bears are currently farmed for bile, predominantly for traditional Chinese medicines. Bears on farms in China are cage confined and undergo repeated daily bile extraction facilitated by surgically implanted catheters or gallbladder fistulas. Numerous health problems have been reported in bile-farmed bears including peritonitis, abdominal hernias, and extraction site abscessation. Between 2009 and 2014, five Asiatic black bears ( Ursus thibetanus) and one Asiatic black/Eurasian brown bear ( Ursus arctos arctos) hybrid, rescued from the bear bile industry in China, died from ruptured and/or dissecting aortic aneurysm. Medical records were reviewed and two bears exhibited no clinical signs prior to death. In four bears, clinical findings varied and included increased stereotypic behavior prior to death, epistaxis, retinal lesions, dysphagia, weight loss, and acute onset of hyporexia. On postmortem examination, hemopericardium with dissection and/or rupture of the ascending aorta and left ventricular wall hypertrophy were present in all cases. No evidence of infectious disease, connective tissue disorders, or congenital cardiac disease was identified. Based on these observations screening thoracic radiography was performed on all bears at the rescue center and aortic dilation was identified in 73 of 134 (54.5%) bile-extracted bears. To the authors' knowledge, aortic aneurysm, rupture, and/or dissection have not been previously reported in any bear species and the high prevalence in this population of bears suggests an association with bile-farming practices. Future studies are needed to investigate the etiopathogenesis of this condition to aid in early diagnosis and improved management of bears being rescued from bile farms across Asia.

The fukutin-related protein P448L mutant mouse replicates many pathologies common to limb girdle muscular dystrophy 2i (LGMD2i) and is a potentially strong candidate for relevant drug screening studies. Because striated muscle function remains relatively uncharacterized in this mouse, we sought to identify metabolic, functional and histological metrics of exercise and cardiac performance. This was accomplished by quantifying voluntary exercise on running wheels, forced exercise on respiratory treadmills and cardiac output with echocardiography and isoproterenol stress tests. Voluntary exercise revealed few differences between wild-type and P448L mice. By contrast, peak oxygen consumption (VO2peak) was either lower in P448L mice or reduced with repeated low intensity treadmill exercise while it increased in wild-type mice. P448L mice fatigued quicker and ran shorter distances while expending 2-fold more calories/meter. They also received over 6-fold more motivational shocks with repeated exercise. Differences in VO2peak and resting metabolic rate were consistent with left ventricle dysfunction, which often develops in human LGMD2i patients and was more evident in female P448L mice, as indicated by lower fractional shortening and ejection fraction values and higher left ventricle systolic volumes. Several traditional markers of dystrophinopathies were expressed in P448L mice and were exacerbated by exercise, some in a muscle-dependent manner. These include elevated serum creatine kinase and muscle central nucleation, smaller muscle fiber cross-sectional area and more striated muscle fibrosis. These studies together identified several markers of disease pathology that are shared between P448L mice and human subjects with LGMD2i. They also identified novel metrics of exercise and cardiac performance that could prove invaluable in preclinical drug trials.NEW & NOTEWORTHY Limb-girdle muscular dystrophy 2i is a rare dystroglycanopathy that until recently lacked an appropriate animal model. Studies with the FKRP P448L mutant mouse began assessing muscle structure and function as well as running gait. Our studies further characterize systemic muscle function using exercise and cardiac performance. They identified many markers of respiratory, cardiac and skeletal muscle function that could prove invaluable to better understanding the disease and more importantly, to preclinical drug trials.

In the USA, maternal mortality has been rising since the 1980s. Cardiovascular disease is recognized as the leading cause of this worrisome trend, and a multidisciplinary approach to the care of patients with cardiovascular conditions during pregnancy is becoming increasingly important. We outline the literature supporting this multidisciplinary approach, highlight our center’s experience in building and expanding an integrated cardio-obstetrics practice, and provide guidance regarding patient selection and management within a combined practice. Antenatal management patterns and delivery planning for patients with cardiovascular disease during pregnancy vary substantially among cardiovascular and obstetric and maternal fetal medicine practices in the USA. The need for multidisciplinary care between cardiologists and obstetricians is evident and has been supported by best practice statements from the American Heart Association, the American College of Obstetrics and Gynecology, and the Cardiac Disease in Pregnancy Study (CARPREG) investigators, whose CARPREG II risk score included “late first antenatal visit” as a predictor of adverse outcomes of pregnancy. We have solid evidence supporting a multidisciplinary approach to the care of patients with cardiac conditions in pregnancy. This approach is optimal because it facilitates a consistent and clear message to the patient (and those caring for each patient) regarding management and risks associated with pregnancy, as well as subsequent risk and postpartum follow-up. We support the extension of clinical collaboration between obstetricians and cardiologists to the research realm and know that working together to investigate the outcomes of moms with heart conditions and their babies will provide clinically meaningful information to support the care of these unique patients.

The purpose of this study was to investigate changes in expression of known cellular regulators of metabolism during hyperphagia (Sept) and hibernation (Jan) in skeletal muscle and adipose tissue of brown bears and determine whether signaling molecules and transcription factors known to respond to changes in cellular energy state are involved in the regulation of these metabolic adaptations. During hibernation, serum levels of cortisol, glycerol, and triglycerides were elevated, and protein expression and activation of AMPK in skeletal muscle and adipose tissue were reduced. mRNA expression of the co-activator PGC-1α was reduced in all tissues in hibernation whereas mRNA expression of the transcription factor PPAR-α was reduced in the vastus lateralis muscle and adipose tissue only. During hibernation, gene expression of ATGL and CD36 was not altered; however, HSL gene expression was reduced in adipose tissue. During hibernation gene expression of the lipogenic enzyme DGAT in all tissues and the expression of the FA oxidative enzyme LCAD in the vastus lateralis muscle were reduced. Gene and protein expression of the glucose transporter GLUT4 was decreased in adipose tissue in hibernation. Our data suggest that high cortisol levels are a key adaptation during hibernation and link cortisol to a reduced activation of the AMPK/PGC-1α/PPAR-α axis in the regulation of metabolism in skeletal muscle and adipose tissue. Moreover, our results indicate that during this phase of hibernation at a time when metabolic rate is significantly reduced metabolic adaptations in peripheral tissues seek to limit the detrimental effects of unduly large energy dissipation.

Maternal mortality in the United States is highest among all developed nations and continues to rise. The leading cause of morbidity and mortality during pregnancy and the postpartum period is cardiovascular disease. While there are large European and Canadian studies exploring the care and outcomes of moms with heart disease in pregnancy, there are no large prospective studies to guide the care of this growing group of patients in the US. We review the current approach to the management of patients with heart disease in pregnancy and the gaps in knowledge thereof. Currently, antenatal management and delivery planning are highly variable for patients with heart disease in pregnancy and maternal risk models’ application to the US patient population is limited by their derivation from an international cohort of patients and their focus on patients with congenital heart disease. As the need for interdisciplinary care between cardiologists and obstetricians becomes evident, and as broad research efforts within this space are very much needed, we propose a research collaborative called the Heart Outcomes in Pregnancy: Expectations (HOPE) for Mom and Baby Registry. The HOPE Registry aims to address key clinical questions surrounding the preconception period, antenatal care, delivery planning and outcomes, and long-term postpartum care and outcomes of these unique patients. We have made progress in recent years by recognizing the clinical need to address and standardize the management of patients with heart disease in pregnancy. We now must initiate and propel US-based cardio-obstetrics research to address key gaps in knowledge and variability in the care of patients with heart disease in pregnancy.

Recent studies suggest that bears have relatively high cognitive capabilities. However, cognitive processes and problem-solving abilities remain relatively unexplored in bear species. We studied the capacity for 8 captive brown bears ( Ursus arctos ) to move and use inanimate objects to obtain a food reward. We recorded their behaviors during the problem-solving process using a behavioral ethogram. Three items, a large log, a small log, and a box, were placed in an outdoor enclosure. As the bears progressed through 3 stages of trials, they would need to manipulate the objects and displace them into the proper location and orientation to climb atop to reach a suspended food reward. Completion of the third and final stage was deemed to be evidence of tool use. Six of the 8 bears were capable of tool use. Most bears (>90% of trials) were successful in completing the final stage in

Training nonhuman animals in captivity for participation in routine husbandry procedures is believed to produce a lower stress environment compared with undergoing a general anesthetic event for the same procedure. This hypothesis rests largely on anecdotal evidence that the captive subjects appear more relaxed with the trained event. Blood markers of physiological stress responses were evaluated in 4 captive grizzly bears (Ursus arctos horribilis) who were clicker-trained for blood collection versus 4 bears who were chemically immobilized for blood collection. Serum cortisol and immunoglobulin A (IgA) and plasma β-endorphin were measured as indicators of responses to stress. Plasma β-endorphin was not different between the groups. Serum IgA was undetectable in all bears. Serum cortisol was undetectable in all trained bears, whereas chemically immobilized bears had marked cortisol elevations (p .05). The highest cortisol elevations were found in 2 bears with extensive recent immobilization experience. These findings support the use of positive reinforcement training for routine health procedures to minimize anxiety.

Increased land use by polar bears (Ursus maritimus) due to climate‐change‐induced reduction of their sea‐ice habitat illustrates the impact of climate change on species distributions and the difficulty of conserving a large, highly specialized carnivore in the face of this global threat. Some authors have suggested that terrestrial food consumption by polar bears will help them withstand sea‐ice loss as they are forced to spend increasing amounts of time on land. Here, we evaluate the nutritional needs of polar bears as well as the physiological and environmental constraints that shape their use of terrestrial ecosystems. Only small numbers of polar bears have been documented consuming terrestrial foods even in modest quantities. Over much of the polar bear's range, limited terrestrial food availability supports only low densities of much smaller, resident brown bears (Ursus arctos), which use low‐quality resources more efficiently and may compete with polar bears in these areas. Where consumption of terrestrial foods has been documented, polar bear body condition and survival rates have declined even as land use has increased. Thus far, observed consumption of terrestrial food by polar bears has been insufficient to offset lost ice‐based hunting opportunities but can have ecological consequences for other species. Warming‐induced loss of sea ice remains the primary threat faced by polar bears.

Mammalian hibernation has intrigued scientists due to extreme variations in normal seasonal physiological homeostasis. Numerous species manifest a hibernation phenotype although the characteristics of the hypometabolic state can be quite different. Ground squirrels (e.g., Sciuridae) are often considered the prototypical hibernator as individuals in this genus transition from an active, euthermic state (37 °C) to a nonresponsive hibernating state where torpid body temperature commonly falls to 3-5 °C. However, the hibernating state is not continuous as periodic warming and arousals occur. In contrast, the larger hibernators of genus Ursus are less hypothermic (body temperatures decline from approximately 37°-33 °C), are more reactive, and cyclical arousals do not occur. Both species dramatically reduce cardiac output during hibernation from the active state (bears ~75 % reduction in bears and ~97 % reduction in ground squirrels), and both species demonstrate hypokinetic atrial chamber activity. However, there are several important differences in cardiac function between the two groups during hibernation. Left ventricular diastolic filling volumes and stroke volumes do not differ in bears between seasons, but increased diastolic and stroke volumes during hibernation are important contributors to cardiac output in ground squirrels. Decreased cardiac muscle mass and increased ventricular stiffness have been found in bears, whereas ground squirrels have increased cardiac muscle mass and decreased ventricular stiffness during hibernation. Molecular pathways of cardiac muscle plasticity reveal differences between the species in the modification of sarcomeric proteins such as titin and α myosin heavy chain during hibernation. The differences in hibernation character are likely to account for the alternative cardiac phenotypes and functional strategies manifested by the two species. Molecular investigation coupled with better knowledge of seasonal physiological alterations is dramatically advancing our understanding of small and large hibernators and their evolutionary differences.

The pace at which science continues to advance is astonishing. From cosmology, microprocessors, structural engineering, and DNA sequencing our lives are continually affected by science-based technology. However, progress in treating human ailments, especially age-related conditions such as cancer and Alzheimer's disease, moves at a relative snail's pace. Given that the amount of investment is not disproportionately low, one has to question why our hopes for the development of efficacious drugs for such grievous illnesses have been frustratingly unrealized. Here we discuss one aspect of drug development –rodent models – and propose an alternative approach to discovery research rooted in evolutionary experimentation. Our goal is to accelerate the conversation around how we can move towards more translative preclinical work.

The confluence of obesity and diabetes as a worldwide epidemic necessitates the discovery of new therapies. Success in this endeavor requires translatable preclinical studies, which traditionally employ rodent models. As an alternative approach, we explored hibernation where obesity is a natural adaptation to survive months of fasting. Here we report that grizzly bears exhibit seasonal tripartite insulin responsiveness such that obese animals augment insulin sensitivity but only weeks later enter hibernation-specific insulin resistance (IR) and subsequently reinitiate responsiveness upon awakening. Preparation for hibernation is characterized by adiposity coupled to increased insulin sensitivity via modified PTEN/AKT signaling specifically in adipose tissue, suggesting a state of "healthy" obesity analogous to humans with PTEN haploinsufficiency. Collectively, we show that bears reversibly cope with homeostatic perturbations considered detrimental to humans and describe a mechanism whereby IR functions not as a late-stage metabolic adaptation to obesity, but rather a gatekeeper of the fed-fasting transition.

We used enzyme immunoassays to measure testosterone, progesterone, estradiol and cortisol concentrations in serial hair samples collected from captive adult brown bears. Reproductive hormone levels changed throughout the year in step with different reproductive events underscoring the strong potential for these measurement to be used to augment non-invasive genetic sampling., Recognizing the potential value of steroid hormone measurements to augment non-invasive genetic sampling, we developed procedures based on enzyme-linked immunoassays to quantify reproductive steroid hormone concentrations in brown bear (Ursus arctos) hair. Then, using 94 hair samples collected from eight captive adult bears over a 2-year period, we evaluated (i) associations between hair concentrations of testosterone, progesterone, estradiol and cortisol; (ii) the effect of collecting by shaving vs. plucking; and (iii) the utility of reproductive hormone profiles to differentiate sex and reproductive state. Sample requirements (125 mg of guard hair) to assay all hormones exceeded amounts typically obtained by non-invasive sampling. Thus, broad application of this approach will require modification of non-invasive techniques to collect larger samples, use of mixed (guard and undercoat) hair samples and/or application of more sensitive laboratory procedures. Concentrations of hormones were highly correlated suggesting their sequestration in hair reflects underlying physiological processes. Marked changes in hair hormone levels during the quiescent phase of the hair cycle, coupled with the finding that progesterone concentrations, and their association with testosterone levels, differed markedly between plucked and shaved hair samples, suggests steroids sequestered in hair were likely derived from various sources, including skin. Changes in hair hormone concentrations over time, and in conjunction with key reproductive events, were similar to what has been reported concerning hormonal changes in the blood serum of brown bears. Thus, potential for the measurement of hair reproductive hormone levels to augment non-invasive genetic sampling appears compelling. Nonetheless, we are conducting additional validation studies on hair collected from free-ranging bears, representative of all sex, age and reproductive classes, to fully evaluate the utility of this approach for brown bear conservation and research.

The majority of terrestrial locomotion studies have focused on parasagittal motion and paid less attention to forces or movement in the frontal plane. Our previous research has shown that grizzly bears produce higher medial ground reaction forces (lateral pushing from the animal) than would be expected for an upright mammal, suggesting frontal plane movement may be an important aspect of their locomotion. To examine this, we conducted an inverse dynamics analysis in the sagittal and frontal planes, using ground reaction forces and position data from three high-speed cameras of four adult female grizzly bears. Over the speed range collected, the bears used walks, running walks and canters. The scapulohumeral joint, wrist and the limb overall absorb energy (average total net work of the forelimb joints, -0.97 W kg

Global warming has the potential to reduce arctic sea ice and thereby increase the length of summer–fall fasting when polar bears (Ursus maritimus) lose access to most marine mammals. To evaluate the consequences of such changes, we compared the cost of fasting by polar bears with hibernation by brown bears (U. arctos), American black bears (U. americanus), and polar bears and made projections about tissue reserves polar bears will need to survive and reproduce as fasts become longer. Hibernating polar bears expend energy at the same rate per unit mass as do brown bears and black bears. However, daily mass losses, energy expenditures, and the losses of lean mass are much higher in fasting, active polar bears than in hibernating bears. The average pregnant polar bear living around Hudson Bay during the 1980s and 1990s could fast for 10.0 6 2.3 months (¯ X 6 SD), and the average lactating female with cubs born during the preceding winter could fast for 4.2 6 1.9 months. Thus, some pregnant or lactating females with lower levels of body fat content were already approaching or beyond the constraint of being able to produce cubs and survive the required 8 months of fasting if producing new offspring or 4 months if accompanied by older offspring. Pregnant or lactating females and their dependent offspring have the most tenuous future as global warming occurs. Thus, we predict a significant reduction in productivity with even modest increases in global warming for polar bears living in the very southern part of their range and are concerned about more northern populations depending on their ability to accumulate increasing amounts of fat.

Seasonal cycles of reproduction, migration, and hibernation are often synchronized to changes in daylength (photoperiod). Ecological and evolutionary pressures have resulted in physiological specializations enabling animals to occupy a particular temporal niche within the diel cycle leading to characteristic activity patterns. In this study, we characterized the annual locomotor activity of captive brown bears (Ursus arctos). Locomotor activity was observed in 18 bears of varying ages and sexes during the active (Mar-Oct) and hibernating (Nov-Feb) seasons. All bears exhibited either crepuscular or diurnal activity patterns. Estimates of activity duration (α) and synchronization to the daily light:dark cycle (phase angles) indirectly measured photoresponsiveness. α increased as daylength increased but diverged near the autumnal equinox. Phase angles varied widely between active and hibernating seasons and exhibited a clear annual rhythm. To directly test the role of photoperiod, bears were exposed to controlled photoperiod alterations. Bears failed to alter their daily activity patterns (entrain) to experimental photoperiods during the active season. In contrast, photic entrainment was evident during hibernation when the daily photocycle was shifted and when bears were exposed to a skeleton (11:1:11:1) photoperiod. To test whether entrainment to nonphotic cues superseded photic entrainment during the active season, bears were exposed to a reversed feeding regimen (dark-fed) under a natural photocycle. Activity shifted entirely to a nocturnal pattern. Thus daily activity in brown bears is highly modifiable by photoperiod and food availability in a stereotypic seasonal fashion.

The number, size, and survival of bear cubs emerging from winter dens depend on maternal condition prior to entering the den. We hypothesized that delayed implantation provides flexibility in timing of birth such that pregnant females are able to track environmental or body conditions long after conception to optimize reproductive output in a changing environment. We tested the hypotheses that causative links between maternal condition and size of newly emerging brown bear (Ursus arctos) cubs were females in superior condition give birth earlier and, thereby, lactate longer in the den than females in poorer condition; and females in superior condition produce more milk or higher quality milk, which accelerates cub growth relative to females in poorer condition. No brown bear with a body fat content 20% produced cubs even though breeding occurred. Brown bears that were fat gave birth earlier than those that were lean. Cubs nursing from fat mothers grew faster than those nursing from lean mothers. The combination of an earlier birth date and faster growth by cubs produced from fat mothers increased mass of brown bear and polar bear (U. maritimus) twins at den emergence by 330– 360 g for each unit increase in percent maternal body fat content when entering hibernation.

The natural aging process results in the physiological decline of multiple tissues and organ systems. Changes commonly occur with middle age and include decreased skeletal muscle mass, bone mineral density, cardiac output, and insulin sensitivity, and increased adiposity, all of which can contribute to the onset of sarcopenia, osteoporosis, heart failure, or type 2 diabetes. Recent studies suggest that myostatin may influence many of these systems. We therefore sought to determine whether they are affected by aging, especially in ‘middle-aged’Mstn−/−mice (12–20 months old (m.o.)). Although body weights were similar in wild-type (WT) andMstn−/−mice, lean fat-free mass and skeletal muscles composed of predominantly type I, II, and mixed fibers were significantly heavier inMstn−/−mice. These differences were accompanied by lower total adiposity, especially in female mice, white and brown fat pad weights, and adipocyte size. Hearts were heavier inMstn−/−mice across a large age range (3–24 m.o.) and exhibited signs of dilated cardiomyopathy at rest, which include lower strain measurements compared with WT myocardium. However,Mstn−/−mice responded better to isoproterenol stress tests with greater increases in fractional shortening and ejection fraction—differences that were again more apparent in females and which are consistent with physiological cardiac hypertrophy. Spleens and kidneys were also smaller, although histologically normal, inMstn−/−mice. These data together suggest that attenuating myostatin could potentially prevent or possibly treat pathological conditions that develop with age. Additional studies are nevertheless needed to definitively assess potential risks to cardiac function.

Reproductive physiology in North American ursids is characterized by mating from spring to early summer, delayed implantation, and birth during hibernation. During spring 2008, a captive adult female brown bear was mated with two adult males. Pregnancy was determined by elevated progesterone concentrations during late fall before hibernation. Two male cubs were born on December 31, 2008, and a third female cub was born 17 days later on January 16. All were successfully raised and all were confirmed to have identical paternity. When normalized to age, cub growth rates did not differ. To our knowledge, this is the first documented case of markedly different birth dates in a single litter of brown bear cubs. Zoo Biol 31: 255–259, 2012. © 2011 Wiley Periodicals, Inc.

Disuse typically causes an imbalance in bone formation and bone resorption, leading to losses of cortical and trabecular bone. In contrast, bears maintain balanced intracortical remodeling and prevent cortical bone loss during disuse (hibernation). Trabecular bone, however, is more detrimentally affected than cortical bone in other animal models of disuse. Here we investigated the effects of hibernation on bone remodeling, architectural properties, and mineral density of grizzly bear (Ursus arctos horribilis) and black bear (Ursus americanus) trabecular bone in several skeletal locations. There were no differences in bone volume fraction or tissue mineral density between hibernating and active bears or between pre- and post-hibernation bears in the ilium, distal femur, or calcaneus. Though indices of cellular activity level (mineral apposition rate, osteoid thickness) decreased, trabecular bone resorption and formation indices remained balanced in hibernating grizzly bears. These data suggest that bears prevent bone loss during disuse by maintaining a balance between bone formation and bone resorption, which consequently preserves bone structure and strength. Further investigation of bone metabolism in hibernating bears may lead to the translation of mechanisms preventing disuse induced bone loss in bears into novel treatments for osteoporosis.

Although myostatin negatively regulates skeletal muscle growth, its function in heart is virtually unknown. Herein we demonstrate that it inhibits basal and IGF-stimulated proliferation and differentiation and also modulates cardiac excitation–contraction (EC) coupling. Loss of myostatin induced eccentric hypertrophy and enhanced cardiac responsiveness to β-adrenergic stimulation in vivo. This was due to myostatin null ventricular myocytes having larger [Ca2+]i transients and contractions and responding more strongly to β-adrenergic stimulation than wild-type cells. Enhanced cardiac output and β-adrenergic responsiveness of myostatin null mice was therefore due to increased SR Ca2+ release during EC coupling and to physiological hypertrophy, but not to enhanced myofilament function as determined by simultaneous measurement of force and ATPase activity. Our studies support the novel concept that myostatin is a repressor of physiological cardiac muscle growth and function. Thus, the controlled inhibition of myostatin action could potentially help repair damaged cardiac muscle by inducing physiological hypertrophy.

Rationale: The giant protein titin plays key roles in myofilament assembly and determines the passive mechanical properties of the sarcomere. The cardiac titin molecule has 2 mayor elastic elements, the N2B and the PEVK region. Both have been suggested to determine the elastic properties of the heart with loss of function data only available for the N2B region. Objective: The purpose of this study was to investigate the contribution of titin’s proline–glutamate–valine–lysine (PEVK) region to biomechanics and growth of the heart. Methods and Results: We removed a portion of the PEVK segment (exons 219 to 225; 282 aa) that corresponds to the PEVK element of N2B titin, the main cardiac titin isoform. Adult homozygous PEVK knockout (KO) mice developed diastolic dysfunction, as determined by pressure-volume loops, echocardiography, isolated heart experiments, and muscle mechanics. Immunoelectron microscopy revealed increased strain of the N2B element, a spring region retained in the PEVK-KO. Interestingly, the PEVK-KO mice had hypertrophied hearts with an induction of the hypertrophy and fetal gene response that includes upregulation of FHL proteins. This contrasts the cardiac atrophy phenotype with decreased FHL2 levels that result from the deletion of the N2B element. Conclusions: Titin’s PEVK region contributes to the elastic properties of the cardiac ventricle. Our findings are consistent with a model in which strain of the N2B spring element and expression of FHL proteins trigger cardiac hypertrophy. These novel findings provide a molecular basis for the future differential therapy of isolated diastolic dysfunction versus more complex cardiomyopathies.

Records were reviewed from 83 cases to determine the main causes and clinical significance of feline pericardial effusion. The most common causes included hypertrophic cardiomyopathy with congestive heart failure, neoplasia, and systemic infection. Most cases had concurrent or secondary pleural effusion or pulmonary edema, with clinical signs of respiratory disease. However, several cases appeared to be affected solely by pericardial effusion rather than pulmonary pathology. Feline pericardial effusion remains an infrequent diagnosis, but its clinical relevance and association with severe cardiac and extracardiac disease warrant diagnostic evaluation.

Titin is a giant protein that is in charge of the assembly and passive mechanical properties of the sarcomere. Cardiac titin contains a unique N2B region, which has been proposed to modulate elasticity of the titin filament and to be important for hypertrophy signaling and the ischemic stress response through its binding proteins FHL2 and αB-crystallin, respectively. To study the role of the titin N2B region in systole and diastole of the heart, we generated a knockout (KO) mouse deleting only the N2B exon 49 and leaving the remainder of the titin gene intact. The resulting mice survived to adulthood and were fertile. Although KO hearts were small, they produced normal ejection volumes because of an increased ejection fraction. FHL2 protein levels were significantly reduced in the KO mice, a finding consistent with the reduced size of KO hearts. Ultrastructural analysis revealed an increased extension of the remaining spring elements of titin (tandem Ig segments and the PEVK region), which, together with the reduced sarcomere length and increased passive tension derived from skinned cardiomyocyte experiments, translates to diastolic dysfunction as documented by echocardiography. We conclude from our work that the titin N2B region is dispensable for cardiac development and systolic properties but is important to integrate trophic and elastic functions of the heart. The N2B-KO mouse is the first titin-based model of diastolic dysfunction and, considering the high prevalence of diastolic heart failure, it could provide future mechanistic insights into the disease process.

The accuracy of bioptome placement for endomyocardial biopsy was evaluated using standard fluoroscopic guidance and compared simultaneously with two-dimensional echocardiography in six healthy subadult grizzly bears (Ursus arctos horribilis). Despite perceived adequate positioning of the bioptome toward the septum when judged using fluoroscopy, only one out of the six placements were actually positioned in the right ventricular apex toward the septum when evaluated using two-dimensional echocardiography. The bioptome was readily relocated to the right ventricular apex/septal location by echocardiography. The forceps were easily visualized at all times and the open cups were readily directed into the desired location for biopsy. Based on a subjective score for tissue quantity from 1 to 4 (poor to excellent), biopsies collected by echocardiographic-guided technique had a mean score of 3.4, while biopsies collected by fluoroscopic-guided technique had a mean score of 1.8. In summary, this study suggests that endomyocardial biopsy locations can be accurately positioned using two-dimensional echocardiography with the advantages of less radiation, lower procedural costs, and direct visualization of the sampling site. Clear definition of endocardial surface as afforded by echocardiography may enhance tissue sample quality and lower potential complications from this procedure.

This prospective study was designed to investigate D-dimer concentrations in clinically healthy dogs, clinically ill dogs without thromboembolic disease (TE), and dogs with TE. The goals of this study were to determine whether the coagulation cascade is activated in nonembolic metabolic and inflammatory conditions and whether differentiation from TE is possible. Group 1 consisted of 30 clinically healthy dogs presented for routine care. Group 2 consisted of 67 clinically ill dogs without TE. This group was subdivided into the following categories: postoperative surgical procedures, congestive heart failure, renal failure, hepatic disease, and neoplastic disease. Group 3 consisted of 20 dogs diagnosed with TE. A CBC and a measurement of prothrombin time (PT), activated partial thromboplastin time (PTT), fibrinogen degradation product (FDP) concentration, and plasma D-dimer concentration was performed on dogs in all groups. D-dimer concentrations were highest in dogs with TE; next highest was the hepatic disease group. Only these 2 groups had median D-dimer concentrations markedly different from clinically healthy dogs. The frequency of platelet abnormalities was markedly greater for the TE and neoplastic disease groups. The sensitivity of D-dimer concentrations >500 ng/mL for predicting TE was 100%; however, the specificity of D-dimer for TE at that concentration was 70%. The specificity of D-dimer concentrations >1,000 ng/mL to predict TE was 94% (sensitivity, 80%), and the specificity of D-dimer concentrations >2,000 ng/mL was 98.5% (sensitivity, 36%). FDPs were not high in any TE patient; thus, they may be an insensitive indicator of thromboembolism, with or without overt disseminated intravascular coagulation (DIC).

Objective—To evaluate cardiac function parameters in a group of active and hibernating grizzly bears. Design—Prospective study. Animals—6 subadult grizzly bears. Procedure—Indirect blood pressure, a 12-lead ECG, and a routine echocardiogram were obtained in each bear during the summer active phase and during hibernation. Results—All measurements of myocardial contractility were significantly lower in all bears during hibernation, compared with the active period. Mean rate of circumferential left ventricular shortening, percentage fractional shortening, and percentage left ventricular ejection fraction were significantly lower in bears during hibernation, compared with the active period. Certain indices of diastolic function appeared to indicate enhanced ventricular compliance during the hibernation period. Mean mitral inflow ratio and isovolumic relaxation time were greater during hibernation. Heart rate was significantly lower for hibernating bears, and mean cardiac index was lower but not significantly different from cardiac index during the active phase. Contrary to results obtained in hibernating rodent species, cardiac index was not significantly correlated with heart rate. Conclusions and Clinical Relevance—Cardiac function parameters in hibernating bears are opposite to the chronic bradycardic effects detected in nonhibernating species, likely because of intrinsic cardiac muscle adaptations during hibernation. Understanding mechanisms and responses of the myocardium during hibernation could yield insight into mechanisms of cardiac function regulation in various disease states in nonhibernating species. (J Am Vet Med Assoc 2003;223:1170–1175)

The N-terminal extension (NTE; residues 42-73) of mouse cardiac troponin T (TnT) desensitizes cardiac myofilaments to Ca2+ by stabilizing thin filaments in the blocked-state. We arrived at this conclusion using detergent-skinned muscle from transgenic (TG) mouse hearts that expressed 54% of chimeric TnT (residues 1-73 of mouse cardiac TnT were replaced by residues 1-41 of mouse fast skeletal TnT). Here, we extended our investigation to include higher dose effects of the modified TnT on cardiac myofilament function/phenotype using detergent-skinned fiber studies and echocardiography measurements in two different TG mouse lines (TG-55 and TG-64 that expressed 55% and 64% of chimeric TnT, respectively). Both TG-55 and TG-64 mice showed a similar increase in myofilament Ca2+ sensitivity at sarcomere lengths (SL) of 1.9 and 2.3 μm. However, Ca2+-activated maximal tension increased significantly only in TG-64 mice at either SL. There was a progressive decrease in the overall heart size and heart-to-body weight ratios in both TG-55 and TG-64 mice. Left ventricular diastolic functional parameters (isovolumic relaxation time and E-wave deceleration time) showed a graded increase in TG-55 and TG-64 mice; however, such effects were only significant in TG-64 mice, suggesting impaired relaxation. Systolic functional parameters (stroke volume, ejection fraction and fractional shortening) were unaffected in TG-55 mice, but significantly decreased in TG-64 mice. Thus, higher levels of chimeric TnT (64%) depressed both diastolic and systolic function significantly in TG-64 mice. We will discuss the link between the effects of the modified N-terminus of TnT on cardiac myofilament function and the resultant pathological remodeling of the heart. Our findings have pathological relevance because a growing number of disease-related mutations are found both in and near the NTE of cardiac TnT.

Locomotion of plantigrade generalists has been relatively little studied compared with more specialised postures even though plantigrady is ancestral among quadrupeds. Bears (Ursidae) are a representative family for plantigrade carnivorans, they have the majority of the morphological characteristics identified for plantigrade species, and they have the full range of generalist behaviours. This study compared the locomotion of adult grizzly bears (Ursus arctos horribilis Linnaeus 1758), including stride parameters, gaits and analysis of three-dimensional ground reaction forces, with that of previously studied quadrupeds. At slow to moderate speeds, grizzly bears use walks, running walks and canters. Vertical ground reaction forces demonstrated the typical M-shaped curve for walks; however, this was significantly more pronounced in the hindlimb. The rate of force development was also significantly higher for the hindlimbs than for the forelimbs at all speeds. Mediolateral forces were significantly higher than would be expected for a large erect mammal, almost to the extent of a sprawling crocodilian. There may be morphological or energetic explanations for the use of the running walk rather than the trot. The high medial forces (produced from a lateral push by the animal) could be caused by frontal plane movement of the carpus and elbow by bears. Overall, while grizzly bears share some similarities with large cursorial species, their locomotor kinetics have unique characteristics. Additional studies are needed to determine whether these characters are a feature of all bears or plantigrade species.

Grizzly bears (Ursus arctos horribilis) are inactive for up to 6 months during hibernation. They undergo profound seasonal changes in food intake, body mass, and energy expenditure. The circa-annual regulation of metabolism is poorly understood. In the present study, we measured plasma ghrelin, leptin, obestatin, and neuropeptide-Y (NPY) levels, hormones known to be involved in the regulation of energy homeostasis, in ten grizzly bears. Blood samples were collected during the active summer period, early hibernation and late hibernation. Plasma levels of leptin, obestatin, and NPY did not change between the active and the hibernation periods. Plasma total ghrelin and desacyl-ghrelin concentrations significantly decreased during the inactive winter period compared to summer levels. The elevated ghrelin levels may help enhance body mass during pre-hibernation, while the low plasma ghrelin concentrations during hibernation season may contribute to the maintenance of hypophagia, low energy utilization and behavioral inactivity. Our results suggest that ghrelin plays a potential role in the regulation of metabolic changes and energy homeostasis during hibernation in grizzly bears.