Cichorium intybus L. is a potential Cd-accumulator for phytoremediation of agricultural soil with strong tolerance and detoxification to Cd

Identifying suitable plants for phytoremediation of Cd (cadmium) contaminated agricultural soil is critical. In this study, whether chicory (Cichorium intybus L.) qualified as an ideal accumulator for phytoremediation was investigated. The hydroponic and pot experiments showed that Cd concentration in chicory leaves exceeded 100 mg kg-1 (BCF >1, TF >1) with 40 mg kg-1 Cd in pot; No significant effects on chicory growth, leaf protein and physiological and biochemical aspects when treated with ≤ 20 μM or 40 mg kg-1 Cd, because chicory could relieve Cd toxicity by increasing activities of photoprotection mechanisms, the reactive oxygen species scavenging system and concentrations of functional groups in plant tissues. In field experiment, 16.2 and 26.6 t ha-1 of chicory leaves was harvested in winter and summer, respectively. The highest Cd concentration in leaves was close to 25.0 mg kg-1 (BCF >1, TF >1) from the acid soil with 0.980 mg kg-1 Cd. Over 320 g ha-1 Cd was extracted from soil by harvesting chicory leaves both in winter and summer, with 9.24% and 12.9% of theoretical phytoremediation efficiency. Therefore, chicory can be as an ideal Cd-accumulator for phytoremediation of slight-to-moderate Cd-contaminated agricultural soil in any season.

Swimming exercise and nano-l-arginine supplementation improve oxidative capacity and some autophagy-related genes in the soleus muscle of aging rats

The present research aims to evaluate the effect of swimming exercise and chitosan-coated l-arginine on mitochondrial oxidation, BCL2 Interacting Protein 3 (Bnip3), NIP-like protein × (Nix), B-cell lymphoma-extra-large (Bcl-xL) and autophagy-related protein light chain 3(LC3) expression in soleus muscle of aging rats. In this experimental research, 25 male Wistar rats were assigned into five groups randomly: young, old, old + Nano l-arginine (Nano L-a), old + exercise (Ex), and old + Nano l-arginine (Nano L-a) + exercise (Ex) (n = 5 in each). They performed a swimming exercise program five days a week for six weeks. To determine the relative strength for rats before and after performing these interventions, the 1repetition maximum (1RM) test was done as a pre and post-test. The exercise program started with 20 min and after four sessions, gradually increased to 60 min and this time was maintained until the completion of the training period. l-arginine coated with chitosan nanoparticles was given to the rats in the l-arginine-supplemented group via gavage at a dosage of 500 mg/kg/day, five days a week, for six weeks. Additionally, the rats in all groups were fed a normal diet (2.87 kcal/g and 15 % energy from fat). Upon the completion of the protocol implementation, the rats were sacrificed and the soleus muscle was fixed and frozen to determine hematoxylin and eosin (H&E) staining, immunohistochemistry (IHC), gene expression analysis, levels of reactive oxygen species (ROS), and total antioxidant capacity (TAC). The results from the present research indicated that swimming exercise and Nano l-arginine improve the strength and histology of muscle tissue in old rats (p < 0.05). Aging significantly increased the expression of Nix and Bnip3 (p < 0.05) and reduced the Bcl-xL gene expression (p < 0.05). The expression of LC3 protein also increased with aging (p < 0.05). Therapeutic interventions, such as combined treatment (old + Nano L-a + Ex) for old animals, reduced the amount of this protein in soleus muscle (p < 0.05). The ROS values also showed a significant reduction only in the old + Nano L-a + Ex group compared to the old group. Moreover, TAC values show a significant decrease in the old and old + Ex groups in comparison to the young group. The use of arginine supplement, especially in nano form, along with swimming exercise seems to reduce the oxidative damage to the elderly muscle tissue, which has a positive effect on the structure and function of the soleus muscle. Since these interventions only had a significant effect on LC3 protein, further studies with more diverse measurement methods for autophagy are suggested.

Long term treadmill exercise affects age-related oxidative stress in the spinal cord of rats

Age-induced apoptosis is believed to be caused by the imbalance between production of reactive oxygen species (ROS) and human body antioxidant defence. Regular aerobic treadmill-exercise has been suggested to enhance the antioxidant defence. This study aimed to investigate the effects of long-term treadmill exercise on age-related oxidative stress and the apoptosis of oligodendrocytes in the spinal cord of the rat. Sixty male rats were divided into six groups: three exercised groups, which underwent 6, 9 and 12 months of mild-to-moderate treadmill exercise and three non-exercised control groups. Spinal cord white or grey matter tissue sampling was done through mid-thoracic laminectomy. The malondialdehyde (MDA; indicator of oxidative stress) levels, the number of apoptotic oligodendrocytes and ultrastructural alterations were also evaluated. Our data showed that treadmill exercise resulted in decreased lipid peroxidation and the number of apoptotic oligodendrocytes in the spinal cord of rats, as compared to non-exercised animals. These results were confirmed by TUNEL (terminal deoxynucleotidyl transferase dUTP nick end labelling) staining and electron microscope. This study suggests that the long-term treadmill exercise can affect oxidative stress and oligodendrocytes apoptosis in the spinal cord of aged rats and further studies are needed to validate these findings in humans.

Taurine Reverses Oxidative Damages and Restores the Muscle Function in Overuse of Exercised Muscle

Exercise-induced oxidative stress is linked with the expression level of endogenous antioxidants, but these antioxidants cannot overcome all oxidative stress-related damages in the cells, particularly when cells are under physiological stress. Sometimes, compounds are needed for cellular function, which are produced/activated within the cells, and these compounds can be synthesized by performing exercise, especially high-performance exercise. Taurine is a sulfur-containing amino acid used for various physiological functions. However, its synthesis and accumulation under the oxidative environment may be compromised. Recently, we have shown that taurine level is increased during exercise performance with a decrease in oxidative damage in overused muscles. Other studies have also shown that short-term supplementation with taurine increased physiological performance during severe work intensities, suggesting the role of taurine in improving muscle performance during exercise. However, its precursor cysteine is used in the synthesis of other compounds like GSH and Coenzyme A, which are important for regulating the redox system and energy homeostasis. It is, therefore, important to understand whether taurine synthesis within the cells can blunt the activity of other compounds that are beneficial in preventing oxidative damage during intense exercise. Furthermore, it is important to understand whether taurine supplementation can prevent the conditions observed in the physiological stress of muscles. This review discusses how taurine synthesis could alter exercise-induced ROS generation and the relationship between the physiological stress of muscle and subsequent improvements in exercise performance.

Oxidative costs of cooperation in cooperatively breeding Damaraland mole-rats

Within cooperatively breeding societies, individuals adjust cooperative contributions to maximize indirect fitness and minimize direct fitness costs. Yet, little is known about the physiological costs of cooperation, which may be detrimental to direct fitness. Oxidative stress, the imbalance between reactive oxygen species (by-products of energy production) and antioxidant protection, may represent such a cost when cooperative behaviours are energetically demanding. Oxidative stress can lead to the accumulation of cellular damage, compromising survival and reproduction, thus mediating the trade-off between these competing life-history traits. Here, we experimentally increased energetically demanding cooperative contributions in captive Damaraland mole-rats (Fukomys damarensis). We quantified oxidative stress-related effects of increased cooperation on somatic and germline tissues, and the trade-off between them. Increased cooperative contributions induced oxidative stress in females and males, without increasing somatic damage. Males accumulated oxidative damage in their germline despite an increase in antioxidant defences. Finally, oxidative damage accumulation became biased towards the germline, while antioxidant protection remained biased towards the soma, suggesting that males favour the maintenance of somatic tissues (i.e. survival over reproduction). Our results show that heightened cooperative contributions can ultimately affect direct fitness through oxidative stress costs, which may represent a key selective pressure for the evolution of cooperation.

Cellular Turnover: A Potential Metabolic Rate-Driven Mechanism to Mitigate Accumulation of DNA Damage

Oxidative stress, the imbalance of reactive oxygen species and antioxidant capacity, may cause damage to biomolecules pivotal for cellular processes (e.g., DNA). This may impair physiological performance and, therefore, drive life-history variation and aging rate. Because aerobic metabolism is supposed to be the main source of such oxidative risk, the rate of oxygen consumption should be positively associated with the level of damage and/or antioxidants. Empirical support for such relationships remains unclear, and recent considerations suggest even a negative relationship between metabolic rate and oxidative stress. We investigated the relationship between standard metabolic rate (SMR), antioxidants, and damage in blood plasma and erythrocytes for 35 grass snakes (Natrix natrix). Reactive oxygen metabolites (dROMs) and nonenzymatic antioxidants were assessed in plasma, while two measures of DNA damage and the capacity to neutralize H₂O₂ were measured in erythrocytes. Plasma antioxidants showed no correlation to SMR, and the level of dROMs was positively related to SMR. A negative relationship between antioxidant capacity and SMR was found in erythrocytes, but no association of SMR with either measure of DNA damage was detected. No increase in DNA damage, despite lower antioxidant capacity at high SMR, indicates an upregulation in other defense mechanisms (e.g., damage repair and/or removal). Indeed, we observed a higher frequency of immature red blood cells in individuals with higher SMR, which indicates that highly metabolic individuals had increased erythrocyte turnover, a mechanism of damage removal. Such DNA protection through upregulated cellular turnover might explain the negligible senescence observed in some ectotherm taxa.

Pheomelanin synthesis varies with protein food abundance in developing goshawks

The accumulation of the amino acid cysteine in lysosomes produces toxic substances, which are avoided by a gene (CTNS) coding for a transporter that pumps cystine out of lysosomes. Melanosomes are lysosome-related organelles that synthesize melanins, the most widespread pigments in animals. The synthesis of the orange melanin, termed pheomelanin, depends on cysteine levels because the sulfhydryl group is used to form the pigment. Pheomelanin synthesis may, therefore, be affected by cysteine homeostasis, although this has never been explored in a natural system. As diet is an important source of cysteine, here we indirectly tested for such an effect by searching for an association between food abundance and pheomelanin content of feathers in a wild population of Northern goshawk Accipiter gentilis. As predicted on the basis that CTNS expression may inhibit pheomelanin synthesis and increase with food abundance as previously found in other strictly carnivorous birds, we found that the feather pheomelanin content in nestling goshawks, but not in adults, decreased as the abundance of prey available to them increased. In contrast, variation in the feather content of the non-sulphurated melanin form (eumelanin) was only explained by sex in both nestlings and adults. We also found that the feather pheomelanin content of nestlings was negatively related to that of their mothers, suggesting a relevant environmental influence on pheomelanin synthesis. Overall, our findings suggest that variation in pheomelanin synthesis may be a side effect of the maintenance of cysteine homeostasis. This may help explaining variability in the expression of pigmented phenotypes.

Mitochondrial haplotypes are not associated with mice selectively bred for high voluntary wheel running

Mitochondrial haplotypes have been associated with human and rodent phenotypes, including nonshivering thermogenesis capacity, learning capability, and disease risk. Although the mammalian mitochondrial D-loop is highly polymorphic, D-loops in laboratory mice are identical, and variation occurs elsewhere mainly between nucleotides 9820 and 9830. Part of this region codes for the tRNA^Arg gene and is associated with mitochondrial densities and number of mtDNA copies. We hypothesized that the capacity for high levels of voluntary wheel-running behavior would be associated with mitochondrial haplotype. Here, we analyzed the mtDNA polymorphic region in mice from each of four replicate lines selectively bred for 54 generations for high voluntary wheel running (HR) and from four control lines (Control) randomly bred for 54 generations. Sequencing the polymorphic region revealed a variable number of adenine repeats. Single nucleotide polymorphisms (SNPs) varied from 2 to 3 adenine insertions, resulting in three haplotypes. We found significant genetic differentiations between the HR and Control groups (F_st = 0.779, p ≤ 0.0001), as well as among the replicate lines of mice within groups (F_sc = 0.757, p ≤ 0.0001). Haplotypes, however, were not strongly associated with voluntary wheel running (revolutions run per day), nor with either body mass or litter size. This system provides a useful experimental model to dissect the physiological processes linking mitochondrial, genomic SNPs, epigenetics, or nuclear-mitochondrial cross-talk to exercise activity.

Systematic evaluation of the adaptability of the non-radioactive SUnSET assay to measure cardiac protein synthesis

Heart is a dynamic organ that undergoes remodeling in response to both physiological and pathological stimuli. One of the fundamental cellular processes that facilitates changes in the size and shape of this muscular organ is the protein synthesis. Traditionally changes in cardiac protein synthesis levels were measured by radiolabeled tracers. However, these methods are often cumbersome and suffer from radioactive risk. Recently a nonradioactive method for detecting protein synthesis under in vitro conditions called the Surface Sensing of Translation (SUnSET) was described in cell lines of mouse dendrites and T cells. In this work, we provide multiple lines of evidence that the SUnSET assay can be applied to reliably detect changes in protein synthesis both in isolated neonatal primary cardiomyocytes and heart. We successfully tracked the changes in protein synthesis by western blotting as well as immunohistochemical variants of the SUnSET assay. Applying the SUnSET assay, we measured the cardiac protein synthesis during the different ages of mice. Further, we successfully tracked the increase in cardiac protein synthesis during different stages of a well-established model for pathological hypertrophy. Overall, we propose SUnSET assay as a simple, reliable and robust method to measure protein synthesis in the cardiac milieu.

Condition-dependence of pheomelanin-based coloration in nuthatches Sitta europaea suggests a detoxifying function: implications for the evolution of juvenile plumage patterns

Adult-like juvenile plumage patterns often signal genotypic quality to parents. During adulthood, the same patterns often signal quality to mates. This has led to assume that adult-like juvenile plumage is a developmental consequence of sexual selection operating in adults. Many of these patterns are produced by the pigment pheomelanin, whose synthesis may help remove toxic excess cysteine. Excess cysteine is likely to arise under conditions of relatively low stress, such as those experienced by nestling birds. Thus, adult-like plumage may be advantageous for juveniles if produced by pheomelanin. In the Eurasian nuthatch Sitta europaea, juveniles are sexually dichromatic and identical to adults. Nestling nuthatches in poorer condition develop more intense pheomelanin-based feathers, indicating greater pigment production. The same is not observed in adults. This is contrary to a function related to signaling quality and instead suggests that, at least in the Eurasian nuthatch, adult-like juvenile plumage has evolved because of the detoxifying function of pheomelanin-based pigmentation. Given the prevalence of colors typically conferred by pheomelanin in juvenile plumage patterns, the detoxifying capacity of pheomelanin under low stress levels should be considered as an explanation for the evolution of both adult-like and distinctively juvenile plumage patterns.

Age-related changes of physiological performance and survivorship of bank voles selected for high aerobic capacity

Variation in lifespans is an intriguing phenomenon, but how metabolic rate influence this variation remains unclear. High aerobic capacity can result in health benefits, but also in increased oxidative damage and accelerated ageing. We tested these contradictory predictions using bank voles (Myodes=Clethrionomys glareolus) from lines selected for high swim-induced aerobic metabolism (A), which had about 50% higher maximum metabolic rate and a higher basal and routine metabolic rates, than those from unselected control lines (C). We measured sprint speed (VSmax), forced-running maximum metabolic rate (VO₂run), maximum long-distance running speed (VLmax), running speed at VO₂run (VVO₂), and respiratory quotient at VO₂run (RQ) at three age classes (I: 3-5, II: 12-14, III: 17-19months), and analysed survivorship. We asked if ageing, understood as the age-related decline of the performance traits, differs between the A and C lines. At age class I, voles from A lines had 19% higher VO₂run, and 12% higher VLmax, but tended to have 19% lower VSmax, than those from C lines. RQ was nearly 1.0 for both A and C lines. The pattern of age-related changes differed between the lines mainly between age classes I and II, but not in older animals. VSmax increased by 27% in A lines and by 10% in C lines between age class I and II, but between classes II and III, it increased by 16% in both selection directions. VO₂run decreased by 7% between age class I and II in A lines only, but in C lines it remained constant across all age classes. VLmax decreased by 8% and VVO₂ by 12% between age classes II and III, but similarly in both selection directions. Mortality was higher in A than in C lines only between the age of 1 and 4months. The only trait for which the changes in old animals differed between the lines was RQ. In A lines, RQ increased between age classes II and III, whereas in C lines such an increase occurred between age classes I and II. Thus, we did not find obvious effects of selection on the pattern of ageing. However, the physiological performance and mortality of bank voles remained surprisingly robust to ageing, at least until the age of 17-19months, similar to the maximum lifespan under natural conditions. Therefore, it is possible that the selection could affect the pattern of ageing in even older individuals when symptoms of senility might be more profound.

Long-term exercise in mice has sex-dependent benefits on body composition and metabolism during aging

Aging is associated with declining exercise and unhealthy changes in body composition. Exercise ameliorates certain adverse age‐related physiological changes and protects against many chronic diseases. Despite these benefits, willingness to exercise and physiological responses to exercise vary widely, and long‐term exercise and its benefits are difficult and costly to measure in humans. Furthermore, physiological effects of aging in humans are confounded with changes in lifestyle and environment. We used C57BL/6J mice to examine long‐term patterns of exercise during aging and its physiological effects in a well‐controlled environment. One‐year‐old male (n = 30) and female (n = 30) mice were divided into equal size cohorts and aged for an additional year. One cohort was given access to voluntary running wheels while another was denied exercise other than home cage movement. Body mass, composition, and metabolic traits were measured before, throughout, and after 1 year of treatment. Long‐term exercise significantly prevented gains in body mass and body fat, while preventing loss of lean mass. We observed sex‐dependent differences in body mass and composition trajectories during aging. Wheel running (distance, speed, duration) was greater in females than males and declined with age. We conclude that long‐term exercise may serve as a preventive measure against age‐related weight gain and body composition changes, and that mouse inbred strains can be used to characterize effects of long‐term exercise and factors (e.g. sex, age) modulating these effects. These findings will facilitate studies on relationships between exercise and health in aging populations, including genetic predisposition and genotype‐by‐environment interactions.

Advanced Running Performance by Genetic Predisposition in Male Dummerstorf Marathon Mice (DUhTP) Reveals Higher Sterol Regulatory Element-Binding Protein (SREBP) Related mRNA Expression in the Liver and Higher Serum Levels of Progesterone

Long-term-selected DUhTP mice represent a non-inbred model for inborn physical high-performance without previous training. Abundance of hepatic mRNA in 70-day male DUhTP and control mice was analyzed using the Affymetrix mouse array 430A 2.0. Differential expression analysis with PLIER corrected data was performed using AltAnalyze. Searching for over-representation in biochemical pathways revealed cholesterol metabolism being most prominently affected in DUhTP compared to unselected control mice. Furthermore, pathway analysis by AltAnalyze plus PathVisio indicated significant induction of glycolysis, fatty acid synthesis and cholesterol biosynthesis in the liver of DUhTP mice versus unselected control mice. In contrast, gluconeogenesis was partially inactivated as judged from the analysis of hepatic mRNA transcript abundance in DUhTP mice. Analysis of mRNA transcripts related to steroid hormone metabolism inferred elevated synthesis of progesterone and reduced levels of sex steroids. Abundance of steroid delta isomerase-5 mRNA (Hsd3b5, FC 4.97) was increased and steroid 17-alpha-monooxygenase mRNA (Cyp17a1, FC -11.6) was massively diminished in the liver of DUhTP mice. Assessment of steroid profiles by LC-MS revealed increased levels of progesterone and decreased levels of sex steroids in serum from DUhTP mice versus controls. Analysis of hepatic mRNA transcript abundance indicates that sterol regulatory element-binding protein-1 (SREBP-1) may play a major role in metabolic pathway activation in the marathon mouse model DUhTP. Thus, results from bioinformatics modeling of hepatic mRNA transcript abundance correlated with direct steroid analysis by mass spectrometry and further indicated functions of SREBP-1 and steroid hormones for endurance performance in DUhTP mice.

Voluntary Exercise Protects Heart from Oxidative Stress in Diabetic Rats

PURPOSE

Oxidative stress plays a key role in the onset and development of diabetes complications. In this study, we evaluated whether voluntary exercise could alleviate oxidative stress in the heart and blood of streptozotocin - induced diabetic rats.

METHODS

28 male Wistar rats were randomly divided into four groups (n=7): control, exercise, diabetes and exercise + diabetes. Diabetes was induced by injection of streptozotocin in male rats. Rats in the trained groups were subjected to voluntary running wheel exercise for 6 weeks. At the end of six weeks blood and heart tissue samples were collected and used for determination of antioxidant enzymes (including SOD, GPX and CAT activities) and MDA level.

RESULTS

Exercise significantly reduced MDA levels both in the heart tissue (p<0.01) and blood samples (p<0.05). In addition, exercise significantly increased SOD (p<0.05), GPX (p<0.001) and CAT (p<0.05) in the heart tissue. Voluntary exercise also significantly increased SOD (p<0.01), GPX (p<0.05) and CAT (p<0.001) in the blood.

CONCLUSION

Voluntary exercise diminishes the MDA level in blood and heart tissue of diabetic rats. It also accentuates activities of SOD, GPX and CAT. Therefore, it may be considered a useful tool for the reduction of oxidative stress in diabetes.

Redox biology of exercise: an integrative and comparative consideration of some overlooked issues

The central aim of this review is to address the highly multidisciplinary topic of redox biology as related to exercise using an integrative and comparative approach rather than focusing on blood, skeletal muscle or humans. An attempt is also made to re-define ‘oxidative stress’ as well as to introduce the term ‘alterations in redox homeostasis’ to describe changes in redox homeostasis indicating oxidative stress, reductive stress or both. The literature analysis shows that the effects of non-muscle-damaging exercise and muscle-damaging exercise on redox homeostasis are completely different. Non-muscle-damaging exercise induces alterations in redox homeostasis that last a few hours post exercise, whereas muscle-damaging exercise causes alterations in redox homeostasis that may persist for and/or appear several days post exercise. Both exhaustive maximal exercise lasting only 30 s and isometric exercise lasting 1–3 min (the latter activating in addition a small muscle mass) induce systemic oxidative stress. With the necessary modifications, exercise is capable of inducing redox homeostasis alterations in all fluids, cells, tissues and organs studied so far, irrespective of strains and species. More importantly, ‘exercise-induced oxidative stress’ is not an ‘oddity’ associated with a particular type of exercise, tissue or species. Rather, oxidative stress constitutes a ubiquitous fundamental biological response to the alteration of redox homeostasis imposed by exercise. The hormesis concept could provide an interpretative framework to reconcile differences that emerge among studies in the field of exercise redox biology. Integrative and comparative approaches can help determine the interactions of key redox responses at multiple levels of biological organization.

Exercise-induced cardiac preconditioning: how exercise protects your achy-breaky heart

The ability of exercise to protect the heart against ischemia-reperfusion (I/R) injury is well known in both human epidemiological studies and experimental animal models. In this review article, we describe what is currently known about the ability of exercise to precondition the heart against infarction. Just 1 day of exercise can protect the heart against ischemia/reperfusion damage, and this protection is upheld with months of exercise, making exercise one of the few sustainable preconditioning stimuli. Exercise preconditioning depends on the model and intensity of exercise, and appears to involve heightened oxidant buffering capacity, upregulated subunits of sarcolemmal ATP-sensitive potassium channels, and adaptations to cardiac mitochondria. We review the putative mechanisms involved in exercise preconditioning and point out many areas where future research is necessary to advance our understanding of how this stimulus confers resistance against I/R damage.

Voluntary wheel running is beneficial to the amino acid profile of lysine-deficient rats

Rats voluntarily run up to a dozen kilometers per night when their cages are equipped with a running wheel. Daily voluntary running is generally thought to enhance protein turnover. Thus, we sought to determine whether running worsens or improves protein degradation caused by a lysine-deficient diet and whether it changes the utilization of free amino acids released by proteolysis. Rats were fed a lysine-deficient diet and were given free access to a running wheel or remained sedentary (control) for 4 wk. Amino acid levels in plasma, muscle, and liver were measured together with plasma insulin levels and tissue weight. The lysine-deficient diet induced anorexia, skeletal muscle loss, and serine and threonine aminoacidemia, and it depleted plasma insulin and essential amino acids in skeletal muscle. Allowing rats to run voluntarily improved these symptoms; thus, voluntary wheel running made the rats less susceptible to dietary lysine deficiency. Amelioration of the declines in muscular leucine and plasma insulin observed in running rats could contribute to protein synthesis together with the enhanced availability of lysine and other essential amino acids in skeletal muscle. These results indicate that voluntary wheel running under lysine-deficient conditions does not enhance protein catabolism; on the contrary, it accelerates protein synthesis and contributes to the maintenance of muscle mass. The intense nocturnal voluntary running that characterizes rodents might be an adaptation of lysine-deficient grain eaters that allows them to maximize opportunities for food acquisition.

NADPH oxidase-derived superoxide impairs calcium transients and contraction in aged murine ventricular myocytes

Since aging increases oxidative stress, we analyzed the contribution of reactive oxygen species (ROS) to the contractile dysfunction of aged ventricular myocytes and investigated whether short-term interference with ROS formation could normalize contractile performance. Isolated ventricular myocytes from young (2-4 months) and aged (24-26 months) male mice (C57BL/6) were used. We analyzed sarcomere shortening and calcium transients (Indo-1 fluorescence) of voltage clamped ventricular myocytes and myofilament ATPase activity (malachite green assay). Expression of calcium handling proteins (Western blots) and NADPH oxidase subunits (real-time PCR) was quantified, as well as NADPH oxidase activity (lucigenin chemiluminescence). We found that aged myocytes showed decelerated shortening/relengthening without changes in fractional shortening. Calcium transient decay was similarly decelerated, but the amplitude of calcium transients was increased with aging. Calcium sensitivity of myofilaments of aged myocytes was reduced. These age-dependent changes occurred without altered calcium handling protein expression but were reversed by the superoxide scavenger tiron. Aged myocytes showed increased NADPH oxidase expression and activity. Pharmacological inhibition of NADPH oxidase (diphenylene iodonium; apocynin) normalized age-dependent deceleration of shortening/relengthening. In summary, we show that increased superoxide formation by upregulated NADPH oxidase contributes significantly to age-dependent alterations in calcium handling and contractility of murine ventricular myocytes.

Does the difference between physically active and couch potato lie in the dopamine system?

Obesity and other inactivity related diseases are increasing at an alarming rate especially in Western societies. Because of this, it is important to understand the regulating mechanisms involved in physical activity behavior. Much research has been done in regard to the psychological determinants of physical activity behavior; however, little is known about the underlying genetic and biological factors that may contribute to regulation of this complex trait. It is true that a significant portion of any trait is regulated by genetic and biological factors. In the case of voluntary physical activity behavior, these regulating mechanisms appear to be concentrated in the central nervous system. In particular, the dopamine system has been shown to regulate motor movement, as well as motivation and reward behavior. The pattern of regulation of voluntary physical activity by the dopamine system is yet to be fully elucidated. This review will summarize what is known about the dopamine system and regulation of physical activity, and will present a hypothesis of how this signaling pathway is mechanistically involved in regulating voluntary physical activity behavior. Future research in this area will aid in developing personalized strategies to prevent inactivity related diseases.

Trade-offs between activity and thermoregulation in a small carnivore, the least weasel Mustela nivalis

We studied factors influencing daily energy expenditures (DEE) of male least weasels (Mustela nivalis) using the doubly labelled water technique. The relationship between ambient temperature and DEE formed a triangular pattern, characterized by invariance of the maximum DEE and an inverse relationship between minimum DEE and temperature. A simple energetic model relating the DEE of male weasels to activity time (AT) and ambient temperature predicted that, across seasons, less than 10 per cent of measurements approach the upper bound of observed DEE. Male weasels were able to maintain a relatively constant maximum energy output across varying temperatures by adjusting their AT to changes in temperature. They achieved maximum energy expenditures in winter due to high thermoregulatory costs, and in spring and summer due to high levels of physical activity. This pattern exemplifies a 'metabolic niche' of a small mammal having extremely high energy expenditures primarily driven by ambient temperature.

Oxidative stress as a mediator of life history trade-offs: mechanisms, measurements and interpretation

The concept of trade-offs is central to our understanding of life-history evolution. The underlying mechanisms, however, have been little studied. Oxidative stress results from a mismatch between the production of damaging reactive oxygen species (ROS) and the organism's capacity to mitigate their damaging effects. Managing oxidative stress is likely to be a major determinant of life histories, as virtually all activities generate ROS. There is a recent burgeoning of interest in how oxidative stress is related to different components of animal performance. The emphasis to date has been on immediate or short-term effects, but there is an increasing realization that oxidative stress will influence life histories over longer time scales. The concept of oxidative stress is currently used somewhat loosely by many ecologists, and the erroneous assumption often made that dietary antioxidants are necessarily the major line of defence against ROS-induced damage. We summarize current knowledge on how oxidative stress occurs and the different methods for measuring it, and highlight where ecologists can be too simplistic in their approach. We critically review the potential role of oxidative stress in mediating life-history trade-offs, and present a framework for formulating appropriate hypotheses and guiding experimental design. We indicate throughout potentially fruitful areas for further research.