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Greater Capacity (greater + capacity)
Selected AbstractsGreater capacity for division of labour in clones of Fragaria chiloensis from patchier habitatsJOURNAL OF ECOLOGY, Issue 3 2007SERGIO R. ROILOA Summary 1Unlike non-clonal plants, clonal plants can develop a division of labour in which connected ramets specialize to acquire different, locally abundant resources. This occurs as a plastic response to a patchy environment where two resources tend not to occur together and different ramets experience high availabilities of different resources. We hypothesized that if division of labour is an important advantage of clonal growth in such environments in nature, then clones from habitats where resource availabilities are negatively associated should show a greater capacity for division of labour than clones from habitats where resource availabilities are more uniform. 2To test this, we collected clones of Fragaria chiloensis from sand dune and grassland sites in each of three regions of the central coast of California, grew pairs of connected or severed ramets under low light and high N or under high light and low N, and measured leaf area, chlorophyll content and final dry mass. Given that previous work has indicated that high availabilities of light and N show a stronger tendency not to occur together in the dune than in the grassland sites, we expected that clones from dunes would show greater capacity for division of labour than clones from grasslands. 3Clones from dunes showed a greater capacity than clones from grasslands to specialize for acquisition of abundant N via high proportional mass of roots. Clones from the two types of habitats showed similar capacity to specialize for acquisition of abundant light via high leaf area and chlorophyll content of leaves. Specialization via leaf area and chlorophyll content took place mainly within the first half of the 60-day experiment. 4These results provide evidence that division of labour in a clonal plant has been selected for in natural habitats where high levels of different resources tend to be spatially separated. Results also show that division of labour can occur, not just via allocation of mass, but also via physiological traits, and that both morphological and physiological specialization can take place within a few weeks. 5Clonal plants dominate many habitats and include many highly invasive species. Division of labour is one of the most striking potential advantages of clonal growth, and is a remarkable instance of phenotypic plasticity in plants. This study further suggests that division of labour in clonal plants is an instance of adaptive plasticity and could therefore play a part in their widespread ecological success. [source] Tumor expression of CD200 inhibits IL-10 production by tumor-associated myeloid cells and prevents tumor immune evasion of CTL therapyEUROPEAN JOURNAL OF IMMUNOLOGY, Issue 9 2010Lixin Wang Abstract CD200 is a cell-surface glycoprotein that functions through interaction with the CD200 receptor on myeloid lineage cells to regulate myeloid cell functions. Expression of CD200 has been implicated in multiple types of human cancer; however, the impact of tumor expression of CD200 on tumor immunity remains poorly understood. To evaluate this issue, we generated CD200-positive mouse plasmacytoma J558 and mastocytoma P815 cells. We found that established CD200-positive tumors were often completely rejected by adoptively transferred CTL without tumor recurrence; in contrast, CD200-negative tumors were initially rejected by adoptively transferred CTL but the majority of tumors recurred. Tumor expression of CD200 significantly inhibited suppressive activity and IL-10 production by tumor-associated myeloid cells (TAMC), and as a result, more CTL accumulated in the tumor and exhibited a greater capacity to produce IFN-, in CD200-positive tumors than in CD200-negative tumors. Neutralization of IL-10 significantly inhibited the suppressor activity of TAMC, and IL-10-deficiency allowed TAMC to kill cancer cells and their antigenic variants, which prevented tumor recurrence during CTL therapy. Thus, tumor expression of CD200 prevents tumor recurrence via inhibiting IL-10 production by TAMC. [source] Evolutionary origins of invasive populationsEVOLUTIONARY APPLICATIONS (ELECTRONIC), Issue 3 2008Carol Eunmi Lee Abstract What factors shape the evolution of invasive populations? Recent theoretical and empirical studies suggest that an evolutionary history of disturbance might be an important factor. This perspective presents hypotheses regarding the impact of disturbance on the evolution of invasive populations, based on a synthesis of the existing literature. Disturbance might select for life-history traits that are favorable for colonizing novel habitats, such as rapid population growth and persistence. Theoretical results suggest that disturbance in the form of fluctuating environments might select for organismal flexibility, or alternatively, the evolution of evolvability. Rapidly fluctuating environments might favor organismal flexibility, such as broad tolerance or plasticity. Alternatively, longer fluctuations or environmental stress might lead to the evolution of evolvability by acting on features of the mutation matrix. Once genetic variance is generated via mutations, temporally fluctuating selection across generations might promote the accumulation and maintenance of genetic variation. Deeper insights into how disturbance in native habitats affects evolutionary and physiological responses of populations would give us greater capacity to predict the populations that are most likely to tolerate or adapt to novel environments during habitat invasions. Moreover, we would gain fundamental insights into the evolutionary origins of invasive populations. [source] A comparative analysis of the diving behaviour of birds and mammalsFUNCTIONAL ECOLOGY, Issue 5 2006L. G. HALSEY Summary 1We use a large interspecific data set on diving variables for birds and mammals, and statistical techniques to control for the effects of phylogenetic non-independence, to assess evolutionary associations among different elements of diving behaviour across a broad and diverse range of diving species. Our aim is to assess whether the diving ability of homeothermic vertebrates is influenced by factors other than the physiology of the species. 2Body mass is related to dive duration even when dive depth is controlled for and thus for a given dive depth, larger species dive for longer. This implies that larger species have a greater capacity for diving than is expressed in their dive depth. Larger animals that dive shallowly, probably for ecological reasons such as water depth, make use of the physiological advantage that their size confers by diving for longer. 3Dive duration correlates with dive depth more strongly than with body mass. This confirms that some animals are poor divers for their body mass, either because of a lower physiological capacity or because their behaviour limits their diving. 4Surface duration relates not only to dive duration but also to dive depth, as well as to both independently. This indicates a relationship between dive depth and surface duration controlling for dive duration, which suggests that deeper dives are energetically more expensive than shallow dives of the same duration. 5Taxonomic class does not improve any of the dive variable models in the present study. There is thus an unsuspected consistency in the broad responses of different groups to the effects on diving of the environment, which are therefore general features of diving evolution. [source] Comparative fire ecology of tropical savanna and forest treesFUNCTIONAL ECOLOGY, Issue 6 2003William A. Hoffmann Summary 1Fire is important in the dynamics of savanna,forest boundaries, often maintaining a balance between forest advance and retreat. 2We performed a comparative ecological study to understand how savanna and forest species differ in traits related to fire tolerance. We compared bark thickness, root and stem carbohydrates, and height of reproductive individuals within 10 congeneric pairs, each containing one savanna and one forest species. 3Bark thickness of savanna species averaged nearly three times that of forest species, thereby reducing the risk of stem death during fire. The allometric relationship between bark thickness and stem diameter differed between these two tree types, with forest species tending to have a larger allometric coefficient. 4The height of reproductive individuals of forest species averaged twice that of congeneric savanna species. This should increase the time necessary for forest species to reach reproductive size, thereby reducing their capacity to reach maturity in the time between consecutive fires. 5There was no difference in total non-structural carbohydrate content of stems or roots between savanna and forest species, though greater allocation to total root biomass by savanna species probably confers greater capacity to resprout following fire. 6These differences in fire-related traits may largely explain the greater capacity of savanna species to persist in the savanna environment. [source] After the Public Interest Prevails: The Political Sustainability of Policy ReformGOVERNANCE, Issue 2 2003Eric Patashnik The prevailing political science wisdom is that narrow interests regularly triumph over the general public. Yet the stunning passage of broad-based policy reforms in the face of intense clientele opposition suggests that the U.S. political system has a greater capacity to serve diffuse interests than has often been thought. Some of the most provocative policy-oriented political-science research during the 1980s and 1990s examined how these surprising reform victories occurred. Unfortunately, general-interest reforms do not always stick; reforms may be corrupted or reversed after their enactment. The long-term sustainability of any given policy reform hinges on the successful reworking of political institutions and on the generation of positive policy-feedback effects, especially the empowerment of social groups with a stake in the reform&s maintenance. This paper explores the postenactment dynamics of three canonical instances of general-interest reform legislation: tax reform, agricultural subsidy reform, and airline deregulation. Only in the airline-deregulation case has the self-reinforcing dynamic required for political sustainability been unmistakably evident. For analysts and advocates of general-interest reform measures alike, the clear lesson is to attend far more closely to what happens after reforms become law. [source] Response surface methodology study of the combined effects of temperature, pH, and aw on the growth rate of Trichoderma asperellumJOURNAL OF APPLIED MICROBIOLOGY, Issue 4 2007B.A.D. Begoude Abstract Aims:, To evaluate the influence of environmental parameters (water activity aw, temperature, and pH) on the radial growth rate of Trichoderma asperellum (strains PR10, PR11, PR12, and 659-7), an antagonist of Phytophthora megakarya, the causal agent of cocoa black pod disease. Methods and Results:, The radial growth of four strains of T. asperellum was monitored for 30 days on modified PDA medium. Six levels of aw (0·995, 0·980, 0·960, 0·930, 0·910, and 0·880) were combined with three values of pH (4·5, 6·5, and 8·5) and three incubation temperatures (20, 25, and 30°C). Whatever the strain, mycelial growth rate was optimal at aw between 0·995 and 0·980, independently of the temperature and pH. Each strain appeared to be very sensitive to aw reduction. In addition, all four strains were able to grow at all temperatures and pH values (4·5,8·5) tested, highest growth rate being observed at 30°C and at pH 4·5,6·5. The use of response surface methodology to model the combined effects of aw, temperature, and pH on the radial growth rate of the T. asperellum strains confirmed the observed results. In our model, growth of the T. asperellum strains showed a greater dependence on aw than on temperature or pH under in vitro conditions. Conclusion:,aw is a crucial environmental factor. Low aw can prevent growth of T. asperellum strains under some conditions. The observed and predicted radial growth rate of strain PR11 showed its greater capacity to support low aw (0·93) as compared with other tested strains at 20°C. This is in agreement with its better protective level when applied in medium-scale trials on cocoa plantations. Significance and Impact of the Study:, This study should contribute towards improving the biocontrol efficacy of T. asperellum strains used against P. megakarya. Integrated into a broader study of the impact of environmental factors on the biocontrol agent,pathogen system, this work should help to build a more rational control strategy, possibly involving the use of a compatible adjuvant protecting T. asperellum against desiccation. [source] Gender divergent expression of Nqo1 in Sprague Dawley and August Copenhagen x Irish ratsJOURNAL OF BIOCHEMICAL AND MOLECULAR TOXICOLOGY, Issue 2 2008Lisa M. Augustine In the mammalian liver, there is an abundance of enzymes that function to enable the safe and efficient elimination of potentially harmful xenobiotics that are encountered through environmental exposure. A variety of factors, including gender and genetic polymorphisms, contribute to the variation between an individual system's detoxification capacity and thus its ability to protect itself against oxidative stress, cellular damage, cell death, etc. NAD(P)H:quinone oxidoreducatase 1 (Nqo1) is an antioxidant enzyme that plays a major role in reducing reactive electrophiles, thereby protecting cells from free-radical damage and oxidative stress. The goal of this study was to determine the gender-specific expression and inducibility of Nqo1 in the Sprague Dawley (SD) and August Copenhagen x Irish (ACI) rat strains, two strains that are commonly used in drug metabolism and drug-induced enzyme induction, toxicity, and carcinogenesis studies. Nqo1 mRNA, protein, and activity levels were determined through 96 h in SD and ACI males and females following treatment with known Nqo1 inducers oltipraz and butylated hydroxyanisole. In the SD strain, gender dimorphic expression of Nqo1 was observed with female mRNA, protein, and activity levels being significantly higher than in males. In contrast, there were minimal differences in Nqo1 mRNA, protein, and activity levels between ACI males and females. The gender dimorphic expression of Nqo1 in the SD rats was maintained through the course of induction, with female-induced levels greater than male-induced levels indicating that SD females may have a greater capacity to protect against oxidative stress and thus a decreased susceptibility to carcinogens. © 2008 Wiley Periodicals, Inc. J Biochem Mol Toxicol 22:93,100, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/jbt.20224 [source] Greater capacity for division of labour in clones of Fragaria chiloensis from patchier habitatsJOURNAL OF ECOLOGY, Issue 3 2007SERGIO R. ROILOA Summary 1Unlike non-clonal plants, clonal plants can develop a division of labour in which connected ramets specialize to acquire different, locally abundant resources. This occurs as a plastic response to a patchy environment where two resources tend not to occur together and different ramets experience high availabilities of different resources. We hypothesized that if division of labour is an important advantage of clonal growth in such environments in nature, then clones from habitats where resource availabilities are negatively associated should show a greater capacity for division of labour than clones from habitats where resource availabilities are more uniform. 2To test this, we collected clones of Fragaria chiloensis from sand dune and grassland sites in each of three regions of the central coast of California, grew pairs of connected or severed ramets under low light and high N or under high light and low N, and measured leaf area, chlorophyll content and final dry mass. Given that previous work has indicated that high availabilities of light and N show a stronger tendency not to occur together in the dune than in the grassland sites, we expected that clones from dunes would show greater capacity for division of labour than clones from grasslands. 3Clones from dunes showed a greater capacity than clones from grasslands to specialize for acquisition of abundant N via high proportional mass of roots. Clones from the two types of habitats showed similar capacity to specialize for acquisition of abundant light via high leaf area and chlorophyll content of leaves. Specialization via leaf area and chlorophyll content took place mainly within the first half of the 60-day experiment. 4These results provide evidence that division of labour in a clonal plant has been selected for in natural habitats where high levels of different resources tend to be spatially separated. Results also show that division of labour can occur, not just via allocation of mass, but also via physiological traits, and that both morphological and physiological specialization can take place within a few weeks. 5Clonal plants dominate many habitats and include many highly invasive species. Division of labour is one of the most striking potential advantages of clonal growth, and is a remarkable instance of phenotypic plasticity in plants. This study further suggests that division of labour in clonal plants is an instance of adaptive plasticity and could therefore play a part in their widespread ecological success. [source] A study of juvenile rat spinal cord injuryJOURNAL OF NEUROCHEMISTRY, Issue 2002J. M. Wingrave Greater than 5% of all spinal cord injuries (SCI) in the US occur in people younger than 16, although a minority, children will require extended attention during their lifetime. While facing increased mortality in the initial 24 h after trauma, children with incomplete injuries seem to have a greater capacity for recovery of function compared to adults suggesting that there is a difference in injury tolerance in the young over the adult. Knowledge of the factors involved in this difference would not only increase understanding of SCI, but also potentiate new avenues for SCI treatment. Yet there has not been a model for the study of youth SCI. For these reasons, we developed a model of SCI in juvenile rats equivalent to an adult injury of 25 g cm force (GCF). To do so, we recorded spinal cord masses of Sprague,Dawley rats at 21, 30, 45, and 60 days of age, compared them to adult cord masses, and assembled a conversion factor that provides youth injuries comparable to adult. To investigate the pathophysiology in juvenile SCI, two cord segments, 1 cm long, were removed from animals 24 h following injury. One segment was centered at the impact site, the other immediately caudal. After homogenization, the samples were assayed by Western blot analysis for calpain content and degradation of 68K Neuro-Filament Protein (68K NFP), a neuronal structural protein. mCalpain expression, a neutral protease previously implicated in secondary SCI, was reduced in juvenile animals relative to adult cohorts. The degradation of 68K NFP was also found to be reduced in juvenile animals. From these analyses, it seems plausible that calpain expression and pathogenic activity is abated in the setting of young rat SCI. Acknowledgements:, Supported by grants from NIH-NINDS. [source] Predictability of plant species composition from environmental conditions is constrained by dispersal limitationOIKOS, Issue 3 2005Wim A. Ozinga Despite recent modelling approaches integrating the effects of niche-based processes and dispersal-based processes on local plant species composition, their relative importance is still not clear. We test whether the predictability of local species composition from environmental conditions is influenced by dispersal traits. We analyzed a large database with co-occurrence data, using ordination techniques (DCA and CCA) to identify the major environmental determinants of species composition. The percentage of explained variance in occurrence was quantified for individual species with CCA. Effects of life-history traits on the predictability of occurrence patterns were tested by means of regression analysis, using a generalized linear models approach. The results reveal close correlations between species composition and environmental conditions, implying that the predictability of the set of species that might occur in a given environmental setting ("habitat species pool") is high. The habitat species pool, however, reflects the potential species composition, and not the actual local situation. At the level of individual species, a large proportion (>90%) of the variation in occurrence remained unexplained. Predictability of species occurrence patterns was increased by a greater capacity for long-distance dispersal, greater adult longevity and the capacity to build a persistent seed bank. The results indicate that the predictability of species composition from environmental conditions is reduced by a few orders of magnitude by dispersal limitation and that poor dispersers are underrepresented. [source] Damage-induced changes in woody plants and their effects on insect herbivore performance: a meta-analysisOIKOS, Issue 2 2004Heli Nykänen We conducted a meta-analysis of 68 studies published between 1982 and 2000 in which the responses of woody plants to natural or simulated herbivore damage and/or insect herbivore performance on control and damaged plants were measured. Cumulative meta-analyses revealed dramatic temporal changes in the magnitude and direction of the plant and herbivore responses reported during the last two decades. Studies conducted in the 1980s reported increase in phenolic concentrations, reduction in nutrient concentrations and negative effect on herbivore performance, consistently with the idea of induced resistance. In contrast, in the early 1990s when the idea that some types of plant damage may result in induced susceptibility was generally accepted, studies reported non-significant results or induced susceptibility, and smaller effects on herbivores. The above changes may reflect paradigm shifts in the theory of induced defenses and/or the differences between study systems used in the early and the more recent studies. Overall, plant growth and carbohydrate concentrations were reduced in damaged plants despite enhanced photosynthetic rates. Damage increased the concentrations of carbon and phenolics, while terpene concentrations tended to decrease after damage; changes in nutrient concentrations after damage varied according to nutrient mobility, inherent plant growth rate, ontogenetic stage and plant type (deciduous/evergreen). Early season damage caused more pronounced changes in plants than late season damage, which is in accordance with the assumption that vigorously growing foliage has a greater capacity to respond to damage. Insect growth rate and female pupal weight decreased on previously damaged plants, while herbivore survival, consumption and male pupal weight were not significantly affected. The magnitude and direction of herbivore responses depended on the type of plant, the type of damage, the time interval between the damage and insect feeding (rapid/delayed induced resistance), and the timing of the damage. [source] Abnormality of the Left Ventricular Sympathetic Nervous Function Assessed by I-123 Metaiodobenzylguanidine Imaging in Pediatric Patients with Neurocardiogenic SyncopePACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 10 2003RANA OLGUNTÜRK The purpose of this study was to assess the left ventricular sympathetic nervous system function in the patients with neurocardiogenic syncope (NCS) using I-123 metaiodobenzylguanidine (MIBG) imaging of the heart, and to compare the plasma noradrenaline (NA) and MIBG results of tilt positive and tilt negative patients following a head-up tilt test (HUT). The study included 30 patients. Their physical and laboratory examinations did not show a pathology that may be the cause of their syncope. HUT test was positive in 13 patients and negative in 17 patients. Plasma NA concentrations were higher in the HUT positive than the HUT negative group at the beginning and at the 10th minute of the test. Specific I-123 MIBG uptake assessed as the cardiac to mediastinal activity ratio in the delayed image was significantly higher in HUT positive group. The higher levels of MIBG uptake and plasma NA observed in HUT positive patients may reflect the greater capacity of NA storage in cardiac adrenergic neuronal tissue in patients with NCS. The results of this study support the critical role of autonomic nervous system in the pathophysiology of NCS and the excessive sympathetic nervous stimulation as the trigger of paradox reflex. (PACE 2003; 26:1926,1930) [source] Crops and genotypes differ in efficiency of potassium uptake and usePHYSIOLOGIA PLANTARUM, Issue 4 2008Zed Rengel Cultivars with increased efficiency of uptake and utilization of soil nutrients are likely to have positive environmental effects through reduced usage of chemicals in agriculture. This review assesses the available literature on differential uptake and utilization efficiency of K in farming systems. Large areas of agricultural land in the world are deficient in K (e.g. 3/4 of paddy soils in China, 2/3 of the wheatbelt in Southern Australia), with export in agricultural produce (especially hay) and leaching (especially in sandy soils) contributing to lowering of K content in the soil. The capacity of a genotype to grow and yield well in soils low in available K is K efficiency. Genotypic differences in efficiency of K uptake and utilization have been reported for all major economically important plants. The K-efficient phenotype is a complex one comprising a mixture of uptake and utilization efficiency mechanisms. Differential exudation of organic compounds to facilitate release of non-exchangeable K is one of the mechanisms of differential K uptake efficiency. Genotypes efficient in K uptake may have a larger surface area of contact between roots and soil and increased uptake at the root,soil interface to maintain a larger diffusive gradient towards roots. Better translocation of K into different organs, greater capacity to maintain cytosolic K+ concentration within optimal ranges and increased capacity to substitute Na+ for K+ are the main mechanisms underlying K utilization efficiency. Further breeding for increased K efficiency will be dependent on identification of suitable markers and compounding of efficiency mechanisms into locally adapted germplasm. [source] Ovarian Structure in Mice Lines Selected for WeightANATOMIA, HISTOLOGIA, EMBRYOLOGIA, Issue 3 2009S. F. Bernardi Summary Selection for body weight at 49 day of age (s and h, downward selected lines; s, and h,, upward selected lines) affected reproductive traits in CF1 mice lines. The objective of this study was to compare ovarian structures in females of these lines, as well as in unselected controls (Line t). The number of ovarian follicles (N), follicle diameter (FD), number of corpora lutea (CL), litter size (LS), and body weight (W), were recorded. There were significant differences among lines for N, FD, CL, LS and W; means values for the lines with the greatest difference for post-pubertal females were: Ns = 19.3 and Ns, = 32.7; FDh, = 161.7 and FDs, = 178.2; CLh = 10.3 and CLs, = 21.9; LSs = 6.0 and LSh, = 11.1; Wh = 18.9 and Ws, = 32.4. There were also differences between positive lines; Line s, had a higher proportion of large follicles in pre-pubertal females, a greater capacity to convert these follicles into CL, but a lower capacity to maintain embryos until term than Line h,. For negative lines, Line h apparently had a reduced incidence of embryonic loss when compared with Line s. In conclusion, selection for body weight modified ovarian structure, as well as reproductive efficiency. [source] Sustained neocortical neurogenesis after neonatal hypoxic/ischemic injuryANNALS OF NEUROLOGY, Issue 3 2007Zhengang Yang PhD Objective Neocortical neurons are sensitive to hypoxic-ischemic (H-I) injuries at term and their demise contributes to neurological disorders. Here we tested the hypothesis that the subventricular zone of the immature brain regenerates neocortical neurons, and that this response is sustained. Methods Systemic injections of 5-bromo-2,-deoxyuridine (BrdU) and intraventricular injections of replication-deficient retroviruses were used to label newly born cells, and confocal microscopy after immunofluorescence was used to phenotype the new cells from several days to several months after perinatal H-I in the postnatal day 6 rat. Quantitative polymerase chain reaction was used to evaluate chemoattractants, growth factors, and receptors. Results Robust production of new neocortical neurons after perinatal H-I occurs. These new neurons are descendants of the subventricular zone, and they colonize the cell-sparse columns produced by the injury to the neocortex. These columns are populated by reactive astrocytes and microglia. Surprisingly, this neuronogenesis is sustained for months. Molecular analyses demonstrated increased neocortical production of insulin-like growth factor-1 and monocyte chemoattractant factor-1 (but statistically insignificant production of erythropoietin, brain-derived neurotrophic factor, glial-derived neurotrophic factor, and transforming growth factor-,). Interpretation The young nervous system has long been known to possess a greater capacity to recover from injury than the adult system. Our data indicate that H-I injury in the neonatal brain initiates an enduring regenerative response from the subventricular zone. These data suggest that additional mechanisms than those previously surmised contribute to the remarkable ability of the immature brain to recover from injury. Ann Neurol 2007 [source] MOUSE STRAIN-SPECIFIC DIFFERENCES IN CARDIAC METABOLIC ENZYME ACTIVITIES OBSERVED IN A MODEL OF ISOPROTERENOL-INDUCED CARDIAC HYPERTROPHYCLINICAL AND EXPERIMENTAL PHARMACOLOGY AND PHYSIOLOGY, Issue 1-2 2007Michael D Faulx SUMMARY 1Alterations in myocardial energy metabolism accompany pressure overload-induced hypertrophy. We previously described a novel model of catecholamine-induced hypertrophy in which A/J mice exhibit more robust cardiac hypertrophy than B6 mice. Accordingly, we assessed the influence of mouse strain on the activities of key myocardial metabolic enzymes and whether there are strain-related metabolic adaptations to short-term, high-dose isoproterenol (ISO) administration. 2Thirty-nine male mice (19 A/J mice, 20 B6 mice), aged 12,15 weeks, were randomly assigned to receive either ISO (100 mg/kg, s.c.) or vehicle (sterile water) daily for 5 days. On Day 6, all hearts were excised, weighed, freeze clamped and assayed for pyruvate dehydrogenase (PDH), medium chain acyl-CoA dehydrogenase, carnitine palmitoyl transferase I and citrate synthase activities. Plasma fatty acids (FA) were also measured. 3The ISO-treated A/J mice demonstrated greater percentage increases in gravimetric heart weight/bodyweight ratio than ISO-treated B6 mice (24 vs 3%, respectively; P < 0.001). All enzyme activities were significantly greater in vehicle-treated B6 mice than in A/J mice, illustrating a greater capacity for aerobic metabolism in B6 mice. Administration of ISO reduced PDHa (active form) activity in B6 mice by 47% (P < 0.001), with no significant change seen in A/J mice. Free FA levels were not significantly different between groups; thus, the differences in PDHa were not due to changes in FA. 4The basal activity of myocardial metabolic enzymes is greater in B6 mice than in A/J mice and ISO alters myocardial PDH activity in a mouse strain-dependent manner. Compared with A/J mice, B6 mice demonstrate less ISO-induced cardiac hypertrophy, but greater activity of key enzymes regulating FA and carbohydrate oxidation, which may protect against the development of hypertrophy. The metabolic adaptations associated with ISO-induced hypertrophy differ from those reported with pressure overload hypertrophy. [source] | ||||||||||||||||