Daily exposure to a touchscreen-paradigm and associated food restriction evokes an increase in adrenocortical and neural activity in mice

The translational assessment of mechanisms underlying cognitive functions using touchscreen-based approaches for rodents is growing in popularity. In these paradigms, daily training is usually accompanied by extended food restriction to maintain animals' motivation to respond for rewards. Here, we show a transient elevation in stress hormone levels due to food restriction and touchscreen training, with subsequent adaptation effects, in fecal corticosterone metabolite concentrations, indicating effective coping in response to physical and psychological stressors. Corticosterone concentrations of experienced but training-deprived mice revealed a potential anticipation of task exposure, indicating a possible temporary environmental enrichment-like effect caused by cognitive challenge. Furthermore, the analyses of immediate early gene (IEG) immunoreactivity in the hippocampus revealed alterations in Arc, c-Fos and zif268 expression immediately following training. In addition, BDNF expression was altered as a function of satiation state during food restriction. These findings suggest that standard protocols for touchscreen-based training induce changes in hippocampal neuronal activity related to satiation and learning that should be considered when using this paradigm.     

Microarray expression analysis of effects of exercise training: increase in atrial MLC-1 in rat ventricles

Previous studies have shown that endurance exercise training increases myocardial contractility. We have previously described training-induced alterations in myocardial contractile function at the cellular level, including an increase in the Ca(2+) sensitivity of tension. To determine the molecular mechanism(s) of these changes, oligonucleotide microarrays were used to analyze the gene expression profile in ventricles from endurance-trained rats. We used an 11-wk treadmill training protocol that we have previously shown results in increased contractility in cardiac myocytes. After the training, the hearts were removed and RNA was isolated from the ventricles of nine trained and nine control rats. With the use of an Affymetrix Rat Genome U34A Array, we detected altered expression of 27 genes. Several genes previously found to have increased expression in hypertrophied myocardium, such as atrial natriuretic factor and skeletal alpha-actin, were decreased with training in this study. From the standpoint of altered contractile performance, the most significant finding was an increase in the expression of atrial myosin light chain 1 (aMLC-1) in the trained ventricular tissue. We confirmed microarray results for aMLC-1 using RT-PCR and also confirmed a training-induced increase in aMLC-1 protein using two-dimensional gel electrophoresis. aMLC-1 content has been previously shown to be increased in human cardiac hypertrophy and has been associated with increased Ca(2+) sensitivity of tension and increased power output. These results suggest that increased expression of aMLC-1 in response to training may be responsible, at least in part, for previously observed training-induced enhancement of contractile function.     

Coordinate changes in Myosin heavy chain isoform gene expression are selectively associated with alterations in dilated cardiomyopathy phenotype

BACKGROUND: The most common cause of chronic heart failure in the US is secondary or primary dilated cardiomyopathy (DCM). The DCM phenotype exhibits changes in the expression of genes that regulate contractile function and pathologic hypertrophy. However, it is unclear if any of these alterations in gene expression are disease producing or modifying. MATERIALS AND METHODS: One approach to providing evidence for cause-effect of a disease-influencing gene is to quantitatively compare changes in phenotype to changes in gene expression by employing serial measurements in a longitudinal experimental design. We investigated the quantitative relationships between changes in gene expression and phenotype n 47 patients with idiopathic DCM. In endomyocardial biopsies at baseline and 6 months later, we measured mRNA expression of genes regulating contractile function (beta-adrenergic receptors, sarcoplasmic reticulum Ca(2) + ATPase, and alpha- and beta-myosin heavy chain isoforms) or associated with pathologic hypertrophy (beta-myosin heavy chain and atrial natriuretic peptide), plus beta-adrenergic receptor protein expression. Left ventricular phenotype was assessed by radionuclide ejection fraction. RESULTS: Improvement in DCM phenotype was directly related to a coordinate increase in alpha- and a decrease in beta-myosin heavy chain mRNA expression. In contrast, modification of phenotype was unrelated to changes in the expression of beta(1)- or beta(2)-adrenergic receptor mRNA or protein, or to the mRNA expression of sarcoplasmic reticulum Ca(2) + ATPase and atrial natriuretic peptide. CONCLUSION: We conclude that in human DCM, phenotypic modification is selectively associated with myosin heavy chain isoform changes. These data support the hypothesis that myosin heavy chain isoform changes contribute to disease progression in human DCM.     

Concentration of macroergic phosphates and oxidative potential of skeletal muscles

It is known that a long-duration decline of high-energy phosphate (HP) level in skeletal muscles, induced by administration of beta-guanidinpropionic acid (beta-GPA), is followed by an increase in mitochondrial enzyme activities (MEA). The same increase in MEA was observed in the course of physical exercise training. Under gravitational inloading decrease in MEA and increase in the level of high-energy phosphates occurred. If changes in (HP) level are believed to trigger the alterations in MEA, the increase in high-energy phosphate levels in muscles is to lead to a decline in MEA as well. The present work was purposed to reveal if changes in HP level under different contractile activity levels may be associated with changes in oxidative potential in the skeletal muscles.     

Regulation of exercise-induced fiber type transformation, mitochondrial biogenesis, and angiogenesis in skeletal muscle

Skeletal muscle exhibits superb plasticity in response to changes in functional demands. Chronic increases of skeletal muscle contractile activity, such as endurance exercise, lead to a variety of physiological and biochemical adaptations in skeletal muscle, including mitochondrial biogenesis, angiogenesis, and fiber type transformation. These adaptive changes are the basis for the improvement of physical performance and other health benefits. This review focuses on recent findings in genetically engineered animal models designed to elucidate the mechanisms and functions of various signal transduction pathways and gene expression programs in exercise-induced skeletal muscle adaptations.     

大肠杆菌中rnc与era基因的共表达

 rnc,era基因是大肠杆菌两个相邻的基因。用S_1核酸酶图谱法测得转录从rnc基因伸延到era基因。当rnc基因突变使所产生的RNaseⅢ丧失活性时,大肠杆菌中RNaseⅢ和Era蛋白的合成速度同对上升,且上升幅度相同,合成量相等。将此二基因分别或一起克隆入质粒并置于P_L起动子下游时,rnc能表达产生RNaseⅢ;rnc-era能表达产生RNaseⅢ和Era两种蛋白质,单独era则虽能转录却不产生Era蛋白。实验证明:era基因的表达依赖于rnc基因的表达,在体内两者共表达体现在转录和翻译水平上,两个基因同属于一个操纵子,共同受RNaseⅢ活性的反馈调节。单独转录的era-mRNA因缺乏有效的翻译起始序列而不能被翻译。     

The pleiotropic effects induced by therolC gene in transgenic plants are caused by expression restricted to protophloem and companion cells

Expression of therolC gene fromAgrobacterium rhizogenes causes morphological and developmental alterations in transgenic plants. The histological alterations underlying the macroscopic changes and the cellular localization of the site of expression of therolC gene have shown that: (i) the expression of therolC gene is developmentally regulated, (ii) in vegetative transgenic plants, the expression of therolC gene under the control of its own promoter is restricted to companion and protophloem cells, (iii) the site of action of the product(s) of the activity of the rolC enzyme is distinct from its site of expression, (iv) precise localization of the rolC peptide has been achieved by immunocytochemistry but not by the histochemical GUS assay. These results imply that the sites of action and expression of therolC gene in trangenic plants are physically separated. Thus the product(s) of the activity of the rolC enzyme must be a factor capable of being transported. Current models forrolC gene action are discussed taking into account the reported results.     

Physical conditioning modulates rat cardiac vascular endothelial growth factor gene expression in nitric oxide-deficient hypertension

Many individuals with cardiac diseases undergo periodic physical conditioning with or without medication to improve cardiovascular health. Therefore, this study investigated the interaction of physical training and chronic nitric oxide synthase (NOS) inhibitor (nitro-L-arginine methyl ester, L-NAME) treatment on blood pressure (BP), cardiac vascular endothelial factor (VEGF) gene expression, and nitric oxide (NO) systems in rats. Fisher 344 rats were divided into four groups and treated as follows: (1) sedentary control, (2) exercise training (ET) for 8 weeks, (3) L-NAME (10mg/kg, s.c. for 8 weeks), and (4) ET+L-NAME. BP was monitored with tail-cuff method. The animals were sacrificed 24h after last treatments and hearts were isolated and analyzed. Physical conditioning significantly increased respiratory exchange ratio, cardiac NO levels, NOS activity, endothelial eNOS, and inducible iNOS protein expression as well as VEGF gene expression. Training also caused depletion of cardiac malondialdehyde (MDA) levels indicating the beneficial effects of the training. Chronic L-NAME administration resulted in a depletion of cardiac NO level, NOS activity, and eNOS, nNOS, and iNOS protein expressions, as well as VEGF gene expression (2-fold increase in VEGF mRNA). Chronic L-NAME administration also enhanced cardiac MDA levels indicating cardiac oxidative injury. These biochemical changes were accompanied by increases in BP after L-NAME administration. Interaction of training and NOS inhibitor treatment resulted in normalization of BP and up-regulation of cardiac VEGF gene expression. The data suggest that physical conditioning attenuated the oxidative injury caused by chronic NOS inhibition by up-regulating the cardiac VEGF and NO levels and lowering the BP in rats.     

Translational control in stress and apoptosis

Cells respond to stress stimuli through coordinated changes in gene expression. The regulation of translation is often used under these circumstances because it allows immediate and selective changes in protein levels. There are many examples of translational control in response to stress. Here we examine two representative models, the regulation of eukaryotic initiation factor-2alpha by phosphorylation and internal ribosome initiation through the internal ribosome-entry site, which illustrate the importance of translational control in the cellular stress response and apoptosis.     

Proteomics of ischemia/reperfusion injury in rabbit myocardium reveals alterations to proteins of essential functional systems

Brief periods of myocardial ischemia prior to timely reperfusion result in prolonged, yet reversible, contractile dysfunction of the myocardium, or "myocardial stunning". It has been hypothesized that the delayed recovery of contractile function in stunned myocardium reflects damage to one or a few key sarcomeric proteins. However, damage to such proteins does not explain observed physiological alterations to myocardial oxygen consumption and ATP requirements observed following myocardial stunning, and therefore the impact of alterations to additional functional groups is unresolved. We utilized two-dimensional gel electrophoresis and mass spectrometry to identify changes to the protein profiles in whole cell, cytosolic- and myofilament-enriched subcellular fractions from isolated, perfused rabbit hearts following 15 min or 60 min low-flow (1 mL/min) ischemia. Comparative gel analysis revealed 53 protein spot differences (> 1.5-fold difference in visible abundance) in reperfused myocardium. The majority of changes were observed to proteins from four functional groups: (i) the sarcomere and cytoskeleton, notably myosin light chain-2 and troponin C; (ii) redox regulation, in particular several components of the NADH ubiquinone oxidoreductase complex; (iii) energy metabolism, encompassing creatine kinase; and (iv) the stress response. Protein differences appeared to be the result of isoelectric point shifts most probably resulting from chemical modifications, and molecular mass shifts resulting from proteolytic or physical fragmentation. This is consistent with our hypothesis that the time course for the onset of injury associated with myocardial stunning is too brief to be mediated by large changes to gene/protein expression, but rather that more subtle, rapid and potentially transient changes are occurring to the proteome. The physical manifestation of stunned myocardium is therefore the likely result of the summed functional impairment resulting from these multiple changes, rather than a result of damage to a single key protein.     

Morphological and functional characteristics of models of experimental myocardial injury induced by isoproterenol

The animal models of myocardial injury induced by systemic β-adrenergic receptor agonist administration represent an experimental approach of persisting interest. These models were found useful especially for studies of structural and functional adaptation of myocardium during the progression of cardiac adaptive response towards maladaptive hypertrophy and insufficiency. The pathological alterations induced by isoproterenol (ISO) do not develop evenly. The ISO models may contribute effectively to understanding of pathologies in signal transduction, energetics, excitability and contractility that may contribute concomitantly to cardiac dysfunction and heart failure. In this minireview we focused on the alterations in general characteristics and heart function as well as on the morphological changes of cardiomyocytes developed during ISO administration. The morphological alterations within the cellular macro- and microdomains correspond to the electrical remodelling and contractile dysfunction of ventricular myocardium that could be used to identify pathological changes ranging from hypertrophy to failing heart.     

The role of store-operated calcium influx in skeletal muscle signaling

In cardiac and skeletal muscle Ca(2+) release from intracellular stores triggers actomyosin cross-bridge formation and the generation of contractile force. In the face of large fluctuations of intracellular calcium ([Ca(2+)](i)) that occur with contractile activity, myocytes are able to sense and respond to changes in workload and patterns of activation through calcium signaling pathways which modulate gene expression and cellular metabolism. Store-operated calcium influx has emerged as a mechanism by which calcium signaling pathways are activated in order to respond to the changing demands of the myocyte. Abnormalities of store-operated calcium influx may contribute to maladaptive muscle remodeling in multiple disease states. The importance of store-operated calcium influx in muscle is confirmed in mice lacking STIM1 which die perinatally and in patients with mutations on STIM1 or Orai1 who exhibit a myopathy exhibited by hypotonia. In this review, we consider the role of store-operated Ca(2+) entry into skeletal muscle as a critical mediator of Ca(2+) dependent gene expression and how alterations in Ca(2+) influx may influence muscle development and disease.