Reperfusion after global brain ischemia results initially in a widespread suppression of protein synthesis in neurons, which persists in vulnerable neurons, that is caused by the inhibition of translation initiation as a result of the phosphorylation of the a-subunit of eukaryotic initiation factor 2 (eIF2a). To identify kinases responsible for eIF2a phosphorylation [eIF2a(P)] during brain reperfusion, we induced ischemia by bilateral carotid artery occlusion followed by post-ischemic assessment of brain eIF2a(P) in mice with homozygous functional knockouts in the genes encoding the heme-regulated eIF2a kinase (HRI), or the amino acidregulated eIF2a kinase (GCN2). A 10-fold increase in eIF2a(P) was observed in reperfused wild-type mice and in the HRI±/± or GCN2±/± mice. However, in all reperfused groups, the RNA-dependent protein kinase (PKR)-like endoplasmic reticulum eIF2a kinase (PERK) exhibited an isoform mobility shift on SDS±PAGE, consistent with the activation of the kinase. These data indicate that neither HRI nor GCN2 are required for the large increase in post-ischemic brain eIF2a(P), and in conjunction with our previous report that eIF2a(P) is produced in the brain of reperfused PKR±/± mice, provides evidence that PERK is the kinase responsible for eIF2a phosphorylation in the early post-ischemic brain.

Berthiaume JM, Bray MS, McElfresh TA, Chen X, Azam S, Young ME, Hoit BD, Chandler MP. The myocardial contractile response to physiological stress improves with high saturated fat feeding in heart failure. Am J Physiol Heart Circ Physiol 299: H410 -H421, 2010. First published May 28, 2010 doi:10.1152/ajpheart.00270.2010.-Impaired myocardial contractile function is a hallmark of heart failure (HF), which may present under resting conditions and/or during physiological stress. Previous studies have reported that high fat feeding in mild to moderate HF/left ventricular (LV) dysfunction is associated with improved contractile function at baseline. The goal of this study was to determine whether myocardial function is compromised in response to physiological stress and to evaluate the global gene expression profile of rats fed high dietary fat after infarction. Male Wistar rats underwent ligation or sham surgery and were fed normal chow (NC; 10% kcal fat; Sham ϩ NC and HF ϩ NC groups) or high-fat chow (SAT; 60% kcal saturated fat; Sham ϩ SAT and HF ϩ SAT groups) for 8 wk. Myocardial contractile function was assessed using a Millar pressure-volume conductance catheter at baseline and during inferior vena caval occlusions and dobutamine stress. Steady-state indexes of systolic function, LV ϩdP/dt max, stroke work, and maximal power were increased in the HF ϩ SAT group versus the HF ϩ NC group and reduced in the HF ϩ NC group versus the Sham ϩ NC group. Preload recruitable measures of contractility were decreased in HF ϩ NC group but not in the HF ϩ SAT group. ␤-Adrenergic responsiveness [change in LV ϩdP/dt max and change in cardiac output with dobutamine (0 -10 g·kg Ϫ1 ·min Ϫ1 )] was reduced in HF, but high fat feeding did not further impact the contractile reserve in HF. The contractile reserve was reduced by the high-fat diet in the Sham ϩ SAT group. Microarray gene expression analysis revealed that the majority of significantly altered pathways identified contained multiple gene targets correspond to cell signaling pathways and energy metabolism. These findings suggest that high saturated fat improves myocardial function at rest and during physiological stress in infarcted hearts but may negatively impact the contractile reserve under nonpathological conditions. Furthermore, high fat feeding-induced alterations in gene expression related to energy metabolism and specific signaling pathways revealed promising targets through which high saturated fat potentially mediates cardioprotection in mild to moderate HF/LV dysfunction. contractile function; infarction; high-fat diet; gene array analysis CHRONIC DISEASES AND CONDITIONS including obesity, insulin resistance, and diabetes are linked to elevations in plasma free fatty acids (FFA) leading to enhanced lipid accumulation in nonadipose tissue (24). Enhanced myocardial lipid accumulation has been associated with decreases in myocardial contractile function, resulting in the progression of heart failure (HF). Nutritional guidelines from the American Heart Association (2...

Background Myocardial strain imaging using echocardiography can be a cost-effective method to objectively quantify ventricular wall motion but few studies have compared strain measured with echocardiography against MRI in small animals. Methods and Results We compared circumferential (CS) and radial strain (RS) measured with echocardiography (vector velocity imaging [VVI]) to displacement encoding with stimulated-echo (DENSE) MRI in two mouse models of cardiomyopathy. In 3 month old mice with gene targeted deficiency of cardiac myosin binding protein-C (cMyBP-C−/−, n=6) or muscle LIM protein (MLP−/−, n=6), and wild-type (WT) mice (n=8), myocardial strains were measured at three cross-sectional levels and averaged to obtain global strains. There was modest correlation between VVI and MRI measured strains, with global CS yielding stronger correlation compared to global RS (CS R2 = 0.4452 vs. RS R2 = 0.2794, both p<0.05). Overall, strain measured by VVI was more variable than MRI (p<0.05) and the limits of agreement were slightly, but not significantly (p=0.14) closer for global CS than RS. Both VVI and MRI strain measurements showed significantly lower global CS strain in the knockout groups compared to the wild-type. The VVI (but not MRI) CS strain measurements were different between the two knockout groups (−14.5 ± 3.8% vs. −6.6 ± 4.0%, cMyBP-C−/− vs. MLP−/− respectively, p<0.05). Conclusions Measurements of LV circumferential and radial strains are feasible in small animals using 2D echocardiography. VVI and MRI strain measurements correlated modestly and the agreement between the modalities tended to be greater for circumferential than radial strain. Although VVI and MRI strains were able to differentiate between wild-type and knockout mice, only global circumferential VVI strain differentiated between the two models of cardiomyopathy.

The goals of this study were to determine whether functional outcome after motor training in rats was linked to synaptic plasticity in thalamus, and whether the Rota-rod apparatus, widely used to test motor function, could be used as an easy and quantitative motor skill training procedure. Adult female Sprague-Dawley rats (n = 39) were evaluated under three training conditions: 1. Movement requiring balance and coordination skills on Rota-rod; 2. simple exercise on treadmill; 3. nontrained controls. Motor function was evaluated by a series of motor tests (foot fault placing, parallel bar crossing, rope and ladder climbing) before and 14 or 28 days after training procedure. Synaptic strength in brain was assessed by synaptophysin immunocytochemistry. After 14 days of training, Rota-rod-trained animals significantly (p < 0.01) improved motor performance, compared to treadmill and nontrained animals. Animals with up to 28 days of simple exercises on the treadmill did not show a significantly improved performance on most motor tasks, except for an improvement in foot fault placing. Intensive synaptophysin immunoreactivity was present in the right but not the left mediodorsal and ventromedial nuclei of thalamus in Rota-rod-trained rats at 14 and 28 days, and in treadmill-trained rats at 28 days. The data suggested that functional outcome is effectively improved by motor skill training rather than by simple exercises, and this may be related, at least partially, to uniquely lateralized synaptogenesis in the thalamus. Both Rota-rod and treadmill could be quantitatively used in rats for motor training of different complexity.