Small Amounts of α-Myosin Heavy Chain Isoform Expression Significantly Increase Power Output of Rat Cardiac Myocyte Fragments

The publisher's version of this article may be found at http://circres.ahajournals.org/cgi/content/abstract/90/11/1150?maxtoshow=&HITS=10&hits=10&RESULTFORMAT=&searchid=1049671889562_931&stored_search=&FIRSTINDEX=0&volume=90&firstpage=1150&search_url=http%3A%2F%2Fcircres.ahajournals.org%2Fcgi%2Fsearch&journalMyocardial performance is likely affected by the relative expression of the two myosin heavy chain (MyHC) isoforms, namely {alpha}-MyHC and ß-MyHC. The relative expression of each isoform is regulated developmentally and in pathophysiological states. Many pathophysiological states are associated with small shifts in the relative expression of each MyHC isoform, yet the functional consequence of these shifts remains unclear. The purpose of this study was to determine the functional effect of a small shift in the relative expression of {alpha}-MyHC. To this end, power output was measured in rat cardiac myocyte fragments that expressed {approx}12% {alpha}-MyHC and in myocyte fragments that expressed {approx}0% {alpha}-MyHC, as determined in the same cells by SDS-PAGE analysis after mechanical experiments. Myocyte fragments expressing {approx}12% {alpha}-MyHC developed {approx}52% greater peak normalized power output than myocyte fragments expressing {approx}0% {alpha}-MyHC. These results indicate that small amounts of {alpha}-MyHC expression significantly augment myocyte power output.This work was supported by National Heart, Lung, and Blood Institute Grant HL-57852 (K.S.M.) and a predoctoral fellowship granted by the Heartland Affiliate of the American Heart Association (T.J.H.)

Modulation of Cardiac Performance by Motor Protein Gene Transfer

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/75444/1/annals.1420.011.pd

Power Output Is Increased After Phosphorylation of Myofibrillar Proteins in Rat Skinned Cardiac Myocytes

This work was supported by American Heart Association Beginning Grant-in-Aid 9914291 and NIH Grant HL57852.The publisher's version may be found at http://circres.ahajournals.org/cgi/content/full/89/12/1184ß-Adrenergic stimulation increases stroke volume in mammalian hearts as a result of protein kinase A (PKA)-induced phosphorylation of several myocyte proteins. This study investigated whether PKA-induced phosphorylation of myofibrillar proteins directly affects myocyte contractility. To test this possibility, we compared isometric force, loaded shortening velocity, and power output in skinned rat cardiac myocytes before and after treatment with the catalytic subunit of PKA. Consistent with previous studies, PKA increased phosphorylation levels of myosin binding protein C and troponin I, and reduced Ca2+ sensitivity of force. PKA also significantly increased both maximal force (25.4±8.3 versus 31.6±11.3 µN [P<0.001, n=12]) and peak absolute power output (2.48±1.33 versus 3.38±1.52 µW/mg [P<0.05, n=5]) during maximal Ca2+ activations. Furthermore, PKA elevated power output at nearly all loads even after normalizing for the increase in force. After PKA treatment, peak normalized power output increased {approx}20% during maximal Ca2+ activations (n=5) and {approx}33% during half-maximal Ca2+ activations (n=9). These results indicate that PKA-induced phosphorylation of myofibrillar proteins increases the power output-generating capacity of skinned cardiac myocytes, in part, by speeding the step(s) in the crossbridge cycle that limit loaded shortening rates, and these changes likely contribute to greater contractility in hearts after ß-adrenergic stimulation

Spatial gradients in action potential duration created by regional magnetofection of hERG are a substrate for wavebreak and turbulent propagation in cardiomyocyte monolayers

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/95178/1/jphysiol.2012.238758.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/95178/2/TJP_5439_sm_SuppMat.pd

Spatial gradients in action potential duration created by regional magnetofection of hERG are a substrate for wavebreak and turbulent propagation in cardiomyocyte monolayers

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/95178/1/jphysiol.2012.238758.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/95178/2/TJP_5439_sm_SuppMat.pd

Human Cardiomyocytes Prior to Birth by Integrationâ Free Reprogramming of Amniotic Fluid Cells

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/135525/1/Supplemental_Information.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/135525/2/sct320165121595.pd

Comparative mitochondrial genomics of snakes: extraordinary substitution rate dynamics and functionality of the duplicate control region

<p>Abstract</p> <p>Background</p> <p>The mitochondrial genomes of snakes are characterized by an overall evolutionary rate that appears to be one of the most accelerated among vertebrates. They also possess other unusual features, including short tRNAs and other genes, and a duplicated control region that has been stably maintained since it originated more than 70 million years ago. Here, we provide a detailed analysis of evolutionary dynamics in snake mitochondrial genomes to better understand the basis of these extreme characteristics, and to explore the relationship between mitochondrial genome molecular evolution, genome architecture, and molecular function. We sequenced complete mitochondrial genomes from Slowinski's corn snake (<it>Pantherophis slowinskii</it>) and two cottonmouths (<it>Agkistrodon piscivorus</it>) to complement previously existing mitochondrial genomes, and to provide an improved comparative view of how genome architecture affects molecular evolution at contrasting levels of divergence.</p> <p>Results</p> <p>We present a Bayesian genetic approach that suggests that the duplicated control region can function as an additional origin of heavy strand replication. The two control regions also appear to have different intra-specific versus inter-specific evolutionary dynamics that may be associated with complex modes of concerted evolution. We find that different genomic regions have experienced substantial accelerated evolution along early branches in snakes, with different genes having experienced dramatic accelerations along specific branches. Some of these accelerations appear to coincide with, or subsequent to, the shortening of various mitochondrial genes and the duplication of the control region and flanking tRNAs.</p> <p>Conclusion</p> <p>Fluctuations in the strength and pattern of selection during snake evolution have had widely varying gene-specific effects on substitution rates, and these rate accelerations may have been functionally related to unusual changes in genomic architecture. The among-lineage and among-gene variation in rate dynamics observed in snakes is the most extreme thus far observed in animal genomes, and provides an important study system for further evaluating the biochemical and physiological basis of evolutionary pressures in vertebrate mitochondria.</p

Functional cardiac fibroblasts derived from human pluripotent stem cells via second heart field progenitors

Cardiac fibroblasts (CFs) play critical roles in heart development, homeostasis, and disease. The limited availability of human CFs from native heart impedes investigations of CF biology and their role in disease. Human pluripotent stem cells (hPSCs) provide a highly renewable and genetically defined cell source, but efficient methods to generate CFs from hPSCs have not been described. Here, we show differentiation of hPSCs using sequential modulation of Wnt and FGF signaling to generate second heart field progenitors that efficiently give rise to hPSC-CFs. The hPSC-CFs resemble native heart CFs in cell morphology, proliferation, gene expression, fibroblast marker expression, production of extracellular matrix and myofibroblast transformation induced by TGFβ1 and angiotensin II. Furthermore, hPSC-CFs exhibit a more embryonic phenotype when compared to fetal and adult primary human CFs. Co-culture of hPSC-CFs with hPSC-derived cardiomyocytes distinctly alters the electrophysiological properties of the cardiomyocytes compared to co-culture with dermal fibroblasts. The hPSC-CFs provide a powerful cell source for research, drug discovery, precision medicine, and therapeutic applications in cardiac regeneration.J.L.C. received funding from Coordenação de Aperfeiçoamento de Pessoal de Nível Superior and Fundação de Amparo à Pesquisa do Distrito Federal. The work was funded by NIH R01 HL129798 (T.J.K.); NIH U01 HL134764 (T.J.K.); S10RR025644 (T.J.K.); and the UW Institute for Clinical and Translational Research, grant UL1TR000427, from the Clinical and Translational Science Award of the NCATS/NIH.S

Role of extracellular histones in the cardiomyopathy of sepsis

The purpose of this study was to define the relationship in polymicrobial sepsis (in adult male C57BL/6 mice) between heart dysfunction and the appearance in plasma of extracellular histones. Procedures included induction of sepsis by cecal ligation and puncture and measurement of heart function using echocardiogram/Doppler parameters. We assessed the ability of histones to cause disequilibrium in the redox status and intracellular [Ca2+]i levels in cardiomyocytes (CMs) (from mice and rats). We also studied the ability of histones to disturb both functional and electrical responses of hearts perfused with histones. Main findings revealed that extracellular histones appearing in septic plasma required C5a receptors, polymorphonuclear leukocytes (PMNs), and the Nachtâ , LRRâ , and PYDâ domainsâ containing protein 3 (NLRP3) inflammasome. In vitro exposure of CMs to histones caused loss of homeostasis of the redox system and in [Ca2+]i, as wellas defects in mitochondrial function. Perfusion of hearts with histones caused electrical and functional dysfunction. Finally, in vivo neutralization of histones in septic mice markedly reduced the parameters of heart dysfunction. Histones caused dysfunction in hearts during polymicrobial sepsis. These events could be attenuated by histone neutralization, suggesting that histones may be targets in the setting of sepsis to reduce cardiac dysfunction.â Kalbitz, M., Grailer, J. J., Fattahi, F., Jajou, L., Herron, T. J., Campbell, K. F., Zetoune, F. S., Bosmann, M., Sarma, J. V., Huberâ Lang, M., Gebhard, F., Loaiza, R., Valdivia, H. H., Jalife, J., Russell, M. W., Ward, P. A. Role of extracellular histones in the cardiomyopathy of sepsis. FASEB J. 29, 2185â 2193 (2015). www.fasebj.orgPeer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/154273/1/fsb2fj14268730.pd

Across-arc geochemical variations in the Southern Volcanic Zone, Chile (34.5- 38.0°S): Constraints on Mantle Wedge and Input Compositions

Crustal assimilation (e.g. Hildreth and Moorbath, 1988) and/or subduction erosion (e.g. Stern, 1991; Kay et al., 2005) are believed to control the geochemical variations along the northern portion of the Chilean Southern Volcanic Zone. In order to evaluate these hypotheses, we present a comprehensive geochemical data set (major and trace elements and O-Sr-Nd-Hf-Pb isotopes) from Holocene primarily olivine-bearing volcanic rocks across the arc between 34.5-38.0°S, including volcanic front centers from Tinguiririca to Callaqui, the rear arc centers of Infernillo Volcanic Field, Laguna del Maule and Copahue, and extending 300 km into the backarc. We also present an equivalent data set for Chile Trench sediments outboard of this profile. The volcanic arc (including volcanic front and rear arc) samples primarily range from basalt to andesite/trachyandesite, whereas the backarc rocks are low-silica alkali basalts and trachybasalts. All samples show some characteristic subduction zone trace element enrichments and depletions, but the backarc samples show the least. Backarc basalts have higher Ce/Pb, Nb/U, Nb/Zr, and Ta/Hf, and lower Ba/Nb and Ba/La, consistent with less of a slab-derived component in the backarc and, consequently, lower degrees of mantle melting. The mantle-like δ18O in olivine and plagioclase phenocrysts (volcanic arc = 4.9-5.6 and backarc = 5.0-5.4 per mil) and lack of correlation between δ18O and indices of differentiation and other isotope ratios, argue against significant crustal assimilation. Volcanic arc and backarc samples almost completely overlap in Sr and Nd isotopic composition. High precision (double-spike) Pb isotope ratios are tightly correlated, precluding significant assimilation of older sialic crust but indicating mixing between a South Atlantic Mid Ocean-Ridge Basalt (MORB) source and a slab component derived from subducted sediments and altered oceanic crust. Hf-Nd isotope ratios define separate linear arrays for the volcanic arc and backarc, neither of which trend toward subducting sediment, possibly reflecting a primarily asthenospheric mantle array for the volcanic arc and involvement of enriched Proterozoic lithospheric mantle in the backarc. We propose a quantitative mixing model between a mixed-source, slab-derived melt and a heterogeneous mantle beneath the volcanic arc. The model is consistent with local geodynamic parameters, assuming water-saturated conditions within the slab