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  • 11
    Online Resource
    Online Resource
    Towards standardization of echocardiography for the evaluation of left ventricular function in adult rodents: a position paper of the ESC Working Group on Myocardial Function
    Oxford University Press (OUP) ; 2021
    In:  Cardiovascular Research Vol. 117, No. 1 ( 2021-01-01), p. 43-59
    Details
    In: Cardiovascular Research, Oxford University Press (OUP), Vol. 117, No. 1 ( 2021-01-01), p. 43-59
    Abstract: Echocardiography is a reliable and reproducible method to assess non-invasively cardiac function in clinical and experimental research. Significant progress in the development of echocardiographic equipment and transducers has led to the successful translation of this methodology from humans to rodents, allowing for the scoring of disease severity and progression, testing of new drugs, and monitoring cardiac function in genetically modified or pharmacologically treated animals. However, as yet, there is no standardization in the procedure to acquire echocardiographic measurements in small animals. This position paper focuses on the appropriate acquisition and analysis of echocardiographic parameters in adult mice and rats, and provides reference values, representative images, and videos for the accurate and reproducible quantification of left ventricular function in healthy and pathological conditions.
    Type of Medium: Online Resource
    ISSN: 0008-6363 , 1755-3245
    URL: Article
    DOI: 10.1093/cvr/cvaa110
    RVK:
    WA 15000
    Language: English
    Publisher: Oxford University Press (OUP)
    Publication Date: 2021
    detail.hit.zdb_id: 1499917-1
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  • 12
    Online Resource
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    Titin as a force-generating muscle protein under regulatory control
    American Physiological Society ; 2019
    In:  Journal of Applied Physiology Vol. 126, No. 5 ( 2019-05-01), p. 1474-1482
    Details
    In: Journal of Applied Physiology, American Physiological Society, Vol. 126, No. 5 ( 2019-05-01), p. 1474-1482
    Abstract: Titin has long been recognized as a mechanical protein in muscle cells that has a main function as a molecular spring in the contractile units, the sarcomeres. Recent work suggests that the titin spring contributes to muscle contraction in a more active manner than previously thought. In this review, we highlight this property, specifically the ability of the immunoglobulin-like (Ig) domains of titin to undergo unfolding-refolding transitions when isolated titin molecules or skeletal myofibrils are held at physiological force levels. Folding of titin Ig domains under force is a hitherto unappreciated, putative source of work production in muscle cells, which could work in synergy with the actomyosin system to maximize the energy delivered by a stretched, actively contracting muscle. This review also focuses on the mechanisms shown to modulate titin-based viscoelastic forces in skeletal muscle cells, including chaperone binding, titin oxidation, phosphorylation, Ca 2+ binding, and interaction with actin filaments. Along the way, we discuss which of these modulatory mechanisms might contribute to the phenomenon of residual force enhancement relevant for eccentric muscle contractions. Finally, a brief perspective is added on the potential for the alterations in titin-based force to dynamically alter mechano-chemical signaling pathways in the muscle cell. We conclude that titin from skeletal muscle is a determinant of both passive and active tension and a bona fide mechanosensor, whose stiffness is tuned by various independent mechanisms.
    Type of Medium: Online Resource
    ISSN: 8750-7587 , 1522-1601
    URL: Article
    DOI: 10.1152/japplphysiol.00865.2018
    RVK:
    WA 15000
    RVK:
    XA 52094
    Language: English
    Publisher: American Physiological Society
    Publication Date: 2019
    detail.hit.zdb_id: 1404365-8
    SSG: 12
    SSG: 31
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  • 13
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    A porcine model of hypertensive cardiomyopathy: implications for heart failure with preserved ejection fraction
    American Physiological Society ; 2015
    In:  American Journal of Physiology-Heart and Circulatory Physiology Vol. 309, No. 9 ( 2015-11), p. H1407-H1418
    Details
    In: American Journal of Physiology-Heart and Circulatory Physiology, American Physiological Society, Vol. 309, No. 9 ( 2015-11), p. H1407-H1418
    Abstract: Heart failure with preserved ejection fraction (HFPEF) evolves with the accumulation of risk factors. Relevant animal models to identify potential therapeutic targets and to test novel therapies for HFPEF are missing. We induced hypertension and hyperlipidemia in landrace pigs ( n = 8) by deoxycorticosteroneacetate (DOCA, 100 mg/kg, 90-day-release subcutaneous depot) and a Western diet (WD) containing high amounts of salt, fat, cholesterol, and sugar for 12 wk. Compared with weight-matched controls ( n = 8), DOCA/WD-treated pigs showed left ventricular (LV) concentric hypertrophy and left atrial dilatation in the absence of significant changes in LV ejection fraction or symptoms of heart failure at rest. The LV end-diastolic pressure-volume relationship was markedly shifted leftward. During simultaneous right atrial pacing and dobutamine infusion, cardiac output reserve and LV peak inflow velocities were lower in DOCA/WD-treated pigs at higher LV end-diastolic pressures. In LV biopsies, we observed myocyte hypertrophy, a shift toward the stiffer titin isoform N2B, and reduced total titin phosphorylation. LV superoxide production was increased, in part attributable to nitric oxide synthase (NOS) uncoupling, whereas AKT and NOS isoform expression and phosphorylation were unchanged. In conclusion, we developed a large-animal model in which loss of LV capacitance was associated with a titin isoform shift and dysfunctional NOS, in the presence of preserved LV ejection fraction. Our findings identify potential targets for the treatment of HFPEF in a relevant large-animal model.
    Type of Medium: Online Resource
    ISSN: 0363-6135 , 1522-1539
    URL: Article
    DOI: 10.1152/ajpheart.00542.2015
    RVK:
    WA 15000
    Language: English
    Publisher: American Physiological Society
    Publication Date: 2015
    detail.hit.zdb_id: 1477308-9
    SSG: 12
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  • 14
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    Multiple sources of passive stress relaxation in muscle fibres
    IOP Publishing ; 2004
    In:  Physics in Medicine and Biology Vol. 49, No. 16 ( 2004-08-21), p. 3613-3627
    Details
    In: Physics in Medicine and Biology, IOP Publishing, Vol. 49, No. 16 ( 2004-08-21), p. 3613-3627
    Type of Medium: Online Resource
    ISSN: 0031-9155 , 1361-6560
    URL: Article
    DOI: 10.1088/0031-9155/49/16/009
    RVK:
    WA 15000
    Language: Unknown
    Publisher: IOP Publishing
    Publication Date: 2004
    detail.hit.zdb_id: 1473501-5
    SSG: 12
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  • 15
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    Developmental changes in passive stiffness and myofilament Ca 2+ sensitivity due to titin and troponin-I isoform switching are not critically triggered by birth
    American Physiological Society ; 2006
    In:  American Journal of Physiology-Heart and Circulatory Physiology Vol. 291, No. 2 ( 2006-08), p. H496-H506
    Details
    In: American Journal of Physiology-Heart and Circulatory Physiology, American Physiological Society, Vol. 291, No. 2 ( 2006-08), p. H496-H506
    Abstract: The giant protein titin, a major contributor to myocardial mechanics, is expressed in two main cardiac isoforms: stiff N2B (3.0 MDa) and more compliant N2BA ( 〉 3.2 MDa). Fetal hearts of mice, rats, and pigs express a unique N2BA isoform (∼3.7 MDa) but no N2B. Around birth the fetal N2BA titin is replaced by smaller-size N2BA isoforms and N2B, which predominates in adult hearts, stiffening their sarcomeres. Here we show that perinatal titin-isoform switching and corresponding passive stiffness (ST p ) changes do not occur in the hearts of guinea pig and sheep. In these species the shift toward “adult” proportions of N2B isoform is almost completed by midgestation. The relative contributions of titin and collagen to ST p were estimated in force measurements on skinned cardiac muscle strips by selective titin proteolysis, leaving the collagen matrix unaffected. Titin-based ST p contributed between 42% and 58% to total ST p in late-fetal and adult sheep/guinea pigs and adult rats. However, only ∼20% of total ST p was titin based in late-fetal rat. Titin-borne passive tension and the proportion of titin-based ST p generally scaled with the N2B isoform percentage. The titin isoform transitions were correlated to a switch in troponin-I (TnI) isoform expression. In rats, fetal slow skeletal TnI (ssTnI) was replaced by adult carciac TnI (cTnI) shortly after birth, thereby reducing the Ca 2+ sensitivity of force development. In contrast, guinea pig and sheep coexpressed ssTnI and cTnI in fetal hearts, and skinned fibers from guinea pig showed almost no perinatal shift in Ca 2+ sensitivity. We conclude that TnI-isoform and titin-isoform switching and corresponding functional changes during heart development are not initiated by birth but are genetically programmed, species-specific regulated events.
    Type of Medium: Online Resource
    ISSN: 0363-6135 , 1522-1539
    URL: Article
    DOI: 10.1152/ajpheart.00114.2006
    RVK:
    WA 15000
    Language: English
    Publisher: American Physiological Society
    Publication Date: 2006
    detail.hit.zdb_id: 1477308-9
    SSG: 12
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  • 16
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    I-Band Titin in Cardiac Muscle Is a Three-Element Molecular Spring and Is Critical for Maintaining Thin Filament Structure
    Rockefeller University Press ; 1999
    In:  The Journal of Cell Biology Vol. 146, No. 3 ( 1999-08-09), p. 631-644
    Details
    In: The Journal of Cell Biology, Rockefeller University Press, Vol. 146, No. 3 ( 1999-08-09), p. 631-644
    Abstract: In cardiac muscle, the giant protein titin exists in different length isoforms expressed in the molecule's I-band region. Both isoforms, termed N2-A and N2-B, comprise stretches of Ig-like modules separated by the PEVK domain. Central I-band titin also contains isoform-specific Ig-motifs and nonmodular sequences, notably a longer insertion in N2-B. We investigated the elastic behavior of the I-band isoforms by using single-myofibril mechanics, immunofluorescence microscopy, and immunoelectron microscopy of rabbit cardiac sarcomeres stained with sequence-assigned antibodies. Moreover, we overexpressed constructs from the N2-B region in chick cardiac cells to search for possible structural properties of this cardiac-specific segment. We found that cardiac titin contains three distinct elastic elements: poly-Ig regions, the PEVK domain, and the N2-B sequence insertion, which extends ∼60 nm at high physiological stretch. Recruitment of all three elements allows cardiac titin to extend fully reversibly at physiological sarcomere lengths, without the need to unfold Ig domains. Overexpressing the entire N2-B region or its NH2 terminus in cardiac myocytes greatly disrupted thin filament, but not thick filament structure. Our results strongly suggest that the NH2-terminal N2-B domains are necessary to stabilize thin filament integrity. N2-B–titin emerges as a unique region critical for both reversible extensibility and structural maintenance of cardiac myofibrils.
    Type of Medium: Online Resource
    ISSN: 0021-9525 , 1540-8140
    URL: Article
    DOI: 10.1083/jcb.146.3.631
    RVK:
    WA 15000
    Language: English
    Publisher: Rockefeller University Press
    Publication Date: 1999
    detail.hit.zdb_id: 1421310-2
    SSG: 12
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  • 17
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    Titin Gene and Protein Functions in Passive and Active Muscle
    Annual Reviews ; 2018
    In:  Annual Review of Physiology Vol. 80, No. 1 ( 2018-02-10), p. 389-411
    Details
    In: Annual Review of Physiology, Annual Reviews, Vol. 80, No. 1 ( 2018-02-10), p. 389-411
    Abstract: The thin and thick filaments of muscle sarcomeres are interconnected by the giant protein titin, which is a scaffolding filament, signaling platform, and provider of passive tension and elasticity in myocytes. This review summarizes recent insight into the mechanisms behind how titin gene mutations cause hereditary cardiomyopathy and how titin protein is mechanically active in skeletal and cardiac myocytes. A main theme is the evolving role of titin as a modulator of contraction. Topics include strain-sensing via titin in the sarcomeric A-band as the basis for length-dependent activation, titin elastic recoil and refolding of titin domains as an energy source, and Ca 2+ -dependent stiffening of titin stretched during eccentric muscle contractions. Findings suggest that titin stiffness is a principal regulator of the contractile behavior of striated muscle. Physiological or pathological changes to titin stiffness therefore affect contractility. Taken together, titin emerges as a linker element between passive and active myocyte properties.
    Type of Medium: Online Resource
    ISSN: 0066-4278 , 1545-1585
    URL: Issue
    URL: Article
    DOI: 10.1146/physiol.2018.80.issue-1
    DOI: 10.1146/annurev-physiol-021317-121234
    RVK:
    WA 15000
    Language: English
    Publisher: Annual Reviews
    Publication Date: 2018
    detail.hit.zdb_id: 1474465-X
    SSG: 12
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  • 18
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    Titin (TTN): from molecule to modifications, mechanics, and medical significance
    Oxford University Press (OUP) ; 2022
    In:  Cardiovascular Research Vol. 118, No. 14 ( 2022-11-10), p. 2903-2918
    Details
    In: Cardiovascular Research, Oxford University Press (OUP), Vol. 118, No. 14 ( 2022-11-10), p. 2903-2918
    Abstract: The giant sarcomere protein titin is a major determinant of cardiomyocyte stiffness and contributor to cardiac strain sensing. Titin-based forces are highly regulated in health and disease, which aids in the regulation of myocardial function, including cardiac filling and output. Due to the enormous size, complexity, and malleability of the titin molecule, titin properties are also vulnerable to dysregulation, as observed in various cardiac disorders. This review provides an overview of how cardiac titin properties can be changed at a molecular level, including the role isoform diversity and post-translational modifications (acetylation, oxidation, and phosphorylation) play in regulating myocardial stiffness and contractility. We then consider how this regulation becomes unbalanced in heart disease, with an emphasis on changes in titin stiffness and protein quality control. In this context, new insights into the key pathomechanisms of human cardiomyopathy due to a truncation in the titin gene (TTN) are discussed. Along the way, we touch on the potential for titin to be therapeutically targeted to treat acquired or inherited cardiac conditions, such as HFpEF or TTN-truncation cardiomyopathy.
    Type of Medium: Online Resource
    ISSN: 0008-6363 , 1755-3245
    URL: Article
    DOI: 10.1093/cvr/cvab328
    RVK:
    WA 15000
    Language: English
    Publisher: Oxford University Press (OUP)
    Publication Date: 2022
    detail.hit.zdb_id: 1499917-1
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  • 19
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    Differential changes in titin domain phosphorylation increase myofilament stiffness in failing human hearts
    Oxford University Press (OUP) ; 2013
    In:  Cardiovascular Research Vol. 99, No. 4 ( 2013-9-1), p. 648-656
    Details
    In: Cardiovascular Research, Oxford University Press (OUP), Vol. 99, No. 4 ( 2013-9-1), p. 648-656
    Type of Medium: Online Resource
    ISSN: 1755-3245 , 0008-6363
    URL: Article
    DOI: 10.1093/cvr/cvt144
    RVK:
    WA 15000
    Language: English
    Publisher: Oxford University Press (OUP)
    Publication Date: 2013
    detail.hit.zdb_id: 1499917-1
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  • 20
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    Deranged myofilament phosphorylation and function in experimental heart failure with preserved ejection fraction
    Oxford University Press (OUP) ; 2013
    In:  Cardiovascular Research Vol. 97, No. 3 ( 2013-3-1), p. 464-471
    Details
    In: Cardiovascular Research, Oxford University Press (OUP), Vol. 97, No. 3 ( 2013-3-1), p. 464-471
    Type of Medium: Online Resource
    ISSN: 1755-3245 , 0008-6363
    URL: Article
    DOI: 10.1093/cvr/cvs353
    RVK:
    WA 15000
    Language: English
    Publisher: Oxford University Press (OUP)
    Publication Date: 2013
    detail.hit.zdb_id: 1499917-1
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