Página 1 dos resultados de 378 itens digitais encontrados em 0.002 segundos

Physical properties of edible films based on bovine myofibril proteins

Almeida de Souza, Silvia Maria; Sobral, Paulo Jose do Amaral; Menegalli, Florencia Cecilia
Fonte: UNIV ESTADUAL LONDRINA; LONDRINA Publicador: UNIV ESTADUAL LONDRINA; LONDRINA
Tipo: Artigo de Revista Científica
POR
Relevância na Pesquisa
27.23%
Myofibril proteins have excellent filmogenic properties. The objective of this article was to study the effect of the thermal treatment, of the pH and of the plasticizer concentration (Cp) of the filmogenic solution (FS), using over some physical properties of edible films, using a surface and response methodology (SRM). Films were made of lyophilized myofibril proteins (LMP) extracted from bovine muscle, employing the technique of solubility obtained from diluted saline solutions. The films were elaborated from FS containing 1 g of LMP/100g of FS and from Cp of 50 g to 79 g of glycerin/100 g of LMP. The LMP was dispersed in water under moderate agitation, and the pH was kept at 2.5-3.5 with the use of acetic acid. The FS were submitted to thermal treatment at different temperatures for 45 minutes. Films were dried in ventilated oven at 37 degrees C/18hr, conditioned at 75% of relative humidity at 25 degrees C/48 hr before analysis of: mechanical properties by puncture test; apparent opacity by spectrophotometer; solubility by immersion in water; and water vapor permeability by the gravimetric method. In general, films showed good appearance, translucent, easily handled and touchable, except for the films formed with pH 2.5 and at a low temperature (35 degrees C)...

Proteólise miofibrilar e maciez da carne de bovinos (Bos indicus) submetidos a diferentes técnicas pós-morte de resfriamento das carcaças; Myofibril fragmentation index and shear force of Bos indicus steers and heifers submitted to different hanging positions during chilling

Silva, Eliane Bonifácio
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 18/11/2005 PT
Relevância na Pesquisa
37.23%
O objetivo deste trabalho foi avaliar a posição da suspensão de carcaças durante o período de resfriamento, no primeiro experimento lados alternados de dez animais Nelores machos castrados, foram suspensos pelo método tradicional (Tendão de Aquiles) ou dispostos horizontalmente em pallets, no segundo experimento lados alternados de 16 animais machos castrados e 16 fêmeas foram suspensos pelo método tradicional (Tendão de Aquiles) ou pelo músculo Carpo Radial. Amostras do músculo Longissimus dorsi na 12ª costela foram coletadas de todos os lados (42 lados esquerdos e 42 lados direitos) após o período de 24 horas de resfriamento, estas amostras foram embaladas a vácuo e maturadas por sete dias antes de serem congeladas e armazenadas até a realização das analises de força de cisalhamento, perdas de água por cocção e índice de fragmentação miofibrilar (MFI). Para a primeira experiência nenhuma diferença foi observada para espessura de gordura subcutânea, perdas de água por cocção, força de cisalhamento e MFI.Na segunda experiência não houve diferença para espessura de gordura entre os tratamentos, mas as fêmeas apresentavam maior espessura que os machos. Para perdas de água por cocção e força de cisalhamento não houve diferença...

Physical properties of edible films based on bovine myofibril proteins

Almeida de Souza, Silvia Maria; do Amaral Sobral, Paulo Jose; Menegalli, Florencia Cecilia
Fonte: Univ Estadual Londrina; Londrina Publicador: Univ Estadual Londrina; Londrina
Tipo: Artigo de Revista Científica
POR
Relevância na Pesquisa
27.23%
Myofibril proteins have excellent filmogenic properties. The objective of this article was to study the effect of the thermal treatment, of the pH and of the plasticizer concentration (Cp) of the filmogenic solution (FS), using over some physical properties of edible films, using a surface and response methodology (SRM). Films were made of lyophilized myofibril proteins (LMP) extracted from bovine muscle, employing the technique of solubility obtained from diluted saline solutions. The films were elaborated from FS containing 1 g of LMP/100g of FS and from Cp of 50 g to 79 g of glycerin/100 g of LMP. The LMP was dispersed in water under moderate agitation, and the pH was kept at 2.5-3.5 with the use of acetic acid. The FS were submitted to thermal treatment at different temperatures for 45 minutes. Films were dried in ventilated oven at 37 degrees C/18hr, conditioned at 75% of relative humidity at 25 degrees C/48 hr before analysis of: mechanical properties by puncture test; apparent opacity by spectrophotometer; solubility by immersion in water; and water vapor permeability by the gravimetric method. In general, films showed good appearance, translucent, easily handled and touchable, except for the films formed with pH 2.5 and at a low temperature (35 degrees C)...

Myosin heavy chain isoforms regulate muscle function but not myofibril assembly.

Wells, L; Edwards, K A; Bernstein, S I
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em 02/09/1996 EN
Relevância na Pesquisa
27.23%
Myosin heavy chain (MHC) is the motor protein of muscle thick filaments. Most organisms produce many muscle MHC isoforms with temporally and spatially regulated expression patterns. This suggests that isoforms of MHC have different characteristics necessary for defining specific muscle properties. The single Drosophila muscle Mhc gene yields various isoforms as a result of alternative RNA splicing. To determine whether this multiplicity of MHC isoforms is critical to myofibril assembly and function, we introduced a gene encoding only an embryonic MHC into Drosophila melanogaster. The embryonic transgene acts in a dominant antimorphic manner to disrupt flight muscle function. The transgene was genetically crossed into an MHC null background. Unexpectedly, transformed flies expressing only the embryonic isoform are viable. Adult muscles containing embryonic MHC assemble normally, indicating that the isoform of MHC does not determine the dramatic ultrastructural variation among different muscle types. However, transformed flies are flightless and show reduced jumping and mating ability. Their indirect flight muscle myofibrils progressively deteriorate. Our data show that the proper MHC isoform is critical for specialized muscle function and myofibril stability.

Myofibril degeneration caused by tropomodulin overexpression leads to dilated cardiomyopathy in juvenile mice.

Sussman, M A; Welch, S; Cambon, N; Klevitsky, R; Hewett, T E; Price, R; Witt, S A; Kimball, T R
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em 01/01/1998 EN
Relevância na Pesquisa
27.61%
Loss of myofibril organization is a common feature of chronic dilated and progressive cardiomyopathy. To study how the heart compensates for myofibril degeneration, transgenic mice were created that undergo progressive loss of myofibrils after birth. Myofibril degeneration was induced by overexpression of tropomodulin, a component of the thin filament complex which determines and maintains sarcomeric actin filament length. The tropomodulin cDNA was placed under control of the alpha-myosin heavy chain gene promoter to overexpress tropomodulin specifically in the myocardium. Offspring with the most severe phenotype showed cardiomyopathic changes between 2 and 4 wk after birth. Hearts from these mice present characteristics consistent with dilated cardiomyopathy and a failed hypertrophic response. Histological analysis showed widespread loss of myofibril organization. Confocal microscopy of isolated cardiomyocytes revealed intense tropomodulin immunoreactivity in transgenic mice together with abnormal coincidence of tropomodulin and alpha-actinin reactivity at Z discs. Contractile function was compromised severely as determined by echocardiographic analyses and isolated Langendorff heart preparations. This novel experimentally induced cardiomyopathy will be useful for understanding dilated cardiomyopathy and the effect of thin filament-based myofibril degeneration upon cardiac structure and function.

The effect of Mg2+ on cardiac muscle function: Is CaATP the substrate for priming myofibril cross-bridge formation and Ca2+ reuptake by the sarcoplasmic reticulum?

Smith, G A; Vandenberg, J I; Freestone, N S; Dixon, H B
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em 15/03/2001 EN
Relevância na Pesquisa
27.76%
Kinetics are established for the activation of the myofibril from the relaxed state [Smith, Dixon, Kirschenlohr, Grace, Metcalfe and Vandenberg (2000) Biochem. J. 346, 393-402]. These require two troponin Ca2+-binding sites, one for each myosin head, to act as a single unit in initial cross-bridge formation. This defines the first, or activating, ATPase reaction, as distinct from the further activity of the enzyme that continues when a cross-bridge to actin is already established. The pairing of myosin heads to act as one unit suggests a possible alternating mechanism for muscle action. A large positive inotropic (contraction-intensifying) effect of loading the Mg2+ chelator citrate, via its acetoxymethyl ester, into the heart has confirmed the competitive inhibition of the Ca2+ activation by Mg2+, previously seen in vitro. In the absence of a recognized second Ca2+ binding site on the myofibril, with appropriate binding properties, the bound ATP is proposed as the second activating Ca2+-binding site. As ATP, free or bound to protein, can bind either Mg2+ or Ca2+, this leads to competitive inhibition by Mg2+. Published physico-chemical studies on skeletal muscle have shown that CaATP is potentially a more effective substrate than MgATP for cross-bridge formation. The above considerations allow calculation of the observed variation of fractional activation by Ca2+ as a function of [Mg2+] and in turn reveal simple Michaelis-Menten kinetics for the activation of the ATPase by sub-millimolar [Mg2+]. Furthermore the ability of bound ATP to bind either cation...

SmyD1, a histone methyltransferase, is required for myofibril organization and muscle contraction in zebrafish embryos

Tan, Xungang; Rotllant, Josep; Li, Huiqing; DeDeyne, Patrick; Du, Shao Jun
Fonte: National Academy of Sciences Publicador: National Academy of Sciences
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
27.23%
Histone modification has emerged as a fundamental mechanism for control of gene expression and cell differentiation. Recent studies suggest that SmyD1, a novo SET domain-containing protein, may play a critical role in cardiac muscle differentiation. However, its role in skeletal muscle development and its mechanism of actions remains elusive. Here we report that SmyD1a and SmyD1b, generated by alternative splicing of SmyD1 gene, are histone methyltransferases that play a key role in skeletal and cardiac muscle contraction. SmyD1a and SmyD1b are specifically expressed in skeletal and cardiac muscles of zebrafish embryos. Knockdown of SmyD1a and SmyD1b expression by morpholino antisense oligos resulted in malfunction of skeletal and cardiac muscles. The SmyD1 morphant embryos (embryos injected with morpholino oligos) could not swim and had no heartbeat. Myofibril organization in the morphant embryos was severely disrupted. The affected myofibers appeared as immature fibers with centrally located nuclei. Together, these data indicate that SmyD1a and SmyD1b are histone methyltransferases and play a critical role in myofibril organization during myofiber maturation.

Selective deletion of the NH2-terminal variable region of cardiac troponin T in ischemia-reperfusion by myofibril-associated μ-calpain cleavage†

Zhang, Zhiling; Biesiadecki, Brandon J.; Jin, Jian-Ping
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em 26/09/2006 EN
Relevância na Pesquisa
27.41%
The structure of the NH2-terminal region of troponin T (TnT) is hypervariable among the muscle type-specific isoforms and is also regulated by alternative RNA splicing. This region does not contain binding sites for other thin filament proteins but alteration of its structure affects the Ca2+-regulation of muscle contraction. Here we report a truncated cardiac TnT produced during myocardial ischemia-reperfusion. Amino acid sequencing and protein fragment reconstruction determined that it is generated by a posttranslational modification selectively removing the NH2-terminal variable region and preserving the conserved core structure of TnT. Triton X-100 extraction of cardiac muscle fibers promoted production of the NH2-terminal truncated cardiac TnT (cTnT-ND), indicating a myofibril-associated proteolytic activity. μ-Calpain is a myofibril-associated protease and is known to degrade TnT. Supporting a role of μ-calpain in producing cTnT-ND in myocardial ischemia-reperfusion, calpain inhibitors decreased the level of cTnT-ND in Triton-extracted myofibrils. μ-Calpain treatment of cardiac myofibril and troponin complex specifically reproduced cTnT-ND. In contrast, μ-calpain treatment of isolated cardiac TnT resulted in non-specific degradation...

Role of Myofibril-Inducing RNA in cardiac TnT expression in developing Mexican axolotl

Sferrazza, Gian-Franco; Zhang, Chi; Jia, Pingping; Lemanski, Sharon L.; Athauda, Gagani; Stassi, Alyssa; Halager, Kristine; Maier, Jennifer A.; Rueda-de-Leon, Elena; Gupta, Amit; Dube, Syamalima; Huang, Xupei; Prentice, Howard M.; Dube, Dipak K.; Lemanski
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
27.23%
The Mexican axolotl, Ambystoma mexicanum, has been a useful animal model to study heart development and cardiac myofibrillogenesis. A naturally-occurring recessive mutant, gene “c”, for cardiac non-function in the Mexican axolotl causes a failure of myofibrillogenesis due to a lack of tropomyosin expression in homozygous mutant (c/c) embryonic hearts.. Myofibril-Inducing RNA (MIR) rescues mutant hearts in vitro by promoting tropomyosin expression and myofibril formation thereafter. We have studied the effect of MIR on the expression of various isoforms of cardiac Troponin-T (cTnT), a component of the thin filament that binds with tropomyosin. Four alternatively spliced cTnT isoforms have been characterized from developing axolotl heart. The expression of various cTnT isoforms in normal, mutant, and mutant hearts corrected with MIR, is evaluated by real-time RT-PCR using isoform specific primer pairs; MIR affects the total transcription as well as the splicing of the cTnT in axolotl heart

Specific fluorescent labeling of chicken myofibril Z-line proteins catalyzed by guinea pig liver transglutaminase

Fonte: The Rockefeller University Press Publicador: The Rockefeller University Press
Tipo: Artigo de Revista Científica
Publicado em 01/05/1979 EN
Relevância na Pesquisa
27.52%
Guinea pig liver transglutaminase has been found to catalyze the covalent incorporation of dansylcadaverine into chicken skeletal muscle myofibril proteins. Epifluorescence microscopy reveals that the incorporated dansylcadaverine is specifically localized at or near the myofibril Z line. SDS-polyacrylamide gel electrophoresis (SDS-PAGE) indicates that actin constitutes a major fraction of the labeled material; the Z-line proteins alpha-actinin and desmin also show significant labeling, as well as tropomyosin, several additional unidentified proteins, and material with an extremely high molecular weight. The Z-line-specific fluorescence can be removed by brief trypsinization, which releases fluorescent alpha-actinin into the supernate. The majority of the fluorescent protein species are resistant to extraction by either 0.6 M KCl or KI. These results, in conjunction with the microscopic localization, suggest that the dansyl- labeled proteins are constituents of the myofibril Z line. A significant amount of fluorescently labeled transglutaminase is also present in labeled myofibrils, which is resistant to extraction with either 0.6 M KCl or KI. This result indicates a strong, noncovalent interaction between the transglutaminase molecule and the myofibril Z line.

Heat-shock protein 90α1 is required for organized myofibril assembly in skeletal muscles of zebrafish embryos

Du, Shao Jun; Li, Huiqing; Bian, Yuehong; Zhong, Yongwang
Fonte: National Academy of Sciences Publicador: National Academy of Sciences
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
27.41%
Heat-shock protein 90α (Hsp90α) is a member of the molecular chaperone family involved in protein folding and assembly. The role of Hsp90α in the developmental process, however, remains unclear. Here we report that zebrafish contains two Hsp90α genes, Hsp90α1, and Hsp90α2. Hsp90α1 is specifically expressed in developing somites and skeletal muscles of zebrafish embryos. We have demonstrated that Hsp90α1 is essential for myofibril organization in skeletal muscles of zebrafish embryos. Knockdown of Hsp90α1 resulted in paralyzed zebrafish embryos with poorly organized myofibrils in skeletal muscles. In contrast, knockdown of Hsp90α2 had no effect on muscle contraction and myofibril organization. The filament defects could be rescued in a cell autonomous manner by an ectopic expression of Hsp90α1. Biochemical analyses revealed that knockdown of Hsp90α1 resulted in significant myosin degradation and up-regulation of unc-45b gene expression. These results indicate that Hsp90α1 plays an important role in muscle development, likely through facilitating myosin folding and assembly into organized myofibril filaments.

Role of Nonmuscle Myosin IIB and N-RAP in Cell Spreading and Myofibril Assembly in Primary Mouse Cardiomyocytes

Lu, Shajia; Horowits, Robert
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /09/2008 EN
Relevância na Pesquisa
27.52%
We investigated the role of nonmuscle myosin heavy chain (NMHC) IIB in cultured embryonic mouse cardiomyocytes by specific knockdown using RNA interference. NMHC IIB protein levels decreased 90% compared with mock-transfected cells by 3 days post transfection. NMHC IIB knockdown resulted in a slow decrease in N-RAP protein levels over 6 days with no change in N-RAP transcript levels. N-RAP is a scaffold for α-actinin and actin assembly during myofibrillogenesis, and we quantitated myofibril accumulation by morphometric analysis of α-actinin organization. Between 3 and 6 days, NMHC IIB knockdown was accompanied by the abolishment of cardiomyocyte spreading. During this period the rate of myofibril accumulation steadily decreased, correlating with the slowly decreasing levels of N-RAP. Between 6 and 8 days NMHC IIB and N-RAP protein levels recovered, and cardiomyocyte spreading and myofibril accumulation resumed. Inhibition of proteasome function using MG132 led to accumulation of excess N-RAP, and the secondary decrease in N-RAP that otherwise accompanied NMHC IIB knockdown was abolished. The results show that NMHC IIB knockdown led to decreased N-RAP levels through proteasome-mediated degradation. Furthermore, these proteins have distinct functional roles...

Myofibril Assembly Visualized by Imaging N-RAP, Alpha-Actinin, and Actin in Living Cardiomyocytes

Manisastry, Shyam M.; Zaal, Kristien J. M.; Horowits, Robert
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
27.52%
N-RAP is a striated muscle-specific scaffolding protein that organizes α-actinin and actin into symetrical I-Z-I structures in developing myofibrils. Here we determined the order of events during myofibril assembly through time-lapse confocal microscopy of cultured embryonic chick cardiomyocytes coexpressing fluorescently tagged N-RAP and either α-actinin or actin. During de novo myofibril assembly, N-RAP assembled in fibrillar structures within the cell, with dots of α-actinin subsequently organizing along these structures. The initial fibrillar structures were reminiscent of actin fibrils, and coassembly of N-RAP and actin into newly formed fibrils supported this. The α-actinin dots subsequently broadened to Z-lines that were wider than the underlying N-RAP fibril, and N-RAP fluorescence intensity decreased. FRAP experiments showed that most of the α-actinin dynamically exchanged during all stages of myofibril assembly. In contrast, less than 20% of the N-RAP in premyofibrils was exchanged during 10-20 minutes after photobleaching, but this value increased to 70% during myofibril maturation. The results show that N-RAP assembles into an actin containing scaffold before α-actinin recruitment; that the N-RAP scaffold is much more stable than the assembling structural components; that N-RAP dynamics increase as assembly progresses; and that N-RAP leaves the structure after assembly is complete.

Mutating the converter-relay interface of Drosophila myosin perturbs ATPase activity, actin motility, myofibril stability and flight ability

Kronert, William A.; Melkani, Girish C.; Melkani, Anju; Bernstein, Sanford I.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
27.41%
We used an integrative approach to probe the significance of the interaction between the relay loop and converter domain of the myosin molecular motor from Drosophila melanogaster indirect flight muscle. During the myosin mechanochemical cycle, ATP-induced twisting of the relay loop is hypothesized to reposition the converter, resulting in cocking of the contiguous lever arm into the pre-power stroke configuration. The subsequent movement of the lever arm through its power stroke generates muscle contraction by causing myosin heads to pull on actin filaments. We generated a transgenic line expressing myosin with a mutation in the converter domain (R759E) at a site of relay loop interaction. Molecular modeling suggests that the interface between the relay loop and converter domain of R759E myosin would be significantly disrupted during the mechanochemical cycle. The mutation depressed calcium as well as basal and actin-activated MgATPase (Vmax) by ~60% compared to wild-type myosin, but there is no change in apparent actin affinity (Km). While ATP or AMP-PNP binding to wild-type myosin subfragment-1 enhanced tryptophan fluorescence ~15% or ~8%, respectively, enhancement does not occur in the mutant. This suggests that the mutation reduces lever arm movement. The mutation decreases in vitro motility of actin filaments by ~35%. Mutant pupal indirect flight muscles display normal myofibril assembly...

Thin, a Trim32 ortholog, is essential for myofibril stability and is required for the integrity of the costamere in Drosophila

LaBeau-DiMenna, Elisa M.; Clark, Kathleen A.; Bauman, Kenneth D.; Parker, Daniel S.; Cripps, Richard M.; Geisbrecht, Erika R.
Fonte: National Academy of Sciences Publicador: National Academy of Sciences
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
27.41%
Myofibril stability is required for normal muscle function and maintenance. Mutations that disrupt myofibril stability result in individuals who develop progressive muscle wasting, or muscular dystrophy, and premature mortality. Here we present our investigations of the Drosophila l(2)thin [l(2)tn] mutant. The “thin” phenotype exhibits features of the human muscular disease phenotype in that tn mutant larvae show progressive muscular degeneration. Loss-of-function and rescue experiments determined that l(2)tn is allelic to the tn locus [previously annotated as both CG15105 and another b-box affiliate (abba)]. tn encodes a TRIM (tripartite motif) containing protein highly expressed in skeletal muscle and is orthologous to the human limb-girdle muscular dystrophy type 2H disease gene Trim32. Thin protein is localized at the Z-disk in muscle, but l(2)tn mutants showed no genetic interaction with mutants affecting the Z-line–associated protein muscle LIM protein 84B. l(2)tn, along with loss-of-function mutants generated for tn, showed no relative mislocalization of the Z-disk proteins α-Actinin and muscle LIM protein 84B. In contrast, tn mutants had significant disorganization of the costameric orthologs β-integrin, Spectrin, Talin...

Alp/Enigma Family Proteins Cooperate in Z-Disc Formation and Myofibril Assembly

Katzemich, Anja; Liao, Kuo An; Czerniecki, Stefan; Schöck, Frieder
Fonte: Public Library of Science Publicador: Public Library of Science
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
27.52%
The Drosophila Alp/Enigma family protein Zasp52 localizes to myotendinous junctions and Z-discs. It is required for terminal muscle differentiation and muscle attachment. Its vertebrate ortholog ZASP/Cypher also localizes to Z-discs, interacts with α-actinin through its PDZ domain, and is involved in Z-disc maintenance. Human mutations in ZASP cause myopathies and cardiomyopathies. Here we show that Drosophila Zasp52 is one of the earliest markers of Z-disc assembly, and we use a Zasp52-GFP fusion to document myofibril assembly by live imaging. We demonstrate that Zasp52 is required for adult Z-disc stability and pupal myofibril assembly. In addition, we show that two closely related proteins, Zasp66 and the newly identified Zasp67, are also required for adult Z-disc stability and are participating with Zasp52 in Z-disc assembly resulting in more severe, synergistic myofibril defects in double mutants. Zasp52 and Zasp66 directly bind to α-actinin, and they can also form a ternary complex. Our results indicate that Alp/Enigma family members cooperate in Z-disc assembly and myofibril formation; and we propose, based on sequence analysis, a novel class of PDZ domain likely involved in α-actinin binding.

Liver Cell Line Derived Conditioned Medium Enhances Myofibril Organization of Primary Rat Cardiomyocytes

Kim, Jinseok; Hwang, Yu-Shik; Chung, Alice Mira; Chung, Bong Geun; Khademhosseini, Ali
Fonte: Korea Society for Molecular and Cellular Biology Publicador: Korea Society for Molecular and Cellular Biology
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
27.41%
Cardiomyocytes are the fundamental cells of the heart and play an important role in engineering of tissue constructs for regenerative medicine and drug discovery. Therefore, the development of culture conditions that can be used to generate functional cardiomyocytes to form cardiac tissue may be of great interest. In this study, isolated neonatal rat cardiomyocytes were cultured with several culture conditions in vitro and characterized for cell proliferation, myofibril organization, and cardiac functionality by assessing cell morphology, immunocytochemical staining, and time-lapse confocal scanning microscopy. When cardiomyocytes were cultured in liver cell line derived conditioned medium without exogenous growth factors and cytokines, the cell proliferation increased, cell morphology was highly elongated, and subsequent myofibril organization was highly developed. These developed myofibril organization also showed high level of contractibility and synchronization, representing high functionality of cardiomyocytes. Interestingly, many of the known factors in hepatic conditioned medium, such as insulin-like growth factor II (IGFII), macrophage colony-stimulating factor (MCSF), leukemia inhibitory factor (LIF), did not show similar effects as the hepatic conditioned medium...

Drosophila paramyosin is important for myoblast fusion and essential for myofibril formation

Liu, Hongjun; Mardahl-Dumesnil, Michelle; Sweeney, Sean T.; O'Kane, Cahir J.; Bernstein, Sanford I.
Fonte: The Rockefeller University Press Publicador: The Rockefeller University Press
Tipo: Artigo de Revista Científica
Publicado em 17/03/2003 EN
Relevância na Pesquisa
27.41%
Paramyosin is a major structural protein of thick filaments in invertebrate muscles. Coiled-coil dimers of paramyosin form a paracrystalline core of these filaments, and the motor protein myosin is arranged on the core surface. To investigate the function of paramyosin in myofibril assembly and muscle contraction, we functionally disrupted the Drosophila melanogaster paramyosin gene by mobilizing a P element located in its promoter region. Homozygous paramyosin mutants die at the late embryo stage. Mutants display defects in both myoblast fusion and in myofibril assembly in embryonic body wall muscles. Mutant embryos have an abnormal body wall muscle fiber pattern arising from defects in myoblast fusion. In addition, sarcomeric units do not assemble properly and muscle contractility is impaired. We confirmed that these defects are paramyosin-specific by rescuing the homozygous paramyosin mutant to adulthood with a paramyosin transgene. Antibody analysis of normal embryos demonstrated that paramyosin accumulates as a cytoplasmic protein in early embryo development before assembling into thick filaments. We conclude that paramyosin plays an unexpected role in myoblast fusion and is important for myofibril assembly and muscle contraction.

Thin filaments elongate from their pointed ends during myofibril assembly in Drosophila indirect flight muscle

Mardahl-Dumesnil, Michelle; Fowler, Velia M.
Fonte: The Rockefeller University Press Publicador: The Rockefeller University Press
Tipo: Artigo de Revista Científica
Publicado em 10/12/2001 EN
Relevância na Pesquisa
27.72%
Tropomodulin (Tmod) is an actin pointed-end capping protein that regulates actin dynamics at thin filament pointed ends in striated muscle. Although pointed-end capping by Tmod controls thin filament lengths in assembled myofibrils, its role in length specification during de novo myofibril assembly is not established. We used the Drosophila Tmod homologue, sanpodo (spdo), to investigate Tmod's function during muscle development in the indirect flight muscle. SPDO was associated with the pointed ends of elongating thin filaments throughout myofibril assembly. Transient overexpression of SPDO during myofibril assembly irreversibly arrested elongation of preexisting thin filaments. However, the lengths of thin filaments assembled after SPDO levels had declined were normal. Flies with a preponderance of abnormally short thin filaments were unable to fly. We conclude that: (a) thin filaments elongate from their pointed ends during myofibril assembly; (b) pointed ends are dynamically capped at endogenous levels of SPDO so as to allow elongation; (c) a transient increase in SPDO levels during myofibril assembly converts SPDO from a dynamic to a permanent cap; and (d) developmental regulation of pointed-end capping during myofibril assembly is crucial for specification of final thin filament lengths...

Specific fluorescent labeling of chicken myofibril Z-line proteins catalyzed by guinea pig liver transglutaminase

Gard, David L.; Lazarides, Elias
Fonte: Rockefeller University Press Publicador: Rockefeller University Press
Tipo: Article; PeerReviewed Formato: application/pdf
Publicado em /05/1979
Relevância na Pesquisa
27.52%
Guinea pig liver transglutaminase has been found to catalyze the covalent incorporation of dansylcadaverine into chicken skeletal muscle myofibril proteins. Epifluorescence microscopy reveals that the incorporated dansylcadaverine is specifically localized at or near the myofibril Z line. SDS-polyacrylamide gel electrophoresis (SDS-PAGE) indicates that actin constitutes a major fraction of the labeled material; the Z-line proteins alpha-actinin and desmin also show significant labeling, as well as tropomyosin, several additional unidentified proteins, and material with an extremely high molecular weight. The Z-line-specific fluorescence can be removed by brief trypsinization, which releases fluorescent alpha-actinin into the supernate. The majority of the fluorescent protein species are resistant to extraction by either 0.6 M KCl or KI. These results, in conjunction with the microscopic localization, suggest that the dansyl- labeled proteins are constituents of the myofibril Z line. A significant amount of fluorescently labeled transglutaminase is also present in labeled myofibrils, which is resistant to extraction with either 0.6 M KCl or KI. This result indicates a strong, noncovalent interaction between the transglutaminase molecule and the myofibril Z line.