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At least 595 records · Page 33Linked to original sources
PubMed1983

Non-uniform staining of myofibril a bands by a monoclonal antibody to skeletal muscle myosin S1 heavy chain.

A monoclonal antibody specific for the S1 fragment of skeletal muscle myosin has been identified. The antibody does not inhibit actin-activated Mg2+-ATPase or K+-EDTA-activated ATPase of myosin, indicating that it is not related to the portion of the S1 which carries the ATPase activity. In the absence of relaxing medium, antibody binding to the myosin filament is restricted to narrow regions on each side of the bare zone region of the filament, and to a narrow region at the tapered ends of the filament. This restricted antibody binding is not altered by the attachment of the myosin cross-bridges to the actin filaments. In the presence of relaxing medium, antibody binding occurs along the entire length of the cross-bridge-bearing region of the filament. The restricted binding to only small regions of the filament in the absence of relaxing medium suggests that the molecular packing of the myosin in different portions of the filament may be different, resulting in differences in the availability of the antigenic site on the S1 for antibody binding. The change in availability of the antigenic sites along the filament in the presence of relaxing medium may reflect a perturbation in the molecular packing of the filament, or a conformational change resulting from the binding of MgATP, both of which could affect the availability of the antigenic sites on the S1 for antibody.

Adenosine Triphosphatases↗
PubMed1996

A segment corresponding to amino acids Gln199-Lys208 of murine IL-1 alpha cross-reacts with an antigenic determinant localized in the Z-line of Drosophila melanogaster myofibrils.

Immunofluorescence microscopic observations indicated that a monoclonal antibody, Vmp 18, raised against the peptide 199-208 of murine interleukin 1 alpha, cross-reacted with an antigenic determinant of Drosophila thorax muscles. Immunoelectron microscopic analysis showed that the gold particles were mainly localized in the Z-line which is the attachment site of thin filaments from adjacent sarcomeres. On the contrary, the antibody failed to mark the Z-line in vertebrate skeletal muscle. A Western blot of total protein extract from Drosophila thorax muscles bound a protein of 43 kDa. Our observations suggest that the Vmp 18 antibody could contribute to clarify the composition of the Z-line in insect's flight muscles.

Amino Acid Sequence↗
PubMed1997

Theoretical considerations on myofibril stiffness.

A discrete model of the interaction between individual myofilaments was developed to study the stiffness of a sarcomere for the case in which filament compliance is not negligible. Our model retains, in the limit, the characteristics of the previously published model by Ford et al. (Ford, L. E., A. F. Huxley, and R. M. Simmons. 1981. The relation between stiffness and filament overlap in stimulated frog muscle fibres. J. Physiol. 311:219-249). In addition, the model is able to model the interaction in cases in which few cross-bridges are attached, or when the distribution of attached cross-bridges is not uniform. Our results confirm previous indications that it might be impossible to calculate the number of attached cross-bridges by using only stiffness measurements in quick-stretch (or release) experiments.

Actins↗
PubMed1988

Functional state of myofibrils, mitochondria and bound creatine kinase in skinned ventricular fibers of cardiomyopathic hamsters.

Functional states of cardiac contractile apparatus and mitochondria were studied in hereditary cardiomyopathic hamsters (CHF 146) and control golden hamsters using cardiac fibers skinned by two different techniques. The Triton X-100 skinned fibers obtained from diseased animals of 175 to 200 days old, or from control animals, demonstrated the same resting and maximal Ca-activated tensions, the same stiffness, the same rate of tension recovery after quick stretch; the fibers from cardiomyopathic animals differed only by a slightly increased calcium sensitivity. Functional activity of myofibrillar creatine kinase in cardiomyopathy was decreased as indicated by a smaller shift in the pMgATP/rigor tension curve to lower [MgATP] in the presence of phosphocreatine and by a slower rate of the tension recovery after quick stretch in the presence of phosphocreatine and ADP (without ATP). The saponin-skinned fibers allow evaluation of the respiration properties of the total tissue mitochondria. Data obtained in the preparations isolated from diseased animals of two ages (75 to 100 and 175 to 200 days) showed that the ratio of maximal ADP-stimulated respiration rate to the respiration rate in the absence of ADP (an analog of respiration control index) was unchanged in myopathy as compared with age-matched controls. However stimulation of respiration after an addition of creatine at submaximal ADP concentration was observed to be respectively 1.45 times and 3.5 times less in the preparations from younger and older myopathic animals as compared with their respective controls, thus indicating the impairment of functional coupling between mitochondrial creatine kinase reaction and oxidative phosphorylation. These results suggest that hereditary cardiomyopathy is associated with alterations in myocardial creatine kinase system, while myofilaments and mitochondria preserve their basic functional properties.

Adenosine Diphosphate↗