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Digitale Medien

Functional Differences of Myosin Heavy-Chain Isoforms in Skeletal Muscle (1997)

Hilber, Karlheinz ; Galler, Stefan ; Pette, Dirk

Springer

Naturwissenschaften 84 (1997), S. 201-204

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ISSN: 1432-1904

Quelle: Springer Online Journal Archives 1860-2000

Thema: Biologie , Chemie und Pharmazie , Allgemeine Naturwissenschaft

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/s001140050378

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Digitale Medien

Unloaded shortening of skinned mammalian skeletal muscle fibres: effects of the experimental approach and passive force (1994)

Galler, Stefan ; Hilber, Karlheinz

Springer

Journal of muscle research and cell motility 15 (1994), S. 400-412

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ISSN: 1573-2657

Quelle: Springer Online Journal Archives 1860-2000

Thema: Biologie , Medizin

Notizen: Summary In rabbit, rat and human skinned skeletal muscle fibres the length-time relationship of isotonic releases was determined after maximal Ca2+ activation. Slack test experiments provided information about unloaded conditions. Force clamp experiments of different load were extrapolated for zero load and compared with the slack test data. The course length-time relationship for unloaded conditions was similar using both approaches. However, slack test data showed a triphasic shape which could be fitted by three straight lines (phase I, II, III), whereas the data of force clamp experiments exhibited a steady curved shape. Consequently, the instantaneous slopes differed in the two relationships, but the distance which was shortened during the time interval of phase II was similar in both approaches. The ratio between these unloaded shortening velocities resulting from force clamp and slack test experiments was 1.01 ± 0.05 (sd) (n=25). The effects of passive force on the velocity of fibre shortening was investigated in skinned rabbit muscle fibres using slack test experiments. A significant increase in the unloaded shortening velocity was observed when the sarcomere length of the fibres was increased to values which exhibited considerable amounts of passive force. The high reproducibility of the isotonic releases required in this study was achieved by improving some methodological details. Using these improved techniques an identity between the relative fibre and sarcomere shortening was observed during the isotonic releases.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF00122114

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3

Digitale Medien

Improvement of the measurements on skinned muscle fibres by fixation of the fibre ends with glutaraldehyde (1998)

Hilber, Karlheinz ; Galler, Stefan

Springer

Journal of muscle research and cell motility 19 (1998), S. 365-372

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ISSN: 1573-2657

Quelle: Springer Online Journal Archives 1860-2000

Thema: Biologie , Medizin

Notizen: Abstract Experiments with activated skinned muscle fibre segments are limited by the structural and mechanical instability of the preparations. The present study shows that fixation of the muscle fibre ends with glutaraldehyde significantly improves the reliability of such experiments. We tested the effects of a specific glutaraldehyde fixation technique on the structural stability and the mechanical properties of skinned rat and rabbit skeletal muscle fibres in an approach where the fibre segments are attached to the apparatus by gluing. Preparations with fixed and unfixed ends were compared. During the first few minutes of maximal activation, fibres with fixed and unfixed ends exhibited similar mechanical properties to one another, suggesting that our fixation procedure selectively impregnates the fibre ends without contaminating the remaining active fibre part. During prolonged maximal activations (3–60min), preparations with fixed ends exhibited a better stability, both in the sarcomere length signal (detected by laser diffraction) and in the unloaded shortening velocity. Thus, our technique of muscle fibre end fixation caused a substantial improvement in the mechanical measurements on skinned muscle preparations.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1023/A:1005393519811

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4

Digitale Medien

Calcium-activated and stretch-induced force responses in two biochemically defined muscle fibre types of the Norway lobster (1994)

Galler, Stefan ; Neil, Douglas M.

Springer

Journal of muscle research and cell motility 15 (1994), S. 390-399

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ISSN: 1573-2657

Quelle: Springer Online Journal Archives 1860-2000

Thema: Biologie , Medizin

Notizen: Summary Mechanical properties of thin (〈80 μm) myofibrillar bundles from single rehydrated freeze-dried fibres of the superficial abdominal flexor muscle of the lobster Nephrops norvegicus have been measured, and subsequently the protein content of these fibres has been analysed by SDS-PAGE. Two slow fibre phenotypes can be distinguished on the basis of their myofibrillar assemblages and sarcomere length (type S1: 6.0–7.5 μm, type S2: 8.0–10.9 μm). Differences (means ± sd, average of seven fibres of each type) were observed in the kinetics for Ca2+ activation (half time of force development (ms); S1: 416±174; S2: 762±199 plus a delay of 280±130) and relaxation (half time of force decay (ms); S1: 162±75, S2: 257±53), for Ca2+ sensitivity of force generation (-log [Ca2+] for half maximal activation; S1: 5.40±0.12; S2: 5.55±0.08), and of the kinetics of stretch activation (delay of the peak of stretch-induced force increase (ms); S1: 91±30; S2: 493±436). From these results and partly also in combination with previously obtained mechanical data on intact fibres it can be concluded (1) that S2 fibres are specialized for long-lasting force maintenance whereas S1 fibres are adapted for slow movements; (2) intrinsic myofibrillar kinetics is not the main time-limiting factor for either activation or relaxation of intact fibres under physiological conditions; (3) processes which precede crossbridge cycling seem to be the main time-limiting factors for the Ca2+ activation of the myofibrils.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF00122113

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5

Digitale Medien

Effects of myofibrillar bundle diameter on the unloaded shortening velocity of skinned skeletal muscle fibres (1998)

HILBER, KARLHEINZ ; GALLER, STEFAN

Springer

Journal of muscle research and cell motility 19 (1998), S. 143-155

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ISSN: 1573-2657

Quelle: Springer Online Journal Archives 1860-2000

Thema: Biologie , Medizin

Notizen: Abstract Using both slack tests and force clamp experiments, the velocity of unloaded shortening (Vu; Vu(st), slack test; Vu(fc), force clamp) was determined for maximally Ca2+-activated myofibrillar bundles. These were obtained by mechanically splitting single muscle fibres of rat, rabbit, crab and lobster skeletal muscles. A comparison was made between the Vu of thick (mammalian: 45-70 mum mean diameter; crustacean: 90-175 mum) and thin (mammalian: 25-40 mum; crustacean: 35-85mum) preparations of the same muscle fibre. The bundle diameter had opposite effects on Vu in mammalian and crustacean muscle fibres. The Vu of thin mammalian bundles was about 0.6times that of the thick ones, whereas in crustacean preparations this ratio was about 1.5. The kinetics of stretch-induced delayed force increase of maximally Ca2+-activated fibres (stretch activation) appeared not to differ between the thick and thin bundles from any animal preparation. Control experiments showed that the observed diameter effects on Vu are not due to differences in the chemical environment of the myofilaments. One possible explanation is that the intrinsic physical factors of the myofibrils modify Vu differently during progressive shortening in mammalian and crustacean preparations.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1023/A:1005308628472

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6

Digitale Medien

Activation of skinned muscle fibres from the Norway lobster Nephrops norvegicus L. by manganese ions (1998)

Holmes, Janet M. ; Hilber, Karlheinz ; Galler, Stefan ; [weitere]

Springer

Journal of muscle research and cell motility 19 (1998), S. 537-548

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ISSN: 1573-2657

Quelle: Springer Online Journal Archives 1860-2000

Thema: Biologie , Medizin

Notizen: Abstract Effects of Mn2+ and Ca2+ on the mechanical properties of glycerinated myofibrillar bundles originating from slow S1 type muscle fibres of superficial flexor muscles of the lobster Nephrops norvegicus were investigated. Mn2+ (5–20μm) activated the preparations in a dose-dependent manner. The sensitivity of myofibrillar force generation for Mn2+ was around 30 times lower than that for Ca2+. The maximal tension produced under Mn2+ activation was about 75% of that under Ca2+ activation. At higher free Mn2+ concentrations (〉2mm), the steady-state force decreased; it was completely abolished at 30mm free Mn2+. These high Mn2+ solutions were accompanied by changes in MgATP and MnATP concentrations, and in the ionic strength. Control experiments have shown that none of these parameters seemed fo account fully for the observed force depression in high Mn2+ solutions. It is likely that direct effects of Mn2+ such as a change of the myofilament surface charges are responsible. The maximal unloaded shortening velocity of the myofibrillar preparations was shown to be similar under maximal Mn2+ and Ca2+ activation. Conversely, the kinetics of stretch-induced delayed force increase were about two to three times faster under Mn2+ activation. These results suggest that certain steps of the cross-bridge cycle depend on the ion species bound to the regulatory proteins.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1023/A:1005312610629

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7

Digitale Medien

Shortening properties of two biochemically defined muscle fibre types of the Norway lobster Nephrops norvegicus L. (1999)

Holmes, Janet M. ; Hilber, Karlheinz ; Galler, Stefan ; [weitere]

Springer

Journal of muscle research and cell motility 20 (1999), S. 265-278

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ISSN: 1573-2657

Quelle: Springer Online Journal Archives 1860-2000

Thema: Biologie , Medizin

Notizen: Abstract Mechanical properties of myofibrillar bundles from single chemically skinned fibres from the superficial abdominal flexor muscle of the Norway lobster Nephrops norvegicus were measured, and the protein content of these fibres was analysed by SDS-PAGE. Two slow fibre phenotypes (S1, S2) were distinguished on the basis of their myofibrillar protein assemblages. Data from 9 S1 and 8 S2 fibres obtained at similar sarcomere length demonstrate significant differences between the fibre types in maximal tension (N cm-2, S1: 10.5 ± 3.9; S2: 3.1 ± 0.8), in the delay of the peak of stretch activation (ms, S1: 122 ± 18; S2: 412 ± 202), in fibre stiffness (N cm-2 per nm half sarcomere, S1: 0.36 ± 0.19; S2: 0.09 ± 0.03) and in maximal shortening velocity (fibre length s-1, S1: 0.53 ± 0.10; S2: 0.27 ± 0.06). Furthermore, the maximal power output of the type S1 fibres was about five times larger than that of S2 fibres. The power output was maximal at lower loads in S1 fibres (relative load = 0.37 ± 0.04) than in S2 fibres (relative load = 0.44 ± 0.05). This study represents a comprehensive investigation of two slow muscle fibre types which are thought to be specialized for slow movements (S1 fibres) and for the postural control of the abdomen (S2 fibres).

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1023/A:1005481725344

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