What question did this study set out to answer?

Investigate structural changes and binding distributions of individual myosin cross-bridges following rapid mechanical perturbations in contracting muscle.

June 25, 2012PLoS ONEOpen Access

Structural Changes in Isometrically Contracting Insect Flight Muscle Trapped following a Mechanical Perturbation

Q: What is the clinical evidence from this study?

Study design: Other. Population: Insect flight muscle contraction. Intervention: Mechanical perturbation (quick stretch or release) vs. Isometric contraction (iso-HST). Primary outcome: Structural changes in myosin cross-bridges (distribution of weak and strong binding attachments).

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Key result

A quick stretch or release applied to isometrically contracting insect flight muscle resulted in the near disappearance of a class of weak-binding cross-bridges attached within the target zone.

Population

Insect flight muscle (IFM) fibers

Comparison

0.5% changes in length within 2 ms followed… vs Isometrically contracting IFM without length…

Design

Preclinical

Authors

SWShenping WuYale University JLJun LiuNatural Resources Conservation Service MRMary C. ReedyFlorida State University

Discussion

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Implication

Hypothesis-generating for cross-bridge mechanics in insect muscle; leaves open relevance to vertebrate cardiac contraction.

Key Points

Investigate structural changes and binding distributions of individual myosin cross-bridges following rapid mechanical perturbations in contracting muscle.
Applied 0.5% length steps (stretch or release) within 2 ms to isometrically contracting insect flight muscle fibers.
Rapid-froze fibers 5–6 ms post-perturbation using a liquid helium-cooled copper mirror, followed by freeze-substitution and thin-sectioning.
Generated 3-D electron tomography reconstructions, classified cross-bridge structures into ~40 groups via multivariate data analysis, and conducted quasi-atomic modeling.
Approximately 98% of strong-binding acto-myosin attachments were localized to narrow target zones of two actin subunits midway between troponin complexes.
A specific class of weak-binding target-zone cross-bridges nearly vanished following both stretch and release, supporting their role as immediate precursors to strong-binding cross-bridges.

Structured PICO

Population

Insect flight muscle (IFM) fibers

Intervention

0.5% changes in length (either a stretch or a release) within 2 ms followed after 5-6 ms by rapid freezing

Comparator

Isometrically contracting IFM without length perturbation

Outcome

Structural changes in actin-myosin attachments (cross-bridges) assessed by electron tomography

Electron tomography reveals that mechanical perturbation of insect flight muscle causes the disappearance of weak-binding cross-bridges, providing a detailed structural model for muscle contraction.

Limitations

Severely constrained by combined requirements for low-noise tension records and high-quality EM images
Only the two best specimens were analyzed
Freezing impact times occurred later than ideal

Cite This Study

Wu et al. (2012) studied Insect flight muscle contraction. Mechanical perturbation (quick stretch or release) vs. Isometric contraction (iso-HST) was evaluated on Structural changes in myosin cross-bridges (distribution of weak and strong binding attachments). A quick stretch or release applied to isometrically contracting insect flight muscle resulted in the near disappearance of a class of weak-binding cross-bridges attached within the target zone.

synapsesocial.com/papers/6a86d9e848ef9afcd2a24564 https://doi.org/10.1371/journal.pone.0039422

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Structural Changes in Isometrically Contracting Insect Flight Muscle Trapped following a Mechanical Perturbation

Discussion

Member takes

Implication

Key Points

Structured PICO

Limitations

Cite This Study

Structural Changes in Isometrically Contracting Insect Flight Muscle Trapped following a Mechanical Perturbation

Discussion

Member takes

Implication

Key Points

Structured PICO

Limitations

Cite This Study

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