Article Information

• PDF (721 kb)

PubMed

• Articles by F.V. Brozovich
• Articles by G.H. Pollack

Related Articles

• Low frequency sounds from sustained contraction of human ske...

  Low frequency sounds from sustained contraction of human skeletal muscle Biophysical Journal, Volume 30, Issue 1, 1 April 1980, Pages 119-127 G. Oster and J.S. Jaffe Abstract Low frequency audible vibrations are produced by human skeletal muscles undergoing sustained contraction. The effect is easily demonstrable with an electronic stethoscope which amplifies sound below 50 Hz. Autocorrelation analysis of the signal shows that it is periodic with a frequency 25 +/- 2.5 Hz. The quality of the sound is the same for all the skeletal muscles tested and is unaffected by changes in tension, ambient temperature, and blood flow. Electrically-stimulated contraction produces a sound which is indistinguishable from voluntary contraction. The amplitude of the sound increases linearly with tension. The sound signals are uncorrelated both in frequency and phase with electromyographic signals obtained simultaneously while the muscle is contacted. Arguments are presented to show that the sounds may be an intrinsic property of muscle contraction. Abstract | PDF (643 kb)

• Singular Behavior of Slow Dynamics of Single Excitable Cells...

  Singular Behavior of Slow Dynamics of Single Excitable Cells Biophysical Journal, Volume 96, Issue 1, 7 January 2009, Pages 255-267 Takahiro Harada, Tomomi Yokogawa, Tomoshige Miyaguchi and Hiroshi Kori Abstract In various kinds of cultured cells, it has been reported that the membrane potential exhibits fluctuations with long-term correlations, although the underlying mechanism remains to be elucidated. A cardiac muscle cell culture serves as an excellent experimental system to investigate this phenomenon because timings of excitations can be determined over an extended time period in a noninvasive manner through visualization of contractions, although the properties of beat-timing fluctuations of cardiac muscle cells at the single-cell level remains to be fully clarified. In this article, we report on our investigation of spontaneous contractions of cultured rat cardiac muscle cells at the single-cell level. It was found that single cells exhibit several typical temporal patterns of contractions and spontaneous transitions among them. Detrended fluctuation analysis on the time series of interbeat intervals revealed the presence of 1/ noise at sufficiently large timescales. Furthermore, multifractality was also found in the time series of interbeat intervals. These experimental trends were successfully explained using a simple mathematical model, incorporating correlated noise into ionic currents. From these findings, it was established that singular fluctuations accompanying 1/ noise and multifractality are intrinsic properties of single cardiac muscle cells. Abstract | Full Text | PDF (794 kb)

• Steroid Induction of a Peptide Hormone Gene Leads to Orchest...

  Steroid Induction of a Peptide Hormone Gene Leads to Orchestration of a Defined Behavioral Sequence Neuron, Volume 23, Issue 3, 1 July 1999, Pages 523-535 Dus̆an Z̆itn̆an, Linda S. Ross, Inka Z̆itn̆anova, John L. Hermesman, Sarjeet S. Gill and Michael E. Adams Summary At the end of each molt, insects shed the old cuticle by performing preecdysis and ecdysis behaviors. Regulation of these centrally patterned movements involves peptide signaling between endocrine Inka cells and the CNS. In Inka cells, we have identified the cDNA and gene encoding preecdysis-triggering hormone (PETH) and ecdysis-triggering hormone (ETH), which activate these behaviors. Prior to behavioral onset, rising ecdysteroid levels induce expression of the ecdysone receptor (EcR) and ETH gene in Inka cells and evoke CNS sensitivity to PETH and ETH. Subsequent ecdysteroid decline is required for peptide release, which initiates three motor patterns in specific order: PETH triggers preecdysis I, while ETH activates preecdysis II and ecdysis. The Inka cell provides a model for linking steroid regulation of peptide hormone expression and release with activation of a defined behavioral sequence. Summary | Full Text | PDF (454 kb)

• …more

Abstract

Isolated frog sartorius muscles were stimulated to shorten under lightly loaded conditions. A piezoelectric transducer was placed alongside the muscle to record sounds generated during contraction. Shortening was accompanied by the generation of a series of discrete sound bursts. The bursts were found to be moderately repeatable among successive contractions; 44% repeated from contraction to contraction. The duration of each sound burst was on the order of 400 mus, and the temperature dependence of the interval between successive bursts had a Q10 of approximately 2. Sound intensity was variable: average acoustic power ranged from 0.05–0.4 mW/g, or approximately 1% of the heat generated during contraction. The generation of discrete bursts of sound during contraction, rather than continuous sound, implies that contractile behavior may be discontinuous.