The accessibility and interconnectivity of the tubular system network in toad skeletal muscle

Edwards, Joshua N. and Launikonis, Bradley S. (2008) The accessibility and interconnectivity of the tubular system network in toad skeletal muscle. The Jounal of Physiology, 586 21: 5077-5089. doi:10.1113/jphysiol.2008.155127


Author Edwards, Joshua N.
Launikonis, Bradley S.
Title The accessibility and interconnectivity of the tubular system network in toad skeletal muscle
Journal name The Jounal of Physiology   Check publisher's open access policy
ISSN 0022-3751
Publication date 2008-11-01
Year available 2008
Sub-type Article (original research)
DOI 10.1113/jphysiol.2008.155127
Volume 586
Issue 21
Start page 5077
End page 5089
Total pages 13
Editor W. A. Large
C. Huxley
Place of publication Oxford, England
Publisher Wiley-Blackwell Publishing Ltd.
Language eng
Subject C1
060602 Animal Physiology - Cell
110905 Peripheral Nervous System
Abstract The tubular (t) system is essential for normal function of skeletal muscle fibre, acting as a conduit for molecules and ions within the cell. However, t system accessibility and interconnectivity have been mainly assessed in fixed cells where the t system no longer fully represents that of the living cell. Here, fluorescent dyes of different diameter were allowed to equilibrate within the t system of intact fibres from toad, mechanically skinned to trap the dyes, and then imaged using confocal microscopy to investigate t system accessibility and interconnectivity. Dual imaging of rhod-2 and a 500 kDa fluorescein dextran identified regions throughout the t system that differed in the accessibility to molecules of different molecular weight. Restrictions within the t system lumen occurred at the junctions of the longitudinal and transverse tubules and also where a transverse tubule split into two tubules to maintain their alignment with Z-lines of adjacent mis-registered sarcomeres. Thus, three types of tubule, transverse, longitudinal and Z, can be identified by their lumenal diameter in this network. The latter we define for the first time as a tubule with a narrow lumen that is responsible for the change in register. Stretch-induced t system vacuolation showed exclusive access of rhod-2 to these structures indicating their origin was the longitudinal tubules. Exposing the sealed t system to highly hypertonic solution reversed vacuolation of longitudinal tubules and also revealed that these tubules are not collapsible. Fluorescence recovery after photobleaching (FRAP) measurements of t system-trapped fluo-5 N showed interconnectivity through the t system along the axis of the fibre. However, diffusion occurred at a rate slower than expected given the known number of longitudinal tubules linking adjacent transverse tubules. This could be explained by the observed narrow opening to the longitudinal tubules from transverse tubules, reducing the effective cross-sectional area in which molecules could move within the t system.
Keyword Frog-muscle
Reversible Vacuolation
Sarcotubular system
Mammalian Muscle
T-system
Fibers
Fibres
Rat
Ca2+
Microscopy
Excitation
Q-Index Code C1
Q-Index Status Confirmed Code
Additional Notes Published online before print September 4, 2008

Document type: Journal Article
Sub-type: Article (original research)
Collections: 2009 Higher Education Research Data Collection
School of Biomedical Sciences Publications
 
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Created: Tue, 31 Mar 2009, 21:47:18 EST by Shirley Rey on behalf of School of Biomedical Sciences