Electrical characteristics of rat skeletal muscle in immaturity, adulthood and after sciatic nerve injury, and their relation to muscle fiber size.
Localized impedance methods can provide useful approaches for assessing neuromuscular disease. The mechanism of these impedance changes remains, however, uncertain. In order to begin to understand the relation of muscle pathology to surface impedance values, 8 immature rats, 12 mature rats and 8 mature rats that had undergone sciatic crush were killed. Measurement was made on tissue from the gastrocnemius muscle from each animal in an impedance cell, and the conductivity and relative permittivity of the tissue were calculated in both the longitudinal and transverse directions for frequencies of 2 kHz to 1 MHz. In addition, quantitative histological analysis was performed on the tissue. Significant elevations in transverse conductivity and transverse relative permittivity were found with animal growth, but longitudinal values showed no difference. After sciatic crush, both transverse and longitudinal conductivity increased significantly, with no change in the relative permittivity in either direction. The frequency dependence of the values also changed after nerve injury. In the healthy animals, there was a strong linear relation between measured conductivity and relative permittivity with cell area, but not for the sciatic crush animals. These results provide a first step toward developing a comprehensive understanding of how the electrical properties of muscle alter in neuromuscular disease states.
Ahad
Mohammad A
MA
Division of Neuromuscular Diseases, Department of Neurology, Harvard Medical School, Beth Israel Deaconess Medical Center, Boston, MA 02215, USA.
Fogerson
P Michelle
PM
Rosen
Glenn D
GD
Narayanaswami
Pushpa
P
Rutkove
Seward B
SB
D000375:Aging / Q000502:physiology*; D000818:Animals; D048429:Cell Size; D004553:Electric Conductivity; D017097:Electric Impedance; D016014:Linear Models; D008297:Male; D018485:Muscle Fibers, Skeletal / Q000166:cytology / Q000502:physiology*; D018482:Muscle, Skeletal / Q000166:cytology / Q000502:physiology* / Q000503:physiopathology*; D009409:Nerve Crush; D051381:Rats; D017208:Rats, Wistar; D012584:Sciatic Nerve / Q000293:injuries*