Fractal analysis of cytoskeleton rearrangement in cardiac muscle
during head-down tilt.
Thomason, Donald B., Otis Anderson Iii, and Vandana Menon.
Department of Physiology and Biophysics, University of Tennessee
Health Science Center, Memphis
APStracts 3:0286A, 1996.
Head-down tilt by tail suspension of the rat produces a volume, but
not pressure load on the heart. One response of the heart is
cytoskeleton rearrangement, a phenomenon commonly referred to as
disruption. In these experiments, we used fractal analysis as a means
to measure complexity of the microtubule structures at 8 and 18h
following imposition of head-down tilt. Microtubules in whole tissue
cardiac myocytes were stained with fluorescein colchicine and
visualized by confocal microscopy. The fractal dimension (D) of the
structures were calculated by the dilation method, which involves
successively dilating the outline perimeter of the microtubule
structures and measuring the area enclosed. The head-down tilt
resulted in a progressive decrease in D (decreased complexity) when
measured at small dilations of the perimeter, but the maximum D
(maximum complexity) of the microtubule structures did not change
with treatment. Analysis of the fold change in complexity as a
function of the dilation indicates an almost two-fold decrease in
microtubule complexity at small kernel dilations. This decrease in
complexity is associated with a more gaussian distribution of
microtubule diameters, indicating a less structured microtubule
cytoskeleton. We interpret these data as a microtubule rearrangement,
rather than erosion, because total tubulin fluorescence was not
different between groups. This conclusion is supported by F-actin
fluorescence data indicating a dispersed structure without loss of
actin.
Received 22 January 1996; accepted in final form 22 May 1996.
APS Manuscript Number A74-6.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 28 June 96