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The sarcoplasmic reticulum of the frog's sartorius muscle was examined by electron microscopy following sequential fixation in glutaraldehyde and osmium tetroxide and embedding in Epon. The earlier results of Porter and Palade on Ambystoma muscle were confirmed in the sartorius. In addition, the transverse tubules were observed to be continuous across the(More)
1. Propagated action potentials of striated muscle are calculated using an equivalent circuit that represents the transverse tubular system as a radial cable of sixteen elements. The membrane of the transverse tubules is assumed to have activatable ionic currents similar to those in the fibre surface.2. The configuration of the after-potential and the(More)
1. The membrane potential of isolated muscle fibres in solutions containing tetrodotoxin (TTX) was controlled with a two-electrode voltage clamp. The striation pattern in the region of the electrodes was observed microscopically.2. With square steps of depolarization of increasing magnitude, contraction occurs first in the myofibrils just beneath the(More)
  • 1958
Knowledge of the thickness of sections is important for proper interpretation of electron micrographs. Therefore, the thicknesses of sections of n-butyl methacrylate polymer were determined by ellipsometry, and correlated with the color shown in reflected light. The results are: gray, thinner than 60 mmicro; silver, 60 to 90 mmicro; gold, 90 to 150 mmicro;(More)
We have used 400 kilovolt intermediate voltage electron microscopy (IVEM) to examine thick sections of fibroblasts cultured in collagen gels. In these 3D collagen lattices, the long, narrow pseudopodial extensions that extend out and make contact with the collagen matrix exhibit a complex topography not seen in the processes put out by cells moving on(More)
Reconstruction from thick serial transverse slices of frog skeletal muscle fibers stained with peroxidase and examined by high-voltage electron microscopy has revealed that the T system networks at successive sarcomeres are connected together in a helicoidal fashion. From zero to eight helicoids have been found in each of a group of 21 fibers reconstructed(More)
1. Frog and toad sartorius muscles were soaked in ferritin suspensions and then fixed and prepared for electron microscopy. Ferritin particles were counted in micrographs of regions where fibril striations were in good register, and the number of particles plotted according to position along the sarcomeres.2. The distribution of ferritin particles in both(More)
BACKGROUND The capacity of lupus autoantibodies to enter living cells and bind to molecules for which they have intrinsic affinity is not well appreciated. In previous studies, we identified a subgroup of three murine monoclonal IgG anti-DNA antibodies, derived from lupus-prone MRL-lpr/lpr mice, that localized within nuclei of cells in multiple organs and(More)