Ruben Ramirez-Mitchell

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The mechanical roles of sarcomere-associated cytoskeletal lattices were investigated by studying the resting tension-sarcomere length curves of mechanically skinned rabbit psoas muscle fibers over a wide range of sarcomere strain. Correlative immunoelectron microscopy of the elastic titin filaments of the endosarcomeric lattice revealed biphasic(More)
To explore the role of titin filaments in muscle elasticity, we measured the resting tension-sarcomere length curves of six rabbit skeletal muscles that express three size classes of titin isoform. The stress-strain curves of the split fibers of these muscles displayed a similar multiphasic shape, with an exponential increase in tension at low sarcomere(More)
An extensive network of transverse and longitudinal filamentous bridges was revealed when small myofibril bundles, prepared from Triton-EGTA-treated rabbit skeletal muscles, were extracted with Kl to remove the majority of thin and thick filaments. Transmission and scanning electron microscopic studies of these salt-resistant cytoskeletal residues indicated(More)
" Titin " is a term used to describe a pair of closely related megadalton polypeptides that together are the third most abundant myofibrillar protein in a wide range of striated muscles. It has been proposed that titin and another giant protein, nebulin , are the major components of an elastic cytoskeletal lattice within the sarcomere. We have now purified(More)
Cells of Anacystis nidulans grown at 25 or 30°C were examined both by thin-section and freeze-fracture electron microscopy. Cells grown at either temperature appeared similar when fixed at the growth temperature prior to observation. When cells were chilled to near 0°C for 30 min prior to fixation, those previously grown at 25° appeared unchanged as judged(More)
Cellular changes in hepatocytes of green sunfish (Lepomis cyanellus) exposed to arsenic-contaminated or control lake water were compared with the level of arsenic in the liver. Standard stereological procedures involved conversion of two-dimensional data (i.e. fractional measurements of morphological changes) to three-dimensional data for interpretation.(More)
The effect of medium of low ionic strength on the release of virus from Friend leukemia cells has been studied. The release of infectious Friend leukemia virus is almost completely inhibited in medium of low ionic strength, as measured by a focus-forming assay (XC assay), by endogenous RNA-dependent DNA polymerase activity of released virus particles, and(More)