Mycoplasma pneumoniae was grown on Formvar-and carbon-coated electron microscope grids and treated with the nonionic detergent Triton X-100 to gently remove the membrane and cytoplasm. The detergent mixture was composed of 0.5% Triton X-100 in SSR-2 broth base. After this treatment, the grids were rinsed in a mixture of 0.1 M KC1, 5 mM MgC12, and 6 mM potassium phosphate buffer (pH 7.05) and negatively stained with uranyl acetate. The Triton X-100resistant remains of M. pneumoniae after gentle removal of the membrane and cytoplasm consisted of fibrous structures oriented similarly to the undisrupted cells. The thin fibers displayed a negative staining quality and diameter analogous to that of rabbit muscle F-actin. The fibrous moieties ended in rodlike condensations which appeared striated in negatively stained and shadowed preparations. These striations were regular, and the majority of rod structures had lengths of 220 to 300 nm and widths of 50 to 80 nm. Specific antibody to rabbit muscle actin, produced in guinea pigs, was used in indirect immunofluorescence of the M. pneumoniae colonies. Fluorescence was detected, with concentrations at the colony center and at the tips of filamentous cells.

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Cell migration plays an essential role in cancer cell study. Investigation of a novel method for controlling cell migration movement can help develop new therapeutic strategies. In this paper, a chemoattractant-loaded microbead, which is controlled by optical tweezers, is used to stimulate a target cell to accomplish automated migration along a desired path while avoiding obstacles. Models of both tweezers-bead and bead-cell interactions are investigated. A dual closed-loop control strategy is proposed, which includes an inner tweezers-bead control loop and an outer bead-cell control loop. A proportional-integral feedback plus feedforward controller is used to control the inner loop, and an active disturbance rejection controller is used for the outer loop, which can address the cell migration modeling errors and unknown external disturbances. A traffic rule based on interference-clearing mechanism is also proposed to reduce external disturbances on the system by preventing other particles from interfering with the migration process. The effectiveness of the proposed control approach is verified by simulations and experiments on migrating leukemia cancer cells.

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