Reversible inhibition of cilia regeneration in Stentor coeruleus by isopropyl-n-phenyl carbamate

Antibiotic-induced changes of mycelial growth of Botrytis cinerea

The effect of antibiotics and metabolic inhibitors on mycelial growth of Botrytis cinera was followed. Inhibitors of protein synthesis, chloramphenicol, erythromycin and tetracycline inhibit growth or sporulation of Botrytis cinera. Ethidium bromide, 5-fluorouracil, phenylethylalcohol and K 20 cause granulation, vacuolization and undulation of hyphase. 2,4-Dinitrophenol, boromycin, macrotetrolides, monensin, scopathricin and TX2 at subfungistatic concentrations induce intensive branching of hyphal tips i.e. at the site of synthesis of the cell wall. In older hyphase grown in the absence of the antibiotics the branching begins after their addition, particularly in the septum region. When comparing the results referred to here with those obtained previously and on the basis of literature data it may be assumed that the changes in polarity of growth of Botrytis cinerea might be caused primarily or secondarily by impairing membrane functions and formation of cell walls.

The effects of isopropyl N-phenyl carbamate on the green alga Oedogonium cardiacum. I. Cell division

Cell division in vegetative filaments of the green alga Oedogonium cardiacum is presented as an experimental system. We report on how we have used this system to study the effects of isopropyl N-phenylcarbamate (IPC) on the mitotic apparatus and on the phycoplast, a planar array of cytokinetic microtubules. Polymerization of microtubules was prevented when filaments, synchronized by a light/dark regime and chilled (2 degrees C) while in metaphase or just before phycoplast formation, were exposed to 5.5 x 10(-4) M IPC and then returned to room temperature. Spindles reformed or phycoplasts formed when these filaments were transferred to growth medium free of IPC. However, the orientation of both microtubular systems was disturbed: the mitotic apparatus often contained three poles, frequently forming three daughter nuclei upon karyokinesis; the phycoplast was often stellate rather than planar, and it sometimes was displaced to the side of both daughter nuclei, resulting in a binucleate and an anucleate cell upon cytokinesis. Our results suggest that IPC (a) prevents the assembly of microtubules, (b) increases the number of functional polar bodies, and (c) affects the orientation of microtubules in O. cardiacum. High voltage (1,000 kV) electron microscopy of 0.5-microm thick sections allowed us to visualize the polar structures, which were not discernible in thin sections.

Microtubule biogenesis and cell shape in Ochromonas. 3. Effects of herbicidal mitotic inhibitor isopropyl N-phenylcarbamate on shape and flagellum regeneration

The role of microtubules and microtubule nucleating sites in the unicell, Ochromonas has been examined through the use of two mitotic inhibitors, isopropyl N-phenylcarbamate (IPC) and isopropyl N-3-chlorophenyl carbamate (CIPC). Although IPC and CIPC have little or no effect on intact microtubules, the assembly of three separate sets of microtubules in Ochromonas has been found to be differentially affected by IPC and CIPC. The assembly of flagellar microtubules after mechanical deflagellation is partially inhibited; the reassembly of rhizoplast microtubules after pressure depolymerization is totally inhibited (however, macrotubules may form at the sites of microtubule initiation or elsewhere); and, the reassembly of the beak set of microtubules after pressure depolymerization may be unaffected although similar concentrations of IPC and CICP completely inhibit microtubule regeneration on the rhizoplast. These effects on microtubule assembly, either inhibitory or macrotubule inducing, are fully reversible. The kinetics of inhibition and reversal are found to be generally similar for both flagellar and cell shape regeneration. Incorporation data suggest that neither IPC nor CIPC has significant effects on protein synthesis in short term experiments. Conversely, inhibiting protein synthesis with cycloheximide has little effect on microtubule regeneration when IPC or CIPC is removed. Although the exact target for IPC and CIPC action remains uncertain, the available evidence suggests that the microtubule protein pool or the microtubule nucleating sites are specifically and reversibly affected. Comparative experiments using the mitotic inhibitor colchicine indicate some similarities and differences in its mode of action with respect to that of IPC and CIPC on assembly and disassembly of microtubules in these cells.