Potentiation of the colchicine effect on frog melanocytes by high hydrostatic pressure

Abstract

In dermal melanocytes of Rana pipiens, colchicine is known to produce a gradual, dosage-dependent dispersion of melanin granules, irreversible over several hours. This effect is potentiated by a number of chemical agents that normally produce a reversible dispersion of granules. In the present study we examined the effect of high hydrostatic pressure on changes induced in melanocytes by colchicine.In finger's solution, samples of skin from a single frog were incubated for 30 minutes at room temperature with or without colchicine, 9 X M. Then two samples, one of which had been pretreated with colchicine, were successively subjected to 12,000 psi for one hour at 25 to 26°C. The degree of dispersion of melanin granules in melanocytes was observed before, during and after the period of pressure.In frog skin pretreated with colchicine, the usually gradual, irreversible dispersion of melanin granules in rnelanocytes was potentiated, Since high pressure i s known to produce solational changes in protoplasm, such changes may accompany dispersion of melanin granules in melanocytes. If this be so, then sol-gel equilibria may be important in the action of dispersing and aggregating agents, many of which are hormones and other physiologically active agents. Finally, the present study supports the hypothesis that colchicine shifts protoplasmic sol-gel equilibria toward a less gelated condition.

THE EFFECT OF COLCHICINE ON MIGRATION OF PIGMENT GRANULES IN THE MELANOPHORES OFFUNDULUS HETEROCLITUS

“…Colchicine has also been found to inhibit the aggregation of pigment in tissue cultured melanophores of Xenopus laevis after removal of MSH (Kulemann, 1960). The proposal has been advanced that in frog melanophores this drug has an effect on cytoplasmic viscosity (Malawista, 1965;Malawista, Asterita, and Marsland, 1966).Recently Bikle, Tilney and Porter (1966) have shown that an ordered array of microtubules is present in the branching processes of the melanophores of the killifish, Fundidns hcteroclitus. These observations have been confirmed by Novales and Novales (1966) and Green (T968).…”

Melatonin: Inhibition of Microtubule‐Based Oral Morphogenesis in Stentor coeruleus

“…Organisms were removed from the 100% acetone with a Pasteur pipette and placed in a polyethylene stopper (Nalgene) containing 50% Bojax epoxy mixture (14) plus DMP-30, and 50% acetone. The 1st fixation was in 3% (V/V) glutaraldehyde (0.05 M phosphate buffer at pH 7.2), for 30-45 min at either 4 C or room temperature.…”

“…Isolated ciliary structures were prepared for transmission electron microscopy by the critical-point drying method as described earlier ( 14). Micrographs were made with a JEM 7A electron microscope.…”

“…Ciliates of the order Hypotrichida have been shown to have elaborate fiber systems which are usually associated with the organisms' ciliature (7,14,37,38,40). Function of the infraciliature is considered briefly.…”

“…At present, however, Euplotes is the only hypotrich genus for which there is much information on infraciliary fine structure (9,13,14,15,41). In the latter work some brief information was presented for another hypotrich, Onychodromus grandis.…”