Control of melanosome movement in intact and cultured melanophores in the bitterling, Acheilognathus lanceolatus

Noradrenaline‐ and Melatonin‐Mediated Regulation of Pigment Aggregation in Fish Melanophores

“…The dispersing effect is slightly slower in melanophores preaggregated with melatonin. This is consistent with previous results in the bitterling, Acheilognathus lanceolatus , which show that the aggregating effect of NA is abolished after washing the cells with phosphate‐buffered saline, but the aggregating effect of melatonin is not (21). Thus it seems likely that melatonin binds its receptor stronger than NA.…”

“…Its activation induces an increase in cAMP and results in dispersion (20). Melanophores in many species of fish are very sensitive to melatonin (1, 21, 22), but others have been reported to be refractory (1, 6, 23). Unpublished observations based on behavioural studies of cod in the sea (H. Nilsson Sköld) suggest that cod exhibit a circadian rhythm of colour change, which usually is associated with melatonin secretion.…”

Calponin, caldesmon, and chromatophores: The smooth muscle connection

“…The occasionally contradictory findings with regard to the effect of intracellular chromatophore Ca 2ϩ concentrations (see Rodziel and Haimo, 1986;Sammak et al, 1992, but Fujii, 1993Fujishige et al, 2000;Oshima et al, 1988) might be resolved when the actions of calponin are better understood. Organelle translocations, at least those involving melanophores, are more and more being seen to be both microtubule-as well as actin-dependent (Nilsson et al, 2001).…”

“…The intracellular network of microtubules, intermediate fibres, and microfilaments undoubtedly plays an important role in this (Gyoeva et al, 1987;Nilsson et al, 2001;Obika and Fukuzawa, 1993;Ochs, 1982). A host of microtubule-and microfilament-disrupting agents, too many to list, have been used to elucidate that beyond doubt microtubules provide a surface along which chromatosomes are driven by sliding forces (Fujii, 1993;Fujishige et al, 2000;McNiven et al, 1984;Oshima and Fujii, 1987). Even though no consensus has been reached regarding the nature of all the motor proteins involved (and different fishes may employ different systems), numerous studies indicate that kinesin is responsible for centrifugal movements (causing dispersion) and that dynein drives the aggregation of the pigment grains (Howard et al, 1989;Ogawa et al, 1987;Oshima and Fujii, 1987;Rodionov et al, 1991).…”

“…Aggregation of pigment granules is ATP-dependent (Sammak et al, 1992); it seems to involve dynactin (Nilsson et al 2001) and it is accompanied by a decrease in cAMP (Sammak et al, 1992), whereas increases in intracellular cAMP are known to lead to dispersion. Dispersion, typically requiring much longer times than the relatively fast pigment aggregations (speeds of 20 m/sec and 5 m/sec have been measured for aggregations and dispersions, respectively: Ip et al, 1984;Stearns, 1984), depends not only on cAMP, but, according to Fujishige et al (2000), also on the presence of ATP. Rodziel and Haimo (1986) hold the phosphorylation of an unidentified 57-kD polypeptide responsible for the dispersion.…”