Morphological studies on microfilaments and their organizing center in killifish (Fundulus heteroclitus L.) melanophores.
Fish chromatophores serve as excellent study models for cytoskeleton-dependent organelle translocations because the distribution of pigmentary organelles can be observed against a time frame by microscopy. In this study the distribution of microfilaments along with microtubules in cultured melanophores of the killifish (Fundulus heteroclitus Linneaus) are examined using whole-cell transmission electron microscopy (WCTEM), fluorescence, and laser scanning confocal microscopy. Dispersing, dispersed, aggregating and aggregated states of pigment are induced by adding either caffeine (for dispersion) or epinephrine (for aggregation) to the cells in a standard culture medium. The cells that exhibited a random melanosome distribution in the standard culture media without these two reagents, served as the control. The results indicate that: (i) a structure considered to be the actin-filament organizing center (AFOC) is in close proximity to the microtubule-organizing center (MTOC); (ii) the radial layout of microfilaments remains similar over four physiological states of pigmentary response with the exception of epinephrine-aggregated pigment, in which the aggregate blocks the viewing of the AFOC and central microfilament rays, yet radial microfilaments, whether central and/or peripheral, are apparent in all physiological states of distribution; and (iii) microfilaments serve, together with microtubules, as scaffolding for melanosomes which migrate in bi-directional rows on cross-bridges, thus shedding light on the mechanisms for orderly melanosome translocations in a structural continuum.
Kimler
Victoria A
VA
Department of Biological Sciences, Wayne State University and Gershenson Radiation Oncology Center, Harper Hospital, Detroit, MI, USA.
Palazzolo
Katherine L
KL
Anne
Premchand
P
Haddad
Maher M
MM
Lee
James B
JB
Harkins
Carmel
C
Vallarapu
Bharat
B
Taylor
John D
JD
D008841:Actin Cytoskeleton / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure*; D000818:Animals; D002478:Cells, Cultured; D023781:Fundulidae / Q000033:anatomy & histology / Q000378:metabolism*; D008543:Melanins / Q000378:metabolism*; D008547:Melanophores / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure*; D020460:Melanosomes / Q000378:metabolism / Q000648:ultrastructure; D018613:Microscopy, Confocal; D008854:Microscopy, Electron; D008856:Microscopy, Fluorescence; D008870:Microtubules / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure*; D023421:Models, Animal; D012867:Skin / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure*
D008543:Melanins