The role of microtubules in cell shape and pigment distribution in spreading erythrophores.
In order to investigate the role of microtubules in determining overall shape of the cell and distribution of pigment granules, a correlative whole cell electron microscopic and immunofluorescence light microscopic study was done of microtubule distribution during spreading of cultured erythrophores from scales of the squirrel fish, Holocentrus. After dissociation from the scale and immediately after attachment, erythrophores are round with long thin processes containing bundles of microtubules with associated pigment granules. In time these processes attach, and elongate, and cytoplasmic ground substance fills areas between microtubule bundles, preceding the appearance of microtubules in these areas of the cell. By 8 h cells are fully spread (star-shaped), prominent microtubule bundles have disappeared, and microtubules (along with pigment granules) are more evenly dispersed throughout the cell. After 24 h cells have increased in size, in number of microtubules, and in the length of preexisting tubules. The sequence of events in normal spreading is altered if cytochalasin D, cycloheximide, or nocodazole is included in the culture medium. Cytochalasin D, a microfilament-disrupting drug, prevents attachment and spreading, but allows elongation to occur. Cycloheximide, a protein synthesis inhibitor, allows for attachment and elongation, but no spreading. Nocodazole, a microtubule-disrupting drug, allows for attachment and spreading, but an irregular cell outline is the result. Even though spreading can occur without them, it is concluded that a normal number and distribution of microtubules are required for the development of normal cell shape and pigment distribution.
D000818:Animals; D001562:Benzimidazoles / Q000494:pharmacology; D002465:Cell Movement / Q000187:drug effects; D002856:Chromatophores / Q000032:analysis / Q000502:physiology / Q000648:ultrastructure*; D003513:Cycloheximide / Q000494:pharmacology; D015638:Cytochalasin D; D003572:Cytochalasins / Q000494:pharmacology; D003594:Cytoplasmic Granules / Q000032:analysis; D005399:Fishes / Q000033:anatomy & histology*; D008870:Microtubules / Q000502:physiology*; D015739:Nocodazole; D010860:Pigments, Biological / Q000032:analysis*
D001562:Benzimidazoles; D003572:Cytochalasins; D010860:Pigments, Biological; D015638:Cytochalasin D; D003513:Cycloheximide; D015739:Nocodazole