ISSN:
1432-0878
Keywords:
Microfilaments
;
Contractility
;
Morphogenesis
;
Ascidians
;
Cytochalasin B
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Medicine
Notes:
Summary During tail resorption in Distaplia occidentalis the caudal epidermis contracts to 8.5% of its initial length in about 6 minutes and forces the axial complex (muscle, notochord and nerve cord) into a coiled configuration in the trunk. The contraction of the caudal epidermal cells is accompanied by rapid alignment of arrays of circa 50 Å (diameter) filaments parallel to the axis of contraction in the apical cytoplasm of each epidermal cell. Normal metamorphosis (including tail resorption) can be instantly induced by treating tadpole larvae with 0.5% dimethylsulfoxide. Cytochalasin B, (CCB) 〉 0.25 μg/ml rapidly inhibits contraction of the caudal epidermis. The tail stops shortening, then partly re-extends. When CCB is removed by washing immediately after relaxation, tail resorption resumes. Cytochalasin B reversibly disrupts the organization of central and subterminal arrays of apical filaments in the contractile caudal epidermal cells. Membrane associated filaments near the junctional complexes are not disrupted by 0.25–1.0 μg/ml of CCB. This suggests that CCB does not degrade the filaments into subunits. It is more likely that CCB blocks contraction by disrupting the binding forces between overlapping filaments and facilitates the disorganization of unattached filaments. A second type of filament with a fusiform configuration has been detected in the epidermal cells after CCB treatment. The possibility that these are myosinoid proteins is considered. The data presented in this paper strengthen the hypothesis that the filaments in the epidermal cells are part of a contractile apparatus.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00307009
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