The Biological bulletin (20370547432)

Title: The Biological bulletin

Identifier: biologicalbullet182mari (find matches)

Year: [1] (s)

Authors: Marine Biological Laboratory (Woods Hole, Mass. ); Marine Biological Laboratory (Woods Hole, Mass. ). Annual report 1907/08-1952; Lillie, Frank Rattray, 1870-1947; Moore, Carl Richard, 1892-; Redfield, Alfred Clarence, 1890-1983

Subjects: Biology; Zoology; Biology; Marine Biology

Publisher: Woods Hole, Mass. : Marine Biological Laboratory

Contributing Library: MBLWHOI Library

Digitizing Sponsor: MBLWHOI Library

Text Appearing Before Image:

CONTROL OF CIONA CILIA 387

Text Appearing After Image:

IB. Figure 3. Stigmatal cell models. Cilia lining a stigma are shown on the left and diagrammed on the right. (A) A single stigma in WS. Tufts of immotile cilia (black) stand upright, projecting from the refractile wall of the stigma into the Stigmatal space. In the diagram, the wall (edge) of the stigma is indicated by the irregular horizontal lines. (B) The same stigma after perfusion of RS. The cilia beat vigorously and, to a large extent, synchronously, giving rise to common wavefronts (arrowheads). As a result, the stigma is more open than in A. The Stigmatal wall does not change (compare outlines of stigma in diagrams). Scale bar. 1(1 fim. A. B models of Stigmatal ciliated cells. We were unable to elicit ciliary arrest in our saponin-permeabilized models at any Ca concentration used (10 5 to 10 \UCain RS). Instead, the axonemes stopped in an upright inactive position without passing through an arrest. We were concerned that our permeabilization proce- dure, or possibly subsequent proteolysis, might have re- moved or destroyed critical control factors or Ca-binding proteins (i.e.. calmodulin) necessary for demonstrating Ca-sensitivity of arrest in cell models. For example, ex- traction of calmodulin from sea urchin sperm and protist cilia leads to modification or loss of Ca control of axo- nemal motor responses (Brokaw and Nagayama, 1985; Izumi and Miki-Noumura. 1985; Izumi and Nakaoka, 1987). Extraction and incubation procedures may also modify the calmodulin-binding affinity of the axoneme (Brokaw. 1991). In addition, some detergents commonly used to make cell models (i.e., Triton-X 100) are potent inhibitors of both calmodulin and calmodulin-dependent cyclic nucleotide phosphodiesterase (Sharma and Wang, 1981). However, our attempts to restore presumed Ca sensi- tivity of ciliary arrest in models by trying different deter- gents, extraction times, protease inhibitors, or addition of exogenous bovine brain calmodulin, were uniformly un- successful. Nevertheless, the variable sensitivity of the in- activation response of models to Ca, particularly after longer extraction times (more than 9 min in ES), suggests that the absence of Ca-sensitive arrest in our models may be due to loss or modification of an as yet unidentified factor. Calcium and inaclivalion The upright inactive posture of Stigmatal cilia is clearly Ca-dependent: reactivated cilia are inactivated by 10~5 to 10 3 M Ca, and cilia on living tissue are inactivated by Ca ionophore in the presence of a lower Ca concentration (50 mA/) than that leading to arrest (100 mM. see above). These findings suggest that inactivation has a lower threshold to intracellular Ca than does arrest. Inactive cilia of cell models in RS -f- Ca were induced to beat by the addition of a calmodulin antagonist, either

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