Shell regeneration was induced in the marine archaeogastropod, Tegula, by cutting a window in the first body whorl of the shell. At six hour intervals for six days after the shell window was cut, the mantle, foot, and hepatopancreas were prepared for transmission electron microscopy, and the shell window was prepared for scanning electron microscopy. Transmission electron microscopy of the three tissues showed an increase in rough endoplasmic reticulum, Golgi complexes, and mitochondria, followed by the appearance of three types of inclusions. Later, intracellular space increased and spherites were visible. Scanning electron microscopy showed initial crystal deposition in the shell window to be in the form of small doublypointed crystallites associated with an organic membrane. These spindle-shaped crystals were frequently aggregated into radiating clusters or rosettes which coalesed until a thin sheet of mineralized material covered the shell window, within six days of shell injury.
A window was cut in the first body whorl of the marine snail, Tegula, to induce shell regeneration. At various intervals after the shell window was cut, the window with the regenerated material and the shell surrounding it were prepared for scanning electron microscopy. Initial crystal deposition occurred in association with an organic matrix and appeared as small, spindle-shaped crystals formed by the aggregation of needle-like subunits. The spindles were frequently aggregated into stellate clusters that coalesced to form a sheet of mineralized tissue. After about two months of regeneration, dumbbell-shaped crystal aggregates and spherulites were apparent on the surface of the regenerated shell. The regenerated shell assumed a normal structure after at least four months of regeneration. Crystal deposition also occurred on the normal shell bordering the shell window. The crystals assumed several forms, and their orientation appeared to be determined by the microtopography of the underlying shell.
The ciliated junctions between the gill filaments of scallop gills were studied. Junctional cilia are borne on both sides of spurs of tissue cilifers extending from the filaments. In an intact junction, each cilium is paired with another cilium from a cilifer on a neighboring filament. An electron dense band underlies the plasma membrane of each Junctional cilium along the line of apposition with its mate.Cytochalasins A, B, and E caused gill test square preparations to break up into their component filaments. All three cytochalasins disrupted the electron dense band, and cytochalasins A and E also disrupted the ciliary microtubules. These effects were reversible.The paired adhesion of the Junctional cilia was also reversibly inhibited by treatment with Concanavalin A (Con A; 100 ^g/ml). Con A bound to the surface of the Junctional cilia was labeled with hemocyanin. After treatment with Con A alone, the label was lightly and evenly distributed over the shafts of the cilia, but was more densely concentrated at their tips. In cytochalasin-Con A preparations, the surface labeling of the Junctional cilia increased with the duration of cytochalasin exposure.
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