Figure 5. Periodic axial variation in dim light cycles.

(A) Transgenic frogs expressing Rho-eGFP were kept for six weeks in 168 h (120D:48L) cycle. During the dark periods, there was dim light exposure since the incubator was not completely light-sealed. In these dark periods (asterisks), there was an increase in fluorescent intensity and an additional axial variation superimposed, with a spatial period of 4–6 µm. At the arrow, the animals experienced one 24 h (12D:12L) cycle and followed by 4 days light and finally a 3-day dark period. Animals were sacrificed during the dark period. The intensity profile of the cell is shown below. (B) Transgenic frogs expressing Rho-eGFP were kept first in a 24 h (12D:12L) cycle (LD) and then moved to an incubator was not completely light-sealed(Dim) for two weeks and were moved to a totally light-sealed chamber (Dark). Cells (N = 23) were imaged and a representative cell is shown. The light-sealed chamber did exhibit periodic axial banding as found in the other two regions. The approximate locations of the transitions in lighting are indicated. The intensity profile of the cell is shown below.