First, we can consider some simple cases where objects are more or less stationary and we are simply interested in intensity changes. In such cases, we can simply segment the objects of interest from a single time-point and clone these over the entire series.

In this example, the first time point shows all the cells:

We can use this time point to mark all the cells we are interested in. In this case, a Watershed segmented works adequately, although some smaller objects are incorrectly included:

The segmentation can be followed by a Segment Feature Filter to specifically label only those objects large enough to be considered:

Because the intensities change throughout the series we can't use the same segmentation parameters for every time-point, but since the cells don't move we can simply clone the segmented objects over the entire time series from the Objects menu.

By using the option to create groups for the cloned objects we can easily plot how individual cells change intensity in the time series.

In the Objects table, the Master-Detail view allows us to display the groups in the top table, and the values for the cells at each time-point in the bottom table. Then the Charts can be used to plot any feature of those cells, in this case, mean intensity.

If automatic segmentation of all the cells of interest is not possible from a single time-point, the Projection viewer can be used to create a maximum intensity projection of the entire series over time. The resulting image can be used to segment the cells and then the objects can be copied over to the original time series. 

If no automatic segmentation is possible then manually annotating each cell (either from the first time point or the maximum intensity projection), is also possible.